HK1059003A - Fuel containment and recycling system - Google Patents

Description

Fuel container and recovery system for electric energy conversion device

Technical Field

The present invention relates to the collection of fuel and effluent for energy conversion systems, and more particularly to a fuel container and recovery system for metal-air fuel cells.

Background

Fuel cells, and in particular metal-air battery systems, have long been viewed as ideal power sources in terms of their inherently high energy density. The fuel cell stack includes a cathode, an ionic medium, and an anode. Metal-air batteries use an anode comprised of metal particles that are loaded into the battery and oxidized as the battery effluent. The cathode, which generally consists of a semi-permeable membrane, a mesh of inert wires, and a catalytic layer, is used to reduce oxygen that permeates from outside the cell through the membrane. Since oxygen is readily available from air, fuel cell stacks typically do not require the use of a dedicated oxygen storage container (except in some cases where oxygen supply is limited due to design considerations), which makes metal-air cells efficient on a volumetric energy density and cost basis. The cathode and anode are separated by an insulating medium through which the electrolyte can pass. When zinc reacts with ions passing through the electrolyte, the zinc is oxidized and the zinc-air resupplies the fuel cell to consume zinc particles and oxygen, releasing electrons to produce electricity. The reaction product is generally composed of dissolved zincate and zinc oxide particles suspended in the spent electrolyte.

Prior art metal-air systems have proven to have sufficient electrical capacity to supply electrical power to electrical vehicles. Such metal-air batteries having anodes of recycled metal slurries were constructed by Sony, Sanyo, the Bu l gallium Academy of Science, and Comagniegeneral d' electric in the 1970 s for exemplary purposes. These systems have not achieved any commercial success because their power output is relatively low (acceptable discharge rate and total capacity). Until now, this has been a major obstacle to providing commercially viable systems, for example Sony can only provide 24 Watts per kilogram, Compagnie General d' electric is limited to 82 Watts per kilogram or 84 Watts per kilogram. However, depending on the type of fuel used, the theoretical capacity still exceeds 5 times these values. One version of a recent metal-air battery has achieved an improvement in capacity using a packed bed of fixed anode particles through which the electrolyte can pass without the use of an external electrolyte pump. Although this system has increased the cell capacity to about 200 watts/kg and the energy density to about 150 wh/kg, further improvements are needed before commercial success can be achieved.

The metal-air refuelable battery pack can be refuelable in a short time (i.e., minutes), which makes the metal-air refuelable battery pack well suited for mobile applications such as electronic vehicles, portable power sources, etc., as compared to conventional batteries that typically require hours to charge. During the refuelling operation, fresh anode metal and electrolyte are added to the cell and reaction products and spent electrolyte are removed. The reaction product needs to be sent to an industrial facility for recovery or for other purposes. Various methods have been proposed to refuel metal-air cells. One known system uses two reservoirs, one for storing fresh anode fuel and one for containing the reactant materials from the cell.

U.S. patent No. 4,172,924 discloses a metal-air battery that uses a fluid metal fuel formed from a mixture of pasty metal particles and a liquid electrolyte. The paste is moved from the first storage chamber through an electrochemical cell in which the paste is oxidized at the cathode of the corresponding metal oxide paste and the reaction products (primarily metal oxides) are sent to the second storage chamber. While this device increases the drainage rate by removing reactive materials, the multiple reservoir design wastes space, adds complexity, and increases cost.

Recently published U.S. patent No. 5,952,117 discloses a fuel cell stack designed to overcome the disadvantages associated with the dual storage chamber configuration described above, and the' 117 patent discloses a transportable container to supply anode material and electrolyte to the fuel cell, circulate electrolyte in a closed system, and collect spent anode reaction products. According to this patent, the container is first filled with zinc fuel particles and a fresh electrolyte. The container is then sent to a fuel cell stack and connected to the stack so that it becomes part of the electrolyte flow path. During discharge of the cell, after a period of use of the zinc fuel and electrolyte, the container now containing at least part of the spent electrolyte and reaction products is removed from the cell and returned to the refilling device. The contents of the vessel are then emptied into the refill unit and the process is repeated, with the spent electrolyte and reaction products being regenerated in the zinc regeneration unit and returned to the refill unit. While this device avoids the need for two separate vessels, the collection of reaction products can only be effectively performed after the fuel supply is exhausted and the vessel is emptied into the refill unit.

Another disadvantage of this system relates to the structure used to prevent stray circuit currents between multiple cells injected with fuel in parallel. In this configuration, the cells are not electrically isolated from each other via the electrically conductive fuel feed. To avoid short circuits, the' 117 patent discloses a filter so that larger particles of anode material do not pass through the conduits between the fuel cells. While this is effective for the particulate fuel particles disclosed in this patent, this method does not block the passage of the minute anode particles present in the paste-like fuel material.

Disclosure of Invention

In view of the above, it is an object of the present invention to provide a convenient, economical and environmentally safe fuel supply and waste material recovery system for an energy conversion device.

It is another object of the present invention to provide a single storage vessel to simultaneously supply fuel to and collect effluent from an energy conversion device.

It is another object of the present invention to provide a single storage container for supplying fuel to and collecting reaction products from a fuel cell, respectively, and particularly a metal-air fuel cell using zinc, aluminum, lithium, magnesium, silver, iron, etc.

It is another object of the present invention to provide a metal-air fuel cell system that can be used in a variety of applications with respect to power requirements (i.e., in the range of watts to megawatts). Such applications include, but are not limited to, energy supplied to motor vehicles, portable and consumer electronics, homes, and industries.

It is another object of the present invention to eliminate short circuits between multiple electrochemical cells having a single fuel feed.

In view of the above objects, and additional objects that will become apparent hereinafter, the present invention generally provides a method and system for supplying fuel to an energy conversion device from a single storage vessel while simultaneously collecting effluent from the energy conversion device to the vessel.

In particular, the present invention provides a fuel cell system including a storage vessel that is connectable to a cell to provide fuel while collecting waste and generating reactive materials as cell effluent. The invention is suitable for use in hybrid rechargeable fuel cells and in particular metals having a metallic anode material in fluid form. An air fuel cell. The term "fluid" is defined herein as a paste-like material such as small metal particles and various additives suspended in a fluid electrolyte such as KOH solution. Metal-air fuel cells operate as part of an electrochemical cell reaction by oxidizing the metal anode with oxygen or air (fuel). In the present invention, a fluid anode, particularly a zinc-metal fuel, is supplied to multiple stacks of a battery system from a single storage chamber, during operation, the resulting reaction products as cell effluent are continuously removed from the cell to a storage vessel, and the cell is replenished with fresh anode fuel from the vessel.

According to one aspect of the present invention, a storage vessel is provided in an energy conversion system having at least one energy conversion device for storing a quantity of fuel and a quantity of effluent. The storage vessel includes a vessel body connectable to the at least one energy conversion device, and includes at least two oppositely variable volume chambers within the vessel for respectively storing a quantity of fuel and receiving a quantity of effluent. A structure is provided to reduce the volume of the first chamber while increasing the volume of the second chamber. During operation of the energy conversion device, fuel is supplied from the first chamber and simultaneously receives exhaust in the second chamber. When the fuel supply is exhausted, the reservoir can be removed and sent to another location to regenerate the spent fuel into a new fuel, and then the reservoir is reconnected to the energy conversion device and new fuel is injected from the previously "exhaust" chamber and the exhaust is received in the original fuel supply chamber.

In accordance with a particular implementation of the fuel cell battery system of the present invention, a single storage container is provided to store a quantity of electrochemical anode material and a quantity of reaction products. The reservoir comprises at least two oppositely variable volume compartments and at least one cell element having a cathode and defines a volume to contain the anode materials (metal and electrolyte) to form an electrochemical cell having a cathode. A fluid transfer circuit is in contact with the anode material between the at least one battery element and the first chamber in the reservoir. The same or a separate fluid delivery circuit is in contact with the reaction product between the battery and the second chamber in the reservoir. In a preferred embodiment, the delivery circuit comprises a branch conduit or conduit, respectively, between the battery and the storage container. Each lead tube includes an electrically insulated valve to selectively communicate new anode material and reaction products to/from one cell of a group of cells electrically connected to each other.

In accordance with another aspect of the invention, the fuel cell power system further includes a subsystem for regenerating the reaction products into new electrochemical anode material after the reaction products are removed from the cell to a storage container; and a structure for changing the respective volumes of the first and second chambers as new anode material is delivered to the cell and reaction products are delivered to the reservoir chamber. The subsystem for regenerating the reaction products may be located near the battery or may be located remotely and deliver the storage container thereto after all of the fuel has been dispensed.

In another embodiment, the first chamber of the storage container includes a first sub-chamber containing new anode material and a second sub-chamber containing electrolyte. The components are fed from the respective first and second subchambers to a mixer before being fed to the cell. Similarly, the reservoir may be configured as a first sub-chamber containing the anode reactant material and a second sub-chamber containing the spent electrolyte, the components being separated from each other prior to delivery from the cell to the reservoir.

The present invention further provides a method of supplying fuel to and collecting effluent from an energy conversion device, the method comprising the steps of:

connecting a storage container having at least two chambers to the energy conversion device, the at least two chambers respectively delivering a quantity of fuel to the energy conversion device and receiving effluent from the energy conversion device;

conversely changing the volume of the first and second chambers in the storage chamber to supply fuel to the energy conversion device and to collect exhaust from the energy conversion device;

separating the container from the energy conversion device;

converting the effluent to fuel in the vessel; and

reconnecting the container to the energy conversion device to supply new fuel from the second chamber to the energy conversion device and to receive effluent in the first chamber.

In the above specific application, the present invention provides a method of supplying fuel to at least one fuel cell element and collecting reaction products from at least one fuel cell element, the method comprising the steps of:

connecting a storage container having at least two chambers to a fuel cell to supply anode fluid to the fuel cell element and to receive reaction products from the fuel cell element, respectively;

inversely varying the volume of the first and second chambers in the reservoir chamber to supply anode liquid to the fuel cell and to receive reaction products from the fuel cell element;

separating the container from the fuel cell;

converting the reaction product in the second chamber to fuel; and

reconnecting the container to the fuel cell to supply fresh anode fluid from the second chamber to the fuel cell and to receive reaction products in the first chamber.

The invention will now be described with particular reference to the accompanying drawings

Drawings

FIG. 1 is a schematic view of an energy conversion system and a single storage vessel for supplying fuel to and receiving effluent from an energy conversion device in accordance with the present invention;

FIG. 2 is a schematic diagram of an exemplary fuel cell power system according to the present invention;

FIG. 3 is a schematic illustration of a modified embodiment of FIG. 2 by the addition of a dual chamber mixing section to produce the metal paste in situ;

FIG. 3A is a schematic illustration of a storage chamber of 4 sub-chambers and a separator element to separate the spent fuel into anode metal and electrolyte;

FIG. 4 illustrates a storage container having flexible walls to enable anode material to be delivered by hand pressure compressing the walls of the storage chamber; and

fig. 5 illustrates another embodiment of a storage container having a hand-driven piston mechanism for dispensing anode material from the storage container.

Detailed Description

The low energy density of typical metal-air batteries limits their practical use in high rate applications such as powering motor vehicles. The present invention overcomes the disadvantages of the prior art by using a single storage vessel to dispense fuel and to collect and reconstitute the electrochemical reactants (i.e., most of the metal oxides) in a manner similar to a secondary battery system. The hybrid configuration (i.e., refuelable/rechargeable) provides long discharge periods (or high energy density), faster recharge capacity and longer cycle life that enhances performance during discharge.

The present invention embodies a "fuel split" in which multiple heavy metal/air cell voltages can be obtained using only one fuel source without shorting the cell. As a result, batteries manufactured in the battery configurations of the present invention can provide at least about 330 watt-hours/kilogram or 750 watt-hours/liter, making them well suited for use as a power source for pure or hybrid electric vehicles.

In a preferred embodiment of the invention, the air of the depolarized cathode is designed to handle a discharge current density of 500 to 2000 milliamps per square centimeter and an electrolyte capable of providing a capacity of 5000 amp-hours per liter. It is preferred to use metallic anode materials including corrosion resistance additives and alloys. The anode material is preferably composed of small metal particles having a particle size such that the metal particles are not completely oxidized at the anode surface during the electrochemical reaction. The range of particles selected is preferably between about 10 nanometers and 1 millimeter, although smaller sizes provide greater capacity, better drainage rates, and facilitate easier transport of fluids through the system.

The metal fuel container is shaped to maximize volumetric capacity and increase capacity and discharge. With respect to the shape of the individual cell elements, a cylindrical configuration is preferred for greater power density, although other shapes may be used within the scope of the present invention.

The storage vessel includes a mechanism to inversely vary the respective volumes of the fresh paste (fuel) storage chamber and the reaction product (effluent) chamber as fresh metal paste flows from the storage vessel and into the individual cells and spent metal paste returns from the cells to the storage vessel. The mechanism includes a movable wall defining a boundary between chambers, such as a piston, screw mechanism, or the like. In this way, the reaction product takes up space for previously placing a new metal paste. The mechanical system may be used to force the paste out of the container, or it may operate in conjunction with an external pump in the fluid path. For applications with relatively small power requirements, such as consumer electronics, the storage container may be designed with flexible walls that can be compressed by an external force (e.g., by hand) to force fuel into the cell and to force waste material back into the storage chamber.

When multiple cells are electrically connected together, an insulation/shunt system (ISS) may be used to prevent short circuits. The ISS includes a series of valves that communicate with individual fuel feed lines connected to each cell, respectively. This configuration allows a single fuel reservoir to feed fresh metal paste to a number of electrically isolated cells. The system uses an "on" and "off" mechanism that selectively injects fresh metal paste into individual cells when the reactive material is evacuated in the "on" state, the ISS is turned off during cell operation, and the metal paste in each cell is electrically isolated from the main fuel line.

In an embodiment, the ISS comprises Teflon (or some other insulating material) stopcocks or valves between each cell and the main feed line, which stopcocks/valves can be moved left and right in a known manner to open or close the paste path. In another embodiment, the Teflon taps/valves can be rotated 90 degrees to open or close the paste path, and all taps/valves in the system are intermittently moved or rotated, with the result that the cells in series are filled with fresh metal paste at the same rate, but in a staggered manner. In this way, the ISS can prevent current leakage or short circuits between cells via the metal fuel feed.

To maximize the volumetric efficiency of the system, each cell is preferably cylindrical in shape and includes an air diffusion cathode, a separation chamber, and a nickel-based current collector. The metal paste is continuously injected into a predefined space between the separation chamber and the anode current collection chamber. Examples of conductive polymer gel membrane separator materials for forming anion and cation conductive membranes are disclosed in co-pending U.S. application No. 09/259,068 filed on 26/2/1999, which is incorporated herein by reference. The gel composition of the membrane comprises an ionic material in its solution phase such that the material behaves like a liquid electrolyte, while at the same time the solid gel composition prevents diffusion of the solution phase into the device, such membrane portion comprising a support material or matrix, preferably a woven or non-woven fabric such as a polyolefin, polyvinyl alcohol, cellulose, or a polyamide such as nylon. More specifically, the polymer-based gel or film portion of the membrane includes an electrolyte in a solution containing a polymerization inhibitor and the polymerization product of one or more water-soluble ethylenically unsaturated amide or acid monomers, preferably methylenediacryloyl, acrylamide, methacrylic acid, acrylic acid, 1-vinyl-2-pyrrolidone, or mixtures thereof. In particular, the separator comprises an ion-conducting polymer-based solid gel membrane comprising a support on which is contained within a solution phase a polymer-based gel having an ionic material. The polymer-based gel comprises a polymerization reaction product of one or more monomers selected from the group of water-soluble ethylenically unsaturated amides or acids and an enhancer selected from the group of water-soluble and water-swellable polymers, wherein an ionic material is added to the one or more monomers and the enhancer is added prior to the polymerization reaction. Other separator materials that may be used in the present invention are disclosed in U.S. application No. 09/482,126 filed on 11/1/2000, the same as in the present application, which is incorporated herein by reference. The' 126 application discloses a separator comprising a support or matrix and a polymer gel composition having an ionic material in a solution phase, which separator is prepared by adding the ionic material to the monomer solution prior to polymerization and the ionic material remains embedded within the resulting polymer gel after polymerization. The ionic material behaves like a liquid electrolyte, but at the same time, the polymer matrix solid gel membrane provides a smooth impervious surface that allows ion exchange for battery discharge and charge. Advantageously, the separator reduces dendrite leakage and prevents diffusion of reaction products, such as metal oxides, into other parts of the cell, and the measured ionic conductivity of the separator is much higher than that of prior art solid electrolytes or electrolyte-polymer membranes.

Suitable cathode structures are described in co-pending U.S. application No. 09/415,449, filed on 8/10/1999, which is incorporated herein by reference. The cathode in the' 449 application includes a porous metal foam substrate formed in a network of conveyed pores. The active layer and the hydrophobic microporous gas diffusion layer are both located on one or more surfaces of the metal foam substrate. The metal foam substrate serves as a cathode current collector. The microporous layer is a plastic material such as a fluoropolymer (i.e., PTFE). The cathode may also include a special microstructure reinforced by relatively strong bonds provided by sintering a polymeric binder within the three-dimensionally conveyed pores of the metal foam substrate. The reactive layer is preferably made of the same material as the adhesive. This advantageously allows a single roll compaction operation to simultaneously inject the adhesive into the substrate and form a reactive layer thereon. Methods of forming such electrodes may include mixing carbon and a polymeric binder to form a carbon/polymer blend, preparing the carbon/polymer blend as a liquid dispersion or slurry, placing the carbon/polymer blend within a substrate hole in a substantially continuous process; placing the active layer on a substrate, and in-situ sintering the polymer blend with the current collector apertures.

For the anode current collector, an integrated static mixer and current collector are used to effectively mix the metal paste to fixedly expose the unreacted metal to the cathode surface as the fuel passes through the cell or power supply stack. This static mixer ensures good contact between the cathode and the metal paste anode to optimize the discharge capacity.

A preferred metal paste exhibits high electrochemical activity, good flow, low internal resistance, and corrosion resistance properties. One desirable paste composition includes a metal powder (or metal particles of the foregoing size range), an electrolyte formed of a fluid gel or paste (e.g., a solution having about 30-35% KOH), an anti-corrosive agent, a lubricant, and an electrically conductive agent, and may include other additives as needed or desired.

A fluid paste of metal particles (which is available from, e.g., Aldrich Chemical co. milwaukee, WI), and 35% gel electrolyte (5% polyacrylamide, 35% KOH, 60% water) exhibits desirable characteristics, including low internal resistance and good flow.

Referring now to FIG. 1 of the drawings, a schematic diagram of an energy conversion system 10 is illustrated that includes an energy conversion device 12, a storage container 14, and a fluid path, generally indicated at 16. The energy conversion device 12 converts fuel into energy and exhaust, and can be any of a variety of devices, and illustrative applications of fuel cells are described in more detail below. The reservoir 14 is divided into at least two chambers 18a, 18b to store varying amounts of fuel and exhaust, respectively. In this regard, the chambers 18a, 18b may instead vary in volume such that a certain amount of effluent is collected in the chamber 18b when fuel is first dispensed from the chamber 18 a. After the entire amount of fuel from chamber 18a is supplied to energy conversion device 12 and chamber 18b is filled with effluent, the storage vessel is separated from fluid path 18 by suitable means generally designated 20a, 20 b. The storage vessel is then sent to a facility/plant generally indicated at 27 to convert the effluent into new fuel using known processing techniques, or the fuel cell is recharged directly in situ from the plant for smaller scale applications as described below. The reservoir 14, now containing a fresh supply of fuel in chamber 18b (and chamber 18a empty), is then connected to the flow path 16 and the method of supplying fuel to the energy conversion device is reversed. New fuel is then dispensed from chamber 18b and effluent is collected in chamber 18a, and the entire process is repeated.

The storage container 14 of fig. 1 is schematically illustrated with a movable wall 22, the movable wall 22 defining a boundary between the individual chambers 18a, 18b and which changes the respective volumes of the chambers. The wall 22 may include a separate sealing device 24 (i.e., an-O-ring device) to prevent leakage between the chambers. The wall 22 may be bi-directionally driven via a mechanical device (not shown) that may be operatively coupled to a piston, screw drive, or the like. It is contemplated that numerous methods may be used and those of ordinary skill in the art will appreciate that the particular embodiments shown herein are not intended to be limiting.

The flow path 16 is shown as including a pair of pumps 26a, 26b in communication with a branched delivery tube, conduit or pipe shown in solid and dashed lines. A pair of valves 28a, 28b can be actuated independently to selectively allow fluid in the path to flow to or from each chamber. When fuel is dispensed from chamber 18a or chamber 18b and exhaust is returned to the opposite chamber 18b or chamber 18a, the dotted lines represent the opposite flow paths depending on the operation of the respective pumps 26a, 26 b. The flow path 16 may further include one or more exhaust ports and associated hardware of a type known in the art of fluid expansion (fluid plunging), which elements are not shown for clarity and are known to those skilled in the art.

Referring now to fig. 2, there is shown a schematic diagram of an exemplary fuel cell power system 30 in a first embodiment. The power system 30 generally includes a storage vessel 32, a power supply stack 34, a flow path 36, and a valve/isolation system (ISS) 38. The reservoir includes a pair of oppositely variable volume chambers 40a, 40b as shown in the general embodiment previously described with respect to fig. 1. As shown in fig. 2, the fluid anode material is initially contained in chamber 40 a. Flow path 36 includes a pump 42 (although a single pump is shown, more than one may be installed, with additional pumps located near chamber 40 a) to drive fluid flow through the system. Fuel is initially dispensed from chamber 40a to ISS 38. The ISS 38 includes a fuel feed conduit 44 having individual branches 46a-d to convey anode paste (or cycle reversal to reaction products) from the storage vessel 32 to a plurality of corresponding cell elements 48 a-d. Each cell includes an air-cathode arrangement 49 of the form of the example described above. A similar conduit 50 with individual branches 52a-d is connected to the storage vessel 32 via the pump 42. The battery elements forming the power supply stack are electrically connected to each other in a conventional manner and communicate with an external application via the connectors 53a, 53 b. During example cycle operation, fuel is delivered from chamber 40a and reaction products are delivered from cell elements 48a-d to chamber 40 b. By moving the diaphragm 54 within the reservoir vessel 32 a specific distance, the storage volume of the reaction product in the reservoir chamber 40b is increased, while the storage volume of the anode fluid in the chamber 40a is decreased (with 20% volume compensation due to the volume change when new fuel is converted to reaction product). After the fuel is depleted, the storage vessel 32 is then sent to a recharging station (as shown in fig. 1) to recharge/reconstitute the reaction products into new anode material. Alternatively, the waste product may be charged in situ by applying a voltage to the oxidizing material in a manner known in the art. After charging, the reservoir 32 is reconnected to the system and the cycle is reversed, dispensing fresh anode fuel from chamber 40b and collecting reaction products in chamber 40 a.

Corresponding valves 46a-d and 52a-d, respectively, are operated in pairs to selectively inject fuel and exhaust reaction products to the cell. The inlet and outlet valves of adjacent cells are each independently operated so that only a single cell is fueled and reaction products are discharged at a time. As a result, there is no electrical continuity between individual cells through the conductive metal anode material on the supply/removal path. This battery design has a small number of moving parts and a simple construction with readily available materials. The paste-type fuel including the metal particles and the gel electrolyte as described above can flow freely through the system under the pressure of an external pump in a manner similar to O₂-H₂Hydrogen fuel for fuel cells. The integration of fuel supply and waste material storage into a single container divided into storage volumes of individual components that can be varied in opposite directions provides better space utilization, simplifies fuel storage, supply and delivery and ultimately provides consumers with reduced energy costs.

Referring now to fig. 3, another embodiment of a metal-air battery power system 30' is illustrated, with similar components numbered similarly to the above embodiment. The fuel cell power system 30 ' includes a storage vessel 32 ', a power supply stack 34, a flow path 36 ', and a valve/insulation system (ISS) 38. The storage container has been modified to include a plurality of chambers 56a, 56b and 58. According to the principles discussed above, chambers 56a and 56b are driven together and change in volume in opposition to chamber 58. Here the fluid anode metal is separated from the electrolyte, the metal initially contained in chamber 56a, and the electrolyte contained in chamber 56 b. The flow path 36 includes a pump 42a to drive the liquid through the system, and a mixer 58 communicates with the respective chambers 56a, 56b to mix the fluid metal and electrolyte into an "anode paste" prior to delivery to the cell via the pump 42b and fuel feed conduit 44. A plurality of individual manifolds 46a-d deliver anode paste from the storage vessel 32 to a plurality of corresponding battery elements 48 a-d. A similar conduit 50 with individual branches 52a-d is connected to the storage vessel 32' via pump 42 a. The battery elements forming the power supply stack are electrically connected to each other in a known manner and communicate with the external application via the connectors 53a, 53 b. During operation. Anode metal and electrolyte are delivered from chambers 56a, 56b, respectively, are combined in mixer 58, and delivered to cells 48 a-d. As the cell discharges, the reaction products are sent to chamber 50. By moving the partition 54 within the reservoir 32' a specific distance, the storage volume of the reaction product in the reservoir chamber 58 is increased, while the storage volume of the fuel component in the chambers 56a, 56b is decreased (with 20% volume compensation). After the fuel is consumed, the reaction product fills all of the volume of the storage vessel 32'. The storage container 32' is then sent to a charging station as described above. This configuration reduces the likelihood of corrosion by maintaining the metal and electrolyte separate until the fuel is to be used in the cell.

Fig. 3A shows a modification of the foregoing in that the chamber 58 of the reservoir 32 'may be divided into sub-chambers 58a, 58b and a separator element 60 may be provided between the reservoir 32' and the conduit 50. Anode metal and electrolyte waste products are separated by separator element 60 into individual anode metal and electrolyte components, which are then stored in sub-chambers 58a, 58b, respectively. These chambers are similar to the metal and electrolyte supply chambers 56a, 56b described above. In this manner, the metal oxide in chamber 58a is reduced to a new metal and the electrolyte is reconstituted or replaced in chamber 58 b. Thereafter, the operation cycle is reversed as described above.

Referring now to fig. 4, a storage container 62 for consumer electronic goods, such as household appliances and the like, is illustrated. The storage vessel 62 includes a flexible tank (i.e., plastic) and a stationary partition 64, the partition 64 defining a first chamber 66a and a second chamber 66b for storing anode material and collecting reaction products, respectively. In this embodiment, pressure applied to the walls of the cell forces the anode material from the reservoir 66a through conduit 68 to the electrochemical cell (not shown) and the reaction products back to chamber 66b through second conduit 70. This "compressible" storage container is designed with walls of sufficient thickness and sufficient elasticity to allow the pressure of a hand on the walls of the storage container to "squeeze out" a volume of fuel from the storage container. Although a human hand is schematically depicted in the drawings, it is contemplated that an external compression device may be used. One preferred method may apply radial pressure to the reservoir chamber walls in a "squeeze action" to evenly distribute the fuel.

Referring now to fig. 5, another embodiment of a storage container 72 is illustrated, which includes a body 74, and a plunger 76. The plunger 76 includes a piston 78 having a seal assembly 79 and defining oppositely variable volume chambers 80a, 80b to provide the functions discussed in detail above. A pair of conduits 82, 84 communicate with chambers 80a, 80b, respectively. The plunger 76 includes an extended hollow body 86 and a handle portion 88 to facilitate gripping thereof. Conduit 84 passes through the hollow body 86 and joins with chamber 80b as shown. As shown, when the plunger 76 is advanced to the left, the volume of chamber 80a is reduced and the volume of chamber 80b is simultaneously increased, thereby forcing new fuel out of chamber 80a and allowing reaction products or waste to be collected in chamber 80 b.

It is to be understood that the foregoing drawings and description of the invention are for illustration only and that obvious modifications may be contemplated by those skilled in the art without departing from the scope of the invention as defined by the appended claims. Although the examples are illustrated and described with respect to a metal air tank and a battery, the single storage container of the present invention is well suited for general use with any energy conversion device that requires the collection or storage of waste or reaction products.

Claims (19)

1. A storage vessel for storing a quantity of fuel and a quantity of effluent for an energy conversion system having at least one energy conversion device, the storage vessel comprising:

a container body connectable to the at least one energy conversion device and comprising at least two oppositely varying volume chambers within the container body for storing a quantity of fuel and receiving a quantity of effluent, respectively; and

means for reducing the volume of said first chamber while simultaneously increasing the volume of said second chamber.

2. An energy conversion system, comprising:

a storage vessel comprising at least two oppositely varying volume chambers within the vessel body for storing a quantity of fuel and receiving a quantity of effluent, respectively;

means for reducing the first chamber volume while increasing the second chamber volume.

At least one energy conversion device;

first means for transferring fuel between said at least one energy conversion means and said first chamber in said storage vessel; and

second means for communicating exhaust between said at least one energy conversion means and said second chamber in said storage container.

3. The energy conversion system according to claim 2, wherein the at least one energy conversion device comprises a fuel cell element comprising a cathode, and the storage container is adapted to store a quantity of electrochemical anode material, and a quantity of reaction products.

4. The energy conversion system according to claim 3, further comprising:

means for regenerating the reaction products into new electrochemical anode material in the storage vessel; and

means for changing the respective volumes of said first and second chambers when new anode material is transferred to the fuel cell element and reaction products are transferred to the storage container.

5. The energy conversion system according to claim 3, wherein the first means for transporting and the second means for transporting each comprise at least one conduit coupling the at least one fuel cell element to the storage chamber, each conduit comprising an electrically insulating valve to selectively enable transport of fresh anode material and reaction products to/from a single fuel cell element in a group of cell elements electrically connected to each other.

6. The energy conversion system according to claim 3, wherein the first chamber comprises a first sub-chamber for containing fresh anode material and a second sub-chamber for containing electrolyte for the at least one fuel cell element, and the system further comprises means for mixing fresh anode and electrolyte material from the respective first and second sub-chambers prior to delivery to the at least one fuel cell element.

7. The energy conversion system according to claim 6, wherein the second chamber comprises a first sub-chamber containing the anodic reactive material and a second sub-chamber containing the spent electrolyte, and the system further comprises means for separating the anodic reactive material from the spent electrolyte.

8. The energy conversion system according to claim 3, wherein the anode material comprises a metal and the cathode comprises an air depolarizing element.

9. The energy conversion system according to claim 8, wherein the anode material is a fluid paste consisting of 65 wt% of metal particles, and 35 wt% of a gel electrolyte.

10. The energy conversion system according to claim 9, wherein the gel electrolyte comprises up to 5% polyacrylamide, 35% KOH, and water.

11. The energy conversion system according to claim 3, wherein the cathode is contained within a gel separator element.

12. The energy conversion system according to claim 1, wherein the storage container has at least one flexible wall and the system comprises means for compressing the flexible wall to force anode material out of the storage chamber and into the at least one fuel cell element.

13. The energy conversion system according to claim 3, wherein the cathode comprises a metal foam substrate having an active layer and a hydrophobic microporous gas diffusion layer on at least one surface of the metal foam substrate.

14. A method for supplying fuel to and collecting effluent from an energy conversion device in an energy conversion system, comprising the steps of:

connecting a storage container to the energy conversion device, the storage container having at least two chambers to supply a quantity of fuel to the energy conversion device and to receive effluent from the energy conversion device, respectively; and

reversing the volume of the first and second chambers in the reservoir chamber to supply fuel to the energy conversion device and to receive exhaust from the energy conversion device.

15. The method of claim 14, further comprising the steps of:

separating the vessel from the energy conversion device;

converting the effluent to fuel within the vessel; and

reconnecting the vessel to the energy conversion device to supply fresh fuel from the second chamber and collect effluent in the first chamber.

16. A method of supplying fuel to at least one fuel cell element and collecting reaction products from at least one fuel cell element in a fuel cell power system, comprising the steps of;

connecting a storage container having at least two chambers to a fuel cell to supply anode fluid to and receive reaction products from the fuel cell element, respectively; and

the volumes of the first and second chambers in the reservoir chamber are inversely varied to supply anode fluid to the fuel cell and to receive reaction products from the fuel cell element.

17. The method of claim 16, further comprising the steps of:

separating the container from the fuel cell;

converting the reaction product in the second chamber to fuel; and

reconnecting the container to the fuel cell to supply fresh anode fluid from the second chamber to the fuel cell and to receive reaction products in the first chamber.

18. A fuel supply system for at least one fuel cell stack, comprising:

a storage vessel for storing a quantity of electrochemical anode material and a quantity of reaction products, the storage vessel comprising at least two compartments of oppositely varying volume;

a first means for transferring anode material connected between at least one cell in the storage container and the first chamber in the storage container;

second means for conveying a reaction product between the battery and said second chamber in said storage container;

means for varying the respective volumes of said first and second chambers as new anode material is delivered to said cell and reaction products are delivered to said storage container.

19. The fuel supply system of claim 18, further comprising:

means for regenerating the reaction product in the storage container to a new electrochemical anode material after the reaction product is removed from the cell; and

means for varying the respective volumes of said first and second chambers as new anode material is delivered to said cell element and reaction products are delivered to said storage container.