Sensitivity analysis in key parameters related to wind power production

The development of the offshore wind industry leads to wind turbines increasing in size and power. The aim of this thesis was to investigate how the power output and temporal power variability of an offshore wind turbine change when key parameters related to wind power production are altered.

The increased height and size were investigated by evaluating the NREL 5 MW and NREL 15 MW reference wind turbines for offshore conditions. The new hindcast data set NORA3 was compared to the established hindcast data set NORA10 at seven sites in the North Sea and the Norwegian Sea. The analysis found that NORA3 and NORA10 are in close agreement when used to calculate the capacity factor of the NREL 5 MW.

The wind shear coefficient α was found to be on average 0.070 for NORA3 and 0.058 for NORA10 and to vary in time, with wind speed, and with latitude. The monthly mean α and the mean temperature difference between 100 m asl and the sea surface temperature (SST), a simple measure of the static stability, were closely related. The use of a fixed, time- and space independent α= 0.12 to extrapolate the wind speed from 10 m asl to hub height results in an average overestimation of the capacity factor of 5.8 percentage points for NREL 5 MW and 7 percentage points for NREL 15 MW. The implementation of a storm control was found to increase the power output and decrease the temporal power variability.