WO2010066460A1 - Fuel cell system with reformer - Google Patents

Abstract

Fuel cell system comprising at least one reformer with at least one high-temperature fuel cell, characterized in that the reformer (s) (1, 9) is/are constructed using a material or a combination of materials having a reforming effect, whereby said reformer is in the immediate proximity of at least one high-temperature fuel cell and/or encloses at least one high-temperature fuel cell (2).

Description

Fuel cell system with reformer

The invention refers to a fuel cell system comprising a reformer, whereby said reformer preferably is inte- grated into said system.

Fuel cells have long been known as tertiary galvanic elements. Among the various fuel cell types, solid oxide fuel cells have placed themselves in an excel- lent position due to the largest flexibility of the fuel. However, in general, these types of fuel cell cannot convert all oxidizing gases or fluids without difficulties, in particular, fuel cell types with anodes based on nickel tend to a carbon deposition if hydrocarbons are used as fuel (Handbook of Fuel Cells Fundamentals, ISBN: 0-471-49926-9) . Therefore, the application of a reformer in this type of technology and if hydrocarbon-rich fuels are used, is in many cases essential. However, in order to make the system for mobile or portable applications attractive, it is necessary to construct a compact reformer and in particular to use the generated or consumed heat as efficient as possible, and to use said heat immediately in situ in other heat-consuming or heat -producing components (e.g. fuel cells, heat exchangers, burners) in order to compensate for the thermal losses, in particular in case of smaller systems with high- temperature fuel cells, in order to minimize the sys- tern costs or to increase the efficiency.

Systems of high- temperature fuel cells for lower output ranges present the problem that high working temperatures (several 100 ⁰C), which are required for the operation, are difficult to achieve due to the low heat generated by the system itself. This makes it difficult to guarantee the operating temperature necessary for high- temperature fuel cells in small systems. On the other hand, and depending on the sys- tern design, in particular in the case of larger systems, this makes it necessary to dissipate the waste heat that is produced in the fuel cells as effectively as possible. Depending on the system requirements and/or the type of reformer (e.g. steam reform- ing, partial oxidation reforming) used, the objective of the present invention is, among other things, that the reactions taking place in the reformer supply heat to or remove heat from the fuel cell system in an efficient way and as compact as possible.

The problem to be solved by the invention comprises the provision of a compact fuel cell system, in particular for mobile and portable applications, whereby an increased efficiency can be achieved. According to the present invention this problem can be solved with fuel cell system exhibiting the features of claim 1. Advantageous embodiments and further developments of the invention can be achieved by means of the features disclosed in subordinate claims .

A fuel cell system with reformer according to the present invention comprises at least on high- temperature fuel cell. At least one reformer is constructed of a material that has a reforming effect and whereby said reformer is in the immediate proximity of at least one high- temperature fuel cell or high- temperature fuel cell stack or whereby said re- former encloses said fuel cell or fuel cell stack. Microtubular solid oxide fuel cells are preferred.

The material/material combination used for the construction of the reformer (s) or at least one sub- strate of the component (s) with reforming effect should be open porous and/or fitted with gas channels and therefore should be gas -permeable .

A material with reforming effect can be coated or en- capsulated - in particular if said material is used for the separation of gas chambers and/or for increased compatibility with the existing conditions.

The present invention is preferably used with micro- tubular SOFCs, since said SOFCs exhibit a very high resistance towards variations of temperature or temperature gradients. This allows for the use of a simple thermal management system and with that the control of the reformer(s), in particular under changing operating conditions. In a preferred variant, the reformer can further be utilised as electrical contact of at least one of the two electrodes of the SOFCs used, whereby costs, size and weight can be further optimised.

In a fuel cell system according to the present invention, the reforming material of the reformer can be located in the immediate proximity of an electrode of at least one high- temperature fuel cell. At least one fuel cell of the system can also be directly enclosed by the reforming material or a combination of such material. Thus, an intensive exchange of thermal energy through radiation, convection and thermal conduction can be achieved.

Preferably, the reforming material can be located in the proximity or can enclose the outer electrode of one or several tubular fuel cells and/or fuel cell stacks, whereby said electrode can be the anode or the cathode .

The reforming material can be gas-tight or gas- permeable encapsulated and thus, can be completely or in part spatially separated from the atmosphere of the electrode, located in the immediate proximity. If the reformer is only partly separated (gas exchange of 1 - 99 %, preferably 2 - 10 %) from the atmosphere of the electrode, and if an oxidisable atmosphere is on the reformer side (e.g. reformate with a high concentration of hydrogen) and an oxidizing atmosphere (e.g. air) on the side of the outer electrode, the occurring reaction caused by the mixture can lead to a heat increase. This allows the emission of heat to the fuel cell(s) and/or the reformer. In particular during the endothermic reforming reactions (e.g. wa- ter vapour reformation of hydrocarbons) , said heating process can positively affect the successful reforma- tion. Furthermore, combustion products (e.g. water, carbon dioxide) can lead to a more stable operation of the reformer - in particular through the reduction of a potential carbon deposition (soot formation) . The heat production can also lead to a fast start-up process of the fuel cells. By way of example, such partial mixture can be achieved if the separating wall/layer is porous. Depending on the pressure difference, porosity, concentration difference, tempera- ture and/or exchange interface between both atmospheres, flow direction and amount of gas exchange (and therefore the heat production) can be affected. A preferred embodiment of the invention comprises one or several reformer (s) or the substrate (s) of the re- former (s) whereby the reformer (s) or the substrate (s) of the reformer (s) are constructed from or the reforming material is encapsulated in a gas-tight plate or plate-like structure whereby said plates comprise recesses or concavities for one or several tubular fuel cells and/or fuel cell stacks and whereby said recesses or concavities enclose partially or entirely the outside of the fuel cells or fuel cell stacks so that the atmosphere of the outer electrode (s) of the fuel cell(s) can flow past the reformer and whereby an oxidising component can flow past the side of the separating wall/plate facing the fuel cells and/or fuel cell stacks and the reforming reactions can take place on the side of the separating wall/plate facing away from the fuel cells and/or fuel cell stacks or whereby an oxidising component can flow past the side of the separating wall/plate facing away from the fuel cells and/or fuel cell stacks and the reforming reactions can take place on the side of the separating wall/plate facing the fuel cells and/or fuel cell stacks. Thus an intensive heat exchange between both gaseous atmospheres is possible. The outer electrode of a tubular fuel cell to which a reformer is attached, can also be a cathode if the gas chambers of the cathode and of the immediately ambient reformer gases are completely or at least partially separated, or if said fuel cell is a single chamber fuel cell.

While the reforming reaction takes place, the reforming material of the reformer can emit heat and thereby can be used to heat the fuel cells and the system, or said material can consume heat and thereby contribute to the cooling of the fuel cells and the system. Said reforming material can also have a neutral effect on the system's thermal balance. Ceramic can be used for the reforming material, whereby said ceramic can also be coated with a substance/material that has a reforming effect. A mixture of metal and ceramic, whereby said mixture contains a reforming metal, can also be utilised. Said metal can additionally or alternative also be added or simply mixed in, in order to prevent the extent of an undesirable carbon deposition (e.g. Cu) and/or in order to increase the electrical conductivity of the reformer.

Preferred is a reforming material/combination of materials and/or a substrate (if available) that is electrically conductive - in particular under operating conditions - and these components can serve as current collector for all or parts of the generated electrical power in the fuel cell system, and whereby said electrical power is transferred to other system components, such as heat exchangers, fuel pipes, e- lectrical contacts. In all such embodiments the use of electrical insulation devices will prevent an e- lectrical short circuit between the anodes and cath- odes of the fuel cell system. Said insulators can be made of plastic, ceramic, glass or metal with non- conductive surface layers (e.g. ceramic oxide) . Preferably, the material (s) with reforming effect contained in the reforming component (s) are selected from a reforming metal and/or ceramic, whose activity can be increased by addition of additional substances. Said material can also be applied to the surface of a preferably ceramic or metallic sub- strate . As catalytically active materials, noble metals are preferred (preferred are Pt, Rh, Pd, Ru, Ir, Ag, Au) and/or metals of the subgroup elements (transition metals) (preferred are Ni, Fe, V, W, Mo, Co, Ce, Cu) and/or non-metallic inorganic/ceramic com- pounds (preferred are perovskite, nickelate, copper oxide, zinc oxide) . In order to increase the activity, additives are mixed into the compounds, whereby alkali or alkaline earth metals are preferred. Substrates, which can also have activating effects, can be made of magnesium oxide, aluminium oxide and/or an ion conductive compound, in particular an oxygen ion conductive compound such as doped zirconium oxide, doped cerium oxide, doped gallate and/or doped bismuth oxide or metal such as high- temperature steel can be used. Especially preferred are steels with a ceramic-coated surface, and whereby said surface is coated with a catalytic active material . Combinations of the afore-mentioned compounds (e.g. as alloy) are also possible according to the invention.

The reforming material and/or a substrate of the reforming material can be inserted into the space intended for this purpose, even after the fuel cells have already been installed. Said material can be in- serted as suspension, powder or paste and can be cured subsequently. The curing process can be ini- tialised chemically or physically, where by way of example thermal treatment and/or pressure reduction, additional chemical agents (e.g. precipitating agents, polymerization additives) or radiation (e.g. micro waves, ultraviolet light) can be used. A substrate material for a reforming material or such component can also be applied. To do this, aforementioned procedures can be used. A catalytically active or reforming component can also be applied by means of precipitation from a solution or for example by way of sputtering. The reforming material or its substrate can also contact the outer electrode of a tubular SOFC directly. The reformer or at least its substrate can be manufactured by means of a ceramic process. Said process can be an injection moulding process. To manufacture the reformer, also extrusion can be used or the manufacturing of a porous polymer foam, whereby said foam is subsequently coated with ceramic; a thermal treatment thereafter results in a ceramic structure. By way of example, metallic substrates can be foams or meshes. During the manufacture of the fuel cell system, the reformer can be inserted into the system after the installation of the fuel cell(s), which can be achieved by injecting a foam, spraying, dipping, pumping, plasma-coating, electrochemical separation, electrophoretic deposition and/or sputtering. The cells can be inserted subsequently into reformer, and said reformer exhibits the appropriate recesses for the fuel cells and/or system components (e.g. pipes, afterburner, heat exchanger) , whereby said recesses are already formed during the manufacturing process (e.g. by burning out of lost form elements made of plastic or carbon or other compounds that can be burned out, but also form elements can be etched out or dissolved away) or by using subsequent mechanical processing (e.g. drilling, milling) or using chemical processes (e.g. etching) . Channels to supply the fuel cells with gases and/or for the media flow through the reformer can also be manufactured for the fuel cells according to manufacturing of the recesses. A combination of all above processes can also be applied.

In order to improve the electrical contact between fuel cell and reforming material, an additional pref- erably porous layer can be appliedand/or at least one additional contact (e.g. a metallic web made of silver, nickel, steel, copper) between fuel cell and reforming material can be installed. By way of example, said layer can consist of a ceramic and/or metallic component ( s ), which exhibit a high electrical conductivity and is stable under certain given operating conditions. If the reformer is encapsulated and the atmosphere of the outer electrode is oxidizing (e.g. air), noble metals such as Ag, Au, Pt, Ru, Ir, Rh, Pd, high- temperature steels (if necessary coated in order to reduce the vaporisations of chromium or other compounds that can damage cell and/or system components) , ceramic compounds such as perovskite or nickelate can be used. Under reducing conditions, oxidizable materials can also be used, e.g. nickel, copper, cobalt or iron. By way of example, said layers can be applied by dipping, pumping, squirting, spraying, plasma-coating, electrochemical deposition, electrophoretic deposition, sputtering and/or pre- cipitation. By way of said layers the electrical contact between the reformer or its encapsulating material and the adjacent electrodes can be realised. In a preferred embodiment of the fuel cell system is/are one or several heat exchangers and/or afterburners arranged in the immediate proximity of one or several reformers . This can lead to an intensive heat ex- change between said components and the reformer (s) . In particular, this can be realised whereby the reformer (s), which can also be gas-tight encapsulated, contains recesses which provide the space required for one or several integrated afterburner (s) and/or heat exchangers. In addition or as an alternative one or several of said system components can be attached to or located in immediate proximity of one or several reformer (s) . The direct or indirect spatial vi- cinity of said system components and fuel cell(s) or fuel cell stacks can also be advantageous, whereby this can be a result of an arrangement of the system components inside or in the vicinity of the reformer. Also advantageous is an additional combination of the reformer with an ignition mechanism (electrical, piezo ignition, mechanical spark generation, etc.) and/or external burners in order to heat the system to its operating temperature or whereby said burners acts as a general additional heating system. A fuel cell system according to the invention also offers the option to utilise the supplied amount per time unit of at least one - at least under reforming conditions - gaseous reactant to control the temperature and/or the performance and/or efficiency of the system or parts of the system. By way of example, and in case of a POx (partial oxidation) reformer, an increased oxygen/fuel ratio can be used to start up the system, i.e. a larger amount of air, at a constant supply of fuel, , which leads to a larger amount of complete oxidation inside the reformer and which causes a higher heat production. By selecting the appropriate fuel and/or catalyst, the starting of an exothermic reaction, and with that an increase in heat, is already possible at low temperatures (e.g. this can apply to noble metals and hydrogen, alcohols and hydrocarbon at room temperature) . The option to select an additional burner for heating the system to its operating temperature is also available. If necessary, an external igniter (e.g. filament, piezo ig- nitor, spark-generating mechanism, heated noble metal wire) can also be used to ignite the reaction in the reformer. Once the operating temperature has been reached, the oxygen/carbon ration is reduced, which in turn will reduce the heat production and simultaneously increases the system's efficiency. In order to cool down the system, generally a smaller quantity of reactant is supplied; if necessary, the oxygen/carbon ratio is increased again in order to prevent or reduce the undesirable deposition of carbon inside the system. Based on the high resistance against temperature changes of the microtubular fuel cells, which are preferably used, it is possible to cool down the reformer very rapidly and complex control systems are unnecessary. Since this embodiment uses microtubular cells, temperature fluctuations in- side the reformer during the operating mode do not pose any difficulties. Said resistance to variations of temperature allows for a very compact design, which enables the reformer to be cooled down as well, e.g. by means of increased air supply in the cathode segment of the used fuel cells, which in turn reduces the number of valves, regulator components and other peripheral devices .

The following figures are given by way of example to illustrate the invention.

The accompanying drawings show:

Figure 1 an example of an integrated reformer;

Figure 2 an example with several microtubular SOFCs; Figure 3 an example of an integrated reformer and additional gas channels;

Figure 4 another example of the invention;

Figure 5a & 5b an example showing the reformer encapsulated with a separating wall;

Figure 6a & 6b another example;

Figure 7a & 7b an example showing the reformer with an integrated heat exchanger;

Figure 8a & 8b an example with heat exchangers;

Figure 9 an example with an afterburner;

Figure 10 an example with a peltier element;

Figure 11 an example with a pipe;

Figure 1 shows an example of an integrated reformer

1, which encloses a microtubular SOFC or a stack of microtubular SOFCs 2, whereby said SOFCs are made of at least one inner electrode 3 an outer electrode 5 with one electrolyte 4 located between said electrodes 3,5.

The SOFC system shown in Figure 2 comprises more than one microtubular SOFC or stacks of microtubular SOFCs

2, whereby said SOFCs are directly enclosed by the integrated reformer 1.

The SOFC system shown in Figure 3 illustrates gas channels 6 installed or recessed into the integrated reformer 1, whereby said gas channels improve the gas supply to the outer electrodes 5 of the microtubular SOFCs or of the stacks of microtubular SOFCs 2.

In order to simultaneously tap the electrical current of one of the electrodes of the microtubular SOFCs 2 - preferably of the outer electrode 5 - reformer 1 can be utilised. In the preferred schematic arrangement shown in Figure 4, a direct contact exists - op- tionally by means of additional intermediate layers or other electrically conductive devices - between the outer electrode 5 of the microtubular SOFCs 2 or the electrical contacts of the outer electrode 5 of the stacks of the microtubular SOFCs 2 and the inte- grated reformer 1, which in this case is also electrically conductive. The outer current tap takes place via the electrical power contact 7 adjacent to reformer 1.

Figure 5 shows an example whereby the reformer 9 is encapsulated with a separating wall 10. Inlet pipe 8 supplies reforming gas or gas mixture to reformer 9 and through discharge pipe 15 the reformate leaves reformer 9. In this case, inlet and discharge pipe 8 and 15 respectively, are fitted with a thread in order to provide a connection to additional gas distribution units. Fuel cells or fuel cell stacks 2 are embedded into reformer 9 and outer electrode 5 is e- lectrically connected with reformer 9 via electri- cally conductive ligaments 12. The inner electrodes 3 of fuel cells 2 are connected via gas distribution units 13a and 13b, whereby said gas distribution units 13a and 13b can also serve as current tap of said electrodes 3. Supply of the gas (mixture) to the inner electrodes 3 takes place via pipe 11 through the gas distribution unit 13a and the discharge takes place via discharge pipe 14, gas distribution unit 13b is connected to gas discharge pipe 14. A onesided attachment of reformer 9, a complete enclosure of the entire fuel cells 2 including gas distribution units (13a, 13b) or an enclosure of a fuel cell stack with reformer 9 is also possible. Reformer 9 can comprise of a metal housing, preferably made of high- temperature steel, and the said steel can be coated with ceramic, oxidic or other protective layers (e.g. LSM, LSCF) in order to prevent vaporisation of the chromium. A ceramic housing or metal/ceramic housing can also be used, whereby reforming active metal is applied to the inner side of said housing. By way of example, the active material can be a mesh, a packed bed, foam or similar material. For clarity reason

Figure 5a shows a cross section with the interior of the system partially visible (e.g. fuel cells) . Figure 5b shows a similar cross section vertical to the cross section in 5a.

For clarity reason Figure 6a shows a cross section with the interior of the system partially visible (e.g. fuel cells) . Figure 6b shows a respective vertical cross section of a fuel cell system similar to the system shown in Figure 5. In this system, heat exchanger 35 for air was added into reformer 9. The dissimilar media of reformer 9 and heat exchanger 35 are passed through separate channels within reformer 9, which prevents mixing of the media in reformer 9. Air is supplied to the heat exchanger 35 integrated into reformer 9 via connection 16, which is equipped with a thread in order to connect to other fittings; said air leaves the heat exchanger 35 via pipe 17. Pipe 17 is connected to the gas chamber of the outer electrode (s) 5 of the tubular fuel cells or fuel cell stacks 2 via a bore 18, whereby cool or preferably warmed gas enters the gas chamber of the outer electrode 5 via the heat exchanger 35, which in turn is in intensive thermal exchange with reformer 9. The exhaust gas of the outer electrode (s) 5 then leaves through bore 19 for example. Said exhaust gas can a- gain be utilised for further conversions (e.g. supply- to an afterburner, following fuel cells) or can be used for additional heat exchange. Here, the exhaust gas/product gas of reformer 9 can be supplied - if necessary, electrically isolated via ceramic tubes or other isolation options - via inlet pipe 15 to supply pipe 11 to the inner electrodes 3 of the tubular fuel cells 2.

Figure 7 shows an example with reformer 9. Housing 22 of reformers 9 comprises a metal block or a ceramic block or a block made of a mixture of ceramic and metal, whereby if necessary said block can be partially hollow in order to reduce weight and save costs. Re- actors, which are constructed of foils, and whereby said foils comprise channels, which are pressed in, etched in, carved in by laser, milled in or applied by any other means, can also form reformer 9. The medium to be reformed, e.g. hydrocarbon or alcohols mi- xed with air, oxygen or water vapour, is passed through pipe 20. The inner wall of the pipes can be coated with catalytically active material and/or the material of the inner wall of pipe 20 can comprise catalytically active material. Pipes 20 can also be filled with active material. By way of example, the latter can comprise powders, foams, meshes or monoliths. Preferably, the inner walls are made of steel, whereby a ceramic layer is formed when oxidization by air occurs. Catalytically active components can be applied by using processes such as impregnation, vapour coating, dipping, electrochemical deposition, spraying, chemical vapour deposition (CVD) , physical vapour deposition (PVD) or any other common ceramic or chemical or physical process. The reforming material enters the reactor at 8 and exits the reactor at 15. Air is supplied via connection 17 and exits the reactor at 16. Pipe 21 is the air pipe. The immediate proximity of pipe 20 and 21 enables an intensive heat exchange between both media. Preferably, the pipes have a free flow cross section, which will prevent back flash and/or uncontrollable combustion. By way of example, this can be prevented by utilising so- called micro channels or by filling the inside of the pipes with powders, foams, monoliths or mesh. The critical free flow cross sections are dependent on pressures, concentrations and temperatures. Typically, said cross sections should be less than 2 mm, preferably less than 0.5 mm. Figure 7a shows side A and Figure 7b shows side B. For clarity reasons, some hidden pipes were shown as visible objects.

Figure 8 shows a system similar with Figure 5. In this case, a heat exchanger 24 is shown on the upper surface of Figure 8a, whereby said heat exchanger is used to preheat the atmosphere (e.g. air) for the ou- ter electrode 5 of the tubular SOFCs or stacks of solid oxide fuel cells 2. The reformer 9 is encapsulated and thus, separated from the atmosphere of the outer electrodes 5. In this example reformer 9 is shortened in the direction of side (C) , so that the outer electrodes of the fuel cells or fuel cell stacks 2 are partially not enclosed by reformer 9. In this direction, heat exchanger 24 is elongated and encloses the flow channels of the outer electrodes 5 on side (C) . By using a sealing element (e.g. high- temperature adhesive, metal solder, glas solder, etc.) 23 a preferred flow direction along the direc- tion of side (C) to side (D) can be adjusted. The atmosphere of outer electrode 5 enters heat exchanger 24 via inlet pipe 26. Flow channels (omitted for clarity) are contained in heat exchanger 24, whereby said flow channels guide the fluid through said heat exchanger along side (C) . Sealing element 23 provides a gas-tight connection between heat exchanger 24 and fuel cells or fuel cell units 2, whereby the gas chamber of the outer electrodes 5 of the cells or stacks 2 is separated in direction of side C. At these points the fluid from heat exchanger 24 enters the gas chamber of outer electrode 5 (not shown) , which causes a flow in the direction of side D in the gas chamber of outer electrode 5. Figure 8a below shows an additional heat exchanger 25, which allows an intensive heat exchange between the gas to be reformed and reformer 9. The gas to be reformed, enters heat exchanger 25 via inlet pipe 27 and, by way of example, exits said heat exchanger via pipe 25b, which fluidly connects heat exchanger 25 with reformer 9 via a gas fitting 8 of reformers 9.

Figure 9 shows a system similar to Figure 8. For clarity reason Figure 9 shows a cross section with the interior of the system partially visible (e.g. fuel cells) . In this case, an afterburner 28 was added to the system. By way of example, exhaust gas/product gas of reformer 9 reaches the inner electrode 3 of fuel cell 2 via pipe 30, whereby the released exhaust gas of inner electrodes 3 of fuel cells 2 reach afterburner 28 via pipe 32. Here, said exhaust gas of inner electrode 3 reacts with the exhaust air of outer electrode 5 of the tubular fuel cell 2 and whereby said air is supplied to afterburner 28 via pipe 31. Preferably, said afterburner 28 is a catalytic burner, especially preferrably a porous burner or a burner comprising micro channels. The energy of afterburner's 28 exhaust gas, which by way of example, exits at connection 29, can be used further (e.g. heat exchanger, peltier element, partial return to the reaction chamber of the reformer, fuel cells) . The installation of a jet pump between the cathode gas chamber and afterburner 28 and between the anode gas chamber and afterburner 28 is also beneficial. This way, a pressurised reformate can ingest air or vice versa.

Figure 10 shows a fuel cell element, which is constructed similar to the element shown in Figure 1. By way of example, a peltier element 33 encloses re- former 1, whereby said peltier element is additionally surrounded on the outside by a heat consuming element (e.g. reformer, heat exchanger, ventilation channel, ambient cold temperatures) or a heat emitting element 34 (e.g. reformer, burner, heat ex- changer) . Preferably, the system is built in such a way that in the peltier element 33 the largest possible temperature difference is available.

Figure 11 shows an example, whereby a pipe 35 is pas- sed through reformer 1 and said pipe can serve to heat up or cool down a medium, which flows through pipe 35. Preferably, said pipe absorbs heat in case of an exothermic reaction of reformer 1 and emits heat in case of an endothermic reaction in reformer 1.

Claims

Claims

1. Fuel cell system comprising at least one reformer with at least one high- temperature fuel cell, characterized in that the reformer (s) (1,

9) is/are constructed using a material or a combination of materials having a reforming effect, whereby said reformer is in the immediate proximity of at least one high- temperature fuel cell and/or encloses at least one high- temperature fuel cell (2) .

2. Fuel cell system according to claim 1, characterised whereby one or several high- temperature fuel cell(s) (2) are builded as microtubular solid oxide fuel cells.

3. Fuel cell system according to claim 1 or 2 , characterised in that the material/material combination that has a reforming effect is at least partly open porous and/or gas channels are built into the reformer.

4. Fuel cell system according to one of the preceding claims, characterised in that a ceramic material with a reforming effect is used.

5. Fuel cell system according to one of the preceding claims, characterised in that the material with a reforming effect is applied as a coating to the surface of a ceramic or metallic substrate or to the surface of a substrate made of a mixture of ceramic and metal.

6. Fuel cell system according to one of the preceding claims, characterised whereby the material with a reforming effect is a metal, a metallic alloy, a ceramic or a mixture of ceramic and metallic components.

7. Fuel cell system according to one of the preceeding claims, characterised in that at least one additional material/additiv exhibiting or promoting a higher catalytical activity is contained in and/or coated on the material that has a reforming effect.

8. Fuel cell system according to claim 7, characterised in that the catalytically active materials/additives are noble metals such as Pt, Rh, Pd, Ru, Ir, Ag, Au and/or other metals of the subgroup elements (transition elements) and/or a non-metallic inorganic/ceramic compounds such as perovskites , nickelates, copper oxide, zinc oxide.

9. Fuel cell system according to claim 7, characterised in that the material exhibiting a higher catalytical activity is an alkali or alkali earth metal.

10. Fuel cell system according to one of the preceding claims, characterised in that one substrate with preferably catalyzing effect is made of magnesium oxide, aluminium oxide and/or an ion conductive compound, in particular a oxygen ion conductive compound such as doped zirconium oxide, doped cerium oxide, doped gallate, doped bismuth oxide or a metal such as high- temperature steel.

11. Fuel cell system according to one of the preceding claims, characterised in that a coating is applied to the material with the reforming effect, of which the reformer (1, 9) is built, and/or where said material is encapsulated .

12. Fuel cell system according to one of the preceding claims, characterised in that the reformer (s) (1, 9) is/are encapsulated gas-tight or permeable to gas and thereby entirely or partially spatially separated from the atmosphere of at least one electrode (3 or 5) .

13. Fuel cell system according to one of the preceding claims, characterised in that the reformer (1, 9) or the substrate of the reforming component is at least partly open porous or constructed in form of a mesh.

14. Fuel cell system according to one of the preceding claims, characterised in that each individual fuel cell and/or one or several bundles of fuel cells (2) is/are surrounded by one or several reformers (1, 9) .

15. Fuel cell system according to one of the preceding claims, characterised in that the reformer (s) (1, 9) or the substrate (s) of the reformer (s) (1, 9) are constructed from or the reforming material is encapsulated in a gas- tight plate or plate-like structure whereby said plates comprise recesses or concavities for one or several tubular fuel cells and/or fuel cell stacks and whereby said recesses or concavities enclose partially or entirely the outside of the fuel cells or fuel cell stacks so that the atmosphere of the outer electrode (s) of the fuel cell(s) can flow past the reformer (1, 9) and whereby an oxidising component can flow past on the side of the separating wall/plate (10) fac- ing the fuel cells and/or fuel cell stacks (2) and the reforming reactions can take place on the side of the separating wall/plate (10) facing away from the fuel cells and/or fuel cell stacks (2) or whereby an oxidising component can flow past the side of the separating wall/plate (10) facing away from the fuel cells and/or fuel cell stacks (2) and the reforming reactions can take place on the side of the separating wall/plate (10) facing the fuel cells and/or fuel cell stacks (2) .

16. Fuel cell system according to one of the preceding claims, characterised in that one or several heat exchanger (s) (34) and/or afterburner (s) (28) and/or peltier element (s)

(33) and/or additional reformer (s) is/are arranged in the immediate proximity of the reformer (1, 9) .

17. Fuel cell system according to one of the preceding claims, characterised in that the reformer(s) (1, 9) is/are electrically conductive .

18. Fuel cell system according to one of the preceding claims, characterised in that additionally fuel cells and/or fuel cell stacks

(2) are surrounding the reformer (s) (1, 9) .