Low tech evaporative cooler for produce - charcoal walled cold store

This popped up on my feed and I think is well worth sharing.

The basic idea is to fill the wall void of a chicken wire structure with chunks of char and drip feed water into the top of the wall. The cross breeze allows for evaporative cooling to bring the temperature of the produce quickly down to a lower temperature.
=AZWK8lNiaRK48FNFVF0ARCyHQY--L-sVGsBWxLOp9TMbT6UjHBpMjvIMRfCKW5xiQWGKXW45JgNZhVGuDSrOrd1FqEF9h3ixGSyL5WK9-ZO3W3DcVTuNJzNGFDYvOg-mLumggzf4WWXib2NzvmkXMETUU_Zjsi7qIL2gc2Z79WQjWxYVbUT8bRAJiSI1fjvpn_U&__tn__=%2CO%2CP-R]Facebook discussion of the idea

How to Make a Local Cooler or Fridge using Charcoal
I got over 100 dms and WhatsApp messages since I posted about this few days ago so I have to post this information for us to make use of
Step 1 Identify a suitable location for your fridge. It does not matter whether it is under the sunshine or a shade. What is most important is that you choose a location where you do not have to shift the fridge from place to place – this is a permanent structure.
Step 2 Determine the size of you fridge that you want to construct.
Step 3 Erect a double wire mesh boundary with at least a sizeable width within.
Step 4 Pack large charcoal particles in between while filling the gaps with smaller charcoal particles. Avoid use of charcoal dust because it will pollute your food.
Step 5 For the base, use mud; and for the roof, use dry grass. Do not use wire mesh or charcoal for the base or roof construction.
Step 6 Do not forget to put a door to keep away animals and thieves.
Step 7 Also, you have to be mindful that you have to pour water on this charcoal to maintain the cool temperatures within. You can either do this manually or automatically using constructed structures similar to those used in Drip Irrigation. The pouring of water can be done continuously or at a time depending on weather condition outside. The higher the temperatures, the more the water required.
An interesting concept is was one used by farmers in western Uganda. Their fridges are much smaller both in width, length and height. These women farmers place a bucket full of water on top of the “fridge”; hanging from the bucket onto the charcoal edges are deep thick wicks (like those of a lantern). The logic is that the wicks suck water and drip it on the charcoal, thereby cooling it.
Charcoal is used as it is a good coolant. Wet charcoal does not allow easy passage of heat thus resulting into low temperature inside. Also, use of water on the charcoal is to minimize charcoal dust. Charcoal is made of wood which by nature do not transmit heat easily. Also, charcoal has pore spaces which absorb and store water inside, this reduces heat passing from outside.
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I can think of many applications for this idea. Also a few issues!

1. In areas with a lot of heat, but low humidity, I could see this as a way to keep people cool without electricity, so long as they had sufficient water. As mentioned, one would want to use large bits of charcoal and wash off any dust to protect people's lungs.
2. I do think putting it under shade and where there tends to be a breeze would improve the effect, but that's strictly a hypothesis and would need testing.
3. Where I live, I think rats would be a major problem - using the right kind of mesh, possibly layered, could fix that.

It would have been lovely if they had given some indication of the temperature drop they had managed. I have seen the system of a small clay pot inside a larger one with sand in between the pots. Wet the sand, and you get the same simple cooling effect. However, it's hard to get fridge-sized clay pots, although I have a vague recollection of a company in India building this system with quite large, purpose made clay boxes. This charcoal system would be "build in place" and much lighter, although how long the wire would last before rusting out would be a question also.