Underwater autonomous systems which provide situational awareness and long-term environment monitoring are becoming increasingly more popular. In order to power these systems cables must be laid to supply power created onshore, expensive batteries must be used and constantly changed to ensure a steady power supply, or solar panels must be constructed on an above-water platform.
Photovoltaic cells have been previously tested for underwater use, but due to the lack of sunlight penetrating the water they only had limited success.
Now, a team of scientists from the US Naval Research Laboratory Electronics Science and Technology Division have developed a solar cell specifically designed for use underwater, which can efficiently absorb solar radiation underwater up to a depth of nine metres.
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 team have are using gallium indium phosphide to create their underwater PV cells. Gallium indium phosphide works best for wavelengths between 400 and 700 nanometres, the typical range of light found underwater.
By. Joao Peixe of Oilprice.com
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