http://www.ck12.org Chapter 3. Making A Difference
How to roll better
A widely quoted statistic says something along the lines of “only1 percentof the energy used by a car goes into
moving the driver” – the implication being that, surely, by being a bit smarter, we could make cars 100 times more
efficient? The answer is yes, almost, but only by applying the principles of vehicle design and vehicle use, listed
above, toextremedegrees.
One illustration of extreme vehicle design is an eco-car, which has small frontal area and low weight, and – if any
records are to be broken – is carefully driven at a low and steady speed. TheTeam Crocodileeco-car (figure 20.2)
does 2184 miles per gallon (1.3 kWh per 100 km) at a speed of 15 mph (24 km/h). Weighing 50 kg and shorter in
height than a traffic cone, it comfortably accommodates one teenage driver.
Hmm. I think that the driver of the urban tractor in figure 20.1 might detect a change in “look, feel and performance”
if we switched them to the eco-car and instructed them to keep their speed below 15 miles per hour. So, the idea
that cars could easily be 100 times more energy efficient is a myth. We’ll come back to the challenge of making
energy-efficient cars in a moment. But first, let’s see some other ways of satisfying the principles of more-efficient
surface transport.
Figure 20.3:“Babies on board.” This mode of transportation has an energy cost of 1 kWh per 100 person-km.
Figure 20.3 shows a multi-passenger vehicle that is at least 25 times more energy-efficient than a standard petrol car:
a bicycle. The bicycle’s performance (in terms of energy per distance) is about the same as the eco-car’s. Its speed is
the same, its mass is lower than the eco-car’s (because the human replaces the fuel tank and engine), and its effective
frontal area is higher, because the cyclist is not so well streamlined as the eco-car.