Truck & Off-Highway Engineering - October 2021 - 32

Q&
A
Electrification and the other " E " - E-fuels
While " Electrification and Commercial Vehicles " was the ostensible
topic of Dr. Philip Stephenson's keynote at the recent
SAE COMVEC 2021 conference, the efficacy of e-fuels - or
renewable synthetic fuels - to reduce heavy-vehicle emissions
was brought up more than once.
" E-fuels are an often-overlooked topic, " said Stephenson, the
general manager of the PACCAR Technical Center. He explained
e-fuels are hydrocarbons created by combining " sequestered carbon "
with " green hydrogen " formed
by electrolysis. " Put in the back of
your minds, there's a lot of talk about
electric vehicles but there's this other
[technology], if the regulations went a
little bit different way, where our customers
could continue to operate like
they are, without some of the challenges
[of electrification]. "
PACCAR's praise of e-fuels was
Dr. Philip Stephenson,
general manager
of the PACCAR
Technical Center,
addresses the
2021 SAE COMVEC
crowd.
coordinated. In a separate COMVEC
session on electric propulsion, another
of the company's experts asserted
that combining hybrid powertrains
with e-fuels is a promising
short- to mid-term solution that further
reduces emissions.
Stephenson emphasized the importance
of well-to-wheels emissions
analysis. " Certainly, locally the
emissions from an electric vehicle
are zero, " he said. " One needs to
factor though the whole ecosystem;
there are emissions in manufacturing
battery systems, there are emissions
in producing energy in many cases.
Much of our energy in North
America comes from nonrenewable
sources like coal and natural gas. "
Hydrogen is another option gaining
steam, particularly for long-haul
trucking applications. Kenworth
collaborates with Toyota Motor
North America to develop zeroemissions
Kenworth T680 trucks
powered by Toyota hydrogen fuelcell
electric powertrains. Burning
hydrogen in combustion engines
also is possible, but Stephenson
points out that " burning it does
create some oxides of nitrogen. "
Following his keynote address,
Stephenson took a few questions
from the audience and expanded
on these topics.
32 October 2021
If e-fuels are so clean and easy to transport, store and use,
why are they overlooked?
What's really driving us towards not going the e-fuel route is
that most regulatory pressure right now is focused on local
tailpipe emissions, so zero local emissions. If we take a broader
well-to-wheels approach, if our regulators do that, we have
some more flexibility and transport mechanisms for energy
like liquid fuels could play a part going forward.
When you think about the charging
rate - the fastest charger we
have right now being 350 kW - the
energy going through your hand
when pumping gasoline into your
car, if you take the energy content
and the flow rate, you're 'charging'
your gas tank at 5 MW - 15 times
the fastest electric charger. Of
course, a diesel pump at a truck
stop is another order of magnitude
faster than that. So, there's a lot of
potential [for e-fuels] if the regulations
allow that as an energy transport
mechanism in the future.
[Stephenson did not discuss it,
but prohibitive pricing for at least
the next decade and a dearth of
green-hydrogen production have
been cited as potential barriers to
widespread e-fuel adoption.]
" If we take a broader wellto-wheels
approach, if our
regulators do that, we have
some more flexibility and
liquid fuels could play a
part going forward. "
Battery swapping could be an option
to avoid long charge times.
Why not do this with medium- and
heavy-duty vehicles?
This is my personal opinion: there
are a couple challenges with swapping.
These battery packs have
high-voltage connection between
the pack and the chassis. They have
a communication interface and very
often they have a cooling interface.
These interfaces typically are not
designed to be made and broken
once per day for 5,000 cycles, so
there's a durability risk that would
need to be overcome.
The other issue is what I like to
call the 'propane-bottle exchange
program.' If you have a propane
bottle on your grill at home and it
runs out, typically you don't go and
get it refilled, you swap it. That's
fine, because you pay $25 and you
TRUCK & OFF-HIGHWAY ENGINEERING
RYAN GEHM/SAE
Truck & Off-Highway Engineering - October 2021

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