February 5, 2009
This past semester, in Cornell University’s Engineers for a Sustainable World class, there was a Solar Oven Team that worked on problems presented by Grupo Fenix. Led by Tim Bond, the team advisor, Cornell students have worked alongside Las Mujeres Solares and Grupo Fenix in much the same way that University of Dayton students have. Similar to our Design and Manufacturing Clinic class, their Engineers for a Sustainable World class allows students the opportunity to work on appropriate technology issues while still in the university setting.
Their most recent report on their work, from December 2008, provides much valuable knowledge, much of wish I would like to share with you.
First, the team did an investigation into the best ways to prep the solar cooker before painting it, such that the paint does not chip off. This is important for aesthetic purposes, for the women would like to sell the solar cookers (and eventually autoclaves). The team found that sanding and phosphoric acid treatment are significantly better metal preparation methods than soap, vinegar, or no preparation.
The team also did an investigation into the possibilities of cooking more food with a larger oven. They built a new cooker 50% larger by volume than the original, with one dimension (the width) increased. It was found that the scale up did not affect how well or quickly the oven cooked the food. Along with this conclusion, the team also provided valuable construction suggestions and effective testing procedures in their report. They also found that the amount of water heated is more important to cooking time than the number of pots.
Finally, the Solar Oven Team did an energy and carbon cost analysis on the solar ovens. They compared the costs of the solar ovens with costs of traditional cooking methods in order to prove that the solar ovens are an effective way to decrease energy consumption and carbon emissions. The team concluded that a solar cooker “pays off” its production carbon and energy costs in just 41 days. Because solar cookers last many years, they are obviously effective. Assuming a two year lifetime, each solar cooker offsets over 8000 MJ of energy. Especially important to this is that Las Mujeres Solares use recycled newspaper printing aluminum for the inside of their cookers. Of course, the team points out that many assumptions had to be made in order to reach these conclusions, and transportation costs of the raw materials were neglected. But even after taking this into consideration, solar cookers still are quite effective at reducing energy use and carbon costs.
I would like to congratulate the team on a job well done, and the administrators for the success of their program thus far. The reflections offered by the students at the end of the report illustrate the value of the class to them and to Grupo Fenix. The students learned a lot about engineering and appropriate technology through their experience, as well as gained exposure to development issues unlike those encountered in many engineering courses. Their reflections were inspiring, and I was greatly impressed by their approach to working with the women. They showed respect for the women’s needs and opinions, which I have learned is so important to work like ours.
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