Specifications of the 5kW stack are shown in Table 1. Water management is an important factor to operate PEFCs stably for a long time, especially in the case of large-area electrodes. We have developed a method that intentionally maintains large temperature difference between gas inlet and outlet in a cell, so that the outlet temperature is higher than the inlet temperature. This prevents condensation of water and allows successful water removal even at the gas outlet where water vapor content increases. The temperature distribution can be changed in electrodes by controlling the temperature and the flow rate of cooling water. The stack was operated with O.lMPa abs. H2/air at 70"C. Hydrogen gas and air were humidified externally by passing them through water in a vessel maintained at constant temperature. Air utilization was 25% and H2 utilization was 75%.

Table 1. Specifications of 5kW Stack

Electrode Area

600 cm2

Number of Cells

30 cells

Rated Power


Rated Voltage

0 0

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