A team of research scientists from City University of Hong Kong (CityU) has recently developed a new droplet-based electricity generator (DEG) that has the potential to generate electricity from rainwater.
The team’s findings were recently published in Nature titled: “A droplet-based electricity generator with high instantaneous power density.”
The scientists are referring to this as a groundbreaking achievement. The team used a field-effect transistor (FET)-like structure, which allows for high energy-conversion. When using the FET-like structure, it increases power density thousands of times and provides instantaneous results.
The research team was led by Professor Wang Zukankai from CityU’s Department of Mechanical Engineering, who worked together with, Professor Wang Zhonglin, the Founding Director and Chief Scientist at the Beijing Institute of Nanoenergy and Nanosystems of Chinese Academy of Sciences, and Professor Zeng Xiaocheng from the University of Nebraska-Lincoln.
Professor Wang talks about the exciting results:
Our research shows that a drop of 100 microlitres [1 microlitre = one-millionth liter] of water released from a height of 15 cm can generate a voltage of over 140V, and the power generated can light up 100 small LED lights.
The team spent two years developing the DEG to improve conversion efficiency. They used a polytetrafluoroethylene film on an indium tin oxide substrate plus an aluminum electrode.
Professor Wang said two crucial factors enabled this new invention. This is explained in the official CityU media press release:
First, the team found that the continuous droplets impinging on PTFE, an electret material with a quasi-permanent electric charge, provides a new route for the accumulation and storage of high-density surface charges. They found that when water droplets continuously hit the surface of PTFE, the surface charge generated will accumulate and gradually reach saturation. This discovery has helped to overcome the bottleneck of the low-charge density encountered in previous work.
Another key feature is a unique set of structures similar to the FET that won the Nobel Prize in Physics in 1956 and has become the basic building block for modern electronic devices. The device consists of an aluminum electrode and an indium tin oxide (ITO) electrode with a film of PTFE deposited on it. The PTFE/ITO electrode is responsible for the charge generation, storage, and induction. When a falling water droplet hits and spreads on the PTFE/ITO surface, it naturally “bridges” the aluminum electrode and the PTFE/ITO electrode, translating the original system into a closed-loop electric circuit.
Professor Wang said he hopes the results of this discovery can be helpful in the future to harvest water energy in response to the global problem of renewable energy shortage. He thinks this design can be applied on many different surfaces in which liquids are in contact with solids, including the surface of umbrellas or inside water bottles. This will fully utilize the low-frequency and kinetic energy in water.
This may end up being an amazing discovery if we can harness the power from rain, this could add another extremely renewable form of energy. Nature has had the answers for us all along, we just needed scientists like Professor Wang to come along and figure this out.
