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Microcavity
Processes For Hydrogen Storage, Transport, and Supply Systems
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BACKGROUND
Hydrogen
is a viable, zero polluting, automotive fuel. It can be utilized
to replace gasoline and diesel fuels for internal combustion engines
and in hydrogen fuel cells. Much is known about its production
and utilization. Its full commercialization as a fuel depends
upon the development of cost effective technology for its purification,
distribution, storage and transportation. Currently hydrogen is
either pressurized and stored in metal or fiber reinforced plastic
tanks; or it is liquefied and stored in insulated vessels; or
it is reacted with metals to form metal hydrides which are stored
in containers and are later dissociated to recover the hydrogen.
All of these storage systems are either heavy, expensive, energy
intensive or unsafe.
For
the past twenty years, Dr. Robert J. Teitel has been actively
engaged in the research and development of new technology employing
hollow glass microspheres to contain high pressure hydrogen gas.
Hydrogen gas supply Systems employing the new technology can be
designed for both mobile and stationary storage of hydrogen. In
1980, 1981 and 1982, Dr. Teitel was awarded patents by the United
States Patent office for the Micro Cavity Hydrogen Storage System.
Since then, he has obtained patents in Germany, Japan and Canada.
Robert
J. Teitel Associates (RJTA) was formed in 1976 to research and
develop Micro Cavity Process technology. During 1979-1981, substantial
funding (over $300,000) was obtained from the United States Department
of Energy to investigate all commercially available hollow glass
microspheres for the storage system. In 1981, federal policy changed
and substantially eliminated government funding for all alternative
fuel research. Since then, Robert J. Teitel Associates continued
the development on its own limited funds. The Micro Cavity Hydrogen
Storage System has been proof tested on a milliwatt scale and
is ready for full scale development.
THE
ENERGY PROBLEM AND THE "HYDROGEN ECONOMY" SOLUTION
The
energy industry is now in a transition period. Current fossil
fuel supplies are being depleted and/or restricted by pollution
or economic concerns. Utilization of carbon based fuels has started
to affect the global ecology by the release of combustion products
into the atmosphere or the accidental release of crude oil into
our rivers, lakes and oceans. Solutions to this problem by anti-smog
devices and altered gasoline for cars have resulted in increased
energy costs but they do not solve the problem. The future of
the world's energy industry depends upon the development of new,
cost effective, non-polluting alternative fuels such as hydrogen.
The
"Hydrogen Economy" came under consideration in 1975.
This economy envisions hydrogen as the key automotive fuel form
of the future because it can be generated using any natural energy
resource thus increasing the USA and world's viable energy resources.
Hydrogen is a clean burning fuel whose combustion product is water,
making it ecologically preferable.
The
technology for both the production and the utilization of hydrogen
are well developed. A broad spectrum of commercial processes utilizing
many known energy resources are available for the production of
hydrogen as illustrated in Figure 1. Figure 2 presents the vast
industrial applications of hydrogen. Safe and economical methods
for separating, purifying, handling, storing and transporting
hydrogen are needed to tie the production and applications together.
RJTA's Micro Cavity Processes are the answer.
MICRO
CAVITY HYDROGEN STORAGE SYSTEM DESCRIPTION
In
a Micro Cavity System, high pressure hydrogen gas is contained
and transported in tiny hollow glass microspheres. A photomicrograph
of typical microspheres are shown in Figure 3. Commercially available
glass microspheres range in size from 5 to 200 micrometers (0.0002
to 0.008 inches) in diameter and have wall thicknesses from 0.5
to 2 micrometers. They are currently available in tonnage quantities
in various sizes and glass compositions from several sources.
Microspheres are handled and transported commercially in the form
of a free flowing powder.
Hydrogen
encapsulation is accomplished by heating a bed of empty hollow
glass microspheres in an atmosphere of hydrogen. Hydrogen diffuses
into the hollow cores of the microspheres through the thin glass
shells at practical rates at temperatures between 100 and 400>C.
Eventually, the hydrogen pressure within the microspheres approaches
that external to the microspheres. The bed is cooled and the hydrogen
external to the microspheres released or retrieved. Hydrogen within
the microspheres is trapped since the diffusion rate is drastically
lower at room temperature. The filled microspheres are recovered.
They are stored, handled and transported as a fine powder under
ambient conditions. To extract the hydrogen from the microspheres,
the filled microspheres are placed in a low pressure vessel, reheated
to a lower temperature than that required for filling. The stored
hydrogen diffuses out of the microspheres until the contained
hydrogen pressure approaches the lower vessel pressure. Empty
microspheres are recovered and recycled to the filling operation.
The rate at which hydrogen diffuses in or out of the microsphere
bed depends upon the temperature of the bed, microsphere hydrogen
pressures (internal and external), the chemical composition of
the microsphere glass, the microsphere dimensions and the volume
of the microsphere bed. Early speculations, using diffusion data
from the literature and well known diffusion formulae, indicated
that hydrogen recovery rates would be high enough to meet vehicle
fuel demands at the temperatures (below 2OO° C) . The thermal
energy needed to reheat the microsphere bed may be supplied by
a electric heater powered by a small hydrogen fuel cell or a battery,
recharged by a mechanically driven generator. It is estimated
that the energy needed to release the hydrogen will be less than
5% of the energy produced by the combustion of hydrogen in a well
designed system.
Using
experimental data on the tensile strength of glass fibers having
diameters similar to the microsphere wall thicknesses and the
hoop stress formulae, it was speculated that the tensile strength
of the microsphere walls will be about 500,000 psi. and that microspheres
will be able to retain gas pressures above 10,000 psi. These speculations
have been verified experimentally.
Dr.
Teitel conceived and patented a Micro Cavity Hydrogen Storage
Process by combining Micro Cavity storage with Metal Hydride storage.
The metal hydride component may be used to absorb hydrogen released
during cool down and can provide a source of hydrogen for cold
starts and car accelerations in automotive applications.
Figure
4 is a block flow diagram of the Micro Cavity Hydrogen Storage
System applied to a automotive application. In step 1, hydrogen
is produced using any of the processes given in Figure 1. The
effluent gas is pressurized to 12,000 psi, for example. Microspheres
are selected according to their ability to hold or release hydrogen.
The gas is admitted into a heated high pressure vessel containing
unfilled hollow glass microspheres, shown in Figure 3. The vessel
and microsphere bed are maintained at 350° C, for example.
After a short period (less than 15 minutes, for example), the
hydrogen pressure inside the microspheres approaches that in the
pressure vessel. The microsphere bed is then cooled and transferred
to low pressure vessels for long term storage (Step 3), transportation
(Step 4), short term storage (Step 5) and on-board vehicle storage
(Step 6). The hydrogen is extracted from the microspheres at a
low temperature (less than 200° C, for example) and a low
pressure (25-50 psi, for example). A small metal hydride system
(Step 7) may be used to regulate the hydrogen pressure supplied
to a stationary or mobile internal combustion or a fuel cell engine.
CURRENT
STATUS OF MICRO CAVITY PROCESS RESEARCH AND DEVELOPMENT
The
current status of RJTA development of Micro Cavity Systems for
hydrogen supply systems are summarized thus:
1.
Between 1979-1980, RJTA conducted an experimental evaluation of
all commercially available grades of hollow glass microspheres.
The information collected and the equipment used in the survey
have been stored and are available for future demonstrations and
evaluations.
2.
An engineering comparison of the RJTA Micro Cavity Hydrogen Storage
System to an advanced Metal Hydride Storage System showed that
the Micro Cavity System would weigh less and cost less than the
Hydride System.
3.
Fill plant engineering and economic studies, conducted in 1979,
indicated that the filling operation is much less expensive than
the base cost of hydrogen. Plants utilizing current design information
would lower these filling costs substantially.
4.
As a result of the engineering studies to date, the characteristics
of an ideal microsphere bed for vehicle fuel storage have been
identified. Experimental studies on eight commercial grades of
microspheres have resulted in finding a commercial grade that
comes close to meeting those requirements set forth in an earlier
vehicle drive cycle engineering study. Other grades of microspheres
have shown promise for applications other than automotive.
5.
Experimental techniques for the measurement of microsphere bed
properties have been fully developed.
6.
Safety tests were performed by a qualified testing company in
1979 and concluded that microsphere storage was as safe as metal
hydride storage. The microsphere storage system does not require
a sealed container and is not degraded by exposure to air. Over
the past 12 years, Robert J. Teitel Associates has demonstrated
the safety of handling high pressure hydrogen encapsulated in
hollow glass microspheres by storing them in a glass jar under
uncontrolled conditions
7.
Recent RJTA progress led to the development of a microsphere source
that shows negligible breakage when subjected to the thermal and
physical handling conditions anticipated in a Hydrogen Economy.
Microspheres were filled to 6000 psi hydrogen at room temperature.
A hydrogen storage bed weight density of 0.06 grams of H2/gram
of bed and a hydrogen storage bed volume density of 0.02 grams
of H2/cc of bed have been achieved. A liter of these filled microspheres
have been stored in a glass jar under ambient temperatures and
pressures for 12 years. No significant breakage has been detected
and the hydrogen pressure within the microspheres is about 1500
psi. today. This hydrogen loss is due to the gas diffusing out
of the microspheres during storage. The addition of a metal hydride
component to the system would increase the hydrogen volume density
and reduce the hydrogen weight density.
8.
Micro Cavity Processes have been designed to separate hydrogen
from producer gases and purify hydrogen to levels greater than
those available commercially today. Some of the basic features
of those processes have been demonstrated on a small scale.
9.
Hydrogen released from microspheres, which were filled and stored
as reported under accomplishment 6, was used to fuel a solid electrolyte
PEM fuel cell. The electrical energy produced by the cell was
used to operate a motor. This completes a full hydrogen economy
cycle demonstration in miniature.
HOW
DOES THE MICRO CAVITY SYSTEM COMPARE TO OTHER HYDROGEN STORAGE
SYSTEMS?
Table
1 is a compilation of volumetric and gravimetric energy densities
for current and advanced hydrogen storage technologies. Most of
the data was obtained from the referenced DOE Report, which did
not include Micro Cavity Storage. A set of data for the RJTA Micro
Cavity Storage is presented in the last line of the table. Excluding
the hydrocarbon fuels (gasoline, natural gas and methanol), the
Micro Cavity Storage System is competitive and viable. It is interesting
to note that the energy density figures for liquid hydrogen and
Micro Cavity storage are almost the same when the liquid hydrogen
container is included. Micro Cavity storage densities appear to
be competitive with current natural gas stored at 2400 psi. In
addition, the RJTA system enjoys safety, economic and energy efficiency
advantages which cannot be appreciated until "full scale"
comparisons are conducted.
ROBERT
J. TEITEL ASSOCIATES IS ACTIVELY ENGAGED IN THE DEVELOPMENT OF
HYDROGEN AS AN ECONOMICAL, NON-POLLUTING, COMMERCIAL FUEL
Dr.
Robert J. Teitel, President of RJTA, has made significant contributions
to the development of nuclear fission, nuclear fusion and fossil
energy systems. He was awarded United States Patents for Micro
Cavity Hydrogen Storage in 1980. Patents have since issued in
Canada, Japan and Germany. Patent applications on associated technologies
have also been submitted. Dr. Teitel has invested substantial
funds of his own for the development of the patents and for performing
experimental and engineering evaluations of the Micro Cavity Hydrogen
Storage System.
Research
and development conducted by Robert J. Teitel Associates to date
has been directed primarily toward the development of vehicular
hydrogen fuel supply systems. Study results have established that
the Micro Cavity Hydrogen Storage System is viable and, in many
ways superior, to other automotive hydrogen storage systems either
developed or conceptual. The system has economic potential with
it's low cost, light weight, low energy requirements, safety and
distributional advantages. An inherent advantage of the system
is one that it shares with all hydrogen fuel systems. Hydrogen
is a clean fuel since it's combustion product is water.
RJTA
is also interested in developing other applications for the system.
Hydrogen is used in many industries (Figure 2) including: ammonia
production for agriculture; conversion of heavy oils and coal
to light oils for petroleum fuels; hydrogenation of fats for food
production; a chemical reducing agent for the conversion of ores
into metals; as a cover gas for treating micro chips for electronic
devises and, others. The Micro Cavity Processes being developed
by Robert J. Teitel Associates can be applied in all these industries.
Robert
J. Teitel Associates research and development has reached a stage
where "full scale" demonstrations of the Micro Cavity
Processes for specific applications are needed to establish a
detailed commercial development plan. RJTA has the technical expertise
and "know-how" to design, construct, operate and evaluate
these demonstrations and develop commercial plans. RJTA wishes
to join forces with organizations already active in specific applications
of hydrogen technology or fleet vehicle operations.
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