Science Limitless electromagnetic energy ?

[thripd]

:tumbleweedLEEEASE someone shoot my idea down, it's bugging me...

Two concentric rings encircling our planet's equator. The inner, smaller, ring tethered at multiple points to the planet's surface in a geostationary fashion. The outer, larger, ring spinning in the opposite direction. Magnets studded along the rings' surfaces whizzing past each other creating electrical currents which pass along the tethers to mass storage batteries or feeding directly into the grid.

Clean electricity on a global scale... an end to fossil fuel use... Could the end justify the means?

 

[garyw]

There is always a net energy loss in any energy generation system.

If you have an idea that you think will work show us the math.

 

[johan]

It will work, for a while: You're essentially generating electrical current from the velocity difference between the rings.

As this happens, you will find a force on both rings that tends to normalize the velocity difference... i.e. the outer ring that's spinning in the opposite direction will slow down, start spinning the other way and eventually match speed with the inner ring.

In the process the amount of current you generate will become less and less, eventually to zero.

 

[jedidia]

PLEEEASE someone shoot my idea down, it's bugging me...

the rings will slow each other down, so it's not free energy at all. satisfied?

 

[thripd]

There is always a net energy loss in any energy generation system.

If you have an idea that you think will work show us the math.

Math not my strong point, I'm guessing the math will eventually shoot this down.

I get what your saying Johan, magnetic attraction would eventually cause the rings to equalise. Whatif, instead of the outer being, say positive and the inner being, say negative, you have both negative and positive points on both rings, and points are aligned (or movable) so forces of attraction are closely followed by forces of repulsion to keep the thing going. Energy loss on the inner ring would equate to slowing down the planet's spin (unlikely) and perhaps energy loss on the outer ring could be mitigated with minimal input compared to the enegy generated from electromagnetism? The spin of the earth is a net force. Perhaps in millions of years this contraption could diminish the earth's spin slightly.

 

[johan]

Math not my strong point, I'm guessing the math will eventually shoot this down.

I get what your saying Johan, magnetic attraction would eventually cause the rings to equalise.

I'm not talking about magnetic attraction - I'm talking about the magnetic fields generating a current. What you're doing, is transferring energy from kinetic to electric. This transfer process will inevitably cause some of the velocity differential to be lost. Like garyw said, there will be a net loss too, no matter how efficient you make it. This is all intuition by the way...

Energy loss on the inner ring would equate to slowing down the planet's spin

True - not unlikely, just not very visible given the earth's mass.

perhaps energy loss on the outer ring could be mitigated with minimal input compared to the enegy generated from electromagnetism?

Instead, intuitively I think you will tend to see the whole effect in the velocity of the outer ring. So your input wouldn't be minimal, it would be equal to the electricity you're generating.

The spin of the earth is a net force.

No it isn't... it's a large angular momentum, not a force. You can use that momentum to generate a force (like on the inner ring), but all that will do, is it will increase the accelleration on the outer ring to equalise their speed in the same amount of time as would otherwise have been the case.

No free lunch for you, sorry!:cook:

At this point I probably need to take my intuition to one side and let somebody with more rigorous math step in, before I embarrass myself by saying something stupid. If I haven't already! :facepalm:

 

[Urwumpe]

Math not my strong point, I'm guessing the math will eventually shoot this down.

Not even that, alone some coarse knowledge of the physical phenomena is enough. For example what induction is, and what the magnetic field of the induced current produces (drag).

I get what your saying Johan, magnetic attraction would eventually cause the rings to equalise. Whatif, instead of the outer being, say positive and the inner being, say negative, you have both negative and positive points on both rings, and points are aligned (or movable) so forces of attraction are closely followed by forces of repulsion to keep the thing going.

What you essentially suggest is a synchronous electric motor, for keeping things running, powered by....what? It would not produce electricity, it would consume it.

[ame="http://en.wikipedia.org/wiki/Synchronous_motor"]Synchronous motor - Wikipedia, the free encyclopedia[/ame]

Energy loss on the inner ring would equate to slowing down the planet's spin (unlikely) and perhaps energy loss on the outer ring could be mitigated with minimal input compared to the enegy generated from electromagnetism? The spin of the earth is a net force. Perhaps in millions of years this contraption could diminish the earth's spin slightly.

It would only have a effect as long as the spin rate of the planet is different to the spin rate of the outer ring. And the spin rate of the outer ring would be equalized to the spin rate of the inner ring by the energy that you tap of it by induction (once a current flows in the inner ring). So, you are essentially limited to the energy that is stored in the ring while you assemble it: It is no way to generate energy, but a viable way to store energy with pretty good efficiency.

 

[thripd]

No free lunch for you, sorry!:cook:

Quite right. The only free lunch we have is the planet's spin, that would keep the inner ring going. So, the outer ring would eat more than it bakes!

Thanks chaps, it's been enlightening!

 

[Artlav]

powered by....what?

What if we tie one ring to the Moon, and anchor another to the Earth?
I guess a full Moon of kinetic energy would last well until the time we could build a Dyson sphere or something.

---------- Post added at 16:00 ---------- Previous post was at 15:55 ----------

Maybe even something simpler and stupider:

 

[RisingFury]

Math not my strong point, I'm guessing the math will eventually shoot this down.

Please try to avoid this excuse. What would you think of me if I said I'm not good with nouns and verbs?

 

[jedidia]

What if we tie one ring to the Moon, and anchor another to the Earth?

This got to be the crasiest idea I've ever heard :lol:

It's even worse that, theoretically, it should work! Practically, it's too bad that the moons gravity will mess up any rings in orbit anyways, the rings would have to be at distances so far apart that you'd not be getting much out of it. And the environmentalists will have your scalp for this!

 

[johan]

What if we tie one ring to the Moon, and anchor another to the Earth?
I guess a full Moon of kinetic energy would last well until the time we could build a Dyson sphere or something.

Now there's an idea! You'd have a number of practical difficulties though... like what to make the belt out of, how to anchor it without having it burn up in the atmosphere or destroy whole cities, etc.

You'd still be tapping stored energy (angular momentum in the moon's orbit), but I have a feeling there's a whole lot there to tap. You might want to be careful about stopping sooner rather than later though, otherwise you'd mess up Earth's tidal pattern pretty badly.

Won't this be a whole lot easier on Mars? Assuming, of course, you can find a way to get all the necessary raw materials to Mars in the first place. Plus, if you end up having to blow Phobos to a million pieces to stop it plowing into the planet, who cares?

 

[T.Neo]

Actually there have been proposals to generate energy from the Earth's magnetic field. Of course it isn't free energy, and I don't think tinkering with the thing that protects our magnetic field is particularly safe, but still...

I actually did a calculation on solar power satellites and becoming a Kardashev type I civilisation. A type I civilisation is said to be able to access 174 petawatts of power, or 174000 terawatts.

Atomic Rockets gives a mass estimate for a 1 terawatt solar power satellite of
1 900 000 tons. You would need 174000 of these power stations to produce 174 petawatts.

This is 330600000000 tons. At a launch cost of 250$ per KG, it would be 82.65 quadrillion dollars just to get this mass to orbit, or about 6200 times the current US national debt. And that does not include the actual cost of the hardware itself, or the supporting equipment both on the ground and in space (microwave recievers, space tugs, construction stations). Nevermind the ecological damage that would arise from constructing such a system and launching it.

Of course, it's supposed to make use of lunar construction materials, cheaper launch prices, etc, but still...

 

[TMac3000]

The sun, the other stars, the moon, the Earth's spin, the Earth's core, the loose hydrogen in space...there is a lot of energy in the universe. To say that is a massive understatement would be a massive understatement. Suffice it to say that nature contains all the energy we could possibly need for the lifetime of the human race, even if we built a big interstellar empire with a population in the trillions. The problem is harnessing that energy without using even more energy to do so.

We could tap the Earth's core with thermal boreholes, but that would probably release more energy than we could control (and the environmentalists would scalp us all:chainsaw We could build a Dyson sphere out of solar cells around a nearby star, which would probably require more energy than the human race could ever generate, not to mention an impossible feat of engineering.

I suspect that far into the distant future, we will continue to generate energy the way we always have: fossil fuels, hydroelectric dams, and the occasional windmill.

 

[T.Neo]

I suspect that far into the distant future, we will continue to generate energy the way we always have: fossil fuels, hydroelectric dams, and the occasional windmill.

Good luck doing that. Fossil fuels are a finite resource, you cannot keep using them forever.

And there is also the issue of growth in needs; sure we consume so much power now, but we're going to consume more in the future, just as our power requirements have grown in the past. We'll have to look into other sources of energy, like solar power satellites, for example, to support such growing needs.

We could build a Dyson sphere out of solar cells around a nearby star, which would probably require more energy than the human race could ever generate, not to mention an impossible feat of engineering.

Actually Dyson proposed a swarm of orbiting satellites, or an array of non-orbiting statites suspended by radiation pressure. A solid sphere is really little more than science fiction.

An imaginary sphere around the Sun at a distance of 1 AU would have a surface area of 2.81e23 square meters. Assuming only 1% of that, 2.81e21 m^2, is used to generate power;

-Solar energy at 1 AU is about 1366 watts per m^2.
-The sysem has an efficiency of around 30% (the highest demonstrated of photovoltaic cells in a laboratory, although more primitive and less efficient solar thermal systems could be constructed out of more abundant materials).

This equates to about 1.15e24 watts, or 1151538 exawatts. This is about 347 times less than the 4e26 watts required to qualify as a type II civilisation.

If the system has a mass of 20 kg per kilowatt, it will mass 2.3e22 kilograms. Which is about 0.38% of Earth's mass, or 15.56 million times more massive than the Martian moon Deimos. This would of course exclude supporting systems, power transferrance systems, etc.

 

[Jarvitä]

This would of course exclude supporting systems, power transferrance systems, etc.

Nothing of the kind is required. Construct the Dyson sphere out of [ame=http://en.wikipedia.org/wiki/Computronium]computronium[/ame] and, after expending much of the resources of the entire solar system for the construction, upload the human civilisation on it.

 

[HAL9001]

well, moon will stop mving in a few billion years.
somewhere the nergie for tides must come from...

 

[T.Neo]

Nothing of the kind is required. Construct the Dyson sphere out of
computronium
and, after expending much of the resources of the entire solar system for the construction, upload the human civilisation on it.

I was talking about things like beaming power to interplanetary or interstellar spacecraft, industrial processes, and power for habitats on planetary surfaces or orbital habitats. Note that anything else that you attach to the power collectors will cost mass, not only the systems I suggested. The mass figure is for the power collection system alone.

Though of course if you want to destroy everything in the solar system and replace it all with a gigantic version of Second Life, be my guest. I'm sure it'll go swimmingly.

Note that I never suggested a solid shell sphere; I was implying seperate orbiting satellites (or statites). A solid shell would be a massive, unstable, implausible structure. My figure of 0.38% the mass of the Earth, is around 6.9% of Mercury. Hardly solar system destroying, but still an utterly monumental task. One that would likely be undertaken over centuries or decades, as power requirements slowly grow.

It may make more sense to position the satellites closer to the sun, perhaps at Mercury's orbit. There are about 9116 watts per m^2 at Mercury's orbit, versus 1366 at 1 AU. A system similar to the one discussed earlier (with the same area) could harness 7.68e24 watts, or 7684788 exawatts. This is 52 times less than the 4e26 watts required to qualify as a Kardashev class II civilisation.

Using a number of 20 kilograms per kilowatt, the power collectors would mass 2.5% that of the Earth, or about 45% the mass of Mercury. Something tells me though, that the system would have much lower mass at this distance from the sun.

well, moon will stop mving in a few billion years.
somewhere the nergie for tides must come from...

The Moon will not stop moving, it is constantly moving through space.

If you mean stop spinning relative to the Earth, it has already done that. It is currently escaping the Earth at a rate of 1 cm per year due to tidal acceleration, but the timescale for this to become troublesome is so long as not to be worrisome.

 

[TMac3000]

I think we don't need to focus so much on generating energy, since there are already 10^God-only-knows how many gigawatts of energy right here in the solar system; enough to sustain the human race indefinitely. I think we should focus on developing whatever technologies would be required to harness and control that energy in a predictable and efficient way.

 

[jedidia]

well, moon will stop mving in a few billion years.

I think the sun will go boom a lot earlier than the moon deorbits...