This short video demonstrates how simple it is to make a very basic evaporative cooler for produce.
You can watch the video at www.youtube.com
Obtain two large clay or terracotta pots. One pot must be smaller than the other pot. Check that the smaller pot fits inside the larger and that there is a space around it of at least one centimeter, up to three centimeters. Fill the base of the larger pot with coarse sand to about 2.5 cm/1 inch deep, and only fill to a height that will ensure the smaller pot sits even in height with the larger pot. Place the small clay pot into the large pot. Arrange its base flat on top of the lower layer of sand. Fill all around the small pot with sand gap at the top. Pour cold water over the sand. Do this until the sand is completely soaked and unable to take any more water. as you pour, do so gradually in order to give the water time to soak into the terracotta. Take a COTTON CLOTH, dip into the water and place it over the top of the the inner pot so that it covers it completely.
Allow the inner pot to cool down. If you have a thermometer, you can use this, otherwise test the temperature with your hands. Keep the pot-in-pot refrigerator in a dry, ventilated space for the water to evaporate effectively towards the outside. Place fruits or vegetables inside for storage. Keep checking regularly for the dampness of the sand. Pour in more water as it becomes drier to keep it well moistened. Usually this will need to be done twice a day. You can add food or drinks to the natural refrigerator as well.
This technology requires a dry environment and is not suited for everywhere. To be an “appropriate technology” there needs to take into account the local conditions and factors.
This is true and should have been pointed out in the video.