Effect of complex terrain topography on wind farm reliability and performances

Terrain topography affects the atmospheric boundary layer over a vertical region where wind turbines are usually located. It is commonly believed that placing wind turbines on the top of a ridge is beneficial because of the more energetic flow impinging on the turbines. However, the presence of topography with even modest altitude upstream of the wind farm may generate turbulent structures that significantly increase fluctuations in blade loads and power production.

In this study, we analyze a 9-turbine wind farm located on a ridge in the State of Bahia in Brazil. For the main wind direction, a hill with a lower altitude respect to the turbine locations is located upstream of 3 turbines of the farm. This allows a direct comparison of the impact of the upstream topography based on the turbine location. Large Eddy Simulations are used to reproduce the prevalent wind conditions at the wind farm site. Numerical simulations are then compared with the wind farm SCADA data. Turbines are found to be significantly affected by the dynamics of the large turbulent structures that detach from the upstream hill. This study shows the importance of considering the dynamics of the wind flow when assessing wind resources in presence of complex terrain topography.