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Bi-functional, self-tinting smart window doubles as rechargeable battery


 [Image above] Credit: Nanyang Technological University 


During winter, it’s easy to feel as though I’m not getting enough quality time with the sun. (Perhaps a quick jaunt to Pantelleria is in order?) So when the sun’s out, my blinds are open long and wide.

Wouldn’t it be nice if on those sunny days we didn’t have to draw back and close the shades?


Credit: Nanyang Technological University

Researchers at Nanyang Technological University (NTU) have found a solution to this admittedly first-world problem by developing a self-tinting smart window that brightens and darkens on its own and without an external power source.

This smart window is extra smart, say researchers. It doubles as a recharageble battery, requires no electricity, and can store enough juice to power low-power electronics like LEDs. Cool blue in daylight and clear at night, the tint-shifting window also reduces light penetration by close to 50%.

The work of the NTU team, led by Sun Xiaowei, professor at the university’s School of Electrical and Electronic Engineering, has been published in Nature Communications.

“Our new smart electrochromic window is bi-functional; it is also a transparent battery,” says Sun in an NTU news release. “It charges up and turns blue when there is oxygen present in the electrolyte—in other words, it breathes.”

To create their bi-functional battery-window, Sun and colleagues placed liquid electrolyte between two indium tin oxide-coated sheets of glass connected by electrical cables. On one of the two sheets, they added Prussian Blue, and to the other, a strip of aluminum foil.

According to the release, “When the electrical circuit between them is broken, a chemical reaction starts between Prussian Blue and the dissolved oxygen in the electrolyte, turning the glass blue. To turn off the blue tint, the electrical circuit is closed to discharge the battery, turning the Prussian Blue into a colorless Prussian White.”


Credit: Nanyang Technological University

Because it’s energy independent and adjusts on its own, Sun and team believe that their smart window could provide “significant” cooling and lighting savings for homeowners and businesses.

“Our technology is very attractive as a zero-sum consumption smart window,” says Sun. “Buildings owners and even common households can reap energy savings right from the outset and over the long term. Developers who are looking at constructing environmentally-friendly green buildings will find our technology attractive for their building plans.”

The paper is “A bi-functional device for self-powered electrochromic window and self-rechargeable transparent battery applications,” (DOI: 10.1038/ncomms5921).

Would you install a smart window in your home or office? Why or why not?

For some related reading, click here for a recent post about another window that proves it can be both beautiful and smart.