Undersea electronics powered by large surface area Benthic Microbial Fuel Cells

Benthic Microbial Fuel Cells (BMFC) have the potential to provide long-term, sustainable power for undersea devices. BMFCs operate by harnessing organic matter in the sediment as a fuel source. They typically output 10 to 100mW. To increase the power output, BMFCs with larger electrodes are needed. However, past work has shown that power output does not scale linearly with electrode surface area. To build a large surface area BMFC capable of greater than 100mW power output, experiments were conducted to: 1. determine at what surface area the power output deviates from scaling linearly; 2. determine if independent anodes could be wired together and maintain their power density; 3. determine the proximity independent anodes could be from one another and maintain their power densities; 4. Determine the anode to cathode relationship that prevent cathode limitations. Experiments showed that: 1. anode surface areas of 1-2m² provide a good balance between power output and complexity when incorporated into a larger system; 2. independent anodes could be wired together and maintain their power density; 3. anodes could be 2-3cm apart and maintain their power densities; 4. 1:1 anode to cathode surface areas prevent cathode limitations. Based on the results of lab experiments, a BMFC deployment sled was designed to deploy a BMFC with two 10m² modular anodes, spaced 5cm from one another, and successfully deployed this BMFC in San Diego Bay without the use of a diver. The BMFC sustained 250mW and powered environmental sensors and transmitted data over an acoustic modem.