Automotive Engineering - October 2023 - 19

COVER STORY
When Cadillac
unveiled the 2025
Escalade IQ, not only
did it emphasize
the various
customer comforts
and technologies
packaged in its
newest EV,
it also called
attention to
the heat pumpbased
thermalmanagement
system
that helps to optimize
energy use.
Otherwise, it is less efficient overall. "
This situation means thermal management -
which Douglas describes as " the underpinning of everything "
- has several functions to perform in an
EV, from maintaining the comfort in the cabin to handling
the thermal needs of the batteries and associated
onboard electronics.
Clever tech
This all results in a situation where engineers must
develop what Douglas calls " clever technologies. "
An internal-combustion engine generates waste heat
that can be used to condition the cabin in the winter. In
the summer, things are different. " Air conditioning has
never been free on the engine, " said Harry Husted, chief
technology officer at BorgWarner. " When the car is
sitting at idle and the air conditioning compressor kicks
in, extra fuel must be dumped in to generate the torque
to spin the air-conditioning compressor. "
Generally, that fuel is not considered to be a huge
loss. Husted points out that when EV owners fully
charge their battery pack, they want the vehicle to go
to the stated range. But there are more demands on the
battery than just providing energy to produce torque.
This means that action must be taken so that the use
of energy drawn from the battery is kept to a minimum
for non-propulsion needs and any waste heat is efficiently
used. " The more energy we pull from the battery,
the less we have for traction, " said Vitesco's Eser.
" That's the reason why we have to connect all the waste
energy in the system - from the e-machine, from the
battery, from the electronics - and put it all together.
The major difference between an ICE and a BEV is that
AUTOMOTIVE ENGINEERING
The BorgWarner 800V
high-voltage coolant
heater. It is a compact
unit that deploys
thick-film heating
and brazed aluminum
fin technologies and
facilitates heat transfer
for fast-charging
applications.
we have to be really careful with our precious energy. "
Bosch's Douglas says that whereas in ICEs " components were
largely thought of thermally in a discrete manner, " the approach they
are taking at Bosch for EVs is " looking at it holistically: what are demands
of subsystems and developing products and technologies to
move energy as efficiently as we can from one to the other. "
In other words, they are developing systems that determine where
there is a need for or an excess of thermal energy and apply it to or
extract it from those subsystems.
What's more, attention is paid to the ambient temperature and
using it when possible. BorgWarner's Husted says, for example, " If
you are trying to cool the battery pack, you might be lucky enough if
the battery is on the warmer side and the ambient air is on the cooler
side, so you can cool the coolant with outside air. "
At Bosch, Douglas said, the company even is considering solar energy
as an input to help with the energy load.
The packaging challenge
But there is a limiting factor that is being faced by those developing
thermal management systems for EVs: packaging.
Douglas said that for EVs, packaging is a key performance indicator.
Consider frunks, he said. Although there is space freed up from
October 2023 19
FROM TOP: CADILLAC; BORGWARNER
Automotive Engineering - October 2023

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