US20100323255A1 - Fuel cell system suitable for complex fuels and a method of operation of the same - Google Patents
Fuel cell system suitable for complex fuels and a method of operation of the same Download PDFInfo
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- US20100323255A1 US20100323255A1 US12/869,167 US86916710A US2010323255A1 US 20100323255 A1 US20100323255 A1 US 20100323255A1 US 86916710 A US86916710 A US 86916710A US 2010323255 A1 US2010323255 A1 US 2010323255A1
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- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/10—Fuel cells with solid electrolytes
- H01M8/1004—Fuel cells with solid electrolytes characterised by membrane-electrode assemblies [MEA]
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- H01M16/00—Structural combinations of different types of electrochemical generators
- H01M16/003—Structural combinations of different types of electrochemical generators of fuel cells with other electrochemical devices, e.g. capacitors, electrolysers
- H01M16/006—Structural combinations of different types of electrochemical generators of fuel cells with other electrochemical devices, e.g. capacitors, electrolysers of fuel cells with rechargeable batteries
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- H01M4/8605—Porous electrodes
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- H01M4/94—Non-porous diffusion electrodes, e.g. palladium membranes, ion exchange membranes
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- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/02—Details
- H01M8/0202—Collectors; Separators, e.g. bipolar separators; Interconnectors
- H01M8/023—Porous and characterised by the material
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- H01M8/0202—Collectors; Separators, e.g. bipolar separators; Interconnectors
- H01M8/0247—Collectors; Separators, e.g. bipolar separators; Interconnectors characterised by the form
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- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/06—Combination of fuel cells with means for production of reactants or for treatment of residues
- H01M8/0606—Combination of fuel cells with means for production of reactants or for treatment of residues with means for production of gaseous reactants
- H01M8/0612—Combination of fuel cells with means for production of reactants or for treatment of residues with means for production of gaseous reactants from carbon-containing material
- H01M8/0625—Combination of fuel cells with means for production of reactants or for treatment of residues with means for production of gaseous reactants from carbon-containing material in a modular combined reactor/fuel cell structure
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- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/06—Combination of fuel cells with means for production of reactants or for treatment of residues
- H01M8/0606—Combination of fuel cells with means for production of reactants or for treatment of residues with means for production of gaseous reactants
- H01M8/0656—Combination of fuel cells with means for production of reactants or for treatment of residues with means for production of gaseous reactants by electrochemical means
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- H01M8/184—Regeneration by electrochemical means
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- H01M8/186—Regeneration by electrochemical means by electrolytic decomposition of the electrolytic solution or the formed water product
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- H01M8/22—Fuel cells in which the fuel is based on materials comprising carbon or oxygen or hydrogen and other elements; Fuel cells in which the fuel is based on materials comprising only elements other than carbon, oxygen or hydrogen
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- H01M8/22—Fuel cells in which the fuel is based on materials comprising carbon or oxygen or hydrogen and other elements; Fuel cells in which the fuel is based on materials comprising only elements other than carbon, oxygen or hydrogen
- H01M8/222—Fuel cells in which the fuel is based on compounds containing nitrogen, e.g. hydrazine, ammonia
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- 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
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- H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
- H01M2004/8678—Inert electrodes with catalytic activity, e.g. for fuel cells characterised by the polarity
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- H01M2008/1095—Fuel cells with polymeric electrolytes
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- H01M8/02—Details
- H01M8/0271—Sealing or supporting means around electrodes, matrices or membranes
- H01M8/0273—Sealing or supporting means around electrodes, matrices or membranes with sealing or supporting means in the form of a frame
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- H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
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- H01M8/04089—Arrangements for control of reactant parameters, e.g. pressure or concentration of gaseous reactants
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- 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
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- H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
- H01M8/04298—Processes for controlling fuel cells or fuel cell systems
- H01M8/04694—Processes for controlling fuel cells or fuel cell systems characterised by variables to be controlled
- H01M8/04858—Electric variables
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- H01M8/04947—Power, energy, capacity or load of auxiliary devices, e.g. batteries, capacitors
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- H01M8/0668—Removal of carbon monoxide or carbon dioxide
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- H01M8/0681—Reactant purification by the use of electrochemical cells
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- H01M8/24—Grouping of fuel cells, e.g. stacking of fuel cells
- H01M8/2455—Grouping of fuel cells, e.g. stacking of fuel cells with liquid, solid or electrolyte-charged reactants
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- 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
- Y02E60/10—Energy storage using batteries
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- 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
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Abstract
A fuel cell system including an electrode-electrolyte assembly having a first catalytic electrode coupled to one side of the electrode-electrolyte assembly, and a second catalytic electrode coupled to a generally opposite side of the electrode-electrolyte assembly. The fuel cell system includes a first conduit in fluid communication with the first catalytic electrode for delivering fuel to the first catalytic electrode at ambient temperature and a second conduit in fluid communication with the second catalytic electrode for delivering oxidant thereto. The fuel cell system also includes means for providing an electrical potential across the first catalytic electrode, the electrode-electrolyte assembly and the second catalytic electrode and the fuel cell system further includes an electrical load circuit for using an energy output generated across the first catalytic electrode, the electrode-electrolyte assembly and the second catalytic electrode.
Description
- This application is a divisional of U.S. non-provisional patent application Ser. No. 11/588,200, filed on Oct. 26, 2006, which claims priority from provisional application Ser. No. 60/731,054, filed Oct. 28, 2005, the disclosures of both are incorporated by reference herein in its entirety.
- The present invention is generally directed to a fuel cell and fuel processing system and a method of operating the same; and is more specifically directed to ambient temperature processing of organic fuels internal to the fuel cell system by electrochemical means.
- Fuel cells are comprised of electrochemical cells used for providing an environmentally clean method for generating electricity. What makes fuel cells different from another electrochemical energy converter, such as a battery, is the fact that both fuel and oxidant are continuously supplied to their respective electrodes, and reaction products are continuously removed from the fuel cell. Electric current will continue to flow essentially as long as fuel and oxidant are supplied to the electrodes. Fuel cell systems can be formed by stacking and electrically connecting many electrochemical cells together to provide power generation for residential, commercial and industrial scale power applications. Individual fuel cells in fuel cell systems each include at least two catalytic electrodes in contact with an electrolyte medium comprising an electrode-electrolyte assembly. The individual fuel cells also include devices for managing fuel and oxidant flows thereto and for controlling temperature within operating limits. Use of pure hydrogen as a fuel results in higher fuel cell energy density outputs compared to other fuels. However, hydrogen has a number of drawbacks including: flammability; storage difficulties; and comparatively high production costs.
- In addition to hydrogen, naturally occurring organic fuels and synthetic fuels can be used in fuel cells. Naturally occurring fuels are preferred over synthetic fuels because of their abundance and lower cost compared to cost prohibitive synthetic fuels. Naturally occurring organic fuels as well as synthetic fuels can form hydrogen external to the fuel cell system using an endothermic chemical reaction such as steam reforming. However, steam reforming is a slow responding process because it relies on thermal energy input to accommodate load changes. As such, steam reforming is limited mostly to steady state fuel cell operations at temperatures much higher than ambient temperature. The steady state operating limitation makes such fuel cells impractical for varying power output to follow transient electric load demands. Moreover, operation of fuel cells at such high temperatures precludes the use of most polymer electrolyte membranes. Various fuel cell designs have utilized steam reformers external to the fuel to allow for fuel cell operation at ambient temperatures. However, steam reforming outside a fuel cell increases cost and does not provide improved transient load following capability. Hydrogen generated by steam reformers external to the fuel cell could be accumulated in a storage facility. However, storage of highly flammable fuels such as hydrogen is dangerous. Moreover hydrogen storage facilities generally limit fuel cells to stationary applications.
- Modifications of fuel cell electrodes to utilize hydrogen from naturally occurring organic matter include use of ruthenium in the catalyst on the electrodes, which can lower operating temperature requirements below the boiling point of water. However, fuel cells comprising ruthenium containing catalytic electrodes are typically operated above ambient temperature.
- Hydrogen can be obtained at ambient temperature (i.e., without steam reforming) from simple forms of water-soluble organic fuels such as methanol. However, use of methanol is generally not cost-effective enough for widespread application. Use of complex organic fuels, such as hexose, is desirable for use in fuel cells because of their natural abundance and competitive cost. When used in fuel cells, complex organic fuels such as hexose react to release hydrogen in a sequence of electrochemical de-hydrogenation reactions. Typically, intermediates are produced as a result of such de-hydrogenation reactions. These intermediates are further reacted to waste products. Some of these intermediates, however, are known to poison and deactivate the fuel side of catalytic electrodes, essentially stopping the production of hydrogen. Certain fuels such as methanol are less likely to cause fuel side catalytic electrode poisoning if operated at elevated temperatures. However, methanol has a high permeability through electrolyte membranes and can diffuse through the membrane thereby polarizing the oxidant side of the catalytic electrode. Such polarization reduces the performance of the fuel cell.
- Hydrogen permeable metal barriers have been used to limit the diffusion of methanol across electrolyte membranes. However, use of metal barriers also limits the transport of electrochemically active species such as hydrogen ions and neutral atoms and thus, limits the performance achievable directly from methanol fuel. The approach where the access of methanol to the electrode is controlled by means of other permeable membranes, such as polymers, has the disadvantage of requiring elevated temperature for proper operation and to exceed the performance levels of fuel cells having metal barriers.
- The performance of fuel cells using catalytic electrodes can degrade due to catalyst deactivation and poisoning by reaction intermediates, especially near ambient operating temperature. For catalytic electrodes comprising platinum, carbon monoxide is a likely poisoning intermediate. Elevation of the operating temperature of the fuel cell to about 200° C. can eliminate such poisoning. While elevating the operating temperature of the fuel cell may be practical in fuel cell applications operating continuously at or near steady state, it is difficult to implement for applications that use the fuel cell on a transient or as-needed basis and makes the use of polymer electrolyte assemblies impractical.
- There is a need to provide a fuel cell system including a fuel processing device/system capable of processing complex fuels internal to the fuel cell at near ambient temperature. Prior art methods and systems for addressing these needs for portable or transient applications were either too expensive, inefficient, or ineffective or a combination of all of these. Based on the foregoing, it is the general object of the present invention to improve upon or overcome the problems and drawbacks of the prior art.
- According to one aspect of the present invention, a fuel cell system capable of processing organic fuels at ambient temperature and generating an electrical energy output is provided. The fuel cell system comprises two electrode-electrolyte assemblies each having a catalytic electrode coupled to opposing sides thereof and an electrically conductive mesh disposed in sealing engagement therebetween. A first conduit delivers a fuel at ambient temperature to one side of one of the electrode-electrolyte assemblies. The electrically conductive mesh has a plurality of apertures extending therethrough, such that portions of catalytic electrodes, adjacent to the mesh, extend through the apertures and engage each other. A second conduit delivers an oxidant to one side of another of the electrode-electrolyte assemblies. The fuel cell system includes means for providing an electrical potential across one of the electrode-electrolyte assemblies and an electrical load circuit for using the energy output generated across the other electrode-electrolyte assembly.
- In another aspect of the present invention, the means for providing the electrical potential has a positive terminal in electrically conductive communication with one side of one of the electrode-electrolyte assemblies and a negative terminal in electrically conductive communication with the opposing side of the same electrode-electrolyte assembly for providing process energy for a hydrogen formation reaction and removing poisons from the catalytic electrode, and for causing hydrogen to diffuse through the electrode-electrolyte assembly to the other electrode-electrolyte assembly.
- In another aspect of the present invention, a fuel cell system operable with one electrode-electrolyte assembly for processing organic fuels at ambient temperature and generating an electrical energy output is provided. The fuel cell system comprises an electrode-electrolyte assembly having a first catalytic electrode coupled to one side of the electrode-electrolyte assembly, and a second catalytic electrode coupled to a generally opposite side of the electrode-electrolyte assembly. A first conduit delivers fuel to the first catalytic electrode at ambient temperature and a second conduit delivers an oxidant to the second catalytic electrode. The fuel cell system includes means for providing an electrical potential across the first catalytic electrode, the electrode-electrolyte assembly and the second catalytic electrode. In addition, an electrical load circuit is included for using an energy output generated across the first catalytic electrode, the electrode-electrolyte assembly and the second catalytic electrode.
- In yet another aspect of the present invention, the means for providing the electrical potential has a positive terminal in electrically conductive communication with the first catalytic electrode and a negative terminal in electrically conductive communication with the second catalytic electrode for providing process energy for a hydrogen formation reaction and removing poisons from the first catalytic electrode, and for causing hydrogen to diffuse through the electrode-electrolyte assembly to the second catalytic electrode. The fuel cell system also includes a first electrical circuit comprising the means for providing the electrical potential. The first electrical circuit and the electrical load circuit are interlocked such that during operation the first electrical circuit is closed when the electrical load circuit is open and the electrical load circuit is closed when the first electrical circuit is open. During operation, the first electrical circuit and the electrical load circuit are opened and closed for predetermined periods of time.
- Another aspect of the present invention involves a method of operation of the fuel cell system wherein fuel and oxidant are delivered to the electrode-electrolyte assemblies by respective conduits. Process energy for an ambient temperature electrochemical reaction to form hydrogen and remove poisons from one of the catalytic electrodes is provided by establishing electrically conductive communication between a positive terminal of the means for providing the electrical potential and one of the catalytic electrodes; and establishing electrically conductive communication between a negative terminal of the means for providing the electrical potential and another catalytic electrode. Hydrogen is diffused through one of the electrode-electrolyte assemblies for use in generating an energy output across the other electrode-electrolyte assembly.
- In yet another aspect of the present invention wherein a fuel cell system is operated with one electrode-electrolyte membrane the method of operation includes providing a first electrical circuit comprising means for providing an electrical potential. The first electrical circuit is interlocked with an electrical load circuit such that during operation the first electrical circuit is closed when the electrical load circuit is open and the electrical load circuit is closed when the first electrical circuit is open. The first electrical circuit and the electrical load circuit are cyclically opened and closed for predetermined periods of time for alternating between fuel processing and power generation cycles.
- Another embodiment of the present invention involves a method of selecting a preferred fuel for a fuel cell system comprising the steps of selecting the fuel capable of being dissolved in water; and selecting an aqueous solution of the fuel, wherein the Gibbs free energy of the fuel is preferably greater than the heat of reaction of the fuel.
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FIG. 1 is a schematic drawing of the fuel cell system of the present invention. -
FIG. 2 is a top view of an electrode-electrolyte assembly. -
FIG. 3 is a schematic drawing of the present invention illustrating the process energy being provided by the energy output of the fuel cell. -
FIG. 4 is a schematic drawing of the fuel cell ofFIG. 3 including an inductive device for providing the process energy. -
FIG. 5 is a top view of the mesh. -
FIG. 6 is a cross sectional view of the mesh ofFIG. 5 . -
FIG. 7 is a cross sectional view of a portion of the mesh ofFIG. 5 positioned between the first and second electrode-electrolyte assemblies. -
FIG. 8 is a cross sectional view of the fuel cell system having meshes embedded in the electrodes. -
FIG. 9 is a cross sectional view of the fuel cell system including a common electrode having a mesh embedded therein. -
FIG. 10 is a top view of a conduit. -
FIG. 11 is a schematic drawing of a cross section of the conduit. -
FIG. 12 is a schematic drawing of an exploded view of an assembled fuel cell system. -
FIG. 13 is a schematic drawing of a plurality of fuel cell systems ofFIG. 1 arranged in a stack. -
FIG. 14 is a schematic drawing of a fuel cell system having one electrode-electrolyte assembly. -
FIG. 15 is a schematic drawing of the fuel cell system ofFIG. 14 shown with the electrical load circuit de-energized. -
FIG. 16 is a schematic drawing of the fuel cell system ofFIG. 14 shown with the electrical load circuit energized. -
FIG. 17 is a graph of operational parameters of the fuel cell system during fuel processing and power generation cycles. -
FIG. 18 is a graph of voltage and power density as a function of current density for the fuel cell system. -
FIG. 19 is a schematic drawing of a plurality of fuel cells ofFIG. 14 . - Referring to
FIG. 1 , a single cell fuel cell system is shown generally at 2. Thefuel cell system 2 includes a first electrode-electrolyte assembly 4, a second electrode-electrolyte assembly 6 and an electricallyconductive mesh 8 disposed therebetween and in sealing engagement therewith. Afirst conduit 10 is in fluid communication with one side of the first electrode-electrolyte assembly 4 and a secondfluid conduit 12 is in fluid communication with one side of the second electrode-electrolyte assembly 6. At least portions of the first andsecond conduits fuel cell system 2 includes a firstelectrical circuit 14 including anenergy storage device 16 for providing process energy in the form of a first electrical potential across the first electrode-electrolyte assembly 4. In addition, anelectrical load circuit 18 is connected across the second electrode-electrolyte assembly 6 for consuming energy output therefrom in the form of a second electrical potential generated thereacross. A plurality of thefuel cell systems 2 may be connected together in an electrical series circuit or arranged in a stack with suitable fluid distribution hardware. While the firstelectrical circuit 14 is shown to include anenergy storage device 16, the present invention is not limited in this regard as a battery, capacitor, or a combination of a plurality thereof capable of providing the process energy can be used. - Referring to
FIGS. 1-2 , the first electrode-electrolyte assembly 4 includes anelectrolyte membrane 5, preferably formed of an ion exchanging polymer, the electrolyte membrane having afirst electrode 21 and asecond electrode 22 preferably catalytic electrodes hot-pressed onto opposing surfaces thereof. Similarly, the second electrode-electrolyte assembly 6 includes anelectrolyte membrane 5, preferably formed of an ion exchanging polymer, the electrolyte membrane having athird electrode 23 and afourth electrode 24 preferably catalytic electrodes hot-pressed onto opposing surfaces thereof. Thepolymer electrolyte membrane 5 is generally a soft compliant material, comprising any ion-conductive material and is generally a hydrocarbon resin or a fluorocarbon resin capable of facilitating ion transfer in two directions. For hydrocarbon resins, phenolic-based materials are of particular use. Fluorocarbon resins are particularly useful for providing resistance in chemically corrosive environments. Suitable materials from which the electrodes can be fabricated include, but are not limited to, platinum, palladium, rhodium, gold, tungsten, tantalum, ruthenium, and alloys and combinations of the foregoing. The present invention is not limited in this regard, and other membrane materials and electrode materials are within the scope of the invention. - The first electrode-
electrolyte assembly 4 also includes throughholes area 28. The second electrode-electrolyte assembly 6 is configured similar to the first electrode-electrolyte assembly 4. The second andthird electrodes mesh 8, thefirst electrode 21 is in electrically conductive communication with the firstfluid conduit 10 and thefourth electrode 24 is in electrically conductive communication with the secondfluid conduit 12. When the first and second electrode-electrolyte assemblies are assembled with other componentry, the throughholes fuel cell system 2. While the first and second electrode-electrolyte assemblies - Referring to
FIG. 1 , when assembled, thefirst conduit 10 is in fluid communication with the firstcatalytic electrode 21 for delivering fuel to the first catalytic electrode at ambient temperature. Preferably, the temperature of the fuel is from about 60° F. to about 100° F. when delivered and during fuel processing for the formation of hydrogen thereby facilitating use of polymer electrolytes. Transient load following capability of the fuel cell system is enabled by processing fuel and operating the fuel cell at ambient temperatures because ramp-up time associated with heating the fuel cell and/or fuel processing system are eliminated. While ambient temperature operation from about 60° F. to about 100° F. is described, the present invention is not limited in this regard as the fuel cell system of the present invention may also be operated at temperatures up to about 180° F. - The
second conduit 12 is in fluid communication with the fourthcatalytic electrode 24 for delivering an oxidant thereto. Preferably, the first andsecond conduits first electrode 21 and delivering oxidant to thefourth electrode 24, respectively. Reaction products and excess heat are transported away from thefuel cell 2 by the fuel and oxidant flowing through the first andsecond conduits - Still referring to
FIG. 1 , theenergy storage device 16 has a positive terminal in electrically conductive communication with thefirst conduit 10 and the firstcatalytic electrode 21 and a negative terminal in electrically conductive communication with themesh 8 and the secondcatalytic electrode 22. Theenergy storage device 16 in the firstelectrical circuit 14 is polarized to provide the process energy for an electrochemical reaction to form hydrogen and remove carbon monoxide (CO) poisons formed on firstcatalytic electrode 21. The hydrogen diffuses through the first electrode-electrolyte assembly 4 to the thirdcatalytic electrode 23. Equation 1 (Eq. 1) illustrates the total electrochemical reaction across the first electrode-electrolyte assembly 4. In particular, Eq. 1 illustrates the formation of hydrogen species such as hydrogen ions (H+) and the removal of CO poison from thefirst electrode 21 when the first electrical potential is applied across the first electrode-electrolyte assembly 4 in the presence of water on the first catalytic electrode. The Gibbs free energy for the reaction defines the maximum theoretical work that can be extracted by means of a specific reaction path. The heat of reaction is the enthalpy change that occurs in a system when one mole of matter is transformed by a chemical reaction under standard conditions. Thus, a fuel having the absolute value of the Gibbs free energy of reaction greater than the absolute value of the heat of reaction is preferred. In particular, complex organic fuels having more than one hydrogen bond are preferred. Suitable complex organic fuels include aqueous solutions of carbohydrates including but not limited to hexose C6H12O6 which has a heat of reaction of −669.92 kcal/mole and a Gibbs free energy of −688.33 kcal/mole. Other complex organic fuels suitable for ambient temperature processing include hydrazine and most light hydrocarbons. - Referring to
FIG. 3 , theenergy storage device 16 is shown, after start-up of thefuel cell system 2, disconnected from the firstelectrical circuit 14 and a portion of the energy output across the second electrode-electrolyte assembly 6 is used to provide the process energy of the electrochemical reaction. The remainder of the electrical output is shown being consumed by a useful electrical load L connected in theelectrical load circuit 18. The electrical energy output across the second electrode-electrolyte assembly 6 is greater than the process energy used in the electrochemical reaction. -
FIG. 3 illustrates aballast resistor 9 connected in a thirdelectrical circuit 17. Theballast resistor 9 has one terminal in electrically conductive communication with thefirst conduit 10 and carries a positive charge. Theballast resistor 9 has another terminal in electrically conductive communication with thesecond conduit 12 and also carries a positive charge. The thirdelectrical circuit 17 provides and regulates current flow from theelectrical load circuit 18 to provide the process energy for the electrochemical reaction to form hydrogen. The thirdelectrical circuit 17 diverts at least a portion of the current flow from theelectrical load circuit 18. Current flowing through theelectrical load circuit 18 is greater than current flowing through the thirdelectrical circuit 17 for providing the process energy. Theballast resistor 9 regulates the flow of the electrical current through the third electrical circuit such that thefirst conduit 10 is at a less positive electrical potential than that at thesecond conduit 12. Although aballast resistor 9 is illustrated for regulating current flow in the thirdelectrical circuit 17, the present invention is not limited in this regard as other devices can also be used including, but not limited to, a semiconductor device and electronic current controls for a finer match between the fuel processing current and the external load. - Referring to
FIG. 4 , theenergy storage device 16 is shown, after start-up of thefuel cell system 2, disconnected from the firstelectrical circuit 14. During operation, the fuel cell system is electrically connected to aninductive device 29 having a primary side P and a secondary side S. The primary side (P) comprisesprimary circuit 11 and abranch circuit 13. Theprimary circuit 11 includes aswitching device 35 for the repeated opening and closing thereof to charge theinductive device 29. Theprimary circuit 11 is electrically connected across the second electrode-electrolyte assembly 6 thereby terminating at thesecond conduit 12 and themesh 8. Thebranch circuit 13 has a terminal in electrically communication with thefirst conduit 10 and another terminal in electrically conductive communication with themesh 8. The secondary side (S) comprises asecondary side circuit 15 and a load L. The primary, branch andsecondary circuits mesh 8, the second most negative polarity at theconduit 10 such that the conduit appears positive with respect tomesh 8 and the most positive atfluid conduit 12 upon the repeated opening and closing of theswitching device 35. - Referring to
FIG. 4 , theprimary circuit 11 consumes the electrical energy output across the second electrode-electrolyte assembly 6 by flowing current to thebranch circuit 13 thereby providing the process energy of the electrochemical reaction. The remainder of the electrical energy output across the second electrode-electrolyte assembly 6 is consumed by charging theinductive device 29 for consumption by the useful electrical load L connected in theelectrical load circuit 15. Although a portion of the electrical energy output across the second electrode-electrolyte assembly 6 is shown connected to the branch circuit and the remainder charging an inductive device, the present invention is not limited in this regard as other configurations are also within the scope of the present invention, including but not limited to consuming substantially the entire energy output for charging the inductive device to generate electrical current on the secondary side for the process energy and for consumption by a useful load. - The Referring to
FIGS. 5-7 , themesh 8 comprises an electrically conductive material having a plurality ofapertures 30 extending through a firstactive area 32. Theapertures 30 are defined by a plurality ofwalls 31 spaced apart from one another such that, in the preferred embodiment, when the mesh is positioned between the first and second electrode-electrolyte assemblies third electrodes apertures 30 and engage each other. During operation of thefuel cell assembly 2, hydrogen species such as hydrogen ions diffuse from the first electrode-electrolyte assembly 4 to the second electrode-electrolyte assembly 6 through the portions of the second andthird electrodes mesh 8 has a greater electrical conductivity than that of at least theelectrodes active area 32 and portions of the second and third electrodes engaged therewith. Themesh 8 provides electrical terminals for at least the firstelectrical circuit 14 and theelectrical load circuit 18. - One side of the
mesh 8 has a sealingarea 34 substantially along the periphery thereof. The sealingarea 34 comprises an interference pattern 36 (e.g., grooves) that forms a positive interlocking seal with the soft polymer material of the electrode-electrolyte assembly. Theinterference pattern 36 used for illustration includes a plurality of parallel ridges that form grooves. An opposing side of themesh 8 has a similar sealing area and interference pattern. When themesh 8 is positioned between the first and second electrode-electrolyte assemblies the ridges of the sealingarea 34 are pressed onto the material of the electrode-electrolyte assemblies and can deform to ensure fluid containment in their respective designated cavities. - Referring back to
FIG. 5 , themesh 8 also includes throughholes mesh 8 is assembled with other componentry, the throughholes fuel cell system 2. The sealingarea 34 also extends substantially around the perimeter of the throughholes - Referring now to
FIG. 8 , the fuel cell system is shown generally at 102. Thefuel cell system 102 includes a first electrode-electrolyte assembly 104 and a second electrode-electrolyte assembly 106. The first electrode-electrolyte assembly 104 includes anelectrolyte membrane 105, preferably formed of an ion exchanging polymer, the electrolyte membrane having afirst electrode 121 and asecond electrode 122, preferably catalytic electrodes hot pressed onto opposing surfaces thereof. Thesecond electrode 122 includes an electricallyconductive mesh 108 embedded therein. Similarly, the second electrode-electrolyte assembly 104 includes anelectrolyte membrane 105, preferably formed of an ion exchanging polymer, the electrolyte membrane having athird electrode 123 and afourth electrode 124, preferably catalytic electrodes hot pressed onto opposing surfaces thereof. Thethird electrode 123 includes an electricallyconductive mesh 108 embedded therein. Afirst conduit 110 is in fluid communication withfirst electrode 121 and a secondfluid conduit 112 is in fluid communication with thefourth electrode 124. The first and second electrode-electrolyte assemblies second conduits fuel cell system 102 includes a firstelectrical circuit 114 including anenergy storage device 116 for providing a first electrical potential across the first electrode-electrolyte assembly 104. In addition, anelectrical load circuit 118 is connected across the second electrode-electrolyte assembly 106 for consuming an energy output in the form of a second electrical potential generated thereacross. - The
meshes 108 are similar to themesh 8 described above. In particular, preferably, themeshes 108 have a greater electrical conductivity than that of at least theelectrodes third electrodes meshes 108 provide electrical terminals at least for the firstelectrical circuit 114 and theelectrical load circuit 118. When assembled, the second andthird electrodes - Referring now to
FIG. 9 , the fuel cell system is shown generally at 202. Thefuel cell system 202 includes a first electrode-electrolyte assembly 204 and a second electrode-electrolyte assembly 206. The first electrode-electrolyte assembly 204 includes anelectrolyte membrane 205, preferably formed of an ion exchanging polymer, the electrolyte membrane having afirst electrode 221, preferably a catalytic electrode hot pressed onto one surface thereof. The fuel cell system includes second and third electrodes combined into onecommon electrode 222 having an electricallyconductive mesh 208 embedded therein. The second electrode-electrolyte assembly 204 includes anelectrolyte membrane 205, preferably formed of an ion exchanging polymer, the electrolyte membrane having afourth electrode 224, preferably a catalytic electrode hot pressed onto opposing surfaces thereof. Thecommon electrode 222 is disposed betweenmembrane surfaces 205 of the first and second electrode-electrolyte assemblies. Afirst conduit 210 is in fluid communication withfirst electrode 221 and a secondfluid conduit 212 is in fluid communication with thefourth electrode 224. The first and second electrode-electrolyte assemblies second conduits fuel cell system 202 includes a firstelectrical circuit 214 including anenergy storage device 216 for providing a first electrical potential across the first electrode-electrolyte assembly 204. In addition, anelectrical load circuit 218 is connected across the second electrode-electrolyte assembly 206 for consuming an energy output in the form of a second electrical potential generated thereacross. - The
mesh 208 is similar to themesh mesh 208 has a greater electrical conductivity than that of at least thecommon electrode 222 for distributing electrical current throughout portions thereof. Themesh 208 provides electrical terminals at least for the firstelectrical circuit 214 and theelectrical load circuit 218. - Referring now to the exemplary embodiment in
FIG. 10 , an electrode-side of theconduit 10 includes a secondactive area 51 defined by a plurality ofpassages 40, through which fluid communication can be maintained between the adjacently positioned first catalytic electrode. Preferably, at least portions of theconduit 10 have a greater electrical conductivity than that of the catalytic electrodes for distributing electrical current throughout the secondactive area 51 and portions of the first catalytic electrode engaged therewith. Thefirst conduit 10 provides an electrical terminal for the firstelectrical circuit 14. Asecond conduit 12 provides an electrical terminal for theelectrical load circuit 18. While theconduits - The electrode-side of the
conduit 10 has a sealingarea 44 substantially along the periphery thereof. The sealingarea 44 has an interference pattern (e.g., grooves) that forms a positive interlocking seal with the soft polymer material of the electrode/electrolyte assembly, similar to that described above for themesh 8. The electrode-side also includes throughholes fluid conduit 10 is assembled with other componentry, the throughholes fuel cell system 2. The sealingarea 44 also extends substantially around the throughholes - Referring now to
FIGS. 10 and 11 the conduit includes aflow distribution inlet 50 and aflow distribution structure 52. The conduit also includes aflow distribution outlet 54 and a flowdistribution receiving structure 56. Theflow distribution inlet 50 is in fluid communication with the throughhole 48 and provides process fluid to theflow distribution structure 52. Theflow distribution structure 52 distributes the process fluid to the secondactive area 51, generally in the direction of thearrow 57, which allows the fluid to be dispensed through the secondactive area 51 of conduit over the surface area of the electrode-electrolyte assembly when assembled. Excess fluid in the secondactive area 51 is received in the flowdistribution receiving structure 56, which channels the process fluid, in the general direction of thearrow 59, to theflow distribution outlet 54 and to the throughhole 48 that defines part of the outlet manifold of the cell. The secondfluid conduit 12 is similar in configuration to and has materials of manufacture similar to that of thefirst conduit 10. - Referring now to
FIG. 12 , the assembledfuel cell system 2, comprises the first electrode-electrolyte assembly 4, the second electrode-electrolyte assembly 6 and the electricallyconductive mesh 8 disposed therebetween and in sealing engagement therewith. Thefirst conduit 10 is in fluid communication with one side of the first electrode-electrolyte assembly 4 and the secondfluid conduit 12 is in fluid communication with one side of the second electrode-electrolyte assembly 6. Thefuel cell system 2 is assembled such that throughholes inlet fluid manifolds 60; throughholes holes holes outlet fluid manifold 63. - Referring to
FIG. 13 , it is sometimes advantageous to assemble a plurality offuel cell systems 2 in astack 66. Thestack 66 configuration illustrates the individualfuel cell systems 2 connected electrically inseries using conductors 27, and the flow of fuel and oxidant through the respective fluid conduits is managed in a parallel flow configuration whereindielectric separators 68 are disposed between adjacent fuel cell systems and upon terminating ends thereof. Each of thefuel cell systems 2 comprises the firstelectrical circuit 14 including theenergy storage device 16 for providing a first electrical potential across the first electrode-electrolyte assembly 4. In addition, anelectrical load circuit 19 is connected between themesh 8 of afuel cell system 2 on one end of thestack 66, and thefluid conduit 12 of a fuel cell system on the opposing end of the stack for consuming energy output in the form of a second electrical potential generated thereacross. Electrically conductive communication is provided between the secondfluid conduit 12 of onefuel cell system 2 and themesh 8 of an adjacent fuel cell system byconductors 27. In particular, thefuel cell systems 2 are shown connected to each other in an electrical series circuit. Thestack 66 is configured to operate similar to that described above for the single cellfuel cell systems 2 ofFIG. 1 . Although individualfuel cell systems 2 are shown connected electrically inseries using conductors 27, and the flow of fuel and oxidant through the respective fluid conduits is managed in a parallel flow configuration, it the present invention is not limited in this regard as other fuel cell system stacking configurations are also within the scope of the present invention. - Referring to
FIG. 14 , a single cellfuel cell system 302 comprises anelectrolyte assembly 304 which operates alternately as fuel processing and fuel cell device. The electrode-electrolyte assembly 304 is disposed between afirst conduit 310 and asecond conduit 312. The electrode-electrolyte assembly 304 includes a firstcatalytic electrode 321 coupled to one side of the electrode-electrolyte assembly and a secondcatalytic electrode 322 coupled to a generally opposing side of the electrode-electrolyte assembly. The electrode-electrolyte assembly 304 includes anelectrolyte membrane 305, preferably formed of an ion exchanging polymer similar to that described above for the electrode-electrolyte assembly 4. - The
first conduit 310 is in fluid communication with the firstcatalytic electrode 321 for delivering fuel thereto at ambient temperature. Thesecond conduit 312 is in fluid communication with the second catalytic electrode for delivering an oxidant thereto. Thefuel cell system 302 includes a firstelectrical circuit 314 including anenergy storage device 316 for providing a first electrical potential across the electrode-electrolyte assembly 304. In addition, anelectrical load circuit 318 is connected across the electrode-electrolyte assembly 304 for consuming energy output in the form of a second electrical potential generated thereacross. A plurality of thefuel cell systems 302 may be connected individually together in an electrical series circuit or arranged in a stack with suitable fluid distribution hardware. While the firstelectrical circuit 314 is shown to include anenergy storage device 316, the present invention is not limited in this regard as a battery, capacitor or a combination of a plurality thereof can be used. - The electrode-
electrolyte assembly 304 and theconduits conduits fuel cell system 302 is similarly configured to thefuel cell system 2 for processing aqueous solutions of complex organic fuels at ambient temperature. - Referring to
FIG. 14 , theenergy storage device 316 has a positive terminal in temporary electrically conductive communication with thefirst conduit 310 and firstcatalytic electrode 321 and a negative terminal in intermittent electrically conductive communication with thesecond conduit 312 and the secondcatalytic electrode 322. Theconduit 310 is generally used for supplying an organic fuel to thecatalytic electrode 321 and theconduit 312 is generally used for supplying an oxidant to thecatalytic electrode 322. The polarity of theenergy storage device 316 in the firstelectrical circuit 314 thus provides the process energy for an electrochemical reaction to remove carbon monoxide (CO) poisons formed on firstcatalytic electrode 321 and form hydrogen species. The hydrogen diffuses through the electrode-electrolyte assembly 304. Anelectrical load circuit 318 is intermittently connected across the electrode-electrolyte assembly for consuming energy output in the form of the second electrical potential generated therefrom. - Referring now to
FIGS. 15-16 the firstelectrical circuit 314 and theelectrical load circuit 318 are interlocked such that during operation the first electrical circuit is energized for at least a portion of a period of time when the electrical load circuit is de-energized and the electrical load circuit is energized for at least a portion of a following period of time when the first electrical circuit is de-energized. During operation theelectrical load circuit 318 is alternately opened and closed for a first predetermined period of time while the firstelectrical circuit 314 is cyclically toggled between fuel processing and storage recharge for a second predetermined period of time. - Referring now to
FIG. 15 , thefuel cell system 302 is illustrated in a fuel processing cycle whereinswitches energy storage device 316 is in electrically conductive communication with the firstcatalytic electrode 321 and a negative terminal of the energy storage device in electrically conductive communication with the secondcatalytic electrode 322 causing electrical current to flow in the firstelectrical circuit 314 in the direction of thearrow 373. During the fuel processing cycle,switch 372 is positioned to open theelectrical load circuit 318 resulting in no current flow therethrough. During the fuel processing cycle, the energy storage device provides the process energy for removing carbon monoxide (CO) poisons formed on firstcatalytic electrode 321, and for the electrochemical reaction for formation of hydrogen. - Referring now to
FIG. 16 , thefuel cell system 302 is illustrated in a power generation cycle wherein the position ofswitches energy storage device 316 is in electrically conductive communication with the secondcatalytic electrode 322 and the negative terminal of the energy storage device is in electrically conductive communication with the firstcatalytic electrode 321 causing electric current to flow in the firstelectrical circuit 314 in the direction of thearrow 374, thereby replenishing theenergy storage device 316. In addition, theswitch 372 is positioned to close theelectrical load circuit 318 thereby providing the energy output in the form of the second electrical potential and causing electrical current to flow in the direction ofarrow 375. - Referring to
FIGS. 15-17 , during the power generation cycle, the electric current is shown as positive value whenswitch 372 is closed and switches 370, 371 are in the recharge positions. The relative magnitude of the electric current flowing in the firstelectrical circuit 314 for recharging theenergy storage device 316 is illustrated onFIG. 17 asarrow 384; and the relative magnitude of the excess electrical current flowing in the secondelectrical circuit 318 for consumption by the electrical load is illustrated onFIG. 17 asarrow 385. Preferably, the magnitude of the electrical current required for recharging theenergy storage device 316 is less than that available for consumption by the electrical load. In addition it is preferred that the total energy consumed for recharging is less than the energy available for consumption by the electrical load during the entire power generation cycle. - Still referring to
FIGS. 15-17 , during the fuel processing cycle, electrical current flowing from theenergy storage device 316 is shown as a negative value when switches 370, 371 are in the fuel processing positions and switch 372 is open. The magnitude of the electrical current required to provide the process energy for the hydrogen formation reaction is illustrated onFIG. 17 asarrow 383. During the fuel processing cycle, essentially no current flows in the secondelectrical circuit 318. Preferably, the process energy is less than the total energy available for consumption by the electrical load. - In addition, a first period of
time 387 during which switches 370, 371 are in the fuel processing positions and switch 372 is open is preferably less than a second period oftime 386 during which switch 372 is closed and switches 370, 371 are in the recharge positions. Preferably, the first period oftime 387 is from about 0.01 seconds to about 10 seconds and the second period oftime 386 is from about 0.5 minutes to about 10 minutes. Such cyclical switching between the fuel processing and the power generating cycles allows one electrode-electrolyte membrane to be used for both fuel processing and power generation, thus reducing the complexity of thefuel cell system 302. - While the first and second periods of time are preferred to be from about 0.01 seconds to about 10 seconds and from about 0.5 minutes to about 10 minutes, respectively, the present invention is not limited in this regard as other time durations may be used including but not limited to a performance based control including selecting the second period of time considering parameters indicative of degradation of power generation performance and selecting the first period of time based on fuel processing requirements corresponding to the magnitude of poisons formed on first
catalytic electrode 21 during the power generation cycle. Selecting the first and second periods of time in this manner can increase overall power output and minimize energy requirements for fuel processing thereby improving fuel cell system efficiency. Parameters indicative of degradation of power generation performance used in the performance based control include fuel temperature, electrode temperature, fuel flow rate, oxidant flow rate, electric load, power output, and voltage across the fuel cell system and individual cells. - As shown in
FIG. 18 ,curve 88, the initial power density of the fuel cell system varies as a function of current density. Similarly,curve 89 illustrates the initial voltage across the fuel cell system varies as a function of current density. The fuel cell system illustrated has a peak power density of approximately 0.34 W/cm2 as designated bypoint 93. After three minutes of operation, poisons build up on the firstcatalytic electrode 21 resulting in a degradation of fuel cell system performance. After the three minute period of operation, power density of the fuel cell is degraded as illustrated bycurve 90 and voltage across the fuel cell system is degraded as illustrated bycurve 91. The degradation in fuel cell performance reduces the peak power density to approximately 0.21 W/cm2, as illustrated bypoint 94. Power output of the fuel cell system is consumed by an external load of approximately 0.175 W/cm2 as illustrated byline 92. The performance based control logic temporarily interrupts power generation in order to remove poisons from the firstcatalytic electrode 21 in the fuel reprocessing cycle, prior to thepeak power density 94 decreasing below theexternal load 92. The performance based control logic is advantageous for fuel cells required to supply power for transient loads because the second period of time can be adjusted as a function of load. - Referring to
FIG. 19 , thefuel cell systems 302 can be assembled in abipolar stack 366. Each of thefuel cell systems 302 include an electrode-electrolyte assembly 304 disposed between a firstfluid conduit 310 and a secondfluid conduit 312. For illustration, a plurality offuel cell systems 302 can be assembled in thebipolar stack 366 usingbipolar separator plates 369 positioned between adjacentfirst conduits 310 andsecond conduits 312 for maintaining electrically conductive communication therebetween. Afirst terminal conductor 377 is positioned on one end of thefuel cell system 302 between adielectric cover 368 and thefirst conduit 310 adjacent thereto; and asecond terminal conductor 379 is positioned on an opposing end of the fuel cell system between another of the dielectric covers and thesecond conduit 312 adjacent thereto. The first and secondterminal conductors second conduits bipolar stack 366. - The
fuel cell system 302 also includes a firstelectrical circuit 314 having anenergy storage device 316 for providing an electrical potential across the first and secondterminal conductors electrical load circuit 318 is also connected across the first and secondterminal conductors electrical circuit 314 is shown withswitches bipolar stack 366 includes interlocking circuitry and is configured to operate similar to that described above for the single cellfuel cell systems 302 ofFIGS. 11-14 . - The present invention includes a method for operating a
fuel cell system 2. The method for operating thefuel cell system 2 includes the first step of providing a first electrode-electrolyte assembly 4 having a firstcatalytic electrode 21 coupled to one side of the first electrode-electrolyte assembly, and a secondcatalytic electrode 22 coupled to a generally opposite side of the first electrode-electrolyte assembly, afirst conduit 10 in fluid communication with the first catalytic electrode; a second electrode-electrolyte assembly 6 having a thirdcatalytic electrode 23 coupled to one side of the second electrode-electrolyte assembly, and a fourthcatalytic electrode 24 coupled to a generally opposite side of the second electrode-electrolyte assembly, an electricallyconductive mesh 8 having a plurality of apertures extending therethrough, the mesh being positioned between and in sealing engagement with the second catalytic electrode and the third catalytic electrode wherein the second and third catalytic electrode engage each other through the apertures, asecond conduit 12 in fluid communication with the fourth catalytic electrode, a firstelectrical circuit 14 including an electricalenergy storage device 16 and anelectrical load circuit 18. - The method of operating the
fuel cell system 2 also includes the steps of flowing an aqueous solution of a fuel having a complex organic structure through thefirst conduit 10, preferably the fuel being at ambient temperature for at least a portion of time during operation of the fuel cell system and flowing an oxidant through the secondfluid conduit 12. The method of operating thefuel cell system 2 further includes the steps of establishing electrically conductive communication between a positive terminal of theenergy storage device 16, thefirst conduit 10 and the firstcatalytic electrode 21. Electrically conductive communication is also established between a negative terminal of theenergy storage device 16, themesh 8 and the secondcatalytic electrode 22. Connecting the energy storage device in this manner provides the process energy for activating an ambient temperature electrochemical reaction to form hydrogen and remove poisons from the first catalytic electrode. - The method of operating the
fuel cell system 2 also includes the steps of charging the first catalytic electrode with hydrogen and diffusing the hydrogen through the first electrode-electrolyte assembly to the third catalytic electrode. By connecting the electrical load circuit having an electrical consumer, across the second electrode-electrolyte assembly an energy output is generated across the second electrode-electrolyte assembly which causes the hydrogen to be consumed from the thirdcatalytic electrode 23 and the oxidant to be consumed through the fourthcatalytic electrode 24 in an electrochemical reaction. As a result, an electric current flows through theelectrical load circuit 18. - The present invention also includes a method for operating a
fuel cell system 302. The method for operating thefuel cell system 302 includes the first step of providing an electrode-electrolyte assembly having a first catalytic electrode coupled to one side of the electrode-electrolyte assembly, and a second catalytic electrode coupled to a generally opposite side of the electrode-electrolyte assembly, a first conduit in fluid communication with the first catalytic electrode, a second conduit in fluid communication with the second catalytic electrode, a firstelectrical circuit 314 including an electricalenergy storage device 316, and anelectrical load circuit 318. - The method of operation of the
fuel cell system 302 includes the step of flowing an aqueous solution of a fuel having a complex organic structure through thefirst conduit 310, preferably the fuel being at ambient temperature and flowing an oxidant through the secondfluid conduit 312. The method of operation of thefuel cell system 302 includes the steps of establishing electrically conductive communication between a positive terminal of theenergy storage device 316 and the first catalytic electrode and establishing electrically conductive communication between a negative terminal of theenergy storage device 316 and the second catalytic electrode. Connecting the energy storage device in this manner provides the process energy for activating an ambient temperature electrochemical reaction to remove poisons from the first catalytic electrode and to form hydrogen fuel. - The method of operating the
fuel cell 302 also includes the steps of charging the firstcatalytic electrode 310 with hydrogen. After a period of time, preferably for about 0.01 seconds to about 10 seconds, the first electrical potential is electrically disconnected from thefuel cell system 302. By subsequently connecting theelectrical load circuit 318 having an electrical load in electrically conductive communication across the electrode-electrolyte assembly 304 an energy output is generated across the electrode-electrolyte assembly thereby consuming most of the hydrogen from the electrode-electrolyte assembly and the oxidant in an electrochemical reaction. As a result, an electric current flows through theelectrical load circuit 318. - The method of operating the
fuel cell system 302 includes interlocking the firstelectrical circuit 314 and theelectrical load circuit 318 such that during operation the first electrical circuit is closed when the electrical load circuit is open; the electrical load circuit is closed when the first electrical circuit is open; and cyclically opening and closing the first electrical circuit and the electrical load circuit for predetermined periods of time. Preferably, the first electrical circuit is closed and the electrical load circuit is open for about 0.01 seconds to about 10 seconds and the electrical load circuit is cyclically closed and the first electrical circuit is open for about 0.5 minutes to about 10 minutes, in a recurring sequence of fuel processing and power generation cycles, respectively. Theelectrical load circuit 318 is cyclically opened and closed for a first predetermined period of time while the firstelectrical circuit 314 is cyclically toggled between fuel processing and storage recharge for a second predetermined period of time. - The present invention also includes a method for selecting a preferred fuel for a fuel cell system comprising the steps of selecting the fuel capable of being dissolved in water; and selecting an aqueous solution of the fuel, wherein the Gibbs free energy of the fuel is greater than the heat of reaction of the fuel. Although the present invention has been disclosed and described with reference to certain embodiments thereof, it should be noted that other variations and modifications may be made, and it is intended that the following claims cover the variations and modifications within the true scope of the invention.
Claims (9)
1. A fuel cell system comprising:
an electrode-electrolyte assembly having a first catalytic electrode coupled to one side of said electrode-electrolyte assembly, and a second catalytic electrode coupled to a generally opposite side of said electrode-electrolyte assembly;
a first conduit in fluid communication with said first catalytic electrode for delivering fuel to said first catalytic electrode at ambient temperature;
a second conduit in fluid communication with said second catalytic electrode for delivering oxidant thereto;
means for providing an electrical potential across said first catalytic electrode, said electrode-electrolyte assembly and said second catalytic electrode; and
an electrical load circuit for using an energy output generated across said first catalytic electrode, said electrode-electrolyte assembly and said second catalytic electrode.
2. The fuel cell system of claim 1 wherein:
said means for providing the electrical potential has a positive terminal in electrically conductive communication with said first catalytic electrode and a negative terminal in electrically conductive communication with said second catalytic electrode for providing process energy for a hydrogen formation reaction and removing poisons from said first catalytic electrode.
3. The fuel cell system of claim 1 further including:
a first electrical circuit comprising said means for providing the electrical potential;
said first electrical circuit and said electrical load circuit being interlocked such that during operation said first electrical circuit is closed when said electrical load circuit is open and said electrical load circuit is closed when said first electrical circuit is open; and
wherein during operation said first electrical circuit and said electrical load circuit are opened and closed for predetermined periods of time.
4. The fuel cell system of claim 1 wherein said means for providing the electrical potential comprises at least one of an electrical energy storage device, a battery and a capacitor.
5. The fuel cell system of claim 2 wherein the process energy is less than the energy output and during operation of said fuel cell, a portion of the energy output replenishes said means for providing the electrical potential.
6. The fuel cell system of claim 3 wherein said first electrical circuit is maintained closed for a shorter period of time than said second electrical circuit is maintained closed.
7. The fuel cell system of claim 2 wherein said first conduit is configured to deliver an aqueous solution of the fuel.
8. The fuel cell system of claim 7 wherein the fuel comprises a complex organic structure.
9. The fuel cell system of claim 1 further including:
a plurality of said fuel cell systems each having one of said first conduit, said electrode-electrolyte assembly, and said second fluid conduit sequentially disposed one upon another;
a bipolar separator disposed between adjacent cells and a dielectric separator disposed on terminal ends of said plurality of said fuel cell systems;
means for providing an electrical potential across said plurality of said fuel cell systems;
an electrical load circuit electrically connected across said plurality of said fuel cell systems for using an energy output generated therefrom; and
wherein said plurality of said fuel cell systems are in electrically conductive communication with one another.
Priority Applications (2)
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US12/869,167 US20100323255A1 (en) | 2005-10-28 | 2010-08-26 | Fuel cell system suitable for complex fuels and a method of operation of the same |
US13/154,886 US8105722B2 (en) | 2005-10-28 | 2011-06-07 | Fuel cell system suitable for organic fuels and a method of operation of the same |
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US73105405P | 2005-10-28 | 2005-10-28 | |
US11/588,200 US7807305B2 (en) | 2005-10-28 | 2006-10-26 | Fuel cell system suitable for complex fuels and a method of operation of the same |
US12/869,167 US20100323255A1 (en) | 2005-10-28 | 2010-08-26 | Fuel cell system suitable for complex fuels and a method of operation of the same |
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US11/588,200 Division US7807305B2 (en) | 2005-10-28 | 2006-10-26 | Fuel cell system suitable for complex fuels and a method of operation of the same |
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US13/154,886 Continuation-In-Part US8105722B2 (en) | 2005-10-28 | 2011-06-07 | Fuel cell system suitable for organic fuels and a method of operation of the same |
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US11/588,200 Active 2029-07-19 US7807305B2 (en) | 2005-10-28 | 2006-10-26 | Fuel cell system suitable for complex fuels and a method of operation of the same |
US12/869,167 Abandoned US20100323255A1 (en) | 2005-10-28 | 2010-08-26 | Fuel cell system suitable for complex fuels and a method of operation of the same |
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US (2) | US7807305B2 (en) |
EP (1) | EP1946399A2 (en) |
JP (1) | JP5322339B2 (en) |
WO (1) | WO2007051010A2 (en) |
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Also Published As
Publication number | Publication date |
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US7807305B2 (en) | 2010-10-05 |
US20070099062A1 (en) | 2007-05-03 |
WO2007051010A2 (en) | 2007-05-03 |
WO2007051010A3 (en) | 2007-08-02 |
EP1946399A2 (en) | 2008-07-23 |
JP5322339B2 (en) | 2013-10-23 |
JP2009514175A (en) | 2009-04-02 |
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