Offshore Wind 101 - mainefishermensforum.org

Offshore Wind 101Fishermen’s Forum

March 5, 2020

Richard Akers

Maine Marine Composites LLC

2 Portland Fish Pier, Suite 211

Portland, Maine 04101

Parts of an Offshore Wind Farm

March 5, 2020 Offshore Wind 101 2

Certification of Wind Farms

(DNV-GL, 2014)

• Wind farms north of Cape Cod will be floating,

not fixed

o Floating can be more economical than fixed

because FOWT is constructed shoreside

• Growth Rate: 10MW prototype 50MW

test field 300MW to 500MW wind farm

• Floating

(Hall, 2020)

Scale Factors


• �� = � �

�⁄ � � ��

• Goes up by the square of the rotor diameter

• Goes up by the cube of the air speed (clean, high speed wind is good!)

• GE Haliade-X 12 MW turbine: Each blade longer than football field

Offshore Wind Turbine Foundations


Fixed Foundations:

• Monopile

• Tripod/jacket

Floating Foundations:

• Tension Leg

Platform (TLP)

• Semi-submersible

(Semi-sub)

• Spar Buoy (Spar).

0-100 feet 80-150 feet >150 feet >400 feet

Jacket foundations for Block Island

Wind Farm (Providence Journal,

2015)

EWEA (2013)

Source: Principle Power

Parts of an Offshore Wind Farm


San Jose Mercury News (2015)

DolWin2 high voltage direct current (HVDC)

transmission link between 3 offshore wind

farms and Germany’s mainland (ABB, 2017)

Mooring Components

Sound & Sea

Technology (2009)

6March 5, 2020 Offshore Wind 101

Mooring Materials: Chain, Wire & Synthetic Rope

Source: API RP 2SK


Stud Link Chain Properties (Paduca, 2020)

High Tensile

UHMWPE Rope

12 Strand

Mooring Rope,

ROPENET

GROUP CO.,

LTD, China

Tidal Anchor, 3”

studlink chain (MMC)

0

50

100

150

200

250

0

20

40

60

80

100

120

0 1 2 3 4

We

igh

t o

f Li

nk (

lb.)

Len

gth

of

6 L

inks

(in

.)

Wire Size (inches)

Anchor Types

Sound & Sea Technology (2009)


Gryphon, 35 tonne refurbished Stevpris Anchors

Source : Toal et al. (2014)

Drilled and

grouted

micropiles

(Robertson,

2018)

Drag/Embedment Anchors

• Lots of drag anchor choices

– Vryhof Stevpris, Stevmanta shown

• Uplift in anchor/mooring design?

– Depends on how deep the anchor is imbedded

– Inverse catenary of mooring line (E) allows for uplift

up to 20 degrees before anchor loads change

• Proof load test

required

– 50% of breaking

load of chain

Anchor Manual

2010, “The Guide to

Anchoring,” Vryhof

Anchors.

(Vryhof , 2014)


Suction Pile Anchor

Sound & Sea Technology, "Advanced Anchoring and

Mooring Study," November 30, 2009

Source:

API RP 2SK


Mooring System


Pieces of a Mooring Line

Top: Entire line including synth.

Rope and bottom chain

Left: Anchor yoke, crown line

(to retrieve anchor)

Source: MMC

What is a Wind Turbine’s Footprint?


Anchor

Safety

Zone

Chain on

Seabed

Pull on Wind Turbine

until mooring line load

limit. Trace chain

locations



Anchor

Safety

Zone

Chain on

Seabed

Pull mooring lines

out of line until

nylon breaking load



Extreme Footprint:

Circle around all anchors



Triangular Footprint:

Around all anchors


• Maine Aqua Ventus Projecto Demonstration project at UMaine Deepwater Offshore Wind Test Site off

Monhegan Island

• Blog entry (March 27, 2018, Josh Plourde)– “…no plans for exclusion zones or setbacks for fishing around the two

turbines [now one turbine] once installed off Monhegan Island.”

– “MAV will work with fishermen that fish around the two turbines to determine an acceptable standoff distance for safe operations near the floating hulls, mooring chains, anchors and electrical cables.

– “Experience from Europe’s first floating farm is a 150 ft safety setback from the hulls.”

http://maineaquaventus.com/index.php/2018/03/27/project-update-zone-d-zone-e-license-holders/


Power Lines to Shore


AC Line from

other Turbines

(typ. 34.5 kV)

HVDC (or HVDV)

Line to shore

Approx. 5.5” diameter 34.5 kV, three

conductors with fiber-optic

communications cable (Plourde, 2017).

Electrical Connection


(Baring-Gould, 2014)

Protecting the Power Cable• Cables are trenched and laid in place

– Jet the trench, then drop cable in behind jet

– 6' underground (2M)

– Use mechanical plow to minimize impact in

sensitive areas

• If trenching not feasible (or near shore)

use cast iron armor, 10" to 12" diameter

– Small anchors won’t catch, heavy anchors

won’t damage

• Use polyurethane bend restrictors for

dynamic cable

• Trenches allow lobstering

– Only precludes fixed gear trawlers


Cast iron,

articulated

bend restrictor.

(PCS Italiana,

2017)

Polyurethane Vertebrae

Bend Restrictor (ABCO

Subsea, 2020)

Articulated

concrete

mat.

(Kokosing,

2018)

Trenching the Power Cable


Jet plow on Town Beach in preparation

for connecting Block Island to Wind Farm.

Photo by K. Curtis (Shuman, 2016)

Van den Berghe (2008)

Block Island Cable Installation (Henrikson, 2017)

QUESTIONS?


References

• ABB Power Grids. ABB delivers DolWin2 wind connection. June 2017. https://i.ytimg.com/vi/SYwDHH4rN2w/maxresdefault.jpg

• ABCO Subsea. Polyurethane Vertebrae Bend Restrictor. 2020. (https://www.abcosubsea.com/products/bend-limiters)

• American Petroleum Institute (API). Design and Analysis of Stationkeeping Systems for Floating Structures. API Recommended Practice 2SK Third Edition, Washington DC, 2005.

• Baring-Gould, Ian (NREL). Offshore Wind Plant Electrical Systems. BOEM Offshore Renewable Energy Workshop. July 29-30, 2014.

• DNV-GL SERVICE SPECIFICATION: Project certification of wind farms according to IEC 61400-22. DNVGL-SE-0073, December 2014. https://rules.dnvgl.com/docs/pdf/DNVGL/SE/2014-12/DNVGL-SE-0073.pdf

• European Wind Energy Association (EWEA): Deep Water: The Next Step for Offshore Wind Energy. Brussels, Belgium, 2013. https://windeurope.org/fileadmin/files/library/publications/reports/Deep_Water.pdf

• Hall, Dick. SGC (private conversation with author, 3/2020).

• Henrikson, Mark. Ocean News. Subsea Cable Installation For the Block island Wind Farm. August 2017.

• Kokosing Industrial. Cable Protection. Oct. 2018. https://kokosingindustrial.com/marine/special-cable-installation-handling-equipment/.

• Paduca Rigging. Stud Link. https://www.paducahrigging.com/product/stud-link/, accessed Mar., 2020.

• PCS Italiana srl. Articulated Protection Shell. 2017. http://www.pcsitaly.it/index_htm_files/Ariculated%20Protection%20Shell.pdf

• Plourde, Josh. Electrical Engineering Overview,St. George, Maine. Aqua Ventus Maine.November 27, 2017.

• Providence Journal, Jacket foundations for Block Island Wind Farm, July, 2015. (source: https://www.providencejournal.com/storyimage/PJ/20150629/NEWS/150629272/AR/0/AR-150629272.jpg)

• San Jose Mercury News. California’s first offshore wind farm proposed near Hearst Castle. 2015. (source: https://www.mercurynews.com/2015/11/07/californias-first-offshore-wind-farm-proposed-near-hearst-castle/)

• Shuman, C. Deepwater Wind connects its cable at Fred Benson Town Beach. Block Island Times. 05/20/2016 https://www.blockislandtimes.com/article/deepwater-wind-connects-its-cable/46346

• Sound & Sea Technology. Advanced Anchoring and Mooring Study. November 30, 2009 (source: https://tethys.pnnl.gov/sites/default/files/publications/Advanced_Anchoring_and_Mooring_Study.pdf)

• Toal et al. Gryphon Alpha FPSO – Experience gained during moorings replacement and hook-up. OTC-25322, Houston, Texas, May 5-8, 2014.

• Van den Berghe, J. Jet-Induced Trenching Operations: Mechanisms Involved. Offshore Technology Conference, OTC-19441-MS, Houston, TX. 2008

• Vryhof Anchors, Source: http://www.vryhof.com/products.html, Accessed July 15, 2014


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