Solid Oxide Electrolyzers Process Integration: A Comprehensive Review

Solid oxide electrolysis (SOEL) has emerged as a promising technology for efficient hydrogen production. Its main advantages lie in the high operating temperatures, which enhance thermodynamic efficiency, and in the ability to supply part of the required energy in the form of heat. Nevertheless, improving the long-term durability of stack materials remains a key challenge. Thermal energy can be supplied by dedicated integration with different industrial processes, where the main challenge lies in the elevated stack operating temperature (700–900 ◦C). This review provides a comprehensive analysis of the integration of solid oxide electrolysis cells (SOECs) into different industrial applications. Main processes cover methanol production, methane production, Power-to-Hydrogen systems, or the use of reversible solid oxide electrolysis cell (rSOEC) stacks that can operate in both electrolysis and fuel cell mode. The potential of co-electrolysis to increase process flexibility and broaden application areas is also analyzed. The aim is to provide a comprehensive analysis of the integration strategies, identify the main technical and economic challenges, and highlight recent developments and future trends in the field. A detailed comparison assessment of the different processes is being discussed in terms of electrical and thermal efficiencies and operating parameters, as well as Key Performance Indicators (KPIs) for each process. Technical-economic challenges that are currently a barrier to their implementation in industry are also analyzed.