Evaluation of Solar Radiation on Vertical Walls of Buildings in Hong Kong

The worldwide concerns of sustainable building design have elevated the demands on advanced building thermal analysis. Various building simulation software are in use to help in the dynamic thermal analysis and building design work. Some simulation exercises are targeted for fulfilling the requirements of the performance-based building energy codes. Our examinations on several well-known simulation programs found that different modeling algorithms were employed to determine the solar radiation falling on external walls. A brief review of the slope irradiance models is given in this paper. Based on the typical weather conditions in Hong Kong, the results from three simulation programs, namely DOE2, TRNSYS, and EnergyPlus, were compared. It was observed that though all the three default models predicted that the southwest-facing wall would receive the highest annual solar radiation, there were considerable discrepancies in the numerical results for walls facing other directions. The deviations among the three approaches could come up to 19%.