Ellpea's Terra Cotta "heater" experiment

[EllPea in CA]

Hello friends,

I haven't checked in for a while, but we've been busy. We had another great outing in the LilBea, but I'll post photos and trip report in another thread.

One thing we did discover was that our furnace did not light, and it got kind of cold... around 50 degrees inside when we woke up. We slept comfortably though, no problems there. And after making coffee and cooking breakfast, we were plenty warm.

But that got me thinking about what other kinds of heat we might use if the furnace doesn't light and we're off grid? I wanted to experiment with the terra cotta heaters (or radiators) others have discussed on blogs and vlogs. I read most of what is out there and watched the videos. There were people who said they worked great, and others who said they did not work at all.

I wanted to try for myself.

I purchased 3 pots in graduated sizes, several saucers, a bolt, pan washers, and nuts to fit. Putting the thing together was easy. (I'll post some photos soon)

This morning I took it out to LilB and lit three tea lights. I kept record of temperatures (and humidity) outside and inside at "fairly" regular intervals. I also used my laser temperature thing to measure the temp of the "heater" itself, and also a pot of water I had placed on top. These can probably go into a spreadsheet, maybe, but for now here is the general info:

Trailer temp/humidity at 9am: 55/44
Heater/pot water surface temp: 62.9/65.9

Same info at 2pm today:
76.6/42%
167/134

Tea lights usually only last 4.5 hours or so, but these were still burning. I imagine more candles would equal more heat sooner.

I also placed this setup on a large cookie sheet on the stove as a precaution, so the temp down on the floor was not as warm. The next thing I'll do is place it on the floor and take a few more hourly readings.

For ventilation, I had the roof vent and two windows cracked about 1/2", but I'm not certain (at all) if that's enough ventilation. What do you all think?

Looking forward to your comments!

[charlsara]

The heat you get will be the same as from three tea lights without the terra cotta. The terra cotta wIll store the heat for awhile. It will not increase it.


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[EllPea in CA]

Originally Posted by charlsara

The heat you get will be the same as from three tea lights without the terra cotta. The terra cotta wIll store the heat for awhile. It will not increase it.


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I understand what you're saying. However, I don't see how three tea lights on their own could manage to heat the trailer up to 76 degrees, which is what happened with the terra cotta. While it does not increase the heat output, it does allow the heat to "build up" and radiate...

Anyway, am still interested in how much ventilation would be required to be safe overnight with 3 tea lights burning.

[Byron Kinnaman]

Originally Posted by Ellpea in CA

I understand what you're saying. However, I don't see how three tea lights on their own could manage to heat the trailer up to 76 degrees, which is what happened with the terra cotta. While it does not increase the heat output, it does allow the heat to "build up" and radiate...

Anyway, am still interested in how much ventilation would be required to be safe overnight with 3 tea lights burning.

76°F??? Are you kidding me? Put on a sweater or sweatshirt.

[EllPea in CA]

Originally Posted by Byron Kinnaman

76°F??? Are you kidding me? Put on a sweater or sweatshirt.

Which is what we DID, when we got up and it was 50 degrees inside the trailer.

This is an, uhm EXPERIMENT, okay?

[Glenn Baglo]

First law of thermodynamics:

Energy can be neither created nor be destroyed, but it transforms from one form to another, for instance chemical energy can be converted to kinetic energy in the explosion of a stick of dynamite. A consequence of the law of conservation of energy is that a perpetual motion machine of the first kind cannot exist.
Conservation of energy - Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Conservation_of_energy

[David Tilston]

Well, according to this site:
https://www.quora.com/How-much-energ...candle-produce
Three tea lights should put out about 100W of heat. Not much, but it will raise the temperature of your trailer.

What you are not figuring into your experiment is that the sun was heating your trailer, and the ambient temperature was also rising. I suspect that these factors may have been the largest contributors to your warming.

[EllPea in CA]

Originally Posted by David Tilston

Well, according to this site:
https://www.quora.com/How-much-energ...candle-produce
Three tea lights should put out about 100W of heat. Not much, but it will raise the temperature of your trailer.

What you are not figuring into your experiment is that the sun was heating your trailer, and the ambient temperature was also rising. I suspect that these factors may have been the largest contributors to your warming.

I wondered about that also, which is why I took outside temp readings as well (and can provide if you're curious). And yes, I realize that the outside temp is not the same as the effect of the sun heating the trailer. That's hard to judge that (any clues on how to are welcome). However, I did take the temp on the east (shade) side of the trailer this afternoon: 66.7 degrees. Temp on west side: 68.7 degrees.

The day has been completely overcast, with just sprinkles of rain. But my amateur guesstimate is that the solar effect on the trailer might affect the temp by about two degrees. Discuss?

[EllPea in CA]

Oh, one more thing. On my last two checks, *one* tea light had died out, and the temp had marginally dropped. Hypothesis: three tea lights needed to increase temp inside trailer. Two tea lights will no doubt slow the progress of cooling down, but three (at least) needed to warm.

I'm curious about using beefier candles, sterno, and other types of "warming."

I can also try just lighting three tea lights tomorrow without the *heater,* and see if I get a similar result sans terra cotta. But what I'd really like to do is run the same experiment again, only using 6 tea lights.

Still looking for some scientific mind to suggest minimum ventilation for this application!

[charlsara]

Any candle produces heat which will heat up an enclosed space. More candles will produce more heat. Put your hand close to one. You will move it pretty quick.😃


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[Glenn Baglo]

And terra cotta does not produce heat.
As an experiment, try lighting a piece of paper with a flower pot.

[Donna D.]

I'm always interested if someone finds a cheap/easy heat source especially when camping. But the tea lights and terracotta pots and heating a trailer (or shelter) to a liveable temperature is an urban legend. LOTS of stuff about it on Google. It's reality when the sun comes up, things heat up. So, do you think the rise in temperature you experienced was from your experiment or just the sun rising?

[EllPea in CA]

Originally Posted by Donna D.

I'm always interested if someone finds a cheap/easy heat source especially when camping. But the tea lights and terracotta pots and heating a trailer (or shelter) to a liveable temperature is an urban legend. LOTS of stuff about it on Google. It's reality when the sun comes up, things heat up. So, do you think the rise in temperature you experienced was from your experiment or just the sun rising?

Well, as I said, it was overcast today, so there was not much sun.

I understand (and have read) almost everything, pro and con you can find on Google, which is why I wanted to do this myself. But I'm perfectly willing to try this again after the sun goes down.

Full disclosure: I'd use more than 3 tea lights because I've been there, done that already.

It's already too late tonight, but tomorrow it's supposed to rain, so that's a good opportunity.

Cheers!

[EllPea in CA]

Originally Posted by Glenn Baglo

And terra cotta does not produce heat.
As an experiment, try lighting a piece of paper with a flower pot.

Sigh.

Y'all are so much fun. Flower pots won't light a piece of paper. However, terra cotta has a THERMAL MASS component, which has the capacity to absorb, store and release heat energy.

If objects such as concrete, stone, brick, or ceramic tile did not have the capacity to absorb heat energy, solar heating would also be an urban legend.

I think the terra cotta pots (more than one) together act as thermal storage. When homes are heated with solar heat on a large scale, the solar heat is STORED and used later. "An example of one of the several kinds of STES [seasonal thermal energy storage] illustrates well the capability of interseasonal heat storage. In Alberta, Canada, the homes of the Drake Landing Solar Community (in operation since 2007), get 97% of their year-round heat from a district heat system that is supplied by solar heat from solar-thermal panels on garage roofs. This feat – a world record – is enabled by interseasonal heat storage in a large mass of native rock that is under a central park." https://en.wikipedia.org/wiki/Season...energy_storage

Clearly the sun's heat for one day might not be enough to warm a home (or trailer) in the winter. However, if it is STORED UP, it appears plausible.

One hundred watts of energy from three candles might not be enough to warm an entire trailer. But it appears that their energy can be "stored" via thermal mass, and that mass does seem to warm a trailer.

Cheers

[Glenn Baglo]

You need a lot more energy and a lot more mass.

[EllPea in CA]

Originally Posted by Glenn Baglo

You need a lot more energy and a lot more mass.

I'd readily accept more energy, but am perfectly satisfied with my current "mass," thank you.

[Borrego Dave]

Interesting testing LP, I might have add a few candles as I don't have a LP heater and don't use hookups. Glad you're getting out with your rig after all the problems you had early on.

[C&G in FL]

Try taking a general science class. It is solar radiation that heats the earth. Even on cloudy days some of it, particularly the UV wavelengths penetrate the clouds. Anyone with a solar panel knows that, as they may not have as great an output on cloudy days, but they still produce current. And if you can successfully negotiate a 9th grade general science course, take physics next and learn about thermodynamics. Any increase in the trailer's internal temperature after sunrise is mostly due to solar radiation (even in cloudy or rainy conditions) and not 100 watts of candle heat stored by terra cotta. Ask yourself this: Why do people like to sit in the shade during the summer months, but avoid shaded areas during the winter?

If you really want a meaningful experiment, get your terra cotta "heater" hot during the afternoon and evening outside of the trailer. Wait until after sunset and the trailer cools off, and move the "heaters" inside the trailer. Then, since it will be nighttime and there will be no solar radiation striking the trailer, let us know how much of a temperature change is noted inside the trailer from the "terra cotta stored heat," and how long that increase actually lasts. Better yet, try using the terra cotta heater in below freezing temperatures even if the sun is shining and see how comfortable it is inside the trailer.


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[charlsara]

Originally Posted by charlsara

The heat you get will be the same as from three tea lights without the terra cotta. The terra cotta wIll store the heat for awhile. It will not increase it.


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I rest my case...

[David Tilston]

Carl has a good idea. Try your experiment after dark. Remove the sun from the equation. I would start around 11 pm, but I am a bit of a night hawk.