Energy and Sustainability II
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SECOND INTERNATIONAL CONFERENCE ON ENERGY AND SUSTAINABILITY
ENERGY 2009 CONFERENCE CHAIRMEN C.A. Brebbia Wessex Institute of Technology, UK A.A. Mammoli University of New Mexico, USA
INTERNATIONAL SCIENTIFIC ADVISORY COMMITTEE N. Abatzoglou S. Basbas B. Bieda M. Ektesabi M. El-Genk M.A. Haggag G. Passerini F. Patania F.M. Pulselli E. Tiezzi A. van Timmeren T. Zdankus
Organised by Wessex Institute of Technology, UK University of New Mexico, USA Sponsored by WIT Transactions on Ecology and the Environment
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, USA P L Aguilar University of Extremadura, Spain K S Al Jabri Sultan Qaboos University, Oman E Alarcon Universidad Politecnica de Madrid, 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 G Belingardi Politecnico di Torino, Italy R Belmans Katholieke Universiteit Leuven, Belgium C D Bertram The University of New South 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 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 A El-Zafrany Cranfield 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, UK D Gross Technische Hochschule Darmstadt, Germany R Grundmann Technische Universitat Dresden, Germany A Gualtierotti IDHEAP, Switzerland R C Gupta National University of Singapore, Singapore J M Hale University of Newcastle, UK K Hameyer Katholieke Universiteit Leuven, Belgium C Hanke Danish Technical University, Denmark K Hayami National Institute of Informatics, 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 M Karlsson Linkoping University, Sweden T Katayama Doshisha University, Japan K L Katsifarakis Aristotle University of Thessaloniki, Greece J T Katsikadelis National Technical University of Athens, Greece E Kausel Massachusetts Institute of 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 A Konrad University of Toronto, Canada 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 UrbanaChampaign, 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 M Tanaka Shinshu University, Japan 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 E Tiezzi University of Siena, Italy A G Tijhuis Technische Universiteit Eindhoven, Netherlands T Tirabassi Institute FISBAT-CNR, Italy S Tkachenko Otto-von-GuerickeUniversity, 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 Leuven, Belgium D Van den Poel Ghent University, Belgium R van der Heijden Radboud University, Netherlands R van Duin Delft University of Technology, Netherlands P Vas University of Aberdeen, UK W S Venturini University of Sao Paulo, Brazil
R Verhoeven Ghent University, Belgium A Viguri Universitat Jaume I, Spain Y Villacampa Esteve Universidad de Alicante, Spain 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, Germany J R Whiteman Brunel University, UK Z-Y Yan Peking University, China S Yanniotis Agricultural University of Athens, Greece 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 & Technology, Hong Kong M Zador Technical University of Budapest, Hungary K Zakrzewski Politechnika Lodzka, Poland M Zamir University of Western Ontario, Canada R Zarnic University of Ljubljana, Slovenia G Zharkova Institute of Theoretical and Applied Mechanics, Russia N Zhong Maebashi Institute of Technology, Japan H G Zimmermann Siemens AG, Germany
Energy and Sustainability II
Editors: C.A. Brebbia Wessex Institute of Technology, UK A.A. Mammoli Univeristy of New Mexico, USA
Editors: C.A. Brebbia Wessex Institute of Technology, UK A.A. Mammoli Univeristy 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:
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[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: 978-1-84564-191-7 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 2009 Printed in Great Britain by MPG Book Group. 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 economic system is driven by easily available energy. Few of the advances made in the past two centuries would have been possible without the large-scale exploitation of fossil fuels. Resource depletion and predictions of severe environmental effects deriving from continued use of fossil fuels are spurring renewed interest in sustainable energy. The effort that will be required to shift from a fossil-based economy to one hinged on sustainability is massive, requiring advances in the basic sciences (materials, electrochemistry, heat transfer to name a few) through to systems engineering (buildings, electric grids, transportation) and all the way to international policymaking. The evolution of new energy technologies and systems cannot follow the compartmentalized model that has worked so well in the past, because of the time constraint imposed by oil and global warming. All parts of the new energy economy are strongly interlinked, and researchers in the field must be aware of the entire enterprise to maximize their own contribution. This second Conference on Energy and Sustainability, offers an opportunity for scientists, professionals, policymakers and other parties to review recent developments in this rapidly changing environment. The papers contained in this book span many of the critical aspects of the new energy economy, including renewable energy technology, energy management, policy, environmental impacts, systems analysis, and efficiency. The role of the International Scientific Advisory Committee was instrumental in promoting the meeting and attracting the many excellent contributions contained here, each of which represents years of dedicated efforts. The Editors would like to thank both the ISAC and the paper authors for their contribution. The Editors Bologna, 2009
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Contents Section 1: Renewable energy technologies Solar thermal heating and cooling: experience of a practical implementation A. Mammoli, P. Vorobieff, H. Barsun & M. Ortiz ............................................... 3 A multicriteria space model to locate grid-connected photovoltaic power plants in Granada (Spain), case study M. Zamorano, J. Arán, A. Ramos & M. L. Rodríguez........................................ 13 Numerical analysis of a minichannel solar collector for CO2-based Rankine cycle applications G. Diaz............................................................................................................... 23 Biomass refineries: relationships between feedstock and conversion approach J.-M. Lavoie, M. Chornet & E. Chornet ............................................................ 35 Elimination of siloxanes by adsorption process as a way of upgrading biogas D. Ricaurte Ortega & A. Subrenat..................................................................... 49 Gasified residual/waste biomass as solid oxide fuel cell feed for renewable electricity production J. Jurewicz & N. Abatzoglou ............................................................................. 59 Lighting the world with LEDs S. J. Riley & M. Telugu...................................................................................... 71 The optical and electrical properties of Eu3+-Y3+codoped ITO transparent conductive electrodes as luminescent solar concentrators C.-C. Ting & C.-H. Tsai..................................................................................... 79
Towards a Southern Africa Development Community (SADC) model to assess financing options of renewable energy technologies V. H. van Zyl-Bulitta, B. Amigun & A. C. Brent ................................................ 91 Hydrogen fuelled agricultural diesel engine with electronically controlled timed manifold induction: an experimental approach P. K. Bose, S. Mitra, R. Banerjee, D. Maji & P. Bardhan............................... 103 Selection of renewable energy technologies in Africa: the case of efficient stoves in Malawi M. L. Barry, H. Steyn & A. C. Brent ................................................................ 117 The sustainable energy service company (ESCO) experience at DIC Corporation Y. Ishida, M. Bannai, K. Ishimaru, R. Yokoyama, S. Nakazawa & H. Yunoue............................................................................... 129 Renewable energy from restored prairie plots in southeastern Minnesota, USA B. Borsari, I. Onwueme, E. Kreidermacher & T. Terril .................................. 137 Iron catalysts supported on carbon nanotubes for Fischer–Tropsch synthesis: effect of pore size R. M. Malek Abbaslou, J. Soltan, S. Sigurdson & A. K. Dalai ........................ 147 Pyrolysis of physic nut (Jatropha curcas L.) residue under isothermal and dynamic heating processes D. Atong, C. Pechyen, D. Aht-Ong & V. Sricharoenchaikul ........................... 157 Section 2: Energy management Energy and sustainability through integrated water network management M. Ektesabi, A. H. Moradi-Motlagh & A. H. Abdekhodaee............................. 175 Vanadium battery technology – integration in future renewable energy systems C. K. Ekman, H. Bindner, T. Cronin & O. Gehrke .......................................... 187 Short-term wind forecasting using artificial neural networks (ANNs) M. G. De Giorgi, A. Ficarella & M. G. Russo................................................. 197
Section 3: Energy policies A review of the Bioenergy potential of residual materials in Quebec S. David & N. Abatzoglou................................................................................ 211 Potential transport energy demand and oil dependency mitigation measures T. E. Lane & M. J. W. A. Vanderschuren......................................................... 225 Sustainable energy policy choice: an economic assessment of Japanese renewable energy public support programs A. Suwa, K. Noda, T. Oka & K. Watanabe ...................................................... 237 An energy and environmental meta-model for strategic sustainable planning D. S. Zachary, U. Leopold, L. Aleluia Reis, C. Braun, G. Kneip & O. O'Nagy..................................................................................... 247 The Italian gas retail market: a cluster analysis based on performance indexes G. Capece, L. Cricelli, F. Di Pillo & N. Levialdi ............................................ 257 Participatory assessment of sustainable end-user technology in Austria M. Ornetzeder, U. Bechtold & M. Nentwich.................................................... 269 Towards a SADC model to assess financing options of renewable energy technologies V. H. van Zyl-Bulitta, B. Amigun & A. C. Brent .............................................. 279 Energy from biomass: decision support system for integrating Sustainability into technology assessment P. Lacquaniti & S. Sala ................................................................................... 291 Recovering energy from liquid sanitary waste for Direct Alcohol Fuel Cell V. Pelillo & D. Laforgia .................................................................................. 303 An innovative concept leveraging mass volunteerism and the viral nature of the Web to substantially reduce global carbon emissions H. Gandhi & B. S. Thompson .......................................................................... 311
Section 4: Energy and the environment Integrating intelligent glass facades into sustainable buildings: cases from Abu Dhabi, UAE M. A. Haggag................................................................................................... 323 Case study ‘the Vela Roof – UNIPOL’, Bologna: use of on-site climate and energy resources A. van Timmeren & M. Turrin ......................................................................... 333 Gap analysis of current research in the area of IT for energy in buildings K. U. Gokce, A. Hryshchenko & K. Menzel ..................................................... 343 Development of a sustainability assessment framework for planning for sustainability for biofuel production at the policy, programme or project level L. K. Haywood, B. de Wet, G. P. von Maltitz & A. C. Brent............................ 355 Production of biodiesel from Jatropha curcas and performance along with emission characteristics of an agricultural diesel engine using biodiesel S. Mitra, P. K. Bose & S. Choudhury .............................................................. 367 Environmental and exergetic performance of electrolytic hydrogen using life cycle assessment J. L. Gálvez, L. Pazos, C. García, G. Martínez & A. González García-Conde...................................................... 377 Section 5: Energy analysis Heat transfer from in-line tube bundles to downward aqueous foam flow J. Gylys, S. Sinkunas, T. Zdankus, R. Jonynas & R. Maladauskas .................. 389 Mathematical models of air-cooled condensers for thermoelectric units S. Bracco, O. Caligaris & A. Trucco ............................................................... 399 Optimisation of cogeneration systems – combined production of methanol and electricity C. Werner & H. L. Estrada Hummelt .............................................................. 411
Section 6: Energy efficiency The promotion of energy efficiency of the building envelope in the rehabilitation process. Case study: a minor centre in Abruzzo P. De Berardinis & M. Rotilio ......................................................................... 425 Domestic appliances end-use efficiencies: the case of eleven suburbs in greater Johannesburg M. V. Shuma-Iwisi & G. J. Gibbon .................................................................. 437 Analysis of energy conversion in ship propulsion system in off-design operation conditions W. Shi, D. Stapersma & H. T. Grimmelius ...................................................... 449 Development of combustion efficiency tables for biofuels D. F. Dyer........................................................................................................ 461 Combustion of urban solid wastes in an experimental fluidized bed combustor C. A. Torres-Balcazar, G. Lopez-Ocaña, R. G. Bautista-Margulis, J. R. Hernandez-Barajas, H. O. Rubio-Arias & R. A. Saucedo-Teran ............ 469 Optimisation of ammonia injection for an efficient nitric oxide reduction S. Ogriseck & G. P. Galindo Vanegas............................................................. 481 Conversion of waste rubber as an alternative rout to renewable fuel production M. Stelmachowski & K. Słowiński ................................................................... 489 Energy efficiency development in the German and Colombian energy intensive sectors: a non-parametric analysis C. I. Pardo M. .................................................................................................. 499 Section 7: Energy storage and management Assessing European power grid reliability by means of topological measures M. Rosas-Casals & B. Corominas-Murtra ...................................................... 515 Application of energy storage systems for DC electric railways R. Takagi.......................................................................................................... 527 Author Index .................................................................................................. 537
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Section 1 Renewable energy technologies
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Energy and Sustainability II
3
Solar thermal heating and cooling: experience of a practical implementation A. Mammoli1, P. Vorobieff1 , H. Barsun2 & M. Ortiz1 1 Department
of Mechanical Engineering, The University of New Mexico, USA 2 Physical Plant Department, The University of New Mexico, USA
Abstract The Mechanical Engineering building at the University of New Mexico was an example of the state of the art in environmentally conscious architecture in the early 1980s. Along with many passive energy-conserving features, it had an active solar thermal heating and energy storage system. In the first decade of the twentyfirst century, we were presented with an opportunity to radically modernize this solar thermal system, preserving many of the original features, but also implementing solar cooling and making this project a part of a bigger plan involving a smart energy grid. Here we describe our work, the results in terms of energy savings, and discuss future improvements.
1 Introduction The solar thermal system at the University of New Mexico Mechanical Engineering (UNM ME) building was a part of the original design of the building, dating back to the 1970s energy crisis. At the time of its inauguration, the UNM ME building was hailed as “a true step in the future of energy.” (From the inauguration address by US Senator Pete Domenici, R-N.M., October 11, 1980.) Components of the original system [1] included thermal storage (400 tons of water in eight concrete underground tanks), a 300 m2 solar collector array, and a Rankine cycle engine driving an electric generator. Thus solar heat could be used to heat the building or to produce electricity. The original system performed quite well for a while, but gradually fell into disrepair due to lack of maintenance. In 2006, a grant from the State of New Mexico, along with additional funding and support from the University of New Mexico and the US Department of Energy, made it possible WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESU090011
4 Energy and Sustainability II to re-implement the UNM ME solar thermal system using modern hardware and controls, as described in our earlier paper [2]. Since the system commissioning on October 15, 2008, we have operated the thermal solar / storage system at the UNM Mechanical Engineering building and measured its performance. As a consequence of the late onset of cold weather, we were able to test summer, shoulder season, and winter conditions, and are now able to estimate the potential energy cost savings that the system will provide. Here we will base the cost savings on the system installed in the building prior to project implementation, which consisted of a stand-alone, 100 ton, 30 year old electric chiller, with a nominal coefficient of performance (COP) of 3.8 and actual (based on meter readings and estimated building load) COP of approximately 2.0. We will also use the electricity rates provided by the PNM utility company [3] to calculate costs, although the real situation is complicated by the fact that the University of New Mexico generates part of its electricity using a co-generation gas turbine. In summer operation, the system will be able to provide cost savings through its ability to store chilled water during the night, taking advantage of lower electricity rates, through an extremely efficient electric district chiller (COP of over 6.5), and through the production of chilled water by the solar water-fired absorption chiller (which has an equivalent electric COP of approximately 10, when the solar circulation pump and the cooling tower pump are included). The principal cost saving is provided by the chilled water storage system. Chilled water production from the absorption chiller further reduces the cost of cooling, especially in comparison to the stand-alone electric chillers that were operating prior to the project implementation. In the shoulder seasons, the solar system is able to provide all of the heating and cooling required by the building. We devised a control strategy that allows us to heat the building in the morning, and cool it in the afternoon, in the proportions required by weather condition. In the winter, we have shown that during sunny conditions, the system can provide over 90% of the weekly heating requirement, and we estimate an average of 70% to account for a fraction of cloudy days.
2 Cooling In 2008, the cooling season extended well into October, so we were able to test the cooling capacity of the solar assisted chiller, and to devise optimal operating procedures. As shown in the plot of Fig. 1, the absorption chiller produces a temperature drop of about or 5.5◦ C. Chilled water flow through the chiller was measured at 3.15 l/s. This corresponds to a cooling capacity of 72.4 kWt (the rated capacity of the chiller is 20 tons of cooling, or 70 kWt ). On days with little cloud cover, such as October 9, 2008, the chiller operates for approximately 5 hours, producing a total cooling effect of 362 kWh. This value matches exactly with our model calculations (TRNSYS [4]) for high temperature operation. In peak summer operation, we expect to produce over 400 kWh of cooling. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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Figure 1: Typical ‘summer’ operation: Measured radiation on a flat plate with South orientation and 30◦ tilt for October 9, 2008 (top), and absorption chiller operating parameters, showing temperatures for heating, cooling and chilled water loops (bottom).
The total solar energy available throughout a day in October with collectors tilted at 30◦ is approximately 6 kWh/m2 , corresponding to 1392 kWh for perfectly efficient collectors with an area of 232 m2 . However, collector efficiency decreases substantially with low solar radiation values (below 500 W/m2 ) and high heat medium temperatures, so that useful energy collection only occurs between WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
6 Energy and Sustainability II approximately 10AM and 4PM, as can be seen from Fig. 1. Thus, the total energy collected daily in this period in October is approximately 566 kWh. The corresponding chiller COP is 64%, well within specification. We did not operate the solar system continuously through the summer, so we do not have sufficient data to show the total fraction of cooling load that is met by the absorption chiller. However, our detailed TRNSYS model of the system predicts a yearly cooling fraction of approximately 35% at high operating temperatures [5]. We also note that, somewhat surprisingly, the cooling fraction may increase if we operate at lower heat medium temperatures, as shown in Fig. 2. We plan to investigate this option during the 2009 cooling season.
Figure 2: Yearly fraction of cooling, and average absorption chiller C.O.P., as a function of solar loop outlet temperature.
The seven chilled water storage tanks contain up to a total of 350,000 liters of water. They are equipped with linear diffusers which allow stratification, with ∆T between the cool and warm layers anywhere above 5◦ C. The design ∆T of 11◦ C results in a total capacity of 4470 kWh, sufficient to meet the peak building load (approximately 2000 kWh) for two days, accounting for losses. In general, we will use fewer than seven tanks, to reduce thermal losses. We were able to observe that stable tank stratification indeed takes place. However, we were not able to fully test the chilled water storage last summer due to the degraded performance of the chilled water coil in the primary air handling unit, which was only able to provide a 5◦ C temperature difference, thereby halving the stored chilled water capacity. The coil has now been replaced in preparation for the 2009 cooling season, so that we will be able to take full advantage of night-time chilled water storage. The cost savings due to operation of the chilled water storage are the most significant. During the months of June, July and August, the daytime (8AM to 8PM) electricity cost is USD 0.054/kWh, versus a night-time cost of USD 0.026/kWh [3]. For a typical load of 1600 kWh/day, assuming a chiller COP of 6.5 (this is a 2000-ton Trane chiller located at UNM’s Ford Utilities Center, which now provides chilled water to the ME building), the cost of night-time storage versus daytime ondemand operation is USD 6.45/day and USD 13.23/day respectively. In addition, a reduction in monthly peak demand of up to 16kW results in an additional daily WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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saving of USD 4.20/day. The cost of producing chilled water is therefore reduced from USD 17.42/day to USD 6.45/day (a 63% reduction) solely by off-peak operation of the chiller. Meter readings from the stand-alone chiller prior to project implementation show an average power consumption of 43kW for the summer of 2006. Since the chillers were used primarily during the day, directly to offset load, this corresponds to a daily electricity cost of USD 55.50 for the energy charge, plus a demand charge of USD 23.45. Compared with the original cost of chilled water production, the new system results in a saving of 91.8%. The cost of circulating air in the building was also reduced by the installation of VFDs (variable frequency drives) on all the air handler fan motors, so that air handlers no longer operate at full power all the time. Over the next year, we will program the air handlers so that they provide the required minimum amount of outside air, as a function of building occupancy, if the outside air temperature is warmer than the building return air. If the outside air temperature is lower that of the than building return air, then the fraction of outside air will be increased to reduce the cooling load.
3 Shoulder season The shoulder season, generally occurring mid-October to mid-November, and midMarch to mid-April, posed a particular problem. Operating in cooling mode would make the building too cold, while operating in heating mode would make it too hot. At the same time, the solar collectors produce a large amount of hot water, which must be cooled to prevent tank overheating the next day. The building air handler schedule is such that the fans begin moving air at 6:00AM, including a fraction of cold outside air, making the building relatively cold and uncomfortable in the morning. As the day progresses, the building becomes progressively warmer, sometimes exceeding comfort levels. For a period of approximately one week, we cooled the building by operating the absorption chiller in the early to late afternoon, until the heat storage tank high temperature dropped to 74◦ C. The following morning, we operated the heating system until the air handlers no longer required hot water. We took advantage of the fact that the air handlers can function with a wide range of temperatures - if the supply water is very hot, the control valves reduce the flow rate to maintain a set air temperature. Usually, heating water is no longer required by mid-morning. At this time, the solar collectors begin to produce hot water at the set temperature for absorption chiller operation, 87◦ C. However, because of the heating, the tank lower temperature is colder than usual, so that the rate of hot water production is also lower than usual. This results in a lower total amount of hot water which is usable for cooling, reducing the chiller run time. This operating strategy is self-balancing: cooler days will result in longer heating operation and shorter cooling operation, and vice-versa. The implementation of the strategy merely required allowing the hot air handlers to request hot water from the tank in the morning within the summer operating strategy. The winter WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
8 Energy and Sustainability II operating strategy was left unaltered, with no possibility of cooling owing to the shutdown of the cooling tower. In the shoulder season, the solar system was able to supply all of the heating water and cooling water needs for the building. The night-time chilled water tank recharging was turned off.
4 Heating In late October, we switched the system operation to heating. We were able to provide comfortable conditions throughout, with temperatures in the vicinity of 22◦ C. A typical scenario of a sunny, cold day is shown in Fig. 3. At 6:00AM on November 20, the heating pump begins drawing hot water from the hot tank and circulating it thought the air handlers. The hot water temperature trace shows that some hot water (at 54 to 49◦ C) remained in the tank from the previous day. This hot water, however, was used up within the first hour of operation. The corresponding steam heat exchanger valve position trend plot shows that the steam valve gradually opens to maintain the temperature of the water entering the heating coils above a set point (49◦ C). At around 9:00AM, the solar array begins producing hot water, and the steam valve closes until around 8:00PM, when it opens briefly, until the system shuts down for the night. The solar system is able to provide heating water for over 9 hours out of 14 hours of operation, with a small amount of steam assistance for the remaining 5 hours. On a mostly cloudy day (see the solar radiation measurement in Fig. 4 for December 9, 2008), virtually no hot water was produced. As shown in Fig. 4, the steam valve remained open at an average value of approximately 40% for the entire heating cycle, from 6:00AM to 8:00PM. Thus, under the current operating schedule (7 days a week), the solar system reduces steam usage by 64%. However, it is UNM procedure to shut down ventilation over the week-end. In this case, we could accumulate enough hot water over the week-end to supply the heating system for an additional 18 hours. The hot storage tank can easily accumulate this amount of heat, and distribute it through the remainder of the week. This would result in the ability to operate for approximately 63 hours out of 70 with solar hot water only, a saving of 90%. Given that some days will be cloudy, it is more likely that the average saving in steam will be closer to 70%.
5 Energy cost savings Based on the observed performance of the system, the cost savings in chilled water production cost for a typical summer day are summarized in Table 1. We note that these costs represent only electricity savings, not operation and maintenance. The total daily electricity cost of the new system, including stored chilled water and solar chilled water, is USD 10.3. The cost of operating the old electric chiller, assuming peak performance (C.O.P. of 3.8) directly against the load would be WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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Figure 3: Typical ‘winter’ operation: feedwater temperature to the heating coils from the hot storage tank for November 20, 2008 (top) and steam 1/3 valve position for the same day. Note that steam is only required in the early morning (bottom).
USD 49.9. The predicted saving in energy cost for cooling is therefore at least 79%. Because of the limited size of hot storage, the absorption chiller must be operated during peak time for at least part of the time. However, it is possible to stop WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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Figure 4: Typical cloudy winter operation: measured solar radiation (top) and steam 1/3 valve position (bottom).
operation when the residual storage tank capacity is larger than the estimated remaining solar energy that will be collected during the remainder of the day. During the next cooling season, we will operate the absorption chiller at night to further reduce electricity cost. The calculation of energy savings with heating is more straight-forward. For example, on December 9, 2008, virtually no solar hot water was produced due to WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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Table 1: Parameters and costs of chilled water production, assuming 90% storage efficiency. Cooling C.O.P. kWht
Equiv.
Energy
elec.
price
Energy Demand cost
cost
Total
kWhe
$/kWh
$/day
$/day
$/day
Original
1600
2.0
800
0.05379
43.0
27.2
70.2
Original
1600
3.8
421
0.05379
22.7
27.2
49.9
∗
0.026210
5.4
0.0
5.4
0.053769
2.15
2.72
4.87
Storage
1200
6.5
205
Solar
400
10.0
40
cloud cover. From meter data, 1534 kg of steam were used for heating, corresponding to 887 kWh of thermal energy. With a cost of USD 0.0686/kWh for steam, the cost of heating the building for December 9 was USD 60.70. Using the assumed 70% reduction in steam consumption from our observations discussed in the previous section, we expect to save, on average, USD 42.50 per weekday during the heating season. Sadly, we do not have conclusive meter data to confirm the above calculations, since the system has not operated at full capacity for a long enough period.
6 Discussion The overall efficiency of the absorption cooling cycle is offset by the need to operate several pumps for fluid circulation. In our case, both solar water and cooling water operate on an open cycle. We will install a high efficiency heat exchanger between the solar loop and the heat storage tank. The solar loop would become closed, and the heat medium would be changed from water to water-glycol mix. A closed loop would allow us to operate the solar circulation pump on VFD, greatly reducing the part load electricity consumption. furthermore, circulation of water through the solar loop during winter nights would no longer be necessary, and the risk of freezing would be eliminated. A loss of thermal efficiency of approximately 5% is estimated during summer high-temperature operation. The cooling tower pump is the most significant source of pumping loss in the system. There are two options for reducing the cooling tower power consumption. Relocating the cooling tower from the roof to the Rankine room is feasible but expensive. The second alternative is to recover the potential energy of the cooling tower return water by installing a small Pelton turbine, which would produce approximately 3kW. This could be fed back into the grid with a small inverter. Thermal storage is an often overlooked component of energy-conscious buildings. Aside from the cost benefit deriving from the ability to store chilled water off-peak, thermal storage could play a significant role in ‘smart grids’ of the future, WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
12 Energy and Sustainability II where bidirectional information allows a much more efficient optimization of the electricity generation, transmission, distribution and end use. For example, wellorganized storage strategies could reduce demand peaks, allowing for reduced generation infrastructure cost, as well as increase the penetration of intermittent resources, such as wind and photovoltaic. Our current activities are now heavily focused on determining an appropriate architecture for decentralized optimization of electricity generation and end-use.
References [1] Maurice W. Wildin. Results from the 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, Oak Ridge National Laboratory, 1982. [2] A.A. Mammoli, P. Vorobieff, and D. Menicucci. Promoting solar thermal design: the Mechanical Engineering building at the University of New Mexico. In C.A. Brebbia, M.E. Conti, and E. Tiezzi, editors, Management of Natural Resources, Sustainable Development and Ecological Hazards, volume 1, pages 265–274. WIT Press, Southhampton, Boston, 2006. [3] Public Service Company of New Mexico. 5th revised rate no. 15B – large service for public universities greater than 8,000 kW minimum with customerowned generation facilities served at 115 kV, May 2008. c 2002, The Board of [4] TRansient SYstems Simulation program. Copyright Regents of the University of Wisconsin System. [5] Mario Leroy Ortiz. A TRNSYS model of a solar thermal system with thermal storage and absorption cooling. Master’s thesis, The University of New Mexico, 2008.
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A multicriteria space model to locate grid-connected photovoltaic power plants in Granada (Spain), case study M. Zamorano1, J. Arán1, A. Ramos1 & M. L. Rodríguez2 1
Department of Civil Engineering, Section of Environmental Technology, University of Granada, Spain 2 Department of Applied Mathematics, University of Granada, Spain
Abstract Energy consumption grows year on year but present reserves of fossil fuels can only cover consumption at current rates for the next 40 years, in the case of oil, and for the next 60 in the case of natural gas. The emissions generated by the use of fossil fuels are the source of serious environmental problems which in many cases are irreversible. The use of renewable energy technologies seems to be a viable solution for environmental problems produced by other energy sources so today environmental policies are largely promoted to foresting the implementation of renewable energy technologies. In this sense, some countries, for example Spain, have taken an important step to foment grid-connected photovoltaic solar energy but the efficiency of these installations depends on location characteristics. This paper describes the structure and the principal phases of an environmental decision-support system, which combines multicriteria analysis as well as the analytic hierarchy process with geographical information systems technology, to make easier site selection of grid-connected photovoltaic power plants; it combines. The developed model has considered climate features that directly influence the performance of solar energy installation, environmental aspects, legal aspects, orography and finally social and economic factors. This model has been applied in Granada (Spain) and results have been test through a validation process consisting in sensibility analysis. Results have shown applicability and consistence of the model. Keywords: decision-support systems, multi-criteria analysis, renewable energy, photovoltaic systems. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESU090021
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Introduction
Energy demands are growing day by day, one consequence of the growing population of the world and of energy consumption tied to industrialization and development; current previsions estimate the energy demand for the year 2020 to be 50-80% greater than that of 1990. As a result of this level of consumption, millions of metric tons of greenhouse-effect gases are released into the atmosphere contributing to progressive global warming, air pollution and reduction of the ozone layer, more frequently severe meteorological effects, an impact on agricultural yields, the proliferation of diseases and on the rising sea level [1–3]; indeed, the mean temperature of our planet has increased by 0.7ºC and by the year 2050 we may expect to see an increase of 4 to 5ºC. Aside from these drawbacks, the fossil fuel reserves themselves are running out, so the scarcity will account for a hike in their price, affecting economic development worldwide [4, 5]. In response to the need to fight global warming, a number of measures have been put forth. At the international level, the Kyoto Protocol set the goal to reduce by 5%, by the year 2012, global emissions of six of the gases responsible for global warming [6]. To reach these goals, it is necessary to take action in the priority areas of energy generation and use, as well as with regard to emissions. Up until now, energy planning have been focused on foreseeing demands in a given time period, with the objective of covering the corresponding demand, under an approach that treated energy as a never-ending resource. Yet the effects of the current system of energy generation, distribution and use on the environment and its impact on the global warming of the planet urge the introduction of a new energy model. From this standpoint, renewable energy resources are destined to satisfy part of the future demands currently placed upon fossil fuels. For this reason, current policies focus on fomenting their development and used in Europe as stated in currently legislation. In this sense Photovoltaic is the field of technology and research related to the application of solar cells for energy by converting sunlight directly into electricity. Photovoltaic energy production has been doubling every two years, increasing by an average of 48 percent each year since 2002, making it the world’s fastest-growing energy technology. At the end of 2007, according to preliminary data, cumulative global production was 12,400 megawatts [7]; roughly 90% of this generating capacity consists of grid-tied electrical systems. However, the main effect of the increase in projected and built grid connected photovoltaic power plants is to spot numerous optimal location errors regarding output efficiency, law observing and costs reduction. In consequence it is imperative that project designers have access to local information on climate, soil characteristics and extensive power transmission grid to absorb the electricity generated, used of soil and legal measures; without such data, optimal site selection for solar power installations cannot be guaranteed [8]. The objective of this research is the definition of a model to choose optimal sites for grid-connected photovoltaic power plants, which fulfil the requirements established by a decision rule. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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Materials and methods
2.1 Area of study The area selected in this study is located in the far northeast of the province of Granada (southeast of Spain), in the district of Huéscar. This area has been selected because it is representative of all the uses considered in the model, allowing us to test the behaviour of each variable in the final result. The geographic location of Andalusia in the south of Spain signifies that it is in a key position to play an important strategic role in the implementation of renewable energy technology in Europe, as well as providing sufficient energy for its own needs and even exporting such projects to other countries [9]. 2.2 Geographical information systems Since grid-connected photovoltaic power plants location requires processing a lot of spatial data, we have used Geographical Information Systems and its spatial analysis tools to create the digital geodatabase. GIS are defined as an integrated collection of computer software used to analyze, create, acquire, store, edit, transform, view and distribute geographic data GIS. The combination of spatial data with quantitative, qualitative and descriptive information databases, capable of dealing with a wide range of spatial queries, has made GIS an indispensable tool for location studies [10]. Commercial GIS software packages ESRI ArcGIS 9.2, has been used in this research. It is an integrated system for the creation, management, integration, and analysis of geographic data. It consists of a geo-referenced spatial database, which includes the parameters required for photovoltaic power plants location. The GIS Desktop includes various integrated applications and extensions. One of them is ArcView; it is geographic information system (GIS) software for visualizing, managing, creating, and analyzing geographic data. 2.3 Multi-criteria evaluation When making decisions, decision makers (DMs) always try to choose the optimal solution. Unfortunately, a true optimal solution only exists if you are considering a single criterion. In most real decision situations, basing a decision solely on one criterion is insufficient. Probably several conflicting and often noncommensurable objectives should be considered. Because of this, it is impossible to find a genuine optimal solution, a solution that is optimal for all DMs under each of the criteria considered [11]. The term multiple-criteria decision analysis (MCDA) describes various methods developed for aiding decision makers in reaching better decisions. Using MCDA can be said to be a way of dealing with complex problems by breaking the problems into smaller pieces. After weighing some considerations and making judgments about smaller components, the pieces are reassembled to present an overall picture to the DMs [12]. These techniques have been applied
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16 Energy and Sustainability II to solve energy planning problems, based on complex problems with multiple decision makers and multiple criteria [13, 14]. MCDA methods can be divided in three main groups, each of which differs in its respective characteristics, evaluation, data type and objectives: compensatory techniques, non-compensatory techniques and fuzzy techniques. The model described in this article is a system based on multi-criteria evaluation with one objective and several criteria and it have been used Analytical Hierarchy Process (AHP) developed by Saaty’s because it can handle decision-making problems which require a high degree of flexibility and reliability.
3
Decision-making model to optimally place grid-connected photovoltaic power plants
The phases of the elaboration of the decision-making model are: (i) specification of the criteria, (ii) establishment of the decision rule, (iii) determination of the suitability of the land area for grid-connected photovoltaic power plants, (iv) sensibility analysis. 3.1 Definition of criteria A criterion is a measurable aspect of a judgement which makes it possible to characterize and quantify alternatives in the decision-making process [15, 16]. Table 1:
Criteria and factors considered in the model.
Criteria
Factors Land use Visual Impact Slopes (%) Orientation Highway access (km) Distance to substations (km) Distance to urban areas > 5000 inhabitants (km) Distance to urban areas < 5000 inhabitants (km) Global irradiance (Wh/m2/day) Diffuse radiation (%) Equivalent sun hours (ESH) (Kwh/Kwp) Average temperature (ºC)
Environment Orography Location
Climate
3.2 Definition of decision rule A suitable decision rule which integrated the criteria established was created to assign a weight to each criterion. Climate criteria have been considered the most important for the decision rule, following in order of importance by orography, environment and finally location criteria. Saaty’s AHP [17] has been used to WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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assign weights to each criterion and determine their relative importance in the final decision adopted within the model establishing a comparison matrix between pairs of criteria and contrasting the importance of each pair with all the others. 18 alternative scales have been considered {1/9, 1/8, 1/7, 1/6, 1/5, 1/4, 1/3, 1/2, 1, 2, 3, 4, 5, 6, 7, 8, 9}. If we compare two criteria, for example 2 and 3, and consider the relative importance “Intermediate”, the relative weighting is a23=4/1; then the relative importance of this attribute is its reciprocal a32=1/3. Table 2:
Indicators of land use factor.
Factor
Indicators Area without vegetation Dryland herbaceous crops Irrigated herbaceous crops Herbaceous and woody crops Woody crops Other uses
Land use
Table 3: Criteria Environment Orography Location Climate Total
∑a j
ij
Comparison matrix of the criteria.
Environment a11=1.00 a12=3.00 a13=0.33 a14=5.00
Orography a21=0.33 a22=1.00 a23=0.20 a24=3.00
Location a31=3.00 a32=5.00 a33=1.00 a34=9.00
Climate a41=0.20 a42=0.33 a43=0.11 a44=1.00
9.33
4.53
18.00
1.64
For example Table 3 shows comparison matrix of the criteria and Table 4 shows normalized values obtained for each criteria considering expressions [1, 2]. The same process has been followed to each factor and indicator.
Aij =
aij
∑a
(1) ij
j
Wj =
∑A
ij
i
4
(2)
3.3 Validation of the model Although the method has shown to be an excellent model to locate gridconnected photovoltaic power plants, it is necessary to accomplish a sensibility analysis in order to guarantee that it offers a reliable representation of the systems represented [18]. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
18 Energy and Sustainability II Table 4: Criteria Environment Orography Location Climate Total
Comparison matrix of the normalized values of criteria. Environment
Orography
Location
Climate
A11= 0.11 A12= 0.32 A13= 0.04 A14= 0.54
A21= 0.07 A22= 0.22 A23= 0.04 A24= 0.66
A31= 0.17 A32= 0.28 A33= 0.06 A34= 0.50
A41= 0.12 A42= 0.20 A43= 0.07 A44= 0.61
Normalized priority vector (wj) 0.1172 0.2556 0.0507 0.5764
Final weights (%) 12 26 5 58 100
The aim of sensitivity analysis is to estimate the rate of change in the output of a model with respect to changes in model inputs. Such knowledge is important for evaluating the applicability of the model, determining parameters for which it is important to have more accurate values, and understanding the behaviour of the system being modelled. The choice of a sensitivity analysis method depends to a great extent on the sensitivity measure employed, the desired accuracy in the estimates of the sensitivity measure, and the computational cost involved. Based on the choice of a sensitivity metric and the variation in the model parameters, sensitivity analysis methods can be broadly classified into the following categories [19]: (i) Variation of parameters or model formulation; in this approach, the model is run at a set of sample points (different combinations of parameters of concern) or with straightforward changes in model structure (e.g., in model resolution); sensitivity measures that are appropriate for this type of analysis include the response from arbitrary parameter variation, normalized response and extrema; of these measures, the extreme values are often of critical importance in environmental applications; (ii) Domain-wide sensitivity analysis; here, the sensitivity involves the study of the system behaviour over the entire range of parameter variation, often taking the uncertainty in the parameter estimates into account; (iii) local sensitivity analysis; here, the focus is on estimates of model sensitivity to input and parameter variation in the vicinity of a sample point. This sensitivity is often characterized through gradients or partial derivatives at the sample point. In this research the second category has been applied. To validate the model, using sensibility analysis, all factors and criteria have been compared with their final values after the model has been generated, so it has been possible analyzed their changes.
4
Applying the model in Granada (Spain)
4.1 Site suitability for the location of grid-connected photovoltaic power plants Layer related to criteria, factors and positive and negative indicators have been generated using the database of the Department of the Environment and the Department of Public Works of the Andalusian Regional Government; some layers have been carried out by the authors of the research study. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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One the weights were obtained, the criteria, factors and indicators were ordered according to their degree of importance and they have been normalized on a scale for 0 to 10. The criteria, factors and indicators were entered into a GIS. Layers of indicators were established in a first step. Taking into account decision rules and weights assigned to each one and by means of arithmetic overlay, layer of factors were also obtained. Layers of criteria were calculated in the last step. Finally carrying capacity of a territory for grid-connected photovoltaic power plants was determined on a scale from 1 to 10, corresponding 1 to the lowest suitability and 10 to the highest.
a
c Figure 1:
b
d
a) Map of restrictions; b) Map of the factor Global Irradiance; c) Environmental criteria; d) Suitability for the location of gridconnected photovoltaic power plants.
Figure 1 shows maps of restrictions obtained (Figure 1a), as so as the “Global Irradiance” map, one of the factors of the “Climate” criteria map (Figure 1b), the map of “Environment” criterion (Figure 1c) and, finally, the final layer obtained (Figure 1d). The study area does not show the presence of the lower levels of the final layer and any land with the maximum value for each factor; this can be explained because a large sector of the study area is not suitable for gridconnected photovoltaic power plants, located in protected areas, near rivers, etc. (Figure 1a). WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
20 Energy and Sustainability II Areas with values 7-9 signifies that they are many suitable sites for the location of grid-connected photovoltaic power plants because of their favourable characteristics related to favourable climate, with uncultivated dryland or with herbaceous vegetation and out of protected areas (Figure 1d). The validation process has concluded that uncertainty is higher in the case of models that consider priority factors orography and location. It has also shown that the most important factors are those related to climate and the environment; factors related to location, for example distance to populated areas and road, do not influence the result, so if it is necessary to simplify the model they could be removed.
5
Conclusions
The decision-making model summarized in this paper provides very valuable information to select optimal site for location of grid-connected photovoltaic power plants, due chiefly to the generation of a final suitability index. Analysis of results for the other layers may also facilitate the study of potential problems related to the different environmental and climatic components as so as restricted areas, contributing to the decision of whether or not to locate grid-connected photovoltaic power plants in a particular setting. On the basis of the results of the practical application of the model in Granada as well as the sensitivity analysis, we may conclude that Multiple Criteria Decision Analysis, supported by on Geographical Information Systems, may be usefully applied to the optimal siting of facilities with such exceptional characteristics as this type of installations. It seems reasonable, moreover, to predict that this instrument has the potential to assist planners, decision-makers and other agents involved in the process of selecting suitable sites for photovoltaic power plants, by extending their knowledge of the physical terrain and facilitating the analysis and execution of plans of action. Energetic efficiency and lower environmental impact have been the main objectives to choose best location, although more criteria have been also considered, for example accessibility and power substations proximity. Finally, the application of the model in Granada and the validation process has shown applicability and consistency of the model.
Acknowledgement This research has been partially funded by Parque Metropolitano Industrial y Tecnológico de Granada, S.L, with the R+D Project entitled “Análisis de rendimientos y optimización de producción de distintas soluciones fotovoltaicas conectadas a red” (Fundación Empresa Universidad de Granada 3158-00).
References [1] Karakosta, C., Doukas, H. & Psarras, J. 2009. Sustainable energy technologies in Israel under the CDM: Needs and prospects. Renewable Energy, 34, pp. 1399-1409 WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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[2] Randall et al., 2005, Energy and the World Summit on Sustainable Development: what next, Energy Policy, 33, pp. 99–112. [3] Omer, A.M. 2008. Energy, environment and sustainable development. Renewable Sustainable Energy Reviews, 12, pp. 1988-1996. [4] Ramachandra, T.V., Kamakshi, G. & Shruthi, B.V. 2004. Bioresource status in Karnataka. Renewable Sustainable Energy Reviews, 8, pp. 1–47. [5] BP. 2006. Statistical Review of World Energy 2006. BP p.l.c., London [6] UNFCCC. The Kyoto protocol to the United Nations framework convention on climate change. United Nations, http://unfccc.int/resource/docs/convkp/kpeng.pdf; 1998. [7] Earth Policy Institute, 2007. Solar Cell Production Jumps 50 Percent in 2007. http://www.earth-policy.org/Indicators/Solar/2007.htm [8] Aran, J. 2008. Space model of analysis for the evaluation of the capacity of welcome of the territory in the location of connected photovoltaic power stations to network. PhD Thesis. University of Granada (Spain). http://hera.ugr.es/tesisugr/1764625x.pdf [9] Ramos, A., Hontoria, E., Moreno, B. & Zamorano, M. 2007. solar energy in Andalusia (Spain): present state and prospects for the future. Renewable and sustainable Energy Reviews, 11, pp. 148-161. [10] Church, R. 2002. Geographical information systems and location science, Computers & Operations Research , 29(6), pp. 541-562. [11] Loken, E. 2007. Use of multicriteria decision analysis methods for energy planning problems. Renewable and Sustainable Energy Reviews, 11, pp. 1584–1595. [12] Dodgson, J., Spackman, M., Pearman, A., Phillips, L. 2001. DTLR multicriteria analysis manual. UK Department for Transport, Local Government and the Regions. [13] Chatzimouratidis, A.M.A. & Pilavachi, P. 2008. Sensitivity analysis of technological, economic and sustainability evaluation of power plant using the analytic hierarchy process. Energy Policy, 36, pp. 1074-1089. [14] Ben Salah, C., Chaabene, M. & Ben Ammar, M. 2008. Multi-criteria fuzzy algorithm for energy management of a domestic photovoltaic panel. Renewable Energy, 22, pp. 993-1001. [15] Eastman, J.R, Jiang, H & Toledano, J. 1993. Multi-criteria and multiobjective decision making for land allocation using GIS. Dordrecht: Kluwer Academic Publishers, pp. 227-251. [16] Voogd, S.H. 1983. Multi-criteria Evaluation for Urban and Regional Planning. London: Pion. [17] Saaty, T.A. 1997. Scaling method for priorities in hierarchical structures. Journal of Mathematical Psychology, 15, pp. 234-281. [18] Rai & Kewski. 1998. Uncertainty and variability analysis in multiplicative risk models. Risk Analysis, 18(1), pp. 37-45. [19] Saltelli, A., Chan, K. & Scout, E.M. 2000. Sensitivity Analysis. Chichester. John Willey & sons, LTD.
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Numerical analysis of a minichannel solar collector for CO2-based Rankine cycle applications G. Diaz School of Engineering, University of California, USA
Abstract The combined effects of increasing energy consumption, higher fuel prices, and green-house-related climate change are challenging universities and industry to develop more efficient and sustainable ways to produce power, heating, and cooling for industrial, commercial, and residential applications. The utilization of renewable energy sources is receiving considerable attention as a non-resource-depleting approach that reduces the emissions of pollutants and green-house gases to the atmosphere. Solar thermal systems have the capacity to provide heat in a sustainable way for a variety of applications due to the relatively large range of temperatures that different collector configurations can attain. Non-imaging-optics based compound parabolic concentrating reflectors combined with evacuated-tube collectors can operate at 200oC at efficiencies near 50% without the need for tracking. In addition, a trend towards natural working fluids to reduce the effects of global warming and ozone-layer depletion has sparked the proposal of several refrigeration and combined cooling, heating and power cycles using CO2. This paper analyzes the performance of a minichannel-based evacuated-tube solar collector operating with supercritical CO2 suitable for solar-driven Rankine cycle applications. Keywords: minichannel, solar collector, Rankine cycle, cogeneration.
1
Introduction
The fluctuating costs of fuel prices, the increasing demand for energy, and the evident signs of climate change have fostered the development of technologies that utilize renewable energy sources, use more environmentally-friendly WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESU090031
24 Energy and Sustainability II working fluids, utilize low-grade heat sources, and/or have higher energy efficiencies than the more traditional thermal applications. At the legislative level, some states have taken strong action to increase energy efficiency and power generation from renewable energy sources, and to promote the utilization of combined heat and power (CHP) and combined cooling, heating, and power (CCHP) systems. For instance, the California Air Resources Board is planning to increase CHP electricity production by 30,000 GWh by 2020. An important part of a CHP system is the power-generating cycle. In this respect, power cycles that utilize low-grade heat sources such as waste heat or heat from evacuated-tube solar collectors, have been proposed by several researchers. Organic Rankine cycles [1–2] have been proposed but they tend to use working fluids such as isobutane, propane, benzene, or toluene that are either flammable or toxic. Kalina cycles [3] utilize an ammonia/water mixture and consist of extensive internal heat recovery to improve efficiency in thermal power cycles. Although ammonia is a natural working fluid with zero ozone depleting and global warming potentials, it is toxic. Thus, one alternative natural working fluid for power generating cycle or CHP applications corresponds to CO2 [4–7]. Minichannels have successfully been utilized in heat exchangers by the residential air conditioning industry due to their improved performance and compact size compared to round-tube and fin heat exchangers [8, 9]. Minichannel tubes are classified with respect to their hydraulic diameter which covers the range between 200m and 3mm [8]. This technology will allow a reduction of 4.2 quadrillion Btus of electric energy consumption, between 2006 and 2030, and a decrease of 33 million metric tons in carbon emissions [10]. Non-imaging-optics based compound parabolic concentrating (CPC) reflectors [11] combined with evacuated-tube collectors have been shown to operate at temperatures near 200oC with efficiencies of 50% without the need of tracking. Solar collectors vary in performance depending on their design. One key issue that remains a subject of intense research relates to effectively transferring the heat obtained from the sun to the working fluid. Minichannelbased evacuated tube solar collectors have been proposed to improve the efficiency of the collector [12]. This paper analyzes the performance of an evacuated-tube solar collector utilizing minichannel tubes for a solar-driven Rankine cycle producing electric power and hot water.
2
Transcritical cycle
In recent years there has been a trend towards utilizing more environmentally friendly working fluids in air conditioning and low-grade power generating cycles. Carbon dioxide, water, air, hydrocarbons, and ammonia constitute a set of the natural working fluids that provides an environmentally friendly option to reduce ozone depletion and green-house-gas emissions. Table 1 shows a comparison of properties of commonly used working fluids, where global warming potential (GWP) is an index that relates the potency of a greenhouse gas relative to the emission of CO2 over a 100-year period. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
Energy and Sustainability II
Table 1:
R-744 R-12 R-22 R-134 R-407C R-410A R-717 R-290
25
Working fluid property comparison [13]. ODP/ GWP
FLAMMABLE/ TOXIC
0/1 1/8500 0.05/1700 0/1300 0/1600 0/1900 0/0 0/3
N/N N/N N/N N/N N/N N/N Y/Y Y/N
REFRIG. CAPACITY
(kJ/m3) 22545 2734 4356 2868 4029 6763 4382 3907
Carbon dioxide, R-744, has a higher volumetric capacity, higher heat transfer coefficients, and it is readily available which makes it low cost. One drawback is that it requires higher operating pressures. Its ODP and GWP compare favourably with other commonly used working fluids.
3
Minichannel solar collector
A variety of solar collectors available in the market serve different purposes depending on their optimal operating temperature. Absorber surfaces, flat-plate collectors, evacuated-plate collectors, evacuated-tube collectors, and external or internal concentrator with evacuated-tube collector are some of the different options available today. The most common evacuated-tube collectors include a U-tube, a concentric-pipe, or a heat pipe attached to a metal absorber that has a selective coating applied on its external surface. In these designs, heat transfer from the metal absorber to the working fluid encounters several thermal resistances. Heat flows from the absorber to the working fluid by conduction through the absorber fin. Cost reduction results in the absorber thickness being very thin, usually less than a millimetre, creating a resistance to the flow of heat. Also, the absorber is usually wrapped around the pipe carrying the working fluid and ultrasonic-welding is utilized at discrete points to attach the absorber fin to the pipe. Poor contact is obtained at points where the fin is not welded to the pipe. Figure 1a shows a schematic of a counter-flow evacuated-tube solar collector. A minichannel tube can have a similar free flow area as a round-tube but a much larger wetted perimeter. The port dimensions, shown in fig. 1b, tend to be small so that pressure-drop needs to be considered in performance analyses [12]. In solar collectors, the path of the heat transfer involves less thermal resistances than in absorber/round-tube designs. Also, the large wetted perimeter combined with the excellent heat transfer properties of CO2 reduce the amount of working fluid needed inside the collector. Charge minimization is an important safety advantage of minichannel tubes that operate at the high pressures required by CO2. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
26 Energy and Sustainability II Evacuated glass tube
Absorber
Fluid
Mini-channels
Selective coating Evacuated glass tube
(a)
Figure 1:
4
(b)
Schematic of evacuated-tube solar collectors. (a) Absorber/roundtube counter-flow design. (b) Minichannel solar collector.
Model description
In the following subsections we derive the models for the minichannel-based solar collector and the Rankine cycle operating with CO2. 4.1 Solar collector The radiation heat transfer coefficient between the tube and the glass is given by
1 D 1 g ( Ae ) A Dg g
hr Ag , 1
To model the heat transfer to the fluid using minichannels, we need to consider the resistance from the external tube surface to the fluid.
RT 0
t wall 1 kCu P0 L 0 Atot h f
where twall is the tube wall thickness, PO is the tube perimeter, and surface efficiency is given by
0 1 (
NA fin )(1 fin ) Atot
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where N is the number of webs inside the tube, Afin is the cross sectional area of the fin, Atot is the total heat transfer area inside the tube, and the fin efficiency is given by
fin
tanh(m f L fin / 2) m f L fin / 2
1/2
where mf =(hf P/(kCuAfin)) , P is the perimeter of the fin, and Lfin corresponds to half of the length of the tube webs. The energy balance at the glass becomes
Age ( g Gs hair (Tg T ) (Tg Tsky )) AAehr , Ag (Tb Tg ) 0 4
4
4
4
(1) An energy balance at the external tube surface gives
A g
AAe ( Gs hr , Ag (Tb Tg )) Q 1 (1 A ) g 4
where
Q
4
(2)
Tb T f
(3)
RT 0
where Tb and Tf are the tube and fluid temperatures, respectively. 4.2 Solar-powered Rankine cycle The solar-driven Rankine cycle for heat and electric power generation, shown if fig. 2, is modelled using thermodynamic relations.
Solar collectors
b
c Wt Turbine
Heat Exchanger
Condenser e
d
a Pump
Wp
T w out Tw HW
Figure 2:
Tw in
Solar-powered Rankine cycle.
The power generated by the expander and the power used by the pump are modelled as:
W t m(hc hd ) WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
(4)
28 Energy and Sustainability II
where
W p m(hb ha )
(5)
hd hc t ( hds hc ) , hb ha (hbs ha ) / p
(6) (7)
The isentropic efficiencies of the expander and pump have been considered as ηt = 0.7 and ηp = 0.85, respectively. The heat added to the working fluid at the solar collectors is calculated as:
Q m(hc hb )
(8)
The heating of water at the heat exchanger and condenser are modelled as:
m PH (hd he ) m W c pw (TWHW TWout )
(9)
m PH (he ha ) m W c pw (TWout TWin )
(10)
The efficiency () of the CHP system is obtained as:
CHP (W t W p ) / Q 5
(11)
Numerical simulations
Numerical simulations were obtained using the Engineering Equation Solver (EES) software [15] that includes the thermophysical properties of carbon dioxide. The parameters used for the simulations, including the specifications of the evacuated-tube solar collector, are described in table 2 [12]. 5.1 Evacuated-tube solar collector The evacuated-tube solar collector is subdivided in sections along the length and eqns. (1) to (3) are utilized to obtain the performance of a single collector. Figure 3 shows the outlet temperature of the CO2 (solid line) as well as the Table 2: Property Glass tube length Glass external diameter Glass internal diameter Tube major Tube minor Tube wall Web thickness Number of webs Free flow area
Parameters used for the simulations.
Value 1,640mm 65 mm
Dimension External tube perimeter Wetted tube perimeter
Value 183 mm 240 mm
56 mm
α selective coating
0.90
88 mm 3.58 mm 0.7 mm 0.7 mm 21 1.6x10-5 mm2
ε selective coating Solar irradiation ηt ηp Inlet water temperature
0.1 1000 W/m2 0.7 0.85 17oC
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29
0.57 0.56 0.55 0.54
135
0.53 90
0.52
efficiency
Tout [oC]
180
0.51
45
0.5 0 0
0.01
0.02
0.03
0.04
0.49 0.05
mass flow rate [kg/s]
Figure 3:
Tout and efficiency versus mass flow rate for a single solar collector at Tin = 160 (oC). 250
0.7 0.65
200
0.55 100 0.5 50
0 50
Figure 4:
efficiency
Tout [oC]
0.6 150
0.45
85
120
155
T in [oC]
190
0.4 225
Tout and efficiency versus mass flow rate for a single solar collector at mass flow rate of 0.01(kg/s).
efficiency (dashed line) of the minichannel solar collector as a function of mass flow rate for a fixed inlet CO2 temperature of 160 (oC). It is observed that there is no significant gain in efficiency of the collector with mass flow rates higher than 0.02 (kg/s). The outlet temperature of CO2, Tout, remains above 200 (oC) at very low flow rates but it levels off approximately at 164 (oC) as the mass flow rate is increased. Figure 4 shows the performance of a single collector in terms of outlet CO2 temperature and collector efficiency as a function of inlet temperature for a fixed mass flow rate of 0.01 kg/s. The outlet temperature of the working fluid increases linearly with respect to Tin while the efficiency displays a nonlinear behaviour. It is observed that the collector operates at nearly 50% of efficiency WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
30 Energy and Sustainability II at 190 (oC). This is assuming the use of a non-tracking external compound parabolic concentrator designed using non-imaging optics [16]. 5.2 Rankine cycle operation We combined the model of the minichannel evacuated-tube solar collector with eqns. (4) to (11) that describe the performance of the Rankine cycle. The heat obtained at the collectors in eqn. (3) corresponds to the heat added to the Rankine cycle in eqn. (8). Twenty squared meters of collector area are utilized for the simulations. In order to increase the outlet temperature of the CO2, the collectors are connected in a combination of series and parallel configuration. Figure 5 shows the performance of two collectors connected in series operating at a pressure at state (b) of 13 (MPa). No significant gain in collector efficiency is obtained with mass flow rates higher than 0.002 (kg/s). 225
0.7 0.69
190
0.67
155
0.66
120
0.65 0.64
85
collector efficiency
Tout [oC]
0.68
0.63 50 0.001
0.0015
0.002
0.0025
0.003
0.0035
0.004
0.0045
0.62 0.005
mass flow rate [kg/s]
Figure 5:
Collector performance in Rankine cycle as a function of mass flow rate at Pb = 13(MPa). The figure shows the results for two collectors connected in series.
Figure 6 shows the outlet temperature of the hot water TwHW and the efficiency of the Rankine cycle as a function of mass flow rate. It is seen that the maximum efficiency of the Rankine cycle does not correspond to the maximum efficiency of the solar collector. The efficiency of the Rankine cycle decreases with higher mass flow rate mainly because the work of the pump increases at a higher rate than the work of the turbine. The change in the outlet water temperature is not significant, remaining near 30 (oC) for a water flow rate of 0.2 (kg/s). Figures 7 and 8 show the effect of changing the operating pressure of the solar collector in the Rankine cycle at a constant mass flow rate of CO2 of 0.002 (kg/s). The efficiency of the collector in the Rankine cycle decreases only WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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slightly with increasing operating pressure. On the other hand, outlet collector temperature of the CO2 increases significantly with pressure. Figure 8 shows an increase in Rankine-cycle efficiency with increasing solar-collector operating pressure and a small decrease in TwHW with increasing pressure at the collector. The results indicate that an optimization process needs to be performed to obtain the optimum operating point for efficiency of the solar collectors and overall Rankine cycle. 0.08 0.07
31
0.06
TwHW [oC]
30.5
0.05
30
0.04 0.03
29.5
0.02 29
0.01
28.5 0.001
0.0015
0.002
0.0025
0.003
0.0035
0.004
0.0045
Efficiency (Rankine cycle)
31.5
0 0.005
mass flow rate [kg/s]
Figure 6:
Rankine cycle efficiency P collector = 13 MPa. The figure shows the results for two collectors connected in series. 105
0.698 0.696 0.694
95
0.692 0.69
90 0.688 85
0.686
efficiency
Tout [oC]
100
0.684
80
0.682
75 0.68 9500 10000 10500 11000 11500 12000 12500 13000 13500 14000
PCO2 [kPa]
Figure 7:
Tout and efficiency versus pressure at the collector in Rankine cycle for a fixed mass flow rate of 0.002 (kg/s). The figure shows the results for two collectors connected in series.
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32 Energy and Sustainability II
30.9
0.065
30.8
0.06
TwHW [oC]
30.7
0.055
30.6 0.05 30.5 0.045
30.4
0.04
30.3
efficiency (Rankine cycle)
Figure 9 shows a schematic of the pressure-enthalpy diagram for an arbitrarily chosen solar collector pressure of 13 (MPa) and a mass flow rate of 0.0015 (kg/s). The solar collectors outlet CO2 temperature reaches 145 (oC) and TwHW reaches 30 (oC) with a water flow rate of 0.2 (kg/s). It is noted that the carbon dioxide temperature at the exit of the turbine corresponds to 86 (oC). Thus, for residential or small commercial applications that require less amount of water at higher temperature, there is still the potential to increase TwHW.
30.2 0.035 9500 10000 10500 11000 11500 12000 12500 13000 13500 14000
PCO2 [kPa]
TwHW and Rankine-cycle efficiency versus pressure at the collector for a fixed mass flow rate of 0.002 (kg/s). The figure shows the results for two collectors connected in series.
Figure 8:
16 80oC
14
120oC 160oC 200oC
b
c
Pressu re [MPa
12 10 8 a
e
6
20oC
4
10oC 0oC
d
2 0 0
100
200
300
400
500
600
700
800
Enthalpy [kJ/kg]
Figure 9:
Pressure-Enthalpy diagram of the solar powered Rankine cycle.
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33
Conclusions
The thermal analysis of a minichannel-based evacuated-tube solar collector has been performed. The numerical model developed has been combined with the model of a Rankine cycle operating with carbon dioxide. The results show that parameters such as mass flow rate and operating pressure at the solar collector have a significant influence in the performance of the solar collector as well as the overall Rankine cycle.
References [1] Hung, T.C., Waste heat recovery from organic Rankine cycle using dry fluids. Energy Conversion and Management, 42, pp. 539-553, 2001. [2] Vijayaraghavan, S. & Goswami, D.Y., Organic working fluids for a combined power and cooling cycle, Journal of Energy Resources Technology. 127, pp. 125-130, 2005. [3] Kalina, A.I., Combined cycle and waste-heat recovery power systems based on a novel thermodynamic energy cycle utilizing low-temperature heat for power generation, ASME Paper; 83-JPGC-GT-3. 1983 [4] Zhang, X.R., Yamaguchi, H., Fujima, K., Enomoto, M. & Sawada, N., A feasibility study of CO2-based ranking cycle powered by solar energy. JSME International Journal; Series B, 48(3), pp. 540-547, 2005. [5] Yamaguchi, H., Zhang, X.R., Fujima, K., Enomoto, M. & Sawada, N. Solar energy powered Rankine cycle using supercritical CO2. Applied Thermal Engineering, 26, pp. 2345-2354, 2006. [6] Chen, Y., Pridasawas, W. & Lundqvist, P. Low-grade heat source utilization by carbon dioxide transcritical power cycle. Proceedings of ASME-JSME Thermal Engineering Summer Heat Transfer Conference, Vancouver, BC; HT2007-32774, pp. 1-7, 2007. [7] Diaz, G., Performance Improvement of a CO2 Combined Cooling, Heating, and Power Cycle Using Solar Thermal Collectors. Proceedings of SOLAR, San Diego, CA, Paper # 0238, pp. 1-6, 2008. [8] Steinke, M.E. & Kandlikar, S.G., Single-phase heat transfer enhancement techniques in microchannel and minichannel flows. Proceedings of Microchannels and Minichannels ASME Conference, ICMM2004-2328, pp. 141–148, 2004. [9] Yun, R., Kim, Y., and Park, C., Numerical analysis on a microchannel evaporator designed for CO2 air-conditioning systems. Applied Thermal Engineering, 27, pp. 1320-1326, 2007. [10] Air conditioning efficiency standards: seer 12 vs. seer 13. Environmental and energy study institute report, 2001. http://www.eesi.org/030602_ SEER_13 [11] Winston, R., Principles of solar concentrators of a novel design. Solar Energy, 20, pp. 59-67, 1974.
WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
34 Energy and Sustainability II [12] Diaz, G., Performance Analysis and Design Optimization of a Minichannel Evacuated-tube Solar Collector. Proceedings of ASME IMECE, Paper # IMECE2008-67858, Boston, MA, Nov. 2008. [13] Kim, M-H, Pettersen, J., Bullard, C.W., Fundamental process and system design issues in CO2 vapour compression systems, Progress in Energy and Combustion Science; 30, pp. 119-174, 2004. [14] Rahman, F., Al-Zakri, A.S., Rahman, M.A.A., Two-dimensional mathematical model of evacuated tubular solar collector. ASME Journal of Solar Energy Engineering, 106, pp. 341-346, 1984. [15] Klein, S.A. Engineering Equation Solver. Madison, WI, F-Chart Software. [16] Winston, R., Minano, J.C., Benitez, P.G. Nonimaging optics. Elsevier Academic Press, 2005.
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Biomass refineries: relationships between feedstock and conversion approach J.-M. Lavoie1,2, M. Chornet2,3 & E. Chornet1,2,3 1
Industrial Research Chair on Cellulosic Ethanol and 2nd Generation Biofuels, Department of Chemical Engineering, Université de Sherbrooke, Canada 2 CRB Innovations Inc., Canada 3 Enerkem Inc., Canada
Abstract For conversion purposes, biomass can be classified into three main categories: homogeneous biomass (ex.: corn grains), quasi-homogeneous biomass (ex.: forest residues, straws and plantations in marginal lands) and non-homogeneous biomass (ex.: mixed forest residues, MSW, etc.). In North America homogeneous biomass costs (FOB plant) are over 100 $US/tonne in 2009 (anhydrous basis; 1 tonne = 18 GJ), therefore its conversion to biofuels requires subsidies. As well, alternate and added value uses (food and fibre) compete for such category of feedstock. Quasi-homogeneous biomass, whose cost (FOB plant) 30 - 60 $US/tonne in 2009 (anhydrous basis) for forest residues and straws and estimated between 80 and 100 $US/tonne for plantation biomass (i.e. willows, switchgrass, etc.), is suitable for bio-refineries aiming at co-products biofuels, green chemicals and fibres. However, the availability of large quantities of quasi-homogeneous residual biomass is strongly linked to the existing biomass industrial sector since mills processing sugar cane, corn, wheat and wood also have access to such biomass category whose competing use is the generation of bioenergy (process heat and, in some cases, power). It is however possible to integrate a pre-treatment (a better term is “fractionation”) of the quasi-homogeneous biomass to produce useful fractions for biofuels, green chemicals and fibres while using the residual fractions for bioenergy. Nonhomogeneous biomass is available in all urban centers of the planet and constitutes a major opportunity for biofuels and green chemicals since its cost is negative (i.e. it is a disposal cost paid by municipalities to landfills or incineration facilities) and a sustainable society ought to aim at zero residues. Non-homogeneous biomass can be prepared and converted into a homogeneous and clean syngas intermediate. The latter contains typically two thirds of the carbon in the feedstock and technologies to convert it into biofuels and green chemicals are being developed. Keywords: biodiesel, biorefineries, cellulose, ethanol, extractible, gasification, hemicelluloses, homogeneous biomass, lignin, quasi-homogeneous biomass, non-homogeneous biomass. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESU090041
36 Energy and Sustainability II
1
Introduction
The utilization of biomass as a source of energy products requires considering its nature, cost, availability and the potential conversion approaches. Biomass cost is directly influenced by the quality of the carbon structures. As an example, homogeneous biomass obtained from a selected tissue of a defined tree species will be logically more expensive than an ensemble of different tissues from mixed plant species as well as more heterogeneous carbon matrices (such as municipal solid waste). In North America, cost of biomass ranges (2009) from more than 100 $US per anhydrous tonne (ex.: debarked wood chips) to -50 $US per anhydrous tonne (ex.: MSW). Three distinctive categories of biomass can be considered ; homogeneous, quasi-homogeneous and non-homogeneous biomass. Plantations can also be considered for energy products, even though their biomass cost will likely be higher than forest or agricultural straws. Their eventual use is of interest since they may help to reduce the pressure on the forest, particularly when such plantation biomass is grown on marginal lands. 1.1 Homogeneous biomass Lignocellulosic homogeneous biomass has as key example the wood chips from debarked single species used in the pulp and paper mills. Such a biomass has a cost (FOB plant) higher than 100 $US per anhydrous tonne (> 6 $US/GJ), thus rendering it difficult to consider for energy products. Only with co-products from specific fractions of the biomass, can such high-grade biomass be considered for this purpose. 1.2 Quasi-homogeneous biomass Quasi-homogeneous biomass refers to mixed tissues of a single species or of a mixture of closely related species such as residual straws and forest residues. Non-limiting examples are: corn stover [1,2], bagasse and straw from sugar cane plantations [3,4], straw from wheat [5], residual grape biomass [6] and residues from olives processing [7]. Also included in this category is “whole biomass” planted in marginal land: Arundo donax, Cynara cardunculus, Miscanthus sinensis, Panicum virgatum, Sorghum bicolor [8], Eucalyptus gunnii, Populus trichocarpa, Salix viminalis [9,10] and Miscanthus x Giganteus [11] among others. The forest residues produced during forest operations are also included in this category. Such forest residues have been estimated to about 6,9 million tons (anhydrous) per year in the province of Quebec alone [12]. Degraded biomass forest such as the large quantities of pines killed by the mountain pine beetle [13] fall within the quasi-homogeneous biomass category as well. Quasi-homogeneous biomass is composed of chemical structures derived from several types of tissues, thus more complex than homogeneous biomass which comes from specific tissues. Cost for this quasi-homogeneous biomass varies, in North America (2009) from 30 to 60 $US per ton (anhydrous base)
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when residues are considered. Such biomass is a readily available feedstock for conversion processes whether biological, thermo-chemical or in combination. 1.3 Non-homogeneous biomass Non-homogeneous biomass is a category for which the cost ranges from 30 $US/ton (anhydrous basis) to negative values (tipping fee) for “waste”. Such negative value is related to the avoided cost of landfills. The key example of such biomass is municipal solid wastes (MSW) which comprise (i) residential residues (the «garbage»); (ii) institutional, commercial and small industries (ICI) wastes; and (iii) construction and demolition wood (C&W). Included in the latter are contaminated woods such as spent poles and railroad ties and sludge from rendering operations and wastewater treatment plants. These residues are available in large volumes and could become a significant source of carbon for which the supply would be local and recurrent. It is estimated that in the western world each person “produces” close to 1,0 kg of residential MSW per day with an equal amount of ICIs also generated. Only a fraction of such residual materials can be effectively recycled and biocomposted, leaving about half available for conversion processes. Since such materials are highly heterogeneous (MSW contains food remnants, paper, cardboard, plastics, glass and metals), the production of a homogeneous intermediate that can be better used than the original material limits the conversion technologies to a few options. Among these options, biogasification (i.e. anaerobic digestion) of sludge often preceded by a pre-treatment to improve digestibility and thermal gasification of sorted, dried and shredded solid wastes are efficient techniques which allow the production of a homogeneous gas (biogas or syngas). Purification of this gas and neutralization of contaminants allows its utilisation for heat and power production or in catalytic synthesis.
2
Choice of conversion process
The choice of an appropriate conversion technique very much depends on the availability, category and composition of the biomass. With quasi-homogeneous biomass a co-products strategy is possible. Such strategy is related to chemical pulping which is, overall, the isolation of the cellulose fibre from a lignocellulosic matrix. Most of the pulping processes used in the industry coproduce fibres and energy from the residues. The approach implies further separation/isolation of the macromolecular compounds and their conversion to “green chemicals” and/or alternative fuels from the lignin, hemicelluloses and the short chain cellulosic fibres. On the other hand, non-homogeneous and often heterogeneous biomass can, via higher severity conversion processes (pyrolysis or gasification) be transformed to intermediate uniform feeds (char and bio-oil via pyrolysis or syngas via gasification) which are more suitable that the original material for additional conversion into final products.
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38 Energy and Sustainability II 2.1 Biorefineries based on fractionation A general illustration is depicted in Figure 1.
Figure 1:
Illustration of the biorefinery concept (courtesy of CRB) that could be used for the conversion of forest and agricultural quasihomogeneous biomass into biofuels and added value products.
The key goal in fractionation is to isolate the constitutive chemical families present in the feedstock. Thermocatalytic processes of low severity such as solvolysis or steam treatments accomplish this. The fractions produced will subsequently be transformed into defined chemicals and fuels. Any residue is used as source of heat and/or power. 2.1.1 Removal of extractives The quasi-homogeneous biomass contains a certain amount of extractives. These molecules are not part of the structural macromolecules in lignocellulosic plants and are often categorized as secondary metabolites. Extractives are used by plants against insects, fungus and bacteria [14]. They range between 3 to 10 wt% of the dry weight of the biomass. Removal and recovery of the extractives is the first unit operation to consider. Liquid-solid extractions are generally used [15]. Extracts are usually a complex mixture of molecules. Isolation and purification of extractives has lured researchers and industrial groups given the potential applications from aroma chemicals to the pharmaceutical potentials. However the purity required in fine chemicals has limited the use of “bulk extractives” as raw material. The simplest utilization of the bulk extractives in a generic biorefinery would be as input to a cogeneration plant. 2.1.2 Aqueous/steam and organo-solvolytic treatments After removal of bulk extractives, the fractionation of lignocellulosics into constitutive macromolecular families is central to the biorefinery concept. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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Aqueous/steam treatments, of which steam treatments are a well known variation dating back to the beginning of the 20th century [16] are, essentially, hydrolytic processes (with or without soluble catalysts) applied for a few minutes in the temperature range from 170 to 230oC and at a steam pressure equal or higher than the vapour pressure of water at the chosen temperature. In the simplest application, the heated biomass saturated with water is suddenly depressurized and flown at high speed through an appropriately designed nozzle. The downstream side of the nozzle is at lower pressure than the upstream side and thus sudden vaporization of water occurs. The force generated by the sudden vaporization separates the fibres inducing a partial hydrolysis of the hemicelluloses. This technique is actually used as pre-treatment for the production of low cost fermentable sugars [17] for the production of paper [18] and for the production of fiber for board (masonite board as an example). Organo-solvolysis is a process by means of which an organic solvent, mixed generally with water, is used to solubilise specific macromolecules (a large fraction of the hemicelluloses and lignin) liberating cellulose. This technique (also called organosolv pulping) has been demonstrated using acidic water/alcohols media but it has not gained commercial status. The “liquefaction” of cellulose in a mixture of water, acetone and HCl has also been proposed [19]. The utilization of acid ethylene glycol [20] and formic acid [21] has also been studied as organosolv approaches. In both steam treatment and organosolv approaches, the process can be tuned for optimal results on the production of cellulose or sugars depending on severity. Steam treatments allow separation of hemicelluloses and cellulose fractions. Solvolysis usually allows recuperation of native lignin with little modification of the original macromolecule. 2.1.3 Hemicelluloses The hemicelluloses are macromolecules that are produced following a branched polymerization of C5 and C6 carbohydrates. Usually, the hemicelluloses found in ligneous plants are composed of xylose and glucose but also, in lower concentrations, of arabinose and mannose. The constraint concerning this heterogeneous composition of sugars is that the pentoses (xylose and arabinose) are difficult to ferment when using classical micro-organisms. Nevertheless, it has been shown in the last few years that it is possible to ferment xylose using genetically modified organisms [22]. The latter are promising but they are difficult to be used given inhibitors present in the hydrolyzates at industrial level. An alternative is to ferment C6 sugars using known microorganisms (such as yeasts), then use the C5 for dehydration to furfural with simple acid catalysts. At high temperatures, the hexoses are converted to 5-hydroxymethyl-2-furfural while pentoses are converted to furfural (see Figure 2). Furfural could serve as an added value chemical for polymerisation or, through conversion (mainly selective hydrogenation), could yield furanic oxygenates which blend well with established hydrocarbon fuels. The 5-hydroxymethyl-2-furfural is a relatively unstable compound in presence of water and acid catalyst and tends to be converted to levulinic acid and formic acid (see Figure 2). While formic acid WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
40 Energy and Sustainability II could be used as a green chemical, esterification of levulinic acid could lead to the production of biodiesel grade esters. Most of the previously mentioned molecules will likely be significant as a forthcoming generation of ‘green’ chemicals and biofuels [23]. O H HO H H
OH
OH O
H OH
O
H H3C O
OH
O
A
OH
O H HO H
+
O OH H
O
OH
O
H OH
OH
H
B
OH
Figure 2:
Dehydration of glucose to 5-hydroxyméthyl-2-furfural and then to levulinic acid and formic acid (A) and dehydration of xylose to furfural (B).
2.1.4 Delignification In case of solvolysis, lignin is directly solubilised during the treatment. When using steam treatments, delignification of the cellulose-rich fibres obtained from the removal of the hemicelluloses can be performed using either an organosolv method or, as in the Kraft pulping process, with NaOH at concentrations varying in the range 5-20% (wt∞). Abundance of the hydroxide ions will produce partial hydrolysis (the extent of which depends upon severity) of the C-O-C bonds in the lignin macromolecule thus generating monomeric, dimeric and trimeric structures. The alkaline solution allows the solubilisation of the lignin fragments and of the residual lignin itself. The dissolved dimers, trimers and the lignin itself can then be recovered after neutralization of the basic solution using a common acid as H2SO4. The latter will provide a proton to the aromatic structures thus rendering them un-miscible with water. The recovered mix (dimers, trimers and residual lignin) could be used as a source of energy via cogeneration. However, its subsequent secondary hydrolysis (at higher severities than those used in the delignification) could provide (i) additional monomeric units to those initially produced in the delignification step: catechols or aldehydes (vanillin or syryngaldehyde) could thus be isolated; and (ii) dimeric and trimeric compounds which both posses carbon-carbon bonds between the aromatic rings which could be transformed in high octane fuels via hydrotreatment techniques available in petroleum refineries. 2.1.5 Cellulosic fibers and fines Cellulosic fibres are the product derived from biomass having the most important market as a non-food material. In general, steam treatments and organosolv processes provide fibres that have a quality comparable or even better than the classical chemical pulps. Along with the (long) fibres required for pulp, the WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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accompanying short fines are of interest. They could readily be brought to their microcrystalline structure which contains cellulosic chains at polymerization levels not exceeding 220 units. Such chains are linked together with hydrogen bonds. Although the crystalline system is highly polar because of the numerous alcohol functions found on the macromolecules, it is also highly resistant to aqueous solvation because the functional groups are generally oriented toward the center of the crystal. It is therefore usually difficult to attack the bond linking the glucose units and force the depolymerization of cellulose into its monomeric units (glucose). Enzymes are prime candidates as biocatalysts for the depolymerization [24]. Alternatively cellulose can be swollen by water or organic solutions having sufficient ionic strength to break the H-bonded matrix. Once cellulose is swollen its depolymerization (i.e. hydrolysis) to glucose, fermentation to ethanol or other end products is possible. 2.2 Pyrolysis and Gasification Non-homogeneous biomass is a complex and often variable mixture of numerous carbon-based structures. The amount of different compounds renders this type of feedstock difficult to fractionate. The biorefinery approach needs to yield homogeneous intermediates that can be upgraded to defined and marketable end products. Pyrolysis and gasification accomplish such goal by forcing major changes in the carbon-based structures. Pyrolysis (also known as thermal decomposition or thermal cracking), produces three streams: gas (normally used to fuel the process itself), a “bio-oil” (a complex mixture of dehydration water, organic compounds derived from carbohydrates, lignin and their cracked carbon structures) and residual charcoal (char as it is commonly known). In rapid pyrolysis processes, bio-oil (50 -70 wt% of the biomass) and char (10 – 20 wt% of the biomass) are the two intermediates that can be conveniently transported (they have higher bulk energy densities than the original solid feedstock) and used directly for their energy content (case of bio-oil replacing petroleum-based products in furnaces) and char as a soil additive. The bio-oil can also be fractionated into an essentially waterfree oligomeric lignin-rich fraction and an aqueous fraction which contains carbohydrate-derived compounds (aldehydes to a large extent). The oligomeric lignin fraction can be used very much like a near-petroleum feedstock (oxygenated since it has a phenolic structure) in crackers and hydrocrackers located in petroleum refineries. Alternatively, the oligomeric lignin-rich fraction can be catalytically converted into oxyaromatics having value as green chemicals (for instance, catechols) and biofuels (for instance, alkoxyaromatics). The aqueous fraction containing carbohydrate-derived compounds can also be upgradable to simpler intermediates, such as hydrogen. It can also be concentrated, via membranes, and used directly as fuel. With heterogeneous feedstock (such as “urban biomass”: sorted municipal solid waste residues), the pyrolysis route is constrained because of possible contaminants in the bio-oil. With such feedstock, synthetic gas is by far the best alternative because independently of the nature of the biomass used, it is essentially a homogenous intermediate. When oxygen and steam are used as WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
42 Energy and Sustainability II partial oxidation agents, the synthetic gas becomes syngas, which can be used for chemical synthesis if its conditioning and purification reaches levels that make it compatible with catalysts. Gasification is thus attractive because of its flexibility regarding feedstock. Urban biomass is a preferred input material because of its negative cost (i.e., the avoided landfill cost). Gasification of bio-oil can also be carried out. Biomass can thus be pyrolyzed in regional plants, the bio-oil transported and converted in a larger gasification and synthesis plant. Economies of scale may thus offset the high cost of the quasi-homogeneous biomass. Gasification of biomass is usually performed at temperatures close to 800oC [25]. However, the choice of temperature as well as the process conditions leading to the formation of syngas are highly dependent on the nature of the feedstock given the presence of inorganic salts (recognized as ‘ash”) having lowsoftening points often at near or lower temperatures than 800oC. Chlorides are particularly low melting point salts. Temperatures in the thermal decomposition zone thus need to be adjusted to the nature of the inorganics present in the raw material. The chemistry of the reactions involves the following sequence: dehydration, thermal decomposition, partial oxidation and steamdriven and, to a lesser extent, CO2-driven reactions. The initial products of this complex process will be gas, intermediates and char. Such a mixture undergoes the reactions shown in Table 1. Table 1:
Identification of the major chemical reactions associated with the gasification of carbon-based compounds.
Reaction C + ½O2 = CO CO + ½O2 = CO2 H2 + ½O2 = H2O C + CO2 2CO C + H2O CO + H2 C + 2H2 CH4 CnHmOk + aO2 + bH2O = cCO + dCO2 + eH2
Identification 1 2 3 4 5 6 7
Among these reactions it is possible to identify oxidation reactions (1,2,3), the Boudouard reaction (4), the water-gas shift (5), the methanation reaction (6) and the autothermal reforming reaction of the oxygenated compounds produced by dehydration and by thermal decomposition (7). The latter reaction (7) includes CO2 + H2]. All these reactions permit to the shift reaction [CO + H2O understand the importance of an oxygen input when feedstock as coal or plastic is gasified. Reactions 4, 5, 6 and 7 shows that it should be possible to control the composition of the syngas by partial oxydation of the char produced during its thermal decomposition. This particularity is important when it is necessary to homogenize the composition of the syngas independently of the gasified feedstock. The reforming of the oxygenated compounds is also an important aspect allowing the generation of a syngas with a limited amount of chemical WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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compounds as output. Carbon monoxide and hydrogen are the key compounds for synthesis and will also allow the utilization of advanced concepts such as coupling gasification with fuel cells. In equation (7), the coefficients a-e will depend upon the temperature and the composition of the oxygenated intermediates. Yields of synthetic gas vary within a range of 1.8 – 2.2 Nm3/kg biomass (dry) for air gasification and 0.8 to 1.0 Nm3/kg biomass (dry basis) for O2/steam gasification. The dry synthetic gas contains about 75% of the energy in the biomass being gasified. In addition heat recovered from the hot synthetic gas adds about 10% for a total of 85% as recovered energy. Low grade heat accounts for 5% and the rest and the remaining energy balance is due to the endothermic reactions and losses. Gas composition varies somewhat with technology and operating conditions. Table 2 shows typical compositions from Enerkem’s gasifiers operated with air and O2 / steam. Note the beneficial effect of reforming in reducing the gas mix components. The gasification technologies are usually categorized in three families; the slowly moving (often named “fixed”) bed reactor (in either downdraft or updraft Table 2:
Typical syngas compositions from biomass.
Gas compound
Air Gasification (Low severity)
Air gasification (Low severity) + steam reforming
O2 / steam Gasification (Low Severity)
O2 / Steam Gasification (Low severity) + steam reforming
N2 Ar H2 CO CO2 CH4 C2H4 CxHy (C2C5) CxHy (C6 and higher)
55.8 0.8 9.5 10.3 14.1 4.2 2.2 2.1
35.5 0.5 35.2 17.9 10.9 0.5 0 0
0.5 0.3 11.8 20.4 41.1 10.0 8.6 6.6
0.3 0.1 47.0 23.2 29.4 traces 0 0
O2 / Steam Gasification (Low severity) + steam reforming + CO2 scrubbing (partial removal) 0.4 0.2 65.0 32.0 2.4 traces 0 0
1.0
0
0.7
0
0
*Composition can be varied by adjusting the reforming step with steam and CO2 for specific applications. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
44 Energy and Sustainability II mode), the fluidized bed reactor and the entrained flow gasifier with or without slag formation. The fixed bed gasification relies on establishing a “pile” of solid material that is reacting progressively, and thus slowly moving downwards due to gravity. Addition of oxidant and of steam is done at strategic zones of the “pile”. Such approach, with numerous geometrical variations and feeding systems is the most ancient configuration used for the formation of synthesis gas. Coke or anthracite which are relatively pure carbon structures were used early on readily producing “water gas”. Lignocellulosic biomass can also be used as a feedstock but due care is needed for the management of the intermediate tar. Downdraft gasifiers where the gas is flown through a hot incandescent char zone permits to reach low tar levels in the synthetic gas produced. Fluidized beds imply inert solids (sand, alumina or olivine) being fluidized by air or oxygen/steam. The carbonaceous material is inserted in or just on top of the bed where the heat and mass transfer coefficients are high (200 – 500 watts/m2). This technique was identified as the most suitable for the gasification of biomass [25]. It requires that the size of the biomass particles that are introduced in the reactor is not superior to a few centimetres. The fine carbon particles that exit the bed entrained by the gas undergo additional conversion in the upper part of the reactor. A cyclone permits to recycle unconverted solids. The entrained flow gasifier is well developed for the gasification of fine coal particles and could also be used for biomass. In this type of process, the grinded feedstock is converted co-currently with the oxiding agent and steam in essentially a flow reactor. If the temperature at which the conversion is done is sufficiently high, the biomass will not produce any char residues and the slag will be solidified by contacting it with a liquid phase from which the solids are recovered. Unwanted components of synthetic gas comprise tars (composed of polyphenolics and poly-aromatics compounds), chlorine-based compounds (as HCl), sulphur (as H2S and COS), un-converted carbon particles as well as metal salts (mainly oxides). For further use the synthetic gas (syngas), needs to be purified. The sequential treatment used for the purification of the syngas is directly related to the utilization that is intended for it. When the gas is produced for the synthesis of alcohols or alkanes, removal of particulates and tar, as well as reduction of chlorine-based and sulphur-based compounds must reach essentially zero levels. As well carbon dioxide levels need to be compatible with desired synthesis strategies. In the last few years, numerous papers have been published on the purification of syngas. Experimental data points to sequential hot gas conditioning and wet scrubbing techniques capable of producing a clean syngas ready to be used for catalytic synthesis. Neutralization of chlorine using CaO is an efficient technique that permits to get rid off residual HCl. But reducing sulphur to sub-ppm levels (ppm = mg/Nm3) is a difficult task and thus catalytic reforming of the tar and low molecular weight hydrocarbons has not, to our knowledge (2009) been successfully implemented for long period of times (in excess of 200 h). If thermal reforming (without catalyst) is used, the destruction of the tar is not complete yet its removal can be achieved via scrubbing techniques. The latter use either aqueous or oil-based systems or a combination. The H2/CO ratio is adjusted during the thermal reforming step by WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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conducting such step at appropriate severities and steam/carbon ratios. Particulate levels are lowered to ppm levels via a combination of cyclones and scrubbers. Alternatively metal and ceramic filters have been tested. Final purification of the syngas for catalytic synthesis uses CaO and ZnO filters as well as chilled methanol (other solvents can also achieve the same result) which permits, as well, to adjust the CO2 concentration in the syngas to the desired level. Nitrogen gases, namely NH3 and HCN are not an issue since during the thermal reforming and subsequent scrubbing they are removed. Cleaning and recirculating the scrubbing liquids is an inherent component of the gas conditioning strategy. It implies stripping the dissolved gases and vapours and, as well, precipitating out as sludge the fine particulates present in the liquid phase.
3
Conversion of syngas to biofuels
Production of methanol from syngas is industrially practiced. Copper/zinc oxidebased catalysts show high productivities up to 2 kg of MeOH per kg of catalyst per hour [26] with selectivities reaching near the 100% level. Production of ethanol and long chain alcohols is one of the most researched areas currently (2009) in this field. Conversion of syngas to ethanol can be done using two distinct pathways: the direct catalytic conversion (associated with drastically lower conversion yields if compared to the methanol synthesis) or via the separate homologation of methanol. The latter pathway allows one to take advantage of high production yields associated with methanol synthesis yet it has a higher complexity than the direct pathway because of the additional synthesis steps required. Production of alkanes from synthesis gas is known as the Fisher-Tropsch synthesis (FT). At the industrial level, cobalt and iron are used as catalysts at temperatures close to 340oC. Such conditions allow converting close to 40% of the syngas into gasoline and 20% in propene and butene which can be partially inserted in synthetic fuel to increase its octane level [27]. The yields of useful product that can be commercialized as gasoline or as diesel following a FT synthesis are lower than those observed in the methanol synthesis [28]. The latter can be converted to gasoline via catalytic oligomerization, which constitute an alternative to the FT synthesis.
4
Conclusions
For the conversion of lignocellulosics to biofuels a decision on the technological route to be followed very much depends on the type and cost of biomass and availability within a reasonable transportation distance that does not exceed 100 km, as the norm in North America. For this purpose biomass can be categorized as follows: homogeneous biomass (>100 $US/t), quasi-homogeneous biomass (30-60 $US/t) and non-homogeneous biomass (≤ 0 $US/t, dry basis). Among the biofuel production techniques that are actually entering the market, gasification is by far the most versatile because it can be applied to all the different types of WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
46 Energy and Sustainability II biomass previously mentioned. However, because of the biomass availability and cost, the feedstock targeted by gasification will be preferentially nonhomogeneous biomass which permits moderate capacity plants (100 000 t biomass input, dry basis, per day) and, as well, quasi-homogenous biomass, the latter requiring, via gasification, large economies of scale. The homogeneous and quasi-homogeneous biomass, because of their higher costs (about 100 $US for homogeneous to a range of 30-60 $US per anhydrous tonne for quasihomogeneous) could be adapted to a co-product strategy. The biorefinery concept, using fractionation approaches, will allow the isolation and the utilization of the constitutive fractions of the biomass. Such approaches should also be designed to be self-sufficient in terms of energy. The isolated constitutive fractions are the “secondary biomass feedstock” for upgrading to marketable end products” green chemicals, biofuels and fibres.
Acknowledgements The authors would like to show their appreciation to the companies that are funding the Industrial research chair on cellulosic ethanol and 2nd generation biofuels: Enerkem, CRB Innovations and Ethanol Greenfield. We would also like to acknowledge NSERC for the strategic grant provided for the conversion of hemicelluloses and to the ABIP grant for the conversion of lignin. We would also like to acknowledge our colleagues Prof. J. Lessard for his input on hemicellulosic sugars conversion and Prof. N. Abatzoglou for his pioneering work on gasification and gas conditioning technologies.
References [1] Yan, L., Zhang, H., Chen, J., Lin, Z., Jin, Q., Jia, H. & Huang, He. Dilute sulfuric acid cycle spray flow-through pretreatment of corn stover for enhancement of sugar recovery. Bioresource Technology, 100(5), pp. 18031808, 2009. [2] Dasari, R.K., Dunaway, K. & Berson, R.E. A Scraped Surface Bioreactor for Enzymatic Saccharification of Pretreated Corn Stover Slurries. Energy & Fuels, 23(1), pp. 492-497, 2008. [3] Rabelo, S.C., Maciel Filho, R., & Costa, A.C. A comparison between lime and alkaline hydrogen peroxide pretreatments of sugarcane bagasse for ethanol production. Applied Biochemistry and Biotechnology, 148(1-3), pp. 45-58, 2008. [4] Martin, C., Marcet, M. & Thomsen, A.B. Comparison between wet oxidation and steam explosion as pretreatment methods for enzymatic hydrolysis of sugarcane bagasse. BioResources, 3(3), pp. 670-683, 2008. [5] Georgieva, T.I., Hou, X., Hilstrom, T. & Ahring, B.K. Enzymatic hydrolysis and ethanol fermentation of high dry matter wet-exploded wheat straw at low enzyme loading. Applied Biochemistry and Biotechnology, 148(1-3), pp. 35-44, 2008.
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[6] Lapuerta, M., Hernandez, J.J., Pazo, A. & Lopez, J. Gasification and cogasification of biomass waste: Effect of the biomass origin and the gasifier operating conditions. Fuel Processing Technology, 89(9), pp. 828-837, 2008. [7] Link, S., Arvelakis, S., Spliethoff, H., De Waard, P. & Samoson, A. Investigation of Biomasses and Chars Obtained from Pyrolysis of Different Biomasses with Solid-State 13C and 23Na Nuclear Magnetic Resonance Spectroscopy. Energy & Fuels, 22(5), pp. 3523-3530, 2008. [8] Monti, A., Di Virgilio, N. & Venturi, G. Mineral composition and ash content of six major energy crops. Biomass and Bioenergy, 32(3), 216-223, 2008. [9] Sugiura, A., Tyrrel, S.F., Seymour, I. & Burgess, P.J. Water renew systems: wastewater polishing using renewable energy crops. Water Science and Technology, 57(9), pp. 1421-1428, 2008. [10] Labrecque, M. & Teodorescu, T.I. The influence of site and wastewater sludge fertilizer on the growth of two willow species in southern Quebec. Biomass: A Growth Opportunity in Green Energy and Value-Added Products, 4th Proceedings of the Biomass Conference of the Americas, Oakland, pp. 31-37, 1999. [11] Cappelletto, P., Mongardini, F., Barberi, B., Sannibale, M., Brizzi, M. & Pignatelli, V. Papermaking pulps from the fibrous fraction of Miscanthus x Giganteus. Industrial Crops and Products, 11(2-3), pp. 205-210, 2000. [12] Goyette, J. & Boucher, S. Communication from the engineering firm Roche, november 2008 Établissement d’une chaufferie centrale à la biomasse forestière : Lignes directrices dans un contexte québécois. [13] Pan, X., Xie, D., Yu, R.W. & Saddler J.N. The bioconversion of mountain pine beetle-killed lodgepole pine to fuel ethanol using the organosolv process. Biotechnology and Bioengineering, 101(1), pp. 39-48, 2008. [14] Canales, M., Hernandez, T., Rodriguez-Monroy, M.A., Jimenez-Estrada, M., Flores, C.M., Hernandez, L.B., Gijon, I.C., Quiroz, S., Garcia, A.M. & Avila, G. Antimicrobial Activity of the Extracts and Essential Oil of Viguiera dentata. Pharmaceutical Biology, 46(10-11), pp. 719-723, 2008. [15] Lavoie J.-M. & Stevanovic T. Ultrasonic Extraction of Lipophilic Constituents of Yellow Birch (Betula alleghaniensis) and White Birch (Betula papyrifera) Wood, Phytochemical analysis, 18(4), p. 291-299, 2007. [16] Marshall, G.H. Preparing cellulose from pithy or woody stalks, US 982379 19110124 Patent, 1911. [17] Viola, E., Cardinale, M., Santarcangelo, R., Villone, A. & Zimbardi, F. Ethanol from eel grass via steam explosion and enzymatic hydrolysis, Biomass and Bioenergy, 32(7), pp. 613-618, 2008. [18] Westenbroek, A.P.H., van Kessel, L.P.M., Hooimeijer, A., Thuene, P.C., Nierstrasz, V.A., Koopal, L.K., Lamot, J.E., Waubert de Puisseau, M., van Willige, R.W.G., Adriaanse, M., Lund, H., Dorschu, M. & Theunissen J. Fibre raw material technology for sustainable paper and board production, Paper Technology, 46(7), pp. 17-24, 2005. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
48 Energy and Sustainability II [19] Paszner, H.L. & Chang P.-C. Separation of cellulose fibers from lignocellulose. BE 870112 19781218 Patent, 1978. [20] Rezzoug, S.-A. & Capart, R. Liquefaction of wood in two successive steps: solvolysis in ethylene glycol and catalytic hydro-treatment. Applied Energy, 72(3-4), pp. 631-644, 2002. [21] Kleinert, M. & Barth, T. Towards a Lignincellulosic Biorefinery: Direct One-Step Conversion of Lignin to Hydrogen-Enriched Biofuel. Energy & Fuels, 22(2), pp. 1371-1379, 2008. [22] Jeffries T.W. Engineering the Pichia stipitis genome for fermentation of hemicellulose hydrolysates, Bioenergy , pp. 37-47, 2008. [23] Qi, X., Watanabe, M., Aida, T.M. & Smith R.L. Catalytical conversion of fructose and glucose into 5-hydroxymethylfurfural in hot compressed water by microwave heating, Catalysis Communications, 9(13), pp. 2244-2249, 2008. [24] Mussatto, S.I., Dragone, G., Fernandes, M., Milagres, A.M.F. & Roberto, I.C. The effect of agitation speed, enzyme loading and substrate concentration on enzymatic hydrolysis of cellulose from brewer's spent grain, Cellulose, 15(5), pp. 711-721, 2008. [25] Higman, C. & van der Burgt, M. Gasification. Elsevier: New York. 391 pp., 2003. [26] Pass, G., Holzhauser, C., Akgerman, A. & Anthony, R.G. Methanol synthesis in a trickle-bed reactor. AIChE Journal, 36(7), pp. 1054-60, 1990. [27] Dry, M.E. The Fischer-Tropsch process: 1950-2000. Catalysis Today, 71(34), pp. 227-241, 2002. [28] Luo, M., O'Brien, R. & Davis, B.H. Effect of Palladium on Iron FischerTropsch Synthesis Catalysts. Catalysis Letters, 98(1), pp. 17-22, 2004.
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Elimination of siloxanes by adsorption process as a way of upgrading biogas D. Ricaurte Ortega & A. Subrenat GEPEA - UMR CNRS 6144, Ecole des Mines de Nantes, France
Abstract Biogas is increasingly being investigated as a source of renewable energy, however its utilisation requires an improvement of its quality. Certain biogases contain compounds called siloxanes; these compounds are the origin of some problems when using biogas. At high temperatures siloxanes are transformed to silicate oxides which can damage equipment (i.e. engines corrosion, the clogging of fuel cell membranes.). This paper provides details of the research done in the treatment of siloxane by adsorption process of adsorption. Different porous materials were studied in order to evaluate adsorption capacities. Influences of humidity and temperature on the mass transfer were evaluated. Moreover, reactors were filled with a mixture of methane and carbon dioxide (principal compounds on the biogas) in order to evaluate the impact of the gas composition in the adsorption capacities. Finally the capacity of adsorption is also evaluated in the presence of an organic volatile compound (VOC). Activated carbon cloth was chosen to continue with the experiences realised for the adsorption – desorption process. This porous material has shown good adsorption capacities. Furthermore, desorption process can be performed in situ and their implementation in industrial process is more easy. Adsorption-desorption cycles were performed and the possibilities of the material regeneration evaluated. Joule effect was employed in the desorption process in order to reduce the duration of regeneration. First cycles have been accomplished. Results are promising, even if the operational conditions of the process must be optimised. Keywords: siloxanes, biogas, adsorption, desorption, activated carbon cloth, zeolite, Joule effect.
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50 Energy and Sustainability II
1
Introduction
Research in alternative sources of energy and the commitment of industrial countries towards a reduction of fossil fuel dependency have resulted in a growing interest in the use of biogas. This gas is produced in most of the Europeans countries, from landfills and digesters. The composition is basically methane (50-60%), carbon dioxide (3040%), nitrogen (2-5%), oxygen (0.1-1%) and others different compounds (less than 0.2%) [1], though the composition varies according to its origin. Biogas can be used in many different applications, fuel for vehicle, CHP engines, fuel cells, and all applications designed for natural gas, among others. However, suppliers and manufacturers often hesitate to use it due to the presence of organometallic compounds such as siloxanes [2]. The term siloxane makes allusion to a subgroup of silicones containing Si-O bonds with organic radicals attached to the atom of silicon.. These compounds can be viewed as a hybrid of both organic and inorganic compounds. The organic side chains confer hydrophobic properties while the -Si-O-Si-Obackbone is purely inorganic. Siloxanes are widely used in different applications: health care, dry cleaning, household products, paints and coatings, paper, personal care and so on. Due to their volatile nature, they are usually dispersed into the atmosphere. Siloxanes can also be presents in slurry from landfills. Due to this physical structure they can be classified in two groups, linear and cyclical molecules. During anaerobic digestion, when the temperature goes up to 60°C siloxanes are volatilised, forming part of the biogas. The growing consumption of siloxanes and silicones in industry has increased its predominance n the environment, restricting the possibilities of biogas upgrading and its utilisation as a source « of green energy ». At high temperatures siloxanes are transformed to silicate oxides (SiO2 or/and SiO3). An atom of silicone is liberated and bonded to the free oxygen (present in the environment). The main problem with silicate is the damage sustained by the equipment, seriously reducing its efficiency. In engines, silicate may adhere to metal or catalytic substrate surfaces forming a thickness of several millimetres difficult to remove by chemical or mechanical means, Priebe et al. [3]. In fuel cells, siloxanes can generate clogging in the membrane, Peregrina and Audic [4]. Depending on the origin of biogas, the amount of siloxane in the biogas can vary from 0 to 140 mg.m-3, Huppmann et al. [5]. Engine manufacturers usually recommend not to exceeding a limit of 5 mg.m-3 siloxane in biogas. There are no exhaustive studies in the literature concerning the treatment of siloxanes in biogases. Some of these researches are enunciated. Absorption into tetradecane, Schweigkofler and Niessner [6], cryogenic condensation, Ajhar and Melin [7], gas permeation, Wheless and Pierce [8], etc. on this paper adsorption technology will be performed. Nevertheless, for different reasons (costs, generation of secondary products, recycling material and low adsorption capacities) these techniques are not well adapted to a procedure of siloxane’s elimination.
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The main objective of this study is to evaluate de feasibility of an adsorption process. This process is developed as a treatment of siloxane to reduce its presence in biogas. Three different porous materials are studied, activated carbon cloths, granular activated carbon and zeolite. The influence in the adsorption capacities of siloxanes is studied under the presence of methane and carbon dioxide in excess (representative of a biogas), humidity, and other volatile organic compounds (VOC). Temperature is also another determinant factor on this study.
2
Adsorption in batch reactor
2.1 Experimental procedure The porous material sample is confining into a batch reactor in order to proceed with the adsorption process. The mass of the material remains constant in each reactors (0.5g approximately). All the reactors are maintained under the same operative conditions. A certain volume of siloxanes is injected into the reactors, this quantity changes in each reactor and so the initial concentration of the pollutant. Therefore the adsorption capacity can be measured. All the measurements are performed by a Gas Chromatograph (y) connected to a Flame Ionisation Detector (GC-FID). Isotherms can be modelled with the Freundlich model. This model is based on the adsorption on monolayer (isotherm type I). Equilibrium adsorption capacity (qe) can be calculated according to the equation:
qe = KC
1 n e
(1)
Where Ce is the concentration in the rector after adsorption, K and n are the parameters of the equation, which depend on the nature of the gas. The siloxane compounds used in this study were selected due to their presence in biogas, McBean [9] and because of their physical structure. Octaméthylcyclotetrasiloxane (D4) was chosen as a cyclical compound and Hexaméthyldisiloxane (L2) as a linear compound. Some of their properties are listed below: Table 1: Name (Symbol) Hexaméthyldisiloxane (L2) Octamethylcyclotetrasi loxane (D4)
Physicochemical properties of siloxanes. Molecular formula
Molecular weight (g.mol-1)
Density at 20°C (g.m-3)
Melting point (°C)
Boiling point (°C)
Vapour pressure at 25°C (kPa)
C6H18OSi2
162.4
0.764
-67
100
4.12
C8H24O4Si4
296.6
0.956
17.4
175
0.17
Three different porous materials are studied; zeolite (DAY 40), chosen by its hydrophobic character and the presence of silicon atoms as part of its composition. Activated carbon in grain (ACG - NC 60) commonly used in VOC WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
52 Energy and Sustainability II adsorption, Le Cloirec and Faur [10]. Activated carbon cloth (ACC - FM 30K) recently studied with very good adsorption capacities, Subrenat and Le Cloirec [11]. Physical characterisations of these adsorbents are assembled in table 2. Table 2: Material
Texture
ACC - FM 30K ACG - NC 60 Zeolite - DAY40
Cloths Grain Grain
Physical properties of the materials. BET Surface (m2.g-1) 1000 1220 607
Micro porous Volume (cm3. g-1)
Total porous Volume (cm3.g-1)
0.371 0.320 0.227
0.494 0.670 0.328
% Volume Micro porous 75 47 69
2.2 Results and discussions Classical isotherms were obtained after adsorption. Modelling can be developed from the Freundlich model, eqn (1). In this model the coefficient K represents the maximal adsorption capacity, bigger is the coefficient K bigger is the capacity of the material to adsorbed the pollutant. For the coefficient n, the adsorption capacity will increase rapidly when the coefficient approaches to zero. As mentioned before, influence in adsorption capacity is studied under different operative conditions. Freundlich coefficients are presented in table 3. Table 3: Compound
Coefficients of Freundlich model for the isotherms adsorption. RH (%) 0
L2 70
D4
0
VOC 0 Tol g.m-3 0 Tol g.m-3 1 g.m-3 10 g.m-3
RH (%) 0 70
Dry Air Adsorbent K FM 30K 293.97 25 NC 60 341.17 DAY 40 123.60 60 FM 30K 265.05 FM 30K 290.01 25 NC 60 294.61 DAY40 104.82 FM 30K 386.73 25 DAY 40 124.10 60 FM 30K 302.92 Methane and carbon dioxide mixture with L2 Temperature (°C) Adsorbent K 286.57 271.98 25 FM 30K 257.02 226.09
Temperature (°C)
1/n 0.048 0.115 0.133 0.057 0.061 0.068 0.179 0.041 0.047 0.055
R2 0.938 0.944 0.953 0.999 0.988 0.950 0.908 0.825 0.909 0.925
1/n 0.077 0.064 0.058 0.056
R2 0.922 0.894 0.977 0.945
2.2.1 Influence of the porous material To observe the influence of the porous material, isotherms were realised under the same operative conditions. In the following example, siloxane L2 was used at 25°C with 0% humidity. The results are showed in fig. 1. The highest adsorption capacity was observed with the ACG – NC 60 (350 mg.g-1), while the lowest was obtained with zeolite DAY 40 (less than 150 mg.g-1). As a matter of fact, the WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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Figure 1:
53
Influence of the porous material.
B.E.T. surface is related to the adsorption capacity, the larger the surface, the larger the capacity (see table 2.). 2.2.2 Influence of temperature Two temperatures were tested, 25°C and 60°C. Temperature was found to be inversely proportional to the adsorption capacity. The capacity decreases over 40 mg.g-1. In fact, siloxanes at high temperature tend to remain suspended in the atmosphere and not absorbed into the material. These results are supported by previous studies, Le Cloirec [12]. 2.2.3 Influence of the gas composition The adsorption capacity of siloxanes is studied according to various compositions of the gases enclosed in the reactors. The principle of these experiences is to emulate to the composition of a real biogas. As mentioned before, mainly methane, carbon dioxide, water, and some organic volatile compounds (VOC) form biogas. - Influence of humidity Adsorption capacities were measured under a relative humidity of 70% in the reactors. Results depend on the material. For the activated carbon cloth, no difference was appreciated. However for the activated carbon in grain this WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
54 Energy and Sustainability II difference is more perceptible, the dissimilarity is due to their micro porosity, more open for activated carbon in grain (NC 60) (approximately 20 mg.g-1 of difference). In the case of zeolite, a reduction on the adsorption capacity is noticed. This small discrepancy (5 mg.g-1) can be explained because of the hydrophobic character of zeolite. It is important to remark upon the low solubility of siloxanes in water, which also explains the small difference obtained between the adsorption capacities in presence of humidity versus a dry atmosphere. - Influence of methane and carbon dioxide Biogas can be described as basically a mixture between methane (CH4) and carbon dioxide (CO2). It is important to analyse their influence on the adsorption. A mixture of CH4 (50%) and CO2 (50%) was made and introduced into the reactors. This resulted in an adsorption capacity decrease (over 20 mg.g-1), as there competition between the methane and the siloxanes for being absorbed into the material. The results are shown in fig 2.
Figure 2:
Influence of methane and carbon dioxide mixture.
- Influence of volatile organic compound (VOC) Finally, toluene is used to analyse the implication of a VOC in the mass transfer. Two different concentrations of toluene (1 g.m-3 and 10 g.m-3) were used. In order to continue with the “biogas simulation”, reactors were also filled with, a WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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CH4 – CO2 mixture and a humidity of 70%. The adsorption capacity decreases considerably. More than 50 mg.g-1 of difference between the capacities was observed. Compounds such as methane, toluene, water and siloxanes are in competition to get adsorbed into the material, reducing in this way the final capacity of the adsorption of siloxanes. Fig 3. shows these results.
Figure 3:
3
Influence of VOC – Toluene.
Adsorption in dynamic system
3.1 Experimental procedure Activated carbon cloth was chosen to perform adsorption – desorption cycles. This porous material has shown good adsorption capacities compared to the others porous materials used in this study. However, these capacities remain low. For that reason a growing interest to develop shorts cycles in time. Moreover different studies over the utilisation of activated carbon cloth and their advantages in desorption process has been analysed by Subrenat and Le Cloirec [13] and Subrenat et al. [14]. Capacity for recycling of the material is very important in the selection of a treatment technology for siloxane, reducing times and costs. Adsorption – desorption cycles are performed. Electrical heating of the material known as a Joule effect is used in the desorption process. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
56 Energy and Sustainability II The adsorbent material (approximately 10g) is placed into a tubular canalisation of stainless steel and a small diameter. A thermocouple is installed into the material for posterior control of its heating. A flow of air charged with siloxane (L2) passes through the filter (adsorption process). When the adsorption time finishes, the filter starts to be heated by an electrical current, fig. 4. Once the target temperature is reached, a new air current (without siloxane) pass through the filter to carry out the desorbed compounds (desorption process).
Figure 4:
Dynamic system.
A control panel installed on a computer is related to the adsorption – desorption system. The characteristics of the adsorption – desorption cycles experiences are listed below and they are easily modifiable on the operative system. Table 4:
Adsorption – desorption cycles characteristics.
Time (min) Temperature (°C) Flow ( m3.h-1) Siloxane (L2 – mg.m-3)
Adsorption
Desorption
20
90
25
100
2.5
2.5
250
0
The adsorption capacity on dynamic systems can be calculated from the mass balance transfer. 3.2 Results and discussions First cycles are accomplished. The experiments of adsorption - desorption cycles have shown the feasibility of a treatment process for siloxane removal. Nevertheless, adsorption capacities decrease considerably over time. The stabilisation of cycles is reached after the third cycle. Fig 5 shows the capacities obtained for the first six cycles. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
Energy and Sustainability II
Figure 5:
4
57
Adsorption capacity on adsorption – desorption cycles.
Conclusion
The viability of siloxane elimination by an adsorption process into a porous material is demonstrated. Good adsorption capacities were found with the materials. The adsorption capacity decreases with the increase of the temperature. Mass transfer is reduced in the presence of water (humidity), VOC (Toluene), methane, and carbon dioxide (principal compounds on a typical biogas). Competition between these compounds results in the material lowering of the adsorption capacity of siloxanes into the material. Activated carbon cloth was chosen to continue with the study on adsorption – desorption cycles, not only because of its adsorption capacities, but also for the ease of implementation into industrial processes. Moreover, this material can be heated in situ by Joule’s effect. Parameters of the adsorption – desorption cycles were established from the experiences in batch reactors. First cycles are accomplished. The adsorption capacity shut down remarkably, the interest of realise rapid cycles is know more important. Electrical heating reduces the duration required for regeneration. In this way material can be regenerated quickly and so the size of the installation reduced. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
58 Energy and Sustainability II Results are promising, even if the operational conditions of the process must be optimised.
References [1] Le biogaz energie renouvelable, http://www.biogaz-energierenouvelable.info/biogaz_composition.html [2] Biogas upgrading and utilisation, http://www.iea-biogas.net/ Dokumente/Biogas%20upgrading.pdf [3] Priebe, C. Grooterhorst, A., Jansen, T., Los siloxanos pueden poner en peligro la viabilidad del aprovechamiento energetico del biogas. Residuos: Revista técnica, pp. 88, 2002. [4] Peregrina C, Audic J, De la boue de station d'épuration à l'hydrogène : Un grand défi technologique, Xèmes Journées Cathala-Letort de prospective scientifique et technique, SFGP,(2008). [5] Huppmann R., Lohoff H.W. and Schröder H.F., Cyclic siloxanes in the biological waste water treatment process—determination, quantification and possibilities of elimination, Fr J Anal Chem, pp. 66–7, 1996 [6] Schweigkofler M. and Niessner R., Determination of siloxanes and VOC in landfill gas and sewage gas by canister sampling and GC–MS/AES analysis, Environ Sci Technol, pp. 3680–3685, 1999 [7] Ajhar M., Melin T., Siloxane removal with gas permeation membranes. Elsevir desalination, 234-235, 2006. [8] Wheless, E., Pierce, J., Siloxanes in landfill and digester gas update Swana 27th LFG Conference, 2004. [9] McBean, E.A., Siloxanes in biogases from landfills and wastewater digesters. Canadian Journal of civil engineering. Canada, pp. 431–436, 2008. [10] Le Cloirec, P., Faur, C., Adsorption of organic compounds onto activated carbon – applications in water and air treatments (chapter 8). Interface science and technology. pp. 375–419, 2006. [11] Subrenat A., Le Cloirec P., Volatile organic compound (VOC) removal by adsorption onto activated carbon fiber cloth and electrothermal desorption: an industrial application, Chem. Eng. Comm., pp. 1–9, 2006. [12] Le Cloirec P., Les composés organiques volatils (COV) dans l'environnement, Tech.& Doc./Lavoisier .1997. [13] Subrenat, A., Le Cloirec, P., Thermal behaviour of activated carbon cloths heated by Joule effect, Journal of Environmental Engineering, pp. 1077– 1084, 2003 [14] Subrenat, A., Baléo, J. N., Le Cloirec, P., Electrical behaviour of activated carbon cloth heated by Joule effect. Carbon, pp. 707–716, 2001
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Gasified residual/waste biomass as solid oxide
fuel cell feed for renewable electricity production J. Jurewicz & N. Abatzoglou Chemical and Biotechnological Engineering Department, Université de Sherbrooke, Sherbrooke Québec, Canada
Abstract Gasification of waste biomass, a renewable feedstock, is considered as a sustainable technology for producing environmentally friendly feed (biosyngas) for fuel cells. This work examines the contaminants contents (i.e. sulphur and halogens) of typical waste biomass sources and evaluates their nuisance to Solid Oxide Fuel Cells (SOFC) performance for the two most considered types of anodes: metal-ceramic composites (cermets) and composite oxides. The necessity and the extent of physico-chemical purification of the bio-syngas and its cost depend upon the chemical stability of the anode material. These needs as well as their associated costs are evaluated and a first assessment of the sustainability of such solutions is undertaken and commented. Keywords: waste, biomass, gasification, sulphur, halogens, SOFC, syngas, gas purification, anode, cermet, composite oxide ceramics.
1
Introduction
As world energy consumption increases (currently ≈ 2% per annum [1]), the analysis [2] of energy scenarios concluded that it is possible to address simultaneously various sustainable development objectives, using available resources and technical options. The foreseen solutions are based on some combination of better exploitation of renewable resources, higher energy conversion efficiencies, and advanced energy conversion technologies. The latter includes the development of a variety of fuel cells, now widely identified [2] as a long term solution for higher than conventional energy conversion to electricity, WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESU090061
60 Energy and Sustainability II co-generation (combined heat and power or CHP), motive power and transport. Some important characteristics of the studied fuel cell technologies are presented in Table 1. The high operating temperatures of molten carbonate (MCFC) and solid oxide fuel cells (SOFC) make them well suited for co-generation [4]. Moreover, SOFC technology offers considerably higher CHP efficiencies, potentially longer operating lifetimes [5], safer operation due to the absence of a molten solid phase and lower capital and operational costs than MCFC. The typical «sandwich» type SOFC assemblies are composed of three, functionally distinct, layers (anode – electrolyte – cathode) where the anode is designed for electrochemical oxidation of the fuel associated with the charge transfer to a conducting contact. The most critical characteristics of materials considered as potential candidates for SOFC anodes are: electronic conductivity; oxygen diffusivity (ionic conductivity); oxygen surface exchange (reactivity); chemical stability and compatibility; thermal expansion; mechanical strength and dimensional stability under redox cycling. The particular advantage of the SOFC concept over all other types of fuel cells, is its ability to operate with a variety of fuels, both gaseous – such as methane, biogas, biosyngas, and liquids – such as gasoline, jet fuel, diesel fuels and oxygenates, e.g. methanol, ethanol (and bio-ethanol) and “green diesel”. However such a variety of fuels with their inherent contaminants make more stringent the requirements of anode’s chemical stability and compatibility. This capacity of solid oxide fuel cells to work with fuels originating from renewable resources like biomass is of particular interest. Table 1: Fuel Cell Type Polymer Electrolyte Membrane (PEM) Alkaline (AFC) Phosphoric Acid (PAFC) Molten Carbonate (MCFC) Solid Oxide (SOFC)
Comparison of fuel cell technologies [3].
Operating Temperature [oC]
System Output [kW]
Electrical Efficiency [%] 53 – 58 (transportation) 25-35 (stationary)
50 – 100
< 1 – 250
90 – 100
10 – 100
60
< 80 (low grade waste heat)
150 – 200
50 – 1000
> 40
< 85
600 – 700
< 1 – 1000
45-47
< 80
600 – 1000
< 1 – 3000
35-43
< 90
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CHP Efficiency [%] 70 – 90 (low grade waste heat)
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The aim of this work is to detail the constraints imposed in order to render compatible the use of syngas originating from residual and waste biomass gasification with the SOFC anodes.
2
Residual biomass availability
While renewable, so called “Green Power”, resources (hydro, wind, solar thermal and photovoltaic, geothermal, marine and biomass) are geographically more evenly distributed than fossil and nuclear resources, and energy flows from renewable resources are several thousand times higher than current total global energy use, the statistics [2] indicate that only 13,7% of worldwide primary energy use comes from renewable resources. The observed [6] most recent increase of global trade of woody biomass, primarily for energy, from 5,6 million tons in 2003 to over 11 million tons in 2007, witnesses the interest in such source of green energy. The economic potential of renewable sources is affected by many constrains including competing land use, the amount and timing of solar irradiation and wind patterns, as well as some other environmental factors. The land use is to be given priority for both human and animal feeding and, in most cases where the soil allows it, even the residuals from crop and forest harvesting are preferably to be left to replenish land’s nutrients [7]. However it is proposed [6] to periodically harvest for long-lived wood products which results in substantially greater carbon storage than when forests are left in an unmanaged state. The US Energy Information Administration, which forecasts US energy production, considers four components to the biomass supply schedule: agricultural residues, energy crops, forestry residues and urban wood waste/mill residues. The analysis [8] of their price and availability reveals that the less costly (1,42 $/GJ) is almost exclusively post-consumer urban wood waste/mill residue. Next (at 1,90 $/GJ and higher) come the agricultural residues followed by energy crops and forestry residues (at 2,18 $/GJ or higher). Such results confirmed similar projections obtained earlier [9]. The post consumer urban wood waste/mill residues include: - wood materials (like slabs, edgings, trimmings, sawdust, veneer clippings and cores, and pulp screening) and bark generated at primary (lumber) manufacturing plant; - similar wood scraps and sawdust from woodworking shops, furniture factories, wood container and pallet mills; - wood residues from Municipal Solid Waste (wood chips and pallets), utility tree trimmings and construction and demolition sites. At the European market [10] the post consumer wood is classified as: - A - quality wood: clean wood; - B - quality wood: slightly contaminated, e.g. with paints, glues and coatings; - C - quality wood: hazardous wood waste contaminated with heavy metals, fire retardants and wood preservatives.
WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
62 Energy and Sustainability II The analysis [11] of markets for recovered wood in Europe indicates, that in Germany only in year 2003 up to 6,531 million tonnes of post consumer wood were available for the price of 20-30 euro/ton air dry of A – quality wood and 717 euro/ton air dry for B – quality wood. Such variety of wood residue feedstock is usually mechanically homogenized and converted into commercially available product - wood pellets.
3
Wood pellets as a fuel
Wood pellets as heating fuel originated in the US during the 1970s in response to high energy prices [12] but became recently a significant form of biomass consumption for energetic purposes with world market trades exceeding 3 000 000 tonnes per year [13]. Quite thorough analyses of global wood pellets markets and industry including policy drivers, market status and raw materials have been published recently [14]. Sweden, Canada and USA are world leading pellets producers with an annual production capacity exceeding 3 500 000 tonnes [14]. The production of wood pellets is based on several mechanical operations of milling interlaced with drying. This sequence is ending up with pressing through a mould with simultaneous plasticizing (due to lignin and resin content) of the wood. The latter operation may require some additives (like starch) for sawdust originating from hardwood (less rich in lignin) feedstock for preservation of the final shape of the pellet. The chemical elemental composition of such biomass-derived fuels depends upon the biomass type [15], the origin of the residue and its pre-processing prior to its final destination (use). The fuel components, once consumed, will all end up transformed preferably to element’s oxides either in the gaseous (i.e. CO2) or in solid form (ashes) and will be released to environment. While carbon dioxide and water are neutral, the release of all other compounds to the environment is regulated by norms; namely by standardization of the biomass fuels initial composition. Table 2 presents the acceptable limits of sulphur and chlorine, both Table 2:
Tolerated limits of sulphur and chlorine according to prevailing worldwide legislation.
Austrian ÖNORME M7135
Element: Wood pellets: Bark pellets :
German DIN51731 / DIN plus Swedish SS 187120
Group 1 : Group 2 : Group 3 :
Sulphur ≤ 0,04%* ≤ 0,08%* ≤ 0,08% ≤ 0,08% ≤ 0,08%
Chlorine ≤ 0,02% ≤ 0,04% ≤ 0,03% ≤ 0,03% ≤ 0,03%
CEN (draft) ** ≤ 0,05% CEN/TS 14961: 2005 Annex A * Dry basis; ** Recommended to be stated in category: Cl 0,03 ; Cl 0,07 ; Cl 0,10 ; Cl 0,10+ (if Cl > 0,10% the actual value to be stated) WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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elements being considered as hindering the long term operation of SOFC devices. The comparison of the sulphur limits, as imposed by different legislations, with residual sulphur contents in a variety of clean (pristine – without any manmade additives) biomass [16] indicates, that pure bark pellets, as well as many herbaceous fuels, could not be accepted – their residual sulphur content being above the imposed limits. The combustion of contaminated (B - quality) wood pellets for heating purposes bears some environmental consequences like increase of particulate emissions [17] beyond the current EU emission limit for dust as well as formation of dioxins [18].
4
Wood pellets from Canadian sources and their life cycle analysis
Canada has substantial Green Power resources and the natural potential to generate about half of its current electricity needs (∼590 TWh) using Green Power [19]. While current installed, biomass based technologies, count for 1 935 MW (just above 1% of its total generation capacity) percentage substantial rise might be expected when co-generation technologies will be used [19]. The Canadian wood pellet industry is predominantly located in 3 provinces: British Columbia (33% of production), Quebec (28% of production) and Ontario (20% of production) [20]. Its production capacity, as well as different market sales, are presented in Fig. 1. The origins of the raw materials for wood pellets production are the following:
3500 3000 2500
[kT]
2000 1500 1000 500 0 1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
Year Production Capacity
Figure 1:
Actual Production
Domestic Sales
US Sales
Overseas Sales
Evolution of Canadian wood pellet industry and different markets [21].
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64 Energy and Sustainability II -
Saw mills; where harvested wood (pine, Douglas fir, spruce, birch and Western Red Cedar) is converted into lumber (construction wood) and remaining saw dust, bark and other residues like shavings, standing for about 15% [3] of the total volume of the harvested wood, are transformed into pellets. - Standing dead wood either after a forest fire or as a result of infestation (e.g. infestation of pine forest by Mountain Pine Beetle). Both reasons are making remaining wood unsuitable for usual application in timber or paper industries. Such raw material (whole tree trunk) requires more energy to convert it into the shavings size needed by pellet industry. Such sources might be extended significantly by harvesting forest thinning, which are considered not only unnecessary to replenish forest nutrients but also the main reason for rapid spreading of forest fires. According to Canadian Forest Service [22] between 2,5 to 3 million hectares of forests are lost to about 10 000 forest fires every year. Canada is the world’s most prominent exporter of wood pellets and its main partner is Europe. Such long haul transport, means an energy consumption (mainly fossil) estimated [23] at 2,40 $/GJ for a 35000 ton vessel travelling a distance of 18000 km [24]. Moreover, it represents a high environmental nuisance because of the Green-House-effect Gases (GHG) generated during the overseas transport [25]. The life-cycle assessments of Canadian wood pellets exported from province of British Columbia (Prince George) to Sweden (port of Stockholm) are presented in Table 3. Energy consumed for each stage of the wood pellet production and transport (adapted from [26]).
Natural Gas as fuel
2,60
Sawdust as fuel
Energy consumed [GJ/ton] 0,52 0,07 3,78 2,97 0,26 Energy consumed if 7 1 52 4 sawdust as fuel [%] Energy consumed if 8 1 46 4 Natural Gas as fuel [%] *Trucking of lumber to mill (110 km) and residues to pellet plant (27 km)
Parameter
Transport*
Transport by ocean vessel (15500 km)
Process stage Production Transport by train (750 km)
Harvesting of lumber
Table 3:
36 40
The analysis of above data suggests, that while half of the energy is consumed for actual pellets production, their post-production transport requires between 40 and 44% of total energy. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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65
Gasified biomass as a feed for SOFC devices
Gasification appears to be the dominant biomass conversion technology. The gaseous products (syngas or biosyngas) from gasification processes are considered as vectors of high-efficiency power production or of the synthesis of chemicals and fuels. Each application requires specific syngas composition and the existing gasification technologies offer this possibility because this composition depends upon the gasification process, the gasification agent (air, oxygen, oxygen-enriched air and their mixtures with steam) and the processing temperature. Generally [27], for gasification processes carried-out at high temperatures (above 1200oC) the biomass is completely converted into CO and H2 (besides H2O and CO2) with an absence of tars which makes this technology interesting for a variety of chemical synthesis routes leading to high-end products. For processing temperatures between 800-1000oC the as-produced gas composition is characterized by a larger variety of chemical species including (besides CO2 and H2O) CO, H2, CH4, aliphatic hydrocarbons, benzene, toluene, and heavier compounds under the generic name “tars”. A thorough review on tar is available in the literature [28]. The energy contained in typical syngas components (CO, H2) stands for about 50% of the total, the remaining 50% being carried by CH4 and higher (aliphatic and aromatic) hydrocarbons making such gas useful for power generation purposes or for production of synthetic natural gas (SNG) [27]. Such as-obtained gas requires important post-gasification treatment like thermal cracking or reforming to match the quality of the gas produced during gasification at higher temperatures. Among the variety of gasification technologies classified as direct (autothermal) and indirect (or allo-thermal) processes the latter group is of particular interest as it offers nitrogen-free product gas as no oxygen is required for the gasification as well as carbon-free ashes. Another advantage of this technology is the possibility of operating it at smaller scale (less then 5 MWth) making it interesting candidate for distributed generation devices where the produced gas is fed into solid oxide fuel cells unit. During the analysis of such an option it is important, among others, to compare the produced gas composition with that required by SOFC unit. The composition of the gas produced from wood by three different indirect gasification technologies is presented in Table 4. An analysis of the gas composition reveals that all combustibles contained in the produced gas are ¨consumable¨ at typical, Ni-based cermet type SOFC’s anode: • Both hydrogen and carbon monoxide are desired SOFC fuels; • Methane, C2+ hydrocarbons and benzene are being reformed to CO and H2 at high temperature over such anodes with catalytic reforming activity in the presence of steam originating from hydrogen consumption over anode’s surface; • Ammonia is considered [29–31] as very interesting SOFC fuel; • Carbon deposition over anode’s surface due to tar presence may be avoided under specific current density [32];
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66 Energy and Sustainability II •
Solid particles are filtered [33] from the gaseous fuel prior to SOFC unit. The only component of biomass gasification product, which is undesired, is the hydrogen sulphide. At very low concentrations of 0,05; 0,5 and 2 ppm, tested at 1023, 1173 and 1273 K respectively, the anode activity losses are reported [34] to be reversible once the fuel no longer contains H2S. At temperatures below 1073 K the sulphur poisoning was found [35] to be irreversible. The cell voltage drop increases significantly with H2S concentration in the fuel from 1 to 3 ppm and saturates at 5 ppm [36]. The reforming of methane on catalytically active sites is affected [37] as well. Table 4:
Typical gas composition of three indirect gasification processes [27].
Process Gas component, dry basis 1 2 Hydrogen H2 [vol%] 30 – 45 20 – 22 Carbon monoxide CO [vol%] 20 – 30 41 – 44 Carbon dioxide CO2 [vol%] 15 – 25 11 – 14 Methane CH4 [vol%] 8 – 12 12 – 16 C2+ hydrocarbons [vol%] 1–3 4–6 Benzene C6H6 [vol%] 1 Nitrogen N2 [vol%] 1–3 2 – 10 Ammonia NH3 [ppmV] 500 – 1000 Hydrogen sulphide H2S [ppmV] 50 – 120 Tar [g/mn3] 0,5 – 1,5 40 Particles [g/mn3] 10 – 20 1 – Fast Internal Circulation Fluidised Bed (FCIB) process; 2 – SilvaGas process; 3 – MILENA process
3 15 – 20 40 – 43 10 – 12 15 – 17 5–6 1 1–4 500 – 1000 40 – 100 40 -
To prevent such decrease in Nickel cermet based SOFC performances the removal of sulphur bearing compounds from the feed gas to acceptable level is required. A recent thorough review on H2S removal technologies is available in the literature [38]. Although this review covers the biogas purification most of the reviewed technologies can be used as well in the case of the syngases. The extrapolation of the permissible sulphur concentration in the natural gas feed, considering a deactivation rate of Ni-based planar SOFC of 0.75% per 1000 h (6.4% per year) has indicated the value of 18 ppb [35]. Such ¨deep¨ cleaning is very difficult to reach; only zinc-based sorbents operating at 673-823 K are reported [39] to be effective in removing of H2S to 1 ppm levels at elevated temperatures but not high enough to match typical operating temperatures of gasifier/SOFC tandem. The known deep gas cleaning technologies offers the possibility to lower the residual sulphur content but with excessive cost making such operation much less profitable from the economic stand point. The reported [40] cost of fuel processing module (sulphur removal unit, catalyst, fuel preheater and ejector) accounts for 33% of the total (without stack) balance of power (BOP) investment for 5 kW unit for building applications. The model for WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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250 kW planar SOFC unit for CHP application specifies [41] the cost of fuel system as 8% where the stack counts for 31% of total cost. It is clear that high sensitivity of Ni-cermet based anodes to sulphur bearing compounds inherently present even in pristine biomass makes the gas conditioning circuit more complex and increase overall investment and operational costs of BOP. The possible Nickel-free, sulphur-tolerant replacement for SOFC anode materials like fluorite, rutile, tungsten bronze, pyrochlore, perovskite and spinel structures were identified [42] and reviewed [43–45]. The direct oxidation of methane [46, 47] or diesel fuel [48] over substituted perovskites anodes are reported as well. The all-perovskite (anode, electrolyte and cathode) SOFC may be of particular interest due to structural similarity of layers. Such fuel cell [49], based on the “sandwich” of the (La0,75Sr0,25)0,95Cr0,5Mn0,5O3-δ (LSCM) as the anode, La0,8Sr0,2Ga0,8Mg0,15Co0,05O3-δ (LSGMCo) as the electrolyte and Gd0,4Sr0,6CoO3-δ (GSC) as the cathode, can minimize the polarization losses between electrolyte and electrodes, where the slight inter-diffusion between the perovskite components observed results in better contact at the interface, allowing for smoother transfer of oxygen ions between the electrodes and electrolyte. However the actual performances of composite oxide anodes do not match these obtained for Ni-based cermet anodes. More research efforts have to be carried out for optimization of both their composition and performances. For such complex structures the application of the combinatorial chemistry approach in their synthesis is of particular interest. Another concern for more widespread SOFC usage is the cost of their fabrication. The thermal plasma spraying, which is industrially proven and widely accepted technology, offers both rapid prototyping through combinatorial chemistry method as well as less-costly industrial mass-production allowing integrated deposition of all subsequent layers (anode, electrolyte and cathode) in one operation.
6
Conclusion
The possibility of the significant increase of biomass energy conversion efficiency for SOFC based Combined Heat and Power generation cycle is of special interest especially for colder climate regions like northern Canada. The export of Canadian biomass as far as to Europe makes overall energy balance (energy contained in biomass vs. energy consumed for its transport) less favourable – up to 40% of energy is lost to transport. The gasification process, compared to simple combustion or incineration, offers a better control of the release to environment of undesired conversion products, like manmade impurities contained in lesser quality wood’s residues, while still allowing for the full usage of their energy content. The direct gasification of as-obtained biomass (without drying, size reduction and pelletizing stages) may preserve both energy spent for pellets formation and that contained in the volatiles (mainly terpenes) usually lost [50] during drying process. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
68 Energy and Sustainability II The sulphur content represents a technological challenge for the gas conditioning technologies because Nickel-based SOFCs are ultra sensitive to sulphur bearing compounds. Consequently, the cleaning is usually complex and costly. The SOFC based on composite oxide anodes are sulphur tolerant and are considered as a replacement to Ni cermet anodes; however their actual electrochemical performances are still inferior to the Nickel based ones. The variety of the possible structures of composite oxides (perovskite-related like titanates, chromites, vanadates, gallates, niobates and ferrites; cubic fluorite related like zirconia-based and ceria-based as well as pyrochlores and spinels) makes combinatorial chemistry useful promising tool towards optimizing SOFC anode’s elemental composition and structure. The thermal plasma deposition technology allows for rapid SOFC prototyping using combinatorial chemistry approach as well as further industrial mass production of entire multi-layered fuel cells.
References [1] Mason J.E., World energy analysis: H2 now or later, Energy Policy, 35, pp. 1315-1329 (2007) [2] Goldemberg J. et al, World Energy Assessment, Overview 2004 Update, United Nations Report, (2004) [3] U.S. Department of Energy [4] Williams R.H., Advanced energy supply technologies, in World energy assessment, United Nations Report, (1998) [5] Bakker W., Advances in Solid Oxide Fuel Cells’ EPRI Journal, 21, (5), pp. 42-45, (1996) [6] UNECE/FAO, Forest products annual market review, (2008) [7] Pimentel D., et al, Biomass Energy from Crop and Forest Residues, Science, 212, pp. 1110-1115, (1981) [8] Haq Z., et al, Agricultural Residue Availability in the United States, Applied Biochemistry and Biotechnology, 129-132, pp. 3-21, (2006) [9] Easterly J., et al, Overview of biomass and waste fuel resources for power production, Biomass and Bioenergy, 10, 2-3, pp. 79-92, (1996) [10] Leek N., Data collection for post consumer wood in the Netherlands, Probos [11] Van Benthem M., et al, Markets for recovered wood in Europe; Case studies for the Netherlands and Germany based on the BioXchange project, Proc. 3rd European COST E31 Conf., 2-4 May 2007, Klagenfurt, Austria [12] Kotrba R., Closing the Wood Pellet Gap, Biomass Magazine, February (2009) [13] Forest News WIRE, June (2008); PR press release at: http://www.pr.com/press-release/89107 [14] Peksa-Blanchard M., et al, Global Wood Pellets Markets and Industry : Policy drivers, Market Status and Raw Material Potential, IEA Bioenergy Task 40 report, November (2007) WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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[15] Nordin A., Chemical elemental characteristics of biomass fuels, Biomass and Bioenergy, 6, 5, pp. 339-347, (1994) [16] Obernberger I., et al., Chemical properties of solid biofuels – significance and impact, Biomass and Bioenergy, 30, pp. 973-982, (2006) [17] Khan A., et al., Scale-up study on combustibility and emission formation with two biomass fuels (B quality wood and pepper plant resudue) under BFB conditions, Biomass and Bioenergy, 32, pp. 1311-1321, (2008) [18] Lavric A.D., et al., Dioxin levels in wood combustion – a review, Biomass and Bioenergy, 26, pp. 115-145, (2004) [19] Canadian Renewable Energy Alliance, Green Power for Electricity Generation – Creating an Industry in Canada, August (2006) [20] EUBioNet2, No 10-2 [21] Adapted from Canadian Wood Pellet Industry web page [22] Canadian Forest Service, The nature of forest fires, (2004) (http://canadaforests.nrcan.gc.ca/articletopic/32) [23] Aruna P., et al., An analysis of wood pellets for export: a case study of Sweden as an importer, Forest Products Journal, 47, 6, pp. 49-52, (1997) [24] Duffy A., et al., Embodied transport energy analysis of imported wood pellets, Transactions of the Wessex Institute, [25] Svedberg U., et al., Hazardous Off-Gassing of Carbon Monoxide and Oxygen Depletion during Ocean Transportation of Wood Pellets, Annals of Occupational Hygiene, 52 (4), pp. 259-266 (2008) [26] Magelli F., et al., An environmental impact assessment of exported wood pellets from Canada to Europe, Biomass & Bioenergy, 33, pp. 434-441, (2009) [27] Boerrigter H., et al., Review of applications of gases from biomass gasification, Rapport ECN.RX-06-066, (2006) [28] Milne T., et al., Biomass Gasifier "Tars": their Nature, Formation, and Conversion, The Biomass Energy Foundation Press, ISBN 1-890607-14-2 (1998) [29] Fournier G.G.M., et al., High performance direct ammonia solid oxide fuel cell, J. Power Sources, 162, pp. 198-206, (2006) [30] Meng G., et al., Comparative study on the performance of an SDC-based SOFC fuelled by ammonia and hydrogen, J. Power Sources, 173, pp. 189193, (2007) [31] Fuerte A., et al., Ammonia as efficient fuel for SOFC, J. Power Sources, (2008), doi:10.1016/j.jpowsour.2008.11.037 [32] Singh D., et al., Carbon deposition in an SOFC fuelled by tar-laden biomass gas: a thermodynamic analysis, J. Power Sources, 142, pp. 194199, (2005) [33] Sharma S.D., et al., A critical review of syngas cleaning technologies – fundamental limitations and practical problems, Powder Technology, 180, pp. 115-121, (2008) [34] Matsuzaki Y., et al., The poisoning effect of sulphur-containing impurity gas on a SOFC anode: Part I. Dependence on temperature, time, and impurity concentration, Solid State Ionics, 132, pp. 261-269, (2000) WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
70 Energy and Sustainability II [35] Cunningham R.H., et al., Sulphur poisoning of the active materials used in SOFCs, Report to Rolls-Royce, F/01/00222/REP, URN 04/559, (2004) [36] Sasaki K., et al., H2S Poisoning of Solid Oxide Fuel Cells, J. Electrochem. Soc., 153 (11) A2023-A2029 (2006) [37] Ouweltjes J.P., et al., Biosyngas Utilization in Solid Oxide Fuel Cells with Ni/GDC Anodes, (EFC2005-86089), 1st European Fuel Cell Technology and Applications Conf., Rome (2005), [38] Abatzoglou N., et al., A Review of Biogas Purification Processes, Biofuels, Bioproducts & Biorefining, 3, pp. 42-71 (2009) [39] Aravind P.V., et al., Impact of biosyngas and its components on SOFC anodes, Electrochem. Soc. Proc., 2005-07, pp. 1459-1467, (2005) [40] Brown J.R., et al., Assessment of SOFC in Building Applications, Solar Energy Laboratory, University of Wisconsin Madison, prepared for: Energy Center of Wisconsin, Nov. (2001) [41] Fontell E., et al., Conceptual study of a 250 kW planar SOFC system for CHP application, J. Power Sources, 131, pp. 49-56 (2004) [42] Tao S., et al., Discovery and Characterization of Novel Oxide Anodes for Solid Oxide Fuel Cells, Chemical Record, 4, pp. 83-95 (2004) [43] Gong M., et al., Sulfur-tolerant anode materials for solid oxide fuel cell application, J. Power Sources, 168, pp. 289-298 (2007) [44] Sun C., et al., Recent anode advances in solid oxide fuel cells, J. Power Sources, 171, pp. 247-260 (2007) [45] Goodenough J.B., et al., Alternative anode materials for solid oxide fuel cells, J. Power Sources, 173, pp. 1-10 (2007) [46] Tu H., et al., Performance of Alternative Oxide Anodes for the Electrochemical Oxidation of Hydrogen and Methane in Solid Oxide Fuel Cells, Fuel Cells, No 3-4, pp. 303-306, (2006) [47] Tao S., et al., Methane oxidation at Redox Stable Fuel Cell Electrode La0,75Sr0,25Cr0,5Mn0,5O3 - δ, J. Phys. Chem B. 110, pp.21771-21776, (2006) [48] Liu D.J., et al., Activity and Structure of Perovskites as Diesel-Reforming Catalysts for Solid Oxide Fuel Cell, Int. J. Appl. Ceram. Technol., 2, No.4, pp. 301-317 (2005) [49] Tao S., et al., An Efficient Solid Oxide Fuel Cell Based upon Single-Phase Perovskites, Adv. Mater., 17, pp. 1734-1737 (2005). [50] Stahl M., et al., Industrial processes for biomass drying and their effect on the quality properties of wood pellets, Biomass & Bioenergy, 27, pp. 621628 (2004)
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Lighting the world with LEDs S. J. Riley1 & M. Telugu2 1
Sustainable Technology and Engineering Research Group, University of Western Sydney, NSW, Australia 2 MIC Technologies (Australia) Pty Ltd, NSW, Australia
Abstract Light Emitting Diodes (LEDs) present an opportunity to improve public health and to provide low-cost lighting to villages while significantly reducing CO2 emissions, petroleum fuel consumption, and hazardous waste. Lighting accounts for approximately 19% of the world’s greenhouse gas emissions and widespread use of LED lighting would significantly reduce this. Aspects of LED technology, the use of LED in lighting the developing world, and means of rapidly deploying the technology in an affordable manner are discussed. Keywords: LED lighting, public health, appropriate technology, energy conservation.
1
Introduction
The world’s population of 6 billion is expected to expand to 9 billion in the next 40 years [1]. In the absence of apocalyptic population reduction or a political will to reduce population growth the additional 3 billion people will have to be fed, clothed, housed, educated and provided with gainful employment. The consequences of this increase in population will be significant increases in resource use, particularly energy, whose availability underlies the technological and life-style advances of the last 3 centuries [2]. However, an increase in energy, using existing technology, will result in increased greenhouse gas emissions, which may impact on already stressed populations through climate change. Predictions of the problems of resource availability for the future of humanity are not new. The predictions of Malthus [3] and the Club of Rome [4] were addressed by technology development [5], which increased the availability and WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESU090071
72 Energy and Sustainability II security of food supplies, accessed energy resources in previously unavailable situations, and housed people in ever increasing clusters of high population density. These developments have required increased per capita energy consumption. There are several sources of energy that do not significantly impact on the environment, but supply is only half of the solution of managing the impact of energy use. The other part of the solution is to provide increased efficiency in energy use. Significantly reducing the per-capita demand for energy may meet the energy demands of increased population growth without increasing energy production. There are many national energy efficiency programs [6, 7]. Yet it has to be noted that a 50% increase in population requires a 33% improvement in energy efficiency to maintain today’s level of energy consumption per capita, and this does not allow for improving life-styles in the majority of the world that has the lowest per capita energy consumption, i.e. the developing economies. Energy efficiency savings will not be similar across all sectors of the economy, or all nations of the world, but the hope is that there will be a net decrease in per capita energy use. The most likely positive scenario to meet the future energy needs will be a combination of energy efficiency and energy production that has low impact on the environment in order to obtain the necessary target of providing energy for all without sacrificing the planet. This paper addresses the issue of providing cheap low-cost lighting to communities while addressing the energy consumption issue at the same time. The technology based around Light Emitting Diodes (LEDs) provides the opportunity of improving energy efficiency (in this case watts per lumens) which, when combined with PhotoVoltaic power generation, also provides the opportunity for alternative energy sources to be implemented to provide the power. The issue of ensuring the rapid uptake of this technology in an environment of poverty, low-technology training, and lack of familiarity with the technology is also addressed.
2
LEDs and energy efficiency
An LED is a PN junction semi conductor diode that emits monochromatic light as electrons, which move from the anode (p-side) to cathode (n-side), fall into a lower energy state and release energy. The wavelength of the light depends on the gap energy of the p-n junction. Light emitting diodes are not a new technology, by the standards of the rapid development in technology of the last 50 years [8], but there have been significant improvements in the last 20 years that are now available in the market place. These developments are part of continuing technological improvement, and research in a number of places around the world is improving the cost of production, efficiency and capacity of LEDs [9, 10]. It is estimated that 19% of the world’s energy is used for lighting: equivalent to the energy required for all transport and in equivalent greenhouse gas emissions equal to that produced from domesticated animals [11]. So the potential for energy and greenhouse gas emission savings is significant [12, 13]. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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At this stage LEDs are the most efficient light production system in terms of lumens per watt, having overtaken CFLs, and are still improving at a significant rate [14, 15]. Compact Fluorescent Lights (CFLs) are now widely used in domestic, commercial and industrial circumstances. They are very efficient compared with the incandescent lights and have much longer design lives, but have an environmental issue of mercury contamination, which neither discarded incandescent lights nor LED lights have. This contamination issue is well recognised, but is being rationalised against savings in energy. The savings in energy compensate the release of mercury in coal-fired powered stations. A CFL light may have 5-15mg of mercury (Hg) while a tonne of coal can release 0.1g of Hg or more [16]. LEDs do not pose a significant environmental problem, and have longer design lives and energy efficiency than CFLs. Short-term costs may be higher, but long term savings are significant. Their reduced power consumption results in a reduction of Hg production at power stations. The price of LEDs is higher than CFLs and much higher than incandescent lights, but when maintenance and longevity are considered, are significantly cheaper. LEDs have design lives of 20 years, and can last much longer than this, though at a slowly decreasing level of luminosity per watt [17]. The significant decrease in the power demand (Watts) of LED-based lighting per lumen and their reducing cost now means that battery-LED lantern systems with inbuilt solar recharges are affordable. Such system are suited for the majority of people who are forced to use alternative lighting systems because they are in areas not connected to the national power grids or have unreliable power supplies (presently estimated at 25-50% of the world’s population [18]). An issue with PV-based rechargeable LED lanterns in terms of future breakthroughs lies in the area of battery technology. PV and LED systems have design lives of approximately 20 years, and are known to continue to work after this time, albeit with reduced efficiency. The cheapest battery systems are leadacid systems, which are recyclable, but have design lives of 3 to 5 years, depending on the power drain regime, recharge cycles and quality. Clearly there would be great advantage in having a battery system whose design life was the same as the LED and PV systems, as all could be recycled at the one time. Work on battery technology is progressing the design life and power of batteries [19], but is not yet in the range of the PV and LED systems. New battery systems will have to be price competitive with lead-acid batteries, which are also being improved all the time.
3 Examples of LED lighting systems and alternative power LED lighting systems are now widely used. LED-powered lights are used in camping lights, helmet lights, torches, industries of various types, and community lighting projects. Some of these will be briefly discussed in the following. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
74 Energy and Sustainability II Probably one of the most ambitious projects in the world is to provide LED lanterns to the communities of the developing world, as ably illustrated in India [20,21] and Africa [22]. For most villages in India the kerosene lantern has been the standard source of light for many years but they present serious health and risk hazards associated with kerosene fumes and fire. In addition the luminosity is relatively low (10-20 lumins [23]). In many countries the kerosene has to be imported, so there is a significant drain on national budgets, not only in foreign exchange but through the subsidy programs that often apply to support the poor [24–27]. It is estimated that families use approximately 100L of kerosene per year and the subsidy at Rs8-9 per L is estimated at Rs340billion in India The indirect costs of poor lighting on eyesight, education, business and community activity probably dwarfs the direct cost.
Figure 1:
LED lanterns without solar power attachments (photo courtesy MIC Electronics).
LED lanterns that can be solar powered are now cost-effective, can be demonstrated to recover purchase and maintenance costs in terms of savings on kerosene purchases over a period of 2 to 5 years (depending on national kerosene prices). Solar power recharging can be achieved by fixing a PV panel to a lantern unit or through village (community based) recharging stations, which provide the recharging service for very small cost. The later saves on the cost of the lanterns. Battery recycling systems are also needed at the village and district level, as are servicing facilities. Indian railways have commenced the process of converting to LED lighting across their stations and rolling stock. A variety of facilities are being provided, from LED reading lamps in carriages to LED lights for stations. LED street lighting is an exciting opportunity to reduce power consumption and provide communities with security. LED street lights, with and without solar WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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power, are being roll-out in several cities in India. Rather than abandon existing infrastructure LED lights are replacing existing street lights, thus achieving an increase in luminosity while reducing power costs. For green-field sites the opportunity to install solar powered lights, supplied with the poles, is obvious. The reduction in cost in installation is also associated with not having to provide external power to each light. Self-contained solar-recharging LED street lights are an obvious choice in areas subject to natural hazards that may suffer cuts to power supplies. While there is no guarantee that any particular pole and light might survive a hazard, it is likely that enough will survive to provide lighting at the critical times of relief and recovery.
Figure 2:
4
Examples of PV powered LED street lights in India (photo courtesy MIC Electronics).
Lighting the World
While the technology is available, distributing LED-lighting technology is another matter. The urgency for savings in the consumption of petroleum products, improved health, and reduced greenhouse gas emissions is obvious. The Indian government, and others, are committed to distributing the technology as soon as possible. Recent improvements in efficiency and reduction in costs have made distribution more financially feasible in developing economies, as well as developed economies. Distribution is part of the story. There needs to be mechanisms for maintenance, recycling and recharging when PV facilities are not sold with each lighting unit. In addition, rapid roll-out requires financial management to enable communities and individuals to access the technology. Finally, the need for the technology is so great that manufacturing and distribution networks are also required. For communities, as in the case of street lighting, BOOT schemes (BuildOwn-Operate-Transfer) are viable options, as long as financial backing is provided. It should be noted that LED-based street lighting using PV generating systems is ideally suited to areas where rapid roll-out of lighting is required. A refugee camp could have a kilometre of street lighting (one light every 20 metres, offset on opposite sites of the street = 500 lights) in a matter of a week WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
76 Energy and Sustainability II given access to the site and landing of equipment and work teams. A health compound could be provided with light in a day. Small scale PV generators could also provide light within the buildings and this could be installed in a day. The advantages in savings on fuel cartage for conventional diesel powered generators are obvious. For families and individuals the conversion from kerosene lanterns to PV recharged LED lanterns could take place rapidly provided funding for the technological transition is provided in the form of loans. Micro-financing systems [28] are ideally suited to this, as the loans could be repaid from the savings on kerosene purchases. PV recharge stations would provide employment at the village and district level, as would recycling and financial management systems based around the micro-finance. Capital for the micro-finance could be derived from several sources, including direct government support as well as donor support. The advantage of microfinancing is that the capital injection is repaid within a matter of years, and the small profit margin on the sale of the goods finances the microfinance structure and, if care is taken with maintenance contracts, the maintenance and recycling of systems.
5
Conclusions
The rollout of LED lighting, replacing both incandescent and CFL lighting, should bring about considerable savings in energy use per capita, provide improved lighting to people at the bottom of the pyramid, who comprise the majority of the world’s population, reduce per capita greenhouse gas emissions, and stimulate employment and training. The rollout will have to happen in a micro-finance environment in order to maximise benefits of transferring to the new technology and to bring about the transference in the minimum possible time. A number of countries are already aggressively pursing the transformation, and coupled with photovoltaic power generation, should bring significant commercial, health and educational benefits to their people.
Acknowledgements Thanks are due to the many people of MIC Electronics in Hyderabad and elsewhere, particularly Dr Rao who initiated this work.
References [1]
US Census Bureau (2008), World Population Trends: International Data Base (IDB),US Census Bureau, Population Division, viewed 23 June 2008,
. [2] Byrne, J., Toly, N., Glover, L (eds) 2006. Transforming power. Energy, Environment and Society in conflict. Energy and Environment Policy 9, New Brunswick, NJ. Transaction Publishers. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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[3] Malthus, T. 1798. An essay on the principal of population. Johnson, London. http://www.ac. wwu.edul ~stephan/malthus/malthus. 0.html [4] Meadows, D.H., Meadows, D.L., Randers, J., Behrebs, W.W. 1972. The limits to growth. Club of Rome. [5] Trewavas, A. 2002. Mal!hus foiled again and again. Nature 418, 668-670 [6] Australian government. 2006. Energy Efficiency Opportunities Act 2006. Australian Government Publishing Service [7] World energy Council. 2008. Energy Efficiency Policies around the World – Review and Evaluation [8] Zheludev, N. 2007. The life and times of the LED – a 100 year history. Nature Photonics, 1,179-182. [9] Oikubo, S. 2006. Nichia unveils white LED with 150lm/W luminous efficiency. Tech-on. http://techon.nikkeibp.co.jp/english/NEWS_EN /20061221/125713/ [10] US Department of Energy. 2008. Solid-state lighting portfolio. http://www1.eere.energy.gov/buildings/ssl/\ [11] Mills, E. 2002. The $230-billion global lighting energy bill. [12] Mills, E. 2002 Global lighting energy savings potential. Light and Engineering, 10(4),5-10. [13] Mills, E. 2005. The spectre of fuel-based lighting. Science, 308(5726),1236-1264 [14] Mr Beams. 2009. Comparison chart LED lights vs Incandescent Light Bulbs vs CFLs. http://www.mrbeams.com/index.asp?PageAction= Custom&ID=2 [15] Murkerjee, A.K. 2007. Comparison of DFL-based and LED-based solar lanterns. Energy and Sustainable Development, 11(3),24-32. [16] Australian Government. 2008. Fact sheet – fluorescent lamps, mercury and end-of-life management. http://www.environment.gov.au/settlements /energyefficiency/lighting/publications/fs.html [17] Narendran, N., Gu, Y. 2005. Life of LED-based white light sources. J Display Technology, 1(1),167-171. [18] Thong, V.V. Driesen, J., Belmans, R. 2008. How to electrify one fourth of the world population. 16th International Congress of Electrical Applications in a Modern World. Opening session paper. 4pp. [19] Lambert, D.W.H., Holland, R., Crawley, K. 2000. Appropriate battery technology for a new rechargeable micro-solar lantern. J Power Sources, 88,108-114. [20] Government of India. Ministry of New and Renewable Energy. 2009 http://mnes.nic.in/ [21] Velayudan, G.K. 2003. Dissemination of solar photovoltaics: a study on the government program to promote solar lantern in India. Energy Policy, 31(14),1509-1518. [22] Lighting Africa. 2009. http://lightingafrica.org/ [23] Tavaranan, S. and Duffy, J. 2005. Solar lanterns for remote areas. http://energy.caeds.eng.uml.edu/peru-07/ises05-1700-saline-elantern-0205-jjd%5B1%5D.pdf WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
78 Energy and Sustainability II [24] Nieuenhout, F.D.J., van de Rijt, P.J.N.M., Wiggelinkuizen, E.J., van der Plas, R.J. 1998. Rural lighting sources: a comparison of lamps for domestic lighting in developing countries. Netherlands Energy Research Foundation Report. http://www.ecn.nl/docs/library/report/1998/rx98035.pdf [25] Rubab and Kandpal, T.C. 1996. Financial evaluation of SPV lanterns for rural lighting in India. Solar Energy Materials and Solar Cells, 44(3),261270 [26] Gangopadhyau, S., Ramaswami, B., Wadhwa, W. 2005. Reducing subsidies on household fuels: how will it affect the poor? Energy Policy, 33(18),2326-2336. [27] Morris, S., Pandey, A., Barua, S. 2006. A scheme for effective subsidisation of kerosene in India. India Institute of Management, Working Paper 2006-07-06 [28] Yunus, M. 2007, Creating a world without poverty. Social Business and the Future of Capitalism. Public Affair, NY 261pp
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The optical and electrical properties of Eu3+-Y3+codoped ITO transparent conductive electrodes as luminescent solar concentrators C.-C. Ting & C.-H. Tsai Graduate Institute of Opto-Mechatronics Engineering, National Chung Cheng University, Taiwan
Abstract Rare earth ions (Eu3+) and Y3+ ions were codoped into the tin-doped indium oxide (ITO) transparent conductive electrode to make it possess visible luminescent properties. The Eu3+-Y3+codoped transparent conductive thin films with the precise control on the desired stoichiometry of dopants were fabricated by sol-gel spin-coating technologies. We first report that the Eu3+-Y3+codoped ITO thin films show better visible luminescent properties than Eu3+-doped ITO thin films. The higher Y3+ concentration can increase the 611 nm PL intensity of Eu3+-Y3+ codoped ITO thin films. However, the Eu3+ and Y3+ codoping concentrations should be controlled within 0.1% and 0.5%, respectively, to avoid the deterioration of conductivity. We believe that the Eu3+-Y3+codoped ITO thin films can play dual roles as the luminescent solar concentrators and transparent conductive electrode to enhance the efficiency of solar cells. Keywords: ITO, europium, yttrium, pyrocholre, photoluminescence.
1
Introduction
The luminescent solar concentrators (LSC) have attracted lots of attention for the efficiency enhancement of solar cell these past years [1–3]. Most of the LSC is the organic or inorganic fluorescent materials which were coated on the surface of solar cell devices [4–6]. However, this kind of LSC will increase the manufacturing procedures and cost. There is only 5% ultraviolet (UV) and near blue light (300~400 nm) that can reach the Earth surface [7] and most of the solar cells do not have good operating efficiency in this section because of the WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESU090081
80 Energy and Sustainability II absorption of transparent conductive electrode [8, 9]. Therefore we hope that the luminescent solar concentrators can convert this UV light to 500~700 nm visible light, which can be further absorbed by solar cell. In this study, we try to codope Eu3+ and Y3+ ions into the transparent conductive electrode, tin-doped indium oxide (ITO), to make them possess visible luminescent properties. These Eu3+-Y3+ codoped ITO thin films with the precise control on the desired stoichiometry of dopants were fabricated by solgel spin-coating technologies. In order to maintain the conductivity of Eu3+-Y3+ codoped ITO thin films, the doping concentrations of Eu3+ and Y3+ ions were kept at a low contents, i.e. Eu3+ (0.1 mol%) and Y3+ (0~4 mol%). Optical and electrical properties such as fluorescence and sheet resistance (ohms/square) of the resulting Eu3+-doped ITO system were systematically examined in terms of the codoping concentrations and structural evolution of the films at 600°C annealing for 1 h.
2
Experiments
2.1 Preparation of precursor solutions The precursor solutions for the fabrication of Eu3+-Y3+ codoped ITO thin films and powders were synthesized by following procedures. The starting materials is anhydrous indium trichloride (InCl3, 99.995%, Acros) which was dissolved in the mixture of acetic acid (HAc, CH3COOH, 99.5%, Acros) and 2methoxyethanol (2-MOE, C3H8O, 99.5%, Merck) with molar ratio of In/HAc/2MOE=1/20/12. Then the solution was refluxed at 80°C for 3 h. Anhydrous tin chloride (SnCl4, 99%, Acros) was dissolved in ethanol (C2H5OH, 99.9%, JTBaker), which was dropped into the refluxed indium solution at room temperature. Finally, the yttrium acetate [Y(CH3COO)3．4H2O, 99.9%, Alfa] and europium nitrate [Eu(NO3)3．6H2O, 99.9%, Alfa] were dissolved in the solution (a mixture of methanol (CH3OH, ≧99.5%, Merck) and ethylene glycol (HOCH2CH(OH)CH2OH, ≧99.5%, Alfa)], which was added into the abovementioned ITO solution and followed by stirring for 10 h at room temperature in order to process homogeneous hydrolysis and polymerization reaction. The molar ratio of Eu/In and Y/In varied from 0.05/100 to 0.2/100 and 0.5/100 to 4/100, respectively. 2.2 Preparation of thin-film coatings All of the thin films were prepared by sol-gel spin-coating method in a class 100 clean bench. The Eu3+-Y3+ codoped ITO precursor solutions were spin-coated on silica glass substrates of 25 mm×25 mm×0.6 mm dimension (Corning, Eagle 2000). The as-deposited sol-gel films were first dried at 100°C for 10 min, and pyrolyzed in air at 400°C for 10 min at a heating rate of 10°C/min. Finally, the as-formed films were annealed at different temperatures ranging from WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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600-1000°C for 1 h in air. Multiple spin-coating processes were employed to deposit ~300 nm thick films. 2.3 Characteristic measurements The crystal structure was determined by an X-ray diffractometer (Shimadzu, XRD 6000). Scanning electron microscopy (Hitachi, S4800-I) was used for microstructural examination. The thickness of Eu3+-doped ITO films was measured by the SEM cross-sectional image. A monochrometer (Horiba Jobinyvon, MicroHr) equipped with 300 W Xe lamp (Hamamatasu, L2479) and a 325 nm He-Cd laser with an output power of 4 mW were used as the excitation light source. The visible fluorescence was detected by spectrophotometer (Horiba Jobin-yvon, iHR 550) equipped with a PMT detector (Hamamatasu, 7732P-01) at room temperature. Resistivity of the films was measured by using the four-point probe method (Fluke, 8845A).
3 Results and discussions 3.1 Crystal structures and film morphologies Figure 1 shows the XRD patterns of ITO film and Eu3+ (0.1 mol%)-Y3+ (0, 0.5, 1, 2, and 4 mol%) codoped ITO thin films annealed at 600°C for 1 h. All of the samples possessed the well-crystallized bixbyite phase identified by the characteristic XRD peaks: (222), (400), (440), and (622) [10]. Compared to the diffraction intensity of (222) peak between all samples, the addition of 0.5 mol% Eu3+ and 0.5-4 mol% Y3+ ions did not obviously influence the peak intensity of Eu3+-Y3+ codoped ITO thin films, which implies that the slight addition of Eu3+ and Y3+ ions with a total concentration of up to 4.1 mol% into the ITO host did not significantly degrade the crystallinity of ITO thin films. The average crystal size was determined by the Scherrer’s equation depending on the full width at half maximum (FWHM) of XRD peak [11]. For ITO film and Eu3+ (0.1 mol%)Y3+ (1 mol%) codoped ITO thin films annealed at 600°C for 1 h, the FWHM of (222) peak increased from 0.336° to 0.466° and the average crystal sizes decreased from ~22 to ~19 nm. On the other hand, all XRD patterns indicate the formation of single bixbyitestructured phase for Eu3+-Y3+ codoped ITO thin films without any possible other phases such as Y2O3, Eu2O3, SnO2, In4Sn3O12, and Y2Sn2O7. ITO is a kind of solid solution which Sn4+ concentration of up to 10 mol% can dissolve in In2O3 lattice, resulting in the maximum conductivity [12]. Moreover, In2O3, Y2O3, and Eu2O3 possessed the same structures, i.e., bixbyite phase and similar lattice constants (a), as summarized in Table I. Although Eu3+ and Y3+ ions in In2O3 lattice to form the solid solution i.e., YxIn2-xO3 and EuxIn2-xO3. On the other hand, Eu2O3 and Y2O3 can react with SnO2 to form the cubic pyrochlore phase, Y2Sn2O7 and Eu2Sn2O7. A. Ambrosini et. al. investigated that by doping Y3+ ions into In2O3 lattice, the lattice constant can be enlarged because of Y3+ ions has larger radius than that of In3+ ions, which indicates the formation WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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Figure 1:
XRD patterns of ITO film and Eu3+ (0.1 mol%)-Y3+ (0, 0.5, 1, 2, and 4 mol%) codoped ITO thin films annealed at 600°C for 1 h.
Table 1:
Ionic radii and crystallographic data of possible metal oxides in Eu3+-Y3+ codoped ITO thin films.
of solid solution YyIn2--yO3. In addition, any available Y2O3 and SnO2 in the Y3+doped ITO system can react with each other to form Y2Sn2O7 until one of the starting materials is completely depleted. The formation of pyrochlore Y2Sn2O7 at 1400°C annealing was detected by XRD even though the content of Y3+ ions is as low as 2 mol% in a Sn3+-doped In2O3 pellet [13]. Fujihara et. al. [14] reported that sol-gel derived Y2Sn2O7 thin films were in amorphous state for 500~700°C WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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annealing; however, the well-defined pyrochlore Y2Sn2O7 thin films were obtained at 800°C or higher annealing temperatures. In our system, annealing temperature was 600°C and hence, the amorphous pyrochlore Y2Sn2O7 can not crystallize to be detected by XRD. Park et. al. [15] observed that the pyrochlore phase Eu2Sn2O7 was detected in the Eu3+-doped SnO2 thin films annealed at 1200°C for 1 h while the doping concentration reached to 3 mol% [15]. In our experiment even though the light codoping concentration of Eu3+ and 3+ Y ions is as low as ~4 mol%, the pyrochlore phase should be detected if it forms. However, there is no pyrochlore phase can be detected in Eu3+-Y3+ codoped ITO thin films annealed at 600°C for 1 h. Based on the abovementioned reported literatures, therefore, the Eu3+ (0.1 mol%)-Y3+ (0, 0.5, 1, 2, and 4 mol%) codoped ITO thin films annealed at 600°C for 1 h could be composed of the mixture of amorphous EuxYySn2-x-yO7 and crystallized In2zSnzO3-δ (δ: oxygen vacancies) phases. 3.2 Fluorescent properties Fluorescence intensity of the Eu3+-Y3+ codoped ITO thin films with thickness of ~300 nm were found to be extremely low by the excitation of monochrometer equipped with 300 W Xe lamp, which could not be detected due to the limitation of our existing spectrophotometer measurement set-up. However, when the film thickness was up to ~900 nm, the fluorescence intensity was stronger enough to be detected by monochrometer excitation. The ~900 nm thick film appeared to have some cracks, which can not be used for the measurement of sheet resistance but can be used for the measurement of excitation spectrum. Therefore, the fluorescent measurement of all samples with thickness of ~300 nm was executed by using a 325 nm He-Cd laser with an output power of 4 mW as the excitation light source. Figure 2 shows the emission fluorescence spectra of (a) Eu3+ (0.1 mol%)-Y3+ (0, 0.5, 1, 2, and 4 mol%) and (b) Eu3+ (0.05, 0.1, and 0.2 mol%)-Y3+ (1 mol%) codoped ITO thin films annealed at 600°C for 1 h. Obviously, the Eu3+ ions show only one characteristic visible emission, 611 nm red light, which is attributed to the 5D0→7F2 transition of Eu3+ ions. Interestingly, no 5D0→7F1 transition (~590 nm) of Eu3+ ions can be detected for all samples. It is well known that the probability of intra-4f-f transitions strongly depends on the site The electric-dipole 5D0→7F2 transition is allowed for the Eu3+ site without inversion symmetry. On the other hand, the Eu3+ ions can exhibit the magneticdipole 5D0→7F1 transition because of the Eu3+ site with inversion symmetry [16]. In general, both of the electric-dipole and magnetic-dipole transitions coexist in the fluorescent spectra of many Eu3+-doped inorganic materials but one is always much stronger than the other. Further, the intensity ratio of the electric-dipole and magnetic-dipole transitions can be used to investigate the asymmetry of Eu3+ ions in the host lattice site [16]. It is reasonable that only electric-dipole 5D0→7F2 transition was observed in our system because Eu3+ ions is located in the amorphous EuxYySn2-x-yO7 lattice site which results in reducing site symmetry of
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Figure 2:
Emission fluorescence spectra of (a) Eu3+ (0.1 mol%)-Y3+ (0, 0.5, 1, 2, and 4 mol%) and (b) Eu3+ (0.05, 0.1, and 0.2 mol%)-Y3+ (1 mol%) codoped ITO thin films annealed at 600°C for 1 h.
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Eu3+ ions, i.e., no inversion symmetry. Similar spectral structure is also observed in other Eu3+-doped amorphous materials. The more Eu3+ or Y3+ doping concentrations can increase the PL intensity, as shown in Fig. 2 (a) and (b). Because the Eu3+ (0.05, 0.1, and 0.2 mol%)-Y3+ (0, 0.5, 1, 2, and 4 mol%) codoped ITO thin films annealed at 600°C for 1 h could be composed of the mixture of amorphous EuxYySn2-x-yO7 and crystallized In23+ ions replace Y3+ ions and are located at the Y3+ site in zSnzO3-δ phases, Eu 3+ Y2Sn2O7. The more Y ions doped, the more Y2Sn2O7 formed, which results in the more Eu3+ ions can be dissolved in the Y2Sn2O7 lattice to reduce the concentration quenching effect and increase the PL intensity. The excitation spectrum corresponding to the 5D0→7F2 transition of Eu3+ ion in Eu3+-Y3+ codoped ITO thin films annealed at 600°C for 1 h is shown in Figure 3. The broad bands with wavelengths from 350 to 500 nm are ascribed to the f–f transitions of the Eu3+ ions [17]. Within this broad band, a sharp and strong band at 465 nm can be assigned to the 7F0→5D2 transition. Additionally, because the band gap energy of In2O3 nanocrystal is ~4 eV (~300 nm) which is larger than the bulk In2O3 (3.7 eV; ~335 nm), a very small excitation band at 300 nm could be attributed to the energy-transfer transition between Eu3+and In2zSnzO3-δ [18]. The existence of the excitation band corresponding to the band gap energy is the evidence of energy transfer from the In2-zSnzO3-δ nanocrystal to the Eu3+ ions but the very small In2-zSnzO3-δ host band in the excitation spectrum of Eu3+ indicates that there is a little energy transfer from the In2-zSnzO3-δ host to the doped Eu3+ ions.
Figure 3:
Excitation spectrum corresponding to the 5D0→7F2 transition of Eu3+ ion in Eu3+-Y3+ codoped ITO thin films annealed at 600°C/1 h.
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86 Energy and Sustainability II On the other hand, the spectrum consists of two very strong broad peaks centered at 207 and 236 nm. It is well known that the charge-transfer transition between Eu3+ and O2- generally occur at 250~260 nm. L.R. Singh reported that because the covalency of Eu-O bonds in Y2O3 nanocrystals increases, the Eu-O charge transfer energy can be blue shifted in comparison with that of bulk Y2O3 [19]. In our system, the average crystal size of Eu3+-Y3+ codoped ITO thin films annealed at 600°C for 1 h was ~20 nm, which could result in the Eu-O charge transfer energy blue shifting to 236 nm. Moreover, band gap energy of bulk Y2Sn2O7 is 4.45 eV (~279 eV) but because of quantum confinement effect, the band gap energy of nanosized Y2Sn2O7 should be more than 1~2 eV of that value [20]. Therefore, the 207 nm excitation band could be related to the energytransfer transition between Eu3+ and Y2Sn2O7 because the EuxYySn2-x-yO7 is amorphous phase with nanosized crystals. The above-mentioned results reveal that Eu3+-Y3+ codoped ITO thin films annealed at 600°C for 1 h with bixbyite structure can transfer the UV~blue light (200-470 nm) to visible light (611 nm). We believe that Eu3+-Y3+ codoped ITO thin films should have good application in the single crystal or poly crystal Sibased solar cells which have less quantum efficiency in the wavelength range from 300 to 500 nm.
Figure 4:
Sheet resistance of Eu3+-Y3+ codoped ITO thin films annealed at 600°C for 1 h as a function of different doping concentrations.
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3.3 Electrical properties The sheet resistance of Eu3+-Y3+ codoped ITO thin films annealed at 600°C for 1 h as a function of different Eu3+-Y3+ doping concentrations is illustrated in Fig. 4. The resistivity of ITO thin films increased up to ~5 % by light Y3+ or Eu3+ doping concentration (0.5 mol%). However, higher doping concentrations can significantly deteriorate the conductivity. For example, for only 1% Y3+ doping concentration the resistivity of ITO thin film was approximately doubled. The addition of Eu3+ and Y3+ ions into ITO lattice can induce the formation of amorphous pyrochlore phase EuxYySn2-x-yO7, an insulator with the energy gap of 4.46 eV, which results in the increase of resistivity. [20] Furthermore, because Y3+ and Eu3+ ions can react with Sn4+ ions to form the pyrochlore phase EuxYySn2-x-yO7, the Sn4+ content in In2-zSnzO3-δ should be reduced, which also results in the decrease of the carriers created by the dopant and the increase of resistivity. According to the above-mentioned investigations of luminescence and resistivity properties, the result reveals that there exists a kind of tradeoff between the luminescence and conductivity. It is hard to achieve a Eu3+-Y3+ codoped ITO transparent conductive electrode with both of the high luminescent and high conductivity properties. The Eu3+ and Y3+ codoping concentration should be less than ~0.5% in order to avoid the serious deterioration of conductivity.
4
Conclusions
Eu3+ and Y3+ ions were codoped into the tin-doped indium oxide transparent conductive electrode to make it possess visible luminescent and conductive properties. The Eu3+-Y3+codoped ITO transparent conductive thin films with the precise control on the desired stoichiometry of dopants were fabricated by solgel spin-coating technologies. The Eu3+-Y3+ codoped ITO thin films annealed at 600°C for 1 h could be composed of the mixture of amorphous EuxYySn2-x-yO7 and crystallized In2-zSnzO3-δ phases, which results in 611 nm visible luminescence. However, no PL can be detected in Eu3+-doped ITO thin films. The higher Y3+ concentration can increase the PL intensity because of the formation of more EuxYySn2-x-yO7. On the other hand, the Eu3+ and Y3+ codoping concentrations should be controlled within ~0.5% to avoid the deterioration of conductivity. The Eu3+-Y3+codoped ITO thin films should be a good solution as the luminescent solar concentrators to covert the 350~465 nm excited light to 611 nm for the enhancement of solar cell efficiency.
Acknowledgement The authors would like to thank the National Science Council of the Republic of China for financially supporting this research under Contract No. NSC 96-2221E-194-042-MY2.
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References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15]
[16] [17]
Wilkinson, F.J., Farmer, A.J.D. & Geist, J., The near ultraviolet quantum yield of silicon. Journal of Applied Physics, 54(2), pp. 1172-1174, 1983. Koeppe, R., Sariciftci, N.S. & Buchtemann, A., Enhancing photon harvesting in organic solar cells with luminescent concentrators. Applied Physics Letters, 90, 181126, 2007. Bailey, S.T., Lokey, G.E. & Hanes, M.S., et al., Optimized excitation energy transfer in a three-dye luminescent solar concentrator. Solar Energy Materials & Solar Cells, 91, pp. 67-79, 2007. Chatten, A.J., Barnham, K.W.J., Buxton, B.F., Ekins-Daukes, N.J. & Malik, M. A., A new approach to modelling quantum dot concentrators. Solar Energy Materials & Solar Cells, 75, pp. 363-371, 2003. Reisfeld, R., Prospects of sol-gel technology towards luminescent materials. Optical materials, 16, pp. 1-7, 2001. Mansour, A.F., El-Shaarawy, M.G., El-Bashir, S. M., El-Mansy, M.K. & Mammam, A qualitative study and field performance for a fluorescent solar collector. Polymer Testing, 21, 277-281, 2002. Moller, H.J., Semiconductors for Solar Cells, Artech House Press, p. 10, 1993. Sze, S.M., Semiconductor Devices: physics and Technology, Wiley and Sons Inc, 1985. Bhatta, P., Semiconductor Optoelectronic Devices, Prentice Hall, 1997. ASTM JCPDS File No. 44-1087 (In2O3), 1997. Stock, S.R. & Cullity, B.D., Elements of X-Ray Diffraction, Prentice Hall, p. 170, 2001. Alam, M.J. & Cameron, D.C., Optical and electrical properties of transparent conductive ITO thin films deposited by sol–gel process. Thin Solid Films, 377-378, pp. 455-459, 2000. Ambrosini, A., Duarte, A. & Poeppelmeier, K.R., Electrical, Optical, and Structural Properties of Tin-Doped In2O3-M2O3 Solid Solutions (M=Y, Sc). Journal of Solid State Chemistry, 153, pp. 41-47, 2000. Fujihara, S. & Tokumo, K., Multiband Orange-Red Luminescence of Eu3+ Ions Based on the Pyrochlore-Structured Host Crystal. Chemistry of Materials, 17, pp. 5587-5593, 2005. Park, D.H., Cho, Y.H., Do, Y.R. & Ahn, B.T., Characterization of EuDoped SnO2 Thin Films Deposited by Radio-Frequency Sputtering for a Transparent Conductive Phosphor Layer. Journal of The Electrochemical Society, 153(4), pp. H63-H67, 2006. Ollier, N., Concas, G., Panczer, G., Champagnon, B. & Charpentier, T., Structural features of a Eu3+ doped nuclear glass and gels obtained from glass leaching. Journal of Non-Crystalline Solids, 328, pp. 207–214, 2003. Nogami, M., Enomoto, T. & Hayakawa, T., Enhanced fluorescence of Eu3+ induced by energy transfer from nanosized SnO2 crystals in glass. Journal of Luminescence, 97, pp. 147-152, 2002.
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[18]
[19]
[20] [21]
89
Dutta, D.P, Sudarsan, V., Srinivasu, P., Vinu, A. & Tyagi, A.K., Indium Oxide and Europium/Dysprosium Doped Indium Oxide Nanoparticles: Sonochemical Synthesis, Characterization, and Photoluminescence Studies. Journal of Physical Chemistry C, 112, pp. 6781-6785, 2008. Singh, L.R, Ningthoujam, R.S., Sudarsan, V., Srivastava, I., Singh, S.D., Dey, G.K. & Kulshreshtha, S.K., Luminescence study on Eu3+ doped Y2O3 nanoparticles: particle size, concentration and core–shell formation effects. Nanotechnology, 19, 055201, 2008. Subramanian, M.A., Aravamudan, G., & Rao, G.V.S., Oxide pyrochlores - A review. Progress in Solid State Chemistry, 15, pp. 55-143, 1983. Nadaud, N., Lequeux, N., Nanot, M., Jove, J., & Roisnel, T., Structural Studies of Tin-Doped Indium Oxide (ITO) and In4Sn3O12. Journal of Solid State Chemistry, 135, pp. 140-148, 1998.
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Towards a Southern Africa Development Community (SADC) model to assess financing options of renewable energy technologies V. H. van Zyl-Bulitta1, B. Amigun1,2 & A. C. Brent1, 3 1
Sustainable Energy Futures, Resource Based Sustainable Development, Natural Resources and the Environment, Council for Scientific and Industrial Research, South Africa 2 Department of Process Engineering, Stellenbosch University, South Africa 3 Graduate School of Technology Management, University of Pretoria, South Africa
Abstract Access to energy in the form of electricity and fuels is a necessary requirement for sustainable development. Despite the resource abundance for Renewable Energy Technology (RET) in Africa, the potential of RETs is still underexploited. In light of the COP15 meeting, RET is a focal point in the response to global challenges, such as climate change and energy security, and the investment landscape in RET and energy efficiency has recently undergone considerable transformation. To realise its potential, investment in RET infrastructure is critical for Southern Africa. However, the development of sustainable energy is curbed in the region by the lack of adequate and secure finances. A plethora of generic technological and non-technological restrictions, such as scarce political support and poverty, impede RET (financial) support and adoption. A deeper understanding of the consequences of different energy policies could positively influence stakeholders, gain investor confidence, and subsequently contribute to the global community. The financial valuation of factors that are important for RET introduction, pertaining to the risks of RETs, are described through a systems dynamics approach. Specifically, issues in the social and environmental spheres are discussed by means of a Southern African case study. By applying such an approach, through a further research agenda, it is envisaged that RET implementation may be accelerated. Keywords: energy finance, system dynamics, renewable energy, Africa. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESU090091
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1
Introduction
Energy plays a critical role in the development process, firstly as a domestic necessity, but also as a factor of production, where cost directly affects prices of other goods and services [1]. Although better energy supply does not automatically guarantee an acceleration of human development, it is a prerequisite for it. Energy affects all aspects of development - social, economic, and environmental - including livelihoods, access to water, agricultural productivity, health, population levels, education, and gender-related issues. Energy also places excessive strain on investment capital in developing countries. It is not uncommon for an African country to spend in excess of 30% of its development budget on the energy sector; limiting the need for capital expenditure in the energy sector could therefore free up resources for other pressing needs. Therefore, ensuring the provision of adequate, affordable, efficient and reliable high-quality energy services with minimum adverse effects on the environment for a sustained period is not only pivotal for development, but crucial for African countries, most of which are struggling to meet present energy demands. Furthermore, the continent needs such energy services to be in a position to improve its overall net productivity and become a major player in global technological and economic progress [2]. The UN Millennium Development Goals (MDGs), especially MDG 1, i.e. reducing the percentage by half of people living in poverty by 2015, cannot be met without major improvements in the quality and magnitude of energy services in developing countries. In addition, lack of access to such services often exacerbates poverty and leads to unacceptable health risks, for example through exposure to indoor air pollution resulting from cooking with traditional biomass fuels. Africa has a landmass of just over 30.3 million km2, an area equivalent to the US, Europe, Australia, Brazil, and Japan combined. As of 2004, Africa housed 885 million people in 53 countries of varied and diverse sizes, sociocultural entities, and resource endowments, including fossil and renewable energy (RE) resources [3]. Most of these energy resources are yet to be exploited, which is a contributing factor in making the continent the lowest consumer of energy. An African uses only one eleventh, one sixth, and one half of the energy used by a North American, a European, and a Latin American, respectively. There is an urgent need for substantial increases in energy consumption in Africa as a whole if Africa is to become competitive with other developing regions of the world [4]. The Southern African Development Community (SADC) is a treaty organisation comprising 15 member states in the Southern African region. The ultimate objective of SADC is to “build a region in which there will be a high degree of harmonisation and rationalisation to enable the pooling of resources to achieve collective self-reliance in order to improve the living standards of the people of the region” [5,6]. Southern Africa is rich in natural energy resources. With abundant hydropower potential in the north, vast coal fields in the south, oil reserves off the west coast, and fertile land, there is a definite potential to supply low cost energy in the region. However, the disparate distribution of natural, WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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human, and capital resources in the region, as observed in any other transitional country, necessitates regional coordination and cooperation to ensure the development of an efficient and reliable energy system. Trade can improve the security of supply though diversification of supply and sharing of reserve margins. This paper investigates the potential for RET in SADC countries, in particular South Africa, by emphasising the energy geography in Africa, financial aspects thereof, and limitations to RET adoption; future energy paths, with an increased share of RE in the African energy mix, are suggested. It is believed that the paper will assist energy policy makers and future players in the development of sustainable energy finance (SEF), not only in the Southern African context, but also in other transitional and developing countries.
2
International investment climate for RET
The concept of sustainable energy finance (SEF) combines RE and activities for energy efficiency. It is important to distinguish between energy investments for poverty reduction, and for industry and economic development purposes. Carbon Finance (CF) has evolved from the need to develop carbon markets. These entail tradable instruments, such as certificates from Emissions Trading, the Clean Development Mechanism (CDM) and Joint Implementation (JI), all established in the Kyoto Protocol, i.e. articles 17, 12, and 4, respectively. The history of the underlying concepts for carbon trading started in 1968. Flaws of these mechanisms are the insignificant role played by JI projects, the so-called ‘additionality’ requirement of the CDM, and challenges related to the need for projects to assist developing nations achieving sustainable development. [7]. The Global Environment Facility (GEF), the financial mechanism for the United Nations Framework on Climate Change (UNFCCC), currently represents the largest source of funds for RE to developing countries. $900 million have been assigned to 110 projects in 50 countries leveraging nearly $6 billion of added co-financing [8]. Its role is in need for redefinition. In particular, it would ease CF processes immensely if it took a more central, rather than peripheral role. The design of a future global carbon finance market is yet to be defined [9]. RE options are becoming economical in the marketplace, due to the simultaneous decrease in technology costs and rising fossil fuel prices. The design of an energy system incorporating renewables from an energy system that was built around fossil fuels is more than a challenge. Distribution networks and infrastructure are designed around carbon-intensive energy carriers. Funds currently in place are restricted in time until 2012, which more resembles a trial period rather than establishing a “long-term architecture of global environmental funding” [9]. To support the adoption of RETs, sources of investment are needed by developing countries to circumvent the unsustainable energy paths that other, more developed countries, in the world have taken. Funding could be raised from public or private sources, carbon finance, and multilateral funding. The Pew Centre on global climate change sketches a technology funding framework for WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
94 Energy and Sustainability II the period after 2012 [10]. The establishment of a clean energy fund in the African region, the African Biofuels & Renewable Energy Fund (ABREF), also addresses the uncertainty about the post-2012 carbon market setting. The fund aims to exploit Africa’s underexploited resources with a financing strategy between export credit agencies and commercial banks from the viewpoint of perceived risk and bankability. Building on the three pillars climate change, carbon market opportunities and energy security, ABREF manages project performance risk and failure to deliver carbon credits, and it mitigates the market risk that stems from uncertainty in the carbon market. It reports on the number of projects as of April 2008 in the pipeline, where biofuels (14) and solar energy (13) rank second and third after hydro (21) [11]. Many carbon funds (11) have been established under the supervision of the World Bank and another 60 carbon funds have come into being [12]. If the World Bank were to become the central agency for climate change finance, a bias may be introduced towards the interests of industrialised nations [8]. To ensure quality of CDM and JI projects, a gold standard has been proposed to make them comparable and effective. A similar function to ensure best project results is provided by environmental due diligence (EDD) procedures [13, 14]. Sustainable energy (SE) as an investment sector has been on the rise over recent years. Despite RE only serving 5% of global capacity and 3.4% of global power generation, 9.4% of global energy investing and 23% of new electricity generating capacity are based on renewables [15]. Investments have been projected to reach around $450 billion by 2012 and $600 billion by 2020 [16]. Recent increases in the RE investment sector showed that it is able to raise the $200-210 billion needed yearly to return global greenhouse gas (GHG) emissions to current levels, according to the UNFCCC Secretariat. The Copenhagen meeting of the climate convention is approaching, where “governments must reach agreement on a new and decisive climate agreement”; there is a need for carbon markets to evolve and be fostered to achieve their potential of cleaning up current energy infrastructures [16]. Africa strongly lags behind other regions such as India, China, and Brazil. Energy in Southern Africa is largely underexploited, though at the same time presents an unprecedented opportunity to choose “a cleaner development pathway via low-carbon energy alternatives that can reduce GHG emissions and, at the same time, meet current suppressed energy demand and future needs more efficiently and affordably” [12]. Sub-Saharan Africa can gain most from RE. Moreover, this region is stated to be the only one which is not likely to reach the MDGs by 2015 [16]. The role of energy in reaching the MDGs is highlighted in a study by the Forum of Energy Ministers of Africa (FEMA). However, despite the study’s important contribution by identifying links of achieving the MDGs and energy, no priority is assigned to RE [17, 18]. Policies and investment need to be shaped in accordance with the formulation of a coherent strategy to reach the targets set to enable climate change mitigation [19]. The current state of South Africa’s RE sector, for example, is marked by pilot projects, powered by the state-owned electricity utility Eskom. South Africa’s energy service provision structure is largely directed by Eskom. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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Electricity prices, though currently on the rise, are inexpensive in South Africa; one reason being that the true cost of facilities is not accounted for. Feeding externally generated electricity into the grid is currently not possible. The pilot projects in South Africa in line with the South African Bulk Renewable Energy Generation Programme comprise different solar technologies, wind, and biomass [17]. Depending on the energy carriers and technology and equipment needed to convert the energy for consumption, REs differ in their cost structures. The cost of wind and solar energy from the nature of the source used could be accounted for in financial models as a zero fixed cost, while the cost for biofuels is mostly given by feedstock cost, e.g. up to 85% of biodiesel production cost. The dominance of feedstock contribution to total cost decreases orderly as agricultural feedstock, industrial by-products and waste materials are used [20]. While some renewables may incur higher capital costs, immense savings can be achieved in operating costs as compared to fossil fuels or nuclear energy. A comparison of cost, energy supply, and job creation for solar water heaters and the pebble bed nuclear power plant, the construction of which was considered in South Africa has been given and is depicted in Table 1 below [17]. Table 1:
Solar water heaters compared to pebble bed technology nuclear reactor, source: [17], Forex rates (24-02-2009): 1 EUR = 12.73 ZAR, 1 USD = 10.00 ZAR [http://www.xe.com/].
Energy saved/supplied Cost Creation of jobs
3
Solar water heaters
Pebble bed nuclear power plant
890 GWh/annum ZAR 2.6 billion 13 440 jobs
750 GWh/annum ZAR 10 billion 135 jobs
Barriers to RET adoption and a system dynamics-based approach in the southern African energy context
For developed countries, RE sources primarily serve as a means to diversify the national energy supply and a means by which the concept of sustainable development can be implemented, and GHG emissions reduced. However, for developing countries such as those in Africa, RET in general plays a very different role. There is a major difference in the background motives and a resulting performance gap between the South and the North in terms of harnessing RE. Therefore, it has become important to fill this gap with experiences gained in the developed world, but adapted to the needs of developing countries. The fundamental problems to commercialise RETs exist in both developed and developing countries. However, their magnitude and characteristics are more pronounced in developing countries. The multi-dimensional differences among regions and countries make the analysis of the magnitude of these hurdles more complex. Despite national differences, it is possible to generalise some barriers, which have been extensively discussed [2]. For example, various generic barriers WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
96 Energy and Sustainability II currently identified to hinder the adoption and commercialisation of biofuel technologies in Africa, apart from the high cost of raw materials and other economics related constrictions, may be categorised as technological and nontechnological (policy, legal, financial, institutional, cultural, social, etc.) constraints. Table 2 gives a schematic view of barriers to accelerated adoption and commercialisation of RETs in Africa. These barriers are common to RE: Type A: Technologically advanced developing countries, with well diversified and fairly comprehensive industrial, energy and R&D infrastructures – only South Africa. Type B: Technologically advancing developing countries, which are industrialising fairly fast, but are still quite limited in the diversification of their industrial, energy and R&D infrastructure, e.g. Egypt, Morocco, and Algeria. Type C: Slowly industrialising developing countries, with still very limited infrastructure in industry, energy and R&D, such as Nigeria, Mauritius, and Libya. Type D: Technologically least developed countries: Most sub-Saharan African countries, e.g. Ethiopia, Chad, Burundi, Mozambique, Ivory Coast, Niger, DR Congo, Somalia, Mali, and Sudan. Table 2:
Schematic barriers assessment on a classified country basis, source: [2] Low:*, Medium: **, High: ***.
Countrytype
Institutional/ policy hurdle
Technical hurdle
Economic hurdle
Financial hurdle
Information hurdle
Capacity hurdle
Type A
**
*
**
**
*
*
Type B
**
**
**
**
**
**
Type C
***
**
***
***
***
**
Type D
***
***
***
***
***
***
Threshold-21 (T21) models [21] that dynamically link economic, environmental, and societal aspects of a country, sector, or company, have been formulated by the Millennium Institute for Mali, Malawi, South Africa, and Mozambique. Other African countries have also been investigated and modelled to enhance an understanding of policies to support sustainable development and the achievement of the MDGs. The strength of system dynamics models lies in their ability to directly evaluate consequences of different policies [22]. The energy sector has been investigated exclusively in South Africa with a T21 approach, and is detailed elsewhere [23]. The T21 system dynamic model was developed for integrated policy planning to outline future energy paths for South Africa. The study draws on the current energy context in South Africa and WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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projects different energy mix policy scenarios until 2030, using the T21 framework [23]. Energy efficiency measures are considered as well as the influence of GDP, energy price, and demand and supply balances. In this paper the dynamic modelling of the energy sector of South Africa is used as an example with particular attention to biofuels development in the Eastern Cape Province of the country, and possible impacts of such developments on the country’s energy supply as well as consumption patterns. The Eastern Cape Department of Agriculture (ECDoA) is embarking on a large scale biofuels production project that includes the construction of a biodiesel plant in East London, a large city in the Eastern Cape Province, and the development of 500 hectares of land to grow, amongst others, canola and soybeans for biodiesel production. This project is to leverage the Mass Food Production Programme of the Province, which is already in place, and to bring numerous benefits to communities, such as the creation of approximately 350 jobs, Black Economic Empowerment (BEE), empowerment of local farmers, skills development, and food security, since biofuels are not to be produced from maize, which is the staple food for many South Africans. Many potential pitfalls of biofuels production are addressed by dry-land crop cultivation, off-take agreement contracts to prevent adverse effects of price volatility in raw materials, as well as stringent control in the choice of contractors. Exports to other SADC countries that currently import internationally would save transaction costs. The already existing oversupply of glycerine is to be addressed by the development of alternative uses for glycerine and the erection of a methane gas facility is planned to process surplus oilcake [24, 25]. The ECDoA case is used as basis to pave the way for incorporating financial valuation methods to dynamic modelling techniques. By considering, first, South Africa and one of its provinces, African-specific factors to consider would be identified that are also relevant for a future SADC model for RET introduction.
4
Representing the process of sustainable energy finance (SEF) for development
Dynamic modelling techniques have already been shown to contribute to energy modelling, and the evaluation of alternative energy paths. The financial assessment of different energy paths could be facilitated by two methodologies, i.e. the sustainable value (SV) and real options (RO) approach. 4.1 The sustainable value (SV) approach SV assesses the contribution of a company in terms of sustainability and the efficiency with which it uses its resources. It enables environmental performance to be measured in monetary terms, where not only capital, but also environmental and social resources, are considered. SV accounts for different economic actors using resources in different ways to create several possible outputs. The results of their respective activities are weighed in relation to the WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
98 Energy and Sustainability II resources used in the course of such activities. Whenever the resource is used in a better way than possible alternative uses, value is created in financial terms [26]. SV has been applied on company level where a benchmark, such as a stock exchange index, is used to compare performance. If the SV of the company is larger than what could have been achieved with the same resources by the benchmark, value above the opportunity costs, (the equivalent performance of the benchmark had the resources been invested in the benchmark instead of the company) is created. SV enables a differentiation between individual resource uses, and their assessment in sustainable terms. In this way emissions, pollution and health hazards could be rated individually and one may determine which of these costs are incurred in the process of activities in a value-creating way. It “reflects how well companies have reconciled economic output and environmental and social stewardship” [26]. SV aids in decisions regarding the consequences in generating return by the allocation of resources to different possible uses by showing “how a limited and scarce amount of resources should best be used in order to generate highest returns” [26]. SV does not replace other approaches to sustainability assessment. An inherent assumption on the workings of financial markets is that opportunity cost thinking will positively affect the efficiency of resource use. Approaching the development of an emerging market with opportunity cost thinking involves identifying existing resources that would be consumed by RET and the consequences of taking different energy or RE paths. Profit potential, costs and impacts on society and economies of a country may be assessed in monetary terms besides qualitative factors involving quality of life and gender equity. In the SADC context of RET introduction, the SV methodology could be applied in the valuation of alternative uses of resources. The environmental effects of different energy paths as well as vulnerability to future emissions reduction targets can be evaluated [26]. 4.2 The real options (RO) approach The RO approach assesses economic performance by evaluating alternative uses, focusing only on financial measures. They may be incorporated in the analysis through the assessment of when to invest in one or more RETs in a specific country cluster, sector, or area. Furthermore, multiple stakeholders, their actual interactions, as well as believed interactions are important to integrate. Modelling techniques and learning tools to fully understand the consequences of decisions are valuable for investments that are not easily reversible. Modelling techniques that can deal with uncertainty in price fluctuations or changes of fossil fuels and the expected change in prices for renewables would be able to pinpoint the breakeven point of when a technology becomes competitive and under what circumstances it would stay competitive. The RO approach has been used to develop a dynamic programming model for RET diffusion, which features uncertainties in the energy sector and the flexibility to delay. They highlight the use of more sophisticated valuation techniques, the need for WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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financial incentives and the important role of targeted RET policies to achieve widespread adoption [27]. Combining sustainable efficiency using the SV and RE approaches with a model flexible enough to incorporate future changes in economy, politics, society, technology and environment in consideration of requirements and resources in the African context, will aid to pave a financially sound energy path. In view of the above, it is important to consider the risks associated with RET introduction. Risks and mitigation steps were identified for the biofuels project in South Africa. These include market related risks, operating model risks, risks of financial evaluation and funding, as well as project implementation and evaluation and regulatory risks [24]. In a study of climate change for the financial services industry the United Nations Environment Program (UNEP) proposed recommendations for different players in CF [28]. These include the industry as a whole, insurance and reinsurance companies, asset managers, pension funds and financial analysts, investment banks and consultants, political decision makers, and governments in industrialised countries. The recommendations follow the lines of progressive long-term orientated strategies for incorporating climate change and its consequences in the financial sector, as well as raising awareness of the linkages that have not yet been broadly accepted [28]. Approaches from Bayesian statistics have been applied to financial analysis and investment decision support to identify risk measures in valuation processes and future value drivers and cash flows [29].
5
Conclusion and future research agenda
Energy is a key factor in industrial development and the provision of vital services that improve the quality of life. However, its production, use, and byproducts have resulted in major pressures on the environment, both from a resource use (depletion) and pollution point of view. Limited access to energy is a serious constraint to development in the developing world, where the per capita use of energy is far less than in the industrialised world. RET could assist in achieving sustainable development in Africa and keep the UN MDGs on schedule. The decoupling of inefficient, polluting fossil energy use from development represents a major challenge of sustainable development. The long-term aim is for development and prosperity to continue through gains in energy efficiency rather than increased consumption, supported by a transition towards the environmentally responsible use of renewable resources. RETs offer developing countries some prospect of self-reliant energy supplies at national and local levels, with potential economic, ecological, social, and security benefits. Achieving the widespread implementation of RETs may be realised through proper understanding of policies, economics, and financial levers. NEPAD and the African Union (AU) both have roles to play in developing rational energy policy and encouraging biofuel investment across the continent. Information
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100 Energy and Sustainability II exchange and experience sharing should be encouraged amongst institutions and practitioners that are engaged in RET development. Having sketched the landscape of RET investment internationally, as well as specific to the Southern African region, the paper proceeded to describe barriers to its adoption followed by examples of system dynamic modelling for RET embedded in the South African energy market. Tools combining system dynamic and other dynamic modelling approaches are needed for the development of a coherent framework for financing RET options in Southern Africa, time investments and to assess and address related risks. The future research aim is to develop and implement a dynamic model that would be able to capture the problems posed by RETs in the SADC context, and to propose solutions for policy guidance. The previous section has built on the scenario sketched in this study to address the challenges of the SADC region to open the door to a SE path. Learning from South Africa has shown the feasibility of RE projects to some extent, and simultaneously highlighted serious challenges impeding the effective development of RE markets in Southern Africa. Future research will entail a competitive analysis of RET opportunities in SADC countries using critical factors, such as government subsidies and willingness to invest, regional policies in place, the presence of a formal strategy plan for RE, the availability of risk capital, the RET industrial scale, local commercial sector commitment to participate in production and marketing, and availability of raw materials. These factors will be analysed as a composite of their relative ranking of a key attractiveness factor for RET and will be compared amongst several countries in the SADC region. The outcome is to be a matrix of summary measures, which may assist in attracting commercial activity.
References [1] New Partnership for African Development (NEPAD) conference report. Abuja, 2001. http://www.uneca.org/eca- conferencereport/NEPAD.htmlS. [2] Amigun B., Sigamoney, R. & von Blottnitz, H., Commercialisation of biofuel industry in Africa: A review. Renewable and Sustainable Energy Reviews, 12, pp. 690–711, 2008. [3] World Development Report. World Bank: Washington DC, 2005. [4] Davidson, O., Chenene, M., Kituyi, E., Nkomo, J., Turner, C. & Sebitosi, B., International Council for Science (ICSU). Regional Office for Africa Science Plan. Sustainable Energy in sub-Saharan Africa, 2007. http://www.icsu-africa.org/sustainable_energy_rep_2007.pdf [5] Transformation from Conference to Community, 2008. http://www. sadc.int/index/browse/page/53. [6] Alfstad, T., Development of a least cost energy supply model for the SADC region. M.Sc Thesis in Engineering, unpublished, 2005. [7] Bond, P. & Erion, G., South African carbon trading: A counterproductive climate change strategy. Electric Capitalism - Recolonising Africa in the Power Grid, ed. D.A. McDonald, HRSC Press and earthscan: Cape Town and London, 2009. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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[8] Fleming, C., The GEF and Renewable Energy, 2005. http://www.gefweb.org/Projects/focal_areas/climate/documents/GEF_and_ Renewable_Energy.pdf. [9] Porter, G., Bird, N., Kaur, N. & Peskett, L., New finance for climate change and the environment, 2008. http://www.odi.org.uk/fecc/ resources/reports/s0178 final report.pdf. [10] Technology Funding in a post-2012 Climate Framework. Pew Centre on Global Climate Change, 2008. http://www.pewclimate.org/ docUploads/BackgroundNoteTechFunding.pdf. [11] Memorandum of Information for African Biofuels & Renewable Energy Fund, 2008. http://www.faber-abref.org/fichiers/Note FABER. pdf. [12] Faurie, J., Low-carbon Energy Projects for Development in Sub-Saharan Africa - Unveiling the Potential, Addressing the Barriers, 2009. www.carbonfinance.org/docs/Main_Report_Low_Carbon_Energy_projects _for_Development_of_Sub_Saharan_Africa_8-18-08.pdf , http://www.envirovaluation.org/index.php/2008/09/21/low-carbon-energyprojects-for-developme [13] Kenber, M. & Salter, L., The Gold Standard: Quality Standards for CDM and JI Projects. WWF, 2002. http://www.energy-base.org/fileadmin/media/ base/downloads/toolsEDD/eddgeothermal.pdf, http://www.wwf.or.jp/ activity/climate/lib/kyotoprotocol/COP8standards.pdf. [14] Environmental Due Diligence (EDD) of Renewable Energy Projects Guidelines for Geothermal Energy Systems. UNEP, BASE, n.d. http://www.energybase.org/fileadmin/media/base/downloads/toolsEDD/edd geothermal.pdf. [15] Renewables 2007 Global Status Report. World Watch Institute, 2007. http://www.worldwatch.org/node/5633. [16] Boyle, R., Greenwood, C., Hohler, A., Liebreich, M., Sonntag-OBrien, V., Tyne, A. & Usher, E., United Nations Environment Programme, Global Trends in Sustainable Energy Investment 2008, Analysis of Trends and Issues in the Financing of Renewable Energy and Energy Efficiency, 2008. http://sefi.unep.org/fileadmin/media/sefi/docs/publications/GlobalTrends 2008.pdf. [17] McDaid, L., Renewable energy: Harnessing the power of Africa? Electric Capitalism - Recolonising Africa in the Power Grid, ed. D.A. McDonald, HRSC Press and earthscan: Cape Town and London, 2009. [18] Energy and the Millennium Development Goals in Africa. The Forum of Energy Ministers of Africa (FEMA), 2006. http://www.esmap.org/filez/ pubs/FEMAForPrintshop.pdf. [19] Flavin, C., Low-Carbon Energy: A Roadmap, 2008. http://www.worldwatch.org/ taxonomy/term/37. [20] Amigun, B., Processing cost analysis of the African Biofuels industry with Special Reference to Capital Cost Estimation Technique. PhD Thesis, unpublished: University of Cape Town, 2007.
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102 Energy and Sustainability II [21] Bassi, A. M., Modelling U.S. Energy with Threshold 21 (T21), 2006. http://www.systemdynamics.org/conferences/2006/proceed/papers/BASSI2 05.pdf. [22] Africa region. Millennium Institute, 2009. http://www. millenniuminstitute.org/projects/region/africa/. [23] Musango, J. K., Brent, A. C. & Bassi, A. M., South African energy Model: A systems dynamics approach. Conference of the Systems Dynamics Society, Albuquerque, New Mexico, USA, 2009. [24] ECDoA, Business plan for an integrated dry-land cropping and processing plan for rural development in the Eastern Cape. Unpublished, 2007. [25] Jansen, W., ASGISA Eastern Cape integrated cropping and biofuel development programme. KPMG, 2008. www.sacities.net/members/pdfs/ 3.1.2_eastern-cape_case_study.pdf. [26] Figge, F. & Hahn, T., Sustainable Value of European Industry - a Valuebased Analysis of the Environmental Performance of European Manufacturing Companies, 2006. http://sefi.unep.org/fileadmin/media/sefi/ docs/industryreports/advancesurveyfullversion.pdf. [27] Kumbaroglu, G., Madlener, R. & Demirel, M., A real options evaluation model for the diffusion prospects of new renewable power generation technologies. Energy Economics, (30), pp. 1882–1908, 2008. [28] Das Klimarisiko für die Weltwirtschaft / Climate Change and the Financial Services Industry. UNEP Finance Initiative: Paris. http://www.gci. org.uk. [29] Bals, C., Mainstreaming of climate risks and opportunities in the financial sector. http://www.climate-mainstreaming.net/.
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Hydrogen fuelled agricultural diesel engine with electronically controlled timed manifold induction: an experimental approach P. K. Bose1, S. Mitra2, R. Banerjee3, D. Maji3 & P. Bardhan4 1
National Institute of Technology, Silchar, India Jalpaiguri Engineering College, India 3 School Of Automotive Engineering, Jadavpur University, India 4 JIS College of Engineering, India 2
Abstract The important motivations for exploring alternative fuel resources are energy security, air pollution, and climate change; problems that are collectively calling into question the fundamental sustainability of the current energy system. Natural gas and bio fuels are seen as the most important short-term options for meeting these goals, whereas in the long run, a substantial contribution is expected to be delivered by hydrogen which would facilitate the transition from limited non-renewable stocks of fossil fuels to unlimited flows of renewable sources. Hydrogen-fuelled internal combustion engines with near-zero emissions and efficiencies exceeding today's port-fuel-injected (PFI) engines are a potential near-term option and a bridge to hydrogen fuel cell vehicles where fuel cell undergoes development to make it economically viable. The unique combustion properties of hydrogen make it an ideal choice for its use in compression ignition engines. The present work attempts to explore the performance and emission characteristics of an existing single cylinder four-stroke compression ignition engine operated in dual fuel mode with hydrogen as an alternative fuel. The hydrogen was premixed with the incoming air and inducted during the duration of intake valve opening by an indigenously developed electro-mechanical means of solenoid actuation The performance and emission characteristics with hydrogen–diesel blend and neat diesel are compared. In this experiment hydrogen flow rate was kept constant at 0.15 kg/hr. The brake thermal efficiency with hydrogen–diesel blend is about 15.7% greater than that of neat diesel operation at 40% rated load. CO, CO2, HC and smoke emissions were significantly less with hydrogen–diesel blend. Smoke level was 41.6% lower than that of neat diesel operation at 80% load, whereas emission of CO2, CO, and HC levels were lower by 40.5%, 44.3% and 53.2% respectively for hydrogen enrichment at 80% load. In our present work EGR technique was examined in reducing NOx concentration. The NOx level decreased from 1211 ppm to 710 for hydrogen enrichment (0.15kg/hr) at 80% of the rated load. Keywords: hydrogen, diesel, dual-fuel, timed manifold injection, electromechanical actuation, hot EGR, cold EGR. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESU090101
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1
Introduction
With the uncertainty of today's petroleum market with its declining oil reserves, ongoing tensions in oil producing nations, and environmental regulatory activity soaring to new heights, the time has come for the world to embark on the road of independence from the ‘addiction’ of fossil fuel and to find sustainable alternative fuel resources of the future. According to the European Commission’s White Paper ‘European transport policy for 2010: time to decide’, natural gas and bio fuels are seen as the most important short-term options for meeting these goals, whereas in the long run, a substantial contribution is expected to be delivered by hydrogen which would facilitate the transition from limited nonrenewable stocks of fossil fuels to unlimited flows of renewable sources. According to the World Energy Assessment, released in 2000 by several UN agencies and the World Energy Council, which emphasizes “the strategic importance of hydrogen as an energy carrier”, the accelerated replacement of oil and other fossil fuels with hydrogen could help achieve “deep reductions” in carbon emissions and avoid a doubling of pre-industrial carbon dioxide (CO2) concentrations in the atmosphere – a level at which scientists expect major, and potentially irreversible, ecological and economic disruptions. Hydrogen-fuelled internal combustion engines with near-zero emissions and efficiencies exceeding today's port-fuel-injected (PFI) engines are a potential near-term option and a bridge to hydrogen fuel cell vehicles where fuel cell undergoes developments to make it economically viable (Is Hydrogen the Solution? [1]). Under the given circumstances, dual fuel operation with hydrogen within the framework of contemporary existing engine structure is a good alternative. The high flame speed of hydrogen makes engine operation approach the ideal Otto cycle with near constant volume heat addition thus enhancing thermal efficiency. In addition, the potential of hydrogen combustion in reducing green house hydrocarbon, smoke and PM emissions provide the motivation of study of a hydrogen fuelled diesel engine combining both the advantages of a spark ignition engine and a compression ignition engine at the same time. 1.1 Hydrogen as an alternative fuel in compression ignition engines The use of hydrogen as a clean fuel for premixed spark ignited engines is fairly well developed, (Yi et al. [2], Das et al. [3], Das [4], El-Emam and Desoky [5], Karim [6], Subba Rao et al. [7]) but the same is not true for use in diesel engines. However, the unique combustion properties of hydrogen make it an ideal choice for its use in compression ignition engine. The burning velocities of hydrogen air mixture range from 153 to 232 cm/sec for its stoichiometric mixture, (Isadore and Drell [8], Wallace and Ward [9]). This results in a more isochoric, thus thermodynamically more favourable combustion than conventional diesel engines which undergo a pressure and temperature rise spread over several degrees of crank travel. The flammable range is exceptionally wide for hydrogen in air-lower limit 4%, upper limit 75% by volume. (Isadore and Drell [8], Wallace and Ward [9]) This is an equivalence ratio of about 0.24, as compared with a lean flammability limit of about Φ=0.5 for most hydrocarbon fuels. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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A significant advantage is that the engine can work with very lean mixtures, thus omitting a throttle valve–this ideally suits a diesel engine operation. Hydrogen has a higher auto ignition temperature than conventional fossil fuels. This means that a higher compression ratio is allowed than in a gasoline engine and this makes it an ideal candidate for use in high compression ratio engines without any danger of knocking. 1.2 The hydrogen-diesel dual fuel concept The hydrogen-diesel dual fuel concept method combines the advantages of the high part load efficiency, lower specific fuel consumption, of a diesel engine and the clean combustion characteristics of hydrogen and oxygen. However hydrogen with its cetane number being very low, are not directly suited to compression-ignition (CI) engines. Hydrogen has an auto-ignition temperature of about 571°C and as such it is not possible to achieve ignition of hydrogen by compression alone at the compression ratio of 17.5 at the existing engine configuration in the present work. Some source of ignition has to be created inside the combustion chamber to ensure ignition. (Ikegami et al. [10], Lee et al. [11], Mansour et al. [12], Naber and Siebers [13]). A small amount of liquid Diesel fuel is injected by means of the existing fuel injection equipment near the end of the compression stroke to ignite the gaseous mixture. Diesel fuel auto ignites and creates ignition sources for the surrounding air–gaseous fuel mixture. The pilot liquid fuel, which is injected by the conventional diesel injection equipment, normally contributes only a small fraction of the engine power output. In dual-fuel engines both types of combustion coexist together –the primary gaseous fuel of high-octane index is premixed with air in the inlet manifold and compressed and then fired by a small liquid fuel injection which ignites spontaneously at the end of compression phase. The advantage of this type of engine resides in the fact that it is an attempt for the combination of the better of the two combustion processes using the difference of flammability of two fuels at different stages of the combustion process.
2
Hydrogen induction: some considerations
Hydrogen is a peculiar fuel and it has properties distinct from the conventional fossil fuels. (El-Emam and Desoky [5], Isadore and Drell [8], Wallace and Ward [9]) The necessary ignition energy of a hydrogen-air mixture is very low (0.02 mJ), especially at the stoichiometric condition. This enables the ignition of very lean mixtures and ensures immediate ignition. Contact with hot spots or residual gas, can cause the mixture to ignite spontaneously. (Liu and Karim [14]) This pre-ignition tendency results in backfire if the mixture ignites when the inlet valve is still open. The flame in the combustion chamber ignites the mixture in the inlet manifold through the inlet port, which causes a very loud bang and can result in severe engine damage. The backfire phenomenon is also called flashback or back flash and is one of the main issues of hydrogen fuelled internal combustion engines. Hydrogen has a small quenching distance, about three times as small as gasoline. This implies that it can burn slowly in small and narrow WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
106 Energy and Sustainability II clearances, like crevice regions. The burning in these small regions can continue up to and during the intake process. During the intake process, the hot burning gases can flow out of the crevice volumes and ignite the intake charge thus causing backfire. Thus if an existing IC engine without any modification were to be fuelled by hydrogen, some problems, such as small power output, abnormal combustion (e.g. backfire, pre-ignition, high pressure rise rate and even knock) would occur. So its fuel supply system and combustion system need suitable modification. The prevalent modes of hydrogen induction were examined and their merits and demerits were evaluated in the present context on the basis of literature survey (Yi et al. [2], Das et al. [3], Das [15], Lee et al. [11], Zhenzhong et al. [16], HariGanesh et al. [17], Varde and Frame [18]) Timed manifold injection (TMI) systems offer an alternative to load control method by throttling. It possesses the ability to initiate fuel delivery at a timing position sometimes after the beginning of intake stroke ensuring a pre-cooling effect and thus rendering the pre-ignition sources ineffective. Furthermore, it helps to quench and dilute any residual combustion products that could be present in the compression space near TDC. 2.1 Hydrogen induction circuit development The design of the solenoid actuation [Fig1], which formed the heart of the TMI system, was dictated by the necessity of ensuring simplicity in implementation and the reduction of possibility of undesirable effects of abnormal hydrogen combustion such as pre ignition and flashback at the operating loads. The triggering mechanism essentially consisted of a metal plate mounted on a damper spring held in place by an actuator mounting as shown in Fig 1. The metal plate was designed to ensure a positive contact with the free end of the rocker arm during the inlet valve opening. The design ensured a contact only during the maximum valve lift. The contact having made, the metal plate acting as the switch, closed the 12V DC circuit, thereby energizing the solenoid and allowing hydrogen gas to be injected at a predefined rate in the inlet manifold The metal plate lost contact with the rocker arm during the closing of the inlet valve ensuring that hydrogen being injected into the cylinder only during the maximum valve lift as dictated by the dwell period of the valve lift cam and also that hydrogen was inducted only after a definite time lag after the initiation of the opening of the inlet valve. The time lag arising out of mechanical inertia of the valve components ensured that hydrogen was injected only after a sufficient flow of cooler ambient air was inducted in the cylinder during the opening of the inlet valve, this being critical in quenching any residual hot spots remaining in the cylinder thereby removing any possibility of flash back .In the present study, the hydrogen gas was routed to the engine. According to the setup shown in Fig 2. The hydrogen induction inside the cylinder being actuated by a solenoid is periodic in nature rather than continuous. As a result, a surge tank is included in the circuit to dampen out any pressure fluctuations in the hydrogen supply line. A flow regulator in the hydrogen circuit was used to regulate the mass flow rate of hydrogen in the hydrogen circuit. A flame trap was incorporated in the setup keeping in mind the inherent explosive nature of a hydrogen air mixture and the WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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Figure 1:
Figure 2:
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Solenoid actuated electro-mechanical TMI circuit.
Schematic diagram of experimental setup.
flashback and blow off nature of hydrogen flames. This acts a safety buffer against explosive mixtures formed in the intake manifold to travel back to the hydrogen cylinder by quenching any freak flame.
3 Methodology The diesel engine was fired on no load initially and it was run for a period of time until it reached steady state conditions, denoted by the constant cooling water outlet temperature. Then the engine running on diesel as the main fuel was taken on load in steps by means of the Eddy current dynamometer of SAJ TEST PLANTS make and after attaining the steady-state conditions all the pertinent readings were noted. This procedure was repeated for 20%, 40%, 60% and 80% loading. The engine exhaust was analysed by means of a AVL 437 smoke meter while common engine emissions (CO,HC,CO2,O2,NOX) were calculated via a WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
108 Energy and Sustainability II AVL DIGAS 444 -5 gas analyzer fitted with a DIGAS SAMPLER. The engine was again allowed to attain steady state conditions at no load. Then hydrogen was supplied at a pressure of 1 bar using hydrogen pressure regulator. By keeping the flow of hydrogen gas@ 0.15kg/hr, the performance and emissions of the hydrogen enriched engine without EGR were noted at 20%, 40%, 60% and 80% load. At the end of this process, hydrogen flow rate was reduced to zero and the engine was made to run at steady-state condition using diesel at no load condition. For EGR operation the quantity of exhaust gas was regulated by a control valve [Fig 3], installed in the EGR loop. An air box was provided in EGR loop to dampen the fluctuation of recirculated exhaust. An orifice was installed in the EGR loop after the air box in order to measure the flow rate of recirculated exhaust. There was an EGR cooler placed before the air box. The engine was run by using hydrogen enrichment (0.15kg/hr hydrogen flow) with 10% EGR and 20% EGR in hot and cold conditions. In both these cases above mentioned readings are taken on no load, 20% load, 40% load, 60% load and 80% load.
Figure 3:
EGR setup.
4 Results and discussions 4.1 Performance characteristics 4.1.1 Variation of brake thermal efficiency with brake power The variation of brake thermal efficiency with brake power is shown in Fig 4. The brake thermal efficiency for hydrogen with diesel as ignition source is 34.1% at 80% load with a flow rate of hydrogen 0.15kg/hr whereas that of baseline diesel fuel is 30.2% showing an appreciable increase of 12.9%. This increase in thermal efficiency is attributed to an enhanced combustion rate due to high flame velocity of hydrogen. Use of EGR has a negative effect on engine combustion due to fresh air dilution and addition of inert elements such that efficiency decreases for all cases of EGR operation as compared to hydrogen enrichment but is greater at all loads when compared with neat diesel operation. At 80% load with 10% cold EGR brake thermal efficiency is 32.3% and with 10% hot EGR it is 32.45% while that for 20% cold EGR is 30.8%, thus indicating that thermal efficiency under the present conditions was affected by the quantity and quality (hot or cold) of EGR operation. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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Variation of brake thermal efficiency with load.
4.1.2 Variation of brake specific fuel consumption with brake power Fig 5 shows the variation of brake specific fuel consumption with brake power Part load operation (20% load) shows a drastic reduction of 63.3% in bsfc readings during hydrogen enrichment as compared with neat diesel operation proving the excellent combustion properties of hydrogen which helps to achieve the desire brake power at a lower energy input. All EGR cases of operation showed a reduced trend of bsfc while 10% hot EGR showed the best characteristics when compared to pure diesel operation with a 61.71% and 43.3% reduction in bsfc readings at 20% and 80% load. 4.1.3 Variation of volumetric efficiency with brake power The air/fuel ratio (A/F ratio) of stoichiometric combustion of hydrogen in air based on mass is 34.33 kg air/kg and that based on volumetric analysis is 29.6% Volume percent of the combustion chamber occupied by hydrogen is then 29.6%. This means that a significant part of a given combustion chamber volume cannot be filled with air in contrast with conventional liquid fuel that only displaces 1.8% of the combustion chamber.
Figure 5:
Variation of BSFC with load.
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Figure 6:
Variation of volumetric efficiency with load.
This decreases the volumetric efficiency of a given engine when compared to its operation with conventional liquid fossil fuel. Fig 6 shows the variation of volumetric efficiency with brake power. The volumetric efficiency obtained for 0.15kg/hr hydrogen enrichment without EGR is 78.9% compared to neat diesel fuel of 80.1% at 80% load. Volumetric efficiency decreases with all cases of EGR operation. Maximum penalty is suffered during 20% hot EGR operation with a 50.1% efficiency at 80% load .10% cool EGR provided the best volumetric efficiency characteristics among all EGR operations with 70.2% at no load and 63.9% at 80% load. 4.2 Emission characteristics 4.2.1 Carbon dioxide emissions The variation of CO2 emission with brake power for all cases under study is shown in Fig 7. CO2 emissions in case of hydrogen enrichment are lower compared to that of diesel. At 80% load CO2 emission for hydrogen enrichment without EGR is 4.7% by volume where as that of neat diesel is 7.9% by volume. The CO2 emission in case of hydrogen enrichment is lowered because of better combustion characteristics of hydrogen fuel and also due to the absence of carbon atom in hydrogen molecule. Due to the use of EGR, CO2 emissions increase and go on increasing with the increase in EGR percentage. At 80% load CO2 emission for 10% EGR is 4.8% by volume and that of 20% EGR is 5.6% by volume. The reason of this increase in CO2 emissions in case of EGR is the presence of CO2 in exhaust gas being recycled back to the fresh air intake. 4.2.2 Carbon monoxide emissions Fig 8 depicts the variation of carbon monoxide with brake power. Results indicate a drastic reduction of 86.6% as compared to neat diesel operation at no load for hydrogen enrichment while 45.8% reductions at 80% load for the same conditions. Hydrogen does not contain any carbon. This is the reason for low CO emission in case of hydrogen enrichment, and the registered amount being only due to pilot diesel and lube oil. Operation with EGR resulted in reduction of CO WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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Figure 8:
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Variation of CO2 emissions with load.
Variation of carbon monoxide emissions with load.
emissions for all cases as compared to pure diesel operation but had a reduced gain as compared to hydrogen enrichment. Operation under 10% hot EGR produced the best gains in CO emissions among all EGR operations with a reduction of 42.3% at 80% load as compared to neat diesel operation. Further analysis showed that gains in CO emission reduction reduced with increasing load for all cases of dual fuel operation. 4.2.3 Hydro carbon emissions Fig 9 shows the variation of HC with brake power .It can be observed that HC emission for hydrogen enrichment without EGR scores an 83% reduction compared to neat diesel operation at no load and a 57% reduction at 80% load. The best HC reduction characteristics in EGR operations were provided by 10% hot EGR with a 57.6% reduction at 80% load. Diesel engines with their inherent lean combustion are prone to HC emissions due to inhomogeneous local air fuel ratios which are either over lean or fuel rich to support combustion. The interesting observation with dual fuel operation with hydrogen is that though the overall equivalence ratio of the combustible mixture is leaner than that of normal WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
112 Energy and Sustainability II diesel operation the HC emissions are still remarkably lower. This is attributed to a more homogenous air fuel mixture having wide ignitability limits due to hydrogen, which helps sustain combustion even under lean conditions. The gains in mixture quality are penalized with EGR operation where residual gases promote fresh air dilution and increases local equivalence ratios beyond ignitability limits.
Figure 9:
Variation of HC emissions with load.
4.2.4 Smoke emissions The operation range of diesel engines is mainly constrained by the smoke emissions at high loads. This limits the exploitation of the advantages of a compression ignition engine to its fullest potential. The variation of smoke level with brake power is shown in Fig 10. As the load increases, diesel engines tend to generate more smoke. Present analysis showed that gains in smoke reduction were maximum with hydrogen enrichment for all the load ranges but decreasing with increasing load, with a maximum of 64.28% at 40% load and a notable 41.6% at 80% load .EGR operation registered lesser gains in smoke reduction as
Figure 10:
Variation of smoke emissions with load.
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compared to hydrogen enrichment, the 10% hot EGR case showing the best gain trend among all EGR operations. Hydrogen being devoid of any carbon atoms show obvious characteristics of reduction in smoke levels. This is why there is low smoke level in case of hydrogen enrichment. Smoke level increases with increasing EGR rate and increasing engine load. EGR reduces availability of oxygen for combustion of fuel which results is relatively incomplete combustion and increased formation of particulate matter. This results in higher smoke level in case of EGR. 4.3 NOx emissions Fig 11 shows the variation of NOx with brake power. NOx emission for hydrogen enrichment without EGR is 1211 ppm compared to neat diesel fuel of 810 ppm at 80% load. The reason for this higher concentration of NOx in case of hydrogen enrichment without EGR is peak combustion temperature and high residence time of the high temperature gases in the cylinder. Fig 11depicts that with 10% EGR, NOx formation is 760 ppm at 80% load and that of 20% EGR is 710ppm. So the NOx formation decreases with the use of EGR and goes on decreasing with increase in EGR percentage. The primary effect of the burned gas diluents in the unburned mixture on the NOx formation process is that it reduces peak temperatures by increasing the heat capacity of the cylinder charge, per unit mass of fuel. When recirculated to engine inlet, it reduces oxygen concentration and act as a heat sink. All the combustion process is delayed with diluted air consequently the whole combustion process is shifted further into the expansion stroke, leading to lower combustion temp. Lower combustion temp is the reason of decrease of NOx.
Figure 11:
5
Variation of NOx emissions with load.
Conclusion
The present study showed a persistent increase of the brake thermal efficiency over the entire range of operation under all cases of hydrogen enrichment with a maximum increase of 15.73% at 40% load .The bsfc decreased with all cases of WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
114 Energy and Sustainability II hydrogen enrichment (with and without EGR) showing a significant decrease of 63.3% at 20% load. The volumetric efficiency suffers a decrease for all cases of hydrogen enrichment with a decrease of 37.5% at 80% load. Smoke emissions displayed a decrease for all cases of hydrogen enrichment with a decrease of 64.28% and 61.5 at 20% and 40% load respectively for non EGR cases, thereby improving the part load operation characteristics. HC emissions decreased for the entire range of operation for hydrogen enrichment with a substantial decrease of 80.0% at 20% load and a 57.6% decrease at 80% load. CO emissions reduced remarkably by 69.5% and 64.5% at 20% and 40% loading with a trend of decrease for all hydrogen enrichment operations as compared with neat diesel combustion. Hydrogen enrichment as compared to pure diesel operation displayed a steady decrease of CO2 for all ranges of operation with a decrease of 71.05% and 40.05% at 20% and 80% loading. The ultra-lean combustion characteristics of hydrogen provide the perfect environment for NOx emissions which are compounded with the inherent tendency of neat diesel fuel combustion. It thus creates a challenge to solve the paradox of simultaneously reducing NOx emissions and simultaneously reap the benefits of using hydrogen in the context of reduced pollutant emissions of typical diesel engines. In our present work EGR technique was examined in reducing NOx concentration. The NOx level decreased from 1211 ppm to 710 for hydrogen enrichment (0.15kg/hr) at 80% of the rated load. NOx levels showed a decreasing tendency for all EGR induction under these conditions of hydrogen enrichment. The emergence of hydrogen as a sustainable fuel for the future is well established by now. Its pertinence to internal combustion engines which still must be considered the best driving units of the immediate future dictates the exploration of hydrogen as a strategic sustainable energy carrier for internal combustion engines. In view of this, the present study offers a pilot study to extend the operational benefits of using hydrogen in compression ignition engines which form the mainstay of the present industrial powerhouse.
References [1] Hydrogen the Solution? http://www.nrdc.org/air/transportation/ phydrofuel.asp [2] H.S. Yi, K. Min and E.S. Kim. “The Optimised Mixture Formation for Hydrogen Fuelled Engines.” International Journal of Hydrogen Energy 25(7) pp: 685-690. 2000. [3] L.M. Das, Rohit Gulati and P.K. Gupta (June 2000). “Performance Evaluation Of A Hydrogen-Fuelled Spark Ignition Engine Using Electronically Controlled Solenoid-Actuated Injection System.” International Journal of Hydrogen Energy 25(6) pp: 569-579; 2000 [4] Das, L. M. “Hydrogen engine: research and development (R&D) programmes in Indian Institute of Technology (IIT), Delhi” International Journal of Hydrogen Energy 27(9) pp: 953-965; 2002 [5] El-Emam, S. H. and A. A. Desoky (1985). “A study on the combustion of alternative fuels in spark-ignition engines.” International Journal of Hydrogen Energy 10(7-8): 497-504. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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[6] Karim, G. A. (2003). “Hydrogen as a spark ignition engine fuel.” International Journal of Hydrogen Energy 28(5): 569-577. [7] Subba Rao, K., V. Ganesan, et al. (1983). “Modelling of combustion process in a spark ignited hydrogen engine.” International Journal of Hydrogen Energy 8(11-12): 931-933 [8] Isadore L. and Drell, F. E. B. (1958). “Survey of hydrogen combustion properties. http://naca.central.cranfield.ac.uk/reports/1958/naca-report1383.pdf [9] Wallace, J. S. and C. A. Ward (1983). “Hydrogen as a fuel.” International Journal of Hydrogen Energy 8(4): 255-268. [10] Ikegami, M., K. Miwa, et al. (1982). “A study of hydrogen fuelled compression ignition engines.” International Journal of Hydrogen Energy 7(4): 341-353. [11] Lee, C. S., K. H. Lee, et al. (2003). “Experimental and numerical study on the combustion characteristics of partially premixed charge compression ignition engine with dual fuel [small star, filled].” Fuel 82(5): 553-560. [12] Mansour, C., A. Bounif, et al. (2001). “Gas-Diesel (dual-fuel) modelling in diesel engine environment.” International Journal of Thermal Sciences 40(4): 409-424. [13] Naber, J. D. and D. L. Siebers (1998). “Hydrogen combustion under diesel engine conditions.” International Journal of Hydrogen Energy 23(5): 363371. [14] Liu, Z. and G. A. Karim (1995). “Knock characteristics of dual-fuel engines fuelled with hydrogen fuel.” International Journal of Hydrogen Energy 20(11): 919-924. [15] Das, L. M. “Hydrogen engine: research and development (R&D) programmes in Indian Institute of Technology (IIT), Delhi” International Journal of Hydrogen Energy 27(9) pp: 953-965; 2002 [16] Yang Zhenzhong, W. J., Fang Zhuoyi, Li Jinding (February 2002). “An Investigation of Optimum Control of Ignition Timing and Injection System in an In-Cylinder Injection Type Hydrogen Fuelled Engine.” International Journal of Hydrogen Energy 27(2) pp: 213-217 [17] Hari Ganesh, R., V. Subramanian, et al. (2008). “Hydrogen fuelled spark ignition engine with electronically controlled manifold injection: An experimental study.” Renewable Energy 33(6): 1324-1333. [18] Varde, K. S. and G. A. Frame (1983). “Hydrogen aspiration in a direct injection type diesel engine-its effects on smoke and other engine performance parameters.” International Journal of Hydrogen Energy 8(7): 549-555.
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Selection of renewable energy technologies in Africa: the case of efficient stoves in Malawi M. L. Barry, H. Steyn & A. C. Brent Graduate School of Technology Management, University of Pretoria, South Africa
Abstract Malawi is one of the most densely populated and least developed countries in the world. Agriculture is the main source of external revenue and 90% of the population is employed in this sector. The population, 85% of whom live in rural areas, is mostly dependent on biomass in the form of firewood for their energy needs. One of the main challenges facing Malawi is deforestation and the use of efficient stoves provides an opportunity to reduce the dependency on firewood. The purpose of the case study presented in this paper was to validate factors for the selection of renewable energy technologies in Africa which were previously identified during a Delphi study. The focus of this case study was on the efficient stove program currently being undertaken in Malawi. Questionnaires were developed to structure discussions and interviews were conducted in Malawi with individuals from the Malawian Ministry of Energy, producers of efficient stoves and households that use efficient stove installations. Secondary data were also collected in the form of different reports on the project. The primary data obtained from the interviews and the secondary data in the reports were analyzed by comparing the information with the factors previously defined during the Delphi study. This paper discusses the results, which confirm that most of the factors identified during the Delphi study were indeed seen as important for project success during the selection of efficient stove technology in Malawi. Keywords: technology selection for developing countries, renewable energy, case study.
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Introduction
1.1 Renewable energy in Africa Most African countries are faced with reaching maintainable levels of positive economic growth in the 21st century [1]. In order to achieve positive economic growth, industrialisation is needed and in order to industrialise, African countries need sustainable and affordable energy services even where the grid cannot reach [1]. Poverty reduction is linked to economic development and both require affordable and sustainable access to energy [2].
Figure 1:
Electricity deprivation (millions) [3].
According to the World Energy Outlook for 2004 [3], developing countries will contribute to two-thirds of the global energy demand by 2030 but on the other hand also predicts that the population without electricity in Africa will increase from 526 million in 2002 to 584 million in 2030 (see Figure 1). 1.2 Realities of Malawi The Republic of Malawi is a small country in southern Africa. It shares borders with Zambia, Tanzania and Mozambique (see Figure 2). Malawi is one of the least developed countries in the world, ranking 168 out of a total of 174 countries [4] and more than 90% of the export revenue of the country comes from agricultural products. The deforestation rate in Malawi is 2.8% per year and is the highest in Africa which is contributed to by the fact that 95% of Malawi’s primary energy supply and 90% of total energy is from biomass, mainly in the form of firewood and charcoal [4]. Other energy sources used in Malawi include electricity (mainly from hydro) petroleum products, coal and other renewable energy sources but these account for only 7% of the total supply with only 6% of the population of Malawi having access to electricity [4].
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Figure 2:
119
Map of Malawi [5]. Literature survey Focus group
Delphi study
Case studies
Figure 3:
2
Overall research methodology.
Research methodology
2.1 The broader research programme The research described in this paper is the result of a larger study which involved a focus group; Delphi study and case study research (see Figure 3). Three countries in Africa were selected for the purpose of the case study research. This paper only reports on the case study for Malawi as indicated by the text in black in Figure 4. Yin [6] cites three general strategies that can be followed for case studies namely: use of theoretical propositions; generation of rival explanations and development of a case description. For the purpose of the case study reported in this paper, the theoretical propositions approach was followed. The theoretical proposition is that the factors identified during the Delphi study are important for the selection of renewable energy technologies in Africa. The factors identified as important during the Delphi study [7] are shown in Figure 5. These are the WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
120 Energy and Sustainability II factors that were rated feasible, highly desirable and highly important in the Delphi study. The case study design, data collection and data analysis is discussed in detail in the paragraphs that follow. INPUT from Delphi study Case studies Design
Malawi
Tanzania
Rwanda
Data collection
Data collection
Data collection
Data analysis
Data analysis
Data analysis
Final Analysis and Reporting
OUTPUT Final factors
Figure 4:
Process followed of case studies.
Achievability by performing organisation Project management Technological capability Financial capacity
Site selection
Suitable sites for pilot studies Local champion Adoption by community Access to suitable sites can be secured
Figure 5:
Economic
Contribution to economic development Availability of finance
Technology
Ease of maintenance and support Ease of transfer of knowledge and skills
Factors identified in various categories during the Delphi study [7].
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2.2 Case study design The case study research methodology is a research strategy appropriate to test contemporary phenomenon in real-life scenarios and is especially helpful when the boundaries between the phenomenon and scenario are not clearly defined [6]. George and Bennett [8] propose the following six theory building research objectives for case studies namely: i) Theoretical/ configurative idiographic case studies. ii) Disciplined configurative case studies. iii) Heuristic case studies. iv) Theory testing case studies. v) Plausibility probes. vi) Building block studies. The case study research discussed in this paper is of a theory testing nature. Factors have been identified using the Delphi method and the purpose of the proposed case studies is to test these factors in a real-life environment. The research design process advocated by George and Bennet [8] and shown in Figure 6 was followed. The output of the process was the selection of the case study and two questionnaires. In order to gather the data for the case study, interviews were required with both the implementing organizations and the users. Implementing organizations and users have different levels of interaction with the project and for this reason a separate questionnaire was developed for each. The questionnaire for the implementing organizations is called the technical questionnaire and the one for domestic households is called the user questionnaire. Both of the questionnaires start out with demographic questions. Each factor identified during the Delphi study as important for the selection of renewable energy technology in Africa is then explored. Finally the interviewee is asked what other factors, which were not yet discussed, are important.
Data requirements and general questions
Problem specification and research objectives
Variance and variable description
Research strategy
Case selection
Figure 6:
Steps in case study design [8].
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122 Energy and Sustainability II The technical questionnaire was piloted using a Zimbabwe biogas implementation project. The questionnaire was updated during the pilot phase to improve ease of use and comprehension. 2.3 Data collection The Malawi Department of Energy together with Programme for Biomass Energy Conservation (ProBEC) have several efficient energy intervention programmes under implementation. For the purposes of this paper however, the focus will be on the implementation of efficient stoves. Table 1: No i)
ii)
iii) iv)
v)
Document title Promotion of alternative energy sources project (PAESP) [16] Houses Baseline situation for Limbulit, Landerdello and Esparanza Tea Estates in Mulanje district for biomass energy conservation technologies [17] Assessment of durability of portable clay stoves [18] Impact assessment at local level: experiences from Malawi-Mulanje district [19] Impact assessment of Chitetezo Mbaula improved household firewood stove in rural Malawi [20]
Summary of secondary data. Issue date November 2006
Organization(s) Department of energy affairs
Author(s)
April 2007
SADC, ProBEC, GTZ
Vincent Gondwe
November 2006
ProBEC
Kondwani Nyengo
December 2004
ProBEC, GTZ
Verena Brinkmann
March - July 2008
GTZ
Britta Malinski
Data was collected in Malawi from 26 to 28 September 2008. In terms of implementing organisations, the acting director of the department of Energy Affairs [9] and personnel of ProBEC were interviewed [10, 11]. The group estate manager was interviewed at the Minimini tea estate in the Mulanje district regarding the fixed efficient stoves, a group of women who produce efficient stoves was interviewed on the Lujeri tea estate [13], a stove user was interviewed on the Glenorchy estate [14] and a newly trained stove producer was interviewed in the Chigwirizano township [15]. All interviews were captured with a digital WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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recorder and notes on each interview were made by two researchers. Several documents were given to the researchers to use as secondary data. A summary of these documents is shown in Table 1. 2.4 Data analysis Yin [3] advocates five methods for case study data analysis namely: pattern matching; explanation building; time-series analysis; logic models and crosscase synthesis. For purposes of analysis of the data for the Malawian case study, pattern matching was utilized. The proposition that each of the factors identified during the Delphi study (see Figure 5) is important is tested by determining whether the primary and secondary data support this proposition. This is done by studying the transcriptions of the interviews and also the supporting documentation to determine whether support can be found for each proposition. A summary of the data analysis for each of the propositions is discussed below. 2.4.1 Technology factors There was an emphasis on ease of maintenance and support over the life cycle of the technology during the programme design as the aim of the programme was to keep the technology as close as possible to the existing technology that the people know [9]. This ensures that stove maintenance is simple and the same was what the people are used to for their three stone hearths [11]. The quality of the stoves, especially the first ones that were not fired, caused a problem for the programme as some users did not want to replace the stoves when they broke [16, 18–20]. Ease of transfer of knowledge and skills to relevant people in Africa was taken into account from the start as no implementation was done without training and training was seen to be successful [9–20]. In this case, there is an emphasis on the fact that training was required not only in the production and use of the stove but also in peripheral skills such as kitchen management, cooking practices, and firewood management [10, 17–19]. 2.4.2 Site selection factors A strong emphasis is placed on local champions to continue after ProBEC withdraws. To this end local capacity is being built [16], there is a direct connection with the village level leaders and empowerment of local people [10, 12, 18], and partner organisations are sought to help with implementation [11]. Adoption by community is constantly being monitored with two studies on adoption having been conducted in 2004 [19] and 2008 [20] respectively. Adoption by the community was found to be dependent on the education level of the community as well as the availability of firewood whereas non-adoption was found to be influenced by lack of access to information and lack of interest in changing current cooking methods [19]. Adopters noted the following advantages to adoption the technology: less time and effort on wood gathering, improvement in health due to less smoke, less burnt food and less accidents [19]
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124 Energy and Sustainability II and [20]. Petty jealousies in the village [11] and negative attitudes of traditional doctors [18] can also hamper adoption. The following two factors identified during the Delphi study namely suitable sites ready for pilot studies and access to suitable sites can be secured did not seem to be important in the implementation of efficient stoves in Malawi. This is most probably due to the strong emphasis on local champions.
Figure 7:
Images of an efficient stove and a kiln.
2.4.3 Economic/financial factors The main emphasis in terms of economic or financial factors for the implementation of efficient stoves in Malawi is economic development. Economic development is targeted on two levels namely commercialisation of stoves [9–13, 15, 16, 18, 19], which enables producers to be economically active, and saving money on firewood [17–19]. Availability of finance did not seem to affect this project as the cost of a stove is $1 in rural areas and $3 in the cities [10], an amount which is quickly recovered by savings in firewood [19] and in the case of the fixed stoves for tea estate employees, the stoves are supplied free of charge [12]. The payment method is also flexible as credit [13] or payment is kind is allowed [19]. 2.4.4 Achievability by performing organization A large emphasis has been placed on ensuring that the organizations implementing the efficient stoves have sufficient skills for long term sustainability. In the Delphi study project management skills of the performing organization were identified as important but during this case study, it has transpired that the skills required are more general than project management and should also include business development skills such as marketing and market development [10, 11, 16, 17, 19]. It is thus proposed that that the description of this factor be changed to business management skills which would then encompass all of these skills. Financial capacity of the stove producers is not that important for this case study as clay which is available in the area is used for stove manufacture [13] and the only capital outlay is the building of the kiln [10]. Technological capacity was found to be very important in this case study as quality of the stoves is of paramount importance [19, 20]. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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2.4.5 Other factors Governmental support was found to be important in this case study as the implementation is being done with strong support from the government [9, 19]. Environmental imperatives were the main drivers for the implementation of this programme [9, 16].
3
Conclusions and recommendations
The proposition that the factors identified during the Delphi study are important when selecting renewable energy technologies has been partly confirmed by this case study as three of the factors identified in the Delphi study were seen as not important and one factor was seen as not so important. The wording of the one achievability by performing organization factor, project management skills should also be updated to read business management skills. Two additional factors have also been identified namely government support and environmental benefits. The updated list of factors as determined by this case study is shown in Figure 8. Achievability by performing organisation Business management skills Technological capability Site selection
Economic Contribution to economic development Other
Government support Environmental benefits
Technology Ease of maintenance and support
Local champion Adoption by community
Ease of transfer of knowledge and skills
Figure 8:
Updated factors.
It is recommended that these factors be compared to the factors that are identified during the analysis of the other case studies performed (see Figure 4) before a final conclusion is made on which factors are applicable when selection renewable energy technologies in Africa.
Acknowledgements The authors wish to thank the Acting director of the Department of Energy Affairs for giving up so much of his precious time as well as the ProBEC WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
126 Energy and Sustainability II personnel who transported us to all the case study sites and also were very generous with their time. We further wish to thank Maxwell Mapako for his support in conducting the case study.
References [1] UNEA 2007 Energy for sustainable development: Policy options for Africa [online]. UN-Energy/Africa. Available from: http://www.uneca.org/ eca_resources/Publications/UNEA-Publication-toCSD15.pdf [Accessed 12 March 2008]. [2] Huba, E.M and Paul, E. 2007. National Domestic Biogas Program Rwanda Baseline Study Report. MINIFRA. Kigali, Rwanda. [3] IEA. 2004. World Energy Outlook 2004. International energy agency. Available from: http://www.iea.org/textbase/nppdf/free/2004/weo2004.pdf [Accessed 19 March 2008]. [4] GTZ. 2009. ProBEC [online]. Available from: http://www.probec.org/displaysection.php?czacc=&zSelectedSectionID=se c1192750452 [Accessed 6 February 2009] [5] CIA. 2008. The World Factbook – Malawi. [online]. Available from: https://www.cia.gov/library/publications/the-world-factbook/geos/rw.html [Accessed 11 September 2008]. [6] Yin, R.K., 2003. Case Study Research: Design and Methods. . Thousand Oaks, California: SAGE Publications, 3rd edition. Applied Social Research method series. Volume 5. [7] Barry, M-L, Steyn, H.S and Brent, A. 2008. Determining the Most Important Factors for Sustainable Energy Technology Selection in Africa: Application of the Delphi Technique. IAMOT 2008 Proceedings. [8] George, A.L. and Bennett, A., 2005. Case studies and theory development in social sciences. Belfer Centre for Science and International Affairs, Harvard University, Cambridge, Massachusetts. [9] Chitenje, H, Interview, 26 September 2008, Acting director of the department of Energy Affairs, Lilongwe, Malawi. [10] Gondwe, V, Khonje, T, Interview, 27 September 2009, ProBEC personnel, Blantyre, Malawi. [11] Sukasuka, T, Interview, 27 September 2009, ProBEC personnel, From Blantyre to Lilongwe, Malawi. [12] Vutuza, P, Interview, 27 September 2008, Group estate manager Minimini tea estate, Mulanje district, Malawi. [13] Mwalimu, E, Njwambo, L, Nchenga, E, Waisen, A, Nathenwe, T, Timu, E and Nazambe, J, Interview, 27 September 2008, Stove producers, Lujeri tea estate, Mulanje district, Malawi. [14] Chioyoza, K, Interview, 27 September 2008, Stove user, Glenorchy Estate, Mulanje district, Malawi. [15] Banda, W, Interview, 28 September 2008, Stove producer, Chigwirizano township, Malawi.
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[16] Anon. 2006. Promotion of alternative energy sources project (PAESP). Department of energy affairs. [17] Gondwe, V. 2007. Houses Baseline situation for Limbulit, Landerdello and Esparanza Tea Estates in Mulanje district for biomass energy conservation technologies. SADC, ProBEC, GTZ. [18] Nyengo, K. 2006. Assessment of durability of portable clay stoves. ProBEC. [19] Brinkmann, V. 2004. Impact assessment at local level: experiences from Malawi-Mulanje district. ProBEC, GTZ. [20] Malinski, B. 2008. Impact assessment of Chitetezo Mbaula - improved household firewood stove in rural Malawi. GTZ.
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The sustainable energy service company (ESCO) experience at DIC Corporation Y. Ishida1, M. Bannai1, K. Ishimaru2, R. Yokoyama3, S. Nakazawa1 & H. Yunoue1 1
Urban Planning and Development Systems, Hitachi, Ltd., Japan DIC Corporation, Japan 3 Waseda University Graduate School of Environment and Energy Engineering, Japan 2
Abstract An ink manufacturing company in Japan is focused on reducing its energy consumption and CO2 emissions. This paper describes energy supply systems that have been applied to actual plants in recent years. We have planned and installed new sustainable systems that combine heat and power (CHP) facilities driven by biomass fuel with large-scale wind power facilities. In our biomass boiler and steam turbine system, the boiler produces high-pressure steam to drive the extraction and condensing steam turbine. The steam turbine generates power (electricity) and heat (process steam) simultaneously. The ratio of heat and power can be controlled according to factory energy demand. We have also built a wind power plant capable of generating total power of 4 MW. An ink factory consumes all the power internally generated by the wind power plant, except that exceeding factory demand. In this way, we plan to reduce the CO2 emission rate. These facilities will be able to reduce our previous use of fossil fuels by 65%, and consequently reduce CO2 emissions by 75%. This paper also introduces the content of our project, subsequent effects and evaluation results. Keywords: energy saving, CO2 emission, energy service company, biomass, wind turbine.
1
Introduction
Effective February 2005, the Kyoto Protocol dictates that measures designed to reduce greenhouse gas emissions will be implemented over a five-year period from 2008 to 2012. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESU090121
130 Energy and Sustainability II Since Japanese manufacturing industries have already devoted considerable efforts to practicing energy-saving measures designed to curtail their energy usage, an approach based on a new perspective is being sought to speed up the pace of energy savings. Toward achieving the goal of drastically reducing carbon dioxide (CO2) emissions, a conversion from fossil fuels to sources of carbon-free energy or those of lower CO2 emissions would prove useful in exhibiting the heightening effectiveness of such sustainable sources of energy as wind power, solar energy and biomass. This paper provides a summary insight into ongoing approaches to saving energy consumption at DIC Corporation and its Energy Service Company (ESCO) business through sustainable sources of energy.
2
Efforts made to date at the DIC Kashima Plant
DIC is a fine chemicals manufacturer extensively involved in four sectors of business including printing materials, based on printing inks and organic pigment inks. The manufacturer has publicly committed itself to a management policy of environmental preservation and operational safety in the form of a Responsible Care (RC) program, a voluntary management activity that implements measures related to the environment, safety and health in pursuit of further reducing environmental pollution, minimizing environmental impact and saving energy. With organic inks, base inks and other inks as its principal line of products, the Kashima Plant is the largest energy consumer among all the plants of DIC Corporation, consuming about 20,000 kL of energy a year in crude equivalents. The environmentally-conscious, energy-saving activities undertaken at the Kashima Plant to date include installing woodchip boilers fueled by waste materials in 1985 and setting up a gas turbine co-generation system in 1997, thereby enabling the plant to achieve about a 40% savings on its electric contract demand over a five-year period from 2001 to 2005, and cutting its annual energy operating cost by about 120 million yen [1].
3
Introduction of ESCO for the purpose of reconstructing energy supply systems
The Kashima Plant has explored various ways to achieve further cuts in energy usage and a drastic reduction in CO2 emissions. It has therefore decided to install a combined heat and power (CHP) system and wind turbine generators (run by the Hitachi Group as an ESCO operator) in an effort to proceed further with an eco-friendly energy reconstruction scheme. Installing such systems entails such a huge amount of investment that it will be implemented on an ESCO contract basis. Leveraging the ESCO business offers the following benefits: (1) Assuring a constant rate of energy savings at all times; WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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(2) Eliminating the need for capital investment on DIC’s part, with the ESCO operator providing the funding necessary to finance facility procurement; and (3) Off-balance sheet treatment of energy-saving facilities. Still another benefit is utilizing the operational experience accumulated by Kashima Plant operators for more than 20 years to operate and maintain biomass-fueled boilers.
4
Overview of the sustainable energy ESCO business
4.1 Overview of the ESCO business Table 1 summarizes the ESCO business under discussion [2]. Because the contract concluded between DIC and an ESCO operator is signed on a shared-saving ESCO basis, all facilities needed to achieve energy savings are procured and owned by the ESCO operator. The ESCO operator also operates and maintains these facilities, and assumes responsibility for the successful functionality of all equipment during the contract period. DIC, on the other hand, assumes responsibility for procuring biomass fuels. Since all sets of facilities are scheduled to be commissioned into service in April 2009, the ESCO contract package will be started from now on. Table 1:
Overview of ESCO business.
1. Contract method
Shared savings (investment costs borne by the ESCO operator)
2. Contract period
15 years
3. Installed facilities
(a) Woody biomass-fueled boiler: 30 t/h x 1 set (b) Extraction-condensing turbine generator: 4,000 kW x 1 set (c) Auxiliary boilers (for backup): 5.5 t/h x 6 sets, 2 t/h x 1 set (d) Wind turbine generator: 2,300 kW x 2 sets
4. Facility and contract startup times
(a) Biomass boiler and turbine generator facility: Commissioned into service in April 2008 (b) Wind turbine generator facility: To be commissioned into service in April 2009 (scheduled) (c) ESCO contract: At the beginning of 1st April 2009 (scheduled)
Figure 1 shows a general flowsheet of the ESCO facilities. The ESCO facilities are organized into the following two systems: (1) Facility which generates steam and electricity by biomass, in which a biomass fuel is combusted at high temperature to generate steam energy in a boiler, from which electricity is recovered in a turbine. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
132 Energy and Sustainability II (2) Wind turbine generator facility that recovers wind energy as electricity. Any lacking portion of energy supplied from these facilities is met by purchasing electricity from a power company or producing steam energy by running an auxiliary boilers. These ESCO facilities offer such significant energy-saving effects that Hitachi and DIC have been granted jointly the following two types of subsidies for operators: (1) Biomass generator facility: Energy Use Rationalization Subsidy (New Energy and Industrial Technology Development Organization) (2) Wind turbine generator facility: Supportive Measures applicable to the Promotion of ESCO Projects (Agency for Natural Resources and Energy)
Abbreviation CGS: Co-generation system
Figure 1:
General flowsheet of ESCO facilities.
Figure 2 shows the expected energy consumption rate, CO2 emission rate, and their reductions for a one-year period. Plans call for annual energy usage at the Kashima Plant to be cut from its year 2006 level of 20,000 kL by 11,220 kL(to 8,780 kL), and CO2 emissions from 39,300 tons by 30,500 tons (to 8,800 tons). 4.2 Woody biomass generator facility The plant requires large volumes of electricity and steam to operate its production equipments. These energy demands fluctuate widely on a seasonal, daily and hourly basis. The required steam pressure used at the plant is at a medium pressure (of 1.1 MPa (G)). This value must be maintained at all times. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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Figure 2:
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Expected energy consumption rate, CO2 emission rate, and their reductions (compared between existing and new ESCO facilities).
To enhance the efficiency with which energy is recovered from biomass fuels, the following design enhancements have been factored into the steam usage system: (1) Higher-enthalpy steam recovered from waste heat Steam requirements for the biomass-fueled boilers have been enhanced to a higher pressure (of 6.08 MPa (G)) and higher temperature (of 683 K) to increase the amount of power recovered by the steam turbine. Steam of higher enthalpy is able to efficiently produce heat and electricity. (2) Combined heat and power (CHP) generation by a steam turbine generator facility Electricity is recovered by a back-pressure turbine to enable the effective utilization of energy from high to medium pressures. Should the steam demand be lower than the amount of steam generated from the boiler, excess steam is generated. In such a case, a condensing steam turbine is used to recover electricity from excess steam energy as it generated. An extraction-condensing turbine generator facility is planned in order to meet both requirements. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
134 Energy and Sustainability II This system feeds steam to meet the heating demand, with any excess proportion of steam being dedicated to generating electric power (free from CO2 emissions) in order to make effective fuel derived from biomass. Woody biomass fuels that vary in terms of heating value and shape would require enhancing the reliable supply of fuel (woodchips) to ensure stable and consistent system operation. To achieve the projected increase in the volume of woody biomass fuel procurement from 40,000 tons to 60,000 tons a year, more procurement sources are needed, and entail a specifically designed fuel supply system. Based on past experience, the following two improvement measures have been incorporated into the fuel supply system: (1) The previously manual night-time fuel charging system has been automated through the use of a hoist crane. This method significantly lessens operator workload at night. (2) The sharp-angled (75-degree), chain-driven flight conveyor previously used in the fuel charging system often impeded successful travel as it developed problems, such as a cut chain or deformed flight. As a solution, loading over a belt conveyor gradually angled at 45 degrees has been introduced to alleviate such problems.
Figure 3:
Woody biomass-fueled steam and generator facility commissioned into service at the DIC Kashima Plant.
Figure 3 shows an overview of the newly installed woody biomass-fueled steam and generator facility commissioned into service in April 2008. The facility has since been successfully running as of March 2009. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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4.3 Wind turbine generator system Conveniently located along on the Pacific coast, the Kashima area is such an appropriate location in terms of wind conditions (e.g., wind intensity, occurrence probability) that wind turbine generator facilities have already been constructed in this area, mainly for the purpose of selling the electricity generated to power companies. Power producers who sell electricity generated by wind turbines to a power company are called “independent power producers (IPPs).” In contrast, all electricity generated by the generator facility at the DIC Kashima Plant is dedicated to its internal consumption in order to enhance energy saving effects, thereby marking the first time in Japan where the total amount of electricity generated by a total 4 MW-class large wind turbine generator facility is consumed in-house. It is generally known that the higher above ground level, the better the wind conditions. This wind turbine generator facility has an elevated hub height of 64 m to generate more wind power, and also features a diameter of 71 m to produce as much as 2,300 kW of generated power. Two sets of the wind turbine generator facility capable of generating 2,300 kW are currently planned. As of February 2009, both were in the final
Figure 4:
Overview of the wind turbine generator facility (2,300 kW class x 2 sets).
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136 Energy and Sustainability II stage of construction. Figure 4 shows an overview of the wind turbine generator facility nearing completion.
5
Conclusions
This paper has introduced an example of an energy restructuring ESCO business that makes positive use of sustainable forms of energy free from carbon dioxide emissions. While the market for fossil fuels has fluctuated erratically in recent years amid the perceived peaking of crude oil supply and a rapidly developing world recession, sustainable forms of energy are predicted to gain accelerating popularity in response to these situations. Sustainable forms of energy are subject to certain uncertainties, however, such as wind conditions, heating value and shape, thereby demanding handling experience essentially and expertise to put them to positive use. We would like to take advantage of the experience gained from operating these and other systems, and also promote their ongoing popularity by releasing relevant information.
References [1] Ishimaru: Energy Saving Effort in Practice at a Fine Chemicals Plant, The Institute of Electrical Engineers of Japan, General Industry Workshop Literature (February 2008) (in Japanese). [2] Yunoue et al.: Carbon Dioxide Gas Reduction Using Renewable Energy, Hitachi Hyoron, 89, 3, pp. 294-297 (March 2007) (in Japanese).
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Renewable energy from restored prairie plots in southeastern Minnesota, USA B. Borsari1, I. Onwueme2, E. Kreidermacher3 & T. Terril4 1
Department of Biology, Winona State University, Winona, MN, USA College of Natural & Applied Sciences, Missouri State University, Springfield, MO, USA 3 Pork & Plants, Altura, MN, USA 4 Winona County Soil & Water Conservation District, Lewiston, MN, USA 2
Abstract Although prairies occupied most of North America prior to European settlement, an extirpation of these habitats has inevitably occurred since the expansion of intensive, agricultural systems. In recent years, however, a renewed interest in prairie restoration has spurred increasing efforts for looking at prairies as possible sources of renewable energy. The purpose of our work was to establish a prairie community on marginal farmland with the goal of producing pellets from its biomass to be burned on site for heating greenhouses, instead of relying on corn (Zea mays) as a biomass source. Plots of grass only and plots of mixtures of forbs and grass species were planted in 2007 on a farm in southeastern Minnesota. In its second year of growth, the biomass produced was compared to what was obtained from corn stover cultivated at the farm. The biomass yield data produced from the different plots of equal hectarage were analyzed through a one-way ANOVA and Scheffe’s test to verify significant differences among the three different cropping conditions (grass, grass and forbs, corn). Our data indicated that prairie plots with mixtures of grass species can be the most productive for biomass production. This preliminary work is of value in this part of the world and should inspire more farmers in the Midwest region of the U.S. to restore prairies on marginal lands. Keywords: biofuel, forb, grass, pellet production, prairie, renewable energy, sustainability.
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1
Introduction
The extirpation of American prairies allowed for an expansion of gigantic agricultural systems, dominated by corn (Zea mays) monocultures cultivated in rotation with soy beans (Glycine max) to support a highly centralized, fossil fuel dependent food system. In more recent times however, a chronic agricultural crisis has been affecting US agriculture and the current fluctuation in oil prices upon which modern agriculture depends remains a chronic threat to large scale agriculture, both economically and environmentally [1]. The recent enthusiasm for producing ethanol from corn as a new source of renewable energy has not contributed to aid U.S. agriculture, nor to alleviate the compelling need for employing renewable fuels as alternatives to petroleum, although Mielenz [2] contends that there is great potential for corn and more plant species in the emerging world of bioenergy, through an application of biotechnological approaches and genetic engineering. Thus, U.S. economy remains heavily reliant on oil and other non renewable fuels while the effort to produce ethanol from corn remains challenged in its reductionist attempt to resolve the current energy crisis. This effort has contributed to amplify visions and ideas about the obsolescence of an agricultural paradigm, which demands instead a more careful consideration to be designed to fulfil the needs of 21st century society with more sustainability in mind and a higher level of commitment to stewardship.
2
A quest for developing more sustainable energy systems
The challenge of designing renewable and more sustainable energy systems is often hampered by several barriers, including the difficulty of evolving farming systems from large annual monocultures to perennial polycultures. To this end, Fargione et al. [3] have demonstrated that a conversion of natural ecosystems into agricultural monocultures for biofuel production like ethanol releases a much larger amount of CO2 in the atmosphere than the one that can be offset by biofuel use, and thus proving a major fallacy for making this and similar approaches feasible. On the other hand, recent studies [4, 5] have suggested that perennial, rhizomatous grasses like switchgrass (Panicum virgatum) and many other species possess great attributes to be grown for energy purposes [6]. Concurrently, opportunities wait to be further explored in the agro industry of North America when herbaceous feedstock is converted into pellets to be burned for heating purposes [7]. We remain critical however that the emerging biofuel model of production be constructed with the similar approaches that led to the design of annual monocultural systems but rather, we envision agroecosystems of perennial polycultures dominating the future landscape of our bioregion. As a matter of fact, at the opposite end of this epistemological spectrum, low-input polycultures of native grasses and forbs appear to possess even higher potential for renewable biofuels production [8] and for attenuating the gas emissions during the conversion process. Inspired by this approach, we decided in 2007 to verify the initial findings of Tilman and his collaborators by establishing prairie patches on a larger scale than the typical size of a few squared meter plots. The WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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intent of this endeavour consisted in developing an on-farm biomass production system, capable of weaning itself from propane and corn combustion for heating its greenhouses [9]. The purpose of this study focused on assessing the yields of prairie biomass from mixed perennial grasses, and grasses with forbs when these were compared to corn (Zea mays) stover for the production of pellets that were going to be used on site, thus attempting to achieve a greater level of sustainability for the farm. The need for this study was spurred by the increasing necessities of developing more sustainable and renewable energy systems, especially after the disappointing outcomes of ethanol production from corn in recent years. There may be significant opportunities for farmers interested in developing markets for agropellets as the estimated 500,000 pellet burning stoves and furnaces in North America [10] provide an indication for a viable market niche from biomass in most of the USA. In addition to this, there is an increasing need to restore the ecological equilibria and services that regulate food production systems and enterprises [11] as fast anthropogenic changes upon the landscape continue to obliterate the natural attributes of the same [12]. The Canadian experience in producing pellets from prairie biomass appears to have already made major steps forward in developing an efficient pellet production system, while identifying promising plant species, best management practices and while proposing viable solutions to technical challenges for employing native perennial plants as biofuels. A similarity of environmental conditions and resources to the above mentioned Canadian studies provided us with another significant stimulus to work towards the development of a renewable energy system feasible for our bioregion.
3
Materials and methods
In the early summer of 2007, 7.9 hectares of a 16.2 hectare farm (Pork &Plants), located in south eastern Minnesota (Winona County), were planted with mixed grasses (4.7 Ha.) and mixtures of grass with forbs species (3.2 Ha.), fig. 1. This approach stemmed from the idea of reducing reliance on corn and propane gas, which are burned on-site for heating purposes [9]. The seed was drilled into the soil with equipment already available at the farm and no other inputs were used to establish the prairie plots. Adjacent fields were planted to corn and raised with the standard inputs for corn production in Minnesota. Toward the end of the first growing season (2007) an evaluation of prairie establishment was conducted to assess prairie establishment and species richness in the grass with forbs plots, when these were compared to the grass only plots [9]. For the three cropping conditions (corn, grass polyculture, grass with forbs polyculture) we considered 1-acre parcels (0.405ha) as our units of analysis. Thus, we collected 10 biomass weights from the corn field, 8 from the grass polyculture field (these plots were harvested twice). Twenty four sample weights were collected from 9.7ha of adjacent prairie of the Minnesota Department of Natural Resources (MNDNR), which has been restored for 15 years. The decision of harvesting the DNR prairie was made in order to collect more reliable data from the grass with forbs cropping system since the one WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
140 Energy and Sustainability II planted at Pork & Plants in 2007 was flooded in the summer of 2008 and thus, mostly inaccessible. In 2008 the prairie plots were harvested and biomass yield data were collected in order to verify which one of the three systems was most productive and thus substantiate or refute experimental data obtained in Minnesota a few years ago by Tilman and his collaborators [8]. The harvest took place in mid-November 2008. Plots planted with a mixture of prairie grasses (4.7 Ha) were harvested in August in addition to the autumn harvest. The biomass was mowed and subsequently baled with a rotobaler.
Figure 1:
Aereal photograph of Pork & Plant Farm, showing the five prairie plots that were established in the early summer of 2007. The grid in the lower left corner shows the location of the farm in Winona County (south eastern Minnesota).
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Results and data analysis
Biomass yields (Mg/ha) were measured as the fields were harvested in the summer and autumn of 2008. A summary of quantitative and qualitative data for the three different types of fields are reported in table 1. Table 1:
Summary statistics for yields, plot type and crop species.
Plot
Mean Yield (Mg/ha)
Crop type
Number of Harvests
polyculture
Land type (agricultural vs. marginal) Marginal
Grasses and forbs Prairie grasses Corn
1.14+0.78 2.17+0.87
polyculture
Marginal
3.15+0.68
Corn
Agricultural
Summer and autumn Autumn
Autumn
A description of biomass yield (Mg/ha) for the three different cropping systems is reported in figure 2. In addition to this, the data were analysed with a one-way ANOVA in order to identify any significant difference [10].
Figure 2:
Biomass yields for each plot (0.405ha) and for the three cropping systems (grass with forbs polyculture, corn, grass polyculture).
Although the mean biomass yield was the highest in the corn stover plots (fig. 3), the analysis of the variance (ANOVA) indicated that the type of vegetation composition (monoculture versus polyculture) had a significant effect on biomass yield, F (2, 39) = 149, p < 0.01. Furthermore, a post hoc test (Scheffe’s test) was also employed to identify differences among pairs of bioenergy cropping systems [13, 14]. This analysis WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
142 Energy and Sustainability II did not indicate any significant difference between the biomass yields of prairie grasses versus those of grasses and forbs, nor between those of prairie grasses with forbs and those from the corn stover crop. However, the data provided sufficient evidence to suggest that there was a difference between the grass mixture plots versus the corn fields. Our findings did not support entirely the data of Tilman and his collaborators [8]. However, these preliminary results indicate that there is a realistic match with those data (fig. 3) and that these will emerge with greater emphasis as more yield measurements will be taken in future growing seasons.
Figure 3:
5
Mean biomass yields for the three cultivation conditions (grass with forbs polyculture, corn, grass polyculture) and standard errors.
Discussion
The mean biomass yield from corn stover was higher than yields obtained from 0.405ha plots where mixed perennial grasses and grasses with forbs were grown. For this reason the skepticism for producing biofuels from low-input highdiversity (LIHD) grassland biomass remains consistent and in favour of corn cultivation rather than perennial polycultures. However, it must be pointed out that corn cultivation requires several off-farm inputs such as: 148 kg/ha of nitrogen, 23 kg/ha of phosphorus, 50 kg/ha of potassium on a yearly basis [15], in addition to water for irrigation and the inevitable loss of topsoil due to erosion and leaching of nutrients into underground aquifer and other water reservoirs [11]. In addition to this, corn must be grown on fertile soils whereas prairie plant communities can be productive on marginal land and be successful without the inputs necessary to grow corn and other annual agronomic crops. Thus, the WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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lower the inputs and fertility conditions, the better the relative performance of the prairie grasses compared to corn. Finally, our experiment yielded data from one growing season only since establishment of native vegetation plots at the farm. An unusually rainy summer in 2008 affected harvesting operations and did not allow the first of the two planned harvests. Concurrently, a variety of grass species have been identified as possible crops for pellet production [4, 6, 7, 16, 17] and are studied to be genetically modified so that they may acquire the desirable traits to be grown on a large scale and to yield pellets of superior quality, that burn completely and leave minimum ash residue in the burner, after combustion [7, 10]. A long-term field study by Varvel et al [16] to compare the potential for ethanol production between corn (Zea mays) and switchgrass (Panicum virgatum) indicated that the potential of switchgrass was superior to the annual grass (corn) and did not require the costly inputs normally used to achieve successful yields. However, the challenge of cultivating native, perennial species consists in utilizing marginal soils and minimum inputs in order to achieve a positive carbon balance between productivity and crop growth. Prairie restoration requires normally a three to five year time frame for the plant community to become sufficiently established and diverse in its floral composition. At Pork & Plants we were in the second year since the restoration effort began in 2007 and thus, despite our ability to substantiate only partially the experimental outcomes obtained by Tilman and co-workers in 2006, we remain convinced that similar results will be achieved as the perennial polycultures at Pork & Plants will enter their fourth, or fifth year since restoration commenced. Ultimately, we remain optimistic that harvests in future years will favour the high diversity plots as supported by the literature. 5.1 Conclusion and implications for future research Wes Jackson envisions a new agricultural paradigm (Natural Systems Agriculture) that relies more and more on perennial species and on a model of food production that mimics the ecological processes and services of the prairie; he foresees this knowledge to become the framework for a 50-year Farm Bill in the U.S. [1]. The compelling need of conserving biodiversity and a more sustainable employment of resources demands an inevitable reconciliation between agriculture and resource use [18]. The prospects of a flourishing agropellet industry in the near future appear to be feasible for large agricultural regions of Canada and the Midwestern region of the U.S. [7]. However, several technical aspects remain to be resolved as prairie biomass contains a high amount of alkali and thus leaves a higher ash residue after combustion than the one left by other types of biomass. Although delaying harvest to late autumn or to the following spring seem to reduce the amount of unwanted elements (as these are translocated into the underground root system), more technical and management issues need to be resolved [2, 7]. A minimization of biomass loss during baling is of great importance also to possible pellet producers, in addition to a development of local market niches. It would be paradoxical to develop such a new agroindustry upon the similar tenets that rule the commercialization of present agricultural commodities, as a majority of the environmental benefits WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
144 Energy and Sustainability II of this enterprise would evaporate inevitably, because of transportation costs. Rather, we envision the feasibility of an agro-pellet production enterprise with prairie biomass for North American territories where a restoration of farmland to prairie is achievable with success, reduced off-farm inputs, and major environmental benefits for the agrarian landscape. This approach is also in tune with present conservation needs of the agricultural environment to limit soil erosion as a loss of topsoil continues to affect the sustainability of agriculture [19] even when the best agronomic practices are employed [20]. Therefore, a cultivation of perennial polycultures is to be encouraged instead of researching the benefits of annual, non-perennial, non-native species like Miscanthus [17] and others, regardless of their potential as bioenergy crops. The next 50 years of land management in the U.S. will require the greatest wisdom to achieve sustainability and to ensure that future generations may continue to enjoy a comparable quality of life and prosperity with a clearer understanding about the finiteness of our natural resource base [1]. To this end, we support the vision of prairie farming to be embraced by farmers in Minnesota and in several other states of the of the U.S. Midwest region.
Acknowledgements We are grateful to the Department of Natural Resources (DNR) of Minnesota for granting access to its land and for allowing us to harvest biomass from its prairie. Daryl Buck of the Soil and Water Conservation Service of Winona County, Minnesota was generous in donating seed and technical service for prairie establishment at Pork & Plants.
References [1] Jackson, W., The Prairie Meets the Farm: The Next 50 Years on the American Land-Perennializing Policy and the Landscape. Proc. of the 21st North Am. Pr. Conf., eds. B. Borsari, N. Mundahl, L. Reuter, E. Peters & P. Cochran, Winona State University: Winona, MN (in press). [2] Mielenz, J.R., Bioenergy for ethanol and beyond. Current Opinion in Biotechnology, 17(3), pp. 303-304, 2006. [3] Fargione, J., Hill, J., Tilman, D., Polasky, S. & Hawthorne, P., Land Clearing and Biofuel Carbon Debt. Science, 319(5867), pp. 1235-1238, 2008. [4] Lewandowski, I., Scurlock, J.M.O., Lindvall, E. & Christou, M., The development and current status of perennial rhizomatous grasses as energy crops in the US and Europe. Biomass and Bioenergy, 25(4), pp. 335-361, 2003. [5] McLaughlin, S.B. & Walsh, M.E., Evaluating environmental consequences of producing herbaceous crops for bioenergy. Biomass and Bioenergy, 14(4), pp. 317-324, 1998.
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[6] Schmer, M.R., Vogel, K.P., Mitchell, R.B., Moser, L.E., Eskridge, K.M. & Perrin, R.K., Establishment Stand Thresholds for Switchgrass Grown as a Bioenergy Crop. Crop Science, 46, pp. 157-161, 2006. [7] Samson, R., Mani, S., Boddery, R., Sokhansanj, S., Quesada, D., Urquiaga, S., Reis, V. & Ho Lem, C., The potential of C4 perennial grasses for developing a global BIO-HEAT industry. Critical Review in Plant Science, 24, pp. 461-495, 2005. [8] Tilman, D., Hill, J. & Lehman, C., Carbon-Negative Biofuels from LowInput High-Diversity Grassland Biomass. Science, 314(5805), pp. 15981600, 2006. [9] Borsari, B. & Onwueme, I., A New Lease on Life for Marginal Farmland: Convergence of Prairie Restoration with Biofuel Production. Proc. of the 16th IFOAM Organic World Congress, eds. D. Neuhoff, N. Halberg, T. Alföldi, W. Lockeretz, A. Thommen, I.A. Rasmussen, J. Hermansen, M. Vaarst, L. Lueck, F. Caporali, H.H. Jensen, P. Migliorini & H. Willer, ISOFAR: Bonn, vol.2, pp. 608-611, 2008. [10] PFI (Pellet Fuels Institute), http://www.pelletheat.org [11] Brown, L.R., Plan B 3.0-Mobilizing to Save Civilization. W.W.Norton & Company Inc., New York, NY, 2008. [12] Tilman, D. & Lehman, C., Human-caused environmental change: Impacts on plant diversity and evolution. PNAS, 98(10), pp. 5433-5440, 2001. [13] Huck, S.W. & Cormier, W.H., Reading Statistics and Research, HarperCollins Publishers Inc.: New York, 1996. [14] Patten, M.L., Understanding Research Methods. An Overview of the Essentials, Pyrczak Publishing: Glendale, CA, 2002. [15] Tilman, D., Hill, J. & Lehman, C., Response to Comment on “CarbonNegative Biofuels from Low-Input High Diversity Grassland Biomass. Science, 316(5831), pp.1567, 2007. [16] Varvel, G.E., Vogel, K.P., Mitchell, R.B., Follett, R.F. & Kimble, J.M., Comparison of corn and switchgrass on marginal soils for bioenergy. Biomassand bioenergy, 32(1), pp. 18-21, 2008. [17] Heaton, E.A., Dohleman, F.G. & Long, S.P., Meeting US biofuel goals with less land: the potential of Miscanthus. Global Change Biology, 14(9), pp. 2000-2014, 2008. [18] Ceroni, M., Liu, S. & Costanza, R., Ecological and Economic Roles of Biodiversity in Agroecosystems, pp. 446-472 In: Managing Biodiversity in Agricultural Ecosystems, eds. Jarvis, D.I., Padoch, C. & Cooper, H.D., Columbia University Press, 2007. [19] Kort, J., Collins, M. & Ditsch, D., A review of soil erosion potential associated with biomass crops. Biomass and Bioenergy, 14(4), pp. 351359, 1998. [20] Zentner, R.P., Lafond, G.P., Derksen, D.A., Nagy, C.N., Wall, D.D. & May, W.E., Effects of tillage method and crop rotation on non-renewable energy use efficiency for a thin Black Chernozem in the Canadian Prairies. Soil and Tillage Research, 77(2), pp. 125-136, 2004.
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Iron catalysts supported on carbon nanotubes for Fischer–Tropsch synthesis: effect of pore size R. M. Malek Abbaslou, J. Soltan, S. Sigurdson & A. K. Dalai Catalysis & Chemical Reaction Engineering Laboratories, Department of Chemical Engineering, University of Saskatchewan, Saskatoon, Canada
Abstract In this report, the effects of pore diameter and structure of iron catalysts supported on carbon nanotubes (CNTs) on Fischer–Tropsch (FT) reaction rates and product selectivities are presented. Two types of CNTs with different average pore sizes (12 and 63 nm) were prepared. The CNTs were chosen in a way to have comparable surface areas so as to eliminate the effects of different surface areas. The iron catalysts (the narrow pore catalyst denoted Fe/np-CNT and wide pore catalyst denoted Fe/wp-CNT) were prepared using incipient wetness impregnation method and characterized by ICP, BET, XRD, TPR, SEM and TEM analyses. The TEM and XRD analysis showed that the iron oxide particles on the Fe/wp-CNT (17 nm) were larger than those on Fe/np-CNT sample (11 nm). TPR analyses of the catalysts showed that the degree of reduction of the Fe/np-CNT catalyst was 17% higher compared to that of the Fe/wp-CNT catalyst. For the FT reactions, it was found that the activity of the np-CNT catalyst (%CO conversion of 31) was much higher than that of the wpCNT catalyst (%CO conversion of 11). Also, the Fe/wp-CNT was more selective toward lighter hydrocarbons with a methane selectivity of 41% whereas, the methane selectivity of the np-CNT catalyst was 14%. It can be concluded that the deposition of the metal particles on the CNT with narrow pore size (in the range of larger than 10 nm) results in more active and selective catalyst due to higher degree of reduction and higher metal dispersion. Keywords: Fischer–Tropsch synthesis, iron, carbon nanotubes, pore size.
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1
Introduction
Fischer–Tropsch (FT) synthesis is a potentially attractive technology for production of clean liquid fuels from syngas. The syngas can be supplied through gasification of coal or biomass and reforming of natural gas. FT synthesis proceeds on metal (Fe, Co and Ru) supported catalysts. The efficiency of the FT synthesis can be enhanced by design of new catalysts with higher syngas conversion, higher C5+ yield, and lower methane selectivity [1–2]. In the FT processes, the catalyst activity and selectivity are influenced by nature and structure of the support, nature of the active metal, catalyst dispersion, metal loading, and catalyst preparation method [3]. Most studies on FT catalysts have been carried out with the metals supported on silica, alumina or titania and their structural properties such as pore size have been studied [4]. Recently, carbon nanotubes (CNTs) as a new support have been investigated for FT reactions [5–11]. Carbon nanotubes with unique properties such as uniform pore size distribution, meso and macro pore structure, inert surface properties, and resistance to acid and base environment can play an important role in a large number of catalytic reactions [11]. CNTs are different than the other supports in that they have graphite layers with a tubular morphology [7–8]. Also, CNT structure such as inner and outer diameter and length of nanotubes can be manipulated using different synthesis processes and operating conditions. Literature review including our previous work on the application of CNTs as support for catalytic reactions especially FT reactions have shown that CNTs can be considered an alternative support which can improve performance of metal catalyst compared to the other supports [4–9,12]. However, the effects of pore size and diameter of carbon nanotubes on the catalytic performance of FT catalysts have not comprehensively been studied. In general, pore size of supported catalysts can influence particle size distribution, dispersion, extent of reduction, and mass transfer rates [4]. In this report, the effects of pore diameter of the support CNTs on FT reaction rates and selectivities over iron catalysts are presented. Two types of CNTs with different average pore sizes (10 and 63 nm) were prepared in a way to have comparable surface areas so as to remove the effects of different surface areas.
2
Experimental
In order to analysis solely the effects of inner pore of CNTs on the performance of the iron catalyst for the FT reactions, two CNT samples with considerable difference in the pore diameters were used. The narrow pore CNT sample (denoted as np-CNT) was purchased. The wide pore CNT sample (denoted as wp-CNT) was synthesized using anodic aluminum oxide (AAO) films and chemical vapor deposition method. The details of synthesis procedure were given in our previous paper [12]. Both CNT samples were treated in nitric acid (60 wt%) at 110oC for 16 hours. The catalysts were prepared according to the incipient wetness impregnation WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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method. For the preparation of the catalyst with iron particles inside the nanotube pores with 20 wt% Fe, an appropriate amount of Fe(NO3)3·9H2O was dissolved in deionised water. The volume of the salt solution was equal to total pore volume of the CNT samples. In this case, the metal solution filled the inner pores of the CNTs due to capillary effects [5]. After drying at 120oC and calcination at 400oC for 3 hours, the catalysts were characterized by nitrogen adsorption, ICP, TPR, XRD, SEM and TEM. The surface area, pore volume of the CNTs and catalysts were measured by an ASAP-2000 Micromeritics system. The samples were degassed at 200oC for 2 h under 50 mTorr vacuum and their BET surface area and pore volume were determined. XRD analysis was performed using a Philips PW1840 X-ray diffractometer with monochromatized Cu/Kα radiation. The crystallite diameter was estimated using Debye–Scherrer equation The reduction behavior of the catalyst precursors was studied by temperature programmed reduction (TPR) using a CHEMBET-3000 equipped with a thermal conductivity detector. 0.1 g of the catalyst was placed in U-shaped quartz tube. A 5% hydrogen/nitrogen mixture was introduced (flow rate = 36 cm3 (STP)/min) and the furnace was ramped from room temperature to 1173K at 10 K/min. Morphology of the samples was studied by transmission electron microscopy (TEM). Sample specimens for TEM studies were prepared by ultrasonic dispersion of the catalysts in ethanol, and the suspensions were dropped onto a copper grid. TEM investigations were carried out using a Hitachi H-7500 (120kV). Several TEM micrographs were recorded for each sample and analyzed to determine the particle size distribution. A Phillips SEM-505 scanning electron microscope operating at 300 kV in SE display mode was also used. For characterization prior to analysis, all the samples were gold coated in a sputter coating unit (Edwards Vacuum Components Ltd., Sussex, England). The Fischer–Tropsch synthesis was performed in a fixed-bed micro reactor. Prior to CO hydrogenation, in-situ reduction was conducted according to the following procedure. The catalyst (0.5 g) was placed in the reactor and diluted with 5 g silicon carbide. Then pure hydrogen flow was established at a rate of 45 ml/min. The reactor temperature was increased from room temperature to 380oC at a rate of 1oC/min and maintained at this activation condition for 14 h. After the activation period, the reactor temperature was decreased to 275oC under flowing hydrogen. Hydrogen and syngas flow rates were controlled by Brooks 5850 mass flow controllers. Argon was used as internal standard gas in the reactor feed. The mixed gases (30%CO, 60%H2, 10% Ar) entered the top of the fixed bed reactor. The temperature of the reactor was controlled via a PID temperature controller. Synthesis gas with a space velocity of 7200 cm3(STP)/(h g) was introduced and the reactor pressure was increased to 2 MPa. Products were continuously removed from the vapor and passed through two traps. The pressure of uncondensed vapor stream was reduced to atmospheric pressure. The composition of the outlet gas stream was determined using an on-line GC-2014 Shimadzu gas chromatograph. The contents of traps were removed every 24 h, the hydrocarbon and water fractions were separated, and then analyzed by Varian WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
150 Energy and Sustainability II 3400 GC. Catalytic activity and product selectivity were calculated after a time on stream of 50 hours.
3 Results and discussions 3.1 Supports and catalysts characterizations SEM images (Figure 1a and 1b) of the acid-treated and purified CNTs samples (np-CNT and wp-CNT) revealed that the samples contained solely CNTs and no other impurities such as amorphous carbon was observed. Figure 1a shows that the np-CNT sample contained woven nanotubes with high aspect ratios. For wpCNT sample, SEM image (Figure 1b) exhibited that nanotubes were well-aligned and the caps of nanotubes were open. TEM images of the acid-treated CNT samples are given in Figure 2a and 2b. Figure 2a shows that the np-CNT sample had uniform nanotubes diameter and their inner and outer diameters varied between 8-12 nm and 20-25 nm, respectively. TEM analysis also revealed that a vast majority (more than 70%) of the np-CNT sample possessed open caps nanotubes (Fig 2a). As seen in Figure 2b, the wp-CNT sample comprised of straight nanotubes with diameter of 50-70 nm along with several Y junctions with inner diameters of 30-50 nm. The thickness of the walls varied in 7-9 nm range.
a
Figure 1:
b
SEM micrograph of the CNT supports, a) np-CNT, b) wp-CNT.
The particle size distribution and position of the iron particles inside or outside of the CNTs were studied using several TEM images from each of the catalyst samples. Figure 3a and 3b show a representative TEM image of the iron catalyst supported on narrow pore CNT sample (Fe/np-CNT) and iron catalyst supported on wide pore CNT sample (Fe/wp-CNT). Dark spots represent the iron oxides which are attached inside or outside of the nanotubes. For both catalysts, a vast majority of the iron particles (80%) were distributed in the inner pores of CNTs (Fig. 3a and 3b). This can be attributed to carbon nanotubes’ tubular structure which can induce capillary forces during the impregnation process. In WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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the case of Fe/np-CNT, the size of iron oxide particles varied from 4 to 14 nm with most abundant particles with a diameter of 8-10 nm. Whereas in the case of Fe/wp-CNT catalyst, particle size covers a wide range varying form 5 to 65 nm with the most abundant particle size of 14-21 nm. The data suggest that inner pore of nanotubes physically restricted the particle size growth unless the particle was located on the exterior surface of the nanotubes.
a
b
Figure 2:
a
Figure 3:
TEM images of CNT supports a) np-CNT b) wp-CNT.
b
TEM images of the iron catalysts a) Fe/np-CNT b) Fe/wp-CNT. Dark spots represent the iron oxide particles inside and outside of the nanotubes.
Table 1 shows the metal content for the Fe/np-CNT and Fe/wp-CNT catalysts. ICP analyses of the catalysts revealed that the metal contents of the catalysts were fairly similar and close (±0.4%) to the target metal content of 20 wt% Fe. Table 1 also shows the results of surface area measurements of both CNT supports and corresponding iron catalyst. As discussed earlier, both CNT samples had a comparable surface areas (212 m2/g for np-CNT and 218 m2/g for WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
152 Energy and Sustainability II wp-CNT). As a result, both Fe/np-CNT and Fe/wp-CNT catalysts held similar metal loading per surface area of the supports. According to the N2 adsorption analysis, the loading of 20% Fe decreased the surface area of Fe/np-CNT and Fe/np-CNT catalysts to 155 and 186 m2/g, respectively. These data show that the BET surface area of the catalysts were lower than that of the supports indicating pore blockage due to iron loading on the supports. However, comparison between BET surface area of the Fe/np-CNT and Fe/wp-CNT catalysts showed that the extent of pore blockage in the Fe/np-CNT was higher than that in Fe/wpCNT.
Figure 4:
XRD spectra of Fe/np-CNT and Fe/wp-CNT. (1: Fe2O3, 2:Fe3O4, 3: CNT).
Table 1:
Metal content and surface properties of CNT samples, Fe/np-CNT and Fe/wp-CNT catalysts.
Catalyst Name np-CNT-support wp-CNT-support np-Fe/CNT wp-Fe/CNT
Metal Content%1 0 0 19.6 20.1
BET Surface Area (m2/g) 212 218 155 186
Total Pore Volume (cm3/g) 0.58 0.55 0.44 0.48
1-Determined by ICP analysis.
Figure 4 shows XRD patterns of the calcined Fe/np-CNT and Fe/np-CNT catalysts. For both catalysts, the peaks at about 26 and 44o correspond to the graphite layers of multi-walled nanotubes. Surprisingly, the Fe/np-CNT and Fe/wp-CNT catalyst did not show similar XRD patterns. According to the XRD spectra, the diffraction peaks for Fe/np-CNT catalyst matched very well with the standard Hematite (Fe2O3) phase. Whereas, for Fe/wp-CNT catalysts, the peaks at 2θ of 30 and 35.7o exhibited the standard Magnetite (Fe3O4) phase.
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Figure 5:
153
H2-TPR profiles for Fe/np-CNT and Fe/np-CNT catalysts.
Table 2 shows the average iron oxides particle sizes on the catalysts calculated from XRD spectrum using Debye–Scherrer equation at the most intense peak of 36o. The data verified that the iron oxide on Fe/wp-CNT (17 nm) grew larger than that of on the Fe/np-CNT catalysts (11nm). To compare the particle size calculated based on XRD with TEM analysis, the size distribution of the particles is also shown in Table 2. There is a good agreement between the data for average particle size calculated based on XRD and the most abundant sizes from TEM analysis. TPR analyses were performed to evaluate the reducibility of the Fe/np-CNT and Fe/wp-CNT catalysts . TPR patterns of Fe/np-CNT and Fe/np-CNT catalysts are shown in Figure 5. Four peaks (A, B, C and D) can be observed on the TPR profile of the Fe/np-CNT catalyst. Whereas, two peaks appeared on the TPR profile of the Fe/wp-CNT catalysts. Generally, the reduction of iron oxides takes place as below [10]: Fe2O3 → Fe3O4→ FeO→ Fe In the case of Fe/np-CNT, the first peak (A) can be assigned to the reduction of Fe2O3 to Fe3O4. The second peak, B, can be assigned to the subsequent reduction of Fe3O4 to FeO. Peak C, observed at 500-700 °C, can be related to the reduction of FeO to metallic Fe. Peak D can be attributed to gasification of CNTs at a temperature higher than 600oC. For Fe/wp-CNT catalyst, since the iron oxide was in the form of Fe3O4, the first peak (A) corresponded to the reduction Table 2:
Particle sizes (iron oxide) based on XRD and TEM analysis. Catalyst
Fe/np-CNT Fe/wp-CNT
d (Fe2O3)a nm 11 17
a) Based on XRD analysis. b) Based on TEM analysis. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
d (Fe2O3)b nm 8-10 14-21
154 Energy and Sustainability II Table 3:
Reduction temperature (°C) and extent of reduction (from 25800oC) based on H2-TPR analysis.
Catalyst
Peak A
Peak B
Peak C
Peak D
Fe/np-CNT Fe/wp-CNT
401 459
438 574
667 -
747 -
Extent of reduction (25-700oC) 69 52
of Fe3O4 to FeO and the second peak, B, can be assigned to the subsequent reduction of FeO to Fe. There was a tailed peak for gasification of wp-CNT as seen in the TPR profile of the Fe/wp-CNT catalyst Table 3 shows reduction temperature for both catalysts. According to the reduction temperature, deposition of iron oxide particles inside the nanotubes with narrow pores results in a decrease in the temperature of the first TPR peak from 459 to 401oC and that of the second TPR peak from 574 to 438oC. The degree of reduction for the Fe/np-CNT and Fe/wp-CNT catalysts is also given in Table 3. The degree of reduction of the metal is the ratio of H2 consumed from ambient temperature to 700oC to the calculated amount of H2 for the complete reduction of metal oxides. According to Table 3, the degree of reduction for Fe/np-CNT (69%) was higher than that of Fe/wp-CNT (52%). This can result in partial reduction of metal sites in the case of the Fe/wp-CNT catalyst and lower FT activity. According to the literature, in the case of FT catalysts with average particle size of larger 10 nm, the particle size does not affect the extent of reduction [4]. Thus, this phenomenon may be attributed to a different interaction of iron oxide with interior surface of the Fe/np-CNT catalyst compared to that of the Fe/wp-CNT catalysts. As reported by other researchers [7, 8], the confinement of iron oxide inside in the CNT pores results in easier reduction at lower temperature. It has been postulated that the electron deficiency of the interior CNT surface is possibly responsible for this phenomenon and extent of this phenomenon decreases as inner diameter of nanotube increases.
4
Fischer–Tropsch synthesis
The performances of the Fe/np-CNT and Fe/wp-CNT catalysts for the FT synthesis were evaluated in a fixed bed reactor. All the reactions were performed under a set of similar conditions (275oC, 2MPa, H2:CO = 2). CO hydrogenation (blank runs with no iron) was performed on both acid treated CNT supports (npCNT and wp-CNT samples) under the same operating conditions as the metal loaded samples. For blank runs, the main product formed with a very low conversion (1%) was methane with almost no higher hydrocarbons. The activity and product selectivity (% CO conversion, CH4, C2-C5, C5+ and CO2) of the catalysts is given in Table 4. According to Table 4, the Fe/np-CNT catalyst showed a CO conversion of 30.7% whereas; this number for the Fe/wpCNT catalyst was only 12.2%. Also, CH4 selectivity of the Fe/np-CNT WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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(14.7 wt%) catalyst was much lower than that of the Fe/wp-CNT catalyst (41.1wt%). Accordingly, C5+ selectivity of the Fe/np-CNT (48.1 wt%) was considerably higher than that of Fe/wp-CNT (11.9 wt%). Table 4:
CO conversion and product selectivity of Fe/np-CNT and Fe/wpCNT.
Catalyst activity and product Fe/np-CNT selectivity CO% 30.7 CH4 14.7 C2-C4 37.3 C5+ 48.1 CO2 19.5 - Process conditions: 7.2 Nl/g-cat/h, 2MPa, H2/CO = 2. -All catalysts contain 20wt% Fe. -HC in wt%; CO2 in mol%.
Fe/wp-CNT 12.2 41.1 47.1 11.9 15.0
The result of FT analysis for both Fe/np-CNT and Fe/wp-CNT catalysts showed that the deposition of iron particles inside the nanotube pores with narrower pores within the range of studied pore diameters (higher than 10 nm) enhances FT activity and product selectivity of the catalyst. Several reasons can be associated with the improvement in activity and product selectivity. As discussed earlier, H2-TPR analysis revealed that the reducibility of the Fe/npCNT catalyst was remarkably better in comparison to the Fe/wp-CNT. This phenomenon can result in the formation of more catalytically active carbide species during FTS. Also, confinement of the reaction intermediates inside the pores can enhance their contact with iron catalysts, favoring the growth of longer chain hydrocarbons. As given in Table 4, CO2 selectivity of the Fe/wp-CNT was less than that of the Fe/np-CNT catalyst. This can be resulted from lower CO conversion for the Fe/wp-CNT catalyst. At a low CO conversion, the amount of the produced water was lower which provided a lower water concentration for water-gas-shift reaction during the FT reactions.
5
Conclusions
The results of this work revealed that the structure and pore diameter of CNTs as support for FT catalysts have significant influence on the catalytic performance of the catalysts. The deposition of metal particles inside the nanotube with narrow pore structure resulted in smaller metal particle sizes and better dispersion due to confinement effects inside CNT pores. Also iron catalyst supported on the narrow pore support improved the reduction behavior of the CNT catalyst most likely due to difference in electronic properties of the inner surface of the CNTs with different diameters. Higher metal dispersion and better extent of reduction resulted in more active and selective catalysts. In the case of WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
156 Energy and Sustainability II catalysts with metal particles inside the narrow pores, confinement of reaction intermediates inside the channels may also increase the contact time with active metal sites, resulting in production of heavier hydrocarbons.
References [1] Dry, M. E., Fischer–Tropsch reactions and the environment. Applied Catalysis A: General 189 pp. 185-190, 1999. [2] van der Laan, G. P. & Beenackers, A. A. C. M., Kinetics and Selectivity of the Fischer–Tropsch Synthesis: A Literature Review. Catalysis Reviews, 41(3&4), pp. 255-318, 1999. [3] Bukur, D. B., Lang, X., Mukesh, D., Zimmerman, W. H., Rosyenek, P. & LI, C., Binder/Support Effects on the Activity and Selectivity of Iron Catalysts in the Fischer–Tropsch Synthesis, Industrial Engineering Chemistry Research. 29, pp. 1588-1599, 1990. [4] Khodakov, A. Y., Griboval-Constant, A., Bechara R. & Zholobenko, V. L., Pore Size Effects in Fischer Tropsch Synthesis over Cobalt-Supported Mesoporous Silicas, Journal of Catalysis 206, pp. 230–241, 2002. [5] Malek Abbaslou, R. M., Tavasoli, A. & Dalai, A. K., Effect of pretreatment on physico-chemical properties and stability of carbon nanotubes supported iron Fischer–Tropsch catalysts, Applied Catalysis A: General 355, pp. 33–41, 2009. [6] Tavasoli A., Malek Abbaslou R. M., Trepanier M. & Dalai A. K., Fischer– Tropsch synthesis over cobalt catalyst supported on carbon nanotubes in a slurry reactor, Applied Catalysis A: General 345, pp. 134–142, 2008. [7] Chen, W., Pan, X. & Bao, X., Tuning of Redox Properties of Iron and Iron Oxides via Encapsulation within Carbon Nanotubes, Journal of American Chemical Society, 129, pp. 7421-7426, 2007. [8] Chen, W., Fan, Z,, Pan, X. & Bao, X., Effect of Confinement in Carbon Nanotubes on the Activity of Fischer–Tropsch Iron Catalyst, Journal of American Chemical Society, 130, pp. 9414-94192008 [9] Bahome, M. C., Jewell, L. L., Hildebrandt, D., Glasser, D. & Coville, N. J., Fischer–Tropsch synthesis over iron catalysts supported on carbon nanotubes, Applied Catalysis A: General 287, 60-67, 2005. [10] Ma, W., Kugler, E. L., Wright, J. & Dadyburjor, D. B., Mo-Fe Catalysts Supported on Activated Carbon for Synthesis of Liquid Fuels by the Fischer–Tropsch Process: Effect of Mo Addition on Reducibility, Activity, and Hydrocarbon Selectivity , Energy & Fuels 20, 2299-2307, 2006. [11] Serp P., Corrias M. & Kalck P., Review Carbon nanotubes and nanofibers in catalysis, Applied Catalysis A: General 253, 337-358, 2003. [12] Eswaramoorthi I., Sundaramurthy V.& Dalai A.K., Partial oxidation of methanol for hydrogen production over carbon nanotubes supported Cu-Zn catalysts, Applied Catalysis A: General 313, pp. 22-28, 2006.
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Pyrolysis of physic nut (Jatropha curcas L.) residue under isothermal and dynamic heating processes D. Atong1, C. Pechyen2, D. Aht-Ong2,3 & V. Sricharoenchaikul4 1
National Metal and Materials Technology Center, Thailand Science Park, Thailand 2 Department of Materials Science, Faculty of Science, Chulalongkorn University, Thailand 3 National Center of Excellence for Petroleum, Petrochemicals, and Advanced Materials, Chulalongkorn University, Thailand 4 Department of Environmental Engineering, Faculty of Engineering, Chulalongkorn University, Thailand
Abstract Pyrolysis of physic nut residues was conducted under isothermal and dynamic heating conditions in a vertical fixed bed type reactor at final temperature of 500, 700 and 900°C under N2. The solid, liquid, and gas products were in the ranges of 26.94-29.04, 9.43-21.36, 51.70-61.54 wt% for slow pyrolysis, while those attained from rapid condition were 11.16-15.25, 15.00-23.43, and 61.3273.84 wt%, respectively. Results indicated that char decreased with increasing temperature and hold time. Char with highest fixed carbon of 85.32% with relatively low volatiles of 9.28% was obtained by pyrolysis at 900°C for 60 min. Release of volatile matter led to development of char porous structure. The maximum liquid product of 21.35% was observed at the pyrolysis temperature of 900°C for 60 min under dynamic heating and 61.54% under isothermal heating at 500°C. Decreasing hold time to 15 min caused 2 times decrease of liquid yields. The liquid product mainly consisted of several fatty acids such as oleic acid, palmitic acid and lignoleic acid in the range of 15-19%, 40-45%, and 2534%, respectively. Increase in temperature and hold time lead to greater production of hydrogen, carbon monoxide, and light hydrocarbons. Mode of heating displayed significant effect to the product distribution, LHV and H2/CO ratio. Higher LHV values were obtained at 900°C under rapid pyrolysis condition. Mole ratio of H2/CO close to unity was found in the case of pyrolysis at 900°C for both slow and rapid trials. The LHV obtained from slow processes were 7.8-15.0 MJ/Nm3 while those from rapid runs were 14.8-17.2 MJ/Nm3. Keywords: pyrolysis, physic nut residue, fixed bed. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESU090151
158 Energy and Sustainability II
1
Introduction
Biomass as an energy source is now at the forefront of the renewable energy developments due to its renewable character and a net carbon neutral energy conversion. Biomass are abundant and can be supplied from various industries which produce organic plant materials as wastes, such as agricultural, sugar, wood processing, food industry, etc., or alternatively, they can be purposely grown for energy supply. The recovery of energy from biomass and residues has centered on biochemical and thermochemical processes. Of the later route, pyrolysis has recently received more interest. It is a thermal destruction of biomass in the absence of air/oxygen that starts at 350°C and goes up to 700°C [1,2]. Process conditions can be optimized to maximize the production of char, liquid or gas. Production of pyrolysis liquids has been investigated for use directly in fuel applications or by upgrading to refined fuels or chemical products. Char can be used as a fuel in the form of briquettes or upgraded to activated carbon. Gas has low to medium heating value and may contain sufficient energy to supply the energy requirements of a pyrolysis plant [3]. The proportion of gas, liquid and solid products depends on the pyrolysis technique used and reaction parameters. High heating rates of up to 100 K·s-1, to temperature less than 650°C with short retention time or rapid quenching, favor the formation of liquid products and minimize char and gas formation. High heating rates to temperatures higher than 650°C tend to favor the formation of gaseous products at the expense of liquids [3,4]. Slow heating processes over long periods of time lead to maximum yield of char with moderate amounts of tar by-products [5,6]. Thailand is an ideal country for abundant supply of various biomass sources. Physic nut (Jatropha curcas L.) is one of the principal sources of plant oil for biodiesel production in the country. Extraction of physic nut oil results in residue that is needed to be disposed. In general, collection and disposal of residues are becoming more difficult and expensive and may create environmental problems if not properly done. Pyrolysis could be a promising way for residue management to convent them to value added products that are easier to transport, storage, handling, and utilizing. Rapid and slow processes are both important for development of renewable energy source for the country. While rapid pyrolysis is generally suitable for large-scale industrial operations, slow pyrolysis may be easily adopted by majority of small operators in the countryside. In this study, the slow (dynamic) and rapid (isothermal) pyrolysis of physic nut waste were investigated in fixed-bed tubular reactor. Particularly, the influences of final pyrolysis temperature, retention time, and mode of heating on product yields were studied. In addition, an in-depth analysis of the properties of the solid and liquid products generated at different pyrolysis conditions was performed for a better understanding of the mechanism of physic nut waste pyrolysis and to determine its possibility of being a potential source of renewable fuel and chemical feedstock.
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Experimental
2.1 Material The physic nut residues from oil-extraction process were obtained from local plant. Samples were grounded, sieved to size fraction of 0.43–0.50 mm, and dried overnight at 80°C. The average proximate and elemental analyses are show in Table 1. Weight fractions of carbon, hydrogen and nitrogen were determined by using elemental analyzer Perkin Elmer PE2400 series II. Large amount of oxygen is reported by difference, so this number is not conclusive since there may be other elements not analyzed by this method. The proximate analysis was performed following ASTM methods to determine moisture (ASTM E871), volatile matter (ASTM E872), fixed carbon (ASTM E872) and ash content (ASTM D1120). Additional chemical components of physic nut residue sample were also identified using Tappi T203 and T222 standard methods and shown in the same table, which are hemicellulose, cellulose and lignin. Bomb calorimeter (Leco model AC-350) was used to determine the higher (gross) heating value following ASTM D240. The heating value of 19.51 MJ/Kg for physic nut waste was comparable to that of palm shell (18.26 MJ/Kg), cane trash (16.80MJ/kg) and greater than some other biomass such as rice husk (14.75 (MJ/Kg), corncob (11.3 MJ/kg), bagasse (9.24 MJ/kg), or tapioca rhizome (7.45 MJ/kg) [7]. Table 1: Ultimate analysis (wt.%) Carbon 47.3 Hydrogen 8.1 Nitrogen 6.4 Oxygen* 38.2
Chemical analysis of physic nut waste. Proximate analysis (wt. %) Volatiles 51.7 Fixed carbon 39.1 Ash 7.5 Moisture 0.7
Component analysis (wt. %) Hemicellulose 20.8 Cellulose 54.6 Lignin 24.6
*By difference
2.2 Pyrolysis experiment Pyrolysis of physic nut residues was conducted under isothermal and dynamic heating conditions in a vertical fixed bed type reactor. The influences of final pyrolysis temperatures and hold time on the product yields were also studied. The experimental set up is shown in Figure 1. The system consisted of a quartz tube reactor (height = 300 mm., i.d. = 12 mm., and o.d. = 13 mm.) with a sample retainer made of quartz frit at the bottom end and a three stage condensers for the collection of water and condensable organics (tar) followed by gas-measurement devices. The reactor is heated by a tubular ceramic furnace equipped with a PID temperature control and K-type thermocouple placed at the center. In each run, approximately 10 grams of sample material was used and the system was purged with 2 L/min of N2 for 15 min to ensure inert conditions in the bed [8]. For dynamic cases, the physic nut waste was placed into the reactor prior to heating and the temperature was raised with 20°C·min-1 from ambient to final temperature of 500, 700 or 900°C. Experiments were carried out in three different hold times, namely, 15 min, 30 min and 60 min. For isothermal WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
160 Energy and Sustainability II g
exhaust
h CO CO2 H2 CH4
j a
b c d
N2 e
i f
a) Tube furnace b) Sample d) Quartz tubing e) Flow controller g) Thermocouple h) Temp. controller j) Online gas analyzer
Figure 1:
c) Retainer f) Condensers i) Bubble flowmeter
Schematic of the pyrolysis system setup.
pyrolysis trials, the reactor was preheated to a final temperature of 500, 700 or 900°C and instantaneous decomposition started as soon as waste sample was rapidly inserted into the reactor. The retention time was kept at 15 min. After each run, char left in sample retainer was carefully weighed, liquid product was collected in cold traps maintained at 0°C. Non-condensable gas was analyzed by online gas analyzer (MRU GmbH, SWG 200-1) which capable of continuous real time quantification of CO, CO2, CxHy (as CH4) and H2 by using thermal conductivity detector (TCD) and non-disperse infrared detector (NDIR). Solid and liquid yields were calculated on a dry basis from the measured weight of each fraction. Yields of identified gas were calculated based on conversion of measured mole (vol.) to mass of that particular gas species. 2.3 Characterization of products 2.3.1 Solid char analysis Major elemental components of the solid were analyzed using a CHNS/O analyzer (Perkin Elmer PE2400 series II). Fixed carbon, volatile, and ash analyses were carried out using a thermogravimetric analyzer. When the sample was heated under an inert atmosphere to 850°C, the weight loss during this step is a volatile component. The gas atmosphere is then switched to air to burn off fixed carbon, while the temperature is reduced to 800°C. Finally, any residue left after the system is cooled to room temperature is considered as ash. The surface property of solid char was examined using an accelerated surface area and porosimetry instrument (ASAP 2020: Micro Merities). It was detected WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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using adsorption of liquid N2 at -196 °C. The N2 adsorption–desorption isotherms were used to determine the following parameters: surface area using the Brunauer–Emmett–Teller (BET) equation, total pore volume, total micropore volume, and total mesopore volume. Scanning electron microscopy (SEM, model JSM 5410, JELO) was also used to characterized the microstructure and pore properties of solid char generated from physic nut waste pyrolysis. 2.3.2 Liquid product analysis The surface organic functional groups of collected liquid product were studied by Fourier transform infrared spectroscopy (Perkin Elmer System 2000 FT-IR). Oil was dissolved in 100 ml of acetone solution, and 1 ml of the solution was added on to a KBr pellet. The pellet was heated at 50°C for 10 min to allow acetone to be fully vaporized to minimize the interference of transparent caused by acetone. A thin film of organics was, thus, formed on the KBr pellet and absorbed IR spectra. The spectra were recorded from a wavenumber of 400-4000 cm-1 [8]. The liquid product was analyzed using gas chromatography coupled with a mass selective detector (SHIMADZU 2010). Only fatty acids components were investigated by conversion to their respective methyl esters. Fatty acid methyl esters were prepared by transesterification and purified by thin-layer chromatography using potassium hydroxide for saponification of glycerides in a reflux condenser attached to the flask and heated to about 200°C until the fat droplets disappeared. Methanol and heptane were added through the condenser and the boiling continued for few minutes. After addition of sodium chloride, the obtained heptane solution was prepared for direct injection into GC for analysis.
3
Results and discussion
3.1 Product yields and gas characterization Pyrolysis of biomass results in solid, liquid, and gas products of different fractions depending on operating condition. In this work, the effect of heating pattern and reaction temperature on product yields is shown in Figure 2. Generally, rapid pyrolysis resulted in greater changes on product yields at different temperature when compared with those of slow conversion processes. For slow heating, solid yields were much higher than those obtained from isothermal runs and decreased slowly with temperature within the range of less than 2.0 wt.%. The effect of hold time at final temperature was insignificant on solid yields from this process. Larger drop on solid yields with increased temperature was obtained by isothermal experiments but still accounted for less than 4.0 wt.% changes. It may be suggested from these results that pyrolysis processes on formation and decomposition of solid are mainly rapid primary reactions and this fraction plays minor role on subsequent secondary reactions during the overall conversion. This also explains small changes on solid yields with temperature for dynamic runs. During slow heating process, all samples were subjected to similar temperature history (identical heating rate) and not on final temperature. Since pyrolysis reactions start early at temperature around WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
162 Energy and Sustainability II 400-500°C, major rapid primary reactions related to solid yields should already take place and mostly finish by the time that reaction temperature increased to final set point for higher temperature experiments. Hence, small reduction on solid yields at higher temperature resulted from insignificant slower secondary decomposition reactions. On the other hand, historical temperature profile for rapid heating at different reaction temperature is different and pyrolysis reactions occur mainly at that particular set point results in larger difference on yields. 30
Solid yield (wt.%)
25 20
Liquid yield (wt. %)
30
Dynamic - 15 min Dynamic - 30 min Dynamic - 60 min Isothermal - 15 min
15 10 5 400
600 800 o Temperature ( C) 80
Gas yield (wt. %)
75
25 20 15 10 5 400
600 800 Temperature (oC)
1000
Dynamic - 15 min Dynamic - 30 min Dynamic - 60 min Isothermal - 15 min
70 65 60 55 50 400
Figure 2:
1000
Dynamic - 15 min Dynamic - 30 min Dynamic - 60 min Isothermal - 15 min
600 800 Temperature (oC)
1000
Product yields from dynamic and isothermal heating of physic nut wastes.
Gas and liquid yields from slow pyrolysis of physic nut displayed opposite trend from those of rapid experiments. For slow pyrolysis, liquid yields increased with temperature while continuous drop on liquid product was obtained from rapid runs. Obviously, decomposition reactions of liquid products resulted in higher gas yields for isothermal trials. During dynamic heating, higher temperature increased the formation of liquid products at the expense of lower gas yields. Generally, gas is major product from pyrolysis of physic nut with yields of more than 50 wt.% to as much as 73 wt.% at any operating conditions. More detail on gas production is exhibited in Figure 3 for isothermal experiment at 900°C. Measured gas concentrations are reported as percentages of carbon or hydrogen in feed material that are converted to carbon or hydrogen in specified gas species. Due to distance from reactor to gas analyzer, there is WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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around one minute lag time for response on gas measurement. As a result, it may be seen from this figure that gas production started immediately as soon as raw material was inserted into the reactor vessel. Most of gas was formed within 15 minutes with CO2, CO, CH4, and H2 as major gas species. However, from material balance, relatively large fraction of gas species is still unaccounted for which probably be those C2-C4 hydrocarbons. Comparisons between gas production profile of H2 and CH4 via isothermal and dynamic experiments are displayed in Figure 4 and 5, respectively. As expected, rapid heating resulted in large production of gas in short time while much slower gas release was typical pattern for dynamic runs due to gradual rise in reaction temperature. 7 CO2- instantaneous CO- instantaneous H2- instantaneous CH4- instantaneous CO2 - accumulated CO -accumulated H2 -accumulated CH4 -accumulated
% C or H input conversion
6 5 4 3 2 1 0 0
5
10
15
Time (min)
Figure 3:
Gas produced from isothermal heating of physic nut wastes at 900°C.
Ratio of H2 to CO and lower heating value (LHV) of gas product which are important parameters with respect to gas utilization viewpoint are shown in Figure 6. LHV of product gas is determined from heat content of each measured gas which is: LHV (MJ/Nm3) = 0.126×[CO] + 0.108×[H2] + 0.358×[CH4] where [CO], [H2], and [CH4] are volume (molar) percentage of these gas species, respectively. At lower temperature, H2/CO ratios of gas from dynamic runs were higher than isothermal experiment while these data were quite similar for runs at higher temperature. Since gas yields and LHVs were also higher at low temperature for dynamic runs, lower reaction temperature would be appropriate for slow heating operation to obtained enriched H2 gas. Since ratios were indifferent for isothermal trials while gas productions were much higher at high temperature, factors including LHV and other operational constraints have to be considered when selecting optimal process temperature in this case. Note that LHVs of gas WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
164 Energy and Sustainability II 0.6 isothermal - 900°C isothermal - 700°C isothermal - 500°C dynamic - 900°C dynamic - 700°C dynamic - 500°C
% H input converted to H2
0.5 0.4 0.3 0.2 0.1 0 0
5
10
15
20
25
Time (min)
Hydrogen gas produced from isothermal and dynamic heating of physic nut wastes. 2.0
1.0 isothermal - 900°C isothermal - 700°C isothermal - 500°C dynamic - 900°C dynamic - 700°C dynamic - 500°C
% H input converted to CH4
1.8 1.6 1.4
0.9 0.8 0.7
1.2
0.6
1.0
0.5
0.8
0.4
0.6
0.3
0.4
0.2
0.2
0.1
0.0
% C input converted to CH4
Figure 4:
0.0 0
5
10
15
20
25
Time (min)
Figure 5:
Methane produced from isothermal and dynamic heating of physic nut wastes.
from any runs were relatively high (more than 3.7 MJ/Nm3) indicating that these gases are at least suitable for power production without need for auxiliary fuels. Table 2 is a summary of overall product distribution as well as other important product gas characteristics obtained from this work. In the table, carbon and hydrogen conversions are determined from total amount of carbon or hydrogen in feed that end up as carbon containing gases (CO, CO2, and CH4) or WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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Energy and Sustainability II
H2/CO ratio
3.6
20.0
Dynamic - 15 min Dynamic - 30 min Dynamic - 60 min Isothermal - 15 min
2.8 2.0 1.2 0.4 400
Figure 6:
Dynamic - 15 min Dynamic - 30 min Dynamic - 60 min Isothermal - 15 min
17.5 LHV (MJ/m3)
4.4
15.0 12.5 10.0 7.5
(a) 600 800 Temperature (oC)
5.0 400
1000
(b) 600 800 Temperature (oC)
1000
(a) H2/CO and (b) lower heating value (LHV) of product gas.
hydrogen containing gases (CH4, H2) as detectable by gas analyzer, respectively. Cold gas efficiency (ηgas) is a parameter that is defined as: η gas (%) =
LHVgas × Ygas LHVraw material
× 100%
where Ygas is yield of product gas per kilogram of fed raw material (Nm3/kg) and LHVraw material may be measured by bomb calorimeter. Table 2:
Effect of reaction temperature, hold time, and mode of heating on product distribution and gas characteristics.
Temperature (°C) Hold time (min) Solid (wt.%) Liquid (wt.%) Gas* (wt.%) LHV (MJ/m3) H2/CO C conversion to gas (wt. %) H conversion to gas (wt. %) Cold gas efficiency, ηgas (%) Gas yield, Ygas (Nm3/kg)
Dynamic heating Isothermal 500 700 900 500 700 900 15 30 60 15 30 60 15 30 60 15 15 15 29.0 9.5 61.5 13.4 2.0 10.4 9.7 8.0 0.12
28.9 11.9 59.2 14.4 2.2 14.2 15.3 12.4 0.17
28.4 13.6 58.0 15.0 4.2 20.8 25.0 19.4 0.25
28.9 13.8 57.3 8.1 1.4 10.8 5.6 4.8 0.12
28.3 14.3 57.4 7.8 0.9 18.1 7.7 7.5 0.19
28.2 16.0 55.8 8.3 1.0 20.3 9.8 9.0 0.21
28.0 17.2 54.8 9.4 1.1 14.3 7.8 7.0 0.15
27.5 20.4 52.1 9.1 1.1 18.9 10.0 8.9 0.19
26.9 21.4 51.7 10.1 1.0 25.6 15.2 13.5 0.26
15.3 23.4 61.3 14.8 0.8 12.6 11.2 10.5 0.14
12.3 18.2 69.5 15.5 0.7 16.9 15.4 14.6 0.18
11.2 15.0 73.8 17.2 1.1 22.7 25.5 22.6 0.26
*by difference
As seen from this table, carbon and hydrogen conversion increased with hold time and temperature. Up to around a quarter of carbon or hydrogen in feed might be transformed to product gases at some operating conditions. Since these experiments were pyrolysis, cold gas efficiencies were relatively low when compared with typical gasification process, ranging from 4.83% to 22.55% at most. Longer hold time and higher reaction temperature resulted in greater cold gas efficiency with maximum value occurred at 900°C for isothermal process WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
166 Energy and Sustainability II though the overall economic analysis of the process has to be carried out to suggest the optimal condition since pyrolysis is mainly endothermic and operation at high temperature is energy intensive process. 3.2 Influence of Pyrolysis conditions on solid-char In this work, “char” is used collectively to represent the solid residue that remained after pyrolysis. Appreciable amount of char with high fixed carbon left after pyrolysis is an important factor to determine optimum operating condition. Results of the proximate analyses of chars obtained from pyrolysis of physic nut waste at different conditions are given in Figure 7. As expected, an increase in temperature results in char with higher fixed carbon and decrease in volatile matter. As the pyrolysis temperature increased from 500 to 900°C, the volatile content of the chars correspondingly decreased from 76.50-81.10 to 9.80-14.40%. The fixed carbon content increased sharply from 16.34-20.28% at 500°C to 57.25-62.20% at 700°C and rose continually to 81.10-85.40% at 900°C. Elemental analysis of char shows similar trend of higher portion of carbon content and lower amount of other elements with temperature (Figure 8). The devolatilization during pyrolysis resulted in the char to be predominantly carbon. Losses in hydrogen and oxygen correspond to the scission of weaker bonds within char structure favored by the higher temperature [9]. Decreasing trends in the volatile content of chars were also observed when the hold time was increased for a particular final temperature. For the hold time increased, larger amount of volatile matters were released, hence the decreasing volatile content thus leaving char with high fixed carbon content. Mode of 100 Ash
Fixed carbon
Volatile
Weight (%dry)
80 60 40 20
50 0° C 50 15 0° C m 50 30 in 0° C m in 60 m in 70 0° C 70 15 0° C m 70 30 in 0° C m in 60 m in 90 0° C 90 15 0° C m 90 30 in 0° C m in 60 m in 50 0° C 70 15 0° C m 90 15 in 0° C m in 15 m in
0
Dynamic
Figure 7:
Isothermal
Proximate analysis of char from dynamic and isothermal heating of Physic nut wastes.
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Energy and Sustainability II Nitrogen
Hydrogen
Oxygen
167
Carbon
Elemental analysis (wt%)
100 80 60 40 20
50 0° C 50 15 0° C mi 50 30 n 0° C min 60 m in 70 0° C 70 15 0° C mi 70 30 n 0° C min 60 m in 90 0° C 90 15 0° C mi 90 30 n 0° C min 60 m in 50 0° C 70 15 0° C mi 90 15 n 0° C min 15 m in
0
Dynamic
Figure 8:
Isothermal
Elemental analysis of char from dynamic and isothermal heating of Physic nut wastes.
Table 3: Temperature (°C)
Surface area and porosity characteristics of chars. Hold time (min)
BET (m2·g-1)
Total volume (cm3·g-1)
Mesopore area (m2·g-1)
Mesopore volume (cm3·g-1)
500 500 500
15 30 60
140.54 154.63 171.85
0.274 0.315 0.352
124.04 131.18 142.62
0.093 0.099 0.104
700 700 700
15 30 60
188.32 197.91 202.37
0.386 0.497 0.545
153.90 178.47 185.51
0.110 0.118 0.123
900 900 900
15 30 60
199.13 215.82 217.55
0.512 0.607 0.628
180.22 189.92 192.38
0.120 0.128 0.131
500 15 114.38 0.204 700 15 154.16 0.295 900 15 169.79 0.332 Pyrolysis conditions: nitrogen flow rate = 2 L·min-1.
100.23 129.76 134.45
0.074 0.096 0.102
Dynamic heating
Isothermal heating
However, char from rapid pyrolysis had higher carbon content and lower amount of oxygen and hydrogen compared to one produced from slow pyrolysis. It was thought that remaining of inorganic substance, e.g. carbonate, after isothermal heating in a short period of time might be the cause for higher amount of carbon. The effects of pyrolysis temperature, hold time and method of heating on the BET surface area, mesopore area and mesopore volume of chars are shown in Table 3. BET surface areas increased progressively with increased pyrolysis WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
168 Energy and Sustainability II temperature and exposure time which was explained with the burnout of carbon that led to the development of porosity [10]. Char obtained from rapid pyrolysis condition had lower surface area and pore volume than ones attained from slow pyrolysis approximately 15-19%. The highest surface area of char was achieved at pyrolysis temperature of 900°C for an exposure time of 60 min. (c)
(b)
(a)
(d)
Figure 9:
(e)
SEM of chars: dynamic heating at (a) 500°C–15 min, (b) 900°C– 15 min, and (c) 900°C–60 min; and isothermal heating at (d) 500°C–15 min, and (e) 900°C–15 min.
SEM was applied to characterize the shape and the size of the char particles, as well as their porous surface structure. Figure 9 shows SEM images of physic nut chars produced under different conditions. At a low temperature of 500°C under dynamic heating, surface of char showed cracked and pitted morphology (Figure 9(a)). At 700°C, the presence of small pores on the surface explained that char was starting to develop an elementary pore network (not shown). After 900°C, surface morphological change was evident. Porous structure and opening pores on the surface was developed, thus char possessed high surface area. Increasing exposure time at a particular pyrolysis temperature also increased the surface area. This trend was less pronounced at high temperature suggesting that decomposition reactions would have been rapid at such high temperature and mostly finished in short time. The SEM image of char pyrolyzed at 900°C for 60 min (Figure 9(c)) exhibited relatively smooth in some regions as well as open pores were being seal off indicating initial stage of sintering at high exposure time. The char particles obtained after isothermal heating were slightly different as seen in Figure 9(d)-(e). While a gradual release of volatile compounds occurred as the temperature increased during dynamic heating; the fast volatile release throughout isothermal condition produces relatively substantial internal overpressure and the coalescence a more open structure (Figure 9(d)). Partial smooth surface of char particles were also observed at a higher pyrolysis temperature of 900°C under isothermal heating.
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3.3 Influence of pyrolysis conditions on liquid product The liquid products from pyrolysis are mostly oxygenated complex mixtures of hundreds of individual substance that can be grouped into many various chemical classes [11]. FT-IR spectra of the liquid product obtained from either isothermal or kinetic pyrolysis of physic nut waste are quite similar as shown in Figure10. The O-H stretching vibrations between 3200 and 3450 cm-1 indicates the presence of phenols and alcohols. The band at the about 3100 cm-1 may indicate the presence of hydrocarbon groups bound to aromatic rings. The C-H stretching vibrations between 2800 and 3000 cm-1 and deformation vibrations between 1350 and 1475 cm-1 indicate the presence of alkane. The C=0 stretching vibrations with absorbance between 1680 and 1780 cm-1 represent the presence of ketone or aldehyde. The presence of both O-H and C=0 stretching vibrations also indicates the presence of carboxylic acids and derivatives. The absorbance peaks between 1575 and 1675 cm-1 represent C=C stretching vibrations which indicate the presence of alkenes and aromatics [12–15].
% Transmittance
Dynamic heating
Isothermal heating
4000
3600
3200
2800
2400
2000
1600
1200
800
400
-1
Wavenumber (cm )
Figure 10:
FT-IR spectra of liquid product: (a) dynamic heating at 700°C for 60 min and (b) isothermal heating at 700°C for 15 min.
Liquid products were further processed and analyzed for fatty acid methyl esters. The relative distribution of fatty acids was determined as percent of chromatographic peak area of following derivative acids: palmitic acid (C16:0:C16H32O2), oleic acid (C18:1:C18H34O2), and lignoleic acid (C18:2:C18H32O2). Example of the distribution of fatty acids in liquid product produced from both isothermal and dynamic heating was shown in Figure 11. It was found that the content of fatty acid was not influenced by hold time, mode of heating, or temperature (not shown). Overall, contents of these components were in the range of 19.05-19.82% for palmitic acid, 45.03-45.77% for oleic acid, and 34.24-35.94% for lignoleic acids. Nevertheless, the results indicated that carbon chain length of liquid product from pyrolysis of physic nut waste is greater than that of diesel fuel and within the range of gas oil. It may be use on slow speed, heavy machinery but further cracking and refining of this product are required in order to utilize it in place of gasoline or diesel. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
170 Energy and Sustainability II Oleic acid(C18:1) 50
Palm itic acid(C16:0)
Lignoleic acid(C18:2)
% Fatty acid
40 30 20 10
Dynamic
Figure 11:
4
70 0° C
15
m in
m in 70 0° C
60
30 70 0° C
70 0° C
15
m in
m in
0
Isothermal
Relative distribution of fatty acids in liquid product.
Conclusions
Pyrolysis of physic nut residue was performed to study the effect of several operating parameters on distribution and characteristic of obtained products. Rapid pyrolysis resulted in greater changes on product yields at different temperature. Char yields were much higher from slow pyrolysis. The effect of hold time was insignificant on char yields which suggested key rapid primary reactions started around 400-500°C on the overall thermal conversion operation. BET surface areas increased progressively with increased pyrolysis temperature and exposure time. Char obtained from rapid pyrolysis condition had lower surface area and pore volume than ones attained from slow pyrolysis. Liquid yields increased with temperature for slow pyrolysis while continuous drop on liquid product was obtained from rapid runs. Functional groups of liquids from any processes are quite similar. Carbon chain length of liquid product from pyrolysis of physic nut waste is within the range of gas oil. Gas is major product from pyrolysis of physic nut with yields greater than 50 wt.% at any operating conditions. Most of gas was formed within 15 minutes with CO2, CO, CH4, and H2 as major gas species. LHVs of gases from any runs were relatively high indicating their suitable for power production without need for additional fuels though cold gas efficiencies were relatively low which is typical for pyrolysis process.
Acknowledgements This research was carried out under the research program of the National Metal and Materials Technology Center (project number MT-B-52-CER-07-249-I). Authors also acknowledge The 90th Anniversary of Chulalongkorn University Fund (Ratchadaphiseksomphot Endowment Fund) for partial support of this work. C. Pechyen also appreciates the scholarship provided by the Thailand Graduate Institute of Science and Technology (TGIST, TG-33-09-49-030D). WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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References [1] Reed, A.R. & William, P.T., Thermal processing of biomass natural fibre wastes by pyrolysis. International Journal of Energy Research, 28(2), pp. 131-145, 2004. [2] Kang, B.-S., Lee, K.H., Park, H.J., Park, Y.-K. & Kim, J.-S., Fast pyrolysis of radiata pine in a bench scale plant with a fluidized bed: Influence of a char separation system and reaction conditions on the production of bio-oil. Journal of Analytical and Applied Pyrolysis, 76(1-2), pp. 32-37, 2006. [3] Horne, P.A. & Williams, P.T., Influence of temperature on the products from the flash pyrolysis of biomass. Fuel, 75(9), pp. 1051-1059, 1996. [4] Bridgwater, A.V., Principles and practice of biomass fast pyrolysis processes for liquids. Journal of Analytical and Applied Pyrolysis, 51(1-2), pp. 3-22, 1999. [5] Maggi, R. & Delmon, B., Comparison between ‘slow’ and ‘flash’ pyrolysis oils from biomass. Fuel, 73(5), pp. 671-677, 1994. [6] Encinar, J.M., Beltrán, F.J., Ramiro, A. & González, J.F., Pyrolysis/gasification of agricultural residues by carbon dioxide in the presence of different additives: influence of variables. Fuel Processing Technology, 55(3), pp. 219-233, 1998. [7] Garivait, S., Chaiyo, U., Patumsawad, S. & Deakhuntod, J., Physical and chemical properties of Thai biomass fuels from agricultural residues. Proc. of the 2nd Joint Int. Conf. on Sustainable Energy and Environment, Bangkok, pp. 541, 2006. [8] Sricharoenchaikul,V., Pechyen, C., Aht-Ong, D. & and Atong, D., Preparation and characterization of activated carbon from the pyrolysis of physic nut (Jatropha curcas L.) waste. Energy and Fuels, 22(1), pp. 31-37, 2008. [9] Demirbas, A., Effect of temperature on pyrolysis products from four nut shells. Journal of Analytical and Applied Pyrolysis, 76(1-2), pp. 285-289, 2006. [10] Pechyen, C., Atong, D., Aht-Ong, D. & Sricharoenchaikul,V., Investigation of pyrolyzed chars from physic nut waste for the preparation of activated carbon. Journal of Solid Mechanics and Materials Engineering, 1(4), pp. 498-507, 2007. [11] Tsai, W.T., Lee, M.K. & Chang, Y.M., Fast pyrolysis of rice husk: Product yields and compositions. Bioresource Technology, 98(1), pp. 22-28, 2007. [12] Onay, O. & Koçkar, O.M., Slow, fast and flash pyrolysis of rapeseed. Renewable Energy, 28(15), pp. 2417-2433, 2003. [13] Onay, O. & Koçkar, O.M., Fixed-bed pyrolysis of rapeseed (Brassica napus L.). Biomass and Bioenergy, 26(3), pp. 289-299, 2004. [14] Ate, F., Pütün, E. & Pütün, A.E., Fast pyrolysis of sesame stalk: yields and structural analysis of bio-oil. Journal of Analytical and Applied Pyrolysis, 71(2), pp. 779-790, 2004. [15] Onay, O., Fast and catalytic pyrolysis of pistacia khinjuk seed in a wellswept fixed bed reactor. Fuel, 86(10-11), pp. 1452-1460, 2007. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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Section 2 Energy management
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Energy and Sustainability II
175
Energy and sustainability through integrated water network management M. Ektesabi, A. H. Moradi-Motlagh & A. H. Abdekhodaee Faculty of Engineering and Industrial Sciences, Swinburne University of Technology, Australia
Abstract Sustainable cities of the future require effective urban water systems that can cope effectively with urban population growth and fluctuations on water resource levels. Existing urban water systems are often old, difficult and/or expensive to change for improvement. Despite literature on water network management being extensive with many interesting papers published, it seems there are still numerous opportunities to be explored in this area. The water distribution system is becoming increasingly a multi-dimensional problem. It is complex as it has many evolving subsystems and there is more competition for this finite resource. At the same time, there are new technologies that can be incorporated for effective and efficient water management. This paper attempts to provide an overview of different types of optimisation techniques available for the water management system and provide an integrated approach to Optimise Water Distribution Chain. The optimisation of each section and the total effect as the result of integration provides reliability improvement and significant energy saving for more sustainable system. Keywords: water management, integrated water distribution management, optimisation technique, sustainability.
1
Introduction
Water, as a basic necessity of human life, had always a special role in different societies. Access to fresh water was fundamental in selecting a land to live on from the very beginning of the human race. Demanding water was not particular to agricultural societies but was also seen increasing after industrial revolution. Many industries such as textile, paper industries, chemical plants, power plants WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESU090161
176 Energy and Sustainability II and almost all industries require substantial water resources to be able to operate. This ever-growing demand for water in urban areas, the agriculture sector as well as manufacturing industries may not be sustainable. The availability of water resource, its acquiring and its distribution, as well as its usage should be closely considered for sustainable cities. In this paper we highlight some of the complexities that are associated with water management and discuss some of the opportunities that seem to be available to improve on efficiency and effectiveness of water management systems. Though this is a major problem which has various perspectives to look at, in this paper we focus mainly on control engineering perspectives and technologies that might be used to convey and deliver water in urban areas. 1.1 Water demand Various reports on supply and demand for water, portray a worrying picture when considering the fact that access to clean water is essential for the health and economic development of communities. Cashman and Ashley [1] wrote that” The water sector is set to continue to face severe challenges in meeting the financial requirements for maintaining, extending and upgrading new and ageing water systems in the face of growing water scarcity, stricter regulatory requirements and competition for capital.” Based on their research, they argue that domestic water usage will rise from 10% of global demand in 1995 to 25% of global demand in 2025 in relative terms. In absolute terms, however, overall domestic consumption will increase by 70%. The World Bank has indicated that worldwide demand for water is doubling every 21 years and supply cannot cope with such demand in growth. The demand in growth can partially be attributed to population growth. It is predicted that world population will reach 9 billion by 2050 from the current 6 billion level. However, the pattern of consumption is also changing and with increasing standards of living, a higher consumption is expected, particularly in developing countries. The quality of water is another dimension to water scarcity. It seems because of human activities, the quality of water is deteriorating rapidly. 1.2 Water and energy Water and energy are closely related resources in many ways. One of the main methods of generating electricity is through hydroelectricity. Moreover, the water is also needed for power plants and water is used to release redundant heat energy to air. On the other hand, energy is required to source water, treat it and deliver it to consumers in urban areas, manufacturing plants and for agricultural purposes. Based on research by Cohen et al. [2], it is estimated that the use of water consumes approximately 8 percent of the nation’s energy for its treatment, conveyance, use (including heating), and disposal. The California Energy Commission estimates that over 20 percent of electricity and 30 percent of natural gas use in that state is associated with the use of water. This report details the energy requirements of a particular water supply at five stages of the water cycle: extraction, treatment, distribution, use, and disposal. It is highlighted that WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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a significant energy saving can be achieved if better water policy decisions are made. 1.3 Water and infrastructure As discussed earlier, the need for new facilities to provide water, electricity and other services to consumers and particularly in urban areas is growing rapidly. The water management and energy consumption are highly related. However, an aspect that should be noted is that water management systems in most countries have been developed over a long period of time. They are often very costly to replace or even maintain. Some of the researchers in the field of water distribution optimisation have considered only optimal design of new networks which are good solutions for future development. There are interesting opportunities in using new control systems with existing infrastructures for water distribution systems. Having online and accurate data from a system could naturally improve the intelligence of the system. And any feed back control parameter will result in improvement. This way, some researchers have tried to develop new techniques for the operational optimisation of existing infrastructures. The objective of the latter method is mainly to generate control strategies ahead of the present time, using predictive techniques to guarantee a competent network service, while simultaneously achieving certain quality objectives. In this method either minimisation of supply and pumping costs, or maximisation of water quality or leak prevention are among the main targets [3]. In many cases the objectives are interrelated and can be managed by an intelligent management technique which is the main objective of this paper.
2
Water supply and distribution network
We can name three main types of water supply and distribution network which are commonly related to the geographical specifications of available resources and location of users: Gravity based water distributing system – in this case source of water is usually surface water accumulated in a dam. After going through water treatment process, usually water is transferred to a reservoir that has been located high enough relative to the lowest point of consumption so that water can be provided with adequate pressure. Elevated reservoirs / Intermediate tank pump based water distribution system – in this system during off peak consumption period; water is pumped to high elevated tanks and during consumption this water is channeled to the water distribution network. Pump based water distribution without intermediate tanks – in this method pumps channel water directly to artillery pipes. This method is not very common as it is highly relied on continuous operations of pumps and might be interrupted by disruption in power etc.
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178 Energy and Sustainability II 2.1 Importance of intermediate reservoir/tank For various reasons, we need to have intermediate reservoirs tanks in a water distribution process. Perhaps the main reason is to stabilise and to regulate water supply and demand. Generally, pumps work at a constant rate while demand for water fluctuates. With the use of intermediate storage, water can be stored in reservoirs to be provided for customers in constant rate. It is also helpful to make the quality of water consistent. Water might be obtained from various resources such as surface water, or through water wells, and in some cases through desalination plants. Use of intermediate reservoirs is helpful to mix different types of water and have acceptable quality levels. Intermediate reservoir/tank systems provide the possibility of off peak pumping which in turn is a part of load management and provides a better use of energy in an appropriate time slot. In this case the pumping system can be ONOFF control type for the required duration of pumping. 2.2 Importance of optimised control system for direct pump based water distribution without intermediate tanks In the case of pump based water distribution without intermediate tanks, pumps require a more advanced type of control. In conventional control system, the pumps run at maximum operating flow rates, whenever the consumer demand changes, the demand for control of flow in the pipes change and this change is normally achieved by throttle valves or by bypass valves. This type of control system results in wasting of energy in throttling or bypassing the water. In the following sections, it is shown that by use of Variable Speed Drives and replacing the conventional control systems with newer techniques, not only energy saving is achieved but it also helps in constant demand based flow in pipes without causing pressure impacts. Smooth flow and reduction of pressure impact in turn increases the useful life time of infrastructure which is one of the main objectives. 2.3 A simplified water distribution process Water distribution process, as illustrated in Figure 1, can be divided into various stages, mainly as follows: Stage 1: In the first stage, water from various sources such as dams, water wells, etc are conveyed to water treatment plants. In the treatment process, water is filtered and its content minerals are adjusted to required set values. It should be noted that if the water source is in a geographically lower level and gravity cannot be used to convey water to treatment plants, then use of pumps is required. This generally requires substantial energy. In plants too, we need energy to do treatment process such as filtration. Stage 2: In the second stage, water need to be conveyed from treatment plants to an echelon of water storage facilities, usually a main reservoir to smaller storage facilities. The main reservoir based on consumption would distribute water to the smaller storage facilities. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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Stage 3: In the third stage, water from smaller storage facilities is distributed to the end users via a network of pipes. These storage facilities are either positioned in higher lands relative to end users or they are elevated from the surface level. In the latter case, energy is required to convey water to these facilities.
Figure 1: Table 1:
Water distribution process. North Tehran division.
North of Tehran Utilities Stage2 Stage3 1710 Km Water 47 Water Well 42 Reservoir Distribution Network 20 Pump Resident Population is about Latian Dam Station 1,450,000 Water Consumption per 30 Km Pipeline year is 140,000,000 m3 Water Treatment Plants 3 & 4* 14407 Valve Stage1
An example of the above three stages can be shown in the following Tehran water distribution system. Tehran is the capital and largest city of Iran, and perhaps it is the largest city in the region. It is the most populated city in South Western Asia with a population of approximately 15 million.
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180 Energy and Sustainability II Water consumption in Tehran is almost three million cubic meter per day and it is sourced from three major dams and one thousands wells. In this case, water management has been divided into six divisions. The information of these divisions (North Tehran division) is presented in Tables 1 & 2 and the geographical relative location of one of the resources is presented in Figure2. One of the Water treatment plants has been operational since 1967 and the other one was added to the system in 1984. Their capacities are similar and they provide 4 cubic meters per second each. Untreated water is conveyed from Latian dam via a 28-kilometer long tunnel with a diameter of 2.7 meter. Table 2:
A section of water supply network.
Water supply network for Tehran North Division Channels
8 km
Dimension 64.1 m × 2.1m
Tunnel
28 km Diameter 2700mm
Steel pipes
73 km Diameter 1000mm
Concrete pipes 67km Diameter 2000mm
Figure 2:
3
Latian dam and its location relative to the capital city, Tehran.
Optimisation possibilities
Figure 3 illustrates six main areas in which optimisation of water and energy can be considered. This classification is helpful to categorize some of the contributions that will be discussed in this paper. Its main purpose is to highlight WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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that optimisation can be viewed in smaller scale and individual component of a system as well as in a larger scale when a control system needs to be integrated. Here a brief description of each area is provided. In Area 1, it can be considered to optimise the amount of water obtained from various sources to have an acceptable mineral content, minimize leakage and energy through transportation. Techniques such as linear programming can be applied. In the Area 2, water levels in intermediate storage are investigated. The level should be set to a value acceptable as level of service while minimising energy in the process, accurate prediction and rapid adjustment could be vital. In Area 3, processes at treatment plant are scrutinised.
Figure 3:
Optimisation areas for a water distribution process.
In Area 4, pump applications can be investigated. We discuss this further later in this paper, however, scheduling of pumping as well as pumping technology has a significant impact on energy consumption. Efficiencies of pumps vary greatly and depend on operational requirements. Fine-tuning the system could significantly reduce energy usage. In Area 5, valve operations can be investigated. ON-OFF control systems can be replaced with more accurate PID control systems. Finally, in Area 6, demand side management as well supply side management could improve the system performance. By active participation of consumers, it is possible to reduce pressure in the distribution network. This not only minimizes leakage but it also might prolong the operating life of a water distribution system. Usually, a water servicing network extends over a region covering a wide area and very long distance and conveys treated water to and from many storage reservoirs to the consumers within the Metropolitan Area. The water is distributed via tunnels/channels/pipes, which branches outwards from the storage WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
182 Energy and Sustainability II reservoirs. The reservoir volumes are measured on-line and sent to a central control system where all of the relevant data are stored. In one example [3], to deliver potable water with an adequate pressure, even in remote parts of the system, there are hundreds pump-stations. Until recently, the topic of optimisation in water systems in the literature has been mainly focused on the design of optimised configurations for pipe-interconnected reservoirs, whereas there are many more parameters which have to be considered for optimum solutions. In this section some of these parameters are presented. Switching between the resources and use of the reservoir with suitable level for optimum pumping is one of the popular techniques discussed in many of the available literatures [4–6]. Mixing of water from different resources requires another type of optimisation. In the case study of Tehran, it was shown that the water supply can be from more than one on-ground or underground resource, each with different treatment requirements. Use of an intelligent mixing system can reduce / optimise the treatment process. This approach is very similar to a chemical plant with dozing of water quantities from each of the resources based on their quality and usage. In most networks, this optimisation problem is equivalent to optimising the scheduling of pumps. Creasey [7] reviewed the appropriate mathematical techniques to solve the problem of operational optimisation for water distribution networks, insisting particularly on the pump-scheduling problem. He concludes that better pump scheduling could save £10 million (1988) a year to the UK water industry alone.
4
Challenges and opportunities
Pump applications account for a large per cent of motive power in the water industry [8]. In this case, the power consumed by pumps is proportional to the operating speed cubed. Efficiencies of pumps vary greatly and depend on operational requirements. Fine-tuning the system can have a big impact on energy consumption. Though pump operation and energy cumsumption are two separate entities, they are totally dependent on each other. Changing the patern of operation of pumps will have a significant impact on the total energy consumption or saving. There are many interrelated chalenges involved when handling the control systems in water industry. There are many places where the power is wasted and can be recovered. There are also places where there are oportunities of energy savings. If there is an excess head (pressure) that must be throttled or there are unnecessary flow paths or excessive frictional losses in the system there is wasted energy. In such places these control challenges surely result in opportunities for improvement. These opportunities may also be linked to the long operating hours which are unavoidable in the water industry, or high horsepower pumps which can cause the highest savings if they are properly controlled. It is also evident that variable applications that use throttling as a form of control and operate below full load for a significant length of time offer potential opportunities for higher efficiency through improved control WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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technologies. And finally, the regular maintanace and removal of blocked filters, cavitation or poorly maintained pipes can deliver huge savings in energy consumption. 4.1 Type of infrastructure Whether it is new requirement or existing infrastructure, proper utilisation of resources for minimum energy consumption and sustainable development is very important. Water levels of resources and the pumping operation of different pump stations remotely by telemetry from the central control room. The old/present infrastructures have been designed for a particular pressure (flow rate). Due to aging the safe operation of the system to service the end users is very important. The continuous monitoring of the pressure in these systems can ensure the safe operation as well as fault detection. This is easily achievable by use of the sensor networks of and adapting a suitable flow management control system as mentioned in section 3. Switching or conversion of old systems for optimization of all sections may be very difficult, but if a new design has to be considered, then the best solution may be applying all the optimization techniques of previous section for the entire system. 4.2 Energy saving opportunities The most basic form of control in the water industry is to manage flow by adding friction at the pump outlet. This is usually achieved by a throttle valve. It is effective, but inefficient. Most industrial systems have pumping requirements with several operating points or variable flow and pressure requirements. Picking the pump with the optimum efficiency for a specific delivery is only part of the story. The other part is controlling the flow rate to match the process requirements. The most efficient control option is by use of the VSD which most closely matches the ideal pump curve. Water industry consumes high share of electricity to operate motor-driven pump systems. With an improvement in energy saving systems, the potential savings are very large - over 100 billion KWh/year energy savings and billions of annual energy cost savings opportunity with new technology [8]. Fig.4 shows the Percentage of Power Consumption in Pumps with Different Control Options and obvious advantages replacing throttle valve or bypass valves in water industry. 4.3 Sensor network and new trends in control/sustainable approach In the report on Energy Using Product (EuP) [9], it was shown that the use of high efficient subsystems can improve the overall efficiency of the system. In a simple example in the same report, it is shown that a normal pumping system with subsections as; a standard motor, coupling system, pump, throttling valve control system and transmitting pipe can result to overall efficiency of 31%, where as by improvement of each subsection and replacement of the components with higher efficient ones the over all efficiency can increase to above 72%. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
184 Energy and Sustainability II To have a sustainable system, optimized management of resources is as important as of using new improved systems. A simple substitution of the conventional old systems with that of more efficient subsystems, such as motorpumps, pips, flow controllers and valves, can result in an increase in overall efficiency of the system. 120
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Percentage of flow Throttle valve
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VSD replacing throttle valve VSD replacing bypass valve
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Figure 4:
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Percentage of power consumption vs. control options.
Creasey [7], in his studies by just considering optimal ON-OFF pump scheduling, claimed a huge saving in the UK water industry. Due to development of technology and improvements in semiconductors and their use in recent control systems caused advancement of flexible hardware systems. Now-a-days, everyone knows the advantages of variable speed drives in speed control of pumps for variable flow control, and their use in implementation of a more flexible feedback loop of controllers to supply the required flow rates based on demand that has made it an attractive technology in the water industry with much higher energy saving [8]. Use of sensors networking for accurate high response monitoring and control of parameters and transfer of data to the control stations eliminates the errors, breakdown and make easier predication of faults/leakage in water network system. The flow sensors placed in the line of flow senses the flow water and feed back signals to VSDs control the proportional speed of pumps. As speed of pumps are related to the flow rate, the speed sensors along with the pressure sensors in pips are part of the control systems determining the control commands/ algorithms for assuring the consumers demand fulfillment as well as fault monitoring system in case of leakages. In the previous section, it was explained that on line monitoring of the pressure in each line, is a measure of the consumer demand. On the other hand, regular monitoring of the flow-speed or pressure-speed characteristics of each section is an indication of regular operation of the system based on required water demand in that section. In this system any irregularity of operation is detected and compared with the regular signature of the system. Hence any deviation from the regular operation can be used as an early fault detection or alarm. System improvement opportunities in many cases may include: improved WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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sizing and proper matching to demand, use of more efficient drive trains, improved system layout, updated and well-maintained controls, improved operation and maintenance.
5
Conclusion
To select the appropriate control option, it is required to balance the capital cost of the control equipment against the savings which are achieveable. Although the more efficient control options generally have higher initial set up costs, they can result in large and reoccurring energy savings over the life cycle of the equipment. This paper suggested savings and optimisation of each section of water network while consdering the overall performance of system. It was shown that by improvement of each subsection and replacement of the components with higher efficient ones the over all efficiency can increase and an advancement in control of water flow to supply consumer demand can result on monitoring of the pressure in each line. In this case, flow-speed or pressure-speed characteristics of each section was an indication of regular operation of the system in that section and any irregularity of operation could be detected and compared with the regular signature of the system.
References [1] A. Cashman and R. Ashley (2008) Costing the long-term demand for water sector infrastructure, Foresight, V10, N3, pp9-26. [2] R. Cohen, B. Nelson, and G. Wolff, (2004), Energy Down the Drain: The Hidden Costs of California’s Water Supply. Natural Resources Defense Council, Oakland, CA. [3] G. Cembrano, G. Wells, J. Quevedo, R. Perez, R. Argelaguet (2000), Optimal control of a water distribution network in a supervisory control system, Control Engineering Practices, V8, pp. 1177-1188. [4] M. C. Cunha and J. Sousa (1999), Water distribution network design optimisation: Simulated annealing approach. J. Water Resour. Planning and Manage. 125 (4) 215-226. [5] J. Schaake and D. Lai (1969) Linear Programming Dynamic Programming Applications to Water Distribution Network Design. Dept. of Civil Eng., Massachusetts Inst. of Technol., Cambridge, Massachusetts. Report no 116. [6] E. Alperovits and U. Shamir (1977) Design of optimal water distribution systems. Water Resour. Res. 13 (6) 885-900. [7] J. G. Creasey, (1988), Pump Scheduling in Water Supply: More Than a Mathematical Problem.n in Coulbeck, B. and Orr, C.H. (eds), ”Computer Applications in Water Supply”, Vol. 2, Research Studies Press, Ltd, U.K, and John Wiley k Sons Inc, U.S. [8] M. Ektesabi and H. Felic, (2007) “Motor Management and Energy Saving by Integration of Motor Drive System”, World Congress on Engineering 2007, Conference Proceeding published by IAENG, Page 421-424
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186 Energy and Sustainability II [9] Aníbal T. de Almeida, (2006), Energy Using Product (EuP) Directive Preparatory Study, Lot 11: Motors Analysis of existing technical and market information, DG TREN, Brussels, June 29 2006, ISR-University of Coimbra
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Vanadium battery technology – integration in future renewable energy systems C. K. Ekman, H. Bindner, T. Cronin & O. Gehrke Risø National Laboratory for Renewable Energy, Denmark
Abstract Energy systems with high penetrations of intermittent renewable energy sources face great challenges when it comes to demand-supply balancing and power reserves. The vanadium battery technology may offer solutions to this by providing both energy storage and power system services. This paper presents the recent research activities on vanadium battery technology integration carried out at Risø National Laboratory. A vanadium battery has been installed in a research energy system SYSLAB. It has been characterized and its capabilities for the balancing of wind power have been demonstrated. A small simulation case study (based on the performance measurements of the real system) is presented and the results with respect to diesel fuel savings discussed. Keywords: vanadium battery, energy storage, load management, wind power integration.
1
Introduction
In future energy systems with an increased share of fluctuating renewable energy sources, the challenge of balancing of electrical load and power production will grow. The need for increased balancing capabilities will be present on both longer (energy management) and shorter (regulation and reserve) timescales. Different electricity storage technologies, that can provide balancing capability and thereby facilitate a higher share of renewable energy, are available today (for an overview see [1]). This paper presents a study of one such technology, namely the vanadium redox flow battery. A 15kW/120kWh vanadium battery was installed at the renewable energy research facility SYSLAB and its performance WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESU090171
188 Energy and Sustainability II characteristics as well as its integration in a renewable energy system have been studied during the last year [2]. This paper presents some of the test results obtained in this period. The results of the battery characterization have also been used as input to a modelling tool, which can provide insight to battery integration in energy systems. The remaining parts of the paper are organised as follows: Section 2 gives a brief overview of the technology. Section 3 describes the battery installed at SYSLAB. Section 4 presents the results of test runs where the battery has been used to balance a wind turbine. Section 5 describes how the results from the battery characterization have been used to model the performance of a power system with a vanadium battery. Finally, Section 6 summarizes the work.
2
Vanadium redox flow battery technology
The vanadium battery technology is based on electron/H+ transfer between different ionic forms of vanadium. The liquid electrolytes containing the vanadium ions flow from two separate containers through an electrochemical cell on each side of the membrane. The electrochemical potential across the cell is used to convert the chemical energy to electrical energy (in the discharge mode) or vice versa (in the charge mode). The chemical reactions are: Positive electrolyte:
Negative electrolyte:
The voltage across one cell is around 1.4V and cells are therefore stacked in order to reach higher voltages. Figure 1 shows a schematic drawing of the battery technology. Note, that the electrolyte does not flow between the electrolyte tanks – the electrolyte is pumped through each of the half cells back to the same tank, ensuring that there is, at all times, sufficient electrolyte in the two half cells available to undergo the chemical reactions. The concept is different from conventional batteries where the electrodes take part in the chemical reaction. The chemical reduction/oxidation and the flow of electrolyte (which facilitates the electron transfer and therefore the energy storage) give rise to the name: (vanadium) redox flow battery. More details on the technology can be found in ref. [1]. The technology has the advantage that the energy storage and power capacity can be sized independently (either by changing the amount of electrolyte in the system or the number of cell stacks). The fast response of the electrochemical reactions makes the technology suitable for primary reserves (real time balancing and frequency support). The lifetime of a vanadium battery system is expected to be long and there is in principle no self discharge since the electrolytes are physically separated. However, vanadium battery systems are still relatively expensive and the low energy density makes the footprint of the system considerable. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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Figure 1:
Schematic drawing of a vanadium battery. The aqueous electrolyte is pumped into the fuel cells (here only one cell is depicted) on each side of the cell membrane. The concentration of the different vanadium ions in the two electrolytes leads to an electrochemical potential over the cells.
Figure 2:
Photo of the vanadium battery installation at SYSLAB. The three blue units in front are the cell stacks, each containing 40 cells. Behind the cell stacks and the pump/pipe system, the two 6500 liter electrolyte tanks are situated. The box to the right is the control unit.
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3 Vanadium battery at SYSLAB SYSlab is a research facility at Risø-DTU that has been built to study integration of energy technologies. It includes two wind turbines (11 and 55kW), solar panels (9kW), office building (max. load of 20kW), hybrid vehicle-to-grid car (9kWh), a diesel generator (48kW), a dump load (75kW) and a vanadium battery (15kW/120kWh). The research activities focus on renewable energy integration, intelligent (distributed) control and communication. For more information on SYSlab see ref. [2]. In 2007 the 15kW/120kWh vanadium redox battery was connected to the system as part of the research project “Characterization of vanadium battery” funded by the PSO framework (ForskEl project 6555). Figure 2 shows a photo of the battery system. In order to understand the battery performance and be able to develop a realistic model, the losses in the different parts of the battery system have been analyzed independently. There are losses in the power converter, losses in the cell stack and parasitic losses (due to the auxiliary system and selfdischarge).
Figure 3:
Battery efficiency as function of power for the stacks only (upper yellow curve), stacks and power converter (middle green curve) and total (lower curve). The widths indicate the spread depending on state of charge. When the power is negative, the battery is being charged.
The losses in the cell stacks are primarily ohmic losses. The area specific resistance has been estimated to be around 0.16Ωcm2. The efficiency of the cell stack can be determined from the ratio of the actual voltage (at a certain current level) and the open circuit voltage (which depends slightly on the state of charge WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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of the battery). The cell stack efficiency lies in the range from 88% to 100% in the DC power range from -15kW to 15kW. The cell stack efficiency is lowest when the battery is close to being discharged and delivering full DC power (+15kW) and highest when the DC power is close to zero. The efficiency of the power converter is about 55% at 1kW, 80% at 2kW and 93% at full power (15kW). The power consumption of the auxiliaries (pumps and control) varies with the power as follows. The pumps have two operational speeds resulting in a power consumption of about 1.2kW at battery powers lower than 4kW and about 1.5kW above 4kW. This auxiliary power consumption could probably be optimized by installing pumps with higher efficiency and an energy saving control unit. The electrolyte level in the tanks may change slightly due to water diffusion through the membranes of the electrochemical cells (caused by the osmotic pressure). The levels are equalized every 24 hours by opening a valve for half an hour, allowing the electrolyte to flow between the two tanks. The losses during this equalization process depend on the state of charge, but on average it corresponds to a constant power loss of about 110W. Figure 3 shows the efficiency of the different parts of the system. It is expected that the energy consumption of the auxiliary system (pumps and control) and the losses in the equalization process can be reduced significantly in larger battery systems.
4 Test run VRB-WT balancing The vanadium battery at the SYSLAB facility at Risø-DTU has been operated in parallel with the 11kW Gaia wind turbine, balancing the combined output to a constant 4kW. The flexible configuration of SYSLAB has allowed for the connection of the two components to the same busbar, which was then connected to the national grid. Measurements of the power flow from the turbine, the battery and the total output to the grid is shown in Figure 4 (5 minute averages). The power from the wind turbine is balanced and the desired output of 4kW is sustained (when the battery state of charge is not zero or 100%). Due to the speed of the communication and control program, complete balance on the shorter timescale has not been achieved. Measurements taken every second show a mean variation of 0.8kW around the 4kW set point. Further studies will include operating the battery in droop mode in an island system together a wind turbine and a variable load. In such a system, the battery can be the grid-forming unit and at the same time provide energy management on the longer timescale.
5
Modelling of vanadium battery in power system
A vanadium battery model has been developed and implemented in the IPSYS modelling environment [3]. IPSYS offers the possibility of modelling energy systems with a special emphasis integration of renewable energy technologies. Detailed modelling of power systems is provided with a quasi-static description of the power flows, voltages, frequencies, as well as losses.
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Figure 4:
Lower panel: Power as function of time for the wind turbine (positive, red line), the battery (blue line) and the sum (around 4kW, black). After a period with no wind (around hour 20 and hour 110), the turbine consumes power in a short period to start up – this can be seen as a small dip below zero in the wind turbine power output. Upper panel: Battery state of charge (SOC). When the battery is fully charged (around hour 260), the 4kW output cannot be sustained.
Based on the power set point (and the state of charge), the battery model recalculates the state of charge after each time step, taking into account the different losses in the system: • Stack losses: The efficiency of the electrochemical cells is simply the cell voltage relative to the electromotoric force (open cell voltage). The model includes the open cell voltage dependence on the state of charge and a linear change in the voltage depending on the current over the stack. • Power converter losses: The power converter efficiency (both AC to DC and DC to AC) and its dependence on power has been used to model the losses in this part of the system. • Parasitic losses: The auxiliary power consumption is modelled a linear function of the AC power of the battery (400W losses at zero power and 7% losses at full power). WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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This parameterization of losses in the battery system is based on the measurements of losses in the vanadium battery installed at Risø-DTU (see section 3), which makes the model both detailed and realistic. 5.1 A small island system simulation case study The IPSYS model including the newly added battery component has been used to simulate a small imaginary island power system including a wind turbine, two diesel generators, a variable load (emulating a number of households), a dump load and a vanadium battery. The layout of the systems is shown in Figure 5.
Figure 5:
Layout of the small island system. The diesel generators, the vanadium battery (VRB) and the dump load are connected the same busbar (bus 2). The wind turbine and the load are connected to the two other busbars (bus 1 and bus 3).
The load has a weekday and a weekend load profile with an additional stochastic behaviour and it ranges from approximately 30 to 70 kW. The wind speed input is based on measurements from the Risø-DTU meteorological mast over a full year. The wind power is determined from the measured wind speed and a simple power curve. The turbine capacity is 75kW. The two diesels can supply 60kW each and they have a lower power limit of 6kW. The battery has a power capacity of 40kW. A quite simple battery load management control strategy has been applied. The battery power is set to balance the wind power plus the load, i.e. charging the battery when there is excess of wind power and discharge the battery when the load exceeds the wind power. When the battery is fully charged, absorbing the excess wind is not possible and the battery power is then set to the standby power. Likewise, when the battery is fully discharged and the load exceeds the wind power. In effect, the battery will save excess wind power and supply power to the system when the wind does not meet the load. One diesel is required to be on constantly in order to maintain frequency and voltage on the grid (being the WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
194 Energy and Sustainability II grid forming unit). The other diesel is turned off when there is sufficient power in the system. The studied time period is one year and simulation has been carried out with 6 different battery capacity sizes: 0, 3, 5, 10, 15 and 20 hours (at full power, i.e. 0, 120, 200, 400, 600 and 800kWh).
Figure 6:
Upper panel: Battery state of charge (SOC) as function of time for an example week. Lower panel: power of the different components. This example is for battery storage capacity of 5 hours.
The lower panel of Figure 6 shows the power of the different system components during one week. The upper panel shows the battery state of charge as function of time. The lower panel shows the power of the different components. The battery power cycles are clearly seen in the figure: first a period of charging followed by a period of discharging that continues until the battery is fully discharged. The dump load is often used simultaneously with the battery – this undesirable behaviour comes from the fact that only the dump load and the diesels can actively react on the system frequency. When the wind exceeds the load, (downward) regulation of the frequency can only be provided by the dump load (the spinning diesel supplies the minimum power of 6kW and WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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cannot regulate downward). Using more intelligent control, where the battery provides a part of the frequency regulation at times with excess wind power, would result in even less power being dumped.
Figure 7:
Amount of energy dumped and lost in the battery as function of battery size. The corresponding diesel fuel consumption is shown as square markers (axis on right side of the plot).
Figure 7 shows the amount of dumped energy, the losses in the battery and the diesel fuel consumption as function of battery storage capacity. The figure illustrates that the energy dumped can be reduced by about 45% if a 20-hour battery storage capacity is used. When the losses in the battery are also taken into account, the reduction in lost energy is about 35%. In terms of diesel fuel savings the battery only saves about 2000 litres per year (with the present control strategy). This is only about 2% of the total fuel consumption and clearly not sufficient to cover the cost of installing and operating a vanadium battery. It is expected that larger saving on the diesel fuel consumption can be achieved by applying more intelligent control strategies. First, the diesels can be turned off during hours where the battery (and wind) can supply the load consumption, i.e. the battery can be the grid-forming unit during some periods. This would prevent the diesels from running close to minimum power, which results in high fuel consumption (per kWh). Secondly, the battery can be controlled so that the diesels primarily are operated at full power. This will also save diesel fuel, since diesels are more efficient at full power. Finally, wind power forecasts can be used to charge and discharge the battery depending on the expected wind power WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
196 Energy and Sustainability II in the coming hours. The potential fuel saving is to the first approximation limited by the total amount dumped energy times the heating value of diesel (about 10kWh/liter) divided by the electrical efficiency of the diesels. If the latter is 30%, the maximum diesel fuel savings is about 7100 litres. Future studies on island systems with wind, diesel and vanadium batteries will be focussed on more intelligent control strategies and the possibilities for diesel fuel saving.
6 Summary and outlook This paper has outlined the research activities on the vanadium battery technology integration carried out at the Risø National Laboratory. A 15kW/120kWh battery has been characterized and its capabilities to balance wind power has been demonstrated at the SYSLAB facility. The results from the battery characterization have been used to implement a realistic battery model in the IPSYS modelling environment. A simulation case study has been presented showing how a battery can be integrated and controlled in a small island system. The case study illustrates a simple strategy for control of the battery depending on the wind power and the load. With this strategy (in this island system) the savings of diesel fuel are very limited, even with a battery storage capacity of 20 hours. More intelligent control strategies are needed in order to decrease diesel fuel consumption further. Whether or not the saving on diesel fuel consumption can become sufficient to ensure economic viability of vanadium battery integration in island systems depends on many factors, like system design, system control, price of diesel fuel and the cost of a battery system. These issues will be treated in further studies.
Acknowledgement The work has been supported by Energinet.dk as part of the project “Characterisation of Vanadium Batteries” (ForskEl project 6555).
References [1] EPRI-DOE Handbook of Energy Storage for Transmission and Distribution Applications, EPRI, Palo Alto, CA, and the U.S. Department of Energy, Washington, DC: 2003. 1001834 [2] Bindner H., et al. Initial tests of vanadium flow battery at Risø-DTU, 4th European PV-Hybrid and Mini-Gird Conference, Glyfada, Greece, 2008 [3] Bindner, H. et al., IPSYS – A Simulation Tool for Performance Assessment and Controller Development of Integrated Power System Distributed Renewable Energy Generated and Storage, WREC VIII, Denver, Colorado, 2004
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Short-term wind forecasting using artificial neural networks (ANNs) M. G. De Giorgi, A. Ficarella & M. G. Russo Department of Engineering Innovation, Centro Ricerche Energia e Ambiente, University of Salento, Italy
Abstract The integration of wind farms in power networks has become an important problem. As electricity cannot be preserved because of the highest cost of storage, electricity production must following market demand, necessarily. Short-long term wind forecasting over different time steps is becoming an important process for the management of wind farms. Time series modelling of wind speeds is based on the valid assumption that all the causative factors are implicitly accounted for in the sequence of occurrence of the process itself. Hence, time series modelling is equivalent to physical modelling. Artificial neural networks (ANNs), which perform a non-linear mapping between inputs and outputs, provide a robust approach for wind prediction. In this work, these models are developed for simulating wind speed and energy production of a wind farm with three wind turbines, comparing different prediction temporal periods. We applied artificial neural networks for short and long term load forecasting using real load data. Keywords: neural artificial networks (ANNs), forecasting wind, turbine, CFD.
1
Introduction
Electricity markets throughout the world are changing to allow the integration of alternative energy sources, in particular wind energy. The major criticality in the use of renewable energy, particularly of wind energy, concerns the management of wind farms. As electricity cannot be preserved because of the highest cost of storage, electricity production must follow the market demand, necessarily. In the state of the art there are two types of approach in the prediction of wind energy [1]: those based on physical WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESU090181
198 Energy and Sustainability II modelling and those based on historical series analysis. The first is used in meteorology to reproduce the atmospheric state, but this is a very complex system since it requires big resources of hardware for the calculation. While, approaches based on historical series estimate the future values on the basis of past values after identification of a model that simulates the process analyzed. This methodology is based on the valid assumption that all the factors influence the process are taken into implicitly using the past values and so it is possible to make a probable prediction. A good prediction model in real time of wind energy must be able to guarantee reliability for the prediction as soon the time horizon is extended. In order to understand the different issues involved in wind energy forecasting it is useful to divide the problem into three difference time scales: very short-term (0-6 hrs), short-term (6-72 hours), and medium range (310 days). In the small terms, in particular when the time horizon swings from a few minutes to some hours, various studies, based on ARMA models [2,8] and ANNs model [3,5–7], obtained a good result in the prediction of wind energy. In [5] an ANN model is presented, based on a back-propagation method, it was evaluated with real data measured at two different locations and demonstrated a correct dynamic performance in all evaluation tests, so it can be concluded that the algorithm is valid for estimating average speed values. The initial point for the approach in [6] is mainly the fact that none of the forecasting approaches for hourly data, that can be found in the literature, based on time series analysis or meteorological models, gives significantly lower prediction error than the elementary persistent approach. This was combined with the characteristics of the wind speed data, which are determined by the power spectrum values, distinguished by the spectral gap in intervals between 20 minutes and 2 hours. The finally proposed methodology is based on the multi-step forecasting of 10 minutes averaged data and the subsequent averaging to generate mean hourly predictions. In [7] the ANNs models are found to perform better for the forecast length of one hour, as seen from the actual and simulated data. For the forecast length of one hour, artificial networks are found to perform better than other methods, but the study suggests that, for increased forecast lengths, modified methods need to be investigated. In [8] a linear, time-varying autoregressive (AR) process is used to model and forecast wind speed. This modelling approach takes into account the non-stationary nature of wind speed. The time-varying parameters of the AR model are modelled by smoothed, integrated random walk processes. A Kalman filter is used to estimate the time-varying parameters of the AR model. The algorithm is used to forecast wind speed from 1 h to a few hours ahead. Other studies, for example in [14], are focused on a real-world application, the long-term wind speed and power forecasting in a wind farm using locally recurrent multilayer networks as forecast models. To improve the performance of the models, considering the complexity of the process, a class of optimal on-line learning algorithms is employed for training the locally recurrent networks based on the recursive prediction error (RPE) algorithm. The experimental results demonstrate that the recurrent forecast models provide better multistep ahead forecasts compared to the persistent method, the atmospheric and time-series models. In [15] the wind speed prediction in wind WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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farms has been performed by using local recurrent neural networks with internal dynamics, as advanced forecast models. The efficiency of the proposed approach is tested on a real-world wind farm problem, where multistep ahead wind speed estimates from 15 min to 3 h are sought. In [16] results are presented of a number of advanced prediction systems performed in the frame of the European project Anemos. The European project Anemos is focused on several topics related to wind power forecasting such as physical and statistical modeling, uncertainty estimation, upscaling and others. From the very first stage of the project it was recognized by both end-users and modelers the necessity to map the existing wind power forecasting technology both in terms of research approaches and also in terms of performance. In [17] a statistical forecasting system is implemented for short-term prediction (up to 48 h ahead) of the wind energy production of a wind farm: for a given wind farm, the input variables are the meteorological predictions of wind (velocity and direction) for the next 48 h and past values of output power. The forecasting system has then to supply, on an hourly basis, the predicted output power up to 48 h ahead. In this work, artificial neural networks have been applied for the prediction of wind energy when the time horizon swings from 1 to 24 hours, using historical series data wind only, for a wind farm. Preliminarily, the statistical analysis of the historical series was processed and the probable distribution of wind speed and direction of the three turbines were represented. Application of a neural network for the prediction of wind energy able to an acceptable error on the observation when the prediction length is under 6 hours. So, with the extension of a prediction time horizon, the reliability of a prediction based only on statistical methods reducing considerably, but the need of planning on mediumlong terms of the wind productivity asks for approaches that are able to integrate knowledge from historical series with the outputs of numerical weather models.
2
Wind farm characteristics
There are a number of complex issues associated with the evaluation of wind energy forecasts. The most significant issue is which parameter(s) should be
Figure 1: Seasonal trend of wind speed in year I of the wind park.
Figure 2:
Wind speed and wind direction – Month of April (year I).
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200 Energy and Sustainability II used as the metric(s) for forecast performance. One’s choice of metrics can have a significant impact on one’s impression of forecast performance. So the first step in the wind forecasting is the statistical analysis of the historical series data. Our data set contains wind speed observations for a period of four years (years I, II, III, IV). In fig. 1 the seasonal trend of average wind speed for the first year of dataset (year I) is represented: in general, the average daily wind speed is higher in the winter than the summer months. In Fig. 2, the peak of wind speed is at a consistent wind direction, this means that a consistent wind direction can be considered as a factor that explains the high wind speed.
3 ANNs models for wind speed and energy prediction 3.1 Artificial neural networks and architectures Neural networks are composed of simple elements operating in parallel. These elements are inspired by biological nervous systems. As in nature, the network function is determined largely by the connections between elements. You can train a neural network to perform a particular function by adjusting the values of the connections (weights) between elements. A typical neural network used in the present study is the Multi Layer Feed Forward (MLFFN) network. In the Feed-Forward networks the data flow from input to output units is strictly feed-forward [13]. The data processing can extend over multiple (layers of) units, but no feedback connections are present, that is, connections extending from outputs of units to inputs of units in the same layer or previous layers. Each layer consists of units which receive their input from units from a layer directly below and send their output to units in a layer directly above the unit. There are no connections within a layer. The ANN learns through the set of examples supplied to it during the training process. Once the network weights and biases are initialized, the network is ready for training. During training the weights and biases of the network are iteratively adjusted to minimize the network performance. The default performance function for feed-forward networks is mean square error – MSE – the average squared error between the network outputs a and the target outputs t. Several algorithms for training use the gradient of the performance function to determine how to adjust the weights to minimize performance. The gradient is determined using a technique called back-propagation, which involves performing computations backward through the network. The goal of the algorithm is to minimise the global error E defined below,
1 n E = ∑ (t (k ) − o( k )) 2 2 k =1
(1)
where o(k) and t(k) are the outputs and target network for any k output node. The summation is carried out over all output nodes for every training pattern. A pair of input and output values constitutes a training pattern. The back-propagation WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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algorithm calculates the error E as per Eq. (1) and distributes it backward from the output to hidden and input neurons. This is done using the steepest gradient descent principle where the change in weight is directed towards negative of the error gradient. The incremental change in the weight may be expressed as,
∆wn = α∆wn −1 − η
∂E ∂w
(2)
where w is the weight between any two nodes ∆wn and ∆wn-1 are the changes in the weight at nth and n-1th iterations; α the momentum factor and η the learning rate. The learning rate governs the size of the weight change during each iteration. The momentum factor prevents the weight oscillations during training iterations and also accelerates the training on flat error surfaces [11]. The activation function used for the hidden neurons of the networks are generally the sigmoid function (‘tansig’). The output neurons can have linear activation function (‘purelin’). In the present study, fast algorithms, developed as modified versions to the standard back propagation algorithm are used, known as the Levenberg-Marquardt algorithm (‘trainlm’). Also, the learning function used are the gradient descent weight/bias learning function (‘learngd’). 3.2 Models In the present work, ANN models are developed to obtain wind speed for forecast length of 1 hour and wind energy for forecast lengths of 3, 6, 12 and 24 hours. The available database concerns the wind farm is in the form of average wind speeds obtained through anemometric measurements and collected every 10 minutes. The wind speed data is divided into training dataset (years I, II, III) and test dataset (year IV). For each of the prediction lengths, results are obtained for Multi Layer Feed Forward Networks. The required functional relationship for the hourly average wind speeds observed for the site may be expressed as, (3) v = f (v , v , v , v ,...) t +1
t −1
t
t −2
t −3
where vti is the hourly average wind speed of periods before t. The required functional relationship for the hourly wind energy observed for the site may be expressed as, ∆t (4)
∑ P = f (v , v i =t
i
t
v
v ,...)
t −1, t − 2, t − 3
where ∆t is the forecast length for the wind energy prediction (3, 6, 12 and 24 hours), Pi is the hourly wind energy and vti is the hourly average wind speed of periods before t. Energy wind is calculated by the mean power curve of turbines of park. There is no systematic approach for selection of the input variables which could be followed, but certain statistical parameters can be used to determine the relevant inputs. In this work an autocorrelation coefficient (ρ) was WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
202 Energy and Sustainability II Table 1:
Statistical properties of wind speed for the site.
Wind speed
Training set (years I,II,III)
Test set (year IV)
Minimum Maximum Mean Standard deviation
0 26.38 6.6 4.1805
0.34 24.837 6.77 4.3148
Table 2:
MSE for different number of inputs and prediction lengths (global training set).
Number of inputs
1 hour
3 hours
6 hours
7 16 24 36 48
0,0167 0,011 0,02 0,033 0,06
0,05 0,047 0,04539 0,1 0,15
0,05 0,039 0,01 0,028 0,03
Table 3:
12 hours 24 hours 0,183 0,1 0,0967 0,09 0,098
0,2 0,1 0,13 0,111 0,08
Architecture network: Multi-layer feed forward networks. (1): (vt, vt-1, vt-2, …vt-16), (2): (vt, vt-1, vt-2, …vt-24), (3): (vt, vt-1, vt-2, …vt-24), (4): (vt, vt-1, vt-2, …vt-36), (5): (vt, vt-1, vt-2, …vt-48).
Parameters Training function Adapt learning function Performance function Number layers Neurons (layer 1) –inputs Neurons (layer 2) Neurons (layer 3) –output Activation function hidden layer Activation function output layer Epochs
Parameters Training function Adapt learning function Performance function Number layers Neurons (layer 1) –inputs Neurons (layer 2) Neurons (layer 3) –output Activation function hidden layer Activation function output layer Epochs
1 hour TRAINLM LEARNGD MSE 3 16 (1) 8 1 (vt+1) Tansig Purelin 150
12 hours TRAINLM LEARNGD MSE 3 36 (4) 18 1(Pt:t+12) Tansig Purelin 200
3 hours
6 hours
TRAINLM LEARNGD MSE 3 24 (2) 12 1 (Pt:t+3) tansig Purelin 300
TRAINLM LEARNGD MSE 3 24 (3) 12 1(Pt:t+6) tansig purelin 100
24 hours TRAINLM LEARNGD MSE 3 48 (5) 24 1(Pt:t+24) tansig purelin 200
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used to obtain the required number of inputs for the models. The values of autocorrelation coefficient give an indication about the number of previous data values which are significant for forecasting the wind speed at a future time point. The database is partitioned into two disjoint subsets: training and test set. The motivation is to assess the network’s ability to generalize supplying a data set different from the one used for parameter estimation. Also, the target’s network for the prediction of 1 hour in advance is wind speed while for the prediction in the time horizon of 3-24 hours is the wind energy. The statistical properties of the wind speed data and for the various sets are given in table 1. Before training, inputs and targets are scaled so that they always fall within a specified range of [-1,1]. Post processing is done while simulating the network after the training process. For the selected network type and architecture, the parameters (weights and bias values) are assumed as random values. The parameters relevant in the training algorithm, error goal and number of epochs. Table 2 shows the observed MSE for different number of inputs and prediction lengths. Table 3 shows the principal parameters assumed for the networks.
4
Results and discussion
ANNs models are developed, simulated and tested for forecast lengths of 1 hour, 3, 6, 12 and 24 hours. So, in the following, results of network simulations were shown. In order to show the model accuracy, the results using the ANNs models, are compared with the observations. The MSE function, expressed as:
MSE =
1 N
(5)
N
∑ (t (k ) − o(k ))2 k =1
measures the network’s performance according to the mean of squared errors. The correspondent values are shown in table 4. Results of network simulations are compared in terms of average percentage error on test data set. As shown in fig. 3, the approximation of the prediction of wind speed in the 1-hour ahead and for the two week of test set is good. During training of network the MSE stabilizes at value of 0.0115968 after 150 epoch. Table 4:
Values of performance function of ANNs – MSE.
ANNs
1 hour
3 hours
6 hours
12 hours
24 hours
MSE
0.0115968
0.04539
0.1
0.09769
0.08069
Forecast errors increase with increasing of prediction length. Fig. 4 shows the simulated of the network’s output for forecast energy for all time horizons in two weeks of test data. In the 3 hours ahead (a) the output of the network approximates the observed energy with an error greater than the error realized for forecasting the wind speed in the 1 hour ahead. The value of the MSE stabilizes at 0.05 after 300 epochs of learning. In the 6 hours ahead (b), the output of the WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
204 Energy and Sustainability II
Adimensional Velocity
1.0
Adimensional Velocity
network approximates the observed energy with an error greater than the error realized obtained for forecasting the wind energy in the 1 and 3 hours ahead. The value of the MSE stabilizes at 0.1 after 100 epochs of learning. (c) shows the simulated of the network’s output for forecast energy in the 12 hours ahead, the value of the MSE stabilizes at 0.09769 after 200 epochs of learning. (d) shows the simulated of the network’s output for forecast energy in the 24 hours ahead, the value of the MSE stabilizes at 0.08069 after 200 epochs of learning.
1.0
observation prediction
0.8 0.6 0.4 0.2 0.0
0
20
0
20
40 60 80 100 120 140 Week from 1 to 7 September - Hours
160
0.8 0.6 0.4 0.2 0.0
40
60
80
100
120
140
160
Week from 1 to 7 February - Hours
Figure 3:
ANN for prediction of wind velocity (adimensionalized with respect to the maximum observed velocity in the period) – Prediction length of 1 hour.
The 24-hour forecast is the longest horizon forecast included in this study, and is well outside the acknowledged boundaries for statistical estimation of wind speed, as described in literature. The ANN method for prediction shows signs of reduced accuracy at this range. Fig. 5 shows the fraction of average errors on wind energy observed for the test set and for all prediction lengths. For prediction length of 1 hour the average percentage error on the power observed changes from a minimum of 1% (April) to a maximum of 2.6% (November). From April to August these figures show a lower error than winter months. This is correlated with the result of the statistical analysis in fact the wind speeds in winter months were higher than summer months: the neural network has major difficult to prediction the high wind speeds, so prediction errors in these months are greater. For prediction length of 3 hours the average percentage error on energy observed changes from a minimum of 7% (July) to a maximum of 12% (January). For prediction length of 6 hours the average percentage error changes from a minimum of 10% (December) to a maximum of 16% (August). For prediction length of 12 hours the average percentage error changes from a WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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Adimensional Wind energy
Adimensional Wind energy
PREDICTION LENGTH OF 3 HOURS (a) Observation Prediction
1.2 1.0 0.8 0.6 0.4 0.2 0.0 0
20
40
60
1.2
observation prediction
1.0 0.8 0.6 0.4 0.2 0.0 0
80 100 120 140 160
20
40
60
80 100 120 140 160
Week from 1 to 7 September - Hours
Week from 1 to 7 February - Hours
1.0 0.8 0.6 0.4 0.2 0.0 0
20
40
60
80 100 120 140 160
Adimensional Wind Energy
Adimensional Wind Energy
PREDICTION LENGTH OF 6 HOURS (b) observed predicted
1.2
observed predicted
1.2 1.0 0.8 0.6 0.4 0.2 0.0 0
20
40
60
80 100 120 140 160
Week from 1 to 7 February - Hours
Week from 1 to 7 February - Hours observation prediction
1.0 0.8 0.6 0.4 0.2 0.0 0
20
40
60
Adimensional Wind Energy
Adimensional Wind Energy
PREDICTION LENGTH OF 12 HOURS (c) 1.2
observation prediction
1.2 1.0 0.8 0.6 0.4 0.2 0.0 0
80 100 120 140 160
20
40
60
80 100 120 140 160
Week from 1 to 7 September - Hours
Week from 1 to 7 February - Hours osevation prediction
1.0 0.8 0.6 0.4 0.2 0.0 0
20
40
60
80 100 120 140 160
Week from 1 to 7 February - Hours
Figure 4:
Adimensional Wind Energy
Adimensional Wind Energy
PREDICTION LENGTH OF 24 HOURS (d) 1.2
observation prediction
1.2 1.0 0.8 0.6 0.4 0.2 0.0 0
20
40
60
80 100 120 140 160
Week from 1 to 7 September - Hours
Forecast of wind energy (adimensionalized with respect to the maximum observed value in the period) – different prediction length.
minimum of 13% (December) to a maximum of 18% (August-February). For prediction length of 24 hours the error on energy observed changes from a minimum of 16% (December) to a maximum of 25,5% (February). WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
206 Energy and Sustainability II So, with the extension of prediction time horizon, the reliability of a prediction based only the statistical methods reducing considerably. The maximum error rate is 25% with time horizon of 12 and 24 hours so we cannot consider acceptable these forecasts. Fig. 6 shows the fraction of standard deviation of prediction errors for all prediction lengths.
Average error of prediction
0,40 0,35 0,30
1 hour
0,25 0,20
3 hours
0,15 0,10
12 hours
6 hours 24 hours
0,05 0,00
n Ja
ua
ry F
r eb
ua
ry M
ch ar
Ap
ril
M
ay
Ju
ne
Ju
ly
g Au
us
t
Se
p
m te
be
r
r r er be be o b em m ct e v c O No De
Test set - Year IV
S tandard deviation of error
Figure 5:
Fraction of average errors on wind energy observed for the test set and for all prediction lengths.
0,40 0,35 0,30
1 hour
0,25
3 hours
0,20 0,15
6 hours
0,10 0,05
24 hours
12 hours
0,00
J
u an
il e y y h y a r uar arc A pr M a J un r M b Fe
Ju
ly
r r e r er b be to be m b m e c v t ce O o p e N D Se
g Au
us
t
em
Test set - Year IV
Figure 6:
Fraction of standard deviation error on wind energy observed for the test set and for all prediction lengths.
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Conclusions and perspectives
The present paper has developed artificial neural networks (ANN) models to forecast the wind power prediction of a wind farm for different time horizons. We have shown how wind power density forecasts, for lead times from one to 24 hours ahead, can be generated from wind speed observations. There is a clear difference in the ability of ANN forecast models applied to different time horizons. The results show that for a forecast horizon under 6 hours this method can be considered a valid instrument to support control by the management of a wind park. The study shows lower errors compared to those found in literature to forecast one hour in advance [7]. The reliability of a prediction based only the statistical methods reducing considerably, with the extension of prediction time horizon. The error rate is 20% with time horizon of 12 and 24 hours so we cannot consider these forecasts to be acceptable. For prediction with time horizons of 12 and 24 hours other methods should be investigated because forecasts with neural networks are not reliable. We believe that the errors obtained could be reduced with a neural network able of taking different atmospheric variables as inputs, such as wind direction (useful particularly for prediction of higher speeds), pressure, temperature, etc. Also, we think that an application, in future work, of mixed methods such as neuro-fuzzy networks, will be useful to obtain reliable wind forecasts.
Nomenclature E= global error o(k)= network’s output t(k)= network’s target vti= average wind speed t i w= connection weight α = momentum factor η = learning rate ∆t =forecast length Pi=hourly wind energy MSE=mean square error
References [1] [2] [3]
Burton, N. J. & Bossanyi, Wind energy handbook, Wiley 2001. Bossanyi, E.A. Short-term stochastic wind prediction and possible control application, Proceedings of the Delphi Workshop on “Wind Energy Application” Greece (1985), pp. 137-142. Kariniotakis, N.E. & Stavrakakis, Advanced short-term forecasting of wind power production, Proceedings of the 1996 European Union Wind Energy Conference EUWEC’97 , Dublin, Ireland, 1997, pp. 751-754.
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208 Energy and Sustainability II [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17]
Dibike, P.C, Temporal neural networks for downscaling climate variability and extremes, Proceedings of the 2005 International Joint Conference on Neural Networks, Montreal, Canada, 2005. Flores, A. T. & G. Tapia, Application of a control algorithm for wind speed prediction and active power generation, Renewable Energy 30,p. 523-536, 2005. A. Sfetsos, A novel approach for the forecasting of mean hourly wind speed time series, Renewable Energy, 27 (2), pp. 163-174 Jayaraj, K. P., E. S. & Arun, Wind speed and power prediction using artificial neural networks, European Wind Energy Conference 2004 (EWEC). Huang, Z.S., Chalabi, Use of time-series analysis to model and forecast wind speed, Journal of Wind Engineering and Industrial Aerodynamics, 56, pp. 311-322, 1995. Giebel, R. B, G. K., The state-of-the-art in short-term prediction of wind power. a literature overview. Wind Energy 6(3), pp.273-280, 2003. C. Mohrlen, Uncertainty in wind energy forecasting, 2004, PhD Thesis. More, D.MC, Forecasting wind with neural networks, Marine Structures 2003, 16: 35-49. Demuth, M. B., M.H, Neural network toolbox 5, User’s Guide, The mathworks. Krose & Van der Smagt, Mathematics, an introduction to neural networks. Eighth edition, November 1996 Barbounis, J.B. T, Locally recurrent neural networks for long-term wind speed and power prediction, Neurocomputing, 69 (4), pp. 466-496, 2006 Barbounis, J.B. T, Locally recurrent neural networks for wind speed prediction using spatial correlation, Information Sciences, 177 (24), pp. 5775-5797, 2007 Martí, G. K., Evaluation of advanced wind power forecasting models – results of the anemos project. http://anemos.cma.fr I. Sanchez, Short-term prediction of wind energy production. International Journal of Forecasting, 22 (1), pp.43-56, 2006.
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Section 3 Energy policies
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A review of the Bioenergy potential of residual materials in Quebec S. David1 & N. Abatzoglou2 1
Laboratoires Shermont Inc., Canada Université de Sherbrook, Department of Chemical Engineering, Canada
2
Abstract In Quebec more than 48% of residual materials produced in 2006 throughout all societal activities have been disposed of finally in landfills. Despite government policies on the 3Rs (Reduction, Reutilization, Recycling) and the total recovery objectives set-up, the total mass landfilled has increased by 120% over the last 10 years. Over the last 50 years, although the agricultural surface decreased by half, the number of pigs tripled. With an annual production of almost 8 million pigs, more than 400 out of a total of 1200 Quebec municipalities have a considerable surplus in liquid manure. The present work undertakes a review of these two growing problems-opportunities in Quebec and proposes alternative and sustainable solutions. Since the building and operation of experimental bioreactors (manure digesters) in some farms in Quebec, the anaerobic co-digestion of the rural and urban putrescible materials seems an interesting avenue. The development of a green energy vector by valorising the so-produced biogas would also contribute in decreasing the rejection of contaminants in the environment. In this work, only the biomass, resulting from the residential sector and the quantity of the liquid manure available in Quebec, is considered to calculate the Bioenergy potential. The Bioenergy output of the various methanisation processes are compared with that abroad, particularly in Europe. The available biomass in Quebec has been calculated based on available statistical data regarding the production of urban waste and manure. The review shows that this Bioenergy vector technology is sustainable and that its commercialization can be profitable at a cost no higher than that of disposal in landfills. Keywords: biomass, organic waste, anaerobic methanisation, bioreactor, codigestion, green energy, Bioenergy. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESU090191
212 Energy and Sustainability II
1
Introduction
It is well established that the actual prices of the majority of the goods and services do not integrate the real social and environmental cost. This is ecologically unacceptable. This is mainly due to the fact that the markets, in their current structure, are unaware of the limits of the natural processes. In nature, all residual matter generated by a living organism is used as a resource by another; this insures the natural recycling of all used resources. The challenge of our society is to reproduce this process in its economy. Putrescible matter is one of the principal causes of contamination in the places of disposal. In landfills, the anaerobic fermentation generates GreenHouse Gases (GHG). The organic compounds released by this fermentation migrate with water of leaching (leachates) and can contaminate surface as well as subsoil waters and aquifers, thus rendering them unsuitable for human consumption and to the surrounding biotopes. The recovery of the putrescible matter at the end of valorisation reduces the polluting load and the GHG emissions while providing us with Bioenergy and valued products (i.e. compost). The reduction of residual materials that end up in landfills is a positive element on the economy and the environment for a variety of reasons, including the reduction of the transport of these residual materials. Hog farm activities and the resulting manure spreading for fertilizing purposes contribute considerably to the release of ammonia emissions, the increase of the phosphorous content in the soil and the pathogenic organisms in the environment. The emissions of ammonia contribute to the GHG emissions as well as to an imbalance of the nutritive elements in the ecosystems, including surface water. Long-term liquid manure spreading in Quebec, based on directives inspired by soil nitrogen enrichment, led to an excess of phosphorus. Moreover, spreading of the liquid manure also increases the water-soluble phosphorus concentrations, which causes direct eutrophication conditions in surface waters. Currently the farm-by-farm approach, stipulated in 2002 by the Law on agricultural production, led to a serious problem. Indeed, instead of calculating the rate of available phosphorus by catchment area, the quantity of phosphorus surplus is calculated based on the surface of the so-fertilized soil. This approach does not consider the type of soil, the zones easily flooded, the antibiotics present in the liquid manures and the initial quality of the surface waters (lakes and rivers) near the ground of spreading. These factors can have direct repercussions for certain rivers and more sensitive underground sheets of water. In an effort to minimize the harmful effects on the environment by the actual residual materials disposal and by the management of the liquid manure, this review tries to establish if methanisation of the organic residues and the liquid manure can be a sustainable solution.
2
Solid waste management in Quebec
In Quebec, based on data from 2006, only half of the materials that may undergo beneficiation were recovered. The landfill of the putrescible materials, the WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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spreading of the animal manure and their storage are not sustainable solutions. These practices contribute to higher management costs, to increasing GHGs and other environmental nuisances, including the direct effect on the natural resources availability. 2.1 Waste recycling in Quebec Since 1989, the year of the publication of the Integrated Solid Waste Management Policy, Quebec made a significant step in the direction of sustainable development. However, 17 years later, according to a Recyc-Quebec [1] assessment in 2006, Quebec recovered hardly 52% of its residual materials. More specifically, inasmuch as organic matter is concerned, its collection is at present under development in Quebec. This collection comprises green residues, such as branches, grass and sheets, as well as waste from food. There are currently 44 composting installations in Quebec. Moreover, the cities or municipalities of Laval, Victoriaville, Lachute, Saint-Donat, Rawdon and the Island-of-the-Madeleine, have successful organic matter collection activities. However, the rate of recovery of all putrescible residual materials is as low as 8%. In 2006, the quantity of recovered organic matter rose to 0.36 million tons on a potential of approximately 4.5 million tons. It should be noted that the objectives of the Policy are expressed according to the potential that may undergo beneficiation. It is estimated that 85% to 90% of the residual materials of the various branches of activity have a potential of being valuably recovered. Recyc-Quebec announced in 2006 that nearly 13 million tons of residual materials are generated annually in Quebec. As Quebec’s population in 2006 was 7.651 million inhabitants, the total rate of production of residual matters per capita and year is estimated at 1.69 tons, including industries, trade activities and institutions. A noticeable fact is that, in 2006, the rate of final disposal of these materials through landfill and incineration was estimated at 880kg/year/inhabitant, whereas ten years earlier, this quantity was lower; 740kg/year/habitant in 1996. Thus, the average inhabitant of Quebec, including industrial, trade, construction, restoration/demolition and institutional activities, as well as the municipalities, in 2006 eliminated 875 kg/year/inhabitant and recovered 940 kg/year/inhabitant. 2.2 Compostable material coming from the municipal residential sector The municipal sector generates an average of 23%w/w of Quebec’s residual materials. Thus, in 2006, the municipal sector generated 3.015 million tons. This represents an average of 400 kg/year/inhabitant. Although 95% of these materials are theoretically recyclable, only 31% of them were recovered. Thus, 255 kg/year/inhabitant were disposed of finally in landfills or incinerated. The putrescible materials represent 44% of the total 3.015 million tons generated annually. This is 1.327 million tons of compostable organic material per year that may undergo beneficiation. The available statistical data give us the information that only 0,110 million organic tons of materials were recovered in 2006. Table 1 presents Quebec’s population by administrative areas, according WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
214 Energy and Sustainability II to the 2001 census, and an estimation of the quantity of putrescible materials available by areas. This estimation was done by assuming that the residual material generation is geographically uniform in Quebec. Globally it is easy to calculate that the remaining available compostable material is 183kg/year/inhabitant. Table 1:
Generation of organic compostable materials by the residential sector in the different administrative regions in Quebec.
Administrative regions Bas-Saint-Laurent Saguenay-Lac-Saint-Jean Capitale-Nationale Mauricie Estrie Montréal Outaouais Abitibi-Témiscamingue Côte-Nord Nord-du-Québec Gaspésie-îles-de-laMadeleine Chaudière-Appalaches Laval Lanaudière Laurentides Montérégie Centre-du-Québec Total :
200 630 278 279 638 917 255 268 285 613 1 812 723 315 546 146 097 97 766 38 575
Organic compostable materials (tons/year) 36 715 50 925 116 922 46 714 52 267 331 728 57 745 26 736 17 891 7 059
96 924
17 737
383 376 343 005 388 495 461 366 1 276 397 218 502 7 237 479
70 159 62 770 71 095 84 430 233 581 39 986 1 324 460
Population
2.3 Landfill sites The average maintenance costs of the landfill sites is approximately 65 cnd$/ton. The law “Règlement sur l’enfouissement et l’incinération de matières résiduelles” (c. Q-2, r.6.02) adds an additional fee (tax) of 10.22 cnd$/ton. On this basis, approximately 504 million cnd$ have been spent in Quebec only in 2006 for the landfill of the residual materials. These numbers do not include the transport cost. Moreover, these costs do not contain the management of the animal manure, mining, paper mills and sawmills residues, the contaminated soils as well as all materials characterized as dangerous and biomedical. According to the “Règlement sur l’enfouissement et l’incinération de matières résiduelles” (c. Q-2, r.6.02), a soil of minimal thickness of 30cm must cover each WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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day the landfilled residual materials in order to prevent from vermin and biogas spreading. 2.4 The porcine industry In June 2002, Quebec adopted the law “Règlement sur les exploitations agricoles” (REA); this law is aimed at agricultural activities within the context of the sustainable development. Its main objective is to have the farmers being more concerned about the management of the animal manure and other fertilizing matters, more particularly phosphorus. The phosphorus assessment, required by the REA, is one of the main tools of this law. The farms having a surplus of fertilizing potential will be in the obligation, according to REA, to reach a balance between the capacity of the soil to receive phosphorus and the quantities of manure to be spread out in these lands. For some of them, the only solution enabling them to reach this balance will be the treatment of the liquid manure. In Quebec, the number of farms passed from 135 000 in 1951 to 35 000 in 1996. Moreover, the agricultural surfaces decreased by about 50% since 1951; from 3.4 to 1.9 million hectares. However, during the same period the number of pigs has tripled. The annual volume of production should not be confused with the number of pigs in inventory on the porcine exploitations during the year. Quebec counted approximately 3.9 million pigs in inventory in 2004 and 4.2 million in 2006. There were 4097 producers of pigs in 2004 and 4309 in 2003, a fall of 212 in one year. Such a geographically uniform space reduction, in one year only, accompanied by a production increase, can be explained by the increase of the activities of the existing integrators. Indeed, since the total annual volume of animal manure appears constant in Quebec (at approximately 32 million m3 of animal manure, of which approximately 10 million m3 of liquid manure), the farms have to manage an increasingly larger volume of manure. The quantity of liquid manure was multiplied by a factor of 90 between 1951 and 2001! Approximately 60% of the hog farms must have to establish local agreements for manure land spreading, because they do not possess enough arable land to respect the law. According to the Quebec Ministry of the Environment, more than 400 municipalities out of 1200 are in theoretical surplus of manure and/or liquid manure. Table 2 presents the quantity of liquid manures produced in Quebec. In March 2006, a refundable temporary tax credit was founded for the acquisition of installations for the treatment of pig liquid manure. This credit accounts for 30% of the acquisition and the installation costs of such a system of manure treatment; a maximum of 200 000 cnd$ is allocated by agricultural establishment. Only porcine companies, which do not qualify or make use of the provisions of chapter 6 of the program Premium-Green, qualify for this tax credit. All technologies of liquid manure treatment decrease the volume of the final disposal; this means that all fertilizing elements are concentrated in smaller volumes. They also contribute to reduce the odours associated with the management of liquid manures. Denmark is a pioneer in the management of livestock wastes and the optimal use of the nutritive elements contained in them. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
216 Energy and Sustainability II Table 2:
Manure production by region in Quebec.
Administrative regions Bas-Saint-Laurent Saguenay-Lac-Saint-Jean Capitale-Nationale Mauricie Estrie Montréal Outaouais Abitibi-Témiscamingue Côte-Nord Nord-du-Québec Gaspésie-îles-de-la-Madeleine Chaudière-Appalaches Laval Lanaudière Laurentides Montérégie Centre-du-Québec Total :
Number of pigs [2] (2006) 153 459 16 954 97 433 142 945 249 363 n.d. 365 n.d. n.d. n.d. n.d. 1 296 635 n.d. 274 458 31 178 1 420 141 519 365 4 202 296
Manure (tons / year) 475 723 52 557 302 042 443 130 773 025 n.d. 1 132 n.d. n.d. n.d. n.d. 4 019 569 n.d. 850 820 96 652 4 402 437 1 610 032 13 027 119
Several successful programs have directly risen from Denmark’s agricultural policy: for example, the installation of V and W shaped sludge pits leads to a reduction of the ammonia evaporation by as high as 25%, while the cooling of the sludge in the pits results in an additional reduction of 20%. 2.5 The methanisation industry The management of the organic residues is not only one a concern in Quebec. In Europe there are already biogas production facilities from the anaerobic fermentation of organic residues. In Quebec, the final disposal of the majority of organic compostable material is done systematically as follows: Incineration for the municipal wastewater treatment sludge; Landfill disposal for the residential (table) residues; Composting for the green residues; Land spreading for the animal manure. 2.5.1 Legal context for the energy in Quebec In Canada, energy is under provincial jurisdiction and the law provisions vary considerably from one province to another. The new strict regulations covering the management of waste and the high costs of energy seem to boost the interest in all provinces. In fact, the province of Ontario has recently put in application a regulation establishing the price of 0.11$/kWh (0.14$/kWh at the peak hours) for green electricity. This makes biogas more attractive to the Ontario’s farmers. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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Ontario and Quebec are the only provinces to offer subsidies to those who install and operate biogas production systems. In fact, Quebec pays 70% of the costs incurred to install a manure handling system (maximum of 200 000$). The Ontarian producers can obtain a subsidy up to 60 000$ for a system of manure treatment and storage capacity in the farm. Currently in Quebec, no law exists covering specifically the production of biogas. However, some regulations like the one covering the Waste elimination activities (Landfill and Incineration) and the production of electricity contain some clauses on biogases. For example, the landfills must be appropriately sealed in order to avoid the migration of biogases through the air or the subsoil. Thus, biogases from these sites must be collected and, in the absence of energetic exploitation, this biogas must be burned safely and in accordance with the law for the atmospheric quality preservation. It is rather obvious that, without a specific regulation covering the production of biogas, and which defined clearly all constraints to be respected, it is difficult to establish a long-term biogas production system. However, according to the article 22 of Quebec’s Law on the Environmental Quality (LQE), a certificate of authorization is requested for the establishment of a residues management activity. To produce such a certificate, an Environmental Impact Assessment study must be deposited to the Ministry of the Sustainable Development, the Environment and Parks (MDDEP). In the case of the construction of a high capacity power station, the project team has to deposit the preliminary draft of such a study to the Office of the Public Hearings (Bureau d’audiences publiques sur l’environnement - BAPE), such as defined in article 31.1 of the LQE. In Canada, under the article 5 of the Canadian Law on the environment, an environmental assessment is requested also for having the project authorized. If the project contributes in establishing more sustainable management activities, the Ministry of the Natural Resources Canada could even provide financial assistance to the project in order to help respecting the Environmental Law provisions. Moreover, the Federal Government brought modifications to the rates of the deduction for goods amortization (DGA). The maximum rate of DGA for each type of redeemable good is fixed in the Law covering the field of income tax payment. The rate of DGA applicable to certain high efficiency cogeneration units and renewable energy production passes from 30% (rate of category 43.1) to 50% because of the inclusion of these goods in the new category 43.2. To qualify for this new increased rate, the material used in building such a unit must generally be new and be acquired after February 22, 2005 and before 2012. This new rate will also apply to any biogas production material and district energy distribution networks which use efficient cogeneration technology after February 22, 2005 and before 2012. 2.5.2 Biogas production Methanisation represents a possible sustainable solution for the recycling of organic matter. All organic materials can produce biogas: i.e. animal dejections, fruits, vegetables, remainders of slaughter-house, rejections of dairy, brewery, distilling. The organic matter rich in fibre like the grass, sheets and wood is WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
218 Energy and Sustainability II however difficult to digest and are not recommended to use as source of biogas. The biogas composition depends upon the nature of the treated waste and the treatment conditions which depend largely on the local climate. The average composition of biogas is 60% methane (CH4) and 40% carbon dioxide (CO2). The bioreactor is an anaerobic tank where organic matter is introduced and the temperature has to be maintained at an appropriate level depending upon the nature and the activity of the anaerobic digestion microorganisms. Under the selected conditions, anaerobic bacteria use the organic matter as feed to multiply and produce biogas as a result of their metabolism. The quantity of organic matter which exits the bioreactor is equal to that at the entrance minus the produced biogas. The digested organic matter is practically odourless, has a high fertilizing value, it is less polluting and reduced in organic load (DBO5). The exiting solid/liquid mixture can be separated; the solid muddy part (sludge) can be composted and the liquid part can be used directly as a fertilizer or treated and disposed of safely according to the existing regulations. The collection and energetic exploitation of the biogas produced during the anaerobic methanisation decreases the GES by a factor of just as 20. Since the digestion conditions are better controlled within a bioreactor, the total quantity of biogas per unit of organic matter extracted from a bioreactor is higher than that extracted from a landfill site. A bioreactor is 3 to 10 times more energy efficient than landfill. The quantity of biogas which can be extracted from the organic matter also depends on the type of organic residues and the performance of the bioreactor. Therefore, the production of biogas varies from 20 to 800 m3 per ton of organic material. Each m3 of biogas contains the equivalent of 6kWh of energy. However the conversion of biogas into electricity by an electric generator produces 2kWhe; the other 4 kWh is dissipated in the form of heat and at least 75% of this which can be recovered and used for thermal energy needs. The capital investment for a bioreactor is relatively high [3]. The payback period for such an investment is estimated [4] at 7-10 years and it is due to the value of the biogas and more precisely its value as an electrical and/or thermal energy vector. Regarding the biogas as an energy vector, three uses are tested industrially: (a) combustion in a boiler for heat generation; (b) fuel of internal combustion engines for the production of electricity or for car motors and (c) in cogeneration for the simultaneous production of heat and electricity. The treatment by methanisation of a tone of agricultural organic matter produces 500 m3 of methane at standard conditions. The Methanisation by anaerobic digestion utilizes the organic matter which most easily digestible, that is 30-80% of the oven dry organic material. Besides, this is the part which generates organic pollution, unpleasant odours and biogas. The part remaining after methanisation (20-70%) can be used as fertilizer in agriculture. The methanisation of wastewater treatment plants sludge as well as all putrescible domestic (residential) and industrial waste, reduced their quantity up to 35%. A ton of these organic residues generates up to 175 m3 of biogas. A landfill recovers an average of 100 m3 of methane per ton of treated waste, whereas in agriculture, a ton of manure produces in 90 days approximately 60 m3 of biogas containing 55% of methane. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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The oldest and more mature methanisation technology through anaerobic digestion is that of "the infinitely mixed" bioreactor in whom mixing is ensured hydraulically or more frequently by biogas recirculation. This type of bioreactor is generally operated with mesophilic organisms towards 35ºC. In the last years several technological novelties have been proposed and improved the efficiency of this type of bioreactor in such a way that streams like domestic organic materials, which are generally more complex than manure, could be received and methanised as well. Degrémont, for example, has proposed the upstream use of a "hydropulpor", a metal tank equipped with a central propeller which lyses the vegetable cells and puts the organic matter in full suspension in the recycle stream of the process (proceeded BTA). In this process the inorganic matters which could enter the unit (e.g. plastic, textile) float on the surface and are recovered by a hydraulic comb; the heavy mineral elements (e.g. glass, stones, bones) decant and are extracted by the bottom. The thus produced liquid pulp passes then in a hydrocyclone which removes the heavy fine and abrasive particles like sand. In Germany and Austria, appeared bioreactors in ovoid forms [5]. This form has a smaller footprint per volume, allows a more homogeneous and regular mixing thus reducing the dead zones or those of preferential fermentation and facilitates decantation. The second generation bioreactors use the technology of the fixed cells or "anaerobic filter". This technology allows a quasi continuous flow bioreactor operation because the bacteria are fixed in a preselected support and they are not entrained by the treated liquid flow. In France, the process suggested by Proserpol, comprises a support made up of plastic rings in bulk and the injection of the feed is carried out by the top of the bioreactor all over and through the bacterial stabilization rings. In the Netherlands introduced the process UASB (Upflow Anaerobic Sludge Blanket) [found in 5] in which the support is biological and flow is ascending. Compared to the old technique, this technology has the advantage of being much faster (a few hours or a few days instead of two weeks). It is possible to still speed up the process by adopting the thermophilic fermentation, which multiplies the productivity by a factor of 4-10 and produces a biogas richer in methane (up to about 80%v CH4). For the hog farms manure, the process must proceed in two stages, the preliminary acidification, then methanisation, which call upon families of different bacteria, which must, thus, be held in distinct tanks. The Tilburg bioreactors in the Netherlands (1994, 52 000 tons/year) and that of Engelskirchen in Germany (1998, 35 000 tons/year), are fed only with organic materials coming from domestic waste. The methane produced in Tilburg’s bioreactors is introduced into the gas network of the municipality for domestic use. The Engelskirchen’s biogas is used for the production of electricity. Thanks to a sorting at the source, both produce a compost of high quality. During its high output operation, the factory of Tilburg produces 4 million m3 of biogas per year. This biogas contains 56% CH4, very small amounts of hydrogen sulphide, and 31 000 tons/year of organic soil conditioner which may undergo beneficiation in agriculture. The idea of a selective and centralized co-digestion of agricultural biomasses was born in Denmark and was applied since 1988 thanks to the support of the government. It consists in collecting in the vicinity of the manures WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
220 Energy and Sustainability II production sites the existing domestic and/or industrial organic waste, sludge from wastewater treatment stations and methanise them together. The economic assessment of the operation is mitigated. With a starting investment of 8 million $ and operating costs of 600 000 $/an, the payback period has been 8-10 years thanks to the subsidy of 3 million $ granted by the Danish Ministry of Energy. The main part of the incomes comes from the sale of biogas (800 000 to 1 000 000 $/year) and from the waste management tipping fee which the industrialists pay to get rid of their waste (approximately 200 000 $/year).
3
Methanisation in Quebec?
Methanisation represents a complement of activity for the farmers, who can develop economically and energetically the liquid manure and even the organic part of the domestic residues. Methanisation is synonymous with energetic autonomy for the biogas producers. While bringing an energetic and ecological response to the problem of the treatment of the liquid manures and organic residues, methanisation is an activity of depollution and an alternative to landfill. The environmental cost of the deterioration of nature by hog farming must be taken into account in the market price of the pig. This cost can be attenuated by agreements between eco-energy the hog farms; thus, hog farms manure can be a feedstock for eco-energy farms producing compost and biogas as an energy vector. Only the cost of transport would be the responsibility of the producer, whereas the eco-energy farms would recover and market the green energy. Producers' cooperatives can also contribute financially in order to install common bigger bioreactors. As explained below, the establishment of a “two ways” selective waste sorting at the source and pick-up could be a sustainable solution. Our residues would be split in putrescible organic and non-putrescible materials. This strategy would allow recovering nearly 95% of all residual matters in the domestic sector. The codigestion of putrescible organic residues and liquid manure would be beneficial to both the agricultural and municipal sectors. The accessibility of this putrescible resource was established by administrative regions in Quebec. The density of the population is not an important factor, since in rural as well as in urban areas, the transport of the organic matter to an eco-energy farm is at least as easy as in any existing landfill site. The only element which differentiates the administrative regions between themselves is that certain among them do not have or have few hog farms, which would be favourable to install and operate bioreactors because of their characteristics as large urban Number of eco-energy farms required per administrative region and potential revenues. However, due to the proximity of the territories of Montérégie and Lanaudière, the administrative areas of Montreal and Laval, which are such urban centres, could easily transport their organic residues in bioreactors operated in these two other areas. Table 3 presents the energetic potential of the combined domestic putrescible organic material and the manure in Quebec. Each ton of organic matter was estimated as having a potential of production of 100 m3 of biogas. This is very conservative because it represents the equivalent of the production in a landfill WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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which is at least 3 times lower than that in a bioreactor. The energy, which can be recovered by a biogas, was evaluated to 2 kWh/m3. Thus, according to Table 3, an energy potential of 2 844 656 000 kWh is available in Quebec. Considering that in Quebec, a one-family residence consumes 17 000 kWh annually, the energy needs of about 167 000 houses can be covered. Since the cost of residential electricity in Quebec is approximately 0.05 cnd$/kWh, the green energy worth is roughly 142 millions of cnd$. The number of eco-energy farms was evaluated according to a self capacity of 50 000 tons of organic matter per year. The cost for the establishment of such a farm was estimated at 0.3 millions of cnd$. It should be noted that the actual cost of the management of the organic matter coming from the domestic (residential) sector is equal to 90% of the capital cost of the installation of the 285 bioreactors necessary for methanise annually the 14 million tons of the available putrescible materials (domestic + manure). Considering the contribution of income of the residential sector, only the areas of the Boiler-Appalachian Mountains and Centre-of-Quebec, do not offer an income higher than the cost of establishment of an eco-energy farm.
4
Conclusion
The establishment of a two ways (putrescible and non-putrescible) selective sorting and pick-up of the domestic residues in Quebec would increase the rate of recovery of all the residual matters. The non-putrescible matters can be recycled up to 95%, whereas the organic matter can be used as a renewable energy vector. The only problem comes from the green residues (grass, sheets, paper and paperboard) which contain a high percentage of non-easily digestible collection which is already established in some municipalities (i.e. Victoriaville, Sherbrooke). A good sorting of the putrescibles at the source (residential) is important because the efficiency of the methanisation bioreactors and the quality of the resulting compost are strong function of the feedstock quality. The existence of incentives and the appropriate enforcement of a regulation establishing an obligation to treat the manure of all hog farms in eco-energy farms using bioreactors would also contribute to the reduction of contaminants in the environment. All putrescible matters (domestic putrescible organic materials and liquid manure) can be treated (methanised) in eco-energy farms, equipped co-digestion bioreactors. As it is well established that the ideal operation conditions of the anaerobic digestion of these two distinct families of putrescible organic materials are not the same some additional fundamental and applied research is necessary to have a sustainable operation. The existence of two parallel bioreactors might be an appropriate solution since it is known that different bacterial populations are needed. By considering only the income received from the production of green energy, the payback period of a bioreactor at an average Quebec hog farm is approximately 10 years. As for the eco-energy farms, they could require higher initial investments because of the combined feed complexity. These additional costs can be set-off by the perception of the equivalent landfill disposal tipping fee which in Quebec is in average 65$/ton. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
Administrative regions
Montérégie (+Montréal) Chaudière-Appalaches Centre-du-Québec Lanaudière (+ Laval) Estrie Bas-Saint-Laurent Mauricie Capitale-Nationale Laurentides Saguenay/Lac-Saint Jean Total :
(a) (b) (c) (d) (e) (f) (g) (h)
Energetic potential of the domestic putrescible organic material and manure in Quebec. (a) Domestic organic residues (tons/yr) 565 309 70 159 39 986 133 865 52 267 36 715 46 714 116 922 84 430 50 925
(b) Revenue Residential Sector (M$cnd/yr) 36.7 4.6 2.6 8.7 3.4 2.4 3.0 7.6 5.5 3.3
1 197 292
77.8
(c) Manure (tons/yr) 4 402 437 4 019 569 1 610 032 850 820 773 025 475 723 443 130 302 042 96 652 52 557 13 025 987
(d) No
(e) Capital cost
(f) Power (MWh)
(g) Revenue from energy (M$cnd/yr)
(h) Mixed Revenue (M$cnd/farm/yr)
99 82 33 20 17 10 10 8 4 2
(M$cnd) 29.7 24.6 9.9 6.0 5.1 3.0 3.0 2.4 2.1 0.6
993 549 817 946 330 004 196 937 165 058 102 488 97 969 83 793 36 216 20 696
49.7 40.9 16.5 9.8 8.3 5.1 4.9 4.2 1.8 1.0
0.573 0.255 0.279 0.625 0.388 0.450 0.490 1.175 1.300 1.850
285
86.4
2 844 656
142.2
0.469
Tons of domestic organic materials = Table 1 Revenue residential sector = 65$cnd * tons of domestic organic materials Tons of manure = Table 2 Number of farms = (tons of domestic organic materials + tons of manure) / 50 000 tons Capital cost for bioreactor installation and operation = 0,300 M$cnd * number of eco-energy farms Power = (tons of domestic organic materials + tons of manure) * 100 m3 of biogas * 2 kWh Revenue from energy = Power * 0.05 $cnd/kWh Mixed Revenue = Revenue from energy + Revenue from domestic sector – Capital cost for bioreactor installation and operation
222 Energy and Sustainability II
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Table 3:
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If this scenario becomes a reality, nearly 13 million tons of liquid manure and 1 million tons of putrescible domestic organic materials produced annually in Quebec could become a source of green, renewable energy in a sustainable development context, without any economic or social sacrifice.
Acknowledgements The contributions of Steve Boivin, Eng. and Richard Royer, Eng. of Bio-Terre Systems Inc., (150, rue Vimy, Sherbrooke, Québec, Canada, J1J 3M7) are gratefully acknowledged.
References [1] Recyc-Québec, Bilan 2006 de la gestion des matières résiduelles au Québec, Bibliothèque et Archives nationales du Québec, 2007. [2] Institut de la statistique du Québec, Inventaire de fin de semestre de porcs, par région administrative, Québec 2005-2006, Gouvernement du Québec, 2007. [3] Électrigaz, Le biogaz est une énergie renouvelable issue de la décomposition naturelle de la matière organique par des bactéries anaérobiques. 2007. http://www.electrigaz.com [4] Électrigaz, Le biogaz est une énergie renouvelable issue de la décomposition naturelle de la matière organique par des bactéries anaérobiques. 2007.
http://www.electrigaz.com [5] Énergie Plus, Rapport, études France, 2007. http://www.energie-
plus.com
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Potential transport energy demand and oil dependency mitigation measures T. E. Lane & M. J. W. A. Vanderschuren Centre for Transport Studies, University of Cape Town, South Africa
Abstract Transportation, including the movement of both people and freight, accounts for over 60% of all oil consumed globally, while the world’s transportation systems are over 90% dependent on oil and oil by-products. The predicted depletion of oil and subsequent rising fuel prices pose a significant threat to transportation systems worldwide. The choice of transportation system technologies and the use of transportation systems will influence a country’s vulnerability to ‘oil shocks’. Transport and energy planning policies must prepare for the likelihood of such shocks and ameliorate them via policy options. A precautionary approach needs to be adopted to reduce the dependency on oil, in order to improve the sustainability of transportation systems. This paper addresses the need for oil independence and describes potential ways in which Europe can progress towards this goal. Various mitigation measures for various transport modes are discussed. These measures are ultimately combined into strategies to bridge the gap between oil supply and demand. The objective of the paper is to alert the reader to energy demand management measures available, to the potential impacts of these measures and to the definite need for a move towards new transportation technologies if oil depletion is to be successfully traversed. Keywords: peak oil, oil dependence, transport energy, energy mitigation.
1
Introduction
Transportation, the platform for economic activity and personal mobility, is entirely dependent on the energy supply that powers it. The transport sector has been the fastest growing consumer of energy in the European Union (EU), accounting for a share of nearly 31% of total final energy demand in 2004 [1] WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESU090201
226 Energy and Sustainability II and 71% of all oil consumption in the EU [2]. The sustainability of the transport sector depends on both the quantity of energy consumed and the sources of energy used. Currently, European transport is powered by petrol, diesel, liquefied petroleum gas (LPG), electricity and jet fuel. Apart from electricity (that is not generated from oil-based resources), all of these energy sources are dependent on crude oil. In fact, 95% of European transport is dependent on oil and, therefore, exposed to oil supply risks. This is highly unsustainable. This paper addresses the EU’s need for oil independence (section 2) and potential mitigation measures and strategies (sections 3 and 4) to facilitate the achievement of reducing oil dependence.
2
The need for oil independence
Oil is a finite, non-renewable energy source. Although it has been abundant and cheap for the past century, at some stage oil production will start to taper off. Current oil fields are rapidly depleting, but there is little consensus about the rate of decline. The International Energy Agency (IEA) predicts the rate of decline to be 6.7% [3], whilst Colin Campbell, the chairman of the Association for the study of Peak Oil and Gas, expects it to be around 2.6% per annum [4]. Another item under dispute is the timing of the production peak. Geopolitical events (such as wars in oil producing countries), extreme weather conditions (like hurricanes in the Gulf of Mexico) and economic factors (e.g. an international recession) could all influence either supply or demand for oil [4]. The IEA does not expect peaking before 2030 [5], while Schoppers and Murphy are 97.5% certain that the peak will occur by 2015 ( 1.26 years) [6]. Many others believe that the peak might have occurred already. To reflect this uncertainty, three oil supply depletion possibilities are considered: firstly that nothing will change before 2030, secondly that a peak is reached in 2020 and, pessimistically third, that peaking occurs in 2012. Figure 1 showcases the resulting transport energy supply trajectories. Global demand for oil has been growing for decades, resulting from both population expansion and economic growth. In 2007, the IEA forecasted that global oil demand will grow from 85 million barrels of oil per day to 130 million barrels of oil per day by 2030 [7], corresponding to a growth rate of around 2.15% per annum. In 2008, the IEA made a significant downward revision to the 2007 forecast, lowering the expected growth rate to 1% per annum [5]. This revision reflects the impact of higher prices and slightly slower GDP growth, as well as new policies to promote more fuel-efficient vehicles and encourage biofuels. Both an optimistic and conservative growth trajectory is reflected in figure 1. If oil does peak in 2012, transport energy demand will exceed supply somewhere between 2018 and 2022 (see fig. 1). This leaves a preparatory window of opportunity of 9 to 13 years. Should the peak happen in 2020, problems will start somewhere between 2023 and 2029, leaving a 14 to 20 year period to prepare for it. Even if peaking does not occur before 2030, demand still outstrips supply (from 2029), if demand grows at the optimistic rate. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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Transport energy supply and demand projections Index Base year value = 2006 Demand
170.0
165.6 163.3
160.0 150.0 140.0 130.0
127.9
120.0
120.0
110.0 100.0 91.5
90.0 80.0
Year Supply (No Peak)
Supply (Peak 2020)
Demand (Optimistic)
Demand (Conservative)
Supply (Peak 2012)
Source: Adapted from IEA [5, 7], Eurostat [8] and ASPO [3, 4]
Figure 1:
Transport energy supply and demand projections.
It is highly unlikely that demand continues along the slow growth trend for the entire period, because demand is linked to economic growth and economic growth is the main aim of most countries around the world. It can be concluded that, if oil remains the world’s primary transport energy resource, transportation systems will face serious obstacles from anywhere between 2018 and 2029. The maximum lead time to try and avoid this is thus 20 years.
3
Measures to mitigate oil and energy dependency
There are various ways and means of either reducing transport’s oil or total energy demand. The most important measures are those that reduce the demand for transport, thereby reducing both energy and oil demand. These measures aim to eliminate excessive travel, although this can only be done to a certain level – some travel will always be required. For the remaining travel demand, the highest priority measures are those that improve energy efficiency. Energy efficiency measures also reduce total energy demand, regardless of the energy source used or the effective modal split. These measures can assist the EU in achieving the target of increasing energy efficiency by 20% by 2020, set by the European Commission in 2007 [9]. The third type of measure is aimed at reducing the demand for oil-based transport fuels, by substituting conventional fuels with alternative energy sources. 3.1 Transport demand reduction measures Developments in information and communications technology allows for the possibility of telecommuting, online shopping and distance learning, where the WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
228 Energy and Sustainability II use of technology substitutes physical travel. The development of sophisticated logistics chains is also enabled. Although many jobs lean themselves towards telecommuting, a certain amount of travel will always be required to allow face to face meetings and facilitate the shared use of equipment. An estimated reduction of between 1% and 10% in car trips is plausible [10]. Route optimisation entails planning trips along a route with the lowest generalised energy cost, by taking congestion penalties and empty running into account. In aviation, the shortest available routes are underused due to a lack of real-time and precise information, as well as the unavailability of certain parts of airspace [9]. The potential reduction in aviation emissions through optimised routing is estimated at 6% to 12% [9]. Emissions are related to fuel consumption; hence, emissions savings indicate relative fuel savings. Efficient usage of passenger vehicles results in less vehicle-kilometres needed to transport the same amount of passengers [11]. A high occupancy rate in passenger cars and buses has relatively little impact on the overall vehicle weight and, therefore, on energy consumption. Measures to increase occupancy rates include ridesharing, carpooling and high-occupancy vehicle lanes. Increasing vehicle load factors is a way to reduce the growth in freight transport vehicle-kilometres. The fact that some freight transport companies achieve much higher load factors than others in the same sector, suggests that load factors can be improved in the EU [12]. Methods to improve load factors include abandoning just-in-time manufacturing practices, promoting cabotage, avoiding empty return trips and load consolidation (bundling of products via advanced information systems). Estimates are that bundling could reduce the expected future doubling of vehicle-kilometres by 20% to 30% [12]. Land-use planning can have a dramatic influence on the amount of transport required in a settlement. Mixed use developments negate the need for long commuter trips and promote the use of non-motorised transport. Although this measure can potentially have the largest impact, it is difficult to estimate the extent to which it can be applied in the EU region. 3.2 Energy efficiency improvement measures Improving vehicle design increases the distance covered per unit of fuel consumed, by: reducing air and rolling resistance, improving engine technology or using light weight materials. New cars consumed approximately 10% less fuel in 2002 than they did in 1990 [13] and this trend is expected to continue. Airlines are aiming for a 25% fuel efficiency improvement through vehicle design by 2020 [14]. Railways can realise large potential savings from light-weighting (up to 20%) and cutting drag and friction (up to 10%) [15]. Technology options for reducing energy use in the shipping industry include hydrodynamic improvements and machinery; these technologies could reduce energy use by 5% to 30% on new ships and 4% to 20% on retrofitted old ships [16]. Vehicle maintenance is very influential in terms of fuel efficiency. According to estimations, fitting appropriate tyres and maintaining proper tyre pressure can improve vehicle fuel efficiency by more than 5% [10]. Keeping engines properly tuned can save 4%, checking and replacing air filters regularly WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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up to 10% and using the recommended grade of motor oil can save up to 2% [10]. Flight Sciences International [17] indicates that improved maintenance reduces aviation energy consumption between 5% and 10% over the long term. Another key area to improving energy efficiency is vehicle renewal practice. This affects the average age of the vehicle fleet, as well as the average size and efficiency of vehicles. Old vehicles should only be replaced with newer, more efficient technology vehicles. To illustrate: new aircraft are typically 70% more fuel efficient than 40 year old aircraft and 20% better than 10 year old aircraft [14]. The majority of new heavy vehicle engines are electronically controlled, providing a 7% to 15% improvement in fuel economy [18]. The European Commission (EC) has launched initiatives to promote a market for greener vehicles (i.e. the Car Fuel Efficiency Labelling Directive (1999/94/EC)) [19]. Vehicles with smaller engines are more fuel efficient, especially in urban areas. It is estimated that the move towards smaller vehicles will reduce total fuel consumption by between 10% and 20% [10]. In freight transport, matching engine size to the required task will give the best fuel economy. Better driver education and public campaigns provide the possibility to reduce fuel consumption substantially. Aggressive driving (rapid acceleration and braking) wastes energy. In road-based transport, improved driving behaviour can reduce fuel consumption by up to 33% [10]. The ECODRIVEN project (2006 to 2008) is an example of such an education programme [9]. In rail transport, fuel usage can vary by 12% to 20% between crews [20]. Intelligent transport systems (ITS) can be utilised to manage traffic in a more efficient manner. This would entail reducing idle time (when fuel efficiency is at its lowest) through optimised signal settings and managing speed (with variable speed limits, for example) to improve traffic flows. Such measures have been demonstrated to save between 5% and 20% of fuel consumption [10]. Air traffic management enhancements could improve fuel efficiency and reduce CO2 emissions by up to 12% [14]. Information on actual traffic flows can help drivers to avoid routes that are heavily congested, thereby reducing idling time and fuel consumption, accordingly. Modelling studies estimate that, if between 20% and 40% of road users are fully informed, network efficiency improves with up to 10% [10]. Live information on a vehicle’s fuel demand can assist drivers in driving more economically. Fully automated driver assistance systems can save up to 23% [21]. Fleet vehicle tracking systems introduced by freight companies can result in a reduction in fuel consumption by between 15% and 25% [19, 22]. ITS initiatives underway in the EU include: the Intelligent Car Initiative, the SESAR programme, the ERTMS system and the River Information Services (RIS) system [2]. The Commission is currently involved in two global navigation satellite system projects: EGNOS and GALILEO [9]. Inter-modality (the efficient use of different modes on their own and in combination) results in the optimal utilisation of resources, including energy [19]. Inter-modal systems typically make use of the most efficient modes (i.e. rail or water) for long segments of a journey between hubs, combined with road transport for shorter segments (spokes). Trans-European Networks for Transport WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
230 Energy and Sustainability II (TEN-T) aims to promote the interconnection and interoperability of and access to national networks [9]. All modes of transport are not equally energy efficient. The most efficient modes should enjoy the highest priority in terms of planning and development. In passenger transport, air transport has the lowest energy efficiency, followed by private cars, motorcycles, buses, rail and non-motorised transport (NMT) respectively. For freight the order of increasing efficiency is: air, road, rail, water and pipeline transport. Presently, road transport accounts for the lion share of both passenger and freight transport (see figure 2). Public transport (excluding air) constitutes 16.1% of passenger transport. There appears to be quite some scope for a modal shift towards public transport in the EU. A shift between motorised transport and NMT (cycling or walking), results in a 100% transport energy reduction for the same amount of travel. The utilisation of rail, pipelines and inland waterways in freight transport can also be increased.
Figure 2:
European passenger and freight transport modal shares [1].
Economic instruments (taxes, charges or emission trading schemes) can encourage transport users to switch to cleaner vehicles or modes, to use less congested infrastructure or to travel at different times [23]. Price signals are the most effective when the market offers realistic alternatives (e.g. cleaner vehicles at an affordable price or appropriate levels of service in other modes). Fuel prices can influence consumer choice, both in terms of the quantities and the type of fuel purchased. Moreover, persistent price differences can influence decisions on the type of vehicle purchased, leading to changes in the vehicle stock and fuel mix over time [1]. The extent of potential savings needs to be assessed on a case by case basis, as many factors can influence the effectiveness of this measure. 3.3 Alternative fuels and propulsion systems In 2001 the European Commission (EC) set out a strategy to achieve a 20% substitution of conventional automotive fuel by 2020, identifying biofuels, WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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natural gas and hydrogen as the main replacement possibilities [9]. Subsequently, in 2008, the EC proposed a directive requiring each member state to have at least 10% of its petrol and diesel fuels for transport coming from alternative fuels by 2020 [9]. Biofuels (mainly biodiesel and bioethanol) are slowly, but steadily, increasing its market share in the EU, although it is still limited at present [24]. The main driving force behind the increase is government policies introduced in response to the EU Biofuels Directive (2003/30/EC), which sets the European biofuels market penetration target at 5.75% in 2010 [1, 13]. To increase volumes further, fuel standards need to be adapted, distribution needs improvement and the compatibility of the vehicles with biofuels needs to be improved. The maximum biofuels market penetration percentage is 5% [1, 13] with existing fuel standards. Though biofuels will lessen the reliance on crude oil, it cannot untie itself completely from oil at present. This places a question mark on the long term sustainability of the biofuels industry. However, in the 2006 review of the Biofuels Directive, respondents proposed market penetration targets of 8% by 2015 and between 15% and 20% by 2020 [25]. Alternative fossil fuels currently commercially available are Liquid Propane Gas (LPG) and Compressed Natural Gas (CNG), but their market shares are limited to specific niches [24]. Because these fuels are dependent on nonrenewable resources, they are not considered a viable alternative to oil. The IEA does not expect any major shift away from conventionally-fuelled vehicles before 2030, although the penetration of hybrid-electric cars is projected to rise, reducing oil demand growth [7]. The fuel efficiency improvement obtained from switching to a hybrid-electric car can be more than 100% [26]. These vehicles are already on the market. It is believed that this is a very viable option to reduce oil dependency, if combined with government incentives. However, the number of hybrid car models available on the European market has changed little between 2001 and 2006 [24]. It should be noted that the concept of hybrid propulsion can also be applied to other transport modes. Electricity is a budding contender in the alternative fuels industry. Some advantages of using electricity to power the transport sector include: the existence of the core infrastructure, the relatively high efficiency of electric propulsion and the possibility to generate electricity from renewable sources (increasing sustainability and mitigating environmental impacts). Electricity already powers rail lines and some public transport vehicles. Disadvantages are that transport will have to compete with other sectors of the economy for electricity in a system that is currently quite strained, the problem of centralised filling stations needs to be solved, exposure to the risk of power failures and the current state of technology development in terms of vehicle range, cost, availability and the need for expensive battery replacements [26]. Some alternative propulsion systems can be powered by electricity, for example magnetic levitation (maglev) and tubular freight systems. Maglev systems are incredibly energy efficient and have high performance levels. They consume approximately a tenth of the energy required by an average automobile per passenger-kilometre [27]. In low pressure tunnels the average energy WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
232 Energy and Sustainability II efficiency could potentially be increased to around 4000 km/l [27]. Even though the advantages of maglev seem to outweigh the disadvantages, the main obstacle to the wide-scale adoption of this technology is cost. There are six functioning maglev systems in the world at present and new systems are currently being considered in 12 countries. Many maglev research projects are underway [27]. Tubular freight transportation is a group of unmanned transportation systems in which close-fitting capsules or trains of capsules carry freight through tubes between terminals [10]. Although research and development around tubular freight (and passenger) systems has been emerging for several decades, no final conclusion regarding the feasibility and energy efficiency benefits have been reported. Hydrogen (fuel cell technology) is a clean alternative fuel that is not necessarily dependent on fossil fuels and causes very low to zero emissions when used in fuel cells (assuming good production and transportation practice). The future of hydrogen within the transport sector is uncertain, as there are still many issues that need to be resolved (such as the storage and transportation of hydrogen, safety concerns, infrastructure requirements, high costs involved, vehicle performance and low energy efficiency) [26]. Hydrogen is an energy carrier, not an energy source. Energy thus needs to be converted to hydrogen from another source and from hydrogen to electricity, incurring energy losses of between 57% and 80% [28]. So much energy is lost in the manufacture, distribution and final use of hydrogen in the fuel cell, that it is less energy efficient than a petrol-electric hybrid car [10]. Creating hydrogen through electrolysis is less efficient than using electricity directly in electric vehicles [10]. Developing the infrastructure required to convert to a hydrogen economy has very long lead times (10–15 years) [26]. Despite all the obstacles facing the wide-scale adoption of hydrogen as a transport fuel, a lot of research is currently being invested in. An example is the Zero Emissions Ships project (ZEMSHIPS), which demonstrated the functioning of the first hydrogen and fuel cell powered ship (with a capacity of more than 100 persons) [9]. In 2007, the EC proposed extending the scope of the EU's type approval system for cars, vans, trucks and buses to include hydrogen as a fuel, to facilitate the introduction of this technology into the EU market [9]. Prototype vehicles incorporating compressed air technology (CAT) have recently been introduced to the market by Moteur Development International [26]. CAT vehicles are claimed to have a driving range close to 2000 km, with zero pollution in cities and considerably reduced pollution outside urban areas. These vehicles are a very recent addition to the alternative propulsion arena and thus little verified information is available on them. 3.4 Summary of energy demand and oil dependency mitigation measures Based on the literature available, projections were made regarding the potential energy savings that could be achieved by 2030, through the implementation of measures. These projections take the modal split, as well as the split between passenger and freight transport per mode, into account. A modal shift (comprising a 15% road to rail freight shift and roughly a 25% shift from air and WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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private vehicles to public transport an NMT) proves to be the measure with the highest savings potential (26%). This is followed by the wide-scale adoption of hybrid cars (21%) and biofuels (17%). Measures are not mutually exclusive and, when they are combined into groups, the interaction between measures must be taken into account. For example: improved traffic signal settings will decrease the potential for savings from improved driver behaviour (which minimises stop and go driving). It is very unlikely that the full potential of any measure will be realised. All elements that could influence the success of a measure cannot be controlled or foreseen. Alternative fuels can reduce oil demand (but not necessarily energy demand) the most. If 55% of all road vehicles were replaced with alternative fuels (20% E-85 biofuels, 25% hybrids and 10% either electric or hydrogen), an estimated maximum of 34% of oil demand could be eliminated by 2030. A potential pitfall for alternative fuel technologies is described by the Khazzoom-Brookes postulate [29]. It states that, when a person acquires a vehicle that is more efficient, (s)he will simply drive it more, negating the potential benefits. Time constraints counteract this tendency [26]. Combining alternative fuel strategies are ultimately expected to realise an estimated 18% saving by 2030. Of all the efficiency improvement measures, the modal shift is the best, seconded by the roll-out of intelligent transport systems (13% saving). Combined, a saving of 17% can be expected from the implementation of efficiency improvement measures. Demand reduction measures can, similarly, account for a 15% saving by 2030. Vehicle load factor and passenger occupancy optimisation is the most effective demand reduction measure.
4
Bridging the oil supply and demand gap
Tables 1 and 2 indicate the shortfall (negative) or surplus (positive) oil supply by 2030 (expressed as a percentage of demand) in each of the three supply scenarios and for three mitigation strategies. If demand grows at a conservative rate (as explained in section 1), there is excess supply in the no peak scenario (see table 1). If a peak is expected, however, demand reduction strategies (strategy 1) will suffice to bridge the oil gap, if peaking happens during the latter half of the period. A combination of energy efficiency and demand reduction measures (strategy 2) are sufficient to close the gap in this scenario. Considering the optimistic demand growth scenario (as explained in section 1), if there is no oil peak before 2030, the supply of oil will not be enough to satisfy the projected demand. None of the three mitigation measure groups can alone traverse the oil gap successfully, regardless of when peaking occurs. The measure groups will, thus, have to be combined. It is prudent to remove unnecessary demand from the system before trying to improve the efficiency of the demand that cannot be removed; therefore, demand reduction measures are applied first (strategy 1). Only if there is no oil peak will this be enough to bridge the gap (see table 2). Combining demand reduction and efficiency improvement measures (strategy 2), results in a supply deficit in the 2012 oil peak scenario only, requiring a combination of all three measure groups (strategy 3). WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
234 Energy and Sustainability II Reducing the demand for oil has additional benefits to avoiding a devastating supply shortfall. Every barrel of oil saved (dubbed nega-barrels) is worth just as much money as a regular barrel of oil to the EU, either due to reduced production or reduced import costs [15]. A 16% saving in oil imports converts to 696.65 million barrels saved. At a (low) crude oil rate of $35.30 per barrel, this equals a saving of €19.43 billion. Similarly, a 45% saving would be worth €54.64 billion. At a high oil price ($150 a barrel), the 16% saving is worth €80.88 billion. This analysis showcases the value of reducing oil dependency, regardless of the occurrence of an oil peak. Table 1:
Transport energy supply scenarios – conservative demand growth. Oil Supply Scenarios
CONSERVATIVE demand Demand Reduction (1) (1) + Efficiency improvement (2) (1) + (2) + Alternative fuels (3)
Table 2:
No Peak
2020 Peak
2012 Peak
29% 50% 88% 157%
-6% 10% 38% 89%
-28% -16% 5% 44%
Transport energy supply scenarios – optimistic demand growth. Oil Supply Scenarios
OPTIMISTIC demand Demand Reduction (1) (1) + Efficiency improvement (2) (1) + (2) + Alternative fuels (3)
5
No Peak
2020 Peak
2012 Peak
-1% 16% 45% 99%
-28% -15% 6% 46%
-45% -35% -19% 11%
Conclusions and recommendations
There is an important distinction between mitigation measures: those that save energy, regardless of the energy source, and those that only reduce oil dependency. Because the measures only focused at oil dependency (mostly alternative fuels and propulsion systems) will stimulate greater demand for other energy sources (such as electricity, natural gas, etc.) and resources (agricultural land for biofuels), it is important to evaluate the sustainability of switching energy sources. It is unwise to solve one problem by creating another; hence it is recommended that measures reducing total energy demand be given preference over measures simply aimed at reducing the demand for oil. Demand reduction and energy efficiency improvement measures are generally less expensive and have shorter lead times than that required for a switch to alternative fuels. For many viable mitigation options to have substantial impact, they must be initiated more than a decade in advance of peaking. An analysis of the European disposition regarding oil depletion (section 2) shows that the maximum lead time at the EU’s disposal is 20 years. The lead time required to implement mitigation measures (often in excess of 10 years) stresses need for governing bodies to start reducing oil dependency now. It can be concluded from section 4 that applying measures individually will not suffice to bridge the supply and demand gap that will follow peak oil. Depending on the timing and extent of the peak, different combinations of WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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measures are required. The most promising mitigation measures are the facilitation of modal shifts, increased market penetration of hybrid vehicles, the implementation of intelligent transport systems and increased average vehicle occupancies (load factors for freight). It should be kept in mind that demand will eventually overtake supply, albeit not before 2029. Regardless of whether there is an oil peak or not, it is worthwhile to reduce a country’s oil dependency, because every nega-barrel is worth as much as a regular barrel of oil. Likewise, reducing the demand for other forms of energy can also lead to monetary savings. At the time when this paper is written, the world is moving into an economic recession. This significantly impacts global oil demand, delaying the impending oil peak. In terms of transport readiness, this is somewhat of a blessing in disguise. The opportunity now exists to start planning for the oil peak in a timely fashion, because the lead time for preparation is extended. During recessionary periods, governments tend to increase their infrastructure spending, in order to stimulate the economy. This creates the opportunity to start investing in the infrastructure required to step away from oil. Budgets should not be allocated to projects that will foster the current transport status quo. Reduced global oil demand has resulted in low prices. It is relatively inexpensive to undertake infrastructure projects at present, compared to what it will cost after the oil peak has occurred. The authors would like to highlight the need for governments to start peak oil mitigation now, although it might seem like an unlikely time to do so. Carpe diem.
References [1] European Commission, Panorama of Transport, Eurostat Statistical Books: Belgium, 2007. [2] European Commission, Keep Europe Moving – Sustainable mobility for our continent, Communication from the commission to the council and the European parliament, Brussels, 2006. Online. http://ec.europa.eu/transport/ strategies/2006_keep_europe_moving_en.htm [3] Association for the study of Peak Oil and Gas, www.peakoil.net [4] Hendler, P., Lane, T., Ratcliffe, S., Vanderschuren, M. & Wakeford, J., Energy and Transport Status Quo: Demand and Vulnerabilities, Section 2 of report submitted to the National Department of Transport, 2008. [5] International Energy Agency, World Energy Outlook 2008, IEA Publications, France, 2008. [6] Schoppers, M. & Murphy, N., Uncertainty in Peak Oil Timing, Presentation, ASPO, 2005. [7] International Energy Agency, World Energy Outlook 2007, IEA Publications, France, 2007. [8] European Commission, Energy – Yearly Statistics 2006, Eurostat Statistical Books: Luxembourg, 2008. Online. http://ec.europa.eu/eurostat [9] European Commission, Greening transport inventory, Commission staff working document, Brussels, 2008. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
236 Energy and Sustainability II [10] Hendler, P., Lane, T., Ratcliffe, S., Vanderschuren, M. & Wakeford, J., Reducing oil dependency and alternatives to oil-based liquid fuel transport, Section 3 of report submitted to the National Department of Transport, 2008. [11] European Environment Agency, TERM 2005 29 – Occupancy rates in passenger transport, Indicator fact sheet, 2007. [12] European Environment Agency, TERM 2005 30 – Load factors in freight transport, Indicator fact sheet, 2007. [13] European Environment Agency, Transport and environment: on the way to a common transport policy, EEA Report, Copenhagen, 2007. [14] European Environment Agency, TERM 2005 27 – Overall energy efficiency and specific CO2 emissions for passenger and freight transport, Indicator fact sheet, 2005. [15] International Air Transport Association (IATA), www.iata.org [16] Lovins, A., Datta, K.E., Bustnes, O., Koomey, J.G. & Glasgow, N.J., Winning the oil endgame: innovation for profits, jobs and security, Rocky Mountain Institute, Colorado, 2005. [17] InterAcademy Council, Lighting the way: Toward a sustainable energy future, A’dam, 2007. [18] Flight Sciences International, www.flightsciences.com [19] Baas, P. & Latto, D., Heavy vehicle efficiency, Report prepared for the Energy Efficiency and Conservation Authority, New Zealand, 2005. [20] European Commission, Action plan for energy efficiency: Realising the potential, Communication from the commission, Brussels, 2006. [21] Stodolsky F. et al, Railroad and Locomotive Technology Roadmap, Centre for Transportation Research, Energy Systems Division, Argonne National Laboratory, 2002. [22] Van der Voort, M.C., Design and evaluation of a new fuel-efficiency support tool, University Twente (NL), PhD dissertation, 2001. [23] Vanderschuren, M.J.W.A., Intelligent Transport Systems in South Africa, Impact assessment through microscopic simulation in the South African context, TRAIL Thesis Series T2006/4, ISBN: 9055840777, August 2006. [24] European Commission, Greening transport, Communication from the Commission to the European Parliament and the Council, Brussels, 2008. [25] Londo, H.M., Deurwaarder, E.P. & van Thuijl, E., Review of EU Biofuels Directive Public consultation exercise, Amsterdam, 2006. [26] Vanderschuren, M., Jobanputra, R. & Lane, T., Potential transportation measures to reduce South Africa’s dependency on crude oil, Journal of Energy in Southern Africa, Volume 19, Issue 3, August 2008. [27] Lane, T., MAGLEV – Moving around by magnetic force, Mobility Magazine, June 2008. [28] Gilbert, R. & Perl, A., Transport revolutions: moving people and freight without oil, Earthscan, ISBN: 9781844072484, 2008. [29] Strahan, D., The Last Oil Shock, London: John Murray, 2007.
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Sustainable energy policy choice: an economic assessment of Japanese renewable energy public support programs A. Suwa1, K. Noda1, T. Oka2 & K. Watanabe3 1
Environmental Division, Musashino University, Japan New Industries Promotion Division, City of Kitakyushu, Japan 3 Department of Sociology, Teikyo University, Japan 2
Abstract Given the associated environmental and economic benefits, electricity from renewable energy sources (RES-Es) is expected to play a significant role in shaping the human energy future. For the development of RES-E, the Japanese government introduced a national public support system based on a renewable portfolio standard (RPS) scheme. There is, however, a gap in the international and domestic literature about the Japanese renewable deployment policy. As a result, lessons to be learned from the Japanese experience have not been shared by the academic community. This paper fills this gap by paying a focused attention on the Japanese renewable portfolio standard (J-RPS) scheme, with an assessment on whether the scheme is promoting effective and efficient RES-E development. It reveals how certain types of RES-Es are marginalized from the market under the RPS equimarginality rule. Clear policy recommendations are made for a better design of the J-RPS, based on the exclusive empirical analysis. Keywords: renewable energy, feed-in tariff, renewable portfolio standard.
1
Introduction
With the scarce fossil fuel reserves, renewable energy deployment has been on the Japanese government energy policy agenda for decades. It had been especially so after the oil crisis, with a significant amount of government budget allocated to renewables research and development. Surprisingly little attention has been paid to public support for renewable energy deployment, where WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESU090211
238 Energy and Sustainability II government subsidy for specific renewable energy technologies had been the only explicit official mechanism for supporting renewables. Against this background, in 2003 the Japanese government enacted a legislation based on the renewable portfolio standard (RPS) scheme, which requires electricity retailers to supply a certain amount of renewable electricity to grid consumers. The RPS legislation was expected to ensure market efficiency, as well as bringing a steady increase of renewable capacity. There is, however, very little research conducted to evaluate the real effect of the Japanese RPS (J-RPS). This paper aims to establish the position of RPS in the environmental economics theory, and assess whether the Japanese RPS delivers the expected renewable capacity increase and efficiency gains. This paper is therefore structured as: 1) a general discussion on renewable public support schemes, 2) overviews on the Japanese RPS and an updated information on its effect on renewables development in Japan, and 3) discussion on market condition and RPS using the Japanese example, with concluding remarks.
2
Overviews on renewable public support schemes
2.1 Renewable energy sources: its barriers for common use Renewable energy sources are defined as those that are replenished by natural processes at rates exceeding their use for human purposes (Eblen and Eblen [1]). If natural replenishment is either non-existent or slower than the rate of usage, the energy resources (e.g. nuclear and fossil fuels) are non-renewable. Renewable energy sources have several advantages over the conventional energy sources, being not likely to be depleted, and having less impact on the environment. Although physically abundant as energy sources, there are several significant barriers upon transition to more common use of renewable energy technologies. Those barriers are generally identified as follows (Mendonca [2]): 1) Costs and pricing Renewable energy technologies are regarded as having less impact in terms of environmental externalities, but the market often has a problem to sufficiently evaluate the externalities resulting from the use of conventional energy fuels. In addition, renewable energy sources have not received subsidies to the extent that conventional energy sources had. This constitutes another reason for renewable technologies being perceived as “expensive”. 2) Legal and regulatory The development of renewable energy technology is frustrated by the lack of appropriate legal and regulatory frameworks. If restrictions are too strict, for example, on siting and construction for renewables, they often become major limitations on renewable development. The requirement of transmission access and utility interconnection could also be significant barriers for grid-connected renewable electricity. 3) Market performance Lack of credibility, resulted from unfamiliarity with renewable energy technology can increase the perceived uncertainty and risks associated with WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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them. Basic information and understanding on the installation and operation of renewables many not be sufficiently shared among members of the society. 2.2 Public support schemes for renewables Government intervention is theoretically justified as a means to correct the negative externalities relating to the use of conventional energy sources and technologies. Adding to that, government policy is highly important for the support of renewable energy technologies, especially to protect the technologies in their initial phases. Currently, there are broadly two major approaches for supporting renewable technologies (Menanteau et al. [3]). 2.2.1 Feed-in tariff Feed in tariff (FIT) consists of an obligation for electric utilities to allow electricity from renewable sources (RES-E) to be transmitted through the electricity grid (feed-in), and to purchase RES-E at a regulated price. It is generally known as a price-based approach that establishes a premium per generated kWh. Under FIT, the regulated price (tariff) determines the overall volume of RES-E production (Figure 1).
Figure 1:
Price-based approach (Source: Menanteau et al. [3]).
Since FIT normally contributes to the correction of price inequality between conventional and renewable energy technologies, it has been proved as a very powerful mechanism for RES-E deployment in many EU countries (e.g. Germany, Spain, etc). 2.2.2 Renewable portfolio standard (RPS) Renewable portfolio standard (RPS) requires electricity operators to supply a fixed quota of RES-E in the market. Tradable certificates (tradable green certificate, TGC) may be purchased for the fulfilment of the quota obligation. It is a quantity-based instrument, where regulators determine the RES-E sales volume and quotas are allocated among electricity operators (Figure 2). The prices of RES-E purchase are open to individual contracts, thus it is to follow the equi-marginality rule, where RES-E at lowest price would be deployed. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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Figure 2:
Quantity-based approach (Source: ibid.).
The majority of the US states and some EU countries, together with Japan, have adopted the RPS scheme, though the target levels and details of policy designs vary.
3
The regulatory and other frameworks for RES-E in Japan
3.1 Historical overviews: net-metering and government subsidy Renewable energy first won public recognition in Japan in 1960-70s, when the oil crisis hit the country’s economy. The Japanese government initiated a series of projects to support renewable technologies. Its primary focus, however, was mainly on technology research and development, while less attention was paid to public policy to support and deploy the renewables. It was only after 1992, when “net-metering” was launched as a voluntary scheme by the electricity utilities, that the rate of deployment of, at least specific RES-Es (PV and Wind), gained the momentum. Net-metering enables customers to use their own electric generation to offset their consumption over a billing period. This offset means that customers receive retail prices for the excess electricity they generate. This has been a crucial mechanism in supporting RES-E generation. Its introduction was clearly the turning point in the history of Japanese RES-E development. The deployment rate of RES-E has picked up since the beginning of 1990s when the net-metering started (Figure 3). Apart from the voluntary net-metering scheme, a government subsidy program was in place from 1994 to 2005. Since there was a significant increase in renewable capacity and the average cost of a residential PV system dropped by more than half during 1990s, the effect of the subsidy program is often overemphasised (Haas et al. [4]). It is important to remember that the capacity increase and cost reduction were the combined results of net-metering and the subsidy program. It is, however, not clear whether the utilities will continue the voluntary netmetering scheme, because the costs associated with the power purchase are increasingly felt as a financial burden. This creates an uncertainty for future renewable development. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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250000
1000 net-metering Total cumulative PV subsidised PV
MWh
600
150000
500
Net-metering started 100000
National subsidy started 50000
Figure 3:
800 700
200000
0
900
400
cummulative M
300000
241
300 200 100
1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 year
0
The Japanese residential PV growth, with an annual increase of net metering and subsidised PVs.
BOX 1 The main programs related to RES-E promotion in Japan before RPS introduction was summarised as follows: 1) Voluntary net-metering (Since 1992) The 10 main electric companies set the basic conditions for contracts with PV and wind power producers 2) Government subsidy program (1994-2005) Providing subsidies for initial investment for residential roof-top PVs 3.2 Adoption of RPS over FIT Apart from the private sector’s voluntary net-metering scheme, there has been awareness that there should be an official program to support renewables more effectively. With the recognition that FIT being a powerful mechanism for RESE development in several EU countries, a political initiative (the Parliamentary Initiative for Renewable Energy Promotion) was established by some members of the Parliament to address the introduction of FIT in Japan. The momentum for FIT was, however, lost when the government announced its intention to adapt a RPS-based system instead. The Japanese government launched a RPS legislation (J-RPS) in 2003, which requires 30 electricity retail companies to supply RES-E. The eligible RES-Es are “new energies”, a unique definition by the Japanese government, meaning PV, wind, geothermal, small hydro-power (less than 1MW) and biomass. It is WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
242 Energy and Sustainability II notable that power from municipal waste incineration can be counted as “biomass” on the basis of biomass content in waste, though critics disagree with allowing power from waste being included into the green basket. The national target was initially set as 3.3 TWh in 2003 (1.35% of the total electricity sales), which gradually increases to 12.2 TWh in 2010, then 16 TWh in 2014 (about 1.6% of total electricity sales). For the fulfilment of the quota, retail suppliers are either to 1) generate RES-E themselves, 2) purchase RES-E from RES-E generators or 3) purchase RPS certificates. The maximum certificate price is regulated as 11 JPY/kWh (approximately 9 US cents/kWh). The retail suppliers are allowed to carry out banking and borrowing. 3.3 Assessment of the Japanese RPS system The Japanese government is highly optimistic about the effect of J-RPS in stimulating RES-E development. Unfortunately, this government view is widely shared by the academic community so far. It is stated, for example, that RES-E generation has steadily increased since the J-RPS introduction, and the trend is expected to continue. It is argued that the RES-E costs have declined and the certificates are at a stable price range of approximately 5 JPY/kWh (about 6 US cents/kWh) during 2003-5. Also, they explain that the J-RPS national target level is lower than those of the US and some EU member countries, mostly because large hydro and geothermal powers are ineligible under the scheme (Haas et al. [4]). The level of the national J-RPS target and how that relates to RES-E price range requires a more detailed assessment. An integrated evaluation of the Japanese RPS, thus, will be given in this section. Empirical research will be carried out by data obtained from official and other sources. The assessment criteria will be on the following aspects: effectiveness, transaction cost and equimarginality. 3.3.1 Effectiveness The J-RPS target was established as 1.35% of the total electricity sales in 2010, and 1.6% by 2014. The low level of the J-RPS level is usually explained by the exclusion of hydropower (Haas et al. [4]). A detailed comparison without hydropower component, however, clearly reveals that renewable targets in many countries are significantly higher than that of Japan (Figure 4). The level of the J-RPS target, in fact, seems to be too low to reflect the physical potential for renewable development. Since 2003, the RPS initial year, a significant amount of banking has accumulated, to the extent that the banking amount reached to 6.8 TWh in 2007. This is sufficient to supply over 90% of 2008 target of 7.5 TWh (Figure 5). The extremely high level of banking is proof that the initially established J-RPS targets are too low to reflect the RES-E potential in Japan. 3.3.2 Cost and equi-marginality The low target level has resulted in many undesirable effects for the deployment of RES-E. One of the advantages of quota-TGC (tradable green certificate) WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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10.0 5.0 0.0 -5.0
2010 target JP
EU
DE
UK
FR hydropower contribution
-10.0 -15.0 -20.0 Figure 4:
Target level without hydropower contribution. Hydropower contribution level (taken from 1997 data) is deducted from 2010 target level for neck to neck comparison. The Japanese target is significantly lower than others.
140 120
100GWh
100 80 60 Banking
40
Banking+yearly supply Official target
20 Compulsory target
0 2003
Figure 5:
2004
2005
2006
2007
2008
2009
2010
The Japanese RPS targets and the level of banking. The official targets are nominal. The compulsory targets, as legally binding targets, can be satisfied by the banking from previous years.
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30 25 W ind H ydro B iom ass P V(residential) P V(industrial)
100GWh
20 15 10 5 0 2003
Figure 6:
2004
2005 year
2006
2007
The price level for J-RPS eligible renewable technologies.
is to create a certificate market that could raise necessary funding for RES-E generation. The J-RPS target, however, is too low to create a TGC market, as there is little incentive for TGC purchase. The level of certificate price is virtually fixed at “stable range”, because of the absence of the TGC market (Figure 6).
80 70
100GWh
60
O thers B iom ass H ydro PV W i nd
50 40 30 20 10 0 2003
2004
2005
2006
2007
year
Figure 7:
Shares of power produced by J-RPS eligible renewable technologies.
The price inelasticity relates to another problem as to the kinds of RES-E being developed. The eligible J-RPS renewables includes power from municipal waste incineration as “biomass” (the biomass rate is calculated on the basis of its inclusion in municipal waste). Power from “biomass” including waste WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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incineration dominates more than half of the J-RPS contracts, reflecting its relatively inexpensive price range compared with the prices of other RES-E technologies (Figure 7). It is notable that power from incineration of waste are heavily subsidised by public funds, in terms of e.g. waste collection and construction of incineration facilities. This means the equi-marginality rule inherent to the RPS scheme, is applied in the selection of RES-E technologies, to the extent that RES-Es which are more environmentally desirable, but in their initial development stages, are forced into the competition with the subsidised energy technology. As a result, economically competitive (subsidised) RES-E wins market penetration, while economically less competitive RES-Es are marginalized from the market. Figure 8 demonstrates the marginalisation of environmentally desirable but economically less competitive RES-Es. Price
MCA
MCB
QD
Figure 8:
4
MCD
MCc
Quantity
The marginalisation of less competitive RES-Es.
Conclusion
Japan, as a country with high technological capacity, is a leader in solar and other renewable energy technologies. With the increasingly potent effects of climate change, and as a country that hosted one of the historic conferences of the United Nations Framework Convention on Climate Change (UNFCCC), Japan has sufficient reasons to deploy renewable energy technologies. The energy policy and regulation of the country, however, do not necessarily address the potential for the renewables. The great opportunity for RES-E development has been lost due to the lack of an ambitious renewable target being adopted in the J-RPS system. The absence of an ambitious target seems to have resulted in several negative effects. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
246 Energy and Sustainability II 1) The RES-E potential are overlooked and underdeveloped. The level of the J-RPS target is embarrassingly low, to the extent that majority of the target can be satisfied by the accumulated banking. 2) As the TGC market is underdeveloped, the generators are forced into a contract with the utilities, which fixes the price of the certificate at the minimum level. 3) With the equi-marginality rule in operation, only the currently most economically competitive energy technology is deployed, while less developed RES-E technologies being marginalised from the market. In order to boost RES-E development, the current J-RPS needs, at least, to address the following issues: 1) To establish a higher national target, with individual targets for each sources of RES-E at different stages of development; 2) To recognise the significance of fixed-price payment on RES-E deployment, as just demonstrated by the utilities' voluntary netmetering. Net-metering works as a mechanism to concentrate on prices and stabilises the long-term cost-benefit balance related to RES-E investment Currently, J-RPS targets have become more of a limitation than a stimulating objective. Having regard to the fact that many EU countries are actively promoting RES-E through a FIT system, there seem to be much for Japan to learn from their experiences, because FIT, without subscribing to a regulatory quota, will not operate as a limiting factor to renewable development.
References [1] Eblen, R.A. and Eblen, W.R., Encyclopaedia of the Environment, Houghton Mifflin, New York, 1994. [2] Mendonca, M., Feed-in Tariffs: Accelerating the Deployment of Renewable Energy, Earthscan, London, 2007. [3] Menanteau, P., Finon, D., Lamy, M., Prices versus quantities: choosing policies for promoting the development of renewable energy, Energy Policy, 31, pp799-812, 2003. [4] Haas, R., Meyer, N.I., Held, A., Finon, D., Lorenzoni, A., Wiser, R., Nishio, K., Promoting Electricity from Renewable Energy Sources – Lessons Learned from the EU, United States, and Japan, Competitive Electricity Markets, pp 419-468, 2008.
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An energy and environmental meta-model for strategic sustainable planning D. S. Zachary, U. Leopold, L. Aleluia Reis, C. Braun, G. Kneip & O. O’Nagy Resources Centre for Environmental Technologies, Public Research Centre Henri Tudor, Luxembourg
Abstract This paper describes a geo-spatially distributed reference based energy model that is coupled to a reduced-order (efficient) photochemical air quality model. Project LEAQ, the Luxembourg Energy Air Quality Model, is built upon the large-scale systems analytic method, a meta-modelling approach that includes a full geospatial database of energy sources, devices, and their emissions for four broad sectors of the economy: transportation, industrial, residential, and commercial. The energy model is coupled to an air quality transport model, handling nitrous oxides, volatile organic compounds, ozone, particulate matter, carbon dioxides and carbon monoxides. The model assists in choosing lowest cost energy solutions given environmental (air quality) constraints in a spatially distributed map. The application is designed for the Luxembourg context and would later be applied to R other European cities and regions. We present the MATLAB beta-version of the model and describe first results and the development plan and implementation in a proposed European project. We also present the main user functionalities that would assist a researcher in the implementation of the model. We give a first view of the beta-version and its use in modelling Luxembourg’s national energy system. Keywords: meta-model, reference based energy models, convex optimization, air pollution, air quality, NOX , VOC, ozone, reduced-order photo-chemical models, geo-spatial.
1 Overview of sustainability meta-models in European projects The European community has, for some time, been one of the global leaders in the field of sustainable energy and environmental model building and project support [1]. The number of European supported sustainability projects is a clear WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESU090221
248 Energy and Sustainability II indication as to the importance of this research. As a result, the quality of life and the standards of living in Western Europe have benefited from such efforts [2]. Both energy use and environmental concerns are two forefront research agendas that are formulated in sustainable growth research (e.g. Adams [3]); it should be noted that these concerns are essentially ”competitive” in nature. The global importance of both disciplines has introduced the need for a coupled modelling approach that will simultaneously address these issues. We also note here that a ’third leg’ of the sustainability equation, the social aspect, is not discussed in this paper, but is addressed in many other sources (e.g. Adams [3], Ott [4], S¨oderstr¨om et al. [5]). From the modeler’s point-of-view, sustainability can be viewed in terms of a multi-systems analysis, also known as a meta-modelling approach. We define a meta-model as a model with several components that are interconnected forming a complete model that defines the components of a conceptual idea, process, or system and useful for modelling predefined classes of problems (e.g. Gigch [6], S¨oderstr¨om et al. [5]). Metamodel building has become an important activity in interdisciplinary problem solving, and in this paper, we use it to address the diverse modelling field associated with sustainable energy infrastructure growth and its environmental impact. There is an extensive history of European projects leading up to the present state of environmental and energy related meta-models. Our methodology builds on the past several years of European sustainable urban projects, beginning with the Fifth Framework Programme [7] and the Sixth Framework Programme [8] projects. To begin, several projects in the LUTR (Land use and Transportation Research) cluster addressed core issues and ancillary problems concerning urban sustainability. A planning, evaluation and consultancy strategy was formulated in the EcoCity project where seven model settlements provided a test-bed for techniques and tools in carrying out urban planning. CityFreight explored modifications of motorways and its effect on traffic in and around a major metropolitan centre. The project also performed cost modelling for future freight transportation in a European multimodal network using calibrated origin-destination (O-D) matrices in transportation models. Other FP5 projects have focused on setting up guidelines for optimal integrated transportation and land use strategies. The PROSPECTS project, for example, explored this guideline challenge for urban sustainability. The PROPOLIS project also explored issues of sustainability and urban spatial transportation analysis. Finally, the Sustainable Urban Transportation project (SUTRA) came closest to establishing a meta-model ”cascading” methodology where model based quantitative analysis tools were used to construct comprehensive approaches to urban transportation solutions in sustainable cities; overall, the SUTRA project integrated the socio-economic and environmental concepts pertinent to urban transportation planning (Fedra [9]). Several FP6 projects continued in the theme of urban sustainability. The project MATISSE proposed a general tool to study Integrated Sustainability Assessment (ISA). TRIAS explored ISA for transport technologies and transport energy supply together with economic, environmental and social impacts. The SENSOR program WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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added a slight twist to the traditional modelling focus; building, validating and implementing Sustainability Impact Assessment Tools (SIAT) using a spatially referenced framework. Finally, a cost assessment program, CASES, explored the external and internal costs of energy production for different energy sources for the EU-25 countries and for some non-EU countries. These costs are projected in energy scenarios to the year 2030. Sustainability is not limited to air quality management in FP6; Urban Water Management, UWM, was explored in the SWITCH project. What lacks in these previous models, whether it was a FP5 or FP6 project, is the ability to employ a ”feedback” mechanism, where the energy infrastructure expansion can be ’predicted’ or rather suggested, in accordance with the projected quality of air. Thus, a beckoning need for a coupled energy-environmental model has presented itself where future energy infrastructure planning periods will be guided by the determination of future air quality. The LEAQ model will be built within an overall optimization framework and will fulfill this ”feedback” mechanism void in sustainable energy modelling.
Figure 1: Overview of the LEAQ model, showing the connectivity of each submodel. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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2 The Luxembourg Energy Air Quality model – LEAQ 2.1 The model overview The two major models in the LEAQ project include an energy model - GEOECU (GEO-spatial Energy CalCulator) and the air quality model, AYLTP (AsYmptotic Level Transport Pollution Model). Both models are used in an optimization framework as characterized in Fig. 1. Spatial and temporal data are provided as inputs to the GEOECU model, which computes atmospheric emissions of primary pollutants, including spatially distributed VOC, NOX , CO, CO2 SO2 and particulate matter (PM2.5 and PM10). The LEAQ model searches for the lowest cost energy solution for a city or region using an economic model with constraints (e.g. demand, operational, technological, seasonal, . . . etc.). GEOECU is based on ETEM (Energy Technology Environment Model), a bottom-up energy reference model that provides a representation of the energy and technology choices that could best deliver the needed energy services in a city or region. The ETEM model and other models of this type (e.g. MARKAL models) aim to supply energy services at minimum global cost and simultaneously calculates optimal equipment investment, operation level and primary energy importation and exportation (Drouet and Th´eni´e [10]). GEOECU’s emission outputs are subsequently passed to the AYLTP model. In addition to these emissions, AYLTP uses spatio-temporal information, such as meteorological, topographical, and land use information to predict the concentration for the primary pollutants and the secondary pollutant O3 . AYLTP calculates pollutant concentrations with variable space resolution (100 m × 100 m - 1 km × 1 km) and variable temporal resolution (10 min - 1 hr). An optimization routine called ACCPM, the Analytic Centre Cutting Point Method, (Gondzio et al. [11]) is embedded in an open source wrapper, OBOE, an Oracle Based Optimization Engine supported by the ORDECSYS Company [12]. ACCPM is used to efficiently guide an n-dimensional, discrete or continuous convex problem, or a set of problems to an optimal (either minimal or maximal) solution. In our application, ACCPM checks O3 concentration levels against upper limits. If the calculated O3 concentration levels are within bounds, then an update of the precursor maximum bounds, NOX and VOC, are also adjusted in the GEOECU model to reflect this change. If the calculated concentration values of O3 are not satisfied, a cut is made on the limit of the O3 precursors. The GEOECU is then rerun using readjusted upper limits of NOX and VOC. The process is repeated until an optimum energy solution satisfying O3 concentration bounds is obtained. We model the economic activity for each (hypothetical) economic planning period, i = 1, . . . NP where each economic period lasts for 5 years (e.g. 20092014, 2014 - 2019, . . .). Energy related economic activity vector, x and the associated constants c can be formulated in an objective/constraint problem in a compact slack form notation,
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min c, x
251
(1)
x
s.t. Ax = a,
(2)
Ui x = Ui max , i = 0, 1, . . . Np − 1,
(3)
Ui ≥ 0, i = 0, 1, . . . Np − 1,
(4)
x ≥ 0,
(5)
Aj,i (Ui , s) ≤ Aj,i
max (s),
j ∈ J , i = 0, 1, . . . Np − 1,
Gi (Aj,i (Ui ), s)x ≤ Gi,max , i = 0, 1, . . . Np − 1,
(6) (7)
The first constraint Eq. 2 consists of all the technical, operational, seasonal, etc. constraints that are found in the technoeconomic model, the reader is referred to (Carlson et al. [13]) for more information. The conversion vectors Ui convert economic activity to emissions and are constrained against maximum levels, Umax . Spatially dependent air quality levels Ai,j (Ui , s), s ∈ (s1 , s2 , s3 ), the three dimensions of the air shed region, arise from primaries j ∈ J representing NOX and VOC and are also limited by maximum levels, Ai,j . The geo-spatial weight criteria Gi is constructed by factoring the spatial distribution of population density and air quality levels, so as to limit potential economic growth scenarios in poor air quality regions . Details of this development are given in (Zachary [16]). Subtleties of the above problem are numerous and too technical to address in this paper. We note one subtlety, the ‘=’ sign in Eq. 3 results from the fact that the technoeconomic model, GEOECU, allows activity to increase so that the optimal solution always results in activity driven emissions that will match the upper bounds. Eqs. 1–5 are described in GEOECU, while Eqs. 6–7 are described in the air quality model and in an auxiliary routine that combines spatially dependant air quality with population density. The entire objective constraint problem solved by the overseeing ACCPM (OBOE) methodology and tool. The LEAQ project builds on an earlier prototype [13] coupled model scheme, based on a ‘lite’ version of the full MARKAL model (Abilock et al. [14]) and a reduced-order photochemical air quality model (Zachary et al. [15]). The current project brings in several important technical developments, including geo-spatial modelling of both the AYLTP and GEOECU sub-models (detailed in Zachary [16]). The AYLTP simulation is improved using a more accurate meteorology package and spatial terrain package. The AYLTP model will also include an augmented species list as mentioned above and a fast turbulence calculator that will complement the topographical input. Likewise, improvements to the energy model and the development of a spatially distributed energy use database for Luxembourg will allow for a detailed technoeconomic analysis of the region. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
252 Energy and Sustainability II nox
voc
O3
Subgrad Values : mapped to [0 1] space 1
137.3491
C = Total Economic model cost
40.43373 80.06739
271.6995
last subgrad
101.6543101.6543
0.75 271.6995 137.3491
202.3124
137.3491 STN3
STN3 STN1 101.6543 202.3124 101.654
STN1 271.6995 271.6995 137.3491 406.0499 STN2
Air Quality Indexes peak O3 =159.3347 mean O3 =42.3922 AOT60 (avg)=87.4443 iPer/NPer =1/1 time =13:00 dfdy : i/Dim =0/4
(NOX & VPC/5 & O3*5 ppbv)
202.3124 302.9706 STN2
100
80.06739 40.43373 40.43373
STN1 119.7011 80.06739 80.06739 40.43373 119.7011 STN2
Daily variations in concentrations
80 60 40 20 0 12 12.2512.512.75 13
historical subgrads
STN3 40.4337
STN 1 − NOX STN 2 − NOX STN 3 − NOX STN 1 − VOC STN 2 − VOC STN 3 − VOC STN 1 − O3 STN 2 − O3 STN 3 − O3
0.5
0.25
0 dC/di_1
dC/di_2
dC/di_3
dC/di_4
V =−1.4581 and V 3.8448 E
N
Figure 2: The LEAQ active data windows and graphs (Part I): top – (a) in the table, the air quality output; bottom – (b) in the table, the optimization directional information. lux cantons
lux pop. density
LEAQ - β Version lux GEO weights (Period1 only) lux cadaster map
G1 G2 ... = 1.0074
0.99257
Figure 3: The LEAQ active data windows and graphs (Part II): left – (c) in the table, the average O3 levels per iteration; right – (d) in the table, the maps used in the problem.
Other new developments in the LEAQ project include a complete open-source version that will be accessible via the web. This version would first be tested in the Luxembourg context and then is expected to be exported for use in the greater Thessaloniki, Greece region. This project is now in review for development as a European LIFE+ project [17]. A spatial uncertainty analysis is also foreseen in the LEAQ project. Pollutant measurements, as with any measurements, and their simulations are never without uncertainty. A validation campaign posted at several sites in Luxembourg will be critical to test the model against several different weather and air quality episodes. As with all models, the uncertainties from input are propagated throughout the model. An added complexity is created as errors are passed from GEOECU to WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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Table 1: Description of Figs. 2 and 3. R MATLAB window
GUI sub-
Description
(a) The air quality output
The pollutants NOX , VOC, and O3 concentration levels (for Luxembourg). The air quality values and the evolution are shown. Measurement stations are also shown.
(b) Directional Info.
Sensitivity values for the tuning parameters of the problem. The (dot - •) lines are the past (historical) values, the (solid line - ♦) is the current values. This information is used in ACCPM (OBOE) to guide the problem to an optimal solution.
(c) The average O3 profile
The asymptotic ozone level profile is plotted as a function of NOX and VOC levels. The AOT60 cutoff (flat plane) is also shown. Precursor NOX and VOC levels are shown (sharp peaks); iterations 1 and 2 are shown in this example. The point where the peaks cross the O3 curve shows the air quality for that iteration. The iterative steps show the ’walk’ towards lower O3 values. The iterative steps continue until the precursor levels result in a solution that is off the O3 ’hill’. At this point, the sharp peaks will arrive in the flat regions of the figure representing the AOT60 threshold level, and the optimization search engine (ACCPM), will subsequently produce a feasible solution.
(d) Input/output maps
Maps showing the 12 Luxembourg cantons, the population density, the ’canton-weighted’ maps, and land use maps. The 12 cantons are grouped into two regions, the 5 most populous cantons in the south and the 7 less populous cantons in the north (G1 and G2 ). The ’cantonweighted’ maps show the two region weights (see Eq. 7), G1 and G2 . The higher weight (G1 ) calculated for the more populous south of Luxembourg and the smaller weight (G2 ) calculated for the less populous north. R command window (Input of meta-model commands) The MATLAB
(not shown)
and the output data file also used in the β version data analysis. The data file shows the iterative update of the type of cut (feasible, non-feasible), the iterative objective function, the sub-gradient (directionality information), the precursor (NOX and VOC) levels and the O3 concentration levels. A status window, including the air quality and energy models’ basic parameters, the size of the problem, and the current number of optimization iterations is also not shown in the figure.
AYLTP; errors are accumulated in the iterative optimization process as suggested in Fig. 1. The uncertainty analysis must also be considered in the constraint relations given in Eqs. 2–7. The analysis of spatial uncertainties and the treatment of meta-model error propagation will be explored in a Luxembourg national project (under review) (Zachary and Leopold [18]). WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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3 The LEAQ β version The working test version or β-version of LEAQ is shown in Figs. 2 and 3 and described in Table 1. The different parts of the graphical user interface (GUI) are enumerated in the table. The plenary project foresees the entire model as an open-source, web-based decision tool. The tool will determine a lowest cost energy for the current (hypothetical) 5-year economic planning period (2009–2014) and for subsequent periods (2014–2019), (2019–2024), . . . etc., for a total of 5 × 6 = 30 years of planning. The user will be able to assess an easy-to-use GUI, and determine air quality for the current energy infrastructure (for various weather episodes) of the region in question and will be able to predict air quality for future energy infrastructures. The air quality assessment can be done for Business as Usual (BaU) scenarios and various energy expansion scenarios. Finally, the model will be employed as an environmental - energy management tool and will assist in searching for environmentally friendly energy scenarios and in the crafting of cost effective national and transnational action plans.
Acknowledgement This project is supported by the Minist`ere de la Culture, de l’Enseignement Sup´erieur et de la Recherche (MCESR) du Luxembourg under the project identifier CRTE-07-LEAQ.
References [1] UrbanEnvironment2007, Integrated Environmental Management, Guidance in relation to the Thematic Strategy on the Urban Environment, Technical Report – 2007-013, 2–7, 2007. [2] European Sustainable Energy Review (ESER), Russell Publishing media pack; quote from Prof. Arthouros Zervos, President of EWEA – EWEA - European Wind Energy Association, “It is crucial to acknowledge the numerous benefits of renewable energy sources. A renewable energy policy is much more than just a climate policy, promoting renewable energy is giving priority to economic growth, creation of jobs as well as, due to their mainly decentralised nature, rural development. Renewables contribute to securing the future welfare and prosperity of Europes citizens and, not to forget, they are extremely popular among the European population, www.internationalsustainableenergy.com, 2009. [3] Adams, W.M. The Future of Sustainability: Re-thinking Environment and Development in the Twenty-first Century. Report of the IUCN Renowned Thinkers Meeting, 29–31 January, 2006. [4] Ott, K., The Case for Strong Sustainability. In: K. Ott & P.P. Thapa (eds.). Greifswalds environmental ethics. Greifswald: Steinbecker Verlag Ulrich Rose. ISBN 3-931483-32-0. Retrieved on: 2009-02-16, 2003. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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[5] S¨oderstr¨om E., Andersson B., Johannesson P., Perjons E., Wangler B., Towards a Framework for Comparing Process Modelling Languages, in: Lecture Notes In Computer Science; Vol. 2348. Proceedings of the 14th International Conference on Advanced Information Systems Engineering. pp 600–611, 2001. [6] P. van Gigch, System Design Modeling and Metamodeling, Plenum Press, New York, 1991. [7] Fifth framework programme (FP5, 1998-2002), European Commission Community Research. Thematic program of the 5th Framework. Energy, Environment, and Sustainable Development http://cordis.europa.eu/fp5/ [8] Sixth framework programme (FP6, 2002–2006), http://cordis.europa.eu/ fp6/projects.htm [9] Fedra, K. Sustainable Urban Transportation: a model-based approach. Cybernetics and Systems, 35: 455–485, 2004. [10] Drouet L., Th´eni´e J., ETEM An Energy/Technology/Environment Model to Assess Urban Sustainable Development Policies. Reference ManualVersion 1.0 July (2008). www.ORDECSYS.com [11] Gondzio J., O. du Merle, R. Sarkissian and J.-Ph. Vial, PROXIMAL-ACCPM - A Library for Convex Optimization Based on an Analytic Centre Cutting Plane Method, European Journal of Operational Research, 94, 206–211, 1996. [12] The ORDECSYS (Operations Research and DECision support SYSTEMS) consulting company, http://www.ordecsys.com/en [13] Carlson, D., Haurie, A., Vial, J.-P., Zachary, D., Large-scale convex optimization method for air quality policy assessment. Automatica 40 (3), 385–395, 2004. [14] Abilock, H., Bergstrom, C., Brady, J., Doernberg, A., Ek, A., Fishbone, L., Hill, D., Hirano, M., Karvanagh, R., Koyama, S., Larsson, K., Leman, G., Moy, M., Sailor, V., Sato, O., Shore, F., Sira, T., Teichman, T., Wene, C.O. (1980). MARKAL: A multi-period linear programming model for energy system analysis. In R. Kavanagh, (Ed.), Proceedings of the international conference on energy system analysis, Dublin, Ireland (p. 482). Dordrecht: Reidel, 1979. [15] Zachary D.S., Haurie A., Siverguina I., A Reduced-Order Photochemical Air Quality model. Cybernetics and Systems: An International Journal Vol 35, pp. 1–15, 2003. [16] Zachary D.S., An integrated geo-spatial energy - air quality impact assessment tool Draft for Environmental Research Letters, 2009. [17] Zachary D.S. and Leopold U., Urban Horizons, A LIFE+ Project,(LIFE08 ENVL000445, 2008. [18] Zachary D.S. and Leopold U., The unLEAQ project: UNcertainty analysis for the Luxembourg Energy Air Quality project, a Luxembourg national research (FNR) proposal, 2009.
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The Italian gas retail market: a cluster analysis based on performance indexes G. Capece1, L. Cricelli2, F. Di Pillo1 & N. Levialdi1 1
Department of Enterprise Engineering, University of Rome ‘Tor Vergata’, Italy 2 Department of Mechanics, Structures, the Environment and Land Management, University of Cassino, Italy
Abstract The liberalization of the European natural gas sector radically changed the structure of the competitive environment which in turn forced companies to make changes in order to stay in the market. In Italy the liberalization process also had a strong impact on the strategies adopted by the companies involved. This situation instigated various studies of the changing nature of performance through the analysis of company profits and financial positions throughout the first three years following the market liberalization. This paper focuses on the changes in performance in the natural gas retail market by analyzing the profit and financial position of the companies concerned over the first three years following the market liberalization. The balance sheets of 105 Italian companies in this sector are analysed, after which a cluster analysis is performed employing the most significant performance indexes. The companies are then analysed within each cluster with respect to age, size, geographical location. The analysis is further developed by studying the strategies in terms of business diversification adopted by the operators in response to the radically altered competitive environment. The results of our analysis show that the majority of companies attained a high level of performance, although this positive outcome was mitigated by the gradual decrease of the average values of performance indicators during the period concerned. There appear to be several reasons for this decline: the performance observed during the three-year period was strongly influenced by regulatory factors; increased competition resulted in reduced profit margins; and exceptionally mild climatic conditions over this period significantly decreased the volume of gas sales. Finally, it should be noted that the best performance was achieved by companies based in northern Italy which were members of longstanding groups and were single rather than multi-business companies. This result contrasts with the failure of the business diversification strategy, which was widely adopted by enterprises from the utility sectors following the liberalization process. Keywords: Italian gas market liberalization, performance indexes, cluster analysis. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESU090231
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1
Introduction
The fact that natural gas is relatively environmentally compatible and that its use in the thermoelectric sector guarantees a high level of consumption resulted in the European Community deciding to regulate the natural gas market. It was in this regard that on June 22 1998 the European Parliament and the European Council, by means of Directive 98/30/CE [1], began the liberalization of the European natural gas market, which had previously been characterised by vertical integration and public monopoly [2]. This process ended in 2003 with the Gas Directive 2003/55/EC [3], which is the European gas legislation in force at present. The European Gas Directive was transposed into Italian law by Legislative Decree n.164/2000, known as the Letta Decree [4], which laid down important guidelines concerning the definition of the eligible customers, competition, and conditions of reciprocity. The most significant change brought about by this legislation was that the Letta Decree imposed the unbundling of the distribution companies from those in retail, and thus allowed the latter to operate in a more competitive market. Extensive research has previously been conducted in order to analyse one specific aspect of performance in the natural gas market, such as the efficiency or the productivity. Examples of such studies are: Aivazian et al. [5], Jamasb et al. [6], Herbert and Kreil [7], and Sickles and Streitwieser [8] who explore the natural gas industry in the USA; Price and Weyman-Jones [9] who study the United Kingdom's natural gas distribution sector; and Lee et al. [10] who estimate the total factor productivity based on an international comparison. To date, very little research regarding the natural gas market has been carried out in relation to the simultaneous effects of the various aspects of performance, such as financial, liquidity, and profitability indicators. An evaluation of the gas sector with regard to economic performance is carried out by Kim et al. [11], although their work concentrates on the transportation segment. In connection with the Italian natural gas market, a performance analysis is carried out by Erbetta and Fraquelli [12] who focus on the distribution segment. In contrast, the present paper concentrates on the retail segment which, having undergone major transformations in recent years, is the only sector to be opened to free market competition and is therefore deemed more suitable for a comparative analysis of competitiveness. In our study the performance of the gas retail companies are evaluated in relation to the companies’ age, size, geographical location and degree of business diversification. The methodology employed here is divided into two consecutive stages: 1. The evaluation of the main financial, liquidity and profitability indicators; 2. The performance of a cluster analysis utilising the indicators from stage 1. The latter allows the sample to be subdivided into homogeneous groups which are then analysed in relation to the main characteristics of the company. The aim of the analysis is to answer the following research questions: WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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•
Can the Italian natural gas retailers be grouped into clusters characterized by internal homogeneity and external heterogeneity? • Can the clusters be formed by simultaneously considering financial, profitability and liquidity indicators? • If so, do these clusters indicate some market features with respect to the following company characteristics: geographical position, age, size and business diversification? This research paper is organized as follows: Section 2 provides a description of the data set; Section 3 describes the cluster analysis; Section 4 presents an analysis of the results with respect to the following characteristics of the companies: size, geographical position, age and business diversification; Section 5 concludes.
2
Data set
The data set, supplied by the Unione Italiana delle Camere di Commercio (Italian Union of the Chambers of Commerce), is comprised of data relating to 105 companies operating in Italy, including the balance sheet for each company. The present analysis refers to the three year period from January 2004 to December 2006. Most of the retail companies in the sample were formed in 2003 and were consequently still in the start-up phase during the three year period considered here. Thus it was not possible to analyse historical data dating back prior to 2004. On the 1st January 2006 there was a total of 414 companies authorised by the ‘Ministero delle Attività Produttive’ (Ministry of Productive Activities) to practise in the retail market. However, according to research undertaken by the Italian Regulatory Authority for Electricity and Gas (AEEG), only 194 of these companies appeared to be active. Data regarding the three year period considered here were available for 105 of the active companies. Therefore, these 105 companies became our sample representing a significant proportion of the total number of retail companies operating in Italy (approximately 54%). As regards the geographical distribution, 63% of the companies are located in northern Italy, 24% in central Italy and the remaining 13% in southern Italy. In relation to company size, the companies analysed have been divided into three groups according to their revenue: small, medium and large sized companies. Our sample is comprised of 48 small companies (45.7%), 33 medium companies (31.4%) and 24 large companies (22.9%). Approximately 60.8% of the firms in the sample are members of longstanding business groups, while the remaining 39.2% is made up of newly-formed companies. Finally, with regard to the choice of strategy, whether to diversify or to specialise, 81 firms (77%) are single-business companies (specialised), while 24 (23%) are multi-business (diversified).
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3
Cluster analysis
In order to analyse company performance, cluster analysis is applied [13–16]. This analysis is intended to create groups which have the maximum cohesion internally and the maximum separation externally. Among the various clusterisation methods, the technique employed by Ward [17] was chosen as it generates a classification hierarchy while minimising the variance within each of the groups. The cluster analysis is carried out using SPSS (Statistical Package for the Social Sciences): this allows subjects (the companies) to be grouped in relation to the probability of certain values being scored by a set of variables (grouping variables). The grouping variables used in this study are the following profitability indicators: Return on Equity (ROE), Return on Investment (ROI), Return on Sale (ROS), and the following liquidity and financial indicators: Liquid Asset index (LA) and Leverage Ratio (LR). The liquid asset index shows the short-term debtpaying ability and it is determined by subtracting from current assets the current liabilities. The Leverage Ratio provides a view of the company overall debt situation and it is calculated by dividing net debt to equity. The above indicators have been chosen since they have a low level of inter-correlation. Table 1 shows the value ranges chosen for the various performance indicators utilised in the cluster analysis. Table 1:
Performance indicator ranges.
Range
Performance
ROI
ROE
ROS
LA
LR
1
Poor
x<0
x<0
x<0
x<(-)500 000
x>3
2
Mediocre
0≤x<8
0≤x<5
0≤x<6
(-) 500 000≤x<500 000
2<x≤3
3
Good
8≤x<10
5≤x<8
6≤x<8
500 000≤x<10 000 000
1.5<x≤2
4
Excellent
x≥10
x≥8
x≥8
x≥10 000 000
x≤1.5
The statistical analysis is performed for each year of the three year period (2004-2006). The agglomerative hierarchical algorithm starts with n clusters, where n is the number of observations. The Euclidean distance between observations is calculated and the two closest points are merged into a single cluster. The process is repeated until all observations are included in one cluster. Four clusters emerge from the statistical analysis (as seen in the 2006 resulting dendogram in figure 1) in which cluster I contains the companies with the worst performance and cluster IV those with the best results. The results of the Ward method are compared to those of a cluster solution produced by Kmeans method [19] which is shown to be similar confirming their validity. A summary of the distribution of the clusters is shown in table 2 below. Most of the companies attain a high level of performance and are found in clusters III and IV throughout the three year period. However, this positive performance is attenuated by the progressive reduction in the average values of the indicators. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
Energy and Sustainability II C A S E Label Num 5 83 98 14 23 70 46 52 44 59 93 95 20 57 90 92 62 77 28 47 49 97 29 36 56 80 4 48 15 101 35 88 34 94 105 11 32 76 96 37 99 104 18 1 43 81 102 6 58 69 26 53 71 51 73 17 45 85
Figure 1:
0 5 10 +---------+---------+ ─┐ ─┤─┐ ─┤ │ ─┘ │ ─┐ ├───────┐ ─┤ │ │ ─┤ │ │ ─┤ │ │ ─┼─┘ │ ─┤ │ ─┤ │ ─┤ │ ─┤ │ ─┘ │ ─┐ │ ─┤ │ ─┼───┐ │ ─┤ │ │ ─┤ │ │ ─┤ │ │ ─┤ │ │ ─┘ ├─────┘ ─┐ │ ─┤ │ ─┼─┐ │ ─┤ │ │ ─┤ │ │ ─┘ ├─┘ ─┐ │ ─┤ │ ─┼─┘ ─┤ ─┘ ─┐ ─┤ ─┤ ─┤ ─┼─────┐ ─┤ │ ─┤ │ ─┤ │ ─┤ │ ─┘ │ ─┐ │ ─┤ │ ─┤ │ ─┼─┐ │ ─┤ │ │ ─┤ │ │ ─┤ │ │ ─┤ │ │ ─┤ ├───┘ ─┘ │ ─┐ │ ─┤ │ ─┤ │ ─┼─┘ ─┘
C A S E Label Num 24 41 38 87 9 75 61 78 64 91 54 50 86 12 31 42 25 74 21 103 13 72 82 65 68 30 39 40 89 16 33 2 79 84 3 19 55 7 10 100 66 67 22 27 63 8 60
261
0 5 10 +---------+---------+ ─┐ ─┼───┐ ─┤ │ ─┤ │ ─┤ │ ─┘ │ ─┐ │ ─┤ │ ─┤ │ ─┤ │ ─┤ │ ─┼───┘ ─┤ ─┤ ─┤ ─┤ ─┤ ─┤ ─┘ ─┐ ─┤ ─┤ ─┤ ─┤ ─┤ ─┼─────┐ ─┤ │ ─┤ │ ─┤ │ ─┤ │ ─┤ │ ─┘ │ ─┐ │ ─┤ │ ─┤ │ ─┤ │ ─┤ │ ─┤ │ ─┤ │ ─┤ │ ─┼─────┘ ─┤ ─┤ ─┤ ─┤ ─┤ ─┘
The resulting dendogram from the statistical analysis in 2006.
The decline may be attributed to various factors. Firstly, the economic trends recorded over the three year period are strongly influenced by the regulatory and tariff related aspects of the gas market, and secondly, the increase in competition results in reduced profit margins. Furthermore, the uncharacteristically mild climatic trends at the time significantly reduces the volume of sales. On analysing table 2 it is interesting to note that the number of companies in cluster I diminishes over the three year period, indicating that a proportion of the WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
262 Energy and Sustainability II Table 2:
Percentage of companies in each cluster. 2004
2005
2006
I Cluster
20.6%
16.2%
13.3%
II Cluster
12.8%
15.2%
24.8%
III Cluster
28.4%
35.3%
16.2%
IV Cluster
38.2%
33.3%
45.7%
companies which initially perform poorly following liberalization, later improve thanks to economies of learning.
4
Analysis of the results
In this section we analyse the clusters obtained in relation to the following critical factors: age, size, geographical location and business diversification. With regard to the age of the company, there are two company typologies: those which entered the market after the liberalization of the sector and those which stem from the unbundling of larger companies required by the Letta Decree which came into effect on 1 January 2002. Despite being a newly registered company, any firm of the latter typology should be considered a well established enterprise in terms of know-how inherited from the company group to which it belonged. In table 6, ‘new’ denotes the newly formed companies which entered the market after liberalization, whereas ‘established’ refers to those which originated from previously established groups. On further examination of the sample in section 2, the mean of each cluster is compared to the overall mean for each of the critical factors. Company characteristics which have a greater than average concentration within each cluster are shown in table 3. In 2004 the geographical position is seen to be related to the performance of the companies. There is a prevalence of firms from the north in the best cluster, whilst the worst cluster mainly consists of companies from the south. With regard to company size, the smaller companies are found in both the first and third clusters, although the firms are mainly from the south in the first cluster whilst those in third cluster are prevalently from the north. Most of the medium sized companies are to be found in both cluster II and cluster IV, but again these clusters differ geographically. The medium sized companies found in cluster II are predominantly from central Italy, whereas those in cluster IV are chiefly from the north. As regards the age of the companies, the newly formed firms are mainly distributed in the first three clusters while the best cluster is primarily composed of well established companies. It may be noted that regarding business diversification, the clusters reflect the average distribution of the sample, with the exception of cluster II, which has a prevalence of single business companies. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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In 2005 the composition of the clusters does not undergo any significant changes from the previous year, with the exception of the third cluster in which there is now a prevalence of smaller, established companies which are mainly from central Italy. A further difference with respect to 2004 is found in cluster IV, which is mostly formed of single business companies. Regarding the distribution of the companies with respect to their age, it may be observed that there are newly formed companies in the worst clusters, whereas in the best clusters most of the firms belong to established groups. The group background and the ability to maintain stable relationships with clients and suppliers is therefore indicative of success. Table 3:
Company characteristics which have a greater than average concentration within each cluster. Geographical Location
Company Size
Age of Company
Business Diversification
South
small (from South)
new
average
2004 I Cluster II Cluster
Central
medium
new
single
III Cluster
average
small (from North)
new
average
IV Cluster
North
medium
established
average
2005 I Cluster
South
small (from South)
new
average
II Cluster
Central
new
average
III Cluster
Central
established
average
IV Cluster
North
medium-large small (from CentralNorth) medium
established
single average
2006 I Cluster
Central
average
new
II Cluster
average
small
new
average
III Cluster
average
large
new
average
IV Cluster
North
average
established
single
It is interesting to note that both in 2004 and 2005 the companies which attain the best performance are prevalently from the north, medium-sized and belong to established groups, whereas the worst companies are from the south, small and newly formed. The high level of performance attained by the medium-sized companies is due to the fact that they take advantage of economies of scale (in contrast to the smaller firms) and they simultaneously contain operating costs (in contrast to the larger companies). This finding is also supported by previous research [18], which brought to light the way in which medium-sized companies are able to attain better results since they manage to maintain a low level of incidence of setup and labour costs. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
264 Energy and Sustainability II The companies from the north tend to perform better due to the fact that they have to compete against a larger number of competitors and consequently they must contain their operating costs in order to attain the higher levels of efficiency required in a more competitive market. Firms operating in the northern regions account for the greatest percentage of Italian retail gas companies. These areas are the most attractive from an industrial viewpoint and are also those in which the climate is colder and hence there is a greater demand in terms of volume of gas. Furthermore, firms are able to access capital more easily in the north than in the south. This, in conjunction with the other factors stated above, provides the new companies with strong incentives to operate in the north and to leave the south to the older incumbent retail companies. Firms belonging to the well established groups on the other hand achieve good results thanks to economies of learning that are the basis of their greater competitiveness nationwide. In 2006 the changes in the composition of the clusters are more significant. In relation to the geographical position the northern companies again perform the best, whilst the performance of the firms from central Italy worsens. The latter is largely due to the anomalous temperatures in the autumn 2006 that were between 3-5°C higher than the seasonal average [20]. With reference to company size, there is a prevalence of small companies in the second cluster. Throughout the period 2004-2005 the small companies which are found in cluster I improve their performance and move to cluster II by 2006, whilst many small companies which over the same two year period are found in the third cluster perform worse and also move to the second cluster. It should be noted that the companies which perform worse are mostly from central Italy, and that their poor performance is due to the exceptionally mild climatic conditions described above. The small companies which improve their performance, moving from cluster I to cluster II are uniformly distributed with respect to their geographical position. Such an improvement may be explained by the fact that they have increased the number of their end users both by consolidating their market position and by starting to retail further afield across the nation. It may also be observed that there is a prevalence of large companies in cluster III, due to the movement of a significant percentage of such companies which were found in cluster II in 2005. Although the single business companies remain those with the best overall performance, the companies which improve their performance are all multibusiness, illustrating that companies with this typology manage to take advantage of economies of variety over time. Regarding the distribution in relation to company age, the same trend which is observed over the 2004-2005 period continues into 2006. In the worst clusters there are many firms which have recently entered the market, whereas in the best clusters most of the companies belong to well established groups. With regard to business diversification, the single business companies also perform better in 2006. Poor performance in multi-business companies would WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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appear to be counterintuitive since diversified companies ought to obtain better economic and financial results theoretically due to economies of scope. However in practice, given that the process of diversification began relatively recently, it is possible that more rewarding effects of this strategy have yet to mature.
5
Conclusions
This paper analyses the market performance of companies involved in gas retail over the three years following the liberalisation of the sector, i.e., 2004 to 2006. A sample of 105 firms were analysed, representing approximately 54% of the companies operating in the sector. Firstly an analysis of the balance sheets was carried out calculating the main profitability, financial and liquidity indicators (ROI, ROE, ROS, LR and LA) which were then utilized as variables for the cluster analysis. Four clusters were obtained from the statistical analysis, which was carried out using the Ward method. Cluster I contained the companies with the worst performance and cluster IV those which achieved the best results. It may be observed from the cluster analysis that throughout the three years in question most of the companies performed well and thus were to be found in clusters III and IV. However, this positive performance was attenuated by the progressive reduction in the average values of the indicators. This decline was mainly due to two factors: firstly the economic trend recorded over the three year period was strongly influenced by the regulatory and tariff related aspects of the gas market; and secondly the uncharacteristically mild climatic trends at the time significantly reduced the volume of sales. It is interesting to note that the number of companies in cluster I diminished over the three year period, indicating that a proportion of the companies which initially performed poorly following liberalization, later improved thanks to economies of learning. A second analysis was carried out by considering the distribution of the companies throughout the clusters in relation to a number of critical factors: the geographical location, size, age and business diversification. The main findings are summarised below. Throughout the three year period it was observed that with respect to the age of the companies, in the best clusters there was a prevalence of companies which belong to longstanding business groups, whereas in the worst clusters there were more businesses which were new to the market. Thus the know-how of personnel, strong ties with suppliers, and trust building with clients would appear to be factors which are critical to a competitive advantage. In relation to company size there was a prevalence of medium sized companies in the best cluster in both 2004 and 2005. Firms of this size were therefore able to take advantage of economies of scale (as opposed to smaller firms) while at the same time they managed to contain operating costs (in contrast to the larger companies). It should be noted, however, that the WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
266 Energy and Sustainability II companies were more evenly distributed with respect to their size in 2006 thanks to an improvement in the performance of both larger and smaller sized companies. With regard to geographical location, the companies in the north of the country achieved the best performance throughout the three year period. This is due to the greater degree of competition which induces companies to reduce their operating costs and thus attain a higher level of efficiency. Most Italian operators in gas retail are based in northern Italy because it is the most attractive area from an industrial standpoint, and also since there is a greater demand for gas as the climate is colder there than in the rest of the country. It is also interesting to note that the companies in central Italy underwent a downturn in 2006 which was largely due to the unusually mild temperatures that autumn which caused a considerable reduction in the revenues of gas retailers. As regards business diversification, the specialised companies outperformed the diversified companies throughout 2005 and 2006. This result may be due to the fact that the multi-business companies were still in the start-up phase. Newly diversified companies must sustain greater reorganization costs and therefore they are initially unable to take advantage of the economies of scope.
References [1] European Parliament and Council. Directive 98/30/EC of 22 June 1998 concerning common rules for the internal market in natural gas, Bruxelles, http://www.europarl.europa.eu/ [2] Guldmann, J.M., Economies of scale and natural monopoly in urban utilities: the case of natural gas distribution. Geographical Analysis, 17, pp. 302-317, 1985. [3] European parliament and council. Directive 2003/55/EC of 26 June 2003 concerning common rules for the internal market in natural gas and repealing Directive 98/30/EC, Bruxelles, http://www.europarl.europa.eu/ [4] Ministry of Productive Activities. Legislative Decree n. 164 of 23 May 2000, concerning the implementation of the Directive 98/30/EC and the common rules for the internal market in natural gas, Rome, http://www.sviluppoeconomico.gov.it/ [5] Aivazian, V.J., Callen, J.L., Chan, M.W.L. & Mountain, D.C., Economics of scale versus technological change in the natural gas transmission industry. The Review of Economics and Statistics, 69(3), pp. 556-561, 1987. [6] Jamasb, T., Pollitt, M. & Triebs, T., Productivity and efficiency of US gas transmission companies: a European regulatory perspective. Energy Policy, 36, pp. 3398-3412, 2008. [7] Herbert, J.H. & Kreil, E., US natural gas market. How efficient are they?. Energy Policy, 24, pp. 1-5, 1996. [8] Sickles, R.C. & Streitwieser, M.L., An analysis of technology, productivity, and regulatory distortion in the interstate natural gas transmission industry: 1977-1985. Journal of Applied Econometrics, 13(4), pp. 377-395, 1998. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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[9] Price, C.W. & Weyman-Jones, T., Malmquist indices of productivity change in the U.K. gas industry before and after privatisation. Applied Economics, 28(1), pp. 29-39, 1996. [10] Lee, J-D., Oh, K.J. & Kim, T-Y., Productivity growth, capacity utilization, and technological progress in the natural gas industry. Utilities Policy, 8, pp. 109–119, 1999. [11] Kim, T-Y., Lee, J-D. & Park, S-B., Profit, productivity, and price differential: an international comparison of the natural gas transportation industry. Energy Policy, 27, pp. 679-689, 1999. [12] Erbetta, F. & Fraquelli, G., Produttività e redditività nella distribuzione locale di gas naturale in Italia: proprietà, diversificazione e scala operativa. L’Industria, 4, pp. 745-768, 2003. [13] Anderberg, M.R., (eds). Cluster Analysis for Applications. Academic Press: New : New York, 1973. [14] Everitt, B.S., Landau, S. & Leese, M., (eds). Cluster analysis. Arnold: London, 2001. [15] Kaufman, L. & Rousseeuw, P.J., (eds). Finding groups in data an introduction to cluster analysis. John Wiley & Sons: New York, 1990. [16] Tryon, R.C. & Bailey, D.E., (eds). Cluster analysis. McGraw-Hill: New York, 1970. [17] Ward, J.H., Hierarchical grouping to optimize an objective function. Journal of the American Statistical Association, 58, pp. 236-244, 1963. [18] Capece, G., Cricelli L., Di Pillo, F. & Levialdi, N., A Productivity Analysis of the Italian Gas Retail Market. Environmental Economics and Investment Assessment II, ed. K. Aravossis, C.A. Brebbia & N. Gomez, WIT Press: Southampton, UK, pp. 43-52, 2008. [19] McQueen, J., Some methods for classification and analysis of multivariate observations. Proc.of the 5th Berkeley Symp. on Math. Statist. Probab., pp. 281–297, 1967. [20] Aeronautica Militare. Temperature e precipitazioni del 2006 in Italia, Roma, http://www.aeronautica.difesa.it/
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Participatory assessment of sustainable end-user technology in Austria M. Ornetzeder, U. Bechtold & M. Nentwich Institute of Technology Assessment of the Austrian Academy of Sciences, Austria
Abstract This paper reports on experiences using a participative technology assessment (pTA) approach to discuss and evaluate research and development goals for sustainable energy technology in Austria. In a two-day Future Search & Assessment conference in November 2007, 36 per representative quota selected laypeople discussed the future of energy research in Austria on two different levels: general visions of sustainability as well as deduced short-term aspects regarding the present end-user related energy research agenda. The strategy chosen consists of a well-balanced mix of focus groups, plenary sessions, expert inputs, and moderated working groups. The five topics discussed in the laypeople’s conference were: micro combined heat and power (micro-CHP), new system solutions and avoidance strategies, smart metering and ‘intelligent’ end user equipment, innovative contracting and leasing models, and visualization and monitoring devices. We aim to show that pTA can contribute twofold to technical innovation: Firstly, it can contribute to the social robustness of the underlying strategies and scenarios of relevant research programmes; and secondly, the research topics that directly refer to the end-users can be critically evaluated in terms of social acceptability and user friendliness. Moreover the chosen approach serves as a platform to discuss long-term energy policies as well as practical consequences. Keywords: energy technology, applied research, sustainability, end user, technology assessment, laypeople participation.
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Introduction
The current energy system is mainly based upon fossil energy sources. To minimize or avoid severe negative consequences in terms of costs and effects for humankind and the biosphere this system has to face radical changes. The widely accepted goal is an efficient and secure energy supply system mainly based on renewable resources. Research and development activities will undoubtedly have to play a crucial role in this substantial transition, predominantly regarded as the only future option. However, end-users of new technological options will be of decisive importance for the success of such a transition. The relevance of a transition of the energy system can be seen in a twofold manner. In order to avoid or at least mitigate negative effects caused by climate change experts recommend a long list of short-term political and technological measures (IPCC [1]). A great number of them are directly related to the way we serve our energy demand today. The second important aspect of energy relates to the fact that fossil fuels are limited and have to be replaced in the future. Energy supply is of vital interest for end-users too. According to the Austrian Energy Agency households spend more than 10 billion Euros per year for energy needs. Within the last five years the energy demand of private households has increased extraordinarily. In addition, climate change has recently become a problem of great public concern and people are aware, that there is a need to change their behaviour. Beyond doubt this high level of public awareness concerning energy was a good precondition to run a participatory process. This paper reports on a research project funded by three public sponsors: (1) the Austrian Council for Research and Technology Development (RFT), an advisory body to the Austrian Federal Government; (2) the Federal Ministry of Transport, Innovation and Technology (BMVIT) and (3) the Federal Ministry of Economics and Labour (BMWA). The Austrian Council is particularly interested in the project from a technological and research policy perspective. As outlined below in more detail (section 2), the Austrian Council has a role to play in formulating research agendas and wants to do so in the future not only with the help of experts and stakeholders, but is curious to experiment with participatory methodology involving laypeople. At the same time, it sees participatory events as a means to foster awareness of innovation and technology. By contrast, the two ministries joined their forces amongst other things with regard to support research and development in energy technologies and started together in 2007 the research programme “Energy of the Future” (see below in section 3). Their interest in our project is therefore a direct input into future calls of the programme. We developed a tailor-made process (described in more detail below in section 4) that will give answers both to the questions of the Austrian Council and the needs of the ministries. While the former mainly wants to know whether our experiment can serve as a model for future involvement of citizens, what effect the conference had on the perception of those involved, and how the process was perceived in public, the latter are mainly interested in having their concept put in perspective, in supplementing ideas, in adding new perspectives WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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and in receiving user-centred input with regard to their programme. Hence we devised several phases of the process, including a feedback and evaluation phase after the main event. Selected results of the pTA are presented in section 4.3, focussing on the energy technology related outcomes of the citizen’s conference.
2
Participatory TA in the Austrian context
In the context of research and technology policy we frequently face conflicts of values. These conflicts as well as, to some extent, conflicts of knowledge and interests, are perhaps not capable of being solved. Nevertheless, they can be negotiated more transparently, comprehensively by holding a structured dialogue involving citizens (laypeople) who have not previously participated, alongside experts and stakeholders. Thus, there is a chance to arrive, on the one hand, at better decisions, as this would incorporate, on a broader base, knowledge, interests and value judgements; and on the other hand, decisions would be better legitimised. These proposed procedures take effect alongside the established decision-making processes; they extend the decision base but are not intended as a substitute for those processes (Nentwich et al. [2]). While there is a tradition of involving stakeholders – in particular the social partners in all kinds of policy formulation including technology policy –, performing technology assessment (not in the classical expert-oriented manner, but with participatory methodology) has never been widespread in the Austrian context so far. An internationally comparative study at the European level in 2000 (Belucci et al. 2000, published as (Joss and Bellucci [3])) included only a few examples from Austria, not all of which actually involving laypersons, but also stakeholders. The record so far includes two consensus conferences, one on tropospheric ozone in 1997 (Torgersen [4]), the other on genetic data in 2003 (Bogner [5]); the EUROpTA report also describes an interesting stakeholder participation process leading to the Austrian technology Delphi 1996–98 (Aichholzer et al. [6]) and the Salzburg Traffic Forum in 1995/96. Furthermore, a number of experiences with participatory processes have been made in particular in the environmental sector. On the one hand those participatory events have been made within formal activities, for instance in the framework of strategic environmental impact assessment procedures. On the other hand informal endeavours have been carried out in the framework of various research projects. Examples cover ecological building concepts (Ornetzeder [7]), smart home technology (Rohracher [8]), or ecological sanitation technology (Starkl et al. [9]). In those cases new technological options have been discussed and evaluated in focus groups by different types of users. In the particular context of TA the focus was hitherto on stakeholder and expert involvement. More recently an increasing practical interest in including pTA elements in current projects have been implemented, such as the EU project PRISE (Jacobi and Holst [10]), in which lay persons assessed different scenarios of futures with privacy enhancing or threatening security technologies and in particular the project reported in more detail in this paper. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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Focus of the pTA project: energy research in Austria
In Austria, energy research funded by public authorities became more and more mission-oriented in the 1990s. In 1999 the Federal Ministry of Science launched the first Austrian Programme on Technologies for Sustainable Development, originally slated for five years. Although the main focus of this programme was on technological development the authors designing the programme were, however, aware that they would have to seek approaches oriented not only on technological criteria. Research and development with the goal of sustainable development, they have argued, requires balancing a variety of interests. For the first time a research and development programme in Austria called not only for innovation in the field of technology, but also was open for socio-economic aspects. As defined within this first programme, sustainability should refer to the following: An increasingly efficient consumption of energy with respect to the entire life cycle A greater use of renewable sources of energy (especially the use of solar energy) The greatest possible use of organically renewable raw materials as well the efficient use of materials And increased attention to service and use from users' point of view (BMWF [11]). In 2004, based on several years of experience and more than 200 funded research projects, the responsible department within the meanwhile unlabelled Ministry of Transport, Innovation and Technology (BMVIT) started activities to develop a follow-up programme. Within these activities (Austrian Strategy Finding Process ENERGY 2050) a broad range of experts and relevant stakeholders had been invited to discuss requirements for a new research programme. In this preparatory phase it was important to develop long-term strategies and measures along with adequate research goals aiming at the transformation of the existing energy system within the next 40–50 years. Compared to the first programme in this case mitigation of climate change turned out to be the major force behind the reorientation of the Austrian energy research agenda (BMVIT [12]). The following programme “Energy of the Future“ which was launched in 2007 aiming at energy efficiency, the improvement and development of renewable energy technologies and the design of smart energy networks (BMVIT [12]). The programme was subdivided into seven research areas, whereof one was focused on energy and consumer. Research projects in this area should contribute e.g. to the development of new or significantly improved home devices (like new lightning systems, micro-CHP, solutions to avoid stand-by losses or smart meters) or to the design of completely new systems to provide energy services on the household-level. Beside projects with a technological focus the programme supported research concentrating on organisational aspects of energy and the behaviour of users too. Examples for this kind of socioeconomic research cover models for energy contracting or leasing, new concepts WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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for information and education or the interrelation of energy demand and lifestyles. Although end-users of energy – as addressees – play a very prominent role within the programme, laypeople have not at all been involved in the preparatory process. Therefore this lack of direct contact between energy experts and endusers served as one of the starting points for the presented pTA project.
4
The conference on future search & assessment
The overall aim of the future search and assessment conference was to invite laypeople and reflect on selected topics from the research programme “Energy of the Future”. Furthermore the conference should have given the public the opportunity to be involved in the development of a research agenda – by means of the participants as well as through the media. Citizens should have had the opportunity to learn more about ongoing research and development in the field of sustainable energy technology but also to influence the direction of activities. However, to deal with such objectives is quite uncommon in the Austrian context. Given the technological complexity and comprehensiveness of the research programme it was clear that it would not be possible to present all details to the participants. Rather the challenge was to give an overview of the genesis and purpose of that programme and discuss only those issues that more or less relate directly to end-users. In order to reduce complexity and variety we decided to select five research topics previous to the main event. In the preparatory phase it also turned out that we could not focus on specific research issues without discussing the wider socio-political context of sustainable development. Laypeople should have been able to raise common-good issues as well as more individualistic arguments. In order to meet these requirements we chose the following 3-step approach: 1. A preparatory workshop to reduce the number of 11 possible topics down to 5 to be addressed within the following pTA conference 2. A two-day future search & assessment conference with 30 to 40 laypeople and seven external experts concerning three main points: (a) discussion of relevant aspects underlying the long-term visions (“Leitbilder”) for the future of energy research, (b) assessment of five specific energy and end-user related research topics in detail; and (c) presentation of main results and participants’ experiences within a conference for stakeholders and energy experts on behalf of the programme initiators. 3. A follow up ex-post survey of the participants to track potential effects as a consequence of the citizens’ conference. 4.1 Preparatory workshop As a first step to broadly embed the programme design within the end-users’ perception, a three-hour preparatory workshop was held at the end of September WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
274 Energy and Sustainability II 2007. The main idea was to confront the general public in an exploratory manner with the research agenda and discuss and finally prioritise the presented topics. For this aim three different social groups were invited: end-users (3 participants representing diverse lifestyles), representatives of consumer organisations (3 persons), and journalists (5 journalists with experiences in energy issues). Following the workshop outcomes the project-team selected, in cooperation with the sponsors, five topics to be presented and discussed at the main event. Table 1 gives a short overview on the selected topics, each with brief definitions. Table 1:
Selected research topics to be discussed at the conference.
Research topics
Brief description
Micro-CHP
“Micro Combined Heat and Power” is the simultaneous production (cogeneration) of heat and electricity in individual homes. Effectively the micro-CHP unit replaces the central heating boiler and provides heat, hot water and the majority of the home's electrical needs ("power station for every household"). First marketable products are already available. Research could help to improve existing technology.
New system solutions and avoidance strategies
Research in this field should completely explore new ways to provide various energy services on the household-level. Such systems have to be significantly more effective than current practices. System solutions could be realised through miniaturization of devices and/or through the integration of functions into larger units (e.g. by the use of ventilation systems for heating and cooling purposes).
Smart metering and „intelligent“ enduser equipment (IRON)
A smart meter is a type of advanced electrical meter that identifies consumption in more detail than a conventional meter; generally, it communicates this information via a network back to the utility for monitoring and billing purposes (telemetering). Integral Resource Optimization Network (IRON): Electric appliances are equipped with an "IRON-box" that provides information on future energy demands to electricity suppliers. Intelligent end-user equipment enables load management.
Innovative contracting and leasing models
Energy contracting (and leasing) comprises different forms of energy services with main emphasis on the use of energy saving procedures and efficient technologies. The main focus is on a contractual relation between an energy provider (contractor) and its customer (energy consumer). While contracting and leasing is quite common in industry, the public sector products for end-user markets have to be developed.
Visualization and monitoring of energy use
The aim in this field is to visualize the energy consumption of single appliances and/or of a household. It could be displayed directly on the device itself or on a central unit, e.g. on a PC. The presented information may relate to the current consumption and/or to a specific period, such as a year. Visualization of the energy consumption could contribute to the dealing of energy in a more conscious way and and/or shed light on weak points.
4.2 Selection of participants In order to obtain representative results we decided to select participants for the main conference on the basis of a controlled quota sample, roughly typifying the Austrian population. A specialized social research institute conducted the WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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recruiting process. A large number of interviewers all over Austria informed potential participants in short face-to-face interviews. Conditions for attending the conference included the following: an allowance of € 200 for attending the two days, travel costs and accommodation for those not from Vienna, free meals and coffee breaks. In terms of the accountability of the process, the participants were informed at a very early stage that their personal contribution will have an indirect effect in so far as the programme makers and the decision makers are (a) interested in the results and (b) will be given that information in terms of an instantaneous presentation the very next day and of course in an evaluated way in terms of further proceeded reports. It was made clear that the citizens’ contribution would be of great value and a necessary precondition for the further development of the energy research agenda. The recruiting process was successful in terms of the absolute number of participants as well as of the structure of the sample. In the end 36 laypeople from all over Austria attended the conference. 4.3 Recommendations for the energy research agenda On the second day of the conference five end-user-oriented research topics were discussed in detail. Table 2 gives an overview of selected results. Generally, it is important to mention that in spite of some critical discussions the involved laypeople approved of the presented technologies (or subjects) as meaningful approaches to transforming the existing energy system towards sustainability. Based on that general agreement a number of detailed recommendations for each research topic were formulated. The list of recommendations embodies both requirements related to general aspects of social acceptability as well as requirements derived from more individual orientations. For most of the general requirements we can see a strong connection to the common “Leitbild”, which was developed on day 1. All of the discussed research topics are considered to be useful contributions in reaching the desired ecological goals – most importantly finding strategies to address the challenges of climate change. The discussed technologies should be as efficient as possible and based on renewable energy sources only. Moreover they should be treated as integrated parts of larger socio-technical systems. Unsurprisingly such recommendations match up well with the guidelines from the programme “Energy of the Future“ and the laypeople’s “Leitbild”. In this case citizens have more or less confirmed already agreed strategies and programmes. In doing so, laypeople have contributed to the social robustness of these goals and related measures. Compared with the descriptions of end-user related research in the programme “Energy of the Future”, the discussions have brought about some new aspects, too. According to the notion of social justice in the “Leitbild”, laypeople argued for affordable end-user products and guaranteed energy savings; it was generally agreed that social policy issues should be taken into account more seriously. The prominent role of autonomy – defined as being WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
276 Energy and Sustainability II Table 2:
Selected research-orientated recommendations by laypeople.
Research topics
Recommendations by laypeople
Micro-CHP
Micro-CHP should support the energy-independence of households Devices have to be affordable in purchase and maintenance Use of regionally available, renewable resources is important Technology should be improved as part of a larger system (e.g. in accordance with available renewable fuels) Stirling engine and fuel cell technology to be used on the household-level are a high priority Research should aim at highest possible energy efficiency and the ability for effective power-management (micro-CHP as part of virtual plant)
New system solutions and avoidance strategies
Focus on saving resources and foster awareness for resources R&D should lead to concrete outcomes (e.g. sponsorship for ecological housing) The research programme should be aware that involved social players (e.g. architects, planners, handcrafter, users) represent different perspectives which should be included Results of research should be actively disseminated Social aspects should be taken into account
Smart metering and „intelligent“ end-user equipment
Presented information should be simple and plain (in order to support changes in attitude and raising awareness for natural resources) Data security should be guaranteed (concerning recording, interpretation and transmission) Households should profit in financial terms (e.g. by automatic selection of lowest tariff) All relevant players of the energy industry should support the system
Innovative contracting and leasing models
Offer is attractive for users when expertise of contractor is guaranteed Information and recommendations by contractors should be neutral (non-product related) Loss of autonomy should be minimized, contractor should find constructive ways to deal with loss of control and autonomy Provisions of a contract should be highly flexible Overall energy savings should be guaranteed
Visualization and monitoring of energy use
Awareness raising should start as soon as possible (e.g. programmes for different age-groups, cooperation with communities) Usability of monitoring devices is very important (e.g. for the elderly) Monitoring devices should enable households to remain independent from energy suppliers Information on energy consumption should be combined with recommendations Connection to social policy issues should be considered
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independent from energy suppliers – and the importance of privacy issues (data security) may also be seen as new and fruitful inputs for the Austrian energy research agenda.
5
Conclusions
In this paper we have presented experiences with a recently conducted participatory TA process on energy research in Austria. The recently launched research programme “Energy of the Future” served as starting point and subject matter. The main idea of the tailor-made participation process was to combine elements of vision assessment with an innovation-oriented TA approach. In this case, citizens were involved in the development of a research agenda for the first time. Within the conference we provided comprehensive up-to-date information about energy research and citizens had the opportunity to reflect on long-term strategies as well as concrete technologies or energy services. Another goal was to uncover and make use of everyday experiences and attitudes of laypeople as end-users of energy. In other words it was the attempt to assess technology at a very early stage of development. As the results show laypeople clearly support the idea of mission-orientated innovation policy. Research and development in the energy sector should lead directly to solutions to mitigate climate change. Citizens are very aware that problems of the future cannot be solved by technological innovation alone. New technology therefore must be embedded in wider socio-political contexts such as changed price relations and new consumption patterns. The ranking of different political targets made clear that the principal orientation of the Austrian research agenda is widely supported by the general public. However, energy policy should seriously consider social issues as an integrated part. The chosen conference design made it possible to discuss various aspects of future technology in detail. Laypeople came up with a list of recommendations covering general aspects of social acceptability as well as requirements derived from more individual orientations (e.g. aspects of usability). All in all the conference produced a broad range of recommendations and a considerable number of new aspects came to light. The results represent an interesting input for the development of the Austrian energy research agenda.
Acknowledgements This research was funded by the Austrian Council for Research and Technology Development, the Federal Ministry of Transport, Innovation and Technology and the Federal Ministry of Economics and Labour. We would like to thank Wolfgang Gerlich for valuable advice and doing a professional job as main facilitator. We also like to thank Barbara Schmon, Michael Hübner, Monika Auer, Peter Molnar, Lothar Rehse, Friederich Kupzog, Georg Benke, Karen Kastenhofer, Ulrich Fiedeler, André Gazo and 36 persons from all over Austria.
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References [1] IPCC, Ed. (2007). Working Group III contribution to the Intergovernmental Panel on Climate Change, Fourth Assessment Report, Climate Change 2007: Mitigation of Climate Change. Geneva. [2] Nentwich, M., A. Bogner, et al. (2006). Techpol 2.0: Awareness – Partizipation – Legitimität. Vorschläge zur partizipativen Gestaltung der österreichischen Technologiepolitik; Endbericht September. Vienna, Rat für Forschungs und Technologieentwicklung. [3] Joss, S. and S. Bellucci, Eds. (2002). Participatory Technology Assessment. European Perspectives. London, Centre for the Study of Democracy. [4] Torgersen, H. (1999). The Ozone Consensus Conference in Austria. Case Study for EUROpTA. Vienna, EUROpTA. [5] Bogner, A. (2004). Partizipative Politikberatung am Beispiel der BürgerInnenkonferenz 2003 (Analyse); final report, solicited by: Rat für Forschungs- und Technologieentwicklung. Vienna. [6] Aichholzer, G., J. Cas, et al. (1998). Technologie Delphi Austria; 3 volumes: I: Konzept und Überblick; II: Ergebnisse und Maßnahmenvorschläge; III: Materialien. [7] Ornetzeder, M. (2003). Sustainable technology and user participation. Assessing ecological housing concepts by focus group discussions. Culture, Environmental Action and Sustainability. R. G. Mira, J. M. S. Cameselle and J. R. Martinez. Cambridge and Göttingen, Hogrefe & Huber: 145-160. [8] Rohracher, H. (2006). "Sustainability as a matter of social context: information technologies and the environment." International Journal of Environmental Technology and Management 6(6): 539-552. [9] Starkl, M., M. Ornetzeder, et al. (2007). "An Integrated Assessment of Options for Rural Wastewater Management in Austria." Water Science & Technology 56(5): 105-113. [10] Jacobi, A. and M. Holst (2007). Privacy enhancing shaping of security research and technology, European Commission. [11] BMWF, Ed. (1999). Konzept Impulsprogramm Nachhaltig Wirtschaften. Vienna. [12] BMVIT, Ed. (2007). Diskussionspapier. Strategieprozess ENERGIE 2050. Zwischenstand zum Forschungsprogramm. Wien.
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Towards a SADC model to assess financing options of renewable energy technologies V. H. van Zyl-Bulitta1, B. Amigun1, 2 & A. C. Brent1, 3 1
Sustainable Energy Futures, Resource Based Sustainable Development, Natural Resources and the Environment, Council for Scientific and Industrial Research, South Africa 2 Department of Process Engineering, Stellenbosch University, South Africa 3 Graduate School of Technology Management, University of Pretoria, South Africa
Abstract Access to energy in the form of electricity and fuels is a necessary requirement for sustainable development. Despite the resource abundance for Renewable Energy Technology (RET) in Africa, the potential of RETs is still underexploited. In light of the COP15 meeting, RET is a focal point in the response to global challenges, such as climate change and energy security, and the investment landscape in RET and energy efficiency has recently undergone considerable transformation. To realise its potential, investment in RET infrastructure is critical for Southern Africa. However, the development of sustainable energy is curbed in the region by the lack of adequate and secure finances. A plethora of generic technological and non-technological restrictions, such as scarce political support and poverty, impede RET (financial) support and adoption. A deeper understanding of the consequences of different energy policies could positively influence stakeholders, gain investor confidence, and subsequently contribute to the global community. The financial valuation of factors that are important for RET introduction, pertaining to the risks of RETs, are described through a systems dynamics approach. Specifically, issues in the social and environmental spheres are discussed by means of a Southern African case study. By applying such an approach, through a further research agenda, it is envisaged that RET implementation may be accelerated. Keywords: energy finance, system dynamics, renewable energy, Africa. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESU090251
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Introduction
Energy plays a critical role in the development process, first as a domestic necessity, but also as a factor of production, where cost directly affects prices of other goods and services [1]. Although better energy supply does not automatically guarantee an acceleration of human development, it is a prerequisite for it. Energy affects all aspects of development – social, economic, and environmental – including livelihoods, access to water, agricultural productivity, health, population levels, education, and gender-related issues. Energy also places excessive strain on investment capital in developing countries. It is not uncommon for an African country to spend in excess of 30% of its development budget on the energy sector; limiting the need for capital expenditure in the energy sector could therefore free up resources for other pressing needs. Therefore, ensuring the provision of adequate, affordable, efficient and reliable high-quality energy services with minimum adverse effects on the environment for a sustained period is not only pivotal for development, but crucial for African countries, most of which are struggling to meet present energy demands. Furthermore, the continent needs such energy services to be in a position to improve its overall net productivity and become a major player in global technological and economic progress [2]. The UN Millennium Development Goals (MDGs), especially MDG 1, i.e. reducing the percentage by half of people living in poverty by 2015, cannot be met without major improvements in the quality and magnitude of energy services in developing countries. In addition, lack of access to such services often exacerbates poverty and leads to unacceptable health risks, for example through exposure to indoor air pollution resulting from cooking with traditional biomass fuels. Africa has a landmass of just over 30.3 million km2, an area equivalent to the US, Europe, Australia, Brazil, and Japan combined. As of 2004, Africa housed 885 million people in 53 countries of varied and diverse sizes, sociocultural entities, and resource endowments, including fossil and renewable energy (RE) resources [3]. Most of these energy resources are yet to be exploited, which is a contributing factor in making the continent the lowest consumer of energy. An African uses only one eleventh, one sixth, and one half of the energy used by a North American, a European, and a Latin American, respectively. There is an urgent need for substantial increases in energy consumption in Africa as a whole if Africa is to become competitive with other developing regions of the world [4]. The Southern African Development Community (SADC) is a treaty organisation comprising 15 member states in the Southern African region. The ultimate objective of SADC is to “build a region in which there will be a high degree of harmonisation and rationalisation to enable the pooling of resources to achieve collective self-reliance in order to improve the living standards of the people of the region” [5,6]. Southern Africa is rich in natural energy resources. With abundant hydropower potential in the north, vast coalfields in the south, oil reserves off the west coast, and fertile land, there is a definite potential to supply low cost energy in the region. However, the disparate distribution of natural, WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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human, and capital resources in the region, as observed in any other transitional country, necessitates regional coordination and cooperation to ensure the development of an efficient and reliable energy system. Trade can improve the security of supply though diversification of supply and sharing of reserve margins. This paper investigates the potential for RET in SADC countries, in particular South Africa, by emphasising the energy geography in Africa, financial aspects thereof, and limitations to RET adoption; future energy paths, with an increased share of RE in the African energy mix, are suggested. It is believed that the paper will assist energy policy makers and future players in the development of sustainable energy finance (SEF), not only in the Southern African context, but also in other transitional and developing countries.
2
International investment climate for RET
The concept of sustainable energy finance (SEF) combines RE and activities for energy efficiency. It is important to distinguish between energy investments for poverty reduction, and for industry and economic development purposes. Carbon Finance (CF) has evolved from the need to develop carbon markets. These entail tradable instruments, such as certificates from Emissions Trading, the Clean Development Mechanism (CDM) and Joint Implementation (JI), all established in the Kyoto Protocol, i.e. articles 17, 12, and 4, respectively. The history of the underlying concepts for carbon trading started in 1968. Flaws of these mechanisms are the insignificant role played by JI projects, the so-called ‘additionality’ requirement of the CDM, and challenges related to the need for projects to assist developing nations achieving sustainable development [7]. The Global Environment Facility (GEF), the financial mechanism for the United Nations Framework on Climate Change (UNFCCC), currently represents the largest source of funds for RE to developing countries. $900 million have been assigned to 110 projects in 50 countries leveraging nearly $6 billion of added co-financing [8]. Its role is in need for redefinition. In particular, it would ease CF processes immensely if it took a more central, rather than peripheral role. The design of a future global carbon finance market is yet to be defined [9]. RE options are becoming economical in the marketplace, due to the simultaneous decrease in technology costs and rising fossil fuel prices. The design of an energy system incorporating renewables from an energy system that was built around fossil fuels is more than a challenge. Distribution networks and infrastructure are designed around carbon-intensive energy carriers. Funds currently in place are restricted in time until 2012, which more resembles a trial period rather than establishing a “long-term architecture of global environmental funding” [9]. To support the adoption of RETs, sources of investment are needed by developing countries to circumvent the unsustainable energy paths that other, more developed countries, in the world have taken. Funding could be raised from public or private sources, carbon finance, and multilateral funding. The Pew Center on global climate change sketches a technology funding framework for WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
282 Energy and Sustainability II the period after 2012 [10]. The establishment of a clean energy fund in the African region, the African Biofuels & Renewable Energy Fund (ABREF), also addresses the uncertainty about the post-2012 carbon market setting. The fund aims to exploit Africa’s underexploited resources with a financing strategy between export credit agencies and commercial banks from the viewpoint of perceived risk and bankability. Building on the three pillars climate change, carbon market opportunities and energy security, ABREF manages project performance risk and failure to deliver carbon credits, and it mitigates the market risk that stems from uncertainty in the carbon market. It reports on the number of projects as of April 2008 in the pipeline, where biofuels (14) and solar energy (13) rank second and third after hydro (21) [11]. Many carbon funds (11) have been established under the supervision of the World Bank and another 60 carbon funds have come into being [12]. If the World Bank were to become the central agency for climate change finance, a bias may be introduced towards the interests of industrialised nations [8]. To ensure quality of CDM and JI projects, a gold standard has been proposed to make them comparable and effective. A similar function to ensure best project results is provided by environmental due diligence (EDD) procedures [13, 14]. Sustainable energy (SE) as an investment sector has been on the rise over recent years. Despite RE only serving 5% of global capacity and 3.4% of global power generation, 9.4% of global energy investing and 23% of new electricity generating capacity are based on renewables [15]. Investments have been projected to reach around $450 billion by 2012 and $600 billion by 2020 [16]. Recent increases in the RE investment sector showed that it is able to raise the $200-210 billion needed yearly to return global greenhouse gas (GHG) emissions to current levels, according to the UNFCCC Secretariat. The Copenhagen meeting of the climate convention is approaching, where “governments must reach agreement on a new and decisive climate agreement”; there is a need for carbon markets to evolve and be fostered to achieve their potential of cleaning up current energy infrastructures [16]. Africa strongly lags behind other regions such as India, China, and Brazil. Energy in Southern Africa is largely underexploited, though at the same time presents an unprecedented opportunity to choose “a cleaner development pathway via low-carbon energy alternatives that can reduce GHG emissions and, at the same time, meet current suppressed energy demand and future needs more efficiently and affordably” [12]. Sub-Saharan Africa can gain most from RE. Moreover, this region is stated to be the only one which is not likely to reach the MDGs by 2015 [16]. The role of energy in reaching the MDGs is highlighted in a study by the Forum of Energy Ministers of Africa (FEMA). However, despite the study’s important contribution by identifying links of achieving the MDGs and energy, no priority is assigned to RE [17, 18]. Policies and investment need to be shaped in accordance with the formulation of a coherent strategy to reach the targets set to enable climate change mitigation [19]. The current state of South Africa’s RE sector, for example, is marked by pilot projects, powered by the state-owned electricity utility Eskom. South Africa’s energy service provision structure is largely directed by Eskom. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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Electricity prices, though currently on the rise, are inexpensive in South Africa; one reason being that the true cost of facilities is not accounted for. Feeding externally generated electricity into the grid is currently not possible. The pilot projects in South Africa in line with the South African Bulk Renewable Energy Generation Programme comprise different solar technologies, wind, and biomass [17]. Depending on the energy carriers and technology and equipment needed to convert the energy for consumption, REs differ in their cost structures. The cost of wind and solar energy from the nature of the source used could be accounted for in financial models as a zero fixed cost, while the cost for biofuels is mostly given by feedstock cost, e.g. up to 85% of biodiesel production cost. The dominance of feedstock contribution to total cost decreases orderly as agricultural feedstock, industrial by-products and waste materials are used [20]. While some renewables may incur higher capital costs, immense savings can be achieved in operating costs as compared to fossil fuels or nuclear energy. A comparison of cost, energy supply, and job creation for solar water heaters and the pebble bed nuclear power plant, the construction of which was considered in South Africa has been given and is depicted in Table 1 below [17]. Table 1:
Solar water heaters compared to pebble bed technology nuclear reactor, source: [17], Forex rates (24-02-2009): 1 EUR = 12.73 ZAR, 1 USD = 10.00 ZAR [http://www.xe.com/].
Energy saved/supplied Cost Creation of jobs
Solar water heaters
Pebble bed nuclear power plant
890 GWh/annum ZAR 2.6 billion 13 440 jobs
750 GWh/annum ZAR 10 billion 135 jobs
3 Barriers to RET adoption and a system dynamics-based approach in the Southern African energy context For developed countries, RE sources primarily serve as a means to diversify the national energy supply and a means by which the concept of sustainable development can be implemented, and GHG emissions reduced. However, for developing countries such as those in Africa, RET in general plays a very different role. There is a major difference in the background motives and a resulting performance gap between the South and the North in terms of harnessing RE. Therefore, it has become important to fill this gap with experiences gained in the developed world, but adapted to the needs of developing countries. The fundamental problems to commercialise RETs exist in both developed and developing countries. However, their magnitude and characteristics are more pronounced in developing countries. The multi-dimensional differences among regions and countries make the analysis of the magnitude of these hurdles more complex. Despite national differences, it is possible to generalise some barriers, which have been extensively discussed [2]. For example, various generic barriers WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
284 Energy and Sustainability II currently identified to hinder the adoption and commercialisation of biofuel technologies in Africa, apart from the high cost of raw materials and other economics related constrictions, may be categorised as technological and nontechnological (policy, legal, financial, institutional, cultural, social, etc.) constraints. Table 2 gives a schematic view of barriers to accelerated adoption and commercialisation of RETs in Africa. These barriers are common to RE: • Type A: Technologically advanced developing countries, with well diversified and fairly comprehensive industrial, energy and R&D infrastructures – only South Africa. • Type B: Technologically advancing developing countries, which are industrialising fairly fast, but are still quite limited in the diversification of their industrial, energy and R&D infrastructure, e.g. Egypt, Morocco, and Algeria. • Type C: Slowly industrialising developing countries, with still very limited infrastructure in industry, energy and R&D, such as Nigeria, Mauritius, and Libya. • Type D: Technologically least developed countries: Most sub-Saharan African countries, e.g. Ethiopia, Chad, Burundi, Mozambique, Ivory Coast, Niger, DR Congo, Somalia, Mali, and Sudan. Table 2:
Schematic barriers assessment on a classified country basis, source: [2] Low:*, Medium: **, High: ***.
Countrytype
Institutional/ policy hurdle
Technical hurdle
Economic hurdle
Financial hurdle
Information hurdle
Capacity hurdle
Type A
**
*
**
**
*
*
Type B
**
**
**
**
**
**
Type C
***
**
***
***
***
**
Type D
***
***
***
***
***
***
Threshold-21 (T21) models [21] that dynamically link economic, environmen-tal, and societal aspects of a country, sector, or company, have been formulated by the Millennium Institute for Mali, Malawi, South Africa, and Mozambique. Other African countries have also been investigated and modelled to enhance an understanding of policies to support sustainable development and the achievement of the MDGs. The strength of system dynamics models lies in their ability to directly evaluate consequences of different policies [22]. The energy sector has been investigated exclusively in South Africa with a T21 approach, and is detailed elsewhere [23]. The T21 system dynamic model was developed for integrated policy planning to outline future energy paths for South Africa. The study draws on the current energy context in South Africa and WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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projects different energy mix policy scenarios until 2030, using the T21 framework [23]. Energy efficiency measures are considered as well as the influence of GDP, energy price, and demand and supply balances. In this paper the dynamic modelling of the energy sector of South Africa is used as an example with particular attention to biofuels development in the Eastern Cape Province of the country, and possible impacts of such developments on the country’s energy supply as well as consumption patterns. The Eastern Cape Department of Agriculture (ECDoA) is embarking on a large scale biofuels production project that includes the construction of a biodiesel plant in East London, a large city in the Eastern Cape Province, and the development of 500 hectares of land to grow, amongst others, canola and soybeans for biodiesel production. This project is to leverage the Mass Food Production Programme of the Province, which is already in place, and to bring numerous benefits to communities, such as the creation of approximately 350 jobs, Black Economic Empowerment (BEE), empowerment of local farmers, skills development, and food security, since biofuels are not to be produced from maize, which is the staple food for many South Africans. Many potential pitfalls of biofuels production are addressed by dry-land crop cultivation, off-take agreement contracts to prevent adverse effects of price volatility in raw materials, as well as stringent control in the choice of contractors. Exports to other SADC countries that currently import internationally would save transaction costs. The already existing oversupply of glycerine is to be addressed by the development of alternative uses for glycerine and the erection of a methane gas facility is planned to process surplus oilcake [24, 25]. The ECDoA case is used as basis to pave the way for incorporating financial valuation methods to dynamic modelling techniques. By considering, first, South Africa and one of its provinces, African-specific factors to consider would be identified that are also relevant for a future SADC model for RET introduction.
4
Representing the process of sustainable energy finance (SEF) for development
Dynamic modelling techniques have already been shown to contribute to energy modelling, and the evaluation of alternative energy paths. The financial assessment of different energy paths could be facilitated by two methodologies, i.e. the sustainable value (SV) and real options (RO) approach. 4.1 The sustainable value (SV) approach SV assesses the contribution of a company in terms of sustainability and the efficiency with which it uses its resources. It enables environmental performance to be measured in monetary terms, where not only capital, but also environmental and social resources, are considered. SV accounts for different economic actors using resources in different ways to create several possible outputs. The results of their respective activities are weighed in relation to the resources used WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
286 Energy and Sustainability II in the course of such activities. Whenever the resource is used in a better way than possible alternative uses, value is created in financial terms [26]. SV has been applied on company level where a benchmark, such as a stock exchange index, is used to compare performance. If the SV of the company is larger than what could have been achieved with the same resources by the benchmark, value above the opportunity costs, (the equivalent performance of the benchmark had the resources been invested in the benchmark instead of the company) is created. SV enables a differentiation between individual resource uses, and their assessment in sustainable terms. In this way emissions, pollution and health hazards could be rated individually and one may determine which of these costs are incurred in the process of activities in a value-creating way. It “reflects how well companies have reconciled economic output and environmental and social stewardship” [26]. SV aids in decisions regarding the consequences in generating return by the allocation of resources to different possible uses by showing “how a limited and scarce amount of resources should best be used in order to generate highest returns” [26]. SV does not replace other approaches to sustainability assessment. An inherent assumption on the workings of financial markets is that opportunity cost thinking will positively affect the efficiency of resource use. Approaching the development of an emerging market with opportunity cost thinking involves identifying existing resources that would be consumed by RET and the consequences of taking different energy or RE paths. Profit potential, costs and impacts on society and economies of a country may be assessed in monetary terms besides qualitative factors involving quality of life and gender equity. In the SADC context of RET introduction, the SV methodology could be applied in the valuation of alternative uses of resources. The environmental effects of different energy paths as well as vulnerability to future emissions reduction targets can be evaluated [26]. 4.2 The real options (RO) approach The RO approach assesses economic performance by evaluating alternative uses, focusing only on financial measures. They may be incorporated in the analysis through the assessment of when to invest in one or more RETs in a specific country cluster, sector, or area. Furthermore, multiple stakeholders, their actual interactions, as well as believed interactions are important to integrate. Modelling techniques and learning tools to fully understand the consequences of decisions are valuable for investments that are not easily reversible. Modelling techniques that can deal with uncertainty in price fluctuations or changes of fossil fuels and the expected change in prices for renewables would be able to pinpoint the breakeven point of when a technology becomes competitive and under what circumstances it would stay competitive. The RO approach has been used to develop a dynamic programming model for RET diffusion, which features uncertainties in the energy sector and the flexibility to delay. They highlight the use of more sophisticated valuation techniques, the need for financial incentives and the important role of targeted RET policies to achieve widespread adoption [27]. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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Combining sustainable efficiency using the SV and RE approaches with a model flexible enough to incorporate future changes in economy, politics, society, technology and environment in consideration of requirements and resources in the African context, will aid to pave a financially sound energy path. In view of the above, it is important to consider the risks associated with RET introduction. Risks and mitigation steps were identified for the biofuels project in South Africa. These include market related risks, operating model risks, risks of financial evaluation and funding, as well as project implementation and evaluation and regulatory risks [24]. In a study of climate change for the financial services industry the United Nations Environment Program (UNEP) proposed recommendations for different players in CF [28]. These include the industry as a whole, insurance and reinsurance companies, asset managers, pension funds and financial analysts, investment banks and consultants, political decision makers, and governments in industrialised countries. The recommendations follow the lines of progressive long-term orientated strategies for incorporating climate change and its consequences in the financial sector, as well as raising awareness of the linkages that have not yet been broadly accepted [28]. Approaches from Bayesian statistics have been applied to financial analysis and investment decision support to identify risk measures in valuation processes and future value drivers and cash flows [29].
5
Conclusion and future research agenda
Energy is a key factor in industrial development and the provision of vital services that improve the quality of life. However, its production, use, and byproducts have resulted in major pressures on the environment, both from a resource use (depletion) and pollution point of view. Limited access to energy is a serious constraint to development in the developing world, where the per capita use of energy is far less than in the industrialised world. RET could assist in achieving sustainable development in Africa and keep the UN MDGs on schedule. The decoupling of inefficient, polluting fossil energy use from development represents a major challenge of sustainable development. The long-term aim is for development and prosperity to continue through gains in energy efficiency rather than increased consumption, supported by a transition towards the environmentally responsible use of renewable resources. RETs offer developing countries some prospect of self-reliant energy supplies at national and local levels, with potential economic, ecological, social, and security benefits. Achieving the widespread implementation of RETs may be realised through proper understanding of policies, economics, and financial levers. NEPAD and the African Union (AU) both have roles to play in developing rational energy policy and encouraging biofuel investment across the continent. Information exchange and experience sharing should be encouraged amongst institutions and practitioners that are engaged in RET development.
WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
288 Energy and Sustainability II Having sketched the landscape of RET investment internationally, as well as specific to the Southern African region, the paper proceeded to describe barriers to its adoption followed by examples of system dynamic modelling for RET embedded in the South African energy market. Tools combining system dynamic and other dynamic modelling approaches are needed for the development of a coherent framework for financing RET options in Southern Africa, time investments and to assess and address related risks. The future research aim is to develop and implement a dynamic model that would be able to capture the problems posed by RETs in the SADC context, and to propose solutions for policy guidance. The previous section has built on the scenario sketched in this study to address the challenges of the SADC region to open the door to a SE path. Learning from South Africa has shown the feasibility of RE projects to some extent, and simultaneously highlighted serious challenges impeding the effective development of RE markets in Southern Africa. Future research will entail a competitive analysis of RET opportunities in SADC countries using critical factors, such as government subsidies and willingness to invest, regional policies in place, the presence of a formal strategy plan for RE, the availability of risk capital, the RET industrial scale, local commercial sector commitment to participate in production and marketing, and availability of raw materials. These factors will be analysed as a composite of their relative ranking of a key attractiveness factor for RET and will be compared amongst several countries in the SADC region. The outcome is to be a matrix of summary measures, which may assist in attracting commercial activity.
References [1] New Partnership for African Development (NEPAD) conference report. Abuja, 2001. http://www.uneca.org/eca- conferencereport/NEPAD.htmlS. [2] Amigun B., Sigamoney, R. & von Blottnitz, H., Commercialisation of biofuel industry in Africa: A review. Renewable and Sustainable Energy Reviews, 12, pp. 690–711, 2008. [3] World Development Report. World Bank: Washington DC, 2005. [4] Davidson, O., Chenene, M., Kituyi, E., Nkomo, J., Turner, C. & Sebitosi, B., International Council for Science (ICSU). Regional Office for Africa Science Plan. Sustainable Energy in sub-Saharan Africa, 2007. http://www.icsu-africa.org/sustainable_energy_rep_2007.pdf [5] Transformation from Conference to Community, 2008. http://www. sadc.int/index/browse/page/53. [6] Alfstad, T., Development of a least cost energy supply model for the SADC region. M.Sc Thesis in Engineering, unpublished, 2005. [7] Bond, P. & Erion, G., South African carbon trading: A counterproductive climate change strategy. Electric Capitalism - Recolonising Africa in the Power Grid, ed. D.A. McDonald, HRSC Press and earthscan: Cape Town and London, 2009.
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[8] Fleming, C., The GEF and Renewable Energy, 2005. http://www.gefweb.org/Projects/focal_areas/climate/documents/GEF_and_ Renewable_Energy.pdf. [9] Porter, G., Bird, N., Kaur, N. & Peskett, L., New finance for climate change and the environment, 2008. http://www.odi.org.uk/fecc/ resources/reports/s0178 final report.pdf. [10] Technology Funding in a post-2012 Climate Framework. Pew Center on Global Climate Change, 2008. http://www.pewclimate.org/ docUploads/BackgroundNoteTechFunding.pdf. [11] Memorandum of Information for African Biofuels & Renewable Energy Fund, 2008. http://www.faber-abref.org/fichiers/Note FABER. pdf. [12] Faurie, J., Low-carbon Energy Projects for Development in Sub-Saharan Africa - Unveiling the Potential, Addressing the Barriers, 2009. www.carbonfinance.org/docs/Main_Report_Low_Carbon_Energy_projects _for_Development_of_Sub_Saharan_Africa_8-18-08.pdf , http://www.envirovaluation.org/index.php/2008/09/21/low-carbon-energyprojects-for-developme [13] Kenber, M. & Salter, L., The Gold Standard: Quality Standards for CDM and JI Projects. WWF, 2002. http://www.energy-base.org/fileadmin/ media/base/downloads/toolsEDD/eddgeothermal.pdf, http://www.wwf. or.jp/activity/climate/lib/kyotoprotocol/COP8standards.pdf. [14] Environmental Due Diligence (EDD) of Renewable Energy Projects Guidelines for Geothermal Energy Systems. UNEP, BASE, n.d. http://www.energybase.org/fileadmin/media/base/downloads/toolsEDD/edd geothermal.pdf. [15] Renewables 2007 Global Status Report. World Watch Institute, 2007. http://www.worldwatch.org/node/5633. [16] Boyle, R., Greenwood, C., Hohler, A., Liebreich, M., Sonntag-OBrien, V., Tyne, A. & Usher, E., United Nations Environment Programme, Global Trends in Sustainable Energy Investment 2008, Analysis of Trends and Issues in the Financing of Renewable Energy and Energy Efficiency, 2008. http://sefi.unep.org/fileadmin/media/sefi/docs/publications/GlobalTrends 2008.pdf. [17] McDaid, L., Renewable energy: Harnessing the power of Africa? Electric Capitalism - Recolonising Africa in the Power Grid, ed. D.A. McDonald, HRSC Press and earthscan: Cape Town and London, 2009. [18] Energy and the Millennium Development Goals in Africa. The Forum of Energy Ministers of Africa (FEMA), 2006. http://www.esmap.org/filez/ pubs/FEMAForPrintshop.pdf. [19] Flavin, C., Low-Carbon Energy: A Roadmap, 2008. http://www.worldwatch.org/taxonomy/term/37. [20] Amigun, B., Processing cost analysis of the African Biofuels industry with Special Reference to Capital Cost Estimation Technique. PhD Thesis, unpublished: University of Cape Town, 2007.
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290 Energy and Sustainability II [21] Bassi, A. M., Modeling U.S. Energy with Threshold 21 (T21), 2006. http://www.systemdynamics.org/conferences/2006/proceed/papers/BASSI2 05.pdf. [22] Africa region. Millennium Institute, 2009. http://www. millenniuminstitute.org/projects/region/africa/. [23] Musango, J. K., Brent, A. C. & Bassi, A. M., South African energy Model: A systems dynamics approach. Conference of the Systems Dynamics Society, Albuquerque, New Mexico, USA., 2009. [24] ECDoA, Business plan for an integrated dry-land cropping and processing plan for rural development in the Eastern Cape. unpublished, 2007. [25] Jansen, W., ASGISA Eastern Cape integrated cropping and biofuel development programme. KPMG, 2008. www.sacities.net/members/ pdfs/3.1.2_eastern-cape_case_study.pdf. [26] Figge, F. & Hahn, T., Sustainable Value of European Industry - a Valuebased Analysis of the Environmental Performance of European Manufacturing Companies, 2006. http://sefi.unep.org/fileadmin/media/ sefi/docs/industryreports/advancesurveyfullversion.pdf. [27] Kumbaroglu, G., Madlener, R. & Demirel, M., A real options evaluation model for the diffusion prospects of new renewable power generation technologies. Energy Economics, (30), pp. 1882–1908, 2008. [28] Das Klimarisiko für die Weltwirtschaft / Climate Change and the Financial Services Industry. UNEP Finance Initiative: Paris. http://www.gci. org.uk. [29] Bals, C., Mainstreaming of climate risks and opportunities in the financial sector. http://www.climate-mainstreaming.net/.
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Energy from biomass: decision support system for integrating sustainability into technology assessment P. Lacquaniti & S. Sala University of Milano Bicocca, Department of Environmental Science, Italy
Abstract The Kyoto Protocol set specific targets of CO2 reduction and furthermore, the European climate and energy policy package by 2020 fixed a set of actions encompassing: cutting energy consumption by 20% of the projected 2020 levels by improving energy efficiency; cutting greenhouse gases by at least 20% of 1990 levels; and increasing the use of renewable energy (wind, solar, biomass, etc) to 20% of total energy production. Within this context, a number of actions have to be implemented in order to comply with environmental targets, in particular defining a framework for energy planning at the local scale. To be sustainable, the energy planning process at the local scale requires an integrated assessment to individuate the best solution, considering resources of all types (physical, human and capital) available in the specific context. Many environmental, economic, technological and social issues should be considered to define the sustainability level of a technological choice. In this study, we present a decision support system (DSS) for assessing the sustainability of using local biomasses as an energetic source. The aim of the research is to define a set of indicators to assess the feasibility of the exploitation of biomass sources, the underlying critical issues and potential areas of optimization, providing a valuable DSS for decision makers. This work was based on the analysis of the different energetic potentialities of local contexts in terms of forest biomass resources availability, also taking into account local environmental, economic and social conditions. The assessment of environmental, economic and social sustainability of a plant producing electricity powered by Syngas, which comes from the gasification of woody forest biomasses, was performed. The case of an Italian mountain community (Comunità Montana delle Alpi Lepontine) in northern Italy is presented. Keywords: biomass, sustainability assessment, gasification, renewable energy, energy planning. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESU090261
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1
Introduction
Recently, the European Council has enacted the EU’s Climate and Energy Policy, providing a major contribution to reduce climate change impact and trying to overcome difficulties in reaching the Kyoto Protocol’s objectives. The European Climate and Energy policy package by 2020 fixes a set of actions encompassing: cutting energy consumption by 20% of the projected 2020 levels by improving energy efficiency; cutting greenhouse gases by at least 20% of 1990 levels; and increasing the use of renewable energy sources (wind, solar, biomass, etc) to 20% of total energy production. According to the principle of subsidiarity, European Policy requires the involvement of local communities in energy planning at different levels. Among renewable energy sources, an important role is attributed to biomass resources, considering their versatility of use and actual and potential exploitation of this resource, as shown in table 1 (Parikka [1]). Table 1:
Biomass energy potentials and current use in different regions (EJ/a) (EJ= 1018).
Biomass Potential Woody biomass Energy crops Straw Other Potential Sum (EJ/a) Use (EJ/A) Use /potential (%)
North America 12.8 4.1 2.2 0.8 19.9 3.1 16
Latin America 5.9 12.1 1.7 1.8 21.5 2.6 12
Asia
Africa
Europe
7.7 1.1 9.9 2.9 21.4 23.2 108
5.4 13.9 0.9 1.2 21.4 8.3 39
4.0 2.6 1.6 0.7 8.9 2.0 22
Middle East 0.4 0.0 0.2 0.1 0.7 0.0 7
Former USSR 5.4 3.6 0.7 0.3 10.0 0.2 5
World 41.6 37.4 17.2 7.6 103.8 39.7 38
The term “biomass” covers a very large and very heterogeneous number of organic materials, vegetables or animals, which involve different methods of energy production. Energy production may be directly through combustion or indirectly through, e.g. fermentation or gasification. The development of energy systems based on the use of biomass can be advantageous for the following reasons: widespread resources are available; biomass has the capacity to penetrate every energy sector: heating, power and transport; bio-fuels can be stored easily and bio-energy produced when needed; bio-fuels are generally bio-degradable and non toxic, which is important when accidents occur. Nevertheless, bio-energy expansion encounters several barriers: costs of bioenergy technologies and resources; amount of externalities included in the cost calculations which strongly affect competitiveness; resource potentials and distributions; local land-use and environmental aspects, especially in the developing countries; administrative and legislative bottlenecks (EUBIA) [2]. Indeed, biomass exploitation‘s technologies are many, from the boiler to produce domestic heat to central heating plants and combined heat and electricity plants for cogeneration. Thermo-chemical energy conversion processes (“dry way”) are mainly used for forest biomass: thermo chemistry conversion plants are based on combustion, gasification and pyrolysis processes. Some forest WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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biomass features are particularly appropriate for the gasification process, such as high volatility, the high reactivity of carbon, low ash and sulphur content. In addition to heat, derived fuels used to power electricity generating engine can be obtained from gasification and pyrolysis. Use of biomass as energetic source can be considered sustainable in relation to: the reduction of energy dependency on energy imports; the increased security of supply; the climate change mitigation; the zero emission of CO2 in atmosphere in a global balance. Although technology solution are many, before evaluating the feasibility of the a technological solution in a specific local context, it is important to define guidelines for assessing sustainability of local biomasses sources exploitation, underlying critical issues and potential areas of optimization. A methodology for sustainability assessment is important to support local energy planning, taking into account several technological options to optimise local resources exploitation and to promote positive effects in the specific context.
2
Technology sustainability assessment
Sustainable development is recognised as the “development that meets the needs of present generations without compromising the ability of future generations to meet their own needs [3] staying within system carrying capacity limits”. Sustainability concept refers to the integration of environmental, economic and social dimensions of development. Therefore, sustainability assessment of a technology requires a complex and multidimensional evaluation performed in order to consider a number of different issues and to take into account local context conditions. This complex and multidimensional evaluation can be performed using a Decision Support System (DSS). A DSS can be defined as an interactive system that is able to produce data and information and, in some cases, even promote understanding related to a given application domain in order to give useful assistance in resolving complex and ill-defined problems [4]. In the context of the present work, a DSS was developed to assess sustainability of a technological application for the energy exploitation of forest biomass taking into account specific local condition, defining a set of sustainability criteria and indicators based on local environmental, economic and social context. A set of specific indicators is developed to assess the performance of a number of potential options for the implementation of forest biomass system exploitation. This may help decision makers in choosing not only the technology that seems more efficient, in theoretical condition, but the best solution in the specific local context. Therefore, the proposed methodology is developed widening previous approaches, concerning sustainability indicators for particular energy exploitation, such as those in [5, 6]. The approach is typical of multicriteria analysis for decisions on projects/systems that may have potential environmental impacts. This is a WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
294 Energy and Sustainability II particular DSS application, where each indicator is individually assessed and the aspects of the problem are analyzed using specific techniques [7]. These models application is wide recognised as a useful tool for decision making [8]. This work refers to quantitative cardinal scales, which are a tool for multicriteria analysis application where all used indicators are related to a conventional scale with the aim to allow comparability between different criteria, reducing heterogeneous values to comparable measures [9]. This approach can be useful because sustainability indicators refer to different areas, not directly comparable, i.e. environmental, economic, social and technological ones. 2.1 Methodology description The methodology allows assessing the sustainability level of a technological option applied in a specific context, taking into account sustainability criteria. Sustainability criteria are defined considering also other studies on energy system assessment based on biomass exploitation [10]. Considering forest biomasses, sustainability criteria for a technological solution are: use of local resource considering carrying capacity of the system (forests where substantial limitations to an intensive management doesn’t subsist and the system resilience is good); short supply chain (resource use within 70 km distance from production/supply site) greenhouse gases compensation ability, limited environmental impact, financial profitability, capability of positive economic and social effect in the local context. A comparison may be done among a number of different technologies to choose the best option in term of environmental, economic and social performance. In literature, a number of studies assess impact of RES (renewable energy sources) deployment assessment or evaluate the amount of materials used in relation to energy produced by a particular RES energy system [11], but only some attempts to integrate social -economic aspect in RES assessment are available [12]. The present study extends the perspective of the assessment of energy systems sustainability, performing an integrated assessment of environmental, economic and social issues. To choose the best option, the steps of a technology sustainability assessment may be listed as follows: 1. collecting information about available technological options for biomass exploitation to populate technological efficiency indicators 2. collecting information about local resource, environmental, social and economical condition to populate indicators of: resource availability; environmental impact; economic efficiency; social impact related to the specific technological option 3. definition of an optimum of application 4. score attribution to each indicators, related to level of achievement of the optimum and development of an aggregated index 5. comparison among sustainability level achieved by each technological option WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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Technological option
Resource availability
Environmental impacts
Economic efficiency
Social impacts
performance
performance
performance
performance
Index aggregation
Sustainability level
Figure 1:
Technological sustainability assessment.
Figure 1 shows the conceptual scheme for sustainability assessment. Focusing on indicators, among the previews categories, some indicators are directly related to the particular technological application; others indicators do not depend directly on the technology, but they depend on the context (environmental, economic, social and political context) in which technology has to be implemented. All indicators were individually assessed by comparing the value obtained in the specific case study with potential value of optimum situation of implementation. This methodology is suitable to assess a wide range of technologies, regardless of the type of application. For results aggregation, the information expressed by indicators has been normalized on a conventional scale, therefore the results can take values between 0 and 1, where 1 represent optimal solution. Sustainability level achieved by application come from values achieved by each indicator according to considered sustainability dimensions and is expressed as a percentage of achievement. 2.2 Technological efficiency indicators Sustainability assessment requires, firstly, to gather technology characteristics of the chosen option related to the used resource. In table 2, the technological indicators are listed. 2.3 Resource availability indicators Resources availability indicators are listed in table 3. They are directly related to local context in term of biomass availability (quantity, quality and accessibility) because potential resource in term of quantity/ quality could be not usable due to lack of local resource supply capability. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
296 Energy and Sustainability II Table 2:
Technology’s characteristics.
Indicator
Definition
BC
Minimum amount of primary resource Biomass consumption needed to implement the chosen technology.
Name
Unit Kg/h
FR
Replacing fossil fuel ability.
Replacing fossil fuel
toe/y
TE
Technological energy conversion efficiency based on used resource.
Technological efficiency
kWhe/kg
Toe= tonnes oil equivalent.
Table 3:
Resource availability indicators.
Indicator
Definition
Name
Unit
BA
Actual woody biomass for energy conversion available in the local territory.
Biomass availability
t/y
BE FA
Available woody biomass energy content. Biomass energy content Accessibility level assessment related to Forest accessibility forest paths presence.
BT
Woody biomass transport system.
LE
Land use assessment to individuate which Land use portions can be used.
Table 4:
Biomass transport
kcal/kg Km Km ha/use
Environmental impact indicators.
Indicator
Definition
Name
EI
Potential environmental impacts with reference to local national/regional Environmental impacts law.
AE
CO2 avoided emission through chosen CO2 avoided emission technology use.
Unit Related to law limits for each environmental issues tCO2/y
Several capabilities (technological, logistic, management) are required to exploit biomass resource. For a complete survey, also spatial aspects related to materials movement have to be taken into account, especially accessibility: an index of the relative ease of travel between two or more areas in terms of distance, time and cost has been included in the assessment. Furthermore, in a complex landscape context, land use distribution and forest patches dimension are crucial indicators. 2.4 Environmental impact indicators Indicators of environmental impact are related to environmental consequences of implementation of energy exploitation system of forest biomass (table 4). The potential environmental impacts are related to air, water, soil, waste production and noise. Impact on biodiversity could be also considered, but a specific methodology of assessment needs to be developed [13]. A specific indicator is related to CO2 avoided emission in order to assess the specific contribution of technology implementation in the achievement of CO2 reduction target. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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2.5 Economic efficiency indicators Economic efficiency indicators reflect the performance of implementation of chosen technology. In tables 5 and 6 indicators related to economics of the specific technology (table 5) and economics issues related to local context (table 6) are listed. 2.6 Social impact indicators Social sustainability of a technology is commonly related to social acceptability. Other important social issues are related to: possibility of generating local employment (for biomass supply or to manage the plant); stakeholder’s involvement in terms of level of commitment of the political–administrative context in which the plant is foreseen to be implemented; ownership of land, because public or private land properties could affect the resources availability. In literature, it is possible to find some attempts of social indicator integration [12]. Social indicators are listed in table 7. 2.7 Indicators aggregation To establish a sustainability level of chosen technology it is necessary to aggregate the gathered information. The aggregation method uses cardinal quantitative scales. Indicators are intended to express the performance of the considered application with regard to an optimally potential application. Indices that refer to a conventional scale that Table 5:
Economic efficiency indicators: technology.
Indicator
Definition
TI
Technology investment cost, in relation with Technology investment cost market availability and energy efficiency.
€/kWh
EP
Estimated value in accordance with different operating costs incurred for the investment Energy production cost over the amount of produced electricity.
€/kWh
AC
Estimated value in accordance with different operating costs incurred for the investment Avoided emission cost over CO2 avoided emission through chosen technology use.
€/kgCO2
Table 6: Indicator BS LC TP P
Name
Unit
Economic efficiency indicators related to local context.
Definition Operating costs for woody biomass supply. Labour costs required to manage global system. Economic benefits related to energy production system management. Profit of economic management.
Name
Unit
Biomass cost supply
€/y
Labour cost
€/y
Tax , proceeds
incentives
Profit
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€/y €/y
298 Energy and Sustainability II Table 7: Indicator SA EG SA PP
Social indicators.
Definition
Name
Unit
Popularity rating for the project.
Social Acceptability
%
Ability to develop an employment system within considered local context. Actual existence of entities in local context, public and private, suitable and available for implementing the chosen technology. Resource origin assessment, from public or private areas.
Employment generation
Employees number
Stakeholders
%
Private and Property
Public
ha/origin
takes values from 0 to 1 were associated to indicators values, depending on the performance of assessed indicator (value x) compared to the performance of potential optimal solution (value 1). Aggregation was done first for each set of indicators (resource availability, environmental impacts, economic efficiency, social impacts) and then globally, integrating in single information sustainability level achieved in every dimension. Sustainability of each dimension was assessed in percentage terms by summing the standardized indices of each indicator and comparing this value with the sum of standardized indices of potential optimal situations. The aggregation method: 1 Resource indicator (a) = x; optimal = x 1 Sustainability level of (a) (A) = (∑ x / ∑ x ) x 100
Environmental impact indicator (b) = y; optimal = y1 Sustainability level of (b) (B) = (∑ y / ∑ y1) x 100 Economic efficiency indicator (c) = z; optimal = z1 Sustainability level of (c) (C) = (∑ z / ∑ z1) x 100 Social impact indicator (d) = k; optimal = k1 Sustainability level of (d) (D) = (∑ k / ∑ k1) x 100 Chosen technology sustainability level = [∑ (x, y, z, k) / ∑ (x1, y1, z1, k1)] x 100
This method allows obtaining global sustainability level of chosen technology in the specific local context. This feature allows identifying the strengths and weaknesses of considered application and to assume and implement measures to optimize the system where convenient and possible.
3
Methodology application and results
3.1 Sustainability assessment of a gasification system in Northern Italy In 2007 the region of Lombardy in Italy signed up for the Energy Action Plan, based on an energetic mix analysis on regional scale. In this program, one important topic is the use of renewable sources, e.g. biomasses for energy WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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production, also supported by funds of Community Agriculture Policy (CAP) 2007-2013 and European Regional Development Fund 2007-2013. To investigate the feasibility of these actions at local scale, the methodology developed for the evaluation of sustainability of biomass use for energy production has been applied to Alpi Lepontine Mountain Community (CMAL), in Lombardy Region. Regarding technical option, a wood biomass gasification plant with production of Syngas (that can power an endothermic engine connected to a generator for electricity production) was selected. This technology was chosen for the pilot application because it allows using a wide range of organic materials and can be modulated according to the quantity of biomass which is available in the area. 3.2 Pilot application in Alpi Lepontine Mountain Community Alpi Lepontine territory consists in an area between Como Lake, in Italy, and Lugano Lake, in Switzerland, and has an extent of 18.469 ha. The territory is mainly mountainous and includes 6.844 ha of forest, mainly not managed. The territory, rich in natural, environmental and countryside resources, has a strong tourist orientation, based especially on Porlezza and its surroundings. Alpi Lepontine area can be divided in two different sub-areas: the first consists of some municipalities near Lugano and Como lakes (Porlezza and Menaggio), with relevant tourists’ flows and high levels of urbanization; the second consists of some other municipalities in mountain areas, where there are only few villages with low population density and a lower level of tourism development. Alpi Lepontine Mountain Community, which is a union of 13 municipalities, has 16003 inhabitants. Some relevant topics are identified as main threats for local development: low socio-economic development of mountain areas, low entrepreneurship, especially among young people, high level of urbanization in plain areas (related especially to tourism sector). For this reason, it was considered an interesting area for testing the methodology presented in this study. At the moment, woody biomass is used mainly in domestic biomass heating systems, with a very low efficiency and a lot of fine particulate emissions. The local authorities are developing strategic urban and energy planning in order to: promote energy production from renewable energy sources and energetic self-sufficiency; create social-economic condition to improve forest management both for recreational and energy use; maintain local economic activities related to forest (casual and permanent forest worker, sawmill, general joinery etc); reduce environmental impact related to both domestic or industrial biomass heating systems. Therefore, CMAL was directly involved in the development of the DSS, expected to be a tool to assess sustainability level of a number of technological options for local biomass exploitation. First of all, CMAL provided a forest inventory to assess the carrying capacity of the forest system taking into consideration the amount of biomass required by several technological options. A map of forest ownership was also developed in order to highlight areas where forest is managed by public authorities or by WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
300 Energy and Sustainability II private owner. Furthermore, actual and future socio-economic condition was assessed to identify areas of potential biomass related economic activities. In the present work, the example of sustainability assessment of a modular gasification system with a power of 250 kW is presented. The plant has to be realised in a mountain municipalities in order to provide heat and electricity to a renewed public building and to its surroundings. 3.3 Sustainability levels Gathering all the information required by the methodology, some interesting results about the sustainability level of the system under investigation were found. Some of the indicators included in the methodological framework cannot be evaluated because of the lack of information. Nevertheless, this lack of information was included in the evaluation and considered as a negative issue for the sustainability of the system, applying a precautionary principle. Table 8 shows an extract of final results, normalized as explained in the methodology section, with reference to every dimension of sustainability (environmental, economic and social) and to the global sustainability of the system under investigation. According to the values of the indicators considered, CMAL gets a sustainability level of 66%. Considering some results presented in table 8, it is possible to identify the issues with a lower level of sustainability, i.e. the areas in which CMAL performance can be improved. Even if TE (technological energy conversion efficiency) and P (profit of management) gets a sustainability level of 100%, BA (actual woody biomass for energy conversion available) gets 75%, local condition such as FA (accessibility related to forest path presence), and EG (ability to develop an employment system) gets only 50%. In this example, even though the technology is efficient and profitable, a further effort in the social and institutional context has to be made to achieve a 100% level of sustainability. Table 8:
Case study sustainability levels of some indicators. Sustainability level
%
Indicators TE
100
P
100
BT
75
BA
75
EI
50
FA
50
BS
50
LC
50
EG
50
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Conclusions
The DSS presented in this paper can be an operational and easily understandable tool for the sustainability evaluation of a local plan for biomass use in energy production. One of the most interesting aspects of this methodology is that it is possible to identify strengths and weaknesses of the system under investigation, supporting decision makers in the definition of actions to improve sustainability with optimal cost-benefit effectiveness. In particular, the methodology focuses on the feasibility assessment of the implementation of a specific technology in a specific area, considering all the parameters involved (e.g. local biomass availability, community acceptance, environmental impact, economic costs, etc): final aim of the evaluation is to perform a sustainability assessment which considers not only the performance of the technology under evaluation in an ideal optimal condition, but also the existing operational limits for an effective implementation in the area under investigation. Moreover, the methodology allows investigating in detail sustainability of biomass use for energy production at local scale, with particular reference to local characteristics of the area under investigation, but, at the same time, can be easily adapted also to different conditions (i.e. applied in several areas). Therefore, a further effort to integrate sustainability assessment in technology assessment has to be done. In the specific example, considering woody biomass exploitation, important issues have to be taken into account in a technological sustainability assessment: stable employment opportunities in rural areas, involvement of small and medium enterprises and possibility of a better landscape management, especially where forests are abandoned.
Acknowledgements The authors want to acknowledge Renato Ornaghi (Energy Saving) for providing data about the Syngas technology and project economics; Elena Tarelli and Luca Leoni (Comunità Montana Alpi Lepontine) for providing data about local resource availability
References [1] [2] [3] [4] [5]
Parikka, M., Global biomass fuel resources. Biomass and Bioenergy, 27, pp. 613-620, 2004. EUBIA. The European Biomass Industry Association (www.eubia.org, February 2009) consulted February 2009. WCED, Our Common Future. In: Brundtland, G. (Ed.), Oxford University Press, London. 1987 Cavallaro, F. & Ciraolo, L., A multicriteria approach to evaluate wind energy plants on an Italian island. Energy Policy, 33, pp. 235-244, 2005. Brandli, L., Kohler, R. & Frandoloso, M.A.L., Sustainability indicators for the housing market: proposal and applications. In: E. Tiezzi, J. C. Marques, C.A. Brebbia & S. E. Jørgensen (Editors) Ecosystems and WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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[6]
[7] [8] [9] [10] [11] [12] [13]
sustainable development VI. WIT Press, Southampton, UK, pp. 165-172, 2007. Oktay, M. & Dincyurek, O., An investigation on sustainability indicators of vernacular environments: the case of Cyprus. In: E. Tiezzi, J. C. Marques, C.A. Brebbia & S. E. Jørgensen (Editors) Ecosystems and sustainable development VI. WIT Press, Southampton, UK, pp. 155-164, 2007. Nijkamp, P., Multiple Criteria Analysis and Integrated Impact Analysis. Proc. of the Conf. of the International Association for Impact Assessment, Utecht, 1985. Pohekar, S.D. & Ramachandran, M., Application of multi-criteria decision making to sustainable energy planning – A review. Renewable and Sustainable Energy Reviews, 8, pp. 365-381, 2004. Zeppetella, A., Bresso, M. & Gamba, G., Valutazione ambientale e processi di decisione: metodi e tecniche di valutazione di impatto ambientale, La Nuova Italia Scientifica (Ed.), Roma, 1992. Komiyama, H., Mitsumori, T., Yamaji, K. & Yamada, K., Assessment of energy systems by using biomass plantation. Fuel, 80, pp. 707-715, 2001. Afgan, N.H., Carvalho, M.G. & Nikolai, V., Energy system assessment with sustainability indicators. Energy Policy, 28, pp. 603-612, 2000. Del Rio, P. & Burguillo, M., Assessing the impact of renewable energy deployment in local sustainability: Towards a Theoretical frame work. Renewable and Sustainable Energy Reviews, 12, pp. 1325-1344, 2008. Sala S.& Vighi M., 2008 “Risk Assessment for Biodiversity: an integrated approach” in: J Stadler, F. Schöppe, M. Frenzel editors, proceedings of EURECO – GFOE 2008 conference, p 162, ISBN 978-300-025522-9
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Recovering energy from liquid sanitary waste for Direct Alcohol Fuel Cell V. Pelillo & D. Laforgia Department of Engineering for Innovation, University of Salento, Italy
Abstract The evolution of energy systems can take place through different ways and, sometimes, by using processes already known but to be improved by the evolution of continuous research. That is the case of DAFC (Direct Alcohol Fuel Cell), known for a century, but whose operating mode consists of employing alcohol (at determined conditions). The objective of this work is not only to show the sustainability of these devices but mainly their application for supplying re-cycled ethanol and glycol, recovered from sanitary liquid waste, to be used for biomedical apparatus and plant located inside hospital pavilions, such as Neonatology, Resuscitation and Surgery rooms, where, the electric energy, must not be interruptible for safety reason because the DAFC must always be working. The proposed solution is supported by the U.E. Act (Directive 2006/12/CE) that allows waste recovery in order to produce energy. It is an innovating and alternative manner to provide a good use of sanitary liquid waste instead of sending them to common and regular disposal. Keywords: sanitary waste, cell fuel, disposal, waste recovery, waste legislation.
1
Introduction
Hospital or clinical or sanitary waste requires more particular management procedures than general waste. There are specific classifications according to each western country’s legislation. They include not only the so-called conventional waste but also the so-called unconventional ones, that is, radioactive waste. To dispose of this waste, the main technique consists of using appropriate incineration plants capable of achieving the task in such a way that the environment is protected. Different studies suggest that as much as 50% of waste sent for incineration as clinical waste is in fact general waste, leading to WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESU090271
304 Energy and Sustainability II Table 1:
European Waste Catalogue (2002) categorization of some sanitary waste.
unnecessarily high disposal costs [1]. Improved segregation can generate substantial savings. In an ideal world, segregation of waste should take place at the point of production, for example on the wards or in operating rooms. Encouraging segregation at production site may help to save money and provide a secure a correct way of disposing of hazardous materials in order to prevent irreversible damages on the environment. For the purposes of this research, we use the acceptation sanitary because it includes any waste produced by any structure where health activities are operated for the interest of humans and animals. While the acceptations hospital and clinical could generate a little bit confusing meaning. First of all, it is suitable to recall the origin of sanitary waste and its contents. Sanitary waste comes from the following sources: private and public hospitals, health centers, research facilities, health laboratories, veterinary surgeries, dental surgeries, etc. [2]. Instead, the contents consist wholly and partly of the following items: syringes, needles, glasses, human or animal tissue, swabs, dressings, excretions, blood, physiological fluids, pharmaceutical waste, incontinence bags, etc [3]. Sanitary liquids play a key role in hospitals, especially if they contain solvents that could be extracted in order to be regenerated for recycling in a new process. Improving the mechanism of waste segregation means money saving and keeping the environment safe. Different western countries, before the introduction of new regulations, namely EWC (European Waste Code) in its diverse versions, have faced the sanitary waste issue in many ways. The increasing costs and technology development may impose a new vision and a new approach for seeking to segregate waste in hospital facilities. This segregation must be enhanced especially by separating liquids from solids, hazardous from non-hazardous, flammable from inflammable. England [4], France [5] and Italy [6], for example regulated, in an
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appropriate way, the matter in the 1990s by distinguishing the type of sanitary waste and the procedures for final disposal according to [7] the WHO too. There has been an underlying disparity across Europe in the approach to the management of sanitary waste, both within hospitals [8] and in the commercial sector. Differences have been harmonized by the European Hazardous Waste Directive 91/ 689/EC (HWD), which seeks to provide a precise and uniform European-wide definition of hazardous waste, including clinical waste, and to ensure its regulation and correct management. The classification of a waste as hazardous has considerable impact in determining how that waste is regulated, and thereby on the care required at all stages from initial disposal to final destruction. A detailed classification of waste is set out in the European Waste Catalogue 2000/532/EC (EWC), an essential first step in the implementation of the HWD. EWC classification permits downregulation of some clinical waste. The EWC is pivotal to this legislation, enabling classification of waste based upon composition and hazard (Table 1). Non-hazardous waste escape stringent control in disposal that had previously been applied blanket fashion, permitting correspondingly lower disposal costs.
2 DAFC Fuel cells generate electric power from an electrochemical process using fuels such as hydrogen or methanol. Compared with batteries, fuel cells typically have a higher energy density and a lower weight. In addition, fuel cells are environment-friendly (especially if the fuel is taken from a renewable resource) and can be recharged instantly. Fuel cells are being used in prototype applications to power vehicles, cellular telephones, homes, commercial properties, laptops, household appliances and industrial machinery. Direct Alcohol Fuel Cell (DAFC) uses liquid alcohols as a fuel and is very attractive as power sources for mobile, stationary and portable applications. However, alcohols are very difficult to electro-oxidize completely and up to now methanol has been considered the most promising organic fuel. Carbon-supported PtRu nanoparticles (PtRu/C) are the best electrocatalysts for Direct Methanol Fuel Cell (DMFC), however, the synthesis of highly dispersed carbon supported PtRu nanoparticles with high loading remains a challenger. The conventional methods of preparation, like wet impregnation and reduction, do not provide satisfactory control of the particle size and distribution.
3
Waste segregation and recovery for DAFC supply
Further segregation is proposed as an effective method of reducing costs in waste disposal, and to achieve compliance with the new legislative controls that prohibit mixing of waste [9]. Directed principally to the elimination of packaging waste from the more costly sanitary waste stream, space constraints in clinical areas can present practical problems that limit the options for additional segregation. Though attractive on environmental, ecological and administrative criteria, such complex and comprehensive waste management procedures are WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
306 Energy and Sustainability II likely to succeed only in new-build hospitals where sufficient space is devoted to these core functions at the design and construction stages. Since space is at a premium in the majority of existing building stock the elimination of packaging waste from clinical waste might best be achieved by removal at source, in the supply department, though this requires care to protect the integrity of sterile supplies. In circumstances where segregation of waste is undertaken solely at the point of arising, in the busy and often cramped hospital ward, the risks associated with incorrect segregation that might result in clinical waste entering a more general domestic waste stream cannot be dismissed. Efficient supply chain management may thus offer an effective response to demands for the improved segregation of waste, reducing costs without compromise of safety, and supporting effective risk reduction. However, based on the evidence reported here, it is apparent that there has been little if any improvement and that much still remains to be done to improve the standards of clinical waste management in hospitals. Amid the aforementioned sanitary waste, solvents containing alcohol are very interesting as fuel for DAFC. So, in hospital facilities, there is a need of creating specific areas for stocking waste in a segregated way, especially for solvents containing alcohol (ethanol and ethylene glycol). This procedure would be permitted by some legislation, for instance, European directive 2006/12/EC and Italian one [10]. Ethanol and ethylene glycol are used in hospital facilities and they are good energetic vectors of with respect to hydrogen and to hydrocarbons. They have a high solubility in water and energy density (We) like [11] gasoline (10-11 kWh kg-1). Moreover, since energy efficiency (εr) of DAFC is great than (Table 2) that of hydrogen/oxygen-based cell fuel, that is, 83% at 25°C, this the interesting reason of recovering ethanol and ethylene glycol from sanitary liquids for energetic objectives. Ethanol and ethylene glycol are a good source of energy, even if it is necessary their electrochemical reaction entails the increasing of anode overvoltage towards high values with respect to those reached by hydrogen (Figure 1). This inconvenient could be overcome by allowing the reaction to be performed on binary or ternary catalyzer based on platinum which allow to obtain molecules with small dimensions that are easily oxidizable to CO2 [12].
Table 2:
Thermodynamic data of related to electrochemical oxydation of some alcohols.
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307
Comparison between voltage-current of an H2/O2-based cell fuel with platinum electrodes and DAFC ethanol with anodic ternary catalyzer (Pt-Sn-X).
Electric power Fractionation unit
Figure 2:
DAFC
Block scheme of proposed architecture.
Figure 2 illustrates the proposed architecture of processing segregated liquid waste extracted from sanitary waste and from sanitary decayed radioactive waste. Both types of waste, included other solvents that have not been segregated before, are stocked in a specific tank of figure 2. Afterwards, the liquids are treated in a fractionation unit according to the plant of figure 3. Thanks to Antoine Equation [13], using the appropriate constants, it is possible to calculate the vapor tension of both alcohols (ethanol and ethylene glycol), then, their volatility and the relative one.
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Figure 3:
Fractionation plant/unit.
To calculate the number of steps necessary to obtain the destre separation, it is appropriate to use the FUG (Fenske-Underwood-Gilliland) method according to the following procedure:
N min
xD xB log i ⋅ j xB xD j i = log α *
1− q = ∑
α i xF αi − Θ
Rmin +1= ∑
i
ai xDi ai - Q
( 1+ 54.4X )( X - 1) N - N min = 1- exp N +1 (11+117.2X ) X
(1)
(2)
(3)
(4)
where X is equal to
X=
R - Rmin R +1
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(5)
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Finally, to establish in which stage it is better to feed, Kirkbride Equation has been used in empirical way, that is,
N R B xF , HK = N S D xF , LK
xB , LK x D , HK
0.206
(6)
The FUG method has allowed to get the following parameters for the design of the system: Nmin =2, Rmin=0.24, N=7, R=0.31, number of feeding stage=5.
Nomenclature Fw xFw xDw F xF xD PMethanol PMglycol PMmix Teb P B D xB p° α α* Nmin Rmin N R NR NS
Flow for fractionation tower in kg/h Fraction in weight of ethanol Fraction in weight of ethanol in the distilled Flow for tower in kmol/h Fraction in moles of ethanol in the feeding Fraction in moles of ethanol in the distilled Ethanol molecular weight Ethylene Glycol molecular weight Mixed feeding molecular weight Ebullition temperature Operating pressure Residual flow in kmol/h Residual flow in kmol/h Fraction in moles of ethanol in residual Vapor tension Viscosity Relative viscosity Minimal number of necessary stages for separation Minimal reflux Effective number of stage for separation Reflux Number of stages over feeding Number of stages under feeding
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4 Summary and conclusions This research has illustrated the opportunity of recovering alcohols from sanitary waste in order to use them for feeding a DAFC. In general, even if segregation is carried out in clinical and hospital facilities, solvents containing alcohols are used in these facilities for different reasons. But an oversegregration that allows for recovery of alcohols from conventional sanitary waste and decayed radioactive ones will produce great benefits for saving money and protecting environment. The use of DAFC fuelled by recovered alcohols is essential for hospital pavilions like Neonatology, Resuscitation and Surgery rooms, where, the electric energy must not be interruptible for health and safety reasons. The proposed research agrees with European and national legislations.
References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13]
Mercier C and Ellam T, 1996. Waste Not Want Not. Health Service Journal 4 April 1996, UK. Department of the Environment, Transport and the Regions (DETR), 1999. A better quality of life: A strategy for sustainable development for the United Kingdom. HMSO, London. Health Services Advisory Committee (HSAC), 1999. Safe Disposal of Clinical Waste. 2nd Edition, HSE Books, The Stationery Office. Audit Commission, 1997b. Pembrokeshire NHS Trust 1996. Act of 13 July 1992 Italian act DPR 254/2003 Organisation Mondiale de la Santé, la gestion des déchets des hopitaux et autres établissements de soins de santé, Rapport sur une reunion de l’OMS, Bergen 28 juillet – 1 juin 1983, Danemark, ISBN 9289022639. Muhlich M, Scherrer M, Daschner FD. Comparison of infectious waste management in European hospitals. J Hosp Infect 2003;55:260—268. Townend WK, Cheeseman CR. Guidelines for the evaluation and assessment of the sustainable use of resources and of wastes management at healthcare facilities. Waste Manage Res 2005;23:398–408. Italian act Dlgs.152/06 Parte IV, art.179 s.m.i. Lamy et al., J. Power Sources, 105 (2002) 283 H. Laborde et al., Proceeding of the Symposium on ‘Electrode Material and Processes for Energy Conversion and Storage’, The Electrochem. Society, PV – 94-23 (1994) 275. Coulson, Richardson, Chemical Engineering, Vol 6, Terza Edizione, 858.
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An innovative concept leveraging mass volunteerism and the viral nature of the Web to substantially reduce global carbon emissions H. Gandhi1 & B. S. Thompson2 1 2
Carbonneutralvolunteers.org, Okemos, MI, USA Michigan State University, East Lansing, MI, USA
Abstract Global warming and climate change pose one of the most serious most serious challenges that humanity has ever confronted. But there has been a limited concerted response to this challenge of global warming and climate change and the response has been primarily through the vehicles of the Kyoto Protocol and the Voluntary Carbon Markets. While the Kyoto Protocol is focused on nations and voluntary carbon markets are driven by corporations, there has been one fundamental missing link in this equation: people, the 6.5 billion people who inhabit this earth. These individuals account for more than 50% of all green house gas emissions. Clearly there is a leadership vacuum when it comes to educating and mobilizing the masses to substantially impact climate change. It is the opinion of the authors that this must be rectified, and a vision is offered herein. The authors present an innovative concept of Volunteer Carbon Credits (VCCs) and utilize this concept for leveraging mass volunteerism and the viral nature of the web to demonstrate a platform for substantially impacting global carbon emissions. Specifically, they present the case study of Okemos High School, Michigan, USA which is the first high school in the world that has pledged to go carbon-neutral. Keywords: global warming, climate change, volunteer carbon credits.
1
Introduction
Global warming and climate change pose one of the most serious challenges that humanity has ever confronted. Today, the atmospheric concentration of carbon WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESU090281
312 Energy and Sustainability II dioxide has risen to 380 parts per million (ppm) due to anthropogenic emissions from burning fossil fuels and the loss of natural carbon sinks such as natural vegetation. This is in stark contrast to the carbon dioxide levels of 280 ppm prior to the industrial revolution of the 18th century. Most scientists agree that 7 billion tons of carbon dioxide must be prevented from entering the atmosphere (for) during the next 50 years in order to stabilize the carbon dioxide levels at 500 ppm, a target that is almost double that of the pre-industrial era [1, 2]. The clear and imminent danger to the planet was further reinforced by the 2007 report of the United Nations sponsored Intergovernmental Panel on Climate Change (IPCC). After reviewing thousands of peer-reviewed scientific studies pertaining to the impact of climate change, an august group of climate experts unanimously concluded that global warming is real and “unequivocal”. They further concluded that there is strong evidence that the increase in temperature since 1950 can be directly attributed to man-made greenhouse gas (GHG) emissions. The scientists also highlighted the fact that without a dramatic reduction in carbon dioxide emissions by 2012, climate change may bring about “abrupt or irreversible” effects on air quality, oceans, glaciers, coastlines, agriculture and a variety of species. The gravity of the problem can be appreciated if one examines only a few facts: • The Greenland Icecap Is Melting Faster Than Predicted • Greenland And THE West Antarctic Ice Sheet Melt Would Result In A 20+ Foot Rise In Sea Levels • Substantial Rise In Sea Levels Will Result In More Than 600 Million Refugees In Coastal Regions There has been a limited concerted response to this challenge of global warming and climate change primarily through the vehicles of the Kyoto Protocol and the Voluntary Carbon Markets. The Kyoto Protocol, which is an international treaty linked to the United Nations Framework Convention on Climate Change, committed 36 developed and industrialized countries to reduce their collective GHGs by 5.4% below 1990 levels by 2012. The Kyoto Protocol provides three major flexibility mechanisms which form the basis for the regulated international compliance carbon market based on the cap-and-trade scheme. These are, emissions trading between countries with emissions targets; purchasing carbon credits (Emission Reduction Units (ERUs)) from GHG reduction projects implemented in another developed country or an economy in transition; and finally, earning carbon credits (Certified Emissions Reductions (CERs)) by financing Clean Development Mechanism (CDM) projects in developing countries. Typical projects are highly structured, they require substantial upfront investment, and they involve substantial transaction costs and a major investment of time because of compliance and regulatory reasons. Recognizing the absence of a much larger global focus on making a dent in the metaphorical GHG emissions pie [3] several institutions and companies (and some individuals) have taken it upon themselves to act as responsible citizens of the world and make voluntary commitments to reduce their contributions to climate change by offsetting their carbon dioxide emissions. This initiative has led to the evolution of the voluntary carbon markets. Since the voluntary carbon WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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market is not driven by legally mandated regulatory oversight, the market is highly fragmented and lacks uniformity, transparency and certification. However these drawbacks are offset by innovation, flexibility and lower transaction costs. The voluntary carbon market is relatively small accounting for approximately 100 million tons of carbon dioxide in 2007 [4].
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An innovative concept: volunteer carbon credits
While the Kyoto Protocol is focused on nations and voluntary carbon markets are driven by corporations, there has been one fundamental missing link in this equation: people, the 6.5 billion people who inhabit this earth. These individuals account for more than 50% of all green house gas emissions. Clearly there is a leadership vacuum when it comes to educating and mobilizing the masses to substantially impact climate change. With this purpose in mind, the authors have developed an innovative concept of volunteer carbon credits, which are earned through volunteer action via behavioral change and contributions to green projects. These credits can then be applied to offset the carbon emissions of a volunteer’s favorite institution, typically referred to as the carbon footprint. This concept empowers individuals and fosters behavioral change at the grass roots level. Human beings, as social animals belong to several groups and they are passionate about their schools, colleges, universities, churches, and companies. The volunteer carbon credit concept unleashes the passion that people have for their groups, teams, and institutions in order to make a significant impact on global climate change. 6.5 billion people: 1 person at a time. The great thing about leveraging institutions and the goodwill people have towards them is that they serve as a community rallying point. This innovative concept has the potential to mobilize millions of people at zero cost and is ideally suited for massively growing emerging economies and also developed economies as well. Given the enormous scope of this target and the relative lack of global action the authors propose mass education of individuals and mass volunteerism of individuals who are responsible for almost 50% of the GHG emissions. This paper presents an innovative concept and a framework for leveraging mass volunteerism and the viral nature of the web to substantially impact global carbon emissions. This framework educates individuals and provides incentives to make lifestyle choices and contribute to GHG reduction projects. The authors introduce a pioneering concept of Volunteer Carbon Credits (VCCs), which are earned through volunteer action and in turn employed as credits to make carbon neutral the volunteers’ favorite institutions such as, schools, colleges, churches, and clubs. The authors are convinced that this innovative concept could mobilize large masses of individuals and provide data for real-life case studies. Specifically, the authors present the case study of Okemos High School, Okemos, Michigan, USA which is the first high school in the world that has pledged to go carbon-neutral. In order to achieve this very ambitious goal the school embarked on an internal sustainability initiative, partnered with businesses and employed volunteerism to make lifestyle changes, launch CFL adoption drives, plant trees and provide solar ovens to Tanzania. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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Case study: Okemos high school pledges to go carbon neutral
Okemos High School launched its Alternative Energy and Sustainability program and pledged to become the first high school in the world to go carbon neutral. Given the enormous challenge of global warming and climate change Dr. John Lanzetta, Principal; Okemos High School said “This program has been conceived by the students with a very ambitious and noble goal of making Okemos High School the first carbon neutral high school in the world. The program aspires to attain this through energy efficiency, offsets through mass volunteerism and global outreach programs.” A multi-pronged approach was adopted to start the ambitious journey towards making Okemos High School the first “carbon neutral” high school in the world:Provide Leadership • Empower The Individual • Educate/Raise Energy Awareness • Involve Students in Community/Global Outreach Programs • Foster Mass Volunteerism and Community Awareness • Propagate Behavior Change Using Grassroots Level Mechanisms • Assess Carbon Footprint • Reduce Carbon Footprint Through Energy Conservation • Offset Carbon Footprint Using Volunteer Carbon Credits • Capitalize On The Innovative Concept of Volunteer Carbon Credits By Leveraging The Viral Nature of the Web Education and green awareness was created using a variety of approaches: door to door drives, inviting speakers to create energy awareness, organizing fairs for sustainability and alternative energy technologies and exploring options with the National Energy Education Development Project. Students were also involved in exploring demonstrator projects, energy conservation/recycling, fun activities like solar cookout and windmill design and home energy conservation projects. The carbon footprint of the school was assessed and energy conservation programs employed to reduce the footprint within budgetary constraints. In order to offset the carbon footprint of the school by capitalizing on the innovative concept of volunteer carbon credits by leveraging the viral nature of the web, a new website (www.carbonneutralvolunteers.org) was established. This website enables individuals to earn Volunteer Carbon Credits through volunteer action by making • Pledges for Behavioral Change • Contributions for Green Projects. Pledges for behavioral and personal lifestyle choices are listed in Figure 2. For each pledge an estimate of the Volunteer Carbon Credits earned is displayed as shown in Figure 2. For example, an individual pledging to replace a dozen incandescent bulbs with Compact Fluorescent Lamps will earn 1200 Volunteer Carbon Credits, which represent 1200 pounds of carbon dioxide. The WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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Figure 1:
Home page of carbon neutral volunteers.
Figure 2:
Personal lifestyle choices.
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316 Energy and Sustainability II default units for Volunteer Carbon Credits are pounds of carbon dioxide versus tons of carbon dioxide that are used in Voluntary carbon markets and the Kyoto protocol. This is primarily due to the scale of each individual action as compared to the emissions of a country or a company. The website also offers individuals an option to make contributions to green projects including solar ovens in Tanzania, planting trees and Okemos High School projects as shown in Figure 3.
Figure 3:
Green projects.
For example, by contributing to a solar oven for deployment in Tanzania an individual earns 4000 Volunteer Carbon Credits as shown in Figure 4. These credits accrue due to the impact of the solar ovens on climate change by reducing the destruction of trees, the burning of fossil fuels and the related soil degradation. Figure 5 shows the plant based fossil fuels utilized in Morogoro and the related soil degradation. In addition to making an impact on climate change contributions to the solar oven project have a significant social impact. The Solar Oven program initiated in Morogoro, Tanzania is focused on designing and building solar ovens indigenously. This work is being undertaken in close collaboration with Sokoine University of Agriculture and the Vocational Education and Training Authority (VETA). This project will make a significant impact on the quality of life of the villagers, particularly women and children. Impact assessment studies are planned for two pilot villages in Dodoma region of Tanzania to evaluate the social, economic, environmental and health impact of the solar ovens. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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Figure 4:
Figure 5:
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Contribution for green projects.
Burning of fossil fuels and the related soil degradation.
The Volunteer Carbon Credits earned by individuals through these volunteer actions are then employed as credits to offset the carbon footprint of Okemos High School. The success of this program demonstrates the viability of WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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Figure 6:
Social impact of solar ovens.
Volunteer Carbon Credits to make a significant impact on climate change. These concepts can be readily extended towards mobilizing zero cost volunteer carbon credits in massive growing economies and also towards mining hidden assets of corporations and institutions.
4
Concluding remarks
The authors have developed an innovative concept of Volunteer Carbon Credits (VCCs) and utilized this concept for leveraging mass volunteerism and the viral nature of the web to demonstrate a platform for substantially reducing global carbon emissions. Specifically, the authors have presented the case study of Okemos High School, Okemos, Michigan, USA which is the first high school in the world that has pledged to go carbon-neutral. In order to achieve this very ambitious goal the school embarked on an internal sustainability initiative, partnered with businesses and employed volunteerism to make lifestyle changes, launch CFL adoption drives, plant trees and provide solar ovens to Tanzania. The authors would like to capitalize on this success to challenge high schools and other institutions globally to adopt the Volunteer Carbon Credit concepts and principles highlighted herein to make a substantial impact on global carbon emissions.
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Figure 7:
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An all volunteer team.
Acknowledgements The authors gratefully acknowledge the significant contributions of the Carbon Neutral Volunteers team and the Okemos High School Alternative Energy and Sustainability Initiative team, highlighted in Figure 7.
References [1] Brown, LR, Plan B 3.0: Mobilizing to Save Civilization, W. W. Norton; pp 48 – 67, 2008 [2] Friedman, TL, Hot, Flat, and Crowded: Why We Need a Green Revolution-and How It Can Renew America; Farrar, Straus and Giroux; pp 117–127, 2008. [3] Pacala, S & Socolow, R, Stabilization Wedges Solving the Climate Problem for the Next 50 Years Using Current Technologies, Science, pp 968–972, August 2004 [4] Bayon, R, Hawn, A & Hamilton, K, Voluntary Carbon Markets, Earthscan, London and Sterling, VA, pp 14–15, 2008
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Integrating intelligent glass facades into sustainable buildings: cases from Abu Dhabi, UAE M. A. Haggag UAE University, United Arab Emirates
Abstract Recent developments in the United Arab Emirates (UAE) have had consequences on the urban environment. Minimizing the impact of urban development on the natural environment and the trend to improve the ecological performance of buildings are the main concerns of sustainable and low energy building practices in Abu Dhabi. These ideologies have been acknowledged by international architectural firms to designing and constructing new projects that are energy efficient, environmental friendly, and architecturally remarkable. Despite the fact that the UAE is one of the hottest countries in the Gulf region, the use of glazed façades in modern buildings has gained increasing popularity because of the better views, pleasant indoor environment, and the building's prestige. These design approaches usually come with an increased operational cost due to the higher solar gain. This paper investigates the increasing interest in integrating intelligent glass façades into sustainable buildings in the UAE in order to increase energy efficiency by improving thermal comfort and reducing cooling loads; improve occupants’ performance and comfort; and save the environment by minimizing the negative environmental impact. The study investigates typical glazed façade buildings exposed to the UAE environment, to understand the effect of the building skin on the energy demands in a hot climate. To reduce energy uses in buildings, advanced systems, including Double Skin Façade strategies have been tested and integrated into a high performance building. These strategies are to be developed, based on an individual funded research project carried out by the author, and the experience of previous researchers and building users Keywords: Abu Dhabi, energy efficiency, intelligent glass façade, sustainability.
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Introduction
Despite the fact that Abu Dhabi is one of the hottest cities in the Gulf region, the use of glazed facades in modern buildings has gained increasing popularity. These design approaches usually come with an increased operational cost. It is important, therefore, to turn the principles of sustainable development into practice by increasing energy efficiency in buildings. Building engineers and architects should understand the behaviour of buildings they design if environmental performance and comfort are to be maximized. There are various approaches to increasing energy efficiency in buildings. These approaches take into consideration the total environmental and economical impact, energy sources, the performance of building material, design and construction, and operation and maintenance. The building façade is an important concept for energy efficiency. All components of the building façade need to work together to regulate the indoor environment. It is considered a selective pathway for a building to work with the climate, responding to heating, cooling, ventilation, and natural lighting needs. It must balance requirements for ventilation and daylight while providing thermal protection appropriate to the climatic condition [1]. Architects and building engineers should integrate the design of building façades with other design aspects including material selection, daylight, heating, ventilation, and air-conditioning. The study examines the performance of building façades in the UAE environment in response to energy saving strategies. Intelligent dynamic systems, including Double Skin Façades (DSF) have been integrated into a high performance building in Abu Dhabi to reduce energy consumption and cooling load by reducing the overall heat transfer coefficient “U-value” and shading coefficient. To achieve the aim of the study, the following objectives have been highlighted: to investigate the role of glazed building façades that provide energy efficiency in buildings; to reduce cooling loads by enhancing thermal comfort and identifying the optimal parameters for building façades; and to reduce building operating costs by minimizing cooling energy use and enhancing daylighting. In this context, various issues including urban transformation patterns of Abu Dhabi; the sustainable development of Masdar city; and the performance of intelligent glass façade are to be considered.
2
Abu Dhabi and its urban development
Abu Dhabi is one of the seven emirates of the UAE. It is the largest emirate by area (about 85% of the total area), and the second largest by population after Dubai with about 1.2 million people. It is located in the oil-rich and strategic Persian Gulf region, bordered by Saudi Arabia, Oman, and Dubai. As far as oil production and reserves are concerned, Abu Dhabi is the first among other Emirates forming the UAE, it owns about 11% of the total world reserves [2]. Adopting a free market economy policy, the Emirate is a business centre for international firms. Abu Dhabi is characterized by a hot and humid climate with an average temperature of 40◦C (in summer) and 28◦C (in winter). WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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The Emirate of Abu Dhabi is divided into three major regions: Abu Dhabi City, the federal capital of the UAE; the Eastern Region; and the Western Region. Moreover, there are a number of important islands within the emirate including Das, Mubarraz, Dalma, Sir Bani Yas, Abu Al-Abyadh, and Saadiyat. Abu Dhabi has become one of the most modern cities not only in the Gulf region but also in the world. The city started its urbanization process in the late 18th century when the Bani Yas Tribe first settled it in 1761, and the economy was centred on camel herding, date oases, fishing and pearl diving. The fast urban development that followed the discovery of oil in 1958, and the 1971 UAE federation completely changed the character of the city from a traditional architectural pattern to a modern style. Three issues motivate this transformation pattern: a) Abu Dhabi is an international trading centre; b) the dramatic nature of the city development; and c) the emerging status of the city as an urban region. Architectural ideologies in Abu Dhabi have moved from a traditional vernacular pattern to a modern style. The traditional fabric style, as shown in figure 1, reflects the climatic condition, the cultures and customs of the residents, and the locally available building materials. High-density buildings, narrow shaded alleys, courtyard houses and wind-towers characterize this pattern. The modern approach, which was established during the second half of the 20th century, was concerned with highly specialized building techniques. The building industry and urban fabric had been strongly affected by two factors. First: the importing of building materials and the establishment of foreign factories in the city. Second: planning organization was based mainly on occidental codes and dominated by foreign professionals [3]. This modern style is highly recognized within the newly developed areas of Abu Dhabi. A number of enormous mega-projects have been constructed, including Marina Mall; Abu Dhabi Investment Authority Tower; and Emirates Palace Hotel and Conference Centre. Other large projects are now under construction, including Al-Raha Beach; Abu Dhabi World Trade Centre; Saadiyat Island Development Project, and Masdar City Development Project.
Figure 1:
Traditional architectural fabric of UAE.
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326 Energy and Sustainability II Saadiyat Island, with its area of 27 km2, represents one of the most significant development projects in the history of Abu Dhabi. The island, which has 30 km of water frontage and boasts many natural eco-features including mangrove forests, is being developed as a strategic international tourism destination for about 150,000 residents. Saadiyat Island project, which will be completed in 2018, comprises seven individual districts (figure 2). They include a range of museums and cultural centres (Sheikh Zayed National Museum designed by Norman Foster, Louvre Abu Dhabi designed by Jean Novel, Guggenhein Abu Dhabi designed by Frank Gehry, and Performing Art Centre); hotels and resorts (nine 5 star hotels along 9 km of sea-front), civic and leisure facilities, and sea-front apartments and luxury houses [4]. The island will be linked to Abu Dhabi mainland via light rail system and a 10 km long highway with a bridge [5].
a) Guggenhein Abu Dhabi museum
Figure 2:
b) Louvre Abu Dhabi
c) Performing Art Centre
Saddiyat Island development project, Abu Dhabi [5].
The trend of urban development, which is rapidly experienced in Abu Dhabi, has negative impacts on the environmental aspects including high consumption levels of non-renewable recourses, and a high level of air pollution. Minimizing this impact on the natural environment and the efforts to improve the ecological performance of any project are the main concerns of sustainable building development during and after construction period [6]. In UAE, buildings consume more than 45% of total energy use; 25% of total water consumption; 70% of total electricity consumption, and 40% of total carbon dioxide emissions [7]. Abu Dhabi has been listed as one of the highest per capita fossil fuel consumers and carbon dioxide generators. Meanwhile, it has been listed as the top in consumer of energy per capita. Despite that fact, the environmental impact of buildings is often underestimated in most of the new urban developments, while the costs of building green are overestimated. Therefore, minimizing the impact of urban development on the natural environment and the trend to improve the ecological performance of buildings are the main concerns of the sustainable building practices in Abu Dhabi. These ideologies have been acknowledged by international architectural firms designing and constructing WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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new projects that are energy efficient, environmental friendly, and architecturally remarkable. Architects like Foster and Partners already incorporated ecological and sustainable approaches in their designs. Masdar City, which is considered a unique project to maintain the new vision of Abu Dhabi 2030 master plan, is a significant development regarding sustainable practices that aim to reduce energy consumption, reduce waste and pollutions, and create a manifesto for sustainable life.
3
Toward sustainability: Masdar City
The concept of sustainability states that there is a need to improve the living conditions of the present generations without compromising the ability of future generations to meet their needs. Sustainable development refers to a socioecological process characterized by the fulfilment of human needs while maintaining the quality of the natural environment [8]. Sustainable development could be achieved by architects, engineers, designers, town planners, and manufacturers of building products working cooperatively to produce green buildings that are designed, built, renovated, operated, or reused in an ecological and resource efficient manner. Sustainable design, which refers to “green design”, “eco-design”, or “design for environment” reduces the use of nonrenewable resources, and minimize environmental impact. Green Building or Green Architecture is an approach to architectural design that emphasizes the place of buildings within both local ecosystems and the global environment. Green building is the practice of increasing energy efficiency, while reducing building impact on human health and the environment through better design, construction, operation and maintenance [9]. Effective green buildings require careful attention to the full life cycle impact of resources. Building materials, one of the key issues, should be "green" and obtained from local sources. Low impact building materials should be used wherever feasible [9]. Reducing energy loads is another issue for green architecture. It is important to orient the building to take advantage of cooling breezes in a hot climate, and sunlight in a cold climate. To minimize the energy loads, passive solar design can be effective. Masonry building materials with high thermal mass are efficient for retaining the cool temperatures of night throughout the day. Moreover, buildings are often designed to capture cool winds. Many of these valuable passive strategies are employed in the traditional architecture of Abu Dhabi, as well as in new development plan of Masdar City. Passive solar design helps conserve valuable fossil fuel resources and reduces greenhouse gases that contribute to global warming. The most important step in the passive cooling process is to develop an energy efficient building envelope to minimize heat gains and to catch cooling breezes. Depending on the climatic condition, passive solar design of the building envelope might comprise the following concerns: orienting more windows to the north; incorporating adequate shading devices that prevent solar radiation; incorporating thermally massive building materials; providing suitable insulation; using high performance glazing that reduces heat gain and admits natural light. Landscape and outdoor spaces also play an important role in WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
328 Energy and Sustainability II passive cooling strategies. Vegetation, water ponds and fountains are efficient elements in the cooling techniques [10]. In Abu Dhabi's hot climate, where cooling is a primary concern, much can be done to accelerate passive solar design and capture natural breezes to keep buildings cool and comfortable. Combining proper ventilation, courtyards, wind-towers, shading devices, thermal mass, incorporating advanced glazing elements into more comprehensive intelligent façades and building systems can reduce energy loads. Masdar City, with an estimated cost of US$22 billion, was initiated in 2006 as the World’s first carbon-free eco-city. It is being constructed 17 km away from the centre of Abu Dhabi, and targeted to a 2016 completion date. Designed by the famous architect, Norman Foster, Masdar city is planned to be the first city where carbon emissions are zero, waste is converted to energy, desalinated water production reduced by 75%, and 80% of water will be recycled and powered by 100% renewable energy [11]. The city includes Masdar Institute of Technology, laboratories and research facilities, commercial spaces for energy related companies, and science museum. The city will host 50,000 people, in addition to 40,000 commuters. Masdar, as a car-free city, will be linked to the centre of Abu Dhabi by a new mass transit railway [11]. A personalized rapid transport system will be provided with a pedestrian-friendly environment. The city is designed to be self-sustaining; therefore, the surrounding land outside the city will contain photovoltaic and wind farms, research fields and plantations, desalination plant, water treatment plant, a recycling centre, and visitors’ parking. The outstanding architectural concept of Masdar city was based on traditional planning ideologies, which are characterized by narrow shaded alleys, courtyards, and wind-towers; together with advanced technologies to create a unique green-community (figure 3). The city was designed in an ecological and resource-efficient manner. The combination of green design techniques will not only reduce energy consumption and environmental impact, but also reduce running costs, create more pleasant spaces, and improve occupants' health. To produce lower greenhouse gas emissions, a variety of renewable energies are considered within the city development [11]. These technologies include: a) Solar Energy: the use of Photovoltaic technology, as a solar power system is planned to provide almost 50 percent of the electricity required and it will be integrated into building structures within the development. b) Wind Power: large-scale wind farms with their turbines are proposed and will be connected to the city electric power transmission network. c) Concentrating Solar Power: a field of mirrors and tracking systems is provided to focus a large area of sunlight onto a specific small beam. The concentrated light is used as a heat source for a conventional power station. d) Geothermal Heat: a heating and/or cooling system that uses the earth’s ability to store heat in the ground or water thermal masses. e) Waste-to-Energy: the process of creating energy in the form of electricity from the controlled combustion of municipal solid wastes. Water management has also been planned in an environmental manner. A solar-powered desalination plant will be constructed to provide the city with a water supply. About 80 percent of the water used will be recycled and reused for WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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irrigation and other domestic uses. It is also planned to reduce the city’s waste to zero [11]. Biological waste will be used as fertilizer; municipal solid wastes will be utilized as an additional power source; and industrial wastes will be recycled.
Figure 3:
4
Architectural fabric of Masdar City [11].
Intelligent façade performance
The intelligent glass façade system is known as a dynamic and flexible system that accommodates change in the environment and in occupant needs; using selfregulating thermal protection and solar control measures [12]. This could be achieved by the use of natural, renewable energy sources such as solar energy, airflow, and geothermal heat. The dynamic glass façade has ecological and economical significance since it reduces the global greenhouse effect by limiting carbon emissions; and reduces the investment and operational cost of building technology. In designing a dynamic glass façade, two strategies should be implemented: keeping heat losses low, and avoiding undesired heat gains through solar radiation. This could be achieved by the number of glazing skins incorporated in the design (single-skin façades and multiple-skin façades) and the use of solar control devices. To achieve a certain level of solar control, as pointed out by Compagno [12], a coating can be applied to glass such as infrared-reflecting coatings. This glazing can change solar and light transmittance dynamically to respond to occupants’ needs and building conditions. It is necessary to provide additional adjustable solar control devices; including exterior or interior solar devices, or integrated shading devices incorporated in the cavity between the glass panels in the case of single-skin façade or between the glazing skins in the case of DSF. The use of DSF technique as an intelligent glass façade has gained increasing popularity in many part of the world. It introduces at least two primary glazing layers separated by a cavity space that provides greater thermal insulation. This could be integrated with solar control systems, light reductions systems, and ventilation systems. The construction of the DSF usually provides better solar protection that can reduce the effect of the external load and the cooling need. The additional layer of glazing can reduce the insulation by about 10 percent. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
330 Energy and Sustainability II Further reduction could be achieved by placing shading devices in the cavity space [13]. Shading devices help in absorbing heat and liberating it within the cavity. The absorbed heat is transmitted to the surrounding air and adjoining surface by means of radiation and convection. The position of the shading devices plays a major role in the distribution of the heat gains. As pointed out by Oesterle et al. [13], the optimal location of the shading device is in the outer half of the cavity. The air-tightness of the DSF also contributes to the qualities of thermal insulation. The improved U-value of the DSF depends mainly on the ventilation level of the intermediate space and the direction of the façade. The ventilation systems for the cavity and the inner spaces play an important role in sound transmission. The acoustical insulation between rooms depends on the differences in the ventilation strategy of the DSF (active, passive, and interactive types). Active types have internal mechanical ventilation with a high level of acoustical insulation. Passive types have natural ventilation of the cavity with a low level of acoustical insulation between rooms. Interactive types have natural ventilation with the aid of mechanical ventilator in the cavity. The degree of sound insulation provided by the DSF depends mainly on the size and position of the openings in the outer layer. Sound insulation can also be influenced by absorbent surfaces of the cavity [13].
5
Analytical study: the use of DSF
Despite its advantages in terms of energy efficiency, the use of the DSF system is limited in Abu Dhabi. The absolute construction cost of the DSF will always be higher than an SSF system. However advanced intelligent façades may allow tradeoffs with building systems including cooling and heating systems. To get a clear picture of the real economical incentives of using DSF, the author carried out an analytical study in 2006 as part of an individual funded research project on "Thermal performance of double skin façades in hot and arid climates". The methodology of the study was based on interviews with building designers and maintenance engineers; and simulation of single glazed façades and double skin façades. The study emphasized that the potential energy savings offered by the DSF strategy can overcome the high construction cost. Moreover, building performance and comfort can be maximized. A fully glazed double skin façade has been tested and analyzed. It incorporates an outer single glazed panel fastened to aluminum frames; inner double glazed operable windows with internal blinds, and a 40 cm cavity between the two skins. The cavity is divided horizontally and vertically along the construction axes and between the individual windows. The horizontal platforms are covered by laminated sheets, which act as horizontal shading devices. The comparison analysis of the performance of various glazing technologies with the performance of the used DFS showed that the solar heat gain coefficient for DSF systems with shading devices is between 0.09 and 0.30 W/m2. As shown in table (1), this level of solar control can be achieved by a typical double glazing unit with reflective coatings, but at the cost of much higher thermal transmission, and lower natural light transmission. On the other hand, the use of clear double-glazing would result in a WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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solar heat gain coefficient much higher than a DSF and hence a higher cooling load. The U-value of the used DSF was found to be in the range of 0.9 – 1.4 W/m2. It has also been concluded that this type of DSF has an acoustical insulation that is far better than that of a conventional double glazing single-skin façade. The difference can be as much as 10 dB. The airflow inside the cavity and the divisions between the outer and inner skins play an important role not only in thermal performance but also in sound control. As a result, the U-value is reduced, less energy is required, visual transmittance is high, and acoustical insulation is provided. Table 1:
Performance characteristics of different façade systems including DSF.
Façade type Masonry wall Double glazing single skin facade Double glazing single skin with reflective coating Double skin – vented with laminated shades within cavity space
Solar Heat Gain Coefficient <0.03 0.30 – 0.40 0.07 – 0.20 0.09 – 0.30
Thermal transmission coefficient (U-value) <0..40 1.1 – 1.5 1.3 – 1.5 0.9 – 1.4
The advantages of the DSF application depend mainly on the characteristics of the site, the function of the building, and the design of the façade and its integration with the inner spaces. In general, DSF can provide different functional approaches, including: a) sun protection and cooling load control, b) improving thermal comfort and providing daylight, c) enhancing natural ventilation schemes, d) reducing operating costs by optimizing the daylightthermal trade-offs, and e) improving indoor environments and enhancing occupant health, comfort, and performance [14]. Generally, DSF strategy is a good approach to overcome the large energy conservation and comfort problems that are created by the use of excessive glazing areas. Economically, there is an additional cost for the construction of DSF compared with single skin façades. This additional cost has to be offset by the lower costs achieved through greater functional efficiency.
6
Conclusions
Modern developments in the Abu Dhabi have had consequences on the urban environment. Minimizing the impact of such development and the trend to improve the ecological performance of buildings are the main concerns of Abu Dhabi 2030 Vision toward sustainability. These ideologies have been acknowledged by international architectural firms, such as Norman Foster, to design and construct projects that are energy efficient, environmental friendly, and architecturally remarkable. Masdar city is a good example where carbon emissions are zero, waste is converted to energy, and 80% of water will be recycled and powered by 100% renewable energy. The use of natural ventilation, thermal mass, proper shading, careful siting and landscaping should be adopted WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
332 Energy and Sustainability II in sustainable buildings to reduce energy uses and increase occupants’ comfort. In addition to these strategies, the use of dynamic glass façade systems that accommodate change in the environment and in occupant needs is highly appreciated by architects and building engineers particularly in hot climates since it keeps heat losses low, and avoids undesired heat gains through solar radiation. The use of DSF techniques; integrated with solar control systems, light reductions systems, and ventilation systems, provides better solar protection that can reduce the effect of the external load and the cooling need, and improve the indoor environment.
References [1] Reid, E., Understanding Buildings: a Multidisciplinary Approach, Longman, London, 2001. [2] www.aldar.com/about_abu_dhabi.en [3] Haggag, M. "The Impact of Globalization on Urban Spaces in Arab Cities", Proc. of the International Conference on Globalization and Construction, Bangkok, 2004. [4] www.saadiyat.ae [5] www.guggenheim.org/abu-dhabi/about/cultural-district [6] Botta, M., Towards Sustainable Renovation, KTH, Stockholm, 2005. [7] Walters, L. et al, Miracle or Mirage: Is Development Sustainable in the United Arab Emirates? Middle East Review of International Affair, vol. 103 2006. [8] Rees, W., “Understanding Sustainable Development”, Sustainable Development and Future Cities, Hamm, P. and P. Muttagi (eds), Intermediate Technology Publications, London, 1998. [9] Wheeler, S. and T. Beatley, The Sustainable Urban Development, New York, 2004 [10] Brown, G. and M. Dekay, Sun, Wind, and Light: Architectural Design Strategies, Wiley, London, 2006. [11] Masdar Initiative and Masdar Development. www.masdaruae.com [12] Compagno, A., Intelligent Glass Façades, Birkauser, Berlin, 2002. [13] Oesterle et al., Double-Skin Facades, Prestel Verlag, London, 2001. [14] Selkowitz, S., Integrating advanced facades into high performance building. Proc. of the 7th International Glass Processing Day, Tampere, Finland, 2001.
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Case study ‘the Vela Roof – UNIPOL’, Bologna: use of on-site climate and energy resources A. van Timmeren1 & M. Turrin2 1
Climate Design, Delft University of Technology, Faculty of Architecture, Building Technology, The Netherlands 2 Design Informatics, Delft University of Technology, Faculty of Architecture, Building Technology, The Netherlands
Abstract The case study presented in this paper focuses on the so-called “Vela roof”. This roof is part of a larger project under construction in Bologna. The focus of the study concerns the use of on-site renewable climate (energy) resources for thermal comfort with special attention given to passive cooling and heating. The very first conceptual design developed by the architectural office is assumed as a starting point for the inclusion of performance criteria at this stage in the process, taking into account a large chain of dependencies that need to be integrated in the design process. Due to extremely low wind speeds on-site, early evaluations pointed out how wind should be caught in order to provide some cooling effect; secondly, side openings at the wrong location on the roof would contribute to a green house effect more than to a passive cooling effect. As a result, in the preliminary design of the roof uncomfortable conditions were highly expected under the whole roof in the summer, with an even higher critical level in the space between the lower buildings’ roof and the Vela. Two main issues of the Vela are therefore highlighted especially related to the improvement of the existing design (configuration and shape). On one hand, in the preliminary design the overheated air was going to be kept at the top enclosed spaces without being passively extracted. On the other hand, the system of side openings could be related better to the local wind behaviour. The latter has been analyzed and digitally simulated and the first results are presented in this paper. Integration of these main issues in larger strategies was also investigated, considering both active solar technologies and passive systems for heating and cooling. Keywords: on-site renewable energy resources, urban space related comfort. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESU090301
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1
Introduction
By presenting the case study of a roof structure, in this paper we discuss design explorations aimed at integrating strategies for on-site energy use in the early architectural and structural design phase. The first section briefly introduces the context of the roof and offers an overview of the larger project the Case study object – the “Vela roof”– is a part of. The role of the roof in relation to the use of on-site energy resources for climate comfort is explained, especially referring to passive strategies for thermal reasons. These strategies enable achieving indoor thermal comfort by using on-site renewable energies, and reducing the need for imported energies. Taking advantage of periodic climatic changes enables one to store the solar thermal energy needed for heating the indoor spaces or to disperse excessive heat to the outside. The architectural geometry of the overall shape and the roof details can support this effect and were both investigated. As part of this general context and according with the fundamental role played by the shape in order to design a climate efficient environment, the subsequent sections focus on the relation between the local conditions and the conceptual design of the shape, with a more detailed level of design addressed in the last two sections The research was commissioned to Delft University of Technology (TUD), in The Netherlands, section Climate Design and Design Informatics as part of a PhD research on Reconfigurable Structures for Passive Solar Strategies and a design process based on parametric modelling.
2
Context and tasks
The “Vela” roof structure is part of a larger active project referred to here as the UNIPOL Project. The latter consists of a high-rise office building, a hotel, a system of lower buildings for shops and services, referred to here as Piastra, and a public square, partially covered by the Vela. The overall area is illustrated in Figure 1, showing the concept developed for the site by the architectural office. The project is located in Bologna, Italy; the architectural process is lead by Open Project Office; the structural design is lead by Prof. Massimo Majowiecki
Figure 1:
Design Sketch UNIPOL [images courtesy of Open Project Office].
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and his office. While the office tower and the building facing it are in an advanced stage of the design and construction process, the low-rise buildings and the public space including the roof are still at a conceptual level. In designing them, one main criterion is the development of a system that joins the specific architectural, functional and climatic requirements. Following this direction, various strategies are being investigated considering both active solar technologies and passive systems for heating and cooling. Reflecting on an expected critical summer overheating, especially the second kind of systems has been analyzed more deeply. With respect to these issues, the roof is expected to play a key role in contributing to the climate control. The structure is thought as a roof opening on the sides. With reference to natural ventilation both for quality air and passive cooling, as well as to evacuation of smoke in case of fire, the openings are a key aspect; relations between their location and shape and the overall geometry of the roof are therefore investigated as well as the potential integration with kinetic systems to open and close some of the modules of the roof (cf Figure 1).
3
Thermal comfort, summer overheating and passive cooling
The general character of the proposed investigation aims at defining the architectural geometry of the roof through an integral approach involving climate comfort performance evaluations across the project scales. Since the covered space is a semi-indoor (or outdoor) space partially surrounded by adjacent indoor spaces, the concept of thermal comfort needs some specification. The determination of the indoor thermal comfort and the evaluations of the best way to achieve this are in fact a complex issue. They have to take into consideration the interaction of a big number of related internal as well external factors and human needs. These are depending on particular specifications, such as the building use type with its occupancy schedules and use profiles, the internal heat gains from lighting, office equipment, machinery and people and so on. However, since the spaces enclosed by the Vela are supposed to be between indoor and outdoor, the demands for the thermal comfort are less strict. On the other hand, uncomfortable conditions of summer overheating have to be avoided and cold winter conditions and too strong daylight have to be mitigated as well. Due to the need of only mitigating the worst thermal conditions, a simplified approach is proposed. As a consequence, the presented suggestions only focus on passive cooling for summer time and passive solar heating for winter conditions. Without aiming at modeling the concept of thermal comfort and all the factors influencing it, these would in any case strongly contribute to achieving the thermal comfort in a passive way. Partially achieving the thermal comfort in a passive way would positively affect not only the direct use of the spaces covered by the Vela, but also the indoor thermal behaviour of the surrounding buildings with specific reference to the Piastra. Passively avoiding uncomfortable (coldest and overheated) conditions in this semi-indoor space would relevantly reduce the energy demand for thermal comfort, by improving the energy performance of the system of buildings and is therefore strongly recommended. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
336 Energy and Sustainability II According with these specifications, local climate aspects have been evaluated and design aspects have been analyzed. Particularly, in a climate like in Bologna, summer hot temperatures reach critical levels (EERE, 2008), showing uncomfortable temperatures during all the working hours for a relevant period of the year. In addition, the site is quite exposed to direct sunlight. Due to this combined situation affecting south facing enclosed spaces, hot weather during summer time will require not only to limit the incoming of solar heat, but also to cool the indoor spaces. As a consequence, a shadow system to reduce the incoming radiance is strongly recommended, but will not be enough to prevent uncomfortable conditions of overheating in the covered spaces. A strong contribution can be given by passive cooling. In respect to that, rainwater, green roofs, wind and natural ventilation have a key role. Next paragraphs will focus on each of these aspects.
4 Wind and wind driven ventilation for passive cooling On one hand, the role of the shape of the roof in directing the airflows is an example of the close relationship between aspects affecting the passive thermal behaviour of a build system and its geometrical shape. Bologna is interesting with respect to wind due to the low speeds and the local wind rose shows almost no dominant wind direction. This means average wind is weak and coming almost equally from all sides. However, the climate related data analysis (EERE, 2008) made clear that the summer condition and the winter condition are the most relevant situations regarding the local wind behaviour.
Figure 2:
Analyzed wind directions and summary of EERE dominant wind data.
In wintertime, the calm wind periods equal around 70% of the measured conditions; in case of wind, there is a 30% predominance of West Winds. In summer time, calm wind periods decrease to 35% of measured conditions; the dominant direction is more variable and less identifiable, even if some predominance from East has to be acknowledged especially in daily hours. During night hours calms of wind are more frequent and there is a predominance WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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of West Winds. During May, July and August no relevant amount of wind is coming from the Northwest. Winds selected according to these data have been digitally analyzed (Figure 2). Referring to the simulated winds, two main general aspects have emerged as relevant for the Vela (square) design. On one hand, the average wind not only never reaches an uncomfortable speed, but it even needs to be captured in order to provide the desired cooling effect. On the other hand, natural wind shadows are caused on the square by the configuration of the built environment, but some useful draughts are created by the high-rise building. In the latter case, special attention should be given to using the roof to direct the wind in order to provide some cooling effect. More precisely, wind simulation showed that concerning winds from Southeast, due to the hotel, the whole square is within the wind lee. Simulation also showed that trying to redirect the wind from the hotel’s roof does not seem effective. However, when the South-East wind blows, a relevant draught is brought on the square by the high-rise building. This means that when the South-East wind blows the only wind affecting the square comes from the North-East. Wind from the North-East converges on the square under effect of the built environment with specific influences brought by the high-rise building and the hotel. Since these latter drive the wind within the square, in their proximity higher wind velocity is evident. The wind simulation also showed that a similar behaviour is expected by the East wind. On the basis of the analyzed wind behaviours and with respect to the specific context of a roof such as the Vela, two main possible strategies for passive cooling can be followed, the chimney effect and the wing effect. The first one is based on the natural temperature between the bottom and the top air enclosed by the roof; as result of the consequent convection air drafts, warmer air is extracted through a hole at the top point. The latter is based on the cooling effect provided by incoming colder air drafts that have to be made to blow correctly through the enclosed spaces.
Figure 3:
Schematic examples of some general cooling categories whose behaviours were taken into consideration in the Vela’s case.
Evaluating the early design developed for the roof, both strategies were partially shown in the lengthwise and width wise sections. Longitudinally, the section drives the warm air to the top point, while transversally the section would drive the outdoor winds to pass trough the covered spaces. The coexistence of the two approaches is a possible solution with a high potential, but the balance between the two behaviours has to be considered in order to improve their reciprocal principles without negatively interfering with each other. The two aspects described in Figure 4 are indeed identified as possible main problem areas. As a result, the warm air is expected to remain under the roof. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
338 Energy and Sustainability II The preliminary designed geometry of the roof was expected to cause relevant problems and thus variations were advised, e.g., with respect to the lengthwise section, the absence of a top opening or openable point on the roof could be solved by introducing a hole correctly shaped in correspondence to the top point (chimney like effect). In this context, various curvatures were tested satisfying architectural issues. The chimney effect can be further improved by a small wing located at the top hole. (Figure 5).
Figure 4:
Figure 5:
Lengthwise and width wise sections of the Vela.
One of the proposed alternatives; a different curvature with opening.
With respect to the wing effect of the whole structure, both orientation and dimensions of the analyzed open sides should be reviewed by shaping the curvature of the roof more suitably. This point assumes even more importance since it is also related with a third critical point: the roof in fact runs close to the so-called “Piastra” below (the roof level of the surrounding low rise buildings). On the west sides, outdoor fitness activities as well as the terrace restaurant are located on the first and top levels of the surrounding building volumes. The need for a comfortable area protected both from overheating and from uncontrolled air draughts was found to strongly conflict with the actual geometry of the roof. Even in the case outdoor activities were supposed to stop during summer time, avoiding the actual risk of critical overheating between the Vela and the Piastra’s roof is important in order to reduce the negative effect on the below indoor spaces at the level of the covered square. Therefore air ventilation between the Vela and the Piastra’s roof had to be increased. Also specifically with respect to WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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the former mentioned, variations on the geometry were suggested here in order to introduce an improved wing effect (cf Figure 6). Major openings on the sides would both allow easier incoming of cooling winds supporting the whole wing effect of the roof and diminish the heating effect of the radiations from the roof on the fitness and restaurant areas. By combining the explained thermal considerations with these local wind factors, two main suggestions are recommended. On the one hand, opening the roof close to the Hotel on the East side and, even more, close to the high-rise building is quite important. This would in fact allow to catch the South-West, East and North East winds, while openings on the west to the Piastra’s roof have to be increased and shaped differently to achieve a Venturi effect on the West side (cf Figure 6). Modelling the geometry and the curvature of the roof for this wind effect affects the large-scale definition of the early design concept. However, reducing summer over-heating should be considered an important goal. Discussion with the structural engineers also pointed out undesired structural behaviours in case of anomalous winds and these need to be taken into consideration as well.
Figure 6:
5
One of the proposed alternatives wing effect related.
Heat gain reduction
Different ways of regulating the sun coming in through the roof and the air permeability of the roof with respect to passive cooling are of importance to heat gain reduction. Originally the roof is thought of as a partially transparent system. It is located on the south side of the tower and as an architectural requirement it has to allow the view of the tower from the inside. While natural light has to be used, at the same time, solar thermal energy has to be filtered (esp. in summertime) in order to passively achieve the indoor thermal comfort in the square and to avoid as much as possible summer thermal loads on the surrounding buildings. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
340 Energy and Sustainability II As a different option, the combination of different cladding systems can reduce the need for adding extra material in support of the reduction of heat gain. As proposed by Open Office, by combining a translucent, opaque fabric and transparent glass cladding material the heat gain can be lowered by reducing the amount of direct sunlight inside the space. In this case, a high percentage of translucent or opaque cladding system is required in order to reduce the incoming sun. Besides this aspect, the budget does not allow for a complete glazed roof and Teflon or EFTE has been proposed as a possible alternative material. To achieve heat gain reduction additional options such as the use of rainwater collected from the roof and green roofs on the low surrounding buildings could be realized as well. As stated in the previous section, integrating the thermal behaviour of the Piastra’s roof and the Vela is strongly advised. Particularly, thermal performance evaluations while choosing the materials covering the Piastra’s roof are needed. Green roofs are a good option when dealing with passive thermal comfort. The low-rise buildings would benefit themselves from it due to the insulation capacity of green roofs. However the most relevant aim is avoiding heat reflection toward the higher adjacent buildings as well as cooling the air drafts entering below the roof. Due to this latter aspect, the green part can be mostly concentrated in the areas right outside the roof borderline. Planting of Sedum species should be preferred to grass. This also allows extensive green roof systems that need less water, thin soil layer and minor maintenance labour. (Considering the near highway, Sedum species keep more fine particles (PM10) than grass. While an open water surface could be even more effective than grass and Sedum for cooling, risks of leaking, weight and evaporation are relevant disadvantages.) Collecting the rainwater strongly contributes to passively achieving the thermal comfort goal, by providing the feeling of a lower temperature concerning the air lying above it. Applying this effect to the whole semi-indoor space under the Vela is impossible due to its dimensions. However, localizing the effect on selected areas where people stay can provide a relevant help. The actual configuration of the Vela offers a surface up to 3.000 square meters, allowing a relevant water collection (approx. 788mms/a). Focusing on thermal performances, an optimal condition would require the collected water to lie within the covered spaces during the daytime and outside during night time. This can be achieved by moving the collected water between two connected pools or two parts of the same pool, one located under the roof, the other one outside. Moving the water from inside to outside and vice versa provides benefits; however, a balance needs to be found between the need of providing evaporation for thermal comfort and the quantity of available rain water, due to the relevant but not abundant average summer rain. Integrating the rainwater with filtered and cleaned water from the surrounding buildings was analyzed to be an option. In both options, a pool for rain water collection is to be included. The pool could best be located at the ground base of the roof and it is recommended to be large enough to avoid dispersion of water falling from the curved surface. Apart WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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from possibilities for collection and reuse it also introduces adiabatic cooling possibilities and interesting reflection of the roof shape near the entrance. If desired, water could be reused for cooling purposes of covered spaces (as a form of ‘adiabatic cooling’). In this case, it could best be distributed as soon as possible once collected below the floor in order to avoid outdoor evaporation and in this way improve availability of harvested water for cooling purposes (among other) (cf Figure 7). Additionally, if the water is distributed below the floor, then it could be used also for green trees’ irrigation under the roof. The system could refer to ancient Moorish techniques of irrigation and combined cooling of outdoor areas.
Figure 7:
One of the proposed alternatives; rainwater collection and reuse.
6 Passive heating and active solar gain During wintertime, cold weather will require to keep the solar gain inside. More detailed calculations still have to be made in order to verify whether there can be winter sunny days when the solar gain is too high, leading to overheating. Except for that, the main aim in wintertime is to avoid the dissipation of the solar heat and, possibly, gaining as much as possible thermal load. The latter aspect is directly related to the choice that will be made about the shading system. Both aspects at the moment concern work in progress and will not be addressed to in detail in this paper. In case the shading system will be a separate layer of the roof, it can be either adjustable or studied in order to optimize the lamellas’ inclination to protect from the summer sun radiation and to allow the winter solar rays entering the roof. On the other hand, avoiding the dissipation of the solar gain can be effectively supported by closing the top as well as the west side openings of the roof. Closing the top openings would avoid the chimney effect. While west openings in summertime play a key role in driving the cooling winds under the roof, in winter time closing them has high potential in limiting the air circulation. Particularly for the west side openings, e.g. by using a space frame structure, a deployable bar systems can be effectively used to achieve the desired adjustability. In the case of using tensile structure, adaptability can be achieved by adjustable tensile properties. In the case of dividing the roof into smaller roofs, rotating elements can differently address wind behaviour. Also the integration of active solar systems is advisable. However, its benefits have to be combined with a passive suitable behaviour of the roof. The passive WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
342 Energy and Sustainability II behaviour has to be developed and later on further supported by the introduction of active technologies like, for example, photovoltaic cells. Differently, active systems simply become a way to mitigate negative effects not avoided or, even worst, created by the built environment. Once a suitable passive behaviour is defined, very interesting options can be introduced in relation to energy production, optimized on the specific conditions.
7
Conclusion
As a result of the stated work in progress on passive heating, active solar gain and improved design alternatives on the basis of climate design and parametric modelling, final conclusions still cannot be made. The focus will be on introducing a way for the extraction of overheated air with as little adjustment of the geometrical shape as possible. Dimension and exact positions of the openings therefore need to be calculated, while the shape could easily follow the existing proposed structure. They are expected to be efficient if located where the shape starts its curvature. There could be either three openings, distributed along the structure, or one bigger, centred. To improve the effect of passive extraction of heated air and avoiding incoming rainwater, it is important to add a small elevated sub-roof which is aerodynamically shaped to increase wind speeds and in that way improve the thermal stack effect (‘chimney effect’). The effect would be improved if the overall shape is reviewed in order to make the location of the openings higher in order to favour warm air flow extraction and to avoid annoying air draughts at the height of the ground floor surface in the covered area. Making the top openings closable would be best, in order to be able of regulating the extraction of heated air with respect to the indoor comfort (i.e. wintertime / summertime). The mentioned regulation capacity would be strongly improved by making closable also the openings along the sides of the roof in order to regulate both incoming airflows and the extraction of air. Specifically this airflow regulation requires switching the roof between a closed (barrier like) to an open (filter like) condition and at the moment related kinetic components are studied with respect to two possible approaches. The first is based on largescale kinematism of the overall shape. The second is based on the repetition of openable modules, integrated in the structural morphology.
References [1] EERE (Energy Efficiency and Renewable Energy) Statistics. [2] Open project Bologna, Complesso Unipol first meeting report, 07 July, 2008, Bologna, Italy. [3] Timmeren, A. van, Killian, A., Aanen, L., Turrin, M. Ruiter, P. de The “Vela”roof –UNIPOL, Bologna. Use of on-site energy resources Report 01 – Design Direction Decisions, TU Delft, The Netherlands, 2008. [4] Timmeren, A. van, Turrin, M. The “Vela” roof –UNIPOL, Bologna. Use of on-site energy resources Report 02, TU Delft, The Netherlands, 2009.
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Gap analysis of current research in the area of IT for energy in buildings K. U. Gokce, A. Hryshchenko & K. Menzel Department of Civil and Environmental Engineering, N.U.I. University College Cork, Ireland
Abstract This paper analyses the status of current research in the area of Information and Communication Technologies for the improvement of energy efficiency design and operation of buildings. Currently, research and technology developers focus on different domains and sub-domains in the area of energy efficiency, such as the integration of renewable energy sources and related monitoring, simulation, and management software. In order to enhance harmonisation between different research and technology developments including international and European research projects and scientific programs these activities need to be categorised and analysed. As a result challenges, commonalities, deficits, and potentials for collaboration are identified contributing to the development of a “Scientific Road Map”. This paper proposes a systematic categorization approach to identify gaps in the current research agenda in the area of IT for Energy in Buildings. More than 200 research projects related to this area have been analysed. Our gap analysis is based on a qualitative categorization specifying common classification criteria. The proposed method allows the identification of deficits of the related research activities within the specified categories. Finally, areas which require substantial improvements are identified. Keywords: information and communication technologies, energy efficiency, research and developments, categorization.
1
Introduction
There are many scientific and commercial organizations around the globe who are dealing with brand new technologies in the area of energy efficiency in built WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESU090311
344 Energy and Sustainability II artefacts. On the basis of our survey, many of the projects and research activities are effectively managed in accordance with the norms of open source modelling, since information about current RTD achievements is open to public (cf. [1]). However, there is a significant amount of variation in the control, structure, planning and management of individual projects. Included in these variations are size, time, participants profile consortium, composition, etc. To provide a common structure for a gap analysis which will lead to a shared vision of the impact of ICT on future building design and energy-efficient operation, three main issues should be considered, namely: (1) examination of projects structure based on open source information, (2) tracing their progress over time, and (3) creating a common “structural picture”. This process facilitates the description of the virtual borders of research areas and defines required limits of information. Our proposed analysis of existing research projects will not only describe the areas which have to be considered but also will lead to integration and better collaboration of on-going and future research activities in the area of ICT implementation for improvement of energy efficiency of buildings. This paper presents a systematic selection and categorization approach as part of the EU-FP7 REEB project (“European Roadmap to ICT enabled EnergyEfficiency in Buildings”, cf. [5]). The REEB project was launched in May 2008.
2
Background of the categorization method development
In order to identify common points between different projects which lead to a categorization and analysis structure, the input from the following sources was examined: (I) The method of projects’ categorization according to market share and strategic intent which has been developed by Edward J. Fern in 2004 (cf. [2]). In this method the products of projects are described as a set of deliverables intended to be a service to the customer of the project. To be useful, a project categorization system should achieve all of the following: • It must provide an appropriate category for any project we may encounter, • It must permit classifications within each category, • It must provide useful insight about differences between projects in one category and projects in every other category, and • Its categories must be readily translatable and comprehensible across different disciplines. A systematic approach to research project categorization is believed to be more desirable, since this will accelerate the development progress and avoid duplicated scientific efforts. Therefore, it is important to assure that all significant parameters of RTDs should be considered. (II) A project library, originally developed as part of the “ManuBuild” Project (cf. [3]) – an industry-led collaborative research project on industrialised construction – consisting of more than 200 RTD-related activities for open system manufactured buildings, value driven business processes, ambient and scalable ICT-supported manufacturing methods were analysed. In the WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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“ManuBuild” project general information about R&D developers, technology platforms, national and international scientific programs and commercial organizations have been organised in such a way that filtering based on several main categories and sub-categories becomes possible through an easy understandable interface. (III) The “ManagEnergy” project (cf. [4]) – an initiative of the European Commission, Directorate-General for Energy and Transport, which aims to support the work of actors working on energy efficiency and renewable energies at the local and regional level. This project provides a partner search system with some 4000 organisations, including 380 energy agencies, which can give search options by country, activities, program and type of organization. In this regard the REEB project aims to form a generic approach for identifying, categorising, and prioritising a comprehensive set of prescribed Research and Technology Developments (RTD) for new ICT-based solutions, related to improvement of Energy Efficiency (EE) in buildings. It is also accepted that announced future results of the research projects would not always be delivered in an expected granularity, so the global picture of the research activities in the area of Energy Efficiency improvement for built artefacts might change in time.
3
Approach to RTD selection and categorization within REEB project
The main approach of REEB is to examine current research projects and best practices for ICT applications and tools which are relevant to energy efficiency in built environments, with emphasis on standardization initiatives and developed regulations. This provides a definition of common research points and a “Scientific Roadmap” for the implementation of actions related to ICT support of energy efficiency in the built environment and a strategy for information exchange and dissemination between all energy-related ICT projects, initiatives, and stakeholders within European Union. For a better understanding and more efficient coordination of the current scientific efforts in this specific area – “Information and Communication Technologies for Energy Efficiency in Buildings”, a systematic selection and categorisation approach is developed as part of the REEB project. 3.1 Selection criteria for recent key research projects The objective of the systematic selection and categorisation approach proposed in this paper is to provide a comprehensive set of criteria for the selection and qualitative evaluation of key research projects focusing on ICT-based energyefficient management of built artefacts and systems, including novel methods for modelling, financing, operation, and maintenance processes. Based on the focus and requirements of the REEB project we initially defined three main areas which were suggested as Key Selection Criteria (cf. Figure 1), namely: WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
346 Energy and Sustainability II (I) Implementation of Information and Communication Technologies, (II) Control Energy Efficiency and Energy-Management, (III) Applied to Build Artefacts. Key Selection Criteri a
& (I) Info rmation and Communi cation Technolog ies
(II) Energ y Efficiency
(III) Built Ar tefacts
Hardw are
Intake / Production
EE Design
Software
Contr ol
Commissioning
Demand
Retro fit
Maintenance, Inspection
Operation
Domain Specification of Selection Criteria
Figure 1:
Key selection criteria.
The main RTD target challenges related to ICT implementation are defined as “Domain Specification of Selection Criteria” and include: (I.1) Hardware Development, which specifies different types (wireless and wired) of network components such as: smart mobile devices, desktop devices, sensors, meters, controllers, actuators. (I.2) Software Development, which represents modern software used to provide efficient hardware usage and smart energy management. It includes network operating systems, design tools for buildings and networks, modelling and simulation tools, construction support software, operational software for data management and analysis, building control and automation software, and software for energy-efficient facility management. Additionally, challenges related to the improvement of energy efficiency within buildings can be described as strategies for effective energy management with IT support and optimization of buildings’ energy consumption and production: (II.1) Intake and Production, which includes efficient measurement and optimised control of the intake of various energy sources (gas, electricity, WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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renewable sources); maximisation of the renewable energy generation; minimisation of building CO2 emission; (II.2) Demand through monitoring of building occupants comfort (temperature, humidity, CO2 level) and energy demand of production utilities (e.g. computers). (III) Moreover, the general Life-cycle Phases of buildings should be considered for ICT implementation – from energy-efficient design and commissioning through installation and modification of different equipment (retrofit), to operation phases. On that basis, it is proposed that if any of these selection criteria are not matched RTD activities – this activity should not be further analysed. This selection process narrows the scope of research projects to be analysed which have the greatest potential to improve the modern ICT usage for energy-efficient operation of built artefacts. 3.2 Categorization “top – down” approach The methods for categorizing a group of research projects typically depend on a well-specified set of attributes for each project, which facilitate the classification of these RTDs within specific categories. We decided to use a “Top-Down” approach in REEB as an appropriate method for the RTD categorization process. This method essentially breaks down a whole number of selected RTDs into separate groups of compositional categories. Each category then will be refined in more detail on the following sub-category levels until the complete specification of each RTD will satisfy the requirements on a logical basis. The aims of this task are: (1) to select the most appropriate characteristics of each selected RTD; (2) to find similar research targets/final products, and (3) to define these results as categories. In the first step of the categorization it is necessary to identify and classify the providers of selected RTDs. This means to answer the questions “Who are they?” and “Where are they from?” It is possible to name those developers in terms of “Academic”, “Government”, “Public Organizations”, “Contractors”, “Suppliers” or “Others”. During the analysis of RTDs we realised that “Contractors”, “Public Organizations” and “Suppliers” are less involved in basic scientific researches. However, these stakeholders are involved in physical implementation of RTD results in practice. Examples of their activities are presented in another work-package of the REEB (WP2, cf. [5]), entitled “Best Practices”. In order to narrow the scope of our analysis, the centre of attention is concentrated on the categories “Academic” and “Government” since they are often tied together in terms of sponsorship (government funding academia). Any other RTD developers are subsequently named as “Others”. The distribution of scientific forces in domain of “ICT for EE in Buildings” by the countries of European Union is presented in Figure 2. The categorisation of non-EU research activities was not considered as there is a deficiency in present and future non-EU RTD results. In the next step of categorization process we use the Domain Specification of the Selection Criteria for the development of an initial definition of WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
348 Energy and Sustainability II
Figure 2:
Distribution of RTDs per EU country.
categorization attributes. These sub-categories should be able to define the relevance of RTD results. They can include development of: (1) modern ICT hardware, (2) building concepts, (3) methods and tools supporting optimal design, (4) simulation and integration of products and services related to efficient energy consumption and environmental impact in the Construction Industry, (5) dynamic building simulation tools that enhance the efficiency of the design process and support design decisions, and (6) novel control and monitoring systems supporting the integration of global and local control strategies applicable to industrial processes and living environments. The development of sub-categories is a result of separate analysis and evaluation of more than 200 R&D projects. The overlapping issues and similarities are extracted during the analysis process. It is accepted that each single research project is unique because of its different developers and different approaches to specific problems and solutions. However, it is possible to find similar (overlapping) areas, i.e. a limited number of projects is supposed to develop similar results. The number of these sub-categories must be relatively small in order to not mislay the understanding of the global situation. Otherwise, there will be a risk of losing the “sharpness” of the borders between them. On the basis of examined RTDs aims and current results, we propose the definition there are eight main categories. They reflect the main interest areas which are given in Figure 2. These eight main categories are: (I) Hardware – sensors, meters, actuators, controllers; (II) Operating Systems and Wireless Networks Implementation – meshed self-adaptable, easy to install;
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(III) Network Design (of sensors and other hardware) – including methodologies and tools (software); (IV) Building Design – special building projects with emphasis on interoperability, advanced modelling and simulation; (V) Performance Data Analysis – RTDs dealing with improved data consolidation, aggregation, interpretation of data collected in a building in order to improve its EE; (VI) Improved Diagnostics – RTDs focusing on improved data analysis from sensors, meters, actuators, and controllers; (VII) Predictive building control – the final product of the related RTDs should improve the EE of buildings because of contained implementations such as an “intelligent” controlling system. Such a system would predict actuation based on surrounding environmental changes. (VIII) Value Driven Operational process – Result of RTD is software for intelligent, predictive and real-time EE calculations. Categories of RTDs PERFORMANCE DATA ANALYSIS
Improved data consolidation, aggregation, interpretation
BUILDING DESIGN methodologies, tools
IMPROVED DIAGNOSTICS
Interoperability, Advanced modelling, Advanced simulation
NETWORK DESIGN
Improved Data analysis from Sensors, Meters, Actuators, Controllers so on.
V
IV
VI
ICT for Energy Efficiency in Buildings
III
Methodologies, tools
PREDICTIVE BUILDING CONTROL
e.g. Usage of "Artificial
VII intelligence" systems
II "OPERATING SYSTEMS" for Wireless Networks
Meshed, Self-adaptable, easy to install
I
VIII
HARDWARE
VALUE DRIVEN OPERATIONAL PROCESS
Intelligent predictive and real-time EE calculations
Sensors, Meters, Actuators, Controllers
Figure 3:
Main categories for qualitative RTD analysis.
All selected RTDs were compiled in tabular form, as is presented below, where the project name, countries of RTD participants, the information source (web-link), categories and brief description of each project (see Table 1 below). WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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No
1
4
Country, Developer
Ireland, UCC
RTD Name
ITOBO
Example of selected RTD (cf. [6]). Web -link
http://zuse. ucc.ie/itobo
Table 1:
Category
I-VIII
Short description of Research ITOBO develops an anticipated (smart) building that operates on an energyefficient and user-friendly basis while reducing its maintenance costs, including: • Hardware Design • Wireless Systems integration and network protocol development • Constraint-based Decision Support • N-dimensional Information Modelling • Facilities Management with access to sophisticated built infrastructure and co-operation with standardisation bodies.
Statistic analysis of categorization results
During the first phase of the REEB project the 44 RTDs were selected and categorized. The results of categorization are compiled in an Excel file especially for extraction of statistic information (see Figures 2, 3), such as distribution per EU country, coverage of RTD per category. It is always possible to extend the number of RTD-characteristics and extract more information for better understanding.
Figure 4:
Statistic data of RTDs.
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Gap analysis and proposed potential improvements
The analysis of the finally selected 44 European research projects in the area of “IT for Energy-Efficient Design and Operation of Buildings” has shown that Finland and Ireland lead research activities in EE in buildings, however Sweden, Belgium, Greece contribute with one project each. Moreover, countries like Cyprus, Czech Republic, Estonia, Latvia, Lithuanian, Luxemburg, Malta, Portugal, etc. are currently not represented in our analysis covering the area of “EE in buildings”. According to our analysis, most of the projects focus on the improvement of single aspects of the overall area. However, since the launch of the 7th Framework Programme of the European Union an increasing number of projects focus on the development of more holistic solutions. The consolidated results based on categories shows those three important issues: (1) Hardware Development, (2) Predictive Building Control and (3) Value Driven Operational Processes are not considered in an expected level within the analysed projects. The intelligent control, which leads to EE improvement in buildings, not only requires operating system, wireless network implementation and efficient sensor-network design, but also requires new component (hardware) development and predictive control on the basis of historic operational process data. 5.1 Hardware development The products of the construction industry have an extremely long life-span. The degree of systems integration is very high. Therefore, it is essential that monitoring and control devices are designed and manufactured in a way that addresses the requirements of the construction sector, such as (1) innovative, robust packaging of wireless components, (2) innovative energy harvesting for wireless components, and (3) innovative firmware and network management systems to ensure long operational time for devices without a need to replace batteries. 5.2 Predictive building control The integration of renewable energy sources and the Co-Generation of Energy was identified as a major challenge for R&D activities. Currently, buildings consume energy to provide user comfort. However, through the integration of multiple energy generation systems buildings have the potential to contribute to the generation of energy. However, so called “Intelligent Building Control and Energy Management Systems” are required to manage the “bi-lateral” energy-exchange between the building and the supply grid. Furthermore, the capability to “predict” the energy demand is required in order to allow the optimal usage of “local” storage capacities, such as the thermal mass of building systems and components, etc. Furthermore, the availability of new “integrated” devices, such as “intelligent facade elements” and the availability of wireless sensing, metering, actuation and WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
352 Energy and Sustainability II control components enable the installation of improved micro-zone control systems. Researchers argue that improved micro-zone control contributes to improved indoor climate. However, many stakeholders in industry request the development of design and installation strategies which aim to compile an optimum amount of building performance data with a minimum amount of sensors, meters and further wireless hardware components. Additionally, we could identify a demand to support the maintenance and renovation of existing buildings. Most of the buildings designed and commissioned in the 1980ies and early 1990ies are equipped with Building Automation Systems. However, the documentation of these systems is weak. Therefore, we identified a need for software tools supporting the analysis and reengineering of existing building automation systems in old buildings. 5.3 Value driven operational processes The pure availability of innovative hardware components and improved control software is only a sufficient condition for the implementation and implantation of IT for EE in Buildings. These two areas need to be complemented by the development of innovative business models for “Energy Service Provision” and the supportive IT-infrastructure. Our gap analysis has shown: (1) that there is a deficit in IT-support for improved management of “bulk” performance data, including standardised information models and robust tools for multidimensional data management and analysis, (2) that there is a deficit of eServices providing support for the analysis of complex performance data as well as improved building performance diagnosis, and (3) that there is a deficit of eServices supporting the efficient management of maintenance and upgrade activities.
6
Conclusions
Instead of ad-hoc analysis of projects/RTDs that are prevalent today a more systematic approach to this important aspect should be developed. This systematic approach should be hierarchical in nature. Firstly, simple and robust filter criteria should be defined to allow a clear selection of relevant projects. Secondly, the initial categorization/grouping should support the identification of potential working collaborations and enhance harmonisation between different RTD developers, International European RTD projects and various European scientific programs.
Disclaimer All results presented in this analysis are based on open information sources such as websites with information presented in English, German, Chinese and Russian languages. The authors do not claim that the analysis result is complete. It is possible that information about projects is missing or information is presented in other languages or is available as protected commercial information. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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References [1] Lucie Guibault, P. B. Hugenholtz “The future of the public domain: identifying the commons in information law”, 2006, Page 304 [2] Edward J. Fern, “Strategic Categorization of Projects”, http://www.time-toprofit.com/TTPcategories.asp [3] Open Building Manufacturing, European Integrated Project on Industrial Construction “ManuBuild”, http://cic.vtt.fi/projects/manubuild/public.html [4] The “ManagEnergy” project from EU commission, http://www.managenergy.net /submenu/Sorg.htm [5] The “European Roadmap to ICT enabled Energy-Efficiency in Buildings” project, http://www.ict-reeb.eu/Objectives.html [6] “Information and Communication Technology for Sustainable and Optimised Building Operation” project, http://zuse.ucc.ie/itobo/ [7] The purposes and methods of practical project categorization, Russell D. Archibald, 2005, http://www.x25.com.br/peter/Basic_Russ_P_ Categories.doc [8] Russell Archibald, “The purpose and methods of practical projects categorization” 2005, http://www.maxwideman.com/guests/ categorization /methods.htm
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Development of a sustainability assessment framework for planning for sustainability for biofuel production at the policy, programme or project level L. K. Haywood, B. de Wet, G. P. von Maltitz & A. C. Brent Natural Resources and the Environment, CSIR, South Africa
Abstract Biofuel development projects are proceeding at a pace that outstrips normal planning and feasibility evaluation. We present a theoretical framework for planning for sustainability for biofuel production at the policy, plan/programme or project (PPP) level. The objective of this framework is to foster and preserve the social ecological system in which the PPP is to occur so that the system remains dynamic, adaptive, resilient and durable through time. The overall approach to the framework is the understanding of the function and relationships within the social ecological system in which the proposed biofuel PPP is to occur. The system is analysed through stakeholder engagement and expert analysis. Sustainability is assessed through the development of sustainability principles and criteria with sustainability indicators to measure the progression. The framework has developed through a long history of impact assessment and strategic environmental assessment in the environmental sector. Keywords: biofuel, sustainability assessment, planning, social ecological system, sustainability vision, principle, criteria and indicators.
1
Introduction
The world is facing looming energy shortages in the light of ever increasing energy demand and it is predicted that by 2025 the global demand for petroleum will have increased by 40-50% over current levels [1, 2]. This is extremely concerning considering that petroleum is the largest single source of energy consumed, exceeding coal, natural gas, nuclear, hydro and renewables [3]. The WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESU090321
356 Energy and Sustainability II rise in oil price, energy security and the realisations of the impact of global warming has sparked worldwide concern to rapidly address the replacement of petroleum with an alternative energy source. Biofuels, a renewable energy source derived from biomass, would appear to offers potential as an alternative energy supply as it is one of the few alternatives to fossil fuel derived liquid fuels. Despite the appeal of biofuels, a number of key concerns around the long term sustainability of a biofuels industry have recently been raised, and it is now clear that careful, case specific, assessment and planning needs to underpin any proposed biofuels initiative [4, 5]. The development of technologies to utilize biomass as a source of energy has advanced on many fronts to produce solid fuels (chips, pellets, briquette, logs), liquid fuels (methanol, ethanol, diesel), gaseous fuels (synthesis gas, biogas, hydrogen) and heat [6, 7]. Through modern technologies such as pyrolysis, gasification and anaerobic digestion countries such as the United States of America (USA) and the European Union (EU) are focusing on the use of biofuels as a replacement fuel to petroleum [6, 8, 9]. The advancement of bioenergy technologies has created a situation where the implementation of biofuel programmes, or specific biofuel development projects, is proceeding at a pace which outstrips that of normal planning and feasibility evaluation. It is not enough to have a renewable source of energy but this source must be sustainable in its supply thereby meeting the objectives of the Johannesburg Plan of Implementation and The Millennium Development Goals. Unless a number of measures are successfully put in place to ensure sustainable agricultural practices and sustainable biofuel conversion practices, particularly during the inception phase of any biofuel project, no matter the technological advancements, this industry may cause more ecological and social damage than the envisaged benefits. Serous concerns have been raised about the sustainability of future biofuel development, both for a global environmental perspective as well as from local socio-economics perspective [10, 11]. Research on sustainable biofuel systems is a very young science so that few studies and empirical, field-derived data are available as yet. While reducing carbon emissions and security of energy supply are perceived positive benefits at a global level, developing nations and local communities are likely to consider job creation, income improvement, the local environment and regional development as more important considerations for engaging in biofuels [11]. These differing and potentially competing benefits may be regarded as aspects of assessing biofuel developments within a framework of sustainability, generally recognised as having three sets of criteria: economic viability, environmental performance and social acceptability [10]. Sustainability is not a measureable target or an accurate science. Sustainability and sustainable biofuel production is subjective depending on the desired outcomes of the end user. This paper sets out the basis of an approach for planning for sustainability for biofuel production at the policy, plan/programme or project (PPP) level. The objective of planning for sustainability at the onset is to foster and preserve the social ecological system in which the PPP is to occur so that it remains dynamic, adaptive, resilient and WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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therefore durable through time. This is different from the conventional approach to environmental assessment, which is used to provide information for decisionmaking, based on the level of potential environmental impacts that are considered acceptable, or which through mitigation can be managed. This research comprises a theoretical sustainability assessment framework to be used to guide and support planning and decision making for sustainable biofuel production.
2
Theoretical background to planning for sustainability
2.1 Environmental assessment vs. sustainability assessment Environmental Impact Assessment (EIA) has been firmly entrenched for the analysis of potential effects of developments on the environment. The technique and process of EIA have an established history of application spanning the past 40 years, having first been legislated in the USA in the National Environmental Policy Act of 1969. Although the use of EIA has brought environmental concerns into project level development planning, its success in promoting sustainability as an outcome of planning has been limited. The reasons for this limited success, is that EIA focuses primarily on identifying and evaluating the potential ecological, social and economic effects of proposed projects separately and in isolation from each other, and only thereafter are attempts made to integrate the implications of these effects, so that a more comprehensive picture of the impact of the proposed development can be obtained [12, 13]. In addition, EIA traditionally does not address the potential effects that may manifest over time, and is usually used to evaluate a proposal at a ‘snap shot’ in time meaning that the nature, extent and dimensions of the project must be constant for the analysis to take place, and so changes in the project over time constitute a ‘new project’, which must then be subjected to a new EIA [13, 14]. Finally, project level EIA is commonly focused only on the investigation of potential effects on the proposed project site and seldom broader and it is seldom that environmental impacts stay within a confined site boundary [14]. Strategic Environmental Assessment (SEA) attempts to address the limitations of EIA in that it is a tool designed to move environmental assessment in the development planning process [15]. SEA is intended to facilitate the consideration of environmental effects from a strategic perspective, so that broader considerations than only those applicable to individual projects are taken into account in planning. The strategic perspective changes both the nature and number of potential effects that may result from a particular development proposal, since many of the potential effects can be avoided by informed policy and development plan/programme formulation [15, 16]. Although SEA has made a substantive contribution to the incorporation of environmental concerns into development planning, the manner in which it is applied and the purpose that is defined for individual SEAs, also do not necessarily constitute planning for sustainability.
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358 Energy and Sustainability II Sustainability Assessment is expressly to prepare and design a development policy, plan, programme or project with sustainability as the desired outcome, rather than merely to prevent or mitigate potential environmental impacts [17, 18]. The approach is inherently positive as well as prospective. It is about considering the relationships between social, ecological and economic factors. Gibson [19] advocates that sustainability assessment must be focused on these interrelationships and their character, resilience to change and adaptability. Since sustainability is an integrative concept, it is important to design sustainability assessment as an essentially integrative process that can act as a framework for better decision-making at all levels of development planning that may have lasting effects [19]. These relationships need to be characterised and explored at the earliest stages of a sustainability assessment process to inform the accurate formulation of appropriate sustainability criteria.
3
Fundamental methodological aspects of the planning for sustainability assessment framework
3.1 Stakeholder participation The overall approach to this framework is the understanding of the function and relationships of the social ecological system in which the proposed biofuel PPP falls. Instead of taking a reductionist approach, in which various technical experts analysis aspects of the social ecological system and provide recommendations thereof, this framework works on the premise that wholeness of the system is best described by a wide variety of stakeholders. The explicit inclusion of those who have a stake in the planning scenario is now a development-planning orthodoxy. A holistic approach to sustainability defined as a participatory deconstruction and negotiation of what sustainability means to a group of people, along with the identification of indicators to assess such deconstructed vision of sustainability. Planning for sustainability is thus driven by broad based stakeholder participation coupled with evidence-based information throughout the entire planning process. The success of the planning process relies on drawing on the inputs of as many interested and affected parties as far possible to ensure that all the components of the social ecological system and the relationships between them are both identified and where necessary investigated. The participation is facilitated within a deliberative process which can include workshops, discussion groups, participatory rural appraisal or even the use of the rich picture technique. This process needs to be supplemented by evidence based data and information, and this might require the commissioning of specialist studies based on early scoping of important issues as well as the use of models and multi-criteria tools to aid stakeholders understand alternative scenarios. Without this comprehensive involvement, there is a high risk of excluding important considerations of the system in effectively planning for sustainability. Gibson [19] refers to this as a process that creates spaces for values and perceptions are considered alongside technical data; and identification
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of modifications or alternatives to a proposal that would deliver more sustainable outcomes encouraged. 3.2 Sustainability goals and vision Sustainability is based largely on the integration of social, economic and biophysical elements that exist within social ecological systems. The sustainability goals of any sustainability assessment must therefore address these elements as they are ultimately the drivers of change within a social ecological system. These sustainability goals form the starting point of the sustainability assessment as they provide the platform to stimulate the visioning process among the stakeholders. At a global scale there are commonly three broad sustainability goals for biofuel production. These include [4] 1. Rural development and food security; 2. Environmental change (including maintenance of ecosystem services and reducing future climate change; and 3. Security of energy supply. The most important step in sustainability assessment is to define a sustainability vision [17, 19] The vision is equivalent to a desired end state or sustainability scenario for the social ecological system in question, as defined by all interested and affected parties during the participation process. Elements of the above three sustainability goals (where appropriate) as well as any other local important sustainability goals should be infused within the end vision. In other words, the biofuel PPP vision becomes a locally accepted statement giving appropriate weighting to varying aspects of sustainability. If a common vision for biofuel development cannot be created amongst the stakeholders and there is no consensus on the vision, then this is where the sustainability assessment process stops. The PPP for biofuel development may thus not be appropriate for the specific area or regional/national context, and the desired state of sustainability will not be achieved. 3.3 Sustainability principles, criteria and indicators Assessing whether a proposed biofuel development will be sustainable or not, requires that sustainability principles, criteria and indicator be defined. A sustainability principle is a broad based statement for achieving the sustainability vision. Sustainability criteria are management objectives that are set in order to achieve the broad principles as set out in principles. Sustainability criteria essentially indicate how the sustainability principles can be achieved. All the sustainability criteria that have been set must be satisfied to ensure that the sustainability principles and thereby the sustainability goal will be achieved in the implementation of the proposed PPP for biofuels development. In essence the criteria represent the minimum acceptable condition that is agreeable to all stakeholders, and as such any proposal that cannot meet the criteria should be rejected. Sustainability indicators provide a measure of the criteria. Practical, meaningful and measurable indicators should be identified for each of the criteria, so that it is possible to measure whether individual sustainability criteria WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
360 Energy and Sustainability II have been met or not. Indicators may be qualitative or quantitative in response to the specific criterion. Great care needs to be taken to ensure that indicators do not unintentionally bias the interpretation of the criteria or prevent innovative and novel means to ensure that the criteria is met. Table 1 provides a theoretical example of sustainability principles, criteria and indicators for an associated sustainability goal. Table 1:
Example of the application of the sustainability goal and the development of sustainability principles, criteria and indicators.
Sustainability Goal: The biofuel production project promotes/ensures improved rural and social economic development whilst maintaining integrity of supply of environmental goods and services Sustainability Principles Sustainability criteria Sustainability indicator Household food security does not No household should have The biofuel program has a decline as a result of the biofuels reduced household food security as a direct net positive impact on the project consequence of the project livelihoods of rural dwellers in the project area There is no reduction in overall No high potential food provision from the entire agricultural land is used for region biofuel production Biofuel projects shall not violate Compliance with Land existing formal or informal land Reform Act rights
Biofuel production shall not violate human rights or labour rights, and shall ensure decent work and the well-being of workers.
Key Ecosystem services are maintained
There is no local extinction of species Downstream uses continue to maintain good quality water
The project greenhouse reductions
results in net gas emission
Workers will enjoy freedom of association, the right to organise, and the right to collectively bargain No child labour shall occur, except on family farms and then only when work does not interfere with the child’s schooling. No conservation areas or areas of high biodiversity importance are used for biofuel plantations Stream flow does not change substantially as a consequence of the project No pesticide of nutrient pollution enters streams Only feedstock with proven positive GHG benefits are used There is no deforestation of existing forests
The principles, criteria and indicators are context specific, taking into account local social, economic and ecological conditions and the relationships between them, as well as the unique group of stakeholders. Setting a sustainability vision and determining principles and criteria for the achievement of sustainability at WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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the start of a sustainability assessment process, provides robustness to the analytical process required for decision making later in the process. 3.4 Mapping of the receiving environment Mapping the social ecological system entails describing and characterising in detail, the baseline status quo of the specific social ecological system within which the PPP for biofuel development is proposed. The outcome of this task should be a comprehensive description of the receiving social ecological system or context in which the biofuels PPP is to be implemented and all internal and external influences on it. At the level of a proposed biofuels development policy, the social ecological system could be the interacting natural and social components of an entire country. The analysis should be expected to be conducted in a more abstract sense. In the case of a plan or programme, the social ecological system could be limited to a specific catchment, or geographic region, or to the social ecological systems in a range of different non-contiguous geographical regions / locations, or a specific vegetation or ecological zone. At the level of a biofuels development project, the social ecological system will likely be primarily bounded by the immediate environment in which the project would be situated. The analysis should be expected to be less abstract and based more on direct empiricism. The information will provide baseline values and trends against which to assess the sustainability performance of the PPP for biofuel development. 3.5 Opportunities, constraints and trade-offs The purpose of the sustainability assessment analysis is to identify characteristics of the social ecological system or context that provide opportunities for achieving a sustainability vision for the PPP for biofuel development, and characteristics that would constrain achieving the sustainability vision. The analysis should be conducted in a process of deliberation with all stakeholders. Where possible the opportunities and constraints should be captured and illustrated visually and in combination to assist in determining the potential for the implementation of the PPP for biofuels development i.e. whether the vision is realistic and achievable. It is inevitable that for social and economic gain there will be a trade-off with biophysical or ecological elements. Given the complex nature of biofuel tradeoffs, the need arises for an evidence based understanding of likely tradeoffs as well as appropriate tools for assisting stakeholder in understanding the consequences of likely tradeoffs. When planning for sustainability and in sustainability assessments the one essential rule is that trade-off decisions must not compromise the fundamental objective of net sustainability. As the sustainability framework is participatory based all trade-offs and compromises identified must be openly discussed and explicitly justified and the most desirable option chosen. In this regard, the following generalise rules must be applied [19]:
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362 Energy and Sustainability II •
No trade-off or compromises will be permitted unless approved by all relevant stakeholders; or • Only undertakings that are likely to provide neutral or positive overall effects for each core sustainability requirement can be acceptable; or • No significant adverse effects in any core category can be justified by compensations of other kinds, or in other places. As far as possible tradeoffs should already have been considered at the point of developing the criteria, and the agreed criteria should be set up in such a way as to accommodate tradeoffs, whilst drawing a clear limit as to what adverse impacts are non-negotiable.
4
Planning for sustainability framework
The sustainability assessment framework comprises of four tasks. The tasks are as follows: I. Planning for sustainability for proposed biofuel PPP (Preparation for Sustainability Assessment) II. Sustainability Assessment for proposed biofuel PPP. III. Re-design or modification of proposed PPP to improve sustainability performance IV. Project appraisal (if required, e.g. EIA mandated by legislation) Figure 1 diagrammatical represents the planning for sustainability framework. In the case of a new PPP where no development planning has yet been undertaken then only Task I should be completed (followed by Task IV for any project). This task will ensure that the biofuel PPP is planned at the vey onset with sustainability as its main goal. The outcome will be a set of principle, criteria and indicator that can be used through the PPP life span to ensure that sustainability is applied. For any PPP for which there currently are development plans (i.e. there are current infrastructure) in place then Tasks I to III must be completed as a minimum, in sequence, for the process of planning for sustainability to be effective. Task I forms the foundation for assessments or further work in subsequent tasks (II – IV) and must always precede any assessment forming part of those. Any assessment conducted without this foundation, will not deliver a biofuel PPP with sustainability as its focus, but merely PPP in which the prevention, tradeoff and mitigation of potential environmental (social, economic and ecological) impacts might have been identified and addressed. All planning, assessment and analysis conducted within the processes outlined in the framework, should focus on the entire biofuels production value chain i.e. the complete life cycle. This applies to all types of biofuels development proposals – policies, plans / programmes and projects. Only in the case of specific biofuels development projects, which only address specific portions of the value chain, might it be permissible to evaluate only the relevant portion of the value chain, for example feedstock production only to delivery at a refinery, or the industrial process of biofuel production in isolation from WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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TASK I : Preparation for Sustainability Assessment STEP 1 Define the purpose of the PPP
STEP 2 Formulation of a vision Environmental boundary of the PPP
Input Identification of opportunities and constraints
Input Mapping of receiving environment
SUSTAINABILITY VISION
Input Negotiation of trade off and off sets
STEP 3 Develop sustainability principles Develop sustainability criteria
Develop sustainability indicators
TASK II: Sustainability Assessment Evaluate the PPP
TASK III: Improve design for sustainability performance Improve/update the design of the PPP
TASK IV: Project Appraisal Environmental Impact Assessment or other project specific assessments
Figure 1:
Planning for Sustainability Framework.
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364 Energy and Sustainability II feedstock supply. The intention behind the Planning for Sustainability Framework is to ensure that the focus of any particular analysis of proposed biofuel development is as comprehensive as possible, and that proponents should strive to conduct tiered or nested analysis of policies, to plans/programmes, and then ultimately to projects.
5
Conclusion
The undertaking of a sustainability assessment would be initiated mainly by some form of legislation promoting sustainable development principles, environmental management best practice and natural resource protection. Another driver initiating the use of this framework is that of international biofuel sales. Due to the potential negative elements of biofuel production such as loss of biodiversity, changing land use patterns, social economic impacts and green house gas emissions, sustainable biofuel production is becoming a key concern and is being considered as a requirement for market access. Setting standards and establishing certification systems is currently being promoted, however, a process that promotes a vigorous planning for sustainability for the life span of the biofuel PPP could help strength trade agreements. Sustainability assessment is an emerging science. The current principles have developed through a long history of impact assessment and strategic environmental assessment in the environmental sector. The framework presented will improve and mature over time as its application is tested on actually planned biofuel production PPP’s. It is likely that over time new and innovative methods and tools will be developed to assist the process. The CSIR is current involved in a European Union funded project known as Re-impact, which has started to test the planning for sustainability framework methodologies in India [20]. The CSIR is also looking to opportunities to test this in South Africa
References [1] [2] [3] [4] [5]
Rooney, W.L., Blumenthal, J., Bean, B. & Mullet, J.E., Designing sorghum as a dedicated bioenergy feedstock. Biofuels, Bioproduction & Biorefining, 1, 147-157, 2007. Johnston, M. & Holloway, T., A Global Comparison of National Biodiesel Production Potentials. Environmental Science & Technology, 41, 7967-7973, 2007. Energy Information Administration. International Energy Outlook 2005, ed. Energy Information Administration, Paris, 2005. The Royal Society, Sustainable Biofuels: Prospects and Challenges. ed. The Royal Society, London, United Kingdom, Policy Document 01/08. 2008. Gallagher, E., The Gallagher Review of the indirect effects of biofuel production. The Renewable Fuel Agency. 2008.
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Sims, R.H., Hastings, A., Schlamadinger, B., Taylors, G. & Smith, P., Energy crops: current status and future prospects. Global Change Biology, 12, 2054-2076, 2006. [7] Bridgwater, T., Review: Biomass for energy. Journal of the Science of Food and Agriculture, 86, 1755-1768, 2006. [8] Demirbas, A., Bioenergy, global warming, and environmental impacts. Energy Sources, 26, 225-236, 2004. [9] Blanco, M.I., & Azqueta, D., Can the environmental benefits of biomass support agriculture? – The case of cereals for electricity and bioethanol production in Northern Spain. Energy Policy, 36, 357-366, 2008. [10] Elghali, L., Clift, R., Sinclair, P., Panoutsou, C. & Bauen, A., Developing a sustainability framework for the assessment of the bioenergy systems, Energy Policy, 35, 6075-6083, 2007. [11] Groom, M.J., Gray, E.M. & Townsend, P.A., Biofuels and biodiversity: Principles for creating better policies for biofuel production, Conservation Biology, 22, 602-609, 2008. [12] Burdge, R.J., A brief history and major trends in the field of impact assessment, Impact Assessment Bulletin, 9, 93-104, 1991. [13] Caldwell, LK., Analysis-assessment-decision: the anatomy of rational policymaking, Impact Assessment Bulletin, 9, 81-92, 1991. [14] Noble, BF., Strengthening EIA through adaptive management: a systems perspective, Environmental Impact Assessment Review, 20, 97-111, 2000. [15] Govender, K & Audouin, M. Introduction to SEA. (Chapter 1). Enhancing the effectiveness of Strategic Environmental Assessment in South Africa, ed. K. Govender, M. Audouin & S. Brownlie, CSIR Report CSIR/NRE/RBSD/EXP/2007/0068/A, pp 2-19, 2007. [16] Runhaar, H. & Driessen, P.P.J., What makes strategic environmental assessment successful environmental assessment? The role of context in the contribution of SEA to decision-making, Impact Assessment and Project Appraisal, 25, 2-14, 2007. [17] Pope, J., Annandale, D. & Morrison-Saunders, A., Conceptualising Sustainability Assessment, Environmental Impact Assessment Review, 24, 595-616, 2004. [18] Pope, J. & Grace, W., Sustainability Assessment in context: Issues of process, policy and governance, Journal of Environmental Assessment Policy and Management, 8, 373-398, 2006. [19] Gibson, R.B., Beyond the pillars: Sustainability assessment as a framework for the effective integration of social, economic and ecological Considerations in significant decision-making, Journal of Environmental Assessment Policy and Management, 8, 259-280, 2006. [20] Re-impact, http://www.ceg.ncl.ac.uk/reimpact/index.htm.
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Production of biodiesel from Jatropha curcas and performance along with emission characteristics of an agricultural diesel engine using biodiesel S. Mitra1, P. K. Bose2 & S. Choudhury3 1
Department of Mechanical Engineering, Jalpaiguri Government Engineering College, India 2 Director, NIT – Silchar, India 3 Department of Mechanical Engineering, Dr. B. C. Roy Engineering College, India
Abstract The objective of the present experimental work is the production of biodiesel and to examine the effects of different blends of biodiesel with diesel on the exhaust emission and performance characteristics of an existing agricultural diesel engine and to select a suitable blend of biodiesel with diesel. The suitability of a blend of biodiesel with diesel is related with the reduction in exhaust emissions and brake specific fuel consumption (BSFC), together with an increase in brake thermal efficiency (BTE). Experimental work started with the production of biodiesel obtained from Jatropha curcas in our own mini biodiesel plant. Biodiesel is blended with diesel at different ratios to obtain different blends, such as B10 (10% biodiesel + 90% diesel by volume), B20, B30, B40, B50, B60, B70, B80, B90 and B100. Experimental results show that BSFC at all loads is less for blends B10 to B50 compared to that of diesel. BTE at all loads is higher for blends up to B60 compared to diesel and after B60 it is more or less the same as diesel. Engine emissions of CO, HC, and also NOx to some extent, are less for all blends from B10 to B100. Among the blends, B10 has lowest BSFC, lowest emission and highest BTE. Higher biodiesel blends can also be used with suitable modifications to arrest some NOx. The present investigation is thus directed to the on-going research towards the search for viable alternative fuels for energy security, environmental problem mitigation and sustainable development. Keywords: biodiesel, Jatropha curcas, diesel engine, performance and emission. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESU090331
368 Energy and Sustainability II
1
Introduction
For any country to become self sustainable, efficient use of natural resources is very much essential. Nowadays, the internal combustion (IC) engine has become indispensable both in the business and private sectors. The diesel engine dominates in the field due to its ease of operation and higher fuel efficiency. In India the demand for diesel (HSD) is projected to grow by 5.5% per annum. The emission of hazardous gases from the exhausts of heavy duty vehicles have also increased tremendously. This has resulted in environmental degradation, such as air pollution, climatic changes, etc. The primary need today is to create a clean environment. Added to this, the gradual depletion of the world petroleum reserve is causing an energy crisis and generating an intense international interest in developing alternative non-petroleum fuels for diesel alternatives. In recent years, systematic efforts were undertaken by many researchers to determine the best solution among alternative fuels. Thermodynamic tests based on engine performance evaluations have established the feasibility of using a variety of alternative fuels, such as hydrogen, Compressed Natural Gas (CNG), alcohols, bio-gas, producer gas, animal fats (including their derivatives) and a host of vegetable oils. In recent years, vegetable oils have received significant attention both as a possible renewable alternative fuel and as an additive to the petroleum based fuels, as they are renewable, biodegradable, non-toxic, environmentally friendly and have a lower emission profile compared to diesel fuel (Srivastava and Prasad [1]). Biodiesel exhibits several merits when compared to that of the existing petroleum fuels. Many researchers have shown that particulate matter, unburned hydrocarbons, carbon monoxide and sulphur levels are significantly less in the exhaust gas for biodiesel in comparison to petroleum fuel. Major problems associated with vegetable oil as a diesel substitute in IC engines have been recognized, such as its high viscosity, low volatility and poly unsaturated character. These problems are due to the large molecular mass and chemical structure of vegetable oils. The use of non-edible vegetable oils compared to edible oils is very significant in developing countries such as India, because of the tremendous demand for edible oils as food – they are far too expensive to be used as fuel at present. There are many tree species that bear seeds rich in non-edible vegetable oils. Some of the promising tree species are Pongamia pinnata (karanja), Melia azadirachta (neem), Jatropha curcas (Ratanjyot), linseed, castor, rubber, cashew, etc. However, most surprisingly as per their potential, only a maximum of 6% is used. Utilization of this oil/biodiesel as fuel in IC engines is not only reducing petroleum usage, but also improves the rural economy. Therefore, in India the feasibility of producing biodiesel as a diesel substitute can be thought of as significant. Along with the non-utilization of the available potential of the nonedible oil sources, there are large areas of degraded forest lands, unutilized public lands, waste lands, and fallow lands of farmers, which may be exploited easily for systematic plantation to obtain biodiesels. This will also be beneficial for overall economic growth. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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Jatropha – assortment and decisive factor
The basic composition of any vegetable oil is triglyceride (fatty esters of glycerol). Structurally, a triglyceride is a reaction product of one molecule of glycerol (C3H8O3), with three molecules of fatty acids to yield three molecules of water and one molecule of triglyceride. The carbon chain length and number of unsaturated bonds varies in fatty acids. Various acids present in vegetable oil are Myristic(14:0), Palmitic(16:0), Stearic(18:0), Arachidic(20:0), Behenic(22:0), Linoceric(24:0), Oleic(18:1), Erucle(22:1), Linoleic(18:2) and Linoleinic(18:3) (Barnwal and Sharma [2]). There are a number of varieties of Jatropha, such as Jatropha integerrima, Jatropha podagrica, Jatropha multifida, Jatropha tanjorensis, Jatropha glandulifera, Jatropha gossypifolia and Jatropha curcas. Best among these is Jatropha curcas. Mass spectroscopy and elemental analysis supported a C20 H24O3 formula for Jatropha curcas. The ideal diesel fuel molecule is a structural non-branched hydrocarbon molecule (C16H34), whereas Jatropha oil molecules are cyclic with branched hydrocarbon molecules (fig.1). As Jatropha oil contains a substantial amount of oxygen in its structure, it is expected to have a lower heating value than diesel fuel. The heat value also decreases with unsaturation as a result of fewer hydrogen atoms and decreases with increasing saponification number. This unsaturation causes vegetable oils to be more reactive than diesel fuel. The proportion and location of double bonds present in Jatropha also affects the cetane number.
Figure 1:
3
Molecular structure of Jatropha and diesel oil.
Preparation of laboratory samples
Biodiesel is basically monoalkyl esters of long-chain fatty acids derived from renewable feedstocks, such as vegetable oil or animal fats, for use in compression ignition engines, etc. (Barnwal and Sharma [2]). Many standardized procedures are available for the production of biodiesel. The commonly used methods for bio-fuel are blending, micro-emulsification, cracking and transesterification. In the current study, the transesterification process was adopted for the production of biodiesel in the authors’ indigenous laboratory. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
370 Energy and Sustainability II Transesterification, otherwise known as alcoholysis, is the reaction of fat or vegetable oil with an alcohol to form esters and glycerine. A catalyst is used to improve the reaction rate and yield. At first the catalyst sodium hydroxide (NaOH) is dissolved into anhydrous methanol in the catalyst pre-mix tank in proper proportions and then stirred. When the catalyst is fully dissolved into the methanol, the catalyst premix is mixed with the requisite amount of heated untreated vegetable oil (Jatropha). The mixtures are maintained at a temperature a little below 65oC and stirred vigorously for around three hours. After completion of stirring, the mixture is allowed to settle down for 24 hours. The layer of glycerol (heavier phase), which settled at the bottom, is carefully taken out and the upper layer is the ester of Jatropha oil, which is tapped separately. The washing of the transesterified vegetable oils are done for the removal of additional ester followed by evaporation for the removal of water particles and alcohol. The preparation process of biodiesel is elaborated by Barnwal and Sharma [2] and Otera [3]. The derived biodiesel is then mixed or blended with diesel in various proportions (like B10, B20,…,B60, etc.) for engine operations. The block diagram of the experimental setup is shown in fig. 2. 3.1 Measurements of fuel properties The progress in the performance of the IC engines over the past century has resulted from the pleasing erudition of the engine design and fuel properties. The replacement of existing fuels with new fuels requires understanding of the critical fuel properties in order to ensure that the new fuels can be used. Some key fuel properties of Jatropha oil, determined by standard methods, and the comparison with the standard diesel fuel are given in table 1. The results obtained are in reasonable agreement with reported values (Raheman and Phadatare [4], Clark and Lyons [5] & Ramadhas et al. [6]).
Figure 2:
Block diagram of experimental setup.
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Table 1:
371
Comparative study of fuel properties of diesel and biodiesel. Properties
Raw
Viscosity(cSt ) at 300C Calorific value (kJ/kg ) Flash point (0C ) Fire point (0C ) Cloud point (0C ) Pour point (0C ) Specific gravity (at 300C ) Cetane Number
53.79 39570 261 302 7 4 0.902 36
Jatropha oil Derived biodiesel 7.2 42640 248 295 6 4 0.876 57.1
Diesel 2.5 43500 52 63 5 4 0.835 51
3.2 Performance and emission testing To study engine performance and emission, the experiments were done in a Kirloskar vertical single cylinder, direct injected compression ignition diesel engine (engine model – avi). The power output of the engine is 5hp at 1500rpm, having a compression ratio of 16.5:1. The emission, as well as engine performance, was studied at different engine loads (25, 50, 75 and 100%).
4
Results and discussion
4.1 Physical and chemical properties As shown in table 1, the viscosity and specific gravity of the biodiesel obtained are very high compared to suitability for the IC engine. Major problems encountered with biodiesel used in IC engines are its low volatility and high viscosity due to the long chain structure. The common problems faced are excessive pumping power, improper combustion and poor atomization of fuel particles. It is evident that dilution or blending of biodiesel with other fuels, such as diesel, would bring the viscosity and density close to the specification range. Therefore, biodiesels obtained from Jatropha were blended with diesel oil in varying proportions to achieve the required viscosity and density close to that of a diesel fuel. 4.2 Effect of dilution The biodiesel was mixed with diesel oil in proportions in steps of 10% i.e. B10, B20, B30…. B100, and the dilution of biodiesel results in a homogeneous mixture for all level of mixing. The physical and chemical properties of all blends were determined. The results show, as given in fig. 3, that blends up to 50% biodiesel have viscosity and density equivalent to the specified range for IC engine fuel. Therefore, it can be suggested that up to 50% blend (B50) biodiesel may be used to run the compression ignition (CI) engine.
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Figure 3:
Variation of specific gravity and viscosity for different blends.
Figure 4:
Viscosity at different temperature.
A comparative study of viscosity and specific gravity dependencies of Jatropha oil (raw and derived) is made at different temperatures. The results show, as in fig. 4, that the viscosity reduces at a higher temperature and comes close to that of diesel fuel. Therefore, it can also be suggested that a higher percentage of blend is possible if preheating is done on the fuel in use. 4.3 Effect of engine performance At different engine loads for different blends, the BTEs are as plotted in fig. 5. It is observed that the values are quite compatible with standard diesel fuel. As is suggested for B50 blend, the maximum BTE was found to be 36.9%. However, at part load, an increase of 1.86% (at 50% load) and 1.37% (at 75% load) efficiencies proves to be a better option than diesel fuel on which most of the engines run. As the density of esterified fuel is higher, it leads to greater discharge of fuel for the same displacement of the plunger in the fuel injection pump, as a result of
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Figure 5:
373
Variation of thermal efficiency for different biodiesel–diesel blends.
Figure 6:
Figure 7:
Variation of BSFC for different biodiesel–diesel blends.
Variation of HC for different biodiesel–diesel blends.
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374 Energy and Sustainability II which a higher Break Specific Fuel Consumption (BSFC) value of the biodiesel– diesel blend than that of diesel may be expected. However, from fig. 6, almost the reverse trend is observed in BSFC values against different percentage loads and blend variations. A change in combustion time due to a higher cetane number may be a reason for this reduction of BSFC. 4.4 Effect of engine emission The variations of unburnt hydrocarbons (HC) at different engine loads are plotted in fig.7. It is observed that the levels of unburnt hydrocarbons for the different biodiesel–diesel blends are lower than diesel fuel. Transesterification of Jatropha converts the complex structure of glycerides to the simple structure of glycerols, which ensures the completeness of combustion. The shorter ignition delay associated with a higher cetane number could also reduce the over mixed fuel, which is the primary source of unburnt hydrocarbons. From figs. 8 and 9 it
Figure 8:
Variation of NOX for different biodiesel–diesel blends.
Figure 9:
Variation of CO for different biodiesel–diesel blends.
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is observed that blends of biodiesel–diesel are good from a pollution point of view. The amount of NOx produced is less to some extent and the CO produced is much less than diesel fuel. This may be due to complete combustion of the biodiesel being an oxygenated fuel. Similar trends of observations on CO and NOx production were also reported while running diesel engines with esterified karanja, rapeseed, sunflower and soyabean oil, such as Raheman and Phadatare [4], Clark and Lyons [5] and Alfuso et al. [7]. A comparison between Jatropha derived biodiesel and that of karanja on various parameters is given in table 2. Table 2:
Comparison between Jatropha and karanja derived biodiesel. Karanja derived by Raheman et al. [4]
Jatropha derived (present investigation)
01. Fuel Properties Viscosity(cSt) at 300C
B100 9.60
B100 7.20
Calorific value (MJ/kg)
36.12
42.64
26.19
36.91
0.52
0.59
9 - 12 < 0.02
10 - 13 0.02 - 0.03
02. Engine Performance Brake thermal efficiency (% [maximum ] BSFC (kg/kW-hr) [max.] 03. Engine emission NOx (ppm) CO (% volume)
It is clear that the calorific value and maximum BTE for Jatropha derived biodiesel is higher than that of karanja. The engine emission parameters and BSFC are of comparable magnitude for both the fuels.
5
Conclusion
The effect of the delay period, heat release rates and pressure rise are definitely better selection criterion for biodiesel, but this work is primarily concentrated on the performance and emission characteristics of the engine, which are also very important parameters. The physical and chemical properties of biodiesel obtained suggest that it cannot be used directly due to higher viscosity and density. Low volatility will cause poor atomization of biodiesel, resulting in incomplete combustion and carbon deposits, and subsequently jamming of the injector nozzle. A higher cloud point may result in cold starting problems during winter. Hence, it can be concluded that a 50% blend (B50) of biodiesel–diesel will partially replace the fuel in CI engines on a short term basis. The engine works smoothly on methyl ester of Jatropha and a diesel blend with comparable WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
376 Energy and Sustainability II performance to diesel operation. With transesterification, the emission concentration of CO, NOX, and HC have decreased in the exhaust. As the viscosity reduces with temperature, the preheating of the biodiesel blend and multi fuel injection will definitely cause the use of a higher percentage of blends without alteration of much performance in comparison to a diesel engine.
References [1] Srivastava, A. & Prasad, R., Triglycerides-based diesel fuels. Renewable & Sustainable Energy Reviews, 4, pp. 111-113, 2000. [2] Barnwal, B. K. & Sharma, M. P., Prospects of biodiesel production from vegetable oils in India. Renewable & Sustainable Energy Reviews, 9, pp. 363-378, 2005. [3] Otera, J., Transesterification. Chem. Rev., 93(4), pp.1449-1470, 1993. [4] Raheman, H. & Phadatare, A. G., Diesel engine emissions and performance from blends of karanja methyl ester and diesel. Biomass and Bioenergy, 27, pp. 393-397, 2004. [5] Clark, N. N. & Lyons, D.W., Class 8 truck emission testing: effects of test cycles and data on biodiesel operation. Transactions of ASAE, 42(5), pp. 1211-1219, 1999. [6] Ramadhas, A. S., Jayaraj, S. & Muraleedharan, C., Use of vegetable oils as I.C. engine fuels – A review. Renewable Energy, 29, pp. 727-742, 2004. [7] Alfuso, S., Auriemma, M., Police, G. & Prati, M.V., The effect of methylester of rapeseed oil on combustion and emissions of DI diesel engines. SAE paper 93-2801, 1993.
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Environmental and exergetic performance of electrolytic hydrogen using life cycle assessment J. L. Gálvez, L. Pazos, C. García, G. Martínez & A. González García-Conde Renewable Energy Area, National Institute for Aerospace Technology (INTA), Spain
Abstract Hydrogen is proposed as the most promising solution as a mid and long-term energy carrier for transport and electricity generation, attending to fossil fuels scarcity and the necessity of reducing greenhouse gas emissions. Several problems have to be solved before hydrogen technology could be applied. One of the main challenges is to develop a sustainable and cost-efficient process for hydrogen production. In this regard, this work intends to evaluate several possibilities of electrolytic hydrogen production from different scales (from a few Nm3/h to several hundred) and different electricity origins (solar, wind and grid) and to compare electrolysis with steam methane reforming, (which is, nowadays, the preferred method for hydrogen production). The evaluation and comparison are made by Life Cycle Assessment tools. The results are focused on the environmental performances of each process, energy ‘renewability’ and their exergetic behavior. The performed analysis shows that electrolytic hydrogen from wind electricity is the best alternative because of its low associated greenhouse gas emissions, its low environmental impact and the best grade of renewability of the produced hydrogen. Keywords: life cycle assessment, hydrogen production, electrolysis, greenhouse gases.
1
Introduction
Current energy research is mainly focused on two aspects: climate change mitigation through fossil fuel substitution and safety in energy supply in order to WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESU090341
378 Energy and Sustainability II increase the energy independence of regions. In this sense, hydrogen has become the most promising solution because of its great heating value, clean origin, low CO2 associated emissions and the possibility of being generated from renewable sources, which would lead to increased autonomy of regions. However, hydrogen is an energy carrier, not an energy source, so it has to be generated from primary sources. The conventional origin is steam reforming of hydrocarbons, which being natural gas reforming is the preferred and cleanest option. This hydrogen route has a high amount of associated emissions, as well as not solving the problem of fossil fuel dependence. Another way to produce hydrogen is water electrolysis, which leads to very low yields and a high amount of emissions if the electricity origin is the regional grid. Renewable sources integrated with water electrolysis are being investigated around the world and promising results are being obtained. This work evaluates the feasibility of renewable sources of electricity to produce hydrogen from the environmental point of view. This purpose is achieved by Life Cycle Assessment (LCA) tools. LCA is a systematic procedure that collects and evaluates material and energy inputs, outputs and the derived potential impacts of all stages of a product life, i.e., its life cycle [1]. It is divided into four stages: i) Goal and Scope. The goal of the LCA and system burdens is defined at this stage. The functional unit, the system’s function, and assumptions are faced at this point. ii) Life Cycle Inventory Analysis. The life cycle is divided into stages and each one is responsible for emissions, wastes and material or energy consumption. iii) Life Cycle Impact Evaluation. When every flow stream is identified, impacts are characterized into categories. For example, the greenhouse gases category would include all substances producing the greenhouse effect in the atmosphere. A category unit is defined, such as the mass of equivalent CO2, i.e. the substance effect is referred to the CO2 greenhouse effect. These categories lead analysts to normalize results or give each category a weight in order to calculate a final score. iv) Interpretation of results. Results from the LCA and each sensitivity analysis that has been done must be evaluated by analysts to achieve the main goal of the LCA. In this work, results from the LCA of hydrogen produced by electrolysis are shown. The effect of scale and the source of electricity (grid, wind or solar) are assessed through sensitivity analyses. The results are compared to those produced by previous analyses of steam methane reforming [2]. Exergy balances are also solved in order to establish the efficiency of each assessed case.
2
System definition
Electrolysis is the water decomposition reaction by means of electrical voltage application between two electrodes. Reactions for alkaline media are:
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Cathode : 4 H 2 O 4e 2 H 2 4OH Anode : 4OH
O 2 2 H 2 O 4e
2 H 2 O2 Total : 2 H 2 O In this work, obtained hydrogen from electrolysis is assumed to be used at a fuel cell system. Functional unit is 1 m3 of hydrogen at standard conditions with a purity of 99.99%. Five configurations with different scales, from domestic to centralized production, are analyzed. These cases are those proposed by [3]: E1. Monopolar electrolyser. Alkaline. Domestic use. 4.5 Nm3H2 / h. Yield 89%. E2. Proton exchange membrane electrolyser. Neighborhood. 10 Nm3H2 / h. Yield 95%. E3. Bipolar alkaline electrolyser. Fuel service. 42 Nm3H2 / h. Yield 80%. E4. Bipolar alkaline electrolyser. Fuel service. 60 Nm3H2 / h. Yield 80%. E5. Bipolar alkaline electrolyser. Centralized production. 485 Nm3H2 / h. Yield 80%
2.1 Mass and energy balances Proposed process flowchart for alkaline options is shown in Figure 1. PEM electrolyser option is not shown because it is the same process, but without electrolyte conditioning. Water is demineralized by ionic exchange and decarbonisation techniques. Electrolyte is composed by 25% (w/w) of potassium hydroxide and it is pumped and heated to 70ºC for all cases. Gases from electrolyser are dried by condensation and compressed to 37 bar. Material and energy balances have been calculated through simulations with operating conditions that appear in the literature [3]. Cathode and anode compartments separation diaphragm is needed for alkaline electrolyser. Membrane thickness is assumed to be 100 m. Diaphragm is supposed to be made of polytetrafluoroethylene, which consume 1.8 kg of CH2ClF and 5 MJ of natural gas in its manufacturing. Electrolyser E2 is a PEM electrolyser which employs Nafion membranes, made of polytetrafluoroetyleneperfluoroalkilvinyl ether copolymer activated with phosphoric acid. Origin of electricity when the tag ‘grid’ is added is assumed to be mean contribution per source for Europe-25 at year 2004 [4]: 53% of fossil fuels, 30% of nuclear power, hydro 14%, biomass 2% and 1% renewable. Data obtained from material balance and energy balance are shown in Table 1. 2.2 Sensitivity to energy sources The aim of this LCA is also to evaluate environmental performance when hydrogen is produced from the integration of renewable energy source and electrolysis.
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380 Energy and Sustainability II Solar photovoltaic system was considered to obtain ‘clean’ hydrogen. However, photovoltaic (PV) panel life cycle has an important environmental impact. Stoppato, 2008 [5], shows that polycrystalline siliceous materials are responsible of high energy consumption during its manufacture. One of the main concerns of PV research is the reduction of energy payback time (EPT) of panels [5–7]. For instance, EPT of a conventional PV panel is 6 years for central Europe.
Figure 1: Table 1:
Flowchart of water alkaline electrolysis.
Main parameters from material and energy balances. Parameter
E1
E2
E3
E4
E5
Flow, Nm3/h Voltage, V Power, kW Yield Electric energy consumption, MJ Nm-3 H2 Heat consumption, MJ Nm-3 H2 Consumed membrane, 103·kg Nm-3 H2 Electrode Materials. Stainless steel + nickel 105·kg Nm-3 H2 Electrode Materials: graphitePTFE, graphite – Pt 106 kg Nm-3 H2 Electrolyte, KOH 106 kg Nm-3 H2
4.5 105 24 89%
10 200 52.3 95%
42 211 220 80%
60 305 280 80%
485 485 2530 80%
19.7
23.0
20.4
17.6
17.6
0.82
0.76
0.75
0.75
0.75
6.5
5.0
1.25
0.9
0.01
1.5
0
1.6
1.1
0.13
0
0
0
0.55
0.39
0.05
0 2.9
6.6 0
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Wind turbines materials are simpler than those for PV panels. Main difference in integration is that generated current is alternate, so a rectifier for electrolysis system is needed. Currently, there are many references in the literature dedicated to LCA of wind turbines [8–12]. In both cases, wind and solar sources, proportional response of electrolyser to variability has been assumed with no yield loss. Other main assumptions for renewable systems are shown in Table 2. Table 2:
Main parameters of PV panels and wind turbine life cycles.
Parameter Life time
Solar-PV 30000 h
Wind turbine 20 years
Power
3kW
2MW
Energy efficiency Type
15% Polycrystalline
25% Onshore
Embodied energy, MJ
4610 (per panel)
1.6·107 (per turbine)
Embodied CO2, kg
213 (per panel)
865000 (per turbine)
2.3 Exergy analysis Exergy is the maximum work that can be done by a system for a given reference environment. Environment is assumed to be infinite and to enclose all systems. Exergy is frequently defined as energy availability: although a system has a lot of energy, it cannot produce work if its state is near to environment conditions or it is not available. When exergy in life cycles is analyzed, procedure is called ‘Exergetic Life Cycle Assessment’, ExLCA [13, 14]. For this methodology, two kinds of exergy are defined: direct exergy, which is that obtained from fuels, and indirect exergy, which is consumed exergy in manufacturing processes of construction materials, equipment, etc. Cumulative Exergy Demand has been employed for calculation of exergy balance of hydrogen life cycle. When this method is used, indirect exergy is not equal to embodied exergy. Embodied exergy reflects the environmental impact of materials life cycle, but this is usually inconsistent with its economic value, that reflects its scarcity. Exergy equivalence of materials is the sum of material costs (including operating costs) divided by the cost of 1MJ of fuel exergy [13, 14]. For the purpose of this work, exergy efficiency has been calculated as:
H2
Ex H 2 Ex LC
(1)
where ExH2 is the exergy of produced hydrogen (its formation free energy) and ExLC is Life Cycle exergy consumption. When evaluating renewable source, exergy from sun or from wind must be considered ‘free of charge’, i.e., there is not consumption of exergy if it is renewable. Then, exergy efficiencies can be higher than 1 if there is a great contribution of renewable sources. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
382 Energy and Sustainability II 2.4 Assessment methodology Life cycle analysis would comprise all production chains, from raw materials to final disposal. Energy supply chain and electrolyser components will have a special influence on results. Life cycle boundary has been established in production process ending because further stages, like hydrogen storage or fuel cell, are the same for all assessed options. Some aspects, as plant decommissioning or water treatment plant, are discarded, not only because of its low mass relevance, but also because of its low environmental relevance. Results have been compared to those obtained for steam methane reforming, with and without carbon capture and storage system, in reference [2]. SimaPro 7.1 has been used to calculate environmental impact, based on ISO 14040:2006 standard [1]. The ecoinvent database has been employed for secondary processes. Single issue IPCC method for evaluating GHG emissions has been employed [15]. Cumulative energy demand method has been used to evaluate the renewability [16] of produced hydrogen energy content: Life Cycle Renewable Energy Consumption, MJ (2) Renewability Lyfe Cycle Energy Consumption, MJ Total impact has been studied through IMPACT2002+ evaluation method. It employs 14 midpoint categories and four final damage categories. They are based on categorization factors from IPCC, CML, EcoIndicator and Cumulative Energy Demand. Global impact score is calculated with this method.
3
LCA results
As mentioned in the previous chapter, SimaPro 7.1 was used to evaluate hydrogen Life Cycle. Equivalent CO2 emissions, i.e. amount of substances producing greenhouse effect, are shown in Figure 2. As observed in Figure 2, highest emissions rate is produced when flow is low and energy source comes from electric grid. Increasing amount of produced hydrogen produces a decrease in emissions per volume unit. This situation occurs because of the less materials consumption in equipment commissioning and the lower energy consumption. Steam methane reforming emissions are lower than any grid option. When energy source is varied, great reduction on emissions are achieved, being semi-centralized configuration, E5, the one with less emissions. This option is competitive with steam reforming with or without carbon capture. Best renewable option is wind-electrolysis. Figure 2 also reveals that, in order to minimize CO2 emissions, higher scales must be considered, although it is a problem when renewable systems are integrated. These systems tend to use small installations for improving control systems and minimize system’s inertia. This last issue is of great importance because of variability character of renewable sources, especially wind and solar sources. The, E5 process is not suitable for integration because it is not a realistic option. However, E3 or E4 options have better performances than conventional reforming or reforming with a carbon capture and storage (CCS) system. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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Figure 2:
383
Equivalent CO2 emissions per Nm3 of hydrogen for each assessed case.
Solar options emissions are higher than those produced by wind because of the high energy consumption in PV panel production. This is a main concern in photovoltaic research and development, as more than two years can be needed to recover ‘invested’ energy. Mean renewability, defined as the ‘renewable energy content’ in produced hydrogen, is shown in Table 3. It hardly depends on scale, as an increase in energy consumption does not vary renewable ratio at energy input, except that input from embodied energy in materials, which have very low influence in total energy input. Table 3:
Mean renewability of produced hydrogen.
Grid
Solar-PV
7.8%
93.3%
Wind Turbine 96.7%
SMR 1.0%
SMRCCS 1.8%
Renewable energy content of electrolytic hydrogen is higher than that coming from steam reforming of methane for each assessed case. Natural gas is the raw material for SMR option, so, contribution of renewable energy is minimal. SMRCCS case has higher renewability because of the higher electricity consumption of this process. Best achieved value is that obtained with the wind energy source. Exergy efficiency, as defined in equation (1), varies with scale, because of different energy input for each option. Obtained values from Life Cycle Impact Evaluation for Exergy Efficiency are shown in Figure 3. As shown in this Figure, WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
384 Energy and Sustainability II
Figure 3:
Figure 4:
Exergy efficiency for each assessed case.
Impact single score (IMPACT 2002+) for each assessed case.
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wind H2 exergy efficiency is higher than 1. Exergy input from wind and solar sources is considered null, as renewable exergy is considered free and, then, not consumed. In one hand, wind hydrogen produce more useful work (exergy) than required input from nature. In other words, exergy is being ‘created’. In the other hand, solar-PV hydrogen is consuming exergy, as a consequence of high indirect exergy associated to materials for solar panels. Exergy efficiency of solar hydrogen is quite similar to that produced by steam methane reforming with and without carbon capture system. An increase in scale produces an increase in efficiency. Total score of global impact is shown in Figure 4 for each assessed case. The evaluation method is IMPACT 2002+, which gives a weight value for each impact category (greenhouse, ozone layer, resources consumption, etc.) and calculates the total impact score. Assessed total impact gives great advantage to wind hydrogen over other technologies, even at processes with lowest scale. Environmentally, grid electrolysis as hydrogen generation must be discarded for all considered scales because it has the highest impact for all cases. Impact of solar hydrogen is quite similar to the impact produced by SMR hydrogen.
4
Conclusions
Wind electrolysis is, from environmental and exergetic point of view, the best option for hydrogen generation. This result has been achieved through Life Cycle Assessment tool, including an exergy balance, of electrolytic hydrogen production technologies. Increasing scale of electrolyser decreases greenhouse gases emissions, augments exergy efficiency and reduces global impact, while renewability of hydrogen is not varied, as clean energy sources ratio for electricity does not depend on the amount of produced hydrogen. High renewability of produced hydrogen is achieved by solar and wind options, while steam reforming or grid-electrolysis hardly gives renewable character to hydrogen. Solar-PV hydrogen has very low exergy efficiency for its life cycle because of large indirect exergy needs of the process, while wind-H2 has a life cycle exergy efficiency higher than 1, ‘creating’ exergy.
Acknowledgements The authors acknowledge received funding from Comunidad de Madrid and the European Social Fund through PHISICO2 program S-0505/ENE/000404.
References [1] International Standard Organization. Environmental management. Life cycle assessment. Requirements and guidelines. UNE-EN-ISO 14044:2006.
WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
386 Energy and Sustainability II [2] Dufour, J., Serrano, D.P., Gálvez, J.L., Moreno, J., García, C. Life cycle assessment of hydrogen production processes. Environmental feasibility and reduction of greenhouse gases emissions. International Journal of Hydrogen Energy, 34(3), 1370-1376, 2009 [3] Ivy, J. Summary of electrolytic hydrogen production. NREL Report MP560-36734, available at www.nrel.gov, 2004 [4] International Energy Agency (IEA). World Energy Outlook 2007. Ed. By OECD/IEA, Paris. 2007. [5] Stoppato, A. Life cycle assessment of photovoltaic electricity generation. Energy 33(2), 224-232, 2008 [6] Nawaz, I., Tiwari, G.N. Embodied energy analysis of photovoltaic system based on macro and micro level. Energy Policy, 34, 3144-3152, 2006 [7] Raugei, M., Bargigli, S., Ulgiati, S. Life cycle assessment and energy payback time of advanced photovoltaic modules: CdTe and CIS compared to poly-Si. Energy, 32, 1310-1318. 2007. [8] Martínez, E., Snaz, D., Pellegrini, S., Jiménez, E., Blanco, J. Life cycle assessment of a multi-megawatt wind turbine. Renewable Energy, 34(3), 667-673, 2009 [9] Weinzettel, J., Reenaas, M., Solli, C., Hertwich, E.G. Life cycle assessment of a floating offshore wind turbine. Renewable Energy, 34(3), 742-747, 2009 [10] Schleisner, L., Life cycle assessment of a wind farm and related externalities. Renewable Energy, 20, 279-288, 2000 [11] Ardente, F., Becalli, M., Cellura, M., LoBrano, V. Energy performances and life cycle assessment of an Italian wind farm. Renewable and Sust. Energy Reviews, 12, 200-217, 2008 [12] Vestas Wind Systems. Life cycle assessment of offshore and onshore sited wind farms. Elsam Engineering Reports 28768, 2004 [13] Dincer, I., Rosen, M.A. Exergetic life cycle assessment. (Chapter 19). Exergy: Energy, environment and sustainable development. Ed. By Elsevier. Oxford, UK. 397-416, 2007 [14] Granovskii, M., Dincer, I., Rosen, M.A. Exergetic life cycle assessment of hydrogen production from renewables. Journal of Power Sources, 167, 461-471, 2007 [15] Goedkoop, M., Oele, M., de Schryver, A., Vieira, M. (Prè Consultants) SimaPro data base manual. Methods. Library. www.pre.nl, 2008 [16] Malca, J., Freire, F. Renewability and life-cycle energy efficiency of bioethanol and bio-ethyl tertiary butyl ether (bioETBE): Assessing the implications of allocation. Energy,31(15), 3362-3380, 2006
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Section 5 Energy analysis
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Heat transfer from in-line tube bundles to downward aqueous foam flow J. Gylys1, S. Sinkunas2, T. Zdankus1, R. Jonynas2 & R. Maladauskas2 1
Energy Technology Institute, Kaunas University of Technology, Lithuania 2 Department of Thermal and Nuclear Energy, Kaunas University of Technology, Lithuania
Abstract An experimental investigation of heat transfer from in-line tube bundle to foam flow was performed. One type of aqueous foam – statically stable foam was used as a coolant. The experimental setup consisted of the foam generator, experimental channel, in-line tube bundle, measurement instrumentation and auxiliary equipment. During the experiments aqueous foam initially moved vertically upward, then made a 180 degree turning and moved vertically downward crossing the in-line tube bundle. Three tube bundles with different geometry were used for investigation. Spacing among the centres of the tubes across the first in-line tube bundle was 0.03 m and spacing along the bundle was 0.03 m. In the second case spacing among the centres of the tubes across the bundle was 0.03 m; spacing along the bundle was 0.06 m. In the last case spacing was accordingly 0.06 m and 0.06 m. Initially, the first tube bundle was installed at the experimental channel, next the second tube bundle was installed instead of the previous bundle and so on. The laminar downward foam flow crossed the tube bundle and the mean velocity of foam flow was changed from 0.14 m/s to 0.30 m/s. The volumetric void fraction of foam was changed from 0.996 to 0.998. During an experimental investigation it was determined dependence of heat transfer intensity on flow parameters: flow velocity, volumetric void fraction of foam and liquid drainage from foam. Apart from this, influence of tube position of the bundle on heat transfer intensity was investigated. Keywords: aqueous foam flow, flow turn, in-line tube bundle, void fraction of foam. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESU090351
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1
Introduction
Application of aqueous foam flow for heated surfaces cooling is an area of our researches. Aqueous foam as coolant with small density has additional possibility to change the intensity of heat transfer by changing volumetric void fraction of foam. The foam type coolant enables to create compact, light and economic heat exchanger with simple and safe operation using two-phase foam flow. Heat exchangers with different type and geometry of tube bundles are usually used in industry. However, only heat transfer between different types of tube bundles and single-phase coolants (water, oil, air) has been investigated particularly [1, 2]. Investigation of heat transfer from tube bundles to foam flow are yet in initial stage. Therefore in our previous works heat transfer from alone cylindrical surface – tube and then from tube line to upward foam flow was investigated [3]. Next an experimental series with staggered tube bundle in upward and downward foam flow followed [4, 5]. Research of heat transfer between in-line tube bundles of different geometry and upward foam flow [6, 7] was performed later. Presently heat transfer of in-line tube bundles to downward after 180 degree turning foam flow was investigated. Heat transfer from the tubes to upward and downward after 180 degree turning foam flow was investigated in order to obtain data necessary for the designing of real heat exchanger. Objectives of this research are to determine and estimate influence of in-line tube bundles geometry on the intensity of tube bundles heat transfer to foam flow, since bundles (behaving as an obstacles in a flow) induce substantial changes of foam structure: bubbles are transformed by collapsing, dividing, appearing new bubbles. This, together with gravity and capillary forces, facilitates the liquid drainage from the foam [8, 9] and affects the thickness of liquid film, composing on the heated surfaces and channel walls. Such effects can significantly increase or decrease heat transfer rates. Therefore experimental investigation of heat transfer process from three in-line tube bundles with different geometries to the vertical downward after 180 degree turning foam flow was performed. Dependence of heat transfer intensity on flow parameters: velocity, direction, volumetric void fraction and liquid drainage from foam, was determined. Apart of this, influence of tube position in the bundle was investigated. The further researches will be committed to estimate an optimal geometry of in-line tube bundle, which maximally increases the intensity of heat transfer to foam flow.
2
Experimental set-up
An experimental investigation was performed on the experimental laboratory setup consisting of foam generator, experimental channel, tube bundle, measurement instrumentation and auxiliary equipment [5, 7]. One type of aqueous foam – statically stable foam [3, 9] was used as coolant (heat carrier) for our experiments. Statically stable foam flow was generated from the detergents water solution. Concentration of the detergents was kept WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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constant at 0.5% in all experiments. Foam-able liquid was supplied from the reservoir onto the special perforated plate; gas (air) was delivered through the plate from the bottom gas chamber. Foam flow was generated during gas and liquid contact. Foam flow parameters control was fulfilled using gas and liquid valves. Perforated plate for foam generation was installed at the bottom of the experimental channel and was made from stainless steel plate with a thickness of 2 mm; orifices were located in a staggered order; their diameter equal 1 mm; spacing among the centres of the holes equal 5 mm. The experimental channel was composed of three main parts: the vertical channel for upward foam flow; the channel for flow turn and the vertical channel for downward foam flow. The radius R of the channel turn was equal to 0.17 m. Cross-section dimensions of the channel were 0.14 x 0.14 m2; height was equal to 1.8 m; walls were made from the transparent material in order to observe foam flow visually. The in-line tube bundle was installed in the vertical channel for downward foam flow. Three in-line tube bundles with different spacing between tubes centres were used during experimental investigation. A schematic view of the experimental channel with tube bundles is shown in the Fig. 1.
B1
C1
A2
B2
C2
A3
B3
C3
A4
B4
C4
A5
B5
C5
A6
B6
C6
D1
E1
F1
D2
E2
F2
D3
E3
F3
s1
G1
G2
Foam
Figure 1:
Foam
d
d
d
A1
Bundle No. 3
s2
s1
s2
Bundle No. 2
s1
s2
Bundle No. 1
G3
Foam
In-line tube bundles: No. 1, No. 2 and No. 3.
The in-line tube bundle No. 1 consisted of five columns with six tubes in each (Fig. 1). Spacing between centres of the tubes was s1=s2=0.03 m. The in-line tube bundle No. 2 consisted of five columns with three tubes in each. Spacing between centres of the tubes across the experimental channel was s1=0.03 m and spacing along the channel was s2=0.06 m. The in-line tube bundle No. 3 consisted of three columns with three tubes in each. Spacing between centres of the tubes was s1=s2=0.06 m. External diameter (d) of all the tubes was equal to WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
392 Energy and Sustainability II 0.02 m. Electrically heated tube – calorimeter had an external diameter equal to 0.02 m also. Endings of the calorimeter were sealed and insulated. During the experiments calorimeter was placed instead of one tube of the bundle. An electric current value of heated tube was measured by an ammeter and voltage by a voltmeter. Temperature of the calorimeter surface was measured by eight calibrated thermocouples: six of them were placed around the central part of the tube and two of them were placed in both sides of the tube at a distance of 50 mm from the central part. Temperature of the foam flow was measured by two calibrated thermocouples: one in front of the bundle and one behind it. Measurement accuracies for flows, temperatures and heat fluxes range were correspondingly 1.5%, 0.15–0.20% and 0.6–6.0%. During the experimental investigation a relationship was obtained between an average heat transfer coefficient h from one side and foam flow volumetric void fraction β and gas flow Reynolds number Reg from the other side: Nu f = f (β , Reg ) . (1) Nusselt number was computed by formula hd . (2) Nu f =
λf
Here λf is the thermal conductivity of the statically stable foam flow, W/(m·K), λf was computed by the equation λ f = βλ g + (1 − β )λl . (3) An average heat transfer coefficient was calculated as q h= w . ∆T Gas Reynolds number of foam flow was computed by formula Gg d Re g = . Aν g
(4)
(5)
Foam flow volumetric void fraction was expressed by the equation Gg β= . (6) G g + Gl Experiments were performed within limits of Reynolds number diapason for gas (Reg): 190–410 (laminar flow regime) and foam volumetric void fraction (β): 0.996–0.998. Gas velocity for foam flow was changed from 0.14 to 0.30 m/s.
3
Results
In the case of the single-phase flow, heat transfer intensity of the fourth and further tubes of the in-line tube bundles are the same as that of the third tubes [1]. Distribution of local flow velocity across the experimental channel is the main flow parameter which influences on heat transfer intensity of different
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tubes of the bundle in that case. In our previous works [3, 4] there was noticed that it is different for the aqueous foam flow. Heat transfer from the tube bundle No. 1 to the vertical downward after 180 degree turning foam flow was investigated initially. Then the experiments with the tube bundle No. 2 were performed. Heat transfer intensities from the third tubes of the bundle No. 1 and No. 2 to downward wettest (β=0.996) foam flow were compared and analysed (see Fig. 2).
Nu f
A3 D3
1200
B3 E3
C3 F3
1000 800 600 400 200 0 150
Figure 2:
200
250
300
350
400
Re g
Heat transfer intensity of the tubes A3, B3, C3 (bundle No. 1) and D3, E3, F3 (bundle No. 2) to downward foam flow, β=0.996.
Three main parameters [3] of the foam flow have an influence on the heat transfer intensity of the different tubes: changes of foam structure along the experimental channel, distribution of local flow velocity and distribution of local void fraction of foam across and along the experimental channel. While foam flow makes a 180 degree turn the gravity forces act across and along the foam flow. Liquid drains down from the upper channel wall and local void fraction increases (foam becomes drier) here as well. After the turn, local void fraction of foam is less (foam is wetter) on the inner – left side of the cross-section (tubes A and D). Heat transfer intensity of the third tubes of the in-line bundle No. 2 is higher than that of the bundle No. 1. This phenomenon can be explained by the fact, that the effect of “shadow” is slight and heat transfer is higher for the tubes of the in-line tube bundle with more spacing between the tube centres along the bundle (tube bundle No. 2). Increasing foam flow gas Reynolds number (Reg) from 190 to 410, heat transfer intensity (Nuf) of the tube A3 increases by 1.8 times (from 677 to 1187), by 2.1 times (from 454 to 965) of the tube B3, and by WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
394 Energy and Sustainability II 1.6 times (from 219 to 345) of the tube C3 for foam volumetric void fraction β=0.996. Heat transfer intensity of the tubes D3 for the same Reg increases by 1.7 times (from 743 to 1287), by 2.1 times (from 468 to 975) of the tube E3, and by 2.3 (from 252 to 591) of the tube F3 for β=0.996. Heat transfer intensity of the tube D3 is higher than that of the tube A3 on average by 9%, the heat transfer of the tube E3 is higher than that of the tube B3 on average by 1.5%, and the heat transfer of the tube F3 is higher than that of the tube C3 on average by 56% for β=0.996 and Reg=190–410. Comparison of heat transfer intensity of the tubes A3, B3, C3 and D3, E3, F3 to the downward foam flow at the volumetric void fraction β=0.998 is shown in Fig. 3. Heat transfer intensity of the tube D3 is higher than that of the tube A3 on average by 19%, the heat transfer of the tube E3 is higher than that of the tube B3 on average by 18%, and the heat transfer of the tube F3 is higher than that of the tube C3 on average by 27% for β=0.998 and Reg=190–410.
Nu f A3 D3
600
B3 E3
C3 F3
500 400 300 200 100 0 150
Figure 3:
200
250
300
350
400
Re g
Heat transfer intensity of the tubes A3, B3, C3 (bundle No. 1) and D3, E3, F3 (bundle No. 2) to downward foam flow, β=0.998.
An average heat transfer rate of middle-column tubes was calculated in order to analyse and compare the experimental results of different in-line tube bundles. An average heat transfer intensity of the middle-column tubes of the bundle No. 1 and No. 2 to downward after 180 degree turning foam flow is shown in Fig. 4. An average heat transfer intensity of middle-column tubes of the bundle No. 2 is higher than that of the bundle No. 1 on average by 7% for β=0.997 and by 20% for β =0.998. When foam volumetric void fraction (β) is equal to 0.996 heat transfer intensity of middle-column tubes of the bundle No. 1 is higher than that of the bundle No. 2 till Reg=270. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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395
0.996 (No. 1) 0.997 (No. 1) 0.998 (No. 1) 0.996 (No. 2) 0.997 (No. 2) 0.998 (No. 2)
400 200 0 150
Figure 4:
200
250
300
350
400
Re g
An average heat transfer intensity of the middle-column tubes of the bundles No. 1 and No. 2 to downward foam flow, β=0.996, 0.997 and 0.998.
Next, the experiments with tube bundle No. 3 followed. Comparison of heat transfer intensity of the tubes E3 and G3 to the downward foam flow at the volumetric void fraction β=0.996, 0.997 and 0.998 is shown in Fig. 5. Heat transfer intensity of the third tubes of the in-line bundle No. 2 is higher than that of the bundle No. 3. Increasing foam flow gas Reynolds number (Reg) from 190 to 410, heat transfer intensity (Nuf) of the tube G3 increases by 1.5 times (from 369 to 549) for β=0.996, by 1.5 times (from 297 to 433) for β=0.997, and by 1.4 times (from 204 to 292) for β=0.998. Heat transfer intensity of the tube E3 (bundle No. 2) is higher than that of the tube G3 (bundle No. 3) on average by 56% for β=0.996, by 55% for β=0.997 and by 86% for β=0.998 to downward foam flow for Reg=190–410. An average heat transfer intensity of the middle-column tubes of the bundle No. 2 and No. 3 to downward after turning foam flow is shown in Fig. 6. The local foam flow velocity increases while foam passes the rows of tubes. The value of local velocity is higher in the cases of tube rows with more tubes in each (tube bundle No. 1 and No. 2). Therefore the heat transfer intensity from the tubes of the bundle No. 3 to foam flow is less in comparison with tube bundles No. 1 and No. 2. Changing Reg from 190 to 410, an average heat transfer intensity of the middle-column tubes of the in-line bundle No. 2 to downward foam flow increases by 2.4 times for β=0.996; by 2.1 times for β=0.997, and by 1.8 times for β=0.998; and that for the tubes of the in-line bundle No. 3 is by 1.5 times for β=0.996; by 1.4 times for β=0.997, and by 1.3 times for β=0.998. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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Nu f 1000
E3 (0.996)
E3 (0.997)
E3 (0.998)
G3 (0.996)
G3 (0.997)
G3 (0.998)
800 600 400 200 0 150
Figure 5:
Nu f 800 600
200
250
300
350
400
Re g
Heat transfer intensity of the tubes E3 (bundle No. 2) and G3 (bundle No. 3), β=0.996, 0.997 and 0.998. 0.996 (No. 2) 0.997 (No. 2) 0.998 (No. 2) 0.996 (No. 3) 0.997 (No. 3) 0.998 (No. 3)
400 200 0 150
Figure 6:
200
250
300
350
400
Re g
An average heat transfer intensity of the middle-column tubes of the bundles No. 2 and No. 3 to downward foam flow: β=0.996, 0.997 and 0.998.
An average heat transfer intensity of the middle-column tubes of the in-line bundle No. 2 is higher than that of the tubes of the in-line bundle No. 3 on average by 43% for β=0.996, by 48% for β=0.997 and by 67% for β=0.998 to downward foam flow for Reg=190–410. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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Experimental results of investigation of heat transfer of the in-line tube bundles to downward after 180 degree turning statically stable foam flow were generalized by criterion equation using dependence between Nusselt number Nuf and gas Reynolds Reg number. This dependence within the interval 190
m
Nu f = cβ Reg .
(7)
On average, for whole middle-column (B) of the in-line tube bundle No. 1 (s1=s2=0.03 m) to the downward foam flow: c=16.1, n=518, m=140.7(1.003–β). On average, for whole middle-column (E) of the in-line tube bundle No. 2 (s1=0.03 and s2=0.06 m) to the downward foam flow: c=29.6, n=952, m=202.5(1.002–β). On average, for whole middle-column (G) of the in-line tube bundle No. 3 (s1=s2=0.06 m) to the downward foam flow: c=29.4, n=53.3, m=59(1.005–β).
4
Conclusions
Heat transfer from three in-line tube bundles with different geometries to downward laminar statically stable foam flow was investigated experimentally. Three main parameters of foam flow influence on heat transfer intensity of different tubes of the bundles: changes of foam structure along the experimental channel, distribution of local flow velocity and distribution of local foam void fraction across and along the experimental channel. The effect of “shadow” is slight and heat transfer intensity is higher for the tubes of the in-line tube bundle No. 2 (with more spacing between the tube centres along the bundle) in comparison with tube bundle No. 1. Heat transfer is higher for the tubes of the in-line tube bundle No. 2 (with less spacing between the tube centres across the bundle) in comparison with tube bundle No. 3. Results of investigation were generalized by criterion equation, which can be used for the calculation and design of the statically stable foam heat exchangers with in-line tube bundles.
Nomenclature A – cross section area of experimental channel, m2; c, m, n – coefficients; d – outside diameter of tube, m; G – volumetric flow rate, m3/s; h – average coefficient of heat transfer, W/(m2⋅K); Nu– Nusselt number; q – heat flux density, W/m2; Re – Reynolds number; T – average temperature, K; β – volumetric void fraction; λ – thermal conductivity, W/(m⋅K); ν – kinematic viscosity, m2/s.
Indexes f – foam; g – gas; WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
398 Energy and Sustainability II l – liquid; w – wall of heated tube.
References [1] Zukauskas, A., Convectional Heat Transfer in Heat Exchangers, Moscow: Nauka, pp. 245–268, 1982. [2] Kuppan, T., Heat Exchanger Design Handbook, New York: Marcel Dekker, pp. 229–303, 2000. [3] Gylys, J., Hydrodynamics and Heat Transfer Under the Cellular Foam Systems, Kaunas: Technologija, pp. 50–314, 1998. [4] Gylys, J., Zdankus, T., Miliauskas, G.; Sinkunas, S., Influence of vertical foam flow liquid drainage on tube bundle heat transfer intensity. Experimental Heat Transfer, 20(2), pp. 159–169, 2007. [5] Gylys, J., Sinkunas, S., Zdankus, T., Analysis of staggered tube bundle heat transfer to vertical foam flow. International Journal of Heat and Mass Transfer, 51(1–2), pp. 253–262, 2008. [6] Gylys, J., Zdankus, T., Sinkunas, S., Giedraitis, V., Study of In-line Tube Bundle Cooling in Vertical Foam Flow, WSEAS Transactions on Heat and Mass Transfer, 6(1), pp. 632–637, 2006. [7] Gylys, J., Sinkunas, S., Zdankus, T., Giedraitis, V., Different type tube bundle heat transfer to vertical foam flow. Proc. of the 5th International Conference on Nanochannels, Microchannels and Minichannels, ICNMM 2007, Pueble, Mexico, pp. 449–455, 2007. [8] Nguyen A. V., Liquid Drainage in Single Plateau Borders of Foam. Journal of Colloid and Interface Science, 249(1), pp. 194–199, 2002. [9] Tichomirov V., Foams. Theory and Practice of Foam Generation and Destruction, Chimija: Moscow, pp. 11–106, 1983.
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Mathematical models of air-cooled condensers for thermoelectric units S. Bracco1, O. Caligaris2 & A. Trucco1 1
Department of Machinery, Energy Systems and Transportation, Genoa University, Italy 2 Department of Production Engineering, Thermoenergetics and Mathematical Models, Genoa University, Italy
Abstract The present paper deals with the use of air-cooled condensers in thermoelectric units, such as steam power plants or combined cycle units. The paper describes the main features of air-cooled condensers, showing the problems related to their use, such as the presence of non-condensable gases inside the steam flow or the condenser performances variability due to ambient conditions. The present study refers to A-frame air-cooled condensers characterized by single-pass and multiple-row arrangement. A phenomenological study has been done in order to calculate the main physical parameters which describe the condenser operating conditions. In particular, three mathematical models have been developed: while both the first and the second model consider a condenser with tubes characterized by the same finned surface, with or without the use of throttling valves upstream of each tube, the third model examines the behaviour of a condenser with different row effectiveness. The three mathematical models permit one also to investigate the possible vapour back flow inside each row of tubes, by calculating the axial coordinate value along each tube at which the condensing steam mass flow rate becomes null; the third mathematical model has been implemented in the Matlab/Simulink environment in order to couple the simulator of the condenser with the whole plant simulation model. Keywords: air-cooled condenser, non-condensable gases, simulation model.
1
Introduction
Nowadays air-cooled condensers are more and more installed in thermoelectric units, taking the place of water cooled condensers, because their use allows to WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESU090361
400 Energy and Sustainability II save a lot of cooling water, in accordance with strict environmental rules, and to build power plants in sites far from rivers or the sea [1]. But, as reported by Fabbri [2–4], Kröger [5] and Larinoff et al [6], air-cooled condensers are also characterized by several technical and practical problems: the heat exchange process between the ambient air and the condensing steam needs large heat exchange areas which have to be cleaned periodically; the condenser operating pressure depends on the site conditions such as ambient temperature, humidity and windiness; the large number of fans are characterized by high electricity consumptions and noise. Furthermore one of the major problems of a single-pass air-cooled condenser is the accumulation of non-condensable gases inside the finned tubes, as analysed by Fabbri [2], Kröger [5] and Berg and Berg [7]; this undesired phenomenon determines the reduction of the effective heat exchange area and possible condensate freezing in several finned tubes. The aim of this paper is that of describing three different simplified mathematical models which have been implemented in order to predict the steady-state behaviour of an A-frame air-cooled condenser, considering different design data and operating conditions. Both the first and the second model have been implemented using the Fortran code and are used to study the condenser from a phenomenological point view while the third simulator, tuned-up in the Matlab/Simulink environment, has been created and validated taking into account the design and operating data of a condenser installed in a 400 MW combined cycle power plant still operative in the Italian electricity market.
2
The air-cooled condenser
The air-cooled condenser is a steam-air heat exchanger composed by several modules such as that sketched by fig. 1.
Figure 1:
The cross-section of a single module of the air-cooled condenser.
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The exhaust steam, leaving the low pressure turbine, comes up to the horizontal main duct and then enters the “parallel-flow” modules flowing down inside banks of finned tubes where its condensation occurs owing to the heat exchange with the ambient air moved by axial fans; the condensate accumulates into two outlet headers, in order to be withdrawn, while the remaining condensing steam goes to the “dephlegmator” characterized by the steam and condensate in counterflow arrangement. The “dephlegmator” modules are also equipped with steam jet air ejectors for the removal of non-condensable gases. Each fan is usually moved by a two-speed motor and the finned tubes are installed in staggered rows; tubes can be round, elliptical or flat and several types of fins are on the market with the aim of optimising the technical performance of condensers subjected to different operating conditions.
3
The mathematical models
The developed mathematical and simulation models are based on the “NTU effectiveness method” which permits to determine the condenser operating parameters beginning from the calculation of the rows effectiveness and the condenser effectiveness, as suggested by Fabbri [2]: Tair _ out − Tair _ in T −T Erow _ i = i +1 i , Econdenser = (1) Ts − Ti Ts − Tair _ in where Ti is the air temperature upstream the ith row while Ts is the condensation temperature. Furthermore the system thermal balance equation is: M air ⋅ c p air ⋅ Tair _ out − Tair _ in = M s ⋅ r ⋅ xs (2)
(
)
where M air and M s denote the air and steam flow rates, c pair is the air average specific heat at constant pressure, r the condensation latent heat and xs the steam quality at the condenser inlet. In accordance with the model proposed by Fabbri [2], the steam condensation rate per unit of tube length is assumed constant along each tube: M air ⋅ c p air ⋅ (Ti +1 − Ti ) (3) m si = r ⋅ xs ⋅ L where L denotes the tubes length. The first two models analyse the steady-state behaviour of a single module of the condenser, coupled with the corresponding fan, and characterized by four rows of finned tubes while the third one refers to a condenser composed of 21 modules (18 parallel-flow and 3 dephlegmator) with three tubes rows. The first step of the analysis has been the design calculation of the condenser main operating parameters: the steam mass flow rate entering each row, the pressure drop inside the tubes, the air intermediate temperatures Ti, the rows effectiveness and the axial coordinate value ai along each tube at which the condensing steam mass flow rate becomes null and the pressure reaches the minimum value. All models assume the pressure drop per unit of tube length proportional to the square of the current steam flow rate and consider the same pressure drop WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
402 Energy and Sustainability II between the inlet and the outlet of each finned tube, the main duct and the lower headers being in common. 3.1 The first model The main inputs of the first simulator are: the air inlet temperature, the exhaust steam flow rate at the turbine outlet, the pressure in the main duct and the geometrical data of the condenser. The model considers four tubes rows having the same effectiveness. For this case, in absence of non-condensable gases, the first rows, which are those in contact with the coldest air, have pressure minimum values inside the tubes instead of at their outlet (ai < L); as a consequence, there is vapour back flow from the other rows to the first ones. If the presence of non-condensable gases is considered, these gases accumulate along the first rows from the ai axial coordinate to the tubes outlet and determine the reduction of the heat exchange effectiveness. The following considerations refers to the simulation of a parallel-flow module belonging to a condenser characterised by the next design data: - Total thermal flux = 218.05 MWth; - Total steam mass flow rate = 97.51 kg/s; - Nominal condensation temperature = 41.53 °C; - Steam quality at the condenser inlet = 0.9308; - Ambient temperature = 15 °C, ambient pressure = 100.4 kPa; - 20 modules each composed of 6 bundles; - 4 rows per bundle; - Condensing steam mass flow rate per bundle = 0.81 kg/s.
Figure 2:
Condensing steam flow rates (E1=E2=E3=E4).
Assuming that each row has an effectiveness equal to 35%, the following air intermediate temperatures have been calculated by means of eqn. (1): T2 = 24.2 °C, T3 = 30.31°C, T4 = 34.24°C, T5 = 36.79°C. The condensing steam mass flow rate and pressure along each tube row are plotted by fig. 2 and fig. 3, considering the presence of non-condensable gases inside the flow. It is possible to notice WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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that the steam condenses completely inside both row 1 and row 2, which operate in better conditions in terms of air lower temperatures and higher steam mass flow rates; the condensing steam flow rate becomes null at the end of the 3rd row while the steam which enters the 4th row does not condensate completely inside the tubes and goes to the dephlegmator unit. If non-condensable gases had not been considered, the steam exiting the 4th row would have gone back into the tubes of the first two rows. So it is clear that the vapour back-flow does not occur inside the tubes where non-condensable gases accumulate.
Figure 3:
The pressure along each tube (E1=E2=E3=E4).
Being the operating conditions depicted by fig. 2 and fig. 3 not optimal, in terms of heat exchange effectiveness and steam flow rate distribution between the tubes rows, it has been necessary to find better design data for the condenser in order to optimise its technical performance; it would be better to have the same flow rate at each tube inlet, the same air temperature increase through each tubes row and the steam complete condensation at the end of tubes (ai ≥ L), in order to avoid any vapour back flow and non-condensable gases accumulation. 3.2 The second model Different solutions have been adopted in order to optimise the condenser operating conditions. The first is relative to a condenser with tubes characterized by the same finned surface and consists in installing a gauged throttle upstream of each tube with the aim of completing the steam condensation not before the tube end. The condensing steam mass flow rate and pressure along each tube row are plotted by fig. 4 and fig. 5, considering gauged pressure drops upstream of each tube and row effectiveness equal to 35%. The results show that the steam flow rate at the tubes inlet is not the same for all rows and it is higher for row 1 in contact with cold air; as a consequence, this solution does not seem to be the most adequate. It appears clear that the best
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Figure 4:
Condensing steam flow rates (E1=E2=E3=E4, gauged pressure drops).
Figure 5:
The pressure along each tube (E1=E2=E3=E4, gauged pressure drops).
solution is that of designing condensers with tubes rows characterized by different effectiveness values, as nowadays proposed by manufacturers. 3.3 The rows effectiveness optimization From the considerations drawn in 3.1 and 3.2 it derives that a well-designed multi-row air-cooled condenser needs differently finned tube rows; in particular, it is necessary to increase the fin surface of the more external rows which are those exposed to a hotter air flow. The optimization of the rows effectiveness for the condenser described in 3.1 has determined the following best values: E1 = 20.7%, E2 = 26.2 %, E3 = 35.5 %, E4 = 55.0%. Considering these nominal values, the condensing steam mass flow rate and pressure along each tube become the same for all rows, as shown by fig. 6. Furthermore, there is not vapour back flow and the air temperature increase is the same through each row. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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Figure 6:
405
The pressure and steam flow rate along each tube (E1≠E2≠E3≠E4).
3.4 The third model The third simulation model, implemented in the Matlab/Simulink environment, is called “operative” because it is going to be linked to the dynamic simulator of the whole combined cycle power plant; it is used to calculate off-line the condenser performance parameters in off-design operating conditions. In this case the steam flow rate is an important datum while the pressure downstream the turbine is unknown. In the following the main equations used to simulate a single module of the condenser are reported. The main inputs of the simulator are: - the ambient temperature (T1) and pressure (p1); - the exhaust steam mass flow rate and quality at the condenser inlet; - the condenser design operating parameters: condensation temperature (Ts-nom = 37.90°C), ambient temperature and pressure (T1-nom = 15°C, p1-nom = 101.6 kPa), exhaust steam mass flow rate and quality ( m s − nom = 5.52 kg/s, xs-nom = 0.9256), air volume flow rate and density ( Q air −nom = 581 m3/s, ρair-nom = 1.228 kg/m3), air intermediate temperatures (T2-nom = 20.74°C, T3-nom = 26.48°C , T4-nom = 32.22 °C), rows effectiveness (E1-nom = 25.07%, E2-nom = 33.45%, E3-nom = 50.27%), condenser global effectiveness (Econdenser = 75.2%); - the condenser geometrical data. The heat balance equation for the ith row can be written as: M air ⋅ c p air ⋅ (Ti +1 − T1 ) = U i ⋅ Si ⋅ ∆Tlm _ i − i +1 (4) where Ui is the global transmittance, Si the heat exchange area and ∆Tlm the logmean temperature difference. Since the NTU (Number of Transfer Units) corresponds to the ratio [8]: U i ⋅ Si NTU i = , (5) M air ⋅ c p air WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
406 Energy and Sustainability II after a little algebra one gets:
Erow _ i = 1 − e − NTU i .
(6)
Considering constant the average values of Ui, Si and cp air, it derives that the product ( M air ⋅ NTU i ) must be kept constant and so the effectiveness values can be calculated from the current air mass flow rate, which depends on the fan rotational speed, as follows:
Erow _ i = 1 − e
−
M air −nom ⋅ NTU i − nom M air
.
(7)
The next step is the calculation of the condensation temperature Ts: it is determined by eqn. (2), after having expressed the condensation latent heat as a polynomial function of Ts and the air outlet temperature T4 as a function of E1, E2, E3, T1 and Ts. The Ts calculated value permits to determine the condensation pressure, by means of the water-steam properties, and the air intermediate temperatures T2, T3 and T4, by means of eqn. (1). As a consequence the steam condensation rates per unit of tube length can be determined by eqn. (3). As proposed by Fabbri [2], it is necessary to distinguish the tubes characterized by vapour back flow (bf) from those where the steam does not condense completely (nbf). In the first case, the steam mass flow rate at the axial coordinate x along the ith tube is calculated by: M si = m si ⋅ (ai − x ) (8)
( )bf
where ai is the length of the tube segment in which the steam flows from the main duct to the lower header. The steam flow rate crossing the outlet end of each tube is equal to: = −m ⋅ (L − a ) . Π (9) si
si
i
On the other hand the steam flow rate at the axial coordinate x along the tubes without back flow is calculated by: . M si = m si ⋅ (L − x ) + Π (10) si
( )nbf
The calculation of the pressure drop between the inlet and the outlet of each tube has been done referring to the model reported by Fabbri [2]. In particular, for the tubes with back flow the following equation has been adopted: k ⋅ m 2 (∆pi )bf = i si ⋅ 2ai3 − 3ai2 L + 3ai L2 − L3 (11) 3 ki denoting a friction coefficient which depends on the tubes material. On the other hand, the tubes without back flow are characterized by a pressure drop equal to: k ⋅ m 2 (∆pi )nbf = i si ⋅ L3 − 3ai L + 3ai2 L . (12) 3 Since all tubes rows have the inlet and outlet plena in common, the pressure drops have to be the same: (∆pi )bf = (∆pi )nbf ∀i. (13)
(
)
(
)
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In order to calculate pressure drops within the Matlab/Simulink model efficiently, eqn. (12) and (13) have been implemented in non-dimensional form, as done by Fabbri [2] by proper choice of reference variables, as a function of the steam flow rates defined by eqn. (8) and (10). Assuming the steam total flow rate at the exit of tubes without back flow equal to the one flowing back to the other tubes, that is equivalent to not considering a dephlegmator module downstream, the model calculates the pressure drop between the inlet and outlet plena. Once this value has been determined, it is possible to solve eqn. (11) and (12) in order to calculate the axial coordinate ai along each tube at which the condensing steam mass flow rate becomes null. As a consequence, the steam flow rate at each row inlet can be evaluated by the following equation: M si = m s i ⋅ ai . (14) In order to consider the presence of a dephlegmator unit downstream of the parallel-flow module, it is necessary to modify the tubes length as follows: L* = α −1L , α < 1 (15) where the coefficient α is connected with the steam flow rate to the dephlegmator: M si _ dph ∝ (1 − α ) ⋅ M si . (16) Consequently, the steam total flow rate at the parallel-flow module inlet is equal to: M si = m si ⋅ ai = M si _ dph + M si _ c (17)
∑
∑
i
where:
∑
i
∑ M
∑
i
si _ c
= α ⋅ L* ⋅
i
i
∑ m
si
(18)
i
is the steam flow rate which condenses inside the parallel-flow module. The rows length increase is equivalent to impose the steam complete condensation inside the system composed of one parallel-flow module and one dephlegmator unit connected in series. 3.5 The condenser performance curves The aim of the present analysis has been that of determining, by the third simulator, the condenser performance curves which show, on the pressure – steam flow rate plane, how the condensation pressure ps is influenced by both the air inlet temperature T1 and the fans rotational speed. Figure 7 reports the performance curves considering all fans running at full speed. It is clear that, for the same value of steam flow rate, the higher is T1 the higher is the condenser pressure; on the other hand, considering the same temperature T1, the lower is the steam flow rate the lower is the condenser pressure. The curves in fig. 7 are not parallel lines but their slope increases with the air inlet temperature. Since this type of air-cooled condensers are equipped with fans running at two different speed values, respectively 100% and 50% of the nominal rotational WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
408 Energy and Sustainability II speed, it has been interesting to calculate the performance curves also for the case of all fans at half speed, that is an operative condition to which the condenser is subjected both during startup and cold days. The results are plotted in fig. 8: the curves have the same shape as those depicted by fig. 7 but are characterized by a higher slope. In fact in this case, considering the same values of air inlet temperature T1 and steam flow rate, the air flow rate is lower and so the air temperature T4 at the condenser outlet is higher; as a consequence, the condensation temperature increases as well as the pressure.
Figure 7:
The condenser performance curves with all fans at full speed.
Figure 8:
The condenser performance curves with all fans at half speed.
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The curves obtained by the third simulation model have been compared with those supplied by Ansaldo Energia SpA, an Italian company which installs aircooled condensers in its power plants sites. The model validation has been done with reference to different steady-state operating conditions and it is important to remark that the calculated performance curves are in good agreement with manufacturers ones.
4
Conclusions
The mathematical and simulations model described in this paper have been developed to study a multi-row A-frame air-cooled condenser for combined cycle power plants. The analysis has been focused on the simulation of the condenser behaviour under different steady-state operating conditions with the aim of evaluating the influence of the air inlet temperature on the system performance. The problem of the non-condensable gases accumulation inside the finned tubes rows has been analysed from a phenomenological point of view and some technical solutions have been proposed in order to reduce the risk of their formation, as well as the vapour back flow inside the tubes. The condenser performance curves have been determined considering two different fans operating conditions, full or half speed, and varying both the air inlet temperature and the saturated exhaust steam flow rate. The calculated curves validation phase has confirmed the model validity over a wide range of operating conditions. The next step of the study is going to be the development of a dynamic simulation model to study the condenser behaviour under different transient conditions; this model will be integrated with the combined cycle power plant dynamic simulator and validated with experimental data coming from the plant.
References [1] Nagel, P. & Wurtz, W., Dry cooling for power plants: an innovative modularization concept. PowerGen Europe SPX Conference, Cologne, 2006. [2] Fabbri, G., Analysis of vapor back flow in single-pass air-cooled condensers. Int. J. of Heat and Mass Transfer, Vol. 40, No. 16, pp. 39693979, 1997. [3] Fabbri, G., Effect of disuniformities in vapour saturation pressure and coolant velocity on vapour back flow phenomena in single-pass air-cooled condensers. Int. J. of Heat and Mass Transfer, Vol. 43, pp. 147-159, 2000. [4] Fabbri, G., Analysis of the noncondensable contaminant accumulation in single-pass air-cooled condensers. Heat Transfer Engineering, Vol. 18, No. 2, pp. 50-60, 1997. [5] Kröger, D.G., Air-cooled Heat Exchangers and Cooling Towers, Penn Well Corporation, 2004. [6] Larinoff, M.W., Moles, W.E. & Reichhelm, R., Design and specification of air-cooled steam condensers. Texas Chemical Engineering, 1978. WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
410 Energy and Sustainability II [7] Berg, W.F. & Berg, J.L., Flow patterns for isothermal condensation in one pass air cooled heat exchanger. Heat Transfer Engineering, Vol. 1, No. 4, pp. 21-31, 1980. [8] Ricard, J., Equipement Thermique des Usines Génératrices d’Energie Electrique, Dunod, Paris, 1962.
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Optimisation of cogeneration systems – combined production of methanol and electricity C. Werner & H. L. Estrada Hummelt Technische Universität Berlin, Germany
Abstract This paper discusses an example of cogeneration, viz. the combined production of methanol and electricity. In this regard technical and economic criteria of a typical MegaMethanol plant (capacity: 5000 metric tons per day) and a gassteam power plant on natural gas basis (capacity: 750 MW) are presented. A mathematical simulation model summarises the specific criteria of both systems. Aim of this study is the optimisation of the combined production of methanol and electricity. A specific approach to optimise the exergy and/or cost efficiency is applied. Therefore, the energy supply design of the MegaMethanol plant is analysed and evaluated in terms of combined thermodynamic and economic aspects. The significance of different dimensioning parameters of the energy supply design is demonstrated by means of sensitivity analyses. These sensitivity analyses categorise the power plant design parameters in relation to the potential to affect the methanol and electricity costs. Accordingly the energy supply design of the MegaMethanol plant is modified successively in an iteration process. The optimisation results in a gas-steam power plant design characterised by increased exergy efficiency and decreased cost efficiency. Recommendations for advanced optimisation studies of cogeneration concepts are made. Keywords: cogeneration, methanol, electricity, thermoeconomics.
1
Introduction
Parameters like fuel, energy and capital costs as well as the methods of financing qualify the degree of the rational use of energy in industrial processes [1]. Due to the latest development of the fuel and energy costs the interest in primary energy saving concepts increased. An option to reduce the primary energy consumption WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line) doi:10.2495/ESU090371
412 Energy and Sustainability II is the application of cogeneration systems. This paper discusses an example of cogeneration, a combined MegaMethanol plant and a gas-steam power plant on natural gas basis. The energy supply design of the MegaMethanol plant is analysed and evaluated concerning thermodynamic and economic aspects. Objective of the study is the optimisation of the exergy and cost efficiency.
2
State of the art
The following sections refer to the state of the art and the development trends of methanol plants and gas-steam power plants on natural gas basis. 2.1 Methanol production The first synthetic methanol was produced in 1923. Since then, the methanol production processes were developed continuously. The latest improvements are related to the catalyst system and the reactor particularly. These improvements resulted in a robust higher efficiency operation under larger scale conditions [2]. The actual global methanol demand is estimated at 38.1 million metric tons per annum (basis: 2007) [3]. The methanol produced is mainly processed to formaldehyde, methyl-tertiary-butyl aether and acetic acid. Further applications are solvents, petrol and other chemicals. 82% of the actual production capacity is based on natural gas technology. Coal based methanol units account for 15% of the installed capacity. Further portions are represented by fuel oil and stranded natural gas based methanol units [3]. These investigations exemplify the natural gas based technology: A Lurgi MegaMethanol plant with a capacity of 5000 metric tons per day. Sections 2.1.1 and 2.1.2 describe the technical and economic parameters of this Lurgi MegaMethanol plant. 2.1.1 Technical parameters The Lurgi MegaMethanol technology (Figure 1) is characterised by the following process features [4]: - oxygen-blown natural gas reforming combined with steam reforming or autothermal reforming, respectively, - adjustment of synthesis gas composition by hydrogen recycle, - double-stage methanol synthesis in water- and gas-cooled reactors. air
hydrogen recovery
air separation unit
natural gas
sulphur removal
Figure 1:
pre-reforming
autothermal reforming
methanol synthesis
methanol distillation
methanol
Lurgi MegaMethanol technology with autothermal reforming [4].
The desulfurised and pre-reformed feedstock is converted autothermally into synthesis gas. Oxygen and medium pressure steam are required and high pressure steam is produced within the autothermal reforming. The reforming unit WIT Transactions on Ecology and the Environment, Vol 121, © 2009 WIT Press www.witpress.com, ISSN 1743-3541 (on-line)
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includes a heat recovery system to superheat this high pressure steam and the medium pressure steam generated in the methanol synthesis process upstream. After superheating the steam could be used to generate power required internally. Hydrogen is added to the synthesis gas to achieve the required gas composition for the methanol synthesis in the dual reactor system. The purification of the crude methanol is realised in a three-column distillation unit [4]. The distillation process demands low pressure steam. The technical parameters of the non-steamself-sustaining operation of this plant are summarised in Table 1. Table 1: (1) (2) (3) (4) (5)
Technical parameters of the MegaMethanol plant.
310 t/h / 100 bar / 500 °C 160 t/h / 40 bar / 380 °C 75 t/h / 47 bar / 400 °C 135 t/h / 6 bar / 159 °C 110 MW
steam production (reforming) steam production (synthesis) steam requirement (reforming) steam requirement (distillation) electric power requirement
Moreover the operation of the MegaMethanol plant requires 510 t/h potable water as well as 35000 t/h cooling water (∆T=10 K). 2.1.2 Economic parameters The following economic analysis of the MegaMethanol plant is based on the parameters related to [5] and the data in Table 6 (Appendix). The Total Revenue Requirement Method (TRR-Method) is used to evaluate the economics. The cost composition of the MegaMethanol plant investigated is given in Table 2. The credit for the steam produced in the MegaMethanol plant is calculated in dependence on the value of the electricity achievable by the steam. Table 2:
Cost composition of the MegaMethanol plant.
capital cost operation and maintenance cost fuel cost credit steam production
33.2% 27.5% 54.1% - 14.8%
2.2 Electricity production Gas-steam power plants are available on the market up to 1000 MW electric power [6]. An electricity yield of actual gas-steam power plants on natural gas basis of up to 60% is realised [6]. A further improvement of the electricity yield is expected. Therefore the latest research and development in the field of the power plant technology considers material, cooling, construction, combustion and fluid mechanic aspects [7–8]. Sections 2.2.1 and 2.2.2 outline the technical and economic parameters of the gas-steam power plant Seabank/UK on natural gas basis, which are used for these investigations.
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414 Energy and Sustainability II 2.2.1 Technical parameters Since 2000 the gas-steam power plant Seabank/UK is applied to the electric base and mid-load supply [9]. This power plant achieves an electric power output of 756 MW and an electricity yield of 57.8%. The power plant structure is shown in Figure 6 (Appendix). This power plant structure is characterised by two gas turbine systems/heat recovery steam generators (HRSG) and one steam turbine system. The actual operation mode of the gas-steam power plant Seabank/UK is electricity-oriented without any admission or extraction of steam. The option to pre-heat the natural gas of the gas turbine system is available according to Figure A.1 (Appendix). The unfired heat recovery steam generator includes three pressure stages and a single reheat. Table 3 illustrates the steam parameters at the entrance of the high, medium and low pressure steam turbines as well as the reheat steam parameters. The heat recovery steam generator is also used to preheat the condensate/feed water. Table 3:
Triple-pressure process and single reheat in Seabank/UK [9].
high pressure parameter medium pressure parameter low pressure parameter reheat parameter
253.3 t/h / 110 bar / 550 °C 52.1 t/h / 30 bar / 320 °C 36.2 t/h / 4.8 bar / 235 °C 247.6 t/h / 28.5 bar / 550 °C
2.2.2 Economic parameters The description of the economics of the power plant is based on cost equations according to [10–11] and the economic data in Table A.1 (Appendix). Table 4 documents the resulting cost composition of the gas-steam power plant calculated by the application of the TRR-Method. Table 4:
Cost composition of the gas-steam power plant.
capital cost operation and maintenance cost fuel cost
44.2% 7.3% 48.5%
2.3 Combination of the MegaMethanol plant and the gas-steam power plant The combination of the MegaMethanol plant and the gas-steam power plant requires the transfer of energy and material between the subsystems according to Figure 2. Therefore the model of the gas-steam power plant discussed in section 2.2 has to be modified. For this purpose data of the KRAFTWERKSSCHULE E.V. [12] are used. Furthermore, the interfaces (1)-(5) to the MegaMethanol plant are added to realise the energy and material import/export between the subsystems (cp. Table 1 and Figure A.1 (Appendix)).
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MegaMethanol plant air
air separation unit reforming process
hydrogen recovery
syngas
methanol synthesis
crude methanol
process steam medium pressure steam high pressure steam
natural gas
methanol
methanol distillation low pressure steam
gas-steam power plant steam gas turbines
air
flue gas
HRSG
water
steam turbines
power
flue gas
Figure 2:
3
Cogeneration concept: MegaMethanol plant/gas-steam power plant.
Recent research
On the basis of thermoeconomics cost formation processes in a system are definable at component level, thermodynamic losses of components are valuable in terms of economic aspects and exergy based cost allocations for co- or trigeneration systems are feasible. Therefore, the results of the exergy analysis and the economic analysis are combined at component level according to eqn. (1): C j = c j ⋅ E j = c j ⋅ m j ⋅ e j (1) The cost balances of the component k (Figure 3) are presented in eqn. (2) and eqn. (3). Z k = Z kCI + Z kOM C 1 , k , in
1
1
C 1 , k , out
C 2 , k , in
2
2
C 2 , k , out
C 3 , k , in
3
3
C 3 , k , out
C n , k , in
n
m
C m , k , out
Figure 3:
component k
Balance of the component k [13].
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416 Energy and Sustainability II n
∑ C
j , k , in
j =1
n
∑ (c j =1
j
⋅ E j
+ Z kCI + Z kOM =
m
∑ C
j , k , out
(2)
j =1 m
)k ,in + Z kCI + Z kOM = ∑ (c j ⋅ E j )k ,out
(3)
j =1
The specific costs of the incoming streams n of the component k are commonly known from the investigation of downstream components or defined externally (e.g. fuel cost). A part of the cost balances is the exergy stream known from the exergy analysis. The cost balance of the component k considers the levelised capital cost (Figure 3 – superscript: CI) and the operation and maintenance cost (Figure 3 – superscript: OM) from the economic analysis (TRR-Method). To calculate the cost balances of the component k with m outcoming streams (m-1) auxiliary equations are required, cp. [13].
4 Simulations The study of the MegaMethanol/gas-steam power plant concept requires the combination of the technical and economic parameters discussed. The investigations focus on the stationary nominal operation of both subsystems. The simulation software GateCycle is applied to describe the energy supply of the MegaMethanol plant. The software GATEX, MATLAB and Microsoft Excel is used for the thermoeconomic analysis.
5
Results
In the 0th iteration (base case cp. Table 5) an exergy efficiency of 54.84% is achieved by the gas-steam power plant combined with the MegaMethanol plant. The combined operation of the MegaMethanol plant and the gas-steam power plant results in methanol cost of 198.72 EUR/t and electricity cost of 3.67 ct/kWh. Figure 4 documents the correlation between the relative exergy destructtion and the relative specific cost of each component in the gas-steam power plant related to the 0th iteration. To improve the total exergy efficiency the optimisation approach according to [14] recommends an increase of the capital cost of components with medium-high relative exergy destruction values and low relative specific cost. This is ascertainable for the following components during the 0th iteration: combustion chamber, condenser, expander, compressor and low pressure steam turbine. The capital cost reduction of components with low relative exergy destruction values and medium-high relative specific cost is recommended to improve the total cost efficiency, respectively. The high pressure economiser and superheater, the low pressure evaporator, the pumps and the medium pressure steam turbine meet these criteria.
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Each component is characterised by specific dimensioning parameters, which qualify the relative exergy destruction values and the relative specific cost. The following sensitivity analyses explain the significance of the efficiency of the combustion process affected by fuel pre-heat. The options to reduce the relative exergy destruction value by condenser pressure variations are exemplified. To specify the relative exergy destruction and the relative specific costs of the fluidic components (expander, compressor, low/medium pressure steam turbine and pumps) variations of the isentropic efficiency are presented. The interrelation of the minimal temperature difference of the high pressure economiser/ superheater as well as the low pressure evaporator and the relative specific cost of these components will be outlined. Figure 5 illustrates the sensitivity analyses of the MegaMethanol plant/gas-steam power plant concept using the examples of the methanol cost and electricity cost. low 8.25
medium
high
high
high pressure economiser HPECO2/HPEC22
.
low pressure evaporator LPEVA/LPEVA2
low pressure steam turbine ST 3
high pressure pump PUMP 1
2.75
medium
low/medium pressure pump PUMP 2/3
5.50
expander EX1/EX2 condenser CND1
medium pressure steam turbine ST 2
combustion chamber CMB1/CMB2
low
.
(Zk/ED)/Σ (Zk/ED) in %
high pressure superheater HPSHT 3/HPSHT 23
compressor C1/C2
0.00 0
Figure 4:
2
ED/ΣED in %
4
6
Relative exergy destruction vs. relative specific cost of the gassteam power plant components (0th iteration – base case).
The variation of the component parameters in the range of ± 5% is less significant to the methanol cost compared to the electricity cost (Figure 5). The sensitivity analyses document the substantial influence of the gas turbine components expander (EX1/EX2) and compressor (C1/C2) to the production costs. The following iterative optimisation aims to increase the exergy efficiency of the energy supply of the MegaMethanol plant and the total cost efficiency. Table 5