It takes a lot of energy to keep buildings comfortably cool in hot parts of the world. Researchers hope to reduce that energy use with a new window coating. Unlike air conditioners and fans, it doesn’t need power to work.
As it comes through windows, sunshine is a big source of heat in buildings, explains Tengfei Luo. He hopes to change that. Luo is an engineer at the University of Notre Dame in Indiana. His team has just designed a new coating for windows the work a bit like sunglasses.
Sunlight contains both the visible light that we can see ― and the light our eyes can’t see. Those unseen rays fall in the ultraviolet and near infrared wavelengths. All three types can pass through glass. Windows need to let visible light through, but not the other two, explains Luo. “Except for heating up the room, they really don’t do anything,” he says.
Luo and his team set out to design a clear coating that blocked the warming wavelengths. But they didn’t just want to keep it out of buildings. They wanted to keep it from contributing to climate change. So, the perfect coating would achieve three things. First, it should let in as much visible light as possible. At the same time, it should block all the ultraviolet and near-infrared light it can. Finally, it should radiate any heat energy at wavelengths likely to escape back into space - rather than heat up the neighborhood.
The result is a coating that uses common, inexpensive materials. It requires no exotic techniques. So it could be bonded to new windows as they’re made or possibly added to existing ones.
Luo sees potential for widespread use of this glass coating in hot climates. That's very good news as, to seriously address climate change, energy-efficient buildings are a must.
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