Mohammed Bah Abba is from northern Nigerian. He won the 2001 Rolex Awards for Enterprise for his invention of a simple cooling system that can help preserve food in rural areas where there is no electricity. Eggplants stay fresh for 27 days, instead of the usual three. Tomatoes and peppers last for up to three weeks. The Pot-in-Pot system works by putting a smaller clay pot inside a larger one. The two are separated by constantly moist sand. Evaporation causes a cooling affect in the inner pot.

At a recent SEED workshop in Malaysia we decided to try this for ourselves.  We also replicated the experiment later with different pots.

Tools and Materials

• Two clay pots, one larger than the other
• Sand
• Water
• Cloth to cover the pots
• Clay, cork or other material to plug holes in the pots if they have them
• Thermometer
• GoGo Board with temperature sensors (optional)

What To Do

1. The smaller pot should fit inside the larger one with a space of one to three centimeters. If the pots have holes in the bottoms, as flower pots usually do, plug them with clay, cork or some other suitable substance.  This prevents the sand from running out of the larger pot and keeps water from flowing into the inner pot.

2.Put a small amount of sand into the larger pot. The layer should be thick enough so that when you put the small pot inside the larger one, the tops of the two pots are at the same level.

3. Fill the space between the pots with sand.

4. Pour water on the sand until it can absorb no more

5. Dampen the cloth and cover the inner pot.

6. Use a thermometer to check the temperature inside and outside the pot every few minutes and keep track of your results in a chart like the one below. We used a digital thermometer, but an alcohol one will do as well.

7. If you have a GoGo Board, click here to find out how to use it with the Pot-in-Pot Refrigerator.