Evaluating Urban Geometry Impacts on Incident Solar Radiation on Building Envelopes

Abstract

The present study investigated the impacts of urban geometry on incident solar radiation on building envelopes. A three-dimensional model was developed and applied to examine these relationships, with implications for building landscapes as a potential heat source for urban heat islands. In the model, we classified building envelopes into three types, including ground, roofs, and building facades. Satisfactory model performance was confirmed by comparing measured and predicted incident solar radiation results. Furthermore, we developed the Incident Solar Radiation Prediction Index (ISRPI) to address relationships between urban geometry and incident solar radiation. Our overall results showed the solar irradiance incident on building envelopes was significantly affected by urban geometry. Building facades consistently shared a large amount of the building landscape’s total surface area and therefore determined more influence on variation in incident solar radiation. Weather conditions showed strong influence on incident solar radiation, primarily due to variation in atmospheric transmittance. Diffuse radiation demonstrated a larger share of incident solar radiation on the cloudy sampling day. ISRPI, which cumulatively combined the strengths of several traditional urban morphological metrics, exhibited a strong linear relationship with incident solar radiation under sunny and cloudy weather conditions. This index provided a more convenient approach to estimate the spatial-temporal variations of solar radiations at urban scale.