Multiscale load collective modelling for an electrolyser cell frame under market-driven operation

The increasing penetration of renewable energy in power systems results in highly intermittent operating conditions for power-to-hydrogen assets. Alkaline water electrolysers are traditionally designed for and operated in a base load scenario, i.e. permanently at high load. Consequently, intermittency means that assets are increasingly operated under market-driven dispatch, involving partial-load operation, frequent start-stop events, and idle periods, yielding additional component stress. To support reliable design and assessment of such systems, realistic and traceable methods are required to derive mechanical load collectives for critical components. This paper presents a multiscale modelling framework, quantifying fatigue-relevant load spectra for an electrolyser cell frame, with a particular focus on mechanical loads during idle operation. Long-term operating profiles are generated using a coupled electricity and hydrogen market model that captures price variability, energy availability, and dispatch behaviour. Idle periods are identified and mapped to temperature and pressure cycles due to shutdown, via a reduced physical model. A mechanical model translates these cycles into stress ranges and occurrence counts for the stack cell frame. The resulting load collectives provide a transparent link between market-driven operation and component-level mechanical loading, highlighting the contribution of idle periods to variable-amplitude stress histories, supporting the fatigue-oriented assessment of electrolyser components under flexible operation.

Keywords: Pressurised alkaline water electrolysis, intermittent power profile, mechanical load collective derivation..