Considerable uncertainty exists about how technology will evolve over
the next 20 to 30 years. While various studies differ in their estimates of
the exact magnitude of fuel consumption reductions possible and the costs
of doing so, the following conclusions can be drawn from these technology
and cost assessments (Weiss et al., 2000; GM/ANL, 2001; An et al., 2001;
NESCCAF, 2004):
Mainstream gasoline internal combustion engines (ICEs) and vehicle
technologies have significant potential to reduce energy consumption and
GHG emissions. These technologies can improve at a rate of 1 to 2
percent annually over the next 20 years, which translates to up to 35
percent reduction in energy use at constant performance, size, and weight,
at an additional cost of $500 to $1,500 per vehicle.
Diesel vehicles are likely to be about 20 percent more efficient than gaso-
line vehicles in about two decades, but the difficulties in meeting strin-
gent U.S. nitrogen oxide emissions standards, higher cost, and consumer
perception are significant obstacles to their large scale adoption.
Hybrid electric vehicles (HEVs), with batteries, electric motors, and ICEs,
can provide an additional 30 percent benefit in energy reduction at an
additional cost of $2,000 to $3,000 compared to the cost of conventional
ICE vehicles.
Fuel cell technology is currently very costly and probably a few decades
away in terms of making a substantial contribution to GHG emissions
reductions. However, in the longer term—roughly 30 to 50 years—fuel
cells could make a difference if the hydrogen used in fuel cells is made
from carbon neutral energy generation technologies such as renewable
resources, nuclear power, or fossil fuels with carbon sequestration.
It is not clear if the current price of fuels in the U.S. market, even at
levels above $2.00 per gallon of gasoline, can justify the development of new
technologies for improving fuel consumption performance. It is possible
that the current trend of sacrificing efficiency improvements for faster, more
powerful, and bigger vehicles may continue.
Projections of LDV Fuel Use and GHG Emissions
The potential effects of new technologies on LDV fuel use can be evaluated
based on a vehicle fleet simulation model developed by Bassene (Bassene,
2001; Heywood et al., 2004). The model examines car and light truck fleets
based on vehicle sales, retirement, average fuel consumption, and miles
driven per year. It allows the exploration of the sensitivity of fleet fuel use
to growth in driving, vehicle ownership, and the share of light trucks in
the fleet.
Different scenarios project the fuel use of LDVs under different market
and policy conditions. Examining these scenarios allows us to understand
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