Operating region characterization for electric-hydrogen coupling systems considering degradation of key components in PEM electrolyzers

Accurately assessing the impact of key-component degradation in proton exchange membrane (PEM) electrolyzers on the long-term hydrogen production and renewable energy consumption capacity of electric‑hydrogen coupling systems (EHCS) poses a significant challenge. To address this challenge, this paper proposes a region-based operation analysis framework that visually captures the full life-cycle performance change of EHCS. First, an electrochemical-thermal-mass-transfer model is developed, explicitly incorporating the degradation mechanisms of the membrane, catalyst, bipolar plates, and porous transport layers. Based on this, an operating model is established, accounting for dynamic efficiency, thermal safety, anode hydrogen concentration safety, and overload constraints. Then, the concept and model of the EHCS operating region (EHCS-OR) are defined, which characterizes the feasible space of daily hydrogen production under varying renewable energy generation levels and electrolyzer degradation states. Furthermore, owing to the non-convexity of the operating region caused by the numerous discrete variables in the model, a tailored branch-and-bound-based algorithm is proposed to efficiently solve the boundaries of this complex region. Finally, case studies validate that the derived EHCS-OR intuitively reveals the impact of component degradation on system capabilities. The proposed framework provides comprehensive and visual decision support for the lifecycle management, day-ahead scheduling, and parameter setting of EHCS.