Page 76 - North American Clean Energy March April 2015

energy storage

Geological Storage

Holding hydrogen for electric Salt caverns, such as the one
depicted here, could provide a
vehicles & more
low-cost solution for the geologic

storage of hydrogen. he colors in
the illustration represent depth,
with blue as the deepest part

In the power market, the amount of electricity that can be generated is often relatively of the cavern and red the most
ixed over short periods of time, even if the demand is not. his is especially true for shallow (Image courtesy of Sandia
renewables, as the sun isn’t always shining and neither is the wind always blowing. Not National Laboratories)
surprisingly, the energy storage industry has evolved over the last few years, converting

energy from forms that can be diicult to store, into more economically storable and us-
able forms.
Usually, this involves a battery. However, when it comes to storing energy for the grow- To examine the cost of geologic hydrogen storage, Lord started by selecting geologic
ing fuel cell and electric vehicle market, researchers have begun to study the possibility of formations that currently store natural gas. Working with Sandia economist Peter Kobos,

geologic storage via the use of underground formations. Large-scale storage of low-pres- Lord analyzed costs to store hydrogen gas in depleted oil and gas reservoirs, aquifers, salt
sure, gaseous hydrogen in salt caverns and other underground sites, for example, could be caverns, and hard rock caverns. (Note: heir paper, “Geologic storage of hydrogen: Scaling
advantageous for transportation fuel and grid-scale energy applications.
up to meet city transportation demands,” was published in the International Journal of
According to a study* recently released by the Sandia National Laboratories, and spon- Hydrogen Energy).

sored by the Department of Energy’s Fuel Cell Technologies Oice, geologic storage solu-
tions can service a number of key hydrogen markets and ofer several advantages over Meeting peak period storage
above-ground storage.
Geological storage isn’t anything new. In fact, other fuels are already stored geologically.
Case-in-point: Geologic storage of hydrogen gas could make it possible to produce and Oil from the Strategic Petroleum Reserve, for example, is held in large man-made caverns

distribute large quantities of hydrogen fuel for the electric vehicle market. “[As] costs are along the Gulf Coast. Natural gas is stored in more than 400 geologic sites to meet winter
more inluenced by the geology available, rather than the size of the hydrogen market de- heating demands.
mand,” explained Sandia Lab’s Anna Snider Lord, the study’s principal investigator.
Lord envisions that excess hydrogen produced throughout the year could be brought to
Storage above ground requires tanks, which cost three to ive times more than geologic geologic storage sites, and then piped to cities during the summer, when the demand for

storage, Lord said. In addition to cost savings, underground storage of hydrogen gas ofers driving fuels peaks. It seems depleted oil and gas reservoirs, as well as aquifers are most
advantages in volume. “Above-ground tanks can’t even begin to match the amount of hy- economically attractive options for now.
drogen gas that can be stored underground,” she said**.
“Just looking at numbers,” said Lord, “because they can hold such a larger volume rela-
his research could provide a roadmap for further research and demonstration activities, tive to any cavern you create, they look cheaper.”

such as an examination of environmental issues and geologic formations in major metro- But hydrogen gas is a challenging substance to store. “Because it’s a smaller molecule
politan areas, which could hold hydrogen gas.
than methane, for example, it has the potential to leak easier and move faster through the
rock,” Lord said.
Advancing hydrogen’s potential
Depleted oil and gas reservoirs and aquifers could leak hydrogen, and cycling—illing a

Should the market demands for hydrogen fuel increase with the introduction of fuel cell storage site, pulling hydrogen out for use and reilling the site—apparently, can’t be done
electric vehicles, the United States will need to produce and store large amounts of cost-ef- more than once or twice a year to preserve the integrity of the rock formation.
fective hydrogen from domestic energy sources, such as natural gas, solar, and wind power, With a salt cavern or hard rock cavern, “there are no permeability issues, there’s really no
acknowledged Daniel Dedrick, Sandia hydrogen program manager.
way anything can leak,” Lord explained. “You can bring more product in and out, and that

As Toyota, General Motors, Hyundai and others move ahead with plans to develop and will, in the long run, decrease your costs.”
sell or lease hydrogen fuel cell electric vehicles, practical storage of hydrogen fuel at large Hard rock caverns are relatively unproven; only one site holds natural gas. But salt cav-
scale is necessary to enable widespread hydrogen-powered transportation infrastructure.
erns, which are created 1,000 to 6,000 feet below ground by drilling wells in salt forma-

According to Dedrick, these storage options are required if the full potential of hydrogen tions, pumping in under-saturated water to dissolve the salt, then pumping out the result-
for transportation is to be realized and attained.
ing brine, are used more extensively and already store hydrogen on a limited scale.
Moreover, installation of electrolyzer systems on electrical grids for power-to-gas ap-
plications, which integrate renewable energy, grid services, and energy storage, will also Future challenges

require large-capacity, cost-efective hydrogen storage.
Lord said her work could lead to demonstration projects to further cement the viability of
As cost and quantity wouldn’t be a major issue, the massive quantities of hydrogen that underground hydrogen storage. Salt caverns are the logical choice for a pilot project due to
can be stored in geologic features can subsequently be distributed as a high-pressure gas or their proven ability to hold hydrogen, she said. Environmental concerns such as contami-
liquid to supply the hydrogen fuel markets.
nation could also be further analyzed. However, salt formations are limited. None exist in

the Paciic Northwest, much of the East Coast and much of the South, except for the Gulf
Finding favorable storage locations
Coast area. Other options are needed for development of a nationwide hydrogen storage
Although geologic storage may very well prove to be a viable option, several issues still system.
need to be explored, said Lord, including permeability of various geologic formations.

For her study on geologic storage, Lord and her colleagues analyzed and reworked the * Download the full study at www.sciencedirect.com/science/article/pii/S0360319914021223
geologic storage module of Argonne National Laboratory’s Hydrogen Delivery Scenario ** Quotes and information from Sandia Labs News Releases’: “Storing hydrogen underground
Analysis Model (learn more at: www.hydrogen.energy.gov/h2a_delivery.html). To help re- could boost transportation, energy security”
ine this model, however, Lord studied storing hydrogen in salt caverns to meet peak sum-

mer driving demand for four cities: Los Angeles, Houston, Pittsburgh, and Detroit.
Anna Snider Lord’s work adds to Sandia’s capabilities and decades of experience in hydrogen and
She determined that 10% above the average daily demand for 120 days should be stored. fuel cells systems. Sandia leads a number of other hydrogen research eforts, including the Hy-
She then modeled how much hydrogen each city would need if hydrogen met 10%, 25%, drogen Fueling Infrastructure Research and Station Technology (H2FIRST) project co-led by the
and 100% percent of its driving fuel needs.
National Renewable Energy Laboratory (NREL).

Los Angeles has three times the population of Detroit, and more than six-and-a-half
times the population of Pittsburgh. But, the nearest salt formations are in Arizona, so Lord Sandia National Laboratories is a multi-program laboratory operated by Sandia Corporation, a
included the cost of getting the stored hydrogen from Arizona to Los Angeles.
wholly owned subsidiary of Lockheed Martin Corp., for the US Department of Energy’s National
Even so, Los Angeles’ modeled costs are signiicantly less than those for Detroit and Nuclear Security Administration. Sandia has major R&D responsibilities in national security, en-

Pittsburgh. Salt formations in Arizona are thicker than those for Detroit and Pittsburgh, ergy, and environmental technologies, as well as economic competitiveness.
with larger and fewer caverns. As a result, Houston was found to have the best conditions
of the four cities because the Gulf Coast ofers large, deep salt formations.
Sandia National Laboratories | www.sandia.gov

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