Enhancement of reversible solid oxide cell stack design and operation via thermal systems analogs

Reversible solid oxide cell (RSOC) stacks can approach ultra-high stack efficiencies (>70%) and reduce voltage swings by operating at low current densities with high reactant utilizations. However, such conditions may lead to excessively low electrochemical driving forces, particularly in conventional single-stage stacks that lack operational flexibility. A novel pathway to address these limitations lies in drawing analogies from thermal systems, including the mapping of thermal system analyses onto electrochemical systems. Of particular interest are the concepts of multi-staging and pinch points. Multi-physics MATLAB models were developed to simulate multi-stage configurations under varying operating conditions. Results show that multi-staging significantly improves the practicality of achieving high stack efficiencies while mitigating voltage swings, especially at low current densities. At 0.1 A/cm 2 , the multi-stage configuration achieved a round-trip stack voltage efficiency (RTSVE) of 87%, an absolute improvement of 6.5 percentage points, while reducing the voltage swing by more than 30% relative to a conventional single-stage configuration. Electrochemical pinch-point analysis further indicates improved feasibility despite the higher stack efficiencies achieved through multi-staging. These results demonstrate that thermal system analogs offer a viable pathway toward high-efficiency, durable RSOC operation. • Thermal system analogs: A complementary approach to enhance RSOC operation. • Multi-staging with flow reversal improves efficiency and lowers voltage swing. • Electrochemical pinch points proposed as a novel diagnostic for RSOC feasibility. • Multi-staged RSOCs achieved RTSVEs up to 87% at 0.1 A/cm 2 , 6.5 pp above baseline.