Systems and methods for optimizing thermal efficiency of a compressed air energy storage system

An apparatus suitable for use in a compressed gas-based energy storage and recovery system, the apparatus comprising:

• a first hydraulic cylinder comprising a first working piston disposed therein for reciprocating movement, 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 comprising a second working piston disposed therein for reciprocating movement, the second working piston dividing the second hydraulic cylinder into, and defining therewith, a third hydraulic chamber and a fourth hydraulic chamber;
• and
• an actuator coupled to and configured to move the first working piston and the second working piston:
• a) in a first direction such that liquid contained in the first hydraulic chamber and the third hydraulic chamber is discharged from the first hydraulic chamber and the third hydraulic chamber, and
• b) in a second direction, opposite the first direction, such that liquid contained in the second hydraulic chamber and the fourth hydraulic chamber is discharged from the second hydraulic chamber and the fourth hydraulic chamber.

A method of controlling thermal efficiency of a compressed gas-based energy storage and recovery system, the system comprising:

• a first hydraulic cylinder comprising a first working piston disposed therein for reciprocating movement, 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 comprising a second working piston disposed therein for reciprocating movement, the second working piston dividing the second hydraulic cylinder into, and defining therewith, a third hydraulic chamber and a fourth hydraulic chamber;
• and
• an actuator coupled to the first working piston and the second working piston, the method comprising:
• moving, using the actuator, the first and second working pistons:
• a) in a first direction such that liquid contained in the first hydraulic chamber and the third hydraulic chamber is discharged from the first hydraulic chamber and the third hydraulic chamber, and
• b) in a second direction, opposite the first direction, such that liquid contained in the second hydraulic chamber and the fourth hydraulic chamber is discharged from the second hydraulic chamber and the fourth hydraulic chamber.