Solar-powered fridge invented by British student helps poverty-stricken Africans

This is a well known technology. The classic example uses 2 clay pot's, sand, and water.

http://www.seed.slb.com/en/scictr/lab/pot_refrigerator/index...

PS: Clay pot fr get's google to popup "Clay pot Frige" with 88k responses.

Spoiler: It's not solar powered, theres no carnot heat engine or solar cells involved. It's evaporative.