HomeMy WebLinkAboutPoint Lay Wind Resource Report - Sep 2010 - REF Grant 7040027Point Lay Wind Resource Report
By: Douglas Vaught, P.E., V3 Energy, LLC, Eagle River, Alaska
Date: September 16, 2010
Contents
Summary Information...................................................................................................................................1
Test Site Location..........................................................................................................................................2
Data Recovery...............................................................................................................................................3
Wind Speed...................................................................................................................................................3
Time Series................................................................................................................................................4
Daily Wind Profile .....................................................................................................................................5
Probability Distribution Function..................................................................................................................5
Wind Shear and Roughness..........................................................................................................................6
Temperature and Density.............................................................................................................................7
Wind Direction..............................................................................................................................................8
Turbulence....................................................................................................................................................9
Summary Information
The wind resource measured in Point Lay is very good, measured at high wind power class 4 (good) to
low wind power class 5 (excellent). In addition to strong average wind speed and wind power density,
the site experiences highly directional prevailing winds and low turbulence.
Met tower data synopsis
Data dates October 5, 2006 to September 11, 2007
Wind power class High 4 (good) to low 5 (excellent)
Power density mean, 30 meters 403 W/m2
Wind speed mean, 30 meters 6.63 m/s
Weibull distribution parameters k = 1.74, c = 7.44 m/s
Wind shear power law exponent 0.142 (moderate), June to September data only
Roughness class 0.54 (snow surface), June to September only
IEC 61400-1, 3rd ed. classification Class III-c (likely, based on nearby Wainwright data)
Turbulence intensity, mean 0.072 (at 15 m/s)
Calm wind frequency 23% (less than 3.5 m/s)
Point Lay community profile (DCCED)
Current Population: 234 (2009 Estimated Population (not Certified))
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Pronunciation/Other Names: a.k.a. Kali
Incorporation Type: Unincorporated
Borough Located In: North Slope Borough
School District: North Slope Borough Schools
Regional Native Corporation: Arctic Slope Regional Corp.
Test Site Location
The Point Lay met tower was supplied to the Cully Corporation in Point Lay in 2006 as part of the
National Renewable Energy Laboratory’s (NREL) anemometer loan program. Details of the project are
not known, such as rationale for choosing the test site, but plotting the latitude and longitude of the
met tower (keyed into the datalogger and readable in the data file) with Google Earth indicates a site
well away from obstructions such as buildings and well exposed to winds from all directions.
Site information
Site number 5430
Latitude/longitude N 69°44.123’ W 163°01.349’
Site elevation 1 meter AMSL
Datalogger type NRG Symphonie, 10 minute time step
Tower type NRG 30 meter tall tower
Google Earth image
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Tower sensor information
Channel Sensor Type Height Scale Offset Orientation
1 NRG #40 anemometer 99 ft 1.711 0.78 unknown
2 NRG #40 anemometer 99 ft
3 NRG #40 anemometer 66 ft
7 NRG #200P wind vane 99 ft 0.351 0 000°
8 NRG #200P wind vane 66 ft 000°
9 NRG #100S Temperature 5 ft 0.244 -123.5
Note: logger was programmed with English units and later converted to metric units for analysis
Data Recovery
Specific sensor data recovery problems typical of Alaska met tower operations, such as freezing rain,
hoarfrost, and rime icing, likely occurred to some extent during the nearly one year met tower study in
Point Lay, but original data was not available, other than in an Excel file with data from June 7 through
September 11, 2007. Although this three month data set could be reviewed for data loss typically due
to atmospheric icing conditions, such weather does not occur during the months of June, July, August
and (early) September. All met tower data (including that not included in the Excel file download of
original data) is summarized in several WindPRO software reports prepared by the National Renewable
Energy Laboratory.
Wind Speed
Wind data collected from the met tower and summarized in the NREL WindPRO reports, from the
perspective of both mean wind speed and mean power density, indicates an excellent wind resource.
Note that temperature data was not included in the analysis of power density. Given the extremely cold
temperatures, and hence high air densities, of Point Lay, true wind power density will be higher yet,
categorizing Point Lay more solidly as wind power class 5. For purposes of analysis, wind data monthly
wind speed summaries contained in the 30 meter WindPRO report, along with other statistical data
gleaned from the three-month Excel data, was used to synthesize a virtual data set. This enabled certain
mathematic and graphical analyses not contained in the WindPRO reports.
Anemometer data summary
Variable Speed 30 m
Measurement height (m) 30
Mean wind speed (m/s) 6.63
Median wind speed (m/s) 5.99
Max wind speed (m/s) 26.8
Weibull k 1.74
Weibull c (m/s) 7.44
Mean power density (W/m²) 403
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Mean energy content (kWh/m²/yr) 3,528
Energy pattern factor 2.26
Frequency of calms (%) 23.4
1-hr autocorrelation coefficient 0.945
Diurnal pattern strength 0.041
Hour of peak wind speed 19
Time Series
Monthly average wind speeds indicate relatively high winds throughout the year, even during summer.
Monthly variations appear significant but likely would smooth considerably in a multi-year view.
30 meter anemometer data summary
Month Mean Median
Max 10-
min
Std.
Dev.
Weibull
k
Weibull
c
(m/s) (m/s) (m/s) (m/s) (m/s)
Jan 7.70 7.11 25.9 4.39 1.82 8.66
Feb 8.30 7.64 26.8 4.73 1.82 9.33
Mar 6.20 5.68 21.1 3.53 1.82 6.97
Apr 7.90 7.22 25.4 4.49 1.81 8.88
May 5.00 4.63 15.9 2.84 1.82 5.62
Jun 6.30 5.79 20.3 3.57 1.83 7.08
Jul 5.60 5.19 18.5 3.18 1.83 6.30
Aug 5.70 5.24 19.8 3.25 1.82 6.41
Sep 5.40 4.94 18.0 3.07 1.82 6.07
Oct 7.40 6.81 24.3 4.21 1.82 8.32
Nov 7.20 6.61 23.4 4.09 1.82 8.10
Dec 7.00 6.48 22.7 3.97 1.83 7.87
Annual 6.63 5.99 26.8 3.95 1.74 7.44
Time series graph
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
0
2
4
6
8
10 Seasonal Wind Speed Profile
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Daily Wind Profile
The daily wind profile indicates a relatively minor variation of wind speeds throughout the day, with
lowest wind speeds in the early and mid-morning hours and highest wind speeds during the late
afternoon and early evening hours. More variation, however, can be expected with a monthly view of
daily wind profiles.
Annual-basis daily wind profile
Monthly (daily) wind profiles
Probability Distribution Function
The probability distribution function (or histogram) of wind speed indicates a near-normal shape curve,
defined as the Raleigh distribution (where k=2.0), considered standard for wind power sites.
0 6 12 18 24
0
1
2
3
4
5
6
7 Daily Wind Speed Profile
Hour of Day
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Wind Shear and Roughness
Considering just the June through September data, a calculated wind shear power law exponent of
0.142 indicates relatively low wind shear (change of wind speed with increasing height above the
ground) at the site, which is desirable for wind power development. Related to wind shear, a calculated
surface roughness of 0.0096 meters (indicating the height above ground level where the wind velocity
would be zero) indicates very smooth air terrain (roughness description: snow surface) surrounding the
met tower.
Vertical wind shear profile, wind >4 m/s, June thru Sept data
0 5 10 15 20 25 30
0
1
2
3
4
5
6 Probability Distibution Function, All Sectors
Speed 30 m (m/s)
0 5 10 15 20
0
50
100
150
200
250
300
350 Vertical Wind Shear Profile, All Sectors, 9 - 100 m/s
Mean Wind Speed (mph)
Measured data
Power law fit (alpha = 0.142)
Log law fit (z0 = 0.0700 m)
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Wind shear by direction table, wind >4 m/s, June thru Sept data
Time
Steps
Mean Wind Speed (m/s)Best-fit
Power Law
Exp
Surface
Roughness
(m)Direction Sector
Speed
30m A
Speed
30m B
Speed
20m
348.75° - 11.25° 1,236 6.68 6.71 6.63 0.024 0.000
11.25° - 33.75° 1,003 6.83 6.89 6.45 0.154 0.122
33.75° - 56.25° 1,832 7.64 7.58 7.03 0.193 0.458
56.25° - 78.75° 2,156 9.16 8.98 8.48 0.164 0.178
78.75° - 101.25° 531 6.06 5.92 5.28 0.314 3.324
101.25° - 123.75° 115 6.03 5.91 5.38 0.254 1.581
123.75° - 146.25° 83 4.82 4.86 4.57 0.142 0.070
146.25° - 168.75° 72 5.64 6.50 6.11 -0.018
168.75° - 191.25° 203 10.09 10.11 9.51 0.150 0.102
191.25° - 213.75° 471 8.20 8.31 7.93 0.099 0.003
213.75° - 236.25° 323 7.06 7.04 6.37 0.249 1.457
236.25° - 258.75° 200 6.37 6.17 5.96 0.125 0.026
258.75° - 281.25° 176 5.39 5.23 5.11 0.093 0.002
281.25° - 303.75° 159 4.80 3.74 4.67 -0.222
303.75° - 326.25° 131 5.23 5.03 5.19 -0.031
326.25° - 348.75° 458 5.30 5.30 5.32 -0.010
Extreme Winds
Data obtained for this wind resource analysis was not sufficient to calculate extreme wind probabilities.
However, extreme wind probability calculations for the relatively nearby Wainwright met tower indicate
a 50 year Vref, or 50-year probable maximum 10 minute wind speed, of 24.8 m/s, well below the
threshold criteria for International Electrotechnical Commission (IEC) 61400-1, 3rd edition, Class III
classification. Note that Class III is the lowest defined wind class and all wind turbines are designed for
this wind regime.
Temperature and Density
Data obtained for this wind resource analysis did not include an annual temperature or air density
summary, other than the June through September data in the Excel file. However, it is a reasonable
presumption that Point Lay experiences similar temperatures as the village of Wainwright, hence
Wainwright temperature and density data is presented below for information. Note that Wainwright
experiences cool summers and extremely cold winters. The result is high air density; calculated air
density exceeds standard air density for a sea level elevation (1.225 Kg/m3) by nine 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.
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Temperature and density table, Wainwright, 2009-2010
Temperature Air Density
Month Mean Min Max Mean Min Max
(°C) (°C) (°C) (kg/m³) (kg/m³) (kg/m³)
Jan -25.1 -40.6 -9.1 1.421 1.334 1.515
Feb -23.1 -43.0 -13.2 1.410 1.355 1.531
Mar -23.7 -41.1 -12.5 1.413 1.352 1.518
Apr -11.9 -33.4 0.3 1.349 1.288 1.469
May -5.3 -19.7 3.2 1.316 1.275 1.390
Jun 4.0 -1.5 19.0 1.272 1.206 1.297
Jul 8.2 0.7 27.2 1.252 1.173 1.286
Aug 6.6 0.9 17.0 1.260 1.214 1.286
Sep 2.1 -9.0 14.3 1.280 1.226 1.334
Oct -3.7 -15.7 5.2 1.308 1.266 1.368
Nov -18.5 -35.1 -6.7 1.384 1.322 1.480
Dec -18.8 -34.3 -0.5 1.386 1.292 1.475
Annual -9.0 -43.0 27.2 1.337 1.173 1.531
Monthly temperature boxplot, Wainwright, 2009-2010
Wind Direction
Wind frequency rose data (from NREL’s WindPRO report) indicates highly directional winds from
northeast to east-northeast. Although the NREL report did not show a power density rose, Wainwright
data confirms the Point Lay directional frequency and indicates that power winds are nearly exclusively
northeast to east-northeast, which presumably is representative of Point Lay.
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Ann
-60
-40
-20
0
20
40 Monthly Statistics for Temperature
max
daily high
mean
daily low
min
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Wind frequency rose
Turbulence
From the NREL report, turbulence intensity at the Point Lay 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. Mean turbulence intensity at 15 m/s is 0.072
Turbulence graphs
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Turbulence table