Optimization and air supply management of a polymer electrolyte fuel cell

A mathematical model of the polymer electrolyte fuel cell (PEFC), including air compression process and humidification has been developed to study the performances of the fuel cell. The study is focused on the air supply management with the objective to optimize the inlet air pressure and stoichiometry given by the compression system. A simple optimization method is given to maximize the voltage gain including the voltage drop due to the compression process. The optimization has to take into account the outlet relative air humidity (optimization constraint) leaving the fuel cell to avoid drying or flooding problems. The optimization results show that working at fully humidified air at the inlet is not always a good solution especially for low air mass flow rates because of the high level of air stoichiometry to avoid flooding of the polymer membrane. On the other hand, it is better to work at fully humidified air at the inlet at high air mass flow rates. In all the cases, the optimal pressure is less than 2.5 bar which gives an indication for the design of air compressor for fuel cells.