Zeer Pot

The underlying principle behind the Zeer Pot is that as water evaporates it will remove heat from it’s surroundings. To take advantage of the evaporative cooling effect, take two earthen pots of the same shape but different sizes, put one within the other, fill the space between the them with sand and pour water into the same cavity (or other substrate e.g. coconut fiber) to make the sand wet. The result is that when you place food items into the inner pot, cover with a lid or damp cloth you can keep the temperature up to 10-15 degrees cooler than the external environment. Store the pot-in-pot refrigerator in a dry, well-ventilated space; and let the laws of thermodynamics do the rest. As the moisture in the sand evaporates, it draws heat away from the inner pot, cooling its contents. The only maintenance required is the addition of more water, around twice a day.

Zeer pots designs are open-source. Technical support can be provided by the local manufacturer (ex. local artisan or potter).

Detailed information regarding construction and use can be found in MIT D-Lab’s Evaporative Cooling Best Practices Guide.

Zeer pots last until contaminated or damaged at which point they can be used for cooking bowls or returned to soil and can be used to make new clay based products.

A report by MIT D-Lab and World Vegetation Center presents extensive testing comparing various evaporative cooling technologies, including the Zeer Pot. This study determined that evaporative cooling technologies could improve vegetable shelf life by providing a stable environment with low temperature and high humidity while also protecting food from insects.

A report by Practical Action evaluated different materials and shapes for Zeer Pot designs. The report claims that the shelf life of vegetables can last up to five times longer when they are stored in a Zeer Pot.

The only risks associated with evaporative cooling is possible contamination and spoiling of foods; however, this is already a threat to vegetables and the Zeer Pot serves to reduce rate of decay and frequency of contamination. It must be understood though that use of evaporative cooling refrigerators may not be effective in all conditions and environments and this is especially important if it is used to store vaccines and other medicines. Users may require some education about maintenance and ideal storage for them to be effective.