An electricity-free terracotta fridge

Patrick Whitefield
Thursday, 1st July 2010

Chill your veg and dairy products without drawing a single watt...

A fridge uses around a third of the electricity in the average kitchen. Although it doesn’t use much at a time it’s always on. Most things don’t actually need refrigerating, but milk and its substitutes do, and purchased vegetables last much longer when chilled.

This simple design for a power-free fridge is much used in Africa. It works on the principle that wherever water evaporates there’s a local drop in temperature.

Take two big terracotta plant pots, one with around 8cm wider diameter than the other. Place the smaller inside the larger and fill the space in between them with sand, so that the tops of the pots are level. Wet the sand and keep it wet. A lid is needed. Until we can find a suitable one with a handle we use an old dinner plate. A tray below to catch surplus water is useful, and an old saucer placed upside down in the bottom makes sure that the things in the bottom of the storage space don’t accidentally get wet.

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Theresa Wood |
Sat, 05/02/2011 - 17:08

Such a simple idea and so easy to make. This would be useful for camping rather than buying an expensive and bulky gas fridge.

Aranya |
Wed, 04/05/2011 - 10:20

It's a great design that works well in hotter climes, though the ones I've seen to date in Britain (Landmatters for instance) suggests that we might not have enough heat (ironically) for there to be sufficient evaporation to cool this well. I'd be interested to hear more about the effectiveness of this design in our cool temperate climates through the year (since July 2010?) & in different sites (in the sun for increased evaporation or in the shade for less heat?).

bobirving |
Sun, 08/05/2011 - 12:21

I tried one for a while back in 2006 - like Aranya said, it was not hot enough to cause evaporation to make it work. Also I have a suspicion that industrially-made flower pots on sale in garden centres are too dense for water to evaporate through them and this would be a bit of a killer too.

ptpermaculture |
Thu, 12/05/2011 - 13:57

@bobirving - its not usually the density so much as the surface - if the surface (which is usually almost burnished) is sanded back, most pots work fine.

Happily, this is a great technology for hot Western Australia.

Harry
Peactree Permaculture
http://www.ptpc.com.au

Angel Cereceda |
Thu, 29/09/2011 - 18:36

Thank you very much for sharing this simple solution for fridging. I was trying to use my small studio an maximize the permaculture use and production of it. Little by little and thanks by you and other sources Im getting better ideas.

Im glad the world and earth can enjoy the benefits of your publications.

Jean-Francois Talbot |
Wed, 26/10/2011 - 00:29

In cooler climate, keep it in the shade but put in a wind drift.

Nicola Thomas |
Wed, 02/11/2011 - 18:01

Does the lid need to fit over the two pots or just the centre pot?

Michael McDonnough |
Mon, 07/05/2012 - 08:34

This gives me some interesting construction ideas for a kind of siding for brick and cinder block homes. I envision a kind of modular panel system with composite hangers and standoffs and terracotta panels. The retrofit system will have sand poured between the terracotta panels and the cinder block or brick exterior wall. I think a 2 inch standoff would be enough for this to work. The install kit would include a soaker hose system or a kind of drip irrigation system at the top of the panels and moisture sensors at the bottom of the panels. These would control the flow of water into the sand core. There would be filters that would allow some water flow through the panel system so that it would not become moldy. I think this system would lower the cost of cooling a house in a hot climate by about 70% if my crude calculations are correct. It would be very cheap to operate and not that expensive to build out with new or retrofit construction. The limitation is that it would require a very water safe skin on the house. I think brick or cinder block or concrete walls will work best. Of course the siding would be complemented by a terracotta/sand/water roof cooling system of the same type.

Berkana |
Thu, 31/07/2014 - 01:10

I recently prepared an instructable for how to build a zeer pot optimized for the developed world, along with an explanation of its operating principles, limitations, and risks. For your consideration:

www.instructables.com/id/A-Practical-Zeer-Pot-evaporative-cooler-non-electr/

Theodora Cochrane |
Sat, 02/08/2014 - 10:19

Initally cool the interior using an already frozen bottle water, milk or any other frozen package. This will chill the inner pot. Limit the time you open lid. Works well in any conditions. No terracotta pots? Use an ordinary cheap cool box.

Emma Austin-Jones |
Wed, 13/08/2014 - 22:18

I tried it, the weather was nice and hot but evaporation was quite poor. The other problem was that I stood the pots outside (to try and improve evaporation), they had a firmly attached lid and looked okay. They did become quite cool and so I put my fridge type food inside. The next morning it was covered in slugs, inside.
I don't know how they got in, but my food was ruined. I would not recommend this method of keeping food cool in any outdoor place, for that reason.
Indoors was too hot for food to be kept out of a cool place and too cool for evaporation to work.
I have now returned to keeping a fridge plugged in at Parents house (fortunately in same village) and using ice packs and cool box at my home, with just a few items here at any time.
I purchased a mini-fridge too for £50 from Argos, it's suitable for use in a car apparently and even has a cigarette lighter attachment for power. I have a small solar panel at home, so tried plugging the fridge (with an adaptor) into my inverter. It shut my power down instantly.
As yet I have found no better solution than the cool box.
without mains electricity the green deal scheme does not assist people, so I have to save in advance to buy my solar panels. with limited funds it's not easy. But living with no landlord and fully owning our converted Sawmill makes it worth while. We will succeed eventually in keeping our food fresh for longer.

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