Characterization of the inflow wind field using SpinnerLiDAR measurements in ScanFlow project

Abstract

The height of wind turbines continues to increase, making the need for more and higher wind measurements for wind turbine model calibrations also increase. The Energy-research Centre of the Netherlands (ECN) and the Danish Technical University (DTU) have conducted the ScanFlow campaign in the winter of 2016/2017 to study the inflow wind field of one of ECN's research turbines by deploying multiple lidar instruments. One of the instruments used in this campaign was a SpinnerLidar. A SpinnerLidar is a forward looking, nacelle-mounted, continuous wave wind lidar system. It measures Line-of-Sight components of the wind in a plane 60 meters in front of the turbine, which need to be transformed into 3D wind vectors. To do so necessary assumptions were made about the free inflow periods, namely that a vertical shear is present and that a wind direction misalignment is more likely than horizontal deviations in wind speed. With these applied assumptions the 3D wind components were determined and used in a validation study with a pulsed lidar instrument, the WindCube V2. The proposed method seems robust as a high correlation in wind speeds at hub-height between two distinctly different lidar systems was found. Using the validated SpinnerLidar measurement to find the turbulent characteristics of the free inflow wind field resulted in turbulence intensity plots showing a higher turbulent component in the lower regions of the measurement plane. Also indications for a induction zone are visible in the SpinnerLidar measurements when compared to the WindCube measurements.