Solar Baking Under the Sonoran Sun

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Courtesy of Solar Energy International

Walk down almost any city street in Sonora, Mexico and you’re likely to see bakeries filled with sweet breads, empenadas and Mexican cookies. Ciudad Obregon is no different. In a small, poor neighborhood on the outskirts of Ciudad Obregon (a city of 400,000), a group of women have started their own bakery. Along the dirt roads of Aves del Castillo and under the heat of the Sonoran sun, this small group of women make and sell their own breads and empenadas. These women are taking a different approach—they’re baking with the sun.

Two years ago, Ken Olson and I, of Solar Energy International (SEI), had the pleasure of visiting Aves del Castillo. Through the Tucson based Farmer to Farmer organization and the Sonoran branch of Save the Children (FAI), we were introduced to a woman’s group called Mujeres Activas (Active Women). And active they are. These women, from one of the poorest neighborhoods of Ciudad Obregon, have not let their economic problems impede their desire for an improved quality of life. With the help of FAI, Mujeres Activas have held nutrition clinics, started a program to sell soy products, learned to build straw-bale houses, and have been building and cooking with solar ovens.

There is a great need for employment in Aves del Castillo. The women of Mujeres Activas were looking for a micro-enterprise that could help support their families. Of all the different possibilities presented before them, they felt a solar bakery could best meet their needs. And having solar cooked for their families for months, they were already hooked on solar cooking.

For the next two years while we looked for funding, the women worked out their plan. They decided who would be involved, what they would bake, and how they would advertise. With the help of the Tides, Greenville, and International Foundations, SEI was able to return to Ciudad Obregon to help the women with the solar oven. Ed Eaton, Cholla Eaton (Ed’s daughter and our trusty photographer), Laurie Loeb, and I, all of SEI, headed down to Sonora to meet the women involved, teach them to build commercial size solar ovens, and try out numerous solar baked mexican pastries.

The Oven
Ed had designed a large commercial size solar oven which we use to bake cookies at our local summer fair. With adjustments to the materials and the angle of the glass we had a great model for the bakery in Sonora.

We built two ovens for the Aves del Castillo bakery. The first one was built at our office in Colorado. We made this oven into a kit for easy assembly. This made it much simpler to teach all the steps involved in building the oven while we helped them put together the kit. It also made the second oven, built from scratch in Ciudad Obregon with local materials, come together quicker than we could have ever imagined.

Each oven is 76 by 34 inches to accommodate a standard sized glass pane. They are made of 3/4 inch plywood and ductboard insulation. The double pane tempered glass is angled at 30° (the latitude of Ciudad Obregon is 28°). There are two side reflectors (40 by 42 inches), angled at 60°, and a back reflector (76 by 42 inches) which hinges so it can be adjusted to any angle depending on the season and time of day. The reflectors are covered with Everbright, a shiny aluminum. The ovens are divided in half with a door on the back side of each. We have found in our cookie baking experience that using a fan to circulate the air does wonders for cookies and pastries. We included one PV powered fan in each side of the oven. The fans are run by a 6 Volt, 5 Amp module.

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