Analysis of factors influencing actual absorption of solar energy by building walls

Abstract

The reduced heat loss of a solid wall caused by solar radiation is the solar energy actually absorbed by the solid wall (SEW). The absorbed solar energy calculated by using the radiation absorption coefficient of the wall surface is thus not the SEW. This study analyzes the parameters that may affect the SEW, including the heat accumulation coefficient of the wall (S), the heat-transfer coefficient of the south wall’s outer surface (h), the radiation intensity (I), the consecutive sunny days (D), and the outdoor air temperature (T). These influential factors on the solar absorptance of the south-facing wall (εwall) were synthetically evaluated with multiple nonlinear regression analysis. The results indicate that εwall is significantly affected by three parameters (i.e., S, h, D): εwall is high when S is large or h is small or D is small. I and T have little impact on εwall. A prediction model of εwall was further developed by using multivariate nonlinear regression, which can greatly improve the efficiency of building energy consumption analysis. The prediction model can also efficiently determine the effect of wind speed and direction on εwall in winter for optimizing building orientation and layout.