Pressurized Solid Oxide Electrolysis—Operational Strategies

ABSTRACT Pressurized high‐temperature electrolysis is a promising pathway for high‐efficiency hydrogen production that enables direct compression and heat recovery opportunities not accessible to low‐temperature electrolysis. While laboratory testing is routinely conducted near atmospheric pressure, there is increasing interest in commercial deployment of pressurized solid oxide electrolysis (SOE). However, pressurization introduces material degradation risks and constrains stack and system design. This work introduces a component‐based thermodynamic model to examine SOE systems for both near‐term deployment and long‐term optimization. The model resolves performance trade‐offs across varying cell voltage, system pressure, heat integration, humidification, and recirculation strategies. Results show a minimum specific energy consumption of 37.7 kWh/kg using heat recovery with 5% water makeup and 90% electrolysis stack utilization. Direct steam feed systems have a limited operating window due to temperature sensitivity. In contrast, water feed systems use sensible heat to regulate stack temperature and provide a broader voltage range for efficient operation. A thermally self‐sustaining window is identified, where sufficient high‐temperature heat is recovered to vaporize feed water without external heat input. The system is particularly suitable for flexible operation due to the minimal sensitivity of specific energy to operating power in the self‐sustaining window. The work provides detailed design targets for component selection, operational guidance, and strategies to improve system durability, efficiency, and cost.