Comment on wes-2023-11

Abstract

<strong class="journal-contentHeaderColor">Abstract.</strong> Inflow wind field measurements from nacelle based lidar systems offer great potential for different applications including turbine control, load validation and power performance measurements. On floating wind turbines nacelle based lidar measurements are affected by the dynamic behaviour of the floating foundations. Therefore, effects on lidar wind speed measurements induced by floater dynamics must be well understood. In this work we investigate the influence of floater motions on wind speed measurements from forward looking nacelle based lidar systems mounted on floating offshore wind turbines (FOWT) and suggest approaches for the correction of motion induced effects. We use an analytical model, employing the GUM methodology and a numerical lidar simulation for the quantification of uncertainties. It is found that the uncertainty of lidar wind speed estimates is mainly caused by fore-aft motion of the lidar, resulting from the pitch displacement of the floater. Therefore, the uncertainty is heavily dependent on the amplitude and the frequency of the pitch motion. The bias of 10 min mean wind speed estimates is mainly influenced by the mean pitch angle of the floater and the pitch amplitude. Further, we discuss the need for motion compensation for different applications of lidar inflow measurements on FOWT and introduce two approaches for the correction of motion induced effects in lidar wind speed measurements. We correct motion induced biases in time averaged lidar wind speed measurements with a model based approach employing the developed analytical model for uncertainty and bias quantification. Testing of the approach with simulated dynamics from two different FOWT concepts shows good results with remaining mean errors below 0.1 ms^&minus;1. For the correction of motion induced fluctuation in instantaneous measurements we use a frequency filter to correct fluctuations caused by floater pitch motions for instantaneous measurements. The performance of the correction approach is dependent on the pitch period and amplitude of the FOWT design.