Estimating the ake deflection donstream of a ind turbine in different atmospheric stabilities: An les study

Abstract

An intentional ya misalignment of ind turbines is currently discussed as one possibility to increase the overall energy yield of ind farms. The idea behind this control is to decrease ake losses of donstream turbines by altering the ake trajectory of the controlled upind turbines. For an application of such an operational control, precise knoledge about the inflo ind conditions, the magnitude of ake deflection by a yaed turbine and the propagation of the ake is crucial. The dependency of the ake deflection on the ambient wind conditions as well as the uncertainty of its trajectory are not sufficiently covered in current wind farm control models. In this study we analyze multiple sources that contribute to the uncertainty of the estimation of the wake deflection downstream of yawed wind turbines in different ambient wind conditions. We find that the wake shapes and the magnitude of deflection differ in the three evaluated atmospheric boundary layers of neutral, stable and unstable thermal stability. Uncertainty in the wake deflection estimation increases for smaller temporal averaging intervals. We also consider the choice of the method to define the wake center as a source of uncertainty as it modifies the result. The variance of the wake deflection estimation increases with decreasing atmospheric stability. Control of the wake position in a highly convective environment is therefore not recommended.