1. Shadow Flicker Monitoring 5/21/13 to 8/28/13 Mary Reilly Mason County Zoning and Building Director 102 E. 5 th St., Scottville, MI 49454 mreilly@masoncounty.net (231) 757-9272 Credits: Kirk Josvai, Flicker Observation Dr. Paul Drelles, WSCC, Model/Data Assistance

2. Zoning Ordinance Requirements Mason County Zoning (Section 17.70.21 a): Shadow flicker on the external wall of a unpooled dwelling shall not exceed 10 hours per year (cumulative for all turbines). Consumers Energy installed Vestas Shadow Detection System (VSDS) to curtail turbines during flicker event. 1 st system installed in N. America.

3. Basics: Location of Sun in Sky Sun location is based on earths rotation (season) so flicker events are always changing– minute to minute. The sun rises and sets at changing times.

4. Basics- Season and Distance from Turbine Affect Shadow Duration

5. VSDS components

6. Evening Flicker, summer

7. Morning flicker

8. Heavier in Winter Morning and Evening

9. Shadow Flicker Monitoring 1. ARE TURBINES PAUSING THAT ARE PROGRAMED TO? Periodic review of turbines under VSDS. 2. HOW MUCH FLICKER IS OCCURING COMPARED TO THE MODEL? Sampling of specific properties modeled to receive under 8 hours. 3. HOW LONG IS THE FLICKER SHADOW? Review of length of shadow flicker.

10. ARE TURBINES PAUSING THAT ARE PROGRAMED TO? Based on 16 observations: 14 observations, turbines turned off during scheduled shut downs. 2 observations, turbines did not shut down. One clear day (WTG 39), One hazy/humid day (WTG 15) Consumers to manually override light sensors on WTG 14, 15, and others due to these and other observations.

11. The Data –5400 feet from a WTG Worst Case Scenario 2sunrisesunset Date Turbine ID:51Turbine ID:52 Start Time (hrs)Duration (hrs)Start Time (hrs)Duration (hrs) 18.327211817.2998521-Jan0.0 9.00.3 28.328106117.3146092-Jan0.0 9.00.3 38.32830317.3298713-Jan0.0 9.00.3 48.327801617.3456244-Jan0.0 9.00.3 58.326601717.3618525-Jan0.0 9.20.2 68.32470417.3785376-Jan0.0 9.20.2 78.322109817.3956627-Jan0.0 9.20.2 88.318820917.4132128-Jan0.0 9.20.2 98.3148417.4311699-Jan0.0 108.310170417.44951510-Jan0.0 118.304815817.46823411-Jan0.0 128.298780717.48730812-Jan0.0 138.2920717.50672113-Jan0.0 148.284689417.52645414-Jan0.0 158.276644717.5464915-Jan0.0 168.267942617.56681316-Jan0.0 178.258589917.58740717-Jan0.0 188.24859417.60825318-Jan0.0 198.237962817.62933619-Jan0.0 208.226704317.6506420-Jan8.70.20.0 218.21482717.67214921-Jan8.70.20.0 228.202339817.69384822-Jan8.70.20.0 238.189251817.7157223-Jan8.70.20.0 248.175572317.73775224-Jan8.70.20.0 258.16131117.7599325-Jan8.70.20.0 268.146477817.78223826-Jan8.70.20.0 278.131082617.80466327-Jan8.70.20.0 288.115135817.82719228-Jan8.70.20.0 298.098647617.84981329-Jan8.70.20.0 308.081628717.87251430-Jan8.70.20.0 318.064089617.89528131-Jan8.70.20.0

12. 2. HOW MUCH FLICKER IS OCCURING COMPARED TO THE MODEL? Turbine Hours per turbine Total Note: Total flicker in model derived from multiplying “worst case” cumulative total in graphs shown by.3 blade pass across the sun and.4 clearness index or.12--.15 was used to account for variability in climatic conditions. SAMPLE DATA SHOWING TURBINE, HOURS PER TURBINE and TOTAL

13. 2. HOW MUCH FLICKER IS OCCURING COMPARED TO THE MODEL? EXAMPLE: 45 hours modeled under “worst case scenario” meaning always sunny, always windy, no down time for maintenance, no trees, no structures, no hills, and turbine direction oriented to create flicker. 45 hours X.15 = 6.75 hours per year THE QUESTION: is 6.75 hours accurate or is the actual observed flicker something higher or lower?

14. Finding Potential Sites Time of year (late spring, summer for project). Will the turbines causing flicker be paused for another residence nearby? Will this site receive less than 8 hours but more than 6 hours*. Total flicker received primarily in the summer for observational period. *initial sites were selected above 6 hours, later to sites above 4 hours to be see if additional sites could be added for month of August.

15. Site Selection 8 sites selected based on data. 3 sites: turbines completely obstructed by vegetation or topography. No flicker. 2 sites: only the tip of the blade was visible over trees such that flicker would be nearly imperceptible and highly wind direction sensitive. Little or no flicker. 3 sites: good candidates (two AM, one PM)

16. Observations: Flicker appearance highly variable. Level 0-- modeled to receive, none exists Level 1– receive on non-living space, in small areas with obstructions by trees, topography Level 2- receive in living space, at distance that diffuses light/partial diffusion by trees. Level 3- receive in living space, bright in appearance (less than 2000-3000 feet to turbine), unobstructed.

17. Videos – Variable Appearance of Flicker

18. Kistler Road (Level 1/2) Site 1- 2600’ to Turbine Modeled to receive 7.1 hours Observed 8.38 hours w/October potential Modeled days: May 1- August 12 (WTG 13, minor WTG 11) Observed days: May 21- August 8 (no flicker at end). May 1 Aug. 12 Actual Observed Modeled Period May 21 Aug 8

19. Observations at Kistler Foliage gradually increases and obstructs flicker July-Aug. Wind direction (blade direction) has a significant impact on duration of flicker and can cause no flicker for extended periods. SE/NW =no flicker. W/E=most flicker. Morning flicker is prone to cloud banks low on the horizon that evaporate soon after dawn. FALL observation: WTG 17 pausing for other dwelling.

20. Wind Direction- Variability Minimal or no Flicker Maximum Flicker Moderate or no Flicker

21. PM Hwy (Level 1) Site 2- 2500 feet to turbine Modeled to receive 6.7 hours/year Observed 2.45 hours Modeled 5-20 to 8-1 (WTG 17) Observed 5-21 to 7-18 (ended early due to consistently viewing no flicker/obstruction). 5-20 5-21 7-18 8-1 Actual observed days Modeled period

22. Observations at PM Hwy Flicker observed on upper level of house Briefly occurred through window. Most often on corner of house/not inside the home. Foliage/location of sun completely obstructed flicker toward end of observation.

23. Modeled to receive 7.7 hours Observed 3.95 hours in 15 observational days (total possible=80 observational days) Turbine 40 shut down August 8-Aug 29 (22 days) due to mechanical issues. Model does not accurately forecast “worst- case scenario” for this property. Stiles Road (Level 3) Site 3- 1600 feet to turbine Modeled Observed Shut Down 40 days Modeled

24. Observations at Stiles Rd. Flicker here is stronger/clearer compared to other sites (Level 3). Flicker observation clearly above modeled worst case No trees to obstruct flicker to living room window and upstairs windows. Recommend future observation.

25. 3. HOW FAR IS THE FLICKER SHADOW? Max distance observed is about 6,000 feet. As distance increases, light diffuses reducing appearance of shadow and potential for obstruction (trees, topo, buildings) increases. Adjustments to model if flicker over 5400 feet done on a case-by-case basis.

26. CONCLUSION: ARE TURBINES PAUSING THAT ARE PROGRAMED TO? 1.Turbines pause majority of the time at expected time period. 2.Exceptions exist- VSDS and model not perfect. 3.Morning flicker – trees east of light sensors can obstruct light from reaching sensor and require manual override.

27. CONCLUSION: HOW MUCH FLICKER IS OCCURING COMPARED TO THE MODEL? Cannot make broad assumptions about under estimation or over estimation of model. In three cases*, the model under predicted worst case flicker in daily duration (event) and/or total estimated flicker. In three cases, the model over predicted total estimated flicker when none exists due to obstructions or topography. * Data of private party included here. Two cases observed by County.

28. Turbines pause if modeled over 8 hours Ordinance maximum 10 hours 20% factor included for climatic variation (8 to 10 hours) 20% factor included in probability (.12 to.15) Kistler road, minutes observed (8.5 hours) exceeds model (7.1 hours)- not a zoning violation. CONCLUSION: HOW MUCH FLICKER IS OCCURING COMPARED TO THE MODEL?

29. Moving Forward Where the model under predicts “worst case scenario” it must be corrected to be valid and statistically useful. With flicker complaints, immediate and continued response is needed (not 30-days). Correct model/obtain more data in order to move toward valid “sampling” at sites. Some sites need further study- Level 3 types where impact is greatest (Stiles Road)

30. Questions? mreilly@masoncounty.net (231) 757-9272