Solution to AERMOD/PRIME PM10 Overpredictions for Extremely Short, Long and Wide Buildings
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The current formulation in AERMOD/PRIME is prone to downwash overestimations as documented by Petersen et al. Some of these overpredictions can be minimized by conducting a wind tunnel study to refine the building inputs used in AERMOD/PRIME for critical stacks and wind directions. Most of the wind tunnel studies conducted to date involve taller building structures of at least 20 meters in height. However, a recent wind tunnel study was conducted for the Basic American Foods, Blackfoot, Idaho facility, which has extremely short buildings (7 to 12 meters in height) with very long and wide footprints and many exhaust stacks which are less than 25 meters above ground The wind tunnel study confirmed that AERMOD was vastly overstating downwash effects for certain critical wind directions. In some cases, AERMOD-predicted concentrations were almost four times higher without the wind tunnel refinements. This study indicates that the previously identified tendency of AERMOD to overpredict downwash using the traditional BPIP-derived building inputs also applies to sites with shorter buildings. Because shorter buildings with shorter stacks are common in many sources subject to the minor New Source Review program (such as most food and beverage and manufacturing facilities), AERMOD’s overpredictions may be causing significantly higher predicted concentrations for many industrial sources. This paper describes the wind tunnel study performed for this site, presents the benefits obtained from these building input refinements, and reviews comments received on the project from regulatory agencies.
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EPA is under a Court order to complete the remaining SO2 designations for the rest of the country in three additional rounds. On March 20, 2015 the EPA released an updated guidance for 1-hr SO2 area designations. The two options included are compliance through dispersion modeling or ambient monitoring. Of these two options, dispersion modeling is the fastest and most cost effective one to characterize SO2 air quality. However, this compliance demonstration can be challenging given that AERMOD tends to produce overly conservative concentration estimates. Source characterization techniques and probabilistic techniques may be used to achieve compliance with the 1-hour NAAQS. Three advanced methods discussed: 1) Equivalent Building Dimensions (EBD); 2) Emission Variability Processor (EMVAP); 3) 50th Percentile Background Concentrations.
PRIME2 Model Evaluation
The Plume Rise Model Enhancements (PRIME) formulation in AERMOD has been updated based new equations developed from wind tunnel measurements taken downwind of various solid and streamlined structures. These new equations, along with other building downwash improvements have been included as alpha options in the upcoming new version of AERMOD. The PRIME2 options include: • PRIME2UTurb which enables enhanced calculations of turbulence and wind speed • PRIME2Ueff which defines the height used to compute effective parameters Ueff, Sweff, Sveff and Tgeff at plume height and at 30 m • Streamline defines the set of constants for modeling all structures as streamlined. If omitted, rectangular building constants are used. The ORD Options include: • PRIMEUeff which controls the heights for which the wind speed is calculated for the main plume concentrations. • Average between plume height and receptor height recommended in ORD version • Default is current method in AERMOD, stack height wind speed. • PRIMETurb which adjusts the vertical turbulence intensity, wiz0 from 0.6 to 0.7. • PRIMECav modifies the cavity calculations These improvements aim to address important theoretical issues that significantly affect the accuracy of predicted concentrations subject to downwash effects. This research effort was funded in part by the American Petroleum Institute, the Electric Power Research Institute, the Corn Refiners Association and the American Forest & Paper Association. As part of it, the PRIME2 subcommittee under the A&WMA APM committee was formed to: (1) establish a mechanism to review, approve and implement new science into the model for this and future improvements; and (2) provide a technical review forum to improve the PRIME building downwash algorithms. Collaboration and cooperation from the EPA Office of Research and Development (ORD) has been on-going during the research project resulting in new alpha options aimed at solving known issues with the treatment of building downwash effects in AERMOD. The intent is that these experimental options will be tested by the user community to create enough justification to make these beta (approved on a case-by-case basis) and eventually default options in AERMOD. A preliminary evaluation for the following four cases will be presented: • Arconic- Davenport, IA (formerly Alcoa) • Mirant Potomac River Generating Station- Alexandria, VA • Basic American Foods- Blackfoot, ID • Oakley Generating Station- Oakley, CA The evaluation includes comparing 1-hr, 24-hr and annual averages along with Q-Q plots and isopleths. A discussion related to the results obtained will also be presented.
PRIME2_consequence_analysis_and _model_evaluation
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 companion paper titled “PRIME2: Development and Evaluation of Improved Building Downwash Algorithms for Solid and Streamlined Structures (MO13)”. 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 consequence analysis comparing the current AERMOD/PRIME model versus the new AERMOD/PRIME2 model was performed. Additionally, a field data evaluation was conducted with the Bowline Point database. The results from these analyses are discussed below.
EVALUATION OF SO2 AND NOX OFFSET RATIOS TO ACCOUNT FOR SECONDARY PM2.5 FORMATION
On January 4, 2012, the EPA committed to engage in rulemaking to evaluate updates to the Guideline on Air Quality Models (AppendixWof 40 CFR 51) and, as appropriate, incorporate new analytical techniques or models for secondary PM2.5. As a result, the National Association of Clean Air Agencies (NACAA) developed a screening method involving offset ratios to account for
secondary PM2.5 formation. This method can be used to evaluate total (direct and indirect) PM2.5 impacts for permitting purposes. Therefore, the evaluation of this method is important to determine its viability for widespread use.
Background Concentrations and the Need for a New System to Update AERMOD
Presentation delivered at the EPA 11th Conference on Air Quality Modeling at RTP, NC.
Topics covered include background concentrations and the need for a new system to update AERMOD. An evaluation of what is being proposed in the draft guidance related to background concentrations and an alternative approach to determine background concentrations for dispersion modeling evaluations is presented. A review of the lessons learned from Appendix W and a proposed new method to incorporate science into the model.
Using Physical Modeling to Refine Downwash Inputs to AERMOD
Achieving compliance in dispersion modeling can be quite challenging because of the tight National Ambient Air Quality Standards (NAAQS). In addition, AERMOD’s limitations can, in many cases, produce higher than normal concentrations due to the inherent assumptions and simplifications in its formulation. In the case of downwash, the theory used to estimate these effects was developed for a limited set of building types. However, these formulations are commonly used indiscriminately for all types of buildings. This presentation will cover how the basics of wind tunnel modeling can overcome some of these limitations and be used to mitigate downwash induced overpredictions to achieve compliance.
Highlights from the 2016 Guideline on Air Quality Models Conference
The revision of the Guideline on AQ Models (Appendix W) will prompt many changes in the way dispersion modeling is conducted for regulatory purposes. Some of the changes to the Guideline include enhancements and bug fixes to the AERMOD modeling system, new screening techniques to address ozone and secondary PM2.5, delisting CALPUFF as the preferred long-range transport model, and updates on the use of meteorological input data. These changes will have a significant impact on the regulated community. In anticipation of these updates, the Air & Waste Management Association will hold its 6th Specialty Conference: “Guideline on Air Quality Models: The New Path” to provide a technical forum to discuss the Guideline. This talk covered the main highlights from this conference including the presentations from EPA on the status and future direction of the Guideline. Learn how these changes may impact dispersion modeling evaluations for short and long range transport.
New Guideline on Air Quality Models and the Electric Utility Industry
The new EPA guideline on air quality models makes several changes, including adopting AERMOD version 16216r as the new default model. It establishes a two-tiered approach for modeling ozone and secondary PM2.5 formation, using existing empirical relationships (Tier 1) or chemical transport models (Tier 2). CALPUFF is no longer preferred for long-range transport modeling beyond 50 km. The guideline also allows the use of prognostic meteorological data in some cases. While the changes aim to promote consistency, the increased flexibility may lead to legal challenges and delays.
AERMET's Beta u-star Option
This document discusses the beta u-star option in AERMET for adjusting friction velocity (u*) calculations under low wind stable conditions. It provides background on studies conducted by AECOM and EPA to evaluate AERMOD's performance at low wind speeds. The document outlines the timeline of updates to u* in AERMET and reviews AECOM's 2014 evaluation of new meteorological databases using the beta u* option, finding impacts were most sensitive for low-level sources and tall buoyant stacks in complex terrain. It closes with considerations for justifying the beta u* option as an alternative refined model under EPA regulations.
AIR DISPERSION MODELING HIGHLIGHTS FROM 2012 ACE
Presentation includes some highlights from the dispersion modeling papers presented at the Annual AWMA conference in San Antonio, TX. Topics covered include: EMVAP, distance limitations of AERMOD, and two case studies comparing predicted and monitoring data,
Presented at the A&WMA UMS Board Meeting on August 21, 2012.
Using Physical Modeling to Evaluate Re-entrainment of Stack Emissions
Fume re-entry is an important concern for many types of facilities such as hospitals and laboratories that emit pathogens and toxic chemicals that may impact public health by being re-entrained into the building though nearby air intakes. Numerical methods can be used to evaluate dispersion of pollutants from stacks at sensitive receptors. However, numerical methods have limitations and simplifications that can significantly affect its predictions. An alternate way of analyzing stack re-entrainment is with physical modeling in a wind tunnel. In such a study, a scale model that accounts for buildings, topography, and vegetation is used with planned and alternate stack designs to determine the toxic emission impacts on air intakes and other sensitive locations. In a wind tunnel study different stack designs and possible mitigation options can be evaluated. This method is superior to numerical methods (e.g., dispersion models) because it accounts for the immediate structures, topography, and vegetation that is often ignored or oversimplified in numerical methods.
This presentation will show a hypothetical case study evaluating a site with toxic air emissions using AERMOD and physical modeling.
CPP's Advanced Dispersion Modeling Services
CPP is an air quality and wind engineering consulting firm that provides air permitting and advanced dispersion modeling services. They have expertise in AERMOD modeling, wind tunnel modeling, and other advanced analysis methods like equivalent building dimensions and emission variability processing. Using these advanced methods, CPP can help optimize clients' emission control equipment and stack heights to make projects compliant with permitting requirements in cases where initial modeling shows exceedances.
PRIME2 Model Evaluation
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.
NOVEL DATA ANALYSIS TECHNIQUE USED TO EVALUATE NOX AND CO2 CONTINUOUS EMISSIO...
The current study presents a new data analysis technique developed while evaluating continuous emission data collected from a trash compactor. The evaluation involved tailpipe sampling with a portable emission monitoring system (PEMS) from a diesel fueled 525-horsepower trash
compactor. The sampling campaign took place by running the compactor with regular no. 2 diesel, B20 and ULSD fuels. The purpose was to determine the possible emission reductions in nitrous oxides (NOx) and carbon dioxide (CO2) from the use of B20 and ULSD in an off-road
vehicle. The results from the NOx analysis are discussed.
The initial data analysis identified two important issues. The first concern related to a bias in the calculated F values due to the very large number of samples (N). The large N influenced the probability values and indicated a false statistical significance for all factors tested. Additionally,
the data observations were found to be highly autocorrelated. Thus, a time interval data reduction
technique was used to address these two statistical limitations to the robustness of the statistical
analyses. The result in each case was a subset of quasi-independent observations sampled at an interval of 800 seconds. The autocorrelation and false statistical significance issues were promptly resolved by using this technique. Since the issues of false statistical significance and autocorrelation are inherent in continuous data, the positive results obtained from the use of this technique can be far-reaching. This technique allowed for a valid use of the general linear model (GLM) with engine speed as the covariate factor to test day, fuel type and compactor factors. This technique is most relevant given the advancements in data collection capabilities that
require data handling techniques to satisfy the statistical assumptions necessary for valid analyses to ensue.
INNOVATIVE DISPERSION MODELING PRACTICES TO ACHIEVE A REASONABLE LEVEL OF CON...
Presentation delivered at the Annual Air and Waste Management Association conference in Long beach, California on June 26, 2014.
Innovative dispersion modeling techniques are presented including ARM2, EMVAP and the 50th percentile background concentration. Case study involves peaking engines that are used 250 hour per year. These intermittent sources are required to undergo a modeling evaluation in many states. Current modeling techniques grossly overestimate the emissions from these sporadic sources.
Pairing aermod concentrations with the 50th percentile monitored value
This document proposes a new method for combining modeled concentrations from AERMOD with monitored background concentrations.
The current practice of adding the maximum or 98th percentile monitored concentration is overly conservative. Instead, the document suggests using the 50th percentile (median) monitored concentration.
Pairing the 98th percentile modeled concentration with the 50th percentile monitored concentration results in a combined 99th percentile concentration. This provides a more conservative estimate than the form of the short-term air quality standards, while avoiding the mismatch of temporal pairing in AERMOD and the influence of exceptional events.
The proposed method is presented as a simple, protective approach for demonstrating compliance with air quality standards when considering both modeled and monitored background concentrations.
AERMOD CHANGES AND UPDATES
Presentation includes information related to gently sloping terrain, AERMINUTE, and EPA formula height.
Presented at the 27th Annual Conference on the Environment on November 13, 2012.
Case Studies in Air Dispersion Modeling for Young Professionals
Background on:
-origin of air quality regulations
-Gaussian models
-AERMOD
-Case study for an Aluminum Manufacturing Facilty
Critical Review of the Building Downwash Algorithms in AERMOD
The only documentation on the building downwash algorithm in AERMOD, referred to as PRIME, is found in the 2000 A&WMA Journal article by Schulman, Strimaitis and Scire. Recent field and wind tunnel studies have shown that AERMOD overpredicts concentrations by factors of 2 to 8 for certain building configurations. While a wind tunnel equivalent building dimension study (EBD) can be conducted to approximately correct the overprediction bias, past field and wind tunnel studies indicate that there are notable flaws in the PRIME building downwash theory. A detailed review of the theory supported by CFD and wind tunnel simulations of flow over simple rectangular buildings revealed the following serious theoretical flaws: enhanced turbulence in the building wake starting at the wrong longitudinal location; constant enhanced turbulence extending up to the wake height; constant initial enhanced turbulence in the building wake (does not vary with roughness or stability); discontinuities in the streamline calculations; and no method to account for streamlined or porous structures.
This paper documents some of the theoretical flaws that have been found in PRIME and provides supporting CFD and wind tunnel observations that confirm these findings. A suggested path forward to correct these problems is also outlined in accordance to Appendix W’s mandate that a model should be based on sound science and that its components are validated accordingly. In other words, corrections to the downwash theory in the model would ensure that the right answer is obtained for the right reason.
INNOVATIVE DISPERSION MODELING PRACTICES TO ACHIEVE A REASONABLE LEVEL OF CON...
Presentation delivered at the Board meeting for the Upper Midwest section of the Air and Waste Management Association meeting on September 16, 2014.
Innovative dispersion modeling techniques are presented including ARM2, EMVAP and the 50th percentile background concentration. Case study involves peaking engines that are used 250 hour per year. These intermittent sources are required to undergo a modeling evaluation in many states. Current modeling techniques grossly overestimate the emissions from these sporadic sources.
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Complying with EPA's Guidance for SO2 Designations
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Highlights from the 2016 Guideline on Air Quality Models Conference
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New Guideline on Air Quality Models and the Electric Utility Industry
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Air monitoring data for the City of Rhinelander, WI shows SO2 concentrations exceeding the 1-hour standard at the water tower monitoring location (WTM) and, as a result, this area has been designated a SO2 non-attainment area. An analysis of emission sources and air quality modeling indicates that the Expera Rhinelander Mill 63 m tall cyclone boiler stack (S09) appears to be the primary contributor to the ambient air impact at this monitor. One solution being evaluated for showing compliance with the 1-hr SO2 NAAQS is raising the 63 m tall S09 stack to the GEP stack height. Based on the Boiler 7 building dimensions the formula GEP stack height is 75 m.
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Use of Probabilistic Statistical Techniques in AERMOD Modeling Evaluations
The advent of the short term National Ambient Air Quality Standards (NAAQS) prompted modelers to reassess the common practices in dispersion modeling analyses. The probabilistic nature of the new short term standards also opens the door to alternative modeling techniques that are based on probability. One of these is the Monte Carlo technique that can be used to account for emission variability in permit modeling.
Currently, it is assumed that a given emission unit is in operation at its maximum capacity every hour of the year. This assumption may be appropriate for facilities that operate at full capacity most of the time. However, in most cases, emission units operate at variable loads that produce variable emissions. Thus, assuming constant maximum emissions is overly conservative for facilities such as power plants that are not in operation all the time and which exhibit high concentrations during very short periods of time.
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A case study is presented to evaluate the use of alternative probabilistic methods to complement the shortcomings of current dispersion modeling practices. This case study includes the use of the Monte Carlo technique and the use of a reasonable background concentration to combine with the AERMOD predicted concentrations. The use of these methods is in harmony with the probabilistic nature of the NAAQS and can help demonstrate compliance through dispersion modeling analyses, while still being protective of the NAAQS.
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Advance modeling techniques can be used in AERMOD to refine the inputs that are entered in the model to get more accurate results. This presentation covers:
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-Building Downwash Limitations in BPIP/PRIME
-Advanced Modeling Techniques to Overcome these Limitations
Solutions include:
Equivalent Building Dimensions (EBD)
Emission Variability Processor (EMVAP)
Updated ambient ratio method (ARM2)
Pairing AERMOD values with the 50th % background concentrations in cumulative analyses.
Conference on the Environment- GUERRA presentation Nov 19, 2014
This document discusses innovative dispersion modeling practices to achieve reasonable conservatism in regulatory modeling demonstrations. It presents a case study evaluating the Emissions and Meteorological Variability Processor (EMVAP) and approaches to establish background concentrations. The case study models SO2 concentrations from a power plant using 1) constant emissions, 2) variable emissions, and 3) EMVAP. EMVAP provides more realistic concentrations while accounting for emission variability. Using the 50th percentile monitored background concentration when combining with modeled values provides statistical conservatism compared to using high percentile values.
Pairing aermod concentrations with the 50th percentile monitored value
Presentation delivered to the Background Concentrations Workgroup for Air Dispersion Modeling organized by the Minnesota Pollution Control Agency. delivered on March 25, 2014. Three topics covered include 1) Screening monitoring data, 2) AERMOD’s time-space mismatch, and
3) Proposed 50th % Bkg Method
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官方认证美国密歇根州立大学毕业证学位证书原版一模一样
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Solution to AERMOD/PRIME PM10 Overpredictions for Extremely Short, Long and Wide Buildings
- 1. Solution to AERMOD/PRIME Overpredictions for Extremely Short, Long, and Wide Buildings Guideline on Air Quality Models: The Changes Chapel Hill, NC Sergio A. Guerra, Ron Petersen; CPP Inc. Steve Nelson; Coal Creek Environmental John S. Kirkpatrick; Basic American Foods November 15, 2017 COAL CREEK ENVIRONMENTAL ASSOCIATES
- 3. Basic American Foods (BAF) Overview • Family owned and operated since 1933 – Ongoing innovation (40+ patents) – Shelf-stable potatoes and beans • Food Service • Limited Retail – Hungry Jack • Facility Locations – Idaho • Blackfoot • Shelley • Rexburg – Washington • Moses Lake
- 6. Baseline Case (with BPIP values)
- 7. Permitting and Modeling Challenges • BAF is updating a PM10 compliance demonstration • No clear path to show needed reductions in PM10 impacts (needed 80% reduc8ons in impacts) ̵ Modeling op8ons exhausted ̵ No apparent treatment options (most of the PM10 is non-filterable material) ̵ Stack height increases unfeasible • Wind tunnel analysis of downwash appeared promising
- 8. BPIPPRM Derived Values Flow Wind BUILDHGT BUILDWID BUILDLEN Vector Direction Hb W L Hs/Hb W/Hb L/Hb (Deg.) (Deg.) (m) (m) (m) 10 190 7.92 61.66 35.92 2.1 7.8 4.5 20 200 7.92 62.29 44.07 2.1 7.9 5.6 180 360 7.92 59.22 26.93 2.1 7.5 3.4 StackEU_13BPIP DimensionsDiagnostic Aspect Ratio
- 9. Downwash Screening – Stack CXX
- 10. Downwash Screening – Stack EU_15
- 11. Equivalent Building Dimension Method for Downwash
- 12. Model Design and Construction • Obtain source/site data • Specify test wind speeds and directions • Compute model operating conditions • Construct scale model
- 13. Phase 1 Testing: Flakers
- 14. Phase 2 Testing: Dehydrators
- 15. Measure Ground-level Concentrations Data taken until good fit and max obtained Automated Max GL Concentration Mapper
- 16. Identify Wind Tunnel Determined EBD that Match Dispersion with Site Structures Present
- 18. Baseline Case (with BPIP values)
- 19. WT EBD values for Flakers and Dehys Max PM10 H6H = 82 ug/m3
- 23. Conclusions • EPA provided technical assistance to IDEQ in reviewing the EBD study • IDEQ has accepted the results of the EBD study • BAF has resubmitted the Alternate Compliance Plan using the EBD study results • This study demonstrated the applicability of EBD method to shorter buildings and stacks • Case study provides an opportunity to revisit the use of wind tunnel testing for regulatory purposes
- 24. Questions?