It’s not quite hot enough to fry an egg on the sidewalk, but a hot summer day like today would be perfect for making a solar oven from a pizza box! (This is a repost of one of our summer favorites.)
When my friend Sheila, who works at NREL (the National Renewable Energy Laboratory) sent me this project, I couldn’t wait to try it out. We first tried it out on a cool spring day in Minnesota and to my surprise, it worked. The oven didn’t get very hot, but we were able to warm a chocolate chip cookie enough to make it soft and melt the chips.
NREL suggests using your oven to make s’mores, which we’ve tried and is really fun. (We did it on Kare11 last summer.) The solar oven is surprisingly easy to make. It only took us 10 or 15 minutes..
You will need: 1 pizza box from a local pizza delivery store (Little Caesars, Domino’s, Pizza Hut, etc.), newspapers, tape, scissors, black construction paper, clear plastic wrap, aluminum foil and a dowel or stick to prop the lid up. You will also want to have some food to warm in your oven-marshmallows, chocolate, etc.
Make sure the cardboard is folded into its box shape. Carefully cut out 3 sides of a square in the lid of the box. Do not cut out the fourth side of the square, which is the one closest to where the pizza box lid hinges. Gently fold the flap back along the uncut edge to form a crease. See photo below!
Now, Wrap the underside (inside) face of the flap that you made with aluminum foil. Tape it so that the foil is help firmly but so that there’s not too much tape showing on the foil side of the flap.
Open the box and place a piece of black construction paper so that it fits the bottom of the box. Tape it by the edges. (We used two pieces.)
Roll up some newspaper and fit it around the inside edges of the box. This is the insulation. It should be about 1-1 ½” thick. Use tape (or other materials you can think of) to hold the newspaper in place. Tape it to the bottom of the box so that you can close the lid. (We taped it to the sides and had to cut the tape so that we could close the lid. Luckily our newspaper fit in tightly enough that we didn’t really even need the tape.)
Finally, cut plastic wrap an inch larger than the lid opening on the box top. Tape it on the underside of the lid opening. Add another piece of plastic wrap to the top of the lid opening. This creates a layer of air as insulation that keeps heat in the box. It also makes a window you can look through at the food you’re “cooking.” BE SURE THE PLASTIC WRAP IS TIGHT.
You are almost done! According to NREL, the oven needs to sit at an angle facing the sun directly so you’ll need to make a prop. You could probably just use a book or something under the hinged side of the oven. However, I missed this when I read the directions and we just put it flat on the ground. The flap of the box top needs to be propped open—a dowel or ruler works great. We used a wooden skewer that I broke the sharp point off of. This way you can change the amount of sunlight striking the oven window. Play with the angle of the flap to see how much sunlight you can get to reflect on the food.
Check every once in a while to see how well your food is being heated by solar thermal energy. If you’re is interested in finding out how the sun cooked your food, go to http://www.nrel.gov/ NREL’s website has great information on solar energy and many other sources of renewable energy.