Defect analysis system for a fuel cell, fuel cell, method, computer program product and computer-readable storage medium

Abstract

The invention relates to a defect analysis system (100) for a fuel cell (10) with a total air path (11) which is divided into a main air path (12) and a secondary air path (13), comprising: - a total air path flow sensor (110) which can be arranged in the total air path (11) and is designed to measure an air flow in the total air path (11), - a main air path flow sensor (120) which can be arranged in the main air path (12) and is designed to measure an air flow in the main air path (12), - a secondary air path flow sensor (130) which can be arranged in the secondary air path (13) and is designed to measure an air flow in the secondary air path (13), - a shut-off valve (140) which is designed to release the main air path (12) or the secondary air path (13) in a release position and to close it in a closed position, and - a comparator (150) which is designed to check the plausibility of the measurements of at least the total air path flow sensor (110), the main air path flow sensor (120) or the secondary air path flow sensor (130) with each other or on the basis of an air flow model. The invention further relates to a fuel cell (10), a method, a computer program product and a computer-readable storage medium.

Description

State of the art

[0001] The invention relates to a defect analysis system for a fuel cell, a fuel cell, a method, a computer program product and a computer-readable storage medium.

[0002] Fuel cells, particularly solid oxide fuel cells (SOFCs), can have an air and a fuel path to supply the two process gases, oxygen and methane or hydrogen, to the fuel cell stack. The air and fuel mass flows required at each operating point of the fuel cell system are determined by the system control system. The air serves not only as a carrier of the process gas oxygen, but also to regulate the temperature of the fuel cell stack. In a high-temperature fuel cell, in order to be ready for operation, the stack must first be brought to a minimum temperature below which the desired reactions in the stack would not take place. As soon as fuel gas is supplied and the reactions in the stack start, process heat must be dissipated to prevent the stack from overheating. The overall system also has further requirements for the air mass flow, e.g.in the form of a minimum amount of air that must be provided for safety reasons to prevent the formation of an ignitable fuel-air mixture in the event of a fault (e.g. leakage within the fuel cell stack from the anode (fuel) to the cathode (air) side).

[0003] If a leak occurs in the air path upstream of the stack, the air mass flow above the stack decreases, meaning less process heat can be dissipated. If the air flow drops too much, overheating can occur. To prevent this, the fuel cell system will stop supplying fuel gas and interrupt power output once a maximum stack temperature threshold is reached. A leak in the air path therefore always poses a risk to the uninterrupted operation of the system. Disclosure of the invention

[0004] The invention proposes a defect analysis system for a fuel cell, a fuel cell, a method, a computer program product, and a computer-readable storage medium. Further features and details of the invention emerge from the subclaims, the description, and the drawings. Features and details described in connection with the defect analysis system according to the invention naturally also apply in connection with the fuel cell according to the invention and / or in connection with the method according to the invention and / or in connection with the computer program product according to the invention and / or in connection with the computer-readable storage medium according to the invention, and vice versa, so that with regard to the disclosure of the individual aspects of the invention, reference is always made to each other.

[0005] According to the invention, a defect analysis system is provided for a fuel cell with a total air path, via which a total air flow can be supplied to the fuel cell, which is divided into a main air path and a secondary air path, comprising at least one total air path flow sensor, which can be arranged in the total air path and is designed to measure an air flow in the total air path, at least one main air path flow sensor, which can be arranged in the main air path and is designed to measure an air flow in the main air path, at least one secondary air path flow sensor, which can be arranged in the secondary air path and is designed to measure an air flow in the secondary air path, a shut-off valve, which is designed to release at least the main air path or the secondary air path in a release position and to close it in a closed position, and a comparator, which is designed to measure the measurements of at least the total air path flow sensor,of the main air path flow sensor or the secondary air path flow sensor at least with each other or using an air flow model.

[0006] In other words, the invention provides a device for determining a fault in a fuel cell through which a fluid flows, wherein the fuel cell has an overall fluid path divided into a main fluid path and a bypass. The device has three fluid sensors, each designed to measure a fluid flow in the overall fluid path, the main fluid path, and the bypass. Furthermore, the device has a valve with which at least the main fluid path or bypass can be blocked or opened for the fluid. A comparison unit allows the measurements of the three fluid sensors to be compared with each other and with a fluid flow model.

[0007] A defect analysis system can be understood as a device designed to detect a defect in a fuel cell. A defect can be embodied at least as a leak and / or sensor error, in particular sensor drift.

[0008] Within the scope of the invention, a fuel cell can be understood as a device designed to convert the chemical reaction energy of a continuously supplied fuel and an oxidizing agent into electrical energy. The fuel cell can be stationary. In particular, the fuel cell can be designed as a solid oxide fuel cell (SOFC). Furthermore, the fuel cell can be designed as a high-temperature fuel cell.

[0009] A total air path can be understood as a flow channel suitable for supplying air to the fuel cell and defining the total air volume in the main air path and the secondary air path. The total air path can be arranged upstream of a stack of the fuel cell. It can also be provided that the air passed through the fuel cell is partially recirculated.

[0010] In the context of the invention, air is assumed to be the transported fluid. In principle, at least some of the advantages of the invention also apply to any other fluid supplied to the fuel cell. Furthermore, the fluid can be at least one of fuel, hydrogen, or oxygen.

[0011] The main air path and the secondary air path can be thought of as two channels branching off from the overall air path. In other words, the overall air path, together with the main air path and the secondary air path, forms a Y-branch.

[0012] At least the total air path flow sensor, the main air path flow sensor, or the secondary air path flow sensor can be designed as flow sensors. The sensors can measure a mass and / or volume flow of the air. Advantageously, at least the main air path flow sensor can be designed as a mass flow controller and, in addition to measuring the mass flow, also have a control valve to regulate the air mass flow to a setpoint.

[0013] The term "arrangable in the overall air path, main air path, or secondary air path" can be understood to mean that the respective sensor can be inserted into the flow path in such a way that the flow in the respective path can be measured. Depending on the measuring principle, for example, a portion of the flow from the respective path can also be directed via a measuring bypass and flowing with the flow in the path in which the sensor is located.

[0014] The measurement may include capturing at least one measured value. It may be provided to filter raw signals, particularly with a low-pass filter. This filters out short-term interference and improves measurement accuracy. Alternatively or additionally, averaging may also be performed, particularly over a specified time interval. This also increases the accuracy of the measurement. Furthermore, at least one cyclical or continuous evaluation can be performed. A cyclical evaluation can preferably always be performed at the end of a measurement interval.

[0015] According to the invention, the shut-off valve is designed to open at least the main air path or the secondary air path in a release position and to close it in a closed position. For this purpose, the shut-off valve can be arranged in one of the two paths. Furthermore, it can be provided that the shut-off valve can assume additional states and, in particular, regulate the flow according to a setpoint. It can be provided that the shut-off valve is designed as a flap.

[0016] A comparator can be understood as a device designed to compare the measurements of the flow sensors with each other and / or with the calculated flow values ​​of an air flow model. The comparator can be designed as a dedicated computing unit, in particular as an integrated circuit (IC). The IC can be designed in particular as a field-programmable gate array (FPGA) or application-specific integrated circuit (ASIC). Furthermore, the comparator can be designed as part of a control unit of the fuel cell.

[0017] Plausibility checking can be understood as comparing the measured values ​​of the sensors with each other and / or with calculated flow values ​​of an air flow model. Ultimately, a comparison of the measured values ​​of the sensors with each other can also be understood as a comparison with an air flow model, since certain assumptions are made for this too. The air flow model can, for example, include the assumption that, without the presence of a leak and / or a defect in a sensor, the total air flow between the total air path, the main air path, and the secondary air path is maintained. Also part of the air flow model can be the assumption that, when the valve is closed and without the presence of a leak and / or a defect in a sensor, the flow in this path is zero. In addition, a number of flow models are known to those skilled in the art that are not discussed in detail here.

[0018] Overall, the defect analysis system according to the invention achieves the advantage of making it possible to detect a leak in a fuel cell. At the same time, the proposed linking of the information offers the possibility of checking the plausibility of the signals from the measuring devices used and detecting a defect in one of the measuring devices. This results in further advantages. Early detection of a leak in the air path can prevent a critical temperature increase in the fuel cell, particularly in the stack, which would subsequently necessitate a safety shutdown. The safety shutdown can lead to a sudden interruption of the power supply during operation or, in network operation with several units connected in series, to a sudden drop in performance.The device according to the invention can trigger preventative maintenance when problems are emerging, thus preventing a sudden, unexpected drop in performance. Detection of a defective measuring device in the air path can also reduce the likelihood of misdiagnosis, resulting in fewer and shorter downtimes.

[0019] Within the scope of the invention, it may be advantageous for at least one additional sensor, in particular at least a temperature or pressure sensor, to be arranged at least in the overall air path, the main air path, or the secondary air path. The additional sensors can be used particularly advantageously in conjunction with complex air flow models. This makes the plausibility check even more precise.

[0020] Also proposed is a fuel cell, in particular a solid oxide fuel cell, having a total air path via which a total air flow can be supplied to the fuel cell, which is divided into a main air path and a secondary air path, further comprising at least one defect analysis system according to the invention.

[0021] This results in the same advantages for the fuel cell as have already been described in detail in connection with the defect analysis system.

[0022] Within the scope of the invention, it is conceivable to provide an air blower that is suitable for generating an air flow at least in the overall air path, the main air path, or the secondary air path. The air blower can be provided, in particular, upstream of a fuel cell stack of a fuel cell.

[0023] Also proposed is a method according to the invention for detecting a defect in a fuel cell, in particular a solid oxide fuel cell, having a total air path via which a total air flow can be supplied to the fuel cell, which is divided into a main air path and a secondary air path, comprising: Measuring an air flow in the overall air path, in particular by means of at least one overall air path flow sensor which can be arranged in the overall air path, measuring an air flow in the main air path, in particular by means of at least one main air path flow sensor which can be arranged in the main air path, measuring at least one air flow in the secondary air path, in particular by means of a secondary air path flow sensor which can be arranged in the secondary air path, switching a shut-off valve at least into a release position in which the main air path or the secondary air path is released, or a closed position in which the main air path or the secondary air path is closed, and checking the plausibility of the measurements in the overall air path, in the main air path and in the secondary air path using an air flow model, in particular using a comparator.

[0024] This results in the same advantages for the process as have already been described in detail in connection with the defect analysis system and / or the fuel cell.

[0025] It can be specified that the plausibility check is only performed at fuel cell operating points where the air flow rate exceeds the maximum tolerance of the measuring devices and / or the air blower. This prevents misdiagnosis.

[0026] Furthermore, plausibility checks can only be performed at fuel cell operating points where the flow behavior, especially that of the air blower, can be reliably calculated. This measure also prevents misdiagnoses.

[0027] It may be provided that a negative plausibility check result is rejected if the result has not been confirmed by further plausibility checks. Alternatively or additionally, it may be provided that a result is only classified as implausible, in particular that an error code is set, if the plausibility check result is confirmed multiple times, especially consecutively. A lack of plausibility may indicate a leak, a fault in the air blower, or the total air path flow sensor.

[0028] Within the scope of the invention, a comparison can be made between the measured air flow in the overall air path and the calculated air flow of the air flow model. In particular, if the calculated and measured air flow agree, the measurement is classified as plausible, and / or if the calculated and measured air flow do not agree, the measurement is classified as implausible. In other words, it can be checked whether the measured air flow agrees with that expected by the air flow model. The air flow model can calculate the air flow, in particular based on a model of an air blower.

[0029] It is also conceivable that a comparison is made between the measurement of the air flow in the overall air path and the sum of the air flow in the main air path and the air flow in the secondary air path. In particular, if the two values ​​match, the measurements are classified as plausible, and / or if the two values ​​do not match, the measurements in the main air path and / or the secondary air path are classified as implausible. In other words, it is determined whether air is escaping between the overall pad and the main and secondary air paths through a leak, or whether one of the sensors is faulty.

[0030] It is also conceivable that if a comparison between the measurement of the air flow in the overall air path and the sum of the air flow in the main air path and the air flow in the secondary air path reveals a discrepancy between the two values, at least the main air path or secondary air path is closed, with the air flow of the closed path being compared to zero and / or the air flow of the open path being compared to the measurement of the air flow in the overall air path. Measuring in a closed path offers the possibility of narrowing down the error to a single path or a single sensor.

[0031] It can further be provided that the shut-off valve actively closes a path in order to compare the measured air flow in the overall air path with the sum of the air flow in the main air path and the air flow in the secondary air path. To prevent the system from being placed in an undesirable or dangerous state by actively blocking a path, it can at least be provided that the desired position of the shut-off valve is requested from a control unit of the fuel cell, which decides whether and when the request is implemented, or a diagnostic function, in particular of the defect analysis system, can independently check whether a changed position of the shut-off valve is permissible or not and then bring about this, in particular independently of the control unit.

[0032] Also proposed is a computer program product according to the invention, comprising instructions which, when the program is executed by a computer, in particular a control unit of a defect analysis system according to the invention, cause the computer to carry out a method according to the invention.

[0033] This results in the same advantages for the computer program product as have already been described in detail in connection with the method and / or the defect analysis system and / or the fuel cell.

[0034] Also proposed is a computer-readable storage medium according to the invention, comprising instructions which, when the program is executed by a computer, in particular a control unit of a defect analysis system according to the invention, cause the computer to carry out a method according to the invention.

[0035] This results in the same advantages for the computer-readable storage medium as have already been described in detail in connection with the computer program product and / or the method and / or the defect analysis system and / or the fuel cell.

[0036] Further advantages, features, and details of the invention will become apparent from the following description, which describes several embodiments of the invention in detail with reference to the drawings. The features mentioned in the claims and in the description may be essential to the invention individually or in any combination. The invention is illustrated in the following figures: Fig. 1 a defect analysis system according to the invention on a fuel cell according to the invention, Fig. 2 a plausibility check of the measurement signals when the main air path and secondary air path are open, Fig. 3 a plausibility check of the measurement signals when one of the paths is closed, and Fig. 4 Plausibility check of the measurement signals when both branch paths are open.

[0037] The Fig. 1 shows a defect analysis system 100 according to the invention for a fuel cell 10 with a total air path 11, via which a total air flow can be supplied to the fuel cell 10, which is divided into a main air path 12 and a secondary air path 13. The defect analysis system 100 comprises at least one total air path flow sensor 110, which can be arranged in the total air path 11 and is designed to measure an air flow in the total air path 11, at least one main air path flow sensor 120, which can be arranged in the main air path 12 and is designed to measure an air flow in the main air path 12, at least one secondary air path flow sensor 130, which can be arranged in the secondary air path 13 and is designed to measure an air flow in the secondary air path 13, a shut-off valve 140, which is designed to release at least the main air path 12 or the secondary air path 13 in a release position and to close it in a closed position, and a comparator 150,which is designed to verify the plausibility of the measurements of at least the total air path flow sensor 110, the main air path flow sensor 120 or the secondary air path flow sensor 130 at least with each other or using an air flow model.

[0038] The total air path flow sensor 110 can be arranged downstream of an air blower 14, as shown. Alternatively or additionally, the total air path flow sensor 110 can also be arranged upstream of the air blower 14.

[0039] Overall, the defect analysis system 100 according to the invention achieves the advantage of making it possible to detect a leak in a fuel cell 10. At the same time, the proposed linking of the information offers the possibility of checking the plausibility of the signals from the measuring devices used and of detecting a defect in one of the measuring devices. This results in further advantages. Early detection of a leak in the air path can prevent a critical temperature increase in the fuel cell 10, particularly in the stack, which would subsequently necessitate a safety shutdown. The safety shutdown can lead to a sudden interruption of the power supply during operation or, in network operation with several units connected in series, to a sudden drop in power.The device according to the invention can trigger preventative maintenance when problems are emerging, thus preventing a sudden, unexpected drop in performance. Detection of a defective measuring device in the air path can also reduce the likelihood of misdiagnosis, resulting in fewer and shorter downtimes.

[0040] In Fig. Figure 2 shows a possible starting point for the plausibility check. Values ​​between the air flow model, in particular a model of the air blower 14, preferably a blower mass flow, are compared with the measurement signal of the total air path flow sensor 110. If these match, it is determined that the total air path flow sensor 110 is not defective, and its measured values ​​can be used for further plausibility checks.

[0041] Based on this, it can now be determined whether there is a defect or a leak in one of the two downstream main air path flow sensors 120 and / or secondary air path flow sensors 130. For this purpose, the sum of the measured values ​​can be calculated and compared with the measured value of the total air path flow sensor 110. If the deviation of the sum from the measured value of the total air path flow sensor 110 is greater than would be expected with the usual tolerances of the path flow sensors 120, 130, then either one of the path flow sensors 120, 130 or both has drifted, or there is a leak. The latter would be the case if the sum of the measured signals from the main air path flow sensor 120 and secondary air path flow sensor 130 is smaller than the measured signal of the total air path flow sensor 110.

[0042] A more precise distinction is possible if one of the two branch paths is closed. This case is described in Fig. 3 is shown schematically. The shut-off valve 140 is closed, for example, in the secondary air path 13. The secondary air path flow sensor 130 is assigned to the path and should now display 0 due to the closed shut-off valve 140. If the measurement signals of the total air path flow sensor 110 and the main air path flow sensor 120 are identical, the secondary air path flow sensor 130 can be identified as defective, or a possible leak can be localized to the area of ​​the secondary air path 13. If the measurement signals of the total air path flow sensor 110 and the main air path flow sensor 120 are different, depending on the starting point of the analysis, it can be concluded that the main air path flow sensor 120 is defective, that the main air path flow sensor 120 and the secondary air path flow sensor 130 are both sending implausible signals, or that a possible leak is localized to the area of ​​the main air path 12.

[0043] The same pattern is followed by Fig. 4 illustrates the case distinctions in which the measurement signal of the total air path flow sensor 110 is greater or smaller than the calculated value of the air flow model, in particular the model value of the blower model. If the signal of the total air path flow sensor 110 and the sum of the signals from the main air path flow sensor 120 and the secondary air path flow sensor 130 are identical, it can be concluded that the air blower 14 has drifted (generally due to age). If the model value is identical to the sum of the signals from the main air path flow sensor 120 and the secondary air path flow sensor 130, the total air path flow sensor 110 may be defective. For example, the total air path flow sensor 110 has drifted, or there is a leak upstream of the air blower 14.

[0044] A negative drift of an air path flow sensor 110, 120, 130 and a leak in the corresponding air path cannot be distinguished from one another. However, for troubleshooting purposes, it is already advantageous if a problem at a specific location in the air path is indicated. In general, a leak is easy for service personnel to identify (e.g., using commercially available leak detection spray), making further pinpointing between drift and leak at the indicated location straightforward.

Claims

[1] Defect analysis system (100) for a fuel cell (10) with a total air path (11), via which a total air flow can be supplied to the fuel cell (10), which is divided into a main air path (12) and a secondary air path (13), comprising: - at least one total air path flow sensor (110) which can be arranged in the total air path (11) and is designed to measure an air flow in the total air path (11), - at least one main air path flow sensor (120) which can be arranged in the main air path (12) and is designed to measure an air flow in the main air path (12), - at least one secondary air path flow sensor (130) which can be arranged in the secondary air path (13) and is designed to measure an air flow in the secondary air path (13), - a shut-off valve (140) which is designed to release at least the main air path (12) or the secondary air path (13) in a release position and to close it in a closed position, and - a comparator (150) which is designed to check the plausibility of the measurements of at least the total air path flow sensor (110), the main air path flow sensor (120) or the secondary air path flow sensor (130) at least with each other or on the basis of an air flow model. [2] Defect analysis system (100) according to claim 1, characterized by that at least one further sensor, in particular at least one temperature or pressure sensor, is arranged at least in the overall air path (11), in the main air path (12) or in the secondary air path (13). [3] Fuel cell (10), in particular a solid oxide fuel cell (10), with a total air path (11) via which a total air flow can be supplied to the fuel cell (10), which is divided into a main air path (12) and a secondary air path (13), further comprising at least one defect analysis system (100) according to one of claims 1 or 2. [4] Fuel cell (10) according to claim 3, characterized by that an air blower (14) is provided which is suitable for generating an air flow at least in the overall air path (11), in the main air path (12) or in the secondary air path (13). [5] Method for detecting a defect in a fuel cell (10), in particular a solid oxide fuel cell (10), having a total air path (11) via which a total air flow can be supplied to the fuel cell (10), which is divided into a main air path (12) and a secondary air path (13), comprising: - measuring an air flow in the total air path (11), - measuring an air flow in the main air path (12), - measuring at least one air flow in the secondary air path (13), - switching a shut-off valve (140) at least into a release position in which the main air path (12) or the secondary air path (13) is released, or a closed position in which the main air path (12) or the secondary air path (13) is closed, and - Plausibility check of at least the measurements in the overall air path (11), in the main air path (12) or in the secondary air path (13) at least among each other or using an air flow model. [6] Method according to claim 5, characterized bythat a comparison is provided between the measurement of the air flow in the overall air path (11) and the calculated air flow of the air flow model, wherein in particular if the calculated and the measured air flow agree, the measurement is classified as plausible and / or if the calculated and the measured air flow do not agree, the measurement is classified as implausible. [7] Method according to claim 5 or 6, characterized by that a comparison is provided between the measurement of the air flow in the total air path (11) with the sum of the air flow in the main air path (12) and the air flow in the secondary air path (13), wherein in particular if the two values ​​agree, the measurements are classified as plausible and / or if the two values ​​do not agree, the measurements in the main air path (12) and / or in the secondary air path (13) are classified as implausible. [8] Method according to one of claims 5 to 7, characterized bythat if a comparison between the measurement of the air flow in the total air path (11) with the sum of the air flow in the main air path (12) and the air flow in the secondary air path (13) results in a deviation of both values, at least the main air path (12) or secondary air path (13) is closed, wherein the air flow of the closed path (12, 13) is compared with zero and / or the air flow of the open path (12, 13) is compared with the measurement of the air flow in the total air path (11). [9] Computer program product, comprising instructions which, when the program is executed by a computer, in particular a control unit (160) of a defect analysis system (100) according to one of claims 1 to 2, cause the computer to carry out a method according to one of claims 5 to 8. [10] Computer-readable storage medium, comprising instructions which, when the program is executed by a computer, in particular a control unit (160) of a defect analysis system (100) according to one of claims 1 to 2, cause the computer to carry out a method according to one of claims 5 to 8.

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