Our sun provides an abundance of free power, yet we don’t even use 1 percent of it. Even if everyone were to put solar power on their homes, we still would use only a miniscule fraction of the power that it provides.
It is easy to cook with solar power by using a solar oven. A solar oven operates under the principle of concentrating the sun’s rays, intensifying them and the heat that they create. If enough sunlight is concentrated on the same spot, it’s possible to use it to melt steel.
Reflective Solar Oven
There are a number of solar oven designs out there, with most of them working by reflection. The most basic style is with a reflective box. These are commercially available, or can be made fairly easily from aluminum coated home sheathing. The “ears” of the solar oven need to be adjustable, so that they can be positioned to reflect the sun onto the cooking pot.
While these are not the most effective solar ovens, they do work. The larger the reflective “ears” are, the better they work, because they reflect more light onto the target area.
Parabolic Solar Oven
To improve the solar oven, it is necessary to increase the amount of sunlight hitting the cooking area. The easiest way to do this is with a parabolic reflector. While you can’t pick up a parabolic reflector at the corner hardware store, they are fairly easy to make.
One way to make a parabolic reflector is to use an old satellite TV antenna; one of the large ones that they used before going to the two foot diameter models. Those old satellite antennas were a perfect parabolic dish, about five to six feet in diameter. The inside of the dish has to be covered with aluminum foil (shiny side up) which should be glued on carefully as to prevent wrinkling.
The satellite TV antenna’s collector (the part at the end of the pole sticking up in the middle) is at the exact focal point of the antenna. By putting the cooking pot there, the sun’s rays will hit it the most effectively, creating the most possible heat.
Another way that I’ve seen a parabolic solar oven built is to use an umbrella for the parabolic reflector. Most umbrellas are shaped in a fairly good parabola, making them an ideal, if very light structure for a solar oven. Like the satellite TV lens that we just talked about, you’ll need to coat the inside of the umbrella with aluminum foil to act as a reflector. The less you wrinkle the foil in the process of gluing it on, the better the reflector will work.
You’ll also want to lock the umbrella into place, so that it can’t be collapsed. While the idea of a collapsible solar oven might be nice, collapsing it would wrinkle the foil, reducing the efficiency of it. To lock the umbrella open permanently, drill a small hole through the slider and center rod and put a pin through it.
Fresnel Lens Solar Oven
The third type of solar oven is one made using a Fresnel lens. These lenses are plastic magnifying glasses. They are molded with a series of concentric rings on the backside, which work like a magnifying glass to bend light. Old big-screen projection televisions used these lenses behind the screen. You can find them for sale on eBay. The lens will need to be mounted in a frame to hold it, with the ability to adjust the position and angle of the lens.
The focal length of this type of lens is about two feet. So the pot with the food in it will need to be located about two feet from the lens. Ideally, an adjustable stand is needed for the pot, so that its height and position can be changed relative to the lens for optimum focus.
In the picture, the top of the cast-iron Dutch oven being used as a cooking pot appears to be made of a different material than the rest of the pot. It isn’t; that’s the focal point of the sun shining on the pot. This type of solar oven can actually produce temperatures in excess of 2,000 degrees, so you should be careful using it.
Tips for Cooking with a Solar Oven
For best results, whatever pot is used with the solar oven should be black. That will allow for the best light absorbency, converting the most possible light to heat. The position of the pot has to be at the optimal focus point for the sun. That may mean adjusting the height or the position of the pot in relation to the reflector or lens.
Keep in mind that the sun moves throughout the sky. This will make it so that the position of the pot and the reflector or lens will have to change in relation to one another to keep the sun focused. You should check the solar oven at least hourly, adjusting the position of everything to keep the sun’s rays focused on the pot.
While pretty much anything can be cooked in a solar oven, it’s like cooking in a crockpot, rather than cooking in a regular oven; in other words, slow cooking. Temperatures will vary from day to day, depending upon the ambient temperature, height of the sun above the horizon, cloud cover, pollution levels and even humidity. Therefore, it is necessary to cook by checking your food and using a thermometer, rather than going by time. When cooking meats, for example, go by the internal temperature of the meat to ensure that it is properly cooked.