Natural gas compressing and refueling system and method

A method of using a two-stage gas compression system to compress gas, the system comprising a rotary power source having an output shaft;

• a positive-displacement first stage rotary compressor having a first stage gas inlet and a first stage gas outlet, the first stage rotary compressor being operatively connected to the rotary power source to be driven by the output shaft;
• a hydraulic pump operatively connected to the rotary power source to be driven by the output shaft, the pump having a hydraulic liquid inlet and a hydraulic liquid outlet;
• and a positive-displacement second stage compressor having a second stage gas inlet fluidly connected to the first stage gas outlet, and a second stage gas outlet configured to provide second stage compressed gas to a user, wherein the second stage compressor operatively connects to the liquid outlet of the pump so as to be driven by pressurized liquid provided by the pump, the method comprising:
• receiving a gas at the first stage gas inlet;
• operating the rotary power source, which causes the output shaft to drive the first stage compressor, thereby compressing the gas in the first stage compressor into first stage compressed gas;
• causing the first stage compressed gas to flow from the first stage gas outlet into the second stage compressor via the second stage gas inlet;
• operating the rotary power source, which causes the output shaft to drive the pump and pump hydraulic liquid into the second stage compressor, thereby compressing the first stage compressed gas disposed within the second stage compressor into second stage compressed gas;
• and
• discharging the second stage compressed gas from the second stage compressor to a user.