Experimental comparison on the performance of radiative, reflective and evaporative cooling in extremely hot climate: a case study in Chongqing, China

Conventional energy-intensive cooling methods are inadequate for addressing the growing cooling demand exacerbated by severe heat waves. Passive cooling technologies with no energy consumption hold substantial promise as favorable alternatives. Radiative, reflective and evaporative cooling are three emerging passive cooling techniques that operate through either spectrum modification or phase change to effectively reject or dissipate heat. In this study, we investigate the cooling performance of four roof models equipped with a bare surface, as well as radiative, reflective and evaporative cooling technologies on the exterior under extremely hot conditions. The results highlight the remarkable superiority of radiative cooling, particularly during extremely hot periods, wherein it achieves subambient exterior surface temperature by 2.0°C during working hours. On sunny days following a rain event, the evaporative cooling exhibited a distinctive cooling performance. However, during working hours from 09:00 to 18:00, the average exterior surface temperature of the evaporative cooling model remained 1.9°C higher than the ambient temperature and 2.7°C higher than that of the radiative cooling model. Therefore, radiative cooling demonstrated the most effective cooling performance, and its applications should be further investigated to address the growing demand for cooling under global warming.