The present disclosure provides systems and methods for removing heat from closed-cycle thermodynamic engines that generate electrical energy through a reciprocating piston operated by thermal expansion. The present invention includes a heat exchange mechanism for a closed-cycle thermodynamic engine that exchanges hot working fluid and cold fluid at different points in a heat cycle thereby increasing efficiency of the closed-cycle thermodynamic engine. The heat exchange mechanism allows the engine to remove heat faster from the working fluid and therefore lowers the low temperature of the thermodynamic cycle resulting in better efficiency. The heat exchange mechanism also allows the engine to operate at a faster cycle frequency.