Construct a Wind Power Generator: Determine Rotor Size for 3V & .2W

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Discussion Overview

The discussion revolves around the construction of a wind power generator using straws, focusing on determining the appropriate rotor size to achieve a minimum output of 3V and 0.2W while withstanding a horizontal force of 15N. Participants explore various aspects of the design, including materials, rotor types, and testing methods.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Homework-related

Main Points Raised

  • Some participants inquire about the rotor material and design, suggesting options like a cup-style anemometer.
  • There is a discussion about the height of the tower, with one participant stating it will be 40cm and questioning if that is sufficient.
  • One participant emphasizes the need to determine the motor's RPM that corresponds to the required voltage and power output.
  • Concerns are raised about how to apply the specified 15N force to test the tower's rigidity and the method for measuring the motor's output.
  • Participants discuss the implications of using different numbers of blades for the rotor, considering weight and efficiency.
  • Questions arise regarding the wind velocity during testing and how it relates to the force exerted by the fan.

Areas of Agreement / Disagreement

Participants express various viewpoints on rotor design and testing methods, with no clear consensus on the best approach or the adequacy of the tower height. Multiple competing ideas about rotor construction and testing remain unresolved.

Contextual Notes

Participants mention the need for specific measurements and testing methods, but there are uncertainties regarding the formulas applicable to the situation, particularly concerning the relationship between wind force and power output.

Who May Find This Useful

This discussion may be useful for students and hobbyists interested in renewable energy projects, particularly those focused on wind power generation and experimental design using basic materials.

Ry122
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I have to construct a wind power generator out of straws. It has to provide no less than 3V and .2W for a period of 1 minute and be able to withstand a horizontal force of 15N.
How would I determine what size the rotor would have to be to create this voltage and current from 15N ?
 
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Ry122 said:
I have to construct a wind power generator out of straws. It has to provide no less than 3V and .2W for a period of 1 minute and be able to withstand a horizontal force of 15N.
How would I determine what size the rotor would have to be to create this voltage and current from 15N ?

Can you say any more about how you're going to form the rotor out of straws?
 
The tower is going to be made out of straws, the rotor can be made out of anything. I am not sure about what I am going to use yet for the rotors, got any ideas?
The only formula I have found for wind tower power output has a velocity variable and since I only know the force the wind will have I can't use it.
 
Ry122 said:
The tower is going to be made out of straws, the rotor can be made out of anything. I am not sure about what I am going to use yet for the rotors, got any ideas?
The only formula I have found for wind tower power output has a velocity variable and since I only know the force the wind will have I can't use it.

Can you use an cup style anemometer as a rotor? I believe the formulas for these are readily available. How tall will your tower be?

Chris
 
The tower has to be 40cm tall. Is that tall enough?
 
They way I would approach this is:
First I would have to figure out what motor I should use -- if you are provided with one, what motor RPM corresponds to an output voltage of 3V with a given load that would consume .2W (this can probably be tested).

Once I know the RPM, I need to know what torque is required to maintain that rpm.
As was said above, a cup anemometer is probably the easiest to build. The force on the device would be the the difference in drag between the cups facing one way and the other, and the bigger radius they sweep the larger the torque.
 
Ry122 said:
The tower has to be 40cm tall. Is that tall enough?

I'm not sure why you're concerned about the height.
 
Ry122 said:
I have to construct a wind power generator out of straws. It has to provide no less than 3V and .2W for a period of 1 minute and be able to withstand a horizontal force of 15N.
How would I determine what size the rotor would have to be to create this voltage and current from 15N ?

What will be the velocity of the wind source used to test this device?

How will you apply the 15N horizontal force to test the tower for rigidity?

Chris
 
ctjen said:
What will be the velocity of the wind source used to test this device?

ry122 said:
The only formula I have found for wind tower power output has a velocity variable and since I only know the force the wind will have I can't use it.


ctjen said:
How will you apply the 15N horizontal force to test the tower for rigidity?

With a 350mm diamater, 3 blade household fan running at full speed.


ctjen said:
I'm not sure why you're concerned about the height.

ctjen said:
How tall will your tower be?
 
  • #10
How did you determine that the fan exerts a force of 15N?

Do you have a controlled way to rotate the electric motor? For example, an eggbeater crank style hand drill or a variable speed electric hand drill?

Do you have a volt meter and some resistors so you can put a load on the motor and test it's output?

What other materials besides straws can you use to assemble the tower? Are they paper or plastic straws?

Regarding the design of the rotor the first thing you need to determine is how much rpm you need on the motor to output .2W at 3V. Unless you already have an rpm specification for the particular motor you're using you're going to have to measure it. Do you have a method in mind for doing that?

Chris
 
  • #11
It says in the assignment task sheet that the wind will be 15N.
What do u mean by control the rotation of the rotor? Do you mean the speed? If so, then this would be unnecessary since the fan will provide a constant velocity wind.
Do you think I should build it with 2 or 3 blades? We get marked down the heavier the tower is.
 
  • #12
What grade level is this project?

Chris
 

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