HomeMy WebLinkAboutKoliganek Wind Resource Report - Apr 2012 - REF Grant 7040011Koliganek, Alaska Wind Resource Report,
revision 1
Hannah Willard photo (2006)
April 30, 2012
Douglas Vaught, P.E.
V3 Energy, LLC
Eagle River, Alaska
Koliganek, Alaska Wind Resource Report, rev. 1 Page | 2
Summary
The wind resource in Koliganek is good with measured wind power class 4 by measurement of wind
power density and class 3 by measurement of wind speed. Given the cool temperatures of Koliganek,
air density is higher than standard conditions,
leading to relatively high wind power densities.
By other measures important for wind power
analysis, the site has a low extreme wind
probability and experiences relatively low
turbulence at the 30 meter level.
One advantage for wind power development in
Koliganek is the availability of the former and
now abandoned airstrip where the
meteorological test tower had been located.
Because the village and surrounding area is
comprised of permafrost soils, construction of wind turbines on the old airstrip could significantly
reduce foundation construction costs.
This revised wind resource report is an update of the original version written in 2007. Additional data
filtering was accomplished, specifically for tower shading and icing conditions. Also, an analysis of
extreme wind probability was added.
Met tower data synopsis
Data dates July 8, 2005 to July 13, 2006
Wind power class Class 4 (good), based on wind power density; Class 3 (fair),
based on wind speed (measured at 30 meters)
Wind power density mean, 30 m 337 W/m
2
Wind speed mean, 30 m 5.82 m/s
Max. 10-min wind speed 27.5 m/s
Maximum 2-sec. wind gust 35.9 m/s; December, 2005
Weibull distribution parameters k = 1.58, c = 6.49 m/s
Wind shear power law exponent 0.276 (very high)
Roughness class 3.16 (description: forest)
IEC 61400-1, 3rd ed. classification Class III-C (at 30 and 20 meters)
Turbulence intensity, mean 0.099 (at 15 m/s)
Calm wind frequency 36% (winds < 4 m/s)
Test Site Location
A 30 meter NRG Systems, Inc. tubular-type meteorological (met) tower was installed on the south end of
the old and now abandoned cross-wind runway in Koliganek. The old runway is on the immediate
southern edge of the village and the met tower site easily accessible by automobile, ATV, snowmachine
Koliganek, Alaska Wind Resource Report, rev. 1 Page | 3
or foot. In 2011 a 61 meter (200 ft) high cellular telephone communications tower owned by GCI was
erected at the site of the met tower placement.
Lake and Peninsular Borough, with their contractor Marsh Creek LLC, has begun feasibility studies and
planning for a wind turbine project in Koliganek. With consideration to the location of the GCI
communications tower, it is anticipated that wind turbines will be located on the runway opposite the
GCI tower and on the alternate runway near its southwest end (see Dept. of Community and Regional
Affairs DCRA photo below).
Site information
Site number 3296
Site Description On south end of crosswind runway of old airport
Latitude/longitude N 59° 43.384’ W 157° 17.056’
Site elevation 95 meters
Datalogger type NRG Symphonie
Tower type NRG 30-meter tall tower, 152 mm (6 in) diameter
Tower sensor information
Site number 3296
Site Description On south end of crosswind runway of previous airport
Latitude/longitude N 59° 43.384’ W 157° 17.056’
Site elevation 95 meters
Datalogger type NRG Symphonie
Tower type NRG 30-meter tall tower, 152 mm (6 in) diameter
DCRA area map of Koliganek and old airport
Met tower location;
GCI tower now on
this site.
Anticipated locations
of wind turbines
Koliganek, Alaska Wind Resource Report, rev. 1 Page | 4
Topographic map of Koliganek and region
Data Quality Control
Data quality was very good with relatively minimal data loss except for an icing event in November
(discussed below). Data was automatically filtered with three methods and summarized in the sensor
data recovery table. The filter criteria were:
x Anemometer icing – data filtered if temperature < 1°C, speed SD = 0, and speed changes < 0.25
m/s for minimum 2 hours
x Vane icing – data filtered if temperature < 1°C and vane SD = 0 for minimum of 2 hours
x Tower shading of 30m A and 30m B paired sensors – refer to graphic below
Koliganek
Koliganek, Alaska Wind Resource Report, rev. 1 Page | 5
Sensor data recovery table
30m (A) anemometer 30m (B) anemometer 20m anemometer
Year Month Records Recovery Records Recovery Records Recovery
Rate (%) Rate (%) Rate (%)
2005 Jul 3,007 87.0 3,215 93.0 3,353 97.0
2005 Aug 3,948 88.4 4,212 94.4 4,464 100.0
2005 Sep 3,707 85.8 4,172 96.6 4,320 100.0
2005 Oct 4,064 91.0 3,346 75.0 4,278 95.8
2005 Nov 2,404 55.7 1,344 31.1 2,875 66.6
2005 Dec 4,158 93.2 3,557 79.7 3,960 88.7
2006 Jan 4,458 99.9 3,105 69.6 4,464 100.0
2006 Feb 3,762 93.3 3,666 90.9 4,032 100.0
2006 Mar 4,262 95.5 3,783 84.7 4,464 100.0
2006 Apr 4,070 94.2 3,947 91.4 4,320 100.0
2006 May 3,931 88.1 4,146 92.9 4,464 100.0
2006 Jun 3,746 86.7 3,933 91.0 4,320 100.0
2006 Jul 1,416 78.2 1,676 92.5 1,812 100.0
All data 46,933 88.0 44,102 82.6 51,126 95.8
Wind direction Temperature
Records Recovery Records Recovery
Rate (%) Rate (%)
2005 Jul 3,354 97.1 3,456 100.0
2005 Aug 4,464 100.0 4,464 100.0
2005 Sep 4,306 99.7 4,320 100.0
2005 Oct 4,277 95.8 4,464 100.0
2005 Nov 2,411 55.8 4,320 100.0
2005 Dec 3,285 73.6 4,464 100.0
2006 Jan 4,239 95.0 4,464 100.0
2006 Feb 3,807 94.4 4,032 100.0
2006 Mar 4,362 97.7 4,464 100.0
2006 Apr 4,266 98.8 4,320 100.0
2006 May 4,438 99.4 4,464 100.0
2006 Jun 4,320 100.0 4,320 100.0
2006 Jul 1,812 100.0 1,812 100.0
All data 49,341 92.5 53,364 100.0
Data loss due to icing
30 m A 30 m B 20 m
Year Month
Unflagged
data
Icing
records
Percent
icing
Icing
records
Percent
icing
Icing
records
Percent
icing
2005 Jul 3,007 0 0.0% 0 0.0% 0 0.0%
2005 Aug 3,948 0 0.0% 0 0.0% 0 0.0%
2005 Sep 3,707 0 0.0% 0 0.0% 0 0.0%
2005 Oct 4,064 101 2.3% 70 1.6% 186 4.2%
2005 Nov 2,404 1,892 43.8% 1,897 43.9% 1,445 33.4%
2005 Dec 4,158 32 0.7% 442 9.9% 504 11.3%
2006 Jan 4,458 0 0.0% 0 0.0% 0 0.0%
2006 Feb 3,762 0 0.0% 182 4.5% 0 0.0%
2006 Mar 4,262 0 0.0% 0 0.0% 0 0.0%
2006 Apr 4,070 0 0.0% 0 0.0% 0 0.0%
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2006 May 3,931 0 0.0% 0 0.0% 0 0.0%
2006 Jun 3,746 0 0.0% 0 0.0% 0 0.0%
2006 Jul 1,416 0 0.0% 0 0.0% 0 0.0%
All data 46,933 2,128 4.0% 2,694 5.0% 2,238 4.2%
30m A and 30m B tower shading filter plot
Documentation of Icing
Rime icing is more problematic for wind turbine operations than freezing rain (clear ice) given its
tenacity and longevity in certain climatic conditions, but at an elevation of only 95 meters, Koliganek is
below the zone of rime icing risk. Data collected from the Koliganek met tower does indicate, however,
the presence of more typical freezing rain, sleet and similar-type icing conditions, particularly one severe
icing event in late November that rendered the anemometers inoperative for approximately two weeks.
This is not unusual in Alaska and is indicative of typical maritime-influenced cool climate conditions.
Active anti-icing and de-icing measures on wind turbines are probably not necessary in Koliganek,
although black-colored rotor blades with an anti-ice coating may be desirable.
Koliganek Icing Event, November 2005
Koliganek, Alaska Wind Resource Report, rev. 1 Page | 7
Wind Speed
Anemometer data obtained from the met tower, from the perspectives of both mean wind speed and
mean wind power density, indicate a very good wind resource, especially for a non-coastal site. Note
that cold temperatures contributed to a higher wind power density than standard conditions would
yield for the measured mean wind speeds.
Anemometer data summary
Variable
Speed 30 m
A
Speed 30 m
B Speed 20 m
Measurement height (m) 30 30 20
Mean wind speed (m/s) 5.82 5.76 5.17
Median wind speed (m/s) 5.00 5.00 4.40
Max wind speed (m/s) 27.7 27.5 26.4
Max gust wind speed (m/s) 35.5 35.9 34.8
Weibull k 1.58 1.50 1.48
Weibull c (m/s) 6.49 6.38 5.72
Mean power density (W/m²) 337 342 261
Mean energy content (kWh/m²/yr) 2,956 2,997 2,282
Energy pattern factor 2.70 2.83 2.97
Frequency of calms (%) 36.9 38.0 44.6
Time Series
Time series calculations indicate higher wind speeds during the winter months with more moderate
wind speeds during summer months. This is typical of other wind power sites in Alaska and correlates
well with the a typical village load profile where winter months have a high electric load and heat
demand and summer months have a much lower demand for electricity and heat. The daily wind
profiles indicate higher wind speeds during afternoon hours when electric and thermal loads are
highest.
30 m A anemometer data summary table
Mean
Max 10-
min avg
Gust
(2 sec) Std. Dev.
Weibull
k Weibull c
Month (m/s) (m/s) (m/s) (m/s) (m/s)
Jan 4.58 13.0 18.7 2.31 2.09 5.17
Feb 8.76 25.8 32.1 5.48 1.60 9.74
Mar 6.28 20.6 27.1 4.28 1.50 6.96
Apr 5.89 20.4 24.8 3.32 1.84 6.62
May 6.19 16.2 20.2 2.86 2.29 6.98
Jun 6.37 25.0 32.4 4.17 1.59 7.11
Jul 4.88 20.8 25.6 3.19 1.59 5.44
Aug 4.58 16.3 22.1 2.85 1.59 5.08
Sep 5.74 18.0 25.2 3.21 1.84 6.45
Oct 5.01 21.2 27.1 3.47 1.48 5.52
Nov 5.93 15.0 18.3 2.88 2.06 6.63
Dec 6.12 27.7 35.5 4.73 1.42 6.77
Annual 5.82 27.7 35.5 3.83 1.58 6.49
Koliganek, Alaska Wind Resource Report, rev. 1 Page | 8
Wind speed time series
Daily wind profiles (annual)
Probability Distribution Function
The probability distribution function (PDF), or histogram, of wind speed measured by the Koliganek met
tower indicates a shape curve dominated by lower wind speeds with a Weibull k shape factor value of
1.59. This compares 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 observed in the PDF of
the 30 m anemometer, the most frequently occurring wind speeds are between 3 and 5 m/s with a few
wind events exceeding 25 m/s (the cutout speed of most wind turbines; see following wind speed
statistical table).
Koliganek, Alaska Wind Resource Report, rev. 1 Page | 9
PDF of 30m anemometer
Weibull k shape curve table
Weibull values table, 30 m A anemometer
Weibull Mean Proportion Power R
Weibull c Above Density Squared
Algorithm k (m/s) (m/s) 5.823 m/s (W/m2)
Maximum
likelihood 1.581 6.491 5.827 0.431 305.3 0.9639
Least squares 1.696 6.477 5.780 0.434 271.9 0.9732
WAsP 1.424 6.223 5.657 0.403 326.5 0.9245
Actual data 5.823 0.403 326.5
Koliganek, Alaska Wind Resource Report, rev. 1 Page | 10
Occurrence by wind speed bin (30 m anemometer)
Bin Endpoints
(m/s) Occurrences
Bin Endpoints
(m/s) Occurrences
Lower Upper No. Percent Cumul. Lower Upper No. Percent Cumul.
0 1 1,914 4.08 4.08 15 16 430 0.92 97.30
1 2 3,250 6.92 11.00 16 17 350 0.75 98.04
2 3 5,224 11.13 22.13 17 18 294 0.63 98.67
3 4 6,273 13.37 35.50 18 19 222 0.47 99.14
4 5 6,384 13.60 49.10 19 20 130 0.28 99.42
5 6 5,447 11.61 60.71 20 21 76 0.16 99.58
6 7 4,498 9.58 70.29 21 22 56 0.12 99.70
7 8 3,557 7.58 77.87 22 23 34 0.07 99.77
8 9 2,643 5.63 83.50 23 24 28 0.06 99.83
9 10 1,934 4.12 87.62 24 25 28 0.06 99.89
10 11 1,362 2.90 90.52 25 26 33 0.07 99.96
11 12 1,107 2.36 92.88 26 27 14 0.03 99.99
12 13 727 1.55 94.43 27 28 3 0.01 100.00
13 14 463 0.99 95.42 28 29 0 0.00 100.00
14 15 452 0.96 96.38
Wind Shear and Roughness
A wind shear power law exponent (ɲ) of 0.276 indicates high wind shear at the site. Related to wind
shear, a calculated surface roughness of 0.403 meters (indicating the height above ground level where
wind velocity would be zero) indicates rough terrain (roughness description: forest) surrounding the met
tower. In the power law exponent wind rose graphic, note the wind shear coefficient variability by wind
direction.
These calculations of power law exponent are unexpected in that the terrain surrounding the Koliganek
met tower is for the most part open tundra and hence should result in smooth air flow. The 20 meter
anemometer appeared to function normally throughout the measurement period and turbulence
intensity of the 20 meter anemometer is similar to that calculated with the 30 meter anemometers, so it
not obvious that the lower anemometer was compromised in any manner. Given the odd nature of a
calculated high shear exponent in relatively flat, open terrain, it would be prudent to be conservative if
extrapolating wind speed data to heights greater than 30 meters and use a lower exponent value more
typical of tundra terrain.
Koliganek, Alaska Wind Resource Report, rev. 1 Page | 11
Vertical wind shear profile
Power law exponent rose
Extreme Winds
A modified Gumbel distribution analysis, based on monthly maximum winds vice annual maximum
winds, was used to predict extreme winds at the Koliganek met tower site. Thirteen months of data
though are minimal at best and hence results should be viewed with caution. Nevertheless, with data
available the predicted Vref (maximum ten-minute average wind speed) in a 50 year return period (in
other words, predicted to occur once every 50 years) is 36.0 m/s. This result classifies the site as Class III
by International Electrotechnical Commission 61400-1, 3
rd edition (IEC3) criteria. IEC extreme wind
Koliganek, Alaska Wind Resource Report, rev. 1 Page | 12
probability classification is one criteria – with turbulence the other – that describes a site with respect to
suitability for particular wind turbine models. Note that the IEC3 Class III extreme wind classification,
which appears to apply to the Koliganek met tower site, is the lowest and most common classification.
All wind turbines are designed to operate in IEC3 Class III sites.
Site extreme wind probability table, 30 m data
Vref Gust IEC 61400-1, 3rd ed.
Period (years) (m/s) (m/s) Class Vref, m/s
3 27.6 35.7 I 50.0
10 31.2 40.4 II 42.5
20 33.3 43.1 III 37.5
30 34.5 44.7 S designer-
specified5036.0 46.6
100 38.1 49.3
average gust
factor: 1.30
Extreme wind graph, by return period
Temperature and Density
Over the reporting period, Koliganek had an average temperature of 1.3° C. The minimum recorded
temperature during the measurement period was -40.4° C and the maximum temperature was 30.5° C,
indicating a wide variability of the ambient temperature operating environment important to wind
turbine operations. Consequent to Koliganek’s cool temperatures, the average air density of 1.274
kg/m3 is 4.9% higher than the standard air density of 1.214 kg/m
3 (at 14.39° C temperature and 101.17
kPa pressure at 95 m elevation), indicating that Koliganek, due to its cool average annual temperature,
has denser air than standard. This is relevant as wind turbine power curves are generally published with
standard temperature and pressure conditions.
25.0
30.0
35.0
40.0
45.0
50.0
55.0
0 102030405060708090100Wind Speed, m/sPeriod, years
Koliganek Extreme Winds
10-min max
gust
Koliganek, Alaska Wind Resource Report, rev. 1 Page | 13
Temperature and density table
Temperature Density
Year Month Mean Min Max Mean Min Max
(°C) (°C) (°C) (kg/m³) (kg/m³) (kg/m³)
2005 Jul 15.8 7.6 29.0 1.208 1.155 1.243
2005 Aug 14.8 3.1 29.3 1.212 1.154 1.263
2005 Sep 9.7 -1.8 18.2 1.234 1.198 1.286
2005 Oct 1.4 -11.0 12.5 1.271 1.222 1.331
2005 Nov -13.9 -32.2 0.8 1.347 1.274 1.448
2005 Dec -4.1 -28.8 5.9 1.298 1.251 1.428
2006 Jan -18.0 -37.0 -1.7 1.369 1.286 1.478
2006 Feb -5.4 -40.4 3.8 1.305 1.260 1.499
2006 Mar -7.5 -22.6 3.8 1.314 1.260 1.393
2006 Apr -1.1 -15.7 9.3 1.283 1.235 1.355
2006 May 8.2 -5.8 27.3 1.241 1.161 1.305
2006 Jun 12.2 -0.2 24.4 1.223 1.173 1.278
2006 Jul 16.3 5.6 30.5 1.206 1.149 1.252
All data 1.3 -40.4 30.5 1.274 1.149 1.499
Temperature annual boxplot graph
Wind Speed Scatterplot
The wind speed versus temperature scatterplot below indicates very cool temperatures at the Koliganek
met tower site with highest wind speeds occurring at temperatures between approximately -15° C and
18° C. During the met tower test periods, temperatures fell below -40° C on a few occasions. Note that
arctic-capable wind turbines are rated to -40°C, hence it’s possible during very cold winters that some
power production might be lost due to low temperature shutdown of the turbine.
Koliganek, Alaska Wind Resource Report, rev. 1 Page | 14
Wind speed/temperature scatterplot
Wind Direction
Wind frequency rose data indicates that winds at the Koliganek met tower site are multi-directional,
with east-southeast, south-southwest, and northwest predominating. The mean value rose indicates,
however, that east-southeasterly winds, when they do occur, are high energy and hence are likely storm
winds. The wind energy rose indicates that for wind turbine operations, power-producing winds are
dominated by east-southeasterly winds. Calm frequency (the percent of time that winds at the 30
meter level are less than 4 m/s, a typical cut-in speed of larger wind turbines) was a relatively high 36
percent during the met tower test period.
Wind frequency rose Mean value rose (30m A anem.)
Koliganek, Alaska Wind Resource Report, rev. 1 Page | 15
Wind energy rose (30 m A anem.) Scatterplot rose of 30m A wind power density
Wind density roses by month (common scale)
Koliganek, Alaska Wind Resource Report, rev. 1 Page | 16
Turbulence
Turbulence intensity (TI) at the Koliganek met tower site is reasonably low with an IEC 61400-1, 3
rd
edition (IEC3) classification of turbulence category C, which is the lowest defined. A review of TI
coefficients by sector indicates that category C turbulence wind occurs from all wind sectors, except for
northerly/northwesterly winds where TI is high enough to classify as category B. Northwesterly winds
occur frequently but are of low energy, so are of minor consequence.
Turbulence synopsis
30 m A speed 20 m speed Legend
Sector
Mean TI
at 15
m/s
Repres.
TI at 15
m/s
IEC3
Category
Mean TI
at 15
m/s
Repres.
TI at 15
m/s
IEC3
Category
IEC3
Categ.
Mean TI
at 15
m/s
all 0.099 0.128 C 0.105 0.135 C S >0.16
315° to 045° 0.126 0.147 B 0.134 0.141 B A
0.14-
0.16
045° to 135° 0.098 0.126 C 0.247 0.088 C B
0.12-
0.14
135° to 225° 0.104 0.133 C 0.112 0.149 B C 0-0.12
225° to 315° 0.124 0.124 B n/a n/a n/a
Turbulence rose, 30 m A anemometer
Koliganek, Alaska Wind Resource Report, rev. 1 Page | 17
Turbulence intensity, 30 m A, all direction sectors
Turbulence table, 30 m data, all sectors, > 4 m/s
Bin Bin Endpoints Records Standard
Midpoint Lower Upper In Mean Deviation Repres. Peak
(m/s) (m/s) (m/s) Bin TI of TI TI TI
10.51.50
21.52.50
32.53.50
4 3.5 4.5 3342 0.130 0.059 0.205 0.659
5 4.5 5.5 5914 0.122 0.050 0.186 0.511
6 5.5 6.5 4908 0.121 0.047 0.181 0.763
7 6.5 7.5 4109 0.122 0.042 0.175 0.364
8 7.5 8.5 3052 0.118 0.038 0.167 0.438
9 8.5 9.5 2231 0.114 0.035 0.159 0.279
10 9.5 10.5 1642 0.112 0.031 0.152 0.265
11 10.5 11.5 1256 0.109 0.029 0.146 0.238
12 11.5 12.5 889 0.104 0.027 0.139 0.241
13 12.5 13.5 564 0.099 0.026 0.133 0.227
14 13.5 14.5 425 0.101 0.026 0.134 0.196
15 14.5 15.5 467 0.099 0.023 0.128 0.179
16 15.5 16.5 378 0.097 0.021 0.124 0.154
17 16.5 17.5 332 0.097 0.020 0.123 0.151
18 17.5 18.5 254 0.097 0.021 0.124 0.205
19 18.5 19.5 178 0.094 0.017 0.115 0.141
20 19.5 20.5 99 0.092 0.016 0.113 0.137
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21 20.5 21.5 65 0.098 0.017 0.120 0.151
22 21.5 22.5 52 0.093 0.015 0.112 0.142
23 22.5 23.5 27 0.097 0.011 0.112 0.128
24 23.5 24.5 25 0.091 0.013 0.108 0.133
25 24.5 25.5 34 0.093 0.010 0.106 0.116
26 25.5 26.5 20 0.093 0.012 0.108 0.121
27 26.5 27.5 8 0.095 0.007 0.104 0.104
28 27.5 28.5 1 0.079 0.000 0.079 0.079