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HomeMy WebLinkAboutSaint George Wind Resource Assessment - Nov 2005 DRAFT Page 1 of 14 DRAFT 813 W. Northern Lights Blvd. Anchorage, AK 99503 Phone: 907-269-3000 Fax: 907-269-3044 www.aidea.org/wind.htm Wind Resource Assessment for ST GEORGE, ALASKA Site # 2401 Date last modified: 11/22/2005 Prepared by: Mia Devine St.George Met Tower (right) and unidentified tower (left) Elevation: 130 ft Latitude: (NAD27) 56Û 35’ 11.6” N 56Û 35.193 Tower Type: 30-meter NRG Tall Tower Longitude: (NAD27) 169Û 36’ 52.7” W -169Û 36.878 Monitor Start: Monitor End: 9/14/2004 In operation INTRODUCTION In September 2004 the Alaska Energy Authority, Aleutian/Pribilof Islands Association, TDX Power, and members of the community installed a 30-meter tall meteorological tower on Saint George Island. The purpose of this monitoring effort is to evaluate the feasibility of utilizing utility-scale wind energy in the community. This report summarizes the wind resource data collected to date and the long-term energy production potential of the site. SITE DESCRIPTION The community of Saint George is located on the northeast shore of Saint George Island. Saint George Island is located about 750 miles west of Anchorage and 250 miles northwest of Unalaska. Figure 1 shows the location of the met tower. Figure 1. Map of Met Tower Site and Surrounding Area Alaska Energy Authority SAINT GEORGE, AK Wind Resource Assessment DRAFT Page 2 of 14 DRAFT Table 1 lists the types of sensors that were mounted on the met tower, the channel of the data logger that each sensor was wired into, and where each sensor was mounted on the tower. Table 1. Summary of Sensors Installed on the Met Tower Ch # Sensor Type Height Offset Boom Orientation 1 #40 Anemometer 30 m NRG Standard 260Û True 2 #40 Anemometer 20 m NRG Standard 80Û True 7 #200P Wind Vane 30 m True North True North 9 #110S Temperature 5 m 0 - Arial view of equipment on tower N NE E SE S SW W NW CH1 CH2 Tower CH7 The photos below illustrate the surrounding ground cover and any major obstructions, which could have an affect on how the wind flows over the terrain from a particular direction. Alaska Energy Authority SAINT GEORGE, AK Wind Resource Assessment DRAFT Page 3 of 14 DRAFT DATA PROCESSING PROCEDURES AND DEFINITIONS The following information summarizes the data processing procedures that were performed on the raw measured data in order to create an annual dataset of “typical” wind speeds, which could then be used to calculate potential power production from wind turbines. There are various methods and reasons for adjusting the raw data, so the purpose of these notes is to document what was done in this situation. The raw data set is available on the Alaska Energy Authority website (www.akenergyauthority.org) so one could perform their own data processing procedures. Units – Since most wind turbine manufacturer data is provided in metric units, those units are used here. 1 meter/second = 2.24 mph = 1.95 knots 1 meter = 3.28 feet 1 ÛC = 5/9 (ÛF – 32) Max/Min Test – All of the 10-minute data values were evaluated to ensure that none of them fell outside of the normal range for which the equipment is rated. Tower Shadow – The tower itself can affect readings from the anemometer at times when the anemometer is located downwind of the tower. In this case, the 30-meter anemometer may record slightly lower values than the free stream velocity when the wind is coming from the east. Icing – Anomalies in the data can suggest when the sensors were not recording accurately due to icing events. Since wind vanes tend to freeze before the anemometers, icing events are typically identified whenever the 10- minute standard deviation of the wind vane is zero (the wind vane is not moving) and the temperature is at or below freezing. Some additional time before and after the icing event are filtered out to account for the slow build up and shedding of ice. Filling Gaps – Whenever measured met tower data is available, it is used. Two different methods are used to fill in the remaining portion of the year. First, nearby airport data is used if available. A linear correlation equation is defined between the airport and met tower site, which is used to adjust the hourly airport data recorded at the time of the gap. If neither met tower nor airport data is available for a given timestep, the software program Windographer (www.mistaya.ca) is used. Windographer uses statistical methods based on patterns in the data surrounding the gap, and is good for filling short gaps in data. Long-term Estimates – The year of data collected at the met tower site can be adjusted to account for inter-annual fluctuations in the wind resource. To do this, a nearby weather station with a consistent historical record of wind data and with a strong correlation to the met tower location is needed. If a suitable station is not available, there is a higher level of uncertainty in the wind speed that is measured being representative of a typical year. Turbulence Intensity – Turbulence intensity is the most basic measure of the turbulence of the wind. Turbulence intensity is calculated at each 10-minute timestep by dividing the standard deviation of the wind speed during that timestep by the average wind speed over that timestep. It is calculated only when the mean wind speed is at least 4 m/s. Typically, a turbulence intensity of 0.10 or less is desired for minimal wear on wind turbine components. Wind Shear – Typically, wind speeds increase with height above ground level. This vertical variation in wind speed is called wind shear and is influenced by surface roughness, surrounding terrain, and atmospheric stability. The met tower is equipped with anemometers at different heights so that the wind shear exponent, Į, can be calculated according to the power law formula: ¸¸ ¹ · ¨¨ © § ¸¸ ¹ · ¨¨ © § 2 1 2 1 v v H H D where H1 and H2 are the measurement heights and v1 and v2 are the measured wind speeds. Wind shear is calculated only with wind speed data above 4 m/s. Values can range from 0.05 to 0.25, with a typical value of 0.14. Scaling to Hub Height – If the wind turbine hub height is different from the height at which the wind resource is measured, the wind resource can be adjusted using the power law formula described above and using the wind shear data calculated at the site. Alaska Energy Authority SAINT GEORGE, AK Wind Resource Assessment DRAFT Page 4 of 14 DRAFT Air Density Adjustment – The power that can be extracted from the wind is directly related to the density of the air. Air density, ȡ, is a function of temperature and pressure and is calculated for each 10-minute timestep according to the following equation (units for air density are kg/m3): TR P u U , where P is pressure (kPa), R is the gas constant for air (287.1 J/kgK), and T is temperature in Kelvin. Since air pressure is not measured at the met tower site, the site elevation is used to calculate an annual average air pressure value according to the following equation: P = 1.225 – (1.194 x 10-4) x elevation Since wind turbine power curves are based on a standard air density of 1.225 kg/m3, the wind speeds measured at the met tower site are adjusted to create standard wind speed values that can be compared to the standard power curves. The adjustment is made according to the following formula: 3 1 tan tan ¸¸ ¹ · ¨¨ © §u dards measured measureddardsVV U U Wind Power Density – Wind power density provides a more accurate representation of a site’s wind energy potential than the annual average wind speed because it includes how wind speeds are distributed around the average as well as the local air density. The units of wind power density are watts per square meter and represent the power produced per square meter of area that the blades sweep as they rotate around the rotor. Wind Power Class – A seven level classification system based on wind power density is used to simplify the comparison of potential wind sites. Areas of Class 4 and higher are considered suitable for utility-scale wind power development. Weibull Distribution – The Weibull distribution is commonly used to approximate the wind speed frequency distribution in many areas when measured data is not available. In this case, the Weibull distribution is used to compare with our measured data. The Weibull is defined as follows: kk c v c v c kvP ¸¹ ·¨© §¸¹ ·¨© §  exp)( 1 Where P(v) is the probability of wind speed v occurring, c is the scale factor which is related to the average wind speed, and k is the shape factor which describes the distribution of the wind speeds. Typical k values range from 1.5 to 3.0, with lower k values resulting in higher average wind power densities. Alaska Energy Authority SAINT GEORGE, AK Wind Resource Assessment DRAFT Page 5 of 14 DRAFT WIND DATA RESULTS FOR ST GEORGE MET TOWER SITE Table 2 summarizes the amount of data that was successfully retrieved from the anemometers at the met tower site. There was minimal data loss due to icing or equipment failure. Table 2. Data Recovery Rates for St George Met Tower Data Month % Data Recovered January 100.0% February 99.9% March 99.7% April 99.9% May 100.0% June 100.0% July 100.0% August 100.0% September 100.0% October 100.0% November 100.0% December 99.9% Annual Avg 100% Table 3 summarizes the wind resource data measured at the met tower site. As shown, the highest wind month is November and the lowest wind month is July. The annual average wind speed is 9.6 m/s (21.5 mph). Table 3. Measured Wind Speeds at St. George Met Tower Location, 30-m Height (m/s) Hour Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Annual 0 10.4 9.1 9.8 10.8 8.3 7.0 5.9 8.3 10.1 11.4 13.2 11.3 9.6 1 10.2 9.6 9.7 10.5 8.4 6.9 6.0 8.4 10.2 11.5 13.2 11.3 9.7 2 10.1 9.6 9.5 10.5 8.4 6.9 6.1 8.2 10.3 12.1 13.4 11.2 9.7 3 9.8 9.0 9.4 10.4 8.5 6.9 6.0 8.6 10.2 12.3 13.2 10.8 9.6 4 9.8 9.2 9.3 10.4 8.4 6.9 5.7 8.6 10.3 12.0 12.5 11.0 9.5 5 9.7 9.4 9.2 10.3 8.2 7.2 5.5 8.7 10.5 12.0 11.7 11.0 9.4 6 9.5 9.7 9.2 10.3 8.1 6.9 5.7 8.6 10.8 11.8 11.6 11.1 9.4 7 9.6 9.5 9.5 10.3 8.2 6.7 5.8 8.5 10.9 11.6 11.7 11.0 9.4 8 9.5 9.4 9.5 10.1 8.3 6.7 6.1 8.3 10.8 11.4 11.8 10.9 9.4 9 9.6 9.1 9.1 10.2 8.4 6.6 6.2 8.4 10.8 11.2 12.0 10.4 9.3 10 9.5 9.0 9.2 10.3 8.2 6.7 6.3 8.5 10.8 11.1 12.4 10.5 9.4 11 9.4 8.7 9.2 10.2 8.6 6.8 6.6 8.7 11.1 11.4 12.6 10.5 9.5 12 9.6 8.5 9.3 10.1 8.7 6.9 6.8 8.8 11.4 11.2 12.5 10.5 9.5 13 10.0 8.9 9.4 10.1 8.7 7.1 6.9 8.7 11.4 11.6 12.4 10.4 9.6 14 9.8 9.2 9.7 10.4 9.1 7.1 6.9 8.6 11.4 11.8 12.3 10.4 9.7 15 9.8 9.5 9.8 10.4 9.1 7.2 7.1 8.4 11.4 12.0 12.3 10.4 9.8 16 9.6 9.6 10.0 10.4 8.9 7.0 7.0 8.5 11.2 12.1 12.1 10.3 9.7 17 9.4 9.8 9.9 10.2 8.8 6.9 7.0 8.4 11.1 12.1 12.1 10.4 9.7 18 9.4 9.7 9.6 10.2 8.6 6.9 7.0 8.3 11.0 12.0 12.4 10.6 9.6 19 9.3 9.4 9.4 10.2 8.6 6.8 6.9 8.5 11.0 11.8 12.5 11.0 9.6 20 9.7 9.6 9.4 10.1 8.5 6.6 6.6 8.9 10.7 11.6 12.5 10.9 9.6 21 10.1 9.5 9.7 9.9 8.4 6.7 6.4 8.8 10.6 11.7 12.2 11.1 9.6 22 10.1 9.2 9.9 9.8 8.3 6.7 6.4 8.4 10.4 11.7 12.5 11.2 9.6 23 10.4 9.1 10.3 10.0 8.3 6.7 6.0 8.3 10.3 11.7 12.4 11.3 9.6 Avg 9.8 9.3 9.5 10.3 8.5 6.9 6.4 8.5 10.8 11.7 12.4 10.8 9.6 Alaska Energy Authority SAINT GEORGE, AK Wind Resource Assessment DRAFT Page 6 of 14 DRAFT A common method of displaying a year of wind data is a wind frequency distribution, which shows the percent of the year that each wind speed occurs. Figure 2 shows the measured wind frequency distribution as well as the best matched Weibull distribution (c = 11, k= 2.13). 0 2 4 6 8 10 024681012141618202224262830 Wind Speed (m/s)Percent of TimeMeasured Weibull Bin m/s Measured Hours Bin m/s Measured Hours 083 18140 1 112 19 106 2 221 20 79 3 400 21 68 4 580 22 55 5 651 23 37 6 760 24 22 7757 25 9 8691 26 4 9661 27 1 10 594 28 0 11 586 29 1 12 546 30 1 13 465 31 1 14 387 32 0 15 317 33 0 16 239 34 0 17 189 Total: 8,760 Figure 2. Wind Speed Frequency Distribution of St George Met Tower Data, Sept 2004 – Oct 2005 The cut-in wind speed of many wind turbines is 4 m/s and the cut-out wind speed is around 25 m/s. The frequency distribution shows that a large percentage of the wind in Saint George occurs within this operational zone. TEMPERATURE The air temperature can affect wind power production in two primary ways: 1) colder temperatures lead to higher air densities and therefore more power production, and 2) some wind turbines shut down in very cold situations (usually around –25qC). The monthly average temperatures measured at the met tower are shown in Figure 3. The temperature never dropped below -15qC from mid September 2004 through the end of October 2005. 0.7 -1.5 -1.5 -1.6 2.5 6.2 8.4 9.4 7.2 4.1 0.3 -1.6 -4 -2 0 2 4 6 8 10 JanFebMarAprMayJunJulAugSepOctNovDecWind Speed (m/s) Figure 3. Monthly Average Air Temperatures at St George Met Tower Site Alaska Energy Authority SAINT GEORGE, AK Wind Resource Assessment DRAFT Page 7 of 14 DRAFT Table 4 shows the monthly wind roses for the year of data measured at the Saint George met tower. Table 4. Monthly Wind Roses for Saint George Met Tower Site January February March N EW S N EW S N EW S April May June N EW S N EW S N EW S July August September N EW S N EW S N EW S October November December N EW S N EW S N EW S Alaska Energy Authority SAINT GEORGE, AK Wind Resource Assessment DRAFT Page 8 of 14 DRAFT Table 5. Annual Wind Rose for Saint George Met Tower Site (Sept 2004 – Oct 2005) Legend Percent of Total Wind Energy Percent of Total Time NRG Systems SDR Version 5.03 N EW S Table 6 summarizes the monthly turbulence intensity and wind shear at the met tower site. A turbulence intensity value of less than 0.10 is considered low and unlikely to contribute to excessive wear of wind turbines. Turbulence intensity is based on recordings of the 30-meter level anemometer. Wind shear is calculated between the 30-meter anemometer and the 20-meter anemometer. Due to the different directions those booms are facing, shear can only be calculated from certain directions when both anemometers are exposed to free stream wind speeds. Both turbulence intensity and wind shear are only calculated for wind speeds greater than 4 m/s. Figure 4 shows the turbulence intensity and wind shear by direction. Table 6. Monthly Turbulence Intensity and Wind Shear at St George Met Tower Site Month Turbulence Intensity 20m to 30m Wind Shear Jan 0.11 0.20 Feb 0.11 0.06 Mar 0.11 0.07 Apr 0.11 0.06 May 0.11 0.09 Jun 0.11 0.06 Jul 0.10 0.15 Aug 0.10 0.12 Sep 0.10 0.11 Oct 0.11 0.13 Nov 0.10 0.09 Dec 0.11 0.10 Annual Avg 0.11 0.10 Average of CH1Avg Turbulence Intensity N NE E SE S SW W NW 0.06 0.12 0.18 Average of Power Law Exponent N NE E SE S SW W NW 0.06 0.12 0.18 Figure 4. Turbulence Intensity and Wind Shear by Direction at St George Met Tower Site Alaska Energy Authority SAINT GEORGE, AK Wind Resource Assessment DRAFT Page 9 of 14 DRAFT LONG-TERM REFERENCE STATION Wind data from the Saint George Airport weather station (shown in Figure 5), located about 15 miles southeast of the met tower site, serves as a long-term reference for the wind resource in the area. The Automated Surface Observing System (ASOS) was installed in September of 1996. The wind data is measured at a height of 10 meters above ground level and at an elevation of 38.1 meters. Figure 5. ASOS Equipment in Saint George (source: Ed Doerr, NOAA) Seven years of wind speed data from the Saint George ASOS are summarized in Table 7 and Figure 6. The average wind speed over the 7-year period is 7.5 m/s. The annual wind speed rarely deviates more than 3% above or below this long-term average. Table 7. Monthly Wind Speeds at Saint George Airport, 10-m Height (m/s) Year JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC AVE % of long-term average 1998 7.2 7.1 8.6 6.9 6.0 4.6 6.0 7.7 7.1 8.2 9.7 7.2 96% 1999 9.0 10.2 9.5 7.8 6.5 6.6 6.1 5.6 5.8 7.5 9.1 8.2 7.6 102% 2000 9.2 10.1 8.1 7.1 5.2 6.4 5.0 5.0 7.2 7.8 8.9 7.1 7.3 97% 2001 9.4 9.9 7.2 8.1 6.3 5.9 5.5 5.3 6.5 8.0 9.1 10.9 7.7 102% 2002 9.6 7.4 8.7 8.6 7.5 5.9 4.9 6.1 7.7 8.5 7.3 6.1 7.4 98% 2003 9.6 7.9 8.2 7.7 6.9 5.4 5.9 6.0 6.4 8.7 9.6 10.0 7.7 102% 2004 9.4 9.4 6.5 7.8 7.4 5.5 4.5 5.4 6.2 10.0 10.0 9.2 7.6 101% AVE 9.4 8.9 7.9 7.9 6.7 6.0 5.2 5.6 6.8 8.2 8.9 8.8 7.5 100% 7.6 7.7 7.7 7.6 7.2 7.47.3 0 2 4 6 8 10 1998 1999 2000 2001 2002 2003 2004Average Wind Speed (m/s) Figure 6. Annual Average Wind Speeds at Saint George Airport Weather Station, 10-m Height Alaska Energy Authority SAINT GEORGE, AK Wind Resource Assessment DRAFT Page 10 of 14 DRAFT Hourly wind speed measurements from the Saint George Airport weather station that are concurrent with recordings from the met tower site were purchased from the National Climatic Data Center. Data between these two sites was compared and a correlation coefficient of 0.87 was calculated (a value of 1 is perfect). This suggests that, although the actual wind speed values at the two sites are different, the pattern of wind speed fluctuations is similar between the sites. Figure 7 compares the met tower data with the ASOS data. Wind data from the Saint Paul Island ASOS, located about 45 miles to the northwest, is also included for comparison. 0 2 4 6 8 10 12 14 Jan-01Apr-01Jul-01Oct-01Jan-02Apr-02Jul-02Oct-02Jan-03Apr-03Jul-03Oct-03Jan-04Apr-04Jul-04Oct-04Jan-05Apr-05Jul-05MonthWind Speed (m/s)St George Met Tower St. George Island ASOS St. Paul Island ASOS Figure 7. Comparison of Average Monthly Wind Speeds Between Met Tower and ASOS Measurements A ratio of the short-term ASOS data to the long-term ASOS average was calculated for each month of the year. This ratio was then applied to adjust the met tower data to what could be expected at the site over the long term. Overall, the period of measured data was 3% windier than the estimated long-term average. Figure 8 and Figure 9 compare the measured data set to the long-term estimates. Table 8 presents the calculated long-term data set. Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 0 2 4 6 8 10 12 14 S(/)Seasonal Wind Speed Profile Longterm estimate Measured data Figure 8. Monthly Average Wind Speeds at St George Met Tower Site, 30m Height Alaska Energy Authority SAINT GEORGE, AK Wind Resource Assessment DRAFT Page 11 of 14 DRAFT Figure 9. Diurnal Profiles of Wind Speeds at St George Met Tower Site, 30m Height Table 8. Estimated Long-term Wind Speeds at St. George Met Tower Location, 30-m Height (m/s) Hour Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Annual 0 11.5 9.7 9.2 10.0 7.6 6.5 6.2 8.0 10.0 10.4 12.0 11.2 9.3 1 11.3 10.2 9.1 9.8 7.7 6.5 6.3 8.0 10.0 10.4 12.0 11.1 9.4 2 11.1 10.3 9.0 9.7 7.7 6.4 6.5 7.9 10.1 11.1 12.2 11.0 9.4 3 10.9 9.8 8.8 9.6 7.8 6.4 6.4 8.2 9.8 11.5 12.1 10.6 9.3 4 10.8 9.9 8.8 9.6 7.7 6.4 6.2 8.2 9.9 11.3 11.5 10.7 9.3 5 10.7 10.1 8.7 9.5 7.6 6.6 5.8 8.3 10.2 11.4 10.8 10.8 9.2 6 10.5 10.3 8.6 9.6 7.5 6.5 6.0 8.2 10.4 11.1 10.5 10.8 9.2 7 10.6 10.3 8.9 9.5 7.5 6.3 6.1 8.1 10.6 10.7 10.6 10.8 9.2 8 10.5 10.1 9.0 9.4 7.6 6.2 6.4 7.9 10.9 10.6 10.7 10.7 9.2 9 10.6 9.8 8.7 9.3 7.8 6.1 6.6 8.1 10.9 10.2 10.9 10.3 9.1 10 10.5 9.7 8.6 9.5 7.5 6.3 6.6 8.1 11.2 10.0 11.2 10.3 9.1 11 10.4 9.4 8.7 9.5 7.9 6.3 7.0 8.3 11.3 10.5 11.4 10.2 9.2 12 10.6 9.1 8.7 9.3 8.0 6.4 7.2 8.5 11.5 10.7 11.4 10.4 9.3 13 11.0 9.4 8.8 9.3 8.0 6.6 7.3 8.4 11.6 11.0 11.3 10.1 9.4 14 10.9 9.8 9.1 9.6 8.3 6.6 7.3 8.2 11.6 11.4 11.2 10.2 9.5 15 10.8 10.1 9.3 9.6 8.4 6.7 7.5 8.1 11.5 11.5 11.2 10.2 9.6 16 10.6 10.3 9.3 9.6 8.2 6.6 7.4 8.2 11.4 11.5 11.1 10.1 9.5 17 10.4 10.5 9.3 9.5 8.1 6.4 7.4 8.0 11.3 11.5 11.1 10.2 9.5 18 10.4 10.6 9.0 9.4 8.0 6.4 7.4 7.9 11.2 11.3 11.2 10.4 9.4 19 10.2 10.0 8.9 9.4 7.9 6.4 7.3 8.1 10.8 11.1 11.4 10.6 9.3 20 10.8 10.3 8.8 9.3 7.9 6.2 7.1 8.5 10.5 10.7 11.4 10.7 9.4 21 11.0 10.3 9.0 9.2 7.8 6.2 6.8 8.5 10.3 10.8 11.2 10.8 9.3 22 11.2 9.9 9.2 9.1 7.7 6.2 6.8 8.1 10.2 10.8 11.3 10.9 9.3 23 11.5 9.7 9.5 9.2 7.6 6.2 6.4 8.0 10.1 10.8 11.3 10.9 9.3 Avg 10.810.0 9.0 9.5 7.8 6.4 6.8 8.2 10.710.911.310.6 9.3 Alaska Energy Authority SAINT GEORGE, AK Wind Resource Assessment DRAFT Page 12 of 14 DRAFT POTENTIAL POWER PRODUCTION FROM WIND TURBINES IN SAINT GEORGE Table 9 lists a number of parameters that are typically used to characterize the power production potential of a particular site. Table 9. Summary of Power Production Potential of Saint George Met Tower Site Average Wind Power Density (30m height) 921 W/m2 Wind Power Class 7+ Rating Superior Various wind turbines, listed in Table 12, were used to calculate the energy production at the met tower site based on the long-term wind resource data set. Although different wind turbines are offered with different tower heights, to be consistent it is assumed that any wind turbine rated at 100 kW or less would be mounted on a 30-meter tall tower, while anything larger would be mounted on a 50-meter tower. The wind resource was adjusted to these heights based on the measured wind shear at the site. Table 10 summarizes the estimated energy production from various wind turbines at the Saint George met tower site. Table 10. Gross Annual Energy Production from Various Wind Turbines at St. George Met Tower Site (kWh) Month Proven 2.5kW Proven 6kW Bergey 10 kW FL30 Entegrity FL100 NW100 FL250 V27 V47 Jan 1,319 3,206 3,473 15,923 29,141 55,817 45,440 126,120 112,818 357,880 Feb 1,055 2,584 2,639 12,956 23,016 43,635 35,293 96,754 86,423 281,692 Mar 1,069 2,712 3,073 13,660 23,094 45,184 37,189 96,855 88,991 296,701 Apr 1,109 2,815 3,182 14,160 24,006 46,817 38,513 100,224 92,233 308,637 May 806 2,089 2,207 10,495 16,559 32,397 26,431 73,607 66,697 230,586 Jun 527 1,416 1,478 7,030 9,749 19,772 16,100 43,980 40,205 146,474 Jul 613 1,653 1,761 8,365 11,894 23,835 19,505 59,198 54,393 196,870 Aug 857 2,123 2,324 10,621 17,563 34,711 27,917 78,119 70,400 233,802 Sep 1,286 3,239 3,530 16,187 28,389 54,360 44,766 121,431 110,653 363,452 Oct 1,323 3,230 3,283 16,284 29,347 55,354 44,762 127,676 112,981 364,483 Nov 1,318 3,249 3,408 16,229 29,252 55,325 45,208 122,446 111,023 361,566 Dec 1,190 2,915 2,874 14,142 26,094 48,609 39,691 108,336 99,077 321,405 Annual 12,473 31,230 33,233 156,052 268,103 515,815 420,815 1,154,747 1,045,895 3,463,546 Annual kWh/m^2 1,299 1,312 863 1,173 1,515 1,482 1,482 1,688 1,825 1,996 Table 10 also lists the annual energy production per square meter of swept area (kWh/m 2). This allows one to directly compare the efficiency of one wind turbine against another, as shown in Figure 10. Alaska Energy Authority SAINT GEORGE, AK Wind Resource Assessment DRAFT Page 13 of 14 DRAFT Figure 10. Comparison of Power Production per Square Meter of Swept Area from Various Wind Turbines 0 50 100 150 200 250 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecEnergy Production by Swept Area (kWh/m^2)V47 V27 FL250 Entegrity NW100 FL100 Proven 2.5kW Proven 6kW FL30 Bergey 10kW Table 11 summarizes the gross capacity factor of the different wind turbines per month. Gross capacity factor is the amount of energy produced based on the given wind resource divided by the maximum amount of energy that could be produced if the wind turbine were to operate at rated power during that entire period. The gross capacity factor could be further reduced by up to 10% to account for transformer/line losses, turbine downtime, soiling of the blades, icing of the blades, yaw losses, and extreme weather conditions. Table 11. Gross Capacity Factor of Different Wind Turbines at Met Tower Site Month Proven 2.5kW Proven 6kW Bergey 10 kW FL30 Entegrity FL100 NW100 FL250 V27 V47 Jan 71% 72% 47% 71% 59% 75% 61% 68% 67% 73% Feb 63% 64% 39% 64% 52% 65% 53% 58% 57% 64% Mar 57% 61% 41% 61% 47% 61% 50% 52% 53% 60% Apr 62% 65% 44% 66% 51% 65% 53% 56% 57% 65% May 43% 47% 30% 47% 34% 44% 36% 40% 40% 47% Jun 29% 33% 21% 33% 21% 27% 22% 24% 25% 31% Jul 33% 37% 24% 37% 24% 32% 26% 32% 32% 40% Aug 46% 48% 31% 48% 36% 47% 38% 42% 42% 48% Sep 71% 75% 49% 75% 60% 76% 62% 67% 68% 76% Oct 71% 72% 44% 73% 60% 74% 60% 69% 67% 74% Nov 73% 75% 47% 75% 62% 77% 63% 68% 69% 76% Dec 64% 65% 39% 63% 53% 65% 53% 58% 59% 65% Annual 57% 59% 38% 59% 46% 59% 48% 53% 53% 60% CONCLUSION This report provides a summary of wind resource data collected from mid September 2004 through October 2005 on Saint George Island, Alaska. The data was compared to long-term trends in the area. Based on correlations with the Saint George ASOS weather data, estimates were made to create a long-term dataset for the Saint George met tower site. This information was used to make predictions as to the potential energy production from various wind turbines at the site. It is estimated that the long-term annual average wind speed at the site is 9.3 m/s at a height of 30 meters above ground level. Taking the local air density into account, the average wind power density for the site is 921 W/m2. This information means that Saint George Island has at least a Class 7 wind resource, which is superior for wind power development. Alaska Energy Authority SAINT GEORGE, AK Wind Resource Assessment DRAFT Page 14 of 14 DRAFT Table 12. Wind Turbine Models Used in Power Production Analysis Proven 2.5 kW http://www.provenenergy.com Tower Height: 30 meters Swept Area: 9.6 m2 Turbine Weight: 190 kg Proven 6 kW http://www.provenenergy.com Tower Height: 30 meters Swept Area: 23.8 m2 Turbine Weight: 500 kg Bergey 10 kW www.bergey.com Tower Height: 30 meters Swept Area: 38.5 m2 Weight: not available Fuhrlander FL30 30 kW www.lorax-energy.com Tower Height: 30 meters Swept Area: 133 m2 Weight (nacelle & rotor): 410 kg Entegrity 66 kW www.entegritywind.com Tower Height: 30 meters Swept Area: 177 m2 Weight (drivetrain & rotor): 2,420 kg Fuhrlander FL100 100 kW www.lorax-energy.com Tower Height: 30 meters Swept Area: 348 m2 Weight (nacelle & rotor): 2,380 kg Northern Power NW100/19 100 kW www.northernpower.com Tower Height: 30 meters Swept Area: 284 m2 Weight (nacelle & rotor): 7,086 kg Fuhrlander FL250 250 kW www.lorax-energy.com Tower Height: 50 meters Swept Area: 684 m2 Weight (nacelle & rotor): 4,050 kg Vestas V27 225 kW (refurbished, various suppliers) Tower Height: 50 meters Swept Area: 573 m2 Weight: not available Vestas V47 660 kW www.vestas.com Tower Height: 50 meters Swept Area: 1,735 m2 Weight: not available