solar and geothermal energy

solar and geothermal energy

(Parte 1 de 5)

EnErgy And THE EnvironmEnT

Solar and

Geothermal Energy

JOHN TABAK, Ph.D.

EnErgy And THE EnvironmEnT

Solar and

Geothermal Energy

SOLAR AND GEOTHERMAL ENERGY Copyright © 2009 by John Tabak, Ph.D.

All rights reserved. No part of this book may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, or by any information storage or retrieval systems, without permission in writing from the publisher. For information contact:

Facts On File, Inc. An imprint of Infobase Publishing 132 West 31st Street New York NY 10001

Library of Congress Cataloging-in-Publication Data

Tabak, John.

Solar and geothermal energy / John Tabak. p. cm.—(Energy and the environment)

621.47—dc222008026741

Includes bibliographical references and index. ISBN-13: 978-0-8160-7086-2 ISBN-10: 0-8160-7086-5 1. Renewable energy sources—Juvenile literature. I. Title. TJ808.2.T32 2009

Facts On File books are available at special discounts when purchased in bulk quantities for businesses, associations, institutions, or sales promotions. Please call our Special Sales Department in New York at (212) 967-80 or (800) 322-8755.

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Text design by Erik Lindstrom Illustrations by Accurate Art Photo research by Elizabeth H. Oakes

Printed in the United States of America Bang Hermitage 10 9 8 7 6 5 4 3 2 1 This book is printed on acid-free paper.

For Archie Shepp, who worked hard to teach me what I wasn’t ready to learn. Thank you.

Preface ix Acknowledgments xiii Introduction xiv

Part I Solar EnErgy 1

1 a Brief History of Solar Power 3

Sunlight and Heat 4 The Photophone: A Solar-Powered Telephone 1 Early Photovoltaic Technology 12

2 Sunlight and geometry 16

The Electromagnetic Spectrum 17 Geometry and Sunlight 23 Space-Based Solar Power 24

3 Photovoltaics 31

Light versus Electricity 32 Technical Considerations 36 Photons and Electricity 39 Net Metering 41

4 Heat Engines and Solar Power 4 Converting Thermal Energy into Electrical Energy 45

Contents

Advantages and Disadvantages of CSP Technology 51 Storing Solar Energy 52

5 two other Important Solar technologies 56

Solar Water Heaters 57 Demand Management 62 Greener Architecture 64

6 Economic and Environmental Consequences of Solar Power 69 Matching Solar Supply with Consumer Demand 70 Connecting Electricity Producers with Consumers:

A Case Study 75 Available Energy 7

7 government Policies and Solar Energy 81

Solar Energy Policy in the United States 82 Distributed Generation 86 Solar Energy in Germany 89

Part I gEotHErmal EnErgy 95

8 a Brief History of geothermal Energy 97

Heat, Geology, and the Age of Earth 9 Magma Chambers 102 Location of Geothermal Sites 104 Early Geothermal Technology 108

9 geology and Heat 112

Mining Thermal Energy 113 Fenton Hill, New Mexico: The First Enhanced

Geothermal System 118 Heat Engines 121

10 the generating Station 124

Technical Considerations 125 An Interview with John Farison on the Challenges of Producing Power at the Geysers 132 Coproduction of Geothermal Energy 141

1 two other geothermal technologies 144

Direct-Piped Hot Water 146 Geothermal Heat Pumps 149

12 the Economics and Environmental Impacts of Electricity from geothermal Sources 155 Economic Costs and the Problem of Scale 157 Global Warming and Geothermal Power 162 Geothermal Energy and the Environment 164

13 government Policies and geothermal Energy 169

The International Energy Agency 171 The Cost of Energy 174 Geothermal Power Production Today 176

Chronology 180 List of Acronyms 184 Glossary 185 Further Resources 188 Index 193

Preface

N ations around the world already require staggering amounts of energy for use in the transportation, manufacturing, heat- ing and cooling, and electricity sectors, and energy requirements continue to increase as more people adopt more energy-intensive lifestyles. Meeting this ever-growing demand in a way that minimizes environmental disruption is one of the central problems of the 21st century. Proposed solutions are complex and fraught with unintended consequences.

The six-volume Energy and the Environment set is intended to provide an accessible and comprehensive examination of the history, technology, economics, science, and environmental and social implications, including issues of environmental justice, associated with the acquisition of energy and the production of power. Each volume describes one or more sources of energy and the technology needed to convert it to useful working energy. Considerable empha- x Solar aNd Geothermal eNerGy sis is placed on the science on which the technology is based, the limitations of each technology, the environmental implications of its use, questions of availability and cost, and the way that government policies and energy markets interact. All of these issues are essential to understanding energy. Each volume also includes an interview with a prominent person in the field addressed. Interview topics range from the scientific to the highly personal, and reveal additional and sometimes surprising facts and perspectives.

Nuclear Energy discusses the physics and technology of energy production, reactor design, nuclear safety, the relationship between commercial nuclear power and nuclear proliferation, and attempts by the United States to resolve the problem of nuclear waste disposal. It concludes by contrasting the nuclear policies of Germany, the United States, and France. Harold Denton, former director of the Office of Nuclear Reactor Regulation at the U.S. Nuclear Regulatory Commission, is interviewed about the commercial nuclear industry in the United States.

Biofuels describes the main fuels and the methods by which they are produced as well as their uses in the transportation and electricity-production sectors. It also describes the implications of large-scale biofuel use on the environment and on the economy with special consideration given to its effects on the price of food. The small-scale use of biofuels—for example, biofuel use as a form of recycling—are described in some detail, and the volume concludes with a discussion of some of the effects that government policies have had on the development of biofuel markets. This volume contains an interview with economist Dr. Amani Elobeid, a widely respected expert on ethanol, food security, trade policy, and the international sugar markets. She shares her thoughts on ethanol markets and their effects on the price of food.

Coal and Oil describes the history of these sources of energy.

The technology of coal and oil—that is, the mining of coal and the drilling for oil as well as the processing of coal and the refining of oil—are discussed in detail, as are the methods by which these

Preface xi primary energy sources are converted into useful working energy. Special attention is given to the environmental effects, both local and global, associated with their use and the relationships that have developed between governments and industries in the coal and oil sectors. The volume contains an interview with Charlene Marshall, member of the West Virginia House of Delegates and vice chair of the Select Committee on Mine Safety, about some of the personal costs of the nation’s dependence on coal.

Natural Gas and Hydrogen describes the technology and scale of the infrastructure that have evolved to produce, transport, and consume natural gas. It emphasizes the business of natural gas production and the energy futures markets that have evolved as vehicles for both speculation and risk management. Hydrogen, a fuel that continues to attract a great deal of attention and research, is also described. The book focuses on possible advantages to the adoption of hydrogen as well as the barriers that have so far prevented large-scale fuel-switching. This volume contains an interview with Dr. Ray Boswell of the U.S. Department of Energy’s National Energy Technology Laboratory about his work in identifying and characterizing methane hydrate reserves, certainly one of the most promising fields of energy research today.

Wind and Water describes conventional hydropower, now-conventional wind power, and newer technologies (with less certain futures) that are being introduced to harness the power of ocean currents, ocean waves, and the temperature difference between the upper and lower layers of the ocean. The strengths and limitations of each technology are discussed at some length, as are mathematical models that describe the maximum amount of energy that can be harnessed by such devices. This volume contains an interview with Dr. Stan Bull, former associate director for science and technology at the National Renewable Energy Laboratory, in which he shares his views about how scientific research is (or should be) managed, nurtured, and evaluated.

Solar and Geothermal Energy describes two of the least objectionable means by which electricity is generated today. In addition to describing the nature of solar and geothermal energy and the xii Solar aNd Geothermal eNerGy processes by which these sources of energy can be harnessed, it details how they are used in practice to supply electricity to the power markets. In particular, the reader is introduced to the difference between base load and peak power and some of the practical differences between harnessing an intermittent energy source (solar) and a source that can work virtually continuously (geothermal). Each section also contains a discussion of some of the ways that governmental policies have been used to encourage the growth of these sectors of the energy markets. The interview in this volume is with John Farison, director of Process Engineering for Calpine Corporation at the Geysers Geothermal Field, one of the world’s largest and most productive geothermal facilities, about some of the challenges of running and maintaining output at the facility.

Energy and the Environment is an accessible and comprehensive introduction to the science, economics, technology, and environmental and societal consequences of large-scale energy production and consumption. Photographs, graphs, and line art accompany the text. While each volume stands alone, the set can also be used as a reference work in a multidisciplinary science curriculum.

xiii acknowledgments the author gratefully acknowledges the contributions of John Farison, Director of Process Engineering for Calpine Corpora- tion at the Geysers Geothermal Field, who generously shared his insights and expertise; Elizabeth Oakes, who researched the photos used in this volume; Leela Christian-Tabak, who helped with the statistics; and Frank Darmstadt, executive editor, Facts On File, for his patience and support.

xiv

Introduction

Solar energy and geothermal energy have a good deal in common. They are abundant and widely, if unevenly, distributed.

They are two of the least environmentally disruptive sources of power available. They are, for the most part, expensive to develop, and compared to more conventional sources of energy, relatively little power is produced from either one.

There is also much to distinguish these two energy sources. Solar energy is intermittent; geothermal energy can be harnessed to produce a continuous stream of power. Solar energy is renewable in the following sense: No matter how much solar energy is converted into heat or electricity at a given location on a given day, there will be more solar energy available for conversion the next day. One cannot ruin a good solar energy site by developing it. Solar energy is inexhaustible. The same cannot be said of geothermal energy. It is

Introduction xv possible to destroy even the most productive geothermal site by careless development. This has, in fact, already occurred at some sites.

The subject of solar energy comprises the first half of Solar and

Geothermal Energy. This section begins by recounting the history of attempts to harness energy from the Sun. The first attempts occurred thousands of years ago, but in the 19th century, efforts to harness the Sun’s energy took a surprisingly modern turn due to the efforts of the French engineer and educator Augustin Mouchot. He sought to create heat engines powered by the Sun. The chapter concludes by describing early efforts to convert sunlight directly into electricity via photovoltaic technology.

Chapter 2 describes sunlight in terms of its energy content and availability. Chapters 3 through 5 describe the principal ways that solar energy is harnessed to produce electricity and heat. Chapter 6 describes how solar power plants, which are intermittent power producers, are used to generate power for the grid, and chapter 7 describes some of the ways that the United States and Germany have encouraged the development of the solar power industry. Government policies are important because at its present level of development, the solar industry would collapse without substantial government support.

The second half of the book is concerned with geothermal energy. Chapter 8 describes how geothermal heat sources were first discovered and how they are distributed about the globe. It concludes with a brief history of early efforts to convert thermal energy from Earth’s interior into electricity. Chapter 9 provides an overview of geothermal technology, and chapter 10 describes some of the details of geothermal heat engine design, and contains an interview with John Farison, director of process engineering for Calpine Corporation at the Geysers Geothermal Field, about maintaining power production at the Geysers. Chapter 1 describes so-called direct use technology, which uses thermal energy from beneath Earth’s surface without converting it into electricity. Chapter 12 describes xvi Solar aNd Geothermal eNerGy some of the economic aspects of geothermal energy, and chapter 13 describes some of the ways that various agencies, national and international, are working to develop the technology needed to expand the use of geothermal energy in the power-generation sector.

A strange relationship exists between the amount of energy available from a particular source and the extent to which that source is used: The greater the amount available, the less it is utilized. In particular, solar energy and geothermal energy are two of the most abundant sources of energy available, and yet they are two of the least utilized. For those interested in the environmentally responsible production of electric power, it is important to understand the potential of these energy sources and why, so far, that potential has yet to be realized.

Part I Solar Energy

the impact of solar technology on society has, so far, been small, with one major exception—the use of solar panels to power space- craft. In the United States, for example, less than one-tenth of 1 percent of the nation’s electricity supply comes from solar generating stations.

But if the contribution made by solar energy technologies has been modest compared with many other more conventional energy sources, the same cannot be said for claims about its potential. For decades, advocates of solar power have downplayed the difficulties involved in harnessing the Sun’s energy, preferring instead to predict quick and widespread adoption of various solar technologies. A great deal of 1970s literature, for example, confidently predicted that by the year 2000 the United States would have a solar-powered economy in which solar arrays and solar water heaters would be everywhere, and dependence on oil would be much reduced. This, of course, has yet to happen. There is little evidence of an imminent solar revolution. But a Brief history of Solar Power

(Parte 1 de 5)

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