Refrigeration, the African way [DARFUR] Hawa Osman is a farmer in Darfur, Sudan. She grows tomatoes, okra, carrots, and rocket lettuce, and also has small orchard of guava trees. In the hot weather of Darfur, Hawa used to lose half of the crops she hoped to sell each day in the market of Al Fashir, the capital city of North Darfur, because of inadequate storage facilities — and no electricity or refrigerator — in her small canteen, the shed made out of wood and palm leaves in which she displays her products to clients. But these days she is selling fresher produce and making bigger profit. The zeer is a large pot inside which fits another smaller pot with a clay lid. Each zeer can contain 12 kg of vegetables, and costs less than US$2 to produce. Experiments assessing its ability to extend shelf life show that tomatoes and guavas can be kept for 20 days, compared to just two without. Hawa was the first person to use the zeer technology in her canteen. Preservation is a key issue for food security.
Zeer pot refrigeration (design) See also: Zeer pot refrigerator (basic topic article) Figure 1: Conceptual Flow of Energy and Water in Zeer Refrigerator The following shelf-life comparison has been adapted from a case study performed by the Practical Action Organization and can be directly accessed here. The impact of the pot-in-pot refrigerator is immediately realized as the shelf life for most produce is extended by 5 to 10 times. When evaporation occurs from a surface, there is an energy associated with the phase change known as the latent heat of vaporization. In the case of the Zeer refrigerator, water evaporates out of the sand through the surface of the outer clay pot and from the whole top surface of the moist sand exposed to the solar radiation, removing energy from the system. The success of the pot-in-pot refrigerator is heavily dependent on the surrounding conditions. It should be noted that the values presented in the following sections indicate the maximum cooling effect for a given set of parameters.
Misconceptions Spinning the Moon Bad Astronomy: The Moon only shows one face to us because it is not rotating. Better astronomy: The Moon only shows one face because it is rotating, once every time it revolves around the Earth. Best astronomy: The Moon does not appear to rotate in the reference frame where the Earth-Moon line is fixed in direction, but it does rotate as seen by an outside observer. Image of the Earth and Moon taken in 1994 by NASA's Galileo spacecraft, on its way to Jupiter. How it works: If you go out on several different nights and look at the Moon, you will always see the same features, at about the same position. This can be seen using a model. Surprise! Now, I have been a bit tricky here. We've actually learned three things: There is a bit more to this story. [Note added December 6, 2001: Bad Reader Charlie Kluepfel pointed out to me that I had a mistake in the original version of the above paragraph; I had said libration was maximized at apogee and perigee.
Takachar Mutualiser l’épargne des immigrés subsahariens en france pour le dévéloppement en Afrique « Ouedraogo's Blog Les Objectifs du millénaire pour le développement (OMD) sont huit objectifs1 adoptés en 2000, par 189 États, que les États membres de l’ONU ont convenu d’atteindre d’ici à 2015. La déclaration fut signée en septembre 2000. Ces objectifs sont certes nobles puisqu’il s’agit de sortir la majorité des habitants de notre planète, du trou noir dans lequel ils sont plongés et de les soulager des énormes difficultés auxquelles elles sont confrontées au quotidien pour satisfaire leurs besoins primaires. Les 8 OMD se divisent en 21 cibles quantifiables, et mesurées selon 60 indicateurs. Dans ce mémo, nous allons nous intéresser à l’OBJECTIF 1 – Réduction de l’extrême pauvreté et de la faim Cet OMD se compose de trois cibles, mais nous allons aborder la question des moyens mis en œuvre pour atteindre la première. La première cible. La Banque mondiale estime qu’en 2005, 1,4 milliard d’individus vivaient dans une pauvreté extrême. Like this: J'aime chargement…
Evaporative Cooling (original) Much of the post-harvest loss of fruits and vegetables in developing countries is due to the lack of proper storage facilities. While refrigerated cool stores are the best method of preserving fruits and vegetables they are expensive to buy and run. Consequently, in developing countries there is an interest in simple low-cost alternatives, many of which depend on evaporative cooling which is simple and does not require any external power supply. The basic principle relies on cooling by evaporation. Generally, an evaporative cooler is made of a porous material that is fed with water. Figure 1: A Janata Cooler These are simple designs of evaporative coolers that can be used in the home. One adaptation on the basic double pot design is the Janata cooler, developed by the Food & Nutrition Board of India. Mohammed Bah Abba a teacher in Nigeria, developed a small-scale storage "pot-in-pot" system that uses two pots of slightly different size. Figure 2: A charcoal cooler Mr.
Fears, Rules, Words, Questions « Teaching Science A quick lesson description here; I’ve been far too focused on political stuff recently. I thought I’d blogged this before, but apparently not. (And while I’m reviewing – 120 posts. Yeah, really.) Anyway. It’s the time of year, after summative exams for our KS3 classes, that we teach Reproduction to year 7. Stop giggling at the back there! This is my approach to starting off what can be a challenging topic. Fears “What might make a student nervous about this topic?” Rules I remind the students of the rules we have agreed and followed all year. Words I write ‘F***’ on the board, with asterisks, and explain over the gasps and giggles that we all know which word this is. I then circle the ‘polite’ words and explain that we can consider these as ‘classroom English’. Important: clean the board very thoroughly. :) Questions I give each student a piece of paper and ask them to spread out, as if doing a test. Comments? Like this: Like Loading...
10 Cases of Appropriate Technology Technology The goal of Appropriate Technology (AT) is to increase the standard of living for the developing world without condescension, complication, or environmental damage. Typical AT inventions are more labor intensive, require fewer resources, and use low cost or readily available materials wherever possible. The developing world may be falling behind when competing for resources, but it hasn’t even started regarding technology. Solar Powered Lightbulb Though we can’t really fathom it, much of the world is still prisoner to darkness. Concrete Canvas Shelters UK firm Concrete Canvas knows too well that “temporary” tent cities for refugees offer little protection from the elements, and a more sturdy solution is needed using local materials. Prior to Jock Brandis’ Universal Nut Sheller, growing and harvesting peanuts in Africa was a time-and-labor intensive affair relegated to women and children. Pot-In-Pot Refrigerator Bike Powered Water Pump Free Wheelchair Mission
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