Impact of cloud and total column water vapor on annual performance of passive daytime radiative cooler

Abstract

The surface temperature of a passive daytime radiative cooler (PDRC) can be lower than the ambient temperature without consuming any extra energy. Thus, the technology of the PDRC has attracted the attention of researchers recently. However, most current studies only focused on the short-term performance of the PDRC during sunny and cloudless days. The influence of clouds and variations of atmosphere total column water vapor on the long-term performance of PDRC have not been investigated in previous research. In this study, a radiative cooling model considering the influence of total column water vapor and clouds was developed for PDRC, and TMY weather data files with total column water vapor were generated for estimating the annual performance of PDRC in five selected major climate zones in China. The results showed that the high total column water vapor would deteriorate the performance of the PDRC. Considering the impact of cloud or not, the difference in potential of achieving sub-ambient cooling during daytime annually ranged from 12.68 % to 43.35 % in five cities, i.e., Harbin, Beijing, Shanghai, Kunming, and Guangzhou. The results also indicated that the selective PDRC always achieved a slightly better performance than the broadband one. Finally, the potential of applying PDRC in five selected cities was estimated. The results demonstrated that the PDRC could yield satisfying performance in Beijing, Shanghai, Guangzhou, and Kunming, with the energy-saving potential of 39.53 kWh/m2, 221.40 kWh/m2, 435.82 kWh/m2, 97.26 kWh/m2, respectively.