For many years Amish have used similar machines to power fans. The fan sits on top the heater and when the air becomes warm, the fan turns. The hotter the stove, the faster the fan turns.
If I remember correctly, a heat driven motor is several hundred dollars.
REMEMBER the AMISH HATE being in the crid, they are experts at solar energy, gas powered refrigeration, kerosine water heaters, etc., etc..............