LONG TERM SITE WIND DATA ANNUAL REPORT. Paxton, MA

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1 LONG TERM SITE WIND DATA ANNUAL REPORT Paxton, MA July 1, 2012 June 30, 2013 Prepared for Massachusetts Clean Energy Center Summer Street, 9th Floor Boston, MA 021 by Dylan D. Chase James F. Manwell Anthony F. Ellis September 27, 2013 Report template version 1.0 Wind Energy Center 160 Governors Drive, (413)

2 NOTICE AND ACKNOWLEDGEMENTS This report was prepared by the Wind Energy Center (WEC) at the University of Massachusetts, Amherst in the course of performing work sponsored by the Renewable Energy Trust (RET), as administered by the Massachusetts Clean Energy Center (MassCEC). The opinions expressed in this report do not necessarily reflect those of MTC or the Commonwealth of Massachusetts, and reference to any specific product, service, process, or method does not constitute an implied or expressed recommendation or endorsement of it. Further, MassCEC, the Commonwealth of Massachusetts, and the Wind Energy Center make no warranties or representations, expressed or implied, as to the fitness for particular purpose or merchantability of any product, apparatus, or service, or the usefulness, completeness, or accuracy of any processes, methods or other information contained, described, disclosed, or referred to in this report. MassCEC, the Commonwealth of Massachusetts, and the Wind Energy Center make no representation that the use of any product, apparatus, process, method, or other information will not infringe privately owned rights and will assume no liability for any loss, injury, or damage directly or indirectly resulting from, or occurring in connection with, the use of information contained, described, disclosed, or referred to in this report. September 27, 2013 Wind Energy Center Page 1

3 TABLE OF CONTENTS Notice and Acknowledgements... 1 Table of Contents... 2 Table of Figures... 3 Executive Summary... 4 SECTION 1 - Station Location... Terrain... SECTION 2 - Instrumentation and Equipment... 6 SECTION 3 - Data Summary... 7 SECTION 4 - Graphs Wind Speed Time Series Wind Speed Distributions Monthly Average Wind Speeds Diurnal Average Wind Speeds Turbulence Intensities... 1 Wind Roses Annual Average Wind Speed Significant Meteorological Events SECTION - Data Collection and Maintenance SECTION 6 - Data Recovery and Validation Test Definitions Sensor Statistics APPENDIX A - Sensor Performance Report Test Definitions Sensor Statistics APPENDIX B - Plot Data... 2 Wind Speed Distribution Data... 2 Monthly Average Wind Speed Data Diurnal Average Wind Speed Data Wind Rose Data September 27, 2013 Wind Energy Center Page 2

4 TABLE OF FIGURES Figure 1 - Site Location... Figure 2- Instrumentation at top of Yankee Network Tower note the anemometers on the left (horizontal boom and at the top of the left-hand vertical tube Figure 3- Bottom view of sensor array, anemometer is at photo top and wind vanes are mounted on the shorter side booms Figure 4 Wind Speed Time Series Figure Wind Speed Distribution Jul 2012 Sep Figure 6 Monthly Average Wind Speed Figure 7 Diurnal Average Wind Speeds Jul 2012 Sep Figure 8 Turbulence Intensity Jul 2012 Sep Figure 9 Wind Rose Jul 2012 Sep Figure Annual Average Wind Speed September 27, 2013 Wind Energy Center Page 3

5 EXECUTIVE SUMMARY All the work presented in this Wind Data Report including installation and decommissioning of the meteorological tower and instrumentation, and the data analysis and reporting was performed by the Wind Energy Center (WEC) at the University of Massachusetts, Amherst. One anemometers and one wind vane are mounted each at the 77 m (22.6 ft) tower height and at the 78 m (2.9 ft) tower height and a temperature sensor is installed near the base of the tower. On November th, 2012 an anemometer was replaced and on April 11 th, 2013 the data logger was replaced. During the period covered by this annual report, July, 2012 June, 2013, the mean recorded wind speed at 78 m was 7.61 m/s (17.03 mph*). The prevailing wind direction during the monitoring period was from the West-Northwest. The average turbulence intensity measured at wind speeds near m/s at 78 m was 0.6. The gross data recovery percentage (the actual percentage of expected data received) was 6.1% and the net data recovery percentage (the percentage of expected data which passed all of the quality assurance tests) was 64.80%. Additional information about interpreting the data presented in this report can be found in the Fact Sheet, Interpreting Your Wind Resource Data, produced by the WEC and the Massachusetts Technology Collaborative (MTC). This document is found through the WEC website: ERL_Fact_Sheet_6_Wind_resource_interpretation.pdf * 1 m/s = mph. September 27, 2013 Wind Energy Center Page 4

6 SECTION 1 - Station Location The Yankee Network Tower is located on Mount Asnebumskit. The tower is at a 417 m elevation, and located southeast of the town of Paxton,. The wind monitoring equipment is located at North, West, per the WGS84 standard (the World Geodetic System 1984, an international standard for absolute localization with earthly coordinates). The white circle in Figure 1 marks the site location. Figure 1 - Site Location Terrain The site is located in a fairly wooded area as can be seen in Figure 1. However there is some clearing due to a parking lot and road to the west of the tower. There is also a road and some buildings located to the north of the tower. September 27, 2013 Wind Energy Center Page

7 SECTION 2 - Instrumentation and Equipment The wind monitoring equipment is mounted on an 8.2 foot aluminum tube that is attached vertically to the main network tower. The primary and secondary anemometers and two vanes are attached on short booms off the tube. A picture of the setup is below note the horizontal booms where the anemometers and vanes are attached: Figure 2- Instrumentation at top of Yankee Network Tower note the anemometers on the left (horizontal boom and at the top of the left-hand vertical tube. Figure 3- Bottom view of sensor array, anemometer is at photo top and wind vanes are mounted on the shorter side booms. September 27, 2013 Wind Energy Center Page 6

8 The installed equipment of note comprises: NRG Symphonie data logger with ipack modem One NRG #Max 40c cup anemometer, custom calibration (slope m/s, offset 0.4 m/s) One Riso p246a class 1 anemometer, custom calibration (serial # 6800 til 11//12 (slope m/s, offset m/s), serial # 6799 (slope m/s, offset m/s) afterwards) Two NRG #200P wind direction vanes One NRG #1S temperature sensor Short booms for vanes, 14 from mast Long side boom for Riso anemometer, 43 from mast One stub mast for NRG anemometer Lightning rod and ground cable Shielded sensor wire SECTION 3- Data Summary A summary of the wind speeds and wind directions measured during the reporting period is included in Table 1. Table 1 includes the mean wind speeds measured at each measurement height, the maximum instantaneous wind speed measured at each measurement height and the prevailing wind direction measured at each measurement height. These values are provided for each month of the reporting period and for the whole reporting period. September 27, 2013 Wind Energy Center Page 7

9 Table 1. Wind Speed and Direction Data Summary 78 m 77 m Month Mean Wind Speed [m/s] NDR [%] Max Wind Speed [m/s] NDR [%] Prevailing Direction [deg] 12-Jul * 0 12-Aug * 0 12-Sep * 0 12-Oct * 0 12-Nov * 0 12-Dec * 0 13-Jan * 0 13-Feb * 0 13-Mar * 0 13-Apr * 0 13-May * 0 13-Jun * 0 FY * 0 12-Jul NW Aug NW Sep NW Oct NNW Nov NNE Dec WNW Jan WNW Feb WNW Mar WNW Apr SSW May WNW Jun W FY WNW NDR [%] * Invalid data, 78 meter wind vane shifted during the monitoring period September 27, 2013 Wind Energy Center Page 8

10 Wind data statistics in the table are reported when more than 90% of the data during the reporting period that are valid. In cases when a large amount of data is missing, the percent of the available data that are used to determine the data statistics is noted. No measurement of wind speed or direction can be perfectly accurate. Wind speed measurement errors occur due to anemometer manufacturing variability, anemometer calibration errors, the response of anemometers to turbulence and vertical air flow and due to air flows caused by the anemometer mounting system. Every effort is made to reduce the sources of these errors. Nevertheless, the values reported in this report have an expected uncertainty of about ± 2% or ± 0.2 m/s, whichever is greater. Wind direction measurement errors occur due to sensor measurement uncertainty, tower effects, boom alignment measurement errors and twisting of pipe sections during the raising of a pipe tower. Efforts are also made to reduce these errors, but the reported wind directions are estimated to have an uncertainty of +/- degrees. A summary of the turbulence intensity and mean wind shear measured at each measurement height during the reporting period is included in Table 2. These values are provided for each month of the reporting period and for the whole reporting period. Turbulence Intensity is calculated by dividing the standard deviation of the wind speed by the mean wind speed and is a measure of the gustiness of a wind resource. Lower turbulence results in lower mechanical loads on a wind turbine. Turbulence intensity varies with wind speed. The average turbulence intensity presented in Table 2 is the mean turbulence intensity when the wind speed at each measurement height is between and 11 m/s. Shear coefficients provide a measure of the change in wind speed with height. When data at multiple heights are available, shear coefficients, α, have been determined. They can be used in the following formula to estimate the average wind speed, U(z), at height z, when the average wind speed, U(z r ), at height z r is known: U ( z) U ( z r ) The change in wind speed with height is a very complicated relationship related to atmospheric conditions, wind speed, wind direction, time of day and time of year. This formula will not always provide the correct answer at any given site. Nevertheless the calculated shear coefficient, based on measurements at two heights, can be used to characterize the degree of increase in wind speed with height at a site. The mean wind shear coefficient that is provided here is calculated based on the mean wind speeds in Table 1, where z high and z low are the heights of the higher and lower mean wind speeds used in the calculation and U (z low ) and U(z high ) are the mean wind speeds at the two heights. z z r U( z log U( z high low ) ) z log z high low September 27, 2013 Wind Energy Center Page 9

11 Table 2. Shear and Turbulence Intensity Data Summary 78 m 77 m TI at m/s [-] NDR [%] Month 12-Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun FY Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun FY Wind shear is not calculated for the site because the anemometers are at very similar heights. September 27, 2013 Wind Energy Center Page

12 SECTION 4- Graphs This report contains several types of wind data graphs. Unless otherwise noted, each graph represents data from 1 quarter (3 months). Each quarterly graph corresponds to a quarter of fiscal year 2013: Quarter 1 (July 2012-September 2012), Quarter 2 (October 2012 to December 2012), Quarter 3 (January 2013 March 2013), or Quarter 4 (April 2013 June 2013). The following graphs are included: Time Series -minute average wind speeds are plotted against time. Wind Speed Distribution A histogram plot giving the percentage of time that the wind is at a given wind speed. Monthly Average A plot of the monthly average wind speed over the threemonth period. This graph shows the trends in the wind speed over the year. Diurnal A plot of the average wind speed for each hour of the day. Turbulence Intensity A plot of turbulence intensity as a function of wind speed. Turbulence Intensity is calculated as the standard deviation of the wind speed divided by the wind speed and is a measure of the gustiness of a wind resource. Lower turbulence results in lower mechanical loads on a wind turbine. Wind Rose A plot, by compass direction showing the percentage of time that the wind comes from a given direction and the average wind speed in that direction. Annual Average Wind Speed A plot of the annual average wind speed at the site for each fiscal year. With regard to the Paxton site, the following observations are noted. Time Series The winds were primarily less than 1 m/s during the monitoring period. Wind Speed Distribution The wind speed distributions show that the most common wind speeds are in the range of 4 or m/s at the site. Monthly Average The winter months show higher average wind speeds than the summer months. Diurnal A plot of the average wind speed for each hour of the day. Turbulence Intensity In each quarter turbulence intensities for high wind speeds generally stay below 0.3 September 27, 2013 Wind Energy Center Page 11

13 Percent Time [%] Wind Speed [m/s] Wind Rose The wind direction data varied during each of the four quarters but the prevailing wind directions were between the West and the Northwest directions. Annual Average Wind Speed The annual average wind speed at the site is similar to past annual average wind speeds. The annual average wind speed is not reported for 2009 and 20 because there was not enough data during these periods to calculate the annual average wind speed. Data for the wind speed histograms, quarterly and diurnal average plots, and wind roses are included in APPENDIX B. Wind Speed Time Series 2 Paxton Wind Speed Time Series, 78m - 01-Jul-2012 through 01-Jul Oct-2012 Jan-2013 Apr-2013 Jul-2013 Time NDR: 90.46% Figure 4 Wind Speed Time Series Wind Speed Distributions 1 Paxton Wind Speed Distribution, 78m - Jul 2012 through Sep Wind Speed [m/s] NDR: 99.48% Figure a Wind Speed Distribution Jul 2012 Sep 2012 September 27, 2013 Wind Energy Center Page 12

14 Percent Time [%] Percent Time [%] Percent Time [%] 1 Paxton Wind Speed Distribution, 78m - Oct 2012 through Dec Wind Speed [m/s] NDR: 92.49% Figure b Wind Speed Distribution Oct 2012 Dec Paxton Wind Speed Distribution, 78m - Jan 2013 through Mar Wind Speed [m/s] NDR: 92.4% Figure c Wind Speed Distribution Jan 2013 Mar Paxton Wind Speed Distribution, 78m - Apr 2013 through Jun Wind Speed [m/s] NDR: 76.92% Figure d Wind Speed Distribution Apr 2013 Jun 2013 September 27, 2013 Wind Energy Center Page 13

15 Mean Wind Speed [m/s] Mean Wind Speed [m/s] Wind Speed [m/s] Monthly Average Wind Speeds Paxton Monthly Average Wind Speed, 78m - 01-Jul-2012 through 01-Jul Jul-12 Aug-12 Sep-12 Oct-12 Nov-12 Dec-12 Jan-13 Feb-13 Mar-13 Apr-13 May-13 Jun-13 Jul-13 Time Figure 6 Monthly Average Wind Speed Diurnal Average Wind Speeds Paxton Diurnal Average Wind Speed, 78m - Jul 2012 through Sep Hour of Day NDR: 99.48% Figure 7a Diurnal Average Wind Speeds Jul 2012 Sep 2012 Paxton Diurnal Average Wind Speed, 78m - Oct 2012 through Dec Hour of Day NDR: 92.49% Figure 7b Diurnal Average Wind Speeds Oct 2012 Dec 2012 September 27, 2013 Wind Energy Center Page 14

16 Turbulence Intensity [-] Mean Wind Speed [m/s] Mean Wind Speed [m/s] Paxton Diurnal Average Wind Speed, 78m - Jan 2013 through Mar Hour of Day NDR: 92.4% Figure 7c Diurnal Average Wind Speeds Jan 2013 Mar Paxton Diurnal Average Wind Speed, 78m - Apr 2013 through Jun Hour of Day NDR: 76.92% Figure 7d Diurnal Average Wind Speeds Apr 2013 Jun 2013 Turbulence Intensities Paxton Turbulence Intensity, 78m - Jul 2012 through Sep Wind Speed [m/s] NDR: 99.48% Figure 8a Turbulence Intensity Jul 2012 Sep 2012 September 27, 2013 Wind Energy Center Page 1

17 Turbulence Intensity [-] Paxton Turbulence Intensity, 78m - Oct 2012 through Dec Wind Speed [m/s] NDR: 92.49% Figure 8b Turbulence Intensity Oct 2012 Dec 2012 Turbulence Intensity [-] Paxton Turbulence Intensity, 78m - Jan 2013 through Mar Wind Speed [m/s] NDR: 92.4% Figure 8c Turbulence Intensity Jan 2013 Mar 2013 Turbulence Intensity [-] Paxton Turbulence Intensity, 78m - Apr 2013 through Jun Wind Speed [m/s] NDR: 76.92% Figure 8d Turbulence Intensity Apr 2013 Jun 2013 September 27, 2013 Wind Energy Center Page 16

18 Wind Roses Percent Time [%] Mean Wind Speed [m/s] NDR: 76.78% Figure 9a Wind Rose Jul 2012 Sep 2012 September 27, 2013 Wind Energy Center Page 17

19 Percent Time [%] Mean Wind Speed [m/s] NDR: 8.91% Figure 9b Wind Rose Oct 2012 Dec 2012 September 27, 2013 Wind Energy Center Page 18

20 Percent Time [%] Mean Wind Speed [m/s] NDR: 89.27% Figure 9c Wind Rose Jan 2013 Mar 2013 September 27, 2013 Wind Energy Center Page 19

21 Percent Time [%] Mean Wind Speed [m/s] NDR: 77.04% Figure 9d Wind Rose Apr 2013 Jun 2013 September 27, 2013 Wind Energy Center Page 20

22 Mean Wind Speed [m/s] Annual Average Wind Speed Paxton Annual Average Wind Speed, 78 m through Fiscal Year Figure Annual Average Wind Speed Significant Meteorological Events There was a high wind event on October 30 th, 2012 which had maximum wind gusts in excess of 3 m/s. SECTION - Data Collection and Maintenance On September 3 rd, 2012 it was noted that the channel 7 wind vane boom was pivoting in the wind. This resulted in invalid wind direction data from the channel 7 wind vane. On November th, 2012 a broken Riso P246a anemometer was replaced by a new Riso P246a anemometer. The channel 7 wind vane was rotated 90 degrees to the correct position. However the repositioning of the vane did not keep the boom from moving so the wind vane data was invalid for the entire monitoring period. On April 11 th, 2013 the data logger was replaced. The failing data logger resulted in some data loss prior to the logger replacement. SECTION 6- Data Recovery and Validation All raw wind data are subjected to a series of tests and filters to weed out data that are faulty or corrupted. Definitions of these quality assurance (QA) controls are given below under Test Definitions and Sensor Statistics. These control filters were designed to automate the quality control process and used many of the previous hand-worked data sets made at UMass to affect a suitable emulation. The gross percentage of data September 27, 2013 Wind Energy Center Page 21

23 recovered (ratio of the number of raw data points received to data points expected) and net percentage (ratio of raw data points which passed all QA control tests to data points expected) are shown below. Gross Data Recovered [%] 6.1 Net Data Recovered [%] Test Definitions All raw data were subjected to a series of validation tests, as described below. The sensors tested and the parameters specific to each sensor are given in the Sensor Performance Report which is included in APPENDIX A. Data which were flagged as invalid were not included in the statistics presented in this report. MinMax Test: All sensors are expected to report data values within a range specified by the sensor and logger manufacturers. If a value falls outside this range, it is flagged as invalid. A data value from the sensor listed in Test Field 1 (TF1) is flagged if it is less than Factor 1 (F1) or greater than Factor 2. This test has been applied to the following sensors (as applicable): wind speed, wind speed standard deviation, wind direction, temperature, and solar insolation. F1 > TF1 > F2 MinMaxT Test: This is a MinMax test for wind direction standard deviation with different ranges applied for high and low wind speeds. A wind direction standard deviation data value (TF1) is flagged either if it is less than Factor 1, if the wind speed (TF2) is less than Factor 4 and the wind direction standard deviation is greater than Factor 2, or if the wind speed is greater than or equal to Factor 4 and the wind direction standard deviation is greater than Factor 3. (TF1 < F1) or (TF2 < F4 and TF1 > F2) or (TF2 F4 and TF1 > F3) Icing Test: An icing event occurs when ice collects on a sensor and degrades its performance. Icing events are characterized by the simultaneous measurements of nearzero standard deviation of wind direction, non-zero wind speed, and near- or belowfreezing temperatures. Wind speed, wind speed standard deviation, wind direction, and wind direction standard deviation data values are flagged if the wind direction standard deviation (CF1) is less than or equal to Factor 1 (F1), the wind speed (TF1) is greater than Factor 2 (F2), and the temperature (CF2) is less than Factor 3 (F3). To exit an icing event, the wind direction standard deviation must be greater than Factor 4. September 27, 2013 Wind Energy Center Page 22

24 CF1 F1 and TF1 > F2 and CF2 < F3 CompareSensors Test: Where primary and redundant sensors are used, it is possible to determine when one of the sensors is not performing properly. For anemometers, poor performance is characterized by low data values. Therefore, if one sensor of the pair reports values significantly below the other, the low values are flagged. At low wind speeds (Test Fields 1 and 2 less than or equal to Factor 3) wind speed data are flagged if the absolute difference between the two wind speeds is greater than Factor 1. At high wind speeds (Test Fields 1 or 2 greater than Factor 3) wind speed data are flagged if the absolute value of the ratio of the two wind speeds is greater is greater than Factor 2. [ TF1 F3 and TF2 F3 and abs(tf1 - TF2) > F1 ] or [ (TF1 > F3 or TF2 > F3) and (abs(1 - TF1 / TF2) > F2 or abs(1 - TF2 / TF1) > F2) ] Sensor Statistics A summary of the results of the data collection and filtering are given in the Sensor Performance Report which is included in APPENDIX A. The following categories of information, tabulated for each sensor, are included in that report. Expected Data Points: the total number of sample intervals between the start and end dates (inclusive). Actual Data Points: the total number of data points recorded between the start and end dates. % Data Recovered: the ratio of actual and expected data points (this is the gross data recovered percentage). Hours Out of Range: total number of hours for which data were flagged according to MinMax and MinMaxT tests. These tests flag data which fall outside of an expected range. Hours of Icing: total number of hours for which data were flagged according to Icing tests. This test uses the standard deviation of wind direction, air temperature, and wind speed to determine when sensor icing has occurred. Hours of Fault: total number of hours for which data were flagged according to CompareSensors tests. These tests compare two sensors (e.g. primary and redundant anemometers installed at the same height) and flag data points where one sensor differs significantly from the other. % Data Good: the filter results are subtracted from the gross data recovery percentage to yield the net data recovered percentage. September 27, 2013 Wind Energy Center Page 23

25 APPENDIX A - Sensor Performance Report Test Definitions Test Order Test Field1 Batt ch9>v_val Batt ch9>v_sd Etmp ch>t_val Vane77b ch8>wd_val Vane77b ch8>wd_sd Vane77a ch7>wd_val Vane77a ch7>wd_sd Anem78a ch1>ws_val Anem78a ch1>ws_sd Riso77a ch4>ws_val Riso77a ch4>ws_sd Test Field2 Test Field3 Calc Field1 Calc Field2 Calc Field3 Test Factor 1 Factor 2 Factor 3 MinMax MinMax MinMax MinMax MinMax MinMax MinMax MinMax MinMax MinMax MinMax Factor 4 Sensor Statistics Expected Data Points Actual Data Points % Data Recovered Hours Out of Range Hours of Icing Hours of Fault %Data Good Battery ch Temp ch Vane77b ch Vane77a ch Anem78a ch Anem77a ch Total September 27, 2013 Wind Energy Center Page 24

26 APPENDIX B- Plot Data Wind Speed Distribution Data Percent Time [%] Bin Center [m/s] Q1 Q2 Q3 Q September 27, 2013 Wind Energy Center Page 2

27 Monthly Average Wind Speed Data Wind Speed at 118 m min Average Month [m/s] 12-Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun September 27, 2013 Wind Energy Center Page 26

28 Hour of Day Diurnal Average Wind Speed Data Q1 Q2 Q3 Q4 Mean Wind Speed Mean Wind Speed Mean Wind Speed Mean Wind Speed [m/s] [m/s] [m/s] [m/s] September 27, 2013 Wind Energy Center Page 27

29 Direction Sector [deg] Percent Time [%] Wind Rose Data Q1 Q2 Q3 Q4 Mean Wind Speed [m/s] Percent Time [%] Mean Wind Speed [m/s] Percent Time [%] Mean Wind Speed [m/s] Percent Time [%] Mean Wind Speed [m/s] September 27, 2013 Wind Energy Center Page 28