Green Energy, Air motors, Free Energy motors and generators

I hesitate to include this video because it shows a bald-faced attempt to claim some kind of perpetual motion engine. What's demonstrated is an air motor coupled to the shaft of a generator. They twist the knob to release air from the air tank, and a lightbulb connected to the generator changes brightness. It's very responsive and looks very simple to set up.

However they then mention you could use this to drive an air compressor. An air engine, that requires compressed air, being used to drive an air compressor. Sounds like they want you to believe the engine could power itself to compress the air it needs to run. That's what I meant by perpetual motion machine. In truth that would not work, according to physics, because of efficiency losses in the engine and air compressor.