There are stringent legislative policies now in place across the EU to curb harmful emissions, ensuring future generations can enjoy cleaner
air and preventing irrevocable damage to the
environment. At the same time, increasing effort is
being made to reduce dependency on the planet’s
dwindling oil reserves.
These dynamics both point towards a migration
away from automobiles based on combustion
engines alone and heavier use of hybrid and electric
vehicles (HEVs). However, a series of obstacles
have prevented widespread HEV proliferation from
taking place. Recent technological breakthroughs have
demonstrated the challenges are surmountable.
Carbon emission levels have been addressed through
better air management and thermal management
systems, which has allowed a certain degree of engine
downsizing. The next major step toward reducing CO2
output will be increased usage of electrification and
hybridization. This reduces the load on the engine
(through more on-demand systems), and optimizes
the combustion engine efficiency.
Electric cars are becoming increasingly popular.
They already form the basis of many established
elements of modern automobile design. For example,
the replacement of hydraulic steering mechanisms
with electric power steering has led to significant
reductions in CO2 emissions (as much as 5 percent in
some models). Through uptake of HEVs, things can be
taken much further.
Though up until quite recently, automobile
manufacturers doubted their validity, commercial
acceptance of HEVs is taking place around the world.
Industry analyst firm Freedonia has predicted that
worldwide hybrid and electric vehicle (HEV) sales
will more than double between now and 2018.
Currently, Japan leads the way with regard to the
endorsement of HEVs (representing over 20 percent
of its annual vehicle sales). This is followed by North
America, then Europe —though in both of these
cases the percentages are far lower. Various types of
different HEV now exist, including micro hybrids,
mild hybrids, full hybrids, plug-in hybrids, and electric
vehicles. The options available stand as a testament to
the popularity and importance of the HEVs.
Improving Energy Efficiency
Vehicle manufacturers are looking at different ways
by which they can downsize engines and reduce
emissions. Turbos have long been able to optimize the
efficiency of conventional combustion engines as part
of their air management function (with lower CO2/
k Wh figures resulting). Turbos use high temperature
compressed exhaust gas to drive a secondary ‘cold
side’ circuit, compressing the air intake for the next
combustion cycle. Combinations of exhaust gas can
be fed into the secondary side air intake in exhaust
gas recirculation (EGR) systems, allowing compliance
with the strictest of emission standards—such as those
concerning nitrogen oxides (NOx), the other pillar in
the cleaner air mantra. One of the handicaps intrinsic
to turbos is the response lag caused because the turbo
only works once a certain RPM threshold has been
reached. Even with optimizations, such as variable
geometry turbines (VGTs), which maintain the
optimal aspect ratio as a function of the RPM, the lag
can never be eliminated. One solution to this problem
could be electric superchargers because compression
of the air intake is not achieved via the exhaust gas’s
high pressure, but through an electric motor, which is
effectively ‘on demand’, with no lag to worry about.
It is generally accepted that all cars will eventually,
at the very least, have start/stop functionality.
Nonetheless start/stop alone will not pave the full
road to the 2020 targets being carved in legislation.
The hybridization/electrification needs to be brought
to the next level.
Full hybrids normally rely on a 40k W to 70k W electric
motor, which works in tandem with the vehicle’s
combustion engine. Some of the most prominent
examples of full hybrid vehicles are able to reduce
CO2 emissions compared to equivalent combustion
engine models by as much as 35 percent. The electric
motor should be in operation for the whole time
The Increasing Adoption of
Hybrid and Electric Vehicles
A look at popular types of hybrid and electric vehicles.
By Bruno Boury, Melexis