I have been looking at solar cookers for some time now since I am intrigued by the idea of cooking using only the energy from the sun. Besides being fun and interesting, imagine a time when you had no electricity and the propane tank was empty–how would you prepare any kind of hot meal? I scoured the Internet looking for plans for the type of solar oven I wanted. I knew that I wanted something permanent; many solar ovens are made from cardboard and aluminum foil and while I understand they work quite well, I wanted a model I could use for years to come. I finally found plans on the Internet by William Becker that I was happy with: http://www.williamgbecker.com/MakeSolarOven.html
When my husband, Terry, asked me what I wanted for Christmas this year I was ready! I handed him the plans I had printed from the Internet and told him this was what I wanted. This type of solar cooker is known as a solar box oven and is made of wood and sheet metal to render it permanent. The insulation and metal inside the box can bring the temperatures inside as high as 400 degrees, however you will either need basic carpentry skills or a husband or friend who has those skills. If you don’t have these carpentry skills or know anyone who does, don’t despair–the plans to make a similar solar box oven from cardboard are available from Backwoods Home Magazine at http://www.backwoodshome.com/articles/radabaugh30.html.
My husband made some modifications to the oven, based on his over three decades of building as well as installing solar pv systems. He made the cooker bigger than the original plans, with the idea that you could cook multiple items at once if you chose. He used three layers of glass for the top, making it super-insulated, however knowing the extra glass would add weight he used a relatively thin plywood for the bottom and sides to minimize the overall weight, but added reinforcement wood along the top and bottom edges.
Although Mr. Becker’s plans used sheet metal to line the inside of the solar cooker, my husband had an old hot water heating solar panel someone had given him which was lined with copper which had been painted with a heat reflecting black paint, so he substituted the copper for the sheet metal. We debated about the type of insulation to use; we initially planned on ordering the type of insulation which is used in a regular kitchen range, but after finding out how expensive it was, we ended up using regular 1″ rigid foam insulation. To ensure it would not deteriorate–or worse–at high temperatures, we put a piece of it into a small cast iron skillet and “baked” it at 400 degrees for an hour or so. There was no change in the piece of insulation, so we decided it would work just fine.
The basic structure of the solar box oven was built, then it was time to install the copper. Terry not only lined the interior with the copper, but shaped it over the sides and front as well, screwing it in as he went along.
Once the copper was completely screwed in, he then attached the glass lid, hinging it at the back and adding chains to the side so it could be opened without the glass falling backward and tipping the oven over. He added insulation tape around the entire top, then installed a window-type closure which pulls the lid down tightly so no heat escapes. The oven was caulked, then given a couple of coats of primer paint, and finally the green paint–no energy efficient reason for the color, I just like it!
My first cooking experiment in my new solar oven was a gingerbread cake recipe that my grandmother used to make. Because it is the end of December, even in South central Texas we are getting cloudy days and temperatures in the 45-55 degree range as a high, so I wasn’t sure how well it would work. I caught a sunny afternoon and put the cake into bake. It took about three hours to fully cook, but baked in exactly the same way as a conventional oven. Yesterday I made granola, then made a burgundy beef stew. Again, because we were not getting the amount of sun that we do in the spring and summer time it took about four hours for the stew to cook, but it cooked perfectly. You rarely have to worry about burning anything in a solar oven, just check on it occasionally and make minor adjustments to the placement of the oven as the sun moves across the sky. The oven reached temperatures of between 160 and 220. I would guess that in the 105-plus unbearably hot sunshine we had last summer that the oven would easily reach 400 degrees, cooking as quickly as a regular oven.
I love my solar oven–truly one of my very favorite Christmas gifts–and I plan to use it for a long time to come. I ordered two solar cookbooks from Amazon: Cooking With the Sun: How to Build and Use Solar Cookers and Cooking With Sunshine: The Complete Guide to Solar Cuisine with 150 Easy Sun-Cooked Recipes, and also downloaded some recipes from the Internet at: http://www.solarcooker-at-cantinawest.com/solarcookingrecipes.html. This website also had lots of really good information regarding solar cookers. I plan on trying to dry some foods in the solar cooker, and plan to try sun-dried tomatoes first. If you are drying or cooking something without a lid which has lots of moisture, you may need to prop the lid open to allow the steam to escape. I used a lid when cooking the burgundy beef stew, so it was fine, and although the cake created a little moisture, it was not enough to worry about. You can cook in your normal cookware in a solar oven, although I plan to purchase a smaller cast iron dutch oven with a lid to see how it works in the solar cooker. Dark, non-stick baking pans or cookie sheets are said to work best, but I cooked the gingerbread in a clear glass 9″ x 9″ pan and it worked fine.
Here’s wishing everyone a wonderful 2012–give solar cooking a try–you will be surprised at how efficient it is, not to mention fun!