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New Material Cools When Exposed to Sunlight, Could Make Us Ditch Air Conditioning

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Stanford School of  engineering graduate students Linxiano Zhu, Shanhui Fan, a Professor of Electrical Engineering  and grad student Aaswath Raman on Friday, October 10, 2014.  ( Norbert von der Groeben )
Stanford School of engineering graduate students Linxiano Zhu, Shanhui Fan, a Professor of Electrical Engineering and grad student Aaswath Raman on Friday, October 10, 2014. Picture (c) Norbert von der Groeben

A team of researchers at Stanford have invented a new and weird type of material that cools when exposed to sunlight. It could be used to insulate buildings, and reduce the need for energy-consuming air conditioning.

The material, developed by Shanhui Fan, uses optical tricks to radiate heat whose frequency lies in our planet’s “thermal window” – a range of wavelenghts from 8 to 13 micrometers. At these frequencies, the heat passes through the atmosphere, doesn’t become trapped in it anymore, and gets in outer space, which acts as a heat sink.

Previously, other scientists have harvested this effect, called passive radiative cooling, but the materials they made were also black, so in addition to releasing the heat at night, they also captured a lot of during the day. Fan’s material behaves like a mirror that reflects 97% of heat back into space.

“Something that cools down rather than heating up in the sun is counterintuitive, but that’s what the device is designed to do,” he says.

His next step is to build a square-meter of this material. The proof of concept piece only had 8 square inches.

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1 COMMENT

  1. Incandescent light (bulbs) presented the perfect business model to increase the use, and thereby the profit, of the A/C power grid – FOREVER. As a youngster, I tinkered and literally took everything apart, out of curiosity. . . that’s when I discovered ‘light transfer’ without loss of illumination, and without ‘heat’ through ‘fiber optics’ (before there WAS fiber optics). It was in a 1958 or 60-ish Cadillac. The car had little miniature exterior, fender-mounted turn-signal, headlight, and high-beam, lighted indicators. You see, I had to take it apart. I was ‘curious’ about this ‘tiny exterior bulb’, it’s colored lense and it’s wiring. Well, to my surprise there was no bulb or wiring, instead the dashboard turn-signal indicator, a standard 12v light (the source) transferred it’s illumination (without loss), with twists and turns through the cars firewall, under the hood, and through the steal fender, to be terminated in that ‘colored lense’ indicator (the destination) on the exterior of the appropriate fender, and all three indicator lenses for each fender (L or R) were terminated in the same uniform fashion. The ‘media’ was 8-10 fiber optic strands (wrapped opaque).

    Pretty simple concept for the 1950-60’s. We also had L.E.D.’s back then as well (but that another story). But you have to admit, the concept of transferring ‘light’ or illumination, without heat or loss of illumination 15 feet or 15 miles is very interesting. . . . . Now all we really need is a ‘virgin’ to drop into the volcano, as a sacrifice to appease the A/C Grid ‘Powers that be’. Lord knows we don’t want to light an entire room with one light source terminated very simply through as many ‘magnified’ lenses, as we please – and that ‘one light source’ will undoubtedly be a flourescent, because after 50 yrs we’ve finally started phasing-out incandescent bulbs . . . . . and that probably took a 50 yr old virgin.

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