Which alternative drive will ultimately come out on top in this race? Relevant studies see the technological concept of battery electric trains as having the advantage. A BEMU is basically an electric railcar with a rechargeable battery as energy storage. On electrified lines, the vehicle draws its traction current from the overhead contact line. When it reaches a section without its own overhead contact wire, the train automatically switches to battery mode – in this case, the storage batteries supply the energy for further propulsion. Charging takes place under the overhead line while the train is moving or stationary, with charging powers of one megawatt and more. Another charging option is offered by so-called electrification islands, for which individual sections of a line would have to be specially equipped with contact wire. Special charging stations are also a possibility – the first examples are already being tested in southern Germany. Range remains the crucial issue for the use of battery trains: Most manufacturers calculate a range of 80 to 120 kilometers that a vehicle can travel in one go. Since around 90 percent of non-electrified routes in Germany are shorter than 70 kilometers, it should be possible to bridge most power gaps in the rail network with a BEMU. A perfect reference in terms of range is the Flirt Akku battery train from vehicle manufacturer Stadler, which made it into the Guinness Book of Records late last year with a record-breaking run. A range of 224 kilometers was measured, which the vehicle covered in battery mode on the route from Berlin-Gesundbrunnen to Warnemünde in sub-zero temperatures and snowfall.
In terms of range, the hydrogen train clearly demonstrates its strengths
Even if battery-powered trains demonstrate enormous performance capability, they can’t always replace a compression-ignition engine. After all, every diesel route has its own special driving requirements. Topography, routing, and climatic conditions, as well as the charging infrastructure obviously have an impact on range. “In the case of higher energy requirements, such as those needed for strong grades or extreme climatic conditions, a battery-powered train can sometimes run out of breath,” knows Dr. Christoph Flink, Vice President Hydrogen Economy Program Management in DEKRA’s Service Division Industrial Inspection. As the expert explains, a hydrogen train would have no problems with such a scenario – after all, the range can be up to 1,000 kilometers.
DEKRA Rail in Utrecht, Netherlands, has also added hydrogen trains to their agenda. At the beginning of 2020, experts from the railway division accompanied a pilot project of the Groningen province, which investigated the suitability of a train powered by green hydrogen on the train line from Groningen to Leeuwarden. “We officially accompanied the project as experts in matters of technology, safety, and approval,” reports Jean-Paul van Hengstum, Managing Director of DEKRA Rail. The clear result: Hydrogen trains are a sustainable alternative to diesel operation.
In technical terms, the HEMU ranks in the category of electric motor drives – fuel cell and battery work hand in hand during operation. When there is a power peak during acceleration, the electricity from the fuel cells alone is not sufficient. The battery must provide additional capacity. Only when less traction is required, does the fuel cell recharge the battery. However, drawing power from the overhead line is out of the question for a HEMU – the vehicle concept simply does not provide for a current collector. The hydrogen trains are therefore primarily used on routes without overhead lines, which makes the operating concept exactly the same as for diesel. But why not go one step further with hybridization? DEKRA expert Dr. Flink can imagine that combining hydrogen propulsion with an overhead line could once again significantly increase the efficiency and flexibility of the vehicles.
The diesel engine finds its niche in alternative vehicle concepts