DOE/EIA-0561(92)

Distribution Category UC-950

Renewable Resources

in the U.S. Electricity Supply

February 1993

Energy Information Administration

Office of Coal, Nuclear, Electric and Alternate Fuels

U.S. Department of Energy

Washington, DC 20585
ii Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 

This report was prepared by the Energy Information Administration, the independent statistical

and analytical agency within the Department of Energy. The information contained herein

should not be construed as advocating or reflecting any policy position of the Department of

Energy or of any other organization.
Energy Information Administration/Renewable Resources in the U.S. Electricity Supply iii

Contacts

This report was prepared by the staff of the Energy Nikodem, Chief, Energy Resources Assessment Branch

Resources Assessment Branch, Analysis and Systems (202/254-5550). Specific questions regarding the prepDivision, Office of Coal, Nuclear, Electric and Alternate aration and content of the report should be directed to Dr.

Fuels. General information regarding this publication may Thomas Petersik (202/254-5320; forecasts, geothermal,

be obtained from John Geidl, Director, Office of Coal, solar, wind, resources, generating technologies); John

Nuclear, Electric and Alternate Fuels (202/254-5570); Carlin (202/254-5562; municipal solid waste, wood,

Robert M. Schnapp, Director, Analysis and Systems biomass); or Chris V. Buckner (202/254-5368;

Division (202/254-5392); or Dr. Z.D. (Dan) hydroelectricity).
iv Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 

Preface

Section 205(a)(2) of the Department of Energy Organ- analysts, policy and financial analysts, investment firms,

ization Act of 1977 (Public Law 95-91) requires the trade associations, Federal and State regulators, and

Administrator of the Energy Information Administration legislators. While it does not address major policy issues,

(EIA) to carry out a comprehensive program that will it does provide important basic factual information on

collect, evaluate, assemble, analyze, and disseminate data which useful discussion, analyses, and policies can be

and information relevant to energy resources, reserves, built.

production, demand, technology, and related economic

and statistical information. To assist in meeting these The legislation that created the EIA vested the organresponsibilities in the area of electric power and ization with an element of statutory independence. The

renewable energy resources, the EIA has prepared this EIA's responsibility is to provide timely, high-quality

report, Renewable Resources in the U.S. Electricity Supply.

The report provides an introductory overview of current

and long-term forecasted uses of renewable resources in

the Nation's electricity market-place, the largest domestic

application of renewable resources today. It is intended

for a general audience, but it should be of particular

interest to public utility

information and to perform objective, credible analyses in

support of deliberations by both public and private

decisionmakers. The EIA does not take positions on policy

questions. Accordingly, this report does not purport to

represent the policy positions of the U.S. Department of

Energy or the Administration.
vi Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 

Contents

Page

Executive Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vii

1. The Current Use of Renewable Resources in Electric Power .............................................. 1

Introduction ..................................................................................... 1

History of the Use of Renewable Resources in Electricity Generation ................................... 3

California, Home to Renewable Energy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

2. Projections of Renewable Resources in the U.S. Electricity Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Energy Information Administration (EIA) Projections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

The Energy Policy Act of 1992 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Comparison With Other Forecasts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Solar Two . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Overall Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

3. Issues Affecting the Growth of Renewable Resources in Electric Power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Demand Growth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Prices of Other Fuels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Technology Costs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Externalities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Resource-Specific Challenges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Appendices

A. Assumptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

B. Renewable Resources for Electricity Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

C. Electricity Generating Technologies Using Renewable Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

D. The Federal Regions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
Energy Information Administration/Renewable Resources in the U.S. Electricity Supply vii

Contents (Continued) Page

Tables

ES1. U.S. Electricity Net Generation Using Renewable Resources, 1990 and 2010 ............................... viii

1. Total U.S. Energy Resources, Accessible Resources, and Reserves ......................................... 2

2. U.S. Energy Consumption, 1990 ....................................................................... 3

3. U.S. Electricity Generating Capacity, 1970, 1980, 1990 ................................................... 4

4. U.S. Electricity Generating Capacity and Net Generation, 1990, By Fuel Type .............................. 7

5. U.S. Generating Capacity Using Renewable Resources, 1990 ............................................. 8

6. U.S. Generating Capacity Using Renewable Resources, 1990, by Federal Region ............................ 9

7. U.S. Net Generation Using Renewable Resources, 1990, by Federal Region ................................ 9

8. World Oil Price and Economic Growth Assumptions for the Annual Energy Outlook 1993 . . . . . . . . . . . . . . . . . . . 13

9. U.S. Electric Generating Capacity and Net Generation Projections for 2010 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

10. Comparison of Macroeconomic Forecasts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

11. Comparison of Electricity Forecasts, 2010 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

A1. Projections of Utility and Nonutility Electric Capability for Renewable Technologies . . . . . . . . . . . . . . . . . . . . . . 30

A2. Average Annual Capacity Factors for Generating Technologies Using Renewable Resources . . . . . . . . . . . . . . . 31

Figures

1. Cost of Electricity Using Wind Power Plants, 1980-1990 ................................................. 6

2. Cost of Electricity Using Solar Thermal Generating Plants, 1980-1990 ..................................... 7

3. Photovoltaic Cell Conversion Efficiencies, 1978-1990 .................................................... 7

4. Solar Thermal Generating Facility, Kramer Junction, California . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

5. Wind Power Plant, Altamont, California . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

B1. U.S. Conventional Hydroelectric Generating Capacity, Developed and Undeveloped . . . . . . . . . . . . . . . . . . . . . . 35

B2. U.S. Known and Potential Geothermal Energy Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

B3. Average Annual Direct Solar Radiation for Concentrator Collectors for the United States . . . . . . . . . . . . . . . . . . . 38

B4. Selected U.S. Biomass Energy Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

B5. U.S. Wind Energy Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

C1. Hydroelectric Plant Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

C2. Kaplan, Pelton, and Francis Turbines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

C3. Geothermal Electricity Generating System for Vapor-Dominated Hydrothermal Resources . . . . . . . . . . . . . . . . . 48

C4. Single-Flash Geothermal Electricity Generating System for Liquid-Dominated

Hydrothermal Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

C5. Double-Flash Geothermal Electricity Generating System for Liquid-Dominated

Hydrothermal Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

C6. Binary Geothermal Electricity Generating System for Liquid-Dominated

Hydrothermal Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

C7. Biomass Electric Generation System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

C8. Burner Systems for Biomass Electric Generation Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

C9. Municipal Solid Waste Mass Burn System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

C10. Refuse Derived Fuel Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

C11. Landfill Gas Collection and Conversion Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

C12. Parabolic Trough System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

C13. Parabolic Dish System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58

C14. Central Receiver System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59

C15. Photovoltaic Cell Structure and Photovoltaic System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

C16. Photovoltaic Cell Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62

C17. Amorphous Silicon Cell Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
viii Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 

C18. Photovoltaic Flat Plate and Concentrator Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64

C19. Horizontal Axis Wind Turbine (HAWT) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

C20. Vertical Axis Wind Turbine (VAWT) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
Energy Information Administration/Renewable Resources in the U.S. Electricity Supply ix

Executive Summary

Renewable resources (solar, wind, geothermal, hydro- reasons, the uses of geothermal, solar, and wind resources

electric, biomass, and waste) currently provide nearly 12 have been most frequently found in California.

percent of the Nation's electricity supply. Almost 10 of this

12 percent is provided by hydroelectric resources alone. Many different scenarios for the future of the U.S.

Biomass and municipal solid waste (MSW) together economy, energy markets, and renewable resources can

contribute more than 1 percent. All other renewable

resources, including geothermal, wind, and solar, together

provide less than 1 percent of the total.

Many renewable resources are relative newcomers to the

electric power market. In particular, electricity generation

using geothermal, wind, solar, and MSW resources have

had their greatest expansion in the 1980's. This was a

result of significant technological improvements, the

implementation of favorable Federal and State policies,

and the reaction to the increasing costs of using fossil and

nuclear fuels. The use of renewable resources for

electricity generation has also been encouraged as less

environmentally damaging than fossil fuels. Because

renewable energy is available domestically, renewable

resources are viewed as more secure than imported fossil

fuels.

This report, Renewable Resources in the U.S. Electricity

Supply, presents descriptions of the history, current use,

and forecasted future applications of renewable re-sources

for electricity generation and of the factors that influence

those applications.

Renewable resources account for more than 93 percent of

total U.S. energy resources. Geothermal, solar, and wind

resources are particularly plentiful, raising prospects for

their expanded use in the future. However, today

renewable resources are usually not economically

accessible, and annually contribute only 7.4 percent of the

Nation's marketed (bought or sold) energy consumption

for all purposes, including for electricity.

Renewable resources are used for electricity supply today

where natural resources, electricity demands, and public

policies combine to make them competitive. For these
x Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 

be envisioned. The Energy Information Administration's

(EIA) long-term projections used in the Annual Energy

Outlook 1993 portray future conditions based upon what

is currently known or reasonably likely to occur. From

these forecasts, some general conclusions emerge.

First, as technologies and market experiences improve,

renewable resources are likely to increase their contributions to the U.S. electricity supply (Table ES-1).

Nationwide, electricity generation from renewable energy

is projected to grow at a rate averaging 1.8 percent per

year through 2010, expanding at a somewhat higher rate

than total U.S. electricity generation. On a regional basis,

renewable resources could make more significant

contributions where they are available and the costs of

alternatives are higher. Nevertheless, renewable resources

are not likely to replace fossil fuels as the major

contributors to electricity supply over the next two

decades.

The use of renewable resources other than hydroelectricity

should increase very rapidly. According to the EIA

Reference Case projections, electricity generation using

MSW, biomass, and geothermal resources is projected to

increase significantly, from 56 billion kilowatthours in

1990 to 175 billion kilowatthours in 2010. Through 2010,

electricity generation using geothermal resources will

grow at a rate averaging over 7 percent annually, and the

use of MSW is expected to grow at a rate of over 9 percent

annually through 2010. Wind-powered electricity

generation is projected to increase, growing more than 10

percent annually, from 2 billion kilowatthours in 1990 to

16 billion kilowatthours in 2010.

Second, conventional hydroelectric power, the mainstay

of renewable resources in electric power today, is unlikely

to enjoy rapid growth under current expectations, even if

more favorable regulatory policies emerge. The lack of

many additional large sites for hydroelectric facilities

constrains major hydroelectric power growth. However,

the rapid growth in the use of other renewable resources

should offset the slow growth in hydropower, allowing

renewable resources to slightly increase their current

share of the electricity market during the forecast period.
Energy Information Administration/Renewable Resources in the U.S. Electricity Supply xi

(Billion Kilowatthours)

1990

Reference Case 

2010

Annual Percentage Rate

of Growth

1990-2010a

Conventional Hydroelectric . . . . . . . . . . . . . . . . . . . 288 306 0.3

Geothermal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 62 7.2

Municipal Solid Waste . . . . . . . . . . . . . . . . . . . . . . . 10 54 8.5

Biomass . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 59 3.2

Solar .................................... b 1 4 9.2

Wind . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 16 10.4

 Total, Renewable Resources .............. 348 501 1.8

Fossil/Storage/Other ........................ 2,098 2,975 1.8

Nuclear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 577 636 0.5

 Total Generation ......................... 3,023 4,112 1.5

 Annual percentage rates of growth are calculated using unrounded values. a

 Includes solar thermal and less than 0.02 billion kilowatthours grid-connected photovoltaic generation. b

 Notes: Totals may not equal sum of components due to independent rounding. Electric utility generation data exclude internal

generating station use (net); nonutility data include internal use (gross).

 Sources: Energy Information Administration. 1990 data: For utilities, EIA-861 “Annual Electric Utility Report”; for nonutilities, EIA867, “Annual Nonutility Power Producer Report.” 2010 projections: Annual Energy Outlook 1993, DOE/EIA-0383(93), AEO 1993

Forecasting System run AEO93B.D0918921 (Washington, DC, January 1993).

Table ES1. U.S. Electricity Net Generation Using Renewable Resources, 1990 and 2010

If renewable resources are to provide a greater share of penetration. Of course, other events may also work to

the Nation's electricity supply, the costs of using them will accelerate the use of renewable resources. Increases in

need to decline relative to alternatives. In some cases, such fossil-fuel costs and additional environmental regulations

as wind and solar thermal generation, small on fossil-fueled plants could make the use of renewable

improvements in generating costs may significantly resources economically more attractive. In addition, social

increase their market penetration. In other cases, such as policies, including favorable tax treatments or other forms

photovoltaic and most forms of geothermal power, large of assistance, could promote interest in renewable

cost reductions are needed to spur greater market resource use.
Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 1

1. The Current Use of Renewable Resources in

Electric Power

Introduction

When considering U.S. energy supplies, national security,

and environmental quality, discussion often turns to

renewable energy resources such as solar, wind,

hydroelectric, geothermal, and biomass. Renewable

resources are characterized as secure domestic supplies of

energy insulated from threats and interruptions by

foreign suppliers. In addition, they are viewed as free of

most of the harmful emissions (such as the carbon, sulfur,

and nitrogen oxides) that are byproducts of burning coal

and other fossil fuels. Renewable resources, therefore, are

viewed as potential candidates for much more

widespread use in meeting U.S. energy needs.

To help inform public discussion, this publication

provides an overview of current and projected long-term

uses of renewable resources in the U.S. electricity supply,

the largest domestic use of renewable resources today.

While the publication does not address major policy

issues, it provides an important base of information on

which useful discussion, analyses, and policies can be

built.

The report has four parts. This chapter introduces basic

concepts and discusses the history and current uses of

renewable resources in U.S. electricity supply. Chapter 2

presents long-term projections for the use of renewable

resources through 2010. Chapter 3 discusses factors likely

to affect the projections over the next four decades.

Finally, appendices to the report provide additional

information on renewable resources, such as their

locations and other physical characteristics (Appendix B),

and on the technologies used in generating electricity

(Appendix C).

The publication discusses seven categories of electric

power generation using renewable resources: conventional hydroelectric power, biomass, municipal solid 1

waste (MSW), geothermal, solar thermal, solar photovoltaic, and wind power.

The report features two major qualifications. First, it is

important to recognize that markets do not completely

reflect all the economically useful contributions of

renewable resources, because many (if not most) applications of renewable energy are not bought or sold in the

marketplace. Whereas, for example, most coal production 2

in the United States is accounted for by marketplace

statistics of firms buying or selling coal, most solar energy

is neither bought nor sold. For example, the sun warms a

house, reducing the need for electricity to warm it, yet no

one pays for the use of the solar heat. In addition, solar

energy sometimes is accounted for only indirectly in the

prices of goods and services (as in the higher rents paid

for sunlit buildings). Wind, water, solar and geothermal

energy also make significant energy contributions outside

the marketplace. Therefore, because of the incomplete

representation of the value of renewable energy in

marketplace data, information in this publication about

renewable energy use may underestimate the value of

renewable energy.

Second, although comparisons of fossil, nuclear, and

renewable energy are made, in at least one respect

renewable resources are intrinsically different from fossil

and nuclear resources. Fossil and nuclear resources are,

for all intents and purposes, fixed stocks, that is, measured

at single points in time, such as on December 31 of each

year. Moreover, whatever their absolute size, these

resources are exhaustible. Once consumed they do not

regenerate in any relevant time period. On the other hand,

by definition, renewable resources are not fixed stocks;

renewable resources are variable flows. “Flows” are

products measured as a function of time, such as from

January 1 through
2 Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 

 Pumped storage hydroelectric facilities, at which off-peak nuclear or coal-fired generation is used to pump water from lower to upper 1

reservoirs for hydroelectric generation during peak periods, are excluded from this report as use of renewable resources, because these plants

are typically fossil or nuclear energy storage devices.

 In addition to their nonmarket characteristics, both nonmarketed and marketed uses of renewable resources can be affected by externalities. 2

For a discussion of the relationship of externalities to renewable energy use, see Chapter 3.
Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 3

(Quadrillion Btu)

Resources

Accessible

Resourcesa Reservesb

Geothermal ................................. 1,497,925 22,782 247

Solar (including biomass) ..................... c 1,034,940 586,687 352c

Wind ....................................... 1,026,078 5,046 5

Shale Oil ................................... 159,604 11,704 1

Coal ....................................... 87,458 38,147 5,266

Petroleum ................................... 2,767 1,102 156

Natural Gas ................................. 1,705 887 231

Peat ....................................... 1,415 354 -

Uranium .................................... 1,177 731 42

Conventional Hydroelectric . . . . . . . . . . . . . . . . . . . . . 986 157 58

 Total ..................................... 3,814,057 667,597 6,358

 That part of resources able to be accessed with existing technologies regardless of cost. The term “accessible resources” is a

definitionally similar to the term “recoverable resources” for oil and gas resources.

 That part of accessible resources able to be cost effectively recovered today. b

 Solar includes all biomass and the natural resource base for municipal solid waste energy. Although biomass is not estimated c

separately for resources or accessible resources, biomass is estimated to account for 334 quadrillion Btu (95 percent) of total solar

reserves.

 - = Less than 0.5 quadrillion Btu.

 Notes: The resource values shown in Table 1 are broad estimates that result from estimation procedures highly dependent upon

critical assumptions. They should be considered useful mainly for approximating the broad boundaries placed on future energy

choices. For metric conversion, one British thermal unit equals 1,055 joules. For example, total reserves equal approximately 6.7x1021

joules. Totals may not equal sum of components due to independent rounding.

 Source: U.S. Department of Energy, Office of Conservation and Renewable Energy, Characterization of U.S. Energy Resources

and Reserves, DOE/CE-0279 (Washington, DC, December 1989).

Table 1. Total U.S. Energy Resources, Accessible Resources, and Reserves

December 31 of each year. Renewable energy supplies Nation's energy resource supply would be renewable

regenerate over time. As a result, when comparisons of energy. Geothermal energy accounts for nearly 40 percent

fossil, nuclear, and renewable energy resources are made, of the total, almost 1.5 million quads (quadrillion Btu);

compromises are necessary; fixed fossil and nuclear stocks well over half (54 percent) are solar (including biomass)

are compared with renewable energy flows for a selected and wind resources; only hydroelectric resources,

time period. For this publication, 30-year accumulated accounting for less than 1 percent, are less plentiful than

flows of renewable energy are compared with fixed fossil fossil or nuclear (uranium) resources. By contrast, fossil

energy stocks, to approximate long-term supplies for resources (shale oil, coal, petroleum, natural gas, and

energy planning purposes. peat) represent less than 7 percent of domestic energy

U.S. Energy Resources, Accessible

Resources, and Reserves

Renewable resources are the most plentiful energy

resources in the United States (Table 1). If they were

economically exploitable, more than 93 percent of the

3

resources, and uranium far less than 1 percent.

However, both technology and cost drastically reduce the

current opportunities for the efficient use of renewable

resources and shift the economic balance in energy supply

in favor of fossil fuels and uranium. Whereas some fossil

and uranium resources can be
Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 5

(Quadrillion Btu)

Energy Source Consumption Percent

Petroleum ................. 33.55 39.8

Natural Gas ............... 19.30 22.9

Coal ..................... 19.12 22.7

Nuclear ................... 6.16 7.3

Renewable Resources ...... 6.26 7.4

 Conventional

 Hydroelectric ............ 2.97 3.5

 Geothermal .............. 0.32 0.4

 Biomass ................ 2.90 3.4

 Solar ................... 0.04 a b

 Wind ................... 0.02 a b

Total ..................... 84.40 100.0

 Excludes unmeasured direct use. a

 Less than 0.05 percent b

 Note: Totals may not equal sum of components due to

independent rounding.

 Source: Energy Information Administration, Annual Energy

Review 1991, DOE/EIA-0384(91) (Washington, DC, June 1992)

Tables 3 and 107.

found in sufficiently high concentrations to afford cost- Table 2. U.S. Energy Consumption, 1990

effective use, renewable resources are generally less

accessible (for example, most geothermal resources are at

depths below current drilling access); too scattered (for

example, solar energy is very dispersed); or too costly to

employ, given current technologies and costs. When

technology is taken into consideration to estimate

resources which are accessible, the availability of

renewable resources is significantly reduced. Furthermore, when the costs of extraction and use are considered

to determine reserves, the Nation's current energy reserve

base becomes predominantly fossil rather than renewable

resources.

In fact, most U.S. energy use today (except for unmeasured direct use of wind and solar energy) is from fossil

fuels (Table 2). In 1990, more than 85 percent of all U.S.

energy consumption for all purposes, including for

electricity, transportation, and heat, was supplied by

petroleum, natural gas, and coal. Renewable resources

provided 7.4 percent of energy in the United States, with

most of that from conventional hydroelectric power,

biomass, and waste.

Despite difficulties in utilizing them today, the vast stores

of renewable resources indicate possible oppor-tunities for

the future. If technologies can be developed to access

renewable resources economically, and if the

electricity generating technologies using them can be Conventional hydroelectric power has been a major

made competitive, renewable resources have the potential contributor to the electricity industry and an important

to provide a larger share of the Nation's electricity engine of U.S. economic development. Conventional

consumption. Many decades from now, renewable re- hydroelectric power predates the electric utility industry.

sources could remain generally undiminished and Michigan's Grand Rapids Electric Light and Power

available for use. Company illuminated 16 lamps with hydroelectric power

History of the Use of Renewable

Resources in Electricity Generation

The use of most technologies employing renewable power for long distances over alter-nating current (AC)

resources for electricity generation has occurred within lines established the superiority of AC transmission and

the last 20 years. However, two resources, hydropower helped defeat Edison-backed reliance on direct current

and wood, have provided significant amounts of elec- (DC) power. Over the following years, the use of

tricity since the early days of electricity generation. hydroelectric power grew rapidly.

Before 1970

in 1880, 2 years before Thomas Edison's Pearl Street

Station inaugurated the modern electric utility industry.

The installation of huge hydroelectric generators at

Niagara Falls by George Westinghouse in 1896

transformed the industry. The generators at Niagara Falls

dwarfed earlier units, and the project's ability to transmit

Federal interest in economic development further boosted

the stature of hydroelectricity in the 1930's and beyond.

The Mussel Shoals (Alabama) development during World
6 Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 

War I was the first large-scale Federal hydroelectric

project. Massive hydroelectricity programs of the

Tennessee Valley Authority, the Bureau of Reclamation of

the U.S. Department of the Interior, and the U.S. Army

Corps of Engineers aided economic development with

water and low-cost power. Federal hydroelectric

development was especially extensive in the Northwest,

where unprecedented hydroelectric expansion began on

the Columbia River in the 1930's including construction of

the largest U.S. hydroelectric facility, Grand Coulee (6,500

megawatts). Hydroelectric dams generated electricity for

production of defense goods during World War II and

continued to assist
Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 7

(Gigawatts)a

1970 1980 1990

Fossil ................... a 284.9 472.4 548.1

Nuclear . . . . . . . . . . . . . . . . . . . 7.0 51.8 99.6

Conventional Hydroelectric . . . 61.5 69.1 72.9

Other Renewable . . . . . . . . . . 1.4 2.8 12.3

 Total ................... 354.9 596.0 733.0

 Net summer capability. For nonutilities, nameplate capacity a

is used.

 Fossil includes coal, oil, natural gas, waste heat, and pumped b

storage hydroelectric.

 Note: Totals may not equal sum of components due to

independent rounding.

 Sources: Electric Utility Data: Energy Information

Administration, Annual Energy Review 1991, DOE/EIA-0384(91)

(Washington, DC, June 1992); Nonutility Data: for 1970 and

1980, Energy Information Administration, derived from Federal

Energy Regulatory Commission, FPC-4, “Monthly Power Plant

Report” and Science Applications International Corporation,

“Technical Report Preparation, Final Report,” prepared for the

Energy Information Administration, July, 1992; and for 1990,

Energy Information Administration, EIA-867, “Annual Nonutility

Power Producer Report.”

Table 3. U.S. Electricity Generating Capacity,

1970, 1980, 1990

agriculture and economic development afterwards. By able resources totalled about 63 gigawatts (Table 3),

1940, hydroelectricity provided one-third of U.S. electric almost 18 percent of total U.S. generating capacity. Over

power. 61 gigawatts was conventional hydroelectric, about 1

The hydroelectricity share of the market has declined

since that time. Major dam construction has continued,

but at a slower rate. Most large productive hydroelectric

sites either have been already developed or have been

precluded from hydroelectric development to serve other

demands. At the same time, Federal investments in

hydroelectric power, both for economic development and

for other purposes, have slowed. As a result, growth in

hydroelectric capacity has given way to much faster

growth in investments in fossil and nuclear powered

electric generating capacity.

Wood has also been used extensively to generate

electricity. Since early in the century, scrap wood and

wastes have provided the wood, wood products, and pulp

and paper industries with steam and heat for industrial

processes and also with significant proportions of their

electric power needs. The industries collect large volumes

of scrap wood and waste, and face the challenge of

disposing of a bulky and otherwise useless waste

byproduct. As a result, electric power generation from

these industry byproducts has offered both less expensive

electric power and waste disposal advantages. 

The overwhelming majority of wood-fired electric power

generation facilities (184 of the total 190 plants in 1990)

exist outside the electric utility sector. The same factors

that make wood and wood wastes attractive to industries

have made them generally unattractive to electric utilities.

For electric utility plants, the costs of accumulating large

fuel stocks with relatively low energy content almost

always outweigh the benefits achieved by using these

fuels.

Other than hydroelectric power and electricity generation

from wood and wood wastes, no renewable resource

provided any significant proportion of U.S. electric power

before the 1970's. Until then, facilities powered by wind,

solar thermal, photovoltaic, or geothermal resources,

either remained small, isolated facilities disconnected

from electric power networks, or took the form of

experiments. The first geothermal site in the United States,

The Geysers (north of San Francisco), was introduced in

1960, although its capacity did not exceed 100 megawatts

until the 1970's. By 1970, U.S. generating capacity using 4

renewgigawatt was capacity using wood and wood wastes, and

the remainder was scattered among the other

technologies.

The 1970's

The use of renewable resources did not increase rapidly in

the 1970's. However, the decade did set the stage for later

expansion. Few new generating technologies entered the

marketplace, although the newly created U.S. Department

of Energy, electric utilities, and other entities were actively

involved in research and demonstration programs.

Although conventional hydroelectric and geothermal

capacity grew substantially, the use of most categories
Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 9

of renewable resources for electricity generation did not At the same time, concerns about the environment and

grow significantly. No wind, solar thermal, or photo- nuclear power safety continued to grow, and added to the

voltaic systems were providing electricity to the electric public interest in renewable resources. Amendments to

power network. Less than one-half gigawatt of gener- the Clean Air Act of 1970 (P.L. 91-604) in 1977 and 1979

ating capacity fueled by municipal solid waste (MSW) added new restrictions on sulfur dioxide (SO ) emissions

had been built. On the other hand, geothermal generating from new fossil-fueled power plants, forcing the wider

capacity grew to almost 0.7 gigawatt by 1980, and use of low-sulfur coal or installation of flue gas

conventional hydroelectric generating capacity expanded desulfurization (FGD) systems. Such actions increased the

from 62 gigawatts in 1970 to around 70 gigawatts by 1980. costs of generating electricity from coal and further

Nevertheless, because of the much greater expansion of spurred interest in less polluting sources of electric power,

fossil- and nuclear-fueled capacity, by the end of the including renewable resources. Concerns about the safety

decade renewable resources as a whole provided a of nuclear power were heightened in 1979 by an incident

smaller share of total U.S. electricity generating capacity at the Three Mile Island number 2 reactor in

than at the beginning. By 1980 renewable resources Pennsylvania.

provided 15 percent of total capacity compared to 19

percent in 1970.

During the 1970's fossil fuel costs rose dramatically,

spurring interest in renewable resource alternatives. Oil

prices rose rapidly following the energy crises of 1973 and

1979, when actual or threatened restrictions in petroleum

supplies from the Organization of Petroleum Exporting

Countries (OPEC) sharply affected oil markets. Adjusted

for inflation, crude oil prices more than tripled during the

decade, and natural gas prices accelerated even more

rapidly. These increases in fossil fuel prices, coupled with 5

concerns about national security and dependence upon

foreign supplies, helped increase interest in renewable

resources as alternative power supplies.

The increasing capital costs of electricity supply also

raised interest in alternatives to traditional sources of

electric power. Throughout the decade, ambitious capital

building programs, plagued by high inflation and high

interest rates, as well as with growing technical and

regulatory requirements, endured rapid increases in

capital costs. Large coal and nuclear-powered generating

facilities, which had seemed economically inviting in

earlier years, became less and less attractive as the decade

wore on.

The rate of growth of electricity demand also slowed

significantly during the 1970's. Partly in response to

rapidly increasing prices, growth in electricity consumption, which average 7.3 percent a year in the 1960's,

slipped to 4.2 percent through the 1970's. As a result, 6

utilities often found themselves with surplus generating

capacity. Demands for new generating ca-pacity of all

types declined dramatically, including for capacity using

renewable resources.

2

Possibly the single most important event in the 1970's

creating a market for renewable resources in electric

power was the passage of the Public Utility Regulatory

Policies Act of 1978 (PURPA, P.L. 95-617). Before PURPA,

electric utilities were reluctant to purchase electricity from

nonutility firms. However, PURPA amended the Federal

Power Act by requiring electric utilities to purchase

electricity offered by “qualifying” nonutility producers,

specifically including small facilities using renewable

resources. PURPA exempted qualifying facilities (QFs)

from some Federal and State regulations imposed on

electric utilities. Finally, PURPA required electric utilities

to pay QF “avoided cost” rates, i.e., rates equal to the

additional costs the electric utilities would have incurred

had they generated the power themselves or purchased it

from other sources. Coupled with public expectations of

generally rising electricity costs and other interests in

renewable energy for security and environmental reasons,

the PURPA requirements encouraged the more rapid

entry of renewable resources into the electric power

market. The addition of Federal and, occasionally, State

tax credits for projects using renewable resources also set

the stage for investments in new electric generating

capacity.

The 1980's

During the 1980's, new technologies using renewable

resources began to appear in commercial markets.

Although large quantities of generating capacity using

renewable resources were not added during the 1980's,

the decade was marked by significant technical progress,

declines in costs, productive commercial experience, and
10 Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 

 Energy Information Administration, Annual Energy Review 1991 DOE/EIA-0384 (91) (Washington, DC, June 1992). 5

 Energy Information Administration, Annual Energy Review 1991, DOE/EIA-0384(91) (Washington, DC, June 1992). 6

greatly expanded contributions in specific segments of the

electric power market.
40

35

30

25

20

15

10

5

0

1980 1984 1988

Year

Cents per Kilowatthour

1982 1986 1990

Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 11

 U.S. Department of Energy, The Secretary's Annual Report to Congress 1990 DOE/S-0010P(91) (Washington, DC, 1991). 7

 California Energy Commission, “California Wind Project Performance: A Review of Wind Performance Results From 1985 to 1990,” from 8

Proceedings, Windpower 91).

Figure 1. Cost of Electricity Using Wind Power

Plants, 1980-1990

 Source: U.S. Department of Energy, The Secretary's Annual Report to

Congress 1990, DOE/S-0010P(91) (Washington, DC, 1991).

In general, each technology benefitted from public

(usually Federal) and private investment during the

1980's, both for research, development and demonstration

facilities, and for commercial projects. Operating

experiences revealed opportunities for improvements in

resource selection and site placement, materials and

equipment selection, and manufacturing and operating

efficiencies. More useful applications of technologies

using renewable resources as part of the overall electricity

supply mix were also found. (Appendix C, “Electricity

Generating Technologies Using Renewable Resources,”

provides descriptions of generating technologies using

renewable resources today. It also identifies specific

applications appropriate to each technology.)

As a result, the total costs (capital plus operating costs) of

producing electricity using renewable resources dropped

significantly during the 1980's. Data assembled by the

DOE and others reflect the progress in lowering costs.

Figure 1 illustrates the progress for wind powered

generation, with costs dropping from around 40 cents per

kilowatthour in 1980 to below 10 cents in 1988. Some of 7

the most efficient units in California now produce

electricity for less than 5 cents per kilowatthour.8

Similarly, costs of electricity from solar thermal generating

systems are estimated by the DOE to have fallen from

about 60 cents per kilowatthour in 1980 to below 10 cents

per kilowatthour by 1990 (Figure 2). The costs of 9

generating electricity using photovoltaics has fallen from

above $19 dollars per kilowatthour in the early 1970's to kilowatthour-level, where wood fuel can be obtained for

about 30 cents today (in utility-grade applications). $2.00 per million Btu or less, usually within about a 50- 10

The costs of using geothermal energy, biomass, and MSW handling, MSW facilities can only be competitive

have also dropped. The least expensive geo-thermal today when tipping fees (the per-ton fees paid to MSW

plants in California are estimated to be producing power facilities for accepting trash) become sufficiently high to

at 4.5 to 6.5 cents per kilowatthour, rates that may not be offset the higher costs of producing electricity using

duplicated elsewhere, but which show that the technology MSW. Finally, photovoltaic systems made substantial

can compete with fossil fuels. Costs of generating power progress in the 1980's, despite remaining much more 11

from wood are estimated to be competitive at about the expensive than traditional sources of electricity for most

5-cent-per purposes. Although the proportion of received sunlight

mile radius. Because of the additional costs of trash

12

converted to electricity (conversion efficiency) improved

significantly over the decade (Figure 3), costs for utility

scale (megawatt sized) photovoltaic systems today are still

about 30 cents per kilowatthour, according to DOE

estimates.13
12 Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 

 U.S. Department of Energy, The Secretary's Annual Report to Congress 1990, DOE/S-0010P(91) (Washington, DC, 1991). 9

 U.S. Department of Energy, Renewable Energy Technology Evolution Rationales, Internal Working Draft, Geothermal Section, October 5, 1990. 10

 U.S. Department of Energy, Office of Policy, Planning and Analysis, The Potential of Renewable Energy, An Interlaboratory White Paper, 11

SERI/TP-260-3674, (March 1990).

 U.S. Department of Energy, Office of Policy, Planning and Analysis, The Potential of Renewable Energy, An Interlaboratory White Paper, 12

SERI/TP-260-3674, (March 1990).

 U.S. Department of Energy, Office of Policy, Planning and Analysis, The Potential of Renewable Energy, An Interlaboratory White Paper, 13

SERI/TP-260-3674, (March 1990).
60

50

40

30

20

10

0

1980 1985 1990

Year

Cents per kilowatthour

Historical Projected

35

30

25

20

15

10

5

0

78 79 80 81 82 83 84 85 86 87 88 89 90

Conversion efficiency (%)

Year

34% High efficiency concentrator

cell

23% Flat-plate

silicon cell

single-crystal

16% Flat-plate

thin films

Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 13

Figure 2. Cost of Electricity Using Solar Thermal

Generating Plants, 1980-1990

 Source: U.S. Department of Energy, The Secretary's Annual Report to

Congress 1990, DOE/S-0010P(91) (Washington, DC, 1991).

Figure 3. Photovoltaic Cell Conversion Efficiencies,

1978-1990

 Note: Conversion efficiency is the proportion of received sunlight

converted to electricity.

 Source: U.S. Department of Energy, The Secretary's Annual Report to

Congress 1990, DOE/S-0010P(91) (Washington, DC, 1991).

Current Status

Renewable resources provided 348 billion kilowatthours

of the more than 3 trillion kilowatthours of electricity

generated in the United States in 1990 (Table 4); that is

nearly 12 percent of total electricity generation. Almost 10

of this 12 percent (288 billion kilowatthours) was provided

by hydroelectric resources alone. Biomass and MSW

contributed more than 1 percent. All other renewable

resources, including geothermal, wind, and solar, together

provided less than 1 percent of the total. Conversely, fossil

resources, primarily coal, provided 69 percent of the

Nation's electricity, and nuclear power provided 19

percent.
14 Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 

Fuel

Net Summer

Capabilitya

(Gigawatts)

Net

Generationb

(Billion

Kilowatthours)

Fossil .................. c 528.7 2,100

Storage ................. 19.5 -2

Nuclear .................. 99.6 577

Renewable ............... 85.2 348

 Conventional Hydroelectric 72.9 288

 Geothermal . . . . . . . . . . . . . 2.6 15

 Municipal Solid Waste . . . . 2.0 10

 Biomass . . . . . . . . . . . . . . . 6.0 31

 Solar ................. d 0.4 1

 Wind . . . . . . . . . . . . . . . . . . 1.4 2

Total .................... 733.0 3,023

 For nonutilities, nameplate capacity is used. a

 For nonutilities, gross generation including internal station b

use is shown.

 Fossil includes coal, oil, natural gas, petroleum coke, waste c

gases, and waste heat.

 Includes both solar thermal and less than 0.02 billion d

kilowatthours grid-connected photovoltaic generation. 

 Note: Totals may not equal sum of components due to

independent rounding.

 Source: Energy Information Administration. 1990 data: For

utilities, EIA-861 “Annual Electric Utility Report”; for nonutilities,

EIA-867, “Annual Nonutility Power Producer Report.”

Table 4. U.S. Electricity Generating Capacity and

Net Generation, 1990, By Fuel Type
Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 15

Electric utilities (investor-owned, Federal, municipal, rural in particular, has experienced all three factors, plus strong

electric cooperative, and other publicly owned) own most public preferences for and policies promoting the use of

of the generating capacity using renewable resources renewable resources. Also, electric utilities in California

(Table 5). In addition to owning most hydro-electric have made a concerted effort to research and invest in

facilities, electric utilities also own most of the geothermal renewable resource-fueled projects.

capacity. However, most of the generating capacity using

other renewable resources (MSW, biomass, solar, and The use of renewable resources for electricity generation

wind) has been provided by the nonutility sector, is highly concentrated regionally (Tables 6 and 7), with

particularly in recent years. Of the 9,746 megawatts of most renewable resources being used for power in either

generating capacity using biomass, MSW, wind, and solar, the easternmost or westernmost States. Often the use

95 percent is nonutility-owned. follows the concentrations of the natural resource bases

The dominance of nonutilities in the use of these part. These factors include the overall rate of growth of

renewable resources for electricity supply can be traced to demand for new generating capacity and the rate of

three factors. First, nonutility electricity generation is often growth of costs in an associated activity (such as waste

a byproduct of other industrial activities. Biomass-fueled disposal). Over three-fourths of all renewable generating

electricity is generally a byproduct of the forest, wood, capacity can be found in three regions: the Northwest,

and paper industries, which use biomass waste to West, and South Atlantic (Table 6). Of the total 85

generate steam and electricity for their own use. MSW- gigawatts of electric generating capacity fueled by

powered generation is a byproduct of the trash disposal renewable resources, almost 39 percent is located in the

industry. Second, renewable resources are encouraged in Northwest alone.

nonutility markets by PURPA, which exempts renewablefueled power plants built by non-utilities from being The predominance of renewable resources in these three

regulated as electric utilities, while at the same time regions occurs both for conventional hydroelectric

requiring utilities to purchase the output from them at full capacity and for all other renewable resources taken

avoided cost. Finally, during the 1980's, electric utilities together. Hydroelectric resources are concentrated in the

slowed capacity expansion and increasingly turned to the Northwest, West, and South Atlantic regions, and reflect

nonutility sector to meet all forms of new generating the natural distribution of favorable hydroelectric sites in

capacity needs. California, the country.

(Appendix B). But other factors also play an important
16 Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 

(Net Summer Capability, Megawatts, by Ownership Group)

Source Electric Utilitya Nonutilityb Totalb

Conventional Hydroelectric ......................... 71,423 1,476 72,899

Geothermal ..................................... 1,614 961 2,575

Municipal Solid Waste . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 244 1,765 2,009

Biomass . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221 5,750 5,971

Solar .......................................... a 3 360 363

Wind ........................................... d 1,403 1,403

 Total ......................................... 73,505 11,715 85,220

 Electric utilities include investor-owned, federal, rural electric cooperative, municipal and other publicly owned electric utilities. a

 For nonutilities, nameplate capacity is used. b

 Includes solar thermal and grid-connected photovoltaics. c

 Less than 0.5 megawatts. d

 Note: Totals may not equal sum of components due to independent rounding.

 Source: Energy Information Administration. For utilities, EIA-861 “Annual Electric Utility Report”; for nonutilities, EIA-867, “Annual

Nonutility Power Producer Report.”

Table 5. U.S. Generating Capacity Using Renewable Resources, 1990
Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 17

(Net Summer Capability, Megawatts)a

Federal Regionb

Conventional

Hydroelectric

Other

Renewable

Total

Renewable

Total

 Capacity,

 All Sources

New England ........................... 1,875 1,268 3,143 26,655

New York/New Jersey .................... 1,802 347 2,149 46,836

Mid-Atlantic ............................ 2,172 681 2,853 78,087

South Atlantic ........................... 10,900 2,654 13,554 152,750

Midwest ............................... 1,217 762 1,979 127,452

Southwest ............................. 2,702 830 3,532 118,001

Central . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 838 c 838 38,488

North Central ........................... 5,931 53 5,984 29,870

West .................................. 13,120 5,196 18,316 74,730

Northwest .............................. 32,343 529 32,872 40,141

 United States ......................... 72,899 12,321 85,220 733,009

 For nonutilities, nameplate capacity is used. a

 For a list identifying the States in each Federal region, see Appendix D. b

 Less than 0.5 megawatts. c

 Note: Totals may not equal sum of components due to independent rounding.

 Source: Energy Information Administration. For utilities, EIA-861 “Annual Electric Utility Report”; for nonutilities, EIA-867, “Annual

Nonutility Power Producer Report.”

Table 6. U.S. Generating Capacity Using Renewable Resources, 1990, by Federal Region
18 Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 

(Billion Kilowatthours)a

Federal Regionb

Conventional

Hydroelectric

Other

Renewable

Total

Renewable

Total

 Capacity,

 All Sources

New England . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.6 7.4 16.0 108.5

New York/New Jersey .................... 27.5 2.0 29.5 174.0

Mid-Atlantic . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.7 3.2 10.9 347.0

South Atlantic ........................... 38.0 13.0 50.9 642.5

Midwest . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.0 3.8 8.8 549.4

Southwest . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.1 5.1 13.2 472.0

Central . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2 c 4.2 144.8

North Central ........................... 18.7 0.3 19.0 164.0

West .................................. 31.9 23.2 55.1 254.7

Northwest .............................. 138.4 2.3 140.7 166.4

 United States ......................... 288.1 60.3 348.3 3,023.3

 For nonutilities, gross generation including internal station use is shown. a

 For a list identifying the States in each Federal region, see Appendix D. b

 Less than 0.05 billion kilowatthours. c

 Note: Totals may not equal sum of components due to independent rounding.

 Source: Energy Information Administration. For utilities, EIA-861 “Annual Electric Utility Report”; for nonutilities, EIA-867, “Annual

Nonutility Power Producer Report.”

Table 7. U.S. Net Generation Using Renewable Resources, 1990, by Federal Region
Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 19

Other regions, particularly the more arid regions or Clearly, most regions of the United States feature little use

regions lacking large vertical drops, are unlikely ever to of renewable resources other than hydroelectricity for

have significant hydroelectric capacities. After the electricity supply. Five regions—New York/New Jersey,

Northwest and West, the South Atlantic region features the Midwest, Southwest, North Central, and Central

the greatest absolute use of renewable resources to regions—each rely on nonhydroelectric renewable

generate electricity, reflecting the region's abundant resources for less than 1 percent of their total electricity

hydroelectric capacity and extensive use of wood and supply. Four of these regions—the Midwest, Southwest,

wood waste in electricity generation. Similarly, New North Central, and Central—have adequate electric

England's use of renewable resources is predominantly in generating capacity and low fossil-energy prices,

hydroelectric and wood/wood waste-fired generation. relatively meager wood supplies, and low land- fill costs,

The use of nonhydroelectric renewable resources is also the other hand, the Midwest and Southwest have

regionally concentrated. The West (especially California) extensive solar and wind resources available to them.

employs policies that encourage the development of

renewable resources. Laws, regulations, and electric utility Use of each individual renewable resource is highly

choices in California reflect a preference for renewable concentrated. Almost all geothermal capacity is located in

fuels there. Of a total of 12.3 gigawatts of other generating the West, with the remainder in the Northwest. Similarly,

capacity powered by renewable resources, 5.2 gigawatts, the vast majorities of solar and wind-powered systems are

42 percent, is located in the West, overwhelmingly in located in the West. Because most biomass-fueled

California. In fact, nonhydroelectric renewable resources generating capacity is forest-products based, biomassprovide nearly 7 percent of all generating capacity in the fired capacity is concentrated in the Southeast, West, New

West, a substantially higher proportion than for most England, and Mid-Atlantic regions, where forests are most

other regions. Geo-thermal resources are concentrated in abundant. MSW facilities are most heavily concentrated in

the West, along with useful wind and solar conditions. regions with high trash-volume, especially in urban

making continued use of fossil-fueled capacity likely. On

areas that face
20 Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 

California, Home to Renewable Energy

California stands out as a premier area for the use of renewable resources in electric power generation. About 90

percent of the Nation's geothermal capacity is in California, including the oldest and largest geothermal field, The

Geysers (1,866 megawatts) in northern California; three other major sites, Coso Hot Springs, East Mesa, and the

Salton Sea project, are in southern California. California hosts over 95 percent of the Nation's solar thermal capacity,

including facilities in the Harper Lake and Kramer Junction areas of the Mojave desert, north of Los Angeles (Figure

4). The Nation's largest central station photovoltaic facility, PVUSA (1 megawatt) is located in California. Finally,

almost all the major wind systems in the United States are located in California. The largest, Altamont, east of San

Francisco, operates more than 7,000 wind turbines serving Pacific Gas and Electric Company. The second and third,

Tehachapi and San Gorgonio, near Los Angeles, serve Southern California Edison.

California's prominence in using renewable resources results from a number of factors, including natural resource

endowments, continuing demand growth, support from business, government, and the public; and favorable tax and

regulatory treatment. Certainly the existence of favorable wind, solar, and geothermal resources situated near

demand centers plays a part. California has also responded to a strong public preference for renewable resources.

Favorable attitudes and actions by citizens, electric utilities, and State regulatory agencies provided the interest and

business conditions under which capacity that used renewable resources could be built. Concerns about the

environmental consequences (as well as the cost) of coal-fired generation precluded siting coal-fired generators in

the State, opening the way for alternative sources. Public encouragement and other factors aided California in

offering favorable prices and conditions to renewable resources during the decade; favorable treatment of renewable

resources under PURPA, and state tax incentives also spurred uses of renewable alternatives.
Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 21

Figure 4. Solar Thermal Generating Facility, Kramer Junction, California

 Source: U.S. Department of Energy, Sandia National Laboratories.

high and growing landfill costs, generally along the hundreds of miles. Also, in many areas, demand for

Eastern seaboard and in the Midwest. electricity has not grown rapidly enough to induce

The absence of extensive generating capacity using opportunities for exploitation of renewable resources.

renewable resources in the Nation's heartland is more Finally, many areas of the country have less expensive

easily explained by market conditions than by the lack of fossil resources, especially coal and natural gas. Where

renewable resources. Many areas have abundant excellent additional electric generating capacity has been built, coal

solar and wind resources (Appendix B). Certainly many and natural gas have often been competitive, providing

areas appear to be better endowed than California. consumers with less expensive power. For these regions,

However, many renewable resources are located far from the increased use of renewable resources in electric power

demand centers; the costs of transmitting the electricity generation will likely have to await higher electricity

may raise its delivered cost above the cost of generating demand growth rates, lower costs of technologies using

electricity closer to the demand. North Dakota's winds, for renewable resources, and additional access to electricity

example, can only serve major demands if the power is transmission.

transmitted many

significant capacity growth of any sort, which reduces
Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 23

2. Projections of Renewable Resources in the

U.S. Electricity Supply

Introduction

To assist the energy industry and to provide policymakers

with information about the energy supply and demand in

the United States, the EIA has prepared long-term

projections, including for renewable resources, in the

Annual Energy Outlook 1993 (AEO93). These projections 14

consider renewable resource supplies within the context

of overall energy demands and supplies. This chapter

presents and discusses these projections to draw

conclusions relevant to the use of renewable resources.

Energy Information Administration

(EIA) Projections

The AEO93 offers a baseline case, called the Reference

Case, and three pairs of other cases that give high and low

projections based on various assumptions. The Reference

Case is used to facilitate comparisons among the other six

cases and with forecasts prepared by other organizations.

However, the Reference Case should not be viewed as a

most likely scenario. Four of the six other cases illustrate

the effects of changes in factors known to be important to

renewable energy markets. The High Economic Growth

Case and the Low Economic Growth Case show the long

term effects of different rates of U.S. economic growth.

The High

World Oil Price Case and the Low World Oil Price Case

show the effects of different fossil fuel prices. The final

two cases demonstrate the effects of the uncertainties

inherent in recoverable oil and natural gas resource

estimates. These two cases are not considered relevant for

the renewable energy projections and are not discussed

here.

Assumptions

The Reference Case combines the assumption of an

economic growth rate (Gross Domestic Product, GDP) of

2.0 percent per year with a mid-level path for the world

oil price (Table 8). The High Economic Growth Case

assumes the same mid-level world oil prices, but

combines them with an assumption of higher macroeconomic growth, 2.4 percent per year; the Low Economic

Growth Case also assumes a mid-level world oil price

path, but combines it with a lower macroeconomic growth

rate of 1.6 percent a year.

World oil prices are defined as the average refiner

acquisition cost of imported crude oil in the United States.

The High World Oil Price Case combines the Reference

Case economic growth trend with a higher world oil price

path, starting at $19 per barrel in 1991 and rising

gradually to $38 in 2010 (using real 1991 dollars). Because

the world oil price is higher than that assumed for the

Reference Case, the effective rate of
24 Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 

 Energy Information Administration, Annual Energy Outlook 1993, DOE/EIA-0383(93) (Washington, DC, January 1993). 14

Assumptions

Reference

Case

Low

Economic

Growth Case

High

Economic

Growth Case

Low Oil Price

Case

High Oil

Price Case

Oil Price in 2010 ($1991 per barrel) ......... $29.30 $29.30 $29.30 $18.10 $38.10

Economic Growth (GDP) Rate (1990-2010) . . 2.0 1.6 2.4 2.1 2.0

 Source: Energy Information Administration, Assumptions for the Annual Energy Outlook 1993, DOE/EIA-0527(93) (Washington, DC,

January 1993).

Table 8. World Oil Price and Economic Growth Assumptions for the Annual Energy Outlook 1993
Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 25

economic growth and the level of GDP in 2010 in this case a combination of utility- and nonutility-declared plans,

are slightly lower than in the Reference Case, yielding a separate models, macroecoslightly lower overall demand for energy. The Low World

Oil Price Case combines Reference Case economic growth

with an assumption that world oil prices will fall to about

$18 per barrel by 2010. Once again, the world oil price

results in macroeconomic feedback resulting in a slightly

higher overall demand for energy than in the Reference

Case.

Although the major source of renewable energy for

electricity generation is hydroelectric power, projections

for conventional hydroelectricity are assumed not to vary

across the cases. Overlapping regulatory processes,

conflicting requirements for licenses and permits,

disagreements over environmental issues, as well as a lack

of available sites, have constrained the develop-ment of

hydroelectric power plants. Additions to hydroelectric

generating capability have been small during the 1980's

and are not likely to increase significantly in the

foreseeable future.

The costs of electricity generating technologies using

renewable resources are implicitly considered in the

projections by assumptions that the relative costs and

efficiencies of technologies using them will not fall

significantly in comparison with traditional fossil-fueled

technologies. Further, the EIA projections do not pre-sume

any legal or regulatory actions, such as additional taxes or

subsidies, beyond those occurring under existing

legislation, that might affect the relative prices of energy

choices.

The AEO93 also assumes the provisions of the Energy

Policy Act of 1992 (see Box). The resulting projections for

renewable resources include the net effects of the

production tax credits for wind and biomass, and the 10

percent investment tax credit for solar and geothermal

projects. The effects of the Act on renewable energy are

assessed in the overall context of U.S. energy markets.

A fuller explanation of the assumptions and references for

the AEO93, including the effects of the Energy Policy Act,

can be found in Assumptions for the Annual Energy Outlook

1993. The Electricity Market Module (EMM) of the 15

“Intermediate Future Forecasting System” (IFFS) is used

to develop the projections for the electricity markets.

However, in general, projections for renewable resources

in electricity generation are pro-vided exogenously using
26 Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 

nomic and world oil price assumptions and demand

growth forecasts from the AEO, and expert judgment. For

a summary description of specific assumptions for

renewable energy markets, see Appendix A of this report.

EIA Reference Case Results

In the Reference Case, U.S. electricity generation is

projected to grow moderately through 2010, at an average rate of 1.5 percent a year. During the 1990-2010

forecast period, all U.S. electricity generating capacity is

expected to increase slowly, growing at an average annual

rate of about 0.9 percent (Table 9). The EIA expects most

of the growth in electric generating capacity to continue to

be provided by fossil fuels—coal, natural gas and oil.

According to the EIA Reference Case, through 2010

electricity generation using renewable resources is

projected to increase more rapidly than overall U.S.

generation. Generation using renewable resources is

forecast to increase at an average annual rate of growth of

1.8 percent. Net generation that relies on renewable

resources increases from 348 billion kilowatthours in 1990

to 501 billion kilowatthours in 2010.

As a result, the renewable resource share of the electricity

marketplace should grow slightly over the next 20 years.

By 2010, renewable resources are projected to capture 12.2

percent of the U.S. electricity generation. Of course, on a

regional basis, where they are available and costs of

alternatives are high, renewable resources, particularly

MSW, biomass, geothermal, and wind, could make

increasingly significant contributions.

The mix of renewable resources in electricity supply is

expected to change noticeably over the forecast period.

Hydroelectric capacity is expected to grow little, losing

some of its relative share, while electricity generation

using other renewable resources, particularly MSW and

geothermal, is expected to grow more rapidly than overall

demand. 

From 1990 through 2010, total U.S. conventional hydroelectric capacity is expected to grow by only 4 gigawatts;

its growth rate will average 0.3 percent a year. Little

additional conventional hydroelectric capacity expansion

is expected after 1995. The EIA Reference Case projections

indicate that the increased use of other renewable

resources will offset the lower rate of growth for

hydroelectric power. Electricity
28 Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 

The Energy Policy Act of 1992

The Energy Policy Act of 1992 (P.L. 102-485), signed into law by President Bush on October 24, 1992, affects virtually every

part of U.S. energy markets. As a result, the Act is likely to have both direct and indirect effects on the Nation's use of

renewable resources for electric power supply.

Some parts of the law are explicitly designed to directly increase the use of renewable resources. The law establishes a

permanent 10 percent investment tax credit for solar and geothermal projects. It also establishes a 1.5 cent per kilowatthour

production tax credit or payment for electricity produced from the use of wind or biomass (from crops dedicated to energy

use) in plants brought on line before July 1, 1999. A facility may earn the credit or payment for 10 years. The Act also

authorizes the Department of Energy to assist demonstration and commercialization projects using renewable resources,

and authorizes a range of actions to encourage growth in exports of technologies using renewable resources. The net effect

of these provisions should be to encourage expanded use of these resources.

Other parts of the legislation, while designed to improve the efficiency of energy markets overall, may or may not result in

increased use of renewable energy resources. The law sets higher energy efficiency standards for some classes of

buildings, motors, lights, and commercial and industrial equipment. These standards will reduce the growth in energy

demands, including from renewable resources. The law also encourages alternatives to renewable energy. It reforms the

nuclear power plant licensing process and promotes the development of advanced nuclear power plants. It encourages

environmentally sound uses of coal, streamlines the regulation of oil pipelines, and promotes the use of natural gas. These

features will act to increase the competitiveness of fossil and nuclear energy sources. Other features have less clear effects

on renewable energy. For example, the Act exempts some classes of electricity generating firms from regulation as public

utilities and increases access to electricity transmission networks by electricity producers other than electric utilities. These

exemptions are generally viewed as favorable to renewable energy sources, but as favorable to their fossil fuel competitors

as well.

generation from other renewable energy sources is Geothermal-based electric generating capacity is also

expected to grow at an average annual rate of 6.2 percent. projected to expand rapidly, from about 2.6 gigawatts in

Collectively, geothermal, MSW, biomass, wind, and solar- 1990 to 8.5 gigawatts by 2010. Electricity generation using

powered capacity are projected to grow from 12.3 geothermal resources is expected to grow at an average

gigawatts in 1990 to 36.2 gigawatts by 2010. Over the 20- rate of 7.2 percent, helped by the provisions of the Energy

year period, the average annual rate of growth in Policy Act. Given that hydrothermal and hot dry rock

generating capacity for this group is 5.5 percent—over six resources are concentrated in the West, it is not surprising

times the average rate of growth of total capacity (from all that almost all of the expansion is expected to occur in the

sources). Western region, especially in California. No geothermal

The greatest expansion in renewable energy for electricity east of the North Central region.

supply over the 20-year forecast period is expected to

occur in the use of MSW. Electric generating capacity In the Reference Case, the EIA projects wind-powered

using MSW is expected to expand from 2.0 gigawatts in capacity to increase from 1.4 gigawatts in 1990 to over 6.3

1990 to 11.4 gigawatts by 2010, increasing at an average gigawatts by 2010, increasing at a rate almost 9 times the

rate of 9.1 percent resulting from population and projected overall rate of total U.S. electric generating

economic growth and the reduced availability of landfill capacity expansion. Nevertheless, with wind accounting

space. Of the total projected non-hydroelectric capacity for less than 0.2 percent of U.S. electric generating

growth of 23.9 gigawatts, 39 percent will be provided by capacity in 1990, by 2010 wind still will provide only

additional MSW plants. about 0.7 percent of the U.S. total. Some expansion in solar

generating capacity growth is anticipated in any States
Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 29

thermal electricity generation is expected over the period.

The projections do not include forecasts for photovoltaic

systems disconnected from the utility transmission 

network (dispersed
30 Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 

Technology 1990a

2010

Reference

High Economic

Growth

Low

Economic

Growth

High

World Oil

 Price

Low

World Oil Price

Net Summer Capability (Gigawatts)

Conventional Hydropower ...................... 72.9 76.9 76.9 76.9 76.9 76.9

Geothermal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.6 8.5 8.5 8.5 9.7 7.3

Municipal Solid Waste . . . . . . . . . . . . . . . . . . . . . . . . . 2.0 11.4 13.9 10.9 11.4 11.4

Biomass/Other Waste ......................... b 6.0 8.1 8.3 7.2 8.1 8.1

Solar ...................................... c 0.4 1.9 1.9 1.9 2.2 1.7

Wind . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.4 6.3 6.3 6.3 7.3 5.3

 Total Capacity, Renewable ................... 85.2 113.1 115.9 111.7 115.5 110.7

Fossil/Nuclear/Other .......................... d 647.8 767.0 814.2 722.1 759.4 780.6

 Total Generating Capacity ................... 733.0 880.1 930.1 833.8 874.9 891.3

 Percent Renewable ......................... 11.6 12.9 12.5 13.4 13.2 12.4

Net Generation (Billion Kilowatthours)

Conventional Hydropower . . . . . . . . . . . . . . . . . . . . . . 288 306 306 306 306 306

Geothermal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 62 62 62 72 53

Municipal Solid Waste . . . . . . . . . . . . . . . . . . . . . . . . . 10 54 70 50 54 54

Biomass/Other Waste ......................... b 31 59 60 54 59 59

Solar ..................................... c e 1 4 4 4 4 3

Wind . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 16 16 16 19 14

 Total Renewable ........................... 348 501 519 492 513 488

Fossil/Nuclear/Other .......................... d 2,675 3,611 3,816 3,393 3,576 3,679

 Total Net Generation ........................ 3,023 4,112 4,335 3,885 4,089 4,167

 Percent Renewable ......................... 11.5 12.2 12.0 12.7 12.5 11.7 

 The 1990 data shown in the table are actual EIA published values (preliminary data), while the 1990 values published in the Annual Energy Outlook 1993 are a

estimates.

 Includes wood, wood waste, and other biomass. b

 Includes both solar thermal and grid-connected photovoltaic capacity. Solar does not include dispersed photovoltaics. c

 Includes pumped storage hydroelectric. d

 Includes solar thermal and less than 0.02 billion kilowatthours grid-connected photovoltaic generation. e

 Notes: Forecasts of renewable electric generating capacity for the High and Low Oil and Gas Recovery Cases are the same as for the Reference Case. Totals

may not equal sum of components due to independent rounding.

 Sources: Energy Information Administration, 1990 data: For utilities, EIA-861 Annual Electric Utility Report; for nonutilities, EIA-867, Annual Nonutility Power

Producer Report. Projections for 2000 and 2010: Annual Energy Outlook 1993, DOE/EIA-0383(93).

Table 9. U.S. Electric Generating Capacity and Net Generation Projections for 2010

photovoltaics). However, applications of very small but Nonutilities, including independent power producers,

high-value photovoltaic devices, such as for powering and also cogenerators and small facilities qualifying under

monitoring devices, lights, pumps, remote building PURPA, will build about four-fifths of the 28

electricity supply, and other uses for which connection to

transmission lines is too costly, are expected to proliferate

over the forecast period.
Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 31

gigawatts of new electricity generating capacity using

renewable resources. Much of the new capacity, such as

that fueled by MSW and biomass, will be provided by

municipalities and industries. Also, PURPA benefits for

electricity production from renewable resources apply to

nonutility producers and not to electric utilities. Finally, in

some instances (for example, wind and solar thermal),

investment in the technologies should continue to occur

outside the electric utility sector.
32 Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 

Alternative EIA Case Results

In the four alternative EIA projection cases, long-term

renewable energy projections for electric power are

developed under economic growth and world oil price

assumptions different from the Reference Case. The

alternative cases suggest that both higher rates of

economic growth and higher world oil prices (of the

magnitudes assumed in the cases) could result in

increased use of renewable resources over the forecast

period.

Changes in the assumed rate of economic growth through

2010 directly affect electricity supply using renewable

energy resources. High economic growth (2.4 percent per

year) yields over 4 gigawatts more generating capacity

using renewable resources than low economic growth (1.6

percent per year) (Table 9). The higher economic growth

causes additional waste generation and expansion in

electricity generation from MSW; similarly, high economic

growth causes the use of more biomass (wood) for

electricity in the paper and lumber industries. By the same

token, low economic growth results in lower rates of

growth in MSW and biomass available for use in electric

power generation.

Changes in world oil prices also have a direct affect on the

growth of electricity supply from renewable resources.

Because Reference Case assumptions for economic growth

are retained, results for MSW and biomass are unchanged

for these cases. In the High World Oil Price Case, with

resulting higher natural gas prices, a total of nearly 5

gigawatts more geothermal, solar, and wind-powered

generating capacity is built by 2010 than under low world

oil price assumptions. This occurs despite a drop of 78

billion kilowatthours in overall electricity

generation—geothermal, solar, and wind resources

become more competitive relative to fossil fuels. All three

resources are responsive to the increases in natural gas

prices, particularly in the West. 

Comparison With Other Forecasts

To put the EIA forecast into perspective, this section

compares the EIA Reference Case projections with nonEIA forecasts. Several differences among the forecasts

make comparisons difficult. First, the EIA projections

incorporate the provisions of the Energy Policy Act of

1992, whereas the non-EIA projections were completed

before enactment of this law. Second, details concerning
Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 33

Solar Two

The U.S. Department of Energy and a consortium of 12 electric utilities and others is retrofitting the Solar One solar thermal

central receiver pilot plant (Appendix C) for operation beginning in 1995.

The original 10-megawatt Solar One facility, located near Barstow, California, demonstrated that the central receiver concept

can operate reliably. Solar One, however, used oil as the energy storage medium, a medium inefficient for more than brief

energy storage. As a result, the Solar One facility acted as a peaking unit during times of maximum sunlight.

Solar Two will reuse much of the original facility, including the 300-foot tower, the turbine, the generator, and its field of dualaxis (horizontal and vertical) mirrors called heliostats. However, the newer facility will introduce a molten-salt heat transfer

medium to collect and store heat energy, replacing the earlier oil system. “Cold” (550 degrees Fahrenheit) molten salt, a

mixture of sodium and potassium nitrate, will be pumped from a cold storage tank to the receiver at the top of the tower.

Concentrated sunlight from the heliostat field will heat the molten salt to 1,050 degrees Fahrenheit, either for direct use (via

a heat exchanger) or for storage and later use in generating electricity.

The molten-salt receiver system is expected to permit the power from Solar Two to be dispatchable (available when needed

rather than only when the sun shines), and, in later large-scale commercial applications, to operate at capacity factors up

to 60 percent, allowing electricity production even at night or during bad weather, and to produce electricity with zero

emissions, all at a cost (when the system is fully commercial) no greater than from alternatives.

Solar Two is expected to cost $39 million. The cost will be shared equally by the DOE and the consortium.
34 Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 

(Average Annual Percentage Change, 1990-2010)

Projection

EIA AEO93 Other Forecasts

Reference

High Economic

Growth

Low Economic

Growth WEFA DRI GRI UCS

Real Gross Domestic Product (GDP) ......... a 2.0 2.4 1.6 2.4 2.2 c 2.0 2.7

Inflation ................................ b 3.9 3.3 5.3 3.6 3.7 d 4.1 NA

 Real GDP in 1987 dollars except where noted. a

 Based on GDP deflators in 1987 dollars, except where noted. b

 Real GNP in 1982 dollars. Represents the average growth, assuming annual growth of 2.4 percent between 1990 and 2000 and 2.1 percent between 2000 and c

2010.

 Average of 1990 to 2000 inflation (3.2 percent) and 2000 to 2010 inflation (4.1 percent), then rounded. d

 Sources: EIA: AEO93 Forecasting System runs AEO93B.D0918921 (Reference Case), HMAC93.D091692C (High Economic Growth Case), and

LMAC93.D0916924 (Low Economic Growth Case). WEFA: The WEFA Group, U.S. Long-Term Economic Outlook, Vol. 1 (Second Quarter 1992). GRI: Gas

Research Institute, Implications of the GRI Baseline Projection of U.S. Energy Supply and Demand, 1993 Edition (Aug. 11, 1992), and Draft of GRI93 Baseline

Projections (Aug. 21, 1992). DRI: DRI/McGraw-Hill, Energy Review (Second Quarter 1992). UCS: The Union of Concerned Scientists, America's Energy Choices:

Investing In A Strong Economy and A Clean Environment (Cambridge, Massachusetts 1991).

Table 10. Comparison of Macroeconomic Forecasts

different assumptions and definitions used in the non- EIA's Low Economic Growth (averaging 1.6 percent a

EIA forecasts are often not readily available. Third, the year) and High Economic Growth case assumptions (2.4

various forecasts typically do not use directly comparable percent a year), although the UCS projections assumed a

fuel categories for measurement. 2.7 percent annual real growth rate.

Fourth, some of the forecasts use nameplate capability,

rather than net summer capability. Nameplate capability

represents the manufacturer's reported capacity for each

turbine generator, while net summer capability

represents the actual tested capacity of the unit at peak

summer demand. Nameplate capability is generally 5 to

10 percent greater than net summer capability. 

And finally, some of the projections are limited to electric

utility forecasts, and either omit nonutilities altogether or

lump together all fuels for nonutilities, eliminating the

possibility of completely comparable resource

comparisons for the total electricity market.

Four major alternative projections are compared with the

EIA Reference Case for U.S. renewable energy markets in

2010: the WEFA Group (WEFA), the DRI/McGraw-Hill

(DRI), the Gas Research Institute (GRI), and finally, the

projections provided by the Union of Concerned Scientists

(UCS). Generally, the macroeconomic assumptions 16

(Table 10) used by the EIA and the other organizations are

similar for the 1990-2010 forecast period. Most of them

fall between the

Results

Despite major differences in underlying assumptions and

presentation, some common conclusions emerge from a

comparison of the EIA projections for renewable energy

with other forecasts through 2010 (Table 11). 

In all the projections, renewable energy is expected to

increase its contribution to U.S. electricity supply. The

alternative projections (DRI and GRI) for electric utilities

only (i.e., excluding nonutilities) forecast a total of

between 76 and 82 gigawatts of generating capacity using

renewable resources in 2010. These projections are similar

to the EIA forecast of 81 gigawatts in 2010. The WEFA

projections, including both electric utilities and

nonutilities, forecast a total of 107 gigawatts of generating

capacity using renewable resources in 2010. The UCS

Reference Case projects the most expansion, to 135

gigawatts of renewable capacity in 2010, a result of

assumed higher economic growth (and consequent

electricity demand expansion) and greater competitiveness of renewable resources in the electric power

marketplace.
Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 35

 Sources: WEFA: The WEFA Group, U.S. Long-Term Economic Outlook, Vol. 1 (Second Quarter 1992). DRI: DRI/McGraw-Hill, Energy Review (Second Quarter 16

1992). GRI: Gas Research Institute, Implications of the GRI Baseline Projection of U.S. Energy Supply and Demand, 1993 Edition (Aug. 11, 1992) and Draft of GRI93

Baseline Projections (Aug. 21, 1992). UCS: The Union of Concerned Scientists, America's Energy Choices, Investing in a Strong Economy and a Clean Environment

(Cambridge, Massachusetts 1991).
36 Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 

EIA

Reference Case WEFA DRIa GRIa

UCS

Reference Case

UCS

Climate

Stabilization Case

Generating Capability

(Net Summer Capability)

(Gigawatts)

Conventional Hydroelectric .................. 76.9 97.9 b 71.6 71.5 99 NA

Geothermal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.5 7 NA

Biomass/Waste (MSW) ..................... 19.5 9.1 c 9.9 c 4.1 15 NA

Solar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.9 6 NA

Wind . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3 8 NA

 

 Total Renewables (Utilities and

 Nonutilities ............................ 113.1 107.0 NA NA 135 NA

 Total Capacity ........................... 880.1 879.8 NA NA 953 NA

 Percent Renewables ...................... 12.9 12.2 NA NA 14.2 NA

 Total Renewables (Utilities Only) ............ 81.0 NA 81.5 75.6 NA NA

 Total Capacity ........................... 766.3 NA 920.4 827.9 NA NA

 Percent Renewables ...................... 10.6 NA 8.9 9.1 NA NA

Net Generation

(Billion Kilowatthours)

Conventional Hydroelectric .................. 306.5 331.2 335.8 283.3b 326 343

Geothermal ............................... 62.1 53 60

Biomass/Waste (MSW) ..................... 112.4 30.5 c 17.7 c 9.9 113 136

Solar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.8 13 39

Wind .................................... 16.2 17 117

 Total Renewables (Utilities and

 Nonutilities) ............................ 500.9 361.7 NA NA 522 695

 Total Generation ......................... 4,112.0 3,867.6 NA NA 4,430 2,576

 Percent Renewables ...................... 12.2 9.4 NA NA 11.8 27.0 

 Total Renewables (Utilities Only) ............ 335.2 NA 353.5 293.2 NA NA

 Total Generation ......................... 3,522.4 NA 3,867.1 3,394.8 NA NA

 Percent Renewables . . . . . . . . . . . . . . . . . . . . . . 9.5 NA 9.1 8.6 NA NA

 Electric utilities only (excluding nonutilities), nameplate capacity. a

 Includes pumped storage hydroelectric. b

 Includes small amounts of “other,” such as waste heat and petroleum coke. c

 NA = Not available.

 Sources: EIA: AEO93 Forecasting System runs AEO93B.D0918921 (Reference Case). WEFA: The WEFA Group, Energy Analysis Quarterly (Summer 1992).

DRI: DRI/McGraw-Hill, Energy Review (Second Quarter 1992). GRI: Gas Research Institute, Implications of the GRI Baseline Projection of U.S. Energy Supply

and Demand, 1993 Edition (August, 1992), and Draft of GRI93 Baseline Projections (August, 1992). UCS: The Union of Concerned Scientists, America's Energy

Choices, Investing in a Strong Economy and a Clean Environment (Cambridge, Massachusetts 1991).

Table 11. Comparison of Electricity Forecasts, 2010

Further, no projections expect large increases in hydro- alternative forecasts also indicate more rapid growth for

electricity contributions over the forecast period. The the use of renewable resources other than hydroelectricity.
Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 37

Although specific resources are not identified, the use of

geothermal, biomass and waste (including MSW), solar,

and wind resources is generally expected to expand more

rapidly than capacity from fossil resources.
38 Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 

Finally, the alternative projections suggest a general these assumptions, aggregate electricity demand is greatly

consensus that renewable resources will continue to reduced from the Reference Case, while renew-able

supply less than 13 percent of total U.S. electricity supply resources are able to garner 27 percent of the total

through 2010. electricity market.

Only the Union of Concerned Scientists provided resource

specific projections for comparison with the EIA forecasts.

Most of the difference in the UCS higher forecasts for

renewable resources is accounted by its projecting 20

billion kilowatthours more hydroelectric generation in

2010 than the EIA expects. Its forecasts for electricity

generation using biomass and municipal solid waste

(combined) and wind are very similar, despite differing

capacity projections for these resource choices. On the

other hand, the UCS projections forecast significantly less

generation (9 billion kilowatthours) from geothermal

resources, while projecting far more output from solar

resources than does the EIA (13 billion kilowatthours

compared with less than 4). 

The UCS also provided another set of forecasts under

assumptions very different from both the EIA and all

other major projections. These forecasts give an alternative

view of future electricity markets. The Climate

Stabilization Case results in the greatest use of renew-able

resources. The assumed introduction of end-use efficiency

measures greatly cuts demands for capacity additions,

coal-fired plants become much less com-petitive because

of environmental constraints, and renewable energy is

assumed much more competitive, particularly wind, solar,

and geothermal. As a result of

Overall Conclusions

Many different scenarios for the U.S. economy, energy

markets, electricity markets, and renewable resources

could be envisioned. The EIA Reference Case portrays

potential futures based upon what is currently known and

what is reasonably likely to occur. From this forecast two

general conclusions emerge:

First, hydroelectric power, the mainstay of renewable

resources in electric power generation today, is not likely

to enjoy rapid growth under current expectations. Even if

somewhat more favorable regulatory policies are put into

place, the lack of many additional large sites and

environmental considerations constrains hydroelectric

growth.

Second, the rapid growth of non-hydroelectric renewable

resource use will offset the slow hydroelectric expansion,

allowing renewables to increase their share of the electric

market slightly, to over 12 percent of national electric

generation. Nevertheless, as a general matter, renewable

resources are not likely to replace fossil fuels as the major

contributors of electricity supply over the next 20 years.
Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 39

3. Issues Affecting the Growth of Renewable

Resources in Electric Power

The current EIA forecast indicates that renewable facilities of any type, including those using renewable

resources will continue to play an important but resources, are limited.

nevertheless secondary role in U.S. electricity supply

through 2010. Of course, events that might increase the

future role of renewable resources could occur. This

chapter identifies and briefly discusses the kinds of events

that the EIA currently considers most likely to result in the

increased use of renewable resources in electricity markets

over the coming decades. Not all are certain, or even

highly likely, to occur. Additional events that might

reduce opportunities for increased use could also take

place. Nevertheless, at least some of them will have to

occur if the use of renewable resources for electricity

supply is to expand more rapidly than in the EIA

Reference Case.

Demand Growth

The rate of growth of electricity demand will affect

opportunities for renewable resources. The rates of overall

U.S. economic growth and the consequent expansion in

electricity demand are major determinants of all electric

generating capacity growth, including capacity using

renewable resources. Current projections assume a

moderate growth in the Gross Domestic Product (GDP),

averaging 2.0 percent a year; growth in electricity

generation will average 1.5 percent a year. 

Growth in electricity demand spurs demands for new

electric generating capacity. During the 1960's, when

electricity demand (as measured by electric utility sales)

grew at a rate of more than 7 percent a year, electric utility

generating capacity grew at a nearly identical rate,

doubling within 10 years. In contrast, under the current

EIA projections, over the next 20 years, total electric utility

plus nonutility capacity will expand at an average rate of

only 0.9 percent a year. As a result, opportunities for new

If, as a result of more rapid economic expansion, overall

electricity demand grows faster than currently projected,

demands for all types of new electric generating capacity

will be greater, and additional growth of capacity using

renewable resources could occur.

Of course, the exact amounts of new growth, their

proportional contributions, their fuel types, and the

technologies used, along with many other features, will

depend on the specific characteristics of the new electricity

demands, including the types of demand and where they

occur. Growing baseload electricity demands (needed at

all times) will tend to elicit baseload capacity, such as

geothermal, MSW, biomass, or hydroelectric (or possibly

wind or solar thermal generating capacity if energy

storage devices are added). A disproportionate growth in

peaking demand (only needed for short periods) may

favor other technologies, such as solar thermal,

photovoltaic, or wind. Wood use for electricity generation

will be heavily affected by the rates of growth of demand

for the products of the timber and wood products

industries. The locations of growth will also affect the

choice of technology. Heavy demand growth in Illinois

(the Midwest region), for example, would not likely spur

major geothermal expansion because Illinois lacks readily

available geothermal resources. 

Changes in markets for alternative uses of renewable

resources and in substitutes for electricity use will also

affect the growth rate of demand for electricity generating

capacity using renewable resources. Some renewable

resources can be used to produce goods or services other

than electricity. Changes in demands for those alternatives

can be expected to affect the rate of growth of generating

capacity using renewable resources. MSW, for example,

can be recycled. The greater the Nation's success in

recycling combustible materials, the less MSW will be
40 Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 

available to fuel waste-to-energy plants. Also, MSW can using renewable resources will grow more rapidly.

be used to provide steam for heat or industrial processes, Should fossil fuel prices rise more slowly, or should they

rather than electricity. Water too has many alternative decline, the use of renewable resources may slow.

uses, some incompatible with hydroelectric generation. However, general economic growth, on which all

For example, water may be stored or diverted for expansion depends, is tied to world oil prices. Relatively

agricultural uses, or released around (rather than through) low world oil prices spur economic growth, while high oil

turbines to protect migrating fish. Biomass, such as forest prices retard it. Therefore, the growing use of renewable

waste, may be left to help replenish the soil or for habitat; resources may need low fossil fuel prices to drive

some forest wastes, found to be commercially useful, may economic growth, which will increase demands for all

no longer be available for combustion. Land suitable for kinds of new electric generating capacity.

the development of wind power plants may have more

lucrative applications in recreational or agricultural

development. To the extent these alternative uses of

renewable resources grow more or less rapidly than

currently assumed, the rate of growth of renewable

resources in electric power will be affected.

Demand is also affected by substitutes. Consumers may

also choose nonelectricity substitutes (for example,

wearing warmer clothing rather than increasing use of

electric furnace), thereby reducing the demand for electric

power. Solar water heaters could substitute for electricity

in water heating. Conservation could reduce the demand

for electricity. To the extent energy saving measures such

as insulation, high efficiency motors and lamps, and

timing and control devices, become cost effective, the

growth of electricity demands from all sources could be

inhibited. Or they may find additional uses for electricity,

thereby increasing its demand. For example, the AEO93

assumes the addition of 4.6 million electric vehicles by

2010, increasing total U.S. electricity demand by 17.6

billion kilowatthours (a little less than one-half percent).

As a result, demand for all kinds of generating capacity is

increased, including capacity powered by renewable

resources.

Prices of Other Fuels

The prices of other fuels, particularly of coal, natural gas,

and oil, can be expected to heavily influence opportunities

for renewable resources over the forecast period, both

competing for some markets (as substitutes) and assisting

in the general market growth (as complements). Currently

in the EIA Reference Case, world oil prices are projected

to rise by only 1.3 percent a year through 2010; natural gas

wellhead prices are expected to rise by 3.7 percent a year.

If the prices of fossil fuels rise more rapidly than

projected, renewable resources will serve as more

competitive substitutes, and electric generating capacity
Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 41

Technology Costs

Although true costs of electricity from all sources is

debated, the general reluctance of the electricity marketplace to select technologies using renewable resources on

a large scale suggests that often they are not cost

competitive today. Costs need to be lowered if technologies using renewable resources are to compete with

technologies using fossil fuels. In addition, operating

reliabilities and efficiencies need to be improved (see

Appendix C for technology descriptions).

Very little consistently defined historical data exists on the

trend of costs in generating electricity using renewable

resources. Nevertheless, some general characteristics are

clear. First, the costs per kilowatthour of generating

electricity using fossil resources dropped dramatically

during the first eight decades of the U.S. electric power

industry (into the 1960's), but flattened and continue to

face the increasing burdens of environmental

requirements.17

Second, the costs of generating electricity using some

renewable resources have also dropped dramatically in

recent years, in a manner analogous to those earlier years

of fossil fuel use. As displayed in Chapter 1, the costs of

generation for wind, solar photovoltaic, and solar thermal

generation have dropped from far above most practical

applications to be competitive in niche markets and in

some locales. Some, such as wind power, seem poised for

far wider applications. 

Clearly if costs for technologies using renewable resources

can continue to decline, wider use of these resources for

electricity generation will occur. Where technology costs

are not likely to decline significantly, such as for

hydroelectric, municipal solid waste, or geothermal

power, opportunities for expansion are likely to be as

much affected by increases in costs of alternatives (such as

for fossil fuels) or in related markets (such as for waste

disposal). 

The Energy Policy Act of 1992 could serve to lower the

costs of technologies using renewable resources if

authorized demonstration and commercialization provisions are funded. The Act authorizes the Department of

Energy, on a cost-shared basis with industry, to fund

demonstration and commercialization programs using

renewable resources. Eligible technologies include those

using biomass, solar, wind, or geothermal resources. If

these programs were funded, the costs of using these

technologies to produce electricity could decline.
42 Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 

 For historical information on electricity prices and the costs of generating electric power using fossil resources, see the Energy Information 17

Administration report, Annual Outlook for U.S. Electric Power 1985, DOE/EIA-0474(85) (Washington, DC, 1985).
Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 43

Externalities 

Consideration of externalities could accelerate the use of

renewable resources. The term “externality” refers to

some economically valuable cost or benefit imposed on or

enjoyed by a third party (not the buyer or seller) in a

transaction. The price the buyer pays to the seller does not

reflect this external cost or benefit and the buyer pays less

or more than the total social value of the product. Some

contend that, because of external costs imposed on society,

the true (higher) costs of using fossil fuels are not

accurately represented in current market prices. In energy

markets today, two general categories of externality are

discussed: preferential tax treatment or subsidies and

environmental costs and benefits. For example, depletion

allowances granted to the extractive industries such as

coal, oil, and natural gas, are viewed by some as tax

advantages favoring fossil fuels but denied renewable

resources. Environmental externalities are argued to 18

exist when some environmental costs of fossil fuels are not

borne by fossil fuel users. Sulfur dioxide and nitrogen

oxide emissions, which contribute to acid rain, and carbon

dioxide emissions, viewed by some as principal contributors to global warming, may impose costs on the entire

community which users of the fuels are excused from

paying.

The Clean Air Act Amendments of 1990 (Public Law 101-

549) exemplify the possible effects of accounting for

externalities. By requiring electric utilities to reduce sulfur

and nitrogen oxide emissions produced when using fossil

fuels, costs of electricity produced with those fuels rise

relative to other fuels. By “internal-izing” (imposing the

costs of emitting on the electricity consumers), the full

costs of fossil fuels are imposed on the electricity

consumer and not on the public. At the same time, the

costs of using renewable sources for electricity generation

become relatively less expensive and more competitive

with fossil alternatives.

Precise accounting for all externalities for all fuels is

probably impossible. Nevertheless, concerns about the

magnitude of unaccounted external costs of fossil fuels is

prompting some actions at least to estimate the costs and

impose them to assist efficient energy choices. Some States

(among them Massachusetts, New York, Nevada, and

California) include compensatory amounts when

considering proposals for new generating capacity. Many

other states are considering such amounts. For example,

in the competitive bidding process, coal

projects may be assigned a 2-cent-per-kilowatthour

additional cost when compared with other fuels projects.

In effect, projects using renewable resources, whose costs

are no more than 2 cents per kilowatthour greater than the

coal project, would be selected before the coal project.

Therefore, to the extent that costs of externalities favoring

renewable resources are intro-duced into the capacity

selection process, technologies using renewable resources

may be chosen more readily for U.S. electricity supply

additions.

Resource-Specific Challenges

In addition to the generally applicable forces likely to

affect renewable resources over the next two decades,

each renewable resource faces its own challenges in

meeting electricity demand growth. General success in the

marketplace is likely to occur only when investors,

utilities, and consumers become confident that renewableresource based technologies can be counted on to deliver

electricity reliably and at a cost no higher than

conventional alternatives.

Hydroelectricity

Hydroelectric generation faces some of the greatest

challenges to expansion. Concerns over destruction of fish

and fish habitat may lead to marked changes in the

approval of new dams and the operation of existing dams,

lowering hydroelectric output. In the Northwest, for

example, three species of Pacific salmon have been listed

for protection under the Endangered Species Act of 1973

(P.L. 93-205). The Snake River sockeye salmon have been

listed as endangered, as have two species of the Snake

River chinook salmon. In response, hydroelectric

operations along the Columbia River may be changed and

power generation reduced to facilitate migration of the

Pacific salmon between the Pacific Ocean and their

Northwestern spawning grounds. Reservoirs may be

drawn down and waters “spilled” (released without

passing through the turbines) to increase overall water

flow and assist migration without killing fish in the

turbines. While the exact effects on hydroelectric

generation are not known at this time, preserving fish

populations could reduce hydroelectric generation from

current facilities and discourage future hydroelectric

expansion, both in the Northwest and throughout the

country wherever fish populations are at risk.
Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 45

In addition to fish preservation, alternative water and discovery and extraction of heat must be lowered and

watershed uses could also affect potential hydroelectric better methods of prolonging the life of resources must be

generation. Particularly in the West, where growing developed. The costs of exploration and reservoir analysis

populations, agricultural and other water uses, and recent must be reduced. Improved techniques are needed to

droughts have highlighted conflicts over water priorities, map the boundaries of discovered reservoirs, determine

water may be diverted for other uses. Water use for reservoir properties, and improve the success rate of

recreation, including fishing, boating, rafting, and production. Once reservoirs are located, reservoir

swimming, may result in modified operation of reservoirs engineering needs to improve in order to reduce

and streams and reduce the generating opportunities for uncertainty and determine more efficient reservoir use,

hydroelectric facilities. including fewer and better-placed wells.

The Omnibus Western Water Act (P.L. 102-575), signed by The costs of drilling for geothermal resources must be

President Bush in October, 1992, while authorizing several lowered. Because temperatures are much higher for

Western water projects, also raises the importance of geothermal than for oil drilling, and rock types in

protecting fish populations and other natural resources geothermal are generally harder and more abrasive than

(such as the Grand Canyon). Possible revisions to the rock above oil and gas reservoirs, more effective and

Clean Water Act and Endangered Species Act in 1993 durable drill bits and other drilling components must be

could also significantly affect priorities in the use of water developed. At locations where highly corrosive brines and

for electricity generation. gases are present, materials need to be developed for

Relicensing of hydroelectric facilities could also slow drilling costs are a major part of geothermal electricity

development of hydroelectricity. The relicensing process production expenses, improvements in drilling

highlights conflicts in the uses of water resources. technology and locating wells could make electricity

Nonfederal dams require licenses issued by the Federal generation using geothermal resources notably more

Energy Regulatory Commission (FERC). Many of the competitive.

original 50-year licenses issued in the 1940's will expire by

the end of the decade and are subject to reconsideration Future development of hot dry rock geothermal resources

and reissuance—possibly to competing parties. Under the will also be affected by access to water resources for

Electric Consumers Protection Act of 1986 (P.L. 99-495), injection into wells as a heat transfer medium. Because

FERC must consider protection, mitigation, and many hot dry rock resources are located in the arid West,

enhancement of fish and wildlife, energy conservation, water rights and water access are critical issues in

protection of recreation uses, historic preservation, and geothermal development.

other aspects of environmental quality along with power

development when issuing hydroelectric licenses. Finally, the decline of pressure at The Geysers has made

Moreover, in the relicensing process, Federal, State, and well pressure maintenance an issue of major concern.

local interests, many represented by government agencies Market growth for geothermal resources is likely to be

with their own authorities and regulations, confront each contingent partially on developing cost-effective and

other and private and local public power interests in efficient fluid injection methods (to replace extracted

determining who will control the water. Resolving the fluids) to ensure the durability of the resources. 

issues through FERC has itself become a difficult and

time-consuming process, particularly as issues other than

electric power have gained attention. As a result, the

process of obtaining a license to develop hydropower at

any site has become an expensive, uncertain, and

daunting process.

Geothermal

For technologies using geothermal resources to provide a efficiencies of solar thermal concentrators in focusing

greater share of new electricity supply, the costs of sunlight have risen over the last decade and the costs-perbuilding equipment more resistant to corrosion. Because

Solar

Among the most pressing issues affecting the success of

solar technologies are lowering capital costs and

increasing electricity output per unit of capacity. For solar

thermal systems, the highest-cost components are the solar

trough and parabolic dish concentrators (see Appendix

C), which focus sunlight on the fluids to be heated. The
46 Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 

square-meter of concentrator surface have dropped

steadily through the 1980's, but costs need to be lowered

further to become more competitive. Reductions in the

costs of storing and moving energy prior to electricity

generation will also improve the competitive position of

solar thermal power. Also, solar thermal systems must

become more reliable, especially when the sun is

obscured. Improved energy storage, via
Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 47

improved batteries or heat storage media, such as salt,

could extend the operating hours of solar thermal-based

electricity generating facilities. Improved heat engines

should raise the conversion efficiency of parabolic dish

systems.

To increase the market share of photovoltaic systems, cell

and module costs must decline and cell efficiencies must

improve. Improved concentrators may cost-effectively

bring more sunlight to the cells. Thin-film photovoltaic

cells, while less energy efficient, may prove far less

expensive and decrease average costs per kilowatthour.

Whereas current silicon cell manufacturing techniques

require many expensive production steps, thin-film

photovoltaics may allow spraying or otherwise depositing

semiconducting layers on flexible background materials,

which could significantly lower production costs. Module

costs are also considered prime targets for additional cost

savings.

Wind

The market for electricity generating technologies using

wind (Figure 5) will likely expand if costs continue to fall

and reliability continues to improve. Should efforts to

lower the costs of towers and blades prove fruitful,

significant overall cost reductions could result. Simi-larly,

if design problems of the past are overcome, reliability

should continue to improve and maintenance costs should

continue to fall. Success of the variable speed wind

turbine, which adapts to rapidly changing wind speeds,

could improve the reliability and the efficiency of wind

units. As with solar technologies, the market for wind

turbines could be helped by use of cost-effective energy

storage devices, which could increase system reliability

and provide energy during periods of low wind.
Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 49

Biomass and MSW

Because they employ mature generating technologies

used for fossil fuels, biomass- and MSW-powered

electricity generating technologies are not expected to

enjoy large additional breakthroughs that lead to marked

drops in production costs per kilowatthour. Of course,

experience will bring incremental reductions. For biomass

to make significantly greater contributions to the electric

power market, two objectives must be achieved: (1) a

dedicated feedstock (crop) must be developed and (2)

conversion technologies must be improved. Biomass

power stations depend upon the availability and variable

quality of forest and agriculture residues and waste

materials from the wood and paper products industry.

Development of a more effective fuel supply system is

critical to removing the current dependency. Biomass

facilities that burn wood will be affected by the rate of

growth of the parent industries, by alternative uses for

combustible wood waste, and in the future by crops

grown specifically for energy production. Growth in the

use of crops dedicated for energy use is also dependent on

demands for the use of land for other crops or other

purposes.

Three potential paths for energy conversion improvements are available to enhance the competitiveness of

biomass power: 1) improvements in direct combustion

systems, including both conventional and fluidized bed

boilers designed to handle biomass fuels; 2) development

of biomass gasification systems capable of producing a

gas suitable for firing combined gas and steam units; and

3) development of biomass liquefaction processes capable

of producing clean gas turbine fuels.

Several factors will probably loom large in affecting the

future growth rate of MSW. First, the rate of increase in

landfill costs, which determines the per-ton price paid for

accepting trash (tipping fee), will have a significant

influence. If more distant jurisdictions site new landfills at

prices lower than MSW combustion, MSW's opportunities

for growth will be reduced. On the other hand, new

requirements on landfills, such as regulations to install

liners and leachate management equipment, will serve to

raise landfill costs and make MSW plants

relatively more attractive. Similarly, if recycling reduces

the growth in landfill, prices paid to MSW plants could

suffer. Second, environmental objections and industry

responses to these objections could affect MSW expansion.

Despite industry efforts, community resistance to MSW

facilities occurs, both on aesthetic grounds and because of

concerns of known or feared pollutants.

Conclusion

From the beginning days of the electric power industry,

renewable resources have contributed significantly to U.S.

electricity supply. In recent years, hydroelectric

generating capacity growth has slowed. However, other

forms of renewable energy have begun generating electricity on a larger scale, with the result that renewable

resources today provide about 12 percent of U.S.

electricity supply.

Long-term projections indicate that the use of renewable

resources will continue to grow and continue providing

about 12 percent of U.S. electricity supply through 2010.

If technologies do not improve dra-matically and the

economy and energy markets remain structured

essentially as they are today, significant increases in

electricity generation from MSW, geo-thermal, and wind

generating facilities should increase their share of the

overall U.S. electricity market and offset reduced growth

of conventional hydroelectric power.

However, renewable resources could make even more

substantial contributions to future U.S. electricity supplies.

If the relative costs of generating electricity from

renewable resources should fall below generating costs

using fossil fuels, much greater expansions could occur.

Opportunities for such declines exist in achieving

technological advances in the generating technologies; if

recent rates of improvement can be sustained, certainly

greater contributions could be expected. At the same time,

if the costs of fossil fuels rise, either directly or because of

changes in taxes or subsidies, or because of penalties

imposed on them for environmental reasons, increased

electricity generation using renewable resources would be

more likely.
Appendix A

Assumptions
52 Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 

Appendix A

Assumptions

This appendix presents assumptions underlying projec- component computes the price of electricity, accounting

tions in the AEO93 for forecasts of renewable energy use for all costs of construction and operation.

in electricity supply. It also provides an introduction to the

general assumptions and modeling used for the AEO93,

particularly for electricity markets. A detailed discussion

of the assumptions and models underlying the Annual

Energy Outlook 1993 (AEO93) can be found in the EIA

report, Assumptions for the Annual Energy Outlook 1993.

19

AEO93 Forecasting System

The Energy Information Administration (EIA) projections

presented in the AEO93 were prepared using a collection

of individual computer models that forecast annual

production, supply, distribution, and consumption of

energy for the United States. These models produce an

integrated energy market forecast through the use of the

Intermediate Future Forecasting System (IFFS). As a

system, IFFS accounts for many interactions of the

different segments of the energy industries and provides

an internally consistent forecast of prices and quantities

for which supply equals demand.

In general, each of the supply models in the AEO93

Forecasting System determines the supply and delivered

prices for each fuel, given the consumption levels

projected by the demand models. Projections are

generated through the year 2010.

The Electricity Market Module (EMM) of the IFFS represents the supply and price of electricity and computes

the fuel requirements to generate electric power. A

planning component determines the capacity expansion

profiles of electric utilities, using a life-cycle cost

methodology and assumptions of future fuel prices and

electricity demand. A dispatch component allocates

generation capacity to meet current demand by ranking

the fuel and operating costs, subject to the constraints of

the Clean Air Act Amendments of 1990. The financial
Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 53

 Energy Information Administration, Assumptions for the Annual Energy Outlook 1993, DOE/EIA-0527(93) (Washington, DC, January 1993). 19

Production of electricity by cogenerators and by independent and small power producers is forecast by the

nonutility component (Nonutility Generation Supply

Model, NUGS), which competes with utility-generated

electricity at the avoided cost of the utility sector.

Renewable Resources in Electricity

Generation

Generating capacity and electricity generation for

technologies using renewable resources are determined

exogenously from the EMM and NUGS models. The

capacities are provided by technology type, region,

ownership category (electric utility and nonutility), and

whether they are announced or projected additions. The

announced additions for utility-owned capacity were

obtained from the Form EIA-860, “Annual Electric

Generator Report.” The announced additions for

nonutility-owned capacity were obtained from the Form

EIA-867, “Annual Nonutility Power Producer Report.”

Planned and projected capacities for municipal solid

waste (MSW) and wood generation were provided by the

Oak Ridge National Laboratory (ORNL). Appendix Table

A1 shows the projected renewable-fueled capacity, by

technology type and ownership.

These projections assumed passage of the Energy Policy

Act of 1992 (See Chapter 2). Incremental capacity in 2010

as a result of the Act are 1.5 gigawatts of wind-powered

capacity, 0.7 gigawatts of solar thermal, and 0.4 gigawatts

of geothermal generating capacity. 

Biomass (wood) refers to all forms of wood-related

material: logs, pellets, chips, sawdust, planer shavings,

bark, other wood scraps, and black liquor, a waste product

of the pulping process. A stand-alone econometric model

was used to develop estimates of wood consumption by

the industrial sector. The independent variables used in

the model are real GNP, electricity price, world oil price,

and lagged wood energy consumption. Additional

information about modeling
54 Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 

(Gigawatts)

Renewables

2000 2010

Utility Nonutility Utility Nonutility

Conventional Hydroelectric ................... 75.0 1.9 75.0 1.9

Wind . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.0 3.6 0.0 6.3

Solar Thermal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.1 1.2 0.3 1.7

Geothermal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.8 2.4 4.3 4.3

Photovoltaic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.0 0.0 0.0 0.0

Wood . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.4 7.3 0.5 7.6

Municipal Solid Waste . . . . . . . . . . . . . . . . . . . . . . . 0.5 6.2 1.0 10.4

 Total ................................... 78.7 22.5 81.0 32.1

 Note: Totals may not equal sum of components because of independent rounding.

 Source: Energy Information Administration, Office of Integrated Analysis and Forecasting.

Table A1. Projections of Utility and Nonutility Electric Capability for Renewable Technologies

wood energy use can be found in the report, Wood Energy

II, Forecasts of Regional Sectoral Wood Energy Consumption.

20

The energy contribution of municipal solid waste (MSW)

is dependent on post-consumer solid waste generated at

residences, commercial establishments, and institutions.

Excluded from this stream are automobile bodies,

demolition and construction debris, municipal waste

water sludge, ash from industrial boilers, and industrial

solid waste.

The forecasting approach for MSW follows four steps.

First, the total quantity of MSW in the United States is

projected. The current and future heat value of a typical

pound of MSW is assessed in the second step. The third

step addresses the total U.S. capacity to burn MSW with

heat recovery. National projections of energy from MSW

combustion are obtained by multiplying MSW quantity,

Btu value, and percentage of MSW combusted. The final

step disaggregates the national Btu totals into regional

and sectoral projections for electricity and other energy

forms.

Overall national totals on energy derived from MSW were

computed by estimating the expected quantity of MSW

based on real GNP, future heating value, and the share of

MSW being combusted versus recycled or landfilled.

Calculations of the portions of the overall totals used in

the industrial sector are made by using

individual unit data from Government Advisory Associates (GAA).21

The GAA data base includes data on average operating

throughput, design capacity, average Btu per pound of

MSW, and type of energy produced. Plants producing

only steam or electricity are tabulated separately to

compute the dispersed and nondispersed energy. In

plants producing both steam and electricity, the amount

of MSW used for electricity generation is estimated by

taking into account the GAA data on kilowatthour per ton

of MSW processed and the power output rating of each

plant. The amount of electricity sold to the grid versus that

used in-house is calculated using the “gross” and “net”

ratings provided in the data base. The Btu for steam and

electricity for each plant are totaled for all plants and

proportions are calculated on a regional basis, then

applied to develop national totals. 

The major source of renewable energy for electricity is

hydroelectric power. Capacity for the conventional

hydroelectric and pumped storage facilities is assumed

not to vary across scenarios. Overlapping regulatory

processes, conflicting requirements for licenses and

permits, and disagreements over environmental issues

have constrained the development of hydroelectric power

plants. Additions to hydroelectric generating capability

have been small during the 1980's and are not likely to

increase significantly in the foreseeable future.
Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 55

 Oak Ridge National Laboratory, Wood Energy II, Forecasts of Regional Sectoral Wood Energy Consumption (1990-2010), ORNL/TM-12009 (Oak Ridge, TN, October 20

1991).

 Government Advisory Associates, Inc., Resource Recovery Yearbook, 1991. 21
56 Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 

(Percent)

Technology 1995 2000 2005 2010

Hydroelectric . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46 46 46 46

Geothermal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 76 82 83

Municipal Solid Waste . . . . . . . . . . . . . . . . . . . . . 40 42 46 54

Biomass/Other Waste . . . . . . . . . . . . . . . . . . . . . 72 79 82 83

Solar Thermal . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 19 21 22

Solar Photovoltaic ........................ 0 0 0 0

Wind . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 29 29 29

 Source: Energy Information Administration, Office of Integrated Analysis and Forecasting.

Table B1. Average Annual Capacity Factors for Generating Technologies Using Renewable Resources

The expansion of the other renewable resources (geothermal, wind, and solar thermal) are determined mostly

by location of the resource, technological limitations,

environmental requirements, and tax treatments of

various projects. Although assumptions about economic

growth and world oil prices are not the primary factors

driving the development of most renewable energy

sources, these variables are assumed to have impacts on

the projections of MSW and wood.

Capacity Factors

The capacity factors (the proportion of maximum annual

generation a unit is expected to produce) for electricity

generating technologies using renewable resources are

shown in Appendix Table A2. They are based on

historical performance. The capacity factors are assumed

to improve over time with technological advancement

from ongoing research and development.

Costs

Costs for technologies using renewable resources are

included in the EMM only to measure contributions to

overall electricity costs, not for economic competition with

other technologies. Their cost is accounted for in electricity

pricing as an operating expense. The annual expense is

determined as the amount of renewable generation times

a rate equal to the average cost of nonutility generation

sold to the grid. The nonutility renewable energy price is

assumed to be 3.5 cents per kilowatthour (1991 dollars).

EIA Alternative Case Assumptions

In the High Economic Growth Case, capacity projections

for hydroelectric, geothermal, solar thermal, and wind are

the same as the Reference Case. However, higher

economic growth causes more waste generation leading to

its greater use in MSW plants and thus additions to

capacity. Similar relationships are assumed to hold in the

paper and lumber industries, which cause higher

estimates for wood-fueled facilities.

In the Low Economic Growth Case, the capacity projections for the conventional hydroelectric, geothermal,

solar thermal, and wind are the same as the Reference

Case. However, lower economic activity causes less waste

generation and less activity in the paper and lumber

industries, thus lowering the need for additional capacity

in these areas. 

In the High World Oil Price Case, capacity projections for

conventional hydropower, municipal solid waste, and

wood are the same as in the Reference Case. However,

high world oil prices, which are associated with higher

electricity demand, result in slightly higher geothermal,

solar thermal, and wind capacity than in the Reference

Case.

In the Low World Oil Price Case, capacity projections for

conventional hydropower, municipal solid waste, and

wood are the same as in the Reference Case. However,

low world oil prices, which are associated with lower

electricity demand, result in slightly less geothermal, solar

thermal, and wind capacity than in the Reference Case.
Appendix B

Renewable Resources

for Electricity Generation
60 Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 

Figure B1. U.S. Conventional Hydroelectric Generating Capacity, Developed and Undeveloped

(Gigawatts) 

 Source: Federal Energy Regulatory Commission, Hydroelectric Power Resources of the United States, Developed and Undeveloped, FERC0070 (Washington,

DC, January 1992).

Appendix B

Renewable Resources for Electricity Generation

The economic use of any resource for electricity gener- precipitation falling on the United States as the water

ation is affected by its characteristics. The purpose of this flows to sea level, with adjustments for evaporation and

appendix is to provide basic information on the physical consumption.

aspects of renewable resources which affect their

performance in the electric power market. The appendix

presents the basic characteristics of the five major forms of

renewable energy (hydropower, geo-thermal, solar,

biomass and waste, and wind).

Hydropower

Water resources (hydropower) for electricity generation

(hydroelectricity) are the product of water volume and

vertical drop. The total resource base for hydroelectric

power consists of all the potential energy contained in

Hydropower resources are not evenly distributed across

the Nation but are generally concentrated where both

precipitation and mountain altitudes combine to pro-vide

large water volumes. The Nation's most favorable

hydropower regions are in the Northwest, West, and

Southeast, although some major facilities are located in

other areas. According to estimates prepared by the

Federal Energy Regulatory Commission (Figure B1), over

40 percent of the Nation's 146 gigawatts of developed and

undeveloped conventional hydroelectric capacity is found

in California, Oregon, and Wash-ington alone.

Additional generating capacity needs
Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 61

 Energy Information Administration, Annual Energy Review 1991, DOE/EIA-0384(91) (Washington, DC, June 1992). 22

 For additional information on U.S. hydropower resources, see Hydroelectric Power Resources of the United States, Developed and Undeveloped, published by the 23

Federal Energy Regulatory Commission, FERC-0070, (Washington, DC, January 1988).

would more likely be able to be met by hydroelectric Development of other categories of geothermal resources

power in these regions. It is much less likely that major depends on development of new and improved

new hydroelectric facilities could cost-effectively com-pete technology and on water availability. A large resource of

in regions with fewer resources, such as across the geopressured fluids exists along the Gulf Coast of the

Nation's heartland. southern United States, in conjunction with petroleum

Although large storage dams can extend some fraction of methane along with the pressurized hot water. If

total water availability for years, most water must commercial technology emerges to utilize geopressured

ordinarily be used for electricity generation within a few resources, development would be possible in Texas and

days or months of arrival. Therefore, changes in annual Louisiana, as well as in other petroleum producing states

precipitation can dramatically affect the total volume of and off-shore areas. Technology using hot dry rock could

hydroelectric production. After reaching a record 332 extend develop-ment of geothermal resources across the

billion kilowatthours net generation in 1983, for example, entire United States. However, growth in the use of hot

the United States' net hydroelectric generation (including dry rock resources, many of which are in the arid West, is

pumped storage) dropped to 223 billion kilowatthours in dependent upon gaining access to water supplies for

1988. The tremendous variation between the two years injection into the hot dry rock. The geographic distribution 22

represents differences in precipitation. of potential magma resources is only speculative at this

Hydroelectric demands must also compete with other portion of the United States.

needs, e.g., irrigation, drinking, navigation, flood control,

recreation, and environmental priorities. Often, multiple

demands can be met; however, conflicts can occur,

resulting in foregoing dam construction altogether or in

less-than-maximum electricity generation.23

Geothermal

Geothermal resources (Figure B2) account for the largest solar energy reaching any point on the earth (insolation)

portion of the total energy resource base. Unfortunately, vary with changing atmospheric conditions (clouds, dust),

most geothermal energy is trapped below the earth's outer the changing position of the earth relative to the sun, and

crust, well below current economic drilling access. Of four solar conditions (sunspots, flares). Insolation is greatest in

resource categories—hydrothermal (heated water, liquid, the West and Southwest, where atmospheric conditions

and vapor), hot dry rock, geopressured, and are favorable (Figure B3). Average direct-beam solar

magma—only hydrothermal resources are currently being radiation in parts of Nevada is more than twice that found

exploited on a commercial basis. Hydrothermal reservoirs through most of the eastern States or in the Northwest.

are located primarily in the western United States, with Nevertheless, all regions possess useful solar resources.

the most easily accessible high-temperature resources

being in California, Nevada, and Utah. The four States Even so, solar energy also faces limitations for electricity

reporting geothermal electricity production in 1990 were conversion. Solar energy is very dispersed (scattered),

California, Nevada, Utah, and Hawaii, where relatively which increases its cost for electricity generation.

recent geologic activity (creating shallow and accessible Furthermore, solar energy is often not available at low

high temperature sites) has occurred. However, these cost during times of need. Unless storage devices are

resources are frequently remote, so environmental impact employed, solar opportunities decline with each sunset

and transmission costs and access become significant and with increases in cloud cover, limiting applications

issues. for power applications.

reservoirs, where geopressured water contains dissolved

point, but prospects are probably the best in the western 24

Solar

Solar energy is energy received from the sun. For energy

purposes, solar energy generally refers to solar radiation

and not to solar energy converted to organic matter

(biomass). Outside the earth's atmosphere the rate of solar

radiation is nearly constant. However, the amounts of

25
62 Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 

 For additional information on U.S. geothermal resources, see Geothermal Energy in the Western United States and Hawaii: Resources and Projected Electricity 24

Generation Supplies, published by the EIA in September, 1991 (DOE/EIA-0544).

 For additional information on U.S. solar resources, see Solar Radiation Resource Assessment - An Overview, (SERI/SP-220-3978) published by the U.S. Department 25

of Energy Solar Energy Research Institute (now the National Renewable Energy Laboratory), November, 1990. 
Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 67

demand centers to be economically useful as a generating Just as with other renewable resources, winds are not

fuel. It is currently unlikely that crops farther than 50 uniformly distributed (Figure B5). Winds are charactermiles from a demand center would be cost effective for ized by wind-power density classes, ranging from class 1

electricity generation. MSW offers energy producers a (the lowest) to class 7 (the highest). Good wind resources,

distinct advantage in that municipalities pay producers to class 4 and above, with an average annual wind speed of

take the waste (tipping fees). Nevertheless, the additional at least 13 miles per hour, can be found in many regions

costs of handling MSW, both for combustion and for of the country. Wind speed is a critical feature of wind

residue disposal, significantly raise the costs of producing resources, because the energy in wind is proportional to

electricity from such sources. Furthermore, where landfill the cube of the wind speed. Many regions of the country

space can be obtained less expensively, tipping fees may enjoy at least some good wind resources. Only the

be inadequate. As a result, MSW resources are most likely Southeast and parts of the Midwest lack significant

to be used for electricity production where large volumes resources. 

of trash cannot be landfilled at lower cost.

Wind

Wind resources provide kinetic energy in an air medium.

Winds are created by changes in atmospheric pressure

induced by changes in earth and atmospheric

temperature. Wind is also affected by the earth's rotation

and by frictional encounters with the earth's topography.

Uses of wind for electric power generation are constrained by a number of factors. Because of the

uncertainty attending wind occurrences and intensity,

winds are not generally considered sufficiently reliable as

to guarantee performance. Because winds cannot be

stored (unless batteries are used), not all winds can be

harnessed to meet the timing of electricity demands.

Further, winds are often located far from electric power

demands. Finally, wind resources compete with other uses

for the use of land; alternative uses may be preferred for

some sites. Environmental objections include visual and

noise pollution and impacts on birds.27
Appendix C

Electricity Generating 

Technologies Using

Renewable Resources
Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 73

Appendix C

Electricity Generating Technologies Using 

Renewable Resources28

Many techniques are used to convert renewable resources pool back into an upper storage facility for peak power

into electricity. These techniques differ from those used electricity generation.

for fossil fuels to access, prepare, store, handle, and

dispose of the resources. The principal differences occur

in the process of converting the resource to mechanical

power in the turbine and in waste disposal. Aside from

conversion and waste disposal, except when photovoltaics

are used, the actual process of generating electricity is

usually almost identical with electric generation using

fossil fuels. Continuing advances in technology are

lowering the costs of renewable energy use, making it

more competitive with fossil fuels. This appendix presents

the technologies currently using renewable resources

(hydropower, geothermal, solar, biomass and waste, and

wind) to generate electricity. In particular, each section

notes whether each technology is most appropriate for

baseload (able to operate at all times), peaking (able to

operate at times of greatest demand), or intermittent (able

to operate less than all the time and not necessarily at

peak) operation.

Hydroelectricity

Hydroelectricity is obtained when water is directed

through a rotary turbine connected to an electric

generator. The kinetic energy in the falling or moving

water is converted to mechanical energy by the turbine

and then to electricity by the generator. The water can

come from many sources—rivers, streams, canal systems,

or reservoirs. Hydropower projects are typically classified

as either conventional or pumped storage. Conventional

hydroelectric facilities pass water through the turbines

once and discharge into the waterway; pumped storage

facilities repeatedly recycle water, and use low cost, offpeak (usually night-time) electricity generated by other

fuels to pump discharged water from a lower retaining
74 Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 

 Much of the information presented in this appendix was assembled for the Energy Information Administration by Science Applications International 28

Corporation (SAIC), “Technical Report Preparation, Final Report,” (McLean, Virginia, July 1992).

Because pumped storage plants are essentially energy

storage facilities for fossil or nuclear power, the renewable

resource application of hydroelectric power covers only

conventional hydropower options.

Figure C1 shows a conventional hydroelectric plant. The

electricity generation potential of a site is proportional to

the vertical drop (head). Driven by the force of gravity,

water enters the dam through large screened gates and

flows down a pipe, called a penstock, to reach the turbinegenerator system. The turbine blades are connected to a

shaft which converts the kinetic energy in the water into

mechanical shaft power. Water exits the turbines through

another pipe, called the draft tube, into the tail waters.

Regulations such as the Public Utility Regulatory Policies

Act (PURPA), affect the classification of conventional

hydroelectric plants. For instance, PURPA classifies all

hydropower generation plants with a capacity equal to or

less than 30 megawatts as small and all plants with a

capacity greater than 30 megawatts as large. Sometimes

hydroelectric projects are referred to as mini-hydro

(capacity of less than 1 megawatt) or micro-hydro

(capacity of less than 100 kilowatts (kW). The U.S.

Department of Energy (DOE) defines low-head

hydroelectric plants as those with 20 meters of head or

less.

Conventional hydroelectric plants are categorized into

three types: storage, run-of-river, and diversion. The

geographic and hydrological characteristics of specific

sites determine the appropriate type of hydroelectric

development. Storage plants feature reservoirs created

from incoming stream flow. These plants are typically

multipurpose facilities, designed for flood control, water

supply, irrigation, and recreation, as well as electricity

generation. (A reservoir management plan dictates water

uses during the year.) Storage facilities make excellent

baseload and peaking plants. Their high capital and low

operating costs make them most cost
76 Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 

effective when continually used. However, increasingly projects on large rivers can produce several hundred

they are also being used for peaking power because they megawatts of electric power. Run-of-river projects are

can be started or stopped quickly and inexpensively. As typically operated as baseload capacity, running

a result, hydroelectricity's flexibility in meeting both continuously when sufficient water is available. In lowbaseload and peak demands makes it attractive for utility water seasons (i.e., seasons with little precipitation) such

applications. units can run as peaking capacity if they employ some

Run-of-river plants use natural streamflow for power

generation, although a small dam is used to increase head Diversion, or conduit, plants involve a man-made chanin a run-of-river project. The rate at which water flows nel or aqueduct of sufficient slope to create enough head

into the “headpond” upstream from the dam roughly to drive the turbine. Some of these structures are built

equals the flow rate of water through the plant. Therefore, solely for hydroelectric power, although many diversion

such projects impound little or no water. At some projects, projects are located at existing irrigation or municipal

only a portion of the flow is diverted to the turbines. Other water supply conduits. Diversion projects usually have no

plants employ “pondage,” a practice that impounds water storage capacity; however, some projects have reservoirs,

behind the dam to store enough energy to shift maximum which provide storage capacity.

power output to peak electric demand hours. Run-of-river

plants tend to be smaller than reservoir storage projects, Hydropower facilities primarily use three kinds of

although run-of-river turbines (Figure C2). The simplest and the smallest

pondage.
78 Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 

Figure D1. Geothermal Electricity Generating System for Vapor-Dominated Hydrothermal Resources

 Source:

Petroleu

m

Informati

o n

Corporati

on, The

Geother

mal

Resource

, (A.C.

Nielsen

Co.,

1979).

turbine is the Pelton wheel, which is found in small, high technologies. Because the generating plant technologies

head plants. Water jets sequentially strike the concave are not unique, only the resource handling features are

blades (buckets) of the turning wheel, rotating the discussed here.

attached shaft in the generator. The other two turbines, the

Kaplan and the Francis, are featured in larger facilities. A

Kaplan turbine resembles a ship's propeller. Water from

the penstock strikes the blades, turning the turbine shaft.

A Francis turbine resembles a fallen-over waterwheel. In

a Francis turbine, water from the penstock completely

surrounds the turbine and provides a constant pressure

around the wheel. Fixed or adjustable openings called

wicket gates control the water flow. Water strikes the

turbine blades, transfers its energy to the blades and exits

through the turbine's middle.

Geothermal

Geothermal generating technologies can be divided into

two broad categories: (1) resource handling technologies

for access, production, conversion, return, and injection of

geothermal fluids, and (2) generating plant

Hydrothermal (heated water) resources are formed when

water, trapped in fractured rock or sediment below the

surface, is heated. Technologies using hydrothermal

energy are the most technically advanced and cost

competitive of all the geothermal energy types, and

hydrothermal energy is the only geothermal resource

developed commercially in the United States. In 29

hydrothermal reservoirs magma intrusions heat the water,

turning it into steam or high-temperature water.

Vapor-dominated hydrothermal resources (dry-steam)

employ the simplest production technology now being

used. Steam flows through a well from the geothermal

reservoir to the surface and is piped directly to the steam

turbine (Figure C3). The most prominent example of this

technology is at The Geysers in Northern California,

where most of the U.S. electricity currently attributed to

geothermal resources is produced. Scaling
80 Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 

and corrosion of the turbine and other surface equip-ment The binary-cycle system (Figure C6) incorporates two

is reduced by removing corrosive gases before the steam distinct fluid loops, with the heat of the geothermal fluid

enters the turbine. The waste steam is condensed and in the first loop being transferred to a low boiling point

injected back into the reservoir. working fluid in the second loop. The geothermal fluid

Liquid-dominated hydrothermal resources can be used to which rapidly vaporizes. The vaporized working fluid

generate electricity by using any of three technologies: drives the steam turbine. After condensing, the working

single flash, double flash, or binary. In a single-flash fluid is returned to the heat exchanger to begin a new

system (Figure C4), hot water produced from wells is cycle. The used geothermal fluid is injected back into the

allowed to boil (flash) in a boiler by lowering its pressure reservoir to help maintain reservoir pressure. This system

in a separator. The resulting steam is fed directly into a is chosen primarily when the geothermal resource

turbine. The remaining liquid (brine) is injected back into contains high levels of dissolved solids and corrosive

the reservoir, along with the condensed waste steam. liquids or when the resource temperature is too low for a

In a double-flash system (Figure C5), a second separator

is added to extract more steam. The water remaining after Geothermal generating facilities are typically baseload.

the first-stage separation is flashed once more in the Given the high capital costs of exploratory drilling, such

second-stage separator at a lower pressure than in the first plants make best economic sense when operated a high

stage. The two steam stages are used to turn a turbine portion of the time. However, experiments are being

which has both a high and low pressure stage. This conducted to test the ability of hydrothermal resources

additional step makes double-flash systems 10 to 20 operating in a part-time or load-following mode. This

percent more efficient than single-flash systems. would help conserve the pressure reservoir in areas of

transfers its heat to the working fluid (such as isobutane),

flash process to operate efficiently (300 - 400 F). o o

pressure decline, such as The Geysers.
84 Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 

Biomass

Biomass is subdivided into three categories: wood

(fuelwood, wood byproducts and waste wood), waste

(municipal solid waste and manufacturing process waste)

and biofuels for transportation. Electricity generating

technologies using biomass are similar to fossil fuel

burning steam plants because fuels are combusted in a

boiler to produce steam to drive a conventional steam

turbine. The primary differences between the technologies

occur in fuel storage, handling, preparation, and waste

disposal.

Biomass/Wood

Historically, utilities and industry have used direct

combustion-steam boiler and steam turbine technologies

to generate electricity from biomass resources. The

technologies use components (steam boilers, steam

turbines, etc.) similar to those found in coal-fired

electricity generation plants. As a result, biomass fuels can

be used for either baseload or peaking applications. The

differences between coal-fired and biomass-fired

generation requirements arise from differences in the

fuels. For instance, biomass/wood differs from coal in

moisture content. Also, biomass/wood and coal fuels

differ in content of nitrogen and sulfur compounds that

can lead to nitrogen oxides (NO ) and sulfur oxide (SO ) x x

emissions; thus, requirements for environmental control

technology differ.

Direct combustion systems can burn a variety of bio-mass

feedstocks—including chunk wood, chips, bark, wood

pellets, and sawdust—to supply heat to steam boilers.

Biomass/wood-waste electric generation systems are

differentiated by the type of burner used to combust the

biomass. The four kinds of burners used to produce boiler

heat are pile burners, spreader stokers, suspension and

cyclone burners, and fluidized bed combustors. The most

commonly used biomass combustion configurations are

the pile burner and the spreader-stoker. Feedstock 30

particle size and moisture content are critical parameters

for direct combustion systems. Feedstock moisture content

must not exceed 60 percent.31

Direct combustion systems require facilities for handling

the biomass feedstock that is to be combusted and for

removing the ash produced from combustion. Feedstock

must be stored on-site, properly sized for the

combustor, screened to remove non-combustibles, and

conveyed to the burning system. Feedstock is stored onsite in open piles, bins, silos, or drying barns. The biomass

fuel must be protected from absorbing excess moisture.32

Feedstock is sized for use in the combustor either prior to

storage or prior to burning. Common sizing technologies

include hammermills, chippers, grinders, and saws. Prior

to moving the feedstock to a silo that feeds the combustor,

the feedstock is screened to remove any noncombustible

matter. Wood or other biomass wastes are stored on-site.

From a storage silo or bin, the fuel is moved by a conveyor

or other fuel handling system to a metering bin that feeds

the fuel to the boiler at the proper feed rate. The feed

system includes grates to do final wood sorting, sizing,

and removal of non-combustibles. The stoker moves the

feedstock to fixed or moving grates on which the

feedstock is burned. For ash removal the combustion

chamber is secured periodically to remove the

accumulated ash. Once collected, the ash is disposed of in

a landfill.

Combustion of the biomass feedstock occurs in the boiler

(Figure C7). The heat from the combusted biomass is

transferred to water in the boiler pipes, producing steam

for the turbine. Waste steam is sent to a cooling tower,

where it is condensed into water.

Pile and spreader-stokers directly combust biomass to

produce energy. Both technologies burn large-particle

biomass. These stokers are used to provide baseload

electricity because the time needed to burn large particle

size fuel and the rate of heat generation cannot be

adjusted quickly enough to use them for intermediate or

peak power generation. In the boiler combustion chamber,

the wood is suspended on grates, where it is burned.

Different grate system designs lead to four boiler

combustion options: pile burners include incline grate

systems, traveling grate spreader-stokers, fixed grate

spreader-stokers, and dumping grate spreader-stokers.

Cyclone and Suspension burners (Figure C8) combust

biomass mixed in a turbulent stream of air. Particulate

biomass for suspension and cyclone burners must be less

than 0.25 inches in size and have a moisture content of less

than 15 percent. The air-biomass mixture improves 33

combustion efficiency relative to pile burners or spreaderstokers because the surface area of biomass exposed to

oxygen in the air is increased.
Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 85

 California Energy Commission, Energy Technology Status Report, 1988. 30

 United States Biomass Industries Council, The Biofuels Directory, March 1990. 31

 United States Biomass Industries Council, The Biofuels Directory, March 1990. 32

 The U.S. Export Council for Renewable Energy, Private Financing for the Power Sector: The Renewable Energy Option, June 1989. 33
86 Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 

Figure H1. Biomass Electric Generation System

 Source: U.S. Export Council for Renewable Energy, Private Financing for the Power Sector: The Renewable Energy Option, June 1989.

These technologies have the power generation output The fluidized bed combustor (Figure C8) is a combustion

control needed to provide baseload and peak power chamber containing a medium, such as sand or limestone,

needs, since the rate of heat output from such combustion that is suspended in the chamber by hot air. Biomass

systems can be controlled and timed by adjusting the fuel feedstock with a wide variety of size, shape,

feed rate.

The suspension burner mixes particulate biomass in an air

stream over the main fuel bed in the combustion chamber.

The mixing increases combustion surface area, thereby

increasing combustion efficiency. Before the particulate

biomass enters the combustion chamber, the cyclone

burner mixes it with an air stream. The resulting turbulent

mixture is burned in the combustion chamber. In both the

suspension and cyclone burner configurations, the heat

from combustion is transferred to water circulating

through the boiler tubes. The rest of the electricity

generation process is the same as that described above for

the pile and spreader-stoker burners.
Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 87

 California Energy Commission, “Energy Technology Status Report,” 1988. 34

and moisture content specifications can be combusted in

a fluidized bed. Combustion is rapid and efficient because

of the high surface area exposed to air and because of the

heat held in the medium. Heat is transferred to the water

in the boiler tubes in the combustion chamber to generate

steam. The resulting steam flows through a steam turbine

to generate electricity.

Fluidized bed combustors are environmentally favorable

technologies. The limestone in a fluidized bed reacts with

combustion-generated sulfur dioxide (SO ) to form 2

calcium sulfate, a solid waste (gypsum) that can be

handled and disposed using established procedures.

Additionally, low combustion temperatures in fluidized

beds (1,500 F to 1,600 F) result in lower nitrogen oxide o o

production.34

Municipal Solid Waste (MSW)

Municipal solid waste-to-energy facilities are usually less

than 80 megawatts in size. They can serve the
Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 89

electricity market as either baseload or peaking facilities.

The plants are usually located near urban load centers.

Some cogenerate electricity and industrial steam; during

peak hours, steam services can be reduced and electric

power increased.

Energy can be recovered from municipal solid waste

(MSW) through mass burning of unprocessed MSW;

burning of refuse-derived fuel (RDF), which is derived

from unprocessed MSW by removing noncombustible

material; and burning of methane gas mined in landfills.
90 Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 

Mass burn facilities (Figure C9) burn MSW as a boiler In an RDF-fired fluidized-bed boiler, combustion takes

fuel. First, the MSW is received at the plant site and place within a sand and ash bed supported by a strong

stored. Minimal processing prior to combustion usually turbulent stream of air. This strong forced convection

involves removal of materials that are oversized and causes the RDF, sand, and ash combination to behave

difficult to combust, such as mattresses and large tree similar to a liquid throughout the combustion process,

stumps. The MSW is next transferred from the receiving which occurs in suspension. The forced turbulence within

area to a refuse fuel pit and then to a refuse feed hopper the combustor creates a relatively even temperature

that feeds the boiler. Boiler temperatures exceed 2000 F. distribution and high heat transfer rates. The heat storage o

The waste steam is condensed and sent to a cooling tower properties of the sand bed allow a fluidized bed boiler to

where its temperature is lowered through evaporation smooth the operating temperature range in the system,

before it is released into the local water supply. The mass which could otherwise fluctuate because of the different

burn system releases combustion gases and ash. The heat contents of various non-homogeneous RDF sources.

combustion gases must be subjected to flue gas cleaning

in a scrubber to remove toxic substances and gaseous

pollution. Treatment also involves an electrostatic

precipitator or fabric filter to remove particulates from the

waste combustion gas. Finally, ash residue must be

hauled away and disposed of in landfills, some of which

are designed specifically for ash.

Refuse-derived fuel (RDF) is MSW after varying degrees

of waste separation and size reduction (Figure C10).

Noncombustible materials (e.g., glass, metals), which

represent as much as 30 percent of the original MSW, are

removed. Conversion to RDF next includes various stages

of shredding, crushing, and material separation using

sorting screens, magnetic separators, and cyclone

separators. Further processing includes shredding, then

screening out the oversize material via trommel (box) or

disk screens, and removing the ferrous components via

magnetic separation. Oversized material can be returned

to the shredder for reprocessing or discarding. The

remaining refuse is RDF. It has a uniform particle size,

moisture content, and heating value that is desirable for

stable combustion in boilers, easier storage, and

economical transportation. RDF also possesses a higher

energy value per pound than unprocessed MSW.

The RDF can be burned in a dedicated RDF boiler to

produce steam that drives a steam turbine-generator to

produce electricity. The steps from RDF combustion in the

boiler to steam turbine generated electricity are very

similar to the process described for MSW mass burn

facilities (Figure C9). The RDF can be combusted in

spreader-stokers, in multi-fuel suspension, and in

fluidized bed boilers. Dedicated RDF boilers have

typically been designed with traveling grate spreaderstokers.

Landfill gas results from the digestion by anaerobic

(oxygen free) bacteria of MSW in landfills. This digestion

produces a gas that contains methane, carbon dioxide, and

other trace products. Landfill gas is collected through a

network of porous pipes in wells in a landfill (Figure C11).

The gas is filtered and compressed before it is used as a

fuel for a gas engine, gas turbine, or steam boiler.

Solar

Solar technologies collect the sun's energy to generate

electricity. Solar technologies are separated into two

categories by the type of energy used: solar thermal for

heat energy and photovoltaic for radiant energy.

Solar Thermal

Solar thermal technology encompasses a group of mirror

options that use sunlight as a heat source in the process of

creating steam. To concentrate sunlight effectively, the

reflective surfaces for each solar thermal technology are

designed to track the movement of the sun, either only

vertically or horizontally (single-axis tracking), or both

(dual- axis tracking). The heat generated by the

concentrated sunlight, attaining temperatures in the range

of 3600 F, is transferred to a working fluid (e.g., water, or o

oil, salt). The heat transforms the working fluid into

steam. The steam drives a steam turbine-electric

generator. Waste steam is condensed and returned to the

collector to absorb more heat. Alternatively, the heat

absorbed by the working fluid can be used to drive a heat

engine/electricity generation system (e.g., parabolic dish

systems with Stirling engines).
Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 91

Parabolic trough systems act as primary heaters for boiler

steam. A parabolic trough receiver (Figure C12) is a

single- axis tracking collector that concentrates sunlight

onto a receiver tube positioned at the focal line of the

trough. A working fluid (e.g., water or oil) flows through

the receiver tube and absorbs the heat. The
96 Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 

Figure C13. Parabolic Dish System

heated fluid is transported to a central facility to generate expansion causes it to push a piston that drives the shaft

electricity, either directly or for supplementary heating, of an electric generator to produce electricity. The

and is used in a steam turbine. The parabolic trough expanded fluid is then cooled (condensed). When the

technology has been operated in a hybrid mode using a working fluid is cooled, it occupies less volume. The

natural gas-fired heater as a supplementary heat source piston moves back into place, compressing the fluid into

that boosts the temperature of the working fluid. The a smaller volume. The cycle repeats as the heat from the

natural gas heat supplement allows the parabolic trough concentrated sunlight expands the working fluid and

system to operate during periods when sunlight is condensation reduces it.

insufficient.

Parabolic dishes (Figure C13) use dual-axis tracking to working fluid from the focal point to a central electricity

focus sunlight onto receivers located at the focal point of generation station. Solar One, a 10-megawatt pilot plant

each dish. Each dish is limited by the structural near Barstow, California, funded by both the Department

requirements of the movable dish to an electricity of Energy and an industry consortium, generated

generation capacity of 10 to 50 kilowatts. Heat engine- electricity from 1982 to 1988. Central receiver systems

electric generators mounted at the receiver focal point (Figure C14), such as Solar I, use fields of dual-axis

convert solar heat to electricity. The heat engine currently tracking mirrors (called heliostats) to reflect sunlight onto

being developed is the Stirling engine. A Stirling engine a single, tower-mounted central receiver. The central

contains a working fluid that expands when heated by receiver contains a heat transfer fluid for steam

the concentrated sunlight. The fluid production.

An alternative to the heat engine is transporting the
Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 99

Solar thermal generating units are most efficient during photovoltaic cell, the photon may transfer enough energy

times of peak sunlight. As a result, solar thermal to an electron to free it from its position

technologies are not baseload, but peaking technologies.

However, the introduction of energy storage media could

extend solar thermal applications beyond peak hours.

Photovoltaic

Photovoltaic system technology utilizes semiconducting

materials to convert radiant energy (sunlight) into

electricity. It is the only technology that does not convert

renewable resource energy into mechanical energy to

generate electricity. Power is obtained through direct

conversion of radiant energy without moving parts and

emissions. Although photovoltaic systems are most

efficient during peaking hours of sunlight and are

basically viewed as sun-correlated peaking units, these

technologies produce electricity even under reduced

lighting conditions.

Figure C15 illustrates the technology elements in a

photovoltaic system. The basic unit in a photovoltaic

system is a solid-state device called the photovoltaic, or

solar, cell. Solar cells are composed of semiconducting

materials that produce electricity when sunlight is

absorbed. Photons striking a solar cell are reflected or

absorbed by the cell, or they pass through the cell. The

absorbed photons transfer energy to the cell. Several

photovoltaic cells are interconnected and mounted on a

support backing to form a photovoltaic module. Several

modules can be interconnected and mounted together to

form an array. The modularity of photovoltaic systems

makes it possible to design systems to meet a variety of

sizes of electric load. The electricity generated by a

photovoltaic array is in the form of direct current (DC).

Power conditioning equipment, the primary balance of

system component in a photovoltaic system, is used to

transform the DC electricity into alternating current (AC)

and to protect the utility transmission network. From the

power conditioner, electricity may be used directly or

transmitted by power lines to meet the electricity

requirements of end-user loads. Electricity may also be

stored in batteries for future use.

The single crystal silicon photovoltaic cell provides a

simple model for understanding the photovoltaic effect. A

single crystal silicon photovoltaic cell is composed of a

symmetrical lattice of silicon atoms each sharing electrons

with four neighboring silicon atoms. When a photon of

sunlight is absorbed by a single crystal silicon
100 Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 

in the crystal lattice. The space left by the freed electron is absorption. A back-contact electrode is laminated to the

called a “hole.” The electron is now free to move in the bottom of the cell.

crystal lattice.

An electric current is generated in the photovoltaic cell by

bringing together a semiconductor that has a tendency to

be positively charged with a semiconductor that tends to

be negatively charged. The single crystal silicon cell is

actually a sandwich of two different types of silicon, ntype (negatively charged) and p-type (positively charged)

silicon (Figure C15). When p-type and n-type silicon are

put together, an electric field forms where the layers meet.

This is the p-n junction. Free electrons and holes are

attracted to each other by their opposite charges; their

mobility allows them to move across the p-n junction,

creating an electric field. When light (photons) at a

sufficient energy level is absorbed by the photovoltaic cell,

an electron-hole pair is created. Photovoltaic cells are

constructed so that these pairs can move into the electric

field at the p-n junction. This movement creates an electric

current. If an external circuit is connected to the cell,

electrons can flow through the circuit to get from the ntype silicon to the p-type silicon to combine with holes on

the p side. This process enables photovoltaic cells to

provide electricity for external loads.

Photovoltaic technology options can be divided into two

categories: cell technology and module/array technology.

Photovoltaic cell technology includes single crystal (si)

silicon, semicrystalline silicon, polycrystalline silicon,

polycrystalline thin-film, and amorphous silicon.

Photovoltaic module/array technology includes flat plate

and concentrator technology.

The most common photovoltaic cells commercially

available today are made from Si wafers, which are

produced from single crystal Si ingots. Figure B16 shows

the structure of a single crystal silicon cell. Production of

a photovoltaic cell starts with a seed crystal, which is

dipped into molten silicon and withdrawn slowly to form

a cylindrical single crystal silicon ingot. The ingot is sliced

into thin wafers. The single crystal silicon wafer is

converted into a cell by layering: (1) a thin layer of silicon

(usually n-type) about one millionth of a meter thick

(referred to as the collector) and (2) a silicon base layer

(usually p-type), placed opposite the collector. When

these layers are joined, a p-n junction is formed. An

electricity conducting grid is added on top of the njunction layer. The grid and silicon cell surface are

covered with nonreflective coating to maximize sunlight
102 Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 

each crystal grain, electric charges move freely and between two grains, where free electrons and holes are

produce electrical current flow at the boundary likely to combine and produce electricity. Conversely,

polycrystalline cells are made of multiple crystals, or

grains, which form the body of the cell. The single crystal

grains are about 40 to 100 microns in diameter.
Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 103

 Source: Solar Energy Research Institute, Photovoltaic Fundamentals, SERI/TP-220-3957, September 1991.

Figure D1. Photovoltaic Cell Materials

Polycrystalline thin-film cells are composed of materials of randomly arranged noncrys-talline silicon material

such as gallium arsenide (GaAs), copper indium deposited on glass or other

diselenide (CuInSe ), and cadmium telluride (CdTe). 2

Thin-film cells are deposited in very thin, consecutive

layer of atoms, molecules, or ions on a low-cost substrate

(e.g., glass, metal, or plastic). The deposition process

involves three steps: (1) creating an atomic, molecular, or

ionic species; (2) transporting the species to a substrate;

and (3) condensing the species on a substrate. Another

thin-film cell, amorphous silicon, is made from thin layers
104 Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 

 Thin film PV cells are fabricated as films of semiconductor material. The cell thickness is usually 1 to 10 microns, compared to 100 to 300 microns 35

for single crystal silicon cells. A film thickness of only 1 to 2 microns is required to absorb essentially all of the sunlight. The crystal morphology of a

thin film cell may be polycrystalline or amorphous.

substrate (Figure C17). The basic structure of the cell

differs from those used for other photovoltaic

technologies. The primary difference is amorphous

photovoltaic modules are composed of thinner layers of

material.35

Photovoltaic Module/Array Technology

Flat plate photovoltaic systems consist of flat plate

collectors, composed of a number of cell modules,

mounted on a flat surface (Figure C18). The cell surface is

 encapsulated with a transparent covering that
Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 105

 Source:

Solar

Energy

Research

Institute,

Photovolt

aic

Fundame

ntals ,

SERI/TP220-3957,

Septemb

er 1991.

Figure E1. Amorphous Silicon Cell Structure

transmits sunlight to the cell and protects the cell from form that can be fed to the utility grid or the end user.

water and dirt damage. The incidence of sunlight on a flat Power conditioning equipment controls current and

plate photovoltaic cell does not need to be perpendicular. voltage to maximize power output, matches photovoltaic

However, sunlight at a sufficient energy level must be electricity to a utility AC electrical network, and

absorbed by the flat plate cell for electricity generation to safeguards the utility network and its personnel from

occur. possible harm (for example, from transmitting electricity

Photovoltaic concentrator arrays provide another option Photovoltaic system power conditioning equipment also

for utility power generation. A concentrator module includes an inverter, a device used to convert the DC

consists of one or more lenses that focus and concentrate electricity produced by photovoltaic cells into AC

incident sunlight on one or more photovoltaic cells (Figure electricity that can be fed to a utility grid or an end user.

C18). The lenses are usually made of plastic and

essentially replace much of the area that would be

occupied by photovoltaic cells in a flat plate module with

plastic lenses. Unlike flat plate systems, concentrator

systems require a tracking technology which moves the

concentrator cell array so that it is always pointing directly

at the sun to receive directly (perpendicularly) incident

sunlight.

The primary balance-of-system component in a photovoltaic system is the power conditioning technology used

to process the electricity from photovoltaic arrays into a

over lines thought to be disconnected from generators).

Wind

Because winds do not always blow, even at the best sites,

wind power plants are not baseload units. Unfortunately

winds do not necessarily coincide with demand peaks

either, limiting wind applications as peaking units. To

date, wind power plants have most often been viewed as

fuel savers but not as part of the capacity base, that is,
106 Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 

they are viewed as reducing the costs of fuels that utilities

would have consumed, but not as offsets to generating

capacity. However, as experience with winds continue,

on some occasions they may be considered part of

peaking or other capacity.
Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 109

Wind turbines convert the kinetic energy in wind to (VAWT, Figure C20). The turbine designs are differelectricity. The wind turns the turbine rotor, which then entiated by the axis of rotation of the turbine rotor. In the

drives an electric generator. There are basically two wind HAWT design, the rotation occurs on an axis that is

turbine designs, the horizontal axis wind turbine (HAWT, parallel to the ground. In the VAWT design, the axis is

Figure C19) and the vertical axis wind turbine vertical.
Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 111

 Source:

American

Wind

Energy

Associati

on.

Figure H1. Vertical Axis Wind Turbine (VAWT)

The HAWT has two or three bladed rotors, mounted on a the wind (yaw). Such turbines require yaw control

tower to raise them to an elevation of sufficient wind systems to keep the rotor directed into the wind.

speed and lower turbulence. A wind turbine blade is Downwind turbines tend to be self-correcting, since the

similar in design to an airplane propeller blade. Rotors

can be either upwind (in front of the tower) or downwind

in relation to the tower. There are also different designs

for attaching wind turbine blades to the turbine. Fixedpitch turbines have the blades attached to the rotor hub in

a fixed position and rotor orientation. Variable pitch

turbines allow the blades to rotate around their own axes

(pitch) in order to aid in starting, stopping, and regulating

power output. Teetered blades are attached to the hub

with flexible couplings and can help absorb the wind

loads experienced by the turbine.

Upwind turbine rotors may be pushed out of the path of
112 Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 

rotor acts as its own yaw control. However, downwind

turbines suffer interference from the tower in front of the

blades. There are several mechanisms designed to keep

the blade oriented properly in the wind stream. A turbine

may have a tail vane or rudder to control the turning

yawing motion. Typically, larger machines have active

motor-driven systems controlled by micro-processors.

Most of the recently installed horizontal axis turbines have

yaw control systems.

The tower on a HAWT elevates the turbine and rotor

about 90-150 feet above the ground. In current and past

generations of constant speed wind turbines, the tower

had to be composed of materials that gave it rigidity and

strength to withstand wind gusts and varying wind

speeds. With the use of new composite materials, towers

are lighter yet strong. Variable speed wind turbines allow

the wind turbine to generate electricity more efficiently,

making use of gusting winds.
Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 113

The VAWT (Figure C20) has two to four blades that means ensuring that the wind turbine operates at a

revolve around a vertical central shaft. The Darrieus blade constant speed as wind speed changes or as wind gusts

design is the most common commercially available VAWT occur. The variable speed wind turbines now being

turbine. Darrieus wind turbines have curved blades developed can operate in gusty wind conditions. These

connected at the top and bottom of the axis of rotation. turbines require electronic power controls.

Advantages of the Darrieus vertical axis turbines include

not having to track the direction of the wind and easier

access to blade and gear box equipment for servicing and

maintenance. The main disadvantage is that they do not

benefit from the stronger winds farther from the ground,

since the rotors are not suspended as high above ground

as those of a horizontal axis turbine.

Wind systems include electronic power controls that

evaluate wind speed and flow patterns. The system

optimizes turbine operation as wind conditions vary. In

the current generation of wind turbines, optimization

Power conditioning equipment is also important in wind

turbine systems. Variance in wind speed means that the

turbine may not always be operating optimally to produce

a continuous flow of electricity that has the same physical

characteristics as electricity being transported through

electric utility transmission lines. Power conditioning

equipment converts the electricity from a wind turbine

into a form that is compatible. For instance, power

conditioning equipment ensures that the electricity to the

utility transmission lines has the same frequency as

electricity from the utility (60 Hertz).
Appendix D

The Federal Regions
Energy Information Administration/Renewable Resources in the U.S. Electricity Supply 117

Appendix D

____________________________________________________________________________________________________________________

 Region States

____________________________________________________________________________________________________________________

New England .............................. Maine, New Hampshire, Vermont, Massachusetts, Connecticut, Rhode Island

New York/New Jersey ...................... New York, New Jersey a

Mid-Atlantic ................................ Pennsylvania, Maryland, West Virginia, Virginia, District of Columbia, Delaware

South Atlantic .............................. Kentucky, Tennessee, North Carolina, South Carolina, Mississippi, Alabama,

Georgia, Florida

Midwest .................................. Minnesota, Wisconsin, Michigan, Illinois, Indiana, Ohio

Southwest ................................. Texas, New Mexico, Oklahoma, Arkansas, Louisiana

Central ................................... Kansas, Missouri, Iowa, Nebraska

North Central .............................. Montana, North Dakota, South Dakota, Wyoming, Utah, Colorado

West .................................... California, Nevada, Arizona, Hawaii b

Northwest ................................. Washington, Oregon, Idaho, Alaska

____________________________________________________________________________________________________________________

 Puerto Rico and the Virgin Islands are included in the definition of the New York/New Jersey Region, but are excluded from this report. a

 American Samoa and Guam are included in the definition of the West Region, but excluded from this report. b

 Source: Energy Information Administration, Office of Coal, Nuclear, Electric and Alternate Fuels.