Efficiency improvement of straight-bladed vertical-axis wind turbines with an upstream deflector

The effect of an upstream flat deflector on the power output of two counter-rotating straight-bladed vertical-axis wind turbines (VAWTs) was investigated experimentally. Although many studies on the deflector effect have been done for a drag-based Savonius VAWT, there is little information on the performance of a lift-based VAWT with a deflector. If a flat vertical plate is normal to the free-stream wind direction, the local wind speed outside the near-wake region of the plate is larger than the free-stream velocity. Thus, when each of the counter-rotating turbines is positioned outside the near-wake region, its power output increases significantly. The power output increase with the deflector installed is dependent on the width and height of the deflector and the turbine position relative to the deflector.

► Efficiency can increase significantly by placing vertical-axis wind turbines outside the wake of the upstream deflector.
► Efficiency improvement is dependent on the height of the deflector.
► Free streamlines from the deflector edges provide a good indicator for the prediction of the power generation.