Concentric coils for power generation

[samstergurl]

TL;DR

Can nested coils be used for generation power from a magnetic field?

Most generators work by rotating a coil within a magnetic field. This induces a current in the coil and can be harnessed as electricity. I was wondering if it would be possible to generate more power by using more than one coil with each one being progressively larger wrapped around the others. I also know that the current induced in the coil creates a magnetic field that tries to oppose the change in the fields around it.

Does this prevent something like this from working or being useful? Or is there some other reason that this isn't done?

 

[anorlunda]

Nope. Conservation of energy is the dominant effect here. Many electric generators are already 98-99% efficient. The 1-2% losses are due to heating, friction and windage. And >100% efficiency is truly impossible. So there's not much room for improvement, no matter what you do on the electrical side.

It is so much easier evaluating ideas in terms of conservation of energy rather than thinking about amps, and volts, and flux density.

 

[berkeman]

Summary:: Can nested coils be used for generation power from a magnetic field?

I was wondering if it would be possible to generate more power by using more than one coil with each one being progressively larger wrapped around the others.

In addition to the overall energy considerations mentioned by @anorlunda the current induced in the inner coil generates a back-flux that lowers the available flux for the outer coil. If the two coils share the same radius, it's just like using a longer coil if you series connect them, or if you parallel connect the two coils you still get the same energy out but just at a different source impedance.

One way to see the flux-stealing effect is if you put a shorted turn around the same area as your pickup coil. The shorted turn kills almost all of the flux from the source, so your pickup coil picks up almost no energy.

 

[samstergurl]

Nope. Conservation of energy is the dominant effect here. Many electric generators are already 98-99% efficient. The 1-2% losses are due to heating, friction and windage. And >100% efficiency is truly impossible. So there's not much room for improvement, no matter what you do on the electrical side.

It is so much easier evaluating ideas in terms of conservation of energy rather than thinking about amps, and volts, and flux density.

So you're already getting 99% of the energy out of that flux area, adding another coil inside of it doesn't improve that. Like how adding a smaller funnel inside of a bigger one doesn't increase the amount of water you get out in the end?