HomeMy WebLinkAboutAtmautluak_Wind-Data-ReportWind Resource Assessment for
ATMAUTLUAK, ALASKA
Date last modified: 1/5/2007
Compiled by: Cliff Dolchok & James Jensen
SITE SUMMARY
Site #: 1045
Latitude (NAD27): 60˚ 51’ 43.9” N
Longitude (NAD27): 162˚ 16’ 53.6” W
Magnetic Declination: 14˚ 31’ East
Tower Type: 30-meter NRG Tall Tower
Sensor Heights: 30m, 20m
Elevation: 4.3 meters (14 ft)
Monitor Start: 10/21/2005 00:00
Monitor End: 12/4/06 10:50
Atmautluak lies on the west bank of the Pitmiktakik River in the Yukon-Kuskokwim delta, 20 miles northwest of Bethel. Atmautluak is located in the Bethel Recording District. (source:
BearingSea.com)
WIND RESOURCE SUMMARY
Annual Average Wind Speed (30m height): 7.16 m/s (16.0 mph)
Average Wind Power Density (30m height): 451 W/m2
Wind Power Class (range = 1 to 7): 5 Rating (Poor, Marginal, Fair, Good, Excellent, Outstanding, Superb): Excellent
Prevailing Wind Direction: North
In October 2005, a 30-meter meteorological tower was installed in Atmautluak. The purpose of this monitoring effort was to evaluate the feasibility of utilizing utility-scale wind energy
in the community. The meteorological data collected allows us to estimate the potential energy production from various types of wind turbines.
INTRODUCTION
On initial review, the community of Atmautluak appears to be a strong candidate for wind power. The wind resource map below shows that Atmautluak is in close proximity to areas with
wind resource ratings ranging from Class 4 to Class 6. Areas of Class 4 and higher are considered suitable for utility-scale wind power development.
Source: AWS Truewind
Figure 1. Wind Resource Map of Alaska
With support from the Alaska Energy Authority, a 30-meter tall meteorological tower was installed in the village of Atmautluak. The purpose of this monitoring effort was to verify the
wind resource in Atmautluak and evaluate the feasibility of utilizing utility-scale wind energy in the community. This report summarizes the wind resource data collected and the long-term
energy production potential of the site.
SITE DESCRIPTION
The photos below document the meteorological tower equipment that was installed in Atmautluak.
Figure 2. Photos of the Met Tower Installation in Atmautluak, AK
The photos in Figure 3 illustrate the surrounding ground cover and any major obstructions, which could affect how the wind flows over the terrain from a particular direction. As shown,
the landscape surrounding the met tower site is free of obstructions and relatively flat.
SW W NW N
NE E SE S
Figure 3. Views Taken from Met Tower Base
Table 1 lists the types of sensors that were used, the channel of the data logger that each sensor was wired into, and where each sensor was mounted on the tower.
Table 1. Summary of Sensors Installed on the Met Tower
Ch #
Sensor Type
Height
Offset
Boom Orientation
1
#40 Anemometer
30 m
NRG Standard
230˚ True
2
#40 Anemometer
30 m
NRG Standard
90˚ True
3
#40 Anemometer
20 m
NRG Standard
230˚ True
7
#200P Wind Vane
30 m
335˚ True
155˚ True
9
#110S Temperature
2 m
NRG Standard
-
WIND DATA RESULTS FOR ATMAUTLUAK MET TOWER SITE
Table 2 summarizes the amount of data that was successfully retrieved from the data logger at the met tower site. There was a large amount of data loss during March due to icing of
the sensors. A software program called Windographer (www.mistaya.ca) was used to fill the gaps. Windographer uses statistical methods based on patterns in the data surrounding the
gap, and is good for filling short gaps in data. As such, the data from March is the most questionable since Windographer had to fill large gaps in data.
Table 2. Data Recovery Rate for Met Tower Anemometers
Month
Data Recovery Rate
Data Loss Due to Icing
Oct. 2005
98.8%
19
Nov. 2005
85.5%
536
Dec. 2005
98.5%
66
Jan. 2006
94.7%
222
Feb. 2006
99.9%
4
Mar. 2006
27.5%
890
Apr. 2006
87.0%
488
May 2006
97.8%
95
Jun. 2006
100%
0
Jul. 2006
100%
0
Aug. 2006
100%
0
Sep. 2006
100%
0
Oct. 2006
97.7%
102
Nov. 2006
92.4%
302
Dec. 2006
99.6%
2
Wind Speed Measurements
The table below summarizes the wind speed data collected at the Atmautluak met tower site.
Table 3. Summary of Atmautluak Wind Speed Data, 30-meter Height
Annual Average
7.16 m/s
Highest Month
February
Lowest Month
September
Hour of Peak Wind
23
Max 10-minute average
23.1 m/s
Max gust
30.2 m/s
The seasonal wind speed profile shows that the winter months are generally windier than the summer months. The daily wind speed profile shows that wind speeds are typically greater
in the afternoon and evening hours and calmer in the morning. The data that makes up these graphs is listed in Table 4.
Table 4. Estimated Long-Term Wind Speeds at Met Tower Site, 30m Height (m/s)
Hour
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Avg
0
7.1
9.9
9.2
8.5
6.7
6.2
5.9
6.0
5.1
6.8
7.7
8.1
7.3
1
7.2
9.7
8.4
8.5
6.5
6.3
5.9
6.0
5.0
6.9
7.6
8.2
7.2
2
6.9
10.0
7.9
8.4
6.7
6.2
5.9
5.7
5.0
6.8
7.8
8.2
7.1
3
7.0
10.1
7.3
8.7
7.0
6.3
5.7
5.6
5.0
6.6
7.5
8.4
7.1
4
7.1
9.9
8.3
8.5
6.3
6.3
5.9
5.5
5.0
6.5
7.6
8.3
7.1
5
7.1
9.7
9.8
8.4
6.1
6.1
5.9
5.4
5.1
6.6
7.7
8.3
7.2
6
7.1
9.7
9.6
8.2
6.0
6.1
5.8
5.2
5.2
6.7
7.4
8.3
7.1
7
7.0
9.7
10.2
7.9
5.7
6.2
5.6
5.0
4.7
6.5
7.5
8.3
7.0
8
7.2
9.2
10.0
7.9
5.8
6.2
5.6
5.2
4.7
6.5
7.5
8.4
7.0
9
7.1
9.3
9.1
7.9
5.7
6.4
5.6
5.2
4.6
6.3
7.4
8.4
6.9
10
7.0
8.9
8.8
7.8
5.7
6.4
5.7
5.3
4.9
6.4
7.5
8.2
6.9
11
7.2
9.0
9.2
8.0
6.0
6.3
5.7
5.6
4.9
6.4
7.6
8.3
7.0
12
7.2
9.2
10.5
8.1
6.1
6.3
5.9
5.7
4.8
6.6
7.6
8.3
7.2
13
7.3
9.1
9.7
8.4
6.1
6.2
5.9
5.6
5.1
6.7
7.6
8.3
7.2
14
7.2
9.2
9.3
8.7
6.4
6.2
5.7
5.5
5.2
7.0
7.5
8.2
7.2
15
7.4
9.5
9.7
8.2
6.5
6.2
5.7
5.6
5.1
6.9
7.4
8.6
7.2
16
7.3
9.6
9.5
7.6
6.5
6.4
5.9
5.6
5.1
6.6
7.4
8.6
7.2
17
6.8
9.7
9.3
7.5
6.5
6.3
5.9
5.8
5.4
6.3
7.3
8.4
7.1
18
6.8
9.9
10.3
7.6
6.6
6.3
5.9
5.7
5.3
6.2
7.5
8.2
7.2
19
7.0
10.5
10.8
7.6
6.5
6.5
5.7
5.5
5.0
6.4
7.5
8.4
7.3
20
7.0
10.5
10.8
7.6
7.0
6.3
5.7
5.8
5.0
6.6
7.5
8.1
7.3
21
7.1
10.8
10.4
8.0
7.1
6.1
5.7
5.9
5.0
6.6
7.2
8.2
7.3
22
7.1
10.6
9.9
8.1
7.0
5.6
5.6
6.1
5.0
6.7
7.4
8.3
7.3
23
6.9
10.3
10.2
8.6
7.1
5.8
5.7
6.1
5.2
6.6
7.6
8.2
7.4
Avg
7.1
9.8
9.5
8.1
6.4
6.2
5.8
5.6
5.0
6.6
7.5
8.3
7.2
The estimated long-term average wind speed is 7.2 m/s (16.0 mph) at a height of 30 meters above ground level.
Wind Frequency Distribution
A common method of displaying a year of wind data is a wind frequency distribution, which shows the percent of time that each wind speed occurs. Figure 4 shows the measured wind frequency
distribution as well as the best matched Weibull distribution, which is commonly used to approximate the wind speed frequency distribution.
Bin m/s
Hrs/yr
1
72
2
290
3
518
4
728
5
962
6
1020
7
1019
8
952
9
826
10
676
11
487
12
359
13
278
14
190
15
122
16
83
17
60
18
41
Bin m/s
Hrs/yr
19
24
20
16
21
10
22
8
23
4
24
4
25
4
26
2
27
1
28
2
29
1
30
1
31
1
32
0
33
0
34
0
35
0
Total:
8760
Figure 4. Wind Speed Frequency Distribution of Met Tower Data, 30-meter height
The cut-in wind speed of many wind turbines is 4 m/s and the cut-out wind speed is usually 25 m/s. The frequency distribution shows that about 90% of the time the wind in Atmautluak
is within this operational zone.
Wind Direction
Wind power roses show the percent of total power that is available in the wind by direction. The annual wind power rose for the Atmautluak met tower site is shown below.
Figure 5. Annual Wind Power Rose for Met Tower Site
Monthly wind power roses for the Atmautluak met tower site are shown below. The predominant wind direction during the winter months is north, while the summer winds tend to come from
the northwest. The wind rose for March is not accurate due to the large amount of gap filled data.
Figure 6. Monthly Wind Power Roses for Met Tower Site
Turbulence Intensity
Turbulence intensity is the most basic measure of the turbulence of the wind. Typically, a turbulence intensity of around 0.10 is desired for minimal wear on wind turbine components.
As shown in Figure 7, the turbulence intensity from all directions is low and unlikely to contribute to excessive wear of wind turbines.
Dir
Turbulence Intensity
N
0.08
NE
0.10
E
0.09
SE
0.10
S
0.09
SW
0.08
W
0.09
NW
0.07
Ave
0.09
Figure 7. Turbulence Intensity Characteristics of Met Tower Site
Figure 7 plots the average turbulence intensity versus wind speed for the met tower site as well as for Category A and B turbulence sites as defined by the International Electrotechnical
Commission Standard 61400-1, 2nd Edition. Category A represents a higher turbulence model than Category B. In this case, the met tower data is significantly less turbulent than both
categories across the whole range of wind speeds.
Wind Shear
Typically, wind speeds increase with height above ground level. This vertical variation in wind speed is called wind shear and is influenced by surface roughness, surrounding terrain,
and atmospheric stability. The met tower is equipped with anemometers at 20 and 30-meter heights so the wind shear exponent can be calculated and used to adjust the wind resource data
to heights other than those that were measured. Results are summarized below.
Month
Wind Shear
Jan
0.12
Feb
0.26
Mar
0.21
Apr
0.18
May
0.27
Jun
0.11
Jul
0.29
Aug
0.22
Sep
0.29
Oct
0.23
Nov
0.18
Dec
0.14
Ave
0.21
Figure 8. Wind Shear Characteristics of Met Tower Site
As shown, the wind shear varies by month, direction of the wind, and time of day. The average wind shear for the site is 0.21. Typical values range from 0.05 to 0.25. Since 0.21 is
on the high side of “typical” turbine height should have a significant effect on wind power production.
LONG-TERM REFERENCE STATION
The year of data collected at the met tower site can be adjusted to account for inter-annual fluctuations in the wind resource based on long-term measurements at a nearby weather station.
The weather station closest to Atmautluak is the Bethel Airport ASOS, located about 20 miles to the southeast. The hourly measurements from the met tower were not closely correlated
with those from the Bethel airport weather station (correlation coefficient of less than 0.60). Due to the poor correlation between the two sites no adjustments could be made. The
fact that we couldn’t adjust for inter-annual fluctuations in wind speed decreases the confidence in our wind speed estimates. Longer period of monitoring would increase that confidence.
POTENTIAL POWER PRODUCTION FROM WIND TURBINES
Various wind turbines, listed in Table 5, were used to calculate the potential energy production at the met tower site based on the data collected. Although different wind turbines
are offered with different tower heights, to be consistent it is assumed that any wind turbine rated at 100 kW or less would be mounted on a 30-meter tall tower, while anything larger
would be mounted on a 50-meter tower. The wind resource was adjusted to these heights based on the measured wind shear at the site. Also, since wind turbine power curves are based
on a standard air density of 1.225 kg/m3, the wind speeds measured at the met tower site are adjusted to create standard wind speed values that can be compared to the standard power
curves
Results are shown in Table 5. Among the results is the gross capacity factor, which is defined as the actual amount of energy produced divided by the maximum amount of energy that could
be produced if the wind turbine were to operate at rated power for the entire year. Inefficiencies such as transformer/line losses, turbine downtime, soiling of the blades, yaw losses,
array losses, and extreme weather conditions can further reduce turbine output. The gross capacity factor is multiplied by 0.90 to account for these factors, resulting in the net capacity
factor listed.
CONCLUSION
This report provides a summary of wind resource data collected from October 2005 through December 2006 in Atmautluak, Alaska. Both the raw data and the processed data are available
on the Alaska Energy Authority website.
It is a rough estimate that the long-term annual average wind speed at the site is 7.2 m/s at a height of 30 meters above ground level. Taking the local air density and wind speed distribution
into account, the average wind power density for the site is 451 W/m2. This information means that Atmautluak has an estimated Class 5 wind resource, which is “excellent” for wind
power development. The met tower wind data set was used to make predictions as to the potential energy production from wind turbines at the site. The net capacity factor for large
scale wind turbines would range from 24 – 38%.
Table 5. Power Production Analysis of Various Wind Turbine Models
Wind Turbine Options
Manufacturer Information
Bergey
10 kW
Fuhrlander FL30
30 kW
Entegrity 15/50
65 kW
Fuhrlander FL100
100 kW
Northern Power NW100
100 kW
Fuhrlander FL250
250 kW
Vestas
V27*
225 kW
Vestas
V47*
660 kW
Tower Height
30 meters
30 meters
30 meters
50 meters
50 meters
50 meters
50 meters
50 meters
Swept Area
38.5 m2
133 m2
177 m2
348 m2
284 m2
684 m2
573 m2
1,735 m2
Weight
(nacelle & rotor)
N/A
410 kg
2,420 kg
2,380 kg
7,086 kg
4,050 kg
N/A
N/A
Gross Energy Production (kWh/year)
Jan
2,374
11,188
18,740
36,259
29,575
82,121
74,145
248,272
Feb
2,374
11,432
20,290
38,523
31,354
86,292
77,962
256,118
Mar
2,506
11,959
20,609
39,481
32,170
87,654
79,595
263,588
Apr
1,657
7,677
11,686
23,300
19,040
50,789
46,499
162,511
May
1,807
8,349
12,932
25,632
20,950
56,579
51,642
179,533
Jun
1,436
6,686
9,837
19,789
16,153
43,187
39,464
139,897
July
1,250
5,907
8,477
17,139
13,954
40,128
36,619
130,924
Aug
1,791
8,311
12,795
25,407
20,753
62,436
56,969
196,264
Sep
1,910
8,860
14,030
27,645
22,598
67,342
61,685
209,774
Oct
2,071
9,626
15,415
30,273
24,726
70,964
64,580
219,479
Nov
1,892
8,712
13,709
27,106
22,153
63,305
57,723
197,903
Dec
2,165
10,121
16,466
32,146
26,267
73,911
67,079
227,042
Annual
23,233
108,828
174,985
342,696
279,693
784,705
713,961
2,431,302
Annual Average Capacity Factor
Gross CF
27%
41%
30%
39%
32%
36%
36%
42%
Net CF
24%
37%
27%
35%
29%
32%
33%
38%