Enhanced cooling performance using double sided passive radiative cooling

We investigate the efficacy of double-sided passive daytime radiative cooling (PDRC) devices that incorporate an angled spectrally selective fluoride tin oxide (FTO) coated glass mirror beneath the downward facing emitter. Spectral measurements of the FTO coated mirror show that it is highly reflective (greater than 90%) in the mid-infrared, so the mirror can be used to reflect blackbody radiation from the downward-facing emitter upwards towards the atmosphere. In contrast, the FTO-coated mirror is largely transparent (greater than 80%) over visible wavelengths, allowing solar radiation to pass through the mirror without being reflected upward to heat the downward facing side of the PDRC device. Experimental field trials show mirror-angle dependent cooling from a downward facing emitter, consistent with predictions from a power balance model. Potential applications include improved solar panel efficiency and novel thermoelectric generator configurations.