Until now, a large amount of water was required to enjoy some electrical energy. This project, led by scientists from the City University of Hong Kong (CityU), can open a new window to obtain electrical energy with the minimum possible use of water.
A research team has developed a new form of water droplet-based electricity generator (DEG) that could generate enough power from a single droplet of rain to light up 100 LED bulbs.
The droplet-based electricity generator has a structure similar to a field-effect transistor (FET): it allows a very high energy conversion efficiency. It has thousands of times more power density compared to electric generators with a different structure.
“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,” says Professor Wang Zuankai from CityU’s Department of Mechanical Engineering.
The design of the energy generator includes two electrodes – one made of aluminum and the other made of an indium tin oxide (ITO) electrode with a film of PTFE deposited on it, which is responsible for the charge generation, storage, and induction.
When the falling droplet hits the second (PTFE/ ITO) surface, it naturally “bridges” (connects) the two electrodes, translating the original system into a closed-loop electric circuit. It then releases all the stored charges on the PTFE for the generation of electric current to power the lights.
The researchers also found that the technique is not affected by lower relative humidity and works with both rainwater and seawater. According to the research team, the potential capabilities of the project are very remarkable. In fact, it is expected that this technology can generate up to a maximum of 50 megawatts per square meter. It is thousands of times higher than similar devices, and the energy conversion efficiency is also considerably higher.
Professor Wang pointed out that there are two crucial factors for the invention:
- The continuous droplets affecting polytetrafluoroethylene (or PTFE), a material with an almost permanent electric charge, provide a new path for accumulating and storing high-density surface charges.
- When water droplets continually hit the PTFE surface, the generated surface charge builds up and gradually reaches saturation.
This new discovery helped overcome all the problems of previous generators.
Professor Wang believes that the new design can be applied and installed on different surfaces that bring liquids into contact with solids in the long term. For example, the surface of the hull of a ferry, an umbrella, the glass of a window, even the inside water bottles. In this way, it will be possible to take full advantage of the low-frequency kinetic energy in water.
He hoped this research would help collect water energy to address the global problem of renewable energy shortages.