HomeMy WebLinkAboutMountain Village Wind Feasibility and Conceptual Design Wind Resource Report - Aug 2011 - REF Grant 7071067Mountain Village, Alaska Wind Resource
Report
Mountain Village met tower site, view upriver (southeast), D. Vaught photo
August 12, 2011
Douglas Vaught, P.E.
V3 Energy, LLC
Eagle River, Alaska
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Summary
The wind resource measured at the Mountain Village met tower site 0068 is very good with measured
wind power class 5 (excellent). In addition to high average wind speeds and high wind power density,
the site experiences very low turbulence and low extreme wind speed probability.
Met tower data synopsis
Data dates November 5, 2009 to August 9, 2011 (21 months),
status: operational
Wind power class Low Class 5 (excellent)
Power density mean, 50 m 523 W/m
2
Wind speed mean, 50 m 7.62 m/s
Max. 10-min wind speed average 26.5 m/s
Maximum 2-sec. wind gust 31.8 m/s (Feb. 2011)
Weibull distribution parameters k = 2.12, c = 8.65 m/s
Wind shear power law exponent 0.180 (moderate)
Roughness class 2.28 (few trees)
IEC 61400-1, 3rd ed. classification Class III-c
Turbulence intensity, mean 0.072 (at 15 m/s)
Calm wind frequency (at 46 m) 16% (< 4 m/s)
Community Description
Mountain Village has a population of 813 people (2010 census) and is located on north bank of the
Yukon River, approximately 20 miles west of St. Mary's and 470 miles northwest of Anchorage. It is at
the foot of the 500 ft elevation Azachorok Mountain, the first mountain encountered by those traveling
up the Yukon. The climate is continental with maritime influences. Temperatures range from -44 to 80
°F. Annual precipitation averages 16 inches, with snowfall of 44 inches. High winds and low visibility are
common during winter. The Lower Yukon is ice-free from mid-June to October.
Mountain Village was a summer fish camp until the opening of a general store in 1908. This prompted
residents of Liberty Landing and Johnny's Place to immigrate. A Covenant Church missionary school was
also built in that same year. A post office was established in 1923, followed by a salmon saltery in 1956
and a cannery in 1964. The city government was incorporated in 1967. Mountain Village became a
regional education center in 1976 when it was selected as headquarters for the Lower Yukon School
District.
A federally-recognized tribe is located in the community -- the Asa'carsarmiut Tribal Council. Mountain
Village is a Yup'ik Eskimo community with traditional subsistence practices. Commercial fishing and fish
processing provide income. The sale and importation of alcohol is banned in the village.
According to Census 2010, there were 211 housing units in the community and 184 were occupied. The
Mountain Village population is 91.9 percent American Indian or Alaska Native, 4.2 percent white, 0.7
percent Asian, and 3.2 percent of the residents have multi-racial backgrounds. Additionally, 0.4 percent
of the population is of Hispanic descent.
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Water is derived from a well and is treated. Mountain Village operates a piped water and sewer system
that serves 200 households and facilities. A landfill is available. Electricity is provided by AVEC. There is
one school in the community, attended by 242 students. Local hospitals or health clinics include George
Waskey Memorial Clinic in Mountain Village. Emergency service is provided by a health aide.
A summer road links Mountain Village to Pitka's Point, Andreafsky, and St. Mary's. Mountain Village is
accessible by riverboat or barge. A state-owned 3,500' long by 75' wide gravel airstrip is available, and
floatplanes land on the Yukon River. In the winter passengers, cargo, and mail are flown in by plane.
Snowmachines and skiffs are used for local transportation.
Test Site Location
The met tower is installed on an a broad, flat ridge on Mountain Village Native Corporation land east of
the Mountain Village Airport and near the road that connects Mountain Village to the villages of Saint
Mary’s and Pitka’s Point to the east. The site is large enough to accommodate several or more large
turbines. Although the site is not at present near electrical distribution lines, near-term plans call for
construction of an intertie adjacent to the road between Mountain Village and Saint Mary’s, which
would make wind development on the site more advantageous.
Site information
Site number 0068
Latitude/longitude N 62° 05’37.66”W 163° 35’24.68”, WGS 84
Site elevation 44 meters (144 ft)
Datalogger type NRG Symphonie, 10 minute time step
Tower type NRG 50-meter XHD tall tower, 254 mm diameter
Anchor type Plate and /or duckbill
Topographic maps
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Google Earth image
Tower sensor information
Channel Sensor type Height Multiplier Offset Orientation
1 NRG #40 anemometer 50.3 m (50 m A) 0.760 0.36 000° T
2 NRG #40 anemometer 50.5 m (50 m B) 0.757 0.41 135° T
3 NRG #40 anemometer 40.8 m (40 m) 0.761 0.33 000° T
13 NRG #40 anemometer 41.1 m (41 m)0.758 0.33 135°T
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14 NRG #40 anemometer 31.8 m (31 m)0.758 0.34 000°T
15 NRG #40 anemometer 32.0 m (32 m) 0.761 0.33 135° T
7 NRG #200P wind vane 46.1 m 0.351 270 090° T
8 NRG #200P wind vane 40.0 m 0.351 270 090° T
9 NRG #110S Temp C 3 m 0.138 -86.3 N
10 RH-5 relative humidity 2 m 0.098 0 N
12 iPack batter voltmeter n/a 0.021 0 n/a
Data Quality Control
Data quality is generally good with data recovery of all six anemometers greater than 90 percent and
data recovery of the two wind vanes less but also greater than 90 percent. Data loss is limited to winter
months only and is attributable to icing events, which are characterized by non-variant output of the
anemometer at the minimum offset value (essentially zero) and by non-variant output of the direction
vane at the last operable direction. Rime icing conditions have been observed at the nearby Saint
Mary’s and Pitka’s Point met towers, but it is not known if icing conditions observed in the data are due
to rime ice or freezing rain. Given the site elevation and known rime icing experience in Saint Mary’s,
caution would err toward the former.
Data recovery summary table
Possible Valid Recovery
Label Units Height Records Records Rate (%)
Speed 50 m A m/s 50.3 m 92,472 85,955 93.0
Speed 50 m B m/s 50.5 m 92,472 86,241 93.3
Speed 40 m m/s 40.8 m 92,472 87,252 94.4
Speed 41 m m/s 41.1 m 92,472 87,349 94.5
Speed 31 m m/s 31.8 m 92,472 87,168 94.3
Speed 32 m m/s 32 m 92,472 86,449 93.5
Direction 46 m ° 46 m 92,472 83,646 90.5
Direction 40 m ° 40 m 92,472 85,157 92.1
Temperature °C 92,472 92,376 99.9
RH-5 Humidity %RH %RH 92,472 87,632 94.8
Voltmeter volts 92,472 92,382 99.9
Anemometer data recovery
50 m A anem. 50 m B 40 m 41 m 31 m 32 m
Possible Valid Recovery Recovery Recovery Recovery Recovery Recovery
Year Month Records Records Rate (%) Rate (%) Rate (%) Rate (%) Rate (%) Rate (%)
2009 Nov 3,744 3,660 97.8 97.8 97.8 97.8 97.8 94.3
2009 Dec 4,464 4,113 92.1 92.1 92.1 92.1 92.1 92.1
2010 Jan 4,464 4,038 90.5 90.2 98.5 91.9 95.1 93.3
2010 Feb 4,032 3,111 77.2 75.7 77.2 77.2 77.2 77.2
2010 Mar 4,464 3,516 78.8 78.5 87.9 92.5 86.3 85.3
2010 Apr 4,320 4,320 100.0 100.0 100.0 100.0 100.0 100.0
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2010 May 4,464 4,464 100.0 99.8 99.2 99.2 100.0 99.5
2010 Jun 4,320 4,320 100.0 100.0 100.0 100.0 100.0 100.0
2010 Jul 4,464 4,464 100.0 100.0 100.0 100.0 100.0 100.0
2010 Aug 4,464 4,464 100.0 100.0 100.0 100.0 100.0 100.0
2010 Sep 4,320 4,320 100.0 100.0 100.0 100.0 100.0 100.0
2010 Oct 4,464 3,829 85.8 83.5 91.9 91.9 91.9 86.0
2010 Nov 4,320 4,037 93.5 92.3 89.1 91.8 88.3 90.2
2010 Dec 4,464 4,132 92.6 91.8 94.9 96.0 96.5 90.9
2011 Jan 4,464 3,791 84.9 92.4 92.6 91.2 92.5 92.1
2011 Feb 4,032 2,211 54.8 60.5 55.6 57.8 57.4 57.7
2011 Mar 4,464 4,464 100.0 100.0 100.0 100.0 100.0 100.0
2011 Apr 4,320 4,320 100.0 100.0 100.0 100.0 100.0 100.0
2011 May 4,464 4,421 99.0 99.0 99.0 99.0 99.0 99.0
2011 Jun 4,320 4,320 100.0 100.0 100.0 100.0 100.0 100.0
2011 Jul 4,464 4,464 100.0 100.0 100.0 100.0 100.0 100.0
2011 Aug 1,176 1,176 100.0 100.0 100.0 100.0 100.0 100.0
92,472 85,955 93.0 93.3 94.4 94.5 94.3 93.5
Icing Event
Data indicating an apparent icing event in February 2011 is shown below. In the days preceding the
event, characterized by loss of anemometer function, the temperature had been -15° C, warming to 0°
C. Relatively humidity had been moderate but increased to 100 percent coinciding with the
temperature warm-up to the freezing point. At this time, on February 7, all six anemometers ceased
functioning. The moderate temperature and high humidity conditions continued for two days which
were followed by a rapid decrease of temperature to -32° C on February 11. Anemometers remained
inoperative and presumably encased in ice until February 16 and 17 when the temperature again
warmed to 0° C and humidity rose to 100 percent, indicating another precipitation event. High winds
and warming temperatures were sufficient to break loose the anemometers and they resumed normal
function.
Apparent icing event, Feb. 2011, temp. and RH
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Apparent icing event, Feb. 2011, anemometers
Data Gap-fill
Although the overall loss of anemometer data due to icing was less than 90 percent, this includes the
summer months which of course do not experience icing conditions. Wintertime icing loss was much
higher, with data recovery of the anemometers as low as the 50 percent range in February 2011. Ice
event data is removed from the file to avoid biasing the mean wind speed low (zero wind speed when
the wind is likely blowing), but that can create the opposite situation, where the data set bias is high (no
recorded wind speed during the ice periods, leaving just higher wind speeds in the data set). To
overcome these errors, a data gap-fill algorithm contained in Windographer software was employed to
synthesize missing data and create a statistically truer representation of the Mountain Village wind
resource than the file without data gap-fill. Note: dotted lines below are synthesized data.
Gap-fill of Feb. 2011 icing event
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Wind Speed
Anemometer data obtained from the met tower, from the perspectives of both mean wind speed and
mean wind power density, indicate an excellent wind resource. Mean wind speeds are greater at higher
elevations on the met tower, as one would expect. Note that cold temperatures contributed to a higher
wind power density than otherwise might have been expected for the mean wind speeds. Also note, as
discussed in the previous section, that anemometer summary information is the table below is post gap-
fill. None gap-filled mean wind speeds and power densities are slightly higher than below.
Anemometer data summary
Variable
Speed 50
m A
Speed 50
m B
Speed 41
m
Speed 40
m
Speed 32
m
Speed 31
m
Measurement height (m) 50.3 50.5 41.1 40.8 32.0 31.8
Mean wind speed (m/s) 7.57 7.67 7.32 7.31 7.06 7.02
MMM wind speed (m/s) 7.52 7.63 7.28 7.26 7.02 6.97
Max 10-min wind speed (m/s) 26.6 26.5 26.0 26.0 25.4 25.2
Max gust wind speed (m/s) 31.5 31.8 31.8 32.7 31.5 31.4
Weibull k 2.13 2.12 2.09 2.12 2.10 2.12
Weibull c (m/s) 8.54 8.65 8.25 8.24 7.96 7.91
Mean power density (W/m²) 510 534 472 462 421 409
MMM power density (W/m²) 500 523 463 452 413 401
Mean energy content (kWh/m²/yr) 4,469 4,674 4,133 4,047 3,686 3,585
MMM energy content (kWh/m²/yr) 4,379 4,580 4,054 3,958 3,615 3,513
Energy pattern factor 1.79 1.80 1.84 1.81 1.83 1.81
Frequency of calms (< 4 m/s) 17.3 16.8 18.9 18.5 19.8 20.2
1-hr autocorrelation coefficient 0.926 0.929 0.926 0.924 0.922 0.921
Diurnal pattern strength 0.020 0.020 0.022 0.020 0.025 0.021
Hour of peak wind speed 22 22 21 21 19 20
Time Series
Time series calculations indicate high mean wind speeds during the winter months with more moderate
mean wind speeds during summer months. This correlates well with the village load profile where
winter months have a high electric and heat demand and summer months a lesser demand.
50 m B anemometer data summary
Mean Max Gust
Std.
Dev.
Weibull
k
Weibull
c
Year Month (m/s) (m/s) (m/s) (m/s) (-) (m/s)
2009 Nov 7.67 24.8 31.1 3.71 2.16 8.66
2009 Dec 9.40 25.1 28.4 4.50 2.18 10.59
2010 Jan 8.91 19.7 23.5 3.49 2.76 9.97
2010 Feb 8.92 20.6 23.1 3.84 2.49 10.05
2010 Mar 8.02 16.2 19.0 3.06 2.83 8.95
2010 Apr 7.34 22.2 27.3 3.91 1.94 8.26
2010 May 6.05 15.6 17.8 2.87 2.22 6.83
2010 Jun 7.40 20.0 26.5 3.26 2.41 8.34
2010 Jul 5.48 13.9 17.4 2.36 2.47 6.16
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2010 Aug 6.16 19.9 25.0 3.37 1.91 6.94
2010 Sep 8.13 19.6 23.1 3.63 2.39 9.16
2010 Oct 6.91 19.7 25.0 3.57 2.03 7.80
2010 Nov 7.08 17.5 20.5 2.69 2.82 7.93
2010 Dec 7.15 17.0 20.8 3.01 2.52 8.01
2011 Jan 10.70 21.9 25.8 4.19 2.74 11.96
2011 Feb 9.51 26.2 31.8 4.86 2.04 10.72
2011 Mar 7.99 23.6 27.3 3.78 2.15 8.96
2011 Apr 8.28 26.5 30.7 4.06 2.11 9.33
2011 May 7.14 16.9 19.7 2.94 2.62 8.03
2011 Jun 5.91 18.2 21.6 2.97 2.08 6.67
2011 Jul 6.97 19.1 25.0 3.53 2.08 7.88
2011 Aug 8.59 18.4 22.4 3.28 2.81 9.64
All data 7.67 26.5 31.8 3.77 2.12 8.65
Annualized time series graph
Annual daily wind profile
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Monthly daily wind profile
Probability Distribution Function
The probability distribution function (PDF), or histogram, of wind speed indicates a near-normal shape
curve, defined as the Raleigh distribution (k=2.0), defined as standard for wind power sites. As one can
see in the PDF, the most frequently occurring wind speeds are between 5 and 8 m/s with very few wind
events exceeding 25 m/s, the cutout speed of most wind turbines.
PDF of 50 m B anemometer
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Wind Shear and Roughness
A wind shear power law exponent () of 0.180 indicates moderate wind shear at the site. Related to
wind shear, a calculated surface roughness of 0.114 meters (indicating the height above ground level
where wind velocity would be zero) indicates moderately uneven terrain (roughness description: few
trees) surrounding the met tower. This indicates that it would be beneficial to construct turbines at
higher hub heights in order to maximum power production.
Vertical wind shear profile
Comparative wind shear profiles
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Wind shear by direction sector, wind speed > 4 m/s
Mean Wind Speed
Direction Sector
Time
Steps
Wind
Sector
(%)
Speed 50
m A (m/s)
Speed 40
m (m/s)
Speed 31
m (m/s)
Power Law
Surface
Roughness
(m)
345° - 15° 8,938 13.0% 7.91 7.64 7.37 0.148 0.0465
15° - 45° 10,312 15.0% 8.66 8.22 7.81 0.215 0.3811
45° - 75° 7,928 11.6% 8.68 8.18 7.83 0.214 0.3741
75° - 105° 8,142 11.9% 9.98 9.63 9.28 0.153 0.0578
105° - 135° 5,781 8.4% 9.47 9.18 8.75 0.167 0.0970
135° - 165° 5,163 7.5% 9.21 8.98 8.48 0.172 0.1137
165° - 195° 6,024 8.8% 9.55 9.20 8.73 0.189 0.1950
195° - 225° 3,088 4.5% 7.53 7.37 7.08 0.130 0.0179
225° - 255° 2,924 4.3% 7.13 7.16 6.96 0.052 0.0000
255° - 285° 1,946 2.8% 7.45 7.46 7.19 0.076 0.0001
285° - 315° 2,927 4.3% 7.09 6.86 6.61 0.146 0.0407
315° - 345° 5,425 7.9% 7.49 7.25 7.00 0.143 0.0352
Extreme Winds
A modified Gumbel distribution analysis, based on monthly maximum winds vice annual maximum
winds, was used to predict extreme winds at the Mountain Village met tower site. Extreme wind
analysis indicates a highly desirable situation in Mountain Village: relatively high mean wind speeds
combined with low extreme wind speed probabilities.
Industry standard reference of extreme wind is the 50 year 10-minute average probable wind speed,
referred to as Vref. For Mountain Village, this calculates to 31.5 m/s (at 50 meters), 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. All wind turbines are designed for a Class
III wind regime.
Extreme wind probability table, 50 m B data
Vref Gust IEC 61400-1, 3rd ed.
Period (years)(m/s) (m/s) Class Vref, m/s
2 24.7 29.8 I 50.0
10 28.1 33.8 II 42.5
15 28.9 34.9 III 37.5
30 30.4 36.6 S designer-
specified5031.5 37.9
100 32.9 39.6
average gust factor:1.20
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Extreme wind graph
Temperature, Density, and Relative Humidity
Mountain Village experiences cool summers and cold winters with resulting higher than standard air
density. Calculated air density during the met tower test period exceeds the 1.220 kg/m
3 standard air
density for a 44 meter elevation by 6.3 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 Air Density RH
Month Mean Min Max Mean Min Max Mean
(°C) (°C) (°C) (kg/m³) (kg/m³) (kg/m³) (%)
Jan -13.3 -29.5 2.5 1.352 1.274 1.441 65.5
Feb -12.3 -33.3 2.6 1.348 1.273 1.464 73.1
Mar -13.0 -30.6 2.6 1.350 1.273 1.447 59.0
Apr -6.2 -21.1 13.2 1.316 1.226 1.393 71.0
May 5.0 -6.9 23.7 1.263 1.183 1.319 62.9
Jun 9.2 -3.9 24.3 1.244 1.180 1.304 68.2
Jul 10.6 1.2 24.0 1.237 1.181 1.280 78.9
Aug 10.2 3.2 18.3 1.239 1.205 1.270 85.4
Sep 7.7 -5.2 19.2 1.250 1.201 1.310 74.2
Oct -1.1 -10.1 7.8 1.290 1.250 1.335 83.5
Nov -9.3 -23.8 3.2 1.330 1.220 1.408 85.9
Dec -12.5 -29.4 4.0 1.348 1.220 1.440 80.3
MMM -2.0 -33.3 24.3 1.297 1.180 1.464 73.9
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
10-min max
gust
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Temperature boxplot
Relative humidity boxplot
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Air density DMap
Wind Speed Scatterplot
The wind speed versus temperature scatterplot below indicates that a substantial percentage of wind at
the Mountain Village met tower site coincides with cold temperatures, as one would expect. However,
during the met tower test periods, temperatures did not fall below -40°C, which is the minimum
operating temperature for arctic-capable wind turbines, and fell below -30°C on just a few occasions.
Colder temperatures may occur during particular severe winters, but it is likely that temperatures colder
than -40°C are extremely rare at the site. Hence, restrictions of wind turbine operations due to extreme
cold should not be expected.
Wind speed/temperature
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Wind Direction
Wind frequency rose data indicates that winds at the Mountain Village met tower site are not especially
directional, although northerly and easterly winds predominate overall. The mean value rose indicates
that easterly and southerly winds, when they do occur, are of high energy and hence likely storm winds.
The wind energy rose indicates that for wind turbine operations the majority of power-producing winds
are from the north-northeast, east, southeast and south. Calm frequency (percent of time that winds at
the 50 meter level are less than 4 m/s) was 17 percent during the met tower test period.
Wind frequency rose, 46 m Mean value rose, 46 m
Wind energy rose, 46 m Scatterplot rose of 50 m A WPD, 46 m vane
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Wind density roses by month
Turbulence
Turbulence intensity at the Mountain Village met tower 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, 50 m B, all direction sectors
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Turbulence table, 50 m B data
Bin Bin Endpoints
Records
in Bin
Standard
Representative
TI
Midpoint Lower Upper Mean Deviation Peak
(m/s) (m/s) (m/s) TI of TI TI
1 0.5 1.5 1,574 0.407 0.168 0.622 1.538
2 1.5 2.5 2,857 0.206 0.114 0.352 1.500
3 2.5 3.5 5,181 0.136 0.069 0.224 1.030
4 3.5 4.5 7,323 0.102 0.046 0.161 0.564
5 4.5 5.5 8,530 0.090 0.041 0.142 0.440
6 5.5 6.5 9,431 0.082 0.037 0.129 0.452
7 6.5 7.5 9,298 0.078 0.035 0.122 0.439
8 7.5 8.5 9,095 0.074 0.033 0.116 0.346
9 8.5 9.5 7,675 0.071 0.030 0.109 0.447
10 9.5 10.5 6,270 0.071 0.028 0.106 0.242
11 10.5 11.5 5,236 0.069 0.028 0.105 0.245
12 11.5 12.5 4,026 0.069 0.026 0.103 0.203
13 12.5 13.5 2,761 0.070 0.025 0.102 0.167
14 13.5 14.5 2,001 0.070 0.024 0.100 0.163
15 14.5 15.5 1,490 0.072 0.024 0.102 0.171
16 15.5 16.5 979 0.074 0.020 0.100 0.150
17 16.5 17.5 646 0.073 0.019 0.098 0.149
18 17.5 18.5 416 0.071 0.019 0.095 0.125
19 18.5 19.5 251 0.073 0.019 0.097 0.145
20 19.5 20.5 168 0.076 0.017 0.098 0.138
21 20.5 21.5 192 0.081 0.020 0.106 0.189
22 21.5 22.5 137 0.082 0.018 0.106 0.145
23 22.5 23.5 71 0.080 0.020 0.106 0.150
24 23.5 24.5 34 0.074 0.013 0.091 0.113
25 24.5 25.5 20 0.072 0.010 0.084 0.097
26 25.5 26.5 20 0.067 0.009 0.079 0.086
27 26.5 27.5 1 0.064 0 0.064 0.064