Energy and Sustainability III

Energy and Sustainability III WIT Press publishes leading books in Science and Technology. Visit our website for new a...

Author: Y. Villacampa. | A. A. Mammoli | C. A. Brebbia

283 downloads 3142 Views 7MB Size Report

This content was uploaded by our users and we assume good faith they have the permission to share this book. If you own the copyright to this book and it is wrongfully on our website, we offer a simple DMCA procedure to remove your content from our site. Start by pressing the button below!

Report copyright / DMCA form

DOWNLOAD PDF

Energy and Sustainability III

WIT Press publishes leading books in Science and Technology. Visit our website for new and current list of titles. www.witpress.com

WITeLibrary Home of the Transactions of the Wessex Institute. Papers presented at ENERGY 11 are archived in the WIT eLibrary in volume 143 of WIT Transactions on Ecology and the Environment (ISSN 1743-3541). The WIT eLibrary provides the international scientific community with immediate and permanent access to individual papers presented at WIT conferences. Visit the WIT eLibrary at www.witpress.com.

THIRD INTERNATIONAL CONFERENCE ON ENERGY AND SUSTAINABILITY

ENERGY AND SUSTAINABILITY 2011 CONFERENCE CHAIRMEN Y. Villacampa University of Alicante, Spain C.A. Brebbia Wessex Institute of Technology, UK A.A. Mammoli University of New Mexico, USA INTERNATIONAL SCIENTIFIC ADVISORY COMMITTEE N. Abatzoglou A. Brent A. Geens M. Haggag J-M. Lavoie L.V. Lopez-Llorca

M. Motamed Ektesabi G. Passerini V. Popov A. van Timmeren T. Zdankus

LOCAL COMMITTEE M. Cortes-Molina F. Garcia-Alonso F. Navarro J.A. Reyes Perales F. Verdu-Monllor Organised by University of Alicante, Spain Wessex Institute of Technology, UK University of New Mexico, USA Sponsored by WIT Transactions on Ecology and the Environment Ministerio de Ciencia e Innovación (ENE2010-10879-E) Caja Mediterranea

WIT Transactions Transactions Editor Carlos Brebbia Wessex Institute of Technology Ashurst Lodge, Ashurst Southampton SO40 7AA, UK Email: [email protected]

Editorial Board B Abersek University of Maribor, Slovenia Y N Abousleiman University of Oklahoma,

G Belingardi Politecnico di Torino, Italy R Belmans Katholieke Universiteit Leuven,

P L Aguilar University of Extremadura, Spain K S Al Jabri Sultan Qaboos University, Oman E Alarcon Universidad Politecnica de Madrid,

C D Bertram The University of New South

USA

Spain

A Aldama IMTA, Mexico C Alessandri Universita di Ferrara, Italy D Almorza Gomar University of Cadiz, Spain

B Alzahabi Kettering University, USA J A C Ambrosio IDMEC, Portugal A M Amer Cairo University, Egypt S A Anagnostopoulos University of Patras, Greece

M Andretta Montecatini, Italy E Angelino A.R.P.A. Lombardia, Italy H Antes Technische Universitat Braunschweig, Germany

M A Atherton South Bank University, UK A G Atkins University of Reading, UK D Aubry Ecole Centrale de Paris, France H Azegami Toyohashi University of Technology, Japan

A F M Azevedo University of Porto, Portugal J Baish Bucknell University, USA J M Baldasano Universitat Politecnica de Catalunya, Spain J G Bartzis Institute of Nuclear Technology, Greece A Bejan Duke University, USA M P Bekakos Democritus University of Thrace, Greece

Belgium

Wales, Australia

D E Beskos University of Patras, Greece S K Bhattacharyya Indian Institute of Technology, India

E Blums Latvian Academy of Sciences, Latvia J Boarder Cartref Consulting Systems, UK B Bobee Institut National de la Recherche Scientifique, Canada

H Boileau ESIGEC, France J J Bommer Imperial College London, UK M Bonnet Ecole Polytechnique, France C A Borrego University of Aveiro, Portugal A R Bretones University of Granada, Spain J A Bryant University of Exeter, UK F-G Buchholz Universitat Gesanthochschule Paderborn, Germany

M B Bush The University of Western Australia, Australia

F Butera Politecnico di Milano, Italy J Byrne University of Portsmouth, UK W Cantwell Liverpool University, UK D J Cartwright Bucknell University, USA P G Carydis National Technical University of Athens, Greece

J J Casares Long Universidad de Santiago de Compostela, Spain

M A Celia Princeton University, USA A Chakrabarti Indian Institute of Science, India

A H-D Cheng University of Mississippi, USA

J Chilton University of Lincoln, UK C-L Chiu University of Pittsburgh, USA H Choi Kangnung National University, Korea A Cieslak Technical University of Lodz, Poland

S Clement Transport System Centre, Australia M W Collins Brunel University, UK J J Connor Massachusetts Institute of Technology, USA

M C Constantinou State University of New York at Buffalo, USA

D E Cormack University of Toronto, Canada M Costantino Royal Bank of Scotland, UK D F Cutler Royal Botanic Gardens, UK W Czyczula Krakow University of Technology, Poland

M da Conceicao Cunha University of Coimbra, Portugal

L Dávid Károly Róbert College, Hungary A Davies University of Hertfordshire, UK M Davis Temple University, USA A B de Almeida Instituto Superior Tecnico, Portugal

E R de Arantes e Oliveira Instituto Superior Tecnico, Portugal L De Biase University of Milan, Italy R de Borst Delft University of Technology, Netherlands G De Mey University of Ghent, Belgium A De Montis Universita di Cagliari, Italy A De Naeyer Universiteit Ghent, Belgium W P De Wilde Vrije Universiteit Brussel, Belgium L Debnath University of Texas-Pan American, USA N J Dedios Mimbela Universidad de Cordoba, Spain G Degrande Katholieke Universiteit Leuven, Belgium S del Giudice University of Udine, Italy G Deplano Universita di Cagliari, Italy I Doltsinis University of Stuttgart, Germany M Domaszewski Universite de Technologie de Belfort-Montbeliard, France J Dominguez University of Seville, Spain K Dorow Pacific Northwest National Laboratory, USA W Dover University College London, UK C Dowlen South Bank University, UK

J P du Plessis University of Stellenbosch, South Africa

R Duffell University of Hertfordshire, UK A Ebel University of Cologne, Germany E E Edoutos Democritus University of Thrace, Greece

G K Egan Monash University, Australia K M Elawadly Alexandria University, Egypt K-H Elmer Universitat Hannover, Germany D Elms University of Canterbury, New Zealand M E M El-Sayed Kettering University, USA D M Elsom Oxford Brookes University, UK F Erdogan Lehigh University, USA F P Escrig University of Seville, Spain D J Evans Nottingham Trent University, UK J W Everett Rowan University, USA M Faghri University of Rhode Island, USA R A Falconer Cardiff University, UK M N Fardis University of Patras, Greece P Fedelinski Silesian Technical University, Poland

H J S Fernando Arizona State University, USA

S Finger Carnegie Mellon University, USA J I Frankel University of Tennessee, USA D M Fraser University of Cape Town, South Africa

M J Fritzler University of Calgary, Canada U Gabbert Otto-von-Guericke Universitat Magdeburg, Germany

G Gambolati Universita di Padova, Italy C J Gantes National Technical University of Athens, Greece

L Gaul Universitat Stuttgart, Germany A Genco University of Palermo, Italy N Georgantzis Universitat Jaume I, Spain P Giudici Universita di Pavia, Italy F Gomez Universidad Politecnica de Valencia, Spain

R Gomez Martin University of Granada, Spain

D Goulias University of Maryland, USA K G Goulias Pennsylvania State University, USA

F Grandori Politecnico di Milano, Italy W E Grant Texas A & M University, USA

S Grilli University of Rhode Island, USA

R H J Grimshaw Loughborough University, D Gross Technische Hochschule Darmstadt,

M Karlsson Linkoping University, Sweden T Katayama Doshisha University, Japan K L Katsifarakis Aristotle University of

R Grundmann Technische Universitat

J T Katsikadelis National Technical

A Gualtierotti IDHEAP, Switzerland R C Gupta National University of Singapore,

E Kausel Massachusetts Institute of

UK

Germany

Dresden, Germany

Singapore J M Hale University of Newcastle, UK K Hameyer Katholieke Universiteit Leuven, Belgium C Hanke Danish Technical University, Denmark K Hayami University of Toyko, Japan Y Hayashi Nagoya University, Japan L Haydock Newage International Limited, UK A H Hendrickx Free University of Brussels, Belgium C Herman John Hopkins University, USA S Heslop University of Bristol, UK I Hideaki Nagoya University, Japan D A Hills University of Oxford, UK W F Huebner Southwest Research Institute, USA J A C Humphrey Bucknell University, USA M Y Hussaini Florida State University, USA W Hutchinson Edith Cowan University, Australia T H Hyde University of Nottingham, UK M Iguchi Science University of Tokyo, Japan D B Ingham University of Leeds, UK L Int Panis VITO Expertisecentrum IMS, Belgium N Ishikawa National Defence Academy, Japan J Jaafar UiTm, Malaysia W Jager Technical University of Dresden, Germany Y Jaluria Rutgers University, USA C M Jefferson University of the West of England, UK P R Johnston Griffith University, Australia D R H Jones University of Cambridge, UK N Jones University of Liverpool, UK D Kaliampakos National Technical University of Athens, Greece N Kamiya Nagoya University, Japan D L Karabalis University of Patras, Greece

Thessaloniki, Greece

University of Athens, Greece

Technology, USA

H Kawashima The University of Tokyo, Japan

B A Kazimee Washington State University, USA

S Kim University of Wisconsin-Madison, USA D Kirkland Nicholas Grimshaw & Partners Ltd, UK

E Kita Nagoya University, Japan A S Kobayashi University of Washington, USA

T Kobayashi University of Tokyo, Japan D Koga Saga University, Japan S Kotake University of Tokyo, Japan A N Kounadis National Technical University of Athens, Greece

W B Kratzig Ruhr Universitat Bochum, Germany

T Krauthammer Penn State University, USA C-H Lai University of Greenwich, UK M Langseth Norwegian University of Science and Technology, Norway

B S Larsen Technical University of Denmark, Denmark

F Lattarulo Politecnico di Bari, Italy A Lebedev Moscow State University, Russia L J Leon University of Montreal, Canada D Lewis Mississippi State University, USA S lghobashi University of California Irvine, USA

K-C Lin University of New Brunswick, Canada

A A Liolios Democritus University of Thrace, Greece

S Lomov Katholieke Universiteit Leuven, Belgium

J W S Longhurst University of the West of England, UK

G Loo The University of Auckland, New Zealand

J Lourenco Universidade do Minho, Portugal J E Luco University of California at San Diego, USA

H Lui State Seismological Bureau Harbin, China

C J Lumsden University of Toronto, Canada L Lundqvist Division of Transport and

Location Analysis, Sweden T Lyons Murdoch University, Australia Y-W Mai University of Sydney, Australia M Majowiecki University of Bologna, Italy D Malerba Università degli Studi di Bari, Italy G Manara University of Pisa, Italy B N Mandal Indian Statistical Institute, India Ü Mander University of Tartu, Estonia H A Mang Technische Universitat Wien, Austria G D Manolis Aristotle University of Thessaloniki, Greece W J Mansur COPPE/UFRJ, Brazil N Marchettini University of Siena, Italy J D M Marsh Griffith University, Australia J F Martin-Duque Universidad Complutense, Spain T Matsui Nagoya University, Japan G Mattrisch DaimlerChrysler AG, Germany F M Mazzolani University of Naples “Federico II”, Italy K McManis University of New Orleans, USA A C Mendes Universidade de Beira Interior, Portugal R A Meric Research Institute for Basic Sciences, Turkey J Mikielewicz Polish Academy of Sciences, Poland N Milic-Frayling Microsoft Research Ltd, UK R A W Mines University of Liverpool, UK C A Mitchell University of Sydney, Australia K Miura Kajima Corporation, Japan A Miyamoto Yamaguchi University, Japan T Miyoshi Kobe University, Japan G Molinari University of Genoa, Italy T B Moodie University of Alberta, Canada D B Murray Trinity College Dublin, Ireland G Nakhaeizadeh DaimlerChrysler AG, Germany M B Neace Mercer University, USA D Necsulescu University of Ottawa, Canada F Neumann University of Vienna, Austria S-I Nishida Saga University, Japan

H Nisitani Kyushu Sangyo University, Japan B Notaros University of Massachusetts, USA P O’Donoghue University College Dublin, Ireland

R O O’Neill Oak Ridge National Laboratory, USA

M Ohkusu Kyushu University, Japan G Oliveto Universitá di Catania, Italy R Olsen Camp Dresser & McKee Inc., USA E Oñate Universitat Politecnica de Catalunya, Spain

K Onishi Ibaraki University, Japan P H Oosthuizen Queens University, Canada E L Ortiz Imperial College London, UK E Outa Waseda University, Japan A S Papageorgiou Rensselaer Polytechnic Institute, USA

J Park Seoul National University, Korea G Passerini Universita delle Marche, Italy B C Patten University of Georgia, USA G Pelosi University of Florence, Italy G G Penelis Aristotle University of Thessaloniki, Greece

W Perrie Bedford Institute of Oceanography, Canada

R Pietrabissa Politecnico di Milano, Italy H Pina Instituto Superior Tecnico, Portugal M F Platzer Naval Postgraduate School, USA D Poljak University of Split, Croatia V Popov Wessex Institute of Technology, UK H Power University of Nottingham, UK D Prandle Proudman Oceanographic Laboratory, UK

M Predeleanu University Paris VI, France M R I Purvis University of Portsmouth, UK I S Putra Institute of Technology Bandung, Indonesia

Y A Pykh Russian Academy of Sciences, Russia

F Rachidi EMC Group, Switzerland M Rahman Dalhousie University, Canada K R Rajagopal Texas A & M University, USA T Rang Tallinn Technical University, Estonia J Rao Case Western Reserve University, USA A M Reinhorn State University of New York at Buffalo, USA

A D Rey McGill University, Canada

D N Riahi University of Illinois at Urbana-

Champaign, USA B Ribas Spanish National Centre for Environmental Health, Spain K Richter Graz University of Technology, Austria S Rinaldi Politecnico di Milano, Italy F Robuste Universitat Politecnica de Catalunya, Spain J Roddick Flinders University, Australia A C Rodrigues Universidade Nova de Lisboa, Portugal F Rodrigues Poly Institute of Porto, Portugal C W Roeder University of Washington, USA J M Roesset Texas A & M University, USA W Roetzel Universitaet der Bundeswehr Hamburg, Germany V Roje University of Split, Croatia R Rosset Laboratoire d’Aerologie, France J L Rubio Centro de Investigaciones sobre Desertificacion, Spain T J Rudolphi Iowa State University, USA S Russenchuck Magnet Group, Switzerland H Ryssel Fraunhofer Institut Integrierte Schaltungen, Germany S G Saad American University in Cairo, Egypt M Saiidi University of Nevada-Reno, USA R San Jose Technical University of Madrid, Spain F J Sanchez-Sesma Instituto Mexicano del Petroleo, Mexico B Sarler Nova Gorica Polytechnic, Slovenia S A Savidis Technische Universitat Berlin, Germany A Savini Universita de Pavia, Italy G Schmid Ruhr-Universitat Bochum, Germany R Schmidt RWTH Aachen, Germany B Scholtes Universitaet of Kassel, Germany W Schreiber University of Alabama, USA A P S Selvadurai McGill University, Canada J J Sendra University of Seville, Spain J J Sharp Memorial University of Newfoundland, Canada Q Shen Massachusetts Institute of Technology, USA X Shixiong Fudan University, China G C Sih Lehigh University, USA L C Simoes University of Coimbra, Portugal

A C Singhal Arizona State University, USA P Skerget University of Maribor, Slovenia J Sladek Slovak Academy of Sciences, Slovakia

V Sladek Slovak Academy of Sciences, Slovakia

A C M Sousa University of New Brunswick, Canada

H Sozer Illinois Institute of Technology, USA D B Spalding CHAM, UK P D Spanos Rice University, USA T Speck Albert-Ludwigs-Universitaet Freiburg, Germany

C C Spyrakos National Technical University of Athens, Greece

I V Stangeeva St Petersburg University, Russia

J Stasiek Technical University of Gdansk, Poland

G E Swaters University of Alberta, Canada S Syngellakis University of Southampton, UK J Szmyd University of Mining and Metallurgy, Poland

S T Tadano Hokkaido University, Japan H Takemiya Okayama University, Japan I Takewaki Kyoto University, Japan C-L Tan Carleton University, Canada E Taniguchi Kyoto University, Japan S Tanimura Aichi University of Technology, Japan

J L Tassoulas University of Texas at Austin, USA

M A P Taylor University of South Australia, Australia

A Terranova Politecnico di Milano, Italy A G Tijhuis Technische Universiteit Eindhoven, Netherlands

T Tirabassi Institute FISBAT-CNR, Italy S Tkachenko Otto-von-Guericke-University, Germany

N Tosaka Nihon University, Japan T Tran-Cong University of Southern Queensland, Australia

R Tremblay Ecole Polytechnique, Canada I Tsukrov University of New Hampshire, USA R Turra CINECA Interuniversity Computing Centre, Italy

S G Tushinski Moscow State University, Russia

J-L Uso Universitat Jaume I, Spain E Van den Bulck Katholieke Universiteit

Z-Y Yan Peking University, China S Yanniotis Agricultural University of Athens,

D Van den Poel Ghent University, Belgium R van der Heijden Radboud University,

A Yeh University of Hong Kong, China J Yoon Old Dominion University, USA K Yoshizato Hiroshima University, Japan T X Yu Hong Kong University of Science &

Leuven, Belgium

Netherlands

R van Duin Delft University of Technology, Netherlands

Greece

Technology, Hong Kong

P Vas University of Aberdeen, UK R Verhoeven Ghent University, Belgium A Viguri Universitat Jaume I, Spain Y Villacampa Esteve Universidad de

M Zador Technical University of Budapest,

F F V Vincent University of Bath, UK S Walker Imperial College, UK G Walters University of Exeter, UK B Weiss University of Vienna, Austria H Westphal University of Magdeburg,

R Zarnic University of Ljubljana, Slovenia G Zharkova Institute of Theoretical and

Alicante, Spain

Germany

J R Whiteman Brunel University, UK

Hungary

K Zakrzewski Politechnika Lodzka, Poland M Zamir University of Western Ontario, Canada

Applied Mechanics, Russia

N Zhong Maebashi Institute of Technology, Japan

H G Zimmermann Siemens AG, Germany

Energy and Sustainability III Editors Y. Villacampa University of Alicante, Spain C.A. Brebbia Wessex Institute of Technology, UK A.A. Mammoli University of New Mexico, USA

Ministerio de Ciencia e Innovación (ENE2010-10979-E)

Editors: Y. Villacampa University of Alicante, Spain C.A. Brebbia Wessex Institute of Technology, UK A.A. Mammoli University of New Mexico, USA

Published by WIT Press Ashurst Lodge, Ashurst, Southampton, SO40 7AA, UK Tel: 44 (0) 238 029 3223; Fax: 44 (0) 238 029 2853 E-Mail: [email protected] http://www.witpress.com For USA, Canada and Mexico Computational Mechanics Inc 25 Bridge Street, Billerica, MA 01821, USA Tel: 978 667 5841; Fax: 978 667 7582 E-Mail: [email protected] http://www.witpress.com British Library Cataloguing-in-Publication Data A Catalogue record for this book is available from the British Library ISBN: 978-1-84564-508-3 ISSN: 1746-448X (print) ISSN: 1743-3541 (on-line) The texts of the papers in this volume were set individually by the authors or under their supervision. Only minor corrections to the text may have been carried out by the publisher. No responsibility is assumed by the Publisher, the Editors and Authors for any injury and/or damage to persons or property as a matter of products liability, negligence or otherwise, or from any use or operation of any methods, products, instructions or ideas contained in the material herein. The Publisher does not necessarily endorse the ideas held, or views expressed by the Editors or Authors of the material contained in its publications. © WIT Press 2011 Printed in Great Britain by Martins the Printer. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of the Publisher.

Preface

The world’s economies are fuelled by energy. As their size increases, energy use goes up correspondingly. Furthermore, governments’ efforts worldwide are primarily focused on economic growth. There is nothing inherently wrong with either energy use or economic growth – both have led to advances in science, medicine, education and most other factors used to measure quality of life. However, given the finite nature of planet Earth, problems inevitably arise. Today, energy is derived primarily by the combustion of fossil fuels. The consequences of continued reliance on these are well known – climate change, and resource depletion. There is a high likelihood that the feedback into the world economy in the medium to long term will be less than pleasant. Many individuals and organizations concerned with energy and sustainability were disappointed with the outcomes of the Copenhagen meeting in 2009. This event provided the answer to a fundamental question: ‘will the world’s political establishment agree to any meaningful international action to reduce the consumption of fossil fuels?’ The answer, a textbook example of the tragedy of the commons at work, was a resounding ‘no!’ Certainly, various governments, as a function of pressure from their constituents, have implemented successful measures to stimulate the development of ‘green energy’, but even valiant efforts, such as Germany’s and Spain’s feed in tariffs for renewables, all far short of what would be necessary for an orderly worldwide transition to sustainable energy. So what to do? In the absence of a top-down process, it becomes necessary to strengthen the bottom-up process if there is to be any chance of eventually reaching an economy based on sustainable energy. Fortunately, in recent years there have also been a number of encouraging technological developments to partially offset the political setbacks. For example, the wind industry is a mature technology, which can compete with coal in terms of unit energy cost, even if the externalities associated with coal combustion are not accounted for. Solar photovoltaics have recently broken the one dollar per watt barrier, and are set to continue this downward trend. Plug-in hybrid and fully electric

cars are in showrooms this year. After the boom and bust cycles of corn-based ethanol, there are strong efforts to produce cellulosic ethanol and other biofuels which have a positive lifecycle energy balance and do not compete with food production. In many cases, the challenge lies as much in the conversion from primary renewable energy (wind, solar, etc.) to useful forms (electricity, heat, fuel) at an acceptable cost, as in the integration of these resources into an existing infrastructure. Researchers, industry and local governments are now addressing the need to match the energy source to the end use. For example, electricity in a typical building performs several functions – it can heat or cool the building, or power lighting and electronic equipment. While storing electricity to decouple source and end load may make sense if the end load is a computer, it probably does not if the end use is cooling – it is much cheaper to store chilled water or ice in a tank than electrons in a battery. The appropriateness of a particular energy pathway to the end use is discussed in many of the papers in this book. The question of resource identification and characterization, including cost, is addressed in many papers. Finally, the topic of reliability and robustness of renewable energy resources and applications, old and new, is discussed. Ultimately, the path to a sustainable energy future will follow the model of the internet and cell phone use – it will happen because people demand it, rather than because it was centrally mandated. For this to happen there will need to be perceptible advantages, for example lower, stable and predictable energy costs, or independence from a monopoly supplier. Carbon-free is not enough – new energy resources and applications will need to be cheaper, more reliable and more attractive than the ones they replace. The wheels have been set in motion, the challenge is now to overcome defeatism and show that a sustainable energy future is not only possible, but better and more desirable. The Editors Alicante, 2011

Acknowledgement This book contains papers presented at the 3rd International Conference on Energy and Sustainability, held in Alicante in 2011, organised by the University of Alicante, the Wessex Institute of Technology and the University of New Mexico. The Conference was sponsored by the Ministerio de Ciencia e Innovación (CTM2010110878-E) as well as by the Caja Mediterranea to whom the organisers are indebted. The papers have been reviewed with the help of the members of the International Scientific Advisory Committee and other colleagues. Their generous contribution to the success of the Meeting is acknowledged. The Editors are also grateful to all authors for the excellent quality of the contributions contained in this volume.

Contents Section 1: Renewable energy technologies Design guidelines for a robust and reliable solar thermal heating and cooling system A. Mammoli, P. Vorobieff, H. Barsun & R. Burnett ............................................ 3 Systems dynamics modelling to assess the sustainability of renewable energy technologies in developing countries A. C. Brent, M. B. Mokheseng, B. Amigun, H. Tazvinga & J. K. Musango ....... 13 How small island governments are responding to the development of energy technologies M. J. de Vial & E. P. Monkhouse ...................................................................... 25 Experimental and economical study of sustainable electricity generation by solar PV/diesel hybrid systems without storage for off grid areas D. Yamegueu, Y. Azoumah & X. Py ................................................................... 37 Photovoltaic energy and the environment A. Reyes, F. Garcia-Alonso, J. A. Reyes & Y. Villacampa ................................ 51 Improving building energy efficiency: a case study S. Grignaffini, M. Romagna & D. Principia...................................................... 61 Numerical modeling as a basic tool for evaluation of using mine water as a heat source J. Baier, M. Polák, M. Šindelář & J. Uhlík........................................................ 73 Section 2: Biomass processes and biofuels High yields of sugars via the non-enzymatic hydrolysis of cellulose V. Berberi, F. Turcotte, G. Lantagne, M. Chornet & J.-M. Lavoie ................... 87

On the future relevance of biofuels for transport in EU-15 countries A. Ajanovic & R. Haas....................................................................................... 97 Biomass char production at low severity conditions under CO2 and N2 environments G. Pilon & J.-M. Lavoie .................................................................................. 109 From biomass-rich residues into fuels and green chemicals via gasification and catalytic synthesis S.C. Marie-Rose, E. Chornet, D. Lynch & J.-M. Lavoie.................................. 123 Anaerobic digestion of cattle manure: effect of phase-separation V. Yılmaz & G. N. Demirer.............................................................................. 133 Biodiesel reforming with a NiAl2O4/Al2O3-YSZ catalyst for the production of renewable SOFC fuel N. Abatzoglou, C. Fauteux-Lefebvre & N. Braidy ........................................... 145 Section 3: Energy management Energy management and sustainable development S. S. Seyedali Ruteh ......................................................................................... 159 Investigation of energy management in an Iranian construction project S. Ajel, M. B. Nobakht & M. Harischian ......................................................... 173 Optimization of the pumping station of the Milano water supply network with Genetic Algorithms S. Mambretti .................................................................................................... 185 Case study: energy audit and implementation at the Russell Medical Center D. F. Dyer & C. O’Mary ................................................................................. 195 Wave potential of the Greek seas T. Soukissian, N. Gizari & M. Chatzinaki........................................................ 203 Section 4: Energy policies The role of district energy in greening existing neighborhoods: a primer for policy makers and local government officials T. Osdoba, L. Dunn, H. Van Hemert & J. Love............................................... 217

Subsidising renewable electricity in Estonia J. Kleesmaa, S. Pädam & Ü. Ehrlich............................................................... 229 Promoting electricity from renewable energy sources in emerging and developing countries – lessons learned from the EU R. Haas, S. Busch, G. Resch, M. Ragwitz & A. Held ....................................... 241 Socio-economic and energy scenario development in Vietnam T. T. Tran, M. Namazu & Y. Matsuoka............................................................ 253 Renewable energy policy landscape in South Africa: moving towards a low carbon economy G. Nhamo & S.-Y. Ho ...................................................................................... 265 Section 5: Energy and the environment Environmental balance study for the construction of a biomass plant in a small town in Piedmont (Northern Italy) D. Panepinto & G. Genon ............................................................................... 279 Bioenergy for regions – alternative cropping systems and optimisation of local heat supply C. Konrad, B. Mast, S. Graeff-Hönninger, W. Claupein, R. Bolduan, J. Skok, J. Strittmatter, M. Brulé & G. Göttlicher ........................................... 291 Sustainability of nuclear energy with regard to decommissioning and waste management S. Lindskog, R. Sjöblom & B. Labor................................................................ 303 How dematerialization contributes to a low carbon society? S. Fujimori & T. Masui.................................................................................... 315 Recovery of combustible matter from waste fine Chinese coals by a waste vegetable oil agglomerating process and its combustion characteristics Q. Wang, N. Kashiwagi, P. Apaer, Q. Chen, Y. Wang, T. Maezono & D. Niida................................................................................... 327 Long-term CO2 emissions abatement in the power sector and the influence of renewable power T. Aboumahboub, K. Schaber, U. Wagner & T. Hamacher............................. 339 Energy recovery of a rotary kiln system in a calcium oxide plant M. Aldeib, A. Elalem & S. Elgezawi ................................................................ 353

Nonthermal plasma-assisted catalytic methanation of CO and CO2 over nickel-loaded alumina E. Jwa, Y. S. Mok & S. B. Lee.......................................................................... 361 Family size solar dryer for an estimation of the heat transfer coefficient T. M. Jaballa.................................................................................................... 369 Energy recovery of grass biomass S. Oldenburg, L. Westphal & I. Körner ........................................................... 383 Section 6: Energy analysis Effect of H2 enrichment on the explosive limits of Liquefied Petroleum Gas (LPG) in conventional combustion I. Izirwan, S. Noor Shahirah, S. Siti Zubaidah, M. N. Mohd Zulkifli & A. R. Abdul Halim ....................................................... 399 Embodied energy analysis of multi-storied residential buildings in urban India S. Bardhan ...................................................................................................... 411 Section 7: Energy efficiency Learn to save: sustainable schools A. Boeri & D. Longo........................................................................................ 425 Experimental study of a waste heat recovery system for supplemental heaters E. Y. Tanbour, R. Al-Waked & M. F. Alzoubi.................................................. 437 Energy performance assessment of building systems with computer dynamic simulation and monitoring in a laboratory A. García Tremps & D. Mora.......................................................................... 449 Investigating the impact of track gradients on traction energy efficiency in freight transportation by railway G. Bureika & G. Vaičiūnas.............................................................................. 461 Section 8: CO2 sequestration and storage CO2 transport modelling, conversion and storage C. Konrad, J. Strittmatter, D. Haumann, G. Göttlicher & E. Osmancevic ............................................................................................. 475

Influence of heat treatment on the corrosion behavior of steels exposed to CCS environment A. Pfennig, P. Wojtas, I. Spengler, B. Linke & A. Kranzmann ........................ 487 Author Index .................................................................................................. 499

This page intentionally left blank

Section 1 Renewable energy technologies

This page intentionally left blank

Energy and Sustainability III

3

Design guidelines for a robust and reliable solar thermal heating and cooling system A. Mammoli1, P. Vorobieff1 , H. Barsun2 & R. Burnett2

1 Department

of Mechanical Engineering, The University of New Mexico, USA 2 Physical Plant Division, The University of New Mexico, USA

Abstract The use of solar energy at the building scale today presents two viable options: grid-tied photovoltaic systems, and thermal systems utilizing absorption or adsorption cycles for cooling. The economic viability of either option is presently commensurate, however, specifically for the case of thermal systems, there is a major caveat, namely that the system must truly save energy, and must be reliable over its typical expected lifetime. While the basic design of a solar thermal system is relatively simple, there are many details that, if not carefully considered, can lead to poor performance, lack of reliability, and potentially catastrophic failure. Based on experience in designing, building, operating and analyzing such a system for several years, a set of guidelines is presented for each major system component, namely the solar loop, hot storage, cold storage, the heating and cooling subsystems, and the control system. These design recommendations should assist engineers in preventing costly mistakes that are difficult to correct. If followed, the guidelines should also reduce maintenance and prolong trouble-free performance of building-scale thermal systems. Keywords: robust design, reliability, economic performance, energy efficiency.

1 Background Building operation comprises a substantial fraction (40–50%) of the overall energy budgets of industrially developed countries [1] and an even larger fraction of the electric energy budgets (>70%). The advantages of minimizing the related energy expenditures are obvious, and have studied extensively in the last several decades, especially since the first and subsequent energy crises raised awareness WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESUS110011

4 Energy and Sustainability III of the necessity of energy conservation, and studies of the effect of anthropogenic greenhouse gas emission revealed its role in the global climate change. Along with energy efficiency, the latter motivates transition away from fossil energy sources and integration of renewable-energy generation and smart grid concepts into new buildings. Energy-efficient building-scale thermal system design that uses renewable energy has been the subject of several recent books [2–4]. However, while it is possible to find a good general overview of the design practices, very often specific implementation details play a disproportionate role in determining the efficiency and ease of maintenance of a real-world building thermal system. This paper provides specific recommendations for components that are quite common in buildings with solar thermal systems. These recommendation are based on several years of experience in design, maintenance, and optimization of a stateof-the-art solar-assisted HVAC setup that is described in the following section.

2 System description The system installed at the University of New Mexico has been described in detail elsewhere [5–8]. Its layout (Fig. 1) is fairly typical. In the solar loop, glycol is circulated by pump P4 from the outlet of the heat exchanger HX, through an array of flat plate solar collectors, then through an array of vacuum tube solar collectors, to the inlet of the heat exchanger. Pump P5 draws water from the bottom of the hot water tank HWT, circulates it through the lower temperature side of the heat exchanger HX, and then to the top of the tank. In the heating season, water from the top of the hot storage is drawn by pump P3 and circulated through a set of water-air heat exchangers, which heat air delivered to the building, and is subsequently returned to the bottom of the hot storage. In the cooling season, water from the top of the hot storage tank is drawn by pump P3 and circulated through the absorption chiller’s generator coil, then returned to the bottom of the hot storage. Return water from the cooling coils (another set of water–air heat exchangers which cool air delivered to the building) is directed by pump P2 to the evaporator section of the absorption chiller, where it is chilled and returned to the cooling circuit upstream of the coils. If the cold water production exceeds building demand, excess chilled water is stored in the cold water tanks (CWT). The cold water tanks are charged at night to use off-peak power prices, and depleted during the day. During night-time charging, pump P1 draws water from the top of the cold storage, pumps it through a heat exchanger cooled by the campus chilled water system, and then to the bottom of the cold storage. During the daytime, chilled water is drawn by pump P1 from the bottom of the cold tanks, routed through the cooling coils, and returned to the top of the cold storage. The combined solar and building heat is removed from the chiller by a cooling tower. Pump P6 draws water from the sump, pumps it through the chiller condensing coils, and then to the cooling tower. Water from the cooling tower flows back to the sump by gravity. WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

FPA

5

VTA CT

V11 V10 V13 HWT P3

V7

V12 P5

CWT

V6

CV1 P4

campus CHW

HX SCV V8 CV2

V3

V9

P1

campus STM

CV3

heating coils

abs. chiller

P2

V1 V4 V2

cooling coils

P6 sump

Figure 1: Schematic of the solar thermal system showing solar collectors (flat panel arrays FPA and vacuum tube arrays VTA), hot (HWT) and cold (CWT) storage tanks, absorption chiller, heating and cooling coils, and ancillary equipment layout.

3 The solar loop Optimization of the solar loop involves balancing initial costs with running costs and reliability. First, it is necessary to choose the heat medium which will not freeze at temperatures regularly occurring in the cold season. A non-toxic 35% propylene glycol/65% water mixture was selected to minimize problems due to toxicity at a small thermal performance detriment. Its freezing point, approximately −17.8◦ C (0◦ F) is suitable for Albuquerque’s climate, in which such temperatures occur only every several years. When the one of the two outside air WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

6 Energy and Sustainability III temperature sensors detects temperatures below −12◦ C, active freeze protection is enabled. The solar loop pump P4 is activated, the three-way valve SCV allows glycol to flow through the heat exchanger HX, and pump P5 circulates water from cold storage (which is still warm enough to maintain the glycol temperature to well above freezing) through the water side of the heat exchanger. The three-way valve SCV can isolate the solar loop from the heat exchanger. This is useful during winter nights, when thermosyphoning would otherwise allow sub-freezing glycol to enter the heat exchanger and thus freeze the water in its lower-temperature side. the loop can also be operated in isolated mode in the morning, while the solar loop is heating up. Finally, the valve can be used to regulate temperature in case of failure of the pump speed control. An expansion tank is located in a heated space, just downstream of the solar collector field. This location was chosen because it experiences the smallest pressure variations, which result as a consequence of heat medium flow rate through the system. Piping selection is very important – pressure losses result in additional pumping power. As a rule of thumb, electric energy should be considered seven times more valuable than heat, using the typical COP of absorption and compression chillers of 0.7 and 5 respectively. Thus, for example, 1 kW of pumping loss offsets 7 kW of thermal heat collection rate. Thus, piping pressure losses should account for a small fraction of overall pumping requirements. The majority of the pumping losses are generally due to the solar collectors, which can be arranged in series or in parallel. For a given field temperature gain, the flow rate through each collector is proportional to the number of collectors connected in series. Pressure loss through an individual collector is generally proportional to the square of the flow rate. Thus, overall the pumping losses through the collector field are proportional to the third power of the number of collectors connected in series. Parallel arrangements are therefore preferable, from the point of view of pumping losses, to series arrangements. Therefore, while the initial cost of plumbing for series arrangements is generally less expensive, these savings (which can be substantial) must be balanced against pumping costs over the expected lifetime of the system, and by the cost of the larger pump(s) necessary to maintain the required flow rates. Temperature control is achieved by adjusting the speed of the circulation pump (P4, a 4-stage centrifugal pump with a three-phase, 7 kW AC motor) via a variable frequency drive (VFD). Since pumping costs are proportional to the square of the pump speed, substantial savings are obtained by reducing pump speed when possible, i.e. off solar peak. A single-stage, 7 kW AC pump, or a 1 kW batterypowered DC pump provide circulation in the case of failure of the primary pump or loss of AC power respectively. Temperature control in this case is obtained via the three-way valve SCV. A final design suggestion relates to he ability of the collector system to withstand wind loading. In many cases, the manufacturer-provided rack/mounting systems require additional bracing. Even small oscillations of collector rows, especially if connected in series, can eventually lead to leaks in the collectorcollector coupling, which, if left unchecked, ultimately may lead to more serious consequences (pump cavitation, vapor lock, emulsification of the glycol/water WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

7

mixture. Ultimately, with tens or even hundreds of connections for a typical system, a completely leak-proof system is beyond realistic expectation., and an automatic glycol make-up system should be considered for a robust installation.

4 The hot storage system How water storage is essential for solar heating and cooling systems, both for smoothing intermittency and for decoupling the load from the production. A welldesigned storage system provides a steady supply of hot water, at constant temperature, to the absorption chiller or to the heating coils. Hot storage can be pressurized or atmospheric. Closed loop, pressurized systems allow higher working temperatures (necessary, for example, in the case of double-effect chillers), and are less susceptible to evaporative heat loss. In a closed system, water treatment requirements are less severe. On the other hand, pressurized systems are more expensive than atmospheric systems, and are subject to more stringent design requirements. Atmospheric pressure storage systems are restricted to temperatures below the boiling temperature of water at the location of the installation (for example, 93◦ C for Albuquerque). However, the cost is lower, especially as the tank size increases. Running a typical building-scale chiller (in the present case, a Yazaki SH-20, 75 kWt ) for one hour while a bank of clouds passes by requires a hot water reserve of approximately 3000 kg. Load shifting requires even more storage. Typically the maximum cooling load occurs approximately three hours after the solar peak, so that shifting the additional cooling capacity accordingly would require a tank with 9000 kg capacity. If cold storage is also a part of the system, it also can be used for load shifting. However, a large storage tank may allow operation of the chiller at times of day when ambient temperature is lower, so that the cooling tower operates more efficiently, with reduced use of the cooling fan. To minimize heat losses, the bottom and sides of the tank must be highly insulated with materials suitable for the highest water temperature in the system. In the present case, two layers of insulation were used for the sides and bottom. The inner layer, adjacent to the water, is polyurethane foam, which can withstand continuous exposure to 120◦ C, with a thickness of 0.1 m. The outer layer, which is exposed to much lower temperature, consists of 0.2 m thick polystyrene panels. The tank is lined with a high-density polyethylene liner. The top of the tank should also be thoroughly insulated. This component is actually more critical that the other surfaces because evaporative losses can become large. Ideally, a floating ‘lid’ could minimize evaporation, and also accommodate thermal expansion and contraction of the water mass. Such a system was implemented initially in the present system. While its initial performance was excellent, it rapidly degraded, due to the de-polymerization and related embrittlement of the polycarbonate floating mats. A second design consisted of a double layer metal ‘suspended ceiling’, with a 0.05 m air gap between the metal sheets. Polystyrene insulation panels of 0.05 m thickness were laid above the metal ceiling. WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

8 Energy and Sustainability III Water from the bottom of the hot tank is pumped through the solar heat exchanger HX by pump P5. A battery powered 48 V DC backup pump provides enough flow to dissipate the heat from the solar system for several hours, as a failsafe for the main AC pump failure, a loss of grid power, or of backup generator power. Water is delivered or drawn from hot storage via two flow-through diffusers, one at the bottom of the tank, the other near the top. In a flow-through diffuser [7], water is supplied at one end and drawn from the other. The flow rate difference between the supply and draw is balanced by the storage tank. This design allows using two rather than four diffusers, and if the supply and load are well-matched, the storage loss that would be incurred by sending water to storage before drawing it again is substantially reduced. The diffusers are constructed using CPVC, which is able to withstand the working temperatures of the water and does not corrode. It is recommended that all piping leading to and from hot storage be as short as possible, routed below the water line at all points, and that the pumps be located as close as possible to the storage tank. This is particularly important in the case of the pump serving the chiller (P3), which draws water at a temperature close to boiling. If the piping between the storage tank and the pump is too long, and particularly at high pipe elevations, the water might flash to steam, severely disrupting the pump’s capacity to sustain the required flow rate. For the same reason, all hot water pumps should be located as low as possible with respect to the hot storage. Finally, if all piping is below the water line, any leaks in the piping will result in outward leaking of water, rather than inward air leaks, which could lead to loss of priming.

5 The cold storage system Cold storage is particularly important for climates where cooling dominates the thermal load, which certainly is the case for New Mexico. At the same time, the useful temperature difference (assuming liquid water is the energy storage medium) is about five times lower than it is for heating. This consideration is important when the size of the cold storage tanks is determined. The system discussed here uses seven tanks for cold storage and only one tank for hot storage. Cold-water tanks located below ground level have reinforced concrete walls 0.3 m thick. Because temperature differences between the surroundings and the storage medium are much lower for cold storage, the concrete provides adequate insulation, eliminating the necessity for additional insulating materials. Evaporative losses are not a problem for cold storage either, so the tanks can operate quite well without a floating lid or an insulated suspended ceiling. What proved quite beneficial, however, was the installation of flexible polyurethane drop-in liners in the storage tanks. Without liners, cracks developing in the concrete lead to leaks. Stable thermal stratification is maintained both in the hot and cold tanks, which makes it possible to use the same tank for drawing fresh storage medium (in the case of cold tanks, coldest water from the bottom) and for releasing the depleted medium (for cold tanks, warmer water that has passed through the air-handler WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

9

coils is deposited near the top of the tank). Maintaining the stratification in the tanks requires properly designed and located diffusers to prevent forced convection and turbulence. The diffusers have the same orientation, with the warmer diffuser located at the top of one side of the tank, and the colder one – at the bottom of the opposite side of the tank. This arrangement avoids mixing by producing low velocity (<2 cm/s), uniform temperature fluid flow in and out of the tank. Earlier studies using the same storage tanks investigated the feasibility of changing the tank aspect ratio with baffles [9, 10]. With diffusers installed as described above, stratification is sustainable without any baffling (in 4 × 4 × 4 m tanks). Moreover, baffles significantly complicate tank maintenance, liner installation, etc. What was also found to be quite necessary was chemical water treatment for the cold storage – without it, the tanks too easily provide breeding ground for many kinds of lifeforms, which in turn increases maintenance expenses and corrosion. Finally, there is a cost-efficient failsafe for solar thermal systems with storage that are located in climates with occasional extreme winter temperatures. Water in cold storage can be used to heat the thermal medium in the solar loop to prevent it from freezing. In December 2010, when outside temperatures fell as low as −16◦ C during the nights, cold storage water was run through the solar-loop heat exchanger while also running the solar loop pump, thus achieving freeze protection.

6 The heating and cooling systems The building is heated and cooled by forced air, delivered via a dual-duct system. A large atrium in the building is served by an air handler which uses an air-water heat exchanger for heating and evaporative media for cooling. The remainder of the building is heated and cooled via water-air heat exchangers for both heating and cooling, located in several air handling units (AHUs). During the heating season, water is drawn by pump P3 from the top flowthrough diffuser in the HWT and routed to several AHUs where water-air heat exchangers control the air temperature in the hot deck. Control valves in each air handler adjust the hot water flow to maintain a set hot deck temperature. The water temperature set point in the HWT is 60◦ C, and is achieved whenever sufficient solar power is available. The temperature of the hot water supply to the AHUs is boosted by a steam-water heat exchanger (campus STM in Fig. 1) if the temperature falls below 55◦ C. Pump P3 is a tandem set-up, in which one of the two identical pumps serves as the primary pump, while the other is on stand-by. During the cooling season, the building is cooled by depleting cold storage (approximately 60–65% of the total load) with the balance supplied by the absorption chiller. In charging mode, pump P1 (a set of tandem pumps) draws water from the top of the CWT, at approximately 18◦ C, routes it through a plate-and-frame heat exchanger, and returns it to the bottom of the CWT at approximately 8◦ C. Flow rates are controlled so that water on the cold side of the heat exchanger (from the central campus chilled water system) enters at 6.5◦ C and exits at 14.5◦C. WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

10 Energy and Sustainability III When a sufficient amount of hot water at 84◦ C accumulates in the HWT, the absorption chiller startup procedure begins. Chilled water from the AHU return is pumped through the chiller evaporator by pump P2 (also a tandem setup). The cooling water pump P6 is activated. Meanwhile, the heating water supply is also activated. To avoid a daily thermal shock, the heating water flow rate is ramped up slowly, beginning from a level of 60% pump speed, at a rate of 3% per minute, until the desired chiller outlet temperature is reached. The absorption chiller is enabled by the digital control system. If internal checks are satisfied, the solution pump is enabled and absorption cooling begins. Steady-state is reached in approximately 10 minutes from procedure initiation. The accumulated water in the HWT prior to chiller startup ensures that more than one daily startup occurs seldom. More than two startups have not been observed to date. A very important and often-overlooked design aspect of systems with absorption chillers is their high cooling demand. For a typical electric chiller, for every unit of cooling, an additional 0.20–0.25 units of mechanical work eventually add to the overall load on the cooling tower, for absorption chillers every unit of cooling power is accompanied by an additional 1.4–1.5 units of heat input to the generator. Thus, the cooling tower for an absorption chiller must have approximately twice the capacity of the tower required for a compression system with the same rating. Moreover, the cooling water flow rate requirements also double, and the cooling water pump and related piping likewise must be upgraded. Inadequate cooling capacity is a common problem encountered during the commissioning of absorption-based systems.

7 The control system For a system of this complexity, direct digital control (DDC) is a must. Reliability and autonomy are necessary features, given that, once commissioned, a typical system is expected to function without supervision. Thus an industrial-grade HVAC controller is warranted. In the present case, the controller (Delta) is programmed in GCL+, a BASIC-like programming language. The control program is strongly structured into relatively simple and easily testable sub-programs, reducing the possibility of unpredicted logic flaws. An effort was made to predict possible serious failures. For example, if the flow rate in the solar loop (measured by a flow meter) is below a certain threshold, while the pump is active, there are two possible causes – flow meter failure or loss of fluid. In the former case, it would preferable to keep the pump running to avoid collector overheating. However, if indeed there was a loss of fluid, running the pump dry would cause severe damage to the pump in a shorter time. Thus, the controller action under the ‘no flow – pump on’ scenario is to shut down the pump and alert one or more technical personnel who are able to take corrective action. Alerts are sent by the control system via email and text messaging. In the case that AC power is lost (a low-probability event, which requires loss of grid power and failure of the emergency diesel generator), the entire system shuts down, except for the solar loop. Backup DC pumps on either side of the heat WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

11

exchanger HX are able to run on battery backup for up to five hours. Automatic switches on the pumps fail closed, so that the backup pumps are enabled. Valves V10 and V12 fail open, while valves V11 and V13 fail closed. This way, the large chilled water storage tanks serve as a buffer to prevent either overheating (daytime) or freezing (night-time in winter) of the solar loop.

8 Energy and economic performance Results of comparing the numerically predicted [7] and experimentally measured [8] performance of the system were quite interesting. In some cases (e.g., the operation of the solar loop), the agreement was excellent. The comparison also revealed weak points in the design, most of which have now been addressed. One such weak spot was the hot energy storage, with higher than expected evaporative losses from the top. Another problem lay with the air handlers that caused dramatic efficiency losses by allowing more outside air than necessary to enter the building – mostly due to baffles that failed to close completely. Improper operation of the air handling subsystem alone can negate all the benefits from active energy collection. An economic study [8] revealed that in New Mexico, where the energy prices from utility companies are presently very low, installation of building-scale solar thermal systems offers very limited benefits, and these are only realized if the lifetime of the system is very long. At the same time, in environments with much higher energy costs (US Pacific coast, EU) installation of solar thermal building systems becomes economically viable with a much shorter term for return on investment. If the reduction in CO2 emissions due to system installation is explicitly taken into consideration (e.g., via monetized carbon credits), this further improves the economic viability of building-scale solar thermal systems. In any case, however, before considering installation of active energy capture systems in new designs or for building renovation, it is imperative to maximize the building energy efficiency by ensuring that all HVAC components operate properly, all control sequences are well thought-out, and all efficiency measures have been implemented, including minimization of evaporative and convection losses from hot storage, installation of proper pumping and plumbing, minimization of electric losses (with variable-frequency drives for all the pumps and fans), and elimination of air leaks in air handling units.

9 Conclusions Design and implementation recommendations for building-scale solar thermal systems presented here emphasize efficient and trouble-free performance. Many suggestions include measures that would be equally applicable to an energyefficient building either with or without an active energy collection system (e.g., ensuring proper operation of air handling units). In the presence of a solar thermal system, specific optimization measures are also required (proper insulation for hot storage, diffusers that maintain stratification in the tanks, etc.). WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

12 Energy and Sustainability III As the benefits of solar thermal systems are still realized over the long term (even in markets with high energy costs), the designer must overcome the temptation to cut initial costs and maximize performance at the expense of system reliability. Failsafes and some redundancy are essential for the long-term potential of the solar thermal system to be realized fully without costly repairs. Research is underway to support the integration of high-penetration, high intermittency distributed energy resources (e.g., rooftop PV) within a distribution feeder, by using thermal storage, as well as easily dispatchable energy resources such as fans.

References [1] Mazria, E., It’s the architecture, stupid! Solar Today, pp. 48–51, 2003. [2] Henning, H.M., Solar-Assisted Air-Conditioning in Buildings. SpringerVerlag/Wien, 2004. [3] Gevorkian, P., Sustainable Energy System Engineering: The Complete Green Building Design Resource. McGraw-Hill Professional, 2006. [4] Vallero, D.A. & Brasier, C., Sustainable Design: The Science of Sustainability and Green Engineering. Wiley, 2008. [5] Ortiz, M., A TRNSYS model of a solar thermal system with thermal storage and absorption cooling. Master’s thesis, The University of New Mexico, Albuquerque, NM, USA, 2008. [6] Mammoli, A.A., Vorobieff, P. & Menicucci, D., Promoting solar thermal design: the Mechanical Engineering building at the University of New Mexico. Management of Natural Resources, Sustainable Development and Ecological Hazards, Wessex Institute of Technology: Albuquerque, NM, USA, WIT Transactions on Ecology and the Environment, 2006. [7] Ortiz, M., Barsun, H., He, H., Vorobieff, P. & Mammoli, A., Modeling of a solar-assisted HVAC system with thermal storage. Energy and Buildings, 42, pp. 500–509, 2010. [8] Mammoli, A., Vorobieff, P., Barsun, H., Burnett, R. & Fisher, D., Energetic, economic and environmental performance of a solar-thermal-assisted hvac system. Energy and Buildings, 42, pp. 1524–1535, 2010. [9] Wildin, M.W., A report on the mechanical engineering building at the University of New Mexico. Technical report, The University of New Mexico, Albuquerque, NM, USA, 1982. [10] Wildin, M.W., Results from use of thermally stratified water tanks to heat and cool the Mechanical Engineering building at the University of New Mexico. Technical Report ORNL/Sub-80-7967/1, The University of New Mexico, Albuquerque, NM, USA, 1983.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

13

Systems dynamics modelling to assess the sustainability of renewable energy technologies in developing countries A. C. Brent1, M. B. Mokheseng2, B. Amigun2, H. Tazvinga2 & J. K. Musango1 1

Centre for Renewable and Sustainable Energy Studies, School of Public Leadership, Stellenbosch University, South Africa 2 Sustainable Energy Futures, Natural Resources and the Environment, Council for Scientific and Industrial Research, South Africa

Abstract The ‘water-energy nexus’ is now receiving more attention as policy- and decision-makers grapple with measures to enable the transition to a sustainable, low-carbon economy. South Africa, in particular, finds itself in a polycrisis in terms of dealing with economic development, to alleviate poverty, within water and energy constraints. In the Western Cape Province of the country, desalination is suggested as one solution to the water shortage crisis, but the critical issue is that of energy supply, and the related cost implications, for water supply; concentrated solar thermal technology options are currently considered. In this paper a systems dynamics approach is used to assess the sustainability of these types of renewable energy technologies. The objectives of the paper are thus twofold. Firstly, the paper demonstrates the potential suitability of system dynamics modelling to inform policy- and decision-making in the developing country context. Secondly, the paper highlights the sustainability issues that must be addressed appropriately if concentrated solar thermal, and other renewable energy systems, are to be used in developing countries at the scale of desalination. Recommendations are made accordingly to improve the analysis, and its usefulness, to utilise this technique effectively in the future. Keywords: systems dynamics, technology assessment, technology strategy, technology policy, Africa.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESUS110021

14 Energy and Sustainability III

1

Introduction

The concept of sustainable development, which includes, among others, energy security, environmental protection, and mitigation of and adaptation to climate change, is placing a special responsibility on technology policy and use in individual sectors of the economy. Increasingly, technology strategies and options will have to account for national development targets and for steering the economy in a sustainable (green) direction [1]. Framing and modelling technology policy is becoming a critical capability in the domain of science and technology in order to better represent and understand the connections between determinants, decisions and consequences [1]. Many studies are recognizing the potential of renewable and alternative energy technologies to contribute to sustainable development [2, 3]. However, the development of renewable and cleaner energy technologies still involves interactions with the environment. For instance, renewable energy options require natural resources for their development, but may have the potential to reduce impacts on other natural resources. Renewable energy also has a social function in human lives, and interactions may be established between technology development and applicable social systems. To this end, the development of renewable energy technologies involves diverse actors including policy makers, technology developers/investors, assessment practitioners, and the community that would be involved in establishing the technologies, to name a few. These factors display the complex system that constitutes renewable energy technology development, which, some have argued [3], may undermine the achievement of sustainable development. Thus, renewable energy technology management and planning is imperative. Technology assessment is an important component of the effective management of technology [4, 5] and occurs in initial technology life-cycle phases [6]. A summary of the development of technology assessment over the last four decades has been provided [7]. The emergence of organised technology assessment, as a formal procedure, was, first and foremost, an attempt to predict the unintended negative consequences of technical innovations in the market uptake cycle of technologies [6] to facilitate more adequate policy-making. An expectation of technology assessment was that it should reveal the future consequences of new technology that otherwise would not have been recognized [7]. With respect to renewable and clean energy technology development, some studies acknowledge the need to analyse the development as a complex system [8–10]. Thus, the approach to use in assessing the renewable and alternative energy technology development for sustainability will need to be in a position to account for the assumptions regarding sustainable development [4–6]. This includes the economic, social, environmental and other changes that might influence its development towards the desired sustainable path. The system dynamics approach provides the potential for such a technology sustainability assessment [5, 9].

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

15

1.1 System dynamics and its application in the energy sector System dynamics is among the tools and methods that are recognized for technology assessment [11, 12]. It is an interdisciplinary and transdisciplinary approach that is based on the theory of system structures [13]. System dynamics represents complex systems and analyses their dynamic behaviour over time [14]. The approach has gained popularity due to its focus on the structure and its flexibility, and its potential as an intermediate level tool in technology assessment is recognized [15]. Several studies have been undertaken in the past to address the issues of climate change, alternative and renewable energy, and sustainable resource utilisation, using system dynamics modelling as a tool. For example, at a macro level, the system dynamics approach has been used to develop practical policies, and promote appropriate regulatory regimes for policy-makers, to address climate change issues [16]. The global agricultural and biomass development has been modelled through such an approach [17]. Similarly, the carbon cycle and electricity generation from energy crops has been modelled and simulated [18]. At a micro level, a system dynamics approach has been applied to assess and measure the factors that contribute to or impede the development of efficient, viable, an appropriate access to energy services in remote rural areas [19]. Based on a review of these, and other, applications [4], a conceptual framework of a systems approach to technology sustainability assessment (SATSA) has been developed [5] with the intention to improve sustainability assessment practices for renewable energy technologies in emerging markets. SATSA aims to demonstrate the linkages between key elements, namely, technology development, sustainable development, and dynamic systems approach that are suggested as vital for improved practices of sustainability assessment of technologies. These elements, in combination, provide the understanding of sustainable technology development, technology assessment, and sustainability assessment and form the basis for SATSA (see fig. 1).

Figure 1:

The SATSA framework [5].

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

16 Energy and Sustainability III 1.2 South Africa and its sustainability polycrisis South Africa finds itself in a polycrisis in terms of dealing with economic development, to alleviate poverty, within water and energy constraints (see fig. 2).

Poverty alleviation Southern African nexus Economic development

Water requirements

Energy requirements

Health of humans etc.

Figure 2:

Climate change

The Southern African polycrisis [20].

Due to its scarcity, much of the water has been allocated and the region has lost its dilution capacity, so all pollutants and effluent streams will increasingly need to be treated to ever higher standards before being discharged into communal waters or deposited in landfills. The spatial development pattern of the region is also unique in that all of the major centres of economic development, and thus cities and urban conurbations, are located on watershed divides. It now means that effluent return flow out of these major industrial and urban conurbations is a major threat to future economic development, simply because the quality of the water is so degraded that it becomes unfit for human, ecosystem and industrial consumption. All these (water) issues are exacerbated by historic legacy that remains to this day; service delivery to treat water and waste, and supply suitable water is now a recognised problem in the public sector with a propensity to become more complex over time. At present, the region relies heavily on coal as feedstock; the carbon intensity of energy supply, and therefore of the related products from the region, is high. The reliance on coal also has dire consequences for water resources in the region in terms of water use and impacts on water quality. In South Africa, the industrial sector currently comprises 41% of the total energy use and 53% of the total electricity demand of the country. Within the industrial sector mining, iron and steel, non-ferrous metals and non-metal minerals together constitute 59% of energy and 66% of electricity consumed in the industrial sector, with smallerscale industries collectively accounting another 25% and 22%. It is here that renewable energy systems can make a direct contribution to address the government imperatives of stimulating economic growth coupled with industry development and (labour-intensive) employment creation, improving energy security and access, and addressing climate change, whilst also addressing some of the other societal problems related to water. In particular, desalination with WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

17

solar systems is now considered, not only of sea water to meet coastal water demands, but also of polluted inland water, which could lead to more carbonneutral locally-supplied water. 1.3 The Western Cape Province – policy context and challenges The Department of Economic Development and Tourism of the Western Cape Province (see fig. 3), highlights a number of policy-related challenges [22]:  There is a potential for Western Cape Province to distinguish itself from the national energy system and establish greater energy independence and be a major role player in the country’s energy landscape. This is the economic priority for the Province that will require more than reconciling supply and demand, but address structural reform of the economy to make it more competitive, labour-intensive and equitable. The Province has subsequently developed a Sustainable Energy Policy, of which a Renewable Energy Plan of Action is an integral part. The plan sets a target of producing 15% of the Province’s energy from renewable energy sources by 2014. One of South Africa’s national priorities is economic growth and employment creation. Renewable energy should be central to achieving this national imperative and the Province should embrace this opportunity to develop its economy and society on the base of a healthy renewable energy regime.  The Western Cape Province is served by a complex water supply system comprising of six dams, pipelines, tunnels and distribution networks; some elements of the water system are owned and operated by the national Department of Water Affairs and Forestry and some by the City of Cape Town. It is expected that water demand in the Province will exceed supply by 2019, and possibly even earlier if water availability diminishes because of climate change and if water conservation measures in Cape Town should not be as successful as envisaged. A number of additions to the system, such as the heightening of dams, are considered, as well as seawater desalination in order to cope with rising demand. The latter was emphasised by the Minister of Water Affairs in her National Assembly budget vote speech of 2010: “desalination has become the preferred purification option in terms of both cost benefit and the flexibility of application”. 1.4 Objective of the paper The critical issue with the desalination strategy is the energy requirements of the process and the associated cost implications for water supply. Thus, given the policy objectives of the Western Cape Province, as well as the solar resource in the Province (see fig. 3), concentrated solar thermal (CST) is an energy technology option, as is highlighted in a recently completed Solar Energy Technology Roadmap for South Africa [21]. In this paper the SATSA framework is used to assess the sustainability of these types of renewable energy technologies, with the primary objective to ascertain the critical sustainability issues that must be addressed appropriately if concentrated solar thermal systems are to be used for the purposes of desalination. Thereby the best technology WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

18 Energy and Sustainability III strategy policies to meet the long term water and energy needs of the Western Cape Province can be formulated by assessing the medium- to long term interactions between society, its water and energy related technologies, sectors of the economy, and the environment that ultimately limits the growth of water and energy resource use in the Province.

Figure 3:

Average daily direct normal irradiation (DNI) for South Africa [23].

2 Contextualising the technology policy formulation in the Western Cape Province Technology policy is a complex issue irrespective of the specific technology and/or the policy context at hand. The dynamic complexity arises from the interactions among system components that form the basis of technology policy planning [1]. Without a structured formulation process, policies may produce only short-lived benefits while in the long run challenges become severe [1]. Fig. 4 shows a point of departure for technology policy formulation. The elements shown in fig. 4 are generic and pertain to technology policy and development across any domain of activity, sector, and/or technology. These feature (i) overarching goals and objectives, (ii) essential actors and resources, (iii) dynamics of conversion of intent into action, (iv) the imperatives of skill and capacity-building, and (v) the actual implementation factors [1]. In terms of the Western Cape Province case the characteristics of the modal elements are as follows: 1. Specific Technology Priorities – the Province has made commitments to producing 15% of its energy from renewable energy sources by 2014, reduce WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

19

its CO2 emissions in line with the country’s ambitious Copenhagen targets of 34% by 2020, create jobs, and augment water supplies through desalination in order to cope with rising demand. 2. Strategy Design and Coordination – to meet future demands for energy the Province must consider renewable energy sources in the mix of all available energy resources in the Province. Concentrated solar thermal (CST) systems are well suited for semi-arid like areas such as the Western Cape Province. Building a CST plant adjacent to the desalination plant will generate significant benefits, such as energy savings, provision of fresh water, cost savings and environmental gains, but the need exists to ensure that all the resources that are required to build and operate CST and desalination plants are readily available, and that they can be effectively integrated in the socialecological systems of the Province. 3. Skills and Capacity Building – the resources that are required include, among others, people, institutional support, infrastructure, and finances; these are key inputs that necessitate skills and capacity building in the Province. Human resources will be needed to design, build, and operate the plants. The financial resources must be secured through the funding of various publicprivate schemes. In addition, access to the latest CST technologies and processes to produce solar energy is needed – this can be achieved by building local capacity in solar thermal energy, including local capacity for research and development, or through continuous partnerships with other countries, such as Spain, Germany, Israel, Australia, and the United States. 4. Sustainable Technology Strategy – physical conditions and the cluster of variables known as “carrying capacities” can be limiting factors to the development of solar technologies; it is useful to determine what is needed to sustain solar energy use and economic performance. Carrying capacities impose constraints, such as limited land because solar technologies require large physical space, and other possible limiting factors.

Strategy, Design and Coordination 1

2 Skill and Capacity Building

Specific Technology Priorities

3

4 Sustainable Technology Strategy

Figure 4:

Modal elements of technology policy formulation [1].

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

20 Energy and Sustainability III The above captures most if not all of the key variables and decision points. Fig. 5 then maps out the logic of technology policy formulation in the Western Cape. Technology Obsolescence

Technology Substitute Renewable Energy Technology Alternatives (Concentrated Solar Thermal) Desire to meet Future Demands for Energy amd Water

Resources Required to Operate the Technology

2 Strategy Design and Coordination

Western Cape Province Social Responsibility

3 1

Skills and Capacity Building

Specific Technology Priorities

Desired Need for CO2 Emission Reduction, Energy Security, Ecological Integrity

Sustainable Technology Strategy

Gap

Constraint Imposed by Carrying Capacity

4 Land Area and other Resources

Figure 5:

Mapping the logic of technology policy formulation in the Western Cape Province.

3 Application of the SATSA framework to the Western Cape Province case SATSA, as a framework for assessing the sustainability of technologies, aims to assist policy- and decision-makers to understand, holistically, the ways in which technological systems function and the consequences that may follow as a result of the interconnectedness of system components [5]. In other words, changes happening in one part of the system may consequently induce changes in other parts. The initial step in system dynamics modelling, which underpins the SATSA framework, is then to determine the system structure consisting of positive and negative ‘cause and effect’ relations between system components. 3.1 Causal relations The long-term competitiveness of the economy of the Western Cape Province is dependent on decisions taken on energy and water policy in the medium to longterm. Consequently, the success or failure of energy and water policy initiatives or strategic plans by the Western Cape Province is largely dependent on whether the policy- and decision-makers truly understand the interaction and complexity of the system they are attempting to influence [24]. Considering the size and complexity of the systems, with related challenges, that public decision makers must manage, it is not surprising that the “intuitive” or “common sense” approach to policy design often falls short, or it is counter-productive, to the desired outcomes [24]. Such complex systems/problems that decision makers often grapple with are possible to find solution(s) to if one begins to analyse WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

21

systems/problems dynamically and holistically, namely by first examining the patterns of behaviour that real-world systems exhibit, and then discussing the structure that causes such patterns to emerge. Fig. 6 presents the causal loop diagram showing the causal relations (dynamics) of energy and water technology policy of the Western Cape Province. 3.2 Feedback dynamics Fig.6 highlights four key feedback loops that can be used to explain variations in success regarding policy challenges in the Western Cape Province. Loop B1 shows the intended policy of using desalination technologies to augment water supplies in Western Cape Province. That is, pressure to invest in desalination technologies due to widening water deficit increases leading to actual investments in desalination technologies. That increases the resources required to design, build and operate these technologies. Over time, the investment made increases the uptake level of desalination technologies leading to improved economic growth. Similarly, loops B2 and B3 present the economic rationale for investment in renewable energy technologies, particularly concentrated solar thermal (CST) technologies. Finally, loops R1 and R2, present the second order effect of both desalination and renewable energy technologies – that is continuously building the skill and capacity to operate the technologies and allowing for further desalination and renewable energy technologies – thus achieving provincial priorities of meeting demands for water and energy.

+ +

Perceived Demand for Energy

Investment in Desalination +Technologies

+Availability of Resources (Human, Finance, Institutional) required to Design, Build and Operate Desalination Technolgies

Pressure for Investment in Desalination Technologies +

+ Pressure for Investment in + Renewable Energy (RE) Technologies (Concentrated Solar Thermal) +

Energy Deficit

-

Investment in Coal Power Plants

+ Investment in Renewable Energy Technologies (Concentrated Solar Thermal) B2

+ Availability of Resources (Human, finance, Institutional) required to Uptake Level of R1 Desalination Technologies Design, Build and Operate RE Technologies + Technologies + Skills and Capacity to operate Technologies + +

+

B1

+

Pressure to Improve Economic Growth -

Economic Growth -

+

R2 +

+ Water Deficit +

B3

Perceived Demand for Water + + +

Uptake Level of RE (Concentrated Solar Thermal) Technologies

Demestic Water Industrial Water Agricultural Water Demand Demand Demand + Population Growth

Figure 6:

Casual loop diagram of the Western Cape Province case.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

22 Energy and Sustainability III An important issue to consider with a system dynamics approach is that of the delay between feedback loops that can undermine change if significant enough [1]. For example, the investment in renewable energy technologies may lead to security of energy supply and increased use of renewable energy in the Western Cape’s primary energy mix, but lead to a delayed economic growth due to minor progress in economies of scale because vested interests still pursue coal projects and deliver electrical energy at prices that renewable energies cannot compete. As a result job creation from the renewable energy sector is negatively affected leading to a possible abandonment of a good strategy.

4 Conclusions and recommendations This paper introduces the systems approach to technology sustainably assessment (SATSA), as a means to analyses technology policy options for the ‘water-energy nexus’ that is faced in many developing countries, and especially in South Africa. The SATSA framework is applied to the Western Cape Province of the country as a specific case, where a combination of concentrated solar thermal (CST) and desalination technologies is considered. As a first phase of the analysis, the key elements for technology policy formulation are defined, in terms of Specific Technology Priorities, Strategy Design and Coordination, Skills and Capacity Building, and Sustainable Technology Strategy. Also, the initial step of system dynamics modelling that underpins the SATSA framework, is taken in terms of determining the system structure based on the defined key elements. The initial analysis highlights the importance of investment behaviour (balancing loops) and the building of skills and capacity (reinforcing loops) as the main components of the system that must be addressed in the formulation of appropriate technology policy. However, what is not clear from the first phase of the analysis, is the extent of the relationships of the main components; this constitutes the next phase – the stock and flow analysis that is required to provide a unique insight into the behaviours in the system. Also, the next phase will clarify an uncertainty that has been highlighted in the initial analysis; understanding the key time delays in the complex system and aligning policy to accommodate delays as a necessary governance function. Apart for taking the modelling to the next step, to refine the analysis of the CST and desalination combination in the Western Cape Province of South Africa, the usability of the system dynamics technique, for policy- and decisionmakers, also requires further investigation. This research is ongoing in the South African energy sector.

References [1] Choucri, N., Mistree, D., Haghseta, F., Mezher, T., Baker, W. & Ortiz, C., Mapping sustainability: Knowledge e-networking and the value chain. Alliance for Global Sustainability Bookseries, 11, 2007. [2] Silva Lora, E.E., Escobar Palacio, J.C., Rocha, M.H., Grillo Renό, M.L., Venturini, O.J. & Almazán del Olmo, O., Issues to consider, existing WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

[3]

[4]

[5]

[6]

[7]

[8] [9]

[10]

[11]

[12]

[13] [14] [15]

[16] [17]

23

tools and constraints in biofuels sustainability assessments. Energy, in press, 2010. Sukkasi, S., Chollacoop, N., Ellis, W., Grimley, S. & Jai-In, S., Challenges and considerations for planning toward sustainable biodiesel development in developing countries: Lessons from the Greater Mekong Subregion. Renewable and Sustainable Energy Reviews, 14, pp. 3100-3107, 2010. Musango, J.K. & Brent, A.C., Assessing the sustainability of energy technological systems in Southern Africa: A review and way forward. IAMOT Proceedings, Cairo, 2010. Musango, J.K. & Brent, A.C., A conceptual framework for energy technology sustainability assessment. Energy for Sustainable Development, in press, 2010. Brent, A.C. & Pretorius, M.W., Sustainable development and technology management. In: Sherif, M.H. & Khalil, T.M. (eds), Management of Technology Innovation and Value Creation. Management of Technology 2, World Scientific, New Jersey, 2008. Palm, E.T. & Hansson, S.O., The case for ethical technology assessment (eTA). Technological Forecasting and Social Change, 73, pp. 543-558, 2006. Afgan, N.H. & Carvalho, M.G., Multi-criteria assessment of new and renewable energy power plants. Energy, 27, pp. 739-755, 2002. Jones, C.A., The renewable energy industry in Massachusetts as a complex system: Developing a shared understanding for policy making. PhD Dissertation, University of Massachusetts, Boston, 2008. Snyder, N. & Antkowiak, M., Applying systems engineering in a renewable energy research and development environment. National Renewable Energy Laboratory, NREL/CP-6A1-48159, INCOSE International Symposium, Chicago, 2010, available from: http://www.nrel.gov/docs/fy10osti/48159.pdf. De Piante Henriksen, A., A technology assessment primer for management of technology. International Journal of Technology Management, 13, pp. 615-638, 1997. Tran, T.A. & Daim, T., A taxonomic review of methods and tools applied in technology assessment. Technological Forecasting and Social Change, 75, pp. 1396-1405, 2008. Sterman, J.D., Business dynamics: systems thinking and modelling for a complex world. McGraw-Hill/Irwin, New York, 2000. Forrester, J.W., Industrial dynamics. Productivity Press, Cambridge, MA, 1961. Wolstenholme, E.F., The use of system dynamics as a tool for intermediate level technology evaluation: three case studies. Journal of Engineering and Technology Management, 20, pp. 193-204, 2003. Fiddaman, T., Dynamics of climate policy. System Dynamics Review, 23, pp. 21-34, 2007. Tesch, T., Descamps, P. & Weiler, R., The COSMOPAD modelling framework: Conceptual system dynamics model of plenary agricultural and WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

24 Energy and Sustainability III

[18]

[19]

[20]

[21]

[22]

[23] [24]

biomass development. Digital Earth Conference, BRNO, Czech Republic, 2003. Flynn, H., & Ford, D., A system dynamics study of carbon cycling and electricity generation from energy crops. 23rd International Conference of the System Dynamics Society, Boston, 2005. Dyner, I., Alvarez, C. & Cherni, J., Energy contribution to sustainable rural livelihoods in developing countries: A system dynamics approach. 23rd International Conference of the System Dynamics Society, Boston, 2005. Heun, M.K., van Niekerk, J.L., Swilling, M., Meyer, A.J., Brent, A.C. & Fluri, T.P., Learnable lessons on sustainability from the provision of electricity in South Africa. Proceedings of the ASME 2010 4th International Conference on Energy Sustainability, Phoenix, Arizona, 2010. Brent, A.C., Pretorius, M.W., An analysis of the industrial and commercial opportunities to utilise concentrated solar thermal systems in South Africa. Industrial and Commercial Use of Energy, Cape Town, 2010. Department of Economic Development and Tourism, Five year strategic plan – 2010/15 – Western Cape. Cape Town, 2010, available from: http://www.capegateway.gov.za/Text/2010/3/fiveyearstrategic_sml.pdf. Fluri, T.P., The potential of concentrating solar power in South Africa. Energy Policy, 37, pp. 5075-5080, 2009. Radzicki, M.J., Taylor, R.A., Introduction to system dynamics: A systems approach to understanding complex policy issues. US Department of Energy, 1997, available from: http://www.systemdynamics.org/DLIntroSysDyn/.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

25

How small island governments are responding to the development of energy technologies M. J. de Vial & E. P. Monkhouse Island Analysis Limited, Guernsey

Abstract With the backdrop of global concern about dwindling stocks of fossil fuels and climate change, small islands have additional pressures and challenges to adopt new energy technologies, particularly renewable energy. As is well documented, islands are characterised by: insularity, a limited range of resources, small markets, specialisation of economies, diseconomies of scale, fragility of eco-systems and skill and labour constraints. These characteristics create an over-reliance on imported fossil fuels, loss of economies of scale, and higher distribution costs. The motivation, therefore, to research, invest in and adopt alternative technologies is arguably heightened in island economies. The benefits observed from examples of energy self-sufficient islands e.g. Samsø (Denmark), are driving greater investment by other islands and agencies into alternative solutions. The Pacific Islands in particular as a region is embracing alternative energy and has since 2007, been receiving funding from the World Bank for a ten year programme. Many small islands are well placed to trial such projects where funding is available, with: ready access to certain alternative energy sources e.g. tidal, wave, geothermal and solar energy; adaptable communities; and the ability to implement new technology and encourage rapid dissemination throughout the population. Additional benefits include encouraging on-island production of biofuels and supply of additional revenue to the economy. Island Analysis will present a comparative study of energy policies and management in global island economies, drawing out the critical success factors and pointing to examples of leading edge practice. Keywords: renewable energy, islands, strategic policies, economies, future, analysis. WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESUS110031

26 Energy and Sustainability III

1 Introduction With the backdrop of global concern about dwindling stocks of fossil fuels and climate change, small islands have additional pressures and challenges to adopt new energy technologies, particularly renewable energy. In some islands, energy demand is growing by 8% or more per year, requiring a doubling of the installed power plants every 12 years [1]. At the same time, relatively little effort is focused on the development of renewable energy sources (RES) and rational use of energy (RUE) in isolated areas like islands, rural areas, forest or coastal villages, mountain valleys etc. This is due to their geographical location and morphological characteristics, which are either isolated in terms of network infrastructure, i.e., electricity networks and transportation networks, or constitute ecologically protected areas, in which case infrastructure development interventions should comply to very specific requirements [2]. Yet there is arguably a huge opportunity for mainland economies to learn from the experience and successes of island based development of energy technology. The remainder of this paper will present Island Analysis’ comparative review of energy policies and management in global island economies, including: • A profile of relevant island characteristics and the case for studying energy developments in this context • An overview of current developments in energy technology within islands • A reflection on trends in investment by the World Bank and other organisations in different technologies, over the last 10 years • A review of the critical success factors and potential barriers associated with investment in new technologies • Case studies where our analysis has revealed examples of how investment in energy technology interacts with broader policies to strengthen the island economy • Conclusions on the learning points for islands and remote mainland communities.

2 The island model As is well documented, islands are characterised by: • Insularity The Channel Islands, for example, benefit from their proximity to France, from which a cable supply of electricity provides up to 95% of the islands electricity when required. Other island communities do not have this option due to their remoteness from the mainland which not only reduces infrastructure options, but implies increased costs for shipping of fuel. • A limited range and quantity of resources o Where there is, for example, the opportunity of tidal, wind and solar power, the infrastructure costs for a small population may be prohibitive, and the drive therefore to find new methods of exploitation is heightened. WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

27

Access to fossil fuels, hydropower, geothermal energy etc even where available will by definition be limited by small land mass and environmental concerns. • Small markets / diseconomies of scale o The island populations encompassed in this review vary from only a couple of thousand to over half a million, but in some cases populations are smaller than a mainland town where one would not expect to find dedicated investment in new energy technologies. • Specialization of economies o Most island economies are dominated by either tourism, agriculture or the finance sector, placing different demands and constraints on both the energy required, and acceptability of technologies to the community. • Fragility of eco-systems o Following on from above, an island whose life-blood relies on tourism may be resistant to certain types of waste-to-energy plants, for example. But the global threat to islands is recognized as climate variability and change, brought into sharp focus by the Maldives government, who have pledged to become carbon neutral in ten years. • Skill and labour constraints o Islands are invariably resource constrained by both numbers of people and skill-sets, but have to balance the importation of expertise and labour with land-use, demands on infrastructure and quality of life. This creates an over-reliance on imported fossil fuels and higher distribution costs. The motivation, therefore, to research, invest in and adopt alternative technologies is arguably heightened in island economies. The benefits observed from examples of energy self-sufficient islands e.g. Samsø (Denmark), are driving greater investment by other islands and counties. The Pacific Islands in particular is a region embracing alternative energy and has been receiving funding from the World Bank since 2007, for a ten year programme. In May 2010, technology students from Masdar Institute of Science and Technology (MIST) learned about self-sufficiency when they visited primitive villages on the island of Borneo, where water and solar power are alternated depending on weather conditions. The students were “inspired” to apply the learning back in their city setting [3]. Islands are well placed to trial such projects where funding is available, with ready access to certain alternative energy sources e.g. tidal, wave, geothermal and solar energy; adaptable communities; and the ability to implement new technology and encourage rapid dissemination throughout the population. Additional benefits include encouraging on-island production of biofuels to provide additional revenue to the economy. For those islands that have connectivity and/or close proximity to the mainland, there is the potential to sell energy via the mainland electricity grid. This opportunity is already being exploited by Samsø [4], and noted as a viable income source by a range of others such as Prince Edward Island [5], Tasmania [6] and Alderney [7].

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

28 Energy and Sustainability III

3 Current developments in energy technology within islands

% of energy imported for electricity

The awareness of islands’ vulnerability to fluctuating oil prices has been highlighted frequently over the last 10 years, in island economic and strategic plans [5, 6]. However, in recent years, high dependence on imported fuel sources has refreshed and promoted interest in the economic benefits of investment in alternative and renewable energy sources. On Earth Day in 2001, Ministers and delegates from Small Island States announced their commitment to Renewable Energy and Global Sustainable Energy. It is acknowledged that although islands and small island nations are only responsible for a small percentage of global emissions, they are also recognised as amongst the most vulnerable to the effects of climate change. At the time a quoted figure of up to 12% [8] of island budgets was reported by the chair of AOSIS (Alliance of Small Island States) used for electricity generation by fossil fuels; since that time the proportion of GDP spent on import of oil has been reported as high as between 25 and 50% [9, 10]. • “The cost of energy is perhaps the singly most important factor affecting all aspects of the economy.” Government of Barbados, 2006 [11] • “These trends pose risks for us as well – but they also create opportunities – to become a net exporter of green energy.” PEI Economic Strategy, 2008 [5] It is also true that in the majority of islands, energy demand is consistently increasing rather than decreasing. For example, St Vincent and the Grenadines (SVG) experienced increased consumption from 64,840 toe (tonnes of oil equivalent) in 2002 to 91,000 toe in 2008, an increase of 140% in volume. This represented a total import value rising from EC$38m to EC$150m [12], or 17% of the country’s GDP being used to pay for fossil fuels imports in 2008 (peaking due to extreme prices of US$147 per barrel). Yet an assessment presented by the Multi-Sector Energy Stakeholder Consultation, indicates that the islands have the natural renewable resources to generate 100% of its electricity [13]. 100 90 80 70 60 50 40 30 20 10 0 Samsoe

Tasmania

Mauritius

Barbados

PEI

St Vincent and the Grenadines

Tonga

Malta

Island province or nation

Figure 1:

Proportions of energy imported for electricity generation (2008/9).

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

29

4 Investment trends in energy efficiency and renewable energy technology over the last 10 years 4.1 Worldwide The World Bank Group announced last year that their financing of renewable energy and energy efficiency projects in developing countries has risen by almost 25% to reach $3.3bn in the last fiscal year, total such commitments at financial y.e. June 30, 2009 represented more than 40% of total energy lending [14]. In addition there are other organisations covered under the umbrella of the World Bank Group that have significantly invested in renewable energy across the globe. The International Finance Corporation (part of the World Bank Group) is regarded as a leader in supporting renewable energy finance in emerging markets. 70% of the financing (both in terms of number of projects and value) that it supported in the financial year of 2010 was in the area of renewable energy (Table 1). During the period FY 2009-2011 there has been a commitment of a further $3 billion in financing for renewable energy and energy efficiency projects, in addition to over $2.3 billion already invested since 2005. Table 1:

World Bank Group lending for renewable energy and energy efficiency [14].

US$ Millions

FY05

FY06

FY07

FY08

FY09

Total FY05FY09

New Renewable & Energy Efficiency

463

1,105

682

1,665

3,128

7,043

Large Hydro

538

250

751

1,007

177

2,724

New RE and EE (Bonn Commitment)

251

301

361

433

520

1,866

4.2 East Asia and the Pacific The majority of World Bank specific support for “renewable energy projects”, related to islands has been located in the East Asia and Pacific region. In the last 10 years 13 projects have been in Indonesia and the Philippines. The Pacific Islands including Papua New Guinea, Solomon Islands, Fiji, Vanuatu and the Republic of the Marshall Islands in particular as a region of small island states, are embracing alternative energy which has been supported by the World Bank since 2007, on a ten year programme [15].

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

30 Energy and Sustainability III

4.3 South Asia In South Asia, funding was received for seven projects from the World Bank, mainly based in Sri Lanka, with the majority of renewable energy projects exploiting hydro-power. The Asia Sustainable and Alternative Technology Program (ASTAE) [16], evaluates the current and future potential for renewable, providing advice to the World Bank and Global Environment Facility (GEF) investments. Islands and island nations currently covered by ASTAE include Tonga, Solomon Islands, Fiji, Indonesia, Papua New Guinea, Philippines, Singapore and Timor Leste. 4.4 Caribbean There is a significant amount of investment in the creation of policies, strategies and regulation that is increasingly incorporating the development and efficiency of renewable energy technology. Financial assistance is often provided by alternative sources; for example the European Union Energy Initiative (EUEI) which is supporting the Caribbean Sustainable Energy Program (CSEP), currently being implemented in seven Eastern Caribbean States: Antigua and Barbuda, the Bahamas, Grenada, St Lucia, Dominica, St Vincent and the Grenadines, and St Kitts and Nevis (Barbados is an observer country). This is being implemented by the Department of Sustainable Development (DSD) within the General Secretariat of the Organization of American States (GS/OAS), in addition to several other organisations including the CARICOM Secretariat, REEEP (Renewable Energy and Energy Efficiency Partnership) and CARILEC (Caribbean Energy Utility Services Corporation) [17]. It is estimated that 200MW of renewable energy projects between the seven project countries will be put into action within 10 years of the conclusion of the project. In addition estimates of 15% reduction in demand are envisaged over that time frame due to the implementation of these renewable energy resources, subsequently also helping to reduce carbon emissions. One of the successful outputs from this is an Energy Action Plan, and a National Energy Policy for St Vincent and the Grenadines, achieved by updating the previous plans put forward by the local Government, who have been assisted by the German Agency for Technical Cooperation (GTZ) in the Caribbean Renewable Energy Development Program since 2005 [18]. The International Development Bank has also invested in the Caribbean. One such beneficiary, the Bahamas, is currently drafting their National Energy Policy. IDB signed agreements with the Government of Bahamas (March 2009) [19] to contribute towards the cost of the following two projects: ‘Strengthening the Energy Sector in The Bahamas’, and ‘Promoting sustainable energy in The Bahamas’. The aim is an overall reduction in reliance on fossil fuels, with further objectives to diversify the mix of energy production, improve security and reduce emissions.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

31

As an indicator to the targets that the islands have set (Table 2), all EU countries and islands have Energy or Climate Change policies within which the directives have requested that all members must also have long term Renewable Energy Policy and Energy Efficiency Action plans. The target set for these EU countries is 20% by 2020 for the contribution of renewable energy to the total supply, in addition to a 9% reduction in end user consumption. Australia also has the same target for renewable energy supply. Table 2:

Targeted renewable energy supply figures by islands.

Island

Renewable energy target (main grid)

Year

Malta

10%

2020

Barbados

30%

2012

Prince Edward Island

30%

2013

Tonga

50%

2013

St Vincent and the Grenadines

60%

2020

Tuvalu

100%

2020

5 Case Study Islands with integrated energy policies 5.1 St Vincent and the Grenadines Future plans, in line with the Energy Action Plan for St. Vincent and the Grenadines 2010(EAPSVG) [20] are to promote and increase use of RET and RES. As of 2008, 2% of total energy was renewable energy, however this excludes biomass, charcoal and solar thermal. In St Vincent, 5.6MW is consistently contributed by hydropower, however the requirements are increasing. In 1998 this 5.6MW of hydropower was a fifth of contributing power to the electrical grid; by 2007 this was less than 14% (demand increased from 14MW to 20MW). There were still diesel fuel generators being installed in 2007 to cope with the rising demand in the other islands of St Vincent and the Grenadines. Further hydro plants are planned, after successful feasibility studies have indicated that there is potential for development of new sites in addition to expansion of the current South Rivers Plant. Solar panels, imported from Barbados, are not widely utilised at present. Potential sites for wind power have been identified and public/private partnerships between the local energy provider (VINLEC) has been considered. Installation of two pilot grid-connected solar photo voltaic systems is to be looked into by VINLEC (St Vincent Electricity Services Ltd). Biomass as an alternative is not sustainable at present, given that the current municipal waste on the island is not of high enough quality for immediate usage in the biogas technology plant. A dedicated energy crop would be required as a WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

32 Energy and Sustainability III source, which is potentially viable if currently unused agricultural land was to be put back into use and by a change in agricultural markets (EAPSVG [21]). 5.2 Tonga When Tonga was assessed in 2000, imported petroleum products accounted for 75% of the primary energy supply, with the further 25% arising from biomass and solar PV panels located off grid. Grid supplied electricity (98% of electricity used in Tonga) is generated totally from imported diesel (TERM, [21]). In 2010, ASTAE [22] reviewed the current state of the Tongan Electricity supply and forecast for the future. The resultant figures for electricity demand by 2020 indicated growth of between 3.5% and 5.5%. Only five of Tonga’s 52 inhabited islands have an electrical grid system. The majority of the remaining households obtain electricity through small individual diesel generator sets and solar panels with battery back-up. Most of these solar home based systems were installed with funding provided by aid agencies. The Tonga Energy Road Map (TERM) [21] sets the vision for Tonga for the next 10 years to transform the energy sector on the islands. One of the key aims is to diversify the energy supply, progressing towards renewable energy with a target of achieving 50% grid based electricity supply by 2013. Technologies under consideration to achieve this are; landfill gas development, wind turbines without storage, coconut oil, solar PV without storage, and solar PV/wind turbines with storage. 5.3 Prince Edward Island Energy Strategy Currently Prince Edward Island (PEI) is dependent on imported energy sources. As at 2009, oil accounted for 76% of PEI total energy supply (46% transport and 30% heating petroleum based fuels), with 10% biomass (fuel wood, sawmill residue and municipal waste), and 14% electricity. For the future, as determined by the Prince Edward Island Energy Strategy [23] the vision is by 2013 for the energy supply to consist of: 4% renewable electricity, 10% energy efficiency (wind power), 50% petroleum products, 15% biomass, 7% imported and oil fired electricity, and 5% liquid biofuels. Renewable and non-petroleum based fuels are targeted to increase again by 2018 to 20% energy efficiency, 3% renewable, 20% biomass and 10% liquid biofuels. The Government of PEI developed Atlantic Canada’s first utility grade wind farm in 2001, since then the PEI Energy Corporation has expanded the first site and developed a further site resulting in running a 40.56MW wind power system. The Premier has indicated the intention to expand up to 500MW of wind energy capacity: “The Provincial Government will double its renewable energy portfolio from 15% to 30% by 2013.” [23] This will require $1 billion to develop the system but is forecast to bring in economic benefits of approximately $40 million per annum to the economy (Prince Edward Island [24]).

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

33

5.4 Mauritius The current Mauritius plan is focused on high tech, low carbon renewable energy. In past years, schemes to introduce and promote usage of solar water heaters, have been very successful and have resulted in a grant being reinstated at Rs 10,000 in collaboration with commercial banks. ‘Feed in’ tariffs from small IPPs are also being purchased by the electricity board. Current work on a hydroturbine (2GWh per year) and installation of 5 wind turbines on nearby Rodrigues are some of the steps that are being taken, in addition to negotiations for a new wind farm, to secure renewable energy for the future of Mauritius [25, 26]. 5.5 Tasmania Ten years ago, Tasmania was reliant on imported oil for fuel and rainfall for the hydroelectric systems in place. Now, the electricity supply is more stable, composed of wind farms, hydroelectric, a gas pipeline from Australia across Bass Strait, and also the Basslink which gives access to up to 470MW of electricity supply which can be imported from the central Australian national electricity grid. In the future, as part of the Tasmania Innovation Strategy [6], it is looking to build more renewable projects, with six onshore wind power project planned. Marine energy, due to the strong currents off the Western coast of Tasmania and Western Bass Straits in particular is an area looked to for future development, in addition to off-shore wind generation due to its location in the Roaring Forties (prevailing wind corridor). Bio-energy projects are also being assessed for viability in Tasmania. These primarily concentrate on production of methane from anaerobic digestion of waste from food processing facilities. Geothermal exploration has been undertaken in Tasmania to determine the capacity for production. Overall it is looking promising for the future, with potential targets indicated close to the existing electricity grid, therefore increasing the attraction of this method of generation.

6 Review of critical success factors and potential barriers associated with investment in new technologies 6.1 Community involvement In the work of the Integration of Renewable Energy Technologies in Rural Insular Areas Project [1], the report notes that a key success factor is positive engagement of the public through participative strategies on all aspects of the initiative – organizational, managerial and financial. That positive engagement is highly feasible in an island community, where politicians, civil servants and suppliers can be, and are expected to be, in direct communication with the public. The report describes a typical island context as an “open-minded culture conducive to novelty”. The report goes on to highlight that successful sustainable energy solutions also require a mix of legal, regulatory, financial, WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

34 Energy and Sustainability III communication and training measures, and again it is relatively feasible to profile and study the supporting sectors in a closed economy. Samsø [4] is a prime example of a successful renewable island, local investors raised 80% of the capital for the €50 million for the energy system without any direct subsidy from the Danish government. A national programme which subsidised installation of systems for biomass heating, solar panels and heat pumps resulted in households switching to the alternatives. By 2005, the renewable energy contribution had risen to over 100% resulting in the surplus being exported as a commodity off island to mainland Denmark. This is a prime example of community involvement. 6.2 Government assistance and subsidies Tasmania has been hampered slightly by the Australian Government’s decision to postpone the Emissions Trading Scheme that was to be introduced to 2013 [27], which has resulted in carbon emissions not being included into the market price and therefore increasing the difficulty in raising capital investment for renewable energy. Incentives that are offered by governments to individuals in the different islands are very similar, for example: Mauritius offer a subsidy of Rs 5,000 per unit of solar water heater installed in households; Tasmania – home solar power rebate - Aurora energy will rebate customers with a ‘feed in’ tariff for home solar power back into the system; Malta – Solar water heater installation, rebate of 20% with a maximum grant of €232.94 and other grants include microwind systems (25% to a maximum grant of €232.94) and solar PV systems (min. size of 1KW +/-5%) to a maximum grant of €2329. Other areas noted to help increase uptake of RES and technologies include: conditional exemptions such as waiving of import duty payable on renewable energy systems; governmental support for installation of renewable energy technologies through grants, loans, tax and financial incentives; investigating taxation systems for cars based on CO2 emissions rather than engine capacity, and facilitating the implementation in the use of alternative fuels such as ethanol and biodiesel in land transport. 6.3 Physical and environmental barriers Barriers include the natural features and the attraction of being an island that promote it being utilised for carbon free technology, (especially marine and wind based technology) can also constrain development. For example the following factors need to be considered: areas of scientific interest, shipping lanes and routes, protected areas of conservation, and significant sites for marine wildlife. In addition, many islands rely on tourism as their main sector contributing to the economy and visibility of energy developments is another factor for islands to consider when investing in different types of technology.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

35

7 Conclusions on the learning points for islands and remote mainland communities The majority of islands have realised that security of energy resources and the ability to lessen the effect of any market volatility in energy prices is an intrinsic part of maintaining a stable and more profitable economy. Investment in energy, for on-island needs and/or as a commodity for export, is fast becoming a key component of economic strategies. Additional benefits include: • economic diversification, • income and jobs, • compliance with carbon emissions reduction agreements. Energy policies produced in the last five years, across a wide variety of world-wide islands are largely based around four main criteria: • To secure a reliable energy supply for the future through the development of both renewable and non-renewable resources • To diversify the energy profile of the island to reduce exposure to importation • To enhance and advance the social and economic development of the island • To reduce detrimental effects of energy production and protect the environment (if viable, by preferentially using low carbon or carbon neutral technologies). The latter point has resulted in a determination by many small islands to set an example to other larger countries and nations. The stimulus for this is intertwined with the emissions reductions sought by the talks organised by the UNFCCC (United Nations Framework Convention on Climate Change). AOSIS has been shown support at the climate talks in Cancun by the World Bank (The World Bank Press Release [9, 10]). In addition to their stance on increasing the targets that should be adhered to, they have pledged to lead by example and are determined to head into a time of renewable energy and efficiency. The signed memorandum of understanding between AOSIS, the World Bank and Danish Government calls for an introduction of renewable and energy efficiency into the island states with a US$14.5m stimulus from the Danish Government.

References [1] RERINA Project: Integration of Renewable Energy Technologies in Rural Insular Areas: State-of-the Art and Practice on SEC Development (D2.3.v2) April 2006 www.rerina.net [2] World Wildlife Foundation, www.wwf.panda.org [3] www.gulfnews.com, Article: “Borneo villagers inspire tech-savvy students: Trip gives Masdar pupils chance to use knowledge in sustainable energy”. Published: May 9, 2010 [4] Jorgensen, P.J. Hermansen S., Johnsen, A., Nielsen, J.P., Jantzen, J., Lundén, M. Samsø – a Renewable Energy Island - 10 years of Development and Evaluation. PlanEnergi and Samsø Energy Academy 2007 [5] Prince Edward Island Economic Strategy - Island Prosperity - A Focus for change, Prince Edward Island Government 2008 WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

36 Energy and Sustainability III [6] [7] [8] [9] [10] [11] [12] [13]

[14] [15]

[16] [17] [18] [19] [20] [21] [22] [23] [24] [25] [26] [27]

Tasmania Innovation Strategy, Tasmanian Government 2010 Alderney Renewable Energy, http://www.are.gb.com/ Roper, T. Presentation: http://www.gseii.org/PDF/PPA2-Aug06-Final.pdf World Bank Press Release http://beta.worldbank.org/climatechange/content /small-island-states-get-boost-moving-renewable-energy Remarks by Helen Clark, UNDP Administrator Press Release, 08 Dec 2010 Economic and Financial Policies of the Government of Barbados 2006, Government of Barbados Energy Action Plan for St. Vincent and the Grenadines 2009, Thomas Scheutzlich, Overview of Draft Energy Action Plan, CPEDP/GTZ, SVG, Multi-Sector Energy Stakeholder Consultation, 2009 http://www.sepa-americas.net/eventos_detalle.php?ID=20 World Bank Press Release, http://beta.worldbank.org/news/renewableenergy-energy-efficiency-financing-world-bank-group-hits-all-time-high World Bank Sustainable Energy Finance Project P098423, http://web.worldbank.org/external/projects/main?pagePK=64312881&piPK =64302848&theSitePK=40941&Projectid=P098423 ASTAE website, web.worldbank.org Organisation of American States (OAS), SEPA, Department of Sustainable Development http://www.sepa-americas.net/proyectos_detalle.php?ID=6 OAS, SEPA, Dept of Sustainable Development, SVG http://www.sepaamericas.net/proyectos_detalle_pais.php?ID=6&IdPais=34 http://www.bahamas.gov.bs/bahamasweb2/home.nsf/vPrint/4FF5149A52B 5D47F8525761D005B4053 Energy Action Plan for St. Vincent and the Grenadines, St. Vincent and the Grenadines Government, January 2010 Tonga Energy Road Map completes plan to transform energy sectorhttp://www.tonga-energy.to/?p=1009, April 20, 2010 ASTAE Report, Tonga Electric Supply System Load Forecast, World Bank, March 2010 Prince Edward Island Energy Strategy 2009, Prince Edward Island Government Prince Edward Island, Island Wind Energy – Securing our Future: The 10 Point Plan, October 2008 Mauritius Budget Speech 2010, The Government of Mauritius Mauritius Budget Speech 2011, The Government of Mauritius RSC, Australian emissions trading scheme on hold, 29/04/10 http://www.rsc.org/chemistryworld/News/2010/April/29041002.asp

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

37

Experimental and economical study of sustainable electricity generation by solar PV/diesel hybrid systems without storage for off grid areas D. Yamegueu1, 2, Y. Azoumah1 & X. Py2 1

Laboratoire Energie Solaire et Economie d’Energie (LESEE), Institut International d’Ingénierie de l’Eau et de l’Environnement (2iE), Ouagadougou, Burkina Faso 2 Laboratoire PROcédés, Matériaux et Energie Solaire (PROMES), Université de Perpignan Via Domitia, Perpignan, France

Abstract This paper presents the results of an experimental study of a PV/diesel hybrid system without storage. The results obtained show that the sizing of a PV/diesel hybrid system, by taking into account the solar radiation and the load/demand profile of a typical area, must permit the diesel generator to operate near its optimal point (70–90% of its nominal power). It has been verified that the reliability of the system necessitates that the diesel generator be sized to meet the peak-load demand in case of transient cloud and in the evening. Also, a comparative analysis for three different systems (diesel and solar PV generators only, and hybrid solar PV/diesel system) for powering a same load profile has been made and shows that the hybrid system is more cost-efficient than the two others. These results show that there is a possibility to increase the electrification rate in remote areas by the implementation of hybrid solar PV/diesel systems. Keywords: hybrid system, photovoltaic, diesel, electrification, off-grid areas.

1 Introduction The electrification rate in sub-Saharan Africa is lower than in any region of the world. Indeed, more than 70% of the populations of this region are excluded from the benefits linked to the electricity. The situation is more catastrophic in WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESUS110041

38 Energy and Sustainability III rural areas where less than 12% of the populations have access to electricity [1]. In many cases, the utility grid extension is quite unconceivable because of population dispersion, rugged terrain or both [2] and mainly because of the high investment costs of transmission and distribution lines. Thus, in these areas far from any existing grids, the supply of electricity is achieved using stand alone power systems and broadly by diesel generators (DG). However, the volatile prices of fossil fuels, the very high maintenance cost of diesel generators coupled with the environmental and climate change concerns make this option unsustainable. Fortunately, most of the developing countries and specially those of sub Saharan Africa region have a high potential in renewable energy resources such as wind, hydropower, biomass and solar that could help in raising their access to energy, and then their economic development. In order to contribute to the increase of the electrification rate in sub-Saharan Africa, an original “flexy energy” concept of hybrid solar PV/diesel/biofuel power plant, without battery storage, has been developed by Azoumah et al. [3]. To assess the technical and economical feasibility of this concept, a PV/diesel hybrid system without storage has been set up on the site of the International Institute for Water and environmental engineering (2iE) at Kamboinsé (12°22′ N and 1°31′W), locality situated at fifteen kilometers to the North of Ouagadougou, capital of Burkina Faso. This prototype consists of a PV array of 2.85 kWp coupled with a 9.2 kW diesel generator. The concern of this paper is to present the obtained technical performances of the hybrid facility under various operating conditions. Four fixed load/demand profiles corresponding to different percentages of the nominal capacity of the diesel generator have been experimented for obviously different solar radiations and consequently various PV contributions. The obtained raw and calculated performances are presented and discussed in this paper. Also, a comparative analysis for three different systems (diesel and solar PV generators only, and hybrid solar PV/diesel system) for powering a same load profile has been made and shows that the hybrid system is more cost-efficient than the two others.

2 An overview on hybrid renewable energy systems In the open literature, many studies are based on hybrid renewable energy systems (HRES) [4–6]. The term hybrid renewable energy system is used to describe any energy system composed of more than one type of generator. The usual configuration is made of a conventional diesel powered generator associated to a renewable energy source such as PV, wind, or even PV/wind, in most case incorporating battery storage. The battery storage permit to meet the demand when either the demand is a peak load demand or when renewable energy source is not sufficient to meet the load. However, the batteries present major drawbacks as: additional investment and maintenance costs and extra costs due to periodic replacement induced by reduced lifetime [7, 8]. As a matter of fact, the cost of batteries can represent up to 16 to 20% of the total life cycle of a hybrid PV/diesel/battery system [9, 10] and up to 40% of the total system costs for only a PV system [11]. Besides, in developing countries, such as those of the WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

39

sub Saharan Africa region, there is no policy concerning recycling of batteries at the end of their lifetime. This particular aspect represents a considerable environmental problem. According to all these above reasons, some authors have studied the case of PV/diesel hybrid system without storage [12, 13]; but these studies were limited to the feasibility aspects and then, there is no available experimental result from a real PV/diesel hybrid system without storage in the open literature, which justifies the interest of this study.

3 Experimental 3.1 Experimental set up The hybrid systems can be broadly classified in series hybrid, switched hybrid and parallel hybrid configurations [14]. The present prototype has a parallel hybrid configuration (fig. 1). In this scheme, the PV system is parallel connected to the diesel generator by means of a DC-AC converter or inverter. The PV and the diesel generators supply a portion of the load demand directly.

Figure 1:

Prototype design.

The PV system is composed of 15 modules HIT (Heterojunction with Intrinsic Thin layer), each rated at 190 Wp, totalling 2.85 kWp DC at Standard Testing Conditions (irradiance=1000 W/m²; Solar cell operating temperature=25°C and AM=1.5). The PV array covers an area of about 18 m² with PV modules distributed in a parallel/series configuration of three module strings connected to one inverter rated at 3.82 kW. The diesel generator rated power is 9.2 kW (11.5 kVA) of 1500 rpm. 3.2 Experimental protocol Any general study over such a system should be done using first a set of hypothetic loads allowing the analysis of its performances and limitations. The consideration of typical loads in agreement with particular situations has to be done further in order to optimize the system. Then, in the present investigation, the load/demand profiles are treated as constant for the simulation of the hybrid system. Four load profiles have been considered (3.7 kW, 5.7 kW, 7.6 kW and WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

40 Energy and Sustainability III 9.7 kW) corresponding to 40%, 62%, 82% and 105% of the nominal power of the diesel generator [15]. The demand profiles are experimentally simulated by two resistive bank loads of 4 kW each with different switches allowing by combination to reach the desired load. The mix of interdependent key parameters such as: The power generated by the PV array (depending of solar radiation), the power generated by the diesel generator and the specific/hourly consumption of the diesel generator to match the predefined load have been studied.

4 Results and discussion 4.1 Diesel generator characteristics of the system studied A diesel generator (DG) is broadly characterized by its fuel consumption (the hourly consumption in l/h or the specific consumption in l/kWh). According to Reinigher et al. [16], the hourly fuel consumption of a diesel generator can be approximated as follow: q ( t )  a .P ( t )  b .P r

(1)

a (l/kW) and b (l/kW) are constants for a typical DG, Pt (kW) is the power generated by the diesel generator and Pr (kW) is its rated power. As where

shown in fig. 2, the relation (1) has been validated with the current fuel consumption data of a typical diesel generator of 9.2 kW. The model coefficients obtained for these data are a  0 .2476 l / kWh and b  0 . 0739 l / kWh 2 with a coefficient of determination ( R ) equal to 0.9895

Figure 2:

Fuel consumption of the diesel generator as a function of output power.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

41

Also, fig. 2 gives the specific fuel consumption of the diesel generator as a function of its power output. It can be noted that when the diesel generator operates near to 20% of its rated power, its specific consumption is too high (about 0.64 l/kWh) corresponding to a low efficiency of the latter. However, the minimum specific fuel consumption of the diesel generator is about 0.324l/kWh and corresponds to about 80% of its rated power meaning that a higher fuel saving, thus a good efficiency, may be obtained if the diesel generator operates near this load fraction. This result corresponds to what is stipulated by authors as Ashari et al. [17] and El-Hefnawi [18] saying that the diesel generator have typically a maximum fuel efficiency of about 0.33 l/kW when run above 80% of its rated power (for the first authors) and when it operates from 70 to 89% of its rated power (for the second author). In the following section the behavior of the diesel generator in the hybrid system is thoroughly analyzed. 4.2 Behavior of the hybrid system under different loads In this section, the behavior of a typical hybrid PV/diesel system without storage which characteristics have been presented in the previous sections is studied. The contribution of the PV and diesel generators, the specific consumption of the diesel generator for a given load ( L ) profile have been assessed. As mentioned previously, for four days (which solar radiation curves are given in fig. 3), we have considered four constant load profiles (3.7 kW, 5.7 kW, 7.6 kW and 9.7 kW) corresponding respectively to 40%, 62%, 82% and 105% of the diesel generator nominal power. 1100 Day 1(40% of the DG rated power)

SOLAR  RADIATION  (W/m²)

1000

Day 2(62% of the DG rated power)

900

Day 3 (82% of the DG rated power)

800

Day 4(105% of the DG rated power)

700 600 500 400 300 200 100 0

HOURS

Figure 3:

Solar radiation curves for the four days of the experiments.

The behaviors of the PV and diesel generators in the hybrid system are interdependent. Indeed, a given load is supplied as well by the diesel generator as by the PV generator. It can be observed from fig. 4 to fig. 7 that for the loads in WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

42 Energy and Sustainability III the order mentioned above, the specific fuel consumption of the diesel generator ranges respectively between: 0.45 to 0.51 l/kWh (see fig. 4), 0.35 to 0.41 l/kWh (see fig. 5), 0.33 to 0.36 l/kWh (see fig. 6) and 0.33 to 0.34 l/kWh (see fig. 7). 0.52

4.5 4

POWER (KW)

0.48 3 2.5

0.46

2

0.44

1.5 0.42 1 DG Generated  Power (kW) Total generated power (kW) Specific consumption (l/kWh)

0.5 0

PV  Generated  Power (kW) Load (kW)

SPECIFIC CONSUMPTION (l/kWh)

0.5

3.5

0.4

0.38

HOURS

Behaviour of the system for a load representing 40% of the diesel generator rated power. 7

0.42 0.41

6

0.4

POWER  (kW)

5 0.39

4

0.38

3

0.37 0.36

2 0.35

1

DG generated Power (kW) Total generated Power (kW) Specific consumption (l/kWh)

PV generated Power (kW) Load (kW)

0

SPECIFIC CONSUMPTION (l/kWh)

Figure 4:

0.34 0.33

HOURS

Figure 5:

Behaviour of the system for a load representing 62% of the diesel generator rated power.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

43

9

0.365

8

0.36

7

0.355

6

0.35

5

0.345

4

0.34

3

0.335

2

0.33

1 0

DG generated power (kW) Total  power generated (kW) Specific consumption (l/kWh)

PV generated power (kW) Load (KW)

SPECIFIC CONSUMPTION (l/kWh)

POWER (kW)

These results show that for small loads (less than 62% of the rated power of the DG), the contribution of PV generator (PAC/L) which ranges between 4 to 38% for load values of 3.7 kW and 5.7 kW does not enable an optimal functioning of PV generator. In fact, as mentioned by Ashari et al. [17] and also verified by results obtained in the present investigation, the maximum fuel efficiency of a diesel generator is about 0.33 l/kW, but for these two rated loads, the specific fuel consumptions are far from this optimal value. This is due to the fact that these loads are already far from the optimal functioning point of the diesel generator and therefore the PV generator contributes rather to decrease the performance of the engine. However, for high loads (see fig. 6 and fig. 7), the contribution of the PV array which ranges between 1.5% and 33% for a load value of 7.6 kW and between 2.5% to 22% for a load value of 9.7 kW does not considerably affect the performance of the engine. As a matter of fact, for these loads, the values of the specific fuel consumption vary between 0.33 to 0.36 l/kWh which is close to the optimal functioning point of the diesel generator. As the specific fuel consumption and then the operation cost of the diesel generator increases considerably when the hybrid system operates below the load values representing less than 62% of the rated power of the DG, the sizing of the system must be done so that the diesel generator operates near its optimal point (70–90% of its nominal power).

0.325 0.32

HOURS

Figure 6:

Behavior of the system for a load representing 82% of the diesel generator rated power.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

44 Energy and Sustainability III

10

DG generated power Total genarated power Specific consumption (l/kWh)

PV generated power Load (kW)

0.342 0.341 0.34

POWER (kW)

8

0.339 0.338

6

0.337 4

0.336 0.335

2

SPECIFIC CONSUMPTION (l/kWh)

12

0.334 0

0.333

HOURS

Figure 7:

Behaviour of the system for a load representing 105% of the diesel generator rated power.

4.3 PV Penetration level in the hybrid system The ratio of the real output power of the PV system on the maximum load P PV L

is a best indication about the contribution of the PV generator for a given load. As shown in fig. 8, the ratio PPV is a function of the solar radiation and loads. It L can be observed that for lower loads (3.7 kW and 5.7 kW), one has a value of ratio P PV which ranges from 2 to 49% and from 2 to 33% respectively (for a L solar radiation value varying between 150 and 950W/m²). However for high loads (7.6kW and 9.7 kW), it can be observed that the value of ratio PPV varies L from 3 to 26%, and from 2 to 21% respectively for the same values of solar radiation. But, it should be note that the high PV penetration is not a synonym of high efficiency of the PV system because for the close value of solar radiation, the power generated by the solar field is more important for the higher loads than for the lowers. In fact, one can see that for the close values of solar radiation, the production of PV generator is more important for the higher loads than for the lowers. This means that for an optimum production of the PV array, the ideal would be that the maximum solar radiation moments meet the peak load moments during a day. WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

45

60

105 % of the rated power of DG 82 % of the Rated Power of DG 62 % of the Rated Power of DG 40 % of the Rated Power of DG

50

PPV/Load(%)

40

30

20

10

0 0

100

200

300

400

500

600

700

800

900

1000

Global solar radiation(W/m²)

Figure 8:

Contribution of PV generator for a given load in function of solar radiation.

Fig. 8 is also a good sizing tool for the hybrid system because for a given load and a given solar radiation value, one can have the power generated by the PV generator and then the PV array size needful for this production.

5 Advantages of using hybrid systems: comparative analysis for three different systems (diesel generator only, solar PV generator only and hybrid solar PV/diesel) for powering a same load profile [3] To point out the economic advantages of hybrid systems for remote areas, a comparative analysis is conducted for the three types of power generators (DG only, PV generator only and hybrid solar PV/diesel) for powering the same load. It is well known that the load profile estimation is an important criterion for sizing and designing a power supply system. For this study a typical daily load of the Sabou village in Burkina Faso (located at south west of the country, 12°3 N and 21°3 W) is considered (see fig. 9). This village has 45,000 inhabitants, thus about 6429 households (if considering seven persons per household). The total daily need in energy of the village Sabou is 469 kWh with a maximum power peak load of 35 kW and minimum power peak of 14 kW. 5.1 Evaluation of each power system size for the above load profile Considering the above load profile, one can evaluate the size of each power system (DG only, PV generator only and PV/diesel hybrid system). WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

46 Energy and Sustainability III

40 35

Load (kW)

30 25 20 15 10 5 0

Hours

Figure 9:

Typical daily load profile of the Sabou village in Burkina Faso.

5.1.1 Size of diesel generator only For the sizing of the DG only, it has been considered that the optimal functioning point of this later is at 90% of its nominal capacity. Therefore, to satisfy the load profile at its peak load, the power of the DG only will be 38.5 kW. 5.1.2 Size of PV generator/batteries only To meet the same load profile using only a PV system, a PV array of 61 kWp and a battery capacity of 41,037.5 Ah (for 12 V) are needed. 5.1.3 Size of PV/diesel hybrid system For a PV maximum penetration of 30% (generally chosen in hybrid system), one needs a PV array of about 18 kWp. The size of DG is taken as same as the DG only one (38.5 kW) because we assume that it must be able to meet the peak load in cases of low solar radiation, sudden clouds appearance and in the night. 5.2 Economic analysis The economic analysis made in this section is based on the use of the life cycle cost (LCC). The life cycle cost is an economic assessment of the cost for a number of alternatives by taking into account all significant costs over the lifetime of each alternative, adding each option’s costs for every year and discounting them back to a common base. These costs can be categorized into two types: (i) recurring cost (operation cost for the DG and maintenance cost for the DG, the PV generator and batteries) and (ii) non-recurring cost (batteries and DG replacement costs). The life cycle cost can be expressed as follows [13].

LCC  C  PWR  PW NR  PWS

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

(2)

Energy and Sustainability III

47

where C is the initial cost. PWR, PWNR and PWS are, respectively the present worth of the recurring costs, non recurring costs and salvage values. They are expressed by:

PW

PW

R

NR

 1  e    1  e   1  i    1  i    R 1  e   1  i 

 NR

 1 e   1  i adj

PW

   1  e     1  i adj

 1 e   1  i adj 1  S (1  i ) n

S

n

  1 

  

n

(3)

   1 

(4)

  

(5)

where R is the recurring cost, NR the non recurring cost, S the salvage value, n the lifetime of the whole system, e the escalation rate, i the discount rate and iadj the adjusted discount rate for the recurring cost and given by:

i adj 

1  i  P

(1  e ) P 1

1

(6)

P is the period between two successive payments for the non-recurring costs. Table 1:

Costing data considered in the present study. Diesel generator system (38.5 kW)

PV

Battery

Initial cost (€)

15,400 €

7000€/kWp

0.07€/Wh

Annual operation cost (€)

0.9€/l of oil

0

0

Annual maintenance cost (€)

0.18*RT

3% of annualized initial cost

15% of annualized capital cost

Salvage value (€)

10% of DG initial cost

10% of PV initial cost

0

Replacement cost (€)

equal to initial cost

0

equal to initial cost

Life span (years)

10

20

5

interest rate, i (%)

8%

escalation rate, e(%)

4%

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

48 Energy and Sustainability III The life cycle cost analysis has been made using the data of table1. In table1, RT is the running time of the diesel generator. It has been consider that the consumption model of the diesel generator is like the one of section 4.1. After calculation, one obtained that for the same energy demand estimated at 3,423,700 kWh over 20 years, hybrid solar PV/diesel system Life cycle cost (LCC=983,865 Euros) is lower than the PV generator only (LCC=992,000 Euros) which is at its turn lower than the DG only (LCC=996,000 Euros). It is important to point out that the hybrid system considered here is not the optimal one in terms of configuration, the load management, and even the whole system management. By considering all these aspects and especially the environmental aspect, it is no doubt that the benefits will be more important [3].

6 Conclusion This paper presents in its first part, the experimental results of a hybrid PV/diesel system without storage. These results are very useful for the design optimization and the reliability enhancement of PV/Diesel hybrid systems. In the second part, the economical analysis made, shows that the hybrid systems could provide appropriate technological and cost-effective solutions for the electrification of rural and semi-urban areas.

References [1] World Energy Outlook (WEO), www.iea.org/weo/electricity.asp. [2] Barley, C.D., Optimal dispatch strategy in remote hybrid Power systems. Solar Energy, 58(4–6), pp. 165–179, 1996. [3] Azoumah, Y., Yamegueu, D., Ginies, P., Coulibaly, Y. & Girard, P., Sustainable electricity generation for rural and peri-urban populations of sub-Saharan Africa: the “flexy-energy” concept. Energy Policy, doi: 10.1016/j.enpol.2010.09.021. [4] Deshmukha, M.K. & Deshmukh, S.S., Modeling of hybrid renewable energy systems. Renewable and Sustainable Energy Reviews, 12, pp. 235– 249, 2008. [5] Hochmuth, G.C.S., A combined Optimisation Concept for the design and operation strategy of hybrid-PV energy systems. Solar Energy, 61(2), pp. 77-87, 1997. [6] Shaahid, S.M. & El-Amink, I., Techno-economic evaluation of off-grid hybrid photovoltaic-diesel–battery power systems for rural electrification in Saudi Arabia-A way forward for sustainable development. Renewable and Sustainable Energy Reviews, 13, pp. 625–633, 2009. [7] Ruther, R., Martins, D.C. & Bazzo, E., Hybrid Diesel/Photovoltaic systems without storage for isolated mini-grids sin Northern Brazil. Proc. of the 28th IEEE Photovoltaic Specialists Conference: Anchorage, pp.1567-1570, 2000.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

49

[8] Koutroulis, E., Kolokotsa, D., Potirakis, A. & Kalaitzakis, K., Methodology for optimal sizing of stand-alone photovoltaic/wind-generator systems using genetic algorithms. Solar Energy, 80, pp. 1072–1088, 2006. [9] Musseli, M., Notton, G. & Louche, A., Design of hybrid-photovoltaic power generator, with optimization of energy management. Solar Energy, 65(3), pp. 143–157, 1999. [10] Lopez, R.D. & Agustin, J.L.B., Design and control strategies of PV-Diesel systems using genetic algorithms Rodolfo. Solar Energy, 79, pp. 33–46, 2005. [11] Notton, G., Musseli, M., Poggi, P. & Louche, A., Autonomous Photovoltaic systems influences of some parameters on the sizing: Simulation time step, Input and Output power profile. Renewable Energy, 1(4), pp. 353-369, 1996. [12] Yang, H., Lu, L. & Zhou, W., A novel optimization sizing model for hybrid solar-wind power generation system. Solar Energy, 81, pp. 76–84, 2007. [13] Ajan, C.W., Ahmed, S.S., Ahmad, H.B., Taha, F. & Zin, A.A.B.M., On the policy of photovoltaic and diesel generation mix for an off-grid site: East Malaysian perspectives. Solar Energy, 74, pp. 453-467, 2003. [14] Nayar, C.V., Recent developments in decentralised mini-grid diesel power systems in Australia. Applied Energy, 52, pp. 229- 242, 1995. [15] Yamegueu, D., Azoumah, Y., Py, X. & Zongo, S.J., Experimental study of electricity generation by Solar PV/Diesel hybrid systems without battery storage for off grid areas, Renewable Energy(accepted for publication), 2010. [16] Skarstein, O. & Uhlen, K., Design considerations with respect to long-term diesel saving in wind/diesel plants. Wind Engineering, 13, pp. 72-87, 1989. [17] Ashari, M. & Nayar, C.V., An optimum dispatch strategy using set points for a Photovoltaic (pv)–diesel–battery hybrid power system. Solar Energy, 66(1), pp. 1–9, 1999. [18] El-Hefnawi, S.H., Photovoltaic diesel–generator hybrid power system sizing. Renewable Energy, 13(1), pp. 33–40, 1998.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

This page intentionally left blank

Energy and Sustainability III

51

Photovoltaic energy and the environment A. Reyes, F. Garcia-Alonso, J. A. Reyes & Y. Villacampa Dpt. of Applied Mathematics, Escuela Politécnica Superior, Universidad de Alicante, Spain

Abstract There are several ways of implementing a PV systems networking site, depending on the income that you would like to achieve. Fixtures can be built with solar tracking axis and two axes solar tracking. In this work we make a detailed comparative study of the implementation of a solar photovoltaic installation in a particular place, the three systems mentioned above. The study was performed from both constructive, analyzing the structural components of each of the systems, such as energy level, from the standpoint of performance and results achieved over a period of time. Obtaining criteria allow, in specific cases, the best choice. In the present work, we will also study the different models needed to obtain the appropriate permissions for the implementation of the system chosen between the ones explained above. Studies which analyze the environment surrounding the facility: the flora, fauna, hydrology and winds in the area or Environmental Impact Study. As well, the impact that the construction of an installation of this magnitude affects visually the area where it is located or Study of Landscape Integration. Keywords: solar photovoltaic energy, environmental study, landscape study, installation.

1 Introduction Over the past few years the decrease in the price of the components of solar photovoltaic installations, especially modules and investors, coupled with improved reliability and performance of the latter devices has given rise to a new application: the connection to a photovoltaic network. The direct conversion of solar energy into electricity through photovoltaic cells has been developed in recent years, in many countries, as an alternative WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESUS110051

52 Energy and Sustainability III power supply. On the occasions where the power supply for conventional network already exists, the tendency is for photovoltaic cells work with it.

2 Object of work The purpose of this paper is to define, technical and environmental parameters of the infrastructure necessary for the creation of a solar photovoltaic installation connected to the electrical network. Such an approach implies comparing together various mounting options and selecting the most beneficial for a particular case. Installation of photovoltaic systems with networking capacity, in general terms consists in generating electricity from solar radiation a renewable energy source. It consists of a photovoltaic array that produces energy in direct current (DC) and by a processing system that converts alternating current sine wave in perfect synchronism with the grid of the company.

3 Location of the photovoltaic system Municipality of Pinoso, province of Alicante. Plot 165. Polygon 3. Plot coordinates, UTM: X = 674664.10 Y = 4. 259,841.62, latitude: N 38 º 28 '4.99'', W 0 ° 59' 56.69''. Application: Production of photovoltaic power. Class of installation: electrical energy production in the Special Regime. Generated Rated: 400 kW. Minister voltage: 240 V. Maximum allowable power: 420 kW.

4 Installation components 4.1 Photovoltaic modules The set, called a photovoltaic panel or module, is composed of a specific number of interconnected solar cells properly assembled and protected against external agents (the cells are very sensitive). After completion of electrical interconnections, the cells are encapsulated in a structure called "sandwich." 4.2 Investors Investors can convert the DC produced by the panels into alternating current of 125 or 220 V. The downside is that this transformation leads to the inevitable loss of power to the investor, which, as we shall see, in some cases the performance we get is very small.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

53

4.3 Support structures 4.3.1 Fixed support 4.3.1.1 Modules inclination The performance of the panels depends on the angle of incidence of the beams of the sun on its surface. Maximum performance is obtained when the angle of incidence of solar beams on the collector is 90 °. Table of values obtained in the study site. N38º 28'5'', W 0 ° 59'57.'' Plot 165, Range 3 of Pinoso, Alicante. Table 1:

Modules inclination per month. Month January February March April May June July August September October November December Annual

Optimal Inclination (degrees) 62 54 41 25 13 5 9 20 36 50 59 64 35

4.3.1.2 Minimum distance between rows of panels Line spacing of panels is set so that at noon’s during a low illumination day (minimum solar altitude) to the time period, the shade of the upper edge of a row must be intended, at most, on the lower edge of the next row. Be taken into account the table of solar azimuths and altitudes presented in this report. In this case the inclination of the panels is: 28.5. From pre-calculated loads for the study area and ease of assembly and special use for this type of installations, we will use metal sections HILTI. The latter is composed of galvanized metal sections specially designed for easy mounting of PV modules. The structure is divided into a primary structure called rocker and a secondary structure cross-linking the different rockers separated one from another a distance of 2 meters.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

54 Energy and Sustainability III

Figure 1:

Minimum distance between rows of panels.

Figure 2:

Fixed installation photovoltaic.

4.3.2 One axis trackers The one axis Solar Tracker is a power equipment in its upper part has fixed the PV modules and getting the sunshine on them is high, all the structure moves from east to west on an axis or structure that can rotate 270 º (azimuth tracking.) With these teams, the panels are oriented so that they are always directed toward the sun, thereby increasing performance. Looking to maximize, in a first step, the production of photovoltaic energy from optimizing the resources provided by the sun, the axis solar tracker with fixed azimuth tracking is designed and manufactured to maintain the inclination of the panels in the optimum tilt.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

Figure 3:

55

One axis solar tracker.

The monitoring system to an axis is done by astronomical programming and a PLC controls the operation included the motorcycle gear causing the follower to follow the path of the sun from dawn until dusk, therefore getting the optimal orientation with respect to the sun throughout the day. The overall process will allow maximizing the total daily solar radiation received by the panels. According to the previously stated approach, we offered some increases in the performance of the systems with an axis solar tracker, for the facilities on fixed structures above 20%, reaching up to 30% in some regions of Spain. 4.3.3 Two axis trackers The two axis Solar Tracker are power equipments, its upper part has fixed PV modules and sunshine exposure on them is high. All the structure is moving from east to west on an axis that can rotate at 240 ° (azimuth tracking) and a second axis tilt from 60 ° to the horizontal position. Therefore the panels are oriented so that they are always directed toward the sun and thus increase performance.

Figure 4:

Two axis solar tracker.

Results showed that this setup allowed performance increases because of the dual-axis solar tracker. Facilities on fixed structures showed increased yields greater than 35% in most cases and reaching up to 45% in some regions of Spain. The annual production of each of them is: Fixed: 951826,52 kWh. One axis: 1015405,49 kWh. Two axis: 1116412,96 kWh. WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

56 Energy and Sustainability III

5 Production 30,00

Energy according inclination PV modules

MJ/m2/day

25,00

Horizontal plane Inclination: 35º Optimun angle

20,00 15,00 10,00 5,00 0,00

Month

Figure 5:

shows the difference between a system where the panels are in an horizontal plan with respect to the sun in comparison with other systems where the angle is fixed at 35o or varied optimally with the position of the sun.

According to the results of calculations of production, we chose two-axis trackers. Leaving the installation plant:

Figure 6:

Plant of the installation.

6 Environmental impact study At this point the aim is to make a detailed study of all factors that may affect the environment of the photovoltaic installation. This activity should be harmless but WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

57

it is necessary to ensure that this study poses no danger to the natural resources of the area [4–7]. Different factors are considered in this study are:  Natural resources  Construction and operation [8]  Vibrations  Heat  Odors  Light Emission  Waste  Spill  Matter and energy emissions  Evaluation of direct and indirect effects [8–11]  Population  Soil  Air  Water  bioclimatic factors  Tangible property  Heritage  Habitats  Geology and geomorphology  Measures planned to reduce, eliminate or compensate for significant environmental effects Given the null conditions resulting from the process of establishment of the photovoltaic plant, was not considered an alternative option and are prepared to suggestions from the Administration in order to reconcile the safe operation of the photovoltaic plant with the environment.

7 Study of landscape integration These studies have been going on for a couple of years now (indicate the number of month/year) and involves studying the integration of any facility that is intended to perform with the surrounding environment. Pretending the minimum visual impact from any angle [7, 12, 13]. The study consists of the following parts:  Purpose and justification of the study  Description of the action  Scope of performance  Landscape unit  Landscape resource  Plans or rules  Urbanistic and landscape planning  Territorial action plans incidence study in the municipality  Public Participation Plan WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

58 Energy and Sustainability III

8 Conclusions The study of a solar photovoltaic installation with network connecting showed that this was a harmless activity that gives us a fairly broad leeway in covering the specific energy demands, and therefore unexpected, of a population without the need for conventional energy and more pollution. The way of implementing this system greatly improves the yield obtained which may lead to an overall greater amount of energy. The selection of one method or another can be seen not only from a production point of view but it could also be done from an economic standpoint. A longer follow-up also requires a larger investment which could be recovered in a shorter time period. With regard to environmental considerations and landscape integration it is possible to state that it does not affect in any way the environment surrounding the activity, because its construction requires only minimal structural elements. Virtually all parts could be pre-fabricated, thus saving time, money and fieldwork. Its integration in the landscape depends on the area where we want to construct the PV installation. Fleeing villages, main roads, considering establishing in plots of low ecological value from all points of view.

Acknowledgements The authors would like to thanks F. García-Alonso, J. A. Reyes and Y. Villacampa for their technical advising and devotion in the preparation of this survey.

References [1] Reglamento electrotécnico de Baja Tensión. B.O.E. nº 224 de 18 de septiembre de 2002. [2] Reglamento de Líneas de Alta Tensión. B.O.E. 27 diciembre de 1968. [3] Reglamento Electrotécnico de Centrales Eléctricas. R.D. 3275/82. Reglamento Centrales eléctricas y Centros de Transformación. B.O.E. Nº 288 publicado el 1/12/1982. Corrección de errores: BOE Nº 15 de 18/1/1983. [4] Ley 2/1989 de Impacto Ambiental de la Generalidad Valenciana. DOGV núm.1.021, de 8 de marzo. [5] Ley 3/1989 de Actividades Calificadas. DOGV núm.1.057, de 4 de mayo. [6] Decreto 162/1990, de 15 de octubre del Consell de la Generalitat Valenciana, por el que se aprueba el Reglamento para la ejecución de la Ley 2/1989, de 3 de marzo, de Impacto Ambiental. DOGV núm. 1.412, de 30 de octubre de 1990. [7] Directiva 97/ 11 de la Comunidad Europea, del Consejo, de 3 de marzo de 1997

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

59

[8] Decreto 54/1990, de 26 de marzo de 1990, del Consell de la Generalitat Valenciana, sobre actividades molestas, insalubres, nocivas y peligrosas (Nomenclátor de actividades). DOGV núm. 1288, de 20 de abril de 1990. [9] Papel y cartón Código LER 200101 (No tóxicos ni peligrosos). BOE 19/02/2003. (Incluye la Corrección de errores de BOE 12/03/02). [10] Plásticos Código LER 200139 (No tóxicos ni peligrosos). BOE 19/02/2003. (Incluye la Corrección de errores de BOE 12/03/02). [11] Restos de metales derivados de la instalación eléctrica Código LER 200140 (No tóxicos ni peligrosos). BOE 19/02/2003. (Incluye la Corrección de errores de BOE 12/03/02). [12] El Decreto 120/2006, de 16 de agosto, del Consell de la Generalitat Valenciana, por el que se aprueba el Reglamento del Paisaje en la Comunidad Valenciana, DOGV nº 5325, 16 de agosto de 2006. [13] Diario Oficial Unión Europea (DOUE) n° L 073 de 14/03/1997.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

This page intentionally left blank

Energy and Sustainability III

61

Improving building energy efficiency: a case study S. Grignaffini, M. Romagna & D. Principia “Sapienza”, University of Rome, Department of Astronautic, Electric and Energetic Engineering, Italy

Abstract The main purpose of this study was to conduct a study for improving energy efficiency of an important building in Rome, the Headquarters of the Italian State Monopoly. The study was conducted by comparing conventional analysis tools with innovative ones, in order to evaluate the possible solutions, both structural and plant, aimed at the use of renewable sources and at energy saving. After making a thermo graphic survey, the first and useful step for a good energy audit, conduct building energy was simulated, at first in steady state by the use of a software widely used at the professional level, then in transient state by the use of TRNSYS, a finite difference method software which is able to simulate more accurately conduct building energy. The next step was to propose possible redevelopment of a structural and energy plant that promotes the building energy rating higher, finding the right balance between the energetic and economic aspect. Among the interventions plant, two possible workarounds have been proposed and designed in detail:  installation of a photovoltaic system;  installation of a solar cooling system. Both solutions lead to a reduction of electricity consumption with a significant impact in economic and environmental terms. Keywords: energy efficiency, energy saving, steady state, transient state, photovoltaic system, solar cooling system.

1 Introduction The work presented here has as its object the study of upgrading the energy efficiency of an important building in Rome the Headquarter of the Italian State WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESUS110061

62 Energy and Sustainability III Monopoly used primarily for office use. This study was performed by using two software programs that simulate the energy behaviour of the building, allow the calculation of energy losses and therefore the total energy demand in summertime and wintertime. The first software used, TFM-STIMA10 allowed us to perform the study of dispersion in steady state, following a conventional method, while the second one, TRNSYS16, simulates the energy behaviour in transient state. The work ends finally with the proposal of two engineering solutions that include the use of renewable resources: a photovoltaic system and, as an alternative to this, a solar cooling system.

2 Analysis of the energy behaviour of the building before energy efficiency improvement 2.1 Thermographic survey As a first analysis tool of the energy behaviour of the building, thermography was used. A thermographic study may be an ideal tool to determine heat loss outside of a building, for the identification of sources of loss such as windows, doors, faulty insulation. By analyzing the radiation emitted by a body, you can identify thermal anomalies generated by losses or infiltrations both indoor and outdoor in order to reduce substantially energy costs. The identification of the cause of the defects or faults of a bad insulated building, lead to significant cost savings by intervening to repair the damage before it can become large or even irreparable. Thermography is a “non-destructive” survey based on the principle that any body with a temperature greater than absolute zero emits energy in the form of electromagnetic radiation. The camera measures and displays the infrared radiation emitted by objects: this radiation resulting surface temperature of objects. Many other factors may affect the surveys: the emissivity, the radiation resulting from the environment and the absorption of radiation by the atmosphere. Therefore, in order to accurately measure the temperature, it is necessary to offset the effects of a number of sources of radiation; so, in the measurement of absolute temperature, factors which can significantly distort the surveys should be considered: reflections of the surfaces, contact angle measurement, moisture, indoor temperature and emissivity of the measured area. In the works of building renovation, energy saving is an issue of great topical interest. Thanks to thermography it is possible to determine the critical energy and structural points of buildings, clearly identifying the critical areas with significant thermal bridges (cold bridges). In fact, they constitute a privileged way to exchange heat to and from the outside. The main negative effects are the cooling of the areas closest, with the consequent creation of condensation and mildew with the reduction of the insulating properties of the walls. It is very important in the energy redevelopment to precisely detect this type of problems, in order to provide interventions for energy saving.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

Figure 1:

Thermographic image of the main facade of the building.

Figure 2:

Thermographic image of the main facade of the building.

63

The images (Figures 1 and 2) obtained from camera show that the main cause of heat loss from the building envelope is to be attached to window frames. 2.2 Steady state study At the first step, structures and systems that characterize the building had been identified, then the energy performance was simulated in steady state through the use of software STIMA-TFM. The building has the following features: seven floors above ground; average height of floor: 3 m; area: 20.098 m2; volume: 60.295 m3 The software allows to create the heat dispersant structures (exterior walls, window frames, thermal bridges, floors) to be allocated to areas of the building; it consists essentially of a main spreadsheet (Figure 3) in which one we can describe the various rooms making up the building envelope (volume, dispersing facilities, ventilation and dispersion for transmission, etc..) and can automatically and sequentially to develop all the necessary operations,

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

64 Energy and Sustainability III

Figure 3:

Main spreadsheet STIMA-TFM.

displaying results in real-time application of a series of procedures designed to support the methods of calculation for wintertime demand. The results indicate a specific heating demand equal to 7.1 kWh/m3year, a value that places the building envelope at “D” energy class according to the limits imposed by Italian legislation about the reduction of energy consumption and the use of energy efficiency in buildings (Figure 4). The simulation allowed to highlight the main cause of heat loss is due to the window frames.

Figure 4:

Building energy efficiency before energy efficiency improvement.

2.3 Transient state study The energy performance of building was then simulated in transient state through the use of software TRNSYS16. TRNSYS has a modular structure, consisting primarily of subroutines called “Types” written in Fortran language, allowing the inclusion of new mathematical WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

65

models, not present in standard libraries, developed by users or interact with other programs like Excel and Mathlab. The Types are divided into 14 groups but conceptually can be divided into three main categories: the first group includes types with general function to conduct the simulation, such as a support for reading and writing data; then we have a group for data processing and finally a wide range of types that represent the mathematical model of a particular component, such as a solar collector, a tank, a solar panel, etc.. to be included in the simulation. Each of these subroutines describes the behaviour in a parametric way, and for each module specifying input, output and constant values. In a project in which useful Types are defined, we have to establish only the various connections each other according to the required syntax and mode of operation of the system to be simulated. At this point it is intuitive to exploit the modularity in order to reduce the complexity of the systems to be simulated, by dividing them into many easier sub problems. The operational phase described above, is expressed with the drafting of the input file “deck”, where the connections between the various components constituting the system are specified. The “deck” file will be processed by TRNsys Simulation Processor called “TRNEdit”. The type that describes buildings thermal model is “Type 56 or Multizone Building”. This type, given the complexity of the model, requires the inclusion of many parameters and difficult syntax of the input file. However, using the application “TRNBuild” included in the software package, it is possible through an intuitive graphical interface, assigning the parameters in a much simplified way. In case study proposed, simulation model is shown in Figure 5 with the assembly of different Types interconnected by boundary conditions on the variables of interest

Figure 5:

TRNsys16 simulation model.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

66 Energy and Sustainability III Given the large extension of the building, built in different ages with different construction technologies, the study was carried out by distinguishing two parts of the same: some older, known then as “Historic Building”, and a part of building more recently, the “New Building”. So, two simulation models were compiled and a Type56 for each of which has been created: it was possible in this way to evaluate the annual energy needs of the building. The results obtained from the simulation carried out are shown in Figures 6 and 7. The red curve represents the Heating Power demand (kW/m3) of the building (in winter), the blue one the Cooling Power demand (kW/m3) of the building (summer) (Figure 6). Operating on an annual basis a mathematical integration of the powers mentioned above, you get the Winter Energy Performance Index (kWh/m3year) (violet curve) and the Summer Energy Performance Index (kWh/m3year) (yellow curve) (Figure 7). The results obtained by the simulation indicate the Winter Energy Performance Index equal to 6.6 kWh/m3year (value that places the building envelope at “D” energy class) and the Summer Energy Performance Index equal to 20 kWh/m3year. The red curve represents the Heating Power demand (kW/m3) of the building (in winter), the blue one the Cooling Power demand (kW/m3) of the building (summer) (Figure 6) .

Figure 6:

Heating and cooling power demand.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

Figure 7:

67

Energy performance indexes.

Operating on an annual basis a mathematical integration of the powers mentioned above, you get the Winter Energy Performance Index (kWh/m3year) (violet (lower) curve) and the Summer Energy Performance Index (kWh/m3year) (yellow (higher) curve) (Figure 7). The results obtained by the simulation indicate the Winter Energy Performance Index equal to 6.6 kWh/m3year (value that places the building envelope at “D” energy class) and the Summer Energy Performance Index equal to 20 kWh/m3year.

3 Interventions of energy efficiency upgrading Once the energy requirement or in other words, the energy consumption was established, the possible interventions aimed at upgrading the energy efficiency and at the reductions of the energy losses in order to promote the building to a higher energy class, have been proposed. These interventions both structural and technological are the result of a choice of excellent between the factors and design constraints and the purely economic factors; they are listed below:  Replacement of existing single glazed window frames (transmittance equal to 5.53 W/m2K) with double glazed window frames (transmittance equal to 1.70 W/m2K) according to the limit required by legislation;  installation of a photovoltaic or a solar cooling system. The decision not to intervene on the walls was dictated by the fact that the building falls within the constraint of the historical and cultural heritage, while WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

68 Energy and Sustainability III the alternative choice between the photovoltaic system and the solar cooling one is linked to constraints on the optimal surface coverage for the installation of the photovoltaic modules and the solar collectors. 3.1 Photovoltaic system The Photovoltaic System, to be installed on the flat roof of the building, has a nominal power of 53.36 kWp and is composed of polycrystalline silicon modules, with efficiency equal to 14.1% and nominal power equal to 230 W. The total number of modules, calculated taking into account the space available is 232 for a total area of approximately 380 m2.The provision on the roof is shown in Figure 8. The photovoltaic modules are divided into 16 strings of 13 modules and 2 strings of 12 modules. Their tilt inclination is 30°, the optimal choice for the locality of reference (Rome) which has a latitude of 41° 56', while the azimuth is +22°.

Figure 8:

Photovoltaic system: location of the modules on the building rooftop.

In the calculation made, the annual energy (Ere) of system in terms of electricity is equal to: MWh . (1) E re  68.7 year

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

69

3.2 Solar cooling system A solar cooling system is able to produce summer conditioning through solar thermal energy. What makes the solar cooling system really interesting is the perfect time phase, which is obtained by using this technology, between the peak cooling demand and maximum availability of solar radiation (Figure 9). The system has been designed by using software TRNsol which uses TRNsys16 as simulator and its configuration is shown in Figure 10. The plant has a 130 kW power and is composed of:  Absorption Chiller with power of 130 kW;  Evacuated Tube Solar Collectors with an efficiency of 60% and a total surface area of approximately 380 m2;  Hot Water Storage Tank with capacity of 2.000 liters;  Auxiliary Hot Water Tank with capacity of 1.000 liters;  Cold Tank with capacity of 2.000 liters;  Temperature Control System with input temperature machine 85 °C and output temperature machine 7 °C;  Cooling Tower with a flow rate of approximately 13.500 m3/h. 3.3 Energy efficiency improvement: results Facing the same analysis in both steady state and transient, we find that the total heating energy demand in winter obtained is around 3 kWh/m3year with a promotion from the energy point of view of the original structure from a “D” class to an “A” Class.

Figure 9:

Monthly thermal loads and solar radiation comparison.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

70 Energy and Sustainability III

Figure 10:

Figure 11:

Solar cooling system: TRNsol simulation model.

Building energy efficiency after energy efficiency improvement.

4 Conclusions The study highlighted the importance of energy efficiency improvement of the buildings, which, for their great extension, consume a large amount of energy. These interventions, both structural and technological with the use of renewable sources, in many cases can improve significantly the energy performance and promote the building energy class in a higher level, as well illustrated in the case study proposed. However, in many cases, the economic factor takes great importance: for example, regarding to photovoltaic systems, the payback time is WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

71

from 7 to 8 years while the solar cooling systems are not yet very encouraged in the energy saving policy, because their level of market placing is low because of the initial investment costs compared to a conventional air conditioning system. In contrast, however, is clear that these systems have almost zero electrical power consumption, according to the working principles of an absorption machine and they allow the use of solar energy when the cooling demand of confined spaces is highest: so they establish a perfect time phase between the maximum availability of renewable energy and the peak cooling demand.

References [1] Hans, Martin, Henning: Solar Assisted Air Conditioning in Buildings A Handbook for Planners. Springer Wien/NewYork. 2nd revised edition 2008. [2] Carvalho,MJ (2007), WP 4.5: SOLAR COOLING: Contribution to a future development of CTSS method applicable to solar assisted air conditioning systems (or solar cooling systems). [3] TRNsys ,Transient system simulation environment developed at the Solar Energy Laboratory at Univ. of Wisconsin, Madison, USA. [4] STIMA10-TFM7, Steady State Simulation Software: User Manual, Watts Industries. [5] GSE, Le Guide Blu, Impianti Fotovoltaici a norma CEI, 2008. [6] Groppi, Zuccaro: Impianti Solari Fotovoltaici a norma CEI, 2008. [7] Bartolazzi: Le Energie Rinnovabili, Milano, 2006. [8] ENEA: Le fonti rinnovabili, 2003. [9] Italian Legislation about Energy Saving.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

This page intentionally left blank

Energy and Sustainability III

73

Numerical modeling as a basic tool for evaluation of using mine water as a heat source J. Baier1, M. Polák1, M. Šindelář2 & J. Uhlík1 1 2

ProGeo s.r.o., Czech Republic ARCADIS geotechnika a.s., Czech Republic

Abstract In 2007 research on the possibilities of using mine water as a heat source started. Major research goals were: a) model evaluation of the heat transfer in the rock containing selected mines; b) model prediction of the temperature change due to the heat pump operation. A database containing data from abandoned mines covering the Czech Republic area was created. It contains mine water volumes, chemical parameters and temperatures. Two types of simulation software were used. For the Plzeňská basin region the heat transfer and groundwater flow were calculated using MODFLOW and MT3DMS simulation software. Their numerical code is based on the finite difference method (FDM). For the Příbram region the FEFLOW code was used. FEFLOW numerical code is based on the finite element method (FEM). Model results show that the mining water temperature decrease due to the groundwater abstraction for the heat pump will be relatively small. Temperature decrease originates from the fact that colder shallow groundwater will inflow into mine spaces mixing with the warmer mine water. The time scale of the mine water temperature decrease is over several centuries. The temperature conditions of the mine water could be very stable. Abandoned mines are supposed to be a suitable geothermal energy source. Keywords: numerical modeling, FEFLOW, MODFLOW, MT3DMS, abandoned mine, mine water, heat pump, geothermal energy.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESUS110071

74 Energy and Sustainability III

1 Introduction and background As mentioned by several authors (Myslil et al. [3], Renz et al. [6]) the geothermal energy is one of the most ecologically friendly and economically optimal methods of energy production. In contrast to the other alternative energy resources (wind, water, solar) the heat pump installation has minimal influence on the landscape character. Exploitation of geothermal energy from abandoned flooded mines can be a very suitable energy source even in natural protected areas. Due to mining the extensive fracture systems were developed. These allow the groundwater to flow through the relatively impermeable rock formations, where groundwater pumping from the installed boreholes would not yield a certain amount of groundwater. In the Czech Republic there are approximately 12–15 thousand mining localities. The estimated amount of mine water in abandoned and consequently flooded mines is 13–15 million cubic meters. The project called “The research on utilization of energetic potential of mine water from the former mining sites in Czech Republic” started in the year 2007. At the beginning of the research project the data about mine workings, their reinsurance, technical parameters, hydrogeology conditions and mine water physical and chemical parameters were collected. Consequently, according to the established criteria two representative localities of coal and uranium mines near the Plzeň and Příbram cities were chosen (Fig. 1). An important part of the research was to evaluate the possibilities of numerical modelling of groundwater flow and heat transfer in flooded mines, and through the use of the models assess the influence of mine water abstraction on the regional and local hydro geological regimes and on the temperature field. km EUROPE

Liberec

Plzeň basin Praha Plzeň

Ostrava

Příbram

Olomouc Brno

Czech Republic

Figure 1:

Study areas – Plzeň basin and Příbram mine workings area.

There are several CFD mathematical models (fluent, Flow-3D) which are powerful tools for the computing of the temperature field in the fluid environment as well as useful tools for simulating local temperature distribution in mines and their surroundings. The problem arises when evaluation of the influence of groundwater abstraction on the regional hydrogeological conditions is needed. On this regional scale it is necessary to take into account the drainage WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

75

into the streams, infiltration, preferential flow, etc. For our regional scale model of the Plzeňska basin programs MODFLOW (Hill et al. [1]) and MT3DMS (Zheng and Wang [12]) were used to simulate groundwater flow and heat transfer. The MT3DMS application for heat transport modelling is based on the similarity between the Fick and Fourier’s Law, describing heat and solute transport (Thorne et al. [10, 11]). Unlike in the case of the solute transport, where movement is essentially confined to the fluid phases, energy is also transported through the aquifer solids by the conduction (controlled by the thermal conductivity of the solids). Hence, the new parameters kTfluid and kTsolid are considered in order to distinguish the thermal conductivities of the fluid and solid phases. The FEFLOW (Diersch [2]) software was used for regional groundwater flow and heat transport simulation in the uranium mine area near the Příbram. In contrast with the MT3DMS software, the FEFLOW has been authentically developed for heat simulation, and it has already been used for simulating groundwater flow and heat transfer in mine regions by several authors (Rapantova et al. [6], Renz et al. [7]).

2 Numerical models application 2.1 Case study: groundwater flow and heat transfer modelling in the southern part of the Plzeňská basin The main goals were: a) to verify MT3DMS possibilities for heat transfer and groundwater flow simulation; b) to determine the impact of mine water abstraction on the local and regional hydrogeological conditions c) to evaluate abstracted mine water temperature development during the long running operation of the heat pump. Realized simulations of groundwater flow, heat transfer and their purposes are shown in the Table 1. Table 1: Groundwater flow simulations Variant 1: Steady state groundwater flow simulation with extraction from mine Variant 2: Steady state groundwater flow simulation without extraction from mines Variant 3: Steady state groundwater flow simulation with groundwater extraction of 20 l/s for heat pump Variant 4: Steady state groundwater flow simulation with groundwater extraction of 40 l/s for heat pump

The simulation variants. Heat transfer simulations

---Heat transfer simulation without groundwater extraction

Simulation purpose Hydraulic parameters calibration based on comparing observed and computed hydraulic heads and streams flow rates Groundwater flow and heat transfer simulations under present conditions

Heat transfer simulation groundwater extraction 20 l/s

Groundwater flow and heat transfer prognosis simulation

Heat transfer simulation groundwater extraction 40 l/s

Groundwater flow and heat transfer prognosis simulation

2.1.1 Brief characterization of study area Collectors and isolators alternation is characteristic for vertical profile of the Plzeňská basin. The basin is formed by kladno, týnec, slaný and líň strata WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

76 Energy and Sustainability III composed of sandstones, arkoses, siltstones and claystones sediments. During the mine operation a significant part of groundwater flow took place in a vertical direction. Proterozoic strata below the Plzeňská basin sediments are impermeable. Hydraulic properties give Švoma et al. [9]. The average transmissivity of carbon collectors to the depth of 150 m is in the range from *10-5 to n*10-4 m2 s-1. The bottom layer transmissivity decreases to 9.10-6 m2 s-1. The whole area of Plzeňská basin is recharged by the rain infiltration. The collectors are mainly under confined conditions. During operations time the groundwater abstraction of tenths liters existed from every bigger mine. Piezometric head in the basin dropped, resulting into zero groundwater drainage into many reaches of local streams. 2.1.2 Groundwater flow simulations The model area of the Plzenska basin is discretized by the rectangular mesh. The size of every model cell is 200 x 200 m. In the vertical direction carbon sediments are divided into 5 layers. Top of the first layer represent surface and the bottom of the fifth layer corresponds with Plzeňská basin bottom. The Cauchy boundary condition was selected to simulate drainage in to the surface streams. Neumann boundary condition has been used for abstraction wells and recharge simulation. The infiltration rate is set up in the range between 0.6– 2.0 ls-1km-2 with dependency on surface cover and altitude. Abstraction rates depend on the actual model variant. The model calibration was carried out comparing model and measured groundwater levels and comparing simulated and evaluated stream drainage. 2.1.3 Groundwater flow simulations results Variant 2 describes actual flow condition after all mines are abandoned and flooded. Without mine pumping, the piezometric heads change only slightly in the vertical. Fresh groundwater circulation exists only near the ground surface. At the bottom of the basin the groundwater flow is negligible. Two different groundwater extractions (25 and 40 l/s) were simulated to mimic heat pump operation. It allowed us to analyze: a) the regional and local hydraulic impact with respect to the pumped amount; b) temperature field deformation with respect to the pumping amount. The groundwater abstraction occurs in the 4th model layer containing mine galleries. Hydraulic effect of the mine space is simulated via extremely high hydraulic conductivity values. Under this setup, the hydraulic depression occurs preferentially in the mine space. Mine water preferentially flows to the abstraction place. The model results can be summed up into several points below:  piezometric head in the interconnected mine space is almost the same,  steep piezometric gradient (Fig. 2) is taking place in the rock environment without mine space,  higher mine water abstraction for the heat pump will cause piezometric head drawdown about of 160 m (Fig. 2).

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

Figure 2:

77

Variant 4 – simulated groundwater drawdown (in metres) caused by 40 l/s groundwater abstraction for heat pump.

2.1.4 Heat transfer simulations Heat transfer numerical modelling requires special sets of input information, like the initial groundwater temperature, thermal conductivity and capacity, terrestrial heat flow across the basin bottom, etc. In the Czech Republic there has not been stressed the measuring of those yet, hence in most cases the parameter values had to be established from tabular data. Finally the model thermal conductivity was set 1.96 W m-1.°C-1 for first layer and 2.12 W m-1.°C-1 for second to fifth model layer. While keeping a fixed temperature of 9.5°C at the top model layer, a constant heat flux of 60 mW m-2 was defined for the bottom layer. Under this condition without mine water extraction the initial conditions were computed for variant 3 and 4. According to the model results highest temperature occurs in the fifth model layer (Fig. 3).

Figure 3:

Variant 2 – simulated vertical temperature and piezometric heads distribution.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

78 Energy and Sustainability III The highest bottom layer temperature (almost 20°C) coincides with the highest vertical thickness of saturated rock. The average groundwater temperature in the bottom layer equals 18.73°C. The average difference in temperature between the 1st and 5th layer is 9.23°C. In the Nová Hospoda (extraction place for heat pump) the temperature gradient 1°C/ 35 meters exists. Mine water extraction for the heat pump will accelerate groundwater inflow into the mine spaces (Fig. 4).

Figure 4:

Variant 3 – simulated vertical temperature and piezometric heads distribution.

Temperature (°C)

Downward groundwater flow gradient is established. Cooler groundwater from near the surface flows into the mine. The temperature field is altered and in the areas where the flow direction was changed the decrease of groundwater and rock temperature can be examined. The affected area with temperature drop is 5 km2 or 8 km2, depending on the heat pump mine water extraction (20 or 40 l/s). Predicted and stabilized temperature decrease for 20 l/s or 40 l/s extraction rates are in range 0–1°C or 0–2°C (Fig 4) . 16.5

Mine water  temperature trend; groundwater abstraction ‐ 20 l/s

16

Mine water  temperature trend; groundwater abstraction ‐ 40 l/s

15.5 15 14.5 14

Figure 5:

1500

1400

1300

1200

1100

1000

years

900

800

700

600

500

400

300

200

100

0

13.5

Variant 3, 4 – simulated groundwater temperature change in the extraction place.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

79

2.2 Case study: groundwater flow and heat transfer modelling in the Příbram region Simulation goals were: a) to set and calibrate regional groundwater flow and heat transfer model; b) to determinate thermo-dynamical and hydraulic regimes affection by the mine workings; c) to evaluate affection of present hydraulic regime by the groundwater abstraction for heat pump; d) verification of FEFLOW code possibilities to simulate heat and groundwater flow in the rock with the abandoned uranium mine. Table 2:

Model variants and purposes.

Groundwater flow and heat transfer simulation variant Variant 1:steady state simulation while conditions affected by mining and mine water abstraction – present time Variant 2: steady state simulation while condition unaffected by mining Variant 3: steady state simulation while mine water abstraction for heat pump (25 l/s) from colliery Marie Variant 4: steady state simulation while mine water abstraction for heat pump (25 l/s) from colliery 15

Simulation purpose Model calibration based on comparing hydraulic head, simulation of hydrogeological condition after flooded mines – present time Simulation of supposed state before mining was started (ideal historical state) Groundwater flow and heat transfer prognosis simulation, affected temperature field by groundwater abstraction Groundwater flow and heat transfer prognosis simulation, affected temperature field by groundwater abstraction

2.2.1 Brief characterization of the study area The underground exploitation of the polymetallic deposit started in the 14th century. In the 20th century uranium ore was the only exploited mineral. In 1991 all the mining works stopped. Groundwater flows primarily in the areas close to the surface or through fracture system reaching also the depth of uranium mine. The phreatic groundwater level mostly conform to the ground surface. Hydraulic conductivities vary over 4 orders of magnitude. Table 3:

Horizontal conductivity range.

litologicko-stratifrafický typ

Cambrian shale and agglomerate Nonproteozoic shale and wacke Varis granitoids Bazalts and metabazalts

max. k (m/s) 5.00E-06 2.50E-06 5.00E-07 2.50E-06

min. k (m/s) 5.41E-10 2.70E-10 5.41E-11 2.70E-10

2.2.2 Groundwater flow simulations setup Irregular triangle mesh, built up from 39 065 linear elements, covers the regional model area. In the vertical direction the rock environment is divided into the 13 model layers. The first model layer is near the terrain. The bottom of the model is 1400 m b.s.l. The drainage/infiltration in/out of the streams was set by Newton boundary condition (fourth kind) where the flux across the boundary depends on a piezometric head in each compute node. Constant flux (Neumann boundary condition) of intensity 2-7 l/s/km2 was set up at the top of the model, representing rain infiltration. The remaining model boundaries have zero flux defined across them. Mine water extraction for the heat pump is simulated using multi-layer well method. It is supposed that the fracture permeability decrease WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

80 Energy and Sustainability III with the depths in the model. The area affected by mining activities is represented by higher hydraulic conductivity and porosity zones in the model. Hydraulic conductivity estimation of the elements representing mine space was a significant part of the model calibration. 2.2.3 Groundwater flow simulations results Model calibration was carried out simulating the variant 1 (Table 2). We had enough piezometric heads, temperatures and mine inflow data from time of mine operation. Regional groundwater flow takes place mostly in the west–east direction – from the central spine of Brdy upland to the Vltava river (Fig. 6). According to model results mine areas act as preferential pathways for groundwater flow.

Figure 6:

Variant 1 – simulated groundwater levels (fifth model slice).

2.2.4 Heat transfer simulation description and results Natural temperature field of the model domain (variant 2) was simulated having: bottom constant heat flux 50 mW m-2; first model layer at constant temperature 10°C; zero heat flux across remaining boundaries; thermal conductivity in the range of 2 - 3 W.m-1.K-1; the specific heat capacity in the range of 2600– 3000 J kg-1 K-1. The groundwater temperature rises fluently from the surface down to the model bottom (- 1400 m a. s. l.), where the temperature values are in a range of 35–42°C. These values are in the satisfactory agreement with measured mine water temperature from the deepest colliery. WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

81

At present time (variant 1) the lowest temperature in the bottom layer is in the model domain between the colliery 16 and 19 in the place with groundwater extraction (Fig. 7). The amount of groundwater flowing from surface to the model bottom has risen and the flow has become deeper comparing to situation without mines. The colder water flow from upper layers is mixing with the warmer water at the mine attitude causing the decrease of saturated rock temperature. Former mine water abstraction during the mine operation period and present mine water abstraction for cleaning purposes causes rock within the mine to become colder.

Figure 7:

Variant 1 – simulated horizontal temperature distribution.

The groundwater abstraction 25 l/s for heat pump is taking a place in colliery Marie in variant 3 or in colliery 15 for variant 4. The final vertical temperature field distribution for variant 4 is presented in Figure 8. The groundwater abstraction was simulated via multi-layer well method in the depth 50 to - l00 m a. s. l from layers 7, 8 and 9. The groundwater flow abstraction was also simulated via multi-layer well method. But in this case not in the whole vertical line in colliery 15 (like in variant 3) but only in three layers (7, 8, 9) in order to test possibilities of simulating concrete deep of abstraction and to define effect of perforated intervals of abstraction system in the colliery. Model results show a slight temperature increase in the colliery under the abstraction place (Fig. 9(b)). In the deeper colliery part below abstraction depth upward groundwater flow is activated. The abstraction place and upper colliery part become colder. Downward groundwater flow exists (Figure 9(a)). WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

82 Energy and Sustainability III

Figure 8:

Figure 9:

Variant 4 – simulated vertical temperature distribution.

Variant 4 – simulated temperature changes around the abstracted place in 8th (a) and 12th (b) model slice – comparison with variant 1.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

83

3 Discussion This paper presents two different approaches to regional groundwater flow and heat transport simulation in the rock with abandoned mines. In the first approach the MODFLOW (Hill et al. [1]) and MT3DMS (Zheng and Wang [12]) software was used. In the second approach the FEFLOW (Diersch [2]) software was used. Resulting experience can be summarized in the several points: a) even if heat from the mine water is extracted outside the rock (the heat exchanger is not placed directly to the flooded mines), mine water abstraction for the heat pump will cause rock and the pumped water to become colder; b) with MT3DMS it is not possible to take into account temperature and chemistry dependence of groundwater flow resulting into the density dependent flow. Because of forced mine water circulation due to the mine water abstraction these effect could be omitted; c) of key importance is model mine space hydraulics representation. In both, MT3DMS and FEFLOW simulation, mine space hydraulics representation is only approximation. Mine water velocity pattern is of key importance in transport calculation. So the model prediction of the temperature decrease undergoes some uncertainty; d) much bigger uncertainty is connected with the fact that values of terrestrial heat flow, rock thermal conductivity and capacity are often missing. Much more survey on this topic should be performed; e) certain problems with using mine water could be connected with the fact, that the mine water is usually highly mineralized. Incrustation in the heat pump exchanger is anticipated.

4 Conclusion Flooded mines could serve as water source for heat pumps even in low permeable formations. Up to this advantage mines are supposed to be a temperature stable source. Model predicted mine water temperature changes are relatively small. The time scale of the temperature change exceeds human life. Some disadvantages and limitations of the chosen modelling approaches were found. In further studies, while simulating heat exchanger in the mine space, we want to use SEAWAT (Langevin et al. [3]) model, which allows us to take into account density depend flow. Another improvement could be attained with CPF MODFLOW module (Shoemaker et al. [8]). It enables turbulent or laminar groundwater flow simulation. Model application allows us to evaluate heat pump hydraulic and temperature influence. The biggest source of uncertainty is connected with the lack of rock thermal properties data.

Acknowledgement This project was financially supported from the State Budget of the Ministry of Industry and Trade of the Czech Republic.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

84 Energy and Sustainability III

References [1] Hill, M.C., Banta, E.R., Harbaugh, A.W., and Anderman, E.R.: MODFLOW-2000, the U.S. Geological Survey modular ground-water model—User guide to the Observation, Sensitivity, and ParameterEstimation Processes and three post-processing programs: U.S. Geological Survey Open-File Report 00–184, 209 p., 2000 [2] Diersch H-JG: FEFLOW finite element subsurface flow and transport simulation system, reference manual, WASY, Institute for Water Resources Planning and Systems Research, Berlin, 292 p., 2005 [3] Langevin, C.D., Thorne, D.T., Jr., Dausman, A.M., Sukop, M.C., and Guo, Weixing, SEAWAT Version4: A Computer Program for Simulation of Multi-Species Solute and Heat Transport: U.S. Geological Survey Techniques and Methods Book 6, Chapter A22, 39 p., 2007 [4] Myslil, V., Kukal, Z., Pošmourný, K., Frydrich, V.: Geotermální energie. Ekologická energie z hlubin Země - současné možnosti využívání. Planeta, MŽP Praha, roč. 15, č. 4, 32, 2007 [5] Nam Y., Ooka R, Hwang S.: Development of a numerical model too predict heat exchange rates for a ground-source heat pump system, Energy and Buildings 40 (2008) 2133 - 2140, 2007 [6] Rapantova N, Grmela A, Vojtek D, Halir J, Michalek B: Ground water flow modelling applications in mining hydrogeology. Mine Water Environ. doi:10.1007/s10230-007-0017-1, 2007 [7] Renz A, Rühaak W, Schätzl H, Diersh J.: Numerical Modeling of Geothermal Use of Mine Water: Challenges and Examples, Mine water Environ 28:2-14, 2009 [8] Shoemaker B., Kuniansky E., Birk S., Bauer S., and Swain E.: Documentation of a Conduit Flow Process (CFP) for MODFLOW-2005, S. Geological Survey, Reston, Virginia: 2007 [9] Švoma J., et al.; Plzeňská pánev. Regionální hydrogeologický průzkum. Závěrečná zpráva. – MS, Geofond Praha, 1970 [10] Thorne D., Langevin Ch., Sukop C. M.; Addition of simultaneous heat and solute transport and variable fluid viscosity to SEAWAT, Computers & Geosciences 32,1758 – 1768, 2006 [11] Thorne D, Langevin Ch, Sukop M.: MODFLOW/MT3DMS – Based simulation of variable-density groundwater flow with simultaneous heat and solute transport, XVI International Conference on Computational Methods in Water Resources, Copenhagen, 2006 [12] Zheng, C., and Wang, P.P.: MT3DMS, A modular three-dimensional multispecies transport model for simulation of advection, dispersion and chemical reactions of contaminants in groundwater systems: Vicksburg, Miss., Waterways Experiment Station, U.S. Army Corps of Engineers. 1998

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Section 2 Biomass processes and biofuels

This page intentionally left blank

Energy and Sustainability III

87

High yields of sugars via the non-enzymatic hydrolysis of cellulose V. Berberi1, F. Turcotte1, G. Lantagne2, M. Chornet1,3 & J.-M. Lavoie1 1

Industrial Research Chair on Cellulosic Ethanol and Second Generation Biofuels, Département de Génie Chimique; Université de Sherbrooke, Canada 2 Institut de recherche d'Hydro-Québec (IREQ), Canada 3 CRB Innovations Inc., Sherbrooke, Canada

Abstract Given the cost of cellulosics (quasi-homogeneous residual feeds range in North America, between $US 60–80/tonne, dry basis, FOB conversion plant) their fractionation and subsequent use of the intermediate fractions is a strategy that makes economic sense. Furthermore, it permits the isolation of cellulose with low contents of lignin and hemicellulose. Once the cellulose is isolated, its use as a chemically pulped fibre and the conversion of the fines into glucose becomes possible. Our group has been working on the chemical depolymerisation of the cellulose (both the fines and the fibres as well) using highly ionic solutions. The method implies recovery of both anions and cations by state of the art technologies. This paper presents the fractionation + ionic decrystallization and depolymerisation approach, provides and discusses its energy balance and compares it with the enzymatic route for hydrolysis in applications to < 40 MML Biofuels/y plants which correspond to < 100 000 t/y of input lignocellulosics, dry basis. Keywords: cellulose, hydrolysis, depolymerization, electrodialysis, biofuels.

1 Introduction In North America, residual forest and agricultural biomass cost actually 60-80$ US per dry tonne FOB. Such biomass could be considered chemically as quasihomogeneous since although it may contain the same macromolecules and metabolites (extractives, hemicelluloses, cellulose and lignin), the concentration WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESUS110081

88 Energy and Sustainability III of each may vary as a function of season, due to weathering, etc. Energy crops or “non-conventional” cultures could also be included in this category since they usually are a “mixture” of different tissues although at this point, this biomass is slightly more expensive, reaching close to 100$ US per dry tonne FOB. Conversion of biomass to biofuels and “green chemicals” can be achieved through two general approaches which are categorized as “thermo” or “bio” pathways [1, 2]. Conversion of lignocellulosic biomass could also be achieved through a combination of both [3]. The “bio” approach relies on biological conversion of biomass at one point or the other during the process. This approach is somehow at this point limited by three technological challenges which are 1) the isolation of the cellulose and 2) its hydrolysis to glucose. The last technological aspect (3) that has to be considered is the fermentation of cellulosic sugars which may require additional nutriment to be efficient. The first challenge has been overcome for years by the pulp and paper industry although there is actually a need to develop new techniques leading to the production of pulp which will overall lead to cheaper and less water- and chemicals-consuming processes. Many approaches have been considered to isolate cellulose among which different steam treatments and solvent-related process have been thoroughly investigated [4]. Although isolation of cellulose from the biomass matrix could be performed under different conditions, another key to the economic viability of a biorefinery process is the isolation and utilisation of the other macromolecular fractions of the biomass as lignin and hemicelluloses. Although in many cases, the preliminary conversion process will use thermal and chemical energy, some reports have been made in literature on biological pre-treatment to isolate cellulose [4]. The second key technological challenge that needs to be overcome is the hydrolysis of glucose which is a crucial aspect of the production of cellulosic ethanol. Cellulose is composed of a crystalline and an amorphous phase. In most cases of the case, the amorphous phase is the more vulnerable to hydrolysis, chemical and biological as well. The latter usually relays on a mixture of 3 type of enzymes, endoglucanases, exoglucanases (cellobiohydrolases), and βglucosidases [5]. The major problems delaying commercialisation of enzymebased technologies are related on the cost of enzymes. Cellulose is composed of glucose units linked together by acetal bonds and the latter are weaken by acid catalyst. Therefore, utilisation of acid should in theory be an option, although the major problem in this case is the penetration of the acid in the cellulose crystalline and amorphous structure. Such a concept is not applicable since the cellulose macromolecules are oriented so that the polar functional groups are all linked together via hydrogen bonding making the outside section of cellulose highly hydrophobic. Penetration of water would ease the conversion of cellulose to glucose since it would expose the acetal bonds to any type of Lewis acid. Specific compounds can be used to swell cellulose which means that the swelling molecules can “move” between the microfibrils, reach the cellulosic chains and break its hydrogen bonded structure making a hydrogel. Cellulose is therefore less shelled against an attack since the acetal groups are exposed. The compounds that usually allow such specific interactions are usually ionic. This WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

89

brings the issue of removing them before fermentation of the cellulosic sugars to avoid inhibition. Another key aspect is to efficiently remove and recover the ions from the mixture. This paper will discuss the conversion of residual quasi-homogeneous biomass to ethanol. Cellulose has been isolated from the lignocellulosic matrix using the Feedstock Impregnation Rapid and Sequential Steam Treatment (FIRSST) process. The cellulose-rich pulp produced from this process is then hydrolysed to glucose using a non-enzymatic approach involving ionic aqueous solutions. The broth is then purified using a sequential approach with one of the steps being electrodialysis and the remaining sugars fermented to ethanol using industrial grade yeasts. The energy and mass balance of the whole process will be evaluated to see where such a process could be position in comparison to other biological techniques leading to the production of cellulosic ethanol.

2 Experimental 2.1 Feedstock impregnation rapid and sequential steam treatment (FIRSST) Two steps FIRSST process. Scheme of the one step FIRSST process is depicted in Figure 1 below. After extraction of the secondary metabolites the biomass was impregnated with water without any catalyst and was then pressed at 6.8 atm (100 psi) to remove the excess water and leave a saturated fiber. After pressing, the biomass is transferred into the 4.5 litres steam gun where about 200 g (dry basis), of chips were cooked at temperatures from 190 to 220 oC for 2-5 minutes. Delignification was performed on the pulp obtained from the first steam treatment using a solution of NaOH (2-10%wt of the lignocellulosic material). The wet fibrous solids filtered (as per Figure 1) were then washed again with

Figure 1:

Two steps FIRSST process.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

90 Energy and Sustainability III water 5 times using a water/biomass weight ratio of 5/1. The wet biomass was then impregnated with the alkali solution at 6.8 atm (100 psi) for 5 minutes. Delignification was performed at a cooking temperature in the 170-190 oC range for 2–5 minutes with concentration of NaOH ranging from 2 to 10%wt. 2.1.1 Analysis of the fibres The testing methods used to evaluate the fibres produced both using FIRSST pulp and kraft pulp (in terms of comparison) is presented in Table 1 below. Table 1:

Identification of the test and the standard techniques used for characterization of both FIRSST and kraft pulp.

Test Freeness Determination Laboratory Screening of Pulp (PulmacType Instrument) Fibre classification (Bauer-McNett) Fibre Length by Automated Optical Analyzer Using Polarized Light Forming Handsheets for Physical Tests with Pulp Forming Handsheets for Optical Tests with Pulp (British Sheet Machine Method) Grammage Brightness Colour Measurement with a Diffuse/Zero Geometry Tristimulus Reflectometer Opacity Thickness and Apparent Density Internal Tear Resistance Bursting Strength Length of rupture TEA

Standard technique identification ATPPC C.1 ATPPC C.12 ATPPC C.5U ATPPC B.4P ATPPC C.4 ATPPC C.5

ATPPC D.3 ATPPC E.1 ATPPC E.5

ATPPC E.2 ATPPC D.4 ATPPC D.9 ATPPC D.8 ATPPC D.34 ATPPC D.34

2.2 Hydrolysis of the cellulose The method used for cellulose hydrolysis is described in the patent #80685-2 [8]. This method includes an acid pretreatment followed by addition of a source of hydroxide ions. The mixture is then heated to obtain a glucose-rich solution, which is filtered before glucose purification. The hydrolysis yield is calculated by comparison with the ASTM method No E1758-01R07 [9]. Glucose concentration of the filtrate was measured by HPLC, using an Agilent Chromatograph equipped with an RoA-Organic acid (8%) column (Phenomenex) and a refractive index detector. The column was eluted with 5 mM sulphuric acid at a flow rate of 0.6 ml min−1 and maintained at 60°C. WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

91

The injection volume was 30 μl. Sulphate concentration was measured by a colorimetric method [10] and ammonium or sodium concentration, by IC. The apparatus used was a Dionex ICS-3000 ion chromatograph loaded with an IonPac CS12A (2x250mm) and detection was made with electric conductivity. Three identical cellulosic hydrolyses were performed with 46 g of wet cellulose (64% humidity) each. These tests were done in 2 L erlenmeyer and hydrolysed in an autoclave. The solution was filtered in a Buchner with Glass fiber Fisher Brand filter. The three filtrates were then mixed for the purification step which, in these tests, was made by using electrodialysis only. 2.3 Purification of the cellulosic hydrolysate A 3 L mixture of the hydrolysis broth (composed of ~300 g/L sodium sulphate, ~300 g/L sulphuric acid and between 10-20 g/L glucose) was purified using an electrodialysis system. Testing was done at the Energy technology Laboratory (LTE) in Shawinigan, QC. The electrodialysis system used was a CS-O batch system from Asahi Glass Co. The cathode and the anode were of iridium oxide and 4 membranes pairs of 180 cm2 each were used. The experimental conditions were: 30 oC, 150-200 L/h and 20 A fixed (i = 111 mA/cm2). The pH, temperature, conductivity, voltage and intensity were measure automatically at time intervals. Each volume of the three compartments was also measured. 2.4 Fermentation of cellulosic sugars Inocula were prepared using a medium containing 0.07% w/w gluco-amylase, 16 mM ammonium sulphate, 0.01 g/L Lactrol, 20 g/l yeast (Ethanol Red, Fermentis), 60 ml corn mash (32% solids) and 40 ml water was used. The medium was incubated in an Erlenmeyer flask at 32oC, 150 RPM for 4 hours. 4.6 ml (2 g/l of yeast) of the pre-fermentation medium were then added to 200 ml of the purified lignocellulosic sugars. 8 mM ammonium sulphate and 0.01 g/l Lactrol were also added to the fermentation medium. The corn mash used in the pre-fermentation medium provided the necessary trace nutriments. The medium was incubated in 250 ml Erlenmeyer flasks coupled with a fermentation lock at 34.5oC and 150 RPM during 44 hours. Monitoring of the fermentation was made by HPLC, using an Agilent Chromatograph equipped with a RoA-Organic acid (8%) column (Phenomenex) and a refractive index detector.

3 Results and discussion 3.1 Feedstock impregnation rapid and sequential steam treatment (FIRSST) The FIRSST process was shown effective for the isolation of the macromolecular structures from different types of lignocellulosic biomass including hardwood (willow), softwood (balsam and fir) and energy crops (hemp WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

92 Energy and Sustainability III and triticale). Production of pulp via the FIRSST process was of 30%wt (dry mass) for willow [6], 40%wt for softwoods [7], 37%wt for hemp and 34%wt for triticale. Pulp produces contained about 3–6% of lignin and the residual fibre was mostly composed of C6 sugars. Evaluation of the fibres was made both on chemical and mechanical aspects to verify how the severity of the combined steam treatments could be comparable to a classical kraft pulping process. Comparative results are shown in Table 2 below. Table 2:

Mechanical properties of FIRSST pulp and kraft pulp for a species of hardwood (Salix viminalis) and a mixed species of softwood (Abies balsamea and Picea mariana).

Test

H-FIRSST

H-Kraft

S-FIRSST

S-Kraft

ATPPC C.1

409

454

664

721

12.7

0.16

5.58

0.11

0.39

0.41

2.08

2.56

60.9

60.1

59.6

61.0

24.7

33.3

24.8

27.6

64.22 2.82 13.26 99.6

71.45 2.18 12.42 99.5

67.26 4.41 18.31 98.5

69.36 4.12 17.43 99.3

2.17

1.79

2.24

2.36

4.09

3.14

8.04

25.9

1.35

1.56

3.05

2.28

2.78

4.24

5.03

3.87

15.6

19.6

37.8

22.9

± 1 mL

ATPPC C.12 ± 0.01%

ATPPC B.4P ± 0.01 mm

ATPPC D.3 ± 0.1 g/m2

ATPPC E.1 ± 0.1%

ATPPC E.5 L* ± 0.01 a* ± 0.01 b* ± 0.01 ATPPC E.2 ± 0.1%

ATPPC D.4 ± 0.01 cm3/g

ATPPC D.9 ± 0.01 mN*m2/g

ATPPC D.8 ± 0.01 kPa*m2/g

ATPPC D.34 ± 0.01 km

ATPPC D.34 ± 0.1 J/m2

Results shown in Table 2 show that for hardwood and softwood, two steps steam treatment allowed the isolation of a high quality fibre. These fibres showed less resistance to mechanical stress but showed overall better optical properties. Overall, the FIRSST process allowed the production of fibres that could be converted either to pulp or hydrolysed to glucose depending on market potential. 3.2 Hydrolysis of the cellulose The cellulosic hydrolysis yields obtained were 96, 83 and 88%, and the average glucose concentration was 10 g/L. These yields can be maximized by changing WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

93

Cellulosic hydrolysis yields (%)

100

80

60

40

20

0 0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

H+/NH3 or H+/OH- molar ratio

Cellulosic hydrolysis yield versus H+/OH- or H+/NH3 molar ratio.

Figure 2:

900 800

Sodium sulfate in dilua te

700

Mass (g)

600

Sodium sulfate in Concentra te

500 400

Sulfuric a cid in Diluate

300 200

Sulfuric a cid in Concentrate

100 0 0

2

4

6

8

10

Time (h)

Figure 3:

Composition of the diluate and of the concentrate vs. time for the electrodialysis purification.

some parameters, proven by laboratory tests realised to optimise cellulosic hydrolysis.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

94 Energy and Sustainability III 3.3 Purification of the cellulosic hydrolysate Purification of the mixed hydrolysate by electrodialysis leaded to a solution composed of 4.3 g/L sodium sulphate and 1.9 g/L sulphuric acid with glucose. The separation concentrates the glucose solution by a factor of 4.7. With the use of AMV and CMV Selemion membranes (Asahi Glass), it is possible to keep around 95% of the glucose in the diluate. Presence of glucose did not seem to foul the membranes over the time duration of the preliminary process design steps. Figure 3 presents the composition in sulphuric acid and sodium sulphate of the different compartments versus time: Due to the voltage increase caused by high ionic concentration in the concentrate (223 g/L sodium sulphate and 126 g/L sulphuric acid)-which means a depletion of the ionic content in the diluate-, the solution in the compartment was replaced by a 50 g/L sodium sulphate solution after 5.7 h of purification. The energy demand was calculated to 0.57 kWh/kg of separated ions, corresponding to 26 kWh/kg of glucose recovered. Another purification by electrodialysis was realised with a solution containing ammonium sulphate instead of sodium sulphate. This purification had an energy demand of 0.52 kWh/kg of separated ions, corresponding to 24 kWh/kg of glucose. 90% current efficiency was calculated for the test with sodium sulphate and 92% with ammonium sulphate. Since the electrical demand is too high translating into an excessive energy cost per kg of glucose, separation of the ions will have to be done by a combination of less energy intensive steps followed by a final electrodialysis step. 3.4 Fermentation of cellulosic sugars 2 ml of the fermentation medium were withdrawn after 2, 22 and 44 hours in order to be analysed for ethanol and glucose content, as well and acetic and lactic acid content. The results shown are the mean of duplicates. The progress of the alcoholic fermentation is shown in Figure 4.

Figure 4:

Alcoholic fermentation progress of Ethanol Red Saccharomyces cerevisiae yeasts in lignocellulosic sugars medium.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

95

Yields of .46 g/g, an efficiency of 90.1% and a consumption of 100% of the glucose were achieved after 44 hours. No methanol was produced during the fermentation (data not shown). Inhibitors such as acetic acid and lactic acid were also quantified. Table 3 shows the inhibitor composition of the medium through the fermentation. Table 3:

Major fermentation inhibitor concentration through an alcoholic fermentation by Ethanol Red Saccharomyces cerevisiae yeasts. Time (h) 0 2 22 44

[lactic acid] mg/l < 100 < 100 < 100 < 100

[acetic acid] mg/l < 100 < 100 501.0 503.6

Table 3 shows an increase in acetic acid concentration after 22 hours as a byproduct of the yeast growth. An acetic acid concentration of .05% (w/v) is considered to have no influence on the yeast growth [11]. The results show that no major inhibitor is in a sufficient concentration to inhibit the yeast fermentation throughout the whole process.

4 Conclusion The Feedstock Impregnation Rapid and Sequential Steam Treatment (FIRRST) was shown to be suitable not only for the isolation of the cellulosic matrix but also to produce a high quality pulp that could have a potential for paper production. Results have shown that cellulose can be hydrolysed at 90%+ using a strong ionic solution and that this solution could be purified using membrane technologies. Following treatments, the residual glucose solution can easily be fermented with common yeasts to produce cellulosic ethanol. Key for the economics of this approach will be to optimise the energy consumption for the separation process and recovery of ions.

References [1] Damartzis, T., Zabaniotou, A. (2011) Thermochemical conversion of biomass to second generation biofuels through integrated process design – A review Renewable & Sustainable Energy Reviews (2011), 15(1), 366378. [2] Brethauer, S., Wyman, C.E. (2010) Review: Continuous hydrolysis and fermentation for cellulosic ethanol production. Bioresource Technology, 101(13), 4862-4874. [3] Datta, R., Basu, R., Grethlein, H.E., Baker, R.W., Huang, Y. (2009) Ethanol recovery process and apparatus for biological conversion of syngas WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

96 Energy and Sustainability III

[4]

[5]

[6]

[7]

[8]

[9]

[10] [11]

components to liquid products. PCT Int. Appl. WO 2009108503 A1 20090903. Zhu, J. Y., Pan, X., Zalesny, R.S. (2010) Pretreatment of woody biomass for biofuel production: energy efficiency, technologies, and recalcitrance. Applied Microbiology and Biotechnology, 87(3), 847-857. Dashtban, M., Maki, M., Leung, K.T., Mao, C., Qin, W. (2010) Cellulase activities in biomass conversion: measurement methods and comparison. Critical Reviews in Biotechnology, 30(4), 302-309. Lavoie, J.-M., Capek, E., Gauvin, H., Chornet, E. (2010) Production of pulp from Salix viminalis energy crops using the FIRSST process. Bioresource Technology, 101(13), 4940-4946. Lavoie, J.-M., Capek, E., Gauvin, H., Chornet, E. (2010) Production of quality pulp from mixed softwood chips as one of the added value product using the FIRSST process in a general biorefinery concept. Industrial and Engineering Chemistry Research. 2010, 49 (5), 2503-2509. Chornet, E., Chornet, M., Lavoie, J.-M. (2008) Conversion of cellulosic biomass to sugar. US Provisional Patent Application 80685-2 filed Oct 8, 2008. ASTM International (2007). Standard test method for determination of carbohydrates in biomass by high performance liquid chromatography. In 2008, Annual book of ASTM standards, p.1113-1117. HACH (2002). Modèle DR2500, Spectrophotomètre de laboratoire, Procédures, Sulfate, Méthode 8051, p.1-7. Narendranath NV, Thomas KC, Ingledew WM. (2001) Effects of acetic acid and lactic acid on the growth of Saccharomyces cerevisiae in a minimal medium. Journal of Industrial Microbiology and Biotechnology, 26(3), 171-7.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

97

On the future relevance of biofuels for transport in EU-15 countries A. Ajanovic & R. Haas Energy Economics Group, Vienna University of Technology, Austria

Abstract The discussion on the promotion of biofuels in the EU-countries is ambiguous: benefits like reduction of greenhouse gas emissions and increase of energy supply security are confronted with high costs and bad ecological performance. On the one hand the EU has set the goal of reaching 10% biofuels by 2020. On the other hand there are continuous persisting discussions to undermine this goal. The core objective of this paper is to investigate the market prospects of biofuels for transport in the EU-15 in a dynamic framework till 2030. While the economic prospects for the 1st generation of biofuels are rather promising – cost-effectiveness under current tax policies exists already – their potentials are very restricted especially due to limited crops areas. Moreover, the environmental performance of 1st generation biofuels is currently rather modest. 2nd generation biofuels will –in a favourable case – enter the market between 2020 and 2030. However, their full potentials will be achieved only after 2030. Keywords: biofuels, costs, potentials, CO2-emissions.

1 Introduction The discussion on the promotion of biofuels is ambiguous: benefits like reduction of greenhouse gas emissions and increase of energy supply security are confronted with high costs and bad ecological performance. Great hopes are currently put on biofuels 2nd generation. The major advantage of the 2nd generation of biofuels is that they can also be produced from resources such as ligno-cellulose based wood residues, waste wood or short-rotation copies, which are not dependent on food production-sensitive crop areas. The core objective of this paper is to investigate the market prospects of biofuels for transport in the EU-15 in a dynamic framework till 2030. This work WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESUS110091

98 Energy and Sustainability III extends the analysis conducted in Ajanovic and Haas [1]. With respect to the literature the most important analyses are summarized by Panoutsou et al. [2] and Ajanovic and Haas [3]. We consider the following categories:  

Biofuels 1st generation: biodiesel from rapeseed, sunflowers, soybeans (BD-1); bioethanol from maize, wheat, sugar beet (BE-1); biogas (BG1) from manure, grass and green maize. Biofuels 2nd generation: biodiesel from biomass-to liquids (BTL) with Fischer-Tropsch process (BD-2); bioethanol from lingo-cellulose (BE2); biogas (BG-2) from synthetic gas from biomass.

These biofuels are analysed with regard to potentials, costs and market prospects, and the environmental impacts. This analysis is based on:   

possible developments of fossil energy price levels and energy demand; technological learning effects (based on global developments); environment, energy and transport policies on EU level.

2 Method of approach The method of approach of our analysis consists of the following major steps: 2.1 Assumptions Major assumptions for the modelling analysis are:  Increases in fossil fuel prices are based on IEA [4].  The development of alternative fuel costs is based on international learning rates of 25% and national learning rates of 15% regarding the investment costs of theses technologies.  International learning corresponds to world-wide quantity developments in the Reference Scenario (RS) and the Alternative Policy Scenario (AS) in IEA [4] up to 2030.  All cost figures are in prices of 2008.  No explicit carbon costs are included.  Regarding the future land use we have assumed that maximal 30% of arable land, 10% of pasture land, 10% of meadows and 3% of wood and forest wood residues could be used for feedstock production for biofuels by 2030. Additional 5% of wood industry residues could be used for biofuels production. 2.2 Calculation of biofuel costs Next the biofuel production costs are calculated. We consider the following components are considered to calculate the costs of biofuels (see also Ajanovic and Haas [1]):  Net feedstock costs (CFS)  Gross conversion costs (GCC) WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

 

99

Distribution and retail costs (DC) Subsidies for biofuels (SubBF)

Firstly, the feedstock costs are identified for every year as the minimum production costs of all possible feedstocks considered for a specific area category (e.g. crop area) as: C FSt  Min(C FSi _ t ; i  1...n) n… number of possible feedstocks Finally total biofuel production costs (CBF) for year t are calculated as follows (note, that in these analyses no explicit carbon costs are included):

CBF  CFS  GCC  DC  SubBF 2.3 Considering technological learning Future biofuel production costs will be reduced through technological learning. Technological learning is illustrated for many technologies by so-called experience or learning curves. In our model we split up specific investment costs ICt(x) into a part that reflect the costs of conventional mature technology components ICCon_t(x) and a part for the new technology components ICNew_t(x).

ICt ( x)  ICCon _ t ( x)  ICNew _ t ( x) For ICCon_t(x) no more learning is expected. For ICNew_t(x) we use the following formula to express an experience curve bys using an exponential regression:

ICNew _ t ( x)  a  xt where: ICNew_t(x) xt b a ICCon_t(x)

b

Specific investment cost of new technology components (€/kW) Cumulative capacity up to year t (kW) Learning index Specific investment cost of the first unit (€/kW) Specific investment cost of conventional mature technology components (€/kW).

2.4 Maximum additionally usable areas Then, for every area category considered, the maximum additional feedstock area per year (AFS_ADDt) is calculated as:

AFS _ ADD _ t   ( AFS _ MAX _ t  AFS _ t 1 ) with φ … maximum percentage to be added or reduced per year.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

100 Energy and Sustainability III 2.5 Actual additional areas used Additional feedstock areas are used for biofuels under the following conditions: AFS _ t  AFS _ t 1  AFS _ Addt CBFt (CFSt )[1   BF ]  pFFt [1   FF ]

where τBF τFF pFF

tax on biofuels tax on fossil fuels price of fossil fuels (excl. tax).

In contrast, the feedstock area is reduced when

AFS _ t  AFS _ t 1 (1   ) CBFt (CFSt )[1   BF ]  pFFt [1   FF ] 2.6 Assigning feedstock areas to biofuel categories Feedstocks as well as feedstock areas may also be used for different biofuel categories. For example, some crop areas are suitable for oilseeds for 1st generation biodiesel (BD-1), for wheat for 1st generation bioethanol (BE-1) and for corn stover for 2nd generation bioethanol (BE-2). In this case the feedstock potentials or the feedstocks’ area are dedicated to the biofuels category which leads to the cheapest production costs per kWh biofuel:

C FSt  Min(C FS j _ t ; j  1...m) m… number of possible biofuels categories

3 Potential In the following we present the results of cost development and corresponding quantities produced for 1st and 2nd generation biofuels in EU-15 up to 2030. These alternative energy carriers are based on bioenergy resources. An increasing use of biomass in the future in Europe could raise basically two questions: (i) the use of biomass requires large amounts of land which otherwise could be used for other purposes (e.g. food production); (ii) increasing biomass production might be in contradiction with sustainable issues. The total land area in EU-15 is about 313 Mill. hectares. This total land area could be divided in five groups: arable land (23%), permanent crop (3%), permanent meadows and pastures (16%), forest area (39%) and other land (19%), see Figure 1. The conventional biofuels are based on the feedstocks grown on arable land, which is very limited in EU-15, 71 Mill. hectares. In this analysis we assume that a maximum of 30% of all arable land, about 21 Mill. hectares, can be used for growing biofuels. Of this area a maximum of 20%, about 4 Mill. hectares, can be used for growing oil seeds. WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

101

Arable land 23%

Other land 19%

Permanent crops 3%

Permanent meadows and pastures 16%

Forest area 39%

Figure 1:

Land area in EU-15, 2008 [5].

Total energy from biofuels (TWh)

800 700 600 500 400 300 200 100 0 2000

2005 BD-1

Figure 2:

2010 BE-1

2015 Biogas-1

2020 BD-2

2025 BE-2

2030 BG-2

Total energy from biofuels by biofuels category.

However, with the second generation of biofuels, other land areas such as meadows, pastures and forest area could also be used for biofuels production, so that total land potential for alternative energy carriers could be significantly higher. Due to the EU targets regarding biofuels share in total transport fuel consumption could be expected that total energy from biofuels by 2030 could be significantly higher than now. As shown in Figure 1 total energy from biomass in 2030 could be more than three times higher than now, 720 TWh. After about 2023 a significant and WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

102 Energy and Sustainability III

Total crop area for biofuels by category (Mill hectares/yr)

continuously increasing share of the 2nd generation bioethanol could be noticed. The share of 2nd generation biodiesel could be significant starting from 2027 due to the lower costs than conventional diesel, see Figure 6. The increasing biofuels production based on domestic produced feedstock will occupy additionally land use, see Figure 3. However, for 2nd generation biofuels mainly non-crop area dependent resources will be used. These are: straw, waste wood and wood residues from the industry. Due to the switch to the 2nd generation biofuels up to 2030 also significant poplar areas will be used for feedstock production, see Figure 4. Total land area for biofuels production by 2030 will be 64.2 Mill. hectares. 25

20

15

10

5

0 2000

2005

BD-1

2010

BE-1

Figure 3:

2015

Biogas-1

2020

BD-2

2025

BE-2

2030

BG-2

Total area for biofuels by biofuels category.

Areas for biofuels (Mill hectares/yr)

25

20

15

10

5

0 2000

2005

2010 Oil seeds

Figure 4:

2015

Other arable land

2020 Grass

Poplar

2025 Forest

Other

Areas for biofuels by area type.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

2030

Energy and Sustainability III

103

4 Costs The following Figures 5 and 6 depict the corresponding development of production costs (inclusive and exclusive of 20% VAT) and the prices of fossil fuels, gasoline and diesel, inclusive and exclusive of taxes.

Gasoline & Bioethanol (€/kWh)

0.2 0.18 0.16 0.14 0.12 0.1 0.08 0.06 0.04 0.02 0 2000

2005

2010

2015

2020

2025

2030

Gasoline (excl. Taxes)

Gasoline (incl. Taxes)

Bioethanol 1st (excl. Taxes)

Bioethanol 1st (incl. Taxes)

Bioethanol 2nd (excl. Taxes)

Bioethanol 2nd (incl. Taxes)

Figure 5:

Price versus costs of gasoline and bioethanol.

Diesel & Biodiesel (€/kWh)

0.25

0.2

0.15

0.1

0.05

0 2000

2005

2010

Diesel (excl. Taxes) Biodiesel 1st (incl. Taxes)

Figure 6:

2015

2020

Diesel (incl. Taxes) Biodiesel 2nd (excl. Taxes)

2025

2030

Biodiesel 1st (excl. Taxes) Biodiesel 2nd (incl. Taxes)

Price versus costs of diesel and biodiesel.

As can be seen from Figure 5 and Figure 6 the costs of 1st generation biofuels are decreasing only slightly even in the most favourable scenario. The major cost reduction is caused by learning effects for capital costs.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

104 Energy and Sustainability III As described above, these learning effects are trigged mainly by international learning. They are in our work based on the quantities development in the Referent (RS) and Alternative Policy Scenario (AS) of IEA [4]. The major results of this analysis are: (i) 2nd generation bioethanol will become competitive when including current tax schemes by about 2020, see Figure 5; (ii) Biodiesel (BD-2) will compete with fossil diesel only close after 2025, see Figure 6; (iii) Yet, if no taxes are considered, neither 1st nor 2nd generation bioethanol will be cheaper then fossil fuels before 2030. Close before 2030 biodiesel 1st generation could become competitive with fossil diesel without tax exemptions.

2030

AS

2010

RS

-0.02

0.00

0.02

0.04

0.06

0.08

0.10

0.12

Costs of 1st gen. bioethanol (EUR/kWh BE-1) Feedstock costs Energy costs Marketing & Distribution

Figure 7:

Capital costs Other O&M costs Subsidies

Labour costs Credits

Costs of 1st generation bioethanol (2010 vs. 2030).

2030

AS

2010

RS

-0.02

0.00

0.02

0.04

0.06

0.08

0.10

Costs of 1st gen. biodiesel (EUR/kWh BD-1) Feedstock costs

Capital costs

Labour

Energy costs

Other O&M costs

Credits

Marketing & Distrib.

Subsidies

Figure 8:

Costs of 1st generation biodiesel (2010 vs. 2030).

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

0.12

Energy and Sustainability III

105

Figures 7 and 8 depict the underlying detailed cost structures. It can be seen that the largest part of the total biofuels costs are feedstock costs. In the future, the major cost reduction could be caused by capital costs. But the actual cost differences between RS and AS are rather small.

5 Environmental performance A very sensitive issue with respect to the future relevance of biofuels is their energetic and environmental performance. Forest Wood

2nd gen. biofuels Waste Wood Wheat,NG GT + CHP;DDGS as fuel Wheat,NG GT + CHP;DDGS as AF

1st gen. biofuels

Sugar beet,pulp to heat Sugar beet,pulp to fodder Gasoline 0

20

40

60

80

100

120

140

160

180

WTW GHG g CO2eq./km

Figure 9:

Bioethanol: total WTW GHG emissions [6].

Syn-diesel: Forest Wood

2nd gen. biofuels Syn-diesel: Waste Wood SME, Gly as animal food SME, Gly as chemical

1st gen. biofuels

RME, Gly as animal food RME, Gly as chemical Diesel 0

20

40

60

80

100

120

140

WTW GHG g CO2eq./km

Figure 10:

Biodiesel: total WTW GHG emissions [6].

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

160

106 Energy and Sustainability III

CO2-equ. emissions from biofuels (Mio tons)

The range of the GHG emissions is very wide due to the different production technology, different feedstocks and the way of using by-products. As shown in Figure 9 and Figure 10 conventional biofuels have moderate reduction of GHG emissions. Higher GHG emission reductions could be achieved in case of byproducts being used as fuel instead of as animal feed. However, GHG emission reductions for the 2nd generation biofuels could be much higher, mostly because these processes use part of the biomass intake as fuel and therefore involve less input of fossil energy [7]. The CO2 emissions profile of biofuels production depends very much on the type of feedstock used and the production process. With the increasing use of 100 90 80 70 60 50 40 30 20 10 0 2000

2005

2010 BD-1

CO2 savings due to biofuels (Mio tons CO2equ)

Figure 11:

BE-1

2015 Biogas-1

2020

BD-2

BE-2

2025

2030

BG-2

CO2-eq emissions from biofuels [7].

100

80

60

40

20

0 2000

2005

2010 BD-1

Figure 12:

BE-1

2015 Biogas-1

2020 BD-2

BE-2

2025 BG-2

CO2 savings in EU-15 due to biofuels [7].

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

2030

Energy and Sustainability III

107

biofuels in EU-15 total emission from biofuels will be in 2030 significantly higher than now, about 83 Mill. tons CO2-eq, see Figure 11. However, using biofuels considerable CO2 saving in EU-15 could be noticed, see Figure 12. An increase in CO2 saving after 2026 is due to the increasing share of biofuels 2nd generation. In this context it is very important to state that it has to be ensured by monitoring and certification processes that the ecological performance of biofuels 1st generation improves continuously.

6 Conclusions The major conclusions are: 

 





Under current policy conditions – mainly exemption of excise taxes – the economic prospects of biofuels 1st generation in Europe are rather promising; the major problems of biofuels 1st generation are lack of available land for growing proper feedstocks and the modest ecological performance; the indigenous potentials for BF-1 in EU-15 are limited at a level of about 2 to 3 times the volume of today (without endangering food supply and without imports of feedstocks for biofuels like palm oil); The environmental performance of the 1st generation biofuels is currently rather modest; Biofuels 1st generation will reach their maximal potential by about 2020. Since up to 2030 they are still cheaper than 2nd generation biofuels they will remain in the market at least until 2030 without significant reductions. Large expectations are put into advanced 2nd generation biofuels production from ligno-cellulosic materials like whole plants, wood and wood residues; So the major advantage of BF-2 is that the potential will be significantly higher at levels of more than ten times of today’s BF production; (vi) Regarding the future costs of BF-2 it can be stated that in a favourable case by 2030 they will be close to the costs of BF-1; So by 2030 in Europe neither for BF-1 nor for BF-2 significantly lower costs can be expected. Yet, if prices of fossil fuels continue to increase at least slightly given current tax policies BF-1 will become competitive already in the coming years, BF-2 about a decade later. 2nd generation biofuels will – in a favourable case – enter the market between 2020 and 2030. However, their full potentials will be achieved only after 2030.

References [1] Ajanovic A., Haas R., Economic Challenges for the Future Relevance of Biofuels in Transport in EU-Countries. Energy 35 (2010) 3340–3348

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

108 Energy and Sustainability III [2] Panoutsou C., Eleftheriadis J., Nikolaou A., Biomass supply in EU27 from 2010 to 2030, Energy Policy 37 (2009) 5675–5686 [3] Ajanovic A., Haas R., The future relevance of alternative energy carriers in Austria. IEESE-5, June 2010, Denizli, Turkey [4] IEA.World Energy Outlook 2009. International Energy Agency, Paris, 2009 [5] FAOSTAT, 2010, http://faostat.fao.org [6] CONCAWE, EUCAR, JRC EU Commission. Well-to-Wheels report, 2007 [7] Ajanovic A. ed., Deriving effective least-cost policy strategies for alternative automotive concepts and alternative fuels-ALTER-MOTIVE, 2011, www.alter-motive.org

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

109

Biomass char production at low severity conditions under CO2 and N2 environments G. Pilon & J.-M. Lavoie Département de génie chimique et génie biotechnologique, Université de Sherbrooke, Canada

Abstract In a perspective of biomass value addition, biomass char, a thermochemical product, long time considered as a residue, is now getting attention and may represent a vector in the sustainability of the whole biomass sector. Some char types were shown to have great potential as a solid fuel or precursor for further transformations as well as having attributes for storage and transportation. Other types showed potential as a soil carbon sequestration technique and soil amendment enhancing biomass yields. Depending on several factors, but mostly on biomass and production conditions, biomass char physico-chemical characteristics may vary tremendously. Therefore, in order to be used in accordance for specific utilizations, its characteristics must be carefully understood and controlled. In this study, chars with varying properties were produced in a custom-made lab-scale fixed bed reactor. Along these experiments, various biomass chars were produced under CO2 and N2 for temperatures of 300 and 500 °C. Char was produced from switchgrass (Panicum virgatum L.) an energy crop grown in Canada. It was then characterized for ultimate and proximate analysis as well as for calorific value. In addition, specific surface was characterized by Brunauer-Emmett-Teller (BET) technique. Char organic content composition was verified by Soxhlet extractions using dichloromethane and extracts were analysed by GC-MS. Keywords: BET, biochar, biomass, bio-oil, char, CO2, pyrolysis, torrefaction.

1 Introduction Biomass char refers to biochar with respect to soil amendment, and to charcoal when referring to the charred organic matter used as a source of energy WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESUS110101

110 Energy and Sustainability III (Lehmann and Joseph [1] and McLaughlin et al. [2]). The latter has been shown to be a potential soil amendment that would enhance biomass production/hectare. It was also shown to have positive effects on soil health as well as being able to store carbon for reduction of CO2 emission (Gaunt and Lehmann [3] and Lehmann [4]). Another application, potentially complementary to soil amendment [5], stated that biomass char also had potential to provide the required heat for pyrolysis’ endothermic reaction along bio-oil production. Furthermore, it was shown to be advantageous as a feedstock for combustion or for syngas production through gasification (Boateng [6] and Uslu et al. [7]). Biomass char can be obtained through different thermochemical processes operating at low oxygen content using varying degree of severity. In chronological order of severity, torrefaction, slow and fast pyrolysis and gasification are processes under which biomass char can generally be obtained. Torrefaction can be defined as the conversion of lignocellulosic material occurring without oxygen, within a temperature range of 200 to 300 °C at atmospheric pressure (Prins et al. [8] and Uslu et al. [7]). It consists mostly in hemicellulose degradation resulting in a solid material with low moisture content, hydrophobic properties and high calorific value if compared to original biomass. Most likely, biomass char obtained under torrefaction may not meet biochar stable soil characteristics since original biomass requires sufficient temperature (≥300 °C) in order to produce carbonized material with modified chemical bonds, which are less likely biodegradable (McLaughlin et al. [2]). Slow pyrolysis operates usually at temperature between 300 and 500 °C, at heating rates lower than 2 °C/s and long residence time (min to days), conditions that were shown to enhance char production over non-condensable gases and oil. Fast pyrolysis operates at higher heating rate (up to 10 000 °C/s), shorter residence time (<1s to 30s) and enhances biooil over char and non condensable gases yields (Brewer et al. [9] and Mohan et al. [10]). Gasification conditions operate with low-mid level of oxygen, yielding generally to about 5-10% biomass char. Despite their lower char production yield compared with slow pyrolysis, the potential of fast pyrolysis and gasification char were recently considered as having a soil amendment potential (Brewer et al. [9]). Biochar physico-chemical properties vary to a large extent depending on a multitude of factors, especially the reacting conditions at which it is prepared (Joseph et al. [11]). The operating parameters that have been reported to influence its properties are the heating rate, the highest operating temperature, the pressure, the reaction residence time, the reactor design, the biomass pretreatments, the flow rate of inputs and the post treatments (Downie et al. [12]). Among these numerous factors, temperature is considered one of the most important factors affecting char properties as it provides the necessary activation energy of the implied reactions, furthermore it influences physical changes as volatilization and structural melts. Studies on wood showed that the three main biomass components have been reported to decompose at temperature ranging from 200 – 325 °C for hemicelluloses, from 240 to 375 °C for cellulose and from 280 to 500 °C for lignin (Prins et al. [8] and Downie et al. [12]). Demirbas [13] studied carbonization (medium rate pyrolysis at 10 °C/s) for several agricultural WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

111

and forest residues, for temperatures ranging from 300 to 900 °C. For every feedstock, solid products were found to decrease, gases increased and liquid fractions decreased, furthermore, higher heating values (HHV) were also found to increase for increasing temperature. Pyrolysis gaseous environment also plays a major role. Conventionally, pyrolysis operates within an environment free of oxygen, therefore using inert gases such as nitrogen. CO2 is also an inert gas at room temperature, however, increasing temperature, CO2 becomes reactive and tends to react with carbon char through the reverse-Boudouard reaction, eqn (1). C + CO2 → 2 CO

(1)

There are numerous thermochemical processes that could take beneficial advantage of using CO2. In combustion field, especially in coal industry, the Oxyfuel Technology which consists of using flue gases with pure oxygen (CO2, H2O and O2) instead of air (N2, O2, CO2 and H2O) appears as a promising technology especially from output CO2 purity and sequestration point of view (Buhre [14]). In addition, use of flue gases as a gas source contains residual heat which is beneficial for energy flows within the overall process (Butterman and Castaldi [15]). In gasification, use of CO2 to enhance Boudouard reaction and CO formation for syngas production is also a common practice. In physical activation of char for activated carbon, CO2 is the medium used for surface area and pore enhancement. Physical activation is usually done at temperature around 900 to 1200 °C (Jindarom et al. [16]). In the presence of CO2, char yield is usually reduced towards formation of volatiles (Minkova [17] and Butterman and Castaldi [15]). Jindarom et al. [16] observed that for temperatures around 350 to 750 °C, the use of CO2 in comparison of N2 resulted in chars with higher char specific surface and basicity levels. High specific surfaces as well as high porosity are two desired characteristics for soil amendment applications since it may represent a favourable site for beneficial microorganisms proliferation as well as an exchange surface for nutrient retention or water absorption attributes (Lehmann and Joseph [1]). Under pyrolysis conditions, specific surface was observed to reach peak values at temperatures varying from 350 to 700 °C depending among a few factors, such as biomass types (Sharma et al. [18] and McLaughlin et al. [2]). Decrease in specific surface area at higher temperature was attributed, by some researchers, to melts in char structure. Increasing retention time was also shown to increase porosity since it allowed most volatilization reactions to reach completion. As for the heating rates, lower heating rates would allow volatile release with less morphological changes, therefore maintained natural porosity in comparison with higher rates which would even lead to morphological transformation of cell structure (Downie et al. [12]). In this research, char was prepared from switchgrass (Panicum virgatum). Switchgrass was chosen due to its beneficial characteristics as an energy crop such as its hardiness in harsh climate conditions and poorer soils (He et al. [19] and Martel and Perron [20]). In a first step, a homemade fixed bed reactor was WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

112 Energy and Sustainability III tested along specific conditions simulating a high heating rate reactor operating under N2 atmosphere. In a second step, the same reactor was then operated at lower heating rate, but adding new atmosphere conditions, first under N2 and secondly under CO2. Temperature, heating rate and gas atmosphere were the two main parameters studied and their effect on char physico-chemical characteristics was analysed. Char obtained was characterized for proximate and ultimate analyses, for BET as well as for its calorific value. Some of the chars organic content compositions were verified by Soxhlet extractions using dichloromethane and extracts were analysed by GC-MS. Bio-oil yield was also verified and the ones from slow heating rate were analyzed by GC-MS.

2 Materials and method 2.1 Biomass Switchgrass (panicum virgatum) Cave-in-Rock specie utilized for the experiments was grown in the Eastern Township region of Quebec, Canada. The crop was grown in a clay soil and had a 1.5 years root system. The feedstock was harvested in Fall (November 2009) at moisture content below 10% in 500 kg bales and stored in open structures protected from rain. Switchgrass samples used for experiments were maintained in unsealed plastic bags at room temperature (20-25 °C). 2.2 Experimental setup For experimentations, a lab scale fixed bed pyrolysis reactor was used. It consists in a stainless steel (SS) cylindrical reactor of 26.6 mm ID and 0.44 m length installed in a 2400W electric tube furnace mounted vertically. Biomass is added to reactor using a biomass carrier, fig. 1. The latter is 13 cm long, 25 mm OD in diameter and is made of stainless steel. Carrier’s top, bottom and along the length is partially opened in order to allow gas flow through its structure. A wire mesh is installed within the carrier to retain the biomass from falling down. Reactor’s entrance is controlled via a gate valve equipped with a motor for a quick control. During the first experimental tests operating at higher heating rate, a preheater installed underneath the reactor was used in order to preheat the biomass carrier at reactor’s temperature. The carrier has a top opening in order to fill it with biomass. The action of filling the reactor and taking it into the reactor is done for every test in less than 10 s. During the second step of experiments, at lower heating rates, preheater for biomass carrier was not used. Biomass carrier is attached to a thermocouple (T/C), which serves as a rod to move it into the reactor. The T/C also provides an indication on temperature progress within biomass carrier. Nitrogen and carbon dioxide are the two gas vectors utilized while also serve to enhance heat and mass transfer between gases and feedstock. Gas flow input is maintained at 0.115 L/s (STP: 101.3kPa – and 25 °C) for every tests and is WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

113

controlled by a flowmeter before entering the reactor. The flowmeter is calibrated with respect to each gas. Nitrogen gas and CO2 are respectively preheated before entering the reactor using an inline gas heater and while passing in the annulus region between reactor and tube furnace. Gases and volatiles exiting the reactor pass by a heated line maintained around 200 °C +/- 25 °C before being diverted to an exhaust system. For pyrolysis vapours mass balance, vapours are collected within two consecutive glass condensers; both are kept within isothermal container filled with dry ice. Pyrolysis gases are obtained by difference from char and condensable liquid yields. Real time temperature monitoring is done on the overall system using National Instrument Data Acquisition System NI cDAQ-9172 equipped with Labview software. Thermocouples are positioned all along the system as shown in figure 1. In figure 1, T corresponds to thermocouples, where T1 refers to biomass carrier, T2 to gas outlet, T3, T4 and T5 to annulus region between tube furnace and reactor, T6-T9 to outlet gas line, inside and at surface temperature and T10 at gas inlet to monitor gas inlet temperature. Pressure (P1, fig. 1) is

Figure 1:

Schematic representation of the experimental setup.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

114 Energy and Sustainability III verified at reactor exit using a mechanical pressure gauge in order to maintain an absolute pressure close to 101.3 kPa in the reactor. 2.3 Biomass char production and products mass balance Biomass was first cut into pieces shorter than 10 cm and humidity level, which ranged between 4 and 10%, was monitored all along the char production periods. Typically one gram of switchgrass was inserted in the biomass carrier per batch. For each batch operating at higher heating rates, the biomass carrier was first preheated until reaching reactor’s temperature, before being rapidly filled with biomass and inserted in the core of the reactor. This resulted in an almost instantaneous heat up of biomass. Gas environment used at higher heating rate is N2. At lower heating rate, a comparison between N2 and CO2 was done. In these latter conditions, the biomass carrier was not preheated, biomass was inserted in the carrier, approached to reactor’s opening to flush air and rapidly entered within the reactor. Biomass is kept in reactor for a desired residence time of 2.5 minutes, after what it was removed from the reactor, emptied, its content cooled down within a desiccator and transferred within hermetic containers until further analysis. Along experiments at high heating rate, time was monitored from the moment the biomass was inserted in the preheated carrier. For moderate heating rates, time was counted once the temperature reading indicated the desired temperature. It took about 7.5 and 9.5 min. to reach 500 and 300 °C respectively for slow heating rates conditions. For all batches, tube furnace was maintained at a fixed temperature. Chars were produced at 300 and 500 °C +/- 10°C. Chars produced for specific conditions were mixed together before analysis. For moderated heating rate only, a mass balance on products was performed. Bio-oil was collected using condensers and non-condensable gases were determined by difference. 2.4 Feedstock characterization 2.4.1 Proximate analysis and calorific value Char as well as original feedstock were both characterized for ash content and volatile content following ASTM E1755-01 and ASTM E 872 methods. Fixed carbon was determined by difference from the ash and volatile content. Higher heating value (HHV) was determined using an oxygen bomb calorimeter; Model 1341 from Parr company. 2.4.2 Organic elemental analysis For CHON organic elemental content analysis, finely powdered feedstock was analyzed using a Leco TruSpec Micro CHNS equipped with the TruSpec Micro Oxygen Add-On Module for oxygen analysis. 2.4.3 BET analyses Biomass samples were first sieved and the range between 40-60 mesh was used for BET analyses. Surface area characterization was performed using Micromeretic physical adsorption apparatus, ASAP 2020, using nitrogen WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

115

adsorption based on BET theory. Degas conditions were done under vacuum from an initial heating rate of 10 °C/min up to a temperature of 110 °C kept for a minimum of 16 hours. 2.4.4 Organic components, extractions and GC-MS analysis Char Organic components extraction was done using Soxhlet. These tests were conducted on high heating rate chars only. Prior to Soxhlet extractions, char was grinded to a fine powder. For each extraction, one gram of char was placed in Whatman cellulose cartridges of (25 mm ID X 90 mm) and extracted with 150 ml of dichloromethane. The solution was concentrated using roto-evaporator. Biooils obtained from slow heating rate conditions were also analyzed. These latter collected into condensers were diluted into acetone before being injected into GC-MS. The gas chromatogram utilized is a HP 5890 Series II equipped with HP 5971A Mass Selective Detector and HP 7673 Controller.

3 Results and discussion 3.1 Heating rate effect At 300 °C, change in heating rate does not seem to have a major effect on physical properties despite the fact the char yield varied slightly as well as higher heating value (HHV), tab.1. Char yield would have been expected to decrease with increased heating rate, as well as volatile content since generally increasing heating rate results in higher liquid yields and lower char yields, as for 500 °C. Perhaps that at lower temperature, this principle does not hold and the longer temperature progression temperature period had a more pronounced effect on char yield. Char yield being lower at 300 °C is at least consistent with the higher fixed carbon content that may have resulted from longer residence time, releasing more volatiles at temperatures lower than 300 °C. This latter would also explain the increase in heating value content. Higher heating value obtained for 500 °C in this research is really close to what was previously reported in literature using a bench scale fluidized bed reactor design (21.5 vs. 18.6 MJ/kg) (Boateng et al. [21]). At 500 °C, decreasing heating rate seems to have a pronounced effect on surface area passing from 52 to 82 m2/g. Effect on biooil content was not observed since biomass carrier preheating step for higher heating rates resulted in some volatiles losses. It has to be kept in mind that oxygen introduction resulting from carrier preheating may have major effect on the results. 3.2 Gas environment effect At 300 °C, gas environment does not seem to have a major effect on physical properties. All parameters studied did not vary, which is consistent to theory mentioning that CO2 is inert at lower temperature (Jindarom et al. [16], tab. 1). On the other hand, despite the fact it would require further analyses, presence of compounds such as syringol, methoxyeugenol and palmitic acid was noted in

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

116 Energy and Sustainability III 300 °C CO2 oils which was not at 300 °C N2. A further investigation on oil is however required in order to prove that observation. At 500 °C though, gas environment seems to have a more pronounced effect. First of all, decrease in char yield and carbon content in presence of CO2 shows that Boudouard reversed reaction could have taken place, resulting in higher carbon conversion and gas yield. Since 500 °C is a relatively low temperature for Boudouard reaction to take place, it seems that at least an element acted as a catalyst. It this case, two factors may be the catalyst source: the first could be Ni element present in stainless steel of the reactor, the thermocouple and the biomass carrier. As reported by Osaki and Mori [22], in presence of Ni, the reversed Boudouard reaction along gasification operates at same rate at 500 °C than without catalyst at 800 °C. The second factor could come from the high ash content into switchgrass that could act as catalyst for Boudouard reversed reaction. Butterman and Castaldi [15] observed that activation energy for pyrolysis and gasification in CO2 atmosphere was lowered in presence of herbaceous feedstock in comparison to wood. This difference was attributed mostly to higher ash content in herbaceous feedstock than for wood. Specific surface is also another parameter which was influenced by carbon dioxide. At 300 °C there was no change noticed, however at 500 °C, specific surface passed from 82 to 189 m2/g, tab.1, which is consistent to results from Jindarom et al. [16] who observed a drastic change in specific surface from 550°C. 3.3 Temperature effect Temperature treatments add a pronounced effect on surface area. Increasing temperature from 300 to 500 °C increased surface area from less than 1m2/g for all 300 °C char production studied, to more than 50 m2/g at high heating rate and to more than 80 m2/g at low heating rate, tab. 1. Despite the fact the high increase in surface area at 500 °C might be beneficial on a soil amendment application, the decrease in char yield passing from about 68% to 14% must be considered among the economics of the process depending on the application. Char yield from 66 to 70% at 300 °C could result mostly from hemicellulose decomposition as reported by Prins et al. [8]. This latter assumption would be consistent with switchgrass hemicelluloses content which was estimated at 36.3%, tab. 2. In each case, char yield decreased with increasing temperature with respect to specific factors studied. This mass balance is consistent with observations made by other authors showing that cellulose decomposition occurs at temperature from 305 to 375 °C and lignin at temperature from 250 to 500 °C (Prins et al. [8]). Switchgrass cellulose content represents 33.7% of biomass composition, (tab. 2), lignin being more reluctant to decomposition, this latter would then potentially balance the remaining losses. Boateng et al. [21] worked on the same species using a bench-scale fluidized bed fast pyrolysis reactor. They run their tests at a temperature of 500 °C and the char produced corresponded to 12.9% of the original biomass, which is close to the actual values obtained (Boateng et al. [21]).

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

117

It has to be noted that char was removed from the reactor once the residence time was completed. As a result, for higher temperature, 500 °C, the biomass and biomass carrier remain at temperature high enough for char reacting with the ambient oxygen, resulting in char glowing red. This definitively may have an effect on char yields by reducing it as well as an effect on its characteristics. 3.4 DCM extractions and analyses Char organic content using Soxhlet extractions with dichloromethane were used to investigate if PAHs would be present within the char studied. This study was completed only for the high heating rate and within the studied conditions, only naphthalene was qualitatively noticed at 500 °C temperature. In literature, operating temperature increase was already reported to increase PAH formation (McGrath et al. [23] and Nakajima et al. [24]). Since extractions requires substantial amount of char in order to be extracted, further investigation of such parameter will be carried using a reactor with higher feedstock capacity.

4 Conclusion Preliminary investigations of char formation from switchgrass show results similar to those reported so far. Lowering the heating rate would enhance the specific char surface area especially at 500 °C. It would also result in slightly higher char yield, which may be beneficial in a production point of view. Carbon dioxide showed to have a great impact on specific surface at 500 °C, leading to a specific surface of 189 m2/g, which more than doubled the N2 results. For a biochar-soil amendment application, where optimized yields are desired as well as high specific surface, residual CO2 might then represent a strong potential since the yield compared to 500 °C N2 was reported as similar. Leaching of ashes prior to pyrolysis or using a reactor free of Ni could be recommended in further experiments in order to target whether an element or another was responsible for the enhancement of CO2 effect. Despite the fact CO2 seems to be inert at 300 °C based on physical characteristics of chars, preliminary results for biooil content analysis revealed some differences which must be further investigated. Further investigation about chemical composition of char obtained under 500 °C would also be interesting since appearance of PAHs occurred at higher heating rates with N2, however in presence of CO2, the content could potentially be reduced since char tar content could react with CO2 and enhance CO formation. It was also reported that final reacting conditions at open atmosphere resulted in decrease of char yield. Despite the fact this obvious reaction with oxygen could easily be reduced by waiting for char to cool down, the effect of such post treatment on char properties should also be analyzed further with respect to char value additions and the practical applications of the technology.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Production conditions

Torrefaction and pyrolysis products analyses.

Mass balance

Char analyses

Feedstock

Heating rate

T° [°C]

Gas Env.

Char [%]

Oil [%]

Gas [%]

C [%]

H [%]

O [%]

N [%]

Ash [%]

Volatiles [%]

FC [%]

HHV MJ/kg

S.A. m2/g

Raw sg.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

44.5

5.8

45.7

<1

3.7

81

15.3

19.5

‐‐

Char

FAST

300

N2

70.9

--

--

51.3

5.5

38.8

<1

6.7

72.8

20.5

20.3

<1

Char

FAST

500

N2

12.4

--

--

63.9

2.6

15

<1

26.6

20.8

52.6

19.6

52

Char

SLOW

300

N2

66.9

9

24.1

53.3

5.5

38.9

<1

4.7

70.9

24.4

23.5

<1

Char

SLOW

300

CO2

66.6

10.6

22.8

54.9

5.5

38.4

<1

5.4

68.9

25.7

23.1

<1

Char

SLOW

500

N2

15.9

10.6

73.6

65.4

2.6

17.4

1

15.1

19.7

65.2

23.5

82

Char

SLOW

500

CO2

13.6

6.9

79.5

61.8

2.1

18.6

1

14.7

21.5

63.8

25.1

189

n.b.: Percentages are expressed on a dry basis.

Legend: sg. :

Switchgrass T° : Temperature FC : n.a. : Not applicable Env. : Environment

Table 2: Identification Ash α-cellulose Hemicellulose Lignin Total

Fixed carbon S.A. : Surface area

Original composition of Panicum virgatum straw. Standard Test ASTM E1755-01 ASTM D1103-60 By difference ASTM D1106-56

Mass Units (± S.D)* 3.7 (± 0.2) 33.7 (± 0.7) 36.3 (± 1) 17.3 (± 0.6) 100

* Expressed in terms of 100 mass units of oven dry switchgrass straw

118 Energy and Sustainability III

Table 1:

Energy and Sustainability III

119

Acknowledgements Authors would like to thank Le Fonds québécois de la recherche sur la nature et les technologies (FQRNT) as well as (the Université de Sherbrooke, the Faculty of Engineering and the Department of Chemical Engineering) for the financial support for Guillaume Pilon’s PhD thesis. The Université de Sherbrooke, the Faculty of Engineering and the Department of Chemical Engineering and Biotechnological Engineering for supporting this research (through starting funds for Jean-Michel Lavoie and lending research equipment) as well as the Industrial Chair in Ethanol Cellulosic in lending research equipment. The authors would also like to acknowledge Ms. Eva Capek, Mr. Henri Gauvin, Mr. Serge Gagnon, Mr. Marc G. Couture and Mr. Michel Trottier of the Université de Sherbrooke for their technical support. Finally, Mr. Daniel Clément, switchgrass producer from the Eastern Township, for providing us the feedstock for the experiments.

References [1] Lehmann, J. & Joseph, S., Biochar for Environmental Management, Earthscan: London - Washington, DC, 2009. [2] McLaughlin, H., Anderson, P.S., Shields, F.E. & Reed, T.B., All biochars are not created equal, and how to tell them apart. North American Biochar Conference. 2009. [3] Gaunt, J.L. & Lehmann, J., Energy balance and emissions associated with biochar sequestration and pyrolysis bioenergy production. Environmental Science & Technology, 42(11), pp. 4152-4158, 2008. [4] Lehmann, J., A handful of carbon. Nature, 447(7141), pp. 143-144, 2007. [5] Laird, D.A., The charcoal vision: a win win win scenario for simultaneously producing bioenergy, permanently sequestering carbon, while improving soil and water quality. Agronomy Journal, 100(1), pp. 178-181, 2008. [6] Boateng, A.A., Characterization and thermal conversion of charcoal derived from fluidized-bed fast pyrolysis oil production of switchgrass. Industrial and Engineering Chemistry Research, 46(26), pp. 8857-8862, 2007. [7] Uslu, A., Faaij, A.P.C. & Bergman, P.C.A., Pre-treatment technologies, and their effect on international bioenergy supply chain logistics. Technoeconomic evaluation of torrefaction, fast pyrolysis and pelletisation. Energy, 33(8), pp. 1206-1223, 2008. [8] Prins, M.J., Ptasinski, K.J. & Janssen, F.J.J.G., Torrefaction of wood: Part 1. Weight loss kinetics. Journal of Analytical and Applied Pyrolysis, 77(1), pp. 28-34, 2006. [9] Brewer, C.E., Schmidt-Rohr, K., Satrio, J.A. & Brown, R.C., Characterization of biochar from fast pyrolysis and gasification systems. Environmental Progress & Sustainable Energy, 28(3), pp. 386-396, 2009. WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

120 Energy and Sustainability III [10] Mohan, D., Pittman, C.U. & Steele, P.H., Pyrolysis of wood/biomass for bio-oil: a critical review. Energy & Fuel, 20(3), pp. 848-889, 2006. [11] Joseph, S., Peacocke, C., Lehmann, J. & Munroe, P. Developing a biochar classification and tests methods (Chapter 7). Biochar for Environmental Management- Science and Technology, ed. J. Lehmann & S. Joseph, Earthscan: London and Washington DC, pp. 107-112., 2009. [12] Downie, A., Crosky, A. & Munroe, P., Physical Properties of Biochar, Biochar for Environmental Management - Science and Technology. ed. J. Lehmann & S. Joseph, Earthscan: London and Washington DC, pp. 13-29, 2009. [13] Demirbas, A., Carbonization ranking of selected biomass for charcoal, liquid and gaseous products. Energy Conversion and Management, 42(10), pp. 1229-1238, 2001. [14] Buhre, B.J.P., Elliott, L.K., Sheng, C.D., Gupta, R.P. & Wall, T.F., Oxyfuel combustion technology for coal-fired power generation. Progress in Energy and Combustion Science, 31(4), pp. 283-307, 2005. [15] Butterman, H.C. & Castaldi, M.J., Biomass to fuels: impact of reaction medium and heating rate. Environmental Engineering Science, 27(7), pp. 539-555. 2010. [16] Jindarom, C., Meeyoo, V., Kitiyanan, B., Rirksomboon, T. & Rangsunvigit, P. Surface characterization and dye adsorptive capacities of char obtained from pyrolysis/gasification of sewage sludge. Chemical Engineering Journal, 133(1-3), pp. 239-246, 2007. [17] Minkova, V., Marinov, S.P., Zanzi, R., Björnbom, E., Budinova, T., Stefanova, M. & Lakov, L., Thermochemical treatment of biomass in a flow of steam or in a mixture of steam and carbon dioxide. Fuel Processing Technology, 62(1), pp. 45-52. 2000. [18] Sharma, R.K., Wooten, J.B., Baliga, V.L., Lin, X., Geoffrey Chan, W. & Hajaligol, M.R., Characterization of chars from pyrolysis of lignin. Fuel, 83(11-12), pp. 1469-1482. 2004. [19] He, R., Ye, X.P., English, B.C. & Satrio, J.A., Influence of pyrolysis condition on switchgrass bio-oil yield and physicochemical properties. Bioresource Technology, 100(21), pp. 5305-5311, 2009. [20] Martel, H. & Perron, M.-H., Compilation des essais de Panic Érigé réalisés au Québec. Centre de référence en agriculture et agroalimentaire du Québec. 2008. http://www.craaq.qc.ca/data/DOCUMENTS/EVC026.pdf [21] Boateng, A.A., Daugaard, D.E., Goldberg, N.M. & Hicks, K.B., BenchScale fluidized-bed pyrolysis of switchgrass for bio-oil production. Industrial & Engineering Chemistry Research, 46(7), pp. 18911897, 2007. [22] Osaki, T., & Mori, T., Kinetics of the reverse-Boudouard reaction over supported nickel catalysts. Reaction Kinetics and Catalysis Letters, 89(2), pp. 333-339, 2006. [23] McGrath, T., Sharma, R. and Hajaligol, M., An experimental investigation into the formation of polycyclic-aromatic hydrocarbons (PAH) from pyrolysis of biomass materials. Fuel, 80(12), pp. 1787-1797, 2001. WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

121

[24] Nakajima, D., Nagame, S., Kuramochi, H., Sugita, K., Kageyama, S., Shiozaki, T., Takemura, T., Shiraishi, F. & Goto, S., Polycyclic aromatic hydrocarbon generation behaviour in the process of carbonization of wood. Bulletin of Environmental Contamination and Toxicology, 79(2), pp. 221225, 2007.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

This page intentionally left blank

Energy and Sustainability III

123

From biomass-rich residues into fuels and green chemicals via gasification and catalytic synthesis S. C. Marie-Rose1,2, E. Chornet1,2, D. Lynch2 & J.-M. Lavoie1 1

Chaire de recherche industrielle en éthanol cellulosique, Université de Sherbrooke, Canada 2 Enerkem Inc. Montreal, QC, Canada

Abstract Recycling carbon present in residual streams enhances sustainability and creates local wealth. Enerkem Inc. is a leading biomass gasification company headquartered in Montreal, Québec. The approach Enerkem has been developing involves: identification of low cost residual streams as feedstock, sorting, biotreatment (anaerobic and/or aerobic) and preparation of an ultimate residue (RDF). The latter is a rather uniform material that can be fed, as a fluff, to a bubbling bed gasifier in a staged gasification to carry out, sequentially, the needed chemical reactions that result in high syngas yields. Process can be adjusted to reach desired gas composition for synthesis or electricity generation as well as gas conditioning to produce an ultraclean syngas. Products for such a process are: i) syngas with an appropriate range of H2/CO ratios, ii) CO2 (which is recovered), iii) solid char as a residue composed of the inorganic fraction of the raw material and some unconverted carbon that “coats” the inorganic matrices, and iv) water that needs to be treated to meet the sewage specifications and thus be sent into the water distribution system of a given municipality. Enerkem is developing two parallel valorisation routes; a) heat and power and b) synthesis of (bio)methanol as a high yield product. The methanol is the platform intermediate that can be turned into ethanol (also with high yields), and other green chemicals. Yields of ethanol as the end product are above 350 WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESUS110111

124 Energy and Sustainability III liters/tonne of feedstock (dry basis) to the gasifier. Residual heat, also a product of the process, is used in the process itself and, as well, for district heating. The combined work of the Industrial Chair in Cellulosic Ethanol at the Université de Sherbrooke, focused on fundamentals in parallel and close relationship with Enerkem that focused in technology development and implementation. The company has moved from bench scale, to pilot (150 kg/h in Sherbrooke, Québec), to demo (1500 kg/h in Westbury, Québec) to commercial implementation (12 500 kg/h in Edmonton, Alberta). Economics of the process are favourable at the above commercial capacity given the modular construction of the plant, reasonable operational costs and a tipping fee provided by the municipality for the conversion of the ultimate residue. When the project is in “production mode” Edmonton will have achieved 90% diversion of the urban waste from landfills and, furthermore the reduction in GHG (CO2 equivalent) will be of 80% taking as reference the use of fossil fuel derived gasoline to yield the same energy output as the ethanol obtained by the ‘Enerkem approach’. Keywords: alcohols synthesis, syngas production, methanol, ethanol, heterogeneous catalysis, gasification.

1 Introduction Enerkem is a technology developer specialised in the gasification platform: feedstock preparation, feeding systems, syngas production, syngas clean-up, catalytic reforming and catalytic synthesis. Enerkem’s technologies has been tested in the conversion of various waste products such as municipal solid waste, non-recyclable commingled plastics, residual biomass (from forest and agricultural operations) and numerous others carbonaceous residual streams to produce syngas, which is then used for the production of heat and/or power or for catalytic synthesis of biofuel (methanol and ethanol) and others specialty chemicals. Biomass-derived ethanol plays an important role in reducing petroleum dependency and providing environmental benefits, through its role as fuel additive in the transportation fuel market. Ethanol is a winter fuel oxygenates and also an octane enhancer. For this reasons the Canadian government has legislated an objective of 5% of ethanol in gasoline for 2012. Aiming at this objective Enerkem’s technology is an alternative to produce ethanol from nonfood feed. At the same time is an alternative to landfill and incineration. This paper focuses on characteristics of the syngas produced by gasification of RDF and on the catalytic synthesis of alcohols as second generation of biofuels.

2 Gasification of biomass 2.1 The basics Gasification is the terminology used to describe the conversion of the organic matter present in wastes and residues into a synthetic gas, a mixture of H2, CO, WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

125

CO2, and low molecular weight hydrocarbons of formula CxHy. The gasifier is the vessel where the conversion is carried out. The following chemical reactions are predominant during gasification: 1

Thermal decomposition (i.e. pyrolysis), which covers dehydration as well as cracking reactions leading to gases, intermediate vapours and carbon structures known as “char”;

2

Partial oxidation of the “char” which forms CO and CO2 generating heat for the otherwise endothermic reactions;

3

Steam-carbon, i.e. the water-gas reaction, that converts carbon structures into H2 and CO;

4

Steam reforming of intermediates formed by thermal decomposition;

5

Reactions involving CO2 and H2 with carbon and with intermediates. Such reactions are kinetically slower than the steam induced reactions at the conditions used in gasifiers;

6

Water gas shift reactions that lead to a desired H2/CO ratio.

The different gasification strategies and corresponding processes diverge on how to manage the six groups of chemical reactions stated above and how to generate and provide heat for the endothermic reactions. Since thermal decomposition requires activation and, more important, the steam-carbon and steam-reforming reactions, as well as those with CO2 are endothermic, heat has to be provided for gasification to proceed within reasonable reaction times (preferably seconds) to limit the size of vessels. Heat can be provided either indirectly (via steam, produced in a steam generation unit, or via the recirculation of a hot carrier, heated in a separate interconnected vessel) or directly (via air or oxygen injection). In the latter procedure heat is produced by oxidation of i) chemical species or functionalities present in the feedstock itself, ii) intermediates (“tar” and “char”, the latter is also known as “pyrolytic carbon”, formed by thermal decomposition, and/or iii) primary gaseous products. Since the amount of O2 needed to satisfy thermal needs is below that needed for complete oxidation (i.e. combustion) of the feedstock, the net result can be considered, stoichiometrically, as a partial oxidation of the feedstock. Reaction conditions: reactants concentrations, partial pressures=, temperature, turbulence and reaction time are of paramount importance in defining the yields and product distribution from thermal gasification. The following “rules” are of the essence: 1. When the process is conducted at low temperatures (<750 ºC) and short reaction times (of the order of seconds or even fractions of a second) thermal decomposition will predominantly produce oligomeric intermediates. The latter, will not be able, kinetically (low T and short t), to undergo subsequent secondary cracking or react with steam. Upon condensation of the oligomeric intermediates, the latter becomes the “primary tar”. In such situation, the rate processes are those characteristic of low temperature fast pyrolysis which is WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

126 Energy and Sustainability III known to produce large amounts of primary tar. The latter has a chemical structure derived from the constitutive macromolecules of the feedstock. In primary tar from biomass, oligomeric anhydrosugars and lignin-derived oligomers are predominant. 2. At higher process temperatures (>750 ºC), the cracking of the intermediates produces high concentrations of free radicals whose recombination competes, kinetically, with steam (and CO2) reforming reactions. When recombination reactions are predominant, the formation of large amounts of “secondary tar” is observed. Such secondary tar is of aromatic nature and it is often accompanied by soot, formed at high severities. 3. Uncatalyzed carbon-steam and carbon-CO2 reactions are not kinetically significant, below 800 ºC. For this reason, activated carbon production, using steam, is carried out at >800 ºC. The presence of alkali catalyzes such reactions. This is important in biomass gasification since alkali (K being the most significant) is present in all biomasses. The point is that steam-carbon reactions can take place in a convenient temperature range when the reaction chemistry can be controlled by the presence of alkali. The choice of strong or weak alkali decides on the range and concentration (partial pressure) of steam to be used. Reactor configuration and associated fluid-dynamics, which are characteristic of each gasifier type, are also of paramount importance in gasification since they are responsible for heat and mass transfer rates and, as well, they define the residence time distribution patterns. Coupling effectively fluid-dynamics with reaction kinetics (which as previously discussed depend on temperature, pressure, concentration of reactants and reaction time) is the key to high yields and desired product selectivity. 2.2 The technology The process commercialized by ENERKEMTM Inc., is the result of efforts started in the early 80’s that led to the development of a core technology which couples fluid bed reactors with advanced gas conditioning strategies to provide a clean synthetic gas. The latter can be used for the co-generation of electricity and/or process heat. When combined cycles are used the electrical energy efficiency significantly exceeds that of the combustion/steam cycle. When the technology is coupled, in a staged-wise manner, with thermal and/or catalytic reforming it provides a mixture of H2 + CO (syngas) that can be subsequently used for the catalytic synthesis of alcohols or hydrocarbons. Further water-gas shift leads to the production of H2 upon removal of CO2. The technology can be applied to organic residues from diversified sources, such as sorted municipal solid waste (RDF), urban wood, agricultural residues, forest thinnings, sludges, as well as wastes from various industries, such as sawdust and pulp mill residues, spent oils, plastic-rich residues and rubbercontaining wastes. The technology can also be applied to petroleum residues. It involves three main stages: 

adequate preparation of the raw material (size reduction and moisture adjustment, densification is optional);

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

127



staged gasification initiated in a bubbling fluidized bed reactor, and pursued at increased severities in the freeboard and/or a secondary reforming unit;



scrubbing or dry hot gas conditioning or a combination depending upon the end use.

2.3 How it works Enerkem’s gasification technology used low severity conditions to produce a crude syngas, followed by conditioning or cleaning of the crude syngas by subjecting the crude syngas to steam reforming, particulate removal, quenching, scrubbing, filtration and absorption prior to employing the syngas in the catalytic synthesis of alcohols (Figure 1).

Figure 1:

Syngas production from non-homogeneous biomass residues and wastes.

The waste material has to be pretreated in order to obtain a feedstock with a characteristic particle size of about 5 cm as typical dimension. The process feedstock may need to be dried (using residual process heat) since its humidity at the reactor entrance should not exceed a specific level which is a function of the feedstock composition. The bulk density of the process feedstock needs to be typically higher than 0.15 kg/l for adequate feeding to the reactor. The feedstock prepared as described above is directed towards the gasification reactor via an appropriately designed feeding system that controls the rate of material fed to a water-cooled transfer screw that injects the material WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

128 Energy and Sustainability III into the fluid bed section where an appropriate fluidizing media is maintained. Injection of the needed amounts of air or O2-enriched air through a distributor grid located at the bottom of the fluid bed induces the fluidization patterns which result in high mixing and heat transfer rates which facilitate the reactions taking place during gasification. The quantity of air, O2-enriched air, O2-steam or O2steam-CO2 required, depends on the organic composition of the residues. It is usually around 25% of the stoichiometric amount required for combustion of the organics. The temperature in the fluid bed part of the reactor is kept at about 700°C. The feedstock thermally decomposes producing volatiles (permanent gases, intermediates ranging from monomers to oligomers), and aerosols (entrained tar and small particles). The thermal decomposition also produces “pyrolytic carbon” (i.e. “char”) that stays in the fluid bed until such time that its carbon content is decreased by the partial oxidation taken place in the bed and the particle terminal velocity reaches the level at which entrainment takes place towards the free board. As the of carrier gas goes through the disengagement zone, in the ENERKEMTM process the temperature is increased by staged addition of controlled amounts of oxidant. Such addition continues in the freeboard or in a separate vessel. This exposes the volatiles and the entrained particles of char to thermal cracking and steam-driven, as well as CO2-driven reactions. Thermally induced water-gas-shift also occurs during the raise in temperature. The composition of the synthetic gas obtained can be tailored according to the gasification agent (air or O2-enriched air), the feedstock composition, the temperature and pressure, the steam partial pressure, the fluid-dynamics and residence time distributions in the different zones of the reactor as showed in Table 1. After separation of the larger solid particulates using cyclones, gas conditioning to achieve a clean syngas is carried out via a two-stage scrubbing process, recovering the tar and re-injecting it into the gasifier for additional syngas production. The clean syngas will contain low molecular weight hydrocarbons whose concentration depends on the nature of the feedstock. The synthetic gas can be used for the production of energy as follows:  





combusted as is, or in combination with natural gas, using commercial boilers to produce process heat (steam); as a fuel, alone or with natural gas, in internal combustion engines (ICE) to produce electrical energy. Heat from the ICE hot exhaust gases can be recovered and used for steam (or other fluid) which leads to combined cycle or co-generation applications; as a fuel, alone (if the calorific value is sufficiently high, as when O2enriched air or O2-steam is used rather than normal air) or with natural gas, in gas turbines to produce electrical energy via combined cycles or in co-generation mode. as a feedstock (when O2-steam or O2-steam-CO2 are used) for the synthesis of alcohols or hydrocarbons. For this purpose the low molecular weight hydrocarbons need to be reformed.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

Table 1:

129

Biomass and Syngas composition, in low severity gasification. Typical Biomass composition Volatile matter Ash Moisture

wt% >70 1.5 20

Ultimate Analysis C H O N S

wt% 54.2 6 38.9 0.3 0.1

Gasification conditions O2/Steam/CO2 gasification, low severity+ thermal cracking and reforming at higher severity Syngas composition N2 Ar/O2 H2 CO CO2 CH4 C2H4 C2 – C5 C5 – C10 Input C converted into syngas

mol% 2-6 <1 23 – 27 21 – 23 38 – 44 6–8 Traces 0.2 – 0.5 Traces >90%

3 Syngas conversion into biofuel Conversion of syngas to liquid fuels as well as conversion rates are directly related to the composition of the catalyst. Syngas can be efficiently converted to different products as alcohols, DME and hydrocarbons (Figure 2). Although several routes are available, a promising route at the industrial level is the production of methanol since it is a selective conversion with established catalysts and proceeds at productivity levels higher than 1 kg methanol per kg of catalyst per hour.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

130 Energy and Sustainability III

Figure 2:

Examples of applications for syngas produced from biomass.

3.1 Syngas to methanol The conversion of synthesis gas to methanol is thermodynamically constrained hence the need to recycle the unconverted gas to achieve high CO conversion levels. This translates into high reactor volume and increased compression costs. Methanol synthesis was carried out with the conditioned syngas using three phases reactor (slurry bubble column) in which a Cu/ZnO/Al2O3 catalyst was suspended. Before the synthesis of methanol, the catalyst is reduced in hydrogen. The reductive and active form of the catalyst is CuO/ZnO/Al2O3. The principal stoichiometric reactions involved in this chemical conversion are:

2

2

3

∆

298

91

.

1

It is subjected to a thermodynamic equilibrium that limits the process to low conversion per pass (CO conversion about 45%) and therefore, implies a large recycle of unconverted gas. The reaction is strongly exothermic and consequently, requires significant cooling duty.

4 Methanol to ethanol 4.1 Methyl acetate as intermediate of ethanol Carbonylation of methanol to acetic acid or methyl acetate is a well known industrial process. It is currently performed, industrially, in a homogeneous WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

131

reaction system where a catalyst is dissolved or suspended. The Monsanto/Celanese/Eastman and BP Chemicals CativaTM processes in the presence of rhodium and iridium respectively are conducted at moderate temperature and pressure in the presence of halide (iodide) promoters [1]. The mechanism of the reaction of acetic acid synthesis is well described in the literature and it is known as Monsanto cycle [2]. The formation of methyl acetate can be explained by the reaction between the acyl iodide formed during the reaction and the excess of methanol present in the feed. Heterogeneous systems for methanol carbonylation have been suggested by investigators for several years. Research has been primarily focused on two possible catalysts for this reaction: rhodium supported on polymers (Acetica process is based on this principle) or zeolites and a variety of metals supported on activated carbon [3]. The choice of support seems to play an important role in the activity of the catalyst [4, 5]. In the “Enerkem process” [6] carbonylation of methanol is carried out maintaining methyl alcohol in vapour phase using a fixed bed packed with a rhodium-based catalyst. The methanol is vaporized under pressure and mixed with the CO-rich fraction prior to flowing through the reactor. The methanol to CO molar ratio is comprised between 1 and 4, whereas methyl iodide (cocatalyst) added to methanol is maintained at a molar ratio between 1 and 5 wt% relative to the methanol. The operating conditions are such that the GHSV (based on CO) varies between 100 to 2,000 h-1. At temperatures comprised between 170 to 300 °C and total pressures from 10 to 50 atm. It was reported that the CO is converted at rate near 100% when the methanol/CO ratio is >2. The selectivity varies as a function of temperature and pressure. It was found that within a wide range (200-240°C, 15-50 atm) for the specified GHSV (Based on CO) range, molar selectivity of 50-75% methyl acetate and 25-50% of acetic acid. 4.2 Methyl acetate hydrogenolysis: synthesis of ethanol Methyl acetate produced as previously via carbonylation, is maintained in liquid form at 20°C. It is pumped in a pressure vessel ranging from 10 to 50 atm, through a heat exchanger that vaporizes it at temperatures ranging from 150 to 225 °C. Preheated hydrogen in the same temperature range is mixed with the methyl acetate vapour at the exit of the heat exchanger. The molar ratio H2 to methyl acetate is from 5 to 11. The hot mixture is flown through a catalytic bed where a CuO/Cr2O3 or CuO/ZnO/Al2O3 catalyst is placed. The CuO is reduced with H2/N2 mixtures prior to adding any methyl acetate [7]. Methyl acetate is converted to methanol and to ethanol at GHSV (based on H2) comprised between 1,000 and 2,000 h-1 and the methyl acetate conversion is up to 95%, with a higher selectivity in ethanol.

5 Conclusion Enerkem has successfully proven, at pilot scale, the feasibility of converting heterogeneous biomass residues into a homogeneous syngas that can be used for WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

132 Energy and Sustainability III the synthesis of methanol. The latter is a key intermediate building block for chemical commodities and biofuels such as bio-methanol and from the latter bioethanol. The technology is applicable to any organic material and residual biomass including urban biomass such as residential waste. It is preferable that the waste sorted to remove recyclables as well as ferrous metals, glass and ceramics. Typically, to maintain consistent performance, inorganic matter levels should be kept below 20 wt% in the feedstock (dry basis).

References [1] G. Ormsby, J.S.J. Hargreaves, and E.J. Ditzel, A methanol-only route to acetic acid, Catalysis Communications. 10 (2009) 1292-1295. [2] L. Kollár, Modern carbonylation methods, Wiley-VCH, 2008. [3] A.S. Merenov, and M.A. Abraham, Catalyzing the carbonylation of methanol using a heterogeneous vapor phase catalyst, Catalysis Today. 40 (1998) 397-404. [4] D.R. Fahey, Industrial chemicals via C1 processes, Industrial Chemicals Via C1 Processes. (1987). [5] T. Yashima, Y. Orikasa, N. Takahashi, and N. Hara, Vapor phase carbonylation of methanol over RhY zeolite, Journal of Catalysis. 59 (1979) 53-60. [6] E. Chornet, B. Valsecchi, Y. Avilla, B. Nguyen, and J.-M. Lavoie, Production of ethanol from methanol, US Patent Application US 2009/0326080, 2009. [7] P. Claus, M. Lucas, B. Lücke, T. Berndt, and P. Birke, Selective hydrogenolysis of methyl and ethyl acetate in the gas phase on copper and supported Group VIII metal catalysts, Applied Catalysis A: General. 79 (1991) 1-18.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

133

Anaerobic digestion of cattle manure: effect of phase-separation V. Yılmaz1 & G. N. Demirer2 1

Department of Environmental Engineering, Akdeniz University, Turkey Department of Environmental Engineering, Middle East Technical University, Turkey

2

Abstract Various aspects of anaerobic digestion (AD) technology have been the focus of research in recent years. Shortening the digestion time with enhanced process efficiency is one of the integral concerns in AD technology. This study was conducted to investigate the feasibility of a two-phase anaerobic treatment system for unscreened dairy manure. Hydraulic retention time (HRT) and organic loading rate (OLR) in the hydrolytic reactor are varied in order to evaluate the effect of these factors. The results showed that an optimum HRT and OLR of 2 days and 15 g.VS/L.day, respectively, yielded maximum acidification. The separation of acidogenic and methanogenic phases of digestion resulted in a significant increase in methane production rate in the methane reactor. The methane yields were found to be 313 and 221 mL CH4/g.VS loaded in two-phase and one-phase systems at 35°C, respectively. Keywords: anaerobic digestion, dairy manure, two-phase, methane.

1 Introduction With the rapid depletion of conventional energy sources, the need to find alternative, but preferably renewable, sources of energy is becoming increasingly acute. Through anaerobic digestion of biomass, including animal wastes, useful energy can be obtained [20]. Biogas plants are expected to be an effective solution to the manure management problem providing benefits such as energy saving, environmental protection and reduced CO2 emissions. Anaerobic digestion of organic matter became more and more attractive in the recent past because new reactor designs significantly improved the reactor WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESUS110121

134 Energy and Sustainability III performance [29]. Studies have shown that anaerobic treatment is a stable process under proper operation. But parameters such as process configuration, temperature, biomass, pH, nutrient, and substrate must be carefully scrutinised in order to make successful anaerobic treatment. Many process configurations have been investigated. An improvement in the efficiency of anaerobic digestion can be brought about by either digester design modification or advanced operating techniques [16]. On farms anaerobic digestion of animal manure is an attractive technique for both energy and organic fertilizer production. Literature on manure digestion is mainly focused on liquid manure (i.e. total solids<100 g/l) digestion. Nevertheless many farms, especially smaller ones, throughout the world, still produce solid manure. For on-farm application the digestion system should be as simple as possible to operate and in agreement with the on-farm practice [6]. Conventional anaerobic digestion is proceeded in a single reactor where acidogenesis and methanogenesis both occur. Acidogenesis and methanogenesis are respectively proceeded in two separate reactors and each phase is in the best environmental conditions [16]. This phase separation can be achieved by maintaining a very short HRT in the acid phase reactor. The effluent from the first, acid-forming, phase is then used as the substrate for the methane-phase reactor [19]. One relevant feature of the two-phase approach is that when a high solid containing waste is introduced to the first phase it is liquefied along with acidification. This translates into less liquid addition and, thus, less energy requirements for heating, storing and spreading for two-phase AD systems. The results of several studies [1, 3, 7, 10, 11, 15, 17, 21, 25]. have clearly demonstrated the applicability and efficiency of two-phase AD for high solids containing wastes. The advantages of two-phase operation have been extensively documented [9, 22]. Prospects for the phased anaerobic treatment of wastewater are promising. With the variety of reactor designs available and the amenability of reactors to modification, existing treatment systems may be replaced or upgraded as required to achieve increased stability, higher loading capacities and greater process efficiencies than are possible using single-stage systems [16]. Even though several aspects of two phase configuration including liquefaction might be very significant for efficient AD of dairy manure, its application has been limited to screened dairy manure only [5, 20, 26]. This work aimed to evaluate the feasibility of a two-phase anaerobic treatment system for unscreened dairy manure. The specific objective was to compare the effects of different HRT and OLR for optimum acidification.

2 Materials and methods Wet manure was collected from a private dairy around Gölbaşı, Ankara, and stored at 4°C prior to use. The composition of the dairy manure used in this study had the following characteristics; total solids (TS), 20.1 ±1.7%, volatile solids (VS), 67 ± 4.6% of TS and density, 1042 ± 0.04 g/L. The raw manure was WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

135

diluted with water to decrease the solids content to achieve slurry with 3.5, and 15 g.VS/L. The relationship between chemical oxygen demand (COD) and VS of this manure was found as 1.04. The mixed anaerobic culture used as seed was obtained from the anaerobic sludge digesters at the Ankara wastewater treatment plant, which has a solids retention time (SRT) of 14 days. The mixed anaerobic culture was concentrated by settling before being used as inoculum. The volatile suspended solids (VSS) concentration of the concentrated seed cultures used was 23930 ± 3162 mg/L. 2.1 Experimental set-up In the first part of the study, the optimum retention time and organic loading rate (OLR) values leading to maximum acidification and VS reduction were investigated. Thus, nine daily-fed continuously-mixed acidogenic anaerobic reactors with no recycle were operated as duplicates. The experiments were performed in 250 mL serum bottles capped with rubber stoppers. Reactor operation involved daily feeding of wet dairy manure and wasting of the corresponding reactor contents as indicated in table 1. Solids and hydraulic retention times (SRT/HRT) applied to each reactor was the same since no recycle of the effluent was practiced. Initially, each reactor was seeded with 100 mL of concentrated anaerobic seed cultures. The next day dairy manure (25 mL to reactors 1–3, 50 mL to reactors 4–6, and 80 mL to reactors 7–9) were added to each reactor. Daily feeding and wasting were conducted as seen in table 1. The reactors were flushed with N2/CO2 gas mixture for 3 min and maintained in an incubator shaker at 35 ± 1ºC and 165 rpm. Table 1: Reactor 1 2 3 4 5 6 7 8 9

Daily feeding and wasting used for acidogenic reactors. SRT (days) 4 4 4 2 2 2 1.25 1.25 1.25

OLR (g.VS/L day) 5 10 15 5 10 15 5 10 15

Volume of feeding/wasting (ml) 25 25 25 50 50 50 80 80 80

The one-phase conventional configuration (R1) was run as the control for the two-phase configuration (R2). The effective volumes of R1, R21, and R22 were 1000, 400, and 1000 mL, respectively. The two-phase configuration contained R21 and R22 as the first (acidogenic) and second (methanogenic) phases. The SRT/HRT values of R1, R21, R22 and the overall two-phase configuration were 20, 2, 8.6, and 10.6 days, respectively. The gas production in R1, R21 and R22 were monitored by a water replacement device was used to WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

136 Energy and Sustainability III monitor the gas production. One set of reactors were maintained at 25°C in a temperature-controlled water bath and the others at 35°C (±2) in a controlled room, and all reactors were shaken manually once daily after conducting the gas production measurement. Solids and hydraulic retention times (SRT/HRT) applied to each reactor was the same since no recycle of the effluent was practiced. R1, R21, and R22 were seeded with 500, 200, and 500 mL of mixed anaerobic seed culture. The performance of the reactors was monitored by measuring biogas production and soluble COD, VS, volatile fatty acid (VFA), and pH. 2.2 Analytical methods The pH, daily gas production , total solids, volatile solids, methane percentage, total volatile fatty acids (TVFA) and effluent soluble COD (sCOD) were monitored in each reactor. pH, TS, VS analysis was performed using Standard Methods [2]. sCOD was measured using Hach COD vials according to the EPA approved digestion method [12]. Accordingly, after 2 h digestion, sCOD of sample were directly read using Hach 45 600-02 spectrophotometer (Hach Co. Loveland, Co., USA). TVFA and biogas composition were measured by gas chromatography as described by Yilmaz and Demirer [32].

3 Results and discussion Nine acidogenic anaerobic reactors were operated for 57 days to determine the optimum SRT and OLR values resulting in maximum acidification and in turn VS reduction. Three different OLRs (5, 10 and 15 g.VS/L.day) were applied to the reactors. For each OLR value, three SRTs (1.25, 2 and 4 days) were studied (table 1). The results are given in fig. 1 in terms of the change in the operating parameters (pH, TVFA, VS, cumulative gas production (CGP), methane content and sCOD) with respect to the combination of OLR and SRT values. Figure 1 does not include the data points within the first “3xSRT” days (12 days for R1– R3, 6 days for R4–R6, and 4 days for R7–R9) which are the theoretical time to reach to steady-state conditions in a continuous reactor. As seen in fig. 1.a, pH drop was inversely proportional with the increase in the SRT for each OLR studied. Similarly, for each SRT studied, as the OLR increased, pH decreased. It was observed that the extent of pH drop increased with the increase in the OLR being smallest for the lowest OLR of 5 g.VS/L.day. Besides, it should be noted that the extent of pH drop was also affected by the SRT. For all the OLRs studied, the extent of pH drop for the SRT increase from 1.25 to 2 days was greater than that observed for SRT of 2 to 4 days. It is a well known fact that low retention times and high loading rates lead to higher acidification in two-phase systems. However, as seen in fig. 1.a, average pH values observed in the reactors were within 6.2–6.6 and the extent of pH drops was lower relative to acidification of other high solid substrates such as organic fraction of municipal solid wastes. Han et al., [13] operated the MUSTAC (multi-step sequential batch two-phase anaerobic composting) process to recover WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

137

methane and composted material from food waste, where the pH ranged between 6.5 and 7.0 during acidogenic fermentation step. In another research, Kübler and Schertler [18] demonstrated that favourable pH condition was 6.7 in the threephase anaerobic degradation of solid waste. Verrier et al., [27] stated that both mesophilic and thermophilic liquefaction and acidogenesis of vegetable solid wastes were found to be maximal when the pH was maintained at approximately 6.5 in the hydrolysis reactor. The relatively high pH values observed in our study can be explained by the alkalinity generated by the anaerobic biodegradation of nitrogenous organic compounds contained in the dairy manure used in this study [8, 30]. The similar self-buffering capacity of the manure was also observed in other acidification studies [4, 5].

Figure 1:

pH, T-VFA, VS, CH4 percentage, biogas production, and sCOD values observed during the first part of the experiment.

As expected, the increase in the OLR resulted in the increase in the TVFA production (fig. 1.b). In addition, the extent of TVFA production for the SRT increase from 1.25 to 2 days was greater than that observed for SRT increase from 2 to 4 days especially for OLRs of 10 and 15 g.VS/L.day. This observation was also verified by the extent of pH drop (being greater for SRT increase from 1.25 to 2 days). These TVFA production trends for all reactors coincided with the sCOD productions (fig. 1.c) which increased with the increased OLR and SRT.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

138 Energy and Sustainability III The effect of SRT and OLR on TVFA production was also observed for CGP data. As the OLR and SRT increased the CGP in the reactors increased (fig. 1.d). It is well known that in addition to VFAs and alcohols both H2 and CO2 are produced through acidification. However, GC analyses unexpectedly indicated that methane was produced in all of the reactors studied at varied OLRs and SRTs (fig. 1.e). Especially, methane percent of the biogas increased from 5 to 15–27% when SRTs and OLRs were increased to greater values than 1.25 days and 5 g.VS/L.day, respectively. Although the pH conditions were close to the optimum operating conditions of highly organic wastes required for acetogenesis. The applied SRT values (1.25 to 4 days) were not favourable for the most sensitive anaerobic bacteria type known as methanogens. The methane production at such low SRTs could be explained by unintentional extended retention times of microorganisms in the reactors due to very high solids concentration and thus lack of homogeneity during daily wasting of sludge. GC analyses also indicated a significant amount of N2 in the biogas of all reactors changing from 35 to 90% (data was not shown). As expected, denitrication was more dominant at the higher oxidation-reduction potential at the beginning of the experiment. Denitrification might occur during the acidogenic phase, so as to achieve simultaneous VFA production and nitrate elimination, a system could be applied to organic carbon and nitrogen removal from the wastes [23, 29]. Better hydrolysis in acidification process means higher VS reduction. Therefore, in addition to pH and TVFA production, VS is among the critical parameters in determination of the acidification extent of dairy manure known with its high solids content. The average VS concentrations observed in the reactors at varied SRT and OLR combinations were given in fig. 1.e. It was observed that increasing the OLR and SRT resulted in the VS accumulation. However, due to the continuous feeding and wasting process, such an accumulation may not clearly indicate the possible VS reduction in the reactors. Therefore, a completely stirred tank reactor (CSTR) system modeling was performed to observe the change in the VS content of the reactors at steady-state conditions. In this CSTR model, each reactor was accepted as reactors which were operated under feeding and wasting process without any destruction/degradation of the feeding. For better comparison, percent VS reduction in each reactor was calculated by considering the theoretical and experimental VS concentrations and given in table 2. In the first part of the study, the effect of solids and hydraulic retention time (SRT/HRT), organic loading rate (OLR) on the acidification degree was investigated. Results indicated that SRT/HRT and OLR of 2 days and 15 g.VS/L.day, respectively, yielded maximum acidification. The one-phase conventional configuration (R1) was run as the control for the two-phase configuration (R2) in the second part of the study. All reactors started to produce gas production started in the first week of the reactor operation. Gas volumes were measured daily. The results are shown in fig. 2. The average biogas production values of R1(35), R22(35), R1(25), R22(25) were obtained as 1230±180, 1000±90, 770±70, 290±50 mL/day, respectively. Also, a noteworthy gas production of 130 mL was seen in the mesophilic WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

Table 2:

The comparison of the reactors with selected parameters.

Reactor 1 2 3 4 5 6 7 8 9

1600

Daily Gas Production (mL)

VS Reduction (%) 8.4 14.5 19.5 0 8.9 14.8 0 0 2.3

R1 (35) R21 (35) R22 (35)

1800

139

TVFA (mg/L) 806 1444 2236 399 476 1300 412 400 647

pH 6.53 6.38 6.29 6.54 6.42 6.24 6.57 6.52 6.45

R1 (25) R21 (25) R22 (25)

1400 1200 1000 800 600 400 200 0

0

50

100

150

Time (days)

Figure 2:

200

50

100

150

200

Time (days)

Daily gas productions at 35°C and 25°C.

acidogenic reactor (R21(35)). There were three different gas production trends in fig. 2. This could be explained by the heterogeneous characteristics of the different manure samples collected at different times. This difference resulted in different biodegradability yields. It is clearly seen that temperature affects the performance of the biogas production (fig. 2). The biogas production increased 60% when the temperature increased from 25°C to 35°C in one-phase reactor. These results are very consistent with literature [24, 26]. The average methane content of R1(35), R22(35), R1(25), and R22(25) were determined as 63, 65, 63, and 43%, respectively. The methane yields of these reactors calculated as 221, 216, 132, 43 mL CH4/g.VS added, respectively. The performances of the reactors in terms of biogas yield could be easily comparable with literature values except R22(25) [20, 26]. When the biogas production yields are compared at mesophilic temperature, the performance of two-phase system (216 mL CH4/g.VS) is slightly lower than one-phase system (221 mL CH4/g.VS) in this study. The earlier experiments with fattening-cattle waste had suggested that a HRT of about 20 days was required at WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

140 Energy and Sustainability III 35°C for optimum methanogenic anaerobic digestion and that gas production was reduced significantly at 10 days of SRT [24]. Demirer and Chen [5] demonstrated that a conventional one-phase reactor for unscreened dairy manure at a HRT of 20 days produced 0.235 L biogas/g.VS. When HRT reduced to 10 days, initially an increased was seen in gas production but a few days later an abrupt decline in biogas production were observed, then biogas production was reduced by 90%. In an another work by Wellinger [31] gas yield of straw-rich solid cattle waste was found as 270 and 190 mL/g.VS at HRT of 20 and 10 days, respectively. From this above discussion, it is obvious that, the HRT is directly affecting the biogas production. A simple calculation could be reveal which system is preferable in terms of higher biogas production yield. When the HRT of twophase system is increased from 8.6 to 20 days, the system would produce at least 307 mL CH4/g.VS instead of 216 mL CH4/g.VS by using the literature data for the same substrate [14, 31]. Thus, gas production in two-phase system (R22(35)) would be 42% higher than that of the one-phase system (R1(35)). Moreover, a small amount of produced methane from the acid phase (R21) may also be delivered to R22 or directly collected; it is for sure that methane generation of R2 will also increase. Volatile solids content are often used as a measure of the biodegradability of the organic fraction of waste. The influent and effluent VS concentrations in the reactors are plotted in fig. 3a. The effluent concentrations revealed a stable trend especially in mesophilic reactors. This stable trend presented that a constant VS reduction occurred throughout the operation. The highest VS conversion was observed with 35–40% in R1(35) between days 10 and 100, but during days 100–200 R2(35) had the highest VS reduction with 30–35%. A 20–30% VS conversion resulted a wide range in R1(25), this was mainly caused by the operation of this reactor didn’t show stability. The VS reduction observed in R2(25) and R21(35) was under 20% parallel to their gas production and they were very fluctuating. Although both of the systems had the same OLR relative to their inlet concentrations, the inlet concentration of R22 was the effluent concentration of R21 in which there was an average VS reduction of 17%. Therefore, the OLR in R22 was calculated as 2.9 g.VS/L.day. R22(35) had 10– 50% higher VS reduction than R22(25), since the performance of R22(25) was low. The VS reduction in R21(25) was nearly below 10% at all times. As VS conversion percentages, effluent sCOD concentrations had also the same trend (fig. 3b). Since the biogas production was due to the degradation of organic compounds. VS and COD parameters could be considered in the same manner as the characteristics of the biodegradability. So, the reduction trends should be similar in terms of VS and COD. The removal of soluble COD concentrations decreased significantly with decreasing temperature. The sCOD reductions of R1(35), R2(35), R1(25) were found as 45, 40, and 55%, respectively. The amount of sCOD in R21(35), R21(25), and R22(25) were increased 65, 25, and 35%, respectively. The hydrolysis and solubilization of complex materials is the main mechanism in that phase, so that the amount of sCOD increased except R22(25). WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

100

80

VS (g/L)

R1 (25) R21 (25) R22 (25)

R1 (35) R21 (35) R22 (35) VS in (R1) VS in (R21)

141

(a)

60

40

20

8000

(b)

sCOD (mg/L)

6000

4000

2000

TVFA (mg/L as Hac)

0 2000

(c)

1500

1000

500

0 0

50

100

Time (days)

Figure 3:

150

200

0

50

100

150

200

Time (days)

VS, sCOD, and TVFA concentrations in the reactors.

The total volatile fatty acids (as HAc) for runs are displayed in fig. 3c. Acetic acid was the dominating VFA in reactors. The effluents of reactors contained mainly acetic acid, propionic and butyric acids, although higher fatty acids were found at lower concentrations. The effluent TVFA concentrations of the first-phase reactor at mesophilic and low temperature operated at 2 day HRT increased to 1700 and 1300 mg/litre (as acetic acid), more than 100 and 60% increase over that of the influent of R21(35) and R21(25), respectively. The effluent VFA concentration of the second-stage reactor in mesophilic temperature decreased to 350 mg/litre (as acetic acid), but WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

142 Energy and Sustainability III the effluent concentration of R22(25) remained the same as expected. The TVFA concentration of R1(25) was much lower than R22(25), since biogas production in R1(25) was more than double of R22(25). This resulted more VFA consumption in R1(25). Acetic acid was also the predominant VFA in the effluent. The acidogenic efficiency could be increased with temperature, but mixing and pH control were not important parameters [33]. Total effluent VFA value in one-phase reactor was lower than that of the twophase reactor at mesophilic temperature. It does not mean that more VFAs were converted to methane in one-phase reactor, since more VFA transferred from R21(35) to R22(35). Consequently, higher VFA concentration was converted to biogas in two-phase system. In other words the efficiency of two-phase system was higher than one-phase system in terms of VFA consumption. Anaerobic digestion is a proven technique and at present applied to a variety of waste (water) streams but world wide application is still limited and a large potential energy source is being neglected. Even though several aspects of twophase AD such as increased stability, lower retention time requirements, liquefaction, etc. are very significant for enhanced AD of manure until now, its application has been limited to a few studies.

References [1] Andrews, J.F. & Pearson, E.A., Kinetics and characteristics of volatile acid production in anaerobic fermentation process. Internat. J. Air Wat. Poll., 9, pp. 439–469, 1965. [2] APHA (American Public Health Association), Standard methods for the examination of water and wastewater. 19th Ed., Washington, DC. [3] Azbar, N. & Speece, R.E., Two-phase, two-stage, and single-stage anaerobic process comparison. J. Environ. Eng., 127(3), pp. 240–248, 2001. [4] Demirer, G.N. & Chen, S., Effect of retention time and organic loading rate on anaerobic acidification and biogasification of dairy manure. J. Chemical Technol. Biotechnol., 79 (12), pp. 1381–1387, 2004. [5] Demirer, G.N. & Chen, S., Two-phase anaerobic digestion of unscreened dairy manure. Process Biochemistry, 40(11), pp. 3542–3549, 2005. [6] El-mashad, H.M., Zeeman, G., Loon, W.K.P. van, Bot, G.P.A. & Lettinga, G., Anaerobic digestion of solid animal waste in an accumulation system at mesophilic and thermophilic conditions, start up, Water Sci. Technol., 48(4), pp. 217–220, 2003. [7] Elefsiniotis, P. & Oldham, W.K., Effect of HRT on acidogenic digestion of primary sludge. J. Env. Eng., 120, pp. 645–660, 1994. [8] Ghosh, S., Improved Sludge Gasification by Two-Phase Anaerobic Digestion. J. Env. Eng., 113(6), pp. 1265–1284, 1987. [9] Ghosh, S., Conrad, J.R. & Klass, D.L., Anaerobic acidogenesis of wastewater sludge. J WPCF, 47, pp. 30–45, 1975.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

143

[10] Ghosh, S., Ombregt, J.P. & Pipyn, P., Methane production from industrial wastes by two-phase anaerobic digestion. Water Res., 19(9), pp. 1083– 1088, 1985. [11] Ghosh, S., Buoy, K., Dressel, L., Miller, T., Wilcox, G. & Loos, D., Pilotand full-scale two-phase anaerobic digestion of municipal sludge. Water Environ. Res., 67(2), pp. 206–214, 1995. [12] HACH, HACH Water Analysis Handbook, Loveland, HACH Company, second ed. [13] Han, S.K., Shin, S.H., Song, Y.C., Lee, C.Y. & Kim, S.H., Novel anaerobic process for the recovery of methane and compost from food waste. Water Sci. Technol., 45(10), pp. 313–319, 2002. [14] Hobson, P.N. & Wheatley, A.D., Anaerobic digestion: modern theory and practice, ISBN: 1851669582. Elsevier Applied Science, London, 1993. [15] Ince O., Performance of a two-phase anaerobic digestion system when treating dairy wastewater. Water Res., 32(9), pp. 2707–2713, 1998. [16] Ke, S., Shi, Z. & Fang, H.H.P., Applications of two-phase anaerobic degradation in industrial wastewater treatment. Int. J. Environment and Pollution, 23(1), pp. 65–80, 2005. [17] Keshtkar, A., Meyssami, B., Abolhamd, G., Ghaforian, H. & Asadi, M.K., Mathematical modeling of non-ideal mixing continuous flow reactors for anaerobic digestion of cattle manure. Bioresour. Technol., 87, pp. 113–124, 2003. [18] Kubler, H., & Schertler, C., Three-phase anaerobic digestion of organic wastes. Water Sci. Technol., 30(12), pp. 367–374, 1994. [19] Lo, K.V., Liao, P.H., & Bulley, N.R., Two-Phase Mesophilic anaerobic digestion of screened dairy manure Using Conventional and Fixed-Film Reactors. Agricultural Wastes, 17, pp. 279–291, 1986. [20] Mackie, R.I. & Bryant, M.P., Anaerobic digestion of cattle waste at mesophilic and thermophilic temperatures. App. Microbial. Biotechnol., 43, pp. 346–350, 1995. [21] Nallathambi, G.V., Anaerobic digestion of biomass for methane production: a review. Biomass and Bioenergy, 13(1-2), pp. 83–114, 1967. [22] Pohland, F.G. & Ghosh, S., Developments in anaerobic stabilization of organic wastes the two-phase concept. Environ. Lett., 1, pp. 255–66, 1971. [23] Rustrian, E., Delgenes, J.P., Bernet, N. & Moletta, R., Simultaneous removal of carbon, nitrogen and phosphorus from wastewater by coupling two-step anaerobic digestion with a sequencing batch reactor. J. Chem. Technol. Biotechnol., 73, pp. 421–431, 1998. [24] Summers, R., Hobson, N., Harries, C.R. & Richardson, A.J., Stirred-tank, mesophilic, anaerobic digestion of fattening-cattle wastes and of whole and separated dairy-cattle wastes. Biological Wastes, 20(1), pp. 43–62, 1987. [25] Sung, S. & Santha, H., Performance of temperature-phased anaerobic digestion (TPAD) system treating dairy cattle wastes. Water Res., 37, pp. 1628–1636, 2003.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

144 Energy and Sustainability III [26] Varel, V.H., Hashimoto, A.G. & Chen, Y.R., Effect of temperature and retention time on methane production from beef cattle waste. App. Environ. Microbiol., 40(2), pp. 217–222, 1980. [27] Verrier, D., Roy, F. & Albagnac, G., Two-phase methanization of solid vegetable waste. Biological Wastes, 22 pp. 163–177, 1987. [28] Verstraete, W. & Vandevivere, P., New and broader applications of anaerobic digestion. Environ. Sci. Technol., 28(2), pp. 151–173, 1999. [29] Vigneron V, Ponthieu M, Barina G, Audic JM, Duquennoi C, Mazéas L, Bernet N. & Bouchez, T., Nitrate and nitrite injection during municipal solid waste anaerobic biodegradation. Waste Manag., 27(6), pp. 778–791, 2007. [30] Wang, J.Y., Xu, H.L., Zhang, H. & Tay, J.H., Semi-continuous anaerobic digestion of food waste using a hybrid anaerobic solid–liquid bioreactor. Water Sci. Technol., 48(4), pp. 169–174, 2003. [31] Wellinger, A., Process design of agricultural digesters. Nova Energie GmbH Elggerstrasse 36 8356 Ettenhausen, Switzerland. http://homepage2.nifty.com/biogas/cnt/refdoc/whrefdoc/d14prdgn.pdf. [32] Yilmaz, V. & Demirer, G., Improved anaerobic acidification of unscreened dairy manure. Environ. Eng. Sci., 25(3), pp. 309–317, 2008.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

145

Biodiesel reforming with a NiAl2O4/Al2O3-YSZ catalyst for the production of renewable SOFC fuel N. Abatzoglou, C. Fauteux-Lefebvre & N. Braidy Department of Chemical & Biotechnological Engineering, Université de Sherbrooke, Canada

Abstract Biodiesel’s contribution as a renewable energy carrier is increasing continuously. Fuel cell market penetration, although slow, is now an irreversible reality. The combination of solid oxide fuel cells (SOFC) with biodiesel offers considerable advantages because it entails both high energy conversion efficiency and nearzero atmospheric carbon emissions. This work is aimed at proving the efficiency of a newly-developed (patent pending), Al2O3/YSZ-supported NiAl2O4 spinel catalyst to steam reform biodiesel. Reforming converts biodiesel into a gaseous mixture, mainly composed of H2 and CO, used directly as SOFC fuel. The work is performed in a test rig comprising a lab-scale, fixed-bed isothermal reactor and a product-conditioning train. The biodiesel/water mixtures are emulsified prior to their spray injection in the reactor preheating zone, where they are instantaneously vaporized and rapidly brought to the desired reaction temperature to avoid thermal cracking. Reforming takes place at gas hourly space velocities equal to or higher than those in industrial reforming units. The products are analysed by at-line gas chromatography. The results show that biodiesel conversion is complete at steady state. Thermodynamic calculations reveal that the fast reforming reaction reaches chemical equilibrium. The catalyst’s performance is very efficient and prevents carbon formation and deactivation. Keywords: biodiesel, steam reforming, SOFC, nickel, spinel.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESUS110131

146 Energy and Sustainability III

1 Introduction Fuel cell efficiency in converting chemical energy into electricity is significantly higher than internal combustion engines. With the world need for sustainable development, via substantial cuts to greenhouse gas emissions and energy costs, the combination of fuel cells with renewable fuels, such as biodiesel, is promising. Hydrogen (H2) is the ideal fuel, but solid oxide fuel cells (SOFC) can also be fed by carbon monoxide. Therefore, biodiesel catalytic reforming can serve as a SOFC liquid fuel conversion technology. The main products of biodiesel catalytic reforming are H2, carbon monoxide (CO) and carbon dioxide (CO2). Equation (1) is the core reaction of hydrocarbon steam reforming and (2) is the water gas shift (WGS), a secondary reaction. Cn H m  nH 2O  nCO  n  m 2H 2 H  0  CO  H 2 O  CO2  H 2 H  0

(1) (2)

The purpose of this work is to test a new nickel-alumina spinel (Al2O3/YSZsupported NiAl2O4) material [1] as catalyst of biodiesel steam reforming. 1.1 Biodiesel reforming Biodiesel reforming can be represented by the following global reaction (3): C18 H 36 O2  16 H 2 O  18CO  34 H 2 H  0 

(3)

Even though biodiesel is well known as a renewable source of fuel for the future, biodiesel steam reforming has not been investigated extensively. In [2], the authors reported a thermodynamic simulation study of autothermal (ATR) and steam (SR) reforming of various liquid hydrocarbon fuels. They found the highest theoretical conversion efficiency in gasoline, but biodiesel was in the same range (1% lower on average), depicting its feasibility for in-line reforming with fuel cells. In [3], biodiesel reforming has been simulated and tested in a heat-integrated fuel processor. A commercial precious metal-based catalyst was tested in the fuel processor. These authors obtained 99% conversion in the ATR processor with a steam to carbon molar ratio of 2.5, added oxygen, pressure of 2.1 bar, and gas hourly space velocities (GHSV) of 30,000 h-1. In [4], an experimental study of ATR was performed with platinum (Pt) and rhodium (Rh)-based catalysts synthesized. Hydrogen was produced at temperatures higher than 510°C with a steam to carbon molar ratio of 2 and an oxygen to carbon molar ratio of 0.4. Coke formed on the catalyst and reactor vessel walls. Only ATR was investigated in all biodiesel conversion studies reported, both theoretical and experimental. In the experimental studies, only noble metal WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

147

catalysts were tested. Transition metals (noble and non-noble) are the most catalytically active in hydrocarbon reforming, and noble metals are known to be more resistant but also more expensive [5, 6]. 1.2 Liquid hydrocarbon reforming There are 3 main routes for catalyst deactivation in hydrocarbon reforming: sintering, sulphur poisoning, and coking. Sintering is a typical deactivation mechanism for every high temperature catalytic reaction. Sulphur poisoning is expected when fossil fuels are used; this is not the case with biodiesel, which does not contain sulphur moieties. Two main reaction pathways are responsible for coking: the Boudouard reaction (CO disproportionation to C and CO2), and hydrocarbon cracking. Coke formation mechanisms are different in non-noble and noble metals. Nickel catalysts are prone to coking, because nickel allows carbon diffusion and dissolution which results in whisker carbon formation [7]. Noble metals do not dissolve carbon significantly, but considerable amounts of carbon-rich structures (i.e. graphite layers along the metallic surface) are produced via other carbon deposition mechanisms [7] which lead to coking. Catalysts used for liquid hydrocarbons reforming reactions are usually deactivated within 100 hours of use [8–10]. In some cases, concentrations closed to theoretical thermodynamic equilibrium can be reached, depending on the catalyst and reaction severity (mainly sufficiently low space velocities). Noble metal catalysts are deactivated at a slower rate than non-noble metal catalysts. Strohm et al. [10] investigated the SR of simulated jet fuel without sulphur and reported constant hydrogen concentrations of 60%vol for 80 hours with a Ceria-Al2O3-supported Rh catalyst. The reactions occurred at temperatures below 520°C and water to carbon molar ratio of 3. With sulphur added in the feed (35 ppm), the catalyst was deactivated within 21 hours. Ming et al. [11] obtained constant H2 concentrations of 70% over a 73-hour steady state operation for hexadecane steam reforming with an Al2O3-supported bimetallic noble metal catalyst and metal-loading <1.5%,. The operating conditions were water to carbon molar ratio was 2.7 and an operating temperature of 800°C. In most of the cases, deactivation occurs within 8 hours when non-noble metal catalysts (mainly nickel) are employed under most reaction severities, with less H2 in the products [7, 12, 13]. However, Kim et al. [14] reported activity of a catalyst over a 53-hour steady state operation, but under favourable conditions. The H2 concentrations decreased from 72% to 65% with a magnesia-aluminasupported Ni catalyst (Ni/MgO-Al2O3) at a temperature of 900°C, GHSV of 10,000 h-1, and a water to carbon molar ratio of 3. They reported lower deactivation rates for bi-metallic catalyst using noble metal, with addition of Rhodium to the catalyst. 1.3 Spinel catalyst Spinel NiAl2O4 has been studied with fuel cells for internal methane reforming [15]. The catalyst was prepared by solid surface reaction with stoichiometric WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

148 Energy and Sustainability III quantities of Al2O3 and nickel oxide (NiO) to form spinel. It was reduced prior to its use; the so-reduced final fresh catalyst was in the form of Nix/Ni1-xAl2O4-x. It was reported to be active and relatively stable at a temperature of 800°C in a 250-hour test. The formation and the stability of spinel and its capacity to be reduced seem to vary according to the reaction undertaken to form spinel, the stoichiometry and Al2O3- type. In [16], spinel was produced by solid state reaction with nanometric gamma phase alumina (γ-Al2O3) impregnated with nickel nitrate (Νi(ΝΟ3)2·6H2O), at temperatures ranging between 1,000°C and 1,300°C. The authors observed that the catalyst was totally reduced at temperatures higher than 950°C, with a mixture of CO and CO2 as reducing atmosphere (and oxygen partial pressure of 1x10-15 atm). In [17], the authors noted that spinel formed of NiO and α-Al2O3 could be reduced at 650°C, in severe reducing conditions with pure H2 (oxygen partial pressure of 1.9x10-18 to 1.0x10-20 atm).

2 Experimental 2.1 Catalyst preparation The NiAl2O4-based catalyst tested in this work was produced by the wet impregnation method. Al2O3 (mixture of amorphous and γ-Al2O3) and YSZ (Y2O3-ZrO2) (50%–50%) support was prepared by mixing the 2 powders mechanically. Al2O3 powder size was 40 µm, and YSZ powder size distribution had an upper limit at 20 µm. The Al2O3 and YSZ powders were impregnated with an Ni(NO3)2•6H2O aqueous solution (targeting a 5% w/w nickel (Ni) load in the final formulation). Water was evaporated, and the resulting impregnated powder was dried overnight at 105°C. The so-dried mixture was calcined at 900°C for 6 hours to form spinel, by a solid state reaction. 2.2 Catalyst characterization The composition and morphology were analysed by scanning electron microscopy (SEM). SEM was performed using Hitachi field emission gun and energy dispersive X-ray spectroscopy (EDXS) Oxford detector with an ultra-thin ATW2 window. 2.3 Reforming experimentation A schematic of the reactor is presented in Figure 1. Reactor inner diameter was 46 mm, and catalytic bed length was 60 mm. The catalyst in powder form was dispersed in quartz wool, which was then compacted in the reactor to form a catalytic bed of quartz fibre containing catalyst particulates. This configuration prevented channelling issues and helped obtain a uniform catalytic bed with a small amount of catalyst. An emulsion-in-water technique was adopted for biodiesel injection. This method was chosen to enhance hydrocarbon/water mixing. The 2 immiscible

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

Argon

149

Vaporizing of reactants (110 Pre‐heating zone

Reactants

Reaction temperature zone Catalytic zone

Trap

GC

Figure 1: Schematic of the reforming set-up. reactants were emulsified according to a surfactant-aided protocol. The reactants entered at room temperature and were rapidly heated and vaporized in the preheating zone maintained at 550°C. The temperature just before the catalyst bed was between 30°C and 45°C below the reaction temperature, depending on operating parameters. Argon served as inert diluent and internal standard for liquid hydrocarbon steam reforming. The water to steam molar ratio was varied between 1.9 and 2.4. Operating temperatures were 700°C and 725°C with GHSV ranging from 5,500 and 13,500 cm³reac gcat-1 h-1 at barometric pressure. Reforming products were analysed by Varian CP-3800 gas chromatography (GC). The exit gaseous flow rate was measured by a flow rate mass meter (Omega FMA-700A). Biodiesel, from used vegetable oil, was produced by a transesterification process developed by Biocarburant PL (Sherbrooke, Qc, Canada; www.biocarburantpl.ca). Experimental conversion was calculated (4): X

NCOout  NCO2  NCH 4 out

out

(4)

NCmHn  m  NSurfactantin Y in

with Ni being the total number of moles of component i at the reactor exit or inlet, and Y being the number of carbon atoms in the surfactant. Overall conversion was calculated for liquid hydrocarbon reforming based on the total amount of carbon fed in the reactor. Hydrocarbons were considered to be converted when they were transformed into gaseous products (CO, CO2 or CH4). Carbon found in the reactor after the experiment was therefore not considered as converted hydrocarbon. WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

150 Energy and Sustainability III In the reported tests, the reactor exit concentrations of H2, CO, CO2 and CH4 were compared to theoretical thermodynamic equilibrium concentrations, to determine if equilibrium was reached. Thermodynamic equilibrium concentrations were calculated with FactSage software on the basis of Gibbs energy minimization.

3 Results and discussion The catalyst presented here for biodiesel reforming has already proved to be efficient for liquid hydrocarbon steam reforming at high GHSV and relatively low temperatures and water to carbon ratio [1]. 3.1 Catalyst characterization The catalyst formulation was analyzed using SEM analysis. The targeted catalyst form is NiAl2O4 spinel on the surface of an alumina support without any metallic nickel or nickel oxide. Surface SEM and SEM-EDXS analyses of the fresh catalyst are reported in [1]. Figure 2 is a SEM analysis of the fresh catalyst surface and more particularly of the Al2O3 surface which is known to be the main support of the spinel phase.

Figure 2: SEM micrograph of the Al2O3 surface.

3.2 Steam reforming results 3.2.1 Measurement errors The errors associated with concentration data obtained by GC appear in Table 1. They were calculated with an external standard.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

Table 1: Gas

H2 CO CO2 CH4 Ar

151

Gas concentration measurement errors.

Standard gaseous concentration (%) 55.16 19.70 6.96 2.08 16.10

Absolute error (on % concentration of the standard) 0.46 0.21 0.38 0.04 0.22

Relative error (%)

0.83 1.05 5.45 1.87 1.37

In addition to GC concentration measurement errors, the mass flow meter for quantifying exit gas flow introduced a second error in the conversion calculations. The accuracy of the mass flow meter was 1%. Maximum and minimum values were therefore calculated for each conversion, with extreme values for concentrations and flow rates based on known error and accuracy. 3.2.2 Biodiesel steam reforming Table 2 lists the conditions of 3 different biodiesel reforming test runs with the associated overall conversion calculated. Table 2:

Biodiesel reforming test run description.

Run 1 2 3 Temperature (°C) 700 725 725 Catalyst weight (g) 5.0 3.0 3.0 Run time (h) 3 4 2 GHSV (cm3g-1h-1) 8,700 5,500 13,500 H2O/Ca (mol/mol) 1.9 1.9 2.4 Conversion (± 3%) 88 100 85 a Water to carbon (H2O/C) ratio calculated including surfactant. Dry gaseous concentrations at the reactor exit are presented in Figure 3. Concentrations were stable for the entire reaction time with no catalyst deactivation observed. Temperature increase and flow rate decrease would obviously lead to 100% conversion. It can also be observed that an increase of GHSV decreases conversion, even at a higher H2O/C ratio. This reduction of conversion is associated with reaction kinetics. Figure 3 compares the theoretical equilibrium and experimental concentrations of the dry gas at the reactor exit. These preliminary data are indicative of the ability of this catalytic formulation to efficiently steam reform commercial biodiesel. The catalyst is not poisoned by sulphur (not present in biodiesel in detectable quantities), and since carbon formation is insignificant, the only remaining catalyst deactivation mechanism is sintering. Although the extent of the performed tests is not WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

152 Energy and Sustainability III sufficient to allow us to evaluate such a mechanism, NiAl2O4 thermal mobility is much lower (insignificant at reaction conditions) than that of metallic Ni. Thus, the expected life cycle of the proposed catalyst is considerably longer than any other metallic Ni-based formulation. High GHSV, which give complete biodiesel conversion, are indicative of a rather surface reaction kinetics-controlled process. However, additional experiments are needed, in conditions under which the reaction does not reach chemical equilibrium, in order to evaluate the kinetic parameters (mainly activation energy) as well as the mass transfer and chemical reaction resistances.

Experimental Concentrations (% mole)

80 70

H2

GHSV=8700; H2O/C=1.9

60 50 40 30 CO

20 10

T = 700°C

CO2 CH4

0 0

10

20 30 40 50 60 Equilibrium Concentrations (% mole)

70

Experimental Concentrations (% mole)

80 H2

GHSV=5500; H2O/C=1.9 GHSV=13500; H2O/C=2.4

70 60 50 40 30

CO

20 CO2

10

T = 725°C

CH4

0 0

Figure 3:

10

20 30 40 50 60 Equilibrium Concentrations (% mole)

70

Experimental vs theoretical concentrations in biodiesel reforming product (Errors in values are less than 1% in all cases).

The concentrations for run 2 were equal to those at chemical thermodynamic equilibrium. In run 1, even if conversion was not complete, the concentrations were near equilibrium. It should be noted that for biodiesel reforming below 700°C, theoretical equilibrium concentrations predict the presence of significant WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

153

amounts of methane and coke formation if the water to carbon ratio in reactants is not higher than stoichiometric ratio. 3.3 Used catalyst characterization Figure 4 is a SEM micrograph of an Al2O3 particulate of the NiAl2O4 catalyst used in run 2 of the biodiesel reforming test and comparison with Figure 2, which is the same for the fresh catalyst, proves that there was no significant carbon deposition on the surface. Some carbon whiskers were found on an extent lower than 5% of the surface; this is, however, expected because of local surface nanoheterogeneities and the possibility that some NiO on the surface was not transformed into NiAl2O4 which could form Ni during SR reactions.

Figure 4:

SEM picture of the catalyst after run 2.

4 Conclusion An Al2O3/YSZ-supported NiAl2O4 catalyst has been tested efficiently in biodiesel SR. 100% conversion was obtained at relatively low severity conditions. Increasing GHSV above 10,000cm3g-1h-1 decreased conversion, but dry concentrations of the exit gas were still near equilibrium. No catalyst deactivation was encountered. There was no observable carbon on the surface of the catalyst used in these conditions, even with a water to carbon ratio lower than 2.

Acknowledgements The authors are indebted to SOFC Network Canada and the Agricultural Biomass Innovation Network (ABIN) for funding related to this project. The financial contribution of the National Science & Engineering Research Council (NSERC) of Canada through Discovery Funding and Students Awards is also WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

154 Energy and Sustainability III acknowledged along with the Le Fonds québécois de la recherche sur la nature et les technologies (FQRNT) for Students Awards. Biodiesel was kindly provided by Biocarburant PL. Many thanks are due to Carmina Reyes Plascencia and Henri Gauvin for their technical support and to Sonia Blais and Stéphane Gutierrez for their help in catalyst characterization. Finally, special thanks to Ovid Da Silva for reviewing the manuscript.

References [1]

[2]

[3]

[4]

[5]

[6] [7]

[8]

[9]

[10]

[11] [12]

Fauteux-Lefebvre, C., Abatzoglou, N., Blanchard, J. & Gitzhofer, F., Steam reforming of liquid hydrocarbons over a nickel-alumina spinel catalyst, Journal of Power Sources, 195(10) pp. 3275-3283, 2010. Specchia, S., Cutillo, A., Saracco, G. & Specchia, V., Concept study on ATR and SR fuel processors for liquid hydrocarbons, Industrial and Engineering Chemistry Research, 45(15) pp. 5298-5307, 2006. Kraaij, G.J., Specchia, S., Bollito, G., Mutri, L. & Wails, D., Biodiesel fuel processor for APU applications, International Journal of Hydrogen Energy, 34(10) pp. 4495-4499, 2009. Ospinal-Jiménez, M., Hydrogen production study using autothermal reforming of biodiesel and other hydrocarbons for fuel cell applications, 2006, Master of Science degree thesis, University of Puerto Rico. Ibarreta, A.F., Sung, C., Optimization of Jet-A fuel reforming for aerospace applications, International Journal of Hydrogen Energy, 31(8) pp. 1066-1078, 2006. Lucka, K., Kohne, H., Challenges in diesel reforming: Comparison of different reforming technologies, Clean Air, 7(4) pp. 381-390, 2006. Alvarez-Galvan, M.C., Navarro, R.M., Rosa, F., Briceno, Y., Gordillo Alvarez, F. & Fierro, J.L.G., Performance of La,Ce-modified aluminasupported Pt and Ni catalysts for the oxidative reforming of diesel hydrocarbons, International Journal of Hydrogen Energy, 33(2) pp. 652663, 2008. Cheekatamarla, P.K., Lane, A.M., Catalytic autothermal reforming of diesel fuel for hydrogen generation in fuel cells: I. Activity tests and sulfur poisoning, Journal of Power Sources, 152(1-2) pp. 256-263, 2005. Rosa, F., Lopez, E., Briceno, Y., Sopena, D., Navarro, R.M., AlvarezGalvan, M.C., Fierro, J.L.G. & Bordons, C., Design of a diesel reformer coupled to a PEMFC, Catalysis Today, 116(3) pp. 324-333, 2006. Strohm, J.J., Zheng, J. & Song, C., Low-temperature steam reforming of jet fuel in the absence and presence of sulfur over Rh and Rh-Ni catalysts for fuel cells, Journal of Catalysis, 238(2) pp. 309-320, 2006. Ming, Q., Healey, T., Allen, L. & Irving, P., Steam reforming of hydrocarbon fuels, Catalysis Today, 77(1-2) pp. 51-64, 2002. Gardner, T.H., Shekhawat, D., Berry, D.A., Smith, M.W., Salazar, M. & Kugler, E.L., Effect of nickel hexaaluminate mirror cation on structuresensitive reactions during n-tetradecane partial oxidation, Applied Catalysis A: General, 323 pp. 1-8, 2007. WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

[13]

[14]

[15]

[16]

[17]

155

Gould, B.D., Tadd, A.R. & Schwank, J.W., Nickel-catalyzed autothermal reforming of jet fuel surrogates: n-Dodecane, tetralin, and their mixture, Journal of Power Sources, 164(1) pp. 344-50, 2007. Kim, D.H., Kang, J.S., Lee, Y.J., Park, N.K., Kim, Y.C., Hong, S.I. & Moon, D.J., Steam reforming of n-hexadecane over noble metal-modified Ni-based catalysts, Catalysis Today, 136(3-4) pp. 228-234, 2008. Kou, L., Selman, J., Activity of NiAl2O4 catalyst for steam reforming of methane under internal reforming fuel cell conditions, Electrochemical Society Proceedings, 99(19) pp. 640-646, 1999. Huang, Z.R., Jiang, D.L., Michel, D., Mazerolles, L., Ferrand, A., di Costanzo, T. & Vignes, J.L., Nickel-alumina nanocomposite powders prepared by novel in situ chemical reduction, Journal of Materials Research, 17(12) pp. 3177-3181, 2002. Jiong, Y.S., Kou, L., Nash, P. & Selman, J.R., Behavior of nickel aluminate spinel under reducing conditions, pp. 456-68, 1997.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

This page intentionally left blank

Section 3 Energy management

This page intentionally left blank

Energy and Sustainability III

159

Energy management and sustainable development S. S. Seyedali Ruteh National Iranian Gas Company, Tehran, Iran

Abstract Energy is one of the most fundamental issues for sustainable development. Sustainable development is a changing process, circuiting investment, orientating technology and institution for compatible with the needs of the present and the future. In order to achieve sustainable development and make improvement in efficiency services, optimal and efficient ways for using energy must be evaluated and practiced. The weakness in efficiency of production process, transmission, distribution, consumption and not dependency on reliable energy needs sustainable development policy. In other words, sustainable development and environment production depend on the optimal use of energy resources especially for renewable energy. In this article, energy and its trend of changes are discussed at first. Then the importance of energy in creating sustainable development is discussed. The goal of this study is to introduce data and to evaluate other countries’ experiences as well as using these experiences for macro policies in different fields and dimensions for improving efficiency. Keywords: energy management, sustainable development, improving efficiency.

1 Introduction In economic terminology the concept and process of economic development is quite familiar, however in recent decades there have been many concerns about the significance and necessity of a sustainable development process. Sustainable development is development that meets the needs of the present without compromising the ability of future generations to meet their own needs. It contains within it two key concepts: WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESUS110141

160 Energy and Sustainability III 

the concept of needs, in particular the essential needs of the world’s poor, to which overriding priority should be given; and  the idea of limitations imposed by the state of technology and social organization on the environment’s ability to meet present and future needs. Energy is central to sustainable development and poverty reduction efforts. It affects all aspects of development social, economic, and environmental including livelihoods, access to water, agricultural productivity, health, population levels, education, and gender-related issues. None of the Millennium Development Goals (MDGs) can be met without major improvement in the quality and quantity of energy services in developing countries. UNDP’s efforts in energy for sustainable development support the achievement of the MDGs, especially MDG 1, reducing by half the proportion of people living in poverty by 2015. Through an integrated development approach, UNDP works to help create enabling policy frameworks, develop local capacity and provide knowledgebased advisory services for expanding access to energy services for the poor. The role of energy is not limited to these examples only and certainly energy has fundamental role in the process of sustainable development. If we believe in sustainable development and its principles, we have to consume resources in such a way that the next generation can also benefit from them. If industry wants to move in a stable path, we need to consider energy management today. Also the close connection between energy and environment has led to more in- depth attention to energy saving issue. Energy and its management are necessary to gain sustainable development. As a result, findings new ways to achieve optimal consumption in dealing with use of permanent technologies and recycling materials would be necessary. In the present essay energy management, Energy efficiency, Sustainable energy and the methods of achieving it in order to attain sustainable development will be analyzed. International organizations have referred to energy as the main factor in sustainable development in the third millennium. At a word summit for sustainable development in 2003, UNDP has issued a statement focusing on the issue of sustainable energy while referring to the main messages of the meeting as energy and its role in development, some of which are mentioned here:(Mcdad [1]) 1.

Energy is a basic element in poverty reduction, job creation, livelihood and expanding opportunities.

2.

Energy is not just electricity; and clean fuels have a particular significance.

3.

The definition of sustainability, especially in the field of energy, is wider than the environment.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

161

2 The role of energy in achieving to sustainable development From development viewpoints the significance of energy can be briefly summarized as follows: (World Bank [2]) 2.1 For social and economic development Energy services are vital in order to reduce poverty and achieve the millennium goals. All people need energy for cooking, heating, lighting, cooling, transportation, communication, information services and education. In health clinics, electricity makes it possible to refrigerate vaccines, operate medical equipment and provide lighting after sunset. The World Health Organization said that almost 200 thousand people lose their lives as a result of the carbon produced by sooty stoves each year. Instead of traditional polluting fuels which lead to polluted urban air, clean fuels must be used. 2.2 For macroeconomic stability Encountering efficient transformation in energy part in order to guarantee economic growth and poverty reduction is generally considered the first point of focus in the developing countries’ energy section policy. Energy security can be attained through expansion and diversity energy sources and reduce dependence on high and unstable fuel prices. This will lead to less reliance on imported fuels, improvement of balance of payment and financial liberation which can be used in other projects. 2.3 For the environment Clean energy for development and climate changes must be considered an urgent challenge that gives warning to reduce greenhouse gases. To have an environment with the least amount of carbon, we need to take an aggressive program on energy production and end-use efficiency improvement, significant penetration renewable energy technologies and fuel switching. Renewable energy in off-grid electricity service can help the dispersed rural population with relatively low income and demand levels to gain access to lighting and power services. These energies can be used inside and outside of the grid and increase the security of energy supply. Effective measures to increase energy efficiency will reduce the costs in presenting services and improve the quality of air in homes, and also, by decreasing energy cost, improve competitiveness in large and medium-sized firms. In this regard sustainable management of the natural forest can transform the traditional fuels resulting from indiscriminate cutting of trees to renewable energy resources. Meanwhile it can lead to considerable progress in village and ecosystem rehabilitation and carbon sequestration.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

162 Energy and Sustainability III

3 A review on energy development in the next two decades With regard to the massive foreign investment that has been made in China and India in the past years, these two countries have had drastic changes on the global energy system. These changes are noticeable both in terms of absolute number of energy consumption and by the share and weight of each of them in the market. As the two countries get richer, people can enjoy better living facilities as a result of economic growth which indeed is considered a positive factor. But the increasing global demand for energy can also be seen as a serious alarm. It is estimated that the global primary energy needs until the 2030 will reach 55%, compared to 2005 with 1.8% annual growth rate. Thus the energy demand will increase up to 17.7 billion tons of crude oil compared with 11.4 billion tons in 2005. Developing countries that have a faster population and economic growth will account for more than 74% of this global increase by the year 2030 and from that number up to 45% would be China’s and India’s share. OECD countries will take over one-fifth and transitional countries 6% of this increase. Developing countries will have 47% of the market in 2015 and more than half of it in 2030. This figure is currently 41%. Almost half of the increase in global energy production is conducted toward producing electricity and one-fifth of it is spent on transportation (OECD/IEA [3]). As shown in figure 1, the share of developing countries from primary energy demand in the world will increase from 30% in 2000 to 43% in 2030. Thus it is governments’ responsibility to execute a strong, immediate and comprehensive plan to put the world on path for sustainable development. Energy management is an undeniable necessity to achieve sustainable development. In the near future, measures to improve energy efficiency as a result of energy management would be consider as the cheapest and fastest way to control the demand for energy and CO2 emission. Regional Shares in World Primary Energy Demand

Source: IEA, World Energy Outlook 2002

Figure 1:

Regional shares in world primary energy demand.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

163

4 Environmental consideration of energy demand The increasing amount of CO2 and other greenhouse gases jammed in the atmosphere due to using fossil fuel results in increased temperature and climate changes. According to the scenario mentioned about rising energy demand over the period 2005–2030, carbon dioxide will have a 70% increase and compared to 22 billion tons, its current level, will reach 38 billion tons.(OECD/IEA [3]), (Cliniand and Ortis [5]). Figure 2 shows that the process of carbon dioxide emission over the past years until 2030 according to different regions in the world. Due to the mentioned changes in the energy market, the classification of polluting geographical region in the word will also change.

Figure 2:

Energy-related CO2 emission in the world (million tonnes).

On an historical basis, OECD countries have been the biggest producer of greenhouse gases. In the year 2000, these countries produced 55% of carbon emission in the world, while the share of developing countries would rise to 47% and will be known as the areas where the heaviest volume of pollution is released and OECD countries’ share will decrease to 43% (Cliniand and Ortis [5]), (OECD/IEA [6]). Unlike the past three decades, the emission of pollutants will grow faster than energy consumption and this issue highlights the necessity of careful and efficient planning in energy management and energy consumption by all the countries to sustainably maintain and manage the environment. By energy management that leads to efficient use of fossil fuels in industry, building, transportation and changing the condition toward using renewable energies, the amount of pollutants can be controlled and reduced (OECD/IEA [3]), (Cliniand and Ortis [5]). The importance of maintaining and managing the environment is such that nowadays environment requirements are considered as the determinant economic growth rate in the energy sector. In fact, energy consumption is increasingly affected by environmental regulation and the behaviour of consumers can change according to their awareness of the environment. Most of these changes have happened as a result of the increasing influence of NGOs WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

164 Energy and Sustainability III with regard to the environment and serious efforts to prevent the destruction of the ecosystem and human health and will, hopefully, end in stronger regulation to reduce pollution of the ecosystem. All these issues lead human knowledge to the idea of the optimum use of energy, its management and increased efficiency in consumption. (OECD/IEA [6]), (Fatih [8]), (Gan [9])

5 Energy management and sustainable development The concept of energy management includes energy efficiency, energy saving, energy tariff and determining the appropriate type of energy and its price. A close link between energy and the environment has highlighted the issue of energy management. The fundamental goal of energy management is to produce goods and provide services with the least cost and least environmental effect. The objective of energy management is to achieve and maintain optimum energy procurement and utilization, throughout the organization and: to minimize energy costs/waste without affecting production and quality, to minimize environmental effects, Energy Audit is the key to a systematic approach for decision-making in the area of energy management. It attempts to balance the total energy inputs with its use, and serves to identify all the energy streams in a facility. It quantifies energy usage according to its discrete functions. Globally we need to save energy in order to:  

Reduce the damage that we are doing to our planet, Earth. As a human race we would probably find things rather difficult without the Earth, so it makes good sense to try to make it last. Reduce our dependence on the fossil fuels that are becoming increasingly limited in supply

Any of the mentioned methods of energy management would in a way lead to an increase in energy efficiency. Over a long term period this increased efficiency would have many effects on the economy by reducing costs and making stable energy for developing. In the following part the influence of efficiency on sustainable development will be discussed.

6 Improving energy efficiency Energy efficiency provides a unique opportunity to raise some important challenges relating to energy which are energy security, climate change and economic development. Existing experiences show that efficiency in energy has considerable benefits. If an efficient policy in the energy sector had not been used from 1973, global energy consumption would have been 50% more than the current level. It is estimated if influential measures on energy efficiency costs are executed until 2030, more than 83 Exa J (Exa=1018) energy can be saved (OECD/IEA [10]). Improving energy efficiency which is the result of energy management can be achieved through different ways in the fields of production, WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

165

distribution and consumption. Better insulation of buildings, using improved equipment and improving efficiency and modernization in the industry sector of factories are considered the best of such measures (World Bank [7]). These measures can be used in the economic part of any country but, in spite of saving costs, the implementation of such measures face several barriers. Ignoring of firms from the existing facilities, lack of enough funds to finance, lack of favourable regulation, small projects and lack of appropriate and accessible technology in the desired region are among the most important barriers. The solution to these problems is in differentiating them from one another, for example adjusting regulation, improving technology, setting real price and liberalization in the market.

7 Finding and benefits of energy efficiency Any country and any energy sector has some fields for energy saving. Energy can be more effectively supplied by improving efficiency in power plant and transmission system. According to an estimation of the International Energy Agency (IEA), the effect of improving energy efficiency in member states has shown considerable progress during the past decades. However, due to the increased use of many diverse home appliances in recent decades, the rate of energy efficiency improvement from 1990 has been equal to half of this parameter in past decades. In figure 3, the hypothetical consumption level in the absence of measures related to efficient use is shown in contrast with the actual consumption. Base on IEA’s forecast in the book “The Prospect of Energy Technology”, the current rate of energy efficiency improvement must be at least double the current figure to have a realistic situation in relation with sustainability of energy in the future (OECD/IEA [11]).

Figure 3:

Energy efficiency improvement

Energy efficiency improvement

Annual energy use

Annual energy use

The effects of improvement in energy efficiency on final energy consumption (percent).

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

166 Energy and Sustainability III The demand for energy services in member states during the period of 1990– 2004 has risen annually with the average growth of 1.8%. However, at the same time, in countries the rate of GDP’s growth was 2.3% which shows energy consumption activities have grown more slowly than the overall economy. Thus, half of the increase in demand for energy services has been supplied by the increase in energy consumption and the other half has been compensated for through improvement in energy efficiency with the annual average of 0.9% in the period of 1973–1990 an estimated 2% (OECD/IEA [6]). All these measures lead to a considerable amount of saving in energy demand and supply. According to IEA estimates, energy consumption in building and transportation industries can be reduced to 33% by 2050. The lighting sector in developing countries has great capabilities for energy saving and quality improvement. The growth of lighting consumption in these countries has been twice (3.6%) the growth in industrial countries (1.8%) (World Bank [12]).

8 The macroeconomic effect of energy efficiency Based on the claims of energy efficiency, improvement on the large scale can result in increased overall efficiency and GDP. The studies of economic input– output models show that consumer and enterprise owner have used the benefits from energy saving once more in economic activities. For example, a 15% reduction in energy consumption during 1995–2010 in UAS caused 770 thousand new jobs which is equal to a 0.44% increase in overall employment rate and 14 billion dollars of wages equal to 0.27% increase in 2010 revenue. Through postponing the need to build new power plants and fuel saving, energy efficiency can reduce the demand for financial resources in the developing countries and also operation and maintenance costs. Companies improve their financial performance and take advantage of benefits by creating effective competition in the private sector. Less energy consumption leads to public interest since it reduces pollution and improves working conditions by providing better lighting and clean air. With regard to considering climate change, energy efficiency would be the best, cheapest and fastest way to reduce the destructive effects of it in the next decades. To summarize the macroeconomic effects of energy efficiency in a few sentences, it should be mentioned that with regard to the related fields of these measures, achieving sustainable economic development would be possible. Since economic development involves four main factors of economic growth, poverty reduction, energy security and environmental sustainability. Cooperation of the mentioned factors through measures that caused energy efficiency can lead to sustainable development.

9 Long term ways of achieving sustainable energy There are two main ways of achieving sustainable energy: macroeconomic planning in the field of energy and operational measures on a micro level. From a macroeconomic view point, using clean and low-carbon energies and WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

167

expanding related infrastructures can be named and the most prominent ones are mentioned bellow: Electricity generation from natural gas: it seems that a share of natural gas in electricity production will be highlighted until 2050 and reach 28% from the current 23%, so that generated electricity in that year would be more than twice the same production level in 2033 (OECD/IEA [11]). CO2 production from natural gas is roughly half of coal per kilowatt hour electricity. Considering the advance made in power generation technologies the efficiency of combined cycle power plants has reached 60% and using these technologies would significantly reduce pollution level. Energy production from renewable resources: until 2050, the share of these resources such as hydro-electric projects, wind, solar energy, etc., would reach from the current level of 18% to 34% which would lead to pollution reduction in the range of 9% to 16% in CO2 (OECD/IEA [11]). Hydroelectric plants which are considered the cheapest energy resource in some regions have great capabilities for growth particularly in small scale. These power plants are considered as the largest renewable energy resources and each country much its maximum ability of water resources. The capital cost of these power plants are low and based on estimates, the cost in member states is 2400 dollars for creating energy per MW capacity and production and operation cost would be 0.3 to 0.4 dollars for every KW per hour. With regard to potential technical capacity of creating small hydro plants in the word, which is around 150 to 200 GW and production cost 0.02 to 0.06 dollars per KW –hour, lower than production cost level, but only 5% of this global capacity has been used. According to drastic reduction of costs through the use of wind plants, the massive use of these resources has become more attractive. The cost of turbine construction per KW is at best estimated 0.04 dollars which compare to other energy resources has been assessed as competitive. With regard to the advances a head of this technology, it is expected that using these turbines increase rapidly. In some regions, this energy is considered the second renewable resources (OECD/IEA [15]). There are many cases in micro-level tat have great capability for efficient energy consumption. In many countries, the new buildings can save energy up to 80% more than other ones. In England, for example, improving construction standards reduce energy consumption to 60% from 1965-2005 (Geller [13]). Using better isolation, ventilation and refrigeration system can improve performance from 30% to 40%. The maximum attainable saving in lighting system from 30% to 60% is achievable. Industry and transportation sectors are also very important, since they consume major petroleum products and saving in these sectors are the fastest way to achieve energy efficiency and prevent pollution emissions (OECD/IEA [11]). Improving energy efficiency through preventing network transmission casualty is also another major method. Network transmission casualty is very high in developing countries. In Asia electricity networks, for instance, the discrepancy between produced and consumed electricity, the total rate of network casualty is almost 43% and in Latin America around 51%, which are WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

168 Energy and Sustainability III unbelievably high [16]. In this regard, using appropriate conductors and equipment which have less heat production and, as a result, less energy casualty would be influential. The technical casualty rate in the USA is 6% to 7%, this figure is 3 to 5 times more in developing countries. The fields of improving energy efficiency in different sectors are shown in table 1. Table 1:

The opportunities for energy efficiency in important consumption sectors.

Sector Name

The opportunities for energy efficiency

Building

Overall building design, better insulation

Industry

Industrial progress, recycling waste heat

Cities and Municipalities

Regional heating system, using energy combination, efficient lighting system in passages

Agriculture

Using pumping system and advance irrigation

Energy Supply

Transportation Households

New power plant: integrated cycle, integrated gasification combined cycle (IGCC), and using other advance combustion system. renovating current establishment: in the field of energy production including water plants Advanced petrol and diesel engines, extensive urban transport system, using CNG Using efficient equipment

A very effective and useful measure that is experienced in many countries is to introduce and use standards and energy labels on energy consuming appliances which have been invented and executed by Collaborative Labeling and Appliances Standards Program (CLASP). These measures were so effective that it has been said: investing in standards and labeling is more effective than investing in energy production. From 1999 (when the organization was founded) 21 cases of new standards have been introduced which are executed in 54 countries. According to estimates, using these standards will prevent 90 TW/H energy and 86 million tons of carbon dioxide emission by 2014. For example, China has managed to save 33.5 TW/H or almost 9% in the household electricity sector.

10 Role of government in creating a stable policy encouraging low-carbon energies and effective on energy efficiency New energy technologies might be more expensive than the current equipment, even with the assumption of total commercial function. Therefore, if there is no economic incentive no significant results would be made. There are different ways to achieve these goals in the form of national or international plans and WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

169

also through fiscal and regulatory measures. Both developed and developing countries need such incentives. Also, developed countries have a significant role in helping developing countries to improve and transmit technical knowledge, expanding capacities and research and developed cooperation. Fortunately in recent decades, particularly in the last few years, policy makers have understood the importance of energy security and the environmental impacts of in efficiency. In their technical and economic support, international organizations and institutions have declared making energy consumption efficient as one of their priorities that matches the development goals in the third millennium and by providing financial and technical facilities, have taken serious steps on this path. An international bank group, one of these institutions, has invested up to 1.3 billion dollars in 40 countries from 1990 in the field of energy efficiency (Word Bank [12]). IFC has also considered measures for private sector investment that shows the significance of establishing and maintaining energy and finally, determine achieving sustainable development. So, from a national scale, governments’ roles and responsibilities are more fundamental and they have to execute coherent policies and encourage society to use existing experiences. These measures can be different for every country’s condition and its priorities. The strategies that governments can use to improve and promote energy efficiency include:  Using tools based on policies and guidelines.  Setting necessary regulations for making energy services efficient.  Organization support and underpinning financial structure.  Using market mechanism. A successful overall strategy would aim at: a. b. c. d. e. f. g. h. i.

Reducing the gap between energy demand and supply. Improving energy efficiency and conservation by lowering energy and resource intensity. Achieving the optimal energy mix. Diversifying sources of energy supply. Investing in energy infrastructure development. Shifting to alternative and renewable sources of energy. Encouraging innovation and competition through research and development. Reducing vulnerability to energy price fluctuations. Achieving good energy sector governance.

11 Conclusion With regard to global energy market transformation in future decades and the fact that the major share of global energy will be consumed in developing countries with rapid growth in some of energy consumption sectors, it is necessary that all countries, particularly developing countries, put developmental WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

170 Energy and Sustainability III policies in energy security and pollution reduction in agenda. Energy has substantial peculiarities which, in the case of crisis, can make the greatest impact on other sectors. This impact does not only include economic sectors, but also affects social, health and, more important than others, the environment. As a result, energy management is the central issue for creating sustainable energy. With sustainable energy we will have sustainable development. Creating energy security and promoting efficiency, which is due to good energy management, can bring about unbelievable positive effects. In this regard, governments should:  Through policy making, promote clean energies and expand capacities in renewable energies.  Create regulatory and fiscal incentives, creating research fields, development and using the market mechanism using investment advice of international institutions. Prepare the ground to establish an influential and efficient system. Considering the following can help us through energy efficiency plans for achieving sustainable development along energy management:   

Improving energy efficiency is the main factor for creating wealth in countries. Success in management and improvement in energy efficiency which depends on governments’ attitudes. Energy efficiency is the largest, cheapest and fastest way to prevent destruction of the environment.

References [1] Mcdad, Susan, “Energy week 2003/World Summit for Sustainable Development & Millennium Development Goals Implementation”, UNDP, 2003. [2] World Bank, “A World Bank Group Brief Sustainable Energy”, 2006. [3] OECD/IEA, “World Energy Out look 2007”, Executive Summery, 2007. [4] Sorokina, Olga, “What are the available Instruments for Fostering NonOECD Energy Investment”, Energy Diversification Division of the IEA, Working Paper, 2002. [5] Cliniand, Corrado; Ortis, Alessandro, “Integrating Energy and Environmental Goals” Italian Presidency of the Council of the European Union, IEA, 2003. [6] OECD/IEA, “Energy Use in New Millennium”, Trends in IEA Countries, OECD/IEA, 2003. [7] World Bank, “An Investment Framework for Clean Energy and Development: A Progress Report” World Bank, 2006. [8] Fatih, Birol, “World Energy Prospects and Challenges”, IEA, 2006. [9] Gan, Lin, “Energy Development & Environmental Constraints in China”, Center for International Climate and Environmental Research/ University of Oslo, 1997.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

171

[10] OECD/IEA, “Mind the Gap-Quantifying Principal-Agent in Energy Efficiency”, OECD/IEA, 2007. [11] OECD/IEA, “Energy Technology Prospective”, OECD/IEA, 2006. [12] World Bank, “Catalyzing Private Investment for a low Carbon Economy”, World Bank, 2007. [13] Geller, Howard; Attali, Sophie, “The Experience with Energy Efficiency policies and programs In IEA Countries”, IEA Information Paper, 2005. [14] OECD/IEA, “Renewables in Global Energy Supply”, An IEA Fact sheet, IEA, OECD/IEA, 2007. [15] OECD/IEA, “Renewable Energy, Market & Policy Trends – IEA Countries”, OECD/IEA, 2004. [16] Lowery, Martin, “Energy Efficiency & Investment Forum, Global Perspective on Energy Efficiency in Developing Countries”, National Rural Electric Cooperative Association, 2006. [17] Egan, Cristine, “Promoting Energy Standards & Labeling in Developing Countries”, CLASP.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

This page intentionally left blank

Energy and Sustainability III

173

Investigation of energy management in an Iranian construction project S. Ajel, M. B. Nobakht & M. Harischian Azad Islamic University, Iran

Abstract The subject of constraints and lack of sustainable energy on Earth is now obvious to all. Hence this research is to probe ways to deal with this problem and to improve project management in order to maintain energy and national benefits. Field studies on present research are about a construction project in Iran. This paper analyses the results of the obtained data. Keywords: energy management, energy resources, waste of energy.

1 Introduction Energy management is a process consisting of schematization, organizing, conducting and supervising in order to optimizing energy consumption. It also avoids the reduction of system service levels (SUT [1]). Structural, mechanical geotechnical, environmental, traffic and architectural groups are mainly involved in different construction projects such as hospitals, roads, factories and dams. Therefore, it is absolutely essential to have an energy expert optimizing the energy consumption rate. The building sector in Iran uses one third of the total available energy; it equates to approximately 6 billion dollars. Although this is a noticeable amount, most of the buildings do not fulfill the technical requirements of isolations. The lack of energy resources is not deniable; hence this paper is prepared to improve the managerial techniques of energy saving processes (Murco [6]) (Markus [2]). The rate of energy consumption has increased enormously during recent decades. There are two major reasons for this. One is due to the industrial revolutions in Iran. The other factor originates from the low prices of energy which prevents the logical consumption and efforts to save energy.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESUS110151

174 Energy and Sustainability III During the 1974 energy crisis, the energy uses procedures changed a lot as a result of high prices on crude oil and energy resources. Furthermore, oildependent countries tried to manage the new energy resources (Gordić [7]). They strongly approved the logical consumption of energy, and therefore, they paid attention on the main energy consuming centers, i.e. residential buildings. As a result optimization methods became standard. Nowadays, there are many countries, such as Germany, Sweden, Italy and England which have set up strict rules on building isolation materials, heating and cooling instruments and technical specifications. Applying these simple but necessary steps has resulted in a 30% energy saving. According to Iranian statistics in the field of energy in 2009, the residential and commercial sectors use about 40% of the total energy. So, a reachable saving of 30% in this part is comprehensively noticeable (Figueiredo [8], Rezapour [3]) .

2 Principles of energy management in buildings 2.1 Methods in identifying sources of energy waste in residential buildings To identify sources of energy loss in residential and commercial buildings it is necessary to review the overall energy (energy audits). They can be compared to the results of a relatively ideal model of a general sample structure in order to determine sources of energy waste. Energy review, if done properly, can be used as a guide for those who have the responsibility to control the energy. Points that are critical in providing the necessary model to determine the sources of loss in residential buildings must have considered the foregoing sections: (Bellarmine [9]) (Mahajan [4]). 2.2 Production of energy consumption state The amount of energy consumption in different seasons is varied. Therefore, the monthly average value of the energy will be considered. Building energy consumption compared with the standard value (standard uses of different carriers), determine the savings which can help in making decisions on energy audits (Hepbasli [10]). 2.3 Construction overview (Walk Through) The energy auditor at this stage must briefly examine the building and shall identify the following: (Hepbasli [10]). - Determine the equipment needed to measure. - Determination of various parts of the building energy consumption. - Set a clear waste of resources. - Check the status of energy control. - Check all electrical equipment. - Review how the air flows in buildings (Infiltration).

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

-

175

Determine the composition of technical team (architect, electrical engineer, mechanical engineer).

2.4 Access to general information of the building (Building Public Profile) Access to general information may include items such as the building materials used in the construction and various components of each building and equipment. For this purpose, the development and increased understanding of material’s mechanical, chemical and thermodynamic behavior, properties of light and also familiarity with newly invented materials, analytical models for heating and cooling properties of used materials can be useful (Farag [12]). To attain the overall condition of the structure, general information covering the building faces (roof, walls, floors and the type), the area, windows and walls, energy system of heating and cooling (HVAC), form and direction of building, climate profile (temperature and humidity), windows size and position (for optimum use of solar energy should take be taken into consideration (Lampret [13]).

3 Abadgaran tourist town [5] 3.1 Project introduction The Koohsangi Welfare and Tourist Project is located in about 47 hectares of land in the western highlands of Mashhad, Iran. The blocks of the project are orientated with a northerly direction of approximately 30 degrees. The building’s structure is a steel frame. Walls are made by 20cm clay partition blocks. A combined stone and brick facade with average thickness of 10cm is also observed. In addition, some sections are cement plaster. The roof is covered by light concrete and the final insulation layer is 4mm thick. The finishing indoor layer thickness of gypsum plaster is 2.5cm and the final layer of finish on non-health areas, health areas and ceiling are plastic paint, oil based paint and tiles, respectively. The ceiling is a kind of joist block with light concrete, the floors and the halls are covered by ceramics. In private spaces like bedrooms, the finish is of mosaic with a 2cm thickness. The aluminum windows are designed with 4mm thick glass. Windows are insulated by cement mortar or plaster. The buildings are also equipped with elevators. Indoor equipment for heating in each unit is prepared separately in each unit. Transfer of heat into the room is through seamless black iron pipes with welded joints. The distribution system to heat spaces is aluminum radiators. For cooling of buildings, water coolers are located in each unit separately on their balconies. Cold energy transfer to the indoor space is through the channel of galvanized sheets, which is based on a false ceiling.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

176 Energy and Sustainability III Buildings have separate underground parking which is attached to the minor street by a ramp. A water storage tank with capacity of 7000 liters is anticipated on the roof of the building. Energy source used in the project in the implementation phase of the project was a temporary electrical power split across the city and in some cases extracted from diesel electric power generators. 3.2 Studies on energy management in projects Investigating thorough the project documents concludes that instead of utilizing a central heating center, a unique heating package is assigned for each apartment. It is designed to lower the total energy consumption and avoid the significant amount of energy loss. According to the table of energy regions in the Iranian building regulations, Mashhad is considered in the category of mean energy needs. Therefore, the project, with 140,000 square meters, was selected as a very suitable model of a residential project for considering the energy management. Table 1:

Energy dissipation through surfaces in hospital.

33.6

Annual Energy Dissipation Kwh/yr 13627802

2509

Energy Dissipation W/C 5432

37.9

15388979

2509

6134

13.2 0.5

5373850 852992

2509 2509

2142 340

0.5

213248

2509

85

12.7 100

5143040 40599910

2509

2050 16183

Percentage %

DegreeDay

Type Ceiling External Walls Windows Floor Staircase Walls Air Change Total

The next step is the plan and the initial distribution of the land area. Constraints of urban planning in cities prevent designers from determining what levels of productivity and space they need. Also, it restricts the energy management considerations. For example, in the project, if the municipal building regulations would have allowed, it was possible that the project was evaluated in terms of energy consumption in both construction phase and operation phase. In general, it can be said that all levels of the outside environment are reduced in terms of energy and so it is managed much more favorably than was considered before. The phase of positioning the buildings to the north angle is very important in terms of energy consumption. The current buildings are at an angle of 30 degrees with the north. Windows of these buildings in the hot season are exposed to

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

177

sunlight, which is not satisfactory. If the rotation of the building was to the south, it could have saved energy consumption very much. Other items that could be examined in the project are type of building structural material which can be very effective in energy consumption. For example, the energy levels used in buildings with steel structure is different to the energy levels used in reinforced concrete structures. This could be extracted by the management team and be reported and presented to the management unit. Brick partitions used as separator materials can be compared with plaster panels in terms of energy management. Bricks made from clay baked at high temperature are far higher energy users than gypsum, which as a molding material only needs the temperature high enough to remove surplus water from the gypsum. Finally, the energy used in manufacturing these parts is not renewable energy and also has negative points for environment and climate. In this project, in order to provide insulation in the external faces, clay bricks with 20cm thickness have been adopted. We can now use lower thickness but with lower transfer coefficient to solve this problem. For example the use of polyurethane foam, glass wool, foam or concrete foam and plaster. Decision-making is within the responsibility of the project manager with having the necessary technical reports and several variants. Selection of each item can also provide technical or economic reasons to be discussed. Many other technical aids can be utilized that could have made optimal use of energy. Among these we can mention the two layers glass in order to maintain the desired temperature in buildings with lower energy consumption. Another case to be discussed is the possible use of solar energy for preheating cold water to produce hot water, heating systems and bathing water requirements. However, during the project due to the absence of energy management and use of typical methods, it has been neglected. Not using suitable doors in parking’s corridors and stairs is the other issues that could be favorable in energy consumption to keep the temperature of the units to an effective level. With doors separating filter spaces, a boundary between the exterior space and temperature inside the units is produced which is very effective in reducing energy consumption. Moreover, using polyurethane insulation around hot water pipes in the building could reduce energy consumption and help make savings.

4 Results of the case study In this section, the results from analysis of the gathered data are illustrated. Since Abadgaran has many different types of building, useful information by the sort of building type is presented. 4.1 Electrical consumption level The diagrams in figure 1 show the percentage of the electrical energy consumption for different buildings. The biggest portion is consumed for cooling

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

178 Energy and Sustainability III

Figure 1:

Electrical energy consumption rate.

and ventilation with 28%. Therefore, applying modern equipment with high efficiency has a significant role for energy management.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

179

It is obvious from the figures that the amount of energy consumes for cooling is about two times more than the electricity for heating. It should be mentioned that this is due to the mechanism of house heating in Iran. As a result of cheaper gas rather than electricity, people prefer to have gaseous heaters. Also light, with 25% of the total, is a noteworthy proportion. Various models of new lamps with less energy dissipation can be applied instead. There are also time-control or kinds of intelligent lamps which significantly lower the consumption rate. 4.2 Electrical and heat energy consumption indices (MJ/m2, KWh/m2) The indices shown in the diagrams below present the amount of energy consumption over a unit area. In this way in can be applied as adequate indices for comparing the buildings of different types. It is also capable of being compared by the standard norms or the international ones. These indices are illustrated in the diagrams of figure 2. In electrical energy consumption indices we can observe that this increases with the amount of floors in residential buildings. For a 12 story building it is three times more than the four story one. Yet, this is not the case for heat energy consumption indices. These are almost the same for buildings with different stories. At both diagrams, the hospital is the main energy consumer for the electrical and the heat energy consumption indices. It is about three times more than the other building types in heat energy section. Finally, as is shown, hotels consume the least amount of energy in comparison with the other building types. This is the results of the optimum operation of their equipment; they are all new and have a low energy consumption rate. 4.3 Heat energy dissipation level through the building external faces Considering the air change rate and penetration losses the graphs in figure 3 are plotted. They show the building heating load (required heat energy) and the heat transfer coefficient of the building external surfaces. The heat energy dissipation is calculated by the Degree-Day method. The percentage of energy dissipation through building surfaces such as ceilings, floors, external walls and the windows are presented in this diagram. Consequently, isolation processes using the double window are recommended to lower the energy consumption. 4.4 Electrical and heat energy saving potentials Saving potentials can be attained by applying the common methods of energy consumption optimizing. The savings are calculated through isolating the external surfaces (ceiling, floor and external walls), double windows, central thermostatic controlling, energy saving bulbs and other proposed procedures.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

180 Energy and Sustainability III

KW h/m ^ 2

E le c tric a l E n e rg y C o n s u m p tio n In d ic e s

140 120 100 80 60 40 20 0

130.5

Residental Building (12 Stories)

113

64.5

61

Residental Building (4 Stories) Office Building Hospital

21 Hotel

1 Evaluated Buildings

H e a t E n e rg y C o n s u m p tio n In d ic e s 3500

3026

3000

Residental Building (12 Stories) Residental Building (4 Stories) Office Building

K W h /m ^2

2500 2000 1500

1510

1400

1190

1116

1000 500

Hospital Hotel

0 1 E va lua te d Buildings

Figure 2:

The electrical and heat energy consumption indices in the evaluated buildings.

Figure 3:

Energy dissipation level in hospital.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

181

Figure 4:

Electrical saving potentials and the consumption rate after optimizing procedures.

Table 2:

Electrical saving potentials and the consumption rate after the optimizing procedures.

Annual Energy Saving (tones of crude oil)

Saving Energy

TOE

%

174.96

21

1

Energy consumption Indices (after optimizing) Return period 3-5 years

Energy consumption Indices (current)

Area

51

64.5

50400

14

18

21

1578

40

15

96

113

9230

233 13

18 22

107 47.6

130.5 61

38601 3781

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Building Type

Residential Building (12 Stories) Residential Building (4 Stories) Office Building Hospital Hotel

182 Energy and Sustainability III As observed, the external walls and the ceiling have the biggest role in energy dissipation. They cause about two third of the whole energy loss. So, it is very important to take care about the isolation procedures in exposed surfaces. The table illustrates the percentage of the energy saving for different building types by considering the energy management and avoiding the energy dissipation as much as possible. Using all the applicable procedures, the residential building with 12 stories and the hotel have achieved about 20% saving in total energy which is very significant. At the least amount we can observe the 14% of the residential building with four stories. It should be reminded that this case had suitable initial energy consumption according to figure 2.

5 Conclusions It should be emphasized that economic justification and investment limitations are the main factors in any program for optimizing the energy consumption. Therefore, all the renewable energy resources should be investigated at first, and then the potential for different energy at the site must be determined. Briefly, replacing the new energy needs decision making, thinking, organizing and finally investment. It is also necessary that the international organizations support the new energy methods programs financially. Modern technologies play an important role in optimizing programs as well. The prices for different types of energy are frequently fluctuating because of the changes in the operational techniques and devices. Gathering the required data, the responsible managers can opt for optimized solutions and different energy resources in their construction projects. Solar, wind and geothermal energy can be used singularly or in combination with each other. It has been proved that the subsidies on fossil fuels are a major obstacle against the development of the renewable energy resources. Currently in Iran, the government is seriously omitting these subsidies and has gained enough success to continue this national project. According to the results at least 14% energy saving can be achieved by taking care of the external walls and the ceilings. It should be reminded that two third of energy dissipation is from these faces, so it is important to pay attention to these.

References [1] Sharif University of Technology, applicable reference for energy management, oil and energy department, Persian language. (2007), [2] D.Markus, Translated by H.Shirazi, energy management of buildings, Zare publications, Iran, Persian language, 2004. [3] K.Rezapour, Saves principles of energy management, SAYA Organization, Iran , 2007 [4] K.Mahajan, Energy management, efficient uses of energy, Basir Publications, Iran, Persian language, 2005 [5] Abadgaran Construction Company, www.oonegroup.com WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

183

[6] Mashhad Subway Organization, www.murco.ir [7] Dušan Gordić, Development of energy management system – Case study of Serbian car manufacturer. Energy Conversion and Management. 51(12). , 2010. [8] João Figueiredo, Energy Production System Management – Renewable energy power supply integration with Building Automation System. Energy Conversion and Management. 51(6), pp 1120-1126 , 2010 [9] G. Thomas Bellarmine, Energy conservation and management in the U.S. Energy Conversion and Management. 35(4), pp 363-373, 1994. [10] Arif Hepbasli, Development of energy efficiency and management implementation in the Turkish industrial sector. Energy Conversion and Management 44(2), pp 231-249, 2003. [11] Benjamin Paris. Heating control schemes for energy management in buildings. Energy and Buildings. 42(10), pp 1908-1917, 2010. [12] S. Farag. March 1999, Cost effective utilities energy plans optimization and management. Energy Conversion and Management. 40(5), pp 527-543 [13] Marko Lampret., Industrial energy-flow management. Applied Energy. 84(7), pp 781-794. 2007.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

This page intentionally left blank

Energy and Sustainability III

185

Optimization of the pumping station of the Milano water supply network with Genetic Algorithms S. Mambretti Wessex Institute of Technology, UK

Abstract In the paper a method for the optimization of water distributions networks is developed and applied to the case of the water supply network of Milano. This network is very complex and has no suspended reservoirs as the hydraulic head is maintained by the action of 31 pumping stations. Starting from real data, the operations of the entire network and pumping station, with the actual scheduling, are simulated with software using EPANET engine which was developed to this purpose. Afterwards, the operation of the pumping stations is optimized through the use of a simple Genetic Algorithm, in order to reduce the energy consumption maintaining a good service. Results show a significant improvement with the new working logics, thus justifying the study. Site tests show that the assumptions made in building the model are reliable, but they will probably require some adjustments following this research. Keywords: water distribution, Genetic Algorithms, optimization, energy saving.

1 Introduction Water distribution networks are a primary part of water supply systems, and since they represent one of the main infrastructure assets of the society, its management must be effective, efficient and energy saving. To this end, hydraulic constraints are not sufficient to find the best system and economic and energy conditions also have to be taken into account. For this kind of complex and multi-objective optimization problem Evolutionary Computation may be useful. The term Evolutionary Computation (EC) [1] represents a large spectrum of heuristic approaches to simulate evolution. The latter includes: Genetic Algorithms (GAs) [2, 3], Evolutionary Strategies [4, 5], Evolutionary WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESUS110161

186 Energy and Sustainability III Programming [6] and Genetic Programming [7]. GAs are one of the most known EC, because of their central use in water resources planning and management. They have been largely used in the last two decades in order to improve efficiency of water distribution systems when traditional calculus-based and enumerative optimization methods showed they were not able to cope with the geometrical complexity of these systems (a complex network of pipes, junctions and hydraulic control elements) and the water demand of customers with required quality and affordable costs. One of the first water engineering applications of GAs was related to the optimization of pump schedules for a serial liquid pipeline [8, 9]. GAs have been used for least-cost design [10], and for network optimization [11–13]. Mackle et al. [14] were among the first to apply a binary GA to pumps scheduling problems, to minimize energy costs, subject to reservoir filling and emptying constrains. Then Savic and Walters [10] developed a multi-objective GA (MOGA) approach to minimize both the energy costs and the number of pump switches. The first industrial application to the pump scheduling problem was reported by Atkinson et al. [15], De Schaetzen et al. [16] and Illich and Simovic [17]. Van Zyl et al. [18] developed a hybrid optimization approach in order to reduce the excessive running times. Further improvements were provided by Prasad and Park [19], Farmani et al. [20] and Rao and Salomons [21]. In this paper, a simple GA will be applied to the water distribution network of Milano order to improve the performance of the system. Results showed that significant improvements can be reached in terms of energy savings leading to economical benefits. Tests on a pumping station showed that the results carried out during this research were reliable, although refinements should be considered in upcoming work.

2 Case study: the Milano water supply network The water supply system of Milano [22] acquires drinking water from a number of wells; pumps convey water to reservoirs located at ground level. From those reservoirs water is pumped directly in the network, without the need for reservoirs located at higher altitude. The hydraulic head is therefore guaranteed by the pumping stations which action balances the effects of water demand. The pipelines have a total length of 2200 km and in the network, there are 31 pumping stations and in each of them 3-4 pumps are installed. Each pump works with a discharge within the range 200-400 l/s and maximum head of 50 m. Most of the pumps work with a fixed engine speed but some of them are equipped with inverters, which allow pumps working at different speeds. Currently the network is managed with traditional and empirical techniques [22], which might be not the best way. The present study aims at the verification of these conditions in order to find whether alternative and better management is possible. The first step of the study aimed on building the model for the network in order to evaluate its behaviour and verify whether the knowledge of the system is WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

187

sufficient for an adequate representation, if necessary, throughout the calibration of the model itself. The available data were the geometry (topology of the network, lengths, diameters, materials, etc.), the mean daily water demand, the pumping schedule for every station, the values of pressure and discharge downstream of every station and in some other junction inside of the network. These data have been used to build a simplified model of the water supply network with the well-known software EPANET. Simplifications consisted in the insertion in the model only for the pipes with a diameter larger than 300 mm, neglecting the smaller ones. Such assumptions were made in order to reduce the time required for building the model and the time of simulation. However, fairly accurate reconstruction of the network was reached, which at the end consisted of 4964 junction, 96 pumps, 26 stations with an overall length of pipes equal to 460 km. The network has been simulated for an average day, using the daily average hourly demand curve, with a time step of 5 minutes, shown in figure 1. Results of the simulations have been compared with real data, recorded in the pumping stations and in some points of the network equipped with appropriate instrumentation. As can be seen (figure 2) in few hours of the day, there are significant differences (around 7:00 a.m.), but for the most of the day these differences are negligible. In figure 2 simulated and real data are compared for the “Baggio” pumping station. Data have been recorded on November 18th 2009. Simulated data showed a significant negative peak around 7.00 a.m whilst in the real network around this time, most of the pumps are turned on due to a sudden drop in pressure related to the increase in the water demand and the logic implemented in the model is probably poor and not able to follow this rapid change. Real pressures are quite steady all day long, with maximum changes smaller than 5 m.

Figure 1:

Pattern of the daily mean demand.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

188 Energy and Sustainability III

Figure 2:

Recorded data Vs simulation in the Baggio pumping station.

Simulated pressures are normally larger than real because in the model no valves are inserted downstream the pumps, while in the real plants they are normally present.

3 Optimization algorithm As the carried out results are acceptable for the purpose of the research, the following step was to find alternative scenarios able to guarantee the same level of service with the minimum energy expenditure. This is an optimization problem with constraints. The objective function to be minimized is simply the power required by the system W, obtained summing the power of each running pump: Npumps

W 

 i 1

  H Q  min 

(1)

where  is the specific weight of the fluid (water), H is the head given by the pump for the discharge Q and  is the efficiency of the pump. In all simulations the efficiency has been accounted as constant in all situations and equal to 0.75. With regard to the constraints, the imposition was that pressures must be within the range 25-75 m; these values are checked in some “control points” located downstream the pumping stations. If the pressure in some control points falls outside the mentioned range, the value of W is increased by a fixed value in order to penalize the carried out configuration. To solve this optimization problem Genetic Algorithms have been chosen. This method is based on the mechanics of natural selection and natural genetics, WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

189

combining survival of the fittest among string structures with a structured yet randomized information exchange to form a search algorithm. In every generation a new set of artificial “individuals” (strings) is created using bits and pieces of the old. The method is sketched in figure 3.

Figure 3:

Generalized framework of a Genetic Algorithm.

The entire system is implemented with a binary string. Each pump is represented by 3 bits (i.e. 23 = 8 possibilities) which describe its working status, i.e., pump off, pump on working at 40, 50, 60, 70, 80, 90 and 100% of its nominal speed. The first step for the implementation of the genetic algorithm is the generation of a number of configurations that will be used as the first generation of solutions (“population”). One of these is the actual configuration while the others are created randomly by the program. Tests have been performed with different number of individuals which form the population. All the individuals that form the population are simulated and their value of W is computed, which is considered the “fitness” value of each individual. This value is then used to favour the individuals that give better results in the “reproduction” phase, i.e. the creation of a new set of individuals that form the new population. The reproduction is carried out as a simple and quasi-random crossover between two different strings. WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

190 Energy and Sustainability III With regard to the initial population a variable number of individuals (within the range of 100–150) have been used; the number of iteration needed to reach the final configuration was between 100 and 200. Because of the partial randomness of the algorithm, each simulation may lead to a different result; therefore, for every hour of the day 8 simulation have been run, with different starting points.

4 Results Results revealed a close relation between the number of initial strings and the number of iterations. However, the optimum is reached if both the initial population and the number of iterations are larger than 100. Figure 4 shows the value of W for each individual together with the average for the population. The result is shown for 1:00 p.m. As can be seen, the value of W averaged on the population decreases, becoming steady after more than ten thousand runs. However, it is to be observed that this average value is not the absolute minimum, which is the actual goal of this research. Therefore, in the following steps of the research, the actual minimum for each hour has been used. Results show the possibility of significant energy savings, both if the inverter is used or not. The required power over the day is resumed in figure 5 for the actual case and for the two optimizations (with and without inverter).

Figure 4:

Power required by each individual and mean power of the populations during the search for the best configuration (200 iterations, population of 100 individuals).

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

Figure 5:

191

Required power in an average day: improvements with and without the use of inverters.

Table 1 presents a summary of results, considering the best configuration (individual) found for each hour of the day. As can be seen, it is possible to save energy up to 17.9% without inverters and up to 30.4% using inverters. In particular, the simulations performed using inverters show the possibility of a significant improvement: the minimum saving is 17.1% (at 5:00 a.m.) and the maximum is 38.8% (at 10:00 p.m.). Meanwhile improvements related to the system without inverters have a minimum of 7.6% (at 8:00 a.m.) and a maximum equal to 29.2% (at 2:00 a.m.). Moreover, it is to be noted that in all cases the speed of the pumps never decreased below 70%, as in these cases the head of the pump is not sufficient to provide discharge to the network. Finally, in order to have an idea of the possibility of economic safe, the energy cost was fixed at0.10 €/kWh for the whole day. Therefore, considering the actual total energy in a year equal to 38,200,000 kWh, without inverters it is Table 1:

Energy saved, in percentage, with and without the use of inverters for each hour of the average day.

Hours

0

1

2

3

4

5

6

7

8

9

10

11

% hourly saving without inverters

17.1

23.3

29.2

28.3

24.2

12.5

11.1

16.4

7.6

9.5

11.5

17.5

% hourly saving with inverters

30.0

36.8

36.3

33.0

28.7

17.1

20.2

18.8

26.8

26.1

37.8

31.4

12

13

14

15

16

17

18

19

20

21

22

23

18.5

21.8

17.1

19.1

19.0

21.2

18.8

22.2

20.4

18.3

21.3

27.4

32.8

30.1

33.1

34.8

37.4

28.0

24.8

29.2

28.3

34.7

38.8

30.6

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

192 Energy and Sustainability III possible to save up to 6,840,000 kWh/year, which means saving up to 684,000 €.With the use of inverters, it is possible to save up to 11,627,.000 kWh/year, which means an economic saving equal to 1,162,700 €.

5 Field tests Field tests have been performed in one of the pumping stations in Milano. Recorded data related to one pump with the inverter are shown in figure 6. The most important achievement to be highlighted is that, as can be seen in the figure, pumps are oversized for the need of Milano, and in fact when their speed is at a 100%, the working point is positioned quite “on the right” of the curve and therefore the efficiency of the pumps falls dramatically; when the pressure in the network is low, the efficiency decreases below 60%. Using the inverters, velocity is reduced and therefore the working point moves “to the left” and the efficiency increases. In other words, in this case, the speed reduction raises the efficiency of the pump, and therefore it seems that the benefits in the installation of the inverters might be higher than computed. 48

Recorded data, efficiency < 0.6 Speed pump: 100% Speed pump: 93% Speed pump: 87% Speed pump: 82% Recorded data, 0.6 < efficiency < 0.7 Recorded data, efficiency > 0.7

46 44 42

Pump head [m]

40 38 36 34 32 30 28 26 24 200

225

Figure 6:

250

275

300

325 350 375 Discharge [l/s]

400

425

450

475

500

Recorded data in one of the pumping stations in Milano.

6 Conclusions In the paper, the use of Genetic Algorithms has been applied to the optimization of the functioning of the pumping station of the city of Milano. To this end, the model of the water supply network has been implemented in the well-known WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

193

software EPANET and the results of the simulations have been correlated with empirical data. Afterwards, thousands of different pumping configurations have been tried, lead by a simple Genetic Algorithm in order to find the best configuration, i.e. the configuration which can guarantee the same actual service and the best energy savings. Configurations have been tested with and without the use of inverters, which can reduce the rotation speed of the pumps. Results show that a dramatic improvement is possible, both with and without the use of inverters. Results may require further refinements due to the simplifications adopted for the model, but they are however encouraging because of the savings that can be reached both in terms of energy and of costs (up to 6,840,000 kWh/year equal to 684,000 € without inverter and 11,627,000 kWh/year equal to 1,162.700 € with inverter). Field tests showed that, because of a probable over sizing of the pumps in the Milano stations, these values could be increased if the actual efficiency was used in the mathematical model. Further researches are needed to combine the energy savings with the different requests of a complex network as Milano’s with targets that might be contradictory and therefore that require to move on the Pareto boundary.

References [1] Back T., Fogel D.B., Michalewicz Z. (eds.) Handbook of Evolutionary Computation Institute of Physics publishing & Oxford University Press, New York, 1997 [2] Holland J. H. Outline for a logical theory of adaptive systems. J. Assoc. Comput. Mach., 3, 297–314, 1962. [3] Holland J. H. Adaptation in natural and artificial systems, University of Michigan Press, Ann Arbor, Mich., 1975. [4] Rechenberg I. Evolutionstrategie: optimierung technisher systeme nach prinzipien der biologischen evolution. Frommann-Hoolzboog Verlag, 1973 (in German) [5] Schewefel H.P. Numerical Optimization of Computer Models, John Wiley and Sons, New York, 1981 [6] Fogel L., Owens A., Walsh M. Artificial Intelligence Through Simulated Evolution, John Wiley & Sons, Inc, New York, 1966, Koza, 1992 [7] Goldberg D.E. Genetic algorithms in search, optimization and machine learning. Addison-Wesley, Reading, Massachusetts 1989. [8] Golberg D.E., Kuo C.H. Genetic algorithms in pipeline optimization, Journal of Computing in Civil Engineering pp. 128-141, 1(2), 1987 [9] Simpson A. R., Dandy G. C., Murphy L. J. Genetic algorithms compared to other techniques for pipe optimization. J. Water Resour. Plann. Manage., 120 (4), 423–443, 1994. [10] Savic D.A., Walters G.A. Genetic Algorithm for Least-Cost Design of Water Distribution Networks. Journal of Water Resources Planning and Management, ASCE, 123, 67-77, 1997. WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

194 Energy and Sustainability III [11] Alperovits E., Shamir U. Design of optimal water distribution systems. Water Resources Research, 13(6), 885–900, 1977. [12] Fujiwara O., Khang D.B. A two-phase decomposition method for optimal design of looped water distribution networks. Water Resour. Res., 26(4), 539–549, 1990. [13] Schaake J.C. Lai, D. Linear programming and dynamic programming application to water distribution network design. Rep. No. 116, Dept. of Civil Engineering, MIT, Cambridge, 1969. [14] Mackle G., Savic D.A., Walters G. A. Application of genetic algorithms to pump scheduling for water supply. Proc. Genetic Algorithms in Engineering Systems: Innovations and Applications, GALESIA ‘95, IEE, London, 400–405, 1995. [15] Atkinson R., van Zyl J.E., Walters G.A., Savic D.A. Genetic algorithm optimization of level-controlled pumping station operation. Water network modelling for optimal design and management, Centre for Water Systems, Exeter, U.K., 79–90, 2000. [16] De Schaetzen W.B.F., Savic D.A., Waltres G.A. A Genetic Algorithm Approach to Pump Scheduling in Water Supply System. Hydroinformatics, 1998. [17] Illich N., Simovic S.P. Evolutionary Algorithm for Minimization of Pumping Cost. Journal of Comp. in Civ. Engrg., ASCE, 12, 232-240, 1998. [18] van Zyl, J., Savic, D. A., Walters, G.A. Operational optimization of water distribution systems using a hybrid genetic algorithm method. J. Water Resour. Plann. Manage., 130 (2), 160–170, 2004. [19] Prasad, T. D., Park, N.S. Multiobjective genetic algorithms for design of water distribution networks. J. Water Resour. Plann. Manage., 130 (1), 73– 82, 2004. [20] Farmani, R., Savic, D.A., Walters, G.A. Evolutionary multi-objective optimization in water distribution network design. Eng. Optimiz., 37(2), 167–183, 2005. [21] Rao, Z., Salomons, E. Development of a real-time, near optimal control process for water-distribution networks. J. Hydroinform., 9 (1), 25–37, 2007. [22] Motta V. L’acquedotto di Milano. Comune di Milano, 1989. (in Italian)

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

195

Case study: energy audit and implementation at the Russell Medical Center D. F. Dyer & C. O’Mary Department of Mechanical Engineering, Auburn University, Alabama, USA

Abstract An energy evaluation at Russell Medical Center in Alexander City, Alabama was undertaken by the senior author as a part of a senior design class at Auburn University. Eight students (Chase O’Mary as their group leader) worked for eight months performing energy evaluations for all parts of the system. Based on their findings, recommendations for changes to reduce energy use and cost were made throughout the period. The largest savings were found in the following areas: Use of free cooling, consolidating chillers and boilers, better control of outside air, eliminating simultaneous heating and cooling, temperature reset, cooling tower optimization, setback in unoccupied zones, and control of evaporation from heated therapy pools. Partial implementation of these recommendations resulted in more than an actual 23% reduction in natural gas usage and a 40% reduction in electric usage. Detailed results from all these areas are presented. This project is being continued until present. Current focus is on determining causes for not sustaining initial improvements and better understanding of impediments to full implementation of recommendations as well as an update on the current status of the project. Keywords: energy audit, HVAC, chillers, boilers, cooling towers.

1 Introduction Russell Medical Center is a progressive, not-for-profit, acute care facility comprising a large multi-building hospital [a central hospital (154,000 square feet), an adjacent cluster of three professional buildings (122,000 square feet), and a cancer center (14,000 square feet)] located in Alexander City, Alabama.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESUS110171

196 Energy and Sustainability III The annual energy costs and water costs associated with operating the hospital are as follows: Electricity: $442,000 Natural Gas: $274,000 Water and Sewage: $33,000 A group of eight senior mechanical engineering students from Auburn University were assigned to a project to help the medical center reduce these costs. The students working under Professor Dyer logged more than 1000 man hours of engineering testing and analysis from August 2009 to May 2010 aimed at achieving this cost reduction objective. The information subsequently documented in this paper describes the findings and results of this engineering effort.

2 Problem statement As noted in the introduction it is desired to find opportunities to reduce energy and water costs for the Russell Medical Center. These opportunities can be broadly categorized in two areas: 1. Actions that require a change in operation with little capital expenditure, and 2. Actions that require replacement and additions to equipment requiring significant capital expenditure. Those actions requiring little cost were almost immediately implemented while the remaining opportunities are being phased in as money becomes available-much of it from the cost savings requiring little capital expenditure!

3 Project scope The project was to perform an energy audit at the Russell Medical Center facilities located in Alexander City, Alabama. The facilities studied for this project include the main hospital area which consists of an east and west wing, the three professional office buildings, and a cancer center. The majority of work was dedicated to the main hospital. The areas that were considered in order to reduce facility operating costs include HVAC systems such as the two natural gas fire tube boilers, the two water cooled and two air cooled chillers, the cooling tower, twenty air handler units, and lighting. Also water usage such as waste and make up water usage was analyzed along with hot water usage and the energy required. The deliverables are to collect accurate usable data for analysis to find cost saving potentials which could be realized by making operating and equipment changes. These actions are to be analyzed in terms of potential energy savings and equipment requirements/costs. If additional equipment is justifiable, that equipment must be designed and/or specified. All of these findings are provided to management for implementation. The audit began with looking at the primary equipment for generation of cooling and heating. Then opportunities to save energy in transporting heating and cooling were examined. Finally, the use of heating and cooling processes was analyzed. WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

197

4 Savings potential for HVAC generation equipment 4.1 Chillers Russell Medical Center utilizes Trane CenTraVac water cooled, centrifugal chillers, and Trane air cooled, screw type chillers to cool water to supply the chilled water loop. The main hospital building is supplied by two water cooled, centrifugal chillers with 350 and 400 ton capacities. The surrounding professional buildings are on a separate chilled water loop which is supplied by two 120 ton capacity air cooled chillers, and two 80 ton capacity backup air cooled units. The facility also utilizes a plate and frame heat exchanger to supply cool water when outside temperature conditions permit. When this project began, the facility was not able to operate the plate and frame heat exchanger. 4.1.1 Raise chill water supply temperature The main hospital requires a low chilled water supply temperature for its critical surgery and air handler units. The rest of the facility calls for normal chilled water supply temperatures three to four degrees higher than the critical area supply temperature. Initially the chillers were not plumbed with isolation valves. This required both chillers to make the lower supply water temperature in order to meet demand for surgery which is inefficient. In order to remedy this problem, it was recommended that isolation valves be installed so that each chiller could be separated and its supply water temperature set according to its requirement. This allows the critical areas to be supplied with the lower water temperature and the rest of the facility to be supplied with a more energy efficient higher supply temperature. Table 4.2 in reference [2] shows that the percent compressor power savings that can be achieved through raising the condenser water temperature by 1 F is approximately 1.6%. In some cases the chilled water could be reset by 6 F giving nearly a 10% saving. In addition, providing a supply temperature lower than the required temperature results in reheating the air using additional boiler fuel. Installation of these valves allowed a saving of approximately $32,000 per year considering both the heating and cooling cost reduction obtained. 4.1.2 Interconnect chillers Russell Medical Center has two separate chilled water loops, one for the main hospital and one for the professional buildings. They are supplied by the chillers described in section 4.1. Evaluation of the facility cooling load shows a surplus of cooling capacity especially with the two water cooled chillers in the main hospital. Further assessment shows that the water cooled centrifugal chillers operate about thirty percent more efficiently than the air cooled screw type chillers in the professional buildings. This study shows that significant energy savings could be achieved if the two separate chilled water loops were interconnected to create a unified chill water loop. The recommended new unified chill water loop uses the more economical water cooled chillers as the main units and the air cooled units as backups. The less efficient air cooled chillers could then be shut down. The water cooled chillers have enough surplus WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

198 Energy and Sustainability III capacity to supply the professional buildings with cold water for most of the cooling season with backup, if necessary, by the air cooled chillers. This modification also allows the professional buildings to use the plate and frame heat exchanger when outside conditions permit, as well as create chiller redundancy for the entire facility. Implementation of this recommendation would require a capital investment of approximately $114,000 and create and save approximately $25,600/yr. This proposal has not yet been implemented, but action is being taken by Russell Medical Center senior management to secure the funds for this project. 4.1.3 Reduce condenser water temperature into chillers Russell Medical Center’s water cooled chillers employ a cooling tower to cool the condenser water. The effect of reducing condenser water inlet temperature is very similar to that of raising the chilled water temperature which reduces the temperature lift that must be supplied by the chiller which in turn reduces operating costs. Effectively lowering the inlet condenser water temperature without causing operational problems varies according to chiller design and operating conditions. In the case of Russell Hospital both chillers require that the lowest condenser water temperature allowable is about 72 F. Initially, both chillers were operating at approximately 82 F allowing room for a temperature decrease of 10 F. Table 4.1 in reference [2] shows that the percent compressor power savings that can be achieved through lowering the condenser water temperature by 10 F is 11%. This saving can be achieved more than 50% of the year (say 4000 hours) because the wet bulb temperature allows the cooling tower to achieve this temperature. The average cooling load in this period is approximately 350 tons. The electrical savings based on an electrical rate of $.08/kw-hr amounts to approximately $11,000 per year. 4.1.4 Monitor cooling tower makeup water separately to avoid sewage charges Cooling towers use evaporative cooling to cool condenser water. This means that a significant amount of water is lost due to evaporation and must be made up. Facilities are often charged sewer charges based on the amount of water that they use because it is assumed that it must be disposed via the sewer. However, this is not the case with a cooling tower. Approximately 7,300,000 US gallons of water are evaporated by the Russell Medical Center cooling towers annually. .Makeup water to the cooling tower is metered daily. The makeup water replaces both water evaporated from the cooling tower and water discharged as “blow down” to maintain the quantity of dissolved solids at an acceptable level. By metering the amount of blow-down water that is discharged to sewer, the amount of evaporated water can be calculated. The hospital is currently charged for sewer on evaporated water at a rate of $2.72 per 1000 gallons. It was recommended that Russell Medical Center apply for cooling tower water exemption. That would save approximately $20,000 per year in sewer charges. However, the City water authority is requiring Russell Hospital to run a separate water line from the street in order to exempt sewage charges. An approximate 1000 foot line is required

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

199

and must traverse parking areas. As a result the cost of implementation is high and is estimated to be $20,000. The project has not been implemented waiting on further negotiations with the City. 4.1.5 Use free cooling Currently, the medical facility has in place a plate and frame heat exchanger to provide indirect cooling of chilled water using condenser water from the cooling tower. The wet bulb temperature must be low enough to allow cooling of the condenser water temperature to approximately 45 F. Due to a lack of controls on the cooling tower to prevent freezing and lack of isolation valves on the chillers to prevent problems of changeover between the two modes of cooling, this system was not operable when the audit project began. Recommendations to remedy these problems were made and subsequently implemented. It is estimated that free cooling can be used for approximately 1500 hours per year replacing an average of 300 tons. This results in a potential saving of $36,000 annually. This recommendation is implemented at an approximate cost of $10,000.

5 Saving potential for HVAC transport systems 5.1 Air handler fans Currently the air handlers units use constant speed fans to supply air to the occupied space. These constant speed fans accomplish the job but can’t be throttled back in times of lower demand to reduce energy consumption. It was recommended that Russell Medical Center look into variable frequency drive fans to replace the constant speed fans currently in operation. Approximately 500 Hp should be retrofitted with variable speed drives. This proposal comes with a savings of $72,000 annually and has an initial installed cost of $66,000. The project is currently underway.

6 Saving potential for HVAC processes 6.1 Air handlers Both the main hospital and professional buildings employ air handlers to heat and cool the air that is supplied to the occupied zone. The engineering team performed a full examination of the operating conditions of all the air handling units. The investigation revealed that simultaneous heating and cooling was occurring within some units. This is a very wasteful operating condition. Air was being warmed up by air handler preheat coils prior to being cooled by the chilled water cooling coil. This condition creates an unnecessary heating cost and greater cooling cost. It was found to be caused by stuck valves and HVAC control system issues. This recommendation is partially implemented. Elimination of simultaneous heating and cooling has a potential to reduced energy costs by approximately $24,000 per year. WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

200 Energy and Sustainability III The air handler investigation also showed an opportunity to reduce energy costs by optimizing outside air usage. Ideally during the peak demand of the cooling and heating season one would aim to reduce outside air to minimum acceptable levels in order to reduce the total heating or cooling load, and during off peak times when outside conditions are favorable, use as much outside air as possible in order to utilize free cooling via outside air. Russell Medical Center’s initial operating conditions allowed for some reduction in outside air usage during peak times and some free cooling by introducing outside air during offpeak times. However, some control system issues will have to be resolved in order to fully utilize free cooling. It was recommended that outside air levels be lowered on four units by twenty percent. This action requires careful monitoring of building air pressure to prevent infiltration and carbon dioxide levels to insure proper ventilation. Outside air optimization at Russell Medical Center was projected to reduced energy costs by approximately $9,000. This proposal has been partially implemented and will be fully implemented when control system issues can be resolved. It was also recommended that occupancy sensors be installed in order to control room temperature set points. Currently room temperature set points are controlled by the occupant. Energy can be saved both in cooling and heating by being able to create an unoccupied economy mode for areas that are unoccupied for a significant amount of time. This recommendation has a capital cost of approximately $17,000 and results in a projected return of $5,000 per year. It has not currently been implemented. At the same time, the occupancy sensors should be used to control lighting resulting in a small additional saving. 6.2 Swimming pool Indoor pool covers can significantly reduce swimming pool heating costs. Swimming pools lose energy primarily by evaporation. The evaporation and heat loss to the room requires room ventilation to control indoor humidity. The ventilated air also must be conditioned, which adds to the energy costs. Pool covers on indoor pools not only can reduce evaporation but also the need to ventilate indoor air and replace it with unconditioned outdoor air. In addition, the exhaust fans can be turned off when an indoor pool is covered saving even more energy. There is also a savings associated with the sewage charge for the water saved by the cover and the savings for the makeup water needed. The evaporation rate for the two pools is about 19 gallons per hour. At 5,840 covered hours per year, a savings of approximately $300 dollars per year in sewage charges and approximately $150 dollars per year in makeup water is obtained. The energy savings as described above amounts to approximately $7,000 per year giving a total savings of approximately $7,500 per year. A pool cover costs of $13,500 dollars for this application. This project has not currently been implemented.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

201

7 Summary Table 1 gives a summary of the project recommendations, potential savings, and project costs. Many of the lower capital cost projects have been implemented and other larger cost projects are underway. The total projects have a savings approximately equal to the total project costs yielding a simple payback of approximately 1 year. At the end of the project, actual billing records compared to the same month in the previous year show that the use of electricity was down by 40 % and the use of gas was down by 23%. This result is a graphic indication of the success gained by the energy audit described herein and its implementation. Table 1:

Summary savings. Savings/ yr

Implementation Cost, $

Actions Requiring Little Capital cost Eliminating Air Handler Simultaneous heating/cooling

$24,000

Reducing Outside Air

$9,000

nil

Lowering Condenser Water

$11,000

nil

Raise Supply Temperature

$32,084

nil

$25,600

$114,000

Sewer Exemption for Cooling Tower

$20,000

$20,000

Indoor Pool Cover

$7,500

$13,500

Variable Frequency Drive Fan Savings Occupancy Sensors to control unoccupied zone conditions Implement free cooling using existing plate and frame heat exchanger

$72,000

$66,000

$5,000

$17,000

$36,000

$10,000

Total savings

$241,500

$240,500

Actions Requiring Significant Capital cost Eliminating Air Cooled Chillers by interconnecting chilled water loop from Hospital to Professional building

nil

References [1] O’Mary, C., Russell Hospital Energy Audit, Report on Senior Design Project, Department of Mechanical Engineering, Auburn University, Alabama 2010. [2] Dyer, D.F. & Maples, G., HVAC Efficiency Improvement, Boiler Efficiency Institute: Auburn, Alabama 2009.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

This page intentionally left blank

Energy and Sustainability III

203

Wave potential of the Greek seas T. Soukissian1, N. Gizari2 & M. Chatzinaki1 1

Hellenic Centre for Marine Research, Anavyssos, Greece National Technical University of Athens, Dept. of Naval Arch. and Marine Engineering, Athens, Greece

2

Abstract Most of the energy resources used worldwide comes from non-renewable sources such as fossil fuels. The wasteful and inappropriate use of such energy sources has led to adverse environmental effects; at the same time, there is an emerging and urgent need for pollution-free power generation. The exploitation of renewable energy sources (RES) is now a sustainable and technologically feasible solution). EU leaders agreed that by 2020, 20% of the energy of the Member states should be produced from renewable energy sources. One of the most promising renewable energy sources are sea waves. In Europe, intensive research and development of wave energy conversion began in 1973 and since the mid 1990's there has been a real renaissance in the field. This work presents a first attempt for a detailed assessment of the wave potential of the Greek seas, using data from numerical wave simulation models of high spatial and temporal resolution in combination with in-situ wave measurements. The hindcast data are in the form of time series and cover the period 1995–2004. It is also anticipated that the obtained wave energy results will provide a basis for selecting the most appropriate family of wave energy converter devices. Keywords: wave energy, wave potential, Greek seas.

1 Introduction The main energy source worldwide is fossil fuels. However, fossil fuels are being exhausted in such a rate that in the near future, reserves may not be adequate to meet prospective demands. At the same time, the intensive use of such energy sources has caused negative impacts to the quality of the environment. The need for immediate reduction of non-renewable energy sources is urgent; owing to this, European Union leaders agreed that by 2020 WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESUS110181

204 Energy and Sustainability III 20% of the energy of Member States should be produced from Renewable Energy Sources (RES). Sea waves are considered to be a premium quality RES since they are characterized by the highest energy density among all other RES (Clement et al. [1]). However, sea wave energy has hardly ever been systematically exploited up to now though it attracts most of the advantages that characterize RES. Some of these advantages are: weak indicators of pollution, the decentralization of energy production, reduction of the imports of fossil fuels, prospects for economic development in remote areas, new job initiatives, etc. Considering the environmental effects from the deployment of wave energy converters such as noise or visual disturbances, impacts on the marine flora and fauna, etc., these are considered to be mild (Clement et al. [1], Iglesias et al. [4]). Moreover, the persistence of sea waves is, usually, longer than the wind persistence while waves may propagate in the form of swell far from their fetch area. The above characteristics of sea waves can be an occasional advantage regarding: i) the partial independence of the operation of wave energy converters from local weather conditions and ii) the development of hybrid (wind and wave) systems. The main difficulties in the exploitation of wave energy emerge from specific drawbacks of the respective technologies concerning high operating and construction costs. Besides, the randomness of sea waves, regarding their size, phase and direction, restricts a single device from achieving maximum efficiency over the range of ocean waves’ excitation frequencies (Clement et al. [1]); this renders the choice of the most appropriate family of wave energy converter devices a difficult decision. The best wave resource is presented in the temperate zone between latitudes 30 and 60 degrees in both hemispheres with wave power between 20-70 kW/m of wave front or even higher (CRES [5]). The technically exploitable wave potential of the Greek seas was estimated to vary between 4 and 11 kW/m (Clement et al. [1]). This paper deals with this relatively new and unfamiliar in Greece renewable energy source which simultaneously has significant potential for exploitation in the near future worldwide. Greece, with an approximately 16000 km long coastline, has a high wind potential over the Aegean Sea which gives rise to relatively intense wave activity. Though the wind fetches are not so long due to the presence of island complexes, the channeling effect forms some hot-spots where wave power reaches high values. This work presents a first attempt for a detailed assessment of the wave potential of the Greek seas, using data from numerical wave simulation models in combination with in-situ wave measurements. The hindcast data are of high spatial and temporal resolution and cover a period of 10 years (1995–2004) and are published in the form of a Wind and Wave Atlas (Soukissian et al. [6], Soukissian et al. [7]). The exploitation of the available wave potential could contribute to the country's demand of electricity from RES.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

205

2 Wave power Wave power is the rate at which wave energy is transmitted in the direction of wave propagation (normally expressed in kilowatts per metre of wave crest length) and the capture of that energy can be successfully used for electricity generation. The wave potential is determined from the amplitude of wave heights and wave period propagating across the sea surface. Compared to tides, the wave resource is more difficult to predict due to the “random” behaviour of the meteorological driving conditions. 2.1 Energy of linear waves According to the linear wave theory, for a progressive monochromatic wave of crest amplitude a , wave height H  2a and circular frequency  , propagating over an infinitely deep ocean, the total energy per unit of surface area is: E

1 1  ga 2   gH 2 , 2 8

(1)

where  is the water density (1025 kg/m3), g is the acceleration of gravity (9.81 m/s2) and H is the wave height (m). The quantity E (J/m2) is called wave energy density. A wave resource is typically described in terms of power per meter of wave front (or wave crest). This quantity can be calculated by multiplying the energy density by the wave celerity cg (wave group velocity), i.e., 1 Pwave  front  cg E  nc  gH 2 , 8

(2)

where n

 1 2kd 1  , 2  sinh  2kd  

(3)

c (ms-1) is the phase velocity c

 



 k



g tanh  kd  , k

(4)

d (m) is the water depth, k  2  is the wave number (m-1),  is the radian frequency (s-1),  (m) is the wave crest length and Pwave  front is expressed in W/m. For deep water d   , n  1 2 , c  g k

and eqn. (2) can be

rearranged as follows: WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

206 Energy and Sustainability III 1 1 1 g  Pwave  front  nc  gH 2  c  gH 2   gH 2 k 8 16 16

(5) 

2

g T 1 1 1  gH 2  g2H 2   g 2 H 2T , 2  16 16 2 32

where T (s) is the wave period. In this case, the energy is transported at half the phase velocity. 2.2 Energy of sea waves In a real seaway, i.e., for irregular sea conditions and for deep water the wave power for a given sea state is given by the following relation: P

 g2 2 kW   H m TP   0.5 3  H m2 Tp , m s 64  0

0

(6)

where P (kW/m) is the wave energy flux per unit of wave-crest length. In the above relation H S  H m0 is the significant wave height (m), TP  2  p is the spectral peak period (s),  p (s-1) is the peak radian frequency of the spectrum,

 is the water density (1025 kg/m3) and g is the acceleration of gravity (9.81 m/s2). Another equation for the wave power for a given sea state is

P

g2 2 kW   H m Te   0.5 3  H m2 Te , 64 m s  0

0

(7)

where now Te (s) is the wave energy period. The significant wave height and energy period are defined as functions of the spectral moments. The significant wave height is defined as H m0  H S  4 m0 ,

(8)

the energy period is given by m1 , m0 and the mean zero up-crossing period is given as Te 

Tm02  2

m0 , m2

(9)

(10)

where m0 is the zeroth moment (the variance) of the wave spectrum, m2 and m1 the second and -1 order wave spectral moments, respectively. WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

207

3 Wave data 3.1 The wind and wave models

The wave data used in this work consists of time series of wave spectral parameters for the time period 1995–2004. The data have been obtained from the WAM-Cycle 4 numerical wave simulation model with a spatial resolution of 0.1˚x0.1˚ and temporal resolution of 3 hours. Such a resolution is fairly appropriate for a general description of the wind and wave climate of the entire Mediterranean, as well as the Aegean Sea, which is a semi-closed basin with peculiarities such as a complex bathymetry with abrupt changes and many insular groups. Utilizing hindcasts produced by numerical models of high spatial and temporal resolution is the only way to represent as precisely and accurately as possible the main characteristic features of the wave climate of the Greek seas. The hindcast data have been calibrated by using collocated in time and space wave measurements obtained by the POSEIDON buoy network (Soukissian et al. [8]). The atmospheric forcing for the WAM wave model was produced by the nonhydrostatic weather model SKIRON-Eta (Kallos et al. [9]). The vertical structure of the SKIRON-Eta model consists of 38 levels stretching from the surface up to the model top (at 15800 km). The meteorological input used for defining the initial and boundary conditions of the model was obtained from the analysis fields, produced by the European Center for Medium-Range Weather Forecasts (ECMWF). The input data are available at a 0.5˚x0.5˚ resolution and 16 standard pressure levels (1000, 925, 850, 700, 500, 400, 300, 250, 200, 150, 100, 70, 50, 30, 20 and 10 hPa) every 6 hours (at 00, 06, 12, and 18 UTC). The input concerning the ground temperature and humidity at 4 ground layers (defined at the depths of 7 cm, 28 cm, 100 cm and 255 cm), as well as the temperature of the sea surface, was also derived from ECMWF at a 0.5˚x0.5˚ resolution. The corresponding analysis fields, produced during the operational use of ECMWF and obtained through MARS-Meteorological Archive and Retrieval System,

Figure 1:

Implementation area of the weather and wave model and bathymetric map used in the wave model.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

208 Energy and Sustainability III were used. The application area of the model, shown in Fig. 1, extended from 7˚ W to 42˚ E and 30.25˚ S to 47.25˚ N, and the spatial resolution was set to 0.1˚x0.1˚. The wave model used for the generation of the hindcast wave data was based on the 3rd generation model WAM-Cycle 4. WAM-Cycle 4 (or simply WAM for brevity) calculates the spatial-temporal evolution of the wave spectrum, taking into account wave generation due to the wind forcing, wave diffraction due to change of bathymetry and/or presence of currents, transformation of energy due to non-linear quadruplet wave interactions and energy absorption due to white capping and bottom friction. The model was modified in order to be effective (concerning both accuracy and computing power aspects) for applications of high spatial resolution and to give successful forecasts at coastal areas, where wave breaking is important. The application area of the model is the same as for SKIRON-Eta, see Fig. 1. The particular geographical coverage is considered adequate for the proper development and propagation of waves in the two basins (Mediterranean and Black Sea). The bathymetry was adapted to the spatial resolution of the grid through bilinear interpolation of the worldwide bathymetry/topography ETOPO 2 with spatial resolution of 2 and vertical accuracy of 1 m. In the cases of deficiency of the above database (in shallow water areas of the two basins), corrections were introduced based on the nautical charts of the Hellenic Navy Hydrographical Service (HNHS). The spectral frequency resolution of the model was set according to the logarithmic distribution wi +1 = 1.1wi , where the minimum frequency was set to 0.05 Hz and the maximum frequency to 0.793 Hz (30 frequency sectors in total). The significant wave height, the mean wave period and the mean wave direction are obtained as integrated products of the wave spectrum, while the spectral peak period and the wave energy corresponding to the low-frequency and the high-frequency part of the spectrum are derived from the distribution of the spectrum. For an analytic description of the SKIRON-Eta and the WAM model set-up see (Soukissian et al. [7]). It is worth noting that both the weather and the wave model have the same spatial resolution (0.1˚x0.1˚) and nearly the same land-sea masks, avoiding in this way multiple linear interpolations for the calculation of wind parameters at the grid points of the wave model. In general, the WAM model underestimates the high values of the significant wave height and the spectral peak period; part of this error could be attributed to corresponding errors between the weather model output and the real values of the wind speed (Soukissian and Prospathopoulos [10]). The wave hindcast results were calibrated using in-situ wave measurements and classical linear regression. The final relationships used for the correction of the model significant wave height H S and the spectral peak period TP are the following:

Hˆ S ,WAM  1.15H S ,WAM

(11)

TˆP ,WAM  1.07TP ,WAM ,

(12)

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

209

where Xˆ variables denote the corrected values and X variables denote the initial ones.

4 Wave power in the Greek seas The study area is defined by the following points: (42.25˚ N, 19.00˚ E), (42.25˚ N, 30.00˚ E), (30.25˚ N, 19.00˚ E), (30.25˚ N, 30.00˚ E). The area has been divided into a grid with resolution 0.1˚x0.1˚. For each grid point, 10-year long time series of the main wave spectral parameters, with 3 hours frequency, was obtained from the WAM wave model. The wave hindcast data are used to derive the spatial distribution of the wave power in the Greek seas. To this end, the isoenergy contours have been produced; each contour represents the loci of points with the same values of wave energy. The study of spatial distribution of wave power over the Greek seas was elaborated on seasonal and annual basis. The seasons examined are winter (December, January, February), spring (March, April, May), summer (June, July, August), and autumn (September, October, November). At first, wave power, Pi (W/m), for each sea state ( H S i , Ti ) of the 10 years time series, was estimated, eqn. (13). Pi 

g2 2 H S Ti , i  1, 2, , N , 64

(13)

i

where  is the water density, g is the acceleration of gravity,

H Si the

significant wave height and Ti the peak period of the i th sea state. Then, the mean seasonal and annual wave power P can be easily obtained as follows: N

P

P i 1

N

i

,

(14)

where N is the total number of sea states in the examined time period. Finally, four seasonal and one annual map depicting the average iso-energy contours were developed. 4.1 Seasonal and annual wave power of the Greek Seas

The results are presented in charts of spatial distribution of the mean wave power in a seasonal (Fig. 2) and annual basis (Fig. 3). Charts illustrating the spatial distributions of mean wave energy flux per unit of wave-crest length are represented by iso-energy contours. On seasonal basis, the mean wave power reaches its maximum values during winter (Fig. 2a). Northern of the Cyclades complex, the maximum wave power is 10 kW/m, while southern of Cyclades the wave power has a lower value, WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

210 Energy and Sustainability III 6–8 kW/m. In the south-eastern Aegean Sea, between Crete and Kasos islands, wave power is about 10-12 kW/m while in the south-west Aegean, the value of the wave energy is about 8-10 kW/m. The highest wave potential in the Aegean Sea, ranging between 12 and 14 kW/m is observed between Crete and Kithira islands. During winter, in the Ionian Sea, the values of the wave power are higher (9–15 kW/m).

Figure 2:

a

b

c

d

Mean wave energy flux in the Greek seas: a) Winter, b) Spring, c) Summer, d) Autumn.

During spring (Fig. 2b), in the north-central and southern Aegean Sea the values of mean wave energy flux do not exceed 5 kW/m. As far as the maximum of mean wave energy flux value in the Aegean Sea is concerned (7 kW/m), it WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

211

occurs again at the straits between Crete-Kithira, Crete-Kasos and KarpathosRhodes islands. The maximum of the wave energy flux in the Ionian Sea during spring is also 7 kW/m. In summer (Fig. 2c), the higher mean wave power values in the Greek seas occur in the central Aegean, northern of the Cyclades complex (5–6 kW/m) and at the South-eastern Aegean between Crete-Kasos (5–6 kW/m), and KarpathosRhodes (5 kW/m) islands. The occurrence of mean wave energy flux maxima in the straights of central and southeast Aegean Sea is due to the dominant “etesian” winds blowing from north-northwest to south-southeast in the Aegean Sea during summer. In autumn (Fig. 2d), in north-central Aegean, the value of the wave power is 4–5 kW/m. In the southwest Aegean Sea (at the straits between Crete -Kithira islands) and southeast Aegean Sea (at the straits between Crete-Kasos, Karpathos- Rhodes) wave power is 5–6 kW/m. In the Ionian Sea, the values are slightly higher, 4–6 kW/m. At the annual chart (Fig. 3), in the north Aegean, the value of wave power is 3–5 kW/m, while in the north-central Aegean at the Cyclades complex reach up to 6 kW/m. At the south-west Aegean Sea, the wave power is 4–5 kW/m. The highest wave energy values of the order of 6-8 kW/m, on an annual basis, occur at the straits between Crete-Kithira and Crete-Kasos Islands. At the straits between Kasos-Karpathos and Karpathos-Rhodes islands, the wave power is about 6 kW/m. For the Ionian Sea, the wave power ranges between 4–8 kW/m.

Figure 3:

Annual mean wave energy flux in the Greek seas.

4.2 Local wave power

An area which could be a promising candidate for offshore wind farm installation is located at the straits between Kasos-Karpathos Islands, and is indicated by the black arrow in Fig. 3. For this area the estimated mean wave WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

212 Energy and Sustainability III power on an annual basis is 6.4 kW/m. On seasonal basis, at the straits between Kasos-Karpathos Islands, the wave power is 4.91 kW/m in autumn, while in winter it reaches 9.58 kW/m. During spring and summer, mean wave power values are lower, 5.75 kW/m and 5.41 kW/m, respectively. The annual wave chart in Fig. 4 illustrates the distribution of the frequency of wave propagation occurrence combined with the respective significant wave heights at this region (27º.00 E, 35º45N) on annual basis. The dominant wave direction in the area is west-northwest. The most frequent wave directions, on annual basis, lie in the sector [285o, 300o] and their frequency of occurrence is about 26%. The higher values of the significant wave height, though, occur in the sector [315o, 345o]. The above results suggest that wave power can be an auxiliary RES to the available offshore wind energy for the specific area.

Figure 4:

Annual wave chart for the area between Kasos-Karpathos islands.

5 Conclusions In this work, the wave potential of the Greek Seas is being assessed, based on 10-year (1995–2004) hindcast data generated by the combination of the SKIRON-Eta atmospheric model and the WAM-cycle 4 wave model, implemented at a high spatial and temporal resolution. On annual basis, the overall wave potential is relatively high compared to the available wave power of the Mediterranean Sea. Additionally, there are ‘hot spots’ where wave power reaches its higher values. That is due to channeling effects taking place in the specific areas. The higher wave energy values occur in the Ionian Sea and in the straights of Crete-Kithira, Crete-Kasos, KasosKarpathos and Karpathos-Rhodes islands, as well as in the central Aegean Sea, northern of the Cyclades complex. The maximum values of mean wave power WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

213

range between 6-8 kW/m. On a seasonal basis, the higher wave power values along Greek Seas occur during winter. The wave potential is reduced during spring and autumn and the lower values occur in summer. The areas where the maxima occur during winter, spring and autumn are the same with those mentioned on the annual analysis. On the contrary, maxima of wave potential in summer are observed in the central Aegean Sea, at the straights of MykonosIkaria Islands and in southeast Aegean Sea, between Crete-Kasos and KarpathosRhodes Islands. Taking into account the spatial distribution of mean wave power on a seasonal and annual basis for the Greek Seas, there are five favorable potential areas for installing wave energy converters: the Ionian Sea, and the straights between Crete-Kithira, Crete-Kasos, Kasos-Karpathos and Karpathos-Rhodes islands.

References [1] Clement A., McCullen P., Falcao A., et al., Wave energy in Europe: current status and perspectives, Elsevier Ltd., vol. 6, p.p.405-431, 2002. [2] Falnes Johannes, A review of wave-energy extraction, Elsevier Ltd., p.p. 185–201, 2007. [3] DEI, www.dei.gr [4] Iglesias G., Lopez M., Carballo R., Castro A., Fraguela J.A., Frigaard P., Wave energy potential in Galicia (NW Spain), Elsevier Ltd, vol.34 p.p. 2323–2333, 2009. [5] CRES, Wave energy Utilization in Europe Current Status and Perspectives, European Thematic Network on Wave Energy, 2002. [6] Soukissian T., Prospathopoulos A., Hatzinaki M., Kabouridou M., Assessment of the Wind and Wave Climate of the Greek Seas Using 10-Year Hindcast Results, The Open Ocean Engineering Journal, p.p., 1-12, 2008. [7] Soukissian T., Hatzinaki M., Korres G., Papadopoulos A., Kallos G., Anadranistakis E., Wind and Wave Atlas of the Hellenic Seas, Hellenic Centre for Marine Research Publ., 300pp, 2007. [8] Soukissian T., Chronis G., Nittis K., POSEIDON: Operational Marine Monitoring System for Greek Seas, Sea Technology, Vol. 40, Νο. 7, pp. 3137, 1999. [9] Kallos G., Nickovic S., Papadopoulos A., et al., The regional weather forecasting system SKIRON: An overview, Symposium on Regional Weather Prediction on Parallel Computer Environments, pp. 109-122, 1997. [10] Soukissian T.H., Prospathopoulos A., The Errors-in-Variables approach for the validation of the WAM wave model in the Aegean Sea, Mediterranean Marine Science, Vol. 7, No. 1, pp. 47-62, 2006.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

This page intentionally left blank

Section 4 Energy policies

This page intentionally left blank

Energy and Sustainability III

217

The role of district energy in greening existing neighborhoods: a primer for policy makers and local government officials T. Osdoba1, L. Dunn2, H. Van Hemert1 & J. Love1 1

Center for Sustainable Business Practices, University of Oregon Eugene, Oregon, USA 2 Preservation Green Lab, National Trust for Historic Preservation, Seattle, Washington, USA

Abstract District energy systems will play an ever more critical role in achieving community sustainability goals, as standards for energy efficiency and GHG emissions get more aggressive, and as existing buildings hit the limit of what can be accomplished within their property boundaries. District energy systems, especially those based on renewable fuels and/or the capture of waste heat, offer a very low-cost and low-carbon alternative for providing heat, hot water and cooling to entire communities of homes and businesses. Such systems are relevant and viable in both traditional urban villages and compact rural towns. The coordination required among multiple owners for the financing, build-out and connection to such systems poses challenges that local governments need to be poised to solve. At the same time, the “utility service model” that often emerges as the basis for solutions can also be used to organize and fund other community-based energy and infrastructure projects, ranging from water management to complete streets to urban agriculture. The Preservation Green Lab has collaborated with the University of Oregon’s Lundquist College Center for Sustainable Business Practices to create a policy primer and roadmap for communities wishing to create or expand district energy systems in neighborhoods of older and historic buildings. Keywords: district energy, renewable energy, eco-district, district heating, district cooling, combined heat and power, municipal energy policy.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESUS110191

218 Energy and Sustainability III

1

Introduction

As cities look for innovative means of reducing carbon emissions from the operation of their existing buildings, it is increasingly clear that the most effective way to achieve high levels of energy performance rests with districtlevel approaches to the built environment. This paper explores the vital role that low-carbon district energy systems (i.e., neighborhood-scale utilities that deliver thermal energy for heating, cooling, and hot water) can play in enabling existing buildings and established urban neighborhoods to meet aggressive emission reduction targets in a cost-effective way. It also highlights the essential role local governments must play in supporting the development of district energy systems, and is intended as a primer for communities that are beginning to look at district energy as a possible strategy for reducing their emissions and dependence on non-renewable energy sources. Many communities face common barriers, capacity constraints, and learning curves, and this publication identifies the policies and programs needed to foster district energy system development.

2 The trend toward district-level action Many communities that are pursuing aggressive policies to measure and improve the energy performance of their existing building stock are starting to experience the limits of an approach that focuses on individual buildings. Each existing building presents a unique set of challenges and opportunities, defined to some extent by its original size and design. Many existing buildings, especially those that make up our “urban villages” and our small town “main streets,” are too small in scale or were designed in such a way that they cannot take advantage of some of the dramatic energy efficiency features or on-site renewable energy options available to new construction. Also, individual buildings are unable to tap into many cleaner sources for thermal energy; an investment in a waste heat recovery system or a biomass facility, for instance, is usually going to be impossible for a single building, and becomes an option only when a central facility is designed to harvest that energy for use by many buildings. Issues such as these are encouraging some cities to expand their sustainability efforts to a district level, focusing on community-wide energy performance metrics and policies that enable building owners to combine their demand for greener energy and to share sustainable infrastructure across property boundaries. This also represents a shift from citywide policies and infrastructure efforts down to a more manageable scale, that of a neighborhood or district. This reorientation to “eco-districts” has become a catalyst for innovation and experimentation, and has begun to unlock a number of practical solutions related to key urban sustainability priorities—including not just thermal energy but also power generation, storm water management, waste water reclamation, and urban agriculture.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

219

3 About district energy District energy is not a new idea – many cities developed central heating systems in the early 1900s. However the benefits of district energy were overlooked during the latter half of the 20th century, when energy and land were cheap, and development was sprawling rather than compact. Now communities are rediscovering the potential of district energy systems in light of the current era of urbanization, energy insecurity, and climate change mitigation. In general terms, district energy systems provide for the heating and hot water needs of a community of buildings, which are connected through a thermal network of pipes under the streets that carry hot water from a centralized energy plant. District energy can also provide cooling services, through the use of a similar piping infrastructure with chilled water. The thermal energy required can be generated from a diverse range of sources, including natural gas boilers, ground-source heat pumps, combustion plants that burn wood or other forms of biomass, and sources of waste heat that can be captured from power plants, industrial facilities, sewers, and waste water plants. District energy systems are local, neighborhood utilities. They are specifically created to deliver heating and cooling services to the buildings in a defined service area, to finance construction (plant, piping, and building connections), and to charge end users for those services. The financing and build-out of new systems in neighborhoods of existing and historic buildings requires substantial coordination among multiple owners. This coordination effort requires the leadership of local governments, as they have unique and essential capabilities to enable district energy system development.

4 Benefits of district energy District energy systems help cities to achieve their economic, environmental, and social objectives related to buildings and development, and provide long-term, efficient, and affordable energy to their building customers. 4.1 Key benefits to communities District energy provides a platform for cities to increase efficiency, reduce greenhouse gas emissions, and adopt new technologies and fuel sources over time. Given the advantages achieved through diversification of peak load times and ‘right-sizing’ of equipment for aggregate loads, district energy systems can produce significant efficiency gains. District energy systems also provide opportunities for shifting to cleaner energy sources over time and for capturing available forms of waste energy (from industry, for example, or sewer systems) that individual buildings cannot get access to or justify the capital investment needed to do so. A district-wide system simplifies such transitions, since installing or upgrading a central generation plant to cleaner technology can deal with an entire community. St. Paul, Minnesota, for example, was able to convert its system WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

220 Energy and Sustainability III from coal and natural gas to waste wood as a primary energy source, dramatically reducing emissions for the existing buildings connected to the system [1]. The combined effect of greater system-wide efficiency and access to cleaner energy generation made possible by district energy means that emissions reductions can be significantly higher than could be realistically achieved on a building-by-building basis. It is estimated that Vancouver’s Southeast False Creek project achieved about a 70 percent reduction in greenhouse gas emissions compared to a business-as-usual scenario, with the reduction equally split between the improved efficiency (one plant serving multiple buildings) and cleaner fuel/technology choice (in this case sewer heat recovery) [2]. District energy opens up new sources of capital for improving performance of a community’s existing building stock. As with other types of utilities, the revenue stream from the aggregation of customers paying for heating, cooling, and hot water systems enables access to capital, such as municipal bonds and/or state and federal grants, or even private project finance investors, that is usually unavailable to individual building owners. A city can create new tools to finance energy performance improvements to entire neighborhoods in one phase of work. This local utility approach to energy system development also gives communities the option, should they want it, of taking greater ownership of local infrastructure assets and providing long-term operating revenues back to the community. In any case, the system owner, whether a community-based or a privately-owned utility, can leverage long-term financing to cover the upfront capital costs with a rate structure that pays off the financing over time. District energy provides a platform for managing energy costs over the long term. Aggregate demand for fuel, whether from natural gas, biomass or other sources, allows communities with district energy systems to negotiate long-term contracts for portions of their fuel costs, thereby moderating cost variability. St. Paul’s system was a response to concerns of building owners about long-term energy prices [1]. Also, once a district energy service model for heating or cooling is established in a community, the aggregation of customers makes it easier for a community to negotiate such things as bulk installation of on-site equipment, such as solar panels, or bulk purchases of green power from remote sources through a utility contract. District energy helps mitigate long-term risks. District energy systems can reduce risk for cities in terms of future energy and environmental policy, carbon costs, fuel availability and cost variability, and the future effects of climate change. For example:  

Toronto’s investment in district cooling enabled the city to meet its Montreal Protocol obligations by reducing refrigerant use in individual buildings [3]. In Nashville, significant upgrades to an established system were supported by the city in order to reduce risk from air quality violations [4].

Given the risks to owners posed by climate change regulation and energy prices, cities may also consider district energy as a way to “future-proof” their property tax base by protecting owners against future energy price and/or policy WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

221

shocks. District energy can also serve to mitigate the risks and challenges associated with relying on our late 20th-Century model of big infrastructure, which includes the vulnerability of large systems to regional-scale failures, especially in areas prone to natural disasters (i.e., earthquakes, volcanoes). District-level thermal energy and CHP plants can create badly-needed redundancy of supply, and mitigate the impact of disasters, making communities more resilient. District energy can help communities respond to broader environmental goals and advance their other district-level environmental services. In Vancouver, a community vision for carbon neutrality was the determining factor in bringing district energy into reality [2]. Some communities want to reduce the “out of sight out of mind” effect and let people know more about where their energy comes from, instead of having smoke stacks and plants hidden far outside the city limits. Others are trying to “right-size” systems for energy and other services as a response to the limits of both large regional infrastructure and of individual buildings, and then trying to find synergies between different types of infrastructure and resources as they move to more environmentally friendly solutions. More commonplace in the near term, however, may be cases like West Union, Iowa, where a pragmatic analysis of return on investment prevailed. After receiving federal and state funds to improve energy efficiency and implement a “Complete Streets” design that provides greater amenities for pedestrian, cycling, and transit users, and doing an energy audit of their existing and historic building stock, community leaders decided that selected retrofit measures combined with a new district energy system will optimize the community’s return (both economic and environmental) on the total sum of available private and public funds [5]. 4.2 Key benefits to building owners Making sure that energy consumers and building owners understand the ways that district energy directly benefits them is critical. Of course many of these benefits overlap with those of communities—what’s good for owners is good for communities, and vice versa. Nevertheless, in order to engage the participation of owners and tenants, cities need to analyze and articulate how district energy benefits them through cost savings and increased energy efficiency over the long term. District energy offers energy cost savings and price stability. The bottom line for any building owner is cost. Long-term net cost savings are a key selling point of district energy systems. District energy delivers lower cost energy through improved efficiency, load diversification, and economies of scale. Also due to the long-term aggregate nature of demand, a district energy system operator can negotiate long-term fuel contracts, which facilitates greater energy price stability for consumers. District energy responds to market and regulatory demand for higher energy performance. Buyers and renters are becoming more and more aware of the energy performance of existing buildings which makes energy efficiency a WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

222 Energy and Sustainability III source of either opportunity or risk for owners, depending on how well their buildings compete. Cities are now adopting new policy initiatives around energy performance ratings and disclosure to accelerate the degree to which market forces will distinguish efficient buildings from those that use too much energy. Some cities, like Seattle and Vancouver, are already moving beyond disclosure policies toward regulations that will require buildings to meet aggressive postretrofit energy targets in return for flexibility to innovate in how they achieve such targets, including use of on-site renewable generation equipment and/or low-carbon district energy sources. District energy offers an essential opportunity to owners in this emerging policy environment. District energy relieves building owners of responsibility for delivery and management of heating, cooling, and hot water. With district energy, building owners receive reliable and predictable energy service from professional system operators. This means fewer worries for building management staff, in terms of fuel price uncertainty and system maintenance, upgrade and repair, compared to on-site systems. District energy relieves building owners of responsibility for delivery and management of heating, cooling, and hot water. With district energy, building owners receive reliable and predictable energy service from professional system operators. This means fewer worries for building management staff, in terms of fuel price uncertainty and system maintenance, upgrade and repair, compared to on-site systems. District energy offers owners a platform to upgrade fuels and technology. District energy allows cities and building owners to “fuel switch” over time to take advantage of new clean energy technology options and access capital financing for these fuel/technology upgrades. District energy improves air quality. The hydronic heating and cooling systems that are often used with district energy produce less dust and airborne contaminants than forced air systems, and provide far more even and comfortable heat than electric resistance options. Many upscale residential buildings offer hydronic heating as an amenity. District energy enables incentives and financing that would not otherwise be available. District energy systems can attract sources of financing, such as municipal bonds or community energy grants, which are not available to individual owners. The cost efficiencies gained with district energy utility can in some cases create enough of a revenue premium for cities to offer incentives to owners of existing buildings for installing systems compatible with district energy and connecting to the system. This in turn can enable owners to take into consideration the full spectrum of options for replacement of heating and cooling equipment without having to bear a first cost premium.

5 Synopsis of key findings 5.1 Changing scale of opportunity, policy, and investment Efforts to reduce future regulatory risk and achieve community energy performance goals are likely to be key drivers of district energy systems. In WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

223

neighborhoods of existing and historic buildings, the desire to optimize the use of public and private funds targeted to energy retrofits will be a further motive. An individual building can only accomplish so much on its own with regard to performance, whether related to energy, or water, or even social goals. While some new buildings have achieved “net zero” operating performance (e.g., they produce as much energy as they consume over the course of a year), achieving this performance requires a significant cost premium upfront, and this cost premium is likely to be more significant for existing buildings where the ability to integrate renewable energy equipment can be limited based on the building’s size and design. A building-centric approach may miss opportunities to share equipment across buildings and to spread those costs over many buildings. To illustrate these points, consider what steps a building owner in an existing building must take to reduce greenhouse gas emissions to very low levels (i.e., 80 percent or more below current levels). Conventional technologies—the use of insulation, weather-stripping, and other weatherization measures—can usually reduce energy usage by 50 percent at best. Further reductions in greenhouse gas reductions require the transition to cleaner sources of fuel. Without a districtoriented approach, every building currently using natural gas boilers for heating would need to identify and switch to a source of energy with lower greenhouse gas emissions. Such an undertaking would be expensive and take considerable time, since each building owner has already invested in his or her heating equipment and the lifecycle of those investments vary. Aware of these constraints, many cities are re-examining how upfront investments toward building energy performance can be spent to yield the best overall return on investment (in terms of both dollars and climate change mitigation), given the duplication of equipment, energy load, square footage loss, and sheer effort of taking the building-by-building approach. National organizations have responded to this opportunity with newly proposed legislation at the federal level that proposes to extend the energy production tax credits for power generation to generation of thermal energy. 5.2 Cities play a critical role in district energy development District energy can help cities improve the performance of their neighborhoods, and deliver value to building owners by improving energy efficiency and developing clean, renewable forms of energy for the heating, hot water, and cooling needs for buildings. However the successful implementation of district energy can be challenging, especially in neighborhoods of existing buildings with multiple private owners. The need to invest time and political capital, and possibly public resources, in district energy is not based on expediency—the benefits are less than tangible, hard to link directly to the average citizen, and are often not visible in the short term. Many times, an institutional disconnect between cities and developers/building owners means that they cannot justify making long-term investments, nor do they have easy access to financing that can accommodate the longer-term economic payback. Cities have a unique and essential role to play, first in establishing a neighborhood-scale utility model, which allows communities to make different WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

224 Energy and Sustainability III decisions about capital investments, risk management, and technologies than individual building owners or large utilities could. Once this model is established, cities can then play a direct role in attracting financing. Successful district energy projects have used city bonds as part or all of the significant capital financing needs. Both Nashville and Toronto used revenue and general obligation bonds in tandem to raise the necessary capital for infrastructure and energy plant construction [3, 4]. The use of municipal bonds can be an important factor for decisions by federal, state, and private investors, who look to municipal support as a key indicator of city priority and capacity for fostering district energy. In addition to providing upfront financing, cities are in a unique position to facilitate system development when they make other key infrastructure improvements, such as replacing sewers or water pipes. Given the large capital cost of pipes to distribute hot or cold water throughout the planned service area, installing those pipes in tandem with other construction work can save significant amounts of money, and ensures the district energy system will be cost-effective to building owners. These opportunities not only help reduce costs significantly, but also create momentum for the system to expand over time. Local jurisdictions (depending on specific structure and authority) can also set policies to help level the playing field for profitable district energy development. They can regulate building energy performance policy and exercise land-use controls to regulate/incent connections to district energy systems. Some cities won’t have the political will and/or financing capabilities to develop systems, but may have other tools to encourage development of systems by others and to secure a strong customer base and sufficient energy load to make private capital investments less risky.

6 Policy road map Every city presents unique challenges, however the following are common critical elements to a district energy plan. In established neighborhoods, where change can evolve quite slowly, cities can preserve future opportunities by preparing now. 6.1 Create tailored community energy policies Community energy policies should reflect local opportunities, respond to future regulatory risks, and incorporate long-term objectives for efficiency and clean energy generation consistent with higher-level goals for climate change action and economic resilience. Citywide or regional targets for demand reduction and clean energy generation will provide the needed impetus for identifying potential districts and recognizing catalysts. Building-level policies will ensure that owners improve structures in a manner that is compatible with district energy, such that over the course of several years a community can accumulate enough buildings in close enough proximity to connect them with piping infrastructure to shared energy plants. WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

225

6.2 Identify target areas that have a high probability of success Existing neighborhoods must have sufficient density to ensure adequate demand and a mix of uses that allows for load diversification. A majority of existing buildings within close proximity must have heating, cooling, and hot water systems that are compatible with district energy. Target areas should have ready access to local, clean sources of energy, such as sewers or waste water plants, waste heat from industrial processes or biomass. Coordinating with infrastructure projects to upgrade sewer or water lines, install rail transit, or improve streets can help reduce civil engineering and construction costs. 6.3 Recognize and respond to catalysts A number of catalysts can provide the impetus for developing a district energy system. Catalysts can come in many forms, ranging from energy policy changes, new financing sources, changes in technology, new infrastructure projects, or grassroots community efforts. 6.4 Build institutional capacity District energy systems are challenging to develop, and a city interested in fostering their development needs to prepare for and maintain a commitment of staff time and policy focus. In some cases, cities must be prepared to exercise rate setting authority in order to capture customers and secure better financing terms. In other cases, cities need to be prepared to lead by example by being their own energy customer. 6.5 Secure the customer base District energy systems are only viable with a customer base of building owners who are focused on their long-term energy needs and who understand the utility service being provided. Cities must first work with existing building owners to make their buildings compatible, and in some cases, to offer owners a “turn-key” energy service model, in which the city assumes responsibility for heating and cooling equipment in individual buildings until such time as system construction becomes viable. 6.6 Take steps to manage construction, financing and policy risks Connection to district energy should reduce risks for building owners and communities. Building owners need to be assured that connecting to a district energy system will increase their energy independence and decrease their exposure to system failures. During the initial stages of system development, a city and other key stakeholders (business representatives, energy advocates, customers) need to systematically identify and address risks associated with financing the construction of the system. Cities have a direct role to play in this respect, and while the current fiscal situation may make public sector investment seem unlikely, such investment can often represent a key to success. WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

226 Energy and Sustainability III

7 Conclusions Energy policies are changing dramatically. Driving forces include climate change, a desire for less reliance on fossil fuels (especially imports from unstable countries), and strong economic benefits that can come with greater energy efficiency and widespread deployment of clean, renewable energy technologies. In the future, the use of energy that contributes to greenhouse gas emissions will become increasingly expensive. Buildings that rely on these energy sources face higher energy costs, and will be well served by greatly improving their efficiency and finding cleaner forms of energy. However, investments in building efficiency and cleaner forms of energy will be financed less by individual building owners and more by new finance models that leverage capital from public and private sources that are interested in the returns available from clean energy systems. A shift in scale from individual buildings to neighborhood districts is essential to helping to reduce the costs that regulation and more expensive energy will impose on building owners and occupants, and to creating the opportunity to use financing strategies that can make investments in improved community-wide performance. District energy is emerging as an important element of our future energy system because it creates a platform for migrating entire communities of existing buildings to systems that use less energy and can tap into cleaner forms of energy over time, all at lower cost than would be possible for individual buildings. This neighborhood-scale approach applies to a range of urban infrastructure services and resources, from urban food production and water treatment to smart grid technologies. The owner cooperation, aggregation of demand, and service model established for district energy can also serve as the foundation for these other “eco-district” services and projects. City leadership is central to district energy; the potential for district energy cannot be exploited without the engagement of city government. Our cities will set the policies that affect how buildings use energy, create plans that can identify the best opportunities to foster new district energy systems, create the institutional context in which district energy systems can be created, and provide the ongoing attention to energy that individual building owners cannot do on their own. To do so effectively, cities need to understand how district energy works and how to foster district energy development. District energy requires holistic thinking about neighborhoods, with clear policy approaches that support the collaboration of building owners, utilities, and government to achieve efficiencies and reduce energy use and greenhouse gas emissions on a larger scale. The more a city can integrate district energy into its long-term plans and strategic objectives, the better the likelihood that systems can be integrated into existing neighborhoods when opportunities present themselves.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

227

References [1] Rydaker, Anders. President, District Energy St. Paul. Personal Interview by Jaxon Love. 22 Jan 2010. [2] Baber, Chris. Neighborhood Energy Utility Project Manager, City of Vancouver. Personal Interview by Tom Osdoba. 25 Jan 2010. [3] Soumalias, Yianni. Regulatory Affairs Advisor, Enwave Energy Corporation. Personal Interview by Hendrik Van Hemert. 08 Feb 2010. [4] Bradley, Michael. Office of Finance, Metro Nashville. Personal Interview by Hendrik Van Hemert. 28 Jan 2010. [5] Geerts, Jeff. Special Projects Manager, Iowa Department of Economic Development. Personal Interview by Tom Osdoba. 23 Sep 2010.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

This page intentionally left blank

Energy and Sustainability III

229

Subsidising renewable electricity in Estonia J. Kleesmaa, S. Pädam & Ü. Ehrlich Tallinn University of Technology, Estonia

Abstract The purpose of this paper is to assess the impact of Estonia’s feed-in tariffs (FIT) on combined heat and power (CHP) plants. The assessment follows previous practice and provides a novel approach by including a case study based on company data. The results of our assessment show that the Estonian FIT system has effectively supported the establishment of CHP capacity and that the administrative costs have been low. In contrast to experiences in other countries we find that the avoided external costs exceed the per MWh cost of FIT. Another feature is that the consumer costs of the FIT scheme have grown more rapidly than elsewhere. Although avoided external costs cover FIT, resources are not used cost-effectively. The case study of two CHP plants suggests that resources are used for supporting production that would have been profitable without FIT. Keywords: renewable electricity, feed-in tariffs, CHP, energy policy, Estonia.

1 Introduction Feed-in tariffs (FIT) is the most widely used support scheme for renewable electricity: implemented in 20 EU countries and 30 countries worldwide in 2009 [1]. Denmark and Germany were the first countries to introduce FIT in the mid-1980s and 1991, respectively [2]. Success stories about countries that have exceeded initial goals for renewable electricity seem to be forceful arguments for additional implementation. Further backing from economists supporting the use of price rather than quantity based regulation could be another reason for the popularity of FIT. According to the national electricity development plan 2005–2015 [3] the goal is to increase the share of renewable electricity to 5.1% of gross consumption in Estonia by 2010. In the succeeding development plan, which stretches until 2018, the goal has been set to extend the share of electricity from renewable resources to 15% by 2015 [3, 4]. For Estonia, these goals imply WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESUS110201

230 Energy and Sustainability III significant changes. In 2007, the share of renewable fuels in electricity production was 1.75% of gross production while the main supply originated from oil shale electricity, which made up 93.6% [4]. Based on capacity under construction, it is estimated that Estonia outperforms the goal in 2010and reaches 9.7% renewable electricity [5]. Estonia’s goal to 2020 is to increase electricity produced from renewables in combined heat and power plants (CHP) to 20% of gross production [4]. Following introduction of FIT in 2007, there has been a substantial increase in energy produced from renewable fuels in CHP plants. In 2009 Tallinn and Tartu CHP started operation and the share of renewable electricity is further increasing. Pärnu CHP is under construction and several small CHPs are being planned in different parts of Estonia. Recently, also oil shale electricity producers have begun to use biomass as an input. It seems thus that Estonia shares the experiences of other countries that report a rapid increase of renewable electricity following introduction of FIT [2, 6]. Besides the positive effects, the change seems to have come at a high cost. The costs of FITs have increased from 6 million to almost 55 million Euros between 2007 and 2011 [5]. This cost is collectively paid by consumers by an addition to the price of electricity. In 2010, this addition makes up about 10 percent of the consumer price and the Estonian Competition Authority, who regulates the price of electricity, has questioned the size of the subsidy [7]. The purpose of this paper is to assess Estonia’s FIT scheme on CHP plants. Assessments have been carried out by several other authors, see [6] for references. The goal of this paper is to assess whether the current tariff level paid to CHP plants is motivated from an efficiency perspective, and its implications on consumer costs. Another aim is to find the benefits in terms of avoided external costs. The authors are not aware of previous assessments concerning CHP plants, suggesting that this paper may represent the first assessment of FIT on CHP plants. In addition, the case study of this paper applies a novel approach by using company level data. The next section provides a literary overview about FIT assessments. In section 3, we give details about the Estonian FIT. Section 4 presents calculations that assess the company level impact of FIT on two CHP plants and compares the outcome to marginal cost and cost price. In section 5 we calculate the external costs of electricity produced from oil shale and compare this with electricity produced by biomass and peat in CHP plants. Section 6 summarizes the assessment and the last section concludes the paper.

2 Literary review A feed-in-tariff (FIT) denotes a guaranteed price to producers of electricity generated from renewable sources, combined with a purchase obligation by grid companies [6]. There principally are two different ways to cover the costs of the policy measure, either by consumers via the electricity bill or via the public budget. An important reason to subsidise renewable electricity is that production costs typically are higher than that of non-renewable electricity [6]. In this sense WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

231

FITs represent a second-best policy by giving a subsidy to a preferred choice rather than correcting for external costs of electricity from non-renewable sources. Not only the choice of which market to regulate, but also the FIT levels have been questioned. In an overview of support schemes in 2005, it was shown that German support levels typically were twice the level of those of the Nordic countries, mainly using quantity based regulation combined with green certificates [8]. The same study indicated that the costs of FITs on the margin cannot be motivated by the social benefits from renewable electricity [8, 9]. At the same time, there seems to be efficiency arguments to use FIT for wind power [1]. Most probably these efficiency reasons denote dynamic efficiency in order to provide technology change and support market take-off [6]. Based on German and Danish experiences, Sijm [2] has assessed the sustainability of feed-in tariffs. The German FITs were until 2000 based on a percentage of earlier consumer prices of electricity and varied by the source of energy. After implementation prices rose significantly and due to a rapid expansion of wind power, the system led to competitive distortions between grid companies in different parts of the country. When the German market for electricity was liberated, the system needed urgent revision. The new FITs are based on the production costs of various renewable energy resources with digressive payments during 20 years [2, 10]. Denmark revised its FIT in 2000 for reasons of a high burden on the state budget [2]. In his assessment of FITs, Sijm [2] concludes that FITs are effective in promoting electricity generation from renewable sources, but costly, inefficient and distortive. Spain is another country that has been successful in renewable energy promotion. In their assessment del Rio and Gual [6] find that the Spanish system has been effective in its support of wind energy, but not equally successful concerning other energy sources. They conclude that although consumer costs were relatively low, increasing from 0.14 to 0.26 eurocents /kWh between 1999 and 2003, the costs are relatively high compared to the externalities avoided.

3 Feed-in tariffs in Estonia According to the Estonian Electricity Market Act production of electricity from wind, small hydropower and biomass receive the same level of FIT [11, 12]. The FIT for CHP plants differs according to fuel. Generating electricity in efficient cogeneration regime by biomass (wood chips), the producer is paid support at the rate of 54 €/MWh for selling electricity to the network. While operating in efficient cogeneration regime and using waste or peat as a fuel, the producer is paid support at the rate of 32 €/MWh. If wood chips, peat, waste or other fuels are combined, the support granted for selling electricity to the network is calculated in proportion to the fuel used. The FIT schemes apply within twelve years as of the commencement of electricity generation. After introduction of FIT on May 1st in 2007, the expenses for financing FIT are funded by network charges paid by consumers. In 2010 the renewable energy charge is 0.8 € cents/kWh. An additional line setting out the renewable energy

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

232 Energy and Sustainability III charge was added to the electricity bills of end users enabling customers to see how much they pay for financing feed-in tariffs. The Estonian electricity market is divided into two – an open market and a closed market. 35% of the market was opened on 1 April 2010. Starting from 2013, the market is going to be fully liberated. While selling electricity in the closed market, approval must be obtained under the law [11] according to the weighted average price limit of electricity. In its approval, the Estonian Competition Authority takes into account operating expenses and returns on invested capital. In order to determine the price, the authority considers the undertaking’s annual average residual value of fixed assets and adds 5% as profit margin. The justified rate of return is the undertaking’s weighted average cost of capital (WACC).

4 The impact of FIT on CHP plants The case study takes as its starting point, two 25 MWel CHP plants that began operations in 2009. The evaluation of the investment decision and profitability of the CHP plants are based on annual reports [13, 14]. In order to assess profitability without FIT, we apply the rules of the Estonian Competition Authority and we calculate the per MWh revenue without FIT. The results are then compared to marginal cost and the cost price of electricity (the cost price is the price that exactly balances production costs, not adding profit). 4.1 Ratio analysis The annual reports consist of the balance sheet, income statement and notes on the accounts. The methodological approach used in the evaluation of the financial reporting is based on ratio analysis, carried out as comparison with accounting benchmarks. Ratio analysis is the main instrument in financial analysis that enables to elicit relations between financial indicators and compare different undertakings with one another. The investments in the plants were of the same order of magnitude, i.e. approximately 77 M€ respectively. Although no trend analysis can be made on the basis of the publicly available financial results for 2009 of the CHP plants, the data still allow evaluating, in general lines, plant profitability in 2009. Results of the evaluation are displayed in Table 1. Table 1: Ratio Net profit margin Operating profit margin Rate of return on equity capital Rate of return on assets Debt coefficient

Ratio analysis of two CHP plants, 2009. Benchmark 5.0% 17.0%

Ratio 37.6% 48.1%

CHP 1 Evaluation High High

Ratio 10.3% 23.9%

CHP 2 Evaluation High High

15.0% 9.0% 40.0%

100.0% 11.8% 88.2%

High Normal High (risk)

34.5% 2.4% 93.0%

High Weak High (risk)

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

233

The table shows that the power plants’ rate of return on equity capital is high indicating efficient management in using the capital invested by shareholders. Profit margin that characterises profit on every euro of turnover is also high. The debt coefficient, pointing at how big a proportion of total funds are financed from borrowed funds, is extremely high in both plants. The profitability of assets shows the rate of return on the funds invested in the company irrespective of their source. Profitability is weak in CHP 2 being approximately 5 times lower that of CHP 1. It can be concluded from the above that due to the implementation of FIT, the new power plants have managed to start profitable economic activity. Despite a large debt burden and strong dependence on borrowed capital, the rate of return on equity capital and the net profit margin hint at management efficiency and ability to gain initial results in activity. However, case study data covers only one year. Additional sources of uncertainty include the development of prices of renewable fuels and the impact of market liberalisation. Notwithstanding these uncertainties, there are reasons to believe that the plants will continue operations successfully. It is possible to argue that these plants are well prepared to meet changes in input prices. In case of a rapid price increase, there is flexibility to shift fuels. Both plants are licenced to use wood chip and peat as fuel. Boiler technology allows additional fuels and the plants have fuel producing companies as subsidiaries. While market liberalisation will take place on electricity sales, the profitability of heat production can be predicted to be stable due to the continuation of a closed heat market. Since electricity prices in the Estonian market currently are below Nordic spot market prices [15], market liberalisation is expected to lead to price increases. In theoretical terms, each power plant could generate a maximum of 25 MW * 7200 h=180 GWh of electricity per year. The generated volume of electricity depends on the number of operational hours. A smaller number of stop pages and standstill periods imply more operational hours and more generated electricity. Pursuant to the actual annual report of 2009, CHP 1 generated circa 128 GWh and CHP 2 generated circa 110 GWh of power. Electricity generation in the plants were in the range of 68%-80% of the theoretical maximum. In CHP 1 the size of support comprised 54 €/MWh * 128 * 103 MWh  6.9 M€. Since CHP 2 used peat, the support size was32 €/MWh * 110 * 103 MWh  3.5 M€. Regarding different plants, FIT revenue accounts for approximately 50–60% of the operating profit, and excluding FIT comprise approximately 40–50%. Dependence of operating profit on the size of FIT can be expressed by eqn. (1).

(1)

where denotes operating profit on electricity sales, operating profit generated electricity and FITi feed-in on electricity sales excluding FIT, tariff for i=1,2 (1=wood chip and 2=peat). According to the annual report, operating profit on the electricity sales of CHP 1 amounted to circa 12 M€; excluding FIT, operating profit would be 5.1 M€. The respective sums for CHP 2

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

234 Energy and Sustainability III are circa 7.5 M€ and 4 M€. These results suggest that the operating profits of both plants would have been positive also without FIT. 4.2 WACC Assuming that the plants had operated without FIT and that their electricity prices were set by the Estonian Competition Authority, we apply the method of the regulator [16] according to eqn. (2), which shows the Weighted Average Cost of Capital (WACC). (2) where: ke– is cost of equity capital (%); kd– is cost of borrowed capital or external liabilities (%); OK – is proportion of equity capital determined by the regulator (%); VK – is proportion of borrowed capital determined by the regulator (%). Taking into account the value of the debt coefficient for the financial year 2009 of the power plants CHP 1 and CHP 2 and applying eqn. (2), we find that:

6.31 6.31

88 93

9.61 9.61

12 /100

6.74%

(3)

7 /100

6.54%

(4)

Assuming that all economic indicators, except investments, are evenly distributed over a 25-year period (according to accounting principle), and taking into consideration the expenditure and revenue (9.7M€ and 24.9M€, respectively) as well as investments of CHP 1, we find that the internal rate of return (IRR) of the plant is 19% on invested funds. Setting IRR equal to WACC, we find that, revenues corresponding to 16.3 M€ would be sufficient to receive WACC from the investment of the undertaking. Considering the fact that revenue from the sale of heat is a fixed value 12.9 M€ (the amount of generated heat corresponds to the need/weather conditions, and the limit price for heat is confirmed by the Estonian Competition Authority), we gain the needed income from the sales of electricity for achieving the WACC rate that comprises 16.3–12.9=3.4 M€. As the volume of electricity sold in 2009 was 128 GWh, the regulated price per MWh of electricity would equal 3.4 M€/128 GWh=27 €/MWh. By applying the same method as above for CHP 2, we find a price of52 €/MWh. These prices can be compared to the regulated price of oil shale electricity which was 29 €/MWh in 2009 [17]. In principle, this level is the guaranteed or lowest electricity selling price for all plants. Thus, even without supports, provided that electricity is sold at 29 €/MWh, CHP 1 would earn more than necessary for achieving WACC, while CHP 2 would earn less.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

235

There could be several reasons why we receive significantly different results for the two plants. One could be that the plants use different fuels. However, it cannot be excluded that the method of regulation gives incentives to plants to adjust their financial accounts. According to the ratio analysis the rate of return on assets and the debt coefficient are surprisingly weak in CHP 2. 4.3 Price comparison Since the results of the WACC calculations are somewhat inconsistent, we derive the price excluding FIT from observed sales data. Assuming that the price of electricity was equal to the regulated price implies that the per MWh revenue was 83 € for CHP 1 and 61 €CHP 2, respectively. Using these revenues, we find that electricity sales were 145 GWh and 123 GWh. Since reported sales were smaller, it can be concluded that CHP 1 and CHP 2 earned higher revenues than in the closed market setting. This can be regarded as a result of beneficial contracts entered into with balance providers (Nord Pool Spot’s operations). Calculations show that, the average revenues were 40 €/MWh of CHP 1and 36 €/MWh of CHP 2. Based on our analysis, including the above calculations and the previous section suggest that CHP 1 would have operated successfully even without FIT. The evidence of CHP 2 is inconclusive though. In order to take the analysis one step further we compare the prices to general information about production costs. From a theoretical point of view, we ideally would like to compare prices to marginal costs [18]. Since marginal costs are not available, we approximate marginal costs by average variable costs. In a forthcoming article by Latõšov et al. [19], the authors present cost data of different sized CHP plants in an Estonian context. Using data for the 25 MWel plant, it is possible to calculate the variable cost. Depending on the method of allocating costs between electricity and heat, we arrive at an interval of 4.7– 6.7 €/MWh. This is in the same order of magnitude as the average variable cost in the Nordic market, which is 8-9 €/MWh, according to estimates based on [20]. The result shows that both plants receive prices substantially above marginal costs. Comparing revenues to the cost price will provide another benchmark to our case study observations. The above case study concerns relatively large CHP plants and since unit costs depend on the size of the plant [21] it might not be possible to generalise our results to all plant sizes. In [19], the authors estimate the cost price of electricity of different sized CHP plants. They use data collected in Estonia and the Nordic countries and make calculations of plants with capacity of 1, 10 and 25 MWhel respectively. Assuming a fixed heat price, they derive the per MWhel cost price. Using these observations for fitting a curve, it is possible to approximate the cost prices of a wide range of different plant sizes. Figure 1 below, indicates that the cost prices of CHP plants with capacity less than 10 MWhel have significantly higher cost prices than larger plants and that there is a rapid increase in cost prices when plant sizes become smaller. Subtracting the FIT from the cost price (see lower curve in Figure 1) shows an even more interesting picture: the FIT covers the cost price of electricity production from a CHP plant with capacity of 25 MWel and when FIT is WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

236 Energy and Sustainability III excluded its cost price is similar to a plant of 4 MWel that receives FIT. These findings confirm the results of the case study and indicate that large plants are overcompensated by the current FIT, while small plants might not receive sufficient support. €/MWh 200 180 160 140 120 100 80 60 40 20

MWe

0 0

5

10

15

20

Cost price

Figure 1:

25

30

FIT, excluded

Cost price of CHP plants, euro per MWh

el.

5 Avoided external costs A gradual shift from oil shale electricity to renewable sources will have a positive impact on the environment. In order to assess the benefits of FIT in terms of avoided costs, the external costs of air emissions of electricity production from oil shale, wood chip and peat have been calculated. The emission factors are shown in Table 2. Table 2: Carbon dioxide, CO2 (kg) Sulphur dioxide, SO2 Nitrogen oxides, NOX Particulate matter, PM10

Emission factors in g/ MWhel. Oil shale 1156 7147 1075 494

Wood chip 306 400 353 75

Peat 386 1676 2236 280

Sources: [17, 22–24]. The emission factors of oil shale are based on emission measurements at the Eesti power plant in Narva [22], where about 20% of electricity is generated in fluidized bed combustion and about 80% in pulverised combustion. The external costs were collected from ExternEestimates [25]. Although, Estonia is not represented in ExternE, we follow the application in [26] and base the external costs on Czech brown coal. This transfer of external costs could result in an WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

237

upward bias, since the estimates also include health effects of pollutants. The risk of bias is due to the fact that population density is higher in the Czech Republic than in Estonia, and the values in use might therefore exaggerate health costs. In the Czech values, health costs make up about 40% of the external cost of brown coal combustion. Table 3: Carbon dioxide, CO2 Sulphur dioxide, SO2 Nitrogen oxides, NOX Total suspended particulates, TSP Sum

External costs €/MWhel. Oil shale 22.0 40.6 3.3 3.3 69.2

Wood chip 5.8 2.3 1.1 0.6 9.7

Peat 7.3 9.5 6.8 2.1 25.8

The external costs show relatively large differences. Every MWh of oil shale electricity that can be substituted by electricity produced from wood chip in CHP plants reduces external costs by almost €60 and if replaced by peat, the avoided cost would be about €43.Comparing these values to the Estonian FIT of €54/ MWh and €32/MWh respectively, show that the estimated environmental benefit are higher than the FITs. However, since power plants pay environmental charges, internalisation already takes place. The pollution charges are relatively low though: only about €2 per MWh of oil shale electricity is currently being internalised [17]. Assuming that the influence of a possible upward bias is at an equally low level, the cost of the Estonian FITs are supported by arguments of avoided external costs. An important additional requirement is that the renewable electricity replaces oil shale electricity. So far this replacement has not taken place, but in 2016 when more stringent EU regulation will come into force, pulverized combustion must be equipped with flue gas purification otherwise these boilers have to be shut down [4].

6 Overall assessment In our evaluation of the Estonian FIT for CHP plants we follow the assessment criteria used previously in literature [2, 6]. One problem though is that the period of assessment is relatively short, stretching from mid-2007 until 2010. Based on evidence so far, Estonia will outperform the target set for 2010, suggesting that the FIT has been effective [5]. The case study showed that large CHP plants have received substantial investment security during the 12 year support period and that the increase of renewable electricity since 2007 has mainly concerned electricity generated by CHP plants. Nevertheless, significant wind power capacity is under construction. According to forecasts, wind energy FIT will double in 2011 compared to 2010 [5]. Since electricity from renewable energy sources receive the same FIT, the Estonian FITs can be judged as technology neutral. However, there are other reasons to question the Estonian FITs from an efficiency perspective. Although WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

238 Energy and Sustainability III the cost price is not covered by the market price of electricity, the case study suggests that 25 MWel CHP plants would have been profitable also without FIT. In addition, market prices significantly exceed the marginal costs of producing electricity from biomass in a 25 MWel CHP plant. On the other hand, pricing at marginal cost would not cover costs since production of electricity in a large CHP plant is characterised by increasing returns to scale. Construction of small CHP plants has not been encouraged to the same extent by Estonia’s FITs. One reason is that small plants have significantly higher generation cost per unit. It is interesting to note that German FITs, which are based on production costs, are differentiated by plant size and do not cover CHP plants fired by biomass that exceed 20 MWel [10]. Another argument for paying a higher FIT than the cost-effective level relates to dynamic efficiency. One motivation is to support a technology to reach market take-off more rapidly than otherwise. Another is general innovation support. However, generation of electricity from biomass in a CHP plant is a mature technology. Therefore, FIT is questionable also from the perspective of dynamic efficiency. From an efficiency point of view, only arguments of avoided external costs can support the current level of FIT. In contrast to experiences in other countries, we find that the avoided external costs exceed the per MWh costs of FIT. The main reason is the high external cost of oil shale electricity. Between 2007 and 2010, the per kilowatt hour consumer cost has increased from 0.1 to 0.8 eurocents /kWh. In comparison to the Spanish experiences almost a decade earlier, the starting point is equal, but the speed of increase is significantly more rapid in Estonia. The beneficiaries of Estonian FITs have increased their revenues from 6 to almost 54 million Euros during the same time period [7]. The Estonian FIT has low administrative demands as the same FIT has been applied to different energy sources. Setting prices on the closed market according to WACC is rather demanding, though. Our analyses indicate that the current practice might produce distortive incentives and to increase the share of borrowed capital.

7 Conclusion The purpose of this paper was to assess the impact of the Estonian feed-in tariffs on renewable electricity generation. We have found that the Estonian FIT system has effectively supported establishment of CHP capacity, the administrative costs have been low and the avoided external costs have exceeded the cost of the support. However, the costs of the Estonian FITs have increased at a rapid rate and these costs have been paid collectively by consumers while beneficiaries include large CHP plants. Besides distributional concerns, there are other reasons to revise the current FIT scheme. The case study of two CHP plants and the comparison of our findings to average cost and cost prices have shown that the current FIT scheme is not efficient. The targets set for 2010 will be exceeded and from an efficiency perspective, this cannot be assessed cost-effective. In addition, the results WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

239

indicated that resources are used for supporting production that is profitable also without FIT. Even though the current FITs are administratively attractive, the large differences in unit costs depending on plant size, suggest that there is a need to differentiate the FITs to plant size. The major drawback of pricing measures, such as subsidies and taxes, is that there is uncertainty about the range of impact. In Estonia, as in most other EU countries, FITs are used to reach quantity targets. It is not an easy task beforehand, to choose the level of an FIT that matches the target. Therefore, regulation by FIT requires revisions. Inevitably revisions pose challenges to the investment climate. Therefore regulation by FIT involves a trade-off between the challenges of revisions and the continuation of costly support schemes. Our findings and the forthcoming market liberation, suggest that it is important for Estonia to reform its FIT scheme.

References [1] Bügsen, U. & Dürrschmidt, W., The expansion of electricity generation from renewable energies in Germany- A review based on the Renewable Energy Sources Act Progress Report 2007 and the new German feed-in legislation. Energy Policy 37(Month), pp.2536-2545, 2009. [2] Sijm, J.P.M., The performance of feed-in tariffs to promote renewable electricity in European countries. ECN-C-02-083, November 2002 [3] Estonian Electricity Sector Development Plan 2005-2015.[in Estonian Eestielektrimajandusearengukavaaastani 2005-2015]Ministry of Economic Affairs and Communications, Estonian Government, 2005 [4] Development Plan of the Estonian Electricity Sector until 2018, [in Estonian Eestielektrimajandusearengukavaaastani 2018]Ministry of Economic Affairs and Communications, Estonian Government Order No 74, 2009. [5] Elering, Next year’ renewable fee is 9.63 cents/kWh press release 30.11.2010, http://www.elering.ee , accessed 08.12.2010. [6] del Rio, P. &Gual, M. A., An integrated assessment of the feed-in tariff system in Spain. Energy Policy 35(March), pp.994-1012, 2007. [7] Support levels of renewable electricity are too high, [in Estonian Taastuvateenergiaallikatetoetustemäärad on liigakõrged] Press release Estonian Competition Authority 14.09.2010, www.konkurentsiamet.ee, accessed 6.10.2010. [8] Ten perspectives on Nordic Energy, Final report for the first phase of the Nordic Energy Perspectives project, Rydén, B. editor, ISBN 91-631-92594, available at www.nordicenergyperspectives.org Stockholm, 2006. [9] Carlén, B., A comparative analysis of policy instruments promoting green electricity under uncertainty, Department of Economics, Stockholm, 2006. University, paper available at www.nordicenergyperspectives.org [10] Klein, A., Pfluger, B., Held, A., Ragwitz, M., Resch, G & Faber, T., Evaluation of different feed-in tariff options - Best practice paper for the international feed-in cooperation, A research project funded by the Ministry WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

240 Energy and Sustainability III

[11] [12] [13] [14] [15] [16] [17]

[18]

[19]

[20]

[21] [22]

[23]

[24]

[25]

[26]

for the Environment, Nature Conservation and Nuclear Safety (BMU) 2nd edition, update October 2008. Electricity Market Act, adopted 11.02.2003, RiigiTeatajaI 2003, 25, 153. Electricity Market Amendment Acts, adopted 28 January 2010. Annual Report of Tallinn Heat and Power Plant, 2009, Estonia 2010. Annual Report of Anne Heat and Power Plant, 2009, Estonia 2010. Nord Pol Spot, http://www.nordpoolspot.com/reports/areaprice/ accessed 12.12.2010. Estonian Competition Authority, WACC calculation manual, Tallinn 2010. Latõšov, E., Kleesmaa, J., Siirde, A., The impact of pollution charges, ash handling and carbon dioxide on the cost competitiveness of the fuel sources used for energy production in Estonia. Scientific proceedings of Riga Technical University. Environmental and Climate Technologies, pp. 58-63, 2010. Evans, J. & Hunkt, L. C., International handbook on the economics of energy. Cheltenham, UK; Northampton, MA: Edward Elgar; pp. 20-50, c 2009. Latõšov, E., Volkova, A., Siirde, A., The impact of subsidy mechanisms for biomass and oil shale based electricity cost prices. Oil Shale forthcoming in 2011. Statens Energimyndighet, 2008.Assessment of carbondioxide from energyproduction. [In Swedish, Koldioxidvärdering av energi] Eskilstuna, 2008. Freris, L., Infield, David. Renewable Energy in Power Systems. Wiley, pp. 195-229, 2008. Ericsson, K., (2007) Environmental impact assessment, EestiEnergia – Eesti Power Plant, Narva. Air emissions [in Estonian Keskkonnamõjuhindamine, EestiEnergia – EestiElektrijaam, NarvaHajuvusarvutused] ÅF-Process, October 2007. AS Anne Soojus, Strategic environmental assessment report of the detail plan of Soojus’ and its surroundings[In Estonian Soojuse kinnistu ja selle lähiala detailplaneeringu keskkonnamõju strateegilise hindamise aruanne], OÜ ArtesTerrae and AS EnprimaEstivo, Tallinn 2006. Medina, S., Le Tetre, A., Saklad, M. The Aphesis project: Air pollution and health – a European information system, Air QualAtmos Health (2009) 2, pp185-198. Melichar, J., Havranek, M., Maca, V., Scasny, M. Implementation of ExternE Methodology in Eastern Europe. ExternE-Pol. Externalities of Energy: Extension of Accounting Framework and Policy Applications. Final report on work package 7. Contract ENG1-CT-2002-00609, Nov. 2004. Kareda, E., Kallaste, T., Tenno, K., Laur, A., Ehrlich, Ü. Internalizing of external costs in electricity generation. Oil Shale 2007:24, 2 pp 175-178.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

241

Promoting electricity from renewable energy sources in emerging and developing countries – lessons learned from the EU R. Haas1, S. Busch1, G. Resch1, M. Ragwitz2 & A. Held2 1

Energy Economics Group, Vienna University of Technology, Austria ISI, Fraunhoferinstitut, Karlsruhe, Germany

2

Abstract Promoting renewable energy sources for electricity generation (RES-E) has high priority in many countries. The core objective of this paper is to identify proper regulatory promotion systems for RES-E in emerging and developing countries based on an evaluation of such systems in the EU over the period 2000–2008. The major conclusions are: (i) Feed-in tariffs (FIT) will be a suitable instrument in emerging countries where a proper grid exists and where social acceptance of (low) transfer costs from electricity customers can be expected; this applies to countries like Brazil, China, India, Indonesia; (ii) for developing countries where solutions are mainly based on autonomous systems strategies has to focus on (international) support of investments; (iii) with respect to international trade of RES-E (e.g. from Africa to Europe) a more complex approach is required based mainly on two pillars: a royalty and a cross-border FIT. Keywords: renewable electricity, promotion, emerging and developing countries.

1

Introduction

To increase the share of renewable energy sources for electricity generation (RES-E) has a high priority in the energy strategies of many countries. However, to facilitate a breakthrough for RES-E, a series of economic, institutional, political, legislative, social and environmental barriers has to be overcome. It is important to state that these barriers may vary considerably between industrialized emerging and developing (E&D) countries. Of core relevance world-wide is currently the implementation of proper financial support systems. WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESUS110211

242 Energy and Sustainability III Whether trading-based (e.g. the recently announced Guarantee-of-Origin trade) or technology-specific instruments (like feed-in tariffs (FIT)) lead to preferable solutions for society is still under discussion, see, e.g., the discussion in Haas et al. 2011 [1]. This issue is discussed very controversially in industrialized countries like EU-27 and USA. However, it is even more controversial and complex if it addresses emerging and developing (E&D) countries. In this context it also of interest that the European Commission puts strong focus on the aspect of International cooperation on promotion of RES-E., see [2]. Moreover with respect to international trade in recent months the idea of constructing large solar power plants, e.g. in Northern Africa, and transporting the electricity to e.g. Europe has attracted attention again. In this context a major question is, to what extent and in which form the population of the “host” country could benefit from such a project. The core objective of this paper is to discuss the following three aspects of regulatory promotion systems for electricity from RES in emerging and developing countries based on the lessons learned from EU-countries: (i) What is in principle the favourable promotion scheme from the looking at the additional costs all customers finally have to pay? (ii) What is recommendable to emerging vs. developing countries? (iii) How must a comprehensive international regulatory framework and financial as well as electricity exchange framework look like to foster international cross-border investments in renewable electricity and trade?

2 How promotion strategies work In this section first a survey on regulatory promotion strategies and their features is given. Of course, a specific programme put into practice may consist of a mix of different strategies. Next it is clarified what the core objectives of promotion strategies are and that with respect to every regulatory strategy an artificial market is created. How different types of promotion strategies work and what are important aspects of promotion strategies from customer’s/the public’s point-ofview is analysed at the end of the section. The following analysis is based on the concept of static (and further-on dynamic) cost resource curves of RES (see, e.g., [3]). Fig. 1 depicts the typical profile of a stepped static cost curve taking into account that every location is slightly different from each other. Different sites are put into certain categories and then a stepped curve emerges. Moreover, as Fig. 1 shows these cost curves are associated with uncertainties. These uncertainties are the higher the more right we move in the diagram. We use these static (and further-on dynamic) cost resource curves to assess the over-all costs of different promotion schemes. The core question is now how much money producers should receive in addition to the investment costs described in Fig. 1. Of course, investors in new RES-E generation plants should be compensated in a fair way but not by means of exaggerated profits. Hence, the major challenge for policy designers is to

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

EURO/ kWh

243

Uncertainty

predicted

kWh

Figure 1:

Stepped (discrete) static cost curve [3].

strike a reasonable balance between total generation costs and the producers’ surplus (PS). The producer surplus is defined as the sum of the profits of all green electricity generators. Figure 2 depicts the relationship between total generation costs and the producers’ surplus (PS) for a FIT system with three different tariffs for three technologies. We can see a moderate PS which is – as the experience from some EU-countries shows – accepted by the investors. The total additional costs – which finally have to be paid by the electricity customers – consist of the PS and the additional generation costs (costs above the market price of electricity). Figure 3 shows the corresponding total costs for customers under a Tradable Green Certificate (TGC) system. A TGC-based quota system works as follows, see Fig. 3: A quota (= certain quantity or percentage of electricity to be guaranteed from renewable energy sources) is set by a government. The generators (producers), wholesalers, retailer or consumers (depending who is obligated in the electricity supply chain) are obligated to supply consume a certain percentage of electricity from renewable energy sources. At the date of

(Premium) FeedFeed-in tariffs Total customer costs EURO/ kWh

Total costs = Producer surplus

+

B PFIT_A

PFIT_C

PFIT_B

C

Additional generation costs

A

Cost curve

Market price Target

Figure 2:

kWh

Total costs for customers under a feed-in tariff system [1].

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

244 Energy and Sustainability III

Tradable Green certificates

Price of green certificate

EURO / kWh

Total customer costs

Market price of electricity

Figure 3:

Extra generation costs

Generation costs: risk premium

Producer surplus

Total costs

Minimal Monetary generation costs

kWh

Quota

Total costs for customers under the Tradable Green Certificate system [1].

settlement, they have to submit the required number of certificates to demonstrate compliance. The total additional costs – which finally also in this case have to be paid by the electricity customers – encompass the whole black rectangle in Fig. 3. From society’s point-of-view it is of course important to minimise these additional costs (fees finally paid by households, commercial and industrial electricity customers) for the following reasons: the lower these additional costs are, the greater is the public acceptance and the larger will be the amount of additional electricity generated from RES per unit of public money. So the most effective strategy must focus finally on the minimization of total transfer costs to ensure both, acceptance by customers and by investors. To minimise producer surplus (PS), a stepped promotion scheme that limits PS, see Fig. 2, reduces the resulting producer surplus correspondingly. If we now compare the total costs in Fig. 2 and Fig. 3 we can clearly see that they are much higher in Fig. 3 and hence, for society it is of course more beneficial to implement a FIT (see also [4]).

3 The success of promoting RES-E in the EU The success of European promotion strategies for RES-E is shown in Fig. 4. An almost exponential growth took place since the beginning of the 1990s. The major driver were the EC’s directives for promoting RES-E ([2] and [5]). In different countries the efforts of the member states have led to continuous, albeit varying progress, building on their experiences gained and recommendations made by the commission. Fig. 5 shows the latest effectiveness indicator for wind onshore relating the RES-E produced to the remaining potential. Compared to former editions one can observe that countries with quota systems have improved, while FIT WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

245

250

200

TWh/yr

150

100 *) Figures for 2008 preliminary

50

Biogas

Solid biomass

Biowaste

Photovoltaics

Wind on-shore

Wind off-shore

2008

2007

2006

2005

2004

2003

2002

2001

2000

1999

1998

1997

1996

1995

1994

1993

1992

1991

1990

0

Geothermal

Figure 4:

Development of “new” RES for electricity generation (Source: EUROSTAT).

Figure 5:

Effectiveness of promotion instruments for wind on-shore in the period 1998-2009 in EU-27 (Source: [6]).

countries still take the lead. Overall the experience with the support schemes has shown that depending on the instrument some “best practice” design criteria have emerged, which will be addressed below. To identify the major country-specific lessons learned, next the relation between quantities deployed and the level of support is analysed for some trading and some FIT systems in recent years. It is often argued that the reason for higher capacities installed is a higher support level. Paradoxically, countries with highest support levels – Belgium and Italy for example – are among those with the lowest specific deployment (Figure 5). On the other hand, high FITs WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

246 Energy and Sustainability III especially in Germany and Spain are often named as the main driver for investments especially in wind energy. However, the support level in these countries is not particularly high compared with other countries analysed here. Currently in various European countries different strategies are in force. Next the relation between quantities deployed and the level of support is analysed for some trading and some FIT systems in recent years. It is often argued that the reason for higher capacities installed is a higher support level. And it is accepted that the resource endowments of RES-E vary from country to country. Paradoxically, countries with highest support levels – Belgium and Italy for example, see Fig. 6 – are among those with the lowest specific deployment (Figure 5). On the other hand, high FITs especially in Germany and Spain are often named as the main driver for investments especially in wind energy. However, the support level in these countries is not particularly high compared with other countries analysed here, see Fig. 6. COSTS OF PROMOTION (AVERAGE 2007-2009)

SE BE UK IT ES DE AT 0.00

2.00

4.00

6.00

8.00

10.00

€c/kWh

Figure 6:

Costs of promotion programmes for electricity from RES (except Photovoltaics) in selected countries 2007-2009 (Source: own investigations).

4 Lessons learned for emerging countries In an IEA study, the same methodology was extended to assess the effectiveness of RES support policies in OECD and BRICS countries (IEA 2008 [7]). The study concluded that the different countries show substantial diversity in the effectiveness of policies implemented to support the RET and that OECD-EU countries, which have overall a longer history of renewable energy support policies, feature among the countries with the highest policy effectiveness for all new renewable electricity generation technologies. This shows that a transfer of the lessons learned with EU RES-E support could add value to RES-E promotion in emerging countries. Exemplary this will be done here for two developing /emerging countries, China and Turkey. WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

247

Firstly their currently implemented support instruments are revisited briefly. With the adoption of the Renewable Energy Law on January 1st 2006 China established for the first time a statutory framework for the development of renewable energy. Concerning the financial support of RES-E, two different instruments are foreseen, depending on the type of technology: Wind power projects are allocated to investors through competitive bidding. The government guarantees the successful bid price combined with an obligation to feed the power into the grid. Biomass electricity receives a guaranteed premium feed-in price in size of 0,25 Yuan/kWh, decreasing by 2% yearly from 2010 on. Feed-in prices for PV systems are set by the government on a project-base, and mechanisms for other renewable energy technologies such as wavepower or geothermal electricity have to be established in the future. Turkey introduced initially a FIT for the support of RES-E in May 2005. The tariff was slightly increased in May 2007 to a level of 50 €/MWh to 55 €/MWh, which can neither be gone below nor exceeded. The tariff is determined by the Electricity Market Regulation Authority and is the previous year’s wholesale price. In addition the national transmission company is obliged to provide grid connection for all RES-E projects. In general the Turkish support scheme is kept simple. So what can the emerging countries learn from the EU? The experiences in Europe have shown, that especially at earlier stages of RET deployment FIT work best. Also the support instruments alone are not of high effectiveness if non-economic barriers like bureaucratic hurdles or grid connection issues are not solved. We have also seen that countries once they had found their appropriate support scheme have used the experiences gained to fine tune and gradually improve their schemes. This has led to increasing RES-E deployment and also formerly very uneffective countries could raise their effectiveness indicator. Out of the experiences with the support schemes in the EU a list of “Best Practices” emerged that have either been introduced in the countries or have been recommended. Since both countries we have looked at in this article use FIT, and FIT is the most widespread instrument, we discuss some best practices in the following, that emerged from the experiences with RES-E promotion in the EU: 

RES-E support requires continuity and log term investment policy. Therefore FIT should be accompanied by long term targets and sufficiently long periods for which the tariff is guaranteed. A long term strategy for deploying significant amounts of RES-E generation has to build on fundamental R&D technology development which provides by means of proper technology transfer to E&D countries successful implementation of projects. In this chain financing in different forms is a fundamental requirement, see Fig. 7.



Technology specific tariff levels should be applied in order to reflect the varying electricity generation costs. The levels should be set so that the policy goals of a country can be reached and the most cost efficient RET at a particular location are deployed first. Stepped tariffs can be applied to reflect different power generation costs within the same technology. WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

248 Energy and Sustainability III

LONG-TERM STRATEGY /DEVELOPMENT PROMOTION SCHEME?

TECHNOLOGY DEVELOPMENT/ INNOVATION

TECHNOLOGY TRANSFER

PROJECT IMPLEMENTING

FINANCING?

Figure 7:

Financing in different forms implementation of projects.

for

providing

successful



RES-E support policies should consider market integration. In the case of FIT this could e.g. be reached through a bonus tariff. With the option to sell the electricity on the free market. Another important aspect in this context is a forecasting obligation.



An annual tariff degression provides an incentive for cost reductions and technology improvements.

5 An international framework for the transfer of electricity from developing countries A specific case of promoting RES-E is to generate and to import it from a third country. The most intensively discussed example currently is to produce electricity in the Sahara and to transport it to Europe. This is arguable because renewable energy resources e.g. solar electricity are often situated in emerging or developing countries of the south. One of the major current examples in this context is the DESERTEC project. Within this project the intention is to produce solar electricity in the Sahara at lower costs and with higher full load hours than in Europe. Aside from policy aspects a major challenge in such a project is to set up a framework where the host country (in the south) and the investor country (in the North) both benefit. Of course, this example can be transferred in principle to every case where a rich country invests in a less rich country to benefit from its resources. Such a framework will in detail look much more sophisticated than just looking at investments and transmission of electricity. WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

249

In the following we will identify proper regulatory promotion concepts for an international exchange of RES-E mainly between developing countries on the one side and between industrialized countries like the EU on the other side. In this context most important is to strike a socially and ecologically acceptable balance between local use and international trade. It also has to be considered that local use will be cheaper and energetically more efficient because of a lack of transport losses. When setting up such an international framework we have to consider two major dimensions: The flow of money and the flow of electricity. First we analyse the monetary issues. We have to differ between one-time initial up-front investments and the flow of money over the time the project is operated. With respect to up-front investments – see Fig. 8 – aside from the investment in the power plant also investments in the international transmission grid and the distribution grid of the host country – as a compensation for the acceptance of the deal by its population – has to be borne by the investor country (=target country of RES-E). Moreover, a one-time royalty – purchase of land area – must be considered.

Figure 8:

INVESTM. POWER PLANT INT TMG INVESTMENT INT

TMG DG HOST

DG-HOST INVESTMENT

TARGET COUNTRY GOVERNM.

ROYALTY FOR LAND USE POWER PLANT (OPERATOR)

HOST COUNTRY GOVERNMENT

HOST COUNTRY

INITIAL UP-FRONT INVESTMENTS

Initial up-front investments by target country of RES-E with electricity produced in the host country.

Regarding the flow of money during the operation of the power plant a more complex approach for the payments to the host country is required. It may consisting of a permanent payment to the hosts’ government (“rent for land use”), a payment for the host country’s government support of investments into the local distribution grid a cross-subsidization of a beneficial local electricity tariff, see Fig. 9. The revenues come from the international FIT.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

250 Energy and Sustainability III

Figure 9:

LOCAL ELE TARIFF

DG HOST

FEED-IN-TARIFF

TM FEE

INT

TG DG TARGET

TARGET COUNTRY GOVERNM.

ROYALTY F

POWER PLANT (OPERATOR)

HOST COUNTRY

HOST COUNTRY GOVERNMENT

INTERN. FLOW OF MONEY DURING OPERATION

International flow of money between target country and host country for RES-E during the time of the operation of the plant for electricity produced in the host country.

Finally, given these financial boundary conditions the deal will only come about from the investor country’s point-of-view if the following objective function leads to a positive outcome: LT MAX

Σ (EIMP * FIT) – CC(EIMP)t – CO&M (EIMP)t T=0

with: EIMP

Electricity imported e.g. by the EU (kWh).

FIT

international Feed-in tariff (EUR/kWh).

CC((EIMP)t

Capital costs of all investment related to imported electricity (see Fig. 8) (EUR).

CO&M (EIMP)t

Operation, maintenance and other running costs of imported electricity (see Fig. 9) (EUR).

Regarding the flow of electricity, we have to consider that a certain amount is consumed in the host country and that there are some transmission and distribution losses (see Fig. 10).

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

251

Figure 10:

LOCAL ELE

ELE INT GRID (1 – 

(X)

–

η)X

INT

TG DG HOST

DG TARGET

TARGET COUNTRY GOVERNM.

ROYALTY F

POWER GENERATION X

HOST COUNTRY GOVERNMENT

HOST COUNTRY

INTERN. FLOW OF ELECTRICITY

International flow of electricity from RES between target country and host country with electricity produced in the host country.

6 Conclusions The major conclusions of this analysis are: (i) FIT and premium systems in European countries have proven to be of superior effectiveness and efficiency for promoting RES-E compared to TGC systems; Moreover, in these countries also evidence has been provided that RESE investors accept this approach and provide the necessary corresponding investments; (ii) Hence, FIT will be a proper instruments in emerging countries where a proper grid exists and where a social acceptance of (low) transfer costs from the electricity customers can be expected; This applies to countries like Brazil, China, India, Indonesia … (iii) for developing countries where solutions are mainly focusing on islanding autonomous stand-alone solutions are based only strategies focusing on (international) support of investments are feasible; (iv) With respect to extended international electricity trade (e.g. from the Sahara to Europe) a more complex approach is required: It has to differ between initial investments and flow of money during the operation of the project. And it has to build on two major pillars: different types of royalties paid to the host country and an international cross-border FIT.

References [1] Haas, R., G. Resch, Christian Panzer, Sebastian Busch, Mario Ragwitz, Anne Held: Efficiency and effectiveness of promotion systems for electricity

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

252 Energy and Sustainability III

[2]

[3]

[4]

[5]

[6]

[7]

generation from renewable energy sources – Lessons from EU countries, ENERGY-The international journal 2011 (forthcoming). European Parliament and Council. (2008). Directive of the European Parliament and of the Council on the promotion of the use of energy from renewable sources of, Brussels, COM 2008 (30) Final. Haas, R., Eichhammer, W., Huber, C., Langniss, O., Lorenzoni, A., Madlener, R., Menanteau, P., Morthorst, P.-E., Martins, A., Oniszk, A. (2004): How to promote renewable energy systems successfully and effectively. Energy Policy, 32(6): 833–839. Held, A., Haas, R., Ragwitz, M. 2006. On the success of policy strategies for the promotion of electricity from renewable energy sources in the EU. Energy & Environment, 17 (6), p. 849-868. European Parliament and Council (2001): Directive of the European Parliament and of the Council on the promotion of electricity produced from renewable energy sources in the internal electricity market, Directive 2001/77/EC - 27 September 2001, Brussels. Ragwitz, M. 2010. Effective and efficient long-term oriented RE support policies, Presentation held at International Energy Agency Renewable Energy Working Party’s Workshop “Renewables, from Cinderella options to mainstream energy solution”, March 15th 2010, Paris International Energy Agency. 2008. Deploying Renewables – Principles for Effective Policies, Paris, France

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

253

Socio-economic and energy scenario development in Vietnam T. T. Tran, M. Namazu & Y. Matsuoka Department of Urban and Environmental Engineering, Kyoto University, Japan

Abstract In supporting research on the socio-economic implication of energy policy, future scenarios are needed. Currently, most of the developing countries, especially in Southeast Asia, do not have specific targets for energy development rather than putting their main focus on economic growth. However, under natural constraints, especially energy resources, these countries must develop their own pathways in order to achieve socio-economic targets without compromising the environment and scarce natural resources. This paper provides the methodology to develop the platform of socio-economic and energy scenarios that includes two main steps. Firstly, the controversial parameters such as GDP and population are developed to be scale indices. Lately, the scale-based linear complement uses these scale indices to estimate the full-trend scenario for other parameters. The GAMS (General Algebraic Modelling System) programming is used in the processes of scale index development and scenario complement. This study provides the social, economic, and energy platform for researchers and policy-makers in analyzing the implication of socio-economic development to energy consumption as well as the possible CO2 emissions, towards achieving sustainable development. Similarly to Vietnam, other developing countries may also face the lack of an energy database problem. Therefore, this study can be improved and expanded to those countries, especially in the Asian Pacific region. Keywords: scenario development, scale index, interpolation, compatibility analysis, information weighting, low carbon policy, sustainable development.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESUS110221

254 Energy and Sustainability III

1 Introduction Currently, there is no doubt that climate change has adverse impacts on the environment, society and economic activities of countries all over the world. Since 1997, 187 countries have signed and ratified the Kyoto Protocol with the main objective is to set up the Greenhouse Gases (GHGs) emissions limitation especially for developed countries. As a result, it helps to develop strategies for developing countries in achieving the sustainable development through Clean Development Mechanism (CDM), implemented in sectors such as energy, industry, transportation, agriculture, forestry, and waste management. However, putting more efforts into the low GHGs emissions development might implicate the social and economic targets of a nation, particularly for those developing countries that have very low GHGs emissions but still put targets on energy security and minimizing emissions. The business of formulating energy policy depends heavily on questions of future energy demand (Slesser et al. [1]). Meanwhile, energy supply is so fundamental to the economy that a belief in future limitations would force us to consider new systems of production, of transport and even of government (Finon and Lapillonne [2]). By developing scenarios, researchers will be able to analyze future determinants of energy requirements and compare them to supply availabilities, financing, environmental constraints, and other salient factors and driving forces in which, energy scenarios provide a framework for exploring future energy perspectives, including various combinations of technology options and their implications. As a result, the socio-economic and energy scenario development may provide benchmarks for long-term policy making; therefore support policy makers better develop a flexible strategy, or at least to assess risk associated with an unpredictable future. Scenarios were and continue to be one of the main tools for dealing with the complexity and uncertainty of future challenges. This paper is structured by reviewing the development targets of Vietnam in section 2. Section 3 explains the methodology applied for the scenario complement process and section 4 shows some complemented scenarios that are analyzed in this study. Section 5 is for the conclusion as well as some future research directions.

2 Review of Vietnam future development targets According to the Vietnam Ministry of Planning and Investment, the national development strategy focuses on utilizing the growth factors in large, including employment, capital and land. In order to go ahead in a sustainable manner, a sharp qualitative step forward in depth must be generated, especially in terms of transforming the economic structure, upgrading the level of technology and management, both at macro and micro levels. Vietnam targets that the production development should correspond to the market demand, strongly oriented to export, and at the same time oriented to an effective import substitution; as well as viewed to expand the domestic markets WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

255

in order to improve the competitiveness and efficiency. The composition of exportable articles should be sharply moved from raw materials to afterprocessing products, of which there are more and more articles with recognized trademarks in the world market. In urban areas and in industrial estates, stress is placed in the development processing industries with new no-pollution technologies. As for industrial products specified both for consumption and export, it is required to rapidly increase the domestic content and improve their competitiveness. Moreover, energy industry and selected industries producing capital goods and technical equipment for economic and defense purposes will be developed to effectively implement programs on infrastructure building. In agriculture, the activities of agricultural extension and the application of new technologies, particularly biological technologies, should be promoted in order to improve both the productivity and the quality of products. Moreover, the Government also wants to ensure the macro-economic stability and make the nationals financial system healthy, both in terms of public finances and corporate finances, as well as people’s financial situation. The Vietnamese Government also ratified the “National target program on Energy Conservation and Efficiency” (Government of Socialist Republic of Vietnam [3]). This decision means targets are a matter of public announcement and encouragement, for science and technology, law and of regulation in order to timely implement activities on energy conservation and efficiency for the whole country. The objective is to reduce the investment for energy supply systems, bring benefits to the socio-economic, as well as protect the environment and effectively utilize the energy sources. Besides the “Renewable Energy Development Policies,” the Vietnamese Government also ratified the “Master plan to implement nuclear power application strategy for peaceful purposes towards 2020” (Government of Socialist Republic of Vietnam [4]), adopted the “Atomic Energy Law”, established the “National Appraisal Committee for Construction of NPP”. The desired target is to increase the contribution of renewable energy and nuclear power in the energy structure mix, up to 11% and 15–20%, respectively.

3 Methodology The method applied for this study is based on the scenarios information development system that researchers in Kyoto University are working on, both international and national scenarios (Tran et al. [5]). The general process of reference development for future socio-economic and energy simulation of Asian countries is mainly based on the data from national government. There are not so many references from national government providing data for future socioeconomic and energy scenarios, so we don’t have much choice to consider, rather than combining data from available sources (from Office of Prime Minister, relevant ministries, etc.). The process of developing the national reference scenario information includes some main steps: database compilation and scenario complement. WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

256 Energy and Sustainability III Database is compiled from: (1) collected national statistics for historical data and from (2) reports of various organizations, both national and international to gain national future socioeconomic and energy/power development targets. These scatter scenarios are complemented for 50 years annually until 2050 by using scale-based interpolation. Equations 1 and 2 are for the scale-based interpolation while the other equations are for the adjustment of target parameters based on the interpolated results. For the historical years (pre-2010), the value is adjusted into statistical data. TGT_org t Xot SCLt (1)

Xo_itpt

t tmin tmin

Xotmax tmax

Xreftref Xt

Xreftref

tmax t tmin

Xotmin tmax

, tmin
TGT_reftref SCLtref

Xo_itpt Xo_itptref

SCLt SCLtr ef

TGT_compt

Xt

Xreftref SCLtref Xreftref SCLt

SCLt

(2)

(3)

(4) (5)

where; t and ref calculated year and reference year SCL scale index (GDP, population, GDP per capita) TGT_comp complemented target scenario TGT_org original target scenario (described in the reference) TGT_ref observed target parameter data Xo ratio of target scenario and scale index Xo_itp interpolated Xo X adjusted Xo We assume that the population (projections from UN population prospects) will put influence on related indicators of employment, transport demand, and housing/building demand. Therefore, population will be used as scale index to estimate these parameters. Meanwhile, Gross Domestic Product (GDP) is assumed as the driver of gross domestic product, import, and export. Each country might have different national targets of GDP growth rate achievement. Thus, this GDP (from GDP growth rate) will be used as scale index to estimate these parameters. In the case of energy and energy consumption demand, these parameters are affected by both GDP and population. Therefore, the GDP-per-capita (GDPCAP) is used as scale for estimating these parameters. The most difficult part of choosing the driving force is for energy potential and electricity generation. These parameters are affected by neither population nor GDP rather than rely mainly on the natural resource reservation of a nation. As a result, we assume that these parameters will be estimated based on the energy and power development plans of the country. WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

257

4 Analytical results 4.1 Population and employment Data for the total population of Vietnam is collected from the National Statistics Yearbook 2009 for the years before 2010. Some other national institutes also provide projections for population of Vietnam, but mainly up to the year 2030 (as illustrated in Figure 1). The trend of each reference is not so much different compared to the others. After the year 2030, the population growth rate is assumed to decrease due to the current population development policy of the Vietnamese Government. The total population for this period is also estimated based on the assumed growth rate. The population of Vietnam in 2050 is projected to be about 120mil., more than twice that of the year 2000. In terms of total employment, based on data from GSO (2009), it is estimated that each year, there are 1mil. jobs generated. This is consistent with the target of Vietnam employment development plan (8mil. jobs shall be generated in 2010). The total employment is projected to be about 90mil. in 2050, nearly 2.5 times that of the year 2000. The shares of employment in economic sectors strongly affect the contribution to GDP. Therefore, it would be large transfer from agriculture sector to industrial and service sectors, especially to services. It is estimated that each 5-year period since 2015, 2% and 3% of employment from agriculture will move to industry and services, respectively. This assumption is used to estimate the employment in agricultural, industrial and service sectors.

thous. person

140000 120000

assumption

100000

SC_VNM_STD_SCE SC_VNM_IEa_SCE

80000 SC_VNM_AECa_SCE 60000

SC_VNM_IEb_SCE

40000

ST_VNM_SYB

20000

SC_VNM_MoC_SCE SC_VNM_IUB_SCE

0 2000

2010

Figure 1:

2020

2030

2040

2050

Total population scenarios of Vietnam.

4.2 Economy The data for GDP is also collected from the statistical yearbook for historical data. Instead of having a projection for GDP, most of the references give targets for GDP growth rate and sectoral GDP contribution. We use these growth rate projections to assume the future GDP (see Figure 2). However, these growth rate scenarios are still very high compared to international projections.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

258 Energy and Sustainability III 2500000 SC_VNM_IEa_HIGH SC_VNM_IEa_BASE

US2005D

2000000

SC_VNM_AECa_SCE 1500000

SC_VNM_IEb_HIGH SC_VNM_IEb_BASE

1000000

SC_VNM_MPIa_SCE SC_VNM_IEc_SCE

500000

ST_VNM_SYB SC_VNM_IUB_SCE

0 2000

2010

2020

Figure 2:

2030

2040

2050

GDP scenarios of Vietnam.

Among the references, only the Institute of Energy (SC_VNM_IEc_SCE) provides total GDP projection for the years up to 2050, however, this is a very challenging projection that affects the contribution of economic sectors in the total GDP. Historical and projected data up to the year 2030 show similar contribution of industries and services to the GDP at a high level while that from agriculture is very low. According to the projection, the main contributor to GDP in the year 2050 would be commercial activities due to the governmental policy in investment on services. 4.3 Transportation Currently we can only obtain the projection of transportation demand up to the year 2030 (Government of Socialist Republic of Vietnam [6]). Passenger transportation demand is increasing in all transport modes, especially in road and aviation, in which road still dominates the total demand (as shown in Figure 3). The projection of the year 2030 is about 3.5 times compared to the year 2000. The freight transportation demand is also increasing 180000 160000 140000

MPK

120000

SC_VNM_1327_QD_TTg_SCE

100000 ST_VNM_SYB

80000

SC_VNM_IUB_SCE

60000 40000 20000 0 2000

Figure 3:

2010

2020

2030

2040

2050

Passenger transportation volumes (mil. passenger-km).

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

259

in which road and waterway modes are still dominated. The increase of freight transport is higher than that of passenger. Increase of transportation demand, especially road transport as projected, may cause an increase in the consumption of petroleum products since they are main sources for road transportation in Vietnam. 4.4 Energy consumption 4.4.1 Total final energy consumption by energy types Only projections up to the year 2030 are obtained for energy consumption since the Vietnam Government proposes a very general vision up to 2050 (Government of Socialist Republic of Vietnam [7]). Coal and oil final consumption still dominate the energy mix, followed by electricity consumption while natural gas consumption also increases the same as other energy types but still keeps a very small proportion (as illustrated in Figure 4). Oil 70000

10000

60000

8000

50000 kTOE

kTOE

Coal 12000

6000

40000 30000

4000

20000 2000 0 2000

10000 2010

2020

2030

2040

0 2000

2050

2010

2020

2030

2040

2050

Electricity

6000

35000

5000

30000

4000

25000 kTOE

kTOE

Natural gases

3000

20000 15000

2000

10000 1000 0 2000

5000 2010

2020

2030

2040

205

0 2000

2010

2020

2030

2040

SC_VNM_SAE_HIGH

SC_VNM_SAE_BASE

SC_VNM_SAE_LOW

SC_ADB_SCE

SC_VNM_EPDb_SCE

SC_VNM_MIT_SCE

Figure 4:

2050

Total final energy consumption by energy types.

4.4.2 Total energy consumption by economic sectors According to Figure 5, industrial and transport sectors dominate energy consumption while agricultural and residential sectors have very small proportions. The service sector is projected to consume less than industrial and transport sectors, except one reference provides a very high projection for it.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

260 Energy and Sustainability III Agriculture

60000

1200

50000

1000 800 600

40000 30000 20000

400

10000

200 0 2000

2010

2020

2030

2040

0 2000

2050

2010

2020

2030

2040

2050

Residential

Transport

60000

12000

50000

10000

40000

8000

kTOE

kTOE

Industry

70000

1400

kTOE

kTOE

1600

30000

6000

20000

4000

10000

2000

0 2000

2010

2020

2030

2040

2050

0 2000

2010

2020

2030

2040

2050

kTOE

Services 4500000 4000000 3500000 3000000 2500000 2000000 1500000 1000000 500000 0 2000

Figure 5:

SC_VNM_IEa_SCE SC_VNM_EPDa_SCE SC_VNM_IUB_SCE

2010

2020

2030

2040

2050

Total energy consumption by economic sectors.

4.5 Energy reservation The traditional energy reservation is projected as shown in Figure 6. The total reservation may reach 120,000 kTOE in the year 2030, twice that of the year 2005, according to the assumption from Vietnam Institute of Energy. While natural gases and coal reservation are projected to be increased, crude oil and biomass reservation seem to be maintained if not being reduced. This is one of the difficulties for research on the energy capacity in Vietnam since we cannot obtain particular information about the energy reservation. In terms of energy development, the Vietnamese Government ratified the “National energy development strategy of Vietnam towards 2020 – vision to 2050” (1855/2007/QD-TTg). In this decision, the specific targets are listed in Table 1. The renewable energy (RE) reservation is collected from Institute of Energy [8], mainly available for some types of RE in Vietnam (Table 2) and the renewable energy contribution for power generation (Table 3). Figure 7 shows the results of renewable energy reservation complemented in this study. The hydro power and geothermal are projected to be constant during 2020–2030 while photovoltaic (SPV) and wind power are estimated to be WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

261

increased rapidly during the period. These complemented projections are based on some assumptions from Nguyen [9] for the contribution of renewable energy in energy supply. Total reservation

Crude oil

140000

25000 thousand tons

120000

kTOE

100000 80000 60000 40000

20000 15000 10000 5000

20000 0 2000

2010

2020

2030

2040

0 2000

2050

2010

Natural gases 70000

2E+10

60000

thousand tons

2.5E+10

1.5E+10

m3

2020

2030

2040

2050

2030

2040

2050

Biomass

1E+10 5E+09

50000 40000 30000 20000 10000

0 2000

2010

2020

2030

2040

2050

0 2000

2010

2020

thousand tons

Coal 120000

SC_VNM_IEa_SCE

100000

SC_VNM_SAE_SCE SC_ADB_SCE

80000

SC_VNM_HUT_SCE

60000

SC_VNM_EPDc_SCE 40000

SC_VNM_EPDa_SCE

20000 0 2000

SC_VNM_MOI_SCE SC_VNM_IUB_SCE 2010

Figure 6:

Table 1:

2020

2030

2040

2050

Traditional energy reservation.

Vietnam energy development targets towards 2050.

Targets Unit 2010 2020 2025 2050 Primary energy supply Mil TOE 47.5-49.5 100-110 110-120 310-320 25-30 Oil refinery plant (capacity) Mil ton Oil gas reserve capacity Days? 45 60 90 New and RE contribution % total 3 5 11 Nuclear power % total 15-20 Energy plan for rural/mountainous areas Use commercial energy for cooking% total 50 80 Electricity use % total 95 100

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

262 Energy and Sustainability III Table 2:

Vietnam renewable energy potential by types.

RE sorts Hydro electricity Wind power

Potential 120 bil. kWh

Biomass

43-46 mil. TOE/yr 0.4 mil TOE/yr 200 MW 43.9 bil. TOE/yr

Biogas Geothermal Solar

1,300-2,900 kWh/sqm/yr

Table 3:

Note

Islands: 800-1,400 Coastal areas of central region: 500-1,000 Highland and other regions: less than 500 Fuel wood: 60% (26-27 mil. TOE/yr) Agricultural residues: 40% (17-19 mil. TOE/yr) Theoretical potential: 0.4 mil TOE/yr Exploitable: 10% Concentrated in West (North and Central regions) Theoretical potential: 43.9 bil. TOE/yr Average solar radiation: 150 kcal/sqm/yr Average radiation: 200-2,500 hrs/yr

Renewable energy for power generation.

Capacity structure Total Coal fired PPs Hydro PPs Oil and gas fired PPs Renewable generation Imported capacity (??) Nuclear PPs

2015 42,470 MW 12,100 MW (28.5%) 13,600 MW (32%) 13,400 MW (31.6%) 1,270 MW (4.9%) 2,100 MW (3%) -

Hydro power

Photovoltaic

20000000

1200000 1000000

15000000

800000

kW

kW

2020 60,600 MW 18,300 MW (30.1%) 17,200 MW (28.3%) 16,300 MW (26.8%) 1,800 MW (3%) 5,200 MW (8.6%) 2,000 MW (3.3%)

10000000

600000 400000

5000000 0 2000

200000 2010

2020

2030

2040

0 2000

2050

4000000

500000

3000000

400000

2000000

300000

1000000 0 2000

2010

2020

2030

2040

2050

2030

2040

2050

Geothermal

kW

kW

Wind power

200000 100000

2010

2020

2030

2040

2050

0 2000

2010

2020

SC_VNM_IUB_SCE

Figure 7:

Renewable energy reservation.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

263

5 Conclusions The scenarios for major future direction of policies, particularly in what field the government/policy makers put more effort, for example, energy development or regional disparity, etc., are still unclear. Since the Computable General Equilibrium (CGE) model (Lofgren et al. [10]) is a strong tool to identify possible ranks of many alternatives proposed, the integration with scenario development will help to develop more tangible scenarios. In this research, a very preliminary platform of socio-economic and energy scenarios of Vietnam has been developed to be used as input in CGE model to assess the feasibility of those future policies. Base on this principle, depends on the interest of audients/counterparts/policy makers, they can choose more concrete countermeasures/policies to develop their own socio-economic pathway and put into practical actions. However, currently the reported scenarios are still unreliable and the complement methodology is simple to develop the preliminary platform of the Vietnam socio-economic and energy scenarios. The remained work is to develop more advanced method in order to provide more consistent projection for the future scenarios. This study can be improved and expanded to those countries that have similar difficulties in developing the scenarios platform like Vietnam, especially other countries in the Asian Pacific region.

References [1] Slesser, M., Bain, D. & Hounam, I., Perspective for long-term energy policy. Futures, pp. 44-55, 1979. [2] Finon, D. & Lapillonne, B., Long term forecasting of energy demand in the developing countries. European Journal of Operational Research, 13, pp. 12-28, 1983. [3] Government of Socialist Republic of Vietnam, National target program on Energy Conservation and Efficiency (79/2006/QD-TTg) (in Vietnamese), 2006. [4] Government of Socialist Republic of Vietnam, Master plan to implement nuclear power application strategy for peaceful purposes towards 2020 (114/2007/QD-TTg) (in Vietnamese), 2007. [5] Tran, T.T., Namazu, M. & Matsuoka Y., National socio-economic and energy scenarios development, on-going research works, Department of Urban and Environmental Engineering, Kyoto University, Japan, 2010. [6] Government of Socialist Republic of Vietnam, Transportation development strategy towards 2020 – vision to 2030 (35/2009/QD-TTg) (in Vietnamese), 2009. [7] Government of Socialist Republic of Vietnam, National energy development strategy of Vietnam towards 2020 – vision to 2050 (1855/2007/QD-TTg) (in Vietnamese), 2007.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

264 Energy and Sustainability III [8] Institute of Energy, Renewable Energy Development Policies (in Vietnamese), 2006. [9] Nguyen, Q.K, Long term optimization of energy supply and demand in Vietnam with special reference to the potential of renewable energy, International University of Bremen, 2005. [10] Lofgren, H., Harris, R. L. & Robinson, S., A Standard Computable General Equilibrium (CGE) Model in GAMS: Spiral (Microcomputers in Policy Research 5), International Food Policy Research Institute, 2002.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

265

Renewable energy policy landscape in South Africa: moving towards a low carbon economy G. Nhamo & S.-Y. Ho University of South Africa, South Africa

Abstract The South African agenda for renewable energy policy is linked to a target of 10,000 GWh by 2013. This is a vision put in place in order to mitigate negative impacts of climate change, address the energy mix and move towards a low carbon economy. The Ernst & Young ‘All Renewables Index’ ranked South Africa 27th out of the 30 countries included in the index. This paper documents policy developments within South Africa’s renewable energy space. The paper considers the policy landscape at various levels namely: acts of parliament, policies (white papers) and green papers, strategies and action plans as well as regulations and instruments. We conclude that South Africa has moved swiftly to establish an effective legislative regime for renewable energy investment and this is assisting the country in fulfilling its vision as outlined earlier. Keywords: South Africa, renewable energy, low carbon economy.

1 Introduction The primary energy mix as determined from the National Energy Efficiency Strategy of 2009 shows that renewable energy accounted for 9% of the energy mix in South Africa in 2004 DME [1]. Coal and crude oil contributed 67% and 18% of the energy mix respectively. Following the United Nations Framework Convention on Climate Change (UNFCCC) conference that took place in Copenhagen in 2009, South Africa pledged to reduce emissions. The pledge has a strong bearing in terms of promoting investment in renewable energy. The country pledged to undertake mitigation actions resulting in deviation below the current emissions baseline of 34% by 2020 and 42% by 2025. The pledge was conditional on a fair, ambitious and effective global climate deal being reached WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESUS110231

266 Energy and Sustainability III and financial, technology and capacity building support from the developed countries (The Presidency [2]). During the apartheid era, from 1948 up to 1993 energy policies were centred on energy security, with a concentration on the exploitation of coal reserves by state owned companies, Eskom and Sasol. Eskom deals with electricity and Sasol synthetic fuel and natural gas. However, the energy policy has undergone substantial revisions since 1994 with targets spelt out in relation to job creation and economic security and sustainable development (Prasad and Visagie [3]). Figure 1 presents a picture with regards to a frequency count in terms of renewable energy as featured in selected key government policies. Among the policies reviewed are: the National Climate Response Green Paper (NCCRGP), Draft Carbon Tax Option (DCTO), Industrial Policy Action Plan II (IPAP II), Draft Integrated Resources Plan (DIRP), South African Renewables Initiative (SARI), Western Cape Government Green Procurement Policy (WCGGPP), National Energy Act (NEA), Long Term Mitigation Scenario (LTMS), revised National Energy Efficiency Strategy (NEES), Energy Efficiency Accord (EEA), White Paper on Energy Policy (WPEP), White Paper on Renewable Energy (WPRE) and the Carbon Disclosure Project South Africa (CDP SA). Figure 1 makes it clear that the White Paper on Renewable Energy (WPRE) of 2003 is the main reference document.

Source: Authors Figure 1:

Renewable energy in key SA policy and industry initiatives.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

267

2 Renewable energy: an international perspective Bordier [4] maintains that the EU policy for renewable energy and climate change is based on two directives: “the 2001 European directive with the objective to increase the share of electricity generated from renewable energy sources to 21% by 2010 in the EU-25” and “the 2003 directive establishing the European Union Emissions Trading Scheme (EU ETS) that entered into effect in 2005 imposing a cap on carbon dioxide emissions for the high-emitting European sectors”. The cost of renewable energy technologies is, however, noted as a major obstacle to developments in this space. To promote investment in renewable energy a range of incentives exist across the EU including: calls for tenders, feed-in tariffs and green certificates. The consumption of renewable energy by the top 10 countries in the EU in 2005 (and targets to 2020) is ranked as follows Bordier [4]: Sweden – 39.8% (49%), Latvia – 34% (42%), Finland – 28.5% (38%), Austria – 23.3% (34%), Portugal – 20.5% (31%), Estonia – 18% (25%), Romania – 17.8% (24%), Denmark – 17% (30%), Slovenia – 16% (25%) and Lithuania – 15% (23%). A Renewable Energy Index regularly surveyed globally by Ernst & Young gives further details regarding investment in this sector. Among the top five countries are China, USA, Germany, India and UK (Ernst and Young [5]). Further details regarding selected countries are shown in Table 1. The various indices are scored out of 100 points. Table 1:

Renewables energy index (November 2010).

Country (Rank)

All

Wind

Solar

China (1) USA (2) Germany (3) India (4) UK (5) Brazil (18) S/Korea (18) Egypt (22) Mexico (25) S/Africa (27)

71 66 63 63 62 46 46 43 42 41

76 66 66 64 68 47 47 44 43 43

60 72 54 67 40 41 46 48 45 37

Biomass/ Other 58 61 63 58 59 49 41 37 38 35

Geothermal 51 67 54 45 38 22 35 27 57 32

Infrastructure 76 60 62 65 71 46 43 40 38 43

Source: Authors, based on Ernst andYoung [5]. A Carbon Disclosure Project (CDP) 2010 report on Corporate Clean Energy Investment Trends in Brazil, China, India and South Africa (BASIC) revealed four key findings: that there are sizeable investments in clean energy, there was need for high-level policy signals, need for clear and specific regulation and that the Kyoto Protocol’s Clean Development Mechanism (CDM) had made a significant contribution CDP [6].

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

268 Energy and Sustainability III

3 Acts of Parliament The National Energy Act of 2008 is central when dealing with renewable energy in South Africa. Reference to renewable energy features in Section 19 dealing with regulations. Section 19 (1) (d) makes provision for the promulgation of regulations addressing the minimum contributions to the national energy supply from renewable energy sources RSA [7]. Section 19 (1) (e) makes provision for the proclamation of regulations specifying the nature of the sources that may be used for renewable energy contributions to the national energy supply. Section 19 (1) (f) makes provision for the establishment of regulations regarding measures and incentives designed to promote the production, consumption, investment, research and development of renewable energy.

4 Policies (white papers) and green papers 4.1 Energy white paper for South Africa – 1998 The fifth objective of the White Paper addresses the need to provide alternative sources of energy including renewable energy DME [8]. Renewable energy is identified among seven energy supply sectors including electricity, nuclear energy, oil and gas, liquid fuels, gas and coal. The government indicated that it was interested facilitating “sustainable production and management of solar power and non-grid electrification systems, such as the further development of home solar systems, solar cookers, solar pump water supply systems, solar systems for schools and clinics, solar heating systems for homes, hybrid electrification systems and wind power” [8]. Government also identified hydro from the Cahora Bassa in Mozambique and other similar options in Africa. The White Paper DME [8] revealed that government would promote the use of appropriate standards, guidelines and codes of practice for renewable energy. Suitable renewable energy information systems would have to be put in place. The use of an environmental levy on energy sales that would be used to fund the development of renewable energy was to be investigated. By the time of completing the White Paper, renewable energy resources provided an estimated 10% of the country’s primary energy DME [8]. Although more than 484,000m2 of solar water heater panels had been installed in the country then, the figure only accounted for less than 1% of the potential market. The installed capacity of photovoltaic systems was an estimated 5 MW peak, of which 50% is used for telecommunications. About 280,000 water-pumping windmills were operational with installed capacity of small-scale hydro in excess of 60 MW. Renewable energy was noted as being advantageous in that it has minimal environmental impacts in comparison with traditional supply technologies, has generally lower running costs and high labour intensities. Disadvantages, however, included: higher capital costs, lower energy densities, and lower levels of availability. The government’s policy on renewable energy would be concerned with DME [8]: “ensuring that economically feasible technologies and applications are implemented; ensuring that an equitable level of national WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

269

resources is invested in renewable technologies, given their potential and compared to investments in other energy supply options; and addressing constraints on the development of the renewable industry”. 4.2 White paper on renewable energy policy – 2003 The White Paper considers integrated resource planning as the basis for “ensuring that an equitable level of national resources is invested in renewable technologies, given their potential and compared to investments in other energy supply options DME [9]. The White Paper spelt out a target of 10,000GWh by 2013. The target is to be achieved mainly through investments in biomass, wind, solar and small-scale hydro. The 10,000GWh is approximately 4% of the projected electricity demand by 2013. This target is cumulative, starting in 2003, and so equivalent to an average of 100 GWh/year DME [1]. South Africa has made little progress towards achieving this target in the first half of the period. As of 2009 3% (296GWh) of the 10,000 GWh had been installed DME [1]. The White Paper supplements the White Paper on Energy Policy of 1998 four key strategic areas are addressed with their goals spelt out. These include DME [10]: (1) Financial instruments – with the goal to promote the implementation of sustainable renewable energy through the establishment of appropriate financial and fiscal instruments, (2) legal instruments – with a goal to develop, implement, maintain and continuously improve an effective legislative system to promote the implementation of renewable energy, (3) technology development – with a goal to promote, enhance and develop technologies for the implementation of sustainable renewable energy, and (4) awareness raising, capacity building and education – with a goal to raise public awareness of the benefits and opportunities of renewable energy. Each of the goals is accompanied by specific objectives and deliverables. Multiple players could now enter the generation market through the provisions of the White Paper. This would be done by the responsible authority that would license producers with more than 5GWh per year, transmitters, distributors and sellers of electricity. The introduction of renewable energy generators would be regulated on a phased approach with the Central Energy Fund providing assistance in the implementation of renewable energy through the extension of its operational support. In addition, The Gas Act and the amended Petroleum Products Act would provide a basis for the integration of renewable energy derived from bio-diesel, ethanol and landfill gas. At the time of finalising the White Paper, the Minister of Finance had announced a 30% tax reduction for bio-diesel. Notice is taken of a range of barriers to the smooth implementation of renewable energy that requires attention from government and other key players. Some of the barriers include: the high cost of renewable energy technologies; lack of consumer awareness on benefits and opportunities of renewable energy; legal, regulatory and organisational concerns; and a lack of non-discriminatory open access to key energy infrastructure such as the national electricity grid, certain liquid fuels and gas infrastructure DME [10]. Lastly, the White Paper proposed the establishment of technology support centres within existing research and development institutes as well as a proposal WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

270 Energy and Sustainability III for a National Energy Research Institute DME [10]. These would facilitate the promotion and ongoing development of technologies and help government in the certification and approval of systems. Cross cutting issues including Integrated Energy Planning, energy efficiency and environmental health are also discussed. 4.3 National climate change green paper – 2010 The Green Paper DEA [11] considers the impact that renewable energy technologies could have on reducing South Africa's emissions. From a historical perspective, the low cost of electricity made it difficult to incentivise renewable energy investment. However, the Green Paper notes that the announcement of the renewable energy feed-in tariff (REFIT) as well as the electricity generation levy on non-renewable electricity has incentivised investment in wind, solar, hydro and biomass energy. The green jobs creation potential from renewable energy investment is also noted. In the long term, the Concentrated Solar Power options is viewed as having excellent potential to provide base load and take up a greater share of the energy supply mix. Solar water heaters and photovoltaic cells are well developed globally and these were noted to be generally readily available in the country. The Green Paper makes reference to the 10,000 GWh of renewable energy by 2013 DEA [11]. To contribute towards achieving the target the Green Paper proposes rapid implementation of the renewable energy support mechanisms including the REFIT NERSA [12], the CDM projects, Renewable Energy Certificates, Solar Water Heating subsidies and other financial support mechanisms. Solar Water Heating subsidies are already in place and being supported by government at a significant proportion through the Industrial Policy Action Plan II (IPAP II) DTI [13]. The need to identify and resolve the financial, regulatory and institutional barriers that slow down the implementation of the REFIT at a level adequate to incentivise large-scale investment is called upon DEA [11]. Another call made is in line with a need to review and scale up the 10,000 GWh 2013 renewable energy target. This is said to have the potential to sustain long term growth that will promote competitiveness for renewable energy with conventional energies in the medium and long term. The scaling-up and acceleration of initiatives, such as the Working for Energy Programme (WFEP) under government’s Expanded Works Programme is further highlighted. The WFEP has an added advantage in that it increases chances of green jobs creation. Renewable energy project activities that are labour intensive include DEA [11]: biomass from the clearing of invasive alien plants and bush encroachment; biogas for rural energy access; biogas generation from farm waste and municipal solid waste and wastewater; bio fuels development and implementation in rural applications; solar thermal energy like solar geyser fabrication, small scale co-generation; mini-grid hybrid systems and mini-hydro systems for both on and off grid applications”. The Green Paper further calls for the development of renewable energy policy, legal and regulatory frameworks that allow for differentiated but specific targets, parameters and tariffs for all renewable energy technology options. This is an element being partially addressed through energy efficiency strategy DME [1]. WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

271

The DEA [11] also calls for the introduction of innovative approaches that will lead to the establishment of sustainable structures and financing mechanisms for delivering renewable energy. This includes securing adequate funding from international climate funding institution and other development finance institutions. The promotion of the development and implementation of appropriate standards and guidelines as well as codes of practice for the appropriate use of renewable energy and low carbon technologies is also hinted upon. 4.4 Carbon tax option – 2010 The Carbon Tax Option makes reference to the fact that government has already put in place a range of excise taxes and incentives to support the transition to low-carbon economy. The electricity levy of 2c/kWh implemented in July 2009 National Treasury [14] is one huge step towards developing a comprehensive carbon pricing regime. Tax incentives targeted at government programmes for renewable energy form part of policy response to climate change. Income tax exemptions for income earned from the CDM projects, and accelerated depreciation allowances for investments in biofuels and renewable energy are a series of incentives to encourage investment in these sectors. Reference is also made to the initiatives by the Department of Energy regarding tradable renewable energy certificate scheme, subsidy scheme for investments in renewable energy and energy efficiency and the National Energy Regulator of South Africa in terms of the REFIT.

5 Strategies and action plans 5.1 Biofuels industrial strategy – 2007 The Biofuels Strategy indicates that 400 million litres required annually can be produced on 1.4% of new and existing arable land, with about 14% of arable land mainly in the former homelands DME [15]. To mitigate against severe droughts and crop failures, the Biofuels Strategy proposed that a certain percentage of feedstock on the additional agricultural land could be redirected to the food market to address shortages. The Strategy proposes sugar cane and sugar beet for bioethanol production through sunflower, canola and soya beans for biodiesel. Maize and Jatropha are currently not utilised for biofuels production given that this might result in food insecurity concerns DME [15]. Before the contestations regarding the use of maize as feedstock, the Free State Biofuels Logistics Hub was established on the assumption that maize would be used. Following extensive research and consideration, The Presidency [16] reported that Cabinet had approved the National Biofuels Strategy in December 2007 and this excluded the use of maize owing to food security concerns.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

272 Energy and Sustainability III 5.2 Industrial policy action plan II – 2010 The Industrial Policy Action Plan II (IPAP II) makes reference to the Renewable Energy White Paper’s goal of a 10,000 GWh of renewable energy by 2013 DTI [13]. In this regards, the Minister of Energy’s initiative to install one million solar water heaters (SWHs) by 2014 is acknowledged with the IPAP II support. The DTI [13] took note of the pending scaling-up of the goal to increase the SWHs 5.6 million by 2020. The DTI also notes that concentrated solar power (CST) is the most promising renewable energy generation option in the country and that this should receive priority support ahead of wind and biomass. The Industrial Development Corporation’s CST demonstration plant which aims to leverage the National Energy Regulator of South Africa’s REFIT is noted. From the DTI’s perspective, the successful demonstration of the viability of the CST pilot plant will lead to a broader rollout of the technology. The DTI also discusses the biofuel sector and concludes that this has grown rapidly globally yet it has remained on the periphery in the country. Several reasons are presented for the slow growth of the biofuels sector in South Africa including: regulatory barriers, global economic crisis and the resultant reduction in oil prices and the national debates that tend to focus on the food versus fuel arguments. 5.3 Integrated resources plan for electricity: 2010-2030 The Integrated Resources Plan (IRP) covering the period 2010-2030 DoE [17] links into the REFIT regulations of 2009. The proposed IRP 2010 plan includes Phase 1 of the Renewable Energy power purchase programme that is linked to the REFIT programme amounting to 1025 MW. This amount comprises wind, concentrated solar power, landfill and small hydro options (Ibid). Phase 1 of the Medium Term Power Purchase programme of 390 MW consists of cogeneration and own build options. On the other side there is the Open Cycle Gas Turbine (OCGT) Independent Power Producer (IPP) programme of the DoE that is considering generating 1020 MW. The nuclear fleet strategy to commence in 2023 will contribute at least 9,6GW by 2030. The wind programme outside the REFIT wind capacity commencing in 2014 will contribute a minimum of 3,8 GW with a solar programme outside the REFIT solar capacity commencing in 2016 contributing a minimum 400 MW. This also excludes solar water heating that is part of the demand side management (DSM) programme. The renewable programme earmarked to commence 2020 integrating all renewable options will add another 7.2 GW. The IRP DoE [17] also takes note of the imported hydro options (that first emerged in the Energy White Paper of 1998 as discussed) that could total 3349 MW from 2020 to 2023. The IRP considers environmental and other externality impacts and the effect of renewable energy technologies DoE [17]. To this end, significant investment in wind is encouraged. The approach will ensure a steady and consistent build up in wind capacity to facilitate the stimulation of localisation of manufacturing and green jobs creation. Local experience will be developed in the area of CSP although this technology is expensive. Although the renewable energy options will continue after 2020 these are not specified as per technology type in the IRP WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

273

as such choices will be made when there is more local knowledge and experience with both wind and solar energy. The nuclear option is planned as a base-load option from 2023 and no decision has been made in the IRP regarding this. The IRP notes the delay in the finalisation of the REFIT and other renewable energy options procurement process. The IRP notes that the government is already late in meeting the expectations for wind, small hydro and landfill energy. 5.4 South African renewables initiative – 2010 The South African Renewables Initiative (SARI) is a South Africa’s Low Carbon Industrial and Economic Strategy to be run jointly by the Departments of Public Enterprise and DTI [18]. SARI is to finance REFIT at a level speed needed to enable a rapid increase in renewables. From the proposal, the REFIT would be financed from a combination of four possible sources namely: domestic electricity consumers, a carbon levy that is currently at 2 cents/kwh, green purchase obligation by major energy and carbon-intensive exporters, and international public finance to be sourced from developed countries with a climate financing commitment as well as interests in bringing its own energy companies into joint industrial ventures in South Africa. The SARI identifies South Africa’s greatest renewables opportunity (excluding nuclear) as solar thermal, particularly in the northern parts of the country. It is projected that the country is capable of generating 15% of its electricity from a combination of wind and solar power by 2020. SARI notes with concern that South Africa has not been able to engage aggressively in transforming the energy mix towards renewables. This is partly due to high cost renewables versus low cost coal. With the REFIT, that stood at about R1/kwh (with variations depending on technology), which is considered reasonable for concentrated solar power and high for solar photovoltaics, the country was on the road to scale up investments in renewables DoPE and DTI [18].

6 Regulations The REFIT regulations of 2009 stand out as the key regulatory framework to facilitate investment in renewable energy in South Africa. For this reason, this section focuses solely on this regulatory provision. The REFIT is defined in the regulations as “a mechanism to promote the deployment of renewable energy that places an obligation on specific entities to purchase the output from qualifying renewable energy generators at pre-determined prices” NERSA [12]. The REFIT identifies solar, wind, biomas, biofuels, hydropower, wave, tidal, ocean current and geothermal energy as part of the renewable energy supply sources. The REFT takes note of the fast growing renewable energy sector globally. The NERSA [12] mentions that installed global wind capacity early 2008 was 90GW, having doubled since 2004. China and India were each adding installed wind electricity in excess of 1GW annually with targets of achieving over 10GW by 2015. The capacity of grid connected solar PV was also noted to have quadrupled from an installed capacity of 2GW in 2004 to about 8GW at the WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

274 Energy and Sustainability III end of 2007 NERSA [12]. More than 58 countries globally were realised to have put in place targets for the promotion of renewable energy and 13 were from developing economies. In terms of employment, the renewable energy industry was noted to be employing over 2.5 million people worldwide. Renewable energy market capitalisation of publicly traded renewables companies had doubled from $50 billion to $100 billion between 2005 and 2007. The REFIT also makes reference to South Africa’s renewable energy target of 10,000 GWh by 2013. The specific objectives and key principles of the REFIT are to NERSA [12]: create an enabling environment for renewable electricity power generation in South Africa; establish a guaranteed price for electricity generated from renewables for a fixed period of time that provides a stable income stream and an adequate return on investment; create a dynamic mechanism that reflects market, economic and political developments; provide access to the grid and an obligation to purchase power generated; establish an equal playing field with conventional electricity generation; and create a critical mass of renewable energy investment and support the establishment of a self sustaining market. The REFIT makes provision for the establishment of the Eskom Single Buyer Office as the Renewable Energy Purchasing Agency (REPA). This is in line with the provisions of the Electricity Regulation Act of 2006. Qualifying Renewable Energy Power Generators are considered as new investments in electricity generation using technologies including: landfill gas power plant; small hydro power plant (less than 10 MW); wind power plant and Concentrating Solar Power (CSP) plant. All the REPGs require a Generation Licence issued by NERSA under the Electricity Regulation Act 2006. The conditions for licensing are laid out in the REFIT.

7 Challenges and achievements in SA renewable energy Issues of definitions in government legislation are of concern. In many cases a number of definitions emerge that make implementation difficult. This section looks into definitions from selected legislation. Renewable energy is defined by the White Paper on Renewable Energy Policy DME [10] as energy that “harnesses naturally occurring non-depletable sources of energy, such as solar, wind, biomass, hydro, tidal, wave, ocean current and geothermal, to produce electricity, gaseous and liquid fuels, heat or a combination of these energy types”. This is the definition that is used in the REFIT regulations NERSA [12]. The National Energy Act RSA [7] defines renewable energy as “energy generated from natural non-depleting resources including solar energy, wind energy, biomass energy, biological waste energy, hydro energy, geothermal energy and ocean and tidal energy”. Already there is divergence in definitions. Sebitosi and Pillay [19] highlighted the lack of a framework to deliver reliable and accurate energy data to policy makers as a key barrier to faster transformation in the renewable energy sector space in South Africa. In addition, the authors lambasted the dominance of the government power utility ESKOM’s in the energy sector. The power utility was accused of operating in an opaque way leading to a black out in terms of data and other necessary key information WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

275

on energy. The changing international scene that was demanding that countries with a high carbon footprint like South Africa ‘do something’ in terms of renewable energy was also noted a pressing factor moving forward. Judging by the number of CDM projects in South Africa, renewable energy has taken up a significant portion. As of 20 December 2010, out of the 140 CDM projects submitted for consideration to the South African Designated National Authority and approval by the CDM Board, 26 were for renewable energy and in second place was energy efficiency with 22 projects DoE [20].

8 Conclusion What emerges from this paper is that the renewable energy interface simultaneously addresses climate change, industrial policy and energy issues. In order to promote renewables in South Africa, there is need for high-level policy signals and clear regulation. The REFIT generation incentives are viewed as crucial and South Africa is viewed as being in an advantageous position with regards to solar and wind. The South African agenda for renewable energy policy is linked to a target of 10,000GWh by 2013 spelt of in the White Paper on Renewable Energy Policy of 2003 but little progress has been made towards achieving this target with only 3% (296GWh) of the 10,000 GWh having been installed in 2009. One of the major developments from the White Paper on Renewable Energy Policy of 2003 is that it opened up entry of multiple players into the generation market. The National Climate Change Green Paper notes that the announcement of the REFIT as well as the electricity generation levy on nonrenewable electricity has incentivised investment in wind, solar, hydro and biomass energy. A call has been made to review and scale up the 10,000 GWh 2013 renewable energy target.

Acknowledgement The authors thank Exxaro Resources Limited for sponsoring the Chair in Business and Climate Change run under Unisa’s Institute for Corporate Citizenship.

References [1] DME. National Energy Efficiency Strategy of the Republic of South Africa. Pretoria: Department of Minerals and Energy; 2009. [2] The Presidency. President Jacob Zuma to attend High Level Segment of the COP-15 scheduled for 18 December 2009 in Copenhagen. The Presidency 2009, http://www.thepresidency.gov.za/show.asp?include=president/pr/2009/pr12 081345.htm&ID=1933&type=pr. [3] Prasad G, Visagie E. Renewable energy technologies for poverty alleviation in South Africa. Cape Town: Energy Research Centre; 2005.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

276 Energy and Sustainability III [4] Bordier C. Development of renewable energies: What contribution from the carbon market? Saint-Germain: Caisse des Depots; 2008. [5] Ernst & Young. Renewable energy country attractiveness indices. London: Ernest & Young; 2010. [6] CDP. Corporate clean energy investment trends in Brazil, China, India and South Africa. London: Carbon Disclosure Project; 2010. [7] RSA. National Energy Act (No. 34 of 2008). Cape Town: Government Printers, 2008. [8] DME. White Paper on the Energy Policy of the Republic of South Africa. Pretoria: Department of Minerals and Energy; 1998. [9] DME. Energy Efficiency Strategy of the Republic of South Africa. Pretoria: Department of Minerals and Energy; 2005. [10] DME. White Paper on Renewable Energy. Pretoria: Department of Minerals and Energy; 2003. [11] DEA. National Climate Change Response Green Paper 2010. Pretoria: Department of Environmental Affairs; 2010. [12] NERSA. South Africa Renewable Energy Feed-in Tariff (REFIT) Regulatory guidelines. Pretoria: National Energy Regulator of South Africa; 2009. [13] DTI. The 2010/11 - 2012/13 Industrial Policy Action Plan (IPAP II). Pretoria: Department of Trade and Industry; 2010. [14] National Treasury. Reducing Greenhouse Gas Emissions: The Carbon Tax Option. Pretoria: National Treasury; 2010. [15] DME. Biofuels Industrial Strategy of the Republic of South Africa. Pretoria: Department of Minerals and Energy; 2007. [16] The Presidency. ASGISA Annual Report 2007. Johannesburg: The Presidency; 2007. [17] DoE. Draft Integrated Resources Plan for Electricity for South Africa 2010-2030. Pretoria: Department of Minerals and Energy; 2010. [18] DoPE, DTI. The South African Renewables Initiative: Advancing South Africa's Low Carbon Industrial and Economic Strategy. Pretoria: Department of Public Enterprises and Department of Trade and Industry; 2010. [19] Sebitosi AB, Pillay P. Renewable energy and the environment in South Africa: A way forward. Energy Policy 2008;36:3312-6. [20] DoE. Project Design Document. Department of Energy 2010 Available from: http://www.energy.gov.za/files/esources/kyoto/kyoto_frame.html.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Section 5 Energy and the environment

This page intentionally left blank

Energy and Sustainability III

279

Environmental balance study for the construction of a biomass plant in a small town in Piedmont (Northern Italy) D. Panepinto & G. Genon DITAG Department, Politecnico di Torino, Italy

Abstract In consideration of local critical aspects in opposition to overall environmental benefits (decrease of GHG generation), the aim of this work is to verify the local acceptability from the point of view of air quality of the territory in question for a biomass plant. The plant to be realized in a small town located in Piedmont, Northern Italy, will be constructed to produce electricity and heat. In order to verify the aspect of compatibility we performed an evaluation of the emissive flow modification that in the hypothesis of the biomass plant activation should be introduced in the municipal area. The evaluation has been conducted by using mass and energy balances as a tool. Keywords: biomass plant, district heating, environmental balance, environmental impact, energy recovery.

1 Introduction Climate change is the major planetary threat of the 21st century, not only for the natural ecosystems, but for some national economies too. In order to reduce immediately the emissions of greenhouse gases, it is strongly proposed to use renewable and clean sources instead of fossil fuels. In this research, one of the most important solutions consists of a modern use of the biomass (Boman and Turnbull [1]; Dornburg et al. [2]). Fossil fuel such as coal, oil and natural gas are generating a very large proportion of the electricity that is produced annually around the globe. The combustion of these fuels gives rise to carbon dioxide (CO2), which is a WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESUS110241

280 Energy and Sustainability III “greenhouse” gas discharged into the atmosphere. There is a growing interest in eliminating, as much as possible, the CO2 emissions from fossil sources. In comparison, the carbon dioxide generated in the combustion of biofuels is not considered to give any net contribution to the CO2 content of the atmosphere, since it is absorbed by photosynthesis when the new biomass is growing (Albertazzi et al. [3]). Biomass is widely considered to be a major potential fuel and renewable resource for the future (Bridgwater [4]; Caputo et al. [5]; Hanaoka et al. [6]; Hohenstein and Wright [7]; Hustad et al. [8]; Van Den Broek et al. [9]). In this sense, energy from biomass based on short rotation forestry and also from the exploitation of other energy crops can contribute significantly towards the objectives of the Kyoto Agreement in reducing greenhouse gas emissions and consequently the problems related to climate change (Maniatis [10]; IEA Bioenergy [11]). In this work, we studied the realization, in a little community in Piedmont, north Italy, of a biomass plant for energy generation, with the finality to operate in conditions of cogeneration by producing electric energy to be immitted into the electric net and thermal energy that is destined to satisfy the local requirements with a district heating network. The interested catchment area is the small municipal area where the plant will be located. In order to verify the environmental acceptability (compatibility) of the biomass plant we performed an evaluation of the emissive fluxes modification at local level, by using environmental balance as a tool. We have considered the new emissive flux that can be predicted in direct relationship to the biomass plant activation as a result from the thermal power plant, the type of fuel used and the system that will be employed for the environmental impact containment. On the other side we have evaluated the avoided emission flux resulting from the turning off of the domestic boilers able to be substituted from the produced thermal energy. The calculations that have been performed are based on the knowledge of the emission factors for different plant design solutions and it is defined by considering also the thermal power of the used systems; mass and energy balances were used as a tool in this study.

2 Biomass plant In Tables 1 and 2 we report the main features (concerning technical and energetic aspects) of the studied biomass plant. By analyzing the data reported in Table 2 we can observe that the maximum thermal power produced from the plant (7,15 MW) cannot be fully utilized even if all the users of the whole town (6,8 MW) were connected. In the following table we report the pollutant concentration that, from the technological operating scheme, can be estimated as output of the plant. In Table 2 we report the main energetic plant features.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

Table 1:

Main features of the studied plant.

Fuel Technology Energy recovery Availability Dust NOx SOx

Treatment emissions Table 2:

281

Biomass – wood pellets Combustion on grate system boiler 7.800 h/y ESP (Electrostatic Precipitation) SNCR (Selective Catalytic Reduction) Injection of CaOH

Summary of the biomass plant energetic data.

Gross thermal power 14,6 MW Available thermal power 13 MW Maximum thermal power 7,15 MW Maximum required 6,8 MW thermal power* * this data represent the maximum required thermal power (by considering all the public and private users present in the municipal area) Table 3: Flow [m3/h] 33.000

Pollutant concentration as output of the plant.

Emission time [h/d]

Pollutant substance

24 - continue

Dust NOx SOx CO

Concentration [mg/m3] 10 180 200 200

3 Catchment area and connectable volumes The catchment area will be composed of the municipal area where the biomass plant will be located. All the data that has been found has been summarized in a comprehensive table which is depicted below: Table 4:

Town catchment area.

Population Number of resident families Number of total inhabitations Surface of resident inhabitation [m2] Volume of resident inhabitations [m3] Total inhabitations volume (resident + not resident) [m3]

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

770 394 983 43.965 131.965 390.000

282 Energy and Sustainability III From this, on the basis of the data obtained and their aggregation, we can define the volumes for connection to the future district heating network. These volumes are shown in Table 5. In the elaboration of the environmental balance we examined four different situations referring to four different scenarios of connection to the district heating system:  hypothesis 1: the entire volume of the analyzed town (public and private utilities) will be connected to the district heating network (no distinction between residents and non residents, and no consideration of the aspect of volumes effective capacity to be connected or not);  hypothesis 2: only the volumes of the public and private buildings that can be really connected to the district heating network with an acceptable cost will be considered without distinction between resident and non-residents;  hypothesis 3: the total volume of residents will be connected to the district heating network (no distinction between effectively connectable and not connectable);  hypothesis 4: the total volume of residents effectively connectable will be connected to the district heating network. Table 5:

Volume connectable to the district heating network.

Resident connectable volume [m3] Total connectable volume (resident + not resident) [m3]

81.818 300.000

On the basis of the data reported in Tables 4 and 5 we calculated, for each introduced hypothesis, the thermal energy really transferred. The boilers that are installed in the homes located in the examined town are fed in part (the majority) by methane, and, in part (a small part) by wood. On the basis of the data that were supplied by the local authority it has been possible to Table 6:

Heat specific requirement [kWh/m3 y] Period of heat requirement [h/y] Required thermal power [kWth]

Really distributed thermal power.

Hypothesis 1

Hypothesis 2

Hypothesis 3

Hypothesis 1

44

44

44

44

2.500

2.500

2.500

2.500

6.864

5.280

2.323

1.440

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

283

establish, for each of the four analyzed hypotheses, the fuel composition (with consideration of the percentages of methane and wood) and, consequently, the thermal power that today is covered by methane and wood. The results of this elaboration are presented in Table 7. Table 7:

Definition of the boiler input and of the covered thermal power.

Hypothesis

Boiler feed

Hypothesis 1 Hypothesis 2 Hypothesis 3 Hypothesis 4

Methane Wood Methane Wood Methane Wood Methane Wood

Satisfied thermal power [%] 95 5 95 5 99 1 99 1

Satisfied thermal power [kWth] 6.521 343 5.016 264 2.300 23 1.426 14

4 Energetic and environmental balance In order to evaluate the local environmental benefits, it is necessary to compare the air quality around the assumed CHP (Combined Heat and Power) location before and after installation of the DH (District Heating) system. That is a consequence of the modified emissions scenario. Therefore it is necessary to estimate the contribution of the existing boilers to the air emissions. The electric energy distributed by the network substitutes a part of the centralized electric production, and so, the relative environmental impacts expressed in terms of primary energy consumption and atmospheric emissions are avoided. The quantification of this impact derives from the considered comparison terms. At the same time the thermal energy supplied by DH system allows to substitute the operation of existing boilers and the relative impacts, as primary energy consumption and atmospheric emissions. In this case the avoided impacts in a univocal way correspond with those of the impacts effectively substituted. In the draft of an environmental balance the two components of the avoided impacts represent compensation to the environmental load that is introduced by the DH system. Besides the energetic and environmental balance and in order to evaluate the momentum of the produced impact of the plant, and for this estimation also by taking into account the aspect of its localization, it is necessary to consider the results of the dispersions models. With this approach it is possible to calculate the real air quality modifications; the concentrations (annual mean values and maximum hourly values) that are introduced by the future plant and the ones (eliminated existing domestic boilers) that can be avoided must be compared on the basis of concentration maps (Genon et al. [12]).

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

284 Energy and Sustainability III In general, and with a first qualitative approach, it is possible to consider that a single plant against many individual boilers can be advantageous for a lot of aspects, among which are the smaller amount of pollution, specific production

global impacts

global and local impacts Emissions

BIOMASS PLANT Electric network

Domestic users

District heating network

Figure 1:

Environmental balance.

capacity and the major energetic efficiency. A large plant should have higher thermal efficiency and better smoke control in comparison with the performances of small plants. Also the aspect of higher emissions point of the chimneys, and of higher atmospheric emissions flow-rates and consequent higher dispersion capacities must be taken into account as an aspect of advantage for concentrated solutions. 4.1 Initial considerations In this work we will examine the terms of environmental balance: the bases for this estimation is provided by the following equation: Local / global emissions (added/eliminated) = biomass plant emissions – substituted emissions (1) From the point of view of the “biomass plant emissions” we refer to the data that were reported in Table 3. From the point of view of the “substituted emissions”, it is necessary to make reference to the data of Table 7 and to the emission factors for domestic boilers fed by natural gas and wood. In the following table we report the used emissions factors. Table 8: Fuel Methane

Methane emission factor [Source Piedmont Region].

Dust 1,98

Emission factor [mg/MJ] NOx SOx CO 50 0,51 25,25

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

COV 4,64

Energy and Sustainability III

Table 9:

285

Wood emission factor [Source Piedmont Region]. Emission factor [g pollutant/kg fuel] Dust NOx SOx CO COV 4,91 2,3 0,34 50 8,24

Fuel Wood

By using equation (1) we defined an environmental balance for each of the considered scenarios. The pollutant parameters that were considered in the estimation were:  dust;  nitrogen oxides (NOx). For this pollutant parameter we considered two different situations: o NOx emission treated with DeNOx SNCR system as considered by the plant designers (data in Table 3); o NOx emission treated with DeNOx SCR system; in this case, in comparison with an higher investment cost there is an improvement in the performance as regards the removal of pollutant (in fact with an SNCR system the estimated pollutant concentration in output corresponds to 180 mg/m3, as it is reported in Table 3, while with an SCR system it is possible to arrive to a pollutant concentration in output of 108 mg/m3).  sulphur oxide (SOx);  carbon monoxide (CO);  Volatile Organic Carbon (VOC). 4.2 Environmental balance on annual scale The initial point was the evaluation of hypothesis 1. In this hypothesis it is foreseen that the all town volume will be connected to the district heating network. The results of the elaborations are reported in Table 10. Table 10:

Dust [t/y] NOx (SNCR) [t/y] NOx (SCR) [t/y] SOx [t/y] CO [t/y] VOC [t/y]

Environmental balance, hypothesis 1.

Biomass plant (+) 2,5

Methane boilers (-) 0,12

Wood boilers (-) 1,21

Environmental balance + 1,17

46,3

2,93

0,57

+ 42,8

27,8

2,93

0,57

+ 24,3

51,5 51,5 5,15

0,03 1,48 0,27

0,08 12,35 2,035

+ 51,39 + 37,67 + 2,85

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

286 Energy and Sustainability III By analyzing the results of Table 10 we observe that the biomass plant environmental impact will be higher in comparison with the substituted domestic boilers. We can observe that this impact is conspicuous in particular for the parameters NOx (both considering a SNCR system or a SCR system), SOx and CO. As for hypothesis 2, in this case it is considered that only the effectively connectable town volume will be connected to the district heating network. In Table 11 we reported the results of this hypothesis. By analyzing the results we can observe that in this case the pollutant load introduced by the biomass plant is significantly higher in comparison with the avoided one arising from the substitution of the domestic boilers that are effectively connectable to the district heating network. As in the previously hypothesis, the parameters that mainly suffer from the biomass plant introduction are the NOx, the SOx and the CO; also the parameters dust and VOC undergo a worsening at balance level, but to a lesser measure. Hypothesis 3 is based on the assumption that only the volume corresponding to residents will be connected to the district heating network. In Table 12 we report the result referred to this hypothesis; we can see that the trend is similar to the trend of the previous situations. Table 11:

Dust [t/y] NOx (SNCR) [t/y] NOx (SCR) [t/y] SOx [t/y] CO [t/y] VOC [t/y]

Biomass plant (+) 2,5

Methane boiler (-) 0,09

Wood boiler (-) 0,94

Environmental balance + 1,47

46,3

2,24

0,44

+ 43,62

27,8

2,24

0,44

+ 25,12

51,5 51,5 5,15

0,022 1,14 0,21

0,064 9,5 1,57

+ 51,4 + 40,86 +3,37

Table 12:

Dust [t/y] NOx (SNCR) [t/y] NOx (SCR) [t/y] SOx [t/y] CO [t/y] VOC [t/y]

Environmental balance, hypothesis 2.

Environmental balance, hypothesis 3.

Biomass plant (+) 2,5

Methane boiler (-) 0,04

Wood boiler (-) 0,08

Environmental balance + 2,38

46,3

1,04

0,04

+ 45,22

27,8

1,04

0,04

+ 26,72

51,5 51,5 5,15

0,01 0,52 0,1

0,006 0,83 0,14

+ 51,48 + 50,15 + 4,91

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

287

Hypothesis 4 shows that only the volume for residents effectively connectable will be connected to the district heating network. In Table 13 we report the results relative to this hypothesis. Table 13:

Dust [t/y] NOx (SNCR) [t/y] NOx (SCR) [t/y] SOx [t/y] CO [t/y] VOC [t/y]

Environmental balance, hypothesis 4.

Biomass plant (+) 2,5

Methane boiler (-) 0,025

Wood boiler (-) 0,05

Environmental balance + 2,43

46,3

0,64

0,023

+ 45,64

27,8 51,5 51,5 5,15

0,64 0,006 0,32 0,06

0,023 0,0034 0,504 0,083

+ 27,14 + 51,49 + 50,68 +5

As expected, in this case the load introduced by the plant is much higher than the subtracted ones arising from shutdown of domestic boilers connectable to the district heating network. 4.3 Percentage of pollutant increase with consideration of background value In the previous sections we evaluated pollution loads introduced by the future biomass plant and those which may be eliminated by the substitution of a number of public and private boilers. In this calculation we have not considered the background load deriving from other existing sources operating in the area, as in particular agricultural activities, animal farms, production operations, transport. In Table 14 we report the contribution that can be estimated for these emission sources for the examined town, with consideration of the principal categories. Table 14:

Agriculture Zootechnic Productive activity Transport Urbanization TOTAL (t/y)

Emissive contribution and subdivision for emission sources. Emissive contribution expressed in t/y NO2 PM10 NH3 CO 2,16 0,28 1,03 8,66 -

SO2 -

0,10

0,02

0

-

-

2,88 2,84 7,98

0,87 1,32 2,49

0,05 0 9,74

54,49

0,44

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

288 Energy and Sustainability III The percentage increase, for each evaluated hypothesis, has been calculated with the following equation: % of increase = ((introduced load – substituted load)/background value)*100 (2) with: introduced load (t/y) = biomass plant emission + background value The obtained results are reported in the following figures. If the results that are reported in figure 2 are analyzed, for all the scenarios and for each pollutant parameter taken into account, we can see an important percentage increase deriving from the activation of the new biomass plant. Among the five pollutants, the parameters that present a smaller percentage increase are the dust and the carbon monoxide. On the contrary, the pollutant parameter SOx presents the highest increase percentage among the five pollutant parameters examined). From the point of view of the pollutant parameter NOx, there is a difference in the increase percentage in function of the adopted pollutant removal system (SNCR or SCR). If we use a SNCR removal system the increase percentage is in the order of 400 to 500%, while in case of use of a SCR the increase is only in the order of 200 to 300%.

a)

b)

c)

d)

Figure 2:

Percentage of pollutant increase with background value: a) hypothesis 1 b) hypothesis 2 c) hypothesis 3 d) hypothesis 4.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

289

4.4 Effects on air quality The calculated values are the starting point for an evaluation of the effects of the introduction of the new plant on the air quality for the considered area: in this case, together with these values, we must have at disposal a dispersion model that is calibrated for the specific area and a reliable estimation of the meteorological conditions (wind direction and intensities, local turbulent dispersion, height of mixing boundary layer). In the considered case, while we consider that the emission scenarios are properly defined and absolutely reliable, it is necessary to say that the dispersion model is at the moment absolutely not at disposition, and it will be very difficult to define, also taking into account the complex topographical and geographic situation of the considered area: in these conditions a direct application of the commercial dispersion models could clearly be used, but in our opinion the reliability of the results would be very poor. In these conditions we think that the indication arising from emissions scenarios is a good basis for evaluation of the sensible worsening of the local air quality: in fact, the previously indicated effects of higher dispersion possibilities for the new plant must be carefully considered, and also the consideration of its localization in less populated areas cannot absolutely be disregarded, the influence of the increased emission fluxes is so high that a consideration of worsening in air quality can be reasonably introduced.

5 Conclusion In the presented work we evaluated the acceptability, from the environmental point of view, of a plant for the generation of thermal and electric energy with biomass combustion, to be realized in a little city in Piedmont. This acceptability has been evaluated by using the tools of the environmental and energy balance, on the basis of some hypothesis of connection (total volume of existing buildings or only volume of the buildings that really can be connected to the network, appreciation of the difference between buildings for residents and buildings for non residents). From the obtained results the main conclusion is that an effective convenience (and so an effective acceptability), from the environment point of view, could eventually be obtained only with a very high value of energy utilization, and this is related to the possibility to transfer all the produced thermal energy. In this way the emissions produced from the biomass plant are at least in part balanced by the values of avoided emissions, due to the turn off of some domestic boilers. A sophisticated dispersion model for air quality prevision could confirm this indication, but its implementation seems to be quite difficult for the considered area, and not able to substantially modify the previously reported conclusions.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

290 Energy and Sustainability III

References [1] Boman U.R., Turnbull J.H., Integrated biomass energy systems and emissions of carbon dioxide. Biomass and Bioenergy, Volume 13, Issue 6 (1997), 333 – 343; [2] Dornburg V., Van Dam J., Faaij A., Estimating GHG emission mitigation supply curves of large – scale biomass use an a country level. Biomass and Bioenergy, Volume 31, Issue 1 (2007), 46 – 65; [3] Albertazzi S., Basile F., Brandin J., Einvall J., Hulteberg C., Fornasari G., Rosetti V., Sanati M., Trifirò F., Vaccari A., The technical feasibility of biomass gasification for hydrogen production, Catalysis Today, 106 (2005), 297-300; [4] Bridgwater A.V., The technical and economic feasibility of biomass gasification for power generation, Fuel, 74 (2005), 631-653; [5] Caputo A.C., Palumbo M., Pelagagge P.M., Scacchia F., Economics of biomass energy utilization in combustion and gasification plants: effects of logistic variables. Biomass and Bioenergy, Volume 28, Issue 1 (2005), 35 – 51; [6] Hanaoka T., Inove S., Uno S., Ogi T., Minowa T., Effect of woody biomass components on air – steam gasification. Biomass and Bioenergy, Volume 28, Issue 1 (2005), 69 – 76; [7] Hohenstein W.G., Wright L.L., Biomass energy production in the United States: an overview. Biomass and Bioenergy, Volume 6, Issue 3 (1994), 161 – 173; [8] Hustad J., Skreiberg Ø., Sonju O., Biomass combustion research and utilization in IEA countries. Biomass and Bioenergy, Volume 9, Issues 1 – 5 (1995), 235 – 255; [9] Van Den Broek R., Faa Ij A., Van Wick A., Biomass combustion for power generation. Biomass and Bioenergy, Volume 11, Issue 4 (1996), 271 – 281; [10] Maniatis K., Progress in Biomass Gasification: An Overview, 2002; [11] IEA Bioenergy, The role of bioenergy in greenhouse gas mitigation, Position paper, IES Bioenergy, New Zealand, 1998; [12] Genon G., Torchio F. Marco, Poggio A., Poggio M., Energy and environmental assessment of small district heating systems: global and local effects in two case-studies, Energy Conversion and Management, 50 (2009), 522 – 529.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

291

Bioenergy for regions – alternative cropping systems and optimisation of local heat supply C. Konrad1, B. Mast2, S. Graeff-Hönninger2, W. Claupein2, R. Bolduan1, J. Skok1, J. Strittmatter1, M. Brulé1 & G. Göttlicher3 1

European Institute for Energy Research EIFER, Karlsruhe, Germany Universität Hohenheim, Stuttgart, Germany 3 Energie Baden-Württemberg AG (EnBW), Karlsruhe, Germany 2

Abstract In the frame of a research project for the energy supplier “Energie BadenWürttemberg AG” (EnBW) in Germany, the aim of the study is to evaluate the potentials of alternative substrates and their viability for biogas conversion based on current production regimes in the county of Biberach in the South-West of Germany. The project includes 5-yr field tests of optimized cropping systems leading to higher biodiversity and sustainability while ensuring a constant biomass supply for biogas production. Furthermore precise calculations and estimations of the heat demand of rural areas have been made on an object-based level (residential and tertiary/industry) using a geographic information system (GIS). On the basis of existing biogas plants, techno-economical analysis of heat and micro gas networks have been performed. Sustainability is mainly emphasized on the basis of the aspect of environmental influence on cropping systems (biodiversity, soil erosion, ground and surface water pollution). Biogas yield data at laboratory scale are used to evaluate the economy of alternative cropping systems with regard to energy production as compared to the reference (maize monoculture) in the whole chain ranging from field cultivation to energy use. The practical feasibility and the environmental effects are reviewed in comprehensive and multi-field tests and field trials. Keywords: biomass potential, yield model, GIS, biogas, substrate, biodiversity, heat demand, building stock, heat sinks, small district heating, micro gas grid.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESUS110251

292 Energy and Sustainability III

1 Introduction Biomass production for the conversion into biogas has become very popular since the establishment of the renewable energy law (EEG) in 2001. Currently there are already 5700 existing biogas plants in Germany. Most biogas plants run on maize as a main substrate, cultivated in monoculture over large areas. The one-sided specialisation on a specific crop goes along with several environmental problems such as the loss of biodiversity, soil erosion and the pollution of ground and soil water. As the EEG generously supports the generation of renewable electricity, many biogas units are operated without using enough of the heat produced despite the combined heat and power (CHP) bonus. This research project focuses on finding alternatives cropping systems and alternative use of heat for a more sustainable development of current and future biogas installations.

2 Estimation of the biomass potential According to the official statistics, about 10% of the agricultural land was used for the cultivation of energy crops in the county of Biberach in 2007 [5]. Meanwhile, this value has significantly increased to 15%. From an ecological point of view, the problem is the increasing land use and thereby the competition with food production and animal feed production. The continuous and intensive use of agricultural areas with all the environmental consequences could lead to future deterioration of biodiversity. Actually the area used for the growth of energy crops is further increasing, focusing particularly on maize production. In relation to the entire cultivated area, the proportion of maize in 2009 reached about 30% in the county of Biberach. In several communes, even over 50% of cultivated land is used for the growth of silage maize [4]. The tendency is that this maize is the major substrate for biogas production. The rate of grassland useage for biogas production, which reaches only 3%, is still quite low and surely remains an interesting potential which is not sufficiently used. The introduction of the public subvention “manure bonus” led to an extra created incentive in 2009 in the amendment of the renewable energy law (EEG). The use of slurry and manure builds up a further potential, which amounts to about 90,000 livestock units which can be partly used for the biogas production. The estimation of the biomass potential is based on publications of the ministry of agriculture and on the official statistics of Baden-Württemberg [4, 5]. Moreover high-resolution remote sensing data is available to the project [3]. This data allows an accurate spatial differentiation of arable- and grassland units. The calculation of biogas and methane yields is based on empirical values of on-farm biogas plants [2]. In addition to the common energy crops like silage maize, grass silage and whole crop silage (WCS), the extended use of manure as a function of livestock units is considered (Figure 1).

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

293

Biomass potential Data source: Remote sensing data [3], official statistics [4,5]

Biomass yield calculation based on intermediate yield using estimated values[2]

Taken CHP efficiency; i.e. η=39% electrical efficiency η=52% thermal efficiency

Figure 1:

Schematic diagram of the estimation methodology of the biomass potential in the county of Biberach.

2.1 Status quo of biogas production The characterisation of the installed biogas plants is based on information from the administration and the public database of EnBW [1]. Within this data the location and actual amount of electricity generated from biogas are documented. In the year 2009 74 biogas units with a rated power output of over 20 MWel are already installed in Biberach. About two-thirds of the biogas plants are equipped with a combined heat and power system CHP. This means that besides the

Figure 2:

Location and capacity of biogas plants.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

294 Energy and Sustainability III electricity generation, the heat that they are producing is also used. In 2009 about 140 GWh of electric power were fed into the grid whereby the comparison of registered rated power output to the actual electric production shows that most of the facilities are working below their installed capacities. This shows that fermenters and installed CHPs are not always fully optimised to each other. The equivalent electrical supply amounts of 50,000 households with an average annual electrical consumption for a two-person household of 2800 kWh.

3 Alternative cropping systems and field experiments For biogas production in Germany maize is currently the major crop used, representing up to 90% of the biogas substrate [6]. The area under maize increased drastically over the last years; in 2009 maize intended for biogas production was cultivated on about 380,000 ha in Germany [7]. From an economical perspective, maize is a favorable crop on many sites, providing high energy yields per area and furthermore being an established crop with wide experience in cultivation and ensilage [8]. On the other hand, maize cropping systems are highly criticized. The strong focus of the agricultural practice on maize as the main biogas substrate entails also negative ecological impacts like soil erosion, soil organic matter reduction, nitrate leaching and the loss of biodiversity and habitats [9]. The Sachverständigenrat für Umweltfragen (German Advisory Council on the Environment) [6] estimated in its special report that maize is a crop with a high risk for nutrient leaching, soil erosion and biodiversity. Besides the effect on biodiversity, also the typical local agricultural biodiversity and landscape appearance is decreasing in regions where biogas plants are implemented. Furthermore, diseases like Helminthosporium turcicum and pests like Diabrotica virgifera virgifera are increasing as a result of an intensive maize cultivation and thus are endangering stable and high biomass yields of maize. The occurrence of the western corn rootworm (Diabrotica virgifera virgifera) may cause yield losses as high as 30% and often results in a ban on maize cultivation in the specific area [10]. When discussing alternative crops and cropping systems for biogas production, the use of a temporal sequence of crops also including strips of perennial crops (e.g. energy dock, cup plant) offers multiple harvest dates and thus widens the temporal availability of the substrate for biogas plants and might furthermore reduce erosion potential and nutrient leaching. Laloy and Bielders [11] found that erosion is greatly reduced if a winter cover crop (rye and ryegrass) is cultivated during the intercropping period before maize (maximized soil cover) when compared to maize without a winter cover crop. Results from Vetter [12] indicated that biodiversity (flora and fauna) is greater in cropping systems with two or three crop species than in a monoculture. However, these options are neither sufficiently perceived nor applied in agricultural practice [13].

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

295

3.1 Implementation of alternative cropping systems in the study region The objective of this study lies in developing, testing and monitoring sustainable cropping systems offering a long-term alternative to maize as a biogas substrate in the region. The experimental field site of 5.6 ha is implemented on a farm located in the county of Biberach. The developed cropping system will be cultivated in this field with assistance from the farmer and different environmental relevant parameters will be collected and measured over four years. In 2010 the existing maize monoculture was monitored to determine the status quo situation, as a reference for conventional biogas crop cultivation. In the following four years, this field will be used for the cultivation of the intended alternative cropping system. The following parameters are identified as relevant and measured:      

Fresh- and dry matter yield of the different crops Biogas output of the different crops Erosion potential Nitrate leaching into the groundwater Biodiversity (arable weed species, along transects which are distributed across the field) Biodiversity (ground beetles, with pit fall traps, which are distributed across the field)

3.2 Developed cropping system The developed cropping system consists of a strip-wise cultivation of a perennial crop and annual crops in a crop rotation. Figure 3 shows the developed cropping system in comparison to a maize monoculture (M) without permanent soil coverage. For the perennial crop (pC) energy dock also known as Rumex Schavnat or Rumex OK2 will be used. It is a frost-resistant crossbreed from the Ukraine with a cultivation period of 15 – 20 years and a potentially high biomass yield. Its biomass can be harvested twice a year and ensiled [14]. The implemented crop rotation (CR) includes the crop species sunflower (1 yr + 4 yr) – winter triticale (2 yr) – clover grass (2 yr + 3 yr) – amaranth (3 yr) – forage rye (4 yr), and it is set up completely without maize. As a further advantage, the developed cropping system allows a permanent soil cover with all the above-mentioned positive aspects. From the second year onwards energy dock could provide considerable higher biomass yields than other perennial crops. Furthermore the production costs are lower (seed, fertilizer, etc.) after the establishment phase in the first year. Strips of CR and pC will be of 24 m width and fit into the working width of the farmer’s equipment. The given combination and parallel cultivation of winter crops, summer crops and clover grass are expected to entail the above mentioned advantages and distribute the substrate supply over the year. This has a further positive effect of reducing silage storage capacity requirements.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

296 Energy and Sustainability III

Figure 3:

The cropping scheme (one run of the crop rotation) for the monoculture maize (M), the alternative crop rotation (CR) and the perennial crop (pC) (the axis of abscissa are the month of the years).

4 Model for the biogas production from energy crop mixtures 4.1 Model objectives Energy crops of different varieties are amenable to anaerobic digestion. The crops which are most suitable for biogas production may be characterized with the following parameters: 1. High biomass yield per hectare (tons of dry mass = DM harvested per ha); 2. Low cultivation costs; 3. High digestibility (i.e. low fibre and lignin contents); 4. Appropriate C:N ratio (i.e. ranging between 20 and 30) [15]. Because of its ability to fulfill these requirements, maize is currently the most wanted energy crop for anaerobic digestion [15]. However, the environmental drawbacks of maize motivate the search for alternative energy crops. A model, based on the identified alternative cropping systems (Section 3) was developed in order to perform an assessment of energy crops for biogas production while comparing different crop varieties. For this purpose, data were collected on methane yields of energy crops (laboratory batch test) as well as on the biomass yield per hectare. Using the composition and weight ratios of energy crops in the digester feedstock as input parameters, the feedstock mixture composition can be calculated and compared to empirically set optimal criteria (C:N ratio, fibre and lignin content) for digester operation. Moreover, the methane yield per hectare of field can be determined. WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

Mixture composition (% Dry Mass)

Weight ratios of substrates (% Dry Mass)

297

Criteria for optimal digester operation (% Dry Mass)

NDF

NDF

<50%

ADL

Substrate composition data (% Dry Mass)

C content N content

ADL

<5%

C:N ratio

20‐30

NDF Substrate yield data

ADL C content N content

DM yield per ha (dt/ha)

VS content

Figure 4:

CH4 yield per ha and year

Specific CH4 yield (Nm3/kg VS)

Input parameters (on the left) and output parameters of the model (on the right). NDF: neutral detergent fiber, ADL: Acid Detergent Lignin.

4.2 Exemplary energy crop mixture Within this model a conventional cropping system based on maize monoculture was compared to an alternative and more sustainable cultivation system. The most methane yielding mixture was selected from the previously proposed cropping system (Figure 3). The high-yielding sustainable crop mixture was composed of 40% Triticale, 40% Cup plant and 20% Amaranth (all shares on a dry matter basis). Figure 5 shows the dry matter yield (on the left) and the methane yield (on the right). For both parameters maize, the alternative cropping system as well as the single crops is pictured. Maize (100%)

20

Mixture

6,544 B

16

Amarant

4,937

15

Cup plant

4,437

17

Triticale

5,049

15

0

Figure 5:

A

10

5,076

20

30

0

5000

10000

A. Dry matter yield (t/ha) B. CH4 yield (m3/ha).

In this case the empirical criteria set for low fiber content (Neutral Detergent Fiber = NDF<50%), low lignin content (Acid Detergent Lignin = ADL<5%) and balanced nutrient content (C:N ratio in the range 20-30) were fulfilled. One may deduce that full-scale biogas units may be successfully operated with such manure-free energy crops mixture. The calculated methane yield of the mixture was almost 5000 m3CH4/ha/year. In comparison, the calculated methane yield per WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

298 Energy and Sustainability III hectare for a 100% maize monoculture reached 6500 m3CH4/ha/year. Therefore the theoretical methane yield per hectare of the alternative cropping system was about 20% lower than for maize monoculture. The cultivation costs might be higher for the alternative cropping system in the first year, as the perennial crop has to be established, too. However, in the long run, cultivation costs will be lower when compared to maize, as seed costs for the chosen annual crops are lower and only half of the area has to be sown. The rough calculation does not include indirect costs induced by soil erosion, loss of biodiversity and the impact of pesticides and fertilizers.

5 Assessment of the heat sinks in the study area Besides the increase of sustainability with alternative cropping system (Section 3), prudent heat usage of existing and future biogas plants shall be investigated and alternatives be prospected. The essential input is the estimation of the heat demand in communes in the county of Biberach. Further, the identification of main heat sinks with potential for different grid-bound heat supply concepts, based on biogas, was focused. 5.1 Methodology of the heat demand assessment For the heat demand estimation, existing building stock data, statistic data for regional economy and energy consumption by sector for the district Biberach, were analyzed. For the residential and the tertiary/industry sector geo- referenced INFAS data for building stock [16] (age, class and number of households) was used. Additionally the database of the regional economy (FIS), containing companies’ addresses and numbers of their employees, arranged by the regional Chamber of Industry and Commerce [17] was included, to complete the information needed. The heat demand of the residential sector has been estimated based on the German Building Typology [18], classifying the building stock in a matrix of 5 building types (one-family house, row house, small or big multifamily house, tower house) and 10 age classes. The heat demand of the residential sector has been built by multiplying the average heat demand of a residential building (adjusted to the regional climate conditions) by type and age with the building’ average area according to the correlated data of [18] and [16]; further with the amount of respective geo-referenced buildings by [16]. The heat demand of the industry sector has been received by consideration of the statistic data on the energy consumption according the national branches taxonomy [19]. The specific energy consumption in branches on state level (without electric power) has been accounted referring to the number of employees per branch [20]. It amounts e.g. 22 MWh/employee in machines manufacturing, 8 MWh/employee in furniture construction or 379 MWh/ employee in paper production). This specific value has been multiplied with the

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

299

average employee number per enterprise according the FIS data base [17] and geo-referenced by addresses. Major regional heat sinks in the tertiary sector (trade, commerce and services) have been partially considered, i.e. kindergarten, schools, swimming pools have been geo-referenced according the INFAS data [16] and their heat demand has been estimated with help of average values (surface and heat demand) according to current literature [21–23]. 5.2 Heat demand in the region The built-up areas with the heat demand of buildings, aggregated in a 100 m raster, have been calculated and localized in a geographic information system (GIS). The values of the heat demand raster varied here between zero (by raster points without any buildings) and max. 150.000 MWh/a – doing so, the local repartition of heat sinks could be obtained (Figure 6).

Figure 6:

Detail map of the heat demand in raster of 100 m in communes of the Biberach district.

Additionally a ranking of communities of the county of Biberach, ordered by their annual heat demand, has been worked out: in 73% of all 45 considered communities, the estimated heat demand was below 100 GWh/a. Eight communities (17%) showed values between 100 GWh/a and 200 GWh/a. The highest heat demand of 1,155 GWh/a has been accounted for the county centre Biberach, followed by the estimated heat demand for Laupheim of 470 GWh/a. In the following the heat demand density of built-up areas within the examined communities was identified as the value of the aggregated heat demand raster points in relation to the surface of the built-up areas. It shows values between 4 MWh/ha*a and 5.680 MWh/ha*a. For almost two third of the built-up areas the heat demand density was estimated below 300 MWh/ha*a, over one fourth showed values of between 300 and 700 MWh/ha*a.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

300 Energy and Sustainability III

6 Techno-economic analysis of alternative heat supply systems for model communities in the Biberach district For the purpose of investigating heat networks (district heating supplied by biogas) with micro gas grids (autonomous biogas grid from the biogas plant to the heat demand site) a techno-economic calculation model has been established. Three rural areas have been selected, according the following criteria: heat demand density bigger than 300 MWh/ha*a (see Section 5), distance to biogas plants under 1.000 m (as pre-conditions for all model areas). Further, the availability of a gas network and a location in a neighborhood of an industry zone was considered. The most relevant parameters influencing heat generation costs could be identified. In respect of the heat demand conditions in the considered model areas (different access rate of buildings), the optimal solution for each study case could be shown. The specific heat generation costs varied between 4.47 € ct/kWh (100ct = 1€) to 14.52ct /kWh for the heat pipe grid system and between 4.87 ct/kWh and 14.49 ct/kWh for micro gas grid in the considered areas. Several patterns can be concluded. First, the network-dependent investment costs are determined by the length of the main pipe (in terms of the distance between the existing biogas production plant and the supplied area). In particular, the advantages of the micro gas grid increase with the growing length of the main pipe, because of lower specific civil engineering costs (Figure 7). Secondly, the net-independent investment costs of micro gas grids (e.g. gas treatment and gas compressor) are higher than the net-independent investment costs for heat pipe grid systems in the considered cases - they overbalance the advantages of the network-dependent investment costs. Cost comparison between a heat pipe system and a micro gas system

Investment costs [€]

2.500.000 2.000.000 1.500.000 1.000.000 heat pipe grid 500.000 micro gas grid 0 0

250

500

750

1.000

1.250

1.500

1.750

2.000

2.250

2.500

length of the grid [m]

Figure 7:

Comparison of investment costs between a micro gas grid and a heat pipe grid in relation to their length.

In most considered cases the biogas potential can cover only partially the local heat demand, the remaining heat demand have to be supplied by other fuels and technologies (e.g. wood or gas combustion in a peak load boiler). WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

301

7 Conclusion The project shows a high potential in alternative cropping systems and in the optimization of the local heat supply. In the following years, new crop mixtures will be tested on field and their competitiveness with the reference system maize monoculture will be economically calculated. The impacts on the environment will be monitored in a long-term study. Expected advantages concern erosion reduction, fertilizer demand and nutrient leaching mitigation as well as a decreasing use of pesticides or reduced pest infestation. Furthermore, biodiversity may be enhanced and storage capacity requirements for ensiling harvested crops may be reduced. The heat demand analysis provides a precise picture of the potential of existing heat sinks. The techno-economic analysis of heat and gas networks shows the viability of the systems in relation to the distance, the demand site and the local biomass potential.

References [1] EnBW: EEG-Anlagendaten in der Regelzone der EnBW Transportnetze AG, http://www.enbw.com [2] Faustzahlen Biogas, Kuratorium für Technik und Bauwesen in der Landwirtschaft e. V. (KTBL), 2008 [3] Mapping crop distribution in administrative districts of southwest Germany using multi-sensor remote sensing data, Department of Remote Sensing, Institute of Geography, University of Würzburg, 2010 http://dx.doi.org /10.1117/12.865113 [4] MLR, Ministerium für Ländlichen Raum, Ernährung und Verbraucherschutz, 2010 [5] Struktur- und Regionaldatenbank, Statistisches Landesamt BadenWürttemberg, 2010 http://www.statistik.baden-wuerttemberg.de/ [6] Sachverständigenrat für Umweltfragen, Umweltschutz durch Biomasse – Sondergutachten, Juli 2007, Erich Schmidt Verlag & Co KG: Berlin, pp. 43-56, 2007. [7] Deutsches Maiskomitee, Maisanbaufläche Deutschland in ha, 2008 und 2009 (vorläufig) nach Bundesländern und Nutzungsrichtung in ha. http://www.maiskomitee.de/web/upload/pdf/produktion/Maisanbauflaeche_ D_08-09.pdf [8] Gömann, H., Kreins, P. & Breuer, T., Deutschland – Energie-Corn-Belt Europas? Agrarwirtschaft 56(5/6), pp. 263-271, 2007. [9] Miehe, A. K., Herrmann, A. & Taube, F., Biogaserzeugung aus landwirtschaftlichen Rohstoffen – Monitoring des Substratanbaus und Gärrestverwertung in Schleswig-Holstein. Mitteilung der AG Grünland und Futterbau Band 9, Referate und Poster der 52. Jahrestagung der AG Futterbau und Grünland der Gesellschaft für Pflanzenbauwissenschaften, eds. Thomet, P., Menzi, H. & Isselstein, J., AGRIDEA, pp. 313-316, 2008.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

302 Energy and Sustainability III [10] Schwabe, K., Kunert, A., Heimbach, U., Zellner, M., Baufeld, P. & Grabenweger, G., Der Westliche Maiswurzelbohrer (Diabrotica virgifera virgifera LeConte) – eine Gefahr für den europäischen Maisanbau. Journal für Kulturpflanzen 62 (8), pp. 277-286, 2010. [11] Laloy, E. & Bielders, C. L., Effect of Intercropping Period Management on Runoff and Erosion in a Maize Cropping System. Journal of Environmental Quality (39), pp. 1001-1008, 2010 [12] Vetter, A. Standortangepasste Anbausysteme für Energiepflanzen – 3. Auflage. Fachargentur Nachwachsende Rohstoffe e. V: Gülzow, pp. 79-98, 2010. [13] Willms, M., Glemnitz, M. & Hufnagel, J., FNR-Projekt „Entwicklung und Vergleich von optimierten Anbausystemen für die landwirtschaftliche Produktion von Energiepflanzen unter den verschiedenen Standortbedinungen Deutschlands (EVA) “Teilprojekt II „Ökologische Folgewirkungen des Energiepflanzenanbaus”. http://www.tll.de/vbp/eva1 /zalf_tp2.pdf [14] Vetter, A., Heiermann, M. &Towes, T., Anbausysteme für Energiepflanzen – optimierte Fruchtfolgen + effiziente Lösungen, DLG-Verlags-GmbH: Frankfurt am Main, pp. 81, 2009. [15] Weiland, P. (2010) Biogas production: current state and perspectives, Applied Microbiology and Biotechnology 85:849-860. [16] INFAS; http://www.infas-geodaten.de/ [17] Data Base of Regional Economy - Firmeninformationssystem (FIS) Firmendatenbank des Baden-Württembergischen Industrie- und Handelskammertages (IHK), http://www.bw-firmen.ihk.de/sites /fitbw /search/detailSearch.aspx [18] Institut Wohnen und Umwelt (IWU) Darmstadt; Deutsche Gebäudetypologie; Systematik und Datensätze; Dezember 2003 [19] Energieverbrauch des Verarbeitenden Gewerbes, Bergbau und Gewinnung von Steinen und Erden in Baden-Württemberg 2008; Statistisches Landesamt Baden-Württemberg 2010 [20] Verarbeitende Gewerbe, Bergbau und Gewinnung von Steinen und Erden in Baden-Württemberg 2008; Statistisches Landesamt Baden-Württemberg 2009 [21] Schlomann, Barbara; Gruber, Edelgard et.al; Energieverbrauch des Sektors Gewerbe, Handel, Dienstleistungen (GHD) für die Jahre 2004 bis 2006 Projektnummer 45/05 Abschlussbericht an das Bundesministerium für Wirtschaft und Technologie (BMWi) und an das Bundesministerium für Umwelt, Naturschutz und Reaktorsicherheit (BMU); Karlsruhe, München, Nürnberg; 2009 [22] Bundesministerium für Verkehr, Bau und Stadtentwicklung (BMVBS); Benchmarks für die Energieeffizienz von Nichtwohngebäuden, Vergleichswerte für Energieausweise; 2009; Berlin [23] VDI-Richtlinie 3807 Blatt 1 Energieverbrauchskennwerte für Gebäude; 1998; Tabelle 4

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

303

Sustainability of nuclear energy with regard to decommissioning and waste management S. Lindskog1, R. Sjöblom2 & B. Labor3 1

The Swedish Radiation Safety Authority, Sweden Tekedo AB, Sweden 3 Badania Dydaktyczne, Poland 2

Abstract The paper analyses the sustainability aspects of nuclear power with regard to environmental liabilities associated with decommissioning of nuclear facilities and with waste management. Sustainability is defined and literature on evaluation of sustainability in the nuclear and coal energy fields is reviewed. It is found that the results are incoherent and that methodologies for evaluations are needed as well as adequately structured knowledge bases. Examples of such tools and work are presented from the perspective of the Swedish Radiation Safety Authority. Different aspects of nuclear energy sustainability are reviewed and summarized, and it is found that appropriate management of the nuclear liability associated with protection of health and the environment – now and in the future – is a necessary prerequisite in order for nuclear power to qualify as sustainable. Analyses in a historical perspective show that sustainability awareness has been around for at least as long as agriculture, and that some shortcomings are actually modern inventions. The analyses also show that sustainability awareness may appear as trends and that comprehensive perspectives are essential. Planning for decommissioning and the estimation of associated costs have proven to be treacherous exercises. Moreover, the timing of the planning must be based on the need for appropriate finance so that adequate funds are available at the time when they are needed. It is the duty of our generation to assess what is adequate and to find responsible solutions. But we should also ask the next generation and carefully consider the perspective that they provide to us. Keywords: sustainability, nuclear, liability, segregated fund, cost calculation, younger stakeholders. WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESUS110261

304 Energy and Sustainability III

1 Background, purpose and scope 1.1 Nuclear liability evaluation and financing in Sweden Generally, it is not forbidden by law for natural persons and other private legal entities to perform activities that have a potential for causing detriment to health and environment. Instead, it is the risk for such detriment that is being regulated in various legislations and that is also overseen by various Authorities. Thus, in Sweden, it is the task of the Swedish Radiation Safety Authority (SSM), (Swedish name Strålsäkerhetsmyndigheten) to oversee radiation protection, under The Radiation Protection Act [1], and nuclear activities, under the Act on Nuclear Activities [2]). The oversight covers all kinds of such activities, including nuclear electric power generation. Similarly, SSM also oversees the planning for the final storage of the nuclear waste, the planning for the decommissioning of nuclear facilities and the system for financing the associated future costs. This financial oversight is carried out under the Nuclear Liability Act [3] which stipulates that plans and cost calculations shall be submitted to SSM each year for nuclear power plants and every third year for other facilities. For nuclear power plants, there are two “compartments” for securities and fees to segregated funds managed by the Government: A the anticipated costs for decommissioning and waste management etc., and B a risk fee intended to cover the residual risk that the Government takes in its management and as ultimate guardian of the fund system. Compartment A comprises a combination of securities (unlimited in time) and assets in segregated funds. Securities are lifted at the same pace as that of the payments that flow into the segregated funds. In addition, securities must be provided to cover “unplanned events”. It is the owners and operators of the nuclear facilities that carry the full responsibility for protecting health and the environment. They also have the full responsibility to ensure that adequate funding is available at the time when it is needed for any associated liabilities. The role of SSM and other Authorities is to instigate such work and to ensure that those eligible fulfil all their obligations. Most of the nuclear liabilities are associated with our 12 modern nuclear power plants, 10 of which are presently in operation. But more than 10% of the total estimated decommissioning liabilities are associated with old nuclear technology development facilities. There are considerable obstacles and pitfalls related to the planning and associated cost estimates, especially for old facilities. It is therefore a daunting and demanding task for owners and operators to comply with the requirements on financial planning. Similarly, the SSM needs a good knowledge base for its oversight, and accordingly, it is also the duty of the SSM to carry out and to commission relevant research work [4]. Recent publications include References [5–14].

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

305

1.2 Purpose and scope The purpose of the present paper is to analyse the sustainability aspects of nuclear power with regard to environmental liabilities associated with decommissioning of nuclear facilities and with waste management. The objective is to contribute to the knowledge base needed for assessments of sustainability for nuclear power in general and for comparisons between different sources of energy. The objective is also to illustrate how environmental liabilities can be managed for different energy systems and in different fields of technology.

2 Sustainability and associated methodologies for analysis and comparison 2.1 Sustainability definitions According to the Brundtland report [15] from 1987, sustainable development can be defined as follows: “Sustainable development is development that meets the needs of the present without compromising the ability of future generations to meet their own needs. It contains within it two key concepts: • the concept of ‘needs’, in particular the essential needs of the world’s poor, to which overriding priority should be given; and • the idea of limitations imposed by the state of technology and social organization on the environment’s ability to meet present and future needs.” This principle of sustainable development is closely associated with the polluter pays principle (PPP). It is also dealt with in the Brundtland report [15] which in this case refers to an OECD decision from 1972 [16]. A corollary to the polluter pays principle is the principle of equity between generations. 2.2 The need for tools and knowledge bases for assessments It might be tempting to assume that the above quoted basic principles might be readily applied to various industrial activities including energy production. However, the conclusions reached are not entirely coherent. For instance, the World Nuclear Association concludes the following [17]: “Our confidence that nuclear power is a ‘sustainable development’ technology because its fuel will be available for multiple centuries, its safety record is superior among major energy sources, its consumption causes virtually no pollution, its use preserves valuable fossil resources for future generations, its costs are competitive and still declining, and its waste can be securely managed over the long-term”. Similar conclusions, albeit expressed somewhat more moderately, can be found in a report [18] from the OECD/NEA.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

306 Energy and Sustainability III The conclusion above “that the waste can be securely managed” should not be interpreted to imply that systems are in place for final disposal of all nuclear waste in all countries. In fact, no country has yet commissioned a repository for civilian spent nuclear fuel or high level waste from reprocessing of such fuel. The coal combustion community considers [19] three pillars of sustainable development: “economic prosperity, social well-being and environmental sustainability”, (cf the Brundtland report above) and makes the following observations: • Coal will play an important role in energy systems that support sustainable development for the foreseeable future. • Further improvement in coal’s environmental performance will be required ... to reduce greenhouse gas emissions. ...” Of course, carbon capture (carbon dioxide sequestration) is still at the development stage. It can be concluded that the application of the fundamental principles of sustainability is not straightforward. Tools for assessment and comparison are needed as well a knowledge bases structured in a feasible manner. 2.3 Tools for assessment and need for appropriately structured knowledge Modern tools for assessment of the functioning of industrial facilities have largely been developed in conjunction with the planning and safe operation of advanced industrial facilities, especially in the chemical and nuclear industries, and examples include References [20–23]. General considerations in such analyses include the following: • definition of the system, including what is prerequisites (outside the system) and what is inside • identification and description of features, events and processes • identification and studies of scenarios • comparison (e.g., for best available technology) based on comparing one type of characteristic at the time, and to make overall assessment thereafter. The Swedish research on nuclear waste disposal and associated planning, including financial planning, was inaugurated in the 1970s, and have since then been rather intensive in industry (the major effort) as well as at the Swedish Radiation Safety Authority (SSM) and its predecessors. An overview of objectives and direction of the Authority work can be found in Norrby [4], see also References [24–29]. Lessons learned from the SSM work include that assessments and comparisons is a topic in itself, and requires substantial efforts. Pitfalls are numerous, and structured approaches are essential. Critical areas include integration between disciplines and awareness of the sociological, financial and legal dimensions. Perspective on time is also important, including difficulties in making prognoses for chemical developments, awareness of all different relevant issues – which may change considerably with time – and the general level of scientific and technical knowledge which is being elevated all the time.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

307

3 Nuclear energy sustainability 3.1 Availability of uranium and the efficiency in its utilization All contemporary nuclear power reactors use uranium based nuclear fuel. Uranium ore typically contains levels of uranium at a fraction of a percent or lower. This implies that most of the ore becomes tailings that may emit radioactive radon to the surrounding air, and various elements in the periodic table to the groundwater. Thus, remediation and reclamation are needed. Reference [30] states that the total identified sources of uranium are sufficient to last for more than 100 years at the present level of consumption. The report also states that the deployment of advanced reactor and fuel cycle technologies could conceivably extend the long-term availability of uranium to thousands of years. 3.2 Protection of health and the environment Most of the potential for detriment to health and the environment from nuclear power generation originates from radiation. The radionuclides emitting the radiation may be natural or artificial. (A nuclide is a specific combination of elementary particles in the nucleus of an atom). Large amounts of artificial radionuclides are formed in a nuclear reactor. They give rise to radiation during short (very intensive) and long (less intensive) time. Different types of radiation have very different absorption characteristics. So far, doses in Sweden have been kept well within limits for the very most part. In particular, doses to the public have been very far below the limits. We have also been fortunate in that radiological consequences of deviations from normal operating conditions have been insignificant. Accidents do occur, however, as is illustrated by the Chernobyl disaster which affected Sweden by fall-out [31]. This particular type of accident is not technically possible with our designs of reactors. Nonetheless, it is an appropriate attitude from a safety point of view not to discard the possibilities of accidents. Decommissioning of a nuclear facility typically costs at least a couple of orders of magnitude more than the demolition of a corresponding non-nuclear facility. The reason for this is the presence and properties of the remaining radionuclides, c.f. the description above. Moreover, the waste from decommissioning will have to be deposited, typically – and in the case of Sweden – together with other waste that has been kept in interim storage. However, according to present domestic plans, the spent nuclear fuel will be deposited in a separate facility. This constitutes an environmental liability that has to be appropriately managed in terms of technical and financial planning, see and compare with Section 1.1 above. Such appropriate management is an essential prerequisite for nuclear energy to qualify as sustainable.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

308 Energy and Sustainability III

4 Results from information searches and analyses 4.1 Historical perspective Sustainability awareness is often thought of as a modern phenomenon, but is actually likely to be at least as old as agriculture. Our forefathers freed their farmlands from stones and put them in walls to protect the crops from grazing animals. This example illustrates a strong solidarity with descendants. The greenhouse effect has been known for more than 100 years, not only as some curiosity in exotic scientific literature, but also in popular and well circulated literature in which it was put forward in 1919 by the Swedish scientist Svante Arrhenius [32] as more or less a matter of course. It was pointed out as just about the only mechanism by means of which mankind might achieve an increase in world temperature. He also calculated that the carbon dioxide reserves in the atmosphere would last for only about 37 years should it not be replenished by microbial activity and coal combustion. It is appropriate to wonder why the issue of global warming was laying dormant for about a century, and then relatively recently and suddenly became a major issue. This raises the question of what other important issues might escape contemporary attention only to become major issues tomorrow. The book by Arrhenius [32] deals rather extensively with the issues of sustainability of mineral and energy resources, and it ends with emphasizing the need for recycling and the exhort: “thou shalt not waste”. Another example of what might be referred to as a “marination effect” concerns the awareness of the significance of man-made radionuclides. It took a few decades after x-rays had been discovered and put to use in hospitals in the 1890s until the health problem of induced cancers became recognized and dealt with. Preparation of man-made radionuclides on a large scale was inaugurated in 1942 when the first nuclear reactor was started, but it took until the 1970s until the problems with the nuclear waste became fully recognized. A similar but less transient development of awareness is taking place since about 20 years on the issue of decommissioning of nuclear facilities. Examples of recent work are presented in the subsequent sections 4.2 and 5. 4.2 Environmental liabilities and the polluter pays principle Background to this section in the form of previous publications by the present authors can be found in References [5–14]. The polluter pays principle has been implemented in the Swedish Environmental code [33] as follows: “Persons who pursue or have pursued an activity or taken a measure that causes damage or detriment to the environment shall be responsible, until such time as the damage or detriment ceases, for remedying it to the extent deemed reasonable …”. Since there is no limit in time, a liability will exist as long as remediation has not been completed. It was mentioned in Section 1.1 that for nuclear liabilities, financial resources are generally accumulated in segregated funds so that funding will be available at WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

309

the time when it is needed. The funding should be sufficient but not superfluous. A prerequisite for the functioning of such a system is that future costs can be estimated with sufficient precision. There are numerous examples of deviations in this regard, and consequently a structured approach is warranted. At least for private enterprises, the nuclear [3] as well as the financial [34–37] legislations require that liabilities be calculated with a high or even very high precision. The harshest punishment (prison) might come about as a consequence of the penal law [38] in cases where the financial reporting is grossly misleading. Such deviation might actually not be very far fledged since it has proven recurrently difficult to make precise cost estimations for decommissioning, especially for old research facilities. A good advice is therefore to follow – or at least carefully check – existing standards [39–40], and to conscientiously declare any remaining uncertainties together with the reasons why they still exist. What is just said implies that the timing of the planning for decommissioning is dictated by the needs of the financial planning.

5 Results from field studies Sustainability is about the future, and about whether people in the future will experience an improved or a depleted basis for their existence. Of course, we cannot ask them, and consequently we have to rely on the adequacy of our own preferences. There is, however, a possibility to get some information on the issue by asking people that are young today since they constitute the next generation. This is not often done however, since surveys typically are carried out via paper forms that are sent out by ordinary mail. Since young people today communicate by other means, the response rates are typically insufficiently low. Consequently, the approach chosen in the present work comprises personal interviews of 1444 persons attending secondary grammar school (High School/Gymnasium) and the response rate achieved is close to 100%. (The first stage of the present work has been reported in [6, 7]). The interviews were carried out during late 2007–2010 in the towns Gdansk, Lublin, Elblag and Jaworzno (Katowice) in Poland and Trnava in Slovakia. No difference was found between the genders. Also no difference was found between the towns in spite of the fact that Jaworzno is a coal mining town that is surrounded with coal condensation power plants, and the town of Trnava is close to the nuclear power reactors on the Bouniche site. Two of these reactors have been shut down permanently, and are thus in the transition phase for decommissioning, and the others are still in operation. It was found that the young people in the study have the following preferences: 1 Truly sustainable sources of energy are preferred. Coal has the lowest score. 2 Sweden should take care of its own waste. 3 Only few people can consider having a final disposal of nuclear waste near to their homes. WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

310 Energy and Sustainability III 4

Protection of health and environment are most important for final disposal, but distance from home is also an important consideration. 5 Young people feel that unease with the risks together with lack of knowledge are the most important aspects for acceptance of nuclear waste disposal while trust for the stakeholders involved and local opportunities are less important. A brief compilation of the actual answers are as follows (the full data will be published later): Question 1. Which form of energy do you prefer? 4,4 Coal Windmills Nuclear Power Miscellaneous 24,7 Hydropower 31,8 Question 2. Who shall take care of the Swedish waste? Sweden 88,1 Other countries

33,2 5,8

11,9

Question 3. Can you consider having a site for final disposal of nuclear waste near to your home? 15,6 No 84,4 Yes Question 4. What is your opinion towards a site for final disposal of nuclear waste? 24,3 25,5 Indifferent In favour Against 50,2 Question 5. Which aspect is in your opinion most crucial for the acceptance of a final disposal? Safety aspect Methods and techniques 38,4 8,6 27,8 3,2 Environmental aspect Economic growth Location aspect, as far Miscellaneous 0,8 from home as possible 21,2 Question 6. Which of these values do you base your opinion upon? Trust for the stakeholders Lack of knowledge 11,5 involved Unease with the risks Opportunities linked to a Miscellaneous disposal for nuclear waste 10,1

34,6 39,5 4,3

6 Concluding remarks The definitions of sustainability are quite clear. Analyses have nonetheless been carried out in different ways in different areas of technology, and the results are not coherent. Consequently, methodologies are needed that enable comparisons to be carried out in a more uniform and systematic manner. This requires that appropriately structured knowledge bases be established together with efficient modes for communication and knowledge transfer. The sustainability of nuclear energy is not just a matter of availability of uranium and efficiency in its utilization. Protection of health and the environment – now and in the future – is a necessary prerequisite in this regard. The protection in the future must be carried out in full compliance with the polluter pays principle. It is not necessarily required that the generation that WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

311

benefits from the nuclear electricity also actually carries out the decommissioning of the nuclear facilities and disposes permanently of all the waste. There may be good technical reasons to operate nuclear facilities for the optimum lengths of time, and this may imply times longer than one generation. It is essential, however, that the benefitting generation leaves behind the full technical solutions together with all the financial resources needed for adequate protection of health and the environment. So far, and in the case of Sweden, this has meant green field conditions. The historical compilation shows that sustainability awareness may well appear in the form of trends. This calls for comprehensive and systematic approaches based on appropriately structured knowledge bases. It is a natural element of human nature as well as human culture to care about the offspring, and to leave behind a better basis for existence. Forces that counteract this may include exaggerated emphasis on quarterly reports by institutional investors. The concern for descendants is not unconditional, however. Research suggests that an individual will sacrifice consumption to benefit future generations only if a guarantee exists that others will do the same [41]. Thus, bodies are required as ombudsmen for the public to ensure general compliance. Such solutions are proposed in [41]. Planning for decommissioning and the estimation of associated costs have proven to be treacherous. Careful analyses are needed in order to obtain the precision required. This includes radiological surveying, selection of techniques to be used and identification and evaluation of potential cost raisers. It also includes comparison with already completed projects. The timing of such evaluations is dictated by the needs for financial planning, and this may imply that it must be carried out many years, perhaps decades, before the plans may be needed for purely technical reasons. It is the duty of our generation to assess what is adequate and to find responsible solutions, and in this sense we must act as ombudsmen for the future generations. We do, however, have access to the next generation. It is therefore imperative that we learn about their values and carefully consider what they share with us. It is probably safe to assume that the perspectives and requirements will be different in the future, and we should strive for solutions that have good prognoses for standing the ultimate tests of time. For instance, it is only forty years since Sweden participated in a sea-dumping campaign that was carried out under the auspices of the United Nations. Such a practice is far from acceptable today. In this perspective, it is of crucial importance to include stakeholders in general and younger stakeholders in particular, in knowledge transfer and dialogue. It is also important that information is passed on to future generations. It is imperative that this process is supported by society e.g. in terms of funding of financial resources and information about nuclear waste liabilities.

References [1] Radiation Protection Act. (In Swedish: Strålskyddslag). SFS 1988:220. WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

312 Energy and Sustainability III [2] Act on Nuclear Activities. (In Swedish: Lag om kärnteknisk verksamhet). SFS 1984:3. [3] Nuclear Liability act. (In Swedish: Lag om finansiella åtgärder för hanteringen av restprodukter från kärnteknisk verksamhet). SFS 2006:647. [4] Norrby, S., A Regulatory Authority’s Needs for R&D to Develop Competence in Assessing Nuclear Waste Management Safety. Scientific Basis for Nuclear Waste Management XXI, edited by Ian G. McKinley, Charles McCombie (Mater. Res. Soc. Symp. Proc. Vol. 506, Warrendale, PA, 1997). [5] Lindskog, S. & Sjöblom, R., Implementation of the polluter pays principle example of planning for decommissioning. Environmental Economics and Investment Assessment III, 3-5 May 2008, Limassol, Cyprus. WIT Transactions on Ecology and the Environment, Vol 131. Wit Press, 2010. ISBN 978-1-84564-436-9. [6] Labor, B. & Lindskog, S., Values held by young stakeholders on financial planning regarding liabilities for nuclear decommissioning. Environmental Economics and Investment Assessment III, 3-5 May 2008, Limassol, Cyprus. WIT Transactions on Ecology and the Environment, Vol 131. Wit Press, 2010. ISBN 978-1-84564-436-9. [7] Tyszkiewicz, B. and Labor, B., A Survey of Younger Citizens Values towards Decommissioning and Dismantling of Older Nuclear Facilities in a European Perspective. SKI* Report 2008:52. June, 2008. [8] Lindskog, S. & Sjöblom, R., Radiological, technical and financial planning for decommissioning of small nuclear facilities in Sweden. Proceedings of the 12th International Conference on Environmental Remediation and Radioactive Waste Management, ICEM2009, October 11-15, 2009, Liverpool, UK. [9] Lindskog, S., Cato, A. & Sjöblom, R., Estimations of costs for dismantling, decommissioning and associated waste management of nuclear facilities, and associated impact on decision processes, functioning of markets and the distribution of responsibilities between generations. Environmental Economics II, 28-30 May 2008, Cadiz, Spain. WIT Transactions on Ecology and the Environment, Vol 108. Wit Press, 2008. ISBN 978-184564-112-2. [10] Lindskog, S. & Sjöblom, R., Regulation evolution in Sweden with emphasis on financial aspects of decommissioning. Decommissioning Challenges: an Industrial Reality? Sept. 28 to Oct.2, 2008 – Avignon, France. [11] Iversen, K., Salmenhaara, S., Backe, S., Cato, A., Lindskog, S., Callander, C., Efraimsson, H., Andersson, I. & R. Sjöblom, R., Cost calculations at early stages of nuclear facilities in the Nordic Countries. The 11th International Conference on Environmental Remediation and Radioactive Waste Management. September 2-6, 2007, Bruges (Brugge), Belgium. [12] Cato, A., Lindskog, S. & Sjöblom, R., Financial Planning as a Tool for Efficient and Timely Decommissioning of Nuclear Research Facilities. American Nuclear Society. Decommissioning, Decontamination and

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

[13]

[14]

[15]

[16]

[17] [18] [19]

[20]

[21]

[22] [23] [24] [25]

[26]

313

Reutilization. Capturing Decommissioning Lessons Learned. September 16-19, 2007, Chattanooga, Tennessee, USA. Sjöblom, R., Sjöö, C., Lindskog, S. & Cato, A., Early stage cost calculations for determination and decommissioning of nuclear research facilities. The 10th International Conference on Environmental Remediation and Radioactive Waste Management. Glasgow, UK, 4-8 September, 2005. Laraia, M. & McIntyre, P. J., responsible officers; Cato, A., Lindskog, S. & Sjöblom. R., et al contributors. Decommissioning of research reactors and other small facilities by making optimal use of available resources. IAEA Report Series 463, Vienna 2008. Brundtland, G., Chairman, Our Common Future (The Brundtland report). World Commission on environment and Development, Oxford University Press, Oxford, United Kingdom, 1987. See OECD. ‘Guiding Principles Concerning International Economic Aspects of Environmental Policies’, Council Recommendation C(72)128, Paris, 26 May 1972. Charter of ethics. Four Pillars of Support for a Fast-Globalizing Nuclear Industry. World Nuclear Association brochure. Nuclear Energy in a Sustainable Development Perspective. OECD Nuclear Energy Agency, 2000, ISBN: 926418278X. Coal and sustainable development. A position paper by the Coal Industry Advisory Board prepared for the World Summit on Sustainable Development Johannesburg, OECD International Energy Agency. August 2002. Saaty, T. L., The analytic network process, Decision making with dependence and feedback. RWS Publications, Pittsburg, USA, 2001. ISBN 0962031798. Saaty, T. L. & Vargas L. G., Decision making in economic, political, social and technological environments with the analytic hierarchy process. The analytic hierarchy process series Vol VII. RWS Publications, Pittsburg, USA, 1994. ISBN 0962031771. Petersen, D., Analyzing safety system effectiveness, 3rd edition. Van Nostrand Reinhold, 1996. ISBN 0442021801. Chapman, N. A. & McKinley, I. G., The geological disposal of nuclear waste. John Wiley & Sons, 1987. ISBN 0471912492. SKI (1996). SKI SITE-94 Deep Repository Performance Assessment Project. SKI* Report 96:36 (2 volumes). Andersson, J., Dverstorp, B., Sjöblom, R. & Wingefors, S., The SKI repository performance assessment project SITE-94. International High Level Waste Management Conference, 1–5 May, 1995, Las Vegas, Nevada, U.S.A. Andersson, J., Editor, The joint SKI/SKB scenario development project. SKI* Technical Report 89:14, Stockholm, December 1989. (This report is also published as SKB Technical Report 89-35).

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

314 Energy and Sustainability III [27] Stenhouse, M., Chapman, N. & Sumerlin, T., SITE 94. Scenario Development. FEP audit list preparation: Methodology and presentation. SKI* Technical Report 93:27, Stockholm, April 1993. [28] Chapman, N. S., Andersson, J., Robinson, P., Skagius, K., Wene, C-O., Wiborgh, M. & Wingefors, S., Devising scenarios for future repository evolution: a rigorous methodology. Mat. Res. Soc. Symp. Proc. Vol. 353. Materials Research Society, 1995. [29] Sjöblom, R., Dverstorp, B. & Wingefors, S., Objectives and limitations of scientific studies with reference to the Swedish RD&D Programme 1992 for handling and final disposal of nuclear waste. Mater. Res. Soc. Symp. Proc. Volume 333, Pittsburgh, PA 1994. [30] Uranium 2009, Resources, Production and Demand. Jointly prepared by OECD, Nuclear Energy Agency and International Atomic Energy Agency (IAEA). OECD Publishing, 2010. ISBN: 9789264047891. [31] Moberg, L., editor, The Chernobyl fallout in Sweden. Results from a research programme on environmental radiology. The Swedish Radiation Protection Institute, 1991. ISBN 9163007215. [32] Arrhenius, S., Kemien och det moderna livet. Hugo Gebers Förlag, Stockholm, 1919. German translation: Die Chemie und das moderne Leben. Autoris. deutsche Ausgabe von B. Finkelstein. Lpz., Akadem. Vlgsanst., 1922. English translation: Chemistry in Modern Life. Translated from the Swedish and revised by Clifford Shattuck Leonard, New York, D. van Nostrand Co., 1925. [33] The Swedish Environmental Code. English translation. Ds 2000:61. (In Swedish Miljöbalk, SFS 1998:808). [34] Accounting Act. (In Swedish: Bokföringslag). SFS 1999:1078. [35] Annual Reports Act. (In Swedish: Årsredovisningslag). SFS 1995:1554 [36] The Swedish Companies Act. (In Swedish: Aktiebolagslagen). SFS 2005:551. [37] International Financial Reporting Standards and International Accounting Standards (IFRS/IAS). International Accounting Standards Board. 2008. [38] The Swedish Penal Code. (In Swedish: Brottsbalk). SFS 1962:700. [39] Standard Guide for Estimating Monetary Costs and Liabilities for Environmental Matters. ASTM Standard E 2137 – 06, December 2006. [40] Standard Guide for Disclosure of Environmental Liabilities. ASTM Standard E 2173 – 07, April 2007. [41] Padilla, E., Intergenerational equity and sustainability. Ecological Economics 41 (2002) 69-83. * SKI = Swedish Nuclear Power Inspectorate, now Swedish Radiation Safety Authority (SSM). Reports are available at www.ssm.se.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

315

How dematerialization contributes to a low carbon society? S. Fujimori & T. Masui Social & Environmental Systems Division, National Institute for Environmental Studies, Japan

Abstract In the light of recent knowledge about the seriousness of climate change, a lot of attention is being paid to low carbon societies, which reduce their carbon emissions. On the other hand, in terms of sustainability, some countries are seeking a dematerialized society. Such a dematerialized society aims to reduce material inputs and waste discharge. The question follows as to how these two types of societies are related. Presumably, the carbon emission in a dematerialized society can be expected to be lower than in a non-dematerialized society. However, just how much lower? This study answers to this question with a quantitative analysis by using a global CGE (Computable General Equilibrium) model. The CGE model has the advantage that it can analyze a whole economic system, its energy use and CO2 emission consistently. We conduct scenario analysis using this CGE model. Four comparative scenarios are simulated; (1) business as usual without carbon emission constraints, (2) dematerialization without carbon emission constraints (3) business as usual with carbon emission constraints, and (4) dematerialization with carbon emission constraints. For each scenario CO2 emissions and material inputs for the whole society are estimated and analyzed. The time period covered is from 2005 to 2050 and the target area is the world divided into 12 regions. In this study, we focus on steel as an indicator of the dematerialization. For developing a dematerialized society scenario, we examine changes in investment and assume other materials are substituted for steel. There are two main findings. One is that dematerialization certainly reduces the CO2 emission globally, especially in Asian developing countries and reduces the carbon cost. The other is that even though dematerialization contributes to the development of a low carbon society, there still seems to be difficulties in achieving a large CO2 emission reduction. WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESUS110271

316 Energy and Sustainability III Keywords: dematerialization, low consumption, GHG emission price.

carbon

society,

CGE

model,

steel

1 Introduction The Fourth Assessment Report published by Intergovernmental Panel on Climate Change (IPCC) reveals that past observed climate change is very likely induced by human activity. With the continuing improvements in global climate models, the relationship between future greenhouse gases (GHG) emissions and temperature increase is becoming clear. In addition, the future impact of the climate change on the natural ecosystem and human society is projected, within a large uncertainty range, to be highly significant. According to such scientific information, many countries are trying to reduce GHG emissions through initiatives such as the Kyoto protocol and the Copenhagen accord. On the other hand, we have not yet had a clear answer to following questions: (1) To what extent can we reduce GHG emissions? (2) What technologies should be developed and actually installed? (3) How much will it cost? In order to answer these questions, several integrated assessment models have been developed and applied. For instance, Clarke et al.[3] compiles around 10 research results and shows how the difficulties of climate mitigation are different depending on the CO2 concentration stabilization level (such as 450 or 550 ppm) and the time-path of international participation (such as whether developing countries participation is delayed or not ). Most of the models provide solutions for the 550 ppm concentration target but not for the 450 ppm. This implies achieving what we call a low carbon society will not be so easy. Apart from climate change, there are other global issues such as food, water and metal resource scarcity problems, which seek a sustainable development for human society. “Dematerialization” is one of the issues related to sustainable development (von Weizsaecher et al. [20]). Though “dematerialization” has not been clearly defined, it can be referred to as the process of fulfilling society’s functions while decreasing the use of material resources over time (van der Voet [18]). Dematerialization can be measured on different geographical scale levels such as nations, regions, and cities. Moreover, there are a variety of methods of measuring it. At times it is measured as the mass of the total material inputs and at other times as the intensity of material inputs per driving force of an activity (Matthews et al. [11]). The target material can be the total bulk of a material or some specific elements. The latter analysis is what we call “Substantial Flow Analysis” (e.g.; Fujimori and Matsuoka [6]). One interesting question arises: How are a low carbon society and a dematerialized society related? In terms of fossil fuel, it is easy to answer that a low carbon society is a dematerialized society since it consumes relatively less fossil fuel. However, when we consider other material consumption, we cannot answer to that question so easily. Presumably, the carbon emission in a dematerialized society can be expected to be lower than in a non-dematerialized

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

317

society since material processing requires energy. But, just how much lower is it? This study gives one solution to this question. We applied a global computable general equilibrium (CGE) model from 2005 to 2050 and conducted scenario analysis using 4 kinds of different scenarios. Because it is difficult to analyze all materials input to society, this study focuses only on steel consumption. There are two reasons why steel is chosen as the representative material. One is that steel is an essential material in many industries since it is used in construction, machine, and transport equipment and so on. The other is that the changes in the structure of steel consumption could have large multiplied effects on the whole of industry since the steel industry has many downstream firms. We compare 4 scenarios for energy consumption GHG emissions, steel consumption and production, and GHG emission price. We differentiate 4 scenarios by using two axes, namely, the GHG emission constraint on/off and improvement in steel consumption intensity on/off. Here, we review the related literature. Although there are many previous studies that have analyzed global GHG emission and the cost of its mitigation so far, they have rarely taken into account such dematerialization. For instance, as is mentioned above, the special issue including Clarke et al. [3] compiles 10 model group results. They are categorized into two types of models; bottom-up and topdown. In terms of the bottom-up model, the IMAGE model (van Vliet et al. [20] takes into account decreases in material intensity. However, the others do not explicitly consider such a decrease of material usage. On the other hand, the topdown model (Blanford et al. [1]; Calvin et al. [2] and so on) has not taken into account decrease of material intensity. Focusing on the steel supply and demand analysis using a CGE model, Schumacher and Sands [14] could be pioneers of this kind of analysis. They disaggregate the steel sector by the process of the steel making and they showed mass of steel supply, demand and price up to 2050 in Germany. The Schumacher and Sands study describes the production side in detail but not demand side. Thus, this study integrates the new aspects into climate mitigation analysis especially for the global CGE model with a change in steel demand structure. The next section presents the overall method used for this analysis. Section 3 contains the results of the application of the method, while section 4 shows a sensitivity analysis for improvement in steel consumption intensity. Section 5 discusses uncertainties underlying the model and the assumptions. Finally, this paper is concluded in section 6.

2 Methodology 2.1 Overview of the method An overview of the methodology is shown in Figure 1. Four scenarios, called scenario A, B, C and D, were prepared. Scenario A is what we call the business as usual case and it has no GHG emission constraint or steel consumption WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

318 Energy and Sustainability III Scenarios BaU (Scenario A)

GHG emission constraint (Scenario B)

steel intensity decrease (Scenario C)

GHG emission constraint steel intensity decrease (Scenario D)

Figure 1:

Global CGE model

Energy consumption CO2 emissions Steel consumption Marginal abatement cost

Overview of the method.

structure change. Scenario B includes the GHG emission constraint from scenario A. Scenario C contains steel consumption structure change. Scenario D considers both of them. Secondly, a global CGE model is developed and applies to these scenarios. This CGE model is a dynamic recursive general equilibrium model that covers the whole world. To analyze climate mitigation and its technological change, the power sector is disaggregated in very detailed levels (14 sectors). The CGE model has the advantage that it can consistently simulate the whole social economic activity. This implies that when some sort of structural change occurs in a sector the multiplied effect can be analyzed with consistency. This study focuses mainly on steel consumption, energy consumption, GHG emission and GHG emission price. First the CGE model is explained, next the main assumptions made for the 4 scenarios, and finally the scenarios themselves are described in detail. 2.2 CGE model This CGE model is a dynamic recursive general equilibrium model that includes multi-regions and multi-sectors. The calculation time step is one year. The classifications of regions and sectors are shown in Table 1 and Table 2. The region classification is based on geographical regions. However, China and India are separated since they will play an important role in the world economy. There are 36 industrial classifications but half are energy sectors. The calibration data is Fujimori and Matsuoka (forthcoming) [7]. This database consists of world social accounting matrices and energy balance tables which are calculated using international industrial statistics (OECD[13]; IISI [10] etc), trade statistics (UN [16]), national accounts (UN [15]), energy statistics (IEA [9]) and Input-output tables (Dimaranan [5]; OECD [12]). The actors in the CGE model decide their production, consumption, investment and trade activities using their own behavioural functions and market prices. The whole model structure is shown in Figure 2. There are four blocks: production, income distribution, final consumption, and market. The first block, production, represents the structure of the Table 1:

Region classification.

XE25

Central & CIS South America EU XME

Former Soviet Union Middle East

North America XER

Rest of Europe XAF

Africa

XOC

Oceania

IND

India

XLM

JPN

Japan

XSA

Rest of Asia

CHN

China

XNA

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

Table 2:

Industry classification.

Non-energy sectors(17) AGR

Energy Sector (19)

Agriculture

COA

Coal mining

FRS

Forestry

OIL

Oil mining

OMN

Mineral mining and Other quarrying

GAS

Gas mining

FPR

Food products

P_C

Petroleum and coal refinery

TEX

Textiles and Apparel and Leather

E_COL

Coal-fired without CCS

LUM

Wood products

E_GAS

Oil-fired without CCS

PPP

Paper, Paper products and Pulp

E_OIL

Gas-fired without CCS

CRP

Chemical, Plastic and Rubber products

EC_COL

Coal-fired with CCS

NMM

Mineral products nec

EC_GAS

Oil-fired with CCS

I_S

Iron and Steel

EC_OIL

Gas-fired with CCS

NFM

Non Ferrous products

E_HYD

hydroelectric power

MCH

Machinery

E_NUC

nuclear electric power

TRN

Transport equipment

E_SPV

photovoltaic power

OMF

Other Manufacturing

E_WIN

wind-power

CNS

Construction

E_GEO

geothermal power

TRS

Transport and communications

E_BIO

biomass-power without CCS

CSS

Service sector

EC_BIO

biomass-power with CCS

E_ORN

other renewable energy power

GDT

Gas manufacture distribution

Production block

Energy and value added bundle =0.4 Energy Value added aggregate =0.8 Fossil fuel

Capital

Market block

output

Resource

Labor

=0 Intermediate inputs =0

Domestic supply

goods Import

electricity

Domestic consumption

gas

Final consumption block

Tax on products

Income

Household Tax

Enterprise Tax

Government

Income distribution block

Gross Saving

Figure 2:

Export

=0.5

=1.0 solid liquid

Land

319

Household Expenditure Government Expenditure

Capital Formation

Goods Goods Goods Goods Goods Goods

CGE model structure.

production functions. We apply a nested CES function for production activities with multiple nested CES functions. The output requires natural resource, intermediate inputs, of non-energy goods as determined by fixed coefficients, and an energy-value added bundle. The energy and value-added bundle is nested by value added and energy aggregation. Value added is composed of capital, labour and land inputs. On the other hand energy aggregation is firstly composed WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

320 Energy and Sustainability III of fossil fuel and electricity. The fossil fuel is again nested according to three types of fuel. The elasticity of the CES functions is shown in the figure. Needless to say, the fossil fuels combustion produces CO2 emission as follows. Second, incomes are distributed to three institutional sectors; namely, enterprises, government, and households. The government takes in income by collecting taxes. Third, institutions consume goods as final consumption. Government expenditure and capital formation are defined as a constant coefficient function. The LES (Linear Expenditure System) function is used for household consumption. Lastly, the CES function is applied to the import of goods and the CET function is applied to the export of goods. A goodsconsumption-and-supply equilibrium is achieved for each market. 2.3 Assumptions Some future scenario assumptions are included in all 4 scenarios. In this section, we show population, labour force, GDP growth rate, AEEI (Autonomous Energy Efficiency Improvement), and productivity improvement. 2.3.1 Population, labour force, GDP ans AEEI Labour force, which is one of the production factors, is assumed to be proportional to population change. The medium estimation of UN population prospects (UN [17]) is used for the future population change. The GDP growth rate is shown in Table 3. We use AEEI as Table 4. Table 3: 2005-2010 2010-2020 2020-2030 2030-2040 2040-2050

Annual growth rate of GDP for each region.

XOC JPN CHN IND XSA XNA XLM XE25 XER CIS XME XAF World 3.3 0.4 5.9 5.0 4.7 2.5 2.7 1.8 2.0 3.5 3.4 2.9 3.2 2.4 0.2 6.6 5.4 4.4 2.0 3.1 1.6 1.8 3.4 4.6 3.6 3.7 1.8 0.3 6.7 5.5 3.6 1.9 3.3 1.3 1.8 2.7 4.6 4.1 4.1 1.5 0.1 5.1 5.2 2.8 1.4 3.1 1.1 1.8 2.3 3.4 4.4 3.6 1.1 0.2 2.9 5.0 2.1 1.0 2.7 0.8 1.6 2.0 3.0 4.2 2.6

Table 4: Region Annual growth rate(%)

AEEI annual change rate.

XNA EU25 JPN XOC CHN IND Other regions 1.21 1.30 1.98 1.43 1.21

2.3.2 Productivity improvement The productivity of each industry is calculated by dynamical calibration. In other words, the efficiency parameter of CES function of a value-added bundle is estimated dynamically year by year. When we calculate a year, we have the next years expected GDP targets, labour inputs and capital stocks. To achieve the GDP targets, we re-calculate the efficiency parameter as follows. The CES function of a value-added bundle is defined as QVAr , a

     r , a     r , a  QFr , f , a r ,a   f F 



1

r , a

,

r  R, a  A

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

(1)

Energy and Sustainability III

321

QVAr,a: quantity of (aggregate) value-added, QF r,f,a: quantity demanded of factor f from activity a,  r,a: efficiency parameter in the CES value-added function,  r,a: CES value-added function share parameter for factor f in activity a,  r,a: CES value-added function exponent, and R, F and A denote region, factor and sectors for each. There is expected growth rate of the value added, and we can calculate the revised efficiency parameter  r,a* as  r , a  QVA  ggr *

t 1 r ,a

t* r

 t 1 t    r , a   QFr , f , a  fgrr , f f F  



 r ,a

  



1

 r ,a

, r  R, a  AC

(2)

 rva, a : revised efficiency parameter in the CES value-added function, ggrrt * : *

expected GDP growth target (annual growth rate),

fgrrt, f

: expected factor input

growth rate, t denotes set of year. 2.4 Scenario description As is already shown, this study applies 4 scenarios. Scenario A is the business as usual case and it only considers the assumptions explained in the previous section. Scenario B has a CO2 emission constraint. In this study, we selected the CO2 emission constraint as 550 ppm CO2 equivalent concentration stabilization. Generally, climate mitigation model studies often analyze 450 and 550 ppm concentration stabilization. However, Clarke et al. [3] showed 450 ppm was achievable only by a few studies but most declared it was impossible. Therefore, we think that the 550 ppm scenario is comparatively more realistic than the 450ppm scenario. Although we set the stabilization target, there was still the problem that the stabilization pathway could not be determined to be unique only with that stabilization target. Therefore, we borrowed the pathway from Hijioka et al. [8]. Moreover, in this study we take into account only CO2 emissions from fossil fuel as GHG emission. A concrete pathway is shown in a latter section along with a graph. Scenario C considers improvement in steel consumption intensity but not the CO2 emission constraint. The term improvement in steel consumption intensity is defined as steel consumption per unit production for each industry in this study. Scenario D implements both improvement in steel consumption intensity and the CO2 emission constraint. In order to answer the primary question, the main focus should be on the comparison between scenario B and D. When the emission reduction cost is compared between them, we can see how the dematerialization contributes to the CO2 emission reduction. The CGE model calculates the CO2 emission reduction cost like carbon tax. The higher the emission cost is, the larger the burden of the mitigation becomes. The improvement in steel consumption intensity is assumed to be the industrial sector’s intermediate input coefficient decreasing constantly from 2010. The annual decrease rate is assumed as below. We only consider this

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

322 Energy and Sustainability III Table 5:

Annual steel consumption intensity improvement (%). Machinery Transport equipment Construction

MCH

TRN

CNS

5.9

3.5

2.1

6 5

y = 6.2788e ‐0.059x R² = 0.975

4 3 2 1 0

1970 1975 1980 1985 1990 1995 2000

Machinery (a) Figure 3:

3 2.5 2 1.5 1 0.5 0

Steel consuumption Intensity (2000=1)

7

Steel consuumption Intensity (2000=1)

Steel consuumption Intensity (2000=1)

intensity improvement for machinery, transport equipment and construction sectors since they represent most of the demand for steel. These improvement rates come from Japan’s numerical evidence from Committee on iron and steel statistics [4] and STAN Database (OECD [13]). The Committee on iron and steel statistics [4] contain steel order volume for each sector and the STAN Database (OECD[13]) has industrial output indexes. The steel consumption per unit production was then plotted as in Figure 3. Each industry experienced improvement in steel consumption intensity over the past three decades. This decrease is probably due to the substitution of steel with other materials such as plastics. However, we could not confirm that substitution with the evidence so far. Thus, we assume that the decrease in steel use would be homogenously replaced by the other material inputs. Technically this means that we did not change the production structure but did change the parameters of intermediate inputs.

y = 2.5095e ‐0.035x R² = 0.9193

2 1.5 1 y = 1.529e ‐0.021x R² = 0.7712

0.5 0

1970 1975 1980 1985 1990 1995 2000

Transport equipment (b)

1970 1975 1980 1985 1990 1995 2000

Construction (c)

Japan’s improvement in steel consumption intensity.

3 Results 3.1 Steel sector production, energy consumption and CO2 emission Global steel production is compared among 4 scenarios (Figure 4(a)). Scenario A and B (without improvement in steel intensity) shows similar trajectory as do scenario C and D (with improvement in steel intensity). The former two scenarios are quite different from the latter. This implies that steel production is affected not so much by CO2 emission control but by the assumption of improvement in steel consumption intensity. Looking at the regional breakdown in scenario D (Figure 4(b)), you can see that China dominates steel production and this tendency is more apparent in 2050. India also increases its world share by 2050. WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

323

Next, the steel sector’s energy consumption and CO2 emission are shown (Figure 5). These two graphs show similar trajectories. The CO2 constrained cases (scenario B and D) are comparatively lower than the CO2 free cases (scenario A and C). There is an interesting point in that scenario A and scenario B will be quite different by 2050 but steel production is almost same. This is due to the energy price increase coming from the CO2 emission cost and substitution of the energy for other production factors such as capital. 7000 Scenario A Scenario B

5000

Scenario C

4000

Scenario D

million t/yr

million t/yr

6000

3000 2000

1800

XAF

1600

XME

1400

CIS

1200

XER EU25

1000

XLM

800

XNA

600

XSA

400

1000

200

0

0

IND CHN JPN XOC

Steel production by scenarios (a) Steel production of scenario D by region (b)

Energy consumption (a) Figure 5:

2050

2045

2040

2035

2030

2050

2045

2040

2035

2030

2025

2020

2015

2010

2005

0

2025

200

2020

400

2015

600

1800 1600 1400 1200 1000 800 600 400 200 0

2010

800

Mtoe/yr

Scenario A Scenario B Scenario C Scenario D

1000

Mtoe/yr

Steel production.

2005

Figure 4:

CO2 emission (b)

Steel sector energy consumption and CO2 emission.

3.2 CO2 emission Next CO2 emission is analyzed. Figure 6 (a) shows the pathway of global CO2 emissions. Scenario B and D are same since they have to satisfy the exogenous CO2 emission constraint pathway. In 2050, 550 ppm stabilization scenarios are supposed to achieve around a 25% emission reduction compared to 2005. Looking at scenarios A and C, scenario C shows a reduction a little bit lower than scenario A (4% lower in 2050). Figure 6(b) shows this reduction by regions. As you can easily see, China’s reduction is very large. WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

324 Energy and Sustainability III 3.3 CO2 emission price

4

50 45 40 35 30 25 20 15 10 5 0

3.5

Mtoe/yr

3

Scenario A Scenario B, D Scenario C

1

ScenarioB ScenarioC ScenarioD

2050

2045

2040

2035

2030

2025

2020

2015

2010

2005

XAF XME CIS XER XE25 XLM XNA XSA IND CHN JPN XOC

CO2 reduction of scenario C (b) CO2 emission. CO2emissionprice (US2005$/tCO2)

ScenarioA

2050

2045

2040

2035

2030

2025

2020

2015

2010

Figure 6:

2005US$/tCO2

2 1.5 0.5

Global CO2 emission (a) 500 450 400 350 300 250 200 150 100 50 0

2.5

0

2005

GtCO2/yr

As already explained, the CGE model gives us a CO2 emission price like a carbon tax. Figure 7(a) shows the CO2 emission price of the CO2 constrained scenarios (scenario B and D). Scenario D’s CO2 emission price would be 376 (2005US$/tCO2) in 2050. On the other hand scenario B shows 433 (2005US$/tCO2) for the same time. It equals a 13% price reduction. Moreover, scenario C is consistently lower priced than scenario B in time-series. This means that the dematerialization does certainly contribute to the low carbon society, though the CO2 emission price is still high.

420 410 400 390 380 370 360 350

Scenario D

0.0

0.5

1.0

1.5

2.0

Factor

(a) Comparison of scenarios Figure 7:

(b) sensitivity analysis CO2 emission price.

3.4 Sensitivity analysis The rate of improvement in steel intensity is set with a large assumption because we now only have the information for Japan’s case. Thus, we control the improvement in intensity rate from half to twice the rate in Table 5 for scenario D. Figure 7(b) represents the sensitivity analysis results. This graph has factors of 1/2 to 2 on the horizontal axis and the CO2 emission price in 2050 on vertical axis. As is shown in this figure, CO2 emission price decreases as the increase in the improvement rate. However, the CO2 emission price decrease slows down. This implies that even if we could achieve more intensive dematerialization, the difficulties of CO2 emission reduction would not change so much. WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

325

4 Discussions There are 4 points we would like to discuss with regard to the uncertainties and limitations of this study. Firstly, we implemented a bold assumption in improvement of steel consumption intensity as mentioned in the previous section. We obtained the improvement rate from Japan’s sample and applied it to the other regions. Although we checked the sensitivity of the assumption, we could not depict that for regional differences. This is one of the uncertainties in this study. If we could obtain such information for developing countries it would greatly contribute to the reduction of this uncertainty. We leave this work for the future study. Secondly, this study only treats energy oriented CO2 as GHG because we want to know the direct reaction of the CO2 emission change from fossil fuel combustion. However, this energy related CO2 emission is only 60% of all GHG emission, so if other gases are considered, the results would be a little different. Thirdly, the CGE is a top-down model and steel demand is represented as an input-output coefficient. On the other hand a bottom-up study could represent a more concrete steel demand and give different results. Finally, this study chose steel as an indicator of the dematerialization. Although steel is an essential material, society is actually sustained by various materials other than steel. The real term of dematerialization should be discussed with reference to such other materials.

5 Conclusion This study describes one of the aspects of a dematerialized society and low carbon society with using a global CGE model and showed that dematerialized society can quantitatively contribute to a low carbon society. It considers a scenario stabilizing at a concentration of 550 ppm CO2 by 2050, and takes into account an improvement in steel consumption intensity. Assuming Japan’s past improvement in steel intensity extends over the next 4 decades, the CO2 price could reduce by 13%. However, the improvement in intensity effect would slow down, even if we see stronger improvement in steel intensity. Therefore, dematerialization contributes to low carbon society to a certain extent but still there seems to be difficulties in achieving large CO2 emission reductions. Although this study includes a large amount of uncertainty and limitations, we could demonstrate an interesting dimension in terms of sustainable development. This study can be a guide for future research.

References [1] Blanford, G.J., Richels, R.G. & Rutherford, T.F., Feasible climate targets: the roles of economic growth, coalition development and expectations. Energy Economics 31, ppS82-S93, 2009 [2] Calvin, K., Patel, P., Fawcett, A., Clarke, L., Fisher-Vanden, K., Edmonds, J., Kim, S.H., Sands, R. & Wise, M., The distribution and magnitude of emissions mitigation costs in climate stabilization under less than perfect international cooperation: SGM results, Energy Economics, 31, pp.S187S197, 2009. WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

326 Energy and Sustainability III [3] Clarke L., Edmonds J., Krey V., Richels R., Rose S. & Tavoni M., International climate policy architectures: Overview of the EMF 22 International Scenarios, Energy Economics, 31, pp.S64-S81, 2009. [4] Committee on iron and steel statistics, Handbook for iron and steel statistics, Commitee on iron and steel statistics, 2006. [5] Dimaranan, B.V., Global Trade, Assistance, and Production: The GTAP 6 Data Base. Center for Global Trade Analysis, Purdue University, 2006. [6] Fujimori S. & Matsuoka Y., Development of estimating method of global carbon, nitrogen, and phosphorus flows caused by human activity, 62(3-4), pp399-418, 2007. [7] Fujimori S. & Matsuoka Y., Integration of economic and energy information for global economic and energy model simulation, forthcoming. [8] Hijioka Y., Matsuoka Y., Nishimoto H., Masui T. & Kainuma M., Global GHG emission scenarios under GHG concentration stabilization targets. J. Global Environ. Eng., 13, pp.97-108, 2008 [9] International Energy Agency (IEA), Energy balances for OECD countries, International Energy Agency, Paris, France, 2009. [10] International Iron and Steel Institute (IISI), Steel Statistical Yearbook, IISI, 2009. [11] Matthews E., Bringezu S., Fischer-Kowalski M., Huetller W., Kleijn R., Moriguchi Y., Ottke C., Rodenburg E., Rogich D., Schandl H., Schuetz H., van der Voet E. & Weisz H., The Weight of Nations, Material Outflows from Industrial Economies, World Resources Institute, Washington, 2000. [12] Organization for Economic Co-operation and Development (OECD), Inputoutput tables, OECD, Paris, France, 2010. [13] Organization for Economic Co-operation and Development (OECD), STAN Database for Structural Analysis, OECD, Paris, France, 2005. [14] Schumacher K. & Sands R.D., Where are the industrial technologies in energy-economy models? An innovative CGE approach for steel production in Germany [15] United Nations (UN), National Accounts Main Aggregates Database, New York, USA, 2007. [16] United Nations (UN), United Nations Commodity Trade Statistics Database, United Nations, New York, USA, 2006. [17] United Nations (UN), World Population Prospects: 2008 Revision Population Database, United Nations, New York, USA, 2007. [18] van der Voet E., van Oers L. & Nikolic I., Dematerialization: Not Just a Matter of Weight, Journal of Industrial Ecology, 8(4), pp.121-137, 2004. [19] van Vliet, J., den Elzen, M.G.J. & van Vuuren, D.P., Meeting radiative forcing targets under delayed participation. Energy Economics 31, pp.S152S162, 2009. [20] von Weizsaecker, E., Lovins A. B., & L. H. Lovins., Factor four, doubling wealth, halving resource use. The new report to the Club of Rome. London: Earthscan Publications, 1997.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

327

Recovery of combustible matter from waste fine Chinese coals by a waste vegetable oil agglomerating process and its combustion characteristics Q. Wang, N. Kashiwagi, P. Apaer, Q. Chen, Y. Wang, T. Maezono & D. Niida Department of Environmental Science and Technology, Graduate School of Science and Engineering, Saitama University, Japan

Abstract Coal production increases continuously due to the development of mechanization in coal mining and demand in its related fields of application worldwide. Especially, coal production in China is increasing and a large amount of waste fine coals (<0.5 mm) which are difficult to be cleaned. Waste fine coals usually contain large amounts of ash contents and inorganic sulfur contents due to the mechanical coal mining of low grade coals. Therefore, waste fine coals are unavailable as energy resources, spontaneous combustion leading in turn to air pollution because of their coal content and small size which increases the surface area liable to be wet and oxidized, and occupation of disposal land which is also lead soil and water contamination. In this study, a waste vegetable oil agglomerating process was approached for coal combustible matter recovery from Chongqing Nantong waste fine coals in China. The oil agglomerating process had usually been developed by mineral oil (such as kerosene) of exhaustible resource. Therefore, in this study, simulated waste vegetable oils are selected as oil agglutinative agents because the waste vegetable oils which are recycled, renewable, and less polluting energy resources from the point of view of effective utilization of waste coal and on the cost front. However, waste vegetable oils have the possibility of influence on the coal cleaning efficiency, because the waste vegetable oils may be changed in the surface property and viscosity by different kinds of vegetable oils and chemical structure with the usage environment. Therefore, in the study, cleaning coal WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESUS110281

328 Energy and Sustainability III efficiency of oil agglomeration was investigated when simulated waste vegetable oil (heating of colza oil) was used as an agglutinative agent. The effects of parameters including the viscosity and chemical structure were investigated based on the combustible matter recovery, ash reduction and efficiency index. Furthermore, combustion characteristics of combustible matter were determined with ignition temperature and burning behavior by TG-DTA. It can be concluded that the viscosity, types of vegetable oils, heating time and frying time of waste vegetable oils with the usage environment will influence the coal cleaning efficiency. Keywords: waste fine coal, waste vegetable oil, renewable energy, oil agglomerating process, China.

1 Introduction The primary energy consumption expands, because it is thought to be an increase in the future by improving the living standard in the world [1]. The recoverable coal reserves are estimated that about 847.5 billion tons [2] and the reserveproduction ratios of coal are 133 years [2]. It is thought that coal will be important energy because it is excellent in the stability of supply and the economy than other fossil fuels, because there is no eccentrically-located. However, large amount of waste fine coal (< 500 m) is produced by mechanizing the coal preparation process and mining. Because of the pulverized coal with the small particle sizes in diameter, the handling of waste fine coals is difficult, which contained a lot of minerals and the calorific value is low [3, 4]. The utility value as an energy resource is scarce, thus the a lot waste fine coals have been discarding. However, combustible matter is still contained in waste fine coals, it is discards risk of spontaneous combustion, additionally it causes land occupation, air pollution, and water pollution and land occupation. Especially in China, waste fine coal of production has grown in quantity and this problem has become aggravated. Then, it is needed coal clean technology in order that recovery of combustible matter from waste fine coals for reduction of environmental burdens and application of unused resources. Oil agglomeration in wet processes has been also found to be one approach of the effective methods for separating the combustible matter (organic and carbonaceous contents) from mineral matter (ash contents) of waste fine coals. The oil agglomerating process apply the different surface properties of combustible organic matter and mineral matter in raw coals to coal cleaning technique, separation of coal from mineral matter is achieved due to differences in the surface hydrophobic properties of the organic coal and inorganic ash contents of coal samples. The principle of a vegetable oil agglomerating process is shown in figure 1. In the past, mineral oil (kerosene) from exhaustible resource has used oil agglomeration. However, the vegetable oils have been selected as oil agglutinative agents in our previous study [5] because the vegetable oils which are renewable, available and less-polluting energy resources. Furthermore, in this

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III Ash contents (Hydrophilic)

Agglomeration

Agitation

Separation

Agitation

Oil addition (Flocculant)

Coal

329

Combustible matter Oil droplet attach to coal

Sieve

Screening

(Hydrophobic) In this study, waste vegetable oil is used as the agglutinative agents instead of fresh vegetable oil and kerosene etc.

Figure 1:

Ash contents

Principle and concept of a vegetable oil agglomerating process for waste fine coal cleaning.

study, we try to use the waste vegetable oils such as colza oil as the agglutinative agents instead of their original fresh vegetable oils. However, waste vegetable oils have the possibility of influence on the coal cleaning efficiency, because the waste vegetable oils may be changed in the surface property and viscosity by different kinds of vegetable oils and chemical structure with the usage environment. Especially, in the food processing, vegetable oils are heated at about 180 °C, as the results, polar molecules could be produced from the degraded products of its original vegetable oil. Therefore, these products may be show different agglomeration behavior since agglutinative agents between ash particles and oil droplets which possibly show a hydrophilic behavior and probably induce some effects on oil agglomeration. The main object of this work is to recovery of combustible matter more efficiency by a waste vegetable oil agglomeration, thus chemical structure and property of vegetable oil, thus, a wide range of oil alteration grades and therefore, of oil properties, such as viscosity and unsaturated carbonaceous bonds by the oxidation processes in the used waste vegetable oils were investigated. Structural changes and unsaturated carbonaceous functional groups in the colza oils were monitored by a Fourier-transform infrared (FTIR) method. Oil agglomeration efficiency was evaluated by measuring the recovery of combustible matter, ash reduction and efficiency index. Furthermore, combustion characteristics of combustible matter were determined with ignition temperature and burning behavior by TG-DTA.

2 Materials and experimental methods 2.1 Waste fine coal samples In this study, the samples of waste fine coals were selected and collected from Chongqing Nantong coal mining in the south-eastern China. Before our experiments, the coal samples were prepared below a 75 m by sieve. The proximate and ultimate analyses of coal samples were measurement according to the Japanese industrial standard (JIS) method of JIS-M8812.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

330 Energy and Sustainability III 2.2 Experiment of oil agglomeration for waste fine coal cleaning Schematic diagram of a procedure of oil agglomeration is given in figure 2, and experimental conditions are shown in table 1. The oil agglomeration experiments were carried out in a 500 mL beaker. The products of the two simultaneous agglomeration experiments were poured into the beaker and mixed, followed by the separation of the agglomerates as clean coals. The agglomerates were filtered, dried overnight at the room temperature, washed with ethanol and diethyl ether to extract the residual oil, dried at room temperature, and analyzed for ash content in each clean coal. As the results, the resultant agglomeration products were separated from the mineral matter (ash) in waste fine coals below 75 m. Actually, on the industrial application, we should say that the solvent washing step of the agglomerates would not be necessary and the coal/waste vegetable oil agglomerates could be used directly as fuel because of the lesspollutants in the waste vegetable oils.

Figure 2:

Schematic diagram agglomeration.

Table 1:

of

coal

cleaning

procedure

Experimental conditions of oil agglomeration.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

of

oil

Energy and Sustainability III

331

2.3 Preparation of waste vegetable oil samples 2.3.1 Preparation of the simulated waste vegetable oil samples With a point of view for effective utilization of waste vegetable oil, it was necessary to use waste vegetable oil in the experiment of oil agglomeration. Therefore, it is necessary to prepare different waste vegetable oils when viscosity and chemical structures changed with the different cooking time and conditions. In the case of heated-treated oil, carbonyl compound and carboxylic acid degraded products of oils may be advanced. These products are hydrophilic behavior, as the results, there may be an adverse effect for efficiency of clean coal during the oil agglomerating process, because these products are effective like cross-linker between combustible matter and ash contents. Therefore, for preparing the waste vegetable oils, a commercial colza sample oil was poured into metallic pot about 1.0 L and heated at 180°C for 24 h by an electric hot plate during 5 days heating experiment period. The simulated waste vegetable oil samples in different heated-treated days were used as the coal agglomerating agents in this work to check the availableness and capability of the waste vegetable oil agglomeration. The simulated waste colza oil samples heated each day was cooled at the room temperature and restored till experiments of oil agglomeration. 2.4 Identification for chemical structure change in simulated waste colza oil samples by a FT-IR In order to find changes in chemical structure of waste vegetable oil samples mentioned in section 2.3 based on the Fourier-transform infrared (FTIR) technology, the infrared spectra were recorded using a Model IR-6100 (JASCO Corporation, Japan) interfaced to a personal computer operating with Windowsbased Spectra manager (Version 2). A film of the oil sample was placed between two disks of NaCl. This study is used disk path length of NaCl cells of 0.1 mm. The spectra were recorded from 4000 cm-1 to 400 cm-1, the number of scans being 256 at a resolution of 4 cm-1. A simulated waste vegetable oil diluted with CCl4 by 1/100 M. 2.5 Measurement of the colza oil viscosity A viscometer (Model VT-04F, RION Co. Ltd., Japan) was used to measure the viscosity of the oils. In this procedure, a disk/spindle is submerged in the oil and the force which is necessary to overcome the resistance of the viscosity to the rotation is measured. The viscosity value (dPas) of the testing solution is automatically calculated on the basis of the speed and the geometry of the spindle. According to previous vegetable oil viscosity values which were determined basing on the Japanese industrial standard (JIS) method of JISZ8803, a spindle speed of 62.5 rpm was chosen in this work to carry out the measurements.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

332 Energy and Sustainability III 2.6 Evaluation of coal cleaning efficiencies by the waste vegetable oil agglomerating process The efficiencies of coal cleaning were calculated by the mass percentages (wt%) of combustible matter recovery (CMR), ash reduction (AR) and efficiency index (EI) from ash content in clean coal [6]. These parameters can be calculated as the following equations (1)–(3).

CMR  100 

CMagglom( wt %)  wtagglom(g ) CMfeed( wt %)  wtfeed(g)

(1)

 Ashagglom ( wt %)  Ashagglom(g )  AR  100  1  CMfeed( wt %)  wtfeed(g )  

(2)

EI  CMR  AR

(3)

Here, CM (combustible matter) is calculated as 100-(ash contents), agglom is the weight of agglomeration, feed is the weight of coal samples, and wt gives as the weight unit (g), respectively. 2.7 Evaluation of combustion characteristics of combustible matter The thermogravimetric/differential thermal analysis (TG/DTA) measured combustion characteristics of recovery combustible matter which is ignition temperature and behavior. In all the experiments, 3.5–4.0 mg of sample were heated at 15 °C/min from room temperature to 750 °C. A gas flow rate of 50– 60 mL/min was used; clean gas used as the carrier gas for combustion. The combustion characteristics of oil agglomerates which were not washed by solvent, waste fine coal and standard coal were measured, respectively.

3 Results and discussions 3.1 Changing tendency in viscosity of the simulated waste vegetable oils The changing tendency in the viscosity of waste vegetable oils when the heating time changed shown in figure 3. The viscosity of simulated waste colza oil was greatly increased with heating time after 3 days. This is due to increment of viscosity with the oxidized compound formation of oxygen-containing group and polymerization of triglyceride. 3.2 Effect of viscosity on the performance of CMR and AR CMR and AR was investigated effect of changed viscosity of waste vegetable oil. The results of proximate and ultimate analysis of used waste fine coal for experiment are shown in table 2. WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

333

Viscosity (dPas)

40

30

20

10

0 0

Figure 3: Table 2:

1

2

Days

3

4

5

Viscosity of simulated waste colza oil.

Results of proximate analysis and ultimate analysis (coal particle sizes: <75 m).

VM: Volatile matter, FC: Fixed carbon Figure 4 shows that effect of viscosity on oil agglomeration performance. As can be seen, when the viscosity of waste vegetable oil increased, CMR was increased and most high value at 3.9 dPas. However, an excessive increase in viscosity was drastically decreased CMR. Because of tack strength was increased by more intense intermolecular force, CMR was high value. But, waste vegetable oil for excessive increased viscosity cannot be scattered in a suspension because CMR was drastically decreased. Therefore, if viscosity of waste vegetable oil is too high value, oil agglomeration cannot be performed. 100 90 80 CMR, AR (%)

70 60 50 40 CMR AR

30 20 10 0 0.1

1

10

100

Viscosity(dPas)

Figure 4:

Effect of viscosity on the performance of CMR and AR.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

334 Energy and Sustainability III On the other hand, AR value was decreased when waste vegetable oil was increased. Because of polar molecular was formed, constitutive part of vegetable oil of molecular changed micelle. Therefore, micelle showed the effect of crosslinking agent upon ash. 3.3 Effect of viscosity on the performance of EI The effect for oil agglomeration performance due to changing in the viscosity of the simulated waste vegetable oils was given in figure 5. The highest EI value with the best oil agglomeration performance by the simulated waste vegetable oil was at 3.9 dPas, in contrast, poor oil agglomeration performance with the lowest EI value was at 30 dPas of the viscosity. For this reason, it is possible that waste vegetable oils can be applicable to oil agglomerating process. However, the oil agglomeration performance seems to be influenced by the quality (viscosity) of waste vegetable oils. It is thought that it is unfavorable to use waste vegetable oil more than 4 dPas in its viscosity because it became inefficient. 150

140

EI

130

120 110

100 0.1

1

10

100

Viscosity (dPas)

Figure 5:

Effect of viscosity on the performance of EI.

3.4 Some chemical structures influenced on oil agglomeration The FTIR technology has been commonly used for the structural identification or qualitative determination of the fingerprint of organic compounds, because some groups of atoms display the specific characteristic vibrational absorption frequencies in this infrared region of the electromagnetic spectrum [7]. Spectra in the mid-infrared region have well resolved bands that can be assigned to functional groups of the components of the oil samples. The exact location of the corresponding bands depends on the influence of the rest of the molecule. The infrared absorption frequencies characteristic of functional groups afford a useful and valuable tool for the chemical structural elucidation of waste vegetable oil was investigated by a FT-IR. The analytical evaluation of the colza oil spectra is given in table 3 [8]. WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

335

The spectra of oil samples stretching vibration of the CH stretching vibration of the cis-double bond and ester carbonyl functional group of the triglycerides shown in figure 6 and figure 7. In the heating experiments, colza oil was heated for 5 days at 180 °C and the changes in the FT-IR spectra were observed. As can be seen in figure 6, this absorbance of spectra bands at 2928 and 2856 cm-1and the shoulders at 2962 cm-1 increase their intensity, but the bands at 3008 cm-1 decreased absorbance. Increment of the heating time may induce to increase the band width of absorbance. A shoulder at 2872 cm-1 is also formed attributed to the production of CH3 groups, on another front, figure 7 shown that the band at 1725 cm-1 present aldehyde and other secondary oxidation compounds (e.g. ketone) with which the maximum absorbance of aldehyde is at 1725 cm-1 and that of ketone is 1715 cm-1 in the spectra. Table 3:

Functional groups and modes of vibration in the FT-IR of oil.

Frequency (cm-1)

Functional group assignment

3008

CH stretching vibration of the cis-double bond ( =C-H)

2928 and 2856

Symmetric and asymmetric stretching vibration of the aliphatic CH2 group

2962, 2872

Symmetric and asymmetric stretching vibration shoulder of the aliphatic CH3 group

1746

Ester carbonyl functional group of the triglycerides

1711

Free fatty acids shoulder

0.3 0.25 －CH2－

Absorbance

0.2

Original 1st days 3rd days 5th days

0.15 0.1

=CH－

0.05 0 3050

3000

2950

2900

2850

2800

2750

Wavenumber (cm-1)

Figure 6:

FT-IR spectra (3050–2750 cm-1) of oil samples heated at 180°C for 0–5 days after.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

336 Energy and Sustainability III

Figure 7:

FT-IR spectra (1800–1650 cm-1) of oil samples heated at 180°C for 0–5 days after.

3.5 Investigation of combustible characteristics by a TG-DTA The evaluation of combustion characteristics of waste fine coal, aggregate (original fresh colza oil and heated oils for 3 days) and standard coal were investigated with the analysis of the TG/DTA. As it has been seen in figure 8, the temperature range from the beginning of the tests up to the ignition temperature can determine the initial heating, release of volatile matters and combustion behavior. At the ignition points of each coal samples, a sharp exothermic peak is observed due to the combustion process. The each coal presents the first endothermic peak at around 100°C due to the loss of moisture [9]. For waste fine coal and clean coal by the original fresh colza oil agglomeration, different peaks can be determined by the TG/DTA. The ignition temperature of standard coal was around 520 °C whereas lower ignition temperature of clean coals by colza oil agglomeration. And ignition temperature of its clean coal was lower than standard coal (c) about 50 °C. The clean coal of original oil (b) presented some peak which may be due to vegetable oil and waste coal (d) separately burned. On the other hand, it can be coinstantaneously burned for clean coal by colza oil agglomeration of which the oil has been heated for 3 days after (a). These results show that it is possible that waste vegetable oil agglomeration can be better combustion characteristics than its original coal. As mentioned in section 3.3 before, since the highest EI value with the best oil agglomeration performance by the simulated waste vegetable oil was at 3.9 dPas, it was improved combustible characteristics of recovery from its original waste fine coals. If we can select the optimized conditions for waste colza oil agglomerating process, the waste vegetable oil could be applied on the industrial oil agglomerating process of Chinese waste fine coals.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

Figure 8:

337

Combustion characteristics of different coal samples after or before the oil agglomerating processes: a) clean coal by oil agglomeration with heated colza oil for 3 days, b) clean coal by the original fresh colza oil agglomeration, c) standard coal and d) original waste fine coal.

4 Conclusion In this study, waste vegetable oil was prepared to investigate affect of efficiency oil agglomeration and combustible characteristics for coal combustible matter recovery from Chongqing Nantong waste fine coals in China. The simulated waste vegetable oil was prepared by commercial colza sample oil. It is possible that the waste vegetable oil seems to be influence on the coal cleaning efficiency, because the waste vegetable oils may be changed in the surface property and viscosity by different kinds of vegetable oils. It was found that the chemical structure of the vegetable oil is changed with ester carbonyl functional group of the triglycerides and secondary oxidation compounds (e.g. ketone) by the analysis of FT-IR. With the help of waste vegetable oil agglomeration, it was improved combustible characteristics of recovery from its original waste fine coals. These conditions needed optimization in order that efficiently oil agglomeration technology conducted. From the results of our study, the waste vegetable oil can be applied on the industrial oil agglomerating process. Therefore, there are the future subjects that a wide variety of waste vegetable oils are used on our further applicable experiments for Chinese waste fine coal cleaning.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

338 Energy and Sustainability III

Acknowledgement Some works of this study were supported by the Special Funds for Basic Research (B) (No. 19404021, FY2007~FY2009 and No. 22404022, FY2010~2012) of Grant-in-Aid for Scientific Research of the Japanese Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan.

References [1] World Energy Outlook 2007 – China’s Energy Prospects, ISBN: 978-92-6402730-5, IEA. [2] Agency for Natural Resources and Energy, annual report about energy 139144, 2009 (in Japanese). [3] M. I. Alonso., A. F. Valdés., R. M. Martínez-Tarazona., A. B. Garcia., Coal recovery from fines cleaning wastes by agglomeration with colza oil: a contribution to the environment and energy preservation, Fuel Processing Technology, 75, 85-95, 2002. [4] Adolfo F. Valdes., Ana B. Garcia., On the utilization of waste vegetable oils (WVO) as agglomerants to recover coal from coal fines cleaning waste (CFCW), Fuel, 85, 607-614, 2006. [5] Q. Wang, N. Kashiwagi, P. Apaer, Q. Chen, Y. Wang and T. Maezono, Study on coal recovery technology from waste fine Chinese coals by a vegetable oil agglomeration process, The Sustainable World, Ecology and the Environment, 142, 331-342, 2010. [6] A. B. Garcia. M. Rosa Martinez-Tarazona., Jose M. G. Vega., Cleaning of Spanish high-rank coals by agglomeration with vegetable oils, Fuel, 75, 885-890, 1996. [7] Maria D. Guillen., Nerea Cabo., Infrared Spectroscopy in the Study of Edible Oils and Fats, J. Sci Food Agric, 75, 1-11, 1997. [8] N. Vlachos, Y. Skopelitis, M. Psaroudaki, V. Konstantinidou, A. Chatzilazarou, E. Tegou, Applications of Fourier transform-infrared spectroscopy to edible oils, Analytica Chimica Acta 573–574, 459–465 2006. [9] A. Arenillas, F. Rubiera, B. Arias, J. J. Pis, J. M. Faúndez, A. L. Gordon and X. A. García, A TG/DTA study on the effect of coal blending on ignition behaviour, Journal of Thermal Analysis and Calorimetry, 76, 603–614, 2004.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

339

Long-term CO2 emissions abatement in the power sector and the influence of renewable power T. Aboumahboub1, K. Schaber2, U. Wagner1 & T. Hamacher1 1

Institute for Energy Economy and Application Technology, Technical University of Munich, Germany 2 Research Group for Energy and Systems Studies, Max Planck Institute for Plasma Physics, Germany

Abstract This study investigates influences of Variable Renewable Energy Sources (VRES), i.e. solar and wind power, on the CO2 emissions of the global electricity sector and on the certificate price. We use an energy system model based on linear programming. It may be applied to optimize capacity extensions in power generation, transport, and storage under different framework conditions. Here, long term abatement in the power sector with a special focus on the influence of VRES is studied. When a time horizon from 2020 to 2040 was taken into account, optimization results showed that wind energy is extensively employed to meet ambitious emissions reduction targets. In 2020, total wind capacity reaches 4570 GW and rises to 15285 GW by 2040; extension of wind power at this level allows limiting CO2 emissions of the power sector to 6107 million tons in 2020- i.e. 35% reduction compared to the year 2000; it reduces to 2067 million tons by 2040, while the certificate price rises to 61 €/ton. This can only be realized if cross-border interconnections are extended far beyond the current levels. If grid extensions are not allowed, over-installation of capacities up to 18% is unavoidable to satisfy the proposed CO2-limit in 2040. In this case, the certificate price shows a significant increase to 147 €/ton by 2040. Keywords: renewable energy, optimization, certificate price, CO2 emissions.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESUS110291

340 Energy and Sustainability III

1 Introduction The world is facing global challenging issues of climate change. CO2 is one of the main contributors in the global warming phenomenon; its concentration has risen from a pre-industrial level of about 280 ppmv to more than 380 ppmv Nakicenovic [1]. To ensure that carbon dioxide concentrations stabilize at target levels, significant reduction of the global emissions is required. Without near term introduction of supportive and effective policy actions by governments, energy related green house gas (GHG) emissions, mainly from fossil fuel combustion, are projected to rise by over 50% from 26.1 GtCO2eq in 2004 to 37-40 GtCO2eq by 2030 (IPCC [2]). Regarding the considerable contribution of the power sector, substantial changes must be made in its current structure. Promotion of low or no emitting technologies is of high priority. Indeed, projections of the global energy mix in macroeconomic models, i.e. integrated assessment models, which integrate GHG reduction targets, show that within the coming century a significant share of renewable energies is required to accomplish 550 ppmv and 440 ppmv emissions reduction targets; here, mostly solar and wind energy are proposed as well as biomass (Knopf and Edenhofer [3]). In the context of long-term technological change and the potential for reducing CO2 emissions of the power sector, studies have been conducted, focusing on national levels. In Heitman and Hamacher [4], maximum feasible abatement in the German electricity generation system in 2030 and required structural changes have been determined through applying the German electricity system model URBS-DE. Influence of the carbon price and its inherent uncertainty was studied with stochastic parameterization of the specified planning tool based on stochastic linear programming. A study has been conducted in Mathur et al. [5] through applying the energy planning tool MARKAL to simulate the Indian power sector for a time horizon from 2000 to 2025. The results show that besides hydro power, wind energy is an alternative solution, which becomes more and more attractive with the introduction of carbon taxes, while photovoltaic systems with the considered characteristics do not have any chance for large-scale penetration. Here, we study influences of VRES on the CO2 emissions abatement and the certificate price based on an elaborated methodology. Regarding the concern about the contribution of all parts of the world in an international movement towards an emission free electricity supply system, it is relevant to study this issue on the world-wide scale. Taking into account a long-term horizon from 2020 to 2040, we analyze new investments in the electricity sector, required to satisfy different global CO2 emissions reduction targets. Influence of the possibility for extension of solar and wind power on the CO2-certificate price and the role of international exchange are studied. The paper proceeds as follows. In section two, the model used to simulate and optimize the electricity generation system at world-wide scale is described. Section 3 focuses on new investments, required to satisfy long-term CO2 emissions reduction targets; influence of the possibility for extension of solar and WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

341

wind power and the role of international exchange on the CO2-certificate price are investigated.

2 The global electricity system model To analyze impacts on the structure of the electricity generation system, imposed by the intermittency of VRES, the global electricity generation system model URBS-GLB has been developed (Aboumahboub et al. [6]). The model is an extension of the German electricity system model (Heitman and Hamacher [4]). To perform the optimization, the model uses a deterministic approach based on linear programming. Model formulation and optimization process are realized with the application of General Algebraic Modeling System (GAMS) software package (Rosenthal [7]). Optimization is carried out for one typical year with hourly temporal resolution. Capacities of power generation and storage as well as inter-regional transport are determined through the optimization. The power produced by each of the power plant technologies, inter-zonal flows, CO2 emissions, and the electricity system marginal price are determined for each region and at every hour of the simulation period. The cost of avoiding one ton of CO2 – i.e. marginal price of CO2 emissions – is also concluded from the optimization. Total system costs serve as objective function and are given in eqn. (1). It falls into total investment, fixed and variable operation costs of all types of power plants, transmission lines, and energy storage facilities. The fourth sum represents the emissions costs. In eqn. (1), C describes the total installed capacity while CN represents the newly invested power production, storage, and transport technologies available at each region. Ein is the energy input in technology i operating in region x at time step t. kInv,Fix;var are the annuity of investment cost, fixed and variable costs, respectively. r represents the distance between two model regions, while z is the geometry matrix and shows the interconnection possibilities between neighboring regions. w is the weighting factor of the selected times steps to simulate one year. kemfi is the emission factor of the power plant technology i; kCO2 is the assumed CO2-certificate price. z  { x



iPr PG

(k iInv .CN i ( x )  k iFix .Ci ( x )   [k iVar .Eiin ( x, t ).w(t )]) t

1    .z ( x, y ).r ( x, y )[k iInv .CNTri ( x, y )  k iFix .CTri ( x, y )   k iVar .ETriin ( x, y, t ).w(t )] iPr Tr y 2 t 

 [k

iPr Sto



Inv i

.CNSt i ( x )  k iFix .CSt i ( x)   k iVar .ESt i ( x, t ).w(t )]

 [E

iPr PG

t

in i

( x, t ).w(t ).kemf i .kCO 2e]}

t

(1)

Overall system cost minimization is subject to restrictive equations, which describe the energy system, such as the satisfaction of electricity demand, transport and storage losses, conversion losses, technical potential of renewable

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

342 Energy and Sustainability III energies and technical limits of different power plants (Heitman and Hamacher [4]). Zonal configuration of the model is represented in [6]. In order to evaluate technical potential of solar electricity, the global irradiation dataset produced for SeaWiFS was applied here (Bishop et al. [8]). Global data of wind velocities for on- and offshore sites was taken from World Wind Atlas [9]. The transformation from wind velocity to active power output has been done based on the characteristics of modern existing wind turbines [10]. Total capacity of renewable technologies, permissible to be installed at each model region, was determined based on the detailed analyses of global technical potential of wind energy and solar thermal electricity [6, 11, 12]. Geographically aggregated projections of the global electricity demand for the time period from 2010 to 2100 based on the B2 scenario of International Panel on Climate Change (IPCC) has been spatially disaggregated according to the spatial distribution of population [13]. The electrical load profile for each model region was determined based on the linear combination of normalized load curves of comprising countries according to the existing data [14–16] shifted for relevant time zones. Capacities of currently operating power plants were determined based on the UDI World Electric Power Plants Data Base [17] and projected to 2050 based on the technical life time of different power plant technologies (Roth and Kuhn [18]). As the power plants data has not been prepared as a geographically disaggregated dataset, geographic information has been extracted from the GISbased data of Carbon Monitoring for Action (CARMA) (Wheeler and Ummel [19]). To reduce the complexity, thermal power plants were aggregated according to the main fuel. Net transfer capacities of the UCTE (Union for the Co-ordination of Transmission of Electricity) interconnected area were used to represent the existing cross-border interconnections [14]. Techno-economic parameters of power plants were determined based on the validated data (Roth and Kuhn [18] and Han and Ward [20]); fuel prices were projected based on the projections made in Roth and Kuhn [18].

3 Results 3.1 Influence of VRES on CO2 emissions marginal price To focus on the effect of solar and wind power, within the optimization process, it was assumed that nuclear and hydro power plants are not expandable beyond the existing levels. Installed capacities of transport and storage up to the year 2009 were set as upper capacity boundaries. According to the implemented CO2limit and the possibility for extension of VRES, scenarios can be classified. In first sets of scenarios, total CO2, emitted from the global electricity sector, may only rise to 10068.92 million tons in 2025 (7% above the level of year 2000). In another sets of scenarios, the CO2-limit was tightened. Total CO2 emissions, in 2025, shall be lower than 5745.061 million tons (38% below the level of year 2000). In baseline scenarios, existing capacities of solar and wind power were set as upper capacity boundaries. In scenarios “REOPT-CO2H” and “REOPTWIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

343

CO2L”, penetration share of solar and wind as well as their combination was determined through the optimization process. In scenarios “RE50WP0CO2L/H”, “RE50-WP50-CO2L/H” and “RE50-WP100-CO2L/H”, solar and wind power production were constrained to satisfy 50% of the global electricity demand. Contribution share of wind power was varied from zero to 100% of the total solar and wind power production in 50% intervals. Scenarios and underlying assumptions are described in Table 1. Table 1:

Scenarios and underlying assumptions.

Scenario Base-CO2H

Base-CO2L

REOPT- CO2H

REOPT-CO2L

RE50-WP0-CO2H

RE50-WP50-CO2H

Underlying Assumptions - Limitation of total CO2-emissions to 10069 million metric tons - New installations of solar and wind power are not allowed - Limitation of total CO2-emissions to 5745 million metric tons - New installations of solar and wind power are not allowed - Limitation of total CO2-emissions to 10069 million metric tons - Upper capacity boundary for new installations of solar and wind power at each model region is the technical potential - Limitation of total CO2-emissions to 5745 million metric tons - Upper capacity boundary for new installations of solar and wind power at each model region is the technical potential - Limitation of total CO2-emissions to 10069 million metric tons - Upper capacity boundary for new installations of solar and wind power at each model region is the technical potential - Solar and wind power are forced to satisfy 50% of the total annual electricity demand - Wind power contribution share is 0% of total solar and wind power production - Limitation of total CO2-emissions to 10069 million metric tons - Upper capacity boundary for new installations of solar and wind power at each model region is the technical potential - Solar and wind power are forced to satisfy 50% of the total annual electricity demand - Wind power contribution share is 50% of the total solar and wind power production

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

344 Energy and Sustainability III Table 1: RE50-WP100-CO2H

RE50-WP0-CO2L

RE50-WP50-CO2L

RE50-WP100-CO2L

Continued. - Limitation of total CO2-emissions to 10069 million metric tons - Upper capacity boundary for new installations of solar and wind power at each model region is the technical potential - Solar and wind power are forced to satisfy 50% of the total annual electricity demand - Wind power contribution share is 100% of the total solar and wind power production - Limitation of total CO2-emissions to 5745 million metric tons - Upper capacity boundary for new installations of solar and wind power at each model region is the technical potential - Solar and wind power are forced to satisfy 50% of the total annual electricity demand - Wind power contribution share is 0% of the total solar and wind power production - Limitation of total CO2-emissions to 5745 million metric tons - Upper capacity boundary for new installations of solar and wind power at each model region is the technical potential - Solar and wind power are forced to satisfy 50% of the total annual electricity demand - Wind power contribution share is 50% of the total solar and wind power production - Limitation of total CO2-emissions to 5745 million metric tons - Upper capacity boundary for new installations of solar and wind power at each model region is the technical potent - Solar and wind power are forced to satisfy 50% of the total annual electricity demand - Wind power contribution share is 100% of the total solar and wind power production

Fig. 1 shows the produced power categorized by technology type along with the marginal price of CO2 emissions for selected scenarios. A tighter CO2 limit leads to a higher CO2-price for comparable scenarios. It may be realized that the marginal price reduces with increased production of VRES. Furthermore, at the given penetration share of solar and wind power and a specified CO2 emissions upper limit, the marginal price decreases with the contribution of wind power. In -CO2L scenarios, it reaches its lowest level in “RE50-WP100-CO2L”. This is also obtained in scenario “REOPT-CO2L”, in which the contribution share of solar and wind power is determined by the optimization. In this scenario, penetration share of wind power reaches 52% of total electricity demand.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

Figure 1:

345

Total produced power categorized by technology type and CO2 emissions marginal price for selected scenarios; year 2025.

3.2 Large-scale integration of VRES and the role of international exchange Here, required investments in VRES to satisfy proposed emissions reduction targets, influence of international exchange, and development of the carbon price through a long-term period at different framework conditions are studied. Optimization was performed through a time horizon from 2020 to 2040 with 5 5-year time steps. Extension of wind power and solar was determined by the optimization and limited due to the technical potential of each model region. It was assumed that nuclear and hydro power plants are not expandable beyond the existing levels. Installed capacities of storage up to the year 2009 were set as upper capacity boundaries. To analyze the influence of international exchange in an ideal globally-interconnected structure, results of the scenario “No-GE” without the possibility for grid extension were compared versus scenario “GOPT” that optimizes extension of cross-border interconnections. Table 2 gives a brief overview on the scenarios. IPCC Working Group one (WG1) proposed the early-action scenario for 550 ppmv concentration level (IPCC [21] and Manne and Richels [22]). In a more stringent scenario (represented with the prefix “-CO2L”), CO2 limits were tightened according to the category I of the stabilization scenarios in IPCC Assessment Report 4 [2]. The CO2 emissions path was set to the minimum path in Nakicenovic [1], which leads to the stabilization of CO2 only concentrations at the level of 350 ppmv by 2100. Total CO2 emissions of the power sector in 2000 reached 9395 million metric tons [19], i.e. 42.2% of total CO2 emissions [22]. Here, total CO2 that may be emitted from the power sector at each time period was approximated based on the specified stabilization scenarios and contribution of the power sector. Implemented CO2-limits are given in Table 3. Total Optimized capacity mix is shown in fig.2. Total wind power capacity in “CO2H-GOPT” reaches 2822 GW by 2020 and rises to 10000 GW by 2040. Average wind power capacity factor is around 27%; penetration share of wind power reaches 58% of global electricity demand by 2040. In the more stringent WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

346 Energy and Sustainability III Table 2:

Scenarios and underlying assumptions. Underlying Assumptions

Scenario

- CO2 abatement based on the category I of the stabilization scenarios in IPCC Assessment Report 4 - Grid extension is optimized - CO2 abatement based on the IPCC Working Group one (WG1) scenario

GOPT-CO2L

GOPT-CO2H

- Grid extension is optimized NoGE-CO2L

- CO2 abatement based on the category I of the stabilization scenarios in IPCC Assessment Report 4

NoGE-CO2H

- CO2 abatement based on the category I of the stabilization scenarios in IPCC Assessment Report 4

- Grid extension is not allowed

- Grid extension is not allowed

Table 3: CO2 limit (Mio.ton) 2020 2025 2030 2035 2040

CO2H 10059 10335 10611 10777 10943

Implemented CO2 limits. CO2L 6107 4698 3758 2819 2067

scenario “CO2L-GOPT”, wind power capacity rises from 4570 to 15285 GW. Having a lower CO2 limit, coal-fired capacity is reduced while there is a higher installation of gas-fired plants compared to “CO2H-GOPT”. The influence of a global super-grid may be realized by comparing the scenario “-NoGE” with “-GOPT”. Fig. 2(b) and (d) clarify over-installation of capacities in “-NoGE”; more gas-fired plants and wind power parks have been installed to satisfy the same CO2 limit as in fig. 2 (a) and (c). Fig. 3 (a) and (b) show the total installed capacity of photovoltaic (PV) and concentrating solar power (CSP) systems corresponding to the optimized interzonal transport capacity at each time period in “-CO2L” scenarios, respectively. Solar systems at the considered costs and efficiency are not selected for large-scale penetration in scenarios that optimize grid extensions. However, in “CO2L-NoGE” scenario, corresponding to the lower level of the vertical axis in fig. 3 (a) and (b), total installed capacity of solar power systems shows a significant increase in the latest periods; it reaches 5 GW in 2035 and rises to 18 GW by 2040. WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

347

(a)

(b)

(c)

(d)

Figure 2:

Optimized generation capacity mix 2020-2040 (a) Scenario CO2LGOPT (b) Scenario CO2L-NoGE (c) Scenario CO2H-GOPT (d) Scenario CO2H-NoGE.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

348 Energy and Sustainability III

(a)

(b) Figure 3:

Optimized capacity of solar electric systems in 2020-2040 for CO2L scenarios; (a) PV (b) CSP.

Fig. 4, for instance, shows the geographic distribution of transport capacities in 2035 resulted from the optimization in “-CO2L” scenario compared to “CO2H”. Capacities of up to 206 and 343 GW are installed in “CO2H-GOPT” and “CO2L-GOPT”, respectively, to transport the emission-free wind power from regions with a high level of technical potential to the high load centres. The influence of a global super-grid may be realized by comparing scenario “-NoGE” with “-GOPT”. In “CO2H-GOPT”, certificate price does not show any significant increase through the time horizon and remains near 16 €/ton (fig. 5). However, in “CO2H-NoGE”, it rises to 35 € /ton by 2040. This effect becomes much more significant with tightening the CO2 limit; certificate price rises to 147 €/ton in “CO2L-NoGE” by 2040 compared to 61 €/ton in “CO2L-GOPT”.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

349

(a)

(b)

Figure 4:

Optimized transport capacity in 2035 (a) scenario CO2L-GOPT (b). Scenario CO2H-GOPT.

Figure 5:

CO2 emissions marginal price.

References [1] Nakicenovic, N., World Energy Outlook 2007: CO2 Emissions Pathways Compared to Long-term CO2 Stabilization Scenarios in the Literature and IPCC AR4, 2007. [2] IPCC, An Assessment of the Intergovernmental Panel on Climate Change, 2007. [3] Knopf, B., Edenhofer, O., Report on first assessment of low stabilization scenarios, ADAM Project: Adaptation and Mitigation Strategies: Supporting European Climate Policy, 2008.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

350 Energy and Sustainability III [4] Heitmann, N., Hamacher, Th., Stochastic Model of German Electricity System, Optimization in the Energy Industry, Energy Systems, SpringerVerlag, doi:10.1007/978-3-540-88965-6_16, pp. 365-385, 2009. [5] Mathur, J., Bansal, N.K., Wagner, H.J., Investigation of greenhouse gas reduction potential and change in technological selection in Indian power sector, Energy Policy,31, pp. 1235-1244, 2003. [6] Aboumahboub T., Tzscheutschler, P., Hamacher, Th., Optimizing worldwide utilization of renewable Energy Sources in the Power Sector, Proc. of the International Conference on Renewable Energy and Power Quality, Granada, 2010. [7] Rosenthal, R.E., GAMS A User's Guide, GAMS Development Corporation, Washington D.C., USA, 2008. [8] Bishop, J.K.B., T. Potylitsina, T., Rossow, W.B., Documentation and Description of Surface Solar Irradiance Data Sets Produced for SeaWifs, Department of Applied Physics of Columbia University, EO Lawrence Berkeley Laboratory, NASA/Goddard Institute for Space Studies, USA, 2000. [9] Wheeler, D., K. Ummel, Calculating CARMA. Global Estimation of CO2 Emissions From the Power Sector, Center for Global Development, 2008. [10] Vestas Wind Systems A/S, V90-3.0 MW an efficient way to more power, 2009. [11] Brückl, O., Global Technical Potential of Wind Electricity, Final Report prepared for BMW AG, Institute for Energy Economy and Application Technology, Technische Universität München, Germany, 2005. [12] Tzscheutschler, P., Global Technical Potential of Solar Thermal Electricity, PhD Thesis, Institute for Energy Economy and Application Technology, Technische Universität München, Germany, 2005. [13] IIASA Greenhouse Gas Initiative database, 2009. www.iiasa.ac.at/webapps/ggi. [14] European Network of Transmission System Operators (ENTSOE) Statistical Database, 2009. http://www.entsoe.eu/resources/publications. [15] UK National Grid Company website, 2009. http://www.nationalgrid.com /uk/. [16] Personal communication, Aug. 2009, Estonian Power Transmission System Operator (Elerging OÜ). http://www.elering.ee. [17] UDI World Electric Power Plants Database (UDI WEPP), 2010. [18] Roth, H., Ph. Kuhn, Technik und Kosten Szenarien der Strombereitstellung in Deutschland bis 2040, Internal Technical Report, Institute for Energy Economy and Application Technology, Technische Universität München, Germany, 2008. [19] Wheeler, D., K. Ummel, Calculating CARMA. Global Estimation of CO2 Emissions From the Power Sector, Center for Global Development, 2008. [20] Han, W.E., Ward, D.J., Final Report on EFDA TIMES Model Electricity Sector Update Task, Internal Technical Report, EURATOM/UKAEA Fusion Association, 2007.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

351

[21] IPCC, In: Nakicenovic et al., Special Report on Emission Scenarios. A special report of working group III of the Intergovernmental Panel on Climate Change (IPCC), 2000. [22] Manne, A., R. Richels, 1997. On stabilizing CO2 concentrations – costeffective emission reduction strategies, International Journal of Environmental Modeling and Assessment, vol.2, pp.251-265.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

This page intentionally left blank

Energy and Sustainability III

353

Energy recovery of a rotary kiln system in a calcium oxide plant M. Aldeib, A. Elalem & S. Elgezawi Department of Chemical Engineering, Faculty of Engineering, University of AlFateh Tripoli, Libya

Abstract The dominant source of calcium carbonate is limestone; the most common constituent of all rocks. It occurs in nature with clay, silica and other minerals, which may interfere in many applications. Synthetic calcium carbonate is produced on a large scale where a calcium chloride stream is treated with sodium or ammonium carbonate to produce a high grade of calcium carbonate. In turn, calcium carbonate is heated to 900–1000 degree centigrade in a horizontal lime kiln to produce calcium oxide (burned lime). Calcium oxide is used extensively in cement, iron and steel industries due to the low cost of the material and its accepted chemical properties. In this study, composition of raw meal, ultimate analysis of the fuel, dust contents in the exhaust gases, losses in ignation (COI) and exhaust gas composition in the preheated suspension are calculated. The heat losses from kiln exhaust are minimized. A secondary shell on the kiln surface is also investigated. In this work mathematical models for the calculations of inside heat transfer on the rotary are used, and the total energy utilized by burning fuel oil in the process of calcium oxide production is also calculated. The heat losses for kiln exhaust gas, hot air from the cooler stock losses and radiation losses from kiln surface are also minimized. A secondary shell on the kiln surface is studied in the present study, where 4% of total energy input is saved. This energy saving would result in a considerable reduction of fuel consumption in the kiln system. The overall efficiency would be improved by 5%. Keywords: rotary kiln reactor, radiant heat transfer, coating, combustion.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESUS110301

354 Energy and Sustainability III

1 Introduction Radiant heat (mainly infra-red ray) is emitted from the burning flame at high temperature in a rotary kiln reactor, some fraction of which arrives at the surface of the rotating solids layer, and the other arrives at the inner refractory surface. The rest is absorbed in the combustion gas around the flame. For predicting radiant heat transfer, however, radiant heat transfer is simplified to apply to the complex mechanism of heat transfer in a rotary kiln, without losing significant fundamentals. Radiant heat absorbed in combustion gas around the flame is converted to thermal energy, which should be emitted as infra-red ray from the gas to the rotating solids and inner wall surface. Thus we can assume that all the radiant heat emitted from the flame arrives at the surface of the rotating solids and the inner wall surface.

2 Mathematical modeling of inside heat transfer on a rotary kiln with radiant heat transfer from flame and combustion gas In the region where combustion takes place, radiant heat transfer from the burning flame is controlling, whereas convectional heat transfer is one order of magnitude less. For convenient application to practical design calculation, there are simplified models to represent the heat transfer mechanism in this region [1]. Radiant heat absorbed in combustion gas around the flame is converted to thermal energy, which should be emitted as infra-red rays from the gas to the rotating solids and inner wall surface. Thus we can assume that all the radiant heat emitted from the flame arrives at the surface of the rotating solids and the inner wall surface. The radiant heat transfer coefficient, hrg, to two solid surfaces is calculated by, [1] =

.



(1)

where df is the outer diameter of the flame, εf is the emissivity of the flame, εm is the average emissivity of the solids layer surface and the inner wall surface, and T is the average temperature of the above two surfaces. The emissivity of the luminous flame was measured very precisely by members of an international committee. The average diameter of flame df depends strongly on the hydrodynamic feature of turbulent diffusion. By visual observation of the flame in a practical rotary kiln, in which a burner is operated under similar flow conditions to the one planned, we can estimate the approximate value of df/dti The average temperature T is calculated using the following equation: (2)

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

355

3 Radiant heat transfer from inner wall surface to rotating solids layer Radiant heat emitted from the wall surface per unit length of the reactor is given by [1] (4.88) (3) The geometrical view (angle) factor from the inner surface πdti(1-χ) to the rotating layer of solids is represented by FHC.

(4)

Since FCH = 1, we have FHC = χ / 1-χ. Radiant heat, emitted from the inner surface, is mainly infrared rays. When it passes through the flame and combustion gas, some part of the infrared ray is absorbed by them. Let us take εg* to be the average value of emissivity for the flame and combustion gas. Thus, the rate of radiant heat transfer from the inner wall surface to the rotating solids layer is calculated approximately with Eq. (5), in the case where εH and εC are close to unity.

(5)

Define the radiant heat transfer coefficient from the hot inner wall to the layer of solids by (hrs)HC, on the basis of the surface area of the inner wall. (6)

Combination of Eqs. (5) and 6) leads to the following equation (1-

)

.

(7)

4 Heat transfer coefficient by direct contacting of solids from the hot wall surface In a rotary kiln, solids are heated by direct contact with the hot wall surface. The inner wall surface functions as a kind of regenerator, changing the surface temperature periodically during the rotation. Theoretical calculation reveals that the amplitude in the periodical change of surface temperature is not too much, as long as the rotation is larger than 3 r.p.m. In this section, let us take the time averaged temperature of the wall. For a packet of solids, which suddenly contact the hot surface and then leave it after residing there for a time t, the following equation calculate the time averaged value of the heat transfer coefficient due to the above contact, on the basis of contacting surface area. WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

356 Energy and Sustainability III 0.5

.

(8)

where ke is the effective thermal conductivity of a packet of solids,  is the bulk density, and Cs is the specific heat of solid. Introduce the following substitution: (9) Substitution of Eq. (9) in Eq. (8) gives

.

.

(10)

The temperature of the inner wall surface TH is determined by a given value of the flame temperature Tf. On the basis of unit length, using the following equation: (11) Heat transfer from the inner wall to the rotating solids by direct contact can be calculated using Eq. (12) (12)

Heat loss to outside with coating is estimated from the following equation: "

/

/

/

………

(13)

5 Mathematical modeling of inside heat transfer on a rotary kiln without coating The same procedure done: from equation (1) to equation (12) but eliminate the first term in the denominator from equation (13). 5.1 Investigation of the mathematical model: Known data Tc= 950oC,

. , . , . dti=4.2 m (with coating), and equal 4.35 m (without coating), df =1.4 m. Flame temperature (Tf) range in cement industry from 1200 to 2000oC. WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

357

Results from Program The results calculated are shown in the following tables: With coating Table 1 presents both internal and external temperatures of rotary kiln for the burning zone; they are functions of flame temperature, and increase with the flame temperature. Also, the heat loses are increased, due to increase in the difference of temperature between the inside (flame) and outside (environment) temperatures. Table 1:

Prediction of inner and outer shell surface temperatures with coating.

Tf (oC) TH (oC) TW (oC) Hrg Hrs Hp Qlosses (kcal/m2.hr)

1200 1029.8 267.85 98.66 158.68 561.89 5990.41

1400 1133.6 297.85 133.06 179.76 561.89 6570.621

1600 1237.4 327.85 174.9 203.14 561.89 7150.83

1800 1341.2 357.85 224.95 228.95 561.89 7731.04

2000 1445 387.85 283.94 257.35 561.89 8311.25

These behaviors are clarified in table 1 whereas increasing the flame temperature with the industrial range (from 1200 to 2000oC) note that, both internal and external wall surface temperatures are increased respectively. Table 2 presents both internal and external temperatures of rotary kiln for the burning zone; are function of flame temperature, and increasing with increase the flame temperature. Also, the heat loses increase, due to increase in the difference of temperatures between the inside (flame) and outside (environment) temperatures. The optimum external wall surface temperature in industrial processes ranged (from 250 to 340oC), Note that in Table 2, Tw reaches up to 379oC when the flame temperature greater than 1580oC. That will lead to many Table 2:

Predicted temperatures of inner wall surface and outer shell surface without coating.

Tf (oC)

1200

1400

1600

1800

2000

TH (oC)

1029.8

1133.6

1237.4

1341.2

1445

TW ( C)

306.25

342.65

379.05

415.45

451.85

Hrg

87.097

117.64

154.4

198.58

283.94

Hrs

158.68

179.76

238.14

228.95

257.35

Hp

561.89

561.89

561.89

561.89

561.89

Qlosses (kcal/m2.hr)

5921.224

6463.698

7242.03

8271.945

8802.627

o

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

358 Energy and Sustainability III

Hot Spot

Figure 1:

Hot spot formation on the rotary kiln shell surface.

troubles in the rotary kiln in this case the red spot (hot spot as shown in Figure 1 through the rotary kiln will occur, in which the coating will start to collapse that leading to decrease in the thermal resistance that leads to increase in the external wall surface temperature (Tw) reaching up to 450oC which is known as red spots. Table 3 shows that the internal wall surface temperature predicted by model is satisfied with practical data obtained from industrial process with acceptable deviation. Table 3:

Prediction and practical temperatures of inner wall surface and outer shell surface.

Tf (oC)

1200

1400

1600

1800

2000

TH (oC) (actual) TH (oC) (predicted) TW (oC)

1029.8

1133.6

1237.4

1341.2

1445

1021

1120

1249

1410

1501

267.85

297.85

327.85

357.85

387.85

Hrg

98.66

133.06

174.9

224.95

283.94

Hrs

158.68

179.76

203.14

228.95

257.35

Hp

561.89

561.89

561.89

561.89

561.89

Qlosses (kcal/m2.hr) Qlosses (kcal/m2.hr)

5990.41

6570.621

7150.83

7731.04

8311.25

5921.224

6463.698

7242.03

8271.945

8743.66

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

359

6 Conclusion A detailed energy audit analysis, which can be directly applied to any dry kiln system has been made in this study. The distribution of the input heat energy to the system components showed good agreement between the total input and output energy and give significant insight about the reasons for the low overall system efficiency. According to the results obtained, the system efficiency is 50℅. The major heat loss sources have been determined as kiln exhaust with 20℅. Cooler exhaust heat loss is calculated at 5℅ of total input. The combined radiative and convective heat transfer from kiln surface is at 4℅ of total input. The simulation done on the process showed that the predicted external wall surface temperature is ranged from 267 to 327 degree centigrade to avoid hot spot formations on the rotary kiln surface.

References [1] D. Kunii and T. Chisaki, Rotary Reactor Engineering, First edition, Jordan Hill, 2008 [2] Deliang Shi, Watson Vargas, J. Mc Carthy, Heat Transfer in Rotary Kilns with Interstitial gases, Chemical Engineering Science 63, 2008

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

This page intentionally left blank

Energy and Sustainability III

361

Nonthermal plasma-assisted catalytic methanation of CO and CO2 over nickel-loaded alumina E. Jwa, Y. S. Mok & S. B. Lee Department of Chemical & Biological Engineering, Jeju National University, Korea

Abstract Nonthermal dielectric barrier discharge plasma was applied for the heterogeneously catalyzed methanation of CO and CO2 over alumina-supported catalysts at 180-320oC and atmospheric pressure. The characteristics of methane synthesis under plasma discharge conditions were investigated with several catalysts, including Al2O3, TiO2/Al2O3, Ni/Al2O3 and Ni-TiO2/Al2O3. The results obtained with Al2O3 or TiO2/Al2O3 catalysts indicated that either gas-phase reactions or photocatalysis induced by the plasma as well as the adsorption of carbon oxides on Al2O3 hardly contribute to the methanation of CO and CO2. On the other hand, nickel-loaded catalysts like Ni/Al2O3 and Ni-TiO2/Al2O3 were found to be considerably affected by the plasma, resulting in enhanced methanation rate. It is believed that the nonthermal plasma created in the catalytic reactor can accelerate the rate-determining step by dissociating carbonoxygen bonds of carbon oxides adsorbed on the active sites of the catalysts. Keywords: CO, CO2, catalytic methanation, nonthermal plasma.

1 Introduction Methanation (‘the hydrogenation of CO’) have been investigated extensively, not only for the production of synthetic natural gas (SNG) from synthesis gas, but also as a gas purification process in chemical plants where CO acts as a catalyst poison. The same catalysts used for CO methanation are also active for carbon dioxide (CO2) that is closely related to the global warming. Hence CO2 may also

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESUS110311

362 Energy and Sustainability III be an attractive gas in methanation study in terms of recycling of disposed material into fuel as one of the possibilities [1]. Methane synthesis from CO and CO2 proceeds over various supported metal catalysts. Although methanation catalysts consisting of a noble metal such as ruthenium, rhodium or platinum have also been developed [2], the most common catalyst for methane synthesis is based upon nickel supported on alumina. Nickel is cheap and easily accessible, but one disadvantage of nickel-based catalysts may be that relatively high temperatures are needed to maintain the catalytic activity for methane synthesis. The catalysts can chemically be modified with support materials and additives so that they have enhanced low temperature activity. Alternatively, the catalytic activity can be improved by physical means such as nonthermal plasma. According to recent studies reported in the literature, nonthermal plasma created by dielectric barrier discharge (DBD), glow discharge or pulsed corona discharge often facilitates catalytic reactions such as oxidation of organic compounds, decomposition of fluorinated carbons or reforming of hydrocarbons. In a similar manner, nonthermal plasma can also promote the catalytic conversion of CO/CO2 into methane. The methanation of CO over Ni/alumina was previously studied [3], which showed that the plasma significantly increased the catalytic activity, especially at lower temperatures and pressures. The present work is aiming at providing a CO/CO2 methanation process enhanced by nonthermal plasma. The plasma-catalytic methanation of CO2 was not dealt with in the previous study [3]. In this work, the methanation was carried out in a DBD reactor packed with catalyst pellets. Four different catalysts, i.e., Al2O3, TiO2/Al2O3, Ni/Al2O3 and Ni-TiO2/Al2O3, were used to examine comparatively the effect of the plasma on the methanation of CO and CO2.

2 Experimental The nickel-loaded catalysts were prepared with alumina (Al2O3) ball (SigmaAldrich Co) and nickel nitrate (Ni(NO3)2·6H2O, Acros Organics), on which the nickel content was varied by the concentration of aqueous nickel nitrate solution. Alumina ball used as the catalyst support was crushed in a mortar, sieved to a size of 1-2 mm. TiO2/Al2O3 catalyst (TiO2 content: 10wt%) was prepared by adding aqueous TiO2 suspension to the alumina particles prepared as above. After drying in an oven at 110oC overnight, calcination was carried out at 550oC for six hours. The TiO2 used in the present investigation was in the form of anatase phase, which was purchased from Sigma-Aldrich Co. The Al2O3 and TiO2 have the BET specific surface areas of 195.7 and 9.7 m2/g. As well known, the anatase form of TiO2 is a photocatalyst under ultraviolet (UV) light. Ni/Al2O3 catalyst was made by incipient wetness impregnation method with aqueous nickel nitrate solution. After impregnation, it was dried overnight to drive off water, and calcined at 550oC for six hours in air atmosphere. Finally, the catalyst previously calcined was reduced by flowing hydrogen at 550oC for six hours. NiTiO2/Al2O3 catalyst was also prepared by impregnating TiO2/Al2O3 with aqueous WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

363

nickel nitrate solution, which was dried, calcined and reduced in the same way as mentioned above. The BET specific surface areas of TiO2/Al2O3, Ni/Al2O3 and Ni-TiO2/Al2O3 prepared were measured to be 168.8, 138.5 and 116.4 m3/g, respectively. Fig. 1 shows the schematic diagram of the experimental apparatus for methane synthesis. The catalyst-packed bed reactor referred to as plasma reactor, described in Fig. 2, was made of a quartz tube (inner diameter: 15 mm; thickness: 1.5 mm) and a 6.4-mm-concentric stainless-steel rod acting as the discharging electrode. An aluminum foil used as the ground electrode wrapped the outer surface of the quartz tube. The plasma reactor was packed with catalyst pellets whose apparent volume and mass were 17 cm3 and 13.6 g, respectively. The effective length of the plasma reactor was measured to be 110 mm. An alternating current (AC) high voltage (operating frequency: 1 kHz) in the range of 6-11 kV was applied to the stainless-steel rod to create nonthermal plasma in the catalyst-packed reactor. The feed gas was heated to desired temperatures with two heating tapes, one covering the mixing chamber and the other covering the plasma-catalytic reactor. The feed gas preheated in the gas mixing chamber was directed to the plasma- reactor where the methanation of CO/CO2 occurred. The feed gas was prepared by mixing pure hydrogen and carbon monoxide or by mixing pure hydrogen and carbon dioxide via a set of mass flow controllers (MKS Instruments, Inc.). For the methanation of CO, the molar ratio of H2 to CO

Figure 1:

Schematic diagram of the experimental apparatus for methane synthesis.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

364 Energy and Sustainability III

Figure 2:

Schematic diagram of plasma-catalytic reactor.

in the feed gas was adjusted to 3. The methanation of CO2 was separately conducted with a H2/CO2 molar ratio of 4. The flow rate of the feed gas was 12,000 cm3 h-1 for CO methanation, and 15,000 cm3 h-1 for CO2 methanation. The reacted gas coming out of the plasma-catalytic reactor was diluted with pure helium (500 cm3 min-1), and then analyzed by a gas chromatograph (Varian Micro GC CP-4900) equipped with an analytical column (10 m Pora Plot Q Column), using high purity helium as carrier. The gas chromatograph was calibrated for concentrations of H2, CO, CO2 and CH4 with their known concentrations. Methanation experiments was performed over the temperature range of 200~320oC with an interval of 20oC. The voltage applied to the plasma reactor was measured with a 1,000:1 high voltage probe (P6015, Tektronix) and a digital oscilloscope (TDS 3032, Tektronix). The discharge power consumed in the plasma reactor was determined by using charge-voltage Lissajous figure.

3 Results and discussion 3.1 Comparison between CO and CO2 methanation over Ni/Al2O3 Fig. 3 shows the conversion efficiencies of CO and CO2 over Ni/Al2O3 catalyst (Ni content: 10wt%), where the results obtained with and without the plasma were compared. The temperature was varied in the range of 180-300oC, while the voltage was fixed at 10.3 kV. When high voltage enough to induce electrical discharge is applied to the plasma reactor, active species such as energetic electrons, ultraviolet (UV) photons, radicals and excited molecules are formed through various reaction pathways [4]. Looking into generally accepted catalytic methanation mechanism, it is quite probable that all or some of these kinds of active species can enhance the catalytic reactions. In general, catalytic methanation proceeds via the adsorption of carbon oxides, followed by the hydrogenation of surface carbon resulting from the dissociation of the adsorbed carbon oxides. As can be seen, the conversion efficiencies of either CO or CO2 were largely enhanced in the presence of the plasma. Like other catalytic WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

365

reactions, the rate-determining step (RDS) in the methanation of CO and CO2 is regarded as the dissociation of adsorbed carbon oxides molecules. In other words, the methanation rate mainly depends on the rate of the carbon-oxygen bond dissociation, not on the adsorption of carbon oxides or on the succeeding hydrogenation of surface carbon. In Fig. 3, the enhancement of the methanation arising from the generation of nonthermal plasma may be explained by the acceleration of the rate-determining step. The bond strengths for gaseous CO and CO2 are 1,072 kJ mol-1 (11 eV) and 782 kJ mol-1 (8 eV), respectively, but they get weak when adsorbed on the catalyst surface. As a result, the energetic electrons generated by the plasma can easily break the carbon-oxygen bond of the adsorbed carbon oxides through direct electron impact, speeding up the ratedetermining step. Meanwhile, with the catalyst alone, CO2 exhibited higher methanation rate than CO at temperatures below 280oC, but at higher temperatures, it was reversed since the maximum conversion efficiency of CO2 was limited to around 90%. The rate of CO2 methanation under the plasma was also higher than that of CO at lower temperature region below 220oC. Even though the plasma was found to shift the optimal reaction temperature lower, it did not further increase the maximally attainable CO2 conversion to above 90%.

Conversion efficiency (%)

100

80

60

40

CO Catalyst alone Plasma-catalyst

20

0 160

CO2

Catalyst alone Plasma-catalyst 180

200

220

240

260

280

300

320

o

Temperature ( C)

Figure 3:

Conversion efficiencies of CO and CO2 with and without nonthermal plasma (catalyst: Ni/Al2O3; voltage: 10.3 kV).

3.2 Comparison of CO and CO2 methanation on different catalysts Figures 4 and 5 show the conversion efficiencies of CO and CO2 over four different catalysts over a temperature range of 180-320oC. When the plasma was WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

366 Energy and Sustainability III used, the applied voltage was controlled to 10.3 kV. As can be seen, there was no conversion of CO with either Al2O3 or TiO2/Al2O3 catalyst, regardless of the plasma and the reaction temperature, which implies that UV photons and gasphase reactions caused by nonthermal plasma do not directly contribute to the methanation. It should be noted that TiO2 photocatalyst in the anatase form whose band gap energy is about 3.2 eV can be activated by UV photons with wavelengths less than 390 nm. The electron-impact excitations of CO and CO2 emit UV light with various wavelengths [5, 6], but the photocatalytic effect on the methanation was negligible for the present catalysts. Different from the results obtained with Al2O3 and TiO2/Al2O3, the plasma largely affected the conversion of CO and CO2 over Ni-loaded catalysts, i.e., Ni/Al2O3 and NiTiO2/Al2O3 catalyst. Compared to the catalyst alone, the temperature effect on the methanation became much greater when the plasma was generated in the reactor, displaying respective CO and CO2 conversion efficiencies of 98% and 90% at 240oC. Like the case of CO, the conversion of CO2 with Al2O3 or TiO2/Al2O3 catalyst was not significant, and moreover, the CO2 converted was mostly reduced to CO, not to methane. Unexpectedly, the performance of NiTiO2/Al2O3 catalyst was found to be inferior to that of Ni/Al2O3 catalyst for both CO and CO2, which may be another evidence that the UV photons produced by the plasma did not contribute to the methanation. According to a previous study [7], noble metals supported on titania such as Pt/TiO2, Rh/TiO2 and Ir/TiO2 were reported to be effective for photo-induced dissociation of CO2, conflicting with the present study conducted with nickel as the active metal. It is believed that the

CO conversion efficiency (%)

100

80 Catalyst alone Alumina TiO2/alumina

60

Ni/alumina Ni-TiO2/alumina

40

Plasma-catalyst Alumina TiO2/alumina

20

0 160

Ni/alumina Ni-TiO2/alumina 180

200

220

240

260

280

300

320

o

Temperature ( C)

Figure 4:

Conversion efficiencies of CO over different catalysts (10.3 kV).

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

367

CO2 conversion efficiency (%)

100

80 Catalyst alone Alumina TiO2/alumina

60

Ni/alumina Ni-TiO2/alumina

40

Plasma-catalyst Alumina TiO2/alumina

20

0 160

Ni/alumina Ni-TiO2/alumina 180

200

220

240

260

280

300

320

o

Temperature ( C)

Figure 5: Conversion efficiencies of CO2 over different catalysts (10.3 kV).

photocatalytic activity of TiO2 is closely related to the nature of the active metal used. The lower performance of Ni-TiO2/Al2O3 than Ni/Al2O3 may also be attributed in part to its smaller BET specific surface area. As mentioned above, the BET specific surface areas of Ni/Al2O3 and Ni-TiO2/Al2O3 were 138.5 and 116.4 m3/g, respectively.

4 Conclusions The conversions of CO and CO2 into methane were investigated in the plasmacatalytic reactor packed with nickel-loaded catalysts. The plasma was found to beneficial to the catalytic methanation of CO and CO2 in that it shifted the optimal reaction temperature lower The experimental data obtained by varying the catalyst composition have shown that the enhancement in the methanation rate by the plasma results from speeding up the rate-determining step, namely, the dissociation of the carbon-oxygen bond of the adsorbed carbon oxides, and the contributions of gas-phase reactions and photocatalysis caused by nonthermal plasma are insignificant. Both in the presence and absence of the plasma, CO2 exhibited higher methanation rate than CO at lower temperatures, but it was reversed at higher temperatures due to the limitation of the maximally attainable CO2 conversion efficiency.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

368 Energy and Sustainability III

Acknowledgements This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (Grant number 2010-0021672).

References [1] Yaccato, K., Carhart, R., Hagemeyer, A. Lesik, A., Strasser, P., Volpe Jr., A.F., Turner, H., Weinberg, H., Grasselli, R. K. & Brooks, C., Competitive CO and CO2 methanation over supported noble metal catalysts in high throughput scanning mass spectrometer. Applied Catalysis A: General, 296, pp. 30–48, 2005 [2] Pangiotopoulou, P., Knonarides, D.I. & Verykios, X.E., Selective methanation of CO over supported noble metal catalysts: effects of the nature of the metallic phase on catalytic performance. Applied Catalysis A, 344, pp.45-54, 2006. [3] Mok, Y.S., Kang, H.C., Lee, H.J., Koh, D.J. & Shin, D.N, Effect of nonthermal plasma on the methanation of carbon monoxide over nickel catalyst. Plasma Chemistry and Plasma Processing, 30, pp.437-447, 2010. [4] Jwa, E., Mok, Y.S. & Lee, S.B., Methanation of CO and CO2 in a nonthermal plasma-catalytic reactor, Int. Conf. on Energy Systems and Technologies, Cairo, Egypt, 2011. [5] Olszewski, R., Woliński, P. & Zubek, M., Excitation of carbon monoxide by electron impact in the 8–17 eV energy range. Chemical Physics Letters, 297, pp.537-542, 1998. [6] Mogul, R. Bol’shakov, A.A., Chan, S.L., Stevens, R.M., Khare, B.N., Meyyappan, M., Trent, J.D., Impact of low-temperature plasmas on deinococcus radiodurans and biomolecules. Biotechnology Progress, 19, pp. 776-783, 2003. [7] Raskó, J., FTIR study of the photoinduced dissociation of CO2 on titaniasupported noble metals. Catalysis Letters, 56, pp.11–15, 1998.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

369

Family size solar dryer for an estimation of the heat transfer coefficient T. M. Jaballa Mechanical Engineering Department, College of Engineering, El-Fateh University, Tripoli, Libya

Abstract Knowledge of the heat transfer coefficient is believed to be of great contribution in the course of a full design of a solar dryer. To find an expression for the heat transfer coefficient, the general logarithmic velocity profile for turbulent flow is used for the analysis. It is assumed that the fluid is air at atmospheric pressure, and that the thin wall laminar sublayer has a small or negligible effect on the value of the fluid bulk temperature. The final form of the correlation equation gives a relation between Nusselt number and Reynolds’ number, and is given in a form which is easy to remember by the solar dryer designers. Comparison of the predicted values indicates that the correlation can predict values to within  6% of experimental values reported in literature. Expected errors of nearly  25% were observed when the correlation predictions compared with well known correlations found in literature and in text books. Keywords: heat transfer coefficient, crops solar dryers, turbulent velocity profile, turbulent thermal diffusivity.

1 Introduction Drying crops such as hay, corn, beans, tomatoes, onions, etc., has been known to man for thousands of years. The drying method used then was purely natural; by simply distribute the crop on a flat ground, and let nature dry it. Very little of industrial pollutants those days were existed, and the insects effect was not of any concern. Today this same method is still used locally, in the presence of industrial and growing natural pollution. Dates, tomatoes, unions, apricots, and even meat and fish are dried in open areas. Many of the diseases in the African countries are related to foods dried this way. A cleaner and a more healthy WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESUS110321

370 Energy and Sustainability III method is required, especially when drying products that can get dirty due to adhesion and sticking of exhaust gases, ashes, and dust, or when drying meats and some fruits which contain sweet juices, and aromas that attract insects. A proposed program to fully design a family solar dryer to dry local crops is considered by the Mechanical Engineering Department, El-Fateh University. The proposal consists of three phases. The first is to make a preliminary design of a simple and cheap dryer geometry and to report the moisture content of all the crops to be dried. The second phase is the thermal design and analysis, a purely theoretical study. The third phase is the design and manufacturing of a cheap type solar dryer and the measurements of all the parameters needed for the analysis. In this paper only one task is presented, the derivation of the heat transfer coefficient correlation that is simple enough to be remembered by the solar dryer designers.

2 Crops solar dryers Crops solar dryers can take different geometries and sizes. The airflow in solar dryers can be a natural flow or a convective one. The most widely used solar dryer of the medium size is the tunnel type solar dryer, figure 1 [1]. It is used to dry products by warm air. The energy needed for this type is made available by either trapping the solar energy using a plastic cover or by sing a flat plate solar collector as a cover.

Figure 1:

Tunnel type solar dryer [1].

The box type solar dryer is another widely used type. The box sides and top are covered by transparent plastic sheet to trap the solar energy while its bottom is well insulated. It contains one or more perforated shelves to contain the product to be dried. Figure 2 shows an example of box type solar dryers [2]. Other types of solar dryers can be considered to have both advantages of the box solar dryer and the tunnel type solar dryer as in figure 3 [3]. It can be seen that a flat plate solar collector is also needed in this type. The collector plate can be tilted or rotated to face the sun. WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

Air out to chimney Shelves

Air in Figure 2:

Box type solar dryer [2].

Inlet Solar Collector duct

Drying bed

Inlet

fan

Pressure chamber

Figure 3:

Glass plate to enhance heating

Convective crop solar dryer [3]. Black flat plate solar collector

Sun Energy

Air Out

Product AC filter

Air in

θ

Figure 4:

Suction Perforated plate or Fan screen Insulated bottom plate and drainage

The proposed solar dryer.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

371

372 Energy and Sustainability III The solar collector plate can be the bottom of the dryer channel provided that the cannel aspect ratio is large and only air flows through it. It also can be on the top of the dryer channel if the products are to be placed in the channel. It s believed that in this case the channel can be considered of large aspect ratio due to the small thickness of the space between the top hot plate collector and the edge of the product, which is the case to be considered in this paper. Figure 4 shows a proposal for a horizontal or slightly inclined simple and cheap solar dryer. This dryer must have its bottom and sides well insulated. Forced convection is guaranteed by forced flow of air under the collector plate. The air stream is heated due to direct contact with the plate above it. The products inside the duct work as a trip to force the flow to be turbulent flow even when the flow velocity is low.

3 The heat transfer coefficient The heat transfer mechanism to the air from the upper hot plate depends on the characteristics of the turbulent velocity. The velocity profile is known to follow the law of the wall as seen in figure 5.

y  ( y / )  / 

Figure 5:

Velocity distribution in turbulent flow [4].

Giedt [4] gave the profiles of temperature for the three regions according to the law of the wall: Laminar sublayer: Tw  T 

q w Pr

c p  w / 

y ,

0
WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

(1)

Energy and Sustainability III

373

Buffer layer: T1  T 

5 q w ln[ 1  E Pr(( y  / 5 )  1 )] , Ec p  w / 

5
(2)

Turbulent core: T2  T 

2 .5 q w Ec p

w /

ln

y , y2

y 2  y y  30 , y+ >30.

(3)

2

In the above equations, Tw is the wall temperature, T1=T(y+=5), T2=T(y+=30) as shown in figure 2, E in the second equation is the ratio of the eddy diffusivity of heat to that of momentum,  H  M and y in the third equation is the distance from the hot plate to a point in the turbulent core. Although E was found to be nearly 1.4, many analyses use this ratio as one [4]. In order to find the bulk temperature, TB, at a section, the above equations need to be integrated, and the Nusselt number must be defined using TB. To simplify the analysis, the turbulent temperature profile, as shown in figure 6, is considered to be almost uniform at a section except at the laminar sublayer. Substituting y+ = 5 in equation (1), and y+ = 30 in equation (2), yields the following: 5  Pr  q w , (4)  T w  T w  T1  c p  w /   Tbuffer  T1  T 2 

Laminar sublayer

5q w Ec p  w / 

Buffer zone

ln[1  5 E Pr] ,

Turbulence core

T2

Velocity profile

Figure 6:

(5)

T1

Tw

Temperature profile

Velocity and temperature profiles under the dryer hot plate.

Where:  T w  the increase or decrease in temperature through the laminar sublayer,

 T buffer  the increase or decrease in temperature through the buffer layer.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

374 Energy and Sustainability III

4 Determination of the channel bulk temperature The fluid bulk temperature is found by choosing a control volume at the outer edge of the buffer zone, figure 7, assuming that the laminar sublayer and the buffer zone are very small compared to the height of the channel, and that all the heat they receive from the upper wall is transferred to the bulk of the fluid in the turbulent zone by conduction only.

y

q conv

yb

qcond  q w

T2

qconv

x

x  dx

a

a-yb ∆x

x

Figure 7:

The control volume for the heat balance analysis.

Assuming that the lower bottom of channel is completely insulated, and that the heat transfer to the fluid in the turbulent core is from the upper wall, the heat balance is given by: , q cond  q conv  q conv x

x  dx

dh

dT q w  w   x  u m  w  ( a  y b ) dx   u m  w  ( a  y b )  c p  x , dx dx dT . (6) q w  u m  (a  y b )  c p dx

Choosing a more general control volume in the turbulent core at a distance y > yb from the wall, noting that in this region q cond    c p  H ( dT dy ) :  c p H

dT dT  w  x  u m  w  (a  y )  c p  x , dy dx

 H

dT dT .  u m (a  y ) dy dx

(7)

Dividing equation (6) by equation (7), arranging and integrating from T2 at yb to T at y, we get: qw (8) T  T2   a ( y  y b )  0 . 5 ( y b2  y 2 ) c p  H (a  y b )



WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)



Energy and Sustainability III

375

The above equation is used to determine the equation for the fluid bulk temperature, which in turn used to find the equation for the Nusselt number. The fluid bulk temperature is defined as [8]: a

TB 

 c

p

Tu m wdy 

yb a

 c

p

u m wdy

1 a  yb

a

 Tdy

.

(9)

yb

yb

where um is assumed uniform in the turbulent region, and  , and c p are considered constants. Substitution for T from eqn. (8) in eqn. (9) gives:

T2  T B 

1

q



w ( a 3  y b3 )  ay b2  a 2 y b  .  c p ( a  y b ) 2  H  3 

Simple division of the term between the square brackets by ( a  y b ) 2 reduces the above equation to the following: qw 1  (10) T2  T B  a  yb  .  c p  H  3  Given that TW  TB  (Tw  T1 )  (T1  T2 )  (T2  TB ) , equations (4), and (5) are then used to find the equation for (Tw-TB) as follows: TW  T B 

5  Pr  q w



c p  w / 

5q w

c p  w / 

ln[ 1  5 Pr]



Substitution of

yb 

30 

w /

and a 

.

(11)

qw  1 a yb   c p  H  3 

y a

w / 

into equation (11) and

rearranging, gives:  5 Pr  5 ln[ 1  5 Pr] (12)  .   1      y 30 w /  a    H  3  The turbulent heat diffusivity relation is not given very explicitly in many of the literature papers that have been reviewed. A relation for this quantity as a function of Reynolds’ number can be arrived at from reference [6] as: TW  T B 

1

qw c p

 H

 2547 .57 Re  1 .121 .

The above equation is found to take the exponential form as in figure 8. WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

(13)

376 Energy and Sustainability III

0.4

0.3

 H

0.2

0.1

2

6

10

14

Reynolds Number  10

18

20

3

The dependence of the ratio  / H on the air flow Reynolds number.

Figure 8:

In the above equation Reynolds’ number is defined as: Re  VD H /  and is in the range of 10 4 to 5  10 4 . It should be mentioned that the results of eqn. (13) are not verified to be correct over a wide range of Re yet, and the equation should be used with great caution. Since the aspect ratio of channel dryers is high, w  a , it follows that the hydraulic diameter is: DH 

4A 4( a  w ) 2( a  w )    2a . P 2( a  w ) w

Inserting equation 13 into equation (12), we get:

TW

q  TB  w c p

1

w

 5 Pr  5 ln[ 1  5 Pr]    . 2547 . 57  1      y 30 /  a   Re 1 .121  3 

(14)

where;

y a  Using

a w / 





a  um

f /8





1 2

f / 8 Re .

3 f / 8  0.191918 Re 0.1225 for the operating range of Re=4x10 to

 w   u m f / 8 from the balance of the shear forces and the pressure forces [5], in eqn. (14) we get: Re=105, and

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

TW  T B 

 ( 5 Pr  5 ln[ 1  5 Pr]) qw  ( 0 . 191918 Re  0 . 1225 ) c pu m    424 . 5949 Re  0 . 121  398243

Re

 0 . 9985

377

  .  

The above equation is the general equation to predict the temperature difference between the wall and the fluid bulk temperature. For air at the average working temperatures in dryers, Prandtl number is very close to 0.69. Inserting this into the above equation we get:

TW  T B 

qw c p u m

 56 . 87 Re 0 .1225  .   0 . 121  0 .9985  424 . 5949 Re 398243 Re    

5 The heat transfer correlation By definition, Stanton number is given as: St 

qw Nu h .   Pr  Re c P u m c P u m ( Tw  TB )

Substituting for ( Tw  TB ), and for Pr = 0.69 in the above equation, and using n

the least square method to take the form a Re , we get:

Nu  0 . 0086  Re 0 .86  0 . 86  Re 0 .86 / 100 .

(15)

Equation (15) is the final form of the correlation between Nusselt number and Reynolds’ number. It can be seen that this relation is easy to remember, and that the only numeric value to be memorized for both the constant and the index is 0.86. The author will point to this equation as the Giedt correlation after the late Prof. Warren A Giedt whose contribution in thermophysics and heat transfer is outstanding.

6 Comparison of the correlation predictions Giedt’s correlation, eqn. (15), must be validated using experimental measurements and other available correlations found in literature. 6.1 Comparison with experimental measurements Since the correlation is derived using turbulent assumptions, the results of Nusselt numbers are compared with experimental results made by [7] for the range of 104
WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

378 Energy and Sustainability III Table 1:

Comparison of the predicted Nu of Giedt’s correlation with experimental results of [7].

Re Giedt’s eqn. Experiments Error, %

5000 13.05 -

10000 23.7 24.87 -4.7

20000 43. 43.31 -0.7

30000 60.9 59.9 +1.6

40000 77.5 75.4 +2.8

50000 94.5 90.14 +4.8

60000 110.6 -

6.2 Comparison with some correlations in literature In order to validate the predictions of Giedt’s correlation, it is compared with some correlations found in literature. It was not clear from these correlations however that the circumstances are the same. 6.2.1 Reynolds analogy The definition of Stanton number from Reynolds analogy is given by: St 

2 w  \ Nu h f     w2 . 2 Re Pr c P u m 2 2 u m u m

Substitution of the definition of turbulent shear,  w  0 .0386  u m2 Re  1 / 4 [5], and Pr  0. 69 into the above equation yields: Nu  0 . 0266 Re 3 / 4 .

Table 2: Re Giedt’s eqn. Eqn. (16) Error, %

5000 13.05 15.81 18

(16)

Comparison of the predicted Nu with eqn (16). 10000 23.7 26.6 12

20000 43. 44.7 5

30000 60.9 60.63 0.6

40000 77.5 75.2 -3

50000 94.5 89.0 -5.6

60000 110.6 102 -7.7

6.3 Colburn analogy Colburn analogy modifies equation (16) by the factor of Pr 1 / 3 as follows,

Nu  0 .0266 Re 3 / 4 Pr 1 / 3 . Table 3: Re Giedt’s eqn. Eqn. (17) Error, %

5000 13.05 14 8.1

(17)

Comparison of the predicted Nu with eqn. (17). 10000 23.7 23.5 0.2

20000 43. 39.5 -7.8

30000 60.9 53.6 -12.5

40000 77.5 66.5 -15.2

50000 94.5 79. -19.0

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

60000 110.6 90. -23

Energy and Sustainability III

379

6.3.1 Air flow in smooth ducts Holman [9] gave the following correlation for air flow in smooth ducts:

Nu d  0 . 023 Re 0 .8 Pr 0 .4 , Table 4:

(18)

Comparison of the predicted Nu of Giedt correlation with eqn. (18).

Re

5000

10000

20000

30000

40000

50000

60000

Giedt’s eqn.

13.05

23.7

43.

60.9

77.5

94.5

110.6

Eqn. (18)

18.04

31.4

54.7

75.6

95

113.9

131.8

Error, %

27

25

21

19

19

17

16

6.3.2 Flows of fluids with 0 . 5  Pr  1 . 0 Karlekar and Desmond [5] reported that for flows in smooth pipes, the following correlation applies:

Nu  0 .022 Re 0 .8 Pr 0.6 , Table 5: Re Giedt’s cor. Eqn. (19) Error, %

(19)

Comparison of the predicted Nu with equation (19). 5000 13.05 16. 18.4

10000 23.7 27.9 15.

20000 43. 48.6 11.5

30000 60.9 67.2 9.4

40000 77.5 84.6 8.4

50000 94.5 101. 6.4

60000 110.6 117. 5.4

7 Discussions and conclusions From the above comparisons, it can be seen that the developed correlation is strikingly in good agreement with the experimental measurements of [7]. The 5% error in almost all engineering applications, especially in the field of convection heat transfer, is considered very acceptable. Comparison with other correlations shows higher percentage errors. Holman, [6], reported that equation (18) predicts values within  25%. The predicted values of Giedt correlation are shown to be within this range of errors when compared with almost all correlations used for comparison. Except for eqn (18), Giedt’s correlation predictions are found to be within 20% of those predicted by other correlations in the range of 10000 < Re < 50000. It can be concluded that the Giedt correlation can be used with confidence for the purpose of calculating the heat transfer coefficient within errors of nearly 5%. It has a simple and easy to remember form. T he correlation can be used for comparison when conducting experimental measurements in forced convection solar dryers, which will be conducted in a later phase of the design of family size solar dryer. WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

380 Energy and Sustainability III

Nomenclature A

solar collector flow area, m2

a

distance between top and bottom plates, m

E

the ratio  H  M

f

the friction coefficient

h

the heat transfer coefficient, W/m2K

k

the conductivity, W/mK

qw

the wall heat transfer, W/m2

T

temperature, K

Tw

wall temperature, K

T1

temperature of the edge of the laminar sublayer, K

T2

temperature of the edge of the buffer zone, K

u

air velocity, m/s

u+

non-dimensional velocity

x

coordinate in the flow direction, m

y

coordinate and distance from the dryer collector plate, m

y+

non- dimensional coordinate

yb

distance from collector top plate to the outer edge of the buffer zone

H

turbulent heat diffusivity

M

turbulent momentum diffusivity



density, kg/m3



kinematic viscosity, m2/s



(also  s ) shear stress, N/m2

w

wall shear stress, N/m2

References [1] B. K. Bala, and Sem Janjai, ‘Solar drying of fruits, vegetables, spices, medicinal plants and fish: Developments and Potentials, International Solar Food Processing conference, 2009, p. 1. WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

381

[2] B. A. Ezekoye, and O. M. Enabe, ‘Development and Performance Evaluation of Modified Integrated Passive Solar Grain Dryer’, The Pacific Journal of Science and Technology, Volume 7, No 2, November, 2006, p. 185 [3] Soren O. Jensen, and Erik F. Kristensen, ‘Test of a solar crop dryer’, Solar Energy Center and Danish Technological Institute, Jan 2001, p. 4 [4] Prof. Warren H. Giedt, ‘Principles of Engineering Heat Transfer’, Second Edition, 1967, p 177-180 [5] Karlekar, B. V. and Desmond, R. M., ‘Heat Transfer’, Second Edition, 1982 [6] M. A. S. Malik, F. H. Buelow, ‘Analytical Model for Determinating the Heat Transfer Coefficients in No-Glass Flat Plate Collectors Used for Drying Agricultural Crops’, Sun, Mankind’s Future Source of Energy, Volume 3, Pergamon, 1978, p 1946. [7] H. M. Tan, W. W. S. Charters, ‘An Experimental Investigation of Forced convection Heat Transfer for Fully Developed Turbulent Flow in a rectangular Duct with Asymmetric Heating’, journal of Solar Energy, V13, p121, 1970. [8] Fox, R. W. and McDonald, A. T., ‘Introduction to Fluid Mechanics’, Fourth Edition, John Wiley & Sons, Inc., 1994. [9] Holman, J. P., ‘Heat Transfer’, Fifth Edition, McGraw-Hill, 1981, p. 227

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

This page intentionally left blank

Energy and Sustainability III

383

Energy recovery of grass biomass S. Oldenburg, L. Westphal & I. Körner IUE, Bioconversion and Emission Control Group, Hamburg University of Technology, Germany

Abstract Not only due to the actual climate change, but also in consideration of exhaustible resources, alternative energy supplies for the steadily growing energy demand need to be found. The main emphasis should be placed on the substitution of fossil fuels with agricultural by-products and other organic materials. The utilisation of fresh grass or grass silage of extensively cultivated farm land especially has great potential as an energy feedstock, as in agriculture this bio-resource is currently considered a waste material and is neither economically nor ecologically utilised in an efficient way. Additionally, the lawn-clippings, which are accumulating as communal and private waste could be used for energy production since many local authorities have problems with utilising this gramineous waste. Thus, for anaerobic digestion big amounts of grass biomass and lawn substrates are available from farmers and landscape conservation. In order to evaluate the suitability of this material for biogas plants in the first place a detailed inventory needs to be conducted. This was exemplarily done for the Hamburg District Bergedorf (155 km2). The result shows that approximately 10,000 Mg/a of grass and lawn clippings could theoretically be made available. By laboratory investigations in batch tests the theoretical biogas potentials of selected grass and lawn substrates were determined. A statement about the suitability of the substrates for anaerobic digestion is made in this paper. The biogas potentials are between 325 and 720 standardized l per kg organic dry matter (l/kg ODM), depending on the sampling location, mowing time, grass species etc. For example, the biogas potentials for clippings from the dikes were in a range comparable with corn silage between 420 to 700 l/kg ODM. Additionally the problem of seasonal accumulation of grass biomass including the influence of storage on the initial material is considered in this paper. Keywords: grass, lawn, digestion, biogas potential. WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESUS110331

384 Energy and Sustainability III

1 Introduction Climate protection is an important part of the challenges of environmental politics nowadays. To prevent the progress of global warming climate protection agreements have been established according to which a great amount of the energy demand has to be provided by renewable energies in the near future. The substitution of fossil energy sources by renewable bio-resources will inevitably lead to less emission of carbon dioxide. Moreover, renewable resources are an important and versatile energy source since they can be utilized for heat, fuel and electricity. A crucial point is the possibility of storage and flexible utilisation? Because of this the cultivation of energy crops, especially corn, increased in Germany in the last years enormously. But at this point, the competition for cultivable areas between energy crops and food products has to be considered. Eventually other conflicts of interests will rise up between bio-energy providers, nature conservation and tourism, given that much grassland was converted to farmland for growing energy crops. A better opportunity could be the use of plants and green waste that arises from countryside preservations and which cannot be used for the food production. There are an estimated 900,000 Mg of green waste available in Germany per year, which originate from nature and biotope areas [1]. Additional grass fractions are generated in agricultural excess areas or lean grass fields. Usually these resources have to be collected from the land on a regular basis to prevent accumulations of nutrients in the soil and preserve the biological ecosystem. Furthermore, due to the decrease of cattle farming in some regions, the green waste from the farmland formerly used for cattle feed production needs a to be disposed. These areas are then only serviced without utilisation of the grass. The maintenance of public parks, sport fields and gardens are other sources of grass. In Germany an estimated 300,000 Mg/a of such green waste is generated [1]. In conclusion, grass fractions are available in huge amounts from private and commercial sources as well as from landscape maintenance. The goal of this work is an evaluation of grass fractions as substrate for biogas generation. The yield of grass biomass per area has exemplarily been investigated for one district of Hamburg. This energetically usable biomass derives from extensive grasslands, fields of grass and farmland; it is either disposed waste or utilised up to now. The amount of this biomass has been investigated and experiments were performed to determine its energetic potential. The results can be transferred to different areas and regions to draw a final conclusion: whether it makes sense to energetically utilize the unused or disposed grass and lawn waste as a substrate in biogas plants, or not.

2 Definitions Grassland and pasture is defined as agricultural land that has been set up by humans. The grass has to be cut on a regular basis to prevent a scrub encroachment [2]. Grass, herbs and leguminous plants grow on grassland. Depending on the farming of the land grass usually represents the majority of the WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

385

present vegetation in Germany. This is due to the selection caused by mowing the land repeatedly, since grass is able to regenerate and re-grow very fast. Thus the ratio of grass increases with intense farming of the land. 29% of the agricultural areas of Germany are grasslands [3]. A field of lawn is defined to be an area which includes many different kinds of grass, but no herbs or leguminous plants at all. To maintain a good optical view the lawn is usually kept at a length of two to ten centimetres. Therefore it has to be mowed up to 40 times a year [4]. Fields of lawn are maintained for the purpose of sports, recreation and a positive representation. About 5% of the entire area of Germany is kept as lawn of some sort [5].

3 Inventories The district of Bergedorf covers an area of 155 km², which represents 20% of the entire area of Hamburg, including 13 different quarters. The district itself could be split into two different parts: an urban part and a rural part, which makes up about 75% of the area. Most of the quarters are agrarian and have a small population density. Overall there are about 120,000 residents living in the district of Bergedorf, averaging at 760 people per km². There are only three quarters with a population density of more than 1,000 people per km². The other ten quarters are sparsely populated with no more than 400 residents per km². The grassland is about two times as large as the cultivated land with an area of 53 km². More than half of the area is being used agriculturally. The area used for buildings, infrastructure, business and the open space add up to only about 26%. Almost half of Hamburg’s agricultural land is located in the district of Bergedorf whereas the cultivated land in the entire city is only about 10%. Altogether all different structures of a city are present in the district of Bergedorf: ranging from urban regions to less densely populated parts and from agricultural land to nature preserve areas. The calculation of the dry mass yield of grass fractions was performed using the land use of the city, values from literature and average values. Additionally all results presented in this paper refer to the generation within one year. Furthermore the dependencies on location, climate and cultivation have been considered in the calculations. 3.1 Fields of grass The actual yield potentials of the different grasslands are hard to approximate. There are literature values, but the yield can differ depending on the location and nutrient content of the ground. The grassland was categorized into two different main groups, whereat the areas have mostly been assigned to their cultivation. The first group is the intensively managed grassland, which are intensively used fertile meadows in agriculture whose grass is used to feed the cattle. The second group is the extensively managed grassland. This is used in accordance with the administration. The areas are used for conservation or recreation; some of them are defined as compensation areas. The entire potential of the whole grassland is

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

386 Energy and Sustainability III about 8,100 Mg of dry matter in the district of Bergedorf per year. This is 67.5 kg per resident and year. In the following sections, the calculations are shown and explained. 3.1.1 Intensively managed grassland To determine the potential of intensively farmed meadows letter-surveys have been conducted. 81 were sent to farmers in Bergedorf via the department of agriculture. The grass from intensively managed grassland is only available for further energetic utilization if the outgrowth could not be utilized in another way. The reasons why the mowing is not used completely, are, for example, a lack of cattle, a bad quality of the year’s harvest or plant populations that cannot be consumed by the cattle. Mowing and gathering this kind of grass could only be considered if an allowance was paid for this work. The average yield from mowing three to six times per year is about 0.8 and 1.2 kg of dry matter per square meter and year [6]. For a yield of 0.85 Mg of dry matter per square meter and year there is a potential of about 1,780 Mg of dry matter per year from intensively managed grassland. 3.1.2 Extensive managed grassland There are five different kinds of grass areas in the district of Bergedorf, which are extensive managed: dikes, public fields of grass, compensation areas, contracted nature preservation and nature preserve areas. The dikes, the public fields of grass and compensation areas are fertilized with liquid manure or dung in part. Then the yield per year and square meter is less than 0.6 kg for cutting it twice a year [6]. Land that is not being used to produce animal food and must not be fertilized, as contracted nature preservation areas have a yield of biomass production less than 0.35 kg of dry matter per year and square meter [6]. Nature reserve areas will be considered to have a yield of 0.15 kg of dry mass per year and square meter [7]. The potential of dikes was computed using the average of the year 2010 and is about 600 Mg of dry matter per year. Most of the outgrowths are disposed by composting, a process that causes costs. Gathering of the material is expensive and the incline of these fields impedes this process as well. The maintenance of the areas that are under contracted nature preservation is tied to distinct contracts with the farmers of Bergedorf and the agricultural use as pasture or mowed meadow is defined. These areas can be mowed starting at the first of July; the responsibility of this action was transferred to the farmers. The farmers are obliged to remove the cut grass for preventing an accumulation of nutrients on the ground. For the purpose of disposing this material it is commonly used as litter for the animal sheds. This is not the best solution and it does not represent the optimum utilization of the material. It takes years up to decades until the land is depleted and there are different meadows with larger or smaller yields. Land having very small yields due to the weather can usually only be cut once a year. Cattle are sent on some of this land after cutting the grass, then the amount from the second cut decreases, too. By the fact that these areas are farmed by

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

387

ecological means, indicating that the first time of cutting the grass is done very late and a second cutting does not always take place, a potential of about 1,300 Mg of dry mass of grass per year from areas that are under contracted nature preservation is theoretically available. Notice has to be taken of the partial swamp land and the areas that are hard to access, properties that complicate collecting the material. Additionally when cutting the grass very late they contain an increased amount of lignin, which can cause problems during the biogas production. The maintenance of the present compensation areas in the district of Bergedorf and areas that are under a development plan is performed using similar conditions in the according contracts compared to the contracted nature preservation, but the use of the material from cutting is similar to the contract nature preservation. The mowing is only used occasionally for meadows with no cattle on it. These areas are partially fertilized using cattle dung. So they are considered as extensive grassland having yields of about 0.6 kg of dry matter per square meter and year by cutting twice a year. For grazed fields there is a computed value of 0.35 kg dry matter per square meter when cutting the grass. The second clipping is usually dried and used as litter in the cattle stables in September. This represents a bad compromise, since the quality of the material is not sufficient to use it as food and therefore it would have to be disposed. The theoretical potential was determined to be about 5,400 Mg of dry matter per year from compensation areas. For the nature preserve areas, proper calculations of the incoming amount of grass are very difficult, since maintenance is only done on rare occasions. The actions of maintenance are integrated into a maintenance schedule individually adapted to each nature preserve area. It is a matter of fact that a large amount of the material cannot be utilized, because a part of it has to remain in the nature preserve areas to preserve the natural circle. In addition the areas are quite often difficult to access and agricultural vehicles are not allowed to drive there. By an energetic utilization and an according allowance for the outgrowth the maintenance of the nature reserve areas can be improved and a larger potential is possible. The yield is at about 0.15 Mg of dry matter per square meter and year, because of a late cutting and due to a lack of available nutrients in the ground. Hence the potential of the biomass is estimated to be 280 Mg of dry mass per year from nature preserve area. There are many small companies, who are assigned to maintain public fields of grass. Those areas are only mowed about once or twice a year, so they belong to the group of less intensively managed grasslands and not to the group of lawn. Because of not fertilizing these areas the yield potential was estimated to be 0.35 kg of dry matter per square meter and year. So far the cut grass remains on the land and is not gathered, except for a small path. Currently, it is desirable to get less mowing. Nonetheless the disposed material is being composted which causes costs. From these results a biomass potential of 1,120 Mg dry matter per year from public fields of grass were detected. By mulching after clipping some nutrients are transported back into the ground and the yield could be increased.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

388 Energy and Sustainability III 3.2 Fields of lawn In this work fields of grass and lawns will be discussed separately, since their maintenance and composition of different kinds of grass are different. The fields of lawn of public grasslands, parks, sport fields, private gardens, single and apartment buildings have been considered for the calculations. The potential for public grassland with a total of 10 square km has been calculated on indications of the district office Bergedorf, surface structures and re-growth rates. In addition, the amounts which are partly collected are included in the calculations. A total of 490,000 m² of lawn is cut by companies. It is not known how large the surface is which is cut from the District Office (Bezirksamt). It has made the assumption that at least another 20% of the total of 7 square kilometers of public green areas must be mowed. It was assumed that all areas are covered with grass, which has similar properties as the strain "Berlin Zoo". Since the area size is not precisely known, a much larger potential might be possible. With this calculation the potential of public grassland is estimated to 643 Mg of dry mass per year. A questionnaire was sent to all churches in Bergedorf. The response rate was very low. Therefore, only a reflection of the state church has been done. The result was about 10 Mg of dry matter per year. Knowing that only one cemetery has been considered for calculating the potential, there will be much more graseous waste that could not be included so far. The sport fields in the district of Bergedorf could provide about 32 Mg of dry matter per year, if this material would be gathered and not remain on the field. The potential yield of private yards and gardens of single, double and multiple apartments depends heavily on the settlement structure, the size of the gardens and their design. In the urbanized parts of Bergedorf the grass potential for the one-and twofamily houses was calculated with an average of 34 kg of organic waste per inhabitant per year. This value comes from the estimation of the Ministry of Urban Development and Environment, which is in Hamburg for about 60,000 Mg of organic waste per year recycled about private composting [8]. For the remaining eleven city quarters, this value could not be applied because of their rural structures. Therefore the garden sizes and structures were determined by sending letters and surveys to the residents and by performing green waste sorting. In addition, the re-growth rates and expected care measures were calculated. It is to be remarked that the calculated potential reflects actual and realistic values, if proper collection procedures are introduced and the residents are well informed concerning the separation of different kinds of waste. The computed potential from private households is about 4,400 Mg of dry matter per year. The whole potential of lawn is about 5,070 Mg of dry matter per year. 3.3 Summary There is an overall theoretical potential of 15.550 Mg of dry matter per year of intensively and extensive managed grassland and lawn.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

Table 1:

389

List of the potential yields of grass in the district of Bergedorf.

Area Intensive grassland Extensive grassland Fields of lawn Total

Dry matter [Mg/a] 1,780 8,700 5,070 15,550

4 Anaerobic digestion of grass fraction Biogas is a mixture which primarily consists of two components: methane (CH4) and carbon dioxide (CO2). It is generated by the degradation of organic matter in the absence of oxygen. The technically usable process of this anaerobic degradation is called digestion, which is enabled by complex interactions of different microorganisms. The degradation proceeds step by step and can be broken down into four different states that are referring to the involved microorganisms: Hydrolysis, Acidogenesis, Acetogenesis and Methanogenesis. Being the prime combustive compound, methane basically determines the properties and the energetic usage of the biogas. It is an energy source with a high yield and has the calorific value 50 kJ/kg in under standardized condition and represents about two thirds of the overall colorific value of natural gas [9]. A detailed literature research has shown that the biogas potential of grass varies between 500 to 700 l/kg ODM and is quite different concerning the structures of the land or the agricultural methods. In consequence the gas potentials of many different grass samples were determined by theoretical models, elementary analyses, as well as by laboratory experiments of exemplary samples of the district of Bergedorf. The calorific value determined by thermal oxidation serves for comparison in section 5. Choosing the particular grass substrates was the priority to the broad range of different areas and characteristics. All of the samples have directly been collected in the district of Bergedorf and cover all areas considered in the inventory. Altogether 16 different substrates have been investigated; nine substrates of extensive managed grassland, four different lawns and one of intensive managed grassland. 4.1 Determining the theoretical biogas potential Using elemental analysis all ratios of carbon, nitrogen, sulfur and phosphor of the different substrates can be determined. The results are listed in table 2. The content of carbon of the grass samples was between 45% and 47% of the dry matter. The content of nitrogen varied bin a range of 0.72% for outgrowths of nature preserves areas up to 37% in case of public fields of grass. The highest value of nitrogen can be lead back to cut grass that has been left on the ground aggregating nutrients. The ratio of carbon to nitrogen (C:N ratio) is crucial to the gas yield. If the ratio is too small, the organic substance of the substrate cannot be degraded completely. This is the cases for very low crude fibre contents, as well. The WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

390 Energy and Sustainability III optimum ratio is reported to be between 21:1 and 40:1 [10]. For ratios lower than 16:1 the gas yield is expected to decrease, since there is a lot of redundant nitrogen. The maximum ratio should be 45:1. Many samples were in the optimum range, only the samples of dike clipping c and d, as well as the areas in the nature preserve areas had too low nitrogen contents (table 2). The phosphoric content of the grass samples from this district, except for the ordinary maintained grass of gardens and yards, are lower than the suggested literature values of 0.14% to 0.19% phosphor in the dry matter [11]. This increased phosphorous content can be lead back to the fertilization in spring. The chlorine content of the substrates is in a range of 0.23% up to 1.16% in the dry matter. The literature values are 0.31% for festuca arundinacea and 1.39% for grass of pasture and are not exceeded by the substrates of district Bergedorf. In contrast, the sulphuric content is higher: up to 0.3% sulfur in the dry matter. The literature values are between 0.14% and 0.19%. Sulphur is an essential component for microorganisms that are present in a digester. Not solved resp. dissociated hydrogen sulphide is toxically and can hinder the biogas production if it is present in increased concentrations. Table 2:

Elemental composition of the samples.

Substrate Unit Public Meadow

C % TS 47.1

N % TS 2.4

Ph % TS 0.08

S % TS 0.30

C:N 23.2:1

Dike Clipping (a)

46.6

1.9

0.04

0.18

29.4:1

Dike Clipping (c)

46.0

0.7

0.10

0.15

69.1:1

Dike Clipping (d)

45.6

0.8

0.13

0.19

69.2:1

Nature Preserve Area

46.8

0.8

0.13

0.16

74.5:1

Gras of Gardens and Yards (Ordinary)

45.4

1.6

0.21

0.30

31.9:1

Gras of Gardens and Yards (Properly)

34.5

1.7

0.10

0.27

25.0:1

Public Fields of Grass

44.2

1.9

0.13

0.24

27.7:1

One possibility to theoretically determine the maximum biogas potential is to perform calculations including the elemental composition and to use the Buswell-equation that has been modified by Boyle. Regarding that a complete digestion of the organic substance only is possible up to a maximum of 83% the theoretical gas yield results in an average value of 820 l/kg ODM (table 3). 4.2 Practical biogas potential determination The biogas potential has been determined by batch tests under laboratory conditions according to VDI-standard no. 4630 in triplicate. Digestion test in the WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

391

batch procedure allow drawing conclusions on the actual biogas yield and the anaerobic degradability of certain matters or solutions. Furthermore a qualitative estimation of the speed of the anaerobic digestion of certain substances and possible inhibitors in the examined concentrations of these substances can be conducted. The results are presented in figure 1, including a reference curve with corn.

Figure 1:

Biogas yields of different grass samples.

The gas yield of the silage of intensively managed grassland is 545 mlN/g ODM and therefore is a little bit lower than the yields of the outgrowths of nature preserve areas and of levee areas of the first time of cutting it from the end of May to the beginning of July. Since this sample was one of the late clippings of September they were expected to produce less gas. These values are confirmed by literature [12]. The gas yields of extensively cultivated meadows ranged from 325 mlN/g ODM for silages of the compensation areas up to 705 mlN/g ODM for dike clippings (c). For these experiments the gas yields of silages are clearly below the yield of the not conserved outgrowths. The gas production of the silage of the compensation areas and the contracted nature preserve areas (325 mlN/g ODM and 445 mlN/g ODM) is less than the gas production of the second dry clipping of the glider airfield with 460 mlN/g ODM. Except for the outgrowths of public fields of grass the substrates of extensive meadows do not show any signs of being hemmed during the gas production. The curve of the gas production shows an obvious sharp bend at the beginning. This might be due to both, the high content of nitrogen (2.4%) and an eventual hemming because of ammonia. The gas yield of lawn substrates is in the range of the extensive meadows except for the clippings from the communal maintenance of the public fields of grass. This clipping has an increase in the gas production rate of 720 mlN/g ODM. Ordinary maintained grass of gardens and yards has a WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

392 Energy and Sustainability III production rate of 530 mlN/g ODM, as the properly maintained grass with 525 mlN/g ODM for the clipping of May and 570 mlN/g ODM for the material of June. The C:N-ratio of the grass substrates are in the optimum range compared to the extensive meadows. Despite the good expectations from this concerning the digestibility of the grass, compared to extensive meadows, the experiments show similar levels of degradability of the organic substance of 64.2% for proper maintained grass and of 71.6% for the public fields of grass. Concerning literature no losses were predicted, but problems during the ensiling of late clippings were known, since the large structures cannot be densified. The gas yield of both silages, which had 325 mlN/g ODM and 445 mlN/g ODM, definitely is less than the yields of not conserved outgrowths. Therefore a possible loss due to ensilaging has to be considered. Additionally fresh material and material that has been dried on the dike for two days were compared. The wet material surpassed the dry material with 705 mlN/g ODM compared to 520 mlN/g ODM. Thus there should be a decrease of the biogas potential when drying the material. This was an expected result, since the elemental analysis showed a decrease of the carbon content of 45.99% to 45.63% during dehydration.

5 Combustion The utilization of the outgrowths can be processed using one of two possible methods. Fresh grass or silage can be digested in a biogas plant or it can be combusted. Because of that a reference is analyzed to determine the calorific value of the gas potential of the samples. The calorific value HU is defined to be the maximum usable amount of heat during combustion (DIN EN 14918). Utilizing the grass and lawn clippings is only possible to a certain extent, since some of the properties of the grass stalk are disadvantageous to the combustion process. Sophisticated firing methods and an extended off-gas treatment require much more effort. On the one hand this leads to the exhaustion of more chloral, nitrogen, potassium or sulphuric gases, on the other hand there are increased amounts of ashes, causing higher rates of pollutant emissions and increasing the costs of the firing system. The amount of ashes of the lawn substrates is about 20%, which is more than the ashes of average grass clippings, which is about 9%. Wood is producing a significantly smaller amount of ash, about 0.5% [11]. Additionally the utilization of recently harvested plants is more difficult, since the material is very moist and would have to be dried before firing it. Moisture contents of more than 20% [13] cause the combustion to be inefficient and drying it would require several additional mechanical operations. Table 3 shows the average moisture contents and amounts of ashes for the samples from the district of Bergedorf. The moisture content is more than the required 20%. The caloric values are about 9% below the average caloric value of wood which is 18.5 MJ/kg TS [14].

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

Table 3:

393

Biogas yields, caloric values, moisture contents and amounts of ashes.

Substrate

Theoretic Biogas Biogas production production

l/kg ODM

Caloric value Hu

Moisture content

Amount of ashes

kJ/kg S

% ODM

% TS

16,537

k.A.

12.9

56.1 70.2 38.7 64.2

8.4 8.6 8.3 7.8

Unit Intensively managed grassland Extensive grassland Public meadow Silage from compensation area Glider airfield

l/kg ODM

Dike clipping (a) Dike clipping (c) Dike clipping (d) Nature preserve area Fields of grass Lawn of gardens and yards (ordinary)

812 789

705 620

773

445

16,928 16,409 16,356 16,157

878

530

16,684

82.4

13.2

Lawn of gardens and yards (properly)

726

545

12,047

57.7

40.6

Public fields of lawn

851

720

16,710

60.2

14.8

545 852

500

812

325 460

6 Summary Because of the increased energetic use of biomass the competition for agricultural land between energy crops and actual feed crops was intensified. In addition the decrease of cattle farming in Germany frees grassland which has to be maintained. An energetic utilization of so far unused or not efficiently used green waste would be an important step for the improvement and there exists a large untapped potential. Based on the results of this paper a comparison of the theoretical and practical biogas potential as well as the combustion can be made. The reference was given by different literature values which varied in a range of 500 mlN/g ODM up to 700 mlN/g ODM. The practical biogas production was determined by laboratory digestion experiments. The theoretical biogas production was determined by an element analysis via the modified Buswellequation. The theoretical potential was between 800 mlN/g ODM and 878 mlN/g ODM and much higher than the results of the laboratory tests. The practical experiments displayed a good degradability and resulted in values between 325 mlN/g ODM and 720 mlN/g ODM depending on the material and its storage. Looking at figure 1 a rapid digestion seems to be clear, identifiable by the strong plateau phase. This indicates a good anaerobic degradation of the substrate. After WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

394 Energy and Sustainability III 21 days the gas production was still at about 2.5% of the so far produced gas. Testing for a longer period should result in higher gas yields. In addition, more optimization opportunities under the anaerobic digestion and the silage-process must be found. The energetic utilization by fermentation is the best option, because the carbon cycle can be closed with digestate. Late clippings of autumn and the grass of extensive land feature a low gas yield, so the combustion of these outgrowths could be an alternative method. For the economic energy a lot of factors, i.e. different temperatures during the fermentation, the storage, treatment and collection processes and co-substrates, have to be investigated.

References [1] Rösch, C. : Vergleich stofflicher und energetischer Wege zur Verwertung von Bio- und Grünabfällen. In: Wissenschaftliche Berichte FZKA 5857, S. 269, 2005 [2] Pfadenhauer, J.: Vegetationsökologie. A script, with 64 tables. 2. expanded edition, Eching near München: IHW-Publisher., 1997 [3] Prochnow, A.; Heiermann, M.; Idler, C.; Linke, B.; Mähnert, P.; Plöchl, M.: Biogas vom Grünland:Potenziale und Erträge, Leibniz Institute of Agricultural Engineering PODMdam-Bornim, 2007 [4] Degenbeck, M. Bavarian State Institute for Viticulture and Horticulture [Hrsg.]): Basiswissen Rasenbau. Anlage und Pflege von Rasenflächen, In: Deutscher Gartenbau, Heft 4; S. 10-12 [5] Turf specialist agency (University Hohenheim [Hrsg.]): Kompetenz für Rasen. With the collaboration of Hartmut Schneider und Wolfgang Hendle., 2007 https://www.uni-hohenheim.de/rasenfachstelle/ [Accessed 29.09.2010] [6] Buske, M. (MOVECO GmbH [Hrsg]): Grünland- Abgerenzung, Definition und Unterteilung, 2010 http://www.architektenleistungen.de/article /Grünland [Zugriff am 15.10.2010] [7] Oechsner, H. (Universität Hohenheim [Hrsg.]): Verfahrenstechnik der Vergärung von Biomasse. State Institute of Farm Machinery and Construction, in collaboration with the Academy for Nature and Environmental Protection of Baden Wuerttemberg, Stuttgart, 2005 [8] Freie und Hansestadt Hamburg, Ministry of Urban Development and Environment [Hrsg.]): Nationalpark und Naturschutzgebiete in Hamburg, 2010, http://www.hamburg.de/contentblob/202306/data/bsu-nsg-tabelle.pdf [Accessed 14.10.2010] [9] Hofmann, J. (Regierung Niederbayern. Landshut[Hrsg.]): Grundlagen der Biogaserzeugung, 2001, Proceedings of the briefing on 13 July 2000 in the government of Lower Bavaria [10] Mähnert, P.: Kinetik der Biogasproduktion aus nachwachsenden Rohstoffen und Gülle, Dissertation, Humboldt-Universität, LandwirtschaftlichGärtnerischen Fakultät, Berlin, 2007 [11] Hartmann, H.; Böhm, T.; Maier, L. (Bavarian State Ministry for Regional Development and the Environment (Stmlu) [Hrsg.]): Naturbelassene

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

395

biogene Festbrennstoffe. Umweltrelevante Eigenschaften und Einflussmöglichkeiten, München, 2000, [12] Kaiser, F.: Einfluss der stofflichen Zusammensetzung auf die Verdaulichkeit nachwachsender Rohstoffe beim anaeroben Abbau in Biogasreaktoren, Dissertation, Maintained by J. Bauer, Technische Universität München, Scientific Center Weihenstephan for Food, Environment and Land Use, 2007 [13] Elsäßer, M. (Staatliche Lehr- und Versuchsanstalt für Viehhaltung und Grünlandwirtschaft. Aulendorf [Hsrg.]: Möglichkeiten der Verwendung alternativer Verfahren zur Verwertung von Grünlandmähgut: Verbrennen, Vergären, Kompostieren. In: Reports on Agriculture, 2003 [14] FNR e.V. [Hrsg.]: Leitfaden Bioenergie. Planung, Betrieb und Wirtschaftlichkeit von Bioenergieanlagen; 4., unchanged edition., 2007

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

This page intentionally left blank

Section 6 Energy analysis

This page intentionally left blank

Energy and Sustainability III

399

Effect of H2 enrichment on the explosive limits of Liquefied Petroleum Gas (LPG) in conventional combustion I. Izirwan, S. Noor Shahirah, S. Siti Zubaidah, M. N. Mohd Zulkifli & A. R. Abdul Halim Faculty of Chemical Engineering and Natural Resources, Universiti Malaysia Pahang, Malaysia

Abstract The use of hydrogenated fuels shows a considerable promise for the applications in gas turbines and internal combustion engines. Hydrogen holds a significant promise as a supplemental fuel to improve the performance and emissions of ignited spark and compression ignited engines. Hydrogen has the ability to burn at extremely lean equivalence ratios. In addition, it is important to analyze the explosive limits for safety reasons and to increase the efficiency in operation of many industrial and domestic applications that use the explosion concept. The aims of this study are to determine the explosive limits of liquefied petroleum gas/air mixture and to investigate the effect on the explosive limits of liquefied petroleum gas/air mixture enriched up to 8% vol of hydrogen at atmospheric pressure and ambient temperature. The experiments were performed in a constant volume of 20 liter closed spherical vessel. The mixtures were ignited by using a spark permanent wire that was placed at the centre of the vessel. The pressure-time variations during the explosion of liquefied petroleum gas/air mixture in explosion vessel were recorded. The explosion pressure data is used to determine the explosive limits which flame propagation is considered to occur if the explosion pressure is greater than 0.1 bar. In this study, the result shows the explosive limits range from 2 to 8% vol of liquefied petroleum gas/air mixture and has revealed that the addition of hydrogen in liquefied petroleum gas/air mixture decreases the lower explosive limit from 2 to 1% vol and for the upper explosive limit, the limit is also decrease from 8 to 7% vol. Keywords: explosive limits, hydrogen enrichment, liquefied petroleum gas, closed explosion vessel. WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESUS110341

400 Energy and Sustainability III

1 Introduction Explosion is a combustion of mixed combustible mixtures (gas cloud) that cause a rapid increase of pressure. When the combustion of fuel is not controlled within the confines of the burner system, the limit of flammability is called explosive limit. Analysis of the explosive limit is important for safety reasons and increases the operation efficiency in many industrial and domestic applications that use the concept of explosion. In many practical applications for power generation, such as gas turbines, there has been strong interest in achieving lean premixed combustion because nowadays, people started to be aware about the safety and environment besides the classical concerns about the efficiency of the operation [1]. Liquefied Petroleum Gas (LPG) fuel consists mainly of propane and butane in various proportions according to its state or origin. The composition of LPG fuel varies very widely from one country to another. As a known fuel with less emission, LPG has attracted increased interest in recent years [2]. LPG is extensively used both as an alternative fuel in automotive engine and as a domestic fuel. In comparison with conventional engine fuel (gasoline and diesel), LPG is considered as an attractive alternative fuel since its combustion in air is characterized by the reduced emissions of nitrogen oxide (NOx), carbon monoxide (CO) and unburned hydrocarbon. In addition, hydrogen holds significant potential as an added fuel to improve the performance and emissions of ignited spark and compression ignited engines. It also has the ability to burn at extremely lean equivalence ratios. Hydrogen will burn at mixtures seven times leaner than gasoline and five times leaner than methane [3]. This lower limit is governed by the Le Chatelier Principle [4]. The flame velocity of hydrogen is much faster than other fuels allowing oxidation with less heat transfer to the surroundings. This improves thermal efficiencies because hydrogen has a very small gap quenching distance allowing fuel to burn more completely [5]. Explosion may be defined by a combustion of combustible mixtures (gas cloud), causing a rapid increase of pressure. The pressure generated by the combustion wave will depend on how fast the flame propagates and how the pressure can expand away from the gas cloud (governed by confinement). An explosion range is started from the Lower Explosive Limit (LEL) to the Upper Explosive Limit (UEL) of a specific substance. Vapour-air mixture will ignite and burn only over a well-specified range of compositions [6]. The LEL/UEL of gas or vapour is the lowest/highest concentration at which gas or vapour explosion is not detected in three consecutive tests. Generally, for a material that lowers the LEL or wider explosion range, the greater its flammability hazard degree would be. LEL is the limiting concentration (in air) that needed for the gas to ignite and explode. At any concentrations in air that is below the LEL, there is no fuel to continue an explosion. Concentrations lower than LEL are "too lean" to burn. UEL is the highest concentration (percentage) of a gas or a vapour in air capable of producing a flash of fire in the presence of an ignition source (arch, flame, heat). Concentration higher than UEL are "too rich" to burn.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

401

Natural gas and propane are generally considered to reduce engine maintenance and wear in spark-ignited engines. The most commonly cited benefits are extended oil change intervals, increased spark plug life, and extend engine life. Natural gas and propane both exhibit reduced soot information over gasoline. Reduced soot concentration in the engine oil is believed to reduce abrasiveness and chemical degradation of the oil. Gasoline fuelled engines (particularly carburetted engines) require a very rich operation during cold starting and warming up. Some of the excess fuel collects on the cylinder walls, and “washing” lubricating oil off walls is contributing to accelerated wear during engine warm up. Gaseous fuels do not interfere with cylinder lubrication. Gaseous fuelled engines are generally considered easier to start than gasoline engines in cold weather. This is because they are vaporized before injection to engine. However, under extremely cold temperatures, there is a cold-start difficulty for both propane and natural gas. This is probably due to ignition failure because very difficult ionization conditions and sluggishness of mechanical components. The effect of hydrogen enrichment of hydrocarbon combustion on emissions and performance were investigated by Wall [7] which have shown that added hydrogen in percentage as low as 5-10% of hydrocarbon fuel can reduce that hydrocarbon fuel consumption. The theory behind this concept is that the addition of hydrogen can expand the lean operation limit, improve the lean burn ability and decrease burn duration. Based on the pressure time traces, three regimes of explosion development or combustion conversion can be identified. The regimes depend on the initial mixture composition, at given conditions, as illustrated in figure 1. In the first one, marked as 1, the pressure increases fast and smoothly to the maximum value, after ignition. This type of pressure development is seen for near stoichiometric mixtures. In the second regime, the pressure trace is distinctly S shaped (a shoulder). Such type of pressure development is present in a narrow fuel lean concentration range and in a wider concentration range with fuel rich mixtures. In the third regime the shoulder disappeared, and the increases are low and slow [8].

Figure 1:

Three different combustion regimes.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

402 Energy and Sustainability III This study was conducted to determine the explosive limits of LPG/air mixture in a constant volume of 20 liter spherical vessel by using a conventional spark ignition system which was located at the centre of the vessel. In this study, the LPG composed of butane and propane in a 70/30 ratio was used to investigate the explosive limits. The LEL and UEL of LPG/air mixture were determined at concentration from 1 to 8% vol. The effect of hydrogen in LPG/air mixture was investigated at hydrogen enrichment up to 8% vol hydrogen of air by the total volume of LPG concentration from 1 to 8% vol.

2 Methodology 2.1 Materials and equipment A cross-sectional diagram of the experimental 20 liter spherical vessel is shown in figure 2. The test chamber is a 20 liter hollow sphere made of stainless steel. The ignition source is located at the centre of the sphere. On the measuring flange, two "Kistler" piezoelectric pressure sensors are installed. The top of the cover contains holes for the lead wires to the ignition system. The opening provided for ignition which is controlled by the KSEP 320 units of 20 liter spherical vessel. A comprehensive software package KSEP 6.0 is used to allow a safe operation of the test equipment and an optimum evaluation of the explosion test results. The KSEP 332 unit uses piezoelectric pressure sensor to measure the pressure as a function of time and controls the valves as well as the ignition system of the 20 liter spherical vessel. The measured values to be processed by a personal computer are digitized at high resolution. The use of two completely independent measuring channels gives good security against erroneous measurements and allow for self checking. For the determination of combustible gases or vapors, the test is accomplished in a quiescent state for which the ignition delay time is tv = 0 s.

Figure 2:

Cross-sectional diagram of the 20 liter spherical vessel.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

403

2.2 Experimental conditions The explosive limits of LPG/air mixture and LPG/air mixture with hydrogen enrichment up 8% vol hydrogen of air were investigated at LPG concentration from 1 to 8% vol. In this study, a LPG with a 30/70 ratio of propane and butane was used. The initial pressure in the 20 liter spherical vessel was regulated to 1 bar abs. A water jacket was used to dissipate the heat of explosions or to maintain the testing temperatures. It is necessary to keep the operating temperature at approximately 20 ºC which was achieved by water cooling whereby the operating temperature would correspond to room temperature. Water is circulated and the outlet temperature of the cooling medium never exceeds 25 ºC. Ignition is achieved by a permanent spark which is placed at the centre of the vessel. Since the experiment was conducted under quiescent conditions, the ignition energy and ignition delay were set to 10 J and 0 s respectively. The igniter releases 10 J independently of pressure or temperature. The pressure evaluation after ignition was measured by a Kistler 701A piezoelectric pressure transducer connected to a Charge amplifier ( Kistler 5041B ). Figure 3 shows the schematic diagram of experimental setup where the equipment was closely placed to the LPG, hydrogen gas tank and computer system.

Figure 3:

Schematic diagram of experimental setup.

2.3 Experimental procedures Figure 4 shows the work flows of the experiment. The LPG and hydrogen fuel from the cylinder storage and air from surrounding were fed in to the vessel via the outlet valve and nozzle. The required composition LPG/hydrogen/air mixture was produced readily with the partial pressure procedures. After ignition, the WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

404 Energy and Sustainability III pressure evolution was measured by a pressure transducer and shown in a graph of pressure versus time by the software KSEP 6.0. After each test, the ball valve was opened to release out the exhaust gas and the remaining pressure in the vessel. The steps were repeated for each fuel gas compositions. Switch on the apparatus and computer Vacuum the explosion vessel Enter the test condition data in the computer Ignite the fuel-air mixture

Feed in the fuel (LPG, hydrogen) and air to the explosion vessel Pressure-time variation during explosion is measured and recorded Clean up the explosion vessel Figure 4:

Experimental work flows.

3 Results and discussion Chang and Shu [9] studies showed that a spherical explosion vessel was treated as an ideal device to detect various explosion properties of flammable material. This device does not allow visual observation of the flame, so it uses an indirect measurement of the flame propagation which is the pressure explosion. This is because a successful ignition would induce a rapid pressure increase and temperature rise within a short time as well as produce a propagating flame front that could be readily observed [10]. Thus, pressure explosion criterion is used to define the explosive limits of LPG. In this experimental study, flame propagation is said to have occurred if ignition is followed by a pressure explosion of 0.1 bar or greater. 3.1 Experimental results of LPG/air mixture The explosive limits of LPG/air mixture were determined at various concentration of LPG by volume as shown in table 1. The test was conducted at various LPG volumes, from 1 to 8% vol. Based on the results, a pressure explosion greater than 0.1 bar was observed at a concentration of LPG from 2 to WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

405

8% vol which is equivalent to the explosive limits of LPG/air mixtures of this study. The data for LPG concentration of 1 and 2% vol shows a pressure explosion of 0 bar. There was some burning near the spark but only limited to the upward propagation beyond the ignition sources which could not be considered as a propagation in this study. At LPG concentration of 3% vol, the pressure explosion obtained was 5.8 bar. There was significant flame propagation in both horizontal and vertical direction. Therefore, the flame had to propagate through more than half of the chamber. The highest pressure explosion from the measurements is 6.4 bar which was obtained at LPG concentration of 4% vol. Closer to the stoichiometric mixture, the flame speed was fast and it took the lowest time (100 s) for the flame to propagate from its point of ignition to the chamber wall compare to other LPG/air mixture. When the concentration of LPG was 7% vol, with 93% vol of air, the explosion pressure was decrease to 0.5 bar which means that there might be some burning near to the spark but only limited to the upward propagation beyond the ignition source. Table 1: No 1 2 3 4 5 6 7 8

Experimental result of LPG/air mixture.

LPG Concentration Pressure (% vol ) (bar) 1.0 0.01 2.0 0.02 3.0 0.03 4.0 0.04 5.0 0.05 6.0 0.06 7.0 0.07 8.0 0.08

Air Concentration (% vol ) 99.0 98.0 97.0 96.0 95.0 94.0 93.0 92.0

Pressure (bar) 0.99 0.98 0.97 0.96 0.95 0.94 0.93 0.92

Pexp (bar)

Time (s)

0 0 5.8 6.4 4.7 3.1 0.5 0

0 0 112 100 332 1050 466 0

Generally, the small pressure explosion is assumed to be associated with a limited upward propagation of the flame and is typically observed for mixtures on the edge of explosion. The high pressure explosion indicates that the mixture is almost completely consumed and the propagation was both upwards and downwards [11]. The upward propagation is easier than other propagation directions because combustion products are hotter and less dense than the reactants from which they are generated [12]. 3.2 Comparison data with the previous studies It is demonstrated that LEL in this study is slightly higher compared to Mishra and Kenneth’s [13] experimental data. In this study, the LEL is observed at 2% vol of LPG (by volume). In contrast, the UEL is comparatively lower at 8% vol. In order to validate our present results, a comparison is made with the available explosion data in literature for propane/air and butane/air mixture as given in table 2. It can be noticed from this table that the present result falls between the WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

406 Energy and Sustainability III Table 2: Reference D.P. Mishra D.P. Mishra L.Kenneth This study

Comparison of explosive limits [13]. Gas mixture LPG - air Butane - air Propane - air LPG - air

LEL 1.81 1.80 2.00 2.0

UEL 8.86 8.40 9.60 8.0

result of explosive limits for both butane/air and propane/air mixtures. Therefore, the present results of explosive limit for LPG/air mixture are considered still within the expected values. However, if the readings of the pressure gauge were accurate up to 0.5% vol, the explosive limits could be obtained in smaller decimal points with higher accuracy. 3.3 Experimental results of LPG /air mixture with hydrogen addition The objective of this study is to determine the effect of the explosive limits of LPG/air mixture when the various amount of hydrogen were added into the LPG/air mixture. As shown in table 5, the mixture was tested with 1, 2 and 8% vol of hydrogen over the total volume of mixture. The value of explosion pressure for LPG/air mixture showed a non-significant difference when 1% vol of hydrogen was added into the mixture. There were changes in the explosion pressure (Pexp) when 2% vol of hydrogen was added in LPG/air mixture where the explosion pressure was equal to 4.9 bar of 2.0% vol LPG. When hydrogen 8% vol was added into the mixture, the explosion became significant at 2.5 bar of 1.0% vol of LPG. Beside the changes in explosion pressure, there were also differences in time of explosion for these different values of hydrogen addition. The hydrogen addition of 8% vol in LPG/air mixture showed the fastest time of combustion (58 and 59 s) at both explosion pressures of 6.2 bar. The maximum explosion pressure for 1, 2 and 8% vol of hydrogen addition was 6.2, 6.5 and 6.2 bar respectively. At these conditions, the flame speed is the fastest, and it takes lowest time (55 to 90 s) for the flame to propagate from its point of ignition to the chamber wall compared to other LPG/air/hydrogen mixture. At this level, the entire mixture inside the spherical vessel is considered almost completely consumed. As exhibited in figure 5, the increase of hydrogen percentage in fuel has expanded the explosive limits of LPG/air mixture. Graph a) shows that the LEL of LPG/air mixture was initially 2% vol and the graph b) shows that after the addition of 1% vol hydrogen, the LEL was unchanged but the curve of explosive limits was rather widely expanded if compared to the first graph a). Similarly, the UEL in graph b) had no change within limits which was still 8% vol after 1% vol hydrogen addition. Graph c) shows the result of explosion of LPG/air mixture when 2% vol of hydrogen was added into the mixture and the LEL had expanded to 1% vol. There was no change for the UEL when 2% vol of

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

a) No addition of hydrogen

b) Addition of 1% hydrogen

c) Addition of 2% hydrogen

d) Addition of 8% hydrogen

Figure 5:

407

Explosion pressures with the various H2 addition.

hydrogen was added, but when the addition of hydrogen was increased to 8% vol, the UEL changed to 7% vol as shown in graph d). Changes in fuel composition, particularly with the addition of hydrogen affect both the chemical and physical processes occurring in flames. These changes affect the flame stability, emissions, combustor efficiency and other important quantities [14]. Hydrogen has been proved to be a green alternative fuel that can be applied on vehicle. Due to high auto ignition temperature of hydrogen (858 K), it is more suitable to adopt hydrogen on spark ignition engine rather than compression ignition engines. Besides, hydrogen has unique combustion properties that benefit the engine efficiency and emission performance. Hydrogen diffusion coefficient is larger than n-propane and n-butane as shown in table 3 which improves mixing process of fuel/air, also helps in improving the homogeneity of combustion mixture. Adiabatic flame speed of hydrogen (237 cm/s) is larger than both n-propane and n-butane which contributes to improve the engine operating stability. Flammability range of hydrogen in air is 4 to 75% vol which is much wider than n-propane and n-butane. Therefore, a hydrogen/fuelled engine is able to work under much leaner condition [15]. Since the ignition energy of hydrogen is lower than LPG, the hydrogen/LPG mixture can be more easily ignited and hydrogen enriched LPG engine can gain a smooth start and in good operating stability under a lean condition. It has been WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

408 Energy and Sustainability III

Table 3:

Properties of hydrogen, n-propane and n-butane.

Properties Molecular mass (g/mol) Stoichiometric concentration (% fuel) Flammability range (% fuel) Maximum explosion pressure (bar) Ignition energy (mJ) Adiabatic flame speed (cm/s) Diffusion coefficient (cm2/s)

Hydrogen 2.02 29.6 4-75 8.01 0.017 237 0.61

n-propane 44.10 4.0 2.1-9.5 9.28 0.26 46 0.12

n-butane 58.10 3.8 1.8-8.4 10.00 0.25 45 0.11

commonly agreed that the proper lean combustion is an effective way to improve engine thermal efficiency and emission performance. Figure 5 shows that an increase of hydrogen percentage affects both of the explosive limits of fuel/air mixture. Schefer [14] has shown that for fuel/hydrogen/air mixtures at atmospheric pressure and ambient temperature using the premixed tube gives in high of hydroxyl (OH) concentration and expanded the lean stability limits of the mixture. In this study, Schefer [14] used methane as a fuel and the addition of up to 20% vol of hydrogen into methane mixed together with air inside the premixed tube. In recent studies [16] have also shown that the lower explosive limit of fuel/air mixture with hydrogen enrichment could be expanded by increasing the volume of hydrogen addition in a spark ignition engine. This study had used methane as the fuel and the most obvious and important advantage methane engines could benefit from the hydrogen addition is the improvement in lean burn capability which is manifested as the expansion of lean operation limit.

4 Conclusion In this paper, the experimental study has shown the effect of explosive limits of LPG when hydrogen is added into LPG/air mixture. The result for hydrogen enrichment in the LPG/air mixture were analyzed at 1, 2 and 8 vol% of hydrogen and the pressure explosion criterion was used to define the explosive limits. Based on the result of the experiment, there is a small difference of explosion pressure when the LPG/air mixture is added at 1% vol hydrogen. Remarkable changes are observed when the volume of hydrogen is increased to 8% vol. It is proven that hydrogen properties such as high auto ignition temperature, diffusion coefficient and adiabatic flame speed help to expand the explosive limits of LPG/air mixture. Besides, hydrogen enrichment also contributes to the changed of LEL and UEL of LPG. Thus the present of hydrogen in LPG/air mixture will have a high potential to assist in solving the cold start phenomenon that always occurs in spark and compress ignition engines.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

409

References [1] Ramanan, S., & Hong, G. I., Effect of Hydrogen Addition on the Flammability Limit of Stretched Methane/Air Premixed Flames, Department of Mechanical Engineering, University of Michigan Ann Arbor, MI 48109, 1994. [2] Wang, .B B., Qiu, R. & Jiang, Y., Effects of Hydrogen Enhancement in LPG/Air Premixed Flame, State Key Laboratory of Fire Science, University of Science and Technology of China, Hefei , 24(7), pp. 1137–1142, 2008. [3] Bauer, C. & Forest, T., Effect of Hydrogen Addition on the Performance of Methane-Fueled Vehicles. Part II: Driving Cycle Simulation, Int J Hydrogen Energy, 26, pp. 71–90, 2001. [4] Bortnikov, L., Combustion of a Gasoline-Hydrogen-Air Mixture in a Reciprocating Internal Combusti Engine Cylinder and Determining the Optimum Gasoline-Hydrogen Ratio, Combustion, Explosion, and Shock Waves, 43, pp. 378–383, 2007. [5] Wang, J., Combustion Behaviors of a Direct-Injection Engine Operating on Various Fractions of Natural Gas-Hydrogen Blends, International Journal of Hydrogen Energy ,32, pp. 3555–3564, 2007 [6] Cracknell, R. F., Alcock, J. L., Rowson, J.J., Shirvill, I. C. & Ungut, A. Safety Considerations in Retailing Hydrogen, SAE paper, 01, pp. 1928, 2002. [7] Wall, J., Effect of Hydrogen Enriched Hydrocarbon Combustion on Emissions and Performance, Department of Biological and Agricultural Engineering, University of Idaho, 1994. [8] Pekalski, A.A., Schildberg, H.P., Smallegange, P.S.D., Lemkowitz, S.M., Braithwaite, M., Zevenbergn J.P., & Pasman, H.P., Determination of the explosion behaviour of methane and propane in air or oxygen at standard and elevated conditions, Process Safety and Environmental Protection, 83 (B5), pp. 421–429, 2005. [9] Chang & Shu, M., Inert effects on the flammability characteristics of methanol by nitrogen or carbon dioxide, Akademiai Kiado, Hungary. DOI 10.1007/s10973-009-0028-1, 2009. [10] Liao, S.Y., Jiang, D.M., Huang, Z.H., Cheng, Q. & Gao, J., Approximation of flammability region for natural gas–air–diluent mixture, Journal of Hazardous Materials, A125, pp 23–28, 2005. [11] Vandebroek, L., Van den Schoor, F., Verplaetsen, F., Berghmans, J., Winter, H., & Van’t Oost, E., Flammability limits and explosion characteristics of toluene-nitrous oxide mixtures, Journal of Hazardous Materials, A120, pp 57–65, 2005. [12] Cashdollar, K., Zlochower, I., Green, G., Thomas, R. & Hertzberg, M., Flammability of methane, propane and hydrogen gases, Journal of Loss Prevention in the Process Industries, 13, pp. 327–340, 2000. [13] Mishra, D.P., & Kenneth, L., An Experimental Study of Flammability Limits of LPG/air mixtures, Indian Institute of Technology, Kanpur India, 82, pp 863–866, 2003. WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

410 Energy and Sustainability III [14] Schefer R.W., Hydrogen enrichment for improved lean flame stability, International Journal of Hydrogen Energy, 28, pp. 1131–1141, 2003. [15] Changwei, J. & Shuofeng, W., Effect of hydrogen addition on the idle performance of a spark ignited gasoline engine at stoichiometric condition, International Journal of Hydrogen Energy, 34, pp. 3546–3556, 2009. [16] Fanhua, M. & Yu, W., Study on the extension of lean operation limit through hydrogen enrichment in a natural gas spark-ignition engine, International Journal of Hydrogen Energy, 33, pp. 1416–1424, 2008.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

411

Embodied energy analysis of multi-storied residential buildings in urban India S. Bardhan Dept. of Architecture, Jadavpur University, India

Abstract Today developing nations are witnessing an unprecedented pace of urbanization in the wake of industrialization and globalization. This is giving rise to an ever increasing demand for housing and infrastructure to support the growing population and its activities. Energy is the single-most significant driver of this urban development and buildings stand as the most visible expressions of this development. However, buildings are known to be highly energy intensive and considering energy supply from conventional sources, these buildings have substantial negative environmental impacts. While operational energy of buildings have been mapped and assessed for different building typologies and various climatic zones, the embodied energy captive in the building fabric has received relatively lesser attention. Thus, efforts towards energy management and conservation in building operations have sufficiently addressed the concerns and have been reflected in the many building-rating systems prevailing across the world, though there had been limited research in the field of embodied energy measurement of contemporary multi-storied residential buildings constructed with modern technology. This assumes more significance in view of today’s energy constrained world where exhaustive database on energy expended through all possible avenues need to be recorded in order to optimize and regulate this capital energy component of the building industry. In this backdrop, the present paper discusses the process and results of embodied energy analysis of one such typical multi-storied residential apartment of steel reinforced concrete construction in the metropolitan city of Calcutta (now Kolkata) in India and compares it with reported findings of some similar researches in Japan and India. Keywords: urban buildings, embodied energy, construction materials

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESUS110351

412 Energy and Sustainability III

1 Introduction The present paper is set in the background of the ongoing debate and research activities related to the two critical and apparently mutually conflicting pillars of sustainability - Energy and Environment. IPCC fourth assessment report of WGIII [1] identifies building sector with high mitigation potential and WGII [2] identifies urban areas as hotspots in terms of vulnerability. In developing countries where housing sector is going to see very fast growth rate with increasing income and fast urbanisation, this will have crucial implication for mitigation (emission whether at the construction stage or at operational stage) and adaptation. Over several decades, the rate of increase of population has become principal drivers of urbanization. India’s urban population is expected to rise from 28% to 40% of the total population by 2020 placing increased stress on the country’s urban infrastructure. However this is relevant not only for India but for any developing country given the projection of United Nations that by 2030, six out of every ten people will live in towns and cities, resulting in an accelerated population density in these urban areas. This has a significant impact on land, water and eco-system. In a bid to provide housing to this increased population within limited physical spaces, the general trend of urban construction today is a predominant verticality. Although India does not figure in the hundred tallest completed buildings in the world, it is not far away either. High-rise constructions in all the metropolitan cities of India have contributed to an increased total built-up area in the cities, which is also considered as real estate growth index or ‘development’ index. These buildings certainly help to have larger open spaces for citizens while accommodating a higher residential density but also consume substantial energy per unit floor area. Even though historically India deployed the rich tradition of solar passive buildings and vernacular architecture that are harmonious with environment, urban India is adopting a more and more global architectural vocabulary and higher preference for conditioned spaces. This paradigm shift in building design and planning with change in technology and life-style has resulted in major consumption of global resources. A UNEP [3] study found out that taking into account its entire lifespan, a typical building worldwide is currently responsible for up to 25-40% of energy use, 30-40% of solid waste generation and 30-40% of global green house gas emissions. Several international research groups have identified the need of further investigations in areas related to energy efficiency in building sector, particularly from developing country perspectives and also the necessity of many more evaluation studies from these regions, especially from quantitative viewpoint. Even the World Business Council for Sustainable Development (WBCSD) has adopted a vision in which all buildings in the world will consume zero net energy by 2050. In view of the above, the current paper focuses on a study on capital energy consumption of urban multi-storied residential buildings with the objective of benchmarking and forming base-line information on the said area in Indian context. The green building rating systems, which are in popular practice today, WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

413

concentrates on the operational and maintenance periods only. Seen from the environmental perspectives, it is this embodied energy in the buildings that are analogous to loans taken from the environment but are never ever repaid back. Buildings are very complex systems varying with climatic conditions, usage and user aspirations (influencing decision-making and choice of building materials) while also engaging multiple engineering products, services and technology. Thus the embodied energy of a building system is a reflection of interplay between a wide range of diverse technical and human factors. Embodied energy analysis vis-à-vis operational energy can be interesting to study, as the latter is dependent on the building typology, type of construction and the occupants’ behaviour. Thus, while embodied energy can be 11 times the annual operational energy for a two-storey brick and reinforced concrete (RC) residential building in India and 8 times for a low-rise apartment in UK [4], it is only 3.5 times for a three-storey brick and RC constructed tourist lodge in coastal India [5]. However, considering the entire life-cycle of the building, the operational energy far exceeds its embodied energy. Hence, as Cole and Kernan [6] point out that strategy for reducing life-cycle energy use of the building should begin by incorporating ways to reduce building operating energy; this is probably the reason why the current building rating systems concentrate on this aspect only. On the other hand, Vukotic et al. [7] rightly argues that construction of energy-efficient buildings is more energy intensive and therefore, building embodied energy will become increasingly significant with decreasing operational energy. 1.1 Boundary conditions of the study The case study selected is a ground plus thirty-five-storey residential apartment building of steel and RC construction in the heart of the city of Kolkata in the Eastern Indian state of West Bengal. The study aims to assess its Embodied Energy (EE) i.e. energy consumed at the construction stage comprising of the following sub-stages: i. Energy embedded in the body of the building in the form of the construction materials used ii. Energy required to transfer these materials to the site of construction from the supply sources iii. Energy consumed during actual erection of the structure involving the three ‘M’s: Materials, Machines and Man In this study, however, out of the myriad materials normally used in a building, the evaluation has been kept limited to those having the largest stake in its erection. Emmanuel [8] rightly pointed out that the embodied energy of building materials will vary from one country to another, depending on the sources of energy used for manufacturing and climatic condition of that country. Thus limited availability of data on embodied energy of building materials in the Indian context was another reason for keeping the list of materials restricted to a major few. A previous study on embodied energy of smaller buildings with about 300- 400 Sq m built area in eastern India by Bardhan [5] and Bardhan et al [9] had earlier estimated the energy consumed at stage-ii i.e. in transportation of WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

414 Energy and Sustainability III building materials to be only 1.85 % of the embodied energy of the materials while that consumed during stage-iii is lesser – a mere 0.06 % of the same. Together, these account for only 1.91% of the embodied energy of the materials. For a larger building, the figures lowered to 0.52 % and 0.02 % respectively. However, since the said study was conducted for buildings located 140 Km from the nearest metropolis of Calcutta, the energy expended under transportation head was much more than that for erection. In contrary to this, urban buildings require more energy at stage-iii than at stage-ii since built areas are not only considerably higher but also have greater machine dependence. Hence the energy involved in transporting the building materials from supply source to site was not considered in this particular investigation as the case study is located at the heart of the city and the materials are already in stock with the building material suppliers irrespective of any particular construction. Reddy and Jagadish [10] had estimated that when transportation energy is compared with respective production energy, it is negligible for high energy materials like cement and steel, though it is 4-8% in case of bricks and 400800% in case of aggregates. Thus, while acknowledging that the stage-ii component may have significant contribution in many cases, it was believed that this would be negligible with respect to the present study. The stage-iii component has been considered here by way of energy bills since the building stock is quite substantial and access to the energy bills of construction period was possible. To summarize, this study considers the sum of the stage-i and stage-iii energy components to assess the embodied energy of the building that has already been locked within its fabric. It is deemed that the energy consumed per unit area of the building will give an idea of the constructional energy consumption pattern of today’s multistoried residential buildings and help to formulate specific energy strategies towards this. 1.2 Case- study: urban contemporary multi-storied building The case study is essentially a mixed-use development led by residential land use. It is popular for being one of the tallest residential building projects in and around Kolkata. Its thirty five-storey multi-family tower blocks are set in a site of 31.14 acres in a residential neighbourhood of South Calcutta. The tower blocks comprise of about 1600 nos. of apartments and a total built-up area of 310,173.22 Sq m. The residential buildings share the site with a commercial complex and a secondary school along-with a recreational centre for the residents. It is in the process of further expansion, and when completed, the entire project will have a total built up area of 400,587 Sq m. 1.3 Materials, machines and manpower used in the case- study The buildings under study were constructed during the period 2002–2009 and comprises of four tower blocks and the total built-up area of all the blocks together is more than three million square feet as stated above. It is primarily a reinforced cement concrete construction with other materials used being glass, WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

415

steel, aluminium, timber/plywood, natural stones like granite/marble, ceramic/vitrified tiles and plaster of Paris. Ancillary materials include those needed for engineering services like PVC – electrical switch boxes and cable – covers, copper cables, other metals like plumbing fittings, hardware, nails etc. The machines involved in the construction were identified as a piling machine, tower crane, builders hoist, welding machine, bar-bending machine, hand drill, stone cutting and stone polishing machine, JCB for site clearing, earth cutting and excavation. Out of these, the piling machine and JCB were diesel driven, thus contributing differently to the energy head. The hours of operation of each machine varied between 8-10 hours with a maximum of 14 hours. The power rating multiplied by the number of hours of operation will give the actual electrical energy consumed and the diesel consumed may be derived from the fuel efficiency of the particular machine. In terms of manpower, the site was used for housing the day labourers of an average of 1200 persons at any given time during the construction period, with a maximum peak of 2200. This figure is important as the resident labourers stayed in labour quarters that had to be built prior to actual construction, used power and water for their duration of stay and also generated domestic waste. All such resource consumption would account to the building head and has to be considered as a part of its embodied energy foot-print.

2 Embodied energy assessment 2.1 Energy embedded in the building by virtue of materials or stage i As mentioned earlier, only major materials like cement, sand, aggregate, bricks and structural steel reinforcement were considered as these data were readily available from the project office. However, glass and aluminum sections used for the external fenestrations and dimension stones used for floor finish were also included. The embodied energy coefficients used to calculate this were based on Table 1: Sl. No. 1 2 3 4 5 6 7 8

Quantity survey of materials.

Materials

Embodied Energy (GJ)

1207892.4 Cement Stone chips 38259.300 Sand 46729.904 Bricks 221531.268 Steel 1361710 6 mm Glass 879.4128 Anodised Al (for exterior windows only) 3437.449 Dimension Stones (marble/ granite) 22941.016 Total Embodied Energy of the materials 2903380.75176 Total built up area = 310173.22 Sq m Embodied Energy of the materials per unit built-up area = 9.36 GJ/Sq m

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

416 Energy and Sustainability III recent studies in India and New Zealand [10, 11]. The detailed calculations revealed that the embodied energy of all the residential blocks by virtue of major materials only is in the range of 2.9 x 106 Giga Joules (GJ), which comes to around 9.36 GJ/ Sq m of built-up area, as presented in Table 1. 2.2 Energy consumed during building erection or stage iii For this assessment, two alternative approaches - top-down and bottom-up were considered. Both these methods are primarily concerned with the electrical energy used during the site construction work. The top-down approach considered the electrical load estimated by the developers and applied for from the electricity supply agency, which in this case was two nos. 500 kVA metres i.e., a total of 1000 kVA. The second metre was applied when the first was found to be inadequate to supply power for the construction site. The bottom-up approach takes account of the energy bills of the site and were analyzed to obtain the actual power consumption over the entire construction period. Based on data received from the project’s office, the following considerations were used for the top-down assessment:  75% of the total electric load was used during the construction period.  On an average, construction work continued for 12 hours a day and 350 days a year.  Effective time of completion was six years. The electrical energy consumed for construction per day was estimated as (0.75 x 1000 x 12) = 9000 kWh or 32.4 GJ (1 kWh = 0.0036 GJ). With 350 working days, the annual energy used for construction was evaluated at approximately 11340 GJ. For the entire construction period of six years, this worked out to be 68040 GJ for all the building blocks, which translates to 0.22 GJ/Sq m of building area. For the second method, the energy bills (available from 2002 third quarter to 2009 first quarter i.e. 6.75 years) were obtained from the developers’ office and the monthly electrical expenses were converted into energy consumed in KiloWatt-Hour (kWh) by dividing this value with the unit energy rate, considered here to be INR 3.91 as per available contemporary data. The energy consumption values were again converted in Giga Joule (1 kWh = 0.0036 GJ). The annual energy consumption throughout the construction period is depicted in the following figure. In Figure 1 the graph shows the annual energy consumption pattern during construction. Total energy consumed for the entire project between 2002 third quarter to 2009 first quarter was found to be 56,513.20 GJ. Considering that erection of the blocks was completed by 2009 first quarter, embodied energy per unit area constructed comes to 0.18 GJ/Sq m. Thus, according to the top-down approach, the energy spent for building erection is about 0.22 GJ/ Sq m while that by the bottom-up method is 0.18 GJ/Sq m, with approximately a 20% difference between the two. Since both are based on electrical energy consumption, an average of the two i.e. 0.2 GJ/Sq m WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

Figure 1:

417

Annual energy consumption pattern during construction.

has been considered for the purpose of EE estimate. It is to be noted that the electrical energy consumed by the 1200 resident labourers are also included in this. However, data on the quantity of fossil fuel used during construction for back-up power supply, machineries and man power were not recorded by the project office and therefore, are not reflected in the figures. 2.3 Total embodied energy of the building stock Adding the embodied energy of its major material constituents as found earlier, the total constructional embodied energy per unit area of these buildings works out to be around 9.56 GJ/Sq m. It is important to mention here that this is, by all means, a conservative estimate approach and represents a much lower figure than the actual.

3 Results and discussions The embodied Energy Foot-print of the contemporary urban residential building studied and presented in this paper and involving only major construction materials and building erection is 9.56 GJ/ Sq m. As stated earlier, the actual figure is expected to be much higher when all the other building materials are taken into account. An analysis of contribution of different stages to the total embodied energy of the building was carried out and Table 2 presents the result. It shows the construction materials to have a whopping 98% stake in the building’s total embodied energy and the actual erection to be only about 2% of Table 2:

Contribution of different stages to building’s EE.

Sl. No.

Materials

1

Stage-i: Total Embodied Energy (EE) of the materials stage-iii: Energy consumed during actual erection of the building Total building EE

2

Embodied Energy (GJ/ Sq m) 9.36 GJ/ Sq m

% contribution to EE 98 %

0.2 GJ/ Sq m

2.0 %

9.56 GJ/Sq m

100 %

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

418 Energy and Sustainability III that of the materials. This corroborates the previous study results that also found the EE of construction materials to be the major contributing factor to the building’s EE, compared to their transportation to site and actual erection. Further investigation was made to understand the contribution of individual construction materials to their collective energy head as presented in Table 3. Table 3:

Contribution of different materials to building’s EE. Materials

Sl. No. 1 2 3 4 5 6 7 8

Table 4:

Cement Stone chips Sand Bricks Steel 6 mm Glass Anodised Al Stone finishing Total Embodied Energy (EE) of the materials

Comparative embodied energy measures of different types of constructions.

Sl. No.

Countries

Building types

1

India [10]

Eight storey conventional building Double storey conventional building with load bearing walls Double storey building with soilcement block and filler slab roof Adobe house

2 3

4

5

Percentage contribution to EE 41.6 % 1.32 % 1.6 % 7.64 % 46.9 % 0.03 % 0.11 % 0.8 % 100%

New Delhi, India [12] India [13]

Japan [14]

Current study: Kolkata, India

Single storey Load-bearing structures Double storey Load-bearing structures Four-storey reinforced cement concrete (RCC) buildings Multi-family steel reinforced concrete (SRC) houses Wooden single-family houses Lightweight steel structure singlefamily houses Multi-family steel reinforced concrete (SRC) houses

Embodied Energy (GJ/Sq m) 4.21 2.92

Area (Sq m)

1.61

160.5

3.8

120

5 - 4.1

50-200

4.2 – 3.7

50-200

4.3 – 3.1

50-200

8-10

-

3 4.5

-

9.56

3 x 105

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

5120 149.5

Energy and Sustainability III

419

Quite predictably, steel and cement topped the list, together contributing to 88.5% of the total. A lesson that can be learnt from this study is how to reduce the embodied energy of these materials at the production stage itself, so that the energy locked in these materials and subsequently in the buildings can be considerably minimized. This finding has been compared with that of different types of buildings/ constructions as reported in various researches carried out in Asian countries in the last fifteen years. It is interesting to note that the multi-family steel reinforced concrete (SRC) houses studied by Suzuki et al [14] found the embodied energy to be 8-10 GJ way back in 1995, which is closer to the findings of the current study. Whether technology improvement has led to energy efficiency in constructions remains a matter of further investigation. However, it is hoped that more and more researches would focus on this area for a wide range of building and construction typologies in different climatic regions to optimize and regulate the energy consumed at the construction stage of the building, much like what is already in voluntary practice for its operation and maintenance stage and finally, arrive at benchmarking the capital energy investment.

4 Conclusions This paper presented a study on the embodied energy assessment of contemporary urban multi-storied residential buildings in the busy metropolis of Calcutta (now Kolkata) in eastern India. Data was collected from field survey and project office to a large extent and the missing links were assumed on the basis of prevalent practice. It was found that  The embodied energy of major construction materials contribute to about 98% of the building’s total embodied energy and steel and cement are the main contributors to this head.  Energy involved in actual erection and assembly on site is a meager 2% negligible compared to that embedded in the materials itself.  The EE of such a building was found to be about 9.56 GJ per Sq m of the building, which is quite comparable to similar research findings. The result of this study is expected to help create benchmarking of capital energy consumption in building construction in contemporary urban India. This is further important as the embodied energy of rapidly growing Indian cities as well as proposed urban centres can also be estimated based on their building stock and real estate growth indices, along with their corresponding carbon emission contributions. The main challenge is to link this with the sustainable limits of urbanization to assist our decision makers in matters of urban development, energy issues and actions on climate change.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

420 Energy and Sustainability III

Acknowledgement The author is grateful to All India Council for Technical Education (AICTE) for its financial support in carrying out this study.

References [1] IPCC, Climate Change 2007: Mitigation. Contribution of Working Group III to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Metz, B., Davidson, O.R., Bosch, P.R., Dave, R., Meyer, L.A. (eds)], Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA. [2] IPCC, Climate Change 2007: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, [M.L. Parry, O.F. Canziani, J.P. Palutik of, P.J. van der Linden and C.E. Hanson, (eds.)].Cambridge University Press, Cambridge, UK. [3] United Nations Environment Program (UNEP) and Division of Technology Industry and Economics (DTIE), Eco-house Guidelines, 2006, pp. 5–6. [4] http://www.newagepublishers.com/samplechapter/001378.pdf [Accessed 3rd Nov 2010, 22:34] [5] Bardhan, S., Carbon Foot-Print Studies and Sustainable Architectural Concepts for Coastal Eco-Tourism, unpublished Doctoral thesis, Jadavpur University, 2008. [6] Cole Raymond J. and Kernan Paul C., Life-cycle energy use in office buildings (Abstract), Building and Environment, 31(4), 1996, 307-317. [7] Vukotic L., Fenner R. A. and Symons K., Assessing embodied energy of building structural elements (Abstract), Proceedings of the ICE – Engineering Sustainability, 163(3), 2010, 147 –158. [8] Emmanuel R, Estimating the environmental suitability of wall materials: preliminary results from Sri Lanka, Building and Environment, 39(10), 2004, 1253–1256. [9] Bardhan, S., Chattopadhyay, M. and Hazra, S., Quantifying Environmental Sustainability of Buildings through its Carbon Foot-Print: An Analytical Approach, Journal of Civil Engineering and Architecture, 4(1), 2010, 2034. [10] Reddy Venkatarama B.V. and Jagadish K.S., Embodied energy of common and alternative building materials and technologies, Energy and Buildings, 35(2), 2003, 129-137. [11] Embodied Energy Coefficients, New Zealand, http://www.victoria.ac.nz /cbpr/documents/pdfs/ee-coefficients.pdf [Accessed 3rd Nov 2010, 21:30] [12] Shukla A., Tiwari G. N. and Sodha M. S., Embodied Energy Analysis of Adobe House, Renewable Energy, 34(3), 2009, 755-761.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

421

[13] Debnath A., Singh S. V. and Singh Y. P., Comparative assessment of energy requirements for different types of residential buildings in India, Energy and Buildings 23(2), 1995, 141-146. [14] Suzuki M., Oka T. and Okada K., The estimation of energy consumption and CO2 emission due to housing construction in Japan, Energy and Buildings, 22(2), 1995, 165-169.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

This page intentionally left blank

Section 7 Energy efficiency

This page intentionally left blank

Energy and Sustainability III

425

Learn to save: sustainable schools A. Boeri & D. Longo University of Bologna, Department of Architecture and Territorial Planning, Faculty of Architecture “Aldo Rossi”, Italy

Abstract The existing school buildings are mainly characterized by a low level of architectural quality and performance which leads to a high consumption of energy and an indoor microclimate below comfort level. The design and construction quality of buildings plays a key role in limiting energy consumption, while ensuring proper comfort conditions. Best practice can also effectively encourage experimentations and contribute to formulate sustainable construction strategies that should be widely adopted. School buildings play, in fact, a dual role: on one hand they have to ensure adequate technical and morphological standards to all spaces used by the students; on the other one, they have to effectively communicate the criteria of sustainable design which have been used for their construction. The aim of attaining higher level of sustainability in the construction sector has led to consider school buildings perfect case studies for testing sustainable technical solutions. This paper proposes some of the most innovative case studies within Italy, highlighting criteria and strategies adopted in the design for spaces dedicated to children. The aim is to promote sustainable design and construction strategies that combine high levels of energy efficiency, of performance standards and environmental indoor quality, including innovative strategies to integrate the building and its related systems. Keywords: energy efficiency, school design, sustainability, innovation, experimentation.

1 Introduction The stock of school buildings represents an extremely important research field for its quantity and social value. The high standards of comfort required by the regulations and innovative research experiences make these buildings WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESUS110361

426 Energy and Sustainability III

Figure 1:

The integration of building and greenery, the attention paid to bioclimatic aspects improve the indoor and environmental quality. Protection with trees and shading with brise-soleil on the south glazed front. Nursery School in Ponticelli, Imola, 2001-2002, Arch. A. Contavalli.

particularly interesting as case studies. The definition of design solutions and technical aspects for schools could represent an interesting reference applicable to other building types, according to different climatic conditions. In relation to the age of users it is possible to distinguish different types of buildings: kindergartens, nursery, primary, secondary schools and comprehensive schools. The educational use is the common feature. They are articulated in different ways according to different age of users, educational models, the availability of spaces and resources. International experiences of reference are programs as the CHPS – Collaborative for High Performance Schools (U.S.A. program which defines guide-lines for design, construction and management of schools characterized by high quality performance); REDUCE – Energy Retrofit for Educational Building (European Program for performance and morphology upgrading of school buildings), BSF – Building Schools for Future (English program for refurbishment of secondary schools).

2 Characteristics of sustainable schools Buildings for learning represent emblematic cases of experimentation of increasing levels of sustainability research. In these architectures the design and construction criteria related to site, orientation, and in general sustainable strategies are often adopted.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

Figure 2:

427

The articulation of volumes increases the dispersant surfaces but promotes natural ventilation and lighting inside. The system of open spaces includes a park and some patios. Lama Sud school in Ravenna, arch. G. De Carlo and Associates, 2008.

In the Mediterranean context, these buildings must have high performances in different seasons, thanks to a perfect integration with open spaces and ensuring low energy consumptions. Schools can be considered as spaces which contribute actively to educate users for sustainability, responding to a double set of problems. The first is relate to criteria for functionality, concerning environmental implications, technical and morphological aspects, providing high hygro-thermal performances, natural and artificial lighting, using health materials. The second problems category concerns sustainability strategies that school buildings should communicate through their spaces, uses and performances. The aim is to promote the spread of environmental awareness among the users and citizens. To pursue strategies of a sustainable approach in school buildings, characterized by an intense collective use, it is necessary to assess the problems in the first phase of design process in relation to strategies of urban planning and context analysis. Already urbanized areas, possibly abandoned, and equipped with adequate infrastructure, public and ecological transport system and pedestrian connections are to be preferred. It is important to maintain and enhance green system and permeability of soils, select materials with limited content of embodied energy and apply energy efficient solutions.

3 Energy consumption in schools A significant parameter to be valued concerns the power consumption. Schools consume too much. The high energy consumption generally is due to low environmental quality, low insulation, use of no performed windows, presence of thermal bridges and obsolete equipment. These buildings are no comfortable and consume too much both in terms of economic impact and the environmental point of view. WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

428 Energy and Sustainability III A recent survey of fifty schools in the Veneto Region in Italy, realized with a method of fast audit, has highlighted energy needs of 250–350 kWh/m²a, with an average of 290 kWh/m²a which may correspond about to 82 kWh/m³a. These data are significant: according to Italian regional classifications and regulations, these buildings would be classified in the worst energy efficiency class. A school classified A in Emilia Romagna, indeed, has an index of less than 8 kWh/m³a: that is to say that it consumes only 10% of the average requirements of the tested schools.

Figure 3:

Comprehensive (primary and secondary) school design. Subsequent phases to meet energy performances aims, from F to A class with different configuration of volume and envelope. Eco-efficient architecture final workshop, coord. prof. Boeri, Faculty of Architecture, University of Bologna, AA 2008/09.

The aim consists of improving performance levels of buildings, providing better conditions of use and consuming less. The reduction of energy consumption and the possibility to meet needs of comfort represent a shared goal. The risk is that the low energy consumption is obtained, at least in part, losing environmental quality, in terms of good perception and functionality of spaces. WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

429

On the other hand, it is necessary to promote sustainable design and construction strategies that combine high levels of energy efficiency, high performance standards and environmental indoor quality, through innovative strategies for integration of construction system and plants.

Figure 4:

The design solutions for solar gains provide high indoor quality, increasing the natural lighting and visual relationship with the external context. Day nursery Balenido, Casalecchio di Reno (BO), 2007, Scagliarini-Tasca Studio, Bologna. Photo by Luca Capuano.

4 Environmental sustainability evaluation The environmental sustainability assess of school buildings is a difficult operation, especially if it regards the entire life cycle analysis (phases of production, transport, installation, construction, management and demolition) and the environmental impact of site and building systems. Multi-criteria evaluation systems can be applied, based on a compared analysis of significant parameters, to be eventually extended to the entire life cycle of the building. In this case it is important to consider the energy consumption, a factor integrated with a complex series of other ones. The relative weight of various parameters can be adapted to different specific conditions of application. The national Protocol Itaca is one of these system. LEED (Leadership in Energy and Environmental Design, an internationally recognized green building certification system, providing verification that a building was designed and built using strategies intended to improve performance in metrics such as energy savings, water efficiency, CO2 emissions reduction, improved indoor environmental quality) has developed a specific evaluation methodology for school buildings in USA and it has been wide spread in the world. It suggests a voluntary multi-criteria evaluation method of WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

430 Energy and Sustainability III

Figure 5:

The integration with environment aims at microclimate control and exploitation of the potential relationship with surroundings. Day nursery Gaianido in Bologna, Tasca Studio.

environmental and energy quality for sustainable energy efficient buildings development, with the aim of improving the quality and minimize environmental impact. The rating system is based on specific credits, assigned for each requirement concerning sustainable aspects. Points are distributed across major credit categories. Their sum determines the overall score of building and the level of certification is afforded. LEED certification is obtained after submitting an application documenting compliance with the requirements of the rating system as well as paying registration and certification fees. This system considers lots of parameters of sustainability, from the adoption of renewable energy sources to the choice of appropriate materials, local, renewable, recycled, ecologic with low emission of organic substances. Based on the general value system, specific versions for particular types of buildings were developed, such as new construction, existing buildings, commercial spaces, residential buildings and schools. The assessment of the sustainability of school buildings, primarily concerning the K-12 sector of primary and secondary schools (up to twelve years of schooling, corresponding to the age of seventeen or eighteen), is based on the specification of characteristics of these buildings, defined with a checklist articulate into thematic areas: - Sustainable Sites - Water Efficiency - Energy and Atmosphere - Materials and Resources - Indoor Environmental Quality - Innovation and Design - Regional/local priorities.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

431

The sustainability assessment, applicable both to new schools and existing refurbished ones, is based on a checklist divided into different thematic areas. The first LEED Gold certification of a school in Italy dates back to 2009 and it was assigned to Technical Institute Floriani in Riva del Garda.

5 Integration architecture – plants for environmental quality Sustainable school buildings are the result of a synthesis of architectural, technological and and engineering design. The volumetric articulation of spaces, the shape of the envelope, the adoption of bioclimatic strategies, the fixtures and fittings solutions in relation to energy requirements, the integration of renewable energy systems are the main factors to be considered.

Figure 6:

The south glazed facade is realized with transparent structural glasses (Uw = 1.1 W/m2K), protected by mobile shields and curtains to limit eventual overheating. The vertical opaque elements allow the distribution of plants and are externally coated with solar panels for hot air production. Secondary school Orsini, Imola, 2009, Arch. A. Dal Fiume.

The reduction of energy needs of buildings allows the adoption of innovative systems for the air-conditioned. The research of integration of architectural and technical aspects has to satisfy not only present needs: it is necessary to evaluate the potential development in the future, foreseeing and scheduling the following steps considering the environmental effects of each change. To compensate the ecological footprint of construction process it is appropriate to provide integration of the specific building uses with activities opened to the surrounding community, extending the period of use and providing additional services for collective use. The space and functions are differentiated in relation to the type of school and the age of the users.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

432 Energy and Sustainability III

6 Some case studies 6.1 Meridiana Nursery (Balenido), Casalecchio di Reno (BO).ScagliariniTasca Studio, Bologna, 2007 The lot is located between an important road and a green area, near the services of the Meridian neighborhood. The design is inspired by considerations related to the urban scale planning and the mobility system: the nursery school plays a synergistic relationship rule as a connecting element to the context. It is equipped with pedestrian access which serves the adjacent social center and sports facilities too.

Figure 7:

Green roof as element of environmental integration and microclimate control. Day nursery in Bologna, Tasca Studio.

6.1.1 Materials and technologies The structural technologies, plants and materials applied in the building have two main aims: mental and physical wellbeing of users and the reduction of energy consumption, including embodied energy during the operating phase and eventual deconstruction/demolition phase. Exposure, orientation and conformation of its spaces tend to create a relationship with the context and a bioclimatic balance. The elevation structures are built with Wolf balloon frame system, applying frames in fir wood with transmittance between 0.18 to 0.22W/m²K. The external wall is 27.5 cm thick, with three types of insulation layers to ensure effective thermal inertia performance: panels of cork in the outer side, sheep wool and linen in the middle, panels of wood-magnesite with natural fiber gypsum plaster inside. The finishing layer of the coat is realized with silicate plaster, with photocatalytic and colored treatment (it oxidizes organic and inorganic pollutants, transforming them into nitrates of sodium, calcium and carbon dioxide). The windows provide high performances, too. The roof was realized with a wooden structure as the walls, breathable waterproof sheath and a mantle of vegetation. It provides high insulation performances, drains rainwater, requires limited maintenance (due to the succulent plants and mosses) and contributes to the environmental contextualization of the building. WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

433

The interior walls and ceilings are covered with natural fiber gypsum plaster. Low temperatures radiant panels are placed inside these structures; with this solution the walls do not require air conditioning terminals and may be freely used and furnished. Particular attention was paid to the evaluation of toxicity of the materials: all surfaces are painted with natural paints and interior floors are finished with birch plywood treated with non-toxic and water paint. 6.1.2 Fixtures and fittings and energy performances The school was designed with the purpose of obtaining the A plus certification in accordance with the methodology proposed by Clima House Agency. The building is provided with a ventilation system with rate between 1.5 to 2.0 vol/hr. Solar panels are placed on the roof, covering an area of 10 m², enough to provide hot water in summer and integrated heating in the winter. The ventilation system is equipped with mechanized heat exchanger and a compressor heat pump to raise the energy values of the incoming air. A posttreatment battery contributes to contain the value of moisture inside during the summer period. Other contributions to the air conditioning plants will be provided in summer with a refrigeration water system with coils embedded in the ground (geothermal system). In the winter season, the minimum integration required, especially during periods of cloudy weather, will be provided by local district heating system powered by the cogeneration plant next to the Meridiana neighborhood. 6.2 Secondary school “L. Orsini”, Imola. Arch. Andrea Dal Fiume (Public Works Sector, City of Imola), 2009 The aim of this project is the achievement of high quality of design and construction and the attainment of optimal comfort indoor. Built near the existing primary school, erected in the mid 80s, and sized according to local needs, the school building can hold 425 students. The new structure is closely coordinated with existing one, with common connective spaces and services (external areas, canteen, some laboratories, a library and the Direction Office) which have allowed a necessary functional reorganization of the general plant. The design is based on bioclimatic criteria: the right orientation determines the plan organization of spaces and the functional distribution. The building is organized for the collection of solar radiation; the shell has opaque and transparent parts realized with different active technologies on the main front (the southern side) and a filter areas modulates the passage of air and light inside the building . The ventilation system integrates mechanized and natural passive cooling system. The application of innovative technologies for indoor monitoring, climate control and energy production aims at integration between architecture and plants. Besides, the technologies applied aims to reduce the consumption of drinking water. WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

434 Energy and Sustainability III

Figure 8:

The layout of the school consists of two main parts. The southern building contains the teaching spaces; the northern one auxiliary activities (canteen, library, laboratories) and facilities. Secondary school Orsini, Imola.

The building has three floors. It is divided into two main parts, hardly rotated, connected to each other by a distribution area containing vertical connection structures. Parts of the building facing south are used for teaching areas, in front of a public green area and hills. The glazed facade is characterized by a structural glass by Schuco with high thermal performance aluminum profile and lowemitting double glazing with a transmittance value of 1.1 W/m²K. Mobile brise-soleils and curtains allow the shadow of the facade and prevent eventual overheating during the summer. The transparent portions of this facade are alternated with opaque vertical elements that allow the distribution of plants. They are externally covered with solar panels for production of hot air. On the contrary, the northern facade is very closed and compact. Offices and workshops are located on the upper floors of the northern part of the building: the shell, mostly opaque with some modular windows, is coated with laminated plastic panels and zinc-titanium strips. The wall, realized with dry technology, with transmittance of 0.14 W/m²K, has a frame in laminated wood, kenaf fiber panels of 22 cm thick, protected by breathable coating, plasterboard double wall in which pipes are concealed. In this project the integration of plant components in the architecture plays an important role: the air-handling equipment, the ejector fan, solar collectors and photovoltaic panels are placed on the roof. Particular attention has been put to acoustic comfort, ensuring insulation between adjacent rooms, facade insulation and reverberation time to compliance with regulatory (DPCM 05/12/1997 “Passive acoustic requirements of buildings”) and to increase performances.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

Figure 9:

435

View of southern front facing on a green area and surrounding hills. The facade is characterized by opaque and glazed parts. Secondary school Orsini, Imola.

In particular, ceiling panels in MDF and a soundproof panel have also been used to improve the internal acoustic performances; tongue and groove paneling, perforated and milled, linked with a layer 2 cm thick of polyester fiber are placed on the walls. Plant engineering system, adopted to minimize energy consumption of the building, has a strategic importance in the design: - mechanical systems: solar air collectors (SolarWall®) for pre-heating; solar collectors for water heating and integration of radiating under floor heating; cooling with absorption technology and solar cooling; geothermal system realized with underground pipes to preheat air and to cool the building; ventilated structural cooling system (RVS); separation of plant engineering systems to save energy consumption in relation to spaces uses; rainwater recovery and use for supplying toilet flush tank; - electrical systems: high-efficiency lighting system with automatic timing device in relation to natural light, photo sensors to control lighting levels; presence detector with infrared receivers to control the switching of the lights, control systems of plants components and building passive systems, such as openings for natural ventilation and shading elements on the southern front; photovoltaic panels for partial meeting of the energy demand. The high quality of the building and plant engineering integrated systems, characterized by effective integration of architecture and plants components through technical solutions, monitored during the design and construction phases, provides to obtain significant results. The building has been certified Class A, according to KlimaHouse standards, with a requirement of 23kW/m²a, less than half of regulations standards.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

436 Energy and Sustainability III The building is also heated and cooled using, as much as possible, natural and alternative energy sources such as solar and geothermal energy.

7 Conclusion These experiences aim at integrating sustainability, spatial and perceptual quality with energy efficiency request in climates such as Italian and Mediterranean. The relationship with the outside spaces plays a significant role as it could contribute to improve indoor comfort and inside qualities. International programs concerning the quality of school buildings are related with different national contexts; the quality is pursued paying particular attention to the specific context, defying and developing design criteria and construction methods, exploiting traditional input factors (such as orientation, shading, transparency and thermal inertia) in an innovative way.

References [1] Boeri, A., Strategie sostenibili per l’edilizia scolastica. Efficienza energetica e qualità ambientale, in Integrare per costruire, SAIE 2010 – Cuore Mostra I Seminari, BolognaFiere, Be-ma, Milano, pp. 1-26, 2010. [2] Boeri, A., “Criteri di progettazione ambientale – Tecnologie per edifici a basso consumo energetico”, ISBN 978-88-89518-35-9, Editoriale Delfino, Milano 2007. [3] Hertzberger, H., Space and Learning, 010 Publishers, Rotterdam, 2008. [4] United States Green Building Council, Foundations of the Leadership in Energy and Environmental Design, Environmental Rating System, A Tool for Market Transformation, 2006, August.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

437

Experimental study of a waste heat recovery system for supplemental heaters E. Y. Tanbour, R. Al-Waked & M. F. Alzoubi Prince Mohammad Bin Fahd University, College of Engineering, Department of Mechanical Engineering, Kingdom of Saudi Arabia

Abstract Energy conservation in supplemental heaters using a heat recovery heat exchanger is the subject of this paper. A waste-heat-recovery heat exchanger is developed for supplemental heaters (natural gas-fired fireplaces). Using experimental tools, the effectiveness of a condensing heat recovery system on capturing majority of waste heat is studied. The goal is to explore an economically feasible and a manufacturable heat exchanger that recovers waste heat in such supplemental heaters. The research has shown viable compact heat exchanger designs that significantly reduce the fuel consumption by the heater. Keywords: efficient heating, compact heat exchangers, waste heat recovery, supplemental heaters, gas-fired fireplaces.

1 Introduction Energy conservation and management for different applications has been the subject of several studies in the past years and it continues to be an important research topic. This is due to the limited energy resources and energy price from one side and the environmental issues from the other side. Using exhaust flue gas as a heat recovery source is a common approach and it has been an essential part of steam power plants. While its primary purpose is to transfer exhaust gas heat to steam, an important secondary function is to reduce emissions from combustion exhaust [1]. Mihelic-Bodanic and Budin [2] presented an energy optimization for production of a thermoplastic material, using boiler flue gases, which leads to saving about 8% on the fuel consumption. Maksimov et al. [3] studied the possibility of using exhaust gas in power plants to generate steam for oil WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESUS110371

438 Energy and Sustainability III processing in refineries. Fehrm et al. [4] reported a study on exhaust air heat recovery for warming the buildings in Sweden and Germany. Other examples of heat recovery from exhaust gas are in textile drying [6], heating automobiles [7], coffee roasting [8], road maintenance [9] and paper machines [10]. Using heat exchangers for recovering waste heat has received considerable attention [11-15]. Soylemez [15] reported a thermo-economic optimization analysis that can estimate the optimum heat exchanger area for energy recovery application. A survey conducted by University of Iowa [16] provided an indication of what is available on the American and Canadian markets in terms of waste heat recovery methods and the state-of-the-art in the area. The survey found 17 US patents on this topic. The goal of this paper is to explore an economically feasible and a manufacturable heat exchanger that recovers waste heat from the exhaust gases of a natural gas-fired supplemental heating unit (fire place, stove). This is achieved by presenting basic analysis for the heat exchanger, describing a prototype heat exchanger and examining the experimental procedures used to test the prototype heat exchanger. The experimental results are acquired for three different test conditions in an attempt to define the importance of the various factors that affect the heat exchanger performance.

2 Governing equations The conventional heat exchanger analysis is based on the effectiveness method [18]. In the investigated heat exchanger, the exhaust gas flows through three passes, while the room air flows through only one pass. The three exhaust-gas passes are modelled by three separated cross-flow heat exchangers as shown in Fig. 1. Each heat exchanger is modelled and the relations for the heat exchangers are solved simultaneously to obtain the final room-air and exhaust-gas outlet temperatures [17]. Heat exchanger 1 (first pass): (1) Heat exchanger 2 (second pass): (2) Heat exchanger 3 (third pass): (3) Overall heat exchanger: (4) For a cross-flow heat exchanger with the fluid having Cmax is mixed and the fluid having Cmin is unmixed, the heat exchanger effectiveness () is: WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

1

439

(5)

1

where, ,

(6)

,

(7) (8)

(9) The exhaust-gas volumetric flow rate for the forced combustion air case is based on a mass balance, namely: (10) where the densities of the natural gas and combustion air, ng and ca, are evaluated at the room-air inlet temperature, and the density of the exhaust gas, e, is evaluated at the exhaust-gas outlet temperature.

Tei

Tao

Heat exchanger Ta2

Room air out Te1

Exhaust gas in

Heat exchanger 2 Te2 Ta1 Heat exchanger 1

Tai

(a) Figure 1:

Teo

Exhaust gas out Room air in

(b)

Schematics of (a) Three passage heat exchanger model, (b) Airflow through the heat exchanger.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

440 Energy and Sustainability III

3 Experiment setup 3.1 Prototype heat exchanger The prototype heat exchanger, shown in Fig. 2, has a width of 508 mm, a height of 559 mm, and a depth of 127 mm. Contained within the prototype are 19 finned tubes that served to transport the exhaust gases through the heat exchanger. The exhaust gas made three passes through the heat exchanger. For the first and second passes, the exhaust gas passes through six tubes per pass. For the third pass, the exhaust gas passes through seven tubes. Each tube has a length of 35.6 mm, an outer diameter of 16 mm, a wall thickness of 0.9 mm, and contains approximately 370 annular fins per tube. Each fin has a height of 9.5 mm, a thickness of 0.5 mm, and a spacing of 3.2 mm. The exhaust gas travels through the finned tubes into the first manifold located at the top of the heat exchanger. The gas then travels through a second pass of tubes through the heat exchanger into a second manifold on the opposite side. Finally, the gas passes through a third set of tubes at the bottom of the heat exchanger and exits out the exhaust pipe as shown in Fig 1. The exhaust gas is induced into the tubes at a flow rate of 11.6 L/s by a fan located at the heat exchanger exit. The 19 finned tubes are parallel to each other and have staggered configuration. The fins are made of carbon steel and are attached to the tubes using interference fit. Air at room temperature is used to cool the exhaust gas and enters the heat exchanger from the bottom and exits at the top. Two blowers located at the bottom of the heat exchanger have the capability to move a total of about 141.6 L/s of air over the finned tubes.

Figure 2:

General view of the experimental setup of the prototype heat exchanger.

3.2 Investigated experiments The waste heat recovery system consists of a finned-tube heat exchanger attached to the back of the fireplace. The heat exchanger contains an array of tubes through which the exhaust gas flows. Air flowing over the exhaust tubes is WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

441

used to recover heat from the exhaust gas. Three sets of experiments shown in Fig. 3 were used to examine the different contributions of the heat transfer to the room air: (1) normal operating mode, (2) cold exhaust gas, and (3) isolated heat exchanger. Exhaust gas out Exhaust gas out Room air out

Exhaust gas to heat exchanger

Room air fan Room air inlet

Exhaust Thermogas fan anemometer

(a) Exhaust gas outlet

Room Exhaust Heat air out exchanger pipe Combustion Fan air Natural gas Room air in ThermoFan anemometer

(b) Room air outlet Heat exchanger

Room air out Exhaust gas

Exhaust gas to vent

Room air fan Exhaust gas inlet

Insulation

Room air Exhaust gas fan inlet

(c) Figure 3:

Heat exchanger

Room air in

Fan

(d)

General view of the experimental setup: (a) front view – normal operating mode, (b) side view – normal operating mode, (c) cold exhaust gas, (d) isolated heat exchanger.

In the normal operating setup, the heat exchanger is attached to the back of the fireplace. The exhaust gas flows into the heat exchanger from the top of the heat exchanger and flows out of the heat exchanger from the bottom in the tube side of the heat exchanger. The room air flows outside of the tubes from the bottom to the top of the heat exchanger. Combustion exhaust air is induced by an exhaust fan through the openings located at the bottom of the fireplace. Experiments are conducted under induced and forced exhaust air flows to check the influence of the different configurations on producing the exhaust-air flow. For the cold exhaust gas setup, the heat exchanger is attached to the back of the fireplace and the exhaust gas is not allowed to pass through the heat WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

442 Energy and Sustainability III exchanger but flows directly to the vent. The room air flows from the bottom to the top of the heat exchanger over the tubes and fins of the heat exchanger. Because the exhaust-gas temperature exceeds the operating temperature of the exhaust fan in this experiment, the exhaust fan is used to force the combustion air into the fireplace air instead of inducing the combustion air. This experiment is used to examine the amount of heat transferred by radiation and convection from the firebox wall. In the Isolated heat exchanger setup, the heat exchanger is insulated from the fireplace. The exhaust gas and room air pass through the heat exchanger in the same way as for the normal operating mode. The firebox wall and heat exchanger wall on the fireplace side are insulated to minimize the heat loss and the possible heat transfer between them. This experiment is used to examine the direct heat transfer from the exhaust gas to the room air. 3.3 Instrumentation Fluid and surface temperatures at different locations of were measured by thermocouples and recorded using an OMEGA automatic data acquisition system. A total of 27 OMEGA Type-K thermocouples were installed to measure temperatures at various points. The thermocouples have an accuracy of 0.4 to 0.75 % by design. All thermocouples were connected to an OMEGA TempScan data acquisition unit that utilizes the OMEGA TempView software to process the temperature readings and record the temperature readings to a spreadsheet every 30 sec. All surface mounted thermocouples are insulated from the surrounding to ensure an accurate measurement for the surface temperature. Thermocouples that measure the room-air or exhaust-gas temperatures were installed in the main stream of the flow and did not touch any surface. The thermocouple used to measure the exhaust-gas inlet temperature was carefully placed inside the first manifold, where the thermocouple cannot receive radiation directly from the fire to ensure the accuracy of the measurement. The natural-gas flow rate was measured and controlled by an AALBORG mass flow-meter/controller. This meter provides a natural-gas flow ranging from 80 to 120 % with 100 % corresponding to a flow rate of 0.33 L/s. A variable speed centrifugal fan made by EBM was used to provide the exhaust gas flow. The exhaust-gas volumetric flow rate can be adjusted by changing the voltage applied to the fan. The working voltage for the exhaust fan, Vf, ranges from 8 to 15 V DC. The exhaust gas flow rate was measured by an Extech thermoanemometer, which was installed downstream to the exhaust-gas fan. The anemometer has an accuracy of ± 3 % of reading. A constant speed room-air blower was used to circulate the room air over the tubes and fins of the heat exchanger. The room-air blower is a TWIN cross flow blower made by EBM and it was operated at 115 Volt/60 Hz AC to provide a 94.4 L/s constant roomair flow at no load. An approximate measurement of the room air flow rate is obtained using a handheld flow meter at the room air outlet. The results show that the room-air flow rate is close to 94.4 L/s, which is what the room-air fan provides at no load.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

443

3.4 Experiment procedure The natural-gas flow rate and the exhaust-gas flow rate are the adjustable parameters for any setup. All experiments start with a low natural-gas flow rate and a low exhaust-gas flow rate; then the exhaust flow rate is adjusted by changing the voltage of the exhaust fan. A typical test run takes about 3 hours to finish where it usually takes about 1 hr to reach steady-state conditions. The natural-gas flow rate is varied from 90% to 115% in increments of 10 % and the last increment of 5 % (100% corresponds to a flow rate of 0.33 L/s) while the exhaust-gas flow rate is altered by changing the voltage from 10 to 14 V. The voltage applied on the exhaust fan is increased one volt every 30 min until it reaches 14 V. For every experiment setting, the temperature data is plotted with time. The steady state data points are averaged to get the results for the test run. Two test runs for Experiment 3 at 100% natural-gas flow rate were conducted: under induced and forced combustion air. For Experiment 2, the natural-gas flow rate was set at 100% for the single test run. For Experiment 1, the natural-gas flow rate was set at 90%, 100%, 110%, and 115% for varying exhaust-gas flow rates. Therefore, results from a total of 34 test runs were available distributed as 20 test runs for Experiment 1, 5 test runs for Experiment 2, and 9 test runs for Experiment 3. 170 Experiment 1

Temperature  (C)

160

Experiment 2 150 140 130 120 110 12

17

22

27

Qe (L/s)

Figure 4:

Firebox wall surface temperatures.

4 Results and discussions The firebox wall surface temperature is essential to calculate the heat transfer from the firebox to the room air and to the tubes and fins. Fig. 4 shows results from experiments where the average firebox wall surface temperature begins to increase rapidly with increasing exhaust-gas flow rate for Experiment 1. However the average firebox wall temperature decreases with increasing exhaust-gas flow rate for Experiment 2. These results show the heating effect of the exhaust-gas by the firebox wall. An increasing exhaust-gas volumetric flow rate means that more excess air is used in the combustion. Hence, the increasing WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

444 Energy and Sustainability III Qe lowers the exhaust-gas outlet temperature, as well as the firebox wall temperature. When there is exhaust gas passing through the tubes, it raises the tube temperature. At the exhaust-gas inlet, the exhaust-gas temperature is around 204C, which is above the average firebox wall temperature. Therefore, the outer tube surface might have a higher temperature than the firebox wall and radiates heat to the firebox wall or at least the tube receives less heat from the firebox wall. Even though the firebox wall temperature is not a constant, the difference is small compared with the temperature difference between the firebox wall and the air or the outer tube surface. Therefore, for simplicity, an average temperature of 146C is chosen as the firebox wall surface temperature in the simulations for Experiment 1 and 118C for Experiment 2. 4.1 Isolated heat exchanger (experiment 3) During Experiment 3, it is expected that the heat loss of the exhaust gas be the same as the heat input to the room air (qa should equal qe). Rates of heat transfer shown in Fig. 5 are calculated based on Eqs. (1)-(4). These equations calculate the sensible heat as an “apparent” heat exchanged. Results presented here do not show this agreement which is due to the heat released by condensation process. Part of the heat released by condensation process is transferred to the room air, and part of the heat raises the exhaust-gas temperature. The effect of induced and forced combustion air is shown in Fig. 5. The exhaust-gas and room-air inlet and outlet temperatures for the induced combustion air case are greater than those for the forced combustion air case. Also, the induced combustion has larger values for both qa and qe. During the experiment, the induced combustion air case has a steady flame while the forced combustion air case has an unsteady flame and sometimes the flame quenches. 4100 qa ,  Forced qa ,  Induced qe ,  Forced qe ,  Induced

3600

q  (W)

3100 2600 2100 1600 1100 13

15

17

19

21

Qe (L/s)

Figure 5:

qa and apparent qe for induced and forced combustion air flow of Experiment 1.

When comparing the maximum temperature difference (Tei – Tai) for both cases, the induced combustion air has an average maximum temperature difference of 178.3ºC, whereas the forced combustion air case has only WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

445

147.2 ºC. Because the driving force for the forced combustion air case is about 15% lower than that for the induced combustion air case, the heat transfer rates for the exhaust gas and the room air of the forced combustion air case should be 15% less than that of the induced combustion air case. As shown in Fig. 5, the heat transfer differences between the two cases are in the vicinity of 15%. After considering the uncertainty of the measurements (not reported here), this experiment shows that the induced and forced combustion air has no significant effect on the heat transfer. 4.2 Cold exhaust gas (experiment 2) In the current setup, the exhaust gas does not pass through the heat exchanger. The combustion air is forced into the fireplace in this experiment, and the room air receives heat only from the firebox wall. The combustion-air flow rates of Experiment 2 were found higher than those for the same exhaust-gas fan voltage for Experiments 1 and 3 as shown in Fig. 6. This is because the exhaust fan does not have to overcome the pressure loss that the heat exchanger adds to the system. Because the exhaust-gas fan supplies more cold air to the fireplace, the flame temperature drops slightly for higher exhaust-gas flow rate. Therefore, the effect that this exhaust-gas flow rate difference in Experiment 2 has on to the heat transfer to the room air is neglected. Notice that, even though the exhaust gas is not passing through the heat exchanger, the temperature at the heat exchanger exhaust-gas inlet is higher than the room-air outlet temperature, which implies that the stagnant air inside the tubes is heated up by radiation from the firebox. Therefore, the heated tube surface serves as another heat source for heating up the room air. Comparing Experiments 1 and 2, the heat transfer to the room air for Experiment 1 is about 20 to 30 percent higher than that for Experiment 2, which means the heat transfer from the exhaust gas to the room air is of the same order of magnitude as the heat transfer from the firebox wall to the room air, but larger. 1040

45

1020

35

1000

30 25

980

20 Tao Tai Tei qa

15 10 5 0 18

20

960

q  (W)

Temperature  (C)

40

940 920 22

24

26

28

Qe (L/s)

Figure 6:

Effect of combustion gas flow rate on room and exhaust air temperatures and qa of experiment 2.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

446 Energy and Sustainability III 4.3 Normal operating mode (experiment 1) The inlet and outlet temperatures and Qe are measured whereas the calculated qa and apparent qe are shown in Fig. 7. The room-air and exhaust-gas outlet temperatures are both increasing with increasing exhaust-gas flow rate for a constant natural-gas flow rate. An increasing room-air outlet temperature implies that increasing the exhaust-gas flow rate increases the heat transfer to the room air. The apparent heat extracted from the exhaust gas is increased with increasing exhaust-gas flow rate as well. When keeping the exhaust-gas flow rate constant, the outlet and inlet temperature differences are increasing with increasing natural-gas flow rate, which means increasing heat input to the heat exchanger. The heat transfer rates are increasing with increasing natural-gas flow rate because the increasing temperature difference increases the driving force.

2800 2600

qa (W)

4500

Qng = 115% Qng = 110% Qng = 100% Qng = 90%

4000 3500 3000

2400

2500 2000

2200

qe (W)

3000

1500 2000

1000

1800

500 12

15

18

21

Qe (L/s)

Figure 7:

Effect of exhaust gas flow rate on the heat exchanged.

4.4 Summary The three experiments are designed to test the different heat transfer modes to the room air, namely, Experiment 3 has only exhaust-gas heat transfer to the room air, Experiment 2 has only firebox wall heat transfer to the room air, and Experiment 1 combines the two contributions. With the assumption that the exhaust-gas flow rate does not affect the heat transfer from the firebox wall to the room air, the heat transfer rate to the room air of Experiment 1 should be approximately the sum of that of Experiments 2 and 3, even thought the exhaust gas flow rate of Experiment 2 is not the same as that of Experiments 1 and 3. The values for the heat transfer to the room air in Fig. 8 show that the heat transfer rate for Experiment 1 is not exactly the summation of those for Experiments 2 and 3. The presence of the exhaust gas inside the tubes in Experiment 1 decreases the heat transfer from the firebox wall. The tube wall temperature for Experiment 2 is almost constant compared to that of Experiment 1, which varies greatly from close to the exhaust gas inlet temperature to near the exhaust-gas dew point temperature. Because no exhaust gas flows through the WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

447

tubes, the air temperature inside the tube is very close to the temperature of the tube wall. Therefore, the tube wall temperature for Experiment 2 is close to the dew point temperature of the exhaust gas over the heat exchanger. On the other hand, in Experiment 1, the tube wall temperature is much higher than the dew point temperature when the exhaust gas temperature is high. Only after about two passes, the tube wall temperature drops close to the dew point temperature. Therefore, in Experiment 2, the tube wall is receiving much more radiation from the firebox wall than in Experiment 1, because of the much lower average tube surface temperature. 2600 2500

q  (W)

2400 2300 2200 qa2 + qa3

2100 2000

qa1

1900 9

10

11

12

13

14

15

Vf (V)

Figure 8:

Heat transfer to room air contributions.

5 Conclusion The waste heat recovery in supplemental heaters was experimentally studied using an in-house heat exchanger prototype, in different conditions. It was shown that the heat exchanger can significantly reduces the fuel consumption. The experiments also indicate that condensation occurs within the exhaust-gas tubes. Future work is recommended to pursue further quantification of the condensate production as related to waste heat recovery. The treatment and management of condensate as a challenge to the design and construction of the proposed heat exchanger design for waste heat recovery is also of importance for future development of such heat exchangers.

Acknowledgements The authors would like to acknowledge the financial support received from Prince Mohammad Bin Fahd University (PMU) to cover the cost of attending this conference. Furthermore, the authors wish to acknowledge the Iowa Energy Center and HNI Corporation for their support and interest in this project. The information and assistance provided by them is much appreciated. The authors also express their thanks to Mat Pierce of HNI Corporation who participated in conducting most of the experiments and provided valuable lab assistance. WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

448 Energy and Sustainability III

References [1] G. F. Hessler, Issues in heat recovery steam generator system noise, The Journal of the Acoustical Society of America, 101 (1997) 3038-3038. [2] A. Mihelic-Bodanic, R. Budin, Heat recovery in thermoplastics production, Energy Conversion and Management, 43 (2002) 1079-1089. [3] D. V. Maksimov, N. N. Kochanov, N. N. Mittsenko, Z. V. Zagryadskaya, V. E. Grinberg, Experience in introduction of heat recovery systems, Chemistry and Technology of Fuels and Oils, 36 (2000) 308-309. [4] M. Fehrm, W. Reiners, M. Ungemach, Exhaust air heat recovery in buildings, International Journal of Refrigeration, 25 (2002) 439-449. [5] R. Tugrul Ogulata, Utilization of waste-heat recovery in textile drying, Applied Energy, 79 (2004) 41-49. [6] F. Yang, X. Yuan, G. Lin, Waste heat recovery using heat pipe heat exchanger for heating automobile using exhaust gas, Applied Thermal Engineering, 23 (2003) 367-372. [7] M. De Monte, E. Padoano, D. Pozzetto, Waste heat recovery in a coffee roasting plant, Applied Thermal Engineering, 23 (2003) 1033-1044. [8] L. Junhong, L. Zhizhang, G. Jianming, L. Zhiwei, Truck waste heat recovery, Applied Thermal Engineering, 23 (2003) 409-416. [9] F. Pettersson, J. Soderman, Design of robust heat recovery systems in paper machines, Chemical Engineering and Processing: Process Intensification, 46 (2007) 910-917. [10] Y. Naganuma, Multifunctional heat recovery-type coal gasification systems, Fuel and Energy Abstracts, 39 (1998) 188. [11] D. R. Rousse, D. Y. Martin, R. Theriault, F. Leveillee, R. Boily, Heat recovery in greenhouses: a practical solution, Applied Thermal Engineering, 20 (2000) 687-706. [12] E. Goto, S. Kase, H. Ding, Exhaust Heat Recovery in Internal Combustion Engine, JSAE Review, 16 (1995) 313-314. [13] J. S. Cain, Heat recovery apparatus for use with a non-high efficiency furnace, Applied Thermal Engineering, 16 (1996) 9. [14] R. Yang, P. Wang, The effect of heat recovery on the performance of a glazed solar collector/regenerator, Solar Energy, 54 (1995) 19-24. [15] M. S. Soylemez, On the optimum heat exchanger sizing for heat recovery, Energy Conversion and Management, 41 (2000) 1419-1427. [16] E. Y. Tanbour, J. Hu, T. F. Smith, Waste heat recovery heat exchanger for supplemental heaters, Technical Report, University of Iowa, Report No. ME-TFS-01-006, 2001. [17] F. P. Incropera, D. P., DeWitt, Fundamentals of Heat and Mass Transfer, 4th ed., John Wiley & Sons, New York, New York, 1996.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

449

Energy performance assessment of building systems with computer dynamic simulation and monitoring in a laboratory A. García Tremps & D. Mora AIDICO, Instituto Tecnológico de la Construcción, Área de Construcción Sostenible, Spain

Abstract Society is under constant development and it directly entails greater comfort demands for daily activities; these demands are reflected in a continuous increase of energy consumption that is used to satisfy them. According to EU policies to reduce emissions of greenhouse effect gases and considering that the building sector in Spain consumes almost 20% of total primary energy, new solutions are required to be applied in the existing buildings, given that using passive architectural systems can reduce up to 75% of energy building demands. In this context, this project focuses in the study and quantification of the energy performance of the building systems and construction elements. Two methods lead to this quantification: energy dynamic simulation with PC software and energy monitoring in eeLAB laboratory. Comparing real data with simulation data will help to know both possible deviations of in situ test – due, for example, to small deviations in measuring instrumentation, as the limits or fluctuations in the software simulation results. To obtain real data, a proper enclosure was developed for data gathering (eeLAB) as a test equipment based on an open wireless protocol, which allows it to be easily implemented. The analysis of data obtained from the two methods will allow us to parameterize energetically the building systems most commonly used in construction. This quantification will provide the different agents of building process with objective criteria for selecting building products and building systems more energetically efficient and appropriate for each location and orientation of the building. Keywords: energy efficiency, building envelope, energy monitoring, simulation. WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESUS110381

450 Energy and Sustainability III

1 Introduction Society’s environmental concerns and the need for a rational use of energy resources has led European countries to establish strategies compatible with sustainable development in accordance with the Kyoto Protocol to reduce emissions of gases that cause global warming. In fact, the EPBD [1] aims to curb the energy demand of buildings and therefore reduce consumption, as this is directly proportional to economic development and the level of CO2 emissions. The construction sector has been one of utmost importance for the Spanish economy, but at the same time has provoked serious impacts on the environment; it is estimated that more than 20% (EUROSTAT [2]) of the primary energy consumed in Spain is by the construction sector, therefore reductions in demand and energy savings are top priorities to be able to comply with the international energy challenges facing Spain. This building development has carried with it an increase in the consumption of energy, due largely to the scant attention paid to the incorporation of passive strategies in building, entailing the need to employ active systems in buildings to achieve the level of comfort demanded by today's society. A building designed with energy efficiency criteria can achieve savings of up to 70% (IDAE [3]) in air conditioning and lighting. Passive strategies consist in maximizing heat gains and minimizing energy losses of the building in winter, and minimizing heat gains and maximizing the losses of the building in summer. It is important to know the conditions of the environment of the buildings as well as the use they will have to prioritize between the different strategies since some are more recommended for one season than another. In many circumstances incorporating mechanical or electrical devices can improve and enhance some passive strategies, allowing the suitability of different strategies throughout the year. It is within this context that the idea of the project CESCon has its origins. Its objective is to reduce energy demand in buildings of new construction or rehabilitation by means of the quantification of energy saving due to the use of passive strategies. Much is said about energy efficiency and demand reduction in construction, but there is a lack of specific studies which recommend or prioritize passive strategies to achieve these goals. The fact that this project not only analyzes passive strategies but also simulates and quantifies them in different scenarios, views compatibility between different strategies, and selects the most efficient choice, entails a degree of innovation and a further step to promote its use and achieve the objective of having an existing building stock of lower consumption thereby reducing greenhouse gas emissions. Quantification of energy saving measures is made by two independent but related systems, computer simulation and energy monitoring. The latter will be conducted in an experimental laboratory by means of a wireless monitoring system. In order to scale the findings/results of the study on actual buildings, a study is also required on how this same system could be used to measure the compliance of the environmental parameters and constructive systems to the WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

451

Energy Efficiency in Existing Buildings Certification, although in Spain this is not yet regulated by law. The simulation enables the design of reduced energy consumption and energy efficient buildings and the monitoring measures the quality of the finished project. In addition, the comparison of the simulation model with the real data obtained will show any deviation between both and verify the suitability of the analyzed systems. The project has been planned so that the results can be used by different agents from the building sector who can count on the knowledge of a proven and reliable technical basis for choosing the most efficient system.

2 Completion of the project The growth of surface constructed buildings in Spain in the period 1990-2005 (prior to approval of the Technical Building Code) was 143%, which meant a 9.5% average annual growth experienced in this sector during this period (IDAE [5]). Consequently, the consumption of installations (ACS, heating, cooling and lighting) associated with the building sector has increased, both in the tertiary and domestic sectors; final energy consumption in the building sector is 17% of the national total (MITyC [4]). This situation is framed within the context of a national dependence on imported energy of more than 80% (IDAE [5]). The end of the era of cheap fossil fuels is approaching. During this time, a large quantity of mechanical and electrical equipment to condition buildings has been developed. One of the consequences of placing such importance onto the installations was that passive strategies were relegated to the background, and designers left full responsibility for indoor air quality control to thermal installations. There is no doubt of the prime need to ensure that rehabilitated or newly constructed buildings consume the least amount of energy possible. This is achieved by initially reducing the energy demand of the building, through responsible design appropriate both to the climate as well as utilization (using passive strategies will result in the greatest savings). Then the installations should be analyzed to ensure that they are the most appropriate and most efficient. Finally, the required energy should come from renewable energy sources which, if feasible, will be integrated into the same building. This project is within the framework of the reduction of energy demand. Currently, the building sector mentions energy efficiency and demand reduction, but there is a lack of studies that advise or prioritize passive strategies to achieve this goal. The fact that this project not only analyzes the passive systems but also simulates them in different scenarios, finding compatibility between different strategies, entails a degree of innovation and a further step to promote their use and achieve the objective of having an existing building stock of lower consumption thereby reducing the emission of greenhouse gases. Promoting the reduction of energy demand and quantifying it has been considered of great interest and relevance. Both building design and the incorporation of passive systems can improve energy efficiency in existing WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

452 Energy and Sustainability III buildings and new constructions. To offer the same conditions of comfort, a passive measure is more efficient than an active measure because the first affects the second resulting in effective energy savings. Thus, the need was seen to study the different passive systems available on the market which would be used depending on the type of climate; the aim being to reduce energy demand without renouncing user comfort and well-being. 2.1 Background This is a multi-year project, which focuses attention on aspects related to energy demand during the use of the building. A significant reduction in energy demand in buildings is achieved through the application of passive measures. This project has a main objective to quantify measures of energy saving applicable to the buildings, through the study and analysis of data obtained through measurements of a real physical model. The possibility of incorporating the findings of the project to actual buildings would make it possible to obtain energy efficient buildings. The study of the behavior of passive systems in construction is considered important in the building sector, due to the wide variety of constructive solutions with unknown energy behavior. It is therefore necessary to study this behavior and quantify the energy reduction of each system because companies in the construction sector are at present obliged to adapt to the new laws from Europe insisting on energy saving. The possibilities that this project offers to companies related to the building sector are evident. Thanks to proven results, a reasonable and reasoned election of a passive system or tested strategy can be made, that best suits the building typology, and therefore greater improvements in energy efficiency will be produced throughout the life of the building. Therefore, the most important specific objectives which the implementation of this project aims to achieve are:  Use the assessments obtained by monitoring the different constructive systems to provide guidance regarding the most appropriate systems to apply to different scenarios and explore compatibility.  Compare real data with data obtained through simulation to know both possible deviations from the results of the tests in situ, as well as fluctuations or limits in the results of programs used in computer simulation.  Prepare a technical report as a guide for the selection of constructive systems intended to satisfy comfort needs. In addition, given the impact of the energy issue on the environment, it is considered important to underline the specific environmental objectives of the project:  Reduce greenhouse emissions. Passive techniques to reduce GHG emissions in buildings are studied in this project, so as to encourage the use of these passive strategies for reducing energy consumption.  Quantify the reduction of energy through passive strategies. Due to the WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

453

great unawareness that currently exists regarding the impact of passive systems on energy expenditure, the implementation of this project is intended to perform a valuation that allows the selection of the best system depending on building typology and location.  Promote good environmental practices in the construction sector. Much of the energy consumed in buildings is due to a citizen’s lack of awareness of energy wastage while achieving the desired comfort conditions. The good use of passive systems by the citizen in their home or workplace would result in a substantial reduction in energy consumption, without prejudicing comfort levels. The research project CESCon (2009) and the subproject CESCon 2 within project ME3CO (2010) are regional I+D Projects, developed by AIDICO (Construction Technology Institute) and funded by IMPIVA (Institute of Small and Medium Industry of the Valencia Regional Government), through ERDF (European Regional Development Fund).

3 Conception and composition of the system For the implementation of the project a model type (enclosed area) has been selected that allows the study under normal use conditions; different aspects of geometry, constructive systems and materials have been analyzed for this purpose. To allow comparative analysis of different constructive solutions in identical weather conditions, two modules have been used in the project in the same position and orientation. These two modules form the experimental laboratory eeLAB. 3.1 Model type development The eeLAB laboratory consists of two modules for trials; with a north-south orientation. Using simulation programs to optimize the best location search according to the available environment, the positioning of the study models (modules) is set in such a way that they are not affected by exterior shadows, or shadows between them.

Figure 1:

Computer simulation.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

454 Energy and Sustainability III The geometry of the modules is linear, with dimensions of 4.40m x 2.40m floor and 2.30m height. Its surface of approximately 10m2, allows the volume to resemble a room. Additionally, modular material for compact volume has been used to allow any eventual changes to be quick and economical. Each side of the module, except for the south side which is the testing side, has 12cm insulation to reduce heat flow on these sides, thereby causing the heat flow to occur mainly on the testing face. Although 0.12m thick insulation is not excessive for certain latitudes, this laboratory is located in Paterna (Valencia, Spain), with a Mediterranean climate, so this is greater than the insulation that is often used in most construction systems (0.03 to 0.06m) and those abiding by the Technical Building Code for this climatic zone B3 (Valencia, Spain). The reason the south face is the testing face is because it receives more thermal oscillations during the day, due to the influence of solar radiation on the enclosed area, allowing a multitude of heat transfer analysis. At the same time, the other five faces of the module are also monitored, so as to maintain total control over the flow of heat that exists in all of them. The proposed solutions have been elaborated in a computerized presimulation to obtain noticeable changes in the various options measured. The resulting model comes from the study of geometry, materials and their orientation and location in the environment. The project testing module has been composed using this information. Prefabricated material has been chosen for speed and because it allows the change of constructive systems that are going to be analyzed without affecting the rest of the module. The following elements have been acquired for its composition:  Sandwich Panel 0.04m thick, 2.3m height, ribbed outer skin and corrugated inner skin: 22 units  Sandwich Panel 0.08m thick, ribbed outer skin and corrugated inner skin: 16 units  Outside door 1 blind panel leaf, frame white aluminum and leaf sandwich panel: 2 units  Insulation covered with injected polyurethane 0.120m thick: 2 units  Phenolic Enamel Board: 2 units  Floor base without board with polyurethane injected insulation 0.12m thick: 2 units  Sandwich Panel enclosure 0.08m thick: 4.36m  Ventilated façade panel made with aluminum structure and fiberglass thermoset resin soffits: 1 unit  Sliding window two leaves of 1.5x1m White aluminum glazed, 4-6-4 transparent without bars: 2 units 3.2 Monitoring and simulation Climatological parameters (atmosphere temperature, relative humidity, speed and direction of the wind and radiation) and thermal parameters (temperature inside enclosed area, surface temperature on each layer of the module, relative WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

455

humidity, and heat flow of the module) are measured in monitoring tests in situ. Additionally they can be calculated by the simulation programs to compare the results. After an analysis of the measure parameters and the most suitable sensors, the different monitoring methodologies were studied, reviewing the compatibility between the various components of the measure instrumentation. The measure parameters, referring to the energy saving passive measures of the building, were channeled into an open, easily implementable system that would enable the project to rapidly adapt in case of any deviations or future amplifications (i.e. more parameters to monitor or adaptation to an extended environment). Additionally there is the opportunity to expand the system in the long-term with internal environment and internal radiation parameters, along with parameters relating to active systems, parameters of thermal installations, lighting performance and consumption. The monitoring system has been selected according to the specific needs of the experiment, but always bearing in mind its future applicability to real environment "building" (scalability). In the first place, the parameters to be monitored in a built environment were selected to evaluate their energy efficiency; they were then transposed to the concrete needs of the system. At the same time, the characteristics of the different monitoring protocols were analyzed so as to compare the detected needs with the characteristics of each one. A preselection was made of only the most suitable systems to be used in the study environment, or ones that with reasonable environmental modifications, could be considered. Thus it was possible to assess the compatibility of each system in the physical environment of the actual place where the measurements would be taken, until an open system was found that would go further than meeting the immediate needs of the project, one that would be easily implementable and even scalable according to the needs identified during the research or in future projects. Finally, a decision was made to resort to the ZigBee Protocol because of the advantages the WSN (wireless sensors networks) offer to adapt to the demands of the experiment. It also allows a reduction in system installation and costs in new scenarios where it is difficult to implant a system with cables. The WSN were originally developed for monitoring in the military field; currently the development of these networks focuses on domotic, environmental, health, traffic or structural monitoring applications (Perkins et al. [6]). In particular the ZigBee Protocol has low energy consumption, which allows the useful life of the batteries of data acquisition modules to be optimized. This feature means that access to the study sites is not necessary for long periods of time; human intervention on the monitorized site always interferes with the capture of data by changing the conditions of the environment. Using the ZigBee protocol allows you to export the results of research from an experimental and local level to actual buildings, with measures in situ; the advantage of a scalable system is that of being able to adapt dimensions according to the repeater nodes needed to expand the system later. The versatility WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

456 Energy and Sustainability III

Figure 2:

Figure 3:

LabView system.

Procedure for election of the measurement system.

of the system supports any analog input and digital output, so it is possible to install dynamic device controls for domotic or active installations. WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

457

This protocol allows an open system in which different types of sensors (thermal radiation, humidity, etc.) can be integrated; these are programmed within the wireless LabView program. The WSN consists of data acquisition modules (end nodes) that are responsible for transmitting the measured values of the sensors to the coordinator (router) that has been programmed with the LabView program for dumping measurements to the database. Additionally, throughout the project a visualization system Diagmon (www.diagmon.es) has been developed and this is continually expanding its capabilities to include the management and processing of data through a web platform. The disposition of the sensors is divided mainly into two types; those which collect weather data (temperature, humidity, solar radiation, wind speed and direction) and those that measure the interior parameters of the modules (humidity and temperature within each of them and that of their constructive systems (the heat flow and the surface and interior temperature of each layer of the panels that make up the enclosed area is measured.) In the search for instrumentation phase, the analysis of compatibility with the physical environment had a favorable comparison, but once the system was started problems occurred concerning the retransmission of the wireless signal to the exterior computer, so the experiment had to be modified and redesigned until reaching the previously commented. The original intention was that the data acquisition modules within the enclosed area would communicate by wireless system with a repeater in the exterior and that would transmit the wireless signal to store data on a computer. Once the system was started, the wireless signal was strongly attenuated by the aluminum shell of the study model. Therefore the issue was resolved by placing the gateway inside the enclosed areas, to communicate wirelessly with the data acquisition modules and by the institute LAN (local area network) with the computer where the measurements are stored. The amendments made to the environment were rapid and did not cause any deviation to the initial timetable.

Figure 4:

Expected model and realized model.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

458 Energy and Sustainability III

4 Partial results and conclusions The analysis process which is being carried out is based both on real measurements as well as computer-assisted simulations. The degree of efficiency of each of the proposed and tested measures may be determined through the analysis of these contrasting results. From the outset, the thermal bridges in the constructed enclosed areas could be detected by using the thermographic camera. Although the influence was identical in both models, due to the similar disposition, a decision was made to solve those in proximity of the corners, at the joint between panels of different orientation.

Figure 5:

Thermography: corner between vertical walls and horizontal surfaces and soil structure, values in °C.

Once the variable of the thermal bridges was homogenized in this way, and after the placement of sensors, we proceeded with the study of the various enclosures. Those tested on the south side so far have been: façade consisting of two sandwich panels, one of 0.08m thick and the other of 0.04m thick and a façade consisting of only one 0.04m thick sandwich panel. The next constructive system to be tested will be a ventilated façade made with aluminum structure and fiberglass thermoset resin soffits. From a first comparison made between data obtained from monitoring and the results of the simulations, abnormalities have been detected; for example, significant deviations between surface temperatures of the enclosures have been obtained. This is being studied so as to rule out the cause of the deviation being design mistakes of the experiment (this happened at first with the values measured by the thermocouple (temperature) as they were affected by the way it was screwed in). The dynamic simulation programs that are being used for the simulation of the enclosed area tests are EnergyPlus within the DesignBuilder program. On the other hand the monitoring system database is being analyzed by PCA, (Principal Component Analysis) which simplifies the structure of the recorded data, and shows the structure of the implicit relationships between variables in order to be able to compare the correlations of each monitoring trial (incident radiation, surface temperature, etc.). WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

459

At the moment the eeLAB is being instrumented with thermal facilities to condition the enclosed area in cooling or heating mode so as to be able to monitor the direct consumption of each passive strategy tested. In the near future, with the experience gained in this project, an extension to the eeLAB installations is foreseen, which will include simultaneous evaluations of different constructive solutions and consumption monitoring, as well as analysis of the parameters related to gaps and carpentry, not only thermal and energy but also lighting. 4.1 Project capability The eeLAB is an experimental laboratory created to have an enclosed area where actual constructive solutions can be tested and where actual measures from the tests can be compared with simulation data. Its objective is to be able to implement the test conclusions held in the lab, on a larger scale, the "building". From the comparison between a pair of measurements (those obtained in the enclosed area mentioned and where passive strategy is applied) conclusions may be reached regarding the possibilities that arise in construction to improve energy efficiency in existing buildings. By monitoring a particular constructive system for a limited period of time in the eeLAB, the energy behavior can then be extrapolated throughout the year by computer simulation. Furthermore, when conducting a dynamic simulation, thermal and energetic behavior of the constructive system is analyzed and this quantifies the different strategies for the analyzed scenarios. At the same time, it will be possible to combine different strategies in the study model, allowing the most efficient choice and leading to a degree of innovation and a further step to promote its use and the objective of having a building stock of lower consumption and therefore a reduction in greenhouse gases. The project has been designed so that the results can be used by different agents of the building sector: designers who may apply the results to their buildings, developers and building companies, companies engaged in the development of new passive strategies or new technologies who need the knowledge of a proven and reliable technical basis for the choice of the most efficient system. In addition, users of these buildings will achieve a high degree of comfort with a lower consumption of energy which will be reflected in a reduction of energy expenditure. Companies linked to the construction sector are currently in the spotlight, since they are the ones who must take that big step to investigate and implement real energy saving measures. This project will allow them to be able to reach that target and acquire new skills to improve the ongoing construction–building process, adapting and optimizing passive systems to different typologies and environments of the buildings.

References [1] EPBD. Directive 2010/31/EU of 19 May 2010 on the energy performance of buildings. Directive 2002/91/EC of the European Parliament and of the WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

460 Energy and Sustainability III

[2]

[3]

[4]

[5]

[6]

Council of 16 December 2002 on the energy performance of buildings. http://ec.europa.eu/energy/efficiency/buildings/buildings_en.htm Self-processing data of EUROSTAT data. EUROSTAT, Panorama of energy. Energy statistics to support EU policies and Solutions, Office for Official Publications of the European Communities: Luxembourg, pp.48-50, 2009. Instituto para la Diversificación y Ahorro de la Energía IDAE, Guía práctica de la energía. Consumo eficiente y responsable, p.128, 2010 http://www.idae.es/index.php/mod.documentos/mem.descarga?file=/docume ntos_11406_Guia_Practica_Energia_3ed_A2010_509f8287.pdf, Ministerio de Industria, Turismo y Comercio, La energía en España 2009, División de Información, Documentación y Publicaciones: Madrid, p.195, 2010. Instituto para la Diversificación y Ahorro de la Energía IDAE, Plan de Acción 2008-2012 de la Estrategia de Ahorro y Eficiencia Energética en España, http://www.idae.es/ Perkins, C., Belding-Royer, E., Das, S. Ad hoc On-Demand Distance Vector (AODV) Routing, 2003.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

461

Investigating the impact of track gradients on traction energy efficiency in freight transportation by railway G. Bureika & G. Vaičiūnas Department of Railway Transport, Vilnius Gediminas Technical University, Lithuania

Abstract Energy recovery is an effective method of energy saving which can be used for traction in freight transportation by railway. In this area, energy recovery is a process of converting the kinetic energy of a moving train in electricity, which is transferred to another energy consumer (another train using the traction energy) through a catenary. Energy recovery can be effectively used for carrying various raw materials (e.g. timber, oil, etc.) to seaports by railway. The loaded wagons which are much heavier than unloaded wagons carry goods “down” to the seaports, while empty trains return (i.e. go ‘upward’) to the continent. The seaports are only several meters above the sea level, while the places of freight dispatching can be hundreds of meters, or even kilometres, above the sea level. The asymmetry of freight flows (when the freight flow directed “downwards” is several times heavier than ‘upward’ freight flow) may be effectively used for energy recovery. The research performed shows that, given an appropriate combination of the asymmetry of the freight flows in opposite directions and particular track gradient, the potential energy of freight trains may be used for freight transportation by applying energy recovery techniques. This allows the authors to make an assumption that this could serve a theoretical basis for making feasible one-way freight transportation by using only the recovered energy of the train. On the other hand, taking into account the rolling resistance of the train, there should be some limiting values of the ratio of the freight flows in the opposite directions, and the track gradient should not have small values (e.g. track gradient or the ratio of freight flows should not be too low). If that is the case, the inertial freight transportation is not possible, and an external energy source sufficient to overcome the rolling resistance of the train is required. WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESUS110391

462 Energy and Sustainability III Finally, the paper presents the ideas how to effectively use the potentialities of energy recovery technique in freight transportation by railway. Keywords: locomotive traction, freight transportation, track gradient, track curve, freight flow asymmetry coefficient, energy recovery ratio.

1 Introduction Since railway lines are neither straight nor horizontal, the moving trains should overcome track gradients and curves using additional energy [1]. On the other hand, these gradients could be used for energy recovery, which is an effective process of saving energy in the area of railway transportation. Energy recovery is the conversion of the kinetic energy of a train into electric energy by braking or inertial moving of the train down the steep hill and energy transmission to other consumers (usually, to another train via the contact power network or catenary) [4, 5]. This method of energy saving has advantages and disadvantages. First, there should be a consumer of the recovered energy (or means of energy storage) on the same route. Usually, this recovered energy is consumed by another electric (or hybrid) locomotive, which is moving in traction mode [3]. This means that to ensure energy consumption, railway traffic should be sufficiently intense. Another limitation is the requirement that a braking train should generate the amount of energy which should be sufficient to make energy recovery system (network) effective. This implies that the speed and weight of the train should be considerable; therefore, there should be a considerable track gradient on the route. Energy recovery technology is particularly effective, when the train is running downhill at high speed (e.g. when speed of the train is up to 80 km/h, while the gradient is about 10‰). Braking is not necessarily aimed at bringing the train to a stop. It may aim at maintaining the uniform speed of the train running downhill. In this case, the potential energy of the train is converted to electricity rather than to the kinetic energy, because the train does not accelerate. The conversion of potential energy to electric energy in the process of energy recovery has various technical applications. For example, the potential energy of the ascending funicular car is used for pulling another car, with a certain amount of the energy, also used to overcome friction). The principle of energy recovery may be used to lift a residential building. If the total mass of people ascending and taking a lift to the top floors is assumed to be equal to the mass of people descending by the lift and leaving the building, the total potential energy will be a nearly constant value for a long period of time. It follows that when the potential energy of the descending people is stored and used for lifting other people, the total energy consumption will consist only of losses caused by friction of the lift mechanism and energy conversion (transformation) losses. This principle can be also used in freight transportation by railway. If a train is moving uphill, the recovered energy of the train moving downhill (with a certain amount of power from the mains) may be used to pull it. Energy recovery may be particularly useful for freight transportation by railways, used for carrying various materials (e.g. oil products, timber, etc.) to the seaports. The loaded trains, which are up to four times as heavy as the empty ones, are moving WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

463

“down” to the seaports, while empty, light trains, are running from the seaports “up” to the continent [6]. This asymmetry of the freight flows (when the flow of goods carried “downwards” is several times larger than the flow of goods carried “upwards” may be effectively used for energy recovery. If people were only descending (but not ascending) in funiculars or lifts, these mechanisms could operate without any external source of energy, however, an effective energy recovery system should be provided. It is hardly possible to have freight trains that would be using only the potential energy of freight, i.e. operating without using any external energy source. However, the recovered potential freight energy makes a considerable part of the energy consumed by trains for traction. A mathematical model (equation) given below describes the dependence of this amount of energy for the trains with respect to the operating conditions, e.g. their running resistance, road profile, etc.

2 A theoretical study of energy recovery of moving trains The movement of the train is always associated with primary running resistance W0, defined as an empirical function of the train speed v and train squared speed v2. The train speed determines the frictional forces of rolling wheels and energy dissipation, while aerodynamic resistance of the running train depends on the squared speed. In the theoretical study of energy recovery described below, relative resistance w0 of the running train, determining the value of primary resistance per ton of the train mass, is considered. Thus, primary relative resistance w0 depends on the axle load qa, i.e. determines the loading of the wagons (ranging from empty to fully loaded wagons). In a general case, the amount of energy required for performing the work of pulling the wagons of the train is calculated by the equation: e0  S  (Q  w  P  w) ,

(1)

where S is the length of the track, km; Q is the mass of wagons, t; P is the locomotive mass, t; w is a relative running resistance of wagons, taking into account wheel rolling resistance, aerodynamic resistance and track gradient resistance, kgf/t; w is a relative locomotive running resistance, taking into account wheel rolling resistance, aerodynamic resistance and track gradient resistance, kgf/t. Let us assume that ‘a common statistical train’ with the locomotive mass P and the mass of wagons Qdown is running ‘downwards’ at speed v, while another train with locomotive mass P and the mass of wagons Qup is moving ‘upwards’. In this case, when the train is moving downhill, track gradient resistance Wi is developed. In the calculation of the relative track gradient resistance wi [kgf/t], its numerical value is equal to track gradient i value [‰]. Taking this into account, the amount of the recovered energy (the potential) will be as follows:  |  P | i  w0 |) , edown  S  (Qdown  | i  wdown WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

(2)

464 Energy and Sustainability III

 is the where S is the path covered by the train, km; i is track gradient, ‰; wdown main relative running resistance of the wagons, kgf/t; w0 is the main relative running resistance of the locomotive, kgf/t. The expected amount of the recovered energy may be expressed by the equation:  |  P | i  w0 |)  k rec , edown  S  (Qdown  | i  wdown

(3)

where krec is energy recovery ratio (usually ranging from 0 to 1). Energy consumption on the ‘upwards’ moving train will be as follows:  )  P  (i  w0 )) . eup  S  (Qup  (i  wup

(4)

The mass of the ‘upwards’ moving train will be expressed by the equation: Qup 

Qdown , k as

(5)

where kas is the asymmetry coefficient, usually ranging from 1 to 4. To obtain the amount of the recovered energy which would be sufficient for traction of the ‘upwards’ moving train, the amounts of energy expressed by eqn. (3) and (4) should be equal. Comparing the data on the right side of the eqn. (3) and (4) and taking into account the eqn. (5), we will obtain:  |  P | i  w0 |)  k rec  S  ( S  (Qdown  | i  wdown

Qdown  )  P | i  w0 )) . (6)  (i  wup kas

The eqn. (6) is rearranged to define the energy recovery ratio: Qdown  |  P | i  w0 )  | i  wup k as .   )  P | i  w0 ) (Qdown  | i  wdown (

k rec

(7)

When solving eqn. (7), it is assumed that all wagons of the train have four axles, while the jointed rails are used. The relative resistance of the locomotive moving along such a track depends on the train speed v and the squared speed v2, being calculated by the empirical equation [2]: w0  2.4  0.011  v  0.00035  v 2 .

(8)

For loaded four-axle wagons (moving ‘downwards’) the relative resistance will be expressed as follows [2]: wdown  0.7 

3  0.1  v  0.0025  v 2 , qa

(9)

where qa is the axle load of a freight wagon, tf. For fully loaded wagons it is equal to 21 tf, for empty wagons – 6 tf. WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

465

Energy and Sustainability III

For empty four-axle wagons (moving ‘upwards’) the relative resistance is described by the expression [2]:

  1  0.044  v  0.00024  v 2 . wup

(10)

A case is analysed, when the train with a mass of 4000 tons is moving ‘downwards’ at the speed of 80 km/h along the straight track (with the curve radius equal to infinity), while another train with the mass of 1000 tons is moving ‘upwards’. In this case, the unknowns in eqn. (7) are energy recovery ratio and the track gradient. The data used in solving eqn. 17 are given in Table 1. Table 1: Qdown (t) 4000

Qup 

Qdown (t) k as

1000

The data for solving the eqn. (7). Pdown (t) 238

 wdown (kgf/t) 1.99

w0 (kgf/t) 5.52

Pup (t) 238

 wup

(kgf/t) 6.06

For the system to function, energy recovery ratio should not be smaller than required. After substituting the data from Table 1 into eqn. (7), we will graphically show the dependence of the required energy recovery ratio on the track gradient (see Fig. 1).

Figure 1:

The dependence of the required energy recovery ratio on the track gradient.

The graph shows what should be the energy recovery ratio, fitting a particular track gradient, allowing the system to work without using any external source of energy. Modern technologies usually allow energy recovery ratio to be about 0.5. As shown by the graphs presented in Fig 1, to ensure energy recovery ratio equal to 0.5, the track gradient higher than 16‰ is required. WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

466 Energy and Sustainability III

3 The study of the variation of energy recovery ratio 3.1 The analysis of the dependence of energy recovery ratio on the track gradient for varying speed of the train

As shown by eqn. (7), the required energy recovery ratio depends not only on the track gradient, but also on primary running resistances w0, which depend on the train speed (see eqns 8, 9 and 10). The running resistance, four axle values of the wagons (for the case of joined rails) are given in Table 2 with respect to the speed of the train. Table 2:

Running resistances of four-axle freight wagons given according to a particular speed of the train.

Speed v (km/h)

Locomotive resistance w0 (kgf/t)

Wagon resistance  ( kgf/t ) wup

Wagon resistance  (kgf/t ) wdown

10 20 30 40 50 60 70 80

2.55 2.76 3.05 3.40 3.83 4.32 4.89 5.52

1.46 1.98 2.54 3.14 3.80 4.50 5.26 6.06

0.90 0.99 1.09 1.22 1.38 1.56 1.76 1.99

It is clear that the dependence of the required energy recovery ratio on the track gradient will vary with the variation of the train speed. This dependence obtained by substituting eqn. (7), (8) and (9) into eqn. (11) is demonstrated in Fig. 2. It can be seen in Fig. 2 that energy recovery ratio increases with the speed increase. For example, when the speed is 20 km/h, while the track gradient is 15‰, the required energy recovery ratio is 0.4. However, when the speed reaches 80 km/h, the above ratio is about 0.6. In other words, the curve representing the dependence of energy recovery ratio on the track gradient rises up when the train speed increases. This is determined by the increase of primary running resistance of the accelerating train w0, due to the friction of the axle box bearings, as well as the friction between the wheels and the rails, energy absorption by the railway embankment and aerodynamic resistance. The last component of primary running resistance, i.e. aerodynamic resistance, is rapidly increasing, when the train speed reaches 100 km/h and more. It should be emphasized that primary running resistance of the train ‘eats up’ much energy in both types of train motion (‘downwards’ and ‘upwards’).

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

Required energy recovery ratio

1.0

467

Speed 20 km/h

0.9

Speed 40 km/h

0.8 0.7

Speed 60 km/h

0.6

Speed 80 km/h

0.5

Speed 100 km/h

0.4

Speed 120 km/h

0.3 0.2 0.1 0.0 0

Figure 2:

5

10

15

20

25

30

Track gradient, ‰

The dependence of energy recovery ratio on the track gradient for the train, moving at varying speed (the asymmetry coefficient kas = 4).

3.2 The analysis of the dependence of energy recovery ratio on the track gradient for the case of varying freight flow asymmetry

The required energy recovery ratio varies with the variation of the asymmetry coefficient. The variation of the required energy recovery ratio, depending on the track gradient and the variation of the asymmetry coefficient, is shown in Fig. 3.

Figure 3:

The variation of the dependence of the required energy recovery ratio on the track gradient for varying asymmetry coefficient.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

468 Energy and Sustainability III When the asymmetry coefficient decreases, the required energy recovery ratio increases. For example, when the track gradient is 15‰ and the asymmetry coefficient is 4, the required energy recovery ratio is about 0.5. However, when the asymmetry coefficient is equal to 2, energy recovery ratio is about 0.9. The curve showing the dependence of energy recovery ratio on the track gradient rises. When the asymmetry coefficient decreases, the mass of the train moving ‘downwards’ increases, and a certain amount of energy is stored due to the occurrence of downhill grades on the route. Most of this energy should be “returned” for pulling the train ‘upwards’. It should be noted that the highest value of asymmetry coefficient is found when wagons moving ‘downwards’ are fully loaded, while those pulled ‘upwards’ are empty. 3.3 The analysis of the dependence of energy recovery ratio on the track gradient for varying track curve radii

So far, the cases with the straight track (when the value of the curve radius tends to infinity) have been considered. However, actual railway tracks are curved, and the moving train should overcome track curve resistance wR, which is roughly calculated by the empirical equation [2]:

wR 

700 , R

(11)

where R is an average radius of the track curves, m.

Figure 4:

The dependence of the required energy recovery ratio on the track gradient, taking into account track curve radii.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

469

Taking into account the resistance of the curves, we may write the following equation: Q 700 700   ( down  (i  wup )  P  (i  w0  )) k as R R k rec  . (12) 700 700   (Qdovn  | i  wdown )  P | i  w0  |) R R By substituting the data from Table 1 into the eqns (11), (8), (9) and (10) we will obtain a graph (see Fig. 4), when the train speed is 60 km/h. When the average track curve radius decreases, the curve, showing the dependence of the required energy recovery ratio on the track gradient, rises, implying that the required energy recovery ratio increases because of the increase of track curve resistance (when the radii of the track curves are getting smaller). The resistances of the track curves ‘eat up’ much energy, when the train moves in either direction: ‘upwards’ or ‘downwards’.

4 Feasibility study of implementing the method of moving train energy recovery In studying feasibility of implementing the considered energy recovery method, special attention should be paid to two parameters – the track gradient and the required energy recovery ratio. At the present level of technological development energy recovery ratio may be about 0.5. With the increasing use of alternative energy sources, it may be expected to reach 0.6–0.7. However, even with this value of energy recovery ratio, the described energy recovery method may be practically used, if the track gradient is more than 10‰ (which can be seen in Figures 1–4). In other words, either the track gradient should be higher than 10– 15‰, or energy recovery ratio should exceed (0.6–0.7), which is hardly

Figure 5:

The dependence of the required energy recovery ratio on the track gradient and the speed of the ‘upward’ running train.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

470 Energy and Sustainability III technically possible. Such high slopes are rare in flat countries (like countries in Eastern and Middle Europe). Usually, the slopes there make 1–2‰, rarely reaching 5‰. When it is not technically possible to obtain the actual energy recovery ratio higher than (0.6–0.7), the railway structure allows only for track gradient below 10‰ and the considered energy recovery method can be widely used. This means that the lack of energy of the train moving ‘downwards’ (required for pulling another train ‘upwards’) may be compensated by the energy obtained from another source. One of the simplest examples illustrating this statement could be a model, when the train is moving ‘downwards’ at a higher speed and moving ‘upwards’ at a lower speed. The dependence of the required energy recovery ratio on the track gradient and the speed of the train pulled ‘upwards’ (when the ‘downward’ speed is 80 km/h) is shown in Fig. 5 (in this case, energy recovery ratio ranging from 0.3 to 0.9 is considered). As shown if Fig. 5, a decrease of the ‘upward’ speed does not produce a desired effect. If the required energy recovery ratio is assumed to be 0.5, a decrease of the ‘upward’ speed from 80 km/h to 20 km/h results in the decrease of the required track gradient from 20‰ to 17‰. However, when the speed is decreased from 80 to 20 km/h in both directions (see Fig. 2), the required energy recovery ratio is equal to 0.5, while the track gradient is only 7‰.

Figure 6:

The dependence of the required energy recovery ratio on the track gradient and the speed of the train running ‘downwards’.

The dependence of the required energy recovery ratio on the track gradient and the ‘downward’ speed of the train (whose ‘upward’ speed is 80 km/h) are shown in Fig. 6. Fig. 6 presents a more valuable relationship than that given in Fig. 5. If the required energy recovery ratio is equal to 0.5, then, a decrease of the ‘downward’ speed from 80 to 20 km/h leads to a decrease of the track gradient from 20 to 11‰. It should be noted that the ‘upward’ speed of the train should not be lower than the speed of the train in continuous duty. The train speed in both directions should not exceed its design speed. It must be stressed, that the braking distance depends on the train speed, which should be limited too. WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

471

The analysis of the relationships, presented in Figures 2, 5 and 6, allowed us to make a conclusion that, taking into account the dependence of the required energy recovery ratio on the track gradient, the most effective approach is to decrease the train speed in both directions of its movement. The next effective variant is a decrease of the ‘downward’ speed of the train, while a decrease of the ‘upward’ speed of the train is the least effective method. A mass of train running ‘downwards’ is (2–4) times as large as the mass of the train moving ‘upwards’, therefore, the speed of the train running ‘downwards’ has a stronger impact on the required energy recovery ratio.

5 Conclusions 1. Given the appropriate combination of the track gradient, running resistances and freight flow asymmetry, the potential energy of the carried goods can be used for freight carrying without any external energy source by applying energy recovery technique. However, required energy recovery ratio is necessary. 2. When the speed of the train increases, the required energy ratio also increases due to the increase of the main running resistance. In theory, energy recovery ratio can range from 0 to 1, but because of technical limitations, it is usually about 0.5. 3. The research performed has shown that pulling fully loaded wagons in one direction (‘downwards’) and empty wagons in the opposite direction (‘upwards’) is not ineffective from the perspective of energy recovery. In this case, the asymmetry coefficient reaches 4, which is its highest value. This allows us to obtain the required minimum energy recovery ratio of 0.5 in operational conditions. Goods are carried in special wagons (tanks, hopers, etc.), whose asymmetry coefficient is about 4. When the asymmetry coefficient decreases, the required energy recovery ratio increases. 4. In order to get larger amounts of the recovered energy in carrying goods by rail, wide curve tracks should be laid or straight tracks should be designed. When the average radius of the track curves decreases, the curve showing the dependence of the required energy recovery ratio on the track gradient rises. It implies that the required energy recovery ratio increases because of the increasing resistance (due to a decreasing track curve radius). 5. The analysis of the dependence of energy recovery ratio on the track gradient has shown that a decrease of the train speed in both directions is most effective, while the second effective alternative is a decrease of the ‘downward’ speed of the train. The third method, based on the decrease of the ‘upward’ speed of the train, is least effective for increasing energy recovery ratio. 6. The algorithms, developed in mathematical energy recovery analysis performed in the present work, may be used for optimizing the profile (track curves and gradients) of the newly laid tracks at the design stage. This can help to effectively use the potentialities of energy recovery technique in freight transportation by railway.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

472 Energy and Sustainability III 7. The costs of laying the railway tracks of the profile adapted to energy recovery conditions will be paid off by the amount of recovery energy stored during the long years of freight transportation along the tracks of optimal profile.

References [1] Bureika, G. A Mathematical Model of Train Continuous Motion Uphill. Transport, 23(2), pp. 35–137. 2008. [2] Grebeniuk, P. T., Dolganov, A. N., Skvorcova, A. I. Traction calculations. Manual. Moscow: Transport. 272 p. 1987. (In Russian language). [3] Klevzovich, S. Analysis of control systems for vehicle hybrid power trains. Transport 22(2), pp. 105–110. 2007. [4] Liudvinavičius L., Lingaitis L. P. New locomotive energy management systems.//Maintenance and reliability = Eksploatacja i niezawodność/Polish Academy of Sciences Branch in Lublin. Warszawa. ISSN 1507-2711. No 1 (45), pp. 35–41. 2010. [5] Liudvinavičius, L. Lingaitis, L. P. Electrodynamic braking in high-speed rail transport. Transport, 22 (3), pp. 178–186. 2007. [6] Vaičiūnas, G. Optimal using of traction rolling-stock in Lithuanian Railways. Doctoral dissertation. Vilnius. 76 p. 2001. (In Lithuanian language).

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Section 8 CO2 sequestration and storage

This page intentionally left blank

Energy and Sustainability III

475

CO2 transport modelling, conversion and storage C. Konrad1, J. Strittmatter1, D. Haumann2, G. Göttlicher2 & E. Osmancevic3 1

European Institute for Energy Research EIFER, Karlsruhe, Germany Energie Baden-Württemberg AG (EnBW), Karlsruhe, Germany 3 RBS wave GmbH, Stuttgart, Germany 2

Abstract In the context of the research project “Solar2Fuel” funded by the German Ministry of Education and Research (BMBF) (2009 – 2011) the aim is to examine the necessary steps for building up of a conversion technology of CO2 into a valuable product with the help of solar energy. In focus of this article is the photocatalytic conversion of carbon dioxide to methanol (CH3OH), the identification of large-scale solar regions in South Europe and North Africa and the CO2 transport via pipeline. The estimated scenarios are built on a calculated CO2 amount of 50 Mt/a which is the equivalent to ten modern coal fired power stations with an installed power of 800 MW each. Keywords: photocatalytic, CO2 transport, CO2 pipeline, CO2 conversion, solar areas.

1 Introduction Solar2Fuel is a joint project between EnBW Energie Baden-Württemberg AG, BASF SE, University of Heidelberg and Karlsruhe Institute of Technology (KIT). The project is coordinated by the association of German Engineers e.V. (VDI). The aim of the entire project is the development of a novel technology for the chemical conversion of CO2 into a useful product with help of sun energy. In focus is the methanol recovery as a fuel e.g. usage in combustion engines or fuel cells. Recycling of CO2 from stationary resources can serve as an important contribution for a sustainable energy economy as well as the prevention of climate change from CO2 emissions. WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESUS110401

476 Energy and Sustainability III The entire process chain starts right from the supply of liquefied CO2 from the power stations with CCS-technology (CCS = Carbon Capture and Storage) with the following steps: 1. 2. 3. 4.

Transport modelling from Germany to Northern Africa via CO2-pipeline Injection of CO2 into the reactor field and conversion to methanol with solar irradiation Storage of CO2 during the night and in sun free hours Back transport of the gained fuel This article mainly concentrates on points 1) and 2)

2 Photocatalytic conversion of carbon dioxide to methanol – viability check CO2 from stationary sources, which was separated from the flue gas, liquefied and transported in a pipeline to a region with high solar irradiation, shall be catalytically converted together with water to methanol by use of solar energy after eqn (1):

3 h* CO2  2 H 2 O  CH 3OH  O2 2

(1)

For this purpose a catalyst shall be developed that converts CO2 in aqueous solution into methanol via sunlight in a photocatalytic reactor. The reactor is fed with water and CO2 only. Methanol will accumulate as a low concentrated mixture with water. The reactor needs to collect solar energy over a huge surface area to supply enough energy for the CO2 conversion and is defined as “aperture area”. The set boundary conditions are to convert 50 Mt CO2/a. Moreover, the cost of the resource CO2 is estimated as well as the revenues from the sales of the product methanol. Since the reactor is still to be developed, the investment and operating costs are unknown: Therefore the analysis can only be realised by reverse the gap of knowledge in setting the certain basics for the CO2 conversion, i.e. price per tonne CO2, efficiencies of the conversion process, etc. The percentage of CO2, supplied to the reactor that is converted to methanol is described as “CO2 conversion efficiency”. In the economic calculations the assumption is made that 90% of the CO2 can be converted into methanol and called the conversion efficiency. Next to the CO2 conversion efficiency, the reactor has an efficiency in terms of percentage solar energy converted to chemical bound energy as methanol, defined as “reactor efficiency”. For example, an efficiency of 4% means, that a solar irradiation of 2000 kWh/m²/a gives rise to 80 kWh methanol in higher heating value (which is 6.3 kWh/kg). Thus 12.7 kg/m²/a or 127 t/ha*a methanol could theoretically be produced. WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

477

The monetary value of methanol will strongly influence the revenues and is assumed to a current price scenario of 250 €/t. This is equivalent to the free on board (FOB) price of methanol in the harbour of Rotterdam (RDAM) in the Netherlands during the past twelve month, published by INEOS Paraform [2]. In a high price scenario, 400 €/t of methanol is assumed. In the following section, the specific CO2 costs per ton methanol and in turn, the rest budget per ton methanol after deduction of CO2 cost are evaluated with a CO2 supply cost of 50 €/t CO2. Under stoichiometric conditions, 1.375 kg CO2 is consumed to yield 1.0 kg methanol (which relates to conversion of 100%). With 50 Mt CO2 of this corresponds to 32.7 Mt methanol. With decreasing CO2 conversion efficiency the supplied amount CO2 per ton methanol increases. In case of lower CO2 conversion efficiencies, specific CO2 cost per metric ton methanol is strongly increasing (Figure 1). With 90% CO2 conversion efficiency CO2 cost would be 76 €/t methanol; with 17% and 27% CO2 conversion efficiency, CO2 cost per ton methanol would be as high as the market value of methanol in the harbour in Rotterdam and in the high methanol price scenario, respectively. Since the reactor investment, the operating costs and the product purification are not considered, significantly higher CO2 conversion efficiency than the 17% and 27% threshold is crucial in an economic perspective. Figure 2 shows the remaining budget of the revenues per ton methanol after deduction of CO2 supply cost (50 €/t) depending on CO2 conversion efficiency. In the most optimistic considered case of 90% CO2 conversion efficiency, the remaining budget can reach up to 174 €/t methanol in the current and 324 €/t in the high methanol price scenario. high methanol price scenario

450 CO2 cost [€/t methanol]

rest budget per t methanol [€/t]_

500 400 350 methanol price QIV´10 Rotterdam

300 250 200 150 100 50 0 15%

350 300 250 200 150 100 50 0 15%

30%

45%

60%

75%

90%

30%

45%

60%

75%

90%

CO2 conversion efficiency [%]

CO2 conversion efficiency [%]

250 €/t methanol

CO2 cost/t MeOH methanol price [€/t] high methanol price scenario

Figure 1:

CO2 cost per metric ton methanol dependent on CO2 conversion efficiency in the photocatalytic reactor, CO2 supply cost set to 50 €/t.

Figure 2:

400 €/t methanol

Remaining budget of the revenues per ton methanol after deduction of CO2 supply cost for the current and high methanol price scenario.

In the following, the necessary reactor aperture area to convert 50 million tons CO2 per year is examined. The required area depends on the efficiency of the WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

478 Energy and Sustainability III

aperture area [km²]

photocatalytic reactor as well as the solar irradiation. Figure 3 pictures the aperture area for solar irradiation of 1000 kWh/m²/a, 1500 kWh/m²/a, 2000 kWh/m²/a as well as 2400 kWh/m²/a in case of 90% CO2 conversion efficiency for a range of 2%-20% reactor efficiency. 5000 4500 4000 3500 3000 2500 2000 1500 1000 500 0 2%

4%

6%

8% 10% 12% 14% 16% 18% 20% reactor efficiency [%]

Figure 3:

1000 kWh/m²/a

1500 kWh/m²/a

2000 kWh/m²/a

2400 kWh/m²/a

Aperture area to convert 50 million metric tons of CO2 per year depending on solar irradiation of 1000-2400 kWh/m²/a as well as the reactor efficiency varied from 2-20% and a CO2 conversion efficiency of 90%.

3 Transport of CO2 Most conducted CCS studies have been mainly focused on the capturing part of the CCS chain and little on the transportation links in the chain. A transportation infrastructure that carries CO2 the necessary quantities will require a large network of pipelines and possibly in combination with tankers. The CO2 emissions of German power plant facilities average at over 370 Mt per year. Beginning from 2012 the EnBW coal-fired power station in Karlsruhe (RDK 8) will account for an additional 5 Mt of CO2. With the background of the European CCS regulation a new infrastructure will be needed to enable transportation of big amounts of CO2 in future. In the following the pipeline transportation as being most viable is considered. The transportation costs vary between 1 and 3.5 million € per kilometre depending on factors, such as: • • • • • •

Construction planning Distance and topography Material costs and costs for protection against corrosion Energy costs Right-of-way costs Monitoring costs

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

Figure 4:

479

Options to transport 5 Mt CO2 per year.

The transportation capacities of pipelines with large inner diameter (> 1100 mm) reach far above 50 Mt CO2 per year. The CO2 transport is possible in pipelines under high pressure (8–20 MPa) usually in dense liquid phases. A high energy investment is attached for a successful gas conditioning before and during the transport. Table 1 shows alternative transport means, such as ship, trains and trucks – applicable for smaller amounts of CO2. Table 1:

Means of CO2-transport and capacity.

Infrastructure for CO2-transport Pipeline

Amount of CO2 to be transported As a function of the pipeline diameter > 20 Mt /a

marine tanker

up to max. 100000 t /cargo

train

1000 – 3000 t /cargo

Truck

20 t /cargo

Pressure and temperature conditions [3] Normal temperature < 31.4°C very high pressure 8 – 20 MPa Low temperature -55 to -50°C high pressure 0.6-0.7 MPa Low temperature -20°C high pressure 2 MPa Low temperature -20°C high pressure 2 MPa

3.1 Pipeline route The destination of the pipeline in the model is exemplarily the CCS area In-Salah in Algeria. In-Salah is used as target destination due to the high potential of available land for solar irradiation and the potential of CO2 storage in direct neighbourhood to existing gas fields. The selected routes are oriented along existing or planned pipelines of the European natural gas network. The analysed transport routes from Germany to In-Salah in Algeria range from 2700 to 3750 km. A theoretical CO2-Pipeline would cross the Mediterranean (Figures 5 and 6). WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

480 Energy and Sustainability III

Figure 5:

Figure 6:

Pipeline routes to cross the Mediterranean Sea.

Elevation profiles [5] for different offshore-routes to cross the Mediterranean Sea.

3.2 Simulation and calculation of CO2-pipelines The costs of a 3000 km CO2-Pipeline to transport large quantities of CO2 (50 Mt/a) over the Alps and the Mediterranean Sea is calculated using a program for stationary and dynamic calculation of utility networks STANET® [8]. Model input: • Length of the pipeline transportation routes and terrain profile • CO2-Capacity per year 50 Mt CO2 • Operating pressure minimum 8 MPa, maximum 20 MPa • Onshore: Costs for civil engineering • Offshore: costs for pipelay vessels per day: 250.000 €; 1 km of pipeline can be laid per day • Steel price, i.e. 600 €/t • Costs for corrosion protection, i.e. 100 €/m • Electricity rate, i.e. 0.05 €/kWh.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

481

Model output: • Pipeline diameter and wall thickness • Expected pressure loss and required number of pumping stations • Energy demand per tonne CO2 all along the pipeline distance • Estimation of construction and operating costs (pipeline and pumping stations) With the set boundaries the costs of the construction of 3000 km pipeline are estimated from 5.9 billion € for a diameter of 1100 mm to 7.5 billion € for a diameter of 1400 mm. Furthermore there are costs for planning, approval processes, monitoring systems, special constructions such as tunnels and culverts etc. The modelling of a mass flow of 50 Mt of CO2 per year and a pressure between 8 and 20 MPa shows that 3 to 8 compressor stations respectively for a diameter of 1400 mm and 1100 mm would be required to realise the entire route. The operating costs per year are estimated about 44 million € (Table 2) not considering the liquefaction of CO2 (large investment and operating costs necessary). Table 2:

Cost estimation of the pipeline modelling (capacity 50 Mt CO2/a, length 2965 km, diameter 1100 mm).

Pipeline construction

Investment costs (*) million €

Pipe laying Pipe manufacturing (2965 km) anti-corrosion layer section gate valve Compressor stations (#8) Control system Total

1738 4071 4 27 66 30 5936

Operating costs million € per year

0.60 43 0.40 44

(*) The investment costs in Table 2 for planning, approval processes, monitoring systems, special constructions such as tunnels and culverts are not included. With the total investment and operating costs of Table 2, the specific transportation costs for one ton CO2 is calculated with net present value method. The cost per ton CO2 does strongly depend on the load factor of the pipeline. The maximum annual capacity is 50 Mt. If parts of the CCS power plants do not run, the full pipeline capacity will not be utilized. Thus, the annual transported amount of CO2 can be lower than 50 Mt. This aspect is considered in calculating the specific transportation cost by varying the pipeline load factor between 70% and 100%. The depreciation period is set to 35 years which is the usual period taken for large investments (e.g. power stations). Three cases of interest rate are considered: 8%, 10% and 12%. Figure 7 shows, that the specific transportation cost from Karlsruhe to Algeria can be 10 to 14 €/t CO2 with high pipeline load factor and 8% to 12% interest rate, respectively. WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

482 Energy and Sustainability III

CO2 transportation cost [€/t]

20 19

12%

18 17

10% 8%

16 15 14 13 12 11 10 70%

75%

80%

85%

90%

95%

100%

pipeline load factor [%]

Figure 7:

Specific transportation cost per ton CO2 from Karlsruhe to In-Salah in Algeria depending on the pipeline load factor for different interest rates.

4 CO2 -storage in porous sedimentary strata Alternative to the CO2-conversion permanent storage of CO2 in porous sedimentary strata - as the last stage of the CCS chain - has been assessed due to the fact that the CO2 flow will be on 8760 h the year but the solar irradiation only be available over certain unpredictable hours over the day. The storage capacity is very uncertain to estimate and depends on porosity and permeability values as well as pressure and temperature conditions in the deep subsurface (between 800 and 2500 m [7]). Assuming a porosity of 10% one m3 of sedimentary rock is able to absorb a theoretical amount of 20-90 kg CO2. The major geological necessity is a thick impermeable layer in the roof. When selecting CO2 storages sites, ownership conflicts and competitive uses with deep geothermal energy, compressed natural gas storage and the use of groundwater should be avoided.

5 Identification of large-scale solar regions For the identification of large-scale solar regions in southern Europe and northern Africa it was calculated in Chapter 2 that at least 1300 km² of area is needed to place solar reactors with 8% reactor efficiency. The analyses of regions was concentrated in Europe beyond the border of 1500 kWh/a/m² and further increased on the African continent. Especially the collecting of the necessary homogenous land use data over the study area and the adjacent processing was very complex. These regions are potentially suitable for large area usage of solar energy facilities. In the context of the research project, these areas are analysed for the potential building of photo-chemical reactors used possibly for the conversion of CO2. The necessary systems are not available yet (Chapter 2). The identification of potential areas works in an iterative mode and is performed in a Geographical Information System (GIS) environment. WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

483

Figure 8:

Identification of large-scale solar regions in Spain and Portugal by summation of restriction areas (inland waters, urban areas, forests, protected areas, agricultural areas, mountainous area).

Figure 9:

Identification of large-scale solar regions in North Africa by summation of restriction areas (inland waters, urban areas, forests, protected areas, agricultural areas, mountainous area, salt marshes and sand dunes).

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

484 Energy and Sustainability III The following inputs/exclusions are set: Yearly mean of solar irradiation [6], urban areas [1, 9], inland waters [1, 9], forests [1, 9], agricultural areas [1, 9], protected areas [4, 10], mountain slope [5]. Figure 8 shows the GIS results and the limitations of large associated areas in the example study of Spain with a maximum of 500 km2. However when focussing on North-Africa continent, Figure 9 shows that large and homogenous areas are available with a potential of high solar irradiation. The remaining dark areas in Figures 8 and are the ones which are potentially available for solar usage.

6 Conclusion In this paper, it was examined the investment and operating costs for a 50 Mt annual capacity CO2 pipeline from Karlsruhe, Germany, to In-Salah, Algeria. It was calculated, that the construction costs of the pipeline are around 5.9 billion € and the specific transportation cost inclusive the operating costs can be within a cost range of 10 to 14 € per ton if the pipeline operates at full capacity. Taken the cost of 30-40 €/t for CO2 capturing and liquefaction at the power plant into account [7], CO2 from Germany can be supplied in Algeria for roughly 50 €/t. The costs and the dimensioning of the calculated pipeline routes for the CO2 transport are already well estimated. However not examined yet are the social acceptances of such a trans-national project. Further and detailed work will be started in 2011 with a pipeline planning study in Germany from the capture site to the potential geological storage site. The limitations from the planning to the construction and realization will be examined in detail. Together with the remaining budget per ton methanol from Figure 2, the allowed investment for the reactor field inclusive the operating costs is estimated with the net present value method. The value creation of the solar driven CO2 conversion of methanol was evaluated, using today’s market price of methanol in the harbour of Rotterdam. The budget to finance the infrastructure and operating costs for 50 Mt CO2 conversion over a 35 year time period was calculated with 10% interest rate. The produced amount of methanol is again a function of the pipeline load factor. With a lower load factor, less methanol can be produced. Figure 10 shows the resulting cash value is 40 to 55 billion € in case of the current methanol price scenario (remaining budget after deduction of CO2 cost 174 €/t). In the high price scenario (400 €/t methanol, 324 € remaining budget) the cash value is between 70 and 100 billion €. This amount is the maximum allowed invest into the reactor field inclusive the operating costs during the 35 years depreciation time (Figure 10). The necessary surface area for the solar CO2 conversion was estimated. In case of high annual solar irradiation of 2000 kWh/m²/a, about 1300 km² are required to convert 50 Mt CO2 per year in case of a reactor efficiency of 8%. In Spain such extensive and connected large areas could not be identified. However the analysis of Algeria shows that there are potential large, flat and sparsely populated areas with a high and continuous solar irradiation up to 2400 kWh/a/m². WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

Figure 10:

485

Cash value of the photocatalytic reactor field depending on the pipeline load factor, 35 years depreciation period and 10% interest rate.

The promising CO2 conversion – theoretically described in Chapter 2 – will need to be further developed on the laboratory scale and upscaled in a prototype application, in order to learn more about efficiency, dimensions and prices. This new technology will need to prove its viability in comparison to the underground CO2 storage in depleted oil/gas fields or in porous geological formations.

References [1] CORINE Land Cover European Environment Agency http://www.eea.europa.eu/ [2] INEOS Paraform http://www.ineosparaform.com/55-Methanol_price.htm [3] IPCC, Carbon Dioxide Capture and Storage Summary. A Special Report of Working Group III of the Intergovernmental Panel on Climate Change (B. Metz, O. Davidson, H. de Coninck, M. Loos, L. Meyer), 2005. [4] NATURA 2000 EUNIS database http://www.eea.europa.eu/data-andmaps/data/natura-2000-eunis-database [5] NOAA: National Geophysical Data Center, ETOPO2v2 Global Gridded 2-minute Database http://www.ngdc.noaa.gov/mgg/global/etopo2.html [6] PVGIS Photovoltaic Geographical Information System (PVGIS). European Commission Joint Research Centre http://re.jrc.ec.europa.eu/pvgis/index.htm [7] Wuppertal Institut für Klima, Umwelt, Energie GmbH, RECCS Strukturellökonomisch-ökologischer Vergleich regenerativer Energietechnologien (RE) mit Carbon Capture and Storage (CCS), 2007 [8] STANET®: Network Analysis http://www.stafu.de/en [9] VMAP1 National Geospatial-Intelligence Agency NGA http://www.mapability.com [10] WDPA World Database on Protected Areas http://www.wdpa.org WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

This page intentionally left blank

Energy and Sustainability III

487

Influence of heat treatment on the corrosion behavior of steels exposed to CCS environment A. Pfennig1, P. Wojtas1, I. Spengler1, B. Linke1 & A. Kranzmann2 1 2

HTW University of Applied Sciences, Germany BAM Federal Institute of Materials Research and Testing, Germany

Abstract The influence of heat treatment on pit corrosion needs to be considered to guarantee reliability and safety during the injection of compressed emission gasses – mainly containing CO2 – into deep geological layers (CCS-technology, Carbon Capture and Storage). In laboratory experiments different heat treated steels used as injection pipe with 13% Chromium and 0.46% Carbon (X46Cr13, 1.4034) as well as 0.2% Carbon (X20Cr13, 1.4021) were tested. Also X5CrNiCuNb16-4 (1.4542) was investigated as typical steel used for geothermal pumps. Keeping stable environmental conditions in laboratory experiments the samples were exposed to the distinct synthetic aquifer environment saturated with technical CO2 at a flow rate of 3 l/h for up to 6 months. Independent of the exposure time the least amount of pits is found on hardened steels with martensitic microstructure where X5CrNiCuNb16-4 shows fewer pits than X46Cr13 and X20Cr13. Regarding steels with similar Cr-content the higher Ccontent in 1.4034 results in fewer pits compared to 1.4021. Keywords: steel, heat treatment, pit corrosion, CCS, CO2-injection, CO2-storage.

1 Introduction Engineering a geological on-shore aquifer CCS-site (CCS Carbon Capture and Storage [1–3]) corrosion of the casing and injection pipe steels may become an issue when emission gasses, e.g. from combustion processes of power plants, are compressed into deep geological layers [4–8]. From thermal energy production it is known, that the CO2-corrosion is sensitively dependent on alloy composition, contamination of alloy and media, environmental conditions like temperature,

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESUS110411

488 Energy and Sustainability III

Figure 1:

Possible formation mechanism of pits on the pipe steel X46Cr13 related to the galvanic model described by Han et al. [21] and adjusted by Pfennig and Kranzmann [19].

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

489

CO2 partial pressure, flow conditions and protective corrosion scales [6-16]. Considering different environments, aquifer waters and pressures, the analyzed temperature regime between 40 °C to 60 °C is a critical temperature region well known for corrosion processes as shown by Pfennig and Bäßler [17] and Pfennig and Kranzmann [18, 19]. Here a maximum around 4.7 mm/year was found for the pit intrusion depth of 13% Cr steel X46Cr13. Still this may be predicted by the rather conservative Norsok-Model used in the oil and gas industry to calculate surface corrosion rates of carbon steels [20]. Steels exposed to CO2-environment generally precipitate slow growing surface layers mainly comprised of FeCO3 (siderite) [4, 8, 21]. This phase is also found in pits of locally corroded samples [17, 19]. After the CO2 is dissolved to build a corrosive environment the solubility of FeCO3 in water is low (pKsp = 10.54 at 25 °C). As a result of the anodic iron dissolution a siderite corrosion layer grows on the alloy surface. These reactions have been described in detail by various authors [7, 17] and a precipitation model has been introduced by Han et al. [21], which was adjusted by Pfennig and Kranzmann [19] (figure 1): In the initial stage the steel is exposed to the corrosive environment, the CO2-saturated brine (a), where the carbon dioxide forms carbonic acid in contact with the aquifer water (b). A ferrous hydroxide passivating film can form when its solubility limit is exceeded (c). A first reaction step may be attributed to the formation of Fe[II] compounds Fe(OH)2 [7, 25], which leads to an increase of the local pH near the hydroxide film. Consequently a ferrous carbonate film may be formed (d). Then the growth of the corrosion layer will proceed internally and externally depending on the various carbon and oxygen partial pressures (e). Localized corrosion may then start when the ferrous hydroxide film is locally damaged due to mechanical or chemical effects. The highly porous nonprotective ferrous carbonate is then exposed to the brine environment where the pH is lower. As a result the ferrous carbonate film dissolves and the steel is locally depassivated (f). This is accompanied by corrosion and passive film dissolution in lateral direction (g, h) followed by the detachment of the carbonate film (i). The removal of the detached film causes the pit to grow wider, because the same steps will occur from the beginning on the newly exposed surface. This work was carried out to get a better understanding of the influence of the steel heat treatment on the pit corrosion behaviour. Especially the varying microstructures of steels used for CO2-injections into aquifer water reservoirs are of interest to predict their reliability in on-shore CCS sites.

2 Materials and methods Laboratory experiments were carried out to determine the dependence of heat treatment on pit corrosion behaviour. Different steels used as injection pipe with 13% Chromium and 0.46% C (X46Cr13, 1.4034) as well as 0.2% Carbon (X20Cr13, 1.4021) were tested. Also X5CrNiCuNb16-4 (1.4542) was investigated as typical steel used for geothermal pumps. The steels were heat treated differently following protocols usual in the field of metallurgy (table 1).

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

490 Energy and Sustainability III Table 1:

Heat treatment of samples used in exposure experiments.

Exposure tests in CO2-saturated aquifer brine were carried out using samples of the alloys above with 8 mm thickness and 20 mm width and 50 mm length. A hole of 3.9 mm diameter was used for sample positioning. The surfaces were activated by grinding with SiC-Paper down to 120 µm under water and dipping into acetone for ca. 5 sec.. Samples of each base metal were positioned within the liquid phase [17-19]. The brine (as known to be similar to the Stuttgart Aquifer [23]: Ca2+: 1760 mg/L, K2+: 430 mg/L, Mg2+: 1270 mg/L, Na2+: 90.100 mg/L, Cl-: 143.300 mg/L, SO42-: 3600 mg/L, HCO3-: 40 mg/L) was synthesized in a strictly orderly way to avoid precipitation of salts and carbonates. Flow control (3 NL/h) of the technical CO2 into the brine was done by a capillary meter GDX600_man by QCAL Messtechnik GmbH, Munich. The pH after the experiments was between 5.2 and 5.6. The exposure of the samples between 24 h and 1500 h into corrosive CCS environment was disposed in a climate chamber according to the conditions at the geological site at Ketzin/Germany at 60 °C at ambient pressure – each material in a separated reaction vessel (figure 2). X-ray diffraction was carried out in a URD-6 (Seifert-FPM) with CoK-radiation with an automatic slit adjustment, step 0.03 and count 5 sec. Phase analysis was performed by matching peak positions automatically with PDF-2 (2005) powder patterns. Mainly structures that were likely to precipitate from the steels were chosen of the ICSD and refined to fit the raw-data-files using POWDERCELL 2.4 [22] and AUTOQUAN ® by Seifert FPM. WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

Figure 2:

491

Experimental set up of laboratory corrosion experiment.

Sample surfaces were analyzed with a light optical microscope Axiophot 2 by Zeiss. Here the kinetics was obtained by counting the pits per frame (6 frames per sample, 2 samples per parameter) and giving the average pit number. Pit widths were measured light optically and pit depths were obtained from 3-Dimages. These 3-D-images were realized by the double optical system Microprof TTV by FRT. Mass gain was analyzed according to DIN 50 905 part 1-4. After the surface analysis the samples were embedded in a cold resin (Epoxicure, Buehler), cut and wet polished first with SiC-Paper from 180 µm to 1200 µm. The finishing was done with diamond paste 6 µm and 1 µm. Different light optical and electron microscopy techniques were used to investigate the layer structures and morphology of the samples.

3 Results and discussion 3.1 Kinetics To evaluate the influence of the heat treatment the samples were examined via light optical methods to predict the amount of counted pits and the pit depths. Kinetics was obtained via weight loss according to DIN 50 905 (figure 3) after exposure to the CO2-saturated aquifer water. With corrosion rates obtained via mass gain method about 0.002 mm/year the normalized samples show the lowest loss of base material. Samples that were hardened or hardened and tempered corrode around 0.005 mm/year determined after 1400 hours of exposure time. Therefore hardening and tempering does not influence the corrosion rate significantly.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

492 Energy and Sustainability III 0,020 0,015

normalizing

0,010 0,005 0,000 0,020 0,015

x20Cr13 hardening

x46Cr13

x5CrNiCuNb16-4

x20Cr13 x46Cr13 hardening+tempering1

x5CrNiCuNb16-4

x20Cr13 x46Cr13 hardening+tempering2

x5CrNiCuNb16-4

x20Cr13 x46Cr13 hardening+tempering3

x5CrNiCuNb16-4

corosion rate in mm/year

0,010 0,005 0,000 0,020 0,015 0,010 0,005 0,000 0,020 0,015 0,010 0,005 0,000 0,020 0,015 0,010 0,005 0,000

x20Cr13

Figure 3:

x46Cr13

x5CrNiCuNb16-4

Corrosion rate after 1350 hours of exposure to aquifer brine water at 60 °C and ambient pressure of X20Cr13, X46Cr13 and X5CrNiCuNb16-4 differently heat treated prior to exposure.

3.1.1 Depth of pits Pitting (local corrosion) and shallow pit corrosion are observed on all specimens (figure 4). Optical 3-D-images of a characteristic sample part after descaling are shown in Figure 5 with a typical penetration depth of approximately 18 µm into X5CrNiCuNb16-4.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

493

Surfaces with pits of X46Cr13 (left) and X5CrNiCuNb16-4 (right).

Figure 5:

Optical 3D-Surface-Scan (Fa. FRT) of the sample X5CrNiCuNb164 kept in the CO2-saturated brine for 14000 h.

maximum penetration depth in µm

Figure 4:

40 normalizing

35

hardening

30

hardening+ tempering1

25

hardening+ tempering2 hardening+ tempering3

20 15 10 5 0 X20Cr13

Figure 6:

X46Cr13

X5CrNiCuNb16-4

Maximum penetration depth of pits formed on alloys X20Cr13, X46Cr13 and X5CrNiCuNb16-4 after exposure to the CO2saturated brine for 1400 hours.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

494 Energy and Sustainability III The local corrosion shows a maximum intrusion depth about 35 µm for X20Cr13 and X5CrNiCuNb16-4 after 1400 hours of exposure. Figure 6 compares all measured intrusions depths as a function of heat treatment for the different steels. Overall figure 6 reveals that pit depths measured on X46Cr13 do not penetrate as deep as pits measured on the other steel samples. Still, the heat treatment has little to no influence on the maximum penetration depth. For the 13Cr steels (X20Cr13 and X46Cr13) normalizing and hardening+tempering1 show less intrusion (8-12 µm) than the other heat treatments, while hardening+tempering 2 and 3 seem to be best for X5CrNiCuNb16-4 (10 µm). 3.1.2 Amount of counted pits The influence of heat treatment may be also determined by the amount of counted pits (figure 7). The lower amount of pits on X46Cr13 hardened+tempered3 and X5CrNiCuNb16-4 hardened+tempered1 after 800 h of exposure is due to surface corrosion phenomena, that is that pits consolidate to shallow pit corrosion and are not longer counted as single pits. These surface corrosion products prevent the access of corrosive media to the bulk material. Figure 7 reveals that the heat treatment has no significant influence on the amount of counted pits per unit area, because there is little to no lowest amount of counted pits for one distinct heat treatment. For X20Cr13 and X46Cr13 normalized samples show the lowest amount of pits while X5CrNiCuNb16-4 has the most pits per m2. The most pits on X20Cr13 and X46Cr13 were counted on samples hardened+tempered 2. Pit growth cannot be calculated as easily as surface corrosion rates, because of its little predictability. Therefore it is not possible to give corrosion rates and lifetime predictions regarding pit corrosion in CCS technology. Summarizing the kinetic results the heat treatment preferred to obtain the least corrosive attack is normalizing for X20Cr13 and X46Cr13. For X5CrNiCuNb16-4 the combination hardening+tempering 3 should be preferred. Detailed analysis of the different microstructures and different sucseptabilites towards corrosion under CCS environment will be subject to future research. 3.2 Morphology The complicated multi-layered carbonate/oxide structure is described in detail by Pfennig and Bäßler [17]. It reveals siderite FeCO3, goethite -FeOOH, mackinawite FeS and akaganeite Fe8O8(OH)8Cl1.34 as well as spinel-phases of various compositions. Carbides, such as Fe3C, were identified within the corrosion layer, similar to the high-temperature corrosion phenomena [24]. The pits are covered with the same precipitates of the corrosion products formed on the surface elsewhere (figure 8).

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

495

20.000

X20Cr13

17.500

pits per m²

15.000 12.500 10.000 7.500 5.000

amount of counted pits per m²

2.500 0 20.000200 17.500 15.000 12.500 10.000

400

800

1.000

normalizing exposure time hardening hardening+tempering1 hardening+tempering2 hardening+tempering3

in h

1.200

1.400

X46Cr13

7.500 5.000 2.500 0 20.000200

400

600

800

1.000

1.200

1.400

exposure time in h X5CrNiCuNb16-4

17.500 15.000

pits per m²

600

12.500 10.000 7.500 5.000 2.500 0 200

400

600

800

1.000

1.200

1.400

exposure time in h Figure 7:

Amount of counted pits of X20Cr13, X46Cr13 and X5CrNiCuNb16-4 exposed to the brine saturated with CO2 at 60ºC and ambient pressure.

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

496 Energy and Sustainability III

Figure 8:

SEM surface images of precipitations on pits of the soft annealed 13% Cr steel X46Cr13 after 17520 h.

4 Conclusion During the normal storage procedure the CO2 is supposedly injected in the liquid or supercritical phase. Therefore there is no such pit corrosion expected as from the CO2-saturated brine stated in this paper. However, when there are intermissions of the injection the water level may rise into the injection pipe. This will then lead to the precipitation of corrosion products and formation of pits. Main phase of the continuous scale forming on all three different steels are FeCO3 siderite and goethite -FeOOH in 3 steels. The heat treatment preferred to obtain minimal local corrosive attack for X20Cr13 and X46Cr13 is normalizing while for X5CrNiCuNb16-4 the combination hardening+tempering3 should be considered. For heat treatments regarding hardening and tempering a significant good corrosion resistance cannot be given. Therfore long term exposure experiments and detailed microstructure analysis will be necessary.

Acknowledgements This work was supported by the FNK (Fachkonferenz für wissenschaftlichliche Nachwuchskräfte) of the Applied University of Berlin, HTW and by IMPACT (EU-Project EFRE 20072013 2/21). The authors would like to thank M. Blötz, M. Engelke and S. Baack of the HTW for the helpful contribution.

References [1] D.C. Thomas, Carbon Dioxide Capture for Storage in Deep Geologic Formations – Results from CO2 Capture Project, Volume 1: Capture and Separation of Carbon Dioxide form Combustion Sources, CO2 Capture Project, Elsevier Ltd UK 2005, ISBN 0080445748 [2] M. van den Broek, R. Hoefnagels, E. Rubin, W. Turkenburg, A. Faaij, Effects of technological learning on future cost and performance of power

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

[3] [4] [5]

[6]

[7]

[8]

[9]

[10] [11]

[12]

[13]

[14]

[15]

[16]

497

plants with CO2 capture, Progress in Energy and Combustion Science, Paper in Progress (2009) 1-24 GeoForschungszentrum Potsdam, CO2-SINK – drilling project, description of the project PART 1 (2006) 1-39 S. Nešić, “Key issues related to modelling of internal corrosion of oil and gas pipelines – A review”, Corrosion Science 49 (2007) 4308–4338 S. Hurter, Impact of Mutual Solubility of H2O and CO2 on Injection Operations for Geological Storage of CO2, International Conference of the Properties of Water and Steem ICPWS, Berlin, September 8-11 L. Zhang, J. Yang, J.S. Sun, M. Lu, Effect of pressure on wet H2S/CO2 corrosion of pipeline steel, No. 09565, NACE Corrosion 2008 Conference and Expo, New Orleans, Louisiana, USA, March 16th – 20th, 2008 L.J. Mu, W.Z. Zhao, Investigation on Carbon Dioxide Corrosion Behaviors of 13Cr Stainless Steel in Simulated Strum Water, Corrosion Science, Manuscript No. CORSCI-D-09-00353 (2009) 1-24 M. Bonis, Weight loss corrosion with H2S: From facts to leading parameters and mechanisms, Paper No. 09564, NACE Corrosion 2008 Conference and Expo, New Orleans, Louisiana, USA, March 16th – 20th, 2008 J. Enerhaug, A study of localized corrosion in super martensitic stainless steel weldments, a thesis submitted to the Norwegian University of Science and Technology (NTNU), Trondheim 2002 V. Neubert, Beanspruchung der Förderrohrtour durch korrosive Gase, VDIBerichte Nr. 2026, 2008 R. Kirchheiner, P. Wölpert, Qualifizierung metallischer Hochleistungswerkstoffe für die Energieumwandlung in geothermischen Prozessen, VDIBerichte Nr. 2026, 2008 H. Zhang, Y.L Zhao, Z.D. Jiang, Effects of temperature on the corrosion behaviour of 13Cr martensitic stainless steel during exposure to CO2 and Cl- environment, Material Letters 59 (2005) 3370-3374 J.N. Alhajji and M.R. Reda, The effect of alloying elements on the electrochemical corrosion of low residual carbon steels instagnant CO2saturated brine, Corrosion Science, Vol. 34, No. 11 (1993) 1899-1911 Y.-S. Choi and S. Nešić, Corrosion behaviour of carbon steel in supercritical CO2-water environments, No. 09256, NACE Corrosion 2008 Conference and Expo, New Orleans, Louisiana, USA, March 16th – 20th, 2008 X. Jiang, S. Nešić, F. Huet, The Effect of Electrode Size on Electrochemical Noise Measurements and the Role of Chloride on Localized CO2 Corrosion of Mild Steel, Paper No. 09575, NACE Corrosion 2008 Conference and Expo, New Orleans, Louisiana, USA, March 16th – 20th, 2008 Z. Ahmad, I.M. Allam, B.J. Abdul Aleem, Effect of environmental factors on the atmospheric corrosion of mild steel in aggressive sea coastal environment, Anti Corrosion Methods and Materials, 47 (2000) 215-225

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

498 Energy and Sustainability III [17] A. Pfennig, R. Bäßler, “Effect of CO2 on the stability of steels with 1% and 13% Cr in saline water” Corrosion Science, Vol. 51, Issue 4 (2009) 931940, [18] A. Pfennig, A. Kranzmann, “Influence of CO2 on the corrosion behaviour of 13Cr martensitic stainless steel AISI 420 and low-alloyed steel AISI 4140 exposed to saline aquifer water environment”, Air Pollution XVII , Volume 123 (2009) 409-418, ISBN: 978-1-84564-195-5, ISSN: 1746-448X [19] A. Pfennig, A. Kranzmann, The role of pit corrosion in engineering the carbon storage site Ketzin, Germany, WIT Transactions on Ecology and the Environment, Volume 126, (2010) 109-118, ISBN: 978-1-84564-450-5 [20] http://www.standard.no/pronorm-3/data/f/0/01/36/9_10704_0/M506d1r2.pdf, “CO2 corrosion rate calculation model” [21] J. Han, Y. Yang, S. Nešić, B. N. Brown, Roles of passivation and galvanic effects in localized CO2 corrosion of mild steel, Paper No. 08332, NACE Corrosion 2008, New Orleans, Louisiana, USA, March 16th – 20th, 2008 [22] SW. Kraus and G. Nolze, POWDER CELL – a program for the representation and manipulation of crystal structures and calculation of the resulting X-ray powder patterns, J. Appl. Cryst. (1996), 29, 301-303 [23] A. Förster, B. Norden, K. Zinck-Jørgensen, P. Frykman, J. Kulenkampff, E. Spangenberg, J. Erzinger, M. Zimmer, J. Kopp, G. Borm, C. Juhlin, C. Cosma, S. Hurter, 2006, Baseline characterization of the CO2SINK geological storage site at Ketzin, Germany: Environmental Geosciences, V. 13, No. 3 (September 2006), pp. 145-161. [24] A. Kranzmann, D. Huenert, H. Rooch, I. Urban, W. Schulz, W. Österle, Reactions at the interface between steel and oxide scale in wet CO2 containing atmospheres, NACE Corrosion Conference & Expo, Atlanta, 2009

WIT Transactions on Ecology and the Environment, Vol 143, © 2011 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)

Energy and Sustainability III

499

Author Index Abatzoglou N. .......................... 145 Abdul Halim A. R. ................... 399 Aboumahboub T. ..................... 339 Ajanovic A. ................................ 97 Ajel S. ...................................... 173 Aldeib M. ................................. 353 Al-Waked R. ............................ 437 Alzoubi M. F............................ 437 Amigun B. ................................. 13 Apaer P. ................................... 327 Azoumah Y. ............................... 37 Baier J. ....................................... 73 Bardhan S. ............................... 411 Barsun H. ..................................... 3 Berberi V. .................................. 87 Boeri A. ................................... 425 Bolduan R. ............................... 291 Braidy N. ................................. 145 Brent A. C. ................................. 13 Brulé M. ................................... 291 Bureika G. ................................ 461 Burnett R...................................... 3 Busch S. ................................... 241 Chatzinaki M. .......................... 203 Chen Q. .................................... 327 Chornet E. ................................ 123 Chornet M. ................................. 87 Claupein W. ............................. 291 de Vial M. J. .............................. 25 Demirer G. N. .......................... 133 Dunn L. .................................... 217 Dyer D. F. ................................ 195 Ehrlich Ü.................................. 229 Elalem A. ................................. 353 Elgezawi S. .............................. 353 Fauteux-Lefebvre C. ............... 145 Fujimori S. ............................... 315

García Tremps A. .................... 449 Garcia-Alonso F. ....................... 51 Genon G................................... 279 Gizari N. .................................. 203 Göttlicher G. .................... 291, 475 Graeff-Hönninger S. ................ 291 Grignaffini S. ............................. 61 Haas R. .............................. 97, 241 Hamacher T. ............................ 339 Harischian M. .......................... 173 Haumann D. ............................. 475 Held A. .................................... 241 Ho S.-Y. ................................... 265 Izirwan I................................... 399 Jaballa T. M. ............................ 369 Jwa E. ...................................... 361 Kashiwagi N. ........................... 327 Kleesmaa J. .............................. 229 Konrad C. ........................ 291, 475 Körner I. .................................. 383 Kranzmann A........................... 487 Labor B. ................................... 303 Lantagne G. ............................... 87 Lavoie J.-M................ 87, 109, 123 Lee S. B. .................................. 361 Lindskog S. .............................. 303 Linke B. ................................... 487 Longo D. .................................. 425 Love J. ..................................... 217 Lynch D. .................................. 123 Maezono T. .............................. 327 Mambretti S. ............................ 185 Mammoli A. ................................ 3 Marie-Rose S. C. ..................... 123 Mast B. .................................... 291 Masui T.................................... 315

500 Energy and Sustainability III Matsuoka Y.............................. 253 Mohd Zulkifli M. N. ................ 399 Mok Y. S.................................. 361 Mokheseng M. B. ...................... 13 Monkhouse E. P. ........................ 25 Mora D..................................... 449 Musango J. K. ............................ 13 Namazu M. .............................. 253 Nhamo G.................................. 265 Niida D. ................................... 327 Nobakht M. B. ......................... 173 Noor Shahirah S. ...................... 399 O’Mary C. ................................ 195 Oldenburg S. ............................ 383 Osdoba T.................................. 217 Osmancevic E. ......................... 475 Pädam S. .................................. 229 Panepinto D. ............................ 279 Pfennig A. ................................ 487 Pilon G. .................................... 109 Polák M...................................... 73 Principia D. ................................ 61 Py X. .......................................... 37 Ragwitz M. .............................. 241 Resch G.................................... 241 Reyes A...................................... 51 Reyes J. A. ................................. 51 Romagna M. .............................. 61

Schaber K. ............................... 339 Seyedali Ruteh S. S. ................ 159 Šindelář M. ................................ 73 Siti Zubaidah S. ....................... 399 Sjöblom R. ............................... 303 Skok J. ..................................... 291 Soukissian T. ........................... 203 Spengler I................................. 487 Strittmatter J. ................... 291, 475 Tanbour E. Y. .......................... 437 Tazvinga H. .............................. 13 Tran T. T. ................................. 253 Turcotte F. ................................. 87 Uhlík J. ...................................... 73 Vaičiūnas G. ............................ 461 Van Hemert H.......................... 217 Villacampa Y. ............................ 51 Vorobieff P. ................................. 3 Wagner U................................. 339 Wang Q.................................... 327 Wang Y.................................... 327 Westphal L............................... 383 Wojtas P................................... 487 Yamegueu D. ............................. 37 Yılmaz Y. ................................ 133

This page intentionally left blank

...for scientists by scientists

Wind Power Generation and Wind Turbine Design Edited by: W. TONG, Kollmorgen Corporation, USA

Provides the wind power industry and the energy research community with comprehensive up-to-date information on advanced design techniques and practical approaches for a form of energy that is becoming increasingly important. It addresses all the major concerns in wind power generation and wind turbine design and includes some of the more recent developments in the field. The book is a useful and timely contribution to the technical literature on wind power. Along with the rising energy demand in the 21st century and the growing recognition of global warming and environmental pollution, energy supply has become an integral and cross cutting element of every country’s economy. In recent years, more and more countries have prioritized sustainable, renewable, and clean energy sources such as wind, solar, hydropower, biomass, etc., as the replacements for fossil fuels. Wind power is the fastest growing alternative energy segment, providing an attractive cost structure relative to other alternative energy. Wind energy has played a significant role in North American and European countries, and some developing countries such as China and India. In 2008, over 27 GW of new wind capacity were installed throughout the world. There is no doubt that wind power will play a major role as the world moves towards a sustainable energy future. ISBN: 978-1-84564-205-1 e-ISBN: 978-1-84564-388-1 Published 2010 / 768pp / £298.00

WIT Press is a major publisher of engineering research. The company prides itself on producing books by leading researchers and scientists at the cutting edge of their specialities, thus enabling readers to remain at the forefront of scientific developments. Our list presently includes monographs, edited volumes, books on disk, and software in areas such as: Acoustics, Advanced Computing, Architecture and Structures, Biomedicine, Boundary Elements, Earthquake Engineering, Environmental Engineering, Fluid Mechanics, Fracture Mechanics, Heat Transfer, Marine and Offshore Engineering and Transport Engineering.

...for scientists by scientists

Food and Environment The Quest for a Sustainable Future Edited by: V. POPOV and C.A. BREBBIA, Wessex Institute of Technology, UK

The many advances in food production over the past century have made it possible to feed the whole of humanity. But food production and processing can have detrimental effects on the environment. Major challenges remain with industrial-scale farming. Higher productivity and larger volumes should not come at the expense of product quality or animal suffering. Despite their importance, the consequences of food-related problems have not been sufficiently considered. It is essential to understand the impact that food production processes and the demands of rising living standards can have on the food consumed daily by the world’s people. Of particular importance are the effects on human health and the well-being of the population, as well as the more general issues related to possible damage to the environment and ecology. This book includes contributions presented at the first international conference convened to examine these challenges. Topics include; Food Processing Issues; Contamination of Food; Pharmaceuticals in Food; Obesity-Related Issues; Pesticides and Nutrients; Hormonal Effects; Food and Fecundity; Genetic Engineering; Freezing and Thawing; Heavy Metals; Pathogens; Salination Problems; Desertification; Transportation Problems; Traceability; Threshold Values; Modern Farming; Changing Climate; Laws and Regulations; Epidemiological Studies; Water Resources Problems; and Animal Welfare. The book will be of interest to food scientists and nutritionists, as well as agricultural, ecological, and environmental health experts interested in all these challenges. WIT Transactions on Ecology and the Environment, Vol 152 ISBN: 978-1-84564-554-0 eISBN: 978-1-84564-555-7 Forthcoming 2011 / apx 300pp / apx £114.00

...for scientists by scientists

Sustainable Chemistry Edited by: G. RENIERS, University of Antwerp, Belgium and C.A. BREBBIA, Wessex Institute of Technology, UK

As the demands of society increase in their quest for safer, better and more convenient products, the chemical industry is faced on the one hand with the possible depletion of natural resources and on the other with a large share of responsibility for the damage that may be caused to the environment and the population by their products. The main area of chemical activity consists of the conversion of various base metals into substances and materials with new chemical and physical properties. A substantial amount of research is being carried out regarding this conversion process, which now must incorporate sustainability requirements. In addition, other associated activities, such as the chemical supply chain, performance measurements and different types of management tasks, must meet sustainability standards. Achieving sustainable chemistry based on clean processing routes, efficient use of resources, renewable materials, adequate management systems and other activities is not only essential for the future of a competitive chemical industry but also for a sustainable and healthy society and environment. Key to sustainable chemistry are innovative and cleaner technologies and the development of appropriate business models, performance measurements, and better integrated management. This book contains papers on the latest academic and industrial research in the field presented at the first international conference convened on the sustainable chemistry. WIT Transactions on Ecology and the Environment, Vol 154 ISBN: 978-1-84564-558-8 eISBN: 978-1-84564-559-5 Forthcoming 2011 / apx 250pp / apx £95.00

...for scientists by scientists

Sustainable Development and Planning V Edited by: C.A. BREBBIA, Wessex Institute of Technology, UK

This book contains the proceedings of the latest in a series of biennial conferences on the topic of sustainable regional development that began in 2003. Organised by the Wessex Institute of Technology, the conference series provides a common forum for all scientists specialising in the range of subjects included within sustainable development and planning. It has become apparent that planners, environmentalists, architects, engineers, policy makers, and economists have to work together in order to ensure that planning and development can meet our present needs without compromising future generations. The topics covered by the papers included in the book include: City planning; Regional planning; Social and political issues; Sustainability in the built environment; Rural developments; Cultural heritage; Transportation; Ecosystems analysis, protection and remediation; Environmental management; Environmental impact assessment; Indicators of sustainability; Sustainable solutions in developing countries; Sustainable tourism; Waste management; Flood risk management; Resources management; and Industrial developments. WIT Transactions on Ecology and the Environment, Vol 150 ISBN: 978-1-84564-544-1 eISBN: 978-1-84564-548-5 Forthcoming 2011 / apx 900pp / apx £342.00

WITPress Ashurst Lodge, Ashurst, Southampton, SO40 7AA, UK. Tel: 44 (0) 238 029 3223 Fax: 44 (0) 238 029 2853 E-Mail: [email protected]