Flat Head V8 Running Miniature Model Engine - Block is Only 7" Long!

There's a company that makes these things for sale.  I was wondering if one of these can be made that can do useful work, like charging a battery that runs the electrics in a house.








And the guy who puts these together---video here:








There are others out there who dabble with these miniature engines, but not enough time to check out all of the videos.

Update:

Perhaps a Stirling Engine is the best choice, since it is an external combustion engine, and won't produce carbon monoxide, nor nitrous oxides.  Therefore, it can be placed indoors, which would allow recapture of the water molecules and carbon dioxide.  These are therefore recycled, closing both loops.