Get roasting and toasting using your own solar-powered oven!
WARNING: Don't use your oven to cook meat or other foods that could cause illness if not properly cooked.
What you will need:
Pizza box
Aluminium foil
Black paper
Plastic sheet (e.g. overhead transparency)
Newspaper
Glue and sticky tape
String
Scissors
Pen
What to do:
Make a flap on the top of the pizza box that will reflect the sunlight onto your food. To do this, draw a square 2 cm from the edges on the lid of the pizza box.
Cut along the lines you have drawn, leaving one side of the square uncut. This side can be folded up to create a flap.
Once you have your flap cut out, cover it on the inside with aluminium foil.
Sticky tape the plastic sheet over the now open square on the top of the pizza box lid – this will help the heat stay inside your oven.
Now it is time to insulate you pizza box solar oven. Scrunch up newspaper and stuff it into the sides of the pizza box.
Place a sheet of aluminium foil over the top of the newspaper and smooth it out so that there is a box-shaped space in the middle. Use sticky tape to secure the edges of the foil to the box.
Cut out a square piece of black paper and glue it to the inside base of the box. You can now close the pizza box and get ready for some scorching.
Take your pizza box oven outside to a sunny spot. Position your reflective flap so it reflects the sunlight into the oven, remembering the sun will move over time. You can do this by taping string to the back or by propping it up with a straw. You will be able to see the ray of sunlight being reflected by the foil into the oven.
Now for the exciting part - place food inside your oven (e.g. muffins with cheese, marshmallows and chocolate) and watch it warm up!
We tested the heat inside our solar oven with a thermometer and it recorded 35 degrees even on a 15 degree chilly winter day.
What's happening?
The sun radiates heat and light energy. Solar cookers work by capturing sunlight and insulating the heat inside, a bit like a hot car that has been sitting in the sun all day.
The aluminium foil on the flap and walls reflects light inside the box and onto the black base.
When sunlight enters the pizza box, the black base warms, as the colour black absorbs the sunlights light and heat. In contrast, the colour white reflects light and does not get as hot. You can experience this for yourself on a sunny day by walking barefoot on white concrete and then on black bitumen or by wearing different coloured shirts.
The newspaper, foil and plastic sheet insulating the box are all helping to keep all the heat inside. It's better to have the newspaper scrunched up so there is a lot of air inside it. This works because air acts as a very good insulator when it is trapped.
Applications
This oven works on the sheer beauty of solar power. Solar power is a renewable energy source, meaning that we will never run out of it, unlike coal, so it's great for the environment.
More advanced solar cookers are built from metal and use a large magnifying glass to concentrate the sunlight to a central area. These solar cookers can reach temperatures up to 150 degrees Celsius – hot enough to use them like a conventional oven, although it may take a little longer to cook something.
Solar energy
Energy from the sun can be used to supply power to a house or building. Solar panels on the roof collect sunlight and transform light energy into electricity.
A solar panel is made up a number of solar cells. Solar cells are generally made from thin wafers of silicon. When sunlight hits a solar panel, it is absorbed into the solar cells, where its energy creates electricity by shifting the electrons of the silicon.
Solar energy is used in a wide variety of applications, from a household's electrical needs to providing power for watches, highway signs, and space stations.
Rooftop solar hot water heaters can also use the sun's energy by moving water through tubes in panels heated by the sun.
Insulation
Insulation is another way of saving energy in the house so it stays warm in winter and keeps cool in summer. Insulators can be a variety of materials, including fibreglass, aluminium foil, styrofoam, recycled plastic, and even a puffy down jacket.
Insulators reduce the flow of heat from one place to another, and are useful in buildings. Thermal insulation is a material or combination of materials that slows down the rate of heat flow by conduction, convection, and radiation.
It is usually the air entrapped within the insulation which provides the thermal resistance. Materials that make good insulators can keep other things such as food and drinks at a constant temperature. Eskies keep your groceries cool and fresh even though it's sitting in a hot car on the drive home, while a thermos keeps drinks warm. Woollen blankets are also great to keep you warm in winter!
