Discussion papers | Copyright
https://doi.org/10.5194/wes-2018-48
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Research articles 03 Jul 2018

Research articles | 03 Jul 2018

Review status
This discussion paper is a preprint. A revision of this manuscript was accepted for the journal Wind Energy Science (WES) and is expected to appear here in due course.

Inter-annual variability of wind climates and wind turbine annual energy production

Sara C. Pryor1, Tristan J. Shepherd1, and Rebecca J. Barthelmie2 Sara C. Pryor et al.
  • 1Department of Earth and Atmospheric Sciences, Cornell University, Ithaca, NY14853, USA
  • 2Sibley School of Mechanical and Aerospace Engineering, Cornell University, Ithaca, NY14853, USA

Abstract. Inter-annual variability (IAV) of expected annual energy production (AEP) from proposed wind farms plays a key role in dictating project financing. IAV in pre-construction projected AEP and the difference in 50th and 90th percentile (P50 and P90) AEP derives in part from variability in wind climates. However, the magnitude of IAV in wind speeds at/close to wind turbine hub-heights is poorly constrained and maybe overestimated by the 6% standard deviation of annual mean wind speeds that is widely applied within the wind energy industry. Thus there is a need for improved understanding of the long-term wind resource and the inter-annual variability therein in order to generate more robust predictions of the financial value of a wind energy project. Long-term simulations of wind speeds near typical wind turbine hub-heights over the eastern USA indicate median gross capacity factors (computed using 10-minute wind speeds close to wind turbine hub-heights and the power curve of the most common wind turbine deployed in the region) that are in good agreement with values derived from operational wind farms. The IAV of annual mean wind speeds at/near to typical wind turbine hub-heights in these simulations is lower than is implied by assuming a standard deviation of 6%. Indeed, rather than in 9 in 10 years exhibiting AEP within 0.9 and 1.1 times the long-term mean AEP, results presented herein indicate that over 90% of the area in the eastern USA that currently has operating wind turbines simulated AEP lies within 0.94 and 1.06 of the long-term average. Further, IAV of estimated AEP is not substantially larger than IAV in mean wind speeds. These results indicate it may be appropriate to reduce the IAV applied to pre-construction AEP estimates to account for variability in wind climates, which would decrease the cost of capital for wind farm developments.

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Sara C. Pryor et al.
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Sara C. Pryor et al.
Sara C. Pryor et al.
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Short summary
Inter-annual variability (IAV) of annual energy production (AEP) from wind turbines due to IAV of wind speeds from proposed wind farms plays a key role in dictating project financing but is only poorly constrained. This study seeks to improve quantification of IAV using purpose-performed long-term numerical simulations. These results indicate it may be appropriate to reduce the IAV applied to pre-construction AEP estimates, which would decrease the cost of capital for wind farm developments.
Inter-annual variability (IAV) of annual energy production (AEP) from wind turbines due to IAV...
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