In hot climates, fruits and vegetables begin to rot in a few days. Refrigeration gives you a head start in the race against spoilage, but what if you don't have electricity, much less a fridge? A Nigerian teacher, Mohammed Bah Abba, won an award for a simple invention designed to keep food cool without electricity or expensive parts.
Here's how it works: you put fruit, veggies, or other perishable food into a clay pot that's nestled inside another pot. On top of the food, you lay a damp cloth, and between the two pots, there's a layer of wet sand. As hot air dries the outer pot, it draws water from the sand. Water continuously evaporates from the nestled pots, carrying away heat energy and thereby cooling the inside. The principle is similar to the way the evaporation of sweat cools the body. As long as you keep the sand and cloth damp, the evaporation and cooling continue.
The simplicity of this invention makes it practical for poor people in hot climates. Inside the clay pot cooler, fruits and veggies last several weeks, instead of a few days. According to inventor Abba, the cooler is already having an impact on people's lives. Since it was introduced in villages in semi-arid northern Nigeria, more girls have enrolled in school. What's the connection? Produce from family farm plots lasts much longer than before, meaning that families don't need to send girls out every day to sell produce, but can send them to school instead.