Electrochemical device stacking stage and associated electrochemical device

Abstract

The invention relates to a stacking stage (32) (4) of an electrochemical device (2), comprising a first layer (30) and a second layer (30) extending opposite each other, the stage (32) being characterized in that it further comprises at least one optical fiber (14) forming a distributed thermal sensor, each optical fiber being arranged at least partially between the first layer (30) and the second layer (32). Figure 1

Description

Title of the invention: Electrochemical device stacking stage and associated electrochemical device technical field

[0001] The present invention relates to a stacking stage of an electrochemical device.

[0002] The invention also relates to an electrochemical device comprising such a stacking stage.

[0003] The invention applies to the field of electrochemical devices, in particular to solid oxide electrolyzers and solid oxide fuel cells. State of the art

[0004] The fields of dihydrogen production and fuel cells have recently seen the emergence of so-called "solid oxide" electrochemical devices, which notably offer better efficiency than conventional systems.

[0005] For optimal operation, such solid oxide electrochemical devices generally require maintenance at a predetermined nominal operating temperature. Therefore, it has been considered to equip solid oxide electrochemical devices with thermal sensors, such as thermocouples, to monitor their temperature.

[0006] However, such an approach does not give complete satisfaction.

[0007] Indeed, solid oxide electrochemical devices generally have a high nominal operating temperature, typically between 700°C and 800°C. Furthermore, the operation of solid oxide electrochemical devices generally involves the flow of high electric currents and the presence of polarized components.

[0008] For example, the thermocouples mentioned above need to be electrically isolated, which results in additional integration constraints.

[0009] Furthermore, such severe operating conditions limit the type of thermal sensors that can be used, or even their positioning, which is detrimental to reliable temperature monitoring within such electrochemical devices.

[0010] One object of the present invention is to remedy at least one of the drawbacks of the prior art.

[0011] Another object of the invention is to propose an electrochemical device in which temperature measurement is simpler than in conventional electrochemical devices. Description of the invention

[0012] To this end, the invention relates to a stacking stage of an electrochemical device of the aforementioned type, comprising a first layer and a second layer extending opposite each other, the stage further comprising at least one optical fiber forming a distributed thermal sensor, each optical fiber being arranged at least in part between the first layer and the second layer.

[0013] Indeed, due to their low electrical conductivity, the use of optical fibers considerably reduces the need for electrical insulation compared to the use of thermocouples, which is favorable to better integration.

[0014] In addition, due to their compactness, the use of optical fibers is also conducive to better spatial resolution when thermally mapping the electrochemical system.

[0015] Finally, the possibility of carrying out a temperature measurement distributed along the optical fiber significantly reduces the bulk compared to the use of thermocouples.

[0016] Advantageously, the stacking stage according to the invention has one or more of the following characteristics, taken individually or in any technically feasible combination:

[0017] each of the first layer and the second layer is an electrochemical cell, an interconnector, an electrochemical cell electrode or an interconnector plate;

[0018] for each optical fiber, the corresponding portion arranged between the first layer and the second layer comprises at least one Bragg grating etched in said optical fiber;

[0019] each optical fiber is arranged in a spiral or in a staggered pattern between the corresponding first and second layers;

[0020] for each optical fiber, a corresponding minimum radius of curvature is greater than or equal to a predetermined limiting radius of curvature.

[0021] According to another aspect of the invention, an electrochemical device is proposed comprising at least one stack of electrochemical cells and interconnectors, each stack having at least one stage as defined above, the electrochemical device further comprising at least one light source and at least one optical spectrum analyzer, each light source being connected to at least one corresponding optical fiber for injecting light into it, each optical spectrum analyzer being connected to at least one corresponding optical fiber and being configured to calculate a temperature at at least one point of each optical fiber from the light backscattered by said optical fiber in response to the injection of light from the light source.

[0022] Advantageously, the electrochemical device according to the invention has one or more of the following characteristics, taken individually or in any technically feasible combination:

[0023] at least one optical spectrum analyzer is connected to at least one optical fiber comprising at least one Bragg grating, the optical spectrum analyzer being configured to calculate a temperature in the vicinity of each Bragg grating as a function of a spectral shift of a reflection maximum of said Bragg grating with respect to a corresponding reference wavelength;

[0024] at least one optical spectrum analyzer is connected to the light source to receive a portion of the light generated by said light source, forming a local oscillator, the optical spectrum analyzer being configured to calculate the temperature in the vicinity of at least one point of at least one given optical fiber by implementing a frequency domain optical reflectometry process from the local oscillator and a signal backscattered by each optical fiber;

[0025] the electrochemical device is a solid oxide electrochemical device;

[0026] The electrochemical device is a gas-phase electrolyzer or a fuel cell gaseous phase fuel. Brief description of the figures

[0027] The invention will be better understood upon reading the following description, given solely by way of non-limiting example and made with reference to the accompanying drawings in which:

[0028] [Fig.1] is a schematic representation of a first embodiment of an electrochemical device according to the invention;

[0029] [Fig.2] is a detail of a sectional view, along a longitudinal plane, of a stack of the electrochemical device of [Fig.1];

[0030] [Fig.3] is a schematic three-quarter view of a stack of the electrochemical device of [Fig.1];

[0031] [Fig.4] is a cross-sectional view, along a transverse plane, of a stack of the electrochemical device of [Fig.1], in which an optical fiber is arranged according to a first arrangement;

[0032] [Fig.5] is similar to [Fig.4], the optical fiber being arranged in a second arrangement;

[0033] [Fig. 6] is a detail of an optical fiber of the electrochemical device of [Fig. 1]; and

[0034] [Fig.7] is a schematic representation of a second embodiment of an electrochemical device according to the invention.

[0035] It is understood that the embodiments described below are in no way limiting. In particular, variants of the invention may be conceived comprising only a selection of the features described below, isolated from the other features described, if this selection of features is sufficient to confer a technical advantage or to differentiate the invention from the prior art. This selection includes at least one preferably functional feature without structural details, or with only a portion of the structural details if this portion alone is sufficient to confer a technical advantage or to differentiate the invention from the prior art.

[0036] In particular, all the variants and all the embodiments described are combinable with each other if nothing prevents this combination from a technical point of view.

[0037] In the figures and in the rest of the description, elements common to several figures retain the same reference. Detailed description

[0038] An electrochemical device 2 according to the invention is illustrated by [Fig.1].

[0039] In particular, the electrochemical device 2 is a solid oxide electrochemical device.

[0040] For example, the electrochemical device 2 is a gas-phase electrolyzer, intended for the production of dihydrogen from a stream of water vapor and electrical energy.

[0041] Alternatively, the electrochemical device 2 is a gas-phase fuel cell, intended for the production of electrical energy from, in particular, dihydrogen.

[0042] As illustrated by this figure, the electrochemical device 2 comprises at least one stack 4 and an optical interrogation unit 6 (hereafter referred to as the "interrogation unit").

[0043] Each stack 4 is configured to, depending on the mode of use, produce dihydrogen (operation as an electrolyzer) or electrical energy (operation as a fuel cell).

[0044] In addition, the interrogation unit 6 is configured to perform a temperature measurement in at least one zone of each stack 4 of the electrochemical device 2.

[0045] Stack of 4

[0046] Each stack 4 comprises a plurality of electrochemical cells 10 and interconnectors 12. In addition, each stack 4 comprises at least one optical fiber 14.

[0047] More specifically, the electrochemical cells 10 and the interconnectors 12 are staged alternately along a longitudinal direction A. In particular, each electrochemical cell 10 is arranged between (and mechanically and fluidly connected to) two corresponding interconnectors 12, two successive electrochemical cells 10 being mechanically connected to each other by an interconnector 12.

[0048] In a known manner, and as illustrated by [Fig.2], each electrochemical cell 10 comprises two electrodes 16 and 18, forming respectively an anode and a cathode, as well as an electrolyte 20 disposed between the electrodes 16 and 18.

[0049] In addition, each interconnector 12 includes a machined or stamped plate to allow the flow of fluid(s), or a plurality of superimposed plates to give the same properties to the interconnector 12.

[0050] For example, in the case of operation as an electrolyzer, the electrochemical cell 10 is configured to dissociate water molecules into dihydrogen and dioxygen by redox reaction. To do this, water vapor 22 is introduced, via a first interconnector 12A, at the cathode 18, which carries out the electrochemical reduction reaction, resulting in the production of dihydrogen 24 in gaseous form and superoxide ions 26. A potential difference is imposed between the anode 16 and the cathode 18, creating an electric field that causes the superoxide ions 26 to migrate from the cathode 18 to the anode 16 through the electrolyte 20. At the anode 16, the superoxide ions 26 are oxidized, resulting in the production of dioxygen 28 in gaseous form, which is discharged via a second interconnector 12B.

[0051] In the case of operation in a fuel cell, the reverse reactions take place (in particular, oxidation of an incoming flow of dihydrogen), resulting, in particular, in the production of electrical energy.

[0052] Optical fiber 14

[0053] Each optical fiber 14 forms a thermal sensor, and more specifically a distributed thermal sensor.

[0054] As illustrated by [Fig.3], each optical fiber 14 is arranged, at least in part, between a first layer 30 and a second layer 30 of the stack 4 extending opposite each other.

[0055] By "layer", it is understood, in the context of the present invention, to mean an electrochemical cell 10, an interconnector 12, an electrode 16, 18 of an electrochemical cell 10, or even an interconnector plate 12.

[0056] In other words, an optical fiber 14 can be arranged within an electrochemical cell 10 (i.e., between the electrodes 16, 18 of the electrochemical cell 10), within an interconnector 12 (i.e., between two plates of the interconnector 12), or between an electrochemical cell 10 and a interconnector 12 (either on the electrochemical cell 10, or on the interconnector 12).

[0057] The assembly formed by a first layer 30, a second layer 30, and by each optical fiber 14 (or portion of optical fiber) arranged between said first and second layers 30 will, subsequently, be called "stage 32".

[0058] Of course, it is not excluded that the same optical fiber 14 may be shared by several floors 32. Similarly, it is not excluded that the same floor 32 may contain several optical fibers 14.

[0059] Figure 4 illustrates a first example of the arrangement of an optical fiber 14 of a layer 32. As can be seen in this figure, the optical fiber 14 is arranged in a staggered configuration. In other words, the optical fiber 14 has straight segments 33 arranged between the first and second layers 30, connected to each other by curved segments 35 of the optical fiber 14.

[0060] Preferably, the curved segments 35 are arranged outside the delimited volume, along the longitudinal direction A, by the first and second layers 30. Such a feature allows a slightly larger radius of curvature of the optical fiber between two consecutive straight segments 33, as well as easier integration of the optical fiber 14 into the stack 4.

[0061] Alternatively, the curved segments 35 are arranged in the delimited volume, along the longitudinal direction A, by the first and second layers 30.

[0062] According to another example of arrangement, illustrated by [Fig.5], for at least one stage 32, at least one associated optical fiber 14 is arranged between the first and second corresponding layers 30 in a spiral configuration.

[0063] These two configurations are advantageous, insofar as they maximize the optical fiber length 14 between the layers 30 of the corresponding stage 32.

[0064] Of course, the arrangement of optical fiber 14 is not limited to the two preferred variants described above.

[0065] Furthermore, due to the measurement methods implemented by the invention, the position of the distal end of the optical fiber 14 (i.e., the end not connected to the interrogation unit 6) is not critical and can be chosen arbitrarily. Such measurement methods will be described later.

[0066] Advantageously, for each optical fiber 14, a corresponding minimum radius of curvature is greater than or equal to a predetermined limiting radius of curvature.

[0067] Such a feature is advantageous, insofar as it reduces the risk of damage to the optical fiber 14, and limits optical losses by refraction related to excessive curvature.

[0068] Preferably, the limiting radius of curvature is less than or equal to 20 times the diameter of an outer sheath of the optical fiber 14, for example equal to 10 times the diameter of the outer sheath of the optical fiber 14.

[0069] For at least one optical fiber 14, the corresponding portion arranged between the first and second layers 30 of an associated stage 32 advantageously comprises at least one Bragg grating 34 etched into said optical fiber 14, as illustrated in [Fig. 6]. In this case, the optical fiber 14 is used in a temperature measurement exploiting the reflection of light by each Bragg grating.

[0070] Preferably, the Bragg grating 34 is etched into a core 36 of the optical fiber 14, and has a pitch A.

[0071] In particular, the Bragg grating 34 is etched so that a corresponding refractive index gradient is collinear with a local longitudinal direction of the optical fiber 14.

[0072] The reflection wavelength XR of the Bragg grating 34, corresponding to the maximum reflection, depends, in particular, on the pitch A. In addition, the reflection wavelength XR depends on the local refractive index of the optical fiber 14, itself a function of the temperature.

[0073] As illustrated by [Fig.6], for a set of light rays having wavelengths {Xi, X2, ..., X, XR, Xi+2, ..., XN}, the light ray of wavelength XR is reflected, while the light rays having wavelengths {Xb X2, ..., Xi, Xi+2, ..., XN} are transmitted.

[0074] Advantageously, in the case where a single optical fiber 14 comprises a plurality of Bragg gratings 34, then, for a given temperature of the optical fiber 14, the reflection wavelength XR of any one of its Bragg gratings 34 is distinct from the reflection wavelength of each of its other Bragg gratings 34.

[0075] Such a characteristic is advantageous, insofar as it allows a unique association of each reflection wavelength to a respective Bragg grating, and therefore to a respective position in the optical fiber 14.

[0076] Advantageously, for a given optical fiber 14, the smallest difference between the reflection wavelengths of the corresponding Bragg gratings is greater than the largest variation in reflection wavelength with the temperature of the optical fiber 14 over a predetermined temperature range.

[0077] Such a feature is advantageous, insofar as it allows each Bragg grating to be uniquely identified from its reflection wavelength, regardless of the temperature within the predetermined temperature range.

[0078] Preferably, the predetermined temperature range includes the temperatures likely to be reached in the electrochemical device 2. For example, the predetermined temperature range extends from 0°C (degrees Celsius) to 1000°C.

[0079] Preferably, each optical fiber 14 is a single-mode optical fiber. This characteristic is advantageous because this type of optical fiber is widespread in the telecommunications field, allowing the use of components with a high level of technological maturity. However, the use of a multimode optical fiber is not excluded.

[0080] Preferably, each optical fiber 14 is configured to exhibit minimum attenuation within a predetermined wavelength range, in particular the range between 1300 nm (nanometers) and 1600 nm. For example, each optical fiber is a silica optical fiber generally exhibiting a minimum attenuation close to 1300 nm and / or a minimum attenuation close to 1550 nm, which are used as a transmission window.

[0081] Query Unit 6

[0082] As previously stated, the interrogation unit 6 is configured to perform a temperature measurement in at least one area of ​​each stack 4 of the electrochemical device 2, and more specifically in the vicinity of at least a part of an optical fiber 14.

[0083] The interrogation unit 6 comprises at least one light source 38 and at least one optical spectrum analyzer 40 (hereafter referred to as "analyzer"), connected to at least one optical fiber 14.

[0084] For example, the light source 38 and the analyzer 40 are connected to each optical fiber 14 by means of a circulator 42.

[0085] The light source 38 is configured to emit light, and is connected to at least one optical fiber 14 to inject the emitted light into it.

[0086] Preferably, the light source 38 is connected to a first port of the circulator 42. In this case, each associated optical fiber 14 is connected to a second port of the circulator 42 to receive at least part of the light emitted by the light source 38.

[0087] In particular, the light source 38 is configured to generate light having a wavelength compatible with a minimum attenuation of each optical fiber 14.

[0088] Preferably, the light source 38 is a laser source. For example, the light source 38 is a laser source capable of emitting light with a wavelength between 1310 nm and 1550 nm.

[0089] In this case, the light source 38 is advantageously a so-called "broadband" laser source, for example a laser source capable of emitting light occupying at less a part of the wavelength range between 1310 nm and 1550 nm. This is advantageous, particularly in the case of the presence of Bragg gratings, since such a characteristic gives the light source 38 the ability to probe the optical fiber 14 simultaneously at several wavelengths, and therefore to follow the variations of the reflection wavelengths with the temperature of a plurality of Bragg gratings.

[0090] Alternatively, the light source 38 is a tunable source. Such a feature is also advantageous, since it also gives the light source 38 the ability to probe the optical fiber 14 at several points.

[0091] The analyzer 40 is configured to analyze the light received from each optical fiber 14, and to deduce a temperature at at least one point of said optical fiber 14.

[0092] Preferably, the analyzer 40 is connected to a third port of the circulator 42 to receive light from each optical fiber 14.

[0093] In particular, in the case where a given optical fiber 14 comprises at least one Bragg grating 34, the light received from said optical fiber 14 results essentially from the reflection, on the corresponding Bragg gratings 34, of the light emitted by the light source 38. In particular, in the spectral domain, the light received from the optical fiber 14 comprises peaks, each resulting from a reflection on a respective Bragg grating 34 and having a central wavelength equal to the reflection wavelength of said Bragg grating 34.

[0094] In this case, the analyzer is configured to store in memory, for each Bragg grating 34, a corresponding reference reflection wavelength, associated with a predetermined reference temperature.

[0095] Preferably, the analyzer 40 is also configured to store in memory, for each Bragg grating 34, the range in which the corresponding reflection wavelength is assumed to vary with a temperature variation in the predetermined temperature range.

[0096] Preferably, the analyzer 40 is also configured to store, in memory, a position of each Bragg grating 34 in the electrochemical device 2.

[0097] In addition, analyzer 40 is configured to: • determine a spectrum of the light received from each optical fiber 14; • detect each reflection peak in the determined spectrum; and • associate each detected peak with the corresponding Bragg grating 34, in particularly from the central wavelength of said peak.

[0098] In addition, for each detected peak, the analyzer 40 is configured to measure a shift between the corresponding wavelength and the reflection wavelength of reference of the Bragg 34 network corresponding for a predetermined reference temperature.

[0099] The analyzer 40 is also configured so that, for each Bragg grating 34, it converts the measured wavelength shift into a temperature shift.

[0100] Furthermore, the analyzer 40 is configured to determine a current temperature in the vicinity of each Bragg grating 34 from the calculated temperature offset and the corresponding reference temperature. In particular, the current temperature is equal to the sum of the reference temperature and the temperature offset.

[0101] In the case where the analyzer 40 is configured to store the position of each Bragg grating 34 in the electrochemical device 2, then the analyzer is configured to associate each determined current temperature with a position in the electrochemical device 2.

[0102] Case of Rayleigh backscatter

[0103] A variant of the electrochemical device 2 is illustrated by [Fig.7].

[0104] The electrochemical device of [Fig.7] differs from the electrochemical device of [Fig.2] in that, for at least one stack 4, at least one corresponding optical fiber 14 is devoid of a Bragg grating, in particular devoid of a Bragg grating in its part arranged between a first and a second layer 30 of each associated stage 32.

[0105] In this case, the optical fiber 14 is implemented for a temperature measurement exploiting Rayleigh backscattering along said optical fiber 14.

[0106] In particular, in this case, the light source 38 is configured to emit, towards said optical fiber 14, light having a peak intensity whose central wavelength is variable over time, preferably continuously variable over time.

[0107] Preferably, the light source 38 is a laser source. For example, the light source 38 is a laser source capable of emitting light with a time-varying wavelength between 1300 nm and 1600 nm, preferably continuously.

[0108] In addition, part of the light emitted by the light source 38 is taken and routed to the analyzer 40, to form a reference signal 44, called the "local oscillator".

[0109] In this case, the analyzer 40 is configured to implement an optical frequency domain reflectometry (OFDR) method to determine the temperature at at least one point along the optical fiber 14, considered to be a current temperature in the vicinity of said point.

[0110] More specifically, analyzer 40 is configured to: • detect a beat signal resulting from optical interference between the local oscillator 44 and the light received from the optical fiber 14 (i.e., the light backscattered by the optical fiber); • determine a spatial distribution of backscattered light, from a time Fourier transform of the detected beat signal; • measure a variation, over time, of the determined spatial distribution; • calculate the temperature at at least one point of the optical fiber 14 from the measured variation.

[0111] Of course, the invention is not limited to the examples just described.

Claims

Demands

1. Stacking stage (32) of electrochemical device (2), comprising a first layer (30) and a second layer (30) extending opposite each other, the stage (32) being characterized in that it further comprises at least one optical fiber (14) forming a distributed thermal sensor, each optical fiber being arranged at least in part between the first layer (30) and the second layer (32).

2. Stage (32) according to claim 1, wherein each of the first layer (30) and the second layer (30) is an electrochemical cell (10), an interconnector (12), an electrode (16, 18) of electrochemical cell (10) or an interconnector plate (12).

3. Stage (32) according to claim 1 or 2, wherein, for each optical fiber (14), the corresponding portion arranged between the first layer (30) and the second layer (30) comprises at least one Bragg grating (34) etched into said optical fiber (14).

4. Stage (32) according to any one of claims 1 to 3, wherein each optical fiber (14) is arranged in a spiral or in a staggered fashion between the corresponding first layer (30) and second layer (30).

5. Stage (32) according to any one of claims 1 to 4, wherein, for each optical fiber (14), a corresponding minimum radius of curvature is greater than or equal to a predetermined limiting radius of curvature.

6. Electrochemical device (2) comprising at least one stack (4) of electrochemical cells (10) and interconnectors (12), each stack (4) having at least one stage according to any one of claims 1 to 5, the electrochemical device (2) further comprising at least one light source (38) and at least one optical spectrum analyzer (40), each light source (38) being connected to at least one corresponding optical fiber (14) for injecting light into it, each optical spectrum analyzer (40) being connected to at least one corresponding optical fiber (14) and being configured to calculate a temperature at at least one point on each optical fiber (14) from the light backscattered by said optical fiber (14) in response to the injection of light from the light source (38).

7. Electrochemical device (2) according to claim 6, wherein at least one optical spectrum analyzer (40) is connected to at least one optical fiber (14) comprising at least one Bragg grating (34), the optical spectrum analyzer (40) being configured to calculate a temperature in the vicinity of each Bragg grating (34) as a function of a spectral shift of a reflection maximum of said Bragg grating (34) with respect to a corresponding reference wavelength.

8. Electrochemical device (2) according to claim 6 or 7, wherein at least one optical spectrum analyzer (40) is connected to the light source (38) to receive a portion of the light generated by said light source (38), forming a local oscillator (44), the optical spectrum analyzer (40) being configured to calculate the temperature in the vicinity of at least one point of at least one optical fiber (14) given by implementing a frequency-domain optical reflectometry method from the local oscillator (44) and a signal backscattered by each optical fiber (14).

9. Electrochemical device (2) according to any one of claims 6 to 8, the electrochemical device (2) being a solid oxide electrochemical device.

10. Electrochemical device (2) according to claim 9, the electrochemical device being a gas-phase electrolyzer or a gas-phase fuel cell.

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