Case Study

Installing wind screens on Mystic Units 8 & 9

Case Study

Installing wind screens on Mystic Units 8 & 9

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Mystic Units 8 & 9 – Each unit has an ACC which is 9 streets by 4 rows. A meeting was requested in September 2018 to discuss what Galebreaker could do to reduce their wind caused performance deficiencies. A south west wind effected their unit 8 while a North east wind had the most effect on unit 9. Our most extensive CFD Analysis was performed by Ergon. After looking at well over 40 configurations, it was determined that a similarly designed cruciform on each ACC would provide the best benefit. An extensive structural analysis was performed by Kipcon. This analysis determined that reinforcing was necessary. The reinforcing and screens were installed by the end of June, 2019. The original perimeter screens that were installed in 2014, were shortened to avoid overload on the columns.

For more in depth information on this project please see the technical case study

The challenge

Both unit 8 and 9 ACC’s are affected by winds during summer operation. Unit 8 is affected by SW winds, which is the prevalent wind direction in the summer. Unit 9 is affected by NW winds, which occur much less frequently on hot summer days. The decision was made to try Galebreaker wind screens on unit 8, on the south and west sides.

The Solution

The west side of the ACC is fairly clear and access for installation was fairly straightforward. Not the case with the south side. Many obstacles to design around, such as cable trays, conduit, small bore piping, structural attachments. Access for installation on the south side is difficult as well.

The Benefits

  • Unit performance from summer 2013 was compared to summer 2015.
  • Comparisons are based on similar ambient temperature, RH, wind speed and wind direction, and back pressure.
  • Based on the above, the unit has been able to produce an additional 15-20 MW with the wind screens in place.
  • The screens appear most effective for wind speeds up to 20 mph. The screens are less effective for winds exceeding 20 mph, but these don’t occur often.
  • Using a conservative approach and typical summer conditions, payback appears to be in the range of 2-3 yrs.
  • The analysis does not assume any high load, extreme temperature days when clearing prices occasionally spike into the hundreds of $/MWH. Days like these may effect payback significantly.

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