Sub-ambient transparent radiative liquid cooling system enabling simultaneous solar energy utilization

초록

Radiative cooling is a technology that enables sub-ambient cooling even during daytime by radiative heat transfer to outer space, offering potential for reducing building energy use. However, the substantial surface area required for effective operation poses practical limitations, especially in applications where space is constrained or shared with other solar energy technologies. This study demonstrates a sub-ambient transparent radiative liquid cooling system (STRLC) that transmits solar irradiation while maintaining conventional radiative cooling principle. This configuration necessitates low optical absorption along the material thickness rather than merely low surface absorptivity, as required in conventional reflective approaches. The intrinsically low near-infrared absorption of silicone oil enables this more stringent optical requirement to be satisfied. With a total solar absorptivity of 2.8% and a total hemispherical emissivity of 79.4%, the system achieves liquid temperatures 2.4 degrees C below ambient during daytime and 5.1 degrees C below ambient at night under outdoor conditions. The experimental results are in close agreement with the system-level modeling predictions, validating the underlying thermal and optical analyses. Simultaneously, 66.3% of the incoming daily solar energy is transmitted through the panel, highlighting the potential for concurrent solar energy utilization. The cooled liquid can be integrated with vapor compression cycles for building cooling, while the transmitted solar energy can be coupled with fiber-optic daylighting systems, leading to estimated reductions of 10.0% in cooling electricity and 47.6% in lighting electricity. These findings indicate that the STRLC system has the potential to function as a scalable energy saving solution applicable across diverse climatic regions.

키워드