Study on Synchronous Variable-Pitch Vertical Axis Wind Turbine

Little attention has been paid to the study of optimum variable-pitch control laws in the range of low tip speed ratios, as traditional Darrieus turbines operate in the range of high tip speed ratios. In this paper, we obtain the aerodynamic coefficients of the plate airfoil by the method of computational fluid dynamics (CFD). Then, an aerodynamic model is built based on Blade Element Theory, and comparative analysis of the synchronous variable-pitch control law and optimum variable-pitch control laws is done. Afterwards, a prototype based on the synchronous one is made and studied experimentally. We have found that the synchronous variable-pitch control law is approximate to the optimum one in the range of low tip speed ratios (0-0.6), and can optimize the performance of the turbine in this range. Moreover, it is proved that the driving torque on the rotor of the synchronous variable-pitch vertical axis wind turbine is mainly produced by the lift forces on blades rather than the drag forces.