Title of Invention

A FUEL CELL ASSEMBLY

Abstract A fuel cell assembly comprises at least one fuel cell (10). The fuel cell (10) comprises an anode (15) and a cathode (16) held in a spaced apart relationship by at least one spacer element (22) comprising an electrically insulating material. A proximal end of the spacer element (22) is in contact with the cathode (16), and a distal end is in contact with the anode (15). An electrolyte (17) is disposed between, and in contact with the anode (15) and the cathode (16). The electrolyte (17) comprises a molten salt having a hydride ion conductance number greater than about 0.95 at a fuel cell operating temperature. A fuel gas inlet (18), adjacent to the cathode (16), is provided for delivering a fuel gas to the electrolyte. An oxidizing gas inlet (19), adjacent to the anode (15), is provided for delivering an oxidizing gas to the electrolyte (17). An exhaust port (20) is in fluid communication with the anode (15).
Full Text BACKGROUND OF THE INVENTION
The present invention relates generally to a fuel cell assembly and more specifically to
fuel cells comprising liquid electrolytes.
Various types of fuel cells are known in the art as devices that convert energy from a
chemical reaction into electrical energy. Each type of fuel cell has one or more
limitations that currently restrict its use to specialized applications. For example,
thermally regenerative liquid fuel cells induce hydrogen flow by thermal decomposition
of a mixture of lithium hydride and sodium hydride, at a high temperature (for example
from about 800°C to about 1300°C) maintained by a separate heating device to generate
hydrogen. The hydrogen is then passed through the cell at a high pressure (10 atmosphere
or above) to mobilize hydride ions, which release electrons at the electrodes for
generating electricity. Only a small portion of thermal energy is converted to electrical
energy. The requirements of a high temperature heating device and capability of handling
high pressure gas increases design complexity including limitations in size and cost.
Another example is conventional hydrogen-oxygen fuel cells, where the electrolytes used
have a limited mobility for mass transport of positive hydrogen ions (H+) and therefore
the generated electrical energy is much less as compared to that ideally available from the
electrochemical conversion. Furthermore, in other types of fuel cells such as those using
polymer electrolytes, there is a considerable risk of poisoning of electrodes due to the
presence of gaseous impurities such as carbon monoxide, hydrogen sulfide, chlorine etc.
Solid oxide fuel cells use metal oxide ceramic electrolytes in solid state. These
electrolytes operate at a temperature as high as about 1000°C. This high operating
temperature allows transport of oxygen ions, which release electrons at the electrode for
generating electricity. However, the use of fragile ceramic electrolytes, the requirement
of structural materials sustainable at high temperature, and the requirement of additional
cooling systems limit the reliability of solid oxide fuel cells.
Therefore, there is a need in the art for fuel cells that efficiently and reliably operate at
lower temperatures than current fuel cells.
BRIEF DESCRIPTION OF THE INVENTION
An embodiment of the present invention provides a fuel cell assembly comprising at
least one fuel cell. The fuel cell comprises an anode and a cathode held in a spaced
apart relationship by at least one spacer element comprising an electrically insulating
material. A proximal end of the spacer element is in contact with the cathode, and a
distal end is in contact with the anode. An electrolyte is disposed between, and in
contact with the anode and the cathode. The electrolyte comprises a molten salt
having a hydride ion conductance number greater than about 0.95 at a fuel cell
operating temperature. A fuel gas inlet, adjacent to the cathode, is provided for
delivering a fuel gas to the electrolyte. An oxidizing gas inlet, adjacent to the anode, is
provided for delivering a oxidizing gas to the electrolyte. An exhaust port is in fluid
communication with the anode.
Another embodiment of the present invention provides a fuel cell assembly comprising
at least one fuel cell further comprising an anode and a cathode held in a spaced apart
relationship by at least one spacer element. The spacer element comprises an
electrically insulating material. A proximal end of the spacer element is in contact with
the cathode, and a distal end is in contact with the anode. An electrolyte disposed
between, and in contact with, the anode and the cathode comprises at least one molten
alkali metal halide selected from the group consisting of lithium chloride and potassium
chloride and further comprising lithium hydride. A fuel gas inlet adjacent to the
cathode is provided for delivering a fuel gas, comprising hydrogen, to the electrolyte.
An oxidizing gas inlet adjacent to the anode is provided for delivering an oxidizing gas,
comprising oxygen, to the electrolyte. An exhaust port is in fluid communication with
the anode.
Still another embodiment of the present invention provides a fuel cell, which comprises
an anode, a cathode in a spaced-apart relationship with the anode, a source of hydride
ions in fluid in communication with the cathode, a source of oxygen in fluid
communication with the anode, and an electrolyte. The electrolyte comprises a molten
salt, the molten salt having a hydride ion conductance number greater than about 0.95 at a
fuel call operating temperature.
These and other features, aspects and advantages of the present invention will be better
understood with reference to the following description, appended claims, and
accompanying drawings.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 is a cross-sectional view of the fuel cell for converting chemical energy to
electricity.
Figure 2 is a cross-sectional view of the fuel cell showing the mechanism of electricity
generation.
Figure 3 is a typical application of a fuel cell stack in a centralized generation plant.
DETAILED DESCRIPTION OF THE INVENTION
Referring to Figure 1, one embodiment of the present invention is a fuel cell assembly,
which is an array or stack comprising at least one fuel cell 10. A fuel cell 10 according to
this embodiment comprises an anode 15 and a cathode 16 held in a spaced part
relationship by at least one spacer element 22. A spacer element 22 according to this
embodiment comprises an electrically insulating material, such as, but not limited to,
alumina, zirconia, boron nitride, silicon nitride, aluminum nitride and silicate glass. The
spacer element 22 further comprises a proximal end in contact with anode 15.
In one embodiment, at least one of anode 15 and cathode 16 comprises a hydrogen-
permeable solid membrane. The property of hydrogen absorption by these materials
allows rapid diffusion of, for example, a fuel gas, which is supplied through the fuel gas
inlet 18. In particular embodiments, the membrane comprises at least one material
selected from the group consisting of palladium, vanadium, beta titanium, and an alloy
comprising palladium and silver. In another embodiment at least one of the anode 15
and the cathode 16 comprises a sintered refractory material, which also allows rapid
diffusion of gas through the porous structure. Suitable sintered refractory materials
include, but are not necessarily limited to, molybdenum, tungsten, rhenium and
vanadium. In another embodiment, a composite material comprising the sintered
refractory material and the solid membrane is used in at least one of the anode 15 and
the cathode 16, for facilitating faster diffusion of gas.
In certain embodiments, the anode 15 and the cathode 16 are tubular in configuration.
Tubular configuration helps to maintain uniformity in flow thereby establishing stable
density gradient across the fuel cell. This results in stable, time independent current
characteristics of the fuel cell. Additionally, tubular configuration maintains structural
integrity and soundness over a long span of time and enhances packaging compactness.
In other embodiments, the anode 15 and the cathode 16 are planar. Planar geometrical
configuration facilitates in improving diffusion rate, which enhances power density.
Additionally, planar configurations are readily available because of ease of
manufacturing.
In some embodiments at least one of the anode 15 and the cathode 16 has a thickness
in the range from about 50 microns to about 500 microns. In certain embodiments the
thickness of the anode 15 and the cathode 16 is in the range from about 50 microns to
about 250 microns. Still in accordance with some other embodiments the thickness of
the anode 15 and the cathode 16 can be in the range from about 75 microns to about
150 microns. Generally, thickness of the anode 15 and the cathode 16 is designed to be
as low as allowable by mechanical design constraints, in order to minimize resistance of
the fuel cell 10.
An electrolyte 17 is disposed between, and in contact with the anode 15 and the
cathode 16. The electrolyte 17 comprises a molten salt having a hydride ion
conductance number greater than about 0.95 at a fuel cell operating temperature.
Using an electrolyte 17 with a hydride ion (H~) conductance number in this range
ensures that the fuel cell will operate with suitable efficiency to be cost-effective. In
some embodiments, the fuel cell operating temperature is in the range from about 250
°C to about 650 °C, which ensures that certain suitable electrolyte materials are in
molten state and capable of conducting hydride ions at the desired level of efficiency.
In certain embodiments, the fuel cell operating temperature of the electrolyte 17 is in
the range from about 250 °C to about 600 °C. According to particular embodiments of
the invention, the fuel cell operating temperature is in the range from about 300 °C to
about 450 °C.
In some embodiments, the electrolyte 17 comprises at least one molten alkali halide
and at least one molten metal hydride. The present inventors have found that
electrolytes of this type have suitably high hydride ion conductance, at fuel cell
operating temperatures in the range described above, which are to be used in
embodiments of the present invention. In accordance with one embodiment of the
invention the alkali halide is selected from the group consisting of lithium chloride,
lithium bromide, lithium fluoride, potassium chloride, potassium bromide, potassium
fluoride, sodium chloride, sodium bromide, sodium fluoride, and mixtures thereof.
Suitable alkali hydrides include, but are not necessarily limited to, lithium hydride,
potassium hydride, sodium hydride, and mixtures thereof. According to one
embodiment of the invention the molten salt comprises the alkali hydride in the range
from about 5 weight percent to about 25 weight percent of the total molten sah
mixture. This ensures mobility of hydride ions even at initial start up of the fuel cell. In
particular embodiments, the molten salt comprises the alkali hydride in the range from
about 10 weight percent to about 20 weight percent of the molten sah mixture.
A fuel gas inlet 18 adjacent to cathode 16 delivers fuel gas to the electrolyte 17. The
fuel gas, in some embodiments, comprises hydrogen; suitable fuel gasses include, but
are not limited to, gasses comprising at least one of methane and propane. Those
skilled in the art will appreciate that in cases where a hydrocarbon compound, such as
methane or propane, is used as the fuel gas, a reformer (not shown) is used to extract
hydrogen from the hydrocarbon compound, and the hydrogen is then delivered to the
electrolyte 17 through the fuel gas inlet 18. An oxidizing gas inlet 19, adjacent to the
anode 15 delivers an oxidizing gas to the electrolyte 17. In some embodiments, the
oxidizing gas comprises oxygen, and in particular embodiments, the oxidizing gas
comprises air.
Referring to Figure 2, the fuel gas diffuses through the cathode 16. The hydrogen in
the fuel gas reacts with free electrons in the electrode according to the reaction 106.

The hydride ions transported across electrolyte 17 diffuse into and across anode 15,
whereupon they contact the oxidizing gas and react with this gas to produce water and
free electrons. Anode 15 serves as a physical barrier to prevent mixing of the oxidizing
gas and the reaction product water with electrolyte 17. The free electrons flow from
the anode 15 to the cathode 16 when they are connected through an external load 21.
The anode reaction 107 is represented in Figure 2 as follows.

Overall reaction is represented by
The above reaction is exothermic and hence maintains the operating temperature of the
fuel cell at a constant level after initial start up. The water molecules thus formed in
the reaction are converted to vapor phase. Unused gases and water vapor are
exhausted through an exhaust port 20.
Another embodiment of the present invention is a fuel cell comprising an anode 15 a
cathode 16 in a spaced-apart relationship with the anode 15, a source of hydride ions in
fluid communication with the cathode 16, a source of oxygen in fluid communication
with the anode, and an electrolyte 17 comprising a molten salt, the molten salt having a
hydride ion conductance number greater than about 0.95 at a fuel cell operating
temperature. The various alternatives described for elements of the fuel cell assembly
of the present invention also apply to these fuel cell embodiments. In these
embodiments, the source of hydride ions is often a fuel gas. and the source of oxygen
is often an oxidizing gas, as described previously.
The fuel gas and oxidizing gas can be obtained from a variety of sources and therefore
this type of fuel cell is suitable for use in various applications. For example, it can be
used in a skid mounted mobile reformer unit where hydrocarbons are cracked to
produce hydrogen and is therefore suitable to use in electrically powered vehicle or any
other small-scale generation. A typical fuel cell stack for large-scale generation in
central power plants is shown in Figure 3. For large-scale generation in central power
plant, hydrogen may typically be obtained from coal gas by water gas shift reaction.
Hydrogen gas thus produced from a coal reformer gas in a shift converter 201 is fed to
a fuel cell stack 200 at the inlet 204.The fuel cell stack 200 contains individual fuel cell
units 210. Oxygen or atmospheric air is fed into the inlet 205 of the fuel cell stack
200.The unused oxygen and the water vapor produced in the reaction as explained
above are recycled through a condenser 216 and connecting duct 214. The unused
hydrogen is recycled from port 207 though a connecting duct 212. The fuel cell can
also be used for space power applications where hydrogen and oxygen can be supplied
from a cryogenic storage 218.
While various embodiments are described herein, it will be appreciated 'from the
specification that various combinations of elements, variations, equivalents, or
improvements therein may be made by those skilled in the art, and are still within the
scope of the invention as defined in the appended claims.
WE CLAIM
1. A fuel cell assembly comprising:
at least one fuel cell (10) comprising
a. an anode (15) and a cathode (16) held in a spaced apart relationship by at least one
spacer element (22), said at least one spacer element (22) comprising an electrically
insulating material, a proximal end in contact with said cathode (16), and a distal end in
contact with said anode (15);
b. An electrolyte (17) comprising a molten salt having a hydride ion conductance
number greater than about 0.95 at a fuel cell (10) operating temperature, said
electrolyte (17) disposed between, and in contact with, said anode (15) and said
cathode (16);
c. a fuel gas inlet (18) for delivering a fuel gas to said electrolyte (17), wherein said
fuel gas inlet (18) is adjacent to said cathode (16);
d. an oxidizing gas inlet (19) for delivering a oxidizing gas to said electrolyte (17),
wherein said oxidizing gas inlet (19) is adjacent to said anode (15); and
e. an exhaust port (20) in fluid communication with said anode (15).
2. The fuel cell assembly of claim 1, wherein at least one of said anode (15) and said
cathode (16) comprises a hydrogen permeable solid membrane.
3. The fuel cell assembly of claim 2, wherein said membrane comprises at least one
material selected from the group consisting of palladium, vanadium, beta titanium, and
an alloy comprising palladium and silver.
4. The fuel cell assembly of claim 1, wherein at least one of said anode (15) and said
cathode (16) comprises at least one sintered refractory material.
5. The fuel cell assembly of claim 4, wherein said sintered refractory material
comprises at least one material selected from the group consisting of molybdenum.
tungsten, rhenium, and vanadium.
6. The fuel cell assembly of claim 4. wherein at least one of said anode (15) and said
cathode (16) further comprises a composite material, said composite material
comprising said sintered refractory material and a hydrogen-permeable solid
membrane.
7. The fuel cell assembly of claim 1, wherein at least one of said anode (15) and said
cathode (16) has a thickness in the range from about 50 microns to about 500 microns.
8. The fuel cell assembly of claim 1. wherein said molten salt comprises at least one
molten alkali halide and at least one molten metal hydride.
9. A fuel cell assembly comprising:
at least one fuel cell (10) comprising
a. an anode (15) and a cathode (16) held in a spaced apart relationship by at least one
spacer element (22), said at least one spacer element (22) comprising an electrically
insulating material, a proximal end in contact with said cathode (16). and a distal end in
contact with said anode (15);
b. an electrolyte (17) comprising at least one molten alkali metal halide selected from
the group consisting of lithium chloride and potassium chloride and further comprising
lithium hydride, said electrolyte (17) disposed between, and in contact with, said anode
(15) and said cathode (16);
c. a fuel gas inlet (18) for delivering a fuel gas comprising hydrogen to said electrolyte
(17), wherein said fuel gas inlet (18) is adjacent to said cathode (16);
d. a oxidizing gas inlet (19) for delivering a oxidizing gas
comprising oxygen to said electrolyte (17), wherein said oxidizing gas inlet (19) is
adjacent to said anode (15); and
e. an exhaust port (20) in fluid communication with said anode (15).

A fuel cell assembly comprises at least one fuel cell (10). The fuel cell (10) comprises an anode (15) and a cathode (16) held in a spaced apart relationship by at least one spacer element (22) comprising an electrically insulating material. A proximal end of the spacer element (22) is in contact with the cathode (16), and a distal end is in contact with the anode (15). An electrolyte (17) is disposed between, and in contact with the anode (15) and the cathode (16). The electrolyte (17) comprises a molten salt having a hydride ion conductance number greater than about 0.95 at a fuel cell operating temperature. A fuel gas inlet (18), adjacent to the cathode (16), is provided for delivering a fuel gas to the electrolyte. An oxidizing gas inlet (19), adjacent to the anode (15), is provided for delivering an oxidizing gas to the electrolyte (17). An exhaust port (20) is in fluid communication with the anode (15).

Documents:

331-kol-2003-abstract.pdf

331-kol-2003-assignment.pdf

331-kol-2003-claims.pdf

331-kol-2003-correspondence.pdf

331-kol-2003-description (complete).pdf

331-kol-2003-drawings.pdf

331-kol-2003-examination report.pdf

331-kol-2003-form 1.pdf

331-kol-2003-form 18.pdf

331-kol-2003-form 2.pdf

331-kol-2003-form 3.pdf

331-kol-2003-form 5.pdf

331-kol-2003-gpa.pdf

331-kol-2003-granted-abstract.pdf

331-kol-2003-granted-assignment.pdf

331-kol-2003-granted-claims.pdf

331-kol-2003-granted-correspondence.pdf

331-kol-2003-granted-description (complete).pdf

331-kol-2003-granted-drawings.pdf

331-kol-2003-granted-examination report.pdf

331-kol-2003-granted-form 1.pdf

331-kol-2003-granted-form 18.pdf

331-kol-2003-granted-form 2.pdf

331-kol-2003-granted-form 3.pdf

331-kol-2003-granted-form 5.pdf

331-kol-2003-granted-gpa.pdf

331-kol-2003-granted-pa.pdf

331-kol-2003-granted-reply to examination report.pdf

331-kol-2003-granted-specification.pdf

331-kol-2003-granted-translated copy of priority document.pdf

331-kol-2003-pa.pdf

331-kol-2003-reply to examination report.pdf

331-kol-2003-specification.pdf

331-kol-2003-translated copy of priority document.pdf


Patent Number 235095
Indian Patent Application Number 331/KOL/2003
PG Journal Number 26/2009
Publication Date 26-Jun-2009
Grant Date 24-Jun-2009
Date of Filing 11-Jun-2003
Name of Patentee GENERAL ELECTRIC COMPANY
Applicant Address ONE RIVER ROAD, SCHENECTADY, NEW YORK 12345
Inventors:
# Inventor's Name Inventor's Address
1 ROY PRODYOT (NMN) 12980 FOOTHILL LANE, SARATOGA, CALIFORNIA 95070
2 SALAMAH SAMIR ARMANDO 187 LANCASHIRE PLACE NISKAYUNA, NEW YORK 12309
3 RODGERS DOUGLAS NOSS 3182 ISADORA DRIVE, SAN JOSE, CALIFORNIA 95132
PCT International Classification Number H01M 8/00
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 10/064,408 2002-07-10 U.S.A.