Investigating the Iron‐Steam Process for Coupling With SOEC and SOFC: A Step Toward Integrated Hydrogen and Electricity Storage

Thermochemical energy storage based on reversible iron–steam redox reactions, coupled with solid oxide electrolysis (SOEC) and fuel cells (SOFC/rSOC), offers a promising route for high‐temperature power‐to‐power applications. Previous work, notably the solid oxide iron–air redox battery (SOIAB) pioneered by Huang and co‐workers, has demonstrated the fundamental feasibility at material and small‐reactor scale, identifying key challenges in cell efficiency, cycle stability, and material degradation. The present study addresses system‐level integration and reactor‐scale implementation. A thermodynamic and process framework is developed, describing functional interfaces between electrochemical hydrogen production and consumption, gas conditioning, heat management, and redox reactors. To validate the concept beyond laboratory‐scale material tests, a self‐built pilot‐scale fixed‐bed reactor (10 L) was designed, constructed, and commissioned. This facility enables controlled investigation of iron oxide reduction (charging) and oxidation with steam (discharging) under application‐relevant flow rates and temperatures. Continuous monitoring of temperature, pressure, and product gas composition provides quantitative insight into reaction progress, material stability, and oxygen exchange capacity. The results confirm reproducible hydrogen uptake and release, demonstrate the technical feasibility of reactor‐scale integration, and complement existing SOIAB research by providing experimental data and process‐level understanding critical for scaling toward industrial power‐to‐power and sector‐coupling applications.