A Sub-Surface Model of Solar Power for Distributed Marine Sensor Systems

The capabilities of distributed sensor systems, such as wildlife telemetry tags, could be significantly enhanced through the application of energy harvesting. For animal telemetry systems, supplemental energy would allow for longer tag deployments, wherein more data could be collected, enhancing our temporal and spatial comprehension of the hosts activities and/or environments. There are various transduction methods that could be employed for energy harvesting in aquatic environments. Photovoltaic elements have not been widely deployed in the subsurface marine environments despite a significant potential. In addition to wildlife telemetry systems, photovoltaic energy harvesting systems could also serve as a means of energy supply for Autonomous Underwater Vehicles (AUVs), as well as submersible buoys for oceanographic data collection. Until now, the use of photovoltaic cells for underwater energy harvesting has generally been disregarded as a viable energy source in this arena, with only one company currently offering solar modules integrated with marine telemetry tags. In this article, we develop a model of power available from photovoltaic cells deployed in a sub-surface marine environment. We cover the methods and tools used to estimate solar energy at depth, including the effects of: latitude and longitude, reflected solar energy off of the oceans surface, solar irradiance lost due to the absorption and turbidity of the sea water, cloud cover, etc. We present the availability of this solar energy source in the context of the energy requirements of some of these sensor systems, such as marine bio-loggers. Additionally, we apply our model to simulate the energy harvested on specific marine species in which high fidelity depth information is known. We also apply our model to simulate solar cells at certain depths under the ocean to gain a general understanding of the solar energy available at these depths.