Dynamic and prospective life cycle assessment of electrolytic hydrogen production within an evolving energy system: an Irish case study

Renewable hydrogen is expected to play a key role in decarbonising future energy systems. Simultaneously, energy systems which support renewable hydrogen production are rapidly developing. This interconnectedness increases the complexity of evaluating the environmental impacts of hydrogen, and should be modelled with care. This study aims to address these considerations using a life cycle assessment (LCA) model which incorporates both hourly dynamics and prospective modelling to determine the environmental impacts of introducing large-scale electrolytic hydrogen production in Ireland, comparing constant hydrogen production using grid power and variable hydrogen production using otherwise curtailed power. The results show that several important energy system developments such as offshore wind deployment, grid improvements, battery deployment, and interconnector reliance will heavily impact the amount of curtailed power available (0-13.91 TWh/year) and environmental impact of grid electricity (14-62 g CO2-eq/MJ). Nevertheless, in scenarios where curtailed power is higher than 1% of available renewable generation, variable hydrogen production results in 63-79% less water consumption, 65-97% less land use and 88-98% lower GWP compared to constant grid-powered hydrogen production. Hydrogen production from grid power only results in renewable hydrogen compliant with EU regulations (Delegated Regulation (EU) 2023/1184 and 1185) with substantial low carbon electricity imports and an allowable system non-synchronous penetration (SNSP) of 95%. The results support the EU’s decision requiring strict temporal correlation, but warn that extremely low utilisation rates will also render hydrogen production from curtailed power unsustainable. The developed methodology could be applied to any study evaluating the consequences of large-scale energy system changes.