A novel variable pitch control strategy to improve the aerodynamics of vertical axis wind turbine

The low efficiency and complex aerodynamic characteristics of vertical-axis wind turbines (VAWTs) have limited their industrial development and application. An active variable pitch method can improve the aerodynamic performance of VAWTs, and different pitch control strategies yield varying improvements. In this study, a novel pitch control strategy for constant blade angle of attack (AoA) has been proposed to improve the aerodynamic performance of Darrieus H-type VAWTs. Numerical simulations have been performed to investigate the performance of this pitch control strategy by using the computational fluid dynamics (CFD) method based on an in-house Navier-Stokes (N-S) equations solver. The turbulence model is the k-omega shear stress transport (SST) model. The inviscid spatial discretization scheme is the fifth-order modified weighted essentially non-oscillatory (WENO-Z) scheme. The effect of pitch control factor kappa and amplitude angle A of this novel pitch control strategy on the power coefficient C-p, instantaneous torque coefficient CT of single blade and flow fields has been investigated from a low tip speed ratio (TSR) of 1.44 to high TSR of 3.3. The extensive studies show that this novel pitch control strategy can effectively improve the aerodynamic performance of VAWTs, especially at relatively low TSRs, and the optimal values of kappa and A are 3 degrees and 14 degrees, respectively. The maximum absolute increase in power coefficient C-p can reach 0.2444 at TSR of 1.68, and the average absolute increase for all TSRs is 0.1346.