Solid Oxide Electrolysis Technology
Solid oxide electrolysis technology is where solid oxide electrolysis cells produce hydrogen and oxygen (by-product), through an electrochemical process, from water and electricity. If utilised electricity is from renewable sources, produced hydrogen is considered as green hydrogen.
When supplied with renewable power, the hydrogen produced through electrolysis is referred as green hydrogen. The importance of electrolysis is keeping growing with the fast growth of power generation using renewable energy, since electrolysis is an ideal technology for coupling among different energy sectors. Solid oxide electrolysis is the reverse reaction of solid oxide fuel cell.
Compared to low temperature electrolysis technologies, SOEC reaction is thermodynamically and kinetically favourable due to the higher temperatures, and therefore needs less electrical energy to produce the same amount of H2. If heat can be supplied from outside, the electrical efficiency of SOEC can be even higher than 100%. For this reason, SOEC is mostly suitable for applications, where high temperature waste heat is available from the existing processes.
Besides green H2 generation, SOEC can be used also for CO or syngas (i.e., mixture of H2 and CO) production, if CO2 is supplied either alone or together with steam (in this case, the so called co-electrolysis). The composition of the syngas can be well predicated and adjusted in a wide range by controlling the H2O/CO2 ratio, which makes co-electrolysis suitable for integration with different downstream chemical industry.
Furthermore, the unique capability of reverse operation with the same cells/stacks makes RSOC (reversible solid oxide cell) a promising candidate for hydrogen refuelling station (HRS), charging station, energy storage or grid balancing. Switching between SOFC and SOEC modes is kinetically restricted by the availability of the steam, but not the electrochemical properties of the SOC itself.