Charcoal for fridge instead of propane questions

I am new here, and interested in ( I think) charcoal gasification… as I am wanting to experiment with gasification as a heat source for an absorption fridge… ( located outside of the building)

Charcoal gasification because I am under the impression that it is more idiot proof, and may allow less attention on an hour to hour basis?

The last part of these opening questions is something like this: does having charcoal production separate from the gasification stage, create flexibility and a less involved system to create “good gas?”


Welcome to the site Jason.
I like the way you are thinking. As I understand it, absorbtion fridges do not necessarily need a gas flame but just a source of heat, so if you had a self feeding “fine charcoal” rocket stove setup for the heat source
you should be able to make that work. I saw a rocket stove on YouTube that fed wood pellets from a large hopper by gravity without electricity, so a charcoal hopper should work also.


Thanks for the welcome Don, and the added insight.

I have seen a self feeding pellet stove, no idea if it worked as advertised, but I have an image in my mind to play with. Your solution is simpler as well, which is always better…


Welcome to the site!

The main issue I see, is you have to have something to pull gas out of the gasifier to where your fridge heat coil is. So @don_mannes idea of a self-feeding rocket stove is not a bad idea.


Welcome along Jason ,
A friend of mine had one of these fridges , when i next speak to him i shall ask him the pro’s and con’s to that type of fridge , but my understanding is you need a constant heat source ? if that’s the case then do you intend running your charcoal retort or gasifier for constant hours during the day or night or is it a case of maybe just keeping a heat source there for X amount of hours a day ?
And yes once you have made decent engine grade charcoal most systems are a start and walk away for what ever length of time your hopper amount is eg: a 45 gall or 205 litre oil drum will run a 500cc 13hp under load for a average time of 4 hours before it then need shaking or refilling to the top again .
Most of us make charcoal in a retort totally separate from the gasifier itself yes its more flexible because you can make batches of charcoal for a later date while your gasifier is running making power , you can then use that power for electric saws ect for cutting the wood or charging battery banks .


Some years back on a homesteading site I was on, there was a husband and wife experimenting with this, using parabolic focusing collectors to heat hot water for a refrigeration system. Then they disappeared. Never found out it it worked for them. From our discussions it would seem that using a sand battery to store the waste heat from a wood gas powered generator/charcoal production set up would have some merit.


Thank You Dave for the welcome, and experience with running a generator on charcoal.

Most of my experience with my gas fridge, has been less than positive. It is a propane hog, and I have been considering scrapping it, until the idea of exploring a charcoal powered or wood powered heat source occurred to me…

My fridge has a thermostat which ramps up the propane flow when needed to cool down the fridge… otherwise it keeps a flame lit, like a pilot light. I have not observed how much time is needed on 'high" to keep the fridge cool. That is something to begin paying attention to… Essentially when the heat source gets hot enough to boil the ammonia, it starts the process,


Good point. Can an insulated chimney provide enough draw to keep a gasifier “lit” for idle time, and a compressed air source push air from behind to provide the 'high" gas flow needs when the thermostat calls for it?

Essentially I think your point makes it the more complex path, and probably not worth the effort for a fridge… Maybe a commercial setting, but not for a residence…


I remember our absorption fridge we inherit from previous owners of our hut. It worked on PB gas. So far as I remember, the flame was really small, like big candle. There was no thermostat. The whole device kept temperature acording to equilibrium between thermal loses and cooling power of the flame.

For such a device, wood gas does not make sense. The gasifier would need to be pocket size and there is no draft inside the fridge to keep gasifier working. Better thing would be an alcohol burner running on methanol from wood or ethanol from fermentation.


I second Kamil’s idea. An alcohol lamp would be a very low hassle idea.

I’d suggest a waste vegetable oil lamp but that could get sooty.


My fridge does not happen to be that efficient… It should be scrap, but the cooling unit works, so I figured maybe I could make something interesting work…


Ok Jason how about doing just that !
Scrap it and buy a very cheap used fridge freezer and a couple of deep cycle batteries and then a small generator running off your charcoal gasifier and run that for around 4 hours a day to run the fridge freezer while charging up the batteries , Orrrr a few solar panels and a few more batteries for days when you have great sun and too tired to make charcoal .
Just thought if your fridge was outside you could maybe use the exhaust from the generator to heat up your fridge , or does it need to be a flame heat to boil the ammonia ?


Jason, l think the simplest way wuld be to just build a kinda charcoal stove underneeth and hook its air supply to the coolers thermostat. I dont think there is a need to complicate things that much, charcoal burns for a wery long time in a well designed stove will burn for hours.

Or maybe even simpler. Bypass the thermostat, do it like Kamils. Set the air inlet/heat just right so that it constantly runs at a desired setting.


All really good ideas…

Dave, your suggestion of scrapping it is probably wise… and realistic… and the right thing to do… otherwise the sunken cost of a poor design, makes the solutions oversized, and inefficient.

That is the reality, and starting over if the thing to do if I want a fridge that isn’t an exercise in frustration and disappointment.

Now if the fridge would run off the generator’s exhaust… then it becomes an increase in efficiency but my guess is the generator would have to run more than 4 hours a day to keep this fridge cold…

For now I am going to turn my attention towards charcoal making on the D.O.W. forum.
Thanks guys!


There is probably someone who will buy it if it doesn’t leak. They are great for off-grid folks. However, if it is the ammonia based style, the ammonia eats through the pipe and it starts to leak, and the effectiveness starts going to zero.

Otherwise, they are good. BUT they do not cool quickly like a compressor fridge. They take a while to cool stuff down.

I guess I am trying to figure out if it is a poor design as far as insulation. Or if there is an issue or perceived issue with it.


It is an ammonia based style, and it is a commercial fridge top freezer bottom fridge. The strip of metal between the two sweats condensation all summer long… AND I think the “company” used one size burner for all 4 sizes of fridges they made. Mine is the smallest so the burner is oversized… AND it is under insulated. I put additional insulation around it and eventually decided that the most under insulated part was actually the back around the cooling system…

If it was not such a clunker I would sell it… but I don’t feel good about selling something as “good” when yes it works, but nothing about it is actually good other than the cooling system and it’s ability to consume propane.


The insulation may have broken down over time. I believe they used polystyrene foam board on some of the older ones that breaks down and gets brittle. But you can check the seals around the door, that is a common problem. The door might have been bent during transport as well.

As far as the sucking of propane, it is probably a nozzle meant for natural gas which is slightly larger then the propane nozzle or it could have been filed out. I doubt the fridge company made their own, it is probably a standard fitting.

You could add a solar panel and an electric heater to replace the propane. It is what they do on campers.

The other woodgas option is to make methanol and use that in a burner.


The biggest issue I have with the fridge is the sweating between the fridge and freezer… it has done it since day one… and as far as I can tell the seal is fine, and the door is in good shape… there is just not enough insulation, and I believe they have a heat strip from the factory to prevent the condensation…?


We had an old Servel made in Evansville, Indiana. It used a kerosene lamp type burner to heat and expand the gas.


maybe. I would more suspect it is just old insulation. There were people (as well as a company) who took apart the old 50s? style single door fridges with the built-in ice box and repacked the insulation on them because they liked the look of them. Those weren’t insulated very well from the factory either. And I think they used the polyurethane spray instead of styrofoam because it insulated better.