Impact of inflow conditions and turbine placement on the performance of offshore wind turbines exceeding 7 MW

Accurately assessing wind turbine performance in large offshore wind farms requires a nuanced understanding of how inflow parameters, turbulence intensity (TI), wind shear, and wind veer are associated with power production across different turbine rows. In this study, we analyze 13 months of 10 min operational data from more than 40 high-capacity turbines in a North Sea offshore wind farm, complemented by nacelle-based lidar measurements used as an inflow proxy. Our objectives are to (1) quantify how power production differs between the front, middle, and rear sections of the farm under varying TI, shear, and veer and (2) evaluate the effectiveness of International Electrotechnical Commission (IEC)-based normalization methods, including rotor equivalent wind speed (REWS) and turbulence corrections, for both front-row and in-farm conditions.
The results indicate that the relationships between wind shear/veer and power output depend strongly on turbine location: upwind shear and veer correlate negatively with active power deviation in the front row but show positive correlations in the middle and rear rows. In addition, TI in the wake region has a distinct influence on power production, particularly at lower wind speeds, relative to TI observed in the front row. Finally, the rear section of the wind farm exhibits approximately 30 % lower variability in active power relative to the front section. These location-specific changes underscore the evolving nature of inflow conditions within large wind farms. Furthermore, IEC-based REWS may not fully capture the effects of shear and veer in large-scale offshore wind farms. Overall, the findings indicate that turbines operating in waked conditions may require additional inflow-characterization parameters beyond standard IEC norms to enable more accurate performance evaluations and support farm-level efficiency improvements.
To our knowledge, this study provides one of the first empirical assessments spanning the front, middle, and rear sections of a modern offshore wind farm to evaluate IEC-based REWS and TI normalizations, revealing location- and regime-dependent limitations and motivating complementary inflow descriptors for wake-affected operation.