POWER January 2023 - 38

HYDROGEN
nitrogen oxides, or NOx
. Without additional
mitigation strategies, burning pure
hydrogen can emit over 50% higher concentrations
of NOx
(in ppmv) in some circumstances
than pure natural gas due to
the higher hydrogen flame temperatures.
Several strategies can be used to reduce
or eliminate the increase in NOx
emissions, with some potential compromise
in output or efficiency. Even with
the potential to resolve the NOx
emissions
increases by other means, this issue
deserves attention in the discussion
about widespread use of hydrogen as an
energy source.
2. Based on approximately 16,000 TWh of fossil power generation in 2020; electrical demand
of 45,000 TWh in 2050, up from 25,700 TWh in 2020; 26,500 TWh of electricity required for
hydrogen via electrolysis to satisfy 10% of 2050 global primary energy consumption in nonelectricity
uses; all new capacity provided by renewables at 30% capacity factor; and 2020 existing
renewable and nuclear/other generation held constant to 2050 (EIA data). Results rounded
for illustration. Source: Mountain Pass Energy / Gary J. DiElsi
generating capacity of all kinds in 2020.
The International Energy Agency estimates
that in 2020 the world added the
largest amount of renewable capacity up
to that point in any single year-0.28 TW.
It would take more than 82 years at that
rate to add 23 TW of renewable capacity.
Note that if some of the hydrogen was
used for power generation (once fossil
power is completely displaced so all the
hydrogen would be brilliantly green), there
would be an offset from the hydrogen
power generated, but the overall power
requirement would still be immense.
These high-level projections of the
required renewable development do not
even consider the intermittent nature of
most renewable power-in particular,
solar and wind are not available when
it is " dark and still. " For intermittent renewable
power to displace fossil power
at any time of day, large energy storage
capabilities would be required to store
some renewable power for use when it
is not available. This is an even greater
obstacle to overcome, which adds significant
costs for the required facilities, and
the unavoidable losses of the store-andreclaim
process will increase renewable
power requirements even further.
The scale problems caused in part by
the intermittency of renewable power
could be alleviated by using nuclear power
(not generally considered to be renewable),
which has a much higher capacity
factor. While this would reduce the capacity
additions required, the required
development of new nuclear power
sources relative to that currently in use
would be equally staggering.
38
We Only Have Limited Resources-
We Must Make the Most of Them
The more fundamental issue highlighted
by these scale issues is the concept of
optimizing the use of limited resources.
We should be selecting technologies and
applications to maximize CO2
emissions
reductions, so we must select the highest,
best use of the limited resources we
have. From the arguments above, making
power from hydrogen using limited
dispatched renewable electricity only
makes sense after the current CO2
-emitting
electricity generation is displaced
and all growth is satisfied.
In that same light, other resources
required for green hydrogen production
must be considered. An often-overlooked
resource for electrolysis is the water required
to be split into hydrogen and oxygen.
Using green hydrogen to provide
just 10% of 2050 global primary energy
consumption would require about 1.6 trillion
gallons of water annually.
While some electrolyzers can tolerate
water of lower quality, many require a purity
that necessitates additional treatment
facilities for this water. Issues of sourcing
all this fresh water aside, these facilities
will add both capital costs and electricity
demand that are often not included in
discussions of the resources needed and
the emissions for green hydrogen.
Hydrogen Burns Free of CO2, but Not
Free of Pollution
While hydrogen can be converted to electricity
with a fuel cell or burned without
direct CO2
emissions, any combustion of
hydrogen involving air will still generate
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The Path to a Brilliantly Green Future
Hydrogen may hold great promise to
reduce CO2
emissions in a number of
specialized applications or to capture
curtailed renewable electricity when
it cannot be used. However, until we
add sufficient renewable power and
storage to ensure it is on the margin,
we should not convert our limited dispatched
renewable electricity on a
large scale to hydrogen power. Specialized
applications should be evaluated
through the lens of the net CO2
reduction
considering the new standard
of green hydrogen with the marginal
power supply, and against the CO2
reduction
achievable with alternative use
of the resources required.
To drive these outcomes, regulations
should be crafted to directly reward reductions
in CO2
emissions, and as such
must use the new standard to recognize
the difference between ordinary
green hydrogen and brilliantly green
hydrogen. Regulations and incentives
that subsidize the development of a particular
type of renewable energy rather
than emissions reductions run the risk
of rewarding investments with smaller
CO2
emissions reductions (or as shown
here, even emissions increases) at the
expense of those with larger reductions,
distorting incentives and slowing
the progress toward the ultimate goal of
reducing CO2
emissions.
Perhaps most importantly, we must
also be pragmatic about our ability to supply
the massive amount of renewable
power and other resources needed for
large-scale brilliantly green hydrogen generation
while we simultaneously strive to
decarbonize our grid and meet the continuing
growth in electrical demand in an
increasingly electrified world. ■
-Gary J. DiElsi is managing partner
of Mountain Pass Energy
(GaryDiElsi@MountainPassEnergy.com).
POWER| January 2023

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POWER January 2023

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