A group of students from the University of Calgary have developed a simple evaporative refrigerator. It was inspired by the way that animals and insects keep themselves cool.
Warm air from the surroundings is funneled into a pipe network to evaporate water moisture, which carries heat away from the air. Once the air is cooled, it moves into the chamber where the food is kept. The only power requirement to bring the temperature down to 4C is to power a small fan to move this cool air, which can be done with a very small battery setup powered by a small solar panel. The refrigerator still works with no electricity but works best with the fan.
To learn more, go here: http://challenge.biomimicry.org/en/custom/gallery/view/2576