Compressed air energy storage system utilizing two-phase flow to facilitate heat exchange

An apparatus comprising:

• a cylinder device including a moveable piston in communication with a mechanical linkage to transmit power of gas expanding within a chamber, out of the cylinder device;
• a liquid source in fluid communication with the chamber of the cylinder device;
• a compressed gas source in selective fluid communication with the cylinder device through valving;
• the cylinder device in selective fluid communication with an outlet through the valving;
• and
• a control system configured to control timing of the valving electronically to operate in the following states:
• expansion wherein the valving admits compressed gas from the compressed gas source to the cylinder device and does not allow fluid communication between the cylinder device and the outlet such that the compressed gas expands in the cylinder device to drive the piston, and then later the valving blocks fluid communication with the compressed gas source as the compressed gas continues to expand in the cylinder device, and
• exhaust wherein the valving allows expanded gas to pass to the outlet.