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Microbes, like Geobacters, have inhabited the seafloors around the world since the early days of
earth. Such regions are anaerobic and they gain energy by using the widely prevalent iron oxides and
organic matters. Because they appear to colonize conducting surfaces that act as sinks of electrons,
microbial fuel cells have been shown to convert organic matter to electricity. A microbial fuel cell system
has been deployed in Narragansett Bay in Newport, Rhode Island for a year. Currently, the cathode and
anode areas are of the order of that of a small wind mill. Measurements have been carried out to determine
the marine scaling laws of power harvesting in passive benthic microbial fuel cells. The focus has been on
the ocean engineering aspects such as marine scaling laws and the integration of the biochemical and the
electronic systems. The characteristics examined are: the relationship of electrode surface area and power
produced, the stabilization rates of ionic paths, that is, the effects of location depth of cathodes on
stabilization after deployment, the effects of solar and lunar cycles in the Narragansett Bay on the dynamic
components of power produced, and the hysteresis effects between periods of active power harvesting and
dormancy; the effects of 'on sediment surface' versus 'in sediment' anode deployment have been examined
for smaller electrode areas so far. A capacitance model of power consumption and harvesting has been
proposed for the marine environment. It is assumed that the primordial benthic microbe laden layer of the
earth acts like a giant capacitor. In the microbial fuel cell, this charged benthic layer acts in series with a
smaller constant voltage DC power source. This giant benthic capacitance is a result of untapped
accumulated charge from the microbes while the DC source originates from the real-time production due to
the microbes. Finally, the microbial fuel cell is integrated with a power conversion system to intermittently
energize a small incandescent lantern in the NUWC Stillwater Basin located in Narragansett Bay in Rhode
Island.
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