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Do Wind Turbines Slow the Earth's Rotation?

06/08/2009 11:34 AM

Many years ago, an electrical engineer asked me "If the proliferation of wind turbines would slow down the earths rotation due to drag?" At the time, I dismissed the idea as just a foolish question, but after all this time, the question still sticks in my mind. Has anyone ever entertained such an idea and what were the conclusions?

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#1

Re: Wind slows down the earths rotation?

06/08/2009 11:39 AM

So where was all the wind energy dissipating before the wind turbines went up <rhetorical question>?

[It is known that the day length varies by +/- 2mSec depending upon which way the wind is blowing and which side of all the mountains it presses against.]

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#13
In reply to #1

Re: Wind slows down the earths rotation?

06/09/2009 11:45 PM

How did the forum thread title "Do Wind Turbines Slow the Earth's Rotation?" become "Wind slows down the earths rotation?"

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Guru
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#2

Re: Wind slows down the earths rotation?

06/08/2009 11:54 AM

Maybe we should ask the roads department to remove all the air brakes "road signs".

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#3

Re: Wind slows down the earths rotation?

06/08/2009 11:59 AM

Doesn't tis go back to the leaf blower on a sailboat senario?

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#4

Re: Wind slows down the earths rotation?

06/08/2009 12:07 PM

No he is actually correct that windfarms slow the wind.

Enormous wind farms DO slow the winds.

But it is usually welcome or you wouldn't put a windfarm there.

And the wind isn't what rotates the earth, nor is the air going to be a sufficient anchor to slow the earth.

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#5

Re: Wind slows down the earths rotation?

06/08/2009 12:27 PM

Hello Ron,

I think it is a great question. One has to understand how their perspective is affected by the environment from which an observation is made in order to appreciate how tough it can be to make a valid conclusion.

Perhaps we can have some fun with this question. If the prevailing winds come from the west, and the earth rotates so that the sun rises in the east, then perhaps the question should be whether the wind turbines would actually accelerate the rotation of the earth!

In actuality, it is the moon that is slowing down the rotation of the earth and the drag of the massive oceans in what we observe as tides that has a much larger effect than any concern about wind. Not to mention that the tidal drag is always in the same direction. Wind, however, arrives from the northwest, the southwest, and due west so that the net effect, after cancellation of the northern and southern components (quite a bit of the total energy) is then some fraction of the whole and it is a force vector from the west. Trees resist the wind and there are certainly more of them than any number of turbines we could ever build. All of the land based resistance acts like a sail on a sail boat, but the collective energy is minuscule and in the wrong direction for slowing down the rotation.

Now that I think about it, I wonder if the predominate wind direction is from west to east in the southern hemisphere. If so, how did we ever have something called the "trade winds?" And just now, I realized that my own perspective is very limited since I reside in the northern hemisphere. Wow! Now you've done it! I just confused myself.

I believe the correct answer to the original question is "not enough to matter". But now I am wondering why our wind nearly always comes from the west........Uggg! Time for my nap......

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#6

Re: Wind slows down the earths rotation?

06/08/2009 12:55 PM

Wouldn't all the wind have to blow in the same direction in order to have any effect at all. Maybe we can set them up to change the climates where we don't like them.

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#7

Re: Wind slows down the earths rotation?

06/08/2009 1:44 PM

AS I see it and so few others do. Regardless of how you measure and test and poke and prod, nature dictates that it will do what it wants to do!

Wind comes from all directions all over the planet and when you look at it as a whole the earth and the atmosphere are one body in space.

Does the air in your lungs make you heavier and thus slow your acceleration down when you take a step forward? Or is it a part of you that just goes along for the ride? When you breath out does it slow you down? But when you breath in does the small drop in local air pressure in front of you cause you to move forward?

The best theory in the world is still a theory because if it was a fact it would work!

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#8

Re: Wind slows down the earths rotation?

06/08/2009 1:47 PM

Wind is caused by a pressure gradient between high and low pressure systems. The windmill will not alter the difference.

But would the obstruction not change the spiral path of the air movement and thereby alter the direction of the winds? (like vortex breakers)

Maybe cause intensified cyclones or upsetting the Coriolis forces and have water going the wrong way down the drain.

We are doomed!!!

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#11
In reply to #8

Re: Wind slows down the earths rotation?

06/08/2009 3:45 PM

You are right about pressure differences creating wind, but to get an idea of global wind patterns, you have to look at Hadley cells.

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#9

Re: Wind slows down the earths rotation?

06/08/2009 2:20 PM

see http://cr4.globalspec.com/blogentry/7635/A-Really-Big-Butterfly

Address more of the regional scale impacts.

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#10

Re: Wind slows down the earths rotation?

06/08/2009 3:39 PM

Why does this question remind me of another based around a supposed potential danger of knocking the earth out of its current orbit by having lots of people on one side of the planet jump up and down simultaneously.

Its all about scales of cause and effect. As for me, its not going to stop me building and commissioning wind farms.

Also, I believe this question has been answered in depth before on CR4.

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#12

Re: Do Wind Turbines Slow the Earth's Rotation?

06/08/2009 7:10 PM

Of course wind farms slow the rotation of the earth, but not because of drag.

It is a well doccumented and known phenomenon. The relocation of the mass of all of those wind generators farther from the earth's center of gravity slows the rotation of the earth just like a spinning ice skater slows when they extend their arms.

There you go! Not necessarily the answer you were looking for but an answer none the less!

By the way, tall buildings, towers and relocation of any amount of mass from under the surface of the earth to or above the surface of the earth does the same thing if the space it originally occupied is not filled by matter of the same or greater mass.

Mining of coal, oil production, gold mining, salt mining, even drilling for water all cause this same effect.

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#14

Re: Do Wind Turbines Slow the Earth's Rotation?

06/10/2009 12:52 AM

Somtimes I spun on my office chair and pulled my legs in and out to speed up and slow down. I never stuck my arms in and out.

The air travels along with the Earth so the air playing with trees and propellers isn't going to have much effect on the rotation.

As an earlier entry said, extending mass outward from a spinning object slows it. Lots of skyscrapers along the equator would have a measurable effect on Earth's rotation speed like my legs do as I extend them.

The moon has more drag effect on the Earth and the Earth's rotation is gradually slowing. And unsymmetrical distribution of mass in the Moon has allowed Earth's gravity to keep one lunar hemisphere permanently turned toward Earth.

Billions of years from now the Earth will always keep the same face turned toward the Moon, just as the Moon already keeps the same face turned toward the Earth.

The Moon will be in the same place in the sky as it goes through its phases each day.

Imagine living in a place where the moon is always seen in the same place or never seen.

I think the Earth's wobble would cause movement of the Moon's postion in the sky. A figure 8 pattern. The same as for the Geostationary satellites.

The future creatures on Earth could use the moon for a Geostatonary communication satellite or just something to look at.

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#15

Re: Do Wind Turbines Slow the Earth's Rotation?

06/05/2013 1:28 AM

They say China's 3 Gorges dam has slowed down the rotation of earth,why,does it have similar effect like wind farms?.

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