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Stadler: "Individuality In Rail Transport"

posted on 15th May 2023 08:43

On 16 March 2023, Stadler held a conference at the Bussnang plant entitled "Individuality in rail transport", at which its latest products and technologies were presented and it was possible, among other things, to run in a FLIRT H2. In the following we will therefore focus on alternative drives as they are conceived by this vehicle manufacturer.

To begin with a general overview, the Stadler Group has seven divisions, nearly 14,000 employees and 15 production sites and 73 service locations worldwide, serving approximately 270 customers. The production segments, divided into rail and urban transport, include both modular vehicle concepts with adhesion drive and customised vehicles with adhesion or rack-and-pinion drive. In contrast, high-speed trains above 250 km/h and freight wagons are not the focus of Stadler's attention.

Vehicle maintenance is an important pillar of the company, and the Stadler Signalling division is growing rapidly in importance, having grown from the original five employees in 2017 to around 600 today (some of whom come from acquired companies in this field). This division focuses on ETCS, CBTC (Communications-based train control), ATO (Automatic train operation) and anti-collision systems. The dynamism of development is also reflected in the fact that in 2021 the division won orders worth 3.7 million CHF. In 2022, the division will have already secured 49 million CHF.

The Guardia ETCS OBU, developed by AngelStar (a joint venture between Stadler and MerMec), has already been homologated by several European railways and Stadler's initial aim was to replace other manufacturers' on-board ETCS on its vehicles with its own product, thus reducing dependence on external suppliers (and competing train manufacturers) for this sensitive component. This is gradually being achieved, but Stadler has and is developing the capacity to offer the OBU ETCS and the other aforementioned systems to other vehicle manufacturers.

In terms of alternative propulsions, Stadler is promoting a modular vehicle concept that incorporates a battery drive (FLIRT AKKU) or hydrogen drive (FLIRT H2) instead of a combustion engine. However, when introducing a hydrogen solution, Stadler always assesses the efficiency of the entire system in detail in relation to the length of the routes served and the operating conditions, since not everywhere is the "hydrogenisation" of the vehicle a real or sufficiently large environmental benefit.

One of the main criteria is the potential for CO2 emission reductions when switching to hydrogen or other solutions. As shown in the table 1, which includes not only railways but also other sectors of activity for comparison, the effect of introducing HMUs instread of DMUs is surprisingly low, at only 22 kg CO2 per kWh of energy. In contrast, the emission savings are considerably higher, 77 kg CO2 per kWh, when DMUs are replaced by battery trains. In addition, the additional difficulties that the use of hydrogen trains entails, not to mention the significantly higher acquisition costs, must be taken into account (see tables 2 to 4).


The Bussnang conference also included a demonstration of the FLIRT H2, a hydrogen fuel cell unit for the USA, for the SBCTA (San Bernardino County Transit Authority). We described this HMU in detail in our InnoTrans report. It is with this vehicle that Stadler is applying the aforementioned modular concept, whereby in the FLIRT the diesel Power Module in the middle is „only“ replaced by a module that houses the hydrogen technology (six fuel cells, hydrogen tanks and cooling). The hydrogen in the Power Module is stored in a total of 42 (7 x 3 x 2) composite tanks at 350 bar, each weighing 110 kg, but containing only 8 kg of hydrogen. Refuelling takes approximately 30 minutes.

The maximum speed is 127 km/h (79 mph), the maximum traction power 700 kW (including battery power) and the working range is at least 460 km. This value is based on the fact that FLIRT H2 will be operated in California at outdoor temperatures of up to +45 °C and that almost one third of the electricity produced will be needed to power the air-conditioning, while the range per fill-up assumes full occupancy of the train and full operation of the HVAC. Stadler states that the maximum range of a hydrogen FLIRT per fill-up would be 700 - 1,000 km in European conditions.

The procurement cost of a hydrogen train is quite high and is around 10 million CHF compared to a DMU costing around 5 million CHF and a battery unit for around 7.5 million CHF. Of course, these are only indicative prices, which depend on specific customer requirements, and it should be borne in mind that the current FLIRT H2 is still only a unit production. It is also worth noting that the prototype in question, made in Switzerland, was exempted from the "Buy American" provision as a technological invention. All future batch-built vehicles will already be manufactured at the Stadler US works in Salt Lake City.

FLIRT 3501 is now in the test phase. For the test runs, Stadler had to find a suitable line, which was somewhat of a problem, since in Switzerland, where almost 100 % of the network is electrified, it is difficult to find a suitable long stretch without regular traffic. Eventually, the international line Etzwilen (Switzerland) - Singen (Germany) was found, 13 km long, which had been earlier closed for regular service. Today, is operates only as a museum railway belonging to the VES (Verein zur Erhaltung der Bahnlinie Etzwilen - Singen) and specifically the Etzwilen - Ramsen (6 km) section, which lies on Swiss territory, is used for test nd where the first hydrogen FLIRT has been undergoing test runs since 10 December 2022.

The train can use the maximum permitted line speed of 80 km/h. In reality, however, it runs with a maximum speed of around 60 km/h, with an average daily distance of around 40 km. FLIRT runs on without the supervision of any ATP, and during the tests the track is reserved only for it.

The tests should end soon and unit 3501 is expected be shipped to the USA during June. Transporting a hydrogen train across the ocean also poses problems, as the hydrogen tanks must never be completely emptied, even though the vehicle is not in use, so such an explosive cargo poses a safety risk to ships. The hydrogen tanks must always remain at a certain pressure, at least 10 % of the working pressure, to avoid leaks.

Hydrogen is highly volatile because it has the smallest atom in existence, with the smallest atomic radius; simply put, it is a sphere with a radius of 53 pm (picometres). Therefore even the H2 molecule, which looks like a "dumbbell" of two spheres whose nuclei are 74 pm apart, is very small and light and is partially permeable to steel with a lattice constant of 274 pm, so that hydrogen tends to escape from the tanks.

They must therefore be provided with some kind of an internal "wrapping" (e. g. a layer of epoxy integrated with the valve) which prevents this undesirable phenomenon (although probably not always perfectly, as the first operating experience with Coradia iLint HMUs in Germany shows, which suffer from tank leaks and a consequent decrease in the train's working range per filling from the planned 600 km to about a half; another problem is the susceptibility of trains to breakdowns in sub-zero temperatures).

Type approval for the FLIRT H2 and its introduction into passenger service is expected in 2024. In addition, four more, already four-car hydrogen FLIRTs have already been ordered by the California Department of Transportation Caltrans and the California State Transportation Agency CalSTA, with options for up to 25 more.

Regarding the US market and alternative drives, Stadler, ASPIRE and the Utah State University (USU) have signed on 15 February 2023 an agreement to develop and test a battery train for the USA.


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