Research Papers

Wind Climate Parameters for Wind Turbine Fatigue Load Assessment

[+] Author and Article Information
Henrik Stensgaard Toft

Department of Civil Engineering,
Aalborg University,
Sofiendalsvej 11,
Aalborg SV 9200, Denmark
e-mail: hst@civil.aau.dk

Lasse Svenningsen, Morten Lybech Thøgersen

EMD International A/S,
Niels Jernes Vej 10,
Aalborg 9220, Denmark

Wolfgang Moser

Nordex Energy GmbH,
Langenhorner Chaussee 600,
Hamburg 22419, Germany

John Dalsgaard Sørensen

Department of Civil Engineering,
Aalborg University,
Sofiendalsvej 11,
Aalborg SV 9200, Denmark

1Corresponding author.

Contributed by the Solar Energy Division of ASME for publication in the JOURNAL OF SOLAR ENERGY ENGINEERING: INCLUDING WIND ENERGY AND BUILDING ENERGY CONSERVATION. Manuscript received August 2, 2015; final manuscript received March 14, 2016; published online April 5, 2016. Assoc. Editor: Yves Gagnon.

J. Sol. Energy Eng 138(3), 031010 (Apr 05, 2016) (8 pages) Paper No: SOL-15-1245; doi: 10.1115/1.4033111 History: Received August 02, 2015; Revised March 14, 2016

Site-specific assessment of wind turbine design requires verification that the individual wind turbine components can survive the site-specific wind climate. The wind turbine design standard, IEC 61400-1 (third edition), describes how this should be done using a simplified, equivalent wind climate established from the on-site distribution functions of the horizontal mean wind speeds, the 90% quantile of turbulence along with average values of vertical wind shear and air density and the maximum flow inclination. This paper investigates the accuracy of fatigue loads estimated using this equivalent wind climate required by the current design standard by comparing damage equivalent fatigue loads estimated based on wind climate parameters for each 10 min time-series with fatigue loads estimated based on the equivalent wind climate parameters. Wind measurements from Boulder, CO, in the United States and Høvsøre in Denmark have been used to estimate the natural variation in the wind conditions between 10 min time periods. The structural wind turbine loads have been simulated using the aero-elastic model FAST. The results show that using a 90% quantile for the turbulence leads to an accurate assessment of the blade root flapwise bending moment and a conservative assessment of the tower bottom for-aft bending moment and low speed shaft torque. Currently, IEC 61400-1 (third edition) neglects the variation in wind shear by using the average value. This may lead to a nonconservative assessment of blade root flapwise fatigue loads, which are sensitive to wind shear. The results in this paper indicate that using a 75% quantile for the wind shear at each wind speed bin leads to an appropriate, but conservative, assessment of the fatigue loads. However, care should be taken when using this approach for components where low or negative wind shears can lead to large fatigue loads. This is the case for some drivetrain components where a lower quantile may be required.

Copyright © 2016 by ASME
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Fig. 1

Distribution of mean wind speed for measurements

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Fig. 2

Mean and std. dev. for wind speed standard deviation

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Fig. 3

Mean and std. dev. for wind shear

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Fig. 4

Mean and std. dev. for air density

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Fig. 5

Variation of damage equivalent loads with mean wind speed and reference turbulence intensity, wind shear, and air density. Names of load sensors are listed in Table 2.

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Fig. 6

Wind measurements from Boulder and Høvsøre with statistical parameters




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