Abstract:The transportation sector is a major source of California’s greenhouse gas emissions, contributing 41% of the state total[1]. California policy is moving rapidly toward Zero Emission battery electric vehicles (BEV) and hydrogen fuel cell vehicles (FCV). Governor Newsom has issued an executive order that all new in-state sales of passenger vehicles should be Zero Emission Vehicles (ZEV) by 2035. Further, the California Air Resources Board has approved rulemaking requiring that more than half of trucks sold in the state must be zero-emissions by 2035, and all of them by 2045 [1a].California has the ambitious goal of achieving a 60% renewable electricity grid by 2030 and 100% carbon free grid by 2045. High penetration of variable renewable energy (VRE) requires seasonal storage to match supply and demand and hydrogen could be a possible candidate for this purpose [1b]. The author has developed the CALZEEV energy-economic model to study possible roles for hydrogen in a VRE intensive future grid with a large Zero Emission Vehicle fleet, comprised of both BEVs and FCVs. In particular, we study whether we can provide sufficient seasonal storage for a 100% zero carbon electricity grid and the potential role of H2 infrastructure in a BEV/FCEV combination for a sustainable path towards a zero-emission energy system. The role of hydrogen infrastructure in seasonal storage for balancing VRE generation while meeting demand for hydrogen vehicles year around has been studied, including economic impacts.