The Effect of Wind Direction Shear on Turbine Performance in a Wind Farm in Central Iowa

Julie Lundquist, Miguel Gomez

Research output: Contribution to journalArticlepeer-review

31 Scopus Citations


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, and speed shear affect 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. Wind direction and speed shear were found to follow a diurnal cycle; however, they evolved differently with increasing wind speeds. Using a combination of speed and direction shear values, we found large direction and small speed shear to result in underperformance. We further analyzed the effects of wind veering on turbine performance for specific values of speed shear and found detrimental conditions on the order of 10% for wind speed regimes predominantly located in the middle of the power curve. Focusing on a time period of ramping electricity demand (06:00-09:00 LT - local time) exposed the fact that large direction shear occurred during this time and undermined 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.
Original languageAmerican English
Pages (from-to)125-139
Number of pages15
JournalWind Energy Science
Issue number1
StatePublished - 2020

Bibliographical note

See NREL/JA-5000-74197 for article as published in Wind Energy Science Discussions

NREL Publication Number

  • NREL/JA-5000-76100


  • wind direction
  • wind shear
  • wind turbines


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