HomeMy WebLinkAboutCity of Bethel Pt. 2Wind Resource Assessment
for Bethel, Alaska
/mc) ALASKA
401= ENERGY AUTHORITY
Wind Resource Assessment for
BETHEL, ALASKA
Date last modified: 2/21/2006
Compiled by: Mia Devine
SITE SUMMARY
Site #: 5334
Latitude (NAD27): 60° 47' 8" N
N 60.7856
Longitude (NAD27): 161' 53' 6" W
W 161.885
Magnetic Declination: 14' 59' East
Tower Type: 50-meter NRG Tall Tower
Sensor Heights: 30m, 40m, 50m
Elevation: 42.3 meters (128 ft)
Monitor Start: 12/9/2004 18:00
Monitor End: 2/12/2006 11:00
In December 2004, a 50-meter meteorological tower was installed on high ground
west of the Bethel airport. The purpose of this monitoring effort is to evaluate the
feasibility of utilizing utility -scale wind energy in the community. The measured
wind speed and direction data at the site was compared to long-term trends in the
area and estimates were calculated for the potential energy production from
various types of wind turbines.
WIND RESOURCE SUMMARY
Annual Average Wind Speed (50m height):
7.3 m/s (16.3 mph)
Annual Average Wind Speed (30m height):
6.7 m/s (15.0 mph)
Average Wind Power Density (50m height):
440 W/mz
Average Wind Power Density (30m height):
345 W/m2
Wind Power Class (range = 1 to 7):
Class 4
Rating (Poor, Marginal, Fair, Good, Excellent, Outstanding): Good
Prevailing Wind Direction:
Northeast
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www.akenergyauthority.org/programwind.html Page 1 of 13 February 2006
Alaska Energy Authority BETHEL, AK Wind Resource Assessment
INTRODUCTION
Previous wind monitoring efforts have been conducted in the Bethel area with less than favorable results. The
equipment used in those studies was mounted on 20-meter towers and were located adjacent to the buildings that
would be served by a wind turbine. The Alaska Energy Authority (AEA) felt that the close proximity to buildings and
the low elevation of the sites resulted in a wind resource that was not representative of the area and that winds
suitable for a utility -scale wind project could be found a short distance outside of town. In December 2004, AEA,
V3Energy, and local residents installed a 50-meter meteorological tower (leased from Chugach Electric) on private
land west of town. This location is more likely to be representative of Bethel's best wind resource area and was
recommended by wind siting meteorologist John Wade. The purpose of this monitoring effort is to 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
Bethel is located near the mouth of the Kuskokwim River, about 40 miles inland from the Bering Sea and 400 air
miles west of Anchorage. Figure 1 shows the location of the met tower relative to the surrounding terrain. The met
tower is located on a ridge at slightly higher elevation than the town site.
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Figure 1. Topographic Map of Met Tower Site and Surrounding Area
www.akenergyauthority.org/programwind.htmi Page 2 of 13 February 2006
Alaska Energy Authority BETHEL, AK
Wind Resource Assessment
The photos below 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.
NW North NE East
SE South SW West
Figure 2. 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
50 m
NRG Standard
20° True
2
#40 Anemometer
50 m
NRG Standard
290° True
3
#40 Anemometer
40 m
NRG Standard
110' True
4
#40 Anemometer
30 m
NRG Standard
280' True
7
#200P Wind Vane
50 m
290° True
110' True
8
#200P Wind Vane
40 m
110* True
290° True
9
#110S Temperature
4 m
NRG Standard
-
N ■ CH1, 50m anem
NW-------- NE ®CH2, 50m anem
■ CH3, 40m anem
W ; E p Tower
CH4, 30m anem
svv",____ SE CHT 50m vane
S 13 CH8, 40m vane
Aerial view of equipment on tower
www.akenergyauthority.org/programwind.htmi Page 3 of 13 February 2006
Alaska Energy Authority BETHEL, AK Wind Resource Assessment
DATA PROCESSING PROCEDURES AND DEFINITIONS
The following information summarizes the data processing procedures that were
performed on the raw measured data in order to create an annual dataset of "typical'
wind speeds, which could then be used to calculate potential power production from
wind turbines. There are various methods and reasons for adjusting the raw data, so
the purpose of these notes is to document what was done in this situation. The raw
data set is available on the Alaska Energy Authority website
(www.akenergyauthority.org) so one could perform their own data processing
procedures. The processed data set is also available.
Units — Since most wind turbine specifications are provided in metric units, those units
are used in this report.
1 meter/second = 2.24 mph = 1.95 knots
1 meter = 3.28 feet
1 °C = 5/9 (°F — 32)
Tower Shadow — The tower itself can affect readings from the anemometer at times when the anemometer is
located downwind of the tower. To avoid this effect, two anemometers were placed at the top level so that neither
would be in the wake of the tower at the same time. One data set is compiled from the 2 anemometers depending
on the direction of the wind at any given time.
Icing — Anomalies in the data can suggest when the sensors were not recording accurately due to icing events.
Since wind vanes tend to freeze before the anemometers, icing events are typically identified whenever the 10-
minute standard deviation of the wind vane is zero (the wind vane is not moving) and the temperature is at or below
freezing. Some additional time before and after the icing event are removed to account for the slow build up and
shedding of ice on the sensors.
Filling Gaps — Whenever measured met tower data is available, it is used. Two different methods are used to fill in
the remaining portion of the year. First, if nearby airport data is available, a linear correlation equation is defined
between the airport and met tower site, and airport data is adjusted to fill the gap. If neither met tower nor airport
data is available for a given timestep, the software program Windographer (www.mistaya.ca) is used.
Windographer uses statistical methods based on patterns in the data surrounding the gap, and is good for filling
short gaps in data.
Long-term Estimates — The year of data collected at the met tower site can be adjusted to account for inter -annual
fluctuations in the wind resource. To do this, a nearby weather station with a consistent historical record of wind
data and with a strong correlation to the met tower location is needed. If a suitable station is not available, there is
a higher level of uncertainty in the wind speed that is measured being representative of a typical year.
Turbulence Intensity — Turbulence intensity is the most basic measure of the turbulence of the wind. Turbulence
intensity is calculated at each 10-minute timestep by dividing the standard deviation of the wind speed during that
timestep by the average wind speed over that timestep. It is calculated only when the mean wind speed is at least
4 m/s. Typically, a turbulence intensity of 0.10 or less is desired for minimal wear on wind turbine components.
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 different heights so that the wind shear exponent, a, can be calculated
according to the power law formula:
(_,.l
a
= H' where H1 and HZ are the heights and v, and vZ are the measured wind speeds.
HZ v2
Wind shear is calculated only with wind speed data above 4 m/s. Values can range from 0.05 to 0.25, with a typical
value of 0.14.
www.akenergyauthority.org/programwind.htm] Page 4 of 13 February 2006
Alaska Energy Authority BETHEL, AK Wind Resource Assessment
Scaling to Hub Height - If the wind turbine hub height is different from the height at which the wind resource is
measured, the wind resource can be adjusted using the power law formula described above and using the wind
shear data calculated at the site.
Air Density Adjustment - The power that can be extracted from the wind is directly related to the density of the
air. Air density, p, is a function of temperature and pressure and is calculated for each 10-minute timestep
according to the following equation (units for air density are kg/m3):
_ P
P RxT
Where P is pressure (kPa), R is the gas constant for air (287.1 J/kgK), and T is temperature in Kelvin. Since air
pressure is not measured at the met tower site, the site elevation is used to calculate an annual average air
pressure value according to the following equation:
P = 1.225 - (1.194 x 10-4) x elevation
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. The adjustment is made according to the following formula:
i
3
_
Vs tan Bard - Vmeasured x Pmeasured
Ps tan dard
Wind Power Density - Wind power density provides a more accurate representation of a site's wind energy
potential than the annual average wind speed because it includes how wind speeds are distributed around the
average as well as the local air density. Units of wind power density are watts per square meter and represent the
power produced per square meter of area that the blades sweep.
Wind Power Class - A seven level classification system based on wind power density is used to simplify the
comparison of potential wind sites. Areas of Class 4 and higher are considered suitable for utility -scale wind power
development.
Classes of Wind Power Density
mSpeed
Class
Rating
(W )
WPD /m^2
(m/s)
yWpp A30m
(W/m 2)
Speed (m/s)
WPD (1N/m 2)
'2)
Speed (m/s)
1
<100
<4.4
<160
<5.1
<200
<5.6
Poor
2
100 - 150
4.4 - 5.1
160 - 240
5.1 - 5.8
200 - 300
5.6 - 6.4
Marginal
3
150 - 200
5.1 - 5.6
240 - 320
5.8 - 6.5
300 - 400
6.4 - 7.0
Fair
200 - 250
5.6 - 6.0
320 - 400
6.5 - 7.0
400 - 500
7.0 - 7.5
Good
250 - 300
6.0 - 6.4
400 - 480
7.0 - 7.4
500 - 600
7.5 - 8.0
Excellent
300 - 400
6.4 - 7.0
480 - 640
7.4 - 8.2
600 - 800
8.0 - 8.8
Outstanding
>400
>7.0
>640
>8.2
>800
>8.8
Weibull Distribution - The Weibull distribution is commonly used to approximate the wind speed frequency
distribution. The Weibull is defined as follows:
k_v1k
P(v) c (CV)k-'
exp( c
Where P(v) is the probability of wind speed v occurring, c is the scale factor which is related to the average wind
speed, and k is the shape factor which describes the distribution of the wind speeds. Typical k values range from
1.5 to 3.0, with lower k values resulting in higher average wind power densities.
www.akenergyauthority.org/programwind.html Page 5 of 13 February 2006
Alaska Energy Authority BETHEL, AK Wind Resource Assessment
LONG-TERM REFERENCE STATION
Wind data from the Bethel airport weather station, located 2.5
miles east of the met tower site, serves as a long-term reference
for the wind resource in the area. Data is measured at a height of
10 meters above ground level and an elevation of 37.5 meters.
The National Weather Service upgraded the meteorological
monitoring equipment at the Bethel airport to an Automated
Surface Observing System (ASOS) on November 1, 1998. This
new equipment, although more accurate, represents a
discontinuity in the long-term wind speed record. Therefore,
this report is based on measurements beginning January 1, 1999.
1 I ,
3,
Figure 3. ASOS Equipment in Bethel
Hourly wind speed measurements from the Bethel airport weather station that are concurrent with recordings from
the met tower site were purchased from the National Climatic Data Center. The correlation coefficient between
these sites is 0.87 (a value of 1 is perfect). This suggests that, although the actual wind speed values at the two
sites are different, the pattern of wind speed fluctuations is similar between the sites. Any historical patterns in the
airport station data can also be applied to the met tower site with a high degree of certainty.
As shown in Table 2 and Figure 4, the area has a strong seasonal pattern, with greater wind speeds in the winter
months than the summer months. The long-term annual average wind speed at the Bethel airport site is 5.2 m/s,
which is fairly consistent, fluctuating up to 3% from year to year.
Table 2. Monthly Average Wind Speeds at Bethel Airport, 10-meter height (m/s)
Year
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Ave
% of Long -
Term Ave
1999
7.0
4.5
5.8
5.6
4.7
4.0
4.9
4.3
4.7
4.4
5.5
5.7
5.1
99%
2000
6.6
5.0
5.3
5.0
4.3
4.0
4.4
5.2
4.6
4.7
6.2
6.4
5.2
100%
2001
5.4
5.8
6.2
5.9
5.2
4.7
4.5
4.6
4.3
5.0
5.0
5.2
5.2
100%
2002
6.5
6.1
5.2
6.5
4.8
4.2
4.0
4.3
5.3
5.6
5.3
4.7
5.2
101 %
2003
6.3
5.5
7.0
5.5
4.5
4.5
4.9
4.1
4.4
4.8
5.3
4.9
5.2
100%
2004
6.3
6.2
5.2
4.6
4.7
4.3
3.8
4.2
4.2
5.6
6.2
5.8
5.1
98%
2005
7.4
5.2
5.7
5.0
4.6
4.1
4.3
4.8
5.9
4.5
6.3
6.0
5.3
103%
Ave
1 6.5
5.5
5.8
5.5
4.7
4.3
4.4
4.5
4.8
5.0
5.7
5.5
5.2
100%
1999 26" 2001 2002 2003 2004 2005
,sss z000 2= zooz 2oa3 zoo, Zoos
Figure 4. Monthly and Annual Average Wind Speeds at Bethel Airport, 10-meter height
www.akenergyauthority.org/programwind.htmi Page 6 of 13 February 2006
Alaska Energy Authority BETHEL, AK Wind Resource Assessment
According to the ASOS data, the average
12
wind speed in the year 2005 was 3%
greater than the long-term average.
10
Therefore, the wind speed data recorded
`.
8
at the met tower site during the year 2005
was adjusted downwards by 3% to more
6
accurately reflect what would be expected
over the long term. Both measured and
4
long-term data sets at the airport and met
E
tower sites are shown in Figure 5.
2
Measured Met Tower Data (50m height)
�-Longterm Met Tower Estimate
Measured Airport Data (10m height)
Extreme wind speeds recorded at the 0 -m-Longterm Airport Data 0.0
Bethel ASOS are summarized in Table 3. Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
The fastest mile is defined as the speed of
one mile of wind that passes the weather Figure 5. Measured Versus Long -Term Wind Speeds in Bethel
station and can be considered as the maximum sustained wind speed. The fastest mile recorded over a 41-year
period was 27.7 m/s in February 1951. The peak gust over a 16-year period was 34.4 m/s in October 1992.
?2
22.4
17.9 E
13.4 d
n.
Cn
8.9
Table 3. Extreme Wind Speeds in Bethel, 10m height (source: Western Regional Climate Center)
Airport Fastest Mile (1957-1998
Month
m/s
mph
;_ Year
Jan
24.1
54
1979
Feb
27.7
62
1951
Mar
21.9
( 49
( 1977
19.7
I 44
1979 _
May_
18.3
41
1960
Jun
19.2
( 43
( 1978
Jul
17.9
40
1974
Aug
20.6
46
1978
Sep_24.6
( 55
1960
Oct
23.2
52
1992
Nov
26.8
60
1958
_
Dec
_
25.9
58
( 1977
Airport Peak Gust (1982-1998
m/s
mph
Year
27.3
61
1993
26.4
59
1988
25.0
56
1991
22.8
51
1995
23.7
53
1985
_
26.4
59
1980
20.6
46
1982
25.0
56
1994
30.8
69
1982
34.4
77
1992
29.5
66
1990
29.9
67
( 1982
4.5 �:
The air temperature can affect wind power production in two primary ways: 1) colder temperatures lead to higher air
densities and therefore more power production, and 2) some wind turbines shut down in very cold situations
(usually around-250C). The monthly average temperatures for Bethel are shown below. Typically, the
temperature drops below -25°C during 2% of the year, or 185 hours per year.
Measured (met tower) - - Long -Term (airport)
20
v 15T
a) 10
E-
-15
(0 N M Q 75 0) 0 U o N
v_ 2 Q Q cn O Z o
Month
Measured (°C) ;
Long -Term (°C)
Jan
-12.4
-12.7
Feb
-10.4
-8.0
Mar
-8.2
-8.8
-7.0
-2.2
_-Apr
May
7.3
5.3
Jun
13.3
12.6
Jul
13.8
13.1
Aug
12.7
12.3
Sep
8.1
7.0
Oct
-1.2
-0.5
Nov
-14.6
-7.5
Dec
-10.8
-12.6
Ave
-0.8
-0.2
www.akenergyauthority.org/programwind.htmI Page 7 of 13 February 2006
Alaska Energy Authority BETHEL, AK Wind Resource Assessment
WIND DATA RESULTS FOR BETHEL MET TOWER SITE
Table 4 summarizes the amount of data that was successfully retrieved from the data logger at the met tower site.
There was significant data loss during the winter months due to icing of the sensors, particularly in November,
December and February. The airport ASOS data was used to fill these gaps where possible. The remaining gaps
were filled with Windographer.
Table 4. Data Recovery Rate for Met Tower Anemometers
Month
Data Recovery Rate
Data Loss Due to Icing
January2005
100%
11%
February 2005
100%
34%
March 2005
100%
8%
April 2005
100%
6%
May 2005
100%
2%
June 2005
100%
0%
July 2005
100%
0%
August 2005
100%
0%
September 2005
100%
0%
October 2005
100%
16%
November 2005
100%
31 %
December 2005
100%
54%
Annual Average
100%
13%
Wind Speed Measurements
The wind resource was measured at various heights on the tower. Results from the 50-meter and 30-meter heights
are summarized below. More details of the 50-meter level are shown in Table 6.
Table 5. Measured and Lona-Term Average Monthly Wind Sneeds at Met Tower Site
Wind Speeds (m/s)
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Ave
50m Height, Measured
10.7
7.9
8.5
7.0
5.9
5.3
5.5
6.6
8.3
6.9
8.8
9.1
7.5
50m Height, Long-term
9.4
8.3
8.7
7.6
6.0
5.5
5.6
6.2
6.7
7.6
7.9
8.4
7.3
30m Height, Measured
10.0
7.0
7.7
6.2
5.4
4.9
5.1
6.1
7.5
6.1
7.8
8.3
6.9
30m Height, Long-term
8.8
7.4
7.8
6.8
5.5
5.1
5.2
5.7
6.1
6.8
7.0
7.6
6.7
The seasonal wind speed profile shows that the highest wind month is January and the lowest wind month is June.
The daily wind speed profile shows that wind speeds are typically greater in the afternoon and evening hours and
calmer in the morning.
t
N
2
A
Q
8. Daily Wind Profile
- T
4
2
n
- 12
J F M A M J J A S O N D� 0 Hour o1 Day1S 24
Figure 6. Seasonal and Diurnal Wind Speed Profile for Met Tower Site, Long-term Estimate
- Longterm 50m Height
Longterm 30m Height
www.akenergyauthority.org/programwind.htm] Page 8 of 13 February 2006
Alaska Energy Authority BETHEL, AK Wind Resource Assessment
Table 6. Estimated Long -Term Wind Speeds at Met Tower Site, 50m Hei ht (m/s)
Hour
Jan
Feb
Mar
Apr
May
Jun
Jul
AugSep
Oct
Nov
Dec
Avg
0
9.6
8.5
8.8
8.1
6.4
6.0
6.8
6.4
6.8
7.8
8.1
8.4
7.6
1
9.4
8.5
8.7
8.0
6.3
6.0
6.4
6.2
6.5
7.8
7.9
8.3
7.5
2
9.5
8.4
8.6
8.0
6.0
5.9
5.9
6.0
6.4
7.8
7.7
8.8
7.4
3
9.5
8.2
8.4
8.0
6.0
5.8
5.8
5.9
6.5
7.8
7.8
8.7
7.4
4
9.5
8.5
8.7
7.9
6.0
5.6
5.6
5.8
6.5
7.5
7.8
8.5
7.3
5
9.3
8.4
8.8
8.1
5.9
5.4
5.3
6.0
6.5
7.4
7.7
8.3
7.3
6
9.1
8.2
8.7
7.9
5.7
5.0
5.2
5.8
6.4
7.4
7.9
8.3
7.1
7
9.3
8.0
8.7
7.9
5.2
4.7
4.8
5.6
6.3
7.6
7.9
8.3
7.0
8
9.3
8.2
8.6
7.5
5.0
4.7
4.8
5.6
6.3
7.9
7.9
8.5
7.0
9
9.2
8.5
8.7
7.1
5.1
4.8
5.1
5.8
6.3
7.7
8.1
8.4
7.1
10
9.3
8.1
8.9
6.7
5.6
5.0
5.0
6.1
6.7
7.4
8.3
8.2
7.1
11
9.4
8.1
8.8
6.5
5.8
5.2
5.1
6.4
6.9
7.4
8.3
8.1
7.2
12
9.3
8.2
8.8
6.7
5.9
5.3
5.3
6.4
6.9
7.6
8.1
8.2
7.2
13
9.3
8.4
8.6
7.0
6.0
5.3
5.2
6.6
7.2
7.4
7.8
8.2
7.3
14
9.3
8.4
8.4
7.1
6.1
5.3
5.3
6.7
7.3
7.5
7.7
8.7
7.3
15
9.6
8.3
8.7
7.3
6.1
5.4
5.7
6.7
7.0
7.6
7.7
8.3
7.4
16
9.6
8.2
8.7
7.3
6.4
5.6
6.0
6.6
7.0
7.3
7.8
8.3
7.4
17
9.7
8.3
8.6
7.6
6.7
5.7
5.8
6.6
6.9
7.3
7.8
8.3
7.4
18
9.5
8.3
8.3
7.7
6.5
6.0
6.0
6.6
6.8
7.5
8.0
8.7
7.5
19
9.5
8.4
8.5
7.9
6.2
6.0
6.1
6.3
6.7
7.6
8.1
8.7
7.5
20
9.3
8.1
8.8
8.0
6.3
6.0
5.7
5.9
6.7
7.7
7.9
8.4
7.4
21
9.3
8.0
8.8
8.2
6.6
5.9
5.7
6.1
6.7
7.9
7.9
8.3
7.4
22
9.6
8.1
8.8
8.1
6.6
6.0
6.0
6.4
6.8
8.2
7.9
8.7
7.6
23
9.4
8.2
8.6
8.2
6.4
6.2
6.4
6.3
7.0
8.0
8.1
8.6
7.6
Avg
9.4
8.3
8.7
7.6
6.0
5.5
5.6
6.2
6.7
7.6
7.9
8.4
1 7.3
The estimated long-term average wind speed is 7.3 m/s at a height of 50 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 7 shows the measured wind frequency distribution as well as the best
matched Weibull distribution.
\1
0
Probabilitv Distibution Function
0 5 10 15 20 25 30
Longterm 50m Height (m/s)
Actual data - Best -fit Weibull distribution (k=2.31, c=8.27 m(s)
Figure 7. Wind Speed Frequency Distribution of Met Tower Data, 50-meter height
Bin m/s
Hrs/yr
0
60
1
151
2
396
3
722
4
880
5
989
6
1,086
7
1,073
8
942
9
772
10
572
11
365
12
262
13
170
14
103
Bin m/s
Hrs/yr
15
78
16
58
17
27
18
15
19
9
20
8
21
8
22
4
23
3
24
3
25
2
26
2
27
1
28
1
29
0
iotar u,fbu
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 a large percentage of the wind in Bethel is within this operational zone.
www.akenergyauthority.org/programwind.html Page 9 of 13 February 2006
Alaska Energy Authority BETHEL, AK Wind Resource Assessment
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 met tower site is compared to the airport site in Figure 8. The met tower site is based on one year of
data, while the airport site is based on seven years of data. The correlation coefficient between the sites is 0.97.
The predominant wind direction at both locations is northeast.
Met Tower Site (2005) Airport Site (1999-2005)
N N.
NW,"
NE NW NE
W = W
8%
SW 16:/ SE 10.%
SW,, SE
24 % 15 %
S S
Figure 8. Annual Wind Power Roses for Met Tower Site and Airport Site
Monthly wind power roses for the met tower site are shown below. The strong winter winds come from the
northeast, while the lighter summer winds tend to come from the south.
Jan Feb Mar Apr
_ N _ __ N
-5i- -5-...-
1....E NW'. �` +i i•NE
w-'+" E _ 4-n* r-�•, �, -•- E E E
�
If �t
SW _ /$E SW. ' \, _SE Sw ( y $E S f t SE
S S S S
May JuNn Jut Aug
ry1Kak- t (`CIE ��` ;5 eft"'NEE /NUf i ���j`� tf ��NE
y�E E ylY� E ``
ISE E 511f'' 1+ �"- .trs SE
8 S
Sep Oct Nov Dec
�4\f NE Mj/� ,,r''� R�E �y�`�, '[ PIE MISG^>l "-� -`IE
W f Y E E E iE
1 Y- � _ •� Ir- - i t
k ? 4
` rz E ��y t'�i'$E S Y �jE'C ! t SE
` i
S _ -- S
Figure 9. Monthly Wind Power Roses for Met Tower Site
www.akenergyauthority.org/programwind.html Page 10 of 13 February 2006
Alaska Energy Authority BETHEL, AK Wind Resource Assessment
Turbulence Intensity
Various turbulence intensity characteristics are shown in Figure 10. The turbulence intensity from all directions and
for all months is low and unlikely to contribute to excessive wear of wind turbines.
Month
Turbulence
Intensity
Jan
0.06
Feb
0.06
Mar
0.06
Apr
0.07
May
0.12
Jun
0.14
Jul
0.13
Aug
0.11
Sep
0.10
Oct
0.08
Nov
0.06
Dec
0.06
Ave
0.09
Tubuhwwa IntwoRy By Direction
>,0 I1!0
60
a
�0
0 6 10 16 20 26 30
Wuxi Speed (m/s)
—Data — IEA CategoryA IEA Category B
Figure 10. Turbulence Intensity Characteristics of Met Tower Site
Figure 10 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, 2"d Edition.
Category A represents a higher turbulence model than Category B. In this case, the met tower data is less
turbulent than both categories across the whole range of wind speeds.
Wind Shear
Wind shear was calculated between the 50-meter anemometer and the 30-meter anemometer, and results are
summarized in Figure 11.
Month
30m to 50m
Wind Shear
Jan
0.11
Feb
0.26
Mar
0.23
Apr
0.23
May
0.18
Jun
0.17
Jul
0.16
Aug
0.19
Sep
0.18
Oct
0.23
Nov
0.18
Dec
0.23
Ave
0.19
Average of 30-50m Shear
Figure 11. Wind Shear Characteristics of Met Tower Site
Hour
The average wind shear for the site is 0.19. As shown, the wind shear varies by month, direction of the wind, and
time of day. These wind shear values can be used to adjust the wind resource data to heights other than those that
were measured and reported here, as described previously in the Data Processing Procedures and Definitions
section.
www.akenergyauthority.org/programwind.htmI Page 11 of 13 February 2006
Alaska Energy Authority BETHEL, AK Wind Resource Assessment
Various wind turbines, listed in Table 7, were used to calculate the potential energy production at the met tower site
based on the long-term wind resource data set. 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. The wind resource was also adjusted to standard air
density.
Results are shown in Table 7. 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 December 2004 through January 2006 in
Bethel, Alaska. The data was compared to long-term trends in the area and, based on correlations with the Bethel
airport weather station, estimates were made to create a long-term dataset for the Bethel met tower site. This
information was used to make predictions as to the potential energy production from wind turbines at the site.
It is estimated that the long-term annual average wind speed at the site is 7.3 m/s at a height of 50 meters above
ground level and 6.7 m/s at a height of 30 meters. Taking the local air density and wind speed distribution into
account, the average wind power density for the site is 440 W/mz. This information means that Bethel has a
Class 4 wind resource, which is "good" for wind power development. The net capacity factor for large scale wind
turbines would range from 21 — 36%.
www.akenergyauthority.org/programwind.htmi Page 12 of 13 February 2006
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Bethel City Shop Wind Energy Project
The Installation and Operation
of a NorthWind 100: A Feasibility Study
keILKtrk Power SystemsC
onsultingg Engineers
Bethel City Shop Wind Energy Project
The Installation and Operation of a NorthWind 100
A I-
H reasiblilLy study
February 10, 2008
Daniel C. Rogers, P.E.
Ryota Abe
Bethel City Shop Wind Energy Project
NW100 Feasibility Study
Table of Contents
1 Introduction.......................................................................................................................1
1.1 History........................................................................................................................1
1.2 Project Description....................................................................................................1
2 Project Technology and Methodology.............................................................................2
2.1 Turbine/Generator.....................................................................................................2
2.2 Operation and Maintenance......................................................................................2
3 Financial............................................................................................................................3
3.1 Assumptions and Sources of Data...........................................................................3
3.2 Financial Summary....................................................................................................5
4 Conclusions......................................................................................................................5
5 Appendix A — Area Map....................................................................................................6
6 Appendix B — AEA Wind Resource Assessment............................................................7
7 Appendix C — Economic Assessment Supporting Data/Correspondence ....................8
City of Bethel Wind Energy Project
NW100 Feasibility Study
Introduction
In order to provide lower cost alternatives for power consumers in Bethel, the City of Bethel
("COB") has been investigating the feasibility of becoming an independent power producer and
sending electricity generated from wind into the Bethel utility grid. The City invited the local
utility, Bethel Utilities Corporation, ("BUC"), to participate in its endeavor by attending monthly
alternative energy committee meetings, providing information to energy consultants, and
endorsing a small wind turbine project in Bethel.
1.1 History
Bethel, like other rural Alaska hub communities, has relied solely on diesel generation for the
generation of electrical energy. With the increases in cost, both in the base price of fuel and in
the costs of transportation to rural Alaska, communities such as Bethel have seen costs of
electricity escalate.
In order to actively pursue alternatives to diesel generation, the COB hired Electric Power
Systems, Inc. ("EPS") to assist them in analyzing the viability and financial return for various
wind systems. Additionally, the COB, with assistance from the Alaska Energy Authority ("AEA"),
installed a met station in Bethel and logged wind data for the community. According to the
report from AEA, the wind regime was favorable at the met site for wind generation. In
subsequent e-mails, AEA reported that the wind regime captured at the "Rodgers" site could be
generalized to the Bethel area, and in particular, to the City Shop area near the Bethel landfill
and sewer lagoons.'
The COB is continuing to investigate low, medium, and high penetration wind systems, but the
non -firm nature of the higher penetration systems is cause for concern with BUC. While still
considering options for higher penetration systems, the City of Bethel has directed EPS to
pursue a low penetration system option at the City Shop area.
1.2 Project Description
The Bethel City Shop Wind Energy Project calls for the purchase of one 100 kilowatt wind
turbine and tubular tower and installing the tower near the City Shop. The wind turbine and
tower pieces would be manufactured and barged to Bethel from either Seattle or Anchorage.
The Port of Bethel and City's Public Works Department would assist in the transportation of the
turbine and tower pieces to the site, if needed.
The City Shop location was chosen as a site for a 100 kW wind turbine for the following
reasons:
1. Ideal location north of town, away from homes, business buildings, and
infrastructure that could cause distortion in the wind patterns. See the maps attached in
Appendix A.
2. Few residents live within 600 feet of the proposed installation site. The occupants
of six houses will be contacted for their comments on the installation of a wind turbine
tower near their homes.
3. Two large City sewer lagoons are due north of the proposed wind tower site,
making for a flat surface over which wind can travel on its way to the turbine. The City's
strongest winds come from the northeast in the winter time. See Wind Resource
Assessment attached in Appendix B.
' Email from Martina Dabo, AEA Wind Energy Manager.
February 10, 2008 Page 1 Pk* Power S ts�
CLS C--Mv angft— "
City of Bethel Wind Energy Project
NW100 Feasibility Study
4. Proximity of the sewer lagoons and landfill farther north make it unlikely that
residents of Bethel will build homes or businesses close to the site.
5. The City Shop houses the City's property maintenance crew, their tools, and
equipment. The crew will be responsible for operating and maintaining the wind turbine.
6. The City Shop contains heavy equipment (e.g., dump trucks, front-end loaders,
grader) that can be used in the construction of the project and to help maintain the
integrity of the sand pad, foundation, and cable trench.
2 Project Technology and Methodology
2.1 Turbine/Generator
Several wind turbine manufacturers make 100 kW wind turbines or wind turbines in a size range
of 90 kW -120 kW. A wind turbine at or near 100 kW in size is acceptable to the COB and will
accomplish the goal of this project. For the purposes of this analysis, the Northwind 100
("NW100") wind turbine generator was used as the model machine. Figures and calculations
contained in this application are based on the purchase, shipping, installation, and operation of
the NW100, manufactured by Distributed Energy Systems (DES). A quote to purchase and
install a Northwind 100 wind turbine and tower was provided by Distributed Energy Systems and
construction company STG. The actual purchase and installation cost may vary, especially if the
bidding process is used. The STG design/supply/construct quote is included in Appendix C.
The City intends to purchase and install a single 100 kW wind turbine with all associated
hardware and software. The turbine nacelle includes the hub, generator, mainframe, nacelle
cover, and power conversion equipment. The City intends to purchase one 37 meter tubular
tower and associated apparatus to allow for its permanent installation. The wind turbine will
have a 21 meter rotor. There will be a power converter and electrical/control interface at the
base of the tower. The SmartView Monitoring System, a web -based remote monitoring system,
comes with the purchase. A tubular steel monopole tower will be used to support the wind
turbine.
The NW100 installation will be separately metered, and will provide power directly to the BUC
grid. Variations in output power of the single NW100 will have negligible effects on the
regulation of the BUC system.
2.2 Operation and Maintenance
The City of Bethel plans to have all four of its Property Maintenance personnel trained to
operate and maintain the wind turbine. The City may train other Public Works Department
employees who work in the City Shop in order to have knowledgeable people on staff in case of
absences and attrition. A goal of this project is for City personnel to be sufficiently trained such
that the City personnel will not only be able to support the operations and maintenance of the
Bethel units, but also be available as a regional resource for the other units installed in the
Yukon -Lower Kuskokwim region.
Wayne Ogle, COB Public Works Director, will be responsible for insuring that one or more of his
subordinates in the Public Works Department are performing the necessary operations and
monitoring tasks during daily turbine operation. The Public Works Department is open six days
t?�
SYS76M5
City of Bethel Wind Energy Project
NW100 Feasibility Study
a week, Monday through Saturday, 7 am to 5 pm. On Sunday, the turbine's operation will be
monitored using the Smart View Monitoring System. This system will allow a Public Works
employee to monitor the operation of the system from his or her home computer with internet
access. Mr. Ogle will also be responsible for the proper corrective and preventative
maintenance necessary for the Bethel Wind system.
3 Financial
3. 1 Assumptions and Sources of Data
The following general financial parameters are assumed for this analysis:
Internal Economic Factors
Project ROI 3.0%
Project Life 30
Table 1 — Internal Economic Factors
Table 2 is the result of developing a spreadsheet to calculate the economic viability of the COB
wind project. The assumptions for figures used in Table 2 are enumerated below. Backup
material for these assumptions is contained in Appendix C.
• Installed "turnkey" Price — $799,554, per STG quote. Received from COB/John
Sargent on 2/8/08 via email.
• Annual Energy Production — 260,000 kWh annually, per email Message from
DES/Brett Pringree to COB/John Sargent. Received from COB 2/9/08.
• Price per kWh (paid by BUC) - $0.3253 per kWh, per BUC quarterly filing with the
Regulatory Commission of Alaska. Note that the 2004 filing is also included, in order to
get a sense of the increase seen by Bethel consumers in recent history.
• Insurance - $31,982 annually, per Brown quote to COB, received from John Sargent on
2/8/08 via e-mail.
• Annual Maintenance - $6,700 annually, per a 2006 DES bid to COB.2
• Annual Insurance Deductible Account — $2500. A holding account to anticipate
catastrophic damage to the unit. Costs have been included in the estimate for an
insurance policy with a $25K deductible. A ten year event recurrence has been
assumed, and this account would be utilized to cover the deductible should an insurable
event occur.
2 No inflation of this figure was included in the analysis, as it is assumed that any increase in maintenance
due to inflation will be offset by increased income due to an increased avoided cost of power, which is
ultimately due to an increase in fuel prices. Historical increases in avoided cost (income to COB) for the
period from 2005 — 2007 averaged 14%, based on BUC's filings with the RCA (included in Appendix C).
February 10, 2008 Page 3 Pkctrk Power S
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City of Bethel Wind Energy Project
NW100 Feasibility Study
3.2 Financial Summary
The financial analysis shown in Table 2 above illustrates the relative, as well as absolute, costs
and benefits of the NW 100, or similar, wind system in Bethel. Note that the analysis is based
on COB's perspective, relative to the amount of investment that is required by the COB.
The financial analysis for all of the cases are run and analyzed based on an annual return.
Initial capital costs are converted to an annual sum of payments, based on the project life (30
years) and the Project ROI (3%). This cost (Annualized Debt Service), in addition to the
annually recurring O&M cost of the project (Subtotal - Annual recurring Project Expenses
(O&M)) are compared to the income generated from the project by sales to the local utility at
their avoided fuel cost (Subtotal - Annual Income from Energy Production). In all three
cases examined, the project shows a positive rate of return, and a benefit to cost ratio ("BCR")
in excess of 1.0, indicating a beneficial project.
In the "COB Only" case, it is assumed that 100% of investment dollars for the project are
provided by the COB. In this case, and given the assumptions discussed above, the project
generates revenue annually in excess of the cost of debt service plus O&M of approximately
$2600. For the two cases where the COB has subsidized participation by AEA/Denali or
AEA/Denali and USDA, the positive annual economic value to the COB increases, as does the
project BCR.
4 Conclusions
The installation of a wind turbine system similar to the NW100 by the City of Bethel, given the
parameters and assumptions outlined in this document provides a positive benefit to the City of
Bethel. The project reduces the number of gallons of diesel burned to generate power in the
community, will not negatively impact the operation of the BUC system, and utilizes technology
that is becoming relatively common in rural Alaska.
The annual number of gallons of diesel fuel expected to be displaced by the implementation of
the Bethel City Shop Wind Energy Project is 21,541. Over the life of the wind turbine and tower,
646,230 gallons of diesel fuel will be displaced.
The City of Bethel is committed to undertaking the installation of a small wind turbine in the
community, with a vision of adding additional wind energy production as the viability of the
technology, and assumptions regarding the financial performance of that technology, is proven.
Additionally, it is the COB's vision to act as a regional hub of rural wind power expertise, so as
to promulgate the technology regionally throughout the Lower Yukon-Kuskokwim region, similar
to the role that Kotzebue Electric is performing in Northwest Alaska.
As discussed above, given the high price of electricity in rural Alaska, the project is
economically justified, even given 100% COB participation. Given the likelihood that fuel prices
will continue to rise in rural Alaska, the return on investment could ultimately outperform the
analysis above.
Based on the assumptions provided and discussed above, the project appears to be both
technically and financially feasible for the COB, along with their funding partners in which to
invest.
February 10, 2008 Page 5 tmktric Aw S sv tems
City of Bethel Wind Energy Project
NW100 Feasibility Study
5 Appendix A— Area Map
c��4
SYSTEMS
i
Bethel City Shop Wind Energy Project
,A
N
Sewer lagoons �
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v
- — - -- 320 ACRES - — ------ '`
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/3 16
City of Bethel Wind Energy Project
NW100 Feasibility Study
6 Appendix B — AEA Wind Resource Assessment
February 10, : Page 8 �
�4
SY57HM5
%� ENERGY AUTHORITY
ALASKA
Wind Resource Assessment for
BETHEL, ALASKA
Date last modified: 2/21/2006
Compiled by: Mia Devine
SITE SUMMARY
Site #: 5334
4
b�
Latitude (NAD27): 60' 47' 8" N
A L . 5 X A
N 60.7856
;
Longitude (NAD27): 161 ` 53' 6" W
W 161.885
Magnetic Declination: 14' 59' East
8eiing Sea _ GuI d Alashe
Tower Type: 50-meter NRG Tall Tower
M8NMenPomc
Sensor Heights: 30m, 40m, 50m
- - -
Elevation: 42.3 meters (128 ft)
,
Monitor Start: 12/9/2004 18:00
Monitor End: 2/12/2006 11:00
In December 2004, a 50-meter meteorological tower was installed on high ground
west of the Bethel airport. The purpose of this monitoring effort is to evaluate the
feasibility of utilizing utility -scale wind energy in the community. The measured
"°�' �,'t>,,
wind speed and direction data at the site was compared to long-term trends in the
area and estimates were calculated for the potential energy production from
various types of wind turbines.
WIND RESOURCE SUMMARY N
Annual Average Wind Speed (50m height): 7.3 m/s (16.3 mph) NW NE
Annual Average Wind Speed (30m height): 6.7 m/s (15.0 mph)
Average Wind Power Density (50m height): 440 W/m2
Average Wind Power Density (30m height): 345 W/m2 W'
Wind Power Class (range = 1 to 7): Class 4 6
Rating (Poor, Marginal, Fair, Good, Excellent, Outstanding): Good sw 16 % SE
Prevailing Wind Direction: Northeast s 24 i
14 Probal Distibntion Ftniction
12
10
6 _
r. 4 *' # 2 �...
UO S Longterm 6#m Height (mis) d
..A.. Aduei dote — Best-ft Webi cidrb Am (k-2 31, c-827 mis)
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MEN MEN
RE,,,,,"NEW MENNEN
^+8 6aNyWkxl Speed Profile
E
g4
; r
12
4
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6 12 18 2,
Hour d Day
50m Height
— 30m Height
www.akenergyauthority.org/programwind.html Page 1 of 13 February 2006
Alaska Energy Authority BETHEL, AK Wind Resource Assessment
INTRODUCTION
Previous wind monitoring efforts have been conducted in the Bethel area with less than favorable results. The
equipment used in those studies was mounted on 20-meter towers and were located adjacent to the buildings that
would be served by a wind turbine. The Alaska Energy Authority (AEA) felt that the close proximity to buildings and
the low elevation of the sites resulted in a wind resource that was not representative of the area and that winds
suitable for a utility -scale wind project could be found a short distance outside of town. In December 2004, AEA,
V3Energy, and local residents installed a 50-meter meteorological tower (leased from Chugach Electric) on private
land west of town. This location is more likely to be representative of Bethel's best wind resource area and was
recommended by wind siting meteorologist John Wade. The purpose of this monitoring effort is to 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
Bethel is located near the mouth of the Kuskokwim River, about 40 miles inland from the Bering Sea and 400 air
miles west of Anchorage. Figure 1 shows the location of the met tower relative to the surrounding terrain. The met
tower is located on a ridge at slightly higher elevation than the town site.
'
Bet6e1
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FAIRMANMS. ALAERA N701.OENVE4.00t0RA00 60225.OR RESiOM.VdlaftA 2tM
M MW "W"1 G 10090-MAC -n Aw 5YM501.5 d AYAMAELE OM NO"
Figure 1. Topographic Map of Met Tower Site and Surrounding Area
www.akenergyauthority.org/programwind.htmi Page 2 of 13 February 2006
Alaska Energy Authority BETHEL, AK Wind Resource Assessment
The photos below 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.
NW North NE East
t
SE South SW West
Figure 2. 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
50 m
NRG Standard
20' True
2
#40 Anemometer
50 m
NRG Standard
290° True
3
#40 Anemometer
40 m
NRG Standard
110* True
4
#40 Anemometer
30 m
NRG Standard
280` True
7
#200P Wind Vane
50 m
290' True
110' True
8
#200P Wind Vane
40 m
110' True
290° True
9
#110S Temperature
4 m
NRG Standard
-
N ■CH1, 50m anem
NW------', NE ■CH2, 50m anem
■ CH3, 40m anem
W ; E p Tower
CH4, 30m anem
CH7, 50m vane
S 13 CH8, 40m vane
Aerial view of equipment on tower
www.akenergyauthority.org/programwind.htmi Page 3 of 13 February 2006
Alaska Energy Authority BETHEL, AK Wind Resource Assessment
DATA PROCESSING PROCEDURES AND DEFINITIONS
The following information summarizes the data processing procedures that were
performed on the raw measured data in order to create an annual dataset of "typical'
wind speeds, which could then be used to calculate potential power production from
wind turbines. There are various methods and reasons for adjusting the raw data, so
the purpose of these notes is to document what was done in this situation. The raw
data set is available on the Alaska Energy Authority website
(www.akenergyauthority.org) so one could perform their own data processing
procedures. The processed data set is also available.
Units — Since most wind turbine specifications are provided in metric units, those units
are used in this report.
1 meter/second = 2.24 mph = 1.95 knots
1 meter = 3.28 feet
1 °C = 5/9 ff — 32)
Tower Shadow — The tower itself can affect readings from the anemometer at times when the anemometer is
located downwind of the tower. To avoid this effect, two anemometers were placed at the top level so that neither
would be in the wake of the tower at the same time. One data set is compiled from the 2 anemometers depending
on the direction of the wind at any given time.
Icing — Anomalies in the data can suggest when the sensors were not recording accurately due to icing events.
Since wind vanes tend to freeze before the anemometers, icing events are typically identified whenever the 10-
minute standard deviation of the wind vane is zero (the wind vane is not moving) and the temperature is at or below
freezing. Some additional time before and after the icing event are removed to account for the slow build up and
shedding of ice on the sensors.
Filling Gaps — Whenever measured met tower data is available, it is used. Two different methods are used to fill in
the remaining portion of the year. First, if nearby airport data is available, a linear correlation equation is defined
between the airport and met tower site, and airport data is adjusted to fill the gap. If neither met tower nor airport
data is available for a given timestep, the software program Windographer (www.mistava.ca) is used.
Windographer uses statistical methods based on patterns in the data surrounding the gap, and is good for filling
short gaps in data.
Long-term Estimates — The year of data collected at the met tower site can be adjusted to account for inter -annual
fluctuations in the wind resource. To do this, a nearby weather station with a consistent historical record of wind
data and with a strong correlation to the met tower location is needed. If a suitable station is not available, there is
a higher level of uncertainty in the wind speed that is measured being representative of a typical year.
Turbulence Intensity — Turbulence intensity is the most basic measure of the turbulence of the wind. Turbulence
intensity is calculated at each 10-minute timestep by dividing the standard deviation of the wind speed during that
timestep by the average wind speed over that timestep. It is calculated only when the mean wind speed is at least
4 m/s. Typically, a turbulence intensity of 0.10 or less is desired for minimal wear on wind turbine components.
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 different heights so that the wind shear exponent, a, can be calculated
according to the power law formula:
Hv2
H2 a = 2 where H, and H2 are the heights and v, and v2 are the measured wind speeds.
Wind shear is calculated only with wind speed data above 4 m/s. Values can range from 0.05 to 0.25, with a typical
value of 0.14.
www.akenergyauthority.org/programwind.html Page 4 of 13 February 2006
Alaska Energy Authority BETHEL, AK Wind Resource Assessment
Scaling to Hub Height - If the wind turbine hub height is different from the height at which the wind resource is
measured, the wind resource can be adjusted using the power law formula described above and using the wind
shear data calculated at the site.
Air Density Adjustment - The power that can be extracted from the wind is directly related to the density of the
air. Air density, p, is a function of temperature and pressure and is calculated for each 10-minute timestep
according to the following equation (units for air density are kg/m3):
_ P
P RxT
Where P is pressure (kPa), R is the gas constant for air (287.1 J/kgK), and T is temperature in Kelvin. Since air
pressure is not measured at the met tower site, the site elevation is used to calculate an annual average air
pressure value according to the following equation:
P = 1.225 - (1.194 x 10-4) x elevation
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. The adjustment is made according to the following formula:
i
_ Pmeasured 3
Vs tan dard Vmeosured x
Ps tan dard
Wind Power Density - Wind power density provides a more accurate representation of a site's wind energy
potential than the annual average wind speed because it includes how wind speeds are distributed around the
average as well as the local air density. Units of wind power density are watts per square meter and represent the
power produced per square meter of area that the blades sweep.
Wind Power Class - A seven level classification system based on wind power density is used to simplify the
comparison of potential wind sites. Areas of Class 4 and higher are considered suitable for utility -scale wind power
development.
Classes of Wind Power Density
m
Class
Rating
WPD /m^2
Speed m/s
WPD W/m^2
Speed m/s
WPD W/m^2)
Speed (m/s)
1
<100
<4.4
<160
<5.1
<200
<5.6
Poor
2
100 - 150
4.4 - 5.1
160 - 240
5.1 - 5.8
200 - 300
5.6 - 6.4
Marginal
3
150 - 200
5.1 - 5.6
240 - 320
5.8 - 6.5
300 - 400
6.4 - 7.0
Fair
200 - 250
5.6 - 6.0
320 - 400
6.5 - 7.0
400 - 500
7.0 - 7.5
Good
250 - 300
6.0 - 6.4
400 - 480
7.0 - 7.4
500 - 600
7.5 - 8.0
Excellent
300 - 400
6.4 - 7.0
480 - 640
7.4 - 8.2
600 - 800
8.0 - 8.8
Outstanding
>400
>7.0
>640
>8.2
>800
>8.8
Weibull Distribution - The Weibull distribution is commonly used to approximate the wind speed frequency
distribution. The Weibull is defined as follows:
k V1k-1 (_V)k
P(v) c ( c expl c
Where P(v) is the probability of wind speed v occurring, c is the scale factor which is related to the average wind
speed, and k is the shape factor which describes the distribution of the wind speeds. Typical k values range from
1.5 to 3.0, with lower k values resulting in higher average wind power densities.
www.akenergyauthority.org/programwind.html Page 5 of 13 February 2006
Alaska Energy Authority
BETHEL, AK
LONG-TERM REFERENCE STATION
Wind data from the Bethel airport weather station, located 2.5
miles east of the met tower site, serves as a long-term reference
for the wind resource in the area. Data is measured at a height of
10 meters above ground level and an elevation of 37.5 meters.
The National Weather Service upgraded the meteorological
monitoring equipment at the Bethel airport to an Automated
Surface Observing System (ASOS) on November 1, 1998. This
new equipment, although more accurate, represents a
discontinuity in the long-term wind speed record. Therefore,
this report is based on measurements beginning January 1, 1999.
Wind Resource Assessment
t 3
Figure 3. ASOS Equipment in Bethel
Hourly wind speed measurements from the Bethel airport weather station that are concurrent with recordings from
the met tower site were purchased from the National Climatic Data Center. The correlation coefficient between
these sites is 0.87 (a value of 1 is perfect). This suggests that, although the actual wind speed values at the two
sites are different, the pattern of wind speed fluctuations is similar between the sites. Any historical patterns in the
airport station data can also be applied to the met tower site with a high degree of certainty.
As shown in Table 2 and Figure 4, the area has a strong seasonal pattern, with greater wind speeds in the winter
months than the summer months. The long-term annual average wind speed at the Bethel airport site is 5.2 m/s,
which is fairly consistent, fluctuating up to 3% from year to year.
Table 2. Monthly Average Wind Speeds at Bethel Airport, 10-meter height (m/s)
Year
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Ave
% of Long -
Term Ave
1999
7.0
4.5
5.8
5.6
4.7
4.0
4.9
4.3
4.7
4.4
5.5
5.7
5.1
99%
2000
6.6
5.0
5.3
5.0
4.3
4.0
4.4
5.2
4.6
4.7
6.2
6.4
5.2
100%
2001
5.4
5.8
6.2
5.9
5.2
4.7
4.5
4.6
4.3
5.0
5.0
5.2
5.2
100%
2002
6.5
6.1
5.2
6.5
4.8
4.2
4.0
4.3
5.3
5.6
5.3
4.7
5.2
101 %
2003
6.3
5.5
7.0
5.5
4.5
4.5
4.9
4.1
4.4
4.8
5.3
4.9
5.2
100%
2004
6.3
6.2
5.2
4.6
4.7
4.3
3.8
4.2
4.2
5.6
6.2
5.8
5.1
98%
2005
7.4
5.2
5.7
5.0
4.6
4.1
4.3
4.8
5.9
4.5
6.3
6.0
5.3
103%
Ave
1 6.5
5.5
5.8
5.5
4.7
4.3
4.4
4.5
4.8
5.0
5.7
5.5
5.2
100%
1 wi`J JUJU Lwl Lwl LUUJ 2UU4 AM
Figure 4. Monthly and Annual Average Wind Speeds at Bethel Airport, 10-meter height
www.akenergyauthority.org/programwind.html Page 6 of 13 February 2006
Alaska Energy Authority BETHEL, AK Wind Resource Assessment
According to the ASOS data, the average
wind speed in the year 2005 was 3%
greater than the long-term average.
Therefore, the wind speed data recorded
at the met tower site during the year 2005
was adjusted downwards by 3% to more
accurately reflect what would be expected
over the long term. Both measured and
long-term data sets at the airport and met
tower sites are shown in Figure 5.
12
10
r r
.�
10
Measured Met Tower Data (50m height)
- =-Longterm Met Tower Estimate
- - Measured Airport Data (10m height)
Extreme wind speeds recorded at the 0 'Longterm Airport Data 0 1�0
Bethel ASOS are summarized in Table 3. Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
The fastest mile is defined as the speed of
one mile of wind that passes the weather Figure 5. Measured Versus Long -Term Wind Speeds in Bethel
station and can be considered as the maximum sustained wind speed. The fastest mile recorded over a 41-year
period was 27.7 m/s in February 1951. The peak gust over a 16-year period was 34.4 m/s in October 1992.
26.8
22.4
E 8
Q 6
d
n
a 4
c
2
Table 3. Extreme Wind Speeds in Bethel, 10m height (source: Western Regional Climate Center)
Air ort Fastest Mile (1957-1998
m/s
mph
Year
_Month
Jan
24.1
54
1979
Feb
27.7
62
_
1951
21.9
49
1977
__Mar
Apr
19.7
44
_
1979
May
18.3
41
1960
Jun
43
1978
'Jul
_19.2
17.9
40
1974
Auq
20.6
46
1978
Sep
24.6
55
1960
Oct
23 2
52
1992
Nov
26.8
60
1958
_
Dec
25.9
58
1977
Airport Peak Gust 1982-1998
m/s
mph
I Year
27.3
61
1993
26.4
59
1988
25.0
56
1991
22.8
51
1995
23.7
53
1985
26.4
59
1980
20.6
46
1982
25.0
56
1994
_
30.8
69
1982_
34.4
77
1992
29.5v
66
1990
29.9
( 67
1982
CL
17.9 E
13.4
a
Cn
8.9
4.5
The air temperature can affect wind power production in two primary ways: 1) colder temperatures lead to higher air
densities and therefore more power production, and 2) some wind turbines shut down in very cold situations
(usually around-250C). The monthly average temperatures for Bethel are shown below. Typically, the
temperature drops below -250C during 2% of the year, or 185 hours per year.
Measured (met tower) - - Long -Term (airport)
20
v 15
10
5
0
L
a -5
m -10
H
-15
N Q (II j U op
u- � Q -' Q CA 0 Z
Month !
Measured (°C) ;
Long -Term (°C)
Jan
-12.4
-12.7
Feb
-10.4
-8.0
Mar
-8.2
-8.8
Apr
-7.0
-2.2
May
7.3
5.3
Jun
13.3
12.6
Jul
13.8
13.1
Aug
12.7
( 12.3
Sep
8.1
7.0
Oct
-1.2
-0.5
Nov
( -14.6
-7.5
Dec
-10.8
-12.6
Ave
j -0.8
-0.2
www.akenergyauthority.org/programwind.htmi Page 7 of 13 February 2006
Alaska Energy Authority BETHEL, AK Wind Resource Assessment
WIND DATA RESULTS FOR BETHEL MET TOWER SITE
Table 4 summarizes the amount of data that was successfully retrieved from the data logger at the met tower site.
There was significant data loss during the winter months due to icing of the sensors, particularly in November,
December and February. The airport ASOS data was used to fill these gaps where possible. The remaining gaps
were filled with Windographer.
Table 4. Data Recovery Rate for Met Tower Anemometers
Month
Data Recovery Rate
Data Loss Due to Icing
January 2005
100%
11 %
February 2005
100%
34%
March 2005
100%
8%
April 2005
100%
6%
May 2005
100%
2%
June 2005
100%
0%
July 2005
100%
0%
August 2005
100%
0%
September 2005
100%
0%
October 2005
100%
16%
November 2005
100%
31%
December 2005
100%
54%
Annual Average
100%
13%
Wind Speed Measurements
The wind resource was measured at various heights on the tower. Results from the 50-meter and 30-meter heights
are summarized below. More details of the 50-meter level are shown in Table 6.
Table 5. Measured and Long -Term Average Monthly Wind Speeds at Met Tower Site
Wind Speeds (m/s)
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Ave
50m Height, Measured
10.7
7.9
8.5
7.0
5.9
5.3
5.5
6.6
8.3
6.9
8.8
9.1
7.5
50m Height, Long-term
9.4
8.3
8.7
7.6
6.0
5.5
5.6
6.2
6.7
7.6
7.9
8.4
7.3
30m Height, Measured
10.0
7.0
7.7
6.2
5.4
4.9
5.1
6.1
7.5
6.1
7.8
8.3
6.9
30m Height, Long-term
8.8
7.4
7.8
6.8
5.5
5.1
5.2
5.7
6.1
6.8
7.0
7.6
6.7
The seasonal wind speed profile shows that the highest wind month is January and the lowest wind month is June.
The daily wind speed profile shows that wind speeds are typically greater in the afternoon and evening hours and
calmer in the morning.
h1
E
A
Q
a �w easonai ind
31
8 Dail Wind Speed Profile
u1 -,. ,, � Longterm 50m Height
_ - Longterm 30m Height
0.
�5
Co
724
92
00 a 12 18 24
` J F M A M J J A S O N D Hour of Day
Figure 6. Seasonal and Diurnal Wind Speed Profile for Met Tower Site, Long-term Estimate
www.akenergyauthority.org/programwind.html Page 8 of 13 February 2006
Alaska Energy Authority BETHEL, AK Wind Resource Assessment
Table 6. Estimated Long -Term Wind Speeds at Met Tower Site, 50m Hei ht (m/s)
Hour
Jan
Feb
Mar
Apr
May
Jun
Jul
AugSep
Oct
Nov
Dec
Avg
0
9.6
8.5
8.8
8.1
6.4
6.0
6.8
6.4
6.8
7.8
8.1
8.4
7.6
1
9.4
8.5
8.7
8.0
6.3
6.0
6.4
6.2
6.5
7.8
7.9
8.3
7.5
2
9.5
8.4
8.6
8.0
6.0
5.9
5.9
6.0
6.4
7.8
7.7
8.8
7.4
3
9.5
8.2
8.4
8.0
6.0
5.8
5.8
5.9
6.5
7.8
7.8
8.7
7.4
4
9.5
8.5
8.7
7.9
6.0
5.6
5.6
5.8
6.5
7.5
7.8
8.5
7.3
5
9.3
8.4
8.8
8.1
5.9
5.4
5.3
6.0
6.5
7.4
7.7
8.3
7.3
6
9.1
8.2
8.7
7.9
5.7
5.0
5.2
5.8
6.4
7.4
7.9
8.3
7.1
7
9.3
8.0
8.7
7.9
5.2
4.7
4.8
5.6
6.3
7.6
7.9
8.3
7.0
8
9.3
8.2
8.6
7.5
5.0
4.7
4.8
5.6
6.3
7.9
7.9
8.5
7.0
9
9.2
8.5
8.7
7.1
5.1
4.8
5.1
5.8
6.3
7.7
8.1
8.4
7.1
10
9.3
8.1
8.9
6.7
5.6
5.0
5.0
6.1
6.7
7.4
8.3
8.2
7.1
11
9.4
8.1
8.8
6.5
5.8
5.2
5.1
6.4
6.9
7.4
8.3
8.1
7.2
12
9.3
8.2
8.8
6.7
5.9
5.3
5.3
6.4
6.9
7.6
8.1
8.2
7.2
13
9.3
8.4
8.6
7.0
6.0
5.3
5.2
6.6
7.2
7.4
7.8
8.2
7.3
14
9.3
8.4
8.4
7.1
6.1
5.3
5.3
6.7
7.3
7.5
7.7
8.7
7.3
15
9.6
8.3
8.7
7.3
6.1
5.4
5.7
6.7
7.0
7.6
7.7
8.3
7.4
16
9.6
8.2
8.7
7.3
6.4
5.6
6.0
6.6
7.0
7.3
7.8
8.3
7.4
17
9.7
8.3
8.6
7.6
6.7
5.7
5.8
6.6
6.9
7.3
7.8
8.3
7.4
18
9.5
8.3
8.3
7.7
6.5
6.0
6.0
6.6
6.8
7.5
8.0
8.7
7.5
19
9.5
8.4
8.5
7.9
6.2
6.0
6.1
6.3
6.7
7.6
8.1
8.7
7.5
20
9.3
8.1
8.8
8.0
6.3
6.0
5.7
5.9
6.7
7.7
7.9
8.4
7.4
21
9.3
8.0
8.8
8.2
6.6
5.9
5.7
6.1
6.7
7.9
7.9
8.3
7.4
22
9.6
8.1
8.8
8.1
6.6
6.0
6.0
6.4
6.8
8.2
7.9
8.7
7.6
23
9.4
8.2
8.6
8.2
6.4
6.2
6.4
6.3
7.0
8.0
8.1
8.6
7.6
Avg
9.4
8.3
8.7
7.6
6.0
5.5
5.6
6.2
6.7
7.6
7.9
8.4
1 7.3
The estimated long-term average wind speed is 7.3 m/s at a height of 50 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 7 shows the measured wind frequency distribution as well as the best
matched Weibull distribution.
1�
1'
c
m
Cr
2
LL
?�robability&[Stlbution
Function
0 5 10 15 20 25 30
Longterm 50m Height (m/s)
- Actual data - Best -fit Weibull distribution (k=2.31, c=8.27 nYs)
Figure 7. Wind Speed Frequency Distribution of Met Tower Data, 50-meter height
Bin m/s
Hrs/yr
0
60
1
151
2
396
3
722
4
880
5
989
6
1,086
7
1,073
8
942
9
772
10
572
11
365
12
262
13
14
170
103
Bin m/s
Hrs/yr
15
78
16
58
17
27
18
15
19
9
20
8
21
8
22
4
23
3
24
3
25
2
26
2
27
1
28
1
29
0
iotar ts,lbu
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 a large percentage of the wind in Bethel is within this operational zone.
www.akenergyauthority.org/programwind.htmi Page 9 of 13 February 2006
Alaska Energy Authority BETHEL.AK Wind Resource Assessment
Wind Direction
Wind power roses show the percent oftotal power that isavailable inthe wind bydirection. The annual wind power
rose for the met tower site iocompared hothe airport site inFigure 8. The met tower site isbased onone year cf
data, while the airport site iebased onseven years ofdata. The correlation coefficient between the sites ia0.Q7.
The predominant wind direction atboth locations ianortheast.
Met Tower Site (2OO5) _ Airport Site (1QQQ-2DOS)
w w
wvy ` { ` Ns w= ` `. ' Ns
' '
w '�7 ' w ' �
���
vm Q� ` ��nm ��-
x
`iom `
mw16% � ! ss mw SE
24% '
o o mm
Figure 8.Annual Wind Power Roses for Met Tower Site and Airport Site
Monthly wind power roses for the met tower site are shown below. The strong winter winds come from the
northeast, while the lighter summer winds tend bxcome from the south.
Figure 9. Monthly Wind Power Roses for Met Tower Site
vmmw.okenergyauthority.org/programwind.htm| Page 1Uof13 Febmary2OOO
Alaska Energy Authority BETHEL, AK Wind Resource Assessment
Turbulence Intensity
Various turbulence intensity characteristics are shown in Figure 10. The turbulence intensity from all directions and
for all months is low and unlikely to contribute to excessive wear of wind turbines.
Month
Turbulence
Intensity
Jan
0.06
Feb
0.06
Mar
0.06
Apr
0.07
May
0.12
Jun
0.14
Jul
0.13
Aug
0.11
Sep
0.10
Oct
0.08
Nov
0.06
Dec
0.06
Ave
0.09
o
a
0 5 10 16 20 23 30
Wind Speed (m/s)
Data — IEA CategoryA IEA Category B
Figure 10. Turbulence Intensity Characteristics of Met Tower Site
Figure 10 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, 2"d Edition.
Category A represents a higher turbulence model than Category B. In this case, the met tower data is less
turbulent than both categories across the whole range of wind speeds.
Wind Shear
Wind shear was calculated between the 50-meter anemometer and the 30-meter anemometer, and results are
summarized in Figure 11.
Month
30m to 50m
Wind Shear
Jan
0.11
Feb
0.26
Mar
0.23
Apr
0.23
May
0.18
Jun
0.17
Jul
0.16
Aug
0.19
Sep
0.18
Oct
0.23
Nov
0.18
Dec
0.23
Ave
0.19
Average of 30-50m Shear
Figure 11. Wind Shear Characteristics of Met Tower Site
Hair
The average wind shear for the site is 0.19. As shown, the wind shear varies by month, direction of the wind, and
time of day. These wind shear values can be used to adjust the wind resource data to heights other than those that
were measured and reported here, as described previously in the Data Processing Procedures and Definitions
section.
www.akenergyauthority.org/programwind.htmI Page 11 of 13 February 2006
Alaska Energy Authority BETHEL, AK Wind Resource Assessment
POTENTIAL POWER PRODUCTION FROM WIND TURBINES
Various wind turbines, listed in Table 7, were used to calculate the potential energy production at the met tower site
based on the long-term wind resource data set. 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. The wind resource was also adjusted to standard air
density.
Results are shown in Table 7. 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 December 2004 through January 2006 in
Bethel, Alaska. The data was compared to long-term trends in the area and, based on correlations with the Bethel
airport weather station, estimates were made to create a long-term dataset for the Bethel met tower site. This
information was used to make predictions as to the potential energy production from wind turbines at the site.
It is estimated that the long-term annual average wind speed at the site is 7.3 m/s at a height of 50 meters above
ground level and 6.7 m/s at a height of 30 meters. Taking the local air density and wind speed distribution into
account, the average wind power density for the site is 440 W/mz. This information means that Bethel has a
Class 4 wind resource, which is "good" for wind power development. The net capacity factor for large scale wind
turbines would range from 21 — 36%.
www.akenergyauthority.org/programwind.html Page 12 of 13 February 2006
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City of Bethel Wind Energy Project
NW100 Feasibility Study
7 Appendix C — Economic Assessment Supporting Data/Correspondence
February 10, 2008 Page 22 electric Phu S
CouuhLpi}pineen
Email from Martina Dabo, AEA Wind Program Manager
Allowing Use of Wind Data Collected Northwest of Town
to be Used for City Shop in Northeast Section
Dear Mr. Abe,
Please feel free to use the Bethel Met -tower data for your purposes. If you need the data in a different
format or additional information on this met -tower site, please contact Mr. James Jensen
(jjensen(caidea. org, 771-3043).
Thank you.
Best regards,
Martina Dabo
Wild Program Manager
Alaska Energy Authority
813 West Northern Lights Blvd.
Anchorage, AK 99503
Phone: (907) 771-3027
Fax : (907) 771-3044
E-Mail: mdabo@aidea.org
www.akeiiergyauthority.org
NorthMndO 1 OU Wind I urtme i-roposat
For The City of Bethel
Prepared for:
John Sargent
Grant Development Manager
City of Bethel, AK
Submitted by.
STG, Inc.
11820 S Gambell Streeet
Anchorage, AK 99515
David E. Myers
907-522-9018
.7r;'
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YR Wi 00 trod Turbines
Pricing and Payment Terms
Northern Power
The installed costs for this project are in line with the costs incurred with the two previous
installations ,(Toksook and. K.asigluk), which weperformedin remote Alaska. As with
Kasigluk, the foundations require piles that are au-ured in like screws. Concrete also needs to
be used to stMen the base. "T`hernnalsyphons are used to keep the permafrost froin melting in the
summer. Barging in the crane. the concrete equipment, the drill and the aggregate and concrete
adds significant costs to this single turbine pr(ject_ In conclusion, we will continue to work at
finding cost savings with the other pnu,ce that we will he conducting in Chevak, Hooper Bay,
Sa ,voonaa, and Mokoi)'uk in the summer of 300&
To help illustrate the high costs of construction projects in remote . laska., especially for
dif`ficuh sites, the product (turbine, controls, and integration) is S 1 % of the total, while. the
construct and instaH piece (including geotec:h survcys and foundation desicm) are 491% of the
total, n line item breakdown of these: costs can be provided if requested.
Table S. Construct and Install Wind Turbine
Line Item
(All labor, services, materials and work relative to and Line Item Cost
incidental to the items listed)
1. Construction of civil drawings, pile testing and structural
foundation design, and Electrical Design $58,500
2. Construction and installation of the wind turbine. All
transportation of equipment, foundation materials, disposal,
and clean up of the project. includes all as-builts and
warrantees. $389, 454
3. NW100 turbine and tower with necessary controls to
connect with the grid. $304,450
4. Installation and commissioning support, remote monitoring�`�
software. project management and training for site personnel, $47,150
Total for Turnkey Project $799 554
Use or- disrlrjsure ofdata contained cn t}tis sI>Zet is subiect to the restriction on tlae title p; toe of the proposal
Page 13 of -50
110 S. Willow, #106 (907) 283-7834
®4
Kenai, AK 99611 1-800-478-7834
AGE CY j FAX (907) 283-6179
February 15, 2006
John Sargent
City of Bethel
PO Box 1388
Bethel, AK 99559
RE: City of Bethel Insurance
Dear John,
Per our recent telephone conversation:
The City of Bethel has sufficient liability coverage in its existing insurance policy to
cover the purchase, installation, and operation of a small commercial wind turbine on a
100 ft. lattice tower near the Public Works building. The wind turbine will provide
electricity to the Public Works building and be connected to Bethel Utilities
Corporation's grid.
The increased insurance cost expected per year to cover the loss or damage of the
property (wind turbine, tower, foundation, and electrical equipment necessary for
connection, protection, and operation of turbine) is expected to be 4% of the value (cost
to purchase, install, and commission).
Please advise if you have any questions.
Thank you,
Doug Brown
second Revised 1
APUC No. 43 Sheet Na
Cancelling RECEIVED
First Revised _ Sheet No. _ AUG 989
Q} �1
1BETHEL UTI-LITIESCORPORATION
Pubnc Utilities Cammission
TARIFF NUMBER 1
RULES, REGULATIONS AND RATES
OF
BETHEL UTILITIES CORPORATION
3380 C Street, Suite 210
Anchorage, Alaska 99503 C.
APUC No. 43 86'h Revised Sheet No. 30.3 RECEIVED
Canceling
85"..Revised
Sheet No. 30.3
OCT 2 3 2007
STATE OF ALAStUA
fi:EG6'LATi2-P7 OF ALASKA
I RATE FOR PURCHASE OF NON -FIRM POWER FROM QUALIFYING FACILITIES
With variable operating and maintenance expenses set to zero, the rate at which non -firm
power will be purchased from qualifying facilities will include only the avoided fuel cost
of power which is calculated on Sheet No. 30.5 (D) (5).
I Avoided fuel cost of power
I This filing pursuant* to order No. 5 of Docket U-81-3 5.
$ 0.3253/KWH
Pursuant to:
U-07-112(3)
,7-
-ff
Issued by: Bethel Utilities _.rporation
By: Title: Controller
Thomas S. Sterrett,
L '�r
Email from Brett Pingree, Wind Business Manager
With Distributed Energy Systems, Manufacturer of the NW 100
Hi John, 1 just wanted to let you know that things were progressing well with your proposal. One change I
wanted to tell you about is that STG, Inc will submit the turnkey proposal to you and we will subcontract to
them. We decided this was a much better approach for you and for us. STG has an office, vehicles and
staff in Bethel and in addition to being an Alaskan based construction company they are much better
positioned to be your lead on this project.
We have submitted our proposal to STG and we are going over the final details tomorrow. It is for one
turbine, installed. STG will delivery the complete and final proposal to you on Monday. Dave Myers is the
STG lead on this project.
We did not touch the grant proposal as it is my understanding that you already submitted this and
received the award. I will note, to the project and the City of Bethel's benefit, that with this proposal we
are now using a 21 m rotor and a 37 m tower. That will improve the energy production of one
NorthWind100 turbine from 220,000 kWhours to 260,000 kWhours per year! You will want to update your
financial analysis to reflect that.
Call me anytime throughout this process.
Brett Pingree
Wind Business Manager
Distributed Energy Systems
29 Pitman Road
Barre, VT 05641
Direct: +01.802.461.2942
Main: +01.802.461.2955
Fax: +01.802.461.2998
IMPORTANT: The information contained in this communication is confidential
and/or proprietary business or technical data. It is intended for receipt
only by the individual or entity to which it is addressed. If the reader of
this message is not the intended recipient, you are hereby notified that any
dissemination, copying or distribution of this communication is strictly
prohibited. If you have received this communication in error, please
immediately notify us by telephone 203-678-2000 or electronically by return
message, and delete or destroy all copies of this communication.
FUEL COST RATE ADJUSTMENT
A. APPLICABILITY
RECEIVED
SEP 1 7 1991
State of Alaska
Public Utilities ComMISSIOIj
All tariff rate schedules shall be subject to the
applicable fuel cost rate adjustment (FGRA) as set
forth in (D) below.
B. COST 'OF POWER ADJUSTMENT
The base cost of fuel is S 0.0966/kilowatt hour.
Billings to customers will be increased or decreased
to reflect the COPA surcharge calculated to reconcile
the Company's allowable fuel and purchased power
expenses with revenues designed to cover those
expenses.
C. BALANCING ACCOUNT
The Company will maintain a balancing account
beginning September 1, 1991, with balances
thereafter reflecting the sum of monthly
debit and credit entries described as follows:
1. A debit entry for the amount spent for fuel.
2. A debit entry for the amount spent to purchase
power.
3. A credit entry for the amount of kilowatt hours
sold times the base fuel cost of power.
4.-A credit entry for the amount of kilowatt hours
sold times the CCPA actually assessed.
5. Other entries as directed by the Alaska Public
Utilities Commission.
Pursuant to Order No. 2 in Docket U-91-10
Tariff Advice Na 93 Effective: 10/1/91
tss Is -
BETHEL UTILITIES CORPORATION
BY." S__S TZZT, Title, CONTROLLER
THOMAS S. STERRETTA.
APUC No. 43 650'Revised Sheet No. 30.5
Canceling
64'h Revised Sheet No. 30.5
BETIML-UTILITI=ES'CORP•ORATIO.N .
D. DETERMINATION OF COST OF POWER AJDUSTMENT
1. Estimated costs for three months beginning October 1, 2007
RECDVED
OCT 2 3 zoo?
STATE OF ALASKA
RE"u• JtATEi C[F".'.i6i7 Gtt. a OF AtrSttAA
Estimated Estimated
Source Ouanti Unit Cost Total
Diesel Fuel 820,261 gal. $3.906 $3,203,939
Purchased Power 0 KWH 0.0000 0
Total $3,203,939
2. Balance in COPA balancing account as of October 1, 2007 $ 18,806
3. Total of (1) and (2) $3,222,745
4. Estimated KWH's for the period 9,907,574
5. Projected cost of power (3) / (4) $0.3253/KWH I
6. Base cost of power $0.1461/KWH
7. Cost of power adjustment (5) less (6) $0.1792/KWH I
E. REVISION OF FUEL COST RATE ADJUSTMENT
1. Every three months, the Company will submit a filing to the Alaska Public Utilities
Commission and present the revised COPA.
2. The information to be contained in a filing to revise the COPA will include the following:
a. A tariff advice letter.
b. All necessary tariff sheets.
c. A schedule showing the number of gallons and amount spent for fuel in the past 12 months.
Note: Previous surcharge calculation is shown on 651h Revised Sheet No. 3 0. 1
Pursuant to:
f U-07-112(3) _
Effective:.11 /01/07
Issued BY: Bethel Coro�ora_tion
By:
Thomas S. Sterrett, Jr. Title: Controller
E. REVISION OF COST OF POVFP ADJUSTMENT (continued)
2. d) A schedule showing the number of kilowatt hours
and amount spent to purchase power in the past
12 months.
e) Copies of fuel invoices not previously
submitted that support fuel purchases.
f) A schedule of monthly kilowatt hour sales for
the past 12 months.
g) A calculation of the monthly balancing account
used to determine the revised CODA.
Pursuant to Order No. 2 in Docket U-91-10
Tariff Advice Na 93 Effective: 10 J 1 /91
Issued by. BETH L UTIIJTIES CORPORATION
By. Titie_ CONTROLLER
THOMAS S. STERRETT, J .
City of Bethel Land Ownership
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LEGEND CON' T .
t ) Record Data Dill Township Survey.
j } Macord Data Par Plat a2-4.
C JAccord Data Per Plot 84-19.
I
it
SPALE
;..
o coo eoo 1YOJ 1.
.tic Declination 19 Eest
'
Itese Du.d aethOI (D-S)
Pound llll Dr.- Cap eention Corner Monument.
t1(((..
fewfd B.M Sreas C09 !/4 Sept ton Corner W..u�:....
found 94 was. Cap Monucant Par Plot 92-22
-
famtl i i!a' Alu•1nSUe Cop Monument Per Plat a2-4.
Tama V Iron pips MM+ument Per Plot 87-a.
2-1!R' X 32' Aluatniva Monument This Survey.
rL_ 4
(L -,
L--L^
r �
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4:2fy_ _ ilw
RAVEYORS CERTIFICATE
I. Daniel A. Wahl haraby certify that 1 ea a
duly 1fuMea Lend 9arvyor in the state of
Alasken. in[rhea sccoeo "I'd Plat i. e
tru. and correct pr.:.nt•tion of •urvsy
aarfor-a by me or under m' tlI.•et
up.rvision and that Stl u y •a don•
caw... .v{^a,
fro- - Oant. end land marks found se
shown.
' %.T +
' 49T"� :9++
�y �tr�yy
CL..........%wai
D
Daniel A. Mehl L.9. 67f8 Data
aL-Anii
,•'r#f
v i a• ne a a x as
t>Sr
a� rM �� .Th lab 9u ey 9
a
fe� 1t - fa T -� p w p re
to to fa I U
O
L
Qp v 1• la ap -zf—
as
U. S. HAP BETHEL (0-B). ALASKA
,;',Srs B.. 'ICINITY MAP 1' - 1 MILE
CERTIFICATE OF OWNERSHIP
I. the-d—ipnad. hereby cartify that I ea the President of the
Bethel Native Corporation .nd that the Bethel Matt- Corporation is the
owner of those lantls, other than Ouitclaie Traote A. B. C.D and Tract E Plat
a2-4, m ehowl and described hereon. This survey acpurat•ly deacribee
the lands Ihtsndad to be conveyed pursuant to the requlrementa of ANC9A
14(c) (3) and op requested by Bethel City Council Resolution Aoraement
hap. 717.
Bete (4- �S(j{' nt. Dach61 Motive Corporecfor
�DY`!, [7gfC5, S✓7ER1M MHNRfiF�t
NOTARY'S ACKNOWLEDGEMENT
suimmman AND stiom TO BEFam ME mis /6 DAY OFF^ • 19 q' _
G /
Y OR THEE STATE OF A9KA NY 1OMX 99IDN :'M7
;• to Y`
CERTIFICATE OF OWNERSHIP O Y)n'T
I. the undersigned. hereby certify that I am the Mayor t ;ns•, y
Dath.l and
that the City of Bethel Is the owner of O.Itt=q TNpt
A. B. C,0 and Tract E Plat 82-4 an shown and described n• o T15ia"IlGrvay
epcurat•ly d-11... the land Intended to b. conveyetl purduppnnt to the
requirement. of ANCSA 141., (3) -1 a requested by Bathal City Council
Rana lutSon Ag—sent No. 717.
Date. lo'Z7•ii H.YbQ CS f aith.l
NOTARY'S ACKNOWLEDGEMENT /,.
SUBSCRIBED AM SWORN TO BEFORE ME THIS Z 7 DC U'AY OF -3
NOTA NOR THE STATE Of ALASKA MY CO WIS'Siram Lg
PLANNING COMMISSION APPROVAL {
This Plat 12 found to cosoly with the etenderdeiga the City of Bethel.
Alaska end it -00—d by the Plennina Comei.aloh'thia /:i -A
Coy of c ' . • r 1993.
J I
TAX STAT1H T
The lend. contained and d... 11betl hereon or. hot subject to tametion at
in, ties of I... .Inc.
PLAT DF
LAGOON PARCEL
BETHEL NATIVE CORPORATION ANCSA 14(C) SURVEY
SITUATED IN
SECTIONS 4 6 5,TOWNSHIP 8 NORTH, RANGE 71 WEST,
SEWARD MERIDIAN, .ALASKA
CONTAINS aeo.o ACRES MORE OR LESS
PREPARED BY
ALASKAN CONSULTING SURVEYORS,INC
601 West 41st Suite 101
Anchorage, Alaska 99503
(907) 562-7950
SCALE 1'-400' DATE 4/27/93 FILE 93-09 FB NO.92-04
DRAWN D.W. CHKD. L.R. I SHT. 1 of 1