Effects of electrochromic glass window on energy efficiency, thermal and visual performances under tropical climate

This study investigated the thermal, visual environments of real-life climate chambers installed with a full-scale dark gray electrochromic glass window (ECW) under tropical climate in Singapore. Two large-scale climate chambers were built and installed with electrochromic windows or 6 mm single clear glass for comparison, and their thermal and visual performances and effects on the efficiency of air-conditioning were real-time measured and analyzed in detail. Compared to the chamber installed with 6 mm glass, the coefficient of performance (COP) of the air conditioner can be enhanced by 29.64 % and 45.40 % if replaced by bleached and tinted ECWs, respectively. Our study shows that ECW can efficiently reduce around 80 % of the heat flux passing through the indoor under both states, and provide a cooler and more comfortable thermal environment. In contrast, the bleached ECW showed the best performance with 39 % of the daytime spent with a comfortable visual environment without glare. With a 4 % solar heat gain coefficient and a 0.1 % visible light transmission, the fully tinted ECW could reduce the mean radiant temperature and operative temperature by up to 4.7 degrees C and 11.6 degrees C, respectively, when compared to the 6 mm glass. The operative temperature of the chamber with fully tinted ECW was even 0.6 degrees C lower than that of the bleached state. In conclusion, the fully gray tinted ECW showed superior thermal performance with high energy efficiency, and the bleached state gave better visual environment comfortably and economically.