Using Physical Modeling to Refine Downwash Inputs to AERMOD
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Transcript of Using Physical Modeling to Refine Downwash Inputs to AERMOD
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www.cppwind.comwww.cppwind.com
Using Physical Modeling to
Refine Downwash Inputs to
AERMOD
Rocky Mountain States Section –
Air & Waste Management Association
Denver, CO
Sergio A. Guerra, PhD
Ron Petersen, PhD, CCM
April 13, 2017
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Outline1. Building Downwash in AERMOD
2. Equivalent Building Dimensions Method
3. Potential Benefits
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Compliance?Compliance?
BPIPBuilding Geometry
Meteorological Data
Terrain Data
AERMET
AERMAP
Operating Parameters AERMOD
Other Inputs
Building
Inputs
Traditional AERMOD Modeling
ApproachCompliance may
require taller
stacks and/or
additional
emission controls
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Building Downwash
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Image from Lakes Environmental Software
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Building Profile Input Program
(BPIP)
Figure created in BREEZE ® Downwash Analyst
BREEZE is a registered Trademark of Trinity Consultants, Inc.
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PRIME
AERMOD’s Building Downwash Algorithm
• Used EPA wind tunnel data
base and past literature
• Developed analytical
equations for cavity height,
reattachment, streamline
angle, wind speed and
turbulence
• Developed for specific
building dimensions
• When buildings outside of
these dimensions, theory falls
apart
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Overprediction due to Building
Downwash
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AECOM Field Study at Mirant Power
Station (Shea et al., 2012)
Shea, D., O. Kostrova, A. MacNutt, R. Paine, D. Cramer, L. Labrie, “A Model Evaluation Study of AERMOD Using Wind Tunnel
and Ambient Measurements at Elevated Locations,” 100th Annual AWMA Conference, Pittsburgh, PA, June 2007.
• Model overpredicted by factor of
10 on residential tower
• Better agreement with EBD, but
still overpredicted by factor of 4
• Best agreement with no
buildings, still overpredicted by
factor of 2.
• In reality, plume is not affected
by building downwash.
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What’s Causing These
Problems?
9 Using Physical Modeling to Refine Downwash Inputs to AERMOD
Petersen, R., Guerra, S., Bova, A., ”Critical Review of the Building Downwash Algorithms in
AERMOD”, Journal of the Air & Waste Management Association. Accepted author version:
http://www.tandfonline.com/doi/full/10.1080/10962247.2017.1279088
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Long Buildings with Wind
at an Angle
Figure created in BREEZE® Downwash Analyst
BREEZE is a registered trademark of Trinity Consultants, Inc.
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AERMOD Building Wake
AERMOD Overestimates Downwash
Hb = 20 m
Problem even worse for longer buildings
• Wake height
overestimated:
need higher plumes
to avoid downwash.
• Start of maximum
building downwash
farther downwind
than in reality
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AERMOD/PRIME
Overestimates
Downwash
Reality
AERMOD Building DownwashHeight of Building Downwash Zone Overestimated in PRIME
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Refinery Structures Upwind
- Horizontal Flow
Solid BPIP Structure Upwind
No Structures
Streamlines for Lattice Structures
Should be Horizontal
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How to Minimize the Effect from
these Errors?
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Solutions to Downwash Overpredictions
– Refine building dimensions with a wind tunnel study
– Equivalent Building Dimensions (EBDs) are the dimensions (height, width, length and location) that are input into AERMOD in place of BPIP dimensions to more accurately predict building wake effects
– Guerra, S., Petersen, R. “Using Physical Modeling to Refine Downwash Inputs to AERMOD”, EM Magazine, October 2016
http://www.cppwind.com/wp-content/uploads/2016/10/Using-Physical-Modeling-to-Refine-Downwash-Inputs-to-AERMOD_EMMag-Oct-16_PetersenGuerra.pdf
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• Equivalent Building Dimensions (EBDs) are the dimensions (height, width, length and location) that are input into AERMOD in place of BPIP dimensions to more accurately predict building wake effects
• Guidance originally developed when ISC was the preferred model –
– EPA, 1994. Wind Tunnel Modeling Demonstration to Determine Equivalent Building Dimensions for the Cape Industries Facility, Wilmington, North Carolina. Joseph A. Tikvart Memorandum, dated July 25, 1994. U.S. Environmental Protection Agency, Research Triangle Park, NC
– New guidance currently being developed with EPA
• Determined using wind tunnel modeling
EBD Method
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BPIP Diagnostic Toolhttp://www.cppwind.com/what-we-
do/air-permitting/bpip-diagnostic-tool#/Likely Overprediction Factor for each Flow Vector
Source 1
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ComplianceCompliance
CPP’s EBDCPP’s EBD
BPIP Diagnostic
ToolBuilding Geometry
Meteorological Data
Terrain Data
AERMET
AERMAP
Operating Parameters AERMODOther Inputs
Building
Inputs
BPIP Diagnostic Tool
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Summary of Approved Projects• Studies conducted and approved using original guidance for ISC
applications– Amoco Whiting Refinery, Region 5, 1990
– Public Service Electric & Gas, Region 2, 1993
– Cape Industries, Region 4, 1993
– Cambridge Electric Plant, Region 1, 1993
– District Energy, Region 5, 1993
– Hoechst Celanese Celco Plant, Region 3, 1994
– Pleasants Power, Region 3, 2002
• Studies conducted using original guidance for AERMOD/PRIME
applications – Hawaiian Electric (Approved), Region 9, 1998
– Mirant Power Station (Approved), Region 3, 2006
– Cheswick Power Plant (Approved), Region 3, 2006
– Radback Energy (Protocol Approved), Region IX, 2010
– Chevron 1 (Study Approved), Region 4, 2012
– Chevron 2 (Study Approved), Region 4, 2013
– On going confidential study in Region X
– On going confidential study in Region X
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How to Use EBD for Regulatory Purposes?
� Step 1: Develop a protocol outlining the EBD study
� Step 2: Submit EBD protocol for approval to regulatory agency. Also need to
involve Model Clearinghouse
� Step 3: Perform wind tunnel testing
� Step 4: Use building geometry from EBD study in AERMOD to show compliance
� Step 5: Submit final report for agency review and approval
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General EBD Methodology• Specify model operating
conditions
• Construct scale model
• Install model in wind tunnel and
measure concentrations
• Determine EBD
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Measure Ground-level Concentrations
Data taken until good fit and max obtained Automated Max GL Concentration Mapper
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Measure Ground-level Concentrations
With Site Structures Present
Tracer
from stack
Max ground-level concentrations measured versus x
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Measure Ground-level Concentrations with
Various EBD in Place of Site Structures
Tracer
from stack
Max ground-level concentrations measured versus x
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Measure Ground-level Concentrations with
no Structures
Tracer
from stack
Max ground-level concentrations measured versus x
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Specify Wind Tunnel Determined EBD that
Matches Dispersion with Site Structures Present
Wind
Tunnel EBD
much
smaller
than actual
building
No building
works best
for this
case
Site Structures in Wind TunnelEBD in Wind Tunnel
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Typical Result
Wind Tunnel EBD
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Downwash Based on EBD and BPIP
Figures created in BREEZE® Downwash Analyst
BREEZE is a registered trademark of Trinity Consultants, Inc.
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Potential Benefits from use of EBD
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Past CPP Project
Stack S_XXX From Industrial Facility
Stack height = 27 m
Q = 2 g/s
Building height = 17 m
Building width/length > 200 m
5 years of meteorological data
AERMOD Results With Wind
Tunnel EBD
wide/Long/Short Buildings
Description
AERMOD Maximum
Predicted
Concentration
(µg/m3)
Compliance
BPIP Building Dimension Inputs 258.2 No
Wind Tunnel Determined Building Inputs (EBD) 54.9 Yes
PM10 24-hr Standard 150
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AERMOD Results With Wind Tunnel EBD
Very wide/narrow building
Stack height: 47 m
Building height: 31 m
Property line in Red
Emission rate: 20 g/s
AERMOD RESULTS
Five years of met data Description
AERMOD Maximum
Predicted
Concentration
(µg/m3)
Compliance
BPIP Building
Dimension Inputs303.8 No
Wind Tunnel
Determined Building
Inputs (EBD)
79.9 Yes
NO2 1-hr Standard 188
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Sergio A. Guerra, PhD Ron Petersen, PhD, [email protected] [email protected]
Mobile: + 612 584 9595 Mobile:+1 970 690 1344
CPP, Inc.
2400 Midpoint Drive, Suite 190
Fort Collins, CO 80525
+ 970 221 3371
www.cppwind.com @CPPWindExperts
Questions?
32 Using Physical Modeling to Refine Downwash Inputs to AERMOD