Availability Assessment of an Offshore PEM Seawater Electrolysis: A System-level Approach

Green hydrogen is gaining prominence as a sustainable fuel to decarbonize hard-to-electrify industries and complement renewable energy growth. Among clean hydrogen production technologies, seawater-based PEM electrolysis systems hold substantial promise. However, implementing offshore PEM electrolysis systems faces significant challenges in ensuring long-term availability due to technological infancy and harsh environmental conditions. Ensuring safe and reliable operation is therefore critical to advancing global sustainability goals. While existing research has primarily focused on component-level techno-economic feasibility, limited attention has been given to system-level safety and availability analysis, particularly for offshore renewable-powered seawater-based PEM electrolysis systems. This study addresses this gap by conducting a comprehensive availability analysis of containerized plug-and-play PEM systems in offshore environments. A Bayesian Network model is employed, incorporating Fault Tree Analysis and Reliability Block Diagram approaches, for failure and availability analysis at the system level. A maintenance decision support tool using Influence diagram is developed to analyse different maintenance planning strategies impact on system availability improvement. A case study incorporating industrial modular PEM model is utilised to analyse the developed model effectiveness. The study identifies 81 availability states, with the hydrogen generation subsystem being the most critical to system performance. Comparative analysis shows that applying redundancy across all subsystems improves availability by 18.54% but reduces Expected Utility by 4.94%. The optimal strategy involves redundancy for seawater purification, cooling, and monitoring subsystems, with preventive maintenance for hydrogen generation, achieving a maximum EU of 5.29 × 106. This framework supports decision-makers in evaluating system availability under uncertain offshore conditions, optimizing maintenance strategies, and ensuring resilience for large-scale H2 production.