[citation][nom]mgilbert[/nom]Uh, sorry... To be self sustaining would require greater than 100% efficiency, which is impossible.[/citation]
First, don't rain down on our parade.
Second, it would need 100% efficiency, no more (provided we give it the energy it needs to start with). ie.: If it consumes 1 watt and generates 1 watt, provided it already has the 1 watt needed at the start, it is self sustaining.
Impossible? A man can only dream...