The Anonymous Widower

Norwegians Developing Monopile Foundation For 100-Metre Depths

The title of this post, is the same as that of this article on offshoreWIND.biz.

Monopile foundations are a common fixed foundation for offshore wind farms.

The article starts with this paragraph.

Norway’s Entrion Wind and Techano AS have signed a Memorandum of Understanding (MoU) through which Techano AS will join the ongoing development and test project planned to take place in Kristiansand, Norway for the patent-pending fully restrained platform (FRP) offshore wind foundation technology said to extend the operating depth of the monopile technology to up to 100 metres.

It does seem that the Norwegians are intending to take this type of foundation to new heights. Or is it new depths?

A picture in the article shows a tall monopole held in position by three wires securely anchored in the sea-bed. It reminds me slightly of the sort of flag-poles, that we used to build in Scout camps in the 1960s, using Scout staves, ropes and tent pegs.

But seriously in the 1970s, I did the calculations for a company called Balaena Structures, who were trying to develop a reusable oil and gas platform.

  • The company had been started by two Engineering professors from Cambridge University.
  • The platforms were formed of a long steel cylinder, which would have been built horizontally in the sort of ship-yards, that were used to build supertankers.
  • They were to be floated out horizontally and then turned upright.
  • Weight and the gumboot principle would have kept them, in place.

The design also included a square platform on the top end. Originally, they were planning to put the platform on top after erection, but I showed that, it would be possible to erect cylinder and platform, by just allowing water to enter the cylinder.

The project had a somewhat unfulfilling end, in that they never sold the idea to an operator and the company closed.

But I still believe something similar has a future in the offshore energy industry.

It could be a foundation for a wind turbine or possibly as I indicated in The Balaena Lives, it could be used to clear up oil field accidents like Deepwater Horizon.

Could This Be A Design For A Hundred Metre Plus Monopole Foundation?

Construction and installation would be as follows.

  • A long cylinder is built in a ship-yard, where supertankers are built.
  • One end, which will be the sea-bed end after installation, is closed and has a skirt a couple of metres tall.
  • The other end is profiled to take the transition piece that is used as a mount for the wind turbine.
  • A float would be added to the top end for tow-out. This will help the cylinder to float and erect.
  • Water would be added into the cylinder and, if the dimensions are correct, it will turn through ninety degrees and float vertically.
  • It would be towed to a dock, where a large crane on the dock would remove the float and install the turbine.
  • The turbine and its foundation would then be towed into place and by adding more water lowered to the sea-bed.
  • The float would be reused for the next turbine.

Note.

  1. The float is needed to nudge the cylinder to turn vertically.
  2. If the Cambridge professors were right, the skirt and the weight of water would hold it in place.
  3. Traditional moorings could be added if required.
  4. No heavy lifts are performed at sea.
  5. The concept would surely work for a floating turbine as well.

But then what do I know?

I was just a twenty-five year old engineer, mathematician and computer programmer, who did a few calculations and a dynamic simulation fifty years ago.

October 22, 2022 - Posted by | Design, Energy | , , , , ,

2 Comments »

  1. This should work if the hundred metres or so below the sea bed are soft. OK to the point where the pile is part filled and floats vertically in the sea, but to sink into the silt below it would need to be gradually filled with something heavy – ideally heavier than the mud it is sinking into – e.g. steel slag.

    Comment by R. Mark Clayton | October 23, 2022 | Reply

    • Thanks!

      I only did the simulation!

      Comment by AnonW | October 23, 2022 | Reply


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