During the winter season, where short days, high fog and snow strongly reduce PV energy gains, seasonal storage is required to cover the deficit. For this reason SELF is furnished with a hydrogen storage composed of 10 x 10 litre pressure cylinders filled with approximately 50 kg of metal hydride type AB5. In this approach hydrogen is not stored under pressure, but absorbed by the metal hydride. In this way it is possible to operate the complete system without hydrogen compression process.

The assembly of the ten metal hydride cylinders


For seasonal storage hydrogen is a good choice. Hydrogen stored under pressure or bonded to metal hydrate suffers little to no loss during storage. This makes hydrogen storage favorable for long term storage. The hydrogen storage system consists of a metal hydrate cylinder assembly of 10 cylinders, each with a volume of 10 l. The cylinders are able to store 4 kg of hydrogen, or 130 kWh of energy equivalent in respect to the lower heating value of hydrogen. The metal hydride used is alloy AB5 from JMC. Standard pressure cylinders were filled with the metal hydrate at Empa.


Quantity of cylinders


Volume per cylinder

10 l

Hydrogen capacity

4 kg

Energetic capacity (lower heating value)

130 kWh