Homemade Pot-in-Pot Refrigerator "Off Grid Fridge" cools air up to 40F (evaporative cooler/chiller)

pot-in-pot refrigerators (zeer pot coolers) will cool the air up to 40 degrees. no power needed. uses only 2 or 3 clay pots, sand, water and a towel. will cool the inner chamber up to 40 degrees (relative to the outside air). uses no electricity. will keep food fresh longer. note: i tested it when it was 120 degrees out. if you use it when the temperature is 80F-90F it will get down to 40F to 50F.