Scenarios for using hydrogen as energy carrier in the future Danish energy system

System-wide aspects of the choice of hydrogen production technologies, distribution methods, infrastructure requirements and conversion technologies are studied. Particularly, the possibility of using in the future the existing Danish natural gas distribution grid for carrying hydrogen is assessed and being found promising , although some technical investigations remain to be done. For the year 2030, two scenarios are constructed: One using hydrogen primarily in the transportation sector, the other using it as a storage option for the centralised power plants still in operation by this year. For the year 2050, where the existing fossil power plants are expected to have been phased out completely, the scenarios for two possible developments are investigated: Either, there is a complete decentralisation of the use of hydrogen, converting and storing electricity surpluses into hydrogen in individual buildings, for later use in vehicles or regeneration of power and heat. Or, some centralised infrastructure is retained, such as hydrogen cavern stores and a network of vehicle hydrogen filling stations. The project has calculated both the geographical and the temporal distributions of all energy flow, from source over intermediary conversions to the use at the end user. Particularly the hourly time simulations have allowed the determination of hydrogen storage volume requirements, which turn out to be fairly modest, corresponding to the existing natural gas stores or to a third of a cubic metre of metal hydride storage for each of the two million principal buildings in Denmark. The analysis is used to identify the components in an implementation strategy, including the time sequencing of necessary decisions and technology readiness. Uncertainties are identified, and the most significant cost parameter is identified as that of fuel cells, and the decentralised scenario notably of the reversible fuel cell