Patent ID: 8387375

Claim:
An apparatus suitable for use in a compressed gas-based energy storage and recovery system, the apparatus comprising: a first hydraulic cylinder having a first working piston disposed therein for reciprocating movement in the first hydraulic cylinder, the first working piston dividing the first hydraulic cylinder into, and defining therewith, a first hydraulic chamber and a second hydraulic chamber; a second hydraulic cylinder having a second working piston disposed therein for reciprocating movement in the second hydraulic cylinder, the second working piston dividing the second hydraulic cylinder into, and defining therewith, a third hydraulic chamber and a fourth hydraulic chamber; the first working piston having substantially the same diameter as the second working piston, a connecting rod disposed between, and coupled to, the first working piston and the second working piston; a first hydraulic actuator having an actuator cylinder and an actuator piston disposed therein for reciprocating movement in the actuator cylinder, the actuator piston dividing the actuator cylinder into, and defining therewith, a first actuator chamber and a second actuator chamber, the hydraulic actuator being coupled to at least one of the first working piston, the second working piston, and the connecting rod, the hydraulic actuator configured to receive pressurized hydraulic fluid in the first actuator chamber to move the first and second working pistons in a first direction to reduce the volume of the first hydraulic chamber and the third hydraulic chamber, the hydraulic actuator further configured to receive pressurized hydraulic fluid in the second actuator chamber to move the first and second working pistons in a second direction, opposite the first direction, to reduce the volume of the second hydraulic chamber and the fourth hydraulic chamber; and a second hydraulic actuator coupled to at least one of the first working piston, the second working piston, and the connecting rod, the second hydraulic actuator operable to move the first and second working pistons in the first direction and the second direction.