Lidar measurements of yawed wind turbine wakes: characterisation and validation of analytical models

Abstract

Abstract. Wake measurements of a scanning Doppler lidar mounted on the nacelle of a yawed full-scale wind turbine are used for the characterization of the wake flow and the validation of analytical wake models. Inflow scanning Doppler lidars, a meteorological mast and the data of the wind turbine control system complemented the set-up. Results showed an increase of the wake deflection with the yaw angle that agreed with two of the three compared models. For yawed cases, the predicted power of a waked downwind turbine estimated by the two previously successful models had an error of 17 % and 24 % compared to the SCADA data and 12 % and 13 % compared to the power estimated from the Doppler lidar measurements. Shortcomings of the method to compute the power coefficient in an inhomogeneous wind field are likely the reason for disagreement between estimates using the Doppler lidar data versus SCADA data. Further, it was found that some wake steering cases were detrimental to the power output due to errors of the inflow wind direction perceived by the yawed wind turbine and the wake steering design implemented. Lastly, it was observed that the spanwise cross-section of the wake is strongly affected by wind veer, masking the kidney-shaped wake cross-sections observed from wind-tunnel experiments and numerical simulations.

Quantification of wake shape modulation and deflection for tilt and yaw misaligned wind turbines

“…The measured velocity contours for yaw misalignment show good agreement with existing results in the literature from wind tunnel experiments (Bastankhah & Porté-Agel 2016), LES results (Martínez-Tossas et al 2019) and full-scale lidar measurements in a field test (Brugger et al 2020). In comparison with the results of Bastankhah & Porté-Agel (2016), the slightly lower thrust and power coefficient of the scaled wind turbine in…”

“…2019) and full-scale lidar measurements in a field test (Brugger et al. 2020). In comparison with the results of Bastankhah & Porté-Agel (2016), the slightly lower thrust and power coefficient of the scaled wind turbine in this experiment result in a slightly smaller velocity deficit.…”