Off-grid Refrigeration With The Zeer Pot

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Remember the video that made the rounds a while back on how you could heat your home using just a flower pot and a tea light? I have yet to find anyone who actually got that to work, so I was a little skeptical when I heard about making a refrigerator from a couple pots and some sand. It was still intriguing though; if it worked it would be a great way to store medications that need to be kept cool (such as insulin) during a grid-down situation, as well as extending the life of fruits and veggies.

The zeer pot is a container made of two different sized clay pots with a layer of wet sand in between. The pot cools as the water evaporates, which gives you non-electric refrigeration in hot, dry climates. It was invented in rural Nigeria in the 1990s, and sells (over there) for only about 40 cents, giving families that grow their own food the ability to preserve it.

An evaporative cooler like this works as water evaporates, in much the same way that sweating cools you down. The sweat takes the heat from your body as it evaporates and turns to a gas.

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So let’s get building! We purchased almost all the items for the zeer pot at our local Home Depot. You’ll need:

  • 2 unglazed terracotta clay flower pots of different sizes – The small one should be big enough to hold whatever you want to keep cold, and the large one should be big enough to hold the small one with about 2″ – 3″ around the edges.
  • Sand – We used regular play sand
  • Duct tape
  • A lid that will fit the smaller pot (optional)

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To start, use a couple strips of duct tape to cover the holes in each of the pots. Add a layer of sand to the larger pot, smoothing it out as you go. You need enough in the bottom of the large pot so that you can set the small pot inside it and have the lips of the two pots be on the same level. In fact, you should really have the inner pot just a tiny bit higher, maybe 1/8″ if you can.

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Go ahead and center the small pot inside the larger one, and begin adding sand to the space in between.

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Add it evenly around the edges; if you add too much on one side at once you may wind up shifting the inner pot to one side. Continue filling the space until you’ve reached the upper edges, and pack the sand down as much as you can.

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Keep filling and packing until the sand is tight, and then smooth it out.

You may have had some sand spill into the inside pot while you were filling; go ahead and remove it however you want – by hand, a wet rag, vacuum, etc.

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Now it’s time to add the water. You’ll want to pour the water slowly onto the sand while constantly moving your water container – you don’t want to flood just one area. The sand may compact some more as your pour; just add a little more to the holes. Keep filling until the sand is soaked, but don’t fill it so much that water is standing.

If your inner pot is lower than the outer, then you may wind up with some sand and water running down inside it as you fill. It’s no big deal, just wipe it out with a wet rag when you’re done.

Once you’re done adding water, you’re ready to add whatever you want to cool. You may want to wait a little bit, however; if your pots were sitting out in the sun then they’re going to start off pretty hot. No sense baking whatever you put in there, let them cool down a bit first.

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Move your zeer pot to it’s permanent home – it should be in a shaded location with good air circulation. Go ahead and cover the top – if you found a lid that would fit, put it on and cover that with a damp piece of cotton cloth.

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If you don’t have a lid, just use the damp cloth. A solid lid plus the cloth will keep it cooler though.

After a while you should see the outer pot starting to darken – that’s the water soaking out of the sand and evaporating. If only the top half of the pot is turning dark, that’s a sign you need to add more water. You’ll need to water the sand at least twice a day, usually in the morning and the evening. If you’re able to elevate the entire pot on a wire rack, that will give it a little bit more cooling ability, since the bottom of the pot would be exposed to airflow.

So how did it work for us? It definitely got cooler, but not by much. We tested it when the weather was in the low 90s, and the inside of the pot cooled down to about the mid-70s, or a 15 degree difference. But to be honest, I wasn’t expecting much – the zeer pot works best in dry conditions with low humidity, and here in Texas we were at about 50% humidity with very little wind. There’s a reason they don’t sell evaporative coolers here! With very low humidity you could probably get it down into the 50s or 60s.

For us, where we live, this wouldn’t be a practical way of storing medications like insulin during the summer if we had no other refrigeration, at least not long term – for over 30 days you want to keep it under about 46 degrees; this would help keep insulin currently being used at “room temperature” for less than a month. It would also extend the life of fruits and veggies for us. In a more arid (dry) climate, you’d have better results.

  • Mike the Gardener says:

    Bill that is wild! How cool does it get? Have you tested the temperature? Just curious.

    • Bill Osuch says:

      With the high humidity we have here in Texas, we were only able to get it down to about the mid-70s. We probably could have gotten another 5 degrees cooler if we’d had more of a breeze, and WAY cooler if we didn’t have the humidity (we’re at 72% today).

  • Sri says:

    This is a standard practice for us in India. Most people do not have refrigerators, and some simply don’t want that chilly water.

    You could try the same for cooling water too.

    Get a large earthen pot, and fill it with water. Leave it in shade. After a couple hours you’ll notice the water is pretty cool.

  • Leah says:

    We live next to the ocean, so our humidity level also makes clay pot evaporation unviable. What does still work, though, is cloth evaporators. Put the veg in a box (not a cardboard box – something that won’t collapse when moist), place a pan of water on top, and drape a cloth over as if putting a tablecloth on a table. The water will wick down from the pan and evaporate from the cloth, cooling what’s stored inside.
    Having the box turned on it’s side gives you access without moving the water pan. I’ve seen a three-legged stool used instead of a box for even easier access – it worked really well until they stored food that was attractive to squirrels, haha.

  • Cherston says:

    You could get colder temps if you used ice water, but that would require electricity which defeats the purpose, still it’s an option where available. A clay pot buried in the dirt in a shady spot might provide cooler water for use in your above ground Zeer pot. Still, it would certainly keep things cooler than leaving them out in the sun unless you were drying them.

  • Cheryl says:

    I tried that tealight thing, a modified version though. Used several tea lights in a metal baking dish, with another metal baking dish above the tealights. It actually did take the chill out of the room, wasn’t blazing warm but there was a difference. One tealight wouldn’t have made much difference.

  • Mugs says:

    I knew a elderly lady that never had a refrigerator, she had a wooden box fitted in a north window.she would put her food in the box an place a wet burlap bag over the food.I live in north central texsd her food kep around 56 to 70 degres

    • Cynthia says:

      Howdy! Would that work down in SouthCentral Texas? I don’t think I could fit a box into the window but could definitely place it on the back porch which faces north. Or perhaps even putting it in the north-facing sunroom which is quit shaded by a large tree. Thanks!

      • Bill Osuch says:

        It just depends on what level of humidity you have. Here in Dallas it’s high enough that we can only get the interior down into the mid-70s; if you have lower humidity you can get it cooler.

        • Emilie McVey says:

          I grew up in Dallas in the 50s and 60s and evaporative coolers were the standard air conditioners. We were quite comfortable with the mid 70s temps; didn’t have to worry about wearing a sweater bc the buildings were too cold!

  • jean marie edel says:

    Buenos dias y muchas gracias por tantos consejos utiles , yo vivo en venezuela y como desendiente de europeo siempre me atrajeron todo tipo de consejos , recetas , etc. , que sirvieran para almacenar y / o guardar alimentos , lo unico se puede decir que he logrado a sido la conservacion de granos , pastas y otros productos secos por el sistema de adicion de sal en bolsas tipo click , por cada medio kilo de granos dos cucharadas de sopa de sal mas o menos , se mantienen bien , limpias y sin ningun tipo de contaminacion , aunque con el tiempo un poco mas duras y de vez en cuando les dio vuelta , como el problema aqui son las hormigas y gorgojos hay que revisar con cierta frecuencia pero he logrado mantenerlo en buenas condiciones y despues de años consumirlas , gracias , att. jean marie edel

    • Jennifer Osuch says:

      Hi Jean,
      That’s interesting that you use salt to keep away ants and weevils. Do you notice any difference in taste when you eat your dry goods?

  • Jeff Harris says:

    My grandma used a water box.Fresh cold water in one side,from a very cold flowing well,into shelves lined with tin ,that drained
    out h2defferyrwerwwater

  • Jeff Harris says:

    That last part really got screwed up.Different depth shelf for different foods/containers.mason jars worked well.Vented wooden doors

  • Jeff Harris says:

    I love artesian wells.Northern Mi. Still has many,and nice cold springs too.

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