Possible Routes Towards Carbon-Free Vehicles - Hydrogen Fuel Cells for Road Vehicles - page 28

storage capacity. All these organizations have individuated goals to be met by the
innovative batteries in order to fulfil the requirements of electric vehicles
acceptable by the market. As an example, in the United States the Advanced
Battery Consortium (USABC), founded in 1995 by Ford, General Motors and
Chrysler in cooperation with Department of Energy (DOE) have proposed that a
BEV battery should be able to store at least 200 Wh/kg to afford the vehicle an
acceptable driving range [ 59 ], and this value is generally accepted as term of
progress for battery development programs worldwide. For comparison the spe-
cific energy value established by USABC for future acceptable batteries and the
value for gasoline are also reported in Table 1.8 . The actual specific energy data
evidence in detail the fundamental problem of today battery vehicles, i.e. the
driving range connected to limited specific energy of the currently available bat-
teries (maximum 50 Wh/kg for NiMH, and lower values for Pb/acid). On the other
hand, also with lithium systems, which are the presently more promising batteries
still under development, storage capabilities compatible with transportation
applications are not reached (maximum 150 Wh/kg for lithium/ion). The data of
Table 1.8 show also the very significant potentialities of metal air systems (also
regarded as semi-fuel cells, since the oxidant is supplied from outside), in
particular Al/air batteries offer a theoretical specific energy of almost the same
order of magnitude than gasoline, and an actual value about two times higher with
respect to USABC target. However, while lithium systems are in phase of
advanced development [ 62 ], the metal/air batteries require intense efforts of basic
research since they still present important limitations which affect not only actual
OCV and specific energy values, but also power capabilities and durability [ 58 ].
The electric drivetrain is the common denominator for alternative propulsion
systems able to favor the introduction of carbon-free energy resources into the
transport sector, but the possibility to follow for these systems the most efficient
well-to-wheels path is based on the widespread diffusion of BEVs. Since these
types of electric vehicles are totally dependent on batteries as on board energy
source, and the electric storage systems require significant improvements far to be
reached, the extensive affirmation of BEVs appears as a long-term solution. On the
other hand, the urgency of giving fast and reliable answers to the problem of
anthropogenic greenhouse effect imposes scientists and policy makers to suggest
ways practicable on near and mid-term.
In this view, the approach of energy saving should be properly considered as the
first goal to be pursued by any energy policy, independently of nature of the
primary resource. At this regard an estimation of IPCC has argued that by the end
of this century at least 30% of worldwide energy demand could be satisfied by the
consequences of energy saving policies, rather than by novel clean technologies
[ 50 ]. The concept of energy saving should be applied to any type of technology
involved in human activities, such as buildings, industries, production processes,
but above all to the transport sector, with obvious reductions of emissions and
crude oil usage when conventional vehicles are considered. The examination of
Table 1.5 , 1.6 , and 1.7 clearly evidences which are the paths able to favor the
introduction of more efficient transport solutions on near-term, without completely