Numerical Investigation to Assess an Optimal Blade Profile for the Drag Based Vertical Axis Wind Turbine

Abstract

Rapid depletion rate of fossil fuels with an increasing energy demand and their high emission are imposing the evolution activities in the arena of renewable energy. To meet the future demands of renewable energy sources, wind energy is a very promising concept. In this feature, the drag based vertical axis wind turbines (VAWTs) are suitable for small scale wind energy generation for decentralized locations. However, these turbines have low power and torque coefficients as compared to other wind turbines. Numerous blade shapes have been proposed till now to improve the performance of these turbines. In the present paper, a computational study has been performed to simulate the air-flow over different blade profiles using shear stress transport (SST) k–ω turbulence model. The results obtained are validated with the available experimental data. In the dynamic simulations, the power and torque coefficients are calculated considering the blade arc angle as the variable shape parameter. The effects of drag and lift forces on the variable blade shapes are also studied in static simulations at various angular positions. The present paper tries to demonstrate an effective computational methodology to predict the flow behavior around a drag based VAWT. Through this study, it has been found possible to select an optimal blade shape from the point of its aerodynamic performance.

Wind tunnel experiments of a newly developed two-bladed Savonius-style wind turbine

“…1(d) is named as modified Bach type blade profile. This modified Bach type blade has shown an improvement in terms of performance (power and torque coefficients) and aerodynamic characteristics (lift and drag) over the conventional SSWTs [28]. A comparison of the modified Bach type over classical Bach type is discussed in the later sections.…”

“…1c) claimed to be one of the most efficient SSWT blade profiles [15] is also tested. Since long, Bach type blade profiles are among the interests of investigators for SSWTs [26][27][28]. Thus, a modified Bach type SSWT is selected from the recent investigations of Roy and Saha [28].…”

“…Since long, Bach type blade profiles are among the interests of investigators for SSWTs [26][27][28]. Thus, a modified Bach type SSWT is selected from the recent investigations of Roy and Saha [28]. This blade profile has evolved through a series of unsteady simulations on classical Bach type SSWT by varying the overlap distance from 0 to 0.5d (d is the blade chord) and blade arc angle from 90°to 165°.…”

“…19 demonstrates the static torque coefficients for various tested blade profiles at Re = 6.0 Â 10 4 -1.5 Â 10 5 . The rotational angle (h) is the angle between the chord of the advancing blade to the direction of wind flow [28]. At Re = 6.0 Â 10 4 , the conventional semi-circular blades show a very low static torque coefficients in the range of h = 110-170°and 290-350°.…”

“…In this aspect, some studies with modified blade shapes were attempted reporting encouraging results. This has brought a renewed interest among the researchers to pursue further and detailed assessment of the blade design [12,[26][27][28][29]. Thus, in order to boost the applicability of these turbines, a novel but simple SSWT is developed and tested in a low speed wind tunnel.…”