Patent Application
20050014040
The present invention relates to fuel cell technology. In particular, the invention relates to systems for improving efficiency of fuel cell systems used to power electronics devices.
A fuel cell electrochemically combines hydrogen and oxygen to produce electrical energy. The ambient air readily supplies oxygen. Hydrogen provision, however, calls for a working supply. Gaseous hydrogen has a low energy density that reduces its practicality as a portable fuel. Liquid hydrogen, which has a suitable energy density, must be stored at extremely low temperatures and high pressures, making storing and transporting liquid hydrogen burdensome.
A reformed hydrogen supply processes a fuel source to produce hydrogen. The fuel source acts as a hydrogen carrier. Currently available hydrocarbon fuel sources include methanol, ethanol, gasoline, propane and natural gas. Liquid hydrocarbon fuel sources offer high energy densities and the ability to be readily stored and transported. A fuel processor reforms the hydrocarbon fuel source to produce hydrogen.
A reformer in the fuel processor includes a catalyst that processes the fuel source to produce hydrogen. The fuel source is typically heated or vaporized before interaction with the catalyst. A burner in the fuel processor provides heat to a boiler that vaporizes the fuel source before it reaches the reformer. A catalytic burner uses the fuel source to generate heat and reduces the fuel efficiency of the system. An electric burner requires electrical energy to generate heat and reduces electrical efficiency of the system.
Fuel cell evolution so far has concentrated on large-scale applications such as industrial size generators for electrical power back-up. Consumer electronics devices and other portable electrical power applications currently rely on lithium ion and similar battery technologies. Fuel cell systems that generate electrical energy for portable applications such as electronics would be desirable but are not yet commercially available. In addition, techniques that increase fuel cell system efficiency would be beneficial.
The present invention relates to fuel cell systems and methods of increasing fuel cell system efficiency. The systems include a fuel processor that produces hydrogen from a fuel source and a fuel cell that generates electrical energy using the hydrogen. An electronics device that receives the electrical energy may also include the fuel cell system and a heat-generating component. The invention uses heat from the fuel cell and/or heat from the heat-generating electronics component to preheat a liquid fuel source. This reduces or potentially eliminates the need for fuel source heating in the fuel processor.
In one aspect, the present invention relates to an electronics device that receives electrical energy from a fuel cell. The electronics device comprises a component that produces heat during operation of the electronics device. The electronics device also comprises a fuel processor that includes a reformer configured to receive a fuel source, configured to output hydrogen, and including a catalyst that facilitates the production of hydrogen. The electronics device further comprises a fuel cell configured to produce electrical energy using hydrogen output by the fuel processor. The electronics device additionally comprises a heat transfer system configured to receive heat from the electronics component and configured to transfer the heat to the fuel source.
In another aspect, the present invention relates to a fuel cell system for producing electrical energy. The fuel cell system comprises a fuel processor that includes a reformer configured to receive a fuel source, configured to output hydrogen, and including a catalyst that facilitates the production of hydrogen. The fuel cell system also comprises a fuel cell including a fuel cell stack. The fuel cell stack is configured to produce electrical energy using hydrogen output by the fuel processor and includes a heat transfer appendage. The appendage a) includes a portion arranged external to the fuel cell stack and b) is in conductive thermal communication with an internal portion of the fuel cell stack. The fuel cell system further comprises a heat transfer system configured to receive heat from the fuel cell and configured to transfer the heat to the fuel source.
In yet another aspect, the present invention relates to a method for heating a fuel source provided to a fuel processor that is configured to supply hydrogen to a fuel cell. The method comprises generating heat in an electronics component included in an electronics device that is configured to receive electrical energy from the fuel cell. The method also comprises transferring the heat from the electronics component to fuel source.
In still another aspect, the present invention relates to a method for heating a fuel source provided to a fuel processor that is configured to supply hydrogen to a fuel cell. The method comprises generating heat in the fuel cell. The method also comprises transferring the heat from the fuel cell to the fuel source.
These and other features and advantages of the present invention will be described in the following description of the invention and associated figures.
The present invention is described in detail with reference to a few preferred embodiments as illustrated in the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art, that the present invention may be practiced without some or all of these specific details. In other instances, well known process steps and/or structures have not been described in detail in order to not unnecessarily obscure the present invention.
1. Fuel Cells and Portable Electronics
Storage device 16 and fuel processor 15 provide hydrogen to fuel cell 20. Storage device 16 and fuel processor 15 collectively act as a ‘reformed’ hydrogen supply that provides and processes a hydrogen fuel source 17 to produce hydrogen. Hydrogen fuel source 17 acts as a carrier for hydrogen and can be processed to separate hydrogen. Hydrogen fuel source 17 may include any hydrogen bearing fuel stream, aliphatic fuel source or other hydrogen carrier such as ammonia. Currently available hydrocarbon fuel sources 17 suitable for use with the present invention include methanol, ethanol, gasoline, propane, butane and natural gas, for example. Several hydrocarbon and ammonia products may also produce a suitable fuel source 17. Liquid fuel sources 17 offer high energy densities and the ability to be readily stored and shipped.
Storage device 16 may also contain a fuel mixture. When the fuel processor 15 comprises a steam reformer, storage device 16 contains a fuel mixture of a hydrocarbon fuel source and water. Hydrocarbon fuel source/water fuel mixtures are frequently represented as a percentage fuel source in water. In one embodiment, fuel source 17 comprises methanol or ethanol concentrations in water in the range of 1%-99.9%. Other liquid fuels such as butane, propane, gasoline, military grade “JP8” etc. may also be contained in storage device 16 with concentrations in water from 5-100%. In a specific embodiment, fuel source 17 comprises 67% methanol by volume.
Storage device 16 stores fuel source 17, and may comprise a refillable and/or disposable fuel cartridge. A refillable cartridge offers a user instant recharging. In one embodiment, the cartridge includes a collapsible bladder within a hard plastic case. A separate fuel pump controls fuel source 17 flow from storage device 16. If system 10 is load following, then a control system meters fuel source 17 to deliver fuel source 17 to fuel processor 15 at a flow rate determined by the required power level output of fuel cell 20.
Fuel processor 15 processes the hydrocarbon fuel source 17 and outputs hydrogen. A hydrocarbon fuel processor 15 heats and processes a hydrocarbon fuel source 17 in the presence of a catalyst to produce hydrogen. Fuel processor 15 comprises a reformer, which is a catalytic device that converts a liquid or gaseous hydrocarbon fuel source 17 into hydrogen and carbon dioxide. As the term is used herein, reforming refers to the process of producing hydrogen from a fuel source.
Fuel cell 20 electrochemically converts hydrogen and oxygen to water, generating electrical energy and heat in the process. Ambient air commonly supplies oxygen for fuel cell 20. A pure or direct oxygen source may also be used for oxygen supply. The water often forms as a vapor, depending on the temperature of fuel cell 20 components. The electrochemical reaction also produces carbon dioxide as a byproduct for many fuel cells.
Fuel source 17 is typically heated or vaporized before interaction with a catalyst in fuel processor 15. Traditionally, a catalytic or electric burner in fuel processor 15 provides all the heat to a boiler that vaporizes the fuel source before receipt by the reformer. The present invention uses waste heat from fuel cell 20 to preheat fuel source 17. Since many fuel cells operate at elevated temperatures and the electrical energy generating process is exothermic, fuel cell 20 produces heat that is actively removed from the fuel cell. Heat transfer system 11 transfers heat from fuel cell 20 to fuel source 17. This heats, boils or superheats fuel source 17, depending on heat density of fuel cell 20 and fuel source 17 pressure. If the fuel source requires additional heat for vaporization before entry into the reformer, a burner and boiler may be used. At the least, the heat from fuel cell 20 reduces the amount of heat a burner needs to generate, thereby increasing the overall electrical efficiency of system 10. Some systems 10 may eliminate the need for a burner and boiler in fuel processor 15.
In one embodiment, fuel cell 20 is a low volume polymer electrolyte membrane (PEM) fuel cell suitable for use with portable applications such as consumer electronics. A polymer electrolyte membrane fuel cell comprises a membrane electrode assembly 40 that carries out the electrical energy generating electrochemical reaction. The membrane electrode assembly 40 includes a hydrogen catalyst, an oxygen catalyst and an ion conductive membrane that a) selectively conducts protons and b) electrically isolates the hydrogen catalyst from the oxygen catalyst. A hydrogen gas distribution layer contains the hydrogen catalyst and allows the diffusion of hydrogen therethrough. An oxygen gas distribution layer contains the oxygen catalyst and allows the diffusion of oxygen and hydrogen protons therethrough. The ion conductive membrane separates the hydrogen and oxygen gas distribution layers. In chemical terms, the anode comprises the hydrogen gas distribution layer and hydrogen catalyst, while the cathode comprises the oxygen gas distribution layer and oxygen catalyst.
A PEM fuel cell often includes a fuel cell stack having a set of bi-polar plates. A membrane electrode assembly is disposed between two bi-polar plates. Hydrogen distribution 43 occurs via a channel field on one plate while oxygen distribution 45 occurs via a channel field on a second facing plate. Specifically, a first channel field distributes hydrogen to the hydrogen gas distribution layer, while a second channel field distributes oxygen to the oxygen gas distribution layer. The ‘term ’ bi-polar refers electrically to a bi-polar plate (whether comprised of one plate or two plates) sandwiched between two membrane electrode assembly layers. In this case, the bi-polar plate acts as both a negative terminal for one adjacent membrane electrode assembly and a positive terminal for a second adjacent membrane electrode assembly arranged on the opposite face of the bi-polar plate.
In electrical terms, the anode includes the hydrogen gas distribution layer, hydrogen catalyst and bi-polar plate. The anode acts as the negative electrode for fuel cell 20 and conducts electrons that are freed from hydrogen molecules so that they can be used externally, e.g., to power an external circuit. In a fuel cell stack, the bi-polar plates are connected in series to add the potential gained in each layer of the stack. In electrical terms, the cathode includes the oxygen gas distribution layer, oxygen catalyst and bi-polar plate. The cathode represents the positive electrode for fuel cell 20 and conducts the electrons back from the external electrical circuit to the oxygen catalyst, where they can recombine with hydrogen ions and oxygen to form water.
The hydrogen catalyst separates the hydrogen into protons and electrons. The ion conductive membrane blocks the electrons, and electrically isolates the chemical anode (hydrogen gas distribution layer and hydrogen catalyst) from the chemical cathode. The ion conductive membrane also selectively conducts positively charged ions. Electrically, the anode conducts electrons to a load (electrical energy is produced) or battery (energy is stored). Meanwhile, protons move through the ion conductive membrane. The protons and used electrons subsequently meet on the cathode side, and combine with oxygen to form water. The oxygen catalyst in the oxygen gas distribution layer facilitates this reaction. One common oxygen catalyst comprises platinum powder very thinly coated onto a carbon paper or cloth. Many designs employ a rough and porous catalyst to increase surface area of the platinum exposed to the hydrogen and oxygen.
In one embodiment, fuel cell 20 comprises a set of bi-polar plates formed from a single plate. Each plate includes channel fields on opposite faces of the plate. Since the electrical generation process in fuel cell 20 is exothermic, fuel cell 20 may implement a thermal management system to dissipate heat from the fuel cell. Further description of a fuel cell suitable for use with the present invention is included in commonly owned co-pending patent application entitled “Micro Fuel Cell Architecture” naming Ian Kaye as inventor and filed on the same day as this patent application, which is incorporated by reference for all purposes.
While the present invention will mainly be discussed with respect to PEM fuel cells, it is understood that the present invention may be practiced with other fuel cell architectures. The main difference between fuel cell architectures is the type of ion conductive membrane used. In one embodiment, fuel cell 20 is phosphoric acid fuel cell that employs liquid phosphoric acid for ion exchange. Solid oxide fuel cells employ a hard, non-porous ceramic compound for ion exchange and may be suitable for use with the present invention. Generally, any fuel cell architecture may benefit from the fuel storage improvements described herein. Other such fuel cell architectures include direct methanol, alkaline and molten carbonate fuel cells.
Fuel cell 20 generates dc voltage that may be used in a wide variety of applications. For example, electrical energy generated by fuel cell 20 may be used to power a motor or light. In one embodiment, the present invention provides ‘small’ fuel cells that are configured to output less than 200 watts of power (net or total). Fuel cells of this size are commonly referred to as ‘micro fuel cells’ and are well suited to provide energy to portable electronics devices. In one embodiment, fuel cell 20 is configured to generate from about 1 milliwatt to about 200 watts. In another embodiment, fuel cell 20 generates from about 3 W to about 20 W. Fuel cell 20 may also be a stand-alone fuel cell, which is a single unit that produces power as long as it has an a) oxygen and b) hydrogen or a hydrocarbon fuel supply. The system may be internal or external to the electronics device. A stand-alone fuel cell 20 that outputs from about 40 W to about 100 W is well suited for use within a laptop computer.
In one embodiment, fuel processor 15 is a steam reformer that only needs steam and the fuel source 17 to produce hydrogen. Several types of reformers suitable for use in fuel cell system 10 include steam reformers, auto thermal reformers (ATR) or catalytic partial oxidizers (CPOX). ATR and CPOX reformers mix air with the fuel and steam mix. ATR and CPOX systems reform fuels such as methanol, diesel, regular unleaded gasoline and other hydrocarbons. In a specific embodiment, storage device 16 provides methanol 17 to fuel processor 15, which reforms the methanol at about 250° C. or less and allows fuel cell system 10 use in applications where temperature is to be minimized. Further description of a fuel processor suitable for use with the present invention is included in commonly owned co-pending patent application entitled “Efficient Micro Fuel Cell Systems and Methods” naming Ian Kaye as inventor and filed on the same day as this patent application, which is incorporated by reference for all purposes.
Electronics device 22 receives electrical energy from fuel cell 20. Electronics device 22 may comprise any device that relies on electrical power for operation and includes one or more portions that supply heat to fuel source 17. Portable electronics devices 22 may include laptop computers, video projectors, industrial PDAs, video cameras and military radios, for example. Non-portable electronics devices 22 may include desktop computers, routers, household appliances and video projectors.
Electronics component 12 generates heat. Many electronics devices 22 include one or more components 12 that operate at elevated temperatures and produce heat requiring dissipation. In one embodiment, component 12 generates more than one watt of waste heat. As the term is used herein, ‘waste’ heat refers to heat that requires active removal from an electronics device 22 (or fuel cell 20). In another embodiment, component 12 includes any component in an electronics device that can provide at least 5 to 10 percent of the rated power of a fuel cell stack used in fuel cell 20. The present invention uses heat from electronics component 12 to preheat fuel source 17. While
Modern video projectors include a halogen lamp that generates considerable heat. 100+watt lamps are very common, and most lamps convert over 90% of the input energy into heat while less than 10% of the input energy becomes light. Thermal management of the lamp relies on-substantial air flow overlarge heat sinks in the projector housing. The heat sinks and thermal management system consume the majority of the real estate—or ‘footprint’—of a modern projector. Efforts in the projector marketplace to decrease projector size continue. As will be described below, heat exchangers and conductive or convective liquid heat transfer techniques employed by heat transfer system 11 may increase heat dissipation by one or two orders of magnitude relative to air convection cooling systems. Heat transfer system 11 thus significantly increases heat transfer rates and decreases projector size relative to a projector that relies solely on air cooling. In addition, waste heat from a projector lamp accounts for 80-90% of power consumption in the projector. The heat is strictly exhausted to protect one or more thermally sensitive optical modulation chips (e.g., a DMD or LCD chip). The high flow rate cooling fan also consumes additional power. Heat transfer system 11 increases energy efficiency of such a device since the lamp's waste heat is re-used instead of uneconomically exhausted. Heat transfer system 11 also decreases the thermal management burden and permits a smaller or less powerful fan, which further decreases power consumption and projector size.
Electronics component 12 generates heat during operation of the electronics device. However, heat transfer from component 12 to fuel source 17 may continue after shutdown of electronics device 22 as the heated component 12 cools. For example, a cooling fan often actively cools a CPU cool after computer shutdown. In this case, heat transfer system 11 continues heat transfer from component 12 to fuel source 17 after shutdown to cool the CPU and store the heat in fuel source 17.
Heat from component 12 may boil and superheat fuel source 17, depending on heat density of component 12 and fuel source 17 pressure. Dissipating heat into fuel source 17 also provides an additional heat sink for electronics device 22, thereby eliminating the need for or size of a heat sink otherwise employed to dissipate heat from component 12. For example, heat transfer system 11 and heat sinking into fuel source 17 may permit smaller or less powerful CPU cooling fans within device 22.
Heat transfer system 11 transfers heat from one or more heat generating components 12 to fuel source 17. The heat transfer system 11 may include any heat transfer devices or plumbing to pass the heat from a component 12 to fuel source 17. The heat transfer devices may comprise a heat exchanger and/or cooling system. For example, heat transfer system 11 may comprise a) a CPU heat pipe system that removes heat from a CPU and b) a heat exchanger that passes the heat from the heat pipe to a tube that transports fuel source 17. In another embodiment, a liquid or air cooling medium-dissipates heat from component 12 and transports the heat to a heat exchanger, which passes the heat to a tube carrying fuel source 17. Plumbing in heat transfer system 11 may comprise any tubing, piping and/or channeling that communicates a gas or liquid from one location to a second location. The plumbing may also comprise one or more valves, gates or other devices to facilitate and control flow. A fan or pump may also be included to pressurize a line and move the heating medium. A ‘line’ refers to tubing, piping and/or channeling that is dedicated for fluid or gas communication between two locations.
2. Fuel Cell
Referring initially to
The bi-polar plates 44 in stack 60 also each include two heat transfer appendages 46. More specifically, each bi-polar plate 44 includes a heat transfer appendage 46a on one side of the plate and a heat transfer appendage 46b on the opposite side. Heat transfer appendages 46 are discussed in further detail below.
As shown, stack 60 includes twelve membrane electrode assembly layers 62, eleven bi-polar plates 44 and two end plates 64. The number of bi-polar plates 44 and MEA layers 62 in each set may vary with design of fuel cell stack 60. Stacking parallel layers in fuel cell stack 60 permits efficient use of space and increased power density for fuel cell 20. In one embodiment, each membrane electrode assembly 62 produces 0.7 V and the number of MEA layers 62 is selected to achieve a desired voltage. Alternatively, the number of MEA layers 62 and bi-polar plates 44 may be determined by the allowable thickness in an electronics device. A fuel cell stack 60 having from one MEA 62 to several hundred MEAs 62 is suitable for many applications. A stack 60 having from about three MEAs 62 to about twenty MEAs 62 is also suitable for numerous applications. Fuel cell 20 size and layout may also be tailored and configured to output a given power.
Referring to
Fuel cell 20 includes two anode ports that open to the outside of fuel cell stack 60: an inlet anode port or inlet hydrogen port 84, and an outlet anode port or outlet hydrogen port 86. Inlet hydrogen port 84 is disposed on top end plate 64a, couples with an inlet line to receive hydrogen gas, and opens to an inlet hydrogen manifold 102 (see
Fuel cell 20 includes two cathode ports: an inlet cathode port or inlet oxygen port 88, and an outlet cathode port or outlet water/vapor port 90. Inlet oxygen port 88 is disposed on bottom end plate 64b (see
Pressurized hydrogen gas (H2) enters-fuel cell 20 via hydrogen-port 84, proceeds through inlet hydrogen manifold 102 and through hydrogen channels 74 of a hydrogen channel field 72a disposed on the anode face 75 of bi-polar plate 44a. The hydrogen channels 74 open to anode gas diffusion layer 122, which is disposed between the anode face 75 of bi-polar plate 44a and ion conductive membrane 128. The pressure forces hydrogen gas into the hydrogen-permeable anode gas diffusion layer 122 and across the hydrogen catalyst 126, which is disposed in the anode gas diffusion layer 122. When an H2 molecule contacts hydrogen catalyst 126, it splits into two H+ ions (protons) and two electrons (e−). The protons move through the ion conductive membrane 128 to combine with oxygen in cathode gas diffusion layer 124. The electrons conduct through the anode electrode 130, where they build potential for use in an external circuit (e.g., a power supply of a laptop computer) After external use, the electrons flow to the cathode electrode 132 of PEMFC architecture 120.
Hydrogen catalyst 126 breaks hydrogen into protons and electrons. Suitable catalysts 126 include platinum, ruthenium, and platinum black or platinum carbon, and/or platinum on carbon nanotubes, for example. Anode gas diffusion layer 122 comprises any material that allows the diffusion of hydrogen therethrough and is capable of holding the hydrogen catalyst 126 to allow interaction between the catalyst and hydrogen molecules. One such suitable layer comprises a woven or non-woven carbon paper. Other suitable gas diffusion layer 122 materials may comprise a silicon carbide matrix and a mixture of a woven or non-woven carbon paper and Teflon.
On the cathode side of PEMFC architecture 120, pressurized air carrying oxygen gas (02) enters fuel cell 20 via oxygen port 88, proceeds through inlet oxygen manifold 106, and through oxygen channels 76 of an oxygen channel field 72b disposed on the cathode face 77 of bi-polar plate 44b. The oxygen channels 76 open to cathode gas diffusion layer 124, which is disposed between the cathode face 77 of bi-polar plate 44b and ion conductive membrane 128. The pressure forces oxygen into cathode gas diffusion layer 124 and across the oxygen catalyst 134 disposed in the cathode gas diffusion layer 124. When an O2 molecule contacts oxygen catalyst 134, it splits into two oxygen atoms. Two H+ ions that have traveled through the ion selective ion conductive membrane 128 and an oxygen atom combine with two electrons returning from the external circuit to form a water molecule (H2O). Cathode channels 76 exhaust the water, which usually forms as a vapor. This reaction in a single MEA layer 62 produces about 0.7 volts.
Cathode gas diffusion layer 124 comprises a material that permits diffusion of oxygen and hydrogen protons therethrough and is capable of holding the oxygen catalyst 134 to allow interaction between the catalyst 134 with oxygen and hydrogen. Suitable gas diffusion layers 124 may comprise carbon paper or cloth, for example. Other suitable gas diffusion layer 124 materials may comprise a silicon carbide matrix and a mixture of a woven or non-woven carbon paper and Teflon. Oxygen catalyst 134 facilitates the reaction of oxygen and hydrogen to form water. One common catalyst 134 comprises platinum. Many designs employ a rough and porous catalyst 134 to increase surface area of catalyst 134 exposed to the hydrogen or oxygen. For example, the platinum may reside as a powder very thinly coated onto a carbon paper or cloth cathode gas diffusion layer 124.
Ion conductive membrane 128 electrically isolates the anode from the cathode by blocking electrons from passing through membrane 128. Thus, membrane 128 prevents the passage of electrons between gas diffusion layer 122 and gas diffusion layer 124. Ion conductive membrane 128 also selectively conducts positively charged ions, e.g., hydrogen protons from gas diffusion layer 122 to gas diffusion layer 124. For fuel cell 20, protons move through membrane 128 and electrons are conducted away to an electrical load or battery. In one embodiment, ion conductive membrane 128 comprises an electrolyte. One electrolyte suitable for use with fuel cell 20 is Celtec 1000 from PEMEAS USA AG of Murray Hill, N.J. (www.pemeas.com). Fuel cells 20 including this electrolyte are generally more carbon monoxide tolerant and may not require humidification. Ion conductive membrane 128 may also employ a phosphoric acid matrix that includes a porous separator impregnated with phosphoric acid. Alternative ion conductive membranes 128 suitable for use with fuel cell 20 are widely available from companies such as United technologies, DuPont, 3M, and other manufacturers known to those of skill in the art. For example, WL Gore Associates of Elkton, Md. produces the primea Series 58, which is a low temperature MEA suitable for use with the present invention.
In one embodiment, fuel cell 20 requires no external humidifier or heat exchanger and the stack 60 only needs hydrogen and air to produce electrical power. Alternatively, fuel cell 20 may employ humidification of the cathode to fuel cell 20 improve performance. For some fuel cell stack 60 designs, humidifying the cathode increases the power and operating life of fuel cell 20.
Functionally, bi-polar plate 44 a) delivers and distributes reactant gasses to the gas-diffusion layers 122 and 124 and their respective catalysts, b) maintains separation of the reactant gasses from one another between MEA layers 62 in stack 60, c) exhausts electrochemical reaction byproducts from MEA layers 62, d) facilitates heat transfer to and/or from MEA layers 62 and fuel cell stack 60, and e) includes gas intake and gas exhaust manifolds for gas delivery to other bi-polar plates 44 in the fuel stack 60.
Structurally, bi-polar plate 44 has a relatively flat profile and includes opposing top and bottom faces 75a and 75b (only top face 75a is shown) and a number of sides 78. Faces 75 are substantially planar with the exception of channels 76 formed as troughs into substrate 89. Sides 78 comprise portions of bi-polar plate 44 proximate to edges of bi-polar plate 44 between the two faces 75. As shown, bi-polar plate 44 is roughly quadrilateral with features for the intake manifolds, exhaust manifolds and heat transfer appendage 46 that provide deviation from the quadrilateral shape.
The manifold on each plate 44 is configured to deliver a gas to a channel field on a face of the plate 44 or receive a gas from the channel field 72. The manifolds for bi-polar plate 44 include apertures or holes in substrate 89 that, when combined with manifolds of other plates 44 in a stack 60, form an inter-plate 44 gaseous communication manifold (such as 102, 104, 106 and 108). Thus, when plates 44 are stacked and their manifolds substantially align, the manifolds permit gaseous delivery to and from each plate 44.
Bi-polar plate 44 includes a channel field 72 or “flow field” on each face of plate 44. Each channel field 72 includes one or more channels 76 formed into the substrate 89 of plate 44 such that the channel rests below the surface of plate 44. Each channel field 72 distributes one or more reactant gasses to an active area for the fuel cell stack 60. Bi-polar plate 44 includes a first channel field 72a on the anode face 75a of bi-polar plate 44 that distributes hydrogen to an anode (
Bi-polar plate 44 may include one or more heat transfer appendages 46. Heat transfer appendage 46 permits external thermal management of internal portions of fuel cell stack 60. More specifically, appendage 46 may be used to heat or cool internal portions of fuel cell stack 60 such as internal portions of each attached bi-polar plate 44 and any neighboring MEA layers 62, for example. Heat transfer appendage 46 is laterally arranged outside channel field 72. In one embodiment, appendage 46 is disposed on an external portion of bi-polar plate 44. External portions of bi-polar plate 44 include any portions of plate 44 proximate to a side or edge of the substrate included in plate 44. External portions of bi-polar plate 44 typically do not include a channel field 72. For the embodiment shown, heat transfer appendage 46 substantially spans a side of plate 44 that does not include intake and output manifolds 102-108. For the embodiment shown in
Peripherally disposing heat transfer appendage 46 allows heat transfer between inner portions of plate 44 and the externally disposed appendage 46 via the plate substrate 89. Conductive thermal communication refers to heat transfer between bodies that are in contact or that are integrally formed. Thus, lateral conduction of heat between external portions of plate 44 (where the heat transfer appendage 46 attaches) and central portions of bi-polar plate 44 occurs via conductive thermal communication through substrate 89. In one embodiment, heat transfer appendage 46 is integral with substrate material 89 in plate 44. Integral in this sense refers to material continuity between appendage 46 and plate 44. An integrally formed appendage 46 may be formed with plate 44 in a single molding, stamping, machining or MEMs process of a single metal sheet, for example. Integrally forming appendage 46 and plate 44 permits conductive thermal communication and heat transfer between inner portions of plate 44 and the heat transfer appendage 46 via substrate 89. In another embodiment, appendage 46 comprises a material other than that used in substrate 89 that is attached onto plate 44 and conductive thermal communication and heat transfer occurs at the junction of attachment between the two attached materials.
Heat may travel to or form the heat transfer appendage 46. In other words, appendage 46 may be employed as a heat sink or source. Thus, heat transfer appendage 46 may be used as a heat sink to cool internal portions of bi-polar plate 44 or an MEA 62. Fuel cell 20 employs a cooling medium to remove heat from appendage 46. Alternatively, heat transfer appendage 46 may be employed as a heat source to provide heat to internal portions of bi-polar plate 44 or an MEA 62. In this case, a catalyst 192 may be disposed on appendage 46 to generate heat in response to the presence of a heating medium (
For cooling, heat transfer appendage 46 permits integral conductive heat transfer from inner portions of plate 44 to the externally disposed appendage 46. During hydrogen consumption and electrical energy production, the electrochemical reaction generates heat in each MEA 62. Since internal portions of bi-polar plate 44 are in contact with the MEA 62, a heat transfer appendage 46 on a bi-polar plate 44 thus cools an MEA 62 adjacent to the plate via a) conductive heat transfer from MEA 62 to bi-polar plate 44 and b) lateral thermal communication and conductive heat transfer from central portions of the bi-polar plate 44 in contact with the MEA 62 to the external portions of plate 44 that include appendage 46. In this case, heat transfer appendage 46 sinks heat from substrate 89 between a first channel field 72 on one face 75 of plate 44 and a second channel field 72 on the opposite face of plate 44 to heat transfer appendage 46 in a direction parallel to a face 75 of plate 44. When a fuel cell stack 60 includes multiple MEA layers 62, lateral thermal communication through each bi-polar plate 44 in this manner provides interlayer cooling of multiple MEA layers 62 in stack 60—including those layers in central portions of stack 60.
Fuel cell 20 may employ a cooling medium that passes over heat transfer appendage 46. The cooling medium receives heat from appendage 46 and removes the heat from fuel cell 20. Heat generated internal to stack 60 thus conducts through bi-polar plate 44, to appendage 46, and heats the cooling medium via convective heat transfer between the appendage 46 and cooling medium. Air is suitable for use as the cooling medium. A fluid may also be used. The fluid may then travel to a heat exchanger that transfers the heat to fuel source 17.
As shown, heat transfer appendage 46 may be configured with a thickness that is less than the thickness between opposite faces 75 of plate 44. The reduced thickness of appendages 46 on adjacent bi-polar plates 44 in the fuel cell stack 60 forms a channel 190 between adjacent appendages. Multiple adjacent bi-polar plates 44 and appendages 46 in stack form numerous channels 190. Each channel 190 permits a cooling medium or heating medium to pass therethrough and across heat transfer appendages 46. In one embodiment, fuel cell stack 60 includes a mechanical housing that encloses and protects stack 60. Walls of the housing also provide additional ducting for the cooling or heating medium by forming ducts between adjacent appendages 46 and the walls.
The cooling medium may be a gas or liquid. Heat transfer advantages gained by high conductance bi-polar plates 44 allow air to be used as a cooling medium to cool heat transfer appendages 46 and stack 60. For example, a dc-fan may be attached to an external surface of the mechanical housing. The fan moves air through a hole in the mechanical housing, through channels 190 to cool heat transfer appendages 46 and fuel cell stack 60, and out an exhaust hole or port in the mechanical housing. Fuel cell system 10 may then include active thermal controls. Increasing or decreasing coolant fan speed regulates the amount of heat removal from stack 60 and the operating temperature for stack 60. In one embodiment of an air-cooled stack 60, the coolant fan speed increases or decreases as a function of the actual cathode exit temperature, relative to a desired temperature set-point.
Although the present invention provides a bi-polar plate 44 having channel fields 72 that distribute hydrogen and oxygen on opposing sides of a single plate 44, many embodiments described herein are suitable for use with conventional bi-polar plate assemblies that employ two separate plates for distribution of hydrogen and oxygen.
Bi-polar plate 300 includes two plates 302a and 302b that sandwich a cooling layer 304. Top plate 302a includes a channel field 306a on its top face 308 that distributes oxygen. Bottom plate 302b includes a channel field 306b on its bottom face 308 that distributes hydrogen (or oxygen when top plate 302a distributes hydrogen). Cooling layer 304 runs a cooling medium such as de-ionized water through cooling channels 310. The cooling medium actively cools each plate 302. The cooling medium may be routed such that the temperature increase occurs in the same direction as reducing oxygen partial pressure in the cathode. Similar to bi-polar plate 44, bi-polar plate 300 is referred to as a ‘bi-polar plate’ since it acts electrically as a cathode for one MEA and as an anode for another MEA. Bi-polar plate 300 serves similar functions for a fuel cell as those described above for bi-polar plate 44. Top and bottom plates 302a and 302b may each comprise silicon with channels etched in their faces to provide channel fields 306.
While the present invention has mainly been discussed so far with respect to a reformed methanol fuel cell (RMFC), the present invention may also apply to other types of fuel cells, such as a solid oxide fuel cell (SOFC), a direct methanol fuel cell (DMFC), or a direct ethanol fuel cell (DEFC). In this case, fuel cell 20 includes components specific to these architectures, as one of skill in the art will appreciate. A DMFC or DEFC receives and processes a fuel. More specifically, a DMFC or DEFC receives liquid methanol or ethanol, respectively, channels the fuel into the fuel cell stack 60 and processes the liquid fuel to separate hydrogen for electrical energy generation. For a DMFC, channel fields 72 in the bi-polar plates 44 distribute liquid methanol instead of hydrogen. Hydrogen catalyst 126 described above would then comprise a suitable anode catalyst for separating hydrogen from methanol. Oxygen catalyst 128 would comprise a suitable cathode catalyst for processing oxygen or another suitable oxidant used in the DMFC, such as peroxide. In general, hydrogen catalyst 126 is also commonly referred to as an anode catalyst in other fuel cell architectures and may comprise any suitable catalyst that removes hydrogen for electrical energy generation in a fuel cell, such as directly from the fuel as in a DMFC. In general, oxygen catalyst 128 may include any catalyst that processes an oxidant in used in fuel cell 20. The oxidant may include any liquid or gas that oxidizes the fuel and is not limited to oxygen gas as described above. An SOFC, PAFC or MCFC may also benefit from inventions described herein, for example. In this case, fuel cell 20 comprises an anode catalyst 126, cathode catalyst 128, anode fuel and oxidant according to a specific SOFC, PAFC or MCFC design.
3. Fuel Processor
As the term is used herein, ‘monolithic’ refers to a single and integrated structure that includes at least portions of multiple components used in fuel processor 15. As shown, monolithic structure 100 includes reformer 32, burner 30, boiler 34 and boiler 108. Monolithic structure 100 may also include associated plumbing inlets and outlets for reformer 32, burner 30 and boiler 34. Monolithic structure 100 comprises a common material 141 that constitutes the structure. The monolithic structure 100 and common material 141 simplify manufacture of fuel processor 15. For example, using a metal for common material 141 allows monolithic structure 100 to be formed by extrusion. In some cases, monolithic structure 100 is consistent in cross sectional dimensions between end plates 82 and 84 and solely comprises copper formed in a single extrusion.
Housing 152 provides mechanical protection for internal components of fuel processor 15 such as burner 30 and reformer 32. Housing 152 also provides separation from the environment external to processor 15 and includes inlet and outlet ports for gaseous and liquid communication in and out of fuel processor 15. Housing 152 includes a set of housing walls 161 that at least partially contain a dewar 150 and provide external mechanical protection for components in fuel processor 15. Walls 161 may comprises a suitably stiff material such as a metal or a rigid polymer, for example. Dewar 150 improves thermal heat management for fuel processor 15 by a) allowing incoming air to be pre-heated before entering burner 30, b) dissipating heat generated by burner 32 into the incoming air before the heat reaches the outside of housing 152.
Referring to
Reformer 32 is configured to receive methanol from boiler 34. Walls 111 in monolithic structure 100 and end walls 113 on end plates 82 and 84 define dimensions for a reformer chamber 103. In one embodiment, end plate 82 and/or end plate 84 includes also channels 95 that route heated methanol exhausted from boiler 34 into-reformer 32. The heated methanol then enters the reformer chamber 103 at one end of monolithic structure 100 and passes to the other end where the reformer exhaust is disposed. In another embodiment, a hole disposed in a reformer 32 wall receives inlet heated methanol from a line or other supply. The inlet hole or port may be disposed on a suitable wall 111 or 113 of reformer 32.
Reformer 32 includes a catalyst 102 that facilitates the production of hydrogen. Catalyst 102 reacts with methanol 17 and produces hydrogen gas and carbon dioxide. In one embodiment, catalyst 102 comprises pellets packed to form a porous bed or otherwise suitably filled into the volume of reformer chamber 103. Pellet diameters ranging from about 50 microns to about 1.5 millimeters are suitable for many applications. Pellet diameters ranging from about 500 microns to about 1 millimeter are suitable for use with reformer chamber 103. Pellet sizes may be varied relative to the cross sectional size of reformer chamber 103, e.g., as reformer chamber 103 increases in size so do catalyst 102 pellet diameters. Pellet sizes and packing may also be varied to control the pressure drop that occurs through reformer chamber 103. In one embodiment, pressure drops from about 0.2 to about 2 psi gauge are suitable between the inlet and outlet of reformer chamber 103. One suitable catalyst 102 may include CuZn coated onto alumina pellets when methanol is used as a hydrocarbon fuel source 17. Other materials suitable for catalyst 102 include platinum, palladium, a platinum/palladium mix, nickel, and other precious metal catalysts for example. Catalyst 102 pellets are commercially available from a number of vendors known to those of skill in the art. Catalyst 102 may also comprise catalyst materials listed above coated onto a metal sponge or metal foam. A wash coat of the desired metal catalyst material onto the walls of reformer chamber 103 may also be used for reformer 32.
Reformer 32 is configured to output hydrogen and includes an outlet port 87 that communicates hydrogen formed in reformer 32 outside of fuel processor 15. For example, a line 39 may communicate to an anode of fuel cell 20 for electrical energy generation or to a heating port for heating of a catalyst proximate to one or more heat transfer appendages. Port 87 is disposed on a wall of end plate 82 and includes a hole that passes through the wall (see
Hydrogen production in reformer 32 is slightly endothermic and draws heat from burner 30. Burner 30 generates heat and is configured to provide heat to reformer 32. As shown in
In the embodiment shown, burner 30 employs catalytic combustion to produce heat. A catalyst 104 disposed in each burner chamber 105 helps a burner fuel passed through the chamber generate heat. Burner 30 includes an inlet that receives methanol 17 from boiler 108 via a channel in one of end plates 82 or 84. In one embodiment, methanol produces heat in burner 30 and catalyst 104 facilitates the methanol production of heat. In another embodiment, waste hydrogen from fuel cell 20 produces heat in the presence of catalyst 104. Suitable burner catalysts 104 may include platinum or palladium coated onto alumina pellets for example. Other materials suitable for catalyst 104 include iron, tin oxide, other noble-metal catalysts, reducible oxides, and mixtures thereof. The catalyst 104 is commercially available from a number of vendors known to those of skill in the art as small pellets. The pellets that may be packed into burner chamber 105 to form a porous bed or otherwise suitably filled into the burner chamber volume. Catalyst 104 pellet sizes may be varied relative to the cross sectional size of burner chamber 105. Catalyst 104 may also comprise catalyst materials listed above coated onto a metal sponge or metal foam or wash coated onto the walls of burner chamber 105. A burner outlet port 89 (
Some fuel sources generate additional heat in burner 30, or generate heat more efficiently, with elevated temperatures. Fuel processor 15 includes a boiler 108 that heats methanol before burner 30 receives the fuel source. In this case, boiler 108 receives the methanol via fuel source inlet 85. Boiler 108 is disposed in proximity to burner 30 to receive heat generated in burner 30. The heat transfers via conduction through monolithic structure from burner 30 to boiler 108 and via convection from boiler 108 walls to the methanol passing therethrough.
Air including oxygen enters fuel processor 15 via air inlet port 91. Burner 30 uses the oxygen for catalytic combustion of methanol. Dewar 150 is configured such that air passing through dewar chamber 156 receives heat generated in burner 30. Dewar 150 offers thus two functions for fuel processor 15: a) it permits active cooling of components within fuel processor 15 before the heat reaches an outer portion of the fuel processor, and b) it pre-heats the air going to burner 30. Air first passes along the outside of dewar 150 before passing through apertures in the dewar and along the inside of dewar 150. This heats the air before receipt by air inlet port 93 of burner 30. In one embodiment, fuel processor 15 comprises a dewar 150 to improve-thermal management for fuel processor 15. Burner 30 generates heat and typically operates at an elevated temperature. Dewar 150 at least partially thermally isolates components internal to housing 152—such as burner 30- and contains heat within fuel processor 15.
Further description of annular fuel processors suitable for use with the present invention are included in commonly owned co-pending patent application entitled “Annular Fuel Processor and Methods” naming Ian Kaye as inventor and filed on the same day as this patent application, which is incorporated by reference for all purposes. Although the present invention will primarily be described with respect to the annular reformer and burner shown in
4. Fuel Pre-Heat Systems and Methods
Fuel container 16 stores methanol as a hydrogen fuel source 17. An outlet 26 of fuel container 16 provides methanol 17 into hydrogen fuel source line 25. As shown, line 25 divides into two lines: a first line 27 that transports methanol 17 to a burner 30 for fuel processor 15 and a second line 29 that transports methanol 17 to reformer 32 in fuel processor 15. Lines 25, 27 and 29 may comprise plastic tubing, for example. Separate pumps 21a and 21b are provided for lines 27 and 29, respectively, to pressurize the lines and transmit the fuel source at independent rates if desired. A model P625 pump as provided by Instech of Plymouth Meeting, Pa. is suitable to transmit liquid methanol for system 10 is suitable in this embodiment. A flow sensor or valve 23 situated on line 29 between storage device 16 and fuel processor 18 detects and communicates the amount of methanol 17 transfer between storage device 16 and reformer 32. In conjunction with the sensor or valve 23 and suitable control, such as digital control applied by a processor that implements instructions from stored software, pump 21b regulates methanol 17 provision from storage device 16 to reformer 32.
Fan 35a delivers oxygen and air from the ambient room through line 31 to regenerator 36 of fuel processor 15. Fan 35b delivers oxygen and air from the ambient room through line 33 to regenerator 36 of fuel processor 15. In this embodiment, a model AD2005DX-K70 fan as provided by Adda USA of California is suitable to transmit oxygen and air for fuel cell system 10. A fan 37 blows cooling air over fuel cell 20 and its heat transfer appendages 46.
Fan 35b blows cooling air through line 31 and over heat transfer appendages 46 of fuel cell 20. The air receives heat from fuel cell 20 via heat transfer appendages 46, which were described above with respect to
Many fuel cells 20 require elevated temperatures for electrical energy production. More specifically, the electrochemical reaction responsible for hydrogen consumption and electrical energy generation typically requires an elevated temperature. Start temperatures in the MEA layer 62 and its constituent parts greater than 150 degrees Celsius are common. Solid Oxide Fuel Cells (SOFC) may operate at over 800° C. High temperature (up to 300 degrees Celsius) PEM fuel cells are suitable for some portable electronics applications. Generally, the hotter that fuel cell 20 runs, the more heat is available for transfer into fuel source 17.
Heat exchanger 50 is configured to transfer heat from fuel cell 20 to fuel source 17 in line 29. In another embodiment, heat exchanger 50 is configured to transfer heat to fuel source 17 in line 27 going to burner 30. Alternatively, heat exchanger 50 may be configured to transfer heat to fuel source 17 in line 25 before it splits into lines 27 and 29, thereby heating fuel source 17 for both burner 30 and reformer 32. Alternatively, heat exchanger 50 may comprise a custom configuration adapted for the two components transferring heat. For example, one liquid carrying tube may be wrapped around another to provide intimate contact and convective/conductive/convective heat transfer between the liquids or gases in the two tubes. Alternatively, heat exchanger 50 may a copper block that clamps onto two tubes carrying the liquids or gases. An extruding tube that allows a tube carrying fuel source 17 may also be employed. Heat exchanger designs are well known to those of skill in the art and the present invention is not limited to any particular design.
Although the heat transfer system for
For the embodiment shown in
In one embodiment, fuel processor includes a dewar 150 that further pre-heats air entering burner 30. Dewar 150 is arranged such that air passing through a dewar chamber intercepts heat generated in burner 30 before the heat escapes fuel processor 15. Dewar 150 reduces heat loss from fuel cell 20 by heating the incoming air before it escapes fuel processor 15. In one sense, dewar 150 acts as a regenerator that uses waste heat in fuel processor 15 to increase thermal management and thermal efficiency of the fuel processor. Specifically, waste heat from burner 30 pre-heats incoming air provided to burner 30 to reduce heat transfer to the air in the burner so more heat transfers from burner 30 to reformer 32.
Fuel processor 15 receives methanol 17 from storage device 16 and outputs hydrogen. Fuel processor 15 comprises burner 30, reformer 32 and boiler 34 and dewar 150. Burner 30 includes an inlet that receives methanol 17 from line 27 and a catalyst that generates heat with methanol presence. Boiler 34 includes an inlet that receives methanol 17 from line 29. The structure of boiler 34 permits heat produced in burner 30 to heat methanol 17 in boiler 34 before reformer 32 receives the methanol 17. Boiler 34 includes an outlet that provides heated methanol 17 to reformer 32. Reformer 32 includes an inlet that receives heated methanol 17 from boiler 34. A catalyst in reformer 32 reacts with the methanol 17 and produces hydrogen and carbon dioxide. This reaction is slightly endothermic and draws heat from burner 30. A hydrogen outlet of reformer 32 outputs hydrogen to line 39. In one embodiment, fuel processor 15 also includes a preferential oxidizer that intercepts reformer 32 hydrogen exhaust and decreases the amount of carbon monoxide in the exhaust. The preferential oxidizer employs oxygen from an air inlet to the preferential oxidizer and a catalyst, such as ruthenium or platinum, that is preferential to carbon monoxide over carbon dioxide. Efficient systems and methods of the present invention may also transport hydrogen in the fuel cell system to burner 30 in fuel processor 15. A catalyst in the burner then reacts with the hydrogen to produce heat in the burner. The hydrogen may come from the anode exhaust of fuel cell 20 and/or from the reformer 32 exhaust.
Line 39 transports hydrogen from fuel processor 15 to fuel cell 20. In some embodiments, gaseous delivery lines 31, 33, 41, 47 and 39 may comprise plastic tubing, for example. A hydrogen flow sensor (not shown) may also be added on line 39 to detect and communicate the amount of hydrogen being delivered to fuel cell 20. In conjunction with the hydrogen flow sensor and suitable control, such as digital control applied by a processor that implements instructions from stored software, fuel processor 15 regulates hydrogen gas provision to fuel cell 20.
Fuel cell 20 includes an hydrogen inlet port that receives hydrogen from line 39 and delivers it to a hydrogen intake manifold for delivery to one or more bi-polar plates and their hydrogen distribution channels. An oxygen inlet port of fuel cell 20 receives oxygen from line 33 and delivers it to an oxygen intake manifold for delivery to one or more bi-polar plates and their oxygen distribution channels. Fan 35a delivers oxygen and air from the ambient room through line 33 to the cathode of fuel cell 20. In some embodiments, model AD2005DX-K70 fan as provided by Adda USA of California is suitable to transmit oxygen and air for fan 35. An anode exhaust manifold collects gases from the hydrogen distribution channels-and-delivers them to an anode exhaust port, which outlets the exhaust gases into the ambient room. A cathode exhaust manifold collects gases from the oxygen distribution channels and delivers them to a cathode exhaust port.
In addition to the components shown in shown in
The present invention routes at least some heat from CPU 12 to fuel source 17. In one embodiment, the present invention uses a cooling system in the electronics device to transport the heat to fuel source 17. Cooling system 55 removes and dissipates heat from CPU 12. Several cooling systems 55 are known and used in conventional electronics devices. In one embodiment, cooling system 55 comprises a heat pipe 59 that conducts heat away from CPU 12 to a cooling fin 57. Ambient air removes heat from cooling fin 57, while a fan 58 provides additional heat removal by passing air over the fin when required. Heat pipe 59 is in conductive thermal communication with CPU 12 through a heat sink and thermally conductive material attached to the CPU 12. One example of heat pipe 59 includes a copper rod that connects the CPU heat sink to cooling fin 57. Heat transfer system for electronics device 22 passes the copper rod into heat exchanger 50 to transfer heat from CPU 12 to fuel source 17. In one embodiment, heat exchanger 50 wraps the copper rod around a tube carrying fuel source 17.
In another embodiment, cooling system 55 comprises a recirculating single or dual phase liquid coolant to remove heat from CPU 12 (
Cooling system 55 may alternatively comprise a finned heat sink on CPU 12 and a fan mounted directly on the heat sink. This takes up more space than the previous two cooling systems and is typically used on computing systems where space is not at a premium, such as desktop computers.
Cooling system 55 may also include a micro channel heat sink that is bonded directly to the CPU and/or graphics chip. In this case, the heat sink is in direct and conductive thermal communication with component 12. Fuel source 17 is then routed to the heat sink and fed through the micro channels for heating of the fuel source.
Since the overall heat transfer from a solid to liquid in heat exchanger 50 is 1-2 orders of magnitude higher than for solid to air (natural or forced convection), heat exchanger 50 increases heat dissipation rates for heat generating component 12 and reduces the size of cooling system 55 for electronics device 22. This allows a smaller cooling fan 58 to be used on the CPU cooling system 55, further reducing device 22 size. In some cases, the fuel source 17 partial pressure increases and becomes saturated or super heated (depending on the rate of heat transfer into fuel source 17 and fuel source 17 composition). Since the fuel source 17 partial pressure is significantly increased, less or even no fuel source 17 needs to be oxidized in a catalytic burner 30. This increases the overall system electrical efficiency.
Heat exchanger 50 of
The present invention may also combine fuel cell 20 and component 12 heating of fuel source 17.
Process flow 500 then transfers the heat from the electronics component to fuel source (504). Circulating a liquid coolant that is configured to receive heat from the component may actively carry the heat to a heat exchanger that transfers the heat to the fuel source. Other suitable techniques for transferring heat from the electronics component to fuel source are described above. The fuel source may be provided to the reformer and/or a burner in the fuel processor that catalytically heats the reformer using the fuel source. In some cases, heat from the electronics component vaporizes the fuel source.
Process flow 510 then transfers the heat from the fuel cell to fuel source (514). A circulating liquid or gas may accomplish this. If the fuel source is not fully-vaporizes, a burner in the fuel processor may add heat to bring the fuel source to a gaseous state.
5. Electronics Device Implementation
In one embodiment, fuel processor 15 and fuel cell 20 are incorporated into electronics device 22 (within its volume and outer housing) as an integral module, and storage device 16 is a removable device. Fuel cell powered laptop computers 22 may comprise slightly modified existing products, with fuel processor 15 and fuel cell 20 and related system components fitted generally into the space provided for a battery pack. Mating connector 140 is included in this allocated space for connection to a removable storage device 16. Storage device 16 mechanically interfaces with electronics device 22. In one embodiment, connectors 104 and 140 provide sufficient mechanical force to maintain position between the storage device 16 and electronics device 22. In another embodiment, electronics device 22 includes a mechanical slot that storage device 16 fits and slides into.
When connector 104 and mating connector 140 interface, fuel cell system controller 214 digitally communicates with memory 106 using link 217 for bidirectional communication therebetween. In another embodiment, controller 214 uses a wireless interrogator to communicate with an RFID antennae and memory 206 included in storage device 16. Controller 214 may read any information stored in memory 206 such as a fuel type stored in the storage device 16, a model number for storage device 16, a volume capacity for bladder 205 or storage device 16, a number of refills provided to storage device 16, the last refill date, the refilling service provider, and a current volume for the storage device. Controller 214 estimates the remaining power in storage device 16 by comparing the fuel source 17 level since last use or refill against a consumption rate for a particular laptop computer. Controller 214 may also write transient information to memory 106, such as an updated volume for the storage device. The controller 214 communicates with a main controller 210 for computer 22 and computer memory 218 via communications bus 212. Computer memory 218 may store instructions for the control of fuel system 10 such as read and write protocol and instructions for communication with a digital memory 106.
Power management 219 controls power provision by fuel cell system 10 and electrochemical battery 222. Thus, power management 219 may inform controller 214 how much power is needed for laptop computer 22 operation and controller 214 responds by sending signals to fuel cell 20, fuel processor 15 and a pump that draws fuel from storage device 16 to alter fuel cell power production accordingly. If fuel cell system 10 runs out of fuel source 17, then power management 219 switches to electrical power provision from battery 222.
Main controller 210 is preferably a commercially available microprocessor such as one of the Intel (including Pentium™) or Motorola family of chips, a reduced instruction set computer (RISC) chip such as the PowerPC™ microprocessor available from Motorola, Inc, or any other suitable processor. Memory 216 may comprise some form of mass storage but can be eliminated by providing a sufficient amount of RAM to store user application programs and data. Memory 216 may also contain the basic operating system for the computer system 350. It is generally desirable to have some type of long term mass storage such as a commercially available hard disk drive, nonvolatile memory such as flash memory, battery backed RAM, PC-data cards, or the like. Regardless of computer system configuration, it may employ one or more memories or memory modules configured to store program instructions for controlling fuel cell and thermal systems described herein. Such memory or memories may also be configured to store data structures, control programs, or other specific non-program information described herein.
In addition, although the present invention has been described with respect to methods operating on a fuel cell system, many of the methods and techniques described constitute system controls and will comprise digital control applied by control logic that implements instructions from stored software. The stored instructions may correspond to any methods or elements explained in the process flows described herein. The control logic includes any combination of hardware and software needed for control within system 10. For example, the control logic may include instructions stored in memory 216 that are executed by main controller 210. Input/output logic may be employed to facilitate communication between main controller 210 and components of fuel system 10. In one embodiment, the control logic is configured to regulate heat transfer or temperature in system 10 by controlling the routing of liquids and gases between fuel cell 20, fuel processor 15 and electronics device 202. In a specific embodiment, the control logic is configured to regulate the amount of heat provided to a fuel source provided to a fuel processor, wherein the heat was generated in an electronics component. In another specific embodiment, the control logic is configured to regulate the amount of heat provided to a fuel source provided to a fuel processor, wherein the heat was generated in a fuel cell.
While this invention has been described in terms of several preferred embodiments, there are alterations, permutations, and equivalents that fall within the scope of this invention which have been omitted for brevity's sake. For example, although the present invention has been described with respect to reformed methanol systems that process a fuel source to produce hydrogen, the present invention is also useful in direct methanol systems to heat a fuel source provided directly to a direct methanol fuel cell. While not described in detail, such digital control of a mechanical system is well known to one of skill in the art and the present invention may thus relate to instructions stored in software capable of carrying out methods described herein. It is therefore intended that the scope of the invention should be determined with reference to the appended claims.
This application claims priority under 35 U.S.C. §119(e) from co-pending U.S. Provisional Patent Application No. 60/482,996 entitled “Fuel cell system startup procedure and self-heating apparatus”, which is incorporated by reference for all purposes; this application also claims priority under 35 U.S.C. §119(e) from co-pending U.S. Provisional Patent Application No. 60/483,416 entitled “Fuel Preheat in Portable Electronics Powered by Fuel Cells”, which is incorporated by reference for all purposes; and this application additionally claims priority under 35 U.S.C. §119(e) from co-pending U.S. Provisional Patent Application No. 60/482,981 entitled “Micro machined fuel stack with integral cooling and humidification”, which is incorporated by reference for all purposes
| Number | Date | Country | |
|---|---|---|---|
| 60482996 | Jun 2003 | US | |
| 60483416 | Jun 2003 | US | |
| 60482981 | Jun 2003 | US |
