A simple machine that could be heated from a solar reflector or inside a
 woodstove, and built at low cost would be a major step forward in energy
 self sufficiency.

Well that's is the plan ...

 
 A double acting liner-alternator might sound simple, but really there is not
 much additional complexity involved in using a crank and rotating shaft to
 couple the engine up to a conventional rotary generator/alternator. A
 double acting oscillating engine might be just as easy to produce, and
 solves the problems of keeping the magnets away from the heat source.


Well this sound simple but I know that isn't simple. But I'm better in
electronic world and not to mechanic. So crank system is out of order.
To many moving part and side forces to piston's. The idea is to use
coke/graphite piston (like in some oilles compressors) and SS or bras as
cilinder. No ned to lubricate anything. Conventional rotary machines are
ineficient (meaning car alternator) the good ones are expensive. Of
course linear type are hard to find. But seem's that ancient design's
with today control can do job wery good. The idea is to make "switched
reluctance generator". If you google it you can see that there are just
lamination and one (or more) coil needed and a little bit complex
control box.