Method for detecting a temperature change in a fuel cell system

Abstract

Method for detecting a temperature change in a fuel cell system (100) with at least one fuel cell stack (110) and a turbo device (140) with a compressor (142) for supplying intake air (ZL) to an air side (120) of the fuel cell stack (110) and a turbine (144) for removing exhaust air (AL) from the air side (120) of the fuel cell stack (110), characterized by the following steps: - Recording the actual turbo power (ITL) of the turbo device (140) as measured by the turbo device (140), - Comparison of the determined actual turbo power (ITL) with a target turbo power (STL), - Output of a temperature signal (TS) depending on the result of the comparison between actual turbo power (ITL) and target turbo power (STL), whereby temperature deviations are inferred from deviations between the actual turbo power (ITL) and the target turbo power (STL).

Description

[0001] The present invention relates to a method for detecting a temperature change in a fuel cell system, a computer program product for carrying out such a method, a control device for carrying out such a method, and a fuel cell system with such a control device.

[0002] It is known that temperature changes, especially undesirable temperature increases, in a fuel cell system should be detected in a timely manner. If timely detection is not possible, this can lead to reversible or even irreversible damage to the fuel cell system and its components. To provide this safety function, known fuel cells typically include at least one temperature sensor, which is capable of recording explicit temperature values ​​as measured values, particularly on the air side of the fuel cell stack.

[0003] A disadvantage of the known solutions is that the use of temperature sensors is associated with costs. Furthermore, such temperature sensors must be equipped for signal communication in order to transmit the temperature values ​​to a control device. Last but not least, the space required for such necessary temperature sensors is another disadvantage. In addition, these temperature sensors are subject to wear and tear and must be regularly maintained or replaced.

[0004] Methods for detecting a temperature change in a fuel cell system are known from DE 10 2014 016 244 A1, EP 3 435 461 A1 and KR 10 2023 0 025 564 A.

[0005] The object of the present invention is to at least partially overcome the disadvantages described above. In particular, the object of the present invention is to detect temperature changes in a fuel cell stack as early as possible in a cost-effective and simple manner.

[0006] The foregoing problem is solved by a method with the features of claim 1, a computer program product with the features of claim 11, a control device with the features of claim 12, and a fuel cell system with the features of claim 13. Further features and details of the invention will become apparent from the dependent claims, the description, and the drawings. Features and details described in connection with the method according to the invention naturally also apply in connection with the computer program product, the control device, and the fuel cell system according to the invention, and vice versa, so that the disclosure of the individual aspects of the invention always makes, or can make, reciprocal references.

[0007] According to the invention, a method is used for detecting a temperature change in a fuel cell system. Such a fuel cell system comprises at least one fuel cell stack, which is equipped with a turbo device. Such a turbo device comprises a compressor for supplying intake air to an air side of the fuel cell stack and a turbine for removing exhaust air from the air side of the fuel cell stack. A method according to the invention is characterized by the following steps: - Recording the actual turbo power output of the turbo device as measured by the turbo device, - Comparing the measured actual turbo power with a target turbo power, - Output of a temperature signal depending on the result of the comparison between actual turbo power and target turbo power.

[0008] The core concept of the invention is used in fuel cell systems that incorporate a turbo device. For the purposes of this invention, a turbo device is understood to be a device comprising a combination of a compressor and a turbine. The compressor serves to draw in supply air, for example from the environment, and to supply a corresponding compressed volume flow of supply air to the air side of the fuel cell stack. During the chemical reaction within the fuel cell stack with the fuel, the supply air is converted into exhaust air, which can be discharged from the air side of the fuel cell stack, for example, back into the environment, via an air discharge section. Both the supply and discharge sections can, of course, include further components such as heat exchangers and / or a humidifier.To further increase energy efficiency, some of the exhaust air's flow energy can be reused. For this purpose, the turbine of the turbo device is located in the air discharge section, over which the exhaust air from the air side of the fuel cell stack now flows. In other words, some of the kinetic energy of the exhaust airflow is used to rotate the turbine, thus assisting the compression at the compressor for the supply air. Only the necessary difference between the energy absorbed by the turbine and the energy required for compression needs to be supplied to the compressor as external power, primarily in the form of electrical energy.

[0009] As explained above, the actual electrical power required for the compressor depends on the operating conditions and, consequently, the required supply air volume flow. Additionally, the required electrical power depends on the current energy recovery rate from the turbine. Surprisingly, it has now been found that the efficiency of recovering kinetic energy from the exhaust air also depends on the exhaust air temperature at the turbine inlet. Thus, energy recovery, also known as recuperation, in the form of recovered electrical power from the turbine, is particularly high when the exhaust air temperature at the turbine inlet is higher.The higher the temperature of the exhaust air upon entering the turbine, the greater the recovered energy. Consequently, under the same operating conditions, less external electrical power is required for the compressor. Therefore, under steady-state conditions with a constant compression output, the energy required and externally supplied (actual turbine power) depends on the amount of recuperation power provided by the turbine in the current situation. The higher the recuperation power, the less actual turbine power the turbine needs to draw under the same conditions.The described relationship between the recuperation power in the turbine and the temperature at the turbine inlet for the exhaust air allows us to indirectly conclude that increased recuperation power results in a correspondingly higher temperature on the exhaust air side at the turbine inlet. This increased recuperation power, in turn, translates into a reduced actual turbine power input, assuming the same compressor power requirement.

[0010] Based on the relationship described in the preceding paragraph, it can now be determined whether the actual turbo output is related to, or even matches, the expected target turbo output in a specific steady-state operating condition and / or depending on the operating situation explained later. Deviations between the actual and target turbo outputs allow conclusions to be drawn about corresponding temperature values ​​and, in particular, temperature deviations of the exhaust air due to the correlation between the recuperation power and the temperature of the exhaust air. Thus, it is now possible to obtain information about the temperature situation entirely without any actual temperature measurements, simply by correlating the recuperation power with the temperature at the turbine.In particular, this aims to detect an increase in temperature, i.e., excessively hot exhaust air, and to output a corresponding temperature signal.

[0011] It should also be noted that, within the meaning of the present invention, a temperature signal can be configured in various ways. For example, the temperature signal can be a positive signal, as will be explained later, and thus contain information indicating that the current operating situation is consistent with the expected temperature. It is also possible that, additionally or alternatively, the temperature signal is transmitted as a negative signal and can therefore also be interpreted as a warning signal. Such a negative signal can indicate that the current temperature situation does not correspond to the current operating situation, in particular that the current temperature of the exhaust air is too high.

[0012] By using a correlation between recuperation power and turbine temperature, this temperature information, and thus the temperature signal, can be generated without the need for a temperature sensor. For the design of new fuel cells, this means that temperature sensors can even be completely eliminated. This results in reduced costs due to the elimination of physical temperature sensors and less complexity due to the smaller installation space. Since temperature sensors are also subject to wear, especially when they come into contact with aggressive media, the indirect determination of temperature changes also reduces wear and increases the operational reliability of the fuel cell system.By incorporating the method according to the invention, it is also possible to retrofit fuel cell systems with functionality according to the invention by applying the method to existing turbo devices in existing fuel cell systems in the form of the computer program that will be explained later.

[0013] It can be advantageous if, in a method according to the invention, the target turbo output is specified for comparison purposes as a function of the current operating situation of the fuel cell system. An operating situation can be defined by one or more operating parameters of the fuel cell system. In particular, it correlates with the parameter on the compressor side, i.e., especially the required volume flow rate, and the associated required compressor output of the turbo device's compressor. While, in principle, the method according to the invention can be carried out independently of the current operating situation in steady-state operating situations, greater operational flexibility can be achieved by taking current operating situations into account. The corresponding target turbo output for the current operating situation can, for example, be provided from a database.A characteristic map, which has been determined in advance on a test bench for one or more fuel cell systems, can also provide such an operating situation in accordance with and correlation to target turbo performance.

[0014] Further advantages can be achieved if, in a method according to the invention, the temperature signal is output as a positive signal when the actual turbo output matches or substantially matches the target turbo output. As already explained at the outset, a positive signal indicates that the current operating situation with respect to temperature can be considered stable. In other words, a positive signal indicates that the current fuel cell system is in a stable operating condition. This is particularly the case when the target turbo output and the actual turbo output match completely or exhibit only a very small deviation. The maximum permissible deviation for such a positive signal can, for example, be specified within the differential limit value explained later.

[0015] It can also be advantageous if, in a method according to the invention, the temperature signal is output as a negative signal when the actual turbo output deviates from the target turbo output or deviates substantially. The use of the temperature signal as a negative signal can be provided in addition to or as an alternative to a positive signal configuration as described in the preceding paragraph. This can involve a purely qualitative or a quantitative deviation from the target turbo output. A qualitative deviation is understood to mean a simple yes / no distinction, i.e., a digital differentiation between a positive and a negative temperature signal. This results in the temperature signal being output as a negative signal even for minimal deviations from the target turbo output due to the actual turbo output.However, it is preferable if the correlation mentioned later is provided with an actual turbo difference and a difference limit value in order to avoid unwanted false triggers or undesirably frequent negative signals as temperature signals.

[0016] It is further advantageous if, in a method according to the invention, an actual turbo output difference is determined between the actual turbo output and the target turbo output during the comparison, and the temperature signal is output as a function of the determined actual turbo output difference. This applies particularly to the configuration where the temperature signal is to be output as a negative signal. Naturally, the signs of the turbo outputs, as well as the signs of the actual turbo output difference, can be taken into account. An actual turbo output difference is therefore the difference between the expected target turbo output and the actual turbo output.

[0017] The method described in the preceding paragraph can offer advantages if the actual turbo differential is compared with at least one differential limit value, whereby, in particular, the temperature signal is output as a negative signal if the differential limit value is exceeded. The differential limit value can represent a perception threshold or a trigger threshold for the method according to the invention. Naturally, two or more differential limits are also conceivable, which can output one or more different temperature signals, particularly in the form of negative signals, in a graduated manner. This allows different temperature correlations to be taken into account via different differential limits, and the temperature signal can be output with respect to different hazard levels and different correlated differential temperatures at the turbine inlet.The differential limit thus represents the threshold at which the temperature signal is fundamentally output, both qualitatively and especially quantitatively, particularly in the form of the aforementioned negative signal.

[0018] Furthermore, it is advantageous if, in a method according to the invention, at least one differential limit value is specified depending on the current operating situation of the fuel cell system. As explained above, the current operating situation, in particular the compressor power currently required for the volume flow of supply air, influences the current temperature and also the current turbo power of the turbo device. By taking the operating situation into account for the differential limit value, a comparison with this variable, specified differential limit value can also be made, for example, based on appropriately complex characteristic maps recorded from test bench trials.In summary, this leads to an even more precise accuracy of the characteristic map and thus the accuracy of the distinction between outputting a temperature signal or omitting such an output, so that the probability of incorrect assumptions can be reduced and the reliability in the output of real alarms can be increased.

[0019] Further advantages arise if, in a method according to the invention, the temperature signal includes a quantitative temperature parameter determined based on the actual turbo differential. While a temperature signal, through qualitative output in the form of a qualitative positive signal and / or a qualitative negative signal, already offers the advantages of the invention, a temperature parameter can also allow for quantitative evaluation as part of the temperature signal. For example, the quantitative evaluation of the comparison, particularly based on the actual turbo differential, can provide such a quantitative relationship with respect to a temperature parameter.As already explained with reference to several different differential limits, the degree of deviation between actual turbo power and target turbo power can now be output as a temperature parameter as part of the temperature signal, along with a hazard level.

[0020] Furthermore, advantages arise when, in a method according to the invention, an actual temperature value is additionally recorded using a temperature sensor for the air side of the fuel cell stack and compared with a target temperature value. For the output of a temperature signal, the result of the comparison of the actual turbo output with the target turbo output is then used as a plausibility check for the actual temperature value. Particularly when applying and retrofitting existing fuel cell systems with a method according to the invention, an additional plausibility check can thus be provided. Since, as already explained, temperature sensors are subject to wear, such a plausibility check for the indirect determination within the framework of a method according to the invention can detect deviations and thus incorrect determinations in temperature sensors at an early stage.This also makes redundancy testing possible, enabling more accurate detection of unwanted temperature changes in the fuel cell stack.

[0021] Furthermore, advantages arise when the recorded actual turbo output is set as the target turbo output for a defined calibration operating condition of the fuel cell system. While most advantages are generally achieved when the operating condition influences the target turbo output in a detailed and flexible manner, recalibration, pre-calibration, or even a complete calibration can also be performed when the fuel cell system is started and / or shut down. The actual turbo output can be stored as the target turbo output for such defined operating conditions, which are then referred to as calibration operating conditions, and fixed for the execution of the procedure.

[0022] Also related to the present invention is a computer program product comprising instructions which, when executed by a computer, cause it to carry out the steps of a method according to the invention. Thus, a computer program product according to the invention offers the same advantages as those explained in detail with reference to a method according to the invention.

[0023] The present invention also relates to a control device for detecting temperature changes in a fuel cell system. This fuel cell system is equipped with at least one fuel cell stack with a turbo device, which is configured with a compressor for supplying intake air to an air side of the fuel cell stack and with a turbine for extracting exhaust air from the air side of the fuel cell stack. The control device is characterized in that it includes a detection module for detecting the actual turbo power output of the turbo device. Furthermore, a comparison module is provided for comparing the determined actual turbo power output with a target turbo power output.Furthermore, the control device includes an output module for outputting a temperature signal based on the result of a comparison between actual and target turbo output. The acquisition module, the comparison module, and / or the output module are specifically designed for implementing a method according to the invention. Such a control device thus offers the same advantages as those explained in detail with reference to a method according to the invention.

[0024] Furthermore, another object of the present invention is a fuel cell system with at least one fuel cell stack. This fuel cell stack is equipped with an air side and a fuel side. The air side has an air supply section for supplying intake air and an air exhaust section for removing exhaust air. Similarly, the fuel side is equipped with a fuel supply section for supplying fuel and an exhaust gas discharge section for removing exhaust gas. The air side is further equipped with a turbo device comprising a compressor in the air supply section and a turbine in the air exhaust section. Moreover, the turbo device is equipped with a control device according to the present invention for detecting a temperature change in the fuel cell system.Such a fuel cell system also offers the same advantages as have been explained in detail with reference to a method according to the invention.

[0025] Further advantages, features, and details of the invention will become apparent from the following description, in which exemplary embodiments of the invention are described in detail with reference to the drawings. The drawings schematically show: Fig. 1 an embodiment of a control device according to the invention, Fig. 2 an embodiment of a fuel cell system according to the invention, Fig. 3 a further embodiment of a control device according to the invention, Fig. 4 another embodiment of a control device according to the invention, Fig. 5 a further embodiment of a control device according to the invention, Fig. 6 a further embodiment of a fuel cell system according to the invention and Fig. 7 another embodiment of a control device according to the invention.

[0026] The Fig. Figure 1 schematically shows a particularly simple embodiment of a control device 10 according to the invention. This is used, for example, in a fuel cell system 100, as is the case with the Fig. Figure 2 shows that the actual turbo output (ITL) is recorded in the control device 10 using the acquisition module 20 and transferred to the comparison module 30. There, the actual turbo output (ITL) is compared with the target turbo output (STL), either by static preset values ​​or by flexible adjustment, for example, to an operating situation (BS). The comparison result then triggers the output of a temperature signal (TS) in the output module 40 or suppresses it. In this embodiment, the Fig. 1. The actual form of the temperature signal TS is also irrelevant. Positive signals, negative signals, and even quantitative signals can be used as the temperature signal TS.

[0027] Fig. Figure 2 schematically shows the integration of such a control device 10 into a fuel cell system 100. Fig. Figure 2 shows a fuel cell system 100 with a fuel cell stack 110. This stack is equipped with an air side 120 on the left and a fuel side 130 on the right. Fuel B is supplied to the fuel side 130 via a fuel supply section 132. This fuel is then chemically reacted in the fuel cell stack 110, producing exhaust gas AG, which is then discharged via the exhaust gas discharge section 134. Supply air ZL is supplied to the air side 120 via an air supply section 122. After the chemical reaction in the fuel cell stack 110, the generated exhaust air AL is discharged via the air discharge section 124. The air supply section 122 and the air discharge section 124 are connected to each other via a turbo device 140 in an energy-conserving manner. This turbo device 140 is integrated with a compressor 142 in the air supply section 122 and with a turbine 144 in the air discharge section 124.This makes it possible to capture kinetic energy from the exhaust air flow velocity AL and transfer it from turbine 144 to compressor 142. Only the unrecuperated power, in the form of the differential power, is recorded as actual turbo power ITL and can be determined by control device 10.

[0028] The Fig. Figure 3 shows a further development of the control device as well as the associated procedure. Starting from the Fig. 1. Instead of specifying a common, universally valid target turbocharger output (STF), a target turbocharger output (STL) is selected from a database. This database may, for example, contain a characteristic map which, based on an input value such as the operating situation BS, outputs a target turbocharger output (STL) suitable for this operating situation BS and provides a comparison module 30 for comparison purposes.

[0029] Even the Fig. Figure 4 shows a further training process, in which a quantitative evaluation of the generation of an actual turbo differential (ITD) is performed as part of comparison module 30. This actual turbo differential (ITD) is then compared in output module 40 with a predefined differential limit (DGW), and the temperature signal (TS) is prepended accordingly.

[0030] The Fig. 5 represents the embodiment of the Fig. 4. Here, no static differential limit value DW is specified; instead, this value also depends on the operating situation BS and is selected, for example, from a characteristic map stored in a database. Furthermore, in the implementation of the Fig. 5. A temperature signal TS is quantitatively assigned to a temperature parameter TP. This can be, for example, a quantitative statement about the degree of temperature deviation, but also an actual temperature value in degrees Celsius or degrees Kelvin.

[0031] In the Fig. 6 is a further development of the embodiment of Fig. Figure 2 shows the fuel cell system 100 shown here, which is now additionally or as an existing fuel cell system 100 equipped with a temperature sensor 150. This makes it possible to record an actual temperature value ITW and also transmit it to the control device 10.

[0032] In the Fig. Figure 7 shows the integration of such an actual temperature value (ITW). How the Fig.Figure 7 shows that output module 40 now uses not only the actual turbo differential ITD, but also the actual temperature value ITW, specifically in comparison with a target temperature value STW. This provides a second parameter for consideration in the output of the temperature signal TS.

[0033] The preceding explanation of the embodiments describes the present invention exclusively by way of examples. Reference symbol list 10 Control device 20 Data acquisition module 30 Comparison module 40 Output module 100 fuel cell systems 110 fuel cell stacks 120 air side 122 Air supply section 124 Air discharge section 130 Fuel side 132 Fuel supply section 134 Exhaust gas discharge section 140 Turbo device 142 Compressor 144 Turbine 150 temperature sensor ZL supply air AL exhaust air B Fuel Exhaust AG ITL Actual Turbo Power STL target turbo output ITD Actual Turbo Difference DGW difference limit value ITW Actual Temperature Value STW target temperature value TS temperature signal TP temperature parameters BS operational situation

Claims

[1] Method for detecting a temperature change in a fuel cell system (100) with at least one fuel cell stack (110) and a turbo device (140) with a compressor (142) for supplying intake air (ZL) to an air side (120) of the fuel cell stack (110) and a turbine (144) for removing exhaust air (AL) from the air side (120) of the fuel cell stack (110), characterized by the following steps: - Recording the actual turbo power (ITL) of the turbo device (140) as measured by the turbo device (140), - Comparison of the determined actual turbo power (ITL) with a target turbo power (STL), - Output of a temperature signal (TS) depending on the result of the comparison between actual turbo power (ITL) and target turbo power (STL), whereby temperature deviations are inferred from deviations between the actual turbo power (ITL) and the target turbo power (STL). [2] Method according to claim 1, characterized by , that the target turbo power (STL) is specified for comparison depending on the current operating situation (BS) of the fuel cell system (100). [3] Method according to any of the preceding claims, characterized by , that the temperature signal (TS) is output as a positive signal when the actual turbo power (ITL) matches or substantially matches the target turbo power (STL). [4] Method according to any of the preceding claims, characterized by , that the temperature signal (TS) is output as a negative signal if the actual turbo power (ITL) deviates or substantially deviates from the target turbo power (STL). [5] Method according to any of the preceding claims, characterized by, that during the comparison an actual turbo difference (ITD) is determined between the actual turbo power (ITL) and the target turbo power (STL) and the output of the temperature signal (TS) is output depending on the determined actual turbo difference (ITD). [6] Method according to claim 5, characterized by , that the actual turbo difference (ITD) is compared with at least one differential limit value (DGW), whereby, in particular, if the differential limit value (DGW) is exceeded, the temperature signal (TS) is output as a negative signal. [7] Method according to claim 6, characterized by , that at least one differential limit value (DGW) is specified depending on the current operating situation (BS) of the fuel cell system (100). [8] Method according to any one of claims 5 to 7, characterized by , that the temperature signal (TS) contains a quantitative temperature parameter (TP) which is determined on the basis of the actual turbo difference (TD). [9] Method according to any of the preceding claims, characterized by , that in addition an actual temperature value (ITW) is recorded by means of a temperature sensor (150) for the air side (120) of the fuel cell stack (110) and is compared with a target temperature value (STW), whereby for the output of a temperature signal (TS) the result of the comparison of the actual turbo power (ITL) with the target turbo power (STL) is used as a plausibility check for the actual temperature value (ITW). [10] Method according to any of the preceding claims, characterized by , that the recorded actual turbo power (ITL) is set to a defined calibration operating situation of the fuel cell system (100) as the target turbo power (STL). [11] Computer program product comprising instructions which, when executed by a computer, cause it to perform the steps of a method having the features of any one of claims 1 to 10. [12] Control device (10) for detecting a temperature change in a fuel cell system (100) with at least one fuel cell stack (110) and a turbo device (140) with a compressor (142) for supplying intake air (ZL) to an air side (120) of the fuel cell stack (110) and a turbine (144) for removing exhaust air (AL) from the air side (120) of the fuel cell stack (110), the control device (10) characterized bya detection module (20) for detecting the actual turbo power (ITL) of the turbo device (140), a comparison module (30) for comparing the determined actual turbo power (ITL) with a target turbo power (STL), and an output module (40) for outputting a temperature signal (TS) depending on the result of the comparison between actual turbo power (ITL) and target turbo power (STL), wherein the detection module (20), the comparison module (30), and / or the output module (40) are configured for an embodiment of a method with the features of any one of claims 1 to 10. [13] Fuel cell system (100) with at least one fuel cell stack (110), comprising an air side (120) and a fuel side (130), wherein the air side (120) has an air supply section (122) for supplying intake air (ZL) and an air discharge section (124) for removing exhaust air (AL), and the fuel side (130) has a fuel supply section (132) for supplying fuel (B) and an exhaust gas discharge section (134) for removing exhaust gas (AG), wherein a turbo device (140) with a compressor (142) in the air supply section (122) and with a turbine (144) in the air discharge section (124) is further arranged on the air side (120), characterized by , that the turbo device (140) has a control device (10) with the features of claim 12 for detecting a temperature change in the fuel cell system (100).

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