Can solar power work underwater? Scientists test solar panels 10 metres beneath the sea

According to the researchers, perovskite-based solar panels could operate for five and a half years underwater. Ten metres beneath the South China Sea, scientists have found an unlikely place to generate power from the sun. Last week, researchers announced that they had successfully tested solar panels at underwater depths previously considered impractical for the technology. Designed to capture the wavelengths of sunlight that can pass through seawater, the panels could eventually keep underwater equipment running for longer without relying just on batteries, they argue. During a two-hour trial near the Weizhou Islands, off the southern coast of mainland China, the panels generated power from sunlight at a depth of 10 metres. Lab tests suggest that they could operate continuously for years, too. The research, published in the science journal Joule, takes underwater solar well beyond previous studies, which have focused on depths of just two metres or less. How can solar panels work 10 metres underwater? One of the biggest obstacles to generating solar power underwater is that sunlight fades below the surface – and fast. By a depth of 10 metres, much of the sun’s energy has already been absorbed or scattered by the water. But some types of light can reach deeper than others. According to the researchers, enough blue and green light reaches these depths to generate electricity, so the team developed solar cells designed to make the most of it. They used what are known as perovskites, an alternative to the silicon found in most solar panels, which can be adjusted to absorb different wavelengths of light. In laboratory tests recreating conditions 10 metres underwater, the cells turned around 35 per cent of the sunlight that reached them into electricity. The researchers then put bigger versions to the test in the South China Sea. At two metres deep, their 115 square centimetres of solar panels generated 1,416 milliwatt-hours over two hours, or about half the capacity of a rechargeable AA battery. At 10 metres, they generated 324 milliwatt-hours over two hours – a small amount but still far beyond what the researchers expected. Their panels also showed almost no loss in performance after 1,160 hours under simulated underwater conditions. Based on their tests, the researchers estimate they could operate continuously at 10 metres below the sea for around 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,” says study author Wen-Hua Zhang, from China’s Yunnan University and Southwest United Graduate School in Kunming. How solar is going off-grid Once the sole domain of rooftops and wide open spaces, solar power continues to appear in places where electricity and fuel can be difficult to access. Earlier this year, Dutch researchers unveiled the world’s first solar-powered ambulancein rural Kenya, designed to bring healthcare and medical equipment to hard-to-reach communities that lack reliable access to electricity or fuel. In Norway’s Svalbard archipelago, solar has also begun to help power a remote former radio station, a site accessible only by boat or helicopter that previously relied on diesel-fuelled generators. Other projects have found space for solar in existing infrastructure. In Switzerland, solar panels installed between railway tracks are generating electricity without taking up more land. The panels can also be removed for track maintenance, allowing railways to double as solar farms without disrupting services. Underwater solar power could solve a different problem. Ocean sensors, cameras and communication equipment can operate far from power supplies, but they must eventually be retrieved when their batteries run out. The researchers believe the technology they studied could provide a lasting source of power for this kind of equipment. First, however, they need to find out how well their solar panels work deeper undersea. They say their next step is to do just that and establish how far beneath the waves solar power can go.