Sensors and acoustic modems powered by Benthic Microbial Fuel Cells at the MARS observatory

The goals of this project were three-fold: 1) to power underwater instruments with energy harvested from deep sea, organic poor sediments using Benthic Microbial Fuel Cells (BMFCs); 2) to relay instrument data acoustically -and in near-real time- through a cabled seafloor observatory or surface vessel, as appropriate; and 3) to characterize the operational performance of these interactive systems during in situ deployments. Two BMFC- underwater sensing/communications packages were demonstrated near the Monterey Accelerated Research System (MARS) observatory in Monterey Bay, California. MARS is a cabled observatory that resides in deep water (~890 m), about 37 km (23 miles) seaward of the Monterey Bay Aquarium Research Institute (MBARI). The BMFCs were constructed using a cylindrical chamber design with a 0.28 m² footprint. Each BMFC was used to power an Aanderaa dissolved O₂/temperature or conductivity/temperature sensor, as well as a Teledyne Benthos compact acoustic modem which contained an integrated power management platform (PMP) for the complete system. The packages were deployed from a surface vessel and allowed to descend freely to the seafloor, at locations approximately 0. 5 km away from the MARS node, at depths of 863 and 895 m. The PMPs were programmed to record data from both the sensors and the BMFC (whole cell voltage, capacitor voltage, and battery voltage) on an hourly basis, and to monitor overall microbial fuel cell energy production on a daily basis. Post-deployment, BMFC 1 generated a net surplus of energy from days 98 through 166, and remained operational for 210 days. BMFC 2 began generating a surplus of energy on day 54 and remained operational for 158 days. Data recovered from the oceanographic sensors was transmitted acoustically over both the MARS node and to a research vessel, underscoring the utility of this technology.