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Reflections on keeping you cool

By Colin Ricketts - 17 Apr 2013 18:6:34 GMT
Reflections on keeping you cool

This is a mirage, but this research in ,"Nano Letters" on cooling can make this real for many people, as a mirror for the sun's heat; Stop Violence Against Women; Credit: © Shutterstock

If we could get rid of heat into the recesses of outer space, it would hopefully have little effect on the vast universe, but could cool the warming globe we live on. Nanotechnology has been responsible for a lot, but to enlarge on the old physics of heat absorption and reflection is unexpected.

We have a prestigious university (Stanford) here showing what science is all about. Ostensibly to force desert climes to become more comfortable and help sweating office workers in buildings that aren't adequately air-conditioned, cooling panels sound ineffective.

But they are radiating tiny amounts of energy back into space using wavelengths that ensure the air isn't heated on their way out. If you like this is the opposite of the carbon dioxide effect, where heat is trapped.

When the sun shines on this surface the microscopic surface, nearly 100% is reflected, all within the narrow range of wavelengths that is required. "People usually see space as a source of heat from the sun, but away from the sun outer space is really a cold, cold place. We've developed a new type of structure that reflects the vast majority of sunlight, while at the same time it sends heat into that coldness, which cools man-made structures even in the daytime," said Shanhui Fan, the Professor of Electrical Engineering at Stanford.

His research team combine the thermal emitter with a solar reflector to achieve the highly efficient, nanophotonic structure needed. This structure combines quartz and silicon carbide to cool at up to 100W per m2. A solar panel generates the same amount of power from the same solar energy. Installation of this panel would be simpler however as it isn't plugged in to anything, it is passive in its operation. It's simply a "mirror."

Uses are manifold: cars and buildings are obvious targets, with the attraction reducing carbon footprints in hot regions where large amounts of power are needed to cool down every building, day and night.

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Topics: Solar Energy