Performance of Microtabs and Trailing Edge Flaps in Wind Turbine Power Regulation: A Numerical Analysis Using WTSim

The effectiveness of trailing-edge flaps and microtabs in damping 1P-3P loads has been proven through a series of research work during the past decade. This paper presents the results of an investigation into the effectiveness of these devices in power enhancement and power control for responding to the issue of where these devices can be used with dual function of load and power control on a medium size turbine. The 300 kW-AWT27 wind turbine is used as the base wind turbine and the effects of adding trailing-edge flaps and string of microtabs of different lengths positioned at different span locations on the aerodynamic performance of the rotor are studied. In each case, the wind turbine simulator WTSim is used to obtain the aerodynamic performance measures. In the next step, the original blade twist is redesigned to ensure that the blade is optimized upon the addition of these active flow controllers. It is found that blades equipped with flaps can increase the annual average power and reduce the blade loading at the same time for constant speed and variable speed generators. Power enhancement is more visible on constant speed rotors, while load reduction is more significant on variable speed rotors. To achieve constant speed rotors, an average power enhancement of around 12 % is achieved for a flap of size 25 % of the blade span located at about 72 % of the blade span. Microtabs are less effective in power control and can improve the produced power only by a few percentage points.