Experimental investigation of the effects of the phase-shift angle on the performance of a Savonius wind turbine

• Experimental investigation of the combined effects of aspect ratio and phase-shift angle on Savonius wind turbine performance. • An increase in aspect ratio (AR) by 50% improves the turbine power coefficient (Cp) by over 200%. • Two-stage turbines achieve best performance at 90° phase-shift angle, improving Cp by more than 60% compared to conventional turbines. • Three-stage configurations with 60° phase-shift between consecutive stages achieve maximum enhancement of over 260% in power coefficient. • Modular design (multiple stages,) allows systematic performance optimization through phase-shifting between consecutive stages, providing better power extraction. This study aims to investigate, experimentally, in a first step, the performance of a modular Savonius wind turbine function of the number of stages by comparing the power coefficient C p obtained from a two stages Savonius wind turbine to the C p obtained with a three stage Savonius wind turbine. In the second step, we will present the effect of angular offset between turbine stages on the power coefficient by varying the phase-shift angles ( PSA ) between two succeed stages from 0° to 90° with a step of 30°, adjusted before testing. Each stage of turbine is composed of two semi-cylindrical blades made from PLA plastic materiel. The use of double or three stages is done by stacking two or three conventional turbines (one stage). We've designed a system of positioning holes to allow the upper stage to be placed on the lower stage at the required offset angles. A blower can vary the wind speed from 2 to 12 m/s. The effects of the number of stage and the PSA on the power coefficient of the turbine were examined. The results showed an enhancement of the C p when adding a stage or with a PSA =90° and in the case of two stage bi-blade Savonius Wind turbine while PSA =60°-60° when the turbine is composed of three semi-cylindrical stages.