Relative humidity effects membrane resistance

When used for automotive applications, fuel cells must respond to changes in the load. Changing the load alters the water production, changing the balance between water produced and water removed, resulting in a change of the membrane water content. The effect of the load resistance on the water activity can be seen in the polarization curves for the STR PEM fuel cell shown in Figure 3.9A [23]. The STR PEM fuel cell was operated in the autohumidification mode. The STR PEM fuel cell was equilibrated at 80C for 12 h with a fixed load resistance (either 0.2 or 20 fi). After equilibration, the polarization curve was obtained by sweeping the load resistance between 0.2 and 20 ft in 100 s. The relative humidity in the anode and cathode streams... 

FIGURE 10.28 Effect of RH on fuel cell internal resistances (RC = electrode resistance, RM = membrane resistance). (Reprinted from /. Power Sources, 184, L. A. M. Riascos. Relative humidity control in polymer electrolyte membrane fuel cells without extra humidification, 204-211, Copyright (2008), with permission from Elsevier.)... 

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