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.

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 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)

<p>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.</p><p>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.</p><p>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.</p><p>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.</p><p>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.</p><p>Any tips or ideas?</p>
<p>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.</p>
<p>I made this with a few minor changes to heat water. I spray painted the inside of both boxes black and used tin foil over the black paint. I also made my top flap out of the lid of a paper box and kept the overhang at the top to help the sunlight reflect down. From there I covered two 20oz bottles of water in foil and placed them inside the smaller box. Overall it was pretty effective as a solar hot water heater. I'll be sure to cite you in my lab report. ^_^</p>
<p>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. <br><br>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. </p>
<p>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.</p>
<p><strong>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</strong></p>
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
Very beautiful!!!!!!
This is the easiest method thanks
hi this is devang agnihotri from INDIA the design is very good and the best way to save L.P.G IN COUNTRY LIKE MY INDIA
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.
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.
Hi Solaroven,<br><br>Are you worried about the presence of paint and glue chemicals in a food-processing device?<br>
I don't know if the heat would be enough to cause chemicals to be released from the spraypaint, but it may be better to not use spraypaint or use non-toxic black spraypaint. Or you could tape black paper on the inside walls of the box. but the Elmer's glue should be fine since it's non-toxic.
You can use High-Temp grill spray paint. It's designed to be used in high tempratures and won't leech off toxic chemicals.
can i boil water with this <br>
Instead of cutting the flaps off, how about just flattening them to the outside walls of the box? They would add some insulation, then I would try using as many sheets of cardboard as would fit in the spaces instead of the crushed paper. All the corrugated and solid layers would add great insulation, I would think, as well as making the whole box stronger. I'll make one that way and report back.
I agree with you charlis1.&nbsp; If well fitted cardboard sheets were used to fill the space between the two boxes, I think the insulating value would be greater than wadded newspaper.<br> <br> However, IF the wadded newspaper prevents the outer box from heating above ambient, then our cardboard idea would be overkill.<br> <br> Additionally, to use our idea of all cardboard for the insulation, <strong>several </strong>more boxes would be required.&nbsp; I also agree however, that the full cardboard would add excellent rigidity to the assembly.
I really wonder if there is much use in painting the bottom black. Sure, black absorbs heat, but I doubt if that piece of corrugated cardboard is enough of a heatsink. Might as well do the opposite and glue alu foil to it.<br><br>Ofcourse cooking in a black pan in this contraption would be a good use of black
I built this today. I'll try cooking something simple tomorrow afternoon.<br><br>I love the idea of being able to make a simple lunch in one of these rather then using electricity and having the stove warm up my house on these hot days.
very nice, i like anything that deals in solar <br>keep up the good work, and thanks for sharing this <br>David
&nbsp;how hot can the internal temperature get?<br /> <br />
I haven't tested the internal temperature yet, there hasn't been much sun lately.
Hi there,<br /> I&nbsp;made it for a school project and haven't used it yet, but when I&nbsp;do I'll message you.&nbsp;<br /> <br /> Thanks for your interest.<br />
I have a fear of the cold and would like to go camping. How can I make a solar heater for a small tent?<br><br>Mlcanale@ aol.com
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
great simplicity idea!
LOL... whoever that is doing the paper crumpling..... you look like me! (Who's older...lol!)<br /> <br /> Just found that funny..... if that is actually you culture..... then it's even more funny, because I've gotten a glimps of your opinions, views, and obviously you're an inventor, tinkerer, green enthusiest, and out of box thinker..... it's creepy how alike we are.... yet stumbled into meeting eachother.<br />
The person in the picture doing the paper crumpling is also (me)&nbsp;the writer.&nbsp; Here it's definitely the culture, I'm in University right now studying sustainability.&nbsp; Just wrote a paper about ants, how when there's a room of, say, 7 ants they don't get much work done, and actually stop moving. But when there are more ants, they bump into each other and then the ant moves again. So, just like ants, the Sustainability Revolution is about spreading knowledge to each other so we get the revolution going.&nbsp; Good day and pleasure meeting you.<br />
Me encanto la idea de hacer el horno solar para los campamentos.<br /> Voy a probar este lindo invento Muchas gracias.<br />
You can also gain more heat by adding angled wings to the sides of the reflector panel thus:&nbsp; \_/.<br />
did you try it? let us see the results and how long did it take etc, thanks for the idea though its the time of year that a lot of people can start using these to really save.