(from: silence no. 202 - march 1996) solar energy
half the inhabitants of earth burn wood to cook but more than a billion and a half of these people are having difficulty finding the fuel. if nothing is done, this situation can only grow worse because there are ever more inhabitants of earth and fewer and fewer trees. in the year 2000, according to united nations estimates, 2.4 billion people will suffer from a shortage of fuel wood.
increasing deforestation causes numerous other degradations of the environment such as:
because the affected regions generally have high insolation, (sometimes more than 300 days of sun per year), it is reasonable to project the use of solar energy everywhere possible, while reserving wood - that solar energy "in the can" - for sunless hours and days.
much research all around the world has resulted in the production of all kinds of solar
cookers. (1) (2) (3)
recently, this situation is finally changing thanks to the almost simultaneous emergence of the three following factors:
there follows an account of its development.
born in lyons, france
the lyonnaise association for the study and development of solar energy, (aledes), based at the university of lyons i, has been interested in solar cooking for fifteen years. a number of different cookers have been designed there and then tried out in various developing countries: senegal, burkina faso, mali, the central african republic, vietnam, haiti. in general, the cookers functioned well but they proved too sophisticated, thus too difficult to manufacture and too expensive, to lend themselves to mass production.
paradoxically, it was in seeking the solution to another problem that we conceived of a cooker that would finally work well in africa. an organization wishing to demonstrate solar energy to school children asked us to design a cooker simple enough for 10 year olds to build without tools in less than one hour.
we first considered a solar box cooker which is composed of nested boxes with summary insulation like crumpled up paper in between, and covered with a piece of glass to trap solar radiation. (4) (it is possible to improve the performance of this model by lining the interior with aluminum paper that will reflect additional solar rays onto the cooking utensil.) however, it seemed a bit risky for children to be handling glass panes that could be easily dropped, break and cut fingers. so, for safety reasons, we were led to discard the glass, which, in turn, rendered the insolation useless. conversely, we increased the reflective surfaces to compensate for heat loss. the insulation was no longer provided by a fragile piece of glass but by a simple, transparent pyrex salad bowl inverted over the cooking pot, as depicted in fig.1. this apparatus was made simply by cutting up a cardboard carton for bottles and pasting aluminum foil to the resulting panels.
baptized in taylor
at taylor, in the mountains of arizona, lives a pioneer of solar cooking: barbara kerr, who built and distributed the first solar box cookers in the united states back in the 1970s (5). as soon as she heard of our new prototype, she built one and tested it, solar cooking being possible in arizona even in winter. it is she who baptized it the "panel cooker," which is to say a cooker of reflective panels. she also changed its form a bit, permitting sharper folds and greater stability. because this model seemed best suited for campers due to its light weight and modest volume when folded up, barbara kerr replaced the relatively heavy and cumbersome salad bowl with an oven-proof transparent plastic bag, fig. 2.
the february, 1994 issue of the solar box journal, published both a description of the original prototype (6) and of barbara kerr's modification (7). she also presented these models the following july during the international congress on solar cooking at heredia, costa rica (8).
improved in sacramento
since 1987 solar cookers international (sci) had existed in sacramento with the mission of promoting the solar box cooker throughout the world. (see box.) after barbara kerr, several members of this organization built their own "panel cookers" and were agreeably surprised by the results achieved at so modest a cost. each one suggested ways of further improving the stability and efficiency of the prototype. in particular, beverly blum, edwin pejack and jay campbell suggested modifications to adapt the cooker to the torrid zone. in fact, the three vertical reflective panels which functioned well in the temperate zone, (for example in france), lose their efficiency if the sun is very high in the sky because its rays glance off at too shallow an angle. it is therefore better to slant the panels backward, as is shown in fig. 3, where the central panel no longer has the shape of a rectangle, but is, rather, trapezoidal.
the "cookit" weighs only 500 grams and folds into a volume of 33x33x6 centimeters. in sci's newsletter we read (9): "compared to what we have always called our standard 'simple solar box ,' it is even1) simpler, 2) easier to make with fewer materials, (no window! just half one box), 3)more compact, and 4) easier to set up, take down and store in seconds. furthermore, the model made by sci is sold in the united states for75ff ($15) as opposed to 290ff ($58) for the solar box cooker. thus the mass production of the cookit and its distribution in the developing world became a possibility. contributions were solicited from the members of sci to cover expenses. 115,000ff ($23,000) were raised, and this sum was doubled by an anonymous donor. the rotary club added another 97,000ff ($19,500). only the most difficult consideration remained to be confronted: the human equation.
the first field contacts occurred in nairobi in september 1994 between a couple of sci volunteers from california and their kenyan homologues. with the authorization of the unhcr (10), they chose a place to experiment in a semi-arid zone of northwest kenya. it is the refugee camp at kakuma where some 30,000 refugees are surviving in precarious conditions. there is a fortnightly distribution of food and a few sticks of wood inadequate to cook it. some refugees go as far as twelve kilometers (7 miles) from the camp to cut down trees for firewood, which provokes disputes with the locals. others barter some of their meager food ration against some wood with which they can cook what's left.
in january, 1995, the camp was visited by beverly blum, sci executive director, barbara knudson, jay campbell and their kenyan colleague, faustine odaba, who served as interpreter. there was no dearth of difficulties with so many languages spoken in the camp, so many cultures and so many different cooking traditions.
at the outset, a small group of refugees was formed to try solar cooking all the basic foods available at the camp: rice, beans, bread, sorghum and ugali. this experiment having been a notable success, 12 women agreed to try solar cooking at home. after receiving two days of practical training, each was issued a cooker, a black pot, a plastic bag and three supplemental rations of food so as not put their own supplies at risk.
the sci volunteers then organized home visits and meetings to deal with any problems that arose. after a couple of weeks, little girls were learning how to solar cook from their mothers, and one woman began selling solar cooked bread. a month and a half later, 69 families were using their solar cookers on a regular basis, and 16 women had received training as solar cooking instructors, to teach the new technique to other refugees.
after overcoming a few difficulties, and adjusting to a cooking time markedly longer than for wood fires, africans began to discover and appreciate the advantages of solar cooking:
an observer from the united nations high commission for refugees reported: "the planning and execution of the sci training programme has been extremely impressive. refugee participation is very high...the new solar cooking device seems to avoid most of the technical and acceptance problems associated with cumbersome box cookers."
in june, the stock of cookers from the united states having been depleted, cookers "made in kenya," manufactured by africans in nairobi, were put to use. in september, 1995, only two years after the invention of this type of cooker, and thanks to the efficiency of sci, more than 1000 families were using it; more than 5000 people had experienced the proof that the sun could help them.
according to bev blum, "the keys to success are a sunny climate and consumers who:
1) have a motive (such as cooking fuel shortage), 2) receive adequate instruction, and 3)
have group encouragement to adapt solar cooking to their needs,
it remains to be hoped that everyone will now understand the importance of solar cooking; that it should not be considered solely as a life preserver in desperate situations, but also as a means of lightening domestic tasks and preserving the environment everywhere there is the menace of desertification. and that those in authority will act before, rather than after, the desertification occurs.
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