Simple dual-layer emitter for daytime radiative cooling

Abstract

This work experimentally demonstrates a simple dual-layer emitter, which is easy to prepare and can be applied to effective daytime radiative cooling. The emitter consists of a 200-µm-thick polydimethylsiloxane film on top of a 120-nm-thick Ag film, which is coated on a fused silica wafer or a plastic substrate. Due to the high reflectivity from the visible to the near-infrared and near-black emittance in the mid-infrared, the experimental results show that both structures have similar daytime radiative cooling performance. During the testing period, the typical ambient air temperature is 14-26 °C, the local wind speed is 1.6-2.6 m/s, and the relative humidity is 45-73%. We experimentally demonstrate that the emitter can achieve an average temperature reduction of about 3.3 °C from the ambient air temperature under direct sunlight. And the potential cooling power density is about 72.7 W/m 2 . In the presence of non-ideal atmospheric conditions and significant non-radiative heat exchange, theoretical simulations are in good agreement with the measurements. This work indicates that the dual-layer emitter may be a key element in the realization of energy-efficient radiative cooling devices.