I've tried this before. The build in the picture is wasteful of energy and unsafe.

This is cheap to make, can be easily taken down, and if instead of tea candles bigger candles are used it can heat the pot enough to radiate some perceptible heat. It also makes for a good conversation starter.

But would I place all my bets on this? No, not really. It should be considered a dire last resort, for a very small room, in an extreme situation.