Scientists working at the Fraunhofer Institute for Building Physics in Germany, have devised an 'intelligent window' which can automatically modulate the amount of sunlight entering a room.
Just as sunglasses block light, the window's glass surface has a coating which is transparent at cool temperatures but becomes opaque when the temperature shoots up to a given level. In addition, the Institute has also developed a method to harness solar energy by warming the air on the glass facade of the building.
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[1] http://admin.indiaenvironmentportal.org.in/news/shady-windows
[2] http://admin.indiaenvironmentportal.org.in/category/newspaper/down-earth
[3] http://admin.indiaenvironmentportal.org.in/category/thesaurus/solar-energy
[4] http://admin.indiaenvironmentportal.org.in/category/thesaurus/building-technology
[5] http://admin.indiaenvironmentportal.org.in/category/thesaurus/science
[6] http://admin.indiaenvironmentportal.org.in/category/thesaurus/germany