Bypass all the mechanical complexity and just scale up one of these:
I’ve debared the utility and usefulness of these things with several people, who just don’t appear to recognize that it’s a wood-fired generator with very few moving parts, only a fan to aid convection, improve the burn and perhaps keep certain parts of the unit from getting too hot.
It produces enough electricity to charge personal electronic devices from a fire built of sticks and twigs, more or less, with enogh heat and flame out the top to cook or boil water in one pot or pan.
Very small, couple of pounds, no larger than a water bottle. Scale it up, capture all heat for generation of electricity. Maybe a woodstove with this thermoelectric scheme adapted to it would work.
Somebody make a go of it. Sounds eminently doable to me. It would sell if the price was within reason.
How to build your own dirt cheap fridge
Here are some thermoelectric generators for sale - they just need to be hooked up to a heat source and a battery with inverter.
Have one. Would like the “home sized” version.