The top-hatted “drinking bird,” once a fixture in science classrooms for demonstrating the basics of thermodynamics, is making a surprising comeback — as the inspiration for a new clean-energy generator that could one day power your watch and phone.
Scientists in Hong Kong and China have used the famous toy, also known as the “Dippy Bird,” to develop an engine capable of using the power of water evaporation to generate electricity, according to a study published Thursday in the journal Device.
The new method works by converting the energy produced by the bird’s characteristic back-and-forth movement into electrical power.
The physics behind it is relatively simple: The toy is made up of two glass bulbs, representing the head and body of the bird, which are connected by a long glass tube. Methylene chloride, a highly volatile liquid, is contained within the structure.
After the bird’s beak is dipped into a cup of water, it springs back into its natural upstanding position, and the water begins to evaporate and cool the head. This causes the volatile liquid from the lower bulb to rise up the tube, due to a difference in pressure, and as a result, the bird’s centre of gravity begins to shift, tipping its beak back into the water.
It’s a process that has provided amusement to generations of children and adults alike. But it’s also a process that happens naturally on Earth, and can be harnessed to generate clean energy.
In the natural world, evaporation occurs when sunlight warms the surface of the Earth, breaking the bonds which hold water molecules together. This causes liquid water from oceans, lakes and other surface waters to be converted into vapour. It’s the driving force of the Earth’s natural water cycle.
According to the study, this process uses up half the solar energy absorbed in the Earth’s surface and results in the “most significant amount of energy transfer on Earth.”
If scientists can capture this energy and convert it into electricity, the authors say it could present “a substantial renewable energy opportunity.”
Lead author, Hao Wu, a professor at South China University of Technology, says that the drinking bird method offers a “unique” way to generate electricity using water, a “readily available fuel source.”
“I still feel surprised and excited when witnessing the actual results,” Wu said.
While studying for her post-doctorate degree, Wu realized that the drinking bird model could be more than just “a tool to demonstrate a physics concept”.
“I began to contemplate whether we could convert the evaporation energy into mechanical energy first, and then translate it into electricity,” Wu said. “It was then that the idea of utilizing the drinking bird toy came to mind.”
Wu and her colleagues added two nanogenerator modules — small devices which convert mechanical energy into electricity — to both sides of the bird’s “engine,” which was created from a commercial toy.
They then tested the prototype’s ability to power a range of electronics in ambient conditions, including liquid crystal displays (LCDs), temperature sensors and calculators. The idea is that one day the generator could be used in more commonly used everyday devices.
Until now, previous attempts to convert evaporation energy into electricity have suffered from a low conversion efficiency. But using the drinking bird method, scientists have managed to generate an output of 100 volts using just 100 millilitres of water, enough to power small electronic devices.
The authors claim that their drinking bird generator can yield much more power than previous experiments that used other methods were able to.
The team’s next goal is to design its own drinking bird that can harness the power of evaporation more efficiently.
If they’re successful, the retro drinking bird may be here to stay.
