Thursday, October 20, 2011

Adventures in Solar Cookery

This summer with Peris and Mary we explored a subject that has great potential in Kenya, as it does here: solar cooking. In Kenya a significant amount of time and/or money goes into fuel for cooking. Either you pay for coal, gas, or wood, or you wander far and wide (and risk assault) looking for a source of wood, which is scarce in the largely deforested country. The capacity of sunlight to heat a surface offers an endless supply of energy which, when used passively, doesn't even require much in the way of raw materials to harness it.
Much credit for spreading the word about solar cooking must go to the organization aptly named Solar Cookers International. Former Ecology Action Garden Manager Carol Cox was fascinated by their work, and taught many years' worth of EA interns how to make simple and cheap cardboard box cookers. Which is how we, in turn, learned how to share the low-tech, high efficiency tool with others.
Our first foray into the world of solar cooking actually came in the form of a wedding present from our friends Sarah and Jim. This Sun Oven is a portable, high-powered solar cooker that involves a collapsible reflector, adjustable prop, and and a few other features that even make it possible to bake bread (at left) on a clear day.
The one Carol taught us to make, while not as powerful, is still capable of cooking grains, potatoes, meat, etc., pasteurizing water, and canning fruit and tomatoes. It involves two cardboard boxes, some glue, aluminum foil, silicon caulk, and a piece of glass. Plans can be found on the SCI website in book form for a mere $7. The book includes recipes and principles of using the box cooker.
Last but not least, the product of another gift... The Jeavons' gave me a book called The Solar Food Dryer which, among other things, gives plans for building an entirely passive-solar food dehydrator (no electricity involved). Aficionados of the Golden Rule Garden blog will undoubtedly have read my post on constructing it back in 2009, but for a much clearer explanation of the process check out the Gardenerd blog post on the topic. After building a third iteration, pictured at right, I only have a couple points of advice to add to the dialogue. First, the book recommends using stove paint on the metal heat collector. While this paint is good to 1,200°F, it is faaar from environmentally friendly. Plus it's $13 a can. This time I used a few coats of black tempura paint, which is not as durable, but is much cheaper and much less toxic. Second, this time I had to actually go out and buy a piece of metal for the heat collector, and found sheets of galvanized steel for something around $22. But galvanized ductwork was more like $13 for the same area, so I got that and banged it flat. And finally, the screen that the food sits on to dry: I like cheap, but this time I bought the stuff that the book recommends instead of using free (but icky) aluminum or fiberglass screen. And you know what? The dried food comes off like a dream! Well worth the $18-$20.
Without going into great depth on cooking pointers, the basics to solar cooking are as follows: It generally takes more time to cook with the sun, and this is the only downside. The upsides are many. Since there is no danger of your food (or your house) burning if you leave solar cooking food unattended, you can put out a dish in the morning and leave it till lunch or supper. Because of the nature of solar cooking your food will not dry out, and will often be much more moist and flavorful than food cooked on a stove or in a standard oven. And the cardboard box cookers (at left) are very inexpensive to build, so by making a few of them you'd have the capacity to cook for a great many people at once, with no fuel, while you are yourself working somewhere else the whole day long! Even in our climate, with the presence of cloudy days, solar cooking is tremendously practical. It merely takes an understanding of the principles and a willingness to work with the weather.
The solar food dryer, too, is dreamy. In its very first batch, our new one simultaneously dried tomatoes, basil, and bananas (see the close-up at top). The tomatoes and basil have been gracing our sourdough bread for the past couple of months, but I must confess that the bananas didn't last a day before being consumed. I don't have as much experience as others in its use yet, but the aforementioned Gardenerd blog has advice on making Flax Chips and Kale Chips, and drying mint and leeks with the solar dryer. I can tell you, though, that even in this humid climate this simple dryer works well.
I'd encourage anyone interested to give it a shot. In the worst case you'll come out with a conversation piece. In the best case you will change your diet, cut your fuel costs drastically, and become a calmer, happier, and more charmingly eccentric person!


  1. Another inspirational post! Any advice for the city dweller whose limited yard space is perpetually shady?

  2. FYI, if you want to buy the supplies in a kit to make the dehydrator instead of collecting your own, they sell one at And "Mike", who thinks this topic is intriguing, has a website that sells electric dehydrators. Clicking on his name-link will take you to a chart comparing qualities of a few different models. I would love to know what in particular interests you in this post, Mike, if you check back here.