Water management has a major impact in the solid polymer fuel cell on
overall system power, cost and efficiency. Single cell and stack perfo
rmance may be adversely affected by the formation of liquid water, the
dilution of reactant gases by water vapour, or by the dehydration of
the solid polymer membrane. Peak fuel cell power is achieved typically
at current densities at which performance is limited by mass transpor
t. Improved water management at higher current densities not only incr
eases peak power and efficiency but changes the profile of the power c
urve resulting in improved stability near the peak power operating poi
nt. Fuel cell water management can be accomplished by a number of appr
oaches which include system design, stack operating conditions, stack
hardware and membrane electrode assembly design. A number of these tec
hniques have been successfully applied to both single cells and stacks
. However, the options available for water management have to be asses
sed from an overall engineered system point of view.