Diagnosis method for diagnosing a state of an electrolysis system

Abstract

The present invention relates to a diagnosis method (100) for diagnosing a state of an electrolysis system (200), wherein the diagnosis method (100) comprises: - determining (101) a water mass flow balance across a cell stack (201) of the electrolysis system (200), - comparing (103) the water mass flow balance determined with an expected value determined, and - outputting (105) a warning message in the event that the water mass flow balance varies from the expected value.

Description

[0001] R.416510

[0002] - 1 -

[0003] Description

[0004] title

[0005] Diagnostic procedure for diagnosing the condition of an electrolysis system

[0006] The presented invention relates to a diagnostic method for diagnosing a condition of an electrolysis system and an electrolysis system according to the preambles of the independent claims.

[0007] State of the art

[0008] Electrolysis systems are used, among other things, to produce green hydrogen.

[0009] An electrolysis system comprises a cell stack, the so-called "electrolysis stack," in which several electrolysis cells are stacked on top of each other. Within these electrolysis cells, water undergoes electrochemical splitting into hydrogen and oxygen.

[0010] In electrolysis cells with a membrane, such as the Proton Exchange Membrane (PEM) technology or the Anion Exchange Membrane (AEM) technology, the membrane separates the two reaction chambers on the anode side and cathode side from each other, thus ensuring a separation of the two products hydrogen and oxygen.

[0011] Disclosure of the invention

[0012] Within the scope of the presented invention, a diagnostic method for diagnosing the condition of an electrolysis system and an electrolysis system according to the independent claims are presented. Further features and details of the invention will become apparent from the respective dependent claims. R.416510

[0013] - 2 -

[0014] Description and drawings. Features and details described in connection with the diagnostic method according to the invention naturally also apply in connection with the electrolysis system according to the invention, and vice versa, so that the disclosure regarding the individual aspects of the invention always refers to each other or can refer to each other.

[0015] The presented invention is particularly useful for detecting a fault, such as a leak, in an electrolysis system.

[0016] Thus, according to a first aspect of the presented invention, a diagnostic method for diagnosing the condition of an electrolysis system is presented.

[0017] The presented diagnostic procedure includes determining a water mass flow balance across a cell stack of the electrolysis system, comparing the determined water mass flow balance with a determined expected value, and issuing a warning message if the water mass flow balance deviates from the expected value.

[0018] In the context of the presented invention, the output of a warning message means displaying the warning message on an output unit, storing the warning message in a memory, such as an error memory, and / or transmitting the warning message to a target function, in particular to adapt the electrolysis system to an error reported by the warning message.

[0019] To detect a fault, such as a membrane tear or hole, or an internal leak within a cell stack of an electrolysis system, as quickly as possible, a water mass flow balance is determined across the cell stack using mass flow information, e.g., measured by a number of mass flow sensors or calculated from the pump speed at the respective media interfaces, according to the presented diagnostic procedure. If the determined water mass flow balance deviates from an expected value, a fault in the cell stack can be concluded. R.416510

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[0021] A cell stack of an electrolysis system typically has three interfaces: an inlet and outlet on the anode side and an outlet on the cathode side. The water entering at the anode inlet is essentially split as follows.

[0022] Some of the water is split into oxygen and hydrogen as a reactant for hydrogen production. The consumed

[0023] Water mass flow rate (ṁH2O,CnsDes) can be calculated using the stacking flow rate IStck, the cell number NCell, the Faraday constant F and the molar mass of water MH2O according to formula (1) as follows.

[0024] ṁH2O,CnsDes = (IStck·MH2O·NCell) / (2F) (1)

[0025] Another portion of the water migrates across the membrane to the cathode side and exits there along with the hydrogen produced. To determine this mass flow rate mwtrEio, the number of hydrogen ions Ṅ⁺H is calculated according to formula (2) as a function of the stack flow rate Istck, using the Faraday constant F and the number of cells NCell in the cell stack.

[0026] N+ = 'stck^Ncell _2

[0027]

[0028] By means of the so-called "drag factor" n dThe number of water atoms carried along per hydrogen ion, which describes how many, can now be used together with the molar mass of water to calculate the electroosmosis mass flow rate mwtrElo according to formula (3). ṁWtrElo=MH2O·nd·Ṅ⁺H (3)

[0029] The remainder of the liquid water exits at the anode outlet along with the oxygen produced.

[0030] Optionally, the proportion of water that transitions into the gas phase as vapor on both the anode and cathode sides can also be calculated. R.416510

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[0032] Using the formulas (1), (2) and (3) described above, the following relationships on the anode output and the cathode output result for a given stack current according to formulas (4) and (5).

[0033] ṁH2OAnodeOut = ṁH2OAnodeIn − ṁWtrElo − ṁH2O,CnsDes (4)ṁH2OCathodeOut = ṁWtrElo (5)

[0034] In the event that mass flow information is required for the

[0035] Since the anode input ṁH2OAnodeIn and the anode output ṁH2OAnodeOut are available, the following plausibility check can be carried out using the mass flow balance according to formula (6).

[0036] ṁH2OAnodeIn − ṁH2OAnodeOut = ṁWtrElo + ṁH2O,CnsDes (6)

[0037] Accordingly, it can be provided that the water mass flow balance is determined by subtracting an anode output mass flow mmoAnodeout, which is determined at an anode output of the cell stack, from an anode input mass flow ṁH2OAnodeIn, which is determined at an anode input of the cell stack, and that the expected value is determined by adding an electroosmosis mass flow ṁWtrElo to a consumed mass flow ṁH2O,CnsDes or a quantity of consumed water.

[0038] If the mass flow information at the anode output ṁH2OAnodeOut is higher than expected, it can be assumed that water from the cathode side, which is operated at a higher pressure than the anode side, has entered the anode side through a membrane tear or hole or another internal leakage between anode and cathode, such as a sealing defect, so that equation (7) applies.

[0039] ṁH2OAnodeOut + ṁHigh,Thes > ṁH2OAnodeIn − ṁWtrElo − ṁH2O,CnsDes (7)

[0040] To make fault detection more robust, a freely selectable diagnostic threshold ṁHigh,Thes > 0 can be introduced. R.416510

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[0042] If the mass flow information at the anode output ṁH2OAnodeOut is lower than expected, it can be assumed that water has leaked out of the electrolysis system, since the water cannot reach the cathode side against the pressure difference, so equation (8) applies.

[0043] m H2OAnodeOut + H'lLow 'hes < '^'HlOAnodeln ~ fiwtrElo ~ tT^H2O, CnsDes (8)

[0044] To make fault detection more robust, a freely selectable diagnostic threshold can be used. Lo w, The S < 0 will be introduced.

[0045] Accordingly, it may also be provided that, in the event that the anode output mass flow rate is greater than the expected value, the warning message includes a notification indicating a transfer of water from a cathode compartment of the cell stack to an anode compartment of the cell stack, or, in the event that the anode output mass flow rate is less than the expected value, the warning message includes a notification indicating a leakage of water from the electrolysis system.

[0046] It may also be provided that the anode input mass current is determined by means of an anode input mass current sensor at the anode input of the cell stack or by means of a rotational speed of a pump for conveying water through the cell stack, and the anode output mass current is determined by means of an anode output mass current sensor at the anode output of the cell stack.

[0047] By using the rotational speed of a pump to convey water through the cell stack to determine the anode input mass flow rate, a mass flow sensor at the anode input can be dispensed with, making the electrolysis system particularly cost-efficient and robust.

[0048] If only mass flow information is available for the

[0049] If the cathode output ṁH2OCathodeOut is available, it can be made plausible according to equation (9).

[0050] ṁH2OCathodeOut = ṁWtrElo (9)R.416510

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[0052] Accordingly, it can be provided that a cathode output mass flow rate m^ocatiwdeout, which is determined at a cathode output of the cell stack, is chosen as the water mass flow rate balance and an electroosmosis mass flow rate ṁWtrElo is chosen as the expected value.

[0053] If the cathode output mass flow rate ṁH2OCathodeOut is lower than expected, it can be assumed that water from the cathode, which is operated at a higher pressure than the anode, has entered the anode side through a membrane tear or hole or another leakage between the anode and cathode, such as a sealing defect, so that equation (10) applies.

[0054] nT-HiOCathodeOut + W'lLow 'hes < ITT-WtrElo (10)

[0055] To make the error detection more robust, a freely selectable diagnostic threshold niLow, Thes < 0 can be introduced.

[0056] Accordingly, it may be provided that if the cathode output mass flow rate ṁH2OCathodeOut (+ ṁLow,Thes) is smaller than the electroosmosis mass flow rate ṁWtrElo, the warning message includes a notification indicating a transfer of water from a cathode compartment of the cell stack to an anode compartment of the cell stack.

[0057] Based solely on mass current information at the cathode output ṁH2OCathodeOut, it is not possible to distinguish between internal leakage between the anode and cathode sides and external leakage. However, the mass current information at the cathode output ṁH2OCathodeOut, due to its significantly lower values, allows for...

[0058] Water mass flow rates on the cathode side allow for significantly more sensitive diagnoses regarding small mass flow deviations than is possible using mass flow information on the anode side. Accordingly, using mass flow information on the

[0059] Cathode output ṁH2OCathodeOut can also detect small membrane tears or holes. R.416510

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[0061] According to a second aspect, the presented invention relates to an electrolysis system for the electrolysis of water.

[0062] The presented electrolysis system comprises a cell stack including an anode compartment and a cathode compartment, a pump configured to pump water through the anode compartment, and a computing unit configured to perform a possible embodiment of the presented diagnostic procedure.

[0063] In the context of the presented invention, a computing unit is understood to be a computer, in particular a cloud computer, a processor, a control unit or any other programmable circuit.

[0064] It may also be provided that the electrolysis system includes a mass flow sensor at the anode output of the cell stack.

[0065] A mass flow balance across the anode space can be determined by using a mass flow sensor at the anode output of the cell stack in conjunction with the speed of the pump or a mass flow sensor at the anode input of the cell stack.

[0066] Accordingly, the electrolysis system may include a mass flow sensor at the anode input of the cell stack.

[0067] Alternatively or in addition to mass flow sensors at the anode compartment, the electrolysis system may include a mass flow sensor at the cathode output of the cell stack.

[0068] Advantages described for the diagnostic method for diagnosing the condition of an electrolysis system according to the first aspect of the invention apply equally to the electrolysis system for the electrolysis of water according to the second aspect of the invention, and vice versa. R.416510

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[0070] Further advantages, features, and details of the presented 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 features mentioned in the claims and in the description can each be essential to the invention individually or in any combination.

[0071] They each show schematically:

[0072] Figure 1 shows a possible embodiment of the presented diagnostic procedure,

[0073] Figure 2 shows a schematic representation of a first possible embodiment of the presented electrolysis system,

[0074] Figure 3 shows a schematic representation of a second possible embodiment of the presented electrolysis system and

[0075] Figure 4 shows a schematic representation of a third possible embodiment of the presented electrolysis system.

[0076] Fig. 1 shows a diagnostic method 100 for diagnosing a condition, for example, of an electrolysis system 200 shown in Figs. 2 to 4.

[0077] The diagnostic procedure 100 comprises a determination step 101, in which a water mass flow balance is determined via a cell stack 201 of the electrolysis system 200, a comparison step 103, in which the determined water mass flow balance is compared with a determined expected value, and an output step 105, in which a warning message is issued if the water mass flow balance deviates from the expected value.

[0078] To output the warning message, it can be displayed, for example, on an output unit of the electrolysis system 200, stored in a memory of the electrolysis system 200 and / or sent to a target function, in particular R.416510.

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[0080] to adapt the electrolysis system 200 to a condition of the electrolysis system 200 reported by the warning message.

[0081] Figure 2 shows an electrolysis system 200 for the electrolysis of water.

[0082] The electrolysis system 200 comprises a cell stack 201, which includes an anode compartment 203 and a cathode compartment 205, a pump 207 configured to pump water through the anode compartment 203, a computing unit 209 and a mass flow sensor 211 at the anode output.

[0083] The computing unit 209 is configured to execute the diagnostic procedure 100 according to Fig. 1. For this purpose, the computing unit 209 can evaluate mass flow information and the pump speed determined by the mass flow sensor 211 at the anode output.

[0084] Figure 3 shows the electrolysis system 200 with an additional mass flow sensor 213 at the anode input. Accordingly, the processing unit 209 can evaluate mass flow information obtained here by the mass flow sensor 211 at the anode output and the mass flow sensor 213 at the anode input.

[0085] Figure 4 shows the electrolysis system 200 with a mass flow sensor 215 at the cathode output. Accordingly, the processing unit 209 can evaluate the mass flow information determined by the mass flow sensor 215 at the cathode output.

Claims

R.416510 - 10 - Claims 1. Diagnostic procedure (100) for diagnosing a condition of an electrolysis system (200), the diagnostic procedure (100) includes: Determining (101) a water mass flow balance across a cell stack (201) of the electrolysis system (200), Comparing (103) the determined water mass flow balance with a determined expected value and Issue (105) a warning message in case the water mass flow balance deviates from the expected value.

2. Diagnostic method (100) according to claim 1, characterized by that the water mass flow balance is determined by subtracting an anode output mass flow, determined at an anode output of the cell stack (201), from an anode input mass flow, determined at an anode input of the cell stack (201), and that the expected value is determined by a The electroosmosis mass flow is added to a consumed mass flow.

3. Diagnostic method (100) according to claim 2, characterized by that in the event that the anode output mass current is greater than the expected value, the warning message includes an indication reporting a transfer of water from a cathode compartment (205) of the cell stack (201) to an anode compartment (203) of the cell stack (201), or R.416510 - 11 - that in the event that the anode output mass current is less than the expected value, the warning message includes a notification reporting a leak of water from the electrolysis system (200).

4. Diagnostic method (100) according to claim 2 or 3, characterized by that the anode input mass current is determined by means of an anode input mass current sensor at the anode input of the cell stack (201) or by means of a rotational speed of a pump (207) for conveying water through the cell stack (201), and the anode output mass current is determined by means of an anode output mass current sensor at the anode output of the cell stack (201).

5. Diagnostic method (100) according to claim 1, characterized by that a cathode output mass flow rate determined at a cathode output of the cell stack (201) is chosen as the water mass flow rate balance and an electroosmosis mass flow rate is chosen as the expected value.

6. Diagnostic method (100) according to claim 5, characterized by that in the event that the cathode output mass flow is smaller than the electroosmosis mass flow, the warning message includes a notification indicating a transfer of water from a cathode compartment (205) of the cell stack (201) to an anode compartment (203) of the cell stack (201).

7. Electrolysis system (200) for the electrolysis of water, the electrolysis system (200) comprises: a cell stack (201) comprising an anode space (203) and a cathode space (205), a pump (207) configured to pump water through the anode chamber (203) and R.416510 - 12 - a computing unit (209) configured to perform a diagnostic procedure (100) according to any one of claims 1 to 6.

8. Electrolysis system (200) according to claim 7, characterized by that the electrolysis system (200) includes a mass flow sensor (211) at the anode output of the cell stack (201).

9. Electrolysis system (200) according to claim 8, characterized by that the electrolysis system (200) includes a mass flow sensor (213) at the anode input of the cell stack (201).

10. Electrolysis system (200) according to claim 7, characterized by that the electrolysis system (200) includes a mass flow sensor (215) at the cathode output of the cell stack (201).

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