By tapping into wooden flooring as an energy source, researchers from Switzerland have developed an energy-harvesting device that uses wood with a combination of a silicone coating and embedded nanocrystals to produce enough energy to power LED light bulbs and small electronics.
The device, called a nanogenerator, is based on sandwiching two pieces of wood between electrodes, where the wood becomes electrically charged due to contact and separation when stepped on through the 'triboelectric effect'.
This effect occurs when electrons are able to transfer from one object to another, similar to the static electricity produced when you rub a balloon your hair for a few seconds.
Senior study author, Guido Panzarasa explained that when a material is tribo-positive it tends to lose electrons, whereas if it is tribo-negative it tends to attract electrons. He noted that it is beneficial, given the material is a natural and renewable resource that also stores carbon dioxide.
"Wood doesn’t have a strong tendency to lose nor attract electrons. As such, wood is a terrible triboelectric material, but wood is an excellent building material".
To boost wood's triboelectric properties, the researchers coated one piece of it with a common silicone that gains electrons upon contact, while the other piece was embellished with nanocrystals that have a tendency to lose electrons. The scientists found that radially cut spruce generated 80 times more electricity than natural wood.
Using a wood floor prototype slightly smaller than an A4 piece of paper produced enough energy to drive household LED lamps and small electronic devices such as calculators.
Panzarasa added: "Our focus was to demonstrate the possibility of modifying wood with relatively environmentally friendly procedures to make it triboelectric. Spruce is cheap and available and has favourable mechanical properties".
Professor Nick Jenkins, the leader of the centre for integrated renewable energy generation and supply research group at Cardiff University, commented on the research, suggesting the typical application of such an energy source could be powering an Internet of Things device.
"Of course, if a continuous supply of energy were required, such as for lighting, then this would need continuous motion to provide the input power".
Panzarasa warned that the technology needed more work before it could be scaled up for industrial use, and they have been focusing their attention on developing the approach to make it more industrially friendly, which may include sacrificing the overall efficiency in favour of easier methods of a wood modification.
"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".
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