HomeMy WebLinkAboutTeller Wind Resource Report 2015
Teller, Alaska Wind Resource Report
Teller, Google Earth image
June 5, 2015
Douglas Vaught, P.E.
V3 Energy, LLC
www.v3energy.com
Teller, Alaska Wind Resource Report Page | 1
Contents
Summary ....................................................................................................................................................... 3
Site 1 (0037), Near-Village ............................................................................................................................ 4
Met Tower Location .................................................................................................................................. 4
Data Synopsis ............................................................................................................................................ 4
Site information .................................................................................................................................... 5
Tower sensor information .................................................................................................................... 6
Data Quality Control ................................................................................................................................. 6
Wind Speed ............................................................................................................................................... 7
Time Series ................................................................................................................................................ 7
Probability of Exceedance ......................................................................................................................... 9
Probability Distribution Function .............................................................................................................. 9
Wind Shear and Roughness .................................................................................................................... 11
Extreme Winds ........................................................................................................................................ 11
Temperature, Density, and Relative Humidity........................................................................................ 12
Wind Speed Scatterplot .......................................................................................................................... 13
Wind Direction ........................................................................................................................................ 13
Turbulence .............................................................................................................................................. 15
Teller Site 2 (9037), South of Airport .......................................................................................................... 16
Met Tower Location ................................................................................................................................ 16
Data Synopsis .......................................................................................................................................... 16
Site information .................................................................................................................................. 17
Tower sensor information .................................................................................................................. 17
Data Quality Control ............................................................................................................................... 18
Wind Speed ............................................................................................................................................. 19
Time Series .............................................................................................................................................. 19
Probability Distribution Function ............................................................................................................ 21
Wind Shear and Roughness .................................................................................................................... 22
Extreme Winds ........................................................................................................................................ 23
Wind Direction ........................................................................................................................................ 23
Temperature, Density, and Relative Humidity........................................................................................ 24
Teller, Alaska Wind Resource Report Page | 2
Wind Speed Scatterplot .......................................................................................................................... 25
Turbulence .............................................................................................................................................. 26
WAsP Analysis of Site 2 Area ...................................................................................................................... 27
WAsP Analysis Summary ......................................................................................................................... 30
Teller, Alaska Wind Resource Report Page | 3
Summary
Alaska Village Electric Cooperative (AVEC), as the utility for Teller and nearby Brevig Mission, initiated a
wind resource study in Teller in 2009 to identify a suitable site for wind turbines to supply Teller with
wind energy. This initial effort focused on identifying a met tower site (referred to as Site 1) near Teller
as project development construction costs would be relatively low and a project was presumed to be
modest.
After installation of the Site 1 (also referred to as site 0037) met tower, AVEC began planning an
overland electrical intertie to link Teller to the larger village of Brevig Mission located across the bay to
the north. About this time, wind data collected from Site 1 indicated a lower-than-desired wind
resource. Because an intertie with Brevig Mission would enable a larger wind power project, a site with
a more robust wind resource was sought. A second met tower site (Site 2, or site 9037) was chosen
south of the Teller airport.
The first met tower (at Site 1) was erected in November 2009 and was operational through September
2014. The Site 2 met tower was erected in May 2011 and was operational through September 2014.
AEA high resolution wind map, Teller
The high resolution wind map predicted a Class 2 to 3 wind resource at Site 1 and a Class 3 to 4 wind
resource at Site 2. These predictions were verified with met tower data from both towers, which
indicate Class 3 wind as Site 1 (site 0037) and Class 4 winds at Site 2 (site 9037). The tradeoff is that
Teller Site 1
Teller Site 2
Teller, Alaska Wind Resource Report Page | 4
although Site 2 (9037) has a superior wind resource to Site 1 (0037), it is further distance from Teller and
development costs would be significantly higher.
Teller met towers, Site 1 (0037 and Site 2 (9037), Google Earth image, view east
Site 1 (0037), Near-Village
This met tower was erected in 2009 and decommissioned in 2014. It operated concurrently with the
second met tower after it was installed in 2011.
Met Tower Location
At the time of site selection, a wind project was anticipated to serve only Teller, hence the desire to
identify a location with a presumed low cost of development and ease of access.
Data Synopsis
Data dates Nov. 3, 2009 to Sept. 8, 2014 (Jan. 3, 2013 to Aug. 24, 2013
data missing)
Wind power class Class 3 (fair); by wind power density
Wind power density mean, 26 m 272 W/m2
Wind speed mean, 26 m 5.60 m/s (12.5 mph)
Max. 10-min avg. wind speed 28.4 m/s (63.5 mph)
Maximum 2-sec. wind gust 34.8 m/s (77.8 mph), Nov. 2013
Weibull distribution parameters k = 1.63, c = 6.22 m/s
IEC 61400-1, 3rd ed. classification Class III-C at 26 meters
Turbulence intensity, mean (at 40 m) 0.089 (at 15 m/s)
Calm wind frequency (at 26 m) 36% (< 4 m/s)
Teller, Alaska Wind Resource Report Page | 5
Teller met tower Site 1, Google Earth image, view north
Topographic map
Site information
Logger site number 0037
Site description 1,100 meters southeast of village center, near lagoon shore
Latitude/longitude N 65° 15.257’; W 166° 21.237’”, WGS 84
Site elevation 22 meters
Datalogger type NRG Symphonie, 10 minute time step
Tower type NRG 30-meter tall tower, 152 mm diameter, installed at 26
meters
Teller, Alaska Wind Resource Report Page | 6
Tower sensor information
Note installation of all three anemometers at the top of the met tower, hence the inability to calculate
wind shear power law coefficient and site roughness. Due to a missing tower section, also note that the
met tower was installed at 26 meters height, not 30 meters as designed.
Sensor documentation
Channel Sensor type Height Multiplier Offset Orientation
1 NRG #40 anemometer 25.6 m 0.765 0.35 010° T
2 NRG #40 anemometer 25.9 m 0.765 0.35 182° T
3 NRG #40 anemometer 26.2 m 0.765 0.35 092° T
7 NRG #200P wind vane 26 m 0.351 357 002° T
9 NRG #110S Temp C 4.5 m 0.136 -86.383 east
12 Voltmeter 2 m 0.021 0 n/a
Photo, Site 1 met tower
STG photo
Data Quality Control
Data was filtered to remove presumed icing events that yield false zero wind speed data and non-variant
wind direction data. Typically met tower data can be automatically filtered for icing, but icing events
were so minimal that ice data was filtered by manual identification. Because all three anemometers
were installed at the top of the tower, filtering for tower shadow was not accomplished. Note that the
8.5 months of missing data in 2013 are not included in the valid records column, resulting in lower
recovery rate than represented only by icing data, which was extremely minimal.
Sensor data recovery table
Possible Valid Recovery Icing
Label Units Height Records Records Rate (%) Records
Speed 25 m m/s 25.6 m 251,268 220,942 87.9 976
Speed 26 m A m/s 25.9 m 251,268 220,966 87.9 952
Speed 26 m B m/s 26.2 m 251,268 220,885 87.9 1,033
Direction 26 m ° 26 m 251,268 219,326 87.3 2,592
Teller, Alaska Wind Resource Report Page | 7
Possible Valid Recovery Icing
Label Units Height Records Records Rate (%) Records
Temperature °C 251,268 221,918 88.3 0
Wind Speed
Anemometer data obtained from the met tower, from the perspectives of mean wind speed and mean
wind power density, indicate a moderate wind resource. 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 25 m Speed 26 m A Speed 26 m B
Measurement height (m) 25.6 25.9 26.2
Mean wind speed (m/s), raw data 5.48 5.57 5.50
Mean wind speed (m/s), filtered, icing 5.51 5.60 5.52
Median wind speed (m/s) 5.10 5.20 5.10
Max 10 min. avg. wind speed (m/s) 26.2 28.4 26.7
Max 2 second gust (m/s) 34.4 34.0 34.8
Weibull k 1.63 1.63 1.68
Weibull c (m/s) 6.11 6.22 6.16
Mean power density (W/m²) 255 272 253
Mean energy content (kWh/m²/yr) 2,231 2,380 2,214
Energy pattern factor 2.34 2.38 2.30
Frequency of calms (%) 35.9 35.7 36.3
Time Series
Time series calculations indicate higher wind speeds during the winter months with more moderate
wind speeds during summer months, as one would expect. The daily wind profiles indicate relatively
low diurnal variation with highest wind speeds during the afternoon hours.
26 m A anemometer data (filtered) summary
Mean Median Max Gust
Std.
Dev.
Weibull
k
Weibull
c
Month (m/s) (m/s) (m/s) (m/s) (m/s) (-) (m/s)
Jan 6.25 5.90 23.1 28.7 3.82 1.61 6.93
Feb 6.76 6.20 28.4 34.0 4.33 1.60 7.53
Mar 5.75 5.50 19.2 23.7 3.26 1.75 6.41
Apr 5.56 5.10 22.2 26.8 3.37 1.67 6.20
May 4.78 4.50 21.6 24.8 2.78 1.69 5.32
Jun 4.43 4.40 13.5 16.4 2.49 1.70 4.91
Jul 5.23 4.90 21.9 26.8 3.14 1.63 5.79
Aug 5.03 4.70 22.1 30.2 2.99 1.67 5.59
Sep 5.57 5.20 20.6 25.6 3.14 1.77 6.22
Oct 5.46 5.20 22.8 28.7 2.99 1.83 6.11
Nov 6.17 5.40 26.5 31.8 4.04 1.57 6.87
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Mean Median Max Gust
Std.
Dev.
Weibull
k
Weibull
c
Month (m/s) (m/s) (m/s) (m/s) (m/s) (-) (m/s)
Dec 6.29 5.70 25.6 31.3 3.84 1.65 7.01
Annual 5.61 5.23 22.3 34.0 3.35 1.68 6.24
Monthly time series, mean wind speeds
Monthly time series, annualized, mean wind speeds
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Daily wind profile
Probability of Exceedance
Probability of exceedance is an analysis of the distribution of annual mean wind speeds with estimates
of the probability that the annual mean will exceed certain values.
Probability of exceedance table and graph, 26 m A anemometer (filtered)
Actual Normal
Dist. Dist.
% m/s m/s
P99 5.299
P95 5.379
P90 5.423
P75 5.447 5.496
P50 5.473 5.576
P25 5.665 5.656
P10 5.729
P5 5.772
P1 5.852
Probability Distribution Function
The probability distribution function (PDF), or histogram, of the Teller site 0037 wind speed reveals
“normal” shape curve, the latter known as the Rayleigh distribution (Weibull k = 2.0). A Rayleigh
distribution is the standard wind distribution for wind power analysis. As seen below for the 26 meter A
anemometer, the most frequently occurring wind speeds are between 4 and 7 m/s with very few wind
events exceeding 20 m/s.
Teller, Alaska Wind Resource Report Page | 10
Weibull table, 26 m A anemometer (filtered)
Weibull Weibull Mean Proportion Power R
k c Speed Above Density Squared
Algorithm (-) (m/s) (m/s) 5.595 m/s (W/m2) (-)
Maximum likelihood 1.629 6.220 5.568 0.431 256 0.956
Least squares 1.593 6.318 5.666 0.439 278 0.954
WAsP 1.724 6.391 5.697 0.452 255 0.964
Actual data (220,966 time steps) 5.595 0.452 255
PDF of 26 m A anemometer
Weibull k shape curve table
Occurrence by wind speed bin (26 m A anemometer)
Bin Endpoints (m/s) Occurrences Bin Endpoints (m/s) Occurrences
Lower Upper No. Percent Cum. % Lower Upper No. Percent Cum. %
0 1 14,335 6.5% 6.5% 15 16 809 0.4% 99.1%
1 2 16,110 7.3% 13.8% 16 17 635 0.3% 99.3%
2 3 21,819 9.9% 23.7% 17 18 460 0.2% 99.5%
3 4 25,258 11.4% 35.1% 18 19 331 0.1% 99.7%
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Bin Endpoints (m/s) Occurrences Bin Endpoints (m/s) Occurrences
Lower Upper No. Percent Cum. % Lower Upper No. Percent Cum. %
4 5 28,351 12.8% 47.9% 19 20 233 0.1% 99.8%
5 6 27,564 12.5% 60.4% 20 21 171 0.1% 99.9%
6 7 23,923 10.8% 71.2% 21 22 94 0.0% 99.9%
7 8 19,005 8.6% 79.9% 22 23 72 0.0% 100.0%
8 9 13,737 6.2% 86.1% 23 24 51 0.0% 100.0%
9 10 9,577 4.3% 90.4% 24 25 28 0.0% 100.0%
10 11 6,595 3.0% 93.4% 25 26 18 0.0% 100.0%
11 12 4,686 2.1% 95.5% 26 27 4 0.0% 100.0%
12 13 3,274 1.5% 97.0% 27 28 0 0.0% 100.0%
13 14 2,273 1.0% 98.0% 28 29 0 0.0% 100.0%
14 15 1,453 0.7% 98.7% 29 30 0 0.0% 100.0%
Wind Shear and Roughness
Because all three anemometers were installed at the top of the tower, vertical wind shear calculations
are not possible. Given the open tundra terrain surrounding the met tower, however, a power law
exponent of approximately 0.14 would be expected.
Extreme Winds
A modified Gumbel distribution analysis, based on monthly maximum winds vice annual maximum
winds, was used to predict extreme winds at the Teller Site 1 met tower site. The 26 meter A
anemometer was chosen for this calculation as it recorded the highest wind speeds. 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 33.9 m/s. This result classifies the site as Class III
by International Electrotechnical Commission 61400-1, 3rd edition (IEC3) criteria.
IEC extreme wind probability classification is one criteria – turbulence is the other – that describes a site
with respect to suitability for particular wind turbine models. Note that the IEC3 Class III extreme wind
classification indicates relatively well behaved winds. All village and utility-scale wind turbines are
designed for an IEC 61400-1 Class III wind regime and are potentially suitable for Teller.
Site extreme wind probability table, 26 m A data
Vref Gust IEC 61400-1, 3rd ed.
Period (years) (m/s) (m/s) Class Vref, m/s
20 31.1 36.7 I 50.0
30 31.8 37.3 II 42.5
50 33.9 39.3 III 37.5
100 36.0 41.3 S designer-
specified
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Extreme wind graph, 26 m A level
Temperature, Density, and Relative Humidity
Teller Site 1 experiences cool summers and cold winters with resulting higher than standard air density.
Calculated mean-of-monthly-mean (or annual) air density during the met tower test period exceeds the
1.222 kg/m3 standard air density for a 22 meter elevation by 5.5 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.
Temperature and density table
Temperature Air Density
Mean Min Max Mean Min Max
Month (°C) (°C) (°C) (kg/m³) (kg/m³) (kg/m³)
Jan -14.7 -36.2 9.9 1.338 1.222 1.485
Feb -13.0 -37.3 6.1 1.329 1.222 1.492
Mar -14.7 -31.6 3.8 1.335 1.222 1.457
Apr -6.0 -25.1 11.5 1.300 1.222 1.419
May 2.6 -17.0 19.9 1.266 1.201 1.374
Jun 9.9 -2.9 24.7 1.239 1.182 1.302
Jul 12.8 3.2 28.4 1.230 1.167 1.274
Aug 13.1 2.4 27.8 1.230 1.170 1.277
Sep 7.9 -2.6 20.4 1.252 1.199 1.301
Oct 1.7 -9.1 11.7 1.281 1.236 1.333
Nov -7.4 -24.5 6.6 1.324 1.222 1.416
Dec -11.4 -31.4 9.0 1.345 1.222 1.456
Annual -1.6 -37.3 28.4 1.289 1.167 1.492
Temp °F 29.1 -35.1 83.1
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Temperature boxplot graph
Wind Speed Scatterplot
The wind speed versus temperature scatterplot below indicates cold temperatures at the Teller 0037
met tower site with a preponderance of below freezing temperatures. During the met tower test
periods, temperatures were often below -20° C (-4° F), the minimum operating temperature for most
standard-environment wind turbines. Note that arctic-capable (ratings to -40°C) wind turbines would be
required at this site.
Wind speed/temperature
Wind Direction
Wind frequency rose data indicates that winds at the Teller 0037 met tower site are tri-directional, with
predominately easterly winds and northerly and southerly winds to a lesser extent. The mean value
rose indicates, however, that southerly winds are of the highest intensity, followed by northerly and
Teller, Alaska Wind Resource Report Page | 14
easterly winds in that order. Hence, the wind energy roses indicate that power-producing winds are
northerly, easterly, and southerly.
Calm wind frequency (the percent of time that winds at the 26 meter level are less than 4 m/s, a typical
cut-in speed of larger wind turbines) was a somewhat high 36 percent during the four year test period.
Wind frequency rose Mean value rose (26 m A anem.)
Total energy rose (26 m A anem.) Scatterplot (26 m A anem.)
Teller, Alaska Wind Resource Report Page | 15
Turbulence
Site turbulence intensity (TI) is quite good with a mean turbulence intensity of 0.088 and a
representative turbulence intensity of 0.118 at 15 m/s wind speed at 26 meters, indicating smooth air
for wind turbine operations. This equates to an International Electrotechnical Commission (IEC) 3rd
Edition (2005) turbulence category C, which is the lowest defined category. These data are shown in the
turbulence intensity graph below. Representative TI (90th percentile of the turbulence intensity values,
assuming a normal distribution) at 15 m/s is well under IEC Category C criteria at Teller Site 1.
Turbulence table, 26 m A anemometer, by sector
Bin Endpoints (°)
Lower Upper Occurrences Mean Median Min Max Std. Dev.
0 45 42,767 0.141 0.100 0.000 1.500 0.130
45 90 70,982 0.129 0.095 0.000 1.111 0.108
90 135 16,408 0.170 0.119 0.000 1.214 0.145
135 180 15,161 0.150 0.113 0.000 1.235 0.128
180 225 18,269 0.144 0.118 0.000 1.429 0.109
225 270 20,451 0.150 0.108 0.000 1.125 0.124
270 315 11,782 0.175 0.115 0.000 1.167 0.149
315 360 23,506 0.154 0.110 0.000 1.143 0.126
Turbulence intensity, 26 m A, all direction sectors
Teller, Alaska Wind Resource Report Page | 16
Teller Site 2 (9037), South of Airport
This met tower was installed in May, 2012, was the second met tower erected in Teller, and operated
concurrently with the first met tower until both towers were decommissioned in September 2014.
Met Tower Location
The Site 2 met tower location was chosen with consideration of anticipated higher wind speeds south of
the airport and accessibility from the Nome-Teller road.
Data Synopsis
Data dates May 11, 2012 to September 8, 2014 (28 months)
Wind power class Class 4 (good)
Wind power density mean, 50 m 421 W/m2
Wind speed mean, 50 m (filtered) 6.72 m/s (15.0 mph)
Max. 10-min avg. wind speed 28.0 m/s (62.6 mph)
Maximum 2-sec. wind gust 37.1 m/s (77.8 mph), Nov. 2013
Weibull distribution parameters k = 1.76, c = 7.45 m/s
Wind shear power law exponent 0.141 (average)
Roughness class 0.99 (description: fallow field)
IEC 61400-1, 3rd ed. classification Class II-C at 50 meters
Turbulence intensity, mean (at 50 m) 0.075 (at 15 m/s)
Calm wind frequency (at 26 m) 26% (< 4 m/s) (28 mo. measurement period)
Google Earth image, Teller met tower Site 2
Teller, Alaska Wind Resource Report Page | 17
Topographic map
Site information
Logger site number 9037
Site description 6.3 km SSE of Teller; 3.4 km south of airport access road
Latitude/longitude N 65° 12.593’; W 166° 18.454’, WGS 84
Site elevation 124 meters
Datalogger type NRG Symphonie, 10 minute time step
Tower type NRG 50-meter tall tower, 203 mm diameter
Tower sensor information
Although a met tower commissioning sheet was not forwarded by the installation crew and perhaps not
completed, sensor documentation as indicated on the met tower installation instruction form and keyed
into the datalogger are presented below.
Sensor documentation
Channel Sensor type Height Multiplier Offset Orientation
1 NRG #40 anemometer 49 m 0.765 0.39 090° T
2 NRG #40 anemometer 49 m 0.764 0.37 270° T
3 NRG #40 anemometer 40 m 0.762 0.41 090° T
4 NRG #40 anemometer 32 m 0.763 0.40 090° T
5 NRG #40 anemometer 32 m 0.763 0.40 270° T
6 NRG #40 anemometer 24 m 0.767 0.38 090° T
7 NRG #200P wind vane 47 m 0.351 011 000° T
8 NRG #200P wind vane 39 m 0.351 011 000° T
9 NRG #110S temperature 4.5 m 0.136 -86.3 north
10 RH5X relative humidity 2 m 0.097 0.0 south
Teller airport location
Teller, Alaska Wind Resource Report Page | 18
Channel Sensor type Height Multiplier Offset Orientation
11 LI-200SZ pyranometer 4 m 1.32 0.0 180° T
12 Voltmeter 2 m 0.021 0.0 n/a
Photo, Site 2 (9037) met tower
AVEC photo
Data Quality Control
Data was filtered to remove presumed icing events that yield false zero wind speed data and non-variant
wind direction data. Typically met tower data can be automatically filtered for icing, but icing events
were so minimal that ice data was filtered by manual identification. Filtering for tower shadow was
accomplished for the paired anemometers at 49 meters and 32 meters. Wind speed data loss due to
icing was extremely minimal and surprising considering latitude and site elevation.
Sensor data recovery table
Possible Valid Recovery Tower
Label Units Records Records Rate (%) Icing Invalid Shading
Speed 49 m A m/s 122,418 115,826 94.6 1,198 532 5,076
Speed 49 m B m/s 122,418 100,579 82.2 1,041 532 20,436
Speed 40 m m/s 122,418 120,835 98.7 1,196 532 0
Speed 32 m A m/s 122,418 117,091 95.7 1,024 532 3,980
Speed 32 m B m/s 122,418 101,904 83.2 927 532 19,220
Speed 24 m m/s 122,418 121,067 98.9 959 532 0
Direction 47 m ° 122,418 119,553 97.7 2,476 529 0
Teller, Alaska Wind Resource Report Page | 19
Possible Valid Recovery Tower
Label Units Records Records Rate (%) Icing Invalid Shading
Direction 39 m ° 122,418 119,818 97.9 2,211 529 0
Temperature °C 122,418 121,497 99.3 0 535 0
RH-5 Humidity %RH %RH 122,418 121,383 99.2 0 649 0
Wind Speed
Anemometer data obtained from the met tower, from the perspectives of mean wind speed and mean
wind power density, indicate a moderate wind resource. 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 49
m A
Speed 49
m B
Speed 40
m
Speed 32
m A
Speed 32
m B
Speed 24
m
Measurement height (m) 49 49 40 32 32 24
Mean wind speed (m/s) (raw) 6.55 6.42 6.38 6.18 6.12 5.89
Mean wind speed (m/s) (filtered) 6.66 6.51 6.36 6.25 6.23 5.87
MoMM wind speed (m/s) (filtered) 6.72 6.63 6.44 6.31 6.34 5.93
Max 10 min avg wind speed (m/s) 27.9 28 27.3 26 26.3 25.7
Max 2 sec gust wind speed (m/s) 36.7 37.1 35.5 35.1 35.5 35.3
Weibull k 1.77 1.62 1.73 1.77 1.68 1.69
Weibull c (m/s) 7.45 7.22 7.10 6.99 6.95 6.54
MoMM power density (W/m²) 412 426 368 341 360 292
MoMM energy content (kWh/m²/yr) 3,612 3,728 3,223 2,983 3,154 2,557
Energy pattern factor 2.13 2.30 2.17 2.13 2.21 2.19
Frequency of calms (%) 26.4 29.7 28.8 29.0 30.6 32.5
Time Series
Time series calculations indicate higher wind speeds during the winter months with more moderate
wind speeds during summer months, as one would expect. The daily wind profiles indicate moderate
diurnal variation with highest wind speeds during the afternoon hours.
49 m A anemometer data (filtered) summary
Mean Median Max Gust Std. Dev. Weibull k Weibull c
Month (m/s) (m/s) (m/s) (m/s) (m/s) (-) (m/s)
Jan 8.19 7.90 23.2 28.3 4.05 2.07 9.20
Feb 7.35 7.00 25.7 27.5 3.68 2.03 8.25
Mar 6.45 6.20 19.5 23.3 3.45 1.89 7.23
Apr 6.70 6.10 22.8 26.4 3.72 1.86 7.53
May 7.22 6.40 20.7 24.9 4.33 1.68 8.05
Jun 5.43 5.20 22.0 25.6 3.11 1.75 6.07
Jul 6.74 6.10 24.0 28.0 3.99 1.72 7.53
Aug 5.89 5.20 27.9 32.9 3.85 1.58 6.56
Teller, Alaska Wind Resource Report Page | 20
Mean Median Max Gust Std. Dev. Weibull k Weibull c
Month (m/s) (m/s) (m/s) (m/s) (m/s) (-) (m/s)
Sep 5.98 5.50 16.0 20.6 3.11 1.97 6.71
Oct 6.99 6.60 19.7 25.3 3.61 1.98 7.86
Nov 7.02 6.30 27.8 36.7 4.39 1.62 7.82
Dec 6.68 6.60 18.7 21.8 3.41 1.96 7.48
Annual 6.72 6.26 22.3 36.7 3.73 1.84 7.52
Monthly time series, mean wind speeds
Monthly time series, annualized, mean wind speeds
Teller, Alaska Wind Resource Report Page | 21
Daily wind profile
Probability Distribution Function
The probability distribution function (PDF), or histogram, of the Teller Site 2 (9037) wind speed reveals
“normal” shape curve, the latter known as the Rayleigh distribution (Weibull k = 2.0). A Rayleigh
distribution is the standard wind distribution for wind power analysis. As seen below for the 49 meter A
anemometer, the most frequently occurring wind speeds are between 4 and 9 m/s with very few wind
events exceeding 20 m/s (10 minute average).
Weibull table, 49 m A anemometer (filtered)
Weibull Weibull Mean Proportion Power R
k c Speed Above Density Squared
Algorithm (-) (m/s) (m/s) 5.595 m/s (W/m2) (-)
Maximum likelihood 1.769 7.453 6.633 0.441 390.3 0.974
Least squares 1.704 7.549 6.735 0.446 427.5 0.968
WAsP 1.800 7.476 6.648 0.444 385.2 0.976
Actual data (115,826 time steps) 6.658 0.444 385.2
PDF of 49 m A anemometer
Teller, Alaska Wind Resource Report Page | 22
Occurrence by wind speed bin (49 m A anemometer)
Bin Endpoints (m/s) Occurrences Bin Endpoints (m/s) Occurrences
Lower Upper No. Percent Cum. % Lower Upper No. Percent Cum. %
0 1 4,570 3.9% 3.9% 15 16 1,190 1.0% 97.8%
1 2 5,787 5.0% 8.9% 16 17 892 0.8% 98.6%
2 3 8,384 7.2% 16.2% 17 18 646 0.6% 99.2%
3 4 10,665 9.2% 25.4% 18 19 403 0.3% 99.5%
4 5 12,528 10.8% 36.2% 19 20 254 0.2% 99.7%
5 6 13,433 11.6% 47.8% 20 21 133 0.1% 99.8%
6 7 12,675 10.9% 58.7% 21 22 61 0.1% 99.9%
7 8 10,983 9.5% 68.2% 22 23 50 0.0% 99.9%
8 9 8,450 7.3% 75.5% 23 24 27 0.0% 100.0%
9 10 7,141 6.2% 81.7% 24 25 11 0.0% 100.0%
10 11 5,580 4.8% 86.5% 25 26 18 0.0% 100.0%
11 12 4,388 3.8% 90.3% 26 27 8 0.0% 100.0%
12 13 3,338 2.9% 93.2% 27 28 4 0.0% 100.0%
13 14 2,503 2.2% 95.3% 28 29 0 0.0% 100.0%
14 15 1,704 1.5% 96.8% 29 30 0 0.0% 100.0%
Wind Shear and Roughness
Considering only the four anemometers facing 090° T and filtering for icing and tower shadow, a power
law exponent of 0.151 is calculated. This is an expected result for an open, tundra environment.
Vertical wind shear profile
Teller, Alaska Wind Resource Report Page | 23
Extreme Winds
A modified Gumbel distribution analysis, based on monthly maximum winds vice annual maximum
winds, was used to predict extreme winds at Teller Site 2. The 40 meter A anemometer was chosen for
this calculation because it is nearest to the hub height of the Northern Power Systems NPS100 wind
turbine. 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 38.2 m/s. This result classifies
the site as Class II by International Electrotechnical Commission 61400-1, 3rd edition (IEC3) criteria. IEC
extreme wind 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 II extreme wind
classification indicates relatively energetic winds and turbines installed at this location should be IEC3
Class II rated.
Site extreme wind probability table, 40 meter A data
Vref Gust IEC 61400-1, 3rd ed.
Period (years) (m/s) (m/s) Class Vref, m/s
3 27.2 32.8 I 50.0
10 32.7 39.4 II 42.5
20 34.1 41.0 III 37.5
30 36.4 43.9 S designer-
specified 50 38.2 45.9
100 40.5 48.8
average gust factor: 1.20
Wind Direction
Wind frequency rose data indicates that winds at Site 2 (9037) are tri-directional, with predominately
easterly winds and northerly and southerly winds to a lesser extent. The mean value rose indicates,
however, that southerly winds are of the highest intensity, followed by northerly and easterly winds in
that order. Hence, the wind energy roses indicate that power-producing winds are predominately
southerly.
Calm wind frequency (the percent of time that winds at the 26 meter level are less than 4 m/s, a typical
cut-in speed of larger wind turbines) was a moderate 26 percent during the 28 month test period.
Teller, Alaska Wind Resource Report Page | 24
Wind frequency rose, 49 m A, 47 m vane Mean value rose (49 m A anem.)
Total energy rose (49 m A anem.) Scatterplot (49 m A anem.)
Temperature, Density, and Relative Humidity
Teller Site 2 experiences cool summers and cold winters with resulting higher than standard air density.
Calculated mean-of-monthly-mean (or annual) air density during the met tower test period exceeds the
1.210 kg/m3 standard air density for a 124 meter elevation by 6.6 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.
Teller, Alaska Wind Resource Report Page | 25
Temperature and density table
Temperature Air Density
Mean Min Max Mean Min Max
Month (°C) (°C) (°C) (kg/m³) (kg/m³) (kg/m³)
Jan -10.6 -27.1 8.0 1.324 1.210 1.413
Feb -17.2 -32.6 3.6 1.360 1.210 1.446
Mar -13.9 -27.9 4.3 1.342 1.210 1.418
Apr -7.1 -22.8 10.7 1.308 1.225 1.389
May 1.0 -15.6 14.0 1.269 1.211 1.350
Jun 8.8 -2.7 31.8 1.234 1.140 1.286
Jul 10.3 0.6 28.1 1.227 1.154 1.270
Aug 10.9 -0.3 25.0 1.224 1.166 1.274
Sep 3.4 -4.4 15.0 1.258 1.207 1.294
Oct -0.1 -12.6 8.6 1.274 1.234 1.335
Nov -8.7 -19.8 3.9 1.315 1.255 1.373
Dec -14.2 -28.3 4.7 1.344 1.251 1.420
Annual -3.1 -32.6 31.8 1.290 1.140 1.446
Temp °F 26.4 -26.7 89.2
Temperature boxplot graph
Wind Speed Scatterplot
The wind speed versus temperature scatterplot below indicates cold temperatures at the Teller 9037
met tower site with a preponderance of below freezing temperatures. During the met tower test
periods, temperatures were often below -20° C (-4° F), the minimum operating temperature for most
standard-environment wind turbines. Note that arctic-capable (ratings to -40°C) wind turbines would be
required at this site.
Teller, Alaska Wind Resource Report Page | 26
Wind speed/temperature
Turbulence
The turbulence intensity (TI) is very good with a mean turbulence intensity of 0.088 and a representative
turbulence intensity of 0.074 at 15 m/s wind speed at 49 meters, indicating very smooth air for wind
turbine operations. This equates to an International Electrotechnical Commission (IEC) 3rd Edition (2005)
turbulence category C, which is the lowest defined category. These data are shown in the turbulence
intensity graph below. As seen, representative TI (90th percentile of the turbulence intensity values,
assuming a normal distribution) at 15 m/s is well under IEC Category C criteria at the Teller 9037 met
tower site.
Turbulence table, 49 m A anemometer, by sector
Sector Records Standard
Midpoint In Mean Deviation Rep. Peak
Sector (°) Sector TI of TI TI TI
1 0 10,627 0.104 0.041 0.157 0.725
2 45 14,699 0.095 0.044 0.152 0.619
3 90 23,945 0.079 0.042 0.132 0.537
4 135 6,543 0.104 0.053 0.171 0.689
5 180 12,860 0.092 0.042 0.145 0.711
6 225 10,577 0.096 0.041 0.148 0.561
7 270 2,536 0.100 0.034 0.143 0.478
8 315 3,684 0.102 0.042 0.156 0.500
Teller, Alaska Wind Resource Report Page | 27
Turbulence intensity, 49 m A, all direction sectors
WAsP Analysis of Site 2 Area
This section documents an analysis of the Teller wind resource at the Teller 2 (second) met tower site
and surrounding vicinity using WAsP (Wind Atlas, Analysis and Application Program) software. The
purpose of the analysis is to identify alternative sites for wind turbine construction in the Site 2 area.
The criteria for this consideration is that an alternate site must be constructible. In general, and
recognizing that the sites are a fair distance from Teller and that power distribution terminates at the
airport, this means that a site must be relatively near the Teller-Nome Highway, not on Native Allotment
land, and not likely to be opposed by the FAA in reference to airport operations. Additionally, soil
conditions at the site are known or presumed suitable for turbine foundations.
The WAsP software analysis was accomplished by assessing the orographic effects of the wind as
measured by the Teller Site 2 met tower. The terrain was modeled with high accuracy 1 arc-second
digital elevation map (DEM) recently surveyed by USGS. Although the met tower was 50 meters high, an
evaluation height of 37 meters was selected to predict annual energy production from the Northern
Power Systems NPS100-24 wind turbine, a possible turbine choice for Teller.
In WAsP, a resource area was created to visually display wind speed, wind power density, or other data
of interest. This resource area included the village of Teller and the gravel spit to the north, Teller
airport, the Site 2 met tower location and higher elevation terrain to the south. Six representative
turbine locations were selected:
• Turbine Site A; on the gravel spit immediately north of Teller
• Turbine Site B; at Site 1 met tower
• Turbine Site C; immediately north of the airport tarmac
• Turbine Site D; near the Site 2 met tower
• Turbine Site E; at a gravel pit one kilometer south of the Site 2 met tower
• Turbine Site F; on higher terrain approximately 3.5 kilometers south of the Site 2 met tower
Teller, Alaska Wind Resource Report Page | 28
Overlay of WAsP-calculated wind speed on Google Earth image of Teller
Turbine Sites A, B, and C (view to north)
Teller, Alaska Wind Resource Report Page | 29
Turbine Sites D, E, and F (view to north)
Turbine Sites A, B, C and D (view to west)
Teller, Alaska Wind Resource Report Page | 30
Wind speed comparison table (37 meter level, 100% net AEP)
Site Identifier Location
Wind
Speed
(m/s)
Power
Density
(W/m^2)
NPS 100-
24 AEP
(MWh/yr)
NPS 100-24
Turbine CF
(%)
Teller 2 Met
Tower
Near landfill south of
airport 6.47 339 n/a n/a
Turbine Site A On Teller gravel spit 6.16 291 262.8 30.0
Turbine Site B At Site 1 met tower 6.07 275 257.2 29.4
Turbine Site C Near airport tarmac 6.76 407 302.7 34.6
Turbine Site D Near Site 2 met tower 6.51 343 289.5 33.0
Turbine Site E Gravel pit 1 km south of
Site 2 met tower 7.01 444 320.5 36.6
Turbine Site F Higher terrain 3.5 km
south of Site 2 met tower 7.29 502 338.5 38.6
WAsP Analysis Summary
The WAsP analysis indicates that with respect to wind resource, AVEC’s optimal site option for wind
turbines is Turbine Site F, the higher elevation terrain approximately 3.5 km south of the Teller II met
tower and approx. 7.1 km south of the airport. Turbine Site E is also a good alternative to the Site 2 met
tower area. If FAA permitting can be secured, a Turbine Site C (near the airport tarmac) would be
excellent from a cost-of-development perspective. Note that energy estimates assume 100% net AEP.
Actual energy production would be less with consideration of O&M, icing, array efficiency, and other
production losses.