The Pot-in-Pot is a very low tech, no electricity, no compressor, refrigerator. As the name implies it is made from two pots, one inside the other, and the gap filled with wet sand. The evaporation of water from the middle layer is the source of the cooling. Invented by Mohammed Bah Abba of Nigeria.
dead link: http://hinterlands.cc/index.php?showtopic=30