Investigation into wind turbine wake effect on complex terrain

Abstract

In complex-terrain wind fields, the wind speed-up phenomenon is pronounced on highlands, which has huge impact on wake development. This paper comprehensively investigates the wind speed-up and the wake effect in complex terrains. The objective is to develop an advanced process to reveal the complex wake characteristics. Both theoretical and experimental methods are used to the study. First, the wind speed-up characteristics caused by topography are discussed, and the wind speed-up over escarpments with different shapes is numerically studied. Based on the results, the impact of wind speed-up on average wind speed of wind turbine is investigated. Next, a three-dimensional wake model for complex terrains is developed, and the model is applicable for the terrain with slope of less than 0.3. Then, a wind field experiment is conducted on a two-dimensional hill, and the wake model is validated and further improved for application to escarpments. From this research, both large aspect ratio and small rotor diameter have significant influence on the average wind speed. Even in the wake area, the wind speed on highland is stronger than that on flat terrain, and the wind speed increment is the largest at the height of 0.25D. In complex-terrain wind fields, the wind speed-up effect must be carefully considered at least within the 5D downwind distance.