To store large amounts of a compressed gas large volumes are needed which can bear the compressed gas at high pressures. Salt caverns can be leached in salt deposits almost round the world. They are located about 1500 m below surface and allow to sore gas at pressures of about 250 bar.
Large caverns can be built in geological formations of salt. Such salt
caverns are being used in FRG for the storage of petroleum and natural gas. The
storage of natural gas takes place at pressures of about 250 bar, the caverns
are located at depths of 1000 to 2000 m and have a geometrical volume of approximately
500,000 to several million m3. The entire volume of gas storage in
salt caverns in Germany is 14 billion standard cubic meters  which
corresponds to a geometrical volume of approx. 70 million m3, where
an average storage pressure was assumed by 180 bar. "Pressure energy
stored" corresponds to approximately 350 TWh, it should be noted that also
the energy stored in the cushion gas is included in the afore mentioned number.
Cushion gas is the gas portion that is required for the process but due to
technical constraints, such as minimum allowed pressure, these cannot
contribute to the stored active inventory.