Current Status of Research Activity
on Floating Offshore Wind Turbine In Japan

PO.ID
332

Atsushi YAMAGUCHI and Takeshi ISHIHARA
Department of Civil Engineering, School of Engineering, The University of Tokyo

Project overview and visions

Compact semi-sub floater for 2MW turbine

Fukushima offshore wind consortium, which consists ofMarubeni Corporation (Project integrator), the University ofTokyo(Technical advisor), Mitsubishi Corporation, Mitsubishi
Heavy Industries, Japan Marine United Corporation, Mitsui
Shipbuilding & Engineering, Nippon Steel & Sumitomo MetalCorporation, Ltd., Hitachi Ltd., Furukawa Electric Co., Ltd.,Shimizu Corporation and Mizuho information & Research, isproceeding with Fukushima floating offshore wind farmdemonstration project (Fukushima FORWARD) funded by theMinistry of Economy, Trade and Industry.

The construction of compact semi-sub floater for 2MW
downwind turbine was completed in May 2013. This floater
consists of one center column, three side columns and threebraces, and the main deck beams and the pontoon beams
support the wind turbine. The compact semi-sub floater has
advantages for construction and installation due to its shallow
drought. The drought of the floater can be controlled by using
the ballast tank located at the bottom of the side columns.

In this project, three floating wind turbines and one floating
power sub-station will be installed off the coast of Fukushima.
Fukushima
The first phase of the project consists of world first 2MW
downwind floating wind turbine, the world first 25MVA floating
substation and undersea cable, and were completed on 11th ofNovember, 2013. In the second phase, two world largest 7MW
wind turbines will be installed before 2015. The detailed
information is available in the project brochure [1]Installation and grid connection
The compact semisubfloaterwith2MW
downwindturbine left Chiba
dockofMitsui
Shipbuidling&Engineering on 27thof June, 2013. After
testing at Onahama
Port, it was ferried tothe site.
The advanced spar
floater for floating
substation
left
Isogo dock of JMU
and ferried to theinstallationsite
directly. From the16th of June, 2013,
theanchoring
began.

World first 2MW downwind offshore wind turbine was installedon the compact semi-sub floater in June, 2013. The 55m tower
was divided into three sections and after the installation of thenacelle, 40m blades were installed .

In May,y 2013, the anchor and mooringg chain for both floaters
were installed. In June, at the coast of Hirono, where onshore
substation is located, the construction of the undersea cablebegan. The grid connection of the floating offshore wind turbine
and substation was completed on 31st of October.
The project will not onlyfocus
ontechnicalchallenges but also on
social acceptance and therecovery of this region
from the damage of theGreat
EastJapan
Earthquake in 2011.

Fukushima Recovery
 Wind energy industrial accumulation
 Employment creation
 Offshore wind energy introduction

Fukushima ProjectTechnical challenge

Social acceptance Floater concept Marine navigation safety Measurement and predibtion

 Environmental assessment

 Floating substation

 Collaboration with fishery industry

 Advanced steel material Public relation

Research and development
Water tank test
By using a scaled model of 2MW compact semi-submersible
floater, water tank test was carried to clarify the response of thefloater under design wind, wave and current conditions. The
optimum control method during power production for floating
wind turbine was also investigated.

Metocean Measurements
The floating substation is equipped with met-oceanmeasurement devices. Wind velocities are measured by using
cup anemometers, wind vanes and sonic anemometers on themet mast, and the doppler ridar on the main deck. The wave
and current are measured by using the wave meter and ADCPon the middle hull. The floater motion is also measured withaccelerometers, GPS and gyros on the main deck, and a floater
motion compensation algorithm is also developed.

Advanced spar floater for substation
Construction of the floating substations on the advanced spar
floater was completed in June, 2013. On the main deck of theupper hull, a met mast and a helicopter deck are installed. Insidethe upper hull, the world first floating substation is located. The
bottom hull is filled with concrete to lower the center of gravity,
which enabled the construction and ferrying in vertical position.
The floater motion is controlled by using the cob under the upper
hull, and the middle hull.

Conclusions and future plan
The first phase installation of the Fukushima
FORWARD project have finished in the autumn of 2013.
projectj
can be summarized as follows.
The vision of the pFloating grid integration system
An offshore floating transformer system which is both durable
and unsusceptible to floater motion is developed and theperformance against vibration and inclination was evaluatedthrough shaking table tests.
tests Furthermore,
Furthermore a large capacity water
proof riser cable superior to fatigue is developed and optimized
by motion analysis. Based on these technology, the world first
floating offshore transformer system was established against
severe metocean conditions.

1. Fukushima FORWARD project solves technicalproblems in floating offshore wind turbines.
2. Fukushima
FORWARD
project
showsthat
exploitation of deep offshore wind energy is feasible
in the coast of Japan.
3. The project shows that floating offshore wind energy
can contribute the Fukushima’s renewable energy
target that 100% of the regional energy is to be
produced by renewable energy by 2040.
In addition, social acceptance of floating offshore windenergy will be discussed in the next phase of theproject, including the collaboration with fishery industry,
marine navigation safety and environmental impact
assessment .

Acknowledgement
This project is funded by Ministry of Economy, Trade andIndustry, Japan. The authors wish to express their deepest
gratitude to the concerned parties for their assistance andcontribution in this project.

Reference[1] Fukushima FORWARD English brochure,
http://www.fukushima-forward.jp/pdf/pamphlet3.pdf

EWEA OFFSHORE 2013