Researchers at the National University of Singapore have developed a novel system that can convert falling raindrops into usable electricity, enough to power 12 LEDs for 20 seconds. The innovation relies on a process called plug flow, where falling droplets move uniformly through a narrow vertical tube, maximizing the charge generated by each drop.

Led by Associate Professor Siowling Soh, the team demonstrated how this flow pattern significantly enhances the generation of electricity from water movement. Unlike conventional hydroelectric systems that require large-scale infrastructure and abundant water sources, this setup uses a simple, compact design involving a metallic needle and a 12-inch (32 cm) tall, 2-millimeter-wide polymer tube.

The key lies in how the droplets interact with the inner conductive surface of the tube. As rain-sized droplets fall and form segmented slugs of water separated by air, they create a dynamic environment that promotes charge separation—similar to the effect of static electricity when a balloon is rubbed on the skin. These charges accumulate along the tube’s surface and are collected at both ends via electrodes, effectively turning the kinetic energy of rainfall into electrical energy.

The system impressively converts over 10% of the water’s potential energy into electricity, making it five orders of magnitude more efficient than continuous water flow systems previously attempted. Earlier designs that relied on nanoscale channels were limited because water resisted flowing through such tight spaces without extra energy input. By scaling up the channel size and leveraging natural droplet motion, the new method avoids this issue entirely.

In additional tests, the team found that running water through two tubes simultaneously or sequentially could double energy output, indicating promising potential for scalability. While the droplets used in the experiment fell at slower speeds than natural rainfall, the researchers expect even greater efficiency under real-world weather conditions.

This innovation opens the door to compact, low-cost energy harvesting devices for urban environments, particularly in regions with frequent rainfall, contributing to the broader goal of clean, decentralized energy solutions.

By Impact Lab