Last year I signed up to volunteer as an Engineer In Residence. The program matches professional engineers with public schools in Ontario. Once a month I spend a morning working with a class. Usually, we discuss engineering, cover a topic specific to what they are currently learning in science class and then finish with a building project based on what we discussed. So far I’ve done 4 presentations. Some topics have gone more smoothly than others, but I’m learning as I go and overall it has been a great experience. I get the chance to talk about science, technology, engineering, and mathematics (STEM) with the added benefit of promoting women in engineering by just being myself.
I’m back in the classroom after March break and will be working with two Grade 7 classes as part of their Heat in the Environment topic. One lesson I’ve learned is to always, always, ALWAYS test out the building project before setting the kids loose. I spent a morning putting together a solar oven for the building project we’ll be doing and thought I’d share it here.
Full disclosure: My end result was more like an environmentally friendly Easy-Bake (™) oven than a proper cooker. However, my aim was to demonstrate the science principles rather than make something capable of cooking lunch (although S’mores would probably work). I wanted something that will mostly work even if the kids are sloppy putting it together.
Project: Shoebox Solar Oven
Challenge:
Build a simple box cooker using simple materials in less than 1hour
Inspiration Websites:
These sites give directions that are a little more in depth, but should result in a cooker/oven that actually cooks!
http://solarcooking.org/plans/
http://solarcooking.wikia.com/wiki/Minimum_Solar_Box_Cooker
http://solarcooking.wikia.com/wiki/Easy_Lid
http://www.nmsea.org/Curriculum/4_6/pizza_box_oven/pizza_box_ovens.htm
Materials:
- shoe box (any cardboard box with a hinged or removable lid should work)
- aluminum foil (enough to line the inside of the box)
- plastic wrap
- tape (I used a combination of masking and duct tape. Plastic tape would probably work, but I worried that it might melt if the cooker is a big success)
- scissors or exacto (capable of cutting the cardboard)
- string
- thermometer (to measure your success)
Instructions:
1. Line the inside of the box with aluminum foil (shiny side up) and tape in place. 
2. Draw and cut a 3 sided flap in the lid (approx 1in from the sides of the lid). This flap will become the reflector to direct incoming sunlight into the oven box. The 4th side will act as a hinge.
3. Cover the interior side of the reflector flap with aluminum foil and tape in place.
4. Lift the reflector flap, cover the opening with plastic wrap and tape in place. This will allow sunlight into the oven, while keeping the hot air inside. Try to tape the plastic wrap on all sides to get as tight a seal as possible.
5. Tape a piece of string to the reflector flap to allow you to adjust the flap position.
Your oven is done!
- Open the lid.
- Place your food (I used a glass of water) and temperature probe inside.
- Close the lid.
- Place your shoebox oven in the sun.
- Adjust the reflector flap to direct sunlight into the oven box and get cooking!
Results:
Using just the sunlight coming in on a nomal March day in Toronto, it took 5 min for the air inside my oven to go from 20ºC to 30ºC. Success!
Notes:
During the 2hours the sunlight was actually shining through that window the water temperature went up to 38ºC. Not hot enough for actual cooking, but warm enough for a bath or the average load of laundry.
For the wrap up, we can discuss ideas for potential improvements.
- Larger box.
- Sealing the air in better (I only sealed my plastic wrap on 3 sides).
- Wrapping the outside of the box with an insulating material to hold the heat in.
- Adding reflector pieces or making it bigger to direct more sunlight into the oven.
- I’m open to suggestions! Leave a comment 🙂
