As the focus on personal preparedness grows across the U.S., so does the idea that emergencies or disasters may last much longer than some people believe. The ability to not only have food but to cook it without gas or electricity becomes a real concern. Enter the solar oven, a lightweight and simple tool that can be easily purchased or made with little cost or effort.
Solar cookers are able to harness the power of the sun’s energy to produce enough heat to cook food. Light enters the top of the box and is reflected into the device’s center. This action, along with a dark plate or pot, allows the cooker to reach serious temperatures. While the actual temperature inside is determined by factors such as the number of reflectors and glass, simple cookers can easily reach 300 degrees Fahrenheit inside. Most solar cookers are lightweight and portable, making them a solid addition to any disaster kit.
The basic function and principles of a solar cooker are pretty straightforward and can be broken into three sections. First, light is concentrated from the sun onto a cooking surface. This can be magnified by the presence of multiple reflectors. Second is the conversion of light into heat. Solar cookers concentrate sunlight onto a cooking plate or pot that has been made black to maximize absorption. As the light is absorbed into the black material, it creates heat. Finally, the heat is trapped inside, reducing convection and creating a greenhouse effect. When combined, these factors create a system that is easily capable of cooking a variety of foods.
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While there are many variants across the spectrum, there are three general styles of solar cookers. The box cooker is the most common and popular style seen today. A box cooker can be made out of a variety of materials ranging from plywood to cardboard. For maximum effectiveness, this design requires two boxes, with a smaller one placed inside a larger outer box. This creates space for insulation, such as paper or even fiberglass, to be packed, creating a barrier to help prevent heat loss from the internal cooking box.
The top for a box cooker is a clear piece of material that allows the sun to enter the box yet prevents UV rays from escaping. Common covers are plastic sheets and tempered glass. The final part of the cooker is reflector panels that are added to help concentrate the sun’s rays toward the cooking pot.
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Another version of the solar cooker is the panel cooker. Less complicated than a box cooker, it consists of three primary parts: a cooking pot that has been darkened to help absorb heat from the sun, an oven cooking bag or clear glass bowl and a reflector panel to direct the sun onto the cooking device. The reflector panels can be made from a variety of materials, including aluminum foil over cardboard or polished sheet metal. The bag or bowl allows the sun’s rays to enter and drive up the heat while at the same time preventing escape. A panel cooker in most cases is easier to build and less expensive.
The last common style of solar device is the parabolic cooker. Also known as a concentrator cooker, it focuses the sun into a single point. With this focus being on the bottom of a pot or crock, it heats up quickly and to very high temperatures. The design is simple yet effective. A series of formed panels are assembled to create a curved reflecting surface resembling a satellite dish. This allows the sun to be aimed at a small, single point. The speed at which they heat up and the temperatures achieved make the parabolic cooker dangerous if not handled correctly.
While not as portable or inexpensive as other options, the temperatures reached with a parabolic cooker make it an effective survival tool. A point worth noting is that temperatures achieved in parabolic cookers can be dangerous and can cause severe burns. Unattended food can quickly burn just as it would with conventional cooking methods.
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By following good food-handling procedures and using a food thermometer, just about any type of food can be prepared in a solar oven. Additionally, a solar cooker reaches sufficient temperatures to boil water, making it an important tool. While boiling water is a proven method of killing bacteria in water, you can also use your solar cooker for pasteurization. Pasteurization occurs when the water reaches 150 degrees Fahrenheit and is maintained for a minimum of 20 minutes. This doubles the use of the cooker not only as a way to produce hot meals, but as a way to provide safe drinking water.
While not as common, some of the other uses of a solar cooker include dehydrating food, sterilization, drying clothing and coffee/nut roasting. There are a number of commercially available cookers on the market today and it seems to grow weekly. Add to that the fact that anyone can construct at least a basic cooker on their own and these two factors make the solar oven an easy addition to any survival kit.
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This article was originally published in the SURVIVOR’S EDGE™ Fall 2015 edition. Subscription is available in print and digital editions here.