GB2219125A - Fuel cell with heat exchange channels - Google Patents
Fuel cell with heat exchange channels Download PDFInfo
- Publication number
- GB2219125A GB2219125A GB8812641A GB8812641A GB2219125A GB 2219125 A GB2219125 A GB 2219125A GB 8812641 A GB8812641 A GB 8812641A GB 8812641 A GB8812641 A GB 8812641A GB 2219125 A GB2219125 A GB 2219125A
- Authority
- GB
- United Kingdom
- Prior art keywords
- channels
- fuel cell
- fuel
- heat exchange
- holes
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/24—Grouping of fuel cells, e.g. stacking of fuel cells
- H01M8/241—Grouping of fuel cells, e.g. stacking of fuel cells with solid or matrix-supported electrolytes
- H01M8/2425—High-temperature cells with solid electrolytes
- H01M8/2435—High-temperature cells with solid electrolytes with monolithic core structure, e.g. honeycombs
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
- H01M8/04007—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids related to heat exchange
- H01M8/04014—Heat exchange using gaseous fluids; Heat exchange by combustion of reactants
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/24—Grouping of fuel cells, e.g. stacking of fuel cells
- H01M8/2404—Processes or apparatus for grouping fuel cells
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/10—Fuel cells with solid electrolytes
- H01M8/12—Fuel cells with solid electrolytes operating at high temperature, e.g. with stabilised ZrO2 electrolyte
- H01M2008/1293—Fuel cells with solid oxide electrolytes
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M2300/00—Electrolytes
- H01M2300/0017—Non-aqueous electrolytes
- H01M2300/0065—Solid electrolytes
- H01M2300/0068—Solid electrolytes inorganic
- H01M2300/0071—Oxides
- H01M2300/0074—Ion conductive at high temperature
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
- H01M8/04223—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids during start-up or shut-down; Depolarisation or activation, e.g. purging; Means for short-circuiting defective fuel cells
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/24—Grouping of fuel cells, e.g. stacking of fuel cells
- H01M8/241—Grouping of fuel cells, e.g. stacking of fuel cells with solid or matrix-supported electrolytes
- H01M8/2425—High-temperature cells with solid electrolytes
- H01M8/2432—Grouping of unit cells of planar configuration
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/30—Hydrogen technology
- Y02E60/50—Fuel cells
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Life Sciences & Earth Sciences (AREA)
- Manufacturing & Machinery (AREA)
- Sustainable Development (AREA)
- Sustainable Energy (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Fuel Cell (AREA)
Abstract
A solid oxide fuel cell in which the electrolyte is a ceramic oxide, e.g. zirconia, through which oxygen ions migrate from a dissociated oxidant, e.g. oxygen, to a fuel, e.g. methane, which is thereby oxidised to produce electric current. The fuel and the oxygen pass through multiple respective channels in a block of the ceramic oxide so as to maximise the interaction between them. The invention concerns the control of the block temperature at a high level APPROX 1000 DEG K without permitting damage from temperature runaway. This is achieved by means of a 3 dimensional channel arrangement through the block for, fuel, oxygen and inert gas coolant respectively. The channels and hot spots in the block can then be controlled selectively.
Description
Fuel Cell
This invention relates to fuel cells, and particularly to solid oxide fuel cells in which the electrolyte is a ceramic oxide through which oxygen ions migrate from a dissociated oxidant, e.g.
oxygen, to a fuel which is thereby oxidised to produce electric current.
Fuel cells employing solid oxide electrolyte are known in which an oxidising gas is fed through a set of parallel channels in a ceramic body, and a fuel gas, e.g. hydrogen or methane, is fed through an adjacent set of channels. Electrodes formed on the surfaces of the channels have a catalytic effect and cause dissociation of the oxidant providing oxygen ions. These mobile carriers migrate through the solid oxide electrolyte to the fuel gas, which is oxidised to produce electric current . The use of channels to conduct the gases provides an increase in surface area of the catalytic electrode and a consequent increase in current generated per unit volume of the cell.
Further improvement is known, for example from US Patents
Nos. 4396480 and 4463065, whereby a number of channel layers are superimposed, one set of alternate layers having their channels lying across, i.e. perpendicular to, the channels of the other set of layers. The power density of the cell is thereby Increased considerably. One set of channels is fed with fuel gas, ammonia in this case, and the other set with oxygen.
While devices of the above kind are reasonably efficient, a problem arises with regard to the heat produced in operation. In particular the dissipation of energy at the electrodes, and in the electrolyte, results in heat production, and a rise in temperature above the normal operating temperature which typically is 1000 to nm1200K. The ionic conductivity of oxide conductors increases with increasing temperature, leading to increased power dissipation and a possible cumulative "run away" condition. Temperature increase is obviously greatest at the centre of the monolith.
An object of the present invention is therefore to provide a fuel cell in which some control over the temperature rise is provided.
According to one aspect of the present invention, a fuel cell comprises a three dimensional array of channels formed in a ceramic electrolyte, the array comprising a set of fuel channels, a set of oxidant channels and a set of heat exchange channels, the fuel channels and the oxidant channels being coated with anodic and cathodic conducting materials to which terminal connections are made.
Where the fuel channels and the oxidant channels extend parallel to a first plane the heat exchange channels are preferably perpendicular to this first plane.
Where the fuel cell is formed of a plurality of layers of the ceramic electrolyte, each layer preferably comprises a plurality of parallel channels separated by walls through which holes extend perpendicular to the layer, the layers being superimposed so that the channels of the two sets of alternate layers extend along two of the three dimensions, the holes being aligned from layer to layer to form a set of continuous channels. The holes preferably provide the heat exchange channels.
In a fuel cell arrangement including a fuel cell as aforesaid, the arrangement may include temperature sensing means in at least one of the heat exchange channels and means for controlling coolant flow in response to an output signal from the temperature sensing means. Preferably, temperature sensing means are included in a plurality of the heat exchange channels and means are provided for controlling the relative flow of coolant to the various heat exchange channels.
According to another aspect of the invention, in a method of making a fuel cell, ceramic powder and binder are mixed and cast into a sheet having a plurality of upstanding walls forming a plurality of parallel channels, the sheet is dried and then formed into a fuel cell layer by punching holes through the walls transverse to the sheet, and a plurality of the layers are superimposed, the channels of one set of alternate layers extending along one dimension and the channels of the other set of alternate layers extending along another dimension transverse to the one dimension, so that the holes are aligned and continuous through all of the layers, the two sets of channels providing fuel and oxidant channels respectively and the holes providing heat exchange channels.
A fuel cell and a method of making it in accordance with the invention will now be described, by way of example, with reference to the accompanying drawings, of which:
Figure 1 is a known monolithic, crossflow, solid oxide fuel cell;
Figure 2 is a diagram of two 'exploded' layers of a fuel cell according to the invention;
Figure 3 is a cross-section of one of the layers; and
Figure 4 is a diagram of a monolithic block of layers such as in Figure 2.
Referring to Figure 1, showing a known monolithic fuel cell, ten layers of solid oxide, i.e. ceramic, electrolyte, of rectangular form, are superimposed. One set of alternate layers 3 provides oxygen channels 7 extending along one dimension of the three-dimensional block. The other set of alternate layers 5 provides fuel channels 9 extending along a second dimension transverse, and in fact perpendicular, to the first.
Each layer, 3 or 5, consists of zirconia for example and is formed as a sheet with upstanding parallel thin walls 11 which form the channels 7 and 9. The walls are thin and serve only to increase the surface area of the electrolyte in contact with the oxygen/fuel.
The channels of each layer (except the uppermost - which requires a dummy ceramic layer or a plain ceramic sheet) are closed by the back face of the adjacent sheet and the whole surface of each channel, including the 'roof' provided by the next layer, is coated with an electrode material which serves additionally as a catalyst - for dissociation of the oxygen or oxidation of the fuel as the case may be.
The electric charge is collected on these electrodes which are connected together (in each set) and to a terminal 13 for the oxygen channels and 15 for the fuel channels. These terminals then provide the fuel cell output.
As mentioned above, such a construction, while reasonably satisfactory at low powers, is subject to overheating, particularly in the centre of the monolith.
Referring now to Figure 2, this shows two layers of a fuel cell according to the invention, the layers being simplified down to merely two channels each, for convenience. A realistic device would have at least tens of channels in each layer. The features of the layers in Figure 2 are referenced similarly to the features of
Figure 1 for convenience.
The method of manufacture is as follows. Doped zirconia powder and binder are mixed together in a mill jar. The resulting slurry is cast on a shaped mould having a form inverse to that of the required layer shown in Figure 2, taking account of the width, pitch and depth of channel and aiming for a sheet thickness at the bottom of each channel (and thus a separation thickness between the two gases) of about 0.1 to 0.5 mm.
The green 'tape' so formed is dried by the application of moderate heat to produce a leather-hard material which is then punched with holes 21 transverse to the sheet and through the walls 17 and 19.
The spacing of the holes 21 is such that on superimposing the layers, the holes are in register from each layer to the next to provide a continuous heat exchange channel in the third dimension through the monolithic block. An alternative method of manufacturing the layers is to lay strips of green tape 23 (typically of width (W) and height (h) as shown in cross section in Figure 3) on to plates of green tape 25 and bonding strips and plate together by application of moderate heat and pressure as above.
While these holes essentially constitute coolant channels, they may additionally provide a means of heating the monolith from cold on start up - since it has to reach a temperature in the region of 1000 K. A hot inert gas may therefore be pumped through the holes initially until the block is approaching the operating temperature.
The following advantages of using a "heater fluid" follow:
(i) much better control of temperature rise than by using external heating, thereby minimising thermal shock to cell walls and subsequent failure.
(ii) simplified (and safer) gas supply compared with using heated fuel or oxygen to pre-heat the monolith.
A further function of the holes 21 is for several of them to be employed to maintain alignment during subsequent processing.
Electrodes are coated on to the walls and base of each channel; the cathode, on the oxygen channels 7, being a porous metal, e.g. platinum or a metal oxide, e.g. LaMnO3, and the anode, on the fuel channels 9, being doped nickel. The electroded layers are then assembled on a jig having posts fitting in the heat exchange channels and heat and pressure are applied to laminate the layers. The structure is then fired in a furnace to its sintering temperature.
The result is the monolith shown in Figure 4.
The overall reactions taking place are:
(a) cathode: i 2 + 3e- ## O2- (b) electrolyte: n x 02- as mobile ion
(c) anode: 402- + CH4 ## C02 + 2H20 + 8e (d) external: n x 8e~ Control of cooling is by means of temperature sensors in the heat exchange/coolant channels at the surface and centre of the monolith; deviation from pre-set sensor parameters actuates change in coolant gas flow rates to restore the desired conditions.
Claims (10)
1. A fuel cell comprising a three dimensional array of channels formed in a ceramic electrolyte, the array comprising a set of fuel channels, a set of oxidant channels and a set of heat exchange channels, the fuel channels and the oxidant channels being coated with anodic and cathodic conducting materials to which terminal connections are made.
2. A fuel cell according to Claim 1, wherein said fuel channels and said oxidant channels extend parallel to a first plane and said heat exchange channels are perpendicular to said first plane.
3. A fuel cell according to Claim 2, formed of a plurality of layers of said ceramic electrolyte, each layer comprising a plurality of parallel channels separated by walls through which holes extend perpendicular to the layer, the layers being superimposed so that the channels of the two sets of alternate layers extend along two of the three dimensions, said holes being aligned from layer to layer to for a set of continuous channels.
4. A fuel cell according to Claim 3 wherein said holes provide said heat exchange channels.
5. A fuel cell arrangement including a fuel cell according to any preceding claim, the arrangement including temperature sensing means in at least one of said heat exchange channels and means for controlling coolant flow in response to an output signal from said temperature sensing means.
6. A fuel cell arrangement according to Claim 5, including temperature sensing means in a plurality of said heat exchange channels and means for controlling the relative flow of coolant to the various heat exchange channels.
7. A method of making a fuel cell in which ceramic powder and binder are mixed and cast into a sheet having a plurality of upstanding walls forming a plurality of parallel channels, the sheet is dried and then formed into a fuel cell layer by punching holes through said walls transverse to the sheet, and a plurality of said layers are superimposed, the channels of one set of alternate layers extending along one dimension and the channels of the other set of alternate layers extending along another dimension transverse to said one dimension, so that said holes are aligned and continuous through all of said layers, said two sets of channels providing fuel and oxidant channels respectively and said holes providing heat exchange channels.
8. A method of making a fuel cell in which ceramic powder and binder are mixed and cast into rectangular section strips and plates, a plurality of said strips are bonded onto a said plate to form a plurality of parallel channels between upstanding walls formed by said strips, the assembled plate and strips are formed into a fuel cell layer by punching holes through said walls transverse to the sheet, and a plurality of said layers are superimposed, the channels of one set of alternate layers extending along one dimension and the channels of the other set of alternate layers extending along another dimension transverse to said one dimension, so that said holes are aligned and continuous through all of said layers, said two sets of channels providing fuel and oxidant channels respectively and said holes providing heat exchange channels.
9. A fuel cell substantially as hereinbefore described with reference to Figures 2, 3 and 4 of the accompanying drawings.
10. A method of making a fuel cell substantially as hereinbefore described with reference to Figures 2, 3 and 4 of the accompanying drawings.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8812641A GB2219125B (en) | 1988-05-27 | 1988-05-27 | Fuel cell |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8812641A GB2219125B (en) | 1988-05-27 | 1988-05-27 | Fuel cell |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB8812641D0 GB8812641D0 (en) | 1988-06-29 |
| GB2219125A true GB2219125A (en) | 1989-11-29 |
| GB2219125B GB2219125B (en) | 1991-03-06 |
Family
ID=10637683
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB8812641A Expired - Fee Related GB2219125B (en) | 1988-05-27 | 1988-05-27 | Fuel cell |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2219125B (en) |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0378812A1 (en) * | 1989-01-18 | 1990-07-25 | Asea Brown Boveri Ag | Arrangement of fuel cells based on a solid electrolyte operating at a high temperature, consisting of zirconium oxide, to obtain maximum possible power |
| EP0996186A2 (en) * | 1998-10-21 | 2000-04-26 | Sofco | Electrolyte for solid oxide fuel cells |
| WO2001041239A1 (en) | 1999-12-06 | 2001-06-07 | Technology Management, Inc. | Electrochemical apparatus with reactant micro-channels |
| US6399233B1 (en) | 1999-07-29 | 2002-06-04 | Technology Management, Inc. | Technique for rapid cured electrochemical apparatus component fabrication |
| SG113475A1 (en) * | 2002-08-21 | 2005-08-29 | Gen Electric | Improved fluid passages for power generation equipment |
-
1988
- 1988-05-27 GB GB8812641A patent/GB2219125B/en not_active Expired - Fee Related
Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0378812A1 (en) * | 1989-01-18 | 1990-07-25 | Asea Brown Boveri Ag | Arrangement of fuel cells based on a solid electrolyte operating at a high temperature, consisting of zirconium oxide, to obtain maximum possible power |
| US5034288A (en) * | 1989-01-18 | 1991-07-23 | Asea Brown Boveri Ltd. | Arrangement of fuel cells based on a high-temperature solid electrolyte of stabilized zirconium oxide for achieving maximum possible power |
| EP0996186A2 (en) * | 1998-10-21 | 2000-04-26 | Sofco | Electrolyte for solid oxide fuel cells |
| EP0996186A3 (en) * | 1998-10-21 | 2003-09-17 | Sofco | Electrolyte for solid oxide fuel cells |
| US6399233B1 (en) | 1999-07-29 | 2002-06-04 | Technology Management, Inc. | Technique for rapid cured electrochemical apparatus component fabrication |
| WO2001041239A1 (en) | 1999-12-06 | 2001-06-07 | Technology Management, Inc. | Electrochemical apparatus with reactant micro-channels |
| US6361892B1 (en) | 1999-12-06 | 2002-03-26 | Technology Management, Inc. | Electrochemical apparatus with reactant micro-channels |
| US6878480B2 (en) | 1999-12-06 | 2005-04-12 | Technology Management, Inc. | Electrochemical apparatus with reactant micro-channels |
| SG113475A1 (en) * | 2002-08-21 | 2005-08-29 | Gen Electric | Improved fluid passages for power generation equipment |
Also Published As
| Publication number | Publication date |
|---|---|
| GB8812641D0 (en) | 1988-06-29 |
| GB2219125B (en) | 1991-03-06 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| 732 | Registration of transactions, instruments or events in the register (sect. 32/1977) | ||
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 20050527 |