Harvesting energy from the earth rotation

[Low-Q]

Could a gyro be able to harvest the energy from the Earth rotation? If the gyro is locked in space, it must change position relative to the alignment of the earth. This change in position could be the energy output. A gear mechanism is taking energy from the rotating Earth to keep the gyro spinning. Like a gigant powerball.

What do you say?

Vidar

 

[Andrew Mason]

Could a gyro be able to harvest the energy from the Earth rotation? If the gyro is locked in space, it must change position relative to the alignment of the earth. This change in position could be the energy output. A gear mechanism is taking energy from the rotating Earth to keep the gyro spinning. Like a gigant powerball.

What do you say?

Vidar

I am having difficulty understanding the question. Are we to assume that the gyroscope is in orbit around the earth? Why would there be any need to add energy to keep the gyro spinning? How is it losing energy?

Since a spinning gyroscope does not change the direction of the axis of rotation unless a torque is applied to it, it keeps pointing in the same direction in space. Its position relative to the Earth keeps changing if it is in orbit, so its orientation relative to the Earth does change. But apart from work done by tidal forces due to this change in orientation, which would be very small, no work is done on the gyroscope due to the changing orientation.

AM

 

[AlephZero]

In principle, yes, but the numbers don't stack up too well, because the rotation speed of the Earth is so slow.

Suppse you want an output power of 1 watt, just to prove the idea would work.

Power = torque x angular velocity.

Angular velocity = 1 rev per 24 hours = (2 pi) / (24 x 3600) = 72 x 10^-6 rad/sec

Torque = 14,000 N-m.

Scale that up to something useful like 1 MW of power (i.e. one medium size wind turbine), and the shear force would be about 14 million tonnes on a 1-meter radius shaft, at the start of your gear mechanism.

If you want to get energy from the Earth's rotation, or tidal power is a more practical way to go.

 

[Low-Q]

In principle, yes, but the numbers don't stack up too well, because the rotation speed of the Earth is so slow.

Suppse you want an output power of 1 watt, just to prove the idea would work.

Power = torque x angular velocity.

Angular velocity = 1 rev per 24 hours = (2 pi) / (24 x 3600) = 72 x 10^-6 rad/sec

Torque = 14,000 N-m.

Scale that up to something useful like 1 MW of power (i.e. one medium size wind turbine), and the shear force would be about 14 million tonnes on a 1-meter radius shaft, at the start of your gear mechanism.

If you want to get energy from the Earth's rotation, or tidal power is a more practical way to go.

There has been done experiments on this earlier - by Russians. As far as I know they did not succeed... So I will definitely not make it in my backyard.

 

[Stanley514]

In principle, yes, but the numbers don't stack up too well, because the rotation speed of the Earth is so slow.

Is it possible to harness energy of Earth rotating around Sun?
It speed supposed to be closer to 30 km/sec.

Scale that up to something useful like 1 MW of power (i.e. one medium size wind turbine), and the shear force would be about 14 million tonnes on a 1-meter radius shaft, at the start of your gear mechanism.

What do you meen by that?Force will be to strong for a turbine to withstand?Hard to believe,
but as I know gyroscopes not necessarly should be mecanical.For example there exist some kind of electronic gyroscopes.

 

[Drakkith]

Is it possible to harness energy of Earth rotating around Sun?
It speed supposed to be closer to 30 km/sec.

There is no known feasible way to harness energy from Earths orbital velocity other than to gravitationally assist satellites. And even this wouldn't really count as "harnessing" energy in the sense of power generation.

What do you meen by that?Force will be to strong for a turbine to withstand?Hard to believe,
but as I know gyroscopes not necessarly should be mecanical.For example there exist some kind of electronic gyroscopes.

These would not provide power, but are used to detect rotation via interference of light.

 

[willem2]

If you want to harvest energy from the Earth's rotation, you must slow it down.
Because of conservation of angular momentum, this can only happen if you transfer it to an object not on the earth, such as the moon.
If you can't do this, it's impossible to harvest the rotational energy of the earth.

 

[cmb]

Could a gyro be able to harvest the energy from the Earth rotation?

Already been done [by whoever created the solar system] - it's called the Moon!

The Moon used to go around the Earth closer, and the Earth rotated faster. But the Earth has been losing energy to the Moon, through tides, for billions of years.

So [unfortunately] overall it is the Moon that is harvesting energy from the Earth's rotation! But we can intercept some of the work energy that is transferred in that process, by capturing some of the tidal energy.

 

[cmb]

...this can only happen if you transfer it to an object not on the earth, such as the moon...

(Darn - you hit send and beat me to the call, while I went to get my mid-edit drink!)

 

[D H]

Because of conservation of angular momentum, this can only happen if you transfer it to an object not on the earth, such as the moon.

Or to an object that leaves the earth, such as a rocket. Rockets for the most part do "harvest energy from the Earth's rotation." (Satellites launched into retrograde orbits add angular momentum, but not much; most retrograde orbits are only slightly retrograde. So I'll just ignore that minor complication. )

Question: How much mass needs to be launched into geostationary orbit to lengthen a day by one second? Ignore details such as what happens to the exhaust.

 

[LURCH]

I am having difficulty understanding the question. Are we to assume that the gyroscope is in orbit around the earth? Why would there be any need to add energy to keep the gyro spinning? How is it losing energy? ...

AM

It appears from the original post that the gyroscope would be gimbled, and the gimble would be attached to a gearing mechanism which would extract energy. The only way this mechanism could extract energy is if it worked against resistance. This resistance would in turn cause the gyroscope to tumble, which would manifest itself as a type of drag, slowing the gyroscope.

For this reason, I would have disagreed with…

In principle, yes, but the numbers don't stack up too well, because the rotation speed of the Earth is so slow...

… and say that, even in principle, this would not work. The energy needed to keep the gyroscope spinning will always be equal to the energy extracted plus any losses to entropy. I think the Second Law means that this device will end up costing energy, rather than generating it.

 

[Stanley514]

… and say that, even in principle, this would not work. The energy needed to keep the gyroscope spinning will always be equal to the energy extracted plus any losses to entropy. I think the Second Law means that this device will end up costing energy, rather than generating it.

If we are able to harness energy of tides and part of tides energy is purely from Earth rotation, why we can`t harness it in some other way?There exist tidal power plants.
I read to somebodies amateurish mind that in order to increase power output from gyro we need to make it spin as fast as possible and to reduce size of reductor.

 

[willem2]

If we are able to harness energy of tides and part of tides energy is purely from Earth rotation, why we can`t harness it in some other way?There exist tidal power plants.
I read to somebodies amateurish mind that in order to increase power output from gyro we need to make it spin as fast as possible and to reduce size of reductor.

To get energy out, you have to transfer some of the angular momentum of the Earth to an object that isn't on the earth. There's no way to do this with an Earth bound gyroscope.

 

[Stanley514]

Do I understand it right that even there would be no Moon and Sun,some kind of tides or breakers would still take place due to Earth rotation only?
http://www.astronomycafe.net/qadir/q106.htmlIf yes,then you are going to tell we would not be able to capture their enery?Without some outer space object?Are you sure?

 

[nasu]

Do I understand it right that even there would be no Moon and Sun,some kind of tides or breakers would still take place due to Earth rotation only?
http://www.astronomycafe.net/qadir/q106.htmlIf yes,then you are going to tell we would not be able to capture their enery?Without some outer space object?Are you sure?

Where does it say "no Mon and Sun"??

 

[Stanley514]

Where does it say "no Mon and Sun"??

``On a daily basis, we would still have large breakers on the continental west coasts because of the rotation speed of the Earth, and the existence of storms out at sea, and sloping beaches. The waves we are most familiar with from minute to minute are caused by small ripples out at sea caused by storms, which get amplified into majestic breakers by their motion up a sloping beach, and the rotation of the Earth from west to east which gives them added momentum.``
There is only Earth rotation mentioned.

Due to Earth rotation water changes river banks.Do you think Moon and Sun have relation to this?

 

[nasu]

``On a daily basis, we would still have large breakers on the continental west coasts because of the rotation speed of the Earth, and the existence of storms out at sea, and sloping beaches. The waves we are most familiar with from minute to minute are caused by small ripples out at sea caused by storms, which get amplified into majestic breakers by their motion up a sloping beach, and the rotation of the Earth from west to east which gives them added momentum.``
There is only Earth rotation mentioned.

This has nothing to do with the absence of the Sun.
I am afraid you did not read the text carefully. Starting with the title.
"If it did not have Moon" means exactly this: everything else but the Moon stays.
Besides the semantics, how would you account for the seasons, mentioned in the text, in the absence of the Sun?

 

[cmb]

If we are able to harness energy of tides and part of tides energy is purely from Earth rotation, why we can`t harness it in some other way?There exist tidal power plants.

Basically, the Earth's rotation is too slow. You could, indeed, spin up a gyroscope with its axis orthogonal to that of the earth's. You'd then observe a rotation of that gyroscope relative to an earthbound observer - it would rotate once per day. Now, if you could figure out a way to efficiently extract energy from a device with a [relative] gyroscopic precession rotation rate of once per day whilst simultaneously feeding in energy enough to keep a big flywheel rotating at many rpm continuously, then maybe you could progress with the idea?

 

[Stanley514]

Basically, the Earth's rotation is too slow. You could, indeed, spin up a gyroscope with its axis orthogonal to that of the earth's. You'd then observe a rotation of that gyroscope relative to an earthbound observer - it would rotate once per day. Now, if you could figure out a way to efficiently extract energy from a device with a [relative] gyroscopic precession rotation rate of once per day whilst simultaneously feeding in energy enough to keep a big flywheel rotating at many rpm continuously, then maybe you could progress with the idea?

I don`t know.If idea principally working and we would be able to obtain netto energy from Earth rotation then,I guess, the same idea could be extrapolated and we would be able to obtain energy from Earth movement around the Sun (this motion is much faster).Gyroscope not necessarily should be mechanical,I think.Maybe it`s possible to do something based on purelly electronic cycles?Then we may avoid some problems associated with strenghts of materials?

 

[cmb]

I think it is going to be worse than that. There is something about the physics of such an arrangement that will always mean the energy in is greater than the energy out, I'm afraid. You have to keep turning the flywheel to generate the rotation - it's a perpetual motion machine by another definition, and like all perpetual motion machines, you have to put energy in in a manner more efficient that taking it out.

 

[Drakkith]

I think it is going to be worse than that. There is something about the physics of such an arrangement that will always mean the energy in is greater than the energy out, I'm afraid. You have to keep turning the flywheel to generate the rotation - it's a perpetual motion machine by another definition, and like all perpetual motion machines, you have to put energy in in a manner more efficient that taking it out.

It's not a perpetual motion machine, it's just very inefficient due to the long rotation time of the Earth for what you are wanting to do. The energy you might be able to extract from it comes directly from slowing the Earth down slightly, so energy is conserved.

 

[cmb]

The energy you might be able to extract from it comes directly from slowing the Earth down slightly

right, but you only slow down the Earth a little so long as the gyroscope is still rotating. Once you stop the gyroscope, you speed the Earth back up again. This is a bit like accelerating your car eastwards. naively, you have slowed the Earth down, so you must've generated some energy? Not really, because you have to stop the car sometime and you put exactly that energy back into the Earth.

So the physics says that you have to put [at least] the same energy in as you'd get out.

 

[Drakkith]

right, but you only slow down the Earth a little so long as the gyroscope is still rotating. Once you stop the gyroscope, you speed the Earth back up again.

What? I don't think this is correct. Once you extract the energy it is gone unless you intentionally give it back to the Earth.

This is a bit like accelerating your car eastwards. naively, you have slowed the Earth down, so you must've generated some energy? Not really, because you have to stop the car sometime and you put exactly that energy back into the Earth.

No, the gyroscope would apply a torque against Earth's motion. Once stopped it would NOT apply a torque in the opposite direction. You would have to purposely input energy and reverse the gyroscope to make this happen.

 

[cmb]

the gyroscope would apply a torque against Earth's motion. Once stopped it would NOT apply a torque in the opposite direction. You would have to purposely input energy and reverse the gyroscope to make this happen.

So, if you were to extract some energy out of the slow rotation of the gyroscope, then let the gyroscope spin down under its own friction to standstill, then after all that the Earth would be rotating slower that it was before? Right?

OK... so to what was the angular momentum transferred, or does this defeat conservation of angular momentum?

 

[Drakkith]

So, if you were to extract some energy out of the slow rotation of the gyroscope, then let the gyroscope spin down under its own friction to standstill, then after all that the Earth would be rotating slower that it was before? Right?

Yes.

OK... so to what was the angular momentum transferred, or does this defeat conservation of angular momentum?

To the gyroscope and then to whatever you are using to get power out of it.

 

[cmb]

To the gyroscope and then to whatever you are using to get power out of it.

Let's say it fed some high-geared generator that charged up a battery. Now the generator has stopped too, and so the only difference before-to-after is that I've got a charged up battery and a slowed down Earth. Does this not defeat conservation of angular momentum?

 

[Drakkith]

I don't believe so. If it did, then someone should have pointed it out immediately. I recently tried out an example at the local Sci-Port where that had a wheel on an axle that you spun up with your hand. Then you sat in a chair that could turn and rotated the wheel and axle around perpendicular to it's rotational axis. This caused the chair and myself to turn one way. As the wheel spun down I did not return to my original direction.

 

[willem2]

I don't believe so. If it did, then someone should have pointed it out immediately. I recently tried out an example at the local Sci-Port where that had a wheel on an axle that you spun up with your hand. Then you sat in a chair that could turn and rotated the wheel and axle around perpendicular to it's rotational axis. This caused the chair and myself to turn one way. As the wheel spun down I did not return to my original direction.

It does violate conservation of angular momentum, and is therefore impossible. A gyroscope that you let rotate freely won't slow down the earth, or produce any energy. The only way to slow down or speed up the Earth with such a gyroscope, is to let it point more or less in the direction of the Earth's spin. The gyroscopy will have it's lowest energy state when it's spinning in the same direction of the earth, and you can't get any energy out of it anymore.

 

[Drakkith]

It does violate conservation of angular momentum, and is therefore impossible. A gyroscope that you let rotate freely won't slow down the earth, or produce any energy. The only way to slow down or speed up the Earth with such a gyroscope, is to let it point more or less in the direction of the Earth's spin. The gyroscopy will have it's lowest energy state when it's spinning in the same direction of the earth, and you can't get any energy out of it anymore.

Alright, I just re-read the thread again. I guess that it is impossible. Not sure why I was thinking it would work...perhaps I was remembering another thread.

 

[cmb]

The only way to slow down or speed up the Earth with such a gyroscope, is to let it point more or less in the direction of the Earth's spin. The gyroscopy will have it's lowest energy state when it's spinning in the same direction of the earth, and you can't get any energy out of it anymore.

[EDITED OUT A SECTION HERE]... I don't think what I just wrote then was correct. I was discussing that a gyroscope with its axis perpendicular to the Earth's axis would slow the Earth down. I think that's not true, because it would have no component of angular momentum about the same aXIs as the earth, so the two would not interact in that way - is that correct??...

Gyroscopes' behaviour tends to defeat human's intuition (hence a load of 'anti-gravity' devices try to exploit gyroscopes, due to misconceptions on how they work). I suspect that this is, in part, because we have evolved with the 'lizard' parts of our brain never needing to intuitively comprehend gyroscopic motions, as nothing in the natural world behaves in such a way to need that intuitive comprehension.