Ten metres beneath the surface of the South China Sea, researchers have demonstrated that solar panels can generate electricity in conditions long thought too dark for the technology. The trial, conducted near the Weizhou Islands off China's southern coast, opens the possibility of powering underwater sensors and communication equipment without frequent battery replacements.
The findings, published in the journal Joule, represent a significant leap from earlier experiments, which rarely exceeded depths of two metres. By using perovskite-based solar cells—an alternative to conventional silicon—the team was able to capture the blue and green wavelengths that penetrate seawater more effectively than other parts of the spectrum.
How it works
Sunlight diminishes rapidly with depth, but enough blue and green light reaches ten metres to generate a useful current. The researchers engineered their cells to absorb precisely those wavelengths. In laboratory simulations of underwater conditions, the cells converted about 35 per cent of the sunlight that reached them into electricity.
During the field test, a 115-square-centimetre panel array generated 1,416 milliwatt-hours over two hours at a depth of two metres—roughly half the capacity of a rechargeable AA battery. At ten metres, the output dropped to 324 milliwatt-hours, a modest figure but still far above the team's expectations.
More importantly, the cells showed negligible degradation after 1,160 hours of simulated underwater operation. Based on these results, the researchers estimate that the panels could function continuously at ten metres for about five and a half years.
“This work presents the first functional validation of submerged solar cells practically operating at a water depth of up to about 10 meters, greatly broadening their application scope,” said study author Wen-Hua Zhang of Yunnan University and the Southwest United Graduate School in Kunming.
Solar beyond the grid
The underwater experiment is part of a broader trend of deploying solar power in unconventional settings. In Europe, solar is already being integrated into infrastructure in creative ways. For instance, renewable electricity growth in Europe has slowed despite a surge in solar installations, highlighting the need for innovative applications.
In Switzerland, panels installed between railway tracks are generating electricity without occupying additional land, and they can be removed for maintenance. In Norway's Svalbard archipelago, a remote former radio station now relies partly on solar power, reducing its dependence on diesel generators.
Underwater solar could solve a different problem: powering oceanographic sensors, cameras, and communication buoys that are often located far from any grid. These devices currently require periodic retrieval to replace batteries, a costly and logistically challenging operation.
The researchers acknowledge that much work remains. Their next step is to test the panels at greater depths to determine how far beneath the waves solar power can realistically be used. If successful, the technology could provide a reliable, long-lasting energy source for marine monitoring systems across the globe.
While the trial took place in Asian waters, the implications are global. European marine research institutes and offshore industries could benefit from such technology, especially as the EU pushes to expand its blue economy and monitor ocean health more closely. The ability to power underwater equipment without frequent maintenance would be a boon for projects in the Mediterranean, the Baltic, and the Atlantic.
As solar continues to find new niches, from solar-powered trains in Argentina to battery storage in Bulgaria, the underwater breakthrough adds another dimension to the renewable energy landscape.
