Future national electricity, heating, cooling and transport systems need to reach zero emissions. Significant numbers of back-up power plants as well as large-scale energy storage capacity are required to guarantee the reliability of energy supply in 100 percent renewable energy systems. Electricity can be partially converted into hydrogen, which can be transported via pipelines, stored in large quantities in underground salt caverns to overcome seasonal effects and used as electricity storage or as a clean fuel for transport. The question addressed in this paper is how parked and grid-connected hydrogen-fueled Fuel Cell Electric Vehicles might balance 100 per cent renewable electricity, heating, cooling and transport systems at the national level in Denmark, Germany, Great Britain, France and Spain? Five national electricity, heating, cooling and transport systems are modeled for the year 2050 for the five countries, assuming only 50 percent of the passenger cars to be grid-connected Fuel Cell Electric Vehicles, the remaining Battery Electric Vehicles. The grid-connected Fuel Cell Electric Vehicle fleet can always balance the energy systems and their usage is low, having load factors of 2.1–5.5 percent, corresponding to an average use of 190–480 h per car, per year. At peak times, occurring only a few hours per year, 26 to 43 percent of the grid-connected Fuel Cell Electric Vehicle are required and in particular for energy systems with high shares of solar energy, such as Spain, balancing by grid-connected Fuel Cell Electric Vehicles is mainly required during the night, which matches favorably with driving usage.

In a 2050 fully renewable national electricity, heating and road transport system primary energy supply comes from non-dispatchable power generation such as solar and wind energy. Both negative and positive dispatchable balancing power plants need to balance the system. This work investigates whether parked and grid connected (Vehicle-to-Grid) Fuel Cell Electric Vehicles (FCEVs) fueled with pure hydrogen can replace positive dispatchable balancing power plants. These power plants, often gas turbine based, are likely to operate at low capacity factors in future. A simulation for a 2050 scenario is based on German 2015 renewable electricity data and assumes a passenger car mix of 40% FCEVs and 60% Battery Electric Vehicles. On average 0.9 million FCEVs with Vehicle-to-Grid (V2G) output of 10 kWe would be required during evening and night time and approximately 6 million during the annual peak shortage hour to balance the system at all times. These numbers represent respectively 2% and 14% of the total 2015 German passenger car stock and have the potential to replace all positive dispatchable power plants in future.