A system comprising a form stable thermochemical material

Abstract

The present invention relates to a system comprising a form stable thermochemical entity. The present invention also relates to a heat storage system and to the use of a system comprising a thermochemical entity. An object of the present invention is to provide a system comprising a thermochemical entity in which the thermochemical material shows a high cyclic form stability.

Description

[0001] Title: a system comprising a form stable thermochemical material

[0002] Description:

[0003] The present invention relates to a system comprising a thermochemical material (TCM). The present invention also relates to a heat storage system and to the use of a system comprising a thermochemical material (TCM).

[0004] International application WO 2019 / 038292 in the name of the present applicants discloses a closed-cycle thermal energy storage system comprising a thermochemical reactor containing a solid thermochemical material. In the TCM heat storage reaction, the TCM has two states, a salt complex, and a salt. The TCM charging involves the absorption of heat by the TCM and the release of sorbent gas. The TCM discharging involves the release of heat by the TCM and the sorption of a working gas or liquid. The main criteria of success for such storage technique are highly efficient energy density, cost efficiency (short payback time), safety, and durability.

[0005] German Offenlegungsschrift DE102019205788 relates to a heat storage device comprising a plurality of storage units, wherein each storage unit comprises a storage shell which comprises a water-permeable and gas-permeable material, wherein the storage shell encloses a storage material, which is in particular in granular form. The storage units comprise, in particular plate-shaped, heat conducting elements, for conducting and / or distributing heat, wherein the at least one heat conducting structure is within the storage casing of the respective storage unit.

[0006] International application WO 2014 / 104886 relates to a composite for heat storage comprising a thermochemical material encapsulated in a water vapour permeable polymeric material, wherein the particles of thermochemical material are encapsulated in a matrix of the polymeric material, the thermochemical material or a mixture of the thermochemical material with the polymeric material forms a core and wherein the polymeric material forms a shell around the core.

[0007] International application WO 2023 / 053859 relates to a heat storage structure having a sealed container and a chemical heat storage material sealed in the sealed container, wherein the sealed container is formed of a water vapor permeable material.

[0008] US 5,626,936 relates to a thermally insulated wall structure of a building placed in heat exchange relationship between a first space and a second space comprising a first layer of heat insulation material having an insulation value and positioned adjacent the first space, a second layer of heat insulation material overlying the first layer of heat insulation material and positioned adjacent a variable temperature space, an intermediate layer of phase change material dispersed between the first and second layers of heat insulation materials comprising a phase change material. The intermediate layer of phase change material comprises a plurality of bags each having a pouch therein containing the phase change material.

[0009] GB2495938 relates to a component comprising a blister pack for an energy storage and / or management system comprising a plurality of sealed capsules arranged on or at least partially within a carrier, wherein at least one of the sealed capsules contains a phase change material and the carrier is made from a polymeric material, e.g. polyvinylchloride (PVC), or a metallic material such as aluminum.

[0010] Thermochemical composites as such are known in the art. Methods aiming to create thermochemical entities through encapsulation are disclosed in, inter alia, B. G. P. van Ravensteijn et al., “Encapsulation of Salt Hydrates by Polymer Coatings for Low-Temperature Heat Storage Applications,” ACS Appl. Polym. Mater., vol. 3, no. 4, pp. 1712-1726, Apr. 2021 , doi: 10.1021 / acsapm.0c01186 and A. Shkatulov, R. Joosten, H. Fischer, and H. Huinink, “Core-Shell Encapsulation of Salt Hydrates into Mesoporous Silica Shells for Thermochemical Energy Storage,” ACS Appl. Energy Mater., vol. 3, no. 7, pp. 6860-6869, Jul. 2020, doi: 10.1021 / acsaem.0c00971 .

[0011] However, these methods may generate some technical problems, for example an inconsistent and low power output, volume changes over cycles, disintegration, low energy density, difficult recyclability, and difficult preparation method.

[0012] Current thermochemical entities have shortcomings that hamper the introduction of their application in heat batteries and heat pumps, such as agglomeration and mechanical instabilities leading to cracking, dust formation and disintegration. There is thus a need for improved TCM-based heat storage systems.

[0013] An object of the present invention is to provide a system comprising a thermochemical material (TCM) in which the thermochemical material shows a high cyclic form stability.

[0014] An object of the present invention is to provide a system comprising a thermochemical material (TCM) that is easy to manufacture and to recycle. An object of the present invention is to provide a heat storage system comprising a thermochemical material (TCM) in which the heat storage system shows a consistent and high power output over multiple (dis)charge cycles.

[0015] In addition, another object of the present invention is to provide a system comprising a thermochemical material (TCM) in which dust formation and disintegration of the TCM is reduced to a minimum.

[0016] An object of the present invention is to provide a system comprising a thermochemical material (TCM) in which the system has a high structural integrity that can be stacked vertically without a risk of collapse.

[0017] The present invention as mentioned above is related to a system comprising a thermochemical material capable of storing and releasing heat by a thermochemical exchange process under release or binding of a gas or liquid, wherein the thermochemical material comprises particles, a plurality of particles being enclosed by a gas or liquid permeable material, the gas or liquid permeable material being impermeable for the thermochemical material, wherein the particles are enclosed by the gas or liquid permeable material forming an enclosure, said system comprising a plurality of individual enclosures consisting of the permeable material, said enclosures being provided with the particles, wherein said plurality of individual enclosures is provided with a mechanic support located outside the thermochemical material.

[0018] On basis of the above the present inventors found a system that is suitable for heat storage and heat pump applications. The present invention consists of a thermochemical material (TCM) which is surrounded by a gas or liquid permeable shell. Due to the combination of thermochemical material properties and the shell properties, an entity with an exceedingly long cyclic lifetime is created, so it can be used in a heat battery or heat pump without the need of (early) replacement. The present inventors found that the present system comprising a thermochemical material has a high and constant power output over charging / discharging cycles, does not suffer from agglomeration or progressive swelling and is mechanically stable, without chemical material loss in time. The specific position of the mechanic support, namely located outside the thermochemical material, provides the system structural integrity in such a way that the present system can be stacked vertically without a risk of collapse. In addition, the present inventors found that placing such systems in a reactor the edges of the systems are the main failure point. The present system now provides a reinforcement that prevents such failure. The present system thus differs from a heat storage device as disclosed in German Offenlegungsschrift DE102019205788 wherein a mechanic structure is within the storage casing of the respective storage unit resulting in storage unit that will not structurally reinforce the entity.

[0019] Having a continuous boarded around the entity allows for better handling of the entities and even vertical stacking.

[0020] The particles are enclosed by the gas or liquid permeable material forming an enclosure. Such construction ensures that the thermochemical material is confined in an enclosure, i.e. due to the mechanical properties of the enclosure material, i.e. gas or liquid permeable but impermeable for the thermochemical material.

[0021] According to an example the particles in the enclosure are in a loose fit condition.

[0022] According to another example the particles in the enclosure are in a compacted condition.

[0023] The enclosure is provided with a mechanic support.

[0024] The mechanic support can be a free standing structure and incorporated into the entity during assembly.

[0025] The mechanic support can also be formed directly on top of one of the gas or liquid permeable material, namely the semipermeable membrane. The mechanic support can be generated through melting and extrusion (for example 3D printing), application in a liquid form and subsequent curing in desired shape (tracing the pattern with some type of a glue or resin that hardens upon curing) or mechanical shaping (cutting out or moulding a desired shape out of a piece of polymer).

[0026] In an example the entity assembly involves bonding the mechanic support with the semipermeable membrane with the aid of additional adhesives, heat, electrical pulse, mechanical force, or combination thereof.

[0027] In an example the external mechanic support is generated by folding the edges of the semipermeable membrane several times on itself and bonding those layers together with methods described above. In such example the additional stability comes from the thicker membrane layer. Furthermore, a group of polymers stiffen when heated up above a certain temperature, thus although the membrane itself can be somewhat flexible, with the added treatment it can become rigid. According to an example the system comprises a plurality of individual enclosures consisting of the permeable material, said enclosures being provided with the particles.

[0028] According to an example the individual enclosures are interconnected to form a construction consisting of a plurality of individual enclosures.

[0029] According to an example the permeable material is thermal stable in the temperature range where the thermochemical exchange process takes place.

[0030] According to an example the permeable material is chemical compatible with the thermochemical material.

[0031] According to an example the enclosure is not a coating. In addition, the particles are not provided with a coating of the gas or liquid permeable material.

[0032] The present invention also relates to a heat storage system comprising at least one system as discussed above.

[0033] An example of such a heat storage system is a heat battery based on thermochemical principles.

[0034] The present invention also relates to the use of a system as discussed above in beds in convective thermochemical reactors and in vacuum reactors for obtaining a stable reactor performance including power output with charging and discharging cycles.

[0035] The system as discussed above can be used in a chemical heat pump.

[0036] The present invention thus relates to a thermochemical entity based on a combination of a thermally stable and gas or liquid permeable material which contains a thermochemical material. The gas or liquid permeable material can be seen as a shell for the thermochemical material and must not be confused with the function of a coating.

[0037] The present system comprising a thermochemical material is suitable for application inside convective thermochemical reactors as well as vacuum reactors. These can be a heat battery, heat pump or a combination of both systems. In a convective thermochemical reactor, the thermochemical entity results in a constant pressure drop in the reactor due to the shape stable nature of the entity. In a vacuum reactor the shape stable nature prevents creeping of the thermochemical material. The performance of such a thermochemical reactor and power output are therefore constant with consecutive (dis)charge cycles. The shell in the present system comprising a thermochemical material capable of storing and releasing heat by a thermochemical exchange process under release or binding of a gas or liquid has such a vapor permeability that the performance of the thermochemical material is not hindered.

[0038] The shell may consist of a flexible material. The benefit of such a flexible material is that the shell adapts to a reorganization of the thermochemical material it contains. The material of the shell possesses a thermal stability in the charging temperature range of the thermochemical material and is also chemical compatible with the thermochemical material. Initial reorganization of the thermochemical material can exert an outward pressure on the flexible shell, resulting in mechanical stiffening of the whole entity.

[0039] Due to the nature of the shell material, different shapes of the entity are possible, such as particle like structures with varying curvatures, plate like structure, spheres, complex geometries, and combinations thereof. The stiffness of the entity can be changed by varying the content of thermochemical material and the nature of the shell material. The stiffness can range from very flexible to very stiff. Additional stiffness can be achieved through compacting of the thermochemical material inside the shell or the application of a built-in skeleton inside the shell, or a rearrangement of the thermochemical material inside the shell due to the thermochemical reaction.

[0040] The present inventors found that the thermochemical material does not show densification with consecutive (dis)charge cycles. The shell material prevents agglomeration of individual entities. The performance and (high) power output of the entity is stable for all (dis)charge cycles, resulting in stable material performance due to the shell. The entity remains mechanically intact with consecutive (dis)charge cycles. Moreover, the present inventors found that the thermochemical material is shape stable without dust formation or leakage.

[0041] The present invention also relates to a method for manufacturing a system as disclosed, comprising the following:

[0042] Providing a gas or liquid permeable material,

[0043] Positioning a mechanic support consisting of a plurality of individual compartments onto the gas or liquid permeable material,

[0044] Filing the plurality of individual compartments with a thermochemical material, Sealing the compartments filled with a thermochemical material with a gas or liquid permeable material.

[0045] The method is carried out in such a way that the plurality of individual enclosures is provided with a mechanic support located outside the thermochemical material.

[0046] In an example the mechanic support is generated via additive manufacturing (AM) technique, for example extruding a part material to print layers of the 3D object.

[0047] In an example the sealing step involves a step of bonding the mechanic support with the gas or liquid permeable material via one or more of adhesive, heat, electrical pulse and mechanical force.

[0048] In an example the mechanic support is 3D printed on one side of a membrane, for example a nonwoven. Then the square pockets are filled with TCM by spooning it into individual compartment and avoiding the 3D printed borders. When each individual compartment is filled, another membrane layer is placed on the TCM and the mechanic support. The complete structure is sealed together with the aid of heat and pressure. The mechanic support may have a lower melting point than the semipermeable membrane and starts to melt when heated up. The liquid plastic material is then absorbed by the nonwoven membrane, penetrates it and creates a strong seal.

[0049] According to the present invention cartridges can be easily manufactured, wherein such cartridges are useful in an assembly of a reactor.

[0050] The invention will be explained in more detail with the following figures and examples, without being restricted thereto.

[0051] A non-woven material (20-50 g / m2) is used as the gas or liquid permeable material and a bag thereof is manufactured by cutting material and sealing on three sides. The bag thus obtained is filled with TCM and afterwards sealed.

[0052] The bag was processed under the following conditions: dehydration 145 deg. C. in vacuum oven under reduced pressure (3 mbar absolute pressure), hydration in 33% RH or 43% RH with exposure from 1 or 2 sides (desiccator). The average power at 50% conversion (per kg of anhydrous salt) was measured. The results are shown in Table 1. The results of the thermochemical entity, i.e. the bag filled with TCM, is compared to a compacted TCM construction. Table 1 : Power output

[0053] The conditions mentioned in Table 1 are: RH [%], T [deg. C.], # exposed sides

[0054] The bag as manufactured above was subjected to a series of 30 (dis)charge cycles. The TCM material did not show any agglomeration, any swelling, maintained a mechanical stable condition and had a constant power output. Additional experiments were carried out for investigating the variation in thickness during cycles of dehydration and hydration. The experimental results thereof demonstrated form stability for 30 consecutive (dis)charge cycles, with an initial and minor increase in dimension in the first cycle only.

[0055] Figure 1 shows the inside of a system comprising a thermochemical material according to the present invention. Reference number 1 is a space to be filled with thermochemical material (not shown here). Reference number 3 is a gas or liquid permeable material. Reference number 2 is a mechanic support and forms the individual spaces for the thermochemical material. After filing the spaces 1 with thermochemical material the complete construction is covered with another layer of gas or liquid permeable material 3 and both layers of gas or liquid permeable material 3 are connected to each other thereby forming the system comprising a thermochemical entity.

[0056] Figure 2 shows an example of a system comprising a thermochemical material, in which the thermochemical material 5 is enclosed by two layers of gas or liquid permeable material 4.

Claims

CLAIMS1. A system comprising a thermochemical material capable of storing and releasing heat by a thermochemical exchange process under release or binding of a gas or liquid, wherein the thermochemical material comprises particles, a plurality of particles being enclosed by a gas or liquid permeable material, the gas or liquid permeable material being impermeable for the thermochemical material, wherein the particles are enclosed by the gas or liquid permeable material forming an enclosure, said system comprising a plurality of individual enclosures consisting of the permeable material, said enclosures being provided with the particles, wherein said plurality of individual enclosures is provided with a mechanic support located outside the thermochemical material.

2. A system according to claim 1 , wherein each individual enclosure is provided with a mechanic support located outside the thermochemical material.

3. A system according to any one or more of the preceding claims, wherein the particles in the enclosure are in a loose fit condition.

4. A system according to any one or more of claims 1-2, wherein the particles in the enclosure are in a compacted condition.

5. A system according any one or more of claims 1-4, wherein the individual enclosures are interconnected to form a construction consisting of a plurality of individual enclosures.

6. A system according any one or more of claims 1-5, wherein the mechanic support comprises a polymer material.

7. A system according to any one or more of the preceding claims, wherein the permeable material is thermal stable in the temperature range where the thermochemical exchange process takes place.

8. A system according to any one or more of the preceding claims, wherein the permeable material is chemical compatible with the thermochemical material.

9. A system according to any one or more of the preceding claims, wherein the particles are not provided with a coating of the gas or liquid permeable material.

10. A method for manufacturing a system according any one or more of claims 1-9 comprising the following:Providing a gas or liquid permeable material,Positioning a mechanic support consisting of a plurality of individual compartments onto the gas or liquid permeable material,Filing the plurality of individual compartments with a thermochemical material,Sealing the compartments filled with a thermochemical material with a gas or liquid permeable material.

11. A method according to claim 10, wherein the mechanic support is generated via additive manufacturing (AM) technique, for example extruding a part material to print layers of the 3D object.

12. A method according to any one or more of claims 10-11 , wherein the sealing step involves a step of bonding the mechanic support with the gas or liquid permeable material via one or more of adhesive, heat, electrical pulse and mechanical force.

13. A heat storage system comprising at least one system according to any one or more of claims 1-9, or a system obtained according to any one or more of claims IQ- 12.

14. A heat storage system according to claim 12, wherein the heat storage system is a heat battery based on thermochemical principles.

15. The use of a system according to any one or more of claims 1-9 in beds in convective thermochemical reactors and in vacuum reactors for obtaining a stable reactor performance including power output with charging and discharging cycles.

16. The use of a system according to any one or more of claims 1-9 in a chemical heat pump.

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