Assessment of parapet effect on wind flow properties and wind energy potential over roofs of tall buildings

Wind energy harnessing in built environment contributes to the development of sustainable cities. In this study, flow features and wind energy over roofs with various parapet heights were investigated via computational fluid dynamics simulations. Effects of normalized parapet height (hp/H = 0, 1/320, 1/160, 3/320, and 1/80) and wind angle theta were examined. Moreover, flow features and associated aerodynamic mechanisms were investigated. Effect of hp/H on flow features and wind energy potential depended on roof locations and theta. Parapets had the greatest effect on velocity and turbulence intensity at theta = 45 degrees. At theta = 45 degrees, the largest u occurred at large heights as hp/H increased because parapets would lift up the roof flows. The largest amplification factor of wind energy decreased linearly as hp/H increased from 0 to 1/160, whereas no obvious variations for hp/H were observed from 1/160 to 1/80. The average hub height increased from 1.13 to 1.16 as hp/H increased from 0 to 1/80, indicating potential higher installation cost of wind turbines for larger hp/H. Analysis of parapet height is required to fully assess the wind energy potential and determine the layout of rooftop wind turbines.