Reciprocating compressor-expander

A reciprocating compressor-expander comprising:

• a cylinder;
• a piston sliding tightly inside the cylinder;
• a crankshaft converting reciprocating motion of the piston and rotary motion of the crankshaft to each other;
• a first valve that opens when introducing a compressible fluid into the cylinder during a compression process for the compressible fluid or when discharging an expanded compressible fluid in the cylinder during an expansion process for the compressible fluid;
• a second valve that opens when the compressible fluid compressed in the cylinder during the compression process is discharged or when the compressible fluid is introduced into the cylinder during the expansion process;
• a hydraulic cylinder connected to each of the first valve and the second valve;
• actuators connected to each of the hydraulic cylinders;
• a controller capable of opening and closing the first valve and the second valve individually by electrically controlling each of the actuators;
• a motor generator that generates electricity when the crankshaft is driven to rotate based on the reciprocating motion of the piston and also drives the crankshaft to rotate to reciprocate the piston;
• an angle sensor to detect an angle of rotation of the crankshaft;
• and
• a power sensor that detects a rotational power of the motor generator;
• wherein
• the controller adjusts an amount of work in the motor generator by adjusting an opening period of at least one of the first valve or the second valve based on detection signals from the angle sensor and the power sensor.