Transcript Hydrogen Storage

Hydrogen Storage
An application-specific issue.
Hydrogen Storage Overview
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Physical storage of H2
•Compressed
•Cryogenically liquified
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Chemical storage of hydrogen
•Sodium borohydride
•Ammonia
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•Metal Hydride (“sponge”)
•Carbon nanofibers
•Methanol
•Alkali metal hydrides
New emerging methods
•Amminex tablets
•DADB (predicted)
•Solar Zinc production
•Alkali metal hydride slurry
Compressed
•Volumetrically and Gravimetrically inefficient, but
the technology is simple, so by far the most common in
small to medium sized applications.
•3500, 5000, 10,000 psi variants.
Liquid (Cryogenic)
•Compressed, chilled, filtered, condensed
•Boils at 22K (-251 C).
•Gravimetrically and volumetrically efficient
•Slow “waste” evaporation
but very costly to compress
•Kept at 1 atm or just slightly over.
Metal Hydrides (sponge)
•Sold by “Interpower” in Germany
•Filled with “HYDRALLOY” E60/0
(TiFeH2)
•Technically a chemical reaction,
but acts like a physical storage
method
•Hydrogen is absorbed like in a
sponge.
•Operates at 3-30 atm, much
lower than 200-700 for
compressed gas tanks
•Comparatively very heavy, but
with good volumetric efficiency,
good for small storage, or where
weight doesn’t matter
Carbon Nanofibers
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Complex structure
presents a large surface
area for hydrogen to
“dissolve” into
Early claim set the
standard of 65 kgH2/m2
and 6.5 % by weight as a
“goal to beat”
The claim turned out not
to be repeatable
Research continues…
Methanol
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Broken down by reformer, yields CO, CO2,
and H2 gas.
Very common hydrogen transport method
Distribution infrastructure exists – same as
gasoline
Ammonia
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Slightly higher volumetric efficiency than methanol
Must be catalyzed at 800-900 deg. C for hydrogen
release
Toxic
Usually transported as a liquid, at 8 atm.
Some Ammonia remains in the catalyzed hydrogen
stream, forming salts in PEM cells that destroy the
cells
Many drawbacks, thus Methanol considered to be a
better solution
Alkali Metal Hydrides
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“Powerball” company, makes
small (3 mm) coated NaH
spheres.
“Spheres cut and exposed to
water as needed”
H2 gas released
Produces hydroxide solution
waste
Sodium Borohydrate
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Sodium Borohydrate is the most popular of many
hydrate solutions
Solution passed through a catalyst to release H2
Commonly a one-way process (sodium metaborate
must be returned if recycling is desired.)
Some alternative hydrates are too expensive or toxic
The “Millennium Cell” company uses Sodium
Borohydrate technology
Amminex
•Essentially an Ammonia storage method
•Ammonia stored in a salt matrix, very stable
•Ammonia separated & catalyzed for use
•Likely to have non-catalyzed ammonia in hydrogen stream
•Ammonia poisoning contraindicates use with PEM fuel cells,
but compatible with alkaline fuel cells.
Amminex
•High density, but relies on ammonia production for fuel.
•Represents an improvement on ammonia storage,
which still must be catalyzed.
•Ammonia process still problematic.
Diammoniate of Diborane (DADB)
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So far, just a computer
simulation.
Compound discovered
via exploration of
Nitrogen/Boron/Hydrogen
compounds (i.e. similar to
Ammonia Borane)
Thermodynamic
properties point towards
spontaneous hydrogen
re-uptake – would make
DADB reusable (vs. other
borohydrates)
Solar Zinc production
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Isreli research effort
utilizes solar furnace to
produce pure Zinc
Zinc powder can be
easily transported
Zinc can be combined
with water to produce H2
Alternatively could be
made into Zinc-Air
batteries (at higher
energy efficiency)
Alkaline metal hydride slurry
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SafeHydrogen, LLC
Concept proven with
Lithium Hydride, now
working on magnesium
hydride slurry
Like a “PowerBall”
slurry
Hydroxide slurry to be
re-collected to be
“recycled”
Competitive efficiency
to Liquid H2
Storage Method Comparison
Sodium Hydride slurry
.9
1.0
Must reclaim used slurry
DADB
.1 - .2
.09-.1
(numbers for plain “diborane”and sodium
borohydride, should be similar)
Amminex
9.1
.081
Zinc powder
US DOE goal
unsure
9.0
.081
Early Adoption of inefficient system
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Compressed
Hydrogen is one
of the least
efficient both
volumetrically and
gravimetrically,
but is currently
the most common
(because it’s a
simple solution).
Credits
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http://psych.ucsc.edu/faculty/kg/H2Spirit/images2.htm
http://www.photos.gov.ca.gov/essay20.html
http://www.amminex.com/index_files/Page344.htm
http://www.h2interpower.de/deutsch/produkte/zubehoer.html#mhs20
http://www.pnl.gov/news/notes/transportation05.stm
http://www.safehydrogen.com/technology.html
http://www.isracast.com/tech_news/090905_tech.htm
http://www.h2fc.com/industry/infra/storage.shtml
Fuel Cell Systems Explained, by James Larminie and
Andrew Dicks