Commonly polymer electrolyte fuel cell systems (PEFC) in transport applications use oxygen from air as the oxidant. However, in a renewable energy system when hydrogen is obtained from the splitting of water by electrolysis or other water splitting processes then oxygen is obtained as energetically cheap by-product. The use of pure oxygen allows the development of mobile fuel cell systems with interesting properties. The oxygen reduction reaction is the main limiting process in PEFC. Operating PE fuel cells with pure oxygen enables for operation with oxygen partial pressures of up to several bar, which is about an order of magnitude higher than oxygen partial pressures achievable in pressurized hydrogen/air systems. Thus the main advantage of pure oxygen PEFC systems is the high specific power. At gas pressures below 4 bar abs. and a stack efficiency of 0.5 (LHV), a power density of 1.4 W/cm2 has been obtained on the short stack level. This is about a factor of two higher than what is obtained in today's state of the art H2/air technology stacks. Using high oxygen partial pressures is under suspicion of triggering higher degradation of membrane and/or catalyst. Long-term degradation experiments were performed, using cycling protocols, showing that stack life times, useful for the automotive application can be achieved with high oxygen partial pressures and high specific power densities. A compact 7 kW prototype system based on a 24 cell stack was realized. Current densities of 2.1 A/cm2 were obtained using a very compact system with all system components (valves, gas recirculation, coolant pump asf.) except gas tanks and heat exchanger included into the stack endplates.
Hydrogen/oxygen fuel cell system demonstrating high power densityand efficiency
EVS, Electric Vehicle Symposium, 26 ; 1484-1488
2012
5 Seiten, 6 Bilder, 2 Tabellen, 3 Quellen
Aufsatz (Konferenz)
Englisch
Sauerstoff , Sauerstoffpartialdruck , Leistungsdichte , Brennstoffzellenantrieb , Polymerelektrolyt , Oxidationsmittel , Stand der Technik , erneuerbare Energiequelle , Klimaanlage , Luftreinigungssystem , Luftreinhaltungssystem , Wasserstoff , Wasserspaltung , Brennstoffzelle , chemische Reaktion , Verdichtungsgerät , Systemkomponente , Kühlmittelpumpe , Wärmeaustauscher , Zellenstapel , Stromdichte , Wirksamkeit
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