Cluster wakes impact on a far distant offshore wind farm's power

Abstract. Our aim with this paper was the analysis of the influence of offshore cluster wakes on the power of a far distant wind farm. We measured cluster wakes with long range Doppler light detection and ranging (lidar) and satellite synthetic aperture radar (SAR) in different atmospheric stabilities and analysed their impact on the 400 MW offshore wind farm "Global Tech I" in the German North Sea using supervisory control and data acquisition (SCADA) power data. Our results showed clear wind speed deficits that can be related to the wakes of wind farm clusters up to 55 km upstream in stable and weakly unstable stratified boundary layers resulting in a clear reduction in power production. We discussed the influence of cluster wakes on the power production of a far distant wind farm, cluster wake characteristics and methods for cluster wake monitoring. In conclusion, we proved the existence of wake shadowing effects with resulting power losses up to 55 km downstream and encouraged further investigations on far reaching wake shadowing effects for optimized areal planning and reduced uncertainties in offshore wind power resource assessment.