NOTICE: The project that is the subject of this report was approved by the Governing Board of the National Research Council, whose members are drawn from the councils of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The members of the committee responsible for the report were chosen for their special competences and with regard for appropriate balance.
This report has been reviewed by a group other than the authors according to procedures approved by a Report Review Committee consisting of members of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine.
The National Academy of Sciences is a private, nonprofit, self-perpetuating society of distinguished scholars engaged in scientific and engineering research, dedicated to the furtherance of science and technology and to their use for the general welfare. Upon the authority of the charter granted to it by the Congress in 1863, the Academy has a mandate that requires it to advise the federal government on scientific and technical matters. Dr. Frank Press is president of the National Academy of Sciences.
The National Academy of Engineering was established in 1964, under the charter of the National Academy of Sciences, as a parallel organization of outstanding engineers. It is autonomous in its administration and in the selection of its members, sharing with the National Academy of Sciences the responsibility for advising the federal government. The National Academy of Engineering also sponsors engineering programs aimed at meeting national needs, encourages education and research, and recognizes the superior achievements of engineers. Dr. Robert M. White is president of the National Academy of Engineering.
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The National Research Council was organized by the National Academy of Sciences in 1916 to associate the broad community of science and technology with the Academy’s purposes of furthering knowledge and advising the federal government. Functioning in accordance with general policies determined by the Academy, the Council has become the principal operating agency of both the National Academy of Sciences and the National Academy of Engineering in providing services to the government, the public, and the scientific and engineering communities. The Council is administered jointly by both Academies and the Institute of Medicine. Dr. Frank Press and Dr. Robert M. White are chairman and vice chairman, respectively, of the National Research Council.
This report and the study on which it is based were supported by Contract No. DE-AC04-89AL58181 between the U.S. Department of Energy and the National Academy of Sciences-National Research Council.
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NAT S-324
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COMMITTEE ON ASSESSMENT OF RESEARCH NEEDS FOR WIND TURBINE ROTOR MATERIALS TECHNOLOGY
GEORGE E. DIETER (Chairman), Dean,
College of Engineering, University of Maryland, College Park, Maryland
JAMIE CHAPMAN, Power Systems Consultant,
Boston, Massachusetts
H. THOMAS HAHN,
Department of Engineering Science and Mechanics, Pennsylvania State University, University Park, Pennsylvania
DEWEY H. HODGES,
School of Aerospace Engineering, Georgia Institute of Technology, Atlanta, Georgia
CHARLES W. ROGERS,
Bell Helicopter Textron, Inc., Fort Worth, Texas
LENA VALAVANI,
Department of Aeronautics and Astronautics, Massachusetts Institute of Technology, Cambridge, Massachusetts
MICHAEL D. ZUTECK, Consultant,
Kemah, Texas
National Research Council Staff
KAMAL J. ARAJ, Study Director,
Energy Engineering Board
THERESA A. FISHER, Study Assistant (to April 1990)
JAN C. KRONENBURG, Study Assistant (to February 1991)
ENERGY ENGINEERING BOARD
JOHN A. TILLINGHAST (Chairman),
Tiltec, Portsmouth, New Hampshire
DONALD B. ANTHONY,
Bechtel Corporation, Houston, Texas
RICHARD E. BALZHISER,
Electric Power Research Institute, Palo Alto, California
BARBARA R. BARKOVICH, Barkovich and Yap, Consultants,
San Rafael, California
JOHN A. CASAZZA, CSA Energy Consultants,
Arlington, Virginia
RALPH C. CAVANAGH,
Natural Resources Defense Council, San Francisco, California
DAVID E. COLE,
University of Michigan, Ann Arbor, Michigan
H. M. (HUB) HUBBARD,
Midwest Research Institute (retired), Golden, Colorado
ARTHUR E. HUMPHREY,
Lehigh University, Bethlehem, Pennsylvania (to February 1991)
CHARLES IMBRECHT,
California Energy Commission, Sacramento, California
CHARLES D. KOLSTAD,
University of Illinois, Urbana, Illinois
HENRY R. LINDEN,
Gas Research Institute, Chicago, Illinois
JAMES J. MARKOWSKY,
American Electric Power Service Corporation, Columbus, Ohio (to February 1991)
SEYMOUR L. MEISEL,
Mobile R&D Corporation (retired), Princeton, New Jersey
DAVID L. MORRISON,
The MITRE Corporation, McLean, Virginia
MARC H. ROSS,
University of Michigan, Ann Arbor, Michigan
MAXINE L. SAVITZ,
Garrett Ceramic Component Division, Torrance, California
HAROLD H. SCHOBERT,
Pennsylvania State University, University Park, Pennsylvania
GLENN A. SCHURMAN,
Chevron Corporation, San Francisco, California
JON M. VEIGEL,
Oak Ridge Associated Universities, Oak Ridge, Tennessee
BERTRAM WOLFE,
GE Nuclear Energy, San Jose, California
Staff
ARCHIE L. WOOD, Executive Director,
Commission on Engineering and Technical Systems, and
Director,
Energy Engineering Board (to January 1991)
MAHADEVAN (DEV) MANI, Director, Energy Engineering Board
KAMAL J. ARAJ, Senior Program Officer
ROBERT COHEN, Senior Program Officer (retired)
GEORGE LALOS, Senior Program Officer
JAMES J. ZUCCHETTO, Senior Program Officer
JUDITH A. AMRI, Administrative/Financial Assistant
THERESA M. FISHER, Administrative Secretary
JAN C. KRONENBURG, Administrative Secretary
PHILOMINA MAMMEN, Administrative Secretary
NANCY WHITNEY, Administrative Secretary
PREFACE
Wind-driven power systems represent a renewable energy technology that is still in the early stages of development. These wind power plants installed in the early 1980s suffered structural failures chiefly because of incomplete understanding of the wind forces (especially the turbulence component) acting on these large structures and in some cases because of poor quality in manufacture. Failure of the rotor blades was one of the principal and most serious structural failures. Failures from these causes are now somewhat better understood. Another limitation to economical achievement of the potential of wind energy is uncertainty about the long-term response of wind turbine rotor materials to the turbulent stochastic loadings to which they are subjected. These structures can be subjected to as many as a billion stress cycles.
In accordance with its assessment of its long-term research responsibilities, the Department of Energy requested the National Research Council to assess the research needs for wind turbine rotor technology. Such a study would assist in organizing the information about the current status of wind turbine rotor materials, their manufacture into blades, and their operation and life performance in service. Of special importance was an assessment of current materials technology and design methodologies to provide perspective for future investigations.
The Committee on Assessment of Research Needs for Wind Turbine Rotor Materials Technology was formed by the Energy Engineering Board to specifically evaluate the following issues (see Appendix A for Statement of Task):
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the adequacy of existing models to predict dynamic stress patterns;
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the properties of wind turbine materials in dynamic and fatigue failure;
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understanding of the performance of joints, fasteners, and critical sections in relation to failure modes and fracture;
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the tools needed to study these phenomena, such as computer design tools, and materials databases;
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the need for special laboratory facilities, models, and prototypes to improve the design and operation of wind energy systems;
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the opportunities for new materials to improve wind turbine life; the potential for improved design methods, advanced control techniques, and better manufacturing processes and advanced materials for better performance and longevity.
In addition, the committee took as its responsibility the development, in broad outline, of a research and development program that would place U.S. wind power technology in a preeminent world position.
In carrying out its assignment the committee examined an extensive literature on wind machines and wind turbine rotor materials. The emphasis of the study was on wind machines suitable for utility applications. Many U.S. experts on these subjects briefed the committee in two meetings of two-day duration (see Appendix B). The committee wishes to acknowledge with gratitude the assistance of the following individuals for their time and knowledge:
Holt Ashley, Stanford University; Charles Carlson and Marilyn W. Wardle, E.I. duPont de Nemours & Co.; John C. Doyle, California Institute of Technology; Brant Goldsworthy, ALCOA/Goldsworthy Engineering; Richard H. Hilt, Gas Research Institute; William Holley, U.S. Windpower; Donald Hunston, National Institute for Standards and Technology; Edwin T.C. Ing; John Mandell, Montana State University; Robert C. Monroe, Hudson Products; Robert H. Monroe, Gougeon Brothers; Peter Ogle, Dow United Technologies Composite Products; Donald Pederson and Fred J. Policelli, Hercules, Inc.; Lawrence Rehfield, University of California-Davis; Forrest S. Stoddard, Alternative Energy Institute; Robin Whitehead, Northrop; Daniel F. Ancona III, Leonard J. Rogers and Jeffrey H. Rumbaugh, U.S. Department of Energy; James Tangler and Robert Thresher, Solar Energy Research Institute; and Herbert Sutherland, Sandia National Laboratories.
George E. Dieter, Chairman
Committee on Assessment of Research Needs for Wind Turbine Rotor Materials Technology
LIST OF FIGURES
Figure 1-1 |
Wind power plant in Altamont Pass, California |
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Figure 1-2 |
World energy generation by wind power plants during 1989 |
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Figure 1-3 |
Growth of generating capacity for California wind power plants |
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Figure 1-4 |
Growth of annual energy production for California wind power plants |
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Figure 1-5 |
Wind turbine subsystems |
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Figure 1-6 |
Wind turbine power curve |
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Figure 1-7 |
Wind flow field and turbine loads |
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Figure 1-8 |
Comparison of logarithmic power in the wind with a wind turbine power curve |
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Figure 1-9 |
Wind turbine blade control methods |
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Figure 1-10 |
Accumulation of fatigue cycles |
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Figure 2-1 |
Process necessary to analyze composite blades |
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Figure 3-1 |
Trends of longitudinal tensile fatigue S-N data for unidirectional composites with various fibers |
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Figure 3-2 |
Schematics of various fiber preforms |
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Figure 3-3 |
Stress-strain relationships of glass/epoxy laminates under uniaxial tension |
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Figure 3-4 |
Modes of damage growth in composite laminate under fatigue |
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Figure 3-5 |
Laminate directional properties and shear directional nomenclature |
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Figure 3-6 |
Wood strength change due to temperature at two moisture conditions |
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Figure 3-7 |
Wood moisture content versus atmospheric relative humidity |
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Figure 3-8 |
Effect of moisture content on laminate mechanical properties |
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Figure 3-9 |
Typical tensile fatigue strength of wood/epoxy laminate |
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Figure 3-10 |
Typical compression fatigue strength of wood/epoxy laminate |
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Figure 3-11 |
Typical reversed stress fatigue strength of wood/epoxy laminate |
Figure 4-1 |
Commonly used early HAWT airfoils |
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Figure 4-2 |
SERI advanced wind turbine airfoils |
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Figure 4-3 |
Nine-meter GRP wind turbine blade |
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Figure 4-4 |
Eleven-meter wood/epoxy blade airfoil thickness distribution and planform |
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Figure 4-5 |
Flanged GRP blade root design |
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Figure 4-6 |
Flanged root design limitation due to steel/GRP strain incompatibility |
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Figure 4-7a |
Bonded steel root tube GRP hub design |
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Figure 4-7b |
Wood/epoxy blade root |
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Figure 4-8 |
All-wood/epoxy composite hub |
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Figure 5-1 |
UH-1H composite main rotor blade |
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Figure 5-2 |
RTM cooling tower blade |
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Figure 5-3 |
4BW hingeless bearingless rotor |
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Figure 6-1 |
Wind turbine drive train |
LIST OF TABLES
Table 2-1 |
Blade Sectional Analysis Codes |
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Table 3-1 |
Typical Properties of Fibers |
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Table 3-2 |
Typical Properties of Unidirectional Composites |
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Table 3-3 |
Properties of Case Resins |
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Table 3-4 |
High-Performance Thermoplastics Used as Matrix Resins |
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Table 3-5 |
Trade-offs Between Thermosets and Thermoplastics as Matrices |
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Table 3-6 |
Typical Static Strength, Type 110 Laminate |
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Table 6-1 |
Control Effectors and Sensors for a Pitch Controlled Wind Turbine |