Electricity From Raindrops

What is DEG?

DEG’s are constructed on the triboelectric effect and generate electricity by materials becoming electrically charged after they are separated from a different material with which they were previously in contact with.

Unfortunately, the quantity of charge produced on the surface of a material is restricted by interfacial phenomena, consequently resulting in an energy conversion efficiency that is extremely small.

What is FET?

CityU’s generator uses a Field-Effect Transistor (FET) to produce considerably higher and instantaneous voltage from raindrops.

FET is a type of transistor that uses an electric field to control the flow of current by the application of a voltage to the gate, which in turn alters the conductivity between the drain and the source.

Increasing Efficiency

To increase conversion efficiency, CityU’s engineering team spent two years creating their own DEG design. Its’ instantaneous power density is thousands of times higher than similar devices not using the FET-like design.

They use PTFE (an electret material with a quasi-permanent electric charge), which provides a new path for the collection and storing of high-density surface charges and is generated by the continuous droplets impacting on its surface.

When droplets of water continuously impact on the surface of PTFE, the surface charge being generated will amass and slowly reach capacity. This helps overcome the limitations of low charge density of interfacial phenomena.

Get Your Geek On

If you really want to get your DEG geek on The CityU’s research teams’ findings were published in the February 5^th, 2020 issue of Nature under the title “A droplet-based electricity generator with high instantaneous power density”.

Here is an excerpt from the article’s abstract summary:

“Here we develop a device to harvest energy from impinging water droplets by using an architecture that comprises a polytetrafluoroethylene film on an indium tin oxide substrate plus an aluminum electrode. We show that spreading of an impinged water droplet on the device bridges the originally disconnected components into a closed-loop electrical system, transforming the conventional interfacial effect into a bulk effect, and so enhancing the instantaneous power density by several orders of magnitude over equivalent devices that are limited by interfacial effects.”

Looks Promising

This new development looks very promising and it can help further research into water energy generation and helping stem the energy crisis.

The research team has expressed the desire to see their technology applied to a large variety of surfaces, wherever liquid meets a solid surface. The possibilities are endless, but the researchers have suggested it for use on boats, umbrellas, rooftops, and water bottles.

Lots of work needs to be done before this technology can be brought to market as a viable product. They will become one step closer as the challenge of accumulating enough energy to create a continuous source of power is met.