An active gas regenerative refrigerator includes a plurality of compressor-expander units, each having a hermetic cylinder with a drive piston configured to be driven reciprocally therein, and a quantity of working fluid in each end of the cylinder. A piston seal in a central portion of the cylinder prevents passage of the working fluid between ends of the cylinder. Movement of the piston to a first extreme results in radial compression of one of the quantities of working fluid in a cylindrical gap formed between one end of the piston and an inner surface of the cylinder, while the other quantity is expanded in the opposite end of the cylinder. The piston includes a plurality of magnets arranged in pairs, with magnets of each pair positioned with like-poles facing each other. A piston drive is configured to couple with transverse magnetic flux regions formed by the magnets.