External Combustion Engine

An external combustion engine is a reciprocating heat engine in which a working fluid, contained internally, is heated by combustion occurring outside the engine, through the engine wall or a heat exchanger. The heated fluid then expands and acts on the engine mechanism to produce motion and usable work, after which it is either discarded in an open cycle or cooled, compressed and reused in a closed cycle. Because combustion serves only as an external heat source, an external combustion engine can run equally well on other heat sources such as nuclear, solar or geothermal energy.