HomeMy WebLinkAbout1-BlackOakWind_HMMH_ShadowFlickerRevision_January-24-2012.pdfHARRIS MILLER MILLER & HANSON INC.
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TECHNICAL MEMORANDUM
To: Ms. Marguerite Wells, Black Oak Wind, LLC
From: Phil DeVita, HMMH
Cc: Benjamin Brazell, EDR
Date: January 24, 2014
Subject: Revised Shadow Flicker Study for Black Oak Wind Farm Project
Reference: HMMH Project No. 306590.001
1. INTRODUCTION
This technical memorandum summarizes the results of the revised shadow flicker analysis conducted
for Black Oak Wind, LLC by Harris Miller Miller & Hanson Inc. (HMMH). The shadow flicker
assessment was revised from the original analysis dated March 2013 to account for the proposed new
turbine specifications being evaluated by the developer. The original turbine design in the March
2013 analysis assumed seven REpower 100 turbines with a hub height of 80 meters above ground
level (agl) and a rotor diameter of 100 meters. The developer is now proposing to evaluate seven GE
1.7-100 turbines with a hub height of 96 meters agl and a similar rotor diameter of 100 meters.
The analysis evaluated the potential shadow flicker impact from the seven GE turbines located on
land owned and/or leased by Black Oak Wind Farm, LLC (“developer”). A site map showing the
proposed turbine locations is presented in Figure 1 and remains unchanged from the March 2013
analysis.
The shadow flicker analysis estimates the annual hours per year shadow flickering may occur at a
given receptor using geometry, turbine dimensional data and site specific data and assumptions.
This technical memorandum summarizes the estimated shadow results for the GE turbine in hours per
year for each receptor and compares the results to the original assessment conducted in March of
2013. Additional information including maps showing the extent of the isolines (e.g., hours of
occurrence contours) for the study area and model output are also provided. The turbine locations,
assumptions and methodology are the same as discussed in the March 2013 assessment with any
changes related to the turbine manufacturer and hub height.
2. SHADOW FLICKER OVERVIEW
No changes, see Section 2 of the March 2013 Shadow Flicker Assessment for details.
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3. SHADOW FLICKER ANALYSIS
The only change from the original assessment is Table 1 which is revised as follows:
Table 1 Turbine Specification Data
Turbine GE 1.7-100 REpower mm100 Turbine
Hub Height (m) 96 80
Rotor Diameter (m) 100 100
No other changes to the original shadow flicker analysis. See Section 3 of the March 2013 Shadow
Flicker Assessment for details.
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Insert Figure 1
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4. SHADOW FLICKER RESULTS
Using the inputs and assumptions listed in Section 3 of the March 2013 assessment, HMMH revised
the modeling analysis using the WindPRO software and applying it to the GE 1.7 wind turbine
project. Table 2 presents the summarized expected flicker duration in hours per year for the seven
GE turbines at each receptor location along with the REpower project’s expected flicker duration for
comparison. The net change in hours at each location is also quantified.
Table 2 Estimated Hours of Shadow Flicker at Each Sensitive Receptor Location for GE 1.7
and REpower Turbine Specifications
Receptor Description
GE 1.7-100
Expected Hours
of Shadow Per
Year
REpower mm 100
Expected Hours
of Shadow Per
Year
Net
Change
A States Rd 0:00 0:00 0:00
B Cayutaville Rd west 0:00 0:00 0:00
C County Road 6 South 0:00 0:00 0:00
D County Road Second from South 0:00 0:00 0:00
E County Rd. 6 Third from South 0:00 0:00 0:00
F County Road 6 2nd North 3:32 3:41 -0:09
G County Road 6 Sixth from South 0:00 0:00 0:00
H County Rd 6 3rd North 0:00 0:00 0:00
I County Rd 6 4th North 1:27 1:42 -0:15
J County Route 6 5th north 1:06 1:17 -0:11
K County Rd. 6 6th North 1:01 1:10 -0:09
L Chapman Rd. 1:08 1:13 -0:05
M Chapman Road 4th from bottom 0:00 0:00 0:00
N Chapman Road #2 0:00 0:00 0:00
O Chapman Road #3 0:57 1:06 -0:09
P Buck Hill furthest west 1:05 1:11 -0:06
Q Buck Hill Road North 0:00 0:00 0:00
R County Rd 183 furthest west 0:00 0:00 0:00
S County Road 183 2nd west 0:00 0:00 0:00
T County Rd 183 3rd from west 0:00 0:00 0:00
U Chapman Road 6A from left 0:00 0:00 0:00
V County Rd 183 4th from west 0:00 0:00 0:00
W County Road 183 5th from west 5:29 4:49 +0:40
X County Rd 183 6th from west 0:00 0:00 0:00
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Receptor Description
GE 1.7-100
Expected Hours
of Shadow Per
Year
REpower mm 100
Expected Hours
of Shadow Per
Year
Net
Change
Y County Road 183 7th from west 6:01 3:29 +2:32
Z County Road 183 furthest east 0:00 0:00 0:00
AA Black Oak Rd furthest north 13:42 14:08 -0:26
AB Chapman Road 2nd from Top 17:16 6:28 +10:48
AC Black Oak Rd. 2nd from north 4:59 0:00 +4:59
AD Black Oak Rd. 3rd from north 16:08 25:57 -9:49
AE Black Oak Rd. 4th from north 0:00 0:00 0:00
AF Black Oak Rd. 6th from top 13:30 14:58 -1:28
AG Black Oak Rd. 5th from north 9:13 7:39 +1:44
AH Connecticut Hill West 14:04 0:00 +14:04
AI Connecticut Hill 2nd from West 13:40 10:26 +3:14
AJ Connecticut Hill West 3rd from West 16:33 15:44 +0:49
AK Connecticut Hill 4th from West 0:00 0:00 0:00
AL Connecticut Hill seventh from left 6:47 6:04 +0:43
AM Connecticut Hill Rd 5th from West 6:08 1:16 +4:52
AN Connecticut Hill Rd. 6th From West 5:50 4:06 +1:44
AO Connecticut Hill Rd. 4th From east 10:32 10:13 +0:19
AP Connecticut Hill Rd. 3rd From East 11:07 11:03 +0:04
AQ Connecticut Hill and Rumsey Rd 6:39 7:03 -0:24
AR Connecticut Hill and Rumsey Rd. 0:00 0:00 0:00
AS Connecticut Hill 2nd Furthest East 10:56 13:02 -2:06
AT Connecticut Hill Furthest East 6:21 7:25 -1:04
AU Griffin Rd. at Right Corner 0:00 0:00 0:00
AV Griffin Rd. 14th East 0:00 0:00 0:00
AW Griffin Rd. 13th East 0:00 0:00 0:00
AX Griffin Rd. 13th East 0:00 0:00 0:00
AY Griffin Rd. 12th East 0:00 0:00 0:00
AZ Griffin Rd. 10th East 0:00 0:00 0:00
BA Griffin Rd. 8A 0:00 0:00 0:00
BB Griffin Rd. 7th East 0:00 0:00 0:00
BC Griffin Rd. 6th East 2:40 2:20 +0:20
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Receptor Description
GE 1.7-100
Expected Hours
of Shadow Per
Year
REpower mm 100
Expected Hours
of Shadow Per
Year
Net
Change
BD Griffin Rd. 5th East 0:00 0:00 0:00
BE Griffin Road 4A 0:00 0:00 0:00
BF Griffin Rd. 4th East 7:19 3:43 +3:36
BG Griffin Rd. 3rd East 0:00 0:00 0:00
BH Griffin Rd. near Black Oak Rd. 0:00 0:00 0:00
BI Black Oak Rd. 7th from north 19:51 19:08 +0:43
BJ Black Oak Rd. 8th from top 14:48 16:46 -1:58
BK Black Oak Rd. 10th from top 0:00 0:00 0:00
BL Black Oak 9th from north 16:21 3:36 +12:45
BM Black Oak Rd. 11th from north 0:00 0:00 0:00
BN Black Oak Rd. 12th from top 0:00 0:00 0:00
BO Black Oak 13th from north 0:00 0:00 0:00
BP Black Oak Rd. 14th from top 0:00 0:00 0:00
BQ Black Oak Rd at Griffin 7:31 6:50 +0:41
BR Black Oak South of Griffin 0:00 0:00 0:00
BS Black Oak 2A south of Griffin 0:00 0:00 0:00
BT Black Oak Rd. 4th from south 0:00 0:00 0:00
BU Black Oak 2nd from south 0:00 0:00 0:00
BV Cayutaville Rd. 2nd from Black Oak 0:00 0:00 0:00
BW Black Oak Rd. Furthest south 0:00 0:00 0:00
BX Cayutaville Rd. furthest west 0:00 0:00 0:00
BY Tower Rd furthest south 0:00 0:00 0:00
BZ Cayutaville Rd. East 0:00 0:00 0:00
CA State Park furthest north 0:00 0:00 0:00
CB State Park furthest south 0:00 0:00 0:00
CC Tower Rd. 2nd to south 0:00 0:00 0:00
CD Tower Rd. south 0:00 0:00 0:00
Figure 2 depicts the modeling results of the GE turbine design by overlaying the isolines (i.e. total
number of hours per year contour) onto the basemap. This map shows the extent of the shadow
flicker impact from the Project for the seven GE turbines. The figure shows that shadow flicker
decreases in extent (i.e. number of hours of occurrence) as the distance from the turbine increases.
For comparison, Figure 3 presents the expected increases and decreases, or nominal net change of
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shadow flicker, with the proposed GE turbine compared to the REpower 100 shadow flicker results.
These changes are also quantitatively denoted in Table 2 by receptor location. The WindPro
modeling output is contained in Appendix A while the shadow flicker calendar of flicker and
graphical output is presented in Appendix B and Appendix C, respectively.
5. CONCLUSION AND HEALTH EFFECTS
The revised study results indicate relatively low shadow/flicker effects are still expected to a majority
of receptor locations in the project vicinity. There are some locations where expected flicker duration
could increase or decrease with the GE turbine design compared to the REpower turbine design;
however, there are no locations where the total hours per year are estimated to be greater than 30
hours. The location expected to receive the highest impact from the GE turbine design is at receptor
BI on Black Oak Road 7th from the North (19:51 hours) and receptor AB at Chapman Road 2nd from
the top (17:16 hours). The majority of shadow flicker at receptor BI is expected to occur from
Turbine 5 and Turbine 6 in the morning during the late fall and winter months (Oct thru Mar). There
are some incidences when shadow flicker could also occur from Turbine 4 at receptor BI in March
and Sept-Oct during the late afternoon hours. Turbine 5 and Turbine 6 is approximately 1,286 feet
and 2,749 feet, respectively to the southeast of BI and Turbine 4 is approximately 3,379 feet to the
west of the BI receptor location.
For receptor AB, shadow flicker is predicted to occur from Turbine 3 during the early morning hours
in late spring (April thru May) and late summer (July thru Aug). There also some incidences where
shadow flicker could also be expected in the afternoon from Turbine 2 during spring (Mar thru April)
and September. Turbine 3 is located approximately 1,962 feet to the east-northeast of AB and
Turbine 2 is located 1,670 feet to the west of AB.
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Insert Figure 2
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Insert Figure 3
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Shadow flicker impacts of greater than 10 hours were also estimated for the GE turbine at the
following locations (the March 2013 shadow flicker results are denoted in parenthesis):
• Receptor AA (Black Oak Road furthest north) total of 13:42 (14:08) hours;
• Receptor AD (Black Oak Road 3rd from the top) total of 16:08 (25:57) hours
• Receptor AF (Black Oak Road 6th from the top) total of 13:30 (14:58) hours;
• Receptor AH (Connecticut Hill West) total of 14:04 (0:00) hours
• Receptor AI (Connecticut Hill Road Second From the west) total of 13:40 (10:26) hours;
• Receptor AJ (Connecticut Hill Road 3rd from west) total of 16:33 (15:44) hours.
• Receptor AO (Connecticut Hill Road 4th from east) total 10:32 (10:13) hours;
• Receptor AP (Connecticut Hill Road 3rd from east) total 11:07 (11:03) hours;
• Receptor AS (Connecticut Hill Second furthest east) total of 10:56 (13:02) hours;
• Receptor BJ (Black Oak Road 8th from top) total of 14:48 (16:46) hours; and
• Receptor BL (Black Oak Road 9th from the North) total of 16:21 (3:36) hours
All the remaining receptor locations modeled in the analysis are estimated to have less than 10 hours
of shadow flicker impact, and many are still estimated to have zero hours of impact. As shown in
Table 2, there are some receptor locations where shadow flicker hours were estimated to either
increase or decrease with the new GE turbine design; however the maximum worst case predicted
shadow flicker hours are predicted to decrease from 25:57 to 19:51 hours, which is roughly a 24
percent reduction. These changes are due to the increase in hub height which affects the intersection
of the sun, turbine and receptor which is different for the GE turbine compared to the REpower
turbine. As stated earlier, the net change in hours of expected flicker between the GE turbine and the
REpower turbine is shown in Figure 3 and quantitatively in Table 2.
There are currently no applicable local, state or federal regulations that quantify a shadow flicker
impact threshold or limit for wind turbines. The Town of Enfield does have a local wind law which
addresses shadow flicker. It states “the study shall identify locations where shadow flickers could be
caused by the WTG and the expected durations of the same at these locations. Shadow Flickers shall
be mitigated if their impact materially affects any Residence.” Germany has adopted guidelines for
shadow flicker including limiting impacts to a maximum of 30 hours per year (Nordrhein-Westfalen,
2002). Where no other threshold is available, the German standard is often applied in evaluating
shadow flicker impact. Based on this published standard, exceeding 30 hours per year of shadow
flicker was the level applied to this analysis and interpreted as “materially affect any Residence” from
the local wind law and is consistent with other wind turbine studies in the northeast. While none of
the receptors exceed the German standard, including the proposed GE turbine, possible shadow
flicker mitigation measures could include turbine curtailment when shadow flicker is predicted,
permanent physical barriers such as fences or new vegetation, or window treatments like shades or
awnings.
The shadow flicker impacts from the Project with the proposed GE turbines are not expected to pose a
health risk. In the past, concerns have been raised regarding the ability of shadow flicker to cause
seizures in vulnerable individuals, such as people with certain types of epilepsy. However, not all
flashing lights will elicit seizures and the phenomenon is highly dependent on the flashing light’s
frequency (Hz). The Massachusetts Department of Environmental Protection and the Massachusetts
Department of Public Health (MADEP, 2012) recently convened a panel of independent experts to
identify any documented or potential health impacts that may be associated with exposure to wind
turbines. The study consisted of an extensive review of literature and other reports pertaining to noise
and vibration, shadow flicker, and ice throw. The report found that although shadow flicker can be a
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nuisance, there was no evidence that suggested shadow flicker poses a risk for eliciting seizures and
there was limited evidence of potential health effects from prolonged shadow flicker exposure (i.e.
greater than 30 minutes per day). The report indicates that wind turbine shadow flicker is generally in
the range of 0.3 – 1 Hz, which is well below the 5-Hz threshold that has been found to produce
seizures in susceptible individuals
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APPENDIX A – WINDPRO MODELING OUTPUT
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APPENDIX B – SHADOW CALENDAR OF FLICKER
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APPENDIX C – SHADOW CALENDAR GRAPHICAL
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