Inspired by solar panels, researchers harvest energy from raindrops

This could herald a new option in the mix of renewable energy sources.
Ameya Paleja
Stock image of a heavy rain that could be a source of power one day
Stock image of a heavy rain that could be a source of power one day


Researchers at Tsinghua University in Shenzhen, China, have turned to the panel arrangement used in solar cells to harness electricity from raindrops falling from the sky. This has helped them overcome long-standing issues in scaling up the approach to generating electricity.

With the world looking to move away from fossil fuels, newer methods that can tap into renewable energy sources to meet our power requirements are always welcome. Raindrops falling from the sky contain kinetic energy that can be theoretically captured and converted into electricity.

This isn't the first time somebody has considered tapping into this resource. Researchers have previously tapped into liquid-solid contact electrification to harvest electricity from devices. Triboelectric nanogenerators (TENG) can also gather electricity from other sources, such as waves but have issues in scaling up.

Harvesting electricity from raindrops

Previous work in this area has led to the development of droplet-based TENG, commonly called D-TENGs. While these devices have very high instantaneous output, one would need multiple D-TENGs to generate the megawatt-level electricity that power plants usually generate.

Connecting multiple D-TENGs would be the most obvious solution to the problem, but it has an undesirable effect. When multiple D-TENGs are connected, there is an unintended coupling capacitance between the upper and lower electrodes, reducing the devices' output.

Inspired by solar panels, researchers harvest energy from raindrops
Illustration to demonstrate what D-TENG panels could look like

A team of researchers led by Zong Li, a professor at the Tsinghua Shenzhen International Graduate School in China, took inspiration from solar panels to set up bridge array generators and reduce the influence of capacitance.

How do bridge array generators help

When raindrops fall on a surface of a panel of the D-TENG, called the FEP surface, the droplet becomes positively charged while the surface becomes negatively charged.

 “The amount of charge generated by each droplet is small, and the surface charge on the FEP will gradually dissipate. After a long time on the surface, the charges on the FEP surface will gradually accumulate to saturation,” said Li in a press release. “At this point, the dissipation rate of the FEP’s surface charge is balanced with the amount of charge generated by each impact of the droplet."

Researchers used bridge array generators with different sizes of sub-electrodes and panels of various thicknesses to see if there was an impact on the power loss. D-TENG panels built with bridge array generators were found to be independent of each other, and that meant that the unintended power loss could be reduced.

"The peak power output of the bridge array generators is nearly five times higher than that of the conventional large-area raindrop energy with the same size, reaching 200 watts per square meter, which fully shows its advantages in large-area raindrop energy harvesting," Li said in the press release.

Increasing the FEP thickness also led to decreased coupling capacitance without affecting the surface charge density, which could be used to further improve the performance of bridge array generators.

The discovery could open up new ways of harnessing renewable energies, especially in areas that see incessant rain for a large number of days in the year.

The research findings were published in the journal iEnergy


Raindrops contain abundant renewable energy including both kinetic energy and electrostatic energy, and how to effectively harvest it becomes a hot research topic. Recently, a triboelectric nanogenerator (TENG) using liquid-solid contact electrification has been demonstrated for achieving an ultra-high instantaneous power output. However, when harvesting the energy from the dense raindrops instead of a single droplet, a more rational structure to eliminate the mutual influence of individual generation units is needed for maximize the output. In this work, a “solar panel-like” bridge array generators (BAGs) is proposed. By adopting array lower electrodes (ALE) and bridge reflux structure (BRS), BAGs could minimize the sharp drop in the peak power output for large-scale energy harvesting devices. When the area of the raindrop energy harvesting device is 15 × 15 cm 2 , the peak power output of BAGs reached 200 W/m 2 , which is remarkable for paving a potential industrial approach for effective harvesting raindrop energy at a large scale.

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