MIT’s Self-Shading Smart Windows Could Cut Energy Costs

Researchers from the Massachusetts Institute of Technology (MIT) have developed windows that can shift from clear to dark in an instant.

Apart from its "self-shading" capacity, the system also requires little to no electricity to maintain the dark or clear state, and would only require power when the system will be switched back again. According to the researchers, the windows could help homeowners cut cooling costs by using the self-shading capacity to block the sunlight during hot weather.

According to the researchers, the new technology is made up of electrochromic materials, which change their color and transparency in response to an applied voltage. The same system exists in a Boeing 787 aircraft, where electrochromic windows turn dark to prevent the bright sunlight from glaring through the cabin.

"[But] when you flip the switch, it actually takes a few minutes for the window to turn dark. Obviously, you want that to be faster," Mircea Dincă, chemistry professor at MIT and study lead author, said in a press release.

The shade shifting is slow because the positive ions that are responsible for the color change move slowly, and this delays the darkening process. The research team addressed this issue by using materials known as metal-organic frameworks (MOFs), which could conduct both ions and electrons quickly.

According to Dincă, another challenge the team had to tackle is that existing versions of self-shading windows could not change from completely transparent to completely black. Boeing 787 windows could only switch from clear to a dark shade of green.

Dincă and his team have produced a material with this capacity by combining two chemical compounds: an organic material and a metal salt. By combining the compounds, the researchers were able to produce a coating that can switch from perfectly clear to nearly black.

Apart from preventing glare, the windows could also lead to significant energy savings by reducing the need for energy-consuming air conditioning systems in buildings or houses with many windows in warmer climates.

"You could just flip a switch when the sun shines through the window, and turn it dark," Dincă said.

The researchers will proceed with creating a small-scale device for further testing.

The results of the study were published this week in the journal Chem.