FR3003867A1 - COMPOSITION FOR THE STORAGE AND PRODUCTION OF THERMO-CHEMICAL ENERGY, METHOD FOR STORING AND PRODUCING THERMO-CHEMICAL ENERGY, AND DEVICE FOR PRODUCING THERMO-CHEMICAL ENERGY - Google Patents

Abstract

A composition for storing and producing thermochemical energy comprising: - a thermochemical material based on calcium chloride, said material being intended to be hydrated to produce thermochemical energy and to be dehydrated in order to store thermochemical energy; and nucleating agents for promoting the solidification of hydrated calcium chloride, the calcium chloride in the hydrated form being CaCl 2 .xH 2 O with 3 <x <5, and the nucleating agents being particles based on silicon oxide or based on carbide or nitride materials.

Description

Composition for the storage and production of thermochemical energy, thermochemical energy storage and production method and thermochemical energy production device. TECHNICAL FIELD OF THE INVENTION The invention relates to a composition intended for the storage and production of thermochemical energy. The invention also relates to a method for storing and producing thermochemical energy. The invention also relates to a device for producing thermochemical energy. STATE OF THE ART Heat storage has always been a major problem because heat input and heat requirements are shifted in time (day / night, summer / winter). In order to remedy this problem, thermochemical energy storage devices are being developed. To obtain thermal energy, so-called phase change materials can conventionally be used. These materials can store or give energy during a change of state. The thermochemical energy is stored and returned via two reactions: an endothermic reaction and an exothermic reaction respectively. The endothermic reaction occurs when the material passes from liquid phase to solid phase by dehydration. The exothermic reaction

occurs when the material passes from solid phase to liquid phase by hydration. Subsequently, such materials will be called thermochemical materials. The thermochemical energy obtained by these thermochemical materials must be able to be stored and returned at the desired time and at the desired location. For this, the materials can be dehydrated by heating. For example, patent EP 2 163 520 describes a zeolite impregnated with magnesium sulphate. The hygroscopic mineral salt is dehydrated by heating, using industrial heat generated by plants or using solar energy, for example. These materials can then be transported in their dehydrated form and rehydrated to heat buildings or dwellings. Carlsson's article "Phase change behavior of some latent heat storage media on calcium chloride hexahydrate" (Solar Energy 2009, 83, 48515 500) thus describes a storage method based on the phase change of calcium chloride hexahydrate. Another storage principle is thermochemical storage: documents EP 0 063 348 and US 4 303 121 describe, for example, the thermochemical use of calcium salts such as CaCl 2, 6H 2 O or CaSO 4, 2H 2 O. U.S. Patents 4,412,931 and EP 0 063 348 disclose calcium salts, in hexahydrate form CaCl2.6H2O, used in the presence of potassium salts. The potassium salt makes it possible, in particular, to avoid the formation of hydrates other than CaCl 2 · 6H 2 O. Although the general principle of the use of such materials is well known, one of the main challenges of producing thermochemical energy, using such materials, is to be able to easily hydrate these materials while recovering the maximum heat during hydration. In addition, the hydration of the thermochemical material often requires the use of devices comprising fluidized beds, grinders or any other powder handling technology which has hitherto compromised the industrial use of this type of storage.

OBJECT OF THE INVENTION The object of the invention is to overcome the disadvantages of the prior art and, in particular, to provide a composition containing a thermochemical material which can be easily hydrated and can produce a large amount of heat. The invention also aims to provide a hydration device, simple, easy to implement and to recover a maximum of heat during the hydration of the thermochemical material. This object is achieved by a composition for the storage and production of thermochemical energy comprising: a thermochemical material based on calcium chloride, said material being intended to be hydrated to produce thermochemical energy and to be dehydrated to store thermochemical energy, and nucleating agents, to promote solidification of hydrated calcium chloride. Calcium chloride in hydrated form is CaCl 2 .xH 2 O with 3 <x <5, and the nucleating agents are particles based on silicon oxide or based on carburized or nitrided materials. This object is also achieved by a method of storing and producing thermochemical energy comprising the steps of: providing a composition comprising a thermochemical material based on calcium chloride, said material being intended to be hydrated to produce of the thermochemical energy and to be dehydrated to store thermochemical energy, hydrate the composition so as to obtain hydrated calcium chloride CaCl 2 .xH 2 O with 3 <x <5, said hydration producing thermochemical energy , adding nucleating agents to the composition, the nucleating agents being particles based on silicon oxide or based on carburized or nitrided materials.

This objective is also achieved by a thermochemical energy production device comprising: at least one reservoir 8 intended to contain a composition containing: a thermochemical material based on calcium chloride, said material being intended to be hydrated so as to to produce thermochemical energy and to be dehydrated to store thermochemical energy, the hydrated calcium chloride being CaCl 2 .xH 2 O with 3 <x <5 - nucleating agents, to promote solidification of the chloride of hydrated calcium, the nucleating agents being particles based on silicon oxide or based on carburized or nitrided materials, said reservoir 8 being provided with a water inlet 11, the water being intended to hydrate the thermochemical material in order to produce heat, - at least one heat exchanger for containing a coolant, said heat exchanger being in contact with c the tank 8 and being configured to transfer heat from the tank 8 to a heat distribution circuit. BRIEF DESCRIPTION OF THE DRAWINGS Other advantages and features will emerge more clearly from the following description of particular embodiments of the invention given as non-restrictive examples and represented in the accompanying drawings, in which: FIG. , schematically, a centralized installation for dehydrating a thermochemical material, - Figure 2 shows, schematically, the place of use of the thermochemical material, according to a particular embodiment of the invention, - Figures 3 and 4 schematically represent, in section, a device for producing thermochemical energy, according to a particular embodiment of the invention; FIG. 5 is a diagrammatic view in top view of a device for the production of Thermochemical energy, according to a particular embodiment of the invention, - Figure 6 represents, in a dry manner 3, a device for producing thermochemical energy, according to a particular embodiment of the invention; FIG. 7 schematically represents, in section, a thermochemical material reservoir of a device for production of thermochemical energy, according to a particular embodiment of the invention, - Figure 8 shows schematically in section a part of a thermochemical energy production device, according to a particular embodiment of the invention. 'invention. DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION The composition for the production of thermochemical energy comprises: a thermochemical material based on dehydrated calcium chloride, said material being intended to be hydrated in order to produce energy thermochemical, and nucleating agents, to promote the solidification of hydrated calcium chloride. The dehydrated calcium chloride is CaCl 2 .xH 2 O with 3 <x <5 in a dehydrated form. The nucleating agents are particles based on silicon oxide or based on carbide or nitride materials.

Calcium chloride in dehydrated form means that the material CaCl 2 .xH 2 O with 3 <x <5 is either completely dehydrated and thus in the anhydrous CaCl 2 form or in a partially dehydrated form. By partially dehydrated form is meant CaCl 2 with a proportion of water less than 12%. For example, the thermochemical material may be in the form CaCl 2 .xH 2 O with 0.01 <x <0.05. Preferably, the thermochemical material is totally dehydrated in order to increase the storage and therefore the production of thermochemical energy.

Calcium chloride in the form CaCl 2 .xH 2 O with 3 <x <5 is a subhydrate of CaCl 2 · 6H 2 O. Advantageously, these subhydrates involve less water molecules during thermochemical reactions, which improves their energy budgets.

Even more preferably, x is greater than or equal to 3.5 and less than or equal to 4.5 and even more preferably, x is greater than or equal to 3.9 and less than or equal to 4.1.

Even more preferentially, x is equal to 4 and the calcium chloride is in the form CaCl2.4H2O. It is calcium chloride tetrahydrate, it is a subhydrate of CaCl2.6H2O. The melting point of the calcium chloride tetrahydrate is 45.3 ° C. Advantageously, this melting temperature is greater than that of the calcium chloride hexahydrate CaCl 2 · 6H 2 O which is around 30 ° C. Advantageously, it is therefore possible to recover more heat with calcium chloride tetrahydrate. In addition, this calcium chloride has interesting thermochemical properties that can be easily exploited. Its heat of fusion can also be easily stored. It is about 250 J / g and is recovered at 45 ° C. By heat of fusion, also called latent heat of fusion, is meant the heat released during the solidification of the material. The use of a heat source greater than or equal to 80 ° C makes it possible to eliminate all or part of the 4 molecules of water and to store the corresponding energy. Advantageously, even if the material is not completely dehydrated, thermochemical energy can be recovered during hydration. The thermochemical energy thus obtained can be up to 450 J / g. Advantageously, the dehydration of these thermochemical materials takes place in relatively low temperature ranges.

The material can be completely dehydrated using temperatures of the order of 150 ° C for example or lower. The skilled person will choose any device suitable for dehydration and heat recovery. Advantageously, the thermochemical material, once dehydrated, can then be stored cold without heat loss for long storage periods. Long periods of time are of the order of several months, at least six months. The thermochemical heat is then restored by contacting the thermochemical material with water. The water can be in liquid or gaseous form.

The thermochemical heat can thus be restored at temperatures above 90 ° C. During hydration of the anhydrous or poorly hydrated compound, for example by bringing it into contact with water or water vapor, thermochemical energy is then released. Advantageously, such thermochemical materials allow, during their hydration, to provide heat in exploitable temperature ranges in many applications. For example, these may be home heating applications.

The hydration of the thermochemical material makes it possible to rehydrate the said material, preferably up to its CaC12.4H20 form. According to another alternative, the material could be rehydrated to its CaC12.6H20 form, however this form does not recover heat as effectively as the CaC12.4H20 form.

Classically, during the cooling of the under-hydrate type materials unwanted supercooling phenomena take place, which leads to delay in particular the solidification and therefore the heat recovery. By supercooling is meant the state of a material that remains in the liquid state when its temperature is below its solidification temperature. According to a preferred embodiment, the composition contains nucleating agents. The nucleating agents advantageously make it possible to avoid supercooling phenomena during the solidification of the calcium chloride and thus to facilitate its solidification.

Surprisingly, it has been found that the crystallization of different hydrates of calcium chloride occurs differently depending on the materials in the presence of the composition. For example, a supercooled calcium chloride composition in the presence of stainless steel precipitates rapidly when in the presence of pyrex borosilicate glass, said composition forming needles entangled from the glass.

Preferably, the nucleating agents are particles based on silicon oxide or based on carburized or nitrided materials. For example, they are glass particles or SiO 2.

The nucleating agents may also be refractory materials based on carbide and / or nitride. Preferably, it is titanium carbide TiC and titanium nitride TiN as well as silicon carbide SiC. The nucleating agents are, preferably, particles of 10 dimensions, for example between 0.01 μm and 5 μm, and even more preferably between 0.1 μm and 5 μm. The dimensions are relatively small so use little but especially to avoid settling. Preferably, the composition comprises between 0.05% and 5% by weight of nucleating agents. Even more preferentially, the composition comprises between 0.1% and 2% by weight of nucleating agents and even more preferably between 0.1% and 1% by weight. For example, the addition of 0.1% by weight of silicon carbide particles, of 0.5 μm average diameter, in the composition leads to a very dense suspension where the inter-particle distance is of the order from 6pm. Under these conditions the settling speed is infinitely small (of the order of 10-5 m / sec) and the suspension is stable. According to a preferred embodiment, the nucleating agents are introduced before the beginning of the solidification process. According to another embodiment, the nucleating agents are introduced at the desired moment during the cooling of the composition. According to a preferred embodiment, the nucleating agents are introduced during the cooling of the composition when its temperature is of the order of 60 ° C.

Advantageously, in addition to the thermochemical heat when the dehydrated material is brought into contact with the water, during the cooling of the material, the heat of solidification of the thermochemical material under-hydrate can also be recovered and used. It is thus possible to store and recover the sum of thermochemical heat and phase change, this amount can go up to 800 J / g. Advantageously, the thermal losses are negligible because the phase change is only a consequence of the thermochemical reaction whose triggering is controlled.

The composition may also contain additives. It may be, for example, chlorides such as magnesium chloride which enhances the storage capacity of the composition when it is present at low concentration.

The composition may contain impurities such as NaCl and / or Ca (OH) 2. Preferably, the composition comprises less than 10% of impurity. Such a percentage makes it possible not to affect the operation of the process and in particular the hydration / dehydration reactions of the material. The less impurity there is, the greater the amount of exploitable heat.

According to a preferred embodiment, the composition comprises more than 80% of calcium chloride. Even more preferably, the composition contains more than 90% of calcium chloride.

At the end of cooling and solidification, a solid material is obtained. This material is easy to handle, at first, it can be easily melted and then dehydrated, for a subsequent storage phase, then it can be easily rehydrated for a subsequent heat recovery phase. In a preferred embodiment, the method for storing and producing thermochemical energy comprises the following steps: providing a composition comprising a thermochemical material based on calcium chloride, said material being intended to be hydrated in order to produce thermochemical energy and to be dehydrated in order to store thermochemical energy, hydrate the composition so as to obtain hydrated calcium chloride CaCl 2 .xH 2 O with 3 <x <5, said hydration producing thermochemical energy, add nucleating agents in the composition, the nucleating agents being particles based on silicon oxide or based on carburized materials s or nitrides. According to a particular embodiment, the nucleating agents are added before the start of the hydration. For example, they may be added before being placed in the hydration device. According to another particular embodiment, the nucleating agents are added to the composition during hydration, i.e. during thermochemical energy production. For example, the nucleating agents are added when the composition is at a temperature of 60 ° C., during cooling, which makes it possible to facilitate the release of heat during hydration and to avoid supercooling phenomena. During the dehydration of the thermochemical material, the composition may advantageously also contain the nucleating agents. The presence of the nucleating agents in the composition acts not only on the supercooling of the product but also on the boiling point of the solution.

It has been observed, for example, that the presence of borosilicate type glass, such as pyrex, makes it possible to reduce the boiling point of a composition based on calcium chloride from 15% to 30%.

According to a particular embodiment, the method comprises an additional step of dehydrating the thermochemical material. According to various embodiments, the method comprises a step of filtering the thermochemical material so as to remove the nucleating agents from the composition, said dehydration step being carried out before or after the dehydration step. Thus, according to the embodiments, the nucleating agents can be either separated from the thermochemical material during the filtration and, for example, reintroduced into the thermochemical energy production device during the hydration phase or be always left in contact. of the material. Advantageously, the nucleating agents have a beneficial influence on the dehydration and the formation of vapor bubbles. In addition, they do not interfere with the dehydration of the thermochemical material because of their small particle size and their small proportion. These materials advantageously have great flexibility of recharging: indeed, at the place of use, that is to say at the hydration site of the thermochemical material, it is possible, if there is a source opportunity. heat available, to proceed to a partial reloading of the thermochemical material which has been hydrated. By partial reloading it is meant that it is possible to melt said material with low temperatures, for example of the order of 50-55 ° C and then partially dehydrate with a hotter source. This allows it to be partially recharged with thermochemical energy for later rehydration.

The excellent thermochemical properties of these materials allow them to be used in thermochemical energy production devices. These devices can be used to supply homes with heat, for example. According to a particular embodiment of the invention, the heating device is a so-called decentralized device. The hydration and dehydration steps can be carried out in separate devices, a device being dedicated to the hydration of the thermochemical material and the other device being dedicated to dehydration, this makes it possible to capture heat in one place and to restore it to another place. As shown in FIG. 1, the dehydration of the thermochemical material is carried out in a centralized installation 1. It can be a solar power plant, a plant or an industrial site generating heat. This dehydration can also be called regeneration. For example, the thermochemical material is regenerated in an industrial dryer 2 heated by the heat released by the plant 1. The water resulting from the dehydration can also be recovered and loaded into a tank 7. The thermochemical material in the form of powder is then loaded through a circulation pump 3 and an automated system 4 in a thermochemical energy production device. In this embodiment, the thermochemical energy generating device is in the form of a container 6. The thermochemical energy generating device comprises: - at least one reservoir 8 intended to contain a composition containing: - a thermochemical material based on dehydrated calcium chloride, the dehydrated calcium chloride being CaCl 2 .xH 2 O with 3 <x <5 in a dehydrated form, - nucleating agents, intended to promote the solidification of the calcium chloride hydrate, the agents nucleants being silica-based particles, said tank 8 being provided with a water inlet 11, the water being intended to hydrate the thermochemical material to produce heat, - at least one heat exchanger, intended for contain a coolant, said heat exchanger being in contact with the tank 8 and being configured to transfer heat from the tank 8 to a circuit of d istribution of heat.

The container 6 and the tank 7 are then transported from the centralized installation 1 to the place of use 17. The place of use 17 is, for example, a dwelling or a group of dwellings. As shown in FIG. 2, the container 6 is then placed close to the place of use 17 and connected to a heat distribution circuit 16, for example to a heating circuit. The water tank 7 is connected to the container 6 via a pump 15. When the place of use 17 requires heat, the pump 15 sends water to the container 6 to hydrate the thermochemical material disposed in the tank 8 of the container 6 and thus release thermochemical energy. Preferably, the container 6 contains several reservoirs in order to increase the heat exchange surfaces between the heat transfer fluid and the thermochemical material.

According to a preferred embodiment and as shown in Figures 3 to 6, the container 6 has four side walls, a bottom and a roof. The water inlet of the container is located, advantageously, in one of its side walls. A self-obstructing connector 69 connects the container 6 to the tank 7. The valve 15 is disposed between the tank 7 and the self-blocking connector 69.

The container 6 contains a heat transfer fluid. The heat transfer fluid makes it possible to recover the heat released during the thermochemical reaction and transport it to the heating circuit. The heat transfer fluid is for example glycol water.

The container 6 comprises a circulation device for circulating the heat transfer fluid within the container 6, said fluid flowing perpendicularly to the side face of each tank 8. Two fast self-sealing connectors allow to create a heat transfer fluid stream at the same time. The inside of the container 6, so as to create a stream of fluid around the tanks 8. Advantageously, this heat transfer fluid stream is perpendicular to the side wall of each tank 8. The orientation of the fluid stream is achieved by means of baffles 64, 65 and 66.

This orientation advantageously makes it possible to improve heat recovery from the tanks 8 to the coolant. According to a particular embodiment, a heat-insulating material 62 and a skin 63 may be placed inside the container 6, between the reservoirs 8 and the inner wall of the container 6. The heat-insulating material advantageously makes it possible to thermally insulate the heat transfer fluid from the outside of the container and thus prevent heat loss. The material is, for example, rubber or polymer.

The tanks 8 are arranged in the same container 6, parallel to each other inside the container 6, for containing a coolant. Each tank 8 is provided with an upper part called head 9, a lower part called foot 12 and a side wall.

Advantageously, each tank 8 is held in the container 6 by two fasteners. The foot 12 and the head 9 of each tank 8 are inserted into sockets welded respectively to the bottom and the roof of the container. This configuration advantageously makes it possible to effectively hold them in the container 6. Each tank 8, placed in the container 6, contains the thermochemical material. Preferably, when the container is ready for use, i.e. ready to provide thermochemical energy, the thermochemical material is dehydrated. Even more preferably, the container contains the dehydrated thermochemical material and nucleating agents. Each tank 8 is provided with a water inlet 11 at its upper part or head 9, which makes it possible to individualize the water injections. The water distribution network of the tanks 8 is connected to the self-clogging connection of the container 6, itself connected to the tank 7. A valve 18 is disposed at the water inlet 11 of the tank 8, which which makes it possible to control the quantity, the flow rate of the water inlet of each tank 8. Preferably, the valve 18 is a solenoid valve. The electro valve is advantageously controlled by a control device. According to a preferred embodiment, the device comprises a plurality of tanks 8. A solenoid valve is disposed at the water inlet 11 of each tank 8. Each reactor can be supplied with water independently of other reactors. The number of reactors supplied with water and the mass of water introduced into each reactor is determined according to the needs of the place of use and is controlled by a control device. This control device makes it possible to control and actuate individually the solenoid valves arranged at the water inlet 11 of each tank 8. According to one particular embodiment, each tank 8 comprises a drain plug 13 in its bottom 12, which makes it easy to drain said tanks 8. U shaped angle portions 14 advantageously make it possible to raise the drain plugs 13 and thus to empty simultaneously all the reactors.

Bolted hatches 60 allow the opening of the container and thus the assembly and disassembly of the tanks 8. When all the heat stored in the thermochemical material has been released, the container 6 and the tank 7 are returned to the centralized installation 1 for regenerate the thermochemical material. The container 6 is connected by the connections 70 and 71 to the hot source 2 of the installation 1. The circulation pump 3 circulates the heat to fuse the hydrate and purge it in the tank 5.

The container 6 has, advantageously, a role of local boiler and mobile. It allows easy movement and easy use of the thermochemical material. The device is easily connectable to a home or group of dwellings for heating applications. Once the thermochemical material is hydrated and the heat recovered, the containers are returned to the centralized facility to dehydrate the thermochemical material again. During the dehydration of the thermochemical material, the exchange surface 20 is greatest possible between said material and the atmosphere so as to facilitate the removal of water. The drying device is, for example, a device called "trays". The device comprises an enclosure provided with a bottom and a side wall. The enclosure comprises at least one tray called drying tray. The thermochemical material is disposed on drying trays. The material can be placed on the trays either in the form of molten hydrate or in the form of a dry product. Advantageously, the thickness of the layer of thermal material deposited on the plate is low. By weak, we mean of the order of 0.5mm to 5cm and even more preferably of the order of 1mm to 10mm.

A heat transfer fluid circulates in the tray. The thermochemical material is thus in thermal contact with the coolant. The exchange surfaces between the thermochemical material to be dehydrated and the ambient air, for example, obtained with this device, make it possible to considerably increase the heat exchange and the exchange of material. The heat transfer fluid advantageously makes it possible to supply heat to the plateau during the dehydration phase of the thermochemical material or to recover the heat during the heat recovery phase, i.e. the hydration phase of the material. Each tray has an individual introduction system for introducing the thermochemical material and water. The evacuation of the water vapor is carried out by connection with an external condenser and vacuum system. Advantageously, a drain device is disposed at the bottom of the enclosure. The drying device may also be an enclosure containing trays. The enclosure is surrounded by an envelope comprising an inner wall, in contact with the inside of the enclosure, and an outer wall, in contact with the outside. The supply of heat is achieved by a circulation of hot air in each tray. The supply of hot air trays, as well as the evacuation of hot air, are performed by a central tubular inlet device and an evacuation device disposed in the outer casing of the enclosure. The central tubular device also allows the introduction of the material either as a molten hydrate or as a dry product. It also makes it possible to introduce, during the heat recovery phase, air saturated with water in the enclosure. The air stream transfers the water vapor to the dehydrated material and heats up in contact with the thermochemical material. The device in the envelope surrounding the enclosure allows to evacuate the hot air stream and the heat is recovered outside the enclosure for a building heating application for example.

The surface of each tray can be covered with a metal or carbon substrate. The substrate may be porous, in the form of a lattice, a honeycomb, a foam. The substrate makes it possible to improve the thermal conductivity and therefore the performance of the device. The exchanges of material and heat are then advantageously facilitated during the hydration / dehydration and melting / solidification reactions. According to another embodiment, the thermochemical energy generating device comprises different storage compartments, each of them successively having different functions in the operating cycle. The compartments are arranged in a container. This is, for example, a 20-foot container for storing 5 MWh of heat. Each compartment may serve as a storage tank for containing a composition containing at least one dehydrated thermochemical material, a hydrolysis reactor for hydrating the thermochemical material, a reservoir for storing material hydrated first in liquid form and then under solid form at the end of the cooling of said material, heat exchanger, for containing a coolant, said heat exchanger being configured to transfer the heat to a heat distribution circuit. In this embodiment, the heat exchanger also makes it possible to recover heat from an external source in order to remelt the thermochemical material and then dehydrate it. According to a preferred embodiment, the composition disposed in the storage tank for the production of thermochemical energy contains a dehydrated calcium chloride-based thermochemical material, the dehydrated calcium chloride being CaCl 2 .xH 2 O with 3 < x <5 in a dehydrated form as well as nucleating agents, intended to promote the solidification of hydrated calcium chloride. The nucleating agents are preferably silica-based particles.

Each tank is provided with a water inlet for hydrating the thermochemical material. The operating cycle is as follows. Each compartment of the container is loaded with dry thermochemical material, in the form of powder, i.e. each compartment is loaded with thermochemical energy and thus with potential heat. This load is carried out on a site with an excess of heat. It can be industrial heat, solar heat, incineration heat, etc.

The container is then transported and deposited at the place of application. The container may be for example for heating a building, a greenhouse, a pool or to produce steam. The container is connected on the one hand to a water supply, on the other hand distribution circuit for distributing the heat, obtained during the thermochemical reaction of hydration. The compartments of the container are independent of each other. It is possible to use only certain compartments for the production of heat according to the need for heat. Only certain compartments are then supplied with water so as to achieve the hydration and release of heat necessary for the application. Advantageously, the heat recovery takes place until the solidification of the material that has just been hydrated. Advantageously, the devices have low thermal characteristic lengths.

These devices are advantageously used in combination with particles based on silica and / or with a conductive substrate. Thus, the exchanges of heat and material are faster for each compartment.

Devices with containers are, advantageously, easily refillable devices. When all the heat has been supplied and recovered, following the hydration of the thermochemical material, the container is returned to the hot source site for recharging, i.e. to dehydrate the solidified thermochemical material. The material is then easily melted by a low temperature heat source. Then it is dehydrated to form dry powder. The container can also be emptied. Draining can be accomplished by the addition of water to dissolve the under-hydrate and form the main, generally more fuse-hydrate. Other types of devices can be used both for heat storage / de-stocking, i.e. they can both allow hydration and dehydration of the thermochemical material. This configuration is particularly advantageous in the case where the heat source and the application, i.e. the need for heat, are located in the same place. The heat of the extracted steam, upon dehydration of the thermochemical material, may also be used to heat and melt other solidified underhydrate material disposed in a coupled system. Several containers can be recharged simultaneously to optimize the use of heat by coupling and re-looping the heat of the vapor emitted during refilling.

Advantageously, this heating system makes it possible to limit CO2 emissions and to exploit the low temperature heat produced by the industrial processes.

Claims (12)

REVENDICATIONS1. A composition for storing and producing thermochemical energy comprising: a thermochemical material based on calcium chloride, said material being intended to be hydrated to produce thermochemical energy and to be dehydrated to store energy thermochemical, and nucleating agents, for promoting the solidification of hydrated calcium chloride, characterized in that the calcium chloride in the hydrated form is CaCl 2 .xH 2 O with 3 <x <5, and in that the nucleating agents are particles based on silicon oxide or based on carbide or nitride materials. 2. Composition according to claim 1, characterized in that x is greater than or equal to 3.5 and less than or equal to 4.5. 3. Composition according to claim 2, characterized in that x is greater than or equal to 3.9 and less than or equal to 4.1. 4. Composition according to claim 3, characterized in that x is equal to 4. 5. Composition according to one of claims 1 to 4, characterized in that the silica-based particles have dimensions between 0.01pm and 5pm. 6. Composition according to one of claims 1 to 5, characterized in that the composition comprises between 0.05% and 5% by weight of nucleating agents. A method of storing and producing thermochemical energy comprising the steps of: providing a composition comprising a thermochemical material based on calcium chloride, said material being intended to be hydrated to produce thermochemical energy and to be dehydrated in order to store thermochemical energy, hydrate the composition so as to obtain hydrated calcium chloride CaCl 2 .xH 2 O with 3 <x <5, said hydration producing thermochemical energy, add nucleating agents in the composition, the nucleating agents being particles based on silicon oxide or based on carburized or nitrided materials. B B B B B B B B B B B B B B B B B B B 8. Process according to claim 7, characterized in that the nucleating agents are added before the beginning of the hydration. 9. Process according to claim 7, characterized in that the nucleating agents are added to the composition during the production of thermochemical energy. 20 10. Process according to claim 9, characterized in that the nucleating agents are added when the composition is at a temperature of 60 ° C. 11. Process according to any one of claims 7 to 10, characterized in that the process comprises an additional dehydration step of the thermochemical material. 12. The method of claim 11, characterized in that the method comprises a step of filtering the thermochemical material so as to remove the nucleating agents from the composition, said dehydration step being carried out before or after the dehydration step.