Wind turbine wake measurements with automatically adjusting scanning trajectories in a multi-Doppler lidar setup

Abstract

Abstract. In the context of the Perdigão 2017 experiment, the German Aerospace Center (DLR) deployed three long-range scanning Doppler lidars with the dedicated purpose of investigating the wake of a single wind turbine at the experimental site. A novel method was tested for the first time to investigate wake properties with ground-based lidars over a wide range of wind directions. For this method, the three lidars, which were space- and time-synchronized using the WindScanner software, were programmed to measure with crossing beams at individual points up to 10 rotor diameters downstream of the wind turbine. Every half hour, the measurement points were adapted to the current wind direction to obtain a high availability of wake measurements in changing wind conditions. The linearly independent radial velocities where the lidar beams intersect allow the calculation of the wind vector at those points. Two approaches to estimating the prevailing wind direction were tested throughout the campaign. In the first approach, velocity azimuth display (VAD) scans of one of the lidars were used to calculate a 5 min average of wind speed and wind direction every half hour, whereas later in the experiment 5 min averages of sonic anemometer measurements of a meteorological mast close to the wind turbine became available in real time and were used for the scanning adjustment. Results of wind speed deficit measurements are presented for two measurement days with varying northwesterly winds, and it is evaluated how well the lidar beam intersection points match the actual wake location. The new method allowed wake measurements to be obtained over the whole measurement period, whereas a static scanning setup would only have captured short periods of wake occurrences.

Estimation of turbulence dissipation rate from Doppler wind lidars and in situ instrumentation for the Perdigão 2017 campaign

“…Goger et al (2018) found that in the COSMO model, turbulence kinetic energy (TKE) is systematically underestimated with a one-dimensional turbulence parameterization. Recent sensitivity studies by Yang et al (2017) showed that the parameters associated with turbulent mixing in an ABL parametrization have a large impact on 80 m wind speeds in the Weather Research and Forecasting model (WRF). They find that parameters associated with turbulence dissipation rate are responsible for approx-imately 50 % of the variance in 80 m wind speeds.…”

A Review of Progress and Applications of Pulsed Doppler Wind LiDARs

“…In the study on instantaneous wind estimates [194], the turbulent quantities measured by three LiDARs staring at a point close to a sonic anemometer compared well with corresponding sonic anemometer measurements. In synchronized trinal LiDAR configurations, 3D wind velocity variance can be directly obtained by solving 3D linear equations [195,196].…”

Wind Energy Instrumentation Atlas

“…In a major shift from previous field studies, the mean and turbulent velocity fields were measured by six triumvirates of scanning Doppler lidars between a 25-and 75-m resolution over ~ 2−5-km hemispherical volumes. The scanning lidar datasets have already yielded insights into turbine wake behavior in complex terrain (Menke et al 2018;Wildmann et al 2018) as well as atmospheric recirculations in complex terrain (Menke et al 2019). Perdigão publications will be collected at https://www.atmos-chemphys.net/special_issue636_946.html.…”