United States Environmental Protection Agency Air and Energy Engineering Research Laboratory Research Triangle Park, NC 27711 Research and Development EPA/600/SR-95/004 February 1995 EPA Project Summary The Development and Improvement of Temporal Allocation Factor Files Theresa Moody, J. David Winkler, Terry Wilson, and Sharon Kersteter Emissions inventories have tradi- tionally been developed to produce estimates of annual or daily emis- sions. To be used as input to photo- chemical and other atmospheric simulation models, hourly emissions estimates are usually required. Ide- ally, hourly emissions would be mea- sured or calculated directly at the emissions source; however, this ap- proach is normally impractical due to technical and resource restraints. As an alternative, hourly emissions esti- mates can be obtained using surro- gate temporal allocation factors from "temporal profiles" assigned to spe- cific emissions source categories. Hourly emissions may then be esti- mated by applying the appropriate temporal allocation factors to avail- able annual, seasonal, or daily emis- sions values. This approach has been followed in previous air pollution studies, including the National Acid Precipitation Assessment Program (NAPAP) and the Northeast Corridor Regional Modeling Project. Since the performance of atmospheric simula- tion models is dependent upon the availability of accurate, temporally resolved emissions values, suitable methodologies and databases must be available to personnel responsible for developing the daily emissions es- timates needed for model inputs. The purposes of this project were to evaluate the quality and completeness of data and methods being used for temporal allocation of emissions data, to identify and prioritize needed im- provements to the current methods for developing temporal allocation factors, and to collect and use data to improve an existing temporal allocation factor (TAP) file. The TAP file will be used as a source of national default allocation factors by the emissions model pro- cessing systems that calculate tempo- rally resolved emissions estimates for model input. This Project Summary was developed by EPA's Air and Energy Engineering Research Laboratory, Research Triangle Park, NC, to announce key findings of the research project that is fully docu- mented in a separate report of the same title (see Project Report ordering infor- mation at back). Methodology Relevant literature references were iden- tified, acquired, and reviewed to evaluate the quality and completeness of data and methodologies being used for temporal allocation of emissions data. The most comprehensive set of temporal factors de- veloped to date was found to be those for the NAPAP effort. Major limitations of the NAPAP factors are that they were devel- oped only for the NAPAP point and area source categories and were incompletely documented. To augment these data, the following data sources were identified: Business and labor statistics data Department of Energy data pertain- ing to production/consumption from various energy industries California Air Resources Board (CARS) AB-2588 "Hot Spots" pooled source test reports ------- Texas Air Control Board (TACB) stationary source operating sched- ule data Southern Oxidant Study (SOS) data Lake Michigan Ozone Study (LMOS) data Continuous Emissions Monitoring (CEM) data Other data sources, including wastewater data from publicly owned treatment works; operating schedule/parameter data from re- source recovery facilities; acid- modes field study data; and Urban Airshed Model Emissions Prepro- cessor System temporal profiles Source Category Prioritization Emissions source categories were pri- oritized to ensure attention for categories that are major national contributors to air pollution. The prioritization reflected only point source data available from the Aero- metric Information Retrieval System (AIRS) Facility Subsystem. National area and mobile source emissions data were not available at the time of this study. To check for consistency with previous U.S. Environmental Protection Agency (EPA) efforts, high priority source categories listed in the September 24, 1992, Federal Reg- ister notice were reviewed. This notice listed industry groups and source catego- ries targeted for Maximum Achievable Con- trol Technology standard development. The comparison demonstrated consistency with the earlier prioritization effort. Temporal Allocation Factor File Development Data were collected for the high priority source categories. To process and com- bine these data, a number of intermediate data processing steps were required. The product of this effort was a single TAP file in a flat ASCII format. Figure 1 shows the final TAP file format. Key fields for this file are AIRS Source Classification Category (SCC) code, season (winter, spring, sum- mer, fall), and a day code (weekday, Sat- urday, or Sunday). For each record in the file, day and seasonal scenario fractions are given, along with flags to identify the sources of these data. The TAP file also includes hourly allocation factors for hours 00 through 24, along with a flag to identify the source of these data. The final TAP file resides on EPA's mainframe computer at the National Computer Center in Re- search Triangle Park, NC. A three-tiered approach was used to produce the final TAP file data. Tier 1 provided a baseline TAP file, covering all source categories, but including only monthly data. Tier 1 data are useful for constructing seasonal allocation profiles. These profiles were constructed predomi- nantly using monthly labor statistics and energy consumption data. Tier 1 data were used only for sources not included in Tier 2 or 3. Tier 2 data provide increased tem- poral resolution for a large number of cat- egories. Tier 2 data were created based on information from TACB, SOS, and LMOS for specific sources. These files provided hourly profiles. Tier 2 data were used for emissions sources not included in Tier 3. Tier 3 data were developed from CARS reports, CEM data, and other data sources. The data in the Tier 3 files repre- sent efforts focused on improving the de- fault operating profiles for a few important emissions sources. Tier 3 data are the most detailed and desirable data avail- able in the final TAP file. Analysis and Conclusions This project created comprehensive, well-documented, representative national default allocation profiles that may be used to generate hourly emissions estimates from annual estimates. The methodology used to create the TAP file is well-docu- mented, allowing future updates and im- provements. TAP profiles are based on Variable Name Field Format Field Width activity, rather than emissions, making them valid for allocating the emissions of any pollutant. Still, there are many source categories for which further improvements would be desirable. Detailed, Tier 3 level data could be collected and analyzed for high priority categories. A plan for analyzing the TAP file data was developed for this project. A limited implementation of the plan for the highest priority SCC categories revealed inconsis- tent and unexpected data for some SCC categories. Resources available for this project did not permit review of all SCC categories. Inconsistencies in TAP pro- files for electric utility boiler categories were traced to CEM data. It was determined that the CEM data obtained for this project were inappropriate for the calculation of TAP profiles. The CEM data, consisting of only concentration measurements, were found not to be accurate indicators of source activity levels. The CEM data were removed from the final TAP profiles for electric utilities. This project focused primarily on im- proving temporal profiles for stationary point sources. TAP profiles for many point source categories were improved as the result of this effort. A number of other data sources are available that could be Description/Validation SCC DAY_CODE SEA CODE Numeric Numeric Numeric DAY FRAC Real SEA FRAC Real SEA_FLAG DAY_FLAG HOUR FLAG Character Character Character HOUR1-HOUR24 Real 10 Source Classification Code (Point area or mobile) 1 Day scenario identifier (1=Weekday, 2=Saturday, 3=Sunday) 1 Season scenario identifier 1=Spring, 2=Summer, 3=Fall, 4=Winter) 7.5a Day scenario fraction (65 x weekday fraction) + (13 x Saturday fraction) + (13 x Sunday fraction) = 1.0 7.5 a Seasonal scenario fraction (Spring fraction + Summer fraction + Fall fraction +Winter fraction = 1.0) 4 Seasonal profile data source or combination method identifier 4 Daily profile data source or combination method identifier 4 Hourly profile data source or combination method identifier 7.5 Diurnal profile Field width for field type real is defined as X. Y, where X represents the field width and Y represents the allowable number of digits to the right of the decimal. Figure 1. Final TAF file format. 2 ------- used to improve point source data for additional categories and to expand the geographic base for point source tempo- ral data. The report lists recommenda- tions for additional data sets that could be examined. On the other hand, only one existing source of area source temporal data could be obtained for this study. To improve temporal profiles for area source categories, it may be necessary to collect new information through surveys of the most important source categories. This approach was beyond the scope of this project and would require additional cal- endar time and resources to design the surveys, obtain Office of Management and Budget clearance, and perform the sur- veys. One product of this study was sta- tistical methods for the analysis of temporal data. The application of these methods to quality assure the TAP file data would be appropriate. In addition, the development of computer software to access and ana- lyze the TAP file data was recommended. The availability of an improved TAP file does not eliminate the need to collect actual data for temporally resolved emis- sions when these data are needed for an emissions inventory. Whenever inventory development resources permit, actual data should still be collected and quality as- sured for inventory projects where sea- sonal, daily, or hourly emissions estimates are needed. The TAP file provides an improved database of default values that should be used when actual data cannot be collected. ------- Theresa Moody, J. David Winkler, Terry Wilson, andSharon Kersteterare with TRC Environmental Corp., Chapel Hill, NC 27514. Charles O. Mann is the EPA Project Officer (see below). The complete report, entitled "The Development and Improvement of Temporal Allocation Factor Files," (Order No. PB95-166153; Cost: $52.00; subject to change) will be available only from National Technical Information Service 5285 Port Royal Road Springfield, VA 22161 Telephone: 703-487-4650 The EPA Project Officer can be contacted at Air and Energy Engineering Research Laboratory U. S. Environmental Protection Agency Research Triangle Park, NC 27711 United States Environmental Protection Agency Center for Environmental Research Information Cincinnati, OH 45268 Official Business Penalty for Private Use $300 BULK RATE POSTAGE & FEES PAID EPA PERMIT No. G-35 EPA/600/SR-95/004 ------- |