Date: Mar 23, 2016 Author: Vladimir Gintoff Source: MIT Technology Review (
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SkyCool Systems Develops Technique to Cool Buildings Using the Coldness of Outer Space, via MIT Technology Review
Although many have come to question our unwavering devotion to hermetically sealed buildings, most construction budgets are still dominated by costs associated with HVAC and other quality of life standards. With some questioning the efficacy of such practices, and others taking fault with the costs, there is now immense incentive to create new technologies and techniques that could allow us to retain the benefits of such climate control without the environmental and monetary cost they currently carry.
Now a young company known as SkyCool Sytems, founded by Stanford University researcher Aaswath Raman, has developed a cooling method capable of ejecting excess heat out of the atmosphere in the form of infrared rays.
All objects emit infrared thermal radiation, but most wavelengths are absorbed by the atmosphere, creating a limit on how cool the object will become. However, a technique known as radiative cooling tweaks the wavelengths of the emitted radiation to sit only within the narrow band (between 8 and 13 micrometres) that is able to escape the atmosphere. By doing this, an object is allowed to cool to below the ambient air temperature.
A second challenge in using radiative cooling is that during the day - when the building's cooling requirements are highest - it requires the cooling device to be exposed to the sky, and thus to direct sunlight. This added input of radiation from the sun counteracts the effects of radiative cooling during daylight hours. However, in a paper published in Nature in 2014, Raman and his research team demonstrated a system in which the optical properties of three materials are stacked and operate in unison, allowing the team's prototype panel system to overcome the sun's radiation and reduce its temperature to almost 5 degrees celsius below the ambient air temperature.
Although the technology is still in a developmental stage, funding from U.S. Department of Energy's Advanced Research Projects Agency (ARPA-E) will allow SkyCool Systems and two other companies working on daytime radiative cooling to study its potential use in the cooling of thermal power plants. Raman believes there will also be future applications in building and refrigeration.