Solid oxide electrolysis cell core

Method of operating a Solid Oxide Electrolysis Cell (SOEC) core, said core comprising an SOEC core shell with shell thermal insulation cladding at least the outside of said SOEC core shell and comprising within the SOEC core shell a plurality of SOEC stack modules, each SOEC stack module comprises one or more SOEC stacks, wherein said SOEC core has an inner hot zone at least partly surrounded with hot zone thermal insulation within the SOEC core shell and a recuperating space arranged at least partly around the outside of said hot zone thermal insulation and within the SOEC core shell to separate the hot zone from the SOEC core shell and provide a recuperating fluid path for a recuperating fluid, the method comprises the steps of:

• providing electrical power to said SOEC stacks;
• providing a process fluid to the SOEC core through a process fluid inlet, further through said recuperating space where it recuperates thermal energy escaping said inner hot zone, which heats up the process fluid;
• and
• providing the now heated process fluid to said SOEC stacks.