How Alternative Drives Are Changing Bus Depots

Vehicles with zero-emissions drive systems are still the exception rather than the rule on regional and urban bus routes. That will change in the years to come. Against the backdrop of the EU Clean Vehicle Directive among other things, and the need for climate action, more and more fuel cell and above all battery-electric buses are entering service. In the medium term they will almost fully replace conventional diesel buses. That is a huge challenge for public transport. However, replacing bus fleets is only part of the transition to new drives. Equally important and challenging is the upgrading of bus depots that is part of this process.

For today’s depots, the activities surrounding ICE buses are part and parcel of planning and day-to-day operations. Refuelling is not a time-critical factor and a normal procedure. The diesel pump infrastructure at bus depots is tried and tested, and conventional diesel buses have a long range.

Battery-electric bus requirements

The focus is above all on battery-electric buses, which already account for by far the largest share of zero-emissions vehicles in public transport today and will certainly continue to do so in the future. In addition to lower procurement costs compared with fuel cell buses, the fact that electricity is generally always available plays a key role here. However, the reduced range of these vehicles means coordinating recharging periods and operating timetables is necessary. It follows that the energy supply will become an important part of depot operations and vehicle charging procedures will be key to success.

Because charging takes time, bus depots must be equipped with sufficient charging points to simultaneously supply several vehicles. Downtimes due to charging also affect vehicle availability. A bus fleet’s energy demands and charging times determine the energy infrastructure required. That concerns not only the number of chargers and their output, but also the energy supplier’s grid connection and any necessary substations. The time required to plan and set up the infrastructure should not be underestimated.

Infrastructure for fuel cell buses

Fuel cell buses have a range almost on a par with conventional buses, and refuelling is rapid. However, the cost of purchase is higher and they require a hydrogen supply infrastructure. Setting up a dedicated refuelling station is an option, with trucks delivering hydrogen by trailer, or on-site hydrogen production with an electrolyser. Depending on the local situation and fleet size, public refuelling stations are an alternative if the operator can guarantee supplies.

Fuel cell buses are an interesting option if a growing number of battery-electric buses require a grid connection which the energy supplier can only provide long-term or at very high cost. Under these circumstances, depots equipped for both types of zero-emissions transport, i.e. with charging facilities for a battery-electric bus fleet and mobile hydrogen refuelling stations for fuel cell buses, are a conceivable option.

HVO offers an interim solution

Transitioning to zero-emissions transport will require a huge technological effort and investment by the industry over the years to come. Alternative fuels represent an interim solution, and hydrotreated vegetable oil (HVO) has the necessary potential. The refuelling procedure is the same as for diesel, and in HVO 100 (pure HVO) form it reduces the CO2e emissions of ICE vehicles by 90 per cent. While not classified as zero-emissions in accordance with the Clean Vehicle Directive, HVO is a clean fuel nonetheless, and as such helps to meet the requirements of the CVD. Conventionally powered vehicles can run on HVO until the end of their service life, and no infrastructural changes to depots are required. This provides breathing space and the necessary time to upgrade a depot for zero-emissions vehicles.

Expertise for the transition to alternative drives

Replacing fleets will continue to gather pace. DB Regio Straße has been steadily building expertise in this field and operates battery-electric and fuel cell buses in regional and urban transport throughout Germany. The first fuel cell buses began operating in North Frisia in early 2021 and are refuelled using locally produced hydrogen from wind farms. The largest battery-electric bus fleet operates in Frankfurt/Main for traffiQ, the local public transport network. A depot optimised for electric operations with 20 chargers was set up in Frankfurt-Höchst for the 27 buses on route network B and entered service in mid-2023. With Industriepark Höchst nearby, there is also the option of a hydrogen filling station for fuel cell buses.

The Bus Lean Innovation and Technology Centre (BLITZ) in Weiterstadt near Darmstadt also plays a key part in DB Regio Straße’s efforts to meet the challenges of zero-emissions operations. BLITZ designs, tests and optimises processes and technologies for all DB bus companies, including for alternative drive systems.

All market players must face up to the challenge

All market players, transport companies and public transport authorities must face up to the challenge of transitioning away from fossil fuels. For transport companies, converting depots will tie up considerable financial and human resources. In some cases, it will be possible to upgrade step by step, while in others it will be necessary to consider whether a complete new build makes more sense. The employees must also be brought onboard on this journey to the future and be given professional training. This has always proved to be a key factor in a successful project.

The requirements associated with the transition must also be reflected in the contract awarding practices of public transport authorities. The usual period of time that elapses between a contract being awarded and commissioning is insufficient if a depot must first create the necessary infrastructure. In addition, for a company introducing battery-electric buses it means that important operating parameters will change. Shorter ranges and longer downtimes due to charging will generally result in more vehicles being required. Regularly occurring charging intervals also hinder flexible rotation and service planning, making efficiency gains more difficult.

Plan now for the future!

The requirements of the Clean Vehicle Directive cover the period up to 2030. Following their step-by-step introduction the aim is to fully implement zero-emissions public transport. For transport companies and authorities, embarking on this journey as soon as possible will be a tour de force, but also a necessity and above all an opportunity.

Aside from the legal requirements, it follows that environmental and climate protection are necessary hallmarks of public transport and that as a result both passengers and the public have expectations. The opportunity lies in public transport pioneering the electrification of road transport and thus demonstrating its innovativeness. Every battery-electric and fuel cell bus showcases the mobility transition, benefits the climate and contributes to attractive public transport.

Sven Hofmann discusses the topic in more detail in an article in KommunalPraxis magazine, which can be provided.

Contact: Ralf Droste, ralf.droste@deutschebahn.com