This solar refrigerator, invented by Emily Cummins, is a brilliantly simple solution for keeping food cool in a hot, dry environment. It’s basically a metal cylinder surrounded by wet material, surrounded by a mesh sleeve to hold it all together.
Between the outer cylinder and the inner cylinder is an open compartment where any medium capable of holding water can be placed. The medium would usually be sand, wool or soil and is packed into the gap and then water is added.
When the fridge is placed in a warm environment, the sun’s energy causes the water to evaporate from the medium. As the water/medium mix is held against the inner cylinder, heat is removed in the form of energy. Due to heat transfer the inner cylinder becomes cooler. The reduced temperature and completely dry environment of the inner chamber makes it perfect for the storage of perishables as it will allow items to be kept fresh for longer.
It’s encouraging to think that important, real-world problems are still out there to be solved with a bit of ingenuity and the sort of materials that are taking up space in the corner of your garage.