Researchers at the University of Chicago’s Pritzker School of Molecular Engineering have designed a building material that changes its infrared color — and how much heat it absorbs or emits — based on the outside temperature. On hot days, the material can emit up to 92% ofits the infrared heat, helping cool the inside of a building. On colder days, the material emits 7% of its infrared, helping keep a building warm.
“We’ve essentially figured out a low-energy way to treat a building like a person; you add a layer when you’re cold and take off a layer when you’re hot,” said Asst. Prof. Po-Chun Hsu, who led the research published in Nature Sustainability. “This kind of smart material lets us maintain the temperature in a building without huge amounts of energy.”
“A simple way to think about it is that if you have a completely black building facing the sun, it’s going to heat up more easily than other buildings,” said PME graduate student Chenxi Sui, the first author of the new manuscript.
That might be a good thing in the winter, but not in the summer. Since global warming causes frequent extremes in weather, there is a need for buildings to be able to adapt.
Hsu and his colleagues designed this non-flammable “electrochromic” building material that contains a layer that can take on two conformations: solid copper that retains most infrared heat, or a watery solution that emits infrared. At any trigger temperature, the device can use a tiny amount of electricity to induce the chemical shift by either depositing copper into a thin film, or stripping that copper off.
In the paper, researchers revealed how the ability to switch between the two conformations remained efficient even after 1,800 cycles.