US Navy makes a splash with underwater solar cells

US Naval researchers are working on a novel place to keep photovoltaic panels – beneath the waves of the sea.

While solar cells are often found slapped on the top of buildings, a team at the US Naval Research Laboratory have been developing aquatic PV panels in order to capture the sunlight penetrating up to nine metres below the water level.

By chucking the panels into the ocean they hope to be able to power automated systems and sensors, which typically would require on-shore power supplies or batteries.

Problems have been encountered with using traditional solar cells to turn light into electricity, so what the researchers needed was a way to use photons that could travel deep down into the drink. 

The researchers found that although the intensity of solar radiation is lower underwater, high conversion efficiencies are possible due the changes to spectrum.

Working out that the usual crystalline solar cells wouldn’t do the job, they used cells based on a material called gallium indium phosphide (GaInP) which has high efficiency in low light conditions.

Furthermore, the filtered spectrum of the sun underwater is biased towards the blue and green section, and this is much more suited to gallium indium phosphide than conventional cells.

Initial tests were able to reach a depth of 9.1 metres, with output of seven watts per square metre of solar, enough to be useful for areas close to the shore.