Abstract
Wake effects in wind farms can cause significant power losses. In order to reduce these losses layout and control optimization can be applied. For this purpose, simple and fast prediction tools for the wake flow are needed. In the first part of this work, five analytical wind turbine wake models are compared to small-scale turbine wind tunnel measurements. The measurements are conducted at several downstream distances, varying the ambient turbulence intensity and upstream turbine blade pitch angle. Furthermore, an adjustment of a recently developed wake model is proposed. Subsequently, the adjusted model is found to perform best throughout all test cases. In the second part, the performance of an aligned downstream turbine is modelled based on the predicted wake flow using a Blade Element Momentum method with guaranteed convergence. In order to consider the non-uniform inflow velocity a mean-blade-element-velocity method is developed. Moreover, a blockage effect correction is applied. A comparison to wind tunnel measurement data shows that the wake velocity as well as the combined power of two aligned turbines are fairly well predicted. Additionally, the presented analytical framework of wake and downstream turbine performance modelling proposes several model improvements for state-of-the art wind farm simulation tools.
Highlights
Wake effects in wind farms can cause significant power losses
In the first part of this work, five analytical wind turbine wake models are compared to small-scale turbine wind tunnel measurements
The performance of an aligned downstream turbine is modelled based on the predicted wake flow using a Blade Element Momentum method with guaranteed convergence
Summary
Wake effects in wind farms can cause significant power losses. Average offshore wind farm power losses due to wind turbine wakes are in the range of 10 - 20 % [1]. In order to reduce power losses wind farm layout and control optimization can be applied. For this purpose, simple and fast wake modelling tools are needed. The model is based on conservation of momentum and assumes a uniform velocity profile inside the wake It includes a constant approximated thrust coefficient. Katic et al [4] further developed this model in 1986 taking wind turbine characteristics such as a variable thrust coefficient into account. This model is widely known as the Jensen model or PARK model.
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