http://www.ck12.org Chapter 3. Making A Difference
In practice, hybrid technologies seem to give fuel savings of 20 or 30%. So neither these petrol/electric hybrids, nor
the petrol/hydraulic hybrid featured in figure 20.17 seems to me to have really cracked the transport challenge. A
30% reduction in fossil-fuel consumption is impressive, but it’s not enough by this book’s standards. Our opening
assumption was that we want to get off fossil fuels, or at least to reduce fossil fuel use by 90%. Can this goal be
achieved without reverting to bicycles?
Figure 20.20: Electric vehicles. From left to right: the G-Wiz; the rotting corpse of a Sinclair C5; a Citro ̈en
Berlingo; and an Elettrica.
Electric vehicles
The REVA electric car was launched in June 2001 in Bangalore and is exported to the UK as the G-Wiz. The G-
Wiz’s electric motor has a peak power of 13 kW, and can produce a sustained power of 4.8 kW. The motor provides
regenerative braking. It is powered by eight 6-volt lead acid batteries, which when fully charged give a range of “up
to 77 km.” A full charge consumes 9.7 kWh of electricity. These figures imply a transport cost of 13 kWh per 100
km.
Manufacturers always quote the best possible performance of their products. What happens in real life? The real-life
performance of a G-Wiz in London is shown in figure 20.21. Over the course of 19 recharges, the average transport
cost of this G-Wiz is 21 kWh per 100 km – about four times better than an average fossil fuel car. The best result
was 16 kWh per 100 km, and the worst was 33 kWh per 100 km. If you are interested in carbon emissions, 21 kWh
per 100 km is equivalent to 105 gCO 2 per km, assuming that electricity has a footprint of 500 gCO 2 per kWh.