Development of a Transient Stress Analysis Framework for Solid Oxide Electrolysis Cell Stacks and Evaluation of Mechanical Reliability Under Dynamic Operation

Solid oxide electrolysis cells (SOECs) are promising devices for high-efficiency hydrogen production using variable renewable energy. However, dynamic operation involves complex interactions among electrochemical heat generation or absorption, gas heat transfer, temperature-dependent cell voltage, and thermal inertia of stack components. Therefore, mechanical reliability should be evaluated together with load-following performance. In this study, a transient stress analysis framework was developed for an SOEC stack by coupling a transient temperature distribution model, finite element stress analysis, and a surrogate model. The temperature model considers the active cell region, inactive cell region, and edge region, and calculates the evolution of in-plane temperature distributions during power fluctuations. The obtained temperature fields were transferred to finite element stress analysis to evaluate the stress states of the YSZ electrolyte, Ni-YSZ hydrogen-electrode support, and metal interconnector. To enable long-duration evaluation, a surrogate model was constructed from finite element results and applied to time-series temperature distributions under dynamic operating conditions. The suggested framework enables efficient estimation of transient stress histories and clarifies how temperature gradients formed during load changes affect stack components. This approach provides a useful basis for assessing mechanical reliability and designing operating strategies for SOEC stacks coupled with variable renewable energy.