Progress in fuel cell usage as an auxiliary power unit in heavy-duty vehicles

Commercial medium and heavy-duty diesel vehicles in Europe are responsible for transporting an average of 73% of the total freight tonnage over distances up to 150 km as of 2021. These vehicles often operate on routes where no other form of transport is viable while still assuring fast deliveries. However, due to the nature of the journeys performed by the heavy-duty vehicles, which can span over several days or weeks depending on the mileage and the loading and unloading destinations, it becomes essential for the drivers to address the energy demands for heating and for the cabin accessory appliances during resting periods. As a rule, and especially in cold weather conditions, in order to prevent start-up problems, engine idling has traditionally been used. In order to mitigate the negative impact of increased fuel consumption and cut the harmful emissions from the engine’s idling, the usage of a fuel cell auxiliary power unit (APU) is proposed. Fuel cells are more efficient than internal combustion engines and as an APU they could be sized appropriately to specifically power the cabin’s accessories. There are two types of fuel cells that are applied for an APU in heavy-duty vehicles, namely, proton exchange membrane fuel cell (PEMFC) and solid oxide fuel cell (SOFC), each one imposing specific system topology requirements. A brief literary review on fuel cell APUs for heavy-duty vehicles is undertaken in the paper with emphasis being on the most recent advancements and on the advantages and disadvantages for the two possible systems. An estimation of the cabin power consumption during rest periods for European heavy-duty vehicles is presented. Some general suggestions and considerations are laid down, which may be of use when designing such a system, as there is not much information on the topic.