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A new floater for offshore wind

One year on and still on the right path

Henrik Stiesdal, 26.10.16

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In-Float concept presented at 2015 Annual Event

Principles

• Tetrahedral structure with minimal bending moments

• Modular – all components brought in from outside, no

fabrication in harbor

• Components with dimensions and weights known from wind

turbines, assembled with bolts

• Buoyancy with pressurized tanks – lightweight structures with

no need for dimensioning to hydrostatic pressure

• Can be implemented as both TLP and semisub (subject to

design adjustments)

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Two-level innovation presented at 2015 Annual Event

Level 1 - Technical

• New structural concept with industrialization as key focus

Level 2 - Dissemination

• Open source arrangement with royalty-free license to IP offered to any interested party

• Joint Industry Project to firm up on details and prepare best-practice standard

• Invitation to universities and research institutes to participate in further improvement of concept – opportunity for engineering students to create the future

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DNV GL Collaboration offer

• DNV GL has agreed to conduct an independent review of the floating foundation concept with the objective to provide a verification of its feasibility

• The collaboration is driven by the open source arrangement and is carried out through DNV GL’s internal “Extraordinary Innovation” research program

• The results of the project will be provided as a part of the open source material

“We are proud to collaborate on this exciting project. Floating wind turbines has

great potential but the costs need to come down significantly. Open source

innovation is the perfect way to quickly bring new ideas to the market, spur

ingenuity and industry collaboration. This fits very well with DNV GL’s own

purpose and values.” Johan Sandberg, Segment Leader – Floating wind turbine technology

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DNV GL Evaluation Results

Conclusion from DNV GL Evaluation Report

on TLP Variant of TetraSpar

“At the present stage of development, DNV GL

has not identified any unsolvable development

barriers and thus believes the concept is well

suited for further conceptual development”.

Source: DNV GL

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So - how did it go?

Academia, small companies, consultants, small suppliers

• Great interest

• Many offers for collaboration, supplier engagement, etc.

Other floater developers and large substructure suppliers

• Low interest – too much capital (real and emotional) invested already

Large developers

• Great interest, but always with the caveat – “Well, open source … we would

much have preferred if we could have it as an exclusive … we need some

sort of entrepreneurial ownership … come back with something that we can

have to ourselves!”

So – something needed to be developed that could be exclusive

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Idea: Combine benefits from the family of floating concepts

Picture credit: NREL

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Advantages

• Simplest overall concept, Inherently stable

• Moderate wave loads

• Simple mooring

• Moderate dynamics

• Proven

Disadvantages

• Heavy

• Requires minimum 100 m water depth at turbine

installation location, or turbine that can be up-ended,

or very special installation vessel

Spar buoy

Picture credit: Statoil

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Advantages

• Wide range of water depth (40 m )

• Turbine can be installed at quayside and towed to site

• Simple mooring

• Proven

Disadvantages

• Heavy

• Complex steel structure

• Requires either ballast compensation or quite large

dimensions to limit tilt

• Large wave loads, lively dynamics

Semisubmersible

Picture credit: EDPR / Principle Power

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Advantages

• Low weight

• Turbine can be installed at quayside and towed to site

• Moderate wave loads

• Low dynamics

Disadvantages

• Demanding (and expensive) tether arrangements

• Complex steel structure

• Limitations on depth range unless supplementary

mooring used

• Installation typically requires assistance from purpose-

built vessel

Tension Leg Platform

Picture credit: Glosten

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Combining the advantages …

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• Simple tetrahedral structure with a keel

• Keel has ballasted tanks that float when air-filled

• In harbor and during towing keel is air-filled, floating with foundation, requiring no more than 6-8 m depth

• Floater has semisub stability during towing

• On site keel is ballasted, pulling the foundation below the surface to act as spar

… Leads to TetraSpar

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TetraSpar installation process

Tow-out Lower keel Hook up Ballast keel

Keel

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TetraSpar can be installed at water depths from 10 m to >1000 m

Applies the full range of technologies -

• Floated out as semisub

• Can be installed as fixed foundation at low water depths

• Can be Installed as TLP variant at 40-100+ m water depth

• Can be installed as spar variant at water depths above 80 m

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The installation process can be reversed for maintenance

• The structure may be raised to the surface for inspection at 2-5 year intervals, and may be towed to port for main component replacement

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• Offers disruptive reduction in Cost of Energy from

floating offshore wind

• Combines benefits from known floater concepts

• Is suitable for genuine industrialization

• Applies proven technologies

• Can be configured for installation at water depths

from 10 m to more than 1000 m

• Facilitates local manufacturing and truly global

application

The most important part - industriaization

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True industrialization can have tremendous cost-reduction impact

Source: BNEF

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This also applies to large equipment

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And we are also quite good at it!

Onshore wind industry

• Has proven track record in continuous improvement

and cost reductions

• Currently offers lowest cost new capacity

• Installs 500-1000 ton structures in few days

Basis for low cost and high efficiency

• All components factory-made, no fabrication on site

• No special processes outside factory

• All components assembled by bolting

Picture credit: Siemens

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• Design components with dimensions that allow road

transportation

• Manufacture components “the onshore wind way”,

using existing supply chain. No fabrication on site!

• Assemble floater with onshore wind methods

(bolting) in simple harbor areas

• Launch floater, install turbine, commission, tow out,

hook up, operate

Applying best practices from the onshore wind industry

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A practical example of a floater made with onshore technology

• Cast TP, wind turbine hub technology

• Tapered, welded center column,

wind turbine tower technology

• Cylindrical, welded braces, wind

turbine tower technology

• Cast nodes, wind turbine hub

technology

• Steel or GRP tanks, industrial

technology

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How an assembly and installation area might look

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Launching floater using land-based crane

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Low investments, simple methods

• All components manufactured by existing suppliers

• No special harbor requirements (dry docks etc.),

assembly on simple laydown area at quayside

• Turbine mounted in harbor using land-based crane

• Floater towed to site, no installation vessels

Cost implications

• Volume benefits from onshore supply chain

• Short delivery times, low financing costs

• Low weight (1000-1500 t for 7 MW) and low specific

cost ($/kg) due to industrialized manufacturing

• Low mobilization, assembly and installation costs

The combined effects of concept and industrialization

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Predicted cost effects

156

136

63

TetraSpar

50-100

Source: Nature Eneergy

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A radical cost reduction can be achieved with

• A structural design facilitating application of the

onshore wind industry supply chain

• Installation methods facilitating use of low-cost

methods and vessels

But it doesn’t stop here!

• The same approach is needed for the electrical

infrastructure, and for O&M

We have proven that it can be done in onshore

wind power. Let us do the same offshore!

In summary –

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Thanks for your attention

Henrik Stiesdal

[email protected]

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