Steady-state operation of a compressor for a proton exchange membrane fuelcell system

The performance of a system consisting of a proton exchange membrane (PEM) fuel cell coupled to a centrifugal air compressor is simulated. Two modes o f operation of the system are investigated: one in which the speed of the c ompressor is constant, and the other in which the compressor speed is varie d with the electric load on the fuel cell stack. The operating characterist ics of the compressor and the PEM fuel cell stack and their influence on th e system efficiency are analyzed for a step change in the stack current. Th e effects of the fuel cell stack back-pressure and the electric load on the compressor power consumption and the system efficiency are studied. It is found that the system efficiency is higher when the fuel cell stack is oper ated at a constant oxygen gas stoichiometry by varying the compressor speed instead of at a constant compressor speed. The system model can be used to determine the rotation speed of the compressor for various electric loads.