HomeMy WebLinkAboutPoint Hope Wind Diesel Generation Project Wind Resource Report - Aug 2010 - REF Grant 7040026Point Hope Wind Resource Report
Report by: Douglas Vaught, P.E., V3 Energy LLC, Eagle River, Alaska
Date of Report: August 26, 2010
Point Hope met tower; D. Vaught photo
Table of Contents
Summary.......................................................................................................................................................2
Test Site Location......................................................................................................................................2
Photographs..................................................................................................................................................4
Data Recovery...............................................................................................................................................4
Wind Speed...................................................................................................................................................5
Time Series................................................................................................................................................6
Daily Wind Profile .....................................................................................................................................7
Probability Distribution Function..............................................................................................................8
Wind Shear and Roughness......................................................................................................................8
Extreme Winds............................................................................................................................................10
Temperature and Density...........................................................................................................................11
Point Hope Wind Resource Report Page 2
Wind Speed Scatterplot..........................................................................................................................12
Wind Direction............................................................................................................................................13
Turbulence..................................................................................................................................................14
Airport ASOS Data.......................................................................................................................................16
Summary
The wind resource measured in Point Hope is very, very good, with measured wind power class 6
(outstanding). In addition to high average wind speeds and high wind power density, the site
experiences very low turbulence and calculations indicate low extreme wind speed probability.
Met tower data synopsis
Data dates June 16, 2009 to July 15, 2010 (13 months)
Wind power class 6 (outstanding)
Power density mean, 30 m 515 W/m2
Wind speed mean, 30 m 7.12 m/s
Max. 10-min wind speed average 27.9 m/s
Maximum wind gust 32.2 m/s (Dec. 2009)
Weibull distribution parameters k = 1.82, c = 7.92 m/s
Wind shear power law exponent 0.110 (low)
Roughness class 0.27 (rough sea)
IEC 61400-1, 3rd ed. classification Class III-c (lowest defined and most common)
Turbulence intensity, mean 0.073 (at 15 m/s)
Calm wind frequency 20% (<3.5 m/s)
Community profile
Current Population: 713 (2009 DCCED Certified Population)
Incorporation Type: 2nd Class City
Borough Located In: North Slope Borough
Taxes: Sales: None, Property: 18.5 mills (Borough), Special: None
Coastal Management District:North Slope Borough
Test Site Location
Met tower was installed on the northeast corner of Point Hope, between the village water storage tank
and a large snow fence. This site could be considered ideal for wind power development as it is also
near the power plant and other existing electrical power infrastructure.
Point Hope Wind Resource Report Page 3
Site information
Site number 0221
Latitude/longitude N 68° 20.974’ W 166° 43.146’, WGS 84
Site elevation 2 meters
Datalogger type NRG Symphonie, 10 minute time step
Tower type NRG 34-meter tall tower, 152 mm diameter, erected to 30 m
Anchor type 2.5 m shaft, 0.7 m square metal plate, buried
Google Earth image
Tower sensor information
Channel Sensor type Height Multiplier Offset Orientation
1 NRG #40 anemometer 30 m (A) 0.755 0.38 178°T
2 NRG #40 anemometer 30 m (B)0.758 0.37 274°T
3 NRG #40 anemometer 20 m 0.756 0.37 282°T
7 NRG #200P wind vane 29 m 0.351 359 359° T
9 NRG #110S Temp C 3 m 0.136 -86.383 N
10 RH-5 relative humidity 2 m 0.098 0 S
12 Voltmeter 2 m 0.021 0 n/a
Point Hope Wind Resource Report Page 4
Photographs
Datalogger weather box and PV panel; D. Vaught photo Top of met tower; D. Vaught photo
Datalogger with snow in weather box; D. Vaught photo Met tower and village edge; D. Vaught photo
Data Recovery
Data recovery to date in Point Hope was superior, with nearly 100 percent functionality of the
anemometers and wind vane. This is remarkable anywhere in Alaska, but even more so on the Chukchi
Sea coast of the North Slope with its intensely cold winter temperatures. Note that data loss from the
relative humidity (RH) sensor was initially due to voltage drawdown of the iPack battery during the dark
months of winter (the battery is recharged with photovoltaic panels). For unknown reasons,
functionality of the RH sensor did not recover on return of daylight in springtime, even though the iPack
battery recharged fully.
Near perfect anemometer and wind vane data recovery indicates the complete absence of rime icing
conditions, which would not have been expected at a coastal elevation anyways, but also the absence of
heavy hoarfrost conditions which plagued wintertime data recovery on the relatively nearby Wainwright
and Atqasuk met towers.
Point Hope Wind Resource Report Page 5
Data recovery summary table
Possible Valid Recovery
Label Units Records Records Rate (%)
Speed 30 A m/s 56,649 56,171 99.2
Speed 30 B m/s 56,649 56,169 99.2
Speed 20 m/s 56,649 56,468 99.7
Direction 29 ° 56,649 55,911 98.7
Temperature °C 56,649 56,581 99.9
RH-5 Humidity %RH %RH 56,649 22,397 39.5
iPack Voltmeter volts 56,649 56,649 100.0
Anemometer data recovery
30 m A 30 m B 20 m
Possible Valid Recovery Valid Recovery Valid Recovery
Year Month Records Records Rate (%) Records Rate (%) Records Rate (%)
2009 Jun 2,073 2,073 100.0 2,073 100.0 2,073 100.0
2009 Jul 4,464 4,464 100.0 4,464 100.0 4,464 100.0
2009 Aug 4,464 4,464 100.0 4,464 100.0 4,464 100.0
2009 Sep 4,320 4,320 100.0 4,320 100.0 4,320 100.0
2009 Oct 4,464 4,244 95.1 4,240 95.0 4,350 97.5
2009 Nov 4,320 4,263 98.7 4,241 98.2 4,320 100.0
2009 Dec 4,464 4,464 100.0 4,354 97.5 4,464 100.0
2010 Jan 4,464 4,464 100.0 4,464 100.0 4,464 100.0
2010 Feb 4,032 4,032 100.0 4,032 100.0 4,032 100.0
2010 Mar 4,464 4,464 100.0 4,464 100.0 4,464 100.0
2010 Apr 4,320 4,186 96.9 4,320 100.0 4,320 100.0
2010 May 4,464 4,464 100.0 4,464 100.0 4,464 100.0
2010 Jun 4,320 4,320 100.0 4,320 100.0 4,320 100.0
2010 Jul 2,016 1,949 96.7 1,949 96.7 1,949 96.7
All data 56,649 56,171 99.2 56,169 99.2 56,468 99.7
Wind Speed
Wind data collected from the met tower, from the perspective of both mean wind speed and mean
power density, indicates an outstanding wind resource. The minor discrepancy in mean wind speed
between the 30 m A and the 30 m B anemometer is due to the placement of the of the 30 m A
anemometer at 178° T. With frequent northerly winds, the 30m A anemometer experienced some
minor tower shadowing effects. The cold arctic temperatures of Point Hope contributed to the high
wind power density, a key consideration of wind turbine performance.
Point Hope Wind Resource Report Page 6
Anemometer data summary
Variable
Speed 30 A Speed 30 B Speed 20
Measurement height (m) 30 30 20
Mean wind speed (m/s)7.02 7.12 6.79
Max 10-min avg wind speed (m/s) 27.5 27.9 26.1
Max gust wind speed (m/s) 31.7 32.2 31.4
Weibull k 1.85 1.82 1.82
Weibull c (m/s) 7.83 7.92 7.57
Mean power density (W/m²) 487 515 452
Mean energy content (kWh/m²/yr) 4,268 4,515 3,955
Energy pattern factor 2.11 2.14 2.16
Frequency of calms (%) 19.6 19.7 21.7
1-hr autocorrelation coefficient 0.948 0.949 0.950
Diurnal pattern strength 0.033 0.032 0.034
Hour of peak wind speed 19 19 19
Time Series
Time series calculations indicate high wind speed averages throughout the year, even during summer.
Although the October 2009 wind speed average was low compared to September and November, this is
likely a statistical variation that would even out with multi-year data collection.
30m B data summary
Mean
Max 10-
min avg
Max
gust
Std.
Dev.
Weibull
k
Weibull
c
Year Month (m/s) (m/s) (m/s) (m/s) (m/s)
2009 Jun 6.41 15.4 18.2 3.14 2.14 7.23
2009 Jul 6.26 17.5 21.6 2.90 2.28 7.06
2009 Aug 6.64 19.9 23.5 3.57 1.92 7.47
2009 Sep 8.54 21.4 25.8 4.38 2.04 9.63
2009 Oct 6.28 15.9 18.6 3.35 1.97 7.10
2009 Nov 8.67 24.0 26.9 5.00 1.73 9.68
2009 Dec 9.05 27.9 32.2 4.64 2.03 10.20
2010 Jan 7.76 23.6 29.9 4.35 1.84 8.72
2010 Feb 7.03 22.8 24.6 3.66 2.00 7.92
2010 Mar 6.99 20.3 24.6 4.26 1.66 7.81
2010 Apr 6.91 19.0 23.9 3.45 2.09 7.79
2010 May 5.53 19.0 23.1 3.47 1.67 6.20
2010 Jun 5.04 15.7 18.9 2.90 1.82 5.68
2010 Jul 7.41 16.1 19.3 3.70 2.11 8.36
MMM Annual 7.12 27.9 32.2 4.02 1.82 7.92
Point Hope Wind Resource Report Page 7
Time series graph
Daily Wind Profile
The daily wind profile indicates a minor variation of wind speeds throughout the day, with lowest wind
speeds during the morning hours and highest wind speeds during late afternoon and early evening
hours. This perspective changes a bit when considering monthly views of daily profiles as more variation
is observed.
Annual daily wind profile
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
0
2
4
6
8
10 Seasonal Wind Speed Profile
Speed 30 A
Speed 30 B
Speed 20
0 6 12 18 24
0
2
4
6
8 Mean Daily Profile
Hour of Day
Speed 30 A
Speed 30 B
Speed 20
Point Hope Wind Resource Report Page 8
Monthly daily wind profile
Probability Distribution Function
The probability distribution function (or histogram) of wind speed indicates a near-normal shape curve,
defined as the Raleigh distribution (k=2.0), considered standard for wind power sites.
Wind Shear and Roughness
A wind shear power law exponent of 0.110 indicates very low wind shear at the site; hence turbine
construction at a low hub height is feasible. Related to wind shear, a calculated surface roughness of
0.000789 meters (indicating the height above ground level where wind velocity would be zero) indicates
moderately uneven terrain (roughness description: rough sea) surrounding the met tower, especially in
the direction of the prevailing north-northwest winds.
0 5 10 15 20 25 30
0
1
2
3
4
5
6 Probability Distibution Function, All Sectors
Speed 30 B (m/s)
Point Hope Wind Resource Report Page 9
Vertical wind shear profile
Wind shear by direction sector table, wind speed > 4 m/s
Time
Steps
Sector
Wind Mean Wind Speed (m/s)
Best-Fit
Power Law
Exp
Surface
Roughness
(m)Direction Sector (%) Speed 30 B Speed 20
348.75° - 11.25° 8,323 19.6% 9.91 9.45 0.081 0.0001
11.25° - 33.75° 4,374 10.3% 10.75 10.30 0.068 0.0000
33.75° - 56.25° 2,454 5.8% 8.51 8.08 0.108 0.0024
56.25° - 78.75° 1,564 3.7% 6.28 5.86 0.183 0.1047
78.75° - 101.25° 922 2.2% 6.52 5.91 0.274 0.6355
101.25° - 123.75° 1,238 2.9% 8.78 7.92 0.289 0.7712
123.75° - 146.25° 3,151 7.4% 8.99 8.51 0.164 0.0557
146.25° - 168.75° 2,744 6.5% 7.48 7.31 0.065 0.0000
168.75° - 191.25° 1,806 4.2% 7.24 7.19 0.007
191.25° - 213.75° 338 0.8% 6.13 5.50 0.261 0.5313
213.75° - 236.25° 282 0.7% 5.52 5.06 0.225 0.2894
236.25° - 258.75° 207 0.5% 5.76 5.29 0.221 0.2626
258.75° - 281.25° 316 0.7% 6.11 5.65 0.211 0.2156
281.25° - 303.75° 1,028 2.4% 6.34 6.09 0.116 0.0044
303.75° - 326.25° 3,925 9.2% 6.50 6.27 0.067 0.0000
326.25° - 348.75° 9,870 23.2% 8.26 7.94 0.074 0.0000
0 2 4 6 8 10
0
20
40
60
80
100 Vertical Wind Shear Profile, All Sectors
Mean Wind Speed (m/s)
Measured data
Power law fit (alpha = 0.110)
Log law fit (z0 = 0.00268 m)
Point Hope Wind Resource Report Page 10
Extreme Winds
Although thirteen months of data is minimal for calculation of extreme wind probability, use of a
modified Gumbel distribution analysis, based on monthly maximum winds vice annual maximum winds,
yields more realistic results. Extreme wind analysis indicates a highly desirable situation in Point Hope:
high mean wind speeds combined with low extreme wind speed probabilities. This may be explained by
particular climactic aspects of Point Hope which include prominent coastal exposure, offshore wind
conditions, and due to the extreme northerly latitude, lack of exposure to Gulf of Alaska storm winds.
Industry standard reference of extreme wind is the 50 year 10-minute average probable wind speed,
referred to as Vref. For Point Hope, this calculates to 32.1 m/s, below the threshold of International
Electrotechnical Commission (IEC) 61400-1, 3rd edition criteria for a Class III site. Note that Class III
extreme wind classification is the lowest defined and all wind turbines are designed for this wind
regime.
Extreme wind speed probability table
Vref Gust IEC 61400-1, 3rd ed.
Period (years)(m/s) (m/s) Class Vref, m/s
2 24.8 29.6 I 50.0
10 28.4 33.9 II 42.5
15 29.4 35.0 III 37.5
30 30.9 36.8 S designer-
specified5032.1 38.2
100 33.6 40.1
average gust factor:1.19
Extreme wind speed probability graph
20.0
25.0
30.0
35.0
40.0
45.0
0 10 20 30 40 50 60 70 80 90 100
Period, years
(m/s)
(m/s)
Point Hope Wind Resource Report Page 11
Temperature and Density
Point Hope experiences cool summers and very cold winters. The result is high air density. Calculated
air density during the met tower test period exceeds standard air density for a sea level elevation (1.225
Kg/m3) by eight percent. This is advantageous in wind power operations as wind turbines produce more
power at low temperatures (high air density) than at standard temperature and density.
Temperature and density table
Temperature Density
Month Mean Min Max Mean Min Max
(°C) (°C) (°C) (kg/m³) (kg/m³) (kg/m³)
Jan -20.8 -34.3 -9.7 1.399 1.339 1.477
Feb -18.1 -33.4 -1.2 1.384 1.297 1.472
Mar -19.7 -34.6 -0.8 1.393 1.295 1.479
Apr -9.5 -25.4 4.0 1.339 1.273 1.424
May -1.6 -13.1 7.1 1.299 1.259 1.357
Jun 3.9 -3.1 14.6 1.274 1.226 1.306
Jul 9.4 2.0 25.2 1.248 1.182 1.282
Aug 8.3 2.1 15.0 1.254 1.224 1.282
Sep 3.8 -5.3 11.0 1.274 1.242 1.317
Oct -0.3 -10.5 7.5 1.293 1.257 1.343
Nov -12.6 -31.7 -3.9 1.354 1.310 1.461
Dec -11.4 -28.7 1.0 1.349 1.287 1.443
Annual -5.7 -34.6 25.2 1.322 1.182 1.479
Monthly temperature boxplot
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Ann
-40
-30
-20
-10
0
10
20
30 Monthly Statistics for Temperature
max
daily high
mean
daily low
min
Point Hope Wind Resource Report Page 12
Air density DMap
Wind Speed Scatterplot
The wind speed versus temperature scatterplot below indicates that a substantial percentage of wind in
Point Hope coincides with very cold temperatures, as one would expect give the location on the Chukchi
Sea coast. However, during the met tower test periods, temperatures did not fall below -40°C. Other
winters may see colder temperatures, but it is likely that temperatures colder than -40°C are infrequent
and short duration in Point Hope. This compares to relatively nearby Wainwright which recorded a
number of sub-minus 40°C temperature readings.
Wind speed versus temperature scatterplot
-40 -30 -20 -10 0 10 20 30
0
5
10
15
20
25 Speed 30 B vs. Temperature, All Sectors, Speed 30 B 0 m/s - 25 m/s
Temperature (°C)
Point Hope Wind Resource Report Page 13
Wind Direction
Wind frequency rose data indicates highly directional winds from the north and southeast. Power
density rose data (representing the power in the wind) indicates power winds are strongly directional,
from 345°T to 025°T and to a lesser extent from 130°T. Calm frequency (percent of time that winds at
the 30 meter level are less than 3.5 m/s) was 20 percent during the met tower test period.
Wind frequency rose Mean value rose
Wind energy rose Scatterplot rose
Point Hope Wind Resource Report Page 14
Wind density roses by month
Turbulence
Turbulence intensity at the Point Hope test site is well within acceptable standards with an IEC 61400-1,
3rd edition (2005) classification of turbulence category C, which is the lowest defined.
Turbulence intensity, all wind sectors
0 5 10 15 20 25 30
0.0
0.1
0.2
0.3
0.4
0.5
0.6 Turbulence Intensity at 30 m, All Sectors
Wind Speed (m/s)
Representative TI
IEC Category A
IEC Category B
IEC Category C
Point Hope Wind Resource Report Page 15
Turbulence intensity, north (prevailing) wind sector
Turbulence intensity by direction
Turbulence table
Midpoint Bin Endpoints
Records
In Bin
Standard
Deviation RepresentativeLower Upper Mean Peak
(m/s) (m/s) (m/s) TI of TI TI TI
1 0.5 1.5 1,613 0.371 0.165 0.583 1.000
2 1.5 2.5 3,307 0.180 0.095 0.301 0.895
3 2.5 3.5 5,016 0.116 0.055 0.186 0.593
4 3.5 4.5 5,796 0.091 0.043 0.147 0.475
0 5 10 15 20 25 30
0.0
0.1
0.2
0.3
0.4
0.5
0.6 Turbulence Intensity at 30 m, 337.5° - 22.5°
Wind Speed (m/s)
Representative TI
IEC Category A
IEC Category B
IEC Category C
0°15°
30°
45°
60°
75°
90°
105°
120°
135°
150°
165°180°195°
210°
225°
240°
255°
270°
285°
300°
315°
330°345°
0.06
0.12
0.18
Point Hope Wind Resource Report Page 16
5 4.5 5.5 6,124 0.079 0.036 0.125 0.673
6 5.5 6.5 5,779 0.075 0.033 0.118 0.633
7 6.5 7.5 5,779 0.072 0.028 0.107 0.412
8 7.5 8.5 4,680 0.071 0.027 0.105 0.360
9 8.5 9.5 3,924 0.072 0.023 0.101 0.309
10 9.5 10.5 3,349 0.071 0.021 0.099 0.414
11 10.5 11.5 2,421 0.072 0.020 0.097 0.390
12 11.5 12.5 1,906 0.072 0.018 0.095 0.198
13 12.5 13.5 1,438 0.073 0.017 0.095 0.244
14 13.5 14.5 1,207 0.073 0.014 0.092 0.188
15 14.5 15.5 1,062 0.073 0.015 0.093 0.230
16 15.5 16.5 662 0.073 0.016 0.094 0.151
17 16.5 17.5 533 0.074 0.017 0.096 0.211
18 17.5 18.5 343 0.076 0.017 0.097 0.196
19 18.5 19.5 250 0.076 0.016 0.096 0.128
20 19.5 20.5 130 0.074 0.016 0.094 0.114
21 20.5 21.5 75 0.080 0.017 0.102 0.116
22 21.5 22.5 52 0.082 0.015 0.101 0.111
23 22.5 23.5 48 0.071 0.016 0.091 0.104
24 23.5 24.5 28 0.065 0.010 0.078 0.087
25 24.5 25.5 19 0.065 0.009 0.076 0.082
26 25.5 26.5 12 0.057 0.010 0.070 0.076
27 26.5 27.5 6 0.055 0.012 0.070 0.074
28 27.5 28.5 1 0.043 0.000 0.043 0.043
Airport ASOS Data
In 2005, Alaska Energy Authority (AEA) analyzed the wind resource at all Automated Weather Observing
Station (AWOS) and Automated Surface Observing System (ASOS) sites in Alaska. At most stations,
AWOS/ASOS data has been collected for twenty-five or more years. The Point Hope Airport (ICAO
station identifier: PAPO) AWOS has been in place since 1990.
The AEA report documents data from the AWOS sensor, which is 10 meters above ground level. To
compare this data to the met tower upper sensor height of 30 meters, the data was extrapolated with a
power law exponent value of 0.110. Compared to the met tower 30 meter B anemometer, the AWOS
data predicts an annual wind speed average approximately six percent higher. There may be a number
of reasons for this discrepancy, including the more exposed location of the airport to northerly winds
with less upwind terrain (that will cause some wind speed decrease due to drag) and extrapolation
errors in translating the ten meter airport data to thirty meters. Comparison discrepancies aside, the
Point Hope airport data confirms the robust wind resource recorded by the met tower.
Point Hope Wind Resource Report Page 17
Airport/met tower data comparison
Point Hope Airport
AWOS, 10 m
sensor
Data
adjusted to
30 m
Met tower
data, 30m B
anem.
Met
tower/AWOS
adj. data
(m/s) (m/s) (m/s) (%)
Jan 6.90 7.79 7.76 99.7%
Feb 6.80 7.67 7.03 91.6%
Mar 6.10 6.88 6.99 101.5%
Apr 5.90 6.66 6.91 103.8%
May 5.60 6.32 5.53 87.5%
Jun 5.60 6.32 5.49 86.8%
Jul 6.00 6.77 6.61 97.6%
Aug 6.90 7.79 6.64 85.2%
Sep 7.60 8.58 8.54 99.5%
Oct 7.90 8.91 6.28 70.4%
Nov 7.70 8.69 8.67 99.7%
Dec 7.40 8.35 9.05 108.4%
Annual 6.70 7.56 7.12 94.2%