In a hydrogen train, electricity is generated from hydrogen. The electricity is generated by a fuel cell and then stored in a battery. The enormous advantage is that a hydrogen train powered by an electric motor can run entirely without an overhead line. This affects about 1/3 of German rail traffic.
This emission-free* train runs quietly and emits only hydrogen and condensation water. Hydrogen trains play an important role in decarbonizing our economy.
The first hydrogen passenger train was presented back in 2016 at the InnoTrans in Berlin. Alstom has set a milestone with the Coradia iLint model. In 2018, these hydrogen trains were already running on German rail transport and it is being expanded all the time.
But Alstom is not the only company providing hydrogen trains. Siemens has established itself as a strong rival and left its opponent behind with the Mireo Plus H model. Both the Alstom and Siemens hydrogen trains can cover a distance of 1000 km, but Siemens is 20 km/h faster than Alstom at 160 km/h.
*If hydrogen was produced using the electrolysis process
What are the challenges with hydrogen?
Extreme conditions exist in the production, storage, distribution and processing of hydrogen. Zero temperatures of -253°C are reached with liquid hydrogen. Gaseous hydrogen is stored at 700 bar. In addition, there are the effects on the materials and metals.
Especially with hydrogen trains, pay attention to the pressure in the tank. The tank itself is made of carbon fiber composite technology, which is lighter compared to a metal tank and does not allow permeation. Pressure switches with SIL-3 suitability are used in these tanks.
The pressure switches turn off the hydrogen propulsion system as soon as either the tank is almost empty or the pressure becomes too high when the hydrogen is transferred to the propulsion system.
With embrittlement, the hydrogen penetrates the material and leads to poorer performance of mechanical processes. In some cases, embrittlement even leads to complete mechanical failure. The solution to this is that the materials that are in direct contact with hydrogen are made of stainless steel 316L (also possible are: stainless steel 316Ti, Hastelloy C276, Inconel 718, 2.4711).
Hydrogen requires incredibly little energy in contact with metal to dissociate into individual atoms, then into H+ ions. These penetrate the metal and resistance structures and lead to a signal drift of the sensor element in the long run. This effect is intensified by higher occurring energy. A solution to this is a gold coating of the material that is in contact with hydrogen. The gold serves as a barrier.
Leakage must be avoided urgently as there is a risk of explosion. If hydrogen combines with just air, an explosive atmosphere is formed. One solution are metallic seals on the measuring device.
For hydrogen, the conditions differ depending on the state of aggregation. In the gaseous state, hydrogen is stored at up to 700 bar. In order to be able to reliably measure this pressure, since temperature influences and other safety risks have to be taken into account, pressure sensors are required that must measure up to 1050 bar. In liquid form, hydrogen has a temperature of -253 °C. The difficulty here is being able to measure the temperature accurately and at the same time ensure good insulation.
How is hydrogen produced?
To date, the conventional production of hydrogen still supplies the largest amount of hydrogen. It is very energy intensive and is powered by electricity from coal and natural gas. During these processes, pressures of 40 bar and more than 750°C occur. In order to reduce CO2 emissions, processes such as carbon capture storage and carbon capture utilities are downstream. As a result, the CO2 is not released directly into the atmosphere. Instead, it is stored and used elsewhere.
Hydrogen electrolysis is used to produce hydrogen green. Water molecules are split into hydrogen and oxygen. In addition to alkaline electrolyzers, there are proton exchange membrane and solid oxide electrolyzer cell electrolyzers. The three different types of electrolysis are powered by renewable energy.
Climate neutral on the rise
Hydrogen propulsion is seen as the great hope for rail transport. The alternative with electric trains powered by batteries is less attractive due to the short range of 100 to 150 km and the long charging times.
Deutsche Bahn wants to become climate-neutral by 2040 with the help of hydrogen. This could be achieved by replacing the 15,000 diesel locomotives currently in service with hydrogen trains. The diesel locomotives are currently necessary because 1/3 of the German rail network does not have an overhead line.
But not only the German railways rely on hydrogen. There is heavy investment in this decarbonization initiative worldwide.
Japan is making intensive efforts towards a hydrogen-based society. Toyota has released the first hydrogen-powered commercially available car, the Mirai. Equipped with 130 hydrogen filling stations, Japan is at the top in a global comparison.
China plans to overtake Japan by 2030 with planned 1000 hydrogen fueling stations.
France has a national hydrogen strategy with a budget of 7.2 billion euros. 1.5 billion euros have already been invested in electrolysis systems.
Canada's plan is to convert its entire economy to hydrogen by 2050 so that the country can achieve zero greenhouse gas emissions.