How to Make a Simple Cardboard Solar Oven

The sun is arguably one of the humanity's most important tool for survival. It gives off practically unlimited amounts of light that is used by plants to generate energy and animals for heat. It can be used to generate electricity with solar panels, hot water with solar hot water heaters, and many other uses. Even though technology can be very useful, for example gas ovens, natural and simple technologies like solar ovens can reduce fossil fuel use or even replace fossil fuels in places that don't have abundant resources, and it's an enjoyable project. The materials used can mostly be found locally from recycled sources which makes it even more sustainable.

UPDATE:

Thank you all for your insights on a better, more healthy oven.

First: use black cardboard paper or High Temp Black Grill paint for less chemicals in food

Second: Use Pizza Box for less volume to heat up for Pizza, Eggs, Hardboiled eggs, and put a thermometer in there to test that it is up to sufficient temperatures before eating

Third: For increased efficiency, heating use 4 foot aluminum foil reflector next to your oven facing SOUTH. For slow thermal cooking use a 1 - 1.5 cubic foot box with soda cans filled with water in to preserve THERMAL MASS.

Fourth: The larger alumnum foil will STRONGLY INCREASE HEAT in a fast way, with potential temperatures up to 300 degrees. Results will vary with climate and strength of sun.

Cheers and happy Friday,

Step 1: Finding Tools and Materials

I recommend taking one trip to locate/buy tools and materials for this job. The following materials are necessary:

-2 medium to large cardboard boxes that fit inside each other with 3-4 inches or so of space around the sides of the box. Also you can use a LARGE and Medium pizza box and similarly create insulation and a smaller space to heat up. Also necessary is a large piece of cardboard for the reflector that is as wide as the widest part of the large box and about 2-3 feet long. These can be found at most stores, just ask an employee for boxes they don't need anymore.

-1 roll of aluminum foil (75 feet is enough)
-a piece of glass or plastic fits over top of the larger box. This can be found at window stores; they often have extra glass laying around for free.
-tape measurer
-razor knife
-school glue
-black spray paint or black construction paper
-enough newspaper that will, crumpled, fill a bottom row and the sides in between the two boxes. This can be found at recycling centers.
-duct or foil tape
-two small pieces of wood (optional)

Step 2: Cutting Off Flaps of Smaller Box

Cut off the four flaps of the smaller box so they don't get in the way.

Step 3: Crumpled Paper on the Bottom

Crumple up pieces of newspaper one at a time until the bottom of the large box is lined. This will be an insulation that keeps retains heat in the box.

Step 4: Spraypaint the Small Box Black

Either spraypaint with Char-Broil High Temperature Grill Paint on the inside bottom of the small box black or glue a sheet of black construction paper. fitted to the size of the box, to the inside bottom of the small box. I recommend doing this outside and try to not inhale the fumes.

Step 5: Glue Aluminum Foil on Insides of Small Box

Squeeze a generous amount of glue on one side of the inside of the small box and then cover it with aluminum foil with a little bit extra over the top of the box so it the foil stays in place. Then do the same for the remaining three sides.

Step 6: Insulating the Sides

Crumple up one piece of newspaper at a time and fit it around the sides up to the top.

Step 7: Cut the Flap for the Reflector

Cut a piece of cardboard that is as wide as the widest part of the large box and about 2-3 feet long.

Step 8: Installing the Reflector Flap

Put the cut piece of cardboard a few inches down on one side of the box and then tape it to a flap of the large box. (Optional: you can cut two small holes in the piece of cardboard and flap of large box once they are together and put two small pieces of wood in place two help hold the cardboard pieces together.)

Step 9: Putting Aluminum Foil on Reflector Flap

Apply a generous amount of school glue on one side of the reflector flap and cut aluminum foil to cover the entire side of the flap.

Step 10: Place Glass or Plastic on Top of Large Box

Lastly, place the piece of glass or plastic on top of the large box and tilt the reflector in towards the center of the boxes. To cook something, find out how hot your new solar oven gets by putting solar oven in an open place with as few obstacles around to reduce shadows, and then face the reflector towards the sun. Then, place a thermometer inside and check it occasionally to determine how hot your solar oven gets. Feel free to experiment with different methods of cooking things, or look online for guides on how to cook using your solar oven. Thanks for reducing your fossil fuel use, cooking a more natural way, and I hope you make some scrumptious meals!

Comments

[fastermx]

I want to ask if anyone here can give me some good pointers about making a solar oven with cardboard boxes. You know, tips on what to do and what NOT to do, stuff like that. I'd like to know how long it would take to cook about 2 lb of dry beans in water to the point where they're very tender.

I live in Mexico, in a working-class neighborhood. I told them about ovens like this several years ago, but I guess they didn't really believe it would work. Mexico, however, is a perfect place to use these ovens, since most days are sunny.

Lately, though, the price of gas is over 400 pesos, so now I think they may sit up and listen, especially if I can make one and SHOW it to them.

Most Mexicans eat a lot of beans, even if they're well-off. Beans aren't terribly expensive, but the hours on the stove now makes them costly to cook. They usually take 4-6 hours on the stove.

I guess you could say I'm trying a project that I hope will become a fad here. It will help many people struggling to make ends meet.

Any tips or ideas?

[sitaifun]

These links should help you arrive at a design suited for your application.

Solar oven designs:

http://solarcooking.wikia.com/wiki/Category:Solar_cooker_plans

More designs:

http://solarcooking.wikia.com/wiki/Compendium_of_solar_cooker_designs

[Sharrygranny]

First of all, lets talk about cooking beans. Try to get beans picked in the current year, they cook quicker.

Second, beans should not EVER need to be cooked this long. Rinse the beans, pick out the funny stuff--and soak them in lots of water over night. Dump water off, and the next day, if they are fresh, they will cook in in lots of fresh water in less than 2 hours. Then you can add them to sauces or 'bake" them, but boiling them in water, with a few onions, maybe some bacon or ham or ? and salt, is the proper cooking method and can be done on a "Rocket Stove" with a few twigs and small sticks, or try them in the solar oven in a black pot. After the beans are cooked, add seasonings, and bake them in your solar oven. Trying to make baked beans with dry beans ? I don't know how long that would take and how much liquid, but forever' would be a guess.

[GarethP]

Hi change-agent, el Mexicano,

This idea of urs seems great. Dont worry about the opinions other others, as u say that will change when the standard petro/fossil feuls dont stack up.

Just get going and start experimenting with local recycled items..glass or plexi glass may be difficult.

Organise a small feast day and invite positive friends and influencers in ur community.

Maybe have a few starter kits ready to go as door prizes...prendi?

Contact the local scout group and demonstrate to them...in through the back door to the parents.

Contact local social welfare agencies who may want see a demo to lhelp out less privileged , even homeless should able to use it. Let me know how u go?

regardes gareth, Noosa Heads<Australia

[lbrouse]

I have taught school (7th grade, high school technology, chemistry and physics, plus college-level chemistry and instrumental analys) for 13 years. My high schoolers have built models of various passive solar houses. The models that had no thermal mass inside rapidly increased their temperature to over 140 degrees. Several models that had collector flaps with aluminum foil coating that focused 4 square feet of input area into a 4 square inch collection area lined with black paper, reached over 450 degrees F within less than 1 minute. Models that had thermal mass (water inside black painted soda pop cans) increased the interior temperature more slowly but collected and stored more total heat. The high specific heat of water allows the heat to be stored without incrasing the water temperature very many degrees. I suggest experimenting with as many combinations of collection, insulation, and thermal storage as you can. You will begin to get a FEEL for the way these systems work and which variables will give you the characteristics you desire.

[solaroven]

Many thanks for the experience and insights on using soda cans with water to improve thermal mass for longer slow cook times, or no thermal mass to rapidly increase temperature with LARGE ALUMINUM FOIL cardboard with surface area of 4 feet.

[solaroven]

Thanks for the suggestions. I will experiment with more insulation and thermal mass, e.g. soda cans or other metal cans with black paint. It would be more efficient if the heat were stored within the oven, as storing heat can create higher temperatures.

[baoq12]

Hi you. I did try solar cooker like you but not effective as expected. I've tried boiled eggs in 2 hours but still not ripe eggs. You know why not? Thanks

[solaroven]

To increase temperature and heat a smaller area for eggs, pizza, hard-boiled eggs, etc. use a "PIZZA BOX" for the oven box. The rest of the project remains the same--black spray paint inside, 1/8-1/4" glass sheet over top of pizza box, and aluminum foil on the top of box for light refraction into the box, using an arm prop like a dowel rod to keep the box up. It could take 2 hours for an average meal to cook. Warmer day and stronger sun - faster cook time.

[Dylanvan69]

It smells like Mexico

[Mlcanale]

I have a fear of the cold and would like to go camping. How can I make a solar heater for a small tent?

Mlcanale@ aol.com

[Dylanvan69]

have you ever looked it up?

[oakleaf1]

Try this concept from THE MOTHER EARTH NEWS. You'll have to figure out the modification to adapt to a tent, but the design should work. http://www.motherearthnews.com/Do-It-Yourself/1977-09-01/Mothers-Heat-Grabber.aspx

[thomdickey]

I am really glad I found this & it is so very simple that even a person like myself can put one of these together. It is certainly going into my book that I am compiling for DIY Survival. Not that I am going to publish it since it is going to be mostly other people's work but for me, friends, & family. Thank you

[amy.l.marks.9]

Many years ago (may more than a decade?) we made something like this in Girl Scouts. To simplify we had used a oven turkey roasting bag instead of glass or plastic, you can cut some of the sides of the bag to make it a large single thickness. It can stand heat. It was easier (and cheaper because of the little bit of money we had from dues). I think the temperature may have been lowered. But in a situation where you may have to improvise, the idea is there. We did slowly cook some small meat loaf bites that were stuffed in the bottom of muffin pans. We had put it on a metal mesh cookie cooling rack to circulate heat.

[Giesterfarher]

My sister is a school teacher, and has her students make these from time to time. I've looked at a few of the examples her husband has made at home, and he likes to use fiberglass insulation wrapped in aluminum foil for the insulation between the inner and outer boxes.

On a 85 degree day in spring, my digital thermometer showed 540 degrees in less than 4 minutes using a glass top and glass mirrors inside, with aluminum foil reflector flaps. With the flaps folded down out of the sunlight, the temp is a much more manageable 310 degrees.

[jaytea1973]

We made one of these about 20 years ago while camping and it was amazing how well it worked. The whole chicken that we cooked was the juiciest and best tasting ever. It does take a long time, but it can be cooked within a day. The instructions were a little different and they came out of a library book (this was before we had a computer and the Internet), but I'm sure the results come out the same.

[diy_bloke]

I heard once it increases efficacy if you actually place the pan in a plastic bag in the oven and put it on a spacer, like say a pan rack

[joshem]

Very beautiful!!!!!!

[Andy Andikko]

This is the easiest method thanks