Method and test bench for hydrogen detection in electrochemical systems

Abstract

A test bench (1) for hydrogen detection in electrochemical systems comprises a device for accommodating a component (3, 12) of an electrochemical system (2) intended for energy storage or conversion. The test bench (1) further comprises a plasmonic detector array (15) suitable for spatially resolved hydrogen detection using a local color reaction.

Description

[0001] The invention relates to a method and a test bench for detecting hydrogen in an electrochemical system, in particular a fuel cell system.

[0002] EP 1 296 395 B1 relates to a fuel cell including a sealing arrangement. The fuel cell comprises a gas sensor for measuring a hydrogen concentration. The gas sensor comprises a palladium bridge located on an aluminum substrate. The purpose of the gas sensor of the device according to EP 1 296 395 B1 is to detect hydrogen supplied to a unit cell.

[0003] EP 3 407 062 A1 discloses a hydrogen measurement system with a dielectric waveguide. The waveguide is referred to as a hybrid photonic-plasmonic waveguide and, in addition to a dielectric, waveguiding material, comprises an intermediate layer located on this material and a sensor layer covering the intermediate layer. The sensor layer can be metallic or semi-metallic and has a refractive and / or absorption coefficient that depends on a hydrogen partial pressure. A catalytic layer can be located on the sensor layer. Possible applications of the hydrogen measurement system include electrical equipment, particularly transformers.

[0004] A hydrogen sensor comprising optical fibers is known from CN 113 324 949 A. Hydrogen detection is based on plasmonic effects, which are expressed in wavelength shifts. Components of the detector according to CN 113 324 949 A are coated with palladium.

[0005] CZ 308 875 B6 deals with a hydrogen sensor that uses plasmon-active fibers. The fibers are coated with a porous metal-organic coating material. Possible plasmon-active materials include gold, silver, or copper with a thickness of 10 to 50 nm.

[0006] KR 10 1 426 371 B1 describes a leak detector intended for use in a generator's cooling system. In addition to a gas sensor, a flow measurement is provided in this case.

[0007] EP 3 074 531 B1 discloses an optical system and a test chip for probing, detecting, and analyzing molecules. The optical system can comprise a refractive element, a diffractive element, a plasmonic element, or a resonator. Components of a sensor chip can be arranged in the form of a grid, i.e., as an array.

[0008] KR 10 2016 0 022 027 A discloses a device in the form of a test chamber with gas inlets and outlets for checking a membrane for a fuel cell for defects, in this case leaks, using a hydrogen sensor.

[0009] DE 10 2019 219 617 A1 describes an electrical energy storage device, such as a battery cell, with a closed housing and at least one gas-sensitive sensor component arranged in the housing, as well as a method for determining a state of the electrical energy storage device. In one embodiment, the sensor component comprises a color-change material with plasmonic structures, the color of which undergoes a spectral change depending on the gas concentration present in the housing. Hydrogen, among others, can be monitored as the gas.

[0010] Comprehensive information on nanoplasmonic sensors can be found in the following dissertation: FAA Nugroho: Nanoplasmonic Alloy Hydrogen Sensors - A Quest for Fast, Sensitive and Poisoning-Resistant Hydrogen Detection, ISBN: 978-91-7597-717-1, Chalmers University of Technology Gotheburg, Sweden 2018

[0011] Furthermore, reference is made to the following standard, which specifies design, safety and performance requirements for hydrogen gas generation equipment: ISO 22734:2019-09: Hydrogen generators based on the electrolysis of water - Industrial, commercial and domestic applications

[0012] According to this standard, a leak test can be performed as a pressure change test. The detection of a pressure change is generally not informative regarding the nature of the substance causing the pressure change.

[0013] In contrast to testing methods based on pressure measurements, methods based on plasmonic effects are characterized by pronounced selectivity. Plasmons are generally considered collective oscillations of free electrons. Such oscillations are excited by the absorption of incident electromagnetic radiation. Resonance frequencies depend on both particle size and particle composition. The latter dependence can be used for the targeted detection of certain substances, particularly hydrogen.

[0014] The invention is based on the object of providing, compared to the prior art, further developed possibilities for hydrogen detection in electrochemical systems, which are characterized by a particularly favorable ratio between robustness of the test and meaningfulness of the results.

[0015] This object is achieved according to the invention by a method designed according to claim 1 for hydrogen detection in an electrochemical system, in particular a fuel cell system operated with hydrogen as fuel gas or an electrolyzer system for the electrolysis of water. This object is further achieved according to the invention by a test bench designed for hydrogen detection in electrochemical systems, having the features of claim 4. The embodiments and advantages of the invention explained below in connection with the detection method also apply mutatis mutandis to the device, i.e., the test bench, and vice versa.

[0016] The inventive method for hydrogen detection in an electrochemical system assumes that a component of an electrochemical system intended for energy storage or conversion is placed in a test chamber. A plasmonic detector array arranged above said component and covering its entire footprint detects any hydrogen leakage. Subsequently, the position of said component in the test chamber is changed. Finally, in the changed spatial configuration, a further test for the presence and location of a hydrogen leak is performed using the detector array.

[0017] By repeatedly testing in different geometric constellations, a particularly good spatial resolution can be achieved.

[0018] The test bench according to the invention for hydrogen detection in electrochemical systems comprises a device designed to accommodate a component of an electrochemical system intended for energy storage or conversion. The component to be tested using the test bench has, in particular, a prismatic or cylindrical basic shape. This includes, for example, a cylinder with a circular base, a cuboid, or another prism. If a prismatic or cylindrical basic shape of the component is given, deviations from the aforementioned basic shape may occur, in particular on the top and / or bottom side of the component to be tested of the electrochemical system, in particular fuel cell systems operated with hydrogen as fuel gas or electrolyzer systems for the electrolysis of water.

[0019] In any case, the test bench has at least one plasmonic detector array designed for hydrogen detection, which enables spatially resolved detection of hydrogen using a local color reaction. In particular, during operation of the test bench, the detector array covers at least the largest part of a surface, for example a side surface or a top surface of the component to be tested, forming the upper side of the component. This surface can also be a cross-sectional area or other internal surface of the component. In any case, the detector array is capable of spatially resolved detection of hydrogen escaping from the component of the electrochemical system.

[0020] The invention is based on the idea that plasmonic effects are fundamentally suitable for detecting hydrogen escaping from a device. Even small-sized sensors are suitable for this purpose. The test bench according to the application achieves a significant additional benefit compared to test devices with individual, small sensors by arranging a large number of such sensors in a large-area row-column arrangement, i.e., as a detector array. In particular, the detector array comprises at least 100 columns and at least 100 rows of hydrogen sensors. Regardless of the number and positioning of the individual sensors, they contain, in particular, magnesium. In the presence of hydrogen, the following conversion occurs: MgH 2 ↔ Mg + H 2

[0021] Magnesium hydride (MgH 2) exhibits a significantly different color than metallic magnesium. The presence of hydrogen thus leads to a color change, which can be observed either with the naked eye or with suitable sensors.

[0022] According to a first group of embodiments, the test bench is designed for testing components that are a stack of electrochemical cells, i.e., a stack serving as an energy converter. In particular, this is a stack of fuel cells powered by hydrogen as fuel gas or electrolysis cells for the electrolysis of water.

[0023] In cases not according to the invention, the detector array can be arranged, in particular, above the stack of electrochemical cells. In this way, hydrogen escaping upwards from the cell stack reaches a partial area of ​​the detector array, i.e., individual hydrogen sensors. The total area of ​​the detector array can be larger than the base area of ​​the component to be tested, i.e., the cell stack.

[0024] According to the invention, the sensors are arranged within the cell stack in a sandwich-like manner between adjacent electrochemical cells, each at the cell edge, with the detector array being formed by the entirety of the sensors on a side surface of the cell stack. In this design, the sensors can be formed, in particular, by coatings on proton-permeable membranes of the electrochemical cells. Hydrogen escaping from a side surface of the cell stack can be easily detected as a color-contrasting plume that appears on the corresponding side surface of the stack.

[0025] According to a second group of embodiments, the component of the electrochemical system to be tested, which in this case may also have a prismatic, cylindrical, or other basic shape, is a tank, in particular a coolant tank, for example in the form of an expansion tank in a cooling circuit. In this case, energy is contained in the tank as thermal energy.

[0026] A first variant, not according to the invention, which belongs to the second group of embodiments, provides for the detector array to be arranged on an outer wall of the tank. A partial surface of the outer wall can be formed by a lid of the tank. This means that the detector array can be located, in particular, on the lid. If hydrogen, for example, penetrates through seals into the cooling circuit, this can be detected.

[0027] A further developed variant of the invention, which also represents the second group of embodiments, is characterized in that the detector array is arranged on a lid of the tank within an insulating jacket. This means that a space in which coolant is located or can be located is surrounded by the insulating jacket. This space is sealed to the outside by a transparent cover, so that color changes of the sensors are readily visible. If, in a modified embodiment, the cover is not transparent, a possible hydrogen leak can be detected when opening the coolant expansion tank.

[0028] Otherwise, transparency of the cover formed by the lid is not required even if the reading of the colors of the sensors is provided exclusively automatically by a suitable sensor system, which in this case is located in the lid of the container having an insulating jacket.

[0029] Several embodiments of the invention are explained in more detail below with reference to a drawing. In the drawings: Fig. 1 a test bench for carrying out the hydrogen detection method on an electrochemical system, Fig. 2 and Fig. 3 partial view of the test bench Fig. 1 in different usage situations, Fig. 4 a detector array of the test bench according to Fig. 1, Fig. 5 a variant of a test bench according to the invention for hydrogen detection in an electrochemical system, Fig. 6 a detail of the arrangement according to Fig. 5, Fig. 7 an alternative arrangement for hydrogen detection on an electrochemical system, Fig. 8 a detail of a container of the arrangement according to Fig. 7, Fig. 9 a modified design of a container of an electrochemical system in a representation analogous Fig. 8.

[0030] Unless otherwise stated, the following explanations refer to all embodiments. Corresponding or essentially equivalent parts are identified by the same reference numerals in all figures.

[0031] A test bench 1 for carrying out a method according to the invention for detecting hydrogen leaks of an electrochemical system 2, in the present case a fuel cell system, is shown in Fig. 1. The electrochemical system 2, i.e., fuel cell system, comprises an electrochemical converter in the form of a cell stack 3, which is also referred to as a stack. The stack 3 comprises a plurality of electrochemical cells 4 (see Fig. 6) and end plates 5, 6. The stack 3 is supplied with operating and cooling media via connecting lines 7. Two adjacent electrochemical cells 4, i.e. fuel cells, of the cell stack 3 are connected by a bipolar plate 8 (compare Fig. 6) are separated from each other. Within each cell 4 there is, among other things, a membrane 9. The frames of the cells 4 are designated 10.

[0032] To carry out the test for possible escaping hydrogen, Stack 3 is used in the cases of Fig. 1 to 6 in a test chamber 11, which is assigned to the test bench 1. In contrast to this, in the embodiments according to the Fig. 7 to 9, means for hydrogen detection are integrated into a container or tank 12 for holding coolant, as will be explained in more detail below. A pressure vessel in which hydrogen is stored, which is intended for consumption in the cell stack 3, is present in all embodiments, but is not shown in the figures.

[0033] In the variants according to the Fig. 1 to 6, the test bench 1 is configured to detect and locate any leaks in the area of ​​the stack 3. The atmosphere within the test chamber 11 can be adjusted as desired. In particular, the test is conducted in a nitrogen atmosphere. For this purpose, a gas inlet 13 and a gas outlet 14 are located on the test chamber 11. In addition to purging and filling the test chamber 11 with nitrogen, it is also possible to set a defined oxygen content.

[0034] The test chamber 11 has a cuboid shape, with a detector array 15 located across the entire top surface of the test chamber 11. The detector array 15 is formed from individual sensors 16 arranged in rows and columns. The sensors 16 are plasmonic hydrogen sensors. The sensors 16 contain magnesium, which reacts with hydrogen to form MgH 2 Palladium is contained as a catalyst in the sensors 16. This also applies to the embodiments according to the Fig. 7 to 9.

[0035] In all exemplary embodiments, hydrogen causes a color change of the sensors 16, enabling spatially resolved hydrogen detection. After testing, i.e., hydrogen detection by means of a local color change, the color change can be reversed by purging with oxygen. The color change can generally be detected with the naked eye or with optical sensors. The test procedure is fundamentally independent of this.

[0036] According to the Fig. 1 to 4, the cell stack 3 is first placed in a defined position in the test chamber 11, as shown in Fig. 1. Hydrogen escaping due to a leak is referred to as hydrogen emission WE. The hydrogen emission WE causes individual sensors 16 of the detector array 15 to respond. This alone allows at least a rough localization of the leak. To further improve the location of the leak, the test is repeated with a changed position of the cell stack 3, as a comparison of the unrealistically drawn Fig. 2 and Fig. 3. For example, the stack 3 is rotated 90 degrees around an imaginary vertical axis that penetrates the test chamber 11. Likewise, it is possible to perform a larger number of tests; for example, in cases of three or four consecutive tests, the cell stack 3 is rotated 90 degrees between each test. In each case, hydrogen escaping from the stack 3 escapes upwards within the test chamber 11, so that it is detected by the detector array 15. Fig. 4 is a response range in which hydrogen was detected by several sensors 16 of the detector array 15, designated AB.

[0037] In a test bench 1 according to an embodiment of the invention according to the Fig. 5 and Fig. 6, a detector array 15 is realized on the side surfaces of the cell stack 3 by providing edge regions 17 of the membranes 9 with a plasmonic coating 18. Thus, the edge regions 17 of the membranes 9 experience a color change in the presence of hydrogen, just as the sensors 16 of the detector array 15 according to Fig. 1. Due to the coating 18, the membranes 9 are thus designed as sensors 16 in their edge regions 17.

[0038] A hydrogen emission WE is in the example according to the Fig. 5 and Fig. 6 in the lower half of the stack 3. The hydrogen emission WE leads to a discoloration area FB, which is visible both in Fig. 5 as well as in Fig. 6 and extends upwards from the hydrogen exit point in the shape of a wedge. The discoloration area FB replaces the response area AB in the embodiment according to the Fig. 1 to 4. Compared to the embodiment according to the Fig. 1 to 4 allows the design according to the Fig. 5 to 6 allow for even more precise localization of a leak from which hydrogen is escaping. This is made possible primarily by the fact that plasmonically coated carrier foils of membrane electrode assemblies (MEAs) are placed like frames around the electrochemical cells 4.

[0039] In the variants according to the Fig. 7 to 9 concern a leak detection in the container or tank 12, which contains the coolant used to cool the stack 3. During normal operation of the electrochemical system 2, the temperature of the coolant in the present case is approximately 60 to 90°C. The container, i.e., tank 12, has an insulating jacket 20. A lid of the container or tank 12, which is integrated into the cooling circuit of the electrochemical system 2 as an expansion tank, is designated 19. Part of the insulating jacket 20 of the container or tank 12 is formed by the lid 19.

[0040] In the design according to the Fig. 7 and Fig. 8, the lid 19 has a transparent cover 21 that defines the upper edge of the insulation jacket 20. In this case, the detector array 15 is located on the underside of the insulation jacket 20, as far as it is formed by the lid 19. If hydrogen penetrates the coolant due to leaks, this becomes noticeable as a discoloration of the detector array 15 and can be visually detected due to the transparency of the cover 21 of the container or tank 12.

[0041] The Fig. 9 shows a cover 19 which is also suitable for use in the electrochemical system 2 according to Fig. 7. In this case, the detector array 15 is located on top of the cover 19, eliminating the need for an additional transparent cover.

[0042] Monitoring of the container or tank 12 according to the Fig. 7 to 9 is with a monitoring of the stacks 3 according to the Fig. 5 and Fig. 6. It is also possible to arrange the cell stack 3 according to Fig. 7 during operation of this electrochemical system 2 in the test chamber 11 according to Fig. 1 for carrying out the method according to the invention. In all embodiments, the stack 3 can be an energy converter for a mobile or stationary system. List of reference symbols 1 test bench 2 electrochemical system 3 component, cell stack, stack 4 electrochemical cell 5 End plate 6 End plate 7 Connection cable 8 bipolar plate 9 Membran 10 frames 11 Test chamber 12 Component, container, tank 13 Gas inlet 14 Gas outlet 15 detector array 16 sensors 17 Marginal area 18 Coating 19 lids 20 insulation jacket 21 Cover AB response range FB discoloration area WE hydrogen emissions

Claims

[1] Method for hydrogen detection in an electrochemical system (2), wherein a component (3, 12) of the electrochemical system (2) intended for energy storage or conversion is placed in a test chamber (11), a possible hydrogen leak is detected by means of a plasmonic detector array (15) which is arranged above the said component (3, 12) and covers its complete floor plan, then the position of the said component (3, 12) in the test chamber (11) is changed, and in the thus changed spatial constellation a further test for the presence and location of a hydrogen leak is carried out by means of the detector array (15). [2] Method according to claim 1, wherein a stack of electrochemical cells, i.e. a cell stack, is used as component (3). [3] Method according to claim 1, wherein a tank is used as component (12). [4] Test bench (1) for hydrogen detection in electrochemical systems, with a device for receiving a component (3, 12) of an electrochemical system (2) intended for energy storage or conversion, and with a plasmonic detector array (15) suitable for spatially resolved hydrogen detection by means of a local color reaction, wherein said component (3) is designed as a stack of electrochemical cells, i.e. cell stack, and sensors (16) are arranged within the cell stack in a sandwich-like manner between adjacent electrochemical cells (4), in each case at the cell edge, wherein the detector array (15) is formed on a side surface of the cell stack by the entirety of the sensors (16), or wherein said component (12) is designed as a tank and the detector array (15) is arranged on a lid (19) of the tank (12) within an insulating jacket (20). [5] Test bench (1) according to claim 4, wherein, in the case of a component (3) designed as a stack of electrochemical cells, the device for receiving the component (3) designed as a cell stack and intended for energy conversion is designed as a test chamber (11) with gas connections (13, 14). [6] Test bench (1) according to one of claims 4 or 5, wherein the detector array (15) is formed from at least 100 x 100 plasmonic sensors (16), each comprising magnesium as a substance reacting with hydrogen.

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