H2Tech - Q3 2021 - 33

HYDROGEN STORAGE
Long-duration H2
storage
in solution-mined salt caverns-Part 1
L. J. EVANS, Global Gas Group, Houston, Texas and T. SHAW, LK Energy, Houston, Texas
Hydrogen storage in solution-mined caverns can provide
fuel manage2.
Underground storage caverns
created in a salt formation
3. An energy distribution facility that delivers H2
gas
to a combustion gas turbine, gas engine, or fuel cell
for power generation; gaseous H2
supply industrial or mobility fuel markets, and/or
an interconnection to a load-serving H2
truck load-out to
pipeline.
Electrical utilities and other large industrial and commercial
energy consumers are adopting goals to increase the use
of renewable energy in response to government mandates and
customer preference. As a result, renewable generation capacity
(primarily wind and solar) now constitutes 23.4% of generation
capacity in the U.S.
However, matching intermittent and scattered renewable
energy supply with variable, often concentrated, demand is
difficult for several reasons:
* Solar is a diurnal resource
* Wind is weather-dependent
* Extreme hot or cold weather conditions that drive peak
demand are commonly associated with stagnant air
masses and low wind conditions.
The design requirement to reliably serve peak demand
with intermittent resources requires greater gross generation
capacity, a diversity of resources with lower utilization, and/
or combustion peaking capacity fired with carbon-based fuel.
The excess of capacity during seasonal low demand, peak solar
generating hours or transmission congestion increasingly results
in renewable energy being curtailed. These intermittent,
curtailed resources can produce " green " H2
, via electrolysis,
for the industrial gas and mobility fuel markets, if sufficient
long-duration storage is available to provide a rateable, reliable
supply at a predictable cost.
Salt caverns are ideal for long-duration H2
storage for a
number of reasons:
1. Withdrawal, or " discharge, " of H2
is highly
flexible in rate, duration and volume
2. With the proper surface facilities, HES
can simultaneously deliver stored energy
to multiple physical markets
Concentrated solar power
FIG. 1. Future H2 at-scale energy system.1
H2Tech | Q3 2021 33
Nuclear
H2 generation Other end use Metals
generation
H2
Other
end use
Metals
refining refining
Solar PV
utility-scale, long-duration energy storage to support grid integration
of renewable energy generation and H2
ment. An H2 energy storage ( " HES " ) facility consists of:
1. An H2 production plant using electrolysis,
steam reforming and/or other methods
3. Caverns are a mature, financeable storage
technology that have been successfully used for
storage of compressed gases for over 75 yr, and
for H2
specifically at six locations since 1972
4. At scale, solution-mined caverns have the lowest
unit cost of available storage technologies
5. The conditions appropriate for high-quality
renewable generation in much of the U.S. and
Europe, such as the western parts of the regions,
are coincident with areas of suitable salt deposits.
generation by electrolysis coupled with
Consequently, H2
salt caverns is uniquely suited to meet the market need to shift
excess off-peak energy to meet dispatchable on-peak demand,
and to match intermittent, often low-value, renewable generation
resources with stable, rateable, higher-value demand in
industrial and mobility markets.
Why hydrogen? H2
is increasingly viewed as the fuel of the
future (FIG. 1) because it is carbon-free, readily substituted into
electrical, mobility and chemical markets presently served by
natural gas, and meets the increasing need for dispatchable
power generation to match intermittent renewable generation
with asynchronous demand.2,3
HES uses electrolysis to convert surplus electricity to H2
stores H2 in the subsurface, and then uses H2
,
as fuel for power
generation, mobility applications or petrochemical feedstock.
However, due to H2
's small molecular size and high chemical
reactivity, it is more difficult to store than hydrocarbon natuValue-added
applications
Value-added
applications
Electricity
grid
Wind
Power
generation
H2
storage/
distribution
N2
Battery
NH3
H2 storage/
distribution
CO2
Synthetic
fuels
Upgrading
oil/
biomass
Upgrading
oil/biomass
H2/natural gas
infrastructure
H2/natural gas
infrastructure
H2 vehicle
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H2Tech - Q3 2021

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