Modified climate-based daylight modeling methods for buildings

Abstract

This study proposes two methods for calculating direct sunlight contribution, which can replace the sun-coefficient method and obtain two modified five-phase methods for building dynamic daylight modeling, named the M5-PM(A) and M5-PM(B), based on the same accelerating mechanism for different modeling applications. Compared with the 5-PM with MF:3, the M5-PM(A) method can reduce computation time by 73% and 67% for modeling PDRF and specular blind systems, respectively, using Shanghai as the test location. The results also indicate that the simulation accuracy of the M5-PM(A) is similar to the 5-PM for modeling PDRF systems and slightly improved in contrast to the 5-PM for modeling the specular blind. Compared with the 5-PM, the M5-PM(A) can use exact sun positions instead of placing suns at the centers of Reinhart patches. This overcomes the limitation of the 5-PM, where the sun or specular light reflected by blinds may not be predicted accurately in the field of view when modeling fenestration systems sensitive to solar positions and sunlight reflection. This is particularly important for applications such as model-based control for blind systems. However, the time benefits of the M5-PM(A) are influenced by the climate and not fit for parametric analysis. The proposed M5-PM(B) inherits the parametric analysis capabilities of the 5-PM and can accelerates the computation speed. The results demonstrate that the M5-PM(B) with MF:6 can reduce computation time by 90.4% for direct sunlight computation in modeling PDRF, and by 81.1% for direct sunlight computation in modeling specular blinds, compared to the 5-PM with MF:6.