PhD Thesis - Energy Systems Research Unit - University of Strathclyde

the conversion of petrol cars; however, specially designed vehicles take these
issues into account.
The use of alcohol-fuelled vehicles is well tested, and has achieved great success
in countries such as Brazil [16]. A variety of flexible fuelled vehicles (FFVs)
are available which can run on 100% alcohol (ethanol or methanol), 100%
petrol, or a combination of the two [8-13,17-19]. This type of vehicle uses an
internal combustion engine (ICE), which is able to sense the percentage of
alcohol in the mixture, and adjust its parameters accordingly. The use of alcohol
as a fuel does still produce various emissions, though these are substantially
lower than if using petrol or diesel. However, as the carbon dioxide produced
by these vehicles is reused when growing the crops used to make the alcohol,
this process is classed as carbon neutral [7]. Fuel cell vehicles are also being
developed with on-board fuel reformers that convert the alcohol to hydrogen,
and it is estimated that these will achieve 2.1 to 2.6 times greater fuel efficiency
than using the alcohol in an ICE [20]. The efficiency of an FFV is comparable
to a petrol engine.
Fuel cell powered vehicles can run on pure hydrogen, producing clean water as
the only emission. They are also being designed to run on alcohol, biogas or
even petrol, with onboard reformers converting these fuels into hydrogen.
These latter vehicles, therefore, still produce some emissions, though fuel
efficiencies are greater than equivalent use in ICEs. The use of fuel cell vehicles
is less established than the other types of vehicle being considered here, and,
although a number of buses are in operation, commercially available cars are
still three to five years away from the market, so little performance data is
available from manufacturers [13,19,21].
Biodiesel can be used directly in a diesel engine with little or no modifications,
and burns much more cleanly and thoroughly than diesel, giving a substantial
reduction in unburned hydrocarbons, carbon monoxide and particulate matter.
This does still produce carbon dioxide, but this is balanced by the continued
growing of the crops used to produce the biodiesel [7]. It is a well-tested fuel,
and experience shows that the fuel consumption of a diesel vehicle in litres
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