Schematic Layout of Fuel Cell Units

2 SCHEMATIC LAYOUT OF FUEL-CELL UNITS 16.2.1 An Individual Fuel Cell 

Fuel cells, like batteries, are a variety of galvanic cells, that is, devices in which two or more electrodes (electronic conductor) are in contact with an electrolyte (ionie conductors). Another variety of galvanic cells are electrolyzers in which electric current is used to generate chemicals in a process that is the opposite of those oceurring in fuel cells and involving the conversion of electrical to chemical energy. 

So as to exclude accidental contact between anode and cathode (which would produce an internal short of the cell), an electronically insulating porous separator holding an electrolyte solution that supports current transport by ions is often placed into the gap between these electrodes. The solid ion-conducting electrolyte may serve at once as a separator. In any case, the cell circuit continues to be closed. 

For continued work of the fuel cell, provisions must be made to ensure continuous reactant supply to each of the electrodes and continuous withdrawal of reaction products from the electrodes, as well as removal and/or utilization of the heat being evolved. 

As a rule, any individual fuel cell has a low working voltage of less than 1 V. Most users need a much higher voltage of, for instance, 6, 12, 24 V or more. In a real fuel-cell plant, therefore, the appropriate number of individual cells is connected in series, forming stacks (batteries). 

---