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www.voicechronicle.com_tech-and-science 2015 0000462.txt

#Mirror Created By Stanford Scientists Could Replace Air conditioning Researchers in Stanford have created a mirror, that not only reflects 97%of light, but also radiates heat into the cold depths of the universe and which could become an alternative to air-conditioning units. Presently in US air-conditioning in buildings accounts for 15%energy consumption of the total energy consumption of those premises. Places like big building complexes and shopping centers use heavy amounts of electricity for their giant cooling systems. But researchers from Stanford university, California have created a mirror that could slash that consumption. The mirror when placed on surfaces of buildings was found to create 9f cooler temperatures around it. Currently roofs of buildings with black painted surface reach temperatures of close to 140f degree more than the ambient temperature while aluminum roofed building surface becomes 104f hotter than the ambient temperature. Instead the mirror was found to decrease the temperature and also reflected 97%of the light that fell on it. f you cover significant parts of the roof with this mirror, you can see how much power it can save. You can significantly offset the electricity used for air conditioning, said Shanhui Fan, an expert in photonics at Stanford university who led the development of the mirror. n some situations the computations say you can completely offset the air conditioning. Various things heat up the building temperatures. Warm air comes through the windows and doors. Visible light and infrared lights pass heat through the building surfaces. To make things cool again, engineers believe that the surfaces should have ways in which they can dump the heat they get. For that they need a heat sink, which drains that heat out. For example a bucket of ice cools down the wine bottle when it is placed in it. The bucket is the heat sink that drains the bottle heat. The mirror invented by Stanford university helps in some of these circumstances, by behaving like a thermal radiator. When the mirror is warmed up by the sunlight, it releases heat at a specific wavelength of infrared light that passes easily through the atmosphere and out into space. The universe behaves like the heat sink. The two micrometres thick mirror is made of several thin layers of different materials. The first layer is followed reflective silver by alternating layers of silicon dioxide and hafnium oxide. When silicon dioxide heats up, it radiates the heat as infrared light of 10 micrometer wavelength. Since nothing in the atmosphere can absorb that, the heat directly passes straight into space. The mirror would cost between $20 to $70 per square meter and can annually save 100mwh of electricity and will be soon available for commercial use r

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