China’s floating generator turns rain into power

November 08, 2025

A groundbreaking advancement in renewable energy has emerged from China, where researchers have unveiled a floating hydrovoltaic generator capable of turning falling rain into usable electricity — all while floating on water surfaces.

A revolutionary approach to water-based power generation

Developed by scientists at the Nanjing University of Aeronautics and Astronautics (NUAA), the new water-integrated droplet electricity generator (W-DEG) represents a major leap in sustainable rain energy technology. Unlike traditional systems that require solid land structures and heavy metallic components, this innovative generator floats freely, utilizing water as both a structural and electrical component.

Dr. Wanlin Guo, a professor of mechanics at NUAA and the project’s lead author, explained:

“By allowing water to serve as both the supporting base and the electrode, we’ve introduced a lightweight, low-cost, and scalable solution for droplet electricity generation.”

How the floating generator works

Conventional droplet electricity generators (C-DEGs) typically rely on a rigid metal base and dielectric film to capture the energy of falling rain. While capable of generating hundreds of volts, these designs are bulky, costly, and material-intensive.

In contrast, the NUAA team’s W-DEG eliminates the need for heavy substrates. The generator rests directly on a water surface, where the water acts as a natural electrode. This approach reduces total material weight by about 80% and lowers costs by nearly 50% compared to standard setups.

When rain droplets strike the floating dielectric film, the water’s surface tension and incompressibility provide sufficient mechanical stability to absorb impact. Simultaneously, ions within the water serve as charge carriers, enabling efficient current flow. The result: voltages up to 250 volts per droplet — a performance level comparable to land-based metal electrode systems.

Designed for durability and real-world conditions

Beyond its efficiency, the floating hydrovoltaic generator is engineered for long-term resilience. Tests revealed that the W-DEG maintained high performance under temperature variations, salinity changes, and even polluted or biofouled water.

Thanks to the dielectric layer’s chemical resistance and the stability of its water-based design, the device can continue operating even in challenging environmental conditions.

To prevent excess water accumulation during heavy rain, the researchers integrated micro drainage holes. These channels allow water to flow downward but block upward flow, keeping the surface clear for continuous raindrop impacts and maintaining consistent energy output.

Scalable and Sustainable Energy for the Future

The research team also showcased a 3.2-square-foot (0.3-square-meter) prototype — the largest of its kind — capable of powering 50 LEDs simultaneously. The generator can also charge capacitors within minutes, making it a promising candidate for distributed renewable energy systems.

With further development, these floating units could be deployed across lakes, reservoirs, and coastal waters to generate clean electricity without using land resources. Beyond power generation, they could also support environmental monitoring networks that measure water quality, salinity, and pollution in real time.

In areas with frequent rainfall, floating hydrovoltaic systems could supplement existing solar and wind infrastructure, helping stabilize local power grids and enhance off-grid energy independence.

Dr. Guo emphasized the long-term vision:

“This technology opens the door to land-free renewable energy systems that complement solar and wind, accelerating our path toward a greener future.”

Pioneering the future of rain energy harvesting

The NUAA team’s durable, efficient, and scalable prototype demonstrates that harvesting electricity from rain is not only feasible but also commercially promising. Their findings, published in the journal National Science Review, mark a crucial milestone toward practical, sustainable applications of hydrovoltaic energy.