This inelegant-but-shiny cluster of junk is my solar cooker. I adapted the design from one found on the internet and built it out of stuff that would otherwise have been thrown away. My only cash expense was for a can of black heat-resistant spray paint. At the end of this article are instructions for building your own. By the way, the picture on the left is the meal prepared with the solar cooker--hot dog, garden-fresh corn, rice and peas (hot), tomatoes and cucumber (cold).
Lately I've been wondering why solar isn't better exploited in Arkansas, what with the abundance of sunshine here from June to October. This solar cooker is something I could quickly and cheaply investigate, so that's just what I did and here's my take on solar cooking.
First, I was surprised at just how easy it is to achieve temperatures hot enough to be useful using reflectors made of cardboard and aluminum foil. On a partly cloudy 90-in-the-shade day, my Wal-Mart oven thermometer reported that my makeshift solar oven maintained a temperature of 210 degrees. That's hot enough to do just about any cooking you care to do. It's certainly hot enough to heat canned goods or hot dogs or roast corn or poach an egg or make rice. One design I found on the internet claims to achieve temperatures of 350 degrees Fahrenheit for a cardboard-and-aluminum-foil oven. That sounds pretty high, but I don't see any problems in achieving temperatures well above boiling.
So where might solar cooking be appropriate, aside from a junior high school science fair project? How about cook-outs and camping trips? Take a couple of cookers to the lake with you for the weekend and involve the kids in making a hot lunch.
How about on your fishing boat or party barge, where flame cookers carry extra risk?
How about using solar cookers in camping areas where campfires are prohibited?
How about work? At your ten-o'clock break, prepare a rice dish with canned vegetables and set up your cooker outside. At noon, your dish is ready to eat. True, it's more trouble than just poking some leftovers in the breakroom microwave, but just think how many geek-points you'll rack up if you bring a solar cooker to work!
Want to give it a try? Here's how: First, get three clean, empty six-ounce tuna cans and three clean, empty ten-ounce beanie-weenie cans. Paint the outside of the cans with black heat-resistant paint. The black paint is important. If you leave the cans silver, they'll just reflect the sunlight and they won't get hot.
Once the paint is dry, use the tuna cans to cap the larger cans. Arrange them in a stack like you see in the picture here.
Now get yourself a big damn glass pickle jar with a mouth wide enough to fit over the tuna can. A gallon is good.
Find a big cardboard box. Try to get one that's as close to cube-shaped as possible with walls about sixteen inches high. This one is a wine case. Cut down the vertical corners so the box spreads open like a daisy. Cover all the inside surfaces of the box (the parts that are now facing up) with aluminum foil. Glue it or pin it or use thumbtacks or tape, whatever is handy. Now you have an adjustable aluminized cardboard reflector.
Set the reflector in the sun. Put food in the cans. Stack the cans in the middle of the reflector. Fit the big damn pickle jar over the stack of cans. That will allow the sunlight to heat the cans, but will keep the breeze from cooling them off.
Now, adjust the aluminized flaps so that they reflect the sunlight onto the black cans. Prop the flaps in place with rocks or flower pots or whatever you have handy. There! You're cooking without gas! If you're going to take up solar cooking, expect a lot of trial-and-error at the beginning. The cooking times listed below are to be taken as broad guidelines, given the difficulty in controlling temperatures. But since the cooking temperatures are so low, the food will stay hot and ready for a long time without overcooking.
All the recipes go something like that for pretty much anything you want to cook, especially at these crockpot temperatures. So give it a try. Knock yourself out. It cost's practically nothing, requires some practice and no skill; and this kind of thing might even come in handy some day.
For instance, suppose there's a big flood and your children need water to drink. The natural disaster has disabled the service grid, no water, no power, no gas, no phone. All potential fuel sources are soaked from the flood. Relief services haven't made it to you yet. How are you going to heat water to sterilize it? Water heated to 180 degrees for twenty minutes will be free of all known human pathogens. This cooker can achieve that temperature easily. Note that heating water will not remedy chemical contamination, but heck, one problem at a time.
Maybe all that sounds a little like apocalyptic survivalist militia rhetoric, but thousands of people right here in America face exactly that situation every year in one disaster or another. It's good to have relief agencies, but it's also good to be able to handle your own emergencies. And after the emergency is not the best time to start experimenting with stuff like this.
DESIGN VARIATIONS THAT WORK
1) If you want to save weight, or if you just can't find a big damn pickle jar, you can use a big plastic oven bag instead. 2) If you want to boost temperatures further, you can make extra panels to fill in the spaces between the panels of the opened box.
DESIGN VARIATIONS THAT DON'T WORK
1) Magnifiers and parabolic reflectors only create small-but-intense hot spots within your cooker, producing uneven heat. They also introduce unnecessary hazards, unwelcome expense, and they make more work for the cook. In order to be used effectively, magnifiers and parabolic reflectors must be constantly attended and adjusted to track the sun. 2) Don't wrap anything in aluminum foil if you want it heated this way. It just reflects the light you're trying to absorb. 3) Bigger or more numerous reflectors don't necessarily make for higher temperatures if the additional light is not reflected onto the black cans.