Performance enhancement of Savonius wind turbine using a nanofiber-based deflector

This research presented a unique deflector called a nanofiber-based deflector for Savonius wind turbine to achieve the best performance with a high self-starting capability. The objective of this novel deflector produced from nanofibers was to diminish the detrimental effect of the complicated wake zone made behind the standard solid deflector, which had not yet been analyzed. Different PVA and PLA nanofibers concentration ratios were evaluated experimentally before being included in the numerical simulation to find the most appropriate porosity value and average pore size. These nanofibers with concentration ratios of 100:0, 75:25, 50:50, 25:75, and 0:100 (v/v) were fabricated by electrospinning method. Then, the performance of conventional Savonius turbine and deflector arrangements was thoroughly studied using Computational Fluid Dynamics. Variations of power, torque, and flow structure were compared between configurations of the deflector and the conventional Savonius rotor to prove how the nanofiber-based deflector improved the performance of the turbine. It was revealed that a suitable porosity value existed for attaining the maximum performance of the Savonius turbine. Furthermore, utilizing a PVA75/PLA25 deflector with φ = 0.89, greater average torque and power coefficients (C_m and C_P) values were obtained. It is worth mentioning that using PVA75/PLA25 and PVA deflectors with greater porosity values completely eliminated the severe vortices behind the deflector. In rotation angles ranging from 100°–200° to 290°–360°, PVA75/PLA25 deflector substantially increased the C_P. The average C_P was raised by 7 and 9% using solid and PVA75/PLA25 deflectors, respectively. Accordingly, the solid and PVA75/PLA25 deflectors enhance not only the power coefficient but also the ability to self-start. At a rotation angle of 0°, the PVA75/PLA25 deflector outperformed the solid deflector by 87%, improving the static torque coefficient (C_ms).