Performance improvement of a Savonius vertical axis wind turbine using a porous deflector

• Published in: Energy conversion and management 2020-09, Vol.220, p.113062, Article 113062
• Main Authors: Eshagh Nimvari, Majid, Fatahian, Hossein, Fatahian, Esmaeel
• Format: Article
• Language: English
• Subjects: Coefficients; Computational fluid dynamics; Computational Fluid Dynamics (CFD); Configuration management; K-omega turbulence model; Performance enhancement; Porosity; Porous deflector; Reynolds averaged Navier-Stokes method; Savonius wind turbine; Self-starting; Tip speed; Torque; Turbines; Turbulence models; Vertical axis wind turbines; Wake zone; Wind power; Wind turbines
• ISSN: 0196-8904; 1879-2227
• DOI: 10.1016/j.enconman.2020.113062

•A novel porous deflector was proposed to improve the performance of a Savonius turbine.•Torque and power compared between Savonius turbine with and without deflector configurations.•The URANS equation in conjunction with the SST k-ω turbulence model were solved.•Using a porous deflector caused the flow structures became more regular with fewer fluctuations.•There is an appropriate porosity value to obtain the highest torque and power coefficients. The present study proposed a novel porous deflector in front of the Savonius wind turbine to improve the performance. This new deflector was specifically proposed to minimize the severe effects of the complex wake zone created behind the conventional solid deflector that had not been investigated yet. This caused a deeper investigation into the effect of severe negative effects on the turbine performance to achieve an appropriate design configuration. Therefore, different configuration parameters were taken into account during the numerical process. The unsteady Reynolds-averaged Navier-Stokes equation in conjunction with the SST k-ω turbulence model was numerically solved. Comprehensive comparisons of torque, power, and flow structures between deflector configurations and the standard Savonius turbine were performed to illustrate the mechanism of how the porous deflector improved the turbine performance. Using a porous deflector caused the wind flow passed through the porous zone resulted in a breakdown of the wake zone behind the deflector. Thereby, the flow structures became more regular with fewer fluctuations. The results demonstrated that there is an appropriate porosity value to obtain the highest torque and power coefficients. The maximum value of the power coefficient increased by approximately 10% using the favorable configuration of porous deflector at a tip speed ratio of 1. The notable observation was that the appropriate configuration increased the static torque coefficient approximately 2 times in the rotation angles between 0° and 30° which proved the self-starting ability besides power coefficient enhancement.