System-Level Assessment Methodology for PV–AEL–H2–PEMFC Power-to-Power Systems: Constant-Efficiency Versus Quasi-Dynamic Modeling

Hydrogen-based power-to-power (PTP) systems complement batteries for long-duration storage, but their assessment often assumes fixed electrolyzer and fuel-cell efficiencies. The main innovation of this work is developing a system-level methodology to quantify how component-model fidelity affects the annual assessment of photovoltaic-alkaline electrolyzer-hydrogen-proton exchange membrane fuel cell systems. To highlight parameter and operational differences, two approaches are compared for the Santa Cruz–Baltra case study. Case A relies on simplified parameter assumptions, using fixed AEL and PEMFC efficiencies of 0.65 and 0.52. In contrast, Case B resolves operational differences by capturing operating-point-dependent electrochemical behavior, part-load variations, and AEL thermal-state propagation. Both cases use identical system boundaries and supervisory control, allowing model-fidelity effects on hydrogen production, storage utilization, and electricity recovery to be quantified. Annual simulations show that Case A predicts higher recovered electricity than Case B. For a representative configuration, global efficiency decreases from 0.529 to 0.440 (a 17% relative difference). The largest relative difference in recovered electricity (~91%) occurs in constrained configurations. Component-level experimental validation does not constitute full system-level validation. Overall, operating-point-dependent models materially alter annual PTP performance estimates under variable renewable operation.