THERMOELECTRIC DEVICE WITH SEEBECK EFFECT
20220155362 · 2022-05-19
Inventors
- Fabrice CHOPARD (SAINT MARTIN D'HERES, FR)
- Jérémy GUAZZAGALOPPA (POUSSAN, FR)
- Cédric HUILLET (MONTARGIS, FR)
Cpc classification
H10N10/13
ELECTRICITY
H10N10/17
ELECTRICITY
H01M10/425
ELECTRICITY
H01M2010/4278
ELECTRICITY
H01M10/659
ELECTRICITY
Y02T10/70
GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
Y02E60/10
GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
H10N10/857
ELECTRICITY
International classification
Abstract
The invention relates to a porous thermoelectric material (5; 5a, 5b): having, at 20° C. and at atmospheric pressure, a thermal conductivity of less than 100 mW/(m.Math.K) and an electrical conductivity of between 20 S/m and 10.sup.5 S/m, and comprising a matrix of a thermal insulating material which has a porosity of more than 70%, and which may be filled at least locally with an electrically conductive material (5b), the content of the electrically conductive material being comprised between 0% and 90% by weight of the total weight of the thermal insulating material.
Claims
1. A failure-detection device (20) by Seebeck effect comprising: an electrical element (1) comprising: a thermoelectric material (5;5a,5b), and electrically conductive cables (9a,9b) in electrical connection with said thermoelectric material, and in which electrical element: a) the thermoelectric material comprises a matrix (5a) of a thermally insulating material provided at least locally with electrically conductive material (5b) to define a filled matrix material which may occupy, in the electrical element, only a minor part of the matrix (5a) of thermally insulating material, or b) the thermoelectric material (5;5a,5b): is porous, has, at 20° C. and at atmospheric pressure, a thermal conductivity of less than 100 mW/(m.Math.K) and, at the location of at least one zone having a thermoelectric capacity, has an electrical conductivity of between 10 S/m and 10.sup.5 S/m, and, comprises a matrix of a thermally insulating material: which has a porosity of more than 70%, and which may be provided at least locally with an electrically conductive material (5b), the content of the electrically conductive material being between 0% and 90% by weight of the total weight of the thermal insulating material, an envelope (3) enclosing the thermoelectric material (5; 5a, 5b) and which: is air and watertight, vacuum-tight, and is crossed by the electrical conductor cables (9a, 9b), a sensor (69) supplied with voltage from said thermoelectric material (5;5a, 5b), and a processing unit connected to the electrical element (1) and comprising: a calculator (17): to compare a reference data with a data item issued from an input electric signal transmitted from the electric element (1) in said cables, and to output a first signal if the comparison of said data is below a threshold, and a second signal if the comparison of said data is above the threshold, and an information communication device (16) connected to the calculator and addressing information depending on said first or second output signal.
2. The device according to claim 1, wherein: the electrical element (1) further comprises first and second electrically conductive elements (7a, 7b) located towards two opposite sides of the thermoelectric material, and to which the electrical conductor cables (9a, 9b) are connected, each first electrically conductive element and second electrically conductive element (7a, 7b) has an electrical conductivity σ>10.sup.2 S/m and, as a smallest dimension, a thickness of more than 25 μm, and the thermoelectric material (5,5b) has a thickness (e) such that 0.5 mm<e<10 cm.
3. The device according to any of the preceding claims, wherein the thermoelectric material (5; 5a, 5b) defines a single electrical junction, so that it is devoid of a plurality of junction units (40a, 40b) arranged electrically in series, some junction units having a Seebeck coefficient <0, other junction units having a Seebeck coefficient >0, with two adjacent junction units connected, alternately, on a first side of the thermoelectric material (5a) and then on a second side of the thermoelectric material (5b).
4. The device according to any one of the preceding claims, wherein: the filling of the electrically conductive material (5b) is between 1% and 90%, preferably 10% and 80%, by weight of the total weight of the thermal insulating material, and/or the thermoelectric material has a Seebeck coefficient between −100 μV/K and 100 μV/K, and/or the thermoelectric material has a density of less than 300 kg/m.sup.3, preferably less than 200 kg/m.sup.3.
5. An assembly including: the failure-detection device according to any one of claims 1 to 4, and, two elements (11, 13) thermally more conductive than said electrical element (1) on either side of which the thermally more conductive elements (11, 13) are: disposed in thermal contact with the electrical element, and arranged to be capable of being subjected to temperatures different from each other, so that, with a thermal gradient thus created between two opposite faces of the electrical element, electrical energy is generated by the Seebeck effect in the electrical conductor wires (9a, 9b).
6. The assembly according to claim 5, comprising: said failure-detection device, and sensors (240, 261, 263, 290) for sensing a plurality of actual temperatures, connected to the calculator (17) so that said reference data is a function of the actual temperatures and is established as a function of a difference between two of said actual temperatures.
7. A hybrid or electrically driven vehicle (22) disposed in an outdoor environment and comprising: at least one drive motor (27), the failure-detection device according to any of claims 1 to 4.
8. A hybrid or electrically driven vehicle (22) disposed in an outdoor environment and comprising: at least one drive motor (27), and the assembly according to claim 5 or 6, and as one (11) of the two more thermally conductive elements, a cooling system (110, F1, 28): disposed in thermal contact with an electric drive battery (26) of the vehicle and in which a fluid (F1) for supplying calories to the battery or for recovering calories from the battery can circulate, and, as the other (13) of the two more thermally conductive elements, a protective plate (130) exposed to said external environment.
Description
BRIEF DESCRIPTION OF THE FIGURES
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DETAILED DESCRIPTION OF THE TECHNICAL SOLUTION
[0132] In order to prepare a porous thermoelectric material (marked 5/5a, 5b in various figures) which may be used, for example, in the fault detection device 20 below, the following procedure may be followed: [0133] a. preparation of an aqueous colloidal suspension of a sol-gel precursor of phenolic origin [0134] b. possible addition of an electrically conductive material precursor to the aqueous colloidal suspension obtained in step a., depending on the electrical conductivity threshold to be achieved [0135] c. and mixing under ultrasound to a predetermined amount depending on the electrical conductivity to be obtained in the final material, in particular in the range of 20 S/m to 10.sup.5 S/m.
[0136] The electrically conductive material precursor will be intended to be transformed into electrically conductive material, in particular in the form of particles, following a heating step, in particular pyrolysis, at a temperature T≥600° C.
[0137] Then, the following may be done: [0138] d. if necessary, add a complexing agent to the mixture obtained in step b. (participating in the cross-linking of the network and thus creating a favourable porosity in the material), [0139] e. add a catalyst to the mixture obtained in step c., until a pH of 2 is preferably reached in the case of phenolic precursors, the catalyst initiating the polymerization of the mixture, [0140] f. transfer the mixture obtained in step d. into a mould and gelling the mixture with a closed mould cover at a temperature of between 80 and 90° C. for at least 24 hours, [0141] g. once gelling is complete, dry the gel obtained by evaporation of the solvent with the lid removed at a temperature below 100° C., in particular between 90 and 99° C., and [0142] h. pyrolysis of the dried gel obtained in step f. in an inert or reducing environment at a temperature T≥600° C., in particular between 600° C. and 1200° C., more particularly between 850° C. and 1050° C.
[0143] In particular, the precursor of a thermal insulating material in step a. may be a phenolic compound selected from a group consisting of phenol, pyrocatechol, resorcinol, catechol, hydroquinone, pyrogallol, phloroglucinol, salicylic acid, phloroglucinol, methylphenol, dimethylphenol, trimethylphenol, hydroxymethylphenol, methoxyphenol, methylresorcinol, ethylresorcinol, and mixtures thereof.
[0144] The phenolic compound may be suspended or dissolved in water, in an amount between 0.01 to 0.2moles per mole of water, preferably between 0.06 to 0.14 per mole of water.
[0145] Prior to step c., a complexing agent may be added to the mixture obtained in step b., the complexing agent being selected from a group consisting of poly(diallyldimethylammonium chloride), poly(diallyldimethylammonium bromide), quaternary ammonium salts, poly(vinylpyridinium chloride) poly(ethyleneimine), poly(vinylpyridine), poly(allylamine hydrochloride), poly(trimethylammonium chloride ethyl methacrylate), poly(acrylamide) co-dimethylammonium chloride), and mixtures thereof.
[0146] The complexing agent may be added in an amount of 0.06 to 0.5moles per mole of the phenolic compound, preferably 0.08 to 0.1moles per mole of the phenolic compound.
[0147] The catalyst in step c. may be an acid selected from a group consisting of hydrochloric acid, sulfuric acid, nitric acid, acetic acid, phosphoric acid, trifluoroacetic acid, trifluoromethanesulfonic acid, perchloric acid, oxalic acid, toluenesulfonic acid, dichloroacetic acid, formic acid and mixtures thereof.
[0148] Formaldehyde may be added, preferably in a weight ratio of 0.5 to resorcinol, in step a. or after step c. and step d.
[0149] In
[0154] Each of the first and second electrically conductive elements 7a, 7b will favourably exhibit an electrical conductivity σ>10.sup.2 S/m and, as a smaller dimension, a thickness greater than 25 μm, but which may be less than 2 mm or even less than 1 mm.
[0155] Thus, a small footprint will be associated with a proven operational efficiency.
[0156] The envelope 3 may be a plastic film, a thin metal foil or a shaped metal plate—aluminium for example; thickness from some 1/100 mm to 1 mm. It is rather thermally conductive.
[0157] For all purposes, it is specified that at 20° C. and atmospheric pressure: [0158] as thermally conductive, a means with a thermal conductivity λ≥100-150 mW/(m.Math.K) and [0159] as thermally insulating, a means such that λ≤100 mW/(m.Math.K).
[0160] The said first and second electrically conductive elements 7a, 7b, may typically be wafers, small blocks of electrically conductive paste, coatings (electro powder spray coatings) or be formed by screen printing or over-densification.
[0161] They could also be absent, replaced by overdoses of an electrically conductive compound on either side of the junction so that there is in any case a gradient in terms of electrical conductivity between two opposite sides of the porous thermoelectric material 5.
[0162] In the latter case, the pair of electrically conductive cables 9a, 9b will be connected to the thermoelectrically capable zone of the material 5, via the over-doped lateral zones.
[0163] This “thermoelectrically capable zone” is defined: [0164] by the filled matrix 5b, if the material 5 contains at least locally a fill of electrically conductive material, or [0165] by the matrix of thermal insulating material 5a, or even the whole thermal insulating material 5, if the minimum electrical conductivity (σ≥10.sup.3 S.Math.m.sup.−1 to within +/−20%) is intrinsic to the material.
[0166] As already mentioned, in an application as a failure-detection device using the Seebeck effect, the envelope 3 will be favourably airtight and sealed, to allow internal evacuation.
[0167] Thus, it will be possible to couple the detection of a vacuum rupture and a thermal insulation failure.
[0168] This may in particular be the case on an assembly 10 (
[0173] Thus, if the more thermally conductive elements 11, 13 are actually exposed to different temperatures from each other and if, with an airtight envelope 3, an internal vacuum which existed in the internal volume of the envelope is broken (by a leakage of the seal, for example), then an electrical energy arising from the Seebeck effect, which existed before the vacuum was broken, no longer exists: There is no more (or a strong decrease) of thermoelectric activity. In fact, as soon as the vacuum is broken, there will be a modification of the thermal flows involved and a decrease in the thermoelectric efficiency, thus creating an energy gap between a material for which the vacuum is maintained and a material that has lost the vacuum. The temperature of elements 11,13 will tend to a common value.
[0174] It is in this context of identifying a Seebeck effect that the imagined failure-detection device 20 is moreover proposed in
[0181] Thus it may be possible : [0182] via the calculator 17, to detect: [0183] a change in the transmitted electrical signal due to the Seebeck effect, and thus [0184] whether the thermal coefficient λ of the thermally insulating element 1 has changed, and [0185] to provide the information issued from the information-communication device 16 to a user.
[0186] The information-communication device 16 may include a transmitter 161 communicating with a receiver 163, which may itself communicate (be connected) with a display or recorder 165, such as a screen, warning light or accessible memory of an on-board calculator, whereby said addressed information will, immediately or with delay, be communicated to an occupant of the vehicle or a maintenance operator operating to check the state of the vacuum in the envelope 3 and thus the quality of the local thermal insulation.
[0187] Sensors of several actual temperatures connected to the calculator 17 will further allow said “reference data” to be a function of these temperatures and to be established as a function of a difference (TEG hereinafter) between two of these temperatures.
[0188] These sensors (see
[0192] From these real time temperature measurements, one could for example predict the following: [0193] if Text<10° C., then the cooling system 28/110/F1 is not functional (no circulation of fluid F1 in the passages 28) and the temperature difference TEG calculated by the calculator 17 to establish the “reference data” to be used in said comparison is TEG=Text−Teng, [0194] if Text>10° C., then the cooling system is functional (circulation of fluid F1 in the passages 28) and the temperature difference calculated by the calculator 17 becomes TEG=Tcool−Teng=10° C.−Teng.
[0195] The thermoelectric element 1, or thermally insulating module in this case, is continuously subjected to a temperature difference between its cold side (Text or Tcool, always less than or equal to 10° C. in the example) and its hot side (Teng) and therefore produces at the output 9a/9b a certain amount of electrical energy (U; I; P).
[0196] With respect to the processing of this output signal in the processing unit 15 (which could moreover be placed between the elements 163 and 165), this unit 15 has, as input data, the electrical signals issued from: [0197] the various temperature sensors (240, 261, 263, 290), and [0198] said element 1.
[0199] The calculator 17 may have been programmed to determine whether, in the operational situation of the vehicle 22 and depending on the temperature difference experienced by the element 1, the electrical output signal it transmits (e.g. voltage value) is above a certain threshold or not.
[0200] A comparator integrated in the calculator will then define: [0201] whether the value of the signal is above the threshold: element 1 is in good condition, green light on display 165, [0202] whether the value of the signal is below the threshold: element 1 has a system fault (faulty vacuum): red light on display 165.
[0203] The threshold will thus be a reference data available in memory 25 of the calculator 17. This threshold, initially provided in memory 25, will have been calculated on the basis of preliminary tests carried out at different temperatures Text, Teng and Tcool and for one or more materials 5/5a, 5b, and more generally an element 1, or even an assembly 10, identical or at least comparable to the operational solution mounted on the vehicle 22.
[0204] Because even with a small change in electrical signals between the thermally well insulated (effective vacuum) and poorly insulated (broken vacuum) states, this change may be detected, the filled matrix material 5b may occupy only a minor portion (i.e., less than 50%) of the thermally insulating matrix 5a in the electrical element 1. A few centimetres-square might be enough.
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[0209] The thermally conductive (metallic, such as steel) cooling plate 110 may be disposed in thermal contact with a vehicle electrical drive battery 26; see
[0210] In the cooling plate 110 may therefore circulate a fluid F1 for supplying calories to the battery 26 or for recovering heat from the battery, such as water, or a heat transfer or cooling fluid.
[0211] A system for cooling the battery 26 other than the plate 110 could be provided, such as a forced ventilation system for a fluid coming into thermal contact with the battery, on at least one face of the set of electric accumulators 260 of which it is composed.
[0212] The protective plate 130 may be a metal plate—steel for example (thus rather thermally conductive).
[0213] The cooling plate 110 will be able: [0214] to be crossed along its surface parallel to the support surface of the modules/cells of the battery 26, by ducts, or passages, 28 in which the said fluid F1 may circulate, and [0215] to comprise, around these ducts/passages 28, one or more blocks of phase-change material (PCM) 29 adjacent to the said ducts/passages, and therefore in heat exchange with this PCM; see
[0216] Thus, thermal energy may be recovered in this PCM 29 and released later.
[0217] The passages 28 may be integrated with the plate 110, as shown.
[0218] In connection with an application for the generation of electrical energy by the Seebeck effect for purposes other than fault identification, such as in particular from solar radiation (photovoltaics),
[0221] In addition to electrically conductive cables 9a, 9b in electrical connection with said thermoelectric material 5, there may also be provided first and second electrically conductive elements 7a, 7b located, towards two opposite sides of the hereinafter presented junction units each comprising a block of thermoelectric material 5.
[0222] For construction/handling/safety purposes, the thermoelectric element 1 may also comprise, on either side of the electrically conductive elements 7a, 7b, electrically insulating and thermally conductive plates or substrates 36, 38, e.g. made of ceramic, which may be supplemented or replaced by a closed envelope 3.
[0223] As shown in
[0224] More specifically, to obtain a large Seebeck effect, semiconductor assemblies forming said n-type and p-type junction units 40a, 40b are then used to form the material 5.
[0225] These semiconductor assemblies, 40a, 40b, are connected by metal bridges, formed by the electrically conductive elements 7a, 7b, and the charge carriers therein are electrons and holes, respectively, as shown in
[0226] Depending on the thickness of the junction units 40a, 40b, i.e. the material 5, the electrically conductive elements 7a, 7b, here electrically (and preferably thermally) conductive wafers, connect the semiconductors 40a, 40b . . . together, electrically in series.
[0227] The junctions provided by these elements 7a, 7b are of two types: [0228] p-n on one side (upper side, series of conductive elements 7b;
[0230] Thus, the junction unit 40a (n-type) has a Seebeck coefficient <0 ; the adjacent junction unit, 40b (p-type) has a Seebeck coefficient >0.
[0231] Through the Seebeck effect, an electric current (I) may be dissipated in an output resistor symbolized by the bulb 50 in
[0232] As schematised in this
[0233] This supplied thermal power is partly transformed into work by element 1, in the form of an output current (I), through the successive alternating n-p and p-n junctions.
[0234] It is such a principle that operates on the photovoltaic device 60 of the invention, which may also be called a thermoelectric device, because thermal energy 61 provided other than by photons could be supplied to it.
[0235] On this photovoltaic device 60, we find, as schematised in
[0236] The two covers 3a-3b, when joined together peripherally, will form a closed watertight enclosure 3 through which the conductors 9a, 9b cross. This crossing may be airtight.
[0237] For their stability, the 40a (n-type) and 40b (p-type) junction units may be accommodated in an electrically insulating, louvered frame 63.
[0238] Through this frame, the junction units 40a, 40b are in electrical contact with the electrically conductive elements 7a, 7b so that (as illustrated in
[0239] In this case, the vehicle 22 may be thermally driven and the conductors 9a, 9b may be connected to electrical equipment adapted to operate in this way.
[0240] As shown in
[0243] With a porous thermoelectric material 5 forming the junction units 40a, 40b, a significant thermal gradient between the two opposite sides or faces of the electric element 1 will be favoured.
[0244] On the vehicle 22, one 11 of the two aforementioned thermally more conductive elements 11,13 will comprise or be formed by a panel 65, preferably glazed, or a thermal flux concentrator 67, both then adapted to be crossed by the sun's light rays, for the expected photovoltaic effect.
[0245] In the illustrated embodiment, the element 11 covers one of the covers 3a over the conductive element 7b.
[0246] If a heat flux concentrator 67 is used, it will be usefully disposed in a panel 65 which may not be glazed, such as a sheet metal or non-transparent rigid plastic panel of the vehicle 22 exposed on the outer face 65a to the external environment (EXT) and therefore to the sun.
[0247] The second more thermally conductive element 13 will be located further inboard of the vehicle 22 than the element 11. It may be an inner lining panel against which the photovoltaic device 60 is applied by its cover 3b.
[0248] To further cost the proposed solution regardless of the application, and with an eye towards efficiency, light weight and small footprint, it is proposed: [0249] that each first and second electrically conductive element 7a, 7b has an electrical conductivity σ>10.sup.2 S/m and, as smallest dimension, a thickness of between 25 μm and 5 cm, preferably less than 1 cm or even 5 mm, [0250] that the thickness (e) of the thermoelectric material 5 is such that 0.5 mm<e<10 cm and preferably 0.8 mm<e<1 cm.
[0251] Another application is shown in
[0252] The electrical element 1 may be replaced by the failure-detection device 20 (hence the marking 1-20 in
[0253] When used in the context of the vehicle 22, the sensor 69 will be usefully connected to or in communication with the, or provided with the, information-communication device 16 equipped with the transmitter 161 adapted to communicate with the receiver 163.
[0254] The pairing of the electrical element 1 (or failure-detection device 20) and sensor 69 will allow to widen the scope of acquisition of a parameter (energy self-sufficiency/low energy/autonomy).