How To Make A Solar Cooker

What better way to "go green" and be eco-friendly than to cook with nothing more than the power of the sun? We're always looking for fun things to make while being kid-friendly projects and a solar cooker is a great way to teach kids about the power of the sun. Follow along as we show you how we made a simple-to-build solar cooker.

Build A Better Box

The heart of your solar oven is really just a box. You can make one of out wood like we did or even use an old cardboard box. Ideally, you want a box that is at least 12" x 12" inside and at least 8" tall. Going with a larger box will give a bigger cooking area and allow the collection of more solar energy and thus hotter temperatures.

Inside this outer box will be the actual oven / cooking box, so you'll have a box inside a box. The inner box needs to be made out of something that can retain heat. Half inch thick drywall works well so make a box out of that, without a top. We used Liquid Nails construction adhesive to glue our drywall box together.

This inner box sits inside of your wood or cardboard box but needs a gap between the two of a half inch to an inch. Using some scrap wood glued to the bottom of the drywall box, place it inside the outer box. Now fill the gap with expanding foam (affiliate link). A little foam goes a long way as it keeps expanding for quite a while. With that in mind, put weights in your inner box to avoid it lifting as the foam expands.

When the foam is dryer simply cut away any that expanded out of the top. Spray the inside of the box with a high temperature flat black gril paint (affiliate link). Black helps absorb light and thus heat. The expanding foam should have made your oven fairly strong now, even if it was flimsy before.

You now need a piece of glass to cover the top of the oven. This will let solar energy in but also keep a lot of the heat from escaping back out. It also keeps dirt, dust, and critters out of your food while it cooks. The easiest option is to buy a pre-cut piece of glass for a few dollars from a local home improvement store. The main oven box is now done.

Setup Reflectors

The box by itself will get warm, but not hot enough to cook so you need a larger surface area to reflect in more solar energy. To do this we'll add reflectors. Using wood or cardboard, you'll make 4 squares and 4 triangles.

The 4 squares will be the same width as your box. So, if your box width is 12" then make 12" x 12" squares for the reflectors. These can be glued on or use hinges like we did. Either way, you'll cover them with reflective film (affiliate link).

With the 4 squares in place on the main oven box and at roughly 45 degree angles to the box, you can now cut 4 triangles. These triangles will fill the gaps between the squares. We used cardboard scraps and hot glue for the triangles and then covered them with the reflective film. The oven is all done.

Cook!

It's time to test your oven out. This requires a sunny day in most cases. If you've made a large oven with large reflectors you may be able to cook on a slightly cloudy day. With our 12" oven we found that we could only cook if the cloud cover was 25% or less.

In the winter, aim the box at the midday sun by propping up the bottom so it sits on a slight angle towards the sun. In the summer, propping up may not be needed. Your peak cooking times will be when the sun is at its hottest, between noon to 3:00 PM or so.

A good test is something that cooks easily, like bread dough as shown above. For best results, pre-heat the oven for 30-60 minutes and then add your food in. Take temperature readings using a laser infrared thermometer (affiliate link) to see how hot the oven can get.

Our small-ish oven reach temperatures of 200 degrees Fahrenheit which was enough to cooking pizza dough as well as an egg and that was during the winter when the sun was lower in the sky. We expect summer cooking to be even better!