Novel Hydrogen Storage Solutions

Since hydrogen is a volatile gas with a low energy density per volume under ambient pressures and temperatures hydrogen storage is a major challenge for the implementation of a hydrogen based future society. Whoever intends to power his laptop or vehicle with hydrogen and fuel cells requires a tank as compact and lightweight as possible. Scientists around Dr. Martin Dornheim and Dr. Philipp Klaus Pranzas at the Helmholtz-Zentrum Geesthacht, Centre for Materials and Coastal Research focus on the chemical storage of hydrogen in compressed metal powders / powder compacts.

The principle: Many metals absorb hydrogen. Thereby stable metal-hydrogen bonds are formed. When the temperature is increased, these bonds break again and the stored hydrogen is released. “The advantage of light metal-hydride storage is, that large quantities of hydrogen – more than in high pressure storage vessels – can be stored in rather small volumes”, explains Dornheim. “Furthermore, the hydrogen is chemically bound, hence we can work at low pressures and do not need to liquefy the gas. The method is very safe, since the hydrogen bound in metal hydrides cannot escape spontaneously in case of an accident and a consequential failure of the tank shell.” Nevertheless, charging and discharging of such hydrogen storage tanks ought to be possible in short times and at temperatures attuned to the respective surrounding drive system. This would allow using the exhaust heat from the drive system to supply the required heat for hydrogen release. To achieve this, the researchers combine various light metal-hydrides, each with high storage capacity. As RHC – Reactive Hydrid-Composite – these have already been filed as patents. The Clou: The different hydrides react with one another and thereby produce part of the required reaction heat themselves. To further improve the materials, Dornheim, Pranzas and colleagues use experiments with brilliant x-ray radiation at DESY in Hamburg and other European synchrotron sources as well as neutron scattering methods and tomography. Until June 2010, they worked at the Geesthacht Neutron Facility (GeNF) and will concentrate their work more at the neutron source FRM II in Garching in the future. In doing so, they gain insight the nanostructure of the materials and are able to look inside the tank and even monitor how the hydrogen spreads into it.