From an Abandoned Satellite Dish
In many parts of the world outdated, abandoned satellite dishes such as the eight-foot-across (2.4 m) one at the right clutter the landscape. They are abandoned because they have been replaced by much smaller dishes, or by technologies not needing such dishes. These dishes are a valuable resource.
In early 2004 a neighbor gave us the dish at the right, just to get rid of it. We removed the signal-collecting apparatus suspended at the focal point in the center of the dish, and the metal webbing between the ribs. Then we were ready to start adding things.
For $27.50 a 50-ft x 20-inch roll of aluminum flashing was purchased from the local hardware store. After carefully measuring the spaces between the satellite-dish's ribs, with tin-snips I cut out 16 triangular aluminum wedges. The dish was factory-made with each of its ribs having slots along their entire lengths, so we were able to fit the triangular wedges in place by sliding them into their slots. While I cut the wedges, a couple of friends positioned the wedges. It took us about half a day to do the whole thing, with the most time-consuming and difficult part being positioning the wedges.
At the left you see how we built a platform where pots, skillets and the like could be placed during the baking process. The platform was constructed from an upside-down, metal-wire frame used by florists to hold standing flower arrangements of the kind seen at funerals. Then an aluminum tray salvaged from an abandoned refrigerator was attached to that frame, with metal clamps.
The resulting creation boils water, fries eggs in a skillet in ten minutes, and bakes a perfect skillet of cornbread in less than half an hour.
Total cost: $27.50. We had the flower stand and clamps on hand.
WARNING: This is a powerful apparatus. It can surely damage eyes, and I know from experience that it can make painful burns. Notice how I am grimacing in the picture. If you should accidentally put your face at the light's focal point, your vision might be impaired permanently!
In 2005 I found myself in California's Sierra Nevada foothills so I built a second dish, the one shown at the right.
This time the dish a neighbor gave me was larger than my Mississippi model, plus the ground here was so rocky that I couldn't sink a pole for the dish to stand on. You can see the wooden platform I built for the dish. Propping up the dish from behind with a forked stick, the dish can be manhandled enough to follow the sun for several hours. Note the white rope with which the dish's lower rim is tied to the frame's crossbar, and the heavy log section at the right. These keep the dish from rolling off.
I used two rolls of aluminum, costing about $40. Unfortunately, when I got home I found that I had two kinds of aluminum -- a thin, highly reflective kind and a much firmer but powdery-surfaced kind. The thin sheeting was good because of its reflectivity, but it tended to crinkle and warp so that the surface ended up bumpy, causing a more diffuse focused spot. I'm not really sure whether it's better to have a wrinkled surface with high reflectivity, or a firm, powdery surface.
Also, with the larger dish I simply couldn't position the last panel in place, at least not with the thin, curling aluminum.
Whatever the case, this second cooker is quite as good if not better than the first one. I suspect it's less efficient but its large surface compensates for that. It produces far more heat than I need. I've learned when to place my skillet at the focal point around 10:30 AM and just let it sit there as the sun moves the focal point across the skillet's base, and by noon I have a perfectly cooked meal.
Now I'm more convinced than ever that this concept really works, and that there's enormous potential for the abandoned satellite dishes scattered all across the world.
In 2006 I found myself in the Yucatan of Mexico where I made a solar cooker of a completely different design, one made of "found parts," as shown at the right. "Found parts" were used because of the difficulty of finding -- and the expense of -- such things as decent screws and screwdrivers.
This "double cooker" design consists of a smaller container inside a larger box, with both the larger box and the smaller container topped with different-sized plates of glass. Cooking is done in the inner container. The inner container is a stainless-steel pot resting in dry straw. The straw provides insulation. The greenhouse effect causes heat to accumulate in both the inner container and the larger box, since both have glass tops. The outer box gets rather hot, which decreases the temperature gradient between the inner cooking chamber and the outside air. The outer box's hot air, then, compensates for the lack of good insulation and tightly fitting components I would have preferred, but which were hard to accomplish under my circumstances.
Note the mirror at the top, reflecting sunlight into the box. If I'd had more mirrors I would have mounted them, since the more radiant energy that enters the box, the better.
This system fries eggs and bakes bread, but is not hot enough to cook potatoes or carrots. It does exceptionally well baking bananas, which taste quite as sweet as those baked in the embers of a campfire!
In 2007 I found myself in the north-central Mexican state of Querétaro, volunteering at the offices of the Sierra Gorda Biosphere Reserve in Jalpan. We were in an arid, scrubby valley and one thing the Reserve did was to encourage the use of solar ovens in surrounding villages. As such they had a little room full of solar-oven kits. One kit was made of highly reflective metal sheets and sold for about $40 US. The other was of cardboard surfaced with what appeared to be aluminum foil, and it cost about $30 US. When I saw the limited reflective surface area offered by the kits I didn't have much hope that they'd be any good. However, they worked, even the cardboard one, which I used for nearly a year. At the end of that year, however, despite having treated it very delicately, it was getting pretty ragged and falling apart.
The secret to the kit's success is clearly the double bowl that comes with the kit. Its lid and outer bowl is clear glass, but the inner bowl which sits so that a thin air space exists between it and the outer one is black. Heat builds up in this two-bowl system wonderfully! Here's what my cardboard kit looked like as a stew gleefully bubbled away inside:
In the summer of 2009 I found myself in Oregon. Summers there were very dry and the fire hazard was great, so a solar oven was needed. I'd never built an oven for this far north and wasn't sure it'd work. I shouldn't have worried.
This time I built a Solar Funnel Cooker, the design of which was found at www.solarcooking.org. Below is what I came up with:
The instructions called for a sheet of cardboard measuring 2 x 4 feet but I used 3 x 6. They advised gluing the aluminum foil in place but I stapled mine with a simple office stapler. Their design calls for painting a canning jar black and putting it inside a plastic bag, then cooking what's in the black jar. I had access to a clear-glass pan and top large enough to enclose a small skillet with its handle removed,and used that. The blackened top of an old pot just happened to fit the skillet. The skillet and pan top both were blackened with woodsmoke. You can see inside my funnel cooker above. As with the kit profiled above, the real secret here is having a black container inside a clear-glass one, and cooking what's put in the black container.
This worked just as well as the solar-oven kit profiled above. Since everything except the aluminum foil was basically found junk, this oven cost maybe $2 worth of foil and took about two hours to put together. It bakes bread, fries eggs, simmers stews -- covers all the basics. A skillet-sized biscuit made of whole-wheat flour takes about an hour to bake to perfection
In 2013 I find myself in hot, sunny southwestern Texas between San Antonio and the Mexican border at Del Rio. Once again a neighbor gives me an abandoned satellite dish. You can see it cooking below:
This is different from my previous satellite dish cookers. It's a big one, like the one in California, but this one's metal webbing covering the radiating ribs was intact. I thought that this was great, for now I could just "sew" patches of aluminum sheeting onto the webbing. Above you can see how long, narrow strips of aluminum were sewed on with snippets of copper wire.
I wouldn't apply the sheeting to the webbing like that if I were to begin over again. The webbing was a little warped here and there. More important, despite my efforts to conform the curvature of the aluminum sheets with that of the dish, sometimes the sewing caused the sheets to warp so that reflected sunlight was directed away from the desired focal point. It would have been better to attach small squares maybe two feet across. Staple them in the center, to a rib if possible, and not to the webbing, and let the squares' sides conform to the dish below them.
Spacing was allowed between the sheets to let breezes pass through, because dishes this size can easily kite away during storms. Also different with this dish is that the pot is suspended from a pole held in place by tripods. This works well for a pot, but I prefer cooking with a skillet and like my previous designs better.
So, after all my good luck with previous efforts, this one turned out less than perfect. However, like the others, it's so large that even with all its imperfections and inefficiencies, it cooks just fine, makes wonderful cornbread and stews.