Shape effect of thickness of the NREL S815 profile on the performance of the H-rotor Darrieus turbine

With the aim of improving the performance of vertical axis wind turbines, in this article, the flow field and aerodynamic performance of an H-rotor Darrieus turbine are computed using computational fluid dynamics. Specifically, the power coefficient (Cp) of different airfoil profile thicknesses was evaluated as a function of tip-speed ratios (TSRs) and wind speed. Four different thicknesses of the NREL S815 airfoil were evaluated, and the TSR was varied from 0.6 to 2.25 using wind speeds of 6 and 8 m/s. As a result, the power coefficient (Cp) was calculated for each airfoil and the different tip-speed ratios. It was found that for each airfoil profile, the Cp increases when the airfoil thickness and the TSR rise, until reaching a maximum, then the Cp decreases in spite of larger thickness or TSRs. After comparing the performance of each airfoil profile, the Cp is improved 14.96% for 19.2% thicker airfoils, using a TSR of 1.725 and a wind speed of 8 m/s.