AirCRED:
Calculating Ozone Emission Reduction Credits for Clean Cities Vehicles
What is AirCRED?
To assist the U.S. Department of Energy’s (DOE’s) Clean Cities coalitions in estimating the ozone precursor and
winter season carbon monoxide emission reduction credits earned by acquiring original equipment
manufacturer alternative fuel vehicles, Argonne has developed a graphical user
interface-based calculation model called AirCRED.
Argonne’s goal was to provide an easy-to-use and
straightforward procedure to (a) enable the values of those credits to be summed together with Voluntary Mobile
Source Emission Reduction Program credits from other local voluntary strategies and programs earned
pursuant to EPA’s October 1997 guidance and (b) facilitate the calculation of mobile source emission inventories
and budgets required for development of State Implementation Plans (SIPs) responding to 2004 ozone and PM2.5
nonattainment designations.
How does AirCRED work?
AirCRED, written in Visual.net, presents screens to help you input data and then outputs information based on your input. AirCRED allows you to select options by clicking
on buttons from each screen and to enter your own data. AirCRED will lead you through a sequence
of data entry as you use your mouse and keyboard. You can print a copy of every
input and output (results) screen. You can also return to any data input screen
if you want to change the parameter values. AirCRED is user-friendly — each
screen tells you what to do in a straightforward manner, and a clearly understandable
result is provided at the end of the process. AirCRED is not rocket science — it's a handy tool for busy people.
Based on MOBILE. AirCRED is based on the U.S. Environmental Protection Agency's (EPA's) MOBILE
model combined with emission test certification data for new original equipment manufacturer alternative fuel vehicles and their gasoline- or diesel-fueled counterparts.
It starts with the MOBILE-computed emission factor (by vehicle type) appropriate
to (a) the midsummer ozone season or (b) midwinter carbon monoxide conditions.
The "clean gap" between AFV and gasoline or diesel counterpart emissions
of NMHC, carbon monoxide, and nitrogen oxide, according to season, determines the magnitude
of the net gram per mile credit that can be taken for AFVs in each
Clean City, relative to MOBILE's emission rates.
- For light-duty vehicles, credit is based on the entire chassis dynamometer-based
Federal Test Procedure, including supplemental tests.
- For heavy-duty diesel vehicles (transit and school buses and medium to heavy
trucks operating on natural gas), credit derives from engine dynamometer certification
data.
Results. AirCRED reports results in tons and pounds per day. You can then multiply this
value by the number of days that the AFV fleet operates over your entire ozone or carbon monoxide season to take the appropriate annual
credit. (A multiplier equal to the number of days in the year is inappropriate
because the emission factors applied reflect specific seasonal conditions.)
Current Version
The current version of AirCRED (version 4.2, July 26, 2006) allows you to save data entered in prior sessions by creating a unique username to log into the site on return visits. You can retrieve the inputs of a prior session by choosing the appropriate season and Clean City, so you can save data for more than one season and city combination.
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