Wacky Wave Kite Power Idea

I was thinking about wave power and AWE today. How to extract the energy of a wave using a kite.

I based the idea on a bounding one kite one tether base.

Then look at the flow in a wave.



Now look the current at the crest of the wave is heading with the wave, the bough towards offshore.

The kite should fly (under water) along the crest of the wave pulling towards shore then turn 180 degrees and follow the trough back towards the origin, pulling towards offshore.

The sketch shows the basics. We have two winches [purple], one for crest production and one for trough production. Crest production path is colored green, trough red, and the yellow part is a return phase to account for net movement «downwind» during the production cycle. The kite is the black one, tethered to both winches at the same time

I think its a neat idea [I say, patting my own sholder].

Problems is one that the kite must fit in the wave so the wing area is naturally limited. So the concept would require many smaller units coupled together to get big net power output. I would naturally see many kites stacked on a single tether. But if we do that, its hard to align them all with the crest.

I am also like for most wave power just not dealing with such a nimble machinery running underwater for an extended duration.

Also, the kite must be placed carefully just beneath the surface of the sea. The kite must be placed carefully at the crest and trough, and the system must be able to find these and place the kite there in time. And account for a waves irregular shape (at least here in norway).

Except for those solvable details, this should power thousands of homes.

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Could this be some kind of tethered underwater variation of dynamic soaring flight mode?

If we look closely at the moving diagram, we see that the kite would always be close to the surface, and would follow the movement of the wave. This is why a partially submerged float filled with water would seem simpler and more appropriate to me, not subject to such dimensional limitations and being able to form a single power unit.

I think not being a float would be the primary improvement in the design, as the float will perish in the first storm

Floating buoys (like the one below) follow the motion of the waves, and are very robust even during storms and big waves. And I don’t see the usefulness of kites which must only follow the flow and not “fly” in relation to said flow.

Double anchoring with the respective winches would be possible with a model like this:

The idea I suggested had the kites flying?

Yes, as mentioned in the description (see the quote below). And generally kites fly, in the air or underwater, in static or crosswind mode. I don’t see the usefulness of kites for this configuration. Floating buoys are suitable, if of course this scheme is other than “wacky”.

The problem is that at sea even more than in air [well maybe] condition in fair and bad weather vary a lot. In particular, if the waves grow big enough to break, you dont want a floating structure in there.

Being close to the surface could be achieved through sensors and active control.

An additional problem with a floating kite at the surface is the drag it may cause, in particular by waves created on water, and due to disturbances on the water surface and wind.

I think though my initial sketch was misleading, so let me try to improve on it

A farm could look like this

I think about it sometimes, but never going further into design considerations. Do you know the wave glider ? The Wave Glider | How It Works

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I guess this idea is not too far from home for you at Syroco. Especially if the winches were placed above sea level which could be a good idea if tether drag was an issue.

I think we discussed this earlier, that subsea tethers are much more succeptible to tether drag issues, as you have more force for the same wing area, but you cant increase the strength of the tether without increasing the diameter.