'Tunable' smart windows adapt to brightness, opacity

E-ink technology of the kind found in e-readers can be adapted to form the ultimate cheap window covering, with user-controllable brightness, privacy, and color temperature, say scientists.

opacity lead image
Credit: University of Cincinnati

If you thought your IT workload was about to increase dramatically with Internet-connected sensors sprouting in everyday objects, just wait until windows get in on the act. And I don't mean the Microsoft ones.

Researchers at the University of Cincinnati, along with some from private companies, have developed second-generation smart window technology that uses a kind of e-ink to adapt for brightness, color temperatures, and opacity.

They think the technology will allow for privacy while letting light in, and could act as a type of electronic blind.

The technology isn't Internet-connected yet, but you can reckon it will be in time. So add windows to the Internet of Things (IoT).

Why electronic?

Smart windows promise to revolutionize the mechanical shades that we've depended on for years.

But what's wrong with those, you may ask. Isn't there's a reason we've depended on them since the Romans invented the roman shade—a retractable cloth awning developed to keep blood-thirsty mobs cool at the Colosseum in A.D. 80?

Color temperature

Well, the answer is that this new tech does something that ancient and current smart windows can't do—it can adjust its color temperature.

Current smart windows simply adjust opacity.

Color temperature is the variance of cool and warm commonly found in a new light bulbs. Cool being like daylight, and warm being more yellow. Candles are at the extreme of "warm," with incandescent light bulbs in the middle of the range.

"There is already proven demand for color temperature control in the light bulb market, and after all, windows are a source of lighting," Jason Heikenfeld, one of the professors told M.B. Reilly of the University of Cincinnati News website.

Larger surface than e-readers

The scientists, which include partners from Hewlett Packard and EMD/Merck Research Labs, say that they have figured out a way to apply e-paper technology found in e-readers to a larger surface.

Voltage is applied to "repel or attract color into different positions." It uses a cut-to-size film of electrodes that can be applied at manufacturing or rolled-on.

The basic technology is not that different from electronic display devices, lead researcher Sayantika Mukherjee said, according to the University of Cincinnati news article.

The challenge has been to apply the technology to large areas in a cost-effective way. The group thinks that the tech has to be implemented for less than the $30 per square foot industry-standard for window manufacturing, and they believe they can achieve that.

Multidimensional control

Simultaneous adjustment for brightness and color temperature is just one feature.

However, the team says that control between other types of window states is possible, too.

For example, a window could independently control both visible light and infrared heat transmission.

"So, you could block infrared heat from the sun in the summer, but let it into the house in the winter," Reilly says in the article.

Privacy light mix

And what's maybe the most compelling, perhaps more so than the inexpensive color temperature adjustment and the eco-advantages of heat control in a window covering, is to have privacy mixed with light—called opacity.

"Go home to your neighborhood" and look at the privacy-drawn blinds, which also block sunlight.

"What if you could have your privacy and also let the light in at any brightness you want?" Heikenfeld says.

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