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HomeMy WebLinkAboutMekoryuk Surplus Wind Energy Resource Report - circa 2007 - REF Grant 7050870Mekoryuk, Alaska Wind Resource Report Report written by: Douglas Vaught, V3 Energy, LLC, Eagle River, AK Photo © Doug Vaught Summary Information The Mekoryuk wind test site has outstanding potential for wind power development with Class 6 winds, low wind shear, and low turbulence. The wind rose indicates more variability in wind directions than observed elsewhere, but this likely is a consequence of Mekoryuk’s coastal location and maritime climate influence. For a representative village-scale stall controlled turbine and pitch controlled turbine, both yield low thirty percent capacity factors at 32 meter hub heights. One wind turbine operations challenge in Mekoryuk is the occasional extreme low winter temperatures and consequent high air densities experienced. V3 Energy LLC 1 of 26 Mekoryuk, Alaska Wind Resource Report Meteorological Tower Data Synopsis Wind power class Class 6 - Outstanding Average wind speed (30 meters) 7.56 m/s Maximum wind speed (10 min avg) 35.1 m/s Mean wind power density (50 meters) 660 W/m2 Mean wind power density (30 meters) 543 W/m2 Weibull distribution parameters k = 1.97, c = 8.48 m/s Turbulence intensity 0.0952 Roughness class 0.80 (rough pasture) Power law exponent 0.13 (low wind shear) Data start date June 11, 2005 Most recent data date February 19, 2007 Community Profile Location: Mekoryuk is at the mouth of Shoal Bay on the north shore of Nunivak Island in the Bering Sea. The Island lies 30 miles off the coast. It is 149 air miles west of Bethel and 553 miles west of Anchorage. Mekoryuk is part of the Yukon Delta National Wildlife Refuge. The village area encompasses 7.4 sq. miles of land and 0.1 sq. miles of water. History: Nunivak Island has been inhabited for 2,000 years by the Nuniwarmiut people, or Cup'ik (Choop'ik) Eskimos. The first outside contact was in 1821 by the Russian American Company, who recorded 400 people living in 16 villages on the Island. In 1874 a summer camp called "Koot" was noted at the current site of Mekoryuk. An epidemic in 1900 decimated the population, leaving only four surviving families in the village. In the 1930s, the Evangelical Covenant Church was built by an Eskimo missionary followed by a BIA school in 1939. People moved to the village from other areas of the Island to be near the school. Reindeer were introduced for commercial purposes in 1920 by an Eskimo-Russian trader. The operation was purchased by the BIA in the 1940s and a slaughterhouse was constructed in 1945. The reindeer were crossed with caribou from Denali Park; the resulting animals are larger and harder to handle than other reindeer in the state. Thirty-four musk oxen from Greenland were transferred to the Island in 1934 in an effort to save the species from extinction. Today, the musk ox herd numbers around 500 and calves from this herd have been relocated and introduced to other areas of Alaska. The 1950s and 60s brought considerable change. An airstrip was built in 1957 and the Territorial Guard was formed. Mekoryuk had become the only permanent community on the Island. During this time, many families moved to Bethel to be near the high school, returning during late spring for fishing and sea mammal hunting. The City was incorporated in 1969 and a high school was constructed in the village in 1978. Culture: This Cup'ik Eskimo village maintains reindeer and musk ox herds and practices a subsistence lifestyle of fishing and hunting. The sale, importation or possession of alcohol is banned in the V3 Energy LLC 2 of 26 Mekoryuk, Alaska Wind Resource Report village. Economy: Employment by the school, City, village corporation, commercial fishing, construction, and service industries prevails. The Bering Sea Reindeer Products Co. is a major employer. Trapping and Native crafts, such as knitting qiviut (musk ox underwool), provide income to many families. Fifty-five residents hold commercial fishing permits, primarily for halibut and herring roe. Coastal Villages Seafood, Inc. processes halibut and salmon in Mekoryuk. Almost all families engage in subsistence activities and most have fish camps. Salmon, reindeer, seal meat and oil are important staples. Facilities: Water is derived from a well, is treated and stored in a tank. A new flush/haul system currently serves about 90% of homes. The school has its own well and needs a new water treatment system. The washeteria has piped disposal to a new permitted sewage lagoon. Transportation: Mekoryuk relies heavily on air transportation for passenger, mail and cargo service. A State- owned 3,070' long by 75' wide gravel runway allows year-round access. A breakwater protects the shoreline from Bering Sea waves. Barges deliver goods from Bethel once or twice each summer. Boats, snowmachines and ATVs are used for travel within the community. Climate: The Bering Sea which surrounds Nunivak Island strongly influences the climate of the island. Foggy and stormy weather are frequent. Average precipitation is 15 inches; annual snowfall is 57 inches. Summer highs average 48 to 54 degrees F; winter highs run 37 to 44 F. Extremes have been recorded from 76 to -48 F. Meteorological Tower Site Information Site number 0032 Site Description Mekoryuk – AVEC community Latitude/longitude N 060° 23.215’; W 166° 12.112’ Site elevation 13 meters Datalogger type NRG Symphonie Tower type NRG 30-meter tall tower, 152 mm (6-in) diameter V3 Energy LLC 3 of 26 Mekoryuk, Alaska Wind Resource Report Met Tower Sensor Information Channel Sensor type Height Multiplier Offset Orientation 1 (30m A) NRG #40 anemometer 30 m 0.765 0.35 north 2 (30m B) NRG #40 anemometer 30 m 0.765 0.35 south 3 (20m) NRG #40 anemometer 20 m 0.765 0.35 north 7 NRG #200P wind vane 27 m 0.351 245 east 9 NRG #110S Temp C 2 m 0.136 -86.383 N/A V3 Energy LLC 4 of 26 Mekoryuk, Alaska Wind Resource Report Measured Wind Speeds The 30-meter annual average wind speed is 7.56 m/s for channels 1 and 2 (A and B anemometers), and the 20-meter wind speed average is 7.17 m/s. Note that maximum wind data are 10 minute averages. 30 m A anemometer 30 m B anem. 20 m anem. Month Mean Max Std. Dev. Weibull k Weibull c Mean Max Mean Max (m/s) (m/s) (m/s) (m/s) (m/s) (m/s) (m/s) (m/s) Jan 7.89 35.1 4.55 1.79 8.85 7.83 34.6 7.48 31.4 Feb 9.89 28.2 4.53 2.30 11.15 9.99 27.9 9.19 27.2 Mar 8.18 19.7 3.97 2.19 9.26 8.24 19.4 7.81 18.9 Apr 8.64 22.6 3.27 2.80 9.68 8.50 22.4 8.29 20.7 May 6.04 18.9 3.23 1.97 6.83 6.11 18.8 5.76 17.8 Jun 5.81 16.5 2.48 2.46 6.52 5.83 16.3 5.44 15.3 Jul 5.94 20.6 3.14 1.99 6.71 5.93 20.7 5.65 19.6 Aug 6.85 20.8 3.64 1.95 7.72 6.87 21.2 6.58 20.0 Sep 7.52 24.7 3.73 2.11 8.49 7.56 24.6 7.14 23.6 Oct 7.91 29.9 4.05 2.05 8.94 7.90 29.9 7.50 28.5 Nov 9.43 21.8 4.34 2.33 10.65 9.41 21.8 8.99 21.1 Dec 6.62 18.3 3.35 2.07 7.47 6.58 18.4 6.28 17.2 Annual 7.56 35.1 3.69 2.17 8.52 7.56 34.6 7.17 31.4 V3 Energy LLC 5 of 26 Mekoryuk, Alaska Wind Resource Report Daily Wind Profile The daily wind profile indicates that the lowest wind speeds of the day occur in the morning hours of 2 to 6 a.m. and the highest wind speeds of the day occur during the afternoon and early evening hours of 2 to 7 p.m. V3 Energy LLC 6 of 26 Mekoryuk, Alaska Wind Resource Report Time Series of Wind Speed Monthly Averages As expected, winter winds in Mekoryuk are high and summer winds comparatively low, although Mekoryuk is windy by almost any measure. The low winds of December 2005 and January 2006 were due to a persistent high pressure system that yielded cold temperatures and calm winds statewide, but was followed by a very stormy and windy February. Winter 2006/07 was less extreme in nature and perhaps more representative of typical winter weather. V3 Energy LLC 7 of 26 Mekoryuk, Alaska Wind Resource Report Wind Shear Profile The annual average power law exponent was calculated at 0.13, with the seasonal variability shown in the lower graph, indicating low wind shear at the Mekoryuk test site. The practical application of this information is that a lower turbine height is possible as there is a relatively low marginal gain in average wind speed with height. However, a tower height/power recovery/construction cost tradeoff study is advisable. V3 Energy LLC 8 of 26 Mekoryuk, Alaska Wind Resource Report V3 Energy LLC 9 of 26 Mekoryuk, Alaska Wind Resource Report Probability Distribution Function The probability distribution function provides a visual indication of measured wind speeds in one meter per second “bins”. Note that most wind turbines do not begin to generate power until the wind speed at hub height reaches 4 m/s, also known as the “cut-in” speed. The black line in the graph is a best fit Weibull distribution. At the 30 meter level, Weibull parameters are k = 1.97 and c = 8.48 m/s (scale factor for the Weibull distribution). V3 Energy LLC 10 of 26 Mekoryuk, Alaska Wind Resource Report Wind Roses Mekoryuk winds are not especially directional; the wind frequency rose indicates W, NW, NE, SE and SW components of wind. This observation is reinforced with reference to the power density rose, although with slightly more directionality. Power producing winds are chiefly NNE, SSE (most significantly), W and NW. The practical application of this information is that a site should be selected with adequate freedom from ground interference, especially on a northwest to southeast axis, and if more than one turbine is installed, the turbines should be adequately spaced apart to prevent downwind interference problems between the turbines. Wind frequency rose (30 meters) V3 Energy LLC 11 of 26 Mekoryuk, Alaska Wind Resource Report Power density rose (30 meters) Wind Power Density Rose by Month (scale is common) V3 Energy LLC 12 of 26 Mekoryuk, Alaska Wind Resource Report V3 Energy LLC 13 of 26 Mekoryuk, Alaska Wind Resource Report Turbulence Intensity The Mekoryuk turbulence intensity is quite acceptable for all wind directions, with a mean turbulence intensity of 0.0952 (30 meters [A]), 0.0976 (30 meters [B]), and 0.105 (20 meters), indicating very smooth air. These turbulence intensities are calculated with a threshold wind speed of 4 m/s. The spike of relatively high turbulence to the south in channel 1 is due to placement of the 30 meter level anemometers in relation to the wind vane for varying wind directions. 30 meter turbulence intensity (channel 1 – “A” anemometer) 30 meter turbulence intensity (channel 2 – “B” anemometer) V3 Energy LLC 14 of 26 Mekoryuk, Alaska Wind Resource Report 20 meter turbulence intensity IEC Turbulence Intensity Standards ory A and B standards at all measured wind speeds and from all ur quadrants of the wind rose. As indicated below, turbulence at the Mekoryuk project test site is well within International Energy Commission (IEC) Categ fo V3 Energy LLC 15 of 26 Mekoryuk, Alaska Wind Resource Report Turbulence Table 30 meter, channel 1, A anemometer, 6/11/05 to 2/19/07 Bin Bin Endpoints Records Standard Deviation Mean Standard Deviation Characteristic Midpoint Lower Upper In of Wind Speed Turbulence of Turbulence Turbulence (m/s) (m/s) (m/s) Bin (m/s) Intensity Intensity Intensity 1 0.5 1.5 538 0.403 0.413 0.239 0.652 2 1.5 2.5 1062 0.404 0.204 0.123 0.328 3 2.5 3.5 1992 0.397 0.133 0.066 0.199 4 3.5 4.5 2743 0.413 0.104 0.046 0.151 5 4.5 5.5 3146 0.470 0.095 0.039 0.134 6 5.5 6.5 3452 0.526 0.088 0.033 0.121 7 6.5 7.5 3290 0.605 0.087 0.031 0.118 8 7.5 8.5 2467 0.686 0.086 0.029 0.115 9 8.5 9.5 1867 0.789 0.088 0.030 0.118 10 9.5 10.5 1446 0.861 0.087 0.027 0.114 11 10.5 11.5 1162 0.950 0.087 0.030 0.117 12 11.5 12.5 744 0.971 0.081 0.027 0.108 13 12.5 13.5 590 1.049 0.081 0.027 0.108 14 13.5 14.5 450 1.181 0.085 0.025 0.110 15 14.5 15.5 319 1.304 0.087 0.021 0.109 16 15.5 16.5 241 1.430 0.090 0.021 0.111 17 16.5 17.5 123 1.638 0.097 0.026 0.123 18 17.5 18.5 100 1.770 0.099 0.025 0.124 V3 Energy LLC 16 of 26 Mekoryuk, Alaska Wind Resource Report 19 18.5 19.5 50 1.924 0.102 0.028 0.129 20 19.5 20.5 37 2.079 0.105 0.022 0.127 21 20.5 21.5 13 1.977 0.095 0.019 0.115 22 21.5 22.5 7 2.129 0.097 0.017 0.115 23 22.5 23.5 5 2.220 0.096 0.009 0.105 24 23.5 24.5 7 2.400 0.099 0.013 0.113 25 24.5 25.5 13 2.369 0.095 0.006 0.101 26 25.5 26.5 14 2.486 0.095 0.011 0.107 27 26.5 27.5 18 2.511 0.093 0.009 0.102 28 27.5 28.5 11 2.645 0.095 0.015 0.109 29 28.5 29.5 6 2.600 0.090 0.008 0.098 30 29.5 30.5 2 2.150 0.072 0.007 0.079 V3 Energy LLC 17 of 26 Mekoryuk, Alaska Wind Resource Report Air Temperature and Density Mekoryuk measured an annual average temperature of 0.8° C. The minimum recording temperature during the measurement period was -29.2° C and the maximum temperature was 22.9° C, indicating a wide variability of ambient operating environment important to wind turbine operations. Consequent to Mekoryuk’s cool temperatures, the average annual air density of 1.288 kg/m3 is approximately four percent higher than the standard air density of 1.2235 kg/m3 (at 14.9° C temperature and 101.1 kPa pressure at an elevation of 13 meters). Temperature Air Density Month Mean Min Max Std. Dev. Mean Min Max (°C) (°C) (°C) (°C) (kg/m³) (kg/m³) (kg/m³) Jan -12.6 -29.2 5.7 8.13 1.354 1.264 1.444 Feb -4.1 -29.1 3.6 6.60 1.310 1.273 1.444 Mar -6.5 -23.4 2.4 5.85 1.322 1.279 1.411 Apr -5.7 -15.8 4.4 3.69 1.318 1.269 1.369 May 1.8 -7.9 8.1 2.47 1.282 1.253 1.328 Jun 7.8 0.1 20.2 3.64 1.254 1.201 1.289 Jul 11.2 3.7 22.9 2.52 1.239 1.190 1.273 Aug 12.1 3.6 22.4 2.10 1.235 1.192 1.273 Sep 10.3 2.3 15.5 2.24 1.243 1.221 1.279 Oct 5.0 -6.6 13.0 2.97 1.267 1.231 1.322 Nov -2.9 -18.2 6.1 5.19 1.304 1.262 1.382 Dec -7.2 -25.5 3.3 5.31 1.325 1.274 1.423 Annual 0.8 -29.2 22.9 9.57 1.288 1.190 1.444 V3 Energy LLC 18 of 26 Mekoryuk, Alaska Wind Resource Report Air Density DMap This DMap is a visual indication of the seasonal and daily variations in air density, and hence temperature. Air densities higher than standard (STP at sea level) will yield higher turbine power than predicted by turbine power curves, while density lower than standard will yield lower turbine power than predicted. Density variance from standard is accounted for in turbine predictions. V3 Energy LLC 19 of 26 Mekoryuk, Alaska Wind Resource Report Wind Turbine Performance The turbine performance predictions noted below are based on a 90 percent turbine availability with losses assumed as follows: 4% downtime, 2% array, 2% icing, and 2% other for a combined mathematical loss of 9.65% (loss calculations are multiplicative, not additive). Note that these performance estimates were predicted with use of Windographer wind analysis software; power curves provided by manufacturers, are not independently verified and are assumed to be accurate. The power curves are presented for a standard air density of 1.225 kg/m3 at sea level and 15° C. However, the predictions of power production are density compensated by multiplying the standard density power output by the ratio of the measured air density to standard air density, accounting for the site elevation. A number of small to medium turbines are profiled in this report for comparison purposes. These turbines were selected because they have market availability and they are deemed to be within a suitable range for consideration of wind power development in a community the size of Mekoryuk. Entegrity eW-15:65 kW rated power output, 15 meter rotor, stall-controlled (power curve provided by Entegrity Energy Systems). Available tower heights: 25 and 31 meters. Additional information is available at http://www.entegritywind.com/. Vestas V15: 75 kW rated power output, 15 meter rotor, stall-controlled (power curve provided by Powercorp Alaska LLC). Available tower heights: 25, 31 and 34 meters. Additional information is available at http://www.pcorpalaska.com/. V3 Energy LLC 20 of 26 Mekoryuk, Alaska Wind Resource Report Northwind 100/20: 100 kW rated power output, 20 meter rotor (19 meter rotor blades with 0.6 meter blade root extensions added), stall-controlled (power curve provided by Northern Power Systems). Available tower heights: 25 and 32 meters. Additional information is available at http://www.northernpower.com/. eW-15 Entegrity eW-15, 31 meter hub height Hub Height Time At Time At Average Net Average Net Average Net Wind Speed Zero Output Rated Output Power Output Energy Output Capacity Factor Month (m/s) (%) (%) (kW) (kWh) (%) Jan 7.90 19 10 23 17,414 36.0 Feb 9.96 9 18 34 22,620 51.8 Mar 8.21 16 11 26 18,965 39.2 Apr 8.66 6 9 28 20,219 43.2 May 6.10 28 4 13 9,587 19.8 Jun 5.82 22 0 11 7,629 16.3 Jul 5.96 29 1 12 9,008 18.6 V3 Energy LLC 21 of 26 Mekoryuk, Alaska W V3 Energy LLC ind Resource Report 22 of 26 Aug 6.92 23 3 17 12,951 26.8 Sep 7.59 17 3 21 14,844 31.7 Oct 7.96 14 6 22 16,049 33.2 Nov 9.47 10 22 32 23,012 49.2 Dec 6.63 24 4 17 12,896 26.7 Annual 7.6 18.2 7.6 21.3 185,194 32.7 Note: 90% turbine availability V15 Vestas V15, 31 meter hub height Hub Height Time At Time At Average Net Average Net Average Net Wind Speed Zero Output Rated Output Power Output Energy Output Capacity Factor Month (m/s) (%) (%) (kW) (kWh) (%) Jan 7.90 24 5 23 17,084 30.6 Feb 9.96 12 11 34 23,087 45.8 Mar 8.21 22 9 25 18,725 33.6 Apr 8.66 9 6 28 19,776 36.6 May 6.10 37 3 12 8,858 15.9 Jun 5.82 31 0 9 6,738 12.5 Jul 5.96 37 1 11 8,152 14.6 Aug 6.92 29 1 17 12,381 22.2 Sep 7.59 22 1 20 14,388 26.6 Oct 7.96 19 4 21 15,668 28.1 Nov 9.47 14 16 33 23,694 43.9 Dec 6.63 31 2 16 12,140 21.8 Annual 7.6 23.9 4.9 20.8 180,691 27.7 Note: 90% turbine availability NW100/20 NPS Northwind 100/20, 32 meter hub height Hub Height Time At Time At Average Net Average Net Average Net Wind Speed Zero Output Rated Output Power Output Energy Output Capacity Factor Month (m/s) (%) (%) (kW) (kWh) (%) Jan 7.93 19 8 35 25,711 34.6 Feb 10.01 9 16 50 33,693 50.1 Mar 8.24 16 11 38 28,161 37.9 Apr 8.69 6 8 41 29,621 41.1 May 6.12 28 4 19 14,342 19.3 Jun 5.85 22 0 16 11,374 15.8 Jul 5.99 29 1 18 13,351 17.9 Aug 6.95 23 3 26 19,167 25.8 Sep 7.63 16 3 31 21,942 30.5 Oct 8.00 14 5 32 23,724 31.9 Nov 9.51 10 21 48 34,558 48.0 Dec 6.65 24 4 26 19,063 25.6 Annual 7.6 18.1 7.0 31.5 274,707 31.5 Note: 90% turbine availability Mekoryuk, Alaska WV3 Energy LLC ind Resource Report 23 of 26 Annual Fuel Cost Avoided for Electrical Energy Generation by Diesel Genset Fuel Price (dollars delivered) Turbine AnnualEnergyOutput(kW-hr/yr) FuelQuantityAvoided(gallons) $1.75 $2.00 $2.25 $2.50 $2.75 $3.00 $3.25HubHeight (m)eW-15 185,194 13,718 $24,007 $27,436 $30,866 $34,295 $37,725 $41,154 $44,584 31V15 180,691 13,385 $23,423 $26,769 $30,115 $33,461 $36,807 $40,154 $43,500 31NW100/20 274,707 20,349 $35,610 $40,697 $45,785 $50,872 $55,959 $61,046 $66,133 32Note: Mekoryuk electrical energy production efficiency is 13.5 kW-hr/gal Note: Assumes 90% turbine availability with no diversion of power to a thermal or other dump load Mekoryuk, Alaska Wind Resource Update Report Temperature Conversion Chart °C to °F °C °F °C °F °C °F -40 -40.0 -10 14.0 20 68.0 -39 -38.2 -9 15.8 21 69.8 -38 -36.4 -8 17.6 22 71.6 -37 -34.6 -7 19.4 23 73.4 -36 -32.8 -6 21.2 24 75.2 -35 -31.0 -5 23.0 25 77.0 -34 29.2 -4 24.8 26 78.8 -33 -27.4 -3 26.6 27 80.6 -32 -25.6 -2 28.4 28 82.4 -31 -23.8 -1 30.2 29 84.2 -30 -22.0 0 32.0 30 86.0 -29 -20.2 1 33.8 31 87.8 -28 -18.4 2 35.6 32 89.6 -27 -16.6 3 37.4 33 91.4 -26 -14.8 4 39.2 34 93.2 -25 -13.0 5 41.0 35 95.0 -24 -11.2 6 42.8 36 96.8 -23 -9.4 7 44.6 37 98.6 -22 -7.6 8 46.4 38 100.4 -21 -5.8 9 48.2 39 102.2 -20 -4.0 10 50.0 40 104.0 -19 -2.2 11 51.8 41 105.8 -18 -0.4 12 53.6 42 107.6 -17 1.4 13 55.4 43 109.4 -16 3.2 14 57.2 44 111.2 -15 5.0 15 59.0 45 113.0 -14 6.8 16 60.8 46 114.8 -13 8.6 17 62.6 47 116.6 -12 10.4 18 64.4 48 118.4 -11 12.2 19 66.2 49 120.2 V3 Energy LLC 24 of 26 Mekoryuk, Alaska Wind Resource Update Report Wind Speed Conversion Chart, m/s to mph m/s mph m/s mph m/s mph m/s mph m/s mph 0.5 1.1 10.5 23.5 20.5 45.9 30.5 68.2 40.5 90.6 1.0 2.2 11.0 24.6 21.0 47.0 31.0 69.3 41.0 91.7 1.5 3.4 11.5 25.7 21.5 48.1 31.5 70.5 41.5 92.8 2.0 4.5 12.0 26.8 22.0 49.2 32.0 71.6 42.0 93.9 2.5 5.6 12.5 28.0 22.5 50.3 32.5 72.7 42.5 95.1 3.0 6.7 13.0 29.1 23.0 51.4 33.0 73.8 43.0 96.2 3.5 7.8 13.5 30.2 23.5 52.6 33.5 74.9 43.5 97.3 4.0 8.9 14.0 31.3 24.0 53.7 34.0 76.1 44.0 98.4 4.5 10.1 14.5 32.4 24.5 54.8 34.5 77.2 44.5 99.5 5.0 11.2 15.0 33.6 25.0 55.9 35.0 78.3 45.0 100.7 5.5 12.3 15.5 34.7 25.5 57.0 35.5 79.4 45.5 101.8 6.0 13.4 16.0 35.8 26.0 58.2 36.0 80.5 46.0 102.9 6.5 14.5 16.5 36.9 26.5 59.3 36.5 81.6 46.5 104.0 7.0 15.7 17.0 38.0 27.0 60.4 37.0 82.8 47.0 105.1 7.5 16.8 17.5 39.1 27.5 61.5 37.5 83.9 47.5 106.3 8.0 17.9 18.0 40.3 28.0 62.6 38.0 85.0 48.0 107.4 8.5 19.0 18.5 41.4 28.5 63.8 38.5 86.1 48.5 108.5 9.0 20.1 19.0 42.5 29.0 64.9 39.0 87.2 49.0 109.6 9.5 21.3 19.5 43.6 29.5 66.0 39.5 88.4 49.5 110.7 10.0 22.4 20.0 44.7 30.0 67.1 40.0 89.5 50.0 111.8 Distance Conversion m to ft m ft m ft 5 16 35 115 10 33 40 131 15 49 45 148 20 66 50 164 25 82 55 180 30 98 60 197 V3 Energy LLC 25 of 26 Mekoryuk, Alaska Wind Resource Update Report Selected definitions (courtesy of Windographer® software by Mistaya Engineering Inc.) Wind Power Class The wind power class is a number indicating the average energy content of the wind resource. Wind power classes are based on the average wind power density at 50 meters above ground, according to the following table. Source: Wind Energy Resource Atlas of the United States (http://rredc.nrel.gov/wind/pubs/atlas/tables/A-8T.html) Wind Power Class Description Power Density at 50m (W/m 2) 1 Poor 0-200 2 Marginal 200-300 3 Fair 300-400 4 Good 400-500 5 Excellent 500-600 6 Outstanding 600-800 7 Superb 800-2000 Windographer classifies any wind resource with an average wind power density above 2000 W/m2 as class 8. Probability Distribution Function The probability distribution function f(x) gives the probability that a variable will take on the value x. It is often expressed using a frequency histogram, which gives the frequency with which the variable falls within certain ranges or bins. Wind Turbine Power Regulation All wind turbines employ some method of limiting power output at high wind speeds to avoid damage to mechanical or electrical subsystems. Most wind turbines employ either stall control or pitch control to regulate power output. A stall-controlled turbine typically has blades that are fixed in place, and are designed to experience aerodynamic stall at very high wind speeds. Aerodynamic stall dramatically reduces the torque produced by the blades, and therefore the power produced by the turbine. On a pitch-controlled turbine, a controller adjusts the angle (pitch) of the blades to best match the wind speed. At very high wind speeds the controller increasingly feathers the blades out of the wind to limit the power output. V3 Energy LLC 26 of 26