On S’mores and Solar Ovens

On S’mores and Solar Ovens

Who doesn’t like science projects? Tornadoes in a bottle, model solar systems, and of course the iconic baking soda volcanoes. I love science projects, and this one was a perfect way to spend a long pandemic day.

Because of Covid, a science project for me means making a slideshow or study guide outlining the unit. Since not everyone goes to school in person, there’s no way for our teachers to make sure that we are doing the project correctly, or even at all.

That was why, when my science teacher announced that we would be doing a real, physical project, I was SO excited. I hadn’t done a full-on project since the beginning of the pandemic (which is a loooong time), so I almost didn’t know where to start. 

But with some time (ok, about a minute), my rusty science project brain got back to work. We were tasked with making homemade solar ovens using our knowledge of thermal energy.  So I started by researching solar ovens. From campers to technology reviewers, I watched what must have been every YouTube video about solar ovens. By the end of the day, everything on my “watch next” section had to do with solar ovens.

Then, however, I was faced with the classic DIY project designer’s issue… how can I make something at home as good as the products in the store? This annoyed me until I realized that my teacher was not looking for my cardboard-box-turned-solar-oven to steam vegetables or cook meat in the wild. 

So, I grabbed a pen and paper and got to work designing my solar oven. I had big dreams for it, mostly because I wanted it to actually somewhat work. My original design featured two flaps on the top, each with a window carved out of them. I also added some aluminum foil-covered cardboard on the sides, tilted to reflect light into more windows I wanted to add after having an enlightening dream about foil and unicorns (Just kidding! All I did was think about how I could maximize the sun’s rays, but having the idea come to me in a dream feels much more glamorous.). To top (or bottom) it off, I lined the bottom of the box with some black foam board.

The actual science behind the box is quite simple. There are three ways thermal energy is transferred: conduction, convection, and radiation. 

The food heats up using conduction because the black foam board below it heats up. Conduction is the transfer of thermal energy between particles of matter that are touching. The thermal energy transfers from the foam board to the food through conduction. 

The air in the oven also heats up because of convection, meaning the air cycles around, heating up and cooling down. Convection is the transfer of thermal energy by particles moving through a fluid (either a gas or a liquid).  

Finally, the sun’s radiant energy (a.k.a. radiation) comes into the box through the window flaps and reflects in on the sides. Radiation is a way that heat is transferred as waves through air or space. In this context, the sun’s radiant energy travels from the sun and then into the box through the windows or onto the reflective panels.

After much designing, I felt it was finally time to get to work on my actual solar oven. I sat on the floor with my mother and a cardboard box and dictated where my mother should cut out the windows since it’s not the best idea for a 14-year-old to use a boxcutter – safety first! I brought out the big roll of bubble wrap and a ginormous black foam board from CVS and began the construction. My initial design ended up going out the window, as I found that it just wasn’t practical. The two flaps on the top would blow open, so I had to make a cardboard frame to go over them. The windows didn’t seal well, so I did a layer of bubble wrap and then layers of saran wrap on top of that. Even though most of this was annoying to do, I’m glad I got to go through the whole design process – faulty windows and all.

When my solar oven finally sat completed on the kitchen table, there was only one thing left to do… test it!!! Of course, I didn’t want to melt ice cubes or something boring like that, I decided to go all out with s’mores. I put an impromptu “plate” made out of black foam board piled high with graham crackers, chocolate pieces, and marshmallows.

Since solar ovens (especially homemade ones) are not so efficient, I left it out for two hours in the sun so that it could preheat to… probably only a degree or two warmer than outside. Then, I put the plate of s’mores into the solar oven and left them out for another three hours. By the time I returned home, my s’mores were probably as cooked as they were going to get. The chocolate was melty and the marshmallows got the tiniest bit gooey, probably almost as gooey as if they had been held a yard away from a campfire.

But I cannot complain, s’mores are s’mores, even if they were made in a cardboard, bubble wrap, and tinfoil DIY solar oven. They were delicious. The only thing I can’t understand is why it had to take 5 hours to make some poorly cooked s’mores. Designing it was very fun and I guess I did get to use my knowledge of heat and solar energy, but unless you have a lot of time to spare, I’d say you can stick to making your s’mores in a regular oven (or just the microwave!). BUT, if you do have a lot of time on your hands, want to learn about thermal energy, and want some s’mores, I would say this project is perfect for you!

About the Author

Dora