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Author Topic: Can we steal energy from the Earths rotation?  (Read 6140 times)

McKay

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Can we steal energy from the Earths rotation?
« on: 30/03/2015 21:17:38 »
Greetings. If we take some mass from the equator and push it to one of Earths rotational poles trough some tubing (idk, say, super-fluid filled to prevent friction loss or something, just bare with me please), the piece of mass would accelerate in the direction of Earths rotation relative to the ground that now underneath it (Coriolis effect). Its like ice skater pulling in arm while rotating to rotate faster, but in this case, the mass thats pulled in is not rigidly attached and can accelerate on its own without accelerating the whole planet.
Now, that the mass is moving relative to the ground (and the initial energy that was used to push to the pole is not lost/ is absorbed), it can be absorbed and converted how we like (electricity).

Now, how about the angular momentum of the planet?
I understand that if the object we are moving to the pole is rigidly attached to the planet (like arms to an ice skater), the planet would in fact rotate faster, but angular momentum would be conserved.
But what about the scenario about the energy stealing? The mass in question would still end up at one of the rotational poles, but, in this case, we also have some energy extracted. I guess I could think that the planet would slow down (after speed up) and the energy we extract would not come from nowhere, but what about the angular momentum?
Edit: Changed title to a question.
« Last Edit: 31/03/2015 11:20:52 by evan_au »

yor_on

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Re: Can we steal energy from the Earths rotation?
« Reply #1 on: 31/03/2015 22:37:09 »
heh, like everyone using thermal energy for everything? Think I read a (c)old sf about that concept once.

McKay

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Re: Can we steal energy from the Earths rotation?
« Reply #2 on: 02/04/2015 15:38:21 »

syhprum

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Re: Can we steal energy from the Earths rotation?
« Reply #3 on: 05/04/2015 23:10:49 »
Isn't our atmosphere doing just that giving us these westerly's that gives us our mild climate and runs our windmills

Colin2B

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Re: Can we steal energy from the Earths rotation?
« Reply #4 on: 05/04/2015 23:45:53 »
. If we take some mass from the equator and push it to one of Earths rotational poles
The Coriolis effect is really only the tendency of things to travel in straight lines (similar to centrifugal 'force', where an object just continues in a straight line unless acted upon by a diverting force).
When moving mass, think of driving a car north from south. Is there a significant force trying to push you off course?

McKay

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Re: Can we steal energy from the Earths rotation?
« Reply #5 on: 07/04/2015 00:59:56 »

When moving mass, think of driving a car north from south. Is there a significant force trying to push you off course?
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Not on a small scale. But on a large scale + non-friction system that would allow that force to accumulate.. it surely would. Ships, sailing the seas, are known to have this problem, actually, when they move off course and have to adjust for the coriolis effect.

Edit: it also seems that long range snipers (and other long range projectile weapon operators) may need to take this effect in the calculations for best precision.
« Last Edit: 07/04/2015 01:04:23 by McKay »

RD

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Re: Can we steal energy from the Earths rotation?
« Reply #6 on: 07/04/2015 11:52:24 »
Tidal energy is at the expense of angular-momentum in the Earth-Moon system. Tides slow Earth's rotation ... http://en.wikipedia.org/wiki/Tidal_friction#Effects_of_Moon.27s_gravity
« Last Edit: 07/04/2015 11:57:29 by RD »

Colin2B

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Re: Can we steal energy from the Earths rotation?
« Reply #7 on: 07/04/2015 15:32:45 »
Edit: it also seems that long range snipers (and other long range projectile weapon operators) may need to take this effect in the calculations for best precision.

Yes you are correct, however, this is again an effect of the tendency of objects to continue in a straight line and the force is somewhat imaginary.

Imagine a windless day, you fire the long range shell and sight down the barrel, the shell will not deviate left or right but continue on a straight line. But while it is travelling the earth has rotated slightly and the target has moved. Just like any other moving target the shooter needs to lay off the target. However, it was the target moving not the shell being forced off target by an outside force. In the early days of science a hypothetical force was invented to explain the  Coriolis effect. This deviation is also what is happening to the ships, they are having to put energy in to correct for the movement of their destination.

The same for centrifugal force. Again the passenger on the fairground ride thinks they are being pushed outwards, but in fact they are travelling forward in a straight line, and it is only the seat and restraints that are pulling them around the curve. The only way to get work out of this system would be to allow the rider to fly off at a tangent and use their kinetic energy.

One way in which large amounts of energy are moved from equator, north and south, is through the circulation of air. Warm buoyant air rises and moves north and south. When it cools and falls we get winds moving from high pressure to low pressure. We can harness the winds!
As you are aware, it is due to the Coriolis effect that the winds circulate giving the familiar pattern of cyclones and anticyclones. Again there is no outside force, it is the earth rotating below the winds that creates the apparent deviation from a straight line. Whether you see the curve or the straight line depends on your frame of reference, it's all relative.
« Last Edit: 07/04/2015 15:40:57 by Colin2B »

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Re: Can we steal energy from the Earths rotation?
« Reply #7 on: 07/04/2015 15:32:45 »