Abstract
Rooftop wind turbine is a typical utilization form of urban wind power. However, knowledge gaps still exist in the understanding on the wind resources of an urban district, the operation of small rooftop turbines and its effect on the block wind environment. To add new knowledge on this subject, the operation of rooftop wind turbines in an urban district is numerically studied via large-eddy simulation. The turbines are modeled by the actuator disk model and the urban district is represented by 16 idealized cube-shaped buildings. We find that flow above the urban district shows an obvious speedup due to the crowding-out effect of the urban district, and the turbulence intensity is dramatically enhanced. Above the first two rows of buildings, flow adjusts intensely and quickly evolves to a quasi-fully developed regime downstream. Due to the flow characteristics above the rooftop, the relative power increment of the rooftop turbines increases first and then decreases with the hub height, the power and the load fluctuations of the turbines are significantly aggrandized near the rooftop and diminished far away from the rooftop. For the small turbines investigated in this study, the impacts of small rooftop turbines on the wind environment are almost negligible in the blocks.