Researchers have developed a device that can still draw electrical energy from the weak draft of air that occurs during a brisk walk. Instead of rotors, the wind sets two plastic strips in motion in the system, which keep touching each other when they flutter. In doing so, they build up voltage through the so-called triboelectric effect, which can be used. The researchers say that there is potential for the development of alternative concepts for generating wind energy.
Fossil fuels and nuclear power are out – sustainable energy generation is the order of the day! One of the most effective and inexpensive options is to generate electricity from wind energy. In many places, the rotors are turning – but only when the wind is strong enough. Against this background it becomes clear: Much of the wind available on land is too weak to set commercial wind turbine blades in motion. Further disadvantages are noise pollution and negative aesthetic effects of the often large systems. There is thus potential for the development of alternative methods of generating energy from wind.
With the concept that Ya Yang’s researchers from the Chinese Academy of Sciences in Beijing are presenting, nothing needs to be set in a rotary motion. It is a generator, the power of which is based on the fluttering of two closely spaced plastic strips in a tube. Even a weak wind can stimulate them to wave-like movements in which they continuously come into contact with each other and then become separated again.
A well-known effect – used cleverly
As the researchers explain, this leads to a so-called triboelectric effect, the effect of which everyone is familiar with: for example, it leads to an electric shock when touching surfaces, if one has previously been charged by walking over a carpet. Another well-known example is the balloon trick: if you rub the plastic structure on surfaces, you can then use it to make hair stand on end. The triboelectric effect responsible for the electrical charge can, however, also arise from the mere contact and the subsequent separation of certain materials.
For their system, the researchers have produced strips made of a layered material that charges easily and has conductivity mediated by silver molecules. It is also very flexible so that the strips can easily be made to flutter with a movement of air. The scientists explain that through the continuous contact and separation movements of two strips, voltage can be generated by the triboelectric effect, which can be used to generate electricity. The special thing about it is that even very weak air movements are enough to get the system going. In their prototype, the researchers used two eight centimeter long and three centimeter wide strips that are two centimeters apart.
Fluttering alternative?
As the tests showed, a breeze at a speed of 1.6 meters per second was enough to drive the triboelectric generator. This air movement would result from a walk at a speed of 5.7 kilometers per hour. “The system can be used to capture air movements as they arise in everyday life,” says Yang. “We put our generator on a person’s arm once, and the airflow when the arm was swinging was enough to generate electricity,” says the scientist.
The researchers report that the strips begin to flutter particularly efficiently from an air speed of four meters per second. The prototype finally reaches its maximum output at eight meters per second: it can deliver 43 microamps and generate 2.5 milliwatts. This enabled the system to light up 100 LED lamps, among other things. “We do not intend to replace the existing technology for generating wind energy. Our goal is to tackle problems that traditional wind turbines cannot solve, ”emphasizes Yang.
He and his colleagues now want to further explore the potential of the system for both small and large applications. Because it may also be scalable to achieve higher performance. “We could then place such devices where the use of traditional wind turbines is problematic,” says Yang. Triboelectric generators could also be used in nature reserves or cities, for example, since there are no rotating structures, ”says the scientist. So it will be interesting to see what will develop from the “fluttering” energy generation concept.
Source: Cell Press, technical article: Cell Reports Physical Science, doi: 10.1016 / j.xcrp.2020.100207
Video: Chen, Ma, and Ren et al./Cell Reports Physical Science