FUEL CELL SYSTEM FOR PORTABLE APPLICATIONS

Abstract

A fuel cell system component includes a glass ceramic composite.

Claims

1. Fuel cell system component, wherein the fuel cell system component comprises a glass ceramic composite.

2. Fuel cell system component according to claim 1, wherein the glass ceramic composite comprises a fluorphlogopite mica in a borosilicate glass matrix, wherein the glass ceramic composite is MACOR.

3. Fuel cell system component according to claim 1, wherein the fuel cell system component is a fuel cell (F).

4. Fuel cell system component according to claim 3, wherein the fuel cell (F) comprises a substrate made from the glass ceramic composite.

5. Fuel cell system component according to claim 3, wherein the fuel cell (F) comprises a head made from the glass ceramic composite.

6. Fuel cell system component according to claim 5, wherein the fuel cell (F) comprises a multitude of functional parts, wherein the functional parts are sandwiched between the substrate and the head, wherein the substrate and the head are linked to each other by screws and/or by a glass connection created through structure heating and/or glass sealing.

7. Fuel cell system component according to claim 1, wherein the fuel cell system component is a heating system (H) for a fuel cell system (S).

8. Fuel cell system component according to claim 7, wherein the heating system (H) comprises: a heater; and a base plate, wherein the base plate is made from the glass ceramic composite, wherein the heating system comprises a cover plate, wherein the cover plate is made from the glass ceramic composite.

9. Fuel cell system component according to claim 7, wherein the heating system (H) comprises at least one bridge for thermally decoupling a cold zone of the heating system (H) from a hot zone of the heating system (H).

10. Fuel cell system component according to claim 1, wherein the fuel cell system component is a gas processing unit (P).

11. Fuel cell system component according to claim 10, wherein the gas processing unit (P) comprises a channel plate made from the glass ceramic composite, wherein the channel plate comprises a channel network and a reformer chamber, wherein the channel network at least partly surrounds the reformer chamber, wherein the channel network comprises a multitude of fluidic channels and/or a multitude of generally parallel micro-channels.

12. Fuel cell system component according to claim 10, wherein the gas processing unit (P) comprises a reformer cover made from the glass ceramic composite, wherein the reformer cover comprises a catalyst loading window and/or a channel access hole.

13. Fuel cell system component according to claim 10, wherein the gas processing unit (P) comprises at least one bridge, for thermally decoupling a cold zone of the gas processing unit (P) from a hot zone of the gas processing unit (P).

14. Fuel cell system component according to claim 10, wherein the gas processing unit (P) comprises a heating system (H).

15. Fuel cell system (S) comprising a fuel cell system component (F) according to claim 1.

16. Fuel cell system (S) according to claim 15, wherein at least two parts of the fuel cell system (S) made from the glass ceramic composite are linked to each other by screws and/or by a glass connection created through structure heating and/or glass sealing.

17. Method for manufacturing a fuel cell (F) according to claim 3, comprising the steps: deposition of a first electrode on top of an ion conducting sheet by means of a shadow mask, installation of a first conductive grid on a substrate comprising a glass ceramic composite, wherein the substrate is made from MACOR, installation of the ion conducting sheet with the deposited first electrode on the first conductive grid, such that a contact between the first electrode and the first conductive grid is established, polishing down the ion conducting sheet, deposition of a second electrode on top of the ion conducting sheet, installation of a second conductive grid on the second electrode, and installing a head on top of the second conductive grid, such as to press the second conductive grid against the second electrode, wherein the head comprises a glass ceramic composite, wherein the head is made from MACOR.

18. Method for manufacturing a fuel cell element, comprising the step: polishing down an ion conducting sheet to a thickness of 30 μm or less.

19. Use of the material MACOR in a fuel cell system (S).

20. (canceled)

Description

BRIEF DESCRIPTION OF THE FIGURES

[0045] In the following, the disclosure is described in detail by means of drawings, wherein show:

[0046] FIG. 1: A schematic representation of a method for manufacturing a fuel cell according to the disclosure,

[0047] FIG. 2: A schematic representation of a heating system according to the disclosure,

[0048] FIG. 3: A schematic representation of a combination of a gas processing unit according to the disclosure and a heating system according to the disclosure, and

[0049] FIG. 4: A schematic representation of a fuel cell system according to the disclosure.

DETAILED DESCRIPTION

[0050] FIG. 1 shows a schematic representation of a method for manufacturing a fuel cell F according to an embodiment of the disclosure.

[0051] The fabrication process starts (see FIG. 1.1) with the deposition of anode 1 on a commercially available YSZ sheet 2 that can for example come with a minimum thickness of 100 μm and surface area of 1 cm.sup.2 or more. In some embodiments, the thickness of the YSZ sheet 2 is between 100 μm and 500 μm, preferably approximately 300 μm. In order to avoid an extensive clean-room process, the deposition is made through a shadow mask to define the electrode size and the active area.

[0052] FIG. 1.2 shows the installation of a first conductive grid 3 as current collector on top of an essentially square, frame-like MACOR substrate 4. The MACOR substrate 4 typically has a thickness (corresponding to the vertical direction in FIG. 1.2) of approximately 1 mm. Two distinct parts of the MACOR substrate 4 are visible in FIG. 1.2 (and the following FIGS. 1.3 to 1.7) because these Figures show cuts through the fuel cell F (shown in FIG. 1.8).

[0053] FIG. 1.3 shows how the combination of the anode 1 and the YSZ sheet 2 is placed on top of the conductive grid 3, such that a contact between the anode 1 and the conductive grid 3 is established. After that, the sample is heated up to approximately 1050° C. with a heating rate of 4° C./minute and the entire partial fuel cell structure shown in FIG. 1.3 is then exposed to a dwelling time of 30 minutes in order to join the YSZ sheet 2 to MACOR substrate 4.

[0054] Afterwards, the YSZ sheet 2 is mechanically polished down using diamond pads to 30 μm or less to facilitate the oxygen ion conduction at an intermediate temperature, namely a temperature of 700° C. or less. The polished-down YSZ sheet 2 can be seen in FIG. 1.4.

[0055] Next (shown in FIG. 1.5) a cathode 8 is deposited through a shadow mask onto the polished-down YSZ sheet 2 to complete the PEN membrane structure.

[0056] Finally, a second conductive grid 9 is installed on top of the cathode 8 for uniform current distribution (see FIG. 1.6).

[0057] To assure the proper connection of the second conductive grid 9 to the cathode 8, the second conductive grid 9 is pressed to the membrane using a head 10 made from MACOR with a thickness of 1 mm (see FIG. 1.7). The connection of the MACOR substrate 4 and the head 10 around the PEN membrane can be done either via screws 11, 12 or via structure heating up to 1050° C. (the same principle as for MACOR-YSZ joining as explained above). FIG. 1.7 shows the alternative with screws 11, 12.

[0058] FIG. 1.8 shows a schematic, perspective view of the final fuel cell F. In addition to the previously described elements of the fuel cell F, FIG. 1.8 also shows two electrical connections 13, 14. The fuel cell F shown in FIG. 1.8 is essentially square. It can for example have a side length between 1 cm and 10 cm.

[0059] FIG. 2 shows a schematic representation of a heating system H according to the disclosure. The heating system H comprises a base plate 19 and a cover plate 15. The base plate 19 comprises a thick-film heater comprising two separate heating strips 17.1 and 17.2, namely an outer heating strip 17.1 and an inner heating strip 17.2. Two separate heating strips may have the advantage of being able to provide a more uniform heat distribution, but a heater comprising a single heating strip is in principle also possible. The base plate 19 comprises a hot zone and a cold zone. The hot zone and the cold zone are separated by three parallel bridges, namely a first bridge 5, a second bridge 6 and a third bridge 7. The cold zone comprises four electrical pads 18 for connecting the heater to one or more power sources (only two electrical pads 18 are equipped with reference signs and no power source is shown). The hot zone is the area of the base plate 19 which is located on the other side of the bridges 5, 6, 7 when looking at the bridges form the cold zone. The cover plate 15 comprises two opened areas 16 configured to be located on top of the electrical pads 18 when the heating system H is mounted. The arrangement of a hot zone and a cold zone may have the advantage to make it possible to use standard electrical and fluidic interconnections.

[0060] When the heating system H is mounted, the heater is sandwiched between the base plate 19 the cover plate 15, which are both made from MACOR. Thus, when the heating system H is assembled, the heater is embedded within two MACOR plates with opened access to electrical pads 18. The heater itself is fabricated using thick film processing, such as screen-printing of resistive filament, for example through a shadow mask. The material selection is dependent on the operation temperature. The filamentary structure is chosen to obtain the required resistance. In some embodiments, the filament width is 1 mm with the same spacing size between the different meanders of the filament. Narrower structures can be fabricated for better heat distribution. The resistance of the heater should be stable, drift-free and ideally present a significant temperature coefficient of resistance (TCR) that allows the heater to perform as temperature sensor at the same time. At elevated temperature, platinum thick-film is one of the most suitable solutions. The operation temperature of platinum thick-film should ideally be limited to 800° C.—the sintering temperature of platinum paste.

[0061] Another element of the disclosure, per an embodiment, is a gas processing unit for delivering the fuel from the cold zone to the fuel cell membrane, as well as on-site hydrogen production to avoid carbon coking at electrode materials. The idea is to reform the hydrocarbon fuel, propane for instance, into syngas (Fh+CO), with an on-site fuel processor. The conventional reforming systems are not compatible with micro-scale solid oxide fuel cells (SOFCs) as the system is required to be miniaturized and compact, to have accurate reforming control, as well as, showing rapid start-up and shutdown time. Therefore, foreseeing a MACOR-based gas processing unit is advantageous for a fuel cell system to have complete system compatibility and thermal shock resistivity during thermal cycling.

[0062] FIG. 3 shows schematic representation of a combination of a gas processing unit P according to an embodiment of the disclosure and a heating system H according to the disclosure. The gas processing unit P comprises a channel plate 20 made from MACOR as well as a reformer cover 25 also made from MACOR. It becomes clear from FIG. 3 that the gas processing unit 20, is configured to be installed on top of the heating system H, which can also be referred to as hotplate. In some embodiments, the gas processing unit 20 is configured to be installed below the heating system H. The cover plate 15, the base plate 19, the channel plate 20 and the reformer cover 25 can obviously also be referred to as “layers” of the structure shown in FIG. 3.

[0063] The channel plate 20 comprises a multitude of fluidic channels 21 (only one of them is equipped with reference signs for the sake of simplicity), a multitude of micro-channels 22 (only one of them is equipped with reference signs for the sake of simplicity) and a reformer chamber 23 for hosting parts of a fuel cell F (like the one shown in FIG. 1). The fluidic channels 21 are placed partly around a reformer chamber 23 and allow feeding of fuel to the fuel cell through the micro-channels 22 located on two lateral sides of the reformer chamber 23. This configuration may have the advantage to increase the entrance contact area for the fuel, thus improving thermal uniformity. The width of the fluidic channels 21 is less than 1 mm. The channel plate 20 can be seen as a micro-flow distributing structure containing a series of parallel short micro-channels 22 in a width range of 0.3 mm to 1 mm for improving flow dispersion within the reformer chamber 23. After reaction in the fuel cell, the oxidized fuel passes through the heating system H via small openings 26 in the cover plate 15 and the base plate 19 of the heating system H.

[0064] The channel plate 20 is covered with the reformer cover 25. The reformer cover 25 comprises a catalyst loading window 24 and a channel access hole 27. The channel plate 20 comprises a channel access well 28 and a feeder 29. It becomes clear from FIG. 3 that a fuel can be fed to the reformer chamber 23 through the channel access hole 27, the channel access well 28, the feeder 29, the fluidic channels 21 and the micro-channels 22 when the gas processing unit is mounted. The catalyst loading window 24 makes it possible to place a catalyst (not shown) at the end of the feeder 29, thereby allowing straight-forward catalysis of the fuel. The assembly of the different layers 15, 19, 20, 25 of the structure shown in FIG. 3 can be done either by screws or by means of heating up to 1050° C. to benefit from the glass part of MACOR for sealing. It can be observed in FIG. 3 that not only the base plate 19 of the heating system H comprises three parallel bridges: also the layers 15, 20 and 25 each comprise three bridges, wherein the bridges are configured to be congruent when the four layers 15, 19, 20 and 25 are mounted in a stacked fashion on top of each other. This configuration helps to improve the separation between a hot zone and a cold zone. In some embodiments, each layer 15, 19, 20, 25 comprises at least one, preferably at least two, more preferably at least three bridges. However, also four, five or more bridges can be foreseen.

[0065] FIG. 4 shows a schematic representation of a fuel cell system S according to the disclosure. In particular, the fuel cell system S comprises the heating system H shown in FIGS. 2 and 3, the gas processing unit P shown in FIG. 3 and the fuel cell F shown in FIG. 1. The fuel cell F is installed on top of the gas processing unit P and the gas processing unit P is installed on top of the heating system H. The mounting of these three components F, P, H of the fuel cell system S, namely of the fuel cell F, the heating unit h and the gas processing unit P, can either be carried out mechanically, using screws like the screws 11, 12 shown in FIG. 1, or by glass sealing, using the sealing capacities of the MACOR's glass component, as explained before. The electrical connections can be established with the electrical pads 18 using standard methods thanks to the thermally decoupled structure, namely the before-mentioned two zones separated by the bridges 5, 6 and 7 (these reference signs to the bridges are not shown in FIG. 4 but are shown in FIG. 2). The fuel cell system S shown in FIG. 4 typically has a length l between 4 cm and 7 cm, a width w between 3 and 5 cm and a height h between 0.4 cm and 1 cm, preferably approximately 0.8 cm. In some embodiments, a fuel system like the one shown in FIG. 4 has a length I between 5 cm and 15 cm, a width w between 3 cm and 10 cm and a height h between 0.4 cm and 1 cm, preferably approximately 0.8 cm. The bridges 5, 6, 7 typically each have a length between 0.8 cm and 1.2 cm, preferably approximately 1 cm, and each have width between 0.4 cm and 0.6 cm, preferably approximately 0.5 cm. Widths and lengths of the bridges are measured in the same directions as the respective width w and length l of the fuel cell system S. Other dimensions are possible for the bridges 5, 6, 7 and/or the fuel cell system S, depending on the respective needs. The fuel cell system S with these dimensions can be expected to deliver powers up to 10 W, with having an operating area of 10 cm.sup.2, and further assembly of the cells, such as 3-dimensional stacking, can lead to higher power delivery up to several hundreds of watts.

[0066] In some embodiments, a post combustor (not shown), preferably a post combustor similar or essentially identical to the channel plate 20, is placed below the heating system H to guarantee that remaining fuel is being flared and/or oxidized before leaving the fuel cell system S. The post combustor is typically made from the same material as the channel plate, preferably from MACOR. The fuel cell system S and all of its components are particularly adapted for use in portable applications.

[0067] In certain embodiments, the present disclosure takes a unique approach by combining large scale fuel cell technology with advanced micro- and nanotechnology to produce a miniaturized fuel cell system with embedded microchannel channels, resistive heater and gas reformer. This miniaturized fuel cell system is based on a machinable glass-ceramic, for example MACOR. With this approach, it is possible to build a complete and compact stack of fuel cells to be used as power source for portable applications. The high compatibility of MACOR's thermal expansion coefficient with a fuel cell stack reduces the impact of thermal stress during thermal cycling. Moreover, the glass part of MACOR can facilitate the hermetic sealing of all components. Finally, the use of MACOR as machinable ceramic allows complex device designs and reduces the cost of fabrication significantly.

[0068] In some embodiments, the disclosure can have the advantage of proposing a simplified manufacturing method to build an integrated fuel cell, especially a solid oxide fuel cells (SOFC).

[0069] In some embodiments, the disclosure can have the advantage of at least partly solving the thermomechanical challenge of using high temperature fuel cell technology for portable applications.

[0070] In some embodiments, the disclosure can have the advantage of presenting a modular fuel cell unit that can provide a scalable power source delivering electrical powers of a wide range, for example from 5 W up to more than 100 W.

[0071] The invention is not limited to the preferred embodiments described here. The scope of protection is defined by the claims.

[0072] Furthermore, the following claims are hereby incorporated into the Description of Preferred Embodiments, where each claim may stand on its own as a separate embodiment. While each claim may stand on its own as a separate embodiment, it is to be noted that—although a dependent claim may refer in the claims to a specific combination with one or more other claims—other embodiments may also include a combination of the dependent claim with the subject matter of each other dependent or independent claim. Such combinations are proposed herein unless it is stated that a specific combination is not intended. Furthermore, it is intended to include also features of a claim to any other independent claim even if this claim is not directly made dependent to the independent claim.

[0073] It is further to be noted that methods disclosed in the specification or in the claims may be implemented by a device having means for performing each of the respective acts of these methods.

[0074] All the features and advantages, including structural details, spatial arrangements and method steps, which follow from the claims, the description and the drawing can be fundamental to the invention both on their own and in different combinations. It is to be understood that the foregoing is a description of one or more preferred exemplary embodiments of the invention. The invention is not limited to the particular embodiment(s) disclosed herein, but rather is defined solely by the claims below. Furthermore, the statements contained in the foregoing description relate to particular embodiments and are not to be construed as limitations on the scope of the invention or on the definition of terms used in the claims, except where a term or phrase is expressly defined above. Various other embodiments and various changes and modifications to the disclosed embodiment(s) will become apparent to those skilled in the art. All such other embodiments, changes, and modifications are intended to come within the scope of the appended claims.

[0075] As used in this specification and claims, the terms “for example,” “for instance,” “such as,” and “like,” and the verbs “comprising,” “having,” “including,” and their other verb forms, when used in conjunction with a listing of one or more components or other items, are each to be construed as open-ended, meaning that the listing is not to be considered as excluding other, additional components or items. Other terms are to be construed using their broadest reasonable meaning unless they are used in a context that requires a different interpretation.

LIST OF REFERENCE SIGNS

[0076] 1 Anode

[0077] 2 YSZ sheet

[0078] 3 First conductive grid

[0079] 4 MACOR substrate

[0080] 5 First bridge

[0081] 6 Second bridge

[0082] 7 Third bridge

[0083] 8 Cathode

[0084] 9 Second conductive grid

[0085] 10 Head

[0086] 11, 12 Screws

[0087] 13, 14 Electrical connection

[0088] 15 Cover plate

[0089] 16 Opened area

[0090] 17.1, 17.2 Heating strips

[0091] 18 Electrical pads

[0092] 19 Base plate

[0093] 20 Channel plate

[0094] 21 Fluidic channels

[0095] 22 Micro-channels

[0096] 23 Reformer chamber

[0097] 24 Catalyst loading window

[0098] 25 Reformer cover

[0099] 26 Evacuation openings

[0100] 27 Channel access hole

[0101] 28 Channel access well

[0102] 29 Feeder

[0103] F Fuel cell

[0104] H bleating unit

[0105] P Gas processing unit S Fuel cell system

[0106] h Height (of fuel cell system)

[0107] l Length (of fuel cell system) w Width (of fuel cell system)