One of the most important applications of hydrogen is its use as energy storage. This is a key point for its introduction into the market and one of the main advantages and values of hydrogen as an energy carrier. Hydrogen is characterized by a high energy density per unit mass but not per unit volume so its mayor problem is that storage in normal conditions occupies much volume.

For this reason there are several ways to store hydrogen in different stages of development, including:

Compressed Gas:

This is the most often used technique to supply hydrogen in pressures up to 700 bar. It is a generally available and low cost technique. Only relatively small amounts of H2 at 200 bar are stored nowadays and storage at higher pressure (700 bar) is still in a development phase.

Liquid hydrogen:

It is a commonly used and well-known technology, obtaining a good storage density. It requires very low temperatures and therefore greater insulation than normal, so that the cost can be high.

Metal hydrides:

It is a very secure system because hydrogen is stored into a solid (metal). The shape of the storage tanks can be adapted to the needs of each application. As metals are used for securing the gas, weights are raised considerably and its lifetime can be less. Today it is a bit expensive technology.

Chemical hydrides:

Forming reversible hydrides reactions are well known. They are compact systems with small size and they need special infrastructures.

Carbon structures:

Different carbon-based structures are being studied, such as the nanotubes, which allow a high density of hydrogen storage also being very light. They are currently under research and development.