Automotive Engineering - February 2023 - 20

TIME
FOR
HYDROGEN
Gill Pratt of the Toyota Research Institute is bullish on continued
tech improvements to lower stack costs.
Pajarito investor, Hyundai, is helping to fund a catalyst
manufacturing facility that will use the company's
VariPore process.
Costs also can be mitigated by design-engineering
the system for its specific application. " Every electrochemical
cell has some resistance to it, so the higher
the power draw or current, the greater the resistive
losses that occur within the cell, " Pratt explained. " The
stack's efficiency peaks under light power draw and
decreases as the power draw further increases. You
can use a stack that is bigger, to give higher efficiency.
Or you can use a smaller stack, which is lower cost,
lower mass, and fits better in the vehicle, but its efficiency
will be lower unless the platinum loading is increased.
Finally, we can vary durability with different
aspects of the design, which affects cost , " he noted.
Fuel cells offer many " dials to turn " to optimize
the system, the experts state. It comes down to the
amount you want to spend on initial system purchase,
versus its operating cost. To optimize total
cost of ownership, " you weigh them against each
other, " Pratt said.
Electrolyzers' role
Hydrogen is primarily produced by the reforming of
conventional hydrocarbons, typically natural gas (the
so-called 'grey' hydrogen in the accompanying
graphic). Electrolysis, a process in which an electric
current is run through water to produce streams of
hydrogen and oxygen gases, is gaining share in the
hydrogen-production market due to its ability to
generate the gas carbon-free if renewably-sourced
electricity is employed. McCormick calls the electro20
February 2023
At Parjarito Powder's prototype lab, a fuel cell assembly containing the company's
unique catalyst chemistry undergoes a bench test.
lyzers " the way forward " in making fuel cells a truly zero-emission
source of electricity, when the hydrogen is produced from decarbonized
sources.
" Electrolyzers are inevitable, " said GM's Freese, a 30-year veteran
of propulsion-systems technology development. " All the 'green' energy
like wind and solar on the grid introduces cyclical behavior
and irregularities in supply-and-demand that end up causing complexity
to the grid that makes it difficult to manage. The only way
to manage it may be to overcapacitize the grid for everything, then
underutilize the assets you put on the grid. But that's not economical.
You can do that on a transition, but it can't be sustained longterm
to operate an efficient grid. "
What's needed to balance the grid and run it at optimum levels,
Freese asserted, is the ability to store energy for long periods of time
- take it off the grid when there isn't natural demand for it.
" Hydrogen is an excellent way to provide that energy storage, if you
have electrolyzers to take the energy off the grid on demand. "
Freese noted that the optimum type of electrolyzer for this uses
the same PEM-based technology that GM and most others use in
their fuel cells, but with the chemical process running in reverse. In
2022 GM and Nel Hydrogen U.S., a subsidiary of Norwegian company
Nel ASA, began collaborating on more efficient, lower-cost and scalable
electrolyzers that then can be used as a way to do distributed
off-take power agreements with the grid. " It will also enable hydrogen
to be produced closer to the point of use for fleet refueling and
AUTOMOTIVE ENGINEERING
FROM LEFT: TOYOTA; LINDSAY BROOKE
Automotive Engineering - February 2023

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