Degradation modelling and performance prediction of proton exchange membrane electrolyzers for wind-to-hydrogen systems

The integration of proton exchange membrane electrolyzers with intermittent renewable energy sources, particularly wind power, presents both opportunities and challenges for green hydrogen production. In this thesis, a novel degradation model is presented to investigate chemical degradation and operational performance of proton exchange membrane electrolyzers under intermittent renewable energy inputs, with a particular focus on wind integration. Three complementary modelling approaches are employed: long-term continuous and intermittent operation simulations of an electrolyzer, Rayleigh-distributed and real wind data simulations of a 2.8 MW system, and a validated SimulinkTM model for wind integration. Across the three studies presented, a clear picture emerges of the complex interplay between electrolyzer loading, membrane degradation, and hydrogen production. Intermittent operation can more than double the rate of fluoride release compared to continuous operation, with rapid cycling initially increasing degradation before reaching a quasi-steady state. Specifically, continuous operation at full capacity resulted in a membrane lifetime of approximately 9.4 years, compared to only four years under intermittent operation. Frequent partial load operation and prolonged OFF periods intensify degradation due to the electrolyzer operating at open-circuit voltage conditions. Rayleigh-distributed wind speed simulations at average velocities of 6, 8, and 10 ms-1 revealed that moderate wind conditions (8 ms-1) achieved near-maximum hydrogen output (?280,000 kg/year) while significantly minimizing membrane degradation (with the membrane thinning by 9.6 ?m). Dynamic simulations show that higher capacity ratios maximize hydrogen production (up to 269,768 kg), yet they experience the highest absolute degradation. However, efficiency quantified by hydrogen produced per membrane loss is lowest when capacity is fully matched. Faradaic efficiency analyses confirm that part-load and full-load cycling strongly influence electrochemical performance, emphasizing the need for operational strategies that minimize frequent voltage transients. Finally, system-level sensitivity analyses revealed that electrolyzer design parameters, including temperature, membrane thickness, and exchange current density, significantly affect hydrogen production and efficiency. Higher operating temperatures and thinner membranes reduce cell voltage and enhance output, while elevated exchange current densities improve efficiency by reducing activation overpotentials. Pressure effects were minimal, suggesting that thermal and electrochemical control are the dominant levers for optimizing proton exchange membrane performance under variable renewable supply. Collectively, these studies demonstrate that maximizing hydrogen productivity from wind-integrated proton exchange membrane electrolyzers requires careful attention to both system sizing and operational strategy. Achieving a balance between durability and output is essential: excessive cycling or poor load matching can rapidly accelerate membrane degradation, whereas optimal sizing and load distribution can deliver near-maximum hydrogen yield while preserving membrane integrity. The findings provide actionable guidance for designing resilient, high-performance electrolyzer systems for renewable hydrogen production and establish a foundation for future work integrating degradation modeling with techno-economic optimization.