Question on magnetism and possible wave generator design.

[GreenAce92]

You're probably aware of those flashlights that you shake, I've been fortunate to have seen a transparent version which showed the coils and the sliding magnetic core. The coil was say a 1/3 of the cylinder which housed the possible sliding ability of the magnet core.

I was wondering if the coil was the entire length of sliding eg. the whole time the magnet core was sliding, it was always inside the coil, would it generate electricity? Probably a trivial question.

My next question is, given the way the magnetic field "propagates?" from the magnetic core eg. north to south, in a axial/radial symmetry, would it make more sense to arrange smaller coils with their centers positioned around the circumference of a larger circle which is concentric with the magnetic core. This way the radiating lines would go directly or mostly into the entire area of the coils, rather than... well actually maybe it is better to envelope the entire magnetic core with one large-diameter coil as all of the field will be captured when the magnetic core is near the opening of the coil.

See the diagram attached for clarification.

My other concern was regarding a wave-generator design which is not like that design of a floating body, with a pendulum attached hanging below the surface of the water. I think that is a great design. What I'm talking about is using the same idea above of a sliding object, but instead of using the coils idea, design it like an old Grandfather gravity clock. I'm not sure if this has any benefits over the pendulum design but the idea would be a link of these, like the lane line dividers in a pool.

Anyway, regardless of orientation both ends of the generator or perhaps it is one loop with one generator, would start to turn and make energy as the floating buoy rocked and pivoted in waves.

I'm just not sure it would be better to have a more free, faster moving design like the one shown above, where there are no lines attached, and it's a magnet core going through a coil, rather than a weight pulling on motors.

I'd appreciate your thoughts.

The shell competition thing is interesting to me, I was thinking about floating charging stations, like floating solar panels possibly combined with wave/wind based or each are separate, and these submerge in the event of a storm or passing boat (sorry getting off topic).

I apologize I did not bust out 3D rendering, I was simply trying to get the point across.

 

[FvM]

I was wondering if the coil was the entire length of sliding eg. the whole time the magnet core was sliding, it was always inside the coil, would it generate electricity? Probably a trivial question.

Consider that voltage is induced (and in return current generated and power delivered) if the summed flux through individual windings changes. Moving a magnet in an endless coil cylinder induces no voltage at all. So in a short, making the coil geometry of a "shaker" flashlight as you see it is at least one reasonable approach. There may be alternative effective geometries, but the design should be simple and cheap.

The other point is that absorbing energy slows down the magnet movement. A too effective magnet circuit will withhold the moving magnet from swinging freely, making the flashlight usage uncomfortable

 

[GreenAce92]

Right, it should be practically suspended right no resistance so some kind of rail with linear locking and nice bearings?

The pulley design is not using a magnet, but a weight that moves up and down and rotates motors to generate electricity. Probably not that great for rapid motion.

I would probably want short motions, if not some way to make it rotating to make it use momentum.

It also depends on the scale of the waves, the size of these things, more than likely they would be treated as if they were on a flat inclined plane. Rarely reaching the crest? of the wave, so they would spend a lot of time in one direction... I don't know this is just speculation.

 

[BradtheRad]

To have low friction, I picture springs attached to each end of the magnet.

One coil should be for one pole. A second coil can be placed around the other pole.

 

[GreenAce92]

Is there any waste in energy by rectifying it as you've shown? I mean what happens to that other half of the wave?

 

[FvM]

Yes, you better use a bridge rectifier.

 

[Warpspeed]

The problem with waves are the low accelerations in a long slow swell.
The "oscillating pendulum" or whatever it is would need to have a very long time constant, because its the coil attached to the buoy that moves not the weight.

It might work if you can make the whole thing self resonant with a spring, but you can never be sure what the wave frequency is going to be in ever constantly changing sea conditions.
Much more efficient to use the peak to peak motion through a tether to the sea bed, as many of these systems appear to do.

One clever system uses a long linked series of floats (like a segmented worm) all hinged to each other, so as the waves pass, the whole thing flexes along its length. Hydraulic rams at the hinges linking the segments generate very high pressures that drive a series of small high speed hydraulic motors or turbines.

 

[GreenAce92]

Yeah I built one before, four diodes, pretty cool. I remember seeing three-phase shift as a more efficient way for negating losses, the peaks of three waves next to each other, for AC to DC but I can't remember how it becomes DC unless it is the same concept just 3 phase.

Sorry by pendulum I didn't mean that the pendulum swings, the part that makes energy are these flippers that move as the waves go up and down, and the pendulum aspect is just the fact that the flipper mechanism hangs below the surface of the water

Regarding your last sentence, does that also require anchoring so that the line is stretched out and doesn't get coiled up?

 

[D.A.(Tony)Stewart]

Is there any waste in energy by rectifying it as you've shown? I mean what happens to that other half of the wave?

I think a single diode can be better in some cases.

Basically you have a linear motor with a non-linear load which will result in poor efficiency with a prime mover being some external oscillating force and the load being some pulsed force and pulsed current

Energy is stored in the velocity of mass

or stored by compression in the spring

then stored into a charged capacitor

Series ESR during the pulsed current

*duty cycle in cap,diode and coil account for some losses.

So the question remains, how much stored energy can be easily generated?

Like an air pump action, you can get a lot more done with gravity and strong resistance in one direction only allowing potential energy to be created without the extra load.

Thus depending on the force required and direction one might choose a single diode to release in one direction and no diode to store energy in the spring with more velocity and longer swings rather than faster shorter strokes with resistance in both directions and higher frequency required to accumulate the same kinetic energy Em.

In order to maximize energy transfer from kinetic to spring to electromagnetic the impedance of each interface needs to be matched in some way that permits the squared term to rise. This is related to the mass of the object, moving part, spring constant, coil inductance, and permeance as well as reactive load and ESR. Impedance is related to the mechanical and electromotive forces.

Now go do the math and define the requirements first. (that's what this section is all about)