Abstract
In this study, wind climate assessment for offshore wind is conducted using dual-Doppler scanning lidars and validated by a met mast mounted on a break water. The data filtering for dual-Doppler scanning lidars are proposed and overestimation of the standard deviation is improved by removing abnormal data with 3σ filter. It is also found that the measurement accuracy is not affected if 60 or more 1-second data are used to calculate 10 minutes statistical values. A method is then proposed to measure wind speeds and directions at multiple altitudes by switching the target height at 20-second intervals. It is indicated that the measured wind speed, wind direction and turbulent intensity in this way show good agreement with those calculated using 600 seconds data. Finally, the dual-Doppler scanning lidar measurements are validated by a cup anemometer and a wind vane mounted on the met mast. The coefficients of determination for wind speed and direction are larger than 0.98 and the slopes for wind speed and wind direction is 1. The 90 percentile values of turbulence intensity for each wind speed bin show favorable agreement with those obtained from the cup anemometer and the relative error in standard deviation is 3.3%. It is obvious that dual-Doppler scanning lidars can accurately measure wind speed, wind direction and turbulence intensity at multiple altitudes for offshore wind.
