Improved 'smart' window blocks out heat during summer

Researchers have figured out an inexpensive and less harsh way to make a stable, robust smart window.
Written by Tuan Nguyen, Contributor

"Smart" windows have long been had a reputation as that really neat cost-saving idea that never quite caught on with the masses.

What makes them so attractive is that concept is simple: they darken with a special tint to keep rooms cool in the summer and clear up to let heat in during the winter months. The problem, however, is that the underlying technology isn't. For instance, the options on the market tend be expensive and deteriorate, losing effectiveness over time. Factor in the fact that the manufacturing process involves potentially toxic substances and you can see why they're starting to sound a lot less appealing. But now, a Korean research team has developed a window system that overcomes these drawbacks.

Ho Sun Lim, Jeong Ho Cho, Jooyong Kim and Chang Hwan Lee discovered that by combining a polymer called "counterions" and a solvent like methanol resulted in an cheaper and less harsh way to make a stable, robust smart window. They're also easily adjustable, switching from 100% opaque to almost completely clear in seconds.

Their study appears in the journal ACS Nano.

"To our knowledge, such extreme optical switching behavior is unprecedented among established smart windows," the authors wrote. "This type of light control system may provide a new option for saving on heating, cooling and lighting costs through managing the light transmitted into the interior of a house."

The research can be taken as another encouraging sign that the technology is only going to continue to improve, perhaps even to the point that they'll become a practical option for lowering home energy costs. A couple weeks ago, my colleague Melissa Mahony over at the Intelligent Energy blog reported on a window coating that uses a thin film of nanocrystals to allow light to shine through, but keeps the heat out. The net effect is a sunlit room that's brightened with 35 percent less near infrared light.

Here's an exclusive SmartPlanet news segment on how the smart window technology works:

(via press release)

Image: American Chemical Society

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