What if your umbrella could charge your cellphone? That unpredictable tech just got a bit closer to reality now that scientists have made a tiny, highly efficient electricity generator that can create sufficient charge with a single droplet of rain, tap, or seawater to power 100 LED light bulbs.
The researchers hope that, besides solar and wind power, the approach can help fight the world’s energy crisis. Evidently, generating electricity with water is nothing novel. But the research, published on Wednesday in the journal Nature, looked at how an exclusive connection between the generator interface and the water droplets amplified the generator’s overall power.
By covering their droplet generator in a material with a near-permanent electric charge, the team witnessed that their generator was able to leisurely collect charge from steadily falling droplets and store it till it reaches its capacity. This allowed the generator to convert the droplet’s energy more efficiently. From only a single drople,t the generator was able to produce enough power to power 100 small LED light bulbs, and with only four droplet,s it could light 400.
While similar water droplet experiments have also verified the ability to transform water into energy in the same way, the authors write that the instantaneous power created by their coated generator was thousands of times more than former approaches that did not have the coating.
“The importance of this technology is the much improved electric power per falling rain droplet, which turns the device much more efficient to change energy from a falling droplet to electricity,” said Xiao Cheng Zeng, a co-author on the research and professor of chemistry at the University of Nebraska-Lincoln
The generator’s high efficiency didn’t come from only the coating alone. When observing closer at their generator, the team saw that the generator experienced no peak in electric output when droplets at first hit the coated surface. It was only when the droplet started to spread out upon the impact that the spike happened. The team found that the droplet spreading and touching an aluminum electrode on the interface’s surface joined earlier disconnected parts of the interface and made a closed circuit. The authors write that the droplet functioned as the resistor while the surface coating functioned as the capacitor.
This connection permitted for the coated surface to store charge from steadily falling droplets and then emit that charge at peak electrical power when the droplets spread and join the two ends of the circuit.
Although this study looked at how droplets falling from mere centimeters above the generator would behave, the study’s chief author and professor of mechanical engineering at the City University of Hong Kong, Zuankai Wang, said that their design is broad enough to be used in other situations as well.
“Our design is broad, which means the design can be stretched to harvest energy of a water wave and even encircled water inside a tube. It does not have to use the impacting droplet,” says Wang. Wang said that the technology still has hurdles to overcome (for instance, electrode corrosion) before their technology could be progressed beyond the lab, but that he expects within five-years to have a large scale proof-of-concept.