Sustainable smart buildings of the future may get their energy from your footsteps. Researchers from ETH Zurich in Switzerland, Chongqing University in China, and Northwestern University in Illinois have found a way to tap into an unexpected energy source right under our feet, which can make this a reality.
To generate electricity from wooden flooring through our footfalls, the researchers developed an energy-harvesting device, known as a nanogenerator, that employs wood with a silicone covering and embedded nanocrystals. The device can generate energy to power LED lightbulbs and other gadgets, per the study published in the journal Matter.
It's made up of two pieces of wood sandwiched between electrodes, and when stepped on, the wood pieces get electrically charged due to contact and separation, which is a phenomenon known as the triboelectric effect, since the electrons can transfer from one object to another.
However, there is a catch: wood does not have a natural inclination to gain or lose electrons, which limits its potential to generate electricity. To tackle this problem, the researchers coated one piece of wood with silicone, which rapidly acquires electrons when it comes into touch, and embedded the other piece with metal ions and organic molecules, which causes it to lose electrons more readily.
The researchers discovered that using a wood floor prototype with a surface area barely smaller than an A4 piece of paper provided enough energy to power home LED lighting and tiny gadgets such as calculators. They were able to successfully lit a lightbulb using the prototype when a human adult walked on it.
The researchers found that a nanogenerator made with radially cut spruce, which is a common wood in Europe that is cheap and available with desirable mechanical properties, was superior. With the treatments, they were able to get 80 times more electricity than natural wood and the electricity output remained stable under steady forces for up to 1,500 cycles. Guido Panzarasa, senior author and group leader at the professorship of Wood Materials Science at the Eidgenössische Technische Hochschule (ETH) Zürich and the Swiss Federal Laboratories for Materials Science and Technology (Empa) Dübendorf, says their approach is simple and scalable on an industrial scale. "It's only a matter of engineering," he explained.
It should be noted that this was proof-of-concept data, and further work is required before the system can be scaled up for industrial usage.
"We have been focusing our attention on developing the approach to make it even more industrially friendly. And for this we need to maybe sacrifice the overall efficiency in favor of easier methods of a wood modification," Panzarasa said. "So that even though the electrical output of a single device would not be as high as the one we published, the union of many devices across a larger flooring unit will eventually produce a significant amount of energy."
If the gadget can be scaled up, wood nanogenerators could become commonplace in sustainable smart buildings of the future, aiding in the mitigation of climate change over their lifetime.