The Space Heater Powered By A Single Candle
A low tech, low power heatsink radiator that can keep a shelter warm enough to sleep in with only a single 24 hour candle or a tin of canned heat
This ceramic heater is likely not too effective aboveground in cold weather. It would not replace a proper stove or fireplace. It is based on the fact that a single candle wastes 90% of its energy that we’d like to capture somehow as heat. If we could catch that heat and store it in a ceramic mass to radiate slowly out, we would be improving our use of the heat generated by a single candle a hundredfold.
In the confines of an underground shelter or well insulated hideaway, this heat can be sufficient to keep the inhabitants warm because they are making sure that they utilize all of the heat normally exuded by a candle that is allowed to float straight up without being stored anywhere. Most shelters are better insulated than a living room in a house or even a basement. Some so well insulated that heat can become a major issue affecting livability. There was an Army study of inhabitation in an underground shelter that suffered from heat build-up to the degree it drove the participants out of the shelter.
If it’s a snap Ice Age or the middle of a winter with arctic conditions, this high insulation factor for an underground shelter can become a real asset to keeping the shelter residents from freezing. For this reason, this piece of hardware is almost mandatory for keeping as an emergency backup when there isn’t anything more sophisticated on hand. This expedient heating system could be very useful in something like a dual purpose root cellar which a family has taken shelter in during an emergency.
The most important safety concern here is adequate ventilation. Even a little candle can eventually generate enough smoke and carbon soot that it could be a breathing hazard. Under normal conditions, ventilation like that recommended for medium sized shelters as a minimum air flow of 3 cubic feet a minute of incoming air is sufficient for heating and cooking with very small output devices. It’s still wise to put carbon monoxide and fire detectors throughout the shelter to detect conditions where you have a toxic build-up of anything other than breathable air immediately so you can take action on it.
If you wait until you have a throbbing headache, you’re already getting poisoned.
This was covered somewhat in a very early post a while back.
The simple process of assembly is explained in this series of pictures …
Start with the bolt through the bottom, put another washer on the other side and tighten a bolt snugly against the clay pot. Don’t tighten it too much or you could crack the pot.
Put the second pot inside and do the same, tightening the second pot’s bolt to hold it firmly against the interior. The lip of the second pot should end up a couple inches inside so it is clear of the lip of the exterior pot.
Flip it over, put it up on stones or bricks or anything safe against the heat.
Now slide the canned heat underneath it after lighting it or else a single candle as described in most setups.
The pot will grow extremely hot if left undisturbed in about twenty minutes. The heat that is absorbed by the first pot inside will be around 50% of the heat energy released and the pot on the outside will capture the rest, with a much smaller amount lost than is expected of the candle burning alone with no insulator.
Before you know it, the radiated heat will be substantial and in an underground space it could become uncomfortable. This is why a controllable flow of air can be used to adjust the temperature until it is just right.
Some people mount the pot in a wire cage or on stilts to make a more permanent installation and by means of a hook in the top you can suspend the pot inside the wire frame or over a dedicated fuel reservoir. Some people mount this pot onto a clay dish of similar substance as the clay pots to rest one or more candles in. This is not critical but if unsecured, you have to make sure children (and slow adults) do not kick it over accidentally and set something on fire. Keeping it in a corner out of the way can help prevent it from being disturbed. Don’t keep anything flammable near by when this is in use.
If you have a couple of these in an underground space, they should be capable of keeping it warm even with arctic conditions outside. It’s very low tech and very effective at getting a lot of heat out of a very low energy source.
The canned heat can be pricey but bags of these little candles can be purchased at most thrift stores and sometimes you will see cases of a thousand on sale. Good to put up as a last resort just in case it is needed. A useful alternative to a fire or a stove in a small confined space.
Regards, Tex
My head jumped to "cheap sauna".
Also small indoor shade plants with high gas exchange. We exhale what they need and they in turn give us clean air because some species of plants remove toxins. Just wanted to throw that out there.