Nonpropulsion System Improvements in Light-Duty Vehicles
Improvements to nonpropulsion systems can involve better tires with lower rolling resistance, body designs that reduce aerodynamic drag, and reductions in vehicle weight. Weight reduction can be achieved by using lightweight materials, by redesigning vehicles, and by reducing vehicle size. A 10 percent reduction in vehicle weight can reduce fuel consumption by 5–7 percent, when accompanied by appropriate engine downsizing at constant performance (Bandivadekar et al., 2008).
Summary of Potential Improvements and Costs for Light-Duty Vehicles
Table 4.3 shows plausible reductions in fuel consumption and CO2 emissions stemming from evolutionary improvements in LDVs as well as the use of new vehicle types. Evolutionary improvements could reduce the fuel consumption of gasoline ICE vehicles by up to 35 percent over the next 25 years. While diesel engines will also improve, the gap between gasoline and diesel fuel consumption is likely to narrow. Hybrid vehicles—both HEVs and PHEVs—could deliver deeper reductions in fuel consumption, although they would still depend on gasoline or other liquid fuels. Vehicles powered by batteries and hydrogen fuel cells need not depend on hydrocarbon fuels; if they were to run on electricity or hydrogen, they could have zero tailpipe emissions of CO2 and other pollutants. If the electricity or hydrogen were generated without CO2 emissions, they would have the potential to reduce total life-cycle CO2 emissions dramatically.
Table 4.4 shows the approximate incremental retail price of different vehicle systems (including the costs of emission-control systems), as compared with a baseline 2005 gasoline-fueled ICE vehicle. The estimates shown in Table 4.4, when combined with the estimates of fuel-consumption reductions shown in Table 4.3, indicate that from the driver’s perspective evolutionary improvements in gasoline ICE vehicles are likely to prove the most cost-effective choice for reducing petroleum consumption and CO2 emissions. Given that these vehicles will be sold in large quantities in the near term, it is critical that efficiency improvements in these vehicles not be offset by increased power and weight. While the current hybrids appear less competitive than a comparable diesel vehicle, they are likely to become more competitive over time, in part because hybrids can deliver greater absolute emission reduction than diesel vehicles can.
PHEVs, BEVs, and FCVs appear to be more costly alternatives for reducing petroleum consumption and CO2 emissions. Among these three technologies,