The charcoal fridges or coolers of yesteryear were very effective in the days before electricity to keep food cool. The fridge works by evaporative cooling. Water trickles through the charcoal, which is packed between mesh wire in a wooden frame. When a breeze blows over the moist charcoal, the evaporating water vapour draws heat away, reducing the temperature of the contents.
In the photo a Herero woman, wearing one of the older headdresses (’otjikaiva’), is putting some food in the fridge. The fridge is positioned in the shade of a eucalyptus tree with its legs placed in tins filled with either oil or water to keep termites and mice out.
I recently went to an auction where a charcoal cooler was sold for N$10 000, proving that in rural areas these energy-efficient low-tech devices are still being used and remain an effective method to keep food cold.