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refrigerant is essential for air conditioners and freezers. this is the only refrigeration method currently used, though refrigerant may contaminate the environment to a certain degree, cause greenhouse effect and lead to global warming.
recently yang ronggui and yin xiaobo at university of colorado published an article in the journal science, saying they had found an alternative for cooling without the use of refrigerant and electric power. they invented a kind of film to cool buildings with excellent performance. only 20 m2 of such film on rooftop of a house in the united states can bring down indoor temperature to 20℃ when outdoor temperature is 37℃. this film called tpx is now in commercial production, costing only 50 cents per square meter.
the new type of film removes heat from the building roof by using “radiative cooling”. undesired heat generated in the building is converted into specific long-wave infrared radiation and thrown into the sky unhindered by the earth's atmosphere. this film namely tpx is a kind of transparent plastic made from polymethylpentene by yang ronggui and yin xiaobo. tiny glass micro beads are imbedded into tpx and the film is stretched to 50 microns thick. silver plate one side of the film and lay it on rooftop with silver-side down in such a way that sun lights can reflect off the plastic film.
in applications, only a small amount of electric power is required for driving heat transfer in water pipelines. cooling can be realized due to a huge temperature difference between the earth’s surface and outer space.