Making an "African refrigerator"

[oregano]

I had a problem with my standard compressor operated mini fridge. During the summer when it gets hot I found that it cycles on and off repeatedly and quickly drains my house battery into the danger zone while doing so. So I managed to come across an invention called a "pot-in-pot fridge", "clay pot fridge", or "zeer" as it is known in the Middle East.

Sadly I couldn't find clay pots, so I decided to improvise. The outer pot of mine is made from wood pulp instead of clay. I figured wood pulp would be porous enough. The inner pot is plastic which is impermeable, in Africa the inner clay pot is frequently lined to keep the water out. This is before I wet the sand. I used two bags of standard sand from Lowe's branded "Sakrete".

This is a better look at the inside of my zeer. The rough edges around the inner pot are the result of me having to cut off a protruding "lip" which would have made wetting the sand difficult.

In Africa a wet cloth is used to cover the inner pot. Instead I used this weird aluminum disk that looks like it was intended to be a wall decoration. I found it at the Josephine County flea market.

Anyway as of right now I wet the sand but there hasn't been much evaporation yet due to the temperature in my home not being hot enough yet.

 

[Aspychata]

Smart. It's tough living off the grid. But you are figuring this out. Is the isolation okay? How are you dealing with this?

 

[Neonatal RRT]

Evaporative cooling. Nice. Pot-in-pot refrigerator - Wikipedia

 

[Yeshuasdaughter]

Your method is okay for learning HOW to do it, and playing around, experimenting. But what you have created is essentially, a styrofoam cooler.

You need the right building materials for job, if you're going to be successful. Compressed paper and plastic will NOT yield the same results, and people living traditional societies will tell you so. The lid, also, must be much heavier. It is not pourousness that you want. It needs to be thick and sturdy, to hold in that natural cold, that came from the grocery store.

And you need this book. It is a guidebook of how to store and preserve perishable items the way our grandparents did, before the mid 1940s. It was written in France, and outlines the methods that were used, and still are used by many rural farmers.

This book pretty much essential, if you're going to successfully, off grid. Especially if you want to eat more than canned or boxed food.

https://www.amazon.com/Preserving-F...prefix=preserving+food+without,aps,198&sr=8-4

 

[Yeshuasdaughter]

In the aforementioned book, it will teach you to dig out and construct an underground Brick Silo. That's what you need, to start off.

You went to all the trouble of constructing an above-ground cold frame/blanket box. And it will work as well as any Igloo brand cooler (with a missing lid). But did you take into account the fact that your floor is a thin trailer floor, elevated off the ground, with free flowing warm air underneath? In traditional societies, the floor would be wood, stone, or earth, and provide insulation from the bottom, holding in the heat or cold.

You are also losing energy from above. Aluminum is way too light and porous, and not heavy enough to produce a hard seal between the lid and the sides. There should be jugs of water inside, as well.

You're going to have to dig out a cold frame, and place insulated pots like the one you constructed, but made of good, time tested, solid materials, inside the cold frame, and then place the perishable food items inside. You will also need hard, heavy lids for each vessel, and an even heavier, thicker lid for the brick silo. You don't want rats or weasels spoiling your food.

Until then, you will need stacks of thick rugs (Doormats will do) underneath your portable cold frame vessel. And you will need to layer heavy Pendleton style woolen blankets on top. Put it in the corner of your home that recieves the least amount of sun. I would suggest placing it under the trailer, but you've constructed it out of things that any varmint can chew through on a warm, summer's night.

I really think you can make it, but you have to think tough, military style. Trapper/hunter style. You have to change your mindset.

 

[Skittlebisquit]

There is another important work on the topic called of course, "root cellaring" something or other. Its very labor intensive undertaking, to dig a proper cellar, but a hole in the ground is a good starting place. Sadly @Yeshuasdaughter is i think correct about material science with regard to the pot cooler thing. Pretty sure it has to be terracota or glazed to work properly.

The hole in the ground has issues too, usually bugs. I cant really remember all that well but we did that sort of thing back in. The early nineties. I still have one tie dyed t shirt put away sonewhere but no longer own sandals

Fun fact; the appliance from an rv is really ideal. Called a three way fridge, i think. They run on line power, 12 volt or stay cold by using propane, (the campers best ally) hugely expensive and hard to find but worthwhile to have, because you can idle the truck to run it or switch to tanked propane, that most campers have for cooking anyways.

Some other happy thoughts. It works well to freeze water in two litre bottles and use those in the cooler, not such a dangerous soggy mess. Also a seperate cooler that only has ice in it and stays shut with the frozen bottles in it will last a few days. Don't drink the cooler water unless you are going to die of thirst its too easy to get sick.

When do we get pictures anyways? Best of luck

 

[oregano]

The floor of my trailer home is actually thick steel. It was built as a "toy hauler" so the floor needed to be able to hold a lot of weight. I have insulation in the roof. But yeah, I was worried that it wouldn't work unless it was clay. The only clay pots I could find were little tiny ones, and I drove all over Medford. I had to compromise on materials, and I should have just said "forget this" and saved my money.

That book looks really interesting. I tried salting chicken breasts when I was still living in Sacramento, and they inevitably didn't take, and I wound up with rotted smelly chicken. I had been looking online for a source like that book, but couldn't find anything meaningful, and all the recommendations I found were long out of print (like the Firefox books detailing pre-industrial peasant life in the US Deep South). I will definitely buy that book when my credit card statement begins a new rotation.

As for now, I will simply put ice in the bottom of my crappy faux Igloo Playmate thingy. I really just wanted to chill butter and a few other things I get occasionally that need refrigeration.

As for mindset, it's a process, like any other big change.

 

[Yeshuasdaughter]

I read my replies back to myself. I'm sorry if they sound harsh or demeaning. I didn't mean it that way. I actually think your idea is clever. I was just trying to be helpful.

 

[Shevek]

There's nothing magic about clay. You need something that will hold the sand, or whatever else you use as a sponge, and let water through easily. A cotton bag would be fine. In the 30s, it was common to see cars on the highway with a canvas bag hanging off the front bumper, cooling the water inside. On my bike tour, I covered my water bottles with terry cloth. It needed frequent wetting, but so did I.

 

[Skittlebisquit]

So a couple more happy thoughts for you. Its foxfire, not fire fox and there is little of the content thay will help you. They are not out of print either. Readily available from the same outfit that made them years ago. There is a foxfire website, try looking for it on youtube you might be able to find a link.

I was thinking and i believe a concrete culvert section might work pretty well, at a fraction of the cost.

Im familiar with the Medford area, and there is a place that sells giant clay pots just right up the road in central point, its right by the big truckstop near the I-5 freeway.

The resource you should look to is likely called Mother Earth News. Im not sure if its still in print, they grew out of the VITA movement in the seventies. Also permaculture is likely to have some ideas, but the websites are all volunteer and kinda messy.

VITA was a college based outreach program that provided technical assistance to third world countries back in the day, and then the core group from there founded the magazine and they publushed alot of books too. It seems like refrigeration would be a core subject in helping poor people around the world, so there are likely solutions to it. Best of luck

 

[Shevek]

There are many ways to get natural cooling. Holes in the ground sometimes work. For my house, I use a fan at night and insulation in the day. That evaporative cooler will work far better if you are in a dry climate, but basically, you want a container in the shade, with a gentle breeze and a continuously wet surface. A rag and trough, or a drip would work, and full coverage is best.
J. Baldwin, tech editor for Whole Earth, called Mother Earth News the greatest collection of projects that almost work.

 

[WhitewaterWoman]

I think your effort here is a good one. It takes time and experimentation to work these things out.

Have you tried a small hole in the ground? Like a mini root cellar. We had one at the off-grid summer house. It was probably 18 inches to a side.

 

[Aspychata]

Also they have that spray foam out of a can, you may make the bottom of your metal lid tighter, by spraying foam to fit the pot. And you can spray the inside of the ring with foam and that should be a great snug fit. Obviously it's not food safe, so don't store food on it, or touching it

 

[WiffingWaffles]

I had a problem with my standard compressor operated mini fridge. During the summer when it gets hot I found that it cycles on and off repeatedly and quickly drains my house battery into the danger zone while doing so. So I managed to come across an invention called a "pot-in-pot fridge", "clay pot fridge", or "zeer" as it is known in the Middle East.
View attachment 104248

Sadly I couldn't find clay pots, so I decided to improvise. The outer pot of mine is made from wood pulp instead of clay. I figured wood pulp would be porous enough. The inner pot is plastic which is impermeable, in Africa the inner clay pot is frequently lined to keep the water out. This is before I wet the sand. I used two bags of standard sand from Lowe's branded "Sakrete".

View attachment 104249

This is a better look at the inside of my zeer. The rough edges around the inner pot are the result of me having to cut off a protruding "lip" which would have made wetting the sand difficult.

View attachment 104250


View attachment 104251

In Africa a wet cloth is used to cover the inner pot. Instead I used this weird aluminum disk that looks like it was intended to be a wall decoration. I found it at the Josephine County flea market.

Anyway as of right now I wet the sand but there hasn't been much evaporation yet due to the temperature in my home not being hot enough yet.

Certainly some ingenuity here.

 

[oregano]

I should note that @Yeshuasdaughter is right about the lid. When I get over my sinus infection I will buy a better lid, and I have one in mind-a plastic "dish" meant to be put underneath pots to catch water runoff. The "lip" of the dish will be able to rest snugly into the sand, creating a better top barrier.

 

[Shevek]

Also they have that spray foam out of a can, you may make the bottom of your metal lid tighter, by spraying foam to fit the pot. And you can spray the inside of the ring with foam and that should be a great snug fit. Obviously it's not food safe, so don't store food on it, or touching it

There are any number of alternatives to spray foam for creating a tight seal, and most of them are less problematic. Foam is for big gaps, not moving parts. If you don't have use for a whole can of foam, you'll probably waste the rest. I wouldn't worry about a seal, I'd just have a pile of wet rags on top that would automatically conform to the sides. There's no point in having a surface that isn't helping with the cooling when it is so marginal.

 

[Hypnalis]

The effect you're using (see the link in @Neonatal RRT's post) is due to the fact that when water evaporates, it sucks heat out of the environment, which reduces the temperature of whatever it's touching.

So you want to reduce the temperature of the inner container by evaporating water that's (as a whole) in contact with it.

The "pot in pot" system certainly works well, and there are simpler variations.
For example if you just want to cool water all you need is a big porous pot - there's "unlimited" water available in the pot to evaporate.

It's not clear if all parts of your system are set up for this. Certainly the metal lid in the photo isn't. But it could be cooled by putting damp/wet fabric on it (similar to the Coolgardie Safe" approach below).

Porosity of the outer container is important, because that's where the evaporation is happening. The sand seems to be mainly a "balanced" reservoir to handle the water storage and flow (which is critical for effect).
If the outer container you have doesn't let enough water through you'll lose a lot of efficiency.

I've used a (much) simpler variation of this (in 30+ degree Celsius temperatures):
https://en.wikipedia.org/wiki/Coolgardie_safe
They're cooled by keeping the burlap/hessian layer on the outside continuously damp, with the water flow handled via wicking. Unfortunately the connection from the water source to the burlap/hessian isn't shown in the pictures, but you can see the "overflow pan" on the bottom).
Note that they benefit from moving air. Air is a good insulator, so a flow of air at ambient temperature is much better than still, cooler air.

Getting water flow correctly balanced for these is probably tricky.

The "pot-in-pot" looks simpler, but just as efficient.
OTOH it was designed by a pot-maker - getting the porosity perfectly balanced would have been easy for him

 

[oregano]

I finally got a better lid:

This is a plastic "drain pan" intended to put under garden pots to prevent water spillage. I simply turned it upside down. The old lid went to the dump. I wet the sand this morning and will see how it does as the temp warms in here.