Number and Size of Blades on Wind Turbine vs. Electrical Output

Researched by John H.


The purpose of this experiment was to determine which size and number of wind turbine blades would produce the most electricity.

Air pollution is important to me.   I am interested in wind turbines as alternative energy; this experiment will hopefully improve the current wind turbines to produce more electricity.

The information gained from this experiment will help people avoid polluting the air by using wind turbines instead of gas generators, which pollute the air.

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My hypothesis is that the wind turbine with six blades and the largest blade will produce the most electricity.

I base my hypothesis on a helpful book American Windmills which has several windmill designs and I think that the bigger the blade, the more electricity produced.

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Experimental Design

 The constants in this study were 

  •  Speed of the fan for “creating wind”
  •  Shape wind tunnel
  •  Flow straightner
  •  Wind Turbine
  •  Generator
  •  Voltmeter used for measuring electricity
  •  Environment  the tests were  measured  in 
The manipulated variable was the number and size of the wind turbine blades.

The responding variable was electrical out-put from the generator hooked to the windmill.

To measure the responding variable I used a voltmeter.

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Board A and C (55-42cm. card board small end in the center of one end)
 Board B and D  (55-32 card board small end in the center of one end)
Wine box
ply wood board (15-15cm)
 ply wood board (5-5cm.)
1.25 diameter dowel
58-32 cardboard piece
58-30 cardboard piece
One Roll
Duct tape
DC motor
Propellers (3-4cm. balsa wood)
Propellers (3-8cm. balsa wood)
Propellers (3-12cm. balsa wood)
Drill with 1/4 bit and a 1/16 bit
Band saw
Rubber corks cir. (6cm.)
Box fan
Center finder
Drill press

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 Build A Wind Tunnel
1. Connect board A to board B, and B to C, and C to D, and D to A with he small ends together.
2. Tape the large of the funnel to the fan.
3. Duct tape the small end of the funnel to the wine bottle box.
4. Take the two 68cm. by 24cm. and duct tape it to the 68cm. by 32cm. to form a geometric rectangle
5. 11cm. from the wine box, on the left side of the tunnel, cut a vertical slit 3 cm. for the top and bottom.
6. Repeat step five, but make the slit 62cm. from the wine box.
7. cm. from the top and 11cm. from the wine box, make a third slit 51cm. long.
8. Repeat step six, but make the slit 3 cm. from the bottom.
9. Duct tape the Saran Wrap evenly over the hole in the side of the tunnel and tape it down
10. Take the stand pieces and duct tape them together to form a cube. (A tub the right size works to)
11. Tape the stand 10cm. from the end of the tunnel using duct tape.

Build A Wind Turbine
12. Lightly hammer in a nail in the center of the 15-15 board.
13. Drill a hole with a 1/16inch bit about two cm. down.
14. Stick the small hole in the dowel on to the point of the nail.
15. Continue hammering the nail into the dowel.
16. Place the motor on the edge of the 5-5 with the shaft sticking out.  Screw the motor in place.
17. Remove the motor from its stand.
18. Repeat steps 12-14 but with the 5-5.
19. Return the motor to its stand.
20. In the first rubber cork drill four holes exactly across from each other.
21. In the second rubber cork drill six holes exactly across from each other
22. In the exact center of the cork, using the drill press, drill a 1/16 of an inch 1.5 cm. in the cork.
23. Stick the shaft of the motor in the center of the cork.
24. Mark the small dowel in 1cm. increments.  Make 36 of he lines.
25. Cut a vertical slit to the first line with the band saw in the end.
26. Then cut along the second line.
27. Repeat step 25 and 26 until there are 18 pieces
28. Insert the dowel pieces in the propeller’s ends.
29. Hook up the voltmeter to the motor.

Do the Experiment
30. Insert two of the 3x4 propellers in the first cork with four holes across from each other.
31. Turn on the fan and record the reading from the volt meter
32. Insert three 3x4 propellers in the second cork evenly distributed.
33. Repeat step 31.
34. Insert four 3x4 propellers in the first cork.
35. Repeat step 31.
36. Insert six 3x4 propellers in all of the holes in the second cork.
37. Repeat step 31.
38. Repeat steps 23-39 with the 3x6 and the 3x8.
39. Repeat steps 31-39 two more times.

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The original purpose of this experiment was to test the size and the number of the blades against electrical out put.

The results of the experiment were that on average the 3x8 with four blades produced The most electricity.  The 3x6 blade tests were in the middle of the 3x8 and the 3x4.  In the average bars in my graph it shows that the six bladed was the one that produced the least amount of electricity.  The next was the two bladed, three bladed, and the four bladed.

Here is my Graph


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My hypothesis was that the longest and the most number of blades would produce the most electricity. 
The results indicate that this hypothesis should be rejected.  Because of the results of this experiment, I wonder if vertical axis wind turbines produce more electricity than horizontal axis turbines. 
If I were to conduct this project again I would made a bigger wind tunnel and use a more powerful fan so I could test more sizes of blades and styles of wind turbines.

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Research Report

Wind turbines are machines that generate electricity.  They produce no pollution but they also have down sides. Wind turbines are a great way to get energy without pollution.

History of wind mills and wind turbines
 Wind mills date back to the days of the Persians in 7th century A.D.  They were originally used for pumping water for livestock or for grinding grain into flour.  Windmills were used throughout Europe and parts of Asia.  The Dutch are famous for their windmills.  The Dutch built a great wall out in the sea and make something like a lake.  Windmills were used to pump the water out, and dry land was formed.
 The pilgrims at Cape Cod built the first American windmill in 1663.  Many other windmills were built in the New England colonies, most were built on Long Island.  When the wind was not turning the blades, if the blades were at a certain angle, it meant something like a death, birth, sickness or party. 
 Early American windmills had three main levels.  The first level held grain that had been ground.  The second level had several gears and the third level had grain that not been ground and the millstone to grind the grain.  During the westward expansion, pioneers built windmills for pumping water for their live stock.  Windmills were very heavy and when the pioneers would move the windmills were extremely hard to move.  Many men tried to build a sturdy lightweight windmill.  Daniel Hallday and John Burnham built a wood windmill and it looked like a skeleton.  The propeller had about many blades. They needed extra strong wind turbines because of the prairie winds that swept over the vast land. O. Perry, an inventor built a light metal windmill and then he hired L. W. Noyes to sell them for him.  In the early West, 6,200,000 windmills were built.  To day, windmills are used mainly for decorations on ranches and old farms.  They are not used for grinding grain because people can buy flour at the store.

Wind Turbines
 Wind turbines are windmills that generate electricity.  Wind turbines produce electricity with no pollution.  There are many styles of wind turbines. There are vertical axis and horizontal axis turbines.  When most people think of a wind turbine, they think of horizontal axis turbines.  Vertical axis wind turbines are different in many ways.  They do not have to have a swivel in order to catch the wind.  The turbines can produce electricity with less wind than horizontal axis generators.

There are also problems with wind turbines.  Birds fly in the blades and they are slaughtered.  Patterns have been put on the blades to make them more visible.  Sound is another problem.  Wind turbines produce a lot of noise.  Most of the wind farms are out in the desert and this has helped a lot with that problem.  They also interfere with television and radio reception.  This poses a big problem and people do not like these problems, they just want to get the electricity. 
The First
 The first wind turbine was erected in Russia in 1931.  The second was built in 1941 in Vermont on a hill called “Grandpa’s Knob.”  It was the largest windmill built in the world.  One part broke and it was not replaced.  It was finally replaced after World War II.  The third wind turbine was constructed in the Orkney Islands in 1954.

Future of Wind Turbines
 The newest style of windmill is the vertical axis or Darrius.  They look like a giant eggbeater.  There are many test sites in Canada and they have made many contributions to the science of wind power.  These new wind turbines produce more electricity than horizontal axis wind turbines do.  They are more efficient than the old style.  Computers have also helped in the designing of the new wind generators.

 Wind Turbines have a long history and the date back to the ancient times.  They have been used through history and they are still in the process of developing.  Windmills and wind turbines are both an old and new energy sources. 

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Cosner, Sharon,  “American Windmills, ”David McKay Company Inc., 1977

Gary, Chandler and Kevin Graham,  “Alternative Energy Sources,” Fitzhenry and 
Whiteside Ltd., 1996

Mike Eisele, "Which Blade Variable Has the Greatest Effect on Windmill Efficiency," [Online] Available at

Eric Jenkins, "Which Windmill Blades Angle is Most Efficient," [Online] Available at

Manwell, James E.  “Windmill” Encarta 98

McDonald, Lucile  “Windmills New and Old Energy Source” Eliever-Dutton Publishing Co. Inc.

Visich, Marian Jr. “Turbines” World Book Encyclopedia 1995 v.19 pg. 498-500

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