Hydrogen generating fuel cell cartridges

A gas-generating apparatus (10) includes a reaction chamber (18) containing a solid fuel component (24) and a liquid fuel component (22) that is introduced into the reaction chamber by a fluid path, such as a tube, nozzle, or valve. The flow of the liquid fuel to the solid fuel is self-regulated. Other embodiments of the gas-generating apparatus are also disclosed.

BACKGROUND

The invention relates generally to fuel supplies for fuel cells. In particular, the invention relates to fuel cartridges for fuel cells configured to produce a fuel gas on demand.

Fuel cells are devices that directly convert chemical energy of reactants, i.e., fuel and oxidant, into direct current (DC) electricity. For an increasing number of applications, fuel cells are more efficient than conventional power generation, such as combustion of fossil fuel, as well as portable power storage, such as lithium-ion batteries.

In general, fuel cell technology includes a variety of different fuel cells, such as alkali fuel cells, polymer electrolyte fuel cells, phosphoric acid fuel cells, molten carbonate fuel cells, solid oxide fuel cells and enzyme fuel cells. Today's more important fuel cells can be divided into several general categories, namely (i) fuel cells utilizing compressed hydrogen (H2) as fuel; (ii) proton exchange membrane (PEM) fuel cells that use alcohols, e.g., methanol (CH3OH), metal hydrides, e.g., sodium borohydride (NaBH4), hydrocarbons, or other fuels reformed into hydrogen fuel; (iii) PEM fuel cells that can consume non-hydrogen fuel directly or direct oxidation fuel cells; and (iv) solid oxide fuel cells (SOFC) that directly convert hydrocarbon fuels to electricity at high temperature.

Compressed hydrogen is generally kept under high pressure and is therefore difficult to handle. Furthermore, large storage tanks are typically required and cannot be made sufficiently small for consumer electronic devices. Conventional reformat fuel cells require reformers and other vaporization and auxiliary systems to convert fuels to hydrogen to react with oxidant in the fuel cell. Recent advances make reformer or reformat fuel cells promising for consumer electronic devices. The most common direct oxidation fuel cells are direct methanol fuel cells or DMFC. Other direct oxidation fuel cells include direct ethanol fuel cells and direct tetramethyl orthocarbonate fuel cells. DMFC, where methanol is reacted directly with oxidant in the fuel cell, is the simplest and potentially smallest fuel cell and also has promising power application for consumer electronic devices. SOFC convert hydrocarbon fuels, such as butane, at high heat to produce electricity. SOFC requires relatively high temperature in the range of 1000° C. for the fuel cell reaction to occur.

The chemical reactions that produce electricity are different for each type of fuel cell. For DMFC, the chemical-electrical reaction at each electrode and the overall reaction for a direct methanol fuel cell are described as follows:

The Overall Fuel Cell Reaction:
CH3OH+1.5O2→CO2+2H2O

Due to the migration of the hydrogen ions (H+) through the PEM from the anode to the cathode and due to the inability of the free electrons (e−) to pass through the PEM, the electrons flow through an external circuit, thereby producing an electrical current through the external circuit. The external circuit may be used to power many useful consumer electronic devices, such as mobile or cell phones, calculators, personal digital assistants, laptop computers, and power tools, among others.

DMFC is discussed in U.S. Pat. Nos. 5,992,008 and 5,945,231, which are incorporated by reference herein in their entireties. Generally, the PEM is made from a polymer, such as Nafion® available from DuPont, which is a perfluorinated sulfonic acid polymer having a thickness in the range of about 0.05 mm to about 0.50 mm, or other suitable membranes. The anode is typically made from a Teflonized carbon paper support with a thin layer of catalyst, such as platinum-ruthenium, deposited thereon. The cathode is typically a gas diffusion electrode in which platinum particles are bonded to one side of the membrane.

In a chemical metal hydride fuel cell, sodium borohydride is reformed and reacts as follows:
NaBH4+2H2O→(heat or catalyst)→4(H2)+(NaBO2)

Suitable catalysts for this reaction include platinum and ruthenium, and other metals. The hydrogen fuel produced from reforming sodium borohydride is reacted in the fuel cell with an oxidant, such as O2, to create electricity (or a flow of electrons) and water byproduct. Sodium borate (NaBO2) byproduct is also produced by the reforming process. A sodium borohydride fuel cell is discussed in U.S. Pat. No. 4,261,956, which is incorporated by reference herein in its entirety.

One of the most important features for fuel cell application is fuel storage. Another important feature is to regulate the transport of fuel out of the fuel cartridge to the fuel cell. To be commercially useful, fuel cells such as DMFC or PEM systems should have the capability of storing sufficient fuel to satisfy the consumers' normal usage. For example, for mobile or cell phones, for notebook computers, and for personal digital assistants (PDAs), fuel cells need to power these devices for at least as long as the current batteries and, preferably, much longer. Additionally, the fuel cells should have easily replaceable or refillable fuel tanks to minimize or obviate the need for lengthy recharges required by today's rechargeable batteries.

One disadvantage of the known hydrogen gas generators is that once the reaction starts the gas generator cartridge cannot control the reaction. Thus, the reaction will continue until the supply of the reactants run out or the source of the reactant is manually shut down.

Accordingly, a need exists to obtain a hydrogen gas generator apparatus that is capable of self-regulating the flow of at least one reactant into the reaction chamber.

SUMMARY OF THE INVENTION

An aspect of the invention is directed toward a gas-generating apparatus, which includes a reaction chamber containing a solid fuel component and a reservoir containing a liquid fuel component. A fluid path for introducing the liquid fuel component into the reaction chamber is provided. The introduction of the liquid fuel component is in response to a pressure within the reaction chamber.

Another aspect of the invention is directed toward a gas-generating apparatus, wherein the flow of liquid reactant to the reaction chamber is self-regulating.

DETAILED DESCRIPTION

As illustrated in the accompanying drawings and discussed in detail below, the present invention is directed to a fuel supply, which stores fuel cell fuels, such as methanol and water, methanol/water mixture, methanol/water mixtures of varying concentrations, pure methanol, and/or methyl clathrates described in U.S. Pat. Nos. 5,364,977 and 6,512,005 B2, which are incorporated by reference herein in their entirety. Methanol and other alcohols are usable in many types of fuel cells, e.g., DMFC, enzyme fuel cells and reformat fuel cells, among others. The fuel supply may contain other types of fuel cell fuels, such as ethanol or alcohols; metal hydrides, such as sodium borohydrides; other chemicals that can be reformatted into hydrogen; or other chemicals that may improve the performance or efficiency of fuel cells. Fuels also include potassium hydroxide (KOH) electrolyte, which is usable with metal fuel cells or alkali fuel cells, and can be stored in fuel supplies. For metal fuel cells, fuel is in the form of fluid borne zinc particles immersed in a KOH electrolytic reaction solution, and the anodes within the cell cavities are particulate anodes formed of the zinc particles. KOH electrolytic solution is disclosed in U.S. Pat. Appl. Pub. No. US 2003/0077493, entitled “Method of Using Fuel Cell System Configured to Provide Power to One or More Loads,” published on Apr. 24, 2003, which is incorporated by reference herein in its entirety. Fuels can also include a mixture of methanol, hydrogen peroxide and sulfuric acid, which flows past a catalyst formed on silicon chips to create a fuel cell reaction. Moreover, fuels include a blend or mixture of methanol, sodium borohydride, an electrolyte, and other compounds, such as those described in U.S. Pat. Nos. 6,554,877, 6,562,497 and 6,758,871, which are incorporated by reference herein in their entireties. Furthermore, fuels include those compositions that are partially dissolved in a solvent and partially suspended in a solvent, described in U.S. Pat. No. 6,773,470 and those compositions that include both liquid fuel and solid fuels, described in U.S. Pat. Appl. Pub. No. US 2002/0076602. Suitable fuels are also disclosed in a U.S. provisional application entitled “Fuels for Hydrogen-Generating Cartridges” filed on Jun. 13, 2005, bearing Ser. No. 60/689,572. These references are also incorporated by reference herein in their entireties.

Fuels can also include a metal hydride such as sodium borohydride (NaBH4) and water, discussed above. Fuels can further include hydrocarbon fuels, which include, but are not limited to, butane, kerosene, alcohol, and natural gas, as set forth in U.S. Pat. Appl. Pub. No. US 2003/0096150, entitled “Liquid Hereto-Interface Fuel Cell Device,” published on May 22, 2003, which is incorporated by reference herein in its entirety. Fuels can also include liquid oxidants that react with fuels. The present invention is therefore not limited to any type of fuels, electrolytic solutions, oxidant solutions or liquids or solids contained in the supply or otherwise used by the fuel cell system. The term “fuel” as used herein includes all fuels that can be reacted in fuel cells or in the fuel supply, and includes, but is not limited to, all of the above suitable fuels, electrolytic solutions, oxidant solutions, gaseous, liquids, solids, and/or chemicals and mixtures thereof.

As used herein, the term “fuel supply” includes, but is not limited to, disposable cartridges, refillable/reusable cartridges, containers, cartridges that reside inside the electronic device, removable cartridges, cartridges that are outside of the electronic device, fuel tanks, fuel refilling tanks, other containers that store fuel and the tubings connected to the fuel tanks and containers. While a cartridge is described below in conjunction with the exemplary embodiments of the present invention, it is noted that these embodiments are also applicable to other fuel supplies and the present invention is not limited to any particular type of fuel supply.

The fuel supply of the present invention can also be used to store fuels that are not used in fuel cells. These applications can include, but are not limited to, storing hydrocarbons and hydrogen fuels for micro gas-turbine engine built on silicon chips, discussed in “Here Come the Microengines,” published in The Industrial Physicist (December 2001/January 2002) at pp. 20-25. As used in the present application, the term “fuel cell” can also include microengines. Other applications can include storing traditional fuels for internal combustion engines and hydrocarbons, such as butane for pocket and utility lighters and liquid propane.

Suitable known hydrogen generating apparatus are disclosed in commonly-owned, co-pending U.S. patent application Ser. No. 10/679,756 filed on Oct. 6, 2003, Ser. No. 10/854,540 filed on May 26, 2004, Ser. No. 11/067,167 filed on Feb. 25, 2005, and Ser. No. 11/066,573 filed on Feb. 25, 2005. The disclosure of these references is incorporated herein by reference in their entireties.

The gas-generating apparatus of the present invention may include a reaction chamber, which may include an optional first reactant, and a reservoir having a second reactant. The first and second reactants can be a metal hydride, e.g., sodium borohydride, and water. Both reactants can be in gaseous, liquid, aqueous or solid form. Preferably, the first reactant stored in the reaction chamber is a solid metal hydride or metal borohydride, and the second reactant is water optionally mixed with additives and catalysts. One of the reactants may include methyl clathrates, which essentially include methanol enclosed or trapped inside other compounds. Water and metal hydride of the present invention react to produce hydrogen gas, which can be consumed by a fuel cell to produce electricity. Other suitable reactants or reagents are discussed below and are disclosed in the '540 application, previously incorporated above.

Additionally, the gas-generating apparatus can include a device or system that is capable of controlling the transport of a second reactant from the reservoir to the reaction chamber. The operating conditions inside the reaction chamber and/or the reservoir, preferably a pressure inside the reaction chamber, are capable of controlling the transport of the second reactant in the reservoir to the reaction chamber. For example, the second reactant in the reservoir can be introduced into the reaction chamber when the pressure inside the reaction chamber is less than a predetermined value, preferably less than the pressure in the reservoir, and, more preferably less than the pressure in the reservoir by a predetermined amount. It is preferable that the flow of the second reactant from the reservoir into the reaction chamber is self-regulated. Thus, when the reaction chamber reaches a predetermined pressure, preferably a predetermined pressure above the pressure in the reservoir, the flow of the second reactant from the reservoir into the reaction chamber can be stopped to stop the production of hydrogen gas. Similarly, when the pressure of the reaction chamber is reduced below the pressure of the reservoir, preferably below the pressure in the reservoir by a predetermined amount, the second reactant can flow from the reservoir into the reaction chamber. The second reactant in the reservoir can be introduced into the reaction chamber by any known method including, but not limited to, pumping, osmosis, capillary action, pressure differential, valve(s), or combinations thereof.

Referring toFIG. 1, a fuel supply system10is shown. System10includes a gas-generating apparatus12and is configured to be connected to a fuel cell (not shown) via a fuel conduit16and a valve34. Preferably, fuel conduit16initiates within gas-generating apparatus12, and valve34is disposed in a sidewall21bthereof. Fuel conduit16is preferably a flexible tube having a total length that is slightly shorter than the length of gas-generating apparatus12.

Within its sidewalls, gas-generating apparatus12preferably includes three distinct chambers: a fluid fuel component reservoir44, a reaction chamber18, and a void45, with reaction chamber18sealingly but slidably disposed between reservoir44and void45. Reservoir44is preferably a space formed between a sidewall21aand a first sidewall20aof reaction chamber18. Reservoir44may also, however, include a bladder or similar fluid container. A fluid fuel component22, preferably water and/or an additive/catalyst, resides within reservoir44. Additional appropriate fluid fuel components and additives are further discussed herein. Although fluid fuel component22may be pressurized, preferably it is unpressurized. Void45is preferably an empty space on the opposite side of reaction chamber18. Suitable additives/catalysts to the fuels or reactants include, but are not limited to, anti-freezing agents (e.g., methanol, ethanol, propanol and other alcohols), catalysts (e.g., cobalt chloride and other known catalysts), pH adjusting agents (e.g., acids such as sulfuric acid and other common acids).

Reaction chamber18preferably includes four sidewalls20a-dmade of a fluid impenetrable material, such as stainless steel or plastic. Reaction chamber18is sealed within the apparatus sidewalls by deformable members38, which may be O-rings or gaskets. Reaction chamber18is attached to rear apparatus sidewall21bby a biasing spring30. Biasing spring30, which may be any appropriate spring known in the art, provides a force that biases reaction chamber18toward reservoir44. Spring30can be replaced by a pressurized gas or liquid, such as butane, propane or iso-propane, and void45may be opened to ambient when spring30is used to minimize the build-up of a partial vacuum.

Disposed within reaction chamber18is a solid fuel component24. Solid fuel component24is preferably a tablet of NaBH4. However, granules, grains, or other forms of solid material are also appropriate. Additional appropriate solid fuel components are further discussed herein. Fillers, additives and other agents and chemicals can be added to solid fuel NaBH4to improve its contact with the liquid reactant.

A connection point17for fuel conduit16is formed in rear sidewall20cof reaction chamber18. Connection point17may simply be a hole through rear sidewall20c, preferably located at or near the top thereof. In such a case, fuel conduit16is preferably fixedly attached to or within connection point17, such as with an adhesive. However, connection point17may also include a nozzle onto which fuel conduit16may be press fit and then optionally fixed with an adhesive or similar material. Also, optionally, a gas-permeable, liquid impermeable membrane32may be affixed over the reaction chamber-facing side of connection point17. Membrane32prevents liquids or byproducts from being transferred to the fuel cell via fuel conduit16. Fillers or foam can be used in combination with membrane32to retain liquids or byproducts and to reduce clogging. Membrane32may be formed from any liquid impermeable, gas permeable material known to one skilled in the art. Such materials can include, but are not limited to, hydrophobic materials having an alkane group. More specific examples include, but are not limited to: polyethylene compositions, polytetrafluoroethylene, polypropylene, polyglactin (VICRY®), lyophilized dura mater, or combinations thereof. Gas permeable member30may also comprise a gas permeable/liquid impermeable membrane covering a porous member. Examples of such membrane are CELGARD® and GORE-TEX®. Other gas permeable, liquid impermeable members usable in the present invention include, but are not limited to, SURBENT® Polyvinylidene Fluoride (PVDF) having a porous size of from about 0.1 μm to about 0.45 μm, available from Millipore Corporation. The pore size of SURBENT® PVDF regulates the amount of water exiting the system. Materials such as electronic vent type material having 0.2 μm hydro, available from W. L. Gore & Associates, Inc., may also be used in the present invention. Additionally, 0.25 inch diameter rods having a pore size of about 10 μm or 2 inch diameter discs with a thickness of about 0.3 μm available from GenPore, and sintered and/or ceramic porous material having a pore size of less than about 10 μm available from Applied Porous Technologies Inc. are also usable in the present invention. Furthermore, nanograss materials, from Bell Labs, are also usable to filter the liquid. Nanograss controls the behavior of tiny liquid droplets by applying electrical charges to specially engineered silicon surfaces that resemble blades of grass. Additionally, or alternatively, the gas permeable, liquid impermeable materials disclosed in commonly owned, co-pending U.S. patent application Ser. No. 10/356,793 are also usable in the present invention, all of which are incorporated by reference herein in their entireties. Such a membrane32may be used in any of the embodiments discussed herein.

A fluid introduction valve26is disposed in an opposite reaction chamber sidewall20a. Fluid introduction valve26, which is preferably a check valve, controls the communication of fluid fuel component22from reservoir44into reaction chamber18. Valve26may be any pressure-opened, one-way valve known in the art, such as a check valve or a valve having a pressure responsive diaphragm, which opens when a threshold pressure is reached. Within reaction chamber18, valve26preferably includes a nozzle28to disperse the fluid fuel component22within reaction chamber18. As will be recognized by those in the art, valve26may be optionally omitted, as shown inFIG. 2. In that embodiment, which is the same in all other respects to the embodiment shown inFIG. 1, a small diameter hole28aacts as the pressure-triggered nozzle for dispersing fluid fuel component22into reaction chamber18. Hole28ais preferably located at the bottom of chamber18to minimize the migration of gas into reservoir44. Alternatively, solid fuel component24can be positioned adjacent to hole28ato minimize the migration of gas into reservoir44.

When hydrogen gas is needed by the fuel cell, on/off or shut-off valve36, as shown inFIG. 1, is opened. On/off valve36can be any valve known in the art, including but not limited to, solenoid valve, check valve, etc., and can be opened manually by the user or by the controller controlling the fuel cell. To generate gas to be used as fuel for the fuel cell, fluid fuel component22is transferred into reaction chamber18to react with solid fuel component24. Gas-generating apparatus12does this automatically. Spring30pushes reaction chamber18toward reservoir44with a constant force F. Force F, combined with the hydrostatic pressure HP within reservoir44, create a total reservoir pressure P22on the reservoir44side of valve26. While on/off valve36is opened, the reaction chamber pressure P18within reaction chamber18is dynamically cycled from high to low as gas is created and then transferred through fuel conduit16. When total reservoir pressure P22is greater than reaction chamber pressure P18, valve26opens and fluid fuel component22flows into reaction chamber18, which moves toward sidewall21a. When the difference between total reservoir pressure P22and reaction chamber pressure P18falls below the triggering point for valve26, valve26closes and reaction chamber18stops moving while gas accumulates therewithin. When reaction chamber pressure P18reaches a triggering pressure TP, fuel valve34opens, and fuel gas begins to flow out of reaction chamber18. When sufficient fuel gas has been transferred out of reaction chamber18, fluid valve26opens and additional fluid fuel component22enters reaction chamber18while gas is still being transferred out of reaction chamber18through fuel conduit16. Eventually, reaction chamber pressure P18falls below triggering pressure TP to hold open fuel transfer valve34. This allows fuel gas to accumulate within reaction chamber18to eventually close fluid transfer valve26. This cycle is summarized below in Table 1.

FIG. 3shows another embodiment of a fuel supply210including a gas-generating apparatus212where a fluid fuel component222, similar to fluid fuel component22discussed above, is held in a reservoir244and transferred to a reaction chamber218containing a solid fuel component224, similar to solid fuel component24discussed above. In this embodiment, reaction chamber218is formed from three sidewalls220a-c. A bottom of reaction chamber218is sealed by a solid fuel carrier225, which fits snugly and slidably between sidewalls220b,220c. Solid fuel carrier225is sealed in the opening by deformable members238, which may be O-rings, gaskets or the like. Alternatively, solid fuel carrier225may itself be formed from an appropriately sealing deformable material, although carrier225is preferably made from a rigid material such as stainless steel or plastic. Carrier225includes an open container portion filled with solid fuel component224, such as a tablet or granules of sodium borohydride.

Carrier225is biased into reaction chamber218by a biasing spring230, which may be any type of spring known in the art. Biasing spring230is fixedly mounted onto a base231, such as a sidewall of fuel supply210, fuel cell, or other similar platform, and biasing spring230provides a constant force on carrier225.

Fixedly attached to a bottom of carrier225is a crank arm242. Crank arm242extends from the bottom of carrier225, through a sealed opening in reservoir244, and terminates as a stopper240positioned over or a fluid transfer hole226formed at the interface of reservoir244and reaction chamber218. While crank arm242may be made of any rigid material that will not react with fluid fuel component222, stopper240preferably includes an exterior coating of a deformable material, such as rubber or silicone, capable of sealing hole226.

Through top sidewall220a, fluid transfer hole226connects fluid fuel component reservoir244with reaction chamber218. Similar to the embodiment discussed above with respect toFIG. 1, the end of fluid transfer hole226facing into reaction chamber218preferably forms a nozzle228so that any fluid fuel component passing through fluid transfer hole226is dispersed within reaction chamber218. Also disposed in top sidewall220ais a fuel transfer valve234that connects reaction chamber to a fuel conduit216. Similar to valve34discussed above, fuel transfer valve234is preferably a pressure-triggered valve such as a check valve, and is optionally covered by a gas-permeable, liquid impermeable membrane232, which may be any such membrane known in the art.

Similar to the embodiment discussed above with respect toFIG. 1, the operation of gas-generating apparatus212is preferably automatically controlled or cycled by the balance between the pressures and forces within apparatus212. The reaction chamber pressure P218changes dynamically due to the production of fuel gas within reaction chamber218and the transfer of that fuel gas to a fuel cell (not shown) through fuel transfer valve234. Spring230provides a constant F upward on carrier225. When the force from P218is greater than F, carrier225is pushed downward, thereby moving crank arm242downward as well. Eventually, carrier225will move far enough due to the high P218to push stopper240into place, thereby shutting off the flow of fluid fuel component into reaction chamber218. Fuel transfer valve234is opened only when P218is greater than a triggering pressure TP.

Preferably, reaction chamber218is charged with fuel or inert gas so that the initial state of carrier225is in a downward position and spring30is compressed. Alternately, the user may manually unseal stopper240by known mechanical means (e.g., pull tabs, slides, etc.), or stopper240is automatically removed when attached to the fuel cell, so that no initial pressure is necessary.

In an embodiment, fluid fuel component222is stored in a bladder (not shown) and reservoir244is pressurized by compressed gas, liquefied gas, compressed foam or loaded spring, so that fluid component222can exit reservoir244when reservoir244is positioned in any orientation.

Also, preferably, P218is higher than the TP for valve234. When connected to a fuel cell, gas is transferred out of reaction chamber218, thereby reducing P218. Eventually, sufficient gas is transferred such that F from spring230overcomes the force from P218and pushes carrier225upward, thereby unplugging stopper240from fluid transfer hole226via crank arm242. Fluid222is then sprayed into reaction chamber218through nozzle228. However, gas continues to be transferred out of reaction chamber218through valve234until P218falls below the TP. When the valve closes, the pressure in reaction chamber218again builds until the force from P218overcomes F from spring230, and stopper240again plugs fluid transfer hole226. This cycle is summarized in Table 2.

Another device to control the pressure of reaction chamber218is to place a secondary fuel cell214′ on a sidewall220b, as shown inFIG. 3. Secondary fuel cell214′ consumes excess hydrogen to minimize pressure P218when shut-off valve236is closed. As shown, secondary fuel cell214′ is positioned on sidewall220bwith the anode side211facing the reaction chamber218and in contact with the hydrogen gas therein and with the cathode side209facing the ambient air and in contact with oxygen. Preferably, a movable cover gate213is provided to cover the cathode side when the gas-generating apparatus is in operation to prevent air from reaching fuel cell214′ so that hydrogen is not wasted in consumption by secondary fuel cell214′ when desired by the main fuel cell (not shown). When the user or controller opens valve236, gate213is moved to cover secondary fuel cell214′. When the user or controller closes valve236(or when pressure P218exceeds a threshold level) gate213is moved to allow air to contact the cathode side to consume excess hydrogen. An electrical-energy consuming device, such as a resistor215, light emitting diode, or similar electricity consuming and/or dissipating circuit, is provided as shown schematically to consume the electricity produced by fuel cell214′. Secondary fuel cell214′ and cover213can be used with any of the embodiments of the present invention.

FIG. 4shows a similar gas-generating apparatus212to the one shown and discussed above with respect toFIG. 3. In this embodiment, however, instead of a crank arm connected directly to a bottom of carrier225, a shaft247is hingedly attached to the bottom of carrier225and to a crank wheel246. A biasing spring230is fixedly attached to crank wheel246on one end and to a solid base231on the other. Biasing spring230provides a constant force F that tends to push crank wheel246in a clockwise direction.

A crank arm242is fixedly attached to crank wheel246at a lower end of crank wheel246. An upper end of crank arm242is hingedly attached to a tube241at an attachment point239containing a slidable stopper240. The other end of tube241is hingedly attached to an access point237above fluid transfer hole226. Stopper240may be any material or shape, as long as stopper240can move easily within tube241and plug hole226.

As crank wheel246turns, crank arm242moves in the vertical plane. When crank wheel246is turned clockwise, crank arm242moves down toward base231. This downward motion of crank arm242pulls tube241so that attachment point239is positioned below access point237. When tube241is oriented in this manner, stopper240slides toward attachment point239, thereby unplugging hole226. When crank wheel246is turned in a counter-clockwise direction, crank arm242moves in an upward direction, away from base231. Tube241is again tilted such that attachment point239is positioned above access point237. When tube241is oriented in this manner, stopper240slides toward access point237, thereby plugging hole226.

As with the embodiment shown inFIG. 3, this process is preferably controlled automatically by the pressure and force balances within gas-generating apparatus212. For example, reaction chamber218is preferably initially charged such that the force due to P218within reaction chamber218pushes downward on to carrier225, far enough that crank arm242tilts tube241to such an extent that stopper240slides toward access point237and plugs hole226. Also, P218is above TP, so valve234opens when connected to the fuel cell and fuel gas flows out of reaction chamber218. At this point, gas generation within reaction chamber218slows and eventually stops causing P218to decrease. P218eventually decreases to a point where the force from P218is no longer sufficient to overcome F, which causes crank wheel246to turn clockwise. This motion tilts tube241via crank arm242so that stopper240slides toward attachment point239, thereby unplugging fluid transfer hole226, which allows fluid fuel component222to flow into reaction chamber218through nozzle228. Gas is again generated within reaction chamber218. Gas is removed from reaction chamber218through valve234at a rate that is preferably slower than the rate at which gas continues to be generated within reaction chamber218, so that P218continues to build. If P218falls below TP, valve234closes, which allows gas to accumulate within reaction chamber218. This pressure and force cycle is summarized in Table 3.

FIG. 5shows yet another gas-generating apparatus312having a reaction chamber318defined by sidewalls320, similar to those described above with respect toFIGS. 1-4. A fuel transfer valve334, such as a check valve, traverses one of the sidewalls320to allow fuel gas formed within reaction chamber318to pass therethrough and into a fuel conduit316, similar to the fuel conduit described above with respect toFIGS. 3 and 4.

A fluid transfer tube350enters reaction chamber318through a sidewall, preferably an upper sidewall. Fluid transfer tube is attached at one end to a reservoir that holds a fluid fuel component (not shown). The fluid fuel component is preferably similar to the fluid fuel components described above.

Fluid transfer tube350extends into reaction chamber318. Toward the free end of fluid transfer tube350several flow channel holes352are formed along the length of fluid transfer tube350. Fluid fuel component is transferred through fluid transfer tube350so that the fluid fuel component can flow out of flow channel holes352.

Covering flow channel holes352is a covering formed of a solid fuel component324and a material354that quickly absorbs the fluid fuel component and pulls it through solid fuel component324. Preferably, solid fuel component324is in granular form so that the fluid fuel component can be readily passed therethrough. Preferably, material354is capable of absorbing liquid, but which allows gas to pass through the material. One example of such a material is paper fluff containing sodium polyacrylate crystals; such a material is commonly used in diapers. Other examples include, but are not limited to, fillers and foams. In one embodiment, shown inFIG. 6, several-layers of solid fuel component324a,324band material354a,354bare wound around fluid transfer tube350. However, as few as one layer may be used. As the fluid fuel component is pulled through the solid fuel component, fuel gas is formed and passes through material354and into reaction chamber318. Further, fluid may contact a filler or foam first, and then be transferred to the solid fuel through capillary action.

Sodium polyacrylate crystals form a gel with water and the water gel can react with a metal hydride, as shown in commonly owned, co-pending United States patent application entitled “Fuel Compositions for Fuel Cells and Gas-Generators Utilizing Same” bearing Ser. No. 60/782,632, and filed on Mar. 15, 2006. The '632 application is incorporated herein by reference in its entirety.

A fluid control valve326is preferably disposed within fluid transfer tube350to control the flow of the fluid fuel component through to flow channels352. Fluid control valve326is preferably a pressure-triggered valve that is opened and closed in response to pressure P318in reaction chamber318. A pressure transfer tube356allows for the exposure of a small portion of the fuel gas formed within reaction chamber318to fluid control valve. When P318is higher than the triggering pressure for fluid control valve326, fluid control valve326closes and shuts off the flow of fluid fuel component through fluid transfer tube350. When the P318falls below the triggering pressure for fluid control valve326, fluid control valve326opens and allows more fluid fuel component into fluid transfer tube350.

Similarly, the operation of fuel transfer valve334is also controlled by P318. When P318is higher than a triggering pressure TP for fuel transfer valve334, then fuel transfer valve334opens to allow fuel gas to flow through fuel conduit316and into the fuel cell. When P318falls below the triggering pressure for fuel transfer valve334, then fuel transfer valve334closes, which allows gas pressure to build within reaction chamber. As with the embodiments discussed above, reaction chamber is preferably charged upon manufacture so that the production of gas can be initiated.

FIGS. 7 and 8show yet another embodiment of a gas-generating apparatus412of a fuel supply410is shown. In this embodiment a reaction chamber418is defined by an expandable bladder458. Expandable bladder458may be made of any type of material capable of expanding and contracting without the application of external forces. For example, expandable bladder458may be a balloon-like structure made of rubber or latex. Alternatively, expandable bladder458may be made from a plastic material that may be heat set to return to its original configuration when emptied, such as PET.

Expandable bladder458is preferably suspended near the center of gas-generating apparatus412on a support460. Expandable bladder458also sealingly surrounds a cage462filled with a solid fuel component such as sodium borohydride that extends from support460. Preferably, the solid fuel component is granular, although a solid tablet or slug may also be used. Cage462may be made of any material inert to the solid fuel component and a liquid fuel component422that is also disposed within expandable bladder458. For example, cage462may be made of stainless steel or plastic. Holes464are formed in cage462so that liquid fuel component422can come into contact with the solid fuel component. Liquid fuel component422is similar to the liquid fuel components discussed in the above embodiments.

A second end of expandable bladder458is attached to a fuel conduit416, which is configured to transfer fuel gas formed within reaction chamber418to a fuel cell. Fuel conduit416is similar to those fuel conduits discussed above with respect to the embodiments shown inFIGS. 3-6. A fuel transfer valve434, preferably a pressure triggered valve such as a check valve, is configured to control the outflow of fuel gas from reaction chamber418.

In operation, expandable bladder458is initially in a collapsed configuration, such as is shown inFIG. 7. When collapsed, liquid fuel component422is in contact with cage462. As such, liquid fuel component422can flow through holes464to react with the solid fuel component. Fuel gas such as hydrogen is produced. As fuel gas accumulates within reaction chamber418, expandable bladder458expands. When the RCP within reaction chamber418exceeds a triggering pressure TP for fuel transfer valve434, fuel transfer valve434opens to allow the transfer of fuel gas from reaction chamber418to the fuel cell. When expandable bladder458reaches a critical size, such as is shown inFIG. 8, all of liquid fuel component422collects in the bottom of expandable bladder458and is no longer in contact with the solid fuel component within cage462. As such, additional reaction between liquid fuel component422and solid fuel component cannot occur until enough gas has been transferred out of reaction chamber418to the fuel cell. An optional one-way relief valve430may be included to prevent over pressurization of expandable bladder458, such as by venting the fuel gas to the atmosphere. As will be recognized by those in the art, gas-generating apparatus412works in any orientation.

FIGS. 9 and 10show yet another embodiment of a gas-generating apparatus512of a fuel supply510adapted to be connected to a fuel cell (not shown) via a fuel conduit516. Gas-generating apparatus512includes two chambers formed within sidewalls520, a pressurized liquid fuel component chamber544and a reaction chamber518. Sidewalls520are preferably formed of a material inert to a liquid fuel component522, such as water or water with additives, contained within pressurized liquid fuel component chamber544and a solid fuel component524, such as sodium borohydride, contained within reaction chamber518. A fluid transfer conduit588connects pressurized liquid fuel component chamber544and reaction chamber518. As with the embodiments discussed above, a fuel transfer valve534, preferably a pressure-triggered valve such as a check valve, and an on/off valve36(not shown) downstream of valve534allow for the transfer of fuel from reaction chamber518to fuel conduit516and on to a fuel cell.

A spring-biased piston584is sealingly and slidingly disposed, initially, at or near the top of pressurized liquid fuel component chamber544. Preferably, piston584is sealed with a lubricating sealing material586, such as petroleum jelly, although other sealing components such as O-rings or gaskets may be used. A biasing spring530provides a continuous force F on piston584so that liquid fuel component522is constantly being forced toward reaction chamber518. Similar to the discussion above, spring530can be replaced by a pressurized material, such as liquid/gaseous hydrocarbon, e.g., butane, propane or iso-propane.

A flexible fluid tube582is fluidly connected to fluid transfer conduit588, discussed below, and terminates in a nozzle or opening528within reaction chamber518. Fluid fuel component522selectively passes through flexible fluid tube582into reaction chamber518. Flexible fluid tube582passes through or is in contact with a mesh piston580. Mesh piston580is biased toward fuel component524by a biasing spring572. Biasing spring572provides a continuous force on mesh piston580to bias it into fuel component524toward fuel conduit516. Mesh piston580is kept in contact with solid fuel component524, which is preferably formed of granules that are too large to pass through the mesh of piston580, by spring572. However, as fluid fuel component522flows into reaction chamber518through nozzle528and reacts with solid fuel524, as shown inFIG. 10both fuel gas and a slurry590, e.g., aqueous borate, are formed. Slurry590can flow through the mesh of piston580to accumulate underneath mesh piston580. Spring572then continually pushes mesh piston580into the un-reacted portion solid fuel component524. As such, the fluid fuel component flowing out of nozzle528is continually in contact with fresh solid fuel component524that is relatively free from the byproducts.

Similar to the embodiments discussed above, gas generating apparatus512is also self-regulated. Diaphragm574, an optional spring573, and valve526, positioned below mesh piston580, are exposed to the pressure P518within reaction chamber518. A fluid conduit575is formed through diaphragm574and fluidly connects fluid conduit588to flexible tube582. As pressure builds within reaction chamber518, a triggering pressure, TP, of diaphragm574is eventually reached. When the triggering pressure of diaphragm574is reached, diaphragm514deforms to close valve526(not shown), thereby cutting off the flow of fluid fuel component into reaction chamber518. Fuel gas flows out of fuel transfer valve534until the P518decreases to below TP, where diaphragm574opens again to once again initiate the production of fuel gas by introducing additional liquid fuel component522into reaction chamber518. Spring573assists diaphragm574in returning to the open position. Valve526can be any valve that can open and close as diaphragm574reacts to P518, e.g., check valve.

FIG. 11shows yet another embodiment of a gas-generating apparatus612adapted to be connected to a fuel cell (not shown) via a fuel conduit616. In this embodiment, a reaction chamber618contains a quantity of a solid fuel component624, which is preferably in granular or powdered form. Reaction chamber618includes two opposing sidewalls620, which are made of a solid, non-reactive material similar to sidewalls20as discussed above. However, a bottom680of reaction chamber618is preferably made of a porous non-reactive material, such as a mesh or a sheet of material with holes disposed therethrough. Fiberglass is one of many materials appropriate for use as bottom680. The pores of bottom680are dimensioned such that the individual grains of solid fuel component624cannot pass therethrough.

A top632of reaction chamber618is preferably formed of a gas-permeable, liquid impermeable membrane, such as membrane32as described above with respect toFIG. 1. Examples of an appropriate membrane include CELGARD® and GORE-TEX®. A fuel gas reservoir619is positioned adjacent to top membrane632to receive therethrough the fuel gas produced within reaction chamber618. A valve634, such as a check valve, controls the outflow of fuel gas from fuel gas reservoir619to fuel conduit616. Valve634may be any type of valve known in the art and is similar in design and function to valve34as described above with respectFIG. 1.

A manifold679is positioned adjacent to bottom680. Preferably, several flow channels652a-fare formed in manifold679. As will be recognized by those in the art, the number of flow channels will vary widely depending on factors including the type of fuel, the type of fuel cell, and the device being driven by the fuel cell. Preferably, the number of flow channels ranges from 2 to about 100, and more preferably, from about 50 to about 75.

Flow channels652a-fare fluidly connected to a feeder tube650through which a fluid fuel component (not shown) is provided from a reservoir (not shown). The initial flow of fluid through feeder tube650is preferably controlled by a controller (not shown) which signals a need for additional fuel and opens a valve (not shown) disposed between the fluid reservoir and feeder tube650. Alternatively, a user may initiate flow by triggering a switch to open such a valve. Manifold679is configured to allow only one flow channel652a-fto receive the fluid fuel component from feeder tube650at any given time so that different areas of the solid fuel component624are reacted successively. In other words, if the fluid fuel component is flowing through flow channel652a, flow channels652b-fcontain no fluid fuel component so that the solid fuel component624disposed above the unused flow channels652b-fremains dry and unreacted.

This series use of flow channels652a-fis preferably achieved in part by providing each flow channel with a diameter that is different from the other flow channels. Preferably, flow channel652ahas the largest diameter, with each successive flow channel having a slightly smaller diameter progressing in the direction of flow. In other words, the diameter of flow channel652bis greater than the diameter of flow channel652c, and so on. As in known in the art, fluid flows in the path of least resistance. As the narrower diameter of the next flow channel downstream is essentially constricting the flow of the fluid, the fluid tends to follow the path through the largest available channel. For example, if presented with a flow path through flow channel652aor flow channel652b, most of the fluid will flow through flow channel652a.

This tendency of the fluid to flow through the largest available channel is optionally enhanced by configuring feeder tube650with a stepwise construction, where the diameter of feeder tube650increases slightly just prior to reaching the next successive flow channel652. For example, as feeder tube650is relatively narrow in the vicinity of relatively wide flow channel652a, the fluid in feeder tube650will tend to enter flow channel652ainstead of continuing to flow along feeder tube650.

As the fluid fuel component flows into reaction chamber618through flow channel652a, the fluid fuel component reacts with solid fuel624. For example, if the solid fuel component624is sodium borohydride and the fluid fuel component is water or doped water, then hydrogen gas and a slurry of aqueous borate is produced. If the slurry is not removed from the mouth of flow channel652a, the slurry tends to harden like concrete. This hardened slurry eventually entirely clogs flow channel652a. As flow channel652ais now blocked, the fluid in feeder tube650will flow to the next available path, flow channel652b. While some of the fluid may flow past flow channel652b, it is believed that this flow amount is insufficient to flow into any of the remaining flow channels652c-funtil flow channel652bis also clogged with hardened slurry. This process continues until all flow channels652a-fare clogged and/or all of solid fuel component624is consumed.

Optionally, a second mesh681is disposed at the inlet of each of flow channels652a-f. Second mesh681has a very small pore size so that fluid can flow therethrough but any slurry that might escape reaction chamber618is captured so as not to contaminate the fluid fuel component or clog feeder tube650. As will be recognized by those in the art, other hydraulic parameters of flow channels652may also be changed to manipulate the tendency of fluid to choose a particular flow path, such as the height of the flow channels, where each successive downstream channel is taller than the previous flow channel. Any combination of hydraulic parameters may be used.

Referring toFIG. 12, another configuration for a gas-generating apparatus712that allows access to successive flow channels752a-fis shown. In this embodiment, which is similar to the embodiment shown inFIG. 11, access to downstream flow channels752b-fis controlled by a series of valves753a-e. Valves753a-eare preferably pressure-triggered valves such as check valves or diaphragm valves. As fluid flows through a feeder tube750, all valves753a-eare closed so that the fluid must flow into flow channel752a. As described above, flow channel752awill clog with hardened slurry. When flow channel752ais blocked, the pressure of the fluid in feeder tube750will increase until the first valve753ais opened. The fluid may now flow into flow channel752b. Preferably, once valve753ais opened, it will not close again, such as by having an internal frangible member, as the flow pressure typically decreases once the new flow path is opened. As will be recognized by those in the art, each valve753a-emay optionally be replaced with a frangible membrane. This process of clogging flow channels752a-fand opening valves or breaking frangible membranes continues until all flow channels752a-fare clogged and/or all solid fuel component724is spent.

Referring toFIG. 13, yet another gas-generating apparatus812is shown. Similar to previous embodiments, a reaction chamber818is contained within a housing820. Housing820may be made of any material capable of containing a gas-generating reaction, preferably a material inert to the reaction, such as plastic or stainless steel. One end of housing820is sealed with a stopper840. Stopper840is made of any material capable of sealing housing820against the escape of gas produced during reaction or liquid fuel component822. The opposite end of housing820includes a valve834, leading to the fuel cell (not shown) or a conduit leading to the fuel cell (not shown). Valve834is similar to other valves discussed herein and is preferably a check valve or a shut-off valve.

A solid fuel component824such as sodium borohydride lines the sidewalls of housing820. Preferably, solid fuel component824is in powder or granular form, although solid fuel component824may be in tablet form. If solid fuel component824is provided in powder or granular form, a screen or mesh827is disposed over solid fuel component824. The pore size of mesh827is sufficiently small to allow the liquid fuel component822access to solid fuel component824while retaining solid fuel component824. Also, solid fuel component824may be divided into several compartments by dividers825. Dividers825are made of a material capable of sealing each compartment so that liquid fuel component822cannot migrate from one divider to the next. Optionally, the granules of solid fuel component824may be encased in a time-release material, where different time-release materials are used, such as water-soluble materials of varying thicknesses. As such, some of the solid fuel component824may be used quickly, while the remaining solid fuel component824is reserved for use at a later point in time.

Liquid fuel component822is preferably water or a water-based gel, similar to the liquid fuel components discussed above. The water-based gel may be formed by mixing water with a hydrophilic compound, such as sodium polyacrylate crystals. Water gel is discussed above and disclosed in the '632 patent application, previously incorporated by reference. Liquid fuel component822is contained within a bladder844. Bladder844is made of a deformable material which is substantially inert to liquid fuel component822, such as rubber, silicone or thin-walled plastic. Preferably, bladder844is configured with a plurality of corrugations to allow bladder844to collapse more easily and in a controlled manner.

Fluidly connected to bladder844is a fluid conduit882that terminates in a nozzle828. Fluid conduit882and nozzle828provide a fluid path to direct liquid fuel component822to a particular section of solid fuel component824, such as a single compartment. Preferably, fluid conduit882and nozzle828are relatively small bore components, so that only a small quantity of liquid fuel component822may be dispensed at any given point in time. As shown inFIG. 13A, while nozzle828is shown as a single point nozzle inFIG. 13, nozzle828′ connected to fluid conduit882′ may include multiple outlets, such as, for example, a hollow ring fluidly connected to bladder844having multiple holes formed therein that serve as multiple and simultaneous fluid outlets.

A spring830is disposed on the end of bladder844opposite to fluid conduit882and nozzle828. Spring830is preferably a constant force spring. Spring830may be any type of spring capable of providing a constant pulling force, such as a flat or clock spring. Preferably, spring830is made of a material substantially inert to liquid fuel component822, such as plastic or stainless steel. One end of spring830extends through one end of bladder844to be fixedly attached to the opposite end of bladder844at or near fluid conduit882. As such, spring830pulls the nozzle end of bladder844toward stopper840. The pulling of spring830squeezes bladder844, thereby forcing liquid fuel component822through fluid conduit882and out nozzle828to be introduced to solid fuel component824. Gas is produced within reaction chamber818. When the pressure within reaction chamber818reaches a threshold value, valve834opens to allow the gas to be transferred to the fuel cell. Alternatively, valve834is a shut-off valve and can be opened by a user or a controller. As bladder844empties, nozzle828moves toward stopper840as discussed further below, thus ensuring that liquid fuel component822is introduced to a new section of solid fuel component824.

As spring830pulls on bladder844, gas is continuously be produced by the introduction of liquid fuel component822to solid fuel component824. However, it may not be desirable to produce gas without cessation. For example, when shut-off valve such as valve834is closed, the production of hydrogen should stop. Such a valve may be manually triggered, such as by the user or via a controller which monitors the usage of fuel by the fuel cell. When such a shut-off valve is closed, gas cannot be transferred out of housing820to the fuel cell. As such, pressure from the produced gas will build within reaction chamber818or housing820. While the pressure may be relieved with, for example, a pressure relief check valve (not shown) or a secondary fuel cell, as discussed above, disposed in the sidewalls of housing820, the production of gas should stop after closing a shut-off valve.

As such, gas-generating apparatus812is preferably provided with a pressure-sensitive sleeve832configured to stop the winding of spring830. Pressure-sensitive sleeve832is provided adjacent stopper840and is adjacent to at least a portion of spring830. Pressure-sensitive sleeve832is preferably made of a rigid material readily translated by the pressure within housing820, such as plastic, resin, metal or the like. Pressure-sensitive sleeve832is slidably disposed within housing820spaced apart from stopper840to created a gap831so that pressure-sensitive sleeve832is free to translate within housing820into and out of gap831. Pressure-sensitive sleeve832is biased away from stopper840by a spring829, which may be any type of spring known in the art, such as a coiled compression spring or a gas or liquid hydrocarbon.

Once the pressure within reaction chamber818reaches a threshold level, the force provided by spring829biasing pressure-sensitive sleeve832away from stopper840is overcome so that pressure-sensitive sleeve832translates toward stopper840. In so doing, pressure-sensitive sleeve832squeezes spring830, thereby preventing spring830from winding further. As such, spring830can no longer pull on bladder844and no additional liquid fuel component is expelled from bladder844. When gas is once again released from housing820to lower the pressure therewithin below the threshold level, spring829expands and pressure-sensitive sleeve832is translated back to its original position, thereby releasing spring830. Spring830once again may pull on the nozzle end of bladder844, and additional gas may be produced.

Yet another gas-generating apparatus912is shown inFIG. 14. Gas-generating apparatus912includes a housing920similar to the housings for the other gas-generating apparatus shown and discussed above. Housing920is generally configured to define a reaction chamber918containing a solid fuel component924, such as sodium borohydride, and a liquid fuel component chamber944containing a liquid fuel component922, such as water. As will be recognized by those in the art, any of the solid or liquid fuel components discussed in this application are appropriate for use with this embodiment.

A piston980slidably disposed within housing920divides the interior of housing920into liquid fuel component chamber944and reaction chamber918. Piston980is sealingly disposed within housing920. As such, piston980is preferably made from a deformable material which is non-reactive with either liquid fuel component922, solid fuel component924or the gas produced by the reaction therebetween, and is covered with a gel-like material which enhances the sealing aspects of piston980and eases the sliding motion thereof, such as petroleum jelly. Alternatively, as shown inFIG. 14, piston980may be made from any rigid material which is similarly non-reactive as the deformable material discussed above, but includes at least one sealing element938, such as a rubber or silicone O-ring or a gel-like lubricating material such as petroleum jelly. A sprag981or similar structure is provided adjacent piston980within reaction chamber918so that piston980is slidable only toward liquid fuel component chamber944. Sprag981is preferably a plastic or metal concave disk or plate whose edges are sharp and can grip or anchor against the sidewalls of housing920to prevent movement in the direction opposite to the concavity.

One end of housing920is sealed with a stopper940such that liquid fuel component chamber944is defined by stopper940, housing920and piston980. Stopper940is made of any material capable of sealing housing920against the escape of gas produced during reaction or liquid fuel component922, such as rubber, silicone or the like. Liquid fuel component922preferably entirely fills liquid fuel component chamber944. Further, liquid fuel component922may be pressurized with hydrogen or a similar fuel gas so that the flow of liquid fuel component922out of liquid fuel component chamber944is enhanced. The pressurized gas may be contained in an elastic bladder disposed within liquid fuel component chamber944and configured to expand to expel liquid fuel component922from liquid fuel component chamber944. Optionally, a check valve or pressure relief valve (not shown) is provided in the sidewalls of housing920which define liquid fuel component chamber944that allows air or other environmental gases into liquid fuel component chamber944to prevent a vacuum from forming therewithin and possibly stopping the motion of piston980.

The opposite end of housing920includes a second stopper935which is similar in construction and materials as stopper940. As such, reaction chamber918is defined by second stopper935, housing920and piston980. However, a valve934is disposed in second stopper935to create a flow path to the fuel cell (not shown) or a conduit leading to the fuel cell (not shown). Valve934is similar to other valves discussed herein and is preferably a shut-off valve or a check valve configured to open only when the pressure within reaction chamber918reaches a threshold level. Solid fuel component924is disposed on the sidewalls of housing920within reaction chamber adjacent to or near second stopper935. Preferably, solid fuel component924is in a tablet-like form pressed to or otherwise adhered to the sidewalls of housing920to form a ring-like structure. Alternatively, solid fuel component924may be in granular or powder form and held into place against the sidewalls of housing920by a mesh or screen whose pore size is selected such that the granules of solid fuel component924may not pass through the pores, but which allows liquid fuel component922to pass therethrough to react with solid fuel component924.

A fluid transfer tube982is provided through piston980to fluidly connect liquid fuel component chamber944with reaction chamber918. Fluid transfer tube982may be any type of tubing or pipe capable of transferring liquid fuel component922to solid fuel component924. However, fluid transfer tube982is preferably a small-bore, rigid tube made from a material which is substantially inert to liquid fuel component922, solid fuel component924and the gas produced by the reaction therebetween. Preferably, the bore of fluid transfer tube982is between about 0.001 inches and 0.01 inches; more preferably, the bore of fluid transfer tube982is about 0.005 inches.

The length of fluid transfer tube982is selected such that the movement of piston980toward stopper940results in only a drop of fluid being expelled from the end of fluid transfer tube982onto solid fuel component924. Fluid transfer tube982preferably has sufficient length such that when in an initial position, the free end of fluid transfer tube982extends through solid fuel component924to a point at or near second stopper935. As such, when piston980moves, fluid transfer tube982is moved to a fresh supply of solid fuel component924. Also, in the alternative, piston980does not necessarily move, such as if liquid fuel component922is pressurized with a bladder filled with a liquefied hydrocarbon provided within liquid fuel component chamber944. In such a case, the liquefied hydrocarbon expands at constant pressure to expel liquid fuel component922from liquid fuel component chamber944.

In operation, the flow of liquid fuel component922is initially triggered, such as by a user pressurizing liquid fuel component922or puncturing or removing a seal covering the free end of fluid transfer tube982(not shown). Liquid fuel component922then flows through fluid transfer tube982into reaction chamber and drops onto solid fuel component924. Liquid fuel component922and solid fuel component924react to produce hydrogen. When sufficient pressure builds within reaction chamber918, check valve934opens to allow the fuel gas to flow to the fuel cell (not shown) or, alternatively, a user or a controller opens shut-off valve934. If the pressure within reaction chamber918increases further, a reaction chamber pressure P918eventually reaches a level where reaction chamber pressure P918pushes piston980toward stopper940. However, additional increase in reaction chamber pressure P918will eventually prevent additional liquid fuel component922from flowing through fluid transfer tube982, as when reaction chamber pressure P918is greater than liquid fuel component chamber pressure P944, liquid fuel component922cannot flow into reaction chamber918due to the pressure gradient. In other words, the liquid fuel component chamber pressure P944needs to be higher than the reaction chamber pressure P918by at least a fixed amount, such as X psi. Fluid transfer tube982is preferably sufficiently long such that X equals 2 psi, for example, for fluid to flow through fluid transfer tube982. When reaction chamber pressure P918is lowered, such as by transfer out of reaction chamber through valve934, liquid fuel component922again flows through fluid transfer tube982so that additional gas may be produced. In other words, so long as the produced hydrogen is carried out of gas generating apparatus912at a rate sufficient to keep reaction chamber pressure P918relatively low, liquid fuel component922continues to be transported to reaction chamber918.

Some examples of the fuels that are used in the present invention include, but are not limited to, hydrides of elements of Groups IA-IVA of the Periodic Table of Elements and mixtures thereof, such as alkaline or alkali metal hydrides, or mixtures thereof. Other compounds, such as alkali metal-aluminum hydrides (alanates) and alkali metal borohydrides may also be employed. More specific examples of metal hydrides include, but are not limited to, lithium hydride, lithium aluminum hydride, lithium borohydride, sodium hydride, sodium borohydride, potassium hydride, potassium borohydride, magnesium hydride, calcium hydride, and salts and/or derivatives thereof. The preferred hydrides are sodium borohydride, magnesium borohydride, lithium borohydride, and potassium borohydride. Preferably, the hydrogen-bearing fuel comprises the solid form of NaBH4, Mg(BH4)2, or methanol clathrate compound (MCC) is a solid which includes methanol. In solid form, NaBH4does not hydrolyze in the absence of water and therefore improves shelf life of the cartridge. However, the aqueous form of hydrogen-bearing fuel, such as aqueous NaBH4, can also be utilized in the present invention. When an aqueous form of NaBH4is utilized, the chamber containing the aqueous NaBH4also includes a stabilizer. Exemplary stabilizers can include, but are not limited to, metals and metal hydroxides, such as alkali metal hydroxides. Examples of such stabilizers are described in U.S. Pat. No. 6,683,025, which is incorporated by reference herein in its entirety. Preferably, the stabilizer is NaOH.

The solid form of the hydrogen-bearing fuel is preferred over the liquid form. In general, solid fuels are more advantageous than liquid fuels because the liquid fuels contain proportionally less energy than the solid fuels and the liquid fuels are less stable than the counterpart solid fuels. Accordingly, the most preferred fuel for the present invention is powdered or agglomerated powder sodium borohydride.

According to the present invention, the fluid fuel component preferably is capable of reacting with a hydrogen-bearing solid fuel component in the presence of an optional catalyst to generate hydrogen. Preferably, the fluid fuel component includes, but is not limited to, water, alcohols, and/or dilute acids. The most common source of fluid fuel component is water. As indicated above and in the formulation below, water may react with a hydrogen-bearing fuel, such as NaBH4in the presence of an optional catalyst to generate hydrogen.
X(BH4)y+2H2O→X(BO)2+4H2
Where X includes, but is not limited to, Na, Mg, Li and all alkaline metals, and y is an integer.

Fluid fuel component also includes optional additives that reduce or increase the pH of the solution. The pH of fluid fuel component can be used to determine the speed at which hydrogen is produced. For example, additives that reduce the pH of fluid fuel component result in a higher rate of hydrogen generation. Such additives include, but are not limited to, acids, such as acetic acid and sulfuric acid. Conversely, additives that raise the pH can lower the reaction rate to the point where almost no hydrogen evolves. The solution of the present invention can have any pH value less than 7, such as a pH of from about 1 to about 6 and, preferably, from about 3 to about 5.

In some exemplary embodiments, fluid fuel component includes a catalyst that can initiate and/or facilitate the production of hydrogen gas by increasing the rate at which fluid fuel component reacts with a fuel component. The catalyst of these exemplary embodiments includes any shape or size that is capable of promoting the desired reaction. For example, the catalyst may be small enough to form a powder or it may be as large as the reaction chamber, depending on the desired surface area of the catalyst. In some exemplary embodiments, the catalyst is a catalyst bed. The catalyst may be located inside the reaction chamber or proximate to the reaction chamber, as long as at least one of either fluid fuel component or the solid fuel component comes into contact with the catalyst.

The catalyst of the present invention may include one or more transitional metals from Group VIIIB of the Periodic Table of Elements. For example, the catalyst may include transitional metals such as iron (Fe), cobalt (Co), nickel (Ni), ruthenium (Ru), rhodium (Rh), platinum (Pt), palladium (Pd), osmium (Os) and iridium (Ir). Additionally, transitional metals in Group IB, i.e., copper (Cu), silver (Ag) and gold (Au), and in Group IIB, i.e., zinc (Zn), cadmium (Cd) and mercury (Hg), may also be used in the catalyst of the present invention. The catalyst may also include other transitional metals including, but not limited to, scandium (Sc), titanium (Ti), vanadium (V), chromium (Cr) and manganese (Mn). Transition metal catalysts useful in the present invention are described in U.S. Pat. No. 5,804,329, which is incorporated by reference herein in its entirety. The preferred catalyst of the present invention is CoCl2.

Some of the catalysts of the present invention can generically be defined by the following formula:
MaXb

wherein M is the cation of the transition metal, X is the anion, and “a” and “b” are integers from 1 to 6 as needed to balance the charges of the transition metal complex.

In some exemplary embodiments, the optional additive, which is in fluid fuel component and/or in the reaction chamber, is any composition that is capable of substantially preventing the freezing of or reducing the freezing point of fluid fuel component and/or solid fuel component. In some exemplary embodiments, the additive can be an alcohol-based composition, such as an anti-freezing agent. Preferably, the additive of the present invention is CH3OH. However, as stated above, any additive capable of reducing the freezing point of fluid fuel component and/or solid fuel component may be used.

While it is apparent that the illustrative embodiments of the invention disclosed herein fulfill the objectives of the present invention, it is appreciated that numerous modifications and other embodiments may be devised by those skilled in the art. For example, any of the valves herein may be triggered by an electronic controller such as a microprocessor. Further, in those embodiments including both a check valve (34,234,334,434,534,634,834,934) and/or a shut-off valve (36,834,934), one or both of the valves may be omitted and/or the check valve and shut-off valve may be interchanged. Additionally, feature(s) and/or element(s) from any embodiment may be used singly or in combination with feature(s) and/or element(s) from other embodiment(s). Therefore, it will be understood that the appended claims are intended to cover all such modifications and embodiments, which would come within the spirit and scope of the present invention. All publications discussed herein, including but not limited to patents, patent applications, articles, and books, are incorporated by reference in their entireties.