Reply #1: There was another one at another site [View All]

whose name escapes me, but which will work in any climate as long as the sun is shining during the day.

One uses a non porous vessel, surrounds it with something porous, like chicken wire fencing, ubiquitous even in the third world, and fills the space with straw or any other light material, soaking that material down. Place the contraption in the sun and keep the outer material wet.

Although it's counterintuitive to keep a "cooler" in the sun, it was found that this kept the inner vessel at a constant 40-45 degrees, certainly cool enough to preserve things like milk. Although the temperature would rise during the night, it would still stay cooler than the ambient temperature, especially if the inner container itself provided a heat sink, meaning a clay container would work very well.

I love low tech stuff like this.