Fuel cell stacks

Abstract

A fuel cell stack () comprises a plurality of fuel cells each with a chamber (K) for electrolyte with at least one inlet and at least one outlet, and at least one header () to supply electrolyte to all the cells in parallel, and means () to collect electrolyte that has flowed through the cells. For each cell, the electrolyte outlets () feed into an electrolyte flow channel arranged such that in use there is a free surface of electrolyte within the electrolyte flow channel, the electrolyte flow channel being separate from the corresponding electrolyte flow channels for other cells, but such that the free surfaces of all the electrolyte flow channels are at a common pressure. Electrolyte is maintained at a constant depth in this open flow channel by a weir (), and then flows over the weir to trickle or drip down the outside of the stack. This ensures uniform outlet electrolyte pressure throughout the stack () and across the individual cells, and avoids or reduces ionic leakage currents through the electrolyte outlets.