Integrating daylight with solar thermal modeling: A dynamic calculation method for complex fenestration systems

Abstract

This study developed a mathematical model named the DL-E model, which links annual dynamic daylight and solar heat gain calculations for Complex Fenestration Systems (CFSs). The DL-E model utilizes the Klems Bidirectional Scattering Distribution Function (BSDF) to characterize CFSs and can consider the shading effect of obstacles, as well as solar radiation from obstacles and the ground. The DL-E model uses the Perez all-weather model to calculate transmitted solar radiation contributed by diffuse solar radiation, rather than the simplified sky model used in EnergyPlus. Results calculated with the DL-E were compared with those computed with EnergyPlus, and it was found that for most of the results, the both methods yielded closely aligned outcomes. However, for the diffuse transmitted solar radiations, reflected solar radiation from the ground in the case with a vertical obstacle, and the reflected solar radiations from the obstacle, the values calculated with DL-E showed significant differences compared to those calculated with EnergyPlus due to the use of the simplified sky model in EnergyPlus. In contrast, the values calculated with the DL-E model which used the Perez all weather sky model displayed very small difference compared to those calculated with Radiance, which means the values derived with EnergyPlus may produce significant errors. Additionally, a new workflow has been developed for calculating building load and energy for CFSs to avoid the manual conversion of the BSDF file.