Performance evaluation of various strategies to improve sub-ambient radiative sky cooling

Abstract

Since the breakthrough of daytime radiative sky cooling, more and more effort has been devoted to this promising technology. But the low cooling performance places great restrictions on the application of this technology. In this work, various strategies are used to further improve the radiative cooling performance. The theoretical analysis reveals that the parameters corresponding to different strategies have great impact on the cooling performance. The experiments with individual strategy indicate that nano polyethylene wind cover strategy can achieve daytime temperature drop of about 5.6 K, improving by about 143.4% compared to that without wind cover (2.3 K). And ordinary polyethylene wind cover strategy and tilt strategy can also achieve daytime temperature drop of about 3.2 K and 4.3 K, improving by about 78.3% and 39.1%, respectively. But inverted pyramid strategy reduces daytime cooling performance by about 33%, due to the higher solar intensity on the radiative cooler. Subsequently, experiments with combined strategy show that the combination of nano polyethylene wind cover strategy and tilt strategy can enable radiative cooler achieve the higher all-day cooling performance, comparable to the results in arid areas. Further discussion on other strategies indicates that polyethylene aerogel has great potential in further improving the cooling performance.