Garden, Camping & Festival No Electricity Fridge!

It's getting hotter every day and your electricity bills are not environmentally friendly.

This credit crunching fridge is a sure way to be sure your beverages will stay chilled in the hottest of heats.  It's much greener than your average electrical fridge and will work anywhere where there isn't a lot of humidity.

The pot in pot refrigerator or Zeer was made by Professor Mohammed Bah Abba, though there's evidence it was in use in early Egypt.  It works on the principle of evaporative cooling.

You will need:

Two terracotta pots.  One has to fit inside the other with an inch or so between all the way round.
Sand.
Water.
A towel/cloth big enough to go over it
5-10 minutes, maximum!

Step 1: First Pot

Add about 1-2" of sand into the bottom of the big pot.  Don't worry too much about the holes at the bottom, the sand packs down and forms a plug.

Firm down the sand before putting your second pot in.

Step 2: Filling the Pot With Sand

Put the 2nd pot into the first, and start packing the sand round the edge.  Layer it and firm it as you go - this ensures the pot stays straight.  Don't worry too much as it'll self correct in later stages.

The last image shows me stopping filling a little way down from both rims - the pots are pretty much flush with each other.

Step 3: Watering

First use a jug or hose to gently wet the sand.  The first time you wet it, the sand may sink.  This isn't too much of a problem.  You're trying to water log the sand as much as possible.

The terracotta pot is porous, so it wicks the moisture into the external pot.

The sun and wind evaporate the water which causes heat loss - effectively cooling the inside.

To cover, use an old towel and wet this as well.  You could put one end of the towel in a reservoir (a bowl of water) and it would continue to wick water up onto the top and evaporate causing more of a temperature drop.

Step 4: Fin

Within about an hour, the cans had cooled from warm to quite chilled, enough that when removed, they had condensation on them.  Not bad for a particularly varied conditions of Britain.