Hot Air Stirling Engine Generator

A Stirling engine is the simplest type of motor possible, but more precisely  its a heat engine that operates by cyclic compression and expansion of air or other gas. The gasses used inside a Stirling engine never leave the engine. There are no exhaust valves that vent high-pressure gasses, as in a gasoline or diesel engine, and there are no explosions taking place. Because of this, Stirling engines are very quiet. Source

In this video Green Power Science demonstrates a Stirling engine being driven by a focused beam of sunlight via a suspended Fresnel lens, producing about 40 watts of energy.

Green Power Science  says: "We are almost ready to introduce a line of Stirling hot air engines that range from toys to 500 watts of power."

I was simultaneously shocked and amazed when I saw this little machine unsteadily stacked atop of a couple of house bricks, producing seemingly unlimited carbon free energy !