BREEZE AERMOD includes numerous time-saving tools to help with setting up a modeling run. One of these tools is the Hourly Emission File Editor. This modeling tip explains how to use that tool to easily use refined hourly emission rate data in your AERMOD runs.
AERMOD offers many options for capturing the variability of emission rates and other source parameters. Emission rates can be varied by season, day of the week, time of day, wind speed, and more. The highest level of detail that AERMOD allows is the hourly emission file. This option allows the user to specify a different emission rate, exit velocity, exit temperature, and source dimensions for each modeled hour. For example, if historical hourly emissions data is available for a source from a continuous emission monitoring system (CEMS), that hourly data can be paired with meteorological data from the same period to produce a much more refined modeling analysis than if fixed emission rates (usually conservative “maximum” emission rates) were used.
The data in an AERMOD hourly emission rate file must be organized in a very specific text format that can be very time consuming to manually create. To simplify the process, BREEZE AERMOD includes an Hourly Emission File Editor tool that allows the user to simply copy and paste hourly emissions data from a spreadsheet or database. Then, with a click of the mouse, the Hourly Emission File Editor saves the data in the exact text format required by AERMOD. The steps below demonstrate how to use the Hourly Emission file Editor.
- Open your project file in BREEZE AERMOD. The hourly emission rate file can be configured at any point after you have created your emission sources.
- Open the Hourly Emission Rate File Editor in by going to the Project Tab → Project Tools → Hourly Emission File Editor
- Choose the “Create a new hourly emission file” option and click OK.
- Specify the start and end dates for the period you plan to model, and select which sources will use the hourly emission rate data. BREEZE AERMOD allows you to use hourly rates for some sources and fixed emission rates for other sources - in that case, simply set the fixed rates normally (in the Data Tab, for example) and only select the hourly-varying sources here. In this example, all of 2013 is modeled and all sources in the model except “TRN8_TO ” will use a variable emission rate. Click OK once the dates and sources have been set.
- The tool will create a spreadsheet covering the specified time period and sources. The emission rate, exit temperature, and exit velocity fields will be blank. Note that if other source types are used (area or volume), the columns will have different meanings as shown in their headers.
- In the spreadsheet your hourly emissions data is stored in, you may need to do some preparatory calculations or reordering of sources. One important step at this point: AERMOD requires standard units (g/s emission rate, K temperature, m/s exit velocity), so make sure to do any necessary unit conversions at this point.
- Once any calculations have been done, simply click and drag to select the hourly emission data or use CTRL+C to copy it. Then single-click in the first blank cell of the Hourly Emission File Editor window and use CTRL+V to paste the data.
- Click on File → Save as… and save the file. It will have a .HRL extension. Close the Hourly Emission File Editor.
- To use the new hourly emission file you created, go to the Project Tab and click on “Source”.
- Go to the “Hourly file” tab, and check the “Include hourly emission rate file” box. Point the program to the location of the saved .HRL file you created and choose which sources the file applies to. Click OK and you are ready to run with your hourly emission rates!