Introduction: The $5-$6 Solar Oven
So, a while back, being the Ecogeek that I am, I found this on www.ecogeek.org: http://www.ecogeek.org/content/view/2679/
...Which is pretty awesome, because people in less privileged areas would be able to use this, as mentioned in that article. So, my friend and I decided to give this a shot...and where else better to do it than on instructables!
The only part that really cost anything for us was the glass, because we didn't have it on hand. This was bought at Home Depot and a sheet of 12"x36" was bought, which cost a grand total of $10. We only used half, so it technically only costs $5.
All the other materials are from around the office and around the house, which cost us nothing, as it was really just trash.
It's great for cooking cookies, among other things. As you will see, the glass and extra weight provides added pressure, plus the heat which aides in the cooking of the food. As always, we recommend using a food thermometer before you eat the food to ensure the proper temperature of the food that you eat to prevent food poisoning.
**Disclaimer: We do not assume any responsibility for the quality of the food nor the quality of how cooked it is. By using this cooker, you assume that all food is safe to eat and do not hold the author of this Instructable, his affiliates, Instructables.com & their affiliates responsible for any of your misactions.
Step 1: Step 1: Gather Materials
- 2 Cardboard Boxes at different sizes
- Scrap Paper
- Black Spray Paint
- Glass Panel
- Duct Tape
- Aluminum Foil
- X-acto Knife
- Glass Cutter
- Paper Shredder (Optional)
- Bricks or Canned Food
- Food Thermometer
Step 2: Step 2: Check
Make sure that the boxes are not riddled with holes or tears. Also check to see that one of the two boxes fit in the other. The top of the boxes should be level with each other, or the walls of the inner/smaller box maybe a bit shorter than the larger box. The dimensions of the smaller box should be 2-3" smaller than the larger box (ie: Larger box= Width x Length x Depth; Smaller box= (Width-2" x Length-2" x Depth)
A hole can lead to a leak in heat and in pressure which means that your food will not cook properly. If necessary, seal with duct tape and extra cardboard.
Step 3: Step 3: Shred Paper & Fill
Since we didn't have a paper shredder on hand, we tore strips of paper by hand and made them
roughly about 0.5" to about an inch in width.
Make sure that the flaps of the larger box are not folded inwards. The strips of paper were lightly crumpled together and a generous layer of about 1"-2" was placed on the bottom of the larger box.
The smaller box was placed into the larger box.
The rest of the paper was lightly packed into the sides of the box.
Step 4: Step 4: Paint
Painting the smaller box before or after is entirely up to you, but we did it afterwards and it worked just as well.
Take the spray paint and paint the inside of the inner/smaller box. That way, this aides in the radiation from the sun being absorbed by the black paint which can cook the food quicker.
Step 5: Step 5: Attach Foil
Using the duct tape, apply some loops of duct tape with the sticky side out and place on both sides of the flaps of the outer box.
Take the sheet of aluminum foil and, with the dull side down, place securely on the inner part of the flaps on the other box. That way, the shiny side will face out on both sides. Fold excess foil on the outer part of the flap and secure with more duct tape on the outside.
Step 6: Step 6: Cut the Glass
Please be very careful on this part.
When cutting the glass, depending on the size of the glass you bought, you can either measure out the dimensions to fit the dimensions of the inner box or of the outer box. Either way would work.
Cut the glass according to the glass cutting kit that you bought. Using the glass pencil, mark the line that you will cut along, using a straight edge or ruler as a guide.
It is recommended that you place the glass on a piece of cardboard for cutting.
Next, take the glass cutter and apply a firm, but gentle force on the cutter and glass. Make sure that your hand is steady and that the cut is at a steady pace. Flip the piece of glass and repeat.
Place the ball end of the cutter under the glass and apply pressure on the edges of the glass to snap the glass at your line of cut.
Step 7: Step 7: Finally...
Place the cut glass on the top of the box.
And you're done!
Depending on the weight of your glass, you can either have more weight applied to increase the pressure within the cooker. Bricks or cans of food can be used and should be placed at the corners of the box.
Step 8: The Engineering Behind It All
The different parts of the solar oven function as so:
The shreded paper functions as a type of insulation. In its place, straw can be used. The paper and straw actually also holds pockets of air which is heated by the sun. Air is preferred over metal because metal can heat easily being a conductor; likewise, heat can be lost from the metal if the external heat is not constant. The paper acts like an insulator, so once the heat is trapped in the pockets of air within the stuffing, it will not escape as easily.
The foil helps focus the sun's rays down into the box.
The black paint within the box is a demonstration of radiation. Being of black color, there is absorption of the entire spectrum of light. As light is a form of energy which is converted to heat, the food will be able cook.
The glass and bricks keep an even amount of pressure through out the box so that, in addition to the heat, the temperature in the box will also be raised as a result of the pressure applied and that builds up within the box from the sun's rays. This helps the food to cook quicker.
Be forewarned that opening/removing the glass will release all the heat that was building within the box. If checking the temperature of the food, please make sure that you are absolutely sure that it is ready to be checked, otherwise you'll have to wait again for the pressure and heat to build up again.
So, having said that, have fun and get some good food cooking cheaply!