Final: The Pinwheel Experiment

1 05 2012

In light of our experiment, I would just like to make readers aware of Global Wind Day, it is a highly successful phenomenon. It takes place on June 15 and is a day when wind energy is recognized, celebrated and everyone is educated about the importance of wind energy from children to adults. The day includes parades, demonstrations and workshops and over 30 countries participate in 4 continents! The event really took off in 2009 when 1 million people decided to participate! The first major display took place in Brussel, Belgium with a wind turbine blade that reached 30 meters high in 2010. This was a huge achievement towards putting wind power on display!

Source: Wind Day website




Wind Turbine Lab: How Many Blades Are Best?



To determine the optimum number of blades a wind turbine needs for maximum electricity generation.


We believe the 3 bladed turbine will work best because this is the industry standard.

World Wind Capacity

This is the global usage of wind since 2000 to 2011, it has greatly increased fortunately.


  • We must choose how we use our resources to meet our energy needs. By 2060 we will have a 9 billion population from the 6 billion we have right now.
  • Wind energy is used to propel blades and transfer wind energy to kinetic energy.
  • Wind turbines catch the energy of the wind and use that energy to turn it into electricity.

Worldwide fossil fuel reserves are finite, and are expected to be depleted in the near future. Therefore, alternative forms of energy production are in high demand. One example: wind turbines, are an attractive alternative to meet energy demand. Wind turbines work by converting the kinetic energy of wind into mechanical energy, which then gets distributed to the gears of the electric generator, and then that energy is converted into the form of electricity. Voila! We have electricity made from wind. (Technically speaking, wind energy is actually an indirect form of solar energy because as the sun heats up the air; there is an unequal distribution of that heat which causes convection. Convection is the process by which the thermodynamics of non-solids act out. In terms of weather, heated air rises, cooler air fills in the gaps left behind by rising hot air, and the kinetic result is: wind energy.) However, as dire our modern needs are for sustainable forms of energy today. Wind energy has actually been around since ancient times in the form of windmills and sailing vessels. Therefore, many various wind power designs have surfaced. This lab will work to determine which design will generate the most electricity. (Assuming that everything but, the number of blades for each wind turbine variant is identical.) Therefore knowing that the faster wind speeds will generate more electricity. The question is… What is the optimum number of blades for a wind turbine to move at the fastest speeds: if the wind speed is constant for each variant design and if everything else is identical.



Here is an example of a real wind turbine set up



  • Setup:

1.    Gather materials: four square sheets of construction paper (20cm x 20cm), four long straws, four pencils (optional), four tacks, tape, scissors, a ruler, a fan, and a strobe light.

2.    Fold each sheet of paper diagonally so that there are two creases that are both intersecting the middle of the square and are meeting each of the four corners.

3.    Using the ruler, measure and mark 4cm distance points along the crease from the center. Repeat for the remaining three creases.

4.    Using the scissors, cut along the creases until the marked points, from step 3.

5.    Now fold each “triangle” in half with one corner pointing towards the center. Repeat for the remaining eleven “triangles”.

6.    Cut off extraneous blades so that there is one pinwheel with one blade, another with two, another with three, and the last with four. (This experiment is only testing 1-4 blades).

7.    Using tape, tape each folded “triangle” so that they are shaped like blades. If needed, one can prop open these pockets by indenting the sides. Mark one blade for each pinwheel with a solid dot near the corner farthest from center on the back of the pinwheel.

8.    Using tacks, now attach each pinwheel variant to their respective straw or “towers”. (The pencils can be stuffed into the interior of each straw to add more stability.) Note to give enough spacing between the tack, pinwheel, and tower to allow the pinwheel to freely rotate.

9.    Using the fan and strobe light, connect them to a power source and position them on opposite ends with the fan facing towards the pinwheel that is being tested and the strobe light behind the pinwheel.

  • Collecting the Data:

1.    After everything is in their proper positioning, have an observer present to record the data. The pinwheel in question must be 25cm away from fan.

2.    Turn on the fan and set it to a constant speed for the remainder of the experiment.

3.    Now let the pinwheel rotate. (If it isn’t then adjust fan speed accordingly or position the pinwheel so that it does.)

4.    Turn on strobe light to judge speed relative to frequency of strobe. (Adjust strobe accordingly.) The idea is that the pinwheel that is rotating faster will have the dot on the one blade being animated slower. This is due to the beta effect or optical illusion of persistent vision. Relative to the speed of the pinwheel, the pinwheel moving fastest will have the dot be more “animated” against the background strobe light.

5.    Record the data.

6.    Repeat steps 1-5 for each pinwheel variant.

Pictures of Our Experiment:

Our Materials


Martin holding the pinwheel


Other Group Performing Our Exp
4 Bladed Pinwheel
The Strobe
Experiment in Action


Trial 1

Blade 1 Blade 2 Blade 3 Blade 4
Not sufficient 





3800 3800

Trial 2

Blade 1 Blade 2 Blade 3 Blade 4
Not sufficient 


2200 4000 3900

Trial 3

Blade 1 Blade 2 Blade 3 Blade 4
Not sufficient 


1600 3900 4000

Note: Record the frequency setting from strobe light that will indicate the rate of speed of rotating blade(s)


Based on the data, what is the optimum number of blades for a wind turbine to move at the fastest speeds: if the wind speed is constant for each variant design and if everything else is identical?


State which blade variant was fastest beginning with ‘1.’ in descending order.

1. 4

2. 2

3. 3

4. 1


Further Notes/ Evaluation:

1. We believed that previously the symmetrical pinwheels would work the most efficiently and we were correct.

2. Once we turned on the strobe, the key was to go down slowly until you think the pinwheel is going backwards.

3. We could have dealt with the experiment more efficiently by changing a few things. We could have had tape on deck to be more ready, we could have built a more stable pinwheel, and we could have had less friction between the paper and straw.

4. The air pockets had to be as open as possible to actually move the blades and catch the wind.

Here are some links if you would like to learn more:

An idea of annual wind speed and energy generated in kWhrs/ a day and m/s

Our Presentation: —>Turbines in the real world B2C stantpoint


Wind Day Partners:



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