Smart Window Changes Color and Creates Electricity

By Samba Lampich

It’s unsettling when a strong rain storm brings down power lines and leave entire neighborhoods without electricity. But, what if you could simply plug a cell phone into the window and let it charge as the storm rages on outside?

This alternative source of electricity is an idea Dr. Zhong Lin Wang and his colleagues from the Georgia Institute of Technology have been working on. They recently published their research in the March issue of ACS Nano.

Converting ambient mechanical energy into electricity

The idea is relatively simple: glass, such as that in windows and cars, is often subjected to pouring rain, gusting wind and glaring sun; so why not harvest the energy from these to generate electricity?

To do this the researchers needed to create a device that would take advantage of triboelectric effect – a contact electrification that occurs when two materials come into contact with one another. They invented a triboelectric nanogenerator (TENG) which can effectively convert ambient mechanical energy into electricity.

The resulting self-powered smart window is composed of a raindrop-TENG, wind-powered-TENG and an electrochromic device (ECD). The window is also coated with a negatively charged silicone material known as polydimethylsiloxane.

When the two layers of TENGs are activated by rain and wind the resulting electric charge powers an electrochemical reaction in the ECD that tints the window a translucent blue.

According to the research, the windows were able to produce up to 130 milliwatts per square meter of glass which the researchers point out, is enough to charge smart phone in sleep mode.

The Raindro p-TENG

This outermost layer of nanogenerators takes advantage of the positive charge a raindrop gets as it falls from the clouds and rubs against the air on its way down. When this positively charged raindrop hits the negatively charged glass, an electric current is produced.

The Wind-Powered -TENG

The second layer of nanogenerators is made up of two sheets of charged, transparent plastic separated by nanoscopic spring coils. As wind makes contact with the smart window, the springs are compressed and cause the two charged sheets to approach each other, creating an electric current.

Next Steps

The researchers are now looking at ways to store the power that is generated by the smart glass for use when there is no rain or wind. They also suggest that the smart glass could be used with wireless networks because they generate their own power and don’t require an external power source.