POWER May 2021 - 29

HYDROGEN
nearly 3,900 TWh of electricity annually,
roughly 60% more than the combined
global wind and solar photovoltaic generation
in 2020 (2,444 TWh).
At current capital prices, electrolyzers
meet the $2/kg threshold only when
running on " free " electricity 30% of the
time or more, dramatically limiting the
hydrogen supply. In 2020, 1.6 TWh of renewables
were curtailed by the California
Independent System Operator (CAISO),
enough for approximately 28.9 kilotons
of H2
production. However, analysis of
CAISO data shows that only 50 MW of
electrolyzers could achieve a 30% capacity
factor on curtailed energy (Figure 1),
enough to produce only 451 tons of H2
.
While hydrogen is viewed as a solution
to renewable curtailment, converting
excess power to hydrogen that can
be later reclaimed in a turbine or fuel cell
(power-to-gas-to-power) can amount to
a 70% energy loss. For most grid storage
needs-typically several hours at
most-the less than 10% roundtrip
losses of battery storage represent a
considerable advantage.
Chemical energy storage (including
hydrogen) does represent the only
technically feasible and widely scalable
approach to inter-seasonal storage of renewable
energy, but the demand for this
duration only becomes meaningful for renewable
penetration greater than 70% of
demand. Thus, oversupplied renewables
are unlikely to catalyze transformational
use of hydrogen in a timely fashion.
Weighing Hydrogen Options
Hydrogen is best suited to decarbonize
certain difficult-to-abate sectors of the
economy, specifically heavy road freight,
shipping, aviation, chemicals, cement,
and iron and steel manufacturing. These
sectors account for a combined 30% of
global greenhouse gas emissions and
are challenging to electrify. In contrast to
load shifting of renewables, each of these
sectors would have nearly continuous demand
for hydrogen. Thus, those demand
centers for which hydrogen has the best
value proposition are least served by the
capabilities of intermittent, green hydrogen
or require additional costs associated
with storage.
The simplest " solution " to curtailment
would be higher demand on the grid.
However, in a business model where the
electrolyzer is used to maximize utilization
of a renewable resource by avoiding curtailment,
the grid will not see increased
demand, ensuring supply is intermittent.
It is not currently economically feasible
May 2021 | POWER
2. The Department of Energy (DOE) partnered with Air Products Inc. to advance a first-ofa-kind
retrofit system to capture carbon from large-scale industrial steam methane reformer
plants located at the Valero Port Arthur Refinery in Port Arthur, Texas. The project was funded by
the DOE's Office of Fossil Energy, and co-managed by NETL and Air Products. Courtesy: NETL
for most industries to buy power from the
grid to generate green hydrogen continuously.
Conversely, blue hydrogen is decoupled
from power supply and, in many
geographies, leverages low-cost and continuously
available natural gas.
Taken together, there is a clear need
for blue hydrogen to satisfy growing enduses
at affordable pricing and finance the
necessary midstream infrastructure to
sustain growth of the hydrogen economy.
The ubiquity of shale gas plays, along with
growing natural gas infrastructure and CO2
storage sites, creates an opportunity for a
geographically diversified hydrogen economy
and rapid decarbonization. However,
early leaders in the green hydrogen economy,
such as Germany, have left little political
room for blue hydrogen. A substantial
risk exists that a planned obsolescence of
blue hydrogen will limit the participants in
this ecosystem and lead to financing difficulties,
particularly for new capacity.
Despite current advantages of blue hydrogen,
work is still needed to realize a
hydrogen transformation. These challenges
center on the carbon intensity of existing
gray hydrogen production designs
and the relative immaturity of the carbon
sequestration industry. The predominant
mode of gray hydrogen production, steam
methane reforming with a water-gas shift
reaction, will need to be retrofitted to
capture two streams of CO2
: a flue gas
from natural gas combustion for heat and
a process gas stream under pressure. Alternatively,
a shift to auto-thermal reforming
would make CO2
capture considerably
simpler, albeit with decreased hydrogen
yields, and provide blue hydrogen with
lifecycle emissions comparable to those
of green hydrogen from wind and solar.
Once captured, from the current
state of the art or future production
processes, the CO2
must be stored or
utilized. Enhanced oil recovery by CO2
injection is a mature technology, yet, it
is likely to be met with intense scrutiny
as it relates to the market requirement
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of carbon-free hydrogen.
The U.S. Department of Energy, Office
of Fossil Energy's National Energy
Technology Laboratory (NETL) has unique
capabilities and experience to help realize
the potential of a transformed hydrogen
economy and is making investments
across the value chain (Figure 2). NETL is
already determining how to address nearterm
technical gaps with increased use
of hydrogen in both pipelines and power
plants. NETL's advanced turbines program
is enabling the next generation of turbines
to operate efficiently with higher ratios of
hydrogen fuel.
Work at NETL is targeting improvements
to conventional natural gas reforming
methods for hydrogen, as well
as exploring more novel hydrogen production
technologies, including methane
pyrolysis with solid carbon co-production
and
coal/biomass
co-gasification
with
CCUS for carbon-negative hydrogen. In
the mid-term, NETL investment, and research
and development (R&D) in carbon
capture technology, will enable blue hydrogen
to be produced cost-effectively.
NETL is also addressing longer-term
R&D challenges, such as hydrogen storage,
and working with external partners
to assess technical gaps. NETL's systems
analysis capabilities are investigating blue
hydrogen production economics, end-use
markets, and infrastructure constraints.
Finally, realizing the decarbonization potential
of hydrogen demands a collaborative
ecosystem of technology developers,
end-users, and regulators. NETL is wellpositioned
to support each of these stakeholder
groups in rising to this challenge. ■
-Clinton Noack, PhD is a senior consultant
focused on research and development,
and innovation strategy, for NETL's
Crosscutting Materials, Water Management,
and Advanced Energy programs; and
Briggs White, PhD is technology manager
for High Performance Materials, Water
Management, and Energy Storage
with NETL.
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POWER May 2021

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