Environmental Engineering Reference
In-Depth Information
of BEV. In this section the progression from CV to BEV will be investigated in
more detail.
Reducing CO
2
is paramount to any other innovation in the automobile that an
environmentally conscious manufacturer could pursue. Figure 1.13 from EIA, the
energy information agency of the US government, shows the components of annual
CO
2
emissions and some of the key contributors.
What is revealing in this chart is that petroleum (mainly transportation) and
coal (mainly electricity generation) are so close in recent times for annualized CO
2
emissions. Sadly, petroleum now outpaces coal in emissions.
Getting back to vehicle electrification actions, Figure 1.14 traces the energy
flow from 100 units of energy in the vehicle fuel tank through the engine, trans-
mission and driveline to the wheels. At the wheels the remaining energy must
overcome aerodynamic drag, tyre and driveline rolling resistance, inertial effects
and braking energy loss (which a hybrid can partially recuperate). In the hybrid
vehicle, aerodynamic and rolling resistance losses remain unrecoverable losses.
Engine thermal losses
62
Engine mechanical and
pumping losses
12
Driveline losses
3
Engine
Kinetic energy
braking losses
8
Fuel
gasoline, diesel,
methanol, CNG
Transmission
Fuel - 100
Start with 100 'units' of
gasoline fuel energy
Rolling resistance
3
Aerodynamic
losses
2
Transmission losses
9
Accessories
1
Figure 1.14 Energy flows in the conventional vehicle
Thermal management in the automobile is crucial because out of the
62 units lost in the ICE approximately 60% are rejected to the radiator and 40%
to the exhaust. This is important for energy harvesting where thermoelectric or
bottom cycle conversion can be used to recuperate some of this energy. Trans-
mission losses are mainly torque converter in the automatic transmission (AT)
plus gear mesh losses (~1.5%/mesh/stage), plus bearing and clutch friction los-
ses. Out of the 100 units energy input to the CV, only 13 units are available at
the wheels.
For BEV the energy flow diagram is far different, as shown in Figure 1.15.
Here, the energy originates at the charging plug (see Example 1) and is stored in the
vehicle on-board energy storage system, an electrochemical battery of an appro-
priate technology. The energy available at the wheels of the BEV is now 73 units
out of a stored 100 units. But caution is in order regarding the energy storage
component as the following example will illustrate. Currently, there is considerable
