Ministry of the Environment | FLOATING OFFSHORE WIND TURBINE DEMONSTRATION PROJECT

OUTLINE

The windmill which is now floating offshore Kabashima Island, Goto City is the first floating wind power station in Japan and is able to supply electricity to the households.
Most of the existing wind power stations in Japan are located onshore or near coastline and suitable places for the wind power are decreased in Japan of which land is narrow.
On the other hand, Japan is one of seafaring nations which has sixth widest exclusive economic zone in the world.
If this wide ocean had been exploited, huge volume of renewable energy is acquired.
In Europe, offshore wind power became common already.
In Japan, coast lane has many places deepened sharply and few shallow water like in Europe.
Therefore, placing of the wind power plant in rather deeper water is required for utilizing the ocean.
Since there are many scenic spots near the coastline, consideration must be taken to the scenery.
Furthermore, measures against natural disasters such as earthquake, tsunami, typhoon should be prepared.
Ocean is fishery grounds with rich marine resources, so cooperation of people in fisheries is indispensable but impact caused by wind power plant on marine life, mammalian is unknown.
Consequently, Ministry of the Environment is forwarding demonstration project for the floating wind
turbine plant by setting it offshore Kabashima Island with cooperation of people in Kabashima and
Goto City.

Applicable law and regulation

The small-scale test plant has been granted performance evaluation certificate by The Building Center of Japan on January 2012 and acknowledgement by The Minister of Land, Infrastructure, Transport and Tourism on February 2012.
It also has been granted confirmation certificate in response to the application of building permission on April 2012 and confirmation of inspection on July 2012 respectively by Nagasaki Prefecture.
Subsequently, it has been granted vessel inspection certificate by the Head of Nagasaki branch office of The Kyushu District Transport Bureau because of the change regarding the applicable law to the floating offshore wind turbine plant from Building Standard Law to Ship Safety Act.

Design Criterion for the Small-scale test plant

Design Criterion for the Small-scale test plant are as follows

wind speed (average during operation) 7.5m/sec (10minutes average wind speed hub height 23.3m)
   (in the storm condition) 48.3m/sec ( 10minutes average wind speed hub height 23.3m)
(maximum wind speed corresponds to 1.4times of 10minutes average wind speed (IEC Standard))
(Building Standard Law)
sea level (Highest water level) CDL+3.316m (Nagasaki Prefecture Ground Plan)
water depth (average during operation) 97.2m
   (in the storm condition) 99.1m
tidal current (average during operation) 0.4m/s
   (in the storm condition) 0.56m/s
drift current (average during operation) 0.06m/s
   (in the storm condition) 0.40m/s
waves (average during operation) 1.86m 8.0s (maximum wave height, maximum wave height
period)
   (in the storm condition) 7.73m 14.0s
(maximum wave height corresponds to 1.86times of
significant wave height (IEC Standard))

(maximum significant wave height, maximum
significant wave period)
tsunami 1.0m 0.16m/s (hypothetical tsunami wave height , maximum horizontal
current speed)