 Pot-in-Pot Cooling ExperimentDescription:. Mohammed Bah Abba, a Nigerian native, has 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 simply by putting a smaller clay pot inside a larger one. The two are separated by a constantly moist sand. Evaporation causes a cooling affect in the inner pot. This activity will allow students to construct this cooling system. Some simple experiments will then be conducted to evaluate its functionality. Description Amount Clay pots large and small 1 each sand water to keep the sand moist cloth to cover the pot a gogoboard with a temperature sensor Mini Workshop (~2 hours) Overview of the project and describe the experiment (15 min) Hands-on ( ~60-90 min) Construction of the system takes about 20 minutes Students then leave the pot for 40 minutes or longer with a gogoboard inside to measure the temperature. Conclusion and discussion (15 min)
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Welcome to E4C.Sign Into Your Account Forgot Password? Remember Me Don't have an account? Sign Up Home » Articles » Clay Pot Coolers: Keep Produce Fresh Without Electricity  Clay Pot Coolers: Keep Produce Fresh Without ElectricityIntroducing the Guide to Assembling, Using, and Maintaining Clay Pot Coolers, the result of a collaboration by MIT D-Lab, the World Vegetable Center (WVC), and Institut d'Economie Rurale (IER). This is how clay pot coolers can keep produce fresh without electricity, why it matters, and tips on how to make one.  Djiguiba Boureima (left) and Kadidia Nienta demonstrate the use of a clay pot cooler at a training session at the Nyleni Cooperative Society in Mopti, Mali. Photo couretesy of Djiguiba Boureima Fruits and vegetables can spoil quickly in arid climates, leading to the loss of food, time, and money. Roughly 50% of fruits and vegetables harvested in Sub-Saharan Africa are lost between harvest and reaching the consumer, owed in part to poor storage in regions where electricity is scarce or expensive. There is an inexpensive solution, however, and it’s relatively simple: a clay pot cooler. Clay pot coolers can increase the shelf life of many fruits and vegetables, including tomatoes, leafy greens, eggplant, and okra, among others. These coolers take advantage of the evaporative-cooling effect. It works in the same way as perspiration, which evaporates to cool the human body. The evaporation of water from the outer surface of the clay pot removes heat and cools the fruits and vegetables inside. The inside of the pots can be as much as 10°C below the ambient temperature, with increased humidity to better preserve produce. This simple device can improve food security and provide monetary and labor efficiencies for people in areas without access to other kinds of refrigeration. For example, the shelf life of leafy greens can be extended from approximately one day when left out at room temperature, to over four days when stored in a clay pot cooler, reducing the risk of food loss and allowing families to travel to a market twice a week instead of every day. Simple to buildClay pot coolers can be built several ways. A typical design is a smaller pot nested inside a larger cylindrical pot. Or a variation can be a pot placed in a plastic basin. The sizes of the pots can be selected based on what is most practical for a given user. Sand is placed between the inner pot and outer vessel, and a cloth or sack is placed over the cooler as a cover. Clay pot coolers can cost (USD) $5—$40, depending on their size and the cost of local materials. Regardless of the size and design, the best practices for using clay pot coolers include storing them in a shady and well-ventilated area, keeping the sand between the inner and outer pots wet, covering the cooler with a wet cloth or sack, and regularly cleaning the inside of the cooler. The research underwaySince 2016, MIT D-Lab , the World Vegetable Center (WVC), and Institut d’Economie Rurale (IER) have collaborated to evaluate the suitability of clay pot coolers for household use in Mali, how the devices perform, how people use the devices, and the most effective approaches for disseminating the technology. While most people in Mali are familiar with the concept of using clay pots to keep water cool, research found that very few people were aware that two pots, some sand, and a covering could be assembled into a storage device that improves the shelf life of fruits and vegetables. As part of an initial research study to evaluate the performance of clay pot coolers and understand user behavior, the team distributed assembled clay pot coolers to households with basic instructions for using the coolers to store their fruits and vegetables. Based on survey results, participants who used clay pot coolers reported reductions in food lost to spoilage, resulting in financial savings and increased availability of fruits and vegetables for their households. However, there was a lack of awareness about where the devices could be purchased or how to make the coolers themselves. Guidebook: How to build, use and maintain a clay pot coolerIn an effort to bridge this gap, the team has developed “ A Guide to Assembling, Using, and Maintaining Clay Pot Coolers ” to disseminate information about this simple, low-cost technology with great potential to improve nutrition, and, in some cases, livelihoods. The guide is now available in English, Hindi, Swahili, French, Spanish, Bambara, Hausa and Zarma. Each version covers the following:
Training program in MaliThe team is using this guide as the centerpiece of an ongoing training program funded by the Innovation, Technology, & Research Hub at USAID and the Islamic Development Bank in the Mopti region of Mali. The approach we are taking in Mali is to start by sharing this information with agricultural extension agents and clay pot producers through in-depth training-of-trainers (ToT) sessions. The ToT participants will go on to conduct more focused trainings with larger groups of fruit and vegetable sellers, pot makers, farmers, and other community members. About the AuthorsEric Verploegen joined MIT D-Lab in 2014 to expand D-Lab’s research efforts in the areas of food water and energy. His two main areas of work are related to evaporative cooling for vegetable preservation and D-Lab’s Energy Needs Assessment Toolkit, supporting organizations to identify the most pressing energy needs in the communities where they work. Melissa Mangino is Senior Program Associate at MIT D-Lab where she provides administrative support for D-Lab academics and the Scale Ups program. In her previous life, Melissa was a high school social studies teacher and has many years of experience in K-12 education advocacy, community outreach, and engagement. Share This Article Comments from the Community Very useful innovative way to cool vegetables Leave a ReplyYou must be logged in to post a comment. Suggested Articles Sanergy Fresh Life Toilet and Sanergy Fresh Life Waste Management...The Sanergy Fresh Life Toilet is a urine diverting dry toilet housed within a prefabricated concrete structure. The floor has a squat plate and two holes, one for liquid waste... Read Full Article Join a global community of changemakers.
How to Make a Pot in a Pot RefrigeratorLast Updated: June 23, 2024 Approved wikiHow is a “wiki,” similar to Wikipedia, which means that many of our articles are co-written by multiple authors. To create this article, 28 people, some anonymous, worked to edit and improve it over time. wikiHow marks an article as reader-approved once it receives enough positive feedback. This article has 12 testimonials from our readers, earning it our reader-approved status. This article has been viewed 422,518 times. Learn more... In a community or situation without electricity, storage of food long-term can be tricky. One simple solution is to build your own pot-in-pot fridge, using basic pots, sand and water. An idea revived by Mohammed Bah Abba, this refrigerator is now being used by many farmers in warm climates who need to preserve their food for a longer time and keep the insects away. Keeping the sand moist all the time enables evaporation to cool the produce kept inside the inner pot. This enables the storage of freshly grown vegetables to last much longer than usual in a hot climate. It is also great for using at a picnic or outdoor meal where there is no electricity outside but food or drinks need to be kept cool. Here is how to make your own. 
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Power-free system harnesses evaporation to keep items coolPress contact :, media download.  *Terms of Use:Images for download on the MIT News office website are made available to non-commercial entities, press and the general public under a Creative Commons Attribution Non-Commercial No Derivatives license . You may not alter the images provided, other than to crop them to size. A credit line must be used when reproducing images; if one is not provided below, credit the images to "MIT."  Previous image Next image Camels have evolved a seemingly counterintuitive approach to keeping cool while conserving water in a scorching desert environment: They have a thick coat of insulating fur. Applying essentially the same approach, researchers at MIT have now developed a system that could help keep things like pharmaceuticals or fresh produce cool in hot environments, without the need for a power supply. Most people wouldn’t think of wearing a camel-hair coat on a hot summer’s day, but in fact many desert-dwelling people do tend to wear heavy outer garments, for essentially the same reason. It turns out that a camel’s coat, or a person’s clothing, can help to reduce loss of moisture while at the same time allowing enough sweat evaporation to provide a cooling effect. Tests have showed that a shaved camel loses 50 percent more moisture than an unshaved one, under identical conditions, the researchers say. The new system developed by MIT engineers uses a two-layer material to achieve a similar effect. The material’s bottom layer, substituting for sweat glands, consists of hydrogel, a gelatin-like substance that consists mostly of water, contained in a sponge-like matrix from which the water can easily evaporate. This is then covered with an upper layer of aerogel, playing the part of fur by keeping out the external heat while allowing the vapor to pass through. Hydrogels are already used for some cooling applications, but field tests and detailed analysis have shown that this new two-layer material, less than a half-inch thick, can provide cooling of more than 7 degrees Celsius for five times longer than the hydrogel alone — more than eight days versus less than two. The findings are being reported today in a paper in the journal Joule , by MIT postdoc Zhengmao Lu, graduate students Elise Strobach and Ningxin Chen, Research Scientist Nicola Ferralis and Professor Jeffrey Grossman, head of the Department of Materials Science and Engineering. The system, the researchers say, could be used for food packaging to preserve freshness and open up greater distribution options for farmers to sell their perishable crops. It could also allow medicines such as vaccines to be kept safely as they are delivered to remote locations. In addition to providing cooling, the passive system, powered purely by heat, can reduce the variations in temperature that the goods experience, eliminating spikes that can accelerate spoilage. Ferralis explains that such packaging materials could provide constant protection of perishable foods or drugs all the way from the farm or factory, through the distribution chain, and all the way to the consumer’s home. In contrast, existing systems that rely on refrigerated trucks or storage facilities may leave gaps where temperature spikes can happen during loading and unloading. “What happens in just a couple of hours can be very detrimental to some perishable foods,” he says. The basic raw materials involved in the two-layer system are inexpensive — the aerogel is made of silica, which is essentially beach sand, cheap and abundant. But the processing equipment for making the aerogel is large and expensive, so that aspect will require further development in order to scale up the system for useful applications. But at least one startup company is already working on developing such large-scale processing to use the material to make thermally insulating windows. The basic principle of using the evaporation of water to provide a cooling effect has been used for centuries in one form or another, including the use of double-pot systems for food preservation. These use two clay pots, one inside the other, with a layer of wet sand in between. Water evaporates from the sand out through the outer pot, leaving the inner pot cooler. But the idea of combining such evaporative cooling with an insulating layer, as camels and some other desert animals do, has not really been applied to human-designed cooling systems before. For applications such as food packaging, the transparency of the hydrogel and aerogel materials is important, allowing the condition of the food to be clearly seen through the package. But for other applications such as pharmaceuticals or space cooling, an opaque insulating layer could be used instead, providing even more options for the design of materials for specific uses, says Lu, who was the paper’s lead author. The hydrogel material is composed of 97 percent water, which gradually evaporates away. In the experimental setup, it took 200 hours for a 5-millimeter layer of hydrogel, covered with 5 millimeters of aerogel, to lose all its moisture, compared to 40 hours for the bare hydrogel. The two-layered material’s cooling level was slightly less — a reduction of 7 degrees Celsius (about 12.6 degrees Fahrenheit) versus 8 C (14.4 F) — but the effect was much longer-lasting. Once the moisture is gone from the hydrogel, the material can then be recharged with water so the cycle can begin again. Especially in developing countries where access to electricity is often limited, Lu says, such materials could be of great benefit. “Because this passive cooling approach does not rely on electricity at all, this gives you a good pathway for storage and distribution of those perishable products in general,” he says. Share this news article on:Press mentions, popular mechanics. Popular Mechanics reporter Kyro Mitchell spotlights how MIT researchers have created a new material, inspired by camel fur, that could be used to help insulate food and medical supplies. “Field tests on the new material show that it can provide cooling of more than seven degrees Celsius,” writes Mitchell. “It can also maintain that low temperature for five times longer than using hydrogel alone.” New ScientistMIT researchers have created a new material that mimics camel fur and could be used to help keep food and medical supplies cool without electricity, reports Layal Liverpool for New Scientist . “We achieve evaporation and insulation at the same time, extending the cooling period significantly,” explains Prof. Jeffrey Grossman. Smithsonian MagazineSmithsonian reporter Corryn Wetzel spotlights how MIT researchers have developed a new technology inspired by camel fur that could be used to keep food and medical supplies chilled. The researchers hope the new system could be applied to “lots of areas that require passive cooling—meaning no external energy needs to power the process. Possible applications include insulating food storage, medical supplies and buildings.” Previous item Next item Related Links
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Reducing Fruit and Vegetable Losses with Clay Pot Coolers: An Ancient Technology for the Current Moment Share this content: For tens of millions of households, a lack of effective postharvest storage options leads to food loss and waste, and that means a reduced supply of the nutritious fruits and vegetables essential to a healthy diet. Now, what if I told you that there is a simple, traditional technology that can dramatically increase the shelf life of nutritious fruits and vegetables in hot and dry regions, but is being massively underutilized? And what if I told you that it doesn’t even require electricity to operate?  Relying on the evaporation of water to create a cool and humid environment, clay pot coolers are easy to assemble and can be made using materials that are typically available in communities in arid regions. My venture, CoolVeg , is working with governments, nongovernmental organizations (NGOs) and local businesses to raise awareness and promote the usage of this technology. Often, people ask me, “Why should we promote these ancient technologies when the real goal should be to electrify as many communities as possible to enable modern refrigeration?” My answer is that I don’t see this as an either/or choice, clay pot coolers or electric refrigeration. Below, I have outlined three reasons why clay pot coolers should be promoted and adopted alongside efforts to increase electrification and access to modern cooling technologies. 1) Clay pot coolers can be rapidly deployed to help right nowExtending the electric grid to rural communities can take years, even decades. Clay pot coolers can help people in off-grid communities right now. Sustainable Development Goal (SDG) 7 was established in 2015 to address the urgent need to bring modern energy to the over 1 billion people without electricity access. However, even with billions of dollars of investment, 670 million people are projected to still be without electricity access in 2030, 85% of whom will be in Africa. Many of these people would benefit greatly from the improved fruit and vegetable storage that clay pot coolers can deliver. A training and awareness campaign to disseminate clay pot coolers could reach tens of millions of people in hot and dry regions within five years, well before electrification can be reasonably expected to reach many communities. Once the concept of clay pot coolers becomes well-known among early adopters in a community, it can further spread without the need for additional external resources. 2) Clay pot coolers are more cost-effective than electric refrigerators for fruit and vegetable storageClay pot coolers will never replace refrigerators for those looking to store items like dairy, meat or medicines that require temperatures below 10 degrees Celsius, or products that require a low-humidity environment. However, for fruits and vegetables that greatly benefit from cool and humid storage environments, clay pot coolers offer a compelling, cost-effective solution. By relying on inexpensive, locally available materials, clay pot coolers avoid the need for complex refrigeration equipment that requires electricity. Even if electrification becomes widespread in a community, households would still need to purchase a refrigeration unit. A modern electric refrigerator currently costs between $40 and $200 for a device with similar storage capacity to a clay pot cooler (10 to 70 liters), while the materials for a clay pot cooler only cost between $3 and $15 in many regions. Requiring only 1 to 3 liters of water per day, clay pot coolers can store produce for over a week while using less than 1% of the water required to grow the produce being stored. In comparison, a small electric refrigerator can cost between $20 and $80 per year to operate, which is comparable to one month’s income for many people in the Sahel. 3) Clay pot coolers are easy to make, easy to understand and affordable — and can empower communitiesUnlike electric refrigerators, clay pot coolers do not require complex machinery or centralized manufacturing and distribution. Because they can be made with locally available materials and because guidance on how to use and make clay pot coolers is publicly available, this technology is not controlled by any person or institution. This makes them highly adaptable to different cultural and geographical contexts. By drawing on traditional practices and local craftsmanship, communities can be empowered with practical skills and knowledge. What is next?What needs to happen for tens of millions of households to adopt clay pot coolers and benefit from reduced food loss and increased access to nutritious fruits and vegetables? The answer is a matter of communication and awareness. Many households across the Sahel and other arid regions already use clay pots to keep water cool. Creating a clay pot cooler for fruit and vegetable storage only requires a few additional steps. In-person training programs in Mali have shown to be effective in stimulating the adoption, with 73% using clay pot coolers after attending the training. Positive impacts reported by users include:
By using a cascade training model, large numbers of people can be reached quickly and cost-effectively.  Radio and digital tools can be used to supplement in-person training sessions and word-of-mouth to further raise awareness and communicate key concepts. For example, CoolVeg and dooiy have developed a WhatsApp chatbot as a cost-effective way of sharing clay pot cooler training content in text, audio, images and videos. Investment in the dissemination of clay pot coolers will allow this simple technology to quickly reach households facing food loss and lack of access to nutritious fruits and vegetables. This technology is more cost-effective than electric refrigerators for storing many types of produce and can be deployed in a decentralized manner while leveraging local knowledge. If you are interested in learning more or exploring partnerships to disseminate clay pot coolers, please contact Eric Verploegen at [email protected] . Related ResourcesCoolVeg clay pot cooler homepage Infographic about clay pot coolers and impacts on users View more posts from our Food Loss and Waste Theme Month 2023More on this topic from agrilinks, reducing household food waste and improving nutrition with simple technologies, increasing access to fresh fruit and vegetables with forced-air evaporative cooling chamber, drought-induced loss of livestock in horn of africa will impact communities “for years to come”, announcing the 2023 feed the future-agrilinks photo contest winners.
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The coolest way to keep food cold without electricityBy Ilana E. Strauss Updated on Mar 21, 2023 5:29 PM EDT 3 minute read Believe it or not, you don’t need a refrigerator to keep food cold. Just gather some ceramic pots, sand, and water, and you’ve got a portable, non-electric DIY mini-fridge with a time-tested design. After all, people were preserving food for thousands of years before you had to keep that leftover takeout from stinking up your college dorm. In some parts of the world, this clay pot cooler is called a zeer, and its sustainable, inexpensive design is far from new. People in the Middle East and Africa have long used similar contraptions to keep food from spoiling in hot, dry climates. “It’s just amazing,” says Paul Smith Lomas, CEO of Practical Action , a UK charity that helps people in Latin America, East and Southern Africa, and South Asia find solutions to daily challenges, including food preservation. “We like to find ingenious ideas that can help people fix their own problems.” How to make a refrigerator without electricity1. Get two unglazed ceramic pots—one that will fit inside the other—plus some sand and water. 2. Fill the bottom of the larger pot with a couple inches of sand. 3. Put the smaller pot inside the larger one. 4. Fill the space between the pots with sand. 5. Pour water into the sand. 6. Cover the pots with a ceramic lid or wet cloth. Done. You’re ready to store food inside your homemade cooler. Just remember to add water to the sand every day, because zeer pots use evaporation to cool food. How this DIY refrigerator worksAs water evaporates through the clay, it releases energy into the air and cools the space inside the pot. It’s like splashing water on your face on a hot day ; the water evaporates off your skin, cooling it in the process. Refrigerator coolant actually works in a similar way, using evaporation to draw heat out of the fridge itself. That’s why the back of your Frigidaire is so warm. These pot-in-pot coolers are useful in places that don’t have power grids, but they’re also great for people who don’t have fridges, need more space, or want to cut their energy bills. On that last point: they’re also much better for the environment since they don’t require any sort of fuel, much less oil or gas. [Related: The scientifically best way to pack a cooler ] It’s best to keep zeer pots in the shade, since the sun will warm them up, but you can also put them in a breezy area—wind makes the water evaporate faster, which cools the food more quickly. They’re most effective in arid climates, because water evaporates more when there’s less of it in the air. So, these pots will likely work better in Arizona than Florida. They work well in Sudan, where Practical Action has introduced the zeer pot to many in need of refrigeration. Food security is a huge problem in the Northeast African country, and the DIY refrigerators can make food last 10 times longer, Lomas says. “Someone told me they once made ice out of a zeer pot,” he says, laughing. He didn’t believe the guy, but he does find the pots incredibly effective. According to Practical Action’s website, one woman, Hawa Abbas, used to watch half her okra, tomato, and carrot crops spoil. After discovering zeer pots, that changed. “They keep our vegetables fresh for three to four weeks, depending on the type of crop. They are very good in a hot climate such as ours where fruit and vegetables get spoiled in one day,” she told Practical Action. “Since I learned how to make zeer pots, our life has been so much better.” This story has been updated. It was originally published on May 21, 2019. Latest in ProjectsTeacher spends 1800 hours building the hovercraft of his childhood dreams teacher spends 1800 hours building the hovercraft of his childhood dreams. By Keith Wagstaff Should you plant a clover lawn? The pros and cons. Should you plant a clover lawn? The pros and cons.By Debbie Wolfe A Practical Zeer Pot (evaporative Cooler / Non-electrical Refrigerator) Introduction: A Practical Zeer Pot (evaporative Cooler / Non-electrical Refrigerator) A zeer pot is an evaporative cooler used in rural Africa and the Middle East to keep vegetables fresh. They consist of two terra cotta pots, one nested inside the other, with the gap between them filled with wet sand. The sand serves as a thermal mass that helps keep the pot cold once it has cooled down, and acts as a wick to spread the moisture up the walls of the pot. When placed in a shaded, breezy location, the evaporation of water off the outer surface chills the pot. If you have a good breeze, or a fan powered by a solar panel blowing the pot, the pot can get quite cold. Imagine that chill you get when you step out of a pool when the wind is blowing. Now imagine that wet wind chill going on all day. That's what the pot feels with a constant breeze. Unless the air is very dry and the pot is exposed to a constant breeze, they generally do not become as cold as a refrigerator, but they will keep vegetables fresh for a couple of weeks. If you do have cool dry air and a constant stiff breeze, the interior of a zeer pot can chill down to around 40˚F. Think of it as an open-cycle refrigerator. Conventional refrigerators evaporate a refrigerant in a closed circuit to absorb heat from their interiors, then compress the refrigerant vapor in the coils in back to condense it and to expel heat. The zeer pot simply uses water as its refrigerant, and leaves the condensation to nature. Zeer pots were re-discovered and popularized in the early 2000s by the Nigerian teacher Mohammed Bah Abba. By manufacturing and mass distributing zeer pots to the poor, he was able to bring refrigeration to tens of thousands of impoverished farmers and home makers, enabling them to extend the usable life of their produce from days to weeks . For his efforts Bah Abba was awarded the Rolex Award for bringing life-changing technology to people in need. In the under-developed parts of Africa and the Middle East, zeer pots use custom made pots prepared by local potters . Here in the developed world, we need to settle for pre-made pots from the hardware store. There are some drawbacks, but also some advantages afforded by these limitations, as you will see. What makes this zeer pot practical? There are other zeer pot instructables out there, but this one is optimized for practicality. If the capacity is too small, the cooling capacity too low, or if it an eyesore or is annoying to use nobody would want to use it. This zeer pot uses a large glass pot lid, has an interior basket divider, and sits on a rolling cart. It even has a layer of decorative pebbles over the sand to make it look pretty. The terra cotta pot legs hold the pot off the rolling cart with enough clearance to let the bottom surface contribute to evaporation; this adds about 10%-15% more evaporative surface. The inner pot is bolted down so that it doesn't float up when you charge the pot with water. Nearly everything I used in this project was purchased at a hardware store, and it can be made in a few hours, plus a day to let the sealants cure. I will be building a zeer pot array for A Place for Sustainable Living in Oakland (California) based on this design. The goal is to use an array of zeer pots to displace the use of at least one of their refrigerators. The design shown here is the outcome of my experimentation with making zeer pots for them. (Be sure to read all the notes to all of the photos. Many important details are listed there.) Parts list with prices Prices are rounded to the nearest dollar. (I must admit, this is by no means the inexpensive original African zeer pot, which cost $2 to make. You're going to spend well over a hundred dollars on this design. This one is for people are intentionally going out of their way to go off grid or to pursue sustainable options.) Items are mostly from Orchard Supply Hardware (Berkeley, CA). The pot lid was from Kukje market (Daly City, CA), and the sandwich basket was from Web Restaurant Store .
Note: won't work as well in high humidity If you live in a hot and humid area, the zeer pot probably won't work well; high humidity results in much less evaporative cooling. (However, a friend of mine who used a zeer pot to cool water in a humid part of Africa tells me that even with the humidity, it worked surprisingly well, so this is not definitive.) Note: direct sunlight will cancel out all cooling effects On the day I was doing the zeer pot seminar at the Place for Sustainable Living, we accidentally left one in direct sunlight. The amount of heat imparted by the sun totally overwhelmed the evaporative cooling effect. The cooling is supposed to come strictly from wind-induced evaporation, not from evaporation due to sun exposure. Sun exposure causes evaporation by imparting heat; wind exposure causes evaporation by lifting away water molecules, which carries away heat proportional to the heat it takes to evaporate the quantity of water carried away. If you do build a zeer pot, make sure you keep it in the shade for best effect. Note: outer pot must be unglazed clay or terra cotta At the hardware store, I saw a lot of fake terra cotta pots made of orange plastic. These are not usable for the outer pot of the zeer pot; the zeer pot cools by wind evaporating water that has been wicked through the outer surface. Plastic fake terra cotta is not porous, and will not work as an evaporative surface. Glazed terra cotta pots also don't work for the outer pot. The inner pot doesn't necessarily have to be made of unglazed terra cotta, but the outer pot must be unglazed because glazed pots won't wick moisture to the outer surface for evaporation. Note: many medium sized zeer pots work better than one giant zeer pot The ability of a zeer pot to cool its content depends on the surface area to volume ratio. As you make the zeer pot larger, the volume will increases proportional to the cube of the linear dimensions, but the surface area only increases proportional to the square of the linear dimensions. Because the volume increases much faster than the surface area, one huge zeer pot will actually perform much worse than several smaller zeer pots. The size of the zeer pot in this instructable is about as large as you can make them while having a practical rate of cooling. You can always make them smaller; making them larger is not likely to give you reasonable performance. If you are serious about going off-grid, you would do better to make several zeer pots of this size than to make one huge zeer pot. Step 1: Prepare the Central Bolt, Bolt Shut the Hole on the Outer Pot (Be sure to view all of the photos above; much of the explanation is contained in the photo notes.) In this practical zeer pot design, we have a limitation that I turned into an opportunity. The terra cotta pots that we have access to have holes in the bottom for drainage; these need to be plugged so sand and water don't drain out the outer pot, nor into the inner pot. I have found that it is insufficient to merely plug the holes; zeer pots also have another annoying problem where the inner pot will try to float up as you wet the sand in the space between the pots. In order to solve both of these problems, I use a 4" long 1/2 diameter bolt, and a bunch of nuts and broad washers and a bit of silicone sealant to seal the holes in both pots. The secondary benefit of this is that the inner pot can't float up because it is bolted to the same bolt that seals the outer pot. This way, you can be generous with charging the sand with water without worrying about the inner pot floating up. The first thing you need to do is to put a pair of broad washers on your bolt, put some silicone sealant on the threads, and tighten them down with a nut. Then, seal around the nut with more sealant. While the sealant is curing, use your sanding block to remove the clay burr around the hole of both pots. Be sure to sand off the burr both on the inside and the outside of the hole until the washer can lay flat against the pot. If you do not remove the burr, water will leak past the hole. Now, it is time to seal the hole in the outer pot. This works best with an assistant helping you. Lay the pot on its side, and put some silicone sealant on the clay around the hole both the inside and outside the pot; insert the shank of the bolt through the hole, and have your assistant thread on a washer and bolt it down from the other side. Wipe up any sealant that squeezes out around the washer. Then smear sealant around the nut and bolt to prevent water from leaking out around the threads. Step 2: Prepare the Washer on the Bolt to Seal the Inner Pot Turn the outer pot upright, and rest it on pot feet on your rolling pot cart. Put three pot feet into the pot near the bolt, and thread another washer onto the bolt such that when you put your washer down on the nut, the top level of the washer is just a tiny bit higher than the top of the pot feet. The washer must not have its upper surface lower than the upper surface of the pot feet; if it does, the inner pot will rest on the pot feet, and won't have its hole pinched tightly by washers from above and below. Add a little bit of sand to the outer pot; you want just enough to fill the places that will be hard to get to once the inner pot is in place. Be sure there isn't sand on the washer or pot feet; the sand may prevent the inner pot from sitting flat on the washer, and will prevent a good seal. If you decide to dampen the sand to make it more easily shapable, do so BEFORE you put it into the pot, and add water using a spray bottle only until the sand has the consistency of brown sugar. Any more, and the sand sticks to everything. Once the washer is in place, seal the threads with silicone, and thread on the nut that holds the washer in place. Put some silicone on the washer so that it will seal against the bottom of the inner pot, and rest the inner pot on that washer. Then put some sealant around the hole on the inside, add another washer to the bolt, and pinch it down with a nut. Seal the threads and the gap around the nut with silicone, and wipe up any silicone that squishes out around the washer. (Unfortunately, I don't have a picture of the last step where we tightened down another washer to pinch down the inner pot.) Variation: inner pot nested an inch lower In the photos above, I show the pot legs used as spacers positioned upright. You can also position them laying on their sides so that the inner pot sits about an inch lower. (If you do this, be sure to use sand paper or a file to remove the clay burrs from the side edges of the pot feet, or else the inner pot won't sit properly on these spacers. Also, you can use a shorter bolt; I don't know precisely how much shorter, but probably about an inch shorter.) You can see from some of the photos in the other steps that the inner pot's upper lip sits about an inch above the later of decorative rocks. While this affords a little bit more evaporative surface, it also means the inner pot's upper edge is not surrounded by as much thermal mass as it could. Having the inner pot nested a little bit deeper also means you can use a couple of quarts less sand, which will also make the completed zeer pot just a bit lighter. The next zeer pot I build will be this variation. Note: Be sure the pot feet are close to the central bolt I made a couple of mistakes in the pictures which show damp sand in the pot. Firstly, I put too much water in, and the sand started to stick to everything, which was a real hassle. Secondly, the pot feet were too spread out, and I had to move them back toward the central bolt. The reason you must have the pot feet close to the center is that the bottom of the inner pot actually has a raised perimeter. (This slightly raised perimeter can be seen in the photo from the prior step which shows me sanding the burr away from the hole.) If the pot feet end up contacting the raised perimeter, the part of the pot right around the hole won't touch the washer that you matched to the height of the pot feet, and you won't get a good seal around the hole of the inner pot. Step 3: Sand Down the Inner Pot If Pot Lid Won't Fit When you buy your inner pot, you should bring your pot lid to find one that fits well. However, please be aware that terra cotta is an imperfect material, and the pots will not likely be perfectly round. Because of this, you should use some sand paper to sand the inner pot's upper lip to make the lid fit. Try to get the lid to fit as well as you can, and note where it contacts the terra cotta. Mark those areas either with pencil or perhaps with chalk. Use the sand paper to sand away the contacting areas, and keep doing this until the lid fits right. In our case, it took several hours of very careful checking and sanding to get the two zeer pots to fit their lids well. Wipe up or vacuum up all the terra cotta dust before continuing. Step 4: Optional, for the Sheet Metal Blackbelts: Add a Thermometer. If you really want your zeer pot to have that extra nice touch, get a piece of sheet metal, and cut out a bracket to mount your refrigerator thermometer. You'll need a bot and nut that fits the vent hole of your lid to lock down one end of the bracket; the other end will thread through the same screw that holds the handle onto the pot lid. With the thermometer mounted on the lid, you can tell the temperature at a glance. Since the warmest air in the zeer pot rises to the top, you'll know that the temperature inside will be cooler than what the thermometer indicates. Step 5: Fill the Gap With Sand, Add Water, and Top With Decorative Rocks Firstly, adjust the four pot feet on your rolling platform at this time so that they are evenly distributed. Once the sand is in and the pot is wet, the zeer pot will be very heavy. Use a funnel to add sand. You will likely end up using all 50 pounds of sand. Add more if needed; we ended up adding a couple of quarts of extra sand you want about 1/2 inch of a gutter going all the way around, which you will fill with decorative rocks after you wet it all down. Before adding water, let all the sealant on the bolts and washers cure for at least 3 hours, or overnight for best results. Add water one quart at a time; the sand will settle, and you will probably need to add a bit more sand when the pot is saturated. When the sand is saturated, you can add the decorative rocks, and perhaps a bit more water. The rocks are not just for looks; when you re-wet your pot, the rocks dissipate the water that you're pouring into the gutter so that the stream of water doesn't cut a pit into the sand. Once the pots have their sand saturated with water, the pot will darken from water wicking through the terra cotta. Put the pot in a breezy area for the initial cool down. A breeze is absolutely necessary; it simply will not cool down enough without it. A decorative trim is one of those things that sets this zeer pot apart; people are more inclined to use beautiful things. A zeer pot that looks really nice is not going to be something you're embarrassed to use. Note: if you are using beach sand, wash the sand to remove salt If you decide to use beach sand to fill your zeer pot, be sure you wash the sand in a couple of changes of water to purge it of salt. Salt will contribute to the mineral build up on the terra cotta that lessens the cooling effectiveness of the zeer pot. Note: water will likely pool in the inner pot after saturation Do not be alarmed if some water pools up inside your inner pot during the initial cool-down after you saturate it with water. Use a sponge to soak it up and wring the sponge over the decorative pebbles to return the water to the sand. If water accumulates inside quickly, you probably have a leak, which is a whole different problem. If your inner pot is cracked, you will need to replace it. If your washers and nuts are not well sealed, you will need to let the whole thing dry out, and re-seal the entire thing, leaving at least a few hours for the sealant to cure. Step 6: Add a Handle to the Inner Basket Get your eyelet bolt, and a pair of nuts and washers, and bolt it onto the sandwich basket as close to the middle as you can. The basket should be pinched tight between two washers. This inner basket gives you an extra platform to put stuff on, and is one of those features that makes this zeer pot practical compared to some of the other "first world" hardware store zeer pots you may have seen. Insert the basket into the zeer pot, and put the lid on. Adjust the eyelet bolt such that it is as high as possible without touching the glass lid. You want the eyelet bolt to be useful as a handle even if the basket is filled with fruit or other items. Step 7: Root Cellar Variant, and Important Notes About Usage and Limitations of the Zeer PotYou should moisten the zeer pot with a quart of water three times a day. If you store your water in the zeer pot, or have a dedicated water chilling pot, you will have the best results, since the water you add will be cold already, and won't increase the temperature of the pot. Root cellar variant One neat variant for keeping root vegetables and scallions fresh is to build your zeer pot, and to fill the inner pot half way up with damp sand. Then, burry your carrots and beets in the sand to store them. Damp sand will keep your root vegetables as fresh as possible by keeping them alive. You will find that they remain crisp for longer this way. Also, if you have scallions, burry the root parts in damp sand to keep them fresh. This works even better than simply keeping them cold. Please note:
The zeer pot is a greener option only if you use it according to the following rule:
 Third Prize in the Green Design Contest  First Prize in the Outdoor Workshop Contest Recommendations Outdoor Life Contest Farm to Table Contest Woodworking Contest  Why evaporative cooling? A lack of access to affordable and effective post-harvest storage solutions for fruits and vegetables is a significant contributor to high rates of food loss. This issue is particularly acute in off-grid communities in arid climates. Technologies utilizing evaporative cooling have been proven to increase shelf life with little or no reliance on electricity. CoolVeg is a nonprofit organization founded to increase access and adoption of these technologies through collaborations with businesses, research institutions, NGOs, and government agencies. Evaporative Cooling TechnologiesPreserving fruits and vegetables in arid climates  Clay pot coolers and cooling chambers function through evaporative cooling and they provide the most value in hot and dry climates. While fruits and vegetables spoil quickly in these conditions, dry air allows for water to evaporate quickly from the surface of the evaporative cooling devices, creating a cooling effect and increasing the humidity inside the storage chamber. In humid climates, water does not evaporate quickly reducing the cooling effect and limiting the benefits that the devices can provide. The map to the right shows the areas in Africa where these technologies will and will not work well. These technologies will also work well in many parts of Western and South Asia.  Contact us if you are interested in working with us to deploy solutions for improved postharvest storage of fruits and vegetables. CoolVeg Foundation Inc. Eric Verploegen +1-617-947-9762 Thanks for submitting! Subscribe to Our NewsletterThanks for subscribing!  designing for a more equitable world  Twitter Facebook Youtube LinkedIn Evaporative Cooling Best Practices Guide Publication | Jun 01, 2018 | Eric Verploegen, Peter Rinker, Kukom Edoh Ognakossan  D-Lab, in partnership with the World Vegetable Center and Movement e.V. created a best practices guide for clay pot coolers and brick evaporative cooling chambers. This document provides guidance on best practices for:
Eric Verploegen , Research Engineer, Food-Water-Energy Lead Clay Pot Coolers: Keep Produce Fresh Without ElectricityWww.engineeringforchange.org/news/cla...ctricity/.  Fruits and vegetables can spoil quickly in arid climates, leading to the loss of food, time, and money. Roughly 50% of fruits and vegetables harvested in Sub-Saharan Africa are lost between harvest and reaching the consumer, owed in part to poor storage in regions where electricity is scarce or expensive. There is an inexpensive solution, however, and it’s relatively simple: a clay pot cooler. Clay pot coolers can increase the shelf life of many fruits and vegetables, including tomatoes, leafy greens, eggplant, and okra, among others. These coolers take advantage of the evaporative-cooling effect. It works in the same way as perspiration, which evaporates to cool the human body. The evaporation of water from the outer surface of the clay pot removes heat and cools the fruits and vegetables inside. The inside of the pots can be as much as 10°C below the ambient temperature, with increased humidity to better preserve produce. Permanent LinksPermanent links, collections.
Additional Recommended ResourcesThis is a community contributed resource. ECHOcommunity represents a vast network of agriculture and community development practitioners around the world. The sharing of information is a core value in this community of practice. We believe that in sharing knowledge, people are empowered to find, test, and improve available solutions. In order to facilitate this, ECHOcommunity makes available resources produced internally, and those shared by network members. This resource may not necessarily reflect the views of ECHO Inc. Do you have something to share?Many organizations and individuals have chosen to distribute their work through ECHOcommunity. If you have resources you would like to share, we believe in giving credit where credit is due. Community Contributed resources remain the property of their creators, but can benefit millions of people around the world. Conversations going on right now:ECHOcommunity.org is the online collaborative membership community of ECHO, an international nonprofit organization. ECHO exists to reduce hunger and improve lives through agricultural training and resources. Working through regional impact centers around the world ECHO connects small-scale farmers, and those working to eliminate world hunger, with essential resources, and each other. These resources include a vast knowledgebase of practical information, experienced technical support and an extensive seed bank focused on highly beneficial underutilized plants. | |||||
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MIT D-Lab, the World Vegetable Center, and Institut d'Economie Rurale (IER) have developed this guide in order to disseminate information about this simple, low-cost technology that uses the principle of evaporative cooling to provide improved storage for fruits and vegetables. By improving vegetable shelf life, clay pot coolers have great potential to reduce food losses, improve nutrition ...
Clay pot coolers take advantage of the "evaporative cooling" effect in the same way that the evaporation of perspiration cools the human body. The evaporation of water from the outer surface of the clay pot removes heat and creates a cooling effect for the fruits and vegetables inside. By providing a cool—as much as 10°C below the ambient ...
The pot-in-pot system works simply by putting a smaller clay pot inside a larger one. The two are separated by a constantly moist sand. Evaporation causes a cooling affect in the inner pot. This activity will allow students to construct this cooling system. Some simple experiments will then be conducted to evaluate its functionality. Students ...
The sizes of the pots can be selected based on what is most practical for a given user. Sand is placed between the inner pot and outer vessel, and a cloth or sack is placed over the cooler as a cover. Clay pot coolers can cost (USD) $5—$40, depending on their size and the cost of local materials. Regardless of the size and design, the best ...
MIT D-Lab has worked with the World Vegetable Center and Institut d'Economie Rurale (IER) to evaluate the performance of clay pot coolers and other similarly-sized storage devices in a laboratory setting. The current effort are building on design and user research work conducted in 2017 and the development of a heat and mass transfer model for ...
clay pot FIG. 2. Sketches of a) a real pot-in-pot cooler, b) a botijo and c) a model pot-in-pot cooler (a test tube). In order to simplify the system and focus on the main physical parameters, most of the experiments reported in this article were conducted in long cylindrical containers (test tubes or graduated cylinders) as displayed in the
A low cost method of evaporative cooling comes from clay pot coolers. Two common variants are the clay pot in a clay pot (pot-in-pot), commonly referred to as "Zeer pots," and the clay pot in a plastic dish (pot-in-dish) devices shown in Fig. 1 [9].Both devices use a clay pot for vegetable storage, a wet cloth as an evaporation surface and lid, and a sand layer that serves as the medium ...
Fill the base of the larger pot with coarse sand. Fill about 2.5cm/1 inch deep, and only fill to a height that will ensure the smaller pot sits even in height with the larger pot. [2] 4. Place the small clay pot into the large pot. Arrange its base flat on top of the lower layer of sand. 5.
These use two clay pots, one inside the other, with a layer of wet sand in between. Water evaporates from the sand out through the outer pot, leaving the inner pot cooler. But the idea of combining such evaporative cooling with an insulating layer, as camels and some other desert animals do, has not really been applied to human-designed cooling ...
A low cost method of evaporative cooling comes from clay pot coolers. Two common variants are the clay pot in a clay pot (pot-in-pot), commonly referred to as "Zeer pots," and the clay pot in a plastic dish (pot-in-dish) devices shown in Fig. 1 [9]. Both devices use a clay pot for vegetable storage, a wet cloth as an evaporation surface and ...
Evaporative Cooling for Fruit & Vegetable Storage MIT D-Lab, the World Vegetable Center, and Institut d'Economie Rurale (IER) have developed this guide in order to disseminate information about this simple, low-cost technology that uses the principle of evaporative cooling to provide improved storage for fruits and vegetables. By improving vegetable shelf life, clay pot coolers have great ...
In this article, we experimentally investigate the influence of the main physical parameters in model pot-in-pot coolers. The effect of the wind on the evaporation rate of the cooling fluid is studied in model experiments while the influence of the fluid properties (thermal conductivity, specific heat, and latent heat) is elucidated using a ...
of deterioration). The temperature and humidity data shown was collected during the leafy green shelf life experiments. Clay Pot Coolers: Preserving Fruits & Vegetables in Mali | MIT D-Lab | 4 As shown in the table above, clay pot coolers extended the shelf life of vegetable by 50% to 600% compared to storage in ambient conditions.
Clay pot coolers can help people in off-grid communities right now. Sustainable Development Goal (SDG) 7 was established in 2015 to address the urgent need to bring modern energy to the over 1 billion people without electricity access. However, even with billions of dollars of investment, 670 million people are projected to still be without ...
1. Get two unglazed ceramic pots—one that will fit inside the other—plus some sand and water. 2. Fill the bottom of the larger pot with a couple inches of sand. 3. Put the smaller pot inside ...
A Practical Zeer Pot (evaporative Cooler / Non-electrical Refrigerator): A zeer pot is an evaporative cooler used in rural Africa and the Middle East to keep vegetables fresh. They consist of two terra cotta pots, one nested inside the other, with the gap between them filled with wet sand. The sand serves as a thermal ma…
Practical, affordable, and effective devices. By providing a cool humid environment, clay pot coolers can improve the shelf life of many common fruits and vegetables in dry regions. These simple devices can be quickly and easily assembled using locally available materials. Clay pot coolers typically cost between $2 and $15 depending on their size.
In this video, you will learn how to build, fill, and maintain a clay pot evaporative cooler. Scientific Animations Without Borders (SAWBO) is a university based program. SAWBO transforms extension information on relevant topics such as agriculture, disease and women's empowerment, into 2D, 2.5D and 3D animations, which are then voice overlaid into a diversity of languages from around the world.
Clay pot coolers and cooling chambers function through evaporative cooling and they provide the most value in hot and dry climates. While fruits and vegetables spoil quickly in these conditions, dry air allows for water to evaporate quickly from the surface of the evaporative cooling devices, creating a cooling effect and increasing the humidity inside the storage chamber.
Clay pots for storage have been around for centuries. Off-the-grid non-refrigeration Zeer pots were constructed in Africa during the and from clay made from cow dung and local sand, rocks, etc., and distributed to farmers and families to preserve food. ... It worked as an effective air cooler to lower the temperature about 10 degrees. This is ...
CLAY POT COOLERS October 2021 Report 2016-2021: Suitability evaluation, lab testing, training, and dissemination. Food, water, and electricity are what many people con-sider basic needs, but these are still a luxuries to many people around the world. Imagine spending up to an
Evaporative Cooling Best Practices Guide (2018, 31 pages) D-Lab, in partnership with the World Vegetable Center and Movement e.V. created a best practices guide for clay pot coolers and brick evaporative cooling chambers. This document provides guidance on best practices for: Eric Verploegen, Research Engineer, Food-Water-Energy Lead.
Clay pot coolers can increase the shelf life of many fruits and vegetables, including tomatoes, leafy greens, eggplant, and okra, among others. These coolers take advantage of the evaporative-cooling effect. It works in the same way as perspiration, which evaporates to cool the human body.