Solid oxide electrolyzer cell
A solid oxide electrolyser cell (SOEC) is a solid oxide fuel cell set in regenerative mode for the electrolysis of water with a solid oxide, or ceramic, electrolyte to produce oxygen and hydrogen gas[1].
Principle
Solid oxide electrolyser cells operate at temperatures for high-temperature electrolysis[2], typically between 500 and 850°C similar to SOFC. Advantages of this class of regenerative fuel cells include high efficiencies, long term stability, fuel flexibility, low emissions, and cost. The largest disadvantage is the high operating temperature which results in longer start up times and mechanical/chemical compatibility issues. Electrolysis of water is increasingly endothermic with temperature, electricity demand is reduced because the joule heat of an electrolysis cell is utilized in the water splitting process at high temperature. Research is ongoing to add heat from external heat sources such as concentrating solar thermal collectors, and geothermal sources.
By definition, the process of any fuel cell could be reversed. However, a given fuel cell is usually optimized for operating in one mode and may not be built in such a way that it can be operated backwards. Fuel cells operated backwards generally do not make very efficient systems unless they are purpose-built to do so as in solid oxide electrolyser cells, high pressure electrolyzers, unitized regenerative fuel cells and regenerative fuel cells.