Solar Cooking Archive Discussion Forums

webmaster · Posted: Tue Feb 12, 2008 9:29 pm Post subject: Test for trucation

Solar box cookers (SBCs) are the earliest form of solar cooking in Western culture. An early European record of cooking in a solar box was made by Horace de Saussure, a Swiss naturalist experimenting as early as 1767. He reported successfully cooking fruits at that time with initial temperatures of 189.5 F (87.5 C). Over the years, de Saussure and others focused their solar box cooker design work on variations of shape, size, sidings, glazings, insulations, reflectors, and the composition and reflectance of the internal surfaces.

These components have been varied endlessly in an effort to increase solar box temperatures. Our solar boxes now successfully reach temperatures between 275 -300 F (135 -149 C), depending on size and location of use. Since many foods will cook with an internal temperature of 190 F (88 C) and water boils at 212 F (100 C) at sea level, it is clear that solar box cookers have reached adequate cooking temperatures for a long time.

Meanwhile, the higher temperatures of cooking over fire have continued to force us to stir foods and protect them from scorching from excessive bottom heat, while needless amounts of fuel and human labor have been unnecessarily used. Now, we can do better than that by using readily available, free solar energy whenever the sun shines.

At the time I was first exploring solar cooking, my home was dedicated to developing Earth-Conscious Homemaking. I was exploring all the ways that could be used in an urban home to reduce consumption of earth resources. As a part of this effort, I made and used a lot of solar cookers. At one time I had seven different types of solar cookers and some duplicates in my back yard. Most were homemade. There were various parabolic and non-parabolic troughs, one five foot dish parabolic concentrator, and several four-reflector slant-face ovens—one made from the Halacy plans. There was the beautiful octagonal Solar Chef designed by Sam Erwin. Almost daily, neighbors and friends would join me for potluck dinners using the solar cookers.

When I put together my first solar box cooker in March of 1976, I had simply heard that an Indian designer, Ghosh, had made a solar box that cooked, but I had not been able to obtain plans or illustrations of it. Unaware that it "should" be made of metal or wood, I used cardboard boxes and thus opened a new line of SBC development. Had I been more knowledgeable, I would not have been so surprised that it cooked very well, if somewhat slowly, at its initial temperature of 240 F (115.5 C). With improvement in the thermal dynamics of the box, 300 F (149 C) was reached, a more than adequate temperature for boiling, roasting, baking, and gentle frying...surely a solar kitchen range.

During June and July of that year, Sherry Cole, my good friend and neighbor, and I faced a definitive test for solar box cooking. We had a large social action group in our homes. In addition to office and sleeping space, we offered to provide meals for the volunteers, planning to use the backyard solar equipment as much as possible.

Meeting the daily food needs of 35 to 40 hungry adults presented a perfect opportunity to compare the practicality of the various solar cookers. It provided fine tests of comparative function under stress. Our choice of cooking apparatus gradually shifted away from the multiple reflector and parabolic cookers to solar box cookers. While we initially had been aware of some of the special qualities of solar box cooking, it was through the routine serving of large quantities of food that the major strengths of the solar box technology emerged. They reliably cooked large quantities of food but required minimal attention. With a hectic schedule, it was not possible to give focusing cookers the attention they required. When attention lapsed, the focusing collectors would go out of focus and the food would not be done when needed. In addition, little gusts of summer wind would close or topple the multiple reflector cookers—again resulting in partially cooked food. But if food was placed in