Charcoal Coolers, aka Charcoal Powered Refrigeration Systems, Are Used In Very Hot Countries, Where There Is No Electricity To Power Fridges. Evaporation Is Used To Cool Harvested Crops & Other Perishable Foodstuffs.
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Charcoal Coolers aka Charcoal Powered Refrigeration systems use a technology that is so simple it is hard to even use the word technology to describe it.
It uses the same principle that we use to cool ourselves. When hot humans, and many animals, sweat. Our sweat evaporated and that cools us. It works because the moisture on our skin uses the warmth of our skin to evaporate. That causes our skin to cool down a bit.
We harness the same physical process when we wet the floor of a greenhouse to cool it down.
Copying that simple physical process is what many people have to do to cool their harvested crops. Crops harvested in full sun are going to be very warm. They will soon deteriorate if not cooled. So rapid cooling becomes essential if they want to store the crop for more than a few hours.
This is where Charcoal Powered Refrigeration systems aka Charcoal Coolers come in. And they are vital as the biggest lost between seed sowing and eating is during the post harvest period.
What Is a Charcoal Cooler?
A charcoal cooler is basically a box where the walls are made of an open mesh into which charcoal is retained. It can be a small table top box or a huge walk in room, depending on your needs. The charcoal is made wet and takes warmth in the surrounding area to evaporate. this chills the inside of he box and it stays cool for hours, especially if shaded from the sun
This process works extremely well where the outside air is warm and very dry. It doesn’t work very well if the air is very humid and not very warm. So it is well suited to inland African countries, the Middle East and similar regions. It doesn’t work near the sea where the air is more humid. And it is not going to be very effective in the UK because we have a cool wet maritime climate.
How To Make A Charcoal Cooler
Material chosen for the box or room frame will depend on what is to hand. In some areas it will be wood whilst bigger coolers might be fabricated from metal. But essentially they construction is the same.
The cooler is made of open frame with the sides filled with charcoal. A means of adding water is needed as the charcoal needs to be continually kept moist. In some systems this means throwing a bucket of water over the box and in other cases a plumbed in piecework system is added.
Which ever is chosen the principle is the same. The warm, dry air passes through the moist charcoal and uses the heat energy from its surroundings to evaporate the water from the moist charcoal.
Charcoal is used as it has a porous structure and huge surface area, so evaporates water faster, hence making it cooler.
The beauty of the charcoal cooler is that it is usually possible to fabricate it from locally sourced materials, eg wood, charcoal, thatch etc. It works very well in low tech situations including rural areas that don’t have electricity.
Charcoal Cooler Systems For Other Uses
Charcoal coolers can be adapted to be used as an air conditioning system in hot countries. I’ve even seen it used for cooling wine! Indeed the basic principle is used in the Palestinian jarrah or clay pot.
A modification of the principle was employed to cool living areas in countries such as Spain. It came to the fore during the Arabic period, but is still employed to an extent today. And the Iranian Yakhchãls of Yazd employ a similar system by catching breezes that freeze water in ponds overnight, which is then stored in underground storage houses.
Other Charcoal Cooler and Evaporative Cooling Technologies
A wet cloth over a pot that is set in wet sand is perhaps the easiest small scale application of the cooling technologies that can be used. Some work on any country, but usually work better in warmer drier climates.
Indeed my grandfather and grandmother used wet sacking over milk churns to help keep milk cool before the refrigeration era. And it certainly helped prolong the shelf life of their farm produced milk and cream.
A review of various systems used in East African is given in the link Background Research section below. Some work better aha others.
Charcoal Coolers: Practical Applications In Rural Areas
Here are two Charcoal Cooler videos. One is village or field based and made of wood and the other in a tourism environment fabricated from metal. Both employ EXACTLY the same technology. I recommend watching both as they both offer specific insights from differing user perspectives.
Background Research: Evaporative Cooling Systems
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