This research details a global model for the estimation of future hydrogen penetration into the carbon constrained energy system out to 2050. Results show that approximately 2.2% of global energy consumption needs can be met by 2050, with significant contributions in the city gas network and transportation sector. Notably, passenger FCVs dominate the transportation sector contribution, leading to a global deployment of over 100 million FCVs by 2050 across North America, Western Europe, South East Asia, China and Japan. Hydrogen production is focused in non- OECD nations, and derived mainly from fossil fuels. As a result, CCS has a strong role to play in the future energy system in order to underpin the deployment of a significant fleet of FCVs. Policy issues identified include the need for significant additional investment in the energy system and technological progress in renewables and electrolyzers to realize a shift away from a fossil fuel dominated hydrogen economy.