Numerical study on aerodynamic performance improvement and efficiency enhancement of the savonius vertical axis wind turbine with semi-directional airfoil guide vane

The growth of greenhouse gases increased the need for wind energy resource. Savonius vertical axis wind turbines (VAWT) have high potential as a turbomachine. Optimization methods such as flow injection on the rotor suction side to flow control on buckets developed as Savonius VAWTs operating range and efficiency are lower than other VAWTs. In this study, the semi-directional airfoil guide vane (SDAGV) was introduced to improve the aerodynamic performance and increase the efficiency of Savonius VAWT. The results indicate that the vane installation at the lower upstream of the rotor yields a power coefficient (Cp) of 0.12, representing a 140% growth compared to a single Savonius rotor. Furthermore, this installation extended the operating range of the turbine from a tip speed ratio (TSR) of 0.51-0.8. According to the results, it was found that more passages could improve efficiency. Five types of symmetrical airfoil profiles were evaluated for the guide vane. The NACA0010 airfoil profile, which has lower thickness than the others, obtained 7% higher efficiency than the base case consisting of NACA0012. Also, the optimal stagger angle for configurations NACA0021, NACA0018 was found to be 45 degrees, and for NACA0010 and NACA0012 was determined to be 30 degrees, respectively.