Although you may not have encountered any yourself just yet, there are now "smart" windows that can electronically go back and forth between clear and tinted states. While they do help to keep air conditioning bills down by blocking the sun's rays, they still have some drawbacks. An experimental new type of smart window from Stanford University, however, is claimed to address those shortcomings.

The window is made of two glass plates with a transparent sheet of electrically-conductive indium tin oxide sandwiched between them.

In its neutral state, the window remains relatively clear, allowing approximately 80 percent of incoming light to pass through. When an electrical current is applied, however, a solution containing ions of copper and another metal moves out from the edges and across the tin oxide, blocking the light – less than five percent gets through.

According to Stanford's Prof. Michael McGehee, existing smart windows can take over 20 minutes to dim, have a blue tint, and they become less opaque with repeated uses. By contrast, his team's window changes between clear and opaque states within just 30 seconds, it's of neutral color, and has already stood up to over 5,000 switches with no degradation.

So far, the prototypes are only about four square inches (25 sq cm) in size, although McGehee is working on scaling the technology up. He also hopes that the finished product will be approximately half the cost of other smart windows.

"We did not tweak what was out there, we came up with a completely different solution," he says. "We've had a lot of moments where we've thought, 'How is it even possible that we've made something that works so well, so quickly,' and we're now running the technology by glass and other kinds of companies."

A paper on the research was recently published in the journal Joule.

One of the prototypes can be seen in action, in the video below.

Source: Stanford University