Yeah, I think the more conventional way to integrate heat-to-electricty into heating applications is the reverse of that: feed the high-grade heat from fuel com

Yeah, I think the more conventional way to integrate heat-to-electricty into heating applications is the reverse of that: feed the high-grade heat from fuel combustion into the converter, and use the rejected waste heat from it for heating. This gives a big enough thermal gradient to get useful amounts of electricity out, and the waste heat can still be plenty hot enough to be used for heating.