Soec or sofc module comprising a thermal enclosure with one or more thermal management hatches and housing electrochemical cells

Abstract

The invention relates to a module (1) intended to operate at high temperature, with a thermal enclosure in which sub-modules (SM1, SM2) that each comprise a stack of electrochemical cells are housed. At least one hatch (110) for removing heat generated inside the enclosure by the sub-modules in operation makes it possible to manage temperature in a module.

Description

[0001]Description Title: Electrolysis or co-electrolysis module (SOEC) or fuel cell (SOFC) with pre-assembled sub-assemblies of stacked electrochemical cells and with a thermal enclosure housing the sub-assemblies and with thermal management hatch(es). Technical field The present invention relates to the field of solid oxide fuel cells (SOFC, acronym for "Solid Oxide Fuel Cell"), that of high-temperature steam electrolysis (EHT, or EVHT, or HTE acronym for High Temperature Electrolysis, or HTSE acronym for High Temperature Steam Electrolysis) also with solid oxides (SOEC, acronym for "Solid Oxide Electrolysis Cell" or SOE or SOEL for "Solid Oxide Electrolysis"), and that of high-temperature co-electrolysis of water vapor and carbon dioxide CO2.Generically, this technological field is often referred to as SOC (Solid Oxide Cell), which relates to both the electrochemical operating modes of electrolysis or co-electrolysis of high-temperature (EHT) water vapor of the SOEC type, or that of a fuel cell of the SOFC type. The present invention relates to electrochemical devices that can constitute both an EHT electrolysis reactor and reversibly a fuel cell depending on the needs and uses. These devices are usually designated by the English acronym rSOC for "reversible Solid Oxide Cell". The present invention aims firstly to improve the thermal management of such devices with a stack of elementary electrochemical cells, on the scale of a module that integrates several of them.Although described with reference primarily to the application of high-temperature steam electrolysis, the invention applies equally well to co-electrolysis of steam and another gas such as carbon dioxide CO2, as to a SOFC fuel cell, or to a reversible system capable of operating in both modes. The invention applies to a SOFC fuel cell using as fuel either hydrogen, or a hydrocarbon-based fuel, for example methane CH4 or more broadly natural gas, or another non-carbon fuel such as ammonia.Prior Art Water electrolysis is an electrochemical reaction that decomposes water into gaseous oxygen and hydrogen with the help of an electric current according to the reaction: H2O→H2+ 1 / 2 O2To carry out the electrolysis of water, it is advantageous to carry it out at high temperature typically between 600 and 950°C, because part of the energy required for the reaction can be provided by heat which is cheaper than electricity and the activation of the reaction is more efficient at high temperature and does not require a specific catalyst.As shown schematically in Figure 1, a solid oxide electrolysis cell 10, or “SOEC” (an English acronym for “Solid Oxide Electrolysis Cell”) comprises in particular: - a first porous conductive electrode 12, or “cathode”, intended to be supplied with water vapor for the production of dihydrogen, - a second porous conductive electrode 14, or “anode”, through which the dioxygen (O2) produced by the electrolysis of the water vapor injected at the cathode escapes, and - a solid oxide membrane (dense electrolyte) 16 sandwiched between the cathode 12 and the anode 14, the membrane 16 being anionically conductive for high temperatures, usually temperatures above 600°C.By heating the cell 10 to at least this temperature and injecting an electric current I between the cathode 12 and the anode 14, a reduction of the water vapor on the cathode 12 occurs, which generates dihydrogen (H2) at the cathode 12 and dioxygen at the anode 14. To implement high-temperature electrolysis, it is known to use an electrolyzer of the SOEC type (acronym for "Solid Oxide Electrolysis Cell"), consisting of a stack of elementary patterns each comprising a solid oxide electrolysis cell, consisting of three anode / electrolyte / cathode layers superimposed on each other, and interconnection plates made of metal alloys also called bipolar plates, or interconnectors.The function of the interconnectors is to ensure both the passage of electric current and the circulation of gases in the vicinity of each cell (injected water vapor, hydrogen and oxygen extracted in an EHT electrolyzer; injected air and fuel (particularly hydrogen) and extracted water in an SOFC stack) and to separate the anode and cathode compartments which are the compartments for circulation of gases on the side of the anodes and cathodes of the cells respectively. To carry out the electrolysis of water vapor at high temperature EHT, water vapor H2O is injected into the cathode compartment. Under the effect of the current applied to the cell, the dissociation of water molecules in vapor form is carried out at the interface between the hydrogen electrode (cathode) and the electrolyte: this dissociation produces dihydrogen gas H2 and oxygen ions. The dihydrogen is collected and evacuated at the outlet of the hydrogen compartment. The oxygen ions O. 2-migrate through the electrolyte and recombine into oxygen at the interface between the electrolyte and the oxygen electrode (anode). To operate a SOFC fuel cell, air (oxygen) is injected into the cathode compartment and a fuel, particularly hydrogen, is injected into the anode compartment. The oxygen in the air dissociates into oxygen ions O 2-which migrate through the electrolyte and combine with the dihydrogen H2 at the anode to form water vapor and release electrons that are captured by the external electrical circuit. To increase the flow rates of hydrogen and oxygen produced in the case of EHT electrolysis or to increase the electrical power supplied in the case of an SOFC fuel cell, it is known to stack several elementary electrochemical cells on top of each other by separating them by the interconnectors. The assembly is positioned between two end connection plates that support the electrical supplies and the gas supplies / collection of an electrolyzer (electrolysis reactor) or an SOFC fuel cell.Furthermore, to improve the quality of the electrical contacts established between the interconnectors and the electrodes, and therefore the performance of the aforementioned electrochemical devices, electrical contact elements are individually interposed and arranged on the electrodes. In an electrochemical device, a nickel grid is conventionally used for contact with the hydrogen electrode (cathode in an EHT reactor, anode in an SOFC stack), because it gives satisfactory results at low cost. A stack 20 of electrolysis cells, intended to produce a significant quantity of hydrogen, is illustrated in FIG. 2. In particular, the cells 10 are stacked on top of each other while being separated by interconnection plates 18 connected to a water vapor supply collector 22 for injecting this vapor onto the cathodes of the cells 10 in accordance with a water vapor flow rate ^. ^^^regulated by a flow control member, for example a controllable valve 24. The plates 18 are also connected to two gas collectors 24, 26 for collecting the gases from the electrolysis, hydrogen (plus the possibly unconsumed fraction of water vapor (H2O)) and oxygen respectively. An example of stacking and structure of interconnecting plates is described in patent application WO 2011 / 110676. Such an electrolyzer can also operate in co-electrolysis, that is to say with a mixture of gases at the cathode inlet composed of water vapor (H2O) and carbon dioxide (CO2). The mixture at the cathode outlet is then composed of hydrogen (H2), and carbon monoxide (CO), plus the possibly unconsumed fractions of water vapor (H2O) and carbon dioxide (CO2). For the effective implementation of electrolysis by the stack 20, the stack is brought to a temperature above 600°C,usually a temperature between 600°C and 950°C, the gas supply is started at a constant flow rate and an electrical power source 28 is connected between two terminals 30, 32 of the stack 20 in order to circulate the current I therein. The same solid oxide electrochemical device can operate reversibly in high temperature electrolysis mode (SOEC) and in fuel cell mode (SOFC). In other words, a high temperature solid oxide cell and an EVHT electrolyser can have identical structures, only their operating mode being different. Referring to FIG. 3, an electrochemical cell 10 constituting an SOFC cell comprises the same elements, namely the anode 12, the cathode 14, the electrolyte 16, as an electrolysis cell. A cell of the battery is powered, on its anode by dihydrogen or another fuel such as methane CH4, and on its cathode by pure dioxygen or contained in the air sent,and connected to a load C to deliver the produced electric current. On the other hand, the two modes of production, either electric in SOFC or chemical species (H2, O2) in SOEC, have very different thermal regimes in operation. In fuel cell mode (SOFC), the oxidation of the fuel (hydrogen) being exothermic, whatever the operating point (current / voltage), there is a production of heat. This production is supported by the circulation of electric currents generating the Joule effect. The intensity of the thermal power produced thus depends directly on the production of electricity. For a given production, a thermal balance must be established in order to avoid a rise in temperature of a cell, and the stacking of cells, which is detrimental to their operation. To obtain this balance, it is possible, within certain limits, to act on the temperature of the reactants, the flow rates of reactants,particularly of oxidant. But this proves insufficient if the operation is carried out at high utilization rates and currents, sought for economic profitability. In the case of operation of a cell fueled by methane (CH4) or ammonia (NH3), the steam reforming (CH4) or reforming (NH3) reactions (see publication [1]), are endothermic and catalyzed by the nickel present in the anode of the hydrogen compartment which generates a thermal power sink. The net power of this sink is proportional to the quantity of fuel reformed and independent of the current generated. This situation shifts the thermal balance with respect to production from pure H2 as fuel, in a direction which is favorable to the increase, all other things being equal, of the electrical power supplied. Depending on the intensity of the current produced and the fuel supply rate, the thermal balance can be negative,i.e. the heat consumed by the reforming / steam reforming reactions is higher than the heat resulting from the oxidation of the H2, CO fuels. This is true for low currents and utilization rates. It can also be positive, i.e. the heat produced by the oxidations of H2 and CO is higher than that consumed by the reforming / steam reforming reactions. In the case of economically viable systems for which the fuel utilization rate and current production must be maximized, the heat balance leans towards a net production of heat and the need to extract thermal power, as is the case when feeding pure H2. The electrolysis reaction of water vapor is the reverse reaction of the oxidation of hydrogen, it is therefore endothermic. In this case, the quantity of dissociated steam,as ohmic losses depend on the electrolysis current and therefore on the supply voltage. Depending on the voltage at which an electrolysis cell is operated, three thermal regimes are observed. At the thermoneutral voltage (TEN), deduced from the dissociation enthalpy of the water vapor molecule, i.e. approximately 1.3V at the operating temperature of 800°C, the heat generated by the irreversibilities exactly compensates for the endothermicity of the electrolysis reaction. If the operating point of the cell corresponds to a voltage higher than this value, then the operation is exothermic because the production term linked to the irreversibilities is higher than the thermal consumption by electrolysis, and conversely an operating point at a lower voltage leads to an endothermic regime. The different thermal regimes involved for an operating mode in SOEC electrolysis or in SOFC fuel cell are explained in Figure 4,in the form of cell voltage curves as a function of current density. These curves show that it is necessary to evacuate the heat produced in SOFC fuel cell operating mode. As an illustration, for a module comprising several electrochemical devices with a stack of elementary cells, producing in SOFC mode an electrical power of the order of 50 kW with a hydrogen H2 supply and which has an electrical efficiency of 60%, the thermal power to be extracted amounts to 33.3 kW. For fuel cells operating at low temperature, PEMFC type, cooling is carried out by a liquid water circuit. This solution is unthinkable for a SOFC fuel cell at operating temperature. The solutions conventionally considered for evacuating the heat released by SOFC fuel cells,can be listed as follows: - part of the exothermicity of the hydrogen oxidation reaction is compensated by the endothermicity of the steam reforming reaction, when the cell is supplied by carbonaceous fuels (CH4) or ammonia-based fuels. Taking the previous example of a cell producing, this time from natural gas, an electrical power of the order of 50 kW with an efficiency of the order of 60% and an air overfeed of a factor of two, in which 90% of the steam reforming is carried out at the heart of the stacks of the cell, the thermal power to be extracted can be reduced to 5.5 kW. This solution is not possible when the fuel is hydrogen; - sending an air flow to the oxygen electrode much higher than what is necessary for the electrochemical reaction, the excess air flow allowing the heat produced to be evacuated. This solution works, but leads to excess air consumption,with both material consumption and energy required for its distribution, requires upstream / downstream pipes of larger cross-section, with equal pressure loss along the fluid circuit. Thus, the cell becomes less compact and more expensive. This also induces, at constant stack geometry, an increase in pressure in each stack of cells potentially detrimental to its lifespan, with an excess air flow for a complete cell which cannot exceed a certain value, and in this case does not allow the total thermal power produced to be evacuated; - the choice of a low current operating point, inducing limited heat production and easier to extract or compensate for by the two previous solutions. In this case the number of electrochemical cells and / or the size of a stack of cells must be higher for a given power,which has a direct impact on the amount of investment required to develop a module and a complete multi-module system. - an injection of air as an oxidant, at an operating temperature lower than that planned for the cell, in order to allow this air to evacuate more heat. Conversely, in electrolysis operating mode, as shown by the curves in Figure 4, depending on the operating point chosen, it is necessary to either supply or evacuate heat, even if in practice, on the scale of a module integrating several stacked electrochemical devices and a multi-module system, in nominal operation,a thermal regime point around the thermoneutral point is preferred in order to simplify thermal management. The Applicant has proposed in patent EP3494608B1 a solution for an electrochemical device capable of operating reversibly as a SOFC fuel cell or as a SOEC electrolyser. The proposed solution consists of installing a bypass line or circuit to divert, if necessary, part of the hot gases from the so-called oxygen chambers (anode chambers in SOEC mode, cathode chambers in SOFC stack mode), which limits the thermal power exchanged at the heat exchanger arranged in the oxygen circuit and thereby the inlet temperature of the oxygen into the cell stack. Excessive heating of the device is thus prevented in stack operating mode, whereas in electrolysis mode, the bypass line is not used. In this electrolysis mode,there is the possibility of preheating the air at the inlet of the device from the heat collected in the outlet gases, which allows an efficiency gain. Thermal management therefore appears extremely critical in that it leads to the design of electrochemical devices and different thermal management strategies at the level of a module with several electrochemical devices and a system with several modules, depending on their operating mode in SOEC electrolysis or SOFC cell. This is particularly exacerbated when reversible operation is envisaged with the same module which will alternately operate in SOEC electrolysis mode and in SOFC cell mode. There is therefore a need to find flexible thermal management solutions for a module with several electrochemical devices with a stack of elementary electrochemical cells and / or a system with several modules,that it(they) operate(s) in SOEC electrolysis mode or reversibly in SOFC battery mode. The aim of the invention is to meet at least part of this need. Disclosure of the invention To do this, the invention firstly relates to an electrochemical module, comprising: - at least one pre-assembled sub-module, intended to operate at high temperature, comprising: • a stack of electrochemical cells based on solid oxides of the SOEC / SOFC type; • a plurality of interconnectors with electrical and fluid distribution functions, each comprising a component made of electronically conductive and gas-tight material for bringing or collecting the electrical current to the cells and for bringing, collecting and circulating gases on each electrode of each electrochemical cell; the interconnectors being arranged individually on either side of each of the electrochemical cells; - a thermal insulation enclosure,inside which the pre-assembled sub-module(s) is / are housed, and comprising, through at least one of its walls: • at least one group of passages, preferably sealed, through which pass electrical supply lines and fluid lines for supplying reactive gases and for discharging the gases produced, from the at least one pre-assembled sub-module; • at least one discharge hatch, mounted movably between a closed position in which it maintains the thermal insulation of the enclosure from the outside and at least one open position in which the heat released by the at least one sub-module beyond a predetermined value is discharged at least by natural convection. The hot air which is discharged through the hatch solely by natural convection is a function of the initial dimensioning, in particular, the volume of the enclosure, the position,the number and dimensions of the evacuation hatch(es). According to an advantageous embodiment, the module further comprising: - an air or neutral gas blowing system; - at least one blowing hatch connected to the blowing system mounted movably through one of the walls of the thermal enclosure between a closed position in which it maintains the thermal insulation of the enclosure from the outside and an open position in which the air or neutral gas is blown in from the system in operation, so that when the evacuation hatch is also in its open position the heat released by the at least one sub-module beyond the predetermined value is evacuated by forced convection. Thus,we obtain in a way an active mode of heat release which has an increased efficiency compared to the passive mode by simple natural convection of the hot air passing through the exhaust hatch open to the outside. The air flow to be blown is a function of the thermal power to be evacuated. Operating an air blower will consume electrical power and reduce the electrical efficiency of the module, when operating in battery mode of the sub-modules with stacked electrochemical cells. The operation of an air blower will be triggered in the event of overheating linked to the operation of the sub-modules in battery mode or the operation of the sub-modules in electrolysis mode if it becomes too exothermic to the point of risking being detrimental to the life of the stacks of electrochemical cells and / or other components inside the enclosure. For example,these situations may be encountered in battery mode if high currents are applied to the stacks, and in electrolysis mode if voltages higher than the thermo-neutral voltage are applied to them. Advantageously, the opening of the evacuation hatch is controlled by the thermal operating regime of the sub-module(s). Advantageously again, the opening of the insufflation hatch is controlled by that of the evacuation hatch. Thus, as soon as fresh air is blown in, the release of hot air is simultaneous. According to an advantageous embodiment, the enclosure comprises within it one or more of the baffles for circulating the air heated by the heat released to be evacuated by the evacuation hatch(es). According to another advantageous variant, the at least one sub-module is supported by the floor of the enclosure. According to an advantageous configuration,the enclosure comprises at least one exhaust hatch in the wall forming the ceiling of the enclosure and at least one supply hatch in the floor and / or a side wall of the enclosure so that, in at least one open position of said hatches, the air flow generated by the heat released is driven by the chimney effect. According to an advantageous variant embodiment, the enclosure consists of a metal casing filled with at least one thermal insulating material. According to another advantageous variant, each hatch consists of a metal casing filled with at least one thermal insulating material. Preferably, the thermal insulating material is a refractory material, in the form of bricks or fibers or foams or mats. More preferably, the walls of the enclosure have a thickness between 10 and 50 cm. Thus,the invention essentially consists of a module intended to operate at high temperature with a thermal enclosure in which sub-modules with stacks of electrochemical cells are housed. At least one hatch for evacuating the heat released inside the enclosure by the sub-modules in operation makes it possible to manage the thermal at the level of a module. The solution is particularly suitable for operations of the sub-modules which are reversible, that is to say which can switch from operation in fuel cell mode to an electrolysis or co-electrolysis mode, because it makes it possible to manage the thermal of the module according to one or other of the two operating modes of the sub-modules. The solution can of course be implemented with sub-modules which operate solely as fuel cells,or solely as an electrolyzer or co-electrolyzer. An enclosure of a module according to the invention may comprise any number of sub-modules with stacks of electrochemical cells, typically from 1 to several hundred, more reasonably between 1 and 100. In practical implementation, each hatch may be delimited by cutting / machining / drilling through a wall of the thermal insulation enclosure. Its passage section in the open position and the choice of its shape will be determined to take into account the components, in particular the electrochemical sub-modules, present within it. The total air passage section depends on the heat that will be evacuated, the size of the enclosure and the number of electrochemical sub-modules inside. Each hatch may be in the form of a pivoting or sliding opening, in particular in an enclosure wall, or folding back on itself. As an opening system for each hatch,a simple manual handle can be considered, but also a controlled motorized system. A controlled system may be preferred for possibly a partial opening of all the hatches or only some, controlled according to the operating point of the sub-modules and the heat to be evacuated from the enclosure. Other advantages and characteristics will emerge more clearly upon reading the detailed description, given for illustrative and non-limiting purposes, with reference to the following figures. Brief description of the drawings [Fig 1] Figure 1 is a schematic view of an elementary electrochemical cell of an EHT electrolyzer. [Fig 2] Figure 2 is a schematic view of a stack of cells according to Figure 1. [Fig 3] Figure 3 is a schematic view of an electrochemical cell of an SOFC fuel cell. [Fig 4] Figure 4 illustrates in the form of a curve the voltage of a solid oxide electrochemical cell as a function of the current density,when operating in EHT electrolyzer mode or in fuel cell mode. [Fig 5] Figure 5 is a schematic longitudinal sectional view of an example of an electrochemical cell stack assembly with its interconnectors and two clamping plates on either side forming a sub-module operating as an EHT electrolyzer and reversibly as an SOFC fuel cell. [Fig 6] Figure 6 illustrates the different levels of integration from an elementary solid oxide electrochemical cell with an interconnector to a complete system that can operate reversibly in EHT electrolysis mode for hydrogen production or in SOFC fuel cell mode for electricity production. [Fig 7A],[Fig 7B] Figures 7A and 7B schematically illustrate a module with a thermal insulation enclosure according to one embodiment of the invention with the hatches for evacuating by natural convection the heat released by the sub-modules, in the closed and open position respectively. [Fig 8A], [Fig 8B] Figures 8A and 8B schematically illustrate a module with a thermal insulation enclosure according to another embodiment of the invention comprising a system for blowing air or neutral gas to evacuate the heat by forced convection,with the hatches in the closed and open position respectively. [Fig 9] Figure 9 illustrates a variant of recovery of the heat evacuated from the module according to Figures 7A and 7B. [Fig 10] Figure 10 illustrates a variant of recovery of the heat evacuated from the module according to Figures 8A and 8B. Detailed description Figures 1 to 4 have been commented on in the preamble and will therefore not be detailed subsequently. Throughout the present application, the terms "lower", "upper", "above", "below", "inner", "outer", "internal" "external" are to be understood with reference to an electrochemical device according to the invention in the operating configuration, vertically. It is also specified that the electrolysers or fuel cells described are of the solid oxide type (SOEC, acronym for "Solid Oxide Electrolysis Cell" or SOFC, acronym for "Solid Oxide Fuel Cell") operating at high temperature. Thus,all the constituents (anode / electrolyte / cathode) of an electrolysis cell or battery are ceramics. The high operating temperature of an electrolyzer (electrolysis reactor) or a battery is typically between 600°C and 950°C. Figure 5 shows an electrochemical device SM according to the invention that can operate reversibly as a high-temperature electrolyzer EHT or fuel cell SOFC. This device SM is a stack 20 of electrochemical cells based on solid oxides of the SOEC / SOFC type, which makes it possible to increase the power of hydrogen production or reversibly electricity compared to a single cell. Within the stack 20, a plurality of interconnectors with electrical and fluid distribution functions, not shown, is arranged individually on either side of each of the electrochemical cells,as illustrated in Figure 2. Each interconnector consists of a component made of electronically conductive and gas-tight material for supplying or collecting the electric current to the cells and for supplying, collecting and circulating gases on each electrode of each electrochemical cell. Similarly, within the stack 20, a plurality of contact elements is individually arranged on each electrode of electrochemical cells and a plurality of seals around each gas inlet / outlet and around each cell. In other words, the SM device comprises a stack of cells with individual interposition of interconnectors, contact elements and seals as done according to the state of the art for a complete electrochemical device. Furthermore,in order to limit the electrical contact resistance between an interconnector and the elementary electrochemical cells that the interconnector connects and to seal the electrochemical device, the SM device may comprise a clamping system with two clamping plates 200, 201 arranged on either side of the stack of electrochemical cells that it compresses. An example of a clamping system is for example described in application FR3045215Al, which ensures a substantially constant clamping force over a wide operating temperature range. Thus assembled with the clamping system, the SM device forms a preassembled electrochemical sub-module which can operate reversibly in fuel cell mode or in high-temperature electrolysis mode and which can be handled, moved,transported. Figure 6 illustrates the different levels of integration from a solid oxide electrochemical cell to a complete hydrogen or electricity production system as currently envisaged. In this integration, an electrochemical module M comprises several sub-modules such as that described with reference to Figure 5, and a complete system, which may constitute a production site in its own right, may comprise several modules. According to the invention, a thermal insulation enclosure 100 is provided for an electrochemical module M, inside which the pre-assembled sub-module(s) SM1, SM2 are housed. The enclosure 100 may consist of a metal casing filled with at least one thermal insulating material, preferably a refractory material, in the form of bricks or fibers or foams or mats. Advantageously, the pre-assembled sub-modules SM1,SM2 are supported by the wall 102 forming the floor of the enclosure. As illustrated, for each preassembled sub-module SM1, SM2, electrical supply lines 210 (in dotted lines) and fluid lines (in solid lines) for supplying reactive gases and evacuating the produced gases cross the floor 102 of the enclosure by means of bushings, not shown. It should be noted that the representation of the lines is obviously schematic, the electrical lines being cables, the fluid lines being pipes. At least one evacuation hatch 110 is mounted, in one of the walls 101, 102 of the enclosure, movable between a closed position in which it maintains the thermal insulation of the enclosure from the outside (figure 7A) and at least one open position in which the heat released by the sub-modules SM1, SM2 beyond a predetermined value is evacuated by natural convection (figure 7B). In the example illustrated,an evacuation hatch 110 is mounted in the wall 101 forming the ceiling of the enclosure and several supply hatches 111 are mounted in the floor 102 so that, in at least one open position of said hatches, the air flow generated by the heat released is driven by the chimney effect. As symbolized by the arrows in Figure 7B, the fresh air passing through the open hatches 111 heats up in the enclosure with the heat released by the sub-modules SM1, SM2 to evacuate it through the open hatch 110. It is advantageous to provide for the opening of the hatches 111 to be controlled by that of the evacuation hatch 110 itself controlled by the predetermined value beyond which the heat must be evacuated. One or more exhaust hatches may also be mounted in the side wall 103 and / or in the top wall 101 of the enclosure. To improve the evacuation of heated air,one or more of the circulation baffles can be provided in the enclosure 100. The opening of each hatch 110, 111 is preferably controlled by the thermal operating regime of the sub-modules SM1, SM2. To further improve the evacuation of the heat released by the sub-modules SM1, SM2, it is possible to envisage blowing air into the enclosure 100 for evacuation by forced convection. Figures 8A and 8B show a system 300 for blowing air or a neutral gas which is connected to the hatches 111, via pipes 310. Thus, when the hatch 110 and the hatches 111 move from a closed position (Figure 8A) to an open position (Figure 8B), the air or the neutral gas is blown from the system 300 in operation, and the heat released by the sub-modules SM1, SM2 beyond the predetermined value is evacuated by forced convection. Here too,it is advantageous to provide for the opening of the hatches 111 to be controlled by that of the evacuation hatch 110 itself controlled by the predetermined value beyond which the heat must be evacuated. Similarly, to improve the evacuation of the heated air, one or more of the circulation baffles can be provided in the enclosure 100. An advantageous variant may consist of recovering the heat from the air or neutral gas evacuated by the evacuation hatch 110, instead of evacuating it into the atmosphere. It is thus possible to provide a collection circuit including at least one collection pipe 112 at the outlet of the evacuation hatch 110 which, in the open position of the latter, will collect the hot air or neutral gas. This collection circuit incorporates a heat exchanger 300,preferably of the air-water type. It may be a tube and fin exchanger. Care is of course taken to size the exchanger 300 so that the pressure losses it induces in the pipe 112 do not hinder the circulation of the air or neutral gas flow. Thus, the heat coming from the evacuation will be exchanged in the exchanger in order to recover it, for example in a heating network. It may be an air-water type exchanger allowing the heat to be exchanged between the outgoing air or neutral gas and the water. This recovery and recovery of hot air can be carried out in the case of natural convection mode (figure 9) or for hot air or neutral gas in the case of forced convection mode (figure 10). For example, for an enclosure height of around 3 m and an operating temperature of the sub-modules SM1, SM2 within it of 700°C, we can estimate a thermal power to be evacuated of around 2,3 kW. Thermal calculations indicate that the circular section of passage of a fresh air flow, corresponding to the opening cleared by one or more supply hatches 111, must be of the order of 4.6×10, -4m² or a diameter of the order of 2.4 cm². The evacuation hatch 110 may have a larger diameter. The invention is not limited to the examples which have just been described; it is possible in particular to combine characteristics of the illustrated examples within variants not illustrated. Other variants and improvements may be envisaged without departing from the scope of the invention. If in the illustrated examples, the module enclosure contains several sub-modules with stacks of cells next to each other, it is possible to envisage stacks of several sub-modules on top of each other, in addition to one next to the other, housed inside the enclosure in the form of multiple columns of sub-modules. If in the illustrated examples, only two sub-modules SM1, SM2 are shown inside a thermal insulation enclosure, the latter may contain several dozen or even hundreds of them.List of cited references [1]: “Ammonia-Fed Fuel Cells_ a Comprehensive Review | Elsevier Enhanced Reader”. Accessed March 28, 2021. https: / / doi.org / 10.1016 / j.rser.2016.01.120.

Claims

Claims 1. Electrochemical module (1), comprising: - at least one pre-assembled sub-module (SM1, SM2), intended to operate at high temperature, comprising: • a stack (20) of electrochemical cells based on solid oxides of the SOEC / SOFC type; • a plurality of interconnectors with electrical and fluid distribution functions, each comprising a component made of electronically conductive and gas-tight material for supplying or collecting the electrical current to the cells and for supplying, collecting and circulating gases on each electrode of each electrochemical cell; the interconnectors being arranged individually on either side of each of the electrochemical cells;- a thermal insulation enclosure (100), inside which the pre-assembled sub-module(s) is / are housed, and comprising, through at least one of its walls: • at least one group of passages, preferably sealed, through which pass electrical supply lines (210) and fluid lines for supplying reactive gases and for discharging the gases produced, from the at least one pre-assembled sub-module;• at least one evacuation hatch (110), mounted to move between a closed position in which it maintains the thermal insulation of the enclosure from the outside and at least one open position in which the heat released by the at least one sub-module beyond a predetermined value is evacuated at least by natural convection.

2. Electrochemical module according to claim 1, the opening of the evacuation hatch being controlled by the thermal operating regime of the sub-module(s).

3. Electrochemical module according to one of claims 1 or 2, further comprising: - a system (300) for blowing air or a neutral gas;- at least one insufflation hatch connected to the insufflation system mounted movably through one of the walls of the thermal enclosure between a closed position in which it maintains the thermal insulation of the enclosure from the outside and an open position in which the air or neutral gas is insufflated from the system; operation, so that when the exhaust hatch is also in its open position the heat released by the at least one sub-module beyond the predetermined value is evacuated by forced convection.

4. Electrochemical module according to claim 3, the opening of the insufflation hatch being controlled by that of the exhaust hatch.

5. Electrochemical module according to one of the preceding claims, the at least one sub-module being supported by the floor of the enclosure.

6. Electrochemical module according to one of the preceding claims, the enclosure comprising at least one exhaust hatch in the wall forming the ceiling of the enclosure and at least one supply hatch (111) in the floor and / or a side wall of the enclosure so that, in at least one open position of said hatches, the air flow generated by the released heat is driven by the chimney effect. 7.Electrochemical module according to one of the preceding claims, the enclosure comprising within it one or more baffles for circulating the air heated by the heat released to be evacuated through the evacuation hatch(es).

8. Electrochemical module according to one of the preceding claims, the enclosure consisting of a metal casing filled with at least one thermal insulating material.

9. Electrochemical module according to one of the preceding claims, each hatch consisting of a metal casing filled with at least one thermal insulating material.

10. Electrochemical module according to claim 8 or 9, the thermal insulating material being a refractory, in the form of bricks or fibers or foams or mats.

11. Electrochemical module according to one of the preceding claims, the sub-module comprising two clamping plates (200, 201) between which the stack is arranged. 12.Electrochemical module according to one of the preceding claims, the walls of the enclosure having a thickness between 10 and 50 cm.

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