3.2. Better transport http://www.ck12.org
Figure 20.1:This chapter’s starting point: an urban luxury tractor. The average UK car has a fuel consumption of
33 miles per gallon, which corresponds to an energy consumption of 80 kWh per 100 km. Can we do better?
We’ll start this chapter by discussing how to reduce the energy consumption of surface transport. To understand how
to reduce energy consumption, we need to understand where the energy is going in surface transport. Here are the
three key concepts, which are explained in more detail in Technical Chapter Cars II.
a. Inshort-distance travelwith lots of starting and stopping, the energy mainly goes into speeding up the vehicle
and its contents. Key strategies for consuming less in this sort of transportation are therefore toweigh less,
and togo further between stops. Regenerative braking, which captures energy when slowing down, may help
too. In addition, it helps tomove slower, and tomove less.
b. Inlong-distance travelat steady speed, by train or automobile, most of the energy goes into making air swirl
around, because you only have to accelerate the vehicle once. The key strategies for consuming less in this
sort of transportation are therefore tomove slower, and tomove less, and touse long, thin vehicles.
c. In all forms of travel, there’s an energy-conversion chain, which takes energy in some sort of fuel and uses
some of it to push the vehicle forwards. Inevitably this energy chain has inefficiencies. In a standard fossil-fuel
car, for example, only 25% is used for pushing, and roughly 75% of the energy is lost in making the engine
and radiator hot. So a final strategy for consuming less energy is to make the energy-conversion chain more
efficient.These observations lead us to six principles of vehicle design and vehicle use for more-efficient surface transport:a)
reduce the frontal area per person;b) reduce the vehicle’s weight per person;c) when travelling, go at a steady speed
and avoid using brakes;d) travel more slowly;e) travel less; andf) make the energy chain more efficient. We’ll now
discuss a variety of ways to apply these principles.
Figure 20.2: Team Crocodile’s eco-car uses 1.3 kWh per 100 km. Photo kindly provided by Team Crocodile.
http://www.teamcrocodile.com