System-Level Validation of Pem Electrolyser Balance of Plant: An Integrated Framework for Functional Performance

Abstract The study presents a system-level validation framework for assessing the functional performance of the balance of plant (BOP) of a proton exchange membrane (PEM) electrolyser. The proposed approach addresses a methodological gap between individual component testing and verification of the integrated behaviour of interconnected auxiliary systems. The framework establishes traceability between the BOP architecture, subsystem interfaces, functional requirements, validation procedures, operating modes, fault scenarios, acceptance criteria, corrective actions, and final system disposition. Validation covered water management, thermal management, electrical power supply and distribution, hydrogen and oxygen handling, ventilation and HVAC (heating, ventilation, and air conditioning), instrumentation, supervisory control and data acquisition (SCADA), operational-mode transitions, and safety functions. Six principal operating modes – startup, steady-state operation, load following, standby, shutdown, and emergency shutdown – were evaluated together with simulated abnormal conditions, including overpressure, overheating, power loss, gas leakage, and sensor-related faults. The results demonstrate that the principal BOP subsystems fulfilled their intended functional and safety roles within the defined operating envelope and that the interfaces between subsystems supported coordinated system operation. Two initial deviations were identified during validation and subsequently closed through corrective action and re-testing, including thermal-control adjustment and hydrogen-dryer maintenance. The final validation confirmed the absence of unresolved critical deviations and established the BOP as functionally acceptable for its intended application within the investigated operating conditions. The results support the hypothesis that architecture-based, traceable system-level validation provides a more integrated and traceable basis for demonstrating PEM electrolyser BOP functional readiness than isolated component testing. The framework can support commissioning, operational handover, future system modification, and scale-up, while its applicability remains bounded by the tested operating conditions, instrumentation accuracy, simulated fault scenarios, and exclusion of long-term degradation and regulatory certification.