Schriftenreihe .;technologiekompetenz Verkehr in

HYBRID ELECTRIC VEHICLES
TECHNOLOGICAL CHALLENGES
Given the focus on maximum reduction of fuel demand and
emissions, the significance of electric propulsion will increase
further. Different constraints have to be considered for the
development of new concepts and their broad market
introduction. From the ecological, economical and legislative
point of view, vehicles need to offer maximum energy
efficiency, with lowest possible CO 2 emissions and fuel demand,
to be in line with current and future regulations.
The integration of both conventional and electric powertrain
components significantly increases the weight of the entire
powertrain. From the customers’ point of view, the new
concepts have to provide at least the same performance and
drivability as conventional vehicles. In addition the costs have to
be kept as low as possible, since higher costs for additional
powertrain components (e.g. electric machine for hybrids,
energy storage system) hinder broad market introduction. The
development of highly integrated as well as highly optimised
subsystems is therefore essential for the launch of competitive
products.
In case of PHEVs, an appropriate charging infrastructure is also
required, which has a knock-on impact on grid management and
the energy supply. This leads to a complex set of issues that
have to be considered and integrated in the development of
new vehicles. Table 2 summarises the main research topics
relating to HEVs.
16 Austrian Technological Expertise in Transport
Batteries are one of the key components for electric and hybrid
electric propulsion, since they define the performance and range
of the vehicle. Almost all HEVs initially sold used nickel-metal
hydride batteries (Ni-MH); this battery type has been
successfully implemented in Mild and Full HEVs. Current battery
technologies have shown major progress in recent years, but
with regard to HEVs the costs, weight, safety and life time of
the batteries still need to be improved significantly. Lithiumbased
batteries, in particular, offer good potential for advanced
HEVs, but some cell types still arouse major safety concerns.
R&D efforts now strongly focus on lithium-ion batteries (Li-ion)
which are expected to be implemented in the next generations
of HEVs and PHEVs, but development efforts are still required at
both cell and systems level. In general, it needs to be
appreciated that selecting the appropriate cell type – as well as
the design of the battery management system – depends on the
given application. Further efforts are also required to realise
highly efficient and optimised systems based on low-cost
components and highly integrated subsystems.
Concerning the PHEV concept, additional issues to be
considered are the availability of the charging infrastructure and
the additional costs caused by integrating more powerful electric
powertrains and larger batteries.