Compressor and expander device with pressure vessel divider baffle and piston

A method of compressing gas in a pressure vessel, the pressure vessel having a piston disposed therein for reciprocating movement in the pressure vessel along solely a portion of a cross-sectional area of the pressure vessel and a divider fixedly disposed within the pressure vessel along a remaining portion of the cross-sectional area of the pressure vessel, the divider and the piston collectively dividing the pressure vessel into, and defining therewith, a first interior region and a second interior region, the divider forming a seal with the piston to prevent fluid from passing between the first interior region and the second interior region, the first interior region and the second interior region being adapted to simultaneously contain a liquid, the method comprising:

• fluidically isolating the first interior region from a gas source;
• establishing fluid communication between the second interior region and the gas source;
• moving the piston with respect to the divider in a first direction to:
• a) reduce the volume of the first interior region and compress a first mass of gas contained therein from a first pressure to a second pressure higher than the first pressure, and b) increase the volume of the second interior region and receive therein a second mass of gas at a third pressure from the gas source.