Everyday Solar Cooking

By Joel Dufour
Published on July 9, 2015
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A rhubarb pie and an apple tart are baked in two simple, handmade solar ovens.
A rhubarb pie and an apple tart are baked in two simple, handmade solar ovens.
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Sophie Dufour, age 8, the author’s daughter, inspects one of the family’s solar ovens. This large model is on wheels and has collapsible reflectors for simple storage.
Sophie Dufour, age 8, the author’s daughter, inspects one of the family’s solar ovens. This large model is on wheels and has collapsible reflectors for simple storage.
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Joel Dufour, the author, removes a hot skillet from his mobile solar oven. On most solar ovens you must lift off the glass top to check on or remove food. A rear door makes this process a lot faster, and you lose less heat.
Joel Dufour, the author, removes a hot skillet from his mobile solar oven. On most solar ovens you must lift off the glass top to check on or remove food. A rear door makes this process a lot faster, and you lose less heat.
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An All American Sun Oven, one of the most popular ovens on the market, can easily reach temperatures high enough to bake cookies.
An All American Sun Oven, one of the most popular ovens on the market, can easily reach temperatures high enough to bake cookies.
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The Solavore Sport bakes bread to golden perfection. Even better, the company, formerly Solar Oven Society, has a 20 year history of providing clean cooking-fuel alternatives to women all over the world.
The Solavore Sport bakes bread to golden perfection. Even better, the company, formerly Solar Oven Society, has a 20 year history of providing clean cooking-fuel alternatives to women all over the world.
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Roasting vegetables is not out of reach with a solar oven. The slow cooking time at a low heat creates deep and savory flavors.
Roasting vegetables is not out of reach with a solar oven. The slow cooking time at a low heat creates deep and savory flavors.
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Delicias del Sol Villseca, a restaurant north of Santiago, Chile, turned to solar energy when deforestation depleted its fuel source. The restaurant’s fleet of solar ovens can feed up to 120 people every day.
Delicias del Sol Villseca, a restaurant north of Santiago, Chile, turned to solar energy when deforestation depleted its fuel source. The restaurant’s fleet of solar ovens can feed up to 120 people every day.

Summer’s arrived and the heat is inescapable. You don’t want to turn on the stove to make dinner, which will heat up the house even more. If you’re like me and don’t have air conditioning — or if you’re energy conscious and keep the AC low — cooking indoors can be unbearable. Instead, why not use the source of all this heat to your advantage?

Solar radiation is the most prolific source of energy on our planet. About 84 billion kilowatt-hours of light reach Earth every day — more than four times our global energy consumption. The challenge is to efficiently harness this energy. Most people settle for gathering solar energy by eating vegetables from their gardens or catching its reflection with their cameras. Trap that energy in an insulated box with some food — then you’ll really be cookin’!

The functioning principles of a solar oven are simple: concentrate, convert, contain. Sunlight — or visible light — is concentrated by several reflective surfaces to pass through a glass lid into an insulated box. A pot of food you put inside the box will absorb the light and convert it into longer-wavelength infrared energy, or heat. The insulation will inhibit the heat from escaping, and the wavelengths will be too long to pass back through the glass lid. So, they’ll bounce around and heat up your food. Ever leave your car windows closed on a bright, warm day? Then you’ll recognize the basic principles of solar cooking.

How to Build a Solar Oven

Nearly 20 years ago, as I was helping a friend build his straw bale house (at which point he figured out I was into “weird stuff”), he mentioned that some people he knew were teaching a solar-oven-building workshop. I was intrigued, so I sent in my 50 bucks to attend. Three weeks later, I found myself on a homestead out in the Kentucky woods, looking at the piles of plywood, cardboard, tinfoil and glass that were to become solar ovens. The instructors, Mark and Andy, had just returned from a nonprofit-sponsored trip to Peru, where they taught people how to build and use solar cookers. Many of Peru’s mountain villages suffer from deforestation, so solar cooking offers a good alternative to cooking with wood.

That day, using only hand tools, I built my own “yard appliance.” This solar cooker requires only cheap materials and the design is so simple: square, with an inner box and an outer box separated by 1 or 2 inches of insulation, and a glass cover on the inner box to let in sunlight. Additionally, four reflectors are arrayed at obtuse angles to the glass to focus more light into the box and raise its internal temperature enough to make cooking possible. We used plywood for the outer box for rigidity and durability, and crumpled newspapers for insulation. A variety of materials can serve as insulation, including sawdust, chicken feathers or fiberglass batting. Insulation is key, because you want to trap heat in the box as effectively as possible to offset shading by clouds that will invariably show up to block the sun. In optimal conditions, the cookers we built can heat to 400 degrees Fahrenheit in about an hour, which is hot enough to cook anything from a casserole to biscuits. That’s a pretty good appliance for only a $50 investment. For me, the deal was even sweeter — I married Mark’s sister a few years later, and we’ve been solar cooking together ever since.

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