A solar panel that can generate electricity from falling raindrops has been invented, enabling power to flow even when skies cloud over or the sun has set. New device is designed to prevent power output plummeting when the sun isn’t shining – but practical application is still some years off

Solar power installation is soaring globally thanks to costs plunging 90% in the past decade, making it the cheapest electricity in many parts of the world. But the power output can plummet under grey skies and researchers are working to squeeze even more electricity from panels.

The new device, demonstrated in a laboratory at Soochow University in China, places two transparent polymer layers on top of a solar photovoltaic (PV) cell. When raindrops fall on to the layers and then roll off, the friction generates a static electricity charge.

“Our device can always generate electricity in any daytime weather,” said Baoquan Sun, at Soochow University. “In addition, this device even provides electricity at night if there is rain.”

Other researchers have recently created similar devices on solar panels, known as triboelectric nanogenerators (Tengs), but the new design is significantly simpler and more efficient as one of the polymer layers acts as the electrode for both the Teng and the solar cell.

“Due to our unique device design, it becomes a lightweight device,” said Sun, whose team’s work is published in the journal ACS Nano. “In future, we are exploring integrating these into mobile and flexible devices, such as electronic clothes. However, the output power efficiency needs to be further improved before practical application.”

Sun said the field was developing fast and expects to produce a prototype product in three to five years. Other scientists in China have also used Tengs on solar cells to harvest some power from the wind, an approach Sun said could be added to his device. The top layer of the Teng is also grooved to help focus more light on the solar cell, according to The Guardian.