Offshore wind farm global blockage measured with scanning lidar

Abstract. The objective of this paper was the experimental investigation accumulated induction effect a large offshore wind farm as whole, i.e. global-blockage effect, in relation to atmospheric-stability estimates and operational states. We measured inflow 400 MW German North Sea with scanning long-range Doppler lidar. A methodology reduce statistical variability different lidar scans at comparable measurement conditions introduced, an extensive uncertainty assessment averaged fields performed be able identify which is small compared e.g. turbine wake effects ambient variations inflow. Our results showed 4 % decrease speed (accuracy range 2 6 %) transition piece height (24.6 m) upwind turbines operating high thrust coefficients above 0.8 stably stratified atmosphere, we interpreted global blockage. In contrast, unstable stratification similar for situations low (i.e. approx. 0 not ? 0.3 far rated speed) identified no deficit. discussed significance our measurements possible sources error campaigns give recommendations on how measure flow like blockage conclusion, provide strong evidence existence farms stable coefficient by planar field measurements. further conclude that dependent atmospheric stratification.