Fig. 4: Outdoor testing of radiative cooling performance.
a Photograph of the testing platform within the Solar Park of Karlsruhe Institute of Technology. The cooling test chamber was used to test the minimum temperature of the polymer-based micro-photonic multi-function metamaterials (PMMM) sample with radiative cooling. The PMMM-roof box and glass-roof box were used to test the temperature of the experimental enclosures with PMMM and normal glass as the roofs. b Schematics of the cooling test chamber, PMMM-roof box, and glass-roof box. The cooling test chamber was covered with a low-density polyethylene (LDPE) film as the windshield. Detailed dimensions are provided in the Method section. c PMMM sample temperature (TPMMM), ambient temperature (Ta) and global solar irradiance (Gsun). The inserted image shows the sky at 13:00. d Temperature of the PMMM-roof (TPMMM_box) and glass-roof boxes (Tglass_box). The inserted image shows the enlarged view of the two boxes. Source data are provided as a Source Data file.
