The electricity generator, inspired by the drinking bird toy, powers the electronics with evaporating water.

The electricity generator, inspired by the drinking bird toy, powers the electronics with evaporating water.

Inspired by the classic drinking bird toy, scientists from Hong Kong and Guangzhou (China) have developed an engine that efficiently converts the energy of water evaporation into electricity to power small electronics. According to a study published March 14 in the journal Device , the device produces more than 100 volts — far higher than other technologies that generate electricity from water — and can run for days using just 100 milliliters of water as fuel.

“The drinking bird triboelectric hydroelectric generator offers a unique means of powering small electronics in open spaces by using water as a readily available fuel source,” said Hao Wu, a professor at South China University of Technology and first author of the study. “I’m still amazed and excited when I see the real results.”

A toy in the form of a bird has been an integral attribute of science classes for several decades. The toy consists of two glass flasks connected by a glass tube, in which a volatile liquid is stored – methylene chloride.

The top of the bulb, which includes the bird’s beak and decorative cap, is covered with a felt-like material, and the bird’s body is suspended on two plastic legs. After the bird’s head is immersed in a glass of water, the water begins to evaporate. The result is a pressure difference that causes the liquid in the lower flask to rise up the tube until it fills the “head”, forcing the bird to dive into the water to “drink” before the process starts again.

A “Drinking Bird” device that powers 20 LCD displays.

When Wu was a postdoc in Prof. Xuankai Wang’s group at the Hong Kong Polytechnic University and puzzled over how to generate a higher voltage at the output of an evaporative energy generator, she remembered the “Drinking Bird” toy and was struck by the idea that it could be to be used not only as a tool to demonstrate physical concepts.

“I started to think about whether it is possible to first convert the energy of evaporation into mechanical energy and then convert it into electricity,” says Wu. “That’s when I came up with the idea of ​​using a toy in the form of a drinking bird.” Thanks to this inspiration, the concept of the triboelectric hydroelectric generator was born.

To create the generator, Wu and his colleagues placed two triboelectric nanogenerator modules, which harvest mechanical energy, on either side of a drinking bird motor, which they reconstructed from a commercial drinking bird toy. The researchers tested the prototype with a variety of small electronics, using it to power 20 liquid crystal displays (LCDs), temperature sensors and calculators.

Temperature distribution over the bird feeder.

Overcoming the friction that slowed down the generator was one of the research’s main challenges, Wu says. The researchers attached the patterned fibers as charge transfer materials in the triboelectric nanogenerator modules. This strategy helped reduce friction and allowed the device to run more smoothly.

In the next phase of their research, the team plans to develop a new drinking bird, rather than using a commercially available toy, to more efficiently convert water evaporation into electrical energy.

“Furthermore, we will explore the various possibilities of using this device to create a practical product that can be used in everyday life,” says Zhuangkai Wang, the author of this study and a professor at the Hong Kong Polytechnic University.

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