3.2. Better transport http://www.ck12.org
regenerative-braking system should probably use capacitors to store braking energy. Super-capacitors have similar
energy-storage and power-delivery parameters to the flywheel’s.
Figure 20.18:A flywheel regenerative-braking system. Photos courtesy of Flybrid Systems.
Hybrid cars
Hybrid cars such as the Toyota Prius (figure 20.19) have more-efficient engines and electric regenerative braking,
but to be honest, today’s hybrid vehicles don’t really stand out from the crowd (figure 20.9).
Figure 20.19:Toyota Prius – according to Jeremy Clarkson, “a very expensive, very complex, not terribly green,
slow, cheaply made, and pointless way of moving around.”
The horizontal bars in figure 20.9 highlight a few cars including two hybrids. Whereas the average new car in the
UK emits 168 g, the hybrid Prius emits about 100 g ofCO 2 per km, as do several other non-hybrid vehicles – the
VW Polo blue motion emits 99 g/km, and there’s a Smart car that emits 88 g/km.
The Lexus RX 400h is the second hybrid, advertised with the slogan “LOW POLLUTION. ZERO GUILT.” But
itsCO 2 emissions are 192 g/km – worse than the average UK car! The advertising standards authority ruled that
this advertisement breached the advertising codes on Truthfulness, Comparisons and Environmental claims. “We
considered that... readers were likely to understand that the car caused little or no harm to the environment, which
was not the case, and had low emissions in comparison with all cars, which was also not the case.”