Emissions Analysis Techniques for TCMs
Overview - The AirCred model estimates emissions benefits from the fleet use of alternative-fuel vehicles. The model is designed to assist states in estimating emissions credits for non-attainment areas and to help fleet operators meet the Department of Energy's Energy Policy Act fleet-conversion and alternative-fuel market penetration goals.
Strategies Addressed - Alternative-fuel vehicles.
Methodology - The model compares current year alternative fuel vehicle certification values with conventional fuel vehicle emission factors from the MOBILE model. The same incremental benefit is assumed for future years. The model is based on current, area-specific MOBILE inputs for a variety of metropolitan regions throughout the country. Versions using both MOBILE5a and MOBILE5b outputs are available.
Data Requirements - AirCred requires data on the number of new alternative fuel vehicles delivered for last year and the current year by vehicle and fuel type, the average daily distance driven, and the average number of days per week the vehicle is in use. Additional information on vehicle usage patterns is required to compute cold start credits. Vehicle types include light-duty vehicles, light-duty trucks, transit buses, and school buses. Fuel types include compressed natural gas (CNG), liquid propane gas (LPG), and electric. Dual-fuel vehicles can also be included.
Outputs - Emission "credits" (reduction in total and/or cold start emissions) per day for NMHC, CO, and NOx.
Level of Effort - AirCred is easy to use.
Advantages - The model provides a quick way of estimating the emission benefits of alternative-fuel passenger vehicles and buses. The emission rates in the model are based on the best available current information.
Limitations - AirCred is not designed to calculate future year benefits, only current year benefits. Therefore, emission benefits for planned future year purchases may be different if emission standards or deterioration rates for these vehicles are different.
Source/Availability - The AirCred model is available through the Department of Energy's web site (http://www.fleets.doe.gov/). It was initially developed in 2000, and emission factors will be updated regularly.