Feasibility analysis of a Darrieus VAWT installation in the rooftop of a building

Increasing interest is being paid to understand where small wind turbines can effectively be exploited to provide delocalized power in the built environment. The wind conditions in the rooftop area of buildings in urban locations are, however, very complex and the real adaptability of wind turbines to these environments is not yet tested both in terms of real producibility and of structural compatibility with the building themselves. Within this context, Darrieus VAWTs are being considered as one of the most attractive solutions; in addition, recent studies put in evidence that some benefits in terms of power increase can be obtained from a Darrieus turbine operating in a skewed flow. In this work is reported a study to evaluate the energetic convenience of a Darrieus VAWT installation in the rooftop of a building in a conventional European city. With this goal in mind, a numerical CFD analysis was carried out to characterize the flow field in the rooftop area of buildings with different shapes and geometrical proportions. The flow velocity modulus and direction were calculated for different oncoming wind profiles and the results were projected into a net available wind distribution in the rooftop of the building. In addition, a numerical model was developed to account for the effects of the skew angle of the flow on the power performance of the turbine. The results were finally exploited to evaluate the technical and energetic feasibility of an installation in a similar context.