Gas supply system

A gas supply system for supplying gaseous fuel to a power system, comprising:

• a first storage chamber and a second storage chamber, both storage chambers configured to accommodate a portion of gas and a portion of compression fluid,
• a first valve arrangement configured to permit gas to be supplied selectively to the first and second storage chambers from a gas tank and to permit gas to be delivered under pressure selectively from the first and second storage chambers to the power system;
• a second valve arrangement configured to permit compression fluid to be delivered selectively from a compression fluid source to the first and second storage chambers, and to permit compression fluid to be evacuated from the first and second storage chambers to the compression fluid source;
• wherein compression fluid is delivered to the first and second storage chambers via the second valve arrangement by a hydraulic pump having a primary drive input and a secondary drive input,
• and wherein compression fluid is evacuated from the first and second storage chambers via a hydraulic motor having a drive output,
• wherein the drive output of the hydraulic motor is coupled to the secondary drive input of the hydraulic pump, such that when compression fluid is evacuated from the first or second storage chambers through the hydraulic motor, energy is recovered from the compression fluid to drive the hydraulic pump.