〉〉Topics

Ishikari Bay New Port Offshore Wind Power Generation Project
Submarine Cable Installation Completed
Atsushi Kimura*, Hironori Sugano*, Takahiro Ishikawa*
In Japan’s first commercial offshore wind power generation project, we completed an installation of a 66 kV submarine cable without any accident or disaster.
A power plant with a generating capacity of 112 MW, consisting of fourteen wind turbines, each
rated at 8 MW, was built offshore of Ishikari Bay New Port. We designed a submarine cable system with a total length of approximately 16 km to connect the wind turbines and transmit powerfrom the wind turbines to the mainland. This was a one-time contract for “design, manufacturingand installation.”
As a top runner in submarine cables, we will continue to contribute in the construction of offshore
wind power generation and the expansion in the introduction of renewable energy, as well as to
the realization of carbon neutrality through the supply and the installation of submarine cables.

ABSTRACT1.

INTRODUCTION

Green Power Investment Corporaion began the initialdevelopment of the Ishikari Bay New Port offshore wind
power generation project in 2007, and it is the first projectin Japan to use large wind turbines with a single unit output of 8 MW and to construct one of the largest commercial offshore wind power plants in Japan.
The power plant is built approximately 1,600 meters
offshore from Ishikari Bay New Port, in an area of approximately 500 ha, and consists of 14 units of 8 MW windturbines with a power generation capacity of 112 MW.
This project was developed and constructed by GreenPower Ishikari, a limited liability company established by
Green Power Investment Corporation, and a joint venture
formed with Shimizu Corporation and Nippon SteelEngineering Co., Ltd. was in charge of the offshore construction including the installation of offshore wind turbines etc.
The Company was contracted by Shimizu Corporation,
the prime contractor for the offshore construction todesign, manufacture, and install a submarine cable system with a total length of approximately 16 km that connects the wind turbines and transmits power from thewind turbines to the mainland.
Table 1 shows an overview of the project. The amountof power generation is enough to supply approximately
83,000 households in terms of number of households,
and the electricity sales period is planned for 20 years.	Renewable Energy Project & Offshore Engineering Department,
Power Cable Project Department, Power Cable Division,
Energy Infrastructure Division*Table 1

Project summary.

Project company

Green Power Ishikari GK

Power generation equipment
construction site

Ishikari Bay New Port in Hokkaido

Equipment capacity

8000 kw × 14 units 112,000 kW(Connection capacity 99,990 kW)

Conversion to number ofhouseholds

Approximately 83,000 households

CO 2 reduction amount

Approximately 202,000 t-CO 2 / year

Electric sales destination

Hokkaido Electric Power NetworkCo., Ltd.

Start operation

Jan. 1, 2024

Electricity sales period

20 years2.

INSTALLATION PLAN OF THE
SUBMARINE CABLE

Figure 1 shows a layout diagram for Ishikari Bay New Port
offshore wind power generation. Fourteen units of 8 MW
wind turbines are installed, seven on the onshore section
and seven on the offshore section, and these are connected by the submarine cables, which are then landed at
the beach manhole and connected to the land cables.
The wind turbines on the onshore section and the offshore section are also connected by the submarine
cables in a loop, creating a submarine cable system witha total length of approximately 16 km.
The wind turbine consists of four steel pipe pile foundations and a lower steel structure called a jacket, on which
the wind turbine is installed. The wind turbine will beapproximately 200 m above the water level. These works
were carried out according to the schedule shown inTable 2. The process involves installing a jacket on top ofa pre-drilled pile foundation, laying and pulling in the submarine cables, and then installing the wind turbine itself.
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Ishikari Bay New Port Offshore Wind Power Generation Project Submarine Cable Installation CompletedPort area

water depth is shallow, the tow rope and cable terminal
are connected from the land, and then hoisted up with aland winch (Figure 4). When laying submarine cables, thethrusters gradually advance the cable as it is fed out.

Oﬀshore section wind turbine
No.08 to No.14

Pile foundation/Substructure/
Wind turbine installation

Wind turbine

Onshore section wind turbine
No. 01 to No.07

Direction of travel of the laying barge

blSubmarineca

Pile foundation

Wind turbine
assembly location

Submarinecablee

SubstructureSandy
beach300 m

Oﬀshore/land Transition Joint Bay
Beach manhole

Figure 1

Layout of Ishikari Bay New Port offshore wind turbine /Foundation / Submarine cable.
(Provided by Green Power Investment Corporation.)

Table 2

Construction schedule.
(Provided by Green Power Investment Corporation.)
2023

2024
Mar.

Jan.

Feb.

Dec.

Oct.

Nov.

Sep.

Jul.

Aug.

Apr.

Jun.

May

Steel pipe pile construction

Mar.

Jan.

Feb.

Dec.

Oct.

Nov.

Sep.

Jul.

Aug.

Apr.

Submarine cableinstallation (Offshoretransmission line)

Jun.

Wind turbine
foundation/
Substructureconstruction

2022
MayOffshore section
Main construction

Submarine cable

Submarine cable layingJacket construction

Figure 2
Beach manhole construction

Cable laying / buried work

Wind turbine parts
Temporary storage/
preassemblyWind turbine
equipment
construction

The laying barge maintained
a ﬁxed position
Wind turbine

Landing section

Trial run

For the wind turbine’s foundation structure, a jacket
type was chosen as the optimal structure, taking into
consideration the natural conditions of the local sea area,
the construction conditions, and the wind turbine specifications. The submarine cable is laid through a conduit(J-tube) installed in this jacket foundation structure, and is
an important key component that connects the wind turbines and transmits the generated power to the onshore
power grid.

3.

Cable laying barge Awaji.

*DPS: Dynamic Positioning System is an automatic barge positioning systemthat automatically controls the barge's own propulsion device (thruster)
to hold the barge in a fixed position without an anchor.

Cable feedWind turbine

Cable feed

Landing section cable hoisting.

Figure 3

The laying barge direction of travel
Landing section

Submarine cable laying.

Laying operation for the submarine cable at thelanding section.

LAYING OF THE SUBMARINE CABLE

The submarine cable was laid by “Cable laying barge
Awaji” shown in Figure 2. The Awaji is equipped with a
Dynamic Positioning System (DPS*), which allows thesubmarine cable to be sent out while keeping the laying
barge in a fixed position.
The laying barge will monitor the tension management
according to the angle of entry into the water and confirm
that the laid submarine cable does not have excessive
tension or bend more than expected.
3.1 Submarine Cable Laying Work at Landing Section
Figure 3 shows an image of the landing section work.
When sending a submarine cable to the landing section,a tube buoy is attached to the submarine cable, and thecable is sent to the landing section while floating above
the sea surface. After sending it out to a point where theOverview of landing

Shoreline situation
Figure 4

Landing of the submarine cable.

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Ishikari Bay New Port Offshore Wind Power Generation Project Submarine Cable Installation Completed

The laying barge direction of travel

The laying barge maintained
a ﬁxed position

Pull the cable
into the foundation

Cable feed

Pull the cable into a lower structure(Jacket part) (starting side).

ーブル引揚げFigure 5

Pull the cable into a lower structure(Jacket part) (end side).

The submarine cable laying operation between the wind turbines.

The Submarine Cable Laying Between WindTurbines
Figure 5 and Figure 6 show images of a laying between
the wind turbines. When pulling the cable into the jacket
foundation structure, the submarine cable is sent out tothe jacket side with the laying barge held at a fixed pointby the DPS. When pulling the submarine cables into thewind turbine foundation, the cable is first hoisted midway
and dropped into the sea, then gradually pulled into thewind turbine foundation. This is to reduce a friction, as alarge amount of a friction occurs when the cable is laid on
the ocean floor.

4.

Wind turbine
foundation

Pull the cable
into the foundation

A submarine cable laying.

3.2

Figure 6

The laying barge maintained
a ﬁxed position

5.

CONCLUSION

As one of Japan’s leading manufacturers of the submarine cable design, manufacturing and construction, weare participating in the offshore wind power generation
business, and leveraging the knowledge and know-how
we have gained through the Fukushima Floating Offshore
Wind Farm Demonstration Research Project and Nyuzen
Offshore Wind Power Project, we led this project to success.
Going forward, we will continue to contribute to therealization of carbon neutrality by supplying and installing
submarine cables and underground cables that are
essential for interconnecting renewable energy sources
such as the offshore wind power generation with thepower grid.
We received a great deal of support from Green PowerInvestment Corporation, Shimizu Corporation and Nippon
Steel Engineering Co., Ltd. for the construction work andwe would like to express our sincere appreciation for theirsupport.

Laying of the submarine cables to the wind turbines.

BURYING THE SUBMARINE CABLE

The cable is sandwiched between the burial machines, awater flow is supplied from the pump ship to the burying
machine, and the water stream emitted from the burying
machine’s nozzle blows away the soil around the cableand buries the cable (Figure 7).

Cable burial situation.

Figure 7

Burial machine.

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