Effect of surface roughness and blade material on the performance of a stationary Savonius wind turbine under different operating conditions

The Savonius wind turbine is a vertical-axis wind turbine invented in 1930s consisting of a cylindrical drum with semi-circular blades attached to the drum. It is popular for its simple design, low costs, and self-starting ability, making it feasible for rural areas. As a rotating device, the blade is considered an important component of the Savonius turbine because it captures energy from an omni-directional wind flow and converts it into mechanical/electrical energy. Blade corrosion can cause a surface degradation which affects the blade's aerodynamic and structural performance. The relation between surface roughness and turbine performance has been addressed in various studies; however, most of these studies focused on horizontal-axis wind turbine. This study analyzed the performance of a static Savonius turbine using a three-dimensional (3D) computer simulation at different blade angle positions through a one-way fluid-structure interaction in terms of static coefficients, von Mises stresses, and deformation with different surface roughness at different wind velocities. The simulation reveals that the position with highest static torque coefficient is when the turbine is resting at 15° with respect to the flow direction. The flow velocity increases the performance; however, the surface roughness deteriorates the flow and decreases the static coefficient. The simulation herein predicts no structural failure, but different materials exhibit different maximum stress and deformation showing the importance of material selection in the turbine blade development. The findings from this study helps to identify a suitable material for the development of the Savonius turbine from a material point of view to minimize turbine downtime and potentially save cost.