Flow field and performance of a vertical axis wind turbine on cube-shaped buildings

Urban wind energy is a sparsely explored option for decentralized renewable energy generation. One of the main issues is the complexity of urban wind resources. The present study addresses this experimentally, exploring the influence of siting on the efficiency of a roof-mounted vertical axis wind turbine of the Savonius (drag) type. Performance and flow field measurements are conducted on a set-up of two aligned cube shaped buildings in a wind tunnel. The position of the wind turbine on top of the buildings is varied, with three positions on each cube respectively. In addition, the effect of freestream turbulence in the inflow generated by an active grid is examined. The flow field is measured both with and without the turbines using particle image velocimetry along the centerline of the buildings, while the torque and rotational velocity of the turbine are captured simultaneously. It is shown that the turbine itself has a substantial impact on the flow field and on the performance. Thus, it is not sufficient to evaluate the available power in an urban environment based only on the flow field without a turbine present. The ideal position of a roof-mounted vertical axis wind turbine will be discussed based on these results.