SAE Update - November 2021 - 27

SAE Fellows share powertrain thoughts
FOCUS:POWERTRAIN
AND PROPULSION
electric motors mean that a gearbox isn't
really necessary for normal driving but that
means that the available tractive effort at low
speed isn't as high as for an IC engine with a
ratio-changing transmission. This isn't such a
problem with normal driving where the tires
can break traction, but it is an effect on
gradeability and towing.
At King Abdullah University of Science
and Technology, I am working on
prechamber combustion systems and
optimized engines for hydrogen operation,
while also moving into solid oxide fuel cells
for transportation use. To me, the future
cannot be entirely serviced by the electric
motor and battery combination in the way
that the IC engine has served us to date.
That has truly been a silver bullet for
transport, and so trying to replace it with
only one thing will fail. Hydrogen provides
a means to recharge vehicles at a rate that
is important for any vehicle that is used for
commercial purposes.
Most heavy-duty vehicles earn money
only when moving, because people want
themselves and things transported by
them. Having vehicles stationary for a long
period while charging is commercially a
significant problem. Now, if one can
transfer hydrogen at 2 kg/min then that is a
charging (energy transfer) rate of 4 MW,
which is so massive compared to even 350
kW electrical charging that I would suggest
some inefficiency in the powertrain can be
allowed for because recharging is so quick.
This simple fact cannot be ignored
economically.
UPDATE
Piotr Bielaczyc, Ph.D.
SAE Fellow 2020
EVs are often called ZEVs, but this is not
true - until we invent a perpetual motion
machine! The ZEV appellation was used for
the first time in California, but California at
that time imported most of its energy from
other states, so in California EVs could be
called (almost) ZEVs, but in other states the
full CO2 emissions for these cars were
higher than for ICE-powered cars.
EVs are only as clean as clean the energy
that is used for battery charging, but even in
this case significant losses can occur in
power lines, transformers, chargers,and
batteries themselves.
Tank-to-wheel (TTW) is not a good
method to compare overall emissions from
EVs and ICEs. Well-to-wheel (WTW) or full
life-cycle analysis (LCA) should be used for
fair comparisons.
Hybrid vehicles would be a better solution
than EVs because their batteries could be
significantly smaller; the amount of rare
earths (and copper used for wires) would be
not as large and those vehicles could use the
November 2021
27
Piotr Bielaczyc is Vice
President of Polish
Scientific Society of
Combustion Engines.
SAE Update - November 2021

Table of Contents for the Digital Edition of SAE Update - November 2021
