A research team from the Ulsan National Institute of Science and Technology (UNIST) in South Korea has developed a new technology that can generate electricity through the kinetic energy of raindrops hitting roofs, providing a self powered solution for automated drainage control and flood warning during heavy rainfall weather.

The team is led by rofessor Park Young bin from the Department of Mechanical Engineering at UNIST, and has developed a droplet generator (DEG) using carbon fiber reinforced composite materials (CFRP). This device, called the "Superhydrophobic Fiber Reinforced Composite Droplet Generator (S-FRP-DEG)", can convert the impact force of raindrops into electrical signals and drive the rainwater management system without the need for an external power source. Carbon fiber reinforced composite materials have the characteristics of lightweight, durability, high strength, and corrosion resistance, making them very suitable for long-term outdoor installation on roofs and other exposed urban structures.

The power generation principle of this generator is similar to the process of static charge generation. When positively charged raindrops come into contact with the negatively charged superhydrophobic surface of the device, the droplets will quickly detach and roll off, accompanied by charge transfer. This charge movement can drive current to flow through the built-in carbon fiber, almost achieving instantaneous power generation.

Unlike traditional metal based droplet generators that are susceptible to corrosion from moisture and urban pollutants, this carbon fiber reinforced composite (CFRP) based generator can maintain stable performance under harsh environmental conditions. The research team also improved the power generation efficiency by texturing the surface of the device and introducing a lotus leaf like coating - this design enhances hydrophobicity while preventing dust and smoke accumulation.

Traditional metal droplet generators often suffer from corrosion problems due to pollution and moisture erosion. The CFRP based device developed by the UNIST team has overcome this challenge and can maintain excellent durability and stability for a long time.

Laboratory test data shows that a raindrop with a volume of approximately 92 microliters can generate a maximum voltage of 60 volts and a current of several microamperes. After connecting four of these devices in series, the system can briefly light up 144 LED lights, which verifies the scalability of this technology.

The research team also validated the technology in real-life scenarios - they installed the device on building roofs and drainage pipes. The results indicate that as rainfall intensity increases, the electrical signals generated by the device become stronger and more frequent. Based on this characteristic, the system can distinguish between light rain, moderate rain, and heavy rain, and automatically start the drainage pump when necessary.