Instructables
Picture of 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.
 
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Step 1: Step 1: Gather Materials

Materials Needed:
- 2 Cardboard Boxes at different sizes
- Scrap Paper
- Black Spray Paint
- Glass Panel
- Duct Tape
- Aluminum Foil

Tools Needed:
- X-acto Knife
- Scissors
- Glass Cutter
- Paper Shredder (Optional)
- Bricks or Canned Food
- Food Thermometer
Old jeans make for great installation. I am so excited to use a solar oven and this is a great design and I can not wait!!! what have you cooked in it so far and honestly how was it??!!!
wushuair (author)  judgemargaret3 years ago
We made cookies the other day two years ago and they cooked in about 30 mins, using a black pan. So I'd say pretty successful?
wushuair (author)  judgemargaret5 years ago
Unfortunately, it's been nothing but rain here in MD. But, in a couple days it should clear up and we'll keep you posted on what we cook up.
dalesd5 years ago
Nice design.  I like the simplicity.
I would like to correct one aspect of your engineering: I did a quick calc, and the weight of the glass isn't holding in any significant pressure.  I estimate the glass weighs about 5 lbs and has an area of ~200 sq in.  That's 0.025 psi.  Even if you add 15 lbs of bricks, that's only 0.1psi.
wushuair (author)  dalesd3 years ago
Hmmm- good point.
cdltpx5 years ago
I built a solar oven out of a dog house roof a plateglass window and a parabollic mirror made chicken and rice one time after ward could not get the device to cook again never regained its seal. It is important that you keep the device air tight. I will take a pressure cooker and paint it black vent it through the top of the oven and cook something I bet this would be an excellent cooker.
wushuair (author)  cdltpx5 years ago
This model will keep the oven relatively air tight. My partner in crime and I had taken this into account. Being engineering students, we argued about this using the universal gas law (dorky, I know). The Charles & Boyle Laws state that pressure will increase with temperature, and vice-versa, if the volume is held constant. The weight of the glass is sufficient to weigh down the air in the box and prevent most of the air from escaping.
mr_man wushuair4 years ago
Even if the box was air-tight, any internal pressure would cause the cardboard walls to bow outward.  This increase in volume would decrease the pressure until there was essentially no pressure left.  This is why pressure vessels have rounded shapes and no corners (They are never box shaped).  There is simply no way that a box like this will contain any meaningful pressure.  Sorry.

Yes, I'm an engineer and I understand the gas law inside and out.  PV=nRT

Excellent instructable though.


wushuair (author)  mr_man3 years ago
Wow, a year late, but good point!
azeem777_pk3 years ago
I have created a solar oven using WinBoard.
Did pretty good insulation. (spent a lot of money and time as well)

Maximum recorded temperature is 215 Fahrenheit - 101 Celsius
I want to move it up to 250 Fahrenheit.
I think my glass window is not air tight.

How can you air tight a solar oven?
Any idea???

--regards--
wushuair (author)  azeem777_pk3 years ago
You might want to try some caulking that would be able to withstand those temperatures upwards. Or some weather seal rubber. If you're going to use caulking, I would seal it from the outside so that when you're cooking, the fumes won't affect the food. Also, keep in mind you should probably get the weather resistant caulking to prevent wear from the sun/heat.

Hope this helps! Please let me know how it turns out!

Try something like such: http://www.acehardwareoutlet.com/productdetails.aspx?sku=998033846&source=GoogleBase

What does a WinBoard look like? Could it be also that your container is materially porous?
wendilane4 years ago
 Suggestion for cutting glass to ensure a better score mark for snapping - dip the tip of your glass cutter in automatic transmission fluid.  this will help keep the cutting wheel cool, and render less chipping of the score mark, giving you a cleaner cut which is less likely to break under a stress fracture.  If you end up picking up a more expensive reservoir cutter, ATF is the same fluid you use to fill the cutter with.

Another suggestion is to have a finishing grade sanding sponge with you.  After you are done with your cut, lightly sand the edges of the finished glass to they are unable to cut you (this is also called seaming the glass).  This will also protect against stress cracks from a chipped edge.
Don't people usually use a black pot? Wouldn't the black inside make the box catch fire? Or maybe it just won't get that hot cause it's not that focused. Have you used this? What were your cooking times or other heat measurments?
To start a fire you need three things oxygen fuel and an ignition source. Remove anyone of the three and you will have no fire. This is the basics of fire prevention and fire fighting. The oven if constructed properly will not allow an air exchange no oxygen.
wushuair (author)  spamhaterbloodboy5 years ago
You can use a black pot. With a black pot, it is able to more easily capture radiation (due to its color) and is able to conduct better (because of its material composition).

I have cooked cookies in this box (and forgot to take picture =/ ). On a sunny, Maryland day, around 86 degrees (Fahrenheit), it takes about 20 minutes, although they came out burnt. The cooker was in direct sunlight. Our thermometer didn't record the temperature that high, so we couldn't really read the temperature.

I have to agree with you that, because the glass isn't focusing the sun's rays, the box will not catch on fire.
I've read other simple solar oven plans that say to paint the outside of the cooking pot with flat black paint, and to line to inside of the smaller box with aluminum foil. I plan to give this a try very soon. I've collected most of my materials. I've never posted an instructable. Maybe I'll make this my first. Anyway, thanks for showing us your solar oven. I enjoyed reading it.
tstens5 years ago
Can plexi or lexan be substituted for the glass?
wushuair (author)  tstens5 years ago
Originally, we had thought of using Acrylic; but decided to go with something authentic. Plexiglass or Lexan can be substituted: Glass was also preferred for us because it was also heavy as a material which leads to higher pressure being able to be built within the chamber. But if you plan to use bricks or weights to help build the pressure, it shouldn't be a problem. Think "greenhouse effect"...
strmrnnr5 years ago
Nice job! I am wondering if that thermometer stabbed through the side of the boxes might give a pretty accurate reading of the internal temperature? I think it might but am not too sure how they are at taking air temperature. What do you think?
GEEK1 strmrnnr5 years ago
I would say that it might work. Thats a pretty decent idea.
wushuair (author)  GEEK15 years ago
I guess I should have been a bit more clear. Using a food thermometer is very specific to food. If you're cooking meat, it's something you want to use to make sure that you aren't under or over cooking it. Hitting the right temperature usually means that you're getting the right temperature to kill the bacteria and still have something edible. If you want to measure the internal temperature of the oven, however, you should be using a regular thermometer. Or, for the totally awesome engineering version, use thermocouples.