Performance Assessment of an Interactive Three-Rotor Savonius Wind TurbinePerformance Assessment of an Interactive Three-Rotor Savonius Wind TurbinePerformance Assessment of an Interactive Three-Rotor Savonius Wind Turbine

Abstract

Vertical axis type wind turbines have strong potential in small and medium power applications due to their simple design. However, a major disadvantage of this design is the noticeable low conversion efficiency. Therefore, more research is required to improve the efficiency o f this design. The present work introduces a novel design of a two and three rotor Savonius turbine with rotors arranged in a parallel pattern. The performance of the new design is assessed by computational modeling of the flow around the t urbine. A 2D computational model is firstly applied to investigate the performance of a single rotor design to validate the model by comparison with experimental measurements available in the literature. The model introduced an acceptable accuracy compared to the experimental measurements. The performance of the new design is then investigated using the same model. In addition, numerical optimization of the design parameters of two and three rotors Savonius turbine have been performed using the commercial finite volume solver ANSYS FLUENT [14.5] coupled with optimization code ModeFRONTIER®. The new turbine design was found to have higher power coefficient compared with single rotor design. The peak average power coefficient of the two rotors design was computed to be 60 % greater than that of the single rotor design while the three rotors was computed to be 70 % greater than that of the single rotor design. Furthermore, the torque coefficient w as also higher than that of the single rotor turbine at high tip speed ratio. This improved performance is attributed to the favorable aerodynamic interaction between the rotors which accelerates the air flow a round the III rotors and generates higher turning torque in the direction of rotation for each rotor. The optimized arrangement for two-rotor turbine showed that the upper and lower rotor should have an opposite rotation direction. The optimized arrangement of three-rotor turbine showed that the upstream rotor and one downstream rotor should have a similar direction of rotation while the second downstream rotor is rotating in opposite direction. The obtained results encourage developing new applications of the Savonius wind turbine. IV