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Solar Ovens - Basic Guide to Solar Cooking


Publisher: Sustainable Guide, March 15, 2008

I have been using a solar oven for the past 5 years to cook what my family likes to eat. I could list everything it cooks here, but I'd sound like an infomercial. Just know that solar ovens bake, steam and boil. You name it, they can cook it. Okay, maybe not roast, suckling pig. But what it cooks, it cooks without electricity or those yucky, green-house gas (GHG) emissions. And so far, everything I've tasted, barring no mistakes on my part, tastes great. I feel that our solar oven purchase was one of our best investments. It has easily paid for itself in energy savings (not to mention peace of mind).

The questions most people ask me about solar oven cooking generally fall into a few main categories. I'll try to summarize what I know.

How Do Solar Ovens Work?
How Portable are Solar Ovens?
How Do You Cook in a Solar Oven?
What Can Be Cooked in a Solar Oven (besides a solar oven baked potato)?
How Long Does It Take to Cook Food in Solar Ovens?
Can Solar Ovens be Left Unattended?
How Much Money Can be Saved on Electricity by Cooking in Solar Ovens?
How Can Solar Ovens Make the World a Better Place?
History of the Sun Oven

How Do Solar Ovens Work?

There are a few different styles of solar ovens to choose from, but all function on the same basic principle by converting sunlight into heat. There are panel cookers, made up of reflective panels that surround the cooking pot. Generally, the pot is placed in a plastic cooking bag that helps to trap the heat. Curved concentrators, or parabolic cookers, cook at high temperatures by concentrating and focusing reflected light onto the food. Because curved concentrators cook at high temperatures, they need careful adjusting and constant supervision. Box cookers consist of an insulated box, a glass door and a reflective panel. Food is cooked inside the box where the heat is trapped.

There are many different variations of these three main types of solar cookers. You can find solar oven plans and build one, purchase a solar oven ready to use, or even invent your own. All solar ovens benefit from the use of a dark cooking pot with a tight-fitting lid. The Global Sun Oven we use is a combination of the three main types. It uses an insulated, non-toxic, black plastic box with a glass door on top. The box is surrounded by four reflective panels that concentrate sunlight into the center of the box where the food is placed on a hanging rack. The interior dimensions are 14" wide x 14" long x 8-11" deep. The angle of the box is adjusted with a notched leg that raises and lowers the box. The entire oven itself is also adjusted to face the sun. This solar oven easily meets the cooking needs of my five better than average eaters.

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How Portable are Solar Ovens?

Solar ovens can be built into a sunny wall in your home or a spot in your yard as permanent fixtures. More likely they are built for moving here and there. The Global Sun Oven we use is quite portable. It has a handle and is carried much like a suitcase. Still, I wouldn't recommend this solar oven for backpacking trips due to its bulky 21lbs. (9.5 kg) weight. Think home cooking or car camping. If you're on the move, you might go for the CooKit, a foldable panel cooker weighing only .5 kg (pot not included). It can be folded to the size of a large book. Think Pacific Crest Trail! Still, there is the Villager Sun Oven that is so large it is on a trailer. This puppy can cook meals for up to 1,200 people a day. Think micro-business! What I can say with great certainty is solar ovens are far more portable than any conventional oven and no extension cord is necessary.

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How Do You Cook in a Solar Oven?

Sun oven cooking has become part of our daily routine. When the sun comes around to the backyard in the late morning, I set the solar oven out in a level, shade-free spot, unfold the panels, dust them off and clean the glass door with a damp cloth. Then I adjust the box to face the sun and raise the notched leg to adjust the angle of the box, focusing the reflected sunlight into the center of the box. Sometimes I have no idea what I'm going to cook. But, within a hr. the temperature can get up to 350 degrees. The thought of wasting that free heat urges me to open the glass door and set something in the sun oven, even if it's just to steam some rice. Once the food is in the solar oven, it's just like any other cooking. I check on it every hour or so and adjust the box's position and angle as necessary.

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What Can Be Cooked in Solar Ovens (besides a solar oven baked potato)?

Whatever can fit in a solar oven can be cooked. I don't recommend baking anything that needs to cook at over 400 degrees. For example, pie crust. I have a hard time making a crisp, flaky pie crust in the sun oven. But I also feel that with enough tinkering and adjusting I could probably make a great pie. Luckily, I'm a better rule breaker than follower, so I've had a lot of fun inventing and experimenting with my solar oven recipies. Mmm, edible experiments. It's really hard to go wrong.

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How Long Does It Take to Cook Food in Solar Ovens?

Cooking times in a solar oven will vary with the quality of the sunlight, the angle of the sun and diligence used in adjusting the position of the solar oven. If it is partly cloudy or I don't adjust the box regularly, food will take longer to cook. Also, keeping the panels and door clean does decrease the cooking time. With attention to adjusting, on a hot sunny day, cooking times are the same as they would be in my conventional oven and if I plan carefully I can make 3 different dishes. Often, I can tell when food is ready just by the smell. As for the taste? Everyone who tries our solar cooking notices the food's great flavor.

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Can Solar Ovens be Left Unattended While Cooking?

One of the greatest benefits of solar oven cooking is that it can be safely left unattended. We will put chicken and veggies in a glass casserole or dutch oven, adjust the oven so that it will be facing the sun during the hottest part of the day, put the food in and leave for an all-day hike. We come home to a tasty dinner. The house is cool, hasn't burned down and life is good.

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How Much Money Can be Saved on Electricity by Cooking in Solar Ovens?

In my tiny mind, the energy savings is huge. We cook almost exclusively in our Global Sun Oven in the summer. In the spring and the fall it accounts for a lot of our weekend cooking. Our electric bill shows that our average daily use of electricity dropped from 20 KWH in the winter to 13 KWH in the summer. We have no electric or gas heat in the winter. So, the only way I can account for the drop is with the sun oven cooking, clothes line for drying clothes and slightly lower hot water use from the electric water heater. It adds up to be about $.88 a day or $26 a month in savings. Perhaps the dollar amount isn't astounding, but still, it is gratifying to know there are few small things we can do that will make a difference. Solar energy is, after all, the least polluting and most inexhaustible of all known energy sources. Still, if you want to estimate the actual energy savings possible, here's a website for you.

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How Can Solar Ovens Make the World a Better Place?

Beyond the obvious savings in electricity and reduction of GHG emissions, solar ovens are also helping worldwide to slow deforestation, desertification, soil erosion and flooding caused by the burning of firewood for cooking. Along the same lines, access to solar cooking helps women and children living in refugee camps by decreasing the need to search for firewood outside of the camps where they are often targets of violence. Solar ovens eliminate the need for firewood collection for cooking. Here's a short video demonstrating the cooking and insulation process used by a Darfur refugee woman in Chad.

Solar cookers are also being used to pasteurize drinking water. Access to clean drinking water is one of the most fundamental necessities throughout the world today. It is estimated that 5 million deaths a year are due to water-borne diseases. Boil water in a sun oven if you wish, but new research shows that water can be made safe for drinking by heating it to 65C (149F). At that temperature, all of the germs that can cause disease in humans are killed. So drink in peace.

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History of the Sun Oven

Sun Ovens were developed in 1986 by Tom Burns, a retired restaurateur from Milwaukee, Wisconsin, who was very active with Rotary International. From his experience in operating restaurants he knew a great deal about cooking and from his international travel he became aware of the ever-growing problem of deforestation. Tom took a concept that has been around for centuries and engineered into it more recently developed materials to produce the world's most effective solar cooking devices. With the help of the Sandia National Laboratories the oven was refined.

From 1986 to 1997 Sun Ovens were made and marketed by Burns Milwaukee, Inc. Thousands of portable models have been shipped to more than 126 countries around the globe. Sun Ovens have helped feed refugees in relocation camps, natives in remote Third World villages, workers at field sites, climbers on the slopes of Mount Everest, and soldiers during the Persian Gulf War.

In 1998 Sun Ovens International, Inc. was formed and the manufacturing was moved from Milwaukee to Elburn, IL (40 miles west of Chicago). Sun Ovens International, Inc. has expanded the use of the ovens by making them more widely available in the U.S. and around the world. Assemble plants to make Sun Ovens have been established in a number of developing countries to reduce the cost of the ovens and shipping to the people that need them the most. While thousands of ovens have been sent around the world, there are still more than 2 billion people who cook with wood and charcoal and as populations increase so will the need for Sun Ovens.

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