The effects of wind shear and turbulence on rotor fatigue and loads control are explored for a large horizontal axis wind turbine in variable speed operation at wind speeds from 4 to 20 m/s. Two- and three-blade rigid rotors are considered over a range of wind shear exponents up to 1.25 and a range of turbulence intensities up to 17%. RMS blade root flatwise moments are predicted to be very substantially increased at higher wind shear, and resultant fatigue damage is increased by many orders of magnitude. Smaller but similar trends occur with increasing turbulence levels. In-plane fatigue damage is driven by 1P gravity loads and exacerbated by turbulence level at higher wind speeds. This damage is higher by one to two orders of magnitude at the roots of the three-blade rotor compared with the two-blade rotor. Individual blade pitch control of fluctuating flatwise moments markedly reduces flatwise fatigue damage due to this source, and, to a lesser degree, the in-plane damage due to turbulence. The same is true of fluctuating rotor torque moments driven by turbulence and transmitted to the drive train. Blade root moments out of the plane of rotation aggregate to create rotor pitching and yawing moments transmitted to the turbine structure through the drive train to the yaw drive system and the tower. These moments are predicted to be relatively insensitive to turbulence level and essentially proportional to the wind shear exponent for the two-blade rotor. Fluctuating moments are substantially reduced with individual blade pitch control, and addition of a teeter degree-of-freedom should further contribute to this end. Fluctuating pitching and yawing moments of the three-blade rotor are substantially less sensitive to wind shear, more sensitive to turbulence level, and substantially lower than those for the two-blade rotor. Mean rotor torque and, hence, power are essentially the same for both rotors, independent of wind shear, and are somewhat reduced with individual blade pitch control of fluctuating flatwise moments. The same is true of mean rotor thrust; however fluctuations in rotor thrust are substantially reduced with individual blade pitch control.
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November 2003
Technical Papers
Wind Shear and Turbulence Effects on Rotor Fatigue and Loads Control
A. J. Eggers,, Jr.,
A. J. Eggers,, Jr.
RANN Incorporated, 744 San Antonio Road, Suite 26, Palo Alto, California 94303
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R. Digumarthi,
R. Digumarthi
RANN Incorporated, 744 San Antonio Road, Suite 26, Palo Alto, California 94303
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K. Chaney
K. Chaney
RANN Incorporated, 744 San Antonio Road, Suite 26, Palo Alto, California 94303
Search for other works by this author on:
A. J. Eggers,, Jr.
RANN Incorporated, 744 San Antonio Road, Suite 26, Palo Alto, California 94303
R. Digumarthi
RANN Incorporated, 744 San Antonio Road, Suite 26, Palo Alto, California 94303
K. Chaney
RANN Incorporated, 744 San Antonio Road, Suite 26, Palo Alto, California 94303
Contributed by the Solar Energy Division of THE AMERICAN SOCIETY OF MECHANICAL ENGINEERS for publication in the ASME JOURNAL OF SOLAR ENERGY ENGINEERING. Manuscript received by the ASME Solar Energy Division February 27, 2003; final revision, July 15, 2003. Associate Editor: D. Berg.
J. Sol. Energy Eng. Nov 2003, 125(4): 402-409 (8 pages)
Published Online: November 26, 2003
Article history
Received:
February 27, 2003
Revised:
July 15, 2003
Online:
November 26, 2003
Citation
Eggers, , A. J., Jr. , Digumarthi , R., and Chaney, K. (November 26, 2003). "Wind Shear and Turbulence Effects on Rotor Fatigue and Loads Control ." ASME. J. Sol. Energy Eng. November 2003; 125(4): 402–409. https://doi.org/10.1115/1.1629752
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