An investigation into the self-starting of darrieus-savonius hybrid wind turbine and performance enhancement through innovative deflectors: A CFD approach

Abstract

Amidst vertical axis wind turbines, Darrieus turbines stand out for their impressive efficiency. However, these turbines encounter a significant challenge regarding their self-starting ability. Therefore, the current study seeks to explore the effects of combining Savonius and Darrieus turbines on the self-starting capability of the Darrieus turbine and propose a new wind turbine design with superior starting torque. Additionally, the study investigates the effectiveness of novel deflectors placed in front of and alongside the hybrid turbine, focusing on increasing the efficiency of the hybrid turbine. For this purpose, numerical simulations are carried out using a two-dimensional computational fluid dynamics (CFD) approach to simulate the flow field. The SST k-ω turbulence model is employed to provide closure for the Unsteady Reynolds-Averaged Navier-Stokes (URANS) equations. Also, the modeling validation and verification were performed by sensitivity analysis of mesh distribution and time step. The research findings indicated that coupling the Darrieus and Savonius turbines improved the hybrid turbine's self-starting ability, with a 26.91% increase in power coefficient (Cp) at the lowest tip speed ratio (TSR) of 1.45. However, as TSR increases, the hybrid turbine's performance decreases due to the Savonius turbine's limited aerodynamic performance at high TSRs. This issue is solved using front and side deflectors, improving the hybrid turbine's efficiency at the optimum TSR of 2.6 by 30% and 26%, respectively, through increasing wind energy density at the upwind and leeward regions of the turbine. Furthermore, using both deflectors together, known as the double deflector configuration, has shown the best performance at both the lowest and optimum TSR.