Solar-easy-bake oven

During Camp VALOR our environment volunteers taught the kids about solar ovens. I then got so excited about the idea I decided I must have one of my own, and that I would make it a fun project to do with Justin when he arrived. My excitement was so great that I actually led Justin to believe I was more excited about the solar oven then I was for his visit.

The thing about baking in Peru is...it sucks. In most homes where a family has an actual gas oven and stove, they use the oven part as a cupboard. Baking just isn't really part of the culture. All meals are cooked on the stove top as it takes a lot of resources to bake, and if you want bread or a cake you go to the bakery. For those who do want to bake, there is the electric "bubble oven", which looks kind of like a small, round, outdoor grill but with one electric heating unit that only lines the edges. It cooks unevenly, its awkward shape makes it hard for square bake ware, and my host family freaks out every time I use it as they think I'm going to burn down the house. 

So when I told my host family, "I'm going to make an oven that uses solar energy," (AKA--free energy) they got really excited. And when Justin finally got here, all hard feelings aside, he got a little excited about it, too. We spent an entire evening working on it and reading up on different styles and ways to make an inexpensive but functional solar oven.

There are a couple different styles, and they’re all fairly easy. We went with a simple box solar oven design, like the one we used at Camp VALOR.

First off get two cardboard boxes; one that’s slightly bigger than the other by a couple inches on the sides.

Justin readying the boxes we got for free at my local bodega

Line the inside of the smaller box with aluminum foil, except for the bottom which needs to be black. We used black construction paper. This can actually be a little tricky, because you don’t want to use anything like tape or glue on the inside of the box to keep the aluminum foil and construction paper in place, as it may become toxic once it’s heated up. (See step 2 before starting any of this!)

Inside box lined with aluminum, and black construction paper on the bottom.

Place the smaller box inside the bigger box, insulating all of the space between, bottom and sides, with newspaper. You’ll want to take into account how much of the inside box will stick up once padded underneath, as you want both boxes to be the same height (Justin and I didn’t realize that until after, so we had to make adjustments AFTER putting all the foil on the box).

Justin and I decided to line the outside of the larger box with black construction paper just to get things a little toastier. 

I decided to decorate the back of the outside box with leftover paper scraps

You also want to make a back panel (extra cardboard with aluminum on it) to be placed behind the box and reflect additional light back in.

To finish it off, the oven needs a lid of some sort to put over the box. It can be glass or plastic wrap. Justin and I chose glass, as it’s a better conductor of heat, it will last longer, and it was less than 4 soles (less than $2) to have a piece of glass cut to size.

First solar-oven experiment--BROWNIES!

As far as cooking/baking ware, it needs to be all black, AND it needs a lid. The more ways to trap and attract heat, the better.

Our make-shift lid-- a manila folder with black construction paper on one side, aluminum on the other

Pre-heating the oven.

Setting up the backboard

Now, they say solar oven baking takes at least twice as long as regular baking. Well maybe that is true with the fancier solar ovens, but we found a lot of things factor into the solar oven baking process. To name a couple: any cloudiness at all, time of day, and location of the oven. For instance, placing the box in an area that will eventually get shade (D’oh!). We left our first concoction in the sun for more than 2 hours, and came back to find it partially shaded, and partially cooked.

See the shadows already creeping in? Bad location.

Half-baked, womp womp!

So, with all my experience and wisdom gained from our first try, I waited for a really sunny day for my second attempt. Yesterday I woke up to blue skies so I got to work. This time I started earlier, let the box “preheat” longer in the sun, and placed it in a location I knew would get sun all day (but still needed adjustments from time to time). This time I tried chocolate chip cookies.

Let me tell you, that solar oven got hot! When I went to check on the cookies I almost burnt myself!

Notice I said almost. One thing that is different with solar oven cooking is you can’t burn the food you’re cooking. With chocolate chip cookies they are usually crispy on the bottom, and if overcooked they get too hard. Well, even after my cookies were cooked all the way through they were still gooey (and so freaking delicious I could hardly contain myself).

So so so so so so so so so delicious! Host-family approved!

It did take a long time to cook them, though--much longer than twice the baking time. Granted I kind of got distracted with other things and would forget to check on them, but I left them in the solar oven for at least 6 hours.

I’m hoping to get some better baking ware one of these days and get a real lid. I’m sure once it’s summer again the heat alone will cook whatever I put in the solar oven. But until then, I’m going to keep experimenting. It may be a little optimistic, but I’m thinking cornbread next time.