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 (05:30-09:00LT) 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.
Original language | American English |
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Number of pages | 23 |
Journal | Wind Energy Science Discussions |
DOIs | |
State | Published - 2019 |
Bibliographical note
See NREL/JA-5D00-76100 for final paper as published in Wind Energy ScienceNREL Publication Number
- NREL/JA-5000-74197
Keywords
- wind direction
- wind shear
- wind turbines