Mother Earth Monday – Solar Ovens

Living in the land of endless heat, we finally have some cool air around here and I am living it up. Anything under 70 degrees is a blessing and it took until December to get any sort of lasting relief from the heat. Oddly enough, it is the cool weather that has me thinking about solar power. Now, obviously the most common sort we think about is solar panels, but that is the most expensive and least readily done as DIY.

Everyone forgets that solar powered activity doesn’t have to be about energy. If you have a garden, you are harnessing solar power after all. Some houses are wisely designed to apply passive solar heating and cooling principles. A simple skylight can serve far better than a wall light will. On that last, I speak from personal experience and fully intend to add skylights into any future building projects I do. The value of defused sunlight over flipping a light switch can’t be overstated and honestly the light is both easier on the eyes and a bit stronger anyway. Another project is a Trombe wall, of which I have never yet gotten around to building. That is another for my back burner of projects. There are honestly hundreds of potential ways to use the light of the sun to accomplish varied tasks.

Today, I am going to talk about a solar cooker however. There are any number of designs out there, each having their own merits and flaws. Probably the least valuable in my experience is the pizza box oven, which loses far too much of its heat back into the air to be of much use. Solar ‘ovens’ are a little different from solar cookers, since ovens are generally enclosed. Several fancy ones can get up to 400 degrees or more on the interior in the right conditions, but most get around 200 degrees. Solar cookers are generally exposed to the air and are focusing light (and the heat along with it) onto a cooking vessel.

Three designs have stuck out over the years. One was a combination of several designs that was crafted as part of a university study and very efficient, but I have long ago lost the link before I could run my own tests. If I ever find it again, I will post it here. The second was taking an old satellite dish with the round nub at the end replaced with a loop for holding a pot in place. The dish itself was coated in reflective car detailing and it created a nearly perfect parabolic solar cooker. In watching the video, it boiled water quickly and was able to heat up a cast iron pan well enough to pan-fry chicken beautifully. This one is great and needs very little work to create. The down-side is that it does require an unused satellite dish from somewhere such as Dish Network. Obviously the bigger the dish, the stronger the power for cooking and the larger the batches one can do.

So that leaves number 3, the Suntastic Solar Cooker. This one almost anyone has the materials to make and is very inexpensive while being fairly efficient. It is a variation on a panel cooker that I have found to be very good in what it does. Without adding any sort of ‘greenhouse’ style enclosure, it still manages to cook efficiently. The device allows for adjustments to match both high and low altitude sun angles, which is great if you plan on cooking sometime other than midday. One box, some adhering materials and a reflective medium like foil are all it takes to make a very good quality solar cooker.

If you are interested in testing some of the other designs from the site where this one originates, simply go to the Sunny Cooker Home Page and look around. Every cooker there is explained as to why it was created and comes with instructions for construction. Don’t see one you like? Go exploring for other sites. There are countless designs for solar cookers. Some are more efficient than others of course. The one I presented here does pretty well as a stand-alone, but doesn’t do as well as a parabolic cooker would. Expect an hour to an hour and a half to get things up to a good temperature. Slow by direct heating standards, but if you aren’t in a rush or are planning ahead, it is a great free option that won’t heat up the house.

One final note. There are also Fresnel lens cookers, but that is it’s own matter and comes with certain risks I am not willing to have on my conscience if I were to suggest others use these. Using the same technology as old televisions in reverse, they concentrate a lot of sun into a single pinpoint as if it were a giant magnifying glass. Parabolic cookers can light paper in seconds and heat to boiling very fast, but Fresnel lenses can melt glass and other materials with unsettling ease. While this does mean quick cooking times, it also means a lot of risks. Even improper storage of one can lead to major damages or injury.

What are your thoughts?

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