Emily Cummins is a 21 year old student/inventor who has come up with a clever and simple way of using the sun to cool things like perishable food and temperature sensitive medications. The concept works with no electricity and can be built with materials like cardboard, sand, and recycled metal.

It takes advantage of conduction and convection to create an evaporative cooling effect. You place what you want to keep cold in the interior chamber and either some sand, wool, or soil in the outer chamber that gets saturated with water. The sun warms the water soaked material...the water evaporates, reducing the temperature of the inner area to 43 degrees Fahrenheit for days at a time. To recharge you only need to add more water once your material gets dry.