Mohammed Bah Abba, Mobah Rural Horizons
An open-source evaporative cooling storage container for households.
Zeer Pot is a simple fridge made of local materials consisting of one earthenware pot set inside another.
Hot and dry climates worldwide
Janata Cooler, charcoal cooler, Evaporative cooling chambers, Naya Cellar Storage, Solar Powered Refrigerators.
Goal 2: End hunger, achieve food security and improved nutrition and promote sustainable agriculture
Those who could benefit from improved vegetable storage and longer shelf life may include vegetable producers, wholesalers, retailers, and household consumers, particularly off-grid, rural communities dependent on subsistence farming. Produce spoilage causes disease and loss of income for needy farmers and venders who are forced to ‘rush sell’ most agricultural products, even though they are well aware of the negative impact flooding the market has on their profits. Even in towns and cities where erratic power supply is available, most of the urban poor cannot afford refrigerators.
Most groups providing Zeer Refrigeration depend on individual and local manufacturers. Mobah Rural Horizons reported producing on average 30,000 Zeer Pots as of 2005.
Mobah Rural Horizons is the main distributor. Implementation of evaporative cooling refrigeration has been demonstrated throughout Nigeria. Majority of production located in Kano, Jigawa, Borno, Yobe, Sokoto, Zamfara, Kebbi and Katsina States, all in the northern region of Nigeria.
Unknown, but a production capacity of 30,000/year is claimed
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.
Detailed schematics available here. See image below.
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 designs are open-source. If a pot is broken, local clay materials should be used to repair or replace the unit.
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.
If operated in hot and dry climates (greater than 25 °C and less than 40% humidity) they can be expected to provide a storage environment with humidity greater than 80% and temperature at least 8 °C lower than the maximum daily ambient temperature.
Some specific performance targets include:
• Minimum internal temperature of 15ºC
• Storage volume for 12kg of fruit and vegetables
• Consumes 1.5 – 2.5 L water/day
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.
Technologies related to creating clean fuel sources for when firing the pots, sourcing clay and those that ensure that the community has a ready source of water for evaporative cooling (e.g. hand-powered well digging rig).
Verploegen, E., Sanogo, O., Chagomoka, T. (2018). Evaluation of Low-Cost Vegetable Cooling and Storage Technologies in Mali. Copyright © Massachusetts Institute of Technology (Accessed on 30 Oct 2018).
Odesola, I. F., Onyebuchi, O., A review of porous evaporative cooling for the preservation of fruits and vegetables. The Pacific Journal of Science and Technology. 2009 Nov, 10(2):935-941.
Basediya, A. I., Samuel, D. V. K., Veera, V., Evaporative cooling system for storage of fruits and vegetables – a review. Journal of Food Science and Technology. 2013 Jun, 50(3):429-442.
Anyanwu, E. E., Design and measured performance of a porous evaporative cooler for preservation of fruits and vegetables. Energy Conversion and Management. 2004 Aug, 45(13-14):2187-2195.
Performance evaluation should include measurements of the internal temperature as a function of external humidity, external temperature, and the frequency and amount of water added. Additionally, measurement of the average number of days before produce spoils (shelf life) when using the evaporative cooling chamber, compared to alternative storage methods can be used to evaluate performance.
Awards received include 2000 Rolex Awards to Mohammed Bah Abba, 2006 Tech Museum of Innovation Award, 2007 Santa Clara Global Social Benefit Incubator
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