Hydrogen - how to stay mobile

There are now around 100 hydrogen filling stations in Germany. This has created a new situation. “Back in 2016, the key question was how to fit hydrogen tanks in vehicles,” explains Armin Keßler from Fraunhofer ICT. “But in the HySafe project, we are now focusing on the safety of individual components and aspects of hydrogen stations.” Questions here include: how best to prevent a buildup of excess pressure in a hydrogen tank. The solution from Fraunhofer ICT is to make a hole in the tank and then reseal this with epoxy resin. As the pressure rises in the tank, the temperature increases, causing the epoxy plug to melt and rupture within a couple of seconds, thereby releasing the entire tank contents. Fraunhofer researchers are also analyzing what happens in the event of an explosion and which measures are most effective in containing this.

And then there is still the question of how best to store hydrogen at filling stations. At present, the hydrogen is stored in pressurized tanks. Yet there are drawbacks with this method. For example, it requires the use of elaborate pressurizing and cooling systems. Here, too, an alternative is to use liquid organic hydrogen carriers. LOHCs make it possible to safely transport and store – at no loss – this otherwise highly explosive gas. Researchers at Fraunhofer IAO have integrated Europe’s first LOHC storage unit of the latest generation, with a storage capacity of 2000 kilowatt-hours, into the Micro Smart Grid at the Fraunhofer Institute Center in Stuttgart. As for the question of how to use LOHCs for refueling purposes, the requisite technology is currently being developed by researchers at Fraunhofer HHI, as part of the LOReley project. Funded by the German Federal Ministry for Economic Affairs and Energy, this focuses on the high-capacity production of hydrogen by LOHC reactors equipped with efficient surface catalysts. The key component of the project is the reactor, which is currently under development by researchers. Designed for vehicle-re­fueling purposes, this will efficiently extract hydrogen from a carrier oil at a continuous output – in terms of the amount of hydrogen produced – of at least 1 kilowatt and a peak output of 5 kilowatts. In other words, reactor modules should have a simple design, be of compact dimensions and combinable in modular fashion up to the required perfor­mance category, and yet still provide formerly unattainable space-time yields. This is enabled by laser-textured reactor plates, as developed by Fraunhofer HHI, which substantially enhance reaction efficiency. This kind of LOHC refueling station can also be designed as a mobile application. In this case, the LOHC will be stored and transported in a tank truck, along with a mobile reactor.