Design and Performance Analysis of Hybrid VAWTs with Varying Auxiliary Blade Symmetry and Overlap Ratios: An Experimental Study

Abstract

The vertical axis wind turbines (VAWTs) operate efficiently in the low wind speed regions and varying wind directions like urban environments. The current study experimentally examines the performance of a two-bladed hybrid Darrieus–Savonius wind turbine with auxiliary Darrieus blades at three different low wind speeds, namely, 3, 4, and 5 m/s. To test the impact of the auxiliary blades’ location relative to the central shaft, the auxiliary blades were positioned at three different distances, namely, 17, 22, and 27 cm. When investigating the effect of the overlap ratio, three different overlap ratios equal to 0, –0.5, and 0.5 were used to arrange the Savonius blades. According to the results, hybridisation enhances the rotor’s performance. The hybrid Darrieus rotor with main blades, and the Savonius rotor with a  –0.5 overlap ratio ensures the maximum static torque coefficient equal to 0.045 at 0° azimuthal position and the wind speed of 3 m/s. A negative overlap ratio enhances the hybrid rotor’s initial characteristics. The arrangement with auxiliary blades at 17 cm from the central shaft and a fixed overlap ratio of  –0.5 yields the highest coefficient of power, namely, 0.018, at a TSR of 0.78 and a wind speed of 5 m/s.