With the sudden heat wave we have hit over the last few days I thought I would try out a new cooling device that is used in Africa to cool vegetables. It is simple to make and effective at cooling in even the hottest countries.
Simply take two clay pots, one 12in and one a few inches smaller, about 9 inches. Put a few cm of sand in the bottom of the bigger one. Put the smaller pot on the sand ensuring that it does not touch at any point the outer pot. Then fill the gap with sand all the way to the top. Once complete add water to the sand until the outer pot I full. Take a cloth, wet it and put it on the top ensuring it covers both pots. A cheap fridge made from gardening bits lying around and a dishcloth.
I put a couple of cans in for the kids and left it to cool. Checking the dishcloth and wetting it when it started to dry. When they came around, about 1600, the cans were certainly nice and cool. A success.
It doesn’t need electricity but it does need another precious resource; water. It is the evaporating water that cools the inside of the pot.
Water seems to be a very popular way of cooling items down. This way looks like it will conserve water too and it doesn’t rely on the water being cold to begin with. Water from a UK tap tends to be cold as it is in a tank for a while to start. So if you have a water meter in your home consider trying one of these as an no power alternative cooler.
I do have a couple of questions though. Does the external temperature have any impact on the final temperature inside the pot. Since evaporation is the method of cooling does it need to be above a certain temperature to work? What about the pot sizes, I assume the more sand the better it is at cooling. Is this right? I’ll try this again over winter and tomorrow if the temperature is up again I will record the temperatures. Something I should have done today.
Update: Here is a link to the design of Zeer pots that gives the dimensions you should be looking at for the 2 pots, the gap for the sand etc.
I believe the answers to your questions are as follows:
> Does the external temperature have any impact on
> the final temperature inside the pot.
Yes. This cooler is likely to reduce by a few degrees so if it’s hot externally it remains still pretty warm in the inner pot.
> Since evaporation is the method of cooling does
> it need to be above a certain temperature to work?
Above freezing, but if it’s that cold you probably don’t care.
The Humidity needs to be low(ish) but thats not too much of an issue in the UK
> What about the pot sizes, I assume the more
> sand the better it is at cooling. Is this right?
More sand will result in more/longer lasting cooling but also has more mass itself to cool so it’s not uniformly available for your inner pot contents.
Updated after JDs comments on the forum.
I don’t quite get what’s with the sand. Is it that the sand prevents heat getting to the pots?
Water from a UK tap tends to be cold as it is in a tank for a while to start.
It works well in the bath and gives you two days with cooked meat and longer with yoghurt, for example.
From the Zeer Pot site mentioned above.