Susan Kariuki^1,, Churchill Saoke¹, Joseph Kamau², Patrick Muiruri³

Wind is an alternative source of renewable energy following the current surge in energy demand globally. This is attributed to the worldwide call for the alleviation of the use of fossil fuel sources due to climate change. However, the larger part of the global coverage experiences low wind speed, inhibiting the application of medium and large wind turbines in harvesting wind energy with a return on investment. This leads to an increase in the application of small wind turbines. This study focused on studying the Savonius wind turbine, which is one of the potential candidates for harnessing wind energy efficiently in low wind speed areas. The study aimed to analyze the aerodynamic performance of a two-stage Savonius wind turbine using the Computational Fluid Dynamic (CFD) method by varying the phase shift angles (PSA) and tip speed ratio (TSR). The lower and upper rotors were designed such that the phase shift angles varied were 45⁰, 60⁰, 75⁰ and 90⁰. A Shear Stress Transport turbulence model SST k-omega with a steady-state method was used to analyze the influence of PSA and TSR on the performance of a two-stage Savonius wind turbine. The findings of this study indicated that the Savonius wind turbine with a PSA of 45⁰ had the highest torque coefficient of 0.3654 at a TSR of 0.8 and a wind speed of 4m/s. Hence, phase shift angles significantly influence the performance of a two-stage Savonius wind turbine in low wind speed applications.

Phase shift angles, torque coefficient, tip speed ratio, computational fluid dynamics