Power generating floor from waste – thanks to triboelecric effect

Photo: People walking across energy-harvesting floor

Visitors to UW–Madison’s Union South walk across a section of floor designed and installed by College of Engineering researchers to capture the energy of footsteps and turn it into usable electricity. Photo: Adrienne Nienow

As thousands of visitors each day walk across a new flooring installation in UW–Madison’s Union South this fall, they might not realize they’re participating in what could very well represent a leap into the future of renewable energy production.

A research team led by Xudong Wang, a University of Wisconsin–Madison professor of materials science and engineering, in collaboration with the UW–Madison Grainger Institute for Engineering, has installed a high-tech flooring prototype that harvests the energy of footsteps and converts it into electricity.

Photo: Xudong Wang holding piece of wood used in energy-harvesting flooring

Xudong Wang holds a sample of the energy harvesting technology, which uses wood pulp and harnesses nanofibers. Photo: Stephanie Precourt

The prototype is a 96-square-foot rectangle of modified wood flooring panels located inside the building’s West Johnson Street and Orchard Street entrance. It looks just like typical wood flooring, but its low-tech facade masks innovative technology that could soon contribute to the expanding suite of renewable energy options. The power-generating floor includes an additional green credential in that its functional component is mostly made from recycled wood pulp, an abundant waste material.

The wood pulp is central to the technology’s function. The pulp, which is already a common component of flooring, is chemically treated to produce an electrostatic charge when it comes into contact with an embedded electrode.

The charge is transmitted through embedded wires, and can power lights or charge batteries. And because wood pulp is a cheap, abundant and renewable waste product of several industries, flooring that incorporates the new technology could be as affordable as conventional materials.

While there are existing similar materials for harnessing footstep energy, they’re costly, nonrecyclable and impractical at a large scale. That’s why Wang is so excited about the prototype installation in Union South, which is the result of research first published in the journal Nano Energy in 2016.

Photo: Display board showing energy captured

The electricity-producing flooring installation includes a monitor displaying the energy captured as visitors walk across the panels. Photo: Adrienne Nienow

“This is the first on-site demonstration of our technology,” Wang says. “It shows an exciting path leading materials science technology from the lab toward a real product. It’s also an intriguing technology for energy savings, and is beneficial to our environment.”

Wang’s research centers on the use of mechanical energy sources to generate electricity. For years, he has engineered different materials to improve a technology called a triboelectric nanogenerator. Triboelectricity is the same phenomenon that produces static electricity on clothing. Chemically treated cellulose nanofibers are a simple, effective, low-cost alternative for harnessing this mechanical energy source, Wang says.

The UW–Madison team’s advance is the latest in a green energy research field called “roadside energy harvesting” that could, in some settings, rival solar power — and it doesn’t depend on fair weather. Researchers like Wang who study roadside energy harvesting methods see the ground as holding great renewable energy potential well beyond its limited fossil fuel reserves.

“Roadside energy harvesting requires thinking about the places where there is abundant energy we could be harvesting,” Wang says. “We’ve been working a lot on harvesting energy from human activities. One way is to build something to put on people, and another way is to build something that has constant access to people. The ground is the most-used place.”

“This is the first on-site demonstration of our technology. It shows an exciting path leading materials science technology from the lab toward a real product.”

Xudong Wang

Someday soon, flooring like the new prototype in Union South could be used in high-traffic spaces to generate power for overhead lighting or smart building sensor networks. The campus prototype powers an electronic informational sign that explains the technology and tracks the power harnessed by thousands of footsteps over the coming months.

“Our initial test in our lab shows that the technology works for millions of cycles without any problem,” Wang says. “We haven’t converted those numbers into years of life for a floor yet, but I think with appropriate design, the technology can outlast the floor itself.”

The Wisconsin Alumni Research Foundation holds the patent to the flooring technology, and supported its development through its Accelerator Program. The prototype in Union South is the product of a collaboration among UW–Madison’s College of Engineering, Wisconsin Union and offices of Risk Management and Environment, Health and Safety and the U.S. Department of Agriculture’s Forest Products Laboratory.

Material Provided by University of Wisconsin-Madison

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