50

Fig. 4 Results of repeated loading test

(3) Operation of stack in inclined position

Hull inclination and pitching/rolling motions being indispensably required to be taken into account in shipboard operation, this factor was considered in a test in which the stack was operated at positions inclined in the four directions and at 5° intervals to the maximum angles indicated in Fig. 5. It proved that stack performance was the most adversely affected when the inclination placed the air exhaust manifold on the under side. For practical application of the PEFC to ship propulsion, there is need to devise a means of letting the generated water freely flow out .with the stack inclined to angles up to 30°.

Fig. 5 Maximum allowable angles of stack inclination

(4) Effect of salinity

For evaluating the effect on fuel cell brought by the presence of salinity in the sea air, the single cell operating performance was measured after impregnating for a prescribed duration a membrane electrode assembly in water containing salt in parametrically varied concentrations. Test results are presented in Fig. 6, where 120mg/300ml salt concentration corresponds to the__ total quantity of salt entering a single cell upon operation for 100 h at 50% air utilization rate in sea atmosphere (containing 30 mg salt/m3) in heavy sea.

The foregoing data indicate the necessity of passing the air supplied to cell through a filter of 99.3% salt removal efficiency, in order to prevent lowering of cell output_ voltage by the salinity of. marine atmosphere during the course of cell life (40,000 h). This requirement is based on the supposition that heavy seas continue ininterrupted during 40,000 h and that all the salt entering the cathod is trapped in the membrane electrode assembly.

CURRENT DENSITY CA/cnO Fig. 6 Results of salinity effect test
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