Let's learn about: Energy Transfer and Heat Energy

Energy is not a physical substance, but more a substance-like quality that can be stored or transferred through space from place to place.

There are 3 primary methods that heat energy can transfer in: convection, conduction, and radiation.

With conduction, heat is transferred between two objects via physical contact. Think a stove burner heating the bottom of a pan. These two are in physical contact with each other when the burner transfers heat to the pan.

With convection, the heat is transferred by moving a fluid, usually air. An example of this can be seen when you are boiling water. Since the water at the bottom is hotter, it will naturally rise to the surface as it is less dense and cause circulation, which transfers heat throughout the fluid.

With radiation, heat is transferred through some form of electromagnetic radiation, like microwaves, visible light, and so on.

Let's Learn about: Solar Energy

The sun is interacting and changing the surface of the Earth. The sun isn’t physically touching the Earth nor is the heat transfer visible, but remember that energy is present whenever there is movement, sound, light, or heat. The light the sun produces is radiant energy that can be converted into thermal energy. Radiant energy (light) can be stored in objects as thermal energy (heat). Imagine that heat is a bank account: how energy and the light is stored can be thought of as an energy deposit into the bank account.

There are two types of solar power: Photovoltaic solar power (solar panels) and solar thermal energy (direct solar power).

Solar ovens use solar thermal energy to cook food. Designs may vary, but three basic principles are applied to most solar ovens. The three basic principles are:

1. Concentrating sunlight: Materials are used to reflect the sunlight and concentrate it within the device. Foil, mirrors, metal, or other reflective materials can achieve this. Another aspect is the angle of reflection, the light should be as direct as possible.

2. Converting light to heat: Inside the oven, surfaces are colored black to absorb and retain heat. This is when the transfer from radiant to thermal energy occurs.

3. Greenhouse effect: Materials isolate the air inside the oven, separating it from the air outside. The cover allows heat to enter, but not escape.

Solar ovens provide environmental and health benefits. They reduce the demand for wood fuel – a major cause of deforestation. Deforestation contributes to climate change, soil degradation and erosion, and flooding. Solar ovens prevent pollution as they eliminate the need to burn fuels. Open fires contribute to indoor pollution, health risks associated including death, and unintentional fire incidents.

STEM Challenge

In this STEM Challenge, you will be making a solar oven. While a pizza box is ideal, you could also use the box your project was shipped in, or any other box that roughly resembles the dimensions of your pizza box.

WE ASK THAT YOU PLEASE HAVE AN ADULT HELP YOU WITH CUTTING OUT THE WINDOW FOR THE SOLAR OVEN.

1. Select a sunny day (~85°F) with little to no wind.

2. Secure black construction paper onto the bottom of the box with tape to absorb heat.

3. Ask an adult to use a utility knife, scissors, or box-cutter to cut three sides of a square out of the top of the pizza box, leaving the folded edge attached.

4. Attach aluminum foil to the inside of the flap cut from the top of the box. A good bit of adhesive will be necessary to do this. TIP: Flatten the foil using the ruler.

5. Open the ENTIRE top of the box, lift the cut flap, and tape plastic wrap around the opening, sealing the inside of the box. Tape securely so it is AIRTIGHT--as air inside the box begins to heat, it will want to escape. Packing tape is recommended.

6. Place cookies and thermometer inside the pizza box. Use a clear plastic plate or a piece of foil. Make sure the thermometer is visible to be able to record the increasing temperature.

7. Secure the pizza box lid by taping it down to make it airtight.

8. Let cookies bake for 30 minutes.

   1. When placing boxes outside, place them so the angle of the sun is directly hitting the aluminum foil, so the rays can be reflected into the box to bake the cookies. Prop the flap open with a ruler.

9. Check the temperature inside boxes, cookies may be hot. Open the box to allow cookies to cool before eating