Numerical Study of Porous Media Effect on the Blade Surface of Vertical Axis Wind Turbine for Enhancement of Aerodynamic Performance

Highlights: • Effects of adding porous media on airfoil surface of Darrieus VAWT are studied numerically. • Optimum porous media location on blade surface is determined. • Deployment of porous media enhance glide ratio and delaying stall phenomena. • Deployment of porous media improve the self-starting and turbine torque generation. • Porous media attenuate vorticity influence by attaching the flow on airfoil profile. This paper discusses the novel design of VAWT by employing porous media on turbine blades. 2D simulation was performed with CFD package Star CCM to observe flow behavior around VAWT blades. DU 06-W-200 airfoil with six porous configurations including both the pressure and suction side of airfoil have been investigated to obtain optimum porous location. The aerodynamic coefficients of these configurations have been calculated and compared with that of the conventional blade for the broad range of angle of attack. It is found that porous media on the pressure side of airfoil behave more effectively and increase the $C_L/C_D$ values. Then three straight blade Darrieus type rotor performance in presence of porous media has been studied. The results reveal the enhancement of power and torque coefficient in a range including both before and after optimum tip speed ratio. Therefore, the turbine self-starting capability improves and consequently, it starts operating at low wind speed which leads to the reduction of VAWT cut-in and increases annual energy production. Additionally, the blade equipped with porous media experience a higher stall angle of attack and is able to exceed the maximum azimuth angle of the conventional rotor. Hence, stall phenomena delay and occurs at a higher angle of attack. The main reason for these improvements is related to the capability of porous media to attach the flow on blade profile and suppress separation zone.