Wind Power B/C

[PHXcoach]

I don't have a quantitative answer but it looks like the Ward Science test stand also appears to use a DC motor instead of a CD motor. It reports higher voltages than some of the CD motors that I tested and lower than another CD motor. Naturally it depends on the windings in your motor which may be different from the one used in the Ward Science stand.

To get most energy out of a wind turbine you would want to use a geared motor, in which case the torque becomes important, however this years event is using an ungeared motor. So long as your motor is ungeared (which is likely) then you are probably in the same ball park as everyone else.

To be certain you would have to collect data, comparing your stand to other stands and compare the results.

[soyuppy]

Almost like we need to build 2 types of blade. One with high torque low rpm and low torque high rpm Depending on type of motor used, then we can decide which blade to use. I don't think there's any design that can be optimized for both type of motor. Commercial turbin always build/design blade with knowledge on what kind of motor that it will be used. Seem like a fair request in the rule to be changed:
- allow impound of 2 blades
- have 2 trial period of testing for each fan speed. Blade can be exchanged between trial. Best voltage of each trial test is used.

[0ddrenaline]

I second soyuppy idea. My blade is optimized for a high power fan. I've tried it on a low power fan, and it is not nearly as good as other designs. Said designs don't work as well on the high power fan. Luckily I haven't encountered any fans at competitions with power as low as the one mentioned, but this adds an unfair amount of luck in the process. If you can't regulate the fan, then allow more blades to be impounded.

[chalker]

It's near the end of the season, so I"m going to put out my usual offer regarding the rules. We're always interested in hearing feedback / suggestions on changes to make next year. The day after the National Tournament the rules committee will meet to try to lock down the rules for the next season. While I can't guarantee we'll adopt suggestions made here, I can at least promise we'll listen to them and consider them.

Regarding Wind Power in particular, there appeared to be some confusion over the diagrams in the rules and the prohibited areas around the motor. If anyone wants to take a stab at making a new diagram that shows it better, it's likely we'll incorporate it into the actual rules. Please create it in a format that is easy to edit by us (we often just use PowerPoint or Visio).

[lazyguy01]

Could the calculation of the Power score based on Voltage instead of Power? For the current calculation, the difference of the voltage is square and this could be a huge difference in the points and it is much harder to narrow the gap in the written part. If a team has a blade assembly that generate the voltage is 10% higher than the 2nd place, with the current formula, the points different could be 19 points different instead of 10 points. This will pretty much will make the top team rank 1st automatically!

[finagle29]

Could the calculation of the Power score based on Voltage instead of Power? For the current calculation, the difference of the voltage is square and this could be a huge difference in the points and it is much harder to narrow the gap in the written part. If a team has a blade assembly that generate the voltage is 10% higher than the 2nd place, with the current formula, the points different could be 19 points different instead of 10 points. This will pretty much will make the top team rank 1st automatically!

To counter your suggestion, commercial wind turbines are rated in terms of the power they can produce. The Vestas V164 is rated 8.0 MW, not 1000 V. Additionally, transformers can step up and step down voltages, but power is constant (in an ideal transformer), suggesting that power is a more fundamental quantity/measurement than voltage. Therefore, it seems more logical to me to calculate Power Score based on power instead of voltage.

[chalker]

Could the calculation of the Power score based on Voltage instead of Power? For the current calculation, the difference of the voltage is square and this could be a huge difference in the points and it is much harder to narrow the gap in the written part. If a team has a blade assembly that generate the voltage is 10% higher than the 2nd place, with the current formula, the points different could be 19 points different instead of 10 points. This will pretty much will make the top team rank 1st automatically!

Interesting suggestion, however I think you missed a step in the score calculation. We multiply 50 times the part 1 score / best part 1 score. To walk through the math:

Team A has Vha and Vla (high and low speed voltages)
Team B has 10% higher = 1.1*Vha, 1.1*Vla

Team A part 1 score = power score low + power score high = Vha*Vha/R + Vla*Vla/R= (Vha*Vha+Vla+Vla)/R
Team B part 1 score = 1.1*Vha*1.1*Vha/R + 1.1*Vla*1.1*Vla/R = 1.1*1.1*(Vha*Vha+Vla+Vla)/R = 1.21* Team A part 1 score

Hence, Team B will get 50 points, while Team A gets 50*1/1.21 = 41.3 points (a 9.7 point difference)

The Max possible FInal score is 100 points, so all other things being equal, a team with a device that performs 10% better will get ~10% more points, which seems fair to me.

[PHXcoach]

I would like to second the change to using voltage rather than power (v^2/r) for the Part I score.

I understand your point about the scoring that if a blade is 10% better then it should be reflected in a 10% better blade score (i.e. Part 1 score). This however would only contribute 5% to the total score because of the 50/50 weighting between the two parts of the event.

I believe there was an early explanation that the goal was to reflect the power captured, however it seems that the power generated by the turbine is small compared to the wind energy from the fan, so it does not seem to accurately reflect on the blade performance. Commercial turbines are measured in power but they extract up to 30% to 40% of the wind energy. The best I have seen in this event is less than 2% of the wind energy.

To illustrate the original point the top three Part I scores at our state finals were 50 (of course), 24.8 and 9.9 with the other 26 teams below that. (This made the written portion almost moot for the top two teams). While the performance of the top 2 blades were good the final scores don't seem helpful.

If you want to argue that incremental changes are harder as the blade performance increases, I would have to agree, but I still think that using a point system proportional to the voltage would be an improvement.

[PHXcoach]

There are a few other areas that I would like to see clarified in the rules:

1) When are construction violations determined if not checked at impound ? Since modifications can be made after impound (rule 4.d) an argument was made that a team that impounded a device that had construction violations could make changes after the supervisor identified the violations (rule 4.c) after impound, fix the construction violation and hence not get a penalty. I suggest that any violations found by the supervisor after impound cause a construction violation, even if the team then fixes them.

2) A FAQ says that the 5 cm distance from the fan could be measured and confirmed before the 30 second test. There is no mention of this in 4.f so this implies that there is no pausing of the time for the distance measurement to be made (other events include a clause to stop the clock while judges make measurements). This seems fair to me so that teams can make the trade off to either use their full time and risk the penalty, or sacrifice some time to avoid a potential penalty.

3) The same 15 point penalty is imposed for all construction violations - this seems a little draconian for teams that forgot to write their team number on the box vs. size of the rotors. (addressing point 4 below would help)

4) A blade assembly with violations is still allowed to run (with the 15 point construction violation) because rule 4.c does not specify any consequence if the team does not fix the construction violation(s). This opens up an interesting situation if a team finds a way to increase their voltage score by at least 20% by breaking a construction rule ..... Maybe blade assemblies that don't meet the construction rules and don't / can't be fixed get zero in Part I (rule 5.f)

5) There seems to be some variability in the fan speed and the CD motor voltage generation. To some degree I believe that this should be an exercise in design robustness. Is / should there be some limits or suggested operating parameters (e.g. fan wind speed range)?

I am new to this so these are just my thoughts on it.

Thanks for requesting suggestions.

[chalker]

4) A blade assembly with violations is still allowed to run (with the 15 point construction violation) because rule 4.c does not specify any consequence if the team does not fix the construction violation(s). This opens up an interesting situation if a team finds a way to increase their voltage score by at least 20% by breaking a construction rule ..... Maybe blade assemblies that don't meet the construction rules and don't / can't be fixed get zero in Part I (rule 5.f)
.

This is why I like to ask for suggestions / comments. The wording in 4.c. is supposed to prevent blades that don't meet specs from being tested, but I can see how it could be read otherwise.