Influence of position and wind direction on the performance of a roof mounted vertical axis wind turbine

Abstract

The ideal position for a roof mounted wind turbine is investigated experimentally in a wind tunnel. The set-up consists of two cube-shaped buildings. A Savonius (drag driven) vertical axis wind turbine is placed on one of the buildings and its position is varied. Three different locations on the cube and two different turbine heights are examined. Wind from five directions is simulated to obtain a holistic characterization of the problem. The performance of the turbine is evaluated directly through measurements of the converted power. This is complemented by measurements of the surface pressure on the cubes to gain insight into the flow field. A central position on the building was found to maximize the power output for a uniform wind rose, independent of the turbine height. Placing the turbine higher above the roof increased performance for wind normal to the faces of the buildings, while a lower position showed slight advantages for the other wind directions. Overall improved performance for the roof mounted wind turbine was observed compared to the same turbine without a cube present.