DIY HOME Candle Powered Heater - I've been looking a various ways to make these and this guy has by far the best setup. It isn't so much a how-to video. He is just showing what he used to construct his version of the terra cotta pot candle heater.
Warm a Room with Only a Candle and a Few Terra Cotta Pots.The terra cotta pots concentrate the heat using convection. While you won’t heat a whole house with it, it can definitely warm your hands and make a cold night much more bearable .
Wow, great idea, and the manufacturer actually explains it for DIY-ers! It doesn't really heat a whole house, but for a small hut, it could work on cold spring/fall evenings when you don't want to start the wood stove. You could use it in a small room.