Battery trains for the Bavarian forest network? Infrastructure of 30 million would be needed
Experts of the Technical University of Dresden and the Institut für Bahntechnik have examined the energy, technical and operational constraints that need to be taken into account for operation with battery-electric trains for the Bayerwald network. The results are “a bit sobering in terms of time and cost”, because of the needed infrastructure such as overhead line islands to charge the batteries, said Bavaria’s Minister of Transport Christian Bernreiter.
The Bavarian Forest network is currently operated with diesel trains of the RegioShuttle type of Stadler (originally Adtranz). The RegioShuttle vehicles of the Länderbahn, the operator of the Waldbahn under the brand Waldbahn, were put into service in 1996 and 1997. With a service life of 25-30 years, operation after 2030 is “probably technically feasible” according to the experts, but the 33- to 34-year-old vehicles will by then be technically and economically beyond their originally predicted service life and it would involve extra costs to replace worn components to keep them in operation.
All regional transport in Bavaria is to be emission-free by 2040, so there is work to be done to find an alternative for the diesel trains. Classical electrification with overhead lines is currently unrealistic due to the low traffic and utilisation figures. There are other non-electrified lines in Bavaria to be electrified with overhead lines with more priority, according to the Bavarian Railway Company (BEG), the entity that plans, finances and manages local rail transport in the state, which is done by local operators.
For this reason, it is examining the use of battery hybrid vehicles (BEMU-Battery Electric Multiple Units), which could use the existing overhead lines in Plattling and Klatovy for recharging. The BEG therefore commissioned a study to the Competence Centre for High-Performance Railways at the Technical University of Dresden. This centre comprises the engineering company Institut für Bahntechnik GmbH and the Dresden University. They examined the Bayerwald network with the main line from Plattling via Deggendorf and Zwiesel to Bayerisch Eisenstein and an optional extension across the border to Klatovy in the Czech Republic (line RB 35) as well as all lines that branch off from it.
Different scenarios for overhead line islands
Plattling station is currently the only place in the Bayerwald network where an overhead line already exists, and where battery trains could recharge. Five variants of different combinations of infrastructure solutions in different locations were studied using simulation software OpenTrack, of which number 4 was found the most optimal. The core of this is an approximately 10-kilometre-long overhead line island system around Zwiesel station for the lines RB35 to RB37, whereby the RB35 can charge while running under overhead line between Bettmannsäge and Lichtenthal, and the lines RB36 and RB37 charge at standstill at Zwiesel station. Also, a charging station for stationary charging in Grafenau is recommended, and one in Viechtach or Gotteszell. The use of an overhead conductor rail is particularly recommended, optimised for the highest possible transmittable currents which enable faster charging.
The report also points out that an adapted regulation for traction type is required from infrastructure manager DB Netz, so that also charging at standstill is feasible. This because charging at standstill is limited by the maximum possible standstill current via the contact point overhead contact line, as with the current regular contact strip of the overhead lines overheating would take place with a higher current. When the train is running, a higher permissible current is possible for recharging via the overhead line because overheating happens a lot less quickly.
The time-consuming planning approval procedures for sections of overhead line poses a major challenge to the timetable for the start of operations by the end of 2030. Therefore, during the preparation of the study, the start of operations was postponed to the end of 2034.
For the overhead islands construction necessary on the Bayerwald net for the most optimal variant, investments of an estimated 31.8 million euros would be required for BEMU operations. For a connection to Klatovy in the Czech Republic, a further 21.5 million would be needed.
The Czech side is examining the electrification of the section from Klatovy to the border. This could reduce the effort required for the overhead line islands on the German side, since the Bayerisch Eisenstein border station would then have another station with overhead lines in the Bayerwald network. In addition, a direct connection from Plattling to Klatovy could possibly be implemented more easily.
According to BEG specifications, the simulations were done using the Stadler Flirt Akku battery train specifications. The optimal infrastructure design enables traffic with short Stadler Flirt trains with a length of 46 metres, but can also be transferred to other products on the market, such as the Siemens Mireo Plus B, the report says. As for the vehicles, the required number for an assumed 1-hour frequency without a connection to Klatovy is 15 vehicles including reserves, which would cost approximately 83.7 million euros. For the through connection to Klatovy at 2-hour intervals, 19 vehicles are required, with a price tag of approximately 106 million euros.
Battery trains gaining ground
Currently, BEMUs are not yet in use on the German railway network, but several operational launches for BEMUs are planned in the coming years. Local Baden-Württemberg operator SFBW has ordered 20 Siemens Mireo Plus B trains, for which delivery of the first trains is planned for June 2023. In Schleswig-Holstein, operator NAH.SH will put 55 Stadler Flirt Akku trains into operation in 2023-2024. DB Regio has also ordered 44 Flirt Akku BEMUs for operation on the in southwest Palatinate on the Süd Pfalznetz, which will start operations from 2025.
In Saxony, operator ZVMS opted for the Alstom Coradia Continental BEMU for the route Chemnitz-Leipzig, having ordered 11 trains which are scheduled operations starting from 2023. In Mecklenburg-Vorpommern, 14 Stadler Flirt Akku’s should enter operation from 2026 with operator VMV. In the Rhine-Ruhr area, the VRR ordered 63 BEMU trains from CAF of the Civity range for operation on the Niederrhein-Münsterland-Netz with the first trains from 2025, with an additional 10 trains ordered last year. Regional German operator Hessische Landesbahn ordered three battery trains from Siemens Mobility for a railway pilot project in Upper and Lower Westerwald earlier this year.
Bavaria could be the next state where battery trains will be introduced, but the decision is not made yet. On another route in Bavaria, Augsburg – Füssen operated by Bayerische Regiobahn (BRB), a pilot operation with hydrogen trains from Siemens will start this year, which will run for 30 months with support of the Bavarian state.
For the Bayerwald network, the BEG will commission a second part of the report for the Bayerwald network from TU Dresden, in which also the use of hydrogen vehicles in the Bavarian Forest will be investigated. The results of the extended report are expected in the course of the year.
“The results of the study are an important first basis for decision-making”, Bavaria’s Minister of Transport and BEG Supervisory Board Chairman Christian Bernreiter comments on the results. “To be honest, they are also a bit sobering in terms of time and cost. That’s why we want to investigate further possibilities in detail.”
“Which drive technology is most suitable depends to a large extent on the rail infrastructure; there is no one-size-fits-all solution for Bavaria”, says Thomas Prechtl, spokesman for the management of the BEG. “That’s why we take a very close look at each individual route”.
More work to do by DB Netz
According to the experts, in order to deploy battery trains on the Bayerwald network an upgrade of the so-called route class is necessary, which involves the maximum permissible axle load that the railway superstructure can handle. According to findings of TU Dresden, all BEMUs currently available on the market only comply with route class C, while the network is currently route class A on all sections east of Zwiesel. BEMUs have an average 10 percent higher mass due to the addition of the batteries compared to the basic electric multiple units, in addition to the already higher mass of the electrical components (especially transformer & converter) compared to diesel railcars.
Driving with vehicles with higher axle loads is only possible extensive testing and, if necessary, adjustments to bridges, culverts and the superstructure by DB Netz, which, according to information from the BEG, has already designed three new bridges to be built in the Bayerwald network for route class C2. The further costs related to increase the maximum axle load were not taken into account of the study commissioned by BEG, as it says this is a task for network operator DB Netz.
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In my view, the converter stations as proposed in the study could be simplified somewhat in order to shave some of the costs. Optimization of the sections to be electrified, leaving out sections with more complicated terrain and curvy route, might also help to save. In any case, the 32 mio. € for the infrastructure (excluding electric power supply to the public grid) do not appear too significant compared to the 84 mio. € for the vehicles. Oil production for diesel also needs investment.
It could be questioned if Stadler Flirt trains with a length of 46 metres are the best solution, when passenger numbers are low and currently, much shorter “trains” (DSU for diesel single units might be the appropriate term) are in operation and could be converted to “BESU” with battery electric propulsion. Lower power for the converster stations! If more capacity is wanted, operating more frequently (with automated trains) would be more attractive than retaining the hourly manned operation.
The study also disregarded the possibility of electrification with 25 kV / 50 Hz for the electrification “islands”, which is easier to supply from the public grid and would also improve compatibility with the section in Czech republic, which will certainly not use the outdated 16 2/3 Hz of the D-A-CH-region.
Improved services between Regen and Zwiesel, see map, with around 10,000 inhabitants each in a region with short of 80,000 inhabitants in around 1,000 square km, also need consideration.