reement, adopted by virtually all 195 countries of the United Nations, is a binding deal with targets to keep global warming of the earth beneath 2∘C, and reduce emissions of greenhouse gases in 2050 by at least 80% compared to 1990. These targets require significant reductions in energy consumption and switch to carbon free renewable energy sources. Changing to renewable energy sources brings several complications to the electricity system. Supply and demand of electricity need to match at any time. The intermittent nature of renewable energy sources, such as solar and wind, requires energy storage and need to be balanced with dispatchable power generation. Passenger cars could offer dispatchable power as they are parked for 95% of the time. Especially fuel cell electric vehicles (FCEVs) connected to the grid could offer this service in a clean and efficient way. Could parked and unused grid connected FCEVs replace the positive dispatchable power plants to balance 100% renewable energy systems? This research investigates how future 100% renewable national electricity, heating and transport systems can be balanced with the use of hydrogen production and storage, and grid connected FCEVs. A model is developed that simulates the future energy systems of Germany, France, Spain, Great Britain, Denmark and Belgium. The energy systems include electricity generation and consumption, road transport, hot water and space heating. Road transport vehicles are battery electric vehicles (BEVs), FCEVs or a combination of both. Electricity and hydrogen are the only energy carriers. Electricity is mainly supplied by solar and wind power. Hot water and space heating is mainly supplied by solar thermal energy and electric heat pumps. Electricity generation and consumption profiles and temperature data of 2014, 2015 and 2016 serve as inputs. The future 100% renewable energy scenarios are based on scenarios published by government agencies, research institutions or transmission system operators. Demand response heating (DRH) is analysed and applied to all cases. Interconnecting the electricity grids of Germany and France is also investigated.
Hydrogen production and grid connected FCEVs can balance national electricity grids. Electrolysers can act as negative balancing power consuming excess electricity of intermittent renewable energy sources to produce hydrogen. Roughly 0.4-0.6 GW of electrolyser capacity is required to balance 1 GW of renewables in the investigated countries. This requirement can be lower when curtailment is applied and the installed capacity of renewables is slightly increased. Hydrogen can be stored locally in high pressure storage tanks or at large scale in underground salt caverns. A typical salt cavern can store around 6 million kg of working gas. Per TWh of final energy consumption approximately 1-2.5 million kg of hydrogen storage capacity is required. Conventional positive balancing plants such as gas turbines could be replaced by FCEVs connected to the electricity grid. Peak backup demands can be balanced with 25 - 50% of the FCEV passenger fleet, which corresponds to 12.5 - 25% of the total passenger car fleet. The utilisation of FCEVs for V2G varies from 2.5 to 8%. Between 7% and 14% of the electricity consumption in a country is supplied by grid connected FCEVs. Hydrogen can be locally produced at hydrogen fuelling stations or electrolysers can be installed near large scale electricity generation sites or salt caverns where hydrogen can be produced and stored directly. Hydrogen fuelling stations need an average dispensing capacity of 3000 kg/day (∼600 passenger FCEVs/day) to cover all fuelling demands except peak demands.