GB2495938A - Energy storage apparatus - Google Patents

Abstract

A component / blister pack 6 for energy storage comprises a plurality of sealed capsules 8 arranged on a carrier 7, wherein at least one of the sealed capsules contains a phase change material (PCM). All or many of the capsules may contain a PCM and formed from a polymeric (PVC) or metallic (aluminium) material. The carrier may be a rigid or flexible sheet of polymeric (PVC) or metallic (aluminium) material and each capsule may be formed integrally from the carrier. The PCM may be an organic, inorganic or eutectic material and the PCM may be different in a first plurality of capsules to the PCM in a second plurality of capsules. Graphite, metal filings, fines or powder may be mixed with the PCM to increase heat transfer through each capsule. Uses include construction elements (figs 3 6) including plasterboard, building cladding, panels or tiles for ceilings or floors. Other uses are in garments. The PCM may be activated by a mechanical means and includes triggering by mechanical shock, ultrasound or a switch.

Description

ENERGY STORAGE

The present invention relates to energy storage and/or management, more particularly thermal energy storage and/or management. In particular, the invention relates to the use and application of phase change materials in energy storage and/or management.

The phase change process (e.g. liquid -solid) of a material is accompanied by the release or absorption of latent heat. \Iaterials which can be used for latent heat storage are known as phase change materials (PCMs). PCMs generally have the advantage over sensible storage media of relatively large heat storage densities and relatively constant charging/discharging temperatures. In practice, PCMs utilise the liquid <-> solid phase transition rather than the liquid -> gas phase transition, due to the difficulty in dealing with the large volume change associated with the latter.

Generally, it may be necessary to encapsulate a PCM for use, since the liquid phase Broadly, two principal means of encapsulation exist: microencapsulation and ntacroencapsulation. Microencapsulation refers to techniques in which [CM particles are sealed in small microcapsules each less than 1 mm in diameter.

Microencapsulated PCMs can exhibit improved heat transfer properties, due to the relatively large surface areas achieved (compared with volume/mass of [CM).

In one microencapsulation technique, paraffin (an organic PC.M) is dispersed in a polymeric, e.g. polyethylene, micro-network. This is achieved by preparing a liquid mixture of paraffin and polyethylene at a temperature above the melting point of polyethylene (e.g. 120°C). When the liquid mixture is cooled in a process similar to spray or extrusion, a polyethylene network forms to enclose the paraffin and produces a microencapsulated PC.M powder or fibre. A problem with this technique is its relative cost and complexity.

Macroencapsulation typically involves the PC.M being encapsulated in a unit usually larger than 1 cm in diameter. The PCM may be encapsulated in a package such as a tube, a pouch, a sphere or a panel. The packages may serve directly as heat exchangers or be incorporated in building products.

Attempts to incorporate PCMs directly into plasterboard have encountered problems with leaching. Leaching a potentially flammable material is not desirable.

It is a non-exclusive object of the invention to provide a method of encapsulating PCMs that has advantages over known techniques.

It is another non-exclusive object of the invention to provide a PCM-containing product that has advantages over known products.

A first aspect of the invention provides a component for an energy storage and/or management system comprising a plurality of scaled capsules arranged on or at least partially within a carrier, wherein at least one of the sealed capsules contains a phase change material.

In an embodiment, the component may comprise a blister pack.

In an embodiment, all of the scaled capsules may contain a phase change material.

Alternatively, one or more of the sealed capsules may contain other materials, which may be solid, liquid or gas. For instance, one or more of the sealed capsules may be adapted to provide thermal insulation and may contain a fluid, e.g. a gas such as air, a gel or foam, or an at least partial vacuum.

In an embodiment, the scaled capsules may be arranged in a repeating pattern in the plane of the carrier. Such a repeating pattern may comprise at least one row of sealed capsules and/or at least one column of sealed capsulcs. In embodiments in which the sealed capsules are arranged in a plurality of rows and a plurality of columns, the rows and columns may be orthogonal to one another. Alternatively, the sealed capsules in a given row may be offset from the sealed capsules in their neighbouring row(s).

The sealed capsules may be provided on a sheet, comprising the carrier.

The sealed capsules may be regularly spaced out across the carrier.

In an embodiment, a first one of the plurality of sealed capsules may contain a first phase change material and a second one of the plurality of scaled capsules may contain a second phase change material. Additionally, a third one of the plurality of sealed capsules may contain a third phase change material. Additionally, a fourth one of the plurality of sealed capsules may contain a fourth phase change material. In an embodiment, an nth one of the plurality of sealed capsules may contain an nth phase change material; n may be any number from one to the number of capsules arranged on or at least partially within the carrier.

In preferred embodiments, at least one of the capsules may contain a phase change material that is mixed with a thermal conduction-enhancing material, for example graphite or metal filings, fines or powder. Advantageously, this may increase heat transfer through the capsule.

The sealed capsules may have any shape.

In an embodiment, each one of the plurality of sealed capsules may have substantially the same volume as the others of the plurality of sealed capsules.

In an embodiment, the longest dimension of each of the sealed capsules in the plane of the carrier may be no more than 5 cm, preferably no more than 2 cm.

In an embodiment, the longest dimension of each of the sealed capsules in the plane of the carrier may be 1 mm or more, preferably 5 mm or more.

Preferably, each sealed capsule may be situated at least 2 mm away from its nearest neighbouring sealed capsule.

Each sealed capsule may be situated no more than 5 cm from its nearest neighbouring sealed capsule. Preferably, each sealed capsule may be situated no more than 2 cm from its nearest neighbouring sealed capsule.

The or each phase change material may have a latent heat of fusion of at least 140 kJ/mt Preferably, the or each phase change material may have a latent heat of fusion of at least 150 kJ/m5.

The or each phase change material may have a melting point of no more than 120°C.

Preferably, the or each phase change material may have a melting point of no more than 80°C. In an embodiment, the or each phase change material may have a melting point of from 15°C to 40°C..

Many phase change materials (PCMs) may be suitable. The particular phase change material or materials may be selected according to their suitability for a given application.

PCMs can be classified hito three types: organic, inorganic and eutcctic.

Organic PCMs include paraffin compounds and non-paraffin compounds. Organic PCMs may comprise an aliphatic compound or may comprise other organic compounds.

Paraffin is made up of straight chain hydrocarbons with 2-methyl branching groups near the end of the chains. The melting point of paraffin is directly related to the number of carbon atoms within the material structure. Alkanes containing between 14 and 40 carbon atoms have nielting points between 6°C and 80°C. Table I below lists the melting point and specific latent heat of fusion for a number of paraffin compounds.

Name No. of carbon Melting point Latent heat of fusion atoms (°C) (kJ/kg) n-tetradecane 14 4.5-5.6 231 n-pentadecane 15 10 207 n-hcxadecane 16 18.2 238 n-hcptadecane 17 22 215 n-ocladecane 18 28.2 245 n-nonadecane 19 31.9 222 n-eicosane 20 37 247 n-heneicosane 21 41 215 n-docosane 22 44 249 n-tricosane 23 47 234 n-tetracosane 24 51 255 n-pentacosane 25 54 238 Paraffin wax n.a. 32 251 n-hexacosane 26 56 257 n-heptacosane 27 59 236 n-octacosane 28 61 255 n-nonacosane 29 64 240 n-triacontane 30 65 252 n-tritricontane 33 71 189 Paraffin waxes typically contain carbon chains of 8-15 carbon atoms in lcngth. Such paraffin waxes may have melting points of from 2°C to 45°C.

Paraffin compounds may be especially suitable for use in residential heating applications.

Fatty acids, such as coco fatty acid, typically have similar melting points and latent heats of fusion to organic paraffin substances. CH3[CH2]2COOH is an example of a fatty acid that may be suitable.

Typically, inorganic PC.Ms comprise hydrated salt-based compounds. Salt hydrate PCMs may have latent heats of fusion of approximately 300 kJ/m3 and may have melting points from 0°C to 120°C. Accordingly, salt hydrate PCMs may be used in a range of thermal storage applications. Salt hydrate PCMs niay be particularly useful for domestic or residential heating applications, because there are many salt hydrate PCMs with melting points between 18.5°C and 36.4°C. Typically, a salt hydrate PCN'I may comprise M.nH2O where M is an inorganic compound with a high volumetric latent heat storage density. For exaniple, K2HPO4.6H20 has been found to be useful in air conditioning applications. Zn(N03)2.6H20 and Ca(N03).41120 have been found to be useful in space heating applications.

Eutectic PC.Ms may comprise organic-organic compounds, inorganic-inorganic compounds or inorganic-organic compounds.

The or each PCM may include a molecular alloy. By making alloys of molecular materials, it is possible to adjust the melting point over a range of temperatures. The molecular alloy may be a binary or multicomponent solid solution. The components of the binary or multicomponent solid solution may be organic compounds.

Alternatively, compositions of aluminium and silicon (Al-Si alloy) may be suitable.

Compositions of aluminium and silicon may have large latent heats of fusion and may have high thermal conduetivities.

The carrier may be rigid or flexible. For instance, the carrier may comprise a carrier shccl. Alternatively, the carrier may comprise a panel.

In an embodiment, the carrier may be made from a polymeric material, e.g. polyvinylchloride (PVC).

In an embodiment, the carrier may be made from a metallic material such as aluminium.

In an embodiment, at least part of each capsule may be formed integrally from the carrier. Alternatively, the carrier may be provided by a separate component, e.g. a part of a structural element such as a wall panel, floor tile or ceiling tile.

The capsules may be formed at least partially from a polymeric material, e.g. PVC., or a metallic material such as aluminium.

A second aspect of the invention provides a blister pack having a plurality of sealed capsules arranged on or at least partially within a carrier, wherein at least one of the sealed capsules contains a phase change material.

An aspect of the invention provides a construction element comprising at least one component according to the first aspect of the invention or at least one blister pack according to the second aspect of the invention. The construction element may comprise a panel, e.g. a plasterboard panel for a wall, cladding for a building, a panel for a ceiling or a panel for a floor.

An aspect of the invention provides an energy storage and/or management system comprising at least one component according to the first aspect of the invention or at least one blister pack according to the second aspect of the invention.

Another aspect of the invention provides a container, a garment or a building comprising a thermal energy storage and/or management system comprising at least one component according to the first aspect of the invention or at least one blister pack according to the second aspect of the invention.

Advantageously, such a container, garment or building may provide temperature regulation, even in places where there is no energy, e.g. clecticity, supply.

For instance, the container may comprise a storage container for perishable goods such as food, or for storing medicine. Alternatively, the container may comprise a sleeping bag.

A further aspect of the invention provides a method of manufacture comprising: (i) providing a carrier having a plurality of receptacles arranged thereon or at least partially therein; (ii) putting a phase change niaterial into one or more of the receptacles; and (iii) sealing the or each receptacle containing the phase change material, thereby creating one or more capsules containing phase change material.

A further aspect of the invention provides a method of manufacture comprising: (i) providing a plurality of capsules, in which a phase change material is sealed; and (H) fixing the capsules to a carrier.

Specific embodiments of thc invention will now be described by way of example only with reference to Ihe accompanying drawings, in which: Figure 1 illustrates in cross-section a manufacturing process according to the invention; Figure 2 shows a blister pack according to the invention; Figure 3 shows an example of a section of an external wall of a building with a sandwich panel according to the invention in charging mode; Figure 4 shows the section of the external wall of the building with the sandwich panel of Figure 3 in discharging mode; Figure 5 shows another example of a section of an external wall of a building with a sandwich panel according to the invention in charging mode; Figure 6 shows the section of the external wall of the building with the sandwich panel of Figure 4 in discharging mode; and Figure 7 shows a schematic plan view of a blister pack according to the invention.

Figure 1 shows a section of a carrier sheet 1 with three open receptacles 2, 2', 2" depending downwardly from the carrier sheet 1. The receptacles 2, 2', 2" each comprise a cylindrical portion and a concave base. The receptacles 2, 2', 2" are spaced apart from each other. The open receptacles 2, 2', 2" arc integral with the carrier sheet 1. The carrier sheet 1 may be made from a polymeric material, typically PVC, and the open receptacles 2, 2', 2" may be thermoformed in the carrier sheet 1.

Above the carrier sheet I there is a sheet of aluminium foil 3. Alternatively, this could be a sheet of a plastic material. An upper plate 4 and a lower plate 5 are provided which are operable to sandwich the sheet of aluminium foil 3 and the carrier sheet I. When heat (indicated by the wavy arrows in Figure 1) is applied to the upper plate 4, the sheet of aluminium foil 3 is sealed to the carrier sheet 1, thereby closing off the open receptacles 2, 2', 2".

In order to make a blister pack according to the invention, the open receptacles 2, 2', 2" are filled with a phase change material. Preferably, the phase change material will be mixed with metal or graphite fines or powder and poured in its liquid state into the open receptacles 2, 2', 2". Alternatively, solid tablets of the phase change material mixed with the metal or graphite fines or powder could be placed into the open receptacles 2, 2', 2". After the open receptacles 2, 2', 2" have had phase change material put into them, the sheet of aluminium foil 3 is scaled to the carrier sheet 1 as described above.

Figure 2 shows a blister pack 6 according to the invention. The blister pack 6 may have been manufactured as described above in relation to Figure 1. As can be seen in Figure 2, the blister pack comprises an array of 18 capsules 8 containing a PCM mixed with graphite powder on a carrier sheet 7. The capsules 8 are arranged in three rows of six. Each capsule 8 has a diameter of approximately 1 cm.

The applicant has tested several blister packs according to the invention by repeatedly putting them through the phase-change cycle by putting thcm in then removing them from hot water baths. No leakage of PCM into the water bath was observed in any of these tests.

Advantageously, the invention may make use of established manufacturing methods.

As a result it may be relatively, quick, easy and cost effective to manufacture components according to the invention. For instance, blister packs according to the invention may be produced using technology and techniques known from the general packaging industry and, in particular, from the packaging of pharmaceutical products.

Components, e.g. blister packs, may be made in a wide range of sizes. Larger areas may be covered by using a plurality of components. The components, e.g. blister packs, used to cover a particular area need not all be of the same size.

A further advantage of the components, e.g. blister packs, according to the invention is that they may be easily and safely cut to size. Ideally, cutting a component to size would be possible without cutting through any of the capsules. If, for a given application, this is not possible, then potential leakage and loss of PCM would be limited to those capsules that have been cut, since the capsules are not interconnected.

The fact that the capsules are not interconnected may also have further safety benefits, e.g. by reducing fire risk where organic PCMs are used.

Another advantage is that components with relatively flexible carriers, e.g. blister packs, may be bent in use, e.g. to fit into curved containers or around curved objects.

Accordingly, it will be appreciated that components according to the invention may be relatively safe, versatile, easy to use and relatively cheap to manufacture.

Figure 3 shows a section of an external wall 9 of a building, e.g. a house. The external wall 9 may be made from concrete or earth briquettes. On the inner side of the external wall 9 is a layer of insulation 10. The layer of insulation 10 may comprise polystyrene or some other organic insulating material. On the inner side of the layer of insulation 10 is a plasterboard panel 11 according to the invention. The plasterboard panel 11 may be made of gypsum and silica. Within the plasterboard panel II, there is a series of blister packs 12a, 12b, 12c. Each blister pack 12a, 12b, l2c comprises a carrier 13a, 13b, 13c and six rows of capsules 14a, 145, 14c containing PCM mixed with graphite powder.

In Figure 3, the blister packs 12a, 12b, 12c are shown in charging mode. The PCM is in the solid state and is absorbing heat (indicated by the wavy arrows) from the inside of the building. For instance, on sunny days heat may be absorbed from the inside of the building and stored in the PCM, thereby helping to regulate the temperature inside the building.

Figure 4 shows exactly the sanie arrangement as is shown iii Figure 3 with like features indicated by like reference nunierals, except that the blister packs 1 2a, I 2b, 12c are in discharging mode. The PCM is in the liquid state and is emitting heat into the inside of the building. For instance, at night heat that was absorbed during the day may be emitting back into the building, thereby minimising the tcniperature drop experienced by occupants of the building. Advantageously, the load on any heating system, e.g. central heating, in place in the building may be reduced.

Figure 5 shows a section of an external wall 9' of a building, e.g. a house. The external wall 9' may be made from concrete or earth briquettes. On the inner side of the external wall 9' is a layer of insulation 10'. The layer of insulation 10' may comprise a vacuum or an aerogel material. On the inner side of the layer of insulation 10' is a plasterboard panel II' according to the invention. The plasterboard panel 11' may be made of gypsum and silica. Within the plasterboard panel 11', there is a series of blister packs 12a', 12b', 12c'. Each blister pack 12a', 125', 12c' comprises a carrier 1 3a', 1 3b', 1 3c' and six rows of capsules 1 4a', 1 4b', I 4c' containing PCM mixed with graphite powder.

In Figure 5, the blister packs 12a', 12b', 12c' are shown in charging mode. Figure 6 shows exactly the same arrangement as is shown in Figure 5 with like features indicated by like reference numerals, except that the blister packs 12a', 12b', 12e' are in discharging mode.

Figure 7 shows a plan view of a blister pack 15 according to the invention. The aluminium or plastic sheet is not shown, so that the capsules can be seen. As shown in Figure 7, the blister pack 15 comprises a carrier 16 containing 25 capsules 17a-e, iSa-c, 19a-c, 20a-e, 21a-e. The capsules, which are square in shape, but could be any shape, are arranged in five rows. The first row contains capsules 17a, 17b, 17c, 17d and 17e. The second row is located below the first row and contains capsules ISa, 1 Sb, 1 Sc, 1 Sd and 1 Se. The third row is located below the second row and contains capsules 19a, 19b, 19c, 19d and 19e. The fourth row is located below the third row and contains capsules 20a, 20b, 20c, 20d and 20e. The fifth row is located below the fourth row and contains capsules 21a, 21b, 21c, 21d and 21c.

The capsules all contain a PCM mixed with graphite powder, in order to improve heat transfer. Typically, organic PCMs may also be mixed with silica in order to reduce fire risk. However, the PCM in the capsules of each row is different. In this case, the PCM in the first row of capsules has a lower melting point than the PCM in the second row, which in turn has a lower melting point than the PCM in the third row and so on.

By selecting different PCMs in different rows or other groups of capsules, it is possible to create a temperature cascade effect, in use, across at least part of the component, e.g. blister pack. The same effect can be achieved on scales larger than a single component, c.g. blister pack, by positioning components, e.g. blister packs containing different PCMs across an area, e.g. within a panel covering a wall. The temperature cascade effect can be used, for instance, within walls to manage the temperature within a room such that it is warmer towards the floor and cooler at head height and even cooler above head height. Such a temperature profile may be not only efficient, but may also have health benefits for the occupants of the room.

Alternatively, a temperature cascade effect could be achieved without using many differcnt PCMs or enhanced if different PCMs are used by varying the density of PCM within a given area of the component, e.g. blister pack or within a wider area encompassing a plurality of components. This could be achieved by varying the spacing between capsules containing PCM and/or the volume of the capsules containing PCM across a component andior from one component to the next.

Thin-walled, lightweight buildings can benefit from the use of PCMs. Such lightweight buildings may have many advantages, but a problem with them is that they can heat up very quickly on warm days, often leading to uncomfortable conditions inside. In comparison, buildings with very thick walls, e.g. churches and castles, remain relatively cool inside, even on hot days. This is because the large volume of masonry absorbs much of the heat -the building has a large thermal mass. PC.Ms can store from 5 to 14 times more heat per unit volume than sensible storage materials such as water, masonry or rock. Therefore, PCMs can be incorporated into thin, lightweight buildings to increase their thermal mass without greatly increasing their physical mass. Components according to the present invention may provide a way of doing this in a safe, reliable and cost effective way. For instance, the present invention may be much cheaper, less problematic and more versatile than encapsulating PCMs in building materials directly.

Moreover, while components according to the invention may be incorporated into new buildings, advantageously, they may also be retro-fitted to existing buildings and structures. Accordingly, components according to the invention may help to improve the energy efficiency and environmental performance of buildings.

The person skilled in the art will appreciate that he utility of the invention is not limited to buildings and construction. For instance, the invention may be useful in any application where it would be desirable to store waste or excess heat, in particular in fields where weight is an important consideration. For example, the invention may have utility in the automotive, aerospace, storage and logistics, electronics and computing industries.

It will also be appreciated that the PCM blisters may be activated by an activation means, for example a mechanical activation means. For example, PCM handwarmers arc known where recrystalisation of PCM/dissolved materials is triggered by a mechanical shock, which triggers nucleation sites. Ultrasound could be another activation means. We may provide a "switch" to cause the PC.M blisters/panels with PCM blisters to give out or take in heat, under user control: a controllable heat transfer apparatus.

Claims (1)

1. <claim-text>CLAIMS1. A component for an cncrgy storage and/or managcmcnt system comprising a plurality of scaled capsules arranged on or at least partially within a carrier, whcrcin at least one of the sealed capsules contains a phase change material.</claim-text> <claim-text>2. A component according to claim 1, wherein the componcnt comprises a blister p ac Ic.</claim-text> <claim-text>3. A component according to claim I or claim 2, in which all or many of thc sealed capsules contain a phase change material.</claim-text> <claim-text>4. A component according to claim 1 or claim 2 or claim 3, wherein the sealed capsules are provided on a shcct, comprising the carrier.</claim-text> <claim-text>5. A component according to any one of the preceding claims, wherein a first one of thc plurality of sealed capsules contains a first phase change material and a second onc of thc plurality of sealed capsulcs contains a second phasc changc material.</claim-text> <claim-text>6. A component according to any one of the preceding claims, wherein at least one of the capsulcs contains a phase changc material that is mixed with graphitc or metal filings, fincs or powder.</claim-text> <claim-text>7. A component according to any one of the preceding claims, in which each one of the plurality of scaled capsules has substantially the same volume as the others of the plurality of sealed capsules.</claim-text> <claim-text>8. A component according to any one of the preceding claims, wherein the longest dimension of each of the sealed capsules in the plane of the carrier is no more than 5 cm, preferably no more than 2 cm.</claim-text> <claim-text>9. A component according to any one of the preceding claims, wherein the longest dimension of each of the sealed capsules in the plane of the carrier is 1 mm or more, preferably 5 mm or more.</claim-text> <claim-text>10. A component according to any one of the preceding claims, in which each sealed capsule is situated at least 2 mm away from its nearest neighbouring scaled capsule.</claim-text> <claim-text>11. A component according to any one of the preceding claims, in which each sealcd capsule is situated no more than 5 cm from its nearest neighbouring sealed capsule 12. A component according to any one of the preceding claims, wherein the or each phase change material may have a latent heat of fusion of at least 140 Id/rn3.13. A component according to any one of the preceding claims, wherein the or each phase change material has a melting point of no more than 120°C.14. A component according to any one of the preceding claims, in which the or each phase change material has a melting point of from 15°C to 40°C.15. A component according to any one of the preceding claims, in which the or each phase change material is an organic phase change material, an inorganic phase change material or a eutectic phase change material.16. A component according to any one of the preceding claims, wherein the carrier is rigid or flexible.17. A component according to any one of thc preceding claims, wherein the carrier is made from a polymeric material, e.g. polyvinylchloride (PVC). or a metallic material such as aluminium..18. A component according to any one of the preceding claims, wherein at least part of each capsule is formed integrally from the carrier.19. A component according to any one of the preceding claims, in which the capsules is formed at least partially from a polymeric material, e.g. PVC, or a metallic material such as aluminium.20. A blister pack having a plurality of sealed capsules arranged on or at least partially within a carrier, wherein at least one of the sealed capsules contains a phase change material.21. A construction element comprising at least one component according to any one of claims I to 19 or at least one blister pack according to claim 20.22. A construction element according to claim 21, wherein the construction element comprises a panel, e.g. a plasterboard panel for a wall, cladding for a building, a panel or tile for a ceiling or a panel or tile for a tloor.23. An energy storage and/or management system comprising at least one component according to any one of claims I to 19 or at least one blister pack according to claim 20.24. A garment or a building comprising a thermal energy storage and/or management system comprising at least one component according to the first aspect of the invention or at least one blister pack according to the second aspect of the invention.25. A method of manufacture comprising: (i) providing a carrier having a plurality of receptacles arranged thereon or at least partially therein; (ii) putting a phase change material into one or more of the receptacles; and (iii) sealing the or each receptacle containing the phase change material, thereby creating one or more capsules containing phase change material.26. A method of manufacture comprising: (i) providing a plurality of capsules, in which a phase change material is sealed; and (H) fixing the capsules to a carrier.27. A component for an energy storage and/or management system substantially as described herein with reference to the accompanying drawings.28. A method of manufacture substantially as described herein.</claim-text>