The capture and use of solar energy has never been about getting away from fossil fuels as much as it has been about harvesting that ever burning nuclear reactor we call the Sun. The problem we have always faced is not so much the collection of sunlight, but the conversion rate of the sunlight we collect into useable energy. The United States Navy is trying to improve the collection rate of Photovoltaic cells under water.
The Navy has several technology platforms that are just underwater such as sensors to help improve the detection of enemy vessels. Until now these systems have had to rely on on-shore power, batteries, or solar power supplied by an above water platform. The U.S. Naval Research Laboratory, Electronics Science and Technology Division is trying to fix the issue of the lack of penetrating sunlight and the use of solar cells optimized more towards the unimpeded terrestrial solar spectrum. So they have started using photovoltaic cells that are able to have a higher conversion rate due to the lower but more focused solar radiation the penetrates the water.
"The use of autonomous systems to provide situational awareness and long-term environment monitoring underwater is increasing," said Phillip Jenkins, head, NRL Imagers and Detectors Section. "Although water absorbs sunlight, the technical challenge is to develop a solar cell that can efficiently convert these underwater photons to electricity."
The semi-breakthrough comes from the use of High-quality gallium indium phosphide (GaInP) cells are well suited for underwater operation. Previously they were using silicon based cells which had a much lower conversion rate. The cells function at a depth of up to 29 feet and look to make things easier for energy collection moving forward.
Photo and Graph courtesy of the US Navy