Engineers from Stanford University, US, have invented a new ultra-thin, multi-layered coating material that can direct warmth from inside a building into space, in order to lower the temperature.
The new coating material, which is just 1.8 microns thick, controls building temperatures even on sunny days through using visible and invisible light.
Discovery of the energy-saving material was reported in Nature journal by a team led by electrical engineering Professor Shanhui Fan and research associate Aaswath Raman.
According to the researchers, the material uses infrared light and also acts as a mirror to prevent 97% of sunlight from striking the building and heating it up.
Stanford University professor emeritus Burton Richter said: "This team has shown how to passively cool structures by simply radiating heat into the cold darkness of space."
The material has been designed to be cost-effective for large-scale deployment on building rooftops and is expected to reduce the demand for electricity in the future.
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The first part of the coating’s one-two punch radiates heat-bearing infrared light directly into space, which the ultra-thin coating forces away from building at a precise frequency that lets them pass into space without warming the air near the building.
The radiation and reflection together make the photonic radiative cooler nearly 9°F lower in temperature than the surrounding air.
Said to be thinner than the thinnest aluminum foil, the material is made of seven layers of silicon dioxide and hafnium oxide on top of a thin layer of silver.
Advanced Research Project Agency-Energy (ARPA-E) of the US Department of Energy supported the research.
Image: Stanford Professor Shanhui Fan, co-authors Linxiao Zhu (left) and Aaswath Raman (right). Photo: courtesy of Norbert von der Groeben.