Rain usually brings inconvenience—wet streets, overflowing drains, and flood risks.
But researchers in South Korea have found a way to turn falling raindrops into a useful source of electricity, offering a new way for buildings to respond automatically to heavy rainfall without relying on external power.
A research team affiliated with Ulsan National Institute of Science and Technology (UNIST) has developed a device that generates electricity when raindrops hit a rooftop.
Led by Professor Young-Bin Park from UNIST’s Department of Mechanical Engineering, the team created a droplet-based electricity generator made from carbon fiber-reinforced polymer, or CFRP.
Their study was recently published in the journal Advanced Functional Materials.
CFRP is a material already widely used in airplanes, cars, and construction because it is lightweight, strong, and resistant to corrosion.
These qualities make it well suited for long-term outdoor use, especially in harsh urban environments where moisture, pollution, and temperature changes can damage traditional materials.
The new device works using a process similar to static electricity. Raindrops naturally carry a positive electric charge.
When a raindrop hits the generator’s specially designed surface, which holds a negative charge, electricity is transferred at the moment of impact. The surface is superhydrophobic, meaning it strongly repels water. This causes the raindrop to bounce or roll away quickly, helping the electric charge move through carbon fibers embedded in the material. The result is a brief but immediate flow of electricity.
One major advantage of this design is durability. Many earlier raindrop-based generators relied on metal electrodes, which can corrode over time when exposed to rain and air pollution.
The carbon fiber composite avoids this problem and maintains stable performance even under repeated exposure to water and dirt. The researchers also added a textured surface and a coating inspired by lotus leaves, which keeps the surface clean by preventing grime and soot from sticking.
In laboratory tests, a single raindrop produced surprisingly high electrical output—up to 60 volts, along with a small current. When four of the devices were connected together, they briefly powered 144 LED lights, showing that the system can be scaled up.
The team also tested the generator outdoors by installing it on rooftops and drainage pipes. During real rainfall, the electrical signals became stronger and more frequent as rain intensity increased. This allowed the system to tell the difference between light rain and heavy downpours and automatically trigger drainage pumps when needed.
According to Professor Park, the technology could help cities manage stormwater and flood risks using only the energy provided by rain itself.
In the future, similar systems could even be integrated into vehicles or aircraft, where carbon fiber materials are already commonly used.
Source: KSR.
