While the current EBD method is the best available option to determine correct building dimensions in the model, a different method was suggested by EPA in the 2011 Memo: Model Clearinghouse Review of EBD for AERMOD. Attachment B to the 2011 Memo includes an assessment of the Alcoa Davenport Works EBD Study. In this evaluation EPA compared wind tunnel observations with AERMOD derived concentrations. However, this evaluation has important shortcomings. First, to carry out this comparison between wind tunnel and AERMOD concentrations, it is necessary to collect velocity profiles that include longitudinal and vertical turbulent intensity measurements upwind of the stack. These data were not available for the EPA evaluation of the Alcoa Davenport Works EBD Study. Second, the wind tunnel model operating conditions were converted to full scale conditions by using exact similarity. However, exact similarity is not used to specify model operating conditions since only momentum ratios are matched but not buoyancy ones. Whereas EPA did not provide important details on how this study was performed, this paper outlines how to properly carry out this new method where AERMOD is used to determine equivalent building dimensions. The viability of this new method was also evaluated and discussed.
Evaluation of the Theoretical Problems with Building Downwash Using A New Method to Determine Equivalent Building Dimensions
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Evaluating AERMOD and Wind
Tunnel Derived Equivalent
Building Dimensions
Guideline on Air Quality Models: The New Path
A&WMA’s 6th Specialty Conference - Chapel Hill, NC
Abstract #25
April 13, 2016
Sergio A. Guerra, Ph.D. – CPP Inc.
Ron Petersen, Ph.D., CCM – CPP 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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• 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
• Determined using wind tunnel modeling
What is EBD?
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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
• After 2011 EPA Clearinghouse Memo
– Chevron 1 (Study Approved), Region 4, 2012
– Chevron 2 (Study Approved), Region 4, 2013
– Confidential Project (In process), Region 4, 2015
– Confidential Project, Region 10, 2016
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Conclusion
• Adjustments to key parameters in the *.sfc
and *.pfl meteorological files can be used to
get better agreement between WT and
AERMOD MGL concentrations for the no site
structures present case
• After these adjustments the AERMOD-EBD do
not match the Wind Tunnel-EBD