A heat engine having an operating cycle for the combined functions of pneumatic power production and waste heat removal via flow of a working fluid, comprising: a pressure containment component, confining the volume of said working fluid in an interior region thereof; a displacer, variably dividing said interior of said pressure containment into a hot region and a cooler region, such that motion of said displacer causes volume changes in one of said regions and opposite volume changes in the other of said regions; a regenerator, disposed between said hot region and said cooler region, and affecting a transient or oscillatory through-flow of said working fluid such that working fluid flowing toward the hot region is heated in said regenerator and working fluid flowing toward the cooler region is cooled in said regenerator; a heater arranged to add heat to said hot region; a valve, providing intermittent pneumatic coupling periods between one of said hot region and said cooler region and a pneumatic load external to said interior region when said valve is open, and providing intermittent decoupling periods between said region and said load when said valve is closed; wherein said displacer motion causes pressure change in said interior region during said decoupling periods and causes volume displacement with energy transfer during said coupling periods, and wherein said energy transfer includes transfer of pneumatic energy that performs pneumatic output work on a coupled system, characterized in that said coupled system is a Rankine cycle, wherein said pneumatic output work drives said Rankine cycle and wherein said Rankine cycle operates with the same working fluid as said heat engine. a pressure containment component, confining the volume of said working fluid in an interior region thereof; a displacer, variably dividing said interior of said pressure containment into a hot region and a cooler region, such that motion of said displacer causes volume changes in one of said regions and opposite volume changes in the other of said regions; a regenerator, disposed between said hot region and said cooler region, and affecting a transient or oscillatory through-flow of said working fluid such that working fluid flowing toward the hot region is heated in said regenerator and working fluid flowing toward the cooler region is cooled in said regenerator; a heater arranged to add heat to said hot region; a valve, providing intermittent pneumatic coupling periods between one of said hot region and said cooler region and a pneumatic load external to said interior region when said valve is open, and providing intermittent decoupling periods between said region and said load when said valve is closed; wherein said displacer motion causes pressure change in said interior region during said decoupling periods and causes volume displacement with energy transfer during said coupling periods, and wherein said energy transfer includes transfer of pneumatic energy that performs pneumatic output work on a coupled system, characterized in that said coupled system is a Rankine cycle, wherein said pneumatic output work drives said Rankine cycle and wherein said Rankine cycle operates with the same working fluid as said heat engine.