3.1 Necessity to Store and Transport Hydrogen

Challenges in the storage of hydrogen

Due to its special properties hydrogen’s storage and transportation are not trivial. As already described in Chapter 2.1, the challenges result especially from the low volumetric energy density of gaseous hydrogen and the small size of the molecule. The low volumetric energy density leads to the fact that large volumes are required to store and transport gaseous hydrogen. The small size of the molecule in turn makes hydrogen able to diffuse through a lot of material. For example, materials that are used in the natural gas infrastructure are only impermeable to hydrogen to a limited extent. Beside the hydrogen loss, diffusion also causes so-called embrittlement to some pipes, tanks or other devices which get into contact with hydrogen. Affected materials are, e.g., steel and titan.

Various approaches are being pursued to solve the challenges described. For example, gaseous hydrogen can be compressed or liquefied, whereby the volumetric energy density can be significantly increased. In storage and transport systems for compressed or liquid hydrogen, materials are used through which the hydrogen cannot diffuse. Another possibility for increasing the volumetric energy density and loss-free hydrogen storage is to bind the hydrogen to a liquid carrier or to further process it into energy-rich downstream derivatives, e.g. ammonia or methanol. These measures are comprised under the term H2toX. In the next section you will learn more about the different options for hydrogen storage.