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Unformatted text preview: Solar
Projects CONTENTS 2
13 S Solar Air Heater S Solar Water Heater S Solar Hot Dog Cooker S Effects of Amount and Wavelength
of Light on a Solar Cell S Glossary SOLAR ENERGY
Solar energy can be used to heat our homes,
heat water, cook our food, and power our lights.
These science projects will help you learn about solar energy and how it
works. The first three projects focus on different ways to use solar thermal
(or heat) energy. The fourth project focuses on solar electric energy.
Each project is broken into several parts: S The purpose of the experiment
S The materials and equipment you will need to do the experiment
S Where to find some of the materials
S How to assemble and conduct the experiment
S What you may see during the experiment
S How the specific energy type works.
Some of the experiments may require help from an adult.
To help you understand new terms, we have included a glossary in the
back. We have also included a resource list on the back page with
information on where to get equipment for the experiments. The list also
names places where you can find more information on solar energy.
We hope you learn something from the experiments. But most of all, we
hope you have fun! 1 PROJECT 1: SOLAR AIR HEATER
You will construct a solar air heater to attach to a south-facing window.
MATERIALS AND EQUIPMENT
S 1 large piece of
S Measuring tape
S Acrylic gesso paste S Flat black acrylic paint
S Paint brush
S Thumbtacks S Duct tape
S Thin string
S Plastic wrap S Masking tape
S 1 piece of graph paper (not pushpins) RESOURCES Cardboard can come from a large appliance or furniture box. The gesso paste, acrylic paint, paintbrush, and
graph paper can be purchased at art supply stores or hobby shops. String, duct tape, masking tape, and
measuring tape is available at hardware stores. PROCESS
Setting Up the Experiment 1 Find a south-facing window and measure its width and height inside the frame. 2 Cut out a piece of cardboard that is 10 inches
(25 centimeters) wider and taller than the window. 3 Cut a 5-inch (13-centimeter) square out of each
corner to make four 5-inch (13-centimeter) flaps
that extend from the top, bottom, and sides of the
cardboard. Fold the flaps inward. The area inside
the folds should be the same size as the window
area. 4 Apply a coat of gesso paste to the inward side of the cardboard. Allow the paste to dry for 10 minutes. 5 After the paste has dried, paint the same side of the cardboard with flat black acrylic paint. Allow the paint to dry. 6 Cut vent holes 3 inches (8 centimeters) wide by
3 inches high at about 1 inch (2.5 centimeters) from
the top and bottom folds of the cardboard. 7 Push thumbtacks into the unpainted side of the
cardboard around the vent holes on the inside
surface. 8 Weave string around the thumbtacks and across the
vent holes. This keeps the plastic wrap from blowing
through the vent holes.
2 9 Cover the thumbtacks with thin strips of duct tape to
prevent them from falling out of the cardboard. 10 Cut enough plastic wrap to cover the vent holes. Decide which is the top and bottom of the cardboard. Tape
the plastic to the top of the bottom vent holes on the black side so the plastic hangs as a flap. Do not
completely seal the vent holes. Do the same to the top vent holes on the string side. 11 Fold the cardboard flaps toward the black side, and place the cardboard inside the window frame. The plastic
flap on top should be facing the inside of the room. Tape the cardboard to the window frame using masking
tape. You should have air space between the window and the cardboard. Doing the Experiment 1 Draw lines on the graph paper to
make a chart that looks like this. 2 On a sunny day and a cloudy day, take temperature
readings every hour for several hours. To do this, hold
the thermometer under the plastic flaps covering the
vent holes for 2 minutes to measure the collector’s air
intake (bottom) and output (top) temperatures. Mark
your temperature readings on the graph paper. WHAT DID YOU SEE?
During what time of day was the collector’s output temperature the highest? The lowest?
What was the highest output temperature of the collector on a cloudy day? On a sunny day? HOW SOLAR AIR HEATERS WORK
Solar air heaters, also called collectors, trap the sun’s rays to produce heat. They are mostly used to heat homes
and water. Most solar collectors are boxes, frames, or rooms that contain these parts:
• Clear covers that let in solar energy
• Dark surfaces inside, called absorber plates, that soak up heat
• Insulation materials to prevent heat from escaping
• Vents or pipes that carry the heated air or liquid from inside the collector to where it can be used. 3 PROJECT 2: SOLAR WATER HEATER
You will construct a water heater with a collector and storage tank.
MATERIALS AND EQUIPMENT
S 10-inch (25-centimeter) square piece of galvanized S 16-inch (40-centimeter) square sheet of 3- or 4-mil sheet metal (the thinnest available) clear plastic S 20-inch (51-centimeter) square piece of cardboard S Knife or box cutter S Flat black spray paint S Cellophane or masking tape S 10-inch (25-centimeter) square piece of insulation S Tubing bender (or have the copper tubing bent at (styrofoam, corrugated cardboard, newspaper, or
batting) at least 3 inches (8 centimeters) thick the hardware store) S 3-foot (1-meter) soft copper tubing, 3/8-inch to
1/2-inch diameter Water Heater
S 1- or 2-pound coffee can with plastic lid
S 2 2-inch (5-centimeter) pieces of soft copper tubing, S Cardboard box, slightly larger than coffee can
S Insulation material (Styrofoam, corrugated 3/8-inch to 1/2-inch diameter (must be same
diameter as the copper tubing used in collector)
S Thermometer cardboard, newspaper, or batting)
S 100- to 200-watt soldering iron and acid-flux solder RESOURCES
The copper and plastic tubing, tubing bender, box cutter, galvanized sheet metal, and plastic sheet are available at
hardware or building supply stores. Soldering irons and flux are available at hobby stores. PROCESS
Setting Up the Experiment
TO MAKE THE COLLECTOR 1 Bend the copper tubing carefully into an S-shape using
a tubing bender to avoid kinks. 2 Lay the copper tubing onto the galvanized sheet metal
and solder it in place. 3 Spray the plate and tubing with the flat-black paint. 4 4 Draw lines on the cardboard. 5 Cut on the solid lines, and fold on the dotted lines. 6 Cut slots and holes in the cardboard to insert the collector
(sheet metal with tubing). 7 Fold and tape the cardboard to make a box. 8 Put the insulation in the bottom of the box. 9 Slide the collector into the box along the slots, and tape the
slots tightly closed. 10 Place the clear plastic sheet over the top and fold and tape it
down to make a tight but removable cover. TO MAKE THE WATER HEATER 1 Punch two holes on opposite sides of the coffee can. One hole must be 1 inch (2.5 centimeters) from the
top of the can and the other, 1 inch from the bottom of the can. 2 Insert the copper tubing in both holes and solder the joints. The joints must be watertight. 3 Cut holes in a cardboard box that will align with the
tubes in the can. 4 Put the can inside the cardboard box, with the tubes
sticking out the holes in the box. 5 Put insulation around the coffee can. 6 Cut the plastic tubing into two pieces, one slightly larger
than the other. 5 Doing the Experiment
1 Make a chart to record the following data:
Water temperature before:
Water temperature after 20 minutes:
Water temperature after 1 hour: 2 Hook the collector and water heater together. 3 Disconnect the plastic tubing from the inlet. 4 Run water through the tubes and the collector until all
the air is gone. 5 Reconnect the tubing to the inlet, and fill
the coffee can with water to above the level
of the inlet. 6 Measure and record the water temperature and replace the lid. 7 Face the collector directly into the sun, placing the bottom of the
heater above the top of the collector. 8 Measure and record the water temperature after 20 minutes. 9 Measure and record the data every 20 minutes. 6 WHAT DID YOU SEE?
What happened to the water level in the can when you first hooked up the system?
How hot did the water get in 20 minutes? In an hour?
Would the solar water heater work if the storage container was placed lower than the collector?
Will the solar water heater work in reverse on a cold night?
Can you detect the water flow in the system using chalk dust or food coloring in the water?
What was the highest temperature you recorded? HOW SOLAR WATER HEATERS WORK
Solar water heaters use the sun to heat water in collectors mounted on the roof of a house. One type of solar
water heater is called a thermosiphon system. As water in the collector heats, it becomes lighter and rises into the
tank above. Meanwhile, cooler water in the tank sinks down pipes to the bottom of the collector, causing
circulation throughout the system. This is known as thermosiphoning. The storage tank must be above the
collector for the thermosiphoning to work. 7 PROJECT 3: SOLAR HOT DOG COOKER
You will construct a model of a parabolic solar collector that wil l
cook a hot dog.
MATERIALS AND EQUIPMENT
S 14-inch (35-centimeter) sheet of S Cellophane or masking tape aluminum foil S 2 boxes (one for the collector and S 11 x 14-inch (28 x 35-centimeter) one for a stand) piece of poster board S 2 nuts S 1 unpainted wire coat hanger S 2 bolts RESOURCES
You can find poster board at art supply stores and nuts and bolts at a hardware store. You can generally get old
boxes from a grocery store. PROCESS
Setting Up the Experiment 1 Make the ends of the parabolic trough out of the
cardboard using the pattern shown here. (You will need to
enlarge the pattern to match the scale given.) 2 Tape the aluminum foil to the piece of poster board. 3 Curve the the poster board and tape it to the two
curved ends. 4 Attach the trough to the box frame using nuts and bolts. Make sure the
trough can move up and down but will stay in one place. 5 Put holes at either end of the trough focal point. 6 Straighten the wire coat hanger and bend one end to
make a handle. 7 Push the coat hanger through the hole on one side. Put
the hot dog on the coat hanger, and push the coat
hanger through the hole on the other side.
8 Doing the Experiment 1 Place the solar cooker so the mirrored trough faces
the sun. 2 Adjust the trough up and down until the mirrored
surface focuses the sun on the hotdog. 3 Cook the hot dog. WHAT DID YOU SEE?
How long did it take to cook the hot dog?
Did you have to move the cooker to keep the sun focused on the hotdog? HOW PARABOLIC COLLECTORS WORK
A parabolic collector is made up of a trough and a tube running down the center of the trough. The trough is
a long rectangular mirror formed in a U-shape. The mirror is tilted toward the sun to focus the sunlight on
the tube. The paraboloid shape is perfect for focusing the sunlight on the tube. The tube carries the fluid to
be heated. A tracking device keeps the mirrors pointed toward the sun as it moves across the sky.
Parabolic collectors are used mostly to provide hot water for use in industry and sometimes in homes. They
are also used to produce electricity. 9 PROJECT 4: EFFECTS OF AMOUNT AND
WAVELENGTH OF LIGHT ON A SOLAR CELL
You will demonstrate how the amount and wavelength of light
affects a solar cell.
MATERIALS AND EQUIPMENT
S Solar cell S Utility knife S 2 pieces enameled or plastic coated wire (8–10 S Glue (hot or white) inches [20–25 centimeters] each) S Plastic wheel with axle hole in center S Electric motor S Black marking pen S Soldering gun S Stopwatch S Solder (rosin core) S 1 sheet of black construction paper S Sandpaper S Several sheets of colored transparency film in a S Knife or wire stripper (optional) variety of colors S 6-inch (15-centimeter) diameter cardboard circle S Paper and pencil or pen RESOURCES
Solar cells, wheels, and motors are available from science supply stores and hobby shops. Soldering guns and
solder are available at hardware stores. Transparency film is available at hobby shops and office supply stores. PROCESS
Setting Up the Experiment 1 Strip the ends of each coated wire exposing about 1 inch (2.5 centimeters) of the metal. If the wire is plastic
coated, use a knife or wire stripper to remove the plastic. If the wire is enameled, sand the ends to expose
the wire ends. 2 Plug in the soldering gun to heat it up. 3 Melt a drop of solder onto one of the leads on the
solar cell. Quickly place the end of one of the
stripped wires in the drop of molten solder. Add a
tiny drop of solder on top of the wire, making sure
the wire is completely surrounded by the solder. 4 Repeat the process with the other wire. 5 Let the solder cool completely for 10 minutes. Gently pull on the wires to make sure that both are securely
attached. 6 Melt a drop of solder onto one of the leads on the motor. Quickly place the end of one of the wires attached
to the solar cell in the drop of molten solder. Add a tiny drop of solder on top of the wire, making sure the
wire is completely surrounded by the solder. 7 Repeat the process with the other wire.
10 8 Let the solder cool completely for 10 minutes. Gently pull on the wires to make sure that both are
securely attached. 9 Attach the plastic wheel to the motor by gently pushing
the wheel onto the shaft of the motor. Be careful not to
chip the solder or break the wires. 10 Glue a 6-inch (15-centimeter) diameter cardboard circle
on the face of the wheel. 11 Mark a small dot on the edge of the cardboard wheel. This dot will be used as a frame of reference to
measure the speed that the wheel is spinning. Doing the Experiment 1 Place the solar cell, motor, and wheel in bright sunlight.
Observe the spinning motion. (If the motor does not
spin the wheel, check the wire connections. It may be
necessary to resolder the connections.) 2 Using the stopwatch and watching the dot, count the
number of spins in 15 seconds. Multiply this number by
4 to obtain the number of spins per minute. Record
the spinning rate on a piece of paper. HOW THE AMOUNT OF LIGHT AFFECTS A SOLAR CELL 1 Shade one area of the solar cell with the black
construction paper. Diagram the portion of the
cell shaded and record observations on a piece
of paper. 2 Repeat the experiment shading different areas
and amounts of the solar cell. 11 HOW THE WAVELENGTH OF LIGHT AFFECTS A SOLAR CELL
1 Cover the solar cell with a piece of colored
transparency film. Count the number of spins
in 15 seconds. Multiply this number by 4 to
obtain the number of spins per minute.
Record the spinning rate in a chart similar to
the one below.
Black 2 Number of Spins Repeat the experiment with the other colors of transparency film. WHAT DID YOU SEE?
How did the spinning motion change when you covered part of the solar cell? All of the cell?
Which colors slowed the spinning the most?
Which colors slowed the spinning the least? HOW SOLAR CELLS WORK
Solar cells, also called photovoltaic or PV cells, change sunlight directly to electricity. When sunlight strikes the
solar cell, electrons are knocked loose. They move toward the treated front surface. An electron imbalance is
created between the front and back. When the two surfaces are joined by a connector, like a wire, a current of
electricity travels between the negative and positive sides.
Solar cells are used to power calculators and watches as well as lights, refrigerators, and even cars. 12 GLOSSARY
Parabolic collector - A U-shaped mirrored trough that focuses sunlight onto a tube running down the
center of the trough.
Photovoltaic cell - A means of converting sunlight into electricity (see solar cell).
Solar heater - A water or space heating system that uses the sun’s energy to heat homes and water.
Solar cell - A means of converting sunlight into electricity (see photovoltaic cell).
Solar collector - A box, frame, or room that traps the sun’s rays to produce heat. A parabolic trough
is a type of solar collector.
Solar electric energy - Energy from the sun used for electricity.
Solar energy - Energy from the sun. The heat that builds up in your car when it is parked in the sun is
an example of solar energy.
Solar thermal energy - Energy from the sun used for heat.
Thermosiphoning - An event where heated water in a solar collector becomes lighter and rises to the
top and cooler water becomes heavier and sinks to the bottom. 13 RESOURCES
Equipment Suppliers General Resources Edmund Scientific Company
101 East Glouster Pike
Barrington, NJ 08007
(609) 547-3488 Center for Science Education
National Renewable Energy Laboratory
1617 Cole Boulevard
Golden, CO 80401
(800) 639-3649 Frey Science Company, Inc.
905 Hickory Lane
Mansfield, OH 44905
(800) 225-3739 Energy Efficiency and Renewable Energy
U.S. Department of Energy
P.O. Box 3048
Merrifield, VA 22116
(800) 363-3732 Hubbard Scientific Company
1120 Halbleib Road
Chippewa Falls, WI 54729
(800) 323-8368 Florida Solar Energy Center
1679 Clearlake Road
Cocoa, FL 32922
(407) 638-1000 Solar Box Cookers International
1724 Eleventh Street
Sacramento, CA 95814
(916) 444-6616 The Learning Works
PO Box 6187, Dept. NEIC
Santa Barbara, CA 93160
(805) 964-4220 Produced for the U.S. Department of Energy (DOE) by the
National Renewable Energy Laboratory,
a DOE national laboratory
December 1995 Printed with a renewable-source ink on paper
containing at least 50% wastepaper,
including 20% postconsumer waste ...
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