Role of Technology Flexibility and Grid Coupling on Hydrogen Deployment in Net-Zero Energy Systems

Low-carbon hydrogen is anticipated to be a key element of economy-wide decarbonization pathways. Here we employ a multisector energy system model of the contiguous United States to study competition among low-carbon hydrogen production options and the interplay between the electricity and hydrogen sectors in a net-zero energy system. When hydrogen storage is available without constraints and electrolyzers are grid-connected, they account for most hydrogen production, while providing demand-side flexibility to the electricity system. This decreases battery storage deployment to achieve similar shares of variable renewable energy (VRE) in the power system. When electrolyzers are not grid-connected but rely on islanded VRE power to produce "green" H₂, we find that power system flexibility and the share of electrolytic hydrogen are reduced, all else equal. Without hydrogen storage, natural gas-based hydrogen (i.e., "blue" H₂) accounts for most hydrogen production, although increasing flexibility of blue H₂ can enable some electrolytic H₂ production. Finally, we find that hydrogen deployment does not substantially drive energy transmission expansion, although there is a modest increase in CO₂ transmission when blue H₂ is deployed in regions with limited CO₂ storage.