Switchable mirror glass produced for energy efficient windows

Jan 30, 2007 feature
Switchable mirror glass produced for energy efficient windows
Switchable mirror that turns into a color-neutral transparent state. Credit: AIST

Although windows can naturally heat buildings in the cold seasons, some hot sunny days might make you wish that windows would just go away. Scientists from Japan have recently designed new technology that will make windows seem to disappear by turning clear, transparent glass into mirrors.

The group, from the National Institute of Advanced Industrial Science and Technology (AIST), has designed and produced the first full-size sample of switchable mirror glass to be realistically compatible in buildings, houses and cars.

A switchable glass is glass with adjustable transparency or color, or in this case, reflective properties. Scientists Kazuki Yoshimura and Shanhu Bao experimented with improving the characteristics of previous switchable glass by using magnesium-titanium alloy as the switchable film. Two glass sheets of 60 x 70 cm (24 x 28 in) made up the window structure, and each had an interior coating of 40-nm-thick magnesium-titanium alloy, plus a 4-nm-thick layer of palladium.

According to Yoshimura and Bao, finding the correct alloy mixture was essential to producing a transparent and energy efficient switchable glass. Previous attempts at switchable glass faced commercialization problems such as being too expensive (e.g. yttrium and lanthanum), or having a yellowish tint that was unsuitable for cars or clear viewing (e.g. magnesium-nickel).

While other types of switchable glasses have already been commercialized, these varieties tend to have minimal advantages in energy efficiency. For example, electrochromatic glass, which works by using electrical signals to change color and absorb sunlight, reaches high temperatures that often end up re-radiating infrared radiation in the room.

The switching mechanism in Yoshimura and Bao’s window, on the other hand, is done by altering the gas content between the two glass panes. By introducing a small amount of hydrogen into the atmosphere between the panes, the glass acts as a transparent window. Alternatively, adding a small amount of oxygen with no hydrogen forms a reflecting mirror.

“Small amounts of hydrogen and oxygen for use in the switching process can be readily generated by decomposition of water,” the scientists reported. “The thin film showed excellent switching characteristics. . . . The change between states is very impressive.”

By applying this switchable glass to windows in homes, offices and cars, the scientists estimate that reduced air conditioning needs could result in an energy savings of up to 30%. Scientists at the AIST are currently working on maximizing the durability of the switchable glass, and overcoming the deterioration that arises due to repeated switching. Also, because the magnesium-titanium alloy can be applied to transparent materials besides glass, more applications may yet be discovered.

By Lisa Zyga, Copyright 2007 PhysOrg.com.
All rights reserved. This material may not be published, broadcast, rewritten or redistributed in whole or part without the express written permission of PhysOrg.com.

Explore further: Global scientific team 'visualizes' a new crystallization process (w/ video)

add to favorites email to friend print save as pdf

Related Stories

"Intelligent" windows in our future

Sep 03, 2012

Windows are a high-tech venture. Empa researcher Matthias Koebel's "Winsmart" project has garnered the attention of EU experts, recently being recognized as the best in its class and receiving about €3.8 ...

Recommended for you

Novel technique opens door to better solar cells

Apr 14, 2014

A team of scientists, led by Assistant Professor Andrivo Rusydi from the Department of Physics at the National University of Singapore's (NUS) Faculty of Science, has successfully developed a technique to ...

Probing metal solidification nondestructively

Apr 14, 2014

(Phys.org) —Los Alamos researchers and collaborators have used nondestructive imaging techniques to study the solidification of metal alloy samples. The team used complementary methods of proton radiography ...

Glasses strong as steel: A fast way to find the best

Apr 13, 2014

Scientists at Yale University have devised a dramatically faster way of identifying and characterizing complex alloys known as bulk metallic glasses (BMGs), a versatile type of pliable glass that's stronger than steel.

User comments : 0

More news stories

Robotics goes micro-scale

(Phys.org) —The development of light-driven 'micro-robots' that can autonomously investigate and manipulate the nano-scale environment in a microscope comes a step closer, thanks to new research from the ...

Biologists help solve fungi mysteries

(Phys.org) —A new genetic analysis revealing the previously unknown biodiversity and distribution of thousands of fungi in North America might also reveal a previously underappreciated contributor to climate ...