Urban Transport in the OIC Megacities
20
Internal combustion engine
vehicles can alternatively be
modified to use gaseous fuels
such as Auto gas or Liquid
Petroleum Gas (stored in
compressed or liquefied
form).
•One of the most inexpensive
fuels available
• CO2 emissions can be reduced
by around 30 percent
• Potential to extract the gas
from landfill or water/sewage
treatment
• Most gaseous fuels are still
derived from fossil fuels
Fuel cell electric vehicles
make use of hydrogen, the
most abundant element in
the universe. Most hydrogen
is presently formed from the
stream reformation of
methane, a process by which
the hydrogen atoms are
separated from the carbon
atoms along with emissions
of CO2. Reformation can take
place either on a vehicle
using a portable reformer or
could be installed as part of a
hydrogen infrastructure
allowing vehicles to refuel
with pure hydrogen.
• A high quality energy carrier
which can be readily converted
into electricity
• Hydrogen from electrolysis is a
sustainable fuel where the only
emission is pure water,
addressing not only greenhouse
gas emissions but also air and
noise pollution
• Hydrogen has the greatest
potential emission reductions of
any alternative fuel
• Proven popular with niche
applications such as the urban
bus market
• Does not occur naturally and
needs to be liberated from
chemical compounds
• Additional energy is required
for electrolysis
• Electrolysis is currently not
very efficient and just 51 percent
of the energy is actually utilised
after losses.
• Although hydrogen is light, it is
bulky making it expensive to
transport, store and distribute
• Requires a specialist
infrastructure
Battery powered electric
vehicles that also use fuel
cells to convert chemical
energy into electrical energy,
where the electricity
producing reactants are
supplied from an external
source.
• Zero emissions at source
•Electric motors increase
efficiency by 20 percent by using
a direct connection to the
wheels and therefore use no
power when the car is at rest or
coasting
• Additional energy production
can be derived from
regenerative breaking
•90 percent efficient compared
to 25 percent of traditional
internal combustion engines
•Fuel cells are continually
improving, e.g. low cost lithium
ion batteries
• The size of the fuel cells adds to
the weight of the vehicle and
constrains the performance of the
vehicle in terms of maximum
speeds and the distance vehicles
can travel before requiring
recharging
• No storage system is capable of
providing driving ranges
comparable to those of
conventional vehicles
• The source of energy used for
recharging is unlikely to be zero
carbon unless it is produced from
renewables or nuclear
Hybrid electric vehicles
provide an intermittent step
between the internal
combustion engine and the
electric motor. An energy
management system is used
to optimise the fuel economy
of both engines because
electric and combustion
engines work better under
different driving situations.
• Provides the advantages of
electric propulsion without the
need for fuel cells. Electricity is
created with on board
generators or recovered from
braking
• An intermittent technology
that can easily be adopted
• Technology still reliant on the
internal combustion engine
• Expensive, although grants are
often available to help with the
purchase but these rarely cover
the higher costs involved
Source: Chapman, 2007