Hybrid Electric Vehicles: OverviewH Kabza,University of Ulm, Ulm, Germany & 2009 Elsevier B.V.. Introduction Road traffic is one of the major consumers of energy, par-ticularly in wester
Trang 1Hybrid Electric Vehicles: Overview
H Kabza,University of Ulm, Ulm, Germany
& 2009 Elsevier B.V All rights reserved.
Introduction
Road traffic is one of the major consumers of energy,
par-ticularly in western industrialized countries, and globally it
exhibits the highest growth rate in energy consumption of
all sectors In the Organisation for Economic Cooperation
and Development (OECD) countries, more than 33% of
the total final energy consumption goes into the
transpor-tation sector, amounting to more than 11% of the world’s
total primary energy consumed
Virtually all of these vehicles are operated with
in-ternal combustion engines (ICEs) fueled with gasoline,
diesel, or – to a very lower extent – different kinds of
gases (compressed natural gas (CNG), liquefied
pet-roleum gas, liquefied natural gas) or biomass-based fuels
(bio-diesel, ethanol, or vegetable oil)
The combination of two factors made this enormous
quantitative development possible within a century: on the
one hand, the robustness and easy scalability of the
ther-modynamic conversion process from heat to mechanical
energy in the ICE; on the other, the extremely favorable
properties of liquid hydrocarbons as energy carriers, that
is, their unparalleled energy density in terms of weight
and volume, easiness to handle, and the seemingly
abundant availability from oil wells Only the problems associated with the enormous input and output quantities and their implications on a global scale bring the de-ficiencies of the ICE more clearly into view today: it ex-hibits an only very small operational regime with optimum efficiency, and this optimum efficiency is rather poor, approximately between 35% and 45% (cf.Figure 1) Moreover, in practical applications, this optimum effi-ciency regime is used only occasionally, if at all, and there are undesirable emissions associated with the combustion process
In addition, as ICEs do not provide any torque at zero speed, they need an electric motor (EM) for starting, and there are more or fewer idling phases depending on the driving situation
In contrast, an EM is ideal for traction applications It does not consume energy at standstill and provides maximum torque at zero speed It can be operated re-versely not only in the direction of rotation but also by acting as a generator, that is, converting mechanical en-ergy on the shaft into electrical enen-ergy, thus enabling regenerative braking in this way Furthermore, EMs allow short-term overloads, the extent and duration of which depend on the construction of the machine and cooling
240.0 220.0 200.0 180.0 160.0 140.0 120.0 100.0 80.0 60.0 40.0 20.0 0.0
Speed (rpm)
40
20 38 40%
34 36
10 34 32 30 28
20
20 22 24 20 30
50 30 32 34
38 50
70 80
60 36
Figure 1 Typical efficiency map of an internal combustion engine (turbo direct injection diesel) with contour lines of constant efficiency and hyperbolas of constant power in kW Source: EPA; http://www.researchcaucus.org/docs/Charles_Gray_Talk.ppt as of 20 March 2007.
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