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Toward understanding the physical link between turbines and microclimate impacts from in situ measurements in a large wind farm
Journal of Geophysical Research: Atmospheres
  • Daniel A. Rajewski, Iowa State University
  • Eugene S. Takle, Iowa State University
  • John H. Prueger, National Laboratory for Agriculture and the Environment
Document Type
Article
Publication Version
Published Version
Publication Date
11-1-2016
DOI
10.1002/2016JD025297
Abstract

Recent wind farm studies have revealed elevated nighttime surface temperatures but have not validated physical mechanisms that create the observed effects. We report measurements of concurrent differences in surface wind speed, temperature, fluxes, and turbulence upwind and downwind of two turbine lines at the windward edge of a utility-scale wind farm. On the basis of these measurements, we offer a conceptual model based on physical mechanisms of how wind farms affect their own microclimate. Periods of documented curtailment and zero-power production of the wind farm offer useful opportunities to rigorously evaluate the microclimate impact of both stationary and operating turbines. During an 80 min nighttime wind farm curtailment, we measured abrupt and large changes in turbulent fluxes of momentum and heat leeward of the turbines. At night, wind speed decreases in the near wake when turbines are off but abruptly increases when turbine operation is resumed. Our measurements are compared with Moderate Resolution Imaging Spectroradiometer Terra and Aqua satellite measurements reporting wind farms to have higher nighttime surface temperatures. We demonstrate that turbine wakes modify surface fluxes continuously through the night, with similar magnitudes during the Terra and Aqua transit periods. Cooling occurs in the near wake and warming in the far wake when turbines are on, but cooling is negligible when turbines are off. Wind speed and surface stratification have a regulating effect of enhancing or decreasing the impact on surface microclimate due to turbine wake effects.

Comments

This article is from Journal of Geophysical Research: Atmospheres 121 (2016): 13,392, doi:10.1002/2016JD025297. Posted with permission.

Rights
Works produced by employees of the U.S. Government as part of their official duties are not copyrighted within the U.S. The content of this document is not copyrighted.
Language
en
File Format
application/pdf
Citation Information
Daniel A. Rajewski, Eugene S. Takle and John H. Prueger. "Toward understanding the physical link between turbines and microclimate impacts from in situ measurements in a large wind farm" Journal of Geophysical Research: Atmospheres Vol. 121 Iss. 22 (2016)
Available at: http://works.bepress.com/eugene-takle/51/