U.S. patent application number 16/865488 was filed with the patent office on 2021-01-21 for solid oxide fuel cell device.
The applicant listed for this patent is Alan Devoe, Lambert Devoe. Invention is credited to Alan Devoe, Lambert Devoe.
Application Number | 20210020965 16/865488 |
Document ID | / |
Family ID | 1000005134546 |
Filed Date | 2021-01-21 |
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United States Patent
Application |
20210020965 |
Kind Code |
A1 |
Devoe; Alan ; et
al. |
January 21, 2021 |
SOLID OXIDE FUEL CELL DEVICE
Abstract
A fuel cell device with a rectangular solid ceramic substrate
extending in length between first and second end surfaces where
thermal expansion occurs primarily along the length. An active
structure internal to the exterior surface extends along only a
first portion of the length and has an anode, cathode and
electrolyte therebetween. The first portion is heated to generate a
fuel cell reaction. A remaining portion of the length is a
non-heated, non-active section lacking opposing anode and cathode
where heat dissipates along the remaining portion away from the
first portion. A second portion of the length in the remaining
portion is distanced away from the first portion such that its
exterior surface is at low temperature when the first portion is
heated. The anode and cathode have electrical pathways extending
from the internal active structure to the exterior surface in the
second portion for electrical connection at low temperature.
Inventors: |
Devoe; Alan; (La Jolla,
CA) ; Devoe; Lambert; (San Diego, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Devoe; Alan
Devoe; Lambert |
La Jolla
San Diego |
CA
CA |
US
US |
|
|
Family ID: |
1000005134546 |
Appl. No.: |
16/865488 |
Filed: |
May 4, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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16154280 |
Oct 8, 2018 |
10673081 |
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16865488 |
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15615058 |
Jun 6, 2017 |
10096846 |
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16154280 |
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15213825 |
Jul 19, 2016 |
9673459 |
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15615058 |
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14840750 |
Aug 31, 2015 |
9397346 |
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15213825 |
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14107448 |
Dec 16, 2013 |
9123937 |
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14840750 |
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13658370 |
Oct 23, 2012 |
8609290 |
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14107448 |
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13443531 |
Apr 10, 2012 |
8293417 |
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13658370 |
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13185808 |
Jul 19, 2011 |
8153318 |
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13443531 |
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11557894 |
Nov 8, 2006 |
7981565 |
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13185808 |
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60747013 |
May 11, 2006 |
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60734554 |
Nov 8, 2005 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01M 8/243 20130101;
H01M 4/8663 20130101; H01M 8/04007 20130101; H01M 8/2425 20130101;
Y02B 90/10 20130101; H01M 8/1213 20130101; H01M 2300/0074 20130101;
H01M 8/1004 20130101; H01M 8/2404 20160201; H01M 8/04201 20130101;
H01M 8/006 20130101; H01M 8/1286 20130101; H01M 2008/1293 20130101;
H01M 8/2483 20160201; H01M 8/1246 20130101; H01M 8/04074 20130101;
Y02P 70/50 20151101; H01M 2250/30 20130101 |
International
Class: |
H01M 8/04007 20060101
H01M008/04007; H01M 8/2404 20060101 H01M008/2404; H01M 8/2483
20060101 H01M008/2483; H01M 8/243 20060101 H01M008/243; H01M 8/2425
20060101 H01M008/2425; H01M 8/00 20060101 H01M008/00; H01M 8/1286
20060101 H01M008/1286; H01M 8/1213 20060101 H01M008/1213; H01M 4/86
20060101 H01M004/86; H01M 8/04082 20060101 H01M008/04082; H01M
8/1004 20060101 H01M008/1004; H01M 8/1246 20060101
H01M008/1246 |
Claims
1-14. (canceled)
15. A solid oxide fuel cell device comprising: a ceramic monolith
of rectangular dimensions having a length, width, and thickness
with the length being the greatest dimension, the ceramic monolith
including: a fuel passage extending at least in part in the
direction of the length dimension and opening to a surface of the
ceramic monolith at an inlet and opening to a surface at an outlet;
an oxidizer extending at least in part in the direction of the
length dimension and opening to a surface of the ceramic monolith
at an inlet and opening to a surface at an outlet; an electrolyte
disposed between the fuel passage and the oxidizer passage; an
anode exposed in the fuel passage with a first portion between the
electrolyte and the fuel passage; and a cathode exposed in the
oxidizer passage with a first portion between the electrolyte and
the oxidizer passage, wherein the first portion of the anode and
the first portion of the cathode are in opposing relation with the
electrolyte therebetween and forming an active region, and each of
the anode and the cathode includes a second portion extending in
the corresponding passage toward one of the correspondence inlets
or outlets, the second portions of the anode and cathode are not in
opposing relation.
16. The fuel cell device of claim 15 wherein each of the anode and
cathode extends to one of the corresponding inlet or outlet.
17. The fuel cell device of claim 15 wherein each of the anode and
cathode extends to an exterior surface of the ceramic monolith
adjacent to one of the corresponding inlet or outlet.
18. The fuel cell device of claim 15 further including low
temperature rigid electrical connections in electrical
communication with respective ones of the second portion of the
anode and the second portions of the cathode.
19. The fuel cell device of claim 15 further including a contact
pad on an exterior surface of ceramic monolith in electrical
communication with the anode and a contact pad on an exterior
surface of the ceramic monolith in electrical communication with
the cathode.
20. The fuel cell device of claim 15 wherein the ceramic monolith
has dimensions of 0.2 inch thick and 0.5 inch width and the length
is at least 5 times greater than the thickness.
21. The fuel cell device of claim 15 wherein the ceramic monolith
has a first end and a second end and the length between the first
end and the second end is substantially greater than the width and
the thickness whereby the ceramic monolith exhibits thermal
expansion along a dominant axis that is coextensive with the
length.
22. A solid oxide fuel cell system comprising: a hot zone chamber;
a plurality of the solid oxide fuel cell devices of claim 1, each
positioned with the active region in the hot zone chamber and the
second portion of the anode and the second portion of the cathode
extending outside the hot zone chamber; a heat source coupled to
the hot zone chamber and adapted to provide the applied heat to
heat the active regions to an operating reaction temperature within
the hot zone chamber; a fuel gas supply coupled outside the hot
zone chamber to the fuel inlets for supplying a fuel gas flow into
the fuel passages; and an oxidizer gas supply coupled outside the
hot zone chamber to the oxidizer inlets for supplying an oxidizer
gas flow into the oxidizer passages.
23. The fuel cell system of claim 22 further comprising an
insulating region between the heat source and the second portion of
the anode and the second portion of the cathode, the insulating
region being adapted to maintain the second portions at a
temperature below the operating reaction temperature.
24. The fuel cell system of claim 23 wherein the operating reaction
temperature is greater than 700.degree. C. and the temperature of
the second portion where the fuel gas and oxidizer gas supplies are
coupled to the fuel and oxidizer inlets is less than 300.degree.
C.
25. A method of using the device of claim 15, comprising:
positioning the ceramic monolith with the active region in a hot
zone chamber and the second portions extending outside the hot zone
chamber; coupling a fuel gas supply outside the hot zone chamber to
the fuel gas inlet; coupling an oxidizer supply outside the hot
zone chamber to the oxidizer gas inlet; applying heat in the hot
zone chamber to heat the active region to an operating temperature
above 700.degree. C. while maintaining the inlets at a low
temperature less than 300.degree. C.; supplying fuel gas and
oxidizer gas through the respective fuel and oxidizer inlets to the
respective fuel and oxidizer passages in the heated active region
whereby the fuel and oxidizer react and produce electrons to
produce a voltage between the second portion of the anode and the
second portion of the cathode.
26. A method of using the system of claim 22, comprising: applying
heat in the hot zone chamber to heat the active regions to an
operating temperature above 700.degree. C. while maintaining the
fuel and oxidizer inlets at a low temperature less than 300.degree.
C.; supplying fuel and air from the respective fuel gas and
oxidizer gas supplies into the respective fuel and air passages to
the heated active region to react the fuel and oxidizer and produce
electrons whereby a voltage develops between the second portion of
the anode and the second portion of the cathode.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. application Ser.
No. 16/154,280 filed on Oct. 8, 2018, which is a continuation of
No. U.S. Pat. No. 10,096,846 issued Oct. 9, 2018 and entitled SOLID
OXIDE FUEL CELL DEVICE which is a continuation of U.S. Pat. No.
9,673,459 issued Jun. 6, 2017 and entitled SOLID OXIDE FUEL CELL
DEVICE, which is a continuation of U.S. Pat. No. 9,397,346 issued
Jul. 19, 2016 and entitled SOLID OXIDE FUEL CELL DEVICE, which is a
continuation of U.S. Pat. No. 9,123,937 issued Sep. 1, 2015
entitled SOLID OXIDE FUEL CELL DEVICE, which is a continuation of
U.S. Pat. No. 8,609,290 issued Dec. 17, 2013 and entitled SOLID
OXIDE FUEL CELL DEVICE, which is a continuation of U.S. Pat. No.
8,293,417 issued Oct. 23, 2012, and entitled SOLID OXIDE FUEL CELL
DEVICE, which is a continuation of U.S. Pat. No. 8,153,318 issued
Apr. 10, 2012, and entitled METHOD OF MAKING A FUEL CELL DEVICE,
which is a continuation of U.S. Pat. No. 7,981,565 issued Jul. 19,
2011, and entitled SOLID OXIDE FUEL CELL DEVICE AND SYSTEM, which
claims the benefit of and priority to provisional Application No.
60/734,554 filed Nov. 8, 20015, and provisional Application No.
60/747,013 filed May 11, 2006. The disclosures of each are
incorporated herein by reference in their entirety as if completely
set forth herein below.
FIELD OF THE INVENTION
[0002] This invention relates to solid oxide fuel cell devices and
systems, and methods of manufacturing the devices and, more
particularly, to a solid oxide fuel cell device in the form of a
multi-layer monolithic SOFC Stick.TM..
BACKGROUND OF INVENTION
[0003] Ceramic tubes have found a use in the manufacture of Solid
Oxide Fuel Cells (SOFCs). There are several types of fuel cells,
each offering a different mechanism of converting fuel and air to
produce electricity without combustion. In SOFCs, the barrier layer
(the "electrolyte") between the fuel and the air is a ceramic
layer, which allows oxygen atoms to migrate through the layer to
complete a chemical reaction. Because ceramic is a poor conductor
of oxygen atoms at room temperature, the fuel cell is operated at
700.degree. C. to 1000.degree. C., and the ceramic layer is made as
thin as possible.
[0004] Early tubular SOFCs were produced by the Westinghouse
Corporation using long, fairly large diameter, extruded tubes of
zirconia ceramic. Typical tube lengths were several feet long, with
tube diameters ranging from 1/4 inch to 1/2 inch. A complete
structure for a fuel cell typically contained roughly ten tubes.
Over time, researchers and industry groups settled on a formula for
the zirconia ceramic which contains 8 mol % Y.sub.2O.sub.3. This
material is made by, among others, Tosoh of Japan as product
TZ-8Y.
[0005] Another method of making SOFCs makes use of flat plates of
zirconia, stacked together with other anodes and cathodes, to
achieve the fuel cell structure. Compared to the tall, narrow
devices envisioned by Westinghouse, these flat plate structures can
be cube shaped, 6 to 8 inches on an edge, with a clamping mechanism
to hold the entire stack together.
[0006] A still newer method envisions using larger quantities of
small diameter tubes having very thin walls. The use of thin walled
ceramic is important in SOFCs because the transfer rate of oxygen
ions is limited by distance and temperature. If a thinner layer of
zirconia is used, the final device can be operated at a lower
temperature while maintaining the same efficiency. Literature
describes the need to make ceramic tubes at 150 m or less wall
thickness.
[0007] There are several main technical problems that have stymied
the successful implementation of SOFCs. One problem is the need to
prevent cracking of the ceramic elements during heating. For this,
the tubular SOFC approach is better than the competing "stack" type
(made from large, flat ceramic plates) because the tube is
essentially one-dimensional. The tube can get hot in the middle,
for example, and expand but not crack. For example, a tube furnace
can heat a 36'' long alumina tube, 4'' in diameter, and it will
become red hot in the center, and cold enough to touch at the ends.
Because the tube is heated evenly in the center section, that
center section expands, making the tube become longer, but it does
not crack. A ceramic plate heated in the center only would quickly
break into pieces because the center expands while the outside
remains the same size. The key property of the tube is that it is
uniaxial, or one-dimensional.
[0008] A second key challenge is to make contact to the SOFC. The
SOFC ideally operates at high temperature (typically
700-1000.degree. C.), yet it also needs to be connected to the
outside world for air and fuel, and also to make electrical
connection. Ideally, one would like to connect at room temperature.
Connecting at high temperature is problematic because organic
material cannot be used, so one must use glass seals or mechanical
seals. These are unreliable, in part, because of expansion
problems. They can also be expensive.
[0009] Thus, previous SOFC systems have difficulty with at least
the two problems cited above. The plate technology also has
difficulty with the edges of the plates in terms of sealing the gas
ports, and has difficulty with fast heating, as well as cracking.
The tube approach resolves the cracking issue but still has other
problems. An SOFC tube is useful as a gas container only. To work
it must be used inside a larger air container. This is bulky. A key
challenge of using tubes is that you must apply both heat and air
to the outside of the tube; air to provide the O.sub.2 for the
reaction, and heat to accelerate the reaction. Usually, the heat
would be applied by burning fuel, so instead of applying air with
20% O.sub.2 (typical), the air is actually partially reduced
(partially burned to provide the heat) and this lowers the driving
potential of the cell.
[0010] An SOFC tube is also limited in its scalability. To achieve
greater kV output, more tubes must be added. Each tube is a single
electrolyte layer, such that increases are bulky. The solid
electrolyte tube technology is further limited in terms of
achievable electrolyte thinness. A thinner electrolyte is more
efficient. Electrolyte thickness of 2 .mu.m or even 1 .mu.m would
be optimal for high power, but is very difficult to achieve in
solid electrolyte tubes. It is noted that a single fuel cell area
produces about 0.5 to 1 volt (this is inherent due to the driving
force of the chemical reaction, in the same way that a battery
gives off 1.2 volts), but the current, and therefore the power,
depend on several factors. Higher current will result from factors
that make more oxygen ions migrate across the electrolyte in a
given time. These factors are higher temperature, thinner
electrolyte, and larger area.
SUMMARY OF THE INVENTION
[0011] The invention provides a solid oxide fuel cell device with a
rectangular solid ceramic substrate extending in length from a
first end surface to a second end surface, in width from a first
side surface to a second side surface, and in height from a bottom
surface to a top surface, wherein the first and second end
surfaces, first and second side surfaces and bottom and top
surfaces collectively define an exterior surface, and wherein
thermal expansion occurs primarily along the length. An active
structure is internal to the exterior surface and extends along
only a first portion of the length, the active structure comprising
an anode in opposing relation to a cathode with an electrolyte
therebetween, wherein the electrolyte is monolithic with the solid
ceramic substrate, and wherein the first portion of the length
along which the active structure extends is configured to be heated
to an operating reaction temperature greater than 700.degree. C. to
generate a fuel cell reaction when the active structure is supplied
with fuel and oxidizer. A remaining portion of the length from the
first portion is a non-active section of the solid ceramic
substrate lacking the anode in opposing relation to the cathode and
to which no heat is applied such that no fuel cell reaction can be
generated and such that heat is dissipated along the remaining
portion of the length away from the first portion. A second portion
of the length in the remaining portion of the length adjacent the
first end surface and/or the second end surface is sufficiently
distanced away from the first portion of the length such that the
exterior surface in the second portion is at a low temperature
below 300.degree. C. when the first portion of the length is at the
operating reaction temperature due to the heat from the first
portion being dissipated along the remaining portion of the length.
The anode and cathode each have an electrical pathway extending
from the internal active structure to the exterior surface in the
second portion of the length for electrical connection at the low
temperature below the operating reaction temperature.
BRIEF DESCRIPTION OF THE INVENTION
[0012] The accompanying drawings, which are incorporated in and
constitute a part of this specification, illustrate embodiments of
the invention and, together with a general description of the
invention given above, and the detailed description given below,
serve to explain the invention.
[0013] FIGS. 1 and 1A depict, in side cross-sectional view and top
cross-sectional view, respectively, one embodiment of a basic SOFC
Stick.TM. device of the invention, having a single anode layer,
cathode layer and electrolyte layer, and a hot zone between two end
cold zones.
[0014] FIG. 2 depicts in perspective view a first end of one
embodiment of a SOFC Stick.TM. device of the invention with a fuel
supply tube connected thereto.
[0015] FIG. 3A depicts in perspective view a SOFC Stick.TM. device
according to one embodiment of the invention, but having modified
ends.
[0016] FIG. 3B depicts in perspective view a fuel supply tube
connected to one modified end of the device of FIG. 3A.
[0017] FIG. 4A depicts in perspective view a metallurgical bonding
attachment means to a plurality of SOFC Stick.TM. devices to make
electrical connection to positive and negative voltage nodes
according to one embodiment of the invention.
[0018] FIG. 4B depicts in schematic end view a connection between
multiple SOFC Stick.TM. devices according to one embodiment of the
invention, where each SOFC Stick.TM. device includes a plurality of
anodes and cathodes.
[0019] FIG. 5 depicts in schematic end view a mechanical attachment
means for making the electrical connection to positive and negative
voltage nodes according to one embodiment of the invention.
[0020] FIGS. 6A and 6B depict in perspective views an alternative
embodiment having a single cold zone at one end of a SOFC Stick.TM.
device to which fuel and air supply tubes are attached, with the
other end being in the hot zone.
[0021] FIGS. 7A and 7B are cross-sectional side and top views,
respectively, illustrating a plurality of support pillars in the
air and fuel passages according to one embodiment of the
invention.
[0022] FIGS. 7C and 7D are micrographs depicting the use of
spherical balls in the fuel and air passages as the support pillars
according to another embodiment of the invention.
[0023] FIG. 8A depicts in cross-section one embodiment of the
invention containing two fuel cells connected externally in
parallel.
[0024] FIG. 8B depicts in cross-sectional view another embodiment
of the invention similar to FIG. 8A, but having the two fuel cells
connected internally in parallel through the use of vias.
[0025] FIGS. 9A and 9B depict in cross-sectional views a multi-fuel
cell design according to an embodiment of the invention having
shared anodes and cathodes, where FIG. 9A depicts three fuel cell
layers connected in parallel and FIG. 9B depicts three fuel cells
connected in series.
[0026] FIG. 10 depicts in schematic side view an SOFC Stick.TM.
device according to one embodiment of the invention having a fuel
supply tube connected to a cold end of the device and a side of the
device open in the hot zone to an air passage for supply of heated
air to the device in the hot zone.
[0027] FIG. 10A depicts in schematic side view a variation of the
embodiment of FIG. 10, where the hot zone is positioned between
opposing cold ends.
[0028] FIG. 10B depicts the SOFC Stick.TM. device of FIG. 10A in
top cross-sectional view taken along line 10B-10B.
[0029] FIGS. 11-24 schematically depict various embodiments of the
invention, where FIG. 11 provides a key for the components depicted
in FIGS. 12-24.
[0030] FIGS. 25A and 27A depict in schematic top plan view and FIG.
27B depicts in schematic side view an SOFC Stick.TM. device
according to one embodiment of the invention having a panhandle
design with an elongate section at one cold end and a large surface
area section at the opposing hot end.
[0031] FIGS. 25B and 26A depict in schematic top plan view and FIG.
26B depicts in schematic side view an alternative embodiment of the
panhandle design having two elongate sections at opposing cold ends
with a center large surface area section in a central hot zone.
[0032] FIGS. 28A-28D depict an SOFC Stick.TM. device according to
one embodiment of the invention, having a spiral or rolled, tubular
configuration, where FIGS. 28A-28C depict the unrolled structure in
schematic top view, end view and side view, respectively, and FIG.
28D depicts the spiral or rolled, tubular configuration in
schematic perspective view.
[0033] FIGS. 29A-29G depict another alternative embodiment of the
invention wherein the SOFC Stick.TM. device has a tubular
concentric form, and where FIG. 29A depicts the device in schematic
isometric view, FIGS. 29B-29E depict cross-sectional views taken
from FIG. 29A, FIG. 29F depicts an end view at the air input end,
and FIG. 29G depicts an end view at the fuel input end.
[0034] FIG. 30A depicts in schematic cross-sectional side view an
embodiment of an SOFC Stick.TM. device of the invention having an
integrated pre-heat zone preceding an active zone in the hot zone,
and FIGS. 30B and 30C depict the device of FIG. 30A in schematic
cross-sectional view taken along lines 30B-30B and 30C-30C,
respectively.
[0035] FIGS. 31A-31C are similar to FIGS. 30A-30C, but depict two
cold zones with a central hot zone.
[0036] FIGS. 32A-32B depict in schematic cross-sectional side view
and schematic cross-sectional top view taken along line 32B-32B of
FIG. 32A, respectively, an embodiment similar to that depicted in
FIGS. 31A-31C, but further including pre-heat chambers extending
between the fuel inlet and the fuel passage and between the air
inlet and the air passage, each pre-heat chamber extending from the
cold zone into the pre-heat zone of the hot zone.
[0037] FIGS. 33A-33C depict another embodiment of the invention for
pre-heating the air and fuel, where FIG. 33A is a schematic
cross-sectional side view through the longitudinal center of the
SOFC Stick.TM. device, FIG. 33B is a schematic cross-sectional top
view taken along line 33B-33B of FIG. 33A, and FIG. 33C is a
schematic cross-sectional bottom view taken along line 33C-33C of
FIG. 33A.
[0038] FIGS. 34A and 34B depict in schematic oblique front view and
schematic side view, respectively, an embodiment of the invention
having multiple anodes and cathodes interconnected externally in
series.
[0039] FIG. 35 depicts in schematic side view the structure of FIG.
34B doubled with the two structures connected externally by metal
stripes to provide a series-parallel design.
[0040] FIGS. 36A and 36B depict in schematic side view and
perspective view another embodiment of the invention including
metal stripes to connect anodes and cathodes in series and/or
parallel in the hot zone and long metal stripes extending from the
hot zone to the cold zone for making low temperature connection in
the cold zones to the positive and negative voltage nodes.
[0041] FIG. 37 depicts in schematic isometric view an embodiment
similar to that of FIG. 36B, but having a single cold zone for the
air and fuel supply connections and for the voltage node
connection.
[0042] FIGS. 38A and 38B depict in schematic cross-sectional side
view an embodiment of the invention having multiple exit gaps along
the sides of the device for bake-out of organic material used to
form passages within the structure.
[0043] FIG. 39 depicts in schematic cross-sectional end view
another embodiment of the invention in which anode material is used
as the supporting structure, referred to as an anode-supported
version of an SOFC Stick.TM. device.
[0044] FIGS. 40A and 40B depict in schematic cross-sectional end
view and schematic cross-sectional side view, respectively, an
anode-supported version according to another embodiment of an SOFC
Stick.TM. device of the invention in which an open fuel passage is
eliminated in favor of a porous anode that serves the function of
conveying the fuel through the device.
[0045] FIGS. 41A and 41B depict in schematic cross-sectional end
view and schematic cross-sectional top view, respectively, another
embodiment of an anode-supported version of an SOFC Stick.TM.
device of the invention, in which multiple air passages are
provided within the anode-supporting structure, and a single fuel
passage is provided normal to the multiple air passages.
[0046] FIGS. 42A-42C depict in schematic cross-sectional view a
method for forming an electrode layer in a passage of an SOFC
Stick.TM. device of the invention, according to one embodiment.
[0047] FIG. 43 depicts in schematic cross-sectional side view
another embodiment of the invention in which the electrolyte layer
is provided with an uneven topography to increase the surface area
available to receive an electrode layer.
[0048] FIG. 44 depicts in schematic cross-sectional side view an
alternative embodiment of the invention for providing uneven
topography on the electrolyte layer.
[0049] FIG. 45A depicts in schematic top view and FIG. 45B depicts
in cross-sectional view through the hot zone an embodiment of an
SOFC Stick.TM. device of the invention having a plurality of fuel
cells on each of a left and right side of the device, with a
bridging portion therebetween.
[0050] FIGS. 46A and 46B depict in schematic perspective view and
schematic cross-sectional view, respectively, another embodiment of
an SOFC Stick.TM. device of the invention having large exterior
contact pads to provide a large or wide path of low resistance for
electrons to travel to the cold end of the device.
[0051] FIG. 47 depicts in schematic cross-sectional side view an
SOFC Stick.TM. device according to another embodiment of the
invention having a single exhaust passage for both spent fuel and
air.
[0052] FIGS. 48A-48C depict an alternative embodiment referred to
as an "end-rolled SOFC Stick.TM. device" having a thick portion and
a thin rolled portion, wherein FIG. 48A depicts the unrolled device
in perspective view, FIG. 48B depicts the rolled device in
cross-sectional side view, and FIG. 48C depicts the rolled device
in perspective view.
DETAILED DESCRIPTION
[0053] In one embodiment, the invention provides a SOFC device and
system in which the fuel port and the air port are made in one
monolithic structure. In one embodiment, the SOFC device is an
elongate structure, essentially a relatively flat or rectangular
stick (and thus, referred to as a SOFC Stick.TM. device), in which
the length is considerably greater than the width or thickness. The
SOFC Stick.TM. devices are capable of having cold ends while the
center is hot (cold ends being <300.degree. C.; hot center being
>400.degree. C., and most likely >700.degree. C.). Slow heat
conduction of ceramic can prevent the hot center from fully heating
the colder ends. In addition, the ends are quickly radiating away
any heat that arrives there. The invention includes the realization
that by having cold ends for connection, it is possible to make
easier connection to the anode, cathode, fuel inlet and H.sub.2O
CO.sub.2 outlet, and air inlet and air outlet. While tubular fuel
cell constructions are also capable of having cold ends with a hot
center, the prior art does not take advantage of this benefit of
ceramic tubes, but instead, places the entire tube in the furnace,
or the hot zone, such that high temperature connections have been
required. The prior art recognizes the complexity and cost of
making high temperature brazed connections for the fuel input, but
has not recognized the solution presented herein. The SOFC
Stick.TM. device of the invention is long and skinny so that it has
the thermal property advantages discussed above that allow it to be
heated in the center and still have cool ends. This makes it
structurally sound with temperature, and makes it relatively easy
to connect fuel, air and electrodes. The SOFC Stick.TM. device is
essentially a stand-alone system, needing only heat, fuel, and air
to be added in order to make electricity. The structure is designed
so that these things can be readily attached.
[0054] The SOFC Stick.TM. device of the invention is a multi-layer
structure and may be made using a multi-layer co-fired approach,
which offers several other advantages. First, the device is
monolithic, which helps to make it structurally sound. Second, the
device lends itself to traditional high volume manufacturing
techniques such as those used in MLCC (multi-layer co-fired
ceramic) production of capacitor chips. (It is believed that
multi-layer capacitor production is the largest volume use of
technical ceramics, and the technology is proven for high volume
manufacturing.) Third, thin electrolyte layers can be achieved
within the structure at no additional cost or complexity.
Electrolyte layers of 2 .mu.m thicknesses are possible using the
MLCC approach, whereas it is hard to imagine a SOFC tube with less
than a 60 .mu.m electrolyte wall thickness. Hence, the SOFC
Stick.TM. device of the invention can be about 30 times more
efficient than a SOFC tube. Finally, the multi-layer SOFC Stick.TM.
devices of the invention could each have many hundreds, or
thousands, of layers, which would offer the largest area and
greatest density.
[0055] Consider the surface area of a SOFC tube of the prior art
versus a SOFC Stick.TM. device of the invention. For example,
consider a 0.25'' diameter tube versus a 0.25''.times.0.25'' SOFC
Stick.TM. device. In the tube, the circumference is 3.14.times.D,
or 0.785''. In the 0.25'' SOFC Stick.TM. device, the usable width
of one layer is about 0.2 inch. Therefore, it takes about 4 layers
to give the same area as one tube. These figures are dramatically
different than those for capacitor technology. The state of the art
for Japanese multi-layer capacitors is currently 600 layers of 2
.mu.m thicknesses. The Japanese will likely soon launch 1000 layer
parts in production, and they make them now in the laboratory.
These chip capacitors with 600 layers are only 0.060'' (1500
.mu.m). Applying this manufacturing technology to a SOFC Stick.TM.
device of the invention, in a 0.25'' device having a 2 .mu.m
electrolyte thickness and air/fuel passages with respective
cathodes/anodes of 10 .mu.m thickness, it would be feasible to
produce a single device with 529 layers. That would be the
equivalent of 132 tubes. Prior art strategies either add more
tubes, increase diameter, and/or increase tube length to get more
power, with result being very large structures for high power
output. The invention, on the other hand, either adds more layers
to a single SOFC Stick.TM. device to get more power and/or uses
thinner layers or passages in the device, thereby enabling
miniaturization for SOFC technology. Moreover, the benefit in the
present invention is a squared effect, just like in capacitors.
When the electrolyte layers are made half as thick, the power
doubles, and then you can fit more layers in the device so power
doubles again.
[0056] Another key feature of the invention is that it would be
easy to link layers internally to increase the output voltage of
the SOFC Stick.TM. device. Assuming 1 volt per layer, 12 volts
output may be obtained by the SOFC Stick.TM. devices of the
invention using via holes to link groups of 12 together. After
that, further connections may link groups of 12 in parallel to
achieve higher current. This can be done with existing methods used
in capacitor chip technology. The critical difference is that the
invention overcomes the brazing and complex wiring that other
technologies must use.
[0057] The invention also provides a greater variety of electrode
options compared to the prior art. Precious metals will work for
both the anodes and cathodes. Silver is cheaper, but for higher
temperature, a blend with Pd, Pt, or Au would be needed, with Pd
possibly being the lowest priced of the three. Much research has
focused on non-precious metal conductors. On the fuel side,
attempts have been made to use nickel, but any exposure to oxygen
will oxidize the metal at high temperature. Conductive ceramics are
also known, and can be used in the invention. In short, the present
invention may utilize any sort of anode/cathode/electrolyte system
that can be sintered.
[0058] In an embodiment of the invention, it is possible that when
a large area of 2 .mu.m tape is unsupported, with air/gas on both
sides, the layer might become fragile. It is envisioned to leave
pillars across the gap. These would look something like pillars in
caves where a stalactite and stalagmite meet. They could be spaced
evenly and frequently, giving much better strength to the
structure.
[0059] For attachment of the gas and air supply, it is envisioned
that the end temperature is below 300.degree. C., for example,
below 150.degree. C., such that high temperature flexible silicone
tubes or latex rubber tubes, for example, may be used to attach to
the SOFC Stick.TM. devices. These flexible tubes can simply stretch
over the end of the device, and thereby form a seal. These
materials are available in the standard McMaster catalog. Silicone
is commonly used at 150.degree. C. or above as an oven gasket,
without losing its properties. The many silicone or latex rubber
tubes of a multi-stick SOFC Stick.TM. system could be connected to
a supply with barb connections.
[0060] The anode material or the cathode material, or both
electrode materials, may be a metal or alloy. Suitable metals and
alloys for anodes and cathodes are known to those of ordinary skill
in the art. Alternatively, one or both electrode materials may be
an electronically conductive green ceramic, which is also known to
those of ordinary skill in the art. For example, the anode material
may be a partially sintered metallic nickel coated with
yttria-stabilized zirconia, and the cathode material may be a
modified lanthanum manganite, which has a perovskite structure.
[0061] In another embodiment, one or both of the electrode
materials may be a composite of a green ceramic and a conductive
metal present in an amount sufficient to render the composite
conductive. In general, a ceramic matrix becomes electronically
conductive when the metal particles start to touch. The amount of
metal sufficient to render the composite matrix conductive will
vary depending mainly on the metal particle morphology. For
example, the amount of metal will generally need to be higher for
spherical powder metal than for metal flakes. In an exemplary
embodiment, the composite comprises a matrix of the green ceramic
with about 40-90% conductive metal particles dispersed therein. The
green ceramic matrix may be the same or different than the green
ceramic material used for the electrolyte layer.
[0062] In the embodiments in which one or both electrode materials
include a ceramic, i.e., the electronically conductive green
ceramic or the composite, the green ceramic in the electrode
materials and the green ceramic material for the electrolyte may
contain cross-linkable organic binders, such that during
lamination, the pressure is sufficient to cross-link the organic
binder within the layers as well as to link polymer molecular
chains between the layers.
[0063] Reference will now be made to the drawings in which like
numerals are used throughout to refer to like components. Reference
numbers used in the Figures are as follows: [0064] 10 SOFC
Stick.TM. device [0065] 11a First end [0066] 11b Second end [0067]
12 Fuel inlet [0068] 13 Fuel pre-heat chamber [0069] 14 Fuel
passage [0070] 16 Fuel outlet [0071] 18 Air inlet [0072] 19 Air
pre-heat chamber [0073] 20 Air passage [0074] 21 Exhaust passage
[0075] 22 Air outlet [0076] 24 Anode layer [0077] 25 Exposed anode
portion [0078] 26 Cathode layer [0079] 27 Exposed cathode portion
[0080] 28 Electrolyte layer [0081] 30 Cold zone (or second
temperature) [0082] 31 Transition zone [0083] 32 Hot zone (or
heated zone or first temperature zone) [0084] 33a Pre-heat zone
[0085] 33b Active zone [0086] 34 Fuel supply [0087] 36 Air supply
[0088] 38 Negative voltage node [0089] 40 Positive voltage node
[0090] 42 Wire [0091] 44 Contact pad [0092] 46 Solder connection
[0093] 48 Spring clip [0094] 50 Supply tube [0095] 52 Tie wrap
[0096] 54 Ceramic pillars [0097] 56 First via [0098] 58 Second via
[0099] 60 Barrier coating [0100] 62 Surface particles [0101] 64
Textured surface layer [0102] 66 Anode suspension [0103] 70
Openings [0104] 72 Organic material [0105] 80 Left side [0106] 82
Right side [0107] 84 Bridging portion [0108] 90 Bridge [0109] 100
SOFC Stick.TM. device [0110] 102 Elongate section [0111] 104 Large
surface area section [0112] 106 Elongate section [0113] 200 Spiral
Tubular SOFC Stick.TM. device [0114] 300 Concentric Tubular SOFC
Stick.TM. device [0115] 400 End-rolled SOFC Stick.TM. device [0116]
402 Thick portion [0117] 404 Thin portion
[0118] FIGS. 1 and 1A depict, in side cross-sectional view and top
cross-sectional view, respectively, one embodiment of a basic SOFC
Stick.TM. device 10 of the invention, having a single anode layer
24, cathode layer 26 and electrolyte layer 28, wherein the device
is monolithic. The SOFC Stick.TM. device 10 includes a fuel inlet
12, a fuel outlet 16 and a fuel passage 14 therebetween. Device 10
further includes an air inlet 18, an air outlet 22 and an air
passage 20 therebetween. The fuel passage 14 and the air passage 20
are in an opposing and parallel relation, and the flow of fuel from
fuel supply 34 through the fuel passage 14 is in a direction
opposite to the flow of air from air supply 36 through air passage
20. The electrolyte layer 28 is disposed between the fuel passage
14 and the air passage 20. The anode layer 24 is disposed between
the fuel passage 14 and the electrolyte layer 28. Similarly, the
cathode layer 26 is disposed between the air passage 20 and the
electrolyte layer 28. The remainder of the SOFC Stick.TM. device 10
comprises ceramic 29, which may be of the same material as the
electrolyte layer 28 or may be a different but compatible ceramic
material. The electrolyte layer 28 is considered to be that portion
of the ceramic lying between opposing areas of the anode 24 and
cathode 26, as indicated by dashed lines. It is in the electrolyte
layer 28 that oxygen ions pass from the air passage to the fuel
passage. As shown in FIG. 1, 02 from the air supply 36 travels
through the air passage 20 and is ionized by the cathode layer 26
to form 2O.sup.-, which travels through the electrolyte layer 28
and through the anode 24 into the fuel passage 14 where it reacts
with fuel, for example, a hydrocarbon, from the fuel supply 34 to
first form CO and H.sub.2 and then to form H.sub.2O and CO.sub.2.
While FIG. 1 depicts the reaction using a hydrocarbon as the fuel,
the invention is not so limited. Any type of fuel commonly used in
SOFCs may be used in the present invention. Fuel supply 34 may be
any hydrocarbon source or hydrogen source, for example. Methane
(CH.sub.4), propane (C.sub.3H.sub.8) and butane (C.sub.4H.sub.10)
are examples of hydrocarbon fuels.
[0119] For the reaction to occur, heat must be applied to the SOFC
Stick.TM. device 10. In accordance with the invention, the length
of the SOFC Stick.TM. device 10 is long enough that the device can
be divided into a hot zone 32 (or heated zone) in the center of the
device and cold zones 30 at each end 11a and 11b of the device 10.
Between the hot zone 32 and the cold zones 30, a transition zone 31
exists. The hot zone 32 will typically operate above 400.degree. C.
In exemplary embodiments, the hot zone 32 will operate at
temperatures >600.degree. C., for example >700.degree. C. The
cold zones 30 are not exposed to a heat source, and due to the
length of the SOFC Stick.TM. device 10 and the thermal property
advantages of the ceramic materials, heat dissipates outside the
hot zone, such that the cold zones 30 have a temperature
<300.degree. C. It is believed that heat transfer from the hot
zone down the length of the ceramic to the end of the cold zone is
slow, whereas the heat transfer from the ceramic material outside
the heat zone into the air is relatively faster. Thus, most of the
heat inputted in the hot zone is lost to the air (mainly in the
transition zone) before it can reach the end of the cold zone. In
exemplary embodiments of the invention, the cold zones 30 have a
temperature <150.degree. C. In a further exemplary embodiment,
the cold zones 30 are at room temperature. The transition zones 31
have temperatures between the operating temperature of the hot zone
32 and the temperature of the cold zones 30, and it is within the
transition zones 31 that the significant amount of heat dissipation
occurs.
[0120] Because the dominant coefficient of thermal expansion (CTE)
is along the length of the SOFC Stick.TM. device 10, and is
therefore essentially one-dimensional, fast heating of the center
is permitted without cracking. In exemplary embodiments, the length
of the device 10 is at least 5 times greater than the width and
thickness of the device. In further exemplary embodiments, the
length of the device 10 is at least 10 times greater than the width
and thickness of the device. In yet further exemplary embodiments,
the length of the device 10 is at least 15 times greater than the
width and thickness of the device. In addition, in exemplary
embodiments, the width is greater than the thickness, which
provides for greater area. For example, the width may be at least
twice the thickness. By way of further example, a 0.2 inch thick
SOFC Stick.TM. device 10 may have a width of 0.5 inch. It may be
appreciated that the drawings are not shown to scale, but merely
give a general idea of the relative dimensions.
[0121] In accordance with the invention, electrical connections to
the anode and cathode are made in the cold zones 30 of the SOFC
Stick.TM. device 10. In an exemplary embodiment, the anode 24 and
the cathode 26 will each be exposed to an outer surface of the SOFC
Stick.TM. device 10 in a cold zone 30 to allow an electrical
connection to be made. A negative voltage node 38 is connected via
a wire 42, for example, to the exposed anode portion 25 and a
positive voltage node 40 is connected via a wire 42, for example,
to the exposed cathode portion 27. Because the SOFC Stick.TM.
device 10 has cold zones 30 at each end 11a, 11b of the device, low
temperature rigid electrical connections can be made, which is a
significant advantage over the prior art, which generally requires
high temperature brazing methods to make the electrical
connections.
[0122] FIG. 2 depicts in perspective view a first end 11a of SOFC
Stick.TM. device 10 with a supply tube 50 attached over the end and
secured with a tie wrap 52. Fuel from fuel supply 34 will then be
fed through the supply tube 50 and into the fuel inlet 12. As a
result of first end 11a being in the cold zone 30, flexible plastic
tubing or other low temperature type connection material may be
used to connect the fuel supply 34 to the fuel inlet 12. The need
for high temperature brazing to make the fuel connection is
eliminated by the invention.
[0123] FIG. 3A depicts in perspective view a SOFC Stick.TM. device
10 similar to that depicted in FIG. 1, but having modified first
and second ends 11a, 11b. Ends 11a, 11b have been machined to form
cylindrical end portions to facilitate connection of the fuel
supply 34 and air supply 36. FIG. 3B depicts in perspective view a
supply tube 50 connected to the first end 11a for feeding fuel from
fuel supply 34 to the fuel inlet 12. By way of example, supply tube
50 can be a silicone or latex rubber tube that forms a tight seal
by virtue of its elasticity to the first end 11a. It may be
appreciated that the flexibility and elasticity of the supply tubes
50 can provide a shock-absorbing holder for the SOFC Stick.TM.
devices when the use is in a mobile device subject to vibrations.
In the prior art, the tubes or plates were rigidly brazed, and thus
subject to crack failure if used in a dynamic environment.
Therefore, the additional function of the supply tubes 50 as
vibration dampers offers a unique advantage compared to the prior
art.
[0124] Referring back to FIG. 3A, contact pads 44 are provided on
the outer surface of the SOFC Stick.TM. device 10 so as to make
contact with the exposed anode portion 25 and the exposed cathode
portion 27. Material for the contact pads 44 should be electrically
conductive so as to electrically connect the voltage nodes 38, 40
to their respective anode 24 and cathode 26. It may be appreciated
that any suitable method may be used for forming the contact pads
44. For example, metal pads may be printed onto the outer surface
of a sintered SOFC Stick.TM. device 10. The wires 42 are secured to
the contact pads 44 by a solder connection 46, for example, to
establish a reliable connection. Solders are a low temperature
material, which can be used by virtue of being located in the cold
zones 30 of the SOFC Stick.TM. device 10. For example, a common
10Sn88Pb2Ag solder can be used. The present invention eliminates
the need for high temperature voltage connections, thereby
expanding the possibilities to any low temperature connection
material or means.
[0125] Also depicted in FIG. 3A, in perspective view, are the fuel
outlet 16 and the air outlet 22. The fuel enters through the fuel
inlet 12 at first end 11a, which is in one cold zone 30, and exits
out the side of SOFC Stick.TM. device 10 through outlet 16 adjacent
the second end 11b. Air enters through air inlet 18 located in the
second end 11b, which is in the cold zone 30, and exits from the
air outlet 22 in the side of the SOFC Stick.TM. device 10 adjacent
the first end 11a. While the outlets 16 and 22 are depicted as
being on the same side of the SOFC Stick.TM. device 10, it may be
appreciated that they may be positioned at opposing sides, for
example, as depicted below in FIG. 4A.
[0126] By having air outlet 22 close to fuel inlet 12 (and
similarly fuel outlet 16 close to air inlet 18), and through the
close proximity of the overlapping layers (anode, cathode,
electrolyte), the air outlet 22 functions as a heat exchanger,
usefully pre-heating the fuel that enters the device 10 through
fuel inlet 12 (and similarly, fuel outlet 16 pre-heats air entering
through air inlet 18). Heat exchangers improve the efficiency of
the system. The transition zones have overlapping areas of spent
air and fresh fuel (and spent fuel and fresh air), such that heat
is transferred before the fresh fuel (fresh air) reaches the hot
zone. Thus, the SOFC Stick.TM. device 10 of the invention is a
monolithic structure that includes a built-in heat exchanger.
[0127] With respect to FIG. 4A, there is depicted in perspective
view the connection of a plurality of SOFC Stick.TM. devices 10, in
this case two SOFC Stick.TM. devices, by aligning each contact pad
44 connected to the exposed anode portions 25 and soldering (at 46)
a wire 42 connected to the negative voltage node 38 to each of the
contact pads 44. Similarly, the contact pads 44 that are connected
to the exposed cathode portions 27 are aligned and a wire 42
connecting the positive voltage node 40 is soldered (at 46) to each
of those aligned contact pads 44, as shown partially in phantom. As
may be appreciated, because the connection is in the cold zone 30,
and is a relatively simple connection, if one SOFC Stick.TM. device
10 in a multi-SOFC Stick.TM. system or assembly needs replacing, it
is only necessary to break the solder connections to that one
device 10, replace the device with a new device 10, and re-solder
the wires 42 to the contact pads of the new SOFC Stick.TM. device
10.
[0128] FIG. 4B depicts in an end view the connection between
multiple SOFC Stick.TM. devices 10, where each SOFC Stick.TM.
device 10 includes a plurality of anodes and cathodes. For example,
the specific embodiment depicted in FIG. 4B includes three sets of
opposing anodes 24 and cathodes 26, with each anode 24 exposed at
the right side of the SOFC Stick.TM. device 10 and each cathode
exposed at the left side of the SOFC Stick.TM. device 10. A contact
pad is then placed on each side of the SOFC Stick.TM. device 10 to
contact the respective exposed anode portions 25 and exposed
cathode portions 27. On the right side, where the anodes 24 are
exposed, the negative voltage node 38 is connected to the exposed
anode portions 25 by securing wire 42 to the contact pad 44 via a
solder connection 46. Similarly, positive voltage node 40 is
connected electrically to the exposed cathode portions 27 on the
left side of the SOFC Stick.TM. device 10 by securing wire 42 to
contact pad 44 via the solder connection 46. Thus, while FIGS. 1-4A
depicted a single anode 24 opposing a single cathode 26, it may be
appreciated, as shown in FIG. 4B, that each SOFC Stick.TM. device
10 may include multiple anodes 24 and cathodes 26, with each being
exposed to an outer surface of the SOFC Stick.TM. device 10 for
electrical connection by means of a contact pad 44 applied to the
outer surface for connection to the respective voltage node 38 or
40. The number of opposing anodes and cathodes in the structure may
be tens, hundreds and even thousands.
[0129] FIG. 5 depicts in an end view a mechanical attachment for
making the electrical connection between wire 42 and the contact
pad 44. In this embodiment, the SOFC Stick.TM. devices 10 are
oriented such that one set of electrodes is exposed at the top
surface of each SOFC Stick.TM. device 10. The contact pad 44 has
been applied to each top surface at one end (e.g., 11a or 11b) in
the cold zone 30. Spring clips 48 may then be used to removably
secure the wire 42 to the contact pads 44. Thus, metallurgical
bonding may be used to make the electrical connections, such as
depicted in FIGS. 3A, 4A and 4B, or mechanical connection means may
be used, as depicted in FIG. 5. The flexibility in selecting an
appropriate attachment means is enabled by virtue of the cold zones
30 in the SOFC Stick.TM. devices of the invention. Use of spring
clips or other mechanical attachment means further simplifies the
process of replacing a single SOFC Stick.TM. device 10 in a
multi-stick assembly.
[0130] FIGS. 6A and 6B depict in perspective views an alternative
embodiment having a single cold zone 30 at the first end 11a of
SOFC Stick.TM. device 10, with the second end 11b being in the hot
zone 32. In FIG. 6A, the SOFC Stick.TM. device 10 includes three
fuel cells in parallel, whereas the SOFC Stick.TM. device 10 of
FIG. 6B includes a single fuel cell. Thus, embodiments of the
invention may include a single cell design or a multi-cell design.
To enable the single end input of both the fuel and the air, the
air inlet 18 is reoriented to be adjacent the first end 11a at the
side surface of the SOFC Stick.TM. device 10. The air passage 20
(not shown) again runs parallel to the fuel passage 14, but in this
embodiment, the flow of air is in the same direction as the flow of
fuel through the length of the SOFC Stick.TM. device 10. At the
second end 11b of the device 10, the air outlet 22 is positioned
adjacent the fuel outlet 16. It may be appreciated that either the
fuel outlet 16 or the air outlet 22, or both, can exit from a side
surface of the SOFC Stick.TM. device 10, rather than both exiting
at the end surface.
[0131] As depicted in FIG. 6B, the supply tube 50 for the air
supply 36 is formed by making holes through the side of the supply
tube 50 and sliding the device 10 through the side holes so that
the supply tube 50 for the air supply 36 is perpendicular to the
supply tube 50 for the fuel supply 34. Again, a silicone rubber
tube or the like may be used in this embodiment. A bonding material
may be applied around the joint between the tube 50 and the device
10 to form a seal. The electrical connections are also made
adjacent the first end 11a in the cold zone 30. FIGS. 6A and 6B
each depict the positive voltage connection being made on one side
of the SOFC Stick.TM. device 10 and the negative voltage connection
being made on the opposing side of the SOFC Stick.TM. device 10.
However, it may be appreciated that the invention is not so
limited. An advantage of the single end input SOFC Stick.TM. device
10 is that there is only one cold-to-hot transition instead of two
transition zones 31, such that the SOFC Stick.TM. could be made
shorter.
[0132] One benefit of the invention is the ability to make the
active layers very thin, thereby enabling an SOFC Stick.TM. to
incorporate multiple fuel cells within a single device. The thinner
the active layers are, the greater the chance of an air passage 20
or fuel passage 14 caving in during manufacture of the SOFC
Stick.TM. device 10, thereby obstructing flow through the passage.
Therefore, in one embodiment of the invention, depicted in FIGS. 7A
and 7B, a plurality of ceramic pillars 54 are provided in the
passages 14 and 20 to prevent distortion of the electrolyte layer
and obstruction of the passages. FIG. 7A is a cross-sectional side
view, whereas FIG. 7B is a cross-sectional top view through the air
passage 20. According to one method of the invention, using the
tape casting method, a sacrificial tape layer may be used, with a
plurality of holes formed in the sacrificial layer, such as by
means of laser removal of the material. A ceramic material is then
used to fill the holes, such as by spreading a ceramic slurry over
the sacrificial tape layer to penetrate the holes. After the
various layers are assembled together, the sacrificial material of
the sacrificial layer is removed, such as by use of a solvent,
leaving the ceramic pillars 54 remaining.
[0133] In another embodiment for forming the ceramic pillars 54,
large particles of a pre-sintered ceramic can be added to an
organic vehicle, such as plastic dissolved in a solvent, and
stirred to form a random mixture. By way of example and not
limitation, the large particles may be spheres, such as 0.002 in.
diameter balls. The random mixture is then applied to the green
structure, such as by printing in the areas where the fuel and air
passages 14 and 20 are to be located. During the sintering
(bake/fire) process, the organic vehicle leaves the structure (e.g.
is burned out), thereby forming the passages, and the ceramic
particles remain to form the pillars 54 that physically hold open
the passages. The resultant structure is shown in the micrographs
of FIGS. 7C and 7D. The pillars 54 are randomly positioned, with
the average distance being a function of the loading of the ceramic
particles in the organic vehicle.
[0134] FIG. 8A depicts in cross-section one embodiment of the
invention containing two fuel cells in parallel. Each active
electrolyte layer 28 has an air passage 20 and cathode layer 26a or
26b on one side and a fuel passage 14 and anode layer 24a or 24b on
the opposing side. The air passage 20 of one fuel cell is separated
from the fuel passage 14 of the second fuel cell by ceramic
material 29. The exposed anode portions 25 are each connected via
wire 42 to the negative voltage node 38 and the exposed cathode
portions 27 are each connected via a wire 42 to the positive
voltage node 40. A single air supply 36 can then be used to supply
each of the multiple air passages 20 and a single fuel supply 34
may be used to supply each of the multiple fuel passages 14. The
electrical circuit established by this arrangement of the active
layers is depicted at the right side of the figure.
[0135] In the cross-sectional view of FIG. 8B, the SOFC Stick.TM.
device 10 is similar to that depicted in FIG. 8A, but instead of
having multiple exposed anode portions 25 and multiple exposed
cathode portions 27, only anode layer 24a is exposed at 25 and only
one cathode layer 26a is exposed at 27. A first via 56 connects
cathode layer 26a to cathode layer 26b and a second via 58 connects
anode layer 24a to anode layer 24b. By way of example, laser
methods may be used during formation of the green layers to create
open vias, which are then subsequently filled with electrically
conductive material to form the via connections. As shown by the
circuit at the right of FIG. 8B, the same electrical path is formed
in the SOFC Stick.TM. device 10 of FIG. 8B as in the SOFC Stick.TM.
device 10 of FIG. 8A.
[0136] FIGS. 9A and 9B also depict, in cross-section views,
multi-fuel cell designs, but with shared anodes and cathodes. In
the embodiment of FIG. 9A, the SOFC Stick.TM. device 10 includes
two fuel passages 14 and two air passages 20, but rather than
having two fuel cells, this structure includes three fuel cells.
The first fuel cell is formed between anode layer 24a and cathode
layer 26a with intermediate electrolyte layer 28. Anode layer 24a
is on one side of a fuel passage 14, and on the opposing side of
that fuel passage 14 is a second anode layer 24b. Second anode
layer 24b opposes a second cathode layer 26b with another
electrolyte layer there between, thereby forming a second fuel
cell. The second cathode layer 26b is on one side of an air passage
20 and a third cathode layer 26c is on the opposing side of that
air passage 20. Third cathode layer 26c opposes a third anode layer
24c with an electrolyte layer 28 therebetween, thus providing the
third fuel cell. The portion of the device 10 from anode layer 24a
to cathode layer 26c could be repeated numerous times within the
device to provide the shared anodes and cathodes thereby
multiplying the number of fuel cells within a single SOFC
Stick.TM.. Each anode layer 24a, 24b, 24c includes an exposed anode
portion 25 to which electrical connections can be made at the outer
surface of the SOFC Stick.TM. device 10 to connect to a negative
voltage node 38 via a wire 42, for example. Similarly, each cathode
layer 26a, 26b, 26c includes an exposed cathode portion 27 to the
outside surface for connection to a positive voltage node 40 via a
wire 42, for example. A single air supply 36 may be provided at one
cold end to supply each of the air passages 20 and a single fuel
supply 34 may be provided at the opposite cold end to supply each
of the fuel passages 14. The electrical circuit formed by this
structure is provided at the right side of FIG. 9A. This SOFC
Stick.TM. device 10 contains three fuel cell layers in parallel
trebling the available power. For example, if each layer produces 1
volt and 1 amp, then each fuel cell layer produces 1 watt of power
output (volt.times.amp=watt). Therefore, this three-layer layout
would then produce 1 volt and 3 amps for a total of 3 watts of
power output.
[0137] In FIG. 9B, the structure of FIG. 9A is modified to provide
a single electrical connection to each of the voltage nodes to
create three fuel cells in series, as shown by the circuit at the
right side of FIG. 9B. The positive voltage node 40 is connected to
cathode layer 26a at exposed cathode portion 27. Anode layer 24a is
connected to cathode layer 26b by via 58. Anode layer 24b is
connected to cathode layer 26c by via 56. Anode layer 24c is then
connected at exposed anode portion 25 to the negative voltage node
38. Thus, using the same 1 amp/1 volt per layer assumption, this
three cell structure would produce 3 volts and 1 amp for a total of
3 watts of power output.
[0138] Another embodiment of the invention is depicted in side view
in FIG. 10. In this embodiment, the SOFC Stick.TM. device 10 has a
single cold zone 30 at the first end 11a with the second end 11b
being in the hot zone 32. As in other embodiments, the fuel inlets
12 are at the first end 11a and connected to a fuel supply 34 by a
supply tube 50. In this embodiment, the fuel passages 14 extend the
length of the SOFC Stick.TM. device 10 with the fuel outlet 16
being at second end 11b. Thus, the fuel supply connection is made
in the cold zone 30 and the outlet for the fuel reactants (e.g.,
CO.sub.2 and H.sub.2O) is in the hot zone 32. Similarly, the anodes
have an exposed anode portion 25 in the cold zone 30 for connecting
to the negative voltage node 38 via a wire 42.
[0139] In the embodiment of FIG. 10, the SOFC Stick.TM. device 10
is open at at least one side, and potentially at both opposing
sides, to provide both air inlets 18 and air passages 20 in the hot
zone 32. The use of supporting ceramic pillars 54 may be
particularly useful in this embodiment within the air passages 20.
The air outlet can be at the second end 11b, as depicted.
Alternatively, although not shown, the air outlet may be at an
opposing side from the air inlet side if the passages 20 extend
through the width and the air supply is directed only toward the
input side, or if the passages 20 do not extend through the width.
Instead of providing only heat to the hot zone 32, in this
embodiment, air is also provided. In other words, the sides of the
device 10 in the hot zone 32 are open to heated air instead of
supplying air through a forced air tube.
[0140] FIG. 10A shows in side view a variation of the embodiment
depicted in FIG. 10. In FIG. 10A, the SOFC Stick.TM. device 10
includes opposing cold zones 30 with a central heated zone 32
separated from the cold zones 30 by transition zones 31. The air
inlet 18 is provided in the central heated zone 32, in at least a
portion thereof, to receive the heated air. However, in this
embodiment, the air passage is not completely open to the side of
the SOFC Stick.TM. device 10 for an appreciable length as in FIG.
10. Rather, as shown more clearly in FIG. 10B, air passage 20 is
open in a portion of the hot zone 32 and then is close to the sides
for the remainder of the length and then exits at air outlet 22 at
second end 11b of the SOFC Stick.TM. device 10. This embodiment
allows heated air to be supplied in the hot zone 32 rather than a
forced air supply tube, but also allows for the fuel and air to
exit at one end 11b of the device 10 in a cold zone 30.
[0141] While specific embodiments have been depicted and described
in detail, the scope of the invention should not be so limited.
More general embodiments of the invention are described below and
may be understood more fully with reference to the schematic views
depicted in FIGS. 11-24. FIG. 11 provides a key for the components
depicted schematically in FIGS. 12-24. Where fuel (F) or air (A) is
shown by an arrow going into the SOFC Stick.TM. device, that
indicates forced flow, such as through a tube connected to the
input access point. Where air input is not depicted, that indicates
that heated air is supplied in the hot zone by means other than a
forced flow connection and the SOFC Stick.TM. is open to the air
passage at an access point within the hot zone.
[0142] One embodiment of the invention is an SOFC Stick.TM. device
that includes at least one fuel passage and associated anode, at
least one oxidant pathway and associated cathode, and an
electrolyte therebetween, where the cell is substantially longer
than it is wide or thick so as to have a CTE in one dominant axis
and operating with a portion thereof in a heated zone having a
temperature of greater than about 400.degree. C. In this
embodiment, the SOFC Stick.TM. device has integrated access points
for both air and fuel input at one end of the device according to
the dominant CTE direction, or air input at one end and fuel input
at the other end according to the dominant CTE direction, and air
and fuel inputs being located outside the heated zone. For example,
see FIGS. 20 and 24.
[0143] In another embodiment of the invention, the fuel cell has a
first temperature zone and a second temperature zone, wherein the
first temperature zone is the hot zone, which operates at a
temperature sufficient to carry out the fuel cell reaction, and the
second temperature zone is outside the heated zone and operates at
a lower temperature than the first temperature zone. The
temperature of the second temperature zone is sufficiently low to
allow low temperature connections to be made to the electrodes and
a low temperature connection for at least the fuel supply. The fuel
cell structure extends partially into the first temperature zone
and partially into the second temperature zone. For example, see
FIGS. 12, 13 and 17.
[0144] In one embodiment of the invention, the fuel cell includes a
first temperature zone that is the heated zone and a second
temperature zone operating at a temperature below 300.degree. C.
The air and fuel connections are made in the second temperature
zone using rubber tubing or the like as a low temperature
connection. Low temperature solder connections or spring clips are
used to make the electrical connections to the anode and cathode
for connecting them to the respective negative and positive voltage
nodes. Further, the fuel outlet for carbon dioxide and water and
the air outlet for depleted oxygen are located in the first
temperature zone, i.e., the heated zone. For example, see FIG.
17.
[0145] In another embodiment, the fuel cell structure has a central
first temperature zone that is the heated zone, and each end of the
fuel cell is located outside the first temperature zone in a second
temperature zone operating below 300.degree. C. Fuel and air inputs
are located in the second temperature zone, as are solder
connections or spring clips for electrical connection to the anode
and cathode. Finally, output for the carbon dioxide, water and
depleted oxygen are located in the second temperature zone. For
example, see FIGS. 19, 20 and 24.
[0146] In another embodiment of the invention, fuel inputs may be
provided at each end according to the dominant CTE direction in a
second temperature zone operating below 300.degree. C. with a first
temperature zone being the heated zone provided in the center
between the opposing second temperature zones. The output for the
carbon dioxide, water, and depleted oxygen may be located in the
central heated zone. For example, see FIGS. 15 and 18.
Alternatively, the output for the carbon dioxide, water and
depleted oxygen may be located in the second temperature zone,
i.e., outside of the heated zone. For example, see FIGS. 16 and
19.
[0147] In another embodiment, both the fuel and air input access
points are located outside the first temperature zone, which is the
heated zone, in a second temperature zone operating below
300.degree. C. thereby allowing use of low temperature connections,
such as rubber tubing for air and fuel supply. In addition, solder
connections or spring clips are used in the second temperature zone
for connecting the voltage nodes to anodes and cathodes. In one
embodiment, the fuel and air input are both at one end according to
the dominate CTE direction, with the other end of the SOFC
Stick.TM. being in the first heated temperature zone with the
outputs of carbon dioxide, water and depleted oxygen being in the
heated zone. For example, see FIG. 17. Thus, the SOFC Stick.TM. has
one heated end and one non-heated end.
[0148] In another embodiment, fuel and air are inputted into one
end according to the dominant CTE direction outside the heated zone
and exit at the opposite end also outside the heated zone, such
that the heated zone is between two opposing second temperature
zones. For example, see FIG. 20. In yet another alternative, fuel
and air are inputted into both of opposing ends located in second
temperature zones with the fuel and air outputs being in the
central heated zone. For example, see FIG. 18.
[0149] In yet another alternative, fuel and air are inputted into
both of opposing ends located in second temperature zones with the
respective outputs being in the second temperature zone at the
opposite end from the input. For example, see FIG. 19. Thus, the
fuel cell has a central heated zone and opposing ends outside the
heated zone, with fuel and air both inputted into the first end
with the respective reaction outputs exiting adjacent the second
end, and both fuel and air being inputted into the second end and
the reaction outputs exiting adjacent the first end.
[0150] In yet another embodiment, fuel input may be at one end
outside the heated zone and air input may be at the opposite end
outside the heat zone. For example, see FIGS. 21-24. In this
embodiment, the reaction outputs from both the air and fuel may be
within the heated zone (see FIG. 21), or they both may be outside
the heated zone adjacent the opposite end from the respective input
(see FIG. 24). Alternatively, the carbon dioxide and water output
may be in the hot zone while the depleted oxygen output is outside
the hot zone (see FIG. 22), or conversely, the depleted oxygen
output may be in the heated zone and the carbon dioxide and water
output outside the heated zone (see FIG. 23). The variations with
respect to fuel and air output depicted in FIGS. 22 and 23 could
also be applied in the embodiments depicted in FIGS. 18-20, for
example.
[0151] In another embodiment of the invention, depicted in top plan
view in FIGS. 25A and 27A and in side view in FIG. 27B, an SOFC
Stick.TM. device 100 is provided having what may be referred to as
a panhandle design. The SOFC Stick.TM. device 100 has an elongate
section 102, which may be similar in dimension to the SOFC
Stick.TM. devices depicted in prior embodiments, that has a CTE in
one dominant axis, i.e., it is substantially longer than it is wide
or thick. The SOFC Stick.TM. device 100 further has a large surface
area section 104 having a width that more closely matches the
length. Section 104 may have a square surface area or a rectangular
surface area, but the width is not substantially less than the
length, such that the CTE does not have a single dominant axis in
section 104, but rather has a CTE axis in the length direction and
the width direction. The large surface area section 104 is located
in the hot zone 32, whereas the elongate section 102 is at least
partially located in the cold zone 30 and the transition zone 31.
In an exemplary embodiment, a portion of the elongate section 102
extends into the hot zone 32, but this is not essential. By way of
example, the fuel and air supplies may be connected to the elongate
section 102 in the manner depicted in FIG. 6B, as well as the
electrical connections.
[0152] In FIGS. 25B and 26A, a top plan view is provided and in
FIG. 26B a side view is provided of an alternative embodiment
similar to that shown in FIGS. 25A, 27A and 27B but further having
a second elongate section 106 opposite the elongate section 102 so
as to position the large surface area section 104 between the two
elongate sections 102 and 106. Elongate section 106 is also at
least partially located in a cold zone 30 and a transition zone 31.
In this embodiment, fuel may be inputted into elongate section 102
and air inputted into elongate section 106. By way of example, the
air supply and the fuel supply could then be connected to the
elongate sections 106 and 102, respectively, in the manner depicted
in FIG. 2 or FIG. 3B. As depicted in FIG. 25B, the air output may
be located in the elongate section 102 adjacent the fuel input, and
the fuel output may be located in elongate section 106 adjacent the
air input. Alternatively, one or both of the air and fuel outputs
may be located in the large surface area section 104 in the hot
zone 32, as depicted in FIGS. 26A and 26B in top and side views,
respectively. It may be appreciated that in the embodiments of
FIGS. 25A and 25B, the surface area of the opposing anode and
cathode with intervening electrolyte may be increased in the hot
zone to increase the reaction area, thereby increasing the power
generated by the SOFC Stick.TM. device 100.
[0153] Another benefit of the SOFC Stick.TM. devices 10, 100 of the
invention is low weight. Typical combustion engines weigh on the
order of 18-30 lbs per kW of power. An SOFC Stick.TM. device 10,
100 of the invention can be made with a weight on the order of 0.5
lbs per kW of power.
[0154] FIGS. 28A-28D depict an alternative embodiment of a Tubular
SOFC Stick.TM. device 200 of the invention, having a spiral or
rolled, tubular configuration. FIG. 28A is a schematic top view of
device 200, in the unrolled position. The unrolled structure of
device 200 has a first end 202 and a second end 204 of equal length
L that will correspond to the length of the rolled or spiral
Tubular SOFC Stick.TM. device 200. Fuel inlet 12 and air inlet 18
are shown on opposing sides adjacent first end 202. Fuel passage 14
and air passage 20 then extend along the width of the unrolled
structure of device 200 to the second end 204 such that the fuel
outlet 16 and air outlet 22 are at the second end 204, as further
shown in the schematic end view of the unrolled structure of device
200 in FIG. 28B and the schematic side view of the unrolled
structure of device 200 in FIG. 28C. The fuel passage 14 and air
passage 20 are shown as extending nearly the length L of the
unrolled structure of device 200 so as to maximize fuel and air
flow, but the invention is not so limited. To form the spiral
Tubular SOFC Stick.TM. device 200, first end 202 is then rolled
toward second end 204 to form the spiral tube structure of device
200 depicted in the schematic perspective view of FIG. 28D. Air
supply 36 may then be positioned at one end of the spiral Tubular
SOFC Stick.TM. device 200 for input into air inlet 18, while the
fuel supply 34 may be positioned at the opposite end of the spiral
Tubular SOFC Stick.TM. device 200 to input fuel into the fuel inlet
12. The air and the fuel will then exit the spiral Tubular SOFC
Stick.TM. device 200 along the length L of the device 200 through
fuel outlet 16 and air outlet 22. The voltage nodes 38, 40 can be
soldered to contact pads 44 formed on or adjacent to opposing ends
of the spiral Tubular SOFC Stick.TM. device 200.
[0155] FIGS. 29A-29G depict an alternative embodiment of the
invention wherein the SOFC Stick.TM. device is in a tubular
concentric form. FIG. 29A depicts in schematic isometric view a
concentric Tubular SOFC Stick.TM. device 300. FIGS. 29B-29E depict
cross-sectional views of the concentric device 300 of FIG. 29A.
FIG. 29F depicts an end view at the air input end of the device
300, and FIG. 29G depicts an end view at the fuel input end of
device 300. The particular embodiment shown includes three air
passages 20, one being in the center of the tubular structure and
the other two being spaced from and concentric therewith. The
concentric Tubular SOFC Stick.TM. device 300 also has two fuel
passages 14 between and concentric with the air passages 20. As
shown in FIGS. 29A-29D, the concentric Tubular SOFC Stick.TM.
device 300 includes a fuel outlet 16 connecting the fuel passages
14 at one end and an air outlet 22 connecting the air passages 20
at the other end opposite their respective inlets. Each air passage
20 is lined with cathodes 26 and each fuel passage 14 is lined with
anodes 24, with electrolyte 28 separating opposing anodes and
cathodes. As shown in FIGS. 29A-29B and 29F-29G, electrical
connection may be made to the exposed anodes 25 and exposed
cathodes 27 at opposing ends of the concentric Tubular SOFC
Stick.TM. device 300. Contact pads 44 may be applied to the ends to
connect the exposed anodes 25 and exposed cathodes 27, and although
not shown, the contact pads 44 can be run along the outside of the
device 300 to permit the electrical connection to be made at a
point along the length of the device 300 rather than at the ends.
Concentric Tubular SOFC Stick.TM. device 300 may include pillars 54
positioned within the air and fuel passages 14, 20 for structural
support.
[0156] In the embodiments of the invention having two cold zones 30
at opposing ends 11a, 11b, with air input and fuel output at one
end and fuel input and air output at the opposing end, the spent
fuel or air is in a heated state as it exits the central hot zone
32. The heated air and fuel cool as they travel through the
transition zones 31 to the cold zones 30. Thin layers of electrodes
and/or ceramic/electrolyte separate an air passage from a parallel
fuel passage, and vice-versa. In one passage, heated air is exiting
the hot zone, and in an adjacent parallel passage, fuel is entering
the hot zone, and vice-versa. The heated air, through heat exchange
principles, will heat up the incoming fuel in the adjacent parallel
passage, and vice-versa. Thus, there is some pre-heating of the air
and fuel through heat exchange. However, due to the rapid loss of
heat outside the hot zone, as discussed above, heat exchange may
not be sufficient to pre-heat the air and fuel to the optimal
reaction temperature before it enters the active region in the hot
zone. In addition, in embodiments where the SOFC Stick.TM. device
10 includes one cold end and one hot end, fuel and air are inputted
into the same cold end and exit through the same opposing hot end,
such that there is no cross-flow of fuel and air for heat-exchange
to occur. Only limited heat exchange to the incoming fuel and air
is available from the electrode and ceramic materials of the SOFC
Stick.TM. device.
[0157] FIGS. 30A-33C depict various embodiments of an SOFC
Stick.TM. device 10 having integrated pre-heat zones 33a for
heating the fuel and air before it enters an active zone 33b in
which the anodes 24 and cathodes 26 are in opposing relation. These
embodiments include SOFC Stick.TM. devices in which there are two
cold ends with an intermediate hot zone and fuel and air input at
opposing cold ends, and SOFC Stick.TM. devices in which there is
one hot end and one cold end with fuel and air input both at the
single cold end. In these embodiments, the amount of electrode
material used can be limited to the active zone 33b with only a
small amount leading to the cold zone for the external connection
to the voltage nodes 38, 40. Another benefit in these embodiments,
which will be described in more detail later, is that the electrons
have the shortest possible path to travel to the external voltage
connection, which provides a low resistance.
[0158] FIG. 30A depicts a schematic cross-sectional side view of a
first embodiment of an SOFC Stick.TM. device 10 having one cold
zone 30 and one opposing hot zone 32 with an integrated pre-heat
zone 33a. FIG. 30B depicts in cross-section a view through the
anode 24 looking up toward the fuel passage 14, and FIG. 30C
depicts in cross-section a view through the cathode 26 looking down
toward the air passage 20. As shown in FIGS. 30A and 30B, the fuel
from fuel supply 34 enters through fuel inlet 12 and extends along
the length of the device 10 through fuel passage 14 and exits from
the opposite end of the device 10 through fuel outlet 16. The cold
zone 30 is at the first end 11a of SOFC Stick.TM. device 10 and the
hot zone 32 is at the opposing second end 11b. Between the hot and
cold zones is the transition zone 31. The hot zone 32 includes an
initial pre-heat zone 33a through which the fuel first travels, and
an active zone 33b that includes the anode 24 adjacent the fuel
passage 14. As shown in FIG. 30B, the cross-sectional area of the
anode 24 is large in the active zone 33b. The anode 24 extends to
one edge of the SOFC Stick.TM. device 10 and an exterior contact
pad 44 extends along the outside of the device 10 to the cold zone
30 for connection to the negative voltage node 38.
[0159] Similarly, as shown in FIGS. 30A and 30C, the air from air
supply 36 enters through the air inlet 18 positioned in the cold
zone 30 and the air extends along the length of the SOFC Stick.TM.
device 10 through air passage 20 and exits from the hot zone 32
through the air outlet 22. Because the air and fuel are entering at
the same end and traveling along the length of the SOFC Stick.TM.
device 10 in the same direction, there is limited pre-heating of
the air and fuel by heat exchange prior to the hot zone 32. The
cathode 26 is positioned in the active zone 33b in opposing
relation to the anode 24 and extends to the opposite side of the
SOFC Stick.TM. device 10 where it is exposed and connected to an
external contact pad 44 that extends from the active hot zone 33b
to the cold zone 30 for connection to the positive voltage node 40.
It is not necessary, however, that the exposed cathode 27 be on an
opposite side of the device 10 as the exposed anode 25. The exposed
anode 25 and exposed cathode 27 could be on the same side of the
device and the contact pads 44 could be formed as stripes down the
side of the SOFC Stick.TM. device 10. By this structure, the air
and fuel are first heated in the pre-heat zone 33a, where no
reaction is taking place, and the majority of the anode and cathode
material is limited to the active zone 33b where the heated air and
fuel enter and react by virtue of the opposed anode and cathode
layers 24, 26.
[0160] The embodiment depicted in FIGS. 31A-31C is similar to that
depicted in FIGS. 30A-30C, but rather than having one hot end and
one cold end, the embodiment of FIGS. 31A-C includes opposing cold
zones 30 with a central hot zone 32. Fuel from fuel supply 34
enters through the first end 11a of device 10 through fuel inlet 12
in the cold zone 30 and exits from the opposite second end 11b
through fuel outlet 16 positioned in the opposing cold zone 30.
Similarly, air from air supply 36 enters through the opposite cold
zone 30 through air inlet 18 and exits at the first cold zone 30
through air outlet 22. The fuel enters the hot zone 32 and is
pre-heated in pre-heat zone 33a, while the air enters at the
opposite side of the hot zone 32 and is pre-heated in another
pre-heat zone 33a. There is thus a cross-flow of fuel and air. The
anode 24 opposes the cathode 26 in an active zone 33b of hot zone
32 and the reaction occurs in the active zone 33b involving the
pre-heated fuel and air. Again, the majority of electrode material
is limited to the active zone 33b. The anode is exposed at one edge
of the SOFC Stick.TM. device 10, and the cathode is exposed at the
other side of device 10. An external contact pad 44 contacts the
exposed anode 25 in the hot zone 32 and extends toward the first
cold end 11a for connection to negative voltage node 38. Similarly,
an external contact pad 44 contacts the exposed cathode 27 in hot
zone 32 and extends toward the second cold zone 11b for connection
to positive voltage node 40.
[0161] The pre-heat zones 33a provide the advantage of fully
heating the gas to the optimal reaction temperature before it
reaches the active region. If the fuel is colder than the optimum
temperature, the efficiency of the SOFC system will be lower. As
the air and fuel continue on their paths, they warm up. As they
warm up, the efficiency of the electrolyte increases in that
region. When the fuel, air and electrolyte reach the full
temperature of the furnace, then the electrolyte is working under
its optimal efficiency. To save money on the anode and cathode,
which may be made out of precious metal, the metal can be
eliminated in those areas that are still below the optimal
temperature. The amount of the pre-heat zone, in terms of length or
other dimensions, depends on the amount of heat transfer from the
furnace to the SOFC Stick.TM. device, and from the SOFC Stick.TM.
device to the fuel and air, as well as whether any heat exchange is
occurring due to cross-flow of the fuel and air. The dimensions
further depend on the rate of flow of fuel and air; if the fuel or
air is moving quickly down the length of the SOFC Stick.TM. device,
a longer pre-heat zone will be advantageous, whereas if the flow
rate is slow, the pre-heat zone may be shorter.
[0162] FIGS. 32A and 32B depict an embodiment similar to that shown
in FIGS. 31A-31C, but the SOFC Stick.TM. device 10 includes a
pre-heat chamber 13 between the fuel inlet 12 and fuel passage 14
that extends into the hot zone 32 for pre-heating in the pre-heat
zone 33a a large volume of fuel before it passes through the more
narrow fuel passage 14 into the active zone 33b. The SOFC Stick.TM.
device 10 similarly includes a pre-heat chamber 19 between the air
inlet 18 and the air passage 20 that extends into the hot zone 32
for pre-heating a large volume of air in the pre-heat zone 33a
before it passes through the more narrow air passage 20 to the
active zone 33b. As disclosed in embodiments above, the SOFC
Stick.TM. device 10 may include multiple fuel passages 14 and air
passages 20, each of which would receive flow from a respective
pre-heat chamber 13, 19.
[0163] With respect to a high-volume pre-heat chamber instead of a
pre-heat channel, it may be imagined, by way of example only, that
if it takes 5 seconds for a molecule of air to heat up to the
optimal temperature, then if the molecules of air are traveling
down the SOFC Stick.TM. device 10 at 1 inch per second, the SOFC
Stick.TM. device would need a pre-heat channel that is 5 inches in
length before the air enters the active zone 33b. If, however, a
large volume chamber is provided instead of a channel, the volume
permits the molecules to spend additional time in the cavity before
entering the more narrow channel to the active zone, such that the
air molecules are heated in the chamber and then a short length of
channel may be used for feeding the heated air molecules to the
active zone. Such a cavity or pre-heat chamber could be prepared in
a number of different ways, including taking a green (i.e., before
sintering) assembly and drilling into the end of the assembly to
form the chamber, or by incorporating a large mass of organic
material within the green stack as it is formed, whereby the
organic material is baked out of the SOFC Stick.TM. device during
sintering.
[0164] FIGS. 33A-33C depict yet another embodiment for pre-heating
the air and fuel prior to the air and fuel reaching the active zone
33b. FIG. 33A is a schematic cross-sectional side view, essentially
through the longitudinal center of the SOFC Stick.TM. device 10.
FIG. 33B is a cross-sectional top view taken along the line 33B-33B
where the fuel passage 14 and anode 24 intersect, while FIG. 33C is
a cross-sectional bottom view taken along the line 33C-33C where
the air passage 20 intersects the cathode 26. The SOFC Stick.TM.
device 10 has two opposing cold zones 30 and a central hot zone 32,
with a transition zone 31 between each cold zone 30 and the hot
zone 32. Fuel from fuel supply 34 enters the first end 11a of SOFC
Stick.TM. device 10 through fuel inlet 12 and travels through the
fuel passage 14, which extends toward the opposite end of the hot
zone 32, where it makes a U-turn and travels back to the cold zone
30 of first end 11a, where the spent fuel exits through fuel outlet
16. Similarly, air from air supply 36 enters the second end 11b of
SOFC Stick.TM. device 10 through the air inlet 18 and travels
through the air passage 20, which extends toward the opposing end
of the hot zone 32, where it makes a U-turn and travels back to the
second end 11b, where the air exits from the cold zone 30 through
air outlet 22. By means of these U-turned passages, the portion of
the fuel passage 14 and air passage 20 from the initial entry into
the hot zone 32 through the bend (U-turn) constitute a pre-heat
zone for heating the fuel and air. After the bends, or U-turns, in
the passages 14, 20, the passages are lined with a respective anode
24 or cathode 26, which are in opposing relation with an
electrolyte 28 therebetween, which region constitutes the active
zone 33b in hot zone 32. Thus, the fuel and air are heated in the
pre-heat zone 33a prior to entry into the active zone 33b to
increase the efficiency of the SOFC Stick.TM. device 10, and to
minimize the usage of electrode material. The anode 24 is extended
to the exterior of the device 10 in the cold zone 30 for connection
to negative voltage node 38. Similarly, cathode 26 is extended to
the exterior of the device 10 for electrical connection to positive
voltage node 40. The fuel and air outlets 16 and 22 also may exit
from the cold zones 30.
[0165] In many of the embodiments shown and described above, the
anodes 24 and cathodes 26 travel within the layers of the SOFC
Stick.TM. device 10, essentially in the center area of each layer,
i.e., internal to the device, until they reach the end of the
device. At that point, the anodes 24 and cathodes 26 are tabbed to
the outside of the SOFC Stick.TM. device 10 where the exposed anode
25 and exposed cathode 27 are metallized with a contact pad, such
as by applying a silver paste, and then a wire is soldered to the
contact pad. For example, see FIGS. 4A-4B. It may be desirable,
however, to build up the layers in the SOFC Stick.TM. device 10
into higher voltage combinations, for example as shown in FIGS.
8A-9B. If it is desired to make an SOFC Stick.TM. device that
produces 1 kW of power, the power is divided between the voltage
and the current. One standard is to use 12 volts, such that 83 amps
would be needed to create the total 1 kW of power. In FIGS. 8B and
9B, vias were used to interconnect the electrode layers to form
parallel or series combinations.
[0166] Alternative embodiments for interconnecting the electrode
layers are depicted in FIGS. 34A to 37. Rather than interconnecting
the electrode layers in the interior of the SOFC Stick.TM. device
10, these alternative embodiments use exterior stripes (narrow
contact pads), for example of silver paste, along the sides of the
SOFC Stick.TM. device 10, in particular, multiple small stripes.
Using the striping technique, a simple structure is formed that can
provide series and/or parallel combinations to achieve any
current/voltage ratios needed. Moreover, the external stripes will
have loose mechanical tolerances compared to the internal vias,
thereby simplifying manufacturing. Also, the external stripes will
likely have a lower resistance (or equivalent series resistance)
than the vias. Lower resistance in a conductor path will result in
lower power loss along that path, such that the external stripes
provide the ability to remove the power from the SOFC Stick.TM.
device 10 with a lower loss of power.
[0167] Referring now specifically to FIGS. 34A and 34B, an external
anode/cathode interconnect in series is depicted. FIG. 34A provides
a schematic oblique front view of the alternating anodes 24a, 24b,
24c and cathodes 26a, 26b, 26c. Along the length of the SOFC
Stick.TM. device 10, the anodes 24a, 24b, 24c and cathodes 26a,
26b, 26c include a tab out to the edge of the device 10 to provide
the exposed anodes 25 and exposed cathodes 27. An external contact
pad 44 (or stripe) is then provided on the outside of the SOFC
Stick.TM. device over the exposed anodes 25 and cathodes 27, as
best shown in the schematic side view of FIG. 34B. By connecting
the three pairs of opposed anodes 24a, 24b, 24c and cathodes 26a,
26b, 26c in series, the SOFC Stick.TM. device 10 provides 3 volts
and 1 amp. In FIG. 35, the structure is doubled and the two
structures are connected by long stripes down the sides of the
device 10, thereby providing an external anode/cathode interconnect
in a series parallel design that provides 3 volts and 2 amps.
[0168] FIGS. 36A and 36B provide an embodiment for a low equivalent
series resistance path for providing low power loss. In this
embodiment, the hot zone 32 is in the center of the SOFC Stick.TM.
device 10 with the first end 11a and second end 11b being in cold
zones 30. Fuel is inputted through fuel inlets 12 in first end 11a
and air is inputted through air inlets 18 in second end 11b. Within
the hot zone 32, which is the active area of the SOFC Stick.TM.
device 10, the anodes 24 and cathodes 26 are exposed to the sides
of the device, with the anodes 24 exposed to one side, and the
cathodes 26 exposed to the opposite side. Contact pads 44 (or
stripes) are applied over the exposed anodes 25 and cathodes 27.
Then, the edges of the SOFC Stick.TM. device 10 are metallized
along the length of the sides of the device 10 until the
metallization reaches the cold zones 30, where the low temperature
solder connection 46 is made to the negative voltage node 38 and
the positive voltage node 40. The anodes 24 and cathodes 26 cannot
be optimized only for low resistance because they have other
functions. For example, the electrodes must be porous to allow the
air or fuel to pass through to the electrolyte, and porosity
increases resistance. Further, the electrodes must be thin to allow
for good layer density in a multi-layer SOFC Stick.TM. device 10,
and the thinner the electrode, the higher the resistance. By adding
thicker contact pads 44 to the edges (sides) of the SOFC Stick.TM.
device, it is possible to provide a low resistance path toward the
solder connection 46. The thicker the contact pad 44, the lower the
resistance. If an electron must travel 10 inches, for example, down
the electrode within the SOFC Stick.TM. device 10, past all the
voids in the electrode layer, the path of least resistance would be
to travel 0.5 inch, for example, to the side edge of the device 10,
and then travel the 10 inches down the exterior non-porous contact
pad 44. Thus, the long contact pads 44 along the exterior of the
SOFC Stick.TM. device that extend to the cold zones 30 allow for
the power to be removed from the SOFC Stick.TM. device 10 with a
lower loss by providing a lower resistance conductor path. Thus,
the striping technique may be used in the active area (hot zone 32)
of the SOFC Stick.TM. device 10 for making series and parallel
connections to increase power, and a long stripe down the side of
the device to the cold ends allows that power to be efficiently
removed from the SOFC Stick.TM. device 10.
[0169] FIG. 37 depicts, in schematic isometric view, an embodiment
similar to that depicted in FIG. 36B, but having a single cold zone
30 at the first end 11a of the SOFC Stick.TM. device 10, with the
hot zone 32 being at the second end 11b of device 10. Multiple
vertical stripes or contact pads 44 are provided within the hot
zone 32 to make the series and/or parallel connections, and the
horizontal long stripes 44 down the sides of the device 10 are
provided from the hot zone 32 to the cold zone 30 for making the
low temperature solder connections 46 to the positive voltage node
40 and negative voltage node 38.
[0170] One method for forming the fuel passages 14 and air passages
20 is to place an organic material within the green, layered
structure that can then bake out during a later sintering step. To
build individual SOFC Sticks.TM. having high power output, such as
1 kW or 10 kW output, the SOFC Stick.TM. must be long, wide and
have a high layer count. By way of example, the SOFC Stick.TM.
devices may be on the order of 12 inches to 18 inches long. When
baking the green structure to sinter the ceramic and remove the
organic material, the organic material used to form the fuel
passage 14 must exit through openings 12 and 16 that form the fuel
inlet and fuel outlet, respectively. Similarly, the organic
material used to form the air passage 20 must bake out through the
openings 18 and 22 that form the air inlet and air outlet,
respectively. The longer and wider the devices, the more difficult
it is for the organic material to exit through these openings. If
the device is heated too fast during bake-out, the various layers
can delaminate because the decomposition of the organic material
occurs faster than the material can exit the structure.
[0171] FIGS. 38A and 38B depict, in schematic cross-sectional side
view, an alternative embodiment that provides multiple exit gaps
for bake-out of the organic material 72. As shown in FIG. 38A,
multiple openings 70 are provided on one side of the SOFC Stick.TM.
device 10 to provide multiple bake-out paths for the organic
material 72 to exit the structure. As depicted in FIG. 38B, after
bake-out, the multiple openings 70 are then closed by applying a
barrier coating 60 to the side of the SOFC Stick.TM. device 10. By
way of example, the barrier coating may be a glass coating. In
another example, the barrier coating may be a glass containing a
ceramic filler. In yet another embodiment, the barrier coating 60
may be a contact pad 44, for example filled with paste, which would
then also serve as the low resistance path for the generated power.
The silver paste may also contain glass for increased adhesion. In
an exemplary embodiment, the bake-out paths for the cathode are
vented to one side of the SOFC Stick.TM. device 10 and the bake-out
paths for the anode are vented to the opposing side of the device
10 to avoid shorting between opposite electrodes.
[0172] In an alternative embodiment for an SOFC Stick.TM. device
10, 100, 200, 300, rather than having an open air passage 20 and
fuel passage 14 lined with a cathode 26 or anode 24, respectively,
the cathode and air channel may be combined and the anode and fuel
channel may be combined through use of porous electrode materials
that permit flow of the air or fuel. The cathodes and anodes must
be porous anyway to permit the reaction to occur, so in combination
with forced air and fuel input, sufficient flow could be achieved
through the SOFC Stick.TM. device to permit the power generating
reaction to occur.
[0173] Another embodiment of the present invention is depicted in
schematic cross-sectional end view in FIG. 39. This embodiment is
essentially an anode-supported version of an SOFC Stick.TM. device
10. As with other embodiments, the SOFC Stick.TM. device 10 may
have a hot end and a cold end or two cold ends with an intermediate
hot zone. Rather than having the device 10 supported by ceramic 29,
the anode-supported version uses the anode material as the
supporting structure. Within the anode structure, a fuel passage 14
and an air passage 20 are provided in opposing relation. The air
channel 20 is lined with an electrolyte layer 28, and then with a
cathode layer 26. Chemical vapor deposition could be used to
deposit the internal layers, or by using solutions of viscous
pastes.
[0174] In FIGS. 40A and 40B, a further embodiment is shown for an
anode-supported version of the SOFC Stick.TM. device 10. In this
embodiment, the separate open fuel passage 14 is eliminated, such
that the porous anode 24 also serves as the fuel passage 14. In
addition, the SOFC Stick.TM. device 10 is coated with a barrier
coating 60, such as a glass coating or a ceramic coating, to
prevent the fuel from exiting out the sides of the device 10. The
SOFC Stick.TM. device 10 may have as many air passages with
associated electrolyte and cathode in the anode structure as
desired. As depicted in FIG. 40B, the fuel from fuel supply 34 is
forced into first end 11a through the porous anode 24, which serves
as the fuel passage 14, and passes through the electrolyte layers
28 and the cathodes 26 to react with air from air supply 36, and
the spent air and fuel can then exit out the air outlet 22.
[0175] In another embodiment depicted in a schematic
cross-sectional end view in FIG. 41A and a schematic
cross-sectional top view in FIG. 41B, the SOFC Stick.TM. device 10
may include a plurality of air passages 20 provided within the
anode-supporting structure, and a single fuel passage 14 normal to
the multiple air passages 20 for feeding fuel from the fuel supply
34 through the single fuel inlet 12 to multiple air passages 20.
Again, the air passages 20 are lined first with an electrolyte
layer 28 and then with a cathode 26. The fuel passes from the
single fuel passage 14 through the anode structure 24, through the
electrolyte 28, and through the cathode 26 to react with the air in
the air passage 20, and the spent fuel and air exit from the air
outlet 22. The spent fuel can also seep out the side of the SOFC
Stick.TM. device 10 that does not include the barrier coating 60,
which uncoated side would be located on the opposing side of the
device from the orientation of the single fuel passage 14.
[0176] In the embodiments pertaining to an anode-supported
structure, it may be appreciated that the structure may be
essentially reversed to be a cathode-supported structure. Fuel
channels coated with an electrolyte layer and an anode layer would
then be provided within the cathode structure. A separate air
channel or multiple air channels could also be provided, or the
porosity of the cathode could be used for the air flow.
[0177] FIGS. 42A-42C depict a method for forming the electrodes
within the air and fuel passages. Taking the fuel passage 14 and
anode 24 as an example, rather than building up a green structure
layer by layer using layers of green ceramic and metal tape layers,
or printing metallizations, in the present embodiment, the SOFC
Stick.TM. device 10 is first built without the electrodes. In other
words, green ceramic material is used to form the electrolyte and
ceramic supporting portions of the SOFC Stick.TM. and the organic
material is used to form the passages, such as fuel passage 14.
After the SOFC Stick.TM. device has been sintered, the fuel passage
14 is filled with an anode paste or solution. The paste may be
thick like that of a printing ink, or runny like that of a
high-content water solution. The anode material can be filled into
the fuel passage 14 by any desired means, such as sucking it in via
a vacuum, by capillary forces, or forcing it in via air
pressure.
[0178] Alternatively, as shown in FIGS. 42A-42C, the anode material
is dissolved in solution, flowed into the fuel passage 14, and then
precipitated. For example, through a change of pH, the anode
particles can be precipitated and the solution drawn out. In
another alternative, the anode particles can be simply allowed to
settle, and then the liquid dried or baked out of the fuel passage
14. This settling can be accomplished by creating an ink or liquid
carrier that will not keep the particles in suspension for any
extended period of time, for example, due to low viscosity. A
centrifuge could also be used to force the settling. The centrifuge
can easily allow preferential settling of most particles onto one
surface of the fuel passage 14 to thereby conserve electrode
material and to ensure that only one surface of the fuel passage 14
acts as an electrolyte.
[0179] As shown in FIG. 42A, the anode particle-containing solution
66 is pulled into the fuel passage 14 until the passage 14 is
completely filled, as shown in FIG. 42B. The particles then settle
to the bottom of the passage 14 to form an anode layer 24, as shown
in FIG. 42C. Flooding in of the solution 66 can be accelerated by
gravity, vacuum, or centrifuge, as compared to normal capillary
forces. Of course, while the anode 24 and fuel passage 14 were used
as an example, any of these alternative embodiments may also be
used with a cathode paste or solution to create a cathode layer 26
in an air passage 20.
[0180] In another alternative, a ceramic electrode material (anode
or cathode) could be infused into the passage (fuel or air) in a
liquid sol-gel state, and then deposited inside the passage. It is
also possible to repeat the filling operation multiple times, such
as in the case where the concentration of the desired electrode
material in the liquid is low, or to provide a gradient of
properties in the electrode (such as to provide a different amount
of YSZ in the electrode close to the electrolyte versus the amount
of YSZ in the electrode farther from the electrolyte), or if there
is a desire to put multiple layers of dissimilar materials together
(such as a cathode made of LSM near the electrolyte, and then
silver over the top of the LSM for better conductivity).
[0181] Referring back to FIGS. 7C and 7D, in which ceramic spheres
or balls were used to provide structural support to the air and
fuel passages 20, 14, ceramic particles may also be used to
increase the effective surface area for a greater reaction area,
thus giving a higher output. Very fine-sized ceramic balls or
particles can be used inside the fuel passage 14 and the air
passage 20 prior to applying the electrode layer. As shown in FIG.
43 in schematic cross-sectional side view, surface particles 62
line the passage 14 to provide the electrolyte layer 28 with an
uneven topography that increases the surface area available to
receive the electrode layer. The anode 24 is then applied over the
uneven topography with the anode material coating all around the
surface particles 62 thereby increasing the reaction area.
[0182] In an alternative embodiment, depicted in schematic
cross-sectional side view in FIG. 44, the electrolyte layer 28 may
be laminated so as to provide the uneven topography or textured
surface layer 64, such as by pressing the green electrolyte layer
against a fine grading having a V-shaped pattern, which pattern is
then imparted to the electrolyte layer 28. After the electrolyte
layer 28 is sintered to solidify the ceramic and the textured
surface layer 64, the anode layer 24 may then be applied, such as
by using the backfill process described above in FIGS. 42A-42C, to
provide an anode with a high reaction area.
[0183] Yet another embodiment of the invention is depicted in FIGS.
45A and 45B. FIG. 45A is a schematic top view depicting the air and
fuel flow through air and fuel passages and the arrangement of the
electrodes, and FIG. 45B is a cross-sectional view through the hot
zone 32. Along the length of SOFC Stick.TM. device 10, the device
is divided into a left side 80 and a right side 82 with an
intermediate or bridging portion 84 therebetween. A plurality of
air passages 20L extend from the first end 11a of SOFC Stick.TM.
device 10 along the length through the left side 80 and exit out
the left side 80 adjacent second end 11b, and a plurality of air
passages 20R extend from first end 11a along the length through the
right side 82 and exit the SOFC Stick.TM. device 10 on the right
side adjacent the second end 11b. The air passages 20L are offset
from the air passages 20R, as best shown in FIG. 45B. A plurality
of fuel passages 14L extend from the second end 11b of SOFC
Stick.TM. device 10 along the length through the left side 80 and
exit on the left side 80 adjacent first end 11a, and a plurality of
fuel passages 14R extend from second end 11b along the length
through the right side 82 and exit the right side 82 adjacent first
end 11a. The fuel passages 14L are offset from the fuel passages
14R. In addition, with the exception of one fuel passage and one
air passage, each fuel passage 14L is paired with and slightly
offset from an air passage 20R and each air passage 20L is paired
with and slightly offset from a fuel passage 14R. For each offset
pair of fuel passages 14L and air passages 20R, a metallization
extends along each fuel passage 14L from the left side 80 to the
right side 82, where it then extends along the slightly offset air
passage 20R. Similarly, for each offset pair of fuel passages 14R
and air passages 20L, a metallization extends along each air
passage 20L from the left side 80 to the right side 82, where it
then extends along the slightly offset fuel passage 14R. The
metallization serves as an anode 24L or 24R when the metallization
extends along a fuel passage 14L or 14R, and the metallization
serves as a cathode 26L or 26R when the metallization extends along
an air passage 20L or 20R. In the bridging portion 84 of the SOFC
Stick.TM. device 10, where the metallizations do not extend along
any air or fuel passage, the metallization simply serves as a
bridge 90 between an anode and a cathode. In one embodiment of the
present invention, the metallization may comprise the same material
along its length, such that the anode 24L or 24R, the bridge 90 and
the cathode 26L or 26R each comprise the same material. For
example, the metallizations may each comprise platinum metal, which
functions well as either an anode or a cathode. Alternatively, the
metallization may comprise different materials. For example, the
cathodes 26R or 26L may comprise lanthanum strontium manganite
(LSM), while the anodes 24R or 24L comprise nickel, NiO, or
NiO+YSZ. The bridges 90 may comprise palladium, platinum, LSM,
nickel, NiO, or NiO+YSZ. The present invention contemplates any
combination or type of materials suitable for use as a cathode or
an anode, or a bridging material therebetween, and the invention is
not limited to the specific materials identified above.
[0184] On one side of the SOFC Stick.TM. device 10, shown here at
the right side 82, a fuel channel 14R is provided with an
associated anode 24R that extends to the right edge of the SOFC
Stick.TM. device 10 to provide the external exposed anode 25. There
is no offset air passage 20L associated with this fuel passage 14R,
and the anode 24R need not extend into the left side 80. As
depicted in FIG. 45A, an exterior contact pad 44 is applied over
the exposed anode 25 and extends along the length of the SOFC
Stick.TM. device into the cold zone 30. Negative voltage node 38
can then be connected by wire 42 and solder connection 46 to the
contact pad 44. The anode 24R could extend, as shown, to the right
edge throughout the hot zone 32, or could just extend in a small
tab portion to reduce the amount of electrode material used. Also,
the anode 24R could extend to the right edge of the SOFC Stick.TM.
device 10 along the length of the fuel passage 14R, although such
embodiment would involve an unnecessary use of electrode
material.
[0185] Similarly, on the other side of the SOFC Stick.TM. device
10, shown as the left side 80, a single air passage 20L is provided
with an associated cathode 26L that extends to the left side of the
SOFC Stick.TM. device 10 to form the exposed cathode 27. This air
passage 20L is not associated with an offset fuel passage 14R, and
it is not necessary that the cathode 26L extend to the right side
82. A contact pad 44 may be applied along the exterior of the left
side 80 of the SOFC Stick.TM. device 10 from the exposed cathode 27
to a cold end 30, where a positive voltage node 40 may be connected
via wire 42 and solder connection 46 to the contact pad 44.
[0186] In FIG. 45B, the single fuel passage 14R and associated
anode 24R are shown at the top of the right side 82, while the
single air passage 20L and associated cathode 26L are shown at the
bottom of the left side 80 of the SOFC Stick.TM. device 10.
However, the invention is not limited to that arrangement. For
example, air passage 20L and associated cathode 26L could be
provided also at the top of device 10 on the left side 80, in a
similar offset manner to the single fuel passage 14R and its
associated anode 24R, but the metallization would not run from the
left side 80 through the bridging portion 84 to the right side 82.
Rather, the bridge 90 would be absent such that the anode 24R is
electrically separated from the cathode 26L. Additional
arrangements are contemplated in which an SOFC Stick.TM. device 10
may be provided with two unique air pathway stacks and two unique
fuel pathway stacks within a single SOFC Stick.TM. device 10, with
the cells connected in series. The embodiment depicted in FIGS. 45A
and 45B has an advantage of raising the voltage without raising the
current, and while maintaining a low resistance. Further, this
embodiment provides a high density within the SOFC Stick.TM. device
10.
[0187] In FIGS. 46A and 46B, an alternative embodiment is depicted
in schematic perspective view and schematic cross-sectional view,
respectively. Previous embodiments (e.g., FIG. 37) provided
external stripes along the exterior sides or edges of the SOFC
Stick.TM. device 10 from the hot zone 32 to the cold zone(s) 30 to
provide a path of low resistance for the electrons to travel to the
cold-end. In the embodiment of FIGS. 46A and 46B, instead of
stripes down the sides or edges of the device 10, a contact pad 44
is applied along one side and one of the top and bottom surfaces
for the external connection to the anode 24 and another contact pad
44 is applied along the opposing side and the other of the top and
bottom surfaces for the external connection to the cathode 26.
Thus, the electrons have a large or wide path along which to
travel, thereby providing an even lower resistance. These large
conductor pads 44 that are applied on two adjacent surfaces could
be used in any of the embodiments disclosed herein.
[0188] In FIG. 47, yet another embodiment is depicted, in schematic
cross-sectional side view, of an SOFC Stick.TM. device 10 that
takes advantage of heat exchange principles. After the heated air
and fuel pass through the active zone 33b of the hot zone 32 (i.e.,
the portion of the hot zone 32 where the anode 24 is in opposing
relation to the cathode 26 with an electrolyte therebetween), the
fuel passage 14 and air passage 20 are joined into a single exhaust
passage 21. Any un-reacted fuel will burn when combined with the
heated air, thus producing additional heat. The exhaust passage 21
travels back toward the cold zone 30 adjacent the active zone 33b,
with the direction of flow of the exhaust (spent fuel and air)
being opposite that of the incoming fuel and air in the adjacent
fuel and air passages 14, 20. The additional heat generated in the
exhaust passage 21 is transferred to the adjacent passages 14, 20
to heat the incoming fuel and air.
[0189] FIGS. 48A-48C depict an "end-rolled SOFC Stick.TM. device"
400 having a thick portion 402 having a greater thickness than a
thin portion 404, as depicted in FIG. 48A. The fuel and air inlets
12, 18 are positioned adjacent first end 11a, which is at the end
of thick portion 402, and while not shown, the air and fuel outlets
(16, 22) may be provided at the sides of the device 400 adjacent
opposing second end 11b, which is at the end of the thin portion
404. The thick portion 402 should be thick enough to provide
mechanical strength. This may be achieved by providing thick
ceramic 29 around the adjacent fuel and air inlets 12, 18. The thin
portion 404 will include the active zone 33b (not shown) that
includes an anode (not shown) in opposing relation to a cathode
(not shown) with an electrolyte (not shown) therebetween (as in
prior embodiments). The thin portion 404 should be thin enough to
permit it to be rolled while in the green (unfired) state, as shown
in FIG. 48B. After the thin portion 404 is rolled to a desired
tightness, the device 400 is fired. The rolled thin portion 404 can
then be heated to cause the reaction, while the thick portion 402
is a cold end, as discussed in other embodiments. The end-rolled
SOFC Stick.TM. device 400 is a large surface area device that can
fit in a small space by virtue of rolling the thin portion 404.
Moreover, the thin cross-section of the active zone (33b) in the
thin portion 404 reduces the heat transfer out along the ceramic
and allows good temperature cycle performance.
[0190] While the invention has been illustrated by the description
of one or more embodiments thereof, and while the embodiments have
been described in considerable detail, they are not intended to
restrict or in any way limit the scope of the appended claims to
such detail. Additional advantages and modifications will readily
appear to those skilled in the art. The invention in its broader
aspects is therefore not limited to the specific details,
representative apparatus and method and illustrative examples shown
and described. Accordingly, departures may be made from such
details without departing from the scope of the general inventive
concept.
* * * * *