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.