Clean Tech: New Coating Offers Efficiency Double Whammy

By Published On: December 4, 2014

Here’s what may be the ultimate in cool roofs. Stanford University researchers have developed a new material that could be used to coat roofs and lower internal building temperatures by up to 9 degrees Fahrenheit. The coating—which consists of seven layers of silicon dioxide and hafnium oxide on top of a thin layer of silver—is thinner than aluminum foil. When applied to a roof, it reflects the sun’s infrared radiation at a frequency in which heat is not transferred to earth’s atmosphere, but instead travels right back into space. Plus—in an energy efficiency bonus that cuts the need for air conditioning—the coating also radiates energy out of buildings. “We've created something that's a radiator that also happens to be an excellent mirror,” explained Stanford research associate Aaswath Raman. Researchers envision that the coating would be sprayed onto panels that could be mounted on top of buildings. They also point out that while the coating can radiate heat, to take advantage of that property researchers have to figure out how to efficiently transfer heat stored in buildings to the coating. Stanford electrical engineering professor Shanhui Fan led the research team that developed the coating. The team describes the energy saving properties of the coating as “photonic radiative cooling.” The work is published in the scientific journal Nature.

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