Cardboard Solar Oven: Cook Food with Sunlight

A solar oven concentrates sunlight into a small insulated space, converting light energy directly into heat. This project demonstrates renewable energy, greenhouse effect, and thermal insulation concepts — all from materials you likely already have at home.

What You’ll Need

• Large pizza box or similar flat cardboard box
• Aluminium foil
• Clear cling wrap or an old glass pane
• Black construction paper or black paint
• Scissors, craft knife, ruler
• Adhesive tape and white glue
• A wooden skewer or straw (to prop the reflector flap)
• Food thermometer

Step-by-Step Instructions

1. Cut the reflector flap: In the box lid, cut three sides of a square panel, leaving the side nearest the hinge uncut. Fold this flap outward — it becomes your reflector.
2. Line the flap with foil: Glue aluminium foil (shiny side out) over the entire inner surface of the reflector flap. Smooth out bubbles for maximum reflectivity.
3. Seal the window: Cover the opening you just created in the lid with two layers of cling wrap, leaving a 1–2 cm air gap between layers. Tape the edges airtight. This acts as a greenhouse window.
4. Insulate the box interior: Line the bottom inside of the box with black paper or paint it black — black absorbs heat. Optionally stuff the sides with crumpled newspaper for insulation.
5. Prop and aim: Use the skewer to prop the foil reflector at an angle that directs sunlight through the cling-wrap window onto the black interior. Aim the oven directly at the sun.
6. Cook something: Place a small dish of food (chocolate pieces, a hotdog, nachos) inside on the black surface. Close the lid, check every 15 minutes, and record the internal temperature.

Safety Notes

• Temperatures inside can exceed 80 °C — use oven mitts when retrieving food.
• Never look directly at the reflected sunlight — it can damage your eyes.
• Do not leave the oven unattended outdoors on windy days as it can blow over.

Tips & Troubleshooting

• Best results occur between 11 AM and 2 PM when the sun is highest.
• On very hot days (35 °C+) the oven can reach temperatures sufficient to bake biscuits.
• A larger box and more layers of insulation significantly improve performance.