Fuel cells convert chemical energy to low-voltage, direct current electricity. Fuel cells are not limited by Carnot cycle efficiency, and therefore would improve energy-conversion efficiency. Fuel cells operate with a continuous supply of externally-stored fuel and oxidizer. The fuel reactant (e.g., H2 or CO) is fed into the porous electrode (anode); oxidant (e.g., O2 or air) is fed into the other porous electrode (cathode). The chemical products are garbage.
Fuel Cell Diagram [Source: Fuel Cells 2000]
Electric Ocean Fuel Cells Engineering Design