PEM (proton exchange membrane) fuel cell stacks typically have been designed for operation with well-humidified gases at pressures near 3 bar and temperatures of approximately 80 C, or at near ambient pressure and lower temperatures. Current system analysis indicates that continuous or long-term operation of an automotive fuel cell system with the above stack conditions at powers above approximately 50 kW present a thermal subsystem engineering challenge due to insufficient temperature 'driving force'. A water neutrality constraint imposes further power limitations due to the need for lower temperature condensers. Increased stack temperature for improved thermal 'driving force' will likely be required to enable higher power capacity. Simultaneously, higher-pressure operation may be required to offset the temperature-induced increase in condensate water recovery load. Higher-pressure operation has the additional benefit of increasing condenser rejection temperature (increasing driving force), but with an increased parasitic compression work. Alternatively, the development of lower water content membranes can reduce the condensate load, without increased compression loss (though without the benefit of the increased heat rejection temperature). Progress in reducing the anode water requirement is being demonstrated. Development and validation of novel dielectric coolants can further reduce the impact of the thermal load. The above must be balanced against stack performance sensitivities to determine the optimum fuel cell system.
PEM fuel cell system solutions for transportation
PEM-Brennstoffzellenlösungen für den Transporteinsatz
2000
8 Seiten, 12 Bilder
Conference paper
English
Abwärme , Automobilindustrie , Bauelementzuverlässigkeit , Belastungsempfindlichkeit , Betriebsdruck , Betriebsspannung , Betriebstemperatur , Betriebsverhalten , Brennstoffzelle , DC-DC-Wandler , Fahrzeugantriebsart , hoher Druck , integriertes System , Leistungsfähigkeit , Optimierung , Systemanalyse , Wärmebelastung
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