Kingston, MAShadow Flicker Study

Elizabeth King Wind Analyst

Chester Harvey GIS Specialist

256 Farrell Farm Rd.Norwich, VT 05055Ph: 802.649.1511

Goals

1. Estimate shadow flicker timeby location

2. Estimate curtailment time required to meet example shadow flicker thresholds

3. Document areas withline-of-sight to turbine(s)

Site Overview• 5 Wind Turbines

• 1083 Receptors within 1.6 km of turbines

Methodology1. Desktop estimate of shadow flicker exposure

– Shadow flicker modeled using WindPRO

• Incorporates GIS terrain model, daily sun pathsbased on latitude, local weather data and wind data

– Receptors identified using aerial images & GIS data

– No tree or building obstacles are accounted for

2. Field documentation of line-of-sight

– Assessed by car from public streets

Flicker Modeling• Theoretical Worst Case

– Maximum possible shadow hours for a given location

– Sun always shining; wind turbines always operating

– Is a step in process for deriving realistic case estimates

• Realistic Case

– Incorporates sunshine probability and likely wind turbine operational hours

• Sunshine data, 61 years – Boston, MA (National Climatic Data Center)

• Wind data, 1 year (July 05 – July 06) – Kingston, MA (UMass Amherst)

Receptors

• 20 meters wide x 10 meters tall

– Intended to simulate the façade of a house

• Each receptor modeled so that it faces perpendicular to each wind turbine in each iteration of analysis (Greenhouse Mode)

Receptors

Receptors

10meters

tall

20 meters wide

Receptor area facing perpendicular to

direct line to turbineReceptor point at bottom-center of modeled receptor area

Shadow modeled on receptor area

1.5 m figure for scale

WindPRO Inputs

9

WindPRO Inputs

10

WindPRO Inputs

11

WindPRO Inputs

12

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Hours per Yearat 1.5 metersabove ground level

WindPRO Report

WindPRO Report

WindPRO ReportCalendar Graphs

Receptor A Receptor B

WindPRO Report

Flicker Results

Realistic Case

More Than 10 Hours per Year

of Flicker

More Than 30 Hours per Year

of Flicker

More Than 50 Hours per Year

of Flicker

Number of Receptors

Affected189 55 31

Number of Existing

Residential Receptors

Affected

121 38 24

Line-of-Sight Survey

• Assesses line-of-sight to each turbine from public streets within thestudy area

• Accounts for trees and buildings that block line-of-sight to turbines

• Line-of-sight results are not incorporated into modeling results

Photo 27

Curtailment Analysis

• Only receptors for existing residential structures are included

• Accounts for coincident flicker across multiple receptors

Curtailment ResultsRealistic Case Theoretical Worst Case

Estimated Curtailment Required for 10 hrs of

Flicker Per Year(h/yr)

Estimated Curtailment Required for Maximum

30 hrs of Flicker Per Year(h/yr)

NFF West(Gamesa 1)

94 286

NFF Southeast(Gamesa 2)

47 140

NFF North (Gamesa 3)

107 326

KWI (Hyundai)

126 366

MBTA (Northern Power)

6 14