Display and demonstration of solar ovens at science fairs, where both the students and their parents visit, helps in emphasizing the importance of using renewable energy to an audience together. These ovens work on solar power and are therefore, an extremely cheap source of energy. Let us understand how to make a solar-powered oven for the fair. Steps and Execution Here is the process of making a simple solar oven. The materials required to make the oven are as follows:

• 2 cardboard boxes (medium and large sized)
• Cardboard sheet
• Pencil
• Tape
• Knife
• Glue
• Aluminum foil
• Newspaper
• Ruler
• Black paint

Steps

• The large cardboard box should be placed on a clean surface and its flaps closed with tapes. The other medium-sized box should be placed on the larger one and its outline should be traced with a pencil.
• Cut the large box in accordance with the marked outline which would create a rectangular hole at the top.
• Flaps of the medium-sized box should be glued to its sides. The box should be inserted into the larger one in order to check whether it fits snugly; it should be removed thereafter.
• An aluminum foil needs to be glued to the inside of both the medium-sized and large box. Once the glue dries, the medium-sized box should be placed inside the larger one. Top edges of both the boxes need to be adjusted to the same level.
• A cardboard sheet has to be glued to the base of the inner box. It should however, be covered with an aluminum foil that is painted black.
• Larger box fitted with the medium one should be turned upside down and placed on a cardboard sheet. The outline of the top portion of this box needs to be traced with a pencil. Outside the perimeter of this outline, one should draw edges on all the four sides having a width of 3-4 inches.
• The edges need to be folded and sealed with a tape. It acts as a lid for the solar oven.
• The lid should be glued to an aluminum foil on the underside.

More Oven Ideas Apart from the basic model explained above, the following ideas can be used in making simple projects. These models make good use of solar energy. Windshield Shade Solar Funnel Cooker A solar cooker can be made from a car windshield shade. To make a solar oven with the windshield, one has to fold it in the funnel shape. Velcro tabs can be stitched along the edges so as to attach them together. It helps in keeping the funnel shape intact. Once the proper shape is attained, the oven should be kept on a bucket. A square rack or wood block should be placed inside the solar oven which would serve as a platform to place the utensils. A black-colored pot should be placed on the square platform. The shiny surface and funnel shape of the oven helps in reflecting light onto the black pot. 'Parvati' Solar Cooker This type of an oven is made from three cardboard sections that are fixed together to form a conical shape. Let's denote the three parts/sections by the names A, B and C. Section A is the smallest and forms the base of this solar oven. It is a circular, disc-shaped structure with a radius of 4 inches. A circular cardboard piece of 3.6 inches is then pasted or attached to it in the middle. The gap between these two cardboard circles acts as a collar for connecting to part B. The section B is also formed by merging 2 pieces of cardboard each having a radius of 12 inches and 11.3 inches respectively. Paste them together concentrically and draw a concentric circle of 4.8 inches on it and cut the cardboard along this circle, so that section B has a hole at its center. This part B, unlike section A is not completely circular when used; we will have to cut out 125° piece out of it. It is actually a 255° section that remains of the circular B section, that is a 'C' shaped arc and has an inner radius of 4.8 inches which we are going to use. Join the free ends of the 'C' shaped cardboard together to form the middle section of the oven. The last (upper) section is named as C. Cut a cardboard circle of radius 24 inches. Draw a circle with a radius of 16 inches on it. Cut the cardboard half. Now cut the cardboard along the drawn circle. It is a semi-circular arc having an outer radius of 24 inches. The inner radius of this semi-circular arc should be 16 inches. Now paste the ends of this arc together to form the third section of the oven. Now, paste the parts named A, B, and C together. To connect the sections together, V-shaped cuts need to be created along the borders/collars. These V-cuts need to be interlocked to connect the sections properly. Paste aluminum foil on the inner surface of this structure so that it will reflect the sunlight. Your solar oven is ready. While demonstrating, place a tripod and a pot containing whatever you want to cook on the tripod.