HomeMy WebLinkAboutWainwright Wind-Diesel Generation Project Wind Resource Report - Aug 2010 - REF Grant 7030013Wainwright Wind Resource Report
Report by: Douglas Vaught, P.E., V3 Energy LLC, Eagle River, Alaska
Date of Report: August 26, 2010
Photo by D. Vaught
Table of Contents
Summary Information...................................................................................................................................2
Test Site Location......................................................................................................................................2
Photographs..................................................................................................................................................4
Data Recovery...............................................................................................................................................4
Wind Speed...................................................................................................................................................5
Time Series................................................................................................................................................6
Daily Wind Profile .....................................................................................................................................7
Probability Distribution Function..............................................................................................................8
Wind Shear and Roughness......................................................................................................................8
Extreme Winds............................................................................................................................................10
Temperature and Density...........................................................................................................................11
Wainwright Wind Resource Report Page 2
Wind Speed Scatterplot..........................................................................................................................12
Wind Direction............................................................................................................................................13
Turbulence..................................................................................................................................................14
Airport ASOS Data.......................................................................................................................................15
Summary Information
The wind resource measured in Wainwright is very good, with measured high wind power class 4 (good)
to low wind power class 5 (excellent). In addition to strong average wind speeds and wind power
density, the site experiences highly directional prevailing winds, low turbulence and calculations indicate
low extreme wind speed probability.
Met tower data synopsis
Data dates June 19, 2009 to July 16, 2010 (13 months)
Wind power class High 4 (good) to low 5 (excellent)
Power density mean, 30 m 413 W/m2 (QC’d data); 392 W/m2 (with synthetic data)
Wind speed mean, 30 m 7.05 m/s (QC’d data); 6.96 m/s (with synthetic data)
Max. 10-min wind speed average 22.2 m/s
Maximum wind gust 25.8 m/s (Feb. 2010)
Weibull distribution parameters k = 2.2, c = 7.97 m/s
Wind shear power law exponent 0.137 (moderately low)
Roughness class 1.51 (crops)
IEC 61400-1, 3rd ed. classification Class III-c (lowest defined and most common)
Turbulence intensity, mean 0.072 (at 15 m/s)
Calm wind frequency 16% (<3.5 m/s)
Community profile
Current Population: 551 (2009 DCCED Certified Population)
Incorporation Type: 2nd Class City
Borough Located In: North Slope Borough
Taxes: Sales: None, Property: 18.5 mills (Borough), Special: None
Coastal Management District:North Slope Borough
Test Site Location
Met tower was installed approximately 500 meters (1,600 ft) northeast of the village of Wainwright,
near the Chukchi Sea shoreline. This site is relatively near the power plant and well exposed to winter
winds with no upwind obstructions.
Site information
Site number 0222
Latitude/longitude N 70° 38.824’ W 160° 00.698’, WGS 84
Wainwright Wind Resource Report Page 3
Site elevation ASL 14 meters (45 ft)
Datalogger type NRG Symphonie, 10 minute time step
Tower type NRG 34-meter tall tower, 152 mm diameter, erected to 30 m
Anchor type 1.5 m screw-in
Google Earth image
Tower sensor information
Channel Sensor type Height Multiplier Offset Orientation
1 NRG #40 anemometer 30 m (A) 0.757 0.39 187°T
2 NRG #40 anemometer 30 m (B)0.757 0.39 273°T
3 NRG #40 anemometer 20 m 0.758 0.35 273°T
7 NRG #200P wind vane 29 m 0.351 359 358° T
9 NRG #110S Temp C 3 m 0.136 -86.383 N
10 RH-5 relative humidity 2 m 0.098 0 S
12 Voltmeter 2 m 0.021 0 n/a
Wainwright Wind Resource Report Page 4
Photographs
Top of met tower; D. Vaught photo Caribou antler in guy wires; D. Vaught photo
Datalogger weather box and PV panel; D. Vaught photo Datalogger with snow in weather box; D. Vaught photo
Data Recovery
Data recovery in Wainwright was mostly acceptable, with 75 to 80 percent data recovery of the
anemometers and wind vane. The exception is the 30 m A anemometer which lost a cup in December
or January. This rendered the sensor useless and all subsequent data was removed from analysis. Note
that data recovery in December and January was particularly poor, apparently due to hoarfrost
conditions during this deep cold period of mid-winter. It is curious that similar data loss was not
observed at the Point Hope met tower during the same time period. Note also that data loss from the
relative humidity (RH) sensor was due to voltage drawdown of the iPack battery during the dark months
of winter (the battered is recharged with photovoltaic panels). Functionality of the RH sensor eventually
recovered after return of daylight in springtime.
Wainwright Wind Resource Report Page 5
Data recovery summary table
Possible Valid Recovery
Label Units Height Records Records Rate (%)
Speed 30 A m/s 30 m 56,489 22,058 39.0
Speed 30 B m/s 30 m 56,489 44,218 78.3
Speed 20 m/s 20 m 56,489 44,806 79.3
Direction 30 ° 30 m 56,489 43,295 76.6
Temperature °C 56,489 56,436 99.9
RH-5 Humidity %RH %RH 56,489 36,673 64.9
Voltmeter volts 56,489 56,489 100.0
Anemometer data recovery
30 m A 30 m B 20 m
Year Month Possible Valid Recovery Valid Recovery Valid Recovery
Records Records Rate (%) Records Rate (%) Records Rate (%)
2009 Jun 1,637 1,621 99.0 1,621 99.0 1,621 99.0
2009 Jul 4,464 4,464 100.0 4,464 100.0 4,464 100.0
2009 Aug 4,464 4,464 100.0 4,464 100.0 4,464 100.0
2009 Sep 4,320 4,310 99.8 4,320 100.0 4,320 100.0
2009 Oct 4,464 3,805 85.2 3,839 86.0 3,864 86.6
2009 Nov 4,320 2,575 59.6 2,578 59.7 2,567 59.4
2009 Dec 4,464 819 18.4 819 18.4 819 18.4
2010 Jan 4,464 0 0.0 1,086 24.3 1,086 24.3
2010 Feb 4,032 0 0.0 3,623 89.9 4,032 100.0
2010 Mar 4,464 0 0.0 2,523 56.5 2,758 61.8
2010 Apr 4,320 0 0.0 4,158 96.3 4,024 93.2
2010 May 4,464 0 0.0 4,240 95.0 4,275 95.8
2010 Jun 4,320 0 0.0 4,223 97.8 4,252 98.4
2010 Jul 2,292 0 0.0 2,260 98.6 2,260 98.6
All data 56,489 22,058 39.1 44,218 78.3 44,806 79.3
Wind Speed
Wind data collected from the met tower, from the perspective of both mean wind speed and mean
power density, indicates an excellent wind resource. The cold arctic temperatures of Wainwright
contributed to the high wind power density. It is problematic, however, analyzing wind data with
significant concentrated data loss, such as occurred in Wainwright during November through January,
then again in March. To correct this problem, synthetic data was inserted in the data gaps to create a
more realistic wind speed data profile. To be sure, long segments of synthetic data introduce
uncertainty to the data set, but missing data does as well. To overcome this uncertainty, improved data
collection with heated sensors would be necessary. But, considering the robust wind resource
Wainwright Wind Resource Report Page 6
measured and noting the long-term airport AWOS data confirming the wind resource measured by the
met tower, continuing a wind study with heated sensors is not truly necessary in Wainwright.
Anemometer data summary
Original data set Synthesized data set
Variable
Speed
30 A
Speed
30 B
Speed
20
Speed
30 A
Speed
30 B
Speed
20
Measurement height (m) 30 30 20 30 30 20
MMM wind speed (m/s)6.82 7.05 6.62 6.96 6.96 6.56
Max 10-min avg wind speed (m/s) 18.4 22.2 21.7 22.2 22.2 21.7
Max gust wind speed (m/s) 22.7 25.8 25.3
Weibull k 2.28 2.20 2.07 2.18 2.18 2.09
Weibull c (m/s) 7.597 7.975 7.512 7.87 7.87 7.41
MMM power density (W/m²) 347 413 358 393 392 339
MMM energy content (kWh/m²/yr) 3,041 3,620 3,135 3,444 3,437 2,973
Energy pattern factor 1.69 1.71 1.79 1.72 1.72 1.78
Frequency of calms (%) 15.6 15.9 19.4 16.4 16.3 19.3
1-hr autocorrelation coefficient 0.941 0.952 0.952 0.947 0.947 0.947
Diurnal pattern strength 0.031 0.031 0.035 0.029 0.029 0.033
Hour of peak wind speed 18 18 17 18 18 17
Time Series
Time series calculations indicate high wind speed averages throughout the year, even during summer.
Note that the October 2009 wind speed average was high compared to September and November. This
likely is a statistical variation that would even out with multi-year data collection. Curiously, the October
2009 wind speed anomaly in Wainwright is opposite to that observed in Point Hope where wind speeds
that month were unusually low compared to September and November 2009.
30m B data summary
Original Data Synthesized Data
Year Month Mean
Max 10-
min
Max
gust Mean
Std.
Dev.
Weibull
k
Weibull
c
(m/s) (m/s) (m/s) (m/s) (m/s) (m/s)
2009 Jun 8.59 12.8 15.1 8.61 2.30 4.60 9.42
2009 Jul 6.66 14.3 17.4 6.66 3.09 2.27 7.49
2009 Aug 6.39 16.7 21.2 6.39 3.04 2.21 7.20
2009 Sep 6.21 18.1 22.7 6.21 3.25 2.01 7.01
2009 Oct 7.68 18.3 22.4 7.80 3.01 2.75 8.78
2009 Nov 5.88 13.9 16.7 6.00 2.54 2.53 6.76
2009 Dec 6.46 17.9 21.2 6.62 3.19 2.17 7.46
2010 Jan 7.78 16.2 18.9 7.19 3.45 2.19 8.11
2010 Feb 7.98 22.2 25.8 8.11 4.52 1.77 9.05
Wainwright Wind Resource Report Page 7
2010 Mar 7.55 18.0 20.4 6.76 3.79 1.78 7.56
2010 Apr 6.27 14.9 17.4 6.19 3.04 2.10 6.96
2010 May 7.48 16.6 18.9 7.32 3.31 2.37 8.26
2010 Jun 7.73 16.5 19.3 7.74 3.29 2.54 8.71
2010 Jul 7.77 12.9 15.9 7.73 2.48 3.57 8.56
MMM annual 7.05 22.2 25.8 6.96 3.34 2.18 7.87
Time series graph
Daily Wind Profile
The daily wind profile indicates a minor variation of wind speeds throughout the day, with lowest wind
speeds during the morning hours and highest wind speeds during late afternoon and early evening
hours. This perspective changes somewhat when considering monthly views of daily profiles as more
variation is observed.
Annual daily wind profile (synth. data)
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
0
2
4
6
8
10 Seasonal Wind Speed Profile
Speed 30 A
Speed 30 B
Speed 20
0 6 12 18 24
0
2
4
6
8 Mean Daily Profile
Hour of Day
Speed 30 A
Speed 30 B
Speed 20
Wainwright Wind Resource Report Page 8
Monthly daily wind profiles (synth. data)
Probability Distribution Function
The probability distribution function (or histogram) of wind speed indicates a near-normal shape curve,
defined as the Raleigh distribution (k=2.0), considered standard for wind power sites.
Wind Shear and Roughness
A wind shear power law exponent of 0.137 indicates moderately low wind shear at the site; hence
turbine construction at a low hub height is possibly a desirable option. Related to wind shear, a
calculated surface roughness of 0.0557 meters (indicating the height above ground level where wind
velocity would be zero) indicates relatively smooth terrain (roughness description: crops) surrounding
the met tower, especially in the direction of the prevailing northeast to east-northeast winds.
0 5 10 15 20 25
0
1
2
3
4
5
6 Probability Distibution Function, All Sectors
Speed 30 B (m/s)
Wainwright Wind Resource Report Page 9
Vertical wind shear profile, wind > 4 m/s
Wind shear by direction sector table, wind > 4 m/s
Time
Steps
Sector
Wind (%)
Mean Wind Speed (m/s)Best-Fit
Power
Law Exp
Best-Fit
Surface
Roughness
(m)Direction Sector Speed 30 B Speed 20
348.75° - 11.25° 2,010 5.6% 6.44 6.05 0.153 0.0351
11.25° - 33.75° 3,232 9.0% 7.11 6.75 0.128 0.0097
33.75° - 56.25° 8,989 25.1% 8.53 8.17 0.106 0.0019
56.25° - 78.75° 7,687 21.5% 8.57 8.18 0.113 0.0035
78.75° - 101.25° 2,356 6.6% 6.33 5.47 0.357 1.4771
101.25° - 123.75° 1,038 2.9% 5.78 5.25 0.239 0.3688
123.75° - 146.25° 796 2.2% 5.47 5.12 0.163 0.0536
146.25° - 168.75° 715 2.0% 5.39 4.86 0.252 0.4622
168.75° - 191.25° 1,042 2.9% 5.30 4.77 0.261 0.5276
191.25° - 213.75° 1,470 4.1% 7.19 6.38 0.296 0.8288
213.75° - 236.25° 1,488 4.2% 7.42 7.02 0.137 0.0162
236.25° - 258.75° 1,547 4.3% 7.71 7.44 0.091 0.0004
258.75° - 281.25° 972 2.7% 6.52 6.28 0.09 0.0003
281.25° - 303.75° 730 2.0% 6.56 6.32 0.092 0.0005
303.75° - 326.25° 644 1.8% 5.62 5.32 0.137 0.0166
326.25° - 348.75° 1,074 3.0% 5.67 5.29 0.172 0.0728
0 2 4 6 8 10
0
20
40
60
80
100 Vertical Wind Shear Profile, All Sectors, 4 - 100 m/s
Mean Wind Speed (m/s)
Measured data
Power law fit (alpha = 0.137)
Log law fit (z0 = 0.0163 m)
Wainwright Wind Resource Report Page 10
Extreme Winds
Although thirteen months of data is minimal for calculation of extreme wind probability, use of a
modified Gumbel distribution analysis, based on monthly maximum winds vice annual maximum winds,
yields reasonably good results. Extreme wind analysis indicates a highly desirable situation in
Wainwright: moderately high mean wind speeds combined with low extreme wind speed probabilities.
This may be explained by particular climactic aspects of Wainwright which include prominent coastal
exposure, offshore wind conditions, and due to the extreme northerly latitude, lack of exposure to Gulf
of Alaska storm winds.
Industry standard reference of extreme wind is the 50 year, 10-minute average probable wind speed,
referred to as Vref. For Wainwright, this calculates to 24.8 m/s, below the threshold of International
Electrotechnical Commission (IEC) 61400-1, 3rd edition criteria (of 37.5 m/s) for a Class III site. Note that
Class III extreme wind classification is the lowest defined and all wind turbines are designed for this wind
regime.
Extreme wind speed probability table
Period (years)Vref Gust IEC 61400-1, 3rd ed.
(m/s) (m/s) Class Vref, m/s
2 19.8 23.9 I 50.0
10 22.3 26.8 II 42.5
15 22.9 27.6 III 37.5
30 24.0 28.8 S designer-
specified5024.8 29.8
100 25.8 31.1
average gust factor:1.20
Extreme wind speed probability graph
16.0
18.0
20.0
22.0
24.0
26.0
28.0
30.0
32.0
0 10 20 30 40 50 60 70 80 90 100
Period, years
Vref
Gust
Wainwright Wind Resource Report Page 11
Temperature and Density
Wainwright experiences cool summers and extremely cold winters. The result is high air density;
calculated air density exceeds standard air density for a sea level elevation (1.225 Kg/m3) by nine
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
Month Mean Min Max Mean Min Max
(°C) (°C) (°C) (kg/m³) (kg/m³) (kg/m³)
Jan -25.1 -40.6 -9.1 1.421 1.334 1.515
Feb -23.1 -43.0 -13.2 1.410 1.355 1.531
Mar -23.7 -41.1 -12.5 1.413 1.352 1.518
Apr -11.9 -33.4 0.3 1.349 1.288 1.469
May -5.3 -19.7 3.2 1.316 1.275 1.390
Jun 4.0 -1.5 19.0 1.272 1.206 1.297
Jul 8.2 0.7 27.2 1.252 1.173 1.286
Aug 6.6 0.9 17.0 1.260 1.214 1.286
Sep 2.1 -9.0 14.3 1.280 1.226 1.334
Oct -3.7 -15.7 5.2 1.308 1.266 1.368
Nov -18.5 -35.1 -6.7 1.384 1.322 1.480
Dec -18.8 -34.3 -0.5 1.386 1.292 1.475
Annual -9.0 -43.0 27.2 1.337 1.173 1.531
Monthly temperature boxplot
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Ann
-60
-40
-20
0
20
40 Monthly Statistics for Temperature
max
daily high
mean
daily low
min
Wainwright Wind Resource Report Page 12
Air density DMap
Wind Speed Scatterplot
The wind speed versus temperature scatterplot below indicates that a substantial percentage of wind in
Wainwright coincides with very cold temperatures, as one would expect given its location on the
Chukchi Sea coast. During the met tower test period, temperatures fell below -40°C on a number of
occasions.
Wind speed versus temperature scatterplot
Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul
0
6
12
18
24 Air Density
1.16
1.20
1.24
1.28
1.32
1.36
1.40
1.44
1.48
1.52
1.56kg/m³
-60 -40 -20 0 20 40
0
5
10
15
20
25 Speed 30 B vs. Temperature, All Sectors
Temperature (°C)
Wainwright Wind Resource Report Page 13
Wind Direction
Wind frequency rose data indicates highly directional winds from northeast to east-northeast. Power
density rose data (representing the power in the wind) indicates power winds are strongly directional,
from 345°T to 025°T and to a lesser extent from 130°T. Calm frequency (percent of time that winds at
30 meter level are less than 3.5 m/s) was 16 percent during the met tower test period.
Wind frequency rose Mean value rose
Wind energy rose Scatterplot rose
Wainwright Wind Resource Report Page 14
Wind density roses by month
Turbulence
Turbulence intensity at the Wainwright test site is well within acceptable standards with an IEC 61400-1,
3rd edition (2005) classification of turbulence category C, which is the lowest defined. Mean turbulence
intensity at 15 m/s is 0.072.
Turbulence intensity, all wind sectors
0 5 10 15 20 25
0.0
0.1
0.2
0.3
0.4
0.5
0.6 Turbulence Intensity at 30 m, All Sectors
Wind Speed (m/s)
Representative TI
IEC Category A
IEC Category B
IEC Category C
Wainwright Wind Resource Report Page 15
Turbulence intensity, northeast (prevailing) wind sector
Turbulence intensity by direction
Turbulence table
Bin
Midpoint
Bin Endpoints
Records
in Bin
Mean
TI
Std
Deviation
of TI
Representative
TI
Peak
TI
Lower Upper
(m/s) (m/s) (m/s)
1 0.5 1.5 1,073 0.347 0.166 0.559 1.167
2 1.5 2.5 2,164 0.160 0.089 0.274 1.235
3 2.5 3.5 3,123 0.109 0.053 0.177 0.536
4 3.5 4.5 3,742 0.090 0.040 0.140 0.389
5 4.5 5.5 4,541 0.081 0.036 0.128 0.563
0 5 10 15 20
0.0
0.1
0.2
0.3
0.4
0.5
0.6 Turbulence Intensity at 30 m, 22.5° - 67.5°
Wind Speed (m/s)
Representative TI
IEC Category A
IEC Category B
IEC Category C
Wainwright Wind Resource Report Page 16
6 5.5 6.5 4,883 0.080 0.032 0.120 0.435
7 6.5 7.5 4,779 0.078 0.029 0.115 0.303
8 7.5 8.5 4,722 0.076 0.027 0.110 0.320
9 8.5 9.5 4,186 0.078 0.023 0.108 0.298
10 9.5 10.5 3,404 0.078 0.021 0.106 0.182
11 10.5 11.5 2,690 0.078 0.021 0.105 0.274
12 11.5 12.5 1,955 0.078 0.019 0.102 0.168
13 12.5 13.5 1,138 0.079 0.019 0.104 0.157
14 13.5 14.5 545 0.073 0.018 0.095 0.148
15 14.5 15.5 401 0.072 0.017 0.094 0.132
16 15.5 16.5 283 0.074 0.016 0.095 0.135
17 16.5 17.5 152 0.075 0.013 0.092 0.127
18 17.5 18.5 82 0.074 0.013 0.092 0.117
19 18.5 19.5 18 0.070 0.008 0.081 0.086
20 19.5 20.5 11 0.071 0.010 0.084 0.090
21 20.5 21.5 2 0.055 0.004 0.061 0.058
22 21.5 22.5 3 0.063 0.002 0.065 0.065
23 22.5 23.5 0
Airport ASOS Data
In 2005, Alaska Energy Authority (AEA) personnel analyzed the wind resource at all Automated Weather
Observing Station (AWOS) and Automated Surface Observing System (ASOS) sites in Alaska. At most
stations, AWOS/ASOS data has been collected for twenty-five or more years. Wainwright Airport (ICAO
station identifier: PAWI) data was first collected in 1973 by an AWOS which was later upgraded to ASOS.
The AEA report documents data from AWOS/ASOS sensor, which is 8 meters above ground level. To
compare this data to the met tower upper sensor height of 30 meters, the data was adjusted using an
exponent extrapolation function with a power law exponent value of 0.142. Comparing to the met
tower 30 meter B anemometer (both the collected data set and the synthesized data set), one can see
that average wind speeds recorded by the met tower are higher than that predicted by the AWOS/ASOS
data. This would account for the higher wind class prediction of the met tower (high Class 4/low Class 5)
over the airport data (low Class 4). There may be a number of reasons for this discrepancy, including
closer proximity of the met tower to the coast and extrapolation errors in translating the eight meter
airport data to thirty meters. Comparison discrepancies aside, the Wainwright airport data confirms the
robust wind resource recorded by the met tower.
Wainwright Wind Resource Report Page 17
Airport/met tower data comparison
Wainwright Airport Met Tower, 30m B anem.
AWOS/ASOS,
8 m sensor
Data adj. to
30 m
Collected
data
Synthesized
data
(m/s) (m/s) (m/s) (m/s)
Jan 5.50 6.64 7.78 7.19
Feb 5.00 6.03 7.98 8.11
Mar 5.30 6.39 7.55 6.76
Apr 5.30 6.39 6.27 6.19
May 5.40 6.51 7.48 7.32
Jun 4.70 5.67 7.97 7.98
Jul 5.10 6.15 7.03 7.02
Aug 5.20 6.27 6.39 6.39
Sep 4.70 5.67 6.21 6.21
Oct 4.90 5.91 7.68 7.80
Nov 4.60 5.55 5.88 6.00
Dec 4.80 5.79 6.46 6.62
Annual 5.04 6.08 7.05 6.97