Advanced Automotive Technology: Visions of a Super-Efficient Family Car

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Electric Vehicles. These are vehicles that rely on stored electrical energy (in batteries or, conceivably, in

a flywheel) as their sole energy source. Electric motors drive the wheels.

Hybrid Vehicles. Hybrids are vehicles that combine two energy sources in a single vehicle. For

example, an ICE may be paired with a battery or flywheel. In a series hybrid, both energy sources are

used to power one or more electric motors driving the wheels--the engine is connected to a generator

whose output power can be fed into the battery and, in some configurations, directly to the motor as

well. In a parallel hybrid, both the engine and electric motor(s) can directly drive the wheels.

Fuel Cell Vehicles. These are vehicles powered by an electrochemical device called a fuel cell, which

converts a replaceable fuel directly into electricity without combustion. Although considered separately,

they are a type of electric vehicle, and they are also likely to be hybrids.

Four classes of vehicles--subcompact cars, mid-size cars, compact vans, and full size, or
standard pickups--are modeled to capture the effect of size and fictional variations. These
market classes were chosen as they represent the two most popular classes of cars and light
trucks, respectively. Even with this size specification, however, manufacturers have the option of
varying body rigidity, interior volume (within limits), safety and luxury options, and acceleration
performance. In the last decade, all of these have increased significantly for almost every market
class of car and light truck. For this analysis, the median 1995 characteristics of vehicles in each of
the four segments are used as a reference, and these vehicles’ attributes are held constant to define
one maximum technology scenario. Other scenarios such as changed performance and increased
body rigidity are discussed only qualitatively.

We have set performance requirements as follows: Continuous power demand (i.e., power
output that must be sustained indefinitely) is set to a level that enables the vehicle to climb a 6
percent grade at 60 mph with a modest payload, which equates to about 30 kW (40 hp) per ton.
Of course, such a long grade is encountered rarely, but this requirement is to cover numerous of
other situations where the vehicle is fully loaded with five passengers and luggage, such as 55
mph climb up a 3 or 4 percent grade. Peak power demand is based on a O to 60 mph acceleration
time under 11 seconds, with a nominal load. This equates to about 60 kW (8O hp)/ton for a
normal gasoline drivetrain, but about 50 kW (67 hp)/ton for an electric drive because of an
electric motor’s excellent torque characteristics. We have required that peak power be sustained
for over one minute, to cover situations where two highway “merge” cycles are required back-to-
back, or the vehicle must climb a steep highway entrance ramp (for an elevated highway) and then
have enough power to merge into 70 mph traffic. Hence, the 60 kW/ton and 30 kW/ton power
requirements are to cover a wide variety of traffic conditions under full load, not just the example
cases cited above, and most ICE-powered vehicles meet these performance levels.

Vehicle Attributes

This report focuses on vehicles that might essentially replace the conventional ICE-powered

vehicles of our current light-duty fleet. There is some controversy about how well replacement

vehicles must perform to be viable candidates in a competitive market. Some analysts claim that

consumers are unlikely to accept vehicles that have important limitations in performance and