| Posted: January 21, 2010 |
Nanocoating that acts as efficient heat pump could reduce need for energy-guzzling air conditioning |
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(Nanowerk News) A research by Australian scientists has suggested that a heat pump based on nanoparticles could one day cool buildings without the need for energy-intensive air conditioning.
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According to a report by ABC News, the research was carried out by Applied physicist Professor Geoff Smith and Dr Angus Gentle of the University of Technology, Sydney.
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Air conditioning is especially a problem in cities, which have a lot of heat-retaining surfaces, contributing to what is called the "urban heat island effect".
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Smith and Gentle have created a coating that can be used as an efficient heat pump and reduce the need for energy-guzzling air conditioning.
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It relies on a phenomenon known as "night sky cooling", in which energy absorbed by surfaces during the day is emitted back into the atmosphere.
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Smith and Gentle's invention takes advantage of the fact that certain wavelengths of radiation emitted from the Earth are less likely to be reabsorbed by the atmosphere.
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These wavelengths - between 7.9 and 13 micrometres - are more likely to escape all the way back into space than others.
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Smith and Gentle have found that a mixture of silicon carbide and silicon dioxide (CO2) nanoparticles emit heat radiation at wavelengths that best take advantage of this atmospheric 'window'.
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They have found a surface coated with the 50-nanometre sized particles can get down to 15 degrees cooler than ambient temperature in Sydney.
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According to Smith, the nanoparticle coating could be used to make a kind of reverse solar collector.
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Air, or water, would flow in channels beneath a plate coated with the nanoparticle mixture.
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Rather than absorbing the radiation for heating purposes, the set up would emit radiation, cooling air or water that could then be pumped through buildings to cool them.
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As well as cooling buildings, the technology could also be used as a coating on refrigerators, especially in remote areas.
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"The technology would mainly work at night, but could sometimes work on the shady side of buildings," Smith said.
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