Rail E-SSENTIALS

Using hydrogen safety on the track

Hydrogen and battery systems can replace diesel-based traction technology in local transport trains in future rail transport – especially on non-electrified routes. The new traction technology is sustainable but sets high safety and availability requirements.

Extending overhead contact lines for non-electrified routes, is cost-intensive and is not always economically viable on secondary lines. Alternative traction systems with hydrogen close the existing gaps and, depending on the installed technology, enable ranges from 700 to 1000 kilometres. This is generally a complete day’s deployment.

The different forms of hydrogen use in rail transport are summarised in the term–“Hydrail” regardless of whether they involve an efficient fuel cell or an efficiency-optimised hydrogen motor for generating power.

The fuel cell acquires the electrical power for the drive and the on-board systems from the hydrogen stored in tanks and oxygen in the ambient air. A lithium ion-based traction buffer serves as a buffer for the traction energy on the wheel. This is fed on the one hand by the fuel cell and on the other is also recharged by using the kinetic energy of regenerative brakes (recuperation). Depending on the area of use and the so-called duty cycle, approx. 30 percent of the traction energy is recovered in this way.

As an alternative, a motor operated with hydrogen can be used. This technology also meets the requirements for zero emissions.

The focus is also increasingly on hydrogen when retrofitting vehicles with diesel engines. This is particularly interesting for existing vehicles that do not yet have a long life or have only just been put into service and especially those that have a direct mechanical drive. One advantage of the combustion engine: The degree of purity of the hydrogen can be less than with a fuel cell, which reduces the life cycle costs and also enables the use of the hydrogen produced as a waste product in the chemical industry, which would otherwise be burned in thermal processes or burned off as flares via stacks.

Operation of rail vehicles with hydrogen and the associated new technology requires approval on the basis of a safety test. As an independent and accredited inspection body, TÜV SÜD Rail can not only test the safety of the components and the vehicle, but also the operating concept and the required infrastructure, and draws on the know-how and experience of hydrogen experts in the entire TÜV SÜD Group to do so.

In the past eight years, the TÜV SÜD experts have provided advice and support to Alstom in Salzgitter for the development and approval of a motorised train with hydrogen drive. The Coradia iLint uses two fuel cells to convert hydrogen into electrical power. Two lithium-ion batteries serve as a buffer between the fuel cells and the electrical drive.

The TÜV SÜD experts were already involved in defining the requirements for the whole system (vehicle/maintenance/operation/event control) and undertook the safety test of the concept and the final execution. Through continuous tests throughout the development, it was ensured that the safety requirements defined at the start were met at the end for the operating permit. Clear additional planning security – also with regard to any technical modifications for the series production that is just starting up.

The cross-system tests not only covered the power generation technology, the hydrogen stores on the roof and the safety assessment of the interaction of the different hydrogen subsystems in the vehicle, but also the necessary filling station technology, the safety equipment for vehicle servicing in the maintenance facilities. Particular focus was placed on meeting the rail-specific safety requirements and the special operational boundary conditions as well as the associated stress influences.

In addition, TÜV SÜD Rail coordinated all the approval disciplines at TÜV SÜD involved in the project. This included, for example, assessing the stationary hydrogen fuelling systems required for operation or training courses and workshops with the fire service and the local emergency services.

The German Federal Railway Agency (“Eisenbahnbundesamt”) had approved the two pre-series trains in 2018 for testing their fitness for operation. The approval was issued on the basis of a TSI certificate valid Europe-wide regarding technical specifications for interoperability as well as the basis of verification defined during the development. Issue of the approval for the series vehicles is imminent, so that service can start in the LNVG in 2022 (Regional Transport Company Niedersachsen: Landesnahverkehrsgesellschaft Niedersachsen mbH).

The project thus shows a way in which technology that is new for the rail sector can be implemented correctly without extensive standards being available. Hydrogen and battery technologies have already been in use in industry for a long while. There are tried and tested safety and other standards, which can also be used for hydrail technologies.

With the practical experiences acquired from current projects, the TÜV SÜD experts can contribute their technical expertise in the generation and further development of railway-specific standards and thus efficiently support the vehicle and the supplier industry.

For further information please contact Dr. Jürgen Heyn, Head of “Public transport Innovations”, recognised expert and lead assessor at TÜV SÜD Rail GmbH

Source: Technik in Bayern, 4/2021