Demonstration and scale-up of high-temperature electrolysis systems

High-temperature electrolysis (HTE) is a key to link the electricity sector with other industries and to evolve the electricity transition into a full energy transition. After years of development, HTE is now on the threshold to reach market readiness. The present work shows the latest achievements of Sunfire's development based on the results of the project GrInHy2.0 demonstrating hydrogen production (solid oxide electrolysis cell [SOEC]) in an industrial environment and the project SynLink demonstrating co-electrolysis (Co-SOEC) for renewable synthesis gas production. The GrInHy2.0 system is a 720 kW_AC electrolyzer operating in the iron-and-steel works Salzgitter (Germany). It is now in operation for approx. 14,500 h and achieved a mean degradation rate below 23 mOhm cm² kh⁻¹ and an electrical efficiency of up to 84%_LHV. It also proved that HTE now reached industrial-relevant availability of over 90%. While the HTE system in Salzgitter consists of eight modules, a single module was tested in co-electrolysis mode within the project SynLink. It demonstrated synthesis gas generation via Co-SOEC with a flexible H₂/CO ratio between 1 and 4. The work provides insight into how HTE will play a major role in the near future to efficiently produce renewable feedstock for an economy with a drastically reduced carbon footprint.