Power curve performance of coastal turbines subject to low turbulence intensity offshore winds

The power curve performance of wind turbines located on the northeast coast of Brazil was investigated. The coastal site has wind characteristics typical of the offshore environment, where both turbulence intensity (TI) and wind shear are consistently low. The wind farm has 20 turbines with 0.9 MW of rated power, hub height and rotor diameter of 55 and 44 m, respectively. The experiment was carried out from August 2013 to July 2014 and included a 100-m met-mast, with five instrumented levels including two 3D sonic anemometers, and a lidar wind profiler. Both were installed upstream of the wind turbines in the prevailing wind direction. Three turbines near the met-mast were used to determine the average power curve for this site by separating the SCADA dataset according to the quartiles of TI and wind shear. The TI was calculated at 60 m and the wind shear between 40 and 98 m. In addition, at 100 m, the 3D sonic anemometer measured wind speed and sonic temperature with an acquisition rate of 20 Hz, to compute atmospheric stability using the eddy covariance method. The results show that TI is the parameter that has the most significant effect on the power curve performance. At high TI (> 7.5%), the measured power coefficient ( C P ) curve was similar to that provided by the manufacturer, whereas for low TI (