At-Home Stem Activities: Make a Solar Oven
For New Hampshire’s April school vacation week, when none of us is actually going anywhere, we decided to focus on things we could do if we did have some sort of wild vacation adventure and ended up on a deserted island.
Today, we’ll cook lunch on our “island” locale by constructing a simple solar-powered oven. With no more fuel needs than the power of the Sun, this activity is as “green” as it is practical! Note: with cutting and heating components, adult supervision for this activity is a MUST.
two different models of professional solar cookers (image courtesy solarcookingatlas.com/wikimedia commons)
Solar cookers heat food or water by harnessing the power of the Sun. Solar ovens usually include a reflective surface, to concentrate solar energy, and a sealed compartment, to absorb and trap heat.
Because these ovens are solar-powered, they do not rely on the burning of wood or fossil fuels. Globally, the use of solar cookers can help relieve air pollution and deforestation, as well as providing a reliable means of food preparation in areas where fuel is in short supply.
Today we’ll construct a simple solar oven with easily obtainable materials, to get us through lunchtime on our “vacation island.”
Activity: Make Your Own Solar Oven
Materials
Empty pizza box (The best option is the type of box used by pizza delivery restaurants, which are sturdy and have a top that easily opens & shuts. If one of these is not available, a bake-your-own-pizza box from the grocery store will suffice, with modifications—this is what we used for our demonstration.)
Aluminum foil
Plastic kitchen wrap
Box cutter
Black construction paper
Newspaper (preferred—we substituted crinkled white paper rolled in black construction paper)
Tape
Sunny day
Procedure
Have an adult carefully cut a three-sided square panel out of the pizza box lid with a box cutter. Leave about 1” of lid on each side of the panel. You should be able to fold along the fourth (non-cut) side of the square, and pull the panel back while the rest of the lid is still in its “down” position on the bottom of the box.
Wrap aluminum foil around the panel, shiny-side out. Tape in place on the back side of the panel, if needed.
Professional solar ovens use mirrors, rather than foil, for this element.
Keeping the foil-wrapped reflective panel pulled back (out of the way), use plastic wrap to create a double-layered plastic seal over the square hole in the box lid. Tape the plastic in place securely.
Place black construction paper in the bottom of the box
Why do you think we use black instead of another color of paper?
Create insulation for your oven
If you have newspaper, make four rolls of newspaper and place one along each of the edges in the bottom of the box. We didn’t have newspaper, so we rolled up some white paper and wrapped it in black construction paper, then put these black “insulation panels” along the bottom edges of the box.
Put a food item in your oven…Be sure to use a plate or container, so you don’t get the floor of the oven messy!
Put the lid of the box down, and ensure that it is tightly sealed on all edges. You should have a plastic “window” into your sealed cooking compartment, and a reflective panel that points downward toward the window.
Place your oven outside, in a position where the sealed compartment and reflective panel receive as much direct sunlight as possible. The sun’s light is strongest from 11AM to 2PM. If you’re using a pizza delivery-style box, you may need to use a ruler to prop your reflective panel upright, so that it doesn’t fall down onto the plastic window. We had the opposite problem: we had to use a rock on the back side of the reflective panel, to make sure that it stayed upright and directed the sun’s rays toward the cooking compartment. You could even place a small thermometer inside your oven to check on the temperature.
Check back later for a solar-cooked meal!
We melted cheese over tortilla chips. With enough sunlight, you could reheat soup, toast a piece of bread, even make s’mores…What did YOU cook in your homemade solar oven?
Please note: solar ovens take longer than electric- or gas-powered ovens to work—it took us almost an hour, just before noon, to melt the shredded cheese into sufficiently appetizing nacho consistency. For your health, we do not recommend using your solar oven to prepare meat, poultry, fish, frozen items, or other materials that require controlled cooking temperatures for safe consumption.
How Does It Work?
principles of a solar oven (image credit: howstuffworks.com)
As we explored in a previous lesson, energy from the Sun travels to the Earth as electromagnetic waves. Some of this energy is then converted from light to heat, on a molecular level, when the Sun’s rays strike matter on Earth.
In the case of your solar oven, rays of sunlight hit and are reflected off of the foil-covered reflective panel. The angle of the panel then bounces the rays of sunlight into the cooking compartment through the plastic-covered “window.” Once sunlight passes through the plastic wrap, it heats up the air inside the oven. Because the box is sealed, hot air becomes trapped and cannot get out of the oven. (This is similar to the greenhouse effect that we created in our Earth Day diy terrarium activity!) The black paper on the oven floor absorbs additional heat, and the insulator rolls along the edges of the cooking compartment prevent warmed air from escaping out the sides of the box.
Portrait of Horace Benedict de Saussure (image credit: wikimedia commons)
