3D modeling of tree crowns and its application in solar energy potential mapping for urban neighborhoods

Shading cast by tall trees in urban areas can significantly limit the access of direct solar irradiance to building façades. In this paper, we present a method to model tree crowns and quantify tree shadow effect on solar irradiance received by buildings. Three-dimension (3D) models for trees were constructed using Poisson surface reconstruction method from Light Detection and Ranging (LiDAR) point clouds and QuickBird image data. Tree crown shadows were modeled by applying the improved Inclusion-exclusion Principle. Direct normal irradiance was derived from remote sensing data first and then employed to the calculation of solar energy radiation received by building rooftops and façades. The proposed method was applied to a case study in Nanjing City. Results indicated that tree shadow played an important role in determining the solar radiation energy received by a building. The improved solar potential result provided fundamental data for solar-related equipment selection and installment, as well as building energy consumption estimation.