Smart window that tints and powers itself invented

Scientists have developed a smart window which can darken or brighten without the need for an external power source and it can also function as a battery.
The unique self-tinting window developed by scientists from the Nanyang Technological University (NTU) requires zero electricity to operate.
The window can also act as a rechargeable battery. The stored energy can be used for other purposes, such as to light up low-powered electronics like a light emitting diode (LED), researchers said.
Currently, the windows in the market are either using permanent tinting which cannot brighten at night or are windows that can change its light transmission properties only with an external power source.

The NTU smart window however can be turned into a cool blue tint in bright daylight, cutting light penetration by about half, and then reverts back to clear glass at night or as required.
The trick to making the self-powered smart window is a new technology developed by NTU Professor Sun Xiaowei's team.

"Our new smart electrochromic window is bi-functional; it is also a transparent battery. It charges up and turns blue when there is oxygen present in the electrolyte - in other words, it breathes," Sun explained.
The window contains liquid electrolyte placed in between two glass sheets coated with indium tin oxide (ITO), commonly used as transparent conductive coatings for television displays.

One sheet is coated with an additional layer of a pigment known as Prussian Blue and the other one is attached to a thin strip of aluminium foil. The Prussian Blue gives the glass a blue tint when it is fully charged.
The two glass sheets are connected by typical electrical cables. 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 colourless Prussian White.

Such an innovative technology can adjust the amount of sunlight coming into buildings in the day, which promises significant savings on cooling and lighting costs.
The research was published in Nature Communications.