HomeMy WebLinkAboutAtmautluak Wind-Data-Report 2007
www.akenergyauthority.org/programwind.html Page 1 of 9 December 2006
813 W. Northern Lights Blvd.
Anchorage, AK 99503
Phone: 907-269-3000
Fax: 907-269-3044
www.akenergyauthority.org
Wind 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.
Alaska Energy Authority ATMAUTLUAK, AK Wind Resource Assessment
www.akenergyauthority.org/programwind.html Page 2 of 9 December 2006
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.
Alaska Energy Authority ATMAUTLUAK, AK Wind Resource Assessment
www.akenergyauthority.org/programwind.html Page 3 of 9 December 2006
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 Arial view of equipment on tower
N
NE
E
SE
S
SW
W
NW
CH1, 30m anem
CH2, 30m anem
CH3, 20m anem
Tower
CH7, 30m anem
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 -
Alaska Energy Authority ATMAUTLUAK, AK Wind Resource Assessment
www.akenergyauthority.org/programwind.html Page 4 of 9 December 2006
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
Alaska Energy Authority ATMAUTLUAK, AK Wind Resource Assessment
www.akenergyauthority.org/programwind.html Page 5 of 9 December 2006
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 h ours 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
Alaska Energy Authority ATMAUTLUAK, AK Wind Resource Assessment
www.akenergyauthority.org/programwind.html Page 6 of 9 December 2006
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. T he 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
Alaska Energy Authority ATMAUTLUAK, AK Wind Resource Assessment
www.akenergyauthority.org/programwind.html Page 7 of 9 December 2006
Turbulence Intensity
Turbulence intensity is the most basic measure of the turbulence of the wind. Typically, a turbulence intens ity 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 t han 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. T ypical 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.
Alaska Energy Authority ATMAUTLUAK, AK Wind Resource Assessment
www.akenergyauthority.org/programwind.html Page 8 of 9 December 2006
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 accoun t, 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%.
Alaska Energy Authority ATMAUTLUAK, AK Wind Resource Assessment
www.akenergyauthority.org/programwind.html Page 9 of 9 December 2006
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%