Bornish Wind Power Project Shadow Flicker Assessment

GENIVAR #103, 2710 – 3 Ave. NE Calgary, Alberta, Canada T2A 2L5 Phone: (403) 248-9463 Fax: (403) 250-7811 www.genivar.com www.windserver.ca Bornish ...
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GENIVAR #103, 2710 – 3 Ave. NE Calgary, Alberta, Canada T2A 2L5

Phone: (403) 248-9463 Fax: (403) 250-7811 www.genivar.com www.windserver.ca

Bornish Wind Power Project Shadow Flicker Assessment Procedures and Calculation Results

Prepared by: GENIVAR Submitted to: NextEra Energy Canada ULC October 7, 2009

Bornish Wind Power Project Shadow Flicker Assessment

DISCLAIMER The following report was generated for NextEra Energy Canada ULC with the purpose of assessing and documenting the shadow flicker at the Bornish Wind Power Project. The distribution, modification or publication of this report is only permitted with the written agreement from GENIVAR. While this document is believed to contain correct information, neither GENIVAR nor any of its employees makes any warranty, either expressed or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any results or any information disclosed. The interpretation of this and any other data or report related to this project is solely the responsibility of the client.

APPROVALS

Written by: Breanne Gellatly

Date: October 7, 2009

Reviewed by: Mathew Breakey

Date: October 7, 2009

DOCUMENT INFORMATION Client:

NextEra Energy Canada ULC

Issue Date:

October 7, 2009

Document Version:

01

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Table of Contents Executive Summary .............................................................................................................1 Objective ..............................................................................................................................2 Overview of Shadow Flicker ...............................................................................................2 Shadow Flicker Algorithm & Assumptions .........................................................................3 Conclusions & Recommendations .......................................................................................5 Appendix 1: WindPRO Algorithm ....................................................................................10 Introduction to SHADOW ..................................................................................................................10 The SHADOW calculation method ....................................................................................................11 The SHADOW calculation model ......................................................................................................12

Appendix 2: WindPRO Results for the Bornish Wind Power Project...............................14

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EXECUTIVE SUMMARY The Bornish Wind Power Project is located in southern Ontario. The purpose of this analysis was to quantify the impact of shadow flicker in terms of modelled shadow hours per year and minutes per day. The SHADOW module of WindPRO was used to model ‘worst-case’ and ‘real-case’ shadow flicker at 94 receptors (17 participating receptors and 77 non-participating receptors) located within the proposed 75 mega-watt wind farm. The layout considered in the calculation consisted of 50 GE 1.5xle wind turbines and 3 turbines at alternate locations. In both cases receptors were modelled using the green house mode. This assumes that the receptor does not face any particular direction, but instead faces all directions. Additional conservatism was taken by excluding any possible sheltering from nearby vegetation. Modelling is based on terrain data, turbine specifications, location of the sun and on-site meteorological data. Worst-case shadow flicker assumes maximum bright sunshine hours according to geographical location and operation hours; whereas, real-case shadow flicker incorporates Canadian Climate Normals1 and on-site meteorological data into the model. Non-participating receptors experiencing the most shadow flicker are mentioned below: -

The worst-case maximum shadow flicker (minutes per day) is 30 minutes at R76. The real-case maximum shadow flicker (hours per year) is 8.18 hours at receptor R27. The worst-case maximum shadow flicker (hours per year) is 33.98 hours at receptor R76.

In the event that shadow flicker is a concern, placing shutters on windows, planting trees and turbine curtailment for specific wind directions and time of day are all effective mitigation techniques. As the level of annoyance caused by flickering is dependent on time of day and time spent near effected windows, additional information from the affected residents with respect to their level of concern may help to quantify the impact of the results.

1

Agriculture and Agri-Food Canada, A National Ecological Framework for Canada Canadian Ecodistrict Climate Normals 19611990, 8 December 1999, (23 October 2008).

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OBJECTIVE The purpose of this report is to quantify the impact of shadow flicker in terms of modelled shadow hours per year and minutes per day for the Bornish Wind Power Project. This report presents the algorithm, assumptions and results of the shadow flicker calculation at the Bornish Wind Power Project.

OVERVIEW OF SHADOW FLICKER Wind turbines cast a shadow of their rotating blades during periods of bright sunshine. If these shadows are cast on the windows of nearby dwellings, residents may experience a strobe or shadow flicker effect inside the house. Shadow flicker can be calculated using the worst-case scenario or the real-case scenario. The worst-case or ‘astronomical maximum’ shadow considers only relative geographical location between turbines and receptors, assuming the sun is shining during all possible daylight hours. The real-case or ‘meteorologically probable’ shadow uses on-site wind data and expected sunshine probability statistics to account for turbine availability as well as variation in sunlight based on cloud cover and wind directions. The actual amount of shadow flicker measured inside the receptor requires a direct line-of-sight between a window and a turbine. Obstructions and orientation of the turbine and window may result in reduced actual shadow flicker at a receptor. In the event that shadow flicker is a concern, placing shutters on windows, planting trees and turbine curtailment for specific wind directions and time of day are all effective mitigation techniques. There are no proven health impacts caused by shadow flicker; however, a study in Sweden has shown that the flickering effect is annoying to residents, particularly during summer evenings2. Most Canadian jurisdictions do not have established shadow flicker regulations; however, international standards have been followed to produce a best practice facility design. Denmark recommends a maximum real-case shadow flicker of 10 hours per year3 and German guidelines specify a limit of 30 hours per year of worst-case shadow flicker. The County of Bruce in Ontario has followed the German guidelines and limits shadow flicker to 30 hours per year and 30 minutes per day (worst-case) at non-participating receptors4.

2

Wind Power Environmental Impact of Wind Power Station Siting, (VINDKRAFTENS MILJÖPÅVERKAN FALLSTUDIE AV VINDKRAFTVERK I BOENDEMILJÖ), A. Widing et al, Centrum för Vindkraftsinformation Institutionen för naturvetenskap och teknik, Gotland University, Sweden, 2004. 3

Emmanuel et al. Spatial Planning of Wind Turbines, European Action of Renewable Energies. Retrieved March 24, 2009 from www.cler.org/info/IMG/pdf/WP8_ANG_guide.pdf.

4

County of Bruce (2008). Planning & Economic Development Department. Retrieved on March 24, 2009 from http://www.brucecounty.on.ca/downloads/planning/2008-Wind-Farm-Submission-Requirements.pdf.

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SHADOW FLICKER ALGORITHM & ASSUMPTIONS The WindPRO SHADOW module was used to model the shadow flicker at the Bornish Wind Power Project. The SHADOW module calculates how often and in what interval each receptor could be affected by the shadow of nearby turbines. A distance of 2000 metres and a minimum angle of 3º above the horizon were used for calculating the visible range of shadow flicker caused by the turbines. The modelling software executes a site specific simulation of the solar trajectory relative to the wind project for an entire year. The complete description and shadow flicker calculation algorithm of WindPRO is provided in Appendix 1: WindPRO Algorithm. Both modelling scenarios assume that houses within the project have windows oriented in every direction and are susceptible to flicker effect from every direction. This is known as the “green house mode,” and represents a conservative estimate of the impact of shadow flicker. Further conservatism was taken by not including sheltering from nearby vegetation, which could screen some potential flicker. Topography was included in the modelling; however, elevation changes smaller than the resolution of the contour data may not have been captured. The calculation of real-case shadow flicker incorporated probability of sunshine (% of daylight hours with expected sunshine) as reported by Environment Canada1 and on-site meteorological tower data into the modelling. The monthly probability of sunshine used in the modelling is presented in Table 1. On-site wind data were measured for nearly two years at Site 9008. These wind data were provided to GENIVAR in raw wind data files and did not undergo any internal quality control as this was outside the scope of this analysis. Wind speed data were averaged for the 50-metre and the 40metre monitoring heights since there were redundant anemometers. Detailed shear binning was not available to extrapolate the 50-metre dataset; however, since record-by-record wind speed data were available at the 50-metre and the 40-metre heights, the 50-metre wind speed data was extrapolated using the power law on a record-by-record basis. A record-by-record shear value was calculated rather than a constant shear since shear values vary with time of day, season and wind direction. Wind speed data from Site 9008 were loaded into WindPRO to predict operational hours. As a conservative measure, the WindPRO calculation does not account for turbine down time due to maintenance and other atypical circumstances that may curtail turbine production. The GE 1.5xle turbine has a rotor diameter of 82.5 metres and hub height of 80 metres (the power curve used was at an air density of 1.24 kg/m3 for normal turbulence intensity5).

5

Technical details were contained in the document 01.1 1.5XLE Technical Description and Data r0.pdf. and 05.2 XLE Calculated Power Curve r5.pdf.

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Table 1: Probabilities of Bright Sunshine for the Bornish Wind Power Project Month Probability January 28% February 34% March 35% April 45% May 53% June 58% July 62% August 58% September 48% October 42% November 28% December 22%

The yaw system of the wind turbine changes the orientation of the rotor according to the wind direction, thus the shadow of the rotating blades changes according to the wind direction. The wind rose representing the wind direction distribution at the Bornish Wind Power Project is presented in Figure 1. It was assumed that the wind directions from the 50-metre monitoring height were representative of hub height conditions of the entire project.

Figure 1: Wind Direction Distributions (frequency %) at Site 9008 (August 26, 2007 to June 2, 2009) GENIVAR

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CONCLUSIONS & RECOMMENDATIONS The Bornish Wind Power Project consisted of 94 receptors and 53 GE 1.5xle wind turbines. Worstcase and real-case shadow flicker results for each receptor are presented in Table 2. Time is presented in decimal hours (e.g. 2.5 = 2 hours 30 min). Figure 2 shows the real-case shadow hours per year as a contour line and identifies the maximum shadow flicker minutes per day at each nonparticipating receptor. Non-participating receptors experiencing the most shadow flicker are mentioned below: -

The worst-case maximum shadow flicker (minutes per day) is 30 minutes at R76. The real-case maximum shadow flicker (hours per year) is 8.18 hours at receptor R27. The worst-case maximum shadow flicker (hours per year) is 33.98 hours at receptor R76.

Potential mitigations techniques to reduce shadow flicker exposure include placing shutters on windows and strategic placement of vegetation

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Figure 2: Shadow Flicker Contour Map – Bornish Wind Power Project

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Table 2: Shadow Flicker Results for the Bornish Wind Power Project

Receptor

UTM Zone 17 NAD 83 Easting Northing

R1 R2 R3 R4 R5 R6 R7 R8 R9 R10 R11 R15 R16 R17 R18 R19 R20 R21 R22 R23 R24 R25 R26 R27 R28 R29 R30 R33 R34 R41 R42 R43 R44 R45 R46 GENIVAR

447,615 447,074 446,563 446,511 445,664 444,493 444,543 444,496 444,124 442,089 441,521 438,086 437,989 437,496 437,435 439,351 439,421 439,911 440,538 440,666 440,782 441,091 447,191 447,320 447,456 447,683 447,805 444,909 444,657 436,989 437,210 437,540 438,244 438,688 438,788

4,773,387 4,773,519 4,773,650 4,773,750 4,773,957 4,773,978 4,774,133 4,774,220 4,774,335 4,774,807 4,774,943 4,775,744 4,775,657 4,775,876 4,775,794 4,777,038 4,777,027 4,776,901 4,776,745 4,776,840 4,776,706 4,776,727 4,771,732 4,771,865 4,771,732 4,771,839 4,771,673 4,772,422 4,772,426 4,774,194 4,772,352 4,772,183 4,771,973 4,772,081 4,771,895

Worst-Case

Elevation (m)

Real-Case

days/year mins/day hours/year hours/year

241 238 235 232 226 222 222 222 220 212 212 210 211 212 213 201 203 204 203 201 201 205 230 231 232 232 232 244 242 240 246 246 241 241 236

60 0 0 0 0 106 70 79 71 42 138 9 32 26 52 0 0 0 0 0 0 0 26 90 62 110 79 177 200 161 35 0 0 9 0 7

11 0 0 0 0 16 9 9 13 16 16 5 10 5 9 0 0 0 0 0 0 0 17 23 15 16 13 14 16 25 4 0 0 2 0

6.98 0.00 0.00 0.00 0.00 13.85 5.35 7.40 9.72 6.87 17.92 0.52 3.63 2.05 5.80 0.00 0.00 0.00 0.00 0.00 0.00 0.00 5.10 25.23 10.43 15.78 7.77 19.13 25.88 29.28 1.58 0.00 0.00 0.30 0.00

0.93 0.00 0.00 0.00 0.00 2.13 0.93 1.13 1.72 1.12 5.17 0.12 0.52 0.27 0.83 0.00 0.00 0.00 0.00 0.00 0.00 0.00 1.15 8.18 3.32 5.18 2.58 4.38 6.25 5.75 0.48 0.00 0.00 0.08 0.00 October 7, 2009

Bornish Wind Power Project Shadow Flicker Assessment

Receptor

UTM Zone 17 NAD 83 Easting Northing

R47 R48 R49 R50 R51 R52 R53 R54 R55 R56 R57 R59 R60 R61 R62 R63 R64 R66 R67 R69 R71 R72 R73 R74 R75 R76 R77 R79 R80 R81 R82 R83 R84 R85 R86 R87 GENIVAR

439,071 439,307 439,363 439,422 439,532 439,562 439,361 439,966 440,033 440,418 440,492 441,150 441,310 441,490 441,977 442,335 442,469 445,577 445,950 441,576 444,977 444,945 445,193 445,068 445,333 444,972 444,918 444,425 444,442 444,358 446,627 439,354 439,462 439,466 439,458 439,445

4,771,955 4,771,775 4,771,853 4,771,758 4,771,702 4,771,796 4,771,770 4,771,712 4,771,602 4,771,606 4,771,514 4,771,457 4,771,389 4,771,253 4,771,297 4,771,021 4,770,950 4,770,404 4,770,504 4,776,282 4,773,035 4,773,179 4,773,159 4,773,388 4,773,628 4,771,983 4,771,559 4,770,964 4,770,061 4,770,042 4,770,918 4,765,081 4,765,855 4,766,106 4,766,286 4,764,425

Worst-Case

Elevation (m)

Real-Case

days/year mins/day hours/year hours/year

242 237 236 233 237 237 236 241 241 246 246 245 246 242 243 238 238 240 240 205 236 235 236 231 230 248 244 239 239 238 236 232 231 229 228 234

12 20 20 25 39 29 22 25 0 12 21 23 33 25 72 33 38 0 0 69 95 69 80 99 17 184 134 87 0 0 0 0 0 0 0 0 8

6 10 11 12 13 14 11 4 0 3 3 4 5 8 13 16 20 0 0 14 16 15 22 18 5 30 28 20 0 0 0 0 0 0 0 0

0.83 2.13 2.45 3.37 5.75 4.62 2.53 1.40 0.00 0.47 0.88 1.10 2.12 1.85 9.42 4.70 6.87 0.00 0.00 10.00 10.13 8.03 13.48 14.78 0.90 33.98 29.17 12.45 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

0.22 0.63 0.72 1.02 1.80 1.40 0.75 0.45 0.00 0.13 0.28 0.32 0.63 0.55 2.87 1.10 1.75 0.00 0.00 1.35 2.05 1.60 2.37 2.45 0.17 7.68 7.43 3.48 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 October 7, 2009

Bornish Wind Power Project Shadow Flicker Assessment

Receptor

UTM Zone 17 NAD 83 Easting Northing

R88 438,920 4,764,270 R89 438,791 4,764,389 R91 439,771 4,764,338 R92 440,054 4,764,339 R93 440,171 4,764,358 R99 440,684 4,771,333 Participating Receptors R12 440,556 4,775,164 R13 439,974 4,775,313 R14 438,543 4,775,543 R31 446,689 4,772,024 R32 446,141 4,772,012 R35 443,326 4,772,729 R36 443,253 4,772,892 R37 442,080 4,773,157 R38 441,208 4,773,238 R39 440,110 4,773,577 R40 439,608 4,773,718 R58 440,754 4,771,654 R65 442,804 4,771,133 R68 441,090 4,774,106 R70 443,131 4,773,964 R78 444,591 4,771,289 R98 441,116 4,773,272

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Worst-Case

Elevation (m)

Real-Case

days/year mins/day hours/year hours/year

237 235 232 230 229 247

0 0 0 0 0 0

0 0 0 0 0 0

0.00 0.00 0.00 0.00 0.00 0.00

0.00 0.00 0.00 0.00 0.00 0.00

212 210 210 237 244 240 236 232 237 236 236 246 244 218 223 242 233

103 153 32 68 86 103 251 261 290 182 246 37 55 162 145 143 301

12 38 12 25 37 25 57 66 36 30 112 7 28 33 70 53 52

11.95 50.12 3.40 19.30 46.25 20.67 92.12 103.97 73.05 49.27 198.47 3.18 15.62 32.98 74.50 71.85 126.87

2.20 13.80 0.82 3.33 6.55 3.73 23.73 28.83 17.38 9.37 58.63 1.02 3.62 6.37 14.78 23.30 30.07

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APPENDIX 1: WINDPRO ALGORITHM The following appendix has been taken from the WindPRO help files. Introduction to SHADOW SHADOW is the WindPRO calculation module that calculates how often and in which intervals a specific area will be affected by shadows generated by one or more wind turbines. These calculations are expected case scenarios (i.e. calculations which are solely based on the probability of sunshine as calculated from the monthly maximum total duration of bright sunshine and the position of the turbine relative to the sun or the astronomical maximum shadow). Shadow flicker impact may occur when the blades of a wind turbine pass through the sun’s rays seen from a specific spot (e.g. a window in an adjacent settlement). If the weather is overcast or calm, or if the wind direction forces the rotor plane of the wind turbine to stand parallel with the line between the sun and the neighbour, the wind turbine will not produce shadow flicker impacts. Apart from calculating the potential shadow flicker impact at a given neighbour, a map rendering the iso-lines of the shadow flicker impact can be printed. This printout will render the amount of shadow flicker impact for any spot within the project area. The time of the day for which shadow flicker impact is critical and the definition of a receptor for which shadow flicker impact is calculated are less rigidly defined by the guidelines and is often something which should be evaluated in each individual case. As an example, a factory or office building would not be affected if all the shadow flicker impact occurred after business hours, whereas it would be more acceptable for private homes to experience shadow flicker impact during working hours, when the family members are at work/school. Finally, the actual amount of shadow flicker impact as a fraction of the calculated potential risk will depend heavily on the geographic location in question. In areas with high rates of overcast weather the problem would obviously decrease, and during potential hours of shadow flicker impact in the summer the wind turbine may often be stationary due to lack of wind. Statistics regarding the wind conditions and number of hours with clear sky can also be taken into account. As in the other WindPRO modules, input of data can be based solely on entering coordinates and characteristics for the individual wind turbine and shadow flicker receptors manually. A significant strength in the WindPRO system is the option of direct graphic on-screen input of wind turbines and receptors on a map.

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The SHADOW calculation method The calculation of the potential shadow flicker impact at a given receptor is carried out simulating the situation. The position of the sun relative to the wind turbine rotor disk and the resulting shadow flicker is calculated in steps of 1 minute throughout a complete year. If the shadow flicker of the rotor disk (which in the calculation is assumed solid) at any time casts a shadow flicker reflection on the window, which has been defined as a receptor object, then this step will be registered as 1 minute of potential shadow flicker impact. The following information is required: -

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The position of the wind turbines (x, y, z coordinates) The hub height and rotor diameter of the wind turbines The position of the receptor object (x, y, z coordinates) The size of the window and its orientation, both directional (relative to south) and tilt (angle of window plane to the horizontal). The geographic position (latitude and longitude) together with time zone and daylight saving time information. A simulation model, which holds information about the earth’s orbit and rotation relative to the sun.

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The SHADOW calculation model In the shadow flicker calculation model used by WindPRO the following parameters defines the shadow flicker propagation angle behind the rotor disk • • •

The diameter of the sun, D: 1,390,000 km The distance to the sun, d: 150,000,000 km Angle of attack: 0.531 degrees

Theoretically, this would lead to shadow flicker impacts in up to 4.8 km behind a 45 m diameter rotor disk. In reality, however, the shadows never reach the theoretical maximum due to the optic conditions of the atmosphere. When the sun gets too low on the horizon and the distance becomes too long the shadow dissipates before it reaches the ground (or the receptor). How far away from the wind turbine the shadow will be visible is not well documented and so far only the German guidelines set up limits for this (see section 4.2.0). The default distance of WindPRO is 2 km. and the default minimum angle is 3 degrees above the horizon. If the German guidelines are used, the maximum distance from each wind turbine can be calculated using the formula Max. distance = (5*w*d) / 1,097,780 where w is the average width of the blade. The value of 1,097,780 is derived from the diameter of the sun, reduced by a compensation factor for the fact that the sun disk is a circle and not a square.

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APPENDIX 2: WINDPRO RESULTS FOR THE BORNISH WIND POWER PROJECT

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