Zeer Pot help the rural poor in a cost-effective ( desert refrigerator )

Northern Nigeria is an impoverished region where people in rural communities eke out a living from subsistence farming. With no electricity, and therefore no refrigeration, perishable foods spoil within days. Such spoilage causes disease and loss of income for needy farmers, who are forced to sell their produce daily.
SOLUTION ???
I would like to introduce you the Zeer Pot (pot-in-pots)

“ The pot-in-pot to help the rural poor in a cost-effective, participatory and sustainable way.”

The pot-in-pot consists of two earthenware pots of different diameters, one placed inside the other. The space between the two pots is filled with wet sand that is kept constantly moist, thereby keeping both pots damp. Fruit, vegetables and other items such as soft drinks are put in the smaller inner pot, which is covered with a damp cloth. The phenomenon that occurs is based on a simple principle of physics: the water contained in the sand between the two pots evaporates towards the outer surface of the larger pot where the drier outside air is circulating. By virtue of the laws of thermodynamics, the evaporation process automatically causes a drop in temperature of several degrees, cooling the inner container, destroying harmful micro-organisms and preserving the perishable foods inside.