Energy efficiency of hydrogen for vehicle propulsion: On- or off-board H2 to electricity conversion?

If hydrogen fuel is available to support the transportation sector decarbonization, its usage can be placed either directly onboard in a fuel cell vehicle, or indirectly, off-board, by using a fuel cell power station to produce electricity to charge a battery electric vehicle. Therefore, in this work, the direct and indirect conversion scenarios of hydrogen to vehicle propulsion were investigated regarding energy efficiency. Thus, in the first scenario, hydrogen is the fuel for the onboard electricity production to propel a fuel cell vehicle while in the second, hydrogen is the electricity source to charge the battery electric vehicle. When simulated for a drive cycle, results have shown that the scenario with the onboard fuel cell consumed about 20% less hydrogen, demonstrating higher energy efficiency in terms of driving range. However, energy efficiency depends on the outside temperature when heat loss utilization is considered. For outside temperatures of −5 °C or higher, the system composed of the battery electric vehicle fueled with electricity from the off-board fuel cell was shown to be more energy-efficient. For lower temperatures, the system composed of the onboard fuel cell again presented higher total (heat + electricity) efficiency. Therefore, the results provide valuable insights into how hydrogen fuel can be used for vehicle propulsion, supporting the hydrogen economy development. • H 2 allocation for vehicle propulsion onboard or off-board is considered. • Electrical/thermal efficiency of the two hydrogen usage scenarios is investigated. • Hydrogen allocated onboard, i.e. in a fuel cell vehicle, consumed less H 2 per km. • Off-board H 2 usage, i.e. to power a battery vehicle, had high electrical/thermal efficiency.