Friday, April 21, 2017
Passive cooling doesn’t cost the planet - PHYSICS
Motivated by the challenge of cooling power plants in hot weather, Ronggui Yang, Xiaobo Yin, and their colleagues have created a material capable of round-the-clock cooling to below the ambient temperature. The material, a 50-µm-thick glass–polymer film backed with a 200-nm-thick silver coating, can be cost-effectively manufactured by standard industrial roll-to-roll methods. And the material is completely passive: It can cool itself and its surroundings with no power input. The trick is emitting radiation at wavelengths at which the atmosphere is transparent, allowing heat to escape to (the very cold) outer space.
Source & further reading:http://physicstoday.scitation.org/doi/10.1063/PT.3.3513
A glass–polymer cooling panel, depicted here on the roof of a house, must emit more energy into space than it absorbs from other sources: from the Sun, from atmospheric thermal radiation, and from the environment via conductive and convective heat exchange. To keep the sunlight from warming the underlying roof, a film of silver reflects it away.