Refrigerator
Refrigerator

Pot-in-pot refrigerator

A pot-in-pot refrigerator, clay pot cooler or zeer is an evaporative cooling refrigeration device which does not use electricity. It uses a porous outer clay pot (lined with wet sand) containing an inner pot (which can be glazed to prevent penetration by the liquid) within which the food is placed. The evaporation of the outer liquid draws heat from the inner pot. The device can cool any substance, and requires only a flow of relatively dry air and a source of water.
Abba, who hails from a family of potmakers, tapped into the large unemployed local workforce and hired skilled pot makers to mass-produce the first batch of 5,000 Pot-in-Pots. He received the Rolex Award for Enterprise in 2001 and used his $75,000 award to make the invention available throughout Nigeria. Abba devised an educational campaign tailored to village life and the illiterate population featuring a video-recorded play by local actors to dramatise the benefits of the desert refrigerator. The pots sell at 40 US cents a pair.
The device cools as the water evaporates, allowing refrigeration in hot, dry climate. It must be placed in a dry, ventilated space for the water to evaporate effectively towards the outside. Evaporative coolers tend to perform poorly or not at all in climates with high ambient humidity, since the water is not able to evaporate well under these conditions.
Several key considerations are important for determining if an evaporative cooling device will provide effective cooling and storage. ECCs and clay pot coolers provide the most benefits when they are used in low humidity climates (less than 40% relative humidity), the temperature is relatively hot (maximum daily temperature greater than 25 ĄC), water is available to add to the device between one and three times per day, and the device can be located in a shady and well-ventilated area. If any of these key criteria cannot be met at the time when improved vegetable storage is needed, then ECCs or clay pot coolers may not provide sufficient benefits to justify their use.
ECCs or clay pot coolers provide benefits if post-harvest vegetable spoilage is the result of exposure to high temperatures, low humidity, animals, or insects. Some examples of vegetables that are particularly vulnerable to these conditions include eggplants, tomatoes, leafy greens, peppers, and okra. See the ±Conclusions and Additional Resourcesµ section of the Best Practices Guide for a more complete list of vegetables that can benefit from storage in an evaporative cooling device. Non- electric evaporative cooling devices „ such as ECCs and clay pot coolers „ are not suitable for items that require sustained temperatures below 20 ĄC (medicine, meat, and dairy products) or foods that require a low humidity environment (onions, coffee, garlic, millet, and other grains).