Sunlight can be a practical source of energy for such everyday jobs as cooking, heating water, or warming up homes. The challenge is to find ways to transform sunlight into usable heat. The most efficient way to transform sunlight into heat is to shine lots of sunlight onto a dark surface. Dark surfaces absorb most of the visible light that falls upon them, and reflect very little. Visible light that is absorbed this way usually causes the dark-colored surface to warm up. Of all colors, black is able to absorb the most light, and produce the most heat.

The completed solar oven.

You are familiar with what happens to a dark-colored surface when sunlight strikes it: it will get warm. But without a little help, there is usually not enough heat produced to cook foods. To produce enough heat for cooking, it is necessary to shine additional sunlight from a wider area onto the black surface. This is easy to do with mirrors or other reflective surfaces, or with glass or plastic lenses.

The solar oven you will be building from this plan uses aluminum foil to gather sunlight. The foil-covered panels of the oven reflect sunlight into the cooking chamber, which is painted black. Heat is produced when the concentrated sunlight is absorbed by the black surface of the cooking chamber. The heat is contained inside the chamber with the help of insulation and a clear plastic oven bag. The result is a great solar cooker and yummy food!

Safety Precautions

• Use extreme caution when cutting cardboard with the utility knife. Extend the blade only as far as is needed to cut through the cardboard, and lock it into place. Do your cutting on a cutting board or piece of scrap plywood, cardboard, or a kitchen cutting board.
• Use sunglasses when working with shiny materials in sunlight.
• Solar ovens can get very hot! Use oven mitts or gloves to prevent burns.

Build It!

(Click to continue to the construction plans)

Test It!

The solar oven is now ready to be tested. If the glue and paint are all dry and it is a sunny day, you can warm up your oven in preparation for its first cooking job.

Place the baking tin inside the oven bag.

1. Place the oven thermometer inside the painted baking tin.

2. Slip the baking tin into the transparent plastic oven bag by placing the tin inside the oven bag and secure it using the plastic tie that came with the bag. Arrange the bag so that the plastic forms a smooth, unwrinkled window over the baking chamber.

3. Press the baking chamber tightly into the bottom of the reflector.

Warming and Cooking Food with the Sun

• If your cooker reaches 100 degrees C, you can use it for heating foods. If it gets to temperatures of 175 degrees or higher, you can actually use it for baking.

• The plastic oven bag is extremely fragile and easily torn. Handle it carefully, especially when the cooking chamber is hot.

• For cooking and baking, you will need to find small baking tins that fit easily into your baking chamber. To improve the baking efficiency, paint the OUTSIDE of any small baking tins you want to use with the same paint and glue mixture you used to blacken the inside of the baking chamber. Be sure to heat your painted tins in the oven without food to burn off any impurities before cooking with them.

• You can use your oven to bake brownies, cookies, muffins, bread, and other foods. You can also use your oven to warm soups, stews, pizza, and pastries. You can also bake "veggie packs" of mixed vegetables such as carrots, broccoli, onions, and potatoes.

• You may need to support the pot or tin using small stones or metal jar lids to keep them level inside the baking chamber. Whatever you use in the baking chamber, make sure it is oven-safe and free from paints, solvents, plastics, and other substances that you do not want mixing with your food. If you are not sure whether something is oven-safe, ask a teacher, parent, or adult supervisor.