Method for operating a fuel cell system, controller
By detecting the slope of the fuel cell stack and matching the drying duration, the problem of high energy consumption during the drying process of the fuel cell system during shutdown is solved, and the effect of energy saving and anti-freezing of the medium channel is achieved.
Patent Information
- Application Number
- CN202380048598.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2022-06-22
- Filing Date
- 2023-06-22
- Publication Date
- 2025-02-07
AI Technical Summary
When the fuel cell system is shut down, especially the fuel cell stack arranged transversely, it is necessary to perform drying treatment to avoid water freezing and drainage problems, but the prior art increases energy consumption during the drying process.
By detecting the current slope of the fuel cell stack with respect to the reference plane, the drying duration is determined to match the slope changes of the fuel cell stack and reduce energy consumption.
It effectively reduces the energy consumption of fuel cell systems during drying, saves energy and costs, and avoids the problem of water icing in the medium channels.
Smart Images
Figure CN119404343A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to a method for operating a fuel cell system, in particular a mobile fuel cell system or a fuel cell vehicle. In addition, the invention relates to a control unit which is designed to carry out the steps of the method. Background Art
[0002] Fuel cells based on hydrogen are seen as a mobility concept of the future, since they emit only water as exhaust gas and allow for fast refilling times. In a fuel cell, hydrogen is converted together with oxygen into electrical energy, heat and water. To increase the electrical power, a number of such fuel cells are combined into a fuel cell stack, a so-called "stack".
[0003] The membrane electrode assembly forms the core of the fuel cell. The membrane electrode assembly has a membrane, which is coated on both sides with a catalytically active material for forming electrodes, anodes and cathodes. Hydrogen is supplied to the anode side and air is supplied to the cathode side as an oxygen provider. The supply in the stack takes place via a medium channel, which passes through the stack and is also called a distributor. The gas is discharged via another medium channel that passes through the stack, which is also called a collector. In addition, a channel for a coolant for a cooling circuit is provided that passes through the stack, with the help of which the heat generated during operation is discharged.
[0004] Typically, all media, including the coolant, are supplied and discharged on the same end side of the fuel cell stack, so that the distributor and collector extend parallel to each other and perpendicular to the individual fuel cells. In the literature, this flow through the fuel cell stack is also referred to as Pi flow. In this case, the fuel cell stack can be arranged both upright (the fuel cells are oriented orthogonally to the earth's gravity vector) and horizontally (the fuel cells are oriented parallel to the earth's gravity vector).
[0005] The transverse arrangement of the fuel cell stack imposes increased demands on the drainage of the fuel cell stack in the event of a shutdown, since water collects at corresponding low points and these low points - in the event of an unfavorable inclination of the fuel cell stack - can be far from the outlet area of the collector. In this case, drainage cannot be achieved solely in a gravity-driven manner. In particular in the case of mobile fuel cell systems, unfavorable inclinations can occur, for example, when the vehicle is parked on an incline. If the vehicle is shut down at low ambient temperatures, the water that has collected at the low points can freeze and cause problems when the system is restarted.
[0006] In order to avoid this, it has been proposed to introduce a drying process before shutting down, while the medium supply to the fuel cell stack is continued. For this purpose, the cathode-side and anode-side gas delivery units need to be operated further, which increases energy consumption. Summary of the invention
[0007] The invention addresses the object of reducing the energy consumption when drying media channels of a fuel cell stack in order to save energy and costs.
[0008] In order to achieve this object, a method is proposed having the features of claim 1. Advantageous developments of the invention can be derived from the dependent claims. Furthermore, a control unit is specified for carrying out the steps of the method.
[0009] A method for operating a fuel cell system, in particular a mobile fuel cell system, is proposed, the fuel cell system comprising a transversely arranged fuel cell stack, the fuel cell stack having an end side, at which media channels for distributing and collecting at least one medium lead in and out on the end side. Before shutting down the fuel cell system, the media channels are dried by loading with at least one medium. According to the invention, before shutting down, the current inclination of the fuel cell stack relative to a reference plane extending perpendicularly to the earth's gravity vector is detected, and the drying duration is determined as a function of the current inclination of the fuel cell stack.
[0010] The proposed method takes into account the current inclination of the fuel cell stack when shutting down, which inclination can change, in particular in the case of a mobile fuel cell stack. This is because the inclination of the fuel cell stack changes depending on whether the vehicle is shut down on a flat surface or on an inclined surface. Depending on the inclination, the media channels can be dried faster or slower, so that a drying duration adapted thereto can reduce energy consumption. This is because in the case of a shortened drying duration, the loading of the media channels with the corresponding medium can be ended earlier, so that the gas delivery unit required for loading can be switched off earlier.
[0011] In a further development of the invention, it is proposed to detect the inclination direction of the current inclination of the fuel cell stack relative to the reference plane. For example, the vehicle can be parked in such a way that gravity favors the drying of the media channels, so that in this case the drying time can also be reduced. If, on the other hand, the vehicle is parked on an incline in the opposite direction of travel, the inclination prevents the gravity-driven drying of the media channels. In this regard, the inclination direction is of relevance.
[0012] Thus, knowing the direction of inclination, a distinction can be made between an unfavorable and a favorable inclination of the fuel cell stack relative to a reference plane. For example, the reference plane can be laid through the low point of the medium channel to be dried, which is farthest away from the outlet location at the end side of the medium channel. Then, in the case of an unfavorable inclination, the outlet location is located above the reference plane ("+"), and in the case of a favorable inclination, the outlet location is located below the reference plane ("-"). Only in the latter case can the water contained in the gas be removed from the medium channel in a gravity-driven manner or with the support of gravity, so that the drying duration can be shortened.
[0013] As a result, the more unfavorable the current inclination of the fuel cell stack relative to the reference plane, the longer the fuel cell stack needs to be dried. This means that no more energy than is necessary is consumed.
[0014] In order to further reduce the energy consumption, it is proposed that, in the case of a favorable inclination of the fuel cell stack relative to the reference plane, the drying is carried out only in a gravity-driven manner, that is, the gas supply unit for charging the medium channels with the corresponding medium is switched off.
[0015] It is further proposed that during the drying process the current inclination of the fuel cell stack relative to a reference plane is detected and changes in the inclination are taken into account when determining the drying duration. This is advantageous in particular in the case of mobile fuel cell systems or fuel cell vehicles, since the inclination of the fuel cell stack can change repeatedly until the vehicle is shut down. This change is detected and the drying duration is adapted accordingly.
[0016] In the event of a shutdown, the cathode-side and / or anode-side media channels can be dried. Since water can be produced not only on the cathode side but also on the anode side, it is advantageous to dry all media channels before shutting down. This avoids ice formation in the media channels.
[0017] Furthermore, it is preferred that the type of medium of the media channel to be dried is taken into account when determining the drying time, since the water load can be of different magnitudes depending on the medium, so that the drying time can be adapted to this water load.
[0018] In addition, a control unit for a fuel cell system is proposed, which is designed to carry out the steps of the method according to the invention. For example, the drying duration can be controlled by means of the control unit as a function of the current inclination of the fuel cell stack. For this purpose, the control unit can receive measurement data of an inclination sensor, by means of which the current inclination of the fuel cell stack can be detected. Thus, the method can be largely automated. BRIEF DESCRIPTION OF THE DRAWINGS
[0019] Below, the present invention and its advantages are described in more detail according to the accompanying drawings. These drawings show:
[0020] Figure 1 A schematic longitudinal section showing an upright fuel cell stack,
[0021] Figure 2 A schematic longitudinal section of a horizontally arranged fuel cell stack is shown,
[0022] Figure 3 Shown in the case of unfavorable slope Figure 1 A schematic longitudinal cross-sectional view of a fuel cell stack,
[0023] Figure 4 Shown in the case of a favorable slope Figure 1 A schematic longitudinal cross-sectional view of a fuel cell stack, and
[0024] Figure 5 A graph is shown for graphically illustrating the relationship between the slope of a fuel cell stack and the drying duration in a shutdown situation. DETAILED DESCRIPTION
[0025] Figure 1 A fuel cell stack 1 for a fuel cell system is shown, which has a plurality of fuel cells 5 stacked one above the other, and a medium, such as hydrogen, is supplied to the fuel cells via a medium channel 3 ("distributor") extending perpendicularly to the fuel cells 5. The medium flows through the fuel cells 5 horizontally along the arrow 9. The medium flowing out of the fuel cells 5 is discharged from the fuel cell stack 1 via another medium channel 4 ("collector"). The medium channels 3 and 4 extend parallel to each other. The medium channel 3 flows into the lower end side 2 of the fuel cell stack 1. On the same end side 2, the medium channel 4 flows out again. Below the fuel cell stack 1, an anode subsystem 6 is arranged, which has a gas delivery unit 7 and a water separator 8. With the help of the gas delivery unit 7, the medium channel 3 is loaded with the medium. The product water discharged together with the medium via the medium channel 4 is guided to the water separator 8 under the support of gravity.
[0026] from Figure 2 A horizontally arranged fuel cell stack 1 can be seen in FIG. In this case, the fuel cells 5 are not arranged one above the other, but side by side. The media channels 3, 4 extend perpendicularly to the fuel cells 5, i.e. horizontally. The anode subsystem 5 is arranged laterally, since the end side 2 is also placed laterally, at which the media channel 3 opens into the fuel cell stack 1 and at which the media channel 4 opens out of the fuel cell stack 1. In order to be able to use gravity when flowing through the fuel cells 5 (see arrow 9), the media channel 3 used as a distributor is arranged at the top and the media channel 4 used as a collector is arranged at the bottom.
[0027] As exemplified in Figure 3 and 4 As shown in FIG. 1 , a fuel cell stack 1 , in particular a fuel cell stack in a mobile application, can have an inclination when shut down relative to a reference plane E, which extends perpendicularly to the Earth's gravity vector v (see FIG. 1 ). Figure 2 ). In the present case, the height position of the reference plane E is selected such that it passes through the lowest point 10 of the media channel 4. In the case of a horizontal course of the media channel 4, the lower edge of the channel forms the lowest point 10.
[0028] exist Figure 3 In the example of FIG. 1 , the fuel cell stack 1 is tilted relative to the reference plane E in such a way that the outlet region of the media channels 4 on the end side 2 is clearly above the reference plane E (“+”). In this position, the water present in the media channels 4 collects at the lowest point 10 in a gravity-driven manner. In the shutdown situation, gravity therefore prevents the media channels 4 from drying out.
[0029] exist Figure 4 In the example of , the fuel cell stack 1 is tilted relative to the reference plane E such that the outlet regions of the media channels 4 at the end side 2 are located significantly below (“−”) the reference plane E. In this position, gravity supports the drying of the media channels 4 .
[0030] It therefore makes a difference whether the fuel cell stack 1 is tilted advantageously or disadvantageously during shutdown or during drying prior to shutdown. The inclination is therefore taken into account in the method according to the invention by determining the drying duration as a function of the current inclination of the fuel cell stack 1 or by adapting the drying duration to the current inclination of the fuel cell stack 1 .
[0031] exist Figure 5 The relationship between the slope of the fuel cell stack 1 from an unfavorable slope (“-”) to a favorable slope (“+”) and the drying time t is shown by way of example. From the average drying time t for the case where the fuel cell stack 1 has no slope or has a slope of 0° m It is assumed that the drying time is shortened if the fuel cell stack 1 is tilted in a more favorable manner, or that the drying time is prolonged if the fuel cell stack 1 is tilted in a more unfavorable manner.
Claims
1. A method for operating a fuel cell system, in particular a mobile fuel cell system, comprising a transversely arranged fuel cell stack (1), the fuel cell stack having an end side (2) into which media channels (3, 4) for distributing and collecting at least one medium open and out, wherein: Before shutting down the fuel cell system, the medium channels (3, 4) are dried by loading them with the at least one medium. It is characterized in that, before the shutdown, the current inclination of the fuel cell stack (1) relative to a reference plane (E) is detected, the reference plane extending perpendicular to the earth's gravity vector (v), and the drying duration is determined based on the current inclination of the fuel cell stack (1).
2. The method according to claim 1, It is characterized in that The tilt direction of the current slope of the fuel cell stack (1) relative to the reference plane (E) is detected.
3. The method according to claim 1 or 2, It is characterized in that A distinction is made between an unfavorable inclination and a favorable inclination of the fuel cell stack (1) relative to the reference plane (E).
4. The method according to claim 3, It is characterized in that The more unfavorable the current inclination of the fuel cell stack (1) relative to the reference plane (E), the longer the fuel cell stack (1) needs to be dried.
5. The method according to any one of the preceding claims, It is characterized in that In the case of a favorable inclination of the fuel cell stack (1) relative to the reference plane (E), the drying is performed solely in a gravity-driven manner.
6. The method according to any one of the preceding claims, It is characterized in that During the drying, the current inclination of the fuel cell stack (1) relative to the reference plane (E) is detected and the change in the inclination is taken into account when determining the drying duration.
7. The method according to any one of the preceding claims, It is characterized in that In the case of a shutdown, the cathode-side and / or anode-side media channels (3, 4) are dried.
8. The method according to any one of the preceding claims, It is characterized in that When determining the drying duration, the type of medium of the medium channels (3, 4) to be dried is taken into account. 9 . A control unit for a fuel cell system, which is designed to carry out the steps of the method according to claim 1 .