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Magnetic coil for Wave Energry harvesting.

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xRocx

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Hi, I'm new to this forum, I would have to say I am quite the novice in many of the areas this place offers in discussion, so that is why I promote this question to any who can answer.

I pondered up the idea one day of a wave energy harvesting method similar to that of those kinetic magnetic coil flashlights.

Now heres my question, would a ring magnet work on the passing of the outside of a coil in which a normal magnet works by passing through the inside of a coil?

The answer to this drastically changes my design.
 
Yes it would work the same provided the N and S poles are on the ends of the ring magnet (same as a magnet rod).

But it won't work well at all for wave energy. Ocean waves are very slow moving with enormous force. That simple magnet coil generator only works ok if it is moving very fast.

There is a huge amount of energy in waves but it is very hard to harvest as it is difficult to generate electricity from a very slow movement with tons of force, AND have it waterproof and able to withstand very high random loads liek storms and freak waves.

Please don't let me put you off wave energy, this is a very important area of research and not enough people are doing it. But I still think a magnet tube idea is the wrong type of generator because of the speed issues. :)
 
If I'm not mistaken current tidal generators typically duct rising and falling water through low pressure turbines to generate electricity. I'm not sure gigantic coils rising and falling with the water would be particularly efficient.

You will be VERY hard pressed to find ring magnets that are polarized in the manner that you require, but it'd be worth hunting around. You could construct a ring manget using many much smaller bar magnets carefully glued around a ring.
 
The giant ocean wave powered generators use hydraulics.
They have hydraulic cylinders at the flex points that work as massive slow moving piston pumps to generate the high pressures that runs the hydraulic motors that turn the actual generators in the units. Its a very simple system, just very big.

There is a video about how they are built and how they actually work some place on line.

Its worth doing a search for.:)

Most of the tidal current type generators are sort of like ducted underwater fans or wind generators of sorts.
 
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One of the guys on the Feildlines forum showed a beaut setup for an above stream water wheel that gave real good results. Depending where you are in the world will depend on the tidal flow, when I lived in north west Australia 6-8 metre tides were the norm. A town called Derby put in a claim for tidal power with a valid approach but as usual lost out to gas turbines.

Any water wheel would need to be a heavy steel fabrication or in the first day it will become a snag in the river. As the power of water is so strong a slow moving water wheel could easily power a gearbox in reverse to provide power for a generator. On the one above I quoted the guy did just that and used a dual axial flux generator wound to suit the setup.

Something of this nature isn't for the faint hearted and those without deep pockets.........

Cheers Bryan
 
Another way to do this is to have a large heavy float (or buoy) that rides the waves, and a vertical cable that goes down through a pulley attached to a solid anchor point in the sea bed.
As the float rises and falls, the cable runs back and forth through the pulley.

This cable runs along the sea floor and up the beach, with the end wound around a cable drum. As the float rises and falls, the drum slowly rotates backwards and forwards with enormous force.
It will require either a powerful spring, or a suspended weight (with another cable) to rotate the drum backwards on the falling side of the wave.

Anyhow, the cable drum rotates backwards and forwards fairly slowly following the profile of each wave. This is best done in deep water where there are no breaking waves, so the cable needs to be quite long.

There is then a one way clutch fitted between the drum and a shaft, so the shaft always rotates only in the direction of a pull on the cable, and rising water. A speed step up gearbox and a flywheel keep everything turning fairly constantly in one direction to drive an electrical generator at suitably high rpm.

It will work as above with only one float, cable and drum.

But larger and much more efficient systems have been built with many floats and drums, with the floats dispersed over a wide sea area, so they all go up and down out of phase.
Like the pistons in an engine, all going up and down out of phase, the one way clutch in the hub of each individual drum will create almost a constant rotary motion in the main shaft.

The torque developed can be extremely high, but at low rotational speed. A suitably robust gearbox easily solves that problem. With sufficient cable winding capacity on each drum, large tidal changes in water level can be catered for. The one way clutches constantly self adjust for changing sea conditions.
 
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