An Investigation of Single Wind Turbine Wakes with Static LiDAR Wind Profilers

Abstract

Three static LiDAR wind profilers were deployed during the seven month field experiment WINTWEX-W at ECN's test site in Wieringermeer. The campaign was focused on capturing the structure and dynamics of the wake of a NORDEX N80 research wind turbine. The campaign has created a unique dataset for corresponding investigations. For this study also sonic anemometer and temperature difference measurement from a 108 m meteorological mast and SCADA data from the wind turbine have been used, in addition to the static LiDAR wind profiler datasets. The compilation of a reliable LiDAR dataset for the campaign has been accomplished through a thorough re-examination of the raw measurements, and the development and application of an advanced de-spiking routine. Combining atmospheric data with SCADA data from the turbine, measurements of horizontal wind speed deficits and turbulence intensities in the wake region were analysed with respect to both atmospheric boundary layer stability and blade pitch angles. The results show an increased wake effect for stable stratifications in general, with wind speed deficits larger than 40 %, and an increase in absolute TI of more than 10 %. The main effect of the blade pitch happens in the angle interval between 0° and 3°. For pitch angles exceeding 3°, stability seemed to no longer have an affect on the wake strength, which additionally becomes substantially reduced.