POWER December 2021 - 5

SPEAKING OF POWER
Want Long-Term Energy
Storage? Look to Hydrogen
Aaron Larson
T
he power industry has been all
abuzz lately about the potential
role hydrogen could play in decarbonizing
the energy sector. POWER
was quick to notice the excitement surrounding
hydrogen, and launched HydrogeNext,
a conference designed to cover
the full hydrogen value chain from production
to distribution and end-use. The
inaugural show was held in conjunction
with the Experience POWER event in
San Antonio, Texas, Oct. 18-21, 2021.
Among the key takeaways from HydrogeNext
was how important hydrogen
could be in long-duration energy storage
schemes. " A lot of people who are looking
at green hydrogen-or hydrogen in general-are
looking at it as a fuel, " Paul Browning,
CEO of Mitsubishi Power Americas,
said during a panel discussion on the opening
day of the show. " We're looking at it
as an energy storage technology, " he said.
Browning acknowledged that it's more
cost-effective to store renewable power
for short durations, such as two or four
hours, with a battery energy storage system.
However, when storing energy for
a week, a month, or a season, hydrogen
quickly becomes the preferable option.
" In fact, when you get into those really
long timeframes, it's hundreds of times
more cost-effective than battery energy
storage, " he said. " So, to me, the relevant
question is: 'What does it cost relative
to other storage technologies?' And
in that sense, it's very affordable. "
Storing Hydrogen in Underground
Salt Domes
A few years ago, Mitsubishi Power identified
two projects that it thought could tie together
nicely with hydrogen. One was the
Intermountain Power Project. " It's in Delta,
Utah. It's the last coal-fired power plant
that's producing power for the state of California.
It's scheduled to be retired in 2025.
And it happens to be sitting right on top of
a huge salt dome, which is exactly the kind
of geologic formation that we need to store
large quantities of hydrogen for long periods
of time, " explained Browning.
Mitsubishi Power went to the Los AngeDecember
2021 | POWER
les Department of Water and Power, and
the Intermountain Power Agency, with a
proposal, and they ended up selecting Mitsubishi
Power's gas turbines to repower the
plant. The new 840-MW facility will produce
enough power to supply about one-fifth of
the City of Los Angeles, and the gas turbines
will be capable of using hydrogen for fuel.
The hydrogen is expected to come
from the second endeavor: The Advanced
Clean Energy Storage project. In that one,
Mitsubishi Power and its partners will use
220 MW of electrolysis to convert renewable
power into green hydrogen, which
will be stored in the big salt dome that
the power plant sits atop. " We're going to
put two caverns-each one about the size
of the Empire State Building-to store
massive amounts of green hydrogen for
long periods of time, " Browning said. The
company estimates the caverns will each
be capable of storing enough green hydrogen
to provide 150 GWh of clean energy.
It claims more than 40,000 shipping
containers of lithium-ion batteries would
be needed to produce an equivalent number
of GWh.
Cryogenic Hydrogen Storage
As novel as the Mitsubishi Power projects
are, there may be even more exciting work
taking place across town from the company's
headquarters near Orlando, Florida. At
the University of Central Florida, researchers
are trying to prove the feasibility of
an innovative hydrogen storage concept
called a cryogenic flux capacitor (CFC). Although
the name conjures up images of
Doc Brown's invention in the film " Back to
the Future, " this technology could be much
more important for the real-life future.
The project is based on a patent from
NASA's Kennedy Space Center (KSC).
Work is being led by experts from the
Southwest Research Institute (SwRI),
and in addition to researchers from UCF,
the team includes NASA KSC, Air Liquide,
and Turbine Technology Services.
The technology capitalizes on the energy
storage capacity of liquefied gasses. By
exploiting a unique attribute of nanoporous
materials-aerogel in this case-
fluid, such as hydrogen, can be stored in
www.powermag.com
a molecular surface adsorbed state. This
cryogenic fluid can be amassed at lowto
moderate-pressure densities, on par
with liquid, and then quickly converted to
a gas when the need arises.
The goal of the project is to store as
many fluid molecules as possible in the
smallest,
lightest-weight volume possible,
and to supply those molecules rapidly
on demand for end-use applications.
This solution would reduce both safetyrelated
logistics issues and the limitations
of complex storage systems.
Currently, high-pressure gasses are
stored in vessels with heavy, thick walls,
which is effectively what the salt dome
caverns offer. This type of storage requires
constant pressurization and complex
systems to limit boil-off. The CFC
addresses these issues, simplifying current
operations, and opening the possibilities
for new applications and new
markets from cryogenic liquid.
Aerogels are currently
commercially
available and have no significant barriers
to production. Furthermore, scalability of
materials is not an issue, as it may be for
lithium-ion batteries as their scale-up continues.
Estimates suggest that for a reference
CFC plant of 100 MW power output
with a 50% net thermal-to-electric efficiency,
100 hours of storage duration would require
9,090 cubic meters of space, which
could easily be accommodated at most
gas turbine power plants-a primary target
market for the technology.
" The design of a prototype for demonstration
is currently being developed by
the entire team, " Jayanta Kapat, a Pegasus
Professor and the director of UCF's
Center for Advanced Turbomachinery and
Energy Research, told POWER. " While
fabrication, testing, and demonstration
will be performed at UCF, and techno-economic
analysis for use of this technology
will be performed by SwRI. If proven to
be successful, this approach for hydrogen
storage will be superior to other existing
alternatives for integration into power
generation infrastructures in terms of
overall cost and ramp-up time. " ■
-Aaron Larson is POWER's
executive editor.
5
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POWER December 2021

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