Fuel cell system, gas tank system and method for operating a gas tank system

Abstract

A method for operating a gas tank system includes detecting a pressure in a high-pressure line system in a state in which the gas tank system is connected to the high-pressure line system, the high-pressure pipeline system is disconnected from the gas tank through the first valve device in the closed state and is disconnected from the consumption system through the flow adjusting device in the closed state for a predetermined time period; the detected pressure is compared to a pressure threshold. If the detected pressure is less than the pressure threshold value, supplying a limited amount of gas from the gas tank into the high-pressure line system by opening the first valve device in a limited manner in time; ascertaining a leakage mass flow in the high-pressure line system after the supply of the limited amount of gas; comparing the leakage mass flow to a leakage threshold; and the first valve device is opened only if the determined leakage mass flow is less than a leakage threshold value.

Description

Field of the Invention

[0001] The present invention relates to a fuel cell system, in particular a fuel cell system for a vehicle, a gas tank system, in particular a gas tank system for a fuel cell system, and a method for operating a gas tank system. Background Art

[0002] Fuel cells are increasingly being used as transducers, especially also in vehicles, to directly convert the chemical energy stored in a fuel such as hydrogen together with oxygen into electrical energy. A fuel cell has an anode, a cathode, and an electrolyte membrane disposed between the anode and the cathode. Oxidation of the fuel takes place at the anode, and reduction of oxygen takes place at the cathode.

[0003] Generally, fuel is supplied from a tank to the fuel cell via a pipeline system, and the gaseous fuel is stored in the tank under high pressure. A disconnect valve or a shut-off valve is usually provided between the tank and the high-pressure part of the pipeline system. The high-pressure part is usually also connected via a flow control valve to a pipeline part connected to the fuel cell.

[0004] When the fuel cell is shut down, the shut-off valve and the flow control valve are usually closed, so that the high-pressure part forms a sealed volume. Due to a decrease in the sealing effect of the hydraulic components of the pipeline system or due to damage, fuel may leak from the pipeline system. To reduce the associated risks, it is desirable to reliably detect such a leak and, in the event of a leak, keep the outflow of fuel as small as possible.

[0005] U.S. Patent US7127937B2 discloses a method for detecting a leak in a fuel cell system, in which, in the case of the fuel cell being shut down, a first disconnect valve and a second disconnect valve are closed in order to disconnect the supply pipeline from the fuel tank via the first disconnect valve and to disconnect the supply pipeline from the fuel cell via the second disconnect valve. After the valves are closed, the pressure in the supply pipeline is detected and stored. Before the fuel cell is restarted, the pressure in the supply pipeline is re-detected with the disconnect valves closed and compared with the stored value in order to infer the presence of a leak in the event of a pressure difference. Summary of the Invention

[0006] In this context, the present invention provides a method for operating a gas tank system according to the features of claim 1, a gas tank system according to the features of claim 6, and a fuel cell system according to the features of claim 10.

[0007] According to a first aspect of the invention, a method for operating a gas tank system includes: detecting the pressure in a high-pressure pipeline system in a state in which the high-pressure pipeline system is disconnected from the gas tank by a first valve device in a closed state and disconnected from a consumption system by a flow regulating device in a closed state for a predetermined period of time; and comparing the detected pressure with a pressure threshold. If the detected pressure is less than the pressure threshold, a limited amount of gas is also supplied from the gas tank to the high-pressure pipeline system by opening the first valve device in a time-limited manner; after supplying the limited amount of gas, the leakage mass flow in the high-pressure pipeline system is determined; the leakage mass flow is compared with a leakage threshold; and the first valve device is opened only if the determined leakage mass flow is less than the leakage threshold.

[0008] According to a second aspect of the invention, a gas tank system for a consumption system includes: a tank for storing a gas, in particular hydrogen; a high-pressure pipeline system; a first valve device that can be switched between an open state and a closed state, in the open state, the first valve device connects the tank to the high-pressure pipeline system, and in the closed state, the first valve device disconnects the tank from the high-pressure pipeline system; a flow regulating device that can be switched between an open state and a closed state for attaching the high-pressure pipeline system to the consumption system; a pressure sensor for detecting the pressure in the high-pressure pipeline system; and a control device that is connected to the first valve device, the flow regulating device, and the pressure sensor in a signal-transmitting manner and is configured to cause the gas tank system to perform the method according to the first aspect of the invention.

[0009] According to a third aspect of the invention, a fuel cell system, in particular for a motor vehicle, includes a gas tank system according to the second aspect of the invention and a consumption system having a fuel cell assembly, the fuel cell assembly having a fuel supply interface connected to a second valve device.

[0010] The basic concept of the present invention lies in performing a leak check in the high-pressure part of the pipeline system that connects the gas cylinder to a consumption system, such as a fuel cell, after a pre-determined small amount of gas has been introduced from the cylinder into the high-pressure pipeline system. For this purpose, first, it is checked whether there is a suspicion of a leak in the high-pressure pipeline system. This is done by comparing the pressure in the high-pressure pipeline system with a boundary value at a time point after a determined stationary time of the system, when two valves or flow regulating devices have been continuously closed for a determined time, such as continuously closed for more than one minute. If the pressure is lower than this boundary value, a small amount of gas is supplied from the cylinder to the high-pressure pipeline system by switching the first valve device or cylinder valve device from the closed state to the open state and then switching it back to the closed state after a short time, where the flow regulating device preferably remains closed. This causes the pressure in the high-pressure pipeline system to rise. Then, the leak mass flow is determined, for example, based on the pressure change curve and / or temperature change curve determined after supplying a pre-determined amount of gas to the high-pressure pipeline system. According to the present invention, the first valve device is only opened when the leak mass flow is less than a boundary value, preferably close to zero, and optionally, the flow regulating device is also opened.

[0011] One advantage of the present invention is that the leak check can be performed when the system is stationary, and if a leak occurs, the amount of gas flowing out into the surrounding environment is reduced due to the first valve device being opened only limitedly in time.

[0012] The features and advantages disclosed in connection with one aspect of the present invention are also disclosed for each other aspect. In particular, the control device can initiate all method steps and perform various steps itself, such as the step of determining each value based on the measured physical parameters. For example, the control device can have a computing unit, such as a CPU, ASIC, FPGA, etc., and a data memory, especially a non-volatile data memory, such as a flash memory, SD memory, etc., which can be read by the computing unit. The data memory can store software that can be executed by the computing unit to cause the system to perform the steps of the method.

[0013] Advantageous embodiments and improvements can be derived from the other dependent claims and the description with reference to the accompanying drawings.

[0014] According to some embodiments, it may be provided that determining the leakage mass flow includes: detecting a pressure change curve in the high-pressure pipeline system during a predetermined time period in a state where both the first valve device and the flow regulating device are in their closed states; obtaining a pressure gradient from the detected pressure change curve; and determining the leakage mass flow based on the obtained pressure gradient. For example, the leakage mass flow may be obtained from the pressure gradient with the aid of the ideal gas equation. The advantage of using the measured pressure change curve to determine the leakage mass flow is that the pressure is always measured and there is no need to compulsorily require additional sensors.

[0015] According to some embodiments, it may be provided that the method additionally includes: if the determined leakage mass flow is greater than or equal to a leakage threshold, generating a warning signal and / or writing a fault message into the data memory.

[0016] According to some embodiments, it may be provided that, in order to supply a limited amount of gas from the gas tank to the high-pressure pipeline system, the first valve device is opened for a predetermined first time period, for example, a time period between 20 milliseconds and 3 seconds. Thus, the supply of the limited amount of gas can be carried out, for example, in a purely time-controlled manner, where the predetermined first time period may optionally be related to the pressure in the tank, especially in such a way that the higher the pressure in the tank, the shorter the opening time period.

[0017] According to other embodiments, it may be provided that, in order to supply a limited amount of gas from the gas tank to the high-pressure pipeline system, the first valve device is opened until a predetermined pressure is reached in the high-pressure pipeline system. Thus, the supply of the limited amount of gas can be carried out in a closed-loop regulated manner. This has the advantage that the leakage mass flow is always determined under precisely defined conditions, thereby improving the accuracy of determining the leakage mass flow.

[0018] According to some embodiments, it may be provided that, before establishing the first state, a predetermined pressure in the high-pressure pipeline system is adjusted by coordinately opening and closing the first and second valve devices, where the pressure threshold is equal to the adjusted predetermined pressure or is smaller than the adjusted pressure by a predetermined difference, for example, a difference corresponding to 5% to 25% of the adjusted pressure. For example, when the system is shut down, a predetermined pressure in the high-pressure pipeline system can be adjusted in such a way that either the first valve device is first closed and the pressure in the high-pressure pipeline system is further reduced until the second valve device is closed, or the second valve device is first closed and the pressure in the high-pressure pipeline system is increased until the first valve device is closed. The pressure detected in this state is stored, for example, in the control device, and can be used as a reference value for the pressure threshold.

[0019] According to some embodiments, it may be provided that the first valve device has a switchable solenoid valve that can be switched between an open state and a closed state.

[0020] According to some embodiments, it may be provided that the flow rate regulating device has a second valve device, which is in particular in the form of a switchable solenoid valve that can be switched between an open state and a closed state. The flow rate regulating device can generally be arranged to change the flow rate from the high-pressure pipeline system to the consumption system and thus change the mass flow. Similarly, thereby, the pressure of the gas flowing from the high-pressure pipeline system into the consumption system can also be changed by the flow rate regulating device. Therefore, the flow rate regulating device can also be referred to as a pressure regulator.

[0021] According to some embodiments, it may be provided that the high-pressure pipeline system has a supply interface for attaching a filling system, wherein the supply interface is closed by a check valve to prevent gas from flowing out of the high-pressure pipeline system. Description of the Drawings

[0022] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings:

[0023] Figure 1 A schematic diagram showing a hydraulic connection diagram of a fuel cell system according to an embodiment of the present invention; and

[0024] Figure 2 A flowchart showing a method according to an embodiment of the present invention.

[0025] In the drawings, unless otherwise specified, the same reference numerals denote the same or functionally identical components. Detailed Description of the Embodiments

[0026] Figure 1 A fuel cell system 200 is schematically shown, which can be used, for example, in a vehicle. The fuel cell system 200 includes a gas tank system 100 and a consumption system 205.

[0027] As Figure 1 only schematically shown, the consumption system 205 has a fuel cell assembly 210. The fuel cell assembly 210 has at least one fuel cell, preferably a plurality of fuel cells connected in series electrically, and these fuel cells are arranged to directly convert the chemical energy stored in a gaseous fuel such as hydrogen together with oxygen into electrical energy. As Figure 1 further schematically shown, the fuel cell assembly 210 has a fuel supply interface 211 through which gaseous fuel can be supplied to the fuel cell assembly 210, in particular to the anode of at least one fuel cell.

[0028] Next, the gas tank system 100 will be described in conjunction with the fuel cell system 200. However, the gas tank system 100 is not limited to this use, but can also be used in combination with other consumption systems, such as gas engines, etc. As Figure 1 As schematically shown in [reference], the gas tank system 100 has a tank 1, a high-pressure pipeline system 2, a first valve device 3, a flow rate regulating device 5, a pressure sensor 4, and a control device 6. Optionally, the gas tank system 100 may also have a filling interface or a supply interface 20.

[0029] The tank 1 is configured to store gas, especially hydrogen. For example, the tank 1 can be designed to store gas at a pressure of up to 800 bar.

[0030] The high-pressure pipeline system 2 may especially have a connecting pipeline 21 and optionally a supply pipeline 22, as Figure 1 schematically and only exemplarily shown in [reference]. The connecting pipeline 21 connects the tank 1 to the consumption system 205.

[0031] The first valve device 3 may, for example, have a switchable solenoid valve 3 that can be switched between a closed state and an open state. Generally speaking, the first valve device 3 can be switched between a closed state and an open state. As Figure 1 schematically shown in [reference], the valve device 3 is arranged between the tank 1 and the high-pressure pipeline system 2, especially between the tank 1 and the connecting pipeline 21. In the open state, the first valve device 3 connects the tank 1 to the high-pressure pipeline system 2. In the closed state, the first valve device 3 disconnects the tank 1 from the high-pressure pipeline system 2 from each other.

[0032] The flow rate regulating device 5 is configured to change the gas flow rate and / or pressure of the gas flowing through the flow rate regulating device. Generally speaking, the flow rate regulating device 5 can be switched between a closed state and an open state. The second valve device 5 may, for example, have a switchable solenoid valve that can be switched between an open state and a closed state. As Figure 1 schematically shown in [reference], the flow rate regulating device 5 is arranged between the consumption system 205 and the high-pressure pipeline system 2, especially between the consumption system 205 and the connecting pipeline 21. In the open state, the flow rate regulating device 5 connects the consumption system 205 to the high-pressure pipeline system 2. In the closed state, the flow rate regulating device 5 disconnects the consumption system 205 from the high-pressure pipeline system 2 from each other.

[0033] The supply pipeline 22 is connected to the supply interface 20, which can be configured, for example, as a plug-in interface for a tank connection. As Figure 1 shown in [reference], a check valve 8 can be arranged in the supply pipeline 22, and the check valve closes the supply interface 20 to prevent gas from flowing out of the high-pressure pipeline system 2.

[0034] When the first valve device 3 and the flow regulating device 5 are in the closed state, the high-pressure pipeline system 2 thus forms a closed volume, and in the case of non-sealing, a certain mass flow of gas leakage may flow out of this volume.

[0035] As Figure 1 shown, the pressure sensor 4 is connected to the high-pressure pipeline system 2 and is arranged to detect the pressure in the high-pressure pipeline system 2.

[0036] In Figure 1 it, the control device 6 is only schematically shown as a block and is implemented as an electronic control device 6. As Figure 1 exemplarily shown in it, the control device 6 can have a computing unit 61, such as a CPU, ASIC, FPGA, etc. and have a data memory 62, especially a non-volatile data memory, such as a flash memory, SD memory, etc., which can be read by the computing unit. As Figure 1 schematically shown in it, the control device 6 is connected to the first valve device 3, the flow regulating device 5 and the pressure sensor 4 in a signal-transmitting manner, for example, by a wired connection, for example, by a bus system. Alternatively, a wireless connection can also be provided, for example, by WiFi, etc.

[0037] The control device 6 is arranged to cause the gas tank system 100 to execute Figure 2 the method M shown in it. For example, software can be stored in the data memory 62, which can be executed by the computing unit 61 to cause the system 100 to execute the method M.

[0038] In an optional step M0, a predetermined pressure in the high-pressure pipeline system 2 is adjusted by coordinately opening and closing the first valve device 3 and the flow regulating device 5. For example, when the two valve devices 3, 5 are opened to supply gaseous fuel from the tank 1 to the consumption system 205, the control device 6 can first switch the first valve device 3 to the closed state, and then, when a predetermined pressure is reached in the high-pressure pipeline system 2 (this pressure can be detected by the pressure sensor 4, for example), the control device switches the flow regulating device 5 to the closed state. The pressure present in the high-pressure pipeline system 2 after the two valve devices 3, 5 are closed can be stored in the data memory 62, for example.

[0039] In step M1, the pressure in the high-pressure pipeline system 2 is detected by means of the pressure sensor 4. Step M1 is carried out after a predetermined period of time has elapsed since the two valve devices 3, 5 were closed, for example, a period of at least one minute (during which the valve devices 3, 5 are not opened). Step M1 is also carried out in the state where both valve devices 3, 5 are closed, that is, in the state where the high-pressure pipeline system 2 forms a closed volume.

[0040] In step M2, the control device compares the pressure detected in step M1 with a pressure threshold. This pressure threshold can, for example, correspond to the pressure set in step M0 or to the pressure detected after the valve devices 3, 5 are closed. Alternatively, the pressure threshold can also be lower by a difference value than the pressure set in step M0 or the pressure detected after the valve devices 3, 5 are closed, for example, lower by a difference value corresponding to 5% to 25% of the set pressure.

[0041] If the pressure detected in step M2 is greater than or equal to this pressure threshold (as indicated by the symbol "-" herein), Figure 1 then method M can directly transition to step M6, and switch the first valve device 3 and optionally also the flow regulating device 5 to the open state.

[0042] If the pressure detected in step M2 is less than this pressure threshold (as indicated by the symbol "+" herein), Figure 1 then this is an indication of a leak in the high-pressure pipeline system 2, and method M transitions to step M4.

[0043] In step M3, the control device 6 switches the first valve device 3 to the open state in a time-limited manner, so that a limited amount of gas is supplied from the gas tank 2 to the high-pressure pipeline system 2, and then switches the first valve device back to the closed state. For example, the control device 6 can switch the first valve device 3 to the open state for a pre-determined first time period, for example, a time period between 20 milliseconds and 3 seconds, and then close the first valve device 3. Alternatively, the control device 3 can keep the first valve device 3 switched to the open state until a pre-determined pressure is reached in the high-pressure pipeline system, which is detected by the pressure sensor 4, for example.

[0044] In step M4, after supplying the limited amount of gas in M3, that is, supplying under the condition that the valve devices 3, 5 are closed, the leakage mass flow in the high-pressure pipeline system 2 is determined. For example, for this purpose, the pressure change curve in the high-pressure pipeline system 2 can be detected by the pressure sensor 4 for a pre-determined time period (this time period can be between 0.5 seconds and 2 minutes, for example) (step M41). The control device 3 can obtain the pressure gradient from the detected pressure change curve in step M42, and determine the leakage mass flow according to the obtained pressure gradient in another step M43, for example, by using the ideal gas equation.

[0045] In step M5, the control device 3 compares the leakage mass flow with a leakage threshold, for example, by comparing the obtained pressure gradient with the threshold. If the pressure gradient or the leakage mass flow is less than the leakage threshold (as indicated by the symbol "-" herein), Figure 2If it is determined in step M5 that the determined leakage mass flow is greater than or equal to the leakage threshold (as indicated by the symbol “+” therein), then method M transitions to step M6, and control device 6 switches the first valve device 3 and optionally the flow rate regulating device 5 into the open state.

[0046] If it is determined in step M5 that the determined leakage mass flow is greater than or equal to the leakage threshold (as indicated by the symbol “-” therein), then method M transitions to step M7. In step M7, control device 6 can, for example, generate or output a warning signal, for example in the form of a visual signal or an acoustic signal. Alternatively or additionally, computing unit 61 can write a fault message into data memory 62. Figure 2 If it is determined in step M5 that the determined leakage mass flow is greater than or equal to the leakage threshold (as indicated by the symbol “-” therein), then method M transitions to step M7. In step M7, control device 6 can, for example, generate or output a warning signal, for example in the form of a visual signal or an acoustic signal. Alternatively or additionally, computing unit 61 can write a fault message into data memory 62.

[0047] Although the present invention has been exemplarily illustrated by way of embodiments, the present invention is not limited thereto, but can be modified in various ways. In particular, combinations of the above embodiments are also conceivable.

Claims

1. A method (M) for operating a gas tank system (100), the method comprising: Detect (M1) the pressure in the high-pressure pipeline system (2) in the following state, in which the high-pressure pipeline system (2) is disconnected from the gas tank (1) by a first valve device (3) in a closed state and disconnected from the consumption system (205) by a flow regulating device (5) in a closed state for a predetermined period of time; compare (M2) the detected pressure with a pressure threshold; if the detected pressure is less than the pressure threshold, supply (M3) a limited amount of gas from the gas tank (1) into the high-pressure pipeline system (2) by opening the first valve device (3) in a time-limited manner; determine (M4) the leakage mass flow in the high-pressure pipeline system (2) after supplying (M3) the limited amount of gas; compare (M5) the leakage mass flow with a leakage threshold; and open (M6) the first valve device (3) only when the determined leakage mass flow is less than the leakage threshold.

2. The method (M) according to claim 1, wherein, The determination (M4) of the leakage mass flow includes: Detect (M41) the pressure change curve in the high-pressure pipeline system (2) for a predetermined period of time in a state where the first valve device (3) and the flow regulating device (5) are in their closed states; Determine (M42) the pressure gradient from the detected pressure change curve; and Determine (M43) the leakage mass flow based on the determined pressure gradient.

3. The method (M) according to claim 1 or 2, the method additionally having: If the required leakage mass flow is greater than or equal to the leakage threshold, generate (M7) a warning signal and / or write a fault message into the data memory (62).

4. The method (M) according to any one of the above claims, wherein, In order to supply (M3) the limited amount of gas from the gas tank (1) into the high-pressure pipeline system (2), open the first valve device (3) for a predetermined first period of time, for example, a period between 20 milliseconds and 3 seconds, or open the first valve device until a predetermined pressure is reached in the high-pressure pipeline system.

5. The method (M) according to any one of the above claims, the method additionally comprising: Before establishing the first state, adjust (M0) a predetermined pressure in the high-pressure pipeline system (2) by coordinately opening and closing the first valve device and the second valve device (3, 5), where the pressure threshold is equal to the adjusted predetermined pressure or is smaller than the adjusted pressure by a predetermined difference.

6. A gas tank system (100) for a consumption system (205), the gas tank system having: A tank (1) for storing a gas, in particular hydrogen; A high-pressure pipeline system (2); A first valve device (3) capable of switching between an open state and a closed state, in the open state, the first valve device connects the tank (1) to the high-pressure pipeline system (2), and in the closed state, the first valve device disconnects the tank (1) from the high-pressure pipeline system (2); A flow rate regulating device (5) capable of switching between an open state and a closed state for attaching the high-pressure pipeline system (2) to the consumption system (205); A pressure sensor (4) for detecting the pressure in the high-pressure pipeline system (2); and A control device (6) connected to the first valve device (3), to the flow rate regulating device (5) and to the pressure sensor (4) in a signal-transmitting manner and arranged to cause the gas tank system (100) to perform the method (M) according to any one of the above claims.

7. The gas tank system (100) according to claim 6, wherein, The first valve device (3) has a switchable solenoid valve that can be switched between an open state and a closed state.

8. The gas tank system (100) according to claim 6 or 7, wherein, The flow regulating device (5) has a switchable solenoid valve that can be switched between an open state and a closed state.

9. The gas tank system (100) according to one of claims 6 to 8, wherein, The high-pressure pipeline system (2) has a supply interface (20) for attaching a filling system, where the supply interface (20) is closed by a check valve (8) to prevent gas from flowing out of the high-pressure pipeline system (2).

10. A fuel cell system (200), in particular for a motor vehicle, the fuel cell system comprising: The gas tank system (100) according to one of claims 6 to 9; and A consumption system (205) with a fuel cell assembly (210), the fuel cell assembly having a fuel supply interface (211) connected to the flow regulating device (5).

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