Compressed gas storage tank, system and method

A storage tank arranged within a surrounding structure, the storage tank comprising:

• a first chamber configured to store a first gas under pressure, the first chamber being defined by a first wall, a top, and a bottom and having a substantially fixed volume;
• a flexible membrane provided between the first wall and the surrounding structure;
• a second chamber between the first wall and the flexible membrane, wherein the second chamber has a variable volume;
• and
• at least one transfer pipe which supplies the first gas into the first chamber,
• wherein the second chamber surrounds the first chamber such that the first wall is between the first chamber and the second chamber and wherein the flexible membrane extends over the top and bottom of the first chamber;
• and
• further comprising at least one first pipe in communication with the second chamber and at least one second pipe in communication with the second chamber, wherein a fluid is supplied to the second chamber via the at least one first pipe or the at least one second pipe and the fluid returns from the second chamber via the other of the at least one first pipe and the at least one second pipe.