Wind Power B/C

[dragonfruit35]

As I mentioned above, there seemed to be some confusion due to the diagrams in the rules this year. Below are some modified diagrams I've made. Any suggestions / comments on whether these will help clear up the confusion?

Slide2.PNG

Slide1.PNG

Looks good, except it's a little hard to tell what the 3cm is pointing to.

[PHXcoach]

As I mentioned above, there seemed to be some confusion due to the diagrams in the rules this year. Below are some modified diagrams I've made. Any suggestions / comments on whether these will help clear up the confusion?

I am not sure about showing the generator on the front view. This might lead to more questions about the 3 cm keep out being both the front and the back.

Maybe show a front view (without the generator) and a rear view next to it that shows the generator and the 3 cm keep out.

[JustDroobles]

As I mentioned above, there seemed to be some confusion due to the diagrams in the rules this year. Below are some modified diagrams I've made. Any suggestions / comments on whether these will help clear up the confusion?

The biggest area of confusion when I have run Wind Power is the cleared area in a 3 cm radius on the back. So maybe instead of showing a front view, show a back view with the forbidden area outlined with a dashed line. I would also suggest showing the 3 cm radius the same as you show the blade radius, even if you have to make the diagram a bit bigger. Another issue is that competitors may not have put their blade in the 3 cm radius, but put tape or glue of something else that could still interfere with mounting their device. Rule 3f could be reworded to clarify this.

[PHXcoach]

Has anyone seen inconsistency in the test stand voltage results, specifically the Ward Science stand ?

I have been using a test stand based on a CD motor taken from a used portable CD player as my main test stand at all of the invitationals, regionals and state final and it has been consistent in that my reference blade assembly has always returned the same voltage range (305 to 315 mV) all season.

I have also been using a Ward Science test stand as a backup and a comparison. When the test stand first arrived it was reporting approximately 30% higher voltages (430 mV) than my CD motor based stand. Recently I have noticed that the voltages reported by the Ward stand are dropping:
a) The initial high voltage is getting a little lower
b) While a blade assembly is being tested it initially peaks and then the voltage slowly drifts down by 20 to 50% over 5 minutes of continuous running
c) After testing a number of other blade assemblies and then going back to the original reference the voltage reading is significantly (10% to 20%) lower than it measured at the beginning of the test session.
d) If the test stand is left until the next day it seemed to recover but not to the original 30% higher results I used to get with it.

I have tried with two different fans and swapped out the volt meter and power cables and am still seeing the same behavior. The resistor does not seem to be warming up so I don't think that is the problem (but I didn't measure it very scientifically), and I was not able to measure the motor windings temperature.

I am particularly concerned about observation (c) that the voltages are reducing throughout a test session because it could give teams competing later in the day a disadvantage. I am still investigating but in the mean time was wondering if anyone else has seen this test stand behavior.

[Noel]

Has anyone seen inconsistency in the test stand voltage results, specifically the Ward Science stand ?

I have been using a test stand based on a CD motor taken from a used portable CD player as my main test stand at all of the invitationals, regionals and state final and it has been consistent in that my reference blade assembly has always returned the same voltage range (305 to 315 mV) all season.

I have also been using a Ward Science test stand as a backup and a comparison. When the test stand first arrived it was reporting approximately 30% higher voltages (430 mV) than my CD motor based stand. Recently I have noticed that the voltages reported by the Ward stand are dropping:
a) The initial high voltage is getting a little lower
b) While a blade assembly is being tested it initially peaks and then the voltage slowly drifts down by 20 to 50% over 5 minutes of continuous running
c) After testing a number of other blade assemblies and then going back to the original reference the voltage reading is significantly (10% to 20%) lower than it measured at the beginning of the test session.
d) If the test stand is left until the next day it seemed to recover but not to the original 30% higher results I used to get with it.

I have tried with two different fans and swapped out the volt meter and power cables and am still seeing the same behavior. The resistor does not seem to be warming up so I don't think that is the problem (but I didn't measure it very scientifically), and I was not able to measure the motor windings temperature.

I am particularly concerned about observation (c) that the voltages are reducing throughout a test session because it could give teams competing later in the day a disadvantage. I am still investigating but in the mean time was wondering if anyone else has seen this test stand behavior.

It's probably the pitch of your turbine. I also see a consistent drop in the voltage output of my turbine after it peeks and when retested later in the day. This can be corrected by rebending before testing or spraying with a sealant to help maintain shape. Unfortunately, with flimsier materials, such as cardboard or card stock, the pitch will never be entirely consistent and a minuscule change in pitch can significantly affect the voltage output. Ultimately, you shouldn't be concerned with your set-up...just improving the stability and consistency or your turbine blades.

[ASingh]

There are some REALLY good insights and comments in this thread so far. Instead of replying to each of them, I'd like to share some general comments to hopefully steer the conversation. I'd also like to request suggestions on specific, concrete changes to the rules wording.

1. This is a Physics committee event. Hence our general philosophy is that the theoretical and practical portions of the event should contribute equally to the score. What that specifically means is that we don't do tiering in Physics events (as that would make the practical portion outweigh the theoretical portion).

I think the way the event played out, this balance between the theoretical and practical portions was not realized in practice. I am OK with using Power (square function of Voltage) as the metric, but I think normalizing the score with the top team getting a 50 causes a distortion. Most turbine designs are only capturing a very small amount of the energy in the wind, and small differences (compared to the amount of available energy) in their performance are getting exaggerated. So a team may be capturing 2% (score of 50) of the energy and another 1.5% (score of 37.5) of the energy. There is no such scaling on the written part, and even achieving a 5 pt difference would be hard.

A couple of options:
1) An easy thing to do would be to normalize the written score also. So if the top team had a 35/50 and the next team had a 30/50, the scored would be 50 and 42.85. This would make it a little more balanced.
2) Instead of normalizing wrt to max power score in the event, normalize to some target power level (Betz limit, or best turbine power generated at this year's national, etc.). So then as in the written part, no one may get a 50 and your score would be dependent on how good your performance is compared to best possible performance.

Another thing that might help is if the equipment was standardized...box fan type, motor/generator...so that designs can be optimized to known conditions.

[soyuppy]

Has anyone seen inconsistency in the test stand voltage results, specifically the Ward Science stand ?

I have been using a test stand based on a CD motor taken from a used portable CD player as my main test stand at all of the invitationals, regionals and state final and it has been consistent in that my reference blade assembly has always returned the same voltage range (305 to 315 mV) all season.

I have also been using a Ward Science test stand as a backup and a comparison. When the test stand first arrived it was reporting approximately 30% higher voltages (430 mV) than my CD motor based stand. Recently I have noticed that the voltages reported by the Ward stand are dropping:
a) The initial high voltage is getting a little lower
b) While a blade assembly is being tested it initially peaks and then the voltage slowly drifts down by 20 to 50% over 5 minutes of continuous running
c) After testing a number of other blade assemblies and then going back to the original reference the voltage reading is significantly (10% to 20%) lower than it measured at the beginning of the test session.
d) If the test stand is left until the next day it seemed to recover but not to the original 30% higher results I used to get with it.

I have tried with two different fans and swapped out the volt meter and power cables and am still seeing the same behavior. The resistor does not seem to be warming up so I don't think that is the problem (but I didn't measure it very scientifically), and I was not able to measure the motor windings temperature.

I am particularly concerned about observation (c) that the voltages are reducing throughout a test session because it could give teams competing later in the day a disadvantage. I am still investigating but in the mean time was wondering if anyone else has seen this test stand behavior.

We had same issue with the CD motor that we extracted from a CD player. When motor was test initially, reading was consistent. Then over time, the reading start to fluctuate by large amount. Then we got these set of motor from Amazon.
http://www.amazon.com/Water-RC300-FT-08 ... ge_o07_s00. They work much better and has been consistent. Just use the mounting hub from the old motor.

[soyuppy]

There are some REALLY good insights and comments in this thread so far. Instead of replying to each of them, I'd like to share some general comments to hopefully steer the conversation. I'd also like to request suggestions on specific, concrete changes to the rules wording.

1. This is a Physics committee event. Hence our general philosophy is that the theoretical and practical portions of the event should contribute equally to the score. What that specifically means is that we don't do tiering in Physics events (as that would make the practical portion outweigh the theoretical portion).

I think the way the event played out, this balance between the theoretical and practical portions was not realized in practice. I am OK with using Power (square function of Voltage) as the metric, but I think normalizing the score with the top team getting a 50 causes a distortion. Most turbine designs are only capturing a very small amount of the energy in the wind, and small differences (compared to the amount of available energy) in their performance are getting exaggerated. So a team may be capturing 2% (score of 50) of the energy and another 1.5% (score of 37.5) of the energy. There is no such scaling on the written part, and even achieving a 5 pt difference would be hard.

A couple of options:
1) An easy thing to do would be to normalize the written score also. So if the top team had a 35/50 and the next team had a 30/50, the scored would be 50 and 42.85. This would make it a little more balanced.
2) Instead of normalizing wrt to max power score in the event, normalize to some target power level (Betz limit, or best turbine power generated at this year's national, etc.). So then as in the written part, no one may get a 50 and your score would be dependent on how good your performance is compared to best possible performance.

Another thing that might help is if the equipment was standardized...box fan type, motor/generator...so that designs can be optimized to known conditions.

Not sure I agree with with either 1 or 2. The score are always compare among those team that compete in the event for that day. All events in SO follow this scheme. Regardless of what baseline, the placement of your score doesn't change. If you actually score 20/50 or 30/50 and this happen to be the best score for that event for that day, it doesn't matter what normalization takes place, your are still in 1st place.

[soyuppy]

Resistance in the setup
In my setup, I have a 5 Ohm Resistor(verified by Multi-Meter), but when connected to CD motor, resistance drop to 3.5 Ohm.
How do you measure resistance in the setup? Is the 5-7.5 ohm measure on the entire circuit, including the CD motor connect or CD motor disconnect?

[daydreamer0023]

This is very urgent: I just got put on Wind Power for Nationals and I have no idea where to start. My partner has done it before and I can probably study my way through it somewhat (since it's similar to the format of Simple Machines last year), but what I really need help with is building the turbine blades, since we're thinking of remodeling them from what we previously used for states.

Can someone please share some design ideas that have worked well for them (I understand if you all don't want to give away team secrets), or at least some starting points for thoughts on building the device? Thanks in advance!