Material that changes colour to save energy
Researchers at Chicago University have designed a building material that changes its infrared colour and how much heat it absorbs or emits based on the outside temperature.
On hot days, the material can emit up to 92% of the infrared heat it contains, helping cool the inside of a building. On colder days, however, the material emits just 7% of its infrared, helping keep a building warm.
The material was designed a non-flammable electrochromic building how 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 chosen trigger temperature, the device can use a tiny amount of electricity to induce the chemical shift between the states by either depositing copper into a thin film, or stripping that copper off. The ability to switch between the two conformations remain efficient even after 1,800 cycles.
Scient researches have shown, that the electricity used to induce electrochromic changes in the material would be less than 0.2% of the total electricity usage of the building, but could save 8.4% of the building’s annual HVAC energy consumption.
At the moment, a piece of material has been created that is only about 6 cm across. However, researchers imagine that many such patches of the material could be assembled into larger sheets. Also the material could also be tweaked to use different, custom colours—the watery phase is transparent and nearly any colour can be put behind it without impacting its ability to absorb infrared. Also, researchers plan to probe how intermediate states of the material could be useful.