Advances in Energy Research, Volume 4

ADVANCES IN ENERGY RESEARCH

ADVANCES IN ENERGY RESEARCH VOLUME 4

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ADVANCES IN ENERGY RESEARCH Series Editor: Morena J. Acosta Advances in Energy Research, Volume 1 2010. ISBN: 978-1-61668-994-0 Advances in Energy Research, Volume 2 2010. ISBN: 978-1-61728-996-5 Advances in Energy Research, Volume 3 2011. ISBN: 978-1-61761-671-6 Advances in Energy Research, Volume 4 2011. ISBN: 978-1-61761-672-3

ADVANCES IN ENERGY RESEARCH

ADVANCES IN ENERGY RESEARCH VOLUME 4

MORENA J. ACOSTA EDITOR

Nova Science Publishers, Inc. New York

Copyright © 2011 by Nova Science Publishers, Inc. All rights reserved. No part of this book may be reproduced, stored in a retrieval system or transmitted in any form or by any means: electronic, electrostatic, magnetic, tape, mechanical photocopying, recording or otherwise without the written permission of the Publisher. For permission to use material from this book please contact us: Telephone 631-231-7269; Fax 631-231-8175 Web Site: http://www.novapublishers.com NOTICE TO THE READER The Publisher has taken reasonable care in the preparation of this book, but makes no expressed or implied warranty of any kind and assumes no responsibility for any errors or omissions. No liability is assumed for incidental or consequential damages in connection with or arising out of information contained in this book. The Publisher shall not be liable for any special, consequential, or exemplary damages resulting, in whole or in part, from the readers‘ use of, or reliance upon, this material. Any parts of this book based on government reports are so indicated and copyright is claimed for those parts to the extent applicable to compilations of such works. Independent verification should be sought for any data, advice or recommendations contained in this book. In addition, no responsibility is assumed by the publisher for any injury and/or damage to persons or property arising from any methods, products, instructions, ideas or otherwise contained in this publication. This publication is designed to provide accurate and authoritative information with regard to the subject matter covered herein. It is sold with the clear understanding that the Publisher is not engaged in rendering legal or any other professional services. If legal or any other expert assistance is required, the services of a competent person should be sought. FROM A DECLARATION OF PARTICIPANTS JOINTLY ADOPTED BY A COMMITTEE OF THE AMERICAN BAR ASSOCIATION AND A COMMITTEE OF PUBLISHERS. Additional color graphics may be available in the e-book version of this book.

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Published by Nova Science Publishers, Inc. † New York

CONTENTS Preface Chapter 1

vii Investigation of HVAC System Improvement by HAM Numerical Simulation J.A. Orosa

Chapter 2

Research on Heat and Mass Transfer to Improve HVAC Conditions J.A. Orosa

Chapter 3

Rational Attribution of Environmental Emissions of Cogeneration to Products: Allocating Carbon Dioxide and Other Emissions with Exergy Marc A. Rosen

Chapter 4

A New Technique for Biological Monitoring Using Wildlife Mariko Mochizuki, Makoto Mori, Mutsumi Miura, Ryo Hondo, Takashi Ogawa and Fukiko Ueda

Chapter 5

Second Law Based Methods for Improvement of Energy SystemsEconomics and Environmental Impacts: A Brief Overview Sudipta De

1 19

41 87

97

Chapter 6

Physical Formulation of the Expression of Wind Power Reccab M. Ochieng, Frederick N. Onyango and Andrew O. Oduor

Chapter 7

History and Evolution of Fusion Power Plant Studies: Past, Present, and Future Prospects Laila A. El-Guebaly

117

Regional Impacts of the U.S. Environmental Protection Agency‘s SO2 Policy Vladimir Hlasny

171

Recent Developments in Safety and Environmental Aspects of Fusion Experiments and Power Plants Laila A. El-Guebaly and Lee C. Cadwallader

187

Chapter 8

Chapter 9

109

vi Chapter 10

Chapter 11

Contents Is Nuclear Power a Realistic Alternative to the Use of Fossil Fuels for the Production of Electricity? Jorge Morales Pedraza

231

An Analysis of a Closed Cycle Gas Turbine Using CF4 as the Working Fluid Sundar Narayan

277

Chapter 12

Aviation and Climate Change James E. McCarthy

Chapter 13

Greenhouse Gas Emissions: Perspectives on the Top 20 Emitters and Developed Versus Developing Nations Larry Parker and John Blodgett

293

307

Chapter 14

Global Climate Change: Three Policy Perspectives Larry Parker and John Blodgett

323

Chapter 15

Renewable Energy and Energy Efficiency Tax Incentive Resources Lynn J. Cunningham and Beth A. Roberts

355

Chapter 16

Energy Provisions in the American Recovery and Reinvestment Act of 2009 (P.L. 111-5) Fred Sissine, Anthony Andrews, Peter Folger, Stan Mark Kaplan, Daniel Morgan, Deborah D. Stine and Brent D. Yacobucci

Index

361

385

PREFACE This book presents a comprehensive review of improvments of HVAC conditions; biological monitoring using wildlife; second law based methods for improvement of energy systems; the expression of wind power; history and evolution of fusion power plant studies; EPA's SO2 policy and it's regional impacts; global climate change; and energy previsions in the American Recovery and Reinvestment Act of 2009. Chapter 1 - Nowadays, Spanish public buildings employ, during the spring season, the heating system only if indoor conditions are under certain temperature and relative humidity values. A correct HVAC system design and building construction could let us reduce this energy consumption. In the last years software tools were employed to understand and predict these thermal behaviour but they underestimated the energy consumption because its energy models ignore moisture. Actual HAM tools software could be employed to simulate indoor conditions and phenomena of material and energy transfer thought building envelopes and its effects on indoor conditions. Present paper shows an example of HAM tools application to determine modifications that reduce energy consumption or improve HVAC system in real buildings. Results showed the veracity of this simulation software and that parameters like solar gain or air leakages are so important than thermal inertia. Chapter 2 - This paper shows a research about improvement of indoor conditions controlling heat and mass transfer process. To do it, the first step was to sample real data in different kind of typical Spanish buildings like a set of flats, office buildings, museums and schools located in the area of A Coruña, Spain. Once obtained this data, it was analysed to determine indoor ambience problems and possible solutions related with heat and mass transfer process. In this sense, problems related with comfort conditions, energy saving, health, materials conservation and work risk were found and possible solutions like air renovation, thermal inertia, and moisture buffering were found. Chapter 3- Many from industry, government and academe have struggled with the question of how to allocate emissions for an energy process that has multiple products and multiple inputs, like cogeneration. Present methods are not universally accepted, because they are inconsistent, overly complex, difficult to utilize, and not soundly based. The author proposes that exergy methods can form the basis of rational and meaningful allocation methods for emissions. In this article, methods based on exergy for allocating cogeneration emissions are investigated and compared with other methods. Two illustrations are provided. The rationale for the author‘s view that the exergy-based method is the most meaningful and accurate is discussed, as are problems associated with other methods. An analogy is described

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between allocating carbon dioxide emissions and economic costs for cogeneration. The results indicate that the exergy-based emissions allocations method provides a sensible basis for a meaningful overall approach for emissions trading. It is concluded that the exergy-based method of carbon dioxide emissions allocation for cogeneration is rational, useful and superior to other methods. By permitting these emissions to be allocated more appropriately among commodities generated by cogeneration, the results allow the environmental benefits of technologies that produce multiple products to be better understood and exploited. The results should be of most benefit to designers of energy systems, and to decision and policy makers in companies and government. The author proposes that the exergy-based method be used in allocating cogeneration emissions to help ensure proper decision-making regarding such issues as what effect cogeneration may have on overall carbon dioxide emissions and how emissions should be reduced, how and where cogeneration should be used, and fair ways to establish emissions trading schemes. Chapter 4 - Since data obtained from wildlife are useful for the evaluation of risks to human health, importance of biological monitoring has been pointed out in many studies. However, it is fact that there are many problems on the biological monitoring using wildlife. For example, the outliers were often observed on the data obtained from wildlife. Although the outliers could be excluded by statistical data processing in studies of experimental animals, the outliers may indicate potential contamination of animals in studies of wildlife. In the present study, 80 wild ducks were investigated, and the cadmium (Cd) contents of kidney and that of liver were ND-67.44, ND-21.15 μg/g dry weight respectively. Since the outlier has been observed in several species, such as spot-billed duck, mallard, the authors analyzed those outliers using cadmium standard regression line (CSRL). In the authors previous reports, the CSRL was suggested as a useful index for the understanding of Cd contamination of animals. In conclusion, it was suggested that biological monitoring using the CSRL can make full use of the characteristics of all data, including outliers. Chapter 5 - Second law of thermodynamics is a fundamental law of nature and the concept can be utilized for better performance of energy systems. The entropy generation in any real (i.e., irreversible) process is a measure of the irreversibility of that process. Exergy concept includes the combined effect of a system and environment to measure the maximum possible work potential as the system reaches equilibrium with the environment from its initial state. In this article, a brief overview of different methods based on the principles of second law of thermodynamics in design and analysis of energy systems is discussed. The concept of entropy generation and exergy destruction in real-life processes are combined with economics and the overall impact on the environment during the life-cycle of a system to obtain more useful conclusions. Starting from entropy generation minimization principle (EGMP), exergy analysis, thermoeconomics (exergoeconomics) and exergetic life cycle analysis has been discussed. Some discussions on future trends of application of second law concept are also included. Chapter 6 - This paper touches on a fundamental aspect of wind energy calculation, and goes ahead to formulate three expressions of wind power. The paper attempts to answer the question whether the kinetic energy of a unit mass per second is 1/2, 1/3, or 2/3v3. The answer to this question is of importance for fluid dynamic considerations in general. The classical formulation of wind energy for turbines is based on the definition of the kinetic energy due to the wind impinging on the turbine blades. The expression of wind energy obtained is directly related to half (1/2) of the specific mass multiplied by the cube of wind

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velocity. Usually the assumption used is that the mass is constant. However, by changing this condition, different results arise. The approach by Zekai [1] based first on the basic definition of force and then energy (work) reveals that the same equation is valid but with 1/3 instead of factor 1/2. In his derivation, Zakai [1] has not given any reason as to why a factor 2/3 which can be obtained using his approach is not acceptable. The authors advance arguments to show that three expressions of wind energy are possible through physical formulation. Chapter 7 - This chapter provides a brief history of magnetic confinement fusion power plant conceptual designs, beginning with the early development in 1970, focusing on tokamaks. In addition, the evolution of six more magnetic concepts (stellarator, spherical tori, field-reversed configurations, reversed-field pinches, spheromaks, and tandem mirrors) is highlighted. The key issues encountered are discussed, including the technological obstacles and the elements necessary for economic competitiveness. Extensive R&D programs and international collaboration in all areas of fusion research led to a wealth of information generated and analyzed. As a result, fusion promises to be a major part of the energy mix in the 21st century and beyond. Chapter 8 - This study compares sulfur dioxide concentrations and the resulting health damages across U.S. regions under three alternative policies considered by the U.S. Environmental Protection Agency: emission caps, emission tax and tradable permits. Regional modeling is important because SO2 does not diffuse uniformly across regions, and because the U.S. energy industry is divided geographically by regulatory barriers, and differences in infrastructure, costs and energy demand. Regional concentrations of SO2 are found to vary across competing environmental policies significantly. Hundreds of millions of dollars in damages are at stake for individual states from the EPA‘s policy choice. Emission caps favor southern states, including California, Texas and Florida, where they deliver $840 million lower damages than the other policies. They deliver $390 million higher damages in northern, Great Lakes and New England states. Chapter 9 - Electricity generating plants powered by nuclear fusion have long been envisioned as possessing inherent advantages for the health and safety of the public, the health and safety of plant workers, and good stewardship of the environment while supporting modern society. This chapter discusses the progress and state-of-the-art of these three principal aspects of fusion safety and environment. The fusion safety philosophy and advantages over traditional thermal power plants are described. Fusion workers should be protected commensurately with workers in other comparable industrial activities. The fusion radwaste management strategy must accommodate the new trend of recycling and clearance, avoiding geological disposal. Here, the authors discuss the technical elements as well as the US regulatory approach and policy governing the design of safe and environmentally sound fusion devices. Chapter 10 - It is an undisputed reality that the energy production and their sustained growth constitute indispensable elements to ensure the economic and social progress of any country. For this reason, all type of energy sources available in the country, including nuclear energy, should be included in any study about the energy mix to be prepared in order to ensure its future economic an social development. However, there are certain factors that need to be considered by the competent authorities of a country during the selection of the most economic and convenient energy sources for the generation of electricity. For instance, the use of fossil fuels is a major and growing contributor to the emission of carbon dioxide to

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the atmosphere provoking serious changes in the world climate, while nuclear energy and renewables are almost carbon dioxide free. Considering the different available energy sources that the world can use now to satisfy the foresee increase in energy demand in the coming years, there should be no doubt that, at least for the next decades, there are only a few realistic options available to reduce further the CO2 emissions to the atmosphere as result of the electricity generation. These options are, among others, the following: Increase efficiency in electricity generation and use; Expand use of all available renewable energy sources such as wind, solar, biomass and geothermal, among others; Massive introduction of new advanced technology like the capture carbon dioxide emissions technology at fossil-fueled (especially coal) electric generating plants, with the purpose to permanently sequester the carbon produced by these plants; Increase use of new types of nuclear power reactors that are inherent safe and proliferation risk-free; Increase energy saving. Chapter 11 - When the pressure losses occuring in the Brayton cycle are accounted for, the cycle efficiency depends on the ratio of specific heats of the working fluid. The lower the ratio of specific heats, the higher the cycle efficiency. When tetrafluoromethane (CF4 or Refrigerant-14), a non-toxic, non-flammable, thermally stable, fairly inert gas having a specific heat ratio of 1.1 - 1.14, is used as the working fluid in a closed cycle gas turbine, a 22% increase in the thermal efficiency can be obtained than when air is the working fluid. Other organic gases too could be used in the proposed Closed Organic Brayton (COB) cycle which can achieve a thermal efficiency of about 21 % with a heat source temperature of only 5400C (~1000 deg F). Its capital and operating costs will be competitive with existing small Rankine cycle steam power plants that burn biomass, and have typical gas turbine advantages like small plant footprint and quick startup. Chapter 12 - Aircraft are a significant source of greenhouse gases—compounds that trap the sun‘s heat, with effects on the Earth‘s climate. In the United States, aircraft of all kinds are estimated to emit between 2.6% and 3.4% of the nation‘s total greenhouse gas (GHG) emissions, depending on whether one counts international air travel. The impact of U.S. aviation on climate change is perhaps twice that size when other factors are considered. These include the contribution of aircraft emissions to ozone formation, the water vapor and soot that aircraft emit, and the high altitude location of the bulk of aircraft emissions. Worldwide, aviation is projected to be among the faster-growing GHG sources. If Congress or the Administration decides to regulate aircraft GHG emissions, they face several choices. The Administration could use existing authority under Sections 231 and 211 of the Clean Air Act, administered by the Environmental Protection Agency. EPA has already been petitioned to do so by several states, local governments, and environmental organizations. Congress could address aviation or aviation fuels legislatively, through capand-trade or carbon tax proposals, or could require EPA to set emission standards. Among the legislative options, the cap-and-trade approach (setting an economy-wide limit on GHG emissions and distributing tradable allowances to emitters) has received the most attention. Most cap-and-trade bills, including the House-passed energy and climate bill, H.R. 2454, would include aviation indirectly, through emission caps imposed upstream on their source of fuel—the petroleum refining sector. By capping emissions upstream of air carriers and eventually lowering the cap more than 80%, bills such as these would have several effects: they would provide an incentive for refiners to produce lower-carbon fuels; they would increase the price of fuels, and thus increase the demand for more fuel-efficient

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aircraft; and they might increase the cost of aviation services relative to other means of transport, giving airline passengers and shippers of freight incentives to substitute lower-cost, lower-carbon alternatives. Besides regulating emissions directly or through a cap-and-trade program or carbon tax, there are other tools available to policy makers that can lower aviation‘s GHG emissions. These include implementation of the Next Generation Air Traffic Control System (not expected to be complete until 2025, although some elements that could reduce aircraft emissions may be implemented sooner); research and development of more fuel-efficient aircraft and engines; and perhaps the development of lower-carbon jet fuel. This chapter provides background on aviation emissions and the factors affecting them; it discusses the tools available to control emissions, including existing authority under the Clean Air Act and proposed economy-wide cap-and-trade legislation; and it examines international regulatory developments that may affect U.S. commercial airlines. These include the European Union‘s Emissions Trading Scheme for greenhouse gases (EU-ETS), which is to include the aviation sector beginning in 2012, and discussions under the auspices of the International Civil Aviation Organization (ICAO). Chapter 13 - Using the World Resources Institute (WRI) database on greenhouse gas emissions and related data, this chapter examines two issues. The first issue is the separate treatment of developed and developing nations under the United Nations Framework Convention on Climate Change (UNFCCC) and the Kyoto Protocol. This distinction has been a pivotal issue affecting U.S. climate change policy. The second issue is the continuing difficulty of the current approach designed to address climate change through limiting greenhouse gas emissions to a specified percentage of baseline emissions (typically 1990). The data permit examination of alternative approaches, such as focusing on per capita emissions or the greenhouse gas emission intensity (measured as emissions per unit of economic activity). Key findings include: A few countries account for most greenhouse gas emissions: in 2000, the United States led by emitting 19% of the world total, followed by China with 14%; no other country reached 6%; the top seven emitters accounted for 52% of the 185 nations‘ emissions. Land-use effects (e.g., deforestation) on emissions are negligible for most nations, but they cause emissions to rise sharply for certain developing nations, for example, Brazil and Indonesia. While oil- and gas-producing Gulf States have the highest per capita greenhouse gas emissions, in general developed nations rank high in per capita emissions (in 2000, Australia, the United States, and Canada ranked 5, 7, and 9, respectively, in the world), while developing nations tend to rank low (China, India, and Indonesia ranked 98, 156, and 123, respectively). The greenhouse intensity of the economy — the metric by which the George W. Bush Administration addressed climate change — varies substantially among developed countries (the Ukraine emits 667 tons/million international $GDP, while France emits 93 tons/million $GDP, with the United States at 192 tons/million $GDP; developing nations show less variance unless land use is taken into account. The time frame adopted for defining the climate change issue and for taking actions to address greenhouse gas emissions has differential impacts on individual nations, as a result of individual resource endowments (e.g., coal versus natural gas and hydropower) and stage of

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economic development (e.g., conversion of forest land to agriculture occurring before or after the baseline). Differentiating responsibilities between developed and developing nations — as the UNFCCC does — fails to focus efforts on some of the largest emitters. Moreover, many developed countries have not achieved stabilization of their emissions despite the UNFCCC. Given the wide range of situations illustrated by the data, a flexible strategy that allows each country to play to its strengths may be appropriate if diverse countries like the United States and China are ever to reach agreement. Chapter 14 - The 1992 U.N. Framework Convention on Climate Change requires that signatories, including the United States, establish policies for constraining future emission levels of greenhouse gases, including carbon dioxide (CO2). The George H. W. Bush, Clinton, and George W. Bush Administrations each drafted action plans in response to requirements of the convention. These plans have raised significant controversy and debate. This debate intensified following the 1997 Kyoto Agreement, which, had it been ratified by the United States, would have committed the United States to reduce greenhouse gases by 7% over a five-year period (2008-2012) from specified baseline years. Controversy is inherent, in part, because of uncertainties about the likelihood and magnitude of possible future climate change, the consequences for human wellbeing, and the costs and benefits of minimizing or adapting to possible climate change. Controversy also is driven by differences in how competing policy communities view the assumptions underlying approaches to this complex issue. This paper examines three starting points from which a U.S. response to the convention is being framed. These starting points, or policy ―lenses,‖ lead to divergent perceptions of the issue with respect to uncertainty, urgency, costs, and government roles. They also imply differing but overlapping processes and actions for possible implementation, thus shaping recommendations of policy advocates concerning the federal government‘s role in reducing greenhouse gases. A technological lens views environmental problems as the result of inappropriate or misused technologies. The solutions to the problems lie in improving or correcting technology. The implied governmental role would be to provide leadership and incentives for technological development. An economic lens views environmental problems as the result of inappropriate or misleading market signals (prices). The solutions to the problems lie in ensuring that the prices of goods and services reflect their total costs, including environmental damages. The implied governmental role would be to improve the functions of the market to include environmental costs, so the private sector can respond efficiently. An ecological lens views environmental problems as the result of indifference to or disregard for the planet‘s ecosystem on which all life depends. The solutions to the problems lie in developing an understanding of and a respect for that ecosystem, and providing people with mechanisms to express that understanding in their daily choices. The implied governmental role would be to support ecologically based education and values, as well as to promote ―green‖ products and processes, for example through procurement policies, efficiency standards, and regulations. Some initiatives are underway; all the perspectives are relevant in evaluating them and possible further policies. The purpose here is not to suggest that one lens is ―better‖ than

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another, but rather to articulate the implications of the differing perspectives in order to clarify terms of debate among diverse policy communities. Chapter 15 - The following list of authoritative resources is designed to assist in responding to a broad range of constituent questions and concerns about renewable energy and energy efficiency tax incentives. Links are provided for the following: the full text of public laws establishing and extending federal renewable energy and energy efficiency incentives; federal, state, and local incentives resources; incentive resources grouped by technology type (solar, wind, geothermal, and biomass); CRS reports on this topic; and federal grants information resources. The last section of this chapter includes tables displaying popular incentives, the corresponding U.S. Code citations, and current expiration dates of those incentives. This list reflects information that is currently available. Chapter 16 - The American Recovery and Reinvestment Act of 2009 (ARRA, P.L. 111-5) emphasizes jobs, economic recovery, and assistance to those most impacted by the recession. It also stresses investments in technology, transportation, environmental protection, and other infrastructure and proposes strategies to stabilize state and local government budgets. Energy provisions are a featured part of ARRA. More than $45 billion is provided in appropriations for energy programs, mainly for energy efficiency and renewable energy. Most funding must be obligated by the end of FY20 10. ARRA also provides more than $21 billion in energy tax incentives, primarily for energy efficiency and renewable energy. More than $11 billion is provided in grants for state and local governments through three Department of Energy programs. They are the Weatherization Assistance Program, which provides energy efficiency services to low-income households; the State Energy Program, which provides states with discretionary funding that can be used for various energy efficiency and renewable energy purposes; and the new Energy Efficiency and Conservation Block Grant Program, which aims to help reduce energy use and greenhouse gas emissions. The law conditions eligibility for most of the State Energy Program funding on enactment of new building codes and adoption of electric utility rate ―decoupling‖ to encourage energy efficiency. For the Department of Education, about $8.8 billion is provided for ―Other Government Services,‖ which may include renovations of schools and college facilities that meet green building criteria. The Department of Housing and Urban Development ($2 billion),and the Environmental Protection Agency ($1 billion) receive multi-purpose funds that can be used for energy efficiency measures in public housing and state and tribal facilities. New transportation-related grant programs support state and local government and transit agency purchases of alternative fuel and advanced technology vehicles, multi-modal use of transportation electrification, and manufacturers‘ development of facilities for advanced battery production. Nearly $5 billion is provided for ―leadership by example‖ efforts to improve energy efficiency in federal buildings and facilities. The law puts the General Services Administration (GSA) at the forefront of this effort, with $4.5 billion for ―high performance‖ federal facilities. For Department of Defense facilities, ARRA provides $3.7 billion for improvements that have a focus on energy efficiency. ARRA provides $100 million to the Department of Transportation for ―reducing energy consumption or greenhouse gases.‖ The Department of the Interior ($1 billion) and Department of Veterans Affairs ($1 billion) receive multi-purpose funds that can be applied to ―energy efficiency‖ or ―energy projects.‖ Also, GSA receives $300 million for federal purchases of alternative fuel vehicles.

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Nearly $8 billion is provided for energy and other R&D programs, $2.4 billion for energy technology and facility development grants, and $14 billion for electric power transmission grid infrastructure development and energy storage development (including $6 billion for loan guarantees). Also, the $21 billion in tax incentives include $14.1 billion for renewable energy, $2.3 billion for energy efficiency, $2.2 billion for transportation, $1.6 billion for manufacturing, and $1.4 billion for state and local government energy bonds. In response to the weakening value of renewable energy tax credits, caused by the economic recession, ARRA provides a cash grant alternative to both production and investment credits during 2009 and 2010. Chapters 1 - 8 - A version of these chapters was also published in the International Journal of Energy, Environment, and Economics, Volume 18, Issue 1/2, published by Nova Science Publishers. It was submitted for appropriate modifications in an effort to encourage wider dissemination of research. Chapters 9 - 16 - A version of these chapters was also published in the International Journal of Energy, Environment, and Economics, Volume 18, Issue 3/4, published by Nova Science Publishers. It was submitted for appropriate modifications in an effort to encourage wider dissemination of research.

In: Advances in Energy Research. Volume 4 Editor: Morena J. Acosta, pp. 1-18

ISBN: 978-1-61761-672-3 © 2011 Nova Science Publishers, Inc.

Chapter 1

INVESTIGATION OF HVAC SYSTEM IMPROVEMENT BY HAM NUMERICAL SIMULATION J.A. Orosa* Department of Energy and Marine Propulsion, University of A Coruña, Paseo de Ronda 51, 1501. A Coruña, Spain

ABSTRACT Nowadays, Spanish public buildings employ, during the spring season, the heating system only if indoor conditions are under certain temperature and relative humidity values. A correct HVAC system design and building construction could let us reduce this energy consumption. In the last years software tools were employed to understand and predict these thermal behaviour but they underestimated the energy consumption because its energy models ignore moisture. Actual HAM tools software could be employed to simulate indoor conditions and phenomena of material and energy transfer thought building envelopes and its effects on indoor conditions. Present paper shows an example of HAM tools application to determine modifications that reduce energy consumption or improve HVAC system in real buildings. Results showed the veracity of this simulation software and that parameters like solar gain or air leakages are so important than thermal inertia.

NOMENCLATURE Variables Acc C

c c pa H *

Indoor Air Quality acceptable index. Sum of thermal capacity C of each construction. Specific heat capacity of the material (J/kg K). Specific heat capacity of the dry air (J/kg K). Sum of heat loss factor of each construction, ventilation and air leakage.

E-mail address: [email protected], Tel. 034 981 167000 4320, fax. +349811167107. (Corresponding author)

2

J.A. Orosa h

hevap

air enthalpy (kJ/kg). Latent heat of evaporation (J/kg).

ma

Density of moisture flow rate of dry air (kg/m2s).

ml

Density of moisture flow rate of vapour phase (kg/m2s).

PD Psuc Pv Qheat Qloss Qgain

Percentage of dissatisfied (%). Suction pressure (Pa). partial water vapour pressure (Pa). Heat requirement (W). Heat loss (W). Heat gain (W). Density of the air flow rate (m3/m2s).

ra T

t K

w x xa

Temperature (ºC). Time (s). Hydraulic conductivity. Moisture content mass by volume (kg/m3). Space coordinates (m). Water vapour content (kg/kg).

Variables in Greek Letters

p

  a o

Moisture permeability (s). Thermal conductivity (W/mK) Utilisation factor. Density of the material (kg/m3). Density of the dry material (kg/m3).

1. INTRODUCTION A Coruña, located in the north west of Spain, present a mild climate with a high relative humidity as a consequence of winds. Nowadays, Spanish public buildings employ, during the spring season, the heating system only if indoor conditions are under certain temperature and relative humidity values. This HVAC system operation could be improved by some buildings design modifications. In this sense, energy saving methods are focused in the study of heat and mass transfer through buildings envelops [1, 2]. These methods could be employed to reduce or, in some cases substitute, the heating systems. For example, thermal inertia is a parameter that let us reduce energy requirement because in times of abundance (due to solar irradiation…) energy is stored in internal and external building constructions and transferred back into the zone when the indoor temperature decreases [3]. This thermal inertia makes possible to choose a higher design winter temperature or change the working conditions of the

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3

HVAC system like a change from intermittently controlled heat pumps to continuously capacity controlled heat pumps [4-8]. In the last years software tools were employed to understand and predict these thermal behaviour but they underestimated the energy consumption of buildings because the energy models ignore moisture. In this sense, whole building performance can only be realistically evaluated by accounting for the HAM interactions. Through its Energy Conservation in Buildings & Community Systems Program, the International Energy Agency launched Annexes 17 and 41 [9]. It is a working group to address issues surrounding whole building HAM response. The group involved over 50 researchers from 28 institutes and over 20 countries [10]. This Annex 41 tested Building simulation software like H-tools and HAM Tools from Chalmer Institute of Technology to simulate heat and mass transfer through buildings envelops considering heat gains like occupation, solar heat, illumination and air changes and infiltrations between others. Once this software is tested new conclusions could be obtained. In present paper an example of HAM tools application is showed to determine possible modifications to reduce energy consumption or improve HVAC system in real buildings.

2. MATERIALS 2.1. Tiny Tag Data Loggers Temperature and relative humidity were measured using an Innova 1221 data logger equipped with a temperature transducer MM0034, based on thermistor technology, and a humidity transducer MM0037, incorporating a light emitting diode (LED), a light sensitive transistor, a mirror, a cooling element and a thermistor.

2.2. Air Changes One of the components of the measuring apparatus was a multi-gas monitor. The ventilation rate was performed using the concentration decay method, measuring SF6 as tracer gas with a Brüel&Kjaer multi-sampler.

3. METHODS In this sense, two school buildings were sampled during different seasons to relate indoor conditions with weather, heat and moisture balances and HVAC system. ASHRAE Standard 1992 [11] indications and Burch [12, 13] simulations showed that the massiveness of an exterior wall reduces the heating and cooling requirements of buildings, provided the room air temperature floats above the thermostat set point in heating and below the thermostat in the cooling season. The floating temperature occurs more frequently in mild climates and during the spring. Special interest presents the spring season because then the HVAC system could be fully substitute by some passive methods. In consequence, this paper will study thermal inertia effect of two buildings with high and low wall density during the spring season of the mild weather of A Coruña (Spain).

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The week period selected for this study was a weekend and a holiday to identify the appropriate indexes of thermal stability for building envelopes. The focus must consider the solar heat gain and heat storage of building walls under conditions of natural ventilation [14]. During this unoccupied period, occupation and excessive air changes will not interferes the sampled data and an easy environment simulation could be done. After tests the simulations indoor conditions modifications will be proposed for energy saving. In this sense, location of the mass in relation to the insulation has a large effect on the deviation between measured energy use and steady state analysis. In high-density buildings where mass was outside the insulation, the measured energy use closely matched that predicted by steady-state analysis but not when the insulation was outside the mass [11]. In consequence, parameters like thermal inertia, air changes and internal coverings were simulated showing a clear different behaviour in each condition. Conclusions let us understand the passive methods that could let us reach better indoor condition during the first hour of occupation of the morning and evening class periods.

3.1. Schools Two schools are sampled and simulated. One of the areas of the older school was built in 1890, and the other part was built in 1960. The new school was built in 1999. In consequence, the old school presents 0.43 m of Stone and 0.5 cm of concrete in the indoor side of the wall. The wall of the new building consist in layers of insulation, brick, concrete and plaster arranged symmetric respect the middle of the wall and reaching 0.30 m of total thick ness. The classroom sampled, in the old building, is located on the second floor and has a volume of 210 m3, while the new is located on the first floor with a volume of 150 m3. All these buildings present a working period from February to June and an unoccupied period during the weekends and holidays. In those periods classrooms are under natural ventilation and central heating system was not employed. They active period ends in June and, in consequence, it is not interesting for energy saving during summer period. Furthermore, during the winter extreme conditions these schools are not working and, inconsequence heating system will works only when the indoor conditions exceed the thermal comfort during winter and spring.

3.2. Indoor and Outdoor Sampling Conditions The indoor and outdoor humidity and temperature have been monitored simultaneously in the most representative classroom of each school during part of winter and spring seasons. All schools have purely adventitious ventilation. Transducers were hung in the middle of the classrooms. Data has been gathered in Tiny tags data loggers which can store 7,600 readings. Air infiltration was measured by tracer gas method employing SF6 as tracer gas.

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5

3.3. Thermal Comfort and Indoor Air Quality Indexes Local thermal comfort has been evaluated in terms of the parameter PD, Percentage of Dissatisfied Persons, through the equation 1 obtained by Toftum et al (1988) and Simonson et al [15-18].

PD 

100 1  exp( 3.58  0.18(30  T )  0.14(42.5  0.01Pv ))

(1)

An acceptable environment would be that in which less than 15% of the occupants are dissatisfied. The Indoor Air quality has been evaluated through the so-called Acceptable Indoor Air Quality parameter, Acc. The equation 2 was proposed by Fang et al (1988).

Acc  0.033  h  1.622

(2)

3.4. Ham Tools Simulation The mathematical model employed in this simulations is the result of whole building Heat, Air and Moisture (HAM) [19, 20, 21] balance and depends on moisture generated from occupant activities, moisture input or removed by ventilation, and moisture transported and exchanged between indoor air and the envelope [10]. The mathematical model is based in the numerical resolution of the energy and moisture balance through the building. In accordance with the next equations [20], the heat flow presents a conductive and a convective part as we can see in the equation 3 and described in equations 4 and 5.

q  qconductive  qconvective qconductive  

T x

qconvective  ma  c pa  T  hevap

(3)

(4) (5)

The moisture flow transfer was separated in liquid and vapour phases as we can see in the equations 6 and 7.

ml  K 

Psuc x

(6)

The vapour phase was divided in diffusion and convection as we can see in the equation 7.

mv   p 

p  ma  x a x

(7)

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J.A. Orosa

The mass airflow through the structure driven by air pressure differences across the structure is showed in the equation 8.

ma  ra   a

(8)

The finally energy and moisture balance are showed in equations 9 and 10.



 T q  c  o  x t 

 x

m

w t

(9)

(10)

Finally, the numerical model, based on a control volume method present lumped the thermal capacity C in the middle of the total thickness d/2 and, in consequence, the thermal resistances for one half is showed in equations 11, 12 and 13.

R

d /2



Rp 

d /2

Rsuc 

d /2 K suc

p

(11) (12)

(13)

The obtained discretized heat and moisture balance equations are showed in equations 14 and 15.

 (T  T ) (T  Ti )   ( pi 1  pi ) ( pi 1  pi )     i 1 i  i 1   ...   hevap   Ri 1  Ri   Ri 1  Ri  R p ,i 1  R p ,i R p ,i 1  R p ,i   (14) m  c  (T  Ti ) n , ma  0   a pa i 1  n ma  c pa  (T1  Ti 1 ) , ma  0 Ti n 1  Ti n 1  n t C

win 1  win 1  ( p i 1  p i ) ( p i 1  p i )   ( Psuc,i 1  Pisuc,i ) ( Psuc,i 1  p suc,i )          ... t d  R p ,i 1  R p ,i R p ,i 1  R p ,i   Rsuc,i 1  Rsuc,i Rsuc,i 1  Rsuc,i   6.21  10 6  ma  ( pi 1  p i ) n , ma  0   6 n 6.21  10  ma  ( p i  p i 1 ) , ma  0

(15)

Where i is the objective node and i+1 and i-1 are the preceding and following node and n and n+1 de previous and corresponding time steps.

Investigation of HVAC System Improvement by HAM Numerical Simulation

7

To solve these balance equations room models were created from the individual Building Physics Toolbox [22, 23]. Ham –tools library is a Simulink models upgrade version of HTools with the similar structure and specially constructed for thermal system analysis in building physics. The library contains blocks for 1-D calculation of Heat, Air and Moisture transfer thought the building envelope components and ventilated spaces. The library is the part of IBPT-International Building Physics Toolbox, and available for free downloading [24]. This library presents two main blocks; a building envelope construction (walls, windows) and thermal zone (ventilated spaces), which are enclosed by the building envelope. Component models provide detailed calculations of the hydrothermal state of each subcomponent in the structure; according to the surrounding conditions to witch it is exposed. In Figure 1 we can see the principal blocks employed for a building simulation. There we can see a block that represents the different exterior/interior walls, floor, roof and windows components. These constructions are defined respect they physical properties (density of the dry material and open porosity), thermal properties (specific heat capacity of the dry material and thermal conductivity) and moisture properties (sorption isotherm, moisture capacity, water vapour permeability and liquid water conductivity) in accordance with the BESTEST structure. Other parameters are considered in the heat and moisture building balance like, for example, internal gains (convective gains, radioactive gains and moisture gains), air change and heating/cooling system.

Geometry

Geometry Horiz Cat

Construction Zone

Zone S

Radiation

Radiation

Left Node

Geometry

Right Mon

1

Double-pane window Variable solar transmittance IEA Common Excercise

EXTERIOR WALL 1

Constructions

Construction

Horiz Cat

System

One node / CTH 1

Zone

2 T

Geometry

Construction

Zone

Zone

Construction

Gains Radiation

F

ps(T)

Saturation pressure

Horiz Cat

Radiation

3

R

Radiation

FLOOR

Room air / CTH WAVO model

ROOF

Vert Cat simout

System

Zone

Ventilation system AIR IN

Gains

Zone

To Workspace

HEATING/COOLING SYSTEM

In1

Out1

4

Zone out

System

Zone

Ventilation system AIR OUT

Out1

BTweather BESTEST

Internal gains

Figure 1. Matlab blocks for buildings simulations.

Classroom characteristics are defined in the thermal zone block indicating the surface areas, orientations and tilts of each wall. Room volume, solar gain to air and initial temperature is adjusted so. Thermal model of the classroom is based on the WAVO model described by de Witt (2000) [25] and developed by the assumptions that long wave radiation

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J.A. Orosa

is equally distributed over the walls; the room air has the uniform temperature, the surface coefficients for convection and radiation are constant and, finally, that all radioactive heat input is distributed is such a way that all the surfaces except windows absorb the same amount of that energy per unit of surface area. In this paper, wall construction, indoor air changes and internal gains were adjusted in accordance with measured data and simulated for three days of unoccupied period and determine simulations accuracy. Finally, a weather database was done in accordance with meteorological sampled data to be introduced. This database was loaded before simulation adjusting the time step and study period.

3.5. Time Constant The time constant is normally found from a slow cooling down period with a constant low outdoor temperature as (heat capacity)/(heat loss factor) [3]. This method is based on a seasonal steady state energy balance on the building as a whole or on a particular building zone. The thermal inertia is introduced in terms of the utilisation factor that shows the part of energy gains (solar irradiation and others) that can be stored in building construction to be transmitted into the zone when needed, as we can see in equation 16.

Qheat  Qloss  Qgain

(16)

The utilisation factor  is a function of the building periodic time constant and the ratio Qgain/Qloss. The time constant is defined in the standard by the equation 17.



C H

(17)

As [3] recommends, when we want to work in a more precise way, the logarithm of the temperature difference in-outdoors is taken and matched to a straight line by the method of least squares. The time constant is the inverse of the coefficient for the independent variable (time) given by this curve fit. In consequence, after test our simulations with real sampled data; both buildings were simulated under constant weather conditions with the aim to determine building time constants.

4. RESULTS 4.1. Outdoor Conditions Figure 2 shows the outdoor conditions during the unoccupied period.

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9

Outdoor 25

1

Temperature (ºC)

0,8 0,7

15

0,6 0,5

10

0,4 0,3

5

Relative humidity (%)

0,9 20

0,2 0,1 T outdoor

RH outdoor

0

0

17:00 0:00 7:00 14:00 21:00 4:00 11:00 18:00 1:00

8:00 15:00 22:00 5:00 12:00 19:00 2:00

9:00 16:00

Time (hours)

Figure 2. Outdoor sampled temperature and relative humidity.

4.2. Thermal Inertia and Solar Gain: Time Constant Determination Figures 3 and 4 represent the logarithm of the temperature difference between indoor and outdoor temperatures when building is under constant weather conditions. Its linear regression constants will give us the time constant of each building. Old School

2,2

ln(Temperature difference)

2

1,8

1,6

1,4 y = -0,009x + 2,3212 R2 = 0,9947 1,2 Old School

Lineal (Old School)

1 20

40

60

80

Time (hours)

Figure 3. Time constant determination for old school buildings.

100

120

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J.A. Orosa

New School

2,2

ln(Temperature difference)

2

1,8

1,6

1,4 y = -0,0056x + 2,1501 R2 = 0,9364 1,2 New School

Lineal (New School)

1 20

30

40

50

60

70

80

90

100

110

120

Time (hours)

Figure 4. Time constant determination for new school buildings.

Time constant in Old Schools =111 Time constant in New School=178

4.3. Air Changes Sampled air changes were changed from 0.7 during the unoccupied period for the old school and 0.6 in the new school to a lower value of 0.4 air changes with the aim of observant the effect of weather on indoor conditions. Relative humidity 0,80 0,75

Relative humidity (%)

0,70 0,65 0,60 0,55 0,50 0,45 0,40 New School

Covering in New

0,35 17:00 23:00 5:00 11:00 17:00 23:00 5:00 11:00 17:00 23:00 5:00 11:00 17:00 23:00 5:00 11:00 17:00 23:00 5:00 11:00 17:00

Time (hours)

Figure 5. Relative humidity when air changes were reduced in new schools.

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Relative humidity 0,80 0,75

Relative humidity (%)

0,70 0,65 0,60 0,55 0,50 0,45 0,40 Old School

Covering in Old

0,35 17:00 23:00 5:00 11:00 17:00 23:00 5:00 11:00 17:00 23:00 5:00 11:00 17:00 23:00 5:00 11:00 17:00 23:00 5:00 11:00 17:00

Time (hours)

Figure 6. Relative humidity when air changes were reduced in old schools.

5. DISCUSSION As we can see in Figures 2, A Coruña present a mild climate but during all the year exist a certain high relative humidity, nearly 80%, related with some health problems, building maintenance and energy consumption. As was commented previously, simulation and sampled indoor data was compared obtaining a high approach between real and simulated ambiences. Once tested that simulations, the two schools were simulated under a constant weather conditions of 10 ºC and 80% of relative humidity to obtain the time constant, after a linear regression of the logarithm difference temperature respect outdoor ambience. Results of Figures 3 and 4 showed a time constant of 111 for the old and 178 in the new school with an adequate correlation factor in each case. This value shows a higher thermal inertia of the new school than the old. Other simulations were done under different indoor ambience temperatures obtaining the same value. The explanation of this effect is related with heat solar heat gains that the new building experiments respect the old as a consequence of the classroom way and the presence of another nearer buildings that interfere in that heat gain. To understand this solar effect, if we simulate this same process but without this heat gain another time constants were obtained. Once again adequate linear regressions were obtained with correlation values of 0.98 and 1 and time constants of 36.9 and 66.6 for new and old schools respectively. Now the old school present a higher thermal inertia respect the new as a consequence of the purely effect of wall thickness and heat transmission properties.

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J.A. Orosa

Temperature 22,5 22,0

Temperature (ºC)

21,5 21,0 20,5 20,0 19,5 19,0 18,5 18,0 17,5

New School

Covering in New

17,0 17:00 23:00 5:00 11:00 17:00 23:00 5:00 11:00 17:00 23:00 5:00 11:00 17:00 23:00 5:00 11:00 17:00 23:00 5:00 11:00 17:00

Time (hours)

Figure 7. Temperature when air changes were reduced in new schools. Temperature 22,5 22,0 21,5

Temperature (ºC)

21,0 20,5 20,0 19,5 19,0 18,5 18,0 17,5

Old School

Covering in Old"

17,0 0:00 0:00 0:00 0:00 0:00 0:00 0:00 0:00 0:00 0:00 0:00 0:00 0:00 0:00 0:00 0:00 0:00 0:00 0:00 0:00 0:00

Time (hours)

Figure 8. Temperature when air changes were reduced in old schools.

Once obtained these results another change was proposed. For example, old school presents a high air changes during the unoccupied period as a consequence of the air leakages. These air changes reach values upper the 0.5 usually obtained in closed ambiences. When the air changes of the two buildings are changed to 0.4 another curves are showed in the Figures 5 to 14. Indoor air humidity, in the new and old school, experiments a decrease to more adequate values of 60%. This effect is related with the heat and moisture transfer through stonewalls. The indoor air temperature reaches the same maximum values but experiment a slowly decrease in the new building reaching a higher minimum values than under normal conditions of air changes, as we can see in Figures 7 and 8. This thermal effect will be present

Investigation of HVAC System Improvement by HAM Numerical Simulation

13

in the indoor air enthalpy and, in consequence, on the percentage of dissatisfied that reaches slight lower PD maximum values during the night, Figures 13 and 14. The enthalpy conditions indicate that HVAC system is not needed because the indoor air enthalpy under natural ventilation reaches the value of 39kJ/kg, estimated for adequate indoor conditions.

Enthalpy (kJ/kg)

Enthalpy 50 49 48 47 46 45 44 43 42 41 40 39 38 37 36 35 New School Covering in New School 34 17:00 23:00 5:00 11:00 17:00 23:00 5:00 11:00 17:00 23:00 5:00 11:00 17:00 23:00 5:00 11:00 17:00 23:00 5:00 11:00 17:00

Time (hours)

Figure 9. Enthalpy when air changes were reduced in new schools.

Enthalpy (kJ/kg)

Enthalpy 50 49 48 47 46 45 44 43 42 41 40 39 38 37 36 35 Old School Covering in Old School 34 17:00 23:00 5:00 11:00 17:00 23:00 5:00 11:00 17:00 23:00 5:00 11:00 17:00 23:00 5:00 11:00 17:00 23:00 5:00 11:00 17:00

Time (hours)

Figure 10. Enthalpy when air changes were reduced in old schools.

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J.A. Orosa

In resume, we can conclude that a reduction in indoor air changes lead to the new building, where the solar heat gain is more important, to increment its indoor temperature and, in consequence doing an indoor ambience more insensible to outdoor weather change, as we can see in Figure 7 and 8 in the indoor temperature slope after a peak of temperature. PD 22

21

PD (%)

20

19

18

17 New School

Covering in New School

16 17:00 23:00 5:00 11:00 17:00 23:00 5:00 11:00 17:00 23:00 5:00 11:00 17:00 23:00 5:00 11:00 17:00 23:00 5:00 11:00 17:00

Time (hours)

Figure 11. PD when air changes were reduced in new schools.

On the other hand, these buildings were so simulated with a new internal covering as wooden panel. When this permeable covering is employed temperature decay is parallel and slight higher than initial conditions enhancing a reduction on indoor air relative humidity. This increment of indoor air temperature is related with the insulation properties of the wooden panel and let the building reach the highest time constant. PD 22

21

PD (%)

20

19

18

17 Old School

Covering in Old School

16 0:00 0:00 0:00 0:00 0:00 0:00 0:00 0:00 0:00 0:00 0:00 0:00 0:00 0:00 0:00 0:00 0:00 0:00 0:00 0:00 0:00

Time (hours)

Figure 12. PD when air changes were reduced in old schools.

Investigation of HVAC System Improvement by HAM Numerical Simulation

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Acc 0,60

Acceptability

0,50

0,40

0,30

0,20

0,10 New School

Covering in New School

0,00 17:00 23:00 5:00 11:00 17:00 23:00 5:00 11:00 17:00 23:00 5:00 11:00 17:00 23:00 5:00 11:00 17:00 23:00 5:00 11:00 17:00

Time (hours)

Figure 13. PD when air changes were reduced in new schools.

As we have note, the importance of this time constants is based on the fact that the building with the lower time constant reacts faster on weather changes and variation in internal heat gains than the more heavy buildings. Even during a short period of cold weather heat must be supplied in the lightweight building, whereas such periods can be passed without heating in the constructions with higher thermal inertia due to heat stored in the structure from previous warmer periods in accordance with [3]. Furthermore, the amplitude of temperature fluctuation of the inner surfaces of walls made of low time constant buildings under intermittent air-conditioning conditions is 1ºC higher than that of walls of buildings with a higher thermal inertia under continuous air-conditioning conditions in accordance with [14]. Acc 0,60

Acceptability

0,50

0,40

0,30

0,20

0,10 Old School

Covering in Old School

0,00 0:00 0:00 0:00 0:00 0:00 0:00 0:00 0:00 0:00 0:00 0:00 0:00 0:00 0:00 0:00 0:00 0:00 0:00 0:00 0:00 0:00

Time (hours)

Figure 14. PD when air changes were reduced in old schools.

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J.A. Orosa

Time constant 200 180

Time constant

160 140 120 100 80 60 40 20

New

Old

0 Without heat gain

Initial conditions

Air renovation reduction

Permeable coverings

Modification

Figure 15. Time constant for each modification.

These effects can be summarised in their study of time constant of each variant. In our case, when indoor air changes are reduced, the time constant for new and old schools is 185 and 112 respectively. These values are similar to that of 325, 164 and 31 for Heavyweight, Massive wood and Lightweight walls showed by [3]. Despite this, exist an internal gain from convective heat source on new building that lead to a higher effect than the wall construction thermal inertia. In consequence, after understand previous results we can conclude that the energy saving and HVAC system design must be done in accordance with its individual characteristics of each building and not only taking into account meteorological data and general procedures.

6. CONCLUSIONS This paper sample and simulate different indoor conditions in school buildings with the aim to determinate the possibility of energy saving and design considerations on building and HVAC systems. The heat-transfer through the night thermal inertia elements is analysed by using 1D time dependent conduction heat transfer equation that is solved numerically by using HAM tools. The model takes into account in a detailed fashion the inertial heat sources and the air changes. These simulations showed that old building presents the lowest thermal inertia than the new as a consequence of a solar heat gain. In consequence, the building with the lower time constant reacts faster on weather changes and variation in internal heat gains than the more heavy buildings. Parameters like air changes and permeable coverings interact in over the time constant. If the air changes is reduced the old building experiment a slowly increment, while the new will experiment a clear internal temperature increment as a consequence of the heat gain. Finally, the presence of permeable internal coverings like wood panel let us increment the time constant as a consequence of the increment of wall insulation,

Investigation of HVAC System Improvement by HAM Numerical Simulation

17

especially in the old school. In consequence, more research is needed to define new design and corrections of HVAC systems taking into account these individual parameters of each building location.

REFERENCES [1] Orosa, J. A. and Baaliña A. Passive climate control in Spanish office buildings for long periods of time. Building and Environment 2008; doi:10.1016/j.buildenv.2007.12.001 [2] Orosa, J. A. and Baaliña A. Improving PAQ and comfort conditions in Spanish office buildings with passive climate control. Building and Environment 2008; doi:10.1016/j.buildenv.2008.04.013. [3] Norén, A., Akander, J., Isfält, E. and Söderström, O., The effect of Thermal Inertia on Energy Requirement in a Swedish Building-Results Obtained with Three Calculation Models. International Journal of Low Energy and Sustainable Buildings, 1999.Vol.1. [4] Karlsson, F. and Fahlén, P. Impact of design and thermal inertia on the energy saving potential of capacity controlled heat pump heating systems. International Journal of refrigeration 2008. 31. 1094-1103. [5] Roucoult, J. M., Douzane, O. and Langlet, T. Incorporation of thermal inertia in the aim of installing a natural night time ventilation system in buildings. Energy and Buildings. 1999.29. 129-133. [6] Badescu, V. and Sicre, B. Renewable energy for passive house heating II Model. Energy and Buildings. 2003. 35. 1085-1096. [7] Badescu, V. and Sicre, B. Renewable energy for passive house heating Part I. Building description. Energy and Buildings 35 (2003) 1077–1084. [8] Krüger, E. and Givoni, B. Thermal monitoring and indoor temperature predictions in a passive solar building in an arid environment. Building and Environment. 43. 2008 1792-1804. [9] Andreas Hauer. Harald Mehling. Peter Schossig. Motoi Yamaha. Luisa Cabeza. Viktoria Martin. Fredrik Setterwall. International Energy Agency Implementing Agreement on Energy Conservation through Energy Storage. Annex 17. ―Advanced Thermal Energy Storage through Phase Change Materials and Chemical Reactions – Feasibility Studies and Demonstration projects‖. Final Report. [10] International Energy Agency. http://www.iea.org [11] ASHRAE handbook—fundamentals. Load and Energy Calculations, Energy Estimating Methods. 1993. Chap. 28 [12] Burch, M. D. and Chi, J. MOIST A PC Program for Predicting Heat and Moisture Transfer in building Envelopes. NIST Special Publication 917. NIST United States Department of Commerce Technology Administration. National Institute of Standards and Technology.1997. [13] Burch, D. M., Remmert, W. E, Krintz, D. F.and Barnes, C. S. A Field Study of the Effect of Wall Mass on the Heating and Cooling Loads of Residential Buildings (aka Log Home Report). National Bureau of Standards Washington, D.C. 20234. Proceedings of the Building Thermal Mass Seminar. Knoxville, TN; 6/2-3/82. Oak Ridge National Laboratory

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[14] Ya Feng Thermal design standard for energy efficiency of residential buildings in hot summer/cold winter zones. Energy and Buildings. 2004. 36. 1309-1312. [15] Simonson, C. J., Salonvaara, M. and Ojalen, T. The effect of structures on indoor humidity-possibility to improve comfort and perceived air quality. Indoor Air 2002. 2002.12. 243-251. [16] Simonson, C. J., Salonvaara M. and Ojalen T. Improving indoor climate and comfort with wooden structures. Espoo 2001. Technical Research Centre of Finland. VTT Publications. 2001. 431.200p.+ app 91. [17] Toftum, J., Jorgensen, A. S. and Fanger, P. O. Upper limits for indoor air humidity to avoid uncomfortably humid skin. Energy and Buildings. 1998. 28. 1-13. [18] Toftum, J., Jorgensen, A. S. and Fanger, P. O. Upper limits of air humidity for preventing warm respiratory discomfort. Energy and Buildings 28 (1998) 15-23. [19] Kalagasidis, A. S. BFTools H Building physiscs toolbox block documentation. Department of Building Physics. Chalmer Institute of Technology. Sweeden. 2002. [20] Kalagasidis, A. S., HAM-Tools. International Building Physics Toolbox. Block documentation. [21] Weitzmann, P., Kalagasidis, A. S., Nielsen, T. R., Peuhkuri, R. and Hagentoft, C. Presentation of the international building physics toolbox for simulink. [22] Nielsen, T. R., Peuhkuri, R., Weitzmann, P. and Gudum C. (2002). Modelling Building Physics in Simulink. BYG DTU Sr-02-03. ISSN 1601-8605. [23] Rode, C., Gudum, Weitzmann, P., Peuhkuri, R., Nielsen, T. R., Sasic Kalagasidis, A. and Hagentoft, C-E.: International Building Physics Toolbox-General Report. Department of Building Physics. Chalmer Institute of Technology. Sweden. Report R02: 2002. 4. [24] International Building Physics Toolbox in Simulink. www.ibpt.org. [25] Wit, M.: WAVO. A simulation model for the thermal and hygric performance of a building. Faculteit bouwkunde, Technische Universiteit Eindhoven. 2000

In: Advances in Energy Research. Volume 4 Editor: Morena J. Acosta, pp. 19-39

ISBN: 978-1-61761-672-3 © 2011 Nova Science Publishers, Inc.

Chapter 2

RESEARCH ON HEAT AND MASS TRANSFER TO IMPROVE HVAC CONDITIONS J.A. Orosa* Department of Energy and Marine Propulsion. University of A Coruña, Paseo de Ronda 51,1501. A Coruña, Spain

ABSTRACT This paper shows a research about improvement of indoor conditions controlling heat and mass transfer process. To do it, the first step was to sample real data in different kind of typical Spanish buildings like a set of flats, office buildings, museums and schools located in the area of A Coruña, Spain. Once obtained this data, it was analysed to determine indoor ambience problems and possible solutions related with heat and mass transfer process. In this sense, problems related with comfort conditions, energy saving, health, materials conservation and work risk were found and possible solutions like air renovation, thermal inertia, and moisture buffering were found.

NOMENCLATURE Co Cb Vb o S t Pv H

*

Outdoor CO2 concentrations (ppm) Bedroom CO2 concentrations (ppm) Bedroom volume (dm3) Natural ventilation rate (dm3/s) CO2 source in the room due to its occupancy (dm3/s). Temperature (ºC) Partial water vapour pressure (Pa). Air enthalpy (kJ/kg).

E-mail address: [email protected], Tel. 034 981 167000 4320. (Corresponding author)

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1. INTRODUCTION Located in the northwest coast of Spain, the climate of Coruña, population of 280,000, is mild. However, indoors humidity in the area is relatively high over most of the year due to the effect of the Atlantic Ocean winds. Health authorities claim that the level of incidence of respiratory ailments in the area is higher than in the rest of the country. A possible cause of these interior conditions is the resident‘s habits and outdoors conditions. These climatic characteristics influence the study method of indoor ambiences, design of HVAC and generate problems in different kind of buildings. To control this indoor ambience, a thermostatic system is employed and in summer indoor ambience floats freely and natural ventilation is the more employed method of indoor air renovation. If we analyse all different buildings as a function of their indoor activity we can found different problems to be solved and, in consequence, different objectives. For example, in flats the principal objective is to get the better thermal comfort [1], indoor air quality and reduce health problems like allergies. When we analyse the indoor activity, we can observe that a bad indoor air renovation may cause moisture accumulation, especially during cooking time, which affect the others rooms. These moisture problems may be correlated with fungi growth and its respective allergies problems of occupants. In other cases, this bad indoor air renovation will causes problems like a higher CO2 concentration in bedrooms during the night. In offices buildings and schools the objective of study, during the occupied period, is the local thermal comfort condition, perception of indoor air quality, productivity and energy saving but during the unoccupied period this objectives had not been taken into account and could be solved with new techniques [2]. In schools and museums the principal objective is maintain comfort conditions and relic conservation [3, 4]. Furthermore, at the archive, materials must be stored with less energy consumption as possible. In extreme ambiences thermal comfort is not the most interesting objective and work risk is studies are preferential [5]. Solutions of this problems must began with a clear occupants become aware about how employ the natural ventilation like opening windows or employ of passive methods to energy saving. These passive methods may be correlated with the employ of permeable coverings or solar radiance. Furthermore, this methods may induce to low energy consume or substitute the mechanical HVAC systems. In spite of this, energy saving may be low if we compare with an inadequate operative conditions of heating system. This is why, we must combine these methods with correct residents habits. In the other hand, despite the fact that there are a lot of software that can let us to understand the influence of different variables on real indoor conditions, to quantify energy saving, productivity and health effects and materials conservation on indoor ambiences, we must employ real sampled data. This real data let us take into account typical parameters like real weather data, occupant‘s habits and construction materials and to prove the software veracity. Furthermore, to get a more approximate simulation we must complement these simulations with laboratory tests about building properties and questionnaires involving questions such as the state of the flat, living habits, indoor air quality perception, health and symptoms experienced by the occupants. All this complements let us get the better design software taken into account the real activity and indoor conditions existing on a clear zone of building.

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In order to effectively confirm this claim, a systematic investigation of indoor conditions in the area would be needed. This need prompted the research reported in the present paper, in which data obtained in the Coruña area is presented and analysed in four kinds of typical indoor environments; flats, offices, museums, schools and industrial ambiences.

2. MATERIALS One of the components of the measuring apparatus was a multi-gas monitor. The ventilation rate was measured by a Brüel&Kjaer (Denmark) multi-sampler made up of the following main components: (a) a photo-acoustic infrared detection microprocessorcontrolled gas analyzer; (b) An air multi-sampler with six sampling ports; and (c) application software to remote control the gas analyzer and a personal computer. The apparatus was equipped with a temperature transducer to measure the state of the air at the point of sampling. Temperature and humidity were measured through an Innova 1221 data logger equipped with a MM0034 temperature and MM0037 humidity transducers. Temperature and humidity sensors were adequately located so that a typical air condition of the room could be measured. A Casella AFC124 air suction pump was used in sampling air for microbiota analysis. The sample of air used to be filtered by flowing through a 47mm diameter, 0.45 m pore ALBERT-NCS-045-47-BC cellulose nitrate membrane filter with an ALBERT PF-50-P-02 sterilized polycarbonate filter holder.

3. METHODS 3.1. Temperature and Humidity As previously mentioned, the buildings were randomly chosen so that typical every day life of occupants was not disturbed and typical indoor conditions could be obtained during the measurements. Indoor temperature and humidity have been measured in flats, office buildings, schools, museums and ships in the Coruña area. Measurements used to be taken with a sampling frequency between five to ten minutes and have been referred to the ASHRAE Handbook of Fundamentals [6].

3.2. Ventilation Rate The ventilation rate has been determined by performing sampling in intervals varying between 11 and 14 minutes. It was determined through the concentration of carbon dioxide (CO2) procedure, based on the equation 1.

dCb v0 (C0  Cb )  S  dt Vb

(1)

The natural ventilation rate, o, can be determined from equation (1) given the outdoor and indoor CO2 concentrations and the indoor CO2 production. The minimum ventilation rate,

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min, is the one corresponding to a steady state CO2 concentration with a 1000 ppm CO2 room concentration. The equation 2 results from the equation 1.

vmin 

S (C1000  C0 )

(2)

3.3. Microbiological Load A study of respiratory ailments was carried out during the spring season involving family flats, and with total of 100 individuals. Flats were chosen in such a way that at least one of the occupants have suffered or were suffering of a respiratory ailment at the time of the study. Temperature and relative humidity was measured along with sampling of air to determine the microbiological load through culture and count.

3.4. Thermal Comfort/Indoor Air Quality Local thermal comfort has been evaluated in terms of the parameter PD, Percentage of Dissatisfied Persons, through the equation 3 by Toftum et al (1988) and Simonson et al [7-11].

PD 

100 1  exp( 3.58  0.18(30  t )  0.14(42.5  0.01Pv ))

(3)

An acceptable environment would be that in which less than 15% of the occupants are dissatisfied. The Indoor Air quality has been evaluated through the so called Acceptable Indoor Air Quality parameter, Acc. It has been found elsewhere, Fang et al (1988) [12-14], that this parameter is strongly influenced by the temperature and the relative humidity, being linearly related to the air enthalpy. The equation 4 has been proposed by Fang et al (1988).

Acc  aH  b

(4)

Constants a and b are empirical coefficients. For clean air a=0.033 kg of dry air/kJ and b=1.622. It is interesting to note that Acceptable Indoor Air Quality parameter is a measure of the level of acceptability of air with no known contaminants, as determined by a pertinent authority, and a level of dissatisfied occupants relatively small (lower than 20%). The range of variation of this parameter is 1.

3.5. Questionnaires Data gathering was complemented with questionnaires involving questions such as the state of the flat, living habits, indoor air quality perception, health and symptoms experienced by the occupants. In schools, museums and offices questionnaires includes working habits,

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indoor air quality perception and energy consumption. In ships questionnaires are based in working habits and no fatal accidents happened during last years.

3.6. Climatic Data Outdoors conditions have been obtained by means of weather stations next to the city, to avoid the effect of the buildings on the measured values of the outer conditions. The Environmental Information system of Galicia (SIAM [15, 16]), has as main function facilitating the access to the information on environment and climatology. Another organization that provides the meteorological data is the Forest and Environmental Research Center of Lourizán (Ministry of Environment of the Xunta de Galicia). This center was made up of 42 stations of climatologic observation, distributed by all Galician geography. In 1988, it began the installation of a modern network of automatic stations of meteorological observation, arriving in 2000 to 23 stations that transmit the information in real time.

3.7. Flats The first kind of typical indoor environment is present in Spanish flats where the principal parameters to study are the comfort and health conditions as a function of air conditioning design and residents habits. Measurements involved parameters such as temperature and humidity ratio [17] in addition to ventilation [18, 19], carbon dioxide concentration and microbiological load [20-23] were carried out over 24 hour periods by keeping the household life as regular as possible.

3.8. Museums and Schools The second kind of typical indoor ambience is present in museums and schools where the principal parameters to study are the energy saving [24, 25] and materials preservation [26, 27]. This energy saving is concentrated in understand the outdoor climatic conditions effect on indoor ambience as a consequence of wall thermal inertia, especially during the occupational period. Another question that must be answered is if set point temperatures, usually adopted by curators, are adjusted in accordance with comfort conditions or with relic preservations. With this objective, schools indoor conditions were sampled during two years at different zones. Indoors and outdoors humidity and temperature in some typical classrooms have been monitored in seven schools during winter and summer seasons. In particular, two of them, the oldest and the newest, will be considered. The old school (1) was built in 1890 and the new (2) was built in 1999 as we can see in Figures 1 and 2. The air is only conditioned by a heat water system during the winter season and classrooms are naturally ventilated by windows and infiltrations. The old school building present granite blocks with a supposed higher thermal inertia and the new school building wall structure are showed in Figure 3, with a supposed low thermal inertia. This last wall structure consist in; external coverings, concrete, brick, air barrier, polystyrene, brick, concrete and internal covering.

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Figures 1 and 2. Old and new school building of A Coruña respectively.

1. External coating, 2. Concrete (1 cm.), 3. Brick (8 cm.), 4. Air barrier (3 cm.) 5. Polystyrene(3 cm.), 6. Brick (8 cm.), 7. Concrete (1cm.), 8. Internal coating (plaster, 1 cm.) Figure 3. New school wall structure.

The same thermal inertia effect was studied in new and old museums but, this time, during the full day and night with the aim to understand this effect on paintings and sculpture preservation. The modern museum presents a complex HVAC system that controls temperature and relative humidity with a low margin of error and their wall density construction is low. The old museum presents a higher thermal inertia. Despite of these differences, all museums present three characteristic zones as we can see in Figure 4.

3.9. Office Buildings The third kind of typical indoor ambience is the office buildings. In that kind of buildings the principal objective is to get an adequate PDIAQ and low energy consume [28-36] during the occupied period as a consequence of building materials properties [37-39]. To get this objective, we must understand the HVAC system operation and implement the possibility of replacement this mechanical system with passive methods like permeable internal wall coverings. These offices have the same indoor developed activities between them and a wall structure similar to that showed for new school buildings in Figure 3. The only difference is

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the presence of indoor coverings that can be grouped as permeable, semi-permeable or waterproof in accordance with its theoretical permeability.

1. 2. 3.

Entrance: where the indoor air infiltration is high. Archive; where materials are stored. Exposition zone; where paintings and sculptures are located during the exposition period.

Figure 4. Old museum‘s zones.

With this objective, monitoring of temperature and relative humidity of the air has been carried out during long periods of time in offices located at level of the street in buildings of A Coruña city. Parameters like thermal comfort, indoor air quality and energy saving possibility were calculated in accordance with equations 3 and 4 and compared with international regulations such as ASHRAE [6] and ISO 7730 [40] together with Spanish regulation.

Figure 5. Typical Spanish office buildings.

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3.10. Ships The last kind of typical indoor ambience is the industrial ambience. The worst of this ambiences is present in ships where extreme temperature and relative humidity experiment a frequently change in indoor conditions in short intervals of time. In particular, this change is present especially when workers go from the engine room with a high temperature of 32.5 ºC and a low relative humidity of 25 % to the control engine room with a low temperature of 19.7 ºC and a relative humidity of 41.2%.

Figures 6. Control engine room.

Figures 7. Engine room.

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These temperatures are associated with work risk parameters because when temperature increment from 20ºC to 35-40ºC workers will suffer; psychical disorders (irritability), psychical and physiological disorders (work mistakes) and physiological disorders (cardiaccirculatory system overload). Nowadays, Datasheets [5], OIT [47] and standards [48-50] don‘t show clear information about the engine-room ambience, design conditions and behaviour of marine engineers to prevent work risk. With the aim to obtain work risk indexes and get a real analysis a study was carried out monitoring the air temperature, relative humidity and globe temperature in several locations of a merchant ship that covers the sea-lane Las Palmas-Barcelona. For example, it has been determined the corresponding thermal comfort parameters in the control room [51, 40] and heat stress and sweating indexes in the engine room [52-56] in accordance with the human body thermal balance showed by Fanger [51]. These indexes were compared with ISO indications to propose design corrections.

4. RESULTS 4.1. Climatic Data Coruña is located in the northwest of Spain and presents a mild climate; see Figures 8, and 9. In that figures, we can see a higher relative humidity over most of the year due to the effect of the Atlantic Ocean winds. Relative humidity experiments a mean value of 87.5 % with a maximum mean value of 98% in July and a minimum mean value of 48% in September. The mean outdoor temperature is 13.85 ºC with a maximum mean temperature of 25.6 ºC at August and a min mean temperature of 1ºC at December.

Outdoor Temperature (ºC)

Temperature (ºC)

30 25 20 15 10 5 0 1

2

3

4

5

6

7

Month

Figure 8. Outdoor temperature in A Coruña.

8

9

10

11

12

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Outdoor Relative humidity (%) Relative humidity (%)

110 100 90 80 70 60 50 40 1

2

3

4

5

6 7 Month

8

9

10

11

12

Figure 9. Outdoor relative humidity in A Coruña.

4.2. Flats Figure 10 shows the correlation between the percentage of dissatisfied, calculated in accordance with equation 3, and the fungi concentration obtained as was explained in methods.

400

35

350

30

300

25

250

20

200

15

150

10

100

5

50

0

0 1

2

3

4

5

6

7

8

9

10 11

12

13 14

15 16

17 18

Flat PD

Fungi

Figure 10. Indoor percentage of dissatisfied and fungi concentration.

19 20

21

22 23

24

Fungi( CFU/m 3)

PD (%)

Indoor conditions 40

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4.3. Offices Figures 11 and 12 indoor/outdoor partial vapour pressure difference is represented as internal coverings function like permeable (p), semi permeable (s) and waterproof (i), Summer 200

Partrial vapor pressure difference (Pa)

100 0 P1

P2

SP1

P3

P4

P5

SP2 SP3

SI1

E1

SP4

SI2

SP5

E2

SP6 SP7

E3

SP8

E4

E5

I1

E6

I2

I3

I4

SI1

E5

E4

P2

P5

SI2

P1

P3

P4

-100 -200 -300 -400 -500 -600 -700 -800 Office

Figure 11. Summer indoor/outdoor partial vapour pressure difference. Winter 500

Partial vapor pressure difference (pa)

400 300 200 100 0 SP4 SP1 SP2 SP5 SP3

I1

SP7

I2

SP8

I3

SP6

E1

I4

E6

E2

E3

-100 -200 -300 -400 -500 Office

Figure 12. Winter indoor/outdoor partial vapour pressure difference.

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PDWRC 35 30

PD (%)

25 20 15 10 5 0 p1 p2 p3 p4 p5 p6 s1 s2 s3 s4 s5 s6 s7 s8 s9 s10 s11 s12 s13 s14 i1

i2

i3

i4

i5

Office 8:00 Winter

8:00 Summer

Figure 13. Perceived indoor air quality at first hour of occupation.

Figure 13 represents the perceived indoor air quality at first hour of occupation in summer and winter seasons calculated in accordance with the equation 3.

4.4. Schools and Museums Figure 14 shows the daily mean temperature and partial vapour pressure in new and old school buildings and Table 1 shows the mean indoor temperature, relative humidity, perceived indoor air quality and indoor air acceptability in different zones of a new museum. These indexes were calculated in accordance with equations 3 and 4.

4.5. Industrial Ambience: Ships Tables 2 and 3 show the mean, maximum and minimum Predicted Mean Vote (PMV) and Predicted Percentage of Dissatisfied (PPD) at the engine room and control engine room. These indexes were obtained with the globe temperature based in Fanger human body balance as NTP indications, respectively. Table 1. Indoor conditions in the new museum. Winter Archive First floor Engraving Summer Archive First floor Engraving

ºC 18.7 21.3 19.0 ºC 18.0 22.1 18.4

RH (%) 58.3 50.8 58.2 RH (%) 75.6 63.7 79.3

PD 6.81 10.84 7.36 PD 8.96 19.91 11.10

Acc 0.39 0.29 0.37 Acc 0.25 0.05 0.18

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Table 2. Indoor temperature. T (ºC) Average Maximum Minimum

Engine room 32.50 38.50 25.40

Control engine room 19.76 27.30 17.40

Table 3. Predicted Mean Vote. PMV Average Maximum Minimum

Engine room 2.15 3.75 1.54

Control engine room 0.52 1.77 -0.90

Table 4. Predicted Percentage of Dissatisfied. PPD Average Maximum Minimum

Engine room 76.61 99.99 53.06

Control engine room 13.54 65.92 5.00

5. DISCUSSION Methods to control these indoor ambiences were grouped in accordance with air renovation, thermal inertia, moisture buffering and awareness.

5.1. Indoor Air Renovation It has been found that the natural ventilation rate was rather poor reaching values significantly lower than the minimum ventilation rate needed. As a result, the CO2 concentrations in flats were so above the levels found in public buildings. When we analyse the humidity ratio we deduce that the bedroom is the zone of the homestead where the humidity is higher, especially during the sleeping time. These values of the indoor humidity ratio are, generally, higher than the outdoors and varied up to a maximum of 9 g/kg. In consequence of this humidity ratio and the observed relative humidity in some of the rooms to attain, values up to 65%. This level could be considered relatively high. Furthermore, as expected should be expected, this ventilation rate tends to promote more uniform humidity and CO2 content in all zones of the flats. The local comfort level, given by the PD and Acc parameters in Figure 10, remains acceptable during the measurement period for most of the observed indoors conditions. When we associate the indoor humidity at temperatures around 21ºC with the fungi development, the Figure 10 is complemented with another curve. From this figure can be observed that fungi load diminishes the order of 3 CFU/m3 in flats when the indoor relative humidity varied up to a maximum of 60% and that a clear relation ship exists between the PD index and fungi development. The general conclusion to be drawn is that ventilation procedures should be modified to keep the relative humidity lower than the maximum recommended of 65% and that, to get this

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objective, natural ventilation and residents‘ habits must be modified. For example, during the cooking or sleeping time indoor air renovations must be effectively used like opening windows. On the other hand, passive methods are not fully operative in this kind of buildings because there are not clear periods of humidification and dehumidification of ambience.

5.2. Moisture Buffering Capacity To analyse the possibility of passive methods to energy saving [41-46], a statistical analysis of the real indoor conditions data was carry out. From this study, it was observed, in the worker‘s zone, a trend to present higher values of temperature and relative humidity, reaching in many cases values that exceed those fixed by the ISO 7730. Through the statistical analysis of One-Way Anova, the difference between internal coverings permeability effect on indoor conditions was observed and showed in Figure 11. There permeable coverings represented with the letter (p), improve partial indoor vapour pressure. For example, in summer, these permeable coverings show a great tendency to reduce the partial vapour pressure excess while in winter indoor partial vapour pressure is clear higher than the outdoor one. The opposite effect is observed with waterproof coverings represented by the letter (i). As a consequence of this effect, when we compare the existing conditions in an office that has waterproof (plastic) cover to the values obtained in standard offices, a trend to a higher relative humidity during the summer and lower during the winter was observed. These impermeable internal coverings effects worsen the comfort condition and the energy saving possibility. At the same time, it was accomplished the study of the comfort conditions starting from the clean air equations 3 and 4 and applying the combined temperature and relative humidity model. From Figure 13 it was observed that, during the winter, the indoor conditions are close to those of thermal neutrality in higher percentage than in the spring and summer. What is more, when the temperature is increased the acceptability of the air is close to zero.

5.3. Thermal Inertia Schools From Figure 14 we can see that in new school buildings mean indoor air temperature is about 20ºC with a relative humidity of 55% and in old schools the mean indoor temperature and relative humidity is about 19 ºC and 62% respectively. During the weekend indoor conditions change and reach, in new schools, a mean indoor temperature of 19 ºC and a relative humidity of 55% and, in old schools, the mean temperature is about 17 ºC and relative humidity is 62%. Outdoor conditions stay about 12 ºC and at a relative humidity of 85%. From these mean values we can conclude that indoors relative humidity is higher than in new and that indoor temperature is 1 ºC low in old schools. The mean temperature and relative humidity are the statistical indexes that show the wall isolation effect is the mean indoor conditions of temperature and relative humidity. For example, in Figure 14 we can observe that the mean indoor dry bulb temperature in new school is one degree centigrade higher than in the old and seven degrees higher than the outdoor during the winter season. If now we observe the relative humidity value, we can say that is 6% higher in the old than in new schools. This effect is consistent with the same indoor

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air enthalpy for a 1ºC lower and, in consequence, the same indoor air acceptability. In conclusion, this higher relative humidity in old schools, as a consequence of wall infiltrations, let the corresponding energy saving on HVAC system. 22

Temperature (ºC)

20

18

16

14

12

10 Monday

Tuesday

Wednesday

Thursday

Friday

Saturday

Sunday

Day Indoor old school

Indoor new school

Outdoor

Figure 14. Daily Indoor/Outdoor mean temperature in new and old schools.

During the unoccupied period of weekend, new schools present a low decrement of temperature as a consequence of a good wall isolation that let a higher mean indoor temperature for the first hours of occupation of the next Monday and reducing the energy consume peak in that moment. On the other hand, the old school present a fast decrement of indoors temperature as a consequence of infiltrations. When we analyse the partial vapour pressure during the weekend, a tendency to values closer to outdoor air is observed. In this case, indoor air renovations by windows and doors infiltrations are present again. The indexes that show the thermal inertia effect are the minimum and maximum values observed during the occupied and unoccupied periods. From sampled data the maximum temperature achieved during the occupied period was in the old school and the minimum value during the unoccupied periods. In conclusion, schools present an ambience whose thermal isolation is so interesting than thermal inertia because the air renovations by infiltrations are so high that meddle the wall structure temperature absorption.

Museums Nearly the same effects as in schools were obtained when we compare new and old museums. Now it is interesting to maintain the indoor ambience conditions during the occupied and unoccupied periods and, in certain zones, the indoor air renovations must be very low letting work wall structure materials. For example, results showed that old museums present, at the archive, a stable situation with daily variations of temperature of 1ºC as a consequence of the high walls thermal inertia, which is interesting to get a better materials conservancy.

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Vapor pressure (Pa)

1350

1300

1250

1200

1150

1100 Monday

Tuesday

Wednesday

Thursday

Friday

Saturday

Sunday

Day Indo o r o ld scho o l

Indo o r new scho o l

Outdo o r

Figure 15. Daily Indoor/Outdoor mean partial vapour pressure in new and old schools.

It was obtained that the summer difference between archive and engraving room, respect the first floor, reaches a mean difference of 4 ºC. This is a consequence of the high influence of outdoor conditions on first floor by the door and the lower thermal insulation respects the other zones of the building. From this, could be concluded that this zone‘s thermal inertia and isolation effect can be interrupted by an inadequate indoor air renovation. In new museums, the archive presents again better indoor conditions than the first floor and engraving room. In winter, fluctuations are upper 3 ºC as a consequence of a low thermal inertia and that the HVAC system can not get the set point temperature. In summer this fluctuations are lower. In particular, at the archive and engraving room, relative humidity is extremely higher in summer with values that reach 74% and 78%, respectively. These values are extremely higher than 65%, which was indicated to reduce the risk of mould and microorganisms. This could be a consequence of an insufficient mechanical dehumidification process. At the first floor, we can say that the conditions during the summer time present the worst percentage of dissatisfied with a value of 20% respect a limit of 15%, see Table 1. Acceptability is in all zones under a value of 1 but the better indoor acceptability was in the first floor with a value near 0. This could be correlated with a higher indoor air renovation by infiltrations. As we can see, a possible solution to get a better indoor ambience could have ground into combined the effect of thermal inertia and passive methods, like internal permeable coverings, to solve this with higher energy saving. This effect acts especially when the indoor air renovations are low and this is the cause of old museums interest in materials conservancy.

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5.4. Awareness Ships show different thermal environments that must be studied with greater depth. From Table 2 we can observe that the engine room presents air conditions out of any recommendations from standards. The control engine room shows limit conditions of thermal comfort with temperature values too low, as a physical hazard. As the outdoor air conditions are suitable, an increase of renovations with outdoor air can be proposed in both cases. Using the obtained relationship between time and globe temperature for this engine room we can affirm that the worker must be in the engine room for 17 minutes and must have a rest at the control room for at least 10 minutes in order to get the suitable heat release. One more time, results will be useful for marine engineers training education in work risk prevention. Moreover, this real data must be taken into account for future standards revisions to obtain a better engine room design. Four controls that must be chosen are suggested: 1. Drinking water. Sources of drinking water must be available close to work locations and workers must be informed about the necessity of drinking frequently. 2. Acclimatization. OIT indicates that acclimatization is an effective method to reduce the heat stress index. Workers starting new or going back to work require an exposure time for achieving acclimatization. The control room can be employed as acclimatization room reducing the sweating index. 3. Metabolic heat. Adjusting length and frequency of breaks and work periods, and work rates may be reduced the metabolic heat release. If it is possible works must be scheduled in time of less heat. Work periods into engine room must not be higher than seventeen minutes and, after it, worker must be about ten minutes in the control room. The OIT indicates that workers must be kept under constant watch by a trained colleague for detecting any symptom of heat strain but don‘t show the supervision interval values.

6. CONCLUSIONS The following general conclusions can be drawn form the reported investigation: Ventilation rate was considered rather poor in flats and, inconsequence, the level of fungi and mesophiles presence found in some of the flats was relatively high. In offices internal coverings effect on indoor air conditions are real solutions in mild climates. Furthermore, an adequate employ of this methods can let to implement or substitute the HVAC system getting better comfort conditions and perceived indoors air quality, especially during the first hour of occupation. The higher thermal inertia of old museum archive walls get better materials conservation by indoor air temperature control. Otherwise, Indoor air renovation was low and this is why acceptability index was the worst. Schools don‘t present the better ambience to employ the thermal inertia effect as indoor air control method because the air renovation is excessive. Preventive and corrective methods are proposed in industrial ambiences to reduce fatigue risk. It has been possible to define a design correction involving an increase in the renovations

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with outdoor and preventive corrections such as limiting the time that a person can work without heat stress, in accordance with ISO standards and training.

REFERENCES [1] Rodriguez, E., Baaliña, A., Vazquez, A., Castellanos, L., Santaballa, J. A. and Infante, C. R. Indoor air quality evaluation using carbon dioxide levels in bedrooms in La Coruña (Spain). The 8th International Conference on Indoor Air Quality and Climate. Edinburgh. 1999; 5: 335-345. [2] Hameury, S. Moisture buffering capacity of heavy timber structures directly exposed to an indoor climate: a numerical study. Building and Environment 40 (10) (2005) 14001412. [3] Lee, S.C. and Chang, M. Indoor and outdoor air quality investigation at schools in Hong Kong. Chemosphere. 41 (2000) 109-113. [4] Chicora Foundation, 1994. Managing the museum environment (http://palimpsest.stanford.edu/byorg/chicora/chicenv.html). [5] International Hazard Datasheets on Occupation. Ship-Engineer (Machinist). HDOEDIT (© ILO/CIS, 1999) program. Approved by DG [6] ASHRAE (1988) ASHRAE HANDBOOK. HVAC FUNDAMENTALS. Atlanta. American Society of Heating, Refrigeration and Air Conditioning Engineers. 215-260. [7] Simonson, C.J., Salonvaara, M. and Ojalen T. The effect of structures on indoor humidity-possibility to improve comfort and perceived air quality. Indoor Air 2002. 12 (2002) 243-251. [8] Simonson, C. J., Salonvaara, M. and Ojalen, T. Improving indoor climate and comfort with wooden structures. Espoo 2001.Technical Research Centre of Finland, VTT Publications 431.200p.+ app 91 p, 2001. [9] Orosa, J. A., Baaliña, A. Passive climate control in Spanish office buildings for long periods of time. Orosa JA, Baaliña A. Passive climate control in Spanish office buildings for long periods of time. Building and Environment (2008). doi:10.1016/ j.buildenv.2007.12.001 [10] Toftum, J., Jorgensen, A. S. and Fanger, P.O. Upper limits for indoor air humidity to avoid uncomfortably humid skin. Energy and buildings 28 (1998) 1-13. [11] Toftum, J., Jorgensen, A. S. and Fanger, P. O. Upper limits of air humidity for preventing warm respiratory discomfort. Energy and buildings 28 (1998) 15-23. [12] Fang, L., Clausen, G. and Fanger, P. O. Impact of Temperature and Humidity on the Perception of Indoor Air Quality. Indoor Air. 8 (1998) 80-90. [13] Fang, L., Clausen, G. and Fanger, P. O. Impact of Temperature and Humidity on Perception of Indoor Air Quality During Immediate and Longer Whole-Body Exposures. Indoor Air. 8 (1998) 276-284. [14] Fang, L. P. Wargocki, T Witterseh, Clausen, G. and Fanger, P. O. 1999. ―Field study on the impact of temperature, humidity and ventilation on perceived air quality‖. The 8th International Conference on Indoor Air Quality and Climate. Edinburgh, Scotland Vol 2 Pag. 107. 8–13, 1999.

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[15] MeteoGalicia. Anuario climatolóxico de Galicia 2002. Consellería de Medio Ambiente. Xunta de Galicia. 2002. ISBN: 84-453-3520-0, 2002. [16] MeteoGalicia. Anuario climatolóxico de Galicia 2002. Consellería de Medio Ambiente. Xunta de Galicia. ISBN: 84-453-3520-0, 2002. [17] Hens, H. Indoor climate in student rooms: measured values. IEAEXCO energy conservation in buildings and community systems annex 41 ‗‗moist-eng‘‘ Glasgow meeting. [18] Reindl, D. T. Estimating Ventilation Rates Using Dynamic CO2 Measurements. Proceedings of the ISIAQ Fifth International Conference on Healthy Builidings'97 3 (1997) 507-512. [19] Wang, S and Jin, W. CO2-Based Occupancy Detection for On-Line Outdoor Air Flow Control. Indoor Built Environment. 7 (1998) 163-181. [20] Jovanovic, S., Felder-Kennel, A., Gabrio, T., Kouros, B., Link, B., Maisner, V., Piechotowski, I., Schick, K., Schrimpf, M., Weidner, U., Zöllner, I. And Schwenk, M. Indoor fungi levels in homes of children with and without allergy history. International Journal of Hygiene and environmental Health. 207 (2004) 369-378. [21] Liao, C. M, Luo, W. C, Chen, S. C., Chen, J. W, Liang HM.Temporal/seasonal variation of size-dependent airborne fungi indoor/outdoor relationship for a wind-induced naturally ventilated airspace. Atmospheric environment.38 (2004) 4415-4419. [22] Hargreaves, M., Parappukkaran, S., Morawska, L., Hitchins, J., He, C. and Gilbert, D. A pilot investigation into associations between indoor airborne fungal and non-biological particle concentrations in residential houses in Brisbane, Australia. The Science of the Total Environment. 312 (2003) 89-101. [23] Editorial. Housing characteristics and mite allergen levels: to humidity and beyond. Clinical and experimental allergy. 31 (2001) 803-805. [24] Conceicao, E. Z. E., Lúcio, M. M. J. R. Thermal study of school buildings in winter conditions. Building and Environment. 43 (2008) 82–792. [25] Rachel Beckera, Itamar Goldbergera and Monica Paciukb. Improving energy performance of school buildings while ensuring indoor air quality ventilation. Building and Environment. 42 (2007) 3261–3276. [26] Stolow, N. Conservation and exhibitions: packing, transport, storage, and environmental considerations. London, Butterworths, 1987. [27] Padfield, T. and Klenz, P., 2004. ―How to design museums with a naturally stable climate‖. Annual General Meeting of the International Institute for Conservation. [28] Simonson Carey, J. and Salonvaara Mikael, H.. Mass transfer between indoor air and a porous building envelope: Part I- Field measurements. Proceedings of Healthy Buildings 2000, Vol. 3. [29] Simonson Carey J., Tuomo Ojanen. Moisture performance of buildings envelopes with no plastic vapour retarders in cold climates. Proceedings of Healthy Buildings 2000, Vol. 3. [30] Padfield, T. The role of absorbent building materials in moderating changes of relative humidity. Ph.D. thesis The Technical University of Denmark Department of Structural Engineering and Materials, October 1998. [31] Hameury, S. and Lundstrom. T. Contribution of indoor exposed massive wood to a good indoor climate: in situ measurement campaign. Energy and Buildings 36 (2004) 281292.

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[32] Simonson, Carey J., Salonvaara Mikael and Ojalen, Tuomo. Improving Indoor Climate and Comfort with wooden Structures. Espoo 2001.Technical Research Centre of Finland, VTT Publications 431.200p.+ app 91 p, 2001. [33] Salonvaara Mikael, H. and Simonson, Carey J. Mass transfer between indoor air and a porous building envelope: Part II- Validation and numerical studies. Proceedings of Healthy Buildings 2000, Vol. 3. [34] Trechsel Heinz R. (Editor). Moisture control in buildings. ASTM Manual series. February 1994. [35] Meininghaus, R., Knudsen, H. N. and Gunnarsen, L. Impact of sorption and diffusion on indoor air pollution. Proceedings of indoor air quality 99, 1999. [36] Orosa, J. A. and Baaliña, A. Improving PAQ and comfort conditions in Spanish office buildings with passive climate control, Building and Environment (2008). doi:10.1016/j.buildenv.2008.04.013. [37] Osanyintola, O. F. and Simonson, C. J. Moisture buffering capacity of hygroscopic building materials: Experimental facilities and energy impact. Energy and Buildings 38 (2006) 1270-1282. [38] Plathner, P., Littler, J. and Stephen, R. Dynamic water vapour sorption: measurement and modelling. Proceedings of indoor air quality 99, 1999. [39] Kirchner, S., Badey, J. R., Knudsen, H. N., Meininghaus, R., Quenard, D., Saarela, K., Sallee, H. and Saarinen, A. Sorption capacities and diffusion coefficients of indoor surface materials exposed to VOCS: proposal of new test procedures. Proceedings of indoor air quality 99. 1999. [40] International Standard ISO 7730-2005. Ergonomics of the thermal environment. Analytical determination and interpretation of thermal comfort using calculation of the PMV and PPD indices and local thermal comfort criteria, 2005. [41] L. Pérez-Lombard, J. Ortiz and C., Pout. A review on building energy consumption information, Energy and buildings 40 (2008) 394-398. [42] Taylor, P., Fuller, R. J. and Luther, M. B. Energy use and thermal comfort in a rammed earth office building, Energy and buildings.2007. doi:10.1016/j.enbuild.2007.05.013. [43] Omer, A. M. Renewable building energy systems and passive human comfort solutions. Renewable and sustainable Energy Reviews, 12 (2008) 1562-1587. [44] Cardinale, N., Micucci, M. and Ruggiero, F. Analysis of energy saving using natural ventilation in a traditional Italian building, Energy and buildings, 35 (2003) 153-159. [45] Makaka, G., Meyer, E. L. and McPherson, M. Thermal behaviour and ventilation efficiency of a low cost passive solar energy efficient house, Renewable energy. 33. (2008) 1959-1973. [46] Yang, L., Lam, J. C. and Tsang, C.L. energy performance of buildings envelopes in different climate zone in China, Applied Energy 85 (2008) 800-817. [47] Accident prevention on board ship at sea and in port. An ILO code of practice (ISBN 922-109450-2), Ginebra, 1996. [48] ISO 7547 Ships and marine technology. Air-conditioning and ventilation of accommodation spaces. Design conditions and basis of calculations, 2002. [49] Shipbuilding. Engine-room ventilation in diesel-engined ships. Design requirements and basis of calculations, 1998.

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[50] International Standards for the Assessment of the Risk of Thermal Strain on Clothed Workers in Hot Environments. K. C. PARSONS. Ann. occup. Hyg., Vol. 43, No. 5, pp. 297±308, 1999. British Occupational Hygiene Society [51] Fanger, P. O. Thermal Comfort. Danish Technical Press. Copenhagen. 1970. [52] NTP 18 (Heat stress evaluation of sever exposures) [53] NTP 350 (Heat stress evaluation required sweating index) [54] ISO 7243. Hot environments. Estimation of the heat stress on working man, based on the WBGT-index (wet bulb globe temperature), 1989. [55] ISO 7933. Ergonomics of the thermal environment. Analytical determination and interpretation of heat stress using calculation of the predicted heat strain, 2004. [56] O‘Connor, P. J. and O‘Connor. N.. Work-related maritime fatalities. Accident Analysis & Prevention 38 (2006) 737-741.

In: Advances in Energy Research. Volume 4 Editor: Morena J. Acosta, pp. 41-85

ISBN: 978-1-61761-672-3 © 2011 Nova Science Publishers, Inc.

Chapter 3

RATIONAL ATTRIBUTION OF ENVIRONMENTAL EMISSIONS OF COGENERATION TO PRODUCTS: ALLOCATING CARBON DIOXIDE AND OTHER EMISSIONS WITH EXERGY Marc A. Rosen* Faculty of Engineering and Applied Science University of Ontario Institute of Technology 2000 Simcoe Street North, Oshawa, Ontario, L1H 7K4, Canada

ABSTRACT Many from industry, government and academe have struggled with the question of how to allocate emissions for an energy process that has multiple products and multiple inputs, like cogeneration. Present methods are not universally accepted, because they are inconsistent, overly complex, difficult to utilize, and not soundly based. The author proposes that exergy methods can form the basis of rational and meaningful allocation methods for emissions. In this article, methods based on exergy for allocating cogeneration emissions are investigated and compared with other methods. Two illustrations are provided. The rationale for the author‘s view that the exergy-based method is the most meaningful and accurate is discussed, as are problems associated with other methods. An analogy is described between allocating carbon dioxide emissions and economic costs for cogeneration. The results indicate that the exergy-based emissions allocations method provides a sensible basis for a meaningful overall approach for emissions trading. It is concluded that the exergy-based method of carbon dioxide emissions allocation for cogeneration is rational, useful and superior to other methods. By permitting these emissions to be allocated more appropriately among commodities generated by cogeneration, the results allow the environmental benefits of technologies that produce multiple products to be better understood and exploited. The results should be of most benefit to designers of energy systems, and to decision and policy makers in companies and government. The author proposes that the exergy-based method be used in allocating cogeneration emissions to help ensure proper decision-making regarding *

E-mail address: [email protected], Tel: 905/721-8668. (Corresponding author)

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Marc A. Rosen such issues as what effect cogeneration may have on overall carbon dioxide emissions and how emissions should be reduced, how and where cogeneration should be used, and fair ways to establish emissions trading schemes.

1. INTRODUCTION The potential benefits of cogeneration (i.e., combined heat and power) are significant (Klein, 1999a, b, c, d, 2001a, b). But many companies, government agencies and researchers have struggled with the question of how to allocate emissions for an energy system that has multiple products and multiple inputs. Some work has been done for cogeneration, e.g., several attempts have been made to determine how to allocate emissions among the products of cogeneration systems (Strickland and Nyboer, 2002a, 2002b; Upton, 2001; Phylipsen et al., 1998). However, the results are not universally accepted and, in the view of the author, are often not based on sound reasoning. In addition, the results are often conflicting. Further, the methods developed often are overly complex, thus rendering it difficult to use them and to convince decision and policy makers of their potential benefits. For cogeneration, for instance, existing methods of allocating emissions among outputs include ―efficiency methods,‖ ―work potential methods‖ and ―heat content methods,‖ but results obtained with each are generally different and not based on clear reasoning. The challenge becomes even more difficult for more complex systems, such as those involving trigeneration (i.e., simultaneous production of electrical, heating and cooling services). The author feels that much research is needed in this area, and that the direct use of exergy methods can form the basis of sound and meaningful allocation methods for emissions. In this article, we investigate rational methods, based on exergy, for allocating emissions for complex energy systems having multiple inputs and products, like cogeneration. This method is compared with the other allocation methods. Throughout, the results are present in as simple a manner as possible. Consequently, this article focuses on carbon dioxide because it is the primary greenhouse gas, but it is extendable to CO2 equivalent emissions in terms of greenhouse gas potential. Calculations are made for example systems of how much output power is lost and thermal energy gained, when heat is captured or extracted for cogneration purposes. An overall approach with regards to energy efficiency and emissions trading is discussed.

2. BACKGROUND Many governments have launched initiatives involving air issues and the energy sector. For instance, Environment Canada has pursued the Ozone Annex, the NOx/VOC Plan and acid rain initiatives, the Strategic Options Process for air toxics, and the National Plan for Climate Change. Environment Canada is interested in emissions trading, and its implications for air quality issues across Canada. Also, methods for allocating emissions are discussed in relevant publications and correspondences (e.g., letters between the National Council for Air and Stream Improvement and World Resources Institute (Upton, 2001)). Much work on assessing the performance of cogeneration systems and their emissions has been carried out in Europe. For instance, the European Parliament (2004) issued a directive in February 2004 on the promotion of cogeneration based on a useful heat demand

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in the internal energy market. Also, the European Committee for Standardization (CEN) and the European Committee for Electrotechnical Standardization (CENELEC) published in 2004 a workshop agreement manual for the determination of combined heat and power (CEN/CENELEC, 2004). Although these two documents have been criticized (Verbruggen, 2007a, 2007b), they are widely accepted for primary energy savings for cogeneration. They provide indicators for carbon dioxide emissions allocation from cogeneration systems. However, these documents ignore exergy, and thus suffer from the same difficulties as mentioned earlier of allocation methods. With a move towards output-based standards for emission guidelines, various measures on emissions trading, and comparative evaluations of air pollution and greenhouse gases (GHGs) for all energy sources, better information is needed on estimating the equivalence between heat, cooling and electricity. Both shaft mechanical power and electricity are much more valuable than most forms of industrial heat, but this depends on the temperature and quality of the steam or hot water extracted from the process. The normal definition of efficiency (fuel utilization) does not capture this relationship. The concept of comparing emission mass per unit energy output (in kg/MWh, for example) of various emissions must consider the tradeoff between power and heat for cogeneration and district energy, if suitable comparisons are to be made. This has been done in an approximate fashion for the 1992 CCME Gas Turbine emission guideline. More definitive work is needed to address this for energy products such as high- and low-pressure steam, and hot and cold water. Emissions trading will require a shared allocation of credits/allowances for these among several industrial and commercial energy producers and users. Such estimations can also be valuable for the conversion of emission factors from kg/MWh, into $/tonne externalities and $/MWh of reduction measures. Emissions trading of air pollution and GHGs will require a shared allocation of credits/allowances for these among several industrial and commercial energy producers and users. More definitive work on the quality of energy of energy systems is needed to address this for products such as high and low pressure steam, and hot and cold water.

2.1. Cogeneration Cogeneration usually refers to the simultaneous production of two energy forms (electricity, and heat in the form of steam and/or hot water) from one energy source (normally a fossil fuel). Cogeneration has been used, particularly by industry, for approximately a century. A cogenerator can be a utility, an industry, a government, or any other party. Cogeneration systems are often extensions of thermal electricity-generation systems. In thermal electrical generating stations, the energy content of a resource (normally a fossil fuel) is converted to heat (in the form of steam or hot gases) which is then converted to mechanical energy (in the form of a rotating shaft), which in turn is converted to electricity. A portion (normally 20 to 45%) of the heat is converted to electricity, and the remainder is rejected to the environment as waste. Cogeneration systems are similar to thermal electricity-generation systems, except that a percentage of the generated heat is delivered as a product, normally as steam or hot water, and the quantities of electricity and waste heat produced are reduced. Overall cogeneration efficiencies based on both the electrical and thermal energy products of over 80% are

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achievable. Other advantages generally reported from cogenerating thermal and electrical energy rather than generating the same products in separate processes include:   

reduced energy consumption, reduced environmental emissions (due to reduced energy consumption and the use of modern technologies in large, central installations), and more economic, safe and reliable operation.

Most thermal systems for large-scale electricity generation are based on steam and/or gas turbine cycles, and can be modified relatively straightforwardly for cogeneration. Two main categories of heat demands can normally be satisfied through cogeneration: (i) residential, commercial and institutional processes, which require large quantities of heat at relatively low temperatures (e.g., for air and water heating); and (ii) industrial processes, which require heat at a wide range of temperatures (e.g., for drying, heating and boiling in, for instance, chemical processing, manufacturing, metal processing, mining and agriculture). The use of a central heat supply to meet residential, commercial and institutional heat demands is often referred to as district heating. As well as satisfying heat demands, cogenerated heat can drive chillers; this application can be particularly beneficial in locations where the annual peak electrical demand is associated with the summer cooling load. Many general descriptions and studies of cogeneration systems have been reported (MacRae, 1992; Rogner, 1993; FVB/Eltec, 1993; MacLaren, 1988; Henneforth and Todd, 1988; Acres, 1987; Horlock, 1987; Rosen, 1993, 1994, 1998; Rosen et al., 1997; Hart and Rosen, 1994; Rosen and Le, 1994; Sherwood and Rosen, 1996; Simpson and Rosen, 1996). Cogeneration systems are in use throughout the world (e.g., thousands are listed by the Association of Energy Engineers), and the basic technology is proven. Numerous examples exist of large cogeneration systems. The size and type of a cogeneration system are normally selected to match as optimally as possible the thermal and electrical demands. Many matching schemes can be used. Systems can be designed to satisfy the electrical or thermal base-loads, or to follow the electrical or thermal loads. Storage systems for electricity (e.g., batteries) or heat (e.g., hot water or steam tanks) are often used to overcome periods when demands and supplies for either electricity or heat are not coincident. Cogeneration systems are sometimes used to supply only the peak portions of the electrical or thermal demands.

2.2. Exergy The thermodynamic analysis tool exergy analysis is central to this article. The exergy of an energy form or a substance is a measure of its usefulness or quality. Exergy is based on the first and second laws of thermodynamics, and combines the principles of conservation of energy and non-conservation of entropy. Exergy is defined as the maximum amount of work which can be produced by a system or a flow of matter or energy as it comes to equilibrium with a reference environment. Exergy is a measure of the potential of the system or flow to

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cause change, as a consequence of not being completely in stable equilibrium relative to the reference environment. Unlike energy, exergy is not subject to a conservation law (except for ideal, or reversible, processes). Rather exergy is consumed or destroyed, due to irreversibilities in any real process. The exergy consumption during a process is proportional to the entropy created due to irreversibilities associated with the process. Exergy and exergy analysis are discussed further elsewhere (Dincer and Rosen, 2007; Sato, 2005; Szargut, 2005; Hevert and Hevert, 1980; Kotas, 1995; Moran, 1989; Moran and Sciubba, 1994, 2004; Moran and Shapiro, 2007; Szargut et al., 1988; Szargut, 1980; Edgerton, 1992; Rosen, 1999). As a simple illustration, consider an adiabatic system containing fuel and air at ambient conditions. The fuel and air react to form a mixture of hot combustion gases. During the combustion process, the energy in the system remains fixed because it is adiabatic. But the exergy content declines as combustion proceeds due to the irreversibilities associated with the conversion of the high-quality energy of fuel to the lower quality energy of combustion gases. The different behaviours of energy and exergy during this process are illustrated qualitatively in Figure 1.

Figure 1. Qualitative comparison of the energy and exergy changes during fuel combustion.

2.2.1. Exergy Analysis Exergy analysis is a methodology that uses the conservation of mass and conservation of energy principles together with the second law of thermodynamics for the analysis, design and improvement of energy and other systems. The exergy method is useful for improving the efficiency of energy-resource use, for it quantifies the locations, types and magnitudes of wastes and losses. In general, more meaningful efficiencies are evaluated with exergy analysis rather than energy analysis, since exergy efficiencies are always a measure of the approach to the ideal. Therefore, exergy analysis identifies accurately the margin available to design more efficient energy systems by reducing inefficiencies. Many engineers and scientists suggest that thermodynamic performance is best evaluated using exergy analysis because it provides more insights and is more useful in efficiency-improvement efforts than energy analysis. Many applications of exergy analysis to processes and systems have been reported (Dincer and Rosen, 2007; Cownden et al., 2001; Rosen, 1992, 1996, 2000; Rosen

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and Dincer, 2002; Rosen and Horazak, 1995). Some of those have included investigations by the author of cogeneration using exergy methods (Dincer and Rosen, 2007; Rosen, 1990; Rosen and Le, 1996).

Figure 2. The electrical generating station considered. The external inputs are coal and air, and the output is stack gas and solid waste for unit A. The external outputs for unit E are electricity and waste heat. Electricity is input to units G and J, and cooling water enters and exits unit F.

For exergy analysis, the characteristics of the reference environment must be specified completely. This is commonly done by specifying the temperature, pressure and chemical composition of the reference environment. The results of exergy analyses, consequently, are relative to the specified reference environment, which in most applications is modelled after the actual local environment. The exergy of a system is zero when it is in equilibrium with the reference environment. The tie between exergy and the environment has implications regarding environmental impact has been investigated previously (Dincer and Rosen, 2007; Sciubba, 1999, 2004; Ayres et al., 1998; Connelly and Koshland, 1997; Creyts and Carey, 1997; Berthiaume et al., 2001; Crane et al., 1992; Rosen and Dincer, 1997, 1999, 2001; Gunnewiek and Rosen, 1998; Daniel and Rosen, 2002).

2.2.2. Illustrative Applications The use of exergy methods to analyze a device so as to permit its performance to be better understood and its efficiency improved is demonstrated for three illustrative applications.

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The first application considered is electricity generation using a coal-fired steam power plant. The plant considered is the coal-fired Nanticoke generating station, which has been operating since 1981 in Ontario, Canada. Each of the eight units in the station has a net electrical output of 505 MW. A single unit of the electrical generating station is illustrated in Figure 2, and consists of four main sections (Rosen, 2000): a) Steam Generators: Pulverized-coal-fired natural-circulation steam generators combust coal to produce primary and reheat steam. Air is supplied to the furnace by motor-driven forced-draft fans, and regenerative air pre-heaters are used. The flue gas passes through an electrostatic precipitator and exits the plant via multi-flued chimneys. b) Turbine Generators and Transformers: The steam produced passes through a turbine generator, which is connected to a transformer. Each turbine generator has one single-flow high-pressure cylinder, one double-flow intermediate-pressure cylinder and two double-flow low-pressure cylinders. Steam exhausted from the high-pressure cylinder is reheated in the steam generator. Several steam extractions from the turbines preheat feed water in low- and high-pressure heat exchangers and one spray-type open de-aerating heat exchanger. The low-pressure turbines exhaust to the condenser. c) Condensers: Cooling water condenses the steam exhausted from the turbines. d) Preheating Heat Exchangers and Pumps: The temperature and pressure of the condensed steam are increased in a series of pumps and heat exchangers.

(a)

(b)

Figure 3. Overall energy and exergy balances for the station, represented by a rectangle. Widths of flow lines are proportional to the relative magnitudes of the represented quantities. CW denotes cooling water. a) Exergy balance showing flow rates (positive values) and consumption rate (negative value, denoted by hatched region) of exergy (in MW). b) Energy balance showing flow rates of energy (in MW).

Exergy and energy analyses of the station have been performed (Rosen, 2000). Overall balances of exergy and energy for the station are illustrated in Figure 3, and the main findings, which improve understanding of the thermodynamic behaviour of the plant and help identify areas having significant efficiency-improvement potential, follow:

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





For the overall plant, the energy efficiency (ratio of net electrical energy output to coal energy input), was found to be 37%, and the corresponding exergy efficiency 36%. In the steam generators, the energy and exergy efficiencies were evaluated, considering the increase in energy or exergy of the water as the product. The steam generators appear significantly more efficient on an energy basis (95%) than on an exergy basis (50%). Physically, this discrepancy implies that, although most of the input energy is transferred to the preheated water, the energy is degraded as it is transferred. Most of the exergy losses in the steam generators are associated with internal consumptions (mainly due to combustion and heat transfer). In the condensers, a large quantity of energy enters (about 775 MW for each unit), of which close to 100% is rejected; and a small quantity of exergy enters (about 54 MW for each unit), of which about 25% is rejected and 75% internally consumed. In other plant devices, energy losses were found to be very small (about 10 MW total), and exergy losses were found to be moderately small (about 150 MW total). The exergy losses are almost completely associated with internal consumptions.

The second application considered is an electrical resistance space heater which produces heat at a temperature suitable for keeping a room at a comfortable temperature. The energy efficiency of electric resistance space heating is often quoted to exceed 99%. The implication clearly is that the maximum possible energy efficiency for electric resistance heating is 100%, corresponding to the most efficient device possible. This understanding is erroneous, however, as energy analysis ignores the fact that in this process high-quality energy (electricity) is used to produce a relatively low-quality product (warm air). Exergy analysis recognizes this difference in energy qualities, and indicates the exergy of the heat delivered to the room to be about 5% of the exergy entering the heater. Thus, the efficiency, based on exergy, of electric resistance space heating is found to be about 5%. We therefore obtain useful information from the exergy results. Since thermodynamically ideal space heating has an exergy efficiency of 100%, the same space heating can in theory be achieved using as little as 5% of the electricity used in conventional electric resistance space heating. In practical terms, space heating can be achieved with much less electricity input using a high-efficiency heat pump, using 20% of the electricity that electric resistance heating would require, for a heat pump with a ―coefficient of performance‖ of 5. The final application considered is a thermal energy storage (TES), which receives thermal energy and holds the energy until it is required. TESs can store energy at temperatures above or below the environment temperature, and come in many types (e.g., tanks, aquifers, ponds, caverns). The evaluation of a thermal energy storage system requires a measure of performance that is rational, meaningful and practical. The conventional energy storage efficiency is an inadequate measure. A more perceptive basis for comparison is needed if the true usefulness of a thermal storage is to be assessed, and so permit maximization of its economic benefit. Efficiencies based on ratios of exergy do provide rational measures of performance, since they can measure the approach of the performance of a system to the ideal. That the energy efficiency is an inappropriate measure of thermal storage performance can best be appreciated through a simple example. Consider a perfectly insulated thermal storage containing 1000 kg of water, initially at 40C. The ambient temperature is 20C, and

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the specific heat of water is taken to be constant at 4.2 kJ/kg K. A quantity of 4200 kJ of heat is transferred to the storage through a heat exchanger from an external body of 100 kg of water cooling from 100C to 90C. This heat addition raises the storage temperature 1.0C, to 41C. After a period of storage, 4200 kJ of heat are recovered from the storage through a heat exchanger which delivers it to an external body of 100 kg of water, raising the temperature of that water from 20C to 30C. The storage is returned to its initial state at 40C. For this storage cycle the energy efficiency, the ratio of the heat recovered from the storage to the heat injected, is 4200 kJ/4200 kJ = 1, or 100%. But the recovered heat is at only 30C, and of little use, having been degraded even though the storage energy efficiency was 100%. The exergy recovered in this example is evaluated as 70 kJ, and the exergy supplied as 856 kJ. Thus the exergy efficiency, the ratio of the thermal exergy recovered from storage to that injected, is 70/856 = 0.082, or 8.2%, a much more meaningful expression of the achieved performance of the TES. Consequently, a device that appears to be ideal on an energy basis is correctly shown to be far from ideal on an exergy basis, clearly demonstrating the benefits of using exergy analysis for evaluating TESs.

2.3. Existing Allocation Methods for Energy-System Emissions Limited work has been done in general on methods for allocating the emissions from energy systems that produce multiple products. Some methods have been developed for allocating carbon dioxide emissions from cogeneration systems to the electrical and thermal energy products. The need for these methods is premised on the fact that when the owner of the cogeneration plant, the thermal energy user and the electrical energy user are not the same, a method for allocating the emissions is needed to ensure each party is credited with their appropriate share of the emissions from the system. In addition, having a meaningful allocation method allows the sources of carbon dioxide and other emissions to be better understood and, where appropriate, reduced. Strickland and Nyboer (2002a, 2002b) list seven methods of calculating the fuel allocation to the thermal and electrical energy products of a cogeneration system. Allocations in those methods are based on product energy contents, product exergy contents, product economic values, incremental fuel consumption to electrical production, incremental fuel consumption to the heat production, shared emission savings between heat and electricity, and agreement. In their work, Strickland and Nyboer (2002a, 2002b) adapt the calculational methods introduced earlier by Phylipsen et al. (1998). In the methods used, the fuel allocation is multiplied by the appropriate carbon dioxide emission factor to evaluate the share of emissions allocated to each product. Others have also investigated methods for allocating greenhouse gas emissions associated with manufacturing and other industries. Such investigations have been carried out by the World Resources Institute, Washington, DC and the National Council for Air and Stream Improvement, Inc., Corvallis, OR, as evidenced by correspondences between these organizations (Upton, 2001). In general, the allocation methods discussed by Upton (2001) are variations on those discussed by Strickland and Nyboer (2002a, 2002b) and Phylipsen et al. (1998).

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3. SIMPLIFIED SELECTED METHODS FOR ALLOCATING CARBON DIOXIDE EMISSIONS FOR COGENERATION The allocation methods presented by Strickland and Nyboer (2002a, 2002b) based on work by Phylipsen et al. (1998) are further adapted and simplified so that they present the fractions, rather than the total, carbon dioxide emissions allocated to each product. The categorizations follow for convenience those used by Strickland and Nyboer (2002a, 2002b). Of course, emissions can be allocated according to other methods than those described in this section.

3.1. Allocation Based on Energy Content of Products The allocations are evaluated in proportion to the energy contents of the products, as follows: fE = E/(E + Q) fH = Q/(E + Q) where fE and fQ denote respectively the fractions of the emissions allocated to the electrical and thermal products, and E and Q denote respectively the net outputs of electrical energy and thermal energy from the cogeneration system. The term Q can represent an actual transfer of thermal energy, or the net thermal energy transferred via a material flow in and out of a heat exchange device. Although this allocation method is straightforward and simple, it ignores the quality of energy and focuses only on the quantities involved. Consequently, it can be argued that it underestimates the share of the emissions allocated to the electrical product.

3.2. Allocation Based on Exergy Content of Products The allocations are evaluated in proportion to the exergy contents of the products, as follows: fE = ExE/(ExE + ExQ) fQ = ExQ/(ExE + ExQ) where ExE and ExQ denote respectively the net outputs of electrical exergy and thermal exergy from the cogeneration system. It is noted that electrical energy and electrical exergy are equivalent, so that ExE = E. In this allocation method, one can treat the thermal product in two ways: simply thermal energy and thermal energy transfer via moving materials. Both of these ways of treating thermal products are described below. For simple thermal energy, the corresponding thermal exergy can be written as ExQ = Qτ where τ denotes the exergetic temperature factor and can be evaluated as

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τ = 1 – To/T Here, T denotes the temperature at which heat Q crosses the system boundary, and To denotes the temperature of the reference environment. For a reference environment at a temperature of 300 K (27°C), the value of the exergetic temperature factor τ is 0.25 for heat transfers at 400 K, 0.5 for heat transfers at 600 K, and 0.75 for heat transfers at 1200 K. If, on the other hand, the thermal energy is delivered via a material flow into and out of a heat exchange device, then the term ExQ is evaluated as the difference between the exergy of the incoming flow and the outgoing flow. The flowing commodity could be steam, hot water, cold water, etc., and the factors that must be taken into account in determining the corresponding exergy flow rates include mass flow rate, temperature, pressure and sometimes vapour fraction. An additional point regarding the exergy-based allocation method is that the choice of reference environment for determining exergy quantities is important, and can affect the results. Normal practice involves selecting a reference environment that is similar to the actual environment. But other reference environments can be used. For example, Upton (2001), in an exercise to allocate emissions, evaluates exergy values using a referenceenvironment temperature of 100°C, which is well in excess of the actual environment annual mean temperature (perhaps 10°C to 20°C, depending on location). He uses this value because it is related to the process, in that he considers thermal energy below this temperature to be non-useful. Although this choice of a reference-environment temperature is permitted when using exergy methods, it is important to note that care must be exercised to ensure that a consistent reference environment is used throughout an analysis. It is noted that the type of exergy-based allocation method presented by Strickland and Nyboer (2002a, 2002b) is not general, in that it assumes that the thermal product of cogeneration can be modelled only as pure thermal energy, rather than also considering the transfer of heat via flowing materials. This allocation method accounts for the quality and quantity of the commodities involved. Consequently, compared to the energy allocation method, the exergy method avoids underestimating the share of the emissions allocated to the electrical product, and allocates a lower portion of the emissions to the thermal product.

3.3. Allocation Based on Economic Value of Products The allocations are evaluated in proportion to the economic values of the products as follows: fE = cEE/(cEE + cQQ) fQ = cEQ/(cEE + cQQ) where cE and cQ denote respectively the unit economic values of the electrical product and the thermal product of the cogeneration system. Two important points are noted: 

The unit economic values presented here are on an energy basis (i.e., the economic value of a type of energy commodity per unit quantity of energy of that commodity),

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

but the unit economic values based on other quantities—such as exergy—could also be used. The economic values can be determined using several economic measures in several ways. For instance, they can reflect as the costs to produce the commodities, or their prices, or some other economic measure for them.

This method is sometimes considered to have advantages to owners of cogeneration systems that sell electrical and thermal products separately. It is not necessary to know the numerical values of both unit economic values, cE and cQ, when applying this method of emission allocation. Rather, it is the ratio of the unit economic values that is important. This phenomenon can be seen by modifying the expressions for fE and fQ for this method of allocation as follows: fE = E/[E + Q(cE/cQ)-1] fQ = Q/[E(cE/cQ) + Q] Here, cE/cQ denotes ratio of the unit economic value for electricity to that for thermal energy. Since the unit economic value for electricity normally exceeds that for thermal energy, it is normally found that cE/cQ > 1.

3.4. Allocation Based on Incremental Fuel Consumption to Electrical Production The emissions allocations are evaluated here by dividing the total fuel consumed in the cogeneration among the electrical and thermal products, while considering electricity generation to be a by-product of the thermal energy production process. Then, the emissions are allocated in proportion to the fuel division. Two steps are used to divide the fuel consumption. First, the fuel consumption attributed to thermal energy production is evaluated as the hypothetical amount of fuel that would be consumed by an independent device for providing the same thermal energy as the cogeneration system (e.g., a reference steam boiler if the thermal energy is in the form of steam). That is, FQ = Q/ηb where FQ denotes the fuel consumption attributed to the production of thermal energy Q, and ηb denotes the energy efficiency of the independent device for providing the same thermal energy as the cogeneration system (e.g., a reference steam boiler). Second, the fuel consumption attributed to electricity generation, FE, is evaluated by subtracting this hypothetical amount of fuel from the total primary fuel energy consumed by the cogeneration system, F. That is, F E = F – FQ Then, the emission allocation fractions fE and fQ are determined as the ratios FE/F and FQ/F, respectively. That is,

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fQ = Q/(Fηb) f E = 1 – fQ This allocation method is consistent with the ―Fuel Charged to Power‖ (FCP) method used by many cogeneration consulting firms.

3.5. Allocation Based on Incremental Fuel Consumption to Thermal Energy Production This emissions allocation method is similar to the previous one, except the emissions allocations are evaluated here by dividing the total fuel consumed in the cogeneration among the electrical and thermal products, while considering thermal energy production to be a byproduct of the electricity generation process. Again, the emissions are then allocated in proportion to the fuel division, using the following two steps to divide the fuel consumption. First, the fuel consumption attributed to electricity generation is evaluated as the hypothetical amount of fuel that would be consumed by an independent device for providing the same electrical energy as the cogeneration system (e.g., a reference power plant). That is, FE = E/ηpp where ηpp denotes the energy efficiency of the independent device for providing the same electrical energy as the cogeneration system (e.g., a reference power plant). Second, the fuel consumption attributed to thermal energy production, FQ, is evaluated by subtracting this hypothetical amount of fuel from the total primary fuel energy consumed by the cogeneration system. That is, F Q = F – FE Again, the emission allocation fractions fE and fQ are then determined as the ratios FE/F and FQ/F, respectively, as follows: fE = E/(Fηpp) f Q = 1 – fE

3.6. Allocation Based on Shared Emission Savings between Electrical and Thermal Energy The allocations are evaluated for each product in proportion to the hypothetical fuel that would be used to produce that product independently, relative to the total hypothetical fuel that would be used to produce both products independently. Using the terms previously defined, the hypothetical fuel consumption attributed to an independent process for thermal energy production (e.g., a reference steam boiler if the thermal energy is in the form of steam) is evaluated as FQ = Q/ηb

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and the hypothetical fuel consumption attributed to an independent process for electricity generation is evaluated as FE = E/ηpp Then, the emission allocation fractions fE and fQ are determined as the ratios FE/F and FQ/F, respectively, as follows: fE = (E/ηpp)/(E/ηpp + Q/ηb) fQ = (Q/ηb)/(E/ηpp + Q/ηb) This allocation method therefore shares the emissions among the products in a particular format. This method somewhat extends the concepts used in the previous two emissions allocation methods, but is more of a compromise in terms of treating one or the other product as the primary one.

3.7. Allocation by Agreement Allocation of CO2 emissions to each product of cogeneration can be determined purely based on an agreement between the various parties involved in a project.

4. ALLOCATING CARBON DIOXIDE EMISSIONS FOR COGENERATION The author explains in this section his view that the most rational and meaningful method of allocating carbon dioxide emissions for cogeneration processes is based on the exergy content of products. To support this contention, the different emissions allocation methods discussed for cogeneration processes in the previous section are examined and compared in this section. Before discussing and comparing the different emissions allocation methods, however, it is useful to understand the basic intentions and considerations in allocating emissions.

4.1. Objective in Allocating Emissions for Multi-product Production Processes The general objective when allocating a type of emission for a multi-product production process is to allocate the emission to each product according to the actual emission that is in fact attributable to that product, accounting for all thermodynamic losses, when it is produced in the multi-product production process. Usually the emission allocation breakdown is directly proportional to the breakdown of fuel use that is attributable to each product, when it is produced in the multi-product production process.

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4.2. Basic Considerations in Allocating CO2 Emissions for Cogeneration Following this description and considering carbon dioxide emissions for a cogeneration processes, the total CO2 emissions C for a multi-product production process can be expressed as C = C E + CQ where CE and CQ denote respectively the CO2 emissions associated with the electrical and thermal energy products, when they are produced in the cogeneration process. We can also express the total CO2 emissions as C = Fφ where F denotes the total fuel use in the process and φ a CO2 emission coefficient for the fuel. The terms F and φ must be on consistent bases (e.g., if F is in energy units, then φ must be the CO2 emission per unit fuel energy consumed). The total CO2 emissions C can also be written as C = (FE + FQ)φ where FE and FQ denote respectively the fuel consumption associated with the electrical and thermal energy products, when they are produced in the cogeneration process. Clearly, FE + FQ = F. Furthermore, we can write C = (fE + fQ)Fφ where fE = FE/F and fQ = FQ/F Clearly, the fractions of fuel consumption associated with the electrical and thermal energy products relate as follows: fE + fQ = 1.

4.3. Energy-Based Considerations in Allocating CO2 Emissions for Cogeneration Using an energy basis, the fuel consumption associated with generating the electricity in the cogeneration process can be expressed as FE = E/ηE where ηE denotes the energy efficiency of generating the electrical energy product within a cogeneration process. Correspondingly, the fuel consumption associated with producing the thermal energy in the cogeneration process can be expressed as FQ = Q/ηQ

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where ηQ denotes the energy efficiency of producing the thermal energy product within a cogeneration process. Combining the above equations, we can write the following expressions for the fractions fE and fQ: fE = (E/ηE)/(E/ηE + Q/ηQ) and fQ = (Q/ηQ)/(E/ηE + Q/ηQ)

4.4. Exergy-Based Considerations in Allocating CO2 Emissions for Cogeneration Alternatively, we can use an exergy basis rather than an energy basis in establishing the above equations. Then, the fuel exergy consumption, ExFE, associated with generating the electrical exergy, ExE, in the cogeneration process can be expressed as ExFE = ExE/ψE where ψE denotes the exergy efficiency of generating the electrical energy product within the cogeneration process. Correspondingly, the fuel exergy consumption, ExFQ, associated with producing the thermal exergy, ExQ, in the cogeneration process can be expressed as ExFQ = ExQ/ψQ where ψQ denotes the exergy efficiency of producing the thermal energy product within the cogeneration process. Combining the above equations, we can write the following expressions for the fractions fE and fQ, using exergy terms: fE = (ExE/ψE)/(ExE/ψE + ExQ/ψQ) and fQ /ψQ= (ExQ/ψQ)/(ExE/ψE + ExQ)

4.5. Advantages of Allocating Cogeneration CO2 Emissions Using Exergy over Energy 4.5.1. Trade-off between Thermal and Electrical Products of Cogeneration When an electrical generation process is modified so that it becomes a cogeneration process, some of the electrical product is sacrificed for a gain in thermal output. When considering energy quantities, it is usually seen that the thermal energy gain is often very great, even for a small decrease in electrical energy output. In addition, there is often no dependence on the temperature at which the thermal energy is delivered. When considering exergy quantities, however, the trade-off between electrical and thermal exergy products is more balanced. That is, a small decrease in electrical exergy output usually leads to a relatively small and similar in magnitude increase in thermal exergy output, while a large decrease in electrical exergy output usually leads to a correspondingly large increase in

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thermal exergy output. Furthermore, the increase in thermal exergy is directly dependent on the temperature at which the thermal energy is delivered; generally, the greater is the temperature the greater is the thermal exergy. Table 1. Overall Energy and Exergy Efficiencies for an Electricity Generating Station Converted to Various Types of Cogeneration1. Operating mode Electricity generation only Low-temperature cogeneration2 Intermediate-temperature cogeneration2 High-temperature cogeneration2

Temperature of product thermal energy (°C) – 36 243 383

Energy efficiency (%) 37 69 60 55

Exergy efficiency (%) 37 39 37 35

1. Based on data in Rosen (1990). 2. For cogeneration cases, 50% of the resulting process heat is assumed to be useful product.

For example, a previous study (Rosen, 1990) of the effects of modifying a coal-fired electrical generating station for cogeneration showed that the overall variation in exergy efficiency is relatively small, while the corresponding variation for the energy efficiency is large. These results are illustrated in Table 1, where the exergy efficiencies are seen to vary between 35 and 39%, while the energy efficiencies vary between 37 and 69%. An interesting observation can be drawn from Table 1. The exergy results demonstrate that the benefits of cogeneration are not really due to the shift from electricity generation to heat production, since there is a balanced trade-off between the exergy of the two product commodities, and the overall exergy efficiency remains relatively fixed. Rather, the benefits of cogeneration are due to the fact that the heat produced offsets the need for a separate heat production process that uses additional fuel and—on an exergy basis—is inefficient. The energy results present an entirely different perspective, one that is skewed due to the fact that energy analysis values electrical and thermal energy equally.

4.5.2. Implications for CO2 Emissions Allocations The observation that a decrease in electrical exergy output of a cogeneration plant usually leads to a relatively similar magnitude increase in thermal exergy output, but that a decrease in electrical energy output of a cogeneration plant usually leads to a dissimilar magnitude increase in thermal energy output, suggests the following: 



The exergy efficiency of generating the electrical product within the cogeneration process, ψE, is similar to the exergy efficiency of generating the thermal product within the cogeneration process, ψQ. The energy efficiency of generating the electrical product within the cogeneration process, ηE, is not similar to the energy efficiency of generating the thermal product within the cogeneration process, ηQ.

As a consequence of the above two bullets, it can be seen from the analyses presented earlier that

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Marc A. Rosen  

the allocation method based on exergy contents of the products (see section 3) most closely approximates the allocation expressions presented in sections 4.1 through 4.3. the other emissions allocation methods in section 3 are significantly inaccurate relative to the objective of allocating emissions fairly and accurately.

These two bullets are discussed further in the next section, where the different emission allocation methods from section 3 are compared, bearing in mind the information presented in this section. As a consequence of the analysis presented in this section, it can be seen that the exergybased allocation method provides a rational means to determine the more productive modifications for a plant, when the objective is to reduce CO2 emissions. In applying the exergy-based method for allocating CO2 emissions, there is a need to know the exergy contents of the various commodities that may be encountered in cogeneration. Such information is presented in section 5.

4.5.3. Other Advantages of Basing CO2 Emission Allocations for Cogeneration on Exergy Another advantage of the method of allocating CO2 emissions for cogeneration processes based on the exergy content of the products is that the allocation method is generalizable to any number and type of products. For instance, the exergy-based method can accommodate:   

cogeneration processes with multiple electricity and heat outputs, trigeneration processes (i.e., cogeneration processes in which, in addition to electricity and heat outputs, cooling capacity is also a product), and other processes producing two or more products (e.g., a fuel production process to produce hydrogen which also yields pure oxygen as a product or by-product, or a chemical process yielding two different chemical commodities).

Most of the other allocation methods described in section 3 are much less flexible.

4.6. Comparison of CO2 Emission Allocation Methods for Cogeneration Based on the results obtained in this section, the author proposes that the most rational and meaningful method of allocating carbon dioxide emissions for cogeneration processes is to do so based on the exergy content of products. To justify this view, the different emissions allocation methods discussed for cogeneration processes in section 3 are compared. In particular, the problems inherent in the other CO2 emission allocation methods for cogeneration processes are discussed. The allocation method based on energy contents (section 3.1) leads to inaccurate breakdowns of the carbon dioxide emissions, essentially because such a method presumes that the energy efficiency of generating the electrical product within a cogeneration process, ηE, is approximately similar to the energy efficiency of generating the thermal product within the cogeneration process, ηQ. As discussed earlier (section 4.5), this presumption is not valid, as values for ηE and ηQ can vary widely. The allocation method based on shared emission savings between electrical and thermal energy (section 3.6) leads to inaccurate breakdowns of the carbon dioxide emissions,

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essentially because such a method presumes that the energy efficiency of generating the electrical product within a cogeneration process, ηE, is approximately similar to the energy efficiency of generating the electrical product via a separate process, ηpp. This presumption is not valid, as values for ηE and ηpp normally vary widely. Similarly, this allocation method presumes that the energy efficiency of generating the thermal product within a cogeneration process, ηQ, is approximately similar to the energy efficiency of generating the thermal product via a separate process, ηb, again a presumption that is not valid, as values for ηQ and ηb normally vary widely. It makes sense that these efficiencies vary since one of the main reasons to consider cogeneration is that it allows one to generate two products simultaneously with a higher efficiency than would be the case if each product were produced in a separate and independent process. It is noted that one could determine the shared-emissions allocations (section 3.6) based on exergy, rather than energy. Doing so would in fact overcome many of the problems associated with the shared-emissions allocation method based on energy. This observation is attributable to the fact that the exergy-based efficiencies for electricity generation in the part of a cogeneration system responsible for electricity generation and in a pure electricity generation process are similar (i.e., ψE ≈ ψpp), while the exergy-based efficiencies for thermal energy production in the part of a cogeneration system responsible for thermal energy production and in a pure thermal energy production process are similar (i.e., ψQ ≈ ψb). Thus, the shared-emissions allocation method based on exergy reduces approximately to the allocation method based on the exergy contents of the products. The allocation methods based on incremental fuel consumption to either electrical production (section 3.4) or to thermal energy production (section 3.5) both lead to inaccurate breakdowns of the carbon dioxide emissions. The reasons are similar and follow below: 



In essence, the allocation method based on incremental fuel consumption to electrical production presumes erroneously that the energy efficiency of generating the thermal product within a cogeneration process, ηQ, is approximately similar to the energy efficiency of generating the thermal product via a separate process, ηb. Still worse, the method then presumes that the value of the energy efficiency for generating the electrical product within the cogeneration process, ηE, can simply be selected so that the overall emissions total correctly. The ensuing values of ηE can as a result vary radically and for the most part arbitrarily. Similarly, the allocation method based on incremental fuel consumption to thermal energy production essentially presumes erroneously that the energy efficiency of generating the electrical product within a cogeneration process, ηE, is approximately similar to the energy efficiency of generating the electrical product via a separate process, ηpp. Further, the method then presumes that the value of the energy efficiency for generating the thermal product within the cogeneration process, ηQ, can simply be selected so that the overall emissions total correctly. As for the values of ηE in the preceding bullet, the ensuing values of ηQ can as a result vary radically and for the most part arbitrarily.

In general, the effect of the incremental-based allocations is that they arbitrarily underestimate the emissions from one of the products of a cogeneration process at the expense of the other. Both incremental-based allocations methods are thus unfair, since we

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seek the true and fair distribution of emissions among products—based on the efficiency of production for each within the cogeneration process. It is noted that one could determine the incremental-based allocations (sections 3.4 and 3.5) based on exergy. However, this determination is not carried out here since the incremental allocation method is itself somewhat arbitrary and therefore not rational.

Figure 4. Comparison of thermal energy and exergy at various temperatures (using data in Table 2).

A common problem shared by the two incremental-based allocation methods (sections 3.4 and 3.5) and the shared-emissions allocation method (section 3.6) is that they introduce independent devices for providing thermal energy (e.g., a reference steam boiler) and electrical energy (e.g., a reference power plant). The results obtained using these allocation methods are dependent on the energy efficiencies of these independent devices (ηb for the reference steam boiler and ηpp for the reference power plant). But, the values of ηb and ηpp can vary relatively widely depending on the specific devices chosen (e.g., high- versus mediumversus low-efficiency models), and these variations cause the emissions allocations evaluated with these methods to vary over correspondingly wide ranges.

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The allocation method based on economic values of products (section 3.3) leads to inaccurate breakdowns of the carbon dioxide emissions because that method allows economic parameters to skew the allocations. The proper allocations of carbon dioxide emissions for a cogeneration process should be based entirely on principles of thermodynamics or physics. Economic parameters such as costs and prices vary with time and location, but proper emissions allocations do not as they are dependent on characteristics of the technology involved. If one nevertheless chooses to modify the appropriate emissions allocations by penalizing certain products in terms of their emissions, through economic or other means, then it must be recognized that the resulting emissions allocations deviate arbitrarily from the appropriate emissions allocations. Similarly, the allocation method based an agreement between the various stakeholders in a project (section 3.7) leads to inaccurate breakdowns of the carbon dioxide emissions because that method allows arbitrary factors that generally are not based entirely on principles of thermodynamics or physics to affect the allocations. If one nevertheless chooses to modify the appropriate emissions allocations by penalizing certain products in terms of their emissions, through factors such as agreements between various stakeholders, then it must be recognized that the resulting emissions allocations almost certainly deviate arbitrarily from the appropriate emissions allocations. In summary, it is pointed out that all of the allocation methods described in section 3, except the exergy-based one, assign some arbitrary and/or subjective values to the differences between the product commodities. We need, instead, a rigorous scientific method, to help get the correct allocation and to remove the arbitrariness, and the exergy approach provides such a method. If, after determining the exergy-based allocations of CO2 emissions, we nevertheless choose to allocate emissions differently—for economic, political or other reasons—we can do so, but at least we do so knowing the appropriate unbiased allocation.

5. EXERGY VALUES FOR TYPICAL COGENERATION COMMODITIES When allocating carbon dioxide emissions based on the exergy contents of the products in a cogeneration process, it is necessary to know the exergy values associated with electrical and thermal energy. The situation for electrical energy is straightforward, as the energy and exergy contents of electricity are equivalent. For thermal energy, however, the energy and exergy contents generally differ, and the differences in some cases can be quite significant. Values of the energy and exergy associated with thermal energy, when it is treated purely as heat, are presented in Table 2 and illustrated in Figure 4. That table and figure consider heat (i.e., thermal energy transferred at temperatures above the environment temperature) and cold (i.e., thermal energy transferred at temperatures below the environment temperature), for various temperature categories. The ratio of exergy to energy is also shown in Table 2 and illustrated in Figure 5. Some interesting observations can be made: 



For heat, the ratio of exergy to energy varies from zero when the thermal energy is transferred at the environment temperature to unity as the temperature of heat transfer approaches infinity. For cold, the values of exergy rate are negative, implying that although heat is taken out of a system to make it colder, the exergy associated with the thermal energy is

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Marc A. Rosen input to the system to make it colder. That is the flows of energy and exergy in such instances are in opposite directions. This observation implies what is intuitively understood when dealing with systems at below-environment temperatures: cold is the useful commodity. Also for cold, the magnitude of the ratio of exergy to energy varies from zero when the thermal energy is transferred at the environment temperature to greater than unity as the temperature of heat transfer approaches absolute zero. For very cold systems, therefore, the exergy transfer can be larger than the energy transfer.



Table 2. Comparison of Quality of Various Types of Thermal Energy1 Thermal energy type

Temperature category2

Heat

Low Medium

High

3

Cold

Moderate

Very low Cryogenic

Energy rate

Temperature (K) 293

20

(kW) 1000

323 373

50 100

473

(C)

Exergy rate

Exergy-toenergy ratio

(kW) 0

0.000

1000 1000

93 215

0.093 0.215

200

1000

381

0.381

573 773

300 500

1000 1000

489 621

0.489 0.621

1273

1000

1000

770

0.770

1773

1500

1000

835

0.835

2273

2000

1000

871

0.871

283

10

1000

35

0.035

273

0

1000

73

0.073

263 243

10

1000 1000

114

0.114

30

206

0.206

223

50

1000

314

0.314

173 123

100

694

0.694

150

1000 1000

1382

1.382

73

200

1000

3014

3.014

23

250

1000

11,740

11.74

1. Reference-environment temperature To = 20C = 293 K. 2. The breakdown of temperature categories used here is arbitrary. 3. Cold is taken to be a transfer of thermal energy at below environmental temperatures.

Thermal energy is often transferred via a medium, and in cogeneration systems the medium of choice is often water. Values of the energy and exergy of water in various forms are presented in Table 3. That table considers water conveying heating capacity (e.g., superheated steam, dry saturated steam, hot water), and conveying cooling capacity (e.g., cold water). The ratio of exergy to energy is also shown in Table 3. Similar observations as for Table 2 can be made, in that the magnitudes of energy and exergy flows differ and, for cold commodities, the flows of energy and exergy are in opposite directions.

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Figure 5. Ratio of thermal exergy to thermal energy at various temperatures (using data in Table 2).

Table 3. Comparison of Quality of Water in Various Conditions1 Thermal category of water Hot

Condition of water Superheated steam

Dry saturated steam

Liquid hot water

Cold

Liquid cold water

40

Specific energy (kJ/kg) 3822

Specific exergy (kJ/kg) 1677

Ratio of exergy to energy 0.439

500 300 200

40 40 15.54

3361 2919 2709

1372 1146 912

0.408 0.393 0.337

Medium Low High

150 100 100

4.758 1.014 1.014

2663 2592 335

747 525 39.9

0.281 0.203 0.119

Medium Low Moderate

50 30 10

0.126 0.0425 0.0123

125 41.8 42

6.93 0.78 0.778

0.0553 0.0187 0.0185

5 0

0.00872 0.00611

63 84

1.524 3.021

0.0274 0.0360

Temp. (C)

Pressure (bar)

High

700

Medium Low High

Temp. category2

1. Reference-environment temperature and pressure are To = 20C = 293 K and po = 1 bar, respectively. 2. The breakdown of temperature categories used here is arbitrary.

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• Ultra-low-temperature cryogenic cool (≈3 K) • Electricity, work • Hydrocarbon fuels • Very high-temperature heat (≈2000 K) • High-pressure steam, cryogenic cool (≈200 K) • Hot water, normal refrigeration cool • Space heating, space cooling Figure 6. Quality of energy based on exergy (in descending order).

An overall qualitative comparison of the energy quality of a range of energy forms, where exergy is used as the measure of quality, is shown in Figure 6.

6. ANALOGY BETWEEN ALLOCATING CARBON DIOXIDE EMISSIONS AND ECONOMIC COSTS FOR COGENERATION Many researchers have investigated the relations between economics and thermodynamics. In particular, a growing field of study linking exergy and economics, called thermoeconomics or exergoeconomics, has evolved (Dincer and Rosen, 2007). One of the objectives of exergoeconomics, when it is applied to cogeneration processes, is determining the appropriate allocations of costs associated with the system with the coproducts. The types of costs considered include both fixed capital costs as well as operating costs such as fuel costs. A good understanding the proper allocations of costs is important because it allows individual product prices to be established that cover the costs of producing the products and allow for a margin or profit. In addition, such an understanding identifies when the product prices are such that the products are being sold below cost. One of the outcomes of many exergy and economic studies is that the most appropriate way to allocate costs among the products of a cogeneration system may be to do so based on the exergy contents of the products. Other cost allocation methods, particularly those based on energy, are inadequate in that they divide costs in ways that radically differ from market prices. Clearly, then, there appears to be an analogy between the exergy-based method proposed here for allocating carbon dioxide emissions for a cogeneration system, and the exergy-based methods for allocating costs. This topic is beyond the scope of the present article. Nevertheless, it would almost certainly be worthwhile to investigate further this analogy, as it may provide insights that allow the allocation of costs or carbon dioxide emissions to be more appropriately carried out and better understood.

7. ILLUSTRATIVE EXAMPLES The different methods for allocating carbon dioxide emissions for cogeneration plants that are described in section 3 and examined and discussed in subsequent sections are

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illustrated for three example cases in this section. In the first two cases, the different methods of allocating carbon dioxide emissions are illustrated for actual cogeneration plants. In the third case, a hypothetical cogeneration scenario is compared to equivalent separate processes for producing thermal and electrical energy, and the implications of the different allocation methods are discussed. In addition, the third case is used to illustrate how the results could be used to determine carbon dioxide emission credits that might be used in emissions trading. The examples are intended to demonstrate the types of values that can be obtained using the different methods, and to illustrate the attributes of the different methods.

7.1. Illustrations of CO2 Emissions Allocations for Two Actual Cogeneration Plants 7.1.1. Descriptions of the Examples The two example cases considered are  

the University of Toronto Cogeneration System, and the Cornwall Cogeneration and District Energy System.

Data for these systems have been drawn mainly from information sheets by Wiggin (1997) and Consumers Gas (1995) that have been compiled by Klein (1999c). Table 4. Technical Parameters for the Cogeneration Systems Considered. Parameter

University of Toronto Cogeneration System1

Cornwall Cogeneration and District Energy System2

Engine type

Gas turbine

Two reciprocating engines

Heat use

Heating of campus using 6 km steam tunnel system 30,000 lb/hr of 200 psi steam

Municipal district heating using 4.5 km hot-water distribution network 7 MW via 120C and 1585 kPa steam None

Heat quantity and type (base load) Supplemental firing Environmental controls Installation date

Heat recovery steam generator can be supplementary-fired to 90,000 lb/hr steam at 200 psi Water injection to control nitrogen oxide emissions (to 42 ppm) 1993

Engines use lean-burn technology 1995

1. Source is Consumers Gas (1995). 2. Source is Wiggin (1997).

The basic technical parameters for the two cogeneration systems considered, including data on the cogeneration engine and the cogenerated heat, are summarized in Table 4. Some general thermodynamic parameters for the cogeneration systems considered that are specified in the literature (Wiggin, 1997; Consumers Gas, 1995) are presented in the top part of Table 5.

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Emission-allocation fraction

7.1.2. Energy and Exergy Values Energy and exergy data for the cogeneration systems considered are presented in the bottom two parts of Table 5. Those data include efficiencies and flow rates for products and inputs, and are based on data in the literature (Wiggin, 1997; Consumers Gas, 1995) and evaluations by the present author. It can be seen that the energy and exergy flow rates for the fuel are similar, as are the energy and exergy flow rates for the electrical products. However, the product thermal energy and thermal exergy rates differ markedly for both processes, as do the energy and exergy efficiencies. 1.2 1 0.8 0.6 0.4 0.2 0 0

1

2

3

4

5

6

Electricity to heat cost ratio Heat (U. Toronto) Electricity (Cornwall)

Heat (Cornwall) Electricity (U. Toronto)

Figure 7. Carbon dioxide emissions allocations based on economic values of products for two cases.

Table 5. Specified and Evaluated Thermodynamic Parameters for the Cogeneration Systems Considered1 Parameter General Thermodynamic Parameters Fuel type Fuel input rate (kg/s) Thermal-product type Thermal-product temperature (C) Thermal-product absolute pressure3 (bar) Thermal-product flow rate (kg/s) Energy Parameters Fuel energy input rate (MW) Electrical energy generation rate (MW) Product thermal energy rate (MW) Energy efficiency4 (%)

University of Toronto Cogeneration Plant

Cornwall Cogeneration and District Energy System

Natural gas2 0.3949 Steam (dry saturated) 197.6 14.8 3.78

Natural gas2 0.2660 Hot water 120 16.85 15.12

19.75 6 10.393 83

13.3 5 7 90

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Table 5. Continued Parameter Exergy Parameters Fuel exergy input rate5 (MW) Electrical exergy generation rate (MW) Product thermal exergy rate (MW) Exergy efficiency (%)

University of Toronto Cogeneration Plant

Cornwall Cogeneration and District Energy System

20.35 6 3.654 46.0

13.70 5 1.134 44.8

1. Reference-environment temperature and pressure are 10C and 1 bar, respectively. 2. Natural gas is modelled as methane in calculations. 3. Pressure data is assumed to be gauge. 4. Energy efficiencies provided in sources are assumed to be based on lower heating value. 5. Ratio of chemical exergy to lower heating value for methane is evaluated as 1.03 based on data in Moran and Shapiro (2007).

Table 6. Allocation of Emissions for University of Toronto Cogeneration Plant1. Emission-allocation method Based on exergy content of products Based on energy content of products Allocation of incremental fuel consumption to electrical production2 Allocation of incremental fuel consumption to heat production3 Based on a shared emission savings between electricity and heat2,3 Based on economic value of products4

Emission allocation (%) To electrical product To thermal product 62.1 37.9 36.6 63.4 41.5

58.5

86.8

13.2

59.8

40.2 1

5/[5 + 7(cE/cQ) ]  100%

7/(5cE/cQ + 7)  100%

1. Reference-environment temperature and pressure are To = 10C and po = 1 bar, respectively. 2. An efficiency of 90% is assumed for the boiler that would have been used in the production of the same amount of heat as produced by the cogeneration system. 3. An efficiency of 35% is assumed for the power plant that would have been used in the production of the same amount of electricity as produced by the cogeneration system. 4. The parameter cE/cQ denotes the ratio of the economic value of the electricity produced to the economic value of the thermal energy produced.

7.1.3. Results and Discussion The results of applying the methods for allocating CO2 of emissions for the University of Toronto cogeneration plant are presented in Table 6 and Figure 8, and for the Cornwall Cogeneration and District Energy System are presented in Table 7 and Figure 9. For both example cases, it is clear that the allocations of CO2 emissions vary markedly, depending on the allocation method used. The author contends, as discussed throughout this article, that the exergy-based allocations are the most appropriate. Thus, using the other emissions allocation methods can be very misleading, since the resulting emissions may deviate widely from those obtained using the exergy-based method. Some of the problems with the other allocation methods are illustrated in Tables 6 and 7 and Figures 8 and 9. Some examples follow:

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Marc A. Rosen 



In one case (where the allocation is based on incremental fuel consumption to heat production, for the Cornwall system), the absurd situation exists in which the allocations of emissions to the thermal product are evaluated to be negative and the allocations to the electrical product to exceed 100%. This result is simply a consequence of the flaws in that allocation method and its use of an energy efficiency ηpp for an independent device for providing the same electrical energy as the cogeneration system (e.g., a reference power plant). Here, a value of ηpp = 35% is used. If, instead, the value of ηpp is selected such that ηpp = 38%, then the allocations of carbon dioxide emissions to both products would be positive and less than 100%. For the allocation method based on economic value of products, the results depend on the value of the ratio of the economic value of the electricity produced cE to the economic value of the thermal energy produced cQ. The value of this ratio, even considering only the present time, varies with location. In Tables 6 and 7, therefore, the values of the emission allocations for this method are left variable. In Figures 8 and 9, a range of cE/cQ values are considered.

So as appreciate the wide range of possible emissions allocations possible when using the method based on economic value of products, the emissions allocations values are plotted in Figure 7 for a wide range of cE/cQ values, for both the University of Toronto cogeneration plant and the Cornwall Cogeneration and District Energy System. At a cost ratio of 1 (i.e., cE = cQ), electrical and thermal energy have the same economic value, while electricity is the more valuable commodity when cE/cQ > 1 and heat is more valuable when cE/cQ < 1. It is observed in Figure 7 that all emissions are attributable to heat for a value ratio cE/cQ = 0. As the value ratio increases, more emissions are shifted from heat to electricity. As the ratio value approaches infinity, the emissions approach being entirely attributable to electricity. Table 7. Allocation of Emissions for the Cornwall Cogeneration and District Heating System1 Emission-allocation method Based on exergy content of products Based on energy content of products Allocation of incremental fuel consumption to electrical production2 Allocation of incremental fuel consumption to heat production3 Based on a shared emission savings between electricity and heat2,3 Based on economic value of products4

Emission allocation (%) To electrical product To thermal product 81.5 18.5 41.7 58.3 41.5

58.5

107.4

7.4

64.7

35.3 1

6/[6 + 10.4 (cE/cQ) ]  100%

10.4/(6cE/cQ + 10.4)  100%

1. Reference-environment temperature and pressure are To = 10C and po = 1 bar, respectively. 2. An efficiency of 90% is assumed for the boiler that would have been used in the production of the same amount of heat as produced by the cogeneration system. 3. An efficiency of 35% is assumed for the power plant that would have been used in the production of the same amount of electricity as produced by the cogeneration system. 4. The parameter cE/cQ denotes the ratio of the economic value of the electricity produced to the economic value of the thermal energy produced.

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Figure 8. Allocation of emissions for University of Toronto cogeneration plant (based on data in Table 6).

7.2. Illustrative Comparison of CO2 Emissions Allocations for a Cogeneration Plant and Equivalent Independent Plants 7.2.1. Description of Scenario In this section, a hypothetical cogeneration scenario is compared to equivalent separate processes for producing the same thermal and electrical energy, and the implications of the different allocation methods are discussed. The main characteristics of the processes being compared are as follows: 



The hypothetical cogeneration system produces 4 MW of electrical power and 4 MW of thermal power from a fuel energy input rate of 10 MW. The energy efficiency is 80%. The separate processes consist of (i) an electricity generation system which produces 4 MW of electrical power from a fuel energy input rate of 10 MW, and (ii) a heating system which produces 4 MW of thermal power from a fuel energy input rate of 5

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Marc A. Rosen MW. The energy efficiency of the overall (combined) process is 53% (i.e., 8/15  100%).

In both cases, the input fuel is natural gas. The carbon dioxide emissions for natural gas are taken to be 50 kg CO2/GJ natural gas.

Figure 9. Allocation of emissions for Cornwall cogeneration and district heating system (based on data in Table 7).

The 4 MW of thermal energy produced in each case is taken to be made up of 2 MW of steam and 2 MW of hot water. For simplicity, the state of the steam is taken to be the same as for the steam produced in the University of Toronto Cogeneration Plant described in the previous section (dry saturated steam at a pressure of 200 psi gauge), while the state of the hot water is taken to be the same as for the hot water produced in the Cornwall Cogeneration and District Energy System described in the previous section (hot water at a temperature of 120°C and a pressure of 1585 kPa gauge).

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Table 8. Specified and Evaluated Thermodynamic Parameters for the Cogeneration and Independent Processes Considered1. Parameter General Thermodynamic Parameters Fuel type Fuel energy input rate (MW)

Heating

Independent processes Electricity Overall generation (combined)

Cogeneration

Natural gas

Natural gas

Natural gas

Natural gas

5

10

15

10

–

Thermal-product temperature (C)

Steam (dry sat.) Hot water 197.6 (steam) 120 (hot water)

Thermal-product absolute pressure (bar)

14.8 (steam) 16.85 (hot water)

–

Thermal-product flow rate (kg/s) Energy Parameters Fuel energy input rate (MW) Electrical energy generation rate (MW) Product thermal energy rate (MW) Steam Hot water Total Energy efficiency2 (%) Exergy Parameters Fuel exergy input rate3 (MW) Electrical exergy generation rate (MW) Product thermal exergy rate (MW) Steam Hot water Total Exergy efficiency (%)

0.727 (steam) 4.32 (hot water)

–

Steam (dry sat.) Hot water 197.6 (steam) 120 (hot water) 14.8 (steam) 16.85 (hot water) 0.727 (steam) 4.32 (hot water)

Steam (dry sat.) Hot water 197.6 (steam) 120 (hot water) 14.8 (steam) 16.85 (hot water) 0.727 (steam) 4.32 (hot water)

Thermal-product type(s)

–

5

10

15

10

–

4

4

4

2 2 4 80

– – – 40

2 2 4 53.3

2 2 4 80

5.15

10.3

15.45

10.3

–

4

4

4

0.777 0.323 1.100 21.4

– – – 38.8

0.777 0.323 1.100 33.0

0.777 0.323 1.100 49.5

1. Reference-environment temperature and pressure are 10C and 1 bar, respectively. 2. Energy efficiencies provided in sources are assumed to be based on lower heating value. 3. Ratio of chemical exergy to lower heating value for methane is evaluated as 1.03 based on data in Moran and Shapiro (2007).

7.2.2. Energy and Exergy Values Energy and exergy data for the cogeneration and independent processes for heating and electricity generation are presented in Table 8. Those data include efficiencies and flow rates for products and inputs, and are based on evaluations by the present author. The results in Table 8 demonstrate that the energy and exergy flow rates for the fuel are similar, as are the energy and exergy flow rates for the electrical products. However, the

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product thermal energy and thermal exergy rates differ markedly for both processes, as do the energy and exergy efficiencies. Table 9. Allocation (in %) of Emissions for the Cogeneration and Independent Processes Considered1. Process Emission-allocation method Independent Heating Electricity generation Overall (combined) Cogeneration

Based on exergy content of products Based on energy content of products Allocation of incremental fuel consumption to electrical production2 Allocation of incremental fuel consumption to heat production3 Assuming a reference power plant efficiency of ηpp = 35% Assuming a reference power plant efficiency of ηpp = 40% Based on a shared emission savings between electricity and heat2,3 Assuming a reference power plant efficiency of ηpp = 35% Assuming a reference power plant efficiency of ηpp = 40% Based on economic value of products4 Assuming an electrical-to-thermal cost ratio of cE/cQ = 1.5 Assuming an electrical-to-thermal cost ratio of cE/cQ = 1.8 Assuming an electrical-to-thermal cost ratio of cE/cQ = 2.1

Emission allocation (%) To electrical To thermal product product 0 100 66.7 78.4 50.0

100 0 33.3 21.6 50.0

55.6

44.4

114.3

–14.3

100

0

72.0

28.0

69.2

30.8

60.0

40.0

64.3

35.7

67.7

32.3

1. Reference-environment temperature and pressure are To = 10C and po = 1 bar, respectively. 2. An efficiency of 90% is assumed for the boiler that would have been used in the production of the same amount of heat as produced by the cogeneration system. 3. Efficiencies of 35% and 40% are considered for the power plant that would have been used in the production of the same amount of electricity as produced by the cogeneration system. 4. The parameter cE/cQ denotes the ratio of the economic value of the electricity produced to the economic value of the thermal energy produced.

Two particular results are observed in Table 8 regarding efficiency:  

Cogeneration is much more efficient (on energy or exergy bases) than the independent processes for producing the same thermal and electrical products. The exergy efficiencies are lower than the energy efficiencies, reflecting the fact that the thermal energy products are both of lower usefulness (or quality) than electricity. Of the two thermal products, the exergy values indicate that the usefulness of the steam is greater than that for the hot water

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Table 10. Allocation (in g CO2/s) of Emissions for the Cogeneration and Independent Processes Considered1. Process Emission-allocation method Independent Heating Electricity generation Overall (combined) Cogeneration

Based on exergy content of products Based on energy content of products Allocation of incremental fuel consumption to electrical production2 Allocation of incremental fuel consumption to heat production3 Assuming a reference power plant efficiency of ηpp = 35% Assuming a reference power plant efficiency of ηpp = 40% Based on a shared emission savings between electricity and heat2,3 Assuming a reference power plant efficiency of ηpp = 35% Assuming a reference power plant efficiency of ηpp = 40% Based on economic value of products4 Assuming an electrical-to-thermal cost ratio of cE/cQ = 1.5 Assuming an electrical-to-thermal cost ratio of cE/cQ = 1.8 Assuming an electrical-to-thermal cost ratio of cE/cQ = 2.1

Emission allocation (g CO2/s) To electrical To thermal product product

Total

0

250

250

500

0

500

500

250

750

392 250

108 250

500 500

278

222

500

572

–72

500

500

0

500

360

140

500

346

154

500

300

200

500

322

178

500

339

161

500

1. Reference-environment temperature and pressure are To = 10C and po = 1 bar, respectively. 2. An efficiency of 90% is assumed for the boiler that would have been used in the production of the same amount of heat as produced by the cogeneration system. 3. Efficiencies of 35% and 40% are considered for the power plant that would have been used in the production of the same amount of electricity as produced by the cogeneration system. 4. The parameter cE/cQ denotes the ratio of the economic value of the electricity produced to the economic value of the thermal energy produced

7.2.3. Results and Discussion The results of applying the methods for allocating CO2 of emissions for the cogeneration and independent processes are presented in Tables 9 and 10 and Figures 10 and 11. Percentage breakdowns are shown in Table 9 and Figure 10, while absolute emissions rates are shown in Table 10 and Figure 11. For the independent processes, there exists no ambiguity regarding the allocations of emissions to the thermal and electrical products. For the cogeneration process, the appropriate method to allocate emissions is not clear, so the allocations methods discussed earlier are

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applied. It is observed that the allocations of CO2 emissions vary markedly, depending on the allocation method used. The author contends, as discussed throughout this article, that the exergy-based allocations are the most appropriate. Thus, using the other emissions allocation methods can be very misleading, since the resulting emissions may deviate widely from those obtained using the exergy-based method.

Figure 10. Allocation of emissions (in %) for independent and cogeneration processes considered (based on data in Table 9 and a reference power plant efficiency of 40%).

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75

Some of the problems with the other allocation methods are illustrated in Tables 9 and 10 and Figures 10 and 11. Some examples follow: 

In one case (where the allocation is based on incremental fuel consumption to heat production), the absurd situation exists in which the allocations of emissions to the thermal product are evaluated to be negative and the allocations to the electrical product to exceed 100%. This result is simply a consequence of the flaws in that allocation method and its use of an energy efficiency ηpp for an independent device for providing the same electrical energy as the cogeneration system (e.g., a reference power plant). Here, a value of ηpp = 35% is used. For comparison, an alternate value of ηpp is selected (40%); then the allocations of carbon dioxide emissions to both products do not exceed 100%.

Figure 11. Allocation of emissions (in g CO2/s) for independent and cogeneration processes considered (based on data in Table 10 and a reference power plant efficiency of 40%).

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Marc A. Rosen 

For the allocation method based on economic value of products, the results depend on the value of the ratio of the economic value of the electricity produced cE to the economic value of the thermal energy produced cQ. The value of this ratio, even considering only the present time, varies with location. Here, for illustration only, economic parameter values from a recent U.S. report (Harrell, 2002) are used. With these values, the cost of electricity is approximated as US$0.060/kWh, and the cost of steam as US$0.0334. The electrical-to-thermal cost ratio is then cE/cQ = 1.8. In Tables 9 and 10, therefore, this value is used. Also, values of cE/cQ of 1.5 and 2.1 are used to indicate the sensitivity of the allocations to the cost ratio.

7.3. Illustration of Use of Results to Determine CO2 Emissions Credits for Trading Purposes from Switching to Cogeneration from Equivalent Independent Plants In this section, the case illustrated in section 7.2 is used to illustrate how the results could be used to determine carbon dioxide emission credits that might be used in emissions trading. Here, we consider two energy users, one of electricity and one of thermal energy. The types of thermal energy used are the same as those described in section 7.2. The decrease in CO2 emissions attributable to the energy users are evaluated, when each switches from obtaining the energy required (electricity or thermal energy) from a producer of the just the required energy to a supplier using cogeneration. The decrease in CO2 emissions for each energy user is its CO2 emissions credits. The characteristics of the cogeneration plant and the independent electrical power plant and heating plant are as in section 7.2.

7.3.1. CO2 Emissions Credits when an Electricity User Switches to Cogeneration In this situation, we consider an electrical consumer who normally obtains electricity from a power plant. We wish to determine the decrease in CO2 emissions attributable to that consumer (i.e., the CO2 emissions credit for the consumer) if the consumer switches to obtaining electricity from a supplier that uses a cogeneration plant. We consider a multi-step calculation procedure. For simplicity, we consider a unit energy use by the consumer of 1 GJ of electricity. Parameter values that characterize the technologies considered are drawn from section 7.2 The CO2 emissions attributable to the consumer when obtaining electricity from a power plant can be evaluated as the product of the fuel use in the power plant and the carbon dioxide emissions factor for the fuel. That is, CO2 emissions = (Fuel use in power plant)(Fuel CO2 emissions factor) = (Electricity use/Power plant efficiency)(Fuel CO2 emissions factor) = (1 GJ electricity/0.40 GJ electricity/GJ fuel)(50 kg CO2 /GJ fuel) = 125.0 kg CO2 /GJ electricity

The total CO2 emissions of the cogeneration plant (to produce 1 GJ of electricity as well as thermal energy) can be evaluated as the product of the total fuel use in the cogeneration plant and the carbon dioxide emissions factor for the fuel. That is,

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77

CO2 emissions = (Fuel use in cogeneration plant)(Fuel CO2 emissions factor) = (Electricity use/Cogeneration efficiency for elec.)(Fuel CO2 emissions factor) = (1 GJ electricity/0.40 GJ electricity/GJ fuel)(50 kg CO2 /GJ fuel) = 125.0 kg CO2 /GJ electricity

Figure 12. Carbon dioxide emissions for electricity generation via power plant and cogeneration, and carbon dioxide emissions credit.

Of the total CO2 emissions of the cogeneration plant (to produce 1 GJ of electricity as well as thermal energy), the CO2 emissions attributable to the consumer when obtaining electricity from a cogeneration plant can be evaluated as the fraction of the total CO2 emissions of the cogeneration plant attributed to electricity production. In this article, we have argued that the division of CO2 emissions for cogeneration among electrical and thermal products should be based on the exergy contents of the products. For the present case, it was shown in section 7.2 that 78.4% of the total CO2 emissions for the cogeneration plant should be attributed to the electrical product based on exergy (see Table 9). Thus, the CO2 emissions attributable to the consumer when obtaining electricity from a cogeneration plant can be evaluated as follows: CO2 emissions for user = (Total CO2 emissions of cogeneration plant)(Fraction for elec.) = (125.0 kg CO2 /GJ electricity)(0.784) = 98.0 kg CO2 /GJ electricity Finally, the CO2 emissions credit for switching to cogeneration, evaluated as the decrease in CO2 emissions attributable to the electricity user, can be evaluated as the difference between the CO2 emissions attributable to the consumer when obtaining electricity from a power plant and from a cogeneration plant. That is, CO2 emissions credit =(CO2 emissions for elec. from power plant attributed to consumer) – (CO2 emissions for elec. from cogen. attributed to consumer) = (125 kg CO2 /GJ electricity) – (98.0 kg CO2 /GJ electricity) = 27.0 kg CO2 /GJ electricity

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The results are presented in Table 11 and illustrated in Figure 12, and demonstrate the manner in which they can assist in evaluating CO2 emissions credits for electricity users, for trading and other purposes. Table 11. Carbon Dioxide Emissions and Emissions Credit for Switching to Cogeneration for Electricity and Heat Users*. CO2 emissions (kg) For User of Electricity (1 GJ) CO2 emissions for user of electricity from power plant CO2 emissions for user of electricity from cogeneration plant CO2 emissions credit for user of electricity for switching from power plant to cogeneration plant For User of Heat (1 GJ) CO2 emissions for user of heat from heating plant CO2 emissions for user of heat from cogeneration plant CO2 emissions credit for user of heat for switching from heating plant to cogeneration plant

125.0 98.0 27.0

62.5 27.0 35.5

* Allocation of emissions from cogeneration to electrical and heat products is determined based on exergy contents of products.

7.3.2. CO2 Emissions Credits when a Heat User Switches to Cogeneration In this situation, we consider a heat consumer who normally obtains heat from a heating plant. We wish to determine the decrease in CO2 emissions attributable to that consumer (i.e., the CO2 emissions credit for the consumer) if the consumer switches to obtaining heat from a supplier that uses a cogeneration plant. We consider a multi-step calculation procedure. For simplicity, we consider a unit energy use by the consumer of 1 GJ of thermal energy. The thermal energy used by the consumer is of the type described in section 7.2. Parameter values that characterize the technologies considered are drawn from section 7.2

Figure 13. CO2 emissions for heat production via heating plant and cogeneration, and CO2 emissions credit.

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79

The CO2 emissions attributable to the consumer when obtaining heat from a heating plant can be evaluated as the product of the fuel use in the heating plant and the carbon dioxide emissions factor for the fuel. That is, CO2 emissions = (Fuel use in heating plant)(Fuel CO2 emissions factor) = (Heat use/Heating plant efficiency)(Fuel CO2 emissions factor) = (1 GJ heat/0.80 GJ heat/GJ fuel)(50 kg CO2 /GJ fuel) = 62.5 kg CO2 /GJ heat The total CO2 emissions of the cogeneration plant (to produce 1 GJ of heat as well as electrical energy) can be evaluated as the product of the total fuel use in the cogeneration plant and the carbon dioxide emissions factor for the fuel. That is, CO2 emissions = (Fuel use in cogeneration plant)(Fuel CO2 emissions factor) = (Electricity use/Cogeneration efficiency for heat)(Fuel CO2 emissions factor) = (1 GJ heat/0.40 GJ heat/GJ fuel)(50 kg CO2 /GJ fuel) = 125.0 kg CO2 /GJ heat Of the total CO2 emissions of the cogeneration plant (to produce 1 GJ of heat as well as electrical energy), the CO2 emissions attributable to the consumer when obtaining heat from a cogeneration plant can be evaluated as the fraction of the total CO2 emissions of the cogeneration plant attributed to heat production. In this article, we have argued that the division of CO2 emissions for cogeneration among electrical and thermal products should be based on the exergy contents of the products. For the present case, it was shown in section 7.2 that 21.6% of the total CO2 emissions for the cogeneration plant should be attributed to the thermal product based on exergy (see Table 9). Thus, the CO2 emissions attributable to the consumer when obtaining heat from a cogeneration plant can be evaluated as follows: CO2 emissions for user = (Total CO2 emissions of cogeneration plant)(Fraction for heat) = (125.0 kg CO2 /GJ heat)(0.216) = 27.0 kg CO2 /GJ heat Finally, the CO2 emissions credit for switching to cogeneration, evaluated as the decrease in CO2 emissions attributable to the heat user, can be evaluated as the difference between the CO2 emissions attributable to the consumer when obtaining heat from a power plant and from a cogeneration plant. That is, CO2 emissions credit =(CO2 emissions for heat from heating plant attributed to consumer) – (CO2 emissions for heat from cogeneration attributed to consumer) = (62.5 kg CO2 /GJ heat) – (27.0 kg CO2 /GJ heat) = 35.5 kg CO2 /GJ heat The results are presented in Table 11 and illustrated in Figure 13, and demonstrate the manner in which they can assist in evaluating CO2 emissions credits for thermal energy users, for trading and other purposes.

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7.3.3. CO2 Emissions Credits for Other Cases The procedures illustrated in the previous two subsections can be formalized for variations of the cases considered here, as well as for various other cases. Some of the other situations that could be considered include on- and off-site plants, different fuels, different thermal energy requirements and trigeneration systems.

8. CONCLUSIONS The exergy-based method of carbon dioxide emissions allocation allows for rational and meaningful allocations of such emissions for cogeneration, and is superior to other methods. By permitting carbon dioxide emissions to be allocated more appropriately among the different commodities generated in cogeneration, the results allow the environmental benefits of technologies that produce multiple products to be better understood and exploited. These results should therefore allow the more beneficial among competing technologies to be identified in a rational and meaningful manner. The results also indicate that the exergy-based emissions allocations method provides a sensible basis for a meaningful overall approach for emissions trading. Indirectly, due to the analogy between cost and emissions allocations, the results may also lead to economic benefits, as the results should permit the costs associated with cogeneration technologies to be more appropriately allocated among the different commodities generated. The results consequently indicate that the exergy-based method should be used in allocating carbon dioxide emissions for cogeneration devices. Using the exergy-based method would help ensure proper decision-making regarding issues such as    

how emissions should be reduced in a given device, how and where cogeneration technologies should be used, what effect introducing cogeneration will have on overall carbon dioxide emissions, and a fair way to establish detailed schemes for emissions trading.

The results presented in this article should be of benefit to designers of energy systems, and to decision and policy makers in companies and government. If the results are used appropriately, they should allow benefits to accrue to society through the selection and design of better energy technologies, based on environmental considerations. The results may also be useful as input to the regulations developed in Europe for defining and assessing the benefits of cogeneration (European Parliament, 2004; CEN/CENELEC, 2004). In particular, the incorporation of exergy into these regulations would likely improve them markedly, both in general and in particular for allocating emissions. To advance this approach, research is recommended in a number of related areas. First, the work should be expanded from cogeneration to trigeneration (where the products are electricity, heat and cold), and systems that generate multiple products of other types. Also, the exergy-based allocation method needs to be applied with more detailed process (e.g. hourly data for a plant over a year, rather than annual average data). Third, detailed methodologies for emissions trading should be developed that utilize overall exergy-based

Rational Attribution of Environmental Emissions of Cogeneration to Products

81

emissions allocations approach. Finally, the analogy between allocating carbon dioxide emissions and economic costs for cogeneration should be investigated further, with the aim of discovering insights that allow the allocation of costs or carbon dioxide emissions to be more appropriately carried out and better understood.

ACKNOWLEDGMENTS The support provided by the Oil, Gas and Energy Branch of Environment Canada is gratefully acknowledged. The author is especially grateful for the assistance provided by Manfred Klein, formerly at that branch of Environment Canada and now affiliated with the Gas Turbine Laboratory, Institute for Aerospace Research, National Research Council Canada.

NOMENCLATURE cE cQ C CE CQ E ExE ExFE ExFQ ExQ fE fQ F FE FQ Q T To

unit economic value of electrical product of cogeneration unit economic value of thermal product of cogeneration total CO2 emissions from cogeneration CO2 emissions associated with electrical energy produced via cogeneration CO2 emissions associated with thermal energy product produced via cogeneration net output of electrical energy from cogeneration net output of electrical exergy from cogeneration fuel exergy consumption associated with generating electricity via cogeneration fuel exergy consumption associated with producing thermal exergy via cogeneration net output of thermal exergy from cogeneration fraction of cogeneration emissions allocated to electrical product fraction of cogeneration emissions allocated to thermal product total primary fuel energy consumed by cogeneration system fuel consumption attributed to electricity generation fuel consumption attributed to production of thermal energy net output of thermal energy from cogeneration temperature temperature of reference environment

GREEK SYMBOLS φ ηb ηE ηQ

CO2 emission coefficient for a fuel energy efficiency of independent device (e.g., boiler) for thermal energy energy efficiency of generating electrical energy via cogeneration energy efficiency of producing thermal energy via cogeneration

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Marc A. Rosen ηpp ψE ψQ τ

energy efficiency of independent device (e.g., power plant) for electrical energy exergy efficiency of generating electricity via cogeneration exergy efficiency of producing thermal energy product via cogeneration exergetic temperature factor

REFERENCES [1] Acres International Limited (1987). Cogeneration Potential in Ontario and Barriers to its Development, Report for Ontario Ministry of Energy, Toronto. [2] Ayres, R. U., Ayres, L. W. and Martinas, K. (1998). Exergy, waste accounting, and lifecycle analysis. Energy 23, 355-363. [3] Berthiaume, R., Bouchard, C. and Rosen, M. A. (2001). Exergetic evaluation of the renewability of a biofuel. Exergy, An Int. J. 1, 256-268. [4] CEN/CENELEC (2004). Workshop Agreement Manual for Determination of Combined Heat and Power (CHP), CWA 45547, European Committee for Standardization (CEN) and European Committee for Electrotechnical Standardization (CENELEC), Brussels. [5] Consumers Gas (1995, estimated). Cogeneration at the University of Toronto. Information sheet. [6] Connelly, L. and Koshland, C. P. (1997). Two aspects of consumption: using an exergybased measure of degradation to advance the theory and implementation of industrial ecology. Resources, Conservation and Recycling 19, 199-217. [7] Cownden, R., Nahon, M. and Rosen, M. A. (2001). Exergy analysis of a fuel cell power system for transportation applications. Exergy, An Int. J. 1, 112-121. [8] Crane, P., Scott, D. S. and Rosen, M. A. (1992). Comparison of exergy of emissions from two energy conversion technologies, considering potential for environmental impact. Int. J. Hydrogen Energy 17, 345-350. [9] Creyts, J. C. and Carey, V. P. (1997). Use of extended exergy analysis as a tool for assessment of the environmental impact of industrial processes. Proc. ASME Advanced Energy Systems Division, ed. M.L. Ramalingam, ASME, New York, AES-Vol. 37, 129137. [10] Daniel, J. J. and Rosen, M. A. (2002). Exergy-based environmental assessment of life cycle emissions for various automobiles and fuels. Proc. CSME Forum 2002, 21-24 May, Kingston, Ontario, Sec. 20, Paper 4, pp. 1-14. [11] Dincer, I. and Rosen, M. A. (2007). Exergy: Energy, Environment and Sustainable Development, Elsevier, Oxford, UK. [12] Edgerton, R. H. (1982). Available Energy and Environmental Economics, D.C. Heath, Toronto. [13] European Parliament (2004). Directive 2004/8/EC of the European Parliament and of the Council of 11 February 2004 on the Promotion of Cogeneration Based on a Useful Heat Demand in the Internal Energy Market and Amending Directive 92/42/EEC, Official Journal of the European Union (L52) 47, 50-60. [14] FVB/Eltec (1993). Potential Heat Production from Existing and Future Electric Generating Plants, Report No. 9102-G-806 for Canadian Electrical Association.

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[15] Gunnewiek, L. H. and Rosen, M. A. (1998). Relation between the exergy of waste emissions and measures of environmental impact. Int. J. Environment and Pollution 10, 261-272. [16] Harrell, G. (2002). Steam System Survey Guide, Report ORNL/TM-2001/263 for Oak Ridge National Laboratory. [17] Hart, D. R. and Rosen, M. A. (1994). Environmental and health benefits of utility-based cogeneration in Ontario, Canada. Energy and Environment 5, 363-378. [18] Henneforth, J. C. and Todd, D. M. (1988, August). Cogeneration on a large scale. Mechanical Engineering 110, 51-53. [19] Hevert, H. W. and Hevert, S. C. (1980). Second law analysis: an alternative indicator of system efficiency, Energy-The International Journal 5, 865-873. [20] Horlock, J. H. (1987). Some practical CHP schemes. Chapter 5 of Cogeneration: Combined Heat and Power (CHP), Pergamon, Oxford, England, pp. 158-174. [21] Klein, M. (1999a). The need for standards to promote low emission, high efficiency gas turbine facilities. Paper 99-GT-405, presented at the ASME International Gas Turbine and Aeroengine Congress and Exhibition, Indianapolis, Indiana, 7-10 June, pp. 1-10. [22] Klein, M. (1999b). Full fuel cycle emissions estimations. Paper 99-IAGT-402, presented at the 13th Symposium on Industrial Applications of Gas Turbines, Banff, Alberta, 13-15 October, pp. 1-22. [23] Klein, M. (1999c, estimated). Brief Descriptions of Commercial and Institutional CHP Systems in Canada. Report by Oil, Gas and Energy Branch, Environment Canada. [24] Klein, M. (1999d). Canadian Gas Turbine Cogeneration Plants. Report by Oil, Gas and Energy Branch, Environment Canada. [25] Klein, M. (2001a). High efficiency combined heat and power facilities: benefits and barriers. Proceedings of the Canadian Technology Development Conference, Toronto, pp. 1-20. [26] Klein, M. (2001b). Cogeneration and district energy in Canada, Cogeneration and OnSite Power Production, March-April, Vol. 2, No. 2. [27] Kotas, T.J. (1995). The Exergy Method of Thermal Plant Analysis, reprint edition, Krieger, Malabar, Florida. [28] MacLaren Engineers Inc. (1988). Cogeneration Sourcebook, Report for Ontario Ministry of Energy, Toronto. [29] MacRae, K.M. (1992). Realizing the Benefits of Community Integrated Energy Systems, Canadian Energy Research Institute, Calgary, Alberta. [30] Moran, M.J. (1989). Availability Analysis: A Guide to Efficient Energy Use, Revised Ed., ASME, New York. [31] Moran, M.J. and Sciubba, E. (1994). Exergy analysis: principles and practice. J. Engineering for Gas Turbines and Power 116, 285-290. [32] Moran, M.J. and Shapiro, H.N. (2007). Fundamentals of Engineering Thermodynamics, 6th ed., Wiley, New York. [33] Phylipsen, G.J.M., Blok, K. and Worrell, E. (1998). Handbook on International Comparisons of Energy Efficiency in the Manufacturing Industry. Department of Science, Technology and Society, Utrecht University, the Netherlands. [34] Rogner, H.-H. (1993). Clean energy services without pain: district energy systems. Energy Studies Review 5, 114-120.

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[35] Rosen, M.A. (1990). Comparison based on energy and exergy analyses of the potential cogeneration efficiencies for fuel cells and other electricity generation devices. Int. J. Hydrogen Energy 15, 267-274. [36] Rosen, M.A. (1992). Evaluation of energy utilization efficiency in Canada using energy and exergy analyses. Energy-The International Journal 17, 339-350. [37] Rosen, M.A. (1993). Energy utilization efficiency in a macrosystem (Ontario): evaluation and improvement through cogeneration. Proc. Int. Symp. CO2 Fixation and Efficient Utilization of Energy, 29 Nov.-1 Dec., Tokyo, pp. 17-26. [38] Rosen, M.A. (1994). Assessment of various scenarios for utility-based cogeneration in Ontario. Energy-The International Journal 19, 1143-1149. [39] Rosen, M.A. (1996). Thermodynamic investigation and comparison of selected production processes for hydrogen and hydrogen-derived fuels. Energy-The International Journal 21, 1079-1094. [40] Rosen, M.A. (1998). Reductions in energy use and environmental emissions achievable with utility-based cogeneration: simplified illustrations for Ontario. Applied Energy 61, 163-174. [41] Rosen, M.A. (1999). Second law analysis: approaches and implications. Int. J. Energy Research 23, 415-429. [42] Rosen, M.A. (2000). Thermodynamic comparison of coal-fired and nuclear electrical generating stations. Trans. Can. Soc. Mech. Eng. 24 (1B), 273-283. [43] Rosen, M.A. and Dincer, I. (1997). On exergy and environmental impact. Int. J. Energy Research 21, 643-654. [44] Rosen, M.A. and Dincer, I. (1999). Exergy analysis of waste emissions. Int. J. Energy Research 23, 1153-1163. [45] Rosen, M.A. and Dincer, I. (2001). Exergy as the confluence of energy, environment and sustainable development. Exergy, An Int. J. 1, 3-13. [46] Rosen, M.A. and Dincer, I. (2002). Energy and exergy analyses of thermal energy storage systems. Chapter 10 of Thermal Energy Storage Systems and Applications, Wiley, London, pp. 411-510. [47] Rosen, M.A. and Horazak, D.A. (1995). Energy and exergy analyses of PFBC power plants. Chapter 11 of Pressurized Fluidized Bed Combustion, ed. M. Alvarez Cuenca and E.J. Anthony, Chapman and Hall, London, England, pp. 419-448. [48] Rosen, M.A. and Le, M. (1994). Assessment of the potential cumulative benefits of applying utility-based cogeneration in Ontario. Energy Studies Review 6, 154-163. [49] Rosen, M.A. and Le, M. (1996). Efficiency analysis of a process design integrating cogeneration and district energy. Proc. ASME Advanced Energy Systems Division, AESVol. 36, ed. A.B. Duncan, J. Fiszdon, D. O‘Neal and K. Den Braven, ASME, New York, pp. 473-480. [50] Rosen, M.A., Le, M.N. and Dimitriu, J. (1997). Efficiency improvement for large energy systems through utility-based cogeneration and district energy: investigation for Ontario, Canada. World Energy System: An International Journal 1, 56-63. [51] Sato, N. (2005). Chemical Energy and Exergy: An Introduction to Chemical Thermodynamics for Engineers, Elsevier, Oxford, UK. [52] Sciubba, E. (1999). Exergy as a direct measure of environmental impact. Proc. ASME Advanced Energy Systems Division, ed. S.M. Aceves et al., AES-Vol. 39, 573-581.

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[53] Sciubba, E. (2004). From engineering economics to extended exergy accounting: A possible path from monetary to resource-based costing. Journal of Industrial Ecology 8(4), 19-40. [54] Sherwood, M. and Rosen, M.A. (1996). Efficiency comparison of several alternatives for cogeneration-based district heating and cooling. Proc. Symp. on Thermal and Fluids Engineering at the CSME Forum, 7-9 May, Hamilton, Ontario, pp. 293-298. [55] Simpson, J. and Rosen, M.A. (1996). District energy and cogeneration systems: modelling, simulation and analysis. Proc. Symp. on Thermal and Fluids Engineering at the CSME Forum, 7-9 May, Hamilton, Ontario, pp. 275-282. [56] Strickland, C. and Nyboer, J. (2002a). Cogeneration Potential in Canada: Phase 2. Report for Natural Resources Canada, by MK Jaccard and Associates. [57] Strickland, C. and Nyboer, J. (2002b). A Review of Existing Cogeneration Facilities in Canada. Report by Canadian Industrial Energy End-Use Data and Analysis Center, Simon Fraser University. [58] Szargut, J. (1980). International progress in second law analysis, Energy 5, 709-718. [59] Szargut, J. (2005). Exergy Method: Technical and Ecological Applications, WIT Press, Southampton, UK. [60] Szargut, J., Morris, D.R. and Steward, F.R. (1988). Exergy Analysis of Thermal, Chemical and Metallurgical Processes, Hemisphere, New York. [61] Upton, B. (2001). Letter of 16 November 2001 to P. Bhatia, World Resources Institute, Washington, DC, from B. Upton, Senior Research Engineer, National Council for Air and Stream Improvement, Inc., West Coast Regional Center, Corvallis, OR. [62] Verbruggen, A. (2007a). What's needed next to refine the EU directive on cogeneration regulation. The Electricity Journal 20(2), 63-70. [63] Verbruggen, A. (2007b). Quantifying combined heat and power (CHP) activity, Int. J. Energy Tech. and Policy 5(1), 17-35. [64] Wiggin, M. (1997, estimated). Cornwall, Ontario District Heating System. Information sheet, CANMET Energy Technology Centre, Natural Resources Canada.

In: Advances in Energy Research. Volume 4 Editor: Morena J. Acosta, pp. 87-95

ISBN: 978-1-61761-672-3 © 2011 Nova Science Publishers, Inc.

Chapter 4

A NEW TECHNIQUE FOR BIOLOGICAL MONITORING USING WILDLIFE Mariko Mochizuki1, Makoto Mori2, Mutsumi Miura1, Ryo Hondo3, Takashi Ogawa1 and Fukiko Ueda3, 1

Department of Applied Science, School of Veterinary Nursing and Technology, Nippon Veterinary and Life Science University, 1-7-1 Kyounan, Musashino, Tokyo 180-8602, Japan 2 Department of Applied Biological Chemistry, Faculty of Agriculture, Shizuoka University, Shizuoka 422-8529, Japan 3 Laboratory of Veterinary Public Health, School of Veterinary Medicine, Nippon Veterinary and Life Science University, 1-7-1 Kyounan, Musashino, Tokyo 180-8602, Japan

ABSTRACT Since data obtained from wildlife are useful for the evaluation of risks to human health, importance of biological monitoring has been pointed out in many studies. However, it is fact that there are many problems on the biological monitoring using wildlife. For example, the outliers were often observed on the data obtained from wildlife. Although the outliers could be excluded by statistical data processing in studies of experimental animals, the outliers may indicate potential contamination of animals in studies of wildlife. In the present study, 80 wild ducks were investigated, and the cadmium (Cd) contents of kidney and that of liver were ND-67.44, ND-21.15 μg/g dry weight respectively. Since the outlier has been observed in several species, such as spotbilled duck, mallard, we analyzed those outliers using cadmium standard regression line (CSRL). In our previous reports, the CSRL was suggested as a useful index for the understanding of Cd contamination of animals. In conclusion, it was suggested that biological monitoring using the CSRL can make full use of the characteristics of all data, including outliers.

Keywords: Biological Monitoring, Cadmium, ICP-AES, Wildlife. 

E-mail address: [email protected], Tel:+81-422-31-4151, Fax: +81-422-33-2094. (Corresponding author)

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INTRODUCTION Data obtained from wildlife are useful for the evaluation of risks to human health, including those to the next generation. In this study, various environmental pollutants were investigated using samples from wildlife. We have previously investigated the degree of contamination with toxic elements, such as cadmium (Cd), chromium (Cr), molybdenum (Mo), thallium (Tl) and vanadium (V), in kidney and liver samples obtained from wild birds (Mochizuki et al., 1998, Mochizuki et al., 1999, Mochizuki et al., 2002 a,b, Mochizuki et al., 2005, Ueda et al., 1998). Studies that use wildlife are prone to problems (Krimsky, 2000), although the importance of biological monitoring has been pointed out in many studies that have investigated environmental pollution (Colborn et al.,1996). It is known that the levels of several elements, such as Cd, nickel (Ni) and selenium (Se), increase and decrease depending on the age of the animal (Elinder et al.,1981, Sakurai,1996), and detailed analysis of the age of wildlife specimens is usually difficult. Another problem is that it is difficult to draw inferences from the degree of pollution of the habitat of wildlife such as migratory birds. Table 1. The wild birds used in the present study. The sample from wood duck was obtained from a zoo in Japan.

Carnivores are frequently used for studies involving wildlife because they are positioned at the top of the food chain. The greater scaup (Aythya marila) is generally classified as a carnivorous bird that eats animals such as shellfish. However, it is known that this bird also uses feed of vegetable origin, depending on the environments in which it rests during migration. The often narrow classification of feeding habits is a daunting problem for studies

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of wildlife. To obtain a detailed understanding of the actual migratory flight path and the degree of contamination of the environment inhabited by migratory species is even more difficult. Thus, the data obtained from wildlife are usually distributed over a wide range, and outliers are often obtained. We investigated these problems using the data obtained in our studies of wildlife, and suggest the possibility of a new index for biological monitoring. This study is the same in content in our previous study in a book published by NOVA Science Puclisher (Mochizuki et al.,2009).

MATERIALS AND METHODS Samples from Wild Birds A total of 80 wild ducks were used in the present study (Table 1). Most of ducks were captured between 1993 and 1995, for another National legal investigative project being conducted by the Japanese Ministry of the Environment. Other birds were supplied through the Gyotoku Bird Observatory. The samples were put into Pyrex tubes, dried, weighted, and digested. Cd contents of organs were analyzed using an inductively coupled plasma emission spectrometry (ICP-AES, Spectro A.I./Germany). The condition of instrument, sample preparation methods were also described in our previous reports in detail (Mochizuki et al., 1999, 2002 a,b,c, 2005 ).

Statistic Analysis The data were analyzed using Lotus 2001(Lotus Development Corporation), Excel 2003 (Microsoft Corporation) and JMP 7 (SAS Institute Japan). Table 2. The Cd content (μg/g dry wt.) in kidney and liver of 80 wild birds. ND: not detectable data, a); ND was replaced by zero, b); the results except ND.

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RESULTS AND DISCUSSION The Cd content of kidney and liver samples was not detection (ND)-67.44 and ND-21.15 μg/g dry weight (wt.), respectively. The data obtained from dabbling and diving ducks had a wide distribution (Table 2). Previous studies of biological monitoring using wildlife have performed comparisons using mean values, and the comparisons have been made among different species. It is difficult to compare data from different species because the distributions of the data varied greatly with species, as shown in Figure 1 a, b. The data obtained in our studies show that biological monitoring using the comparison only of mean values is not appropriate.

(a)

(b) Figure 1. The distribution of Cd content (μg/g dry wt.) in kidney (Figure 1 –a ) and liver (Figure 1-b) of each species. Dabbling ducks, a: Spot-billed duck, b: Eurasian wigeon, c: Northern pintail, d: Mallard, e: Common teal, f: Northern shoveler, g: Gadwall, h: Gargancy, i: Wood duck, Diving ducks, j: Greater scaup, k: Tufted duck, l: Common pochard, m: Common scoter, □: Mean value, ●: Median.

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The presence of outliers was observed in our study, as shown in Table 2. The outliers may be excluded by statistical data processing in studies that use experimental animals. However, outliers should be not excluded in studies of wildlife because the outliers may indicate potential contamination of the animals. Various problems in the measurement of Cd contamination of animal specimens have been solved using a new index, the cadmium standard regression line (CSRL) (Mochizuki et al., 2008, 2009a, b). The degree of oil contamination in diving ducks was analyzed using CSRL in a previous study (Mochizuki et al., 2009b). In that study, acute Cd poisoning of oiled diving ducks was clearly demonstrated, although the degree of Cd contamination was not made clear by the comparison of mean vales.

Figure 2. The relationship between the Cd contents of kidney and liver based on 101 data points from different wildlife (original data, Mochizuki et al., 2008 a). Filled triangles: land birds and waterfowl; empty triangles: seabirds; empty squares: terrestrial mammals; filled squares: marine mammals.

The 101 points obtained from previous publications that reported Cd levels in wildlife as arithmetic means were plotted on a graph and a straight line (the CSRL) was obtained, as shown in Figure 2. After logarithmic transformation, the parameters of the CSRL were: log10(Y)=0.900 log10(X)-0.580, R2 =0.944, p<0.01). The regression line obtained was thought to be an indicator of non-polluted animals, because any contamination of the wildlife was not indicated by this analysis. The CSRL was compared with data obtained from polluted animals of various species, including humans (Mochizuki et al., 2008, 2009a,b) (Figure 3 & 4). Data from rats were used for the model of acute Cd poisoning, and data from polluted humans and monkeys were used for the model of chronic Cd poisoning. The monkeys were poisoned by a low concentration of Cd in their drinking water over several years (Otaki and Kimura,1992), and the rats were administrated 0.1, 1 or 2 mM CdCl22 over a 2-hr period at a diminishing rate by infusion into a vein and then perfusion of organs (Mochizuki et al., 2008 ). Data from patients with Itai-itai disease and humans living in a polluted area (Friberg et al., 1974,

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Kuzuhara et al., 1992, Yamada et al., 1992) were also compared with the CSRL. Although data from humans living in non-polluted areas (Bem et al., 1993, Piotrowski et al., 1996, Takács and Tatár 1987, Teranishi et al., 1999) still fitted the CSRL, the data from Cd contaminated humans did not fit the regression line. In contrast, interesting information was obtained when data from experimental animals were compared with the CSRL regression line. The data from rats were positioned on the upper part of the CSRL, and those from monkeys were located at the bottom section of the regression line. These results suggest that data from cases of acute Cd poisoning are located on the upper part of the CSRL regression line, as a result of the relatively high Cd content of the liver in such cases. It is known that the distribution of Cd in various organs depends on the number of doses, the dose applied and the period during which Cd is administered. A higher Cd level in the kidney has been reported in animals in the early stage of Cd contamination. It is known that the Cd content of the liver gradually decreases, while the Cd content of the kidney is increased. In the final stages, the Cd content of the liver becomes higher than that of the kidney because Cd accumulation in the kidney ceases as a result of renal lesions. The position of the data from humans exposed to pollution on the regression line may indicate that they were in the final stages of Cd poisoning.

Figure 3. The relation between the CSRL and the values obtained from experimental animals and wild birds. Empty circles: 101 data points from wildlife; filled squares: data from rats; empty triangles: data from monkeys; filled squares; outliers from wild birds

We have previously stressed the importance of outliers in studies involving wildlife; therefore the significance of outliers was analyzed using the CSRL. The outliers obtained from the analysis of 80 wild ducks were compared with the CSRL, as shown in Figure 3 & 4. The Cd content of Kidney or that of liver, whichever was ND were excluded from this analysis. Although two data points from the outliers obtained from wild ducks fitted on to the CSRL, the others divided from the regression line. The results obtained from experimental

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animals and those from wild birds showed different characteristics, as shown in Figure 3. However, the distribution of outliers from wild birds (after log transformation: Y=0.35X+3.04, Y=log(y), X=log(x)) was similar to that of the data from humans living in a polluted area (after log transformation: Y=-0.30X+1.32 Y=log(y), X=log(x)) (Figure 4). There was no significant difference between the slopes of the outlier data and those obtained from humans exposed to pollution (p<0.01). The outliers consisted of data from spot-billed ducks, mallard, Eurasian wigeon, gadwall and northern shoveler ducks. The spot-billed duck is a residential bird in Japan and this species can be observed throughout the year, although the other ducks used in the present study have breeding areas outside Japan (Brazil, 1991). It has recently been pointed out that many mallard breed in Japan, although mallard is also classified as a winter visitor. Higher Cd contents, from a global perspective, have been reported in various environmental samples from Japan, including soil (Asami, 2001), air (Friberg et al., 1974), stream water (WHO, 1992), and lake water (WHO, 1992). The higher Cd content and outliers observed in spot-billed ducks and mallrad may indicate contamination of the environment in Japan. This result is supported by reports that describe high Cd levels in Japanese agricultural products and in the organs of Japanese human (Asami,2001, Friberg et al., 1974, WHO, 1992).

Figure 4. The relation between the CSRL and the values obtained from humans and wild birds. Empty circles: 101 data points from wildlife; filled squares: data from humans (not contaminated); filled triangles: data from patients with itai-itai disease and humans living in polluted areas; filled squares: outliers from wild birds.

In conclusion, we suggest that biological monitoring using the CSRL can make full use of the characteristics of all data, including outliers. Therefore, we propose that this index will be useful for studies that involve the biological monitoring of wildlife.

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ACKNOWLEDGMENTS The authors express their thanks to Mr.H. Kobayashi of Japanese Ministry of the Environment, and Mr.S. Hasuo, Mr. T. Sato of Gyoutoku Bird Observatory for the supply of wild birds. This study was supply by grant 13660328 in 2001-2003, grant 205803440001(2008-)from the Japanese Ministry of Education.

REFERENCES Asami, T (2001). Toxic metal pollution in soil in Japanese soil, AGNE Gijyutu Center, Tokyo, pp3-174. (in Japanese). Brazil, M. A. (1991). The birds of Japan. Christopher Helm, A&C Black, London. Bem, E. M., Kaszper, B. W., Orlowski, C., Piotrowski, J. K., Wojcik, G. and Zolnowska, E.(1993). Cadmium, zinc, copper and metallothionein levels in the kidney and liver of humans from central Poland. Environ Monitor Assess, 25, 1-13. Colborn, T., Dumanoskim, D. and Myersm, J. P. (1996). Our stolen future. trans. into Japanese: Shoeisya, Japanese translation rights arranged with Colborn T, Dumanoski D, Myers JP c/o The Spieler Agency, New York through Tuttle-Mori Agency, Inc., Tokyo. Elinder, C. G., Jonsson, L., Piscator, M. and Rahnster, B. (1981). Histopathological changes in relation to cadmium concentration in horse kidneys. Environ Res, 26, 1-22. Friberg, L., Piscator, M., Nordberg, G. F. and Kjellström, T. (1974). Cadmium in the environment, 2 nd ed. CRC press, Ohio, pp1-400 (trans. into Japanese: Ishiyaku Publisher) Kuzuhara, Y., Sano, K., Hayashi, C. and Kitanura, S. (1992). The concentration of heavy metals in autopsy samples: humans lived in cadmium polluted and non-polluted areas, In: Japanese Society of Public Health,editor, Kankyo Hoken Reports No 59, Japanese Society of Public Health, Tokyo, pp 154-155. (in Japanese) Krimsky, S. (2000). Hormonal chaos, trans. into Japanese: Fujiwara shoten, the translation published by arrangement with the Johns Hopkins University Press through The English Agency（Japan）Ltd. Mochizuki, M., Hondo, R., Kumon, K., Sasaki, R., Matsuba, H. and Ueda, F. (2002a). Cadmium contamination in wild birds as an indicator of environmental pollution. Environ Monit Assess, 73, 229-235. Mochizuki, M., Hondo, R. and Ueda, F. (2002b). Simultaneous analysis for multiple heavy metals in contaminated biological samples. Biol Trace Elem Res, 87, 211-23 Mochizuki, M., Mori, M., Akinaga, M., Yugami K., Oya, C., Hondo, R. and Ueda, F.(2005). Thallium contamination in wild ducks in Japan. J Wildl Dis, 41, 664-668. Mochizuki, M., Mori, M., Hondo, R. and Ueda, F. (2008). A new index for evaluation of cadmium pollution in birds and mammals. Environ Monit Assess, 137, 35-49. Mochizuki, M., Mori, M., Hondo, R. and Ueda, F. (2009a). Biological monitoring using a new technique, in: JD Harris and PL Brown (eds), Wildlife: destruction, conservation and biodiversity, Nova Science Publishers, Inc. pp.293-300. Mochizuki, M., Mori, M., Hondo, R. and Ueda, F. (2009b). ―A cadmium standard regression line‖ A possible new index for biological monitoring, in: Ahmed El Nemr (eds), New

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Developments in Environmental Pollution and Climate Change, Nova Scinece Publishers, Inc.(printing) Mochizuki, M., Sasaki R, Yamashita Y, Akinaga M, Anan N, Sasaki S, Hondo, R., Ueda, F. (2002c). The distribution of molybdenum in the tissues of wild ducks. Environ Monit Assess, 77, 155-61. Mochizuki, M., Ueda, F., Hondo, R. (1998). Vanadium contents in organs of wild birds. J Trace Elem Exp Med, 11, 431. Mochizuki, M., Ueda, F., Sasaki S, Hondo, R. (1999). Vanadium contamination and the relation between vanadium and other elements in wild birds. Environ Pollut, 106, 249-51. Otaki N, Kimura M (1992). Experimental studies on the chronic effect of cadmium - 5. The analysis of heavy metals and specific protein, in: Japanese Society of Public Health (eds), Kankyo Hoken Reports No 59, Japanese Society of Public Health, Tokyo, pp. 34-42. (in Japanese) Piotrowski JK, Orlowski C, Bem EM, Brys M, Baran E (1996). The monitoring of cadmium, zinc and copper in the kidneys and liver of humans deceased in the region of Cracow (Poland). Environ Monitor Assess, 43, 227-236. Sakurai H (1997). Why is the metal necessary for the biological body? Kodansha Ltd, Tokyo (in Japanese). Takács S, Tatár A (1987). Trace elements in the environment and in human organs. Environ Res, 42,312-320. Teranishi A, Ninomiya R, Koizumi N (1999). Relationship of metallothionein to cadmium and to zinc in human liver and kidney. in: C. Klaassen, editor. Metallothionein Ⅱ. Birkhäuser Verlag, Basel, pp. 485-488. Ueda, F., Mochizuki, M., Hondo, R. (1998). Cadmium contamination in liver and kidney in Japanese wild birds. J Trace Elem Exp Med, 11, 258. Yamada Y, Honda R, Tsuritani I, Ishizaki M, Kido T, Nogawa K (1992). Exposure for environmental cadmium and calcium concentration in human organs, in, Japanese Society of Public Health ,editor, Kankyo Hoken Reports No 59. Japanese Society of Public Health, Tokyo, pp127-130. (in Japanese) WHO (1992). Environmental health criteria 134 cadmium. http://www.inchem.org/documents/ehc/ehc/ehc134.htm.

In: Advances in Energy Research. Volume 4 Editor: Morena J. Acosta, pp. 97-107

ISBN: 978-1-61761-672-3 © 2011 Nova Science Publishers, Inc.

Chapter 5

SECOND LAW BASED METHODS FOR IMPROVEMENT OF ENERGY SYSTEMS – ECONOMICS AND ENVIRONMENTAL IMPACTS: A BRIEF OVERVIEW Sudipta De* Mechanical Engineering Department Jadavpur University, Kolkata: 700032, India

ABSTRACT Second law of thermodynamics is a fundamental law of nature and the concept can be utilized for better performance of energy systems. The entropy generation in any real (i.e., irreversible) process is a measure of the irreversibility of that process. Exergy concept includes the combined effect of a system and environment to measure the maximum possible work potential as the system reaches equilibrium with the environment from its initial state. In this article, a brief overview of different methods based on the principles of second law of thermodynamics in design and analysis of energy systems is discussed. The concept of entropy generation and exergy destruction in real-life processes are combined with economics and the overall impact on the environment during the life-cycle of a system to obtain more useful conclusions. Starting from entropy generation minimization principle (EGMP), exergy analysis, thermoeconomics (exergoeconomics) and exergetic life cycle analysis has been discussed. Some discussions on future trends of application of second law concept are also included.

Keywords: 2nd law of thermodynamics, EGMM, Exergy Analysis, Exergoeconomics, ELCA

1. INTRODUCTION The subject of thermodynamics is developed and is still growing based on the observations of natural facts. Of course, the subject is matured by the input of analytical *

E-mail address: [email protected]. (Corresponding author)

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minds of great thinkers over the ages. As expected in any live subject, what was accepted as facts sometimes was proved to be false later, viz., calorific concept of heat. After these transition phases of the subject of thermodynamics, pioneers of this field were successful to conclude the basics of the subject into three fundamental laws, called 1st, 2nd and 3rd law of thermodynamics. Observation of no violation of these laws in nature is the only proof of these laws. However, to organize these basic facts of nature into three laws, especially for second law, some theoretical concepts, that do not at all exist in real life had to be introduced. We know that though ‗reversible process‘ never exists in reality, this abstract concept is useful to fulfill the practical need of estimating the asymptotic limits of maximum possible ‗efficient‘ operation in our material world. Introduction of such abstractness may have caused problems for many students for understanding of the subject as beginners. However, this may be also the prime source of love for this subject in their later life. The main driving force for the development of the subject was to explore and organize the natural facts related to the mutual conversion of heat and work; two most fundamental forms of useful energy for human civilization. People of this subject always looked for more ‗efficient‘ or ‗maximum‘ possible energy conversion. However, it was realized that though energy must be conserved (i.e., 1st law) during its conversion, its full conversion from one form to another would not be possible at all (i.e., 2nd law). Thus it was realized that though different forms of energy were essentially same, there exists different grades for these, which is very crucial during conversion from one form to another. With the realization of this fact, there were sincere drives to estimate the maximum possible high grade form of energy, say work, from an existing system. It was realized that this ‗maximum possible‘ depends not only on the condition (i.e., state) of the system but also on its ‗surroundings‘ or ‗environment‘. The concept was realized partially or to a great extent by many great thinkers, though it took several years to develop the rigorous mathematical formulation of this generalized concept and this is still expanding to include broader perspectives (Bejan, 1996). Thus ‗Die grösste Nutzarbeit‘ (i.e., maximum useful work), conceived by Clausius in 1887, ‗Energie utilisable‘ (i.e., useful energy) proposed by Darrieus in 1931, ‗Die technische Arbeits fähigkeit‘ (i.e., capability of performing work) proposed by Bosnjakovič in 1953 etc. are all essentially different names of the same concept proposed by different people. However, the property ‗availability‘ was made very popular by Keenan in 1941 and the Massachusetts Institute of Technology School of engineering thermodynamics. However the term ‗exergy‘ introduced by Rant (1956) finds wider acceptance, particularly because it can be adopted without translation in other languages. The concept of exergy is now being utilized for improved design and analysis of energy systems. Different new methods and tools are still being developed. Even the exergy concept is combined with other existing methods (like economic analysis, life cycle analysis etc.) to develop more comprehensive and useful methods of system design and analysis for improved performance with wider perspective. In this work, a brief introduction of different concepts of second law based methods will be discussed. However, it must be remembered that this concept is still finding newer areas of applications and it is difficult to include all existing methods.

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1.1. Scope and Limitations of This Article This article is intended to give a general overview of the second law based methods for applications in different areas. However, this is neither a review nor a comprehensive collection of all the possible methods developed and areas of applications till date. The reference list is thus not also a comprehensive one. The article only provides some information to students and researchers interested in this area for a preliminary study on the overview of these applications. Undoubtedly the article is not free from the individual bias of the author (i.e., mostly exergy applications in the area of advanced energy conversion). Application of this concept is increasing rapidly in wide variety of areas. Thus attempt to include all of these in a single article is very difficult. However, a recent article has compiled a ‗brief history of exergy‘ [Sciubba and Wall, 2004]. More detailed information and references are available from that article.

2. SECOND LAW BASED METHODS FOR DESIGN AND ANALYSIS The concept of second law of thermodynamics is found to be useful for the design and analysis of thermal systems in general. It helps to identify the underlying irreversibilities in any natural process and possible measures may be suggested. Different such methods have been developed over time and some newer areas of application are still being explored. Some of these methods are discussed below.

2.1. Entropy Generation Minimization Method According to the second law of thermodynamics for a closed system,

Q  S12 T 1 2



(1)

The right hand side of the equation is the total entropy change of the closed system during the process from state point 1 to 2. The left hand side of the equation is the entropy transfer during the same process. The essence of the second law of thermodynamics is expressed by the inequality in the equation 1. The state point may be changed from 1 to 2 by different ways, formally called via different paths. The difference between possible paths is described by the strength of the inequality sign or quantitatively by the amount of the difference of these two terms, called entropy generation (Sgen). Hence,

Q 0 T 1 2

S gen  S12  

(2)

According to the second law of thermodynamics, only for idealized reversible process, entropy generation is zero. However any real process is accompanied by an entropy generation and its magnitude indicates the degree of irreversibility or ‗imperfections‘ of that process. The corresponding equation for an open system is as follows.

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s m s  0 Sgen  S  (Q / T )   m out

(3)

in

The principle of minimum entropy generation is to explore possible different paths for two given state points to minimize the entropy generation. Design and operational parameters may be optimized to obtain minimum possible entropy generation by this method. A comprehensive discussion of this method is available in [Bejan, 1996 a].

2.2. Exergy Analysis Exergy analysis is carried out to identify the sources of loss of work potential. In the design and analysis of thermal systems this method is used to explore proper parameters to minimize this loss of work potential. The analysis may be carried out either at the system or at the component level depending on the objective of the optimization. Optimization at the component level may not necessarily lead to the optimization at the overall system level. The loss of work potential may either be due to ‗exergy loss‘ or due to ‗exergy destruction‘. Exergy loss may be defined as the loss of work potential due to exergy transfer to the environment, i.e., unused exergy. On the other hand, exergy destruction is the loss of work potential due to irreversibilities within a system. It is alternately named as availability destruction, irreversibility, lost work etc. in the literature. The exergy destruction in a component of a system may or may not have any effect on the same of other components of the system. On the basis of that, part of exegy destruction in a component may be either ‗endogenous‘ or ‗exogenous‘ [Tsatsaronis, 2008]. Endogenous part of exergy destruction occurs due to the irreversibilities within that component only. On the other hand, exogenous part of exergy destruction in a component is due to the irreversibilities caused by other components of the system. Thermal systems are typically supplied with exergy inputs associated directly or indirectly with fossil fuels or other energy sources. Accordingly, destruction and losses of exergy represent the waste of these energy resources. The method of exergy analysis aims at the quantitative evaluation of the exergy destruction and losses associated with a system. An exergy balance, by definition, only exists for reversible processes. For real processes exergy is never in balance, because the total exergy input always exceeds the total exergy output. By calculating the sum of exergy loss and destruction possible process improvements are visualized. In general, when the exergy loss is high, this part should be considered for improvement first. However this strategy is not always appropriate. The reason is that every part of the system depends on the other parts, so that an improvement in one part may cause increased losses in other parts. Some performance parameters are defined to estimate the exergetic performance. Several alternative definitions were proposed over time in published literature (Horlock, 1992). However, the unified concept is presently called exergy efficiency and is defined as the ratio of utilized exergy and used exergy [Wall, 2003; Sciubba and Wall, 2004]. The exergy of a system is usually expressed by the formula:

E  U  P0V  T0 S    0,i ni

(5)

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Where U, V, S and ni denote extensive parameters of the system (internal energy, volume, entropy and the number of moles of different chemical species i) and P0, T0 and μ0.i are intensive parameters of the environment (pressure, temperature and chemical potential). Analogously, the exergy of a flow may be expressed as:

E  H  T0 S    0,i ni

(6)

Also the exergy destruction is related to entropy production by the relation:

E D  T0 S

(7)

Exergy destruction in most of the thermal systems stem from one or more of the three principal causes, i.e., combustion/chemical reaction, heat transfer and friction. Combustion is intrinsically a very significant cause of exergy destruction and a dramatic reduction of its effect by conventional methods cannot be expected. However, the inefficiency of combustion may be reduced by preheating the combustion air and reducing the air fuel ratio. Exergy destruction associated with heat transfer decreases as the temperature difference between the streams is reduced. However, this may increase the size leading to greater friction loss. Thus different measures have to be judiciously optimized in the process of exergy analysis. Present method is to estimate the ‗unavoidable‘ exergy destruction in a real process based on available technology and other aspects (say, incremental cost). Then the attention is focused to reduce the rest ‗avoidable‘ part by adopting suitable alternatives [Tsatsaronis, 2008]

3.3. Thermoeconomics/Exergoeconomics Thermoeconomics is the branch of thermal sciences that combines an exergy analysis with economic principles to provide the designer or operator of a thermal system with information which is not available through conventional thermodynamic analysis and economic evaluation but is crucial to the design and operation of a cost effective system. Thermoeconomics rests on the notion that exergy is the only rational basis for assigning monetary costs to the interactions of an energy conversion system with its surroundings and to the sources of thermodynamic inefficiencies within it. The emergence of the energy crisis about 1973 provided the impetus for new approaches towards thermal system design. Thermal systems typically experience significant work, heat and fluid flow interactions with their surroundings. Thermal systems are wide spread, appearing in diverse industries such as electric power generation and chemical processing and in nearly every kind of manufacturing plant. Thermal system design has two branches: system design and component design. The first refers to overall systems and the second refers to the individual components. The basis of most Engineering decisions is economic. Designing and building a device or system that functions properly is only a part of the engineering task. The device or system must, in addition, be economic. One of the most important factors affecting the selection of a design option for a thermal system is the cost of the final product(s). The cost of an item is the amount of money paid to acquire or to produce it. Previously, economic evaluation and

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optimization of a thermal system design were done once the system had been conceptualized based on modeling and simulation. Then different alternatives were compared on purely economic basis. More recently the use of second law of thermodynamics in thermal system design and optimization has been accepted worldwide as having a considerable merit [Bejan et. al., 1996]. In economic analysis of a thermal system design, exergy aided cost minimization process, formally called, ‗exergoeconomics‘ [Tsatsaronis, 1984] has emerged as a potential tool. Exergoeconomics combines exergy analysis with economic principles to provide the designer or operator of a thermal system with information more than that available through conventional thermodynamic analysis and economic evaluation. This information is crucial to the design and operation of a cost-effective system. The basic idea of exergoeconomics is that exergy (available energy) is the only rational basis for assigning monetary costs to the interactions of a thermal system with its surroundings and to the sources of thermodynamic inefficiencies within it. Since, the thermodynamic considerations of ‗thermoeconomics‘ are based on the exergy concept, the terms ‗exergoeconomics‘and ‗thermoeconomics‘ can be used interchangeably [Tsatsaronis and Cziesla, 2002]. Such analysis is usually carried out at the component level to calculate the costs associated with a) all material and exergy streams in the system and b) exergy destruction (thermodynamic inefficiencies) within each component. A comparison of the cost of exergy destruction with the investment cost for the same component provides useful information for improving the cost-effectiveness of the component and the overall system by pinpointing the required changes in structure and parameter values. It has been established that an iterative exergoeconomic technique is very useful for increasing the cost effectiveness of complex thermal systems particularly in cases where incomplete models as well as the complexity of the system make the application of analytical and numerical optimization techniques very difficult. Though the subject of exergoeconomics has been developed over several decades, it is yet to be frequently used in the actual industrial design. Complex thermal systems cannot usually be optimized using mathematical optimization techniques. The reasons include system complexity, opportunities for structural changes not identified during model development, incomplete cost models and inability to consider in the model additional important factors such as plant availability, maintainability and operability. As an alternative, exergoeconomics provide effective assistance in identifying, evaluating and reducing the thermodynamic inefficiencies and the costs in a thermal system. This improves the engineers‘ understanding of the interactions among the system components and variables and generally reveals opportunities for design improvements that might not be detected by other methods. Therefore, the interest in applying exergoeconomics has significantly increased in the last few years. One major development is to find out the most important system components responsible for avoidable exergy destruction and then focus only on these inefficiencies and costs [Tsatsaronis and Park, 1999]. In another development, a new exergy based approach has been developed [Erlach, 2000] for a) assigning the fuel(s) used in the overall plant to the product streams, and b) calculating the costs associated with each product stream with the aid of a thermoeconomic evaluation. This new approach is general, more objective and flexible than previous approaches. The design and improvement of a thermal system often involve application of heuristic rules. Due to the complexity of energy conversion systems as well as to the uncertainty involved in some design decisions, computer programs using principles from the field of artificial intelligence and soft computing are useful tools for the process

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designer in improving a given design and in developing a new cost-effective thermal system. The benefits of combining knowledge-based system and fuzzy approaches with an iterative thermoeconomic optimization technique are found very useful [Cziesla and Tsatsaronis, 2002]. This is another very recent significant development in the field.

3.4. Exergetic Life Cycle Analysis (ELCA) Different methods are presently on the developmental stage for assessment of a process on the basis of effect on the environment as the concern for environmental degradation is increasing. Life cycle analysis (LCA) is such a method. In late 1960‘s the idea of LCA was explored, especially for raw material flows and waste for industrial processes. However, at this early stage there was no standard methodology or framework to carry out LCA. Environmental issues became more and more prominent on the agenda of production companies during the 1980‘s and 1990‘s when the environmental impact of acidification, global warming etc. became visible to the world. This started the growth of the LCA methodology as it is presented today. The interest in the LCA has grown recently. However, it was not until 1990, when the SETAC (Society of Environmental Toxicology and Chemistry) conference in Vermont took place that a first formulation of the three stages of an LCA was carried out. The development of official guidelines and methodology was at full force during the years 1990-1997. Some of the new publications from this time are the ―code of Practice‖ from SETAC in 1993 (Consoli F. et al) and guidelines from Heijungs et al (1992), and Lindfors et al (1995). To obtain a final compatible methodology for environmental management- including LCA- the International Organization for Standardization established a committee to organize this matter in 1993. The first printed document on environmental management was published in 1996, the ISO 14001, which soon became a helpful tool at the organizational level. In 1997 the published document of LCA was released, titled ISO 14040, which is to be used to determine hazardous contributions to the environment during the lifetime of a product or a service. Within the next three years, the LCA –standard was completed with the ISO14041-14043 and the methodology of performing an LCA was thus established. Exergetic life cycle analysis (ELCA) is a method which attempts to combine exergy analysis with LCA. It originates from exergy analysis, but instead of just considering the operation phase, which is often done in exergy analysis, the whole life cycle is investigated. Unfortunately, ELCA method does not have standard guidelines regarding the calculations as the case with LCA and there are a few publications on this topic till date. Thus to explain ELCA, more of the LCA is explained

3.4.1. Life Cycle Assessment Framework In an LCA, the use of natural resources, discharge of emissions to water, air and ground and waste, are gathered and summarized for the whole life-cycle of the product, i.e., from ‘cradle-to grave‘. This method can be used for any product or service and can serve as an optimization tool during pre-design stage. The different stages of LCA as defined in ISO 14040 are: 

Goal and scope definition: To define clearly the different steps of the process or service involved and the scope of the study.

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Inventory analysis: This implies data acquisition for the defined process above. Life cycle impact assessment: This includes choice of impact categories, classification and characterization of impact on the environment Life cycle interpretation: Describes how the results from the analysis are to be interpreted. The whole idea of interpretation is to advise in the decision-making by considering and weighing all environmental impacts.

3.4.2. ELCA The philosophy of ELCA is that the exergy destruction during the life time of a product is considered as a measure of resource depletion. To be able to decrease the resource depletion, the production of materials used in the components in the plant should be carried out with as high exergetic efficiency as possible. There will always be some entropy generation within all these production processes since a more disordered raw material, for instance an ore, is found into a more dense material such as steel. This introduces an entropy decrease in the material but an increase in entropy in the environment. Each time new ores are extracted to form a useful material, the environmental entropy is disturbed since the average composition of the earth‘s crust is altered.

4. FUTURE TRENDS OF SECOND LAW APPLICATIONS Comprehensive prediction of the future trends of second law applications is very difficult as this concept is finding many new areas of applications day by day. Moreover, the individual bias of the author is also a constraint for this assessment. However, it seems that rapid expansion in some areas of second law application in near future seems obvious. Exergoeconomics is expected to emerge as a standard tool in the ‗pre-design‘ stage of system synthesis and configuration. It is expected to be included in the industrial practice too with its present maturity. Concern about environment may lead to serious effort for the development of methods and tools for the assessment of impact on the environment due to any process. Exergy destruction in a process does not indicate direct impact on the environment in the existing conventional sense. However, the basic ‗irreversibility‘ of exergy destruction may be interpreted as an ‗irreparable‘ damage to the environment. Thus coupling exergy destruction with environmental impact and assessment of associated economics to prevent it may be interesting development. The definitions of different steps of this subject are already available in literature [Dewulf et. al, 2008; Ao et. al, 2008; Meyer et. al, 2009]. More effort and rapid development are expected in this area. Exergy analysis has been applied to almost all existing industrial processes be it energy conversion or other. This has established the exergy analysis as a practically useful method for real processes to find optimum solution, if any. On the other hand, computational fluid dynamics (CFD) is another matured field to assess properties of a system under a given operating condition. As the CFD is capable of calculating local entropy generation, this powerful tool may be combined with principles of exergy destruction to obtain more useful conclusions for design of systems involving heart and fluid flow. Introduction of ‗irreversibility‘ concept into the function of large complex systems beyond conventional industrial systems has already been introduced [Sciubba and Wall, 2004]. Finding guidelines for sustainable development for such systems using exergy principles may be another prospective development.

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5. CONCLUSION A brief overview of different second law based methods for the design and analysis of thermal systems in general has been presented. Entropy generation is the source of exergy destruction in a real process. To minimize loss of work potential, entropy generation has to be minimized according to entropy generation minimization principle (EGMP). General exergy analysis principle has been explained with its objective and methodology adopted. Thermoeconomics or exergoeconomics combines the principle of exergy analysis and engineering economics. Principle of this method is also discussed. Exergetic life cycle analysis (ELCA) is a new method which proposes the combination of exergy analysis and life cycle analysis (LCA) to find out the overall environmental impact in the implementation of a complete project or service. Based on the state of the art situation in this field, some possible future areas of application of second law are also included.

NOMENCLATURE E H m n P Q S T U V

Exergy, kJ Enthalpy mass, kg Number of moles Pressure, kPa Heat transfer, kJ Entropy, kJ/kg-K Temperature, K Internal energy, kJ Volume, m3

SUBSCRIPTS 0 1,2 gen i in out

Environment State points Generation Species in a mixture Incoming Outgoing

GREEK SYMBOLS µ

Chemical potential

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REFERENCES Ao, Y; Gunnewiek, L; Rosen M.A. (2008). Critical Review of Exergy-Based Indicators for the Environmental Impact of Emissions. International Journal of Green Energy, Vol. 5. pp. 87-104. Barclay, F.J. (1995). Combined power and process- an exergy approach, Mechanical Engineering Publications (mep), London. Bejan, A. (1996 a). Entropy Generation Minimization, CRC Press, New York. Bejan, A; Tsatsaronis, G.; Moran, M. (1996 b). Thermal Design and Optimization, John Wiley & Sons, New York. Brodyansky, V.M.; Sorin, M.V.; Goff, P.L. (1994). The efficiency of industrial processes: exergy analysis and optimization, Elsevier, Amsterdam. Consoli, F. et al. (1993). Guidelines for life cycle assessment: a code of practice, SETAC. Dewulf, J; Van Langenhove, H; Muys, B; Bruers, S; Bakshi, B.R.; Grubb, G.F.; Paulus D.M.,; Sciubba, E. (2008). Exergy: its potential and limitations in environmental science and technology. Environ. Sci. Technol., Vol. 42 (7), pp. 2221-2232. El-Sayed, Y.M. (2003). The thermoeconomics of energy conversions. Elsevier, Amsterdam. Erlach, B. (2000), M.S. Thesis, Institute for Energy Engineering, Technical University of Berlin, German. Heijungs, R. et al. (1992). Environmental life cycle assessment of products- backgrounds, CML, Leiden University, Leiden, The Netherlands. Horlock, J.H. (1992). The rational efficiency of power plants and their components. Journal of Engg. For Gas Turbine and Power, Trans. ASME, Vol. 114, pp. 603-611. Lindfors, L.G. (1995). Nordic guidelines on life-cycle assessment, Nord 199:20, Nordic Council of Ministers, Copenhagen, Denmark. Meyer, L; Tsatsaronis, G; Buchgeister, J; Schebek, L. (2009). Exergoenvironmental analysis for evaluation of the environmental impact of energy conversion systems. Energy, Vol. 34(1), pp. 75-89. Olausson, P. (2003). On the selection of methods and tools for analysis of heat and power plants, PhD Thesis, Division of Thermal Power Engineering, Department of Energy Sciences, Lund University, Lund, Sweden. Rant,Z. (1956). Exergy, a new word for technical available work (in German). Forschungenim Ingenieurwesen, Vol. 22(1), pp. 36-37. Sciubba, E; Wall, G. (2004). A brief commented history of exergy from the beginnings to 2004, Int. J. of Thermodynamics, Vol. 10 (No. 1), pp. 1-26. Tsatsaronis, G. (1984). Combination of exergetic and economic analysis in energy conversion processes, Energy Economics and Management in Industry, Pergamon Press, Oxford, pp. 151-157. Tsatsaronis, G; Cziesla F. (2002). Encyclopedia of Physical Science and Technology, 3rd Edition, Vol. 16, Chapter: Thermoeconomics, pp. 659-680, Academic Press. Tsatsaronis, G.; Park, M.H. (1999). On avoidable unavoidable exergy destructions and investment costs in thermal systems, ECOS ‘99, Efficiency, Costs, Optimization Simulation and Environmental Aspects of Energy Systems, June 8-10, Tokyo, Japan, pp. 116-121.

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Tsatsaronis, G. (2008). Recent developments in exergy analysis and exergoeconomics. Int. J. of Exergy, Vol. 5 (No. 5/6), pp. 489-499. Wall, G. (2003). Exergy tools. Proc. Instn. Mech. Engrs. (Part:A, Journal of Power and Energy), Vol. 217, pp. 125-136.

In: Advances in Energy Research. Volume 4 Editor: Morena J. Acosta, pp. 109-115

ISBN: 978-1-61761-672-3 © 2011 Nova Science Publishers, Inc.

Chapter 6

PHYSICAL FORMULATION OF THE EXPRESSION OF WIND POWER Reccab M. Ochieng*, Frederick N. Onyango and Andrew O. Oduor Department of Physics and Materials Science, Maseno University, Maseno, Kenya

ABSTRACT This paper touches on a fundamental aspect of wind energy calculation, and goes ahead to formulate three expressions of wind power. The paper attempts to answer the question whether the kinetic energy of a unit mass per second is 1/2, 1/3, or 2/3v3. The answer to this question is of importance for fluid dynamic considerations in general. The classical formulation of wind energy for turbines is based on the definition of the kinetic energy due to the wind impinging on the turbine blades. The expression of wind energy obtained is directly related to half (1/2) of the specific mass multiplied by the cube of wind velocity. Usually the assumption used is that the mass is constant. However, by changing this condition, different results arise. The approach by Zekai [1] based first on the basic definition of force and then energy (work) reveals that the same equation is valid but with 1/3 instead of factor 1/2. In his derivation, Zakai [1] has not given any reason as to why a factor 2/3 which can be obtained using his approach is not acceptable. We advance arguments to show that three expressions of wind energy are possible through physical formulation.

Keywords: power, wind, energy, velocity, work, force.

1. INTRODUCTION Wind energy is the fastest growing source of electricity in the world. Global installations in 2005 reached more than 11,500 megawatts (MW)–a 40.5 percent increase in annual additions compared with 2004–representing $14 billion in new investments [9]. In the United States, a record 2,431 MW of wind power was installed in 2005, capable of producing enough electricity to power 650,000 typical homes [10]. Despite this rapid growth, wind power is still *

E-mail address: [email protected]. (Corresponding author)

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Reccab M. Ochieng, Frederick N. Onyango and Andrew O. Oduor

a relatively small part of our electricity supply–generating less than one of global electricity mix. The ability to harness and use wind has seen the development of many technologies such as wind electric power generation plants. In 2005, the global wind markets grew by 40.5 %, generating some 12 billion euro, or 14 billion USD, in new generating equipment. While Europe remains the biggest market, other regions such as Asia and North and Latin America are quickly catching up [8]. The move in this direction has been to avert serious negative environmental effects due to fossil fuel usage, and their continuous decrease. With the increase in wind energy costs competing favorably with conventional energy sources, economical advantages are beginning to emerge which make wind power quite attractive such that wind energy farms are gaining prominence as alternative energy source in many developed and developing countries. Even though the amount of wind energy is economically insignificant in many parts of the world, a number of nations have taken advantage of its utilization since early years whenever possible. Water pumping, grinding grains in mills by water, generating electricity have been some of the major applications of wind energy. It is possible to see in some parts of the world these types of marginal benefits from wind power. Recently, the significance of wind energy has been attributed to friendly behavior to the environment in so far as air pollution is concerned although, to some extent, noise pollution has been observed in some modern wind-farms. However, the main advantage of its cleanness seem to outweigh the single disadvantage of noise pollution and wind power is sought wherever possible for many applications with the hope that the air pollution as a result of fossil fuel burning will be reduced [2]. The technology in converter-turbines for the wind energy is advancing rapidly, however, there is a need to assess its accurate behavior with scientific approaches and calculations. The purpose of this paper is to provide some insight by extending the approach for wind energy formulation on the basis of force and then energy definitions [1]. The new formulation provides more physical basis to the derivation of the variations in wind energy calculations.

2. GENERAL CONVENTIONAL APPROACH TO WIND ENERGY CALCULATIONS Wind energy is a form of kinetic energy because of the air movement during wind motion. The kinetic energy is expressed conventionally as a basic physical formulation by

E

1 2 mX 2

(1)

where m is the mass and X is the wind velocity. This expression is conventionally used for solid masses but in the case of wind, air moves as a fluid. It is therefore necessary to express m in terms of the specific mass,  . If the perpendicular area to the wind direction is A , then during time duration



, the total amount of air mass that crosses the wind turbine with

velocity X can be expressed as

Physical Formulation of the Expression of Wind Power

111

m  AX

(2)

Substitution of Eq. (2) into Eq. (1) leads to

E

1 AX 3 2

(3)

which is the amount of total wind energy. The wind energy, Ewind per unit area per time is by definition

Ewind 

E ( A )

(4)

Substitution of Eq. (3) leads to the conventional wind power expression

Ewind 

1 3 X 2

(5)

Eq. (5) is the universal equation used invariably in all wind energy calculations all over the world. The derivation of this classical expression makes direct use of kinetic energy equation, Eq. (1), in which materials used must have solid mass, hence constant.

3. BASIC PHYSICAL FORMULATION To obtain a more reliable and accurate formulation, we take into consideration the fluid property of the air and hence the density prior to the ready kinetic energy formulation. We start the derivations by assuming that, the total force, F , on the turbine area A due to a wind blow acts for a time duration  . According to Newton's second law of physics, the force is defined as

F

dp dt

(6)

where p is the momentum of the material being considered. If we consider the air as a fluid, both the density (mass per unit volume) and velocity can change, the change in density being as a result of the change in velocity. Eq. (6) then takes the form

F m

dX dm  X dt dt

(7)

On the other hand, the energy (or work) is defined physically as the multiplication of force by distance, say, dX as

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Reccab M. Ochieng, Frederick N. Onyango and Andrew O. Oduor

dE  F  dX .

(8)

Using Eq. (2), Eq. (7) takes the form

F  AX

dX d ( AX )  X . dt dt

(9)

Substituting Eq. (9) into Eq. (8) leads to

 dX dX   dE  dX  AX  XA dt dt  

(10)

dX dX   dE  dX  AX  AX . dt dt  

(11)

which simplifies to

If we let

dX to be equal to the physical definition of velocity, this expression becomes dt

dE  dX AXX  AXX 

(12)

dE  2X 2 A dX

(13)

or

The total energy can be obtained after integration of both sides of Eq. (13) resulting in

E



2 AX 3 3



(14)

This can be made similar to Eq.(5), the wind power per unit area per time and becomes

E





2 3 X . 3

(15)

4. DISCUSSION Even though Eq. (15) seems to arise naturally by applying physical considerations, Eq. (7) is decisive in accepting it as a tool for wind power calculation. From Newton‘s second law of motion, the right hand side of Eq. (7) must have the units of Kg.ms -2. The first term on the right hand side satisfy this criterion, however, it does not seem clear that the second term

Physical Formulation of the Expression of Wind Power

does. On substation of Eq. (2) into Eq. (7), the second term takes the form

113

X d ( AX ) dt

which gives the correct unit of force. This term, however, can be evaluated only by a careful analysis of a control volume in which the mass changes with time. Two types of control volumes exist: a‘material‘ volume Vmaterial moving with the flow and covering the same mass of flow, and a volume fixed in space V fixed in space. Suppose we have a material volume covering the area where the force field f [N/m3] acts (see figure 1).

Figure 1. The figure shows a material volume with an area where a force field acts.

This volume is a streamtube, so coincides with the streamlines, except at the inlet and outlet plane ( A1 and A2 respectively) where the normal velocity is zero. The fixed volume, also covering the area where f acts, is also a streamtube, but now with non-zero normal velocity at the inlet and outlet plane. By continuity the mass flow through A1 and A2 is equal. In both cases the streamtube extends so far up- and downstream that the pressure at A1 and A2 is undisturbed: p  p0 . The work done by the force field is equal to the increase of the kinetic energy of the mass contained in the material control volume



Vm

f  vdVmaterial 

d dt

1 v.vdVmaterial . Vm 2



(16)

When this control volume is changed to the fixed volume, the transport theorem is important [5,6,7]. This reads for a certain quantity Q:

d dt



Vm

QdVmaterial 

d dt



Vf

QdV fixed   Qvn dS fixed Sf

(17)

where the first term at the right-hand-side gives the time derivative of the integrated Q, and the second term transport of Q integrated at the surface S of V fixed ,with vn the normal component of v . When we assume that V fixed also covers the area where f  0 , (17) applied to (16) gives:

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Reccab M. Ochieng, Frederick N. Onyango and Andrew O. Oduor



Vf

f  vdVfixed 

d dt



Vf



1 1   vdVfixed   v  vvn dS fixed S f 2 2

Sf

1   vvn dS fixed 2

(18)

(19)

d term at the right hand side vanishes because we have steady flow. Since the dt normal flow at the control volume V fixed is non-zero only at the inlet and outlet plane we The

have:



Vf

f  vdVfixed  

A2 f

1 3 1 v dA2, fixed   v 3 dA1, fixed A1 f 2 2

(20)

The work done by the force field per second, the left hand side, equals the increase of the term

1 3 v during the passage through the streamtube. 2

5. CONCLUSION The difference between Eq. (15) and the conventional expression Eq. (5) and Sekai‘s [1] derivation is the numerical factor of 2/3 instead of 1/2 or 1/3. The factor of 2/3 arises as a result of the inclusion of the second term of Eq. (7) in the calculations. However, according to the argument advanced in this work, this term should drop out and a factor of 1/3 obtained due to the continuity and conservation of mass laws. Through consistent arguments and certain laws of physics Eq. (20) gives a factor of 1/2 but with the apriori that kinetic energy must obey the half mass multiplied by velocity squared. On the other hand, when using the work energy theorem, one starts from the fact that work done on a body gives it a certain amount of kinetic energy. It is therefore important to re-evaluate wind energy calculations to subject the 1/2 or 1/3 factor to thorough experimentation for validity. When a factor of 1/3 is used instead of 1/2 there is about 100/3 percent difference (relative error) between the formulations. If 1/3 is used to calculate the power in the wind using the Betz criterion [3-4], there will be a shift downwards of the energy versus velocity curves.

ACKNOWLEDGMENT One of the authors, Reccab Ochieng would like the Department of Physics, the University of Zambia for hosting him during the writing of this paper. He would also like to extend his appreciation to Dr. S. F Banda, Dean, School of Natural Sciences, the University of Zambia for the support he accorded to him during his stay at the University.

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115

REFERENCES American Wind Energy Association (AWEA). 2006. Windpower outlook 2006. Online at http://www.awea.org/pubs/documents/Outlook_2006.pdf Anderson, M. Current status of wind forms in the UK. Renewable Energy System, 1992. Batchelor, G. K., Introduction to Fluid Dynamics. Cambridge University press, pp 131-136, (1994). Betz Adie Naturwissenschaften XV, 10th Nov (1927). Faber, T. E., Fluid Dynamics for Physicists. Cambridge University press, pp 37-40 (1995). Global Wind Energy Council (GWEC), Global wind report (2005). Online at http://www.greenpeace.org.international/press/report Global Wind Energy Council (GWEC). 2006. Record year for wind energy: Global wind power market increased by 40.5% in 2005. Online at http://www.gwec.net/ index.php?id=30&no_cache=1&tx_ttnews%5Btt_news%5D=21&tx_ttnews%5BbackPid %5D=4&cHash=d0118b8972 Kundu, K. P., Fluid Mechanics. Academic press, pp 75-79, (1990). Shephard, M. L., Chaddock, J. B., Cocks, F. H. and Herman, C. M. Introduction to Energy Technology. Ann Arbor Publisher Inc., Michigan, (1976). Zekai Sen. A. short note on a new wind power formulation. Renewable Energy 28 (2003) 2379-2382.

In: Advances in Energy Research. Volume 4 Editor: Morena J. Acosta, pp. 117-169

ISBN: 978-1-61761-672-3 © 2011 Nova Science Publishers, Inc.

Chapter 7

HISTORY AND EVOLUTION OF FUSION POWER PLANT STUDIES: PAST, PRESENT, AND FUTURE PROSPECTS Laila A. El-Guebaly* University of Wisconsin, Fusion Technology Institute, Madison, WI, USA

ABSTRACT This chapter provides a brief history of magnetic confinement fusion power plant conceptual designs, beginning with the early development in 1970, focusing on tokamaks. In addition, the evolution of six more magnetic concepts (stellarator, spherical tori, field-reversed configurations, reversed-field pinches, spheromaks, and tandem mirrors) is highlighted. The key issues encountered are discussed, including the technological obstacles and the elements necessary for economic competitiveness. Extensive R&D programs and international collaboration in all areas of fusion research led to a wealth of information generated and analyzed. As a result, fusion promises to be a major part of the energy mix in the 21st century and beyond.

1. INTRODUCTION Since the 1958 2nd Conference on the Peaceful Uses of Atomic Energy held by the United Nations in Geneva, Switzerland, the secrecy surrounding controlled thermonuclear fusion by magnetic confinement had been lifted allowing researchers in the US, Russia, and UK to freely share results and discuss challenges. In the 1960s, fusion researchers were engaging in a variety of theoretical analyses and experiments to more fully understand and advance fusion physics and engineering. The energy crisis of the early 1970s encouraged all nations to seriously investigate other nuclear energy sources (like fusion and renewable) to supplement fission. Building on the early progress made in the 1950s and 1960s, the world‘s fusion researchers realized the need for better understanding of the physics and technology of fusion energy. Numerous fusion studies, extensive research and development (R&D) programs, more than 100 operating experiments worldwide, impressive international collaboration in all *

E-mail address: [email protected]. (Corresponding author)

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areas of research, and a large body of accumulated knowledge have led to the current wealth of fusion information and understanding. For decades, the international energy agencies have provided a framework for collaborative programs that covers a broad range of fusion topics (such as plasma physics, materials, safety, environmental, and economic aspects, and social acceptance). These strong national programs along with international cooperation in fusion research programs allowed interested organizations to nurture their R&D activities in particular areas of interest. Even though declining fusion budgets have impeded the progress of fusion research for decades, many scientists around the world strongly believe that fusion could be an option in the 21st century energy mix. The growing concern over environmental, safety, health, and sustainability effects with other current energy sources (fission, coal, solar, and wind) could erode public confidence in these concepts and provide an opportunity for fusion to become a significant energy source.

Figure 1. Timeline of large-scale US conceptual power plant designs.

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In the early 1950s, there were four magnetic confinement fusion concepts pursued internationally: tokamak (donut configuration with toroidal plasma current), stellarator (steady-state toroid without plasma current), mirror (steady-state linear system with magnetic wells), and pinch (simple toroidal device). The tokamak, stellarator, and pinch concepts have experienced substantial modifications over the past 60 years. The mirror concept was actively pursued in the US, but suspended in 1986 due to budgetary constraints, while continuing at a very low level in Japan and Russia. After the first 1969 International Fusion Reactor Conference in Culham, England, more than 50 conceptual power plant design studies have been conducted in the US, EU, Japan, Russia, and China. During the 1970-2008 period, numerous D-T fueled fusion power plant designs were developed for both magnetic and inertial confinement concepts, covering a wide range of new and old design approaches: tokamaks, stellarators, spherical tori (ST), field-reversed configurations (FRC), reversed-field pinches (RFP), spheromaks, tandem mirrors (TM), and direct/indirect-laser/light-ion/heavyion/Z-pinch/electrostatic driven inertial fusion. Most of the studies and experiments are currently devoted to the D-T fuel cycle, since it is the least demanding to reach ignition. The stress on fusion safety has stimulated worldwide research on fuel cycles other than D-T, based on ‗advanced‘ reactions with much less neutron level, such as deuterium-deuterium (DD), deuterium-helium-3 (D-3He), proton-boron-11 (P-11B), and 3He-3He. In addition, a few smaller-scale projects investigated non-electric applications of fusion along with the technological means to lessen the likelihood of proliferation.

Figure 2. Timeline of selected power plants designed recently in EU, Japan, China, and Russia.

Figures 1 and 2 display the timeline of large-scale magnetic fusion power plants designed since the early 1970s by research teams in the US and worldwide. Numerous conceptual commercial plant designs were developed for all seven confinement approaches, especially for the tokamak. The decade of the 1980s witnessed a transition period aimed at temporarily impeding the US large-scale tokamak studies in order to investigate alternate concepts:

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stellarator, ST, FRC, RFP, spheromaks, and TM. In the late 1980s, the US has decided to pursue all concepts, except tandem mirrors. While there are numerous reviews of fusion physics and technology research [1-11], comprehensive reviews of the conceptual power plant designs are scarce. The prime goal of this chapter is to fill this gap and address the engineering aspects of the magnetically confined fusion concepts developed to date. Furthermore, it provides a guide to design criteria for advanced designs, highlights the emerging design issues, identifies technological challenges, and presents a perspective on tokamaks as well as the major alternate toroidal and linear configurations. Throughout the chapter, there are additional materials on the evolution of the various concepts that address the basic issues and concerns for fusion science and technology. Besides focusing on the US designs, the most recent international power plant designs are covered briefly. Furthermore, the early generations of fusion power plants were acknowledged for undertaking a noteworthy work. Section 2 presents the motivation for developing advanced fusion concepts as a viable energy source. Section 3 covers the history and development of tokamaks (Section 3.1), stellarators (Section 3.2), spherical tori (Section 3.3), field-reversed configurations (Section 3.4), reversed-field pinches (Section 3.5), spheromaks (Section 3.6), and tandem mirrors (Section 3.7). Lastly, a brief coverage of the roadmap to fusion power is given in Section 4.

2. MISSION AND MAIN FEATURES OF FUSION POWER PLANTS Power plant studies help the fusion community and the funding agencies understand the major design problems and provide guidance for the R&D program to deliver an attractive and viable end product. Any fusion power plant must be safe, reliable, economically competitive, maintainable, environmentally attractive, and meet public acceptance. The philosophy adopted in international fusion power plant designs varies widely in the degree of physics extrapolation, technology readiness, and economic competitiveness. Some designs are viewed as a roll-forward step with a modest extrapolation beyond the International Thermonuclear Experimental Reactor (ITER) [12], yielding large devices with low power density and unfavorable economics, environmental impact, and perhaps safety concerns. This approach assumes that fusion is needed to fill an energy deficiency and the cost of electricity is not a dominant factor. Other designs suggest using the cost of electricity with its underlying factors as a figure of merit measured against competing energy sources. The latter approach would mandate advanced physics, high performance hardware with related future technologies to be competitive. Clearly, a balance must be achieved regarding the market and technology forces that will spell success or failure for a future energy source. Self-consistency is an essential element of any credible fusion conceptual design assessment. As such, most fusion design study teams are multi-institutional, involving experts in plasma physics, neutronics, magnets, materials, heat transfer, power conversion, maintenance, safety, and economics. High power density machines are compact and could provide many of the positive attributes outlined above, but require higher magnetic fields, more complex coils, and advanced physics, such as high beta (plasma pressure/magnetic field pressure), coupled with advanced technology, such as an innovative first wall design that can operate with > 5 MW/m2 neutron wall loading, an advanced divertor system that can withstand > 10 MW/m2

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heat flux, radiation-resistant low-activation structural materials that can handle > 200 dpa, and high field magnets that can provide ≥ 16 T [13]. Fusion magnets will employ Nb3Sn and/or NbTi superconductors as opposed to resistive Cu magnets that require enormous amounts of recirculating power (30-40%) and decrease the net electricity production. Hightemperature superconductors are being developed that offer higher fields and lower cryogenic demands [14,15]. In all designs, the coils are protected from the energetic neutrons by the invessel components: blanket, shield, and vacuum vessel [16,17,18,19]. The blanket contains lithium compounds to breed tritium for fuel self-sufficiency. The blanket and other power core materials convert the nuclear energy into thermal energy that is transferred to the thermal/electrical conversion system [20-22]. The external heat transfer system must be able to efficiently handle high temperature heat transfer media (700-1100oC) in concert with advanced energy conversion concepts. Advanced low-cost fabrication techniques can be developed for all components to enhance the initial capital and recurring costs [23,24]. Reliability and maintainability are immensely important as the plants will be very expensive and they must run continuously for long periods of time. High reliability is especially important to minimize the number of unscheduled outages and extend the operational periods. Replaceable power core components must be durable and radiation resistant to achieve long service periods between scheduled outages. The plants should be designed around how to maintain the power core in as short a time as possible to minimize the downtime and maximize the productive operational time [25-29]. References 25-29 highlight the importance of designing a spectrum of tokamaks and other magnetically confined power plants to be highly maintainable in order to achieve high availability and low operational cost. The challenging fusion environment (14 MeV neutrons, high heat flux, thermomechanical stresses, and chemical compatibility issues) mandates employing advanced lowactivation structural materials (ferritic steels, vanadium alloys, and SiC/SiC composites) to assure the successful development of economical fusion energy. An advanced materials R&D program has been progressing worldwide for decades to achieve the desired materials characteristics [30]. All fusion materials should contain benign alloying elements and extremely low level of impurities to achieve very low radioactivity, allowing clearance and/or recycling of all fusion components [31]. Methods of obtaining highly pure materials need to be improved at a very competitive cost. Highly elongated (vertical) plasmas are naturally unstable to vertical motions, but a conducting shell can slow down the instability and active feedback coils can stabilize the vertical plasma motions. Integrating these stabilizing elements with the in-vessel components and the plant control system represents a challenging engineering task. It is highly likely that commercial fusion machines will operate in a steady-state mode to eliminate the cyclic fatigue induced in all systems by pulsed operation [32-34]. The cyclic fatigue could limit component lifetimes. Steady-state fusion plants can operate successfully for 50 years or more with regular power core component replacements. Inner power core components, such as the blanket, divertor and other plasma facing components, will have a radiation damage limit and must be replaced every few years (now expected to be in the 3-5 y range). The outer power core components (shield, vacuum vessel, and magnets) are shielded to large degree by the inner components and should be designed to operate reliably for the entire plant lifetime [1619]. Plant availability must exceed 90% in order for fusion to compete economically with other energy sources in the time frame for fusion introduction. Rapid and reliable maintenance schemes with radiation-resistant remote handling equipment, highly reliable

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tools, and system health monitoring technologies will support the high availability goal [2529]. Numerous studies have predicted that fusion potentially has favorable safety and environmental features [35-38]. Top-level safety objectives have been defined to assure public and worker safety (to protect individuals and ensure the likelihood of accidents is small and consequences are bounded within the premises), no need for an evacuation plan during accidents, and an attractive low-level waste reduction scheme through innovative designs and recycling/clearance. The means to minimize the radioactivity level has been developed through choice of low-activation materials, such as ferritic steels (FS), vanadium alloys, and SiC/SiC composites. Besides safety and environmental attractiveness, economics remains an important consideration [39-45]. According to researchers in various countries, fusion is cost-effective compared to other energy sources, particularly when external costs are added to the cost of electricity [46,47]. There is a need to develop low-cost techniques [23,24] to fabricate power core components as existing techniques are too expensive and may not be able to handle the complex shapes that are necessary (ala stellarators). Recent studies [13,48] continue to indicate an economical power plant should deliver at least 1 GWe of net output power. Larger sizes (> 1 GWe) are more economical due to economy of scale, but would present higher financial risk for utilities and more complexities for integrating and handling multi-GW sources [49]. In summary, a few general remarks can be made regarding the mission of fusion power plant studies:   

  

Perform self-consistent integrated designs, stressing constructability, fabricability, operability, and maintainability of fusion power plants Focus on practicality, safety, and economic competitiveness of fusion power Involve experts in plasma physics, neutronics, magnets, materials, heat transfer, mechanical design, power handling, power conversion, maintenance, safety, and economics, requiring multi-institutional design teams Uncover physics and technology problems Help fusion community and funding agencies understand major design issues Guide R&D program to deliver attractive and viable end product. Studies developed to date defined the key features of an attractive tokamak power plant: o Must be safe, reliable, maintainable, economically competitive, environmentally attractive, and meet public acceptance. o Fusion has favorable safety and environmental features: – Low-activation materials to minimize radioactivity – Assurance of public and worker safety – No need for evacuation plan during accidents – Low-level wastes that are recyclable and clearable – Radwaste reduction scheme through compactness, blanket segmentation, permanent components, and recycling/clearance.

History and Evolution of Fusion Power Plant Studies 





123

High power density machines are compact and economical, but require advanced physics and technology: o Innovative first wall design operating > 5 MW/m2 neutron wall loading o Advanced divertor system withstanding > 10 MW/m2 heat flux o Radiation-resistant structural materials handling > 200 dpa o High field magnets providing > 16 T: – Superconductors as opposed to resistive Cu magnets (that require enormous amounts of recirculating power and decrease net electricity production) – High-temperature superconductors are being developed offering higher fields and lower cryogenic demands. Advanced power plants could compete economically with other energy sources, but mandate: o Steady-state operation to eliminate cyclic fatigue induced in all systems by pulsed operation. o Breeding blanket converting nuclear energy at high temperature > 700oC. o External heat transfer system handling high temperatures (700-1100oC) with high energy conversion efficiency (40-60%). o Successful operation for > 50 years with regular blanket and divertor replacements (every 3-5 years). o Outer components (shield, vacuum vessel, and magnets) operating reliably for entire plant lifetime. o Advanced low-cost fabrication techniques for all components to enhance economics. o High availability > 90%: – Highly reliable components to minimize unscheduled outages – Power core maintenance in short time to minimize downtime. Other features include: o Power plant should deliver at least 1 GWe of net output power o Larger sizes (> 1 GWe) are more economical, but present higher financial risk for utilities and more complexities for integrating and handling multi-GW sources o Fusion is cost-effective, particularly when adding external costs to cost of electricity.

3. MAGNETIC FUSION CONCEPTS Over 40 years, since the inception of the large-scale fusion designs in the early 1970s, the worldwide fusion community has gone from an almost exclusively tokamak concept to a variety of alternate magnetic configurations such as stellarators, ST, FRC, RFP, spheromaks, and tandem mirrors, aiming at developing safe, environmentally attractive, and economically competitive fusion power plants for the 21st century.

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3.1. Tokamaks Internationally, the tokamak concept is regarded as the most viable candidate to demonstrate fusion energy generation. Since the 1960s, the fusion program around the world has been dominated by the tokamak – a donut configuration invented in 1951 by Russian physicists Sakharov and Tamm while named a few years later by Golovin. Tokamak is an acronym from the Russian phrase ―Toroidal Chamber with Magnetic Coil.‖ In 1956, the first tokamak experiment began in Kurchatov Institute, Moscow. Ever since, the confinement concept has been successfully demonstrated with more than 100 worldwide experimental facilities, of which ~35 experiments are currently operational in Russia, US, EU, Japan, South Korea, China, India, and other countries [50]. Over the years, strong domestic and international experimental programs addressed the tokamak physics and technology issues. The collaborative worldwide effort materialized in the design and construction of ITER [12] – a large burning plasma experiment that will produce ~500 MW of fusion power. ITER is being designed, constructed, and operated by a consortium of seven parties: EU, Japan, US, Russia, China, South Korea, and India. France has been chosen as the site for ITER with construction starting around 2011 and first plasma in 2018. The tokamak plasma is confined by a large set of equally spaced coils: typically 16 toroidal field coils and approximately 10 poloidal field coils. A second set of divertor, equilibrium field, and central solenoid coils is necessary to shape and position the plasma within a toroidal vessel of elliptical cross section. A tokamak feature is a flowing current through the plasma that generates a helical component of the magnetic field for plasma stability. Tokamaks are capable of reaching steady-state operating conditions using current drive systems. Once the plasma ignites, the alpha particles from the fusion reaction provide nearly all the plasma heating. All tokamaks employ divertors in single or double null configurations to collect the lost alpha particles and plasma ions and electrons. The components surrounding the plasma must breed tritium, convert the neutron energy into thermal energy, protect the magnets and other external components, and accommodate the plasma stabilizing shells.

3.1.1. US Tokamak Power Plant Studies Numerous tokamak conceptual design power plant studies were developed over the last four decades to assess the viability of different approaches and recommend productive R&D directions. In the US, the conceptual studies progressed steadily from the early 1970s pulsed UWMAK series [51-54], to STARFIRE [55] (1980) that first promoted steady-state current drive, to the more advanced 1990s steady-state ARIES series [56-58,48,13]. The earlier designs of the 1970s demonstrated how fusion plants could be designed and operated, but also uncovered undesirable aspects of pulsed operation with an energy storage system, a low power density machine, plasma impurity control problems, and maintainability issues. Nevertheless, these pioneer studies contributed significantly to the basic understanding of the field of fusion power plant design and technology. In fact, many of the proposed 1970s technologies are still considered in recent fusion designs: 316-SS structure, Li and LiPb liquid breeders, LiAlO2 solid breeders, Be multiplier, helium and water coolants, NbTi and Nb3Sn superconductors, low-Z liner for first wall and solid divertor, liquid Li divertor, and remote maintenance.

History and Evolution of Fusion Power Plant Studies

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Beginning in the 1980s with the STARFIRE design [55] and continuing to the present, more in-depth power plant studies were initiated in the US and abroad to identify, understand, and resolve the physics and technology challenges of tokamaks. While these studies proposed solutions for many problems, they uncovered other areas that needed further assessment and development, such as disruption control, current drive technology, high heat flux divertor design, and high temperature blankets. The key engineering parameters of the STARFIRE design, led by Argonne National Laboratory, are listed in Table I while Figure 3 displays the principal features of the design. STARFIRE represented the first tokamak power plant that operated in a steady-state, current drive mode without an energy storage system. Other STARFIRE design features include advanced physics, lower-hybrid current drive, berylliumcoated first wall (FW), modular water-cooled solid breeder blanket, attractive safety characteristics, and a sector maintenance scheme. To help evolve and direct the design, both a Utility Advisory Committee and a Safety Review Committee provided guidance on desirable features of an attractive power plant. Overall, STARFIRE reflects the best understanding at that time for a steady-state power plant with moderate extrapolation in tokamak physics. Table I. Key parameters of STARFIRE and ARIES steady-state power plants. Power Plant Fusion Power (MW) Net Electric Power (MWe) Major Radius (m) Minor Radius (m) Aspect Ratio Ave. Toroidal Beta Max. Field at Coil (T) Number of TF Coils Structural Material Blanket Type Average NWL# (MW/m2) Thermal Conversion Efficiency System Availability COE+ (mills/kWh)

3510

1926

ARIESII [58] 1910

1200

1000

1000

1000

1000

1000

7 1.94 3.6 6.7% 11.1 12 PCA* LiAlO2/H2O/Be

6.75 1.5 4.5 1.9% 21 16 SiC/SiC Li2ZrO3/He/Be

5.6 1.4 4 3.4% 15.9 16 V Li

6.04 1.51 4 3.4% 15.9 16 SiC/SiC Li2O/He/Be

5.52 1.38 4 5% 15.8 16 V Li

5.5 1.3 4 9.2% 11.1 16

3.6

2.5

2.9

2.7

3.96

3.3

36%

49%

46%

49%

46%

59%

75% 110

76% 87

76% 76

76% 68

76% 76

85% 48

STARFIRE [55]

ARIES-I [56,57]

2024

ARIESRS [48] 2167

ARIES -AT [13] 1760

ARIES-IV [58]

SiC/SiC

LiPb

* Primary Candidate Alloy – an advanced austenitic stainless steel. # Neutron wall loading (NWL) evaluated for first wall at separatrix passing through the X point. + in 1992 US dollars.

In the 1980s, the US delayed the large-scale tokamak studies to investigate several alternate concepts. In 1986, a decision was made by the US Department of Energy (DOE) to pursue all concepts except the tandem mirror. Led by the University of California [59], the large-scale tokamak studies resumed in the early 1990s and delivered a series of advanced tokamak power plants: ARIES-I [56,57], ARIES-II and ARIES-IV [58], ARIES-RS [48], and ARIES-AT [13]. The mission of the DOE-funded ARIES program is to perform advanced integrated design studies of the long-term fusion energy embodiments to guide the US R&D program. Improvements were apparent, progressing from ARIES-I to ARIES-AT and all studies stressed the practicality, safety, and economic competitiveness of fusion power. At the

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outset, the ARIES design process took into consideration the fabricability, constructability, operability, and maintainability of the machine. The physics, engineering, and economics proceeded interactively while the ARIES systems code determined the reference parameters by varying the physics and engineering parameters, subject to pre-assigned physics and technology limits, to produce an economic optimum plant design.

Figure 3. Isometric views of STARFIRE and ARIES tokamaks plus vertical cross section of PULSAR (not to scale).

Each ARIES design was conceived to consider various options that may provide an improvement; basically, a technical sounding board that helps judge the viability of different physics and engineering concepts. The first design of the ARIES series (ARIES-I) operates in

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the first-stability plasma regime – the closest to the present database – with ceramic breeder blanket and SiC/SiC composites as the main structure. The ARIES-I physics and engineering models were updated repeatedly to obtain meaningful comparisons with later designs [57]. Even though the high-field toroidal field coils and high thermal conversion efficiency improved the attractiveness of this first-stability regime of operation, ARIES-I did not satisfy the economic requirement. The second-stability regime of ARIES-II/IV [58] had better performance, but the experimental database for this physics regime is very limited. Two blanket options were examined in ARIES-II/IV: liquid lithium with vanadium structure and lithium oxide ceramic breeder with SiC/SiC composites. Next, the ARIES-RS study [48] with reversed-shear (RS) plasma and Li/V blanket offered similar economic performance. Nevertheless, the physics database for this RS regime, while small, is growing rapidly. The advanced tokamak (AT) plasma confinement regime was incorporated in the last ARIES-AT design [13] to assess the physics and technology areas with the highest leverage for achieving attractive and competitive fusion power. Indeed, ARIES-AT demonstrated superior performance and benefited greatly from several developments: new SiC/LiPb blanket operating at high temperature (~1000oC) with high thermal conversion efficiency (59%), high system availability (85%) with an efficient horizontal maintenance scheme, and 9% toroidal beta (compared to 5% beta of ARIES-RS). Noteworthy is that moving the stabilizing shells inward between the outboard blanket segments helped increase the beta significantly. In all ARIES designs, the cost of electricity (COE) involves capital costs, operating costs, financial costs, power core energy production (energy capture, energy multiplication, high temperature operation), thermal to electrical energy conversion efficiency, plant recirculating power, and plant availability (reliability, maintainability, and inspectability). Even the safety and environmental impact as well as the radwaste management scheme have indirect influences on the COE. Improvements in any of these areas enhance the economic performance of the plant. The safety and environmental impact and the smart choice of a favorable radwaste management approach (such as recycling and/or clearance, avoiding disposal) also have other social impacts that will contribute to the attractiveness of any fusion power plant. The STARFIRE and five ARIES tokamaks operated under the assumption that current drive is essential for the steady-state operation and economic feasibility of fusion power plants. The design intent is based on the strong recommendations from the STARFIRE and ARIES industrial advisory committees for steady-state operation. Also the desire to achieve high levels of reliability suggests that steady state operation would minimize fatigue related failures. Economics of the on-site energy storage also proved to be prohibitive. In the mid 1990s, the ARIES team re-evaluated the pulsed operation of an inductively driven tokamak (PULSAR [32,33]) to determine the advantages and drawbacks of operating in a pulsed mode using current plasma physics and updated engineering designs. The main advantage of pulsed operation would be the elimination of the expensive and inefficient current drive system. Besides the need for an efficient energy storage system, many of the plant systems suffer from cyclic thermal and mechanical fatigue, particularly the plasma facing components, toroidal and poloidal field magnets, and pumps and valves. The magnet fatigue was identified as the most critical issue calling for hefty structure to support the magnets (refer to Figure 3). PULSAR-I and –II employed the ARIES-IV and ARIES-II blanket systems, respectively, and suggested utilizing the outboard shield for thermal energy storage to provide the 1000 MWe output between pulses (downtime of ~3 minutes). The smart choice of the largest fusion power core component for energy storage helps buffer the thermal oscillations, assuring

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steady conditions at the steam generator and grids. PULSAR large major radius approaches 8 m and its economic performance is poor (COE > 100 mills/kWh) primarily due to cost penalties associated with pulsed operation. Clearly, pulsed tokamaks cannot compete with steady-state systems due to the added complexity of energy storage, fatigue of critical power systems, and poor economics.

3.1.2. Recent European, Japanese, and Chinese Tokamak Power Plant Studies International institutions, particularly in Europe, Japan, and China, carried out a number of tokamak fusion power plant studies. There are technical similarities and differences between these studies. Some of the underlying differences are related to strategic objectives and technology readiness. For instance, the emphasis given to the economic competitiveness of power plants varies significantly between countries. The US is highly motivated to obtain a fusion power plant that is at least as economically competitive as other available electric power sources. On the other hand, Europe and Japan take the view that the first generation of fusion power plants will enter the energy market because of the major safety and environmental advantages and large fuel reserve, even if they produce electricity at a somewhat higher cost. Table II. Key parameters of recently developed power plants in Europe [62]. PPCS Model A AB B C Fusion Power (MW) 5000 4290 3600 3410 Net Electric Power (MWe) 1546 1500 1332 1449 Major Radius (m) 9.55 9.56 8.6 7.5 Minor Radius (m) 3.18 3.18 2.87 2.5 Aspect Ratio 3 3 3 3 Max. Field at Coil (T) 13.1 13.4 13.2 13.6 Structural Material LAFS* LAFS LAFS LAFS Blanket Type LiPb#/H2O LiPb#/He Li4SiO4/He/Be LiPb+/He Overall Tritium Breeding 1.06 1.12 1.13 1.15 Ratio 2 Average NWL (MW/m ) 2.2 1.8 2 2.2 Peak Divertor Heat Load 15 10 10 10 (MW/m2) Pumping Power (MW) 110 400 375 87 Plant Net Efficiency& 32% 35% 37% 42% Cost++ (Euro Cents/kWh): Internal@ 5-9 5-9 4-8 4-7 External** 0.09 0.08 0.07 0.06 * Low activation ferritic steel: Eurofer. # Stagnant LiPb. + Circulated LiPb. & Ratio of net electric power output to fusion power. ++ in 2004 Euros. @ Tenth-of-a-kind and First-of-a-kind. ** Accounts for cost associated with environmental damage or adverse impacts on health.

D 2530 1527 6.1 2.03 3 13.4 SiC/SiC LiPb+ 1.12 2.4 5 12 60% 3-5 0.06

During the 1990s, a series of EU studies delivered two reports [60,61] on the safety and environmental assessment of fusion power (SEAFP). As the 2000s began, Cook [44] and Ward [45] summarized the prospects of fusion energy that offers acceptable internal cost and

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very low external costs and makes an economically acceptable contribution to the future energy mix. The lessons learned from these studies were applied to the successor EU study of commercial power plants: European Power Plant Conceptual Study (PPCS) [62]. This 4-year study focussed on five models that spanned a wide range of near-term and advanced physics/technology tokamaks operating in steady-state mode. As Table II indicates, the models deliver ~1500 MWe output power, but differ substantially in plasma parameters, size, fusion power, materials, blanket and divertor technologies, breeding capacity, economic performance, and safety and environmental impacts. Models A, AB, and B are considered near-term concepts while Models C and D are more advanced concepts. Figure 4 displays an isometric view of the Model C power plant. The tenth-of-a-kind cost of electricity for all models is thought to be competitive with other sources of energy obtained from the literature. In addition to this valuable comparison, the PPCS study highlighted the need for specific R&D activities as well as the need to establish the basic features of the Demo [63] – a device that bridges the gap between ITER and the first-of-a-kind fusion power plant. In Japan, several studies have been made of tokamak power plants, including the SSTR series [64-68], DREAM [69], CREST [70], and VECTOR [71]. Some of these designs can be broadly classified into two categories [72] according to the peak magnetic field (Bmax) at the magnet and normalized beta (N):  High field tokamaks (Bmax > 16 T): SSTR [64,65], A-SSTR [66], and A-SSTR2 [67,68]  High beta tokamaks (N > 5): CREST [70]

Figure 4. Isometric views of selected EU, Japanese, and Chinese power plants (not to scale).

SSTR [64,65] is a pioneer Japanese study developed in the early 1990s and aimed at achieving high power density through high magnetic field at the magnet (16.5 T). The blanket employs the F82H ferritic steel structure and water-cooled Li2O breeder with a beryllium multiplier. Two more advanced studies followed in 1995 and 1999, recommending higher magnetic fields of 20.5 T at the 20 K magnets of A-SSTR [66] and 23 T for A-SSTR2

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[67,68]. SiC/SiC composites, Li2TiO3 breeder, and Be12Ti multiplier are the materials of choice for A-SSTR2. A major design challenge for such a high magnetic field approach is the sizable magnet structure needed to support the enormous electromagnetic force on the TF coils. In A-SSTR2, a space is provided for the supporting structure by eliminating the central solenoid. In the mid-1990s, the DREAM study [69] promoted the approach of easy maintenance to achieve high overall availability and thus reduce the cost of electricity. With 12 toroidal sectors and a high aspect ratio (A) of 6, an entire sector can be pulled out radially between the outer legs of toroidal field (TF) coils – a similar approach to the ARIES-RS and ARIES-AT maintenance designs. Because of the high A, there is ample space (~1 m) between the inboard legs of the 12 TF coils to easily accommodate all pipes and supply lines. The successor CREST study [70] adopted DREAM‘s maintenance philosophy, but with 14 TF magnets and 14 sectors. CREST is compact with moderate A of 3.4 and operates in the reversed shear mode. As Table III indicates, the most recent VEry Compact TOkamak Reactor (VECTOR) [71], shown in Figure 4, is even more compact with A of 2, N of ~4, major radius of 3.75 m, no central solenoid coils, no inboard blanket, ~0.7 m thick inboard shield, Li/Be/SiC outboard only blanket, and high field Bi2212/Ag/AgMgSb superconducting TF magnets operating at 20 K with low stored energy. In this regard, VECTOR combines two distinct features: the high Bmax of A-SSTR and high N of CREST. These salient features were recently incorporated in the design of a compact DEMO (SlimCS) with low A of 2.6, N of 4.3, 16.4 T at magnet, and slim central solenoid, offering physics and engineering advantages [72]. In addition, Demo-CREST [73] has also been proposed as an alternate Demo based on the CREST approach. Table III. Key parameters of recently developed power plants in Japan and China. Power Plant Fusion Power (MW) Net Electric Power (MWe) Major Radius (m) Minor Radius (m) Aspect Ratio N Max. Field at Coil (T) Number of TF Coils Structural Material Blanket Type Average NWL (MW/m2) Thermal Conversion Efficiency System Availability COE (mills/kWh) # +

CREST A-SSTR2 [70] [67,68] 2930 4000 1000 2550 5.4 6.2 1.6 1.5 3.4 4.1 5.5 4 12.5 23 14 12 Ferritic Steel SiC/SiC Water Cooled Li2TiO3/Be12Ti/He Blanket 5.05 6

VECTOR [71] 1800 1000 3.75 1.4 2 3.75 19.6 12 SiC/SiC

FDS-II [75] 2500 1200 6 2 3 5 10 16 CLAM steel#

Li/Be

LiPb/He/steel#

3.5

2.6

35%

47%

75%

75% 63-105*

China Low Activation Martensitic steel. Range for 60-85% capacity factor and 0.5-2 uncertainty factor in price of blanket materials.

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In China, fusion is highly regarded as a prominent energy source due to the rapid economic growth. As such, a series of FDS fusion power plants [74] has been developed over the past 10 years covering hybrid tokamak to transmute fission products and breed fissile fuels (FDS-I), electricity generator (FDS-II), hydrogen producer (FDS-III), and spherical tokamak (FDS-ST). The FDS-II single-null tokamak design [75] (refer to Figure 4 and Table III) is based on advanced plasma parameters and employs LiPb breeder and reducedactivation ferritic steel structure. The dual-cooled LiPb/He blanket is the reference with 700oC LiPb outlet temperature while the He-cooled quasi-static LiPb blanket is the back-up with 450oC He outlet temperature. The FDS-II configuration is designed with modularized blankets to alleviate the thermal stress and impact of electromagnetic force caused by plasma disruption. The 240 blanket modules and divertor cassettes are maintained through equatorial and lower ports, respectively. A set of preliminary assessments indicated the conceptual design satisfies the FDS-II requirements in terms of tritium breeding, mechanical performance, fabricability, maintainability, safety, and economics.

3.1.3. D-3He Fueled Tokamak Power Plant Studies The D-3He fueled fusion concepts [76] offer advantages, such as no tritium breeding blanket, permanent components, and possibility to obtain electrical power by direct energy conversion of charged particles [77,78]. However, the D-3He plasma has its own set of issues and concerns, such as the availability of 3He [79,80] and the attainment of the higher plasma parameters that are required for D-3He burning. Moreover, the D-3He cycle is not completely aneutronic, requiring shielding components to protect the magnets and externals [81,82]. It has a very low presence of energetic fusion neutrons, due to side D-D reactions generating 2.45 MeV neutrons and T and the side D-T reactions generating 14.1 MeV neutrons.

Figure 5. Vertical cross section of Apollo and isometric view of ARIES-III.

Several studies have addressed the physics and engineering issues of D-3He fueled power plants. As advanced fuel cycles are more suitable for devices with high beta and high magnetic field, most D-3He efforts of the 1970s and 1980s focused on innovative confinement concepts, such as the field-reversed configuration, tandem mirrors, and Ring Trap concept. In the early 1990s, the University of Wisconsin developed a series of tokamak-based D-3He Apollo designs [83-86] while the D-3He ARIES-III tokamak [87] was developed within the ARIES project. The Apollo series and ARIES-III, shown in Figure 5, postulated the reduction

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in radioactivity and the advantageous effect of the D-3He safety characteristics [88-92] that include low activity and decay heat levels, low-level waste, and low releasable radioactive inventory from credible accidents. References 93-95 address the pertinent issues of utilizing today‘s technology and a strategy for D-3He fusion development.

3.1.4. Summary Power plant studies performed worldwide over the past 50 years indicated the tokamak is a highly promising concept for producing large-scale fusion power. These studies have also helped shape the R&D directions for improved physics and engineering. This view of tokamaks is currently shared by many nations and is reflected in the support for the design, construction, and operation of ITER [12]. ITER will help the transition from the present fusion experimental basis toward the goal of electricity-producing power plants. At present, the tokamak concept is well funded and more advanced than any other fusion concept. Undoubtedly, additional theoretical and experimental research into the tokamak confinement concept will continue at the national and the international levels to resolve emerging physics and technology issues necessary to produce a viable fusion power plant.

Figure 6. Isometric view of the six recent stellarator power plants developed in the US, Europe, and Japan (not to scale).

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3.2. Stellarators The stellararor concept was one of the first approaches proposed by Spitzer in 1950 for obtaining a controlled fusion device. The first device was built in the US in 1951 at Princeton. Reference 96 covers the historical development of worldwide stellarator research from 1950 to 1980. The prime interest in stellarators stems from their potential physics advantages over tokamaks. Stellarators are inherently steady-state devices with no need for large plasma current, no external current drive, no risk of plasma disruptions, low recirculating power due to the absence of current-drive requirements, and no instability and positional control systems. For these attractive features, stellarator power plants have been studied for decades in the US, Europe, and Japan to optimize the design parameters and enhance the physics and engineering aspects. Recently, compactness was promoted as an economic advantage for future stellarators, allowing direct comparisons with tokamaks. Numerous stellarator experiments have been constructed worldwide in the US, Germany, Japan, Russia, Spain, and Australia. In addition to seven worldwide smaller experimental devices, the operational HSX experiment in the US [97], the performance-class LHD experiment in Japan [98], and the Wendelstein 7-X under-construction experiment in Germany [99] are capable of approaching fusion-relevant conditions comparable to those attained in today‘s large tokamaks. In 2008, the US decided to terminate the NCSX compact stellarator experiment [100] that is being assembled at the Princeton Plasma Physics Laboratory. Although the stellarator concept has been around for several decades, very little in the way of conceptual design studies has been performed compared to tokamaks, of which many studies have taken place in the US and abroad. During the decade of the 1980s and continuing to the present, six large-scale stellarator power plants have been developed: UWTOR-M [101,102], ASRA-6C [103], SPPS [104], and ARIES-CS [105] in the US, and the most recent HSR [106,107] in Germany and FFHR [108] in Japan. The six studies vary in scope and depth and encompass a broad range of configuration options as shown in Figure 6. The timeline of these studies is given in Figure 7.

Figure 7. History timeline for large-scale studies of stellarator power plants.

The stellarator confines the plasma in a toroidal magnetic configuration in which controlled currents flowing in external coils produce vacuum flux surfaces with rotational transform. Thus, the plasma confining magnetic filed is generated by numerous external coils rotating as they move around the torus. Unlike tokamaks, the coils are not equally spaced on the inboard and outboard for better plasma containment. In this regard, stellarators are clearly distinguished from tokamaks (and other toroidal concepts) that rely entirely on current

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flowing through the plasma for confinement. Moreover, stellarators cover a variety of configurations (helias, torsatron, heliotron, modular torsatron, etc.) and a wider range parameter space than tokamaks (e.g., 8-24 m major radius, 3-12 aspect ratio, 2-5 field periods, and 0.2-1.6 rotational transform), but such parameters are subject to numerous constraints. While the magnetic geometry of tokamaks is intended to be entirely symmetric in the toroidal coordinate, the magnetic field components of the stellarator vary in all three coordinates, deviating from toroidal symmetry. As such, the stellarator physics advantages could be offset by the more complex configurations, harder divertor designs, and challenging maintenance schemes. In most stellarator designs developed so far, the first wall (FW) and surrounding invessel components conform to the plasma and deviate from the uniform toroidal shape to reduce the machine size. The FW shape varies toroidally and poloidally, representing a challenging 3-D engineering problem and making the design of in-vessel components, overall integration process, and maintenance scheme more complex than for tokamaks. Nevertheless, interest in the stellarator concept increased over the years because of the remarkable advances in theory, experimental results, and construction techniques [109]. In the 1970s, researchers were encouraged by the positive physics experimental results and the development of modular twisted coils that can replace the continuous helical coils (for torsatron and heliotron designs) – an early drawback of stellarator power plants that makes maintainability of blanket and coils extremely difficult [101]. In the early 1980s, the Los Alamos study of the Modular Stellarator Reactor (MSR) characterized parametrically the critical relationship between plasma, blanket/shield, coils, and overall power plant performance [110]. The first large-scale stellarator design [101,102] was developed by the University of Wisconsin (UW). UWTOR-M had 18 modular twisted coils with only two different coil geometries arranged in a toroidal configuration. Here, the non-planar modular coils were first used in 2 or 3 field period (FP) applications [111]. The blanket employs FS as the main structure and LiPb for cooling and tritium breeding. In the mid 1980s, the nonplanar axis became more pronounced and non-planar modular coils became more complicated [111]. UWTOR-M was followed by the ASRA-6C study [103] that was performed in collaboration between UW and two German laboratories: FZK at Karlsruhe and IPP at Garching. All 30 coils of ASRA-6C and the internal components (FW, FS/LiPb blanket, and shield) have identical elliptical bores as shown in Figure 6. Next came the Stellarator Power Plant Study (SPPS) [104] initiated in 1995 by the multi-institutional ARIES team to address key issues for stellarators based on the modular Helias-like Heliac approach. As Figure 6 indicates, the baseline configuration has four field periods produced by 32 modular coils of four distinct types. Vanadium structure and liquid lithium breeder are the reference materials for SPPS. On the international level, a Helias Stellarator Reactor (HSR) study was initiated in Germany in the late 1990s based on the W7-X experiment. The most recent HSR4/18 design [106,107] has four FPs with 40 coils and LiPb/FS blanket. Alternatively, the stellarator configuration can be produced using continuous helical coils. An example of this approach is the ongoing Force Free Helical Reactor (FFHR) study in Japan [108]. Ferritic steel structure, Flibe breeder, and beryllium multiplier are the materials of choice for FFHR. Note that all designs developed to date employed liquid breeders (Flibe, LiPb, or Li) for breeding and cooling to cope with the complex geometry of stellarators. The 1980s and 1990s stellarator studies led to large power plants mainly due to the relatively large aspect ratio and the design constraint imposed by the minimum distance between the plasma and coils. For instance, the UWTOR-M design [101,102] had an average

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major radius (Rav) of 24 m in a six FP configuration. Moving toward smaller sizes, the ASRA-6C study [103] suggested 20 m Rav with five FPs. The most recent German HSR4/18 study [106,107] proposed 18 m Rav with four FPs. The ARIES SPPS study [104] was the first step toward a smaller size stellarator, proposing 14 m Rav with four FPs. Japan developed a series of FFHR designs [108], recently calling for 16 m Rav with ten FPs. After two decades of stellarator power plant studies, it was evident that a new design that reflects the advancements in physics and improvements in technology was needed. To realize this vision, the ARIES team launched the ARIES-CS study [105] to provide perspective on the benefits of optimizing the physics and engineering characteristics of the so-called compact stellarator power plant. The primary goal of the study is to develop a more compact machine that retains the cost savings associated with the low recirculating power of stellarators, and benefits from the smaller size and higher power density, and hence lower cost of electricity, than was possible in earlier studies. The benefit of the compact feature can be fully recognized when comparing ARIES-CS to all five large-scale stellarator power plants developed to date (see Table IV and Figure 8). The most recent advanced physics and technology and innovative means of radial build design helped reduce the major radius by more than 3-fold, approaching that of advanced tokamaks. In ARIES-CS, the principle of compactness drove the physics, engineering, and economics. The study aimed at reducing the stellarator size by developing a compact configuration with low aspect ratio (~4.5) along with a combination of advanced physics and technology and by optimizing the minimum plasma-coil distance (min) through rigorous nuclear assessment as min significantly impacts the overall size and cost of stellarator power plants.

Figure 8. Evolution of stellarator size. Advanced tokamak and spherical torus included for comparison.

The FW and surrounding in-vessel components conform to the plasma, as shown in Figures. 9 and 10, and deviate from the uniform toroidal shape in order to achieve compactness. The reference design calls for a 3-FP configuration. Within each FP that covers 120 degrees toroidally, the FW changes from a bean-shape at 0o to a D-shape at 60o, then back to a bean-shape at 120o, continually switching the surfaces from convex to concave over a toroidal length of ~17 m.

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Laila A. El-Guebaly Table IV. Key parameters of stellarator power plants. Power Plant

Fusion Power (MW) Net Electric Power (MWe) Number of Field Periods Average Major Radius (m) Average Minor Radius (m) Aspect Ratio Toroidal Beta Max. Field at Coil (T) Number of Coils Structural Material Blanket Type Average NWL (MW/m2) Thermal Conversion Efficiency System Availability COE (mills/kWh)

UWTOR-M [101,102] 4300 1840 6 24 4.77 14 6% 11.6 18 FS LiPb 1.4

ASRA-6C [103] 3900 1620 5 20 1.6 12.5 5% 10.4 30 FS LiPb 1.4

SPPS [104] 1730 1000 4 14 1.6 8.5 5% 14.5 32 V Li 1.3

HSR [107] 3000

40%

40%

46% 76% 75+

4 18 2.1 8.6 5% 10.3 40 FS LiPb 1

FFHR2m2 [108] 3000 1300 10 16 2.8 5.7 4.1% 13 2 continuous FS Flibe/Be 1.3

ARIES-CS [105] 2436 1000 3 7.75 1.7 4.5 6.4% 15 18 FS LiPb/He 2.6

35%

37%

42%

85% 87*

85% 78#

+

in 1992 US dollars. in 2003 US dollars. # in 2004 US dollars. *

Figure 9. Nine plasma and mid-coil cross sections covering one half field period. Dimensions are in meters. Toroidal angle () measured from beginning of field period.

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Figure 9 displays nine cross sections over a half FP showing the plasma boundary and the mid-coil filament. In each field period, there are four critical regions of min where the magnets move closer to the plasma, constraining the space between the plasma edge and midcoil. min should accommodate the scrapeoff layer (SOL), FW, blanket, shield, vacuum vessel, assembly gaps, coil case, and half of the winding pack. An innovative approach was developed specifically for ARIES-CS to downsize the blanket at min and utilize a highly efficient WC-based shield [19]. This approach placed a premium on the full blanket to supply the majority of the tritium needed for plasma operation. A novel approach based on coupling the CAD model with the 3-D neutronics code was developed to model, for the first time ever, the complex stellarator geometry for nuclear assessments to address the breeding issue and assure tritium self-sufficiency for compact stellarators with Rav > 7.5 m [19].

Figure 10. ARIES-CS cross-section at beginning of field period.

ARIES-CS has 7.75 m average major radius, 6.4% beta, 2.6 MW/m2 average neutron wall loading, and 1000 MWe net electric power. A number of blanket concepts and maintenance schemes were evaluated. The preferred option is a dual-cooled (LiPb and He) FS-based modular blanket concept coupled with a Brayton cycle with a thermal conversion efficiency of 43%, and a port-based maintenance scheme utilizing articulated booms [22]. Analogous to advanced tokamaks, the prospect of using LiPb with SiC/SiC composites as the main structural material offers high operating temperature with high thermal conversion efficiency approaching 56% and lower cost of electricity. The ARIES-CS vacuum vessel is internal to the coils. The overall coil system, consisting of the inter-coil structure, coil cases, and winding packs, is enclosed in a common cryostat. The coils are wound into grooves at the inside of a strong supporting toroidal tube that provides a ring structure to accommodate the electromagnetic forces. A cross-section at the beginning of a FP is shown in Figure 10, depicting the details of the power core components.

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During the 3-y course of the ARIES-CS study, the design point was constantly pushed to the limit in order to understand the constraints imposed by compactness and the impact of the various tradeoffs on the peak neutron wall loading, tritium breeding, peak heat flux at divertor, materials temperatures and stresses, coil complexity, maintenance scheme, and other design constraints [105]. The most notable impact of compactness is the 18 MW/m2 peak heat flux at the divertor that exceeds the 10 MW/m2 engineering limit by a wide margin. The study concluded that increasing the machine size beyond the 7.75 m major radius could be beneficial as it provides more margins for space and engineering constraints with a small cost penalty. Furthermore, alternate aspect ratio (e.g., 6 instead of 4.5), divertor plate orientation, and engineering tradeoffs could lead to more attractive configurations with less complex coils and geometry that help stellarator constructability. Future physics activities should aim at understanding the limiting mechanism for the plasma beta and developing means to reduce the alpha particle losses below the design value of 5% as these energetic particles damage the plasma surrounding wall through blistering [105]. Overall, ARIES-CS has benefited substantially from its compactness, showing economic advantages (with comparable cost to advanced LiPb/SiC tokamaks [42]), and predicting a much brighter future for stellarator power plants than had been anticipated a few decades ago. At this writing, it is premature to state with certainty how the US stellarator community will adapt its research program to the recent cancellation of the compact stellarator NCSX experiment [100]. This cancellation will definitely place the US stellarator development on a longer time scale compared to tokamaks. Nevertheless, a strong collaboration program with the LHD experimental device in Japan [98] and W7-X in Germany [99] will help fill the gap and enhance the physics database. Meanwhile, the national stellarator program should continue the engineering studies to resolve the divertor issues and simplify the coil design.

3.3. Spherical Tori Initiated in the late 1990s, two power plant studies have been made of the spherical torus (ST) concept: the US 3-year ARIES-ST study [112,113] and the UK conceptual ST design [114,115]. The limited number of studies reflects the much smaller ST database compared to tokamaks. Worldwide interest in the ST concept began in the 1980s when Peng et al. [116,117] identified unique physics features of ST as a low aspect ratio (A) device. Key ST features include good plasma confinement, high toroidal beta, and naturally large elongation that allows operation with high bootstrap current (> 90%). Geometrically, the ST device is tall and elongated, having a plasma shape like a football with a central hole to accommodate the inner legs of the TF coils and necessary shielding. This highly elongated shape is quite different from the donut plasma with a D-shape for tokamaks. The strong magnetic field line curvature in STs naturally leads to plasma stability. Consequently, the ST has the ability to operate with high toroidal beta (30-60%) – a major attribute of STs. This particular advantage becomes apparent only at low aspect ratios (A) ≤ 2. Thus, ST plasmas have been produced with A ranging between 1.1 and 2 – low compared to conventional tokamaks with A of 3 or more. Another advantageous feature of STs is the resiliency to major disruptions. Moreover, the toroidal magnetic field is 2-3-fold less in STs compared to tokamaks, calling for normal, non-superconducting magnets with present-day technology and much less shielding requirements. However, the resistive losses in these magnets could be significant, requiring

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large recirculating power (~300 MW), higher fusion power, and a larger machine to deliver 1000 MWe or more. For ST power plants, a challenging task would be to design a divertor system that can handle tens of MW/m2 heat flux with high sputtering rates. On the positive side, the high bootstrap current will reduce the external current drive (CD) power requirements and the high beta will enhance the fusion power and lower the cost of electricity.

Figure 11. Vertical cross section of ARIES-ST [113].

Table V. Key parameters of ARIES-ST and ST design developed in UK. Net Electric Power (MWe) Fusion Power (MW) Major Radius (m) Aspect Ratio Plasma Elongation Toroidal Beta (%) Plasma Current (MA) Bootstrap Current Fraction CD Power to Plasma (MW) Neutron Wall Loading – Peak/Average* (MW/m2) Peak Heat Flux at Divertor (MW/m2) Thermal Conversion Efficiency (%) Peak Magnetic Field at TF Coil (T) Number of TF Coils Normal Magnet Joule Losses (MW) Recirculating Power Fraction *

For FW surface crossing the separatrix.

ARIES-ST [113] 1000 2980 3.2 1.6 3.4 50 29 0.96 28 6.4/4.1 31 45 7.4 continuous shell 329 0.34

ST-UK [114,115] 1224 3260 3.4 1.4 3.2 58 31 0.88 29.3 4.6/3.5 21 43 7.6 16 254 0.39

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START was the first ST experiment, built at Culham, UK in the early 1990s as a smallsize with A=1.3, low-cost device to test the theoretical predictions for low A STs [118]. The combination of small-size, low-cost, and achievable high plasma temperatures and 40% beta in START strengthened the worldwide interest in the ST concept. At present, there are ~20 ST experimental facilities in the US, UK, Italy, Turkey, Russia, Japan, Brazil, and China [119]. The largest two facilities (NSTX [120] in US and MAST [121] in UK) are currently proof-of-principle experiments with D-D plasmas and their successors will burn D-T fuel.

Figure 12. The last closed flux surfaces of ARIES-ST plasma in comparison with ARIES-AT and ITER.

The impressive experimental achievements of the 1990s promoted further interest in exploring the ST potential as a power plant. The first large-scale ST study was undertaken in the US by the ARIES team in 1997, delivering the ARIES-ST power plant [112,113] with 1000 MW net electric power and 1.6 aspect ratio. Table V summarizes the reference parameters and Figure 11 displays a vertical cross section through the main components. To put matters into perspective, Figure 12 compares the plasma boundaries of ARIES-ST with ARIES-AT (an advanced tokamak) and ITER (an experimental device). This illustrates the true compactness of ST only in the radial direction with remarkable increase in height. During the 3-y course of the ARIES-ST study, several tradeoffs between physics and engineering disciplines were necessary to identify a viable baseline design with high beta, high bootstrap current fraction, and well-optimized power balance. Such complex tradeoffs between numerous competing factors became apparent in designing the center post (CP) – the most challenging engineering aspect of STs. In order to reduce the Joule losses and shielding requirements, a single turn coil (without electric insulator) is the preferred option for the CP. Its Cu alloy is water-cooled operating at 35-70oC. The outer legs form a continuous shell (made of water-cooled aluminum) and serve also as a vacuum vessel. The 30 m high CP is tapered at the top for a tight fit to the outer shell and flared at the bottom to reduce the Joule losses [122]. An unshielded CP does not offer an attractive design despite the fact that the

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shield competes with the CP for a valuable space. An effort to reduce the CP Joule losses only and neglect the benefits of the inboard shield led to a non-optimum power balance with degraded system performance. The reference 20 cm thick inboard shield (made of heliumcooled FS) has positive impacts on the tritium breeding, overall power balance, and safety aspects of ARIES-ST [18]. The high recirculating power fraction (0.34) of STs mandates designing a blanket with high thermal conversion efficiency to enhance the power balance. A novel blanket design based on the dual-cooled lithium lead concept was developed in 1997 and used for the first time in ARIES-ST [112,113]. The main blanket features include He-cooled FS structure with flowing LiPb coolant/breeder and SiC inserts to extend the LiPb output temperature to 700oC [20]. A high thermal efficiency of 45% has been obtained and the 3-D nuclear analysis confirmed the ability of the outboard-only blanket to breed the tritium needed for plasma operation [18]. A practical solution was found to handle the high divertor heat flux [20]. First, by inclining the outboard plate by 22o, the peak heat flux can be reduced from 16 to 6 MW/m2. Second, most of the inboard heat flux can be deposited on the W stabilizing shells mounted at the top/bottom of the inboard shield (refer to Figure 11).

Figure 13. Isometric view of ST-UK power plant (courtesy of G. Voss (EURATOM/UKAEA Fusion Association)).

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The maintenance scheme is unique and commensurate with the ARIES-ST simple configuration. The blanket, shield, divertor, and CP are removed as a single unit from the bottom of the device [113]. Demountable joints at the outer TF shell facilitate the replacement of all components. The sliding joint near the lower end of the CP allows its removal and replacement separately, if needed. An advanced fabrication technique led to 20-fold reduction in the cost of the TF coils compared to conventional approaches [25], saving 5 mills/kWh in COE, which is significant. For the same plant capacity factor, the ARIES-ST COE (81 mills/kWh) is comparable to that of the ARIES-RS tokamak [41,39] and ~50% higher than that of ARIES-AT [13] – a more advanced tokamak. An important issue related to the environmental impact of STs is the volume of radwaste generated during operation and after decommissioning. As mentioned earlier, STs are radially compact, but highly elongated compared to tokamaks (refer to Figure 12). The total radwaste volume of ARIES-ST is quite large (3-4 times that of advanced tokamaks). The changeout of the sizable outboard blanket and the ~100 m3 CP every 3-6 years contributes significantly to the operational radwaste. During the ARIES-ST design process, extrapolations beyond the existing physics and technology database were deemed necessary to deliver an attractive end product. Therefore, a list of key R&D needs was compiled for future activities [113]. Experiments with proof-ofperformance are needed to establish the ST-specific physics database. The key technology issues include the compatibility between materials at high operating temperatures [20] and the uncertainties in performance of both advanced FS structure and embrittled Cu alloy of CP [18] under a severe radiation environment. Means to prolong the CP lifetime should be investigated to minimize the radwaste stream. The ST-UK power plant conceptual study [114,115], developed in the early 2000s, provides details for the plasma physics parameters, fusion power core components, power cycle, coil power supply system, and site layout. The key parameters are given in Table V for the design shown in Figure 13. There are similarities and differences between ST-UK and ARIES-ST. Similar engineering features include double-null configuration, single turn watercooled resistive TF coil, 80 cm radius center column containing 15% water and flared at top/bottom, thin inboard shield to protect the center column, outboard-only blanket, and vertical maintenance scheme. Other distinct engineering features [114,115] are related to TF coil construction, blanket and divertor designs, and power cycle. More specifically, these features include:       

16 TF coils made of water-cooled Cu alloy 12 cm thick water-cooled inboard shield 6 y service lifetime for center column 48 blanket modules He-cooled Li4SiO4 blanket with beryllium multiplier and different Li enrichments Cascade flow of SiC pebbles for upper and lower divertors Heat recovery systems for both He coolant (@ 600oC) and water coolant (@ 70200oC).

For consistency, the ST-UK plasma parameters have been iterated with the neutronics, thermodynamic, and mechanical design. The shape and size of the device were arrived at by determining the peak neutron wall loading (4.6 MW/m2) that allows 2 years service lifetime for 100 dpa FS structure [114]. The plasma parameters were then derived self-consistently

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using various physics codes. System studies were performed and several iterations helped guide the design toward the final configuration. The TF coil system influenced the design due to its electrical power requirements that are dominated by the central column. A good compromise and advantages were achieved by shielding the central column with thin inboard shield. The number of outer return legs (16) was determined by the need to reduce the ripple to 2% at the plasma edge. The divertor target surface is composed of SiC pebbles that intercept the particle energy [115]. The pebbles flow under gravity, through ducts embedded in the inboard shield and outboard blanket, cooling the upper divertor first, then the lower divertor before exiting the power core to exchange heat with the helium coolant. The power conversion system handles a spectrum of heat quality (600oC He from blanket and divertor and 70-200oC water from shield and TF coils) to maximize the net efficiency and output power [115]. The maintenance approach takes advantage of the simple extraction of the center column along with its shield, and divertor system from beneath the machine. The blanket is then lowered in groups of four modules and moved to a hot cell [114]. In summary, both the ARIES-ST and ST-UK studies identified the strength and weakness of the ST concept as a power plant, in addition to a set of critical issues to be addressed by dedicated R&D programs. The key technological issues include the high divertor heat flux (> 10 MW/m2), structural integrity of the embrittled Cu center post, blanket materials compatibility issues at > 700oC, and high stream of radwaste. The newly proposed cascading pebble divertor, liquid lithium divertor, and X-divertor (that expands the magnetic flux) overcome the high heat flux and erosion problems, but raise several engineering issues that need serious evaluation. Developing an advanced blanket system, such as the self-cooled LiPb blanket with SiC/SiC composites that delivers high thermal conversion efficiency (5060%), is highly beneficial for STs to help offset the negative impact of the high recirculating power fraction and demonstrate the economic competitiveness of STs with advanced tokamaks. Recycling the CP and all other replaceable components helps minimize the radwaste volume, enhancing the environmental feature of STs. Overall, the prime missions of operational ST experiments and their planned upgrades along with future ST-specific R&D activities are to reduce the gap between existing and next step facilities and to build the physics and engineering database for an attractive ST power plant.

3.4. Field-Reversed Configurations The FRC family of concepts stems from the Astron idea of Christofilos [123], originally invented in the 1950s, and belongs to a set of compact tori that also includes spheromaks. FRC represents one of the simplest configurations that can be envisioned for a fusion device. Geometrically, it is a linear, open-ended cylindrical system, quite different from tokamak, stellarator, ST, and RFP. The FRC configuration, shown in Figure 14, consists of nested magnetic flux surfaces created by currents flowing inside the plasma, with these closed flux surfaces embedded inside a linear magnetic field created by external magnets [124]. The open field lines guide the charged particles to the chamber ends, acting as a natural divertor and carrying 15-20% of the D-T fusion power. Besides removing the impurities from the plasma, this feature offers the possibility of direct energy conversion with high efficiency. The FRC plasma is formed within a set of cylindrical coils that produces the axial magnetic field. Several methods of plasma formation exist. In the most common method

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historically [124], the external field is applied and then reversed in direction, causing the magnetic field trapped in the plasma to spontaneously reconnect and produce closed field lines. This method typically requires more input energy than is desirable for a power plant. Recent FRC research, therefore, focuses on sustainment using rotating magnetic field (RMF) current drive [126], which has been making good progress [127]. Key features of the FRC concept are the well-confined plasma, low magnetic fields, and very high beta (50-100%). The cylindrical chamber is relatively simple and permits easy construction, access, and maintenance of all components. The high beta allows a compact fusion core along with the use of low-field (3-5 T) magnets, simplifying the FRC configuration further. The physics has been studied since the 1950s in the US and Russia [128], plus somewhat later in Japan [124]. The world‘s largest FRC facility, the Translation, Confinement, and Sustainment Upgrade / Large S Experiment (TCSU/LSX) at the University of Washington [129,130] has 0.8 m wall diameter and ~4 m chamber length. Twelve other smaller-scale FRC facilities include IPA, PHDX, PFRC, Rotamak, Co-FRC, Tri-Alpha, FRX-L, and FRCHX in the US, FIX (at Osaka University) and TS-3 (at Tokyo University) in Japan, and KT (at TRINITI) and FIAN (at Lebedev) in Russia.

Figure 14. Isometric view of FRC plasma (courtesy of S. Ryzhkov (Bauman Moscow State Technical University, Russia) [125]). The separatrix divides the closed and open field lines, presenting a natural boundary for the hot plasma.

Figure 15. General layout of UW-FRC power plant (courtesy of J. Santarius (UW-Madison)).

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In the 1970s and 1980s, researchers examined the potential of the FRC concept as an energy producing power plant [131-135]. The latest design of the 1980 series, the FIREBIRD power plant [135], is a D-T fueled, pulsed device with 0.9 m FW radius, 4 MW/m2 neutron wall loading (NWL), and variable chamber length ranging between 33 and 91 m capable of delivering 300-1000 MWe net electric power. The 0.5 m thick He-cooled Li2O blanket contains Pb3Zr5 neutron multiplier. The 46 cm thick water-cooled shield (made of stainless steel, boron carbide, and lead) along with the blanket protects the superconducting magnets. The cyclic pulsing of the design imposed significant transient thermal stresses that affect the fatigue lifetime of the FW and blanket despite the thin 0.5 cm graphite tile placed at the FW to mitigate the stresses during pulsed operation. The 1990s witnessed the emergence of a new steady-state approach that solved many of the pulsed system problems [126]. However, the challenging physics issue was sustaining the plasma current. Reference 136 presents an interesting steady-state D-T power plant design, giving in-depth the RMF current drive parameters, although the engineering systems were not designed in detail. In the early 2000s, a US team from the Universities of Wisconsin, Washington, and Illinois performed a scoping study of critical issues for FRC power plants [137] and invoked the RMF current drive [126] for steady-state operation. The study focused on three main tasks: systems analysis, blanket and shield design, and economic assessment. The 4 m diameter and 25 m long chamber, shown in Figure 15, contains 1.5 m thick heliumcooled Li2O blanket with FS structure followed by 0.6 m thick He-cooled shield and 4 cm thick cylindrical normal magnets. The design utilized thermal and neutronics analyses to design blanket and shield that can handle an average NWL of 5.7 MW/m2. The cost of electricity amounts to ~60 mills/kWh, which is competitive with advanced tokamaks.

Figure 16. Layout of ARTEMIS D-3He fueled FRC power plant [140].

An increased compactness (caused by the high beta) has been identified for the FRC designs to reduce the cost of electricity. As a result of this compactness, the NWL in some FRC designs exceeded the engineering design limit of ~5 MW/m2 and called for advanced fuels (such as D-3He) to alleviate the FW problems or innovative FW protection schemes,

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such as liquid walls [138]. In fact, the Astron concept was the first FRC concept to propose the use of liquid walls [123]. Even though the NWL could reach high values approaching 20 MW/m2, the most serious concern for liquid walls is the potential evaporation of the candidate liquids/breeders (Flibe, LiSn, or Li) that contaminates the plasma [138]. The FRC has been an important platform for investigating the potential advantages of the advanced D-3He fuel cycle that would alleviate many of the problems caused by energetic DT neutrons. In conceptual D-T fusion designs, the magnetic fields optimize at 2-3 T due to engineering constraints. The high FRC beta allows increasing the magnetic field to recover the power density through the fusion power‘s beta2 B4 scaling in order to offset the lower reactivity of D-3He fuel compared to D-T fuel. In the D-3He fuelled RUBY [139], ARTEMIS [140], and joint Bauman Moscow State Technical University/UW FRC [141] designs, there is no need for a breeding blanket and the neutron power is low (≤ 5% of the fusion power), requiring less shielding, while the low neutron-induced radiation damage allows all components to operate for the entire plant life with no need for replacement due to radiation damage consideration. In addition, the device could be built with today‘s technology [142] and, for any D-3He fusion device, the environmental and safety characteristics are superb compared to D-T systems [143]. Moreover, these D-3He designs could obtain electrical power by direct energy conversion of the charged particles with high efficiency, exceeding 70%. Note that while the D-T FRC economics compare favorably with tokamaks, preliminary indications are that the more simple and easy to maintain D-3He FRC reflects an additional 25% cost savings [141]. As an illustration for a typical D-3He configuration, the ARTEMIS [140] central burning section with neutral beams to sustain the plasma and two direct converters for the 14.7 MeV protons are shown in Figure 16 for an overall length of 25 m. Table VI summarizes the engineering parameters for some of the FRC power plant conceptual designs developed to date. All designs are based on 1000 MW net electric power. Table VI. Key engineering parameters for the most recent FRC power plants delivering 1000 MWe. Power Plant Type Fuel Chamber Wall Material Plasma Radius (m) Wall Radius (m) Length (m): Separatrix Chamber Blanket Type Fusion Power (MW) Neutron Power (MW) Average NWL (MW/m2) Surface Heat Load (MW/m2) Energy Conversion Efficiency

UW-FRC [137] Steady-State D-T Solid FS 1.87 2

APEX-FRC [138] Pulsed D-T Liquid Wall 1 2

ARTEMIS [140] Steady-State D-3He Solid FS 1.12 2

RF/UW-FRC [141] Steady-State D-3He Solid FS 1.25 1.8

20 25 Li2O/He/FS 1785 1427 5.7 0.12 52%

8 10 Flibe 2307 1844 18 0.39 40%

17 25 --1610 77 0.4 1.7 62%

30 35 --1937 49 0.14 2.18 60%

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Despite the steady progress made by the FRC community over the past 3-4 decades, the remaining leading issues that hinder the progress of the FRC concept are plasma stability, energy confinement, and an efficient method for current drive. While the D-3He system alleviates the FW problems, exhibits salient environmental and safety characteristics, and offers the benefits of direct energy conversion, its physics is hard to achieve requiring 6-fold higher plasma temperature and 8 times larger density-confinement time product than D-T. Currently, the limited funding worldwide has left many FRC physics and engineering issues unresolved. As such, the FRC community relies heavily on the world-leading US FRC research activities, along with international collaboration, exchange of ideas, and sharing the outcome of theoretical and experimental research.

3.5. Reversed-Field Pinches The RFP is an old concept, first studied in the early 1960s as an axisymmetric, toroidal geometry. At present, the RFP physics is more mature than FRC and spheromak physics. The RFP configuration is much like a tokamak except for the more than 10-fold weaker toroidal magnetic field. The dominant magnetic field at the plasma edge is poloidal. As one moves radially away from the plasma axis, the toroidal field reverses its direction, hence the name reversed-field. Figure 17 displays a schematic view of the RFP plasma configuration. The confining magnetic field is generated primarily by large driven plasma current. Usually, some of the current is self-generated by the plasma through the dynamo effect, although current profile control is being developed to minimize dynamo action as a means to improve energy confinement.

Figure 17. Isometric view of RFP plasma showing typical strength of toroidal and poloidal fields (courtesy of J. Sarff (UW-Madison)).

The distinct feature of RFP that motivates its interest as a fusion energy system is the weak applied toroidal magnetic field. This leads to positive attributes, including high beta values, high mass power density yielding a compact design with favorable economics, normal (non-superconducting) coils with less shielding, weak magnetic forces on coils, single-piece

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maintenance system with high system availability, and free choice of aspect ratio (limited by engineering, rather than physics, constraints). Even though pulsed current scenarios are potentially more attractive at low magnetic fields, the RFP might be operable in a steady-state mode using the Oscillating Field Current Drive inductive AC helicity injection technique, gaining the attractive features of steady-state power plant scenarios. A conducting shell surrounding the plasma is required to stabilize the ideal MHD current-driven instabilities. Hence, resistive wall instability control is required for pulse lengths meaningful for fusion energy application. Furthermore, resistive MHD tearing instabilities are created by gradients in the plasma current density, resulting in magnetic fluctuations that may drive large transport from the plasma core to the edge. Current profile control has proven effective in controlling these instabilities, although for transient periods in experiments to date. An alternate path for improved confinement is to attain a single-helicity dynamo from one tearing mode. To address these challenging issues, the theoretical and experimental bases for RFP have grown remarkably since the late 1970s calling for constructing larger RFP experiments with more intense plasma currents [144,145]. Subsequently, the foremost RFP experiment was built in the US in the mid-1980s at UW-Madison [146]. The Madison Symmetric Torus (MST) research program is focused primarily on developing current profile control to minimize magnetic fluctuations and improve confinement, as well as verify the high beta capability of the RFP. It operates with a thick conducting shell to avoid resistive wall modes. Along with MST, three other modern facilities (RFX in Italy [147], RELAX in Japan [148], and EXTRAP-T2R in Sweden [149]) form the key elements of the international RFP experimental program. The RFX and EXTRAP-T2R devices both use a resistive shell covered by actively controlled saddle coils to mitigate the resistive wall instabilities. Collectively, these experiments have demonstrated that the transport can be reduced significantly by controlling magnetic fluctuations, 26% poloidal beta is achievable, the resistive wall instabilities can be actively suppressed, and the energy confinement time can be increased, enhancing the triple product (nT) by 10 fold. These encouraging results among others promoted the worldwide RFP status to a proof-of-principle program. With appropriate resources, it would be possible to establish the basis for a burning plasma experiment within 20 years. The potential advantages of RFP as a power plant have been demonstrated during the 1980s through a few conceptual studies with 1000 MWe net electric power [150-152]. Major differences between designs occur in the physics parameters and engineering aspects. The earlier 1981 design [150] operated in a pulsed mode, utilized superconducting magnets, and used a relatively low NWL of 5 MW/m2. The 1986 steady-state design parameters with resistive coils were selected from a comprehensive trade-off study taking into consideration the technological issues related to the operation of a high power density RFP with 20 MW/m2 NWL [151]. The full advantages of RFP were validated in 1990 by the multi-institutional ARIES team through the large-scale, self-consistent TITAN study [152]. This study was based on a set of strong physics assumptions and delivered two different designs (TITAN-I and TITAN-II) to demonstrate the possibility of multiple engineering design approaches to small physical size, high mass power density (MPD) power plants. TITAN-I is a self-cooled lithium design with vanadium structure while TITAN-II is a self-cooled aqueous design with FS structure. Using essentially the same plasma parameters, each design has a very high MPD of ~800 kWe/tonne of fusion power core, approaching that of fission reactors. The TITAN study adopted a high NWL of 18 MW/m2 (rather than 3-4 MW/m2 for tokamaks) in order to

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quantify the technical feasibility and physics limits for such high MPD devices. Adding impurities to the plasma to attain very high radiated power fraction helped ease the divertor high heat flux problem. The high NWL requires the replacement of the TITAN torus on a yearly basis. A feasible single-piece maintenance procedure, unique to high MPD devices, was developed for TITAN. Another unique feature for TITAN-I is the use of the integratedblanket-coil concept (IBC) where the Li coolant/breeder flows poloidally in the blanket and also serves as an electrical conductor for poloidal field coils and divertor coils. Designing the power supply is one of the critical issues for IBC, however. Two other types of coils are utilized to control the plasma: normal or superconducting. The general arrangement of TITAN-I is shown in Figure 18. The overall results from the study support the attractiveness of compact, high MPD RFP as an energy system with favorable economics (COE ~40 mills/kWh in 1990 US dollars). Just recently in 2008, Miller [153] modified the TITAN-I characteristics by introducing the modern engineering and economic approaches of ARIESAT, such as the DCLL blanket and updated costing models. Ignoring the ~4 MW/m2 average NWL limit for the DCLL blanket concept, the COE of the modified TITAN (with LSA=2 and NWL of 13 MW/m2) approaches that of ARIES-AT with LSA=1. Besides the economic impact, the major penalty for backing down in the average NWL from 13 to 4 MW/m2 is the larger chamber size that undercuts the rational for compactness, high MPD, and single-piece maintenance [153].

Figure 18. Elevation view of TITAN-I with 3.9 m major radius, 0.6 m minor radius, 0.4 T toroidal field at plasma surface, 23% poloidal beta, 30 cm thick blanket, and 45 cm thick shield.

The 1990 TITAN was based on several strong physics assumptions, such as high plasma current (17.8 MA) and high energy confinement time (0.22 s). Through investigation of the key physics issues of beta limits, energy and particle confinement, transport, and current sustainment, the ongoing US and worldwide RFP experimental program aims to validate the TITAN strong physics assumptions among others.

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3.6. Spheromaks The spheromak belongs to a family of compact tori that includes FRC and field-reversed mirrors. It is a toroidally symmetric configuration distinguished from STs and tokamaks by the simple, compact geometry without toroidal field coils and with no inboard CP or materials, offering a truly compact fusion device with low aspect ratio, high beta (10-20%), and comparable toroidal and poloidal fields. Spheromaks confine the roughly spherical plasma in a cylindrical structure using only a small set of external stabilizing coils. A distinct feature is that the confining magnetic fields are self-generated by the plasma. The super-hot, fast-moving plasma produces magnetic fields that pass through the plasma, generating more current that reinforces the magnetic fields further. The surrounding metallic structure contains the magnetic field. Although the overall design is simple, the plasma dynamo behavior is very complex and difficult to predict or control as it often involves magnetic fluctuations and turbulence. Since the early 1980s, research efforts [154] have focused on understanding how the fluctuations affect the confinement and how to sustain the plasma with sufficient energy confinement and high temperatures.

Figure 19. Schematic of LANL spheromak power core with ~3 m radius chamber [courtesy of R. Miller (Decysive Systems, NM)].

Several spheromak experiments have been constructed in the US, Japan, and UK over the past two decades. The early 1980s experiments did not demonstrate the anticipated higher plasma temperature compared to tokamaks. As a result, interest in spheromaks declined in the US but continued internationally. In the early 1990s, a careful review of the data from the key

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Los Alamos National Laboratory (LANL) experiment triggered interest in reviving the spheromak concept. Subsequently, a thorough reanalysis, led by Fowler and Hooper at the Lawrence Livermore National Laboratory (LLNL), indicated the spheromak plasma parameters are much better than originally calculated. In light of the 1990s reanalysis, several new spheromak experiments were constructed in the US, including SSPX [155], SSX [156], and Caltech Spheromak [157]. Over a period of three decades, numerous scientists believed the simpler spheromak configuration made a better power plant with much lower cost than tokamaks [158-165]. As such, the first US conceptual design [159] was launched by LANL in the mid-1980s to explore the potential of a steady-state spheromak power plant by means of closely coupled physics, engineering, and costing models, using the COE as a figure of merit. Figure 19 displays the LANL spheromak configuration. Several engineering assumptions were made, including 70 cm thick blanket and shield surrounding the plasma, 15 MWy/m2 end-of-life fluence for the blanket structure, and 5 MW/m2 divertor heat flux. A minimum COE occurs near 20 MW/m2 NWL for 2-3 m radius chamber, requiring a blanket replacement every year. The resistive coil thickness (~60 cm), its cost, and recirculating power were closely monitored. The COE varied between 45 and 110 mills/kWh (in 1984 US $) as the net electric power changed from 1000 to 250 MWe. As larger plasma radii yield low NWLs, the relatively low cost of the chamber could allow an economical multiple chambers with lower NWL than 20 MW/m2 to drive a GWe plant [159].

Figure 20. Schematic of LLNL spheromak power core with 4.5 m radius chamber (courtesy of E. Hooper (LLNL) [162]).

The LLNL conceptual 1 GWe spheromak power plant [161,162] is shown in Figure 20 for a configuration with two X-points. The steady-state, high temperature plasma is supported by several solenoidal coils that help produce the shape and elongation of the magnetic flux surfaces. The plasma current is driven by an external coaxial, electrostatic gun. The geometry has a natural divertor with no interference from coils. For such an open system, the divertor heat flux can be spread over a large area as needed. Furthermore, the external location of the divertor offers unique maintenance flexibility for this component. The compactness of

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spheromaks suggests the consideration of a liquid wall (e.g., Li or Flibe) to handle the high NWL and protect the structure against intense radiation [162]. However, several physics and engineering problems must first be addressed before pursuing this option. These include the design impact of a conducting liquid wall, liquid evaporation, liquid flow path, and means for guiding the liquid through the machine. In this respect, the Flibe coolant would have much lower electrical conductivity and vapor pressure. Reference 164 suggests keeping the liquid flow to the outside by centrifugal force for molten salts (Flibe or Flinabe) and by a magnetic guide field for liquid metals (Li or SnLi). For 1 GWe power plant, the divertor heat flux could reach 620 MW/m2 and can be handled by high-speed (100 m/s) liquid jets. The tritium breeding is adequate for 85% blanket coverage. Several inconsistencies were cited in this design calling for engineering resolution and improved physics performance [164]. Overall, the simplicity, compactness, and absence of toroidal field coils make the constructability of spheromaks relatively easy and inexpensive compared to tokamaks. The spheromak will continue to offer an alternate concept if the plasma confinement exhibited in SSPX [155] extrapolates to larger systems. While pulsed power plants, as suggested in Reference 163, may remain viable, experimental results from SSPX cast doubt on a steadystate plant sustained by the simple method of electrostatic gun injection envisioned in Reference 159. However, new theoretical results suggest that an attractive steady-state plant could be developed using neutral beam injection to sustain the plasma current [165]. Even if the spheromak concept is not successful in realizing a path to a power plant, its physics and technology database can be applied to other fusion concepts, such as FRC, RFP, and tokamaks.

3.7. Tandem Mirrors Substantial interest has been generated in tandem mirrors over the two decades of the 1970s and 1980s. In contrast to tokamaks, TM is linear in nature. The basic configuration is a long central cell (90-170 m) terminated by end cells. There are many configurations for the latter, each offering merits and drawbacks. TM is more amenable to maintenance compared to toroidal systems. Other positive attributes include the high beta (30-70%), no driven plasma current eliminating disruptions, the potential for direct conversion of charged particle power into electricity at high efficiency, and the expandable magnetic flux tube to reduce the heat flux on end cell walls. Historically, TM research embarked on decades of single-cell mirror physics beginning in the 1950s [166,167]. Much of the success in TM physics attributes to the achievements gained through research on simple mirrors [168,169]. In the mid 1970s, the TM concept was simultaneously proposed in the US [170] and Russia [171]. Geometrically, there are many possibilities to arrange the various elements of the TM. In 1997, Baldwin and Logan [172] introduced the thermal barrier concept for an attractive power plant, allowing high Q values (10-20) while reducing the technology demand on magnets and end plugs. Over a period of ~10 years, the physics and engineering aspects of TM have been the subject of significant theoretical and experimental studies in the US, Russia, and Japan. By the mid-1980s, a few major TM experimental facilities were operational in the US besides ~10 smaller experiments on the basic mirror approach. The mirror concept was actively pursued in the US by Lawrence Livermore National Laboratory, which built two large mirror and tandem mirror

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experiments in the 1980s, but were never completed nor operated. A variation on the mirror concept was the Elmo Bumpy Torus (EBT) experiment (built in the US at the Oak Ridge National Laboratory) that combined multiple mirror cavities in a toroidal arrangement. The EBT was discontinued when a fatal instability was discovered in the 1980s. The TM-based activities of the 1980s delivered four conceptual power plant designs fuelled with both D-T (WITAMIR [173], MARS [174], and MINIMARS [175]) and D-3He (Ra [176]). Figure 21 displays the overall configurations and Table VII compares the key parameters. It was customary in the 1980s to design plants with high power level exceeding 1 GWe to take advantage of the economy of scale. Normally, the high power requires lengthy TM devices. The overall length of central cell, end plugs, and direct converter system ranges between 140 and 250 m. The shortest length (140 m) belongs to MINIMARS [175] that investigated a lower power level (600 MWe) along with more advanced physics and technology. Most of the magnet problems are in the end plugs where the magnetic field exceeds 14 T. The simplicity of the end cell progressed steadily from WITAMIR-I to MINIMARS, replacing the complex yin-yang coils by C coils and incorporating a gridless direct converter system to handle the wide spread of ion energies. These improvements led to a compact MINIMARS with lower mass and lower end plug cost compared to MARS. The central cell required modest technology such as 3-5 T solenoidal coils, low-activation FS structure operating at 500oC, and a simple maintenance scheme. In 1987, the UW group proposed the Ra [176] TM power plant that burned D and 3He from lunar soil. Most of the energy in the D-3He reaction is in the form of charged particles, commensurate with direct conversion. Thus, Ra channels about half of the 14.7 MeV protons to the direct converter before they thermalize within the central cell, resulting in a high system efficiency of ~50%. The key engineering features of Ra include very low NWL, permanent central cell components, no tritium breeding blanket, and longer overall length compared to MINIMARS [175]. References 177 and 178 present the 1990s view of what needed to be done differently to revitalize the TM program, proposing new configurations for both D-T and D-3He fuel cycles. Only a few minor improvements were recommended for MINIMARS, while several changes were proposed for Ra to enhance the overall efficiency, shorten the length, and lower the cost. Table VII. Selected design parameters for TM power plants. Power Plant

WITAMIR-I [173]

MARS [174]

MINIMARS [175]

Ra [176]

Fuel Net Electric Power (MWe) Overall Length (m) Central Cell Length (m) Central Cell Plasma Radius (m) Average Beta (%) Maximum Field in End Cell (T) Neutron Wall Loading (MW/m2) Blanket/Shield Net Efficiency (%) COE (mills/kWh)

D-T 1530 250 165 0.76 40 14 2.4 FS/LiPb 39 36

D-T 1200 220 131 0.49 28 24 4.3 FS/LiPb 34 46

D-T 600 138 88 0.37 60 24 3.3 FS/LiPb/He/Be 35 41

D-3He 600 158 100 0.51 73 24 0.05 FS/H2O 49 34+3He cost

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Initiated by the US-DOE, Forsen [179] reviewed the progress of the mirror program through the 1980s. Despite Forsen‘s strong recommendations to continue the TM program, the DOE canceled the nearly completed MFTF-B TM experiment in 1986 and began to terminate the TM program in favor of tokamaks and non-TM alternate concepts. Worldwide, the magnetic trap systems with open ends (or mirror machines) were actively developed in Russia during the 1950-1980 time period. However, a shorted magnet kept the planned upgrade of the AMBAL simple mirror to the AMBAL-M tandem mirror from being accomplished [180], exacerbated by budget difficulties. Currently, the development of magnetic traps is progressing at the Budker Institute of Nuclear Physics in Novosibirsk where two facilities are under operation: the gas-dynamic trap and multi-plug trap [181,169]; neither of these is a TM. In Japan, the only operational TM experiment is GAMMA 10 at the University of Tsukuba [182,183]. It is considered by the Japanese fusion society as an educational device, rather than a facility for energy research. Looking forward, there is no strong growth potential for the TM concept. The US DOE made no effort to revive the TM concept for energy applications despite the 1990s effort [177,178] to readdress the TM commercial viability and stimulate interest in the TM concept.

Figure 21. Overall configuration of WITAMIR-I (250 m), MARS (220 m), and MINIMARS (138 m).

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4. FUSION ROADMAPS AND TIMELINE OF FUSION POWER All previous studies have identified the ultimate characteristics of fusion power plants in a fully mature, commercial fusion market (tenth of a kind plant). As will be discussed shortly, the main concept supporting the path from ITER to a power plant is the tokamak. The alternate concepts will help validate the fusion science, offer possible improvements for future tokamaks, and provide risk mitigation (alternate pathways). Since the early 1970s, researchers have been developing roadmaps with the end goal of operating the first fusion power plant in 50 years (i.e., by 2020), believing strongly that fusion should be an option in the 21st century energy mix. But this has been a sliding scale vision with the current expectation still remaining at 50 years in some countries. Recently, optimism about fusion has resurfaced with the construction of ITER in France. Nevertheless, developing fusion energy will cost billions of dollars and would span decades. The key strategic questions are: what technologies remain to be developed and matured for a viable fusion power plant, what other facilities will be needed between ITER and the first power plant, what will it cost, and how long will it take, assuming the existing social and political climate continues? On the other hand, if the social and political climate creates a demand-pull situation, how long will it take to construct the first fusion power plant if the fusion program is treated as a ―Manhattan‖ project with unlimited funds and a limited timetable? In the early 2000s, the US Fusion Energy Sciences Advisory Committee (FESAC) developed a plan with the end goal of the start of operation of a demonstration (Demo) fusion power plant in approximately 35 years. The Demo is viewed as the last step before the first commercial power plant. The FESAC plan recognized the capabilities of all fusion facilities around the world and identified critical milestones, key decision points, needed major facilities, and required budgets for both magnetic fusion energy (MFE) and inertial fusion energy (IFE) [184]. Assuming ITER operates successfully, the FESAC report recommends three MFE facilities before the construction of a tokamak Demo in 2029: Performance Extension Facility, International Fusion Materials Irradiation Facility (IFMIF) [185] operating in parallel with ITER, and Component Test Facility (CTF) operating in 2023. A more recent FESAC study highlighted the specifics of the US Demo [186]. It is a net electrical power producing tokamak plant, demonstrating fusion is practical, reliable, economically competitive, and meeting public acceptance, operating reliably and safely for long periods of time, and employing the same physics and engineering technologies that will be incorporated in commercial power plants. This last requirement is fundamental in determining the unique features of the US Demo that demonstrates and matures the commercial power plant systems. Generally, the US plan has an aggressive vision for Demo (based on advanced modes of performance and operation) with the CTF as an essential element of the US fusion development program. In 2001, the Europeans decided to follow a ―fast track‖ approach [187] and develop the fusion power with one device only (a tokamak Demo) between ITER and the first commercial power plant. Both ITER and Demo will be accompanied by an extensive R&D program and specialized facilities (such as IFMIF) to investigate specific aspects of plasma physics, plasma engineering, fusion technology, and materials [188]. In the reference scenario, the EU Demo construction starts after the completion of ITER phase-I operation and operates around 2027. The EU Demo should satisfy the safety and public acceptance requirements for EU fusion power plants. The near-term Models A, B, and AB of PPCS (refer to Section 3.1.2) are

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currently the main candidates for the EU Demo [188]. For the first power plant, however, more advanced concepts – such as the PPCS Model C – are also being seriously considered. Therefore, in Europe, fusion could be a practical energy source without advanced modes of plasma operation or major material advances, even though the benefits of such advances are clearly recognized and will be integrated in the power plant designs, if proved feasible. The EU Demo will operate in two phases: the first phase confirms the FW lifetime and provides info on compatibility and reliability issues, while the second phase is more oriented towards commercial aspects such as electricity production, tritium self-sufficiency, high availability, and extended operation. The electricity generation from the first EU commercial fusion power plant is anticipated ~40 years from the go-ahead decision on ITER construction. In Japan, the 2005 ―National Policy of Future Nuclear Fusion Research and Development‖ document [189] outlines the four phases of fusion research. The ongoing 3rd phase will help make the decision to construct a tokamak Demo. Besides the basic R&D and Broader Approach (BA) activities, the major supporting facilities during the current 3 rd phase include ITER, IFMIF, and national experimental facilities (JT-60SA, LHD, and FIREX). The 4th phase will assess the technical feasibility of Demo [190,191] that must operate in a steadystate mode without interruption for at least one year. Other characteristics include high availability, high efficiency, tritium breeding ratio > 1, 10-20 MWy/m2 neutron fluence and 1 MW/m2 heat flux at the FW, and higher heat loads at the divertor. Just recently in 2008, the Japanese fusion community proposed a roadmap to Demo as a model case [192]. The success of ITER and ITER-TBM is regarded as the most important milestone in the newly proposed roadmap that has not been officially endorsed by the Japanese government yet. The 2008 roadmap suggests that IFMIF operates in parallel with ITER while Demo operation starts in 2035 (near the completion of ITER Phase-II operation) with electricity production in 2039. Japan will be ready for power plant construction by ~2050 following the demonstration of a stable, long operation of Demo. As noticed, the Japanese strategy suggests advanced operating modes, stressing the importance of technology and materials developments, but without mentioning a CTF. In China, three steps have been envisioned for the Chinese fusion program [193,194]: 1. Speed-up of the domestic fusion program in 2006-2010 2. Establish solid domestic MFE base in 2011-2020 3. Fast track for Demo construction in 2021-2040. The EAST, HT-7, and HL-2M experimental devices play an essential role in establishing the physics and technology bases for steady-state tokamaks. Major new facilities to be constructed in China by 2040 include FDS-I (a hybrid reactor with 150 MW fusion power for transmutation of fission wastes and breeding of fissile fuels) [195], FDS-ST (a spherical tokamak reactor to test the T breeding technology) [196], FDS-II (an electricity generator reactor with 2500 MW fusion power, high power density, high thermal efficiency, and comparable mission to that of US and EU Demos) [75], and FDS-III (a high temperature reactor with 2600 MW fusion power for hydrogen production) [197]. Clearly, the pathway to fusion energy is influenced by the timeline anticipated for the development of the essential physics and technologies for Demo and power plants as well as the demand for safe, environmentally attractive, economical, and sustainable energy sources. Worldwide, the roadmaps take different approaches, depending on the anticipated power

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plant concept and degree of extrapolation beyond ITER. Several Demos with differing approaches should be built in the US, EU, Japan, China, Korea, India, and other countries to cover a wide range of near-term and advanced fusion systems. Recognizing the capabilities of national and international fusion facilities, it appears that, with unlimited funding, the first fusion power plant could add electricity to the grid by 2030-2035. On the other hand, with limited funding and no clear vision, the timetable could extend beyond the proverbial 50 years. Since electricity from fusion is a few decades away, numerous researches [198-203, 49,195,197] suggested a departure from the traditional approach of making electricity and proposed a number of non-electric applications, such as hydrogen production, transmutation of fission waste, breeding of fissile fuels, production of medical radioisotopes, desalination, space propulsion, explosives detection, and altering materials properties. These applications take advantage of the neutron-rich fusion system and offer near-term opportunities to advance fusion development with modest physics and technology requirements. If successful, the public will retain interest in fusion and recognize its potential contributions to society before fusion penetrates the commercial market in 2030 or beyond.

5. CONCLUSION Numerous fusion studies (> 50), extensive R&D programs, more than 100 operating experiments, and an impressive international collaboration led to the current wealth of fusion information and understanding. As a result, fusion promises to be a major part of the energy mix in the 21st century. Power plant studies will continue to be developed and future design processes will deliver more efficient, safe, economical, and maintainable designs that operate at peak conditions. Internationally, the D-T fuelled tokamak is regarded as the most viable candidate for magnetic fusion energy generation. Its program accounts for over 90% of the worldwide magnetic fusion effort. The R&D activities for the six alternate concepts are at different levels of maturity. Even if these alternate concepts are not successful in realizing the path to a power plant, their physics and technology database will offer possible improvements for tokamaks and fusion sciences in general. The philosophy adopted in international designs varies widely in the degree of physics extrapolation, technology readiness, and economic competitiveness:  

US view: power plant must be economically competitive with other available electric power sources, mandating advanced physics and advanced technology EU/Japan view: the first generation of power plants will enter the energy market because of major safety/environmental advantages and large fuel reserve, even if they produce electricity at somewhat higher cost.

The future of fusion power looks bright and fusion will certainly be a major part of the energy mix in 2030 and beyond. The fusion roadmaps take different approaches internationally, depending on the degree of extrapolation beyond ITER. Evidently, several tokamak Demos should be built in the US, EU, Japan, China, and other countries to cover a wide range of near-term and advanced fusion systems. With limited funding and no clear vision, the timetable could extend beyond the famous 50 years that fusion researchers have

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been envisioning since the early 1970s. Nevertheless, with unlimited fusion funding, the first fusion power plant could add electricity to the grid by 2030-2035.

ACKNOWLEDGMENTS The author would like to thank many colleagues in the US, Europe, Japan, and China for reviewing sections of this chapter and providing useful comments. In particular, the author is very appreciative to L. Waganer (Boeing) for his unlimited support and to the following colleagues for their inputs and reviews: J. Santarius (UW), J. Sarff (UW), S. Prager (PPPL), J. Lyon (ORNL), R. Miller (Decysive Systems, NM), K. Fowler, E. Hooper (LLNL), P. Peterson (UCB), D. Maisonnier (EC, Germany), G. Voss (UKAEA, England), H. Wobig (IPP, Germany), K. Tobita (Japan Atomic Energy Agency, Japan), A. Sagara (National Institute for Fusion Science, Japan), S. Ryzhkov (Bauman Moscow State Technical University, Russia), B. Kolbasov (Kurchatov Institute, Russia), and Y. Wu, H. Chen (Chinese Academy of Sciences, China). Special thanks are extended to X. Wang (UCSD), E. Marriott and D. Bruggink (UW) for providing many valuable figures and illustrations.

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[78] Boris, D., Ma, Z., Yuan, H., Ashley, R., Santarius, J., Kulcinski, G. et al., ―Direct Conversion of D-3He Protons Using a Solid-State PIN Junction Diode,‖ Fusion Science and Technology 52, No. 4 (2007) 1066-1069. [79] Miley, G. H. ―3He Sources for D-3He Fusion Power,‖ Nuclear Instruments and Methods in Physics Research A271 (1988) 197. [80] Wittenberg, L., Cameron, E., Kulcinski, G. et al., ―A Review of Helium-3 Resources and Acquisition for Use as Fusion Fuel,‖ Fusion Technology 21 (1992) 2230. [81] El-Guebaly, L. A. "Shielding Design Options and Impact on Reactor Size and Cost for the Advanced Fuel Reactor Apollo," Proceedings of IEEE 13th Symposium on Fusion Engineering, Knoxville, Tennessee, Vol. 1 (Oct. 2-6, 1989) 388. [82] El-Guebaly, L. A. ―Shielding Aspects of D-3He Fusion Power Reactors,‖ Fusion Technology 22, No. 1, (1992) 124. [83] Kulcinski, G. L., Emmert, G. A., Blanchard, J. P. El-Guebaly, L. et al., ―Apollo - An Advanced Fuel Fusion Power Reactor for the 21st Century,‖ Fusion Technology 15, No. 2, Part 2B (1989) 1233. [84] Emmert, G. A., Kulcinski, G. L., Blanchard, J. P., El-Guebaly, L. et al., ―Apollo-L2, An Advanced Fuel Tokamak Reactor Utilizing Direct Conversion,‖ Proceedings of IEEE 13th Symposium on Fusion Engineering, Knoxville, Tennessee, Vol. 2, (Oct. 2-6, 1989) 1043. [85] Kulcinski, G. L., Emmert, G. A., Blanchard, J. P., El-Guebaly, L. A. et al., ―Apollo-L3, An Advanced Fuel Fusion Power Reactor Utilizing Direct and Thermal Energy Conversion,‖ Fusion Technology 19, No. 3, Part 2A (1991) 791. [86] Kulcinski, G. L., Blanchard, J. P., El-Guebaly, L. A. et al., ―Summary of Apollo, a D3 He Tokamak Reactor Design,‖ Fusion Technology 21, No. 4 (1992) 2292. [87] Najmabadi, F., Conn, R. W. et al., ―The ARIES-III Tokamak Fusion Reactor Study -The Final Report,‖ UCLA report UCLA-PPG-1384. Available at: http://aries.ucsd.edu/LIB/REPORT/ARIES-3/final.shtml [88] Vogelsang, W. F. and Khater, H. Y. ―The Impact of D-3He Fusion Reactors on Waste Disposal,‖ Fusion Engineering and Design 5 (1988) 367-377. [89] Attaya, H. M., Sawan, M. E. and Kulcinski, G. L., ―Waste Disposal of Candidate Structural Materials in Fusion Reactors Utilizing Different Fuel Cycles,‖ Fusion Technology 22 (1992) 115-123. [90] Kulcinski, G. L., Blanchard, J. P., Emmert, G. A. et al., ―Safety and Environmental Characteristics of Recent D-3He and D-T Tokamak Power Reactors,‖ Fusion Technology 21 (1992) 1779. [91] Khater, H. Y. and Sawan, M. E. ―Activation Analysis for the D-3He Reactor,‖ Fusion Technology 21 (1992) 2112. [92] El-Guebaly, L. and Zucchetti, M. ―Recent Developments in Environmental Aspects of D-3He Fueled Fusion Devices.‖ Fusion Engineering and Design 82, # 4 (2007) 351361. [93] Santarius, J., Kulcinski, G., El-Guebaly, L., and Khater, H. ―Can Advanced Fusion Fuels be Used with Today‘s Technology?,‖ Journal of Fusion Energy 17, No. 1 (1998) 33-40. [94] Kulcinski, G. L. and Santarius, J. F. ―New Opportunities for Fusion in the 21st Century Advanced Fuels,‖ Fusion Technology 39 (2001) 480-485.

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[95] Santarius, J., Kulcinski, G. and Miley, G. ―A Strategy for D-3He Fusion Development,‖ Transactions of ANS Annual Meeting, Reno, NV. , 4-8 June 2006. [96] Johnson, J. L., Grieger, G., Lees, D. J., Rabinovich, M. S., Shohet, J. L. and Uo, K. ―The Stellarator Program,‖ IEEE Transactions on Plasma Science PS-9, No. 4 (1981) 142-149. [97] The Helically Symmetric Experiment: http://www.hsx.wisc.edu/ [98] The Large Helical Device Project: http://www.lhd.nifs.ac.jp/en/home/lhd.html [99] The WENDELSTEIN 7-X Experiment [100] http://www.ipp.mpg.de/ippcms/eng/pr/forschung/w7x/index.html [101] The NCSX Project: http://www.pppl.gov/ncsx/. [102] Sviatoslavsky, I. N., Van Sciver, S. W., Kulcinski, G. L., Anderson, D. T.,. Bailey, A. W, Callen, J. D. et al., ―UWTOR-M, a Conceptual Design Study of a Modular Stellarator Power Reactor,‖ IEEE Transactions on Plasma Science PS-9, No. 4 (1981) 163-172. [103] Badger, B., Sviatoslavsky, I. N., Van Sciver, S. W., Kulcinski, G. L., Emmert, G. A., Anderson, D.T. et al., ―UWTOR-M, a Conceptual Modular Stellarator Power Reactor,‖ University of Wisconsin Fusion Technology Institute Report UWFDM-550 (1982). Available at: http://fti.neep.wisc.edu/pdf/fdm550.pdf. [104] Böhme, G., El-Guebaly, L. A., Emmert, G. A., Grieger, G., Harmeyer, E., Herrnegger, F. et al., ―Studies of a Modular Advanced Stellarator Reactor ASRA6C,‖ Fusion Power Associates Report FPA-87-2 (1987). Available at: http://fti.neep.wisc.edu/pdf/fpa872.pdf. [105] Miller, R. and The SPPS Team, ―The Stellarator Power Plant Study,‖ University of California San Diego Report UCSD-ENG-004 (1997). [106] Najmabadi, F.,. Raffray, A. R, and the ARIES-CS Team, ―The ARIES-CS Compact Stellarator Fusion Power Plant,‖ Fusion Science & Technology 54, No. 3 (2008) 655672. [107] Beidler, C. D., Harmeyer, E., Herrnegger, F., Igitkhanov, Y., Kendl, A., Kisslinger, J. et al., ―The Helias Reactor HSR4/18,‖ Nuclear Fusion 41, No. 12 (2001) 1759-1766. [108] Beidler, C. D., Harmeyer, E., Herrnegger, F., Igitkhanov, Y., Kendl, A., Kisslinger, J. et al., ―Recent Developments in Helias Reactor Studies, Proceedings of 13th International Stellarator Workshop, Canberra, Australia, Feb. 25-March 1 (2002). [109] Sagara, Mitarai, O., Tanaka, T., Imagawa, S., Kozaki, Y., Kobayashi, M. et al., ―Optimization Activities on Design Studies of LHD-Type Reactor FFHR,‖ Fusion Engineering and Design 83 (2008) 1690-1695. [110] Lyon, J. F. ―Near-Term Directions in the World Stellarator Program,‖ Fusion Technology 17, No. 1 (1990) 19-32. [111] Miller, R. L., Bathke, C. G., Krakowski, R. A., Heck, F. M., Green, L. A., Karbowski, J. et al., ―The Modular Stellarator Reactor: A Fusion Power Plant,‖ LANL report LA9737-MS (July 1983). [112] Wobig, H., Harmeter, E., Kiblinger, J. and Rau, F. ―Some Aspects of Modular Stellarator Reactors,‖ Proceedings of 10th International Conference on Plasma Physics and Controlled Nuclear Fusion Research, London, IAEA-CN44/H-II-4, Vol. III (1985) 363. [113] Najmabadi, F., Jardin, S., Tillack, M., Miller, R., Mau, T. K., Stambaugh, R., Steiner, D., Waganer, L. and the ARIES Team, ―The ARIES-ST Study: Assessment of the

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Spherical Tokamak Concept as Fusion Power Plants,‖ Proceedings of 17th IAEA International Conference on Fusion Energy, Yokohama, Japan (October 1998). Available at: http://www.iaea.org/programmes/ripc/physics/ html/node252.htm [114] Najmabadi, F. and The ARIES Team, ―Spherical Torus Concept as Power Plants–the ARIES-ST Study,‖ Fusion Engineering and Design, 65 (2) (2003) 143-164. [115] Voss, G. M., Allfrey, S., Bond, A., Huang, Q., Knight, P. J., Riccardo, V. and Wilson, H. R. ―A Conceptual Design of a Spherical Tokamak Power Plant,‖ Fusion Engineering and Design, 51-52 (2000) 309-318. [116] Voss, G. M., Bond, A., Hicks, J. B. and Wilson, H. R. ―Development of the ST Power Plant,‖ Fusion Engineering and Design, 63 (2002) 65-71. [117] Peng, Y. K. M. and Strickler, D. J. ―Features of Spherical Torus Plasma,‖ Nuclear Fusion 26 (1986) 576. [118] Peng, Y. K. M. andHicks, J. B. ―Engineering Feasibility of Tight Aspect Ratio Tokamak (Spherical Torus) Reactor,‖ Proceedings of 16th SOFT, London, Elsevier Science Publishers (September 1990) 1287-1291. [119] The Spherical Tokamaks: http://www.fusion.org.uk/st/index.html [120] Worldwide ST Experiments: http://www.toodlepip.com/tokamak/sphericaltokamaks.htm [121] The NSTX Experiment: http://nstx.pppl.gov/ [122] The MAST Experiment: http://www.fusion.org.uk/mast/index.html [123] Reiersen, W., Dahlgren, F., Fan, H-M., Neumeyer, C. and Zatz, I. ―The Toroidal Field Coil Design for ARIES-ST,‖ Fusion Engineering & Design 65 (2003) 303-322. [124] Christofilos, N. C. ―Design for a High Power-Density Astron Reactor,‖ J. Fusion Energy 8 (1989) 93-105. [125] Tuszewski, M. ―Field Reversed Configurations,‖ Nuclear Fusion 28 (1988) 2033. [126] Ryzhkov, S. V. ―Nonlinear Process and Transport in FRC Plasma,‖ Proceedings of International Conference on Frontiers of Nonlinear Physics 2-26 (2007) 118. [127] Alan L. Hoffman, ―Flux Buildup in Field Reversed Configurations Using Rotating Magnetic Fields,‖ Physics of Plasmas 5 (1998) 979. [128] Guo, H. Y., Hoffman, A. L. and Steinhauer, L. C. ―Observations of Improved Confinement in Field Reversed Configurations Sustained by Antisymmetric Rotating Magnetic Fields,‖ Physics of Plasmas 12 (2005) 062507. [129] Ryzhkov, S. V., Khvesyuk, V. I. and Ivanov, A. A. ―Progress in an Alternate Confinement System Called a FRC,‖ Fusion Science and Technology 43 (2003) 304. [130] Guo, H. Y., Hoffman, A. L., Milroy, R. D., Steinhauer L. C. et al., ―Improved Confinement and Current Drive of High Temperature Field Reversed Configurations in the New Translation, Confinement, and Sustainment Upgrade Device,‖ Physics of Plasmas 15 (2008) 056101. [131] Hoffman, A. L., Carey, L. N., Crawford, E. A., Harding, D. G.et al., ―The Large-s Field-Reversed Configuration Experiment,‖ Fusion Technology 23 (1993) 1936. [132] Condit, W. C., Carlson, G. A., Devoto, R. S., Doggett, J. N., Neef, W. S. and Hanson, J. D. ―Preliminary Design Calculations for a Field-Reversed Mirror Reactor,‖ Lawrence Livermore National Laboratory Report UCRL 52170 (1976). [133] Miley, G. H., Choi, C. K. and Gilligan, J. G. ―SAFFIRE---A D-3He Pilot Unit for Advanced-Fuel Development,‖ EPRI Report ER-645-1 (1979).

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[134] Willenberg, H. J., Steinhauer, L.C., Hoffman, A. L., Churchill, T. L. and Rose, R. H. ―TRACT Fusion Reactor Studies,‖ Proceedings on 4th ANS Topical Meeting on Technology of Controlled Nuclear Fusion, King of Prussia, Pennsylvania (1980) 894. [135] Hagenson, R. L. and Krakowski, R. A. ―A Compact Toroidal Fusion Reactor Based on the Reversed Field -Pinch,‖ Los Alamos Scientific Laboratory Report LA-8758-MS (1981). [136] Vlases, G. S. and Rowe, D. S. and the FIREBIRD Design Team, ―Design of a Translating Field-Reversed Configuration Reactor,‖ Fusion Technology 9 (1986) 116135. [137] Hoffman, ―An Ideal Compact Fusion Reactor Based on a Field-Reversed Configuration,‖ Fusion Technology 30 (1996) 1367-1371. [138] Santarius, J. F., Mogahed, E. A., Emmert, G. A., Khater, H. K., Nguyen, C. N., Ryzhkov, S. V.et al., ―Final Report for the Field-Reversed Configuration Power Plant Critical-Issue Scoping Study,‖ University of Wisconsin Fusion Technology Institute Report, UWFDM-1129 (2000). Available at: http://fti.neep.wisc.edu/pdf/fdm1129.pdf. [139] Moir, R. W., Bulmer, R. H., Gulec, K., Fogarty, P., Nelson, B., Ohnishi, M. et al., ―Thick Liquid-Walled, Field-Reversed Configuration Magnetic Fusion Power Plant,‖ Fusion Technology 39 (2001) 758-767. [140] Kernbichler, W., Heindler, H., Momota, H., Tomita, Y., Ishida, A., Ohi, S. et al., ―D3 He in Field Reversed Configurations—Ruby: an International Reactor Study,‖ Proceedings of 13th International Conference on Plasma Physics and Controlled Nuclear Fusion Research, IAEA, Vienna, 3 (1991) 555. [141] Momota, H., Ishida, A., Kohzaki, Y., Miley, G. H., Ohi, S. et al., ―Conceptual Design of the D-3He Reactor ARTEMIS,‖ Fusion Technology 21 (1992) 2307. [142] Khvesyuk, V. I., Ryzhkov, S., Santarius, J. F., Emmert, G. A., Nguyen, C. N., Steinhauer, L. C. ―D-3He Field Reversed Configuration Fusion Power Plant,‖ Fusion Technology 39 (2001) 410-413. [143] Santarius, J., Kulcinski, G., El-Guebaly, L., and Khater, H. ―Can Advanced Fusion Fuels be Used with Today‘s Technology?,‖ Journal of Fusion Energy, 17, No. 1 (1998) 33. [144] El-Guebaly, L. and Zucchetti, M. ―Recent Developments in Environmental Aspects of D-3He Fueled Fusion Devices.‖ Fusion Engineering and Design 82, # 4 (2007) 351361. [145] Bodin, H. A. and Newton, A. A. ―RFP Research,‖ Nuclear Fusion 20, # 10 (1980) 1255-1324. [146] Bodin, H. A., Krakowski, R. A. and Ortolani, O. ―The Reversed-Field Pinch: from Experiment to Reactor,‖ Fusion Technology 10 (1986) 307. [147] The MST Experiment: http://plasma.physics.wisc.edu/mst/html/mst.htm [148] The RFX Experiment: http://www.igi.cnr.it/wwwexp/index.html [149] The RELAX Experiment: http://nuclear.dj.kit.ac.jp/Research_2007.html [150] The EXTRAP-T2R Experiment: http://www.fusion.kth.se/experiment3.html#t2r_device [151] Hancox, R., Krakowski, R. A. and Spears, W. R. ―The Reversed Field Pinch Reactor,‖ Nuclear Engineering and Design 63 (1981) 251-270. [152] Krakowski, R. A., Hagenson, R. L., Schnurr, N. M., Copenhaver, C., Bathke, C. G. Miller, R. L. and Embrechts, M. J. ―Compact Reversed-Field Pinch Reactors (CRFPR),‖ Nuclear Engineering and Design/Fusion 4 (1986) 75-120.

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[153] Najmabadi, F., Conn, R. W., Ghoniem, N., Blanchard, J., Chu, Y., Cooke, P. et al., ―The TITAN Reversed-Field-Pinch Fusion Reactor Study,‖ Final Report, University of California, Los Angeles UCLA-PPG-1200 (1990). [154] Miller, R. L. ―Power Plant Considerations for the Reversed-Field Pinch (RFP),‖ to be published in Fusion Science and Technology (2009). [155] Spheromak Bibliography: [156] http://public.lanl.gov/cbarnes/bib/spheromak_biblio/spheromak_biblio.html [157] The SSPX Experiment: http://www.mfescience.org/sspx/index.html [158] The SSX Experiment: http://plasma.physics.swarthmore.edu/SSX/index.html [159] The Caltech Spheromak Experiment: [160] http://ve4xm.caltech.edu/Bellan_plasma_page/Default.htm. [161] Katsurai, M. and Yamada, M. ―Studies of Conceptual Spheromak Fusion Reactors,‖ Nuclear Fusion 22 (1982) 1407. [162] Hagenson, R. L. and. Krakowski, R. A ―Steady-State Spheromak Reactor Studies,‖ Fusion Technology 8 (1985) 1606-1612. [163] Nishikawa, M., Narikawa, T., Iwamoto, M. and Watanabe, K. ―Conceptual Design of a Cassette Compact Toroid Reactor (the zero-phase study) --- Quick Replacement of the Reactor Core,‖ Fusion Technology 9 (1986) 101. [164] Fowler, T. K. and Hua, D. D ―Prospects for Spheromak Fusion Reactors,‖ Journal of Fusion Energy 14, #2 (1995) 181-185. [165] Hooper, E. B. and Fowler, T. K. ―Spheromak Reactor: Physics Opportunities and Issues,‖ Fusion Technology 30 (1996) 1390-1394. [166] Fowler, T. K., Hua, D. D., Hooper, E. B., Moir, R. W. and Pearlstein, L. D. ―Pulsed Spheromak Fusion Reactors,‖ Comments on Plasma Physics & Controlled Fusion, Comments on Modern Physics 1, Part C (1999) 83-98. [167] Moir, R. W., Bulmer, R. H., Fowler, T. K., Rognlien, T. D. and Youssef, M. Z. ―Thick Liquid-Walled Spheromak Magnetic Fusion Power Plant,‖ Lawrence Livermore National Laboratory Report UCRL-ID-148021-REV-2 (April 2003) [168] Fowler, T. K., Jayakumar, R. and McLean, H. S. ―Stable Spheromaks Sustained by Neutral Beam Injection,‖ Journal of Fusion Energy 28 (2009) 118-123. [169] Bishop, A. S. ―Project Sherwood: The U.S. Program in Controlled Fusion,‖ AddisonWesley Publishing Company, Inc., Massachusetts (1958). [170] Fowler, T. K. ―Fusion Research in Open-Ended Systems,‖ Nuclear Fusion 9 (1969) 3. [171] Post, R. F. ―The Magnetic Mirror Approach to Fusion,‖ Nuclear Fusion 27 (1987) 1579. [172] Ryutov, D. D. ―Open-Ended Traps,‖ Soviet Physics – Uspekhi 31 (1988) 300. [173] Fowler, T. K. and Logan, B. G. ―The Tandem Mirror Reactor,‖ Comments on Plasma Physics and Controlled Fusion 2 (1977) 167. [174] Dimov, G. I., Zakaidakov, V. V. and Kishinevsky, M. E. ―Thermonuclear Confinement with Twin Mirror System,‖ Soviet J. Plasma Physics 2 (1976) 326. [175] Baldwin, D. E. and Logan, B. G. ―Improved Tandem Mirror Fusion Reactor,‖ Physics Review Letter 43 (1979) 1318. [176] Badger, B., Audenaerde, K., Beyer, J. B., Braun, D., Callen, J. D., Emmert, G. A. et al., ―WITAMIR-I, A University of Wisconsin Tandem Mirror Reactor Design,‖ University of Wisconsin Fusion Technology Institute Report, UWFDM-400 (September 1980). Available at: http://fti.neep.wisc.edu/pdf/fdm400.pdf

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[177] Logan, B. G., Henning, C. D., Carlson, G. A., Werner, R. W., Balwin, D. E. et al., ―Mirror Advanced Reactor Study (MARS) Final Report,‖ Lawrence Livermore National Laboratory Report, UCRL-53480 (1984). [178] Lee, J. D (ed.) et al., ―MINIMARS Conceptual Design: Final Report,‖ Lawrence Livermore National Laboratory Report, UCID-20773 (1986). [179] Santarius, J. F., Attaya, H. M., Corradini, M. L., El-Guebaly, L. A., Emmert, G. A. Kulcinski, G. L. et al., ―Ra: A High Efficiency, D-3He, Tandem Mirror Fusion Reactor,‖ Proceedings of 12th IEEE Symposium on Fusion Engineering (1987) 752-755. Available at: http://fti.neep.wisc.edu/pdf/fdm741.pdf [180] Emmert, G. A., Kulcinski, G. L., Santarius, J. F. and Sviatoslavsky, I. N. ―State of Tandem Mirror Physics – 1992,‖ Fusion Power Associates Report, FPA-92-11 (1992). Available at: http://fti.neep.wisc.edu/pdf/fpa92-11.pdf [181] Emmert, G. A., Kulcinski, G. L., Santarius, J. F. and Sviatoslavsky, I. N., Kleefeldt, K., Komarek, P. et al., ―Comparison of Critical Requirements and Prospects for Stellarator and Tandem Mirror Fusion Power,‖ Fusion Power Associates Report, FPA-92-12 (1993). Available at: http://fti.neep.wisc.edu/pdf/fpa93-4.pdf [182] Forsen, H. K. ―Review of the Magnetic Mirror Program,‖ J. Fusion Energy 7 (1988) 269-287. [183] Dimov, G. I. ―The Ambipolar Trap,‖ Soviet Physics – Uspekhi 48 (11) (2005) 11291149. [184] B. Kolbasov, Kurchatov Institute, Moscow, Russia, private communications (July 2008). [185] Tobita, K. Japan Atomic Energy Agency, Ibaraki, Japan, private communications (July 2008). [186] Cho, T., Higaki, H., Hirata, M., Hojo, H., Ichimura, M., Ishii, K. et al., ―Recent Progress in the GAMMA 10 Tandem Mirror,‖ Fusion Science and Technology 47 (2005) 9-16. [187] ―A Plan for the Development of Fusion Energy,‖ Final Report to FESAC (2003). Available at: http://fire.pppl.gov/fesac_dev_path_wksp.htm [188] The International Fusion Materials Irradiation Facility (IFMIF): http://www.frascati.enea.it/ifmif/ [189] ―Priorities, Gaps and Opportunities: Towards A Long-Range Strategic Plan for Magnetic Fusion Energy,‖ Final Report to FESAC (2007). Available at: http://www.science.doe.gov/ofes/fesac.shtml [190] European Council of Ministers Conclusions of the Fusion Fast Track Experts Meeting, held 27 November 2001 on the initiative of Mr. De Donnea (President of the Research Council), EUR (02) CCE-FU/FTC 10/4.1.1, Brussels 5 Dec 2001 (commonly called the ―King Report‖). [191] Maisonnier, D., Campbell, D., Cook, I., Di Pace, L., Giancarli, L., Hayward, J. et al., ―Power Plant Conceptual Studies in Europe,‖ Nuclear Fusion 47, No. 11 (2007) 15241532. [192] ―National Policy of Future Nuclear Fusion Research and Development‖ report (2005). Available at: http://www.aec.go.jp/jicst/NC/senmon/kakuyugo2/siryo/kettei/houkoku 051026_e/index.htm [193] Konishi, S., Nishio, S., Tobita, K. and The DEMO design team, ―DEMO Plant Design Beyond ITER,‖ Fusion Engineering and Design 63-64 (2002) 11-17.

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[194] Tanaka, S. and Takatsu, H. ―Japanese Perspective of Fusion Nuclear Technology from ITER to DEMO,‖ Fusion Engineering and Design 83 (2008) 865-869. [195] Shimizu, Hayashi, T., and Sagara, A. ―Overview of Recent Japanese Activities and Plans in Fusion Technology,‖ to be published in Fusion Science and Technology (2009). [196] Wu, Y., Qian, J. and Yu, J. ―The Fusion-Driven Hybrid System and Its Material Selection,‖ Journal of Nuclear Materials 307-311 (2002) 1629-1636. [197] Wu, Y. ―A Fusion Neutron Source Driven Sub-critical Nuclear Energy System: A Way for Early Application of Fusion Technology,‖ Plasma Science and Technology 3 (6) (2001) 1085-1092. [198] Wu, Y. ―Progress in Fusion-Driven Hybrid System Studies in China,‖ Fusion Engineering and Design 63-64 (2002) 73-80. [199] Wu, Y., Qiu, L. and Chen, Y. ―Conceptual Study on Liquid Metal Center Conductor Post in Spherical Tokamak Reactors,‖ Fusion Engineering and Design 51-52 (2000) 395-399. [200] Chen, H., Wu, Y., Konishi, S. and Hayward, J. ―A High Temperature Blanket Concept for Hydrogen Production,‖ Fusion Engineering and Design 83 (2008) 903-911. [201] Kulcinski, G. L., ―Non-Electrical Applications of Fusion Energy – An Important Precursor to Commercial Electric Power,‖ Fusion Technology 34 (1998) 477-480. [202] Waganer, L. ―Assessing a New Direction for Fusion,‖ Fusion Engineering and Design 48 (2000) 467-472. [203] ―Non-Electric Applications of Fusion,‖ Final Report to FESAC (2003). Available at: http://www.ofes.fusion.doe.gov/More_HTML/FESAC/FESACFinalNon-Elec.pdf [204] Cheng, E. T. ―Performance Characteristics of Actinide-Burning Fusion Power Plants,‖ Fusion Science and Technology 47, No. 4, (2005) 1219-1223. [205] Stacey, W. M. ―Transmutation Missions for Fusion Neutron Sources,‖ Fusion Engineering and Design 82 (2007) 11-20. [206] El-Guebaly, L., Cipiti, B., Wilson, P., Phruksarojanakun, P., Grady, R. and Sviatoslavsky, I. ―Engineering Issues Facing Transmutation of Actinides in Z-Pinch Fusion Power Plant,‖ Fusion Science and Technology 52, No. 3 (2007) 739-743.

In: Advances in Energy Research. Volume 4 Editor: Morena J. Acosta, pp. 171–185

ISBN: 978-1-61761-672-3 c 2011 Nova Science Publishers, Inc.

Chapter 8

R EGIONAL I MPACTS OF THE U.S. E NVIRONMENTAL P ROTECTION AGENCY ’ S SO2 P OLICY Vladimir Hlasny Ewha Womans University, Economics, 401 Posco Building, 11-1 Daehyun-dong, Seodaemun-gu, Seoul, Korea 120-750

Abstract This study compares sulfur dioxide concentrations and the resulting health damages across U.S. regions under three alternative policies considered by the U.S. Environmental Protection Agency: emission caps, emission tax and tradable permits. Regional modeling is important because SO2 does not diffuse uniformly across regions, and because the U.S. energy industry is divided geographically by regulatory barriers, and differences in infrastructure, costs and energy demand. Regional concentrations of SO2 are found to vary across competing environmental policies significantly. Hundreds of millions of dollars in damages are at stake for individual states from the EPA’s policy choice. Emission caps favor southern states, including California, Texas and Florida, where they deliver $840 million lower damages than the other policies. They deliver $390 million higher damages in northern, Great Lakes and New England states.

1.

Introduction

Sulfur dioxide (SO2) emissions from the energy industry cause great damages to human health. The U.S. Environmental Protection Agency (EPA) thus mandates a maximum volume of SO2 that energy generators can jointly emit. Under the Title IV program of the 1990 Clean Air Act Amendment, the EPA assigns generators a fixed number of emission permits, and allows them to trade these permits freely without regard for the location of the respective sources. This policy has been found to lead to significant health improvements compared to previous emission levels. Emission permits are, however, not the only policy that can achieve lower SO2 emissions. Whether emission permits achieve improvements over other policies of similar stringency depends on the spatial distribution of emissions under each policy. Compared to uniformly diffused pollutants such as CO2 , SO2 emissions are not distributed evenly across regions, but stay in the vicinity of their source, where they

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can cause hot spots of pollution and high health-related damages. The impact of SO2 emissions on human health depends on the size of the population affected in each region. If a significant amount of SO2 incidentally lands in densely populated areas, health damages realized across the United States can be greater than if the concentrations were distributed in another way. This paper compares empirically the SO2 concentrations and the damages they cause under the market for emission permits, a uniform emission tax, and a system of emission caps. These policy instruments have all been considered by the U.S. Environmental Protection Agency (EPA) for the control of SO2 emissions from the energy industry. In agreement with the EPA’s objective, the stringency of the three policies compared in this paper is adjusted so that they lead to the same aggregate emissions. The state-by-state comparison determines which regions are winners and which are losers under each policy. A policy that redistributes a given aggregate amount of SO2 from a less populated area to a more populated area could increase total damages (Mendelsohn, 1986). Emission caps, disallowing spatial redistribution of emissions, have been thought to prevent hot spots of concentrations, and pollution in particularly sensitive areas (Shadbegian et al., 2004; Wolverton, 2002). An alternative possibility is that by limiting the movement of emissions, the system of emission caps may restrict even trades that would lower the aggregate damages, such as away from heavily populated states (Ellerman et al., 2000). Theoretical literature suggests that the system of tradable permits and the uniform emission tax should lead to identical outcomes, because they give energy producers the same incentives for emission abatement. Verification of this equality would indicate that the introduction of a competitive permit market without transaction costs does not create other costs of regulation or distortions compared to a tax.

2.

Energy Industry Model

In order to obtain the regional profile of SO2 emissions under each environmental policy, it is necessary to model the behavior of the energy industry. A numerical, partial-equilibrium model of the industry (documented in Hlasny 2006, 2008) is therefore run, and each environmental policy is in turn imposed on energy generators. The customized industry model does not capture all characteristics of the U.S. energy industry, but provides a good approximation of the institutional settings and relationships among the main market participants in the real markets. Care is taken to model regional heterogeneity in regulation, institutions, infrastructure, and cost and demand conditions. To obtain realistic solutions, historic data are used on many industry variables and parameters, including information on current power-generation and emission-cleaning technologies, energy demand and fuel supply. This model obtains the distribution of emissions as generators’ profit-maximizing responses to market forces, constraints and environmental regulation. The model includes all major participants in the U.S. energy industry: generators, consumers and system operators. Implicitly, there is also a federal environmental regulator and state regulators of competition in the energy market. Time frame considered here is short to medium term when generators cannot adjust their capital investment, but can respond by changing the intensity of their production and emission abatement.

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173

Generators

Energy generators choose their output of energy and emission-abatement intensity as optimal responses to other generators’ actions and consumers’ demands. Generators are portrayed carefully as competing in prices in markets with downward sloping demands. The energy market is assumed perfectly competitive and is modeled as static (with perfect foresight and symmetric information). The emission permit trading market is also modeled as static and competitive, and transaction costs and market power play insignificant role in it. The amounts of energy and emission abatement that individual generators can provide are constrained by their production, transmission and emission-abatement capacities, and by federal and state regulation. The nationwide energy market is subject to transmission costs and physical constraints between the North American Electric Reliability Council (NERC) regions. Due to regional differences in the available resources and due to diminishing productivity of these resources, generators’ marginal costs of generation, transmission and emission abatement vary by region and across output levels. Competitive marginal cost pricing is assumed at all generators, regardless of the form of state regulation. This assumption allows easier interpretation of each generator’s motive, and makes modeling convenient. Since over half of U.S. states have already implemented retail restructuring, and the majority of the remaining states expect to restructure in the coming years (DOE–EIA, 2003), modeling the energy industry as pricing competitively is appropriate. Generators in restructured and regulated states are distinguished by their access to transmission grid and ability to compete for customers in other states (refer to Section 2.4.). Variable generating costs are a function of the amount of fuel used, and the administrative, labor and other non-fuel operating and maintenance costs. Non-fuel costs may marginally increase with the generator’s output. Transmission of energy among generators, system operators and customers involves costs that marginally increase in the size of each trade, and in the congestion (or utilization) of capacity on the network segment where each sale is transported. For instance, energy losses from an additional volume traded may increase. Marginal transmission costs thus vary across generators and depend on the volume of trading. Transmission capacities may also be asymmetric across two trading partners. Individual traders view the amount of trading by other traders and the average transmission costs as given. There are many agents using these networks, and each trade represents a small portion of the network capacity. For trades within a region, empirical literature usually ignores the effects of congestion, due to missing data on capacities and utilization of local lines, and a lesser need to consider the presence of multiple traders on a particular network segment. A single generator-buyer pair is assumed on each network segment, so the sellers realize the full impact of their trade on the total transmission costs. 1 Generator’s emissions are linear in the intensity of emission abatement and the preabatement emissions, which depend on the generator’s output, heat rate and fuel sulfur con1

The justification is that generators and consumers in the U.S. are spatially distributed, and the delivery lines to individual customers may be private property of the generator. Even though the model aggregates individual market participants into representative generators (refer to Section 2.5.) and statewide representative consumers, individual generators can reasonably be thought of as serving different areas in a state, or using proprietary network lines.

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tent. Emission abatement costs increase linearly in emissions, holding the abatement intensity constant. This agrees with a commonly made approximation that emission-abatement technologies are capable of removing a certain portion of generator’s emissions, and have a constant variable cost. This means that if a generator removes emissions at a constant rate (in terms of the percent emissions removed), the generator faces a constant per-ton emission abatement cost. Emission abatement costs are convex in the intensity of abatement. Incremental abatement costs per share of emissions removed are low at low levels of abatement intensity, and become large as abatement intensity approaches 100%. This corresponds with the fact that technologies that remove a greater portion of emissions have high relative installation and operating costs, regardless of the generator’s size.

2.2.

Energy Buyers

Consumers in the model come from a single customer class, but differ in their number across states. In each state a representative consumer is modeled. His demand schedule corresponds to the volume purchased at a given price by all real-world customers in a state. Consumers choose the generators offering them the lowest prices. 2

2.3.

Independent System Operators

The energy model distinguishes thirteen NERC regions, in agreement with the institutional setting in the U.S. Each region is modeled as being overseen by a non-profit agent, who enforces open access to the network, routes the energy to comply with all physical constraints, and assigns network losses and transmission fees to the responsible traders. Generators’ sales of energy to consumers in a different NERC region must pass through an interregional network segment common to all trading partners in the two regions. This segment is overseen by an operator, who incurs transmission costs for transporting all energy via this segment. Transmission costs on an interregional network segment depend on the volume of each trade, as well as on the utilization of capacity of the interregional segment by all trades jointly, for instance due to marginally rising line losses. The operator charges each generator a per-unit transmission fee that compensates the operator for the average transmission costs that are due to that generator’s trading activity. This transmission fee covers exactly the average of the trade-specific costs, plus a part of the common, network utilization costs, based on the portion of total trading activity on the network segment that the generator’s trade represents. In the equilibrium, operator exactly recoups all of its costs from generators. 2

In case two generators offer an identical price to the consumer, the consumer assigns them market shares randomly. This decision rule has a spatial interpretation. Generator with the lowest price captures the entire state. If several generators are tied as having the lowest price, these generators can be thought of receiving a service area in the state. Since the representative generators in the model may actually include several realworld generators, these individual generators can be thought of as serving different parts of a state, even when a single representative generator captures the entire state.

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175

Energy Trading Rules

The energy model imposes several rules on interregional trade in energy that approximate well the trends in the U.S. energy industry, and ensure that: • Trading across NERC regions is subject to network capacity constraints which may not be constant or even symmetric across regions. Constraints only affect energy trades among regions, not within them, since information on transmission capacities between individual generators and their local customers is often missing, and these constraints are arguably less important. • Generators sell directly to consumers within their NERC region, but must go through a system operator to sell to other regions. The involvement of a system operator, transmission authority, line owner or another institution is common in literature. This requirement simply forces generators to pass their trades through the agent that maintains interregional network segments and assigns transmission charges to all responsible traders. Trades within a state are conducted directly between the generator and the consumer, and are only subject to transmission costs. • For simplicity, and without effect on the results, it is assumed that the two operators between the dispatching and the receiving region realize a common cost of using the specific interregional network segment, and charge the buyer a single, joint transmission fee. It covers average costs of sending the trade via the particular network segment. • States within each NERC region are divided among those that have permitted restructuring, and those that have not. Generators regulated in the latter states are allowed to import energy to satisfy their requirement to serve local customers, but do not export energy to consumers out of state, so as not to increase prices and risks for their core customers. As an alternative justification, these generators may lack motives to trade. • Energy transmission involves costs including possible energy losses, that are marginally increasing in the volume of the trade.

2.5.

Empirical Issues

The generator-level data come mainly from two sources, the U.S. Department of Energy’s Energy Information Administration (EIA) and the EPA. 3 The EIA data includes generators’ location, ownership, capacity, combustion technology, type of fuel used and fuel characteristics, and other technological specifications. The EPA reports statistics on generators’ compliance with the Title IV, including the permit allocation and trade, pollutant controls installed at the generators, emission factors and total emissions, as well as the generators’ technical specifications, such as fuel usage and coal characteristics.

3

Detailed sources for each model variable and parameter are documented in Hlasny 2006, 2008.

µg $ Figure 1. Marginal Damages from SO2 for Generators in Different States ( ton ) v. Concentrations under the Tradable Permits Scenario ( m 3 ).

Figure 2. NERC Regions and Status of Restructuring by State.

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Statewide energy demands and prices come from the EIA, which reports generators’ monthly energy revenues and sales by consumer class, and also statistics on utilities’ purchases, disposition and energy losses. In-state demands for energy are calibrated using historic volumes demanded and prices, and price elasticities of demand assumed identical across regions and equal to -0.20 (in line with Bohi and Zimmerman 1984, and Wade 2003). Figure 2 shows the geographic definition of each NERC region, and the status of restructuring in each state along with the planned year of restructuring. While the exact regulatory status and its provisions differ by state, this split approximates well the regulatory conditions faced across states, and has been used in previous literature. Transmission capacities for trades across NERC regions are taken from (Paul and Burtraw, 2002). State-specific reserve margin requirements that generators must comply with to ensure uninterrupted service have been adopted from Palmer et al. (2002).

2.6.

Derivation of SO2 Concentrations and Health Damages

Information on emission diffusion and on damages they cause is available only at the state level. After the equilibrium emission profile is found for each policy scenario, emissions are thus aggregated to the state level, and SO2 from non-energy sources in the state are added in. Total state emissions are then mapped into air concentrations of SO2 across U.S. states. Unlike other pollutants (such as CO2 ), SO2 does not accumulate in the air, so its air concentrations depend only on its emissions in the same time period. Transportation coefficients that map state emissions of SO2 to air concentrations in other states come from the Advanced Statistical Trajectory Regional Air Pollution model, as reported by Argonne National Lab (1996). The data on the population’s health responses to the concentrations of sulfur compounds are taken from the EPA (1995). This survey estimates the impacts of air concentrations per microgram of SO2 on human health in various health-impact pathways, and translates the damages into monetary values. Damages from a ton of emissions depend on the size of population affected in each health-impact pathway; the monetary value per incident in each health-impact pathway; and the estimated number of incidents per one unit increase in SO2 concentrations. Figure 1 shows the distribution of marginal damages across generators in different states. Marginal damages are on the vertical axis. The horizontal axis shows SO2 concentrations derived under the tradable permits scenario.4 The figure demonstrates that emissions in low populated parts of the U.S. and near U.S. borders and coasts cause low marginal damages. The U.S. average of these marginal damages, weighted by the amount of regional emissions under the system of tradable permits scenario, is $5,240 per ton of emissions.

3.

Results

This section presents the model results under all environmental policy scenarios. Section 4. compares the impacts of the alternative policies on SO2 concentrations and health damages, and concludes. 4

This figure is thus comparable to figures that follow, where states, on the horizontal axis, are ordered by SO2 concentrations under the tradable permits scenario. One can already see that, incidentally, SO2 concentrations under this scenario are associated positively with marginal damages from SO2 emissions.

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Column 1 in Table 1 gives the range of generators’ emissions and concentrations across the U.S. states resulting under the emission tax scenario. The table accounts for background emissions of SO2 from non-utility sources and from abroad. The average concentration level is obtained by weighting state concentrations by state population. The averages of both variables are closer to the lower bounds of their ranges. Histograms in Figure 7 show that the distribution of SO2 concentrations across the U.S. states is skewed to the right with a long tail, implying that hot spots of pollution may be a problem in parts of the U.S. Interestingly, the average exceeds the median for state emissions, but the ranking is reversed for concentrations. One reason is that adding SO2 emissions from other than energy producing sources changes the distribution of total state-by-state emissions. Another reason is that the effect of generators’ emissions on SO2 concentrations depends on the generators’ location. Redistribution of emissions across generators thus changes the resulting concentrations across U.S. states. Table 1. SO2 Emissions (Pounds per Sq. Mile) and Concentrations (µg/m3) by State across Policy Scenarios Emission Tax

State Minimum

Tradable Permits

Emission Caps

Emissions

Concentrations

Emissions

Concentrations

Emissions

Concentrations

0.17

3.06

0.20

3.10

0.48

3.27

State Average

5,897.65

23.15

5,897.65

23.20

5,898.85

23.02

State Median

5,519.11

28.16

5,491.03

28.18

6,289.23

28.37

State Maximum

31,423.11

84.97

30,854.16

84.69

30,773.81

85.28

The second column in Table 1 shows the emissions and concentrations under the trad¯ able permits scenario. The simulation confirms that in the emission permit market, with E permits freely tradable subject to no restrictions, the market solution is the same as under ¯ the emission-tax scenario with the tax set to achieve the aggregate emissions of E. The third column in Table 1 reports the model results under the emission cap scenario, with the cap on generators’ emissions based on their historic production. Aggregate emissions are very close to those under the emission tax, with a small difference attributable to the small allowed infeasibilities in model equations. Since any non-binding emission caps cannot be transferred among generators, generators cannot directly offset each others’ abatement intensity. Generators with high marginal abatement costs cannot buy a greater emission cap from lower cost generators. To trade the requirement to abate emissions indirectly, generators can trade their energy output, subject to capacity constraints and transmission charges. Column 3 in Table 1 shows the range of emissions and air concentrations observed across U.S. states under the emission cap scenario. Compared to the other columns, the distribution of state emissions changed, resulting in a higher minimum and median, but a lower maximum. The changes from the other scenarios thus occur in states with low and high emissions. These emissions translate into a distribution of air concentrations of SO2 that has a higher minimum, median and even maximum, but a lower mean than the other policy scenarios. Under the emission caps, more states experience an above-average concentration level, but the average of these concentrations is lower.

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Comparison of SO2 Concentrations & Health Damages

The three policy scenarios resulted in almost identical aggregate emissions, 9.2 million short tons, as we desired, with minor deviations due to residuals in the numerical model. Comparing the ranges of statewide concentrations across columns in Table 1, it is interesting to note that higher nationwide emissions do not necessarily translate into higher concentrations. It will turn out that the estimated differences in aggregate damages are also not explained solely by the differences in aggregate emissions. Emission caps based on generators’ historic output are estimated to have the highest minimum and maximum levels of concentrations, but also the lowest average. The permit trading scenario results in lower minimum, median and maximum levels of concentrations, indicating that it does not yield significant hot spots of pollution. Figure 3 shows the distributions of SO2 concentrations across states under the system of tradable permits. States are ordered by their concentrations under this scenario. Figure 3 shows that the distribution of concentrations is skewed to the right (also refer to Figure 7). Thirteen states have SO2 concentrations below ten, and twenty-eight states below thirty micrograms per cubic meter. Only ten states have concentrations above sixty micrograms per cubic meter. The western and northwestern states have the lowest concentrations (below 10 µg µg m3 ), followed by west-central states (15–20 m3 ), and southern and south-central U.S. states µg (mostly 25–40 m3 ). Northeastern and north-central states have overall high concentrations µg under this policy (average is 52 m 3 ). The highest concentrations are in the coal producing µg east-central region (over 72 m 3 ). These results agree with a large number of empirical studies that have found that SO2 pollution is a much smaller problem in the western half of the U.S., and that the greatest pollution levels are in the northeast and the east-central region. Figure 4 shows the differences in concentrations under the emission tax and the emission caps scenarios, against those under the system of tradable permits. Differences in concentrations, rather than the actual values of the concentrations are shown for clarity of comparison. The states in Figure 4 are again ordered according to their concentrations under the system of tradable permits. As expected, the emission tax leads to a very similar distribution of concentrations as the system of permits (the line is close to zero for all states). Emission caps lead to lower concentrations especially in states in the second quartile of the range of concentrations (refer to Figure 7), while they yield higher pollution in states in the third and fourth quartile of the range of concentrations. Any improvement in aggregate damages under the emission caps must therefore come from the low concentrations that they achieve in states that have low concentrations under all policies, and especially in California and Texas. Figure 4 shows that the emission tax and the system of tradable permits lead to lower concentrations than the emission caps in northern states, the northeastern states and several states in New England—Minnesota, Wisconsin, New Jersey and Rhode Island. This agrees with previous findings that the trade of permits resulted in particularly low concentrations in the northeast. The emission caps, in comparison, lead to particularly low concentrations in several states in the southeast and the southwest, such as California, Oklahoma, Texas, Arkansas, Louisiana and Mississippi. Damages from SO2 are a function of SO2 concentrations in each state as well as the population affected by those concentrations. Given that population size and demograph-

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µg Figure 3. SO2 Concentrations under the Tradable Permits Scenario ( m 3 )—States Ordered by Concentrations.

ics vary across U.S. states, concentration profiles under each regulatory policy can lead to different estimated health impacts in each state and nationwide. Emission caps helped to reduce SO2 concentrations in states with overall low concentrations under all policies, particularly several southwestern, midwestern and southeastern states. These states incidentally have high populations. Thanks to this, emission caps achieved the lowest aggregate health damages among the three policies, even though they led to higher concentrations in several northeastern and New England states. Figure 5 presents the health damages realized in each U.S. state under the permit trading scenario. This figure significantly differs from Figure 3, because here the SO2 concentrations in each state are converted to health impacts, and multiplied by the monetary value of the impact and the size of each affected segment of the population. Figure 5 shows that the northwestern states, with low SO2 concentrations, incidentally have low population, and thus enjoy the lowest annual statewide damages from the energy industry emissions, around $78 million (the average of the left-most 12 states). Large states, such as California, Florida, Michigan and Texas incur high damages ($1,698, $1,815, $1,792 and $1,570 million, respectively) even when their SO2 concentrations are low. States incurring the highest damages are New Jersey, New York, Ohio and Pennsylvania, with annual damages of $2,616, $4,542, $4,404 and $4,246 million.

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Figure 4. Differences in SO2 Concentrations against Those under the Tradable Permits µg Scenario ( m 3 )—States Ordered by Concentrations the Tradable Permits Scenario.

Figure 5. Health Damages under the Tradable Permits Scenario ($million)—States Ordered by Concentrations under the Tradable Permits Scenario.

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Figure 6. Differences in Health Damages against Those under the Tradable Permits Scenario ($million)—States Ordered by Concentrations under the Tradable Permits Scenario.

[Emission Tax]

[Tradable Permits]

[Emission Caps] Figure 7. Percent of States with SO2 Concentrations in Different Ranges (%).

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Figure 6 shows the spatial distribution of the differences in damages between the emission tax and the emission caps scenarios, and the system of tradable permits. This figure shows that emission caps redistribute damages across several important states. California, Ohio and Texas receive significantly lower damages (by $478, $66 and $224 million, respectively), while Massachusetts, Michigan, New Jersey, Virginia and Wisconsin see higher damages ($52, $35, $198, $39 and $45 million). In percentage terms, the greatest fall in damages from the system of permits to emission caps occurs in California (-28%), Texas (-14%), Oklahoma (-11%) and Nevada (-9%), while the greatest increase occurs in New Jersey (+8%), Wisconsin (+7%) and New Hampshire (+6%). In sum, the choice of policy instrument affects aggregate health damages even when the aggregate emissions are held constant. Furthermore, damages do not change uniformly for all regions across any two policies, but favor one group of states at the expense of other states. Among the compared policies, emission caps lead to lower concentrations and thus also damages in the southeastern, south-central and southwestern states, including the heavily populated states of Florida, Texas and California. Emission tax and tradable permits, on the other hand, favor the northern, northeastern and New England states, including New Jersey, New York, Virginia and the Great Lakes states.

References Argonne National Lab (1996). Tracking & Analysis Framework (TAF) Model Documentation & User’s Guide. ANL/DIS/TM, 36. Bohi, D. and Zimmerman, M. (1984). An Update on Econometric Studies of Energy Demand Behavior. Annual Review of Energy, 9, 105–154. DOE–EIA (2003). Electric Power Industry Restructuring and Deregulation. DOE–EIA Online Reports, 2003. Ellerman, A., Schmalensee, R., Joskow, P., Montero, J., and Bailey, E. (1997). Emissions Trading Under the US Acid Rain Program: Evaluation of Compliance Costs & Allowance Market Performance. MIT Center for Energy and Environmental Policy Research, 1997. Ellerman, A., Joskow, P., Schmalensee, R., and Bailey, E. (2000). Markets for Clean Air: The U.S. Acid Rain Program. Cambridge University Press. EPA (1995). Human Health Benefits from Sulfate Reductions under Title IV of the 1990 Clean Air Act Amendments. EPA Online Reports, 59. Hlasny, V. (2006). The Impact of Environmental Regulation on SO2 Concentrations and Damages. Ph.D. thesis, Michigan State University. Hlasny, V. (2008). Regulation of Utility Industries in the U.S. Saarbrucken: VDM Publishers. Mendelsohn, R. (1986). Regulating Heterogeneous Emissions. Journal of Environmental Economics and Management, 13(4), 301–312.

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Palmer, K., Burtraw, D., Bharvirkar, R., and Paul, A. (2002). Electricity Restructuring, Environmental Policy, and Emissions. Resources for the Future Report , December 2002. Paul, A. and Burtraw, D. (2002). The RFF Haiku Electricity Market Model. Resources for the Future Policy Report, June 2002. Shadbegian, R., Gray, W., and Morgan, C. (2004). The 1990 Clean Air Act Amendments: Who Got Cleaner Air–and Who Paid For It? Association of Environmental and Resource Economists, 2004. Wade, S. (2003). Price Responsiveness in the AEO2003 NEMS Residential and Commercial Buildings Sector Models. Energy Information Administration , 2003. Wolverton, A. (2002). The Demographic Distribution of Pollution: Does Neighborhood Composition Affect Plant Pollution Behavior? EPA–National Center for Environmental Economics, 2002 Mimeo.

In: Advances in Energy Research. Volume 4 Editor: Morena J. Acosta, pp. 187-230

ISBN: 978-1-61761-672-3 © 2011 Nova Science Publishers, Inc.

Chapter 9

RECENT DEVELOPMENTS IN SAFETY AND ENVIRONMENTAL ASPECTS OF FUSION EXPERIMENTS AND POWER PLANTS Laila A. El-Guebaly1 and Lee C. Cadwallader2 1

University of Wisconsin, Fusion Technology Institute, Madison, WI, USA Idaho National Laboratory, Fusion Safety Program, Idaho Falls, ID, USA

2

ABSTRACT Electricity generating plants powered by nuclear fusion have long been envisioned as possessing inherent advantages for the health and safety of the public, the health and safety of plant workers, and good stewardship of the environment while supporting modern society. This chapter discusses the progress and state-of-the-art of these three principal aspects of fusion safety and environment. The fusion safety philosophy and advantages over traditional thermal power plants are described. Fusion workers should be protected commensurately with workers in other comparable industrial activities. The fusion radwaste management strategy must accommodate the new trend of recycling and clearance, avoiding geological disposal. Here, we discuss the technical elements as well as the US regulatory approach and policy governing the design of safe and environmentally sound fusion devices.

1. INTRODUCTION Safety and environmental concerns for power generation include the health and safety of the public, the health and safety of plant workers, and the short- and long-term environmental impacts. Electricity generating plants powered by nuclear fusion have long been envisioned as possessing inherent advantages for enhanced safety and benign environmental impacts over the presently used fuels. Some of the advantages are the ample and widely distributed source of fuel, inherent plant safety, and avoidance of actinide elements such as uranium, plutonium, and thorium. 

Correspondence to: [email protected]

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At present, there are three primary fuels used in thermal power plants for electric power generation. As shown in Figure 1, the most widely used fuel is coal, followed by natural gas, and then closely followed by fission of uranium (DOE 2007). In this chapter, the safety characteristics of fusion are highlighted and in some cases compared to the three leading fuels for electric power production: coal, natural gas, and fission.

Figure 1. U.S. electric power industry net generation by fuel type, 2006 (DOE 2007).

Many of the nations pursuing fusion research have independently studied the safety and environmental aspects of fusion power. These general studies have been extensive and detailed (Holdren 1989, Sowerby 1990, Brunelli 1990, Raeder 1995, Inabe 1998, Cook 2000). All of these studies, along with numerous design-specific assessments, confirmed that fusion has inherent safety advantages in shutting down the fusion reaction, and in removing the decay heat. Fusion researchers have the advantage of selecting materials based on low neutroninduced activation, which reduces the amount of radioactivity generated over decades of plant operation. However, fusion designs tend to generate a sizable amount of mildly radioactive materials that rapidly fill the low-level waste geological repositories. More environmentally attractive means to keep the volume of fusion radwastes to a minimum are being pursued via clever designs and recycling/clearance so that fusion radwaste would not constitute a permanent burden for future generations. A unique advantage of fusion power is that fusion reactions offer the possibility of direct generation of electricity from the charged particles they emit (Bishop 1958). The direct conversion of charged particle energy into electric power would eliminate the costly and thermo-dynamically inefficient ―balance of plant‖ portion of a thermal power plant: the steam or gas piping, the turbine and electrical generator, the steam condenser and feedwater heaters. At present, the first fusion power plants in the 21st century are still envisioned to be D-T fuelled thermal power plants that require a thermodynamic cycle. However, fusion retains the possibility of direct conversion after the technology has matured, while all other types of power plants do not have this possibility.

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This chapter demonstrates the favorable safety and environmental characteristics of fusion. Sections 2 and 3 highlight the major differences between fusion and other energy sources. Section 4 describes the philosophy of public safety, the minor consequences of accidents, and the technical justification for not needing evacuation of the public. Section 5 covers the safety provisions established to protect the workers from recognized hazards supported with nuclear industrial data on injuries and fatalities. Section 6 outlines the aspects of chemical waste, thermal pollution, and radioactive waste along with a potential radwaste management scheme toward the ultimate goal of radwaste-free fusion.

2. FUSION, FISSION, AND COAL COMPARISON A comprehensive study was performed in the 1980s by a committee of leading energy experts to compare the most promising candidate fusion concepts at that time to existing and conceptual fission power plant designs. The results showed that the most important advantages of fusion were high public protection from reactor accidents, no public fatalities could result from accident releases due to the low radioactive inventories on site and passive barriers to inventory release, substantial amelioration of the radioactive-waste problem by eliminating the high level waste that requires deep geologic disposal, and diminution of links to nuclear weapons – easy safeguards against clandestine use of a power plant to produce weapon materials, and no inherent production of weapons materials that could be diverted or stolen for use in weapons fabrication (Holdren 1989). Fowler (1997) also discussed these safety and environmental advantages, and that the basic processes required for fusion reactor operations (vacuum, magnetic confinement of plasma, plasma heating) are very dissimilar from fusion-based weapons so there is no connection between fusion power plant technology and the hydrogen bomb. Generally, fusion radioactive inventories are less hazardous than in fission, normal and accident releases are smaller than other power plants, and the use of defense in depth design reduces or prevents any radiological or toxicological releases to the public during a power plant accident. The radiotoxicities of neutron-activated fusion materials over the life of the plant are shorter-lived than for fission reactors; many of the fusion products decay over relatively short periods of a hundred years. After that decay period the remaining products are comparable or even below the radiotoxicity of the coal ash at coal-fired power plants (Pease 1991). Fusion offers other potential environmental advantages compared to coal and natural gas. Crocker (1981) stated that thermal power plants using traditional hydrocarbon fuels have concerns with waste heat thermal pollution, release of the so-called ―greenhouse gases‖ (such as carbon monoxide and carbon dioxide), and effluents from impurities in coal and natural gas (such as sulfur) that can lead to sulfurous acid rain. Coal combustion has other gaseous effluents, called flue gases; these include mercury, chlorine, fluorine, and radon gases. Coal combustion has airborne ash particles called fly ash, which contain arsenic, cadmium, potassium, sodium, lead, antimony, titanium, selenium, barium, beryllium, boron, calcium, cobalt, chromium, copper, magnesium, molybdenum, nickel, vanadium, selenium, strontium, and uranium. The fly ash is captured with high efficiency at the plant (Pavageau 2002). Aluminum, iron, manganese, silicon, and thorium are in the heavy ashes called bottom ash retained at the plant (Miller 2005). Certainly, the quantities of these elements are low per ton

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of coal. For example, uranium has roughly 1–100 wppm concentration in many coal samples, although higher concentrations have been seen since coal varies quite widely in impurities (Bisselle 1984). Even with low impurity concentrations, consumption of a thousand tons of coal or more per day at each plant means appreciable masses to filter. McCracken (2005) stated that a coal-fired 1,000 MW electric power plant would consume about 3.5 million tons of coal in a year, and within that coal would be about 5 tons of natural uranium. Burning the coal concentrates the metal impurities inherent in the coal, leaving these metals within the flue gases, fly ash, and bottom ash. Ashes from coal create a disposal problem (Wang 1996), and captured fly ash has been used in road construction and has been investigated for use in building materials (Chou 2003). It is noteworthy that unlike radionuclides, which eventually decay to stable, benign particles (albeit some require very long time periods), chemically toxic elements (such as mercury, selenium, cadmium, chlorine, fluorine, and others) will remain toxic for all future generations. Combustion power plants also release nitrogen oxides into the air. Fusion power plants using a thermodynamic cycle would release heat to the atmosphere or to a body of water, similar to all other thermal power plants. However, fusion power plants would not release greenhouse gases, produce acid rain, release metal aerosols, or release nitrogen oxides. In the more distant future, fusion power plants using direct conversion of charged particle energy into electrical power would release much smaller amounts of waste heat to the environment than present power plants. One of the virtues of coal-fired power plants is that any off-normal events or accidents that have occurred have not typically posed any significant hazards to the public. Coal-fired plant accidents (Frezza 1978), such as steam pipe ruptures, boiler explosions, turbine blade loss, turbine or generator fires, coal stockpile fires, etc., have presented distinct hazards to plant personnel but generally have not threatened the public nor required public evacuation from the plant vicinity (Burgherr 2008). One feature of a coal plant is that it requires a fair amount of land for its site to accommodate fly ash ponds and the piles of coal unloaded from rail cars. With a large site area, the general public is far (e.g., perhaps a mile or more) from the actual plant buildings; this creates a buffer zone called an exclusion area for protection against shrapnel and pressure waves from explosions, radiant heat and smoke from fires, and any other types of energy released from accident events. One of the few direct hazards to the public from coal power plants, besides the plant effluents, is the hazard posed by the railroad trains that deliver coal to the power plant one or more times per day.

3. FUSION FUEL SAFETY Bishop (1958) described some of the earliest recognized benefits of fusion power plants. If mankind could achieve fusion of deuterium then power plants would be fueled by the deuterium (D) isotope of hydrogen. Present ideas for the 21st century fusion power plant are deuterium-tritium (D-T) fuel because the reaction is easier to achieve with less technical challenges than using deuterium fuel alone. D-D fuel is more attractive because D exists in nature and can be separated relatively easily and inexpensively from seawater (Saylor 1983) and also from fresh water, allowing the processed water to be used for other purposes. Thus, D-D fuel can be collected by distillation or other means without the safety issues and environmental impacts inherent in coal mining, uranium mining, or petroleum product drilling for natural gas or oil. The natural abundance of the D isotope in hydrogen is about

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0.015 at% (Weast 1979), which means that there is roughly one D atom per 6500 hydrogen atoms. All countries of the world have access to water and hence to fusion D-D fuel reserves, which leads to a widespread and abundant fuel supply for all countries without constraints on the use of fusion energy for centuries. A unique fuel-related safety benefit is that a controlled fusion power plant is more inherently safe than other power plants because of fusion‘s distributed inventory of fuel. A fusion plant regularly injects fuel in tiny quantities, fractions of a gram per second (Murdoch 1999). The plant operates with deuterium and tritium plasma that, at any given time, weighs on the order of 1 gram (McCracken 2005). Fueling the plasma is accomplished either by injecting tiny frozen pellets of D-T into the plasma or by puffing milligram quantities of gas into the fusion chamber at the edge of the plasma. This fueling process is continuous with small amounts of D-T fuel, similar to a coal-fired power plant that pulverizes coal into small particles and injects these small quantities of coal particles into the combustion chamber of its boiler (Environmental Protection Agency 1997). A fusion plant is inherently safe because if the plant is not continuously refueled, the fusion process is limited to a few seconds burn; the fuel in the plasma would be consumed and the plant would be quickly shut down. A fusion plant stores its D-T kg supply for 1-2 days at room temperature in a chemically benign form within a specially designed building (DOE 2007a) to contain the gaseous tritium fuel against leakage. Therefore, no large quantity of fuel is stored within the machine. To the contrary, a fission power plant has over 100 tons of fuel in the core to operate for 12, 18, or 24 months until shutting down to refuel. Deuterium and tritium are combustible gases; however, the onsite inventories for an advanced fusion plant are less than a few kilograms (Murdoch 1999, El-Guebaly 2009), and this small quantity is a very low combustion hazard compared to the large quantities of natural gas or coal dust found at fossil-fueled power plants. Another inherent fusion safety feature is the lack of a nuclear chain reaction. As stated above, if the plant fuel supply is stopped, the reaction also stops in a few seconds – the plasma will not continue operating. Similarly, if the fusion plasma experienced a postulated thermal runaway event, the extra heat produced would melt or vaporize a small depth of the face of armor tiles on the fusion chamber walls, sending kg amounts of relatively cool temperature impurity particles into the edges of the hot plasma. Such cool (compared to plasma ion temperatures) impurities in quantity at the plasma edge cause a plasma density limit disruption. The plasma would leave its confining magnetic fields, deposit its energy on the armor tiles, quickly and effectively terminating the plasma without any operator or automated safety system intervention. The tiles are built to withstand heat damage from such plasma disruptions. With more study, fusion researchers believe that they will be able to predict plasma performance and control the plasma so that plasma disruptions will be rare and wall armor tiles will no longer be needed (Najmabadi 2006). Fusion power plants do not use actinide elements such as uranium, plutonium, and thorium. Coal (U.S. Geological Survey 1997) and natural gas and oil (American Petroleum Institute 2006) have part per million concentrations of impurity actinide elements uranium and thorium, and their progeny, radium and radon. These radioactive impurities are generally referred to as naturally occurring radioactive materials (NORM). They are not considered to be a public hazard until the amounts of raw material (coal, natural gas, or oil) grow to very large quantities. A coal-fired power plant can use thousands of tons of coal per operating day, depending on its size and electrical output. With that sort of consumption, even small concentrations of NORM present reasonably large masses of concern. Fission power plants

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primarily use ≈100 tons of uranium fuel per year, which generates fission products. Comparatively, an advanced fusion power plant would use 100-200 kg of hydrogen isotope fuel per year (El-Guebaly 2009) and the products from D-D or D-T reactions are not radioactive, they are usually neutrons and helium nuclei. The energetic neutrons activate the plasma surrounding structural materials, but not to the same level as fission products. The primary fuel for fusion is tritium with a radioactive half-life of 12.3 years, decaying to helium-3, versus uranium with a radioactive half-life of 4.47E+09 years and decaying to other radioactive products (Baum, 2002). Thus, a fusion power plant would not use or release any actinide elements, nor would it have the long-lived fission products or the radiotoxicity concerns of storing spent fission fuel. A key safety feature of fusion power is that while fission power plants must use some heavy element (uranium, thorium, or plutonium) for fuel and reactor materials choices are limited by fission neutronics, fusion fuel is hydrogen isotopes and fusion designers can select the most advantageous chamber and armor materials of construction, which are referred to as low activation materials (Kummer 1977). In that way, fusion produces quantities of low-level radioactive waste, which could be recycled or easily disposed of by burial at several sites in the US, versus the high-level radioactive waste (spent uranium or other nuclear fuel) which has become a disposal issue in the fission industry and raises proliferation concerns if reprocessed.

4. PUBLIC SAFETY AND ASSESSMENT 4.1. Fusion Safety Philosophy and Assessment This section describes the efforts taken to ensure the safety of the public and the analyses performed to demonstrate public safety. Public safety in many endeavors is attained by the use of a design principle called defense in depth. This principle is used in nuclear power (Petrangeli 2006), the chemical process industry (Kletz 1991, Pekalski 2005), aerospace (Fortescue 1991), and other applications. Defense in depth is both a design philosophy and an operations philosophy to use multiple levels of protection to prevent accidents and mitigate any accidents that might still occur. There are three tiers to defense in depth (Knief 1992): 



The first tier of defense in depth is prevention, where the designers seek to avoid operational occurrences that would result in radiological or toxicological releases that could harm members of the public. Prevention calls for high reliability components and systems and use of prudent operating procedures. Prevention includes selecting inherently stable plant operating characteristics, passive means to benignly shut down the plant in case of an accident, including: safety margins in the design, performance testing and inspections of systems, adequate operator training, and good quality assurance programs. The second tier of defense in depth is protection. The plant will have safety functions for protection of the public, workers, and the environment. While high reliability is important, inevitably, some component can fail and present an off-normal occurrence or accident in the plant. Safety systems, such as fast plasma shutdown, air and effluent monitoring, and safety interlock systems, are part of protection. In fission power plants, these systems are referred to as engineered safety features.

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The third tier of defense in depth is mitigation. This final tier limits the off-site consequences of any accidents that may occur despite the first two tiers. Mitigation systems are confinement buildings (e.g., vacuum vessel and cryostat), air cleaning systems such as filters and scrubbers, ventilation stacks, emergency power systems, and passive heat sinks (Knief 1992). Existing fusion experiments use defense in depth, commensurate with the energies and hazardous materials in use. In the US, this approach is proven, prudent, and mandated by the US Department of Energy (DOE) for fusion experiments (DOE 1996a). The National Ignition Facility (NIF) at Lawrence Livermore National Laboratory (LLNL) (NIF Project) has used defense in depth, multiple barrier concept to protect its radiological and toxicological inventories (Piet 1995, Brereton 1997). The International Thermonuclear Experimental Reactor (ITER), under construction in Cadarache, France, has used defense in depth, called ―lines of defense,‖ as part of its safety design (Saji 1995). Future fusion power plants will use defense in depth as well.

Because fusion research is presently conducted by DOE, that agency has published a safety directive for fusion (DOE 1996a). The facility safety functions to ensure public safety are:       

Confine radioactive and hazardous material within the plant Ensure afterheat removal from the fusion device Provide rapid plasma shutdown Control coolant internal energy Control chemical energy sources Control magnetic energy Limit routine airborne and liquid radiological releases.

The design approaches to accomplish these public safety functions are defense in depth concepts. These are designing for high reliability of plant systems and use of multiple confinement barriers; this includes the use of redundant and diverse components, system independence, simplicity in design, testability of systems and components, use of fail-safe and fault-tolerant design, and incorporation of best practices in human factors for the plant staff and for the control room human-machine interface. As fusion experiments transition from testing the physics and technology to a demonstration power plant (Demo) and commercial electric power-producing facilities, there will also be a transition from operation and safety regulation by DOE to licensing, operation, and radiation exposure regulation by the U.S. Nuclear Regulatory Commission (NRC). Similar transitions with fission power plants have been seen in the past. The U.S. Atomic Energy Commission, a predecessor to DOE, supported technology development and conducted the Power Reactor Demonstration Program in the 1950s and 60s for light watercooled reactors (Shippingport and Yankee Rowe pressurized water reactors; Elk River and Dresden boiling water reactors), a gas-cooled reactor (Peach Bottom-1), an organic cooled reactor (Piqua Plant), and liquid metal cooled reactors (Hallam Sodium Reactor Experiment and Enrico Fermi-1) (Allen 1977). Therefore, government support of new, complicated technology being entered into the market is a plausible path and it is expected that regulations

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would transition from DOE to NRC when a commercial firm or consortium is a partner in fusion power plant construction and operation. The DOE safety standard for fusion power plants (DOE 1996a) is congruent with NRC regulations. No power plant, or any other engineered facility, can ever be absolutely safe. Absolute safety of any power plant would mean that the designers were infallible and also that the upper limits of effects from natural disasters could be predicted so that a power plant could be protected against these effects with absolute certainty (Lewis 1977). Because absolute safety is not possible, all types of power plants have measures of safety developed so that risks to the public are kept as low as possible. Governments legislate licensing and regulatory requirements on power plants. In the U.S., the Environmental Protection Agency (EPA) regulates the pollutant emissions from fossil-fueled power plants and nuclear fission power plants, while the NRC regulates design, construction, operation, and decommissioning of nuclear fission power plants. The Federal Energy Regulatory Commission (FERC) regulates the sale of electrical power to promote a fair market. Because fusion power plants will generate neutrons that activate its structural materials and the initial technically feasible fusion power plants will be fueled with radioactive tritium fuel, these fusion plants are expected to be regulated with the same safety rules and regulations applied to fission power plants. There will be stringent NRC requirements on plant design, plant location, construction, operation, and decommissioning. Table 1 gives some of the existing public safety limits for operating fission power plants; these limits are expected to be applied to fusion power plants. A question that often arises is: Are these limits safe enough? A fission power plant is mandated by the NRC in its 1986 Safety Goals to: a) limit the accident risk to any member of the public to less than 0.1% of the sum of prompt fatality risks resulting from other accidents to which members of the population are generally exposed, and b) prevent exposure of any member of the public to cancer-causing radiation that would cause greater than 0.1% of the sum of cancer fatality risks from all other causes (NRC 1986, Ramsey 1998). In essence, the NRC tried to answer the question: How safe is safe enough? (Kumamoto 2007). The NRC believes that remaining below a 0.1% additional risk is inconsequential for members of the public. This safety goal is likely to be applied to fusion power plants as well. The experience with ITER (ITER Project) and NIF, both of which easily meet this goal, suggests that future fusion power plants can meet and exceed this safety goal.

4.2. Deterministic Safety Analysis With the public exposure limits established, fusion power plants can be evaluated by analytical methods similar to other nuclear power plants. There are two means to evaluate power plant safety, and they complement each other. The first means is a traditional approach called deterministic safety analysis. Keller (2005) describes that in the early days of the nuclear fission industry, the Atomic Energy Commission (AEC) regulatory engineers—with very little operating experience data available to them—avoided the need to calculate best estimate uncertainties for safety systems by using deterministic approaches that used conservative assumptions and calculations. Safety was defined as the ability of the fission power plant to withstand a fixed set of prescribed, or determined, accident scenarios that the

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AEC judged to be the most significant adverse events that could occur in a fission power plant. Table 1. Safety limits on releases from fission power plants Safety limit Annual total dose to the public from NRC licensed operation Annual airborne release of gaseous effluents to unrestricted areas Annual liquid pathway releases of effluents to unrestricted areas Average annual concentration of beta particle and photon radioactivity in drinking water Annual dose equivalent as a result of planned discharges of radioactive materials from the uranium fuel cycle

Annual dose equivalent of radionuclide emissions to the ambient air Postulated fission product release accident

Dose to a Member of the Public 100 mrem total effective dose equivalent 10 mrem gamma or 20 mrem beta

Regulation

Comment

10CFR20.130 1 10CFR50 Appendix I

3 mrem whole body or 10 mrem to any organ 4 mrem equivalent to the total body or to any organ 25 mrem to the whole body

10CFR50 Appendix I

10 mrem effective dose equivalent

40CFR61.92

25 rem total effective dose equivalent in 2 hr at the site boundary during an accident event

10CFR50.34

40CFR141.66

40CFR190.10

Radon and its daughter products are not included in this limit. Fuel cycle includes milling ore, converting and enriching uranium, fuel fabrication, fuel use in a reactor, and reprocessing spent fuel. This regulation applies only to DOE facilities. The 25 rem is a reference value, not an upper limit for emergency dose to the public. The value is used to evaluate designs and keep public risks as low as reasonable achievable.

If the plant could maintain public safety with these events, then the plant could maintain safety in other, lesser consequence events that were more likely to occur. Therefore, the approach was to determine a set of plausible accident causes, select those causes that had the highest consequences to public health and safety, and thoroughly analyze the set of resulting accidents. If the consequences were tolerably low, then the plant would be termed safe. These events challenge the design basis of the plant. The design basis is the set of requirements used in the basic design of the power plant, including safety, reliability, plant availability, maintainability, and plant efficiency. The accidents analyzed in deterministic safety analysis are referred to as design basis accidents. The set of high-consequence fault events to be

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analyzed is determined by severity rather than identified via frequency of occurrence, so this type of analysis is referred to as deterministic (Pershagen 1989). Calculational models of thermal-hydraulics and neutronics are used for fission power plants to analyze the chosen events. Deterministic analysis is performed to show that permissible values of plant parameters chosen in the design basis are not exceeded to prove that the design is robust against accident events. The deterministic analysis for fission power plants has been guided and refined by the NRC in 10CFR50 to consider a wide variety of specific events; for example, rupture of a large cooling water pipe – called the large break loss of coolant accident. Abramson (1985) and Lillington (1995) give detailed explanations and methods to analyze the accident events that must be considered. The results of the analyses are documented in a safety analysis report (SAR), which is a required document in the plant licensing process. The NRC has a Standard Review Plan (NRC 2007) that outlines what should be included in a SAR and how a review of a SAR for the licensing process should be conducted. A SAR document has been required since the beginning of commercial fission power plants in the U.S. and has many important purposes. One of these is to describe the power plant, its design, fabrication, construction, testing, and expected performance of plant structures, systems, and components important to safety. This document shows compliance with NRC regulations, especially the General Design Criteria specified in Appendix A of 10CFR50. The SAR also presents the power plant‘s site and meteorology, the plant safety limits, safety settings, control settings, limiting conditions of operation, surveillance requirements (testing, calibration, and maintenance), emergency procedures, and technical specifications of operation. A third purpose for a SAR is to demonstrate that the power plant can be constructed, operated, maintained, shut down, and decommissioned both safely and in compliance with all regulations, laws, and design requirements. The SAR and its deterministic analysis have been described in Pershagen (1989). The NRC accepts a preliminary SAR and reviews it as part of the power plant operating license process. The primary NRC concern is that the proposed power plant can be operated without undue risk to the public (Okrent 1981). If the preliminary document were approved by the NRC, then the utility company would be granted a construction permit to begin plant construction. The utility staff then prepares a final SAR. The final SAR gives more detail about the final design and operation of the power plant. No matter what changes occur with the licensing process, a final SAR is required before the NRC will grant an operating license to the plant. Fusion designs with the DOE have followed the same path: to develop a SAR on the design. However, fusion does not have the development effort or the operating experience that fission power plants have had to support identification or determination of accident events.

4.2.1. Experimental Facilities: ITER and NIF The ITER design, shown in Figure 2, followed a progression of steps to build its own safety process that followed the same path that fission power safety had followed. The ITER staff strived to construct a safety analysis framework that accounted for the unique aspects of fusion. An International Atomic Energy Agency (IAEA) report called the General Safety and Environmental Design Criteria (GSEDC) (IAEA 1996) was written early in the ITER engineering design activity; it outlined the safety objectives, public safety functions, and safety design requirements for ITER systems.

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Figure 2. Isometric view of ITER (ITER Project). Published with permission of ITER.

The GSEDC was followed by the Early Safety and Environmental Characterization Study, a project document that identified radiological and toxicological inventories, gave limits for inventories, estimated routine releases, and gave direction about calculating consequences from both routine and accidental releases of radiological and toxicological materials. These documents set the safety and environmental criteria for the design teams to follow. The ITER project team then wrote the Non Site-specific Safety Report (NSSR) to address ITER safety at a generic location because the site had not been selected (Bartels 1995, Bartels 1998). Twenty-five reference accidents were evaluated in the NSSR. ITER reference events are design basis accidents—fundamental events included in safety analyses. These accidents included plasma upset events, cooling upset events, electric power upset events, loss of coolant into the vacuum vessel, loss of coolant outside of the vacuum vessel, loss of coolant flow, loss of vacuum, tritium leaks, maintenance events, magnet arcs, and other events. All events were analyzed and found to have radioactive releases much lower than the stringent ITER release limits, which were set lower than those of the participating countries to ensure ITER would be licensable in any participant country. The analysis proved that the

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ITER design was robust against the reference events. A set of hypothetical accidents were also identified to investigate the ―ultimate safety margins‖ of ITER to verify that no events, at frequencies just below the 1  10−6/yr frequency limit for reference accidents, existed which would pose high consequences to the public (Petti 1999). In DOE terms, the ultimate safety margin events would be called beyond design basis events (DOE 2006). This is referred to as cliff-edge effects, the cliff being the 1  10−6/yr frequency limit. That analysis showed that nearly all of the hypothetical events resulted in public doses of less than 1% of the strict ITER dose limit. The largest dose from the highest consequence accident, an ex-vessel loss of coolant accident with several aggravating failures and a confinement bypass to the environment (which is not plausible in the design), was less than 75% of the ITER noevacuation dose limit of 50 mSv (5 rem). The analysis showed that there were no drastic increases in radiological releases for any events below the frequency limit. Also, ITER had several inherent safety advantages that maintained public safety during accident events:   

The vacuum vessel was designed with adequate structural margins to maintain integrity in all events Any ITER runaway plasma would shut down by impurity ingress from the wall materials or from in-vessel water or air leaks The design values of radioactive inventories were modest so the confinement barriers were not taxed to confine releases.

A passive heat removal system is used that removes radioactive decay heat from the vacuum vessel in case of an accident that includes loss of electrical power to operate the plant shut down equipment (Bartels 1996). The system uses natural convection, buoyancy-driven flow of water to the building roof so that heat is exchanged via an ambient air heat exchanger. The ITER team noted that the ex-vessel loss of coolant event did come close to the noevacuation dose limit and made design provisions to reduce the potential frequency of occurrence and reduce the radiological inventory to decrease the consequences if the event did occur. As the ITER project progressed and developed more design detail, a Generic Site Safety Report (GSSR) was written. It is summarized in an ITER design report (IAEA 2002). The GSSR is a SAR for a generic site that might have been located in any participant country. The GSSR formed the basis of plant-level safety assessment and licensing efforts for ITER (Gordon 2001, Marbach 2003, Gordon 2005, Rodriguez-Rodrigo 2005). After the ITER site was selected in June 2005, additional safety assessment to tailor the GSSR to the Cadarache site in southern France and to account for host safety and environmental regulations was performed (Taylor 2007, Girard 2007). The GSSR and follow-on work was used as the basis for the Rapport Preliminaire de Surete (preliminary SAR) that was requested by the French safety regulator, the Autorite Surete Nucleaire (ASN) (Girard 2007, Taylor 2009). The ASN grants permission to construct and operate nuclear experiments and assigns licenses to nuclear power plants. ITER licensing as a basic nuclear installation has followed the approach of public hearings and reviews by safety experts and the ASN (Girard 2007). The ITER preliminary SAR was delivered to the ASN in early 2008 and is under revision as of this writing. The expectation is that the RPrS will be approved by the ASN in 2010 and after approval it will become a public document. French regulations for nuclear research facilities

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are overall very similar to U.S. regulations for nuclear facilities and power plants, so a regulatory precedent has been set for large fusion experiment projects. A SAR was also required by DOE for licensing operation of the NIF (LLNL 1999). Figure 3 displays the NIF layout. The NIF SAR followed the DOE guide for safety analysis that has evolved over time (DOE 2006). This guidance is very similar to NRC direction for safety analysis, although the DOE guide allows the use of probabilistic techniques (refer to Section 3.3) to apply a graded approach to safety. A graded approach means that as hazards and inventories increase the level of safety assessment, the depth and rigor of safety assessment, also increases commensurately. SARs for past magnetic fusion experiment designs (Motloch 1995) have also used the DOE SAR guide. These fusion experiment SARs are similar to fission reactor SARs but account for the unique aspects of fusion.

Figure 3. Layout of NIF. The photo with a cutaway roof shows the laser beam lines that traverse the length of the facility, converging on the spherical target chamber. Further information is available at the NIF website (NIF Project).

4.2.2. Power Plants Previous studies for setting public safety bounds in both inertial and magnetic fusion used analyst judgment to identify the highest consequence accidents, with good results (Khater 1992a, Khater 1992b, Khater 1996, Steiner 1997, Khater 1998, Petti 2001, Khater 2003, Petti 2006, Merrill 2008, Reyes 2001). In the US, the ARIES design studies look to the future and envision the far end of the fusion power development path past ITER and past a demonstration plant, to the tenth of its kind fusion power plant. The ARIES studies have included deterministic safety analyses

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(Steiner 1997, Khater 2003, Petti 2006, Merrill 2008). Like ITER safety, the radiological inventories and decay heat levels were defined, and traditional accidents such as loss of coolant and loss of flow were analyzed (Khater 2003, Mogahed 1997, Mogahed 2001, Petti 2006, Martin 2007, Merrill 2008). For the ranges of accidents considered in fusion deterministic analyses, including loss of vacuum accidents, in-vessel loss of coolant with confinement barrier bypass, and ex-vessel loss of coolant, the ARIES advanced tokamak and compact stellarator designs meet the no-evacuation dose limit of 1 rem at the site boundary (DOE 1996a) for all events. The most recent advanced tokamak design (ARIES-AT) is shown in Figure 4.

Figure 4. Isometric view of ARIES-AT (Najmabadi 2006).

All ARIES designs incorporate reduced activation materials, passive decay heat removal, and defense in depth confinement strategy of multiple barriers to releases. In summary, past ARIES studies demonstrated an adequate performance for different power plant concepts in several safety and environmental areas: Occupational and public safety:   

No evacuation plan following abnormal events (early dose at site boundary < 1 rem) to avoid disturbing public daily life. Low dose to workers and personnel during operation and maintenance activity (< 2.5 mrem/h). Public safety during normal operation (bio-dose << 2.5 mrem/h) and following credible accidents:

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LOCA, LOFA, LOVA, and by-pass events. External events (seismic, hurricanes, tornadoes, airplane crash, etc.).

No energy and pressurization threats to confinement barriers (vacuum vessel and cryostat):        

No melting, no burning Decay heat problem solved by design Chemical energy controlled by design Chemical reaction avoided Stored magnet energy controlled by design Overpressure protection system No combustible gas generated Rapid, benign plasma shutdown.

Environmental impact: 

  

Minimal radioactive releases (such as T, volatile activated structure, corrosion products, and erosion dust. Or, from liquid and gas leaks) during normal and abnormal operations. Low activation materials with strict impurity control  minimal long-term environmental impact Minimal radwaste  recycling and clearance, avoiding disposal No high-level waste (HLW).

In Europe, a series of studies delivered two reports (Raeder 1995, Cook 2000) on the safety and environmental assessment of fusion power (SEAFP). A wide range of postulated accidents have been analyzed, involving parametric studies, with a special consideration given to the radwaste management approaches. The SEAFP studies conclude: ―it is possible to fully benefit from the advantages of fusion energy if safety and environmental concerns are taken into account when considering the first prospective studies of a reactor design. Improvements in this way will need the continuation of RandD on reactor design and materials as well as specific RandD on safety aspects.‖

4.3. Probabilistic Safety Assessment The second type of safety analysis is probabilistic risk assessment, also known as probabilistic safety assessment (PSA). The PSA approach is the opposite from the ‗What if?‘ deterministic approach to identification of consequential events. PSA identifies a wide spectrum of system and component failures and errors over a wide range of occurrence frequencies, from annual plant off-normal events to very low one event per million years or lower. These failure events or errors initiate plant accidents that can lead to radiological or toxicological releases. The PSA then analyzes the safety system responses to those failures and errors. Of these many possible accident progressions, there are outcomes that are benign

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to the public and outcomes that are slight or moderate hazards to the public; the worst events from the deterministic safety analysis are also included in the spectrum of plant states from the initial failure event. Keller (2005) described the progress of PSA in the nuclear fission industry after the Three Mile Island-2 accident in 1979. While estimates of accident consequences had been examined in preceding years to support federal indemnification of fission power plants (AEC 1957), the NRC embarked on a more definitive risk-based study, called the WASH-1400 study, in the early 1970s when the indemnification process was under review for another approval cycle (NRC 1975). The WASH-1400 study met that purpose, but then was not being utilized for any other purposes. After the Three Mile Island accident in 1979, nuclear safety professionals in the industry noted that the traditional safety analysis report did not treat the small break loss of coolant event as well as the WASH-1400 study (Keller 2005). After consideration, the NRC required each existing power plant to perform a PSA for the Individual Plant Examination study (NRC 1988). While PSA is not an official requirement for new fission power plant licensing, recent US fission licensing changes in 10CFR50.52 state that a summary of the PSA results must appear in the plant‘s SAR. PSA studies are viewed as worth the effort to identify risks and serve as a supplement to the licensing documentation. The US NRC has recognized that PSA enhances and extends the traditional, deterministic safety analysis approach by allowing consideration of a broader set of challenges to plant safety, providing a systematic means to prioritize these challenges and by allowing, or taking credit for, a broader set of plant resources to defend against the challenges (NRC 1995). The NRC has also issued a guide on PSA adequacy for use in riskinformed decision making (NRC 2009). The present view by the US NRC is that PSA is valuable and has been used in safety decisions and plant equipment upgrades. If a new license application does not include a PSA then NRC would request that a PSA be performed to fill in the gap. Early thoughts about PSA benefits for fusion power safety assessment were made by Piet (1985, 1986). Magnetic fusion has made use of PSA techniques in some small safety assessment reports (Holland 1991, Cadwallader 1993, Brereton 1996), some system-level studies (Cambi 1992, Schnauder 1997, Hu 2007) and in ITER as multiple, independent, and exhaustive methods to support completeness in the accident identification process (Taylor 1998, Pinna 1998, Cadwallader 1998). The IGNITOR design has had an entire PSA performed, with updates (Carpignano 1995, Carpignano 1996, Ruscello 2002). Completeness in accident-initiating event identification is one of the greatest criticisms of PSA, that if an accident is not identified it will not be modeled and therefore the PSA is incomplete (Fullwood 1988). Use of multiple means to identify lists of potential initiating events is necessary to achieve practical completeness so that anything left off of the list is inconsequential. There are several good guides for risk assessment (NRC 1983, NRC 1990, McCormick 1981, Kumamoto 1996, Fullwood 1999). Inertial fusion has also applied probabilistic techniques for accident analysis (Lazaro 1996, Cadwallader 2002, Latkowski 2003). At this writing, inertial fusion has not performed an entire PSA study and magnetic fusion has only performed one PSA study on a tokamak and another on a materials test facility (Burgazzi 2004). The most frequent problem cited for not performing a PSA, besides the cost of a PSA and lack of design detail in most fusion conceptual designs, is that there is scarce data on component failure rates available to quantify a PSA. There are two factors to consider regarding quantification data. The first factor is that a fusion experiment is composed of many standard components for cooling

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systems, electric power distribution systems, confinement barriers, ventilation systems, and other systems that do have pertinent data available from other industries. Therefore, some component failure rate data are readily available for the typical support systems in a fusion plant. The fusion-specific components, especially in-vessel components, do not have much failure rate data available, as seen by efforts to quantify such components (Cadwallader 2007a). Some fusion-relevant data are available from particle accelerator operations— accelerators use hundreds to thousands of any single type of component and operate for thousands of hours per year, so they produce statistically significant data. Fusion-specific data on systems unique to fusion are also being collected in the U.S. and the European Union (Cadwallader 2007b). These data arise from the operating experiences of existing tokamak experiments and the components in these experiments do not have very high neutron fluence, so there is skepticism about applicability to future experiments and prototype power plants. Nonetheless, these are the best data available to apply to the fusion-specific equipment used on the next generation of tokamaks. With work to harvest existing, relevant data for fusion balance-of-plant systems and with collection and analysis of fusion-specific data, future fusion projects will have the tools available to make better use of PSA.

5. PERSONNEL SAFETY In nuclear facilities, there are two facets of personnel safety: radiation exposure and industrial safety. Ionizing radiation exposure, either by direct radiation or by absorption of radioactive materials into the body, tends to be a long term or chronic health issue. Industrial safety includes both acute and chronic personal injuries that may lead to debilitation or death, from hazards such as falls from height, vehicle collisions, electrical energy exposure, and workplace exposures to chemicals, noise, repetitive motion, and other hazards. This section describes both of these facets of personnel safety. An important aspect of personnel safety is rules and regulations regarding exposure to radiation and other hazards. Present-day magnetic fusion experiments in the U.S. are either operated by the U.S. DOE and its contractors or by universities. The machines operated by DOE are the largest experiments in the U.S. These machines, notably the DIII-D experiment (DIII-D experiment) at General Atomics in California and the National Spherical Torus Experiment [NSTX] (NSTX experiment) at the Princeton Plasma Physics Laboratory in New Jersey draw fair amounts of power, several megawatts of electricity, and can use large quantities (cubic meters) of cryogenic liquids such as liquid nitrogen and liquid helium. The university machines, with perhaps the exception of the Alcator C-Mod machine (Alcator experiment) at the Massachusetts Institute of Technology, draw more modest power (kW versus MW), are smaller in size, and use protium rather than deuterium fuel. The personnel safety of existing university experiments is maintained by the college or university operating the machine and perhaps by the state hosting the university. Federal safety rules are also often incorporated at university machines for the safety of students and staff. The DOE fusion experiments have personnel safety rules developed from the general DOE worker safety rules (including U.S. Occupational Safety and Health administration [OSHA] regulations) and from identification and treatment of hazards unique to fusion research. Fusion facility safety requirements and guidance are stated in the Fusion Safety Standard and related guidance (DOE 1996a and 1996b).

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The DOE standards outline some basic public and personnel safety rules for fusion power plants. For personnel safety, the DOE standard states that workers in a fusion power plant shall be protected from routine hazards to a level commensurate with that of comparable industrial facilities by a combination of administrative controls and design features. Routine hazards include exposures to radiation, electromagnetic fields, and industrial hazards. During normal operations, workers will be exposed to radiation levels below the limits given in 10CFR20 (5 rem/yr) and DOE (2005) (2 rem/yr). Because tritium is the predominant nuclear material used in fusion facilities, facility designs will include special consideration to limit worker doses from inhalation and skin absorption of tritium fuel. The as-low-as-reasonablyachievable (ALARA) principle in averting radiation exposure would be followed in fusion design like it is in fission reactor designs. Workers will also be protected from exposure to magnetic fields and radiofrequency energy fields, with the facility design keeping worker exposures below the limits published by the American Conference of Governmental Industrial Hygienists (DOE 1996a). Lastly, fusion power plant facilities will comply with all federal safety regulations for workers. Because the industrial hazards are not unique to fusion, the fusion facilities will follow the OSHA regulations and other commonly accepted practices. Safety is a moral obligation of facility management and is a legal requirement mandated by federal law. However, there are also benefits to investing in safety. Safe operations tend to be efficient operations. Mottel, who wrote specifically about industrial safety, states that safety, worker productivity, and high quality in operations all complement each other (Mottel 1995). Fission power plants have apparently learned this lesson: plant capacity factors are high, in the 90% range (Blake 2006), and, as will be discussed later, occupational injury rates are low.

5.1. Radiation Safety Besides decreasing the ionizing radiation source strength as much as possible, the fundamental approach to radiation protection is three-fold: increase distance to the source, reduce exposure time, and use radiation shielding (Gollnick 1994). It should be noted that radioactive inventories in low-activation fusion design have a lower radiation hazard than fission inventories by 1 to 2 orders of magnitude (Pease 1991). The first, and most effective, approach for radiation protection is to increase the distance between the worker and the radiation source. Radiation dose is inversely proportional to the separation distance for ‗line sources‘ (e.g., pipes holding radionuclides in water), which is perhaps the most frequently encountered situation in a power plant. Methods to increase distance include using long-handled ―reach rods,‖ designing rooms to allow work to be carried out at a distance, and using remote handling equipment that allows workers to stay further back from radiation sources. In the second approach, exposure times are decreased as much as possible. Radiation doses are directly proportional to the time spent in a radiation field. If the worker exposure time to the radiation hazard can be reduced, then the worker is safer. Time reductions are usually accomplished by a variety of engineering means: using components designed and constructed for very high reliability so that hands-on maintenance is greatly reduced, using remote handling machines to replace personnel performing hands-on work in high radiation

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areas, and designing to reduce the radiation hazard. Radiation work permits also review the time needed to perform specific tasks in radiation areas. There are a number of federal regulations that give radiation limits for workers. These are given in Table 2. Jones (2005) gives an excellent review of the history behind these regulations. Table 2. Primary U.S. radiation safety regulations Description of Regulation

Regulation Citation

The licensee shall control the occupational dose to individual adults to an annual limit of 5,000 mrem. Derived air concentration (DAC) values and annual limit on intake (ALI) values may be used to determine an individual‘s dose and to demonstrate compliance with occupational dose limits. The occupational dose limits for minors are 10% of the annual dose limits specified for adult workers.

10CFR20.1201 Occupational Dose Limits for Adults

The occupational exposure of a declared pregnant woman, during the entire pregnancy, shall not exceed 500 mrem. The total effective dose equivalent to individual members of the public from licensed operations does not exceed 100 mrem/yr. A site will be considered acceptable for unrestricted use if residual radioactivity after cleanup results in a total effective dose equivalent that does not exceed 25 mrem/yr, including ground water used for drinking water and that radioactivity has been reduced to ALARA levels. The occupational dose received by general employees shall be controlled such that a total effective dose of 5,000 mrem is not exceeded in a year. Note: the US DOE set an Administrative Control Limit of 2,000 mrem/yr (DOE 2005). Any planned special exposures of workers must remain within 10CFR835.202 limits. Any emergency situation that leads to voluntary personnel emergency exposure, for actions whose benefits exceed the risks, can exceed 10CFR835.202 limits Control personnel radiation exposure from external sources in continuous occupancy areas (2000 hr/yr) to levels below an average of 0.5 mrem and as far below as is reasonably achievable. Airborne radioactive material shall be controlled to avoid releases to the workplace atmosphere in normal operations, and in any situation inhalation of such material by workers shall be controlled to levels that are ALARA; confinement and ventilation shall normally be used. No employer shall cause any individual in a restricted area to receive in any one calendar quarter a dose in excess of 1,250 mrem. The annual dose equivalent does not exceed 25 mrem to the whole body of any member of the public as the result of planned discharges of radioactive materials to the general environment from uranium fuel cycle operations. Fuel cycle operations are defined as uranium ore processing (not mining), uranium fuel fabrication, generation of electricity by fission, and reprocessing of spent fuel. The average annual concentration of beta particle and photon radioactivity from man-made radionuclides in public drinking water must not produce an annual dose equivalent to the total body greater than 4 mrem/yr Emissions of radionuclides to the ambient air from DOE facilities or regulated facilities shall not exceed amounts that would cause any member of the public to receive an effective dose equivalent of 10 mrem in a year. No source at a DOE facility shall emit more than 20 picocuries per square meter per second of Radon-222, averaged over the entire source, into the air.

10CFR20.1207 Occupational Dose Limits for Minors 10CFR20.1208 Dose Equivalent to an Embryo/Fetus 10CFR20.1301 Dose Limits for Individual Members of the Public 10CFR20.1402 Radiological Criteria for Unrestricted Use 10CFR835.202 Occupational Dose Limits for General Employees 10CFR835.204 Planned special exposures 10CFR835.1302 Emergency exposure situations 10CFR835.1002 Facility Design and Modifications 10CFR835.1002 Facility Design and Modifications 29CFR1910.1096 Ionizing Radiation 40CFR190.10 Standards for Normal Operations

40CFR141.66 Maximum Contaminant Levels for Radionuclides 40CFR61.92, 40CFR61.102 Standard 40CFR61.192 Standard

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The third approach is radiation shielding. Shielding is material that will attenuate the radiation, reducing radiation energy so that it is less hazardous after traversing the shielding. In fusion devices, all in-vessel components (the blanket, shield, and vacuum vessel) provide a shielding function, and the shielding is close to the source of radiation. The types of radiation to be shielded are generally alpha particles, beta particles, gamma rays, and neutrons. Alpha particles are easily shielded by thin layers of nearly any material. Beta particles are easily shielded by thin coatings of metals. Gamma rays are more penetrating and are best shielded by very dense materials, such as lead (Gollnick 1994). Lead bricks are often stacked up near experiments to form shielding walls for gamma rays, but lead is not as effective for neutrons. Neutrons tend to be more difficult to shield. If neutrons can be slowed down to low energies, then they can be absorbed. Neutron slowing down is best accomplished by heavy metals, such as tungsten, and hydrogen-containing materials, such as water and concrete. The tungsten and hydrogen slow down the high-energy neutrons through collisions, then neutron-absorbing materials, such as boron carbide and tungsten carbide, can be used to absorb the majority of low-energy neutrons (El-Guebaly 1997, El-Guebaly 2006). A concrete-based ‗bioshield‘ normally surrounds the fusion power core to capture the leaked neutrons and protect the workers and public against radiation exposure. Comparing radiation exposure experience between a fusion research reactor and commercial nuclear reactors is an interesting exercise. Presently, fusion experiments operate for only fractions of a year, such as 20 weeks per year, and only for about 8 hr/day. The ITER reactor plans to operate for 25% of a calendar year. Mature nuclear fission power plants operate for nearly an entire year at a time, with refueling outages occurring every 18–24 months. Table 3 shows personnel radiation doses for a fusion experiment; Table 4 shows the same rates for commercial plants. The NIF laser fusion facility has completed installation and testing of the last of its 192 lasers in the fall of 2008. Thus far NIF has operated very little and there are no annual occupational exposure data to present. NIF has set a maximum occupational radiation exposure goal of 500 mrem/yr for individual workers. As seen from Table 2, this is one-tenth of the federal occupational radiation exposure limit (5 rem/y) and one-fourth of the DOE administrative control limit (2 rem/y). The NIF will meet this goal by shielding design and analysis, use of temporary shielding during maintenance activities, use of delay times before personnel access the machine, constraints to allowable stay times in radiation areas, use of remote operated equipment, radiation safety training, and proper procedures (Brereton 1997). The NIF collective dose goal is ≤ 10 person-rem/yr (Latkowski 1999), which is much lower than the annual person-rem estimates given in Table 4 for fission power plants. Using the person-rem data in Table 4 and noting that there are 104 operating power reactors, the average collective dose is approximately 100 person-rem or more annually for a fission power plant. The ITER magnetic fusion project has set radiological exposure goals based on international recommendations. The ITER worker dose limit is 2 rem/yr and a maximum of 200 mrem/shift (Moshonas 2001, IAEA 2002). The IAEA describes the approach to radiation safety at ITER, with radiation zones coded white (unlimited access for all workers, < 0.05 mrem/hr), green (unlimited access for radiation workers, < 1 mrem/hr), amber (limited access for all workers, < 100 mrem/hr), and red (restricted access, > 100 mrem/hr). Considering Table 4, U.S. power plant workers have an individual worker exposure limit of 5 rem/yr and the averaged exposures show that workers are experiencing factors of 15 to 35 times less than the limit. ITER will also strive to have low radiation exposures; ITER will almost certainly be

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between existing fusion experiment doses given in Table 3 and fission power plant doses given in Table 4. The ITER collective personnel radiation dose has been estimated to be 25.8 person-rem/yr with hands-on work and 19.7 person-rem/yr with remote handling assistance to workers (Sandri 2002). The ITER team is using experiences from existing fusion experiments to assist with setting realistic and safe worker radiation exposure goals (Natalizio 2005a; Natalizio 2005b). The ITER limit for collective dose to workers is 50 person-rem/yr (UzanElbez 2005). Table 3. DOE occupational radiation exposure in fusion research at PPPL

Year 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006

Number of Personnel with Less than Measurable Dose 519 474 320 293 240 372 407 376 281 237 231 209 204

Total Number of Personnel Monitored for Dose 620 544 424 381 275 406 466 484 426 348 355 345 359

Collective Dose for Site (person-rem) 3.155 3.254 6.023 2.943 1.080 0.817 2.941 7.420 3.707 0.593 1.141 1.164 1.544

Average Annual Measured Dose per Person (mrem) 31 46 58 33 31 24 50 69 26 5 9 9 10

Source: DOE 1994–2006.

Table 4. NRC occupational radiation exposure in commercial fission power reactors

Year 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006

Number of Personnel with Less than Measurable Dose 68,927 62,080 59,238 58,501 77,080 74,867 73,793 73,206 76,270 77,889 80,473 82,574 84,558

Source: NRC 1994–2006.

Total Number of Personnel Monitored for Dose 142,707 133,066 127,420 126,689 148,424 150,287 147,901 140,776 149,512 152,702 150,322 160,701 164,823

Collective Dose for All Sites (person-rem) 21,695 21,674 18,874 17,136 13,169 13,665.7 12,651.7 11,108.6 12,126.2 11,955.6 10,367.9 11,455.8 11,021.2

Average Annual Measured Dose per Person (mrem) 294.0 305.3 276.8 251.3 184.6 181.2 170.7 164.4 165.6 159.8 148.4 146.6 137.3

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5.2. Industrial Safety Industrial safety includes industrial hygiene and occupational safety. Industrial hygiene is the recognition, evaluation, and mitigation or control of work-related environmental factors or stressors that may cause sickness, impaired health and well-being, or significant discomfort and inefficiency (Goetsch 2008). Occupational safety dwells on identification of energy sources and workplace hazards to workers and mitigation of these hazards so that employers provide a workplace free of recognized hazards that are causing or are likely to cause death or serious physical harm to employees. This is directed by OSHA in the General Duty Clause (29CFR1903.1) and by DOE in 10CFR851.10. Fusion experiments presently have most, if not all, of the typical industrial hazards, including electrical energy, pressurized fluids energy, compressed gas energy, walking and working surfaces, working at elevation, material handling (e.g., fork lift trucks and cranes), welding and hot work, chemical exposures, fire hazards, work with machine tools, and confined spaces. Fusion experiments also incorporate a number of potential hazards that individually may be found in other industries but are grouped together in a fusion facility such as: cryogenic fluids, microwave radiofrequency heating, high magnetic fields, lasers, vacuum chambers that present large vacuum reservoirs, capacitor banks, high voltage power supplies, and ionizing radiation. The expectation is that these hazards will remain inherent in fusion power plants as fusion energy matures to provide electricity. Industrial hazards are presently managed well for fusion by the time-tested combination of engineering controls, administrative controls, and personal protective equipment (PPE). Engineering controls are passive measures designed into the workplace to prevent contact with a harmful substance or other hazard. Engineering controls may include eliminating hazards or substituting lesser hazards, changing the process design, adding barriers, and isolating or enclosing hazards. Administrative controls include limiting the time workers are exposed to hazards, worker rotation to minimize exposure, proper housekeeping in the facility, and good training. PPE refers to supplied air or respirators, anti-contamination clothing, industrial helmets, safety glasses, etc. Engineering and administrative controls reduce or eliminate hazards; these are the preferred means of hazard control. By its nature, PPE is not a strong barrier between the worker and the hazard, and the hazard is still present so PPE is the last means used for hazard control (Laing 1992). Analysis of personal injury reports from fusion experiments has shown that the leading causes of injuries result from standard industrial issues such as falls from height, slips, trips and falls, dropped loads, strains, and sprains (Cadwallader 2005). Therefore, strong occupational safety programs for fusion should give time and attention to the typical industry hazards addressed by OSHA as well as the hazards unique to fusion energy. Occupational safety can be analyzed, rather than merely relying on prescriptive sets of rules. Two good texts for analysis are Harms-Ringdahl (2001), which outlines several proven analysis and modeling techniques, and Brauer (2006), which describes personnel vulnerabilities to many hazards and energies. Table 5 lists the lost workday cases in the electrical power industry. Lost workday means that an injury or illness warranted remaining home from work to recuperate or heal; such cases are more severe than minor needs such as first aid. Workers at fossil-fueled power plants experience injuries and fatalities each year. There have been only a few attempts to analyze the safety of these power plant workers. Frezza

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(1978) described a number of case history events that included electrocutions, burns, boiler explosions, and power plant fires that resulted in injuries and fatalities. More recent work includes discussion of electrical linemen (Sahl 1997) and electric meter readers (Sahl 1998), who are also utility company employees. Loomis (1999) analyzed power plant worker fatalities. Electrical current (45%), homicide (18%), and falls (13%) were the three leading causes that accounted for 76% of the fatalities. The homicides were surprisingly high and include employee confrontations with citizens who are not lawfully purchasing electrical power, workplace violence, and from causes not directly related to employment. Table 5. US occupational injury and illness rates and fatality counts in the electric services industry

Year

Annual Average Employment Count

Injuries and Illnesses Total case Total Lost rate Workday Case Rates

1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006

416,800 399,800 381,300 369,100 363,300 358,400 359,300 357,000 354,000 575,900 563,900 553,300 547,400

5.7 5.7 5.1 5.7 5.1 4.9 4.8 5.0 3.7 4.1 4.5 4.0 3.8

2.6 2.6 2.4 2.4 2.4 2.2 2.4 2.5 2.0 2.0 2.1 2.0 1.9

Count of occupational fatalities in the electric power industry 35 34 29 34 27 24 28 25 35 22 40 22 39

Count of occupational fatalities at nuclear power plants 0 0 0 1 1 0 0 0 1 0 0 0 0

Source: www.bls.gov for illnesses and injuries. Total cases and lost workday cases are per 100 workers per year. The www.bls.gov gave the census of fatal occupational injuries for the overall industry counts. Nuclear power fatalities were counted from the US NRC event notification database at www.nrc.gov – note that only occupational accident events, e.g., electrocution, were counted rather than personal heart attack events, so that the count could be compared to the industry-wide occupational fatalities data collected by the Bureau of Labor Statistics.

In 2001, Yager (2001) noted that the statistical data on utility employee injuries and illnesses was only reported in summary form. Since then, the Electric Power Research Institute has developed a database to track specific information submitted by member utility companies. Thus far, only Kelsh (2004) and Fordyce (2007) have published analyses from these data. As the database is populated with more data from participating utility companies, it will become a valuable tool for worker safety assessment in the electrical energy sector. Total case rate reduction factors of 1.5 to 3 have been seen in recent years at the utility companies following the guidance produced from database analyses (Douglas 2008). Cadwallader (2005) noted that the nuclear fission power plants, which produce on the order of 20% of the nation‘s electricity, employ, in rough figures, about 30–40% of the electrical utility workers. Nuclear power plant worker lost workday cases are on the order of

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0.25 per 100 workers per year (Cadwallader 2007) and are much lower than the electric services total lost workday case values given in Table 5; those average about 2.0 in recent years. Therefore, injury rates in the other types of power plants are higher than in the fission power plants. From Table 5 it is also seen that occupational fatalities in fission power plants are rare. The industry-wide annual worker fatalities are also realized primarily from nonnuclear workers: linemen, electricians, painters, and other groups. As noted above, the roughly 100 nuclear fission plants in the US employ a fairly large percentage of the utility workforce, leaving smaller work crews at the fossil-fueled power plants, where the accident rates and annual fatality counts are the highest. To date, annual lost workday injury rates at fusion experiments vary between 0.3 and 1.1 per 100 workers, and there have not been any work-related fatalities in fusion research experiment operations (Cadwallader 2007). No industrial fatalities are expected in ITER or NIF operations. A proposed worker safety goal for ITER is an annual value of 0.3 lost workday case rate per 100 workers, which is a low value compared to national standards (Cadwallader 2007). The 0.3 value is comparable to the safety performance of particle accelerators and existing fusion experiments and should be possible for ITER to meet. The longer-term goal for fusion power plants is to meet the intent of the Fusion Safety Standard (DOE 1996a), with the most comparable type of power plant being a nuclear fission reactor. Noting the radiation safety analyses and use of occupational safety standards, combined with the use of ‗lessons learned‘ from the present generation of machines, ITER and NIF personnel safety is being treated.

6. ENVIRONMENTAL ISSUES 6.1. Radwaste Management Fusion offers salient safety advantages relative to other sources of energy, but generates a sizable amount of mildly radioactive materials that tend to rapidly fill the low-level waste repositories. Since the early 1970s, the majority of fusion power plant designs have focused on the disposal of radwaste in geological repositories, adopting the preferred fission radwaste management approach of the 1960s. The large volume of radioactive materials that will be generated during fusion plant operation and after decommissioning suggests developing a new framework that takes into account the environmental, political, and present reality in the US and abroad. At present, many US utilities store their radwaste onsite due to the limited and/or expensive offsite disposal option. Because of the limited capacity of existing repositories and the political difficulty of constructing new repositories worldwide, managing the continual stream of radioactive fusion materials cannot be relegated to the back-end as only a disposal issue. Concerns about the environment, radwaste burden for future generations, lack of geological repositories, and high disposal cost directed the attention of many fusion designers to seriously consider more environmentally attractive scenarios, such as:  

Recycling and reuse within the nuclear industry Clearance or release to the commercial market, if materials contain traces of radioactivity.

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The recycling and clearance options have been investigated by many fusion researchers in the 1980s and 1990s, first focusing on selected materials or components (Baker 1980, Ponti 1988, Cheng 1992, Butterworth 1992, Dolan 1994, Butterworth 1998, Cheng 2000), then examining almost all fusion components in the late 1990s and 2000s (Rocco 1998, Cheng 1998, Rocco 2000, Petti 2000, El-Guebaly 2001, Asaoka 2001, Zucchetti 2001, Tobita 2004, Bartenev 2007, El-Guebaly 2007a). Recycling and clearance became more technically feasible during the 2000s with the development of advanced radiation-resistant remote handling tools that can recycle highly irradiated materials (up to 10,000 Sv/h) and with the introduction of the 2003/2004 clearance category for slightly radioactive materials by the US (NRC 2003), IAEA (IAEA 2004), and other agencies. Encouraged by such advancements, ElGuebaly applied the recycling and clearance approaches to all in-vessel and out-vessel components of the most recent ARIES design that are subject to extreme radiation levels: very high levels near the plasma and very low levels at the bioshield (El-Guebaly 2007a). In addition, the technical elements supporting the future management of fusion radioactive materials were identified along with a list of critical issues to be addressed by a dedicated RandD program, as well as the policy and regulatory concerns for all three options: recycling, clearance, and disposal (El-Guebaly 2008, Zucchetti 2009). Several tasks were also examined, including the key issues and challenges for each option, the notable discrepancies between the US and IAEA clearance standards (El-Guebaly 2006a), the need for new clearance guidelines for fusion-specific radioisotopes, the structural properties of recycled materials, the need to address the economic aspect before recycling specific components (ElGuebaly 2004), the must requirement of detritiation of fusion components before recycling and/or disposal, the availability of radiation resistant remote handling equipment (El-Guebaly 2007a, Zucchetti 2007), the need for accurate measurements and reduction of impurities that deter the clearance of in-vessel components, the acceptability of the nuclear industry to recyclable/clearable materials, and the status of the worldwide recycling/clearance infrastructure and commercial market (El-Guebaly 2006a, Zucchetti 2009). All fusion power plants will generate only low-level waste (LLW) that requires nearsurface, shallow-land burial as all fusion materials are carefully chosen to minimize the longlived radioactive products (Steiner 1997, Khater 2003, Petti 2006, El-Guebaly 2007a, Merrill 2008). The vacuum vessel and externals are less radioactive than the in-vessel components, to the extent that they qualify as Class A LLW, the least hazardous type of radwaste according to US classifications (NRC 1982). All fusion components can potentially be recycled using conventional and advanced equipment that can handle 0.01 Sv/h and high doses of 10,000 Sv/h, respectively (El-Guebaly 2007a). Storing the highly irradiated components (blanket and divertor) for several years helps reduce the dose by a few orders of magnitude before recycling. Even though recycling seemed technically feasible and judged, in many cases, a must requirement to control the radwaste stream, the disposal scheme emerged as the preferred option for specific components (target materials of inertial fusion) for economic reasons (El-Guebaly 2004). The clearance indices for all internal components (blanket, shield, manifolds, and vacuum vessel) exceed unity by a wide margin even after an extended period of 100 y (El-Guebaly 2001). 94Nb is the main contributor to the clearance index of steel-based components after 100 y. Controlling the Nb and Mo impurities in the steel structure helps the clearance index (CI) approach unity for some sizable components. In the absence of impurity control, all invessel components should preferably be recycled or disposed of in repositories as LLW. The

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magnet constituents can be cleared within 100 y, except the Nb3Sn conductor and polyimide insulator (El-Guebaly 2007b). The 2 m thick external concrete building (bioshield) that surrounds the torus represents the largest single component of the decommissioned radwaste. Fortunately, it is clearable within a few years after shutdown (El-Guebaly 2007b, El-Guebaly 2008). Overall, 70-80% of all fusion radioactive materials, including the bioshield, can be cleared within 100 y after decommissioning, the remaining 20-30% of materials are recyclable, and a minute amount of reprocessing secondary waste may require disposal as LLW. Advanced fuel cycles offer clear advantages and could be the ultimate response to the safety and environmental requirements for future fusion power plants. The in-vessel components of any D-3He fuelled power plant can easily qualify as Class A LLW and can also be recycled using conventional and advanced remote handling equipment. As for any DT system, the bioshield contains traces of radioactivity and is clearable from regulatory control in ~10 years after decommissioning (El-Guebaly 2007c). The integration of the recycling and clearance processes in fusion power plants is at an early stage of development. It is almost impossible to state how long it will take to refabricate components out of radioactive materials. The minimum time that one can expect is one year temporary storage and two years for fabrication, assembly, inspection, and testing. All processes must be done remotely with no personnel access to fabrication facilities. Figure 5 depicts the essential elements of the recycling/clearance process. Examining the various steps, one could envision the following (El-Guebaly 2008): 1. After extraction from the power core, components are taken to the Hot Cell to disassemble and remove any parts that will be reused, separate into like materials, detritiate, and consolidate into a condensed form. This is one of the most challenging steps. 2. Ship materials to a temporary onsite or centralized facility to store for a period of ~1 year or less. 3. If the CI does not reach unity in less than e.g. 100 y, transfer the materials to a recycling center to refabricate remotely into useful forms. Fresh supply of materials could be added as needed. 4. If the CI can reach unity in less than e.g. 100 y, store the materials for 1-100 y then release to the public sector to reuse without restriction. Clearly, proper handling of fusion radioactive materials is important to the future of fusion energy. The recycling/clearance approach solves fusion‘s large radwaste problem, frees ample space in repositories for non-fusion non-recyclable radwaste, preserves natural resources, minimizes the radwaste burden for future generations, and promotes fusion as an energy source with minimal environmental impact. At present, the experience with recycling/clearance is limited, but will be augmented significantly by advances in fission spent fuel reprocessing (that deals with highly radioactive materials), fission reactor dismantling, and bioshield clearing before fusion is committed to commercialization in the 21st century and beyond. We are forecasting advanced recycling techniques some 50-100 y in the future based on current accomplishments and near term developments within the fission industry in support of the Advanced Fuel Cycle Initiative (AFCI), Mixed Oxide (MOX) fuel fabrication, and Partitioning and Transmutation activities.

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In addition, the US is currently developing guidelines for the unconditional release of clearable materials from fission reactors that could be valuable for fusion. While recycling/clearance is a tense, contentious political situation, there has been some progress. For instance, limited scale recycling within the nuclear industry has been proven feasible in Europe and at several US national laboratories. A clearance market currently exists in Germany, Spain, Sweden, Belgium, and other countries in Europe. In the US, the free release has been performed only on a case-by-case basis during decommissioning projects since the 1990s.

Figure 5. Diagram of recycling and clearance processes.

The worldwide fusion development strategy should be set up to accommodate this new radwaste management trend. A dedicated RandD program should optimize the proposed radwaste management scheme further and address the critical issues identified for each option. Seeking a bright future for fusion, the following general recommendations are essential for making sound decisions to restructure the framework of handling fusion radioactive materials (El-Guebaly 2008): 

Fusion designers should: o Minimize radwaste volume by clever designs o Promote environmentally attractive scenarios such as recycling and clearance, avoiding geological disposal o Continue addressing critical issues for all three options o Continue developing low-activation materials (specifications could be relaxed for some impurities while more stringent specs will be imposed on others to maximize clearance) o Accurately measure and reduce impurities that deter clearance of in-vessel components

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Address technical and economical aspects before selecting the most suitable radwaste management approach for any fusion component. Nuclear industry and regulatory organizations should: o Accept recycled materials from dismantled nuclear facilities o Continue national and international efforts to convince industrial and environmental groups that clearance can be conducted safely with no risk to public health o Continue developing advanced radiation-resistant remote handling equipment capable of handling > 10,000 Sv/h that can be adapted for fusion use o Consider fusion-specific and advanced nuclear materials and issue official guidelines for unconditional release of clearable materials.

The outcome of the recent radwaste assessment will impact the mission of the Demo device to be built after ITER. All members of the US Fusion Energy Sciences Advisory Committee (FESAC) strongly support the recycling and clearance options. The 2007 FESAC report (Greenwald 2007) states ―Beyond the need to avoid the production of high-level waste, there is a need to establish a more complete waste management strategy that examines all the types of waste anticipated for Demo and the anticipated more restricted regulatory environment for disposal of radioactive material. Demo designs should consider recycle and reuse as much as possible. Development of suitable waste reduction recycling and clearance strategies is required for the expected quantities of power plant relevant materials. Of particular concern over the longer term could also be the need to detritiate some of the waste prior to disposal to prevent tritium from eventually reaching underground water sources. This may require special facilities for the large anticipated fusion components. The fission industry will be developing recycling techniques for the Global Nuclear Energy Partnership (GNEP) and the US Nuclear Regulatory Commission (NRC) is developing guidelines for the release of clearable materials from fission reactor wastes both of which may be of value to fusion.‖

6.2. Thermal Pollution Thermal pollution affects creatures living in nature, wildlife as well as plant life. The heat (or lack thereof) in natural water is always an important parameter of any natural water system. Heat influences all biologic activity – fish and shellfish reproduction and lifetime, and photosynthesis, eutrophication, and degradation of organic materials. This is why all thermal power plants, such as coal, oil, natural gas, nuclear, or any other heat-producing plant, have limits on heat rejection to the environment. The EPA has regulations for oncethrough water cooling of power plant condensers in 40CFR125 Subparts I and J. The basic rule is not quantitative; instead, each plant at each location must determine what amount of water heating will not significantly affect fish, shellfish, or wildlife in the area as discussed in Section 316 of the Clean Water Act (EPA 2008). Individual states decide what is a tolerable level of heat release at the plant location. Consider a 3000 MW thermal power plant with a ≈ 33% plant thermal efficiency, such as a fission power plant. This plant rejects 2000 MW thermal from its condenser to the environment. If the cooling water from a lake, river, or ocean is flowing on the order of 50 m3/second, then the cooling water temperature increase is about 10C (El-Hinnawi 1982). A coal-fired power plant might have perhaps a 9C

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temperature increase (ANL 1990). Eventually the warmed water gives up its heat to the atmosphere. Eichholz (1976) gives good discussions of all thermal-related phenomena, including beneficial uses of warm water for fish hatcheries, etc. An important aspect is that the temperature difference of the thermal discharge must be kept small enough so that if the power plant goes off-line for any reason the marine life acclimatized to the higher temperature are not ―cold shocked‖ by a sudden decrease in heat rejection from the plant (Glasstone 1980). Some power plants use a closed system of cooling water that routes to a cooling tower for discharge to the atmosphere, thus avoiding the issue of heat rejection to a body of water. Of the U.S. nuclear power plants, slightly less than half use a closed cooling water system with a cooling tower (Lobner 1990). The ITER facility will reject ≈ 400 MW thermal when operating and will use a cooling tower (IAEA 2002). The initial fusion power plants using a steam cycle for electricity production would be regulated for waste heat like any other thermal power plant. The direct conversion of fusion charged particle energy into electric power would eliminate the costly and thermo-dynamically inefficient ―balance of plant‖ portion of a thermal power plant: the steam piping, the steam turbine and electrical generator, the steam condenser and feedwater heaters. Direct conversion ideas for advanced fuel cycles (D-3He, P11 B, 3He-3He) with less neutron emission have been described by Miley (1970) and Santarius (1995). Achieving direct conversion with efficiency exceeding 70% would eliminate much of the thermal pollution from the power plant. The first fusion power plant in the 21st century is still envisioned to be a thermal power plant that uses steam or gas, a turbine, and a generator for energy conversion to electricity. In the more distant future, fusion power plants using advanced fuels and direct conversion of charged particle energy into electrical power would release only small amounts of waste heat to the environment.

6.3. Other Environmental Concerns Present fusion experiments pose very little hazard to the environment (DOE 1995a, DOE 1995b, Ono 1999). As fusion research progresses toward construction and operation of a demonstration power plant, the demonstration facility is expected to have many of the same environmental concerns as other thermal power plants. Several of the shared concerns are airborne and liquid radiological releases, and chemical effluent releases. Fusion-specific concerns are magnetic field and radiofrequency energy releases to the environment. The U.S. Environmental Protection Agency (EPA) has regulations for some of these concerns. State governments and local governments also have laws for various environmental effluents so the benefits of electrical power can be enjoyed while minimizing harm to the environment.

6.3.1. Gaseous and Liquid Effluent Releases Each year, nuclear power plants release small amounts of radioactive gaseous and liquid effluent wastes to the environment. The U.S. Nuclear Regulatory Commission collects and reviews these data for regulatory compliance. The release data from earlier years were presented in a series of reports (Tichler 1995); more recent reports are available at a website (www.reirs.com/effluent/). Harris (2004) has presented a trend analysis of these data and the trend is fairly constant over the reporting period from 1994 through 2001. Most fission power plants release short-lived radioactive gases, such as activated air, at the rate of a few hundred

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curies per year. Holdup of these gases on charcoal filters and in tanks or delay lines allows time for radioactive decay to low levels so the releases do not pose a hazard to the public or the environment. Cottrell (1974) gives a good description of techniques for air filtration and holdup that are used in gaseous radwaste systems. NIF will release on the order of 26 Ci of Ar-41 and about 150 Ci of the short-lived N-16 (Brereton 2003). ITER will release ≈ 27 Ci of Argon-41 and 0.27 mCi of Carbon-14 each year (IAEA 2002). Fusion power plants will also have some activated air, probably between ITER levels and fission power plant levels. Tritium, in either gas or water form, is the largest concern for gas or liquid releases from fusion plants. Nuclear fission power plants create a small amount of tritium either as a fission product or as the result of neutron reactions, such as with boron. Much of the tritium created in fission power plants enters into water and becomes liquid. Tichler (1995) showed that most fission power plants release approximately 10–100 Ci (0.001–0.01 g) of tritium as gas per year. This is a small fraction of the 10 mrem annual airborne dose allowed at the plant site boundary. Tichler also showed that fission plants release about 200–23,000 Ci (0.02–2.3 g) of tritium in liquid effluent each year. As noted earlier in this chapter, there are limits for tritium concentrations in drinking water, and these releases are well within the safe limits. A design goal for an ARIES power plant is to keep the tritium losses to the environment below 4 g/y (El-Guebaly 2009). The ITER project has design provisions to capture as much tritium as possible so that very little is released to the environment (IAEA 2002). Cristescu (2007) describes the ITER project‘s tritium effluent limits of 10,000 Ci/yr (1 g/yr) of tritium gas and 1,000 Ci/yr (0.1 g/yr) of tritiated water; the ITER estimated annual releases are 0.05 g tritiated water vapor and 0.18 g tritium gas in air and 0.0004 g of tritium in water (IAEA 2002). Note that an annual release of 8 grams of tritiated water vapor from a plant stack would result in a 10 mrem annual dose to any member of the public at the site boundary (Cadwallader 2003). The waste water detritiation system is designed to accept water with tritium concentrations of 1 to 10 Ci/kg and use electrolysis to convert the water into gas and then scavenge the tritium from the hydrogen and oxygen gases. The tritium concentration in the hydrogen gas that is released to the environment is less than 1.9 mCi/m3 of gas, and the tritiated water vapor concentration in the water vapor discharged to the air is less than 0.1 mCi/m3 (Iwai 2002). The NIF project will have a tritium administrative inventory of 500 Curies of tritium on site and routine emissions of tritium are expected to be on the order of 30 Curies per year (0.003 g/y) (Brereton 2003).

6.3.2. Chemical Releases Existing power plants release some non-radioactive chemicals each year. ANL (1990) and Eichholz (1976) describe some of the chemicals used in power plants: sulfuric acid for regenerating demineralizer resin beds that clean the plant coolant water, sulfuric acid and ammonia for cooling water pH control, hydrazine for free hydrogen control in the coolant water, and corrosion inhibitors, biocides, detergents, etc. A steam-electric fusion power plant would use similar chemicals. A fusion power plant would also have some unique chemical releases. One of the larger foreseen releases would be boiloff gases from the cryogenic plant (helium and nitrogen). The present estimate for ITER is 1 to 3 metric tons of helium gas released each year (IAEA 2002), which is considered to be insignificant and no public hazard. Calculations have shown that even very cold helium gas will rise and disperse in ambient air, and very cold nitrogen will initially seek low areas but as it warms in the ambient air it rises and disperses as well (Abbott 1994). The ITER facility will use beryllium as a coating on the

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fusion chamber walls to obtain the benefits of beryllium as a plasma facing material. ITER will also release small amounts of particulate beryllium, on the order of 0.1 gram/year (IAEA 2002). That small amount does not pose a hazard; the US emission standard for airborne beryllium in 40CFR61.32 is up to 10 grams/day. Reyes (2003) noted that some potential materials to encapsulate the inertial fusion D-T targets pose a chemical hazard if released. The results of that study showed that due to the decreasing public exposure concentrations to the chemical elements mercury and lead, the toxicological exposure was a greater concern than the radiological exposure. In most cases the reverse is true. If allowable chemical exposure concentrations continue to decrease to protect the public from such highly hazardous chemicals, then chemical release analyses will become more important for protection of the public and the environment (Cadwallader 2003a). If a plant uses a cooling tower, there may be steam releases from the tower, but many types of thermal power plants currently release steam and it is not found to be a threat even if the steam entrains impurities in the form of chemistry control chemicals. Like other power plants, a fusion plant will have waste oil and grease from lubricating the traditional components and possibly electrical insulating oil or gas (e.g., sulfur hexafluoride) releases from electrical equipment. The routine releases from the NIF experiment are incidental ozone and nitrogen oxides created by operation of the spark gap switches in the laser systems, and some volatile organic solvents for optical lens cleaning (Brereton 2003). These chemical releases are managed by best industrial practices and release levels are regulated by the EPA. None of these types of chemical releases in these quantities are considered to be a present or future threat to the public.

6.3.3. Electromagnetic Energy Emanations Fusion power plants will use high field magnets and radiofrequency heating for the plasma. There are exposure limits to these forms of energy. IEEE (2007) gives general public maximum permissible magnetic field exposure levels for the head/torso of 118 milliTesla (mT), and 353 mT for the arms and legs. The constant magnetic fields of fusion magnets, such as the toroidal field coils, are highest in the magnet bore. There are several factors to decrease the field strength, primarily distance. As one moves away from the magnet, the field strength decreases as 1/distance3 (Thome 1982). Away from the magnets but inside the ITER building, the peak value of the magnetic field is 70 mT (Benfatto 2005). The ITER magnetic fields have been calculated to decrease to less than 0.02 mT at 250 m from the plant building. This 0.02 mT value is less than the earth‘s magnetic field strength, which varies between 0.025 and 0.065 mT (IAEA 2002). Using 0.04 mT as the earth‘s field at Cadarache, then the total magnetic field strength at 250 m from the ITER building would be the earth‘s horizontal field and the vertical ITER field summed. Summing vectors is performed by taking the square root of [(0.02 mT)2 + (0.04 mT)2], which gives 0.045 mT. This magnetic field value is more than three orders of magnitude below the IEEE suggested maximum exposure value of 118 mT. The public exposure to magnetic fields from ITER is well below the IEEE recommended levels. Fusion power plants, whose magnets will not be much more powerful than ITER magnets, are expected to have similar results. Fusion power plants also use electron cyclotron heating in the microwave energy region at nominally 100 GHz and ion cyclotron heating in the radio wave region around 100 MHz. It is possible that these electromagnetic energies could leak at the generation source or from transmission lines that route the energy to the vacuum vessel. The IEEE Standard C95.1

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(IEEE 2005) gives general public maximum permissible exposure (MPE) levels for electromagnetic fields from 3 kHz to 300 GHz. For the ion cyclotron ≈ 100 MHz energy, the basic restriction or action level for public exposure is 80 mW/kg of body weight. For electron cyclotron ≈ 100 GHz energy, the maximum permissible exposure level is found by a formula, (90 x frequency in GHz - 7000)/200. For the 100 GHz case, the MPE power density value is 10 W/m2. Readings taken from the plasma heating systems of existing fusion experiments show that system energy leakage gives worker exposures on the order of 3.5 mW/kg for ion cyclotron and 0.03 mW/kg for electron cyclotron (Wang 2005). The public, being much further from the equipment, would not receive any tangible exposure. Therefore, there is no expected public exposure to radiofrequency heating energy from ITER or a fusion power plant.

CONCLUSION The promise of fusion power has always been that high technology can sustain modern society without harm to the public, workers, or the environment. We outlined the role of fusion in tackling such pertinent safety and environmental issues and demonstrated the positive impact fusion can make worldwide: 



Public and worker safety that protects individuals and society, ensures hazardous material from the premises is controlled, minimized, and kept below allowable limits, and demonstrates the consequences of frequent events, if any, are minor, the likelihood of accidents is small, and their consequences are bounded, needing no evacuation plan. Radwaste reduction schemes that greatly reduce the volume of mildly radioactive materials requiring geological disposal. Supported by clever designs and smart choice of low-activation materials, recycling and clearance are the most environmentally attractive solution toward the goal of radwaste-free fusion energy.

Harnessing the nuclear fusion process to use on the earth is difficult, and the fusion power plants, envisioned to utilize the same power as the core of a sun, are challenging and complicated to build. Nevertheless, the benefits of bountiful power with fuel available to all countries, electric power that is at least as safe as existing plants, and power that has lower environmental impact than existing technologies, are believed to greatly outweigh the challenges and costs of fusion research.

ACKNOWLEDGMENTS The authors would like to acknowledge the support of colleagues at their home institutions: the Fusion Technology Institute at the University of Wisconsin-Madison and the Fusion Safety Program at the Idaho National Laboratory. Partial funding support for this work came from the US Department of Energy, Office of Fusion Energy Sciences, under DOE Idaho Operations Office contract DE-AC07-05ID14517.

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In: Advances in Energy Research. Volume 4 Editor: Morena J. Acosta, pp. 231-275

ISBN: 978-1-61761-672-3 © 2011 Nova Science Publishers, Inc.

Chapter 10

IS NUCLEAR POWER A REALISTIC ALTERNATIVE TO THE USE OF FOSSIL FUELS FOR THE PRODUCTION OF ELECTRICITY? Jorge Morales Pedraza Consultant on International Affairs

ABSTRACT It is an undisputed reality that the energy production and their sustained growth constitute indispensable elements to ensure the economic and social progress of any country. For this reason, all type of energy sources available in the country, including nuclear energy, should be included in any study about the energy mix to be prepared in order to ensure its future economic an social development. However, there are certain factors that need to be considered by the competent authorities of a country during the selection of the most economic and convenient energy sources for the generation of electricity. For instance, the use of fossil fuels is a major and growing contributor to the emission of carbon dioxide to the atmosphere provoking serious changes in the world climate, while nuclear energy and renewables are almost carbon dioxide free. Considering the different available energy sources that the world can use now to satisfy the foresee increase in energy demand in the coming years, there should be no doubt that, at least for the next decades, there are only a few realistic options available to reduce further the CO2 emissions to the atmosphere as result of the electricity generation. These options are, among others, the following:

(a) Increase efficiency in electricity generation and use; 

Jorge Morales Pedraza has a University Diploma in Mathematic and in Economic Sciences. He was diplomatic and Ambassador for more than 25 years and invited University professor in Mathematics and Invited Professor for International Relations in the Diplomatic Academy and other high level academic institutions in his country. He worked as Senior Manager in the International Atomic Energy Agency (IAEA) in the Director‘s Office. In the last 3 years he is the author and co-author of more than 30 papers, chapters of books and books published by different publisher‘s houses in the field of energy, nuclear energy, radiation and tissue banking, Internet training in the field of tissue banking, biosaline agriculture, crisis management, non-proliferation, disarmament, arms control, among others. He is now a Consultant on International Affairs. E-mail: [email protected] or [email protected]

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Jorge Morales Pedraza (b) Expand use of all available renewable energy sources such as wind, solar, biomass and geothermal, among others; (c) Massive introduction of new advanced technology like the capture carbon dioxide emissions technology at fossil-fueled (especially coal) electric generating plants, with the purpose to permanently sequester the carbon produced by these plants; (d) Increase use of new types of nuclear power reactors that are inherent safe and proliferation risk-free; (e) Increase energy saving.

GENERAL OVERVIEW It is an undisputed reality that the energy production and their sustained growth constitute indispensable elements to ensure the economic and social progress of any country. For this reason, all type of energy sources available in the country should be included in any study about the energy mix to be prepared by the national competent authorities of a country in order to ensure its future economic and social development. However, there are certain factors that need to be considered by the national competent authorities of a country during the selection of the most economic and convenient energy sources for the generation of electricity. For instance, the use of fossil fuels is a major and growing contributor to the emission of carbon dioxide to the atmosphere and this should be taking into consideration when decide which type of energies should be included in the energy mix of the country in the future1. Considering the different available energy sources that the world can use now to satisfy the foresee increase in energy demand in the coming years, there should be no doubt that, at least for the next decades, there are only a few realistic options available to reduce further the CO2 emissions as result of the electricity generation. These options are, among others, the following: 1. Increase efficiency in electricity generation and use; 2. Expand use of all available renewable energy sources such as wind, solar, biomass and geothermal, among others; 3. Massive introduction of new advanced technology like the capture carbon dioxide emissions technology at fossil-fueled (especially coal) electric generating plants, with the purpose to permanently sequester the carbon produced by these plants; 4. Increase use of new types of nuclear power reactors that are inherent safe and proliferation risk-free; 5. Increase energy saving. The amount of total energy produced and used per capita is increasing in several countries, particularly in emerging economies countries such as China, India, Republic of Korea, among others. Due to the increase in the demand of energy the world total energy requirements increased from 6,181 GW.yr to 15,311 GW·yr during the period 1970 - 2006. 1

Carbon dioxide is a greenhouse gas that contributes significantly to global warming and produce a significant change in the climate all over the world. These changes are affecting almost all countries in all regions in one way and another in others.

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According with estimates made by the World Energy Council, the International Institute for Applied Systems, among other international organizations, the demand of electricity probably be triple from now until 2050. The following are, among others, the main reasons for this significantly boost: (a) Increase in the world population; (b) Increase in the percentage of the world population living in big cities, which increase the demand of electricity; (c) Improve the quality of life of the world population bringing as consequence an increase in the demand of electricity; (d) Increase in the demand of electricity in the most advanced developing countries such as India, China, Republic of Korea, among others, due to fast economic and social development. According with the IAEA information, in 1990 the world average annual capacity factor for nuclear power plants was 67.7%. In 2005, this figure increases up to 81.4%, which is the equivalent to the construction of some 74 new nuclear power units with a capacity of 1 GWe. In 2008, the average annual capacity factor was 80%. However, it is important to single out that the increase in the capacity factor of the nuclear power reactors in operation and the number of nuclear power reactors under construction are not enough to satisfy the foresee increase in the demand of electricity in the coming years in almost all regions. The problem that the world is now facing is how to satisfy the foresee increase in the demand of energy using all available energy sources in the most efficient manner and without increasing the emission of CO2 to the atmosphere and climate changes. Without any doubt one of the available types of energy that has probed in the past that can be effectively used for the generation of electricity is nuclear energy. Can be confirmed that nuclear energy could be safely used for electricity generation in the future despite of the problems that the nuclear industry faced in the past and is now facing in several countries? The answer to this question is yes, nuclear energy can play again an important role in the energy balance of several countries in almost all regions as it did in the 1960s, 1970s and 1980s. Over the last three years, several international assessments of the possible future of nuclear power in the world have been adjusted to more optimistic prospects for the horizon of 2030. The OECD International Energy Agency‘s World Energy Outlook 2007 presents a reference scenario, an alternative policy scenario and a ―450 stabilization case‖ that include respectively 415 GW, 525 GW and 833 GW of nuclear power. Electricity generation from nuclear power plants under the high scenario would more than double from current levels to reach 6 560 TWh in 2030. Under the reference scenario the share of nuclear power in the world commercial primary energy supply would drop from 6% to 5% in 2030. However, it is important to stress that nuclear power will only become more important if the governments of countries where nuclear power is acceptable play a stronger role in facilitating private investment, especially in liberalized markets and if concerns about plant safety, nuclear waste disposal and the risk of proliferation can be solved to the satisfaction of the public [1, p 7]. According with the document titled ―Nuclear power plants in the world, edition 2008‖ prepared by the Atomic Energy Commission (CEA) of France, there are 439 nuclear power reactors in operation in 31 countries (or 30 if Taiwan is included as part of China), this means around 16% of the total United Nations Member States, with a net capacity of

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372 182 MWe 2 and 33 nuclear power reactors under construction in 14 countries with a net capacity of 27 193 MWe3. During the period 1950-2007, 119 nuclear power reactors were shut down in 18 countries totalizing 35 150 MWe (net). The countries with the highest number of nuclear power reactors shut down are United States of America (USA) with 28 units, following by the United Kingdom (UK) with 26 units, Germany with 19 units and France with 11 units. From the 31 countries now operating nuclear power plants six of them, USA, France, Japan, Germany, Russia and the Republic of Korea, produce three quarters of the world nuclear electricity. However, the role of nuclear power in the overall energy sector remains very limited even in these six countries. In France, for example, the country with the highest participation of nuclear energy in its energy balance in the world generated, in 2007, around 77% of its electricity with nuclear power plants, but the use of this type of energy only provides 17.5% of its final energy demand. Like most of the other countries, France remains highly dependent on fossil fuels that cover over 70% of its final energy consumption. Oil holds the lion share with 45%. None of the other five largest nuclear countries cover more than 7% of their final energy demand by nuclear power. In the specific case of the USA and Russia, the nuclear energy industry participation of both countries is less than 4%. During 2007, three nuclear power reactors were connected to the electric grid in India, China and Romania adding 1 852 MWe to the electric grid in these countries. Seven nuclear power reactors started their construction in 2007 totalizing 5 195 MWe. Countries involved in the construction of these seven nuclear power reactors were China, the Republic of Korea, Russia and France. Nine new orders for the construction of nuclear power reactors were approved in China, the Republic of Korea, Japan and Russia totalizing 11 660 MWe. During 2008, no new unit was connected to the electric grid, while three old nuclear power reactors were closed. These reactors are Hamaoka Units 1 and 2 in Japan and Bohunice Unit 3 in Slovakia. This last unit was closed as condition for the entrance of Slovakia to the EU. In that year the construction of 10 new nuclear power reactors begun: six units in China, two units in the Republic of Korea and two units in Russia, increasing the number of nuclear power reactors under construction from 33 in 2007 to 43 in 2008. In 2009, one new nuclear power reactor was added to the list totalizing 54 units under construction. In addition to what has been said, in Slovakia the works for the conclusion of Mochovce Units 2 and 3 began after years of inactivity. In India two small nuclear power reactors (PHWR) should have entered in service in 2008, but they could not make it due to lack of nuclear fuels. According with the International Energy Outlook for 2009 (IEO 2009), electricity generation from nuclear power is projected to increase from about 2.7 trillion kWh in 2006 to 3.8 trillion kWh in 2030, as concerns about rising fossil fuel prices, energy security and greenhouse gas emissions support the development of new nuclear generation capacity. Higher fossil fuel prices allow nuclear power to become economically competitive with generation from coal, natural gas and liquids despite the relatively high capital and maintenance costs associated with nuclear power plants. Moreover, higher capacity utilization rates have been reported for many existing nuclear facilities, and it is anticipated that most of the older nuclear power plants in the OECD countries and non-OECD Eurasia will be granted extensions to their operating lives. [2, p 4] 2

In 2009 there were 436 nuclear power reactors in operation in the world producing 366 008 MWe according with the IAEA latest information.. 3 According with the IAEA latest information, on December 2009 the number of nuclear power reactors under construction was 54 in 14 countries with a total capacity of 46, 288 MWe.

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THE ENERGY SITUATION IN NORTH AMERICA The IAEA has foresee that the participation of nuclear energy in the worlds energy balance will drop from 16% to 8-10% in 2030, if no decision is adopted by the EU, Canada and the USA to build more nuclear power plants for electricity generation in the coming years. North America is one of the regions of the world with more nuclear power reactors currently in operation. Until April 2009, there were 126 nuclear power reactors in operation in the USA and in Canada. In the case of the USA, there were 104 nuclear power reactors in operation in 2008. Table 1. The production of electricity using nuclear energy in North America Number of units connected to the electric grid April 2009

Nuclear electricity generation (net million kWh) 2007

Nuclear percentage of total electricity supply (%) 2007

United States of America

104

806.6

19.4

Canada

22

88.2

18

Total

126

894.8

-

Country

Source: WANO, 2009.

The construction of new nuclear power reactors in North America, particularly in the USA, was stop after the Three Mile Island and Chernobyl nuclear accidents occurred in Pennsylvania, USA in 1979 and in Ukraine, in the former Soviet Union, in 1986 respectively. The energy crisis the world in now facing, the real possibility of the extinction of the world oil reserves in the coming decades, the significantly increase in oil price in 2007 and 2008 and the negative impact in the environment due to the release to the atmosphere of a significant amount of CO2 as a result of an increase in the consumption of fossil fuel in the USA and Canada, but particularly in the USA, among other relevant factors, are changing the negative perception of the public opinion in these two countries regarding the future use of nuclear energy for electricity generation. According with public information disclose during the last presidential campaign, the USA should plan the construction of around 45 nuclear power reactors for 2030 and around 55 more units after that year in order to satisfy the foresee increase in the energy demand in the coming decades. Why the construction of new nuclear power reactors is so important for North America, but particularly for the USA? The reason is the following: North America had an aging base of nuclear and fossil fuel power plants for electricity generation. In the specific case of nuclear power plants the last unit to enter commercial operation in the USA was TVA's Watts Bar Unit 1 in June 1996, this mean more than 13 years ago. The last successful order for a US commercial nuclear power reactor was presented in 1973, this means 36 years ago. The USA is a pioneer of nuclear power development. Annual nuclear electricity generation in the USA has more than tripled since 1980 reaching 780 billion kWh in 2002. In

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2006, the total energy generated was 4 260 billion kWh of electricity, half of it from coalfired power plants, 19% from nuclear (809.8 billion kWh), 19% from gas and 7% from hydro. In 2007, the 1044 US nuclear power reactors generated 806.5 billion kWh and achieved an average capacity factor of 91.8%, which is a very high capacity factor in the nuclear power sector. The net load factor per type of nuclear power reactor in operation in the USA in 2007 was the following: BWRs 90.4%; PWRs 92.9%. With all 104 nuclear power reactors in operation in 2008, nuclear power now accounts for 20% of total electricity generation in the USA. US annual electricity demand is projected to increase from 4 000 billion kWh in 2008 to 5 000 billion kWh in 2030, this means an increase of 25% in 22 years. From 2006 to 2030, the USA is expected to add 12.7 GW of capacity at newly built nuclear power plants and 3.7 GW from up rates of existing plants—offset in part by the retirement of 4.4 GW of capacity at older nuclear power plants. The increase in US nuclear capacity is attributed to policies enacted to spur nuclear power growth, as well as concerns about greenhouse gas emissions, which limit additions of coal-fired power plants in the projection. [2, p 71] It is important to single out that coal will continue to be the main energy source in the USA in 2030. In Canada, electricity generation from nuclear power it is expected to increase by 1.5% per year during the period 2006-2030. Until April 2009, two nuclear power reactors are under construction in the country with a total net capacity of 1 500 MWe, three nuclear power reactors planned with a total net capacity of 3 300 MWe and six nuclear power reactors proposed with a total net capacity of 6 600 MWe. For most of this coming decade, the construction of new nuclear power reactors in Canada are uncertain based on the most recent electricity market outlooks. According with the Canadian authorities, the return to service of the remaining laid-up nuclear units and the completion of gas-fired power units already under construction should satisfy the foresee energy demand in the coming years . While market prospects for the construction of new nuclear power reactor sales in the near- to medium-term are not too promising, the refurbishment of existing units holds more promise and would avoid, at least in the mediumterm, the replacement of nuclear generating capacity with fossil-fuelled power plants, which will increase the CO2 emission to the atmosphere. Despite of what has been said before, AECL is currently working on the development of the 700 MW Advanced CANDU Reactor (ACR), with the aim to reduce the capital cost to build this type of reactor by up to 40%. The economics of the new CANDU reactor has been ranked highly by international experts in comparison with other advanced nuclear power reactors and has the potential to be cost competitive with other designs now under development. Can not be excluded that in the coming years, the ACR technology could provide an economic incentive to replace existing nuclear power reactors as they reach the end of their service lives, as well as for the construction of some new nuclear power plants in Canada and abroad. Summing up can be stated that in North America (USA and Canada) it is expected that the participation of nuclear energy in the energy balance in 2030 will be somehow similar to the level of participation in 2006 not exceeding 20% of the total generation of electricity of

4

In 2007, 103 licensed power reactors operated at 65 plant sites in 31 States (not including the Tennessee Valley Authority‘s [TVA‘s] Browns Ferry 1, which has not operated since 1985; TVA spent about $1.8 billion to restart the operation of this reactor in 2008.

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the region. The participation of the different energy sources in the energy balance of North America is shown in the following figure.

Sources: 2006: Derived from Energy Information Administration (EIA), international Energy Annual 2006 (June-December 2008), web site www.eia.doe.gov/iea. 2030; EIA, World Energy Projections Plus (2009). Figure 1. Net electricity generation in North America (including Mexico) by fuel during the period 2006-2030.

The current energy crisis that the world is now facing has pushed the government and the local energy industry in the USA and Canada to look again to the use of nuclear energy for electricity generation. But the US local energy industry is adopting a conservative approach to see what measures and incentives the government is ready to adopt in order to encourage the participation of the energy industry in the construction of new nuclear power reactors. Meanwhile, the power industry sat on the sidelines, waiting to see what the government would do next in order to avoid an energy crisis that could affect the whole North America region, particularly the USA.

THE ENERGY SITUATION IN THE EUROPEAN UNION (EU) Due to different reasons, the debate about the use of nuclear energy for electricity generation started again in the European region. The first of the reason is the high price of oil reached during 2007 and 2008, and the tendency to an increment of the gas price. The second reason is the need to reduce the CO2 emissions to the atmosphere due to the commitments of the EU States to the Kyoto Protocol. The third reason is the dependency of the EU to the import of fossil fuels from politically unstable regions like the Middle East. During the consideration of the role that nuclear energy should have in the energy balance in the EU in the coming years, three main realities should be taken into account. These realities are the following:

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Jorge Morales Pedraza 1. Expectations of the use of nuclear energy for electricity generation are rising again in several EU States. The answer to questions like ‗is nuclear power economic‖ cannot be made using a single universal answer. As with just about everything else in life, the answer is ‗it depends‘ — sometimes yes, sometimes no; 2. Economics comparison. Whether the use of nuclear energy for electricity generation is more economics or not than the use of other energy sources will depend on how cheap it is compared to alternative energy sources.

Certainly, the nuclear industry can influence this issue by bringing down costs, but there are factors outside the industry‘s control, such as the price of natural gas or of carbon credits that will also determine, for any particular investor, whether nuclear is a cost-effective option. [6, p 45] Currently, the European region (including Russia and Ukraine) generates around 31% of its electricity from 197 nuclear power plants in operation in 17 countries. According with some expert‘s opinion, and based on the commitments adopted by the EU regarding the Kyoto Protocol, the above-mentioned proportion should be maintained or increased in order to meet the 2020 target, with an increase in the actual wattage generated by the use of nuclear energy to meet increasing power demand. It is a fact that nuclear energy is already making a substantial contribution to an energy policy that is low carbon, costeffective and that provides assured supply. At present, nuclear supplies almost one third of Europe‘s electricity, produces very low CO2 emissions calculated over the entire fuel cycle (comparable to wind energy), and has a quasi ‗indigenous‘ character, i.e., it can rely on a complete European nuclear fuel cycle. In addition, it contributes to the stabilization of electricity prices, owing to the favorable ratio of primary investment costs to fuel costs. [7, p 49] Today a strong debate is happening among the oldest and most industrialized EU Member States, which do not want slower growth, and are beginning to view nuclear energy as a real alternative to the current energy crisis. The increase in the oil price occurred in 2007 and 2008 changed the minds of many people in the European region who turned against nuclear power after the Chernobyl nuclear accident. Although less pronounced than in other parts of the world, energy and electricity consumption in the EU are expected to continue increasing over the foreseeable future, at least until 2030, and most likely beyond. At the same time, energy resources are becoming ever scarcer and more expensive and excessive emissions of the greenhouse gas CO2 to the atmosphere are driving the impending threat of climate change. There is an urgent need for investment in the energy sector in many countries with the purpose to satisfy the growing demands of electricity in the coming years. In Europe alone, to meet expected energy demand and to replace ageing infrastructure, investments of around one trillion Euros will be needed over the next 20 years. [8, p 3] It is a growing demand that the European energy balance include all available energy technology, including nuclear energy. For this reason, there should be no doubt that nuclear energy would contribute to alleviate energy supply dependency, local air pollution and global climate change. In 2004, the nuclear share of electricity production in the EU reached 31%, which represents a ‗non-emission‘ to the atmosphere of nearly 900 million tones of CO2 per year. This represents almost the quantity of carbon dioxide produced annually by the transport sector.

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Table 2. Nuclear power reactors in operation and under construction in the European region Country

Belgium Bulgaria Czech Republic Finland France Germany Hungary Lithuania Netherlands Romania Russian Federation Slovakian Republic(1) Slovenia Spain Sweden Switzerland Ukraine United Kingdom Total

Number or reactors in operation (Until April 2009) 7 2 6 4 59 17 4 1 1 2 31

Net capacity MWe (2007) 5 824 1 906 3 619 2 676 63 260 20 470 1 829 1 185 482 1 300 21 743

Number of reactors under construction (Until April 2009) 2 1 1 8

Net capacity MWe (2007) 1 906 1 600 1 600 5 980

5

2 034

-

-

1 8 10 5 15 19 197

666 7 450 9 014 3 220 13 107 10 222 170 007

2 14

1 900 12 986

Source: WANO and CEA 8th Edition, 2008. Note (1): In 2007, the Slovakian government decided to continue the construction of Units 3 and 4 at Mochovce.

There are other reasons why nuclear energy should be included in the EU energy balance in the future. One of the reasons is the following: Unless the EU make domestic energy more competitive in the next 20 to 30 years, around 70% of the EU energy requirements, compared with 50% today, will be met by imports products some from regions threatened by insecurity. [8, p 3] If the EU does not increase the nuclear share in the coming years, then it is expected that the EU energy dependence would increase up to 60%-70% or even more by 2030, the reliance on imports of gas is expected to increase from 57% to 84% and reliance on imports of oil is expected to increase from 82% to 93%. The EU is consuming more and more energy and importing more and more energy products in order to satisfy it increase energy needs. External dependence for energy is constantly increasing and this situation is considered by many politicians and experts very danger from the political and economical point of view. If no measures are taken, in the next 20 to 30 years, 70% or more of the EU energy requirements will be covered by energy imported from outside the European region. In the other hand, if the EU current energy policy does not change in the coming years, which is something very difficult not to happen, then the major reduction in the use of nuclear energy for electricity production will occur in the EU. There should be no doubt that this situation would have a negative impact in the energy sector of several countries. However, the recently announcement of the UK government to built up to 10 new nuclear power rectors in

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the coming years and the decisions adopted by France, Finland, Bulgaria, Romania and the Czech Republic, among others, to built new nuclear power reactors in the future or the intention of Italy to reintroduce the use of nuclear energy for electricity generation or the intention of some EU governments to revert previous phase out policy adopted by them, will have a positive impact in the current situation of the energy sector within the EU, particularly regarding the use of nuclear energy for electricity generation.

THE ENERGY SITUATION IN ASIA In Asia the situation regarding the use of nuclear energy for electricity generation is completely different from the situation in the EU and in North America. The major increase in nuclear energy capacities for electricity generation in the near future are foresee in China5, Japan, India and the Republic of Korea. It is expected that these four countries, plus the USA and Russia, will have around two-third of the world nuclear energy capacity in 2030, an increase of 16%-17% from the current level6 Nuclear power is an industry still in crisis in the West, due to the panic produced by the nuclear accidents at Three Mile Island and Chernobyl, the concern of the public opinion about the management of the high radioactive nuclear waste and because of the multi-billion-dollar cost overruns that have plagued nuclear energy projects throughout Europe and the USA. But if the nuclear energy genie is dying in the West, it has being reborn in Asia. The booming, fuel-hungry nations across the region are ordering and building new nuclear power reactors at a rate not seen in decades. Why this boom in the construction of new nuclear power reactors in Asia? Asian leaders say they have no choice but to use nuclear energy for the production of electricity due to the explosive rate at which the demand for energy is growing in several countries. According with the IAEA projections, power demands in Asia will triple by 2015. In Asia, they are 103 nuclear power reactors in operation in six countries, including Taiwan. China and India alone have 17 nuclear power reactors under construction and have plans to construct 128 new units in order to elevate the proportion of nuclear energy in the generation of electricity in both countries. In the case of China7, the new nuclear power reactors planned and proposed is 103, for the time being the biggest nuclear power programme in the world. The situation regarding the number of nuclear power reactors in operation and under construction in Asia is shown in the following table.

5

At the end of 2007, China and France signed an agreement for the construction of several nuclear power plants for US$ 11.8 billion up to 2026. This is the major contract signed by the French company Areva up to now for the construction of nuclear power plants outside France and the most ambitious nuclear programme for generation of electricity under discussion and implementation in the world. It is important to stress that for China, the use of nuclear energy for electricity generation is a fundamental option to satisfy the growing demand of energy to sustain the high economic growth of this country. In April 2009, the number of nuclear power reactors planned or proposed in China is 103 according with the latest IAEA information. The capacity of these reactors is 91 060 MWe. 6 The USA, France, Japan, Germany, Russia and the Republic of Korea are now producing three-quarters of the nuclear electricity generated in the world. 7 China has in 2008 nine nuclear power plants in operation and four under construction. China hopes to incorporate 21 new nuclear power plants up to 2020 and at least other 20 or more nuclear power reactors later on. In total China has 103 new nuclear power reactors planned or proposed, with a new nuclear capacity of 91 060 MWe.

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Table 3. Nuclear power in Asia Country

Australia Bangladesh China* India Indonesia Japan S. Korea N. Korea Malaysia Pakistan Philippines Thailand Vietnam Total

Power reactors in operation (Until April 2009) 11 (6) 17 53 20 2 103

Power reactors under construction (Until April 2009) 11 (2) 6 2 5 1 25

Power reactors planned or proposed (Until April 2009) 103 25 6 14 5 1 4 6 10 174

Note: *Including six nuclear power reactors operating and two units under construction in Taiwan. Source: WANO and CEA, 8th Edition, 2008.

There should be no doubt that 2006 and 2007 were years of increasing activities in the field of nuclear power in the Asian region. Asia is the only region in the world where electricity generating capacity and specifically nuclear power is growing significantly. In contrast with North America and most of Western Europe, where growth in electricity generating capacity and particularly nuclear power leveled out for many years, a number of countries in the Asia region, particularly in the East and South Asia sub-region, are planning and building new nuclear power reactors to meet their increasing demands for electricity. [9, p 1] The countries that have announced plans for significant expansion in the use of nuclear energy for electricity generation are the following: China, India, Japan, Pakistan and the Republic of Korea. Other countries such as Indonesia, Vietnam, Bangladesh and the Democratic People Republic of Korea have plans for the introduction of nuclear energy for electricity generation in the coming years. Asia produced in 2007 a total net of 5 546 GWh of electricity, out of which 523 GWh came from nuclear energy, representing 9.4 % of the total electricity produced in the region by all energy sources. The Southeast Asian economies, themselves beneficiaries of an oil and gas export bonanza through the 1970s-1990s, also find themselves in an energy crunch as once ample reserves run down and the search is on for new and cleaner energy supplies. For this reason, regional leaders at the 13th ASEAN Summit meeting held in Singapore in November 2007 issued a statement promoting the use of nuclear energy for electricity generation alongside renewable and alternative energy sources in the future. According to Table 3, there are currently 103 nuclear power reactors operating in six countries of the region, including Taiwan, 25 units under construction in six countries and plans to build about another 174 units in the coming years. In addition, there are about 56 research reactors in 13 countries of the region. The only two major Pacific Rim countries without any research reactor in operation are Singapore and New Zealand.

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Until 2010, the projected new generating capacity in Asia is around 38 GWe per year. For the period 2010 to 2020, the projected new generating capacity is 56 GWe. Much of the growth foresees will be in China, Japan, India and the Republic of Korea. The nuclear share in the region in 2020 is expected to be at least 39 GWe and maybe more if environmental constraints limit fossil fuel expansion. [9, p 1] The largest increase in installed nuclear generating capacity is expected in non-OECD Asia, where annual increases in nuclear capacity average 6.3% and account for 68% of the total projected increase in nuclear power capacity for the non-OECD region as a whole. Of the 58 GWe of additional installed nuclear generating capacity projected for non-OECD Asia between 2004 and 2030, 36 GWe is projected for China and 17 GWe for India. [3, p 4] In the other hand, China, non-OECD Asia‘s largest economy, is expected to continue playing a major role on both the supply and demand sides of the global economy. IEO 2007 projects an average annual growth rate of approximately 6.5% for China‘s economy over the period 2004 to 2030. The country‘s economic growth is expected to be the highest in the world. India is another Asian country with a rapidly emerging economy. Average annual GDP growth in India over the 2004 to 2030 projection period is 5.7%. In the rest of non-OECD Asia, economic activity has remained robust, with exports increasing in response to a rebound in global demand for hightechnology products and stronger import demand from China. Over the medium term, national economic growth rates in the region are expected to be roughly constant over the period 2004 to 2015, before tapering off gradually to an average of 4.3% per year from 2015 to 2030 as labor force growth rates decline and economies mature . [3, pp 11and 12] To satisfy the foresee increase in the energy demand, it is expected that nuclear power continuing to play an important role within the energy balance of several Asian countries. For new nuclear power reactors constructions in the Asian region, however, the economic competitiveness of nuclear power for the generation of electricity will depends on the different energy alternatives available, on the overall electricity demand in a particular country and how fast it is growing, on the market structure and investment environment, on environmental constraints and on investment risks due to possible political and regulatory delays, among others. It is important to single out that economic competitiveness is not the same in all countries and it depends on the countries and on specific situations. For example, in Japan and the Republic of Korea, the relatively high cost of using energy alternatives benefits nuclear power‘s competitiveness. In other countries, such as India and China, rapidly growing energy needs encourage the development of all energy options. [10, p 10] There are different motivations which drove nuclear power developments in different periods in Asia. Three periods can be identified in which different motivations drove nuclear power programmes in the region. These are: 1. The US Atoms for Peace initiative in the 1950's; 2. The oil crisis of the 1970's; 3. The economic growth and need for energy in the 1990's. There are several forces that have limited the use of nuclear energy for electricity generation in Asia. These are the following:

Is Nuclear Power a Realistic Alternative to the Use of Fossil Fuels…? (a) (b) (c) (d)

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Response to the Three Mile Island nuclear accident; The Indian nuclear explosion in 1974; Restraints on international nuclear cooperation by supplier States; The Chernobyl nuclear accident.

Looking ahead, there are six countervailing political movements that might impact nuclear power's future in Asia. First is the concern for global warming which might promote the use of nuclear energy for electricity generation. Second is the growing public distrust of nuclear safety which reduces support for the use of this type of energy for electricity generation. Third is the disposal of high nuclear waste and the lack of a final location for the disposal of this type of waste in the region. Fourth is the high capital cost involved in the construction of a nuclear power plant, despite of the reduction in the construction time achieved by Japan. Fifth the increase use of nuclear energy for electricity production in Asia will depend of the availability of new generation of nuclear power reactors. Sixth is the so-called ―proliferationrisk‖ that is involved in the use of nuclear energy for electricity generation, particularly if the country decided to develop its nuclear fuel cycle.

THE ENERGY SITUATION IN LATIN AMERICA In the case of Latin America, higher world market prices for fossil fuels, the reduction of the current world fossil fuels reserves and the climate changes affecting all countries in the region, have put the use of nuclear energy for electricity generation again on the agenda of many Latin American countries such as Chile, Uruguay and Venezuela without nuclear power programmes and had revived interest in Argentina, Brazil and Mexico, the only three Latin American countries operating nuclear power reactors in the region, in the expansion of their nuclear power programmes. It is important to note that in general the use of nuclear energy for electricity generation in the Latin American region is very low. In 2007, only 3.1% of the electricity generated in the region comes from nuclear energy sources. In 2009, it was 2.3%. The total production of electricity using nuclear energy in the Latin American region in 2007 reached the amount of 28 350 GWe. However, if expansion plans approved by Argentina, Brazil and Mexico are implemented, and if the intention of Chile, Venezuela and Uruguay of constructing new nuclear power reactors are materialized in the near future, then that proportion could be more than double in a decade. Until April 2009, there were six nuclear power reactors operating in three countries of the region, two units in Argentina, two units in Brazil and two units in Mexico. There are plans for the conclusion of the construction of one nuclear power reactor in Argentina (Atucha 2) with a net capacity of 692 MWe and for the construction of two new units with a net capacity of 1 480 MWe. In the case of Brazil, there are plans for the conclusion of the construction of one nuclear power reactor (Angra 2) and for the construction of five new units with a total net capacity of 5 245 MWe. Mexico has plans for the construction of two nuclear power reactors with a total net capacity of 2 000 MWe.

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Jorge Morales Pedraza Table 4. The information on the nuclear power programme in Latin America

Country

No. of units (Until April 2009)

Net Capacity Energy (MWe) Product(2007) 2007 Million of (kWh)

Nuclear share (%) (2007)

6.2

Net Load Factor 2007 (%) (2007) (Until April 2009) 82.1

Number of Reactors Under Construction (Until April 2009) 1

Number of Reactors Planned and Proposed (Until April 2009) 2

Argentina

2

935

6.7

Brazil

2

1 795

11.7

2.8

74.1

1

5

Mexico

2

1 360

9.95

4.6

83.5

-

2

Total

6

4 090

28.35

-

-

2

9

Source: WANO and CEA 8th Edition, 2008.

The potential use of nuclear energy for electricity production in some countries in the Latin American region is an option that cannot be excluded from any future energy balance study to be carried out by them8. The purpose of these studies is to find the most adequate energy mix balance in order to satisfy the future increase in electricity demand in some Latin American countries in the most efficiency manner. Renewable energy sources available in the region are not enough to satisfy the foresee increase in the energy demand. The net electricity generation projections in South and Central America by fuel until 2030 are shown in the following figure.

Figure 2. Net electricity generation in South and Central America by fuel during the period 2006-2030. Sources: 2006: Derived from Energy Information Administration (EIA), International Energy Annual 2006 (June-December 2008), web site: www.eia.doe.gov/iea. Projections: EIA, World Energy Projections Plus (2009).

8

These countries are: Argentina, Brazil, , Chile, , Mexico, Uruguay and Venezuela.

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From the figure above can be confirmed that the projections of the use of nuclear energy for electricity generation until 2030 will continue to be very small, despite of the expansion plans in the use of this type of energy adopted or under consideration in some Latin American countries. Without any doubt, hydropower will continue to be the dominant energy sources for the production of electricity in the region.

THE ENERGY SITUATION IN AFRICA AND THE MIDDLE EAST Elsewhere in Africa, particularly below the Sahara desert, electricity production is unacceptably low. Of the 53 African countries, only a limited number have large energy potential. Hydropower potential is the most evenly spread, but the highest concentration is on the Congo River. Oil and gas are mostly concentrated in Algeria, Nigeria and Libya; coal is mostly found in southern Africa; and geothermal potential exists in eastern Africa. Together with South Africa, the Maghreb countries (Morocco, Algeria, Tunisia, Libya and Mauritania) account for more than 80% of Africa's electricity generating capacity. As a result, in the absence of adequate trans-African resource sharing arrangements and infrastructure, many African countries suffer from scarce energy resources and must pay high prices to import energy. [5, p 1] Until 2008, there are only two nuclear power reactors in operation in one African country: South Africa. These are Koeberg-1 and Koeberg- 2. Koeberg-1 started operation in 1984 and Koeberg-2 in 1985. Both nuclear power reactors have a net capacity of 900 MWe and are PWR type. Based on this information it can be stated that nuclear power is today only a very small part of Africa‘s energy supply, but its contribution could grow in the future if plans to use nuclear energy for the generation of electricity are approved and implemented by Algeria, Egypt, Morocco, Namibia and Nigeria. The governments of these countries are seriously considering the use of nuclear energy for the production of electricity in the future. In the near term for the use of nuclear energy for the production of electricity in Africa would be necessary to bridge the gap between the economies of scale, that favor large nuclear power plants, and the smaller electrical grids and capital capabilities of many African countries. To understand the possibilities in the use of nuclear energy for electricity generation in Africa the following question need to be answered: Which are the real possibilities to use nuclear energy for the production of electricity in the African region in the near future? These possibilities are associated with the solution, among others, of the following important matters: 1. The use of small and medium-size nuclear power reactor designs that should be available in the market in the short term; 2. The integration of electricity grids among neighboring countries; 3. The lack of technological development of many African countries; 4. The safety of the operation of the nuclear power plants; 5. The management of the spent nuclear fuel; 6. The political instability in some African countries, the interstates conflicts and ethnic strife9: 9

Examples of such risks are abundant. A group of armed men attacked Areva uranium prospecting camp in northern Niger, killing a security guard and wounding three other people. In Congo, a nuclear research reactor has an inadequate physical protection, possesses a totally outdated control room and an unguarded radioactive

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Jorge Morales Pedraza 7. The lack of resources to finance the construction of a nuclear power plant; 8. The lack of well-trained professionals and technicians in the use of nuclear energy for the generation of electricity.

The attitudes of African decision makers, experts and public about nuclear power range from negative/cautious to positive/enthusiastic. Supporters perceive nuclear power as a "silver bullet" that would allow the continent to demonstrate both technical progress and competence. The search for cleaner energy sources such as nuclear is also motivated by widespread concern that Africa is more vulnerable than other regions to climate change. Some of the serious consequences of climate change in Africa could include desertification, food shortages, epidemics, insufficient water supply, coastal erosion and increased refugees. It is important to note that from the 436 nuclear power reactors operating around the world in 2009 just two are in located in Africa, and this means only 0.46% of the total. Of the 54 nuclear power reactors under construction around the world in 2009 none of them is located in Africa. However, from a handful of promising new nuclear power reactor designs now reaching the prototype stage in the world, an important one is the South Africa‘s Pebble Bed Modular Reactor (PBMR). This type of nuclear power reactor could represent an acceptable solution regarding the type of reactor to be used not only in South Africa, but in other African countries as well. The net electricity generation projection in Africa by fuel until 2030 is shown in the following figure. As can be easily seen from Figure 3, coal and natural gas are the two main sources of energy for the generation of electricity in Africa. Renewables are the third source of energy in the region. This situation is expected to be maintained until 2030. Based on the above projection, the main questions to be answered are the following: Which is the future role to be played by nuclear energy for the generation of electricity in Africa, and what possible technological and policy adjustments need to be introduced to the current trends in nuclear power development in order to respond to the needs of African countries? Might the PBMR or some other innovative new nuclear power reactor designs be able to represent a technological opportunity for Africa, i.e. an opportunity to move directly to the next generation of nuclear power reactor technology without repeating all the intermediate steps travelled by industrialized countries with long-established nuclear power programmes? It is well known than economies of scale argue for larger and larger nuclear power plants. At the same time, the greater the number of nuclear power reactors to be in operation the lower is the per kilowatt-hour cost of the infrastructure built. However, economies of scale are only valuable where the capital and electricity demand exist to take full advantage of them and this is something that in many countries of Africa does not exist. Then, what are the options available? For these countries, there are at least two routes by which a nuclear power plant might become part of a least-cost energy strategy. These routes are the following: First is the use of small or medium-size reactors (SMRs) for the generation of electricity and the second is the integration of electric grids among neighboring countries, this means the regionalization of electric grids. waste storage building. Through decades of war and political upheaval, the Congo has repeatedly been accused of illegally selling its natural uranium or not preventing smuggling schemes. In November 2007, armed gunmen gained access to a major nuclear research facility in South Africa and reached the emergency control room before guards control de situation.

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Sources: 2006: Derived from Energy Information Administration (EIA), International Energy Annual 2006 (June-December 2008), web site: www.eia.doe.gov/iea. Projections: EIA, World Energy Projections Plus (2009). Figure 3. Net electricity generation projection in Africa by fuel until 2030.

There should be no doubt that the use of nuclear energy for the production of electricity in Africa will be a reality, at least in some of the most advanced African countries in the middle-long term, if small and medium size reactors will be available in the market and the regionalization of the electric grid can be materialized.

Sources: 2006: Derived from Energy Information Administration (EIA), International Energy Annual 2006 (June-December 2008), web site: www.eia.doe.gov/iea. Projections: EIA, World Energy Projections Plus (2009). Figure 4. Net electricity generation in the Middle East by fuel during the period 2006-2030.

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Until April 2009, there were no nuclear power reactors operating in the Middle East and natural gas and oil are the dominant sources of energy for the production of electricity in the region. As can be easily seen from Figure 4 the projection of the participation of nuclear energy in the generation of electricity in the Middle East will continue to be very marginal in 2030, despite of the intention of some countries of the region to use nuclear energy for the production of electricity. However, it is important to stress that the great instability that exist in the region is an important obstacles for the introduction of a nuclear power programme in any Middle East country in the near future. The world energy projection for the Middle East place natural gas as the dominant energy source in the energy balance of the region for 2010, 2020 and 2030. Summing up can be stated the following: The situation regarding the number of nuclear power reactor in operation and under construction by region in 2009 is the following: In Asia the number of nuclear power reactors in operation is 103 in five countries (if Taiwan is included within China) with a net capacity of 76 718 MWe and there are 25 nuclear power reactors under construction in 5 countries, with a net capacity of 21 921 MWe. In the European region there are 197 operating nuclear power reactors in 18 countries with a net capacity of 170 007 MWe and 14 nuclear power reactors under construction in 5 countries with a net capacity of 12 986 MWe. In the following table the evolution of nuclear power plants capacities connected to the grid during the period 1970 to 2007 is shown. As can be clearly see in the table 5 the major increase in the construction of nuclear power reactors occurred in the 1970s, 1980s and 1990s. The increase in the number of nuclear power reactors constructed from the 1970s to 1980s jump from 81 to 243, this means an increase of 200%. From 1980s to 1990s the number of nuclear power reactors constructed increased from 243 to 419, this means an increase of 72%. However, in the last 17 years the number of nuclear power reactors constructed was only 20; this means a modest increase of 5%. The world energy used by fuel type during the period 1980-2005 is shown in Figure 6. From this figure it is easy to see that fossil fuels are the dominant type of energy in the last 25 years. During this period a small progress in the use of the other types of available energy was achieved10. However, there is a great difference between the use of fossil fuels and renewable energies for the production of electricity during the abovementioned period. The contribution of nuclear energy for the electricity generation is third after biomass. Table 5. Evolution of nuclear power plants capacities connected to the grid during the period 1970 to 2007 Year 1970 1980 1990 2000 2007 20091

Number of countries 14 24 30 31 31 31

Units 81 243 419 436 439 436

MWe 16 202 136 164 325 854 351 550 372 182 372 203

Note: The data is until April 2009. Source: CEA 8th edition, 2008 and IAEA data information. 10

Renewables energy was not included in Figure 6 due to its limited contribution (between 0.2 and 0.5% only).

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Source: IAEA SIPRIS, 2007. Figure 5. Nuclear power reactors in operation and net operating capacity in the world from 1956 to 2007.

The following table includes information on the level of contribution of the different types of energy for the generation of electricity by region.

Source: IAEA, 2007. Figure 6. World energy used by fuel type during the period 1980-2005.

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Table 6. Level of contribution of the different types of energies for the generation of electricity by region in 2006 Region

North America Europe Asia Latin America Africa World Total

Thermal Use (EJ) 22.21 32.92 52.84 4.42 4.89 117.28

% 65.71 67.02 84.70 38.28 80.01 73.66

Hydro Use (EJ) 2.43 2.84 2.94 2.46 0.35 11.02

% 14.53 5.82 4.72 58.31 17.74 6.92

Nuclear Use (EJ) 9.61 12.71 5.90 0.33 0.11 28.66

% 18.99 26.03 9.46 2.61 1.84 18

Renewables Use % (EJ) 0.73 0.77 0.55 1.13 0.70 1.12 0.32 0.81 0.04 0.41 2.24 1.42

Total Use % (EJ) 34.98 100 49.02 100 62.38 100 7.54 100 5.4 100 159.22 100

Note: One EJ = 2.78 × 105 GWh or 31.7 GWe. Source: IAEA.

Sources: 2006: Derived from Energy Information Administration (EIA), International Energy Annual 2006 (June-December 2008), web site: www.eia.doe.gov/iea. Projections: EIA, World Energy Projections Plus (2009). Figure 7. Net electricity generation in the Middle East by fuel during the period 2006-2030.

From Table 6 can be concluded that the contribution of nuclear energy to total electricity generation varies considerably among region. In Europe, nuclear generated electricity accounts for 26.03% of the total electricity produced. In North America it is approximately 19%, whereas in Africa and Latin America it is 1.84% and 2.61% respectively. In Asia, nuclear energy accounts for 9.46% of electricity generation. It is not difficult to conclude that the use of nuclear energy for electricity generation is concentrated in technologically advanced countries. Based on the information included in the above paragraphs it is easy to conclude the following: 1. Europe remained the largest nuclear energy user for electricity generation among all regions since 1980. 2. North America was the second largest user of nuclear energy for electricity production since 1980.

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3. With the largest regional population and fast growing economies, Asia became the third largest nuclear energy user for electricity production since 1980. 4. Latin America registered almost the same growth in its nuclear energy use for electricity generation since 1980. Its share remained more or less unchanged between 2.3% to 3.1%. 5. Africa is the region with the smallest nuclear share since 1980. In the following figures the world primary energy demand evolution during the period 1980-2030 and the world net electricity generation from nuclear power by region during the period 2006-2030 are included. From the figures below, it can be stated that the EU will continuing to depend on the import of oil and gas to ensure its economic and social development until 2030.

Source: World Energy Outlook 2006, pp 12. Figure 8. Foreseen EU-27 energy import dependence up to 2030.

Sources: 2006: Derived from Energy Information Administration (EIA), International Energy Annual 2006 (June-December 2008), web site: www.eia.doe.gov/iea. Projections: EIA, World Energy Projections Plus (2009). Figure 9. World net electricity generation from nuclear power by region during the period 2006-2030.

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Jorge Morales Pedraza

LIMITING FACTORS If nuclear energy will be an important component of the energy balance in the non-OECD Asia region in the coming years, then why the use of this type of energy cannot play the same role in other regions as well. The reason is the following: There are a number of limiting factors that are making difficult that the nuclear energy increase significantly its role in the energy balance in other regions now and in the future. These limiting factors are, among others, the following11: 1. 2. 3. 4. 5.

Management of the radioactive waste, particularly high level nuclear waste; Proliferation security; Operational safety of the nuclear power plants; Economic competitiveness; Public acceptance. [11, pp 57 and 58]

Management of the Radioactive Waste Management of the radioactive waste, particularly high–level nuclear waste, is an unresolved problem for many people in different countries all over the world. However, the technology for the safe management of radioactive waste is now available and can be used by any countries with an important nuclear power programme. The USA and Sweden have achieved some progress regarding the final disposal of high radioactive nuclear waste and the technology used by these countries could represents a real and objective solution to this problem for other countries as well. Another problem that several countries have to deal with in the coming years, particularly in the case of North America and Europe, is the increase ageing power-generation capacity, particularly in the field of electricity generation using nuclear energy. To overcome this problem both regions have an urgent need for major investment in the energy power sector in order to meet the expected energy demand and, at the same time, the replacement of ageing energy infrastructures. According to the EC, around 800-900 GWe capacity will be required by 2030 to replace the existing capacity and to address increasing needs. It is reasonable to assume that out of these potential new 800-900 GWe, at least 100 GWe will be produced by Generation-III nuclear power reactors. This corresponds to the construction of 60 to 70 big nuclear power reactors and represents an investment of €150 billion over 20 years (for an average overnight construction cost of €1,500 per kWe). The new reactors should be designed to operate 60 years. [12, p 20].

11

According with the IAEA, other limiting factors are: human resources, transport of uranium, fresh and spent nuclear fuel and waste, infrastructure building and the relationship between electric grids and reactor technology.

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Source: IAEA document GC (52)/INF/6, 2008. Figure 10. Number of nuclear power reactors in operation in the world by age as January 2008.

From the above figure can be single out that the number of nuclear power reactors currently in operation in the world with more than 20 years connected to the electric grid is 342, representing 78.4% of the total nuclear power reactors operating in the world until April 2009. For this reason, the age of the nuclear power reactors now operating in the world is one of the urgent problems that need to be faced by those countries operating these reactors. The decision to be taken by the governments of these countries could be the following: a) Extend the lifetime of the nuclear power reactors in operation; or b) Initiate the process of shut down and decommissioning of these reactors. Taking into account the current energy situation in the world it is expected that the majority of the States will decide to extend the lifetime of these reactors to satisfy the foresee increase in the demand of energy in the coming years. It is important to single out that in the longer term a new generation of nuclear power reactors, the Generation IV system will take over once they have reached technical maturity and met sustainable development criteria, particularly those pertaining to waste management and preservation of energy resources. Commercial deployment of such Generation IV systems is not expected to occur before 2040 since major technological breakthroughs are still needed to develop such reactors". [12, pp 20 and 21] Generation IV reactors would be much smaller in size (100 MW to 200 MW) and capital investment, represent a more flexible solution due to much shorter building times and a lower potential risk due to smaller radioactive inventories and passive safety features [1, p 15]. Based on what has been said before, it is important to stress that the international community should be aware that each of the three generations of nuclear power reactors will coexist during the 21st century. All of these types of nuclear power reactors face specific technological challenges to be overcome on the path to sustainability, but all share the common goal of guaranteeing the highest level of safety.

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Proliferation Risk Nuclear power entails potential proliferation risk, particularly for the possible misuse of nuclear technology, facilities or materials as a precursor to the production of a nuclear weapon. Due to this undisputed fact, it is extremely important to be aware that the future use of nuclear energy for electricity generation in several countries, will depends of the production of new type of nuclear power reactors that are proliferation risk-free. Nuclear power should be expanded in the world if the risk of proliferation from operation of the commercial nuclear fuel cycle associated with the introduction of a nuclear power programme is made acceptably small. How to achieve this goal? First, the international community should strengthen the application of the IAEA safeguards system to all States, by putting into force for all of them the IAEA Additional Protocol. Second, the international community should adopt a multilateral approach to the nuclear fuel cycle and must adopt all necessary measures to prevent the acquisition of weapons-usable material, either by diversion (in the case of plutonium) or by misuse of fuel cycle facilities (including related facilities, such as research reactors or hot cells) now operating in different countries. However, the adoption of a multilateral approach to the nuclear fuel cycle should be done in a way that respect the right of any States to develop their own nuclear fuel cycle in case it feel any political discrimination against the country in their access to the necessary services associated with the nuclear fuel cycle. In this case, States must submit all facilities associated with its nuclear fuel cycle to full scope IAEA safeguards, including the Additional Protocol. There are three issues of particular concern for the international community when the nuclear option is considered to satisfy the foresee increase in the demand of electricity in the coming decades. These issues are the following: (a) The existing stocks of fissionable materials in the hands of several countries that is directly usable for the production of nuclear weapons; (b) The number of nuclear facilities with inadequate physical protection and controls; The lack of adequate physical protection in force in several countries could be used by terrorist groups to have access to certain amount of fissionable materials to use by them for the production of a nuclear weapon; (c) The transfer of sensitive nuclear technology, especially enrichment and reprocessing technology, to countries implementing a nuclear power programme that brings them closer to a nuclear weapons capability. The proliferation risk due to the global growth in the use of nuclear energy for electricity production is an important element that needs to be reduced to the minimum, if the nuclear option is going to be supported by the international community in the coming years.

Operational Safety of the Nuclear Power Plants Nuclear power has been subject of several nuclear accidents heightened by the 1979 Three Mile Island and the 1986 Chernobyl nuclear accidents occurred in the USA and Ukraine respectively, but also by accidents at fuel cycle facilities in the USA, Russia and Japan in the past. Some countries decided to phase out their nuclear power programme or to

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prohibit the use of nuclear energy for electricity generation, based on the consequences for the health and for the environment of some of these accidents, particularly the Chernobyl nuclear accident12. For this reason, the production of new nuclear power reactors with stringent safety requirements is an indispensable condition to spread the use of nuclear energy for electricity generation in the coming years. Nuclear energy produces very few emissions of gases to the atmosphere. If the whole production cycle is considered, this means from the construction of the nuclear power plant to their exploitation, the production of 1 kWh of nuclear origin electricity supposes less than 6g of CO2 emission mainly associated to the construction of the nuclear power plant and the transport of fuel. On the other hand, a combined cycle gas power plant generates 430g of CO2 and a coal power plant between 800 to 1,050g of CO2, according with the type of technology used. Based on this facts it can be stated that the use of nuclear energy for electricity generation is one of the cleanest type of energy available in the world.

Economic Competitiveness Nuclear power is cost competitive with other forms of electricity generation, except where there is direct access to low-cost fossil fuels. Fuel costs for nuclear power plants are a minor proportion of total generating costs, though capital costs are greater than those for coal and oil fired power plants. In assessing the cost competitiveness of the use of nuclear energy for the production of electricity, decommissioning and waste disposal costs should be taken into account. According with expert‘s calculations, decommissioning costs are about 10-20% of the initial capital cost of a nuclear power plant. This make the nuclear energy option more expensive than other sources of energy under specific conditions. However, if the social, health and environmental costs of fossil fuels are also taken into account, then the use of nuclear energy for electricity generation is outstanding. The increase cost due to delay in the construction of a nuclear power plant is another important element that need to be taken into account when the overall cost associated with the use of nuclear energy for electricity generation is analyzed. The future competitiveness of nuclear power will depend substantially on the additional costs, which may accrue to coal generating plants and the cost of gas for gas-fired plants. It is uncertain how the real costs of meeting targets for reducing sulphur dioxide and greenhouse gas emissions will be attributed to fossil fuel plants. [13, page 3]

Public Acceptance The public opinion is another important element that needs to be taken into consideration when planning the introduction of a nuclear power programme by any country. It is important to understand that the future of the use of nuclear energy for the production of electricity depends on the public's perception of the importance of their use with this purpose and the risks involved. The concern of the society arises because, although the probability of a 12

However, it is important to single out that there is any nuclear power reactor design that is totally risk -free for the following two reasons: a) Technical possibilities; b) Work-force problems. Safe operation of a nuclear power reactor requires effective regulation, a management committed to safety and a skilled work-force.

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nuclear accident is very low, the risks to have it can have important consequences on the environment and on the population, particularly those that live in areas close to the plant but even to the population leaving far away to the plant site. This concern is not based on an objective perception but in an intuitive judgement, due to the initial history on how nuclear energy was used in the past for military purpose, due to serious nuclear accidents occurred in some facilities, and due to the optimistic initial expectations associated with the use of nuclear energy for electricity generation that they have not been fulfilled. Different studies carried out so far on the use of nuclear energy for electricity generation indicate that there is a lack of information in the public on this important subject, as well as about the price of the different energy options available for the production of electricity and or their repercussion on the environment. The different nuclear actors, particularly the scientific community, technologists, operators, regulators and legislators have not been able to convince the public opinion on which of the energy options available for electricity generation are the most economic and convenient for a particular country. For this reason, it is extremely important to make additional efforts to provide reliable and impartial information about the use of the different types of energy sources available in the world for electricity generation, including the nuclear energy option, to the public opinion of the country. The aim is to help them to define their position regarding the different energy options for electricity generation available in the world and identify which of them are the most appropriates for the country. The increase in the costs of the construction of a nuclear power plant, the unforeseen delays in the construction of these type of plants due to new safety and security requirements demanded to the operators after the nuclear accidents of the Three Miles Island and Chernobyl, environment impact, among other requirements, has stopped the construction of new nuclear power plants in the USA as well as in other countries, particularly within the European region. The repercussion of these accidents was a public opinion contrary to the use of nuclear energy for electricity generation in the USA and in Western Europe and, as consequence of this position, the rejection of the politicians to support any further development of the nuclear power sector in these two regions. However, and despite of several other nuclear accidents of minor consequences occurred in other countries, the public opinion in several countries in Asia such as Japan, the Republic of Korea and China as well as in Russia, where the energy demand has grown considerably, programmes for the construction of new nuclear power plants have continued to be carried out without major difficulties. It is important to single out that in many countries people are ready to support the nuclear power option, if and only if problems related with the final disposal of high radioactive nuclear waste and the safety of the nuclear power reactors are properly solved. In the particularly case of the USA, the country with the major number of nuclear power reactors in operation in the world (104), the people is unlikely to support nuclear power expansion without substantial improvements in costs and technology. The carbon-free character of nuclear power is one of the main elements used by those that support the use of nuclear energy for electricity generation, particularly in Europe. However, in the case of the USA, the cost-free character of nuclear power does not appear to be one of the main elements that motivate the public opinion to prefer the nuclear power option for electricity generation, compare with other energy sources available in the country. In some developed countries there is an impression that nuclear power is especially unpopular

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among available energy sources. For this reason, it is further assumed that unless and until this unpopularity can be overcome, nuclear power will not flourish, even in the event that the use of this type of energy for electricity generation has solid grounds to support it. Then the question to be answered is the following: Why public opinion in some countries is against the use of nuclear energy for electricity generation? Some of the factors behind the loss of public confidence in some developed countries were caused directly by the industry itself. The construction times and costs of many plants were far higher than projected. The performance of many plants was disappointing. The accidents at Three Mile Island and Chernobyl also served to exacerbate growing mistrust of the nuclear industry and its often vocal supporters within governments. This mistrust had its origin, at least in part, in the arrogance and secretiveness of nuclear spokesmen in many countries. The suspicion that the industry and its supporters were able, for example, to put undue pressure on regulators further damaged their public credibility. Critics of the industry often had no apparent vested interest to do so, while the industry‘s responses increasingly came to be discounted – ‗they would say that, would not they? The passion which has surrounded the nuclear debate in recent years is to a considerable degree a legacy of these factors. [14, p 2] At the same time, perceptions of the availability of alternatives energy sources for electricity generation were changing. When global fossil fuel supplies were under apparent threat (notably in the 1950s and again in the 1970s until the beginning of the 1980s), nuclear power programmes were introduced in many countries with relatively little objection, at least by today‘s standards. The discovery of vast reserves of gas, as well as oil, coupled with low prices and the development of the highly efficient Combined Cycle Gas Turbine by the mid1980s, reduced the apparent need for nuclear power in many developed countries. However, this perception was not shared by some developing countries, notably India and China [14, p 2]. For this reason both countries continuing with the development of important programmes for the construction of new nuclear power reactors. Many developing countries have anti-nuclear movements, even if they may be small, and environmental pressure groups are increasingly establishing themselves in the these countries. A number of specific explanations have been suggested for the apparent special unease felt about nuclear power in many countries. They include: 1. Links to the military, both real (the development of shared facilities) and perceptual; 2. Secrecy, coupled sometimes with an apparent unwillingness to give ‗straight answers‘ (in part, perhaps, because of links to military nuclear operations in some countries, and in part because of commercial issues); 3. The historical arrogance of many in the industry, dismissing opposition, however well-founded or sincerely held, as ‗irrational‘; 4. The apparent vested interest of many nuclear advocates, to be contrasted with the apparent altruism of opponents who, for example, are often not funded to take part in public inquiries; 5. The perceived potential for large and uncontainable accidents and other environmental and health effects, notably those associated with radioactive waste; 6. The overselling of nuclear technology, especially in its early days, in particular with regard to its economics, leading to a degree of disillusionment and distrust;

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Jorge Morales Pedraza 7. A general disillusionment with science and technology, and with the ‗experts know best‘ attitude of mind that was more prevalent in the years immediately after the Second World War; 8. The wider decline of ‗deference‘ towards ‗authority‘ (including, for example, politicians and regulatory bodies). [14, p 3]

Other explanations to the opposition to the introduction of a nuclear power programme or to an extended use of nuclear energy for other peaceful purposes are the following: 1. Radioactivity cannot be smell, fell or seen, this means has no color and is not cold or warm; 2. Radioactivity can only be detected using special equipment.

THE PROJECTION OF THE CONTRIBUTION OF NUCLEAR ENERGY IN THE GLOBAL ENERGY BALANCE The world electricity generation by fuel during the period 2005-2030 is reflected in Figure 11.

Sources: 2006: Derived from Energy Information Administration (EIA), International Energy Annual 2006 (June-December 2008), web site: www.eia.doe.gov/iea. Projections: EIA, World Energy Projections Plus (2009). Figure 11. World electricity generation by fuel during the period 2005-2030.

In the Table 7 the latest IAEA estimates of nuclear electricity generating capacity up to 2030 is included. The table shows that the greatest expansion of nuclear generating capacity for the following 20 years is projected for the Far East. Significant expansion is also projected for Middle East and South Asia, the region that includes India. However, the region with the

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greatest uncertainty, i.e. the greatest difference between the low and high projections, is Western Europe, region that is now debating the future role to be played by nuclear energy in the energy balance mix in the whole region, particularly within the EU. Although approximately 20 new countries are included in the 2030 projections, the global increase in the high projection comes mainly from increases in the 31 countries already using nuclear energy for electricity production. The low projection also includes approximately five new countries that might have their first nuclear power plants in operation by 2030. It is important to note that the IAEA projections have changed over the past few years. In particular the high projection for the rate of increase in installed nuclear power plant capacity between 2020 and 2030 is higher from the projections done in 2004, reflecting an increase in optimism about the use of nuclear energy for electricity production in some regions. The low projection in 2004 showed a declining installed capacity as nuclear power reactors in operation were taken out of service without replacement. Table 7. The IAEA estimates of nuclear electricity generating capacity (GWe)

Source: IAEA GC (52)/INF/6.

It is also important to note that the IAEA has identified several issues that could affect the future introduction or expansion of nuclear power programmes in a group of countries and hence the accuracy of the predictions of nuclear power used. According with the IAEA, these issues are the following: 1. Nuclear power has generated stronger political passions than alternatives. Alternatives to nuclear power, natural gas, coal, hydropower, oil and renewables, have nothing comparable to the prohibitions and phase-out policies that several countries have adopted for nuclear power; 2. Because of the front-loaded cost structure of a nuclear power plant, high interest rates, or uncertainty about interest rates, will weaken the business case for nuclear power more than for alternatives; 3. Nuclear power‘s front-loaded cost structure also means that the cost of regulatory delays during construction is higher for nuclear power than for alternatives. In

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4. 5.

6. 7.

8.

countries where licensing processes were relatively untested in recent years, investors face potentially more costly regulatory risks with nuclear power than with alternatives; The strength, breadth and durability of commitments to reducing GHG emissions will also influence nuclear power‘s growth; The nuclear industry is a global industry with good international cooperation and hence the implications of an accident anywhere will be felt in the industry worldwide; Similarly, nuclear terrorism may have a more far reaching impact than comparable terrorism directed at other fuels; While a nuclear power plant in itself is not a principal contributor to proliferation risk, proliferation worries can affect public and political acceptance of nuclear power; Among energy sources, high level radioactive waste is unique to nuclear power. The nuclear power industry might feel a disproportionately broad impact if major problems are encountered in any of the repository programmes that are most advanced (Finland, France, Sweden and USA). [4, pp 27]

If the world is to meet even a fraction of the economics aspirations of the developing world, energy supplies must expand significantly. If the increase needs of the industrialized countries for its economic development are considered as well, then the world energy supplies must expand even further. The following table includes relevant information regarding the generation of electricity in 2007 and the number of nuclear power plants in operation and in construction in the world until April 2009. During the period of peak construction there were major nuclear system supply companies in Canada, France, Germany, Japan, Russian Federation, Sweden, Switzerland, UK and USA. Today, nuclear system suppliers are in Canada, China, France, India, Japan, Republic of Korea, Russian Federation and USA. There are other potential suppliers who have designs in development such as Argentina and South Africa. The designers of currently available nuclear steam supply systems have been reduced to a small group who increasingly are working very closely together, for example through collaboration between Areva and Mitsubishi, GE and Hitachi, and Toshiba and Westinghouse. As can be easily see from the Figure 13 the number of nuclear power reactors under construction dropped significantly during the period 1980- 1995. After 2005, there is a trend to increase very slowly the total number of nuclear power reactors under construction each year. It is expected that this trend will continue in the coming years.

Types of Nuclear Power Reactors All nuclear power reactors are devices designed to maintain a chain reaction producing a steady flow of neutrons generated by the fission of heavy nuclei inside the devices. The nuclear power reactors are differentiated by their purpose and by their design features.

Table 8. World Nuclear Power Reactors 2008 Country

Argentina Armenia Bangladesh Belarus Belgium Brazil Bulgaria Canada China Czech Republic Egypt Finland France Germany Hungary India Indonesia Iran Israel Italy Japan Kazakhstan Korea DPR (North) Korea RO (South) Lithuania

Nuclear electricity generation 2007 billion kWh 6.7 2.35 0 0 46 11.7 13.7 88.2 59.3 24.6 0 22.5 420.1 133.2 13.9 15.8 0 0 0 0 267 0 0 136.6 9.1

% 6.2 43.5 0 0 54 2.8 32 14.7 1.9 30.3 0 29 77 26 37 2.5 0 0 0 0 27.5 0 0 35.3 64.4

Reactors operable April 2009

Net Capacity

No. 2 1 0 0 7 2 2 18 11 6 0 4 59 17 4 17 0 0 0 0 53 0 0 20 1

MWe 935 376 0 0 5 728 1 901 1 906 12 652 8 587 3 472 0 2 696 63 473 20 339 1 826 3 779 0 0 0 0 46 236 0 0 17 716 1 185

Reactors under construction April 2009 No. 1 0 0 0 0 0 0 2 11 0 0 1 1 0 0 6 0 1 0 0 2 0 0 5 0

Net Capacity

Reactors planned April 2009

MWe 692 0 0 0 0 0 0 1 500 11 000 0 0 1 600 1 630 0 0 2 976 0 915 0 0 2 285 0 0 5 350 0

No. 1 0 0 2 0 1 2 3 26 0 1 0 1 0 0 10 2 2 0 0 13 2 1 3 0

MWe 740 0 0 2 000 0 1 245 1 900 3 300 27 660 0 1 000 0 1 630 0 0 9 760 2 000 1 900 0 0 17 915 600 950 4 050 0

Reactors proposed April 2009 No. 1 1 2 2 0 4 0 6 77 2 1 1 1 0 2 15 4 1 1 10 1 2 0 2 2

Net Capacity

MWe 740 1 000 2 000 2 000 0 4 000 0 6 600 63 400 3 400 1 000 1 000 1 630 0 2 000 11 200 4 000 300 1 200 17 000 1 300 600 0 2 700 3 400

Table 8. (Continued) Country

Mexico Netherlands Pakistan Poland Romania Russia Slovakia Slovenia South Africa Spain Sweden Switzerland Thailand Turkey Ukraine UAE United Kingdom USA Vietnam WORLD**

Nuclear electricity generation 2007

billion kWh 9.95 4.0 2.3 0 7.1 148 14.2 5.4 12.6 52.7 64.3 26.5 0 0 87.2 0 57.5 806.6 0 2 608

% 4.6 4.1 2.34 0 13 16 54 42 5.5 17.4 46 43 0 0 48 0 15 19.4 0 15

Reactors operable April 2009

Net Capacity

No. 2 1 2 0 2 31 4 1 2 8 10 5 0 0 15 0 19 104 0 436

MWe 1 310 485 400 0 1 310 21 743 1 688 696 1 842 7 448 9 016 3 220 0 0 13 168 0 11 035 101 119 0 372 203

Reactors under construction April 2009 No. 0 0 1 0 0 8 2 0 0 0 0 0 0 0 0 0 0 1 0 44

Net Capacity

MWe 0 0 300 0 0 5 980 840 0 0 0 0 0 0 0 0 0 0 1 180 0 38 848

Reactors planned April 2009 No. 0 0 2 0 2 11 0 0 3 0 0 0 2 2 2 3 0 11 2 110

MWe 0 0 600 0 1 310 12 870 0 0 3 565 0 0 0 2 000 2 400 1 900 4 500 0 13 800 2 000 121 595

Sources: WANO April 2009. At the end of December there were 54 units under construction. Note: This table includes only those future reactors envisaged in specific plans and proposals expected to be operating by 2030.

Reactors proposed April 2009 No. 2 0 2 5 1 25 1 1 4 0 0 3 4 1 20 11 6 20 8 243

Net Capacity

MWe 2 000 0 2 000 10 000 655 22 280 1 200 1 000 4 000 0 0 4 000 4 000 1 200 27 000 15 500 9 600 26 000 8 000 268 905

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Table 9. Type of reactor by country

Note: From this table three nuclear power reactors were shut down in 2009. These nuclear power reactors are Hamaoka Units 1 and 2 in Japan and Bohunice Unit 3 in Slovakia. Source: IAEA.

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Source: IAEA, 2008. Note: From this figure three nuclear power reactors were shut down in 2009. These nuclear power reactors are Hamaoka Units 1 and 2 in Japan and Bohunice Unit 3 in Slovakia. Figure 12. Nuclear power reactors in operation worldwide.

Source: IAEA data base. Figure 13. Number of reactors under construction during the period 1995-April 2009.

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Source: IAEA document GC(52)/INF/6 dated 12.8.2009. Figure 14. Number of nuclear power reactors and the total nuclear power reactor capacity under construction from 1951 to 2008.

Considering the purpose of the nuclear power reactors they can be classified in two groups: a) Nuclear research reactors; and b) Nuclear power reactors. Nuclear research reactors are devices that operate at universities and research institutions in many countries, including in countries where no nuclear power reactors are in operation. These types of reactors are used for multiple purposes, including the production of radiopharmaceuticals, medical diagnosis and therapy, testing materials and conducting basic research. Nuclear power reactors are those devices used for generating heat mainly for electricity production. However, this type of reactors is uses also for desalination of water. In the form of smaller units, they also power ships. There are many different types of nuclear power reactors. What is common to all of them is that they produce thermal energy that can be used for its own sake or converted into mechanical energy and ultimately, in the vast majority of cases, into electrical energy. In this type of reactors, the fission of heavy atomic nuclei, the most common of which is uranium235, produces heat that is transferred to a fluid which acts as a coolant. The heated fluid can be gas, water or a liquid metal. The heat stored by the fluid is then used either directly (in the case of gas) or indirectly (in the case of water and liquid metals) to generate steam. The heated gas or the steam is then fed into a turbine driving an alternator, which produce the electricity. Nuclear power reactors can be classified according to the type of fuel they use to generate heat in: a) Uranium-fuelled nuclear power reactors; and b) Plutonium-fuelled nuclear power reactors.

Uranium–Fuelled Nuclear Power Reactors The Uranium–fuelled nuclear power reactors could be classified in the following manner: a) Pressurized Water Reactors (PWR), and b) Boiling Water Reactors (BWR). The main components of the PWRs are shown in the following figure.

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Source: International Nuclear Safety Center at Argonne National Laboratory. Figure 15. Main components of a PWR.

The PWRs is the most common nuclear power reactors operating in the world. There were 265 PWRs in operation in 24 countries all over the world in 2007. The load factor of this type of reactor in that year was 83.4% (first place). In 2007, the net capacity installed of the PWRs was 243 421 MWe. The USA and France are the countries with the highest number of PWRs in operation in the world. In 2007, there were 94 BWRs in operation in nine countries all over the world. The net capacity installed of the BWRs was 85 275 MWe. The load factor of this type of reactor in 2007 was 75.3% (fourth place). The USA and Japan are the two countries with the highest number of BWRs in operation in the world. The main components of the BWRs are shown in the following figure: Graphite-moderated, gas-cooled nuclear power reactors, formerly operated in France and still operated in the UK, are not built any more in spite of some advantages that this type of reactors have. RBMK-reactors (Pressure-Tube Boiling-Water Reactors, LWGR)), which are cooled with light water and moderated with graphite, are now less commonly operated in some former Soviet Union bloc countries. In Russia, there were 15 RBMK in operation in 2007 and one under construction. Following the Chernobyl accident the construction of this reactor type outside Russia ceased.

Plutonium-Fuelled Nuclear Power Reactors Plutonium (Pu) is an artificial element produced in uranium-fuelled nuclear power reactors as a by-product of the chain reaction. It is one hundred times more energetic than

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natural uranium; one gram of Pu can generate as much energy as one tone of oil. As it needs fast neutrons in order to fission, moderating materials must be avoided to sustain the chain reaction in the best conditions. The current Plutonium-fuelled nuclear power reactors, also called "fast reactors", use liquid sodium which displays excellent thermal properties without adversely affecting the chain reaction. These types of reactors are in operation in France, Japan and the Commonwealth of Independent States (CIS).

Boiling Water Reactor System Reactor Building Tubline Generators Electricity to Switch Yard

Reactor Core

Control Rods

Feedwater Pumps

Condenser

Source: International Nuclear Safety Center at Argonne National Laboratory. Figure 16. Principle of a nuclear power plant with Boiling Water Reactor.

The Next Generation of Nuclear Power Reactor The majority of the nuclear power reactors today in operation in the world are from the so-called "second generation" (Generation II) of nuclear power reactors. Some countries are now constructing nuclear power reactors of the "third generation" (Generation III), which are more reliable and with a number of built-in safety features. However, it is important to note that there is no clear definition of what constitutes a third generation design, apart from it being designed in the last 15 years, but the main common features quoted by the nuclear industry are: (a) A standardized design for each type to expedite licensing, reduce capital cost and construction time; (b) A simpler and more rugged design, making them easier to operate and less vulnerable to operational upsets; (c) Higher availability and longer operating life - typically 60 years; (d) Reduced possibility of core melts accidents; (e) Minimal effect on the environment; (f) Higher burn-up to reduce fuel use and the amount of waste; (g) Burnable absorbers (poisons) to extend fuel life.

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These characteristics are clearly very imprecise but do not define very well what a third generation of nuclear power reactors is. It is important to single out that this type of nuclear power reactors are evolved from existing designs of PWR, BWR and CANDU reactors. Until there is much more experience with these technologies, any figures on the generation cost of power from these designs should be treated with the utmost caution. [17, p 9] However, the future belongs to the so-called "fourth generation" of nuclear power reactors (Generation IV). This new generation of nuclear power reactors is a revolutionary type of reactors with innovative fuel cycle technologies. It is expected that they may be available for commercial operation around 2030-2040. The Generation IV responds to the following main sustainability criteria and future market conditions, among others: (a) (b) (c) (d)

Incorporate advanced nuclear safety; Are resistant to proliferation; Are highly economic and competitive; Produce minimal waste.

Challenging Technology Goals The following areas are the main challenging technology goals for Generation IV nuclear energy systems now under development in several countries: 1. 2. 3. 4.

Sustainability; Economics competiveness; Safety and reliability; Proliferation resistance and physical protection;

Sustainability One of the most important features of the new generation of nuclear power reactors is sustainability. Sustainability is the ability to meet the needs of the present generation while enhancing the ability of future generations to meet society‘s needs indefinitely into the future. The benefits of meeting sustainability goals include: (a) Extending the nuclear fuel supply into future centuries by recycling used fuel to recover its energy content and by converting U-238 to new fuel; (b) Having a positive impact on the environment through the displacement of polluting energy and transportation sources by nuclear electricity generation and nuclearproduced hydrogen; (c) Allowing geologic waste repositories to accept the waste of many more plant-years of nuclear plant operation through substantial reduction in the amount of wastes and their decay heat; (d) Greatly simplifying the scientific analysis and demonstration of safe repository performance for very long time periods (beyond 1,000 years), by a large reduction in the lifetime and toxicity of the residual radioactive wastes sent to repositories for final geologic disposal. [18, pp 1 and 2]

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Economic Competitiveness Another important feature of the next generation of nuclear power reactors is economic competiveness. The cost associated to the construction of nuclear power reactors is very high in comparison with the construction of a fossil-fuelled power plant and this factor impede that many countries consider the introduction or the expansion of a nuclear power programme. Economics goals broadly consider competitive costs and financial risks of nuclear energy systems. Looking ahead, the benefits of meeting economics goals include: (a) Achieving economic life-cycle and energy production costs through a number of innovative advances in plant and fuel cycle efficiency, design simplifications and plant sizes; (b) Reducing economic risk to nuclear projects through the development of plants built using innovative fabrication and construction techniques, and possibly modular designs; (c) Allowing the distributed production of hydrogen, fresh water, district heating, and other energy products to be produced where they are needed. [18, pp 2]

Safety and Reliability Systems The third relevant feature associated with the new generation of nuclear power reactors is that the system should be safe and reliable in the generation of electricity. The security of supply is one of the major concerns of any country and, for this reason, the reliability of an energy system is one of the criteria to be used when the selection of a source of energy for electricity generation is going to be made. Maintaining and enhancing the safe and reliable operation is an essential priority in the development of next generation systems. Safety and reliability goals broadly consider safe and reliable operation, improved accident management and minimization of consequences, investment protection and reduced need for off-site emergency response. Looking ahead, the benefit of meeting these goals includes: (a) Increasing the use of inherent safety features, robust designs and transparent safety features that can be understood by non-experts; (b) Enhancing public confidence in the safety of nuclear energy. [18, pp 2]

Proliferation Resistance and Physical Protection It is important to ensure that the next generation of nuclear power reactors has a minimum proliferation risk and allow a high level of physical protection with the purpose to ensure the control and the secure of the nuclear material and facilities. Proliferation risk is one of the major concerns of the international community and one of the reasons why the use of nuclear energy for electricity generation cause concern to many countries, particularly when the nuclear installations, including nuclear power plants. are going to be built in countries located in unstable political regions. Looking ahead, the benefits of meeting these goals include: (a) Providing continued effective proliferation resistance of nuclear energy systems through improved design features and other measures; (b) Increasing physical protection against terrorism by increasing the robustness of new facilities. [18, pp 2]

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The following are the designs of Generation IV nuclear power reactors already selected on the basis of a set of criteria that have been established: (a) (b) (c) (d) (e) (f)

Sodium Cooled Fast Reactor (SFR); Very High Temperature Gas Reactor (VHTR); Super