Annual wake impacts in and between wind farm clusters – Part 1: WRF-simulated wake losses for different atmospheric conditions

Abstract

Abstract. With the rapid increase in wind farm developments, it is essential to evaluate the impacts of newly constructed wind farms on adjacent wind farms, both existing and planned. Numerical weather prediction models are essential tools to predict wake effects, especially under varying atmospheric conditions that occur throughout the year. In this study, we investigate the annual variation in wake effects caused by the planned Belgian Princess Elisabeth (PE) wind farm cluster on adjacent, existing wind farms in the southern North Sea. To represent the annual effect, a representative year is simulated with the Weather Research and Forecasting (WRF) model. The analysis focuses on how variability in atmospheric conditions influences wake interactions throughout the year, which is important for wind farm planning and operational strategies. A distinction is made between external wake energy losses, caused by the new wind farm cluster, and internal wake energy losses, caused by the individual wind farms within the existing area. The diurnal variations in external wake energy losses are driven by changes in atmospheric stability, while the seasonal variations are largely a consequence of seasonal variations in wind direction, wind speed, and atmospheric stability. In contrast, internal wake energy losses are mainly determined by seasonal patterns and show only weak diurnal variability. The spatiotemporally averaged external wake energy losses are limited to 4 %, while the internal wake energy losses can reach 42 % for the closest adjacent BE–NL wind farm. The spatial distribution of wake losses further reveals that turbines located in the center of a wind farm experience higher internal wake energy losses, especially in densely packed layouts, while those at the edges are less affected for internal wake energy losses but more for external wake energy losses. Both the internal and external energy losses decrease with increasing atmospheric instability when wind speeds are in Region II of the wind turbine's power curve, where wind turbine operation maximizes the power coefficient. When binning for wind speed and wind direction, stable stratification results in external wake energy losses that are approximately twice as large as in unstable stratification. The presence of the new wind farm cluster also leads to episodes of negative wake energy losses, implying power gain after the construction of the PE wind farm cluster, which are related to flow speedup around the new wind farm. This paper constitutes Part 1 of a two-part study. In Part 2 (Porchetta et al., 2026), the impacts induced by the PE wind farm cluster are evaluated using fast-running engineering wake models and compared against the WRF results presented here, allowing for a systematic assessment of differences and uncertainties between models.