A numerical study on the performance of a Savonius-type vertical-axis wind turbine in a confined long channel

Abstract

High-rise buildings in urban environments provide tremendous opportunities for harvesting wind energy. For example, a through-building channel is beneficial for wind speed enhancement and thus wind power generation. In this study, we investigate the performance of a Savonius-type vertical-axis wind turbine (VAWT) placed in a confined long channel, based on computational fluid dynamics (CFD) simulations. Two-dimensional (2D) simulations are conducted using ANSYS Fluent, employing the shear-stress transport (SST) k-ω turbulence model. Incoming wind velocity at the channel inlet is Uo = 4.05 m/s, corresponding to a Reynolds number Re = 1.0 × 105, based on Uo and the diameter (D) of the wind turbine. The channel is 45D long. Three different widths, 2D, 3D and 4D, of the channel together with different wind turbine locations in the channel are considered. The performance of the Savonius-type VAWT in the long channel is discussed, taking into account the contribution of pressure drop towards power generation, and is compared with that in open space. Results show that the power output (Pout) of the Savonius-type VAWT placed in the channel can be significantly increased by 200% in the 2D-wide channel compared with that in open space. Furthermore, a higher optimum tip-speed ratio (TSR) is observed for the wind turbine located in the channel than in open space. A comprehensive comparison is made between the wind turbine in the channel and that in open space. Finally, the maximum power coefficient of a Savonius-type VAWT in the channel is predicted based on a correction to that of a propeller-type horizontal-axis wind turbine (HAWT) in a long channel.