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half by switching petrol and Diesel fuelled cars to equivalent electric powered vehicles even when using the
current methods of generation (see figure 11)
35
Figure 11 Carbon emissions from electric and other fuels
(A = present generating mix, B= Modest decarborisation, C= significant decarbonisation) Grey bar = 50/50
mix new gasoline and Diesel vehicles.
A meta-analysis of US data sources also suggests that electric vehicles would reduce CO2 emissions by between
0% to 59% when compared with ICE vehicles depending upon the electric generating source.
36
A further US
source estimates overall BEVs WTW energy efficiency to be 10-30% greater than that of a typical IC engine.
37
However, unlike fossil-fuelled cars BEVs have the potential to nearly eliminate carbon emission altogether by
using electricity generated from low carbon power sources, such as nuclear power stations and renewables.
Since the charging period could be varied in many situations, this would help to balance out supply and demand
in the grid network, allowing power stations to operate at their optimum for longer. The need for additional
nuclear build to meet stationary carbon targets would also create an excess of overnight electricity, which could
be used for charging electric cars (also see conventional output figure 26).
Whilst the environmental advantages of BEVs appear attractive, a major stumbling block to their widespread
use has been their limited range, or the high cost of batteries to travel longer distances. However this assumes
that large capacity vehicles that can travel long distances without stopping for recharging are essential. Later we
assess that this is not always the case and there may be other ways of circumventing this problem.
5.3.2
Economics and range of BEVs with different battery technologies
Whilst BEVs are superior to IC engined vehicles in terms of CO2 in urban driving situations, this will not
necessarily be the case at high speeds especially if the electricity is derived from coal power stations. Driving at
higher speeds for prolonged periods is a major limitation of BEVs since this rapidly drains the battery. The large
mass of batteries required to travel long distances also make BEVs expensive and reduce vehicle efficiency to
some extent due to the greater weight and rolling resistance. Advances in battery technology may reduce the
cost and increase the range of these vehicles, but it will remain very difficult for BEVs to compete with IC
engined vehicles whilst they are treated as isolated vehicles.
35 Low Carbon Transport Innovation Strategy DfT May 2007; Section 9.7 C emissions from replacement of the UK car and taxi fleet under
3 grid mix scenerios.
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