Hydrogen in mobility

During regular operation of a hydrogen car, oxygen and hydrogen cannot come into contact, as the hydrogen is stored separately from the oxygen in tanks. These must be significantly more pressure-resistant than conventional petrol tanks. For large quantities of hydrogen to be released in the event of an accident, it would have to be an incident such as a total loss. Even in crash tests, there was no damage to the tanks and no leakage of hydrogen. Hydrogen poses a higher risk of explosion if it is released in an enclosed space.

This also includes tunnels or garages, which must be protected against the dangers of hydrogen, for example through additional ventilation and other safety measures. However, hydrogen cars are secured in such a way that explosive mixtures are prevented in the event of a fire: Before an explosive mixture can form, the fuelled hydrogen is drained off and burned in the fire. Due to the existing safety measures, hydrogen cars can also be parked in garages and multi-storey car parks.

Hydrogen replaces diesel drive in the railway network

Around 40 % of the German railway network is not electrified. Until now, diesel railcars have been used almost exclusively for passenger transport on these overhead lines. Here, the conversion from diesel to hydrogen technology represents a particularly economical, environmentally friendly and sustainable solution. For example, regional trains can be operated with green hydrogen while retaining the train architecture and without significant changes to the centre of gravity.

Successful test phase of hydrogen trains in Lower Saxony

To test such a platform solution, two hydrogen-powered Coradia iLint trains from the manufacturer Alstom went into operation on the Weser-Ems network in 2018. The trains have a range of 600-800 kilometres and have tanks installed on the roof that are filled with gaseous hydrogen at a pressure of 350 bar. With the addition of oxygen from the environment, the hydrogen is converted into electricity in the fuel cell stacks, which are also located on the roof, and fed into batteries that store the electricity temporarily and release it as required.

In addition to providing the drive energy, the batteries also store the braking energy and thus contribute to the high energy efficiency of the overall system. The trains are powered by a mobile hydrogen refuelling station. Due to the success of the 18-month test phase, Niedersächsische Landesnahverkehrsgesellschaft evb is planning to increase the number of hydrogen-powered regional trains and build a stationary hydrogen refuelling station in Bremervörde with a capacity of around 1,600 kg of hydrogen per day.

Expansion of hydrogen mobility by rail

Following the example of Lower Saxony, the Rhein-Main-Verkehrsverbund is following suit with the world's largest fleet of fuel cell-powered Coradia iLint regional trains to date and its own hydrogen refuelling station for passenger trains. There are also plans in Baden-Württemberg to replace diesel multiple units with fuel cell-powered trains and to install corresponding refuelling stations - a regional train that Deutsche Bahn is developing together with Siemens on the basis of the Mireo Plus regional multiple unit will be used in the Tübingen area.

From the standard-compliant integration of refuelling systems into existing infrastructures to the specific monitoring of hydrogen systems and the inspection of refuelling facilities - with comprehensive services in the areas of testing, inspection and certification, we support you from the concept phase, through production, to the operation of your system.

Gaseous hydrogen is stored in filling stations at H2 refuelling stations in pressure vessel bundles, elevated tanks or underground cylindrical steel tanks. For refuelling, compressors reduce the volume of the hydrogen and compress it to the required pressure levels. Currently, most hydrogen refuelling stations are designed to refuel cars at 700 bar within around three minutes. Fuelling stations with correspondingly large compressors can also supply commercial vehicles with 700 bar.

To refuel hydrogen buses and lorries, filling stations require a 350 bar filling point, while the pressure tanks of trains are filled with 250 bar. Thermal management also plays an important role in the process sequence of a refuelling station. Hydrogen is brought to a temperature of -40 °C for gaseous refuelling. In the case of storage in the gaseous state, this is done using cooling units, while a cryogenic pump is used to heat the -253 °C cold hydrogen for storage in the liquid state.

While the storage and transport of liquid hydrogen has long been common practice, its use as an energy carrier in vehicles is still being researched. Following initial trials with liquid hydrogen-powered cars, the focus of vehicle development and the adaptation of refuelling stations is now primarily on trucks . Refuelling processes are being tested that avoid the boil-off effect of gaseous refuelling and also eliminate the need for complex data communication between the H2 filling station and the vehicle. The term "boil-off" refers to the continuous vapourisation that occurs when heat penetrates tanks containing liquid hydrogen.

Compared to gaseous hydrogen, liquid hydrogen is significantly colder (temperature: -253 °C) and requires significantly improved insulation of pressurised tanks and pipelines. However, due to its higher energy density, it also enables refuelling at a lower pressure level and the use of smaller and lighter tanks with a greater vehicle range. Following the establishment of the first pilot stations for refuelling with liquid hydrogen and a successful test phase, liquid hydrogen technology could therefore also contribute to the decarbonisation of road transport, particularly in the area of long-haul transport.