Background
Wind energy has been used for years to do work. From powering a sailboat to pushing the blades on a windmill in order to pump water and to crush a farmer's grain, wind has been, and still is, used as a viable source of energy. Humans harness energy created from the wind to create electricity to power everyday objects. Objects such as buildings, trees, and hills interfere and disrupt wind patterns. This is why most wind turbines are high up in the air, so they can be away from any objects that cause turbulence or changes in the wind pattern.
Meteorologists have identified areas in the United States, including areas in Wisconsin, that are consistently strong sites for wind power. Because wind is a source of clean and renewable energy, wind farms are growing in popularity.
Historically, sailors did not have accurate equipment to gauge wind speeds. In 1806, Admiral Sir Francis Beaufort of the British Navy designed the Beaufort scale system for estimating wind strength without taking measurements. This provided sailors a consistent way to measure wind speeds. This scale was later adapted to use for multiple applications. The Beaufort scale ranges from zero for calm winds to 12 for hurricane strength winds. Each value represents a range and classification of wind speeds, and is accompanied by descriptions of the effects of surface features.
Another method of determining wind speed is to utilize a simple wind monitor called an Anemometer. Meteorologists and renewable energy experts use advanced equipment and take many measurements throughout the year to determine the wind potential for an area. It is very important that you remember that an area's wind potential is determined by taking measurements many meters above ground level. At ground level, there are many obstacles and barriers that will affect wind speed and direction. Usually measurements for wind speed are taken about ten meters (33 feet) above the ground. Therefore, measurements taken at ground level provide inadequate indications of wind potential. Although there are some conversions that can be used to convert ground wind speed to wind at higher elevations, to truly understand wind potential, homeowners and other individuals interested in wind energy should consult a renewable energy expert or meteorologist.
Build a Wind Gauge
Version 1
Materials
five 3 ounce paper Dixie cups
two straight plastic soda straws
a pin
scissors
paper punch
small stapler
sharp pencil with an eraser
Procedure
1. Take four Dixie cups and using the paper punch, punch one hole in each, about a half inch below the rim.
2. Take the fifth cup and punch four equally spaced holes about a quarter inch below the rim. Then punch a hole in the center of the bottom of the cup.
3. Take one of the four cups and push a soda straw through the hole. Fold the end of the straw, and staple it to the side of the cup across from the hole. Repeat this procedure for another one-hole cup and the second straw.
4. Now slide one cup and straw assembly through two opposite holes in the cup with four holes. Push another one-hole cup onto the end of the straw just pushed through the four-hole cup. Bend the straw and staple it to the one-hole cup, making certain that the cup faces in the opposite direction from the first cup. Repeat this procedure using the other cup and straw assembly and the remaining one-hole cup.
5. Align the four cups so that their open ends face in the same direction (clockwise or counterclockwise) around the center cup. Push the straight pin through the two straws where they intersect. Push the eraser end of the pencil through the bottom hole in the center cup. Push the pin into the end of the pencil eraser as far as it will go. Your anemometer is ready to use.
6. Your anemometer is useful because it rotates with the wind. To calculate the velocity at which your anemometer spins, determine the number of revolutions per minute (RPM). An easy way to count the number of revolutions is to use one different colored cup or mark one cup in a way that is noticeable and easy to count as it spins around. Next calculate the circumference (in feet) of the circle made by the rotating paper cups. Multiply your RPM value by the circumference of the circle, and you will have an approximation of the velocity at which your anemometer spins (in feet per minute). (Note: Other forces, including drag and friction, influence the calculation but are being ignored for this introductory illustration. The velocity at which your anemometer spins is not the same as wind speed.)
The anemometer is an example of a vertical-axis wind collector. It need not be pointed into the wind to spin. (Note: This paper cup anemometer will produce a reasonable approximation of circumferential velocity, but should not be used for any purpose other than educational illustration).
Version 2
Materials
1 ping pong ball
1 piece of fishing line
1 protractor
Red marker
1 ruler
1 bubble level
Glue
1 needle (long enough to go through ping pong ball)
Modified Beaufort Scale (above)
Data Table 1 (below)
Data Table 2 (below)
Graph paper
Procedure
1. Use the needle to thread the ping-pong ball onto the fishing line.
2. Secure the other end of the fishing line to the middle of the straight edge of the protractor (if the protractor has a small hole in the middle, tie the fishing line through the hole).
3. Tape the ruler to the end of the straight edge of the protractor.
4. Secure the bubble level to the other end of the straight part of the protractor.
5. Find four different stations around your school or home property to determine wind speed.
6. Take into consideration that any buildings or other objects will affect wind speed and direction.
7. Hold the monitor so the bubble on the level is centered; face into the wind and record the angle that the fishing line makes with the horizontal plane of the protractor.
8. Take measurements of this angle at four evenly spaced times throughout the day (times are suggested in Data Table 1, below).
9. Record each measurement in Data Table 1.
10. Add these values and divide by four (the number of measurements you took in one day) to determine the average angle of the fishing line; record this value.
11. If possible, repeat these measurements for five consecutive days. You'll have a good idea if you are in a high wind potential area.
12. From Data Table 2, choose the angle closest to your average angle. Record the wind speed determined by this angle on Data Table 1.
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