- Students will explain what solar
energy is
- Students will demonstrate how
different variables increase or decrease solar energy potential
Background
The sun is a giant energy source.
For many years, people have been using the sun’s energy, called solar energy,
to make buildings brighter and warmer. Today, we use special equipment and specially
designed buildings to capture solar energy for lighting, to heat our living spaces
and our water, and even to produce electricity.
Capturing and using solar energy
has become more important than ever. Traditional fuels like natural gas and oil
are limited, and as these fuels become more scarce, their cost increases. Solar
energy also is non-polluting and thus helps us achieve a cleaner environment.
If you collect enough solar heat,
you can use it instead of heat from a furnace. One way to collect heat is to trap
solar energy with solar collectors. Solar collectors allow sunlight in
through plastic or glass, absorbing that sunlight and convert it to heat. Because
the heat is unable to pass easily through the plastic or glass, it is trapped
inside the collector. An example of how a solar collector works is a car that
has all its windows closed tightly. When sunlight passes through the windows of
the car, it is either absorbed by the seats and other surfaces inside the car,
or it is reflected back out through the window. Light that is absorbed changes
into heat. Darker colored surfaces absorb more sunlight than lighter colors. Similarly,
different materials hold heat more efficiently than others and are thus better
suited to store solar energy.
Solar collectors come in many
shapes and sizes. Passive solar collectors move heat from the collectors
to other spaces naturally, without the use of fans or pumps. An attached sunroom
or a south-facing room with a large window area and a tile floor (which serves
to collect, retain, and then release heat) are examples of passive solar heating
systems. Active solar systems use fans (for systems that heat the air)
or pumps (for systems that heat water) to move the heat from the collector to
another part of the building.
Activity
1: Which Material Best Stores Solar Energy?
(Source: Solar
Energy Research and Education Foundation—SEREF)
Materials:
- Cardboard box
- Black paint
- Four small metal cans
- Four thermometers
- Sand
- Salt
- Water
- Torn-up paper
- Scale
Method:
- Paint the entire surface of
the box (inside and outside) with the black paint.
- Place the box in the sun.
- Pick the can to hold the torn
paper, place a thermometer in the can and using the scale, record the combined
weight (grams).
- Position the thermometer in
the middle of the can and pack torn paper into the can; filling the bottom of
the can, around the thermometer, and up to the top of the can.
- Record the weight of the torn-paper
filled can. Subtract the initial weight from the filled weight to determine how
much torn paper you added to the can.
- Use the scale to weigh each
can and then add an equivalent weight of the salt, water, or sand equal to the
weight of the torn paper.
- In each can, attach the thermometer
such that the thermometer is positioned in the middle of the material inside.
- Place the cans in the box.
- Close the box and leave it for
half an hour.
- Remove the cans
- Watch the temperatures in each
can fall and record the temperatures for each on the chart below.
- Using this information, determine
which material best stores heat.
Activity
2: In Collecting Solar Energy, Is Bigger Better?
(Source: Solar Energy
Research and Education Foundation—SEREF)
Materials:
- Large disposable pie plate
- Small disposable pie plate
- Black paint (non-water-soluble
spray paint is easiest)
- Thermometer
- Metric measuring cup
- Clear plastic food wrap
- Newspapers
- Styrofoam cups
- Masking tape
- Water
Method:
- Paint both pie plates black.
- When the paint dries, add 100ml
of water to each pie plate
- Record the temperature of the
water in each plate.
- Wrap plastic tightly over them.
- Tape the plastic securely.
- Place each on a stack of newspapers
in the sun for 10 minutes.
- Pour the water into styrofoam
cups and measure the temperatures, recording the temperatures below.
- Using this information, determine
which plate had hotter water.
|
Temperature (in degrees Celsius) |
|
Before |
After |
| Large |
Small |
Large |
Small |
| |
|
|
|
Wrap-up
Lead a class discussion about
how these concepts would be applied to designing a solar energy system. Your students
should demonstrate an understanding of why surface area of the solar collector
and the choice of storage material will affect the system’s performance.
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