Our prior home had a fireplace insert that circulated air through a "plenum" under and behind the fire, to blow warm air out into the room.
The fan, unfortunately, was electric, so that kind of insert would be of little help during a power failure. A battery and small inverter would have sufficed to run the fan for a couple of days; but I never bothered to try that method since the missing blade on the fan made it a bit noisy.