Recent studies contracted by NASA for a more electric commercial aircraft evaluated SOFCs for auxiliary power units and Regenerative (RSOFC) systems, where the system regenerates its reactants by operating in reverse. One application for RSOFCs is separating pure O2 from air in electrolysis mode for flight crew emergencies and using the enriched N2 stream as an explosion retardant over the fuel tanks and luggage areas. Space applications for RSOFCs are also envisioned, using electrolysis of H2O for Lunar missions and CO2 for Mars missions. NASA Glenn Research Center (GRC) has been evaluating an SOFC concept consisting of a thin YSZ electrolyte, symmetrically supported on both sides by graded, porous yttria-stabilized /zirconia (YSZ) electrode scaffolds, impregnated with active materials, making it a bi-electrode supported cell (BSC). BSC cells were evaluated reversibly and the electrochemical voltage efficiency (fcVh) calculated, the ratio of generated fuel cell power to the required electrolysis power at constant current. The highest EVE measured for a 5 cm diameter cell was 85 % at 200 mA/cm2 and 850 deg C. The NASA BSC design has a number of design advantages since it is all ceramic. The cell and stack are assembled in the green state and sintered to form a 'unitized' block with hermetic electrolytes, interconnects and seals, prior to infiltration of the active electrode materials. Hermeticity is an important requirement for any regenerative SOFC system for space applications where leaks from seals would result in a system failure. Details of the cell design, testing and electrochemical performance will be presented.
Regenerative operation of the NASA symmetrical support solid oxide fuel cell
Regenerativer Betrieb der NASA-Festoxidbrennstoffzelle mit symmetrischem Träger
2008
11 Seiten, 8 Bilder, 1 Tabelle, 8 Quellen
Conference paper
English
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