Wind characteristics in wind farms situated on a hilly terrain

Wind characteristics in wind farms situated on a hilly terrain are considerably different than on a flat terrain. This issue is particularly important in strong-wind situations, when the wind velocity exceeds 25 m/s. In those situations, wind turbines are designed to remain in the parking position (no rotation of rotor blades) to prevent damage or even collapse of wind turbines. The present wind-tunnel study thus focuses on flow and turbulence characteristics in wind farms situated on a hilly terrain subjected to strong winds. A particular emphasis is on wind conditions for wind turbines placed at various positions in wind farms, as well as on a distance between a hill and a wind farm. The hill model is observed to strongly influence flow and turbulence characteristics at the wind-turbine model position in the wind-farm model. The most prominent aerodynamic features are flow retardation and turbulence enhancement, whereas the velocity power spectra show different trends along the height of the wind-turbine tower model. These experimental results present an important input for engineers attempting to design more robust and reliable wind turbines for hilly terrains.