Numerical Simulation of a Double-Layer H-Darrieus Cross-Axis Wind Turbine

Wind turbines have two conventional types, which are the horizontal-axis wind turbine (HAWT) and vertical-axis wind turbine (VAWT). A hybrid of both types is referred to as the cross-axis wind turbine (CAWT) which can extract energy from both horizontally and vertically passing winds. The proposed CAWT used in this research is a double-layer configuration that is designed for rooftop setups. In this study, the proposed CAWT was compared to a reference double-layer VAWT through CFD simulation. The turbines were simulated under various tip speed ratios with freestream wind speeds that are representative of the average wind speed in the Philippines. The power coefficient of the turbines for all simulations are calculated as a performance metric. As a baseline, a non-mounted configuration was also simulated. It is observed that in both non-mounted and roof-mounted configuration, the CAWT performance exceeded the VAWT performance. Contour analysis revealed that the wake effects of the VAWT strut are more significant than that of the CAWT. Furthermore, the VAWT strut tends to be parasitic as compared to the CAWT strut which can capture wind energy from skewed wind as well as vertical wind induced by vortices when the freestream wind is uniformly horizontal.