Visibly Transparent Radiative Cooler under Direct Sunlight

Minkyung Kim, Dasol Lee, Soomin Son, Younghwan Yang, Heon Lee, Junsuk Rho

Research output: Contribution to journalArticlepeer-review

7 Citations (Scopus)

Abstract

Transparency is an important characteristic in practical applications of radiative cooling, but the transmitted sunlight trapped in an inner space is generally the main cause of the increasing temperature. A transparent radiative cooler that can lower a temperature during the daytime by transmitting visible light, reflecting near-infrared (NIR) light, and radiating thermal energy through the atmospheric window is proposed. In contrast to transparent selective emitters that transmit most of the incoming solar irradiance under direct sunlight and opaque radiative coolers that reflect all solar energy, the proposed cooler achieves transparency and the cooling effect simultaneously by selectively blocking solar absorption in the NIR regime. Outdoor rooftop measurements confirm that the cooler can reduce i) the inner temperature of an absorbing system and ii) its own temperature when combined with commercially available paints. During daytime, the cooler provides a temperature reduction of a maximum 14.4 °C and 10.1 °C for the inner and own temperature, respectively, and of an average 5.2 °C and 4.3 °C, respectively, in comparison to the transparent selective emitter. The proposed cooler can reduce the temperature during the daytime while maintaining transparency, confirming its possibilities in practical applications such as passive diurnal cooling of vehicles or buildings and compatibility with current paint technologies for aesthetic use.

Original languageEnglish
Article number2002226
JournalAdvanced Optical Materials
Volume9
Issue number13
DOIs
Publication statusPublished - 2021 Jul 5

Keywords

  • daytime cooling
  • radiative cooling
  • rooftop measurements
  • selective emitter
  • selective reflector
  • transparent devices

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Atomic and Molecular Physics, and Optics

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