A system for barocaloric cooling, heating or thermal storage and methods of operating the system

Abstract

There is described a system for barocaloric cooling, a system for barocaloric heating or a system for barocaloric thermal storage comprising a pressure vessel assembly, the pressure vessel assembly comprising a tubular component and a sealing assembly The tubular component comprises a bore that extends along a longitudinal axis of the tubular component between a first opening and a second opening and defines a chamber configured to receive a barocaloric material. The tubular component is formed of one or more materials having a greater strength in a direction circumferential to the longitudinal axis than in a direction parallel to the longitudinal axis. The sealing assembly comprises a first sealing element that seals the first opening, a second sealing element that seals the second opening and a bracing structure that couples the first sealing element and the second sealing element and is configured to transmit a force between the first sealing element and the second sealing element not via the tubular component. There is also described a method of operating a barocaloric refrigeration system or barocaloric heat pump.

Description

[0001] A SYSTEM FOR BAROCALORIC COOLING, HEATING OR THERMAL STORAGE AND METHODS OF OPERATING THE SYSTEM FIELD OF THE INVENTION

[0002] The invention relates to a system for barocaloric cooling, a system for barocaloric heating or a system for barocaloric thermal storage and methods of operating the system.

[0003] BACKGROUND OF THE INVENTION

[0004] Vapor-compression refrigeration systems and heat pumps incorporating fluid refrigerants are commonly used to provide cooling or heating. In such systems, the fluid refrigerant undergoes temperature and phase changes when subjected to changes in pressure. Such fluid refrigerants typically have high global warming potentials, and there is therefore a desire to develop refrigeration systems and heat pumps that avoid their use.

[0005] To achieve this, systems for barocaloric cooling and heating have been proposed that use a barocaloric material instead of a fluid refrigerant. Conventional barocaloric materials react to an increase in pressure by releasing heat and react to a decrease in pressure by absorbing heat. Conversely, inverse barocaloric materials react to an increase in pressure by absorbing heat and react to a decrease in pressure by releasing heat.

[0006] For the barocaloric material to exhibit suitably high temperature changes during operation, it may be subjected to high pressures in a pressure vessel. However, existing pressure vessels capable of achieving such high pressures have been found to reduce the amount of heat that can be transferred to or from the barocaloric material by a greater than desired extent. It is therefore desirable to provide an improved system for barocaloric cooling, heating or thermal storage and method of operating the system that addresses this issue.

[0007] STATEMENTS OF INVENTION

[0008] According to an aspect there is described a system for barocaloric cooling, a system for barocaloric heating or a system for barocaloric thermal storage comprising a pressure vessel assembly, the pressure vessel assembly comprising a tubular component and a sealing assembly. The tubular component comprises a bore that extends along a longitudinal axis of the tubular component between a first opening and a second opening and defines a chamber configured to receive a barocaloric material. The tubular component is formed of one or morematerials having a greater strength in a direction circumferential to the longitudinal axis than in a direction parallel to the longitudinal axis. The sealing assembly comprises a first sealing element that seals the first opening, a second sealing element that seals the second opening and a bracing structure that couples the first sealing element and the second sealing element and is configured to transmit a force between the first sealing element and the second sealing element not via the tubular component.

[0009] The bracing structure may comprise a first portion that extends radially with respect to the longitudinal axis, a second portion that extends radially with respect to the longitudinal axis and one or more third portions that extend parallel to the longitudinal axis between the first portion and the second portion.

[0010] The first portion may comprise one or more first recesses. The first sealing element and / or the one or more further first sealing elements may be located within a respective one of the one or more first recesses. The second portion may comprise one or more second recesses. The second sealing element and / or the one or more further second sealing elements may be located within a respective one of the one or more second recesses.

[0011] The first sealing element and / or the one or more further first sealing elements may be integrally formed with the first portion. The second sealing element and / or the one or more further second sealing elements may be integrally formed with the second portion.

[0012] The pressure vessel assembly may comprise one or more further tubular components. Each of the one or more further tubular components may comprise a respective bore that extends between a respective further first opening and a respective further second opening and defines a respective chamber configured to receive a respective barocaloric material. The sealing assembly may comprise one or more further first sealing elements and one or more further second sealing elements. Each of the one or more further first sealing elements may seal a respective one of the one or more further first openings. Each of the one or more further second sealing elements may seal a respective one of the one or more further second openings.

[0013] Each of the one or more third portions may comprise a respective elongate member separated from the tubular component by a gap. The elongate member may be disposed external to the tubular component and may not enclose the tubular component.The one or more third portions of the bracing structure may comprise a core and an external layer covering at least part of the core. The core may have a higher tensile strength than the external layer and the external layer may have a lower thermal conductivity than the core.

[0014] The pressure vessel assembly may further comprise a housing within which the tubular component is disposed. The one or more third portions may be disposed external to the housing. The housing may comprise an inlet for receiving a heat-transfer fluid into the housing and an outlet for releasing the heat-transfer fluid from the housing. An interior surface of the housing may be spaced from the tubular component by a gap configured to receive the heattransfer fluid. The housing may have a lower thermal conductivity than the one or more third portions.

[0015] Each of the one or more third portions may comprise a housing that extends between a third opening and a fourth opening and defines a further chamber within which the tubular component is disposed. The first sealing element may be connected to each of the one or more third portions to at least partially seal the third opening. The second sealing element may be connected to each of the one or more third portions to at least partially seal the fourth opening.

[0016] Each of the one or more third portions may comprise an inlet opening for receiving a heattransfer fluid from an exterior of the housing into the further chamber and an outlet opening for releasing the heat-transfer fluid from the further chamber to the exterior of the housing.

[0017] The first portion may comprise an inlet opening for receiving a heat-transfer fluid from an exterior of the housing into the further chamber. The second portion may comprise an outlet opening for releasing the heat-transfer fluid from the further chamber to the exterior of the housing.

[0018] Each of the one or more third portions may comprise an internal layer and an external layer. The internal layer may be disposed between the external layer and the tubular component. The external layer may have a higher tensile strength than the internal layer and the internal layer may have a lower thermal conductivity than the external layer.

[0019] The pressure vessel assembly may comprise an insulating housing within which the tubular component is disposed. The insulating housing may be housed within the housing. The insulating housing may occupy a majority of an internal void defined by the housing. The insulating housing may comprise an inlet for receiving a heat-transfer fluid into the insulatinghousing and an outlet for releasing the heat-transfer fluid from the insulating housing. An interior surface of the insulating housing may be spaced from the tubular component by a gap configured to receive a heat-transfer fluid. The insulating housing may have a lower thermal conductivity than the housing.

[0020] One or more of the first sealing element, the one or more further first sealing elements, the second sealing element and the one or more further second sealing elements may comprise a passageway configured to fluidical ly couple the chamber to a pressure modulating device.

[0021] The first portion may comprise a manifold configured to fluidically couple the chamber of the tubular component and the chamber of the one or more further tubular components to the pressure modulating device.

[0022] One or more of the first sealing element, the one or more further first sealing elements, the second sealing element and the one or more further second sealing elements may comprise a plug configured to be received within the bore.

[0023] One or more of the first sealing element, the one or more further first sealing elements, the second sealing element and the one or more further second sealing elements may comprise a socket within which the tubular component is configured to be received.

[0024] The tubular component may comprise a liner component, one or more cylindrical tube components and one or more annular disc components. The liner component may define the bore. The one or more cylindrical tube components may extend around the liner component and may be configured to resist circumferential expansion of the liner component. The one or more annular disc component may be configured to transmit thermal energy between the liner component and a heat-transfer fluid external to the tubular component. The thermal conductivity of the one or more annular disc components and the thermal conductivity of the liner component may be greater than the thermal conductivity of the one or more cylindrical tube components.

[0025] The pressure vessel assembly may comprise a further bracing structure. The further bracing structure may be configured to couple the tubular component to the bracing structure at a position part way along the tubular component.

[0026] The ratio of the strength of the one or more materials forming the tubular component in the direction circumferential to the longitudinal axis to the strength of the one or more materialsforming the tubular component in the direction parallel to the longitudinal axis may be greater than 2, for example greater than 3, or greater than 4, or greater than 5.

[0027] The one or more materials may comprise a plurality of fibres, strips or elements oriented substantially in the direction circumferential to the longitudinal axis. The one or more materials may comprise fewer or no fibres, strips or elements oriented substantially in the direction parallel to the longitudinal axis. The fibres may be carbon fibres or glass fibres.

[0028] The first sealing element and / or the second sealing element may be fixedly connected to the tubular component.

[0029] The first sealing element and / or the second sealing element may be slidingly connected to the tubular component for movement in an axial direction.

[0030] The system for barocaloric cooling may be a barocaloric refrigeration or air conditioning system. The system for barocaloric heating may be a barocaloric heat pump or water heater.

[0031] According to an aspect there is provided a method of operating a system for barocaloric cooling or a system for barocaloric heating as stated in any preceding statement, wherein the barocaloric material is received in the chamber and is a conventional barocaloric material, the method comprising: increasing the pressure within the chamber to cause the barocaloric material to release heat and / or increase in temperature and conveying heat transfer fluid from a position in which the heat transfer fluid receives a portion of the heat released from the barocaloric material to a position in which an area to be heated receives the portion of heat from the heat transfer fluid; and / or decreasing the pressure within the chamber and conveying heat transfer fluid from a position in which the barocaloric material receives heat from the heat transfer fluid to a position in which the heat transfer fluid receives heat from an area to be cooled.

[0032] According to an aspect there is provided a method of operating a system for barocaloric cooling, a system for barocaloric heating or a system for barocaloric thermal storage as stated in any preceding statement, wherein the barocaloric material is received in the chamber and is an inverse barocaloric material, the method comprising: increasing the pressure within the chamber and conveying heat transfer fluid from a position in which the barocaloric material receives heat from the heat transfer fluid to a position in which the heat transfer fluid receives heat from an area to be cooled; and / or decreasing the pressure within the chamber to cause the barocaloric material to release heat and / or increase in temperature and conveying heattransfer fluid from a position in which the heat transfer fluid receives a portion of the heat released from the barocaloric material to a position in which an area to be heated receives the portion of heat from the heat transfer fluid.

[0033] According to an aspect there is provided a method of operating a system for barocaloric thermal storage as claimed in any preceding statement, wherein the barocaloric material is received in the chamber and is a conventional barocaloric material and the method comprises: increasing the pressure within the chamber to an increased pressure to cause the barocaloric material to release heat and / or increase in temperature; maintaining the pressure within the chamber at the increased pressure until a condition is met; and upon the condition being met, decreasing the pressure within the chamber and conveying heat transfer fluid from a position in which the barocaloric material receives heat from the heat transfer fluid to a position in which the heat transfer fluid receives heat from an area to be cooled.

[0034] According to an aspect there is provided a method of operating a system for barocaloric thermal storage as claimed in any preceding statement, wherein the barocaloric material is received in the chamber and is an inverse barocaloric material and the method comprises: increasing the pressure within the chamber to an increased pressure to cause the barocaloric material to receive heat and / or decrease in temperature; maintaining the pressure within the chamber at the increased pressure until a condition is met; and upon the condition being met, decreasing the pressure within the chamber to cause the barocaloric material to release heat and / or increase in temperature and conveying heat transfer fluid from a position in which the heat transfer fluid receives a portion of the heat released from the barocaloric material to a position in which an area to be heated receives the portion of heat from the heat transfer fluid.

[0035] LIST OF FIGURES

[0036] For a better understanding of the present invention, and to show more clearly how it may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which:

[0037] Figure 1 is a perspective view of a known pressure vessel assembly for a system for barocaloric cooling, heating or thermal storage;

[0038] Figure 2 is a cross-sectional side view of the known pressure vessel assembly;

[0039] Figure 3 is a cross-sectional end view of the known pressure vessel assembly;Figure 4 is a perspective view of a first embodiment of a pressure vessel assembly for a system for barocaloric cooling, heating or thermal storage;

[0040] Figure 5 is an exploded view of the pressure vessel assembly of Figure 4;

[0041] Figure 6 is a cross-sectional view of the pressure vessel assembly of Figure 4;

[0042] Figure 7 is a perspective view of a sealing element of the pressure vessel assembly of Figure 4;

[0043] Figure 8 is a close-up view of the pressure vessel assembly of Figure 4;

[0044] Figure 9A is a schematic diagram of the system for barocaloric cooling, heating or thermal storage while operating during a first period of operation;

[0045] Figure 9B is a schematic diagram of the system for barocaloric cooling, heating or thermal storage while operating during a second period of operation;

[0046] Figure 10 is a flowchart of a method of operating the system for barocaloric cooling or heating;

[0047] Figure 11 is a flowchart of a method of operating the system for barocaloric thermal storage;

[0048] Figure 12 is a perspective view of a second embodiment of a pressure vessel assembly for a system for barocaloric cooling, heating or thermal storage;

[0049] Figure 13A is a cross-sectional view of the second embodiment of the pressure vessel assembly;

[0050] Figure 13B is a cross-sectional view of a third embodiment of a pressure vessel assembly for a system for barocaloric cooling, heating or thermal storage;

[0051] Figure 14A is a perspective view of a fourth embodiment of a pressure vessel assembly for a system for barocaloric cooling, heating or thermal storage;

[0052] Figure 14B is a cross-sectional view of the fourth embodiment of the pressure vessel assembly;Figure 15 is an exploded perspective view of a fifth embodiment of a pressure vessel assembly for a system for barocaloric cooling, heating or thermal storage;

[0053] Figure 16 is a cross-sectional view of a sixth embodiment of a pressure vessel assembly for a system for barocaloric cooling, heating or thermal storage;

[0054] Figure 17 is a perspective view of an alternative sealing element of the pressure vessel assembly of Figure 15 in isolation;

[0055] Figure 18 is a cross-sectional view of a seventh embodiment of a pressure vessel assembly for a system for barocaloric cooling, heating or thermal storage;

[0056] Figure 19 is a perspective view of a further alternative sealing element of the pressure vessel assembly of Figure 18;

[0057] Figure 20 is a cross-sectional view of a eighth embodiment of a pressure vessel assembly for a system for barocaloric cooling, heating or thermal storage;

[0058] Figure 21 is a cross-sectional view of a ninth embodiment of a pressure vessel assembly for a system for barocaloric cooling, heating or thermal storage;

[0059] Figure 22 is a perspective view of an tenth embodiment of a pressure vessel assembly for a system for barocaloric cooling, heating or thermal storage;

[0060] Figure 23 is a partially exploded view of a housing of the pressure vessel assembly of Figure 22;

[0061] Figure 24 is a partially exploded view of the pressure vessel assembly of Figure 22;

[0062] Figure 25A is a cross-sectional view of the tenth embodiment of the pressure vessel assembly;

[0063] Figure 25B is a cross-sectional view of a eleventh embodiment of a pressure vessel assembly for a system for barocaloric cooling, heating or thermal storage;

[0064] Figure 26 is a cross-sectional view of a twelfth embodiment of a pressure vessel assembly for a system for barocaloric cooling, heating or thermal storage;Figure 27 is a perspective view of a thirteenth embodiment of a pressure vessel assembly for a system for barocaloric cooling, heating or thermal storage;

[0065] Figure 28A is a perspective view of an alternative tubular component of a pressure vessel assembly for a system for barocaloric cooling, heating or thermal storage;

[0066] Figure 28B is an exploded view of the alternative tubular component;

[0067] Figure 29A is a perspective view of a first fabrication process for manufacturing a tubular component;

[0068] Figure 29B is a perspective view of a second fabrication process for manufacturing a tubular component;

[0069] Figure 30A is a perspective view of a third fabrication process for manufacturing a tubular component;

[0070] Figure 30B is a perspective view of a fourth fabrication process for manufacturing a tubular component;

[0071] Figure 31 is a cross-sectional view of a first tubular component;

[0072] Figure 32A is a cross-sectional view of a second tubular component; and

[0073] Figure 32B is a cross-sectional view of a third tubular component.

[0074] DETAILED DESCRIPTION

[0075] Figure 1 is a perspective view of a known pressure vessel assembly 2 for a system for barocaloric cooling or heating, Figure 2 is a cross-sectional side view of the known pressure vessel assembly 2 and Figure 3 is a cross-sectional end view of the known pressure vessel assembly 2. As shown in Figures 1 to 3, the pressure vessel assembly 2 comprises a tubular component 6. The tubular component 6 may be formed of a steel such as S355 structural steel. The tubular component 6 comprises a bore 8 that extends between a first opening 10 and a second opening 12. The bore 8 defines a chamber 14 within which a barocaloric material 16 is received (not shown in Figure 1). The remainder of the chamber 14 is filled witha fluid such as an incompressible fluid (e.g. a hydraulic fluid), which surrounds at least a portion of the barocaloric material 16.

[0076] The bore 8 is internally threaded at the first and second openings 10, 12. As shown most clearly in Figure 2, a first plug 20 having an external thread is inserted into the first opening 10 of the bore 8 such that an external thread of the first plug 20 mates with the internal thread at the first opening 10 so as to seal the first opening 10. In a corresponding manner, a second plug 24 having an external thread is inserted into the second opening 12 of the bore 8 such that the external thread of the second plug 24 mates with the internal thread at the second opening 12 so as to seal the second opening 12.

[0077] The barocaloric material 16 comprises a passageway 22 through which a tube 28 extends. The tube 28 is supported within the bore 8 by the second plug 24 through which the tube 28 extends and is sealed against. The tube 28 is connected to a set of valves (not shown) that can be actuated to either place the tube 28 in circuit with an area to be heated or in circuit with an area to be cooled. Although not described above, as shown, the barocaloric material 16 may comprise additional passageways through which additional tubes extend and the first and / or second plugs 20, 24 may comprise additional connecting passageway connecting these additional tubes. A port 34 extends from an exterior of the pressure vessel assembly 2, through the tubular component 6 and into the bore 8. The port 34 is fluidically connected at the exterior of the pressure vessel assembly 2 to a pressure modulating device (not shown).

[0078] During operation, the set of valves are actuated to place the tube 28 in circuit with the area to be heated. The pressure in the interior of the bore 8 applied by the pressure modulating device via the port 34 is increased, which in turn results in an increase in the pressure being applied to the barocaloric material 16. The increased pressure applied to the barocaloric material 16 causes the temperature of the barocaloric material 16 to rise. A heat transfer fluid contained within the tube 28 passes into the area to be heated. Heat released (i.e. generated) by the barocaloric material 16 passes into the heat transfer fluid, which is conveyed to the area to be heated via the circuit. Heat passes from the heat transfer fluid to the area to be heated, and the heat transfer fluid then passes back to the tube 28 to repeat the cycle.

[0079] Subsequently, the set of valves are actuated to place the tube 28 in circuit with the area to be cooled. The pressure in the interior of the bore 8 applied by the pressure modulating device via the port 34 is reduced, which in turn reduces the pressure being applied to the barocaloric material 16. The reduction in pressure applied to the barocaloric material 16 causes the temperature of the barocaloric material 16 to decrease. Heat from the heat transfer fluidpasses into the barocaloric material 16, which results in the heat transfer fluid being cooled. The heat transfer fluid contained within the tube 28 passes from the tube 28 into the area to be cooled. Heat passes from the area to be cooled to the heat transfer fluid, and the heat transfer fluid then passes back to the tube 28 to repeat the cycle.

[0080] The pressure vessel assembly 2 may be operated at a pressure of 2000 bar, and the tubular component 6 may exhibit a yield stress of 350 MPa, and an ultimate tensile strength of 600 MPa. The pressure vessel assembly 2 may be operated at any suitable pressure, for example a pressure of 1500 bar. Such an operating pressure may be determined using a safety factor. A large volume of steel is required to accommodate such high pressures, and, thus, stresses. For example, in the given example, the volume of the material used in the tubular component 6 of the pressure vessel assembly 2 may be at least four times the volume of the chamber 14. This results in a relatively small volume of barocaloric material 16 being able to be accommodated within the chamber 14, which, in turn, reduces the amount of heat that can be released by the barocaloric material 16.

[0081] To address the abovementioned deficiencies with such a known pressure vessel assembly 2, operating the pressure vessel assembly 2 at a lower pressure of 1000 bar has been proposed. Such a modification would reduce the required volume of steel in the tubular component 6. In the given example, the volume of material used in the tubular component 6 of the pressure vessel assembly 2 could be at least equal to the volume of the chamber 14, rather than at least four times the volume of the chamber 14. This would in turn increase the volume of barocaloric material 16 that could be accommodated within the chamber 14. However, although an increased volume of barocaloric material 16 has the potential to release more thermal energy if subjected to the same pressure, this potential benefit would in practice be offset by it being subjected to a lower pressure in a thinner-walled pressure vessel.

[0082] During the pressurisation and depressurisation phases, heat released by the barocaloric material 16 passes into and out of the tubular component 6 from the barocaloric material 16 (i.e. in addition to passing into and out of the heat transfer fluid from the barocaloric material 16 in the manner described above). The additional thermal mass of the tubular component 6 that has to be heated and cooled during each of these phases reduces the extent to which the pressure vessel assembly 2 as a whole increases and decreases in temperature, which reduces its utility as a system for barocaloric cooling or heating.

[0083] To reduce the exchange of heat between the barocaloric material 16 and the tubular component 6, interposing a layer of thermal insulation between the barocaloric material 16and the inner wall of the bore 8 has been proposed. However, the introduction of such thermal insulation into the chamber 14 would reduce the amount of barocaloric material 16 that can be received within the chamber 14. Furthermore, the most effective thermal insulators (e.g. evacuated tubes, gas-filled foams or aerogels) are not capable of being subjected to the very high pressures (e.g. pressures greater than 1000 bar) that are required for the barocaloric material 16 to achieve significant temperature changes without collapsing. Alternative thermal insulators such as solid polymers have greater compressive strength but tend to have a similar thermal conductivity to the barocaloric material 16 (e.g. plastic crystal barocaloric material) and therefore offer little or no thermal barrier benefit compared to packing the chamber 14 more fully with the barocaloric material 16, with the latter option at least having the benefit of contributing additional thermal output to the pressure vessel assembly 6 when pressurised and depressurised.

[0084] Another approach that may be considered is to fabricate the tubular component 6 with composite materials (e.g. those comprising fibres such as glass fibres or carbon fibres). However, although such materials often possess very high intrinsic tensile strengths in uniaxial composite constructions (e.g. in pultruded rods), more complex composite layups having a substantial proportion of fibres in at least two appreciably different orientations are required in constructions such pressure vessels since they require tensile strength along more than one axis (e.g. in the axial and radial directions). This leads to a significant reduction in the ultimate tensile strength of a biaxial or multi-axial composite in any individual direction versus the ultimate tensile strength of a uniaxial composite, and, to account for this, a greater than desired volume of composite material must be used to form the tubular component 6, which in turn reduces the interior volume of the chamber 14.

[0085] Figure 4 is a perspective view of a first embodiment of a pressure vessel assembly 102 for a system for barocaloric cooling, heating or thermal storage 101 in accordance with the invention. The pressure vessel assembly 102 generally comprises a tubular component 106 and a sealing assembly 160. The tubular component 106 has a longitudinal axis 162. The sealing assembly 160 comprises a bracing structure 164, which comprises a first portion 166, a second portion 168 and a plurality of third portions 170A, 170B, 170C, 170D. The first and second portions 166, 168 of the bracing structure 164 extend radially with respect to the longitudinal axis 162 of the tubular component 106. The plurality of third portions 170A, 170B, 170C, 170D include a first elongate member 170A, a second elongate member 170B, a third elongate member 170C and a fourth elongate member 170D. The first to fourth elongate members 170A-D are spaced apart around the longitudinal axis 162. Accordingly, the first to fourth elongate members 170A-D do not enclose the tubular component 106. The first tofourth elongate members 170A-D are high tensile strength rods. Each of the plurality of third portions 170A, 170B, 170C, 170D extend parallel to the longitudinal axis 162 between the first portion 166 and the second portion 168.

[0086] Figure 5 is an exploded view of the pressure vessel assembly 102 of Figure 4. In Figure 5, the components of the sealing assembly 160 are disposed apart from the tubular component 106, for clarity. As shown, the sealing assembly 160 additionally comprises a first sealing element 120 and a second sealing element 124. The first and second sealing elements 120, 124 are plugs. The first and second portions 166, 168 of the bracing structure 164 are in the form of rectangular plates. The first portion 166 of the bracing structure 164 comprises a plurality of through holes 180A, 180C, 180E, 180G positioned at respective corners thereof. Likewise, the second portion 168 of the bracing structure 164 comprises a plurality of through holes 180B, 180D, 180F, 180H positioned at respective corners thereof. The bracing structure 164 further comprises a first nut 172A, a second nut 172B, a third nut 172C, a fourth nut 172D, a fifth nut 172E, a sixth nut 172F, a seventh nut 172G and an eighth nut 172H.

[0087] Figure 6 is a cross-sectional view of the pressure vessel assembly 102 of Figure 4. As shown, the tubular component 106 comprises a bore 108 that extends between a first opening 110 and a second opening 112. The bore 108 defines a chamber 114 that receives a barocaloric material 116. The tubular component 106, and, thus, the bore 108, have a circular crosssection. It will however be appreciated that the tubular component 106 and bore 108 may have any cross-sectional shape. The barocaloric material 116 may comprise plastic crystals such as 2-bromoadamantane, which undergo a temperature rise when subjected to hydrostatic pressure, primarily as a result of a pressure-driven first-order phase transition. The remainder of the chamber 114 is occupied with a fluid such as an incompressible fluid (e.g. a hydraulic fluid), which surrounds at least a portion of the barocaloric material 116.

[0088] The first portion 166 of the bracing structure 164 comprises a first recess 174 in the form of a counterbored hole that extends through the first portion 166 of the bracing structure 164. The first sealing element 120 is located within the first recess 174. The first sealing element 120 extends into the bore 108 at the first opening 110 to seal the first opening 110. In a similar manner, the second portion 168 of the bracing structure 164 comprises a second recess 176 also in the form of a counterbored hole that extends through the second portion 168 of the bracing structure 164. The second sealing element 124 is located within the second recess 176. The second sealing element 124 extends into the bore 108 at the second opening 112 to seal the second opening 112.The first elongate member 170A extends through the through holes 180A and 180B, the second elongate member 170B extends through the through holes 180C and 180D, the third elongate member 170C extends through the through holes 180E and 180F, and the fourth elongate member 170D extends through the through holes 180G and 180H. As shown most clearly in Figure 4, each of the first, second, third and fourth elongate members 170A-D are disposed externally of the tubular component 106. That is, the first, second, third and fourth elongate members 170A-D do not extend through the chamber 114 of the tubular component 106. Each of the first, second, third and fourth elongate members 170A-D are separated from the tubular component 106 by a respective gap. The first and second nut 172A, 172B are threadedly engaged with a first threaded end and a second threaded end of the first elongate member 170A, respectively. The third and fourth nut 172C, 172D are threadedly engaged with a first threaded end and a second threaded end of the second elongate member 170B, respectively. The fifth and sixth nut 172E, 172F are threadedly engaged with a first threaded end and a second threaded end of the third elongate member 170C, respectively. The seventh and eighth nut 172G, 172H are threadedly engaged with a first threaded end and a second threaded end of the fourth elongate member 170D, respectively.

[0089] As mentioned above, the first and second portions 166, 168 of the bracing structure 164 extend radially with respect to the longitudinal axis 162 of the tubular component 106, and the third portions 170A, 170B, 170C, 170D extend parallel to the longitudinal axis 162 between the first portion 166 and the second portion 168. This is illustrated in Figure 6, which shows the first and second portions 166, 168 of the bracing structure 164 extending along respective axes 129A, 129B that extend radially away from the longitudinal axis 162, and the third portions 170A, 170B, 170C, 170D extending along respective axes 131 A, 131 B that are parallel to the longitudinal axis 162. It will be appreciated that the first and second portions 166, 168 need not extend in a solely radial direction and that the third portions 170A, 170B, 170C, 170D need not extend in a solely parallel direction. Instead, references to the first and second portions 166, 168 extending radially with respect to the longitudinal axis 162 include the possibility of the first and second portions 166, 168 also extending in a direction that has a parallel component with respect to the longitudinal axis 162. Likewise, references to the third portions 170A, 170B, 170C, 170D extending parallel with respect to the longitudinal axis 162 include the possibility of the third portions 170A, 170B, 170C, 170D also extending in a direction that has a radial component with respect to the longitudinal axis 162.

[0090] Figure 7 is a perspective view of the first sealing element 120 in isolation. As shown, the first sealing element 120 comprises a first cylindrical portion 184, a second cylindrical portion 186 and a third cylindrical portion 188 disposed between the first and second cylindrical portions184, 186. The diameter of the third cylindrical portion 188 is greater than the diameter of the first and second cylindrical portions 184, 186. A passageway 182 extends through the first, second and third cylindrical portions 184, 186, 188. The second sealing element 124 substantially corresponds to the first sealing element 120 except in that it does not include a passageway. It will be appreciated that reference to the first sealing element 120 sealing the first opening 110 refers to the first sealing element 120 forming a seal with the first opening 110 around the perimeter of the first opening 110, and that this still allows the chamber 114 to be fluidically connected to a pressure modulating device 198 (not shown in Figure 8) via the passageway 182 disposed within the first sealing element 120. The pressure modulating device 182 may be any device (e.g. a pump or valve) capable of modulating (i.e. controlling) the amount of pressure that it generates. The pressure generated by the pressure modulating device may be measured with respect to an external (e.g. atmospheric) pressure, and may be a pressure value of zero. It will also be appreciated that reference to the second sealing element 124 sealing the second opening 112 refers to the second sealing element 124 forming a seal with the second opening 112 around the perimeter of the second opening 112. Although it has been described that the second sealing element 124 does not include a passageway, this need not be the case. The second sealing element 124 may also be provided with a passageway substantially corresponding to the passageway of the first sealing element 120.

[0091] Figure 8 is a close-up view of the pressure vessel assembly 102 of Figure 4 centred on the first sealing element 120. The first cylindrical portion 184 of the first sealing element 120 extends into the bore 108 at the first opening 110. The outer diameter of the first cylindrical portion 184 corresponds to the inner diameter of the first opening 110 such that the first sealing element 120 seals the first opening 110. The second cylindrical portion 186 of the first sealing element 120 is located within the first recess 174 and bears against a corresponding face of the first recess 174. Accordingly, both the first and second cylindrical portions 184, 186 are plugs. The second cylindrical portion 186 of the first sealing element 120 is physically coupled to the pressure modulating device 198 (not shown in Figure 8) such that the chamber 114 is fluidically connected to the pressure modulating device 198 via the passageway 182. In particular, the passageway 182 has an internal thread that engages with an external thread of a high-pressure hydraulic fitting connected to the pressure modulating device 198.

[0092] Figure 9A is a schematic diagram of the system for barocaloric cooling, heating or thermal storage 101 comprising the pressure vessel assembly 102 while operating during a first period of operation. The system for barocaloric cooling, heating or thermal storage 101 comprises a first damper 190 upstream of the pressure vessel assembly 102 and a second damper 192 downstream of the pressure vessel assembly 102. During the first period of operation, thefirst damper 190 is configured to receive a heat transfer fluid (e.g. air or water) from an area to be heated 194 and direct the heat transfer fluid through pressure vessel assembly 102 to the second damper 192. During this process, the heat transfer fluid passes close to the tubular component 106 (e.g. through the gaps between the elongate members 170A-D and the tubular component 106). The second damper 192 is configured to receive the heat transfer fluid from the pressure vessel assembly 102 and direct the heat transfer fluid to the area to be heated 194. Routes through which the heat transfer fluid do not pass during the first period of operation are shown in dashed lines in Figure 9A.

[0093] Figure 9B is a schematic diagram of the system for barocaloric cooling, heating or thermal storage 101 while operating during a second period of operation. During the second period of operation, the first damper 190 is configured to receive heat transfer fluid from an area to be cooled 196 and direct the heat transfer fluid through pressure vessel assembly 102 to the second damper 192. Again, during this process, the heat transfer fluid passes close to the tubular component 106. The second damper 192 is configured to receive heat transfer fluid from the pressure vessel assembly 102 and direct the heat transfer fluid to the area to be cooled 196. Routes through which the heat transfer fluid do not pass during the second period of operation are shown in dashed lines in Figure 9B.

[0094] Figure 10 is a flowchart of a method 1000 of operating the system for barocaloric cooling, heating or thermal storage 101. In a first step S1 of the method 1000, the pressure within the chamber 114 is increased. In particular, an increase in pressure (i.e. a positive change in pressure) is generated by the pressure modulating device 198 that is transmitted via the passageway 182 to the incompressible fluid that surrounds the barocaloric material 116. The increase in pressure in the chamber 114 results in a pressure being applied to the barocaloric material 116. The application of pressure to the barocaloric material 116 causes the barocaloric material 116 to release (i.e. emit) heat.

[0095] In a second step S2 of the method 1000, the system for barocaloric cooling, heating or thermal storage 101 is configured as shown in Figure 9A. That is, the first damper 190 is configured to receive the heat transfer fluid from the area to be heated 194 and direct the heat transfer fluid through pressure vessel assembly 102 to the second damper 192, and the second damper 192 is configured to receive the heat transfer fluid from the pressure vessel assembly 102 and direct the heat transfer fluid to the area to be heated 194. As mentioned above, during this process, the heat transfer fluid passes close to the tubular component 106. Accordingly, the heat transfer fluid is conveyed from a position in which it receives (i.e. absorbs) a portion of the heat emitted from the barocaloric material 116 to a position in which the area to beheated 194 receives the portion of heat from the heat transfer fluid. The heat transfer fluid may be cycled in this manner until a predetermined condition is met (e.g. a predetermined time has elapsed, the temperature of the area to be heated 194 is above a predetermined value or the temperature of the barocaloric material 116 is below a predetermined value).

[0096] In a third step S3 of the method 1000, the pressure within the chamber 114 is reduced. In particular, the pressure modulating device 198 reduces (i.e. negatively changes) the pressure that is transmitted via the passageway 182 to the incompressible fluid that surrounds the barocaloric material 116. The pressure may be reduced to atmospheric pressure, for example. The reduction in pressure in the chamber 114 results in a reduction in the pressure applied to the barocaloric material 116. The reduction in the pressure applied to the barocaloric material 116 causes the temperature of the barocaloric material 116 to reduce.

[0097] In a fourth step S4 of the method 1000, the system for barocaloric cooling, heating or thermal storage 101 is configured as shown in Figure 9B. That is, the first damper 190 is configured to receive the heat transfer fluid from the area to be cooled 196 and direct the heat transfer fluid through pressure vessel assembly 102 to the second damper 192, and the second damper 192 is configured to receive the heat transfer fluid from the pressure vessel assembly 102 and direct the heat transfer fluid to the area to be cooled 196. As mentioned above, during this process, the heat transfer fluid passes close to the tubular component 106. Accordingly, the heat transfer fluid is conveyed from a position in which the barocaloric material 116 receives heat from the heat transfer fluid to a position in which it receives (i.e. absorbs) heat from the area to be cooled 196. The heat transfer fluid may be cycled in this manner until a predetermined condition is met (e.g. a predetermined time has elapsed, the temperature of the area to be cooled 196 is below a predetermined value or the temperature of the barocaloric material 116 is above a predetermined value).

[0098] In the abovementioned method 1000, the first step S1 may be carried out concurrently with the second step S2, and the third step S3 may be carried out concurrently with the fourth step S4. The third step S3 may be carried out immediately or almost immediately after the second step S2.

[0099] The abovementioned system may function as a barocaloric refrigeration system or air conditioning system, for example if the area to be cooled 196 is a partially or completely enclosed space and the area to be heated 194 is an area in which waste heat is deposited (e.g. an outside space). The abovementioned system may function as a barocaloric heat pump or water heater, for example if the area to be heated 194 is a partially or completelyenclosed space or volume of water and the area to be cooled 196 is an area in which the coldness from the heat transfer fluid is deposited (e.g. an outside space). The abovementioned system may function as two or more of a barocaloric refrigeration system, an air conditioning system, a barocaloric heat pump or a water heater, for example if both the area to be cooled 196 is a partially or completely enclosed space and the area to be heated 194 is a partially or completely enclosed space or volume of water.

[0100] It will also be appreciated that the abovementioned system may function as a system for barocaloric thermal storage. In such systems, the third step S3 is not carried out immediately after the first and second steps S1, S2. Instead, after the second step S2 has been carried out, the pressure within the chamber 114 may held at an increased level (i.e. that resulting from the first step S1) until a condition is met. The condition may be a predetermined period of time (e.g. minutes, days, months or years later) having elapsed, for example. Alternatively, the condition may be a temperature threshold in the area to be cooled 196 having been reached (e.g. it being determined via sensors and comparisons between thresholds and measured temperatures that there is a demand for cooling). Alternatively, the condition may be a user manually selecting that cooling is required in the area to be cooled 196. Upon the condition being met, the third and fourth steps S3, S4 are carried out to provide useful cooling to the area to be cooled 196. Accordingly, in such an embodiment, for as long as the barocaloric material 116 remains pressurised, the system stores the ability for the barocaloric material 116 to absorb heat from its surroundings (e.g. from the area to be cooled 196), for example via the heat transfer fluid.

[0101] A flowchart of a such a method 8000 of operating a system for barocaloric thermal storage is shown in Figure 11. A first step P1 of the method 8000 corresponds to the first step S1 of the method 1000.

[0102] In a second step P2 of the method 8000, the pressure within the chamber 114 is maintained at the increased pressure until the condition is met. During part of this period of time, the system for barocaloric cooling, heating or thermal storage 101 may be configured as shown in Figure 9A and the second step S2 described with reference to the method 1000 of Figure 10 may be carried out. Additionally or alternatively, the heat from the barocaloric material 116 may passively dissipate from the barocaloric material 116 into the heat transfer fluid without the heat transfer fluid being actively conveyed. During the second step P2, the pressure modulating device 198 may be disconnected from the system for barocaloric thermal storage 101 and the passageway 182 may be sealed. This may allow the system to be transported, for example.A third step P3 and fourth step P4 of the method 8000 substantially correspond to the third step S3 and fourth step S4 of the method 1000, respectively. However, the third step P3 is carried out upon the condition being met. In embodiments in which the passageway 182 is sealed, the third step P3 may be carried out by automatically or manually removing the seal from the passageway 182. Alternatively, the pressure modulating device 198 may be used to decrease the pressure within the chamber 114.

[0103] The above description of the system for barocaloric thermal storage uses the example of a conventional barocaloric material. However, the barocaloric material may instead be an inverse barocaloric material. Such a system incorporating an inverse barocaloric material may function in a corresponding manner to the system incorporating a conventional barocaloric material, with the opposing temperature changes. In such embodiments, the condition may be a predetermined period of time (e.g. minutes, days, months or years later) having elapsed, for example. Alternatively, the condition may be a temperature threshold in the area to be heated 194 having been reached (e.g. it being determined via sensors and comparisons between thresholds and measured temperatures that there is a demand for heating). Alternatively, the condition may be a user manually selecting that heating is required in the area to be heated 194.

[0104] In existing thermal storage applications, materials are heated or cooled to high or low temperatures, and insulation is provided to maintain such materials at these high or low temperatures. However, since such insulation cannot be completely effective, the materials undesirably lose or gain heat when in their storage state. Such losses reduce the efficiency of thermal storage devices. In contrast, with the abovementioned barocaloric thermal storage applications, when the barocaloric material is in its storage state (i.e. during step S2), only the pressure needs to be maintained (which is achievable in practice) and the barocaloric material does not need to be maintained at a high or low temperature and can revert to ambient temperature. Such barocaloric thermal storage applications could be used to harness heat waste, for example that provided by power plants, and then transport the stored energy without losses where it can be utilised.

[0105] The pressure vessel assembly 102 in accordance with the invention has numerous advantages over the known pressure vessel assembly 2. In the known pressure vessel assembly 2, when the pressure within the chamber 14 is increased (e.g. during step S1 of the method 1000), radial forces oriented away from the chamber 14 are exerted on the tubular component 6 that generate hoop stresses and radial stresses in the wall of the tubularcomponent 6. In addition, when the pressure within the chamber 14 is increased, axial forces oriented away from the chamber 14 are exerted on the first and second plugs 20, 24. As mentioned previously, external threads of the first and second plugs 20, 24 mate with internal threads at the first and second openings 10, 12 of the tubular component 6, respectively. Accordingly, the first and second plugs 20, 24 and the tubular component 6 are fixedly (i.e. rigidly) connected, do not move relative to each other and function as a single unitary body. Therefore, all of the axial forces oriented away from the chamber 14 that are exerted on the first and second plugs 20, 24 are transmitted to the tubular component 6 and place the tubular component 6 in tension, thereby additionally inducing axial stress in the wall of the tubular component 6.

[0106] In the pressure vessel assembly 102 in accordance with the invention, when the pressure within the chamber 114 is increased (e.g. during step S1 of the method 1000), hoop stresses and radial stresses are generated in the wall of the tubular component 106 in a similar manner as described above. Similarly, axial forces oriented away from the chamber 114 are exerted on the first and second sealing elements 120, 124. However, in contrast with the known pressure vessel assembly 2, not all of the axial forces oriented away from the chamber 114 that are exerted on the first and second sealing elements 120, 124 are transmitted to the tubular component 106. Instead, when the first and second sealing elements 120, 124 are subjected to axial loads, the first and second sealing elements 120, 124 are forced against the first and second portions 166, 168, which in turn place the first to fourth elongate members 170A-D in tension. When functioning in this manner, the first and second sealing elements 120, 124, the first and second portions 166, 168 and the first to fourth elongate members 170A-D are fixedly (i.e. rigidly) connected, do not move relative to each other and function as a single unitary body. Accordingly, some or all of the axial forces oriented away from the chamber 114 that are exerted on the first and second sealing elements 120, 124 are transmitted to the first to fourth elongate members 170A-D via the first and second portions 166, 168. By way of further explanation, a force that is exerted on the first to fourth elongate members 170A-D by the first sealing element 120 in a direction from the second sealing element 124 to the first sealing element 120 is counteracted by an opposite force (i.e. a tension) exerted by the first to fourth elongate members 170A-D in a direction from the first sealing element 120 to the second sealing element 124. Likewise, a force that is exerted on the first to fourth elongate members 170A-D by the second sealing element 124 in a direction from the first sealing element 120 to the second sealing element 124 is counteracted by an opposite force (i.e. a tension) exerted by the first to fourth elongate members 170A-D in a direction from the second sealing element 124 to the first sealing element 120. Accordingly, the first to fourth elongate members 170A-D are placed in tension such that an axial force istransmitted between the first and second sealing elements 120, 124 not via the tubular component 106, which either completely or partially reduces the extent to which the tubular component 106 is placed in tension. That is, the first to fourth elongate members 170A-D bear a load between the first and second sealing elements 120, 124 not via the tubular component 106. It thus follows that, in the pressure vessel assembly 102 in accordance with the invention, axial forces oriented away from the chamber 114 that are exerted on the first and second sealing elements 120, 124 do not induce or induce lower axial stresses in the wall of the tubular component 106.

[0107] By providing a bracing structure 164 that functions in the above manner (i.e. to couple the first sealing element 120 and the second sealing element 124 to transmit a force between the first sealing element 120 and the second sealing element 124 not via the tubular component 106), the walls of the tubular component 106 do not need to provide as much strength in the axial direction. Accordingly, the wall of the tubular component 106 can be constructed from materials that predominantly, or entirely, provide uniaxial tensile strength. Such materials may include (but are not limited to) uniaxial fibre composite materials or sheet materials. Sheet materials may be hard-drawn or oriented sheet materials. The materials may be oriented within the wall of the tubular component 106 such that the high tensile strength direction coincides, or largely coincides with the hoop direction of the tubular component 106 rather than the axial direction of the tubular component 106. The material forming the tubular element may comprise a plurality of fibres, strips or elements oriented substantially in the direction circumferential to the longitudinal axis 162. The material forming the tubular element may comprise fewer or no fibres, strips or elements oriented substantially in the direction parallel to the longitudinal axis 162.

[0108] The abovementioned features of the pressure vessel assembly 102 in accordance with the invention are advantageous in that, since the axial forces are largely or entirely borne by the bracing structure 164, the walls of the tubular component 106 do not need to have as much tensile strength in the axial direction as in the known pressure vessel assembly 2 and instead mainly have to resist hoop stresses, a functioning tubular component 106 can be created that has a smaller wall thickness, and, thus, heat capacity (i.e. thermal mass). Since a smaller volume of material of the tubular component 106 is required than in the tubular component 6 of the known pressure vessel assembly 2, the volume of the chamber 114 is larger and able to store a greater volume of barocaloric material 116, which in turn increases the amount of heat that can be released by the pressure vessel assembly 102.Further and as set out in more detail below, since the tubular component 106 does not need to have as much tensile strength in the axial direction as in the hoop direction (i.e. since it is anisotropic in terms of its tensile strength), the tubular component 106 can be made with anisotropic tensile properties. In particular, the tubular component 106 can be made with a material having greater tensile strength in the hoop direction than in the axial direction. For example and as set out in further detail below, the tubular component 106 can be formed of predominantly or largely hoop wound fibres or a directionally orientated sheet material (e.g. from unidirectional pre-preg sheets). This further reduces the required thickness of the walls of the tubular component 106. That is, the thickness of the walls of a tubular component 106 formed of a material having anisotropic tensile properties can be thinner than walls of a tubular component formed of a conventional steel or a multi-directional composite. The use of a materials having highly anisotropic properties (i.e. much greater tensile strength in the axial direction than in the hoop direction) would not be possible if the tubular component 106 had to support the majority, or all, of its own axial loads when pressurised. Instead, such a tubular component 106 would simply pull apart under pressure.

[0109] In addition, since a smaller volume of material of the tubular component 106 of the pressure vessel assembly 102 is required, the heat capacity of the tubular component 106 is reduced compared to the tubular component 6 of the known pressure vessel assembly 2. This allows the internal heat exchanger configuration used in the known pressure vessel assembly 2 (e.g. the tube 28) to be dispensed with and for the tubular component 106 itself to be the structure through which heat is transferred between the barocaloric material 116 and the heat transfer fluid. By freeing up of space within the chamber 114 no longer required for an internal heat exchanger pipework, the chamber 114 is able to store an even greater volume of barocaloric material 116 than the chamber 14 of the known pressure vessel assembly 2. By providing a system in which the tubular component 106 has a lower heat capacity, a higher proportion of the heat released by the barocaloric material 116 can be transferred to the heat transfer fluid (e.g. in steps S1 and S2) and a higher proportion of heat in the heat transfer fluid can be transferred to the barocaloric material 116 (e.g. in steps S3 and S4). This increased temperature span of components that participate in thermal cycling results in efficiency improvements.

[0110] It will be appreciated that the above benefits can be provided in embodiments of the invention in which the first and second plugs (i.e. plugs 120, 124) are fixedly (i.e. rigidly) connected to the tubular component (e.g. tubular component 106), and, thus, do not move relative to each other and function as a single unitary body. In such embodiments, the first and second plugs may be physically sealed to the tubular component by adhesive, solder or other means. Insuch embodiments, the bracing structure (i.e. bracing structure 64) would still couple the first and second sealing elements (i.e. first and second sealing elements 120, 124) to transmit a force between the first and second sealing element not via the tubular component. However, in alternative embodiments, a sliding connection may be formed between the first and second plugs 120, 124 and the tubular component 106.

[0111] This is achieved in part by providing first and second openings 110, 112 and first and second cylindrical portions 184, 186 that are unthreaded. Secondly, this is achieved by providing clearance or transition fits between the first opening 110 and the first cylindrical portion 184 and between the second opening 112 and the second cylindrical portion 186. Thirdly, this is achieved by providing respective axial gaps between the ends of the tubular component 106 and the first and second portions 166, 168 of the bracing structure 164. Accordingly, when the pressure within the chamber 14 is increased (e.g. during step S1 of the method 1000), deformation of the bracing structure 164 in an axial direction resulting from the first and second sealing elements 120, 124 being subjected to axial loads does not induce a corresponding axial deformation of the tubular component 106. Instead, the first and second sealing elements 120, 124 are able to slide in an axial direction relative to the tubular component 106, which reduces the extent to which the tubular component 106 is placed in tension.

[0112] It will be appreciated that that the abovementioned clearance or transition fit still ensures seals are formed between the first and second sealing elements 120, 124 and the first and second opening 110, 112, respectively. Additional sealing elements such as one or more O-rings may be provided between the first and second sealing elements 120, 124 and the first and second opening 110, 112, respectively. The seals formed between the first and second sealing elements 120, 124 and the first and second opening 110, 112 may be lubricated.

[0113] Figure 12 is a perspective view of a second embodiment of a pressure vessel assembly 202 for a system for barocaloric cooling, heating or thermal storage. The pressure vessel assembly 202 substantially corresponds to the pressure vessel assembly 102, and corresponding features are denoted using common reference numerals with the addition of a value of 100. The pressure vessel assembly 202 differs from the pressure vessel assembly 102 in that each of the first, second, third and fourth elongate members 270A, 270B, 270C, 270D comprises a respective core and a respective external layer 271 A, 271 B, 271 C, 271 D covering the core. The external layer 271 A-D covers the core only between the first and second portions 266, 268. Respective gaps are formed between the first to fourth external layers 271A, 271B, 271C, 271D and the tubular component 206. The core of each of the first,second, third and fourth elongate members 270A-D may have the same properties as the first, second, third and fourth elongate members 170A-D.

[0114] The material forming the core of each of the first, second, third and fourth elongate members 270A-D may have a higher tensile strength than the material forming the external layer 271 A-D. Accordingly, the cores may act as the main structural elements for the first, second, third and fourth elongate members 270A-D. The material forming the external layers 271A-D of each of the first, second, third and fourth elongate members 270A-D may have a lower thermal conductivity than the material forming the core of each of the first, second, third and fourth elongate members 270A-D. Accordingly, the external layers 271A-D may insulate the cores and reduce the amount of heat that is transferred between the heat transfer fluid and the first, second, third and fourth elongate members 270A-D.

[0115] In a similar manner, the first and second portions 266, 268 of the bracing structure 264 comprise respective first layers 267, 269 and second layers 273, 275. The material forming the first layers 267, 269 may have a higher tensile strength than the material forming the second layers 273, 275. Accordingly, the first layers 267, 269 may act as the main structural elements for the first and second portions 266, 268 of the bracing structure 264. The material forming the second layers 273, 275 may have a lower thermal conductivity than the material forming the first layers 267, 269. Accordingly, the second layers 273, 275 may insulate the first layers 267, 269 and reduce the amount of heat that is transferred between the heat transfer fluid and the first layers 267, 269. The provision of the layers 271A-271D, 273, 275 completely or partially reduces the extent to which the bracing structure 264 participates in the thermal cycling, which increases the temperature span of components that do participate in thermal cycling (i.e. the tubular component 206) and increases the efficiency of the pressure vessel assembly 202. The layers 271A-271D, 273, 275 may be formed of any suitable material, such as a low density closed-cell polymer foam (e.g. an expanded polystyrene or polyurethane foam).

[0116] Figure 13A is a cross-sectional view of the pressure vessel assembly 202 taken along the cross-sectional plane indicated by dashed lines in Figure 12.

[0117] Figure 13B is a corresponding cross-sectional view of a third embodiment of a pressure vessel assembly 202’ for a system for barocaloric cooling, heating or thermal storage. The pressure vessel assembly 202’ substantially corresponds to the pressure vessel assembly 202, and corresponding features are denoted using common reference numerals with the addition of an apostrophe. The pressure vessel assembly 202’ differs from the pressure vesselassembly 202 in that it comprises a housing 27T within which the tubular component 206’ is disposed. The housing 27T may be provided in place of the layers 271A-271D of the second embodiment of the pressure vessel assembly 202.

[0118] The elongate members 270A’-D’ are disposed external to the housing 27T. As shown, the housing 27T does not touch the elongate members 270A’-D’. The housing 27T comprises a body 255’ within which the tubular component 206’ is disposed, an inlet duct 257’ (i.e. inlet) and an outlet duct 259’ (i.e. outlet). An interior surface of the body 255’ of the housing 27T is spaced from the tubular component by a gap 263’. The inlet duct 257’ is disposed on a first side of body 255’ and the outlet duct 259’ is disposed on a second side of the body 255’. The gap 263’ is configured to receive a heat-transfer fluid. In particular, during operation, the heat transfer fluid may pass into the housing 27T via the inlet duct 257’, pass through the body 255’ and out of the housing 27T via the outlet duct 259’. The housing 27T therefore separates the heat-transfer fluid from the elongate members 270A-D’. The inlet duct 257’ and the outlet duct 259’ are disposed on the same axial plane (i.e. a single plane extending perpendicular to the longitudinal axis 262’). Accordingly, the heat-transfer fluid flows through the housing 27T in a substantially transverse direction. The elongate members 270A-D’ have a higher tensile strength than the housing 27T. The housing 27T has a lower thermal conductivity than the elongate members 270A-D’. Accordingly, heat can transfer between the heat-transfer fluid and the tubular component 206’ while thermal isolation is provided between the heat-transfer fluid and the elongate members 270A-D’. The housing 27T may be formed of any suitable material, such as a low density closed-cell polymer foam (e.g. an expanded polystyrene or polyurethane foam). Although the body 255’ of the housing 27T is shown having a square cross-sectional profile, it may have any other suitable cross-sectional profile such as a circular cross-sectional profile. Although the housing 27T is shown having a single layer, it may comprise multiple layers. In the embodiment shown, the body 255’, the inlet duct 257’ and the outlet duct 259’ are formed integrally with each other. However, it will be appreciated that the body 255’, the inlet duct 257’ and the outlet duct 259’ may be distinct components that are formed separately and subsequently attached to each other.

[0119] Figure 14A is a perspective view of a fourth embodiment of a pressure vessel assembly 202” for a system for barocaloric cooling, heating or thermal storage. The pressure vessel assembly 202” substantially corresponds to the pressure vessel assembly 202’, and corresponding features are denoted using common reference numerals with the addition of a further apostrophe. In contrast to the inlet duct 257’ and the outlet duct 259’ of the third embodiment of the pressure vessel assembly 202’, the inlet duct 257” and the outlet duct 259” of the fourth embodiment of the pressure vessel assembly 202” are disposed on different axialplanes (i.e. two separate axial planes that are spaced from each other along the longitudinal axis 262”). Accordingly, the heat-transfer fluid flows through the housing 271” in a substantially axial direction.

[0120] Figure 14B is a cross-sectional view of the fourth embodiment of a pressure vessel assembly 202” taken along a longitudinal cross-sectional plane. As shown, the tubular component 206’ extends through end walls of the body 255” of the housing 271”. The end walls of the body 255” of the housing 271” are spaced from the first and second portions 266”, 268”” of the bracing structure 264”. The first sealing element 220” is integrally formed with the first portion 266” of the bracing structure 264” and the second sealing element 224” is integrally formed with the second portion 268” of the bracing structure 264”. The first sealing element 220” is defined by an annular channel in the first portion 266” of the bracing structure 264” and the second sealing element 224” is defined by an annular channel in the second portion 268” of the bracing structure 264”. The passageway 282” extends through the first portion 266” and the first sealing element 220” of the bracing structure 264”. A further passageway 282B” corresponding to the passageway 282” extends through the second portion 268” and the second sealing element 224” and of the bracing structure 264”. The features described above in relation to Figure 14B are also present in the third embodiment of the pressure vessel assembly 202’. The housing 271” may again be formed of any suitable material, such as a low density closed-cell polymer foam (e.g. an expanded polystyrene or polyurethane foam).

[0121] Figure 15 is an exploded perspective view of a fifth embodiment of a pressure vessel assembly 302 for a system for barocaloric cooling, heating or thermal storage. The pressure vessel assembly 302 substantially corresponds to the pressure vessel assembly 102, and corresponding features are denoted using common reference numerals with the addition of a value of 200. The pressure vessel assembly 302 differs from the pressure vessel assembly 102 in that it comprises two elongate members 370A, 370B rather than four elongate members. Accordingly, the pressure vessel assembly 302 correspondingly comprises four rather than eight nuts (not shown) and our rather than eight through holes 380A, 380B, 380C, 380D.

[0122] Figure 16 is a cross-sectional view of a sixth embodiment of a pressure vessel assembly 402 for a system for barocaloric cooling, heating or thermal storage. The pressure vessel assembly 402 substantially corresponds to the pressure vessel assembly 102, and corresponding features are denoted using common reference numerals with the addition of a value of 300. The pressure vessel assembly 402 differs from the pressure vessel assembly 102 in that it comprises an alternative first sealing element 420 and an alternative secondsealing element 424 rather than the first sealing element 120 and a second sealing element 124, respectively.

[0123] Figure 17 is a perspective view of the alternative first sealing element 420 in isolation. As shown, the alternative first sealing element 420 comprises a first cylindrical portion 484, a second cylindrical portion 486 and a third cylindrical portion 488 disposed between the first and second cylindrical portions 484, 486. The diameter of the third cylindrical portion 488 is greater than the diameter of the first and second cylindrical portions 484, 486. The diameter of the first cylindrical portion 484 is greater than the diameter of the second cylindrical portion 486. A passageway 482 extends through the second and third cylindrical portions 486, 488. The first cylindrical portion 484 comprises a socket 485 having an internal diameter that is greater than an internal diameter of the passageway 482. The socket 485 receives the tubular component 406. The inner diameter of the socket 485 corresponds to the outer diameter of the tubular component 406 such that the first sealing element 420 seals the first opening 410 of the bore 408. The second cylindrical portion 486 of the first sealing element 420 is located within the first recess 474. Although not shown, the second cylindrical portion 486 comprises an internally threaded socket, able to receive an externally threaded standard high-pressure hydraulic component that connects to the pressure modulating device. Alternatively, the second cylindrical portion 486 may be a plug. The second sealing element 424 substantially corresponds to the first sealing element 420 except in that it does not include a passageway 482.

[0124] Figure 18 is a cross-sectional view of a seventh embodiment of a pressure vessel assembly 502 for a system for barocaloric cooling, heating or thermal storage. The pressure vessel assembly 502 substantially corresponds to the pressure vessel assembly 102, and corresponding features are denoted using common reference numerals with the addition of a value of 400. The pressure vessel assembly 502 differs from the pressure vessel assembly 102 in that it comprises a further alternative first sealing element 520 and a further alternative second sealing element 524 rather than the first sealing element 120 and a second sealing element 124, respectively.

[0125] Figure 19 is a perspective view of the further alternative first sealing element 520 in isolation. As shown, the further alternative first sealing element 520 comprises a first cylindrical portion 584, a second cylindrical portion 586 and a third cylindrical portion 588 disposed between the first and second cylindrical portions 584, 586. The diameter of the third cylindrical portion 588 is greater than the diameter of the first and second cylindrical portions 584, 586. The diameter of the first cylindrical portion 584 is greater than the diameter of the second cylindrical portion586. The first cylindrical portion 584 comprises a socket 585 that receives the tubular component 506. The inner diameter of the socket 585 corresponds to the outer diameter of the tubular component 506 such that the first sealing element 520 seals the first opening 510 of the bore 508. The first cylindrical portion 584 further comprises a cylindrical plug 587 disposed within the socket 585. The outer diameter of the plug 587 corresponds to the inner diameter of the first opening 510 such that the plug 587 also seals the first opening 510. The passageway 582 extends through the plug 587 of the first cylindrical portion 584, the second cylindrical portion 586 and the third cylindrical portion 588. The second sealing element 524 substantially corresponds to the first sealing element 520 except in that it does not include a passageway 582.

[0126] Figure 20 is a cross-sectional view of a eighth embodiment of a pressure vessel assembly 602 for a system for barocaloric cooling, heating or thermal storage. The pressure vessel assembly 602 substantially corresponds to the pressure vessel assembly 102, and corresponding features are denoted using common reference numerals with the addition of a value of 600. The pressure vessel assembly 602 differs from the pressure vessel assembly 102 in that the first sealing element 620 is integrally formed with the first portion 666 of the bracing structure 664 and the second sealing element 624 is integrally formed with the second portion 668 of the bracing structure 664. The passageway 682 extends through the first sealing element 620 and the first portion 666 of the bracing structure 664.

[0127] Figure 21 is a cross-sectional view of a ninth embodiment of a pressure vessel assembly 702 for a system for barocaloric cooling, heating or thermal storage. The pressure vessel assembly 702 substantially corresponds to the pressure vessel assembly 602, and corresponding features are denoted using common reference numerals with the addition of a value of 100.

[0128] The pressure vessel assembly 702 differs from the pressure vessel assembly 602 in that, in addition to the tubular component 706A (which corresponds to the tubular component 606 of the pressure vessel assembly 602), the pressure vessel assembly 702 further comprises a second tubular component 706B and a third tubular component 706C. The provision of additional tubular components 706B, 706B increases the heating and / or cooling power of the system for barocaloric cooling, heating or thermal storage within a given space envelope. The pressure vessel assembly 702 further differs from the pressure vessel assembly 602 in that, in addition to the first and second sealing elements 720A, 724A (which correspond to the first and second sealing elements 620, 624), the pressure vessel assembly 702 further comprises a third sealing element 720B, a fourth sealing element 724B, a fifth sealing element 720C anda sixth sealing element 724C. The third and fifth sealing elements 720B, 720C correspond to the first sealing element 720A, and the fourth and sixth sealing elements 724B, 724C correspond to the second sealing element 724A. The third and fourth sealing elements 720B, 724B interface with the second tubular component 706B and the fifth and sixth sealing elements 720C, 724C interface with the third tubular component 706C in a corresponding manner to the manner in which the first and second sealing elements 720A, 724A interface with the first tubular component 706A. The first portion 766 of the bracing structure 764 comprises a manifold 781 in the form of a fluid passageway that connects the passageways 782A, 782B, 782C of the first, third and fifth sealing elements 720A, 720B, 720C to a single inlet 783 that is in turn connected to the pressure modulating device 198. Accordingly, pressure can be applied to the chambers 714A, 714B, 714C of each of the tubular components 706A, 706B, 706C via the single inlet 783.

[0129] Figure 22 is a perspective view of an tenth embodiment of a pressure vessel assembly 802 for a system for barocaloric cooling, heating or thermal storage. The pressure vessel assembly 802 substantially corresponds to the pressure vessel assembly 702, and corresponding features are denoted using common reference numerals with the addition of a value of 100. The pressure vessel assembly 802 differs from the pressure vessel assembly 702 in that the third portion 870 of the bracing structure 864 that extends parallel to the longitudinal axis 862 between the first portion 866 and the second portion 868 instead comprises a housing 870 (i.e. box-section casing) that extends parallel to the longitudinal axis 862 between the first portion 866 and the second portion 868.

[0130] Figure 23 is a partially exploded view of the housing 870. The housing 870 extends between a third opening 851 and a fourth opening 853 and defines a chamber 877. The housing 870 is fabricated from a material having a high tensile strength in the direction of the longitudinal axis 862. A pair of first slots 893A, 893B are disposed on a first side of the housing 870 and a pair of second slots 895A, 895B are disposed on a second side of the housing 870. The housing 870 comprises an external layer 889 and an internal layer 891. The material forming the external layer 889 may have a higher tensile strength than material forming the internal layer 891. Accordingly, the external layer 889 may act as the main structural element of the third portion 870 of the bracing structure 864. The housing 870, in particular the external layer 889 thereof, comprises a plurality of through holes 879 through which a plurality of bolts 897 extend when in an assembled state. The material forming the internal layer 891 may have a lower thermal conductivity than the material forming the external layer 889. Accordingly, the internal layer 891 may insulate the external layer 889 and reduce the amount of heat that is transferred between the heat transfer fluid and the external layer 889. The internal layer 891may be formed of any suitable material, such as a low density closed-cell polymer foam (e.g. an expanded polystyrene or polyurethane foam).

[0131] Figure 24 is a partially exploded view of the pressure vessel assembly 802 of Figure 22 with the housing 870 not shown. As shown, in addition to the first to third tubular components 806A, 806B, 806C, the pressure vessel assembly 802 comprises fourth to ninth tubular components 806D, 806E, 806F, 806G, 806H, 8061 that interface with sealing elements 820A, 820B, 820C, 820D, 820E, 820F, 820G, 820H, 8201, 824A, 824B, 824C, 824D, 824E, 824F, 824G, 824H, 8241 in a corresponding manner to the manner described above. When assembled, the tubular components 806A-I are disposed within the chamber 877. Accordingly, the housing 870 encloses the tubular components 806A-I. That is, the housing 870 extends around the majority of the space surrounding the tubular components 806A-I.

[0132] The first portion 866 and the second portion 868 comprise a plurality of threaded holes 899. The plurality of bolts 897 extend through the through holes 879 of the housing 870 and into the threaded holes 899 of the first and second portions 866, 868 to secure the first portion 866 and the second portion 868 to the housing 870. However, it will be appreciated that the housing 870 may be secured to the first and second portions 866, 868 by other suitable means. The outer profile of the first and second portions 866, 868 substantially correspond to the inner profile of the third and fourth openings 851 , 853 of the housing 870. Accordingly, the first and second portions 866, 868 seal the third and fourth openings 851, 853, respectively.

[0133] During operation, the heat transfer fluid may pass into the chamber 877 via the pair of first slots 893A, 893B and out of the chamber 877 via the pair of second slots 895A, 895B. Accordingly, the pair of first slots 893A, 893B function as an inlet opening into the chamber 877 and the second slots 895A, 895B function as an outlet opening out of the chamber 877. Heat transfer fluid within the chamber 877 may either receive a portion of the heat emitted from the barocaloric material 816 (e.g. during step S2 described above with reference to Figure 10) or transfer heat to the barocaloric material 816 (e.g. during step S4 described above with reference to Figure 10).

[0134] In the pressure vessel assembly 802, when the sealing elements 820A-I, 824A-I and the first and second portions 866, 868 are subjected to axial loads, the housing 870 is placed in tension. When functioning in this manner, the sealing elements 820A-I, 824A-I and the first and second portions 866, 868 are fixedly (i.e. rigidly) connected to, do not move relative to and function as a single unitary body with the housing 870. Accordingly, some or all of the axial forces oriented away from the chambers of the tubular components 806A-I that areexerted on the sealing elements 820A-I, 824A-I are transmitted to the housing 870 via the integral first and second portions 866,868. Accordingly, the housing 870 is placed in tension such that an axial force is transmitted between the sealing elements sealing elements 820A-I, 824A-I not via the tubular component 806. It thus follows that, in the pressure vessel assembly 802, axial forces oriented away from the chambers of the tubular components 806A-I that are exerted on the sealing elements 820A-I, 824A-I do not induce (or induce lower) axial stresses in the walls of the tubular components 806A-I than would otherwise be the case. The housing 870 also provides burst protection in the event of failure of the tubular components 806A-I.

[0135] Figure 25A is a cross-sectional view of the pressure vessel assembly 802 taken along the cross-sectional plane indicated by dashed lines in Figure 23.

[0136] Figure 25B is a corresponding cross-sectional view of an eleventh embodiment of a pressure vessel assembly 802’ for a system for barocaloric cooling, heating or thermal storage. The pressure vessel assembly 802’ substantially corresponds to the pressure vessel assembly 802, and corresponding features are denoted using common reference numerals with the addition of an apostrophe. The pressure vessel assembly 802’ differs from the pressure vessel assembly 802 in that it comprises a single tubular component 806’ rather a plurality of tubular components 806A-I and in that the third portion of the bracing structure 864’ additionally comprises first, second, third and fourth elongate members 870A’, 870B’ 870C’, 870D’ corresponding to those described above. In addition, the pressure vessel assembly 802’ differs from the pressure vessel assembly 802 in that it additionally comprises an insulating housing 89T within which the tubular component 806’ is disposed. The insulating housing 89T may be provided in place of the internal layer 891 of the tenth embodiment of the pressure vessel assembly 802.

[0137] The insulating housing 89T comprises a body 855’ within which the tubular component 806’ is disposed, an inlet duct 857’ (i.e. inlet) and an outlet duct 859’ (i.e. outlet). The housing 870’ is disposed external to the insulating housing 89T and abuts an exterior surface of the insulating housing 89T. The insulating housing 89T occupies a majority (i.e. greater than 50%) of an internal void defined by the housing 870’. An interior surface of the body 855’ of the insulating housing 89T is spaced from the tubular component 806’ by a gap 863’. The housing 870’ has a higher tensile strength than the insulating housing 89T. The insulating housing 89T has a lower thermal conductivity than the housing 870’. In addition, the elongate members 870A’-D’ have a higher tensile strength than the insulating housing 89T and the insulating housing 89T has a lower thermal conductivity than the elongate members 870A’-D’.The inlet duct 857’ is disposed on a first side of the body 855’ and the outlet duct 859’ is disposed on a second side of the body 855’. The inlet duct 857’ and the outlet duct 859’ extend through respective openings in the housing 870’. The gap 863’ is configured to receive a heattransfer fluid. In particular, during operation, the heat transfer fluid may pass into the housing 870’ via the inlet duct 857’, pass through the body 855’ and pass out of the housing 870’ via the outlet duct 859’. The insulating housing 89T therefore separates the heat-transfer fluid from the elongate members 870A’-D’ and the housing 870’. The inlet duct 857’ and the outlet duct 859’ are disposed on the same axial plane (i.e. a single plane extending perpendicular to the longitudinal axis 862’). Accordingly, the heat-transfer fluid flows through the insulating housing 89T in a substantially transverse direction. Accordingly, heat can transfer between the heat-transfer fluid and the tubular component 806’ while thermal isolation is provided between the heat-transfer fluid and the housing 870’. The insulating housing 89T may be formed of any suitable material, such as a low density closed-cell polymer foam (e.g. an expanded polystyrene or polyurethane foam). Although the insulating housing 89T is shown having a square cross-sectional profile, it may have any other suitable cross-sectional profile such as a circular cross-sectional profile. Although the insulating housing 89T is shown having a single layer, it may comprise multiple layers. It will be appreciated that multiple tubular components 806’ may be provided and additional layers of the insulating housing 89T may extend between adjacent tubular components 806’, such that a grid of insulating layers are provided having a plurality of cells within which respective tubular components 806’ are disposed. It will also be appreciated that, in alternative embodiments, the inlet duct 857’ and the outlet duct 859’ may be disposed on different axial planes (e.g. in the manner described with reference to Figures 14A and 14B) such that the heat-transfer fluid flows through the insulating housing 89T in a substantially axial direction. In addition, it will be appreciated that the inlet duct 857’ and the outlet duct 859’ may in some embodiments swap functions at different times within a cycle of operation such that the flow through the insulating housing 89T is reversed. That is, the heat transfer fluid may pass into the housing 870’ via the outlet duct 859’, pass through the body 855’ and pass out of the housing 870’ via the inlet duct 857’. In this manner, the outlet duct 859’ may temporarily function as an inlet and the inlet duct 857’ may temporarily function as an outlet. It will also be appreciated that either of the housing 870’ or the elongate members 870A-D’ may be dispensed with.

[0138] Figure 26 is a cross-sectional view of a twelfth embodiment of a pressure vessel assembly 1102 for a system for barocaloric cooling, heating or thermal storage. The pressure vessel assembly 1102 substantially corresponds to the pressure vessel assembly 802, and corresponding features are denoted using common reference numerals with the addition of a value of 300. The pressure vessel assembly 1102 differs from the pressure vessel assembly802 in that the first portion 1166 comprises an inlet opening 1165 for receiving a heat-transfer fluid from an exterior of the housing 1170 into the chamber 1177, and the second portion 1168 comprises an outlet opening 1178 for releasing the heat-transfer fluid from the chamber 1177 to the exterior of the housing 1170.

[0139] The inlet opening 1165 functions in a corresponding manner to the pair of first slots 893A, 893B of the tenth embodiment of the pressure vessel assembly 802, and the outlet opening 1178 functions in a corresponding manner to the pair of second slots 895A, 895B of the tenth embodiment of the pressure vessel assembly 802. However, by providing the first and second portions 1166, 1168 with the inlet and outlet openings 1165, 1178, the heat transfer fluid passes through the chamber 1177 in a mainly (although not wholly) longitudinal direction of the pressure vessel assembly 1102 rather than in a mainly (although not wholly) transverse direction. It will be appreciated that there may be a significant transverse direction of flow. By way of example, in the embodiment shown in Figure 26, the heat-transfer fluid may enter the top-left side of the chamber 1177 via the inlet opening 1165 and initially flow mostly in a rightward direction before passing in a downward direction over the tubular components 1106A-C and exiting the bottom-right side of the chamber 1177 via the outlet opening 1178. Although not shown, internal structures (e.g. baffles) within the chamber 1177 may direct the flow of heat-transfer fluid up and down within successive sections of the housing 1170.

[0140] Figure 27 is a perspective view of a thirteenth embodiment of a pressure vessel assembly 902 for a system for barocaloric cooling, heating or thermal storage. The pressure vessel assembly 902 substantially corresponds to the pressure vessel assembly 102, and corresponding features are denoted using common reference numerals with the addition of a value of 800. The pressure vessel assembly 902 differs from the pressure vessel assembly 102 in that it further comprises first and second further bracing structures 927A, 927B. In the embodiment shown, the first and second further bracing structures 927A, 927B are plates.

[0141] Each of the first and second further bracing structures 927A, 927B comprises a respective first opening 950A, 950B through which the first elongate member 970A extends, a respective second opening 952A, 952B through which the second elongate member 970B extends, a respective third opening 954A, 954B through which the third elongate member 970C extends, a respective fourth opening 956A, 956B through which the fourth elongate member 970D extends and a respective fifth opening 958A, 958B through which the tubular component 906 extends. The further bracing structures 927A, 927B couple the tubular component 906 to the bracing structure 964 at positions part way along the tubular component 906. The first and second first portions 966 of the bracing structure 964 and the first and second further bracingstructures 927A, 927B are equally spaced along the longitudinal axis 962. That is, a first distance between the first portion 966 and the first further bracing structure 927A is equal to a second distance between the first and second further bracing structures 927A, 927B, which is equal to a third distance between the second further bracing structure 927B and the second portion 968.

[0142] During operation, if the tubular component 906 has a geometry that is not perfectly cylindrical and aligned with the linear longitudinal axis 962 (e.g. if the tubular component 906 is slightly C-shaped), when the interior of the tubular component 906 is subjected to high pressures (e.g. during steps S1 and S2 of the method 1000), the overall radial force exerted on a first side of the tubular component 906 due to the internal pressure may differ from the overall radial force exerted on a second side of the tubular component 906 due to the internal pressure. This may result in a side of the tubular component 906 that has a greater longitudinal length being in tension and a side of the tubular component 906 that has a shorter longitudinal length being in compression. In long pressure vessel assemblies not having the first and second further lateral bracing structures 927A, 927B, although the above-mentioned tension and compression forces will act so as to counteract buckling, the difference between the overall force on the side of greater longitudinal length and that of shorter overall longitudinal length may exceed these tension and compression forces, thus causing the tubular component to buckle.

[0143] In the pressure vessel assembly 902, one or more of the first and second further bracing structures 927A, 927B counteract the radial force exerted on the tubular component 906 that might otherwise cause the tubular component 906 to buckle. In particular, the first and second further bracing structures 927A, 927B hold the tubular component 906 in a fixed spatial relationship with the first, second, third and fourth elongate members 970A, 970B, 970C, 970D where they meet, such that the first, second, third and fourth elongate members 970A, 970B, 970C, 970D exert a reaction force on the tubular component 906 via the first and second further bracing structures 927A, 927B. The stiffness of the first, second, third and fourth elongate members 970A, 970B, 970C, 970D in a direction perpendicular to the longitudinal axis 962 may be sufficiently large to prevent buckling of the tubular component 906.

[0144] By providing first and second further bracing structures 927A, 927B, the internal pressure within the tubular component 906 required for such buckling to occur for a tubular component 906 having a given stiffness, diameter, wall thickness and length is increased. However, any number of further bracing structures may be selected based on the internal pressure that the tubular component 906 will be subjected to and the stiffness, diameter, wall thickness andlength of the tubular component 906. For example, a tubular component 906 that may be subjected to a lower internal pressure and / or has a higher stiffness, greater diameter and / or smaller length may be provided with only one of the further bracing structures 927A, 927B. Conversely, a tubular component 906 that may be subjected to a higher internal pressure and / or has a lower stiffness, smaller diameter or greater length may be provided with more than two further bracing structures 927A, 927B.

[0145] The first and second further bracing structures 927A, 927B may be formed of a material having a similar or higher thermal conductivity than the tubular component 906, such that the first and second further bracing structures 927A, 927B conduct heat away from the tubular component 906 to the heat transfer fluid (e.g. during steps S1 and S2 of the method 1000) and the conduct heat to the tubular component 906 from the heat transfer fluid (e.g. during steps S3 and S4). The first and second further bracing structures 927A, 927B increase the surface area of thermally conductive components in contact with the heat transfer fluid so as to increase the rate of heat transfer between the tubular component 906 and the heat transfer fluid. The first and second further bracing structures 927A, 927B may also act as baffles that influence the fluid dynamics of the flow of heat transfer fluid passing the tubular component 906. For example, the first and second further bracing structures 927A, 927B may act as flow straighteners to reduce swirl of the heat transfer fluid past the tubular component 906.

[0146] Further bracing structures such as the first and second further bracing structures 927A, 927B may be provided in a pressure vessel assembly 802 such as that described with reference to Figures 22 to 24. In such a pressure vessel assembly 802, the first opening 950A, 950B, second opening 952A, 952B, third opening 954A, 954B, and fourth opening 956A, 956B may not be present, and, rather than being connected to first, second, third and fourth elongate members 970A, 970B, 970C, 970D, the first and second further bracing structures 927A, 927B may be fixed to the interior of the housing 870.

[0147] Although it has been described that the first and second further bracing structures 927A, 927B are plates, it will be appreciated that the further bracing structures 927A, 927B may be any other suitable structure that couples the tubular component 906 to the bracing structure 964 at a position part way along the tubular component 906.

[0148] Figure 28A is a perspective view of an alternative tubular component 1006 of a pressure vessel assembly for a system for barocaloric cooling, heating or thermal storage, and Figure 28B is an exploded view of the alternative tubular component 1006. The alternative tubular component 1006 comprises a liner component 921, a plurality of cylindrical tube components1023A, 1023B, 1023C, 1023D, 1023E, 1023F, 1023G, 1023H, 10231, 1023J and a plurality of annular disc components 1025A, 1025B, 1025C, 1025D, 1025E, 1025F, 1025G, 1025H, 10251. The liner component 1021 defines the bore 1008 and is formed of a material having high thermal conductivity such as metal. Likewise, the plurality of annular disc components 1025A-I are formed of a material having high thermal conductivity such as metal. The cylindrical tube components 1023A-J have a high hoop strength compared to their axial strength and may be formed of sections of hoop-wound carbon fibre composite, for example. The cylindrical tube components 1023A-J are formed of one or more materials having a greater strength in a direction circumferential to the longitudinal axis 1062 than in a direction parallel to the longitudinal axis 1062 (i.e. a greater circumferential or hoop strength than axial strength). The ratio of the strengths of the one or more materials forming the cylindrical tube components 1023A-J in the direction circumferential to the longitudinal axis 1062 to the strength of the one or more materials forming the cylindrical tube components 1023A-J in the direction parallel to the longitudinal axis 1062 may be greater than 2, for example greater than 3, or greater than 4, or greater than 5

[0149] The cylindrical tube components 1023A-J extend around the liner component 1021. The inner profiles of the cylindrical tube components 1023A-J correspond to the outer profile of the liner component 1021 such that an outer surface of the liner component 1021 abuts against respective inner surfaces of the cylindrical tube components 1023A-J. Accordingly, the cylindrical tube components 1023A-J are able to resist circumferential expansion of the liner component 1021 due to hoop stresses in the liner component 1021. The cylindrical tube components 1023A-J are spaced apart along the liner component 1021 and separated by respective gaps within which the annular disc components 1025A-I are disposed.

[0150] The inner profiles of central holes in the annular disc components 1025A-I correspond to the outer profile of the liner component 1021 such that an outer surface of the liner component 1021 abuts against the annular disc components 1025A-I. Once assembled, the alternative tubular component 1006 may be treated to fill in any gaps between the assembled components and to fix the assembled components in position relative to each other. For example, the alternative tubular component 1006 may be cured in an oven (e.g. if the cylindrical tube components 1023A-J are formed of a pre-preg composite) or impregnated with resin. The thermal conductivity of the annular disc components 1025A-I and the thermal conductivity of the liner component 1021 are greater than the thermal conductivity of the one or more cylindrical tube components 1023A-J. The annular disc components 1025A-I transmit thermal energy between the liner component 1021 and the heat-transfer fluid that is external to the tubular component 1006.The alternative tubular component 1006 advantageously combines the high hoop strength of the cylindrical tube components 1023A-J with the high thermal conductivity of the liner component 1021 and the annular disc components 1025A-I, together with the high surface area of the annular disc components 1025A-I, which facilitates heat flow from the surface of the barocaloric material contained within the chamber of the liner component 1021 to the heat transfer fluid via the annular disc components 1025A-I, which function as cooling or heating fins.

[0151] The tubular components 106, 206, 306, 406, 506, 606, 706A-C, 806A-I, 906, 1006 may be formed of a fibre composite. The tubular components are formed of one or more materials having a greater strength in a direction circumferential to the longitudinal axis of the tubular component than in a direction parallel to the longitudinal axis (i.e. a greater circumferential or hoop strength than axial strength). The tubular components as a whole may have a greater strength in a direction circumferential to the longitudinal axis of the tubular component than in a direction parallel to the longitudinal axis. The strength may be an ultimate tensile strength or yield strength. The ratio of the strength of the one or more materials forming the tubular components in the direction circumferential to their respective longitudinal axes to the strength of the one or more materials forming the tubular component in the direction parallel to their respective longitudinal axis may be greater than 2, for example greater than 3, or greater than 4, or greater than 5. The hoop stress of a thin-walled cylinder is twice its axial stress. Accordingly, by forming the tubular components with a material having a ratio greater than 2, resistance to tensile failure in the circumferential mode (rather than the axial mode) may be increased.

[0152] The fibre composite may be a carbon fibre composite. Carbon fibre composites may be formed from materials having unidirectional fibres, for example uniaxial fibre pre-preg sheets. The wall of a tubular component entirely comprising a uniaxial carbon fibre composite, wound in the hoop direction, may have an ultimate tensile strength of approximately 2500 MPa. In comparison, the ultimate tensile strength of an equivalent tubular component comprising entirely structural steel may be approximately 600 MPa. Accordingly, on a like-for-like basis (in terms of the ratio of maximum operating hoop stress versus ultimate tensile strength), the wall of a tubular component comprising carbon fibre composite can be less than a quarter of the thickness of the steel pressure vessel wall. Further gains in terms of reduced wall thickness can be made if the tubular component comprising carbon fibre composite can safely be operated at a higher proportion of its ultimate tensile strength than would be the case for the equivalent tubular component comprising entirely structural steel, which may be the casedue to the different ratio of yield strength to ultimate tensile strength, and taking account of the different fatigue behaviour of the different materials. Furthermore, embodiments of the present invention comprising an external housing may provide burst protection which permits safe operation at a higher proportion of the tensile strength of the pressure vessel than would be possible without such an external housing.

[0153] Figure 29A is a perspective view of a first fabrication process 2000 for manufacturing any of the preceding tubular or cylindrical tube components. In the first fabrication process 2000, a uniaxial fibre pre-preg sheet 2002 is wrapped (i.e. wound or rolled) on a mandrel 2004, with the fibre orientation in the hoop direction. The pre-preg sheet 2002 may be wrapped on the mandrel 2004 in a single operation and in a single direction of rotation 2006 about the longitudinal axis 2062. Once the pre-preg sheet 2002 is wrapped on the mandrel 2004, it may be cured to produce tubular component that is subsequently removed from the mandrel 2004. Alternatively, such a tubular component may be manufactured using a carbon fibre tow that is layered onto the mandrel 2004 by a traversing system that enables layers at a small angle to the pure hoop direction to be built up sequentially. In such embodiments, the carbon fibre material may be concurrently or subsequently impregnated with resin and cured to produce the tubular component.

[0154] Figure 29B is a perspective view of a second fabrication process 3000 for manufacturing any of the preceding tubular or cylindrical tube components. In the second fabrication process 3000, a first uniaxial fibre pre-preg sheet 3002A and a second uniaxial fibre pre-preg sheet 3002B are wrapped at a shallow angle (e.g. 15°) with respect to the hoop direction. Such a configuration may provide the tubular component with a greater tensile strength in the hoop direction than the axial direction, but with more tensile strength in the axial direction than the tubular component formed using the fabrication process 2000 (e.g. in order to facilitate handling, removal of the finished tubular component after curing or to provide a moderate tensile strength in the axial direction so as to increase resistance to buckling failure under high pressure).

[0155] Figure 30A is a perspective view of a third fabrication process 4000 for manufacturing any of the preceding tubular or cylindrical tube components. In the third fabrication process 4000, an orientated material 4002, for example a high strength metal or engineering polymer sheet, foil or film, is wrapped on a mandrel (not shown) about the longitudinal axis 4062 of the tubular component in a single direction of rotation 4006. Prior to or during the abovementioned process, the oriented material 4002 is stretched in the hoop direction 4008 so as to increase its subsequent tensile strength in the hoop direction, whilst not requiring substantial tensilestrength in the axial direction. Successive layers of the oriented material 4002 may be bonded together by means of a suitable adhesive or bonding agent, for example epoxy resin.

[0156] Figure 30B is a perspective view of a fourth fabrication process 5000 for manufacturing any of the preceding tubular or cylindrical tube components. In the fourth fabrication process 5000, a pressure is applied internally to the tubular component 5010 in a radially outward direction 5012. This causes the tubular component 5010 to be uniaxially stretched, as graphically represented by arrows 5014 in Figure 30B, which provides the tubular component 5010 with a higher tensile strength in the hoop direction 5008. During the fourth fabrication process 5000, the openings at the end of the tubular component 5010 may be provided with end caps that are constrained in the axial direction so as to prevent the application of internal pressure to the tubular component 5010 resulting in the tubular component 5010 stretching in the axial direction.

[0157] Figure 31 is a cross-sectional view of a first tubular component 6006 in accordance with any of the preceding tubular or cylindrical tube components taken along a plane perpendicular to its longitudinal axis 6062 showing multiple layers of a hoop-wound, or largely hoop-wound, fibre composite material 6002.

[0158] Figure 32A is a cross-sectional view of a second tubular component 7006 in accordance with any of the preceding tubular or cylindrical tube components taken along a plane perpendicular to its longitudinal axis 7062 showing a hoop-wound tube 7002, with the addition of an inner layer 7014 and outer layer 7016 of unidirectional axially oriented fibres. The inner and outer layers 7014, 7016 of unidirectional axially oriented fibres provide additional tensile strength in the axial direction so as to facilitate handling and removal of the finished tube after curing, for example or to provide a moderate tensile strength in the axial direction so as to increase resistance to buckling failure under high pressure.

[0159] Figure 32B is a cross-sectional view of a third tubular component 8006 in accordance with any of the preceding tubular or cylindrical tube components taken along a plane perpendicular to its longitudinal axis 8062 showing a hoop-wound tube 8002 and a liner 8014 disposed within the hoop-wound tube 8002. The liner 8014 may be an impermeable continuous layer of material, for example a metallic or polymeric continuous tube, film, foil, sheet or coating applied to the inside of the hoop-wound tube 8002, so as to assist with sealing the hoopwound tube 8002 against hydrostatic pressure when pressurised from the inside and to help ensure that the resulting tubular component 8006 is leak-tight under pressure. High pressure fluids may otherwise find their way through microcracks in a composite and open them up.Additionally or alternatively, the liner 8014 may provide additional tensile strength in the axial direction so as to facilitate handling and removal of the tubular component 8006 after fabrication (e.g. removal from a mandrel). The liner 8014 may also facilitate sealing of the first and second sealing elements to the tubular component 8006.

[0160] Although it has been described that fibres are rolled onto a mandrel during the fabrication process, it will be appreciated that they could instead be fed on from the end of the mandrel, grown in situ, 3D printed or provided by any other mechanism that gives rise to a similar structure. Similarly orientated metal structures with high tensile strength in one orientation may likewise be arrived at by many different means.

[0161] High thermal conductivity resin or matrix materials may be incorporated in the composites of the tubular or cylindrical tube components to increase the thermal conductivity of the composite and facilitate heat transfer between the inside and outside of the pressure vessel. For example, high thermal conductivity fillers may be incorporated into the resin materials.

[0162] As mentioned above, the preceding tubular or cylindrical tube components have a greater tensile strength in the hoop direction than their axial tensile strength. The tubular or cylindrical tube components are formed of a material or materials that have a tensile strength in the hoop direction that is more than twice the tensile strength of the material or materials in the axial direction. The preceding tubular or cylindrical tube components may be formed of carbon fire or other high strength fibre materials. Additionally or alternatively to the use of ribbons, wires or other similar components may provide the tensile strength in the hoop direction. The construction and fibre layup for the tubular or cylindrical tube components described and shown herein may be simpler and cheaper than the more complex layups required for pressure vessels that must support the axial forces acting on their end caps or incorporate those end caps into their construction.

[0163] The third portions of the bracing structure (e.g. the elongate members 170A-D, 270A-D, 370A-B, 470A-B, 570A-B, 670A-B, 770A-B, 870, 970A-D or the housing 870) may be formed from steel. The housing 870 may alternatively be formed of extruded aluminium. The third portions of the bracing structure may alternatively be formed from pultruded fibre (e.g. glass or carbon fibre) rods or box-sections. In such embodiments, the fibres may be oriented parallel to the longitudinal axes of the tubular portion in order to provide maximum tensile strength in the direction of the longitudinal axis. It will be appreciated that other composite, metallic or other structures may be used within the scope of the present invention. It will be appreciated thatthe bracing structure 164 has a higher tensile strength in the axial direction than the tubular components.

[0164] Although it has been described that the first, second and third portions of the bracing structure are separate components that are connected together, one or more of the first, second and third portions of the bracing structure may form part of a single component.

[0165] Although it has been described that the elongate members are rods that are threadedly engaged with nuts so as to connect them to the first and second portions of the bracing structure, they may instead be glued to the second first portions of the bracing structure. The rods may be pultruded composite rods.

[0166] Although embodiments have been described in which the bracing structure is external to the bore of the tubular component, it will be appreciated that parts of the bracing structure may instead extend through the bore of the tubular component. For example, the one or more third portions of the bracing structure may extend in a longitudinal direction through the bore between the first and second portions of the bracing structure.

[0167] It will be appreciated that the above embodiments are merely exemplary, and different elements of each embodiment may be present in other embodiments. Merely by way of example, any of the pressure vessel assemblies described and shown herein may be provided with any of the sealing elements or bracing structures described or shown herein. Furthermore, each of the pressure vessel assemblies may have different numbers of components (e.g. tubular components, sealing elements, third portions of the bracing structure, etc.).

[0168] The method 1000 described above uses a conventional barocaloric material (i.e. a barocaloric material that reacts to an increase in pressure by releasing heat and reacts to a decrease in pressure by absorbing heat). However, it will be appreciated that an alternative method can instead be provided that uses an inverse barocaloric material (i.e. a barocaloric material that reacts to an increase in pressure by absorbing heat and reacts to a decrease in pressure by releasing heat). Such an alternative method generally corresponds to the method 1000 but involves increasing the pressure within the chamber in step S3 and reducing the pressure within the chamber in step S1.

[0169] For the avoidance of doubt, the present application extends to the subject-matter described in the following numbered paragraphs (referred to as “Para” or “Paras”):Para 1. A pressure vessel assembly for a system for barocaloric cooling, a system for barocaloric heating or a system for barocaloric thermal storage, the pressure vessel assembly comprising a tubular component and a sealing assembly,

[0170] wherein the tubular component comprises a bore that extends along a longitudinal axis of the tubular component between a first opening and a second opening and defines a chamber configured to receive a barocaloric material, wherein the tubular component is formed of one or more materials having a greater strength in a direction circumferential to the longitudinal axis than in a direction parallel to the longitudinal axis,

[0171] wherein the sealing assembly comprises a first sealing element that seals the first opening, a second sealing element that seals the second opening and a bracing structure that couples the first sealing element and the second sealing element and is configured to transmit a force between the first sealing element and the second sealing element not via the tubular component.

[0172] Para 2. A pressure vessel assembly as in Para 1, wherein the bracing structure comprises a first portion that extends radially with respect to the longitudinal axis, a second portion that extends radially with respect to the longitudinal axis and one or more third portions that extend parallel to the longitudinal axis between the first portion and the second portion.

[0173] Para 3. A pressure vessel assembly as in Para 2, wherein the first portion comprises one or more first recesses, wherein the first sealing element and / or the one or more further first sealing elements are located within a respective one of the one or more first recesses, wherein optionally the second portion comprises one or more second recesses, wherein the second sealing element and / or the one or more further second sealing elements are located within a respective one of the one or more second recesses.

[0174] Para 4. A pressure vessel assembly as in Para 2, wherein the first sealing element and / or the one or more further first sealing elements are integrally formed with the first portion and / or wherein the second sealing element and / or the one or more further second sealing elements are integrally formed with the second portion.

[0175] Para 5. A pressure vessel assembly as in any of Paras 2 to 4, wherein the pressure vessel assembly comprises one or more further tubular components, wherein each of the one or more further tubular components comprises a respective bore that extends between a respective further first opening and a respective further second opening and defines a respective chamber configured to receive a respective barocaloric material, wherein the sealingassembly comprises one or more further first sealing elements and one or more further second sealing elements, wherein each of the one or more further first sealing elements seals a respective one of the one or more further first openings, wherein each of the one or more further second sealing elements seals a respective one of the one or more further second openings.

[0176] Para 6. A pressure vessel assembly as in any of Paras 2 to 5, wherein each of the one or more third portions comprises a respective elongate member separated from the tubular component by a gap, wherein the elongate member is disposed external to the tubular component and does not enclose the tubular component.

[0177] Para 7. A pressure vessel assembly as in Para 6, wherein the one or more third portions of the bracing structure comprise a core and an external layer covering at least part of the core, wherein the core has a higher tensile strength than the external layer and the external layer has a lower thermal conductivity than the core.

[0178] Para 8. A pressure vessel assembly as in any of Paras 2 to 5, wherein each of the one or more third portions comprises a housing that extends between a third opening and a fourth opening and defines a further chamber within which the tubular component is disposed, wherein the first sealing element is connected to each of the one or more third portions to at least partially seal the third opening, wherein the second sealing element is connected to each of the one or more third portions to at least partially seal the fourth opening.

[0179] Para 9. A pressure vessel assembly as in Para 8, wherein each of the one or more third portions comprises an inlet opening for receiving a heat-transfer fluid from an exterior of the housing into the further chamber and an outlet opening for releasing the heat-transfer fluid from the further chamber to the exterior of the housing.

[0180] Para 10. A pressure vessel assembly as in Para 8, wherein the first portion comprises an inlet opening for receiving a heat-transfer fluid from an exterior of the housing into the further chamber, wherein the second portion comprises an outlet opening for releasing the heattransfer fluid from the further chamber to the exterior of the housing.

[0181] Para 11. A pressure vessel assembly as in any of Paras 7 to 10, wherein each of the one or more third portions comprises an internal layer and an external layer, wherein the internal layer is disposed between the external layer and the tubular component, wherein the external layerhas a higher tensile strength than the internal layer and the internal layer has a lower thermal conductivity than the external layer.

[0182] Para 12. A pressure vessel assembly as in any preceding Para, wherein one or more of the first sealing element, the one or more further first sealing elements, the second sealing element and the one or more further second sealing elements comprise a passageway configured to fluidical ly couple the chamber to a pressure modulating device.

[0183] Para 13. A pressure vessel assembly as in Para 12 when appended to Para 5, wherein the first portion comprises a manifold configured to fluidically couple the chamber of the tubular component and the chamber of the one or more further tubular components to the pressure modulating device.

[0184] Para 14. A pressure vessel assembly as in any preceding Para, wherein one or more of the first sealing element, the one or more further first sealing elements, the second sealing element and the one or more further second sealing elements comprises a plug configured to be received within the bore.

[0185] Para 15. A pressure vessel assembly as in any preceding Para, wherein one or more of the first sealing element, the one or more further first sealing elements, the second sealing element and the one or more further second sealing elements comprise a socket within which the tubular component is configured to be received.

[0186] Para 16. A pressure vessel assembly as in any preceding Para, wherein the tubular component comprises a liner component, one or more cylindrical tube components and one or more annular disc components, wherein the liner component defines the bore, wherein the one or more cylindrical tube components extend around the liner component and are configured to resist circumferential expansion of the liner component, wherein the one or more annular disc component are configured to transmit thermal energy between the liner component and a heat-transfer fluid external to the tubular component, wherein the thermal conductivity of the one or more annular disc components and the thermal conductivity of the liner component are greater than the thermal conductivity of the one or more cylindrical tube components.

[0187] Para 17. A pressure vessel assembly as in any preceding Para, comprising a further bracing structure, wherein the further bracing structure is configured to couple the tubular component to the bracing structure at a position part way along the tubular component.Para 18. A pressure vessel assembly as in any preceding Para, wherein the ratio of the strength of the one or more materials forming the tubular component in the direction circumferential to the longitudinal axis to the strength of the one or more materials forming the tubular component in the direction parallel to the longitudinal axis is greater than 2, for example greater than 3, or greater than 4, or greater than 5.

[0188] Para 19. A pressure vessel assembly as in any preceding Para, wherein the one or more materials comprise a plurality of fibres, strips or elements oriented substantially in the direction circumferential to the longitudinal axis, wherein the one or more materials comprise fewer or no fibres, strips or elements oriented substantially in the direction parallel to the longitudinal axis, wherein optionally the fibres are carbon fibres or glass fibres.

[0189] Para 20. A pressure vessel assembly as in any preceding Para, wherein the first sealing element and / or the second sealing element are fixedly connected to the tubular component.

[0190] Para 21. A pressure vessel assembly as in any preceding Para, wherein the first sealing element and / or the second sealing element are slidingly connected to the tubular component for movement in an axial direction.

[0191] Para 22. A system for barocaloric cooling, a system for barocaloric heating or a system for barocaloric thermal storage comprising a pressure vessel assembly as in any preceding Para. Para 23. A system for barocaloric cooling or a system for barocaloric heating, wherein the system for barocaloric cooling is a barocaloric refrigeration or air conditioning system, wherein the system for barocaloric heating is a barocaloric heat pump or water heater.

[0192] Para 24. A method of operating a system for barocaloric cooling or a system for barocaloric heating as in any preceding Para, wherein:

[0193] the barocaloric material is received in the chamber and is a conventional barocaloric material and the method comprises:

[0194] increasing the pressure within the chamber to cause the barocaloric material to release heat and / or increase in temperature, and conveying heat transfer fluid from a position in which the heat transfer fluid receives a portion of the heat released from the barocaloric material to a position in which an area to be heated receives the portion of heat from the heat transfer fluid; and / or

[0195] decreasing the pressure within the chamber and conveying heat transfer fluid from a position in which the barocaloric material receives heat from the heat transferfluid to a position in which the heat transfer fluid receives heat from an area to be cooled; or

[0196] the barocaloric material is received in the chamber and is an inverse barocaloric material and the method comprises:

[0197] increasing the pressure within the chamber and conveying heat transfer fluid from a position in which the barocaloric material receives heat from the heat transfer fluid to a position in which the heat transfer fluid receives heat from an area to be cooled; and / or

[0198] decreasing the pressure within the chamber to cause the barocaloric material to release heat and / or increase in temperature, and conveying heat transfer fluid from a position in which the heat transfer fluid receives a portion of the heat released from the barocaloric material to a position in which an area to be heated receives the portion of heat from the heat transfer fluid.

[0199] Para 25. A method of operating a system for barocaloric thermal storage as in any of Paras 1 to 23, wherein:

[0200] the barocaloric material is received in the chamber and is a conventional barocaloric material and the method comprises:

[0201] increasing the pressure within the chamber to an increased pressure to cause the barocaloric material to release heat and / or increase in temperature;

[0202] maintaining the pressure within the chamber at the increased pressure until a condition is met; and

[0203] upon the condition being met, decreasing the pressure within the chamber and conveying heat transfer fluid from a position in which the barocaloric material receives heat from the heat transfer fluid to a position in which the heat transfer fluid receives heat from an area to be cooled; or

[0204] the barocaloric material is received in the chamber and is an inverse barocaloric material and the method comprises:

[0205] increasing the pressure within the chamber to an increased pressure to cause the barocaloric material to receive heat and / or decrease in temperature;

[0206] maintaining the pressure within the chamber at the increased pressure until a condition is met; and

[0207] upon the condition being met, decreasing the pressure within the chamber to cause the barocaloric material to release heat and / or increase in temperature, and conveying heat transfer fluid from a position in which the heat transfer fluid receives a portion of the heat released from the barocaloric material to a position in which an area to be heated receives the portion of heat from the heat transfer fluid.

Claims

CLAIMS1. A system for barocaloric cooling, a system for barocaloric heating or a system for barocaloric thermal storage comprising a pressure vessel assembly, the pressure vessel assembly comprising a tubular component and a sealing assembly,wherein the tubular component comprises a bore that extends along a longitudinal axis of the tubular component between a first opening and a second opening and defines a chamber configured to receive a barocaloric material, wherein the tubular component is formed of one or more materials having a greater strength in a direction circumferential to the longitudinal axis than in a direction parallel to the longitudinal axis,wherein the sealing assembly comprises a first sealing element that seals the first opening, a second sealing element that seals the second opening and a bracing structure that couples the first sealing element and the second sealing element and is configured to transmit a force between the first sealing element and the second sealing element not via the tubular component.

2. A system for barocaloric cooling, a system for barocaloric heating or a system for barocaloric thermal storage as claimed in claim 1, wherein the bracing structure comprises a first portion that extends radially with respect to the longitudinal axis, a second portion that extends radially with respect to the longitudinal axis and one or more third portions that extend parallel to the longitudinal axis between the first portion and the second portion.

3. A system for barocaloric cooling, a system for barocaloric heating or a system for barocaloric thermal storage as claimed in claim 2, wherein the first portion comprises one or more first recesses, wherein the first sealing element and / or the one or more further first sealing elements are located within a respective one of the one or more first recesses, wherein optionally the second portion comprises one or more second recesses, wherein the second sealing element and / or the one or more further second sealing elements are located within a respective one of the one or more second recesses.

4. A system for barocaloric cooling, a system for barocaloric heating or a system for barocaloric thermal storage as claimed in claim 2, wherein the first sealing element and / or the one or more further first sealing elements are integrally formed with the first portion and / or wherein the second sealing element and / or the one or more further second sealing elements are integrally formed with the second portion.

5. A system for barocaloric cooling, a system for barocaloric heating or a system for barocaloric thermal storage as claimed in any of claims 2 to 4, wherein the pressure vessel assembly comprises one or more further tubular components, wherein each of the one or more further tubular components comprises a respective bore that extends between a respective further first opening and a respective further second opening and defines a respective chamber configured to receive a respective barocaloric material, wherein the sealing assembly comprises one or more further first sealing elements and one or more further second sealing elements, wherein each of the one or more further first sealing elements seals a respective one of the one or more further first openings, wherein each of the one or more further second sealing elements seals a respective one of the one or more further second openings.

6. A system for barocaloric cooling, a system for barocaloric heating or a system for barocaloric thermal storage as claimed in any of claims 2 to 5, wherein each of the one or more third portions comprises a respective elongate member separated from the tubular component by a gap, wherein the elongate member is disposed external to the tubular component and does not enclose the tubular component.

7. A system for barocaloric cooling, a system for barocaloric heating or a system for barocaloric thermal storage as claimed in claim 6, wherein the one or more third portions of the bracing structure comprise a core and an external layer covering at least part of the core, wherein the core has a higher tensile strength than the external layer and the external layer has a lower thermal conductivity than the core.

8. A system for barocaloric cooling, a system for barocaloric heating or a system for barocaloric thermal storage as claimed in claim 6, wherein the pressure vessel assembly comprises a housing within which the tubular component is disposed, wherein the one or more third portions are disposed external to the housing, wherein the housing comprises an inlet for receiving a heat-transfer fluid into the housing and an outlet for releasing the heat-transfer fluid from the housing, wherein an interior surface of the housing is spaced from the tubular component by a gap configured to receive the heat-transfer fluid, wherein the housing has a lower thermal conductivity than the one or more third portions.

9. A system for barocaloric cooling, a system for barocaloric heating or a system for barocaloric thermal storage as claimed in any of claims 2 to 5, wherein each of the one or more third portions comprises a housing that extends between a third opening and a fourth opening and defines a further chamber within which the tubular component is disposed,48wherein the first sealing element is connected to each of the one or more third portions to at least partially seal the third opening, wherein the second sealing element is connected to each of the one or more third portions to at least partially seal the fourth opening.

10. A system for barocaloric cooling, a system for barocaloric heating or a system for barocaloric thermal storage as claimed in claim 9, wherein each of the one or more third portions comprises an inlet opening for receiving a heat-transfer fluid from an exterior of the housing into the further chamber and an outlet opening for releasing the heat-transfer fluid from the further chamber to the exterior of the housing.

11. A system for barocaloric cooling, a system for barocaloric heating or a system for barocaloric thermal storage as claimed in claim 9, wherein the first portion comprises an inlet opening for receiving a heat-transfer fluid from an exterior of the housing into the further chamber, wherein the second portion comprises an outlet opening for releasing the heattransfer fluid from the further chamber to the exterior of the housing.

12. A system for barocaloric cooling, a system for barocaloric heating or a system for barocaloric thermal storage as claimed in any of claims 9 to 11, wherein each of the one or more third portions comprises an internal layer and an external layer, wherein the internal layer is disposed between the external layer and the tubular component, wherein the external layer has a higher tensile strength than the internal layer and the internal layer has a lower thermal conductivity than the external layer.

13. A system for barocaloric cooling, a system for barocaloric heating or a system for barocaloric thermal storage as claimed in any of claims 9 to 11, wherein the pressure vessel assembly comprises an insulating housing within which the tubular component is disposed, wherein the insulating housing is housed within the housing and occupies a majority of an internal void defined by the housing, wherein the insulating housing comprises an inlet for receiving a heat-transfer fluid into the insulating housing and an outlet for releasing the heattransfer fluid from the insulating housing, wherein an interior surface of the insulating housing is spaced from the tubular component by a gap configured to receive the heat-transfer fluid, wherein the insulating housing has a lower thermal conductivity than the housing.

14. A system for barocaloric cooling, a system for barocaloric heating or a system for barocaloric thermal storage as claimed in any preceding claim, wherein one or more of the first sealing element, the one or more further first sealing elements, the second sealingelement and the one or more further second sealing elements comprise a passageway configured to fluidically couple the chamber to a pressure modulating device.

15. A system for barocaloric cooling, a system for barocaloric heating or a system for barocaloric thermal storage as claimed in claim 14 when appended to claim 5, wherein the first portion comprises a manifold configured to fluidically couple the chamber of the tubular component and the chamber of the one or more further tubular components to the pressure modulating device.

16. A system for barocaloric cooling, a system for barocaloric heating or a system for barocaloric thermal storage as claimed in any preceding claim, wherein one or more of the first sealing element, the one or more further first sealing elements, the second sealing element and the one or more further second sealing elements comprises a plug configured to be received within the bore.

17. A system for barocaloric cooling, a system for barocaloric heating or a system for barocaloric thermal storage as claimed in any preceding claim, wherein one or more of the first sealing element, the one or more further first sealing elements, the second sealing element and the one or more further second sealing elements comprise a socket within which the tubular component is configured to be received.

18. A system for barocaloric cooling, a system for barocaloric heating or a system for barocaloric thermal storage as claimed in any preceding claim, wherein the tubular component comprises a liner component, one or more cylindrical tube components and one or more annular disc components, wherein the liner component defines the bore, wherein the one or more cylindrical tube components extend around the liner component and are configured to resist circumferential expansion of the liner component, wherein the one or more annular disc component are configured to transmit thermal energy between the liner component and a heat-transfer fluid external to the tubular component, wherein the thermal conductivity of the one or more annular disc components and the thermal conductivity of the liner component are greater than the thermal conductivity of the one or more cylindrical tube components.

19. A system for barocaloric cooling, a system for barocaloric heating or a system for barocaloric thermal storage as claimed in any preceding claim, wherein the pressure vessel assembly further comprises a further bracing structure, wherein the further bracing structure is configured to couple the tubular component to the bracing structure at a position part way along the tubular component.5020. A system for barocaloric cooling, a system for barocaloric heating or a system for barocaloric thermal storage as claimed in any preceding claim, wherein the ratio of the strength of the one or more materials forming the tubular component in the direction circumferential to the longitudinal axis to the strength of the one or more materials forming the tubular component in the direction parallel to the longitudinal axis is greater than 2, for example greater than 3, or greater than 4, or greater than 5.

21. A system for barocaloric cooling, a system for barocaloric heating or a system for barocaloric thermal storage as claimed in any preceding claim, wherein the one or more materials comprise a plurality of fibres, strips or elements oriented substantially in the direction circumferential to the longitudinal axis, wherein the one or more materials comprise fewer or no fibres, strips or elements oriented substantially in the direction parallel to the longitudinal axis, wherein optionally the fibres are carbon fibres or glass fibres.

22. A system for barocaloric cooling, a system for barocaloric heating or a system for barocaloric thermal storage as claimed in any preceding claim, wherein the first sealing element and / or the second sealing element are fixedly connected to the tubular component.

23. A system for barocaloric cooling, a system for barocaloric heating or a system for barocaloric thermal storage as claimed in any preceding claim, wherein the first sealing element and / or the second sealing element are slidingly connected to the tubular component for movement in an axial direction.

24. A system for barocaloric cooling or a system for barocaloric heating as claimed in any preceding claim, wherein the system for barocaloric cooling is a barocaloric refrigeration or air conditioning system, wherein the system for barocaloric heating is a barocaloric heat pump or water heater.

25. A method of operating a system for barocaloric cooling or a system for barocaloric heating as claimed in any preceding claim, wherein:the barocaloric material is received in the chamber and is a conventional barocaloric material and the method comprises:increasing the pressure within the chamber to cause the barocaloric material to release heat and / or increase in temperature, and conveying heat transfer fluid from a position in which the heat transfer fluid receives a portion of the heat released fromthe barocaloric material to a position in which an area to be heated receives the portion of heat from the heat transfer fluid; and / ordecreasing the pressure within the chamber and conveying heat transfer fluid from a position in which the barocaloric material receives heat from the heat transfer fluid to a position in which the heat transfer fluid receives heat from an area to be cooled; orthe barocaloric material is received in the chamber and is an inverse barocaloric material and the method comprises:increasing the pressure within the chamber and conveying heat transfer fluid from a position in which the barocaloric material receives heat from the heat transfer fluid to a position in which the heat transfer fluid receives heat from an area to be cooled; and / ordecreasing the pressure within the chamber to cause the barocaloric material to release heat and / or increase in temperature, and conveying heat transfer fluid from a position in which the heat transfer fluid receives a portion of the heat released from the barocaloric material to a position in which an area to be heated receives the portion of heat from the heat transfer fluid.

26. A method of operating a system for barocaloric thermal storage as claimed in any of claims 1 to 23, wherein:the barocaloric material is received in the chamber and is a conventional barocaloric material and the method comprises:increasing the pressure within the chamber to an increased pressure to cause the barocaloric material to release heat and / or increase in temperature;maintaining the pressure within the chamber at the increased pressure until a condition is met; andupon the condition being met, decreasing the pressure within the chamber and conveying heat transfer fluid from a position in which the barocaloric material receives heat from the heat transfer fluid to a position in which the heat transfer fluid receives heat from an area to be cooled; orthe barocaloric material is received in the chamber and is an inverse barocaloric material and the method comprises:increasing the pressure within the chamber to an increased pressure to cause the barocaloric material to receive heat and / or decrease in temperature;maintaining the pressure within the chamber at the increased pressure until a condition is met; andupon the condition being met, decreasing the pressure within the chamber to cause the barocaloric material to release heat and / or increase in temperature, and conveying heat transfer fluid from a position in which the heat transfer fluid receives a portion of the heat released from the barocaloric material to a position in which an area to be heated receives the portion of heat from the heat transfer fluid.53

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