Page 174 - Automotive Engineering Powertrain Chassis System and Vehicle Body

CH AP TER 7 .1 Hybrid vehicle design

Fig. 7.1-2 HYZEM research programme: (a) characterizing a hybrid powertrain; (b) use of vehicle per day; (c) daily distances and trip
lengths; (d) synthetic urban drive cycle.

and demonstrate, in quantitative terms, the tradeoff Confirmation was also given to such empirical
between emissions, electrical energy, and fuel consump- assessments that parallel hybrids give particularly good
tion. Only two standard test points are required to de- fuel economy because of the inherent efficiency of
scribe the almost linear relationship: fuel consumption at transferring energy direct to the wheels as against the
point of no overall change in battery state of charge series hybrids’ relatively inefficient energy conversion
(SOC) and point of electrical consumption over the same from mechanical to electrical drive. The need for
cycle in pure electric mode. A linear characteristic a battery which can cope with much more frequent
representing an ideal lossless battery can also be added to charge/discharge cycles than one for a pure electric-
the graph, to show the potential for battery de- drive vehicle was also confirmed. Although electric
velopment, as at (a). energy capability requirement is less stringent, a need

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