Wind Turbine Experiment:

This page demonstrates an example setup of a wind turbine experiment. This activity focuses on variables to keep in mind when recording and interpreting power output. Remember that a good scientific experiment should follow the scientific method:

 

1. Ask a question (i.e. What effect does     wind speed have on voltage?)
2. Do background research
3. Construct a hypothesis
4. Test your hypothesis by doing an     experiment
5. Analyze your data and draw a
    conclusion
6. Change variables and repeat tests
7. Communicate your results

      To learn more about the scientific method,       click here >>

 

What is a wind turbine experiment?:
We’ll begin with the equation that determines how much power you can produce with your wind turbine (from awea.org):

P = 0.5 x rho x A x Cp x V^3(cubed) x Ng x Nb

• P = power in watts (746 watts = 1 hp) (1,000 watts = 1 kilowatt)
• rho = air density (about 1.225 kg/m3 at sea level, less higher up)
• A = rotor swept area, exposed to the wind (m2)
• Cp = Coefficient of performance (.59 {Betz limit} is the maximum theoretically possible, .35 for a good design)
• V = wind speed in meters/sec (20 mph = 9 m/s)
• Ng = generator efficiency (50% for car alternator, 80% or possibly more for a permanent magnet generator or grid-connected induction generator)
• Nb = gearbox/bearings efficiency (depends, could be as high as 95% if good)

The main variables that you should keep in mind for your experiment are

1) Swept area of your rotor

2) Coefficient of performance (this will actually include all aspects of turbine and blade design, discussed below and on other sections of our site)

3) Wind speed

4) Generator (unless you really know about generators, it is advisable to keep the motor constant in your experiments

5) Gear ratio attached to your generator

In order to see the effects these variables have on the power output of a wind turbine, you have to set up an experiment to test each variable. In a wind turbine experiment, when you change one variable, remember to keep all other variables constant.

Setup:

You will need to setup a model wind turbine and a fan. You will also need some kind of meter to measure the power output of your data, unless you are using your turbine to do non-electrical work such as weight lifting.

Here are some materials besides a turbine and a
fan that you may want for the experiment:

• Tape: (for marking a constant spot for your turbine to remain)
• Multimeter or some kind of meter or load device that will measure the amount of electricity your turbine produces.
• Wind Speed Meter : If you want to see how wind speed affects power output, you should
  use an anemometer to measure the wind speed of your fan.

 

Turbines:

For ideas on how to make a turbine, head here >> When you have a turbine completed, set it up in a fixed location. It should remain the same distance from the fan at all times (1.5 – 2ft is usually good).

 

Fans:

You should use a floor fan that has at least 3 settings so you can experiment with how wind speed affects power output. We recommend a fan that has a diameter of at least 20" and that can be propped to the height of your turbine.

 

Variables:

For a discussion of variables, head here >>

1. Blade Design : Without blades, your turbine wouldn’t produce any electricity. Some blade factors to consider are:
   • Size
   • Shape
   • Number
   • Pitch
   • Weight
   • Material
   For information about blade design variables, head here >>
2. Wind speed : Most fans have 3 different speed settings. You can also change the wind speed by moving your turbine closer or further from the fan.
   • Wind tunnel : If you’re really serious and want non-turbulent wind, you can try to smooth the air by making a wind tunnel >>
     
3. Generators
   You will need a generator that produces recordable voltage at relatively low RPM. For a discussion of generators, head here >>
   
4. Gear ratios
   You may want to attach a gear system to your generator.
   For more information about gear ratios, check out the Gear Ratios Document (pdf) >>

Different kinds of experiments :

When conducting an experiment, decide which variables you want to test. Do you want to know how wind speed affects power output? Or do you wan to know how the number of blades affects power output? You can set up different experiments to test different variables. Here are a few examples. Remember to only change one variable per experiment.

 

Voltage based on wind speed (mph)

? v
4 v
3 v
2 v
1 v
	7 mph	8 mph	9 mph	10 mph	11 mph	12 mph

Voltage based on Blade pitch (degrees)

? v
4 v
3 v
2 v
1 v
	5 deg	15 deg	25 deg	35 deg	45 deg	55 deg

Voltage based on Blade shape

? v
4 v
3 v
2 v
1 v
	Rectangle	Trapezoid	Triangle	Bowl	Twist	Bart Simpson