Wind Turbine Wake Characterization for Improvement of the Ainslie Eddy Viscosity Wake Model

Hyungyu Kim,Carlo Bottasso,Kwansu Kim,Filippo Campagnolo,Insu Paek

doi:10.3390/en11102823

Hyungyu Kim, Carlo Bottasso + Show 3 more

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https://doi.org/10.3390/en11102823

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Abstract

This paper presents a modified version of the Ainslie eddy viscosity wake model and its accuracy by comparing it with selected exiting wake models and wind tunnel test results. The wind tunnel test was performed using a 1.9 m rotor diameter wind turbine model operating at a tip speed ratio similar to that of modern megawatt wind turbines. The control algorithms for blade pitch and generator torque used for below and above rated wind speed regions similar to those for multi-MW wind turbines were applied to the scaled wind turbine model. In order to characterize the influence of the wind turbine operating conditions on the wake, the wind turbine model was tested in both below and above rated wind speed regions at which the thrust coefficients of the rotor varied. The correction of the Ainslie eddy viscosity wake model was made by modifying the empirical equation of the original model using the wind tunnel test results with the Nelder-Mead simplex method for function minimization. The wake prediction accuracy of the modified wake model in terms of wind speed deficit was found to be improved by up to 6% compared to that of the original model. Comparisons with other existing wake models are also made in detail.

Highlights

Wind turbine rotors extract energy from wind that passes through them
The initial wind speed profile and filter function of the original wake model were modified by wind tunnel test results
The scaled wind turbine model used in the wind tunnel test is controlled by a programmable logic controller (PLC) with a C code to achieve the power control which is similar to the modern megawatt wind turbines

Summary

Introduction

Wind turbine rotors extract energy from wind that passes through them. This energy extraction makes changes in the wind flow so that the wind speed is reduced and the turbulence intensity is increased downstream. This phenomenon, known as the wind turbine wake, reduces the power production and increases the fatigue load of the downstream wind turbines [1,2]. In a wind farm composed with many wind turbines, this wake effect generally reduces the power production efficiency of the wind farm by 10 to 20%, so it is common to optimize the layout of the wind farm to minimize the wake effect [1,3]. High fidelity computational fluid dynamics (CFD) codes cannot be used for this purpose because of large computational loads, and simplified wind farm simulation codes including wind turbine dynamics and control are used [11]

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