HomeMy WebLinkAboutPoint Lay Wind Resource Report Point Lay Wind Resource Report By: Douglas Vaught, P.E., V3 Energy, LLC, Eagle River, Alaska Date: September 16 , 2010 Contents Summary Information ................................................................................................................................... 1 Test Site Location .......................................................................................................................................... 2 Data Recovery ............................................................................................................................................... 3 Wind Speed ................................................................................................................................................... 3 Time Se ries ................................................................................................................................................ 4 Daily Wind Profile ..................................................................................................................................... 5 Probability Distribution Function .................................................................................................................. 5 Wind Shear and Roughness .......................................................................................................................... 6 Temperature and Density ............................................................................................................................. 7 Wind Direction .............................................................................................................................................. 8 Turbulence .................................................................................................................................................... 9 Summary Information The wind resource measured in Point Lay is very good, measured at high wind power class 4 (good) to low wind power c lass 5 (excellent). In addition to strong average wind speed and wind power density, the site experiences highly directional prevailing winds and low turbulence. Met tower data synopsis Data dates October 5, 2006 to September 11, 2007 Wind power class High 4 (good) to low 5 (excellent) Power density mean, 30 meters 403 W/m2 Wind speed mean, 30 meters 6.63 m/s Weibull distribution parameters k = 1.74, c = 7.44 m/s Wind shear power law exponent 0.142 (moderate ), June to September data only Roughness class 0.54 (snow surface), June to September only IEC 61400 -1, 3 rd ed. classification Class III-c (likely, based on nearby Wainwright data) Turbulence intensity, mean 0.072 (at 15 m/s) Calm wind frequency 23% (less than 3.5 m/s) Point Lay community profile (DCCED) Current Population: 234 (2009 Estimated Population (not Certified))
Point Lay Wind Resource Report Page | 2 Pronunciation/Other Names: a.k.a. Kali Incorporation Type: Unincorporated Borough Located In: North Slope Borough School District: North Slope Borough Schools Regional Native Corporation: Arctic Slope Regional Corp. Test Site Location The Point Lay met tower was supplied to the Cully Corporation in Point Lay in 2006 as part of the National Renewable Energy Laboratory’s (NREL) anemometer loan program. Details of the project are not known, such as rationale for choosing the test site, but plotting the latitude and longitude of the met tower (keyed into the datalogger and readable in the data file) with Google Earth indicates a site well away from obstructions such as buildings and well expos ed to winds from all directions. Site information Site number 5430 Latitude/longitude N 69 ° 44.123’ W 163° 01.349’ Site elevation 1 meter AMSL Datalogger type NRG Symphonie, 10 minute time step Tower type NRG 30 meter tall tower Google Earth image
Point Lay Wind Resource Report Page | 3 Tower sensor information Channel Sensor Type Height Scale Offset Orientation 1 NRG #40 anemometer 99 ft 1.711 0.78 unknown 2 NRG #40 anemometer 99 ft 3 NRG #40 anemometer 66 ft 7 NRG #200P wind vane 99 ft 0.351 0 000 ° 8 NRG #200P wind vane 66 ft 000 ° 9 NRG #100S Temperature 5 ft 0.244 -123.5 Note: logger was programmed with English units and later converted to metric units for analysis Data Recovery Specific sensor data recovery problems typical of Alaska met tower operations, such as freezing rain, hoarfrost, and rime icing, likely occurred to some extent during the nearly one year met tower study in Point Lay, but original data was not available, other than in an Excel file with data from June 7 through September 11, 2007. Although this three month data set could be reviewed for data loss typically due to atmospheric icing conditions, such weather does not occur during the months of June, July, August and (early) September. All met tower data (including that not included in the Excel file download of original data) is summarized in several WindPRO software reports prepared by the Nation al Renewable Energy Laboratory . Wind Speed Wind data collected from the met tower and summarized in the NREL WindPRO reports, from the perspective of both mean wind speed and mean power density, indicates an excellent wind resource. Note that temperature data was not included in the analysis of power density. Given the extremely cold temperatures, and hence high air densities, of Point Lay, true wind power density will be higher yet, categorizing Point Lay more solidly as wind power class 5. For purposes of analysis, wind data monthly wind speed summaries contained in the 30 meter WindPRO report, along with other statistical data gleaned from the three -month Excel data, was used to synthesize a virtual data set. This enabled certain mathematic and graphical analyses not contained in the WindPRO reports. Anemometer data summary Variable Speed 30 m Measurement height (m) 30 Mean wind speed (m/s) 6.63 Median wind speed (m/s) 5.99 Max wind speed (m/s) 26.8 Weibull k 1.74 Weibull c (m/s) 7.44 Mean power density (W/m²) 403
Point Lay Wind Resource Report Page | 4 Mean energy content (kWh/m²/yr) 3,528 Energy pattern factor 2.26 Frequency of calms (%) 23.4 1-hr autocorrelation coefficient 0.945 Diurnal pattern strength 0.041 Hour of peak wind speed 19 Time Series Monthly average wind speeds indicate relatively high winds throughout the year, even during summer. Monthly variations appear significant but likely would smooth considerably in a multi-year view. 30 meter anemometer data summary Month Mean Median Max 10-min Std. Dev. Weibull k Weibull c (m/s) (m/s) (m/s) (m/s) (m/s) Jan 7.70 7.11 25.9 4.39 1.82 8.66 Feb 8.30 7.64 26.8 4.73 1.82 9.33 Mar 6.20 5.68 21.1 3.53 1.82 6.97 Apr 7.90 7.22 25.4 4.49 1.81 8.88 May 5.00 4.63 15.9 2.84 1.82 5.62 Jun 6.30 5.79 20.3 3.57 1.83 7.08 Jul 5.60 5.19 18.5 3.18 1.83 6.30 Aug 5.70 5.24 19.8 3.25 1.82 6.41 Sep 5.40 4.94 18.0 3.07 1.82 6.07 Oct 7.40 6.81 24.3 4.21 1.82 8.32 Nov 7.20 6.61 23.4 4.09 1.82 8.10 Dec 7.00 6.48 22.7 3.97 1.83 7.87 Annual 6.63 5.99 26.8 3.95 1.74 7.44 Time series graph Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec0246810Mean Wind Speed (m/s)Seasonal Wind Speed Profile
Point Lay Wind Resource Report Page | 5 Daily Wind Profile The daily wind profile indicates a relatively minor variation of wind speeds throughout th e day, with lowest wind speeds in the early and mid-morning hours and highest wind speeds during the late afternoon and early evening hours. More variation, however, can be expected with a monthly view of daily wind profiles. Annual -basis daily wind profile Monthly (daily) wind profiles Probability Distribution Function The probability distribution function (or histogram) of wind speed indicates a near -normal shape curve, defined as the Raleigh distribution (where k=2.0), considered standard for wind power sites. 0 6 12 18 2401234567Mean Wind Speed (m/s)Daily Wind Speed ProfileHour of Day
Point Lay Wind Resource Report Page | 6 Wind Shear and Roughness Considering just the June through September data, a calculated wind shear power law exponent of 0.142 indicates relatively low wind shear (change of wind speed with increasing height above the ground) at the site, which is desirable for wind power development. Related to wind shear, a calculated surface roughness of 0.0096 meters (indicating the height above ground level where the wind velocity would be zero) indicates very smooth air terrain (roughness description: s now surface) surrounding the met tower. Vertical wind shear profile, wind >4 m/s, June thru Sept data 0 5 10 15 20 25 300123456Frequency (%)Probability Distibution Function, All SectorsSpeed 30 m (m/s)Actual data Best-fit Weibull distribution (k=1.74, c=7.44 m/s)0 5 10 15 20050100150200250300350Height Above Ground (ft)Vertical Wind Shear Profile, All Sectors, 9 - 100 m/sMean Wind Speed (mph)Measured dataPower law fit (alpha = 0.142)Log law fit (z0 = 0.0700 m)
Point Lay Wind Resource Report Page | 7 Wind shear by direction table, wind >4 m/s, June thru Sept data Time Steps Mean Wind Speed (m/s) Best-fit Power Law Exp Surface Roughness (m) Direction Sector Speed 30m A Speed 30m B Speed 20m 348.75° - 11.25° 1,236 6.68 6.71 6.63 0.024 0.000 11.25° - 33.75° 1,003 6.83 6.89 6.45 0.154 0.122 33.75° - 56.25° 1,832 7.64 7.58 7.03 0.193 0.458 56.25° - 78.75° 2,156 9.16 8.98 8.48 0.164 0.178 78.75° - 101.25° 531 6.06 5.92 5.28 0.314 3.324 101.25° - 123.75° 115 6.03 5.91 5.38 0.254 1.581 123.75° - 146.25° 83 4.82 4.86 4.57 0.142 0.070 146.25° - 168.75° 72 5.64 6.50 6.11 -0.018 168.75° - 191.25° 203 10.09 10.11 9.51 0.150 0.102 191.25° - 213.75° 471 8.20 8.31 7.93 0.099 0.003 213.75° - 236.25° 323 7.06 7.04 6.37 0.249 1.457 236.25° - 258.75° 200 6.37 6.17 5.96 0.125 0.026 258.75° - 281.25° 176 5.39 5.23 5.11 0.093 0.002 281.25° - 303.75° 159 4.80 3.74 4.67 -0.222 303.75° - 326.25° 131 5.23 5.03 5.19 -0.031 326.25° - 348.75° 458 5.30 5.30 5.32 -0.010 Extreme Winds Data obtained for this wind resource analysis was not sufficient to calculate extreme wind probabilities. However, extreme wind probability calculations for the relatively nearby Wainwright met tower indicate a 50 year Vref, or 50 -year probable maximum 10 minute wind speed, of 24.8 m/s, well below the threshold criteria for International Electrotechnical Commission (IEC) 61400-1, 3 rd edition, Class III classification. Note that Class III is the lowest defined wind class and all wind turbines are designed for this wind regime. Temperature and Density Data obtained for this wind resource analysis did not include an annual temperature or air density summary, other than the June through September data in the Excel file. However, it is a reasonable presumption that Point Lay experiences similar temperatures as the village of Wainwright, hence Wainwright temperature and density data is presented below for information. Note that Wainwr ight experiences cool summers and extremely cold winters. The result is high air density; calculated air density exceeds standard air density for a sea level elevation (1.225 Kg/m3) by nine percent. This is advantageous in wind power operations as wind t urbines produce more power at low temperatures (high air density) than at standard temperature and density.
Point Lay Wind Resource Report Page | 8 Temperature and density table, Wainwright, 2009-2010 Temperature Air Density Month Mean Min Max Mean Min Max (°C) (°C) (°C) (kg/m³) (kg/m³) (kg/m³) Jan -25.1 -40.6 -9.1 1.421 1.334 1.515 Feb -23.1 -43.0 -13.2 1.410 1.355 1.531 Mar -23.7 -41.1 -12.5 1.413 1.352 1.518 Apr -11.9 -33.4 0.3 1.349 1.288 1.469 May -5.3 -19.7 3.2 1.316 1.275 1.390 Jun 4.0 -1.5 19.0 1.272 1.206 1.297 Jul 8.2 0.7 27.2 1.252 1.173 1.286 Aug 6.6 0.9 17.0 1.260 1.214 1.286 Sep 2.1 -9.0 14.3 1.280 1.226 1.334 Oct -3.7 -15.7 5.2 1.308 1.266 1.368 Nov -18.5 -35.1 -6.7 1.384 1.322 1.480 Dec -18.8 -34.3 -0.5 1.386 1.292 1.475 Annual -9.0 -43.0 27.2 1.337 1.173 1.531 Monthly temperature boxplot, Wainwright, 2009-2010 Wind Direction Wind frequency rose data (from NREL’s WindPRO report) indicates highly directional winds from northeast to east -northeast. Although the NREL report did not show a power density rose, Wainwright data confirms the Point Lay directional frequency and indicates that power winds are nearly exclusively northeast to east -northeast, which presumably is representative of Point Lay. Jan Feb Ma r Apr Ma y Jun Jul Aug Sep Oct No v De c Ann-60-40-2002040Value (°C)Monthly Statistics for Temperature ma xdaily highmeandaily lowmi n
Point Lay Wind Resource Report Page | 9 Wind frequency rose Turbulence From the NREL report, turbulence intensity at the Point Lay test site is well within acceptable standards with an IEC 61400-1, 3 rd edition (2005), classification of turbulence category C, which is the lowest defined. Mean turbulence intensity at 15 m/s is 0.072 Turbulence graphs
Point Lay Wind Resource Report Page | 10 Turbulence table