HomeMy WebLinkAboutFalse Pass Wind Resource Report - Jan 2012 - REF Grant 7040051False Pass Wind Resource Report
False Pass meteorological tower, view to the east, D. Vaught photo
January 27, 2012
Douglas Vaught, P.E.
V3 Energy, LLC
Eagle River, Alaska
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Summary
The wind resource as the False Pass met tower site is generally good with measured wind power class 4
by measurement of wind power density (Class 3 if considering only mean annual wind speed). Given the
moderately cool temperatures of False Pass test site, air density is moderately higher than standard
conditions. By other measures important for wind power analysis, the site has a low 50-year return
period extreme wind probability but high turbulence; the latter apparently due to the high mountains
that border Isantoski Strait and that are very near the met tower to the north, west and south.
Turbulence intensity calculated from the met tower data indicates much higher than desirable
turbulence conditions. This would require special care with turbine selection and operations.
It is not immediately clear if an alternate wind site that has good wind exposure and less turbulence
exists in the near proximity of the village of False Pass. Siting restrictions include the obvious constraints
of geography – mountains and Isantoski Strait – and the location and orientation of the False Pass
airstrip. Computation fluid dynamics (CFD) modeling may lend insight into wind flow patterns at False
Pass and would be a useful tool to investigate other wind turbine siting options.
Met tower data synopsis
Data dates May 7, 2005 to August 19, 2005 and November 30,
2005 to September 4, 2007 (24 months); status:
operational
Wind power class Class 3 to 4 (fair to good)
Wind power density mean, 30 m 338 W/m
2
Wind speed mean, 30 m 6.11 m/s
Max. 10-min wind speed average 26.5 m/s
Maximum 2-sec. wind gust 39.0 m/s (January, 2007)
Weibull distribution parameters k = 1.62, c = 6.76 m/s
Wind shear power law exponent 0.291 (high)
Roughness class 3.80 (suburban)
IEC 61400-1, 3rd ed. classification Class III-S
Turbulence intensity, mean 0.173 (at 15 m/s)
Calm wind frequency (at 30 m) 35% (winds < 4 m/s)
Test Site Location
Wind measurement instrumentation (anemometers, wind vane, temperature sensor) was installed on a
30 meter tall, six-inch diameter NRG Systems Inc. tubular meteorological (met) test tower in an open
area near the coast, approximately 2.4 km (1.5 miles) north of the village of False Pass. The tower (still
standing and operational again in October 2011) is located on a grassy outwash plain immediately north
of a moderately-sized stream that drains from the extensive mountain range immediately west of the
site. This location had been the village’s preferred site for wind turbines, but more recent thoughts are
to locate wind turbines closer to the village.
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Met tower installation was accomplished on May 6 and 7, 2005 by Doug Vaught of V3 Energy, LLC,
Connie Fredenberg of Aleutian/Pribilof Islands Association, Mia Devine of Alaska Energy Authority, and
George Jackson, power plant operator of the village of False Pass.
Site information
Site number 2399
Latitude/longitude N 54° 52.443’ W 163° 24.646’, WGS 84
Site elevation 17 meters (54 ft)
Datalogger type NRG Symphonie, 10 minute time step
Tower type NRG 6-inch diameter tubular, 30 meter height
Tower installation photographs (May, 2005; D. Vaught photos)
C. Fredenberg and M. Devine heading to the site C. Fredenberg and G. Jackson assembling the tower
Lifting the met tower M. Devine, G. Jackson, C. Fredenber wrapping up
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Topographic maps, 2D views
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Topographic map, 3D view
Tower sensor information
Channel Sensor type Height Multiplier Offset Orientation
1 NRG #40 anemometer 30 m (A) 0.765 0.35 ~275° T
2 NRG #40 anemometer 30 m (B) 0.765 0.35 095° T
3 NRG #40 anemometer 20 m 0.765 0.35 240° T
7 NRG #200P wind vane 27 m 0.351 050 230° T
9 NRG #110S Temp C 3 m 0.138 -86.3 N
Met tower sensors photograph (view to the east)
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Data Quality Control
Data quality is excellent with data recovery of all three anemometers at nearly 100 percent for the time
periods of actual data recovery (8/19/05 to 11/30/05 excluded) and 87.5 percent with that time period
included. On 8/19/05 a bear visiting the site ripped out the sensor wiring inputs to the datalogger; this
damage was repaired on 11/30/05. Although False Pass is located in a cold climate where icing
conditions might be expected, very few icing events were detected in the data. Note that the
temperature sensor was not functional from initial tower installation on 5/7/05 until 11/30/05, the date
that the bear damage to sensor wiring was repaired.
Data recovery summary table
Label Units Height
Possible
Records
Valid
Records
Recovery
Rate (%)
Speed 30 m A m/s 30 m 122,386 107,093 87.5
Speed 30 m B m/s 30 m 122,386 107,087 87.5
Speed 20 m m/s 20 m 122,386 107,090 87.5
Direction 27 m ° 27 m 122,386 107,066 87.5
Temperature °C 3 m 122,386 92,506 75.6
Anemometer and wind vane data recovery
30 m A 30 m B 20 m Vane Temp
Possible Valid Recovery Recovery Recovery Recovery Recovery
Year Month Records Records Rate (%) Rate (%) Rate (%) Rate (%) Rate (%)
2005 May 3,514 3,482 99.1 99.1 99.1 99.1 0.0
2005 Jun 4,320 4,320 100.0 100.0 100.0 100.0 0.0
2005 Jul 4,464 4,464 100.0 100.0 100.0 100.0 0.0
2005 Aug 4,464 2,740 61.4 61.4 61.4 61.4 0.0
2005 Sep 4,320 0 0.0 0.0 0.0 0.0 0.0
2005 Oct 4,464 0 0.0 0.0 0.0 0.0 0.0
2005 Nov 4,320 46 1.1 1.1 1.1 1.1 1.1
2005 Dec 4,464 4,335 97.1 96.9 97.8 91.6 100.0
2006 Jan 4,464 4,460 99.9 100.0 100.0 100.0 100.0
2006 Feb 4,032 4,032 100.0 100.0 99.1 100.0 100.0
2006 Mar 4,464 4,464 100.0 100.0 100.0 100.0 100.0
2006 Apr 4,320 4,320 100.0 100.0 100.0 100.0 100.0
2006 May 4,464 4,464 100.0 100.0 100.0 100.0 100.0
2006 Jun 4,320 4,320 100.0 100.0 100.0 100.0 100.0
2006 Jul 4,464 4,464 100.0 100.0 100.0 100.0 100.0
2006 Aug 4,464 4,464 100.0 100.0 100.0 100.0 100.0
2006 Sep 4,320 4,260 98.6 98.6 98.6 98.6 98.6
2006 Oct 4,464 4,464 100.0 100.0 100.0 100.0 100.0
2006 Nov 4,320 4,320 100.0 100.0 100.0 100.0 100.0
2006 Dec 4,464 4,464 100.0 100.0 100.0 100.0 100.0
2007 Jan 4,464 4,464 100.0 100.0 100.0 100.0 100.0
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2007 Feb 4,032 3,833 95.1 95.1 95.1 100.0 100.0
2007 Mar 4,464 4,377 98.1 98.1 98.1 98.4 100.0
2007 Apr 4,320 4,320 100.0 100.0 100.0 100.0 100.0
2007 May 4,464 4,464 100.0 100.0 100.0 100.0 100.0
2007 Jun 4,320 4,320 100.0 100.0 100.0 100.0 100.0
2007 Jul 4,464 4,464 100.0 100.0 100.0 100.0 100.0
2007 Aug 4,464 4,464 100.0 100.0 100.0 100.0 100.0
2007 Sep 504 504 100.0 100.0 100.0 100.0 100.0
All data 122,386 107,093 87.5 87.5 87.5 87.5 75.6
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. Mean wind speeds are greater at higher
elevations on the met tower, as one would expect. Note that relatively cold temperatures contributed
to higher wind power density than otherwise might have been expected for the 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) 6.01 6.06 5.34
MMM wind speed (m/s) 6.06 6.11 5.38
Max 10-min avg wind speed (m/s) 26.2 26.5 22.4
Max gust wind speed (m/s) 39.0 38.6 37.1
Weibull k 1.59 1.62 1.55
Weibull c (m/s) 6.54 6.76 5.93
Mean power density (W/m²) 329 333 237
MMM power density (W/m²) 333 338 239
Mean energy content (kWh/m²/yr) 2,882 2,920 2,073
MMM energy content (kWh/m²/yr) 2,917 2,961 2,094
Energy pattern factor 2.40 2.38 2.46
Frequency of calms (%) 34.5 34.2 39.3
1-hr autocorrelation coefficient 0.863 0.864 0.859
Diurnal pattern strength 0.105 0.104 0.112
Hour of peak wind speed 16 16 16
MMM = mean of monthly means
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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 a typical village load profile of high
electric and heat demand during the winter months and lower demand during summer months. The
annual and monthly daily wind profiles indicate highest wind during the mid-afternoon hours.
30 m B anemometer data summary
Mean Max Gust
Std.
Dev.
Weibull
k
Weibull
c
Year Month (m/s) (m/s) (m/s) (m/s) (-) (m/s)
2005 May 6.32 19.5 27.1 3.70 1.74 7.08
2005 Jun 5.89 16.9 23.3 3.47 1.66 6.55
2005 Jul 4.44 12.9 18.3 2.61 1.71 4.96
2005 Aug 7.02 17.6 23.3 4.08 1.62 7.76
2005 Sep
2005 Oct
2005 Nov
2005 Dec 5.54 19.7 29.8 3.71 1.45 6.09
2006 Jan 5.73 16.5 27.9 3.13 1.81 6.40
2006 Feb 7.28 20.1 30.9 4.49 1.61 8.09
2006 Mar 6.37 22.2 32.4 4.09 1.51 7.03
2006 Apr 6.84 22.7 31.8 3.98 1.72 7.64
2006 May 6.49 23.1 29.8 4.61 1.35 7.05
2006 Jun 5.77 17.5 24.0 3.75 1.46 6.34
2006 Jul 5.80 17.9 23.7 3.26 1.75 6.47
2006 Aug 4.86 17.1 27.5 3.63 1.26 5.22
2006 Sep 5.34 24.2 35.9 3.88 1.33 5.80
2006 Oct 6.18 21.6 36.3 3.89 1.56 6.85
2006 Nov 8.16 20.6 36.3 3.89 2.17 9.18
2006 Dec 5.11 19.1 24.83.031.67 5.70
2007 Jan 7.17 26.5 38.6 4.60 1.55 7.96
2007 Feb 7.08 18.9 27.1 3.89 1.80 7.90
2007 Mar 8.17 19.3 30.2 3.92 2.17 9.18
2007 Apr 5.67 21.5 36.3 3.54 1.55 6.26
2007 May 5.50 17.5 24.0 3.89 1.33 5.95
2007 Jun 5.37 16.8 24.0 3.27 1.65 5.99
2007 Jul 4.58 13.8 21.8 3.12 1.40 5.00
2007 Aug 5.45 17.9 24.4 3.45 1.52 6.01
2007 Sep 6.63 16.5 27.5 3.82 1.69 7.37
All data 6.06 26.5 38.6 3.86 1.53 6.70
MMM 6.11 3.72 1.62 6.76
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Seasonal time series graph
Annual daily wind profile
Monthly daily wind profile
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Probability Distribution Function
The probability distribution function (PDF), or histogram, of the False Pass met tower site wind speed
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 seen in the PDF of the 30 m B anemometer, the most
frequently occurring wind speeds are between 5 and 7 m/s with essentially no wind events exceeding 25
m/s (the cutout speed of most wind turbines; see following wind speed statistical table).
PDF of 30 m B anemometer
Frequency distribution table
Weibull Weibull Mean Proportion Power R
k c Above Density Squared
Algorithm (m/s) (m/s) Mean (W/m2)
Maximum likelihood 1.53 6.70 6.03 0.427 354 0.896
Least squares 1.38 6.81 6.22 0.414 455 0.903
WAsP 2.35 7.72 6.84 0.471 324 0.751
Actual data
(107,087 time
steps) 6.06 0.471 324
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Occurrence by wind speed bin, 30 m B anemometer
Bin Endpoints
(m/s) Occurrences
Bin Endpoints
(m/s) Occurrences
Lower Upper No. Percent Lower Upper No. Percent
0 1 9,225 8.80% 15 16 923 0.88%
1 2 8,708 8.31% 16 17 588 0.56%
2 3 8,737 8.34% 17 18 365 0.35%
3 4 8,988 8.58% 18 19 195 0.19%
4 5 9,568 9.13% 19 20 104 0.10%
5 6 10,356 9.88% 20 21 77 0.07%
6 7 10,582 10.10% 21 22 44 0.04%
7 8 9,356 8.93% 22 23 8 0.01%
8 9 8,118 7.75% 23 24 6 0.01%
9 10 6,530 6.23% 24 25 4 0.00%
10 11 4,798 4.58% 25 26 0 0.00%
11 12 3,715 3.55% 26 27 1 0.00%
12 13 2,751 2.63% 27 28 0 0.00%
13 14 1,930 1.84% 28 29 0 0.00%
14 15 1,410 1.35% 29 30 0 0.00%
Wind Shear and Roughness
A wind shear power law exponent (ɲ) of 0.291 indicates high wind shear at the site. Related to wind
shear, a calculated surface roughness of 0.878 meters (indicating the height above ground level where
wind velocity would be zero) indicates very rough terrain (roughness description: suburban). This is
somewhat curious as the terrain surrounding the met tower is mostly comprised of low-lying grass and
light brush and presumably snow cover during the winter months. The high wind shear measured at the
site indicates that it would be advantageous to erect wind turbines at higher hub heights if possible.
Vertical wind shear profile
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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 False Pass met tower site. Note below that the
extreme wind analysis shows relatively low extreme winds. 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 False Pass this calculates to 29.1 m/s (at 30 meters), which meets International Electrotechnical
Commission (IEC) 61400-1, 3rd edition Class III criteria. All wind turbines are designed for IEC Class III
extreme winds.
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 23.9 35.4 I 50.0
10 26.1 38.7 II 42.5
20 27.4 40.6 III 37.5
30 28.1 41.7 S designer-
specified5029.1 43.1
100 30.4 45.0
average gust
factor: 1.48
Extreme wind graph
Temperature, Density, and Relative Humidity
False Pass experiences cool summers and moderately cold winters with resulting higher than standard
air density. Calculated mean-of-monthly-mean air density during the met tower test period exceeds the
1.223 kg/m
3 standard air density for a 17 meter elevation by approximately three 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.
20.0
25.0
30.0
35.0
40.0
45.0
50.0
0 102030405060708090100Wind Speed, m/sPeriod, years
False Pass Extreme Wind
10-min max
gust
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Temperature and density table
Temperature Air Density
Month Mean Mean Min Max Mean Min Max
(°C)(°F) (°C) (°C) (kg/m³) (kg/m³) (kg/m³)
Jan -0.9 30.3 -10.5 7.4 1.294 1.255 1.341
Feb 2.6 36.6 -14.1 11.2 1.278 1.239 1.359
Mar -0.3 31.4 -13.3 12.1 1.291 1.235 1.355
Apr 2.9 37.3 -3.2 16.0 1.276 1.218 1.305
May 5.8 42.4 0.1 19.6 1.251 1.203 1.289
Jun 9.4 48.8 3.0 17.5 1.239 1.212 1.275
Jul 12.1 53.9 6.6 22.1 1.231 1.193 1.259
Aug 13.1 55.5 6.4 21.2 1.228 1.196 1.260
Sep 10.6 51.1 3.8 19.0 1.232 1.205 1.272
Oct 7.7 45.9 1.8 13.3 1.238 1.223 1.281
Nov 3.5 38.3 -3.9 8.8 1.248 1.223 1.308
Dec 2.3 36.1 -7.8 8.5 1.279 1.250 1.327
Annual 5.7 42.3 -14.1 22.1 1.257 1.193 1.359
Annual temperature boxplot
Temperature data, measurement period
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Air density DMap
Wind Speed Scatterplot
The wind speed versus temperature scatterplot for the False Pass wind site indicates a relatively even
percentage of wind events across all temperatures. The minimum temperature is relatively warm by
Alaska standards at -14°C (7° F). It is not likely that arctic-capable wind turbines with special low
temperatures lubricants and heaters would be necessary for False Pass.
Wind speed/temperature
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Wind Direction
Wind frequency rose data indicates that winds at False Pass are primarily northwest and south with a
lesser component of north winds. The mean value rose indicates that the primary and secondary
frequency winds occur in strength proportional to their occurrence, but interestingly, when infrequenct
east-southeast winds occur, they are very strong. Combining these roses into a wind energy rose, one
can see that the power-producing winds at the False Pass met tower site are predominately northwest
and south, with a lesser degree of northerly winds. Calm frequency (percent of time that winds at the
30 meter level are less than 4 m/s) was a moderately high 35 percent during the test period.
Observing winds on a monthly basis indicates that northwesterly winds mostly occur during the spring
and summer months while northerly and southerly winds mostly occur during the winter months.
Wind frequency rose Mean value rose (30 m B anem.)
Wind energy rose (30 m B anem.) Scatterplot rose of 30 m B wind power density
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Wind density roses by month (common scale)
Turbulence
Turbulence intensity (TI) at the False Pass met tower site indicates unexpectedly turbulent conditions
that are well above IEC 61400-1, 3rd edition (2005) turbulence category A criteria, which is the most
turbulent defined category. This can be seen in the TI graph of anemometer 30 m B at all directions
sectors, and also in TI graphs of isolating the north, south, and northwest direction sectors that
represent the power-producing winds at the site.
With the high turbulence, the False Pass site classifies by IEC 61400-1, 3rd Edition, criteria as Category S,
or special conditions. The 30 meter B anemometer mean TI at 15 m/s is 0.173 and the representative TI
at 15 m/s is 0.232, both of which are quite high and considered generally undesirable for wind turbine
operations.
High turbulence at the met tower test site is almost certainly due to the high mountains that border
Isantoski Strait and that are very near the met tower to the north, west and south. It’s likely that air
flowing more through the center of Isantoski Strait is less turbulent that at the margins near the
mountains, which is the location of the met tower, but that is an academic consideration as it would be
impractical from a wind power siting perspective. Insight into turbulent airflow in the False Pass area
could be aided by use of computational fluid dynamics analysis to predict airflow patterns.
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Turbulence intensity graph, 30 m B, all direction sectors
Turbulence intensity, 30 m B, north sector power-producing winds
Turbulence intensity, 30 m B, south sector power-producing winds
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Turbulence intensity, 30 m A, northwest sector power-producing winds
Turbulence intensity rose, 30 m B
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Turbulence table, 30 m B data, all wind sectors
Bin Bin Endpoints
Records
in Bin Mean TI SD of TI
Representative
TI Peak TI
Midpoint Lower Upper
(m/s) (m/s) (m/s)
1.0 0.5 1.5 9,100 0.583 0.176 0.808 1.571
2.0 1.5 2.5 8,810 0.395 0.185 0.631 1.300
3.0 2.5 3.5 8,736 0.327 0.162 0.534 1.346
4.0 3.5 4.5 9,327 0.287 0.141 0.468 0.972
5.0 4.5 5.5 9,898 0.262 0.121 0.418 0.844
6.0 5.5 6.5 10,680 0.238 0.107 0.374 0.732
7.0 6.5 7.5 10,107 0.221 0.098 0.346 0.682
8.0 7.5 8.5 8,823 0.209 0.086 0.319 0.603
9.0 8.5 9.5 7,264 0.199 0.080 0.301 0.547
10.0 9.5 10.5 5,643 0.196 0.074 0.291 0.510
11.0 10.5 11.5 4,172 0.193 0.068 0.280 0.458
12.0 11.5 12.5 3,287 0.186 0.059 0.262 0.475
13.0 12.5 13.5 2,266 0.181 0.051 0.246 0.418
14.0 13.5 14.5 1,635 0.180 0.050 0.243 0.424
15.0 14.5 15.5 1,135 0.173 0.046 0.232 0.360
16.0 15.5 16.5 732 0.173 0.048 0.235 0.364
17.0 16.5 17.5 475 0.163 0.040 0.214 0.374
18.0 17.5 18.5 280 0.166 0.039 0.215 0.290
19.0 18.5 19.5 143 0.167 0.035 0.212 0.265
20.0 19.5 20.5 86 0.158 0.029 0.195 0.228
21.0 20.5 21.5 53 0.158 0.027 0.193 0.227
22.0 21.5 22.5 26 0.146 0.022 0.175 0.200
23.0 22.5 23.5 11 0.136 0.028 0.172 0.177
24.0 23.5 24.5 2 0.168 0.002 0.171 0.169
25.0 24.5 25.5 2 0.212 0.022 0.240 0.228
26.0 25.5 26.5 0
27.0 26.5 27.5 1 0.185 0.000 0.185 0.185