Full-scale experimental study of the surface cooling effect of prefabricated buildings utilizing passive radiative cooling under real operating conditions

Abstract

Passive radiative cooling technology, with its low application cost and significant energy-saving potential, is a crucial means to address the explosive growth in demand for building cooling associated with rapid urbanization in developing countries. However, previous studies of this technology focused mainly on small-scale single-factor experiments or industrial buildings, neglecting the internal thermal dynamics, with its application in actual residential buildings, especially prefabricated buildings, remains limited. Therefore, in the present study, we have first achieved the integration of passive radiative cooling technology with prefabricated full-scale buildings to evaluate the cooling performance of the outer surface under various outdoor environments, indoor operating conditions (natural/air conditioned), and radiative coatings. The results showed that cooling was enhanced in the experimental buildings during the daytime compared with the nighttime, where air conditioning was more effective than natural conditions, and roofs outperformed facades. Uniquely shaped areas with white putty and radiative coatings obtained 71.91 % and 17.82 % higher daily temperature differences, respectively, compared with normal areas. We discovered, contrary to established findings, a novel relationship between the cooling effect on the outer surface of buildings and solar radiation. Furthermore, the correlations between complex indoor-outdoor factors and the cooling effect were analyzed. The roof cooling correlated strongly with the coating's radiative properties (r = 0.44) and negatively with indoor wind speed (r = −0.25), whereas facades had the inverse relationships (r = −0.16 and r = 0.12, respectively). Two theoretical equations were derived to calculate daily average cooling temperatures based on correlation analysis. This work can contribute significant theoretical foundations and experimental data to the advancement of passive radiative cooling residential buildings.