Patent Application
20110189555
The invention relates to an apparatus for supplying a fuel cell in a fuel cell system with fuel gas, especially hydrogen.
Fuel cell systems that are typically operated with hydrogen of a hydrogen-containing gas as fuel gas are basically known in the state of the art. These fuel cell systems essentially consist of a fuel cell, for example a fuel cell with a polymer membrane as electrolyte, a so-called PEM fuel cell. The fuel cell will generally consist of a stack of single cells, and thus is also referred to as a fuel cell stack. With systems of this type, an anode side of the fuel cell is supplied with the fuel gas and typically a part of unused fuel gas, which is returned from a region behind an anode side of the fuel cell to the region in front of the anode side of the fuel cell. The cathode side of the corresponding fuel cell is supplied with an oxygen-containing gas, typically air. These fuel cells then generate electrical energy from just this fuel gas and the oxygen in the air. A typical purpose of use is, for example, within the scope of electrical drive trains of vehicles.
The installation space and weight of these fuel cell systems play an important role, particularly during the construction of such a vehicle drive train in the fuel cell system. DE 10 2004 049 623 A1 discloses an end plate for a fuel cell stack, which integrates a conveyor device for a reactant, a reaction product and/or a coolant into an end plate of such a fuel cell stack.
One disadvantage with this construction is that corresponding vibrations enter into the fuel cell stack by the pump, which can affect its leak tightness. Furthermore, dismantling of the fuel cell stack is always required for maintenance of the pump, which is also a disadvantage because the stack is already sensitive with regard to its seals. The exchange of, for example the fuel cell stack or the pump, also always requires the opening of the fuel cell stack, with a subsequent resealing thereof, which is comparatively elaborate particularly with hydrogen as conveyed fuel gas.
DE 102 48 611 A1 discloses a fuel cell system and a method for preheating the fuel cell or the fuel cell stack. So as to design the preheating during a cold start or at a low temperature more efficiently and evenly, this document describes more evenly distributing the thermal energy content contained in the compacted air flowing to the cathode side of the fuel cell. For this, the hydrogen gas flowing to the fuel cell system, which serves as fuel here, is preheated via a heat exchanger via the air heated during compacting by means of a fuel air heat exchanger. Because the heat enters into the gas flow of the fuel originates from the compacted air, the available heat is only distributed differently via this construction, however, the entered heat amount is altogether not increased.
Exemplary embodiments of the present invention provide a fuel cell system with a practical construction that can be maintained easily with a minimal installation space, which is especially suitable for compact and highly loaded fuel cell systems.
The integration of most of the fuel gas relevant components, that is, especially the integration of the mixing region, a water precipitator, a device for heating the fuel gas and receptions for at least one sensor into the one integrated component part offers critical advantages during the use of the installation space available. The integrated component part enables a space-saving arrangement of the essential fuel gas conducting elements and short line lengths, and thus correspondingly low pressure losses in the fuel gas. Furthermore, the integrated component part, which can be designed independently of the fuel cell stack, can be mounted independently of the fuel cell stack, and which can be easily dismantled for maintenance. Possible vibrations or temperature fluctuations in the integrated component part are also not transferred to the fuel cell stack, and thus do not influence its tightness in a negative manner by different thermal expansions or vibrations.
Furthermore, all relevant elements are combined in the integrated component part, so that the fuel gas, especially the hydrogen, can be provided with predetermined pressure, volume flow, predetermined temperature and predetermined gas composition (for example hydrogen concentration and humidity). Water in liquid form is also discharged from the recirculated unused fuel gas. Special attention is directed to the device for heating the fuel gas. During the operation of the fuel cell system, the fuel, typically hydrogen, is supplied to the fuel cell system from a pressure storage device. This fuel is, however, often very cold because the pressure storage device is typically arranged in a region—for example of a vehicle—that is not or only minimally insulated. The fuel in the pressure storage device thus has an ambient temperature, which is rather cold compared to the typical operating temperature in the magnitude of about 70 to 100 ° C. in the fuel cell system. Furthermore, thermal energy is additionally lost from the pressure storage device during the relaxation of the fuel, so that a—at least compared to the system—very cold hydrogen—or fuel flow reaches the fuel cell system. The lower the outer temperature and the shorter time the fuel cell system is operated, the more critical is this cold fuel flow, as it shows heat sinks in the system, where water present in the gases of the system can condense out or possibly even freeze.
This effect is reduced considerably by the integrated device for heating the fuel, so that a better operation and particularly a safer and faster cold start of the fuel cell system of the device can be ensured for generating energy.
The device for heating the fuel has the further advantage, especially with a cold start of the fuel cell system, that the integrated component part itself and all components therein are also heated and can thereby possibly be defrosted, so that for example the one corresponding discharge line for water via which excess inert gases can also be blown off, is already defrosted during the start of the system and is fully functional.
The integrated component part can furthermore be designed in such a manner that it does not need an additional carrier frame, so that a corresponding installation space can be saved in addition to the reduction of the mass, construction volume and also costs, and the gas volume of the fuel gas-conducting elements is furthermore reduced considerably. The shortened line lengths enable, in addition to the compact construction, provide a reduction of the pressure losses also a reduction of the necessary sealing locations, which is an important advantage, especially with the use of hydrogen. The integrated component part can also be manufactured considerably more economical due to the integration and the omitted interface, as the requirement of manufacturing tolerances can be reduced correspondingly.
In a further very beneficial arrangement of the apparatus according to the invention, the cooling water of the fuel cell system passes through the integrated component part. This integration of the cooling water or of the cooling water supply to the fuel cell itself in the integrated component part constitutes a further advantage with regard to the line lengths and the interfaces between the lines. The cooling water is also heated via the at least one device for the at least indirect heating of the supplied fresh fuel gas, as all component parts are connected at least in an indirectly heat-conducting manner in the integrated component part. With this, not only the fresh fuel gas, but also the cooling water can be heated via the device for heating, so that the device for heating can also be used for heating the fuel cell itself, for example in a cold start situation. In reverse, heat from the cooling water can also be used for heating the supplied fresh fuel gas. With this, energy can be saved and waste heat which is present in any case can be used for heating the fresh fuel gas.
In a further very beneficial and advantageous arrangement of the apparatus according to the invention, the at least one device for the at least indirect heating of the supplied fresh fuel gas is formed as an electrical heater. Such an electrical heater can be received very simply and efficiently in the integrated component part, for example by an electrical resistor. By the very easy accessibility and thus the very simple and efficient generation of a desired heat amount in the electrical heater, the supplied fresh fuel gas can be heated very efficiently to a predetermined end temperature. Furthermore, a heating of the entire integrated component unit can take place by additional electrical heating performance, for example to preheat this during a cold start of the fuel cell system and to possibly defrost it.
In the aspect of the device according to the invention where the cooling water of the fuel cell system additionally flows through the integrated component part, the cooling water and thus the fuel cell can also be heated, so that the electrical heater can be used simultaneously as electrical starting heater, without such a heater having to be integrated additionally into the fuel cell system. Thus, with the apparatus according to the invention, the number of component parts can be reduced and the construction volume of the fuel cell system can be reduced.
In a supplemental or alternative arrangement aspect of the apparatus according to the invention, the at least one device for the at least indirect heating of the supplied fresh fuel is formed as a cooling heat exchanger for at least one heat-generating component, wherein the fresh fuel gas at least partially cools the heat-generating component. The heating of the fuel gas via a cooling heat exchanger to a heat-generating component of the fuel cell system enables it to use thermal energy already present in the fuel cell system. As a further positive side effect, the respective heat-supplying component is at least partially cooled by the fuel gas flow, so that its operation can proceed in a temperature region which is suitable for the optimum operation. The cooling heat exchanger and/or the heat-generating component can thereby also be integrated into the integrated component unit or be mounted to it.
The component can thereby be each component actively generating heat or waste heat in a fuel cell system, for example electronics or power electronics, whose waste heat has to be cooled, or also a unit with electromotive drive where the engine should to be cooled to ensure an ideal function. Such a device can, for example, be a fan or a compression unit, however, it can also be a drive motor with use in a transport means. It would be a further possibility that the fuel gas takes on the cooling of an electrochemical component, as for example of the fuel cell stack itself or a battery, which is possibly present in addition to the fuel cell stack, and heats up thereby. Here, a traction battery with a vehicle drive system can be especially considered, which can then be formed as a high performance battery, for example on the basis of the lithium ion technology. However, other components of the fuel cell system are also feasible, for example an electrically supported turbo charger for compacting the conveyed air for the cathode side or the like. Finally, other components are still also feasible, where the heat results through the processes proceeding therein, for example condensers or fluid precipitators, which generate heat through the corresponding condensation heat, which could then be transferred to the fuel. Furthermore, the heat-generating component in the context of the invention could also be a heat exchanger, which is supplied with heat from the outside in a second circuit via a medium.
This heat-generating component in the context of the invention is then cooled at least partially by the fuel flow. Depending on the respective component and the respectively demanded characteristic of the cooling, for example in the partial load operation, under full load, during idling or the like, it is possible that the respectively available fuel gas flow is not sufficient to ensure the cooling. If this is the case, the cooling via the fuel gas can also be set up as an additional cooling, so that the cooling heat exchanger is, for example, present in addition to a further cooling heat exchanger in or at the component. The cooling in situations and operating states where cooling via the volume flow of the inflowing fuel gas is not sufficient can then be ensured via this further heat exchanger for example via a conventional cooling circuit with a cooling fluid.
In a further very beneficial and advantageous arrangement of the apparatus according to the invention, the fuel cell system furthermore comprises a recirculation conveyor device, through which unused fuel gas is returned from one region behind an anode of the fuel cell to a region in front of the anode, wherein this recirculation conveyor device is mounted to the integrated component part. By the mounting of the recirculation conveyor device, for example a hydrogen recirculation fan, the line length between the integrated component unit and the recirculation conveyor device is reduced, and the recirculation conveyor device can be connected to the integrated component unit without further carrier frames or the like and be carried by it. As this typically still has its own cooling, this mounting can be a very advantageous alternative due to reasons of maintenance, so as to ensure accessibility and possibly exchangeability of the recirculation conveyor device. By the mounting of the recirculation conveyor device, an at least indirect heat conduction between the recirculation conveyor device and the integrated component part can furthermore be achieved. The device for the at least indirect heating of the supplied fresh fuel gas can then, especially when using a high heating performance, also heat the recirculation conveyor device in the case of a cold start up to a certain degree, and possibly defrost droplets frozen therein.
In an alternative arrangement of the apparatus according to the invention, it is provided that such a recirculation conveyor device is at least partially implemented in an integral manner in the integrated component part. With this, the recirculation conveyor device could completely be housed in the integrated component part, or only the hydrogen-conducting part can be integrated in the integrated component part. A possible drive motor, for example in a canned construction, could then be mounted from the outside. With this, it would be ensured that all hydrogen-conducting parts are integrated in the integrated component part, so that the problem regarding line lengths and sealing locations are improved still further. Furthermore, a very good heating of the recirculation conveyor device via the device for the at least indirect heating of the supplied fresh fuel gas would be possible by the integration. With this, the recirculation conveyor device could, for example, also be heated via the integrated component unit.
Exemplary uses of such an economic, small, compact and comparatively light component part with regard to its mass, include in a transport means on land, on water or in the air, and particularly in a farm vehicle without rails. The above-mentioned advantages can be used especially effectively here, it is thereby not important if the apparatus is used for additional energy generation or for the generation of energy for the drive train of such a transport means.
Further advantageous arrangements of the invention result from the dependent claims and are explained in more detail in the following by means of an embodiment.
It shows thereby:
With the exemplary highly schematic depiction of the integrated component part 7 in
In addition to the region 7.1 already described, which can comprise the wheel housing for the compactor of the recirculation pump 13, the housing 9 comprises further integrated regions. The region referenced as 7.2 can thus, for example, comprise an electrical heater 14 as device for heating the fresh supplied fuel gas. Basically, a single central electrical heater 14 can be provided, which is connected to heat-conducting materials with all regions or media which are to be heated via corresponding regions. Alternatively, the electrical heater 14 can also be divided into individual elements, so that certain regions within the housing 9 can respectively be heated individually, for example corresponding valve devices, the wheel of the recirculation pump 13, corresponding sensor connectors or also partial regions of a water precipitator 16, which is to be arranged in the region 7.3.
In the region 7.4 of the housing 9, a mixing region is also arranged, in which the fresh hydrogen supplied from the pressure tank 5 via the line 12 mixes with the unused fuel gas recirculated via the recirculation pump 13, which reaches the integrated component part 7 via the recirculation line 8. The corresponding fuel gas then reaches the anode 3 of the fuel cell 2 via the conduction element 15. At least in this mixing region 7.4 in the housing 9 sensors or receptors for sensors are arranged, so that state variables and/or chemical magnitudes of the fuel gas conducted to the anode 3 of the fuel cell 2 can be sensed via the line 15. Typical magnitudes here would be pressure, temperature and volume flow, humidity and hydrogen concentration in the fuel gas.
In the region 7.3, which shall comprise the water precipitator 16, a discharge valve 17 can also be arranged, which is not shown explicitly. Accumulating water can be discharged via this discharge valve via the line element 18. Non-combustible gas accumulated over time in the system due to the recirculation can also be blown off together with the water via this line element 18. These elements are also integrated in the region 7.4 of the housing 9 by integration in such a manner that these are thermally bound to the housing 9 and can thereby also be heated in the region 7.2 via the electrical heater 14. Thus, the function of these component elements is always ensured. The water precipitator 16 can be principally constructed in an arbitrary manner in the region 7.4 of the housing 9. It is, however, also feasible to combine the water precipitator 16 with the recirculation pump 13 in such a manner that the rotary movement of the compactor wheel of the recirculation pump 13 transports possibly occurring droplets by the centrifugal force into the region of the compactor wheel housing, in which a discharge and precipitation of these liquid droplets can be realized via corresponding grooves or the like. The rotary energy of the compactor wheel of the recirculation pump 13 can thus also be used for improving the water precipitation.
It can also be provided in the housing 9 that all fluid-conducting parts, that is, especially the parts reached by water after the precipitation, are formed in such a manner that their walls continuously open in the cross section in the direction to a fuel gas or air cushion. By this opening in the direction of an air cushion, which in the general case of use will typically be in a direction against gravity, a construction is achieved, which will not be damaged during the freezing of the liquid water present therein. The arrangement in which ice forming is not blocked in its expansion, but can slide into the region of an air or fuel gas cushion, avoids the corresponding stresses exerted on the material of the housing 9 by the expansion of the ice, which can lead to material failure.
The housing 9 comprises two additional line elements 19, 20 in
As has already been mentioned, the corresponding sensors are integrated in the region 7.4 of the housing 9 depicted in
After the recirculation conveyor device 13, the anode waste gas flows into the mixing region 7.4, where it is mixed with fresh fuel gas from the pressure tank 5. The fresh fuel gas from the pressure tank 5 thereby flows to the mixing region 7.4 via the valve device 6, which is also formed as a valve device 6 mounted to the integrated component part 7. Before it reaches the mixing region 7.4, the fuel gas also flows through the region 7.2 of the integrated component part 7, in which the electrical heater 14 is arranged as the device for heating the fresh supplied fuel gas. The electrical heater 14 also serves for the conditioning or temperature control of the fresh supplied fuel gas. The gases mixed with one another then reach a water trap 27, in which droplets possibly present in the gas are precipitated, which were, for example, condensed out by the cooler fresh fuel gas in the comparatively warm anode waste gas. This is necessary to prevent liquid water from clogging the channels for distributing the fuel gas in the anode region 3 of the fuel cell 2. The integration of the water trap 27 into the integrated component part 7 thereby offers the advantage that these devices can be omitted in the interior of a fuel cell 2 or in a gas supply region within the fuel cell 2. All of the liquid water thus accumulates in the region of the integrated component part 7. This water can then flow from the water trap 27 via the line 28 shown dashed here into the region of the water precipitator 16, for example, through a suitable arrangement of the water trap 27 at a higher height than the water precipitator 16. The fuel gas free from drops then reaches the region of the anode chamber 3 of the fuel cell 2 and can be correspondingly converted there.
Furthermore, a part of the cooling circuit 21 passes through the integrated component unit 7 in the embodiment according to
In the embodiment shown here, all media supplies and discharges to the anode side 3 of the fuel cell 2 and the supply of the cooling water are integrated in the component part 7. This saves corresponding line elements and can be mounted very simply and efficiently via a suitable interface, for example, between the integrated component unit 7 and an end plate of the fuel cell stack 2. If the integrated component unit 7 is the end plate itself, even this part of the mounting can be omitted.
In the integrated component unit 7 in the depiction of
Alternatives can now be seen in the depictions of
As illustrated in an exemplary manner in the depiction according to
Otherwise, the stated embodiments for the electrical heater 14 are also valid for this type of heat input.
The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102008045170.3 | Aug 2008 | DE | national |
| 102008058960.8 | Nov 2008 | DE | national |
This application is a national stage of PCT International Application No. PCT/EP2009/006223, filed Aug. 27, 2009, which claims priority under 35 U.S.C. § 119 to German Patent Application No. 10200804517.3, filed Aug. 30, 2008 and German Patent Application No. 102008058960.8, filed Nov. 25, 2008, the entire disclosures of which are herein expressly incorporated by reference.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2009/006223 | 8/27/2009 | WO | 00 | 4/6/2011 |
