A research team led by scientists from the City University of Hong Kong (CityU) has developed a new form of water droplet-based electricity generator (DEG).
The DEG electric generator has a structure similar to that of a transistor: it allows a very high energy conversion efficiency. Its instantaneous power density is increased by thousands of times compared to generatori elettrici with a different structure.
This groundbreaking achievement can help advance scientific research on hydroelectricity.
The result is the result of a joint effort between three universities in the USA, China and Hong Kong. To be precise, it was conducted by the professor Wang Zuankai of the mechanical engineering department of the CityU. Professor collaborated with him Zeng Xiaocheng of the University of Nebraska-Lincoln, in the USA. A third phase of the project was then developed by Professor Wang Zhonglin, founding director and chief scientist of the Institute of Nanoenergy and Nanosystems of the Chinese Academy of Sciences in Beijing.
Their discovery was published in the latest issue of the prestigious scientific journal Nature with the title “A droplet electricity generator with high instantaneous power density”.
How the DEG electric generator works
La figure a is the schematic diagram of a DEG, Droplet Energy Generator: a slide coated with indium tin oxide (ITO) and wrapped in a thin Teflon film (PTFE) and an aluminum electrode is placed on top of it. In addition, the water droplets act as a gate to the transistor and complete the circuit when they hit the glass surface. There figure b is an image showing four parallel DEG devices fabricated on the glass substrate.
The difference with other generators
A conventional drip power generator based on the triboelectric effect can generate electricity induced by contact electrification and electrostatic induction when a drop hits a surface. However, the amount of charge generated on the surface is limited by the interfacial effect and, as a result, the energy conversion efficiency is quite low.
To improve conversion efficiency, the research team spent two years developing the DEG. Its instantaneous power density can reach up to 50,1 W / m2. 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:
- Continuous droplets impacting PTFE, a material with a near-permanent electrical charge, provide a new path for the accumulation and storage of 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.
Research shows that a single drop of water released from a height of 15cm can generate a voltage of over 140V, which can illuminate 100 small LED lights.
Professor Wang said he hoped the results of this research could help harvest water energy to address the global problem of renewable energy shortages. He believes that in the long run, the new design can be applied and installed on different surfaces that put liquids in contact with solids. In this way it will be possible to fully exploit the low frequency kinetic energy in the water.
An example? How many do you want? The surface of the hull of a ferry, an umbrella, the glass of a window, even the inside of bottles.
