Exploring internal and external drivers of hydrogen deployment in the energy transition

Hydrogen is increasingly recognized as important for deep decarbonization, but its future deployment remains highly uncertain. Here, we extend the open-source PyPSA-Eur model with country-level carbon constraints and simulate European energy transition pathways from 2025 to 2050 under three carbon budgets. We distinguish external drivers, such as hydrogen use in transport and industry, from internal drivers, such as electrolyzer costs, CO2 capture rates, and sequestration availability. Results show that, within our scenario design, internal drivers and carbon budget stringency explain most variation in EU hydrogen deployment. Endogenous 2050 hydrogen demand ranges from nearly zero to 2,200 TWh/year, and widespread green hydrogen uptake could raise demand to 3,200 TWh/year. Blue hydrogen remains more limited, constrained by sequestration scarcity and tighter carbon budgets, implying competition with other hard-to-abate sectors and greater asset-stranding risk. By quantifying the boundaries and potential evolution of hydrogen deployment, this study provides system-level insights beyond simplified hydrogen roadmap assumptions.