FUEL CELL POWER PLANT DIVERTING AIR IN RESPONSE TO LOW DEMAND

摘要

A fuel cell system, which may be powering a vehicle propulsion system (159), includes a fuel cell power plant having a stack (151) including a plurality of fuel cells (12), each having a cathode (19) and anode (17) separated by a membrane (16), and an air pump (174) connected to reactant air flow fields through a diverter valve (172). A controller (185) is responsive to normal and high demand to cause the diverter valve to allow air to flow from the pump to the reactant air flow fields, and is responsive to low demand to cause said diverter valve to divert air directly into ambient so that it does not reach the cathode, thereby to reduce open circuit voltage conditions that promote degradation of the cathode, and to prevent excessive performance decay. An auxiliary load (220) can be in the diverted air flow, either ahead of or after the diverter valve. Energy storage (200, 201) works with the vehicle propulsion system.