Passive sub-ambient cooling: radiative cooling versus evaporative cooling

Day-and-night radiative sky cooling has emerged as a potential alternative to conventional technologies such refrigeration-based air conditioning and evaporative wet cooling. Both can passively achieve sub-ambient without consuming electricity. Although both techniques are subject impacts from various weather conditions, the extents of under same conditions not well understood. In this work, we experimentally theoretically study thermal performances passive cooler when exposed clear night sky. We show that is better suited for high-temperature low-humidity with measured temperatures coolers being −13.5℃ −15.0℃, respectively, at low relative humidity 13% high ambient temperature 26.0℃. On other hand, relatively more resilient than high-humidity and/or low-temperature −11.5℃ −10.5℃, slightly higher 32.0% lower 17.0℃. Depending on water availability be adopted mutually supplemental technologies.