Options for 'anchoring' a floating structure in deep sea


#1

Hi all.

So just the other day while attending an Eid openhouse, I met a marine engineer who worked for a petroleum firm and we got to talking about our floating island project. When I told him that we intended to hold a floating wave barrier structure in place at sea area with depth of 1000m, he looked at me like I just became a giraffe with three heads. He said it would not be possible for any steel chain made using existing technology to be able to support its own weight at that depth.

He suggested that we use concrete piles driven deep into the soil, but we have already considered that and we didn’t want to use that option. Mainly because it will drive the cost way too high and we’ll end up making a completely fixed structure that becomes useless when the wave change direction. For the record, the floating wave barrier is 150 meters in length and 50 meters in width and although a single pile should be enough to secure it to the sea floor, our design calls for a semi-mobile structure.

So after a short discussion over SMS with the main designer, we came up with a method to make the barrier fully mobile, anchored only by GPS and kept in place by large subsurface turbines. Due to the large and constant energy requirements, it will also double as power generator through undersea current scoop, wind and solar.

The good news is, we save up a lot of space from having to lug around steel chains of about 3000m-long and can use that extra space to put up more power generators. The bad news is, none of these has ever been tested by anyone ever and we’re not sure if it will actually work. Unfortunately all our resources are already tied up on other proof-of-concept projects.

So from design perspective, what do members of TSI think about this idea? Do you have any other idea on how to ‘anchor’ a floating structure in deep sea regions?

For the record, the planned chain before the idea was discarded would’ve been double the size of this chain and there would’ve been three of them on each of these barriers.


(.) #2

the anchoring:
The turbulent zone is the surface. Water air interface is turbulent.
Under the surface is not so turbulent.
A structure that is mostly under the surface, probably needs less
anchor strength.


(Bob LLewellyn) #3

[quote=“Shiina_Ai, post:1, topic:2622”]
Do you have any other idea on how to ‘anchor’ a floating structure in deep sea regions?[/quote]

Graphene rope. ______________________


(Wilfried Ellmer) #4

@Shiina_Ai | check on the anchor solutions in 2400m water depth that are here today and working fine.

At deep sea oil drilling fields.

google terms: | turrett anchor | tension anchor | polypropylene anchor line | weight neutral anchor lines | spread anchor | FPSO mooring |


http://www.lankhorstropes.com/files/uploads/Offshore/Conference%20presentations/HMPE_mooring_lines_for_deepwater_MODUs_OTC_Brasil_2011.pdf

http://www.offshore-mag.com/learning-center/rigs-and-vessels/mooring-systems-offshore-floating-installations.html


Ps your engineer is correct - it is not a normal ship anchor on a chain (the chain would break under its own weight).... and nobody is using dynamic positioning for a permanent installation...

Picture the Ramform | get invested | get started | oceanic business alliance
(Bob LLewellyn) #5

[quote=“ellmer, post:4, topic:2622”]
and nobody is using dynamic positioning for a permanent installation…[/quote]
Nobody yet Wil, but unless I or someone can come up with one of those ah-ha moments, what options are there for deep ocean? Phase 3 is still some time off but one option for dynamic positioning would be to have one of those mini nuclear generators like that on submarines and air craft carriers. Re-positioning would be done in off peak hours.


#6

Look at the anchoring for the FLIP. They use fluke anchors, and a combination of chain and synthetic rope, in deep waters.


(.) #7

I wanted to bring up the idea of the synthetic rope.
Polypropylene rope is cheap but UV (sunlight) corrodes it.
Polyethylene rope is UV resistant but expensive.
Sunlight (UV) does not go deep in the water.
It might be optimal to use polypropylene rope in deep water, with
a polyethylene extension on it close to the surface.
And some chain.


(system) closed #8

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