Automotive Engineering - February 2023 - 19

COVER STORY
" If you're pulling 10,000+ pounds, an electric
truck is not the right solution. "
H2 in IC engines
While enormous progress in developing fuel cells, vehicle systems,
and hydrogen storage and generation solutions has been made and
continues, challenges remain - but engineers are confident they can
be addressed this decade. Hydrogen as IC-engine fuel, substituting
(with modifications) for diesel fuel in commercial-vehicle, stationary
and marine diesels, is controversial. The concept appeals both to diesel-engine
manufacturers and some fleet/equipment operators as a
near-term step while electrification issues are sorted out. Hydrogen
ICEs have been a focus of various OEMs, notably Daimler (which offered
a limited run of H2-fueled passenger cars), Toyota and
Cummins Engine, which is developing its own fuel cells but also sees
great promise for hydrogen with its diesel engine platforms.
Fuel-cell pioneer McCormick quickly disregards burning hydrogen
in a combustion engine: " They tend to make less specific power and
are thus less efficient than diesel, " he told SAE Media. " One reason
fuel cells match so well with H2 is that they're at least 2X more efficient
than combustion engines. So they make up in efficiency what
they lose in more-challenging [fuel] storage. "
Veteran combustion-engineering researcher Dr. David Foster at the
University of Wisconsin-Madison, notes " aspects of hydrogen as a
fuel that are really great. No carbon. Flame speeds are high. You can
go very, very lean with hydrogen, which is good. NOx is reduced and
you may be able to meet NOx emissions without aftertreatment.
Going very lean, with lots of boost, you can start to recover some,
but not all, of your max load limit.
" Viewing it as a system, there are challenges, " Foster admitted.
" The really high energy density that comes with each injection of
liquid fuel into a cylinder is very difficult to replicate with hydrogen
because you're injecting a gas. " He noted ongoing work by Mahle,
with its jet igniter, that's trying to overcome the limitations. Hydrogen
also causes metal embrittlement " so there are some materials issues
to deal with. Not trying to belittle the hurdles, but I classify these as
engineering challenges. In the end, there is nothing that's a stopper
for using hydrogen in an IC engine. "
Cost-reduction crusade
Engineers working in fuel-cell development who spoke with SAE
Media believe most of the technological hurdles of the stack and its
chemistries and ancillaries have been overcome. Continuing to prove
durability and cost reduction are near-term focuses, as are robust
and durable sealing solutions from source to end use: the tiny hydrogen
molecules are notorious escapees. The major cost reductions
that everyone is working on are a function of industrialization of internal
components and hardware. " For a long time, a big concern
was the cost of platinum [catalyst for the hydrogen and oxygen reactions,
determined by the U.S. Dept. of Energy to represent 40 perAUTOMOTIVE
ENGINEERING
Fuel cell architecture lends itself to modular designs that
are easily scaled for various applications. GM Hydrotec
'power cubes' (shown) contain more than 300 fuel cells with
integrated thermal and power management. Each is capable of
generating +80 kW. They're designed to be arrayed in multiple
units per vehicle depending on power requirements. A Class-8
semitractor requires 2-3 modules, a railway locomotive up to
25, to generate 3.3 MW. Aircraft and stationary power are also
in the works.
cent of overall cost at 500,000-unit/year volumes], "
noted Pratt at Toyota. " We've managed to lower that
amount in our latest version and we will keep on doing
that with future versions. "
In working toward platinum-free catalysts, innovators
are looking to reduce the platinum loading per fuel
cell. One of them is Pajarito Powder, a manufacturer of
fuel cell catalysts and electrolyzers. During a visit to
the company's Albuquerque, New Mexico, facility, company
CEO and co-founder Tom Stephenson explained
to SAE Media that Pajarito's quest is to make the diminishing
quantities of platinum in each fuel cell more
efficient. The black catalyst powder Pajarito developed
in a collaboration with LANL and the University of New
Mexico (which licenses the technology to Pajarito
Powder) is under evaluation within the fuel-cell industry.
Stephenson believes his company's patented technology
will reduce fuel-cell catalyst costs by half. One
February 2023 19
GM HYDROTEC
Automotive Engineering - February 2023

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