Puhuri Oy Wind Farm Kopsa Uleåborg, Finland

Transcription

1 REPORT A 1 (19) Please refer to Jens Fredriksson Phone jens.fredriksson@afconsult.com Date Order no Puhuri Oy Wind Farm Kopsa Uleåborg, Finland Sound immission measurement Martin Almgren Responsible Puhuri Oy Wind Farm Kopsa Uleåborg, Finland Sound immission measurement ÅF-Infrastructure AB Sound & Vibration Stockholm Checked by Jens Fredriksson Martin Almgren Phone Fax Org.nr VAT nr SE Certified according to SS-EN ISO 9001 and ISO Report A Puhuri Oy Kopsa wind farm - sound immission measurement

2 REPORT A (19) Table of contents 1 BACKGROUND SCOPE OF MEASUREMENT ANALYSIS OF MEASUREMENT Wind speed determination Determination of sound pressure level Measurement results in MP Measurement results in MP Tonal analysis Amplitude modulation and impulsiveness MEASUREMENT UNCERTAINTY CONCLUSION REFERENCES Appendixes Appendix A Appendix B Appendix C Appendix D Overview and photos Measurement site data and conditions Narrow band Spectrums Amplitude modulation and impulsiveness

3 REPORT A (19) Summary Kopsa wind power plant has 7 wind turbines of the type Siemens SWT-3.0 DD-113 with 142,5 m tower height. Sound immission measurements have been performed in two measurement points at a nearby resident, where complaints about the noise have been raised. The equivalent A- weighted sound pressure level has been determined in the two positions. In one position, MP 1, only an upper limit of 37 dba for the noise could be determined. In the second position, MP 2, situated in a position where the traffic noise was less, the background corrected equivalent sound pressure level was measured to dba depending on wind speed. An overview of the measurement positions are given in Appendix A. There are occasionally tonal components present around 80Hz. From the objective tonal analysis, at measurement position MP 2 where it was most predominant, performed in accordance with IEC , it is however not deemed as a pure tone. 1 Background Kopsa wind power plant has 7 wind turbines of the type Siemens SWT-3.0 DD-113 with 142,5 m tower height. ÅF has been asked to measure the noise from the wind farm at a nearby dwelling and especially investigate the audibility of tones. The residents at the dwelling are annoyed by the noise of the wind farm. The sound level indoors will be measured by another consultant. 2 Scope of measurement Sound measurements at the dwelling were performed parallel in two measurement positions, according to Method A according to YMPÄRISTÖHALLINNON OHJEITA Tuulivoimaloiden melutason mittaaminen altistuvassa kohteessa (1) using a sound level meter that continuously logged the noise level. One microphone measurement position was placed on a field under free-field conditions close to the nearby resident. The other position was placed on the façade of a nearby barn, a position where the influence of traffic noise was deemed less. Both microphones were equipped with a primary and a secondary windscreen. An overview map of the positions and photos from the measurement are presented in Appendix A. After the measurement was completed, the data were analyzed with regard to weather conditions, the produced electric power and background noise. Background noise was composed mostly of traffic noise and wind noise from the trees. Occasionally the sound measurement was influenced by irrelevant disturbances, such as gun shots from nearby hunting etc. These occasions were excluded in the analysis. Measurement site data and conditions that are to be recorded according to the method are presented in Appendix B.

4 REPORT A (19) 3 Analysis of measurement The sound has been measured using a microphone in free field, at measurement position MP 1, and a microphone firmly attached to a façade at measurement position MP 2. Sound reflected from the facade creates higher noise levels compared to measuring in free field. According to the measurement standard the measured levels at MP 2 have been converted to free field values by subtracting the noise levels with 6 db. The sound has also been corrected for the use of a secondary shelter. The correction is 0 db for frequencies up to 315 Hz, and it is greatest, +5 db at 20,000 Hz. All measurement data are based on a measurement time of 1 minute. The wind direction is registered by the hub anemometer and wind speed is always given for 10 m height. The total sound levels, L Aeq,free, (measured with all turbines running) and the background sound levels, L s, (measured with all turbines turned off) have been correlated towards the wind speed at 10 m height measured with the met mast close to the measurement positions MP 1 and MP 2. The average background level at different wind speeds has been estimated with a linear regression line. Total sound levels at different wind speeds, L Aeq,free, are then corrected for the average background noise, for the same wind speed, calculated through the linear regression, to achieve the sound pressure levels caused by the turbines, L Aeq,corr. All the background corrected sound pressure levels, L Aeq,corr, are then plotted against the wind speed at the turbine. Wind speed at turbine are calculated through the average produced power and transformed to 10 m height under the assumption of a logarithmic wind profile and reference roughness length 0,05 m (this is a deviation from the method, for more information see chapter 3.1). The background corrected levels are then approximated by a linear regression from which the equivalent A-weighted sound pressure level is calculated. 3.1 Wind speed determination The wind speed, that the total sound levels L Aeq,free and the background sound levels L s, are correlated towards, are measured at 10 m height close to the measurement points. The wind speed, that the background corrected levels are correlated towards, is mainly determined by the electrical output from the plant and the plant power curve. In the current case, the wind speed is determined from the electric power produced at the nearest wind turbine. The power curve gives the relationship between electrical output and the wind speed at hub height. In this case, the electric power produced converted to wind speed at hub height using the power curve for the current wind model, the intervals produced when electrical power has been lower than 95% of the plant's rated output. This calculated wind speed was corrected for current weather conditions using equation 1 from the standard IEC ed. 2.1 (2). v H = v D ( p 1/3 reft k ) (equation 1) pt ref Where p ref is 101,3 kpa T ref is 288 K v H is the corrected wind speed at hub height (m/s). v D is the wind speed in m/s detected from the diagram showing wind speed as a function of electric power output. When the electric power produced is less than 5% or greater than 95%, it s insufficient to determine the wind speed through the power curve. At these times, the so-called "Nacelle

5 REPORT A (19) anemometer method" is used to determine the wind speed at hub height (see (2) chapter ). For all data points between 5% and 95% of the plant's rated output can be set up a relationship between the wind speed measured at hub height and wind speed at hub height computed by the power curve. The relationship is expressed by a regression line and for data points, where the produced power are outside 5-95 % of rated power, the wind speed measured by the nacelle anemometer is calibrated using this regression line. After that the wind speed at hub height are scaled to the wind speed at 10 m height, V 10, assuming a logarithmic wind profile, see equation 2. All wind speeds quoted in this report are the values at 10 m height. ) v 10 = v h [ ln(10 z 0 ] (equation 2) ln( h z 0 ) Where z 0 is the roughness length of the ground*. h is the hub height of the turbine The wind speed at 10 m height is a reference value which is commonly used in reports for radiation of sound from wind turbines. In the case that the wind speed profile is not logarithmic, this is a theoretical value. *Comment: In this analysis the roughness length is set to reference conditions 0,05 m. The use of the reference roughness length of 0,05 m instead of the actual roughness length of the site is a deviation from the method. The reason for the deviation is to make results correlate with how the suppliers of turbines define the sound power levels at different wind speeds. This makes it easier to make sure that the noise limits are kept, even when the turbines are running at full power (at which they normally produce the highest noise levels). Modern wind turbines usually reach their rated power (and highest noise level) at 6-8 m/s (at 10 m height calculated with logarithmic wind profile and reference roughness length 0,05 m). If instead the actual roughness length of the site is used then the wind speed, for which the turbine reaches its maximum sound level, will be different for different sites which risk causing unnecessary complications. 3.2 Determination of sound pressure level The analysis follows the steps recommended in (1). Values with extraneous sounds were excluded. The figures 1 and 3 below shows the total equivalent noise level, L Aeq,free, in the measurement points with the wind turbines in operation and the background level, L s, with wind turbines on hold. The total noise (with turbines in operation) and the background noise have been related to the wind speed measured at 10 m height close to the measurement points. A linear regression is performed on the background levels and each 1 min sample of total sound pressure level is corrected for background noise from the linear regression. The background corrected levels, L Aeq,corr, are then plotted, see figures 2 and 4, against the wind speed at the nearest turbine, using the wind speed at the turbine.

6 LAeq [dba re 2E-5 Pa] REPORT A (19) Measurement results in MP 1 46 Total sound pressure level and background level Total level (turbines on) - LAeq,free Background level (Turbines off) - Ls y = 0,3774x + 38,627 R² = 0, Wind speed at measurement point (at 10 m height) [m/s] Figure 1. Total sound pressure levels, L Aeq,free, and background levels, L s, from measurement position MP1 are plotted against the measured wind speed from the anemometer on top of the 10 m high met mast positioned close to the measurement position. A linear regression is performed on the background levels. It is noteworthy that the background levels are of the same order of magnitude as the total sound levels. The background noise is therefore dominating the noise in measurement point MP Laeq,corr (< 3dB over background level) y = -0,3195x + 39,298 R² = 0,0117 Background corrected levels Laeq,corr (3-6 db over background level) Wind speed at turbine [m/s] at 10 m height Figure 2. Background corrected sound pressure levels, L Aeq,corr, from measurement position MP1 are plotted against the wind speed at the turbine In measurement point MP 1, see Figure 2 above, the difference between total noise and background level less than 3 db for most measurements. The obtained result is thus an upper limit for wind noise, the exact contribution from the turbines cannot be determined but it is

7 LAeq [dba re 2E-5 Pa] REPORT A (19) lower or equal to the stated values. The equivalent sound pressure levels at different wind speeds are calculated from the regression line in figure 2 and presented in table 1 below. Table 1. Background corrected sound pressure level (L Aeq,corr) at MP 1. Wind speed [m/s] L Aeq,corr [db re 20µPa] (A-weighted) Measurement results in MP 2 The microphone in measurement position MP 2 was placed connected to a wall of a barn. Total sound pressure levels and background levels presented below have been corrected with -6 db, to represent free field values, in accordance with (1). 45 Total sound pressure level and background level Total level (Turbines On) - Laeq,free Background level (Turbines Off) - Ls y = 0,3297x + 31,675 R² = 0, Wind speed at measurement point (at 10 m height) [m/s] Figure 3. Total sound pressure levels, L Aeq,free, and background levels from measurement position MP 2 are plotted against the measured wind speed from the anemometer on top of the 10 m high met mast.

8 LAeq [dba re 2E-5 Pa] REPORT A (19) y = -0,4088x + 36,978 R² = 0,0153 Figure 4. Background corrected sound pressure levels, L Aeq,corr, from measurement position MP 2 are plotted against the wind speed at the turbine In measurement point MP 2, see Figure 2 above, the difference between total noise and background level more than 3 db for most measurements. The equivalent sound pressure levels at different wind speeds are calculated from the regression line in figure 4 and presented in table 2 below. Table 2. Background corrected sound pressure level (L Aeq,corr) at MP 2. Wind speed [m/s] L Aeq,corr [db re 20µPa] (A-weighted) 3.3 Tonal analysis Background corrected levels Laeq,corr (< 3dB over background level) Laeq,corr (3-6 db over background level) Laeq,corr (> 6dB over background level) Wind speed at turbine [m/s] at 10 m height The measurement, especially at Mp2 where the masking noise was lower, showed an increase of energy around 80 Hz. A tonal analysis has therefore been carried out in accordance with the method described in IEC (2), which is the preferred method according to (1). The tonal analysis has been performed on two 1 min samples from MP 2, with low disturbances and where the 80 Hz component is predominant in the corresponding 1 min average spectrum. By 12 investigated periods, of 10s each, 3 periods indicates that there are tonal components present. See Appendix C. The highest tonal audibility dla,k is only -5,7dB which is below the value -3, where further reporting should be carried out according to (2). According ISO :2007, no adjustment K t shall be made due to tonal audibility of this size. 3.4 Amplitude modulation and impulsiveness Figures concerning amplitude modulation and impulsiveness are presented in appendix D. No abnormal amplitude modulation was noted during the measurement or in the analysis of some time intervals. The prominences of the possible noise peaks in the first three diagrams of the instantaneous sound pressure level have been evaluated according to Nordtest NT ACOU 112. For the peak at

9 REPORT A (19) 19:31:02,625, the prominence P is 3,0 and for the peak at 19:31:49,000 is 3,9. The prominence is below 5,0 for both peak, and no adjustment K I shall be made. 4 Measurement uncertainty The result from the measurements is affected by uncertainties which can be derived to uncertainties and variations in the surrounding, weather conditions, measurement duration and the measuring system. There is no method described in (1) for how to calculate the uncertainty of the measurement results, but with a method in (2) the uncertainties have been estimated and are reported in table 3 below. The measuring uncertainties of type A are calculated according to: LAeq, free L U A N 2 Where L, = measured sound pressure level of the total noise, Aeq free L, = corresponding background corrected level. Aeq corr Aeq, corr N = number of measurements for total noise, for each wind speed. The measuring uncertainties of type B are calculated according to: a U B 3 Table 3. Uncertainty analysis 2 (Equation 3) (Equation 4) Typical range Typical standard Used range, U Component ±a [db] uncertainty, U [db] [db] Calibration U B1 ±0,3 0,2 0,2 Chain of acoustic U B2 ±0,3 0,2 0,2 measurement instruments Measuring board U B3 ±0,5 0,3 0,3 Distance U B4 ±0,1 0,1 0,1 Acoustic impedance of air U B5 ±0,2 0,1 0,1 Meteorological variations U B6 ±0,7 0,4 0,4 (including turbulence) Wind speed (derived) U B7 ±0,3 0,2 0,2 Wind direction U B8 ±0,5 0,3 0,3 See formula See formula Background sound U B9 See formula below below below Background sound uncertainty has been determined according to: 2 Ls Ls, est U 9 (Equation 5) B N 2 Where: L s is the background sound pressure level, L s,est is the estimated background sound pressure level from the linear regression at the same wind speed. The systematic uncertainties are combined according to: U B U 2 2 B1 UB2... (Equation 6)

10 REPORT A (19) The combined standard uncertainty is then obtained for all parts according to: U C U 2 A U 2 B (Equation 7) From which the following uncertainties are obtained: For measurement point MP 1 only an upper limit of the noise was determined and it is not possible to calculate the uncertainties. The uncertainty could be expressed as [+0, - ]. For measurement point MP 2 the uncertainty was calculated and presented in table 4 below. Table 4. Standard uncertainty [db] at different wind speeds Standardised wind speed, height 10 m (BIN) [m/s] Standard uncertainty [db] 2,6 3,0 2,8 5 Conclusion Sound immission measurements have been performed in two measurement points at a nearby resident. The equivalent A-weighted sound pressure level has been determined in the two positions presented in the tables below. Background corrected sound pressure level (L Aeq,corr) at MP 1. Wind speed [m/s] L Aeq,corr [db re 20µPa] (A-weighted) Standard [db] [+0, - ] [+0, - ] [+0, - ] uncertainty Background corrected sound pressure level (L Aeq,corr) at MP 2. Wind speed [m/s] L Aeq,corr [db re 20µPa] (A-weighted) Standard [db] 2,6 3,0 2,8 uncertainty An overview of the measurement positions are given in Appendix A. There are occasionally tonal components present around 80Hz. From the tonal analysis performed at measurement position 2, where it was most predominant, in accordance with IEC , it is however not deemed as a tone. No abnormal amplitude modulation or impulsiveness has been found at the measurement occasion.

11 REPORT A (19) 6 References 1. Ministry of Environment. YMPÄRISTÖHALLINNON OHJEITA Tuulivoimaloiden melutason mittaaminen altistuvassa kohteessa. Helsinki : Ministry of Environment, ISBN IEC. IEC Edition 2.1 "Wind turbine generator systems - Part 11: Acoustic noise measurement techniques". Geneve : International Electrtechnical Commission, Ljunggren, Sten. Elforsk rapport 98:24 - Mätning av bullerimmission från vindkraftverk. u.o. : Energimyndigheten, Naturvårdsverket. Mätning och beräkning av ljud från vindkraft. Naturvårdsverket. [Online] den

12 REPORT A (19) Appendix A - Overview and photos Resident MP 1 MP 2 Met mast Wind farm Overview map of resident, sound measurement positions MP 1 and MP 2 and position of the 10 m high met mast that measures metrological data (wind speed, wind direction, air pressure, humidity and temperature at 2 different heights). The direction of the wind farm is marked out with a blue arrow.

13 REPORT A (19) MP 1 Resident Picture of measurement position (MP 1) with the nearby resident visible to the right. Picture of measurement position (MP 2).

14 REPORT A (19) Picture of 10 meter high met mast with nearby resident and measurement position (MP 1) visible in the background.

15 REPORT A (19) Appendix B Measurement site data and conditions INFORMATION ABOUT THE REPORT Measurement report number/identifier: Date of measurement: Time: Author/organization, contact details: Jens Fredriksson, ÅF-Infrastructure AB jens.fredriksson@afconsult.com OFFICERS Measurement personnel: Jens Fredriksson, ÅF-Infrastructure AB Date of approval of report Checked by / approved by: Martin Almgren, ÅF-Infrastructure DEVICES USED FOR MEASUREMENTS Name of manufacturer: Norsonic Gauge type: 140 Meter serial number: AL168 and AL169 (internal serial) Date of the calibration of the apparatus and calibrators: (AL 168) (AL 169) Data on microphone placement disc: - Data on the secondary wind protection: Own construction. Measured sound levels have been corrected for the noise reduction caused by the windscreens. Method and apparatus for determining the wind speed: Campbell logger and wind mast Placing of the anemometer and wind direction gauges: Near dwelling, see appendix A DETAILS OF THE TURBINES Manufacturer: Siemens Type: SWT-3.0 Rated power: 3,0MW DD -113 Hub height: 142,5 m Rotor diameter: 113 Tower type/system: Tube Details of the terrain surrounding the measurement point and the power plant: WIND TURBINE Name, Serial nr., POSITION N,E (WGS 84): Name: KP-WTG-01 Serial nr: N: E: Name: KP-WTG-02 Serial nr: N: E: TYPE OF SOIL Wind Wind turbine 1: turbine 2: Gravel and Gravel and forest forest ground ground Name: KP-WTG-03 Serial nr: N: E: Wind turbine 3: Gravel and forest ground Name: KP-WTG-04 Serial nr: N: E: Wind turbine 4: Gravel and forest ground Name: KP-WTG-05 Serial nr: N: E: Wind turbine 5: Gravel and forest ground Name: KP-WTG-06 Serial nr: N: E: Wind turbine Gravel and forest ground 6: Name: KP-WTG-07 Serial nr: N: E: Wind turbine 7: Gravel and forest ground OPPORTUNITY TO INFLUENCE THE WIND TURBINE NOISE EMISSIONS DURING OPERATION AND POSSIBLE EFFECTS: Blade pitch control: Rotational speed: Other: No No No

16 REPORT A (19) SITE OF MEASUREMENT Position of measurement, N,E (WGS84) Mp1: N , E WGS84 Microphone height: 1,5 m TYPE OF SOIL Type of soil Roughness z0 [m] Share of the area [%] Water, snow, sand 0,0001 Mp1: 0 % Mp2: 0 % Open plain, cut grass 0,01 Mp1: 0 % Mp2: 0 % Cropland with little 0,05 Mp1: 100 % vegetation Mp2: 100 % Residential area with 0,3 Mp1: 0 % dense vegetation Mp2: 0 % TYPES OF NOISE SOURCES OF BACKGROUND NOISE Mp1: Traffic and wind induced noise in vegetation POSITION OF POSSIBLE REFLECTIVE SURFACES Mp1: No reflective surface close to the position. Mp2: N , E WGS84 Microphone height: 2 m Ground surface roughness where the wind speed is measured: 0 % 0 % 100 % 0 % Mp2: Traffic and wind induced noise in vegetation Mp2: Mounted on a barn wall, no other reflective surfaces close to the position. WEATHER DATA Relative humidity: % Temperature: O C Air pressure: 100,8-101,0 kpa Cloud cover x/8: 0-8 (periods with temperature gradient outside the limit has been excluded) Turbulence: - Solstice: - Wind speed and direction: SW-wind Normalized wind speed: 5-8 m/s (average 222 O ) 10m:- m:- m:- m:- m:- m:- m:- m:-

17 REPORT A (19) Appendix C Narrow band Spectrums A tonal analysis has been performed using the method described in IEC (2), which is the preferred method according to (1). The tonal analysis has been performed on two 1-minuite periods from MP 2, with low disturbances and where the 80 Hz component is predominant in the corresponding 1 min average spectrums. The two 1-minuite periods have been split into 12 sapmles of 10s each and analysied in accordance with (2). Narrow band spectrums of the 12 samples are presented below.

18 :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: LpA, db(a) :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: REPORT A (19) Appendix D Amplitude modulation and impulsiveness Instantaneous sound pressure level is shown in the following three diagrams (App-D 1 to App-D 3) with different magnification on the time scale. Sound level at Mp2, uncorrected and T 0.125ms, T=60s Figure App-D 1 Instantaneous sound pressure level, 60 seconds of data. Sound level at Mp2, uncorrected and T 0.125ms, T=30s Figure App-D 2 Instantaneous sound pressure level, 30 seconds of data.

19 :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: :31: LpA, db(a) REPORT A (19) Sound level at Mp2, uncorrected and T 0.125ms, T=10s Figure App-D 3 Instantaneous sound pressure level, 10 seconds of data.

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