Color-changing windows harvest energy from wind, rain

Chuck Bednar for redOrbit.com – @BednarChuck

Smart windows that can harvest electricity from wind or precipitation could be a future source of renewable energy, according to new research published recently in the journal ACS Nano.

According to Science, the windows were able to produce up to 130 milliwatts per square meter, which would be enough to power a smartphone in sleep mode, and Dr. Zhong Lin Wang, co-developer of the technology and a nanoscientist at the Georgia Institute of Technology, and his colleagues believe that it could ultimately serve as a power source for some electronics.

Breaking down the smart window technology

The glass used in this new smart window technology uses nanoscale generators that are powered by static electricity produced by friction when two materials come into contact with one another. The generators are placed in two layers atop a lone pane of glass, and once activated, they create an electric current that tins the clear window a dark shade of blue, Science explained.

The generators that make up the outermost layer harvest static energy from precipitation. As a raindrop falls, the contact between air and water creates a positive charge in the droplets. Since the glass is coated with a negatively charged silicone material known as polydimethylsiloxane, an electric current is produced after the raindrop makes contact with the window’s surface.

Located beneath the first layer of nanogenerators is a second that harvests energy from the wind, the website added. This layer 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 compress and cause charged plates of plastic approach one another, creating an electric current.

Promising research, but there is still work to be done

In their study, Dr. Wang and his colleagues explained that the self-powered system “is a promising concept for wireless networks due to its independent and sustainable operations without an external power source.” They added that their work is “a substantial advancement toward the practical application of nanogenerators and self-powered systems.”

However, Science pointed out that there are still obstacles to overcome before the technology could become commercially available. Currently, the glass has no way to store the energy that it generates, the website said. To fix the issue, Liming Dai, a nanomaterials engineer at Cleveland-based Case Western Reserve University who was not involved in the research, told the website that see-through supercapacitors could be embedded into the glass without harming visibility.

“My research over the last 10 years has been to build the self-powered system so that a device operates by the energy acquired from its working environment without purposely apply an electric power,” Dr. Wang told redOrbit via email, adding that this was the “major motivation” that inspired he and his colleagues to develop the nanogenerator-based system.

He said that the success of their wind- and rain-converting window was an “outstanding” step forward in the field of self-powering technology. Such advances could infinitely extend the life of a battery “by constantly charging it using the energy converted from the environment,” Dr. Wang added. “This type of research has important applications in sensor networks, wearable electronics, personal electronics, medical science, national security and environmental science.”

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