Low Tech Refrigeration Solutions – The Coolgardie Safe & Zeer Pot
Ever wondered how you’d keep your food fresh if your fridge were to suddenly pack it in? What if your power bill became so ridiculously high, you could only afford to use your fridge as a worm-farm? In a world of energy-descent, these are the kind of things we might have to start thinking about.
Luckily, in case of falling-oil or toppling-economy, these two nice little pieces of appropriate technology cover most of your refrigeration needs. They are the Coolgardie Safe and the Zeer Pot.
Both work on the simple principle of evaporative cooling. If you’ve ever draped a wet towel over yourself on a stinking hot day, you’ll know how well evaporation can work. It’s like having your own personal air-conditioner. The Coolgardie Safe and Zeer Pot both work in pretty much the same way and all you need to power them is a light breeze!
The Coolgardie Safe is a good old-fashioned piece of Aussie technology invented during the first gold-rush in the town of the same name, Coolgardie in Western Australia, where the climate is extremely harsh and arid. Without any electricity in those days, food would have gone off incredibly quickly without refrigeration. For a desert town without any power, the Coolgardie safe must have been a blessing. All that is needed to make one is:
-A timber or metal frame covered in wire mesh (so the flies can’t get in)
-jacked up on legs submerged in water (so the ants can’t climb up)
-with a few pieces of hessian draped over the sides
– and a tray of water sitting on the roof with the tops of the hessian hanging into it.
It’s pretty cheap and easy to find all of these as recycled materials, and very simple to build. The idea is that the water in the top tray will be leached down into the hessian (kind of like a wick leaching the oil up in a lamp) and evaporate, leaving the contents of the box a lot cooler. Any excess water can just drain into the bottom to be reused later, and act as a moat to deter ants in the meantime.
No power, no CFCs, just a light breeze in a shady spot on the verandah is all you need for this brilliant little contraption.
The Zeer Pot is a Nigerian invention and has had an incredible impact on the livelihood of small food growers and families all over Africa who can’t afford powered refrigeration.
It works in a slightly different way to the Coolgardie Safe and is a lot simpler to build, depending on your resources. All it consists of is two terracotta pots – a smaller one inside of a larger one – packed in between with wet sand. A damp cloth or hessian can be draped over the top as well for extra insulation. Again, the same principal is at work, with the water in the sand evaporating and keeping the terracotta cool. People using them have reported that a tomato can be stored for up to 20 days in a Zeer Pot whereas before they were lucky to last 2 days in the heat.
This is an excellent example of a very low-impact piece of technology (the only materials needed to build it is the earth you’re standing on!) making use of the tiniest amount of renewable wind energy to preserve and store food for people in a harsh climate with no alternatives. Also, being made of solid fired clay the Zeer Pot has a much longer lifespan than a Coolgardie Safe and is something that could be used for generations.
As far as appropriate technology goes, how much more appropriate can you get? So next time you want to keep your beers cool out on the block where you’ve run out of fuel for the gennie and you haven’t hooked up the solar yet, try scrounging up the materials to give one of these a go instead!