Hydrogen is the simplest gas and the most plentiful element in Universe. Unlike petroleum and carbonaceous fuels, hydrogen is a clean energy carrier made from diverse domestic resources such as renewable energy (e.g. solar, wind, geothermal), nuclear and fossil energy (combined with carbon capture/sequestration).
Hydrogen energy can be harnessed in pollution-free ways and in the long-term will simultaneously reduce dependence on foreign oil and emissions of greenhouse gases and criteria pollutants.

In a H2 based economy, hydrogen storage is a key technology enabling implementation of the hydrogen and fuel cell power technologies in mobile, stationary and portable applications. There are several methods for the hydrogen storage including high-pressure tanks for gaseous hydrogen, cryogenic vessels for liquid hydrogen and metal hydride (solid state) storage systems.
However there are two main drawbacks of the storage of gaseous and liquid hydrogen:

1) even under a high pressure, hydrogen gas is not dense enough for compact storage. (In the figure below the relative volumes for different storage methods and materials are compared)

2) as a fuel, hydrogen in the gaseous and liquid states is very combustible and the related law imposes strict regulations on its transportation;

Hydrogen storage in the metal hydrides doesn't have such deficiencies: metal hydrides are potentially safer and can be safely transported in the widespread daily use.