Wind Energy Background:
1. Define voltage, current, resistance and power.
2. Objective: design a wind turbine that will produce the maximum amount of power utilizing the average wind speed in North
Dakota (15-20 mph).
3. The variables to investigate include the following:
• Type of blades used: straight vs. curved
• The number of blades used: 3 or 4
• The angle of the blades: 30-90o (change in 15o increments)
• Resistance: 30-80 Ω (though the actual range is 0-100 Ω)
Variable: changing one item changes the results of the experiment.
Independent variable: a variable that is changed by the scientist. A good experiment typically has one independent variable.
Dependent variable: the observations of the experiment. The dependent variables are the items that change as a result of changing
the independent variable.
Controlled variable: quantities that the scientist wants to remain constant. The controlled variables must be observed as carefully
as the dependent variables.
Relationship of Voltage, Current, Resistance and Power
Voltage (E): a force that causes free electrons to move from one atom (or point) to another.
Current (I): the rate of electron flow through a material.
Resistance (R): the forces that oppose the flow of electron current in a conductor.
Power (P): the measure of work an electrical current can accomplish in a period of time.
E=IxR
and
P=ExI
So, what’s the difference between energy and power?
Energy is “stuff” – it can’t be created or destroyed, it’s just always there. It can, however, be converted to another form. It may be
converted to heat, moving mass, light, a chemical reaction, or electricity. Power is the rate at which that energy “stuff” is converted.
Instructions:
Set up the windtrainer kit as shown in the picture below. In the table provided, the first six experiments are given. Set up the
variables, and fill in the rest of the table. Using the anemometer, measure set the wind speed to 15 mph. Once the first six
experiments are completed, then it is time to design your own! Design your own experiments with the different variables that are
available to test. Make sure to only change one variable at a time. Be creative and feel free to continue your table and experiments
on the back side of the paper. When all of the experiments are completed, make sure to crank up the wind speed and see how
much energy you can produce (just because it’s fun)!
Blade Design
# of Blades
Angle
Curved
2
45
Curved
2
Neg 45
Curved
3
0
Curved
3
45
Curved
4
45
Straight
2
90
Predicted Design
(1-best, 6-worst)
Wind
Setting
12-15
mph
Predicted
Current
Predicted
Voltage
Design Your Own Experiment – only change one variable at a time.
Now it’s time to crank up the wind speed. Design what you think will give the greatest amount of energy!
30
Measured
Current
Measured
Voltage
Calculated Power
P=Current X Voltage
milliwatts
Observations:
Light
Motor
Discussion:
1. Were your predictions correct?
Answers will vary.
2. When the blades were set at 90 degrees or 0 degrees, what were your observations? What could explain this?
If the students had them at 90 and 0, the blades should not have turned at all.
3. What is the optimal number of blades? Why?
This will vary depending on the angle and curved/straight choice.
4. Can you think of any other variables that you could test with this kit?
The wind speed could be tested to see if there is a direct relationship between the amount of energy generated and the
wind speed.
5. Design a graph with the results of your experiment.
Variable
_______________
Power
6. Is there a relationship on your graph?
Answers will vary. There should be a direct relationship on their graph if only one variable was changed at a time.
7. What is the relationship between voltage and current?
As voltage goes up, current goes down and vice versa. It is an indirect relationship.
8. If you play your Xbox for 1 hour a day, you will use approximately 200 Watts or 200000 milliwatts of power. With
your best windmill design, how many windmills would you need to set up in order to power your Xbox for that hour?
Answers will vary depending on the students design.