Help
Around the world, solar ovens, or "solar cookers" are increasingly used to reduce people's reliance on firewood and other fuels in areas that do not have electricity or have an unreliable supply. Even if you have electricity, however, a solar oven can be an effective, energy-saving addition to your cooking tools. What's more, building your own solar oven is an easy, fun project. The only materials you will need for this simple design can be found around the house or at a local hardware store.
Things You'll Need
Two cardboard or wooden boxes, one smaller than the other
Reflective material such as Mylar, the inside surface of chip bags, metallic auto sunshade, aluminumized or Mylar bubble wrap, Mylar balloons, space blankets, mirrors, or polished metal. Aluminum foil can temporarily be used but will soon tarnish and will need to be replaced often.
* Piece of cardboard or thin wood
* Tape or rubber cement
* 8 sticks/rods (short)
* Newspaper
* Black construction paper/lightweight cardboard
* Stanley knife
* Strong glue
Construction
Line the entire inside of the smaller box with something reflective such as Mylar
Centre the smaller box inside the larger box, and fill the excess space around it with crumpled up newspaper. The more tightly you can stuff the newspaper in, the better.
Find (or cut) four pieces of cardboard or wood that are roughly the width of the smaller box's sides. These will be your reflectors.
Cover each of the reflectors with reflective material. Make sure it sits tightly around the reflector, and smooth out any wrinkles or folds. Secure the material with rubber cement or tape on one side of each reflector.
Hold one of the reflectors at about a 45 degree angle, with the base touching the outside of the small box just below the box's top.
Position one of the sticks or rods on the rim of the larger box (or slightly below the rim on the outside of the box) so that it will support the reflector at the 45 degree angle. Glue the rod in place and hold it until the glue dries so that it will maintain the correct position.
Glue a second rod to the larger box at the same angle as the first. The two rods should be spaced so that the reflector can steadily rest on top of them at a 45 degree angle to the smaller box's rim.
Repeat steps 6-8 for each of the four reflectors (one for each side of the box).
Lay the reflectors down on top of the rods, with the back side of the reflector facing the rod. Glue the reflectors to the rods to add more stability.
Position the oven in full sun and cook. That's all there is to it! Put food in the smaller box to cook it. It is best to cook the food in jars or on a small, dark baking pan. Experiment with cooking times and how and where you place the box. You may need to reposition your box several times during cooking to catch the sun.
Tips
You must use the oven in a sunny area. The heat energy comes from the sun.
Positioning the rods supporting the reflectors will be much easier if you have someone to hold the reflector at the correct angle while you position and glue the support rod.
To make your oven more efficient, and to get it to cook at higher temperatures, you need to trap in the heat. Without a cover hot air will rise bringing in a constant flow of cooler air. Oven cooking bags are cheap and easy to use. Seal the cooking pot in the bag. A pane of glass, preferably double-pane glass is an alternate solution. The glass should be slightly wider and longer than the smaller box, but small enough so that you can easily remove it from the inner box.
Another way to make the oven more efficient is to use specular film instead of aluminum foil for the outside reflectors. It can't be used inside the oven because it can't stand the heat.
In a pinch you can heat precooked foods such as canned goods with the double zip lock bag trick. Put the food in a small zip lock bag and put the small zip lock bag in a big zip lock bag. The bigger bag traps the heat in.
Warnings
Exercise caution with uncooked foods. Solar ovens are effective almost anywhere you can get direct sunlight, but you can't set the temperature and determine cooking times as surely as you can in a conventional oven. Make sure food is cooked to the recommended temperature by using a meat thermometer.
Be careful when handling food or utensils inside the oven or when removing the pane of glass (if present). Since this is an oven, these can get very hot. Use potholders, tongs, etc. as you would when working with a conventional oven or heat source.
