Inventor of Low Tech Fridge Wins Award 369
juju2112 writes "Mohammed Bah Abba of Nigeria won a Rolex award for his pot-in-pot invention. Here's how it works. You take a smaller pot and put it inside a larger pot. Fill the space in between them with wet sand, and cover the top with a wet cloth. When the water evaporates, it pulls the heat out with it, making the inside cold. It's a natural, cheap, easy-to-make refrigerator."
This is 3 years old (Score:5, Informative)
Coolgardie Safe (Score:5, Informative)
But, cut the guy a break. The cool thing here is that he's done it with readily available local materials which is pretty much one of the key features for a real engineer. To paraphrase the old saw:
Anyone can make you an evaporative cooler for $100; this guy's done it for $1.
Re:performance parameters? (Score:1, Informative)
Just do what aquarium keepers do with gravel to kill snails, bake the sand at a very low heat until dry. Normally a 325 setting with the door open. Not sure if cost of sand offsets the cost of the oven, but you get the idea.
Re:keeping beer cool (Score:0, Informative)
Water evaporates - it makes stuff cold. Like when I spray my back when I get too hot cycling.
Simple technology is important - but this is neither news nor does it matter.
Link to rolex awards? (Score:2, Informative)
Re:I'm happy for him and all but.. (Score:5, Informative)
Re:This is kind of stupid... (Score:5, Informative)
The article didn't mention the effectiveness of the device. Say, on a hot summer day, RH of 80%, if we keep the pot under the shade, could we achieve 15 degree C. A temperature ideal for beer.
Also in Mediterranean cultures (Score:5, Informative)
The cooling effect has been scientifically studied. Here is this article describing it [google.com] (Google-translated from Spanish).
Re:This is New? (Score:5, Informative)
No, not particularly. It's a very old trick to make cold water by putting it in an unglazed clay pot, which is porous, and allowing evaporation of the seepage to draw the heat out. I learned it from Mexican Indians 35 years ago and it was effective enough to make water cold enough to make your teeth hurt even in the tropical rainforest. It works even better in the desert where evaporation happens quicker due to the low humidity.
European bicycle racers have been wrapping their water bottles with a damp cloth covering to keep the water chilled for decades as well.
Until a couple of weeks ago I thought everybody knew you could keep cool by wearing a dampened T-shirt, and then I learned that the Pardy's, those paragons of sea lore and self-sufficiency without electrical power, had only just learned this trick. .
Wrap something damp around a pot, as is done with the water bottle, and the air inside the pot chills, as does anything inside the pot. Wrap a porous outer layer around the damp cloth, such as another pot, and you moderate the evaporation rate.
This "invention" seems to miss a few of the finer points of the device, thus requiring the damp cloth over the two pots. You need to use an unglazed pot for the outer one. Then you can even put a real cover on the thing and it still works. Better. Longer. Some sort of batting works better as a wick than sand, although sand will do and is certainly freely available.
I don't mean to denigrate this man's intellectual accomplishment. If he thought it up on his own from basic principles the intellectual feat is equal to the first man that did it.
But it really does amount to the reinvention of folklore that exists in one place in some other place.
And the people from Rolex think of it as a new invention because they are modern, mechanistic folk who don't know how to go about living without modern power and machines or what people who do not have such devices already know about doing so.
The Zapotec Indians I lived among for some months knew lots of tricks that had been handed down over thousands of years for surviving with nothing but what you could make with your own two hands. I've got a poncho just about eight feet from me right now that was woven by them on a backstrap loom they made themselves, with wool from sheep they had grown themselves, sheared themselves, carded themselves, spun themselves, using weaving techniques their ancestors had invented themselves (even though many people throughout the world had invented the same thing). Living with them for a few months taught me more about how to think about living than any number of survival books and hiking expeditions had ever done.
Many of the things they did appeared as magic to me, because I was just an ignorant Americano and their technology was sufficiently advanced. .
I was in Mexico in the late 60s (that's where I first heard Abbey Road). The Zapotecs are starting to lose it too now as they begin to sell their weaving to touristas so that they may buy Tshirts and blue jeans. Most of them buy neon colored acrylic yarn from the store now instead of using their own lovely wool, because the Americanos really like the bright "native" colors instead of the natural tones of wool.
Well, their lot will certainly improve with more money at their disposal, and I certainly won't begrudge them that. Doctors cost serious money no matter how "self-sufficient" they are, and they coul
Re:Link to rolex awards? (Score:3, Informative)
The Rolex Awards website is Flash only, so don't bother going there if you don't have/want to pollute your system with that technology.
I was hoping to find out what the criteria for the award were by going to the source, and hoping that it was for making the idea available in a way they can afford to people who need it by use of appropriate technology. Unfortunately, I was frustrated by an inappropriate use of technology on the web site. Those giving the award would do well to learn from those to whom it was given.
Most pioneer types had similar stuff (Score:4, Informative)
He had replaced the box after the one from his grandfather finally rusted to pieces after just over 75 years of continual use.
Truckers in South Africa also used to also carry a water bag in a wet sand filled canvas bag outside their trucks to provide a constant source of cool water.
I think the principle is probably much older than this, probably going back to the first person realising that the wind chilled him more after taking a dip in a lake that when he was dry.
How it works... (Score:5, Informative)
You'd be surprised at the massive amount of energy that a liquid-to-vapor phase change can carry away. In fact, six times more energy is needed to turn one molecule of 100C liquid water to one molecule of 100C vapor water than is needed to heat liquid water from 0 to 100C!
Boiling, which is a similar phenomenon, is the most efficient way to transfer heat known to science.
Sig--
1. My girlfriend
2. You
3. ???
4. Profit!
Re:so how effective is it? (Score:5, Informative)
Where I live at present (Mount Isa, Queensland), just about every house and business has at least a 6000cfm evaporative air conditioner. Humidity can often get below 30%, meaning that they work particularly well. In fact, they can theoretically cool to the dew point, which if you take note of the last 72 hr readings from Mount Isa [bom.gov.au] can pull down to 10 degrees or so when it's dry.
They are of course completely fucking useless for about 3 weeks of the year when it's hot and humid and you get storms in the afternoon at 35 degrees and 90% humidity. You just sweat like a pig then, or retreat to the refrigerative airconditioner you normally keep in reserve in your bedroom.
Re:Link to rolex awards? (Score:2, Informative)
http://www.rolexawards.com/laureates/pdf/la ureate0 006.pdf
This is my attempt at an excerpt:
He began by studying management sciences at Ahmadu Bello University in the town of Zaria. Equipped with a Bachelor of Science degree in business administration, he became a lecturer at the College of Business and Management Studies at Jigawa State Polytechnic in Dutse in 1990, at the same time heading the college's Student Industrial Work Experience Scheme. When not teaching, Abba serves as a consultant to the regional United Nations Development Programme (UNDP) in Jigawa, organising community activities and giving seminars. A staunch supporter of women's rights, he is also a consultant with the state's Ministry for Women Affairs and Social Mobilization.
These consultancies have brought Abba in close contact with rural communities, where he has observed the extreme hardships suffered by subsistence farmers and their families. "Through these observations, I became motivated to revitalise earthen pot usage and extend the life of perishable foods," he adds.
Vegetables, fruit and drinks cooled by a simple evaporation process The innovative cooling system that Abba developed in 1995 consists of two earthenware pots of different diameters, one placed inside the other. The space between the two pots is filled with wet sand that is kept constantly moist, thereby keeping both pots damp.
Fruit, vegetables and other items such as soft drinks are put in the smaller inner pot, which is
covered with a damp cloth and left in a very dry, ventilated place. The phenomenon that occurs is based on a simple principle of physics: The water contained in the sand between the two pots evaporates towards the outer surface of the larger pot where the drier outside air is circulating. By virtue of the laws of thermodynamics, the evaporation process automatically causes a drop in temperature of several degrees, cooling the inner container, destroying harmful microorganisms and preserving the perishable foods inside.
Abba's first trials proved successful. Eggplants, for example, stayed fresh for 27 days instead of three, and tomatoes and peppers lasted for three weeks or more. African spinach, which usually spoils after a day, remained edible after 12 days in the Pot-in-Pot storage.
The enterprising teacher persistently refined his invention for two years between 1995 and 1997. He then tapped into the large unemployed local workforce and hired skilled pot makers to mass produce the first batch of 5,000 Pot-in-Pots. Manufacturing these devices at his own expense for 30 US cents each, he began distributing them for free to five villages in Jigawa. For this initial phase of his project, he received limited financial backing from his brother and assistance in the form of transportation, fuel and labour from the UNDP, the regional
government, a local women's development group and the Jigawa State Polytechnic.
In 1999, Abba built additional pot-making factories and supplied another dozen local villages with 7,000 pots, again at his expense. He estimates that three-quarters of the rural families in Jigawa are now using his cooling device.
The impact of the Pot-in-Pot on individuals' lives is overwhelming. "Farmers are now able to sell on demand rather than 'rush sell' because of spoilage," says Abba, "and income levels have noticeably risen. Married women also have an important stake in the process, as they can sell food from their homes and overcome their age-old dependency on their husbands as the sole providers." In turn, and perhaps most significantly for the advancement of the female population, Abba's invention liberates girls from having to hawk food each day. Instead,
they are now free to attend school, and the number of girls enrolling in village primary
schools is rising.
These factors, coupled with the effect that the Pot-in-Pot has had in stemming disease and slowing the pace of the rural exodus to cities, ar
Re:Brilliant! (Score:3, Informative)
Re:This is New? (Score:2, Informative)
A better version is a case over which you hang a large thick canves cloth, put it in the shade where the wind blows and make sure the bottom of the cloth is in water, you can keep things much cooler.
Hmm (Score:5, Informative)
The idea that an evaporating liquid draws heat from its surroundings is nothing new.
Basically, the difference between a liquid and a gas is how much the molecules are vibrating: if the vibration is weak, the molecules' affinity for each other bonds them loosely together so they follow one another around, assuming the shape of a container but occupying a definite volume. If the vibration is stronger than that attractive force, then they just fly apart, occupying the whole of the container and exerting a pressure on it. Heating, of course, makes the molecules vibrate more strongly, which is why liquids turn into gases when heated.
If you try to force more molecules into a space, eventually they will be forced into colliding with one another often enough to form a liquid. This is what goes on in a cigarette lighter: there are just too many molecules to behave as a perfect gas, so some of them are forced together and behave as a liquid.
Pressure, volume and {absolute -- i.e. in Kelvins, 0C = 273.15K} temperature are related by the equation: P * V = n * R * T, where n = number of moles of gas and R is the Ideal Gas Constant. No gas is truly ideal, because the assumption is that the individual molecules have neither mass nor volume; however, the relationship holds reasonably well in real life, only deviating sharply around the point where liquefaction actually occurs.
A fridge or air conditioner has three main parts: the compressor, the condenser and the evaporator. The refrigerant gas is first compressed. Pressure goes up and volume goes down, so temperature also goes up. It is then pumped around some pipes at the back of the fridge {or in the outdoor part of the air conditioner; portable units don't have an outdoor section, so the condenser is cooled by blowing air over it and out of a window through a length of flexi-flue -- uncouple this and you've got yourself a de-humidifier} to allow it to cool down. Once the refrigerant has cooled to ambient temperature and become a liquid again, it is forced out by its own pressure through a tiny hole into a larger space {the evaporator - usually the outer jacket of the icemaking compartment of a fridge, or the coil of pipe in the indoor part of an air conditioner that gets covered with ice crystals}. Now the pressure is not sufficient to keep the refrigerant molecules together, so it becomes a gas again. Pressure goes down, volume goes up, so to satisfy the laws of physics, temperature must go down.
The compressor's intake draws the low-pressure refrigerant out of the evaporator and the whole thing starts again. {In an air con., the whole process has to be stopped every so often to allow the accumulated ice to melt off the surface of the evaporator. Plumbed-in units have a permanent drain, portable ones have a tank which needs emptying periodically. The meltwater is pure enough to be used anywhere demineralised water is required.}
You can also get a terracotta butter cooler which works on this principle: the inside of the tray and dome are salt-glazed, the outsides are unglazed. You soak the whole thing in water, which then evaporates slowly from the outer surface, keeping the butter usefully cold {not rock solid, but not runny either}.
this is how much cooling you get... (Score:5, Informative)
Evaporative cooling has been use in kitchens for millenia, although it is usually used to keep water cool (unglazed pots). For storage of more than a few hours, a cellar, solid stone building, or cave is less hassle. You easily get guaranteed 70F or below long-term storage in most regions of the world, and if you are architecturally clever, you can actually get lower-than average-long-term temperatures without any maintenance or needing to re-fill water into little jugs.
Re:Also in Mediterranean cultures (Score:3, Informative)
It's a matter of degree. This guy's invention is suitable to keep vegetables very cool for long periods of time with minimal maintenance. He could have just put some wet burlap over the vegetables kind of like your wet newspaper, but that wouldn't have been as useful to the local people as having in-place, reliable refridgeration.
Your use of evaperative cooling, like others on this thread, is very useful for your needs, but likely would not have solved the long-term food storage needs of these people. His solution answered their needs more fully. More importantly, he was able to actually deliver the product to market in large enough quantities at a price the local propulation could afford.
Re:keeping beer cool (Score:5, Informative)
If you're making a lager, you are supposed to keep it at a relatively cool temperature for an extended period of time while it
If you're not fortunate enough to have an extra fridge (with appropriate temperature regulator), or be living in a cold climate with a cool garage/basement, you can use this technique to keep it fairly cool.
Just put your carboy (or other fermenter) in a tub with a couple inches of water in it and wrap the vessel in a towel (my favorite was a thick Bugs Bunny terrycloth) with the bottom edge of the towel in the water. Just water your beer every couple of days and you're good to go.
One that can even make ice (Score:5, Informative)
Re:keeping beer cool (Score:5, Informative)
The point is, and apparently it was novel enough an application to merit $75,000, is that this makes a dry cool space, a refrigerator, that can keep food cold, and has an enormous economic impact -- "Eggplants stay fresh for 27 days, instead of the usual three. Tomatoes and peppers last for up to three weeks" -- not just a pleasantly cool cup of water.
NB, this was reported in Time magazine in 2001 [time.com].Slashdot is keeping its fine tradition of reporting "news" years late. Expect the dupe tomrrow.
Re:so how effective is it? (Score:5, Informative)
However, during the monsoons, or rainy weather-the humidity renders them useless, as evaporation on the straw mats reduces.
Oh, and clay pots have been used in India too, for generations, for keeping water cool-though not in the way mentioned.
free energy source (Score:3, Informative)
Another way to get free cooling in the summer is to have a lot of plastic pipe buried down in the yard below the surface effect heating. That's a variable that you'll have to determine, the depth, but should be easy to find out. In northern climes, it's roughly equivalent to the mean average frost depth. The pipes (long enough, some hundreds of feet are needed to cool say around a 1500 - 2000 sq ft structure) have a single entrance to them coming out of the ground at the farthest away, lowest, shadiest/coolest spot you have in the yard. They come into the building and have a vent at the lowest most central point, then are open to the room. Depending on how many stories your building is, you have floor vents that may be opened and closed, all the way to the roof, where another vent is located. Heat rises, you are creating a thermo-siphon effect. Air enters at the outside pipe, travels underground through the pipes and gets cooled. The roof vent, being the highest and hottest point, acts as the draw, the pump if you will, drawing the cooler air upwards and out, cooling as it travels. That's why you need a lot of buried pipe, but once constructed, it's relatively maintenance free, just needs take care on adequate screening at both ends to prevent insects and dirt entering, etc, and to keep rainwater out, relatively easy with normal conical vent caps. It's a chimney effect, low tech, no moving parts, but you can get some decent cooling from it. I don't have a link real handy, but I imagine that googling will find you some drawings and real-world examples of this technique in action.
The water based evaporative coolers are in large scale use around the world. Local to me is a rather large commercial poultry operation, all the buildings there have massive evaporative coolers installed, they work fairly well, and save many thousands in electric costs, in fact, I doubt they could operate the farms at a profit without them. Basically they are just huge screens that have water dripping down them, and the exhaust fans in the building draw the air through them.
Large commercial sized greenhouses mostly all have them as well.
Your insulation efforts are bang on. Nothing beats massive insulation as a heat/cold moderator. It's the most productive and efficient way to spend the energy dollar once any sort of artificial heating/cooling is required. In some places, the technique is called "superinsulation", with a usual targeted goal of R-55 to 60 range, as opposed to (in the US anyway) the normal R-18 or so. I've worked on two of those projects, they work pretty well for dropping costs (increasing effieicney really) for both cooling and heating.
Re:performance parameters? (Score:2, Informative)
A bit of sun often means on the edge of the veranda instead of deep in it. Or early in the day for an hour or so, before it gets too hot. Nor do you leave it there. It's just to start the whole process going quickly, which can take quite a while if you start it in the conditions you're going to keep it in to maintain the process as long as possible. You can extend the period of using the sun by wrapping a wet cloth around the pot. Then it takes longer to dry. When it dries either wet it again or roll the pot to where you're going to keep it.
The degree to which you can produce cooling with the direct sun would obviously surprise you though. It certainly did me the first time I experienced it. Let's return to my evisceral example of the wet Tshirt contest. Find yourself a not too humid day about 30 C outside at noon. (If you're near me in New Holland you'll have to wait a few months to try this I'm afraid. Rather closer to Old Holland about the same?(Without Flanders I might not be here. It's where my ancestor was able to flee to to avoid extermination of herself and the child from which I am descended. It's good to be the King. It sucks to be the newly dead King's exmistress.)) Put on a wet, white Tshirt and go stand in the sun.
You will feel cooler as long as you keep the Tshirt damp. The heat from the sun really doesn't heat you all that much because the heat is being used to evaporate the water, and the water is still able to draw heat from you. If you let the Tshirt dry out you will very quickly start to feel hotter. Go ahead, the next time suitable local conditions prevail try it. Now put that Tshirt on a water jug and keep it damp (the Tshirt is the same thing as that wet cloth on the pot above). Chilled water. In direct sun. Now put the jug in your waterbottle cage and yes, the airflow will make it even colder even faster.
If, however, you have a fan, you can plug in a refridgerator, no?
KFG
Re:I'm happy for him and all but.. (Score:3, Informative)
The original Rolex Award was made in 2000. What spurred the submitter was someone posting about it on a buletin board recently. I don't really object to reading about this; but it would have been much better to cite a primary source, like the the RolexAwards site which has full report [rolexawards.com] on this invention and the background.
Re:Coolgardie Safe (Score:3, Informative)
No, because the manufacturing cost is 30 cents [rolexawards.com].
What is new about this is: (Score:5, Informative)
The real "invention" here is his efforts toward making a positive change in the villager's lifestyle. Obviously if someone is awarding $100,000 dollars there is more to it. You folks should do some more research before you nock it!! He plans to use the $100,000 to distibute the pots more widely and to increase his education efforts!
Learn before you look like a fool:
http://www.varaprasad.htmlplanet.com/custo
Re:Invention ? (Score:3, Informative)
Note that Abba's particular method of making pots may also be a refinement for the evaporative characteristics of the clay. More importantly, technology in a vacuum is a useless thing - it's not just that he had the idea, but that he's turning it into a real, widespread change for his countrymen in a way that integrates with what they were already doing. Read the Rolex site for more information on that. This isn't just a technology award, it's a humanitarian award.
The spark of genius isn't just knowing that something can be done, it's doing it in a time and place where it has real applicability. And doing that in an evolutionary way - not throwing out the baby with the bathwater - has all sorts of extra benefits. If this method was known for 4000 years and wasn't being used by these people, then that's 4000 years of failure. Not something to get all puffed up about.
(btw I'm also Indian - though not from India - and like you I know through my family that absolutely everything of any importance was done by Indians first