Highly solar reflectance and infrared transparent porous coating for non-contact heat dissipations

Abstract

Summary: Passive daytime radiative cooling (PDRC) can dissipate heat to outer space with high solar reflectance (R¯solar) and thermal emittance (ε¯LWIR) in the atmospheric transmission window. However, for the non-contact heat dissipation, besides the high R¯solar, a high infrared transmittance (τ¯LWIR) is needed to directly emit thermal radiation through the IR-transparent coating to outer space. In this work, An IR-transparent porous PE (P-PE) coating with R¯solar= 0.96 and τ¯LWIR= 0.88 was prepared for non-contact heat dissipations. Under the direct sunlight of 860 W m−2, the IR-transparent coating obtained a 4°C lower heater temperature than the normal PDRC coating under the same condition. In addition, the spectral reflectance of the P-PE coating after immersing in air or water changed little, which showed excellent durability for long-term outdoor applications. These results indicate the P-PE coating can be a potential IR-transparent coating for non-contact heat dissipations under direct sunlight.

Keywords

• Energy sustainability
• Thermal engineering
• Thermal property