Gamma Stirling configuration and simultaneous production of shaft power and heat pumping

In an ideal gamma configuration Stirling engine, the volume of the cold end of the displacer varies 180(0) out of phase with that at the hot end; therefore, exactly as much heat must be rejected as the hot end absorbs. The power piston, moving with a different phase, produces mechanical energy, so the power piston cylinder must absorb heat for there to be an overall energy balance. In other words, the engine simultaneously produces mechanical power and pumps heat between the two sections of the compression space. Inclusion of a second regenerator, between the cold displacer cylinder and the power piston cylinder, can capture this heat flow; the resulting machine is a heat-actuated heat pump that also produces shaft power. Unlike the duplex Stirling heat pump, the new configuration has only one working space and produces a surplus of shaft power.