Modeling and analysis on the cooling energy efficiency of sun-shading of external windows in hot summer and warm winter zone

In hot summer and warm winter zone, decreasing the inferred transmittance of building glass is an effective way to reduce the shading coefficient of external windows and increase the cooling energy efficient rates. Based on an office building model in Guangzhou, the DeST-c code was used to study the effects of the inferred transmittance of building glass on the cooling energy efficient rates. The results show that the cooling energy efficient rates could be significantly increased while the indoor natural lighting could not be degraded by reducing the inferred transmittance of the building glass. As the inferred transmittance of building glass decreases from 1 to 0 and the visible transmittance keeps at 0.7, the cooling need of the office building reduces by 23.3%. Moreover, the annual cooling energy efficient rate increases by form 0.67% to 18.3% compared with the cooling space load of the office building with the shading coefficient of 1.0. By making hourly analysis on the variations laws of the cooling energy efficient rates at all hours in need of cooling load in a year, it can be found that the cause of the significant increase of annual cooling energy efficient rates is that as the inferred transmittance decreases, the hourly cooling energy efficient rates increase significantly for the hours with higher cooling load. The research results can provide references for the optimization of aerogel glass sun-shading performance and the building cooling energy efficiency in South China.

I. Introduction

Large numbers of research and testing show that the solar radiation carrying much heat transmits through the external building glass and overheats the indoor space in summer mainly because of the poor thermal insulation properties of glass [1]. Especially in hot summer and warm winter zone in China where the outdoor temperature is high, the solar radiation is intense and the hours of daylight are long in summer, the research of the energy efficiency of external building glass has already become one of the critical tasks in building energy efficiency [2].