Can you harness the power of the wind to create energy?
Problem
As you’re looking out the window in class, you notice the sky darkening.
Outside, the air is unusually still, and the sky takes on a pale greenish
hue. You’ve seen this before, you know what it means. A tornado is
approaching. Sirens begin to wail; everyone takes cover as the winds
howl outside. After the storm passes, you go outside and see the
buildings, trees, and telephone poles the winds have toppled. You realize
all this natural energy can be used to do something good, and decide
to find a way to use the power of wind to create clean energy and help
people around the world.
Your Mission
Using the materials provided and your own creativity, make a windmill
that efficiently captures the wind to make as much energy as possible
in the time allotted.
Instructions
To make your windmill blades, draw and cut a shape out of a paper
plate—think about what style of blades will make the windmill move
the fastest. The curve on the edge of the plate can help the air to
spin the windmill faster.
Use the first piece to trace and cut three more shapes just like it.
Think about what to add to your blades to help the windmill spin
faster. For example, you can use duct tape to add a few folded
strips of cardstock along the back of the blades for extra strength.
You could also take a small strip of aluminum foil and tape it at an
angle along the curved edge of the blade.
Clip your blades to the windmill.
Turn the dial on the multimeter to DC, indicated by VDC or by the
symbol . Test your windmill using a fan, then read the numbers on
the meter.
Hint
The more air you redirect to the edge of the blade, the more energy
it will produce. Try curving your blades to direct the oncoming air to the
side, rotating the windmill faster.
Building the Windmill
To build the base of the windmill, turn a paper cup upside
down and hot glue two tongue depressors to opposite
sides of the cup pointing upward. These will hold the motor.
Hot glue a small motor between the upright tongue
depressors, making sure the spindle is pointing out to
the side.
Hot glue two more tongue depressors into an “X.” Then,
hot glue a clothespin at the end of each arm of the “X.”
Hot glue the spindle of the motor to the “X” where the
tongue depressors cross.
Using two alligator clips, connect the tabs on the back of
the motor to the leads on the multimeter.
How to Test
Have the students design four blades that can be gripped
by a clothespin.
Take each student’s blades and clip them into the windmill.
Set up a desk fan pointed towards the windmill.
Turn on your multimeter. We will measure DC Voltage,
which could be indicated by VDC or by the symbol on
your multimeter. Give the windmill a spin in the appropriate
direction for the blades to turn; you should then see
numbers appear on the multimeter. If they are negative,
switch each motor terminal to the reverse probe.
Turn on the fan, and watch the output from the multimeter.
The higher the number, the more DC voltage the blades
are generating on the windmill.
Example Solution
Take two paper plates and cut them in half. These will be
the base of the four blades.
Using duct tape, add a few folded strips of cardstock along
the back of the resulting semicircle to provide strength
against the force of the oncoming air. Fold the cardstock
into a triangular prism shape for maximum strength.
Take a small strip of aluminum foil and tape it at an angle
along the curved edge of the plate. This angle will cause
the air to spin the windmill faster.
Clip to the windmill clothespins and test.
Student Hint
The more air you redirect to the edge of the blade, the more
energy it will produce. Try curving your blades to direct the
oncoming air to the side, rotating the windmill faster.
