Wind turbine wake characterization in complex terrain via integrated Doppler lidar data from the Perdigão experiment

During the intensive period (May-June 2017) of the Perdigäo experiment, three sets of Doppler lidar were operated to scan the wake of the wind turbine (WT) on the southwest ridge. CU operated a Doppler scanning lidar in the valley bottom approximately 1 km northeast of the WT and conducted multiple arc scans and two RHI scans every 10-minutes centred on the WT. DTU used a dual Doppler lidar system scanning almost horizontally from the northeast ridge. Two of the three DLR lidars were in-plane with the WT for the main wind direction, one in the valley and one on the distant mountain ridge. The third DLR lidar was on the southwest ridge. All three systems (CU, DTU and DLR) were operated such that in data processing vertical and/or horizontal profiles of the wake can be derived at different distances from the WT. The paper describes the strategies used to scan the wake by the three groups and compares wake characteristics derived from the different systems.