The system developed by researchers at the National University of Singapore (NUS) exploits a phenomenon known as “plug flow”. Concretely, raindrops penetrating vertical tubes just two millimeters in diameter (thinner than a USB cable) where they alternate with air pockets. Inside, the drops slide across a conductive surface made of a special polymer and stainless steel. This contact causes a separation of the electrical charges naturally carried by each drop, charges then recovered by electrodes placed at the base of the device.

The results are remarkable, the system converts more than 10% of the kinetic energy of the drops into electricity, i.e. a power density of around 100 W/m². This efficiency is 5 times higher than that of a conventional continuous flow of water. In laboratory tests, two tubes are enough to power 12 LED bulbs for 20 consecutive seconds. Installation on building roofs would be the most immediate application, particularly in tropical cities exposed at regular intervals. The researchers point out that the system is even more efficient when the drops flow slowly, which suggests an even greater potential in real conditions.

This advance, although in an experimental phase, draws the contours of a future where each downpour could contribute to the electricity supply of cities.