A microbial fuel cell, set in marine sediments, was
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Microbial fuel cell design sufficient to power a hydrophone over a several month period Drs. Ken Richter and Bart Chadwick SPAWAR Systems Center Pacific 53475 Strothe Rd. San Diego, CA 92152 Dr. Lenny Tender Naval Research Laboratory 4555 Overlook Ave. SW Washington DC, 20375 A microbial fuel cell, set in marine sediments, was designed to power a 20 mW multi-frequency hydrophone. The hydrophone is operating as a detector of acoustically- tagged green sea turtles in San Diego Bay, CA. Initial field studies showed that organic content in the sediment was critical in determining fuel cell energy density, while water oxygen concentrations, varying with the semidiurnal tide, added a small ripple on power output (see figure). Power density is approximately 8 mW m-2 graphite anode. Tidally-driven temperature fluctuations in the sediment and water column were unimportant in power output. Steady-state power output was attained in approximately 4 weeks, accompanied by an explosive growth of bacterial populations near the anode in the sediment. The design and operating characteristics of the fuel cell and hydrophone will be presented as well environmental measurements that led to the design.