If you put a generator on the engine and connect this up to a source of waste heat like a stove chimney or the outlet of a boiler then you could make power out of waste heat. Several boiler companies are looking at making domestic boilers into mini combined heart and power plants (D-CHP) using Stirling Engines. We will be examining these in the near future.

Could the same technology not be used with a wood stove.

The only problem I can see is if you take too much energy out of the smoke you could stop the draw of the fire and break "Betz law". But if you only took say 1kw could it work?

For a full explanation of the engine please see:
http://www.howstuffworks.com/stirling-engine.htm
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Stuart