The variability of wind resources in complex terrain and its relationship with atmospheric stability

One of the greatest challenges of modern wind energy research is to improve our understanding of and ability to model wind farm flows, especially those over complex terrain. In this endeavor, multi-disciplinary field experiments have revealed, with unprecedented detail, the intricate flow patterns formed as winds interact with topography, and these are strongly interconnected with atmospheric stability. Therefore, we investigated how atmospheric stability affects the spatial variability of wind resources across a site set in complex terrain. A dataset obtained from a recent measurement campaign, involving the use of 6 masts and 90 turbine nacelle cup anemometers, as well as processed data on atmospheric stability obtained from a sonic three-component anemometer were used. The results revealed that at night, with low-turbulence and stable conditions, the spatial variability in wind resources can be twice as large as that for daytime, high-turbulence and unstable conditions. Wind resources at 90 locations were ranked from best (R = 1) to worst (R = 90) based on nacelle anemometers. Changes of up to 61 positions occurred at specific locations, depending on conditions associated with atmospheric stability. Therefore, these outcomes raise important questions regarding the current best practices of micro-siting and the capability of wind farm design models. •Atmospheric stability is key for wind resource mapping in complex terrain.•Largest spatial variability of winds for nighttime, low-TI and stable conditions.•Lowest for daytime, high-TI and unstable conditions.•Wind resources at fixed locations change largely owing to atmospheric stability.•The interplay of winds, terrain and atmospheric stability causes such effects.