The Sterling Engine provides clean power via heat.l Invented in 1816 by Reverend Dr. Robert Stirling.

A Stirling Engine is a closed-cycle regenerative hot air engine. In this context; "hot air" may be taken to include other permanent gases, "closed-cycle" to mean the working fluid is permanently contained within the system , and "regenerative" to refer to the use of an internal heat exchanger -the regenerator.