Figure 1 shows the dependence of the stack voltage on the dew point of air at 0.4A/cm2. The dew point of hydrogen gas at the inlet of the stack was 60"C. Cell temperature difference between gas inlet and outlet was fixed at 5"C. When the dew point was higher than 70*0, the voltage was costant. It shows that water in the cell was effectively removed by the temperature difference. When the dew point was lower than 70"C, the voltage gradually decreased. Electrolytes dry at the low dew point, which increases cell resistance. Therefore it is necessary for electrolyte to maintain appropriate water content to obtain good performance. Figure 2 shows I-V and I-P characteristics of the stack operated at 70"C. At the rated current of 240A, the stack showed a voltage of 21V with output power of 5.0kW.

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