| Abstrakt: |
Solid oxide electrolyzers have the potential to play an important role in a hydrogen economy in which energy, for mobile applications and electrical grid load balancing, is stored as hydrogen. The advantages of solid oxide electrolyzers for hydrogen production are 1/ the high operating temperature resulting in high electrical efficiency, 2/ the possibility to use hydrocarbon fuels as counter-feed to further increase the electrical efficiency, and 3/ the flexibility to alternately operate in fuel cell mode. This paper focuses on the use of state-of-the-art SOFC materials for air-assisted and hydrocarbon-assisted hydrogen production. Electrolyte supported cells, with 90 µm thick 3YSZ electrolyte and Ni-GDC electrode, showed comparable ASR-values in electrolyzer and fuel cell mode between 650 and 920{degree sign}C, and exhibited stable hydrogen output during a 100 hours period in both electrolyzer modes at 850{degree sign}C and 70% steam utilization. Anode supported cells, with 5µm thick 8YSZ electrolyte and Ni- YSZ electrode, showed lower ASR-values than electrolyte supported cells, which would make this cell type the most promising. However, in this case the hydrogen production was limited at steam utilizations of 50%, which seems related to mass transport limitations in the anode substrate. |
