Question for Randy and/or other very smart people. I was looking some stuff up and from the basic Force = 1/2 Mass x Velocity squared I expected that a 35 mph gust would have four times the energy of 17 mph. But, in looking up some stuff on windmills, I see that the power output of a windmill goes up by Vcubed. Can someone explain the implications of this to a former econ major?
Quote:
Basics of Wind Energy:
Kinetic Energy of wind is: 1/2 * mass * velocity2
amount of air moving past a given point (e.g. the wind turbine) per unit time depends on the velocity.
Power per unit area = KE * velocity MV2 *V
So Power that can be extracted from the wind goes as velocity cubed (V3)
Power = Force*velocity so that's how the cube comes in.* Implications - well for one - wind turbines have a limit on the range of operation. Too much wind and bad things happen. Also, like wind turbines have a lower generation limit (cut in) which (like planing threshold) makes them sit idle in light winds and increases the problem of integration into the power grid if the wind varies above and below the threshold. Upshot for an econ major - as windsurfers discovered a while back - wind is free but unreliable, it can cost a lot to get it and can really be annoying at time.
*In the real world it's likely a bit more complicated because the turbine blade is moving, the formula probably has to use apparent wind.
—
What happens in a black hole stays in a black hole.
Well, besides videos of my hopes and dreams, I was thinking more about the differences in sailing in 17 mph wind and 35 mph wind since it sounds like there is 2^3 or 8 times as much power per meter of sail.
Hope those who were able to go today had fun. Didn't seem frightfully cold in Atlanta but the wind was noticeable.
For all you armchair analysts, the answer is 5.2m. That's the size sail Gene & I rigged with great success.
I went out first and didn't see what Chris P. rigged. His outhaul let loose and I'll leave it up to Chris to tell how he got it tightened & sailed back in. Rhett did really well with his new all-carbon foil and a 4.2 sail. He got overpowered toward evening and windsurfed his 110 liter board with the same 4.2m. The wind was good, but at 41F, it was cold.
Today looks warmer. I plant to sail again this afternoon at Van Pugh.
Question for Randy and/or other very smart people. I was looking some stuff up and from the basic Force = 1/2 Mass x Velocity squared I expected that a 35 mph gust would have four times the energy of 17 mph. But, in looking up some stuff on windmills, I see that the power output of a windmill goes up by Vcubed. Can someone explain the implications of this to a former econ major?
Quote:
Basics of Wind Energy:
Kinetic Energy of wind is: 1/2 * mass * velocity2
amount of air moving past a given point (e.g. the wind turbine) per unit time depends on the velocity.
Power per unit area = KE * velocity MV2 *V
So Power that can be extracted from the wind goes as velocity cubed (V3)
Power = work/time. Work = force*distance. ergo: power =force*distance/time = force*velocity; force ~v^2 so power ~v^3.
For windsurfing I think it is more force that matters because that is what you are trying to counter with your body. The force of the sail must be balanced by the force of gravity of your body (and whatever muscles you might bring to bear), along with the force of the fin, rails etc. So for getting launched, you worry about force. So the good news force is wind speed squared and that is all you have to worry about, but that's bad enough. If you can sail at 17 mph, going up to 34 makes it at least 4 times more force (and it's really worse than that because the water is all messed up.)
So did anybody sail today? Over at velocity cubed park, I was mainly wishing the cubes we bigger in the lulls and smaller in the gusts. That and wishing my kite wouldn't keep going into trees.
—
What happens in a black hole stays in a black hole.
So did anybody sail today? Over at velocity cubed park, I was mainly wishing the cubes we bigger in the lulls and smaller in the gusts. That and wishing my kite wouldn't keep going into trees.
I used to know a kid who had that problem, too. I forget his name but he had a cute but somewhat odd beagle who slept on top of his doghouse.
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--- The Arrogant Jerk: Crabby and irritable since 1998.
Oh, Atlanta...
21 Mar 12:53 pm 41 27 57 WNW 18G29
21 Mar 12:50 pm 39 26 60 30 WNW 16
Do you rig for 16 or 30?
You rig for neither and come back tomorrow.
Alan
21 Mar 4:53 pm 44 24 45 WNW 17G35
Question for Randy and/or other very smart people. I was looking some stuff up and from the basic Force = 1/2 Mass x Velocity squared I expected that a 35 mph gust would have four times the energy of 17 mph. But, in looking up some stuff on windmills, I see that the power output of a windmill goes up by Vcubed. Can someone explain the implications of this to a former econ major?
Relevant: https://www.nrel.gov/gis/images/80m_wind/USwind300dpe4-11.jpg
Power = Force*velocity so that's how the cube comes in.* Implications - well for one - wind turbines have a limit on the range of operation. Too much wind and bad things happen. Also, like wind turbines have a lower generation limit (cut in) which (like planing threshold) makes them sit idle in light winds and increases the problem of integration into the power grid if the wind varies above and below the threshold. Upshot for an econ major - as windsurfers discovered a while back - wind is free but unreliable, it can cost a lot to get it and can really be annoying at time.
*In the real world it's likely a bit more complicated because the turbine blade is moving, the formula probably has to use apparent wind.
What happens in a black hole stays in a black hole.
Well, besides videos of my hopes and dreams, I was thinking more about the differences in sailing in 17 mph wind and 35 mph wind since it sounds like there is 2^3 or 8 times as much power per meter of sail.
Hope those who were able to go today had fun. Didn't seem frightfully cold in Atlanta but the wind was noticeable.
Oh, then that's easy. Sailing in 17 is a lot easier than sailing in 35. Even I can sail in 17, for example.
What happens in a black hole stays in a black hole.
Your former avatar wants a word with you
--- The Arrogant Jerk: Crabby and irritable since 1998.
Tomorrow looks easy.
Even I can sail.
For all you armchair analysts, the answer is 5.2m. That's the size sail Gene & I rigged with great success.
I went out first and didn't see what Chris P. rigged. His outhaul let loose and I'll leave it up to Chris to tell how he got it tightened & sailed back in. Rhett did really well with his new all-carbon foil and a 4.2 sail. He got overpowered toward evening and windsurfed his 110 liter board with the same 4.2m. The wind was good, but at 41F, it was cold.
Today looks warmer. I plant to sail again this afternoon at Van Pugh.
Barrett
Rig a 5.5
Alan
Power = work/time. Work = force*distance. ergo: power =force*distance/time = force*velocity; force ~v^2 so power ~v^3.
For windsurfing I think it is more force that matters because that is what you are trying to counter with your body. The force of the sail must be balanced by the force of gravity of your body (and whatever muscles you might bring to bear), along with the force of the fin, rails etc. So for getting launched, you worry about force. So the good news force is wind speed squared and that is all you have to worry about, but that's bad enough. If you can sail at 17 mph, going up to 34 makes it at least 4 times more force (and it's really worse than that because the water is all messed up.)
So did anybody sail today? Over at velocity cubed park, I was mainly wishing the cubes we bigger in the lulls and smaller in the gusts. That and wishing my kite wouldn't keep going into trees.
What happens in a black hole stays in a black hole.
I used to know a kid who had that problem, too. I forget his name but he had a cute but somewhat odd beagle who slept on top of his doghouse.
--- The Arrogant Jerk: Crabby and irritable since 1998.