5.0 Fuel Economy
Fuel-cycle emissions, including CO2, correspond largely to the total volume of fuel produced. As such, fuel consumption is a strong driver in determining total fuel-cycle emissions. In general, as more fuel is produced, more feedstocks are extracted and transported, production facilities operate with greater throughput, and trucks and pipelines move more fuel to fueling stations. This section reviews the data inputs used in this study, methods for estimating fuel economy, and fuel economy assumptions that were used for the fuel-cycle analysis.
The goal of the study is to compare fuel cycle emissions from vehicles that are comparable to new Evs that would be produced in the year 2010. The analysis is aimed at a compact type vehicle that is consistent with many EV designs. Alternative fueled vehicles have been produced for a variety of vehicle classes. These include battery EV pick-up trucks and Evs designed for high energy efficiency. A comparison of vehicle types and fuel economy allowed for an estimate of fuel economy for consistent vehicles.
5.1 Fuel Economy Data and Projections
Fuel economy estimates for alternative fuel technologies were derived from comparisons of existing vehicles and model estimates for consistent vehicles. A consistent set of fuel economy estimates was determined by investigating the ratio of energy economy (mi/Btu) for alternative vehicle to comparable gasoline vehicles. These energy economy ratios (EERs) were then applied to a single baseline gasoline fuel economy. While gasoline fuel cycle emissions are not a part of this study, the baseline gasoline fuel economy provides a reference point for estimating alternative vehicle fuel economy.
The U.S. EPA measures fuel economy for all certified vehicles, the U.S. Fuel Economy Guides were used to determine fuel economies for current vehicles. Limited production alternative fuel vehicles are also certified and listed in the Fuel Economy Guide. Advanced technologies, such as hybrids and fuel cells are at the prototype stage, but some tests and model predictions have been made relative to their fuel economy. These sources have been used to predict fuel economy for vehicles produced in 2010.
According to the U.S. EPA, after a surge in average fuel economy during the late 70’s and gradual increases during the 1980’s, average fuel economy has been on the decline. Though per-vehicle fuel economy has remained steady or only slightly decreased, the market shift to heavier SUVs and light trucks in the 1990’s has brought the overall average down about 2.1 mpg to 25.9 mpg (U.S. EPA 1999). Figure 5-1 shows the U.S.