A few tea lights and a couple of flower pots can have a room toasty hot!
How it works: the candles produce gases full of heated particles that are captured and channeled through the pots. As hot gas particles are lighter than the air, they will rise up through the top into the colder area. This causes the cold air to fall into the warm areas creating a convection current; heat is transferred from one pot to another, and then out of the hole.
How to do it: