Design methods of horizontal axis wind turbine rotor blades

Abstract

Horizontal axis wind turbines (HAWTs) development and utilisation is growing rapidly. No such a unique methodology in literature describes the design of HAWT rotor blades. Each researcher usually adopts one of the design methods known to his best knowledge. In this paper, we outline the HAWT design analysis using the blade element momentum (BEM) theory. A total of ten different methods for the calculation of the chord length distribution along the rotor blade, with and without considering wake rotation, are presented. The performance of various methods for the correction of the axial induction factor is also presented. An important outcome of this work is the elimination of the discrepancy encountered when trying to select among the methods of blade design as we found that a few of the published methods are actually different faces of the same coin and they lead to exactly the same final output yet through a different procedure. Several methods based on BEM analysis for optimum chord length and flow angle are found to produce very close blade geometry along the outer half of the blade length. The inclusion of drag in the calculation of the optimal chord length is found to be insignificant.