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PRIME2 Model Evaluation

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Important theoretical issues that significantly affect the accuracy of predicted concentrations subject to downwash effects have been identified in AERMOD/PRIME. These issues have prompted a number of industry groups to fund new research aiming at overcoming these shortcomings. The Plume Rise Model Enhancements (PRIME) building downwash algorithms1 (Schulman et al. 2000) in AERMOD2 are being updated to address some of the most critical limitations in the current theory. These enhancements will incorporate the latest advancements related to building downwash effects. The technical aspects of these enhancements are discussed in more detail in a recent publication "PRIME2: Development and Evaluation of Improved Building Downwash Algorithms for Solid and Streamlined Structures". The updates to the PRIME code include new equations to account for building wake effects that decay rapidly back to ambient levels above the top of the building; reduced wake effects for streamlined structures; and reduced wake effects for high approach roughness. A comparison with field data was conducted with the Bowline Point, Alaska North Slope, Millstone Nuclear Power Station, and the Duane Arnold Energy Center databases. A new experimental BPIP-PRM version is also discussed.

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PRIME2 Model Evaluation

  1. 1. Sergio Guerra, PhD | GHD Ron Petersen, PhD, CCM | CPP June 28, 2018 PRIME2 Model Evaluation A&WMA's 111th Annual Conference & Exhibition, Hartford, CT
  2. 2. Outline 1. Brief Summary of Downwash Summit 2. Field Evaluation 3. BPIP-PRM PRIME2 Model Evaluation
  3. 3. Key Takeaways from 2/16/18 Workshop • EPA OAQPS confirmed that the PRIME2 updates can be included as an Alpha option in a future model release. EPA expects the next release to happen by the end of 2018. • Review from OAQPS before release would take between 3-4 months, but will depend on workload. • EPA OAQPS prefers that the PRIME2 and ORD updates be implemented separately in the model; e.g., PRIME2-A and PRIME2-B updates. • Requirements from App W Section 3.2.2 would be needed before an Alpha version becomes Beta. • Updating BPIPPRM to reduce exaggeration of building footprint for angular approaches to buildings is a top need for OAQPS and ORD. • EPA ORD will continue to investigate and develop new formulation to deal with rotated elongated buildings (lateral shift and effect of corner vortices). PRIME2 Model Evaluation
  4. 4. Next Steps by CPP in 2018 – In Progress Convert PRIME2 into an alpha version of PRIME • Add the necessary commenting • Need to use EPA’s current code and add PRIME2 enhancements as options. • Add switches for height of wind speed used for concentration calculations. • Add switches for Zeff calculation method for approach met conditions and wake met conditions. Evaluate PRIME2 against past permitting projects with wind tunnel EBD studies: Mirant, ALCOA, Basic American Foods, TBD • Current BPIP with AERMOD/PRIME and AERMOD/PRIME2 • EBD with AERMOD/PRIME and AERMOD/PRIME2 PRIME2 Model Evaluation
  5. 5. Field Evaluation PRIME2 Model Evaluation
  6. 6. Bowline Point Field Evaluation for Receptors 1 and 3 Q-Q Plot of Predicted vs. Observed Concs. with BPIP Values Model Version Top 25 Mean X obs Top 25 Mean X predict Top 25 Pre/Obs Fractional Bias R1&3 AERMODv16216r (ug/m3) 422.17 447.71 1.06 0.06 R1&3 PRIME2v17234a (ug/m3) 422.17 684.51 1.62 0.47 6 PRIME2 Model Evaluation
  7. 7. Bowline Point 7 29.6 m 65.2 m 86.9 m Q (g/s) Hs (m) Ts (K) Vs (m/s) Ds (m) STACK 0 - 449.3 86.87 358 - 409 7.9 – 30.9 5.72 • Buoyant , SO2 Source • Hudson River Valley, New York • 100m met tower • No turbulence data • Even split between stable and unstable hours • Hourly emissions data • Full year of data • 4-Receptors (Recs 1 and 3 used) 7 PRIME2 Model Evaluation
  8. 8. Refined BPIP Method Example Bowline Point 8 PRIME2 Model Evaluation
  9. 9. Refined BPIP Method Example: Bowline Point Merged Tiers Building Dimensions BPIP (m) Updated BPIP (m) Building Height(Hb) 65.23 65.23 Building Width (W) 121.95 121.95 Building Length (L) 109.93 35.98 XBADJ -127.62 -97.20 YBADJ -2.47 -2.5 Assumption 1: Tallest tiers combine (green bdg) Assumption 2: BDG WIDTH (W) is crosswind width of merged tier. Assumption 3: XBADJ starts at the upwind edge of the merged tier Assumption 4: BDG LENGTH (L) is calculated by dividing the area of the merged tier by W 9 PRIME2 Model Evaluation
  10. 10. Refined BPIP Method Example: Bowline Point Unmerged Tiers Building Dimensions BPIP (m) Updated BPIP (m) Building Height(Hb) 65.23 65.23 Building Width (W) 94.57 49.9 Building Length (L) 130.27 27.65 XBADJ -132.56 -127.90 YBADJ -27.17 -4.0 Assumption 1: Tallest tiers do not combine (green bdg) Assumption 2: BDG WIDTH (W) is crosswind width of unmerged tier. Assumption 3: XBADJ starts at the upwind edge of the tallest tier Assumption 4: BDG LENGTH (L) is calculated by dividing the area of the tallest tier by W 10 PRIME2 Model Evaluation
  11. 11. Bowline Point Field Evaluation for Receptors 1 and 3 Q-Q Plot of Predicted vs. Observed Concs. with BPIP Values Model Version Top 25 Mean X obs Top 25 Mean X predict Top 25 Pre/Obs Fractional Bias R1&3 AERMODv16216r (ug/m3) 422.17 447.71 1.06 0.06 R1&3 PRIME2v17234a (ug/m3) 422.17 684.51 1.62 0.47 11 PRIME2 Model Evaluation
  12. 12. Model Version Top 25 Mean X obs Top 25 Mean X predict Top 25 Pre/Obs Fractional Bias R1&3 AERMODv16216r (ug/m3) 422.17 237.67 0.56 -0.56 R1&3 PRIME2v17234a (ug/m3) 422.17 535.01 1.27 0.24 Bowline Point Field Evaluation for Receptors 1 and 3 Q-Q Plot of Predicted vs. Observed Concs. with Modified BPIP Values 12 PRIME2 Model Evaluation
  13. 13. Q (g/s) Hs (m) Ts (K) Vs (m/s) Ds (m) STACK 1 39.2 554-584 17-21 3.66 34.0 m 39.2 m Alaska North Slope Field Study • Buoyant , SF6 Source • 33m met tower • Met data include: ws, wd, temp, sigma-theta, and sigma-w • 7 arcs of recs from 50m to 3,000m • 44 hours during light hours (0900- 1600) • Stability conditions generally neutral or slightly stable • Wind speeds at 33-m level • Less than 6 m/s for one test • Between 6 and 15 m/s for four tests • More than 15 m/s during three tests 13
  14. 14. Refined BPIP Method Example Alaska North Slope 14 PRIME2 Model Evaluation
  15. 15. Model Version Top 25 Mean X obs Top 25 Mean X predict Top 25 Pre/Obs Fractional Bias AERMODv16216r 3.13 3.59 1.15 0.137 PRIME2_17234 3.13 7.58 2.42 0.829 Alaska North Slope Field Evaluation Q-Q Plot of Predicted vs. Observed Concs. with BPIP Values 15 PRIME2 Model Evaluation
  16. 16. Building Dimensions BPIP (m) Updated BPIP (m) Building Height(Hb) 34.0 34.0 Building Width (W) 51.26 51.26 Building Length (L) 55.67 25.81 XBADJ -45.24 -43.70 YBADJ 6.58 6.6 Assumption 1: Tallest tier combine (green bdg) Assumption 2: BDG WIDTH (W) is crosswind width of merged tier. Assumption 2: XBADJ starts at the lee edge of the merged tier Assumption 3: YBADJ is calculated by dividing the area of the merged tier by the width of the artificially created building Refined BPIP Method Example: Alaska North Slope Merged Tiers 16 PRIME2 Model Evaluation
  17. 17. Building Dimensions BPIP (m) Updated BPIP (m) Building Height(Hb) 34.0 34.0 Building Width (W) 52.98 20.25 Building Length (L) 28.61 25.30 XBADJ -28.7 -28.6 YBADJ -11.79 4.8 Assumption 1: Tallest tier do not combine (green bdg) Assumption 2: XBADJ starts at the lee edge of the merged tier Assumption 3: YBADJ is calculated by dividing the area of the merged tier by the width of the artificially created building Refined BPIP Method Example: Alaska North Slope Unmerged Tiers 17 PRIME2 Model Evaluation
  18. 18. Model Version Top 25 Mean X obs Top 25 Mean X predict Top 25 Pre/Obs Fractional Bias AERMODv16216r 3.13 3.59 1.15 0.137 PRIME2_17234 3.13 7.58 2.42 0.829 Alaska North Slope Field Evaluation Q-Q Plot of Predicted vs. Observed Concs. with BPIP Values 18 PRIME2 Model Evaluation
  19. 19. Model Version Top 25 Mean X obs Top 25 Mean X predict Top 25 Pre/Obs Fractional Bias AERMODv16216r 3.13 2.78 0.89 -0.120 PRIME2_17234 3.13 6.14 1.96 0.648 Alaska North Slope Field Evaluation Q-Q Plot of Predicted vs. Observed Concs. with Modified BPIP Values 19 PRIME2 Model Evaluation
  20. 20. Millstone Nuclear Power Station (Dominion Millstone Power Station) Q (g/s) Hs (m) Ts (K) Vs (m/s) Ds (m) REAC 1 48.3 291 - 297 4.6 – 8.7 2.12 TURB1 1 29.1 292 - 306 10.5 1.4 TURB2 1 29.1 292 - 306 10.5 1.4 TURB3 1 29.1 292 306 10.5 1.4 41.6 m 44.7 m 27.6 m 29.1 m 48.3 m • Non-buoyant , SF6 Source • Waterford, Connecticut • 36-hrs of SF6 emissions, from 48m stack • 26-hrs of Freon emissions, from 29m stack • 3 arcs at 350, 800 and 1,500 m • Met tower with 10-m and 43-m levels • Even number of stable and unstable hours • Mostly high wind speeds (>7 m/s) 20
  21. 21. 21 Millstone Nuclear Power Station Q-Q Plot of Predicted vs. Observed Concs. with BPIP Values
  22. 22. 22 Millstone Nuclear Power Station Q-Q Plot of Predicted vs. Observed Concs. with BPIP Values
  23. 23. Duane Arnold Energy Center 23.5 m 42.7 m 1 m 23.5 m 45.7 m Q (g/s) Hs (m) Ts (K) Vs (m/s) Ds (m) STACK 5 1 45.7 293 – 299 7.4 - 40.8 1.4 STACK 4 1 23.5 294 - 300 0.01 2.12 STACK 1 1 1.0 299 - 303 0.01 1.4 • Non-buoyant , SF6 Source • Palo, Iowa • Terrain varies by about 30m • Two arcs of monitors at 300m and 1000m • Releases from two rooftops (46-m and 24-m levels) and the ground (1-m level) • Release hours were 12, 16 and 11 for 46m, 24m, and 1m • 1-m and 24-m releases were non- buoyant, non-momentum • 46-m release was close to ambient, but had about a 10 m/s exit velocity • Met data consisted of winds at 10m, 24m, and 50m. • Met conditions mostly convective (30 out of 39 hours), with fairly light wind speeds 23
  24. 24. 24 Duane Arnold Energy Center Q-Q Plot of Predicted vs. Observed Concs. with BPIP Values
  25. 25. 25 Duane Arnold Energy Center Q-Q Plot of Predicted vs. Observed Concs. with BPIP Values
  26. 26. 26 Duane Arnold Energy Center Q-Q Plot of Predicted vs. Observed Concs. with BPIP Values
  27. 27. Additional Evaluations to Consider • American Gas Association SF6 field study (one of the EPA’s 17 AERMOD evaluation databases) – samplers as close as 50 m • Wainwright, Alaska NOx database – monitor at 500 m • Colorado drill rig field study – 12 NOx monitors at about 100 m • Sheldon Station (Nebraska) – EGU with SO2 DRR monitoring at about 600 m from stacks • Other modeling stakeholders are encouraged to conduct and present their own evaluation studies PRIME2 Model Evaluation
  28. 28. Experimental BPIPPRM from EPA’s ORD PRIME2 Model Evaluation
  29. 29. Wind L1 L2 BPIP new building length calculation method New building length = min(L1,L2) = L2 Wind Example 1 Provided by EPA’s Office of Research and Development
  30. 30. Wind L1 L2 New building length = min(L1,L2) = L1 Example 2 Provided by EPA’s Office of Research and Development
  31. 31. Provided by EPA’s Office of Research and Development
  32. 32. Provided by EPA’s Office of Research and Development
  33. 33. Conclusions PRIME2 includes a superior theory to account for building downwash effects for rectangular and streamlined structures. Benefits from improved theory cannot be fully realized due to outstanding issues in the model. Work from EPA ORD complements the work performed by CPP. Plan is to continue EPA collaboration to address model improvements to AERMOD related to building downwash. PRIME2 Model Evaluation
  34. 34. Sergio A. Guerra, PhD Ron Petersen, PhD, CCM sergio.guerra@ghd.com rpetersen@cppwind.com Office: + 720 974 0935 Mobile:+1 970 690 1344 Questions? PRIME2 Model Evaluation
  35. 35. www.ghd.com PRIME2 Model Evaluation

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