Therefore, the simulation study shows that, in accordance to the asymmetrical roles of anode and cathode humidification, as discussed, the inlet relative humidity at anode should be ideally kept at 100% in order to maintain a well hydrated membrane for minimizing ohmic overpotential (at the intermediate current density region), while the inlet relative humidity at cathode should be kept very low to minimize concentration overpotential by preventing the formation of liquid water, i.e., flooding, in cathode GDL and GC. These conditions typically give rise to an absolute maximum power density under a given air flow rate.