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Project Summary

Difficulty	6
Time required	Average (about one week)
Prerequisites	None
Material Availability	Readily available
Cost	Very Low (under $20)
Safety	No issues

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Abstract

Objective

To determine how much power a pinwheel generates at different orientations to a wind source.

Introduction

On a breezy summer afternoon, have you ever watched sailboats zigzagging their way into a strong wind? When the boats point in favorable directions against the wind, they race along with their sails forming smooth, tight curves, but when they "come about" and cross through the wind, their sails temporarily become floppy, and flutter like flags, then power to the boat is lost. In this science fair project, you'll discover that wind-powered devices like wind turbines also experience changes in the amount of power they can produce when the wind direction changes.

Wind turbines are machines that change the energy in wind into mechanical energy or electrical energy. Windmills are examples of wind turbines that convert wind energy into mechanical energy. The Netherlands is a country well-known for its windmills that have been used for centuries to grind corn, drain land, and cut wood. Wind farms, on the other hand, are examples of wind turbines that convert wind energy into electrical energy. In California, you can see rows of wind turbines along windy ridges and mountain passes. The wind turbines on these wind farms connect directly into power grids and produce 30 percent of the entire world's wind-generated electricity. Don't miss the animation in the bibliography of a wind turbine in action, converting wind energy into electrical energy for a power grid.

As shown in Figure 1, below, a wind turbine has a rotor with blades that are connected to a shaft. As wind energy hits the blades, the rotor turns, which causes the shaft to turn as well. As the shaft turns, it is able to do work and produce either mechanical or electrical energy.

Figure 1. This drawing shows two important parts of a wind turbine, the rotor and the shaft. This wind turbine is a horizontal-axis wind turbine because the shaft is parallel (horizontal) to the ground.

In the design of a wind turbine, the shaft can be positioned either horizontally or vertically, relative to the ground. If the shaft is positioned horizontally, parallel to the ground, then the turbine is called a horizontal-axis wind turbine. If the shaft is positioned vertically, perpendicular to the ground, like a flag pole, then it is called a vertical-axis wind turbine.

The horizontal-axis wind turbines are the most commonly used around the world today in wind farms and in windmills. They have greater efficiency than the vertical-axis wind turbines, but also must be kept pointed into the wind. Small horizontal-axis wind turbines point with a simple wind vane tail, which swivels the rotor so that it faces the wind head on. Larger horizontal-axis wind turbines must rely on motors and wind sensors to position them so they point into the wind. They are mounted on tall towers, which give them access to stronger winds, but they have the disadvantages of higher and more complicated installation and higher transportation costs than vertical-axis wind turbines.

Vertical-axis wind turbines have the advantage of not needing to point into the wind, so they are a good choice when the wind direction is highly variable. They are also mounted lower to the ground, usually without a high tower, so they are easier to install and access for maintenance. The drawbacks are that the wind speeds are lower closer to the ground than on the top of a high tower, which means less wind energy is available to generate power, and the winds closer to the ground also tend to be more turbulent (changing in both direction and speed), which puts mechanical stresses on the turbine.

In this science fair project, you will build a horizontal-axis wind turbine that can do real work. OK, don't get too excited—your wind turbine won't be doing your chores or taking out the trash for you, but it will be lifting some small weights a couple of feet off the ground. You'll also figure out how much power your wind turbine can generate as you move the wind source to different places around the rotor.

First, let's cover some important equations you'll need to know in order to do this science fair project. Power is defined in Equation 1 as the rate at which work is performed. Rate means how something changes with time. For example, if you have to raise a rock from the ground to a table, you could raise the rock slowly or you could raise it quickly. Either way, the work you've done will be the same, but the power needed to raise the rock quickly is greater than the power needed to raise it slowly.

Equation 1:

Power =

Work Time

Power is in watts (W). Work is in joules (J) or newton-meters (N . m). Time is in seconds (sec).

You will calculate how much work you did to raise the rock from the ground to the table with Equations 2 and 3, below. First figure out the force on the rock due to gravity (by calculating the rock's weight), and then measure the distance that you moved the rock, as shown in Figure 2.

Figure 2. This drawing shows the force and distance involved in calculating the work required to lift a rock from the ground to the table.

Equation 2:

Force = Mass of rock × Gravitational acceleration

Force is in newtons (N). Mass is in kilograms (kg). Gravitational acceleration is 9.81 meters per second squared (m/sec2)

Equation 3:

Work = Force × Distance

Work is in joules (J) or newton-meters (N . m). Force is in newtons (N). Distance is in meters (m).

The wind turbine you will build is not ambitious enough to lift a rock, but it will be able to hoist several paper clips high into the air. Now it's time to spin some wheels!

Terms, Concepts and Questions to Start Background Research

• Wind turbine
• Mechanical energy
• Electrical energy
• Rotor
• Shaft
• Work
• Horizontal-axis wind turbine
• Vertical-axis wind turbine
• Efficiency
• Wind vane
• Power
• Rate
• Force
• Gravity

Questions

• What are the parts of a wind turbine?
• How does a wind turbine work?
• What are the advantages and disadvantages of horizontal-axis wind turbines and vertical-axis wind turbines?

Bibliography

This source defines and describes different types of wind turbines, and highlights their advantages and disadvantages:

• Wikipedia Contributors. (2008, June 3). Wind Turbine. Wikipedia: The Free Encyclopedia. Retrieved June 3, 2008, from http://en.wikipedia.org/w/index.php?title=Wind_turbine&oldid=216857001

This source shows an animation of a wind turbine in action:

• U.S. Department of Energy: Energy Efficiency and Renewable Energy. (2005, September 14). How Does a Wind Turbine Work? Retrieved June 6, 2008, from http://www1.eere.energy.gov/windandhydro/wind_animation.html

For help creating graphs, try this website:

• National Center for Education Statistics (n.d.). Create a Graph. Retrieved May 23, 2008, from http://nces.ed.gov/nceskids/CreateAGraph/default.aspx

Materials and Equipment

• Pinwheel, store-bought or homemade
• Scissors
• 8.5-inch x 8.5-inch sheet of paper (if making your own pinwheel)
• Ruler
• Pen
• Nail
• Wooden skewer, available at grocery stores
• Tape, any kind
• Empty oatmeal canister with plastic lid
• Handful of rocks (or heavy objects to keep the oatmeal canister weighted down)
• Small compression spring (approximately ½ inch long and able to fit over skewer); available at hardware stores
• Clear tape
• Spool of thread (1)
• Paper clips, #1 size (5)
• Measuring tape
• Room in your home that is free from drafts
• Hair dryer
• Table or chair
• Sticky notes, small size
• A helper
• Stopwatch
• Lab notebook
• Graph paper

Experimental Procedure

Making Your Rotor

1. If you are using a store-bought pinwheel:
   1. Remove the pinwheel blades from the shaft by cutting off the plastic, flanged tip of the shaft. Now you have a store-bought rotor ready to go on the skewer.
2. If you are making your own pinwheel:
   1. Fold the square of paper along the diagonal and then unfold it back into a square again. Fold the square of paper again along the other diagonal and unfold it back into a square again. Your paper will now look like a square with a big "X," made by creases.
   2. Measure approximately 2 inches out from the center along each crease and make a dash mark with your pen, like in Figure 3, below.
   3. Make four holes with a nail near the corners of your square in approximately the same positions as those shown in Figure 3, represented by the black dots (the dots only represent location, not size of the holes). Use caution with the nail and be careful not to poke the nail into the surface underneath the paper.
   4. Make one final hole with the nail in the center of your square.

      Figure 3. This drawing shows the holes, creases, and cuts needed to make your own pinwheel.

   5. From each corner of the square, cut down along the crease with the scissors until you reach the mark you made with the pen. Now you are ready to form your pinwheel and make your homemade rotor.

Building Your Horizontal-Axis Wind Turbine

1. Using scissors or the nail, carefully cut two small holes on opposite sides of the oatmeal canister, approximately 1 inch down from the top of the canister. Use Figure 4 below as a guide.
2. Remove the lid and place the rocks inside the canister.
3. Thread the skewer through the two holes.
4. Thread the compression spring onto one end of the skewer.
5. Thread the rotor, either store-bought or homemade, onto the skewer next to the compression spring.
   1. If using the store-bought rotor, it is ready to thread onto the skewer.
   2. If using the homemade rotor, it must be formed first, as follows:
      • Pick up each of the holes at the corners of the square and fold them, one at a time, over onto the middle hole, so that they are all on top of one another. Then thread all five holes onto the skewer.
6. On the side of the rotor that will face the wind source, tape the rotor, either store-bought or homemade, securely with tape around the skewer so that it cannot "slip" as it rotates. To make sure it is secure, blow on the rotor. If the rotor is taped securely, the skewer shaft will rotate as the blades spin.
7. Cut approximately 1-2 feet of thread with the scissors.
8. Tie one end of the thread to the end of the skewer that does not have the rotor on it.
9. Tie the other end of the thread to one paper clip.
10. Attach 2-4 more paper clips to the first paper clip to increase the weight (load) that your horizontal-axis wind turbine will be lifting. You want enough weight that the thread is not slack, but not so much weight that the turbine cannot lift it. Your wind turbine should look similar to the one in Figure 4.
11. Extend the thread its full length and measure its length with the measuring tape, from the skewer to the top of the first paper clip. Note this measurement in your lab notebook. Now you are ready to start testing!

Figure 4. These photographs show how to build a horizontal-axis wind turbine using a homemade (on the left) or store-bought (on the right) pinwheel.

Testing Your Pinwheel

1. Place your wind turbine at the edge of a chair or table in a room free from drafts and close to an electrical outlet, as in Figure 4.
2. You will be testing your wind turbine at five different points around the rotor, as shown in Figure 5. To mark these points on the table, extend and lock your measuring tape so that it is approximately 6 inches longer than the radius of your rotor. Hold one end of the measuring tape directly below the point where the rotor meets the skewer, and the other end of the measuring tape at the approximate points around the pinwheel, shown in Figure 5. Mark the points on the table with small sticky notes. When you begin the test, you will hold the handle of your hair dryer on the sticky notes and the blower end will point at the rotor. The goal is to have 1-2 inches between the rotor and the blower. If you don't have enough room, or have too much space, then adjust your sticky notes outward or inward.

   Figure 5. This top-view drawing of the homemade wind turbine shows the five approximate points around the rotor that will be marked and tested.

3. Now you're ready to put your wind turbine to work! Although it is possible to do testing with one person, it is easier with a helper. Have one of you operate the stopwatch and the other person hold the hair dryer. To get an idea of what is going to happen, turn your hair dryer on low and slowly move it from one sticky note to the next as you watch the pinwheel spin. Make some notes in your lab notebook about how your pinwheel behaved as you moved the hair dryer around. Now you're ready to test!
4. Extend the thread and its load of paper clips to its full length.
5. Place the handle of your hair dryer on the first sticky note. Point your hair dryer away from the rotor and turn the hair dryer on low.
6. When the helper says, "Go!" and starts the stopwatch, point the hair dryer directly at the rotor and leave it there. Try to keep the hair dryer at the same level for each of your trials.
7. Observe the motion of the paper clips. When the top of the first paperclip reaches the skewer, the helper should stop the stopwatch. If the paper clips fail to rise all the way to the skewer, then stop the stopwatch when the paper clips stop moving.
8. Turn off your hair dryer and fill out the time it took to raise the paper clips or the time at which they stopped moving in a Time Data Table in your lab notebook, like the one below.

   Time Data Table
   Position of Wind Source Around Rotor (deg)	Trial 1: Time to Raise Load (sec)	Trial 2: Time to Raise Load (sec)	Trial 3: Time to Raise Load (sec)	Average Time of Trials (sec)
   0
   45
   90
   135
   180

   
   

   Distance and Work Data Table
   Position of Wind Source Around Rotor (deg)	Trial 1: Distance Paper Clips Were Raised (inches)	Trial 2: Distance Paper Clips Were Raised (inches)	Trial 3: Distance Paper Clips Were Raised (inches)	Average Distance and Conversion to Meters (m) (1 inch =0.0254 m)	Average Work Done = Force Due to Gravity × Average Distance (N . m )
   0
   45
   90
   135
   180

9. Measure and record the distance that the paper clips were raised in a Distance and Work Data Table, like the one above, in your lab notebook.
10. Repeat steps 4-9 for all the sticky note positions.
11. Then perform two more trials with steps 4-9, for each hair dryer position. Be sure to record all your data in the tables in your lab notebook.

Analyzing Your Data

1. Average the times of your trials for each hair dryer position and record your calculations in your Time Data Table.
2. Average the distances that your paper clips were raised for each position of the hair dryer around the rotor, then convert your averages to meters by multiplying each one by 0.0254. Record your calculations in your Distance and Work Data Table.
3. Calculate the mass of your load in kilograms (kg). One #1 paper clip has a mass of 0.00043 kg, so if you used three paperclips, then the mass of your load would be three times this number. Record the combined mass of your paper clips in your lab notebook.
4. Calculate the force (in newtons) that the combined mass of the paper clips experiences due to gravity by multiplying the mass of the paper clips (in kg) by 9.81 (m/sec²). Record this force in your lab notebook.
5. Calculate the average work you did for each position around the rotor by multiplying the force on the paper clips due to gravity by the average distance you raised the paper clips (in meters). Record the average work done in your Distance and Work Data Table.
6. Calculate the power your wind turbine achieved for each position around the rotor using the average work that you calculated in your Distance and Work Data Table and the average time you calculated in your Time Data Table. Record your calculations in a Position vs. Power Data Table, like the one below.

   Position vs. Power Data Table
   Position of Wind Source Around Rotor (deg)	Power=Average Work Done Divided By Average Time (W)
   0
   45
   90
   135
   180

7. Plot how the power changed with position around the rotor. Label the y-axis Power (W) and the x-axis Orientation to the Wind Source (deg). You can make the line graph by hand or use a website like Create a Graph to make the graph on the computer and print it.
8. Which orientation to the wind (position of the hair dryer) produced the most power for your pinwheel? Which orientation produced the least? Were there any orientations that produced nearly equal power?

Variations

• Compare the power to wind-source orientation curves for two different types of pinwheels.
• Determine the best orientation to the wind for an 8-blade pinwheel. Cut off one blade at a time and evaluate how the power changes.

• For more science project ideas in this area of science, see Energy & Power Project Ideas.

Credits

Kristin Strong, Science Buddies

The wind turbine design for this project was modified from:
The NEED Project Contributors. (2007). Wonders of Wind Teacher Guide. Retrieved June 13, 2008, from http://www.need.org/needpdf/WondersofWindTeacher.pdf

This project was inspired by:
Flannery, Morgan P. (2008). Wind Power—Is Bigger Better? Do large, wide wind turbine blades generate more power than small, narrow blades? PG&E 2004 Bay Area Science Fair Awards. Retrieved June 13, 2008, from http://www.pge.com/mybusiness/edusafety/training/pec/basf/sciencefair2004.shtml

Last edit date: 2008-10-09 22:00:00

Career Focus

If you like this project, you might enjoy exploring careers in Energy & Power.

	Nuclear Engineer Nuclear engineers harness the power of the atom to help solve large and difficult problems facing humanity. They design power plants that create energy to power homes and businesses without producing greenhouse gases. They develop machines that image the human body and destroy cancer cells, sterilize food and medical equipment, and create new pest or drought-resistant seeds. They work to make the world a better place.			Power Distributors and Dispatcher Think of all the things in your home or school that use electricity, like the lights, TV, refrigerator, washer, microwave, music players, computer, and electronic devices. Now think of how you feel when the power goes out, even for just a moment. Power plant distributors and dispatchers have an important job—they work to keep electricity flowing to homes and businesses by carefully watching and planning for problems like big storms that could damage transmission lines, heat waves that cause a big surge in demand for power, or normal construction work, which could take transmission lines out of service.
	Power Plant Operator No matter what time of the day or night, or what the weather is like, power plant operators work to ensure that homes and businesses have a reliable source of power. They switch the plant generators on and off, as needed, and monitor and maintain generators, turbines, and pumps to prevent failures.			Nuclear Power Reactor Operator One in five United States homes and businesses is powered by nuclear power, and nuclear power reactor operators are the people who ensure that those reactors are operating safely and efficiently at all times. They monitor all equipment continuously, and implement procedures if malfunctions are observed. They also control and adjust the amount of power being generated, and the reactor coolant temperature as power demands change through the day and during weather events, like heat waves.

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