Hydrogen could offer a perfect solution for CO2-neutral mobility, at least if the gas is generated by electricity from wind power. However, one of the limiting factors for the use of hydrogen is the lack of an efficient storage system. In today's fuel cell cars, hydrogen is filled into compressed gas tanks at pressures of up to 700 bar. This solution is expensive and technically demanding. A promising alternative is solid fuel storage systems based on magnesium-nitrogen.
Magnesium hydrides as storage media for hydrogen have been researched at the Helmholtz Zentrum Geesthacht (Germany) for several years. The advantage over conventional pressure tanks is that they store more hydrogen and thus more energy for the same volume. As an example, a fuel cell car can travel about 500 km with 5 kilograms of hydrogen. For five kilograms of hydrogen, a high-pressure tank requires a volume of 122 litres, while a tank based on magnesium hydride requires a volume of only 46 litres. However, there is also a drawback: high temperatures of around 300°C are required for refueling.
To reduce this temperature, the researchers add additives such as nitrogen. This, however, reduces in turn the absorption capacity of the system. The scientists at the Helmholtz Centre in Geesthacht therefore developed a hydride composite system that should be able to be refueled very quickly at relatively low working temperatures of below 180°C.