A generator comprising heat differential, pressure, and conversion modules, and a heat recovery arrangement; the differential module comprising a first high temperature reservoir containing a work medium at high temperature, a second low temperature reservoir containing a work medium at low temperature and a heat mechanism in fluid communication with the reservoir(s). The heat mechanism maintains a temperature difference therebetween by providing heat to and/or removing heat from the reservoirs; the pressure module comprises a pressure medium in selective fluid communication with the reservoirs for alternately performing a heat exchange process with the work medium. The pressure medium fluctuates between a minimal and maximal temperature corresponding to the high and low temperatures of the work medium; the conversion module utilizes temperature changes of the pressure medium for production of output energy; the recovery arrangement absorbs heat from the pressure medium and provides heat to the differential or pressure module.