An Iterative Method to Optimize the Twist Angle of a Wind Turbine Rotor Blade

Abstract

Maximizing the power output of a wind turbine is possible by ensuring the airfoils along the blade operate at an optimal angle of attack. However, blades deflect under loading but the torsional deflection of wind turbine blades is normally ignored in the blade design process. Since the power output is dependent upon the blade twist angle, an optimized blade shape must take into account the torsional deflection of the blade. The torsional deflection changes the loading of the blade. This necessitates iterative methods to determine the equilibrium loading and deflection and to optimize the blade shape. This paper explains a method to determine the equilibrium torsional deflection of the blade and a method to determine the optimal static blade twist angle to maximize power production. The results are the blade twist angle distribution that will deform to an optimal angle of attack under load, thereby changing the peak of the coefficient of power (C_P) curve to a chosen wind speed.