Optimal power allocation strategy for renewable hydrogen production considering usage-based stack degradation

This study investigates various power allocation strategies (PAS) for a multi-stack proton exchange membrane (PEM) water electrolysis plant (WEP) coupled with variable renewable energy (VRE, including solar photovoltaic (PV) and wind). A key contribution is the incorporation of a usage-based, current–density-driven degradation model, which more accurately captures the operational impacts of PAS on stack degradation and end-of-life replacement requirements compared to commonly used fixed annual degradation rates. The analysis also examines variations in the VRE-to-WEP capacity ratio, PV-to-wind mix, stack sizing, and overload. Results show that the optimal PAS depends strongly on these design parameters. In the base case without overload, the two-phase sequential-then-even PAS — which first brings stacks to their minimum operating level and then allocates power evenly — achieves the highest hydrogen (H 2 ) production and lowest specific energy consumption (SEC). Increasing the VRE:WEP ratio reduces the energy cost component of the levelised cost of hydrogen (LCOH) initially, but beyond a threshold ratio the rising marginal cost of energy outweighs the gains. Allowing overload operation can improve H 2 production and reduce the LCOH under specific conditions, but accelerates stack degradation and raises replacement costs, often offsetting economic benefits. These findings highlight the importance of jointly considering PAS, stack sizing, minimum operating levels, and VRE configuration when designing electrolyser systems for cost-effective green H 2 production.