Experimental investigation on power performance testing using nacelle lidar measurements over excavated terrain

Abstract

Abstract In order to find out the usability of the nacelle mounted light detection and ranging (lidar) for power performance testing under the condition of excavated terrain, an experimental investigation was carried out at the DBK wind farm on Jeju Island, South Korea. A nacelle lidar installed on a 2 MW test wind turbine was used with an 80 m tall met mast and a ground-based lidar for measuring wind conditions. The measurement sector was calculated for the site, which was reduced to the analysed sector for finding out the influence of the excavated landfill. Since the excavated landfill was located near the test wind turbine, the excavated terrain was evaluated according to International Electrotechnical Commission (IEC) 61400-12-1, 2nd edition and the power curve was drawn using met mast wind speeds at the hub height, which was compared with that from the turbine manufacturer. The excavated terrain was further analysed using the Computational Fluid Dynamics (CFD) technique to determine whether it has an influence on wind flow. Then, the wind speed data measured by cup anemometers on the met mast, the ground-based lidar and the nacelle mounted lidar were compared through the linear regression method. The rotor equivalent wind speed (REWS) was calculated using met mast and ground lidar wind speeds according to the IEC 61400-12-1, 2nd edition. The power curves were obtained by applying the REWS and the nacelle lidar measurements. In addition, the relative errors of the power outputs were estimated and further annual energy productions (AEPs) were analysed by applying the Rayleigh wind speed distribution to the power curves. As a result, the effect of the excavated terrain on the power curve was very small. The power curves using the nacelle lidar measurements were mostly the same as the power curve using the REWS.