Wind Power B/C

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Re: Wind Power B/C

Postby maxxxxx » April 24th, 2017, 4:32 am

windu34 wrote:Does anyone know to even approach solving this? I might just not be familiar with the equation:

The power generated by a turbine is 18,000 Watts. If the wind speed, which is initially 30 m/s decreases by 25%, what must the lift force be in order to generate the same amount of power?
Answer
800 N

Edit: Looks like the link I tried isn't working, try this viewtopic.php?f=226&t=9285&start=195#p307423
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Re: Wind Power B/C

Postby Alex-RCHS » April 24th, 2017, 5:18 am

The question you quoted in your first post has been answered on an earlier page, but I think we decided it was a badly worded question.
windu34 wrote:Apologies for the double post, but could use another opinion on this one as well:

A 36% efficient coal power plant burns 8.5 million kilograms of coal in a day. (Assume the heat of combustion of coal is 31 MJ/kg) How many watts of power is produced per day?

Answer
I got 95 TW
Answer key says 1.1 GW


You calculated the joules produced per day, but you need to divide it by the number of seconds in a day to find the power produced.
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Re: Wind Power B/C

Postby wzhang5460 » May 13th, 2017, 5:59 pm

RestingDoll wrote:
daydreamer0023 wrote:What would be considered to be a "great score" for blades in millivolts for Division C, given that a good score would get you placing in the top 10 in nats? I know things have changed since last year, but I kind of want to get a better estimate of how I (belatedly) did last year and what to improve upon this year. Thanks in advance!

Edit: How does the width of a blade affect performance in general in your experiences?


Every competition will have different scores in terms of voltage due to differences in motors/fans/resistance. As long as you do relatively well compared to others, you should be fine. Specific to last years nats, I think 1st place got 650 mV on high power and 450 mV on low power (check old forums).


Do you happen to know what the resistance was?
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Re: Wind Power B/C

Postby daydreamer0023 » May 13th, 2017, 6:41 pm

wzhang5460 wrote:
RestingDoll wrote:
daydreamer0023 wrote:What would be considered to be a "great score" for blades in millivolts for Division C, given that a good score would get you placing in the top 10 in nats? I know things have changed since last year, but I kind of want to get a better estimate of how I (belatedly) did last year and what to improve upon this year. Thanks in advance!

Edit: How does the width of a blade affect performance in general in your experiences?


Every competition will have different scores in terms of voltage due to differences in motors/fans/resistance. As long as you do relatively well compared to others, you should be fine. Specific to last years nats, I think 1st place got 650 mV on high power and 450 mV on low power (check old forums).


Do you happen to know what the resistance was?


It's changed since last year (since now the resistance can be much more), but I suppose it was at 7.5ish ohms because our blade performed better at Nats than at my home setup.
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Re: Wind Power B/C

Postby wzhang5460 » May 13th, 2017, 6:49 pm

daydreamer0023 wrote:
wzhang5460 wrote:
RestingDoll wrote:
Every competition will have different scores in terms of voltage due to differences in motors/fans/resistance. As long as you do relatively well compared to others, you should be fine. Specific to last years nats, I think 1st place got 650 mV on high power and 450 mV on low power (check old forums).


Do you happen to know what the resistance was?


It's changed since last year (since now the resistance can be much more), but I suppose it was at 7.5ish ohms because our blade performed better at Nats than at my home setup.


Oh I see. Our turbine got about 300 mV at States but i don't know what the resistance was.
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Re: Wind Power B/C

Postby wzhang5460 » May 13th, 2017, 6:49 pm

wzhang5460 wrote:
daydreamer0023 wrote:
wzhang5460 wrote:
Do you happen to know what the resistance was?


It's changed since last year (since now the resistance can be much more), but I suppose it was at 7.5ish ohms because our blade performed better at Nats than at my home setup.


Oh I see. Our turbine got about 300 mV at States but i don't know what the resistance was.


I'm guessing 10 ohms?
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Re: Wind Power B/C

Postby Alex-RCHS » May 13th, 2017, 9:02 pm

Knowing the resistance is nice but there are other factors at play as well. The motor itself has an internal resistance, and not every fan is the same.
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Re: Wind Power B/C

Postby daydreamer0023 » May 14th, 2017, 8:08 am

Alex-RCHS wrote:Knowing the resistance is nice but there are other factors at play as well. The motor itself has an internal resistance, and not every fan is the same.


Based off of that, if you want a slightly more accurate comparison, you might want to grab a tachometer and try finding the rpm of your blade - that could give you a sort of guesstimate of performance.
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Re: Wind Power B/C

Postby Ionizer » May 14th, 2017, 9:40 am

daydreamer0023 wrote:
Alex-RCHS wrote:Knowing the resistance is nice but there are other factors at play as well. The motor itself has an internal resistance, and not every fan is the same.


Based off of that, if you want a slightly more accurate comparison, you might want to grab a tachometer and try finding the rpm of your blade - that could give you a sort of guesstimate of performance.

I don't think this will help either. Different fans will still have different strengths. Different motors will have different frictions. Also rpm should depend on resistance as well. Electrical resistance adds a physical component that makes the motor harder to turn.
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Re: Wind Power B/C

Postby chozillla » May 15th, 2017, 8:51 pm

This is a question from an invitational and I still do not understand all parts of question 1. Can someone explain the answers for me? In return I will send you the full invitational test :)
Here's a link to the question: https://docs.google.com/document/d/17Ye ... sp=sharing
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Re: Wind Power B/C

Postby BigBrown » May 20th, 2017, 11:29 pm

Hey anyone know wind power scores for the top at nats?

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Re: Wind Power B/C

Postby vjindal » May 21st, 2017, 7:25 am

Does anyone know what the best blades at nats looked like?
Were they lift-based?
Were they 3d printed?
What material were they made of?
Did they extend to the center of the CD or only near the outside?
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Re: Wind Power B/C

Postby Alex-RCHS » May 21st, 2017, 12:34 pm

vjindal wrote:Does anyone know what the best blades at nats looked like?
Were they lift-based?
Were they 3d printed?
What material were they made of?
Did they extend to the center of the CD or only near the outside?


I'm also curious to know this. Also, anyone know the top voltage scores?
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Re: Wind Power B/C

Postby RestingDoll » May 23rd, 2017, 8:44 am

Alex-RCHS wrote:
vjindal wrote:Does anyone know what the best blades at nats looked like?
Were they lift-based?
Were they 3d printed?
What material were they made of?
Did they extend to the center of the CD or only near the outside?


I'm also curious to know this. Also, anyone know the top voltage scores?

We came in 8th with 335 on low and 593 on high. Test was also ok (@ shadow flicker lol).

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Re: Wind Power B/C

Postby soyuppy » May 23rd, 2017, 5:09 pm

RestingDoll wrote:
Alex-RCHS wrote:
vjindal wrote:Does anyone know what the best blades at nats looked like?
Were they lift-based?
Were they 3d printed?
What material were they made of?
Did they extend to the center of the CD or only near the outside?


I'm also curious to know this. Also, anyone know the top voltage scores?

We came in 8th with 335 on low and 593 on high. Test was also ok (@ shadow flicker lol).


Can't assume that the blade performance alone earn 8th place. There's also the testing part. The combine blade+test exam score = 8th place. No way to know how blade score stack up without seeing raw score...which is somewhat protected from public info.


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