This anemometer cannot not tell the wind speed in miles per hour, but it can give you
an idea of how fast the wind is blowing.
Using your watch, count the number of times the colored cup spins around in one minute.
You are measuring the wind speed in revolutions (turns) per minute. Weather forecasters'
anemometers convert the revolutions per minute into miles per hour (or kilometers per
hour). Keep a record of the wind speeds you're measuring for the next few days.
Measure the wind speed at different times of the day. Is it the same in the morning; the
afternoon; the evening? Move your anemometer to another location. Is it windier in other
places? Do trees or buildings block the wind?
of our readers, Heather Fluehr, and
her mom, Paulina, of Apopka, Florida,
devised a clever way to measure wind
speed in miles per hour. With a slightly
different anemometer, the whole family
got into the car. One person drove
the car, one held the anemometer out
of the window -- these two were adults
-- one held a stop watch, and one
counted the revolutions of the anemometer.
They drove exactly 10 mph. In one
minute their anemometer made 100 revolutions.
Assuming there was no wind that day,
they determined that with their anemometer
100 rpms equals 10 miles per hour.
If they wanted to they could verify
the accuracy of their measurements
by using a real anemometer like the
ones used by weather forecasters and
Wind speed is important for wind energy. Wind turbines -- which are the machines that
change the movement of the wind into electricity -- need a constant, average wind speed of
about 14 miles per hour before the wind turbines can generate electricity. That's why
wind farms, where there are a lot of wind turbines grouped together, are located in windy
spots. In California, these are in three main places -- the Altamont Pass east of San
Francisco, Tehachapi south of Bakersfield, and in San Gorgonio near Palm Springs.
To read more about wind energy, please see
Chapter 10 of our Energy