Variable pitch to high-solidity straight-bladed VAWTs for power enhancement

Abstract

Straight-bladed vertical axis wind turbines (SBVAWTs) are a promising type of vertical axis wind turbines but their power efficiency is relatively low due to continuous variation of attack angle. Variable-pitch techniques are thus proposed to enhance their power generation. The current pitch control techniques for SBVAWTs are mainly based on some empirical forms and seldom adopted for practical use. This study first proposes an algorithm to search optimal pitch angles by means of the hybrid double-disk multiple stream-tube (hybrid DMST) model proposed by the authors and by taking the maximization of blades' tangential forces as an objective function. After optimal pitch curves with a wide range of TSRs are computed and obtained, an optimal pitch function is then established and applied to a high-solidity SBVAWT. The results obtained indicate that the power coefficient of the high-solidity SBVAWT could be enhanced prominently with the proposed optimal pitch function.