Long-term cooling effects and cooling energy conservation of a subambient daytime radiative cooling coating relative to a cool-white coating over distributed telecommunication base stations

Abstract

A superamphiphobic self-cleaning passive subambient daytime radiative cooling (SSC-PSDRC) coating with ultrahigh solar reflectance and emissivity was applied to distributed telecommunication base stations (d-TBSs) in various climatic regions. The SSC-PSDRC surface showed remarkable PSDRC effect both in the absence and presence of heat-producing electronic equipment. After exposure to severe outdoor conditions for more than one year, the top surface of the spotless d-TBS still exhibited a strong subambient cooling effect under peak sunlight conditions, owing to the presence of the SSC topcoat. Regardless of the identical appearance, the top-surface temperature difference during the noon hours between the cool-white- and SSC-PSDRC-coated d-TBSs was as high as 24.2 °C, resulting in a chamber interior temperature decrease of the SSC-SDRC-coated d-TBSs. Consequently, the measured cooling energy consumptions of the SSC-PSDRC-coated d-TBS in Kashgar for one year and that in Panzhihua for 290 d were 1044.9 and 2083.3 kWh, respectively, both of which were underestimated. In the long term, the annual cooling energy conservations estimated using different methods correlated well with the measured value in Kashgar. After five cycles of dirt- and 2200 h of artificial accelerated weathering-resistance tests, the solar reflectance of the SSC-PSDRC coating decreased by only 0.015 and 0.023, respectively. These excellent performances were attributed to the unique molecular structure of the superamphiphobic topcoat which contained networks of –Si–O–.