We show that in the Earth’s clearest natural waters, solar cells can harvest useful power from the sun at depths down to 50 m below sea level with efficiencies ranging from ∼ 55% at 2 m to more than 63% at 50 m. An additional boost in efficiency can be achieved when the solar cells are operated in cold waters.
To assess the potential of underwater solar cells as a useful technology, a range of waters of varying clarity, ranging from the clearest waters found in the Pacific and Atlantic oceans to more turbid lake water found in Finland, were assessed. For comparison, spectra for deionized (DI) water were also considered.
In principle, underwater solar-energy generation can complement the use of batteries and provide a solution, although dedicated research is needed since traditional silicon solar cells do not perform well underwater due to water’s strong absorption of near-infrared light.
All in all, the results indicate that underwater solar cells have the potential to harvest power at depths up to 50 meters in very clear waters with efficiencies ranging from 55% to 65%. For cloudier waters, the technology may operate at depths up to 10 meters.
One of the most promising demonstrated technologies for onboard underwater power generation is solar cells. Solar energy is a consistent source of energy above the ocean surface, but also a surprisingly abundant and consistent source of energy below the ocean surface 9.
Thus, although Si solar cells are a mature solar technology and well-tuned for terrestrial applications, they are far from ideal for powering underwater systems due to the narrow bandgap of Si.