Fukushima Floating offshore Wind Farm Demonstration Project

Fukushima Floating offshore met mast data

Schematic Design of Substation

Outline of the floating offshore met mast

Category Fukushima floating offshore met mast
Meteorology/ Oceanography Wind speed, Wind direction, Wave height, Wave period, Current speed
Water depth 120m
Distance from shore 20km
Tower height 60m
Draft for floater 50m
Installation date 2013.11
Commencement date 2014.9

Measurement parameters

Measurement device Measurement element Measurement location
Metrological Wind Cup anemometer(9) Wind speed
Wind direction
Wind speed, direction
40,50,60m
60m~310m(12 layer)
Wind vane(10)
Doppler rider(1)
Oceanography Wave Wave Buoy(1)* Wave height, period**
Wave height, period**
Sea surface
Wave meter(1) Sea surface
Current Wave meter(1) Current speed,
direction
Water depth 6.5m, 8.5m, 11.0m
ADCP(1) Water depth 5.5m, 7.6m, 11.8m

*Wave buoy is located adjacent to “Fuikushima Mirai” about 20Km offshore from the Fukushima coast and other equipments are installed on the substation.  
**Since the data availability of wave meter is higher than that of wave buoy during last 3 years, the wave meter data is preferentially used. In the last release in 2017, it was assumed that spectral significant wave period (Ts) measured by wave buoy is equal to significant wave period (T1/3) by wave meter. As a result of careful examination, the bios between two data was found. Therefor significant wave period (T1/3) measured by wave meter is regarded as true value and spectral significant wave period (Ts) is corrected. Significant wave height (H1/3) measured by wave meter and spectral significant wave height (Hs) measured by wave buoy is equal as assumed in 2017.

1. Wind Data (2015~2017)

1 : Wind Speed frequency distribution

Description Observation
year
Jan. Feb. Mar. Apr. May. Jun. Jul. Aug. Sept. Oct. Nov. Dec. year
Weibull distribution
Shape parameter(k)
2015 1.85 1.67 1.9 2.05 2.1 2.46 1.47 2.02 1.93 1.55 2.29 2.07 1.88
2016 2.06 2.08 1.96 2.08 2.02 1.88 2.42 1.67 1.79 2.05 2.34 2.06 1.96
2017 2.56 2.23 1.87 1.96 2.16 1.63 2.12 1.94 1.47 1.98 1.98 1.71 1.91
Weibull distribution
Shape parameter(c)
2015 9.07 8.71 8.55 9.15 8.54 7.95 6.24 7.25 6.92 8.08 8.29 8.38 8.12
2016 8.62 8.67 8.24 9.68 9.19 7.36 6.69 8.13 6.7 7.72 8.13 9.46 8.25
2017 10.53 10.60 8.04 9.14 8.59 7.01 8.30 6.91 7.00 7.89 8.01 8.53 8.42

Wind speed frequency distribution(60m)

Comment

Wind speed frequency shows a similar distribution in three years.

2:Wind rose

Obs. year Wind rose[%](60m)
N NNE NE ENE E ESE SE SSE S SSW SW WSW W WNW NW NNW
2015 11.2 7.7 4.0 3.0 2.9 2.5 2.8 4.5 9.6 12.9 3.8 2.5 4.9 6.8 8.6 12.6
2016 11.8 8.2 4.7 3.1 2.4 2.0 2.5 3.7 10.3 12.1 4.0 2.6 4.9 6.7 8.9 11.9
2017 9.6 7.2 4.7 3.6 2.8 2.3 3.0 3.5 8.2 13.0 3.6 2.7 5.8 9.7 10.2 10.2

Wind rose(H=60m)

Comment

The prevailing wind direction at 60m height is Northerly and Southerly. In 2017, unlike other years, one of the prevailing wind direction is West North Westerly.

3:Mean wind speed profile

year α
2015 0.096
2016 0.084
2017 0.075

Shear exponent

Commentary

The mean wind speed profile normalized by the mean wind speed at 100m above sea level has the shear exponent of less than 0.1.

4:Turbulence intensity

Comment

The turbulence intensity is lower than IEC 61400-1 Category C in any year except for the wind speed of 30m/s or higher.

5:Monthly mean wind speed and data availability

Description Measurement
height
Observation
year
Jan. Feb. Mar. Apr. May. Jun. Jul. Aug. Sept. Oct. Nov. Dec. Annual
mean wind
speed
Mean wind speed[m/s] 60m 2015 8.1 8.0 7.5 8.1 7.4 6.8 5.9 6.3 6.2 7.5 7.2 7.4 7.2
2016 7.7 7.7 7.3 8.7 8.0 6.6 5.8 7.1 6.0 6.8 7.0 8.4 7.2
2017 9.4 9.4 7.3 8.2 7.5 6.3 7.3 6.1 6.6 6.8 7.1 7.8 7.5
Data availability[%] 2015 85.7 84.4 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 97.5
2016 100.0 88.2 100.0 93.5 100.0 100.0 98.7 100.0 100.0 100.0 100.0 100.0 98.4
2017 100.0 90.2 97.5 100.0 100.0 100.0 99.6 99.7 100.0 100.0 90.1 100.0 98.1

Monthly mean wind speed and data availability

Comment

The annual mean wind speed is between 7.2m/s and 7.5m/s. The monthly mean value in January is 7.7m/s in 2016 and 9.4m/s in 2017. There is a big difference of 1.7m/s between two value in comparison with other months.

6:Monthly average turbulence intensity

Description Measurement
height
Observation
Year
Jan. Feb. Mar. Apr. May. Jun. Jul. Aug. Sept. Oct. Nov. Dec. Annual mean
value
Mean turbulence
intensity[%]
60m
[All direction]
2015 10.9 9.9 9.6 5.7 7.3 7.1 8.7 8.2 8.4 9.4 9.4 11.4 8.8
2016 12.1 11.0 11.1 7.7 7.7 8.2 8.0 8.4 10.0 10.7 12.4 12.7 10.0
2017 12.1 11.8 9.3 8.1 7.9 10.0 7.5 9.1 9.4 10.9 10.9 13.7 10.1

Monthly average turbulence intensity (H=60m)

Comment

Annual average turbulence intensity is between 8.8% to 10.1%. Annual average turbulence intensity is about 10% in 2016 and 2017 and 8.8% in 2015 which is smaller than the other years.

2. Wave Data (2015~2017)

1:Frequency distribution of significant wave height

Comment

The maximum significant wave height frequency is between 1.00m and 1.25m, and there is no difference depending on the year.

2:Wave rose

Description Year N NNE NE ENE E ESE SE SSE S SSW SW WSW W WNW NW NNW
Frequency
distribution
[%]
2015 3.1 5.0 9.9 13.1 14.4 15.0 15.9 15.1 6.9 0.4 0.0 0.1 0.1 0.1 0.2 0.7
2016 2.9 7.3 12.8 11.9 11.7 16.6 16.4 12.3 6.2 0.4 0.2 0.1 0.0 0.0 0.1 0.9
2017 5.8 7.5 9.0 12.6 14.1 14.1 11.2 12.8 8.1 1.0 0.3 0.1 0.2 0.4 0.8 2.0

Wave rose

Comment

The prevailing wave direction is Easterly and SSE which agree with the fact that the wave comes from the Pacific Ocean because the coast is located on the west side of the project.

3:Frequency distribution of the significant wave period

Comment

The maximum significant wave period frequency in 2015 is between 7 sec and 8 sec., and that in 2016 and 2017 is between 6 sec. and 7 sec.. The significant wave period frequency distribution varies widely from year to year.

4:Joint probability distribution of wave height and wave period

Table 1 Joint probability distribution of wave height and wave period (2015)

0.0~ 1.0~ 2.0~ 3.0~ 4.0~ 5.0~ 6.0~ 7.0~ 8.0~ 9.0~ 10.0~ 11.0~ 12.0~ 13.0~ 14.0~ 15.0~ 16.0~ appearance
frequency
Frequency
distribution
[%]
10.00~                                   0 0.0
9.50~10.00                                   0 0.0
9.00~9.50                                   0 0.0
8.50~9.00                                   0 0.0
8.00~8.50                                   0 0.0
7.50~8.00                                   0 0.0
7.00~7.50                                   0 0.0
6.50~7.00                                   0.0 0.0
6.00~6.50                       1 3 2 2     8 0.1
5.50~6.00                     1 7     1     9 0.1
5.00~5.50                   2 6 1 1 5       15 0.2
4.50~5.00                   5 3 1 1 6 4 1   21 0.2
4.00~4.50               1 8 35 8 6 4 6 7     75 0.9
3.50~4.00               6 46 67 31 17 8 2 6     183 2.1
3.00~3.50             1 19 71 113 31 14 1 13 8     271 3.1
2.50~3.00           1 33 94 172 127 35 4 4 12       482 5.5
2.00~2.50           16 144 283 260 77 61 21 13 12       887 10.1
1.75~2.00           31 122 336 281 80 36 5 7 2       900 10.3
1.50~1.75           96 229 362 266 141 63 8 9         1174 13.4
1.25~1.50         12 125 319 483 321 205 82 32 5         1584 18.1
1.00~1.25         24 193 372 534 300 132 20 6           1581 18.0
0.75~1.00         26 125 314 386 302 104 6             1263 14.4
0.50~0.75         3 45 88 125 44   1             306 3.5
0.25~0.50               1                   1 0.0
~0.25                                   0 0.0
appearance frequency 0 0 0 0 65 632 1622 2630 2071 1088 384 123 56 60 28 1 0 8760 100.0
Frequency distribution[%] 0.0 0.0 0.0 0.0 0.7 7.2 18.5 30.0 23.6 12.4 4.4 1.4 0.6 0.7 0.3 0.0 0.0 100.0  

Table 2 Joint probability distribution of wave height and wave period(2016)

0.0~ 1.0~ 2.0~ 3.0~ 4.0~ 5.0~ 6.0~ 7.0~ 8.0~ 9.0~ 10.0~ 11.0~ 12.0~ 13.0~ 14.0~ 15.0~ 16.0~ appearance
frequency
Frequency
distribution
[%]
10.00~                                   0 0.0
9.50~10.00                                   0 0.0
9.00~9.50                                   0 0.0
8.50~9.00                                   0 0.0
8.00~8.50                         1         1 0.0
7.50~8.00                         1         1 0.0
7.00~7.50                     1 1 1         3 0.0
6.50~7.00                     1 1           2 0.0
6.00~6.50                     6             6 0.1
5.50~6.00                   2   2 3         7 0.1
5.00~5.50                 1 1 7 6 2         17 0.2
4.50~5.00                 1 2 7 8 1         19 0.2
4.00~4.50               1 4 2 12 9 3         31 0.4
3.50~4.00             1 23 26 21 5 11 4         91 1.0
3.00~3.50             14 46 35 34 15 2 3 3       152 1.7
2.50~3.00           8 76 84 99 48 19 7 5 4 1     351 4.0
2.00~2.50         1 79 252 238 181 101 44 35 12 6 6 3   958 10.9
1.75~2.00           145 210 191 138 78 28 14 1   1 4   810 9.2
1.50~1.75         14 233 284 255 177 94 29 10 4         1100 12.5
1.25~1.50         24 346 450 399 198 94 32 11 1   1     1556 17.7
1.00~1.25         46 310 624 610 186 21 16 2           1815 20.7
0.75~1.00         38 231 620 501 132 31 5             1558 17.8
0.50~0.75         6 43 103 103 26 1               282 3.2
0.25~0.50         3 7                       10 0.1
~0.25                                   0 0.0
appearance frequency 0 0 0 0 132 1402 2634 2451 1204 530 227 119 42 13 9 7 0 8770 100.0
Frequency distribution[%] 0.0 0.0 0.0 0.0 1.5 16.0 30.0 27.9 13.7 6.0 2.6 1.4 0.5 0.1 0.1 0.1 0.0 100.0  

Table 3 Joint probability distribution of wave height and wave period(2017)

0.0~ 1.0~ 2.0~ 3.0~ 4.0~ 5.0~ 6.0~ 7.0~ 8.0~ 9.0~ 10.0~ 11.0~ 12.0~ 13.0~ 14.0~ 15.0~ 16.0~ appearance
frequency
Frequency
distribution
[%]
10.00~                                   0 0.0
9.50~10.00                                   0 0.0
9.00~9.50                                   0 0.0
8.50~9.00                                   0 0.0
8.00~8.50                                   0 0.0
7.50~8.00                                   0 0.0
7.00~7.50                                   0 0.0
6.50~7.00                       1           1 0.0
6.00~6.50                       2 2         4 0.0
5.50~6.00                   4 1 4 4         13 0.1
5.00~5.50                 1 13 5 3           22 0.3
4.50~5.00               2 4 9 13 3 2         33 0.4
4.00~4.50               7 5 19 16 8 2         57 0.7
3.50~4.00               22 50 25 23 12 1         133 1.5
3.00~3.50             6 53 78 69 32 13 6         257 2.9
2.50~3.00           1 48 86 80 65 40 24 2         346 4.0
2.00~2.50           50 214 172 106 89 67 51 2 1 2 1   755 8.6
1.75~2.00           87 204 141 154 102 43 19 4 2 2     758 8.7
1.50~1.75         12 145 275 257 183 128 75 12 8 5       1100 12.6
1.25~1.50         21 228 354 477 337 179 61 25 3         1685 19.2
1.00~1.25         54 342 510 490 274 138 38 6 3         1855 21.2
0.75~1.00         28 180 493 358 157 67 5             1288 14.7
0.50~0.75         3 32 183 138 54 33 8             451 5.1
0.25~0.50                                   0 0.0
~0.25                                   0 0.0
appearance frequency 0 0 0 0 118 1065 2287 2203 1483 940 427 183 39 8 4 1 0 8758 100.0
Frequency distribution[%] 0.0 0.0 0.0 0.0 1.3 12.2 26.1 25.2 16.9 10.7 4.9 2.1 0.4 0.1 0.0 0.0 0.0 100.0  

Comment

The frequency of significant wave height between 0.75m and 1.50m and significant wave period between 8 sec and 9 sec have maximum occurrence frequency in 2015. The significant wave height between 0.75m and 1.25 m and the significant period between 6 sec. and 7 sec have maximum occurrence frequency in 2016 and 2017.

5:Monthly mean significant wave height and data availability

Description Year Jan. Feb. Mar. Apr. May. Jun. Jul. Aug. Sept. Oct. Nov. Dec. Annual mean
significant
wave height
Mean significant
wave height(m)
2015 1.60 1.96 1.53 1.48 1.39 1.43 1.41 1.91 1.83 1.76 1.84 1.48 1.63
2016 1.38 1.43 1.55 1.72 1.43 1.49 1.24 2.22 1.53 1.31 1.50 1.49 1.53
2017 1.78 1.72 1.80 1.67 1.33 1.38 1.14 1.54 1.78 1.90 1.37 1.20 1.55
Data acquition
rate(%)
2015 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0
2016 100.0 100.0 100.0 100.0 98.8 99.9 100.0 99.7 100.0 99.7 100.0 100.0 99.8
2017 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 99.7 100.0 100.0 100.0 100.0

Monthly mean significant wave height and data availability

Comment

Monthly mean significant wave height is between 1.20m and 2.32m.

6:Monthly mean significant wave period and data availability

Description Year Jan. Feb. Mar. Apr. May. Jun. Jul. Aug. Sept. Oct. Nov. Dec. Annual mean
significant wave
period
Mean significant
wave period(s)
2015 7.70 8.50 7.85 7.13 7.56 7.46 8.66 8.53 8.53 8.09 7.76 7.41 7.93
2016 7.22 7.13 7.66 7.35 6.58 6.95 6.92 8.73 7.23 6.99 7.35 7.18 7.28
2017 8.05 7.84 8.27 7.34 6.70 7.28 7.40 7.35 8.38 8.22 7.33 6.97 7.59
Data availability
rate(%)
2015 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0
2016 100.0 100.0 100.0 100.0 98.8 99.9 100.0 99.7 100.0 99.7 100.0 100.0 99.8
2017 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 99.7 100.0 100.0 100.0 100.0

Monthly mean significant wave period and data availability

Comment

Monthly mean significant wave period is between 6.58 sec and 8.37 sec. Because of the strong swell from the Pacific Ocean, the significant wave period is long throughout the year.

3. Current Data (2015~2017)

1:Frequency distribution of current speed

Comment

The maximum frequency distribution of current speed is within the range of the low flow velocity in 2016 and 2017, but in 2015 frequency for higher current speed is also significant which is different from the other years.

2:Current direction frequency distribution

Description year N NNE NE ENE E ESE SE SSE S SSW SW WSW W WNW NW NNW
Current
distribution[%]
2015 5.7 5.3 4.0 3.5 3.0 3.3 4.7 9.4 21.4 14.4 7.5 4.7 2.9 2.7 3.1 4.4
2016 4.4 5.8 6.8 6.0 4.9 4.9 5.9 7.1 9.7 11.0 10.2 7.5 5.3 3.9 3.4 3.1
2017 4.8 7.2 6.3 5.8 4.2 4.3 4.8 5.9 9.1 10.8 11.1 8.3 5.3 4.1 3.6 4.3

Current direction frequency distribution

Commentary

The Southbound current is dominant in 2015, while current direction in 2016 and 2017 are slightly spreaded.

3:Mean current speed profile

Comment

The mean current speed profile between 6.5 m and 11 m below the sea level shows little difference. The mean current speed between 6.5 m and 11 m below the sea level in 2015 is between 0.17 m/s and 0.18 m/s and those in 2016 and 2017 are between 0.15 m/s and 0.16 m/s, and the current speed in 2015 tends to be higher than those in other years.

4:Monthly mean current speed and data availability

Description Observation
water depth
Year Jan. Feb. Mar. Apr. May. Jun. Jul. Aug. Sept. Oct. Nov. Dec. Annual mean
current speed
Current speed(m/s) 11.0m 2015 0.11 0.09   0.14 0.17 0.20 0.15 0.31 0.31 0.26 0.14 0.09 0.18
2016 0.13 0.12           0.19 0.16 0.15 0.16 0.21 0.16
2017 0.18 0.16 0.15 0.13 0.13 0.14 0.14 0.15 0.19 0.18 0.17 0.14 0.15
Data availability(%) 2015 83.1 70.2 0.0 48.6 100.0 95.6 100.0 100.0 100.0 100.0 99.3 100.0 83.1
2016 100.0 61.2 5.0 11.4 0.0 0.0 0.0 92.2 100.0 100.0 100.0 98.8 55.7
2017 100.0 90.3 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 90.0 100.0 98.4

Monthly mean current speed (-11m) and data availability

Comment

The current speed from August to October 2015 is about twice higher than in 2016, and the current speed in December 2016 is about twice higher than that in December 2015. In August 2015 the Kuroshio current going up north was suppressed and the Southbound current is dominant. However in December 2016 the Kuroshio current going up north was not suppressed and the North-Eastbound current off the coast of Fukushima is dominant.

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Fukushima Offshore Wind Consortium

  • Marubeni Corporation
  • The University of Tokyo
  • Mitsubishi Heavy industries, Ltd.
  • Japan Marine United Corporation
  • Mitsui Engineering & Shipbuilding Co., Ltd.
  • Nippon Steel & Sumitomo Metal
  • Hitachi Ltd.
  • Furukawa Electric Co., Ltd.
  • Shimizu Corporation
  • Mizuho Information & Research institute, Inc