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Wind Energy Science The interactive open-access journal of the European Academy of Wind Energy
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https://doi.org/10.5194/wes-2019-22
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/wes-2019-22
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research articles 14 May 2019

Research articles | 14 May 2019

Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Wind Energy Science (WES).

The effect of wind direction shear on turbine performance in a wind farm in central Iowa

Miguel Sanchez Gomez1 and Julie K. Lundquist2,3 Miguel Sanchez Gomez and Julie K. Lundquist
  • 1Department of Mechanical Engineering, University of Colorado Boulder, Boulder, 80303, USA
  • 2Department of Atmospheric and Oceanic Sciences, University of Colorado Boulder, Boulder, 80303, USA
  • 3National Renewable Energy Laboratory, Golden, 80401, USA

Abstract. Numerous studies have shown that atmospheric conditions affect wind turbine performance, however, some findings have exposed conflicting results for different locations and diverse analysis methodologies. In this study, we explore how the change in wind direction with height (direction wind shear), a site-differing factor between conflicting studies, affects wind turbine performance. We utilized lidar and turbine data collected from the 2013 Crop Wind Energy eXperiment (CWEX) project between June and September in a wind farm in north-central Iowa. Directional wind shear was found to follow a diurnal cycle and to monotonically decrease with increasing wind speeds. Using different thresholds to distinguish between high- and low-directional wind shear scenarios, we found that larger thresholds evidence statistically-significant effects on turbine power production for lower wind speeds. We further analyzed a threshold of 0.225 deg m−1 and found turbine underperformance in the order of 10 % for wind speed regimes below 8 m s−1. Considering a time period of ramping electricity demand (05:30–09:00 LT) exposed the fact that large direction shear occurs during this time and is undermining turbine performance by more than 10 %. A predominance of clockwise direction shear (wind veering) cases compared to counterclockwise (wind backing) was also observed throughout the campaign. Moreover, large veering was found to have greater detrimental effects on turbine performance compared to small backing values. This study shows that changes in wind direction with height should be considered when analyzing turbine performance, however, future work on segregating speed and direction shear should be pursued to quantify the effects of only one factor on turbine power production.

Miguel Sanchez Gomez and Julie K. Lundquist
Interactive discussion
Status: final response (author comments only)
Status: final response (author comments only)
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Miguel Sanchez Gomez and Julie K. Lundquist
Miguel Sanchez Gomez and Julie K. Lundquist
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Latest update: 23 Jul 2019
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Short summary
Wind turbine performance depends on various atmospheric conditions. We quantified the effect of the change in wind direction with height on turbine power output at a wind farm in Iowa. We found that turbine performance was primarily undermined for below rated wind speeds. Also, performance was more severely affected during a time period of increasing electricity demand. These effects make direction shear significant when analyzing different atmospheric regimes and for wind resource assessment.
Wind turbine performance depends on various atmospheric conditions. We quantified the effect of...
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