HomeMy WebLinkAboutShishmaref Wind Resource Assessment Report - Apr 2023 - REF Grant 7091223Shishmaref Wind Resource
Assessment Report
Shishmaref, view southwest, Google Earth image
April 6, 2023
Douglas Vaught, P.E.
V3 Energy, LLC
Anchorage, Alaska
www.v3energy.com
Shishmaref Wind Resource Assessment Report Page | i
Contents
Introduction..................................................................................................................................................1
Lidar ..............................................................................................................................................................1
Lidar Location and Data Summary................................................................................................................2
Data Quality..............................................................................................................................................3
Wind Speed...............................................................................................................................................4
Wind Direction..........................................................................................................................................5
Temperature and Density.....................................................................................................................5
Shishmaref AWOS Wind Speed.....................................................................................................................6
IEC Classification...........................................................................................................................................7
Extreme Wind...........................................................................................................................................7
Shishmaref Lidar Site ............................................................................................................................7
Turbulence Intensity.................................................................................................................................8
Shishmaref Lidar Site ............................................................................................................................8
Wind Shear................................................................................................................................................8
Shishmaref Lidar Site ............................................................................................................................9
Wake Turbulence......................................................................................................................................9
Shishmaref Lidar Site ............................................................................................................................9
Flow Inclination.........................................................................................................................................9
Shishmaref Lidar Site ..........................................................................................................................10
Wind Distribution....................................................................................................................................10
Shishmaref Lidar Site ..........................................................................................................................10
Met Tower Site IEC 61400-1 Classification.............................................................................................11
Global Wind Atlas........................................................................................................................................11
Conclusion and Recommendations ............................................................................................................12
Figure 1: ZX300 lidar unit in Shishmaref.......................................................................................................1
Figure 2: Shishmaref lidar and airport weather station locations................................................................2
Figure 3: Documentation of lidar orientation (AVEC photo)........................................................................3
Figure 4: Lidar wind rose (6.5 months).........................................................................................................5
Figure 5: Shishmaref Airport wind rose (40 years)........................................................................................5
Figure 6: Shishmaref Airport AWOS wind speed, 10-meter height..............................................................6
Figure 7: Lidar site wind shear profile...........................................................................................................9
Figure 8: Lidar-measured vertical inflow angles.........................................................................................10
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Figure 9: Lidar-derived wind speed distribution, or histogram..................................................................11
Figure 10: Global Wind Atlas for Shishmaref..............................................................................................12
Table 1: Shishmaref lidar location data........................................................................................................3
Table 2: Shishmaref lidar data recovery rates..............................................................................................4
Table 3: Wind speed summary .....................................................................................................................4
Table 4: Shishmaref Airport AWOS temperature and RH, 2000 to 2023 .....................................................6
Table 5: IEC 61400-1, 3rd edition, simplified wind classification...................................................................7
Table 6: IEC 61400-1, 3rd edition, extreme wind classes ..............................................................................7
Table 7: Calculated extreme wind probabilities from lidar ..........................................................................8
Table 8: IEC 61400-1, 3rd edition, turbulence categories..............................................................................8
Table 9: Lidar-measured turbulence intensity..............................................................................................8
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Introduction
V3 Energy LLC was contracted by Alaska Village Electric Cooperative, Inc. (AVEC) to prepare a wind
resource assessment report for the village of Shishmaref, one of its member communities. Wind data
was collected from April 2022 to October 2022 from a light detection and ranging (lidar) unit installed by
AVEC personnel. Analysis of this data, combined with review of 22 years of Shishmaref Airport wind
data, indicates a Class 4 (good) wind resource with IEC 61400-1, 3
rd edition characteristics highly suitable
for the development of wind power.
Lidar
Lidar is a method for determining range or distance by targeting an object or the ground surface with a
laser and measuring the time for reflected light to return to a receiver. It employs ultraviolet, visible, and
near infrared light and can target many materials, including non-metallic objects, rocks, rain, and
aerosols. It is capable of extraordinary resolution, even at long distances.1
Figure 1: ZX300 lidar unit in Shishmaref
For the Shishmaref project, AVEC used the ZX 300 model lidar sold by NRG Systems, Inc. of Hinesburg,
Vermont (see Figure 1). NRG’s website states that it offers full IEC classification and is accepted by DNV
2
1 Lidar - Wikipedia
2 DNV.com - When trust matters - DNV, a risk management and assurance consultancy
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as a Stage 3 bankable lidar.3 The ZX 300 employs three lasers that aim vertically and rotate in a narrow
cone to enable measurement of up to ten discrete heights above the lidar from 10 to 300 meters.
Lidar Location and Data Summary
AVEC technicians securely installed the lidar on a metal shipping container on powerplant property on
the western edge of the community, near the airport (see Figure 1 and Figure 2).
Figure 2: Shishmaref lidar and airport weather station locations
Sensor information (refer to Table 1) was contained in the metadata embedded in the data files sent by
the lidar unit. Notably, compared to sensors attached to a more familiar typically two-dimensional scalar
measurements of anemometers and wind vanes on meteorological (met) towers, lidar measurements
are three-dimensional vectors (magnitude and direction) that detect horizontal speed, vertical speed,
and direction of the wind at each level every second (Figure 3 demonstrates unit orientation to true
north).
For the Shishmaref project, the ZX 300 was programmed to measure wind at six levels: 10, 25, 35, 38,
55, and 95 meters. Environmental data, including air temperature, barometric pressure, and relative
humidity (along with non-laser-measured wind speed and direction) were collected from a met mast on
the lidar unit.
3 Microsoft Word - GLGH-4275 18 14741 258-R-0003-D _RaTav_BScm (nrgsystems.com)
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Table 1: Shishmaref lidar location data
Site name Shishmaref
Installation date April 2022
Data start date 13 April 2022
Data end date 27 October 2022
Unit NRG ZX300 lidar
Site latitude/longitude and elevation 66.2543, -166.0739; 3 meters (10 ft.)
Displacement height (AGL) 3.5 meters (11.5 ft.)
Time Zone Alaska Standard Time (UTC-09:00)
Figure 3: Documentation of lidar orientation (AVEC photo)
The wind resource measured by the Shishmaref lidar is wind power class 4 (good) with a moderately
high mean wind speed, low turbulence, low wind shear, and low extreme wind speeds. Note however
that only 6.5 months of lidar data were collected with the winter months excluded.
Data Quality
Lidar data is very different and more robust than met tower sensor data as the latter typically requires
filtering for icing and other problems. With lidar for wind measurement, data loss does not occur due to
icing as there are no exposed sensors. Data loss can occur though due to heavy precipitation which
prevents proper reflection of the laser signal to the receiver, and operation in very clear, pure air which
does not contain aerosols, dust, or other particulates from which the lasers can reflect.
The lidar had fully functional lasers throughout the 6.5 months data period and there were only two
very brief power outages. Data recovery was excellent at 85+% for all variables (see Table 2).
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Table 2: Shishmaref lidar data recovery rates
Data Channel Height DRR* (%)
Horizontal Wind Speed at 95m 95 m 86.4
Horizontal Wind Speed at 55m 55 m 92.8
Horizontal Wind Speed at 38m 38 m 93.8
Horizontal Wind Speed at 35m 35 m 93.4
Horizontal Wind Speed at 25m 25 m 94.5
Horizontal Wind Speed at 10m 10 m 97.1
Wind Direction at 95m 95 m 86.4
Wind Direction at 55m 55 m 92.8
Wind Direction at 38m 38 m 93.8
Wind Direction at 35m 35 m 93.4
Wind Direction at 25m 25 m 94.5
Wind Direction at 10m 10 m 97.1
Vertical Wind Speed at 95m 95 m 77.8
Vertical Wind Speed at 55m 55 m 83.9
Vertical Wind Speed at 38m 38 m 85.0
Vertical Wind Speed at 35m 35 m 84.8
Vertical Wind Speed at 25m 25 m 85.8
Vertical Wind Speed at 10m 10 m 88.2
Met Air Temp. 2m 2 m 99.8
Met Pressure 2m 2 m 99.8
Met Humidity 2m 2 m 99.8
*Data Recovery Rate
Wind Speed
Horizontal wind speeds calculated from lidar data, from the perspectives of both mean wind speed and
mean wind power density, indicate a good wind resource. Note that cold temperatures contributed to a
higher wind power density than standard conditions would yield for the measured mean wind speeds.
This is reflected in the cubed root mean cubed (CRMC) wind speed, which reflects a calculation of a
steady wind speed, at the measured mean air density, that would yield the measured mean wind power
density. In other words, the winds punch above their weight. But bear in mind that this data represents
only 6.5 months, with winter missing. Inclusion of winter data will increase the mean wind speed and
with a lower mean temperature (and hence higher density) potentially increase the spread between the
mean and CRMC wind speeds.
Table 3: Wind speed summary
Variable
Horizontal
Wind
Speed at
95m
Horizontal
Wind
Speed at
55m
Horizontal
Wind
Speed at
38m
Horizontal
Wind
Speed at
35m
Horizontal
Wind
Speed at
25m
Horizontal
Wind
Speed at
10m
Measurement height (m) 955538352510
Mean wind speed (m/s) 7.87 7.34 6.98 6.91 6.66 5.44
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Variable
Horizontal
Wind
Speed at
95m
Horizontal
Wind
Speed at
55m
Horizontal
Wind
Speed at
38m
Horizontal
Wind
Speed at
35m
Horizontal
Wind
Speed at
25m
Horizontal
Wind
Speed at
10m
Max wind speed (m/s) 24.2 23.3 22.8 22.4 21.6 18.8
CRMC wind speed (m/s) 9.54 8.91 8.53 8.45 8.17 6.81
Weibull k 2.16 2.14 2.10 2.09 2.07 1.95
Weibull A (m/s) 8.89 8.29 7.88 7.80 7.52 6.13
Mean power density (W/m²) 547 446 390 380 344 199
Mean energy content
(kWh/m²/yr) 4,795 3,904 3,419 3,333 3,014 1,740
Energy pattern factor 1.78 1.79 1.83 1.83 1.85 1.96
Frequency of calms (%) 17.1 18.9 21.0 21.3 22.8 37.1
Diurnally, the winds are strongest mid-afternoon and weakest early morning, as one would expect.
Desirably for wind power, this coincides with a typical electric load demand profile.
Wind Direction
Wind direction measured by the lidar does not indicate a prevailing wind direction, but with summer-
only data this can be misleading (see Figure 4). A review of 40 years of Automated Weather Observing
Station (AWOS) data from the nearby Shishmaref Airport is far more representative of wind directions
than the lidar data, but interestingly it too does not indicate particularly dominant prevailing winds,
except that northerly and easterly winds are more common that southerly and westerly winds (see Figure
5).
Figure 4: Lidar wind rose (6.5 months)Figure 5: Shishmaref Airport wind rose (40 years)
Temperature and Density
Twenty-two years (2000 to 2022) of downloaded and processed airport weather station data
demonstrates that Shishmaref is much colder than the 15° C standard air temperature at sea level. This
Shishmaref Wind Resource Assessment Report Page | 6
data also reveals 79% annual relative humidity, which is indicative of Shishmaref’s maritime climate
(refer to Table 4).
Table 4: Shishmaref Airport AWOS temperature and RH, 2000 to 2023
Airport Temperature RH
Month Avg (°C) Max (°C) Min (°C) Avg (°F) Max (°F) Min (°F) Avg (%)
1 -17.8 4.0 -43.0 0.0 39.2 -45.4 74.8
2 -18.0 3.0 -42.0 -0.4 37.4 -43.6 73.6
3 -17.8 2.8 -40.0 0.0 37.0 -40.0 72.1
4 -9.9 7.0 -32.2 14.1 44.6 -26.0 78.1
5 -1.6 22.0 -21.0 29.2 71.6 -5.8 85.6
6 4.4 21.1 -6.0 39.9 70.0 21.2 84.8
7 9.7 23.0 0.0 49.5 73.4 32.0 78.0
8 9.5 24.0 0.0 49.1 75.2 32.0 82.2
9 6.0 17.0 -5.0 42.7 62.6 23.0 79.2
10 -0.4 9.4 -16.0 31.3 48.9 3.2 79.5
11 -7.7 4.0 -34.0 18.2 39.2 -29.2 79.5
12 -13.3 8.0 -36.0 8.0 46.4 -32.8 77.9
Annual -4.6 24.0 -43.0 23.7 75.2 -45.4 79.1
Shishmaref AWOS Wind Speed
A notable observation of 23 years of AWOS data is minimal seasonal wind speed variability, which is
unusual as typically winter winds are much stronger than summer winds (Figure 6). A second notable
observation is that the 22-year mean annual wind speed of 5.0 m/s (note a 10 meter above ground level
sensor height) is modest for a coastal location, equating to wind power class 3 winds (fair) by wind
speed and wind power class 4 (good) by wind power density.
Figure 6: Shishmaref Airport AWOS wind speed, 10-meter height
123456789101112
Avg (m/s)5.3 5.5 4.9 4.5 4.0 3.8 4.5 5.0 5.4 5.3 5.5 5.9
Max (m/s)20 24 21 28 16 16 20 17 17 19 26 23
0
5
10
15
20
25
30
Wind Speed, m/sMonth
Avg (m/s)
Max (m/s)
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IEC Classification
Six parameters or analyses comprise IEC 61400-1 wind classification as listed below, with the simplified
classification comprising only extreme wind probability and turbulence intensity (see Table 5). They are:
x Extreme wind
x Turbulence intensity
x Wind shear
x Wake turbulence
x Flow inclination
x Wind distribution
Table 5: IEC 61400-1, 3rd edition, simplified wind classification
Wind Class I II III S
Vref (m/s) 50.0 42.5 37.5 Values specified
by the designerA (TIref)0.16
B (TIref)0.14
C (TIref)0.12
Extreme Wind
The classification of extreme wind is by Vref, the reference wind speed; the highest measured or
probable 10-minute average wind speed in a 50-year return period. This can be accomplished with a
periodic maxima analysis (by Gumbel distribution), the method of independent storms (also a Gumbel
distribution), and European Wind Turbine Standards II (EWTS II).4
Table 5 includes Vref as presented in Table 4, plus Ve50, the maximum measured or probable 3-second
average or gust wind speed in a 50-year return period. Ve50 is defined as Vref x 1.4 (for equivalent height),
though the latter is not part of the IEC 61400-1, 3rd edition simplified classification noted in Table 4.
Table 6: IEC 61400-1, 3rd edition, extreme wind classes
Wind Class I II III S
Vref (m/s) 50.0 42.5 37.5 Designer spec.
Ve50 (m/s) 70.0 59.5 52.5
Shishmaref Lidar Site
Six and one-half months of data are far too few to estimate extreme wind probability with confidence,
but results are presented as a guide to possible expected site conditions. Note that periodic maxima,
method of independent storms, and Ve50 by any method cannot be calculated with less than 12 months
of data. But by EWTS II the Shishmaref extreme wind probability appears to be low, classifying as IEC
61400-1, 3rd ed. Wind Class III at the 25, 35, and 55 meter levels (see Table 6). The winter wind resource
is not included, but with reference to Figure 6, seasonal mean wind speed variation is minimal, hence a
reasonable assumption that extreme wind probabilities won’t substantially increase from those
presented in Table 7. If true, and with reference to Table 6, Shishmaref classifies as IEC Class III.
4 EWTS II does not consider peak winds, rather only mean wind speed and Weibull k value.
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Table 7: Calculated extreme wind probabilities from lidar
Vref (50 yr) (m/s)
Method 25 m 35 m 55 m
Periodic Maxima n/a n/a n/a
Method of Independent Storms n/a n/a n/a
EWTS II (Exact) 26.9 27.5 28.4
EWTS II (Gumbel) 27.3 27.9 28.8
EWTS II (Davenport) 29.6 30.3 31.3
Turbulence Intensity
The turbulence intensity (TI) is a dimensionless number defined by the standard deviation (ʍ) of the
wind speed within each time step (10 minutes for wind power analysis) divided by the mean wind speed
(V) over that time step (see Equation 1).
Equation 1: Turbulence intensity
ܶܫ =ߪ݅ ܸ݅ൗ
IEC 61400-1, 3rd ed., defined turbulence categories based on mean turbulence intensity at a wind speed
of 15 m/s (see Table 8).
Table 8: IEC 61400-1, 3rd edition, turbulence categories
Turb. Category S A B C
TI at 15 m/s >0.16 0.14-0.16 0.12-0.14 <0.12
Shishmaref Lidar Site
Turbulence calculated from the lidar horizontal speed data indicate very smooth air with TI well the
Category C threshold, except at the 10 meter level (see Table 9). Note however that higher turbulence is
expected near the ground surface due to the influence of ground effect and nearby infrastructure.
Table 9: Lidar-measured turbulence intensity
Wind Shear
A wind shear, or power law, exponent ɲ is calculated by Equation 2 where V = wind speed and Z = height
above ground level. ɲ=0 would indicate no wind shear and ɲ=0.2 would indicate very high wind shear.
Shishmaref Wind Resource Assessment Report Page | 9
Equation 2: Wind shear
ܸ(ݖ)=ܸ (݄ݑܾ)×ቀܼ ܼ݄ݑܾൗቁ
ఈ
Shishmaref Lidar Site
Lidar horizontal wind speed data indicates a power law exponent (ɲ) of 0.102, which is low (0.14 is
considered nominal in the wind power industry) and reflective of excellent wind shear characteristics for
wind turbine operations (see Figure 7). Note that this calculation excluded the 10 meter level, which
likely suffered from some ground effect, to achieve a better curve fit.
Figure 7: Lidar site wind shear profile
Wake Turbulence
In comparison to the normal turbulence model, IEC 61400-1 suggests an effective turbulence intensity,
which is an ideal turbulence independent of wind direction and expected to cause the same fatigue
damage as variable turbulence in winds from all directions. The effective turbulence intensity includes
turbulence from wakes of neighboring turbines.
5
Shishmaref Lidar Site
Given the lack of notable prevailing wind directions, undesirable wake turbulence could be expected
with an array consisting of multiple wind turbines. Careful modeling would be required to avoid
excessive wake loss.
Flow Inclination
A wind flow vector not exceeding 8 degrees from horizontal (plus or minus).
5 The IEC 61400-1 turbine safety standard - WAsP
Shishmaref Wind Resource Assessment Report Page | 10
Shishmaref Lidar Site
Assessment of vertical wind flow from all wind direction sectors and all measurement heights, excluding
10 meters), indicates slight wind downflow at very low wind speeds, which is typical, and slightly
increasing up flow at higher wind speeds. Both are well below the 8-degree threshold (see Figure 8).
Figure 8: Lidar-measured vertical inflow angles
Wind Distribution
A wind speed, or histogram, where a Weibull function 6 yields a unitless shape factor (k) of 2.0 (known as
a Rayleigh distribution) or less.
Shishmaref Lidar Site
Data from the 25-meter lidar measurement level yields a wind speed distribution with Weibull k value of
2.11, which is ideal, indicating a an excellent mixture of lower and higher wind speeds (refer to Figure 9).
Note that winter data is not represented.
6 Weibull distribution - Wikipedia
Shishmaref Wind Resource Assessment Report Page | 11
Figure 9: Lidar-derived wind speed distribution, or histogram
Met Tower Site IEC 61400-1 Classification
Per the simplified IEC 61400-1, 3rd edition classification and noting the paucity of data for extreme wind
probability calculations, the met tower site classifies as likely Class IIC or very low Class IC. Per the
expanded classification criteria, no disqualifying wind behavior is noted in the data set.
Global Wind Atlas
With less than a full year of wind data, the annual mean speed at the lidar site was not measured,
though reference to airport data significantly reduces mean wind speed uncertainty. While not
necessarily problematic for IEC 61400-1 classification, extreme wind speeds aside, estimated wind
turbine annual energy production may be uncertain. An option is to assess the site using one or more
global wind models. One is Global Wind Atlas.7 Selecting a small area at the 50-meter level that
encompasses the lidar site and community, Global Wind Atlas predicts a mean annual wind speed of
6.52 m/s and wind power density of 384 W/m
2, which describes a wind power class 3 (fair) wind
resource (see Figure 10).
7 Global Wind Atlas is a joint initiative of Technical University of Denmark (DTU) and the World Bank Group. Note
that DTU developed WAsP software.
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Figure 10: Global Wind Atlas for Shishmaref
Conclusion and Recommendations
The wind data collected in Shishmaref is shorter than standard (6.5 months vs. normal 12 months
minimum), but it’s sufficient to tentatively characterize the site as IEC 61400-1, 3
rd edition Class IIIC,
which enables one to select a suitable wind turbine for wind power development.
Note that for wind turbine annual energy production, because there’s only 6.5 months of lidar data,
wind resource software such as Global Wind Atlas and/or reference to Shishmaref Airport data should
be referenced along with the lidar data for better accuracy.