The stirling engine is a closed-cycle reciprocating external heat engine that converts heat into useful mechanical work. It was originally invented to compete with the steam engine, but due to its various limitations, even after many years, the Stirling engine has not seen mass-market adoption and is only used in a few specialized applications. 

The gas inside a Stirling engine never leaves the engine. They are heated and cooled down again and again, so are never released in the form of an explosive exhaust. This regenerative engine has the ability to use the same gas repeatedly to generate power; therefore, a Stirling engine can prove to be much more efficient than the internal combustion engine used in modern-day vehicles. Because there are no explosions taking place, Stirling engines are very quiet. There is also no combustion, as the Stirling cycle uses an external heat source, which could be solar energy or even heat produced by decaying plants

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