In this project, you will design and build a functional solar oven using a cardboard box, aluminum foil, and plastic wrap. You will then test your oven by using it to melt chocolate and marshmallows for s'mores, demonstrating the conversion of light energy to heat energy.
If a cardboard box is lined with aluminum foil to reflect sunlight and covered with plastic wrap to trap heat, then it will function as a solar oven, reaching a high enough temperature to melt chocolate and cook a s'more.
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On the lid of the pizza box, draw a square one inch from the edges.
With adult help, use a box cutter to cut along three sides of the square, leaving one side attached to create a flap.
Line the inside of the flap with aluminum foil, shiny side out. This is your reflector.
Open the box and line the bottom with aluminum foil, then place the black construction paper on top of the foil.
Create a double layer of plastic wrap over the opening you cut in the lid, taping it securely to create an airtight window.
Take your oven outside on a sunny day. Prop the reflector flap open with the wooden skewer to direct sunlight into the box.
Place a s'more (graham cracker, chocolate, marshmallow) on the black paper inside the oven.
Close the lid and position the oven so it faces the sun.
Wait for 30-60 minutes, checking periodically, until your s'more is melted and gooey.
You can use a thermometer to measure the temperature inside your oven.
On a sunny day, the solar oven should be able to reach temperatures well over 150°F (65°C), which is hot enough to melt chocolate and soften a marshmallow. The aluminum foil reflects sunlight into the box, the black paper absorbs the light energy and converts it to heat, and the plastic wrap traps the heat inside, just like a greenhouse.
The design of the solar oven and the amount of direct sunlight.
The temperature reached inside the oven and its ability to cook the s'more.
The ingredients of the s'more and the location of the oven.
An adult should do all the cutting with the box cutter. The inside of the oven can get hot, so be careful when removing your s'more. Never leave a solar oven unattended.
Display your solar oven and explain how each part (reflector, black paper, plastic wrap) works.
If possible, make a s'more for the judges during your presentation (this may require a very sunny day or a heat lamp).
Discuss the potential of solar energy as a clean and renewable power source.
Dark, matte surfaces are excellent absorbers of light. The black paper absorbs the sunlight that is reflected into the box and converts the light energy into heat energy, which then cooks the food.
The plastic wrap acts like the glass of a greenhouse. It allows sunlight (shortwave radiation) to pass through into the box, but it prevents the heat (longwave radiation) from escaping. This is called the greenhouse effect, and it traps the heat inside the oven.
To make your oven hotter, you can try using a larger reflector flap, insulating the walls of the box (e.g., with crumpled newspaper), or using a more insulated box (like a styrofoam cooler). Making sure the oven is well-sealed to prevent heat from escaping is also very important.
