Numerical Investigation of Hybrid Darrieus-Savonius Wind Turbine Performance

Abstract

Vertical axis wind turbines (VAWT) as energy saving devices can be used in many engineering fields. There are two types of rotors in VAWT. Savonius rotors require a low torque for starting, but their efficiency is very low and Darrieus rotors have high efficiency, but they are difficult to start up. The hybrid wind turbine obtained by combining these two technologies, has the self-starting ability and high efficiency. A Darrieus-Savonius combined rotor aiming at a high aerodynamic performance with a low start-up requirement has drawn the attention of many researchers. In this paper, the effect of Darrieus-Savonius combined wind turbine performance is investigated in order to improve VAWT efficiency by a CFD (Computational Fluid Dynamics) approach. Unsteady simulations solving the Reynolds Averaged Navier-Stokes equations with standard k-ω SST turbulence model were conducted to obtain the static torque and the power coefficient. This numerical study focused on Darrieus-Savonius wind turbine with Savonius rotor placed in the middle of the Darrieus rotor at different tip speed ratio of 0.4, 0.6, 0.8, 1.0 and 1.2. The commercial CFD software Fluent 15.0 is used for the numerical study. The torque and power coefficient results of single Savonius turbine are compared and validated against experimental and numerical data based on the literature.