These leaf-shaped generators, or “power plants,” could be used in cities, beaches or homes as clean, self-powered energy sources.
Fake plants are more than just a decoration –– they could be part of the next clean energy revolution.
Researchers have created literal power plants, small leaf-shaped generators that produce electricity using wind and rain. The generators, which involve a combination of different kinds of small-scale sensors and electrodes, can be placed among the leaves of fake plants to blend in or encompass the entirety of a fake plant’s foliage. They are small but mighty.
Ravinder Dahiya, a professor of electrical and computer engineering and a member of the research team, says these 21st-century fake plants could be used as clean, self-powered energy sources in cities, beaches or even homes. They could power lights on your balcony or sensors that measure gas levels in a certain area.
“In this case, we thought you always have some wind blowing or breeze going on, particularly in areas like the beach where you don’t have an energy supply as well,” Dahiya says. “Then you can power the sensor, and if sensor powering is not needed, then you can store the extra energy in batteries and use it for later.”
Although there is no shortage of natural energy sources –– the sun, wind and rain –– the researchers realized early on that they would need more than one energy source for their power plants. If it’s not raining, then a purely rain-based, or droplet-based, generator would be useless. But used with a wind-based generator, the team ensured that there would always be a source of energy.
The researchers built two different kinds of energy collectors to integrate into the power plants. The triboelectric nanogenerator (TENG) captures kinetic energy from wind, and the droplet-based energy generator (DEG) collects the energy from falling raindrops.
The TENG is made from a layer of nylon nanofibers placed between layers of Teflon and copper electrodes. When pressed together by wind or other forces, the layers generate static charges that are then converted into electricity.
The DEG, which also uses Teflon, is waterproof and covered in a layer of conductive fabric. As raindrops fall and strike electrodes on the DEG, it generates energy. The longer the droplet travels along the “leaf,” the more energy it generates.
It’s actually one reason why the researchers shaped their energy generator like a leaf, Dahiya says. The surface needs to be hydrophobic to prevent the rain drop from breaking apart as it slides down the “leaf,” losing its energy-generating potential. Some plants, like the lotus flower, are perfect natural examples of how this property works in action, Dahiya says.
The researchers mounted the DEG on top of the TENG and produced a leaf-shaped energy generator that could be placed in an artificial plant or used to create an entire artificial, energy generating power plant. Eventually, Dahiya says the goal is to integrate these generators into organic plants.
Currently, the TENG produces 252 volts and the DEG 113 volts of power, respectively. One leaf was capable of powering 10 LED lights in short bursts. A full power plant with about 20 leaves could, conceivably, power 200 LEDs, Dahiya says.
“As far as this working for a short period, the answer to that is you can always have an energy storage device, such as a supercapacitor,” Dahiya says. “And we have demonstrated in the past how the charge produced from the triboelectric energy harvester can be stored in a supercapacitor. Then, the supercapacitor can provide continuous power.”
Dahiya says the short flickers of power produced by the power plants are actually a benefit, especially when it comes to near-zero power sensors, which have become increasingly popular.
“If it is lighting, you need continuous power, but if it’s sensors designed just to measure, say, gases in a certain area, you don’t need continuous measurement,” Dahiya says. “For that, these short pulses of power supply may be good enough.”
But Dahiya and the team are also thinking bigger. The hope is to create larger networks of these “power plants” that could serve as a new kind of clean energy for entire systems that relies simply on wind, rain and plants. What would a city full of power plants look like?
“Think about an urban setting with road dividers where you have these plants,” Dahiya says. “If we can make these energy harvesters actually integrated with the real leaf, not just on the synthetic, then while traffic is moving, you have some wind going and it’s continuously being generated. That could be a kind of scenario where you could see energy being generated all the time.”