Apparatus for utilizing heat wasted from an engine includes: a Rankine cycle (31); a transmission mechanism that couples an output shaft of an expansion device (37) to a rotary shaft of an engine via an electromagnetic clutch (32) that can be engaged and disengaged; a passage (65) through which refrigerant exiting a heat exchanger (36) flows so as to bypass the expansion device (37); and a bypass valve (66) interposed in the passage. To stop the expansion device (37), the electromagnetic clutch (32) is switched from an engaged state to a disengaged state after switching the bypass valve (66) from a closed state to an open state. If the bypass valve (66) becomes stuck in the closed state, expansion device front-rear differential pressure limiting processing in which a front-rear differential pressure of the expansion device is limited while maintaining the electromagnetic clutch (32) in the engaged state is performed.

Systems, methods, and vehicles for use with internal combustion engines comprising combustion chambers that produce exhaust gases that include a Stirling engine having a hot side and a cold side with the hot side being in thermal contact with exhaust gases produced by the internal combustion engine. The Stirling engine is configured to be powered by heat from the exhaust gases during operation of the internal combustion engine, and a compressor powered by the Stirling engine is configured to provide compressed air to combustion chambers of the internal combustion engine.