While I have some construction to deal with, this is one of the intermittent posts that I will post right now with projects. My own solar cooker is buried at present, so unfortunately no images. But I hope the text explains things well enough. With some additional thinking and waterproof materials, these ovens can be adapted to make water distillers to purify water sources as well. At some point in the future I will be posting specifically about water distillers, but for now just the ovens.
While I reference primarily for nothern hemisphere, adjusting for Southern Hemisphere is easy enough to resolve, the numbers remain the same, the ordinal points differ in the discussion, and seasons are opposite but otherwise the general discussions are still fully applicable. I shall not belabor the matter further.
One of the most obvious “Passive Solar” Project is also quite inexpensive to make. Sadly most of the instructions are a bit lacking, but I did construct one just to see how effective it could be first-hand. Now a cooker can be as simple as a black painted piece of plywood, a truck tire inner tube a pane of glass and a dark cooking vessel it will work.
I made one, from one of the links below, but the “instructions” were severely lacking. I instead used boxes from a 10 ream “paper box” and a 1 bushel apple box. They fit together quite well. You only need the lower part of the paper box. You may not have the same box sizes in your part of the world, essentially you want 2 or 3 boxes- one that can slip over another box will work for what I describe as the “Bushell Apple Box” and then you need one that will sit inside those two that slipped together, with about 2 or three finger widths on all sides (depending how wide your fingers are) to work for the box section that gets cut down to fit inside that I refer to as a “paper box”.
The “short” instructions are to cut the top and bottom of the bushel box down so both still slip together to make a box only about 10 inches tall ( about 1 handspan when you hold your finger open measuring from tip of small finger to tip of thumb.) You then cut a rectangular cutout- cutting only 3 sides into the top of the box part that will become the top and allowing for about 1 inch of the top portion to support a pane of glass. So if you have a piece of glass 9×17 inches, you cut the flap opening to 7 by 15, or if the box is in good condition, 8 by16 inches. So the glass overlaps the edge of the carboard. one inch is about 2.56 centimeters.
Wrap the inside of the cover portion of the bushel box with foil. Using a spray adhesive to retain the foil in place is a good idea. next, place the top or bottom section of the paper box inside the bottom of the bushel box, and trim down the paper box section to be about 1 inch shorter than the bushel box. Take it out to cut it, and then wrap inside and outside of that trimmed box half.
So what you should have is the lower bushel box half with foil inside, the trimmed down portion of the paper box covered with foil inside and outside, the reason why you trimmed it shorter will becom clear in a moment. And the apple box cover with a flap cut in and covered with foil on the inside and the bottom of the flap. with glass secured with tape to the box top where the flap was cut into the box. Ideally you want the glass to be as close to the edges of the box as possible, but do take care as the cut glass edges are very sharp. You can mitigate that by cutting a narrow strip of “Duct tape” and wrapping that over the cut edge. Paper masking tapes can work, but the adhesive degrades quicky in sunlight.
Next wad up some news print paper, or other paper to act as an insulator, or you could use rigid foam but not stryofoam because it can off gas toxic fumes as it gets heated- the idea is you want an insulating layer between the lower portion of the apple box and the portion of the paper box you chose to use. Put in about an inch in the bottom evenly, then place the cut down portion of the paper box and try keep it centered as you continue to add your wadded up paper or rigid foam.
In use:
The foil will act as a reflector and as a radiant barrier. For best results, you may want to tip the box slightly towards the sun, but you will also want to put a wedge under the pot you are heating so it remains level. You can cut the box slightly taller, and cut the glass to a dimension that leaves just a little bit of the box around the edge to allow more light in, but you reach a point where the top starts to shade part of the solar box oven. The flap will serve as a reflector, so you want to use a narrow prop to hold reflector at optimum angle from the front, or tape a strap to the back so you can optimize the reflection for the conditions.
You will have no problem heating 2 quarts of water to 160 degrees in September near the 45th parallel, but it does take a while. Further North in the Northern Hemisphere it gets difficult. Also; you want to point the box cooker so it is slightly ahead of where the sun will be in about an hour. Flat black cast iron will work best as the cooking vessel. The reason you set it ahead is to have it at optimal alignment for something that may take an hour or two to heat.
Additionally:
A black surface facing the sun with a little oil, can be used to fry an egg once it has warmed up. There is actual footage around the web of German soldiers in WW2 during the battles for North Africa that show them putting some oil on the fender of their Panzer and then cracking an egg and putting it on the oiled spot to fry. It did not take long for it to cook. So you can just imagine what it was like for the soldiers of both sides in those conditions inside their tanks. But by applying the principles, you use a black cast iron griddle or shallow pan, heat in direct sunlight, apply your oil and crack your egg. Note: While some people will use the egg whites as a facial peel, the protiens will do their thing, and turn white after a few minutes- this is not quite the same thing, but is similar- your face is nominally about 98 degrees F, that black cast iron pan can become hot enough to cook an egg through, and be hot enough to at least pasturize the egg. (fully cooked and safe to eat). But if you are not sure, set everything up and use thermometers to make sure things get hot enough. Fresh asphalt makes a very good heat absorbing surface, they can exceed 140 degrees F.
As just a side note- you can make the asphalt more reflective and less hot by washing it with a simple mixture of portland cement and water. It also helps absorb oil drips too. This can help reduce your cooling costs of an adjacent building, but this is intuitive, I do not have actual numbers, but is a good suggestion for someone looking for a thesis subject for college.
Some of these links may be out of date, but they are some I have accumulated over the years.
Solar cookers
http://www.solarcooking.org/plans/cookit.htm
http://65.108.108.197/catalog/
http://www.freewebs.com/sunnycooker/index.htm
http://saliers.com/clubs/thermonuclear-cooking/rbc-portable/
http://www.freewebs.com/sunnycooker/datscookergallery.htm
http://sci-toys.com/scitoys/scitoys/light/solar_hotdog_cooker.html
http://www.azsolarcenter.com/technology/solcook-1.html
http://www.solarcooking.org/plans/default.htm
Another way to save money on fuel for cooking food is to use a wood fired oven, Brick ovens have a long history, as do the Terra Cotta vessels in use in the middle East and Asia. Below are a number of useful links for some different brick and clay ovens fired with wood and a few “Rocket Stove” designs as well.
http://www.quarterbyte.com/brian/brickoven.html
http://www.ovencrafters.net/
http://groups.yahoo.com/group/brick-oven/
http://www.fornobravo.com/forum/f6/le-panyol-construction-stability-1556.html
http://blackoven.idkhosting.com/index.html
http://www.ovenguy.blogspot.com/
http://www.traditionaloven.com/
http://heatkit.com/html/bakeoven.htm
http://www.frankspizzaoven.com/
http://www.networkearth.org/naturalbuilding/oven.html
http://www.geocities.com/mosesrocket/
http://clayoven.wordpress.com/
http://bensart1.homestead.com/breadovens.html
http://heatkit.com/html/bakeov06.htm
http://mha-net.org/docs/v8n2/wildac07b.htm
http://people.umass.edu/dac/projects/BrickOven/Instant_BrickOven.htm
http://www.geocities.com/ritashanty/buildoven2.html
http://members.tripod.com/~AoifeFinn/oven.html
http://www.bigoven.com/private/beehive+oven-recipe
http://www.traditionaloven.com/ovens.html
http://www.traditionaloven.com/building/home/incorporated_9x13_flue_steel_chimney_cap.shtml
http://www.traditionaloven.com/tutorials/pizza-az.html
http://www.traditionaloven.com/tutorials/concrete.html
http://www.stevenharris.net/
http://www.thefarm.org/charities/i4at/surv/stove.htm
http://altenciruits.wordpress.com/
The main blog.
http://altencircuits.wordpress.com/
The tangential blog.
https://passivesolarproject.wordpress.com/
The passive solar blog- outgrowth from some projects of mine.
Passive Solar Projects 