ii
i

ACKNOWLEDGEMENTS

This report was prepared for the U.S. Department of Energy (DOE) under Purchase Order No. 908958 

with Sandia National Laboratories, Albuquerque, New Mexico. Sandia is operated by Sandia Corporation, 

a subsidiary of Lockheed Martin Corporation. 

Thomas Pelsoci of Delta Research Co. was the principal researcher and author of the report. Rosalie 

Ruegg of TIA Consulting, Inc. and Patrick Thomas of 1790 Analytics LLC coauthored Chapter 7 of the 

report. Michael Gallaher of RTI International prepared Appendix B, and Rosalie Ruegg and Patrick 

Thomas prepared Appendix C. Gretchen Jordan of Sandia National Laboratories directed the work and 

provided oversight of the contract. Jeff Dowd of DOE's Office of Energy Efficiency and Renewable 

Energy (EERE) was the DOE Project Manager.

The author extends appreciation to the following people who made valuable contributions to the study: 

• To wind research staff of the National Renewable Energy Laboratory’s (NREL’s) National Wind 

Technology Center (NWTC), including Maureen Hand for providing on-going liaison; and the 

following people for granting interviews and assisting the authors with informational needs:

Robert Thresher, Michael Robinson, Sandy Butterfield, Walt Musial, Scott Schreck, Neil Kelley, 

Alan Wright, Palmer Carlin (retired), Marc Schwarz, Larry Flowers, Michael Milligan, Trudy 

Forsyth and Tami Sandberg. 

• To wind research staff at Sandia National Laboratories (SNL): Paul Veers, Jose Zayas, Dale 

Berg, Thomas Ashville, Herbert Sutherland (retired) and Henry Dodd (retired). 

• At Lawrence Berkeley National Laboratory (LBNL): Ryan Wiser and Mark Bolinger. 

• At RISOE National Laboratories, Denmark: Flemming Rasmussen, Jorgen Lemming, Jacob 

Mann. At ECN National Laboratories, Netherlands: Herman Snel and Jos Beurskens. At CRES, 

Greece: Takis Chaviaropoulos. At the Technical University of Delft, Netherlands: Gijs van Kuik 

and Rogier Nijssen. At the University of Massachusetts Amherst: James Manwell. At Montana 

State University: John Mandell. At University of California-Davis: C. P. “Case” VanDam. 

• Appreciation is extended to industry leaders who offered their insights to the study, including Jim 

Lyons (Novus Energy Partners), Craig Christensen and Amir Mikhail (Clipper WindPower), Ian 

Chatting (VESTAS), Henrik Stiesdal (Siemens Wind Power), Peter Fuglsang (LM Blades), Mike 

Anderson (RES Ltd.), and Benjamin Bell and David Quatron (Garrad Hassan). 

The author thanks the following people who reviewed earlier drafts of the report and provided useful 

comments.

DOE Staff, DOE Contractor, National Laboratory Staff, and Project Team Reviewers

Jeff Dowd (DOE EERE), Sam Baldwin (DOE EERE), Allan Hoffman (DOE EERE), Fred Glatstein 

(DOE EERE), Linda Silverman (DOE EERE), Maureen Hand (NREL), Ryan Wiser (LBNL), James 
ii

Browning (BCS Incorporated, DOE Contractor), Albert Link (University of North Carolina at 

Greensboro, Project Team), Rosalie Ruegg (TIA Consulting, Inc., Project Team), Mike Gallaher (RTI 

International, Project Team), and Alan O’Connor (RTI International, Project Team).

External Reviewers

Irwin Feller (Director, Institute for Policy Research and Evaluation, and Professor Emeritus of 

Economics, Pennsylvania State University) and Jeanne Powell (Economic Consultant, and retired Senior 

Economist, Advanced Technology Program, National Institute of Standards and Technology, U.S. 

Department of Commerce)

NOTICE

This document was prepared as an account of work sponsored by an agency of the United States

government. Neither the United States government nor any agency thereof, nor any of their employees, 

makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, 

completeness, usefulness or any information, apparatus, product, or process disclosed, or represents that 

its use would not infringe privately owned rights. Reference herein to any specific commercial product, 

process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute 

or imply its endorsement, recommendation, or favoring by the United States Government or any agency 

thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the 

United States Government or any agency thereof.
iii

Contents

Section Page

Executive Summary..............................................................................................................................ES-1

1. Introduction.....................................................................................................................................1-1

1.1 Purpose of the Study and Background.......................................................................................1-1

1.2 Overview of Evaluation.............................................................................................................1-1

1.3 Overview of the Report .............................................................................................................1-2

2. Wind Energy Technologies.............................................................................................................2-1

2.1 Background................................................................................................................................2-1

2.2 Selection of Technologies to be Evaluated................................................................................2-4

2.3 Infrastructure Technologies & Implications for Analysis .........................................................2-7

2.4 Overview of Selected Infrastructure Technologies .................................................................2-10

2.4.1 Early Turbulence Models for Turbine Inflows and Wakes..............................................2-10

2.4.2 Unsteady Aerodynamics Experiment...............................................................................2-11

2.4.3 Advances in Turbine Blade Materials Database and Analytical Models.........................2-15

2.4.4 WindPact: Wind Partnership for Advanced Component Technologies...........................2-16

2.5 Other Technologies Funded by DOE Wind Energy Program .................................................2-16

3. Analytical Framework & Methodology ........................................................................................3-1

3.1 Mansfield Model: Unifying Framework....................................................................................3-2

3.2 Next Best Alternative Technology ............................................................................................3-2

3.3 Additionality and Attribution ....................................................................................................3-2

3.4 Measures of Economic Performance .........................................................................................3-3

3.5 Data Collection Approach .........................................................................................................3-4

4. Economic Benefits...........................................................................................................................4-1

4.1 Next Best Alternative Technology Scenario .............................................................................4-1

4.2 Implication of the Next Best Alternative: Increased Fossil-Fired Generation ..........................4-2

4.2.1 Alternative Generation Mix ...............................................................................................4-3

4.2.2 System Load Implications with Fossil Fuel Replacement .................................................4-4

4.3 Attribution Analysis: What is the DOE Effect?.........................................................................4-5

4.3.1 Tabular Summary of Attribution Analysis.........................................................................4-5

4.3.2 Estimation of Attribution Levels........................................................................................4-8

4.4 DOE Investments in Wind Energy Technologies....................................................................4-10

4.5 Estimation of Economic Benefits............................................................................................4-12

4.5.1 Wind Energy Generation Levels......................................................................................4-12

4.5.2 Wind Energy Cost Savings..............................................................................................4-13

4.5.3 Health Cost Savings from Reduced Environmental Emissions.......................................4-16
iv

4.5.4 Combined Monetized Benefits and Identifying the DOE Share......................................4-17

4.6 Measures of Economic Performance .......................................................................................4-19

4.7 Sensitivity Analysis.................................................................................................................4-20

5. Environmental Benefits (Non-Monetized) ....................................................................................5-1

5.1 Avoided Greenhouse Gases.......................................................................................................5-1

5.2 Avoided Sulfur Dioxide Emissions...........................................................................................5-2

5.3 Avoided Mortality and Health Care Incidents...........................................................................5-3

5.4 Avoided Water Use for Fossil-Fired Generation.......................................................................5-4

6. Energy Security Benefits ................................................................................................................6-1

7. Knowledge Benefits.........................................................................................................................7-1

7.1 Main Findings of the Review of Knowledge Outputs...............................................................7-1

7.2 Complex Network of Relationships...........................................................................................7-2

7.3 Patents from DOE-Funded R&D...............................................................................................7-4

7.3.1 Patents of Leading Innovative Wind-Energy Companies Linked to Earlier DOE Wind 

Energy Patents....................................................................................................................7-5

7.3.2 DOE-Funded Wind Energy R&D Has Influenced Developments Beyond the 

Wind Energy Industry........................................................................................................7-6

7.3.3 Notable DOE-Attributed Wind Energy Patents.................................................................7-7

7.4 DOE-Funded Publications.........................................................................................................7-9

7.4.1 NREL Publications ..........................................................................................................7-10

7.4.2 SNL Publications.............................................................................................................7-11

7.4.3 Publications Cited by Patents...........................................................................................7-11

7.5 Educated and Trained People ..................................................................................................7-12

7.6 Conclusions .............................................................................................................................7-13

8. Summary of Evidence Based Findings..........................................................................................8-1

References .....................................................................................................................................R-1

Appendix A Interviews...................................................................................................................A-1

Appendix B Summary of the Co-Benefits Risk Assessment (COBRA) Model..........................B-1

Appendix C Bibliometric Methodology Used in the Knowledge Benefits Chapter ..................C-1

Appendix D Discussion of Production Tax Credit and Research and Development Influences 

on Megawatt Capacity Growth ................................................................................D-1
v

Figures

Number Page

Figure ES-1. Annual DOE Wind Energy Program Investments.....................................................ES-3

Figure 2-1. Modern Wind Turbine Configuration...........................................................................2-2

Figure 2-2. Arrays of Utility-Scale Wind Turbines.........................................................................2-3

Figure 2-3. Evidence-Based Process for Technology Selection......................................................2-5

Figure 2-4. Timelines for Selected R&D Activities........................................................................2-7

Figure 2-5. Overcoming the Innovation Risk Spike........................................................................2-9

Figure 2-6. Principles of Wind Turbine Aerodynamic Lift...........................................................2-12

Figure 3-1. Data sources and chains of evidence ............................................................................3-5

Figure 4-1. Capacity and Cost Trends for U.S. Wind Energy (MW and Cents/kWh).................4-14

Figure 6-1. Energy Mix of 2008 U.S. Power Generation................................................................6-1

Figure 7-1. Network of Relationships Between the DOE Wind Energy Program and Other 

Organizations................................................................................................................7-3

Figure 7-2. Number of U.S. Wind Energy Issued Patents Attributed to DOE-Funded Research by 

Five-Year Increment, 1976 through 2008 ....................................................................7-5

Figure 7-3. Organizations Whose Wind Energy Patent Families were Cited by the Largest Number 

of Wind Energy Patent Families of Leading Innovative Wind Energy Companies.....7-6

Figure 7-4. Companies (Excluding Leading Wind Energy Companies) with the Largest Number of 

Patent Families Linked to DOE-Supported Wind Energy Patents Families.................7-7

Figure 7-5. Number of DOE Publications in "Wind Energy" by Organization, 1974 to 2007 .....7-10

Figure 7-6. Organization Citing, by Technology and Period, 1974 through 2007........................7-11

Figure B-1. Cobra Model Overview ...............................................................................................B-1

Figure D-1. Production Tax Credit and Wind MW Capacity Growth ............................................D-1
vi

Tables

Number Page

Table ES-1. Economic Performance Metrics (Attributed DOE Benefits)..........................................ES-6

Table 2-1. Infrastructure Technologies and DOE Wind Energy Program’s Selected Technologies 

for Evaluation....................................................................................................................2-8

Table 4-1. Weighted Average Fossil Fuel Generation Mix in Top Wind Energy 

Producing States................................................................................................................4-4

Table 4-2. Matrix for Assessing Attribution by Technology Stage....................................................4-6

Table 4-3. Summary of Attribution Logic ..........................................................................................4-9

Table 4-4. Total Program Investments and Estimated Investments in Selected Technologies.........4-11

Table 4-5. Actual Wind Generation vs. Generation Levels under Counterfactual Scenario ............4-13

Table 4-6. Cost of Wind Energy With and Without DOE Impact....................................................4-15

Table 4-7. Health Cost Savings in 2008 ...........................................................................................4-16

Table 4-8. Health Cost Savings Over 1990 to 2008 Period (2008 Dollars)......................................4-17

Table 4-9. Cost Savings Attributed to the DOE Wind Energy Program (2008 Dollars)..................4-18

Table 4-10. Net Economic Benefits from DOE Wind Energy Program (2008 Dollars) ....................4-19

Table 4-11. Economic Performance Metrics Based on Total Wind Energy Program Investments....4-20

Table 4-12. Economic Performance Metrics Based on Program Investments in Selected 

Technologies ...................................................................................................................4-20

Table 4-13. Sensitivity of Net Present Value to Attribution Level (2008 Dollars) ............................4-20

Table 5-1. Avoided Greenhouse Gas Emissions (Thousand Tons of CO2)........................................5-2

Table 5-2. Adverse Health Incidents Avoided with DOE Impact ......................................................5-4

Table 6-1. Avoided Barrels of Oil Equivalent (BOE) Associated with a Six-Year Delay .................6-2

Table 7-1. Highly Cited Patents Owned by Leading Wind Energy Companies Linked to DOE .......7-8

Table 7-2. Highly Cited Non-Wind Energy Patents Linked to DOE-supported Wind 

Energy Patents...................................................................................................................7-9

Table B-1. Health Endpoints Included in COBRA ............................................................................B-3

Table C-1. Leading Organizations in Wind Energy Technology Patenting.......................................C-6

Table D-1. Financing Assumptions for Typical Wind Energy Project...............................................D-3
ES-1

EXECUTIVE SUMMARY

The U.S. Department of Energy's (DOE) Wind Energy Program leads the nation's efforts to accelerate the 

deployment of wind power technologies, improve performance, and lower costs. Greater use of the 

nation's abundant wind resources for electric power generation helps stabilize energy costs, enhance 

energy security, and improve the environment.

Under the auspices of the Energy Research and Development Administration (ERDA), the Wind Energy 

Program was established in 1975. Two years later, it was integrated into the newly founded DOE, where 

it has remained a vital part of DOE’s energy efficiency and renewable energy activities.

The Wind Energy Program collaborates with DOE national laboratories, industry partners, and 

stakeholders on research and development (R&D) promoting clean, innovative, and cost-competitive

wind energy technologies. It also works with the U.S. electric power industry to integrate wind power into 

the nation’s electricity supply while maintaining and reinforcing the stability and reliability of the electric 

grid.

This benefit-cost analysis focuses on the DOE Wind Energy Program’s public sector R&D investments 

and returns. The analysis accounts for the Program’s additionality – that is, comparing what has happened 

as a result of the Program to what would have happened without it. The analysis does not address the 

return on the investments of private companies (“private returns”). Public returns on the Program’s 

investments from 1976 to 2008 are identified and analyzed using retrospective analysis.

The study addresses the following key evaluation questions:

1. How has the DOE Wind Energy Program facilitated economic benefits (energy and other 

resource savings, renewable market growth, and other positive economic effects) relative to the 

next best alternative?

2. To what extent has the program promoted environmental benefits and enhanced energy security 

benefits by providing alternative energy sources, energy efficiency, reduced air emissions, and 

protection of existing energy sources?

3. To what extent has the Program produced knowledge benefits and to what extent has the 

knowledge produced been disseminated and used by others?

4. Would today’s commercialized technologies have been introduced at the same time, with the 

same performance characteristics, and with the same extent of deployment without DOE 

involvement?

5. To what extent do benefits attributable to the Program exceed its R&D expenditures?
Retrospective Benefit-Cost Evaluation of U.S. DOE Wind Energy R&D Program: Impact of Selected Energy Technology Investments

ES-2

Selecting Technologies of Evaluative Interest

Using an evidence-based process that relied on subject matter experts and documentation, the study 

selected the following DOE-supported wind energy technologies:

• Wind turbulence models developed between 1978 and 1994. Revised models provided fast and 

efficient methods for numerical simulation of stochastic turbulence processes and high fidelity 

inputs for wind turbine design optimization.

• The unsteady aerodynamic experiment and its antecedent activities conducted between the 

1987 and 2003. The experiment used densely instrumented turbines in a large National 

Aeronautics and Space Administration (NASA) wind tunnel to acquire accurate aerodynamic and 

structural measurements. With this knowledge, researchers were able to simulate the typical 

conditions that full-scale horizontal axis wind turbines experienced with high spatial and temporal 

resolution. Experimental results have exceptional data accuracy and could be used as valuable 

benchmarks for developing and validating wind turbine aerodynamic design codes. This 

facilitated the development of realistic blade geometries

• Turbine blade material characterization and analytical modeling work conducted from 1985 

through the present. Over the economic lifetime of wind turbines, blades will spin hundreds of 

millions of times. Each spin corresponds to the full range of tensile and compressive loads,

potentially giving rise to fatigue-induced material failure. DOE-funded “long material durability 

tests” for composite turbine blades made it possible to better understand and avoid excessive 

fatigue loads, which improved turbine reliability.

• Wind turbine component demonstration programs, including WindPact, started in 1999 and 

continue through the present. These programs have helped to develop larger wind turbines, able 

to reach into higher wind regimes and achieve greater energy capture. The component 

demonstration program supported the fabrication of prototypes and testing components for 

operational viability.

The selected technologies have the characteristics of infrastructure technologies, such as advanced 

analytical tools, testing and measurement methods, and scientific and engineering databases. Competing

industrial firms utilized these technologies to design and field more reliable, efficient, and price 

competitive wind turbine components and systems. In this manner, infrastructure technology investments 

facilitate the market-based development of proprietary products. Despite the difficulty of direct 

appropriation, infrastructure technologies work in concert with each other to reduce the risks of 

subsequent R&D investments and commercialization. 

Due to the crosscutting nature of infrastructural technologies, the benefit-cost study proceeded to evaluate 

the combined impacts of the selected technologies. The study does not attempt to disaggregate benefits of 

individual infrastructure technology elements. The study therefore sets out to estimate economic benefits 
Executive Summary

ES-3

from DOE-supported wind energy infrastructure technologies as a combined set of investments in 

crosscutting technologies. 

The DOE Investment

Over the 1976 to 2008 period, the DOE Wind Energy Program invested $1.073 billion in the development 

of wind energy technologies. In inflation-adjusted 2008 dollars, the entire program investment was $1.719

billion. 

Program investment patterns experienced significant fluctuations, which reflect changing policies of 

successive administrations. Large investments were made during the Program’s early years, but the 1980s 

followed with significant declines in investments. A gradual recovery was seen in the early 1990s and 

those levels have generally been maintained leading up to 2008 (See Figure ES-1).

Figure ES-1. Annual DOE Wind Energy Program Investments

In addition to total program investment, a subset of investments was directly related to the selected 

infrastructure technologies, over the period of 1976 to 2008. In 2008 dollars, the investment in the

selected infrastructure technologies was $1.239 billion, corresponding to 72% of the total program

investment.
Retrospective Benefit-Cost Evaluation of U.S. DOE Wind Energy R&D Program: Impact of Selected Energy Technology Investments

ES-4

The DOE Impact

Knowledge of the complex physics of wind turbines was incomplete in the early days of the DOE Wind 

Energy Program. Designers used trial-and-error methods and large safety factors in order to avoid 

frequent turbine failures. The low reliability of turbines meant that wind energy costs were substantially 

higher than the cost of conventional electricity generation. Over the subsequent decades, significant 

advances in knowledge have made it possible to build large, utility-scale wind turbines with high 

reliability and at costs competitive with conventional electricity generation.

Analyzing the DOE impact involves several steps:

• Identifying a “next best alternative technology.”

• Formulating scenarios for wind energy industry operations with the “next best alternative 

technology” (without DOE R&D investments).

• Estimating the total benefits.

• Determining how much of the total benefits can be attributed to DOE.

The “next best alternative technology” was identified – with input from subject matter experts, and 

through an in-depth review of technical and industry literature – as smaller, less reliable, less costcompetitive wind turbines with reduced energy capture.

Without infrastructure technologies, under the counterfactual “next best alternative technology” scenario, 

wind turbines would still be designed using trial-and-error methods and crude rules of thumb. Wind 

turbine component reliability would be degraded, resulting in higher outage rates, reduced availability, 

and higher operation and maintenance (O&M) expenses. Turbines would also experience more frequent 

systemic failures. Specific consequences include:

• Reduced reliability levels would increase commercial risks and financing costs.

• Without effective analytical models, engineering databases, test protocols and test facilities, 

designers would “overdesign” wind turbines with high safety factors.

• High safety factors would contribute to higher capital costs. 

• Higher capital costs, higher financing costs, and higher O&M expenses would contribute to 

higher cost of wind energy.

• With higher commercial risks and higher energy costs, capacity additions would not have reached

historic levels. 

• With reduced wind generating capacity, wind power generation would be reduced. 

• To compensate for reduced wind power generation, in the context of stable aggregate electricity 

demand, the increment of reduced wind power generation would be replaced with a mix of fossilfired generation. This shift to fossil-fired generation is not an alternative next best scenario. 

Rather, it is a direct implication of what could be expected with reduced wind generating capacity 

and reduced wind power generation under the original next best alternative scenario.
Executive Summary

ES-5

Extensive interviews with subject matter experts indicated that DOE investments in the selected 

technologies avoided a six-year delay on average in technical advances and corresponding wind energy 

generation levels. All estimates by the experts of the avoided delay were closely clustered around a sixyear average. 

Expert interviews also explored the impact of the Production Tax Credit (PTC), indicating that the PTC 

was important. Without the PTC, additional delays beyond the six year delay from R&D underinvestment 

would have been likely. The magnitude of these additional delays could not be identified. Experts 

stressed, however, that without prior R&D investments in infrastructure technologies leading to lower 

cost of energy, improved reliability and availability, the PTC was unlikely to have been effective on its 

own.

Analysis Results

Public benefits from DOE Wind Energy R&D investments were documented along four dimensions: 

economic, environmental, energy security, and knowledge benefits.

Benefits from six years of accelerated technology advances are estimated by comparing actual wind 

energy generation levels to wind energy generation levels under a counterfactual scenario without DOE 

impact. 

Monetized benefits from DOE-funded infrastructure technology advances fall into two categories:

1. Economic benefits: wind energy cost savings are savings from more efficient wind energy 

generation traced to DOE-funded infrastructure technologies – estimated at $3.278 billion (2008 

dollars, undiscounted).

2. Environmental benefits in the form of health care cost savings: savings from avoided adverse 

health incidents due to reduced particulate emissions – estimated at $9.766 billion (2008 dollars, 

undiscounted).

Thus total cost savings were estimated at $13.044 billion (2008 dollars, undiscounted), from 1976 to 

2008.

The portion of the $13.044 billion attributed to DOE was determined by an analysis of additionality. The 

amount of benefits from accelerated technology advances and wind energy generation attributed to the 

DOE Wind Energy Program was determined by accounting for the Program investment that directly 

supported the development of selected infrastructure technologies (without industry cost share), and the 

remaining DOE investments that were cost shared. The resulting DOE attribution factor was found to be 

80%, with an industry attribution of 20% for the four selected infrastructure technologies. Eighty percent 

($10.435 billion) of the total economic and health benefits were attributed to the DOE Wind Energy 

Program. Net benefits were $8.716 billion ($2008, undiscounted). 
Retrospective Benefit-Cost Evaluation of U.S. DOE Wind Energy R&D Program: Impact of Selected Energy Technology Investments

ES-6

Table ES-1 summarizes the economic and health benefits results using conventional performance 

measures – net present value (NPV), benefit-to-cost ratio, and internal rate of return. With reference to

DOE investments for the entire Wind Energy Program over the period 1976 to 2008 (column 1), the NPV 

at 3% is $3.5 billion, the NPV at 7% is $0.9 billion, and the Benefit-Cost Ratio at 3% and at 7 % is 3.9 to 

1 and 2.1 to 1, respectively. The internal rate of return is 12%. Table ES-1 (column) also presents results 

with reference to DOE Wind Energy investments in the four selected infrastructure technologies alone. 

The NPV at 3% is $3.8 billion, NPV at 7% is $1.1 billion, the Benefit-Cost Ratio at 3% and at 7% is 5.3

to 1 and 2.8 to 1, respectively, and the internal rate of return is 14%. 

A sensitivity analysis of these benefits was performed by varying the DOE attribution percentage plus and 

minus 10%. Throughout the 72% to 88% attribution range, net present values remain positive at 

significant levels. With respect to the entire Wind Energy Program investment, the NPV at a 7% discount 

rate varied from $743 million to $1.1 billion.

Table ES-1. Economic and Health Cost Savings Performance Metrics 

(Attributed DOE Benefits)

Metrics Based on 

Entire DOE Wind 

Energy Program 

Investment

Metrics Based on 

DOE Wind Energy 

Investments in Selected 

Technologies

(1) (2)

Net Present Value at 3% $3.5 billion $3.8 billion

Net Present Value at 7% $0.9 billion $1.1 billion

Benefit-cost Ratio at 3% 3.9 to 1 5.3 to 1

Benefit-cost Ratio at 7% 2.1 to 1 2.8 to 1

Internal Rate of Return 12% 14%

Environmental benefits from the DOE Wind Energy Program investments can be traced to avoided

greenhouse gas emissions and sulfur dioxide emissions.

To estimate the magnitude of these environmental benefits, actual wind energy generation levels are 

compared to generation levels corresponding to the counterfactual scenario without DOE impact. Relative 

to actual wind generation levels, this comparison indicates:

• A 68% reduction in clean, renewable wind generation without DOE, and

• A corresponding 140 billion kWh increase in conventional fossil-fired generation to offset 

reduced wind energy generation, given stable levels of aggregate electricity demand.
Executive Summary

ES-7

The resultant DOE-attributed emissions reduction from avoiding this substitution of fossil-fired 

generation and associated harmful emissions was: 

• 83 million tons of carbon dioxide emissions, the main greenhouse gas component from fossilfired conventional power generation; and

• 300,000 tons of sulfur dioxide emissions.

Avoided adverse health incidents were nearly 1,000 mortalities, 1,500 non-fatal heart attacks, and a 

million lost or restricted workdays.

DOE’s Wind Energy Program investments have also resulted in modest energy security gains, estimated 

at one million barrels of oil equivalent, amounting to 20% of a single day’s U.S. passenger car fuel use. 

Finally, the DOE Wind Energy Program has produced considerable knowledge benefits that have 

provided a foundation on which other research organizations have drawn to achieve further advancements 

in wind energy and a technology base for today's commercial wind turbines.

The retrospective benefit-cost study identified and documented benefits from selected DOE-funded wind 

energy infrastructure technologies over the 1976 to 2008 period. Given the study’s retrospective focus,

benefits were estimated only out to 2008. Benefits accruing beyond 2008 from the use of pre-2008 

technology advances are not counted. In addition, it is likely that other DOE Wind Energy Program R&D 

investments in technologies not investigated in this study have generated benefits for the Nation. 

Accordingly, the results of the current retrospective analysis provide a first order, lower-bound estimate 

of DOE Wind Energy Program contributions to the U.S. economy, environment, and energy security, and 

to the U.S. science and technology knowledge base.
Retrospective Benefit-Cost Evaluation of U.S. DOE Wind Energy R&D Program: Impact of Selected Energy Technology Investments

ES-8

COMMON ACRONYMS AND ABBREVIATIONS

BOE Barrels of Oil Equivalent

COBRA U.S. EPA Co-Benefits Risk Assessment Model

CRES Center for Renewable Energy Sources (Greece)

DOE U.S. Department of Energy

ECN Energy Research Centre of the Netherlands

EERE Office of Energy Efficiency and Renewable Energy

IEA International Energy Association

HAWT Horizontal Axis Wind Turbine

LBNL Lawrence Berkeley National Laboratory

NASA National Aeronautics and Space Administration

NREL National Renewable Energy Laboratory

PNNL Pacific Northwest National Laboratory

PTC Production Tax Credit

RISOE National Laboratory for Sustainable Energy (Denmark)

RPS Renewable Portfolio Standard

SNL Sandia National Laboratory

VAWT Vertical Axis Wind Turbine

WindPACT Wind Partnership for Advanced Component Technologies
1-1

1. INTRODUCTION

1.1 Purpose of the Study and Background

This is a retrospective benefit study of selected wind energy technologies that were sponsored by the 

Department of Energy (DOE) Office of Energy Efficiency and Renewable Energy’s (EERE) Wind 

Energy Program over the 1976 to 2008 period. The report sets out to identify, document, and validate four 

categories of impacts from EERE’s technology investments selected for study:

• Economic benefits assessed with multiple performance measures, including total benefits, 

program costs, net benefits (undiscounted), present values of net benefits and benefit-cost ratios, 

discounted at 3% and 7%, and the internal rate of return.

• Environmental benefits from avoided harmful emissions, including associated health benefits. 

• Energy security benefits from reduced reliance on uncertain energy resources (e.g., oil 

displacement).

• Knowledge benefits embodied in patents and publications, and people.

1.2 Overview of Evaluation

To identify the above impacts, the study addresses the following key evaluation questions:

1. How has the DOE Wind Energy Program facilitated economic benefits (energy and other 

resource savings, renewable market growth, and other positive economic effects) relative to the 

next best alternative?

2. To what extent has the Program promoted environmental benefits and enhanced energy security 

benefits by providing alternative energy sources, energy efficiency, reduced air emissions, and 

protection of existing energy sources?

3. To what extent has the Program produced knowledge benefits and to what extent has the 

knowledge produced been disseminated and used by others?

4. Would today’s commercialized technologies have been introduced at the same time, with the 

same performance characteristics, and with the same extent of deployment without DOE 

involvement?

5. To what extent do benefits attributable to the Program exceed its research and development

(R&D) expenditures?

The four technologies of evaluative interest that were identified as successful and notable achievements:

• Early wind turbulence models 

• Unsteady Aerodynamic Experiment results 

• Turbine blade material characterization and analytical models

• Wind turbine component demonstration programs, including WindPact
Retrospective Benefit-Cost Evaluation of U.S. DOE Wind Energy R&D Program: Impact of Selected Energy Technology Investments

1-2

The retrospective analysis followed a “logic chain” that links program investments with activities, 

outcomes, and benefits. It used multiple sources of data to convert partial indicators and chains of 

evidence into integrated and credible analytical results. 

Data were obtained from primary and secondary sources. These include EERE program and planning 

documents, program budgets, prior program evaluations and assessments, domestic and international 

technical literature, and wind energy market information. In addition, in-depth interviews with subject 

matter experts were conducted. This included experts from the DOE Wind Energy Program, National 

Renewable Energy Laboratory (NREL), Sandia National Laboratory (SNL), the National Laboratory for 

Sustainable Energy (RISOE) in Denmark, the Energy Research Centre of the Netherlands (ECN), the 

Center for Renewable Energy Sources (CRES) in Greece, Siemens Wind Power, Vestas Wind Systems, 

General Electric (GE) Wind (retired senior executives), Clipper Windpower, universities, and consulting 

engineers. These interviews provided valuable information for selecting technologies for the study and for 

specifying the “next best alternative” technology, used as a baseline in benefit-cost analysis.

1.3 Overview of the Report

The remainder of the report is structured as follows:

• Chapter 2 provides an overview of wind energy technologies, describes how a subset of DOE 

Wind Program R&D investments was selected for analysis, and points to other technology 

advances that were not included in the present analysis.

• Chapter 3 presents an evaluation framework and describes the methodology and data collection 

approach used for benefit-cost analysis.

• Chapter 4 posits a counterfactual scenario of the next best alternative technology, identifies the 

DOE impact, and presents an approach for assessing the attribution of benefits to DOE and its 

industry partners. Program costs are identified, economic benefits are estimated, and economic 

performance metrics are computed.

• Chapter 5 estimates environmental benefits.

• Chapter 6 estimates energy security benefits.

• Chapter 7 provides an analysis of knowledge benefits.

• Chapter 8 summarizes the evidence-based findings.

• Appendices:

o Appendix A lists interviews.

o Appendix B provides information about the Environmental Protection Agency’s (EPA)

COBRA model used for estimating health benefits linked to reduced environmental 

pollution.

o Appendix C describes the bibliometric techniques used to analyze the knowledge 

benefits.

o Appendix D provides a discussion of Production Tax Credit and research and 

development influences on MegaWatt capacity growth.
2-1

2. WIND ENERGY TECHNOLOGIES

In the early 1970s, wind energy was a limited niche market. Without an understanding of the complex 

physics of wind turbines subject to the variable forcing function of the wind, designers used trial-anderror methods and large engineering design safety factors to ensure that frequent mechanical failures 

would be avoided. Reliability was low and the cost of wind energy was much higher than conventional 

electricity generation. Over the following decades, significant advances in knowledge have made it 

possible to build utility-scale wind turbines with high reliability and at competitive costs with 

conventional generation. The following sections discuss how the DOE Wind Energy Program R&D 

investments contributed to such advances.

2.1 Background

Utility-scale wind turbines are energy conversion systems that capture the kinetic energy of the wind and 

convert it to electric power, synchronized to feed the electrical utility grid. 

Modern utility-scale turbines are typically three bladed-horizontal axis machines with the following 

principal subsystems (Figure 2-1):

• Rotor blades and hub are designed to capture and convert the wind’s kinetic energy into rotational 

energy.

• Drive trains deliver rotational energy to an electric power generator through a system of gears and 

shafts, which increase rotational speed to meet generator requirements.

• Nacelle structures enclose and protect the power train and control mechanisms. The nacelle 

rotates on the tower to keep the turbine faced into the wind.

• Towers and foundations raise wind turbines to sufficient heights to reach desirable wind regimes.

Wind turbines are complex dynamic systems and require tradeoff decisions in search of optimum overall 

performance and economy. Turbines are slender and flexible, acted upon by the inconstant behavior of 

the wind, subject to vibrations and resonance, and operated continuously in all types of weather. These 

characteristics lead to challenging design challenges such as:

• Strength requirements to resist the infrequent application of highest wind loads.

• Fatigue life requirements to resist the repeated application of lesser loads.

• Stiffness requirements to control deflections and vibration frequencies for avoiding resonance 

conditions (Sperra, 2009).

• Competitive cost of energy targets.

In the early days of the wind industry, there was insufficient understanding of complex dynamic physical 

phenomena that characterize the operation of utility-scale wind turbines. Design methods were often 

characterized by trial and error. This sometimes led to catastrophic failures or necessitated the use of high 

safety factors to achieve strength, fatigue, and stiffness requirements. Wind turbines with high safety 
Retrospective Benefit-Cost Evaluation of U.S. DOE Wind Energy R&D Program: Impact of Selected Energy Technology Investments

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factors were “overdesigned” with excess weight to achieve some reliability but lead to low energy 

extraction and high cost of energy.

Figure 2-1. Modern Wind Turbine Configuration

Source: NREL, Power Technologies Energy Data Book, August 2006

NREL/TP-620-39728, page 34.

Trial-and-error methods are no longer suitable for modern wind turbine design, as turbines must meet

increasingly demanding strength, fatigue, and stiffness requirements. This necessitates accurately 

predicting static and dynamic loads caused by wind, gravity, centrifugal forces, and vibrations. 

Considerations of scale, cost, and predictability have led researchers to rely upon computer code 

(software) for horizontal axis wind turbine (HAWT) design. Computer codes must be grounded in sound 

basic and applied knowledge and must be also validated by modal testing of the entire turbine. Once the 

computer codes are validated, design problems can be accurately partitioned into separate modules for:

• Simulation of wind conditions (mean and stochastic turbulence components),

• Airfoil or blade design,

• Rotor aerodynamic performance, and

• Aeroelastic structural performance of the entire system.
Chapter 2 – Wind Energy Technologies

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Respective computer codes for these four modules are used in a stepwise design process. Each design 

module is initialized through a network of feedback loops with the other modules and module outputs are 

incrementally optimized to achieve overall design requirements. 

In recent years, greater design challenges have come with the increasing tower heights, rotor diameters, 

and rated powers needed to enable turbines to capture the more energetic winds that occur at higher 

elevations to produce more electrical energy. Such challenges include:

• Wind speeds increase with hub height, such that higher and more expensive towers are needed.

• Large rotors capture more energy, and rotor costs increase with size increases. As rotor blades 

capture more wind energy when optimized for aerodynamic performance (higher lift and reduced 

drag), greater degrees of aerodynamic complexity must be evaluated and accounted for, leading 

to increased design costs.

• Larger generators to convert more wind energy to electric power also cost more.

• Rotor diameter and generator capacity must be matched and customized to site-specific wind 

conditions.

Additional complexities arise from arranging arrays of wind turbines in wind farms connected to the 

utility grid with common transmission lines (Figure 2-2). While common connection and other economies 

of scale generate economic benefits, the concentration of wind turbines also cause array interference or 

“shielding” by reducing wind velocities and energy capture in the second, third, and subsequent lines of 

turbines. This has led to performance problems that are recognized in the turbine design process, wind 

farm siting and turbine spacing decisions.

Figure 2-2. Arrays of Utility-Scale Wind Turbines

 Source: http://energyissues.blogharbor.com/Wind_Farm.jpg.
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2.2 Selection of Technologies to be Evaluated

Using an evidence-based two-step process, the study selected the following DOE Wind Energy Program 

technology investments as highly successful and notable achievements of evaluative interest:

• Early wind turbulence models

• Results of the Unsteady Aerodynamic Experiment results

• Advances in turbine blade material characterization and analytical models advances

• Wind turbine component demonstration programs, including WindPact

The selected technologies have the characteristics of infrastructure technologies, such as advanced 

analytical tools, testing and measurement methods, and scientific and engineering databases (see section 

2.3). Given the crosscutting nature of infrastructural technologies, it is more meaningful to assess their 

combined impact than to disaggregate the analysis of benefits to individual technology elements. Beyond 

conceptual reasons, disaggregation is also impractical due to data limitations.

To identify technology investments of evaluative interest, the analysis used two screening criteria: (1) 

highly successful and notable technical and commercial achievements and (2) practical for evaluative 

analysis. That is, technical results have been documented in sufficient detail, principal investigators 

continue to be available, and industry participants are available and willing to contribute information. A 

two-step technology selection process, using the above criteria, is depicted in Figure 2-3.

Step 1: After a wide-ranging literature review and preliminary discussions with some subject matter 

experts, the study identified three general technology areas as likely to meet the “notable technical 

achievements” criteria:

• Better understanding of turbulence phenomena in turbine inflows and turbine wakes,

• Achieve increased understanding of turbine blade aerodynamic, and 

• Improve understanding of turbine component dynamic behavior and materials characteristics.

Step 2: Achieve, validate, and more accurately specify the preliminary technology selection. 

The primary information for technology selection and validation came from interviews with leading 

technical and commercial subject matter experts (at U.S. and overseas laboratories, academia, major 

industrial firms, original equipment manufacturers [OEM], component manufacturers, and engineering 

consulting firms). 
Chapter 2 – Wind Energy Technologies

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Figure 2-3. Evidence-Based Process for Technology Selection

Primary information from subject matter experts was supplemented with a wide ranging review of 

program documents and technical literature, including: 

• Office of Program Analysis, U.S. DOE, Office of Energy Research. August 1991. An Assessment 

of Research Projects in the Federal Wind Energy Research Program.

The Atmospheric Fluids Dynamics panel pointed to wind turbulence research as the highest 

priority. The clear need to understand the nature of wind turbulence and its effects on wind 

turbine structures and components was consistently held to be of prime importance. Research 

emphasis into the fundamentals of wind turbine aerodynamics was also highly endorsed.

Determining blade air loads and airflow in a wide range of wind turbine environments and 

designs was necessary for aerodynamic modeling and computer codes. Other important areas 

included the characterization of blade materials and the development of improved design tools.
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• Office of Wind and Hydropower Technologies, EERE, U.S. DOE. May 2008. Top 10 

Accomplishments of the DOE Wind Program.

Top accomplishments relevant to this evaluation included: (1) The AMES large-scale wind tunnel 

experiment was completed in the year 2000. Results from testing wind turbines in controlled 

conditions provided a wealth of technical information that has been used by both U.S. and 

European manufacturers to validate and improve wind turbine design and aerodynamic software 

models, including the FAST and Aerodyne computer codes. (2) Wind turbine components were 

developed and tested. (3) In the 1980s the DOE Wind Energy Program developed advanced wind 

turbine blade designs that produced up to 30% more electricity than previous designs, reflecting 

materials characterization and blade design advances over several decades.

• Johansen, Jeppe, et al. IEA Wind Annex XX Section 3.0 Research Summary, Denmark, RISOE / 

DTU Department of Wind Energy (2008).

This article discusses the development and validation of aerodynamic engineering models and 

design codes for horizontal axis wind turbines. “RISOE has for the last 15 or more years been 

developing computational fluid dynamics (CFD) methods for wind turbine rotor aerodynamics 

and a critical bottleneck has been the lack of detailed high quality experimental data for 

verification. Thanks to the National Renewable Energy Laboratory / NASA Ames wind tunnel 

experiment, this picture has now changed. RISOE participates in the NREL Blind Code 

Comparison and the CFD method showed some very promising results for the upwind 

computations.”

• Schepers, Gerard, et al., IEA Wind Annex XX Section 5.0 Research Summary – The Netherlands.

ECN or Energy Research Center of the Netherlands (2008).

The primary aim of Annex XX was to analyze the measurements that were taken on the large 

AMES wind tunnel. “NREL measurements from the AMES wind tunnel offer a unique 

opportunity to investigate aerodynamic effects and for validating and improving wind turbine 

design codes. An important advantage is that aerodynamic forces are measured at different radial 

positions, by which local aerodynamic effects can be assessed. Usually wind turbine 

measurements give only integrated blade and rotor loads, which hide the details on sectional 

level.”

The above excerpts are part of the DOE Wind Energy Program’s documentation, pointing to the selected 

technologies’ alignment with program priorities. Two of the four excerpts, from leading wind energy 

laboratories in Denmark and the Netherlands, also indicate that the selected technology areas are of 

central technical importance and underline the international recognition of DOE Wind Energy Program 

contributions.
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For the selected technologies of evaluative interest, timelines for technology investments and research 

activities span the 1978 to 2008 period, closely corresponding to the 1976 to 2008 timeframe for benefitcost analysis (Figure 2-4).

Figure 2-4. Timelines for Selected R&D Activities

2.3 Infrastructure Technologies & Implications for Analysis

Gregory Tassey of the National Institute of Standards and Technology (NIST) made a cogent argument 

for differentiating among types of technologies to support meaningful analysis of economic benefits 

derived from technology investments (Tassey, 2008). He recommends differentiating technology 

investments into three categories:

• Generic technology investments to demonstrate proof of concept

• Investments in technology infrastructure development

• Investments in proprietary technologies

Proprietary technology investments directly support the development of industrial products and 

production processes. These investments are readily appropriated by competing industrial firms and can 

be traced to distinct economic benefits associated with separate products and production processes. 
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In contrast, infrastructure technology investments (supporting the development of advanced analytical 

tools, testing and measurement methods, and scientific and engineering databases) have high public goods 

content that competing firms can access and utilize.

As indicated in Table 2-1, infrastructure technologies formulated by Tassey closely correspond to the 

wind energy technology elements selected for evaluation.

Table 2-1. Infrastructure Technologies and DOE Wind Energy Program’s Selected 

Technologies for Evaluation

Infrastructure Technologies per Tassey (2008) DOE Wind Energy Technologies Selected for Evaluation

Scientific and Engineering Databases Results from Ames Unsteady Aerodynamic Experiment;

Material database for composite turbine blades

Advanced Analytical Models Stochastic wind turbulence models developed at Sandia

Testing and Measurement Methods Test equipment and test protocols for component 

demonstrations and validation (WindPact);

Test stands and test protocols for full system demonstrations

The amount and quality of infrastructure technologies available to an industry directly affect technical and 

market risks associated with R&D project selection and the subsequent commercialization of proprietary 

products. The availability of appropriate infrastructure technologies will reduce the risk spike (Figure 2-5) 

and can thereby be expected to accelerate private investment in technology development and 

commercialization (Tassey, 2005). 

Infrastructure technology investments can thus facilitate the market-based development of complex 

technology products. They provide great value in reducing the risk of subsequent R&D investments and 

commercialization costs.
Chapter 2 – Wind Energy Technologies

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Figure 2-5. Overcoming the Innovation Risk Spike

Infrastructure technology investments are often made by public sector agencies and the “identification 

and measurement of the resultant public goods content remains conceptually and empirically difficult” 

(Tassey, 2008).

The current study arrives at the same conclusion: that the selected infrastructure technologies cannot be 

meaningfully segregated into elements to which distinct benefits can be traced. 

• Discussion with subject matter experts strongly suggest that seeking to identify specific benefits 

from quasi-public goods infrastructure technology investments, utilized freely by competing 

industrial firms, would not be feasible or meaningful. 

• Published information or unpublished data that could support tracing benefits to distinct elements 

of infrastructure technologies are also unavailable.

Given the conceptual differentiation of infrastructure technologies from proprietary technologies, data 

limitations, and the tightly coupled dynamic characteristics of wind turbines as physical systems, the 

study does not attempt to trace economic benefits to distinct infrastructure technology elements. Instead, Level of Risk

Source: Adapted from Tassey (2005a, b, 2007).
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the study sets out to estimate economic benefits from selected infrastructure technologies taken as a 

combined set of investments. 

2.4 Overview of Selected Infrastructure Technologies

The four selected technologies of evaluative interest are discussed in separate subsections below.

2.4.1 Early Turbulence Models for Turbine Inflows and Wakes

Wind energy is both the prime mover and the principal structural load for wind turbines. It is a variable 

energy resource that frequently changes in speed and direction, often in just a few seconds. The inconstant 

behavior of wind or turbulence can create sudden and extreme changes in the aerodynamic forces 

impinging on turbine blades, the entire wind turbine, and on sequentially spaced rows of turbines in wind 

farms. Wind turbulence can lead to unique design challenges.

Given the complexity and unpredictable nature of wind turbulence, early turbines were designed with 

simplified assumptions of steady winds across turbine rotor disks while allowing for wind shear variation 

with elevation. The ensuing structural analysis predicted mean loads fairly well but badly underestimated 

cyclic loads from wind turbulence. 

Failure to account for the gusty or turbulent nature of the wind and the associated sudden and extreme 

changes in aerodynamic forces on rotor blades led to the underestimation of fatigue damage and resulted 

in frequent structural failures. Early failures undermined investor confidence and initial market 

acceptance of wind energy technologies.

Experience with turbine failures led to the recognition that knowledge of wind characteristics – including 

both the air entering the turbine rotor as well as exiting in turbine wakes – was critical to understanding 

the performance, dynamics, and structural loads imposed on wind turbines.

To achieve performance goals and system sustainment, the designer must have a good understanding of 

temporal and spatial loads and alternating stress distributions that can be expected from turbulent inflows 

over the turbine’s lifetime. For wind farms, knowledge about vortex shedding patterns in turbine wakes 

was needed to determine effects on downwind turbines including energy losses and changes in structural 

loads.

In recognition of these needs, extensive research was undertaken to understand the expected turbulence 

spectra and to address the associated design challenges. Key milestones included:

• Research programs undertaken at Pacific Northwest National Laboratory (PNNL) led to the 

development of experimental techniques (rotating sampling) for the empirical characterization of 

turbulent inflows at multiple locations on turbine blades. 
Chapter 2 – Wind Energy Technologies

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• Recognizing that turbulent inflows to wind turbines are largely stochastic processes (based on 

well-known descriptors of random fields), Paul Veers and other SNL researchers built on SNL 

weapons program successes in modeling stochastic processes associated with weapons shock and 

vibration phenomena. Numerical methods used to characterize and simulate multiple-input shock 

and vibration processes were used to simulate wind turbulence for turbine inflows. This approach 

is now frequently referenced as the “Sandia Method” and is used by industry as the basis for first 

generation computer codes for stochastic wind turbulence simulation. 

• Simulation results from the “Sandia Method” were field tested by PNNL researchers. Results 

indicated that the method was capable of producing simulations that agree with measurements, 

especially for certain coherence conditions. 

• The “Sandia Method” finite element analysis approach was used at NREL to develop the 

TurbSim stochastic inflow turbulence computer simulation code. This code provided numerical 

simulation of a full-field flow that contains bursts of coherent turbulence (organized turbulent 

structures in the flow that have a well-defined spatial relationship). 

• The TurbSim model reflects the proper spatiotemporal turbulent velocity field relationships seen 

in instabilities associated with nocturnal boundary layer flows of increasing interest as utilityscale turbines increase in size and are affected by nocturnal boundary layer flows (Kelley & 

Jonkman, 2006). 

• “Given the model’s streamlined nature and extensive industrial experience with the “Sandia 

Method,” industry continues to use the “Sandia Method” at this time, 20 years after it was first 

proposed in 1988.

2.4.2 Unsteady Aerodynamics Experiment

Wind turbine aerodynamics is a branch of fluid dynamics concerned with studying the motion of air (flow 

field) when it interacts with turbine rotor blades. As indicated in Figure 2-6, wind passes over the surfaces 

Sandia Method

“Wind simulation has become an important part of ...HAWT structural analysis. Because of the 

highly non-linear relationship between atmospheric turbulence and aerodynamic loads on wind 

turbine blades, there is interest in numerically simulating the winds and then calculating time 

series of blade loads...

...The basic approach of the Sandia method (of full field wind simulation) is to simulate wind 

speed time series at several points in the plane perpendicular to mean wind direction. This is a 

full field method that completely fills 3-D blocks of space with a grid of instantaneous wind 

speeds...

...The Sandia method for full field simulation has already been applied to both HAWT and 

VAWT structural analysis. Input required is single point turbulence for all N points and the 

coherence function which describes how turbulence is correlated as a function of spatial 

separation, mean wind speed, and frequency.” (Veers, 1988)
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of airfoil shaped turbine blades. It passes more rapidly over the longer (upper) side of the airfoil, creating 

a lower pressure area above the airfoil. The pressure differential between top and bottom surfaces results 

in a force called aerodynamic lift. With wind turbine blades constrained to move in a plane with the hub 

as its center, the lift force causes rotation about the hub. In addition to lift force, a drag force 

perpendicular to the lift force acts to impede rotor rotation somewhat. 

Understanding the motion of flow fields around turbine blades enables the calculation of forces and 

moments acting on the blades as a function of position and time. The use of aerodynamics through 

mathematical analysis, empirical approximations, and wind tunnel experimentation form the scientific 

basis of modern design practices for wind turbine rotors and blades.

During the 1980s and 1990s, “wind turbine designers relied on safety factors to compensate for the effects 

of unknown loads acting on turbine blades and structures. This resulted in components that were 

overdesigned because precise load levels and load paths were unknown... If these forces could be more 

accurately characterized, load paths could be better understood and turbine structures could be optimized” 

for improved energy conversion performance and economy (Simms et al., June 2001). 

Figure 2-6. Principles of Wind Turbine Aerodynamic Lift
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Looking to improve design practices – and facilitated by ongoing advances in computer technology that 

provided the means to evolve wind turbine modeling to higher levels of detail and complexity – the wind 

turbine research community set out to develop modeling tools to simulate loads and performance under a 

wide range of conditions. Early design codes were developed with limiting assumptions, including 

aerodynamic forces derived from two-dimensional (2-D) wind tunnel airfoil tests under steady state 

conditions. These simplifying assumptions continued to be used despite field tests that have pointed to the 

prevalence of three-dimensional (3-D) effects and turbines subjected to highly dynamic load conditions 

from turbulent inflows across rotor blades (Hand, Dec 2001).

It was recognized that improving wind energy performance required more accurate and reliable 

aerodynamic models to predict accurate baseline loading and performance data. This would demand that 

theoretical and computational modeling develop in concert with experimental measurements of high 

accuracy and reliability (IEA 2007 Ch 4). In particular, it was considered essential to separate the effects 

of inflow anomalies from the effects of operating in a 3-D environment.

• Beginning in 1987, the NREL research turbine was field tested in various configurations and 

operated in extreme outdoor atmospheric turbulent conditions. Reports summarizing atmospheric 

turbine test results demonstrated the highly complex dynamic nature of the typical wind turbine 

operating environment that precluded clear understanding among inflow, loading, and turbine 

performance variables.

• Testing in a controlled wind tunnel environment would eliminate highly turbulent wind and 

sheared inflow conditions and enable researchers to isolate and characterize baseline dynamic 

responses and 3-D rotational effects under controlled steady state operating conditions to generate 

reliable and accurate loading and performance information.

However, continuing “experimental uncertainties constrained the ability to accurately understand HAWT 

aerodynamics, formalize reliable predictive models, and validate model predictions (Schreck, 2008). 

Turbine aerodynamicists were confronted with the usual dilemma of using either:

• Densely instrumented full-scale turbines in uncontrollable and sparsely characterized flow fields 

of atmospheric winds, where substantial uncertainties were introduced into the aerodynamic data 

by inflow fluctuations and anomalies; or

• Wind tunnel experiments with controlled and uniform inflows but small model sizes with 

significant differences between experimental and field similarity parameters leading to 

uncertainties regarding the validity of extrapolating (scaling up) otherwise high quality data to 

potentially dissimilar physical regimes (Schreck, 2008).

To address this problem, NREL undertook the Unsteady Aerodynamics Experiment (UAE) to test a 10-

meter diameter research wind turbine to acquire turbine aerodynamic measurements typical of full-scale 

turbines under conditions of steady uniform inflow. The objective was to bridge the knowledge “gap 

between 3-D, unsteady operating environments and 2-D design practices, and to acquire accurate 

quantitative aerodynamic and structural measurements on a HAWT wind turbine, geometrically and 
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dynamically representative of full scale machines in an environment free from pronounced inflow 

anomalies.”

Much of the early effort, beginning in 1997, focused on developing instrumentation and data acquisition 

systems for stringent data acquisition requirements. UAE research turbine measured power production, 

loads, blade surface pressures, angle of attack, inflow dynamic pressures, blade root bending moments, 

shaft bending moments and nacelle yaw moments, blade tip accelerations, and tower motion and control 

mechanism variables (Simms, et al, July 1999).

In early 2000, the NREL research turbine was installed and tested in the world’s largest wind tunnel:

NASA’s 24.4 by 36.6 meter (80’ by 120’) wind tunnel. The NREL/NASA-Ames wind tunnel test was 

designed to provide accurate and reliable experimental measurements with high spatial and temporal 

resolution, realistic rotating blade geometry, closely matched conditions of dynamic similarity, and 

strictly controlled inflow conditions.

The research wind turbine was extensively instrumented to characterize the aerodynamic and structural 

responses of a full-scale wind turbine rotor. Measured quantities included inflow conditions, airfoil 

aerodynamic pressure distributions, and machine responses. The turbine was tested in the tunnel in a twobladed, fixed-pitch (stall-controlled) configuration. It was operated at constant RPM with the rotor 

oriented upwind and downwind of the tower, and the hub in either rigid or damped-teetered 

configurations. An extensive range of pitch angles, pitch motions, yaw positions, and wind velocities 

were tested. The three-week test was completed in May 2000. Data sets were acquired from more than 

1,700 different turbine test conditions (Simms, June 2001).

To maximize benefits from the AMES wind tunnel tests, NREL convened a science panel of advisers 

comprised of wind turbine aerodynamics and modeling experts from throughout the world. NREL used 

the science panel’s guidance to specify the conditions and configurations under which the turbine was 

operated in the wind tunnel. 

Following the Ames wind tunnel test, NREL organized a blind code comparison to use wind tunnel data 

for evaluating the fidelity and robustness of wind turbine aerodynamic codes.

Wind turbine modeling experts were invited to predict the behavior of the NREL wind turbine operating 

under precisely controlled conditions in the wind tunnel. This was a significant collaborative effort on the 

part of the international wind turbine research community. Thirty experts from 18 organizations (12 

European) participated in the blind comparison. Results from 19 different wind turbine modeling tools 

were compared, including blade element momentum (BEM) models, prescribed wake models, free wake 

models, and Navier-Stokes codes (Schreck, 2008).
Chapter 2 – Wind Energy Technologies

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Wind tunnel experimental data were not revealed prior to the blind comparison. In order to participate in 

the collaboration, the experts ran their models to predict loads and performance at selected wind velocities 

and yaw angles, in both upwind and downwind configurations (a total of 20 different cases). The 

specified cases corresponded to selected conditions run during the NREL/NASA-Ames wind tunnel test. 

Blind-comparison results were not favorable. Results showed unexpectedly large margins of disagreement 

between predicted and measured data. Modelers were also surprised by the wide variations between their 

various code predictions. For the no-yaw, steady-state, no-stall cases, turbine power predictions ranged 

from 25% to 175% of measured levels, and blade-bending-force predictions ranged from 85% to 150% of 

measured levels. For higher wind speeds in stall, power predictions ranged from 30% to 275% of 

measured levels, and blade-bending predictions ranged from 60% to 125% of measured levels. No 

consistent trends were apparent in the magnitudes and directions of these deviations (IEA, 2007, Ch 4).

IEA Annex XX was established in 2003 to continue to exploit data acquired during the NREL UAE. Over 

the four-year life of Annex XX, data were used by “dozens of researchers representing the eight 

participating countries of Canada, Denmark, Greece, the Netherlands, Norway, Spain, Sweden, and the 

United States to capitalized on high quality experimental aerodynamics data from the NREL UAE wind 

tunnel tests in support of the formulation and validation of improved aerodynamics models” (Schreck, 

Annex XX Final Report, 2008). 

More accurate reliable models based on the continued exploitation of the NREL UAE database are 

expected to improve wind energy machine design and continue the trend toward lower cost wind energy 

(IEA, 2007, Ch 4). 

2.4.3 Advances in Turbine Blade Materials Database and Analytical Models 

Improved blade design, blade manufacturing, and system reliability require advancing the state of 

knowledge in the areas of blade materials and structurally efficient airfoil designs with the use of 

improved aerodynamic and structural computer codes. 

Supported with DOE Wind Energy Program funding, NREL and SNL advanced the state of knowledge in 

collaboration with turbine and component manufacturers and turbine operators. In addition to developing 

advanced aerodynamic tools and a database for composite blade materials, NREL and SNL supported 

laboratory and field-testing of prototypes and full-scale testing of entire turbine systems with new blade 

designs. 

Composite Blade Materials Durability Tests and Materials Database 

Turbine blades are made from composites as combinations of fiberglass, carbon fibers, and resins. 

Modern turbine blades can reach lengths of up to 200 feet and weigh up to 50,000 pounds. During their 

expected 20- to 30-year life-spans, turbine rotors and blades will spin half a billion times or more, each 

spin corresponding to cycling through the full range of tensile and compressive loads.
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For many years, the DOE Wind Energy Program, acting through SNL, has supported an ongoing effort to 

characterize composite materials for wind turbine use. Much of the related fatigue testing of composites is 

performed at Montana State University (MSU), which first published the DOE/MSU Composite Material 

Fatigue Database in 1997. Industry typically does not have testing facilities to conduct long (billions of 

cycles) material durability tests and, without the DOE/MSU database, industry would likely resort to trial 

and error methods for blade material selection with corresponding reliability and cost penalties.

Turbine Blade Analytical Models 

The DOE Wind Energy Program support for HAWT airfoil development began in the mid-1980s. With 

supporting infrastructure provided with DOE Wind Energy Program funding, new airfoil families were 

developed for stall-regulated, variable-pitch, and variable-speed wind turbines. For stall-regulated rotors, 

better peak-power control was achieved through the design of tip airfoils that restrained maximum lift 

coefficients and permitted greater swept disc area for a given generator size. For variable-pitch and 

variable-speed rotors, better peak-power control was achieved with tip airfoils maximizing lift with the 

use of lightweight blades and low solidity. 

An example of a successful Wind Energy Program-supported blade development effort is the Sweep 

Twist Adaptive Rotor (STAR) blade design, developed in collaboration with the Knight & Carver Wind 

Blade Division. The STAR blade is designed to take advantage of all wind speeds, including marginally 

low wind speeds. It is expected to increase energy capture by 5% to 10%.

2.4.4 WindPact: Wind Partnership for Advanced Component Technologies

In 1999, the DOE Wind Energy Program started funding WindPACT to support the development of new 

high-risk technologies that would reduce the cost of wind energy and achieve cost competitiveness with 

conventional forms of generation. WindPACT has focused on developing flexible rotors, new drive trains, 

and improved manufacturing, transportation and installation methods for wind turbines. In addition, 

WindPACT also supported the following: 

• Analytical studies to explore the implications of sizing large wind turbines for reaching higher 

wind regimes;

• Fabricating prototypes and testing components for operational viability; and

• Dynamometer tests to validate gear box designs and turbine blade structural tests as important 

examples of component level testing supported by the Wind Energy Program. 

2.5 Other Technologies Funded by DOE Wind Energy Program

In addition to DOE-funded technologies selected for analysis, the Wind Energy Program continues to 

support other important wind turbine technologies. These additional technology areas, which this benefitcost study does not examine, include advances in knowledge and turbine acoustics, turbine controls, and 

dynamics of offshore turbine systems.
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Government programs may support the development of a proprietary technology (1) when development 

risks are high or other barriers impede private company advancement or (2) when technology

advancement, if achieved, could enable substantial improvements in a broader area. Along these lines the 

Wind Energy Program occasionally supported the development of proprietary technologies. 

One example of such development was that of variable speed drives. With a variable speed drive, the 

turbine rotor and the generator are permitted to respond to a wide range of wind speeds. Because the 

rotors can spin at speeds proportional to the wind’s speed, variable speed wind turbines can achieve 

improved energy recovery over a wide range of speed. Also, the mechanical stresses on the rotors, which 

are caused by strong wind gusts, can be reduced by allowing the rotors to speed up in response to wind 

gusts. As the generator rotor speed varies, so does the frequency of the resulting alternating current (AC) 

output. Using (inverters with power electronics), the output is converted from variable frequency AC to 

constant frequency output that matches the 60 Hertz requirement of the utility power grid (Adduci, 2008). 

Kenetech (with DOE Wind Energy Program investment) “made variable speed drives work using power 

electronics to convert fluctuating AC to direct current (DC) and back to constant AC at 60 Hertz. 

Inverters, using rectifiers with 12 pulse step sine waves were replaced with high speed solid state power 

switches with advanced power electronics with thousands of pulse steps,” providing power output with 

substantially improved power quality (Interview notes). 

Albeit at additional cost for solid-state power electronics, variable speed drives lead to improved overall 

performance along several dimensions, including higher energy capture and power output; improved 

power quality; and reduced mechanical stresses, as turbulence and wind shears can be better absorbed.
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3-1

3. ANALYTICAL FRAMEWORK & METHODOLOGY

The study’s benefit-cost analysis follows a consistent EERE methodology for retrospective benefit-cost 

assessment (as set forth by Ruegg and Jordan, 2009), intended to generate analytical results that will be 

comparable to other EERE assessments, replicable, and provide building blocks for future benefit-cost 

studies. 

Consistent methodology is used to estimate four categories of benefits: economic benefits, environmental 

benefits, energy security benefits, and knowledge benefits.

Key features of the approach used to estimate the economic benefits include:

• Use of the Mansfield Model, which serves as a unifying framework for retrospective analysis of 

economic benefits

• Definition of the next best alternative technology and a comparison of the selected infrastructure 

technologies against the next best alternative

• Discovery and data collection methods for the estimation of year-by-year economic benefits, 

expressed in real, inflation-adjusted dollars

• Identification of the share of benefits attributable to DOE’s Wind Energy Program, eliminating 

rival explanations

• Computation of economic performance metrics: net present values (NPVs), benefit-to-cost ratios, 

and internal rates of return

To estimate environmental benefits, fossil-fired generation that was replaced with wind energy generation 

is identified. The expected fuel mix for fossil-fired generation (coal, natural gas, and petroleum) is 

determined and avoided greenhouse gas emissions (carbon dioxide and nitrous oxides) are estimated for 

each fuel type using emission parameters published by the EPA. Similarly, avoided sulfur dioxide 

emissions are estimated by extending fossil-fired generation levels, for each fuel type, by EPA sulfur 

dioxide emission parameters. Fossil-fired generation levels are also used to estimate negative health 

impacts that could be avoided with wind energy generation. Fossil-fired generation levels are input to the 

EPA COBRA model, which estimates particulate matter emissions and generates first order 

approximations of avoided negative health impacts, including respiratory problems, cardiac problems, and 

cardiac mortality. (For additional details about the COBRA model, see Appendix B).

To estimate energy security benefits, the portion of fossil-fired generation that was replaced with wind 

energy and would otherwise have been fueled with petroleum, is identified. Petroleum use that was 

thereby avoided is estimated and expressed in barrels of oil equivalent units and in terms of passenger car 

use.
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DOE wind energy knowledge benefits are identified and reported, with an emphasis on knowledge 

embodied in patents, publications, and people. (For additional details about bibliometric approaches used 

for knowledge benefit identification, see Appendix C).

3.1 Mansfield Model: Unifying Framework

In the late 1970’s Edwin Mansfield developed an empirically based approach for the analysis of R&D 

investment impact (Mansfield, et. al., 1977). The Mansfield approach, or inductive model, is grounded in 

innovative data collection and discovery techniques. It tends to indicate that social returns (benefits that 

accrue to society, including private investors) from R&D investments can substantially exceed returns to 

private investors, alone. The difference between social and private returns are spillover benefits – benefits

enjoyed by society at large after netting out private returns to industrial R&D investors. In this manner, 

the Mansfield model provides grounds for the hypothesis that R&D investments can generate significant 

benefits to society at large, beyond private benefits to industrial R&D investors. The retrospective 

analysis of public benefits from the Wind Energy Program uses the Mansfield approach as its point of 

departure. 

3.2 Next Best Alternative Technology

Benefits that are derived from technology advances are estimated against the “next best alternative,”

which is what is most likely to have happened without specified technology advances. For the 

retrospective benefit-cost analysis, the “next best alternative” requires looking back in time and 

hypothesizing what technical advances are likely to have been achieved in the absence the selected 

infrastructure technologies being investigated.

Because this area is ultimately conjectural, the selection of the “next best alternative” requires a 

significant element of judgment. To be meaningful and credible, the identification of the “next best 

alternative” must be grounded in expert opinion, representing substantial knowledge of new technologies 

in the specified cluster and their commercial applications. The “next best alternative” can then provide a 

useful baseline for estimating benefits from technology advances.

3.3 Additionality and Attribution 

The long time frame and confounding factors of research and technology development complicate the 

determination of attribution. The EERE R&D benefit-cost studies address this by (1) collecting the most 

lines of evidence from independent sources as possible within practical constraints of data availability, 

time, and resources and (2) transparency in discussion of data collection and analysis.

The key issue is once again conjectural: in the absence of government programs, would industry or others 

have made corresponding R&D investments to reach similar technology advances, and would similar 
Chapter 3 – Analytical Framework and Methodology

3-3

levels of benefits (economic cost savings, reduced environmental emissions, and improved levels of 

energy security) have been achieved? 

Given the complexities of technologies and market uncertainties, identifying degrees of “additionality” –

the effects that would not have happened without government investment – also requires a significant 

element of judgment. To be meaningful and credible, gauging the extent of benefits that government 

programs have generated beyond what industry would have generated without those programs requires 

expert opinion. Once the extent of additionality is established, benefits are attributed to government 

programs with a reference to the extent of additionality.

• If technology is unlikely to have been developed without the government program, additionality 

is deemed to be high; a large portion of public benefits will be attributed to the government 

program.

• In contrast, if technology is likely to have been developed or partially developed without the 

government program, additionality will be deemed to be low; only some limited portion of public 

benefits will be attributed to the government program.

Because a group of technologies are considered here without disaggregation, the attribution analysis 

involves:

• Mapping attribution to technology timelines to show when identified technology investments and 

associated technology advances are estimated to have occurred. 

• Indicating the range of percentage shares of benefits attributable to the DOE R&D program, after 

elimination of rival explanations. 

• Discussing sources and degrees of uncertainty.

• Using degrees of influence (overwhelming influence, dominant influence, very important, 

influential, and no influence or minimal influence) that the DOE R&D program had in causing 

benefits in comparison with the next best alternative. 

3.4 Measures of Economic Performance

Economic benefits are increases in the value of goods and services. Once yearly economic benefits are 

identified and monetized in nominal dollars, they are converted to real, inflation-adjusted (2008) dollars 

and an appropriate portion of benefits is attributed to the DOE Wind Energy Program. Similarly, once 

environmental health benefits from reduced air emissions are estimated in monetary terms, they too are 

expressed in 2008 dollars, and combined with the category of benefits labeled "economic benefits." 

Annual program investments are also identified in nominal dollars and converted to inflation-adjusted 

2008 dollars. Net undiscounted benefits are arrived at by subtracting cumulative dollar investments from 

cumulative dollar estimated benefits. Three conventional measures of economic performance are used to 

characterize economic returns from program investment (Ruegg and Jordan, 2009).
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• Net Present Value of Benefits: NPV is the lump-sum time-equivalent dollar value of all the 

economic benefits less all the costs, where both are discounted using Office of Management and 

Budget (OMB) proscribed discount rates as of the base year (i.e., the first year of the DOE 

technology investment). A positive NPV means that the benefits are sufficient to cover all costs 

plus the required rate of return expressed by the discount rate used to calculate NPV. The larger 

the net benefit, the greater the extent that benefits exceed costs, and the more worthwhile a 

project is considered, other things being equal. 

• Benefit-Cost Ratio: The benefit-cost ratio compares benefits to costs and is a dimensionless 

number that indicates how many dollars of benefit are returned per dollar invested beyond the 

required rate of return expressed by the discount rate. It is computed by dividing total discounted 

benefits by total discounted costs. A ratio greater than one means that benefits exceed costs. A 

ratio of 10 to 1, for example, means that, on average, $10 in benefits are generated for every 

dollar of costs incurred, after adjusting for the time-value of money. (Generally, investment costs 

for the denominator and other costs are deducted from benefits in the numerator.)

• Internal Rate of Return: The internal rate of return gives the rate of return on investment, 

expressed as an interest rate. Unlike the previous two measures, the discount rate is not used 

directly in the internal rate of return calculation. Rather, the internal rate of return is solved for by 

substituting an interest rate (i) with unknown value in place of the discount rate in the discounting

formulas and solving for the value of (i) for which time-adjusted benefits equal time-adjusted 

costs. The solution rate is then compared against the specified discount rate(s) to judge the 

economic value of the investment, where a solution rate less than the discount rate indicates an 

investment whose rate of return does not justify the investment on economic grounds alone.

Common discounting conventions are used for NPV and present value calculations, that is, discounting 

back to the time of initial DOE Wind Energy Program investments starting in 1976. Discount rates of 7% 

and 3% are used according to conventions outlined in the OMB Circulars A-94 and A-4, respectively.

3.5 Data Collection Approach

Multiple data sources are used to convert partial indicators and chains of evidence into integrated and 

credible analytical results. Data were obtained from primary and secondary sources, including:

• EERE program and planning documents

• DOE Wind Energy Program budget data

• Prior program evaluations and assessments

• Wind Technology Linkages Study (Ruegg & Thomas, 2009)

• Technical literature for wind energy

• Commercial and market information for the wind energy industry

• Estimates of industrial R&D funding

• Interviews with 47 subject matter experts:

o Wind Energy Program staff and consultants
Chapter 3 – Analytical Framework and Methodology

3-5

o Senior staff at DOE laboratories (NREL, SNL, LBNL)

o Experts at universities, industry, and overseas research laboratories, unaffiliated with the 

DOE Wind Energy Program

As summarized in Figure 3-1, multiple data sources are used throughout the study to select technologies 

whose benefits are to be analyzed, to identify the “next best alternative” scenario, to estimate the extent of 

DOE additionality, and to determine the DOE Wind Energy Program impact.

Figure 3-1. Data sources and Chains of Evidence

4-1

4. ECONOMIC BENEFITS

This chapter specifies the counterfactual next best alternative technology as a less efficient, less reliable,

and more expensive wind energy generating technology. It posits that the implication of operating under a 

next best alternative scenario would be lower levels of wind energy generation and, given stable levels of 

aggregate electricity demand, more fossil-fired generation to compensate for reduced levels of wind 

energy generation.

Based on an evidence-based process, the DOE effect (from DOE investments in infrastructure 

technologies) is identified as an acceleration of reliability improvements, commercial risk reductions, and 

a competitive cost of energy. The combined effect of changes in reliability, risk, and cost of energy is to 

accelerate clean wind energy generation levels by six years, as discussed in section 4.4.

To fairly allocate benefits from DOE-funded R&D among the Wind Energy Program and its industry 

partners, an attribution scheme was developed. Sensitivity analysis is provided in a 10% band around the 

80% mean attribution rate to DOE.

DOE Wind Energy Program investments over the 1976 to 2008 period are documented, economic 

benefits are estimated and conventional performance metrics (net present values, benefit-cost ratios, and 

internal rates of return) are presented below. 

4.1 Next Best Alternative Technology Scenario

Based on analysis using multiple sources of data (program documents, technical literature, and interviews 

with subject matter experts), the study concludes that infrastructure technologies selected for evaluation 

have enabled the faster adoption of science and knowledge-based engineering design practices. These

have made it possible to build large, reliable, cost competitive wind turbines that have greater energy 

capture, are subject to increased wind loading, and are rated for megawatt scale production. 

Without these infrastructure technologies, the knowledge base for understanding the dynamic interplay of 

forces, scientific and engineering databases, and the analytical tools for avoiding damaging system loads 

would not be available (in the same timeframe) and could not be accessed by industrial designers to 

develop proprietary products (components and turbine systems) unique to each OEM and components 

vendor. 

The next best alternative technology is described as a counterfactual scenario under which wind turbines 

are designed using trial-and-error methods and relatively crude rules of thumb. Under this scenario:

• Turbines would be prone to more frequent systemic failure. This would retard commercial 

activity and preclude building larger, more heavily loaded utility-scale wind turbines.
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• Component reliability (mean times between component failures) would be degraded, resulting in 

higher outage rates, reduced availability, and higher operation and maintenance (O&M) expenses.

• Reduced reliability levels would increase commercial risks and financing costs.

• Without effective analytical models, engineering databases, test protocols and test facilities, 

designers would “overdesign” wind turbines with high safety factors.

• High safety factors would contribute to higher capital costs. 

• Higher capital costs, higher financing costs, and higher O&M expenses would contribute to 

higher wind energy costs.

• With higher commercial risks and higher cost of energy, capacity additions would not have 

reached historic levels. 

• Assuming stable levels of aggregate electricity demand (at historic levels) and reduced wind 

generating capacity (under the next best alternative, using inefficient trial and error methods), 

wind power generation would be lower than existing levels and would be replaced with a mix of 

conventional fossil-fired generation.

To suggest the extent of reliability penalties and cost penalties under the next best alternative scenario, it 

is instructive to compare current reliability levels and costs to early 1980 levels when trial and error 

methods and the use of engineering rules of thumb was the norm.

• In the early 1980s, average O&M cost (a proxy for reliability levels) was $40 per MWh or four 

times higher than the current average $10 per MWh level (Wiser, July 2008), achieved with a 

reliance on advanced infrastructure technologies.

• In the early 1980s, the average capital cost per MW was $4,500, or over three times higher than 

the $1,400 average current capital cost (Wiser, July 2008).

• In the early 1980s, the average cost of energy was estimated at approximately $0.86 per kWh or 

more than 25 times higher than the $0.033 average cost of energy in 2006 (Flowers, 2006). Due 

to higher materials costs and wind turbine component costs, associated with the recent growth in 

wind energy capacity additions, in 2008, the average cost of wind energy increased to $0.05 per 

kWh.

4.2 Implication of the Next Best Alternative: Increased Fossil-Fired Generation

As the widespread use of trial-and-error design methods would have continued to lower reliability levels 

and increase risks for wind project developers, wind energy capacity additions would be lower relative to 

historic levels. At the same time, aggregate electricity demand levels would continue at historic levels.

To compensate for reduced wind generation, in the context of stable aggregate electricity demand, the 

reduced generation would be replaced with a mix of fossil-fired generation (Sutherland & Veers, 1995). 
Chapter 4 – Economic Benefits

4-3

A shift to fossil-fired generation does not represent an alternative next best scenario. Rather it is a direct 

implication of what could be expected with reduced wind generating capacity and reduced wind power 

generation, under the next best scenario specified in Section 4.2.1.

4.2.1 Alternative Generation Mix

To estimate the magnitude of replacement fossil generation by fuel component (coal, natural gas, and 

petroleum), a regional analysis was conducted using Energy Information Administration (EIA) generation 

mix data for the 15 states that account for most U.S. wind power generation. 

As the economic analysis indicates, a substantial share of economic benefits is traced to high historic 

wind generation levels during the 2005 to 2008 timeframe. In this context, information about the 2007 

generation mix is used to conduct regional analysis of fossil generation by fuel component. 

• In 2007, 95% of U.S. wind generation was concentrated in the states of Texas, California, 

Minnesota, Iowa, Washington, Colorado, Oregon, Illinois, Oklahoma, New Mexico, New York,

Kansas, North Dakota, Pennsylvania, and Wyoming (Wiser & Bolinger, May 2008).

• For these 15 states, the 2007 power generation mix from coal, natural gas, and petroleum was

used to compute average utilization of each fossil fuel and weighted for the state’s relative wind 

power generation.

Results from regional analysis, summarized in Table 4-1, indicate that 43% of reduced wind generation 

would be replaced with coal-fired generation, 55% would be replaced with natural gas, and 1% would be 

replaced with petroleum.
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Table 4-1. Weighted Average Fossil Fuel Generation Mix in Top Wind Energy Producing 

States

States

Percent of 

National Wind 

Power

Generation

Coal-Fired 

Generation

(Billion kWh)

Natural GasFired 

Generation

(Billion kWh)

PetroleumFired 

Generation

(Billion kWh)

Texas 28 147 192 2

California 17 2 104 2

Minnesota 8 34 3 1

Iowa 8 37 2 0

Washington 7 10 7 0

Colorado 4 36 12 0

Oregon 4 4 13 0

Illinois 2 92 6 1

Oklahoma 6 36 27 0

New Mexico 4 28 5 0

New York 3 22 37 14

Kansas 4 36 2 1

North Dakota 2 30 0 0

Pennsylvania 1 119 12 3

Wyoming 2 43 0 0

Weighted Average Fuel Use (Weighted 

for % of National Wind Power Gen) 43% 55% 1%

Source: Petroleum-based generation from EIA, Net Generation by State, Type of Producer and Energy Source, State Historical 

Tables 2007, Released January 20, 2009.

4.2.2 System Load Implications with Fossil Fuel Replacement 

Is the replacement of almost half of the wind-generated power with coal-fired base load generation a valid 

substitution? Or does the intermittent nature of wind power suggest that it more likely corresponds to, and 

would be replaced with, natural gas-fired peak power generation?

“Although a single wind turbine is intermittent, this is not generally true for a system of several 

wind farms separated by hundreds of kilometers and experiencing different wind regimes. The 

total output of such a system generally varies smoothly and only rarely experiences a situation 

where there is no wind at any site. As a result (wind generated power) can be made as reliable as 

conventional coal fired (base load) power generation by adding small amount of dedicated peak 

load capacity that is operated to back up wind generation when required” (Energy Sciences, 

2007).

Capacity replacement is not a one-to-one correspondence. “To replace electricity generated by a 1000 

MW coal-fired power station with annual average power output of about 850 MW, a group of wind farms 

with capacity (rated power) of about 2500 MW located in windy sites is required. The higher capacity 

allows for lower capacity factor” (Energy Sciences, 2007).

However, on a power generation output basis, rather than an installed capacity basis, the absence of fuel 

cost for wind generation can make up for the higher capital costs of wind generation as long as total costs 
Chapter 4 – Economic Benefits

4-5

are competitive with conventional power. It would, therefore, appear that using the weighted average 

power generation mix for the top 15 wind producing states is a valid approximation of the average energy 

mix that would replace some wind generation, under the next best alterative scenario.

4.3 Attribution Analysis: What is the DOE Effect?

Based on interviews with subject matter experts, the study found that the DOE effect (from DOE 

investments in infrastructure technologies) was on average a six-year acceleration of reliability 

improvements, commercial risk reductions, and cost of energy reductions. 

Under a counterfactual scenario, without DOE-funded infrastructure technology development, 2008 wind 

energy production and cost of energy would shift back to 2002 levels. For all other years, wind energy 

power production and cost of energy would also shift back by six years.

The study estimates attribution levels of 80% for DOE and 20% for industry partners. These attribution 

levels reflect that several of the selected infrastructure technologies were funded entirely by DOE, 

without industry partner participation. For others, industry partners provided a cost share as a percent of 

DOE investment.

4.3.1 Tabular Summary of Attribution Analysis

Monetized benefits from the DOE technology investments, presented in Section 4.6, include:

• Wind energy cost savings and other resource cost savings (i.e., the category designated 

“economic benefits”) and

• Health cost savings (i.e., part of the category designated "environmental benefits").

What portion of these monetized benefits, as well as the non-monetized benefits of greenhouse gas effects 

and energy security, can be attributed to the DOE Wind Energy Program? 

A summary in table format (Table 4-2) is used to guide the presentation of attribution analysis results. 

This table is organized into rows identifying the work that was supported with DOE-funded investments, 

work that was supported by other investments, the postulated DOE effect, driving forces and rival 

explanations, a description of DOE influence, and the basis of evidence for that influence. Columns 

indicate how items in each row correspond to different stages of research, development, and 

commercialization. 

Starting with the first row (“What DOE Did”) in the selected technology areas, research indicates that the 

primary DOE impact was the development of (1) infrastructure technologies in the areas of advanced test 

and measurement methods, scientific and engineering databases, and advanced simulation methods and 

(2) DOE capital investments in test facilities that industry would have had difficulty replicating and 

without which the advanced test and measurement methods developed under item 1 could not be used to 
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their full effect. Continuing in this row, it is indicated that there was considerable indirect value added 

from infrastructural technologies, freely available to industry designers, facilitating more sophisticated 

design practices that resulted in achieving higher reliability levels, reduced commercial risks and lower 

costs of energy.

Table 4-2. Matrix for Assessing Attribution by Technology Stage

Categories of 

Information 

Needed for

Additionality 

Assessment

Technology Timeline (Stage of Research, Development, and Commercialization)

Preliminary & 

Detailed

Investigation

Develop 

Components

Develop 

System

Validate & 

Demonstrate

Commercialize Market 

Adoption 

What DOE Did 

(in Technology 

Areas Selected 

for Evaluation)?

DOE supported 

basic and applied 

research, resulting in 

infrastructure 

technologies: 

advanced testing and 

measurement 

methods, scientific 

and engineering data 

bases, and 

simulation models 

(in the areas of 

turbulence 

modeling, 

aerodynamic 

experimentation and 

materials data bases 

for advanced 

airfoils)

Advances in Variable 

Speed Drives 

Under WindPact 

program, prototype 

fabrication; gear box 

dynamometer tests, and 

turbine blade structural 

tests 

Results from 

Unsteady 

Aerodynamic 

Experiment 

are used to 

validate 

industrial 

design codes

NREL and 

SNL test 

facilities are 

used to 

demonstrate 

and validate 

components 

and entire 

wind turbine 

systems

Indirect impact as 

infrastructure technologies 

facilitate industrial 

development of proprietary 

products and manufacturing 

processes. Some direct 

impact from Wind Powering 

America (a DOE program 

not evaluated here) which 

supported commercialization 

& market adoption

What Others 

Did? 

(Rival 

Explanations)

Smaller scale wind 

tunnel aerodynamic 

experiment (Mexico 

Project) supported 

by European 

research institutes 

and materials data 

bases developed at 

European research 

institutes. Reported 

to be less advanced

Development of 

components and 

systems primarily 

supported by industry in 

the US and overseas

Industry leads 

commercialization and 

market adoption efforts

Driving / 

Restraining 

Policies and 

Government 

Forces (Rival 

Explanations)

U.S. Government and a number of states 

have established programs to stimulate 

renewable energy production. Key policy 

tool include the production tax credit (PTC) 

and renewable portfolio standards (RPS), 

intended to stimulate late stage industrial 

development of components and systems, 

and promote capacity additions by wind 

energy project developers. Without 

infrastructure technology advances 

facilitating substantially higher reliability 

levels, reduced risks, and lower costs it is 

(Continued)
Chapter 4 – Economic Benefits

4-7

Categories of 

Information 

Needed for

Additionality 

Assessment

Technology Timeline (Stage of Research, Development, and Commercialization)

Preliminary & 

Detailed

Investigation

Develop 

Components

Develop 

System

Validate & 

Demonstrate

Commercialize Market 

Adoption 

unlikely that PTC or RPS would have had 

significant independent impact

Description of 

DOE Influence

Infrastructure technologies have direct and indirect influence during all stages of R&D and 

commercialization. DOE influence was to facilitate accelerated industrial development of 

components and systems with higher reliability, reduced risk, and at lower cost of energy. DOE 

influence on

o Turbulence Modeling – very important

o Unsteady Aerodynamic Experiment – very important

o Materials Data Base Development – important

o Demonstration and Validation programs – important

Evidence for 

DOE influence

Interviews with subject matter experts from research institutes, academia, industry, and project 

developers, technical studies, Wind Energy Program documents, other published and 

unpublished information

The DOE Effect Accelerated 

development of 

infrastructure 

technologies

Infrastructure technologies along with 

test facilities for demonstration and 

validation of components and systems 

resulted in the use of more sophisticated 

industrial design processes that led to 

higher reliability rates, lower commercial 

risks, and lower cost of energy

Commercialization and 

Market Adoption were 

accelerated by 

approximately six years

On the second row, “What Others Did”, noteworthy activities include two European research institute 

projects. First, the Mexico Project, which was a limited extension of the DOE-funded Ames Aerodynamic 

Experiment building on the scientific and engineering data generated through the DOE-funded 

experiment. The Mexico Project used a smaller scale wind tunnel. Second, the composite turbine blade 

material databases, which were bases developed at European research institutes, complemented the DOEfunded materials database developed at the University of Montana. Both of these efforts were considered 

valuable, although less advanced and with more limited infrastructure technology impact than DOEfunded efforts.

Under the third row, “Driving and Restraining Policy Forces,” the U.S. Production Tax Credit (PTC) and 

state Renewable Portfolio Standard (RPS) are noteworthy as policy forces during the later stages of 

commercialization and market adoption. Interviews with subject matter experts explored the likely impact 

of the PTC and other demand-side policies. Experts indicated that the PTC was also important for 

stimulating later-stage development of components and systems and for wind energy capacity additions. 

Without the PTC, experts suggested that additional delays, beyond the six-year delay from R&D 

underinvestment, would have been likely. The magnitude of these additional delays could not be 

identified. 

At the same time, experts consistently stressed that without prior R&D investments in infrastructure 

technologies – leading to lower energy costs, improved reliability, and improved availability – the PTC is 
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unlikely to have been effective by itself. Specifically, the PTC could not have brought about four-fold 

improvements in reliability (as reflected in historic O&M expense reductions), three-fold improvement in 

wind energy capital costs, and the 25-fold reduction in the cost of energy from the $0.85 per kWh level of 

the early 1980s. Without reliability improvements facilitated by DOE-funded infrastructure technologies, 

commercial risks would have remained unacceptably high and project developers would have abstained 

from adding wind capacity under conditions of higher technical and commercial risk. 

Based on the input from experts, the study concludes that, all other things being equal, the PTC and RPS 

may have provided a margin of inducement for the timing of capacity additions and removing these 

demand side policies would have likely resulted in additional delays in capacity addition and cost of 

energy reductions. Appendix D provides additional discussion of the PTC versus R&D influences on 

wind energy capacity growth. 

On the fourth row, “Description of DOE Influence,” interviews with subject matter experts indicate that 

DOE-funded technologies are considered important to very important.

As shown in the fifth row, “Evidence for DOE Influence,” the study relied on extensive interviews with 

subject matter experts at U.S. and overseas research laboratories, executives at wind turbine OEMs, and 

component manufacturers. During these interviews, experts were asked to identify what they considered 

as the most important DOE-funded technical contributions, how they rated the importance of these 

contributions, and what they expected would have happened in the absence of DOE-funded infrastructure 

technologies. Experts were also asked to characterize technology advances as infrastructural or 

proprietary in nature and whether the impact of the specific technology advances could be identified and 

separately analyzed.

Under the sixth row, the study identified “the DOE Effect” as a six-year acceleration of reliability levels, 

reduction of commercial risk, and reduction of wind energy cost. During interviews with subject matter 

experts, follow-up questions probed the likely impact of average acceleration levels on cumulative 

installed capacity and power generation as well as the severability of individual technology elements for 

purposes of analyzing specific technology impacts. Respondents indicated the following:

• A six-year delay without DOE-funded technologies could be expected to have had the impact of 

reducing clean wind energy power generation and cost of wind energy from 2008 to 2002 levels.

• Separating out the independent beneficial impact from turbulence modeling, aerodynamic 

experiments, and materials databases was deemed impractical because advanced infrastructure 

technologies tend to work in concert rather than in isolation to impact reliability levels, technical 

risks, and costs. 

4.3.2 Estimation of Attribution Levels

The estimation of average DOE attribution levels proceeded in two stages. First, subject matter experts at 

research institutes, large industrial companies, component manufacturers, and leading engineering 
Chapter 4 – Economic Benefits

4-9

consulting firms assigned a six-year acceleration to the DOE effect. All of the six-year acceleration is thus 

assigned to DOE (and its industry partners). Second, given that some DOE Wind Energy Program 

technology investments proceeded with industry partners, attribution of economic benefits between DOE 

and its industry partners is the next step. Table 4-3 indicates the logic for specifying attribution levels to 

DOE and its industry partners

Table 4-3. Summary of Attribution Logic

Program Investments in

Nominal Dollars and Estimated

Industry Match ($2008 Millions)

Percent

DOE Industry Match

All DOE Wind Energy Program Technology 

Investments (1976-2008) 1,719

DOE Program Investments in

Selected Technologies 1,239

Selected Technology Investments Without Industry 

Partners (Turbulence Modeling, Ames Experiment, etc.) 371

Selected Technology Investments With Industry Partners 

(Demo & Validation). Average Industry Matching Funds

at 35% of DOE investment or 692 x 0.35

868 304

DOE Attribution Share

Industry Attribution Share

1,239 / (1,239+304)

304 / (1,239+304)

80%

20%

Total DOE Wind Energy Program investment over the 1976 to 2008 period was $1.719 billion (2008 

dollars). Over this period, line items and budget categories have changed and it was not evident which 

budget items should be assigned to Wind Energy Program investments in selected technologies. With 

assistance from a senior member of SNL Wind Energy Technology Department, this data limitation was 

overcome and Wind Energy Program investments that directly supported the selected infrastructure 

technology were estimated as $1.239 billion (see Section 4.5). It was further estimated that approximately 

30% of DOE investments (supporting the development of turbulence models and the Unsteady 

Aerodynamic Experiment) proceeded without industry partners and matching funds. These technology 

investments were fully funded by DOE at approximately $371 million. For the remaining 70% of DOE 

investments in selected technologies ($868 million), the industry match could range from 20% to 50% of 

the DOE investment. Using an average 35% rate for industry match against the $868 million DOE 

investment, industry match was estimated at $304 million. Dividing total DOE investment of $1.239 

billion by the sum of DOE investment and industry match, the DOE attribution rate is estimated at 80% 

and industry attribution rate is estimated at 20%.

The above benefit attribution estimates are conservative. DOE generally led partnering efforts. Without 

DOE leadership, it is safe to say that some of the industry partners, many of them smaller firms and 

sometimes startups, would not have had the ability to lead projects and nothing might have happened. 

Interviews with industry subject matter experts, who at one time in their careers worked for these 

companies, directly confirm this conclusion.
Retrospective Benefit-Cost Evaluation of U.S. DOE Wind Energy R&D Program: Impact of Selected Energy Technology Investments

4-10

4.4 DOE Investments in Wind Energy Technologies

From the 1976 to 2008, the DOE Wind Energy Program invested $1.073 billion (nominal costs) in basic 

and applied research and in support of demonstration, technology development, and testing activities. To 

determine what portion of total investments could be assigned to selected technologies of evaluative 

interest, the magnitude of investments in selected technologies was estimated by using the following 

budget categories as inclusion criteria:

1

• Aerodynamics and structural dynamics research

• Advanced systems and supporting research

• Atmospheric fluid dynamics research

• Turbine research and testing

• Low wind speed technologies

• Advanced components

• Wind Partnerships for Advanced Component Technologies (WindPACT)

• Construction of experimental testing facilities

• Engineering and technology development

• Certification

The resulting Wind Energy Program investments in selected infrastructure technologies and total Wind 

Energy Program investments are indicated in columns 1 and 2 of Table 4-4. Using the Gross Domestic 

Product implicit price deflator, nominal investments in selected technologies and total nominal 

investments are adjusted for inflation to $1.239 billion and $1.719 billion respectively (U.S. Department 

of Commerce [DOC], 2009). Inflation-adjusted investments are indicated in columns 3 and 4 of Table 

4-4.

 1 Paul Veers, SNL Wind Program.
Chapter 4 – Economic Benefits

4-11

Table 4-4. Total Program Investments and Estimated Investments in Selected Technologies

Year

Investments in

Selected 

Technologies 

Nominal

(Thousand 

Dollars)

Total Wind Energy 

Program

Investments

Nominal

(Thousand Dollars)

Inflation Adjusted 

Investments

in Selected 

Technologies

2008 Dollars

(Thousand Dollars)

Inflation Adjusted 

Total Wind Energy 

Program Investments

2008 Dollars

(Thousand Dollars)

(1) (2) (3) (4)

1976 14,403 44,027

1977 20,500 58,910

1978 34,470 35,300 92,560 94,788

1979 58,155 59,555 144,166 147,636

1980 56,254 60,555 127,801 137,572

1981 76,087 77,500 158,050 160,985

1982 37,700 38,400 73,807 75,178

1983 31,290 31,390 58,928 59,116

1984 26,367 26,367 47,860 47,860

1985 28,155 28,355 49,603 49,955

1986 12,536 24,786 21,608 42,723

1987 11,930 16,606 19,983 27,816

1988 8,064 8,464 13,059 13,707

1989 8,260 8,760 12,890 13,670

1990 8,498 8,687 12,768 13,052

1991 10,836 11,034 15,724 16,011

1992 21,082 21,282 29,883 30,167

1993 5,500 23,841 7,628 33,063

1994 9,334 29,151 12,678 39,593

1995 11,784 34,309 15,679 45,648

1996 16,830 31,420 21,974 41,023

1997 20,540 28,646 26,353 36,752

1998 17,301 32,128 21,949 40,759

1999 20,861 34,076 26,082 42,604

2000 17,219 31,734 21,072 38,835

2001 19,902 39,132 23,817 46,830

2002 21,731 38,211 25,592 44,999

2003 26,282 41,640 30,299 48,005

2004 26,188 39,803 29,358 44,621

2005 24,053 40,631 26,093 44,078

2006 17,276 38,333 18,150 40,273

2007 29,839 48,659 30,476 49,698

2008 22,643 49,034 22,643 49,034

Totals

Investments 736,967 1,072,692 1,238,531 1,718,989

Source 1: Unpublished EERE historical budget spreadsheets.

Source 2: GDP Price Deflator from U.S. DOC, 2009.
Retrospective Benefit-Cost Evaluation of U.S. DOE Wind Energy R&D Program: Impact of Selected Energy Technology Investments

4-12

4.5 Estimation of Economic Benefits

Economic benefits from accelerated technology advances supported by DOE Wind Energy Program 

investments are estimated by comparing actual wind energy generation levels to wind energy generation 

levels under the counterfactual scenario.

Cost savings or monetized benefits from DOE-funded technology advances fall into two categories:

1. Wind energy cost savings relative to the next best alternative scenario: The value of these benefits 

is estimated at $3.278 billion (undiscounted 2008 dollars).

2. Health cost savings (i.e., the monetized portion of “environmental benefits”) relative to the next 

best alternative scenario: The value of these benefits is estimated at $9.766 billion (undiscounted 

2008 dollars).

4.5.1 Wind Energy Generation Levels

Wind energy generation levels are a key analytical variable for estimating the economic, environmental, 

and security impacts of selected DOE-funded technologies. Actual historical generation levels are 

compared to generation levels shifted back by six years, corresponding to the counterfactual scenario of a 

next best alternative without DOE impact. 

From the late 1970s through the early 1980s, only nominal wind generation levels can be approximated. 

Reliable historical generation data becomes available starting in 1984. After generation levels are shifted 

back by six years for the counterfactual scenario, reliable counterfactual generation levels become 

available in 1990. Due to these data limitations, the comparison of actual and counterfactual generation 

levels is limited to the 1990 to 2008 period. Over this period, as indicated in Table 4-5, the impact of 

delayed wind energy generation by six years under the counterfactual scenario is:

• 140 billion kWh or 68% reduction in wind generated power (i.e., a decrease from 207 billion 

kWh to 67 billion kWh) (columns 1 and 2).

• With stable levels of aggregate electricity demand, the 140 billion kWh reductions are expected 

to be replaced with conventional fossil-fired generation (based on the average fuel mix of fossil 

fired generation from Table 4-1) (column 3).

• The remaining 67 million kWh of wind energy generation, under the counterfactual scenario 

using less efficient and less reliable wind energy technologies, will be subject to higher costs of 

energy (column 2).
Chapter 4 – Economic Benefits

4-13

Table 4-5. Actual Wind Generation vs. Generation Levels under 

Counterfactual Scenario

Power Generation (Billion kWh)

Year Wind Generation 

Level with DOE 

Impact

Wind Generation 

Under Counterfactual Scenario

Additional Fossil Fuel 

Generation Under 

Counterfactual 

Scenario

(1) (2) (3)

1976

1977

1978 0.002

1979 0.002

1980 0.006

1981 0.012

1982 0.124

1983 0.426

1984 1.06 0.002

1985 1.85 0.002

1986 2.17 0.006

1987 2.41 0.012

1988 2.48 0.124

1989 2.49 0.426

1990 2.80 1.06 1.74

1991 2.80 1.85 0.95

1992 2.90 2.17 0.73

1993 3.00 2.41 0.59

1994 3.10 2.48 0.62

1995 3.20 2.49 0.71

1996 3.20 2.80 0.40

1997 3.30 2.80 0.50

1998 3.00 2.90 0.10

1999 4.50 3.00 1.50

2000 5.59 3.10 2.49

2001 6.74 3.20 3.54

2002 10.35 3.20 7.15

2003 11.19 3.30 7.89

2004 14.14 3.00 11.14

2005 17.81 4.50 13.31

2006 26.59 5.59 21.00

2007 30.98 6.74 24.24

2008 51.52 10.35 41.17

Totals

1990-08

206.72 66.95 139.77

Source: For 1990, 1995-2004: EERE Power Technology Energy Data Book 4th Edition August 2006 NREL/TP-620-39728. 1991 

to 1994 were straight-lined estimates. 2000-2007: EERE Renewable Energy Data Book Sept 2008 Section 4, Page 58.

4.5.2 Wind Energy Cost Savings 

The remaining wind energy generation, under the counterfactual scenario, is subject to higher production 

costs, reflecting the utilization of less efficient and less reliable wind generation technologies. This leads 

to higher per kWh cost of energy. With DOE impact, the higher cost of energy is avoided.

6-Year 

Delay
Retrospective Benefit-Cost Evaluation of U.S. DOE Wind Energy R&D Program: Impact of Selected Energy Technology Investments

4-14

To arrive at cost savings relative to higher cost of energy under the counterfactual scenario: 

• Actual costs for the 1984 to 1998 period are estimated from NREL “Capacity & Cost Trends”

chart (Figure 4-1). 

• Actual costs for the 1998 to 2008 period are obtained from 2008 Wind Technologies Market 

Report (Wiser & Bolinger, 2009).

• Cost of energy for the counterfactual scenario is obtained by shifting actual costs back by six 

years.

• Cost savings on a per kWh basis are derived from comparing actual costs and estimated 

counterfactual costs and are presented in Table 4-6, column 3.

Figure 4-1. Capacity and Cost Trends for U.S. Wind Energy (MW and Cents/kWh)

Source: Flowers, L. “Wind Energy Update”, August 09, 2006.

Cost savings on a per kWh basis are multiplied by remaining wind generation (under the next best 

alternative scenario from Table 4-5, column 2). Resulting wind generation cost savings in nominal dollars 

are presented in Table 4-6, column 4 and in inflation adjusted 2008 dollars (U.S. DOC, 2009) are and 

presented in Table 4-6, column 5.

Increased Turbine Size - R&D Advances - Manufacturing Improvements

Capacity (MW)

Cost of Energy (cents/kWh*)

Cost of Energy and Cumulative Domestic Capacity

*Year 2000 dollars

Increased Turbine Size - R&D Advances - Manufacturing Improvements

Capacity (MW)

Cost of Energy (cents/kWh*)

Cost of Energy and Cumulative Domestic Capacity

*Year 2000 dollars
Chapter 4 – Economic Benefits

4-15

Table 4-6. Cost of Wind Energy With and Without DOE Impact

Cost of Energy - COE

$/kWh (Nominal Dollars)

Wind Energy

Cost Savings

Year COE with

DOE Impact

COE without

DOE Impact

Cost Savings

with DOE 

Impact

Nominal Wind 

Energy Cost Savings

(Thousand Dollars)

Wind Energy Cost 

Savings in 2008 

Dollars

(Thousand Dollars)

(1) (2) (3) (4) (5)

1976

1977

1978 0.900

1979 0.900

1980 0.870

1981 0.770

1982 0.550

1983 0.460

1984 0.340 0.900

1985 0.270 0.900

1986 0.215 0.870

1987 0.192 0.770

1988 0.169 0.550

1989 0.146 0.460

1990 0.123 0.340 0.217 230,020 345,608

1991 0.100 0.270 0.170 313,990 455,626

1992 0.095 0.215 0.120 260,640 369,449

1993 0.090 0.192 0.102 245,922 341,051

1994 0.085 0.169 0.084 208,488 283,171

1995 0.080 0.146 0.066 164,604 219,004

1996 0.075 0.123 0.048 134,400 175,478

1997 0.070 0.100 0.030 84,000 107,771

1998 0.065 0.095 0.030 87,000 110,372

1999 0.060 0.090 0.030 90,000 112,524

2000 0.056 0.085 0.029 89,900 110,016

2001 0.051 0.080 0.029 92,800 111,056

2002 0.042 0.075 0.033 105,600 124,360

2003 0.037 0.070 0.033 108,900 125,545

2004 0.035 0.065 0.030 90,000 100,894

2005 0.033 0.060 0.027 121,500 131,807

2006 0.035 0.056 0.021 117,453 123,397

2007 0.049 0.051 0.002 13,474 13,762

2008 0.050 0.042 (0.008) (82,832) (82,832)

Total 2,475,859 3,278,059

Sources: For 1990, 1995 -2004: EERE Power Technology Energy Data Book 4th Edition August 2006 NREL/TP-620-39728. 

1991 to 1994 were straight-lined estimates. 2000-2007: EERE Renewable Energy Data Book Sept 2008 Section 4, Page 58.

The negative “savings” in the cost of energy for 2008 (Table 4-6, column 5) reflect the higher market 

prices for materials and wind turbine components associated with dramatic recent increases in wind 

energy capacity additions. Due to these market forces, by 2008 the cost of wind energy has increased to 

levels that exceeded the cost of energy in 2002 (i.e., a six-year delay). 

6 Year 

Delay
Retrospective Benefit-Cost Evaluation of U.S. DOE Wind Energy R&D Program: Impact of Selected Energy Technology Investments

4-16

4.5.3 Health Cost Savings from Reduced Environmental Emissions

With DOE-funded research, wind technology advances facilitated higher levels of wind energy generation 

and reduced levels of fossil-fired generation. This resulted in lower levels of particulate emissions and 

other harmful emissions from burning fossil fuels. Levels of fossil-fired generation (Table 4-5, column 3)

along with the average fuel mix of fossil fired generation (Table 4-1) are used as inputs to the EPA 

COBRA model (Mulholland, 2007 and Appendix B) to estimate avoided particulate emissions, avoided 

adverse health incidents, and avoided health costs. Avoided health costs in 2008 from adverse health 

incidents that would have resulted from higher particulate levels are presented in Table 4-7.

Table 4-7. Health Cost Savings in 2008

Avoided Adverse

Health Incident

Health Care

Cost Savings

(Thousand Dollars)

Mortality 2,725,472

Infant Mortality 6,870

Chronic Bronchitis 117,810

Non-Fatal Heart Attacks 72,376

Respiratory Hospital Admissions 1,395

Cardio Vascular Related Hospital Admissions 5,905

Acute Bronchitis 273

Upper Respiratory Symptoms 169

Lower Respiratory Symptoms 142

Asthma Emergency Room Visits 148

Minor Restricted Activity Days (MRAD) 19,630

Work Loss Days 4,371

Total Avoided Costs in 2008 2,954,561

Health cost savings over the 1990 to 2008 period are presented in Table 4-8 and indicate total cost savings 

from avoided fossil-fired generation emissions of $9.766 billion (undiscounted 2008 dollars).
Chapter 4 – Economic Benefits

4-17

Table 4-8. Health Cost Savings Over 1990 to 

2008 Period (2008 Dollars)

Year Avoided Health Costs

(Thousand Dollars)

1990 102,391

1991 56,717

1992 43,820

1993 35,836

1994 37,972

1995 43,791

1996 25,040

1997 31,601

1998 6,378

1999 96,542

2000 166,031

2001 237,955

2002 485,828

2003 540,230

2004 770,375

2005 928,561

2006 1,478,546

2007 1,723,738

2008 2,954,562

Health Cost 

Savings 9,765,914

4.5.4 Combined Monetized Benefits and Identifying the DOE Share

Wind energy cost savings and health care cost savings are added to arrive at total cost savings (monetized 

benefits) and presented in column 3 of Table 4-9. Eighty percent of total cost savings (attribution 

percentage from Table 4-3) are attributed to the DOE Wind Energy Program (Table 4-9, column 5).

Column 5 of Table 4-10 presents yearly net cost savings (undiscounted net benefits) of $8.972 billion 

compared to DOE Wind Energy Program investments. Column 4 presents an annual net cost savings 

(undiscounted net benefits) of $9.447 billion compared to investments in selected technologies.
Retrospective Benefit-Cost Evaluation of U.S. DOE Wind Energy R&D Program: Impact of Selected Energy Technology Investments

4-18

Table 4-9. Cost Savings Attributed to the DOE Wind Energy Program (2008 Dollars)

Year

Wind Energy 

Cost Savings

(Thousand 

Dollars)

Health

Care Cost 

Savings

(Thousand 

Dollars)

Total Cost

Savings

(Thousand 

Dollars)

Attribution

to DOE Wind 

Program

(%)

Cost Savings 

Attributed to

DOE Wind 

Program

(Thousand 

Dollars)

(1) (2) (3) (4) (5)

1990 345,608 102,391 447,999 80% 358,399

1991 455,626 56,717 512,342 80% 409,874

1992 369,449 43,820 413,269 80% 330,615

1993 341,051 35,836 376,887 80% 301,510

1994 283,171 37,972 321,142 80% 256,914

1995 219,004 43,791 262,796 80% 210,237

1996 175,478 25,040 200,518 80% 160,414

1997 107,771 31,601 139,372 80% 111,498

1998 110,372 6,378 116,750 80% 93,400

1999 112,524 96,542 209,066 80% 167,252

2000 110,016 166,031 276,047 80% 220,838

2001 111,056 237,955 349,010 80% 279,208

2002 124,360 485,828 610,188 80% 488,150

2003 125,545 540,230 665,776 80% 532,620

2004 100,894 770,375 871,269 80% 697,015

2005 131,807 928,561 1,060,368 80% 848,294

2006 123,397 1,478,546 1,601,944 80% 1,281,555

2007 13,762 1,723,738 1,737,500 80% 1,390,000

2008 (82,832) 2,954,562 2,871,730 80% 2,297,384

Total

Cost 

Savings

3,278,059 9,765,914 13,043,973 10,435,177
Chapter 4 – Economic Benefits

4-19

Table 4-10. Net Economic Benefits from DOE Wind Energy Program (2008 Dollars)

Year

Cost Savings 

Attributed to 

DOE Wind 

Program

(Thousand 

Dollars)

Investments in 

Selected 

Technologies

(Thousand 

Dollars)

Program

Investments

(Thousand 

Dollars)

Net Benefits 

Against 

Investments in 

Selected 

Technologies

(Thousand 

Dollars)

Net Benefits 

Against 

Program 

Investments

(Thousand 

Dollars)

(1) (2) (3) (4) (5)

1976 0 0 44,027 0 (44,027)

1977 0 0 58,910 0 (58,910)

1978 0 92,560 94,788 (92,560) (94,788)

1979 0 144,166 147,636 (144,166) (147,636)

1980 0 127,801 137,572 (127,801) (137,572)

1981 0 158,050 160,985 (158,050) (160,985)

1982 0 73,807 75,178 (73,807) (75,178)

1983 0 58,928 59,116 (58,928) (59,116)

1984 0 47,860 47,860 (47,860) (47,860)

1985 0 49,603 49,955 (49,603) (49,955)

1986 0 21,608 42,723 (21,608) (42,723)

1987 0 19,983 27,816 (19,983) (27,816)

1988 0 13,059 13,707 (13,059) (13,707)

1989 0 12,890 13,670 (12,890) (13,670)

1990 358,399 12,768 13,052 345,631 345,347

1991 409,874 15,724 16,011 394,150 393,863

1992 330,615 29,883 30,167 300,732 300,449

1993 301,510 7,628 33,063 293,882 268,446

1994 256,914 12,678 39,593 244,236 217,321

1995 210,237 15,679 45,648 194,558 164,589

1996 160,414 21,974 41,023 138,440 119,391

1997 111,498 26,353 36,752 85,145 74,745

1998 93,400 21,949 40,759 71,452 52,641

1999 167,252 26,082 42,604 141,171 124,648

2000 220,838 21,072 38,835 199,766 182,003

2001 279,208 23,817 46,830 255,391 232,378

2002 488,150 25,592 44,999 462,559 443,151

2003 532,620 30,299 48,005 502,321 484,616

2004 697,015 29,358 44,621 667,657 652,394

2005 848,294 26,093 44,078 822,201 804,217

2006 1,281,555 18,150 40,273 1,263,405 1,241,282

2007 1,390,000 30,476 49,698 1,359,523 1,340,301

2008 2,297,384 22,643 49,034 2,274,741 2,248,350

Totals 10,435,177 1,238,531 1,718,989 9,196,648 8,716,190

4.6 Measures of Economic Performance

Three measures of economic performance – NPV, benefit-cost ratio, and internal rates of return – are used 

to compare economic benefits to DOE Wind Energy Program investments and to investments in the 

selected technologies. Performance metrics against total program investments are presented in Table 4-11, 

using OMB-stipulated 3% and 7% discount rates for the computation of NPV and benefit-cost ratios.
Retrospective Benefit-Cost Evaluation of U.S. DOE Wind Energy R&D Program: Impact of Selected Energy Technology Investments

4-20

Table 4-11. Economic Performance Metrics Based on Total 

Wind Energy Program Investments

Total Cost $1,718,989,000

Total Attributed Benefits $10,435,179,000

Net Benefits (undiscounted) $8,716,190,000

NPV of Net Benefits at 3% $3,471,572,000

NPV of Net Benefits at 7% $915,265,000

Benefit-Cost Ratio at 3% 3.9 to 1

Benefit-Cost Ratio at 7% 2.1 to 1

Internal Rate of Return 12%

Performance metrics against investments in the selected technologies are presented in Table 4-12, also 

using 3% and 7% discount rates for the computation of NPV and benefit-cost ratios.

Table 4-12. Economic Performance Metrics Based on 

Program Investments in Selected Technologies

Total Cost $1,238,531,000

Total Attributed Benefits $10,435,179,000

Net Benefits (undiscounted) $9,196,648,000

NPV of Net Benefits at 3% $3,765,607,000

NPV of Net Benefits at 7% $1,098,935,000

Benefit-Cost Ratio at 3% 5.3 to 1

Benefit-Cost Ratio at 7% 2.8 to 1

Internal Rate of Return 14%

4.7 Sensitivity Analysis

As indicated in Tables 4-11 and 4-12, a comparison of total cost savings against only those investments 

that can be directly traced to the selected technologies point to a $294 million higher NPV level (at a 3% 

discount rate) and $183 million higher NPV level (at a 7% discount rate), compared to NPV levels against 

the entire DOE Wind Energy Program investment.

In addition, if attribution levels are varied 10% around an 80% mean attribution level, NPV Value 

estimates against program investments and the benefit-cost ratio estimates display limited variation (Table 

4-13). Note that this is holding the six-year acceleration effect of the combined DOE/industry investment 

constant.

Table 4-13. Sensitivity of Net Present Value to Attribution Level (2008 Dollars)

72%

Attribution to DOE

80%

Attribution to DOE

88%

Attribution to DOE

Net Present Value at 3% $3,006,486,000 $3,471,572,000 $3,936,658,000

Net Present Value at 7% $742,805,000 $915,265,000 $1,087,724,000

Benefit-cost Ratio at 3% 3.5 to 1 3.9 to 1 4.3 to 1

Benefit-cost Ratio at 7% 1.9 to 1 2.1 to 1 2.3 to 1
5-1

5. ENVIRONMENTAL BENEFITS (NON-MONETIZED)

DOE Wind Program investments in selected technologies facilitated increased production of clean 

renewable wind energy. Environmental benefits relative to the next best alternative scenario of six years 

delay in receiving actual levels of clean renewable wind energy production and the associated fossil-fired 

generation to make up for this shortfall in wind energy generation, fall into four categories:

• Avoided greenhouse gases (carbon dioxide)

• Avoided production of other pollutants (sulfur dioxide)

• Avoided mortality and health care incidents that would have resulted from particulate emissions 

of fossil-fired generating stations (previously treated as monetized benefits of environmental 

health effects)

• Avoided water use (withdrawn from surface waters) for fossil-fired generation.

5.1 Avoided Greenhouse Gases

Coal and natural gas fired power generation produces large quantities of carbon dioxide (CO2) emissions. 

These emissions are major contributors to atmospheric levels of greenhouse gases (Edgar, 2005). 

A six-year delay displaces 139.8 billion kWh of clean wind energy with fossil-fuel generation (see Table 

4-5). Based on a generation mix analysis summarized in Table 4-1, it is estimated that:

• Forty-four percent or 61.5 billion kWh of wind energy is displaced by coal-fired generation. Per 

EPA estimates (EPA [1]), average emission rates from coal-fired generation are 2,249 lbs of CO2

per 1,000 kWh. 

(EPA [1]: http://www.epa.gov/cleanrgy/energy-and-you/affect/coal.html).

• Fifty-five percent or 76.9 billion kWh of wind energy is displaced by natural gas-fired generation. 

Per EPA estimates (EPA [2]), average emission rates from natural gas-fired generation are 1,135 

lbs of CO2 per 1,000 kWh. 

(EPA [2]: http://www.epa.gov/cleanrgy/energy-and-you/affect/natural-gas.html).

• One percent or 1.4 billion kWh of wind energy is displaced by petroleum-fired generation. Per 

EPA estimates (EPA [3]), average emission rates from petroleum-fired generation are 1,672 lbs 

of CO2 per 1,000 kWh.

(EPA [3]: http://www.epa.gov/cleanrgy/energy-and-you/affect/oil.html).

The estimated impact of avoided CO2 emissions is summarized in Table 5-1. Avoiding a six-year delay, 

associated with the next best alternative technology, led to the avoidance of almost 103.4 million tons of 

CO2 greenhouse gases of which 82.7 million tons are attributed to DOE and are equivalent to annual CO2

emissions from 14.4 million passenger vehicles.
Retrospective Benefit-Cost Evaluation of U.S. DOE Wind Energy R&D Program: Impact of Selected Energy Technology Investments

5-2

Table 5-1. Avoided Greenhouse Gas Emissions 

(Thousand Tons of CO2)

Avoided 

CO2

(Thousand 

Tons)

80% of CO2

Attributed to 

Wind Program

Avoided Coal Fired 

Generation 62,730

Avoided Gas Fired 

Generation 39,600

Avoided Oil Fired 

Generation 1,064

Total Avoided 

Greenhouse Gases 103,394 82,715

Annual Passenger Car 

Emissions 5.725 tons/year

Passenger Car Single 

Year Equivalent

14.4

million cars

5.2. Avoided Sulfur Dioxide Emissions

Using the same process as above, for estimating greenhouse gas savings, a six-year delay displaces 139.8 

billion kWh of clean wind energy with fossil fuel fired power generation (see Table 4-5). Of this amount,

44% is coal-fired generation, 55% is natural gas-fired generation, and 1% is petroleum fired-generation 

(See Table 4-1). 

Per EPA, average U.S. sulfur dioxide (SO2) emissions are 13 lbs per 1,000 kWh of coal-fired generation, 

0.1 lbs per 1,000 kWh of natural gas-fired generation, and 12 lbs per 1,000 kWh of petroleum-fired 

generation (EPA1, EPA2, and EPA3). Using these average SO2 emission levels for each fossil fuel and 

multiplying by the kWh of fossil-fired generation from each of these sources, a total of 373,725 tons of 

SO2 emissions are avoided. 

Coal: (139.8 billion kWh) x (0.44) x (13 lbs/1000 kWh) = 799.6 million lbs

Natural Gas: (139.8 billion kWh) x (0.55) x (0.1 lbs/1000 kWh) = 7.7 million lbs 

Petroleum: (139.8 billion kWh) x (0.01) x (12 lbs/1000 kWh) = 16.8 million lbs

Total Avoided SO2 emissions = 824.1 million lbs

Number of Metric Tons at 2205 lbs = 373,725 tons

Of this total amount, 80% or 298,980 tons are attributed to the DOE Wind Energy Program.
Chapter 5 – Environmental Benefit (Non-Monetized)

5-3

5.3 Avoided Mortality and Health Care Incidents

Particulate matter from coal-fired plants including coal fly ash, sulfates, and nitrates are associated with 

negative health effects (Grahane, 2007). Particulates can irritate small airways in the lungs, which can 

lead to increased problems with asthma, chronic bronchitis, and other respiratory problems. Studies have 

shown that exposure to particulate matter is related to increased respiratory problems, as well as cardiac 

problems and cardiac mortality (Nel, 2005). 

Without the DOE Wind Energy Program, wind energy capacity additions and generation would have been 

delayed. During the years of delayed technology development and capacity additions, wind generated 

power would have been replaced with fossil-fired generation and the associated harmful emissions. 

To assess adverse health impacts from the emissions of additional fossil-fired generation, the benefit-cost 

analysis utilized the EPA Co-Benefits Risk Assessment (COBRA) model. This model generates first 

order approximations of health benefits from different air pollution mitigation practices. Two sets of 

inputs were provided to the COBRA model:

• Additional electricity generated from fossil fuels in billions of kWh (See Table 4-5).

• The mix of fossil fuel resources (coal, natural gas, and petroleum) that could be expected to 

replace wind generated power (See Table 4-1).

Under the counterfactual scenario of a six-year delay in clean wind energy generation, 140 billion kWh of 

additional conventional fossil fuel generation would replace wind-generated power. The associated health 

impacts avoided due to the DOE impact are estimated using the COBRA model at 1.1 million adverse 

health incidents, including over 1,100 mortalities, over 1,800 non-fatal heart attacks, and over a million 

lost or restricted activity workdays. 

As indicated in Table 5-2, 80% of health benefits are attributed to the DOE Wind Energy Program. The 

monetized value of the avoided adverse health incidents has been included in the economic benefit 

estimates presented in Chapter 4. Here, the incident data that underlie the monetary effects are presented. 

It is recognized that to include both the incident data and their monetized value as benefits would be 

double counting; however, it is instructive to see both displayed. 
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Table 5-2. Adverse Health Incidents Avoided with DOE Impact

Avoided Mortality &

Health Care Incidents

Attributed Benefits to 

DOE Wind Energy 

Program

Mortality 1,190 952

Infant Mortality 3 2

Chronic Bronchitis 737 589

Non-Fatal Heart Attacks 1,836 1,469

Resp. Hosp. Hospital Admissions 280 224

Cardio Vascular Related Hospital Admissions 590 472

Acute Bronchitis 1,764 1,411

Upper Respiratory Symptoms 15,790 12,632

Lower Respiratory Symptoms 20,932 16,745

Asthma Emergency Room Visits 1,123 898

MRAD – Minor Restricted Activity Days (MRAD) 892,556 714,045

Work Loss Days 150,018 120,014

Asthma Exacerbations 20,234 16,188

Total Number of Avoided Health Care Incidents 1,107,053 885,641

5.4 Avoided Water Use for Fossil-Fired Generation

Per the U.S. Geological Survey (USGS) website, the thermoelectric production of electrical power (both 

fossil fueled and nuclear power generation) results in one of the largest uses of water in the United States 

and worldwide. In 2000, about 195,000 million gallons of water were used each day to produce electricity 

(excluding hydroelectric power). Thermoelectric-power withdrawals accounted for 48% of total water 

use, 39% of total freshwater withdrawals for all categories, and 52% of fresh surface-water withdrawals. 

The avoidance of additional fossil-fired generation with clean and renewable wind energy thus avoids 

significant use of freshwater resources in the United States, as well as potentially dangerous pollution 

from power plant water releases into lakes and streams and associated fish kills.
6-1

6. ENERGY SECURITY BENEFITS

When renewable wind energy displaces fossil-fired generation, the energy security impact depends on the 

fossil fuels that are likely to have been used as substitutes for wind energy under the next best alternative 

scenario. 

• Forty-nine percent of U.S. electricity output is generated from coal-fired power plants (Figure 6-

1). Coal is a plentiful domestic resource and the displacement of coal-fired generation by wind 

energy does not have a direct energy security impact.

• Twenty-one percent of U.S. electricity output is generated from natural gas fired power plants 

(Figure 6-1). Natural gas is produced domestically or imported from Canada. Reliance on 

Canadian imports is not considered an energy security risk and the displacement of natural gas 

fired generation by wind energy has limited, if any, direct impact on energy security at this time.

• Just 1.1% of U.S. electricity output is generated from petroleum. As a percent of fossil-fired 

generation, petroleum accounts for 1.55%. Avoiding reliance on imported petroleum directly and 

positively impacts energy security.

Figure 6-1. Energy Mix of 2008 U.S. Power

Generation

Source: U.S. Department of Energy, Energy Information Administration,

Power Plant Operations Report (EIA-923); 2008 preliminary generation data.

Edison Electric Institute (All rights reserved).
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In 2007, 95% of U.S. wind generation was concentrated in 15 states: Texas, California, Minnesota, Iowa, 

Washington, Colorado, Oregon, Illinois, Oklahoma, New Mexico, New York, Kansas, North Dakota, 

Pennsylvania, and Wyoming. Petroleum utilization for power generation in these 15 states was estimated 

from EIA data. Analysis indicates that petroleum-based generation in these 15 states has been less than 

the national average, at 1.2% of all fossil-fueled generation as compared to 1.55% for the nation. 

Based on the 1.2% petroleum fuel component in these 15 states (Table 4-1), petroleum displacement is 

less than one million barrels of oil equivalent, which amounts to 20% of a single day’s 2007 passenger 

automotive fuel use in the U.S. While not insignificant, the DOE Wind Energy Program has had only 

modest impact on energy security through avoided petroleum use for electric power generation.

Table 6-1. Avoided Barrels of Oil Equivalent (BOE) Associated with a Six-Year Delay

Six-Year Delay

(Billion kWh)

U.S. Wind Generation Over Study Period 206.7 

Additional Fossil Fuel Generation to Replace Delayed Wind Generation 

Under Next Best Alternative 139.8

Additional Generation Fueled with Petroleum at 1.2% 1.68

BOE of Additional Petroleum Based Generation

BOE at 1,700 kWh (or 5.8 million BTU) 988,000

Number of Days Equivalent 2007 U.S. Passenger Car

Petroleum Usage (4.850 million barrels / day)

0.204

Sources: BOE kWh equivalent at http://bioenergy.ornl.gov/papers/misc/energy_conv.html;ORNL, Transportation Energy Data 

Book, Edition 28, 2009; Petroleum-based generation from EIA, Net Generation by State, Type of Producer and Energy Source, 

State Historical Tables 2007, Released January 20, 2009.
7-1

7. KNOWLEDGE BENEFITS2

The economic, environmental, and security benefits presented earlier all rest on Program-attributed 

knowledge benefits. However, in addition to providing a foundation on which these specific benefits rest, 

the knowledge base created by the DOE Wind Energy Program is much more extensive and serves a wide 

range of research and industrial activities within the global wind industry, as well as in other industries. 

This chapter presents an overview of selected knowledge outputs and their dissemination. It draws from a 

source study (Ruegg and Thomas, 2010) that used a historical tracing framework and multiple evaluation 

techniques, including bibliometrics, document review, and interview to explore linkages between 

knowledge outputs resulting from the more than three decades of DOE research investments in wind 

energy and downstream developments. Appendix C provides background on the bibliometrics 

methodology used extensively in this brief summary, as well as detail on the construction of data sets 

used in the analysis. The focus of this Chapter is on findings.

7.1 Main Findings of the Review of Knowledge Outputs

• The scientific and technical knowledge base supporting wind energy was meager prior to the 

DOE Wind Energy Program, and it is substantially developed today, in large part due to Programfunded R&D.

• More than 100 R&D partnerships with industry have led to the development of numerous 

innovations. Many of these innovations have led to prototypes and successfully commercialized 

wind energy components and systems that embody Program-generated knowledge.

• Leading domestic manufacturers of wind turbines for utility applications (including GE Wind 

Energy and Clipper Windpower) and distributed applications (including Southwest Windpower) 

attribute key innovations to R&D partnerships with DOE. 

• Intellectual property of leading manufacturers of wind turbines headquartered both in the United 

States and in other countries, such as Vestas Wind (Denmark) and Mitsubishi (Japan), is 

extensively linked to DOE-funded wind patents.

• DOE-funded R&D created highly influential intellectual property in the wind energy industry, 

such as innovative airfoils for blades, retractable rotor blades, variable speed wind turbines, 

doubly fed generator variable speed generation control systems, rotor control systems, and active 

pitch controls.

• DOE-funded R&D intellectual property in wind energy that is also linked to intellectual property 

outside wind energy, such as power conversion systems, hybrid vehicles, and paper and pulp 

machinery.

 2

 This section, prepared by Rosalie Ruegg, TIA Consulting, Inc., and Patrick Thomas, 1790 Analytics, LLC, is based on a 

larger impact evaluation report coauthored by Ruegg and Thomas, entitled Linkages from DOE’s Wind Energy Program R&D 

to Commercial Renewable Power Generation. U.S. Department of Energy, Washington, DC. For more details about the 

approach and findings, consult Appendix C and the larger 2009 source report by Ruegg and Thomas. 
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• The often-intricate paths of knowledge flow revealed that the intellectual property and people 

supported by DOE often survived terminating companies and found their way into later 

successful companies.

• Numerous publications resulted from the DOE Wind Energy Program, many linked directly to 

companies, as well as to domestic and foreign universities and other types of organizations.

• Test data from the Wind Energy Program have enabled international benchmarking of system 

performance and contributed to development of international standards and certification.

• DOE has supported wind research in approximately 50 universities. Students and professors from 

these programs are found among the present generation of DOE program managers and 

researchers, as well as in industry. 

7.2 Complex Network of Relationships

Document review and interview revealed that the DOE Wind Energy Program has developed a complex 

network of relationships with other organizations that has provided many pathways through which its 

explicit and tacit knowledge outputs are created and through which they flow. Figure 7-1 depicts many of 

these relationships. 
Chapter 7 - Knowledge Benefits

7-3

Figure 7-1. Network of Relationships Between the DOE Wind Energy Program and Other 

Organizations

The connections through R&D are principally to organizations that represent the supply side of wind 

energy (i.e., manufacturers of turbines and components, wind farm developers and operators, electric 

utilities, engineering and consulting firms, university research entities, and foreign research laboratories). 

Through DOE's deployment strategies, there are also connections to organizations that represent the 

demand side of wind energy (i.e., associations and user groups, and through these to builders, schools, 

factories, residences, special facilities, and communities). Furthermore, some DOE Wind Energy Program 

knowledge outputs, such as resource maps which show the strength of wind resources geographically, are 

of interest to both suppliers and demanders of systems.

The DOE Wind Energy Program's connection to manufacturers of wind turbines and components through 

partnerships is particularly strong (as indicated in Figure 7-1 by the bolder connecting line). These 

partnerships include both utility-scale global producers and smaller distributed scale producers whose 
Retrospective Benefit-Cost Evaluation of U.S. DOE Wind Energy R&D Program: Impact of Selected Energy Technology Investments

7-4

principal focus is domestic markets. DOE funded more than 65 companies in more than 100 partnerships 

over the past three decades. A view expressed by both DOE and industry leaders in interviews was that 

most wind energy innovations domestically have come from companies in partnership with DOE. 

Moreover, several of the currently leading U.S. commercial wind energy companies attributed their wind 

turbine innovations to partnerships with DOE.

Knowledge creation and dissemination have also been facilitated by the DOE Wind Energy Program's ties 

to associations and user groups working in the field. For example, the program has worked with the 

Utility Wind Integration Group (UWIG) – an association of utilities and others – to commission regional 

wind integration studies aimed at accelerating the integration of wind generation into utility power 

systems. As another example, the Wind Energy Program worked with the Electric Power Research 

Institute (EPRI) to encourage utilities to install and operate wind turbines. The resulting projects served as 

demonstrations to the participating utilities and to the electric power industry. The program's long 

association with the American Wind Energy Association (AWEA) has provided an important link to 

researchers in other organizations and to user groups in advancement of technology and markets. 

Connections with universities have been another principal means of creating and disseminating 

knowledge, discussed in more detail later in this chapter.

7.3 Patents from DOE-Funded R&D

Patents signal knowledge creation. Furthermore, patent citation analysis provides a way to identify the 

past knowledge base on which more recent patents were built. Patent citation analysis enables the 

identification of particularly influential patents, as well as application areas and individual users. The 

results are quantitative and objectively obtained. For these reasons, as well as the fact that patents are 

generally closer to implementation than publications, patents analysis is extensively used to study 

innovation.

Patent citation analysis enables the identification of particularly influential patents, as well as application 

areas and individual users. The results are quantitative and objectively obtained. For these reasons, as well 

as the fact that patents generally signal movement closer to implementation than publications, patents 

analysis is extensively used to study innovation.

A patent family contains all the patents and patent applications resulting from the same original patent 

application. A search identified 112 wind energy patent families derived from DOE-funded R&D. These 

patent families contained 112 U.S. patents, 27 European Patent Office (EPO) patents, and 27 World 

Intellectual Property (WIPO) patents. Figure 7-2 shows the number of DOE wind energy patents issued in 

the United States by time period, demonstrating an evident surge in recent years.
Chapter 7 - Knowledge Benefits

7-5

Figure 7-2. Number of U.S. Wind Energy Issued Patents Attributed to DOE-Funded Research 

by Five-Year Increment, 1976 through 2008

7.3.1 Patent Families of Leading Innovative Wind-Energy Companies Linked to Earlier DOE Wind 

Energy Patent Families

A backward-tracing patent analysis starting with 695 wind energy patent families owned by the wind 

energy industry’s leading innovative companies (defined here as those owning the largest number of wind 

energy patents) was performed to determine to what extent, if any, these patents could be traced back to 

the DOE Wind Energy Program. This was done to find if the program's patent output is linked as intended

to downstream technical and commercial developments in commercial wind power generation. 

The striking result, as shown in Figure 7-3 is that more wind energy patent families of leading innovative 

wind energy companies are linked to DOE research than to the research of any other leading innovator in 

wind energy. A quarter of the 695 wind energy patent families assigned to leading innovators in wind 

energy were found to be linked through two generations of patent citing to earlier DOE-supported windenergy patents.

Key patents from leaders in commercial wind power, such as GE Wind and Vestas, have built extensively 

on earlier DOE-supported patents. DOE-supported patents related to variable speed wind turbines and 

doubly fed generators appear to have been particularly influential in the key patents of these leading 

companies. 
Retrospective Benefit-Cost Evaluation of U.S. DOE Wind Energy R&D Program: Impact of Selected Energy Technology Investments

7-6

Figure 7-3. Organizations Whose Wind Energy Patent Families were Cited by the Largest 

Number of Wind Energy Patent Families of Leading Innovative Wind Energy 

Companies

7.3.2 DOE-Funded Wind Energy R&D Has Influenced Developments Beyond the Wind Energy 

Industry

A forward-tracing patent analysis revealed that DOE-funded R&D led to patents in wind energy that are 

linked not only to downstream developments in electric power generation, but also to a range of other 

industries. Technologies in aerospace, hybrid vehicles, AC-DC power conversion, electric motors and 

generators (including motors for pulp and paper machinery), microturbines, fuel cells, and software are 

among the non-wind applications linked to patent outputs from DOE-funded wind energy research. 

Figure 7-4 shows companies outside the wind energy industry with patents that are linked to earlier DOEsupported wind energy patents. These include: one of the world’s largest engineering and power 

management companies (Asea Brown Boveri [ABB]); two aerospace companies (Hamilton Sundstrand 

and Honeywell); three automotive companies (Ford, Denso, and Honda); a software company 

(Microsoft); a telecommunications company (Sprint Nextel); and a manufacturer of construction and 

0 50 100 150 200

Gamesa

Global Energy Concepts

Mitsubishi Heavy Ind

Mitsubishi Electric

Sulzer-Escher

Doughty Hanson

Aerodyn Engineering

Hitachi

Siemens

Clipper Windpower

Southwest Windpower

LM Glasfiber

Distributed Energy Systems

Vestas Wind Systems

General Electric

Northrop Grumman

United Technologies

Dept of Energy

Number of Citing Patent Families
Chapter 7 - Knowledge Benefits

7-7

mining equipment (Caterpillar). The variety of technologies and companies with linkages back to DOE 

suggests that the different wind energy technologies funded by DOE have influenced developments well 

beyond the wind industry.

Figure 7-4. Companies (Excluding Leading Wind Energy Companies) with the Largest Number 

of Patent Families Linked to DOE-Supported Wind Energy Patents Families

7.3.3 Notable DOE-Attributed Wind Energy Patents

Both the forward- and backward-tracing elements of the patent citation analysis paid particular attention 

to high-impact patents cited by large numbers of subsequent patents. These highly cited patents were 

identified using Citation Indexes, which are normalized impact measures derived by dividing the number 

of citations received by a patent by the mean number of citations received by peer patents from the same 

issue year and technology. A Citation Index of 1.0 means the patent has been cited as often as expected, 

given its age and technology area; a Citation Index of 10.0 means the patent has been cited 10 times as 

often as expected.

0 10 20 30 40 50

Caterpillar

Sikorsky Aircraft

Coleman Co.

Capstone Turbine

Ebara

Toshiba

Sprint Nextel

Microsoft

Toyota

Eurocopter

Alstom

Emerson Electric

Pratt Whitney

Siemens VDO Automotive

Voith J.M.

Honda

Denso

Honeywell

Ford

Hamilton Sundstrand

ABB Asea Brown Boveri

# Patent Families linked to DOE
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7-8

The backward-tracing element of the study identified high impact patents owned by leading wind energy 

companies and assessed their linkages back to earlier DOE-supported patents or papers. Examples of 

these highly cited patents owned by leading wind energy companies and linked back to DOE-funded 

research are shown in Table 7-1. For example, the patent with the highest Citation Index found by the 

study was U.S. #6,566,764, granted to Vestas in 2003 (the last listed in the table). This patent describes a 

variable speed wind turbine with a matrix converter designed to produce output at constant frequency. It 

had been cited by 42 subsequent patents, more than 12 times as many citations as expected given its age 

and technology area. The patents cited as prior art by this Vestas patent include DOE-supported patents 

describing variable speed wind turbines – in particular, patents assigned to Clipper Windpower. These 

Clipper Windpower patents are also cited as prior art by a series of other highly cited Vestas patents 

describing variable speed turbines. This suggests that DOE’s funding of research on variable speed 

turbines formed an important part of the foundation for further development internationally of this 

technology.

Table 7-1. Highly Cited Patents Owned by Leading Wind Energy 

Companies Linked to DOE

Company Technology Citation Index

Clipper WindPower Retractable rotor blades 6.90

GE Wind Variable speed generator 6.16

United Technologies Speed Avoidance Log 3.10

Vestas Wind Systems Variable speed turbine/converter 12.18

The forward-tracing analysis identified the DOE-supported wind energy patents with links to the largest 

number of subsequent patents, from both inside and outside wind energy technology. For example, DOEsponsored patent U.S. #5,320,491, assigned to Distributed Energy Systems (formerly Northern Power) 

and describing an aileron for a wind turbine, is linked to 104 subsequent patent families, 83 of which are 

outside wind energy. Many of the later patents linked to this patent describe rotor systems for helicopters, 

suggesting that much of its impact has been outside the wind energy industry. 

The forward-tracing analysis also identified highly cited non-wind energy patents that are linked to earlier 

DOE-supported wind energy patents. Examples of these are shown in Table 7-2. For instance, Paice 

Corporation's patent U.S. #6,209,672 for hybrid vehicles (listed second in the table) was cited more than 

nine times the expected rate, and it is linked back to a DOE-supported wind energy patent. The variety of 

highly cited technologies outside wind energy that are linked back to DOE-funded research suggests that 

DOE not only influenced developments well beyond the wind energy industry, but that in a number of 

cases the ties were to important developments in those industries.
Chapter 7 - Knowledge Benefits

7-9

Table 7-2. Highly Cited Non-Wind Energy Patents Linked to 

DOE-supported Wind Energy Patents 

Assignee Title Citation Index

Honeywell Power conversion systems 10.91

Paice Corp Hybrid vehicles 9.27

Kadant Black Clawson Paper & pulp machinery 8.24

ABB Asea Brown Boveri High voltage A/C machine 6.36

Siemens VDO Auto. Integrated capacitors 4.71

7.4 DOE-Funded Publications 

Publications comprise another major explicit knowledge output of the Wind Energy Program. Figure 7-5 

shows the approximate total output of DOE-funded publications in wind energy by year and by 

organization from 1974 to 2007. The legend to the right side of the bar chart lists the publishing 

organizations. Using the DOE Office of Scientific and Technical Information (OSTI) database and 

searching on "wind energy" produced a total of 2,392 publications attributed to DOE.3 The peaks and 

valleys of publication output follow closely expansions and contractions in Wind Energy Program 

budgets. 

 3 This is likely an undercount. It appears that not all wind energy publications sponsored by the DOE laboratories are listed in the

OSTI database. Further, the query rules for OSTI are not necessarily the same as those of the individual laboratory databases. 
Retrospective Benefit-Cost Evaluation of U.S. DOE Wind Energy R&D Program: Impact of Selected Energy Technology Investments

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Figure 7-5. Number of DOE Publications in "Wind Energy" by Organization, 1974 to 2007

7.4.1 NREL Publications

Over the last decade, NREL has contributed the largest share of wind energy publications, but SNL’s

sustained output of publications since the beginning of the program adds a notable share. Other parts of 

DOE have also published in wind energy. Among these are – in the earlier years – the Solar Energy 

Research Institute (SERI), the predecessor of NREL; Pacific Northwest National Laboratory (PNNL), 

Lawrence Berkeley National Laboratory (LBNL), and the Office of Energy Efficiency and Renewable 

Energy (EERE) Headquarters.

DOE’s wind energy publications were found frequently linked directly to commercial wind energy 

companies both through co-authoring and through citations – more than would be expected based on 

bibliometric theory, which sees citations of scientific papers by other papers as an acknowledgment of 

scientific and intellectual debts rather than technology debts. NREL’s conference papers and technical 

reports were found to be effective vehicles of collaboration between NREL researchers and 

manufacturing companies, universities, other national laboratories (in the United States and abroad), and

researchers within turbine certification bodies, wind energy associations, international providers of 

technical services in the wind energy industry, wind farm developers, and utilities which supply wind 

power. 

0

50

100

150

200

250

197419771980198319861989199219951998200120042007

years

DOE/Other

DOE/NASA

LBNL

PNL

SERI

SNL

NREL

Years
Chapter 7 - Knowledge Benefits

7-11

7.4.2 SNL Publications

SNL publications, based on a random sample taken over three decades, showed a recent increase in citing 

by companies, universities, and others, as shown by Figure 7-6. The pattern of citing also showed strong 

shifts over time to new topics of apparent growing interest (e.g., data acquisition and field measurement, 

manufacturing, and materials. 

Figure 7-6. Organization Citing, by Technology and Period, 1974 through 2007

7.4.3 Publications Cited by Patents

While patent citations of DOE-funded wind energy publications is much lower than patent-to-patent 

citations, these publications were cited at least 146 times by at least 79 different patents. Furthermore, 

there are patents linked to earlier DOE publications that are not linked to earlier DOE patents. 

Most of the publications cited by patents were conference and workshop papers. Among the publications 

cited the most times by patents are those on variable-speed and multiple-speed generators, a permanentmagnet generator, and modern airfoils.
Retrospective Benefit-Cost Evaluation of U.S. DOE Wind Energy R&D Program: Impact of Selected Energy Technology Investments

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7.5 Educated and Trained People 

Educated, trained, and experienced people embody and transfer knowledge. Measurement of these tacit 

knowledge effects of the DOE Wind Energy Program are, however, more difficult to quantify than 

papers, patents, and partnerships. Insights about this form of knowledge and its importance come from the 

source study's interviews and compilation of program funding of university research.

A conservative estimate of university funding for wind energy research by the program encompasses 

approximately 50 universities. Examples of university partners that received multiple rounds of funding 

from the Program over the years include the University of Massachusetts, Oregon State University, 

Colorado State University, University of Colorado, Massachusetts Institute of Technology, University of 

Utah, Wichita State University, Ohio State University, Montana State University, Stanford University, 

University of Texas, and Georgia Tech. 

The university support contributed to many wind energy innovations, including: computer models to 

predict wind loads and response, estimate costs, measure turbulence and model aerodynamics, and design 

systems and components; research in power electronics, controls, blade design, and spoiler flaps to 

control rotor speed; wind tunnel tests; safety; smart sensor systems; and many other advances. 

The Program's support of university wind energy research also produced trained students and experienced 

faculty, some of whom went on to start companies, manage wind divisions in large companies, and 

become managers and researchers in the DOE Wind Energy Program. 

While information about people was largely anecdotal, the interviews provided insights about the 

importance of DOE’s support of university wind energy research for training people in the field, and the 

importance in turn of these individuals as developers and conveyers of tacit knowledge.

An engineer in NREL's National Wind Technology Center (NWTC), for example, spoke of his early start 

in a DOE-funded university wind research program. He related that his thesis advisor at the University of 

Massachusetts had won a grant from DOE for wind energy research, and the advisor talked him into 

working on the project. "And," he said, "That changed my life. ...And it also changed the University, 

making it a center of excellence in wind energy and in educating students ever since."4 This same 

engineer later started a wind energy company, and still later, joined the engineering staff of the NWTC. 

Other interviews revealed similar career paths beginning with participation in DOE-funded university 

research laboratories and then moving to other organizations involved in wind energy research and 

development. 

Interviews with industry leaders highlighted the important transfer of knowledge by the movement of 

experienced people among companies. Industry leaders also spoke of the importance of different kinds of 

 4 Interview of Rosalie Ruegg with Sandy Butterfield, NREL/NWTC, June 18, 2008.
Chapter 7 - Knowledge Benefits

7-13

Program-produced wind energy knowledge, including both technical and market information, to 

industry.5 While anecdotal, these examples from interviews serve as a reminder of the crucial role of

people in creating and disseminating knowledge.

7.6 Conclusions

Many substantial and compelling lines of evidence were found that identified knowledge creation funded 

by the DOE Wind Energy Program in a range of organizations, and that linked the knowledge to 

commercial applications of wind energy for power generation. Evidence was found linking DOE's 

knowledge outputs to developments in both utility-scale and distributed-use power markets. Evidence was 

also found of linkages from the Wind Energy Program’s knowledge outputs to industries outside of wind 

energy. Interviews emphasized the importance of trained and experienced people in advancing the 

industry. The study identified a complex network of relationships among the DOE Wind Energy Program

and other organizations through which the Program’s knowledge outputs have been both created and 

disseminated.

 5 Interviews with Mr. James Deshler, Chairman of the Board, Clipper Windpower, and Dr. James Walker, Vice Chairman of 

Ensco, an international wind farm developer, and also Vice Chairman of the America Wind Energy Association, 2008.
Retrospective Benefit-Cost Evaluation of U.S. DOE Wind Energy R&D Program: Impact of Selected Energy Technology Investments

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8-1

8. SUMMARY OF EVIDENCE BASED FINDINGS

Retrospective benefit-cost study of the DOE Wind Energy Program R&D investments was undertaken to 

identity the returns on that investment to the nation. Benefits were estimated relative to a “next best 

alternative” (i.e., a hypothetical scenario according to which wind energy cost reductions, wind energy 

capacity additions, and generation output would have been delayed six years, in the absence of DOE 

Wind Energy Program investments). It is hypothesized that during these years of delay, a substantial part 

of clean wind-generated power in the United States would have been replaced with fossil-fired 

generation, with increases in the associated harmful emissions. 

Relative to the counterfactual scenario, the impact of the DOE Wind Energy Program was to increase 

clean power generation by 140 billion kWh. Estimated economic benefits and the entire DOE Wind 

Energy Program investments, in undiscounted 2008 dollars were:

• Savings from lower cost of wind energy of $3.278 billion.

• Savings from lower health costs of $9.766 billion.

• Total cost savings of $13.044 billion.

• 80% of cost savings or $10.435 billion were attributed to the DOE Wind Energy Program and the 

remainder to industry partners who cost shared some of research.

• DOE program investment of $1.719 billion.

• Net savings attributed to DOE of $8.716 billion.

When monetized economic and health benefits are compared to the entire DOE Wind Energy Program 

investments over a 32 year period (1976 to 2008), and OMB-stipulated discount rates are applied, the 

following results are obtained:

• NPVs range from $915 million to $3.472 billion, as a function of discount rates, depending on 

whether the discount rate applied is 7% or 3%.

• Benefit-cost ratios range from 2.1:1 to 3.9:1, again depending on the discount rate used.

• Internal rate of return is 12%.

When monetized economic and health benefits are compared to DOE investments in only the selected 

subset of Wind Energy Program technologies, net benefits are $9.197 billion, NPVs range from $1.099 

billion to $3.766 billion, as a function of discount rates, benefit-cost ratios range from 2.8:1 to 5.3:1, and 

the rate of return is 14%.

Environmental benefits attributed to DOE Wind Energy Program include the avoidance of:

• Over 82.7 million tons of carbon dioxide emissions – the main greenhouse gas component from 

fossil-fired generation.

• 299,000 tons of sulfur dioxide emissions.

• Cooling water use at fossil-fired power plants.
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• Adverse health impacts that would have resulted from particulate emissions of fossil fired 

generation including nearly 1,000 mortalities, 1,500 non-fatal heart attacks, and a million lost or 

restricted workdays.

Energy security benefits attributed to DOE Wind Energy Program are modest. A little over 1% of avoided 

fossil fuel generation would have used 988,000 barrels of oil equivalent petroleum fuel, corresponding to 

20% of a single day’s U.S. passenger car petroleum consumption.

Finally, considerable knowledge benefits, as embodied in patents, publications, and people, were traced to 

DOE Wind Energy Program investments. Knowledge benefits were found to have been disseminated 

widely in the wind energy industry, as well as in other industries.

This retrospective benefit-cost study identified and documented benefits from selected DOE-funded 

technologies, which constitute only a subset of DOE Wind Energy Program investments over the 1976 to 

2008 period. It is, therefore, likely that other Wind Energy Program R&D investments have also 

generated national benefits. (This is strongly suggested by the results of the investigation of knowledge 

effects by Ruegg & Thomas, 2009.) 

Accordingly, the results of this retrospective benefit-cost analysis provide a first-order, lower-bound 

estimate of the DOE Wind Energy Program contributions to the U.S. economy, the environment, U.S. 

energy security, and a knowledge base that will support subsequent technical advancements.
R-1

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A-1

APPENDIX A

INTERVIEWS

DOE Wind Energy Program Staff and Program Contractors

James Ahlgrimm Wind and Hydropower Technologies Program

Joseph Cohen SAIC

Daniel Ancona Princeton Energy Resources International

George Kervitsky BCS Inc.

Jamey Browning BCS Inc.

NREL Wind Technology Center

Robert Thresher Research Fellow and Former Center Director

Michael Robinson Deputy Director 

Scott Schreck Principal Engineer

Neil Kelley Principal Scientist

Alan Wright Senior Engineer

Maureen Hand Senior Engineer

Sandy Butterfield Chief Engineer

Walt Musial Senior Engineer

Palmer Carlin Retired

Marc Schwartz Senior Engineer

Larry Flowers Director, Wind Powering America

Michael Milligan System Integration Team

Trudy Forsyth Senior Project Leader

Tami Sandberg Information Specialist

Sandia National Laboratory Wind Program

Jose Zayas Manager – Wind Energy Technology Department

Paul Veers Distinguished Member of the Technical Staff

Dale Berg Principal Member of the Technical Staff

Thomas Ashwill Principal Member of the Technical Staff

Herbert Sutherland Retired Senior Staff

Henry Dodd Retired Department Manager
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Lawrence Berkeley National Laboratory

Ryan Wiser Staff Scientist

Mark Bolinger Research Scientist

Experts Unaffiliated with DOE Wind Energy Program

Flemming Rasmussen Head of Program, RISOE National Laboratory, Denmark

Jorgen Lemming RISOE National Laboratory, Denmark

Jacob Mann RISOE National Laboratory, Denmark

Herman Snel ECN, The Netherlands

Jos Beurskens ECN, The Netherlands

Takis Chaviaropoulos Head Renewable Energy, CRES, Greece

Gijs van Kuik Technical University of Delft, The Netherlands

Rogier Nijssen Technical University of Delft, The Netherlands

James Manwell University of Massachusetts – Amherst

John Mandell Montana State University

C. P. “Case” VanDam University California – Davis

Wind Industry Experts

Jim Lyons Chief Technology Officer – Novus Energy Partners 

Amir Mikhail SVP Engineering – Clipper Windpower

Craig Christensen Senior Vice President – Clipper Windpower, 

Ian Chatting Vice President – Technology R&D, VESTAS

Henrik Stiesdal Chief Technology Officer, Siemens Wind Power

Peter Fuglsang LM Blades – LM Glassfiber

Mike Anderson RES Ltd. (UK Wind Energy Project Developer)

Benjamin Bell Garad Hassan America Inc.

David Quarton Garrad Hassan & Partners
B-1

APPENDIX B

SUMMARY OF THE CO-BENEFITS RISK ASSESSMENT (COBRA) MODEL6

The COBRA model provides estimates of health effect impacts and the economic value of these impacts 

resulting from emission changes. The COBRA model was developed by the U.S. EPA to be used as a 

screening tool that enables users to obtain a first-order approximation of benefits due to different air 

pollution mitigation policies. 

At the core of the COBRA model is a source-receptor (S-R) matrix that translates changes in emissions to 

changes in particulate matter (PM) concentrations. The changes in ambient PM concentrations are then 

linked to changes in mortality risk and changes in health incidents that lead to health care costs and/or lost 

workdays. Figure B-1 provides an overview of the modeling steps.

Figure B-1. COBRA Model Overview

Source: EPA (2006).

B.1 Changes in Emission  Changes in Ambient PM Concentrations

The user provides changes (decreases) in emissions of pollutants (PM2.5, SO2, NOx) and identifies the 

economic sector from which the emissions are being reduced. These changes are in total tons of pollutants 

by sector for the U.S. economy for the chosen analysis year. The economic sectors chosen determine the 

underlying spatial distribution of emissions and hence the characteristics of the human population that is 

affected.7 For example, emissions reductions due to the use of geothermal technology are typically 

applied to coal plants in electric utilities. Reductions due to the use of wind technology are applied to 

coal, oil, and natural gas plants in electric utilities. Emissions reductions due to improved efficiency of 

diesel engines are applied to both highway diesel engines and off-highway non-road diesel engines.

The S-R matrix consists of fixed transfer coefficients that reflect the relationship between annual average 

PM2.5 concentration values at a single receptor in each county (a hypothetical monitor located at the 

county centroid) and the contribution by PM2.5 species to this concentration from each emission source. 

 6

 This Appendix was prepared by Michael Gallaher, RTI International. 7 The COBRA model has a variety of spatial capabilities. However, for this study there was limited information on the specific 

location of pollution reductions. Thus, a national analysis was conducted where the national distribution of emissions by fuel 

type, by sector (e.g., special distribution of national coal emissions in the electricity sector) was used to determine the 

emission location as input to the S-R matrix.
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This matrix provides quick but rough estimates of the impact of emission changes on ambient PM2.5

levels as compared to the detailed estimates provided by more sophisticated air quality models (U.S. EPA, 

2006).

B.2 Changes in Ambient PM Concentrations  Changes in Health Effects

The model then translates the changes in ambient PM concentration to changes in incidence of human 

health effects using a range of health impact functions and estimated baseline incidence rates for each 

health endpoint. The data used to estimate baseline incidence rates, and the health impact functions used 

vary across the different health endpoints. To be consistent with prior EPA analyses, the health impact 

functions and the unit economic value used in COBRA are the same as the ones used for the Regulatory 

Impact Analysis of the Clean Air Interstate Rule (U.S. EPA, 2005).8

The model provides (in the form of a table or map) changes in the number of cases for each health effect 

between the baseline emissions scenario (included in the model) and the analysis scenario. The different 

health endpoints are included in Table B-1. 

Each health effect is described briefly below. For additional detail on the epidemiological studies, 

functional forms, and coefficients used in COBRA, see Appendices C of the COBRA user’s manual (U.S. 

EPA, 2006) and Abt (2009).

Mortality researchers have linked both short-term and long-term exposures to ambient levels of air 

pollution to increased risk of premature mortality. COBRA uses mortality risk estimates from an 

epidemiological study of the American Cancer Society cohort conducted by Pope et al. (2002). COBRA 

includes different mortality risk estimates for both adults and infants. Because of the high monetary value 

associated with prolonging life, mortality risk reduction is consistently the largest health endpoint valued 

in the study.

Chronic bronchitis is defined as a persistent wet cough and mucus in the lungs for at least three months 

for several consecutive years, and it affects approximate 5% of the population (Abt, 2009). A study by 

Abbey et al. (1995) found statistically significant relationships between PM2.5 and PM10 and chronic 

bronchitis. 

 8 For a detailed discussion of studies used for health impact functions and unit values, see U.S. EPA (2005).
Appendix B – Summary of the Co-benefits Risk Assessment (COBRA) Model

B-3

Table B-1. Health Endpoints Included in COBRA

Health Effect Description/Units

Mortality Number of deaths

Chronic bronchitis Cases of chronic bronchitis

Nonfatal heart attacks Number of nonfatal heart attacks

Respiratory hospital 

admissions

Number of cardiopulmonary-, asthma-, or pneumonia-related hospitalizations

Cardiovascular related 

hospital admissions

Number of cardiovascular-related hospitalizations 

Acute bronchitis Cases of acute bronchitis

Upper respiratory 

symptoms

Episodes of upper respiratory symptoms (runny or stuffy nose; wet cough; 

and burning, aching, or red eyes)

Lower respiratory 

symptoms

Episodes of lower respiratory symptoms: cough, chest pain, phlegm, or 

wheeze

Asthma emergency 

room visits

Number of asthma-related emergency room visits

Minor restricted activity 

days

Number of minor restricted activity days (days on which activity is reduced 

but not severely restricted; missing work or being confined to bed is too 

severe to be MRAD).

Work days lost Number of work days lost due to illness

Nonfatal heart attacks were linked by Peters et al. (2001) to PM exposure. Nonfatal heart attacks are 

modeled separately from hospital admissions because of their lasting impact on long-term health care 

costs and earnings.

Hospital admissions include two major categories: respiratory (such as pneumonia and asthma) and 

cardiovascular (such as heart failure, ischemic heart disease). Using detailed hospital admission and 

discharge records, Sheppard et al. (1999) investigated asthma hospital emissions associated with PM, 

carbon monoxide (CO), and ozone. Moolgavkar (2000 and 2003) and Ito (2003) found a relationship 

between hospital admissions and PM. COBRA includes separate risk factors for hospital admissions for 

people aged 18 to 64 and aged 65 and older. 

Acute bronchitis, defined as coughing, chest discomfort, slight fever, and extreme tiredness lasting for a 

number of days, was found by Dockery et al. (1996) to be related to sulfates, particulate acidity, and, to a 

lesser extent, PM. COBRA estimates the episodes of acute bronchitis in children aged 8 to 12 from 

pollution using the findings from Dockery et al.

Upper respiratory symptoms include episodes of upper respiratory symptoms (runny or stuffy nose; wet 

cough; and burning, aching or red eyes). Pope et al. (2002) found a relationship between PM and the 
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B-4

incidence of a range of minor symptoms, including runny or stuffy nose; wet cough; and burning, aching 

or red eyes.

Lower respiratory symptoms in COBRA are based on Schwarz and Neas (2000) and focus primarily on 

children’s exposure to pollution. Children were selected for the study based on indoor exposure to PM 

and other pollutants resulting from parental smoking and gas stoves. Episodes of lower respiratory 

symptoms are coughing, chest pain, phlegm, or wheezing.

Asthma related emergency room visits are primarily associated with children under the age of 18. 

Norris et al. (1999) found significant associations between asthma ER visits and PM and CO. To avoid 

double counting, hospitalization costs (discussed above) do not include the cost of admission to the 

emergency room.

Minor restricted activity days (MRAD) in COBRA were based on research by Ostro and Rothschild 

(1989). MRADs include days on which activity is reduced but not severely restricted (e.g., missing work 

or being confined to bed is too severe to be an MRAD). They estimated the incidence of MRADs for a 

national sample of the adult working population, aged 18 to 65, in metropolitan areas. Because this study 

is based on a “convenience” sample of nonelderly individuals, the impacts may be underestimated 

because the elderly are likely to be more susceptible to PM-related MRADs).

Work loss days were estimated by Ostro (1987) to be related to PM levels. Based on an annual national 

survey of people aged 18 to 65, Ostro found that 2-week average PM levels were significantly linked to 

work loss days. However, the findings showed some variability across years.

B.3 Changes in Health Effects  Changes in Monetary Impacts

COBRA translates the health effects into changes in monetary impacts using estimated unit values of each 

health endpoint. The per-unit monetary values are described in Appendix F of the COBRA user’s manual 

(U.S. EPA, 2006). Estimation of the monetary unit values varies by the type of health effect. For example, 

reductions in the risk of premature mortality are monetized using value of statistical life (VSL) estimates. 

Other endpoints such as hospital admissions use cost of illness (COI) units that include the hospital costs 

and lost wages of the individual but do not capture the social (personal) value of pain and suffering.

B.4 Limitations

It should be noted that COBRA does not incorporate effects of many pollutants, such as carbon emissions 

or mercury. This has two potential implications. First, other pollutants may cause or exacerbate health 

endpoints that are not included in COBRA. This would imply that reducing incidences of such health 

points are not captured. Second, pollutants other than those included in COBRA may also cause a higher 

number of incidences of the health effects that are part of the model. This is also not captured in this 

analysis. Thus, the economic value of health effects obtained from COBRA may be interpreted as a 

conservative estimate of the health benefits from reducing emissions. 
Appendix B – Summary of the Co-benefits Risk Assessment (COBRA) Model

B-5

B.5 References 

Abbey, D. E., Ostro, B. E., Petersen, F., & Burchette, R. J. (1995). “Chronic respiratory symptoms 

associated with estimated long-term ambient concentrations of fine particulates less than 2.5 

microns in aerodynamic diameter (PM2.5) and other air pollutants.” Journal of Exposure Analysis 

and Environmental Epidemiology, 5(2), 137–159. 

Abt Associates Inc. (2009, January). “Economic impact of Wise County, Virginia coal-fired power plant.”

Prepared for Wise Energy For Virginia Coalition.

Dockery, D. W., Cunningham, J., Damokosh, A. I., Neas, L. M., Spengler, J. D., Koutrakis, P., Ware, J. 

H., Raizenne, M., & Speizer, F. E. (1996). “Health effects of acid aerosols on North American 

children - Respiratory symptoms.” Environmental Health Perspectives, 104(5), 500–505.

EPA (Environmental Protection Agency). (2005, March). “Regulatory impact analysis for the final Clean 

Air Interstate Rule. EPA-452/R-05-002.” Research Triangle Park, NC: Office of Air Quality 

Planning and Standards; Emission, Monitoring, and Analysis Division and Clean Air Markets 

Division. Available at http://www.epa.gov/cair/pdfs/finaltech08.pdf.

EPA. (2006, June). “User’s manual for the Co-Benefits Risk Assessment (COBRA) screening model.”

Developed by Abt Associates Inc.

Ito, K. (2003). “Associations of particulate matter components with daily mortality and morbidity in 

Detroit, Michigan.” In: Revised analyses of time-series studies of air pollution and health.

Boston, MA: Health Effects Institute.

Moolgavkar, S. H. (2000). “Air pollution and hospital admissions for chronic obstructive pulmonary 

disease in three metropolitan areas in the United States.” Inhalation Toxicology, 12 (Suppl 4), 75–

90.

Moolgavkar, S. H. (2003). “Air pollution and daily deaths and hospital admissions in Los Angeles and 

Cook Counties.” In: Revised analyses of time-series studies of air pollution and health. Boston, 

MA: Health Effects Institute.

Norris, G., YoungPong, S. N., Koenig, J. Q., Larson, T. V., Sheppard, L., & Stout, J. W. (1999). “An 

association between fine particles and asthma emergency department visits for children in 

Seattle.” Environmental Health Perspectives, 107(6), 489–93.

Ostro, B. D. (1987). “Air pollution and morbidity revisited: A specification test.” Journal of 

Environmental Economics and Management, 14, 87–98.
Retrospective Benefit-Cost Evaluation of U.S. DOE Wind Energy R&D Program: Impact of Selected Energy Technology Investments

B-6

Ostro, B. D., & Rothschild, S. 1989. “Air pollution and acute respiratory morbidity - an observational 

study of multiple pollutants.” Environmental Research, 50(2), 238–247.

Peters, A., Dockery, D. W., Muller, J. E., & Mittleman, M. A. (2001). “Increased particulate air pollution 

and the triggering of myocardial infarction.” Circulation, 103 (23), 2810–5.

http://www.ncbi.nlm.nih.gov/htbinpost/Entrez/query?db=m&form=6&dopt=r&uid=11401937.

Pope, C. A., 3rd, Burnett, R. T., Thun, M. J., Calle, E. E., Krewski, D., Ito, K., & Thurston, G. D. (2002). 

“Lung cancer, cardiopulmonary mortality, and long-term exposure to fine particulate air 

pollution.” Journal of the American Medical Association, 287(9), 1132–41.

Schwartz, J., & Neas, L. M. (2000). “Fine particles are more strongly associated than coarse particles with 

acute respiratory health effects in schoolchildren.” Epidemiology, 11(1), 6–10.

Sheppard, L., Levy, D., Norris, G., Larson, T. V., & Koenig, J. Q. (1999). “Effects of ambient air 

pollution on nonelderly asthma hospital admissions in Seattle, Washington, 1987–1994.”

Epidemiology, 10(1), 23–30.
C-1

APPENDIX C

BIBLIOMETRIC METHODOLOGY USED IN DEVELOPING THE 

KNOWLEDGE BENEFITS CHAPTER9

This appendix provides a brief treatment of the bibliometric methods of evaluation – particularly patent 

analysis – used in the source report from which this appendix is derived. For additional information about 

these and other methods used, please refer to Ruegg and Thomas (2009). 

Bibliometric methods can be used to provide objectively derived, quantitative measures of linkages from 

the publication and patent outputs of a program to publications and patents of downstream innovators. 

The related analyses can indicate that knowledge has been created, who created it, the extent that it is 

being disseminated and used (or at least referenced) by others, and who is using or referencing it. 

C.1 Why Patent Analysis?

When looking for connections from knowledge creation in a research program to commercialized 

technologies, patents are of particular interest because they are considered close to application. The use of 

patents as indicators of technology creation, and patent citation analysis as indicative of technology 

diffusion, reflects a central role of patents in the innovation system. Indeed, patent citation analysis has 

been used extensively in the study of technological change.10

A patent discloses to society how an invention is practiced, in return for the right during a limited period 

of time to exclude others from using the patented invention without the patent assignee's permission. The 

front page of a patent document contains a list of references to “prior art.” Prior art in patent law refers to 

all information that previously has been made available publicly that might be relevant to a patent’s claim 

of originality and, hence, its validity. Prior art may be in the form of previous patents, or published items 

such as scientific papers, technical disclosures, trade magazines, or other forms of relevant information. 

Patent citation analysis centers upon the links between generations of patents, and between patents and 

scientific papers, that are made by these prior art references. The analysis is based on the idea that the 

prior art referenced by a patent has had some influence on the development of the later patent. The prior 

art is thus regarded as part of the foundation for the later invention. In the patent analysis presented in this 

report, the idea is that the downstream technologies represented by patents that cite earlier DOE-attributed 

wind energy patents have built in some way on the knowledge base generated by DOE-funded R&D. 

Patent citation analysis has also been employed in other studies, as it is here, to evaluate the impact of 

particular patents on technological developments. This approach is based on the idea that highly cited 

patents (i.e., patents cited by many later patents) tend to contain technological information of particular 

 9

 This appendix was prepared by Rosalie Ruegg, TIA Consulting Inc. and Patrick Thomas, 1790 Analytics LLC. 10 For an account of the usefulness of patents and citations data as a window on the process of technological change and the 

“knowledge economy,” and as a research tool for tracing links across inventions, see Jaffe and Trajtenberg (2005).
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importance and form the basis for subsequent innovations. Although it is not true to say that every highly 

cited patent is important, or that every infrequently cited patent is unimportant, research studies have 

shown a correlation between the rate of citations of a patent and its technological importance.11

C.2 Forward and Backward Patent Tracing

Two approaches to patent analysis were used in this study – forward tracing and backward tracing. 

C.2.1 Forward Patent Tracing

The idea of forward tracing is to take a given body of research and to trace its influence on subsequent 

technological developments. In the context of the current analysis, forward tracing involves first 

identifying all wind energy patents resulting from wind energy research funded by DOE. The impact of 

these patents on subsequent generations of technology is then evaluated. This tracing is not restricted to 

later wind energy patents, since the influence of a body of research may extend beyond its immediate 

technology area. Hence, the purpose of the forward tracing element of this project is to determine the 

impact of DOE-funded wind energy patents on developments both inside and outside the area of wind 

energy technology. 

C.2.2 Backward Patent Tracing

The idea of backward tracing is to begin with a set of patents reflecting a particular technology, product, 

or industry and to trace back from it to identify earlier patents on which the set has built. In the context of 

this project, the idea of backward patent tracing is to trace back from a set of wind energy patents of 

leading innovative companies in wind energy to the earlier patents on which the set has built. To do this, 

first the leading innovative companies in wind energy were identified as those with the most patents in 

wind energy. The wind energy patents of these leading companies were the starting point of the backward 

tracing. By tracing backward from this set of wind patents to earlier wind energy patents attributed to 

DOE-funded wind R&D, it is possible to determine the extent to which these later innovations built on 

earlier DOE-funded wind energy research. Further, comparing the extent of the linkage of the patents of 

the leading innovative companies in wind energy back to earlier DOE-attributed patents, with the linkages 

of the same set back to patents of other organizations provides an indication of the relative importance of 

DOE in establishing a knowledge base on which other organizations built further innovations in wind 

energy.

C.3 Extensions of the Patent Citation Analysis

The simplest form of patent tracing is based on a single generation of citation links between U.S. patents. 

Such a study identifies U.S. patents that cite, or are cited by, a given set of U.S. patents as prior art. This 

study extends the patent analysis in three ways. 

 11 For background on using patent citation analysis, including a summary of validation studies supporting its use, see A. 

Breitzman & M. Mogee (2002). For a similar background on the use of paper citation analysis, see Chapter 3 of P. Thomas 

(1999).
Appendix C – Bibliometric Methodology Used in Developing the Knowledge Benefits Chapter

C-3

C.3.1 Extension to Patents Citing Publications 

The study extends the analysis to include patent citations of DOE publications in wind. The rationale for 

this extension is that DOE may produce publications that are considered directly relevant to a 

technology’s development. Adding prior art references to DOE-supported publications thus takes into 

account the influence of the knowledge in these publications that is captured in patents. 

C.3.2 Extension to Multiple Generations of Citation Links

The study extends the analysis by adding a second generation of citation links. This means that the study 

traces forward through two generations of citations starting from DOE-supported wind energy patents and 

papers, and backwards through two generations starting from the body of wind energy patents of leading 

innovative companies in wind energy. 

The idea behind adding a second generation of citations is that federal agencies such as DOE often 

support scientific research that is more basic than applied. It may take time and multiple generations of 

research for the research results to be used in applied technology, such as that described in a patent. The 

impact of the research may therefore be missed in a study based on referencing a single generation of 

prior art. Introducing a second generation of citations provides greater access to the indirect links between 

basic and applied research and technology development, and captures patterns of knowledge diffusion 

over a longer period.

At the same time, a potential problem arises when additional generations of citations are added. This is a 

problem common to many networks, whether these networks consist of people, institutions, or scientific 

documents, as in this case. The problem is that, if one uses enough generations of links, eventually almost 

every node in the network will be linked. The most famous example of this is the idea that every person is 

within six links of any other person in the world. By the same logic, if one takes a starting set of patents, 

and extends the network of prior art references far enough, eventually almost all earlier patents and papers 

will be linked to this starting set. Based on our previous experience, using two generations of citation 

links is appropriate for tracing studies such as this. However, adding additional generations may bring in 

too many patents with little connection to the starting patent and paper sets.

C.3.3 Extension beyond the U.S. Patent System 

The report looked beyond the U.S. patent system to include patents from the European Patent Office 

(EPO) and patent applications filed with the World Intellectual Property Organization (WIPO). The 

analysis thus allows for a wide variety of possible linkages between DOE-funded wind energy research 

and subsequent technological developments. 

C.4 Patent Data Sets for Analysis

The forward tracing starts from the set of wind energy patents attributed to DOE funding. The backward 

tracing elements of the study start from the set of wind energy patents of the leading innovative 
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companies defined in terms of owning the most wind energy patents. Neither of these data sets had been 

compiled in advance of the study; both had to be constructed by the study. The first step was to identify 

more broadly wind energy patents.

C.4.1 Identifying Wind Energy Patents 

This process entailed using a patent filter based on a combination of keywords and Patent Office 

Classifications (POCs) to identify wind energy patents issued by the U.S. Patent Office. Details about the 

patent filter are given in the larger source report by Ruegg and Thomas (2009). It should be noted that this 

filter does not refer to specific wind turbine components, such as blades, towers and airfoils. Searching 

for patents using generic terms such as these returns large numbers of irrelevant patents. For example, the 

term ‘blade’ can have many meanings, such as turbine blades, helicopter blades, and razor blades. 

The patent filter used to identify U.S. wind energy patents is not transferable to the EPO and WIPO 

systems because it is based on U.S. Patent Office Classifications. However, there is an International 

Patent Classification (IPC) - F03D - that is specifically related to wind energy that the study used to 

construct EPO and WIPO patent sets.

The filtering process resulted in overall wind energy patent sets through July 2008 for the U.S. (1,432 

granted patents), EPO (1,604 published applications), and WIPO (1,869 published applications). The next 

step was to search within these sets to identify DOE-funded patents, as well as patents assigned to leading 

wind energy organizations.

C.4.2 Identifying DOE-attributed Wind Energy Patents for Forward Tracing

Identifying patents funded by government agencies is often more difficult than identifying patents funded 

by companies. When a company funds internal research, any patented inventions emerging from this 

research are likely to be assigned to the company itself. To construct a patent set for a company, one 

simply has to identify all patents assigned to the company, along with all of its subsidiaries, acquisitions, 

and any other related parts.

In contrast, a government agency such as DOE may fund research in a variety of organizations. For 

example, DOE operates a number of laboratories and research centers. Patents emerging from these 

laboratories and research centers may be assigned to DOE, or they may be assigned to the organization 

that manages the laboratories or research centers. For example, patents from Sandia may be assigned 

Lockheed Martin, while Livermore patents may be assigned to the University of California.

A further complication is that DOE does not only fund research in its own labs and research centers. It 

also funds research carried out by private companies and universities. If this research results in patented 

inventions, these patents are likely to be assigned to the company or university carrying out the research, 

rather than to DOE.
Appendix C – Bibliometric Methodology Used in Developing the Knowledge Benefits Chapter

C-5

To identify wind patents resulting from DOE-funded research, the study used three sources to find DOEattributed patents within the broader set containing all wind energy patents, plus an additional, fourth 

source.

1. OSTI Database. The first source used was a database provided by OSTI for use in DOErelated projects. This database contains information on research grants provided by DOE 

since its inception. It also links these grants to the organizations or DOE centers carrying out 

the research, the sponsor organization within DOE, and the U.S. patents and publications that 

resulted from these DOE grants.

2. Patents assigned to DOE. The study identified a number of U.S. patents assigned to DOE 

that were not in the OSTI database because they have been issued since the latest version of 

that database. These patents were added to the list of DOE-attributed patents.

3. Patents with DOE Government Interest. A U.S. patent has on its front page a section entitled 

“Government Interest,” which details the rights that the government has in a particular 

invention. For example, if a government agency funds research at a private company, the 

government may have certain rights to patents granted based on this research. The study 

identified all patents within the broader set identified by the wind patent filter that refer to 

“Department of Energy” or “DOE” in their Government Interest field, along with patents that 

refer to government contracts beginning with DE- or ENG-, since these abbreviations denote 

DOE grants. Patents in this set that were not in the OSTI database and were not assigned to 

DOE were added to the list of DOE-attributed patents.

In addition to using the above three sources to identify DOE-attributed patents from the larger wind 

energy database, the study also searched DOE reports for identification of DOE-attributed wind patents. 

In some cases, the DOE reports identified specific wind energy patents resulting from funding by DOE, in 

which case the patents were added to the DOE-attributed patent set resulting from the procedure 

previously described. The reports also in some cases identified organizations whose wind energy research 

has been funded by DOE, the period of funding, and technologies funded, but not specific patents. By 

matching the organizations, time periods, and technologies from these documents with patent data, it was 

possible to identify additional patents from these organizations that are likely to have been funded (at 

least in part) by DOE, even if they did not formally acknowledge DOE’s support.

The next step was to send the resulting list of candidate patents identified through this multistep process 

to DOE scientists and program managers for verification. They provided feedback on which of the 

candidate patents should be included in the study’s final set of DOE-attributed patents and which should 

be omitted. The final DOE-approved list contained a total of 112 DOE-attributed U.S. wind energy 

patents. 

The study then searched the EPO and WIPO systems for equivalents of each of these patents. Of the 112 

U.S. patents defined as DOE funded, 65 were found to have no foreign equivalents, meaning that they 
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have only been filed in the United States. The remaining patents each have at least one EPO or WIPO 

equivalent, and some have multiple equivalents in those two patent systems. In total, the study identified 

27 EPO patents and 27 WIPO patents that are equivalents to the DOE-attributed U.S. patents. The final 

portfolio of DOE-attributed wind energy patents for this analysis contains 112 U.S. patents, 27 EPO 

patents, and 27 WIPO patents.

C.4.3 Identifying the Set of Wind Energy Patents for Leading Organizations in Wind Energy 

Patenting for Backward Tracing

Companies with the most U.S. granted wind energy patents were included on the list of leading 

innovative companies shown in Table C-1. All companies in the table have at least 7 U.S. wind energy 

patents. The study identified a total of 221 U.S. wind energy patents, 367 EPO wind energy patents, and 

313 WIPO wind energy patents assigned to the organizations listed in Table C-1.

Table C-1. Leading Organizations in Wind Energy Technology Patenting

Aerodyne Engineering, GMBH

Clipper Windpower Technology Inc

Clipper Windpower Technology Inc

Distributed Energy Systems Corp

Doughty Hanson & Co. Ltd.

Gamesa

General Electric Company

Global Energy Concepts Inc

Hitachi Ltd

LM Glasfiber A/S

Mitsubishi Electric Corp

Mitsubishi Heavy Industries Ltd.

Nordex Energy GmbH

Northrop Grumman Corp

Siemens Aktiengesellschaft

Southwest Windpower Inc

United Technologies Corp

Vestas Wind Systems A/S

Note: Organizations selected have at least 7 wind energy patents, but they are not listed in order of the number of their patents. 

There are a number of prominent wind energy companies in terms of sales that do not feature in the table, because they do 

not have enough patents in the US, EPO or WIPO systems to qualify. Prominent companies not on the list include Asian 

companies, such as Suzlon, Goldwind and Sinovel; European companies, such as Enercon and Acciona; and US-based 

companies, such as Bergey and TPI Composites. 
Appendix C – Bibliometric Methodology Used in Developing the Knowledge Benefits Chapter

C-7

C.5 Constructing Patent Families

Organizations often file for protection of their inventions across multiple patent systems. For example, a 

U.S. company may file to protect a given invention in the United States and also file for protection of this 

invention in other countries. Also, inventors may apply for a series of patents in the same country based 

on the same underlying invention. As a result, there may be multiple patent documents for the same 

invention. One or more U.S., EPO, and WIPO patents may result from a single invention. 

A search for equivalents of each of the DOE-attributed patents was made in the EPO and WIPO systems 

to avoid counting patents on the same invention more than once. An equivalent is a patent filed in a 

different patent system covering essentially the same invention. A search was also made for U.S. patents 

that are continuations, continuations-in-part, or divisionals of each of these patents. 

Patents that are all based on the same underlying invention are constructed into patent families. A patent 

family contains all of the patents and patent applications that result from the same original patent 

application (named the priority application). A family may include patents/applications from multiple 

countries, and also multiple patents/applications from the same country. 

For this study, it was necessary to construct patent families for DOE and also for the body of wind energy 

patents of the leading companies. To construct these patent families, the priority documents of the U.S., 

EPO and WIPO patents/applications were matched, to group them in the appropriate families. Fuzzy 

matching algorithms were used to achieve this, along with a small amount of manual matching, since 

priority documents have different number formats in different patent systems. It should be noted that the 

priority document does not necessarily need to be a U.S., EPO, or WIPO application. For example, a 

Japanese patent application may result in U.S., EPO, and WIPO patents/applications, which are grouped 

in the same patent family because they share the same Japanese priority document.

As a result of this process, the DOE-attributed U.S., EPO and WIPO wind energy patents were grouped 

into 112 patent families. Meanwhile the U.S., EPO and WIPO wind energy patent/applications assigned 

to leading organizations were grouped into 695 patent families. 

C.6 Publication Coauthoring and Citation Analyses

Publications referenced by patents are of particular interest because of their closeness to innovation. 

Bibliometric theory holds that patent-to-publication citations typically acknowledge an intellectual debt of 

a technology to the science base on which it draws.12 In contrast, the theory holds that citations of 

scientific papers in a field by other papers generally acknowledge scientific, intellectual debts, rather than 

technology debts. Thus, publication-to-publication citation analysis is generally considered a less 

effective approach to tracing linkages from R&D to downstream commercial activity than patent-topatent and patent-to-publication analyses. However, the study found that analyses of publication co-

 12 See Martin S. Meyer, Between Technology and Science: Exploring an Emerging Field, Chapter 4, “Differences between 

Scientific and Patent Citations” (Universal-Publishers, 2005).
Retrospective Benefit-Cost Evaluation of U.S. DOE Wind Energy R&D Program: Impact of Selected Energy Technology Investments

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authorship and citations of publications by other publications offer additional insights into the linkages of 

DOE’s wind R&D to technology development, as well as to other scientific research. 

Extensive coauthoring by DOE wind researchers with researchers from other organizations appears to 

indicate collaboration and close linkages of the DOE researchers to those involved in downstream 

technology development and commercialization. Citations of DOE publications by patents, as well as by 

company publications suggest a closer link to downstream applications than bibliometric theory would 

suggest. 

The publication citation search is facilitated by using a publication citation database and search engine. 

The U.S.-based firm Thomson Scientific (formerly the Institute for Scientific Information [ISI]) was long 

the principal tool facilitating publication citation analysis. But today a growing number of publication 

citation databases and search tools, such as Scopus, CiteSeer, and Google Scholar, provide 

comprehensive coverage beyond the major journals, including, for example, conference proceedings, 

book chapters, dissertations, and research reports.13 For this study’s publication-to-publication citation 

analysis, conference papers and research reports were prominent, and Google Scholar was used because it 

includes these kinds of publications in its search capability. A comparison of alternative publication 

search tools rated Google Scholar among the best.14

Again, for additional coverage of the methodology, see the source study, Ruegg and Thomas (2009).

C.7 References

Breitzman, A. & Mogee, M. (2002). “The Many Applications of Patent Analysis.” Journal of Information 

Science, 28(3): 187–205.

Meho, Lokman I. (2007, January). “The Rise and Rise of Citation Analysis.” Physics World: 32-36.

Meyer, Martin S. (2005). “Differences between Scientific and Patent Citations.” Between Technology and 

Science: Exploring an Emerging Field. Boca Raton, Florida: Dissertation.com. (published 

dissertation, University of Sussex). 

Ruegg, Rosalie & Thomas, Patrick. (2009). Linkages from DOE’s Wind Program R&D to Commercial 

Renewable Power Generation. U.S. Department of Energy, Energy Efficiency and Renewable 

Energy.

Thomas, P. (1999, July). Fashions in Management Research: An Empirical Analysis. Ashgate Publishing.

 13 Lokman I. Meho, “The Rise and Rise of Citation Analysis.” Physics World 20, no. 1, January 2007: 32-36, 32. 14 Ibid., 31-36.
D-1

APPENDIX D 

DISCUSSION OF PRODUCTION TAX CREDIT AND RESEARCH AND 

DEVELOPMENT INFLUENCES ON MEGAWATT CAPACITY GROWTH

The Production Tax Credit (PTC) was enacted in 1992. Some advances from infrastructure technologies 

also started becoming available in the early 1990’s (See Figure 2-4 in Chapter 2). However, widespread 

utilization was only achieved in the mid to late 1990’s.

The interviews conducted as part of this study explored the impact of the PTC indicating that the PTC 

was also important. Without the PTC, additional delays beyond the six year delay from R&D 

underinvestment would have been likely. The magnitude of these additional delays could not be 

identified. Experts stressed, however, that without prior R&D investments in infrastructure technologies 

leading to lower cost of energy, improved reliability, and availability, the PTC is unlikely to have been 

effective on its own.

Also, as suggested by Figure D-1, the PTC by itself and without acceptable reliability and efficiency 

levels did not generate appreciable capacity additions during the 1992-1999 period. Only when reliable 

wind energy technologies became available (due to R&D investments) did capacity additions pick up and 

accelerate.

Figure D-1. Production Tax Credit and Wind MW Capacity Growth 

1,295

MW/year

132 

MW/year

PTC in force with 

minor interruptions

0

1

2

3

4

5

6

7

8

9

1981198219831984198519861987198819891990199119921993199419951996199719981999200020012002200320042005200620072008

0

3

6

9

12

15

18

21

24

27

 Annual US Capacity (left scale) 

 Cumulative US Capacity (right scale) 

Cumulative Capacity (GW)

Annual Capacity (GW)

132 

MW/year

1,295

MW/year
Retrospective Benefit-Cost Evaluation of U.S. DOE Wind Energy R&D Program: Impact of Selected Energy Technology Investments

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During the 1992 through 1999 period, infrastructure technology advances were not yet fully available 

and (per data supplied by Mark Bollinger of LBNL), average annual capacity additions languished at 132 

MW. During the next seven year period, from 1999 to 2006, with infrastructure technologies becoming 

available and facilitating improved design practices and higher reliability levels, average annual capacity 

additions increased 10-fold to 1,295 MW. During two years from 2006 to 2008, with the full impact of 

infrastructure technologies coming to bear, average annual capacity additions increased to 6,898 MW.

Interviewed experts consistently stressed that without prior R&D investments in infrastructure 

technologies, leading to lower cost of energy, improved reliability and availability, the PTC is unlikely to 

have been effective by itself. Specifically, the PTC could not have brought about four fold improvement 

in reliability (as reflected in historic O&M expense reductions), three fold improvement in wind energy 

capital costs, and the 25 fold reduction in the cost of energy from the 85 cents per kWh level of the early 

1980’s. Without reliability improvements facilitated by DOE funded infrastructure technologies, 

commercial risks would have remained unacceptably high and project developers would have abstained 

from investing in additional wind capacity under conditions of higher technical and commercial risk.

Per NREL Wind Finance Website http://analysis.nrel.gov/windfinance, commercially viable wind 

projects are funded with 20% equity and 80% bank loans (See Table D-1 below). They are also 

characterized by 30 year expected operating life and 28 year term to repay bank loan.

Effective demand side subsidies presuppose a working technology. Subsidies are generally effective in 

compensating against high initial capital cost, not for technical failure or significant technical 

underperformance. If banks cannot satisfy themselves that the technology for a proposed wind energy 

project is reliable and will operate as planned for at least 28 of 30 years, the project will not generate 

sufficient cash flows to repay the bank loan. Without the reliability improvements from infrastructure 

technology advances and the associated assurance of debt repayment, the banks would not provide project 

debt and wind energy projects would not get built. This would explain what happened in the 1992 to 1999 

period, when COE was high and when reliability and availability levels were low, the economics of most 

wind projects could not be made to work, even though the PTC was in force throughout the 1992 to 1999 

period. 
Appendix D – Discussion of Production Tax Credit and Research and Development Influences on Megawatt Capacity Growth

D-3

Table D-1. Financing Assumptions for Typical Wind Energy Project 

GENERAL ASSUMPTIONS

Expected Inflation Rate 3 %/year

Rated Capacity 10 MW

Net Capacity Factor 37 %

Start Year 2002

Project Operating Lifetime 30 Years

CAPITAL COSTS (thousand dollars)

Equipment Costs 12000

Balance of Station (buildings, roads, 

interconnect, etc.) 0

Land 0

Developer Soft Costs 0

Construction Loan Interest 480

Other Capital Costs 0

Debt Financing Fees 240

Equity Financing Fees 60

Debt Service Reserve Fund 450

Initial Working Capital 30

Total Capital Costs 13260

OPERATING EXPENSES

Fixed Operation & Maintenance (O&M) 25 $/kW 

Variable O&M 0 $/kWh

Site Owner Royalty

(% of revenues) 3 %

Property Tax

(% of Equipment and Balance of Station 

Costs)

0 %

Insurance

(% of Equipment and Balance of Station 

Costs)

1 %

Other Costs 0 thousand 

dollars/year

Fixed O&M Escalation Rate 3 %/year

Variable O&M Escalation Rate 3 %/year

Property Tax Escalation Rate 0 %/year

Insurance Escalation Rate 3 %/year

Other Costs Escalation Rate 3 %/year

FINANCING ASSUMPTIONS

Grant Percentage (% of Total Capital 

Cost) 0

Interest Earned on Reserves (%/year) 2.00 %

Amount

(thousand dollars) 10608 0

Schedule Type Level 

Mortgage

Level 

Mortgage

Debt Percentage 80.00% 0.00 %

Interest Rate 6.80% 6.80 %

Bank Loan Term (years) 28 28

TAX ASSUMPTIONS

Marginal Federal Tax Rate 0 %/year

Marginal State Tax Rate 0 %/year

Tax Incentive Type REPI

Include PTC/REPI in DSCR Calculation Yes

Incentive Amount 1 cents/kWh

Incentive Length 10 years

Incentive Inflation Rate 3 %/year

ECONOMIC ASSUMPTIONS

Power Purchaser Discount Rate (for 

Levelised Cost of Energy [LCOE] 

Calculation)

5.5 %/year

Project Owner Discount Rate (for Net

Present Value [NPV] Calculation) 6 %/year

Energy Payment Escalation Rate 1 %/year

CONSTRAINING ASSUMPTIONS

Average Debt Service Coverage Ratio 

(DSCR) Constraint Yes

Target Average DSCR 1.34

Minimum DSCR Constraint Yes

Target Minimum DSCR 1.27

Internal Rate of Return (IRR) Constraint Yes

Target IRR 15.22 %

Positive Cash Flow Constraint Yes

Source: From NREL Wind Finance Website: http://analysis.nrel.gov/windfinance.
Retrospective Benefit-Cost Evaluation of U.S. DOE Wind Energy R&D Program: Impact of Selected Energy Technology Investments

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