This is not about better flashlights for Navy Seals.
A team of scientists from the US Naval Research Laboratory Electronics Science and Technology Division has developed a solar cell specifically designed for use underwater, which can efficiently absorb solar radiation up to a depth of nine meters (about 30 feet).
The breakthrough may prove important to the development of underwater autonomous systems — which provide situational awareness and long-term environment monitoring— a growing market.
As it now stands, the power options for these systems are cumbersome and expensive: cables connected to an onshore supply source, expensive batteries requiring frequent replacement to ensure a steady supply, or solar panels constructed on above-water platforms.
Photovoltaic cells have been previously tested for underwater use, but due to the lack of sunlight penetrating the water they only had limited success.
Philip Jenkins, one of the scientists on the team, explained that, “although water absorbs sunlight, the technical challenge is to develop a solar cell that can efficiently convert these underwater photons to electricity.”
Due to the lack of penetration the intensity of solar radiation underwater is lower than on the surface, however the sunlight that does penetrate comes in narrower wavelength concentrations, leading to high conversion efficiency when the solar cells are adjusted to match the wavelength range.
Normal PV cells are constructed from crystalline silicon, however previous tests have shown that this material was inefficient; instead the Navy is using gallium indium phosphide to create the underwater PV cells. Gallium indium phosphide works best for wavelengths between 400 and 700 nanometers, the typical range of light found underwater.
—This story originally appeared on Oilprice.com.