The Solar Stirling engine runs on direct sunlight! Depending upon the sun's incident angle, the engine typically runs at 70 + rpm up. All the moving parts are visible. The engine show the conversion of light into mechanical movement.
The top and bottom plate is made from acrylic glass allowing sunlight or the light from a lamp to heat up the black upper side of the displacer piston. Therefore the internal air is heated to allow the engine to work according to the Stirling principle.