Power players get drop on field

Local | Erin Chan 7 Feb 2020

Erin Chan

Local scientists have found a groundbreaking method to efficiently generate electricity - by making use of falling water.

Despite the prominence of droplet-based energy generators, which collects the kinetic energy of a falling water droplet when it impinges the surface of the device, its potential to be converted into electrical energy cannot be fully maximized due to technological limitations.

However, a research team at the City University of Hong Kong has spent two years developing a new version of the generator by adding a field-effect transistor-like structure - a specially-designed system that uses an electric field to control the devices' current flow.

The field-effect transistor technology is considered the basic building block of modern electronic devices.

The team has proved that the transistor-like structure allows high energy conversion efficiency through higher power density.

Its instantaneous power density can reach up to 50.1 watts per square meter, thousands of times higher than similar devices without the field-effect transistor-like structure.

It is believed that the findings would be able to provide wider insights into hydropower and ease the energy crisis.

"Our research shows that a drop of 100 microliters of water released from a height of 15 centimeters can generate over 140 volts, and that power can light up 100 small LED lights," Wang Zuankai from the department of mechanical engineering said yesterday.

A video released by the university showed that 400 LED light bulbs can be instantly powered by continuous droplets hitting on four individual droplet-based electricity generators that are fitted with the transistor-like structure.

Led by Wang alongside Zeng Xiaocheng from the University of Nebraska-Lincoln's department of chemistry and Wang Zhonglin from Beijing Institute of Nanoenergy and Nanosystems of the Chinese Academy of Sciences, the study was published in the latest issue of the UK-based scientific journal Nature.

According to Wang, two critical factors can be attributed to the efficient energy conversion.

One is the magnetized material named PTFE and the second is the field-effect transistor-like structure. When continuous droplets impinge on the surface of the device, these two critical factors allow the high density of charges to be accumulated so that the device can achieve energy efficiency.

Wang believes the new design could be applied and installed on several different surfaces, ranging from the hull surface of a ferry to the surface of umbrellas and the inner surface of water bottles. With a wide range of uses, he hopes that the results of this research study would help utilize water energy, easing the worldwide shortage of renewable energy.

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