An experimental investigation on the aeromechanics and wake interferences of wind turbines sited over complex terrain

An experimental study was conducted to investigate the aeromechanics and wake interferences of wind turbines sited on two-dimensional hills with different slopes. First, detailed flow field measurements were correlated with dynamic wind load measurements to reveal the effect of topography on the performance of an individual wind turbine sited at different locations on hilly terrains. Compared to a flat surface, wind turbines sited on a hilltop not only generate more power due to the speed-up effect but also experience reduced fatigue loads due to the decreased level of the turbulence on a hilltop. It was also found that a wind turbine located downstream of a steep hill has a greater likelihood of experiencing extreme wind loads compared to one on a gentle hill. Second, wind turbine wake characteristics and their effects on the dynamic wind loads of downstream wind turbines were also assessed. The effect of an upstream turbine wake on the wind turbine sited on a hilltop was found to be much less significant compared to a wind turbine on a flat surface. In addition, while the wake of an upstream turbine sited on hilltop has a significant influence on the dynamic wind loads of a downstream turbine sited behind a gentle hill, the effect of an upstream turbine wake on a downstream turbine placed behind a steep hill was found to be almost negligible. The quantitative measurement results of the present study not only provide a database for the validation of wake models and numerical simulations but can also be used to optimize the layout of wind turbines sited on complex terrain for higher power yield and better durability.