(638c) Electrolysis and Regenerative Operation of the NASA Symmetrical SOFC

Both solid oxide fuel cells and Regenerative SOFCs (RSOFCs) are of interest to NASA for Aeronautics and Space applications. Recent studies performed for future, more electric commercial aircraft have evaluated SOFCs for APUs and have considered RSOFC systems. RSOFCs, based on H₂/O₂, would operate in fuel cell mode while taxiing to the gate and then would perform water electrolysis during flight. The pure O₂ generated in the electrolysis mode could be used for emergency needs. Space applications for RSOFCs are also envisioned, using H₂O for Lunar missions and CO₂ for Mars missions. Interest in H₂ production by DOE has lead to collaboration with DOE/INL with a focus on electrolysis of the hot steam effluent at nuclear power plants.

NASA Glenn Research Center (GRC) has been evaluating a new solid oxide fuel cell concept consisting of a porous YSZ support structure on both sides of a thin YSZ electrolyte, which is later filled with active electrode materials, making it a bi-electrode supported cell (BSC). BSC cells with infiltrated electrodes were evaluated in the regenerative mode of operation, in order to measure the electrochemical voltage efficiency (EVE); which is the ratio of power generated in fuel cell mode (P_out) to the required power for electrolysis (P_in), measured at constant current density. The highest voltage efficiency measured for a 5 cm OD cell was 90 % at a current density of 200 mA/cm² at 850^oC. Details of the cell fabrication, testing and electrochemical performance will be presented.