Evaporative cooling, a low-tech refrigeration technique, can help keep food fresher for longer, using just water and the sun, and Evaptainers is bringing it back.
Here in most of the developed world, refrigeration isn’t a big deal. We have huge electric refrigerators in our homes, and when we head out off the grid, we can easily stop and pick up bags of cheap ice to keep our food cool. Heck, we can even buy a cooler with a built-in blender and waterproof Bluetooth speaker and its own battery bank.
http://www.treehugger.com/clean-technology/evaptainers-electricity-free-refrigeration.html