High temperature electrolysis by reversing the function of a solid oxide fuel cell

The world is increasingly committing to a green energy future. However, to ensure transition of the energy landscape with relatively minimal disruptions, energy storage technologies are required. An energy storage technology of significant promise is the reversible solid oxide cell (rSOC). A reversible solid oxide cell test apparatus was designed, and tests were performed in both constant solid oxide fuel cell (SOFC) and solid oxide electrolysis (SOE) modes, as well as rSOC cyclic operation. It was observed that cell degradation during SOE operation was generally more than double the degradation during SOFC mode. Cell performance losses also increased with decreasing temperature and increasing current density. However, performance losses were more strongly correlated with current density increases than with temperature decreases in all operating modes (SOFC, SOE and rSOC). Like the operating current density, cell degradation also seemed to be strongly correlated with fuel utilisation (which is a function of both current density and reactant flow rates). Cell degradation rate increased with increasing fuel utilisation. It was also observed that some degradation recovery occurred under the subsequent SOFC mode operation after SOE mode operation during reversible cycling. The magnitude of volt-age recoveries was about 40% of the voltage losses during the preceding SOE mode operation. The effect of switching parameters (and associated transient processes during switching) on cell performance was also studied. It was observed that during rSOC cycling, after SOE mode operation, the cell takes about 30 minutes to recover to the SOFC cell voltage prior to the SOFC mode operation. During rSOC cycling, in order to study the effects of switching time on cell performance, some SOFC mode operations were commenced without waiting for the cell to recover to SOFC OCV. No discernible effect of the switching time on subsequent cell performance was apparent