keeping your stuff cold

paul wheaton wrote:
I just got an email from Diana Leaf Christian (a communities author that is mentioned here from time to time).  She mentions that she has a chest fridge and is gonna try to get rid of it to get a normal upright fridge so she doesn't have to dig for her food anymore. 

Fascinating!

The original "chest_fridge.pdf" article made some comments wondering why people didn't think to save energy by using more efficient "chest refrigerators".  I can give one very important reason: space.

Just did a quick search.  The chest freezer he used was about 8 cubic feet.  Using Sears as a baseline, the closest equivalent to his freezer was 41 inches wide.  A 9.6cf upright refrigerator was only 24 inches wide.  Get a tape measure, go to your kitchen, measure out 41 inches of counter space, and tell your wife (or soon-to-be-ex-wife) that you're going to rip out that much counter/storage space for your new chest freezer.  Oh, and that means she'll have to really bend over to get the stuff that's in the bottom of the unit.  (Hope she's not pregnant.)

I'm hoping to build a small house someday.  And when I say small, I mean 20ftx20ft.  The kitchen will be only 10ft wide.  To use this solution, I think I'd have to keep a compact fridge in the kitchen and keep the chest fridge in the basement.  How much energy would THAT use up?

If chest fridges are such space hogs then why do they use them on boats(including houseboats, which don't see heavy seas), where space is more restricted than in any other situation?

Emerson White wrote:
If chest fridges are such space hogs then why do they use them on boats(including houseboats, which don't see heavy seas), where space is more restricted than in any other situation?

I did a search for "Marine/RV refrigerators".  Guess what?  Literally 99% of the fridge/freezers in that market are vertical.  Even the ones that are "sloped" in the back to fit against the hull are vertical.  The chest ones are very small, usually 1 to 2.5cf.  The largest chest one I could find is the Isotherm BI92 ( http://www.indelmarineusa.com/products/BI92.htm ), which is 3.25cf.  Its rated dimensions (HxWxD in inches, including removable compressor) is 24.88x19.06x31.5.  So 19 inches wide.  Except from the photo it's clear that you either have to mount it sideways (31.5 inches) or be prepared to really stretch to reach the stuff in the back at the bottom of the fridge.  It looks like it's designed to fit flush with the counter, so you could use it as counter space unless you're making dinner and your first mate wants in the fridge to get the milk out.  (Which has mysteriously worked its way from the front part of the front shelf to the back part of the back shelf, which is where YOUR beer is SUPPOSED to be.  Funny how that works...)

So unless and until you can find a readily-available marine/RV chest fridge that is over 6cf (approaching our desired 8cf), I stand by my statement.

I see nobody wants to comment on the way to make free refrigeration.
I think that says a lot.
It happened at overunity too.
They spend all their brainpower to create free energy but only 2 have ever commented on it since I posted this over one or maybe 2 years ago.

It is just telling, that is all.

I would like to say this can be made with cement or ferrocement with maybe even better results than cob. Cement likes to be wet, and it will stay cooler naturally more than even the cob.

-------

The answer to how much extra for 2 units?
The answer is about twice.

So if the first $20 per month in electricity goes to your first fridge, then you will be spending $40 per month when you add the extra freezer.

More accurately, most fridge compressors use 4A, and they are on from 20 minutes per hour to 30 minutes per hour... but usually 30 minutes.

Multiply 4Amps x 110v = 440wats per hour so 220w per hour,  if it is on for 30 minutes an hour
220w/h x 24 hours = 5280w or 5.28Kw per day which looks like
158.4 KWH per month on your bill.

If it is on for 20 minutes per hour:
3.520KWH per day and 105.6KWH per month... you can do the math with your own rate charges.

Keep the door closed and remove the light inside.
Find the Amps use and see how much it uses by sitting in the kitchen some day and time it.
It is very edifying.



jeanna

Jeanna, I've been looking at your "Solar Fridge or Air Conditioner" and I'm trying to figure it out.

I'm assuming what you have is a box made out of cob (or it could be made out of concrete, as you point out).  Stuck in the cob are what I assumed are UNOPENED cans of beer, correct?  How much of the can is exposed?  Do they line all 4 sides of the box, and do they go up to the top of the box?  Where in the box do you keep your food?

Muzhik wrote:
Jeanna, I've been looking at your "Solar Fridge or Air Conditioner" and I'm trying to figure it out.

I'm assuming what you have is a box made out of cob (or it could be made out of concrete, as you point out).  Stuck in the cob are what I assumed are UNOPENED cans of beer, correct?  How much of the can is exposed?  Do they line all 4 sides of the box, and do they go up to the top of the box?  Where in the box do you keep your food?

Oh good! Thank you Muzhik.

The box is above or at ground level. And it can be a walk in, so it can be large or small. The thicker the walls (18" for cob) the better, of course.
Yes, unopened cans. The reason for the beer is that it freezes at a lower point than water so it can get colder than water, and not burst, of course.
The bottoms of the cans are exposed. I guess they could be out a bit, but aluminum is fragile and you don't want to poke it, so I say just the bottom surface is exposed.
3 sides of the fridge would have the cans and the fourth side is the door. the more cans,  the colder, so if you can afford the beer, go all the way to the top.
The grate on the bottom is letting the precooled air in to circulate, and if you make it a strong floor around the floor opening that has the grate, you can make a shelf or a few shelves for your food.
I suppose you could put the shelf right on the grate.

When I last spoke with Donkey, he was still needing to add water into the evaporation pot at the bottom , but he said he was fiddling with making a moisture capture and angle so the moisture would condense and drip into the pot again.
I do not know if he was successful, and I am sure there is a need to replenish the water for evaporation at some point even with this capture.

I believe the bigger, the colder, but it should be possible to make a smaller cooler to try out the concept. One could use an electric fan over a cloth with constant wetness so that it blows over a the bottoms of a case of beer and see how many degrees lower the end result is when compared with just air over cloth. One case of beer may not reduce the temperature very much, but if it is lower than just evaporation over cloth it will give you a reason to continue.
And please remember a fan will add heat so this is not the final design, just a comparison with and without the cans.

jeanna

Jeanna, I've been trying to suss out how this puppy works and can provide such efficiency.  Here's what I've go so far (and forgive me for thinking out loud):

As much of the unit as possible is buried underground, especially the evaporator chamber.  Is this correct?

Regarding the cooling chamber, you state that the wall of cob was 18 inches thick.  Cob is great for thermal mass (the heat it gets it keeps) but lousy for insulation (it lets heat through easily.)  Normally, cob has an R value of 0.5 per inch.  You can bring that up to 1.0 if you use cob with 30% pumice, and a LOT of straw.  It's called "Structural Lightweight Insulated Cob (SLIC)".  Assuming the walls are made out of that, you'll have a large thermal mass with an insulation value of R-18.

Except it won't be R-18.  The beer cans are embedded in the cob.  The beer cans are about 5.5 inches and are made of aluminum.  Aluminum has an R value of 0 (I rounded up).  So for all intents and purposes, the cob has an insulation value of R-12.  This means it will take 12 hours for a one degree F. change in temperature to be "transmitted" through the cob from one side to the other.

The beer cans are containing their own thermal mass.  I don't have any information on the thermal properties of beer (are we talking 3.2 beer or 5% beer?) so lets just assume it's water.  (If it's American beer, it might as well be.)

So let's take this through a typical summer's day cycle.  Starting at 5AM, there is very little air moving through the cooling chamber, and the temperature of the aluminum is approaching ambient.  The temperature of the cob will also be close to ambient.  The temperature in the evaporation chamber is lower than ambient, due to the small amount of evaporation still occurring.  When the sun starts rising, the sun heats the stovepipe, warming the air and pulling the cooler air from the evaporation chamber into the cooling chamber.

Now, here is where I'm having problems putting it all together.  Just like water always runs downhill, heat will always flow towards area of lower heat.  If the cob next to the cans is cooler than the liquid in the cans, the cans will give up their heat to the cob, cooling the beer.  Since the aluminum is R-0, it will be taking some of the heat from the air with it, cooling the air, and transferring the heat both to the cob and to the beer, chilling the cooling chamber.  The beer cans will be as cold as the beer inside; and as long as the beer in the aluminum cans stays colder than the dew point of the air in the cooling chamber, the aluminum cans will continue to draw heat from the air, transfer some of it to the beer, and transmit the rest to the cob.

As the day goes on, the cob gets warmer (I'm assuming it's painted white to reflect as much heat as possible) but the stovepipe gets even warmer, drawing more and more air through the evaporation chamber, increasing the evaporation and chilling the air even more.  The thermal mass of the beer gives up some of its heat to the cob but continues to take heat from the air in the chilling chamber.  After the sun sets, though, the stovepipe cools down and stops drawing air through the evaporation chamber.  The question then becomes, has the beer become cold enough to take heat from the cob?

The long and short of it is I can't see the efficiency of the system being sufficient to keep a space close to 40 degrees Fahrenheit on a consistent basis.  Where I live it is not uncommon for the relative humidity to reach 70% (or more) for a few weeks in summer, meaning the efficiency of an evaporative cooler will be GREATLY reduced.  In addition, there's the question of what to do during winter: can you be so sure the beer cans won't burst when it's -20 degrees at night?

Hi Muzhik,

These sound like good questions.
I can only suggest a couple of answers.

1- the ice caves of Idaho which is what was the inspiration for this design.
In 120 degrees outdoor weather there is ice inside when caves and most underground places are around 50-60 degrees F.
2- the cooler was working as a whole house air conditioner and was uncomfortably cold when the door was not yet installed. I would assume it would work even better when finished.

It is also very possible that the intake air continues to flow over the evaporator and cool the night air if the cob is has become as warm as you think. It would cool off the cob to ambient through the night.
I am not able to answer any of the questions about the aluminum specific parts. It must be aluminum and no other conductive metal, according to the designer.

I guess it is the reason I would do a smaller version remembering that bigger would get better results from larger surface area and mass and faster (wind  ) speed inside.

BTW I am also not convinced that adding the kind of dead air insulation will work. The ice caves are lined in bedrock and there is no R-13 value there, so I think the mass is key.

thank you,

jeanna

This is getting beyond me.  What little I know about cooling systems comes from what I had to study to get my HERS (Home Energy Rating Systems) certification.  I don't suppose you could have Donkey send you some more specific drawings, pictures, etc.?

If I owned my own house I would love to experiment with this.  IF it can be replicated, it would be a great advance.  Unfortunately, I live in an apartment.

I also suspect this is something that, when replicating, would have to be done over several parts of the country to see how well this works in different climates.  It might work better in the mountains than in the plains, for example.

1) During an energy talk I've heard Doug Bullock refer to an ice factory where he grew up in San Luis Obispo. Apparently, the factory was located in a spot with high, near-constant winds. They had a series of radiators mounted to the roof where the wind would would blow through them and cool the refrigerant down. As it cooled it would sink inside the building make it really cold. Cold enough to make ice, apparently. According to Doug the walls were made from thick cork and they were super insulated.

When Doug visited as a kid he realized that all the electric lights were tacked onto the ceiling with exposed wires. This is because the the factory was actually build before the era of electricity. In other words, they were manufacturing ice in California with no electricity. In the 70's they were even able to make dry ice.

What I'm picturing looks like a heat sink for a CPU--by running air past the vanes the heat inside is drawn off.  Except that here the core is hollow so food can be put inside.  I suspect it could be put in cold running water, or even water-saturated sand.

I like the alcohol refrigerant idea.  The alky could be run through a radiator before running through the vanes again.  A pump could even be powered by Peltier junctions using the waste heat. 

Hassan Fathy (an Egyptian Architect that studied and wrote about traditional building in the Middle East) write in one of his books about making ice before electricity in Egypt.  They used mud walls to create wind. One part of wall would get hot and other parts still shady and cool creating airflow.  I think the ice was made underground on the shady side.  I read about this some 20 years ago so I don't remember which book or exactly how it was done. 

Natural Energy and Vernacular Architecture is out of print and on-line at
http://www.unu.edu/unupress/unupbooks/80a01e/80A01E00.htm

Didn't explain making ice but has a lot of good info on passive cooling techniques.  (I used diagrams from it for a slide show I did on passive heating and cooling recently.)  Maybe I'll have to revisit his books again soon.

Thanks for the forum.  I am loving the creativity and passion.

marina phillips wrote:
I've heard about old milk houses, stone floors and walls, with cold water constantly running over the floor.  We were inspired by the cold air we can feel walking up the hill to the spring. 

The spring water on our land is 47 degrees all year round.  We took an old fridge and plumbed it with 1/2" pex and water runs through it 24/7.  It keeps butter from melting in the summer and extends leftover shelf life - in the 60s in there at noon when it's 110 outside.  That sounds warm, but the summer of '08 I had nothing at all and it was a real challenge to keep things from spoiling quickly and melting everywhere.  I've learned a lot about what to buy and how long to expect it to last.  This time of year it's a pretty perfect fridge - usually right at 40.  We had a low of 11 the other night and it was 36 in the fridge. 

pics:

http://www.flickr.com/photos/fishermansdaughter/sets/72157621522225919/

We're in the process of building a large, completely buried concrete block cellar.  We plan to have the same 1/2" pex running through the concrete slab of that finished structure. 

I looked through your flickr album and something jumped out at me.  You mentioned you were able to keep the temps where they were with only a blanket stuffed in the top.  I think you can REALLY increase the efficiency of your unit if you were to get some pieces of blue Styrofoam insulating boards cut to fit, and glued on top of each other to reach the top of your fridge or 4", whichever comes first.  If you can glue some to the bottom of your unit that might help too.

When you say "overunity," you mean efficiency greater than 100%, right?

Due to the training I've been through, I have trouble discussing topics like that, often because the people I'm trying to converse with use the same terms in much, much different ways. Each side of the discussion ends up making perfect sense to the person who wrote it, but reads like gibberish to the other side, due to different perspectives.

Joel Hollingsworth wrote:
When you say "overunity," you mean efficiency greater than 100%, right?

I think she is referring to the "Free Energy" board at http://www.overunity.com

Perpetual motion/free energy is not the basket to put permacultures eggs in.

I think the confusing thing here is that we are dealing largely with heat pumps, and with a heat pump you can move 10,000 Calories worth of energy out of your house with 2,500 Calories worth of energy, however you have to be moving it pretty much down hill to get that kind of efficiency. If you aren't keeping track of where the energy it coming from and going too its easy to think there is some to spare, but as always when you try and recapture what you thought was spare energy you find that the system falls just short of running itself forever.

Emerson White wrote:
Perpetual motion/free energy is not the basket to put permacultures eggs in.

But we could put our hams in there, couldn't we?

Oh now you are just mixing metaphores 

Emerson White wrote:Perpetual motion/free energy is not the basket to put permacultures eggs in.

You're preaching to the choir on this.

It could be that anything is possible, but some things are vanishingly unlikely. Lottery tickets are a much better investment than perpetual motion machines.

I don't know, folks.  there seemed to be quite a bit of free energy exiting through my posterior after a friend had me over for sunchoke bisque.  it's all around us, we just have to harness it...

this is a long thread, so I may have missed a mention of this, but it seems to me that a sizable cold trap combined with thermal mass inside good insulation ought to make a passable refrigerator or freezer in temperate and colder zones.  really just a glorified root cellar.  shouldn't need energy input after initial construction.  there would certainly be limits to how much mass could be chilled, but good calculations ahead of time should prevent problems.

I can't remember where I first found the link to this, so if it's a repeat, my apologies.

A refrigerator that uses no electricity

Simply put, it's an icebox.  It is a metal box, surrounded by 16" of foam insulation around it, with shelves for food and a large plastic liner, 3ft x 4ft x 4ft.  Using a very simple system, the ice is frozen in the winter, and it stays frozen for most of the year until next winter, when it freezes again.

There's no freezer, just fridge, but hey, it's free!  Get a small chest freezer for your pizza and ice cream, and you're still saving money.

dragonfly wrote:
Hassan Fathy (an Egyptian Architect that studied and wrote about traditional building in the Middle East) write in one of his books about making ice before electricity in Egypt.  They used mud walls to create wind. One part of wall would get hot and other parts still shady and cool creating airflow.  I think the ice was made underground on the shady side.  I read about this some 20 years ago so I don't remember which book or exactly how it was done. 

Natural Energy and Vernacular Architecture is out of print and on-line at
http://www.unu.edu/unupress/unupbooks/80a01e/80A01E00.htm

Didn't explain making ice but has a lot of good info on passive cooling techniques.  (I used diagrams from it for a slide show I did on passive heating and cooling recently.)  Maybe I'll have to revisit his books again soon.

Thanks for the forum.  I am loving the creativity and passion.

Oh this is wonderful.
I hope you come across the books again someday.
I suspect you need hundreds of feet of breeze to actually make ice.
I have never been to the ice caves, so I do not know how big they are nor how quickly the wind moves, and I think those are essential parts to this.


I want to remind everybody that the breeze which would normally require electricity to pump comes from the effect of heat rising through the black painted tall chimney, and the initial cooler temperatures inside come from the evaporation of the wet cloth, and the rest that  happens in this fridge (Alcohol filled Al cans etc.) carries the temperatures lower still. So, adding a pump would not be necessary.

I think this cannot be made on a flat plain. It needs to have a way for the air to enter maybe 12 feet below the top of the chimney for it to be effective. But that is why I would love to see those books, because maybe there is another way. but maybe those colder walls and warmer hallways in the desert could do it without the height. ??

I have a miniature stand-alone rocket stove and I would love to think I could make a miniature stand alone donkey fridge. 

thank you,

jeanna

This video features a guy that looooooves cheese.  He has lots and lots of cheese.

He converted a room in his house into a "cheese cave" by tricking an air conditioner into being a refrigeration unit for a walk-in-fridge-like-thing.

http://www.youtube.com/paulwheaton12#p/u/0/QIxLw9t1IuA

If you like this, please give a thumbs up, add to your favorites, comment, subscribe and friend.

Thanks!

jeannacav wrote:


When I last spoke with Donkey,


And please remember a fan will add heat so this is not the final design, just a comparison with and without the cans.

jeanna

How is Donkey coming with his project? Any changes or updates?

I just came across an interesting old magazine "The Penny Magazine" Volumn 6 published in  1837  on Amazon.com

It has an interesting article on making ice at using radiant cooling techniques in Calcutta, India.

http://books.google.com/books?id=FKffAAAAMAAJ&pg=PA198&lpg=PA198&dq=calcutta+ice+straw+night&source=bl&ots=JGdqaqhJk9&sig=tfODESTuPdASU2yBz61Po6ZnkJQ&hl=en&ei=8QhWTdyoOYGmsQOZupydDA&sa=X&oi=book_result&ct=result&resnum=2&ved=0CBsQ6AEwAQ#v=onepage&q=calcutta%20ice%20straw%20night&f=false

Feral wrote:
How is Donkey coming with his project? Any changes or updates?

Wow.. Looky here, it's my fridge!!
Well, ALMOST my fridge.. The description here is a little off.
There's no cob in it..

Basically it's a big swamp cooler fed by incoming underground air. It's very well insulated, has flue adjustments for incoming and outflowing air and it's got cheap beer in cans for thermal mass. I chose aluminum cans because they are nicely conductive and won't inhibit or insulate. The whole mess is powered by a solar chimney.
It works pretty well and is MARKEDLY cooler inside than outside ALL of the time. It's NOT going to get 40 deg. inside during the summer, though when the flue adjustments are just right it will provide more than a 10 deg drop in temp..
Using the word "refrigerator" on this thing is a mismatch.. Calls to mind a standard appliance with constant temperatures etc, which this is NOT.. We call it the pantry. It's basically an above ground root cellar and we can keep most things in there though we have a small trailer fridge for meat, dairy and whatnot.

What I need to do to it is improve the solar chimney. It's in an unfinished state and it's likely that right now it's just acting like a regular old chimney. Some of my earlier tests created a noticeable updraft and I'm not seeing as much of that in my gizmo as I'd like. Within limits, the hotter the chimney, the more the updraft, the cooler it should get in the box.

I've been puzzling for a couple of years why my neighbours root cellars had chimneys - mine doesn't! Thanks for the info.

Isn't shade, trees for example, useful in keeping the pantry cool? I remember falling into a woodland (pine) ditch in late April the other year and breaking ice. No sun had reached it.

Perhaps a combination of judicious siting, sunken construction, and choice of a stone floor and shelves might do the trick. I seem to remember a Russian convent where they used stone. Had jars and jars of gherkins there.

The beers you'd keep in an old belfast sink (oldfashioned ceramic sort) filled with water and raised high enough to put a bucket under for a change if the water became too disgusting.

My own root cellar is a bit small - cant get enough beer in - so I'm already planning a new one. I only have to wait till the house is habitable first.

Good luck with the project Jeanna and keep us all informed.

woodlander wrote:
My own root cellar is a bit small - cant get enough beer in - so I'm already planning a new one. I only have to wait till the house is habitable first.

Are you sure you have your priorities in order, there?

Possibly not, but these days I live a quieter life

Paul, I like your idea of adapting the umbrella house concept to storing cold, rather than heat.  In Missoula, looks like you have average nighttime lows of 32 or below roughly 6 months of the year.  Average yearly temps look to be about 44 degrees.  If I'm not mistaken, 20 feet below the surface, the earth should be a constant 44 degrees or so (average yearly temp).  38 degrees is good enough for refrigeration.  Seems like an earthtube could get enough cold air through during the colder months to freeze the earth 20 feet deep.

You would need enough thermal mass and insulation to hold the cold for roughly 6 months.  I'm sure you could manage at least refrigerator temps, if not freezer temps.  Your idea of a cold room with a second door to the freezer is a good one.  An efficient chest freezer would seem to work well. 

To improve my fridge and freezer I'm just going to
stick additional insulation panels on the outside.
Sometimes condensation forms on them and that to me
means the insulation is not sufficient.

Jen0454 wrote:
To improve my fridge and freezer I'm just going to
stick additional insulation panels on the outside.
Sometimes condensation forms on them and that to me
means the insulation is not sufficient.

From a very realistic position, this is the best bet yet.

I present for your consideraton .... no electricity is used ...  cooled by a spring ....  the cool box:

paul wheaton wrote:
Once the fridge becomes super efficient, the amount of heat extracted should be
less than what is put out my a dim light bulb.  Probably not worth the effort of
moving the heat.

Unfortunately this ignores the first function that a fridge and freezer do: remove the energy from the object.

The chill down phase, especially in a freezer, is what takes the most energy.
This is why you can't just stick food in a super insulated box.
You must chill the box and chill the food. Then the insulation helps keep new heat from coming in.

Donkey wrote:
Wow.. Looky here, it's my fridge!!
Well, ALMOST my fridge.. The description here is a little off.
There's no cob in it..

Basically it's a big swamp cooler fed by incoming underground air. It's very well insulated, has flue adjustments for incoming and outflowing air and it's got cheap beer in cans for thermal mass. I chose aluminum cans because they are nicely conductive and won't inhibit or insulate. The whole mess is powered by a solar chimney.
It works pretty well and is MARKEDLY cooler inside than outside ALL of the time. It's NOT going to get 40 deg. inside during the summer, though when the flue adjustments are just right it will provide more than a 10 deg drop in temp..
Using the word "refrigerator" on this thing is a mismatch.. Calls to mind a standard appliance with constant temperatures etc, which this is NOT.. We call it the pantry. It's basically an above ground root cellar and we can keep most things in there though we have a small trailer fridge for meat, dairy and whatnot.

What I need to do to it is improve the solar chimney. It's in an unfinished state and it's likely that right now it's just acting like a regular old chimney. Some of my earlier tests created a noticeable updraft and I'm not seeing as much of that in my gizmo as I'd like. Within limits, the hotter the chimney, the more the updraft, the cooler it should get in the box.

Hi Donkey!

I am so glad to see you are here and that you responded to (my mention of) your fridge design.

Here was my original post with my  drawing of your fridge.
https://permies.com/bb/index.php?topic=2124.msg34490#msg34490

I thought it was clear that there was cob in the beer can area, but maybe not.

When I took your class and you shared this fridge design with us, you were working out a design to get the drip to be self regulating.
Did you get it to work?

And, what IS the temp in the cooler in the summer?
10 degrees cooler than outside? What is that?

Funny, I was just telling someone today about your wet sloppy cob and how fast it was and so much easier on the hands. 

jeanna

Simple design:

Make a building, preferably uphill from your house.

Could be vermiculite-ferro-cement.  A few inches = 20 inches of cement in insulating power.
Do various things to block the sun from it.

Add an outer and inner chamber as desired, for more and less coolth.

Fill it with buckets of water with salt water.

Open the door at night on freezing nights throughout the warmer months, as needed, or  a vent/window, to refreeze the buckets.

IF desired run an air-conveyance tube from the cool cellar to one's fridge inside the home, perhaps kept inside an insulated room, or just superinsulated, to cool the fridge.

We happen to be running a crowd funding campaign at this very moment (6 days left!) to build a root cellar/passive cooler. There is a thread on it here if you'd like to see the conversation that has already happened around it.

https://permies.com/t/54048//Passive-cooling-system-turn-root

Basically we would like to try something similar to the heat pump and ammonia based closed loop cooling systems mentioned in this thread, but using butane as the liquid that drives the temperature difference and creates ice. The method is dependent on having some freezing winter weather to amass enough ice inside a root cellar, so that it will cool the space over the warmer months. Instead of having to cut and haul ice, or freeze mass amounts of buckets or soda bottles, tanks can be frozen in place. We want to experiment with this principle on a scale appropriate for a small farm. I'm not sure if it could be scaled down for home refrigeration or not, as it depends on having a large enough mass of ice to last for months. There is a lot more information about our plans here:
webpage

For a $10 contribution we will keep you updated about our results for the next 2 years. I promise to try to do better with sharing plans than the Gaviotas group that was mentioned.

I like this approach if you want to build a diy refrigerator or freezer.

You can use whatever enclosure or fridge donor chassis you like and service and repair becomes a snap. The company makes thermoelectric devices (delta-t to dc power) that can be plumbed with fluids or simple contact with heat or flame. 30-50 watts constant while running a biofuel heater is nothing to shake a stick at for solar off gridders when strings of cloudy days reach 5-12 days in a row

http://tellurex.com/shop-products/