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HomeMy WebLinkAboutCity of Kongiganak Wind-Diesel Smart Grid Wind Resource Assessment - Nov 2005 - REF Grant 2195411 Page 1 of 14 813 W. Northern Lights Blvd. Anchorage, AK 99503 Phone: 907-269-3000 Fax: 907-269-3044 www.aidea.org/wind.htm Wind Resource Assessment for KONGIGANAK, ALASKA Site # 5045 Date last modified: 11/14/2005 Compiled by: Mia Devine Elevation: 100 ft Latitude: (NAD27) 59 57’ 46.3” N 59 57.772 Tower Type: 30-meter NRG Tall Tower Longitude: (NAD27) 162 51’ 57.5” W -162 51.959 Monitor Start: Monitor End: 10/21/2004 10/19/2005 INTRODUCTION On October 21, 2004, the Alaska Energy Authority and employees of the Purnaq Power Company installed a 30- meter meteorological tower (“met tower”) in Kongiganak. The purpose of this monitoring effort is to evaluate the feasibility of utilizing wind energy in the community. This report summarizes the wind resource data collected and the long-term energy production potential of the site. SITE DESCRIPTION Kongiganak is located at the mouth of the Kuskokwim River on the west shore of the Kuskokwim Bay. It lies about 450 miles west of Anchorage and 70 miles southwest of Bethel. Figure 1 shows the location of the met tower relative to the surrounding terrain. Alaska Energy Authority KONGIGANAK, AK Wind Resource Assessment Page 2 of 14 Figure 1. Topographic Map of Kongiganak Met Tower Site and Surrounding Area Alaska Energy Authority KONGIGANAK, AK Wind Resource Assessment Page 3 of 14 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 Kongiganak Met Tower Ch # Sensor Type Height Offset Boom Orientation 1 #40 Anemometer 30 m NRG Standard 270 True 2 #40 Anemometer 20 m NRG Standard 160 True 7 #200P Wind Vane 30 m 345 True 165 True 9 #110S Temperature 5 m NRG Standard - Arial view of equipment on tower N NE E SE S SW W NW CH1 CH2 CH7 Tower 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. As shown, the area around Kongiganak is flat and free of obstructions. Facing Northwest Facing North Facing Northeast Facing West Looking up the tower Facing East Facing Southeast Facing South Facing Southwest Alaska Energy Authority KONGIGANAK, AK Wind Resource Assessment Page 4 of 14 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 C = 5/9 (F – 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. Since the 30-meter anemometer boom is oriented towards the west, the anemometer will be in the wake of the tower when winds are blowing from the east and may not record an accurate wind speed value. 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, , can be calculated according to the power law formula: 2 1 2 1 v v H H 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 KONGIGANAK, AK Wind Resource Assessment Page 5 of 14 Air Density Adjustment – The power that can be extracted from the wind is directly related to the density of the air. Air density, , 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 , 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 dards measured measureddardsVV 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 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 KONGIGANAK, AK Wind Resource Assessment Page 6 of 14 WIND DATA RESULTS FOR KONGIGANAK MET TOWER SITE Table 2 summarizes the amount of data that was successfully retrieved from the anemometers at the met tower site. The month with the lowest data recovery rate is February, due to icing of the sensors. Table 2. Data Recovery Rates for Met Tower Data Month 30 m January 91% February 72% March 79% April 96% May 100% June 100% July 100% August 100% September 100% October 88% November 77% December 80% Annual Avg 90% Table 3 summarizes the wind resource data measured at the met tower site. Figure 2 and Figure 3 show this same data graphically. As shown, the highest wind month is November and the lowest wind month is June. Table 3. Measured Wind Speeds at Kongiganak Met Tower Location, 30m Height (m/s) Hour Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Annual 0 8.6 8.8 8.7 8.7 6.6 5.2 5.4 7.5 8.7 7.9 11.0 8.9 8.0 1 8.7 8.7 8.7 8.4 6.7 5.3 5.4 7.4 8.7 8.0 10.8 8.7 8.0 2 8.6 9.1 8.8 7.9 6.6 5.4 5.6 7.5 8.8 7.9 10.6 9.1 8.0 3 8.7 9.2 8.9 7.8 6.5 5.4 5.5 7.5 8.9 7.9 11.0 9.0 8.0 4 8.7 9.0 8.5 7.8 6.1 5.2 5.6 7.2 9.0 7.9 10.5 9.0 7.9 5 8.8 9.0 8.5 7.3 6.2 5.0 5.1 7.0 8.9 7.5 10.6 9.3 7.8 6 8.7 9.2 8.6 7.3 6.1 4.9 5.1 6.9 9.1 7.3 10.6 9.6 7.8 7 8.7 8.8 8.6 7.3 5.9 5.0 5.2 6.7 9.4 7.0 10.3 10.0 7.7 8 8.5 9.1 8.7 7.1 6.1 5.1 5.2 6.8 9.5 7.0 10.2 9.8 7.8 9 8.8 9.1 8.8 6.8 6.1 5.1 5.1 7.0 9.4 6.9 10.2 9.8 7.8 10 9.0 9.2 8.9 6.8 6.2 5.2 5.2 7.5 9.3 7.3 10.3 9.7 7.9 11 8.5 9.0 8.8 6.9 6.1 5.2 5.3 7.6 9.7 7.9 10.4 9.4 7.9 12 8.9 9.5 8.5 7.1 5.9 5.5 5.2 7.8 9.9 8.2 10.4 9.2 8.0 13 8.9 9.4 8.1 7.1 6.0 5.6 5.2 7.9 10.0 8.6 10.5 8.9 8.0 14 8.8 9.5 8.3 7.1 5.9 5.6 5.4 8.0 9.8 8.6 10.5 8.8 8.0 15 8.7 9.5 8.8 7.1 6.0 5.8 5.4 7.9 9.8 8.4 10.3 8.4 8.0 16 8.5 9.3 8.5 7.3 6.4 6.1 5.7 8.2 9.8 8.3 10.5 8.5 8.1 17 8.6 9.1 8.5 7.4 6.2 5.9 5.8 8.1 9.6 7.9 10.3 8.6 8.0 18 8.6 9.0 8.6 7.6 6.0 5.8 6.0 7.7 9.2 7.8 10.3 8.4 7.9 19 8.8 9.0 8.4 8.0 5.8 5.8 6.0 7.4 8.9 8.0 10.6 8.6 8.0 20 9.0 9.1 8.9 8.0 6.0 5.5 5.9 6.9 8.6 7.9 10.6 8.5 7.9 21 8.7 8.9 9.0 8.2 6.3 5.3 5.7 7.2 8.6 8.2 10.7 9.1 8.0 22 8.8 9.2 8.9 8.2 6.6 5.2 5.7 7.4 8.4 8.2 10.9 9.0 8.0 23 8.8 9.0 8.6 8.6 6.7 5.1 5.6 7.3 8.6 7.9 10.7 9.1 8.0 Avg 8.7 9.1 8.6 7.6 6.2 5.4 5.5 7.4 9.2 7.9 10.5 9.1 7.9 Alaska Energy Authority KONGIGANAK, AK Wind Resource Assessment Page 7 of 14 Figure 2. Monthly Average Wind Speeds at Kongiganak Met Tower Site (30m Height) 0 2 4 6 8 10 12 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 0.0 4.5 8.9 13.4 17.9 22.4 26.8 As shown below, the diurnal variation is slightly more pronounced during the summer months than the winter months, with winds typically lowest in the morning and increasing in the afternoon. Figure 3. Hourly Average Wind Speeds at Kongiganak Met Tower Site (30m Height) 012345 678910 0 2 4 6 8 10 12 14 16 18 20 22 Hour of Day January July 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 4 shows the measured wind frequency distribution as well as the best matched Weibull distribution (c = 8.8, k= 2.1). 0 2 4 6 8 10 12 14 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 Wind Speed (m/s) Measured Weibull Figure 4. Wind Speed Frequency Distribution of Kongiganak Met Tower Data Alaska Energy Authority KONGIGANAK, AK Wind Resource Assessment Page 8 of 14 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 Kongiganak is within this operational zone. Table 4 displays the annual wind rose at the Kongiganak met tower site and Table 5 breaks the wind rose down by month. As shown, the predominant wind direction is the NE and South. Table 4. Annual Wind Rose for Kongiganak Met Tower Site Annual Wind Rose, Oct 04 – Oct 05 Legend Percent of Total Wind Energy Percent of Total Time NRG Systems SDR Version 5.03 N EW S Alaska Energy Authority KONGIGANAK, AK Wind Resource Assessment Page 9 of 14 Table 5. Monthly Wind Roses for the Kongiganak Met Tower Site Nov 2004 Dec 2004 Jan 2005 N EW S N EW S N EW S Feb 2005 Mar 2005 Apr 2005 N EW S N EW S N EW S May 2005 June 2005 July 2005 N EW S N EW S N EW S Aug 2005 Sept 2005 Oct 2005 N EW S N EW S N EW S Alaska Energy Authority KONGIGANAK, AK Wind Resource Assessment Page 10 of 14 Table 6 summarizes the monthly turbulence intensity and wind shear at the met tower site. The turbulence intensity is less than 0.10, which is considered low and unlikely to contribute to excessive wear of wind turbines. Wind shear was calculated between the 30-meter anemometer and the 20-meter anemometer. Table 6. Monthly Turbulence Intensity and Wind Shear at Met Tower Site Month Turbulence Intensity 20m to 30m Wind Shear Jan 0.06 0.18 Feb 0.07 0.22 Mar 0.06 0.27 Apr 0.06 0.42 May 0.09 0.32 Jun 0.10 0.22 Jul 0.10 0.29 Aug 0.10 0.27 Sep 0.10 0.23 Oct 0.09 0.36 Nov 0.07 0.27 Dec 0.07 0.45 Annual Avg 0.08 0.29 Turbulence Intensity 0.07 0.070.07 0.06 0.09 0.12 0.08 0.080.08 0.08 0.080.09 0.09 0.10 0.10 0.09 0.090.09 Wind Shear0.62 0.400.24 0.18 0.15 -0.10 0.25 0.280.28 0.28 0.240.28 0.26 0.15 0.15 0.23 0.280.40 Figure 5. Turbulence Intensity and Wind Shear by Direction 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 -25C). The average temperatures measured at the Kongiganak met tower are shown in Figure 6. -8.9 -8.6 -6.9 6.4 13.1 14.0 13.3 9.5 2.5 -2.8 -7.1-7.6 -15 -10 -5 0 5 10 15 20 Figure 6. Monthly Average Temperatures in Kongiganak Alaska Energy Authority KONGIGANAK, AK Wind Resource Assessment Page 11 of 14 LONG-TERM REFERENCE STATION The closest weather stations to Kongiganak that have been recording long-term wind speed and direction data are Bethel (70 miles to the northeast) and Mekoryuk (130 miles to the northwest). St Paul Island lies about 300 miles to the southwest of Kongiganak and is representative of winds coming in off the ocean. Meteorological data from the Bethel, Mekoryuk, and St Paul Island airport weather stations were obtained from the National Climatic Data Center. None of the airport weather stations have a high correlation with data recorded at the Kongiganak met tower on an hourly basis; however, the general weather patterns in the area are closely correlated, as shown in Figure 7. The monthly wind speeds in Kongiganak are most closely correlated to those in Mekoryuk, with a correlation coefficient of 0.89 (a value of 1.0 is perfect). 0 2 4 6 8 10 12 Mekoryuk Airport Bethel Airport St Paul Airport Kongiganak Met Tower Figure 7. Comparison of Wind Speeds in Kongiganak to Long-term Weather Stations Simultaneous wind speed measurements at each site were compared to see if the short period of measurement in Kongiganak was representative of what could be expected over the long-term. As shown in Figure 8, wind speeds during Nov 2004 thru Aug 2005 were close to what could be expected over the long-term for that period of the year. 0 1 2 3 4 5 6 7 8 9 Nov01-Aug02 Nov02-Aug03 Nov03-Augt04 Nov04-Aug05 Measurement Period Mekoryuk Airport Mekoryuk Long-term Average Bethel Airport Bethel Long-term Average St Paul Airport St. Paul Long-term Average Kongiganak Met Tower Figure 8. Comparison of Measurement Period to Long-term Averages Alaska Energy Authority KONGIGANAK, AK Wind Resource Assessment Page 12 of 14 POTENTIAL POWER PRODUCTION FROM WIND TURBINES IN KONGIGANAK Table 7 lists a number of parameters used to characterize the power production potential of a particular site. Based on the wind power density of the site, Kongiganak has a Class 6 wind resource, which is rated “outstanding” for wind power development. Table 7. Summary of Power Production Potential of Kongiganak Met Tower Site Average Wind Power Density (30m) 562 W/m2 Wind Power Class 6 Rating Outstanding Various wind turbine power curves, listed in Table 10, were used to calculate the potential energy production of each wind turbine if they were to be installed at the met tower site. These calculations are based on the manufacturer’s published power curve and the measured wind resource data at the site. 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 8 summarizes the estimated energy production from the various wind turbines at the met tower site. Table 8. Gross Annual Energy Production from Wind Turbines at Kongiganak Met Tower Site (kWh) Month Proven 2.5kW Proven 6kW Bergey 10 kW FL30 Entegrity FL100 NW100 FL250 V27 V47 Jan 992 2,575 2,838 13,118 21,286 41,333 33,991 93,685 85,906 295,870 Feb 927 2,366 2,582 11,865 19,907 38,532 31,689 84,593 77,757 262,739 Mar 911 2,370 2,672 12,121 19,360 38,006 31,215 85,597 78,764 272,647 Apr 751 1,991 2,150 9,994 15,365 30,216 24,947 66,536 61,513 218,068 May 529 1,436 1,484 7,240 9,937 20,038 16,306 45,447 41,386 153,465 Jun 375 1,010 998 4,891 6,299 13,197 10,569 31,020 27,909 102,145 Jul 391 1,056 1,042 5,127 6,485 13,575 10,880 30,090 27,066 100,413 Aug 754 1,977 2,199 9,942 15,337 30,495 25,086 68,187 62,799 219,199 Sep 1,003 2,521 2,649 12,622 21,476 41,328 33,658 94,505 85,332 282,677 Oct 788 2,027 2,097 10,096 16,047 31,311 25,499 74,131 67,229 230,346 Nov 1,138 2,837 3,001 14,144 24,751 47,249 38,601 105,897 96,923 319,331 Dec 917 2,338 2,456 11,749 19,409 37,339 30,425 85,231 77,220 264,279 Annual 9,476 24,505 26,167 122,908 195,660 382,618 312,865 864,919 789,802 2,721,178 Annual kWh/m^2 987 1,030 680 924 1,105 1,099 1,102 1,265 1,378 1,568 Table 8 also lists the annual energy production per square meter of swept area (kWh/m2). Normalizing by the swept area allows one to more directly compare the efficiency of one wind turbine against another, as shown in Figure 9. Alaska Energy Authority KONGIGANAK, AK Wind Resource Assessment Page 13 of 14 0 20 40 60 80 100 120 140 160 180 200 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec V47 V27 FL250 Entegrity FL100 NW100 Proven 6kW Proven 2.5kW FL30 Bergey 10 kW Figure 9. Comparison of Power Production per Square Meter of Swept Area from Various Wind Turbines Table 9 summarizes the gross capacity factor of the wind turbines per month. Gross capacity factor is defined as a ratio of the actual amount of energy produced based on the given wind resource to the maximum amount of energy that could be produced if the wind turbine were to operate at rated power during the entire period. The gross capacity factor may be further reduced by up to 10% to account for transformer/line losses, turbine downtime, soiling of the blades, icing of the blades, extreme weather conditions, and yaw losses. Table 9. Gross Capacity Factor of Different Wind Turbines at Kongiganak Met Tower Site Month Proven 2.5kW Proven 6kW Bergey 10 kW FL30 Entegrity FL100 NW100 FL250 V27 V47 Jan 53% 58% 38% 59% 43% 56% 46% 50% 51% 60% Feb 55% 59% 38% 59% 45% 57% 47% 50% 51% 59% Mar 49% 53% 36% 54% 39% 51% 42% 46% 47% 56% Apr 42% 46% 30% 46% 32% 42% 35% 37% 38% 46% May 28% 32% 20% 32% 20% 27% 22% 24% 25% 31% Jun 21% 23% 14% 23% 13% 18% 15% 17% 17% 21% Jul 21% 24% 14% 23% 13% 18% 15% 16% 16% 20% Aug 41% 44% 30% 45% 31% 41% 34% 37% 38% 45% Sep 56% 58% 37% 58% 45% 57% 47% 53% 53% 59% Oct 42% 45% 28% 45% 33% 42% 34% 40% 40% 47% Nov 63% 66% 42% 65% 52% 66% 54% 59% 60% 67% Dec 49% 52% 33% 53% 40% 50% 41% 46% 46% 54% Annual 43% 47% 30% 47% 34% 44% 36% 40% 40% 47% CONCLUSION This report provides a summary of wind resource data collected from Oct 2004 through Oct 2005 in Kongiganak, Alaska. The measured data was compared to long-term trends in the area and it was determined that the data collected is typical of what could be expected in the long term. The annual average wind speed at the site is 7.9 m/s at a height of 30 meters above ground level, primary wind directions are the northeast and south, and the site has low turbulence levels. The wind data was used to make predictions as to the potential energy production from wind turbines at the site. Taking the local air density into account, the average wind power density for the site is 562 w/m2. This information means that Kongiganak has a Class 6 wind resource, which is outstanding for wind power development. Alaska Energy Authority KONGIGANAK, AK Wind Resource Assessment Page 14 of 14 Table 10. 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