HomeMy WebLinkAboutKivalina Wind-Intertie Project Wind Resource Report - May 2012 - REF Grant 7030016Draft Kivalina Wind Resource Report
Kivalina aerial photo by Doug Vaught, July 2011
May 31, 2012
Douglas Vaught, P.E.
dvaught@v3energy.com
V3 Energy, LLC
Eagle River, Alaska
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Purpose
This draft Kivalina wind resource report is a component of a larger feasibility study to install wind
turbines in either Kivalina or at the Red Dog Port facility located 27 km (17 miles) to the southeast. The
feasibility study includes an analysis of a potential electrical intertie connecting Kivalina to Red Dog Port.
A final version of this wind resource report will include a comparison of wind data being collected at Red
Dog Port.
Summary
The wind resource measured at the Kivalina met tower site is good with measured wind power class 4
(good) if considering power density and wind power class 3 (fair) if considering only mean wind speed.
Given the cold temperatures in Kivalina, higher wind density results in a higher power density than at
standard temperature and pressure. In other respects, Kivalina wind characteristics are ideal with
exceptionally low turbulence and low wind shear. Kivalina experiences very cold winter temperatures,
which will increase energy production of both variable pitch and stall-regulated wind turbines, but the
low elevation of the site keeps it free of problematic rime icing problems that have been noted
elsewhere in northern Alaska.
The Kivalina wind resource study was funded by the Alaska Energy Authority and managed by WHPacific
for the Alaska Village Electric Cooperative (AVEC). WHPacific contracted V3 Energy, LLC to write this
wind resource report. AVEC and WHPacific points of contact are Brent Petrie (bpetrie@avec.org) and
Katherine Keith (kkeith@whpacific.com).
Met tower data synopsis
Data dates May 9, 2011 to May 18, 2012 (12.3 months);status:
operational
Wind power class Class 3 to Class 4
Wind power density mean, 30 m 325 W/m2
Wind speed mean, 30 m 5.87 m/s
Max. 10-min wind speed average 26.7 m/s
Maximum 2-sec. wind gust 33.6 m/s (November, 2011)
Weibull distribution parameters k = 1.66, c = 6.56 m/s
Wind shear power law exponent 0.194 (moderate)(see report for notes)
Roughness class 2.11 (few trees)(see report for notes)
IEC 61400-1, 3rd ed. classification Class III-C
Turbulence intensity, mean 0.075 (at 15 m/s)
Calm wind frequency (at 33 m)34% (<4 m/s)
Test Site Location
Wind measurement instrumentation was installed on a six-inch diameter 30 meter NRG tubular Tall
Tower (met tower) approximately three kilometers (two miles) east of the village of Kivalina and
approximately 1.5 km (1 mile) from the Chukchi Sea coast. The tower is located on open tundra in the
general vicinity of the possible location of the new Kivalina should the village be relocated due to
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continuing erosion and flooding risk at the existing village location on a coastal barrier island. The met
tower was installed on May 6, 2011 by Echelon Energy of San Jose, California.
Site information
Site number 9750
Latitude/longitude N 67° 43’29.64”W 164° 26’25.38”, NAD 83
Site elevation 3 meters (10 ft)
Datalogger type NRG Symphonie, 10 minute time step
Tower type NRG Tall Tower, 30 meters, six-inch diameter
Topographic map
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Google Earth image
Tower sensor information
Channel Sensor type Height Multiplier Offset Orientation
1 NRG #40 anemometer 30 m A 0.765 0.35 north
2 NRG #40 anemometer 30 m B 0.765 0.35 south
3 NRG #40 anemometer 20 m 0.765 0.35 north
7 NRG #200P wind vane 29 m 0.351 351 351° T
9 NRG #110S Temp C 3 m 0.138 -86.3 north
Tower sensors photo (view to the southwest)
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Data Quality Control
Data quality is generally very good for the 30 meter level anemometers, excellent for the wind vane and
temperature sensor, and very poor for the 20 meter level anemometer. An installation error with the 20
meter anemometer resulted in it being located directly in line with the north-facing third-level guy wire,
resulting in low quality data return due to fouling of the sensor in the wire. A data filter was used to
remove 20 meter anemometer data significantly different from 30 meter A anemometer data, but that
is not a precise tool and it is not possible to know definitively when the 20 m anemometer is fouled.
Recovered 20 m level anemometer data is not usable by itself for wind speed or other data, but is
usable, with qualification, for wind shear calculation.
Data loss due to icing conditions was very infrequent in Kivalina compared to coastal sites in western
Alaska. This may be due to the extremely cold winter of 2011/2012, extensive sea ice and resulting low
moisture content in the air. Icing conditions are characterized by non-variant output of the
anemometer at the minimum offset value (0.4 m/s) with temperatures less than 1 degree Centigrade
and for the wind vane by non-variant output at the last operable direction and temperature also less
than 1 degree Centigrade.
In addition to icing, 30 meter level anemometer data was filtered for tower shadow using an algorithm
that identifies wind opposite the anemometer (with reference to the met tower) and filters that data.
With frequent northerly winds, the south-facing 30 m B anemometer was filtered more frequently than
the north-facing 30 m A anemometer.
Data recovery summary table
Possible Valid Recovery
Sensor Units Height Records Records Rate (%)
Speed 30 m A m/s 30 m 54,018 51,676 95.7
Speed 30 m B m/s 30 m 54,018 47,240 87.5
Speed 20 m m/s 20 m 54,018 15,965 29.6
Direction 29 m ° 29 m 54,018 53,408 98.9
Temperature °C 54,018 53,868 99.7
Anemometer and wind vane data recovery
30 m A 30 m B 20 m Vane Temp
Year Month Recovery Recovery Recovery Recovery Recovery
Rate (%) Rate (%) Rate (%) Rate (%) Rate (%)
2011 May 88.6 92.2 43.7 95.5 100.0
2011 Jun 93.9 88.5 9.7 100.0 100.0
2011 Jul 93.7 95.5 5.7 100.0 100.0
2011 Aug 94.5 96.2 15.3 100.0 100.0
2011 Sep 96.2 81.4 25.8 100.0 100.0
2011 Oct 99.3 90.5 25.0 98.3 100.0
2011 Nov 99.4 85.5 18.5 100.0 100.0
2011 Dec 90.8 80.5 57.2 91.4 96.8
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30 m A 30 m B 20 m Vane Temp
Year Month Recovery Recovery Recovery Recovery Recovery
Rate (%) Rate (%) Rate (%) Rate (%) Rate (%)
2012 Jan 98.0 87.2 54.7 100.0 100.0
2012 Feb 97.8 84.3 44.0 100.0 100.0
2012 Mar 99.3 74.8 27.0 100.0 100.0
2012 Apr 94.7 93.0 26.0 100.0 100.0
2012 May 96.0 89.1 39.8 99.8 99.8
All Data 95.7 87.5 29.6 98.9 99.7
Data flag statistics
Anemometer
Possible
Records Icing %
Low
quality %
Tower
shading %
Speed 30 m A 54,018 0.4% 0.0% 3.6%
Speed 30 m B 54,018 0.4% 0.0% 11.4%
Speed 20 m 54,018 24.4% 68.6% 0.0%
Note: low quality and icing flags of 20 m anemometer often overlap.
Fouled 20 meter anemometer
Wind Speed
Anemometer data obtained from the met tower, from the perspectives of both mean wind speed and
mean wind power density, indicate an excellent wind resource. Mean wind speeds are greater at higher
elevations on the met tower, as one would expect. Note that cold temperatures contributed to a higher
wind power density than otherwise might have been expected for the mean wind speeds. Also note, as
discussed in the previous section, that anemometer summary information is the table below is post gap-
fill. None gap-filled mean wind speeds and power densities are slightly higher than below.
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Anemometer data summary
Variable
Speed 30 m
A
Speed 30 m
B
Measurement height (m) 30 30
Mean wind speed (m/s) 5.87 5.52
Median wind speed (m/s) 5.20 5.00
Max 10-min avg wind speed (m/s) 26.7 26.7
Max gust wind speed (m/s) 33.2 33.6
Weibull k 1.66 1.62
Weibull c (m/s) 6.56 6.15
Mean power density (W/m²) 325 274
Mean energy content (kWh/m²/yr) 2,845 2,398
Energy pattern factor 2.41 2.47
Frequency of calms (%) 34.4 37.3
Time Series
Time series calculations indicate high mean wind speeds during the winter months with more moderate
mean wind speeds during summer months. This correlates well with the a typical village load profile
where winter months have a high electric and heat demand and summer months a lesser demand. The
opposite load profile exists however at Red Dog Port where summer loads are high and winter low.
30 m A anemometer data summary
Mean
Max 10-
min
Max
Gust
Std.
Dev.
Weibull
k
Weibull
c
Year Month (m/s) (m/s) (m/s) (m/s) (-) (m/s)
2011 May 5.58 14.0 17.2 2.83 2.04 6.29
2011 Jun 5.09 14.9 18.3 2.70 1.95 5.73
2011 Jul 4.71 13.8 17.9 2.53 1.92 5.29
2011 Aug 4.98 12.5 15.6 2.35 2.19 5.60
2011 Sep 6.45 17.8 22.9 3.14 2.15 7.28
2011 Oct 5.69 18.5 22.9 3.08 1.92 6.42
2011 Nov 6.88 26.7 33.2 4.08 3.55 10.12
2011 Dec 8.51 21.2 25.6 4.19 2.14 9.60
2012 Jan 4.81 24.7 27.1 4.24 1.17 5.08
2012 Feb 7.17 21.2 24.8 4.43 1.64 8.00
2012 Mar 5.94 16.7 19.5 3.47 1.71 6.63
2012 Apr 4.94 17.6 22.9 3.87 1.21 5.24
2012 May 5.41 13.5 16.1 2.60 2.19 6.10
All Data 5.87 26.7 33.2 3.63 1.66 6.56
Mean of monthly means 5.88
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Wind speed time series graph
Wind Speed Distribution
The probability distribution function (PDF), or histogram, of Kivalina wind speed data indicates a shape
curve somewhat dominated by lower wind speeds, as opposed to a “normal” shape curve, known as the
Rayleigh distribution (Weibull k = 2.0), which is defined as the standard wind distribution for wind power
analysis. As one can see in the PDF of 30 meter A anemometer, the most frequently occurring wind
speeds are between 4 and 6 m/s with very few wind events exceeding 25 m/s (the cutout speed of most
wind turbines; see following wind speed statistical table).
Wind speed distribution of 30 m A anemometer
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Weibull k shape curve table
Weibull comparison table
Algorithm
Weibull Weibull Proportion Power R
k c Mean Above Density Squared
(-) (m/s) (m/s) 5.872 m/s (W/m2) (-)
Maximum likelihood 1.660 6.560 5.864 0.435 291.8 0.977
Least squares 1.704 6.586 5.875 0.439 283.8 0.980
WAsP 1.603 6.496 5.823 0.427 299.2 0.970
Actual data (51,676 time steps)5.872 0.427 299.2
Occurrence by wind speed bin
Bin Endpoints
(m/s) Occurrences
Bin Endpoints
(m/s) Occurrences
Lower Upper No. Percent Lower Upper No. Percent
0 1 2,224 4.5% 14 15 604 1.2%
1 2 3,420 6.9% 15 16 443 0.9%
2 3 5,226 10.5% 16 17 287 0.6%
3 4 6,219 12.5% 17 18 180 0.4%
4 5 6,821 13.7% 18 19 122 0.2%
5 6 6,261 12.6% 19 20 78 0.2%
6 7 5,213 10.5% 20 21 37 0.1%
7 8 4,327 8.7% 21 22 18 0.0%
8 9 3,236 6.5% 22 23 13 0.0%
9 10 2,271 4.6% 23 24 17 0.0%
10 11 1,610 3.2% 24 25 22 0.0%
11 12 1,270 2.5% 25 26 25 0.1%
12 13 962 1.9% 26 27 13 0.0%
13 14 757 1.5% all 49,817 100.0%
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Wind Shear and Roughness
A wind shear power law exponent () of 0.194 indicates moderate wind shear at the site. Related to
wind shear, a calculated surface roughness of 0.114 meters (indicating the height above ground level
where wind velocity would be zero) indicates moderately rough terrain (roughness description: few
trees) surrounding the met tower. This data is comprised however by very poor data recovery from the
20 meter level anemometer, which was installed such that it was often fouled in the third level north-
facing guy wire. The power law exponent is calculated only with time step data with valid anemometer
data from the selected sensors (the 30 m A anemometer and the 20 meter anemometer); in this case
only 28 percent of the time steps qualified. This is a statistically sufficient amount of data except that
filtering of the 20 meter data to remove the time steps where the anemometer was fouled is not precise
and some data that should have been filtered was undoubtedly retained. Although the power law
exponent and roughness length are generally reasonable, one might expect both values to be lower
considering the flat, featureless terrain surrounding the met tower.
Vertical wind shear profile
Comparative wind shear profiles
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Extreme Winds
A modified Gumbel distribution analysis, based on monthly maximum winds vice annual maximum
winds, was used to predict extreme winds at the Kivalina met tower site. Industry standard reference of
extreme wind is the 50 year probable (50 year return period) ten-minute average wind speed, referred
to as Vref. For Kivalina, this calculates to 35.8 m/s (at 30 meters), which qualifies as a International
Electrotechnical Commission (IEC) 61400-1, 3rd edition criteria Class III site, the lowest defined. All wind
turbines are designed for IEC 61400-1 Class III conditions.
Extreme wind probability table, 30 m A data
Vref Gust IEC 61400-1, 3rd ed.
Period (years) (m/s) (m/s) Class Vref, m/s
3 26.8 32.8 I 50.0
10 30.7 37.5 II 42.5
20 32.9 40.2 III 37.5
30 34.2 41.8 S designer-
specified5035.8 43.8
100 38.0 46.5
average gust
factor:1.22
Extreme wind graph
Temperature and Density
Kivalina experiences cool summers and very cold winters with resulting higher than standard air density.
Calculated annual mean air density during the met tower test period exceeds the 1.225 kg/m
3 standard
air density for a 3 meter elevation by 7.8 percent. This is advantageous in wind power operations as
wind turbines produce more power at low temperatures (high air density) than at standard temperature
and density.
25.0
30.0
35.0
40.0
45.0
50.0
55.0
0 10 20 30 40 50 60 70 80 90 100
Period, years
Vref
gust
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Temperature and density table
Temperature Density
Month Mean Min Max Mean Min Max
(°C) (°C) (°C) (kg/m³) (kg/m³) (kg/m³)
Jan -30.7 -44.5 -8.9 1.456 1.335 1.543
Feb -15.9 -48.7 2.7 1.374 1.279 1.572
Mar -20.2 -34.5 -7.4 1.395 1.327 1.478
Apr -7.9 -28.4 10.6 1.331 1.243 1.441
May 1.8 -15.4 25.0 1.284 1.183 1.369
Jun 12.2 0.7 28.1 1.237 1.171 1.288
Jul 12.9 2.6 28.9 1.234 1.168 1.279
Aug 11.3 0.4 23.5 1.240 1.189 1.290
Sep 6.8 -5.1 19.3 1.260 1.206 1.316
Oct -3.5 -17.6 8.7 1.308 1.252 1.380
Nov -16.5 -31.5 1.8 1.376 1.283 1.460
Dec -15.5 -35.0 0.5 1.367 1.224 1.481
Annual -5.2 -48.7 28.9 1.321 1.168 1.572
Annual temperature boxplot
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Air density DMap
Wind Speed Scatterplot
The wind speed versus temperature scatterplot below indicates that a substantial percentage of wind in
Kivalina coincides with cold temperatures, as one would expect. During the met tower test period,
temperatures fell below -40°C, the minimum operating temperature for arctic-capable wind turbines, on
a number of occasions. Wind speeds during periods of extreme cold are generally low, however, and
loss of wind turbine availability during these times would not be significant. Also note that periods of
high winds (wind speeds greater than 20 m/s) are characterized by cold temperatures, between 0°C and
-25°C.
Wind speed/temperature
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Wind Direction
Wind frequency rose data indicates that winds at Red Dog Port are relatively directional, with north-
northeasterly and east-northeasterly predominating. The mean value rose indicates that infrequent
southeasterly winds, when they do occur, are of high energy and hence likely storm winds. The wind
energy rose indicates that winds for wind turbine operations power-producing are northerly and
southeasterly dominant. Calm frequency (percent of time that winds at the 30 meter level are less than
4 m/s) was 34 percent during the met tower test period.
Wind frequency rose Mean value rose (30 m A anem.)
Wind energy rose (30 m A anem.) Scatterplot rose of 30m A wind power density
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Turbulence
Turbulence intensity (TI) at the Kivalina met tower site is well within acceptable standards with an IEC
61400-1, 3rd edition (2005) classification of turbulence category C, which is the lowest defined. The
mean TI at 15 m/s is 0.075 and the representative TI at 15 m/s is 0.105 (30 m A anemometer), both
which can be considered very low and hence very desirable for wind turbine operations.
Turbulence intensity, 30 m A anemometer, all direction sectors
Turbulence table, 30 m A data
Bin Endpoints
Records
Standard
Representative
TI
Lower Upper Mean Deviation Peak
(m/s) (m/s) in Bin TI of TI TI
0.5 1.5 2,744 0.363 0.155 0.561 1.091
1.5 2.5 4,280 0.180 0.090 0.295 0.800
2.5 3.5 5,847 0.126 0.064 0.209 0.815
3.5 4.5 6,725 0.100 0.049 0.163 0.771
4.5 5.5 6,568 0.086 0.041 0.138 0.633
5.5 6.5 5,732 0.081 0.038 0.130 0.468
6.5 7.5 4,858 0.076 0.032 0.117 0.299
7.5 8.5 3,763 0.076 0.032 0.117 0.364
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Bin Endpoints
Records
Standard
Representative
TI
Lower Upper Mean Deviation Peak
(m/s) (m/s) in Bin TI of TI TI
8.5 9.5 2,704 0.076 0.029 0.114 0.299
9.5 10.5 1,883 0.077 0.028 0.113 0.269
10.5 11.5 1,398 0.078 0.028 0.114 0.252
11.5 12.5 1,155 0.078 0.027 0.112 0.265
12.5 13.5 808 0.074 0.023 0.104 0.167
13.5 14.5 662 0.076 0.023 0.105 0.174
14.5 15.5 545 0.075 0.023 0.105 0.166
15.5 16.5 347 0.076 0.023 0.105 0.167
16.5 17.5 241 0.074 0.019 0.099 0.145
17.5 18.5 151 0.073 0.016 0.094 0.120
18.5 19.5 98 0.068 0.013 0.084 0.115
19.5 20.5 58 0.069 0.012 0.085 0.100
20.5 21.5 24 0.072 0.014 0.089 0.103
21.5 22.5 16 0.078 0.015 0.097 0.103
22.5 23.5 12 0.080 0.024 0.111 0.104
23.5 24.5 17 0.090 0.016 0.110 0.120
24.5 25.5 28 0.087 0.015 0.106 0.108
25.5 26.5 20 0.090 0.006 0.097 0.104
26.5 27.5 4 0.086 0.003 0.091 0.091