I'm curious about an idea I had and thought I should talk it out before investing any money in testing pieces of it. Build a typical two-chamber Stirling engine including a heat-sink for the cold side. For the hot side of the engine, make the chamber out of a material that retains heat well. This will be heated by a typical, widely available 2000mW laser toy hooked up to a timer circuit to shut the laser off periodically to allow the components to cool so the laser doesn't burn up (lasers like this warn you not to run them over 30 sec at a stretch). Typically, the laser runs on a AA battery (around 1.5V) and claims to be outputting around 2W...actual current draw would need to be measured, of course. Regardless, hooking the Stirling's flywheel up to a small DC generator (perhaps a modified PC cooling fan, perhaps something designed for the purpose), would it be possible to generate more than 2W (or the actual draw of the laser) plus the cost of the timing system? Law of conservation of energy says 'no' and I know this, so I don't want to hear all the usual drivel about the physics. My question is about the engineering of it...how do I know how much output I'm getting from the engine, how much input needed for the generator, etc? Also, are there any suggestions for a good material to use for the hot side...something that will let the heat in but not let it out? I'm thinking perhaps a highly heat-conductive metal inside with an insulated cover. A hole in the cover would be enough to let the laser in to heat the metal...? This discussion is intended to be educational and interesting, not literally an attempt at "overunity" and such nonsense.