An innovative augmentation technique of savonius wind turbine performance

Abstract

This work presents an innovative technique to enhance the performance of the Savonius wind turbine. The new technique is based on introducing an upstream deflector and downstream baffle. The shape and location of both devices are optimized using a genetic algorithm. The performance of the turbine with the optimized devices is compared with the single Savonius turbine performance. The study employs the finite volume solver (ANSYS-FLUENT) to solve unsteady Reynolds Averaged Navier–Stokes equations and turbulence model equations. The optimized configuration results in much higher power coefficient than the Savonius turbine. The average peak power coefficient using both deflector and baffle is 0.47 compared to 0.24 of the Savonius turbine. The peak power coefficient of the turbine corresponds to a speed ratio close to unity. This improved performance is attributed to the favorable aerodynamic interaction between the turbine and the downstream baffle which accelerates the flow around the rotor and generates larger turning torque. The baffle generates a jet effect on the advancing bucket and accelerates the flow behind the bucket creating a large zone of negative pressure and thereby increases the driving torque. Furthermore, the upstream deflector (also called shield or curtain) produces a shield for the returning bucket of the turbine which diminishes the adverse effect associated with the returning bucket on the aerodynamic torque of the turbine. This remarkable improvement of turbine performance will encourage the future application of the Savonius wind turbine in small power applications of wind energy.

Recent Development in the Design of Wind Deflectors for Vertical Axis Wind Turbine: A Review

“…Conversely, a vertical axis wind turbine (VAWT) is the most popular and effective device for electrical power generation from the kinetic energy of wind in urban built-up environments. These turbines are cross-flow, drag-driven wind turbines, and their power generation coefficient varies from 4% to 24% as reported in the literature [1,23,29,30]. The VAWTs are easy to manufacture and install, cheaper in price, produce less noise pollution, and can run in omni-directional winds.…”

“…These advantages make them more attractive than HAWTs for harnessing wind energy, but on the downside, VAWTs can not produce appreciable power when compared to HAWTs on a large scale. Hence, vertical turbines are more suitable and cost-effective when considering small-scale power generation and selfstarting at low wind speeds [25,29]. From a general perspective, the most common types of vertical axis wind turbines are the Savonius wind turbine and Darrieus wind turbine, further classifications are shown in Figure 1.…”

“…This velocity can be increased by installing a wind deflector, as the small increase in velocity can lead to a significant increase in efficiency, even exceeding the Betz Limit [69]. Wind deflectors installed in the upstream field of Savonius-type wind turbines have been reported to double the turbines' original performance [29]. The wind deflector-based optimization of a wind turbine depends upon several variables such as shape, angle, and location of the deflectors.…”

Numerical Investigation of a New Modified Savonius Wind Turbines

“…These studies have shown that the performance of the wind rotor decreases as the number of blades increases. To optimize the orientation of the air flow around the blades many augmentation technique have been added such as the shields (Morcos et al, 1981, Alexander & Holownia, (1978, deflector (Roy et al, 2014, Youssef et al, 2020, conveyor/deflector (Tartuferi et al, 2015), curtains (Altan & Atılgan, 2010), venting blade (Alom & Saha, 2018), deflector longitudinal (Salleh et al, 2020), V-shaped deflector (Shaughnessy & Probert, 1992), guide vane (El-Askary et al, 2015), straight deflector (Mohamed et al, 2010), they show a considerable improvement in the power of the Savonius wind turbine. The use of a straight deflector resulted in an increase in power coefficient of 27%.…”

Improvement of Aerodynamic Performance of Savonius Wind Rotor Using Straight-Arc Curtain

“…Regarding the torque coefficient values at various azimuths, they also found that the peak-to-peak values in the profiles for 90 • and 135 • were less than those for 0 • and 45 • . Youssef et al (2019) introduced an upstream deflector and downstream baffle around a Savonius wind turbine and achieve a much higher power coefficient than the conventional Savonius turbine [20].…”