May 2017

Astro-Cooking (5/3/17)

Building a Solar Oven

MATERIALS:

  • Cardboard box (small shipping boxes work very well for this project)
  • Scissors or a Box Knife
  • Craft Glue
  • Clear Tape
  • Aluminum Foil
  • Black construction paper
  • Ruler
  • Cellophane Wrap
  • Pyrex bowl or container
  • Black paper plates
  • S’more ingredients! (Typically: Graham crackers, Milk Chocolate, and Marshmallows)
  • Small oven thermometer
  • Kitchen towel or oven mitt

INSTRUCTIONS:

Solar Oven
  1. Using clear packing tape, securely seal the flaps on one side (the bottom) of your cardboard box. Leave the top flaps open.
  2. To increase the size of the four top flaps, use a pair of sturdy scissors or a box knife to make 2-inch cuts into the corners of the box. Fold down the flaps beyond their original creases.
  3. Coat the top of the four flaps, the inner walls, and floor of the cardboard box with a generous layer of craft glue. Working in sections, apply pieces of Aluminum foil to cover each of these surfaces. Make sure that the shiny side of the foil is showing! Smooth out as many wrinkles as possible.
  4. Cut a piece of black construction paper to snugly fit the bottom of your cardboard box. Glue it in place.
  5. Allow all of the glue to dry (at least overnight).
  6. On a small black paper plate, assemble 2 or 3 S’mores. Place a small oven thermometer on the plate as well. Place the plate into your Solar Oven, and cover it with a Pyrex bowl.
  7. Optional: Tear off a piece of cellophane wrap that is slightly larger than the opening of your solar oven. Loosely tape the cellophane over the box’s opening.
  8. During the middle of the day, set your solar oven outside in a sunny spot. Adjust the reflector flaps so they are casting all of the sunlight into the oven window.
  9. Check on your solar oven after about ten minutes. Has the temperature reading changed on the thermometer? Are the S’mores ready yet? If not, let them cook in the Solar Oven until they are melty and gooey.
  10. Once the S’mores are ready (typically after 15-20 minutes), carefully take out the plate of S’mores from the Solar Oven. Use an oven mitt or kitchen towel to protect your hands, because these Solar Ovens can get VERY hot!
  11. Enjoy your Solar S’mores!

HOW DOES IT WORK:

Solar cooking

While our Solar Ovens are pretty simple to construct, they actually use several interesting scientific processes to heat things up!

The first important part of solar cooking is to collect as much sunlight as possible. The large, shiny reflector flaps help to catch more light than would normally shine directly into the small box. The direction that the solar oven is facing and the angle of the reflectors are important to maximize light collection.

Once the light has entered the solar oven, it will hit the black paper at the bottom of the box and turn into heat. Anyone who has worn a black shirt on a warm summer day probably knows that the color black really heats up in bright sunlight. This is because visible light is absorbed by the color black and creates thermal energy (which is called Infrared radiation).

Finally, the heat that is created in the oven is trapped inside by the plastic covering. Even though the plastic cellophane (and the Pyrex container) are clear—meaning that visible light can travel through them—they do not allow the Infrared radiation to pass through. That is also why it can get really hot inside of a car that is parked in full sunlight for a long time. Sunlight can enter through the car windows, but the heat created by the sunlight will continue to build up inside!

THE MORE YOU KNOW:

The Sun is by far the most important source of energy for life on Earth. For over 4 billion years, this middle-aged star has been fusing Hydrogen atoms into Helium within its nuclear core to produce energy in the form of light and heat. Due to the incredibly strong gravity inside of the Sun as well as the extreme density of its superheated plasma, the light that is created in the center of the Sun can take tens of thousands of years just to travel outward to the surface. Once it has escaped, sunlight whizzes to Earth in just 8 minutes and 19 seconds!

GOING ONE STEP FURTHER:

The Solar Oven is a really neat invention, but it does have some drawbacks or problems. Can you use the Solar Oven in the shadow of a tree? What if it’s cloudy outside, or raining? Does it work at night? The Solar Oven only works if it can receive lots and lots of direct sunlight!