Hydrogen - how to stay mobile

Further research is required for the development of vehicle tanks, not least because hydrogen is highly explosive. Before tanks can be installed in vehicles, the materials to make them must first be tested for strength. This is the work undertaken by researchers from Fraunhofer IWM in the institute’s own hydrogen lab, which has equipment to pressurize hydrogen up to 1000 bar. “Samples of materials used to make the tank are placed in a pressure chamber filled with gaseous hydrogen,” explains Ken Wackermann, research associate at Fraunhofer IWM. “This is pressurized to the same level that will obtain in the actual tank. Samples are then subjected to mechanical stress by means of a special machine that literally tears them apart.” The point is to discover how much strain a material can withstand under realistic conditions. The researchers describe the material’s properties and then apply this to the geometry of the tank as a whole by means of the finite element method, a form of computer simulation. On the basis of these results, the researchers are able to say how thick the tank must be – or decide that other materials are required. In addition, the results of the simulation are checked, together with partners, by pressurizing a complete tank until it bursts. This shows whether the hydrogen tanks can actually withstand as much pressure as was calculated. The hydrogen pressure chambers have only been in operation since the end of August and still look completely new.

Other questions as yet unresolved include how the hydrogen tanks can be recycled. At present, most hydrogen tanks for mobile use are made of thermosetting plastics, which can only be shredded at the end of their useful life. Fraunhofer IPT has therefore switched to thermoplastics: the liner – a hydrogen-proof tank – is wrapped in sections of carbon fiber embedded in a thermoplastic matrix and bonded together thermally. By reversing this process, these materials can then be recycled: the sections are simply separated by means of heat. Researchers are now working to develop a suitable process to produce such tanks. After all, there is so much more at stake than the new HYRAZE motorsport series. Together with battery-powered electric transport, hydrogen offers the greatest hope for a future propulsion system that will enable as many people as possible to remain as mobile as possible.