Passive radiative cooling: promising results for a polymer film

A new material using radiative cooling was tested by a team of researcher at Boulder, Colorado. The results show that is could become a viable solution for supplemental cooling for buildings.

In February 2017, the IIR published a news on a cooling film developed by engineers at the University of Colorado Boulder. The challenge was to create a material that can reflect incoming solar rays back into the atmosphere while still providing a means of escape for infrared radiation. The researchers embedded glass micro-spheres into a polymer film. The spheres scatter visible light while allowing infrared radiation to escape. Then they added a thin silver coating underneath in order to achieve maximum spectral reflectance.

In October, the researchers published an article1 exploring application of radiative sky cooling. They developed a radiative cooled-cold collection (RadiCold) module to cool water below ambient at noon under stationary conditions. The experiment showed that the container of water was kept around 10.6°C below ambient at noon under stationary conditions.

"We can now apply these materials on building roof tops, and even build large-scale water cooling systems like this one with significant advantages over the conventional air conditioning systems, which require high amounts of electricity to function," said Associate Professor Gang Tan of the University of Wyoming's Department of Civil and Architectural Engineering. The technology could increase the efficiency of power generation plants in summer and lead to more efficient, environmentally-friendly temperature control for homes, businesses, utilities and industries.

1 ZHAO D., AILI A., ZHAI Y., et al. Subambient Cooling of Water: Toward Real-World Applications of Daytime Radiative Cooling. Joule. 2018, October 26 issue. Available following this link.