Low Reynolds Number Vertical Axis Wind Turbine for Mars

Abstract

A low Reynolds number wind turbine is designed to extract the power from wind energy on Mars. As compared to solar cells, wind turbine systems have an advantage on Mars, as they can continuously produce power during dust storms and at night. The present work specifically addresses the design of a 500 W Darrieus-type straight-bladed vertical-axis wind turbine (S-VAWT) considering the atmospheric conditions on Mars. The thin atmosphere and wind speed on Mars result in low Reynolds numbers (2000–80000) representing either laminar or transitional flow over airfoils, and influences the aerodynamic loads and performance of the airfoils. Therefore a transitional model is used to predict the lift and drag coefficients for transitional flows over airfoils. The transitional models used in the present work combine existing methods for predicting the onset and extent of transition, which are compatible with the Spalart-Allmaras turbulence model. The model is first validated with the experimental predictions reported in the literature for an NACA 0018 airfoil. The wind turbine is designed and optimized by iteratively stepping through the following tasks: rotor height, rotor diameter, chord length, and aerodynamic loads. The CARDAAV code, based on the “Double-Multiple Streamtube” model, is used to determine the performances and optimize the various parameters of the straight-bladed vertical-axis wind turbine.