Impact of atmospheric stability on wind farm performance: Insights from internal boundary layer dynamics

Abstract

The flow characteristics of the atmospheric boundary layer (ABL) and its interactions with wind farms are critical to assessing the aerodynamic performance of wind turbines. In this study, large eddy simulation (LES) was employed to investigate these interactions across different atmospheric stratifications, with a particular focus on the evolution of the internal boundary layer (IBL) and its effects on turbine wake characteristics and overall wind farm performance. The results indicate that the IBL evolves into distinct scenarios depending on the flow field characteristics, which substantially influence the mixing of turbine wakes with background turbulence, ultimately leading to significant sensitivity of wind farm performance to scale variations across different atmospheric stratifications. For wind farms with fewer than nine rows of turbines, power output progressively decreases as atmospheric stratification intensifies. However, once the number of turbine rows reaches ten, power output under stable stratification increases unexpectedly by 1.4% compared to neutral stratification. As the wind farm scale “expands” beyond ten rows, the difference in power output between stable and convective stratification diminishes and may even reverse, until the IBL reaches a fully-developed regime. These findings contribute to resolving the ongoing controversy regarding the effects of atmospheric stability on wind farm power generation.