Solar Ovens

Solar ovens (solar cookers) use the reflected and concentrated rays of the sun to cook food. In arears with clear, warm, and sunny days solar cookers are an excellent method of cooking food and purifying water.

Commercial solar ovens are available from a number of companies, such as the:

Solavore Sport Solar Oven - Portable Solar Cooking Package Complete with All Season Solar Reflectors, 2 Granite Ware Pots, Oven Thermometer, and Water Pasteurization Tool 

and the ...

Sunflair Portable Solar Oven Deluxe with Complete Cookware, Dehydrating Racks and Thermometer

Both of these solar ovens are excellent products, but tend to be a bit on the expensive side. You can build a solar oven yourself, for just a few rubles, that will be almost as effective as these commercial models. The WikiHow site has simple instructions on How to Make and Use a Solar Oven. There are even instructions on-line that show how to make a solar oven from a pizza box.

Dr. Mary Keith has published an excellent video on YouTube: "How to Make a Solar Cooker" that I recommend for anyone interested in making a solar oven. There are several other YouTube videos that demonstrate the construction and use of solar ovens. Watch a few of these videos to see various solar oven designs, but most importantly make a solar oven yourself as a practical fieldcraft and survival project.

The difference between cooking in a solar oven and cooking in a conventional oven or over an open flame is that solar ovens cook at a lower temperature over a longer period of time. Solar ovens work much like a ‘slow cooker’. The Solar Cooking Wikia offers guidelines for cooking with a solar oven.

To use a solar oven, you will need dark colored (i.e. black) cooking dishes. Darker colors absorb and hold heat better than lighter colors. The Granite Ware 4-Quart Bean Pot and the Granite Ware 3-Quart Covered Casserole Dish are both good choices for use in a solar oven. You should avoid using shiny pots and pans as they reflect the solar rays and thus retain less heat in the solar oven.

An important use of your solar oven is to use it to make water safe to drink by pasteurization. Contrary to common belief, biologically-contaminated water does not need to be boiled to make it safe to drink; it only needs to be brought to a temperature that is sufficient to kill all disease-causing organisms. This is known as water pasteurization. Because the pasteurization temperature is much lower than the boiling temperature, pasteurization results in great fuel savings when compared to boiling.

Pasteurization is a gentle heating process designed to reduce the number of viable microorganisms in a liquid to the point where they are rendered harmless. It is a technique that has been used for decades to lengthen the shelf life of milk and more recently is used to treat a wide variety of liquids - including juices.

The technique is really simple. All you do is gently heat the liquid (in this case water) to just over 65 degrees Celsius (149 degrees Fahrenheit) and then maintain that temperature for at least one minute. If you do that, the water is considered pasteurized and has been rendered safe from any microorganisms that may be lurking in the unpasteurized water.

So if it only takes 65 degrees to make the water potable, why does everyone say to boil the water?

When water boils, we get a visual indicator that it is at a certain temperature, 100 degrees Celsius (212 degrees Fahrenheit.) Unless you have a temperature measurement device - a thermometer or a water pasteurization indicator (WAPI) - the bubbles generated by boiling water are the only visual indicator.

Solar ovens are easy and inexpensive to build. They allow you to cook food and purify water anytime that you have a warm and sunny day. Solar ovens require no additional fuel, and they can operate unattended throughout the day. Of course, solar ovens are not the perfect solution to all of your cooking problems in the field – they don’t work at night, and on cold, cloudy, and rainy days they are much less efficient. Still, I believe that knowing how to build and use a solar oven to prepare food and purify water is a useful skill to have.