WATER MANAGEMENT AND STACK DESIGN FOR SOLID POLYMER FUEL-CELLS

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.