In high temperature electrolysis, only a small percentage of energy is needed as heat -- around 90 kJ/mol for an electrolyzer operating at 950°C. This splits up into \(\approx\)60 kJ/mol of H2 around 200°C to decompose steam and only 30/40 kJ/mol (maximal realistic value) at 950°C for the electrolyzer itself, if it is assumed that the heat of the products is recovered to heat up the reagents \cite{verfondern2007nuclear}.
There are two main types of Solid Oxide Cells which can also be operated in electrolysis mode:
- Oxygen ion conducting Solid Oxide Electrolyzers (O=SOE)
- Proton conducting Solid Oxide Electrolyzers (H+SOE)