New system can rapidly switch glass from transparent to dark — and keep it that way without power.
A team of researchers at MIT has developed a new way of making windows that can switch from transparent to opaque, potentially saving energy by blocking sunlight on hot days and thus reducing air-conditioning costs. While other systems for causing glass to darken do exist, the new method offers significant advantages by combining rapid response times and low power needs.
Once the glass is switched from clear to dark, or vice versa, the new system requires little to no power to maintain its new state; unlike other materials, it only needs electricity when it’s time to switch back again.
The results are reported this week in the online journal Chem, in a paper by MIT professor of chemistry Mircea Dinc?, doctoral student Khalid Al-Kaabi, and former postdoc Casey Wade, now an assistant professor at Brandeis University.
The new discovery uses electrochromic materials, which change their color and transparency in response to an applied voltage, Dinc? explains. These are quite different from photochromic materials, such as those found in some eyeglasses that become darker when the light gets brighter. Such materials tend to have much slower response times and to undergo a smaller change in their levels of opacity.
Existing electrochromic materials suffer from similar limitations and have found only niche applications. For example, Boeing 787 aircraft have electrochromic windows that get darker to prevent bright sunlight from glaring through the cabin. The windows can be darkened by turning on the voltage, Dinc? says, 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.”
The reason for that slowness is that the changes within the material rely on a movement of electrons — an electric current — that gives the whole window a negative charge. Positive ions then move through the material to restore the electrical balance, creating the color-changing effect. But while electrons flow rapidly through materials, ions move much more slowly, limiting the overall reaction speed.
The MIT team overcame that by using sponge-like materials called metal-organic frameworks (MOFs), which can conduct both electrons and ions at very high speeds. Such materials have been used for about 20 years for their ability to store gases within their structure, but the MIT team was the first to harness them for their electrical and optical properties.
The other problem with existing versions of self-shading materials, Dinc? says, is that “it’s hard to get a material that changes from completely transparent to, let’s say, completely black.” Even the windows in the 787 can only change to a dark shade of green, rather than becoming opaque.
In previous research on MOFs, Dinc? and his students had made material that could turn from clear to shades of blue or green, but in this newly reported work they have achieved the long-sought goal of producing a coating that can go all the way from perfectly clear to nearly black (achieved by blending two complementary colors, green and red). The new material is made by combining two chemical compounds, an organic material and a metal salt. Once mixed, these self-assemble into a thin film of the switchable material.
“It’s this combination of these two, of a relatively fast switching time and a nearly black color, that has really got people excited,” Dinc? says.
The new windows have the potential, he says, to do much more than just preventing glare. “These could lead to pretty significant energy savings,” he says, by drastically reducing the need for air conditioning in buildings with many windows in hot climates. “You could just flip a switch when the sun shines through the window, and turn it dark,” or even automatically make that whole side of the building go dark all at once, he says.
While the properties of the material have now been demonstrated in a laboratory setting, the team’s next step is to make a small-scale device for further testing: a 1-inch-square sample, to demonstrate the principle in action for potential investors in the technology, and to help determine what the manufacturing costs for such windows would be.
Further testing is also needed, Dinc? says, to demonstrate what they have determined from preliminary testing: that once the switch is flipped and the material changes color, it requires no further power to maintain its new state. No extra power is needed until the switch is flipped to turn the material back to its former state, whether clear or opaque. Many existing electrochromic materials, by contrast, require a continuous voltage input.
In addition to smart windows, Dinc? says, the material could also be used for some kinds of low-power displays, similar to displays like electronic ink (used in devices such as the Kindle and based on MIT-developed technology) but based on a completely different approach.
Omar K. Farha, a research professor of chemistry at Northwestern University who was not involved in this project, says, “Every time I open a new paper from the Dinc? group, I am guaranteed to read about wonderful discoveries and well-executed science, and this paper no different.” He adds that given this material’s relatively rapid switching time, “I see no reason why the next generation Dreamliner  can’t use MOFs for its electrochromic windows.”
Learn more: MIT develops self-shading windows
The Latest on: Self-shading windows
[google_news title=”” keyword=”self-shading windows” num_posts=”10″ blurb_length=”0″ show_thumb=”left”]
via Google News
The Latest on: Self-shading windows
- Love Is Blind fans accuse Nick Lachey of shading ex-wife Jessica Simpson during reunion: ‘Embarrassing’on November 11, 2022 at 12:33 pm
Nick Lachey has sparked backlash from Love Is Blind viewers after making a reference to his first marriage to Jessica Simpson, which many perceived as a dig at the singer. The Love Is Blind host, 49, ...
- An Electricity-Free Smart Windowon November 10, 2022 at 4:19 am
TBM Designs created InVert self-shading windows to reduce solar heat gain and associated energy consumption. Each window features a cavity of insulated glass containing small pieces of thermo ...
- Curved Shading System in Museum of Motion Pictureson November 7, 2022 at 3:06 am
The new Academy Museum of Motion Pictures building is located in the May Company department store, it features a tailored Draper shading solution ... Since window shades tend to be two-dimensional ...
- Britney Spears clarifies she wasn't shading 'queen' Selena Gomez in Instagram post about 'hypocrite'on October 27, 2022 at 3:24 am
Britney Spears clarified on Wednesday that she wasn’t shading Selena Gomez in a now-deleted Instagram post in which she called out people who talk about not showing their bodies on Instagram ...
- Britney Spears’ Fans Think She’s Shading Selena Gomez In New Post About ‘Hypocrites’on October 25, 2022 at 7:53 pm
Later in the post, the popstar revealed who she was actually referring to in her Oct. 25 post. “…and what I was replying to was honestly Kelis the ‘MILKSHAKE’ video when women were finally ...
- This beginner-friendly drawing bundle is on sale for under £30on October 25, 2022 at 1:00 am
TL;DR: The 2023 Fundamental of Drawing and Shading Bundle(opens in a new tab) is on sale for £26.57, saving you 96% on list price. Drawing may seem like magic when you watch an experienced artist ...
- Kardashian fans think Kylie Jenner and Rojean Kar are shading each otheron October 24, 2022 at 3:23 am
After Travis Scott strongly denied model Rojean Kar's claims she was with him behind Kylie Jenner's back, fans now think the pair have been subtly shading each other on Instagram. Late last week ...
- Swifties are worked up over who they think Taylor is shading on ‘Midnights’on October 21, 2022 at 4:12 pm
If Taylor Swift puts out a new album and fans don’t have a slew of highly complex and potentially accurate theories, did it even really exist? After “Midnights” was released late Thursday ...
- Keeley Hazell's Follower Count Increases After Shading Olivia Wildeon October 21, 2022 at 4:03 am
The latest chapter in the Olivia Wilde and Jason Sudeikis relationship drama has just dropped courtesy of his ex-girlfriend. The Don't Worry Darling director, 38, and the Ted Lasso star, 47, split ...
- No one can tell if this ‘Harry Potter’ star is shading or supporting transphobe JK Rowlingon October 19, 2022 at 2:28 pm
If you capitulate so much on your feelings towards a bigot that outlets can spin your words any way they like, you might need to check what you really stand for. Harry Potter alum Tom Felton ...
via Bing News