Thermal energy storage device, composition and method therefor

Abstract

The present invention relates to the field of thermal energy storage devices comprising phase-change materials. The invention relates to a composition comprising a non-polymeric solid-solid phase-change material and a binder and to a capsule comprising said composition. The invention also relates to a method of preparation of said capsule, to the use of said capsule in thermal energy storage and to products comprising said capsule.

Description

[0001] THERMAL ENERGY STORAGE DEVICE, COMPOSITION AND METHOD THEREFOR

[0002] FIELD OF THE INVENTION

[0003]

[0001] The present invention relates to the field of thermal energy storage devices comprising phase-change materials. The invention relates to a composition comprising a non-polymeric solid-solid phase-change material and a binder and to a capsule comprising said composition. The invention also relates to a method of preparation of said capsule, to the use of said capsule in thermal energy storage and to products comprising said capsule.

[0004] BACKGROUND

[0005]

[0002] The storage of thermal energy (TES) is of utmost importance in a broad range of sectors where energy efficiency is required or heat needs to be dissipated. For instance, thermal energy storage devices can be found in electronic devices, where they are used to dissipate the heat generated by the components of the circuit or in solar plants, where the stored heat is used to produce electricity when the sun is not shining. TES devices can also be found in domestic heating systems, where they are used as hot water buffer supply. Industrial processes also have the potential of becoming more energy efficient thanks to the recovery of waste heat from a first process step, store and re-use of said heat in another process step decoupled in time from the first one. Amongst the available technologies for thermal energy storage, latent heat storage technologies based on Phase-Change Materials (PCMs) are particularly attractive for applications where thermal energy has to be stored or delivered over a narrow temperature range or when compactness is a requirement. Indeed, PCMs are capable of absorbing or releasing great amounts of energy in the form of latent heat during phase transitions at nearly constant temperature. They enable compact TES systems with higher volumetric storage capacitythan of other heat storage systems.

[0006]

[0003] Different types of PCMs are known in the art. When used, PCMs are typically contained in an enclosure that is generally made of a thermally conductive material. Said enclosure may for instance have the shape of a plate, a pouch, a sphere, a panel or a board. PCMs characterized for undergoing a solid-liquid phase transition have been described and are known in the art. These materials generally allow storing larger amounts of energy than PCMs based on solid-liquid phase transitions. In addition, solidliquid PCM typically undergo a substantial volume expansion or contraction upon transition of the phase, which generally leads to the mechanical failure of the capsule containing said PCM unless enough free space inside the capsule is ensured, resulting in less energy storage density. Additionally, the thermal conductivity of these solid-liquid PCMs decreases as a result of the segregation of eventual fillers during the liquid phase transitions with the corresponding flow of molten PCM. Typical solid-liquid PCM known in the art include for instance paraffin waxes, alkanes, fatty acids, fatty acid esters, fatty acid alcohols, alcohols, sugar alcohols, inorganic salts, poly(ethylene glycol).

[0007]

[0004] Also, solid-solid PCMs have been described and are known in the art. While such materials undergo solid-solid phase transitions, which generally are less energy demanding than solid-liquid transitions and thus do not allow storing as large amounts of energy, an advantage of these systems is the lesser extent of volume contraction / expansion upon phase transition, leading to a better preservation of the performance of the system over usage time, hence an extended useful lifetime. In addition, another advantage is the maintenance of the solid state beyond the PCM transition temperature, allowing the use of fillers without the risk of agglomerations or segregations as the phase transitions take place (the PCM does not become molten and does not flow).

[0008]

[0005] For instance, D. K. Benson and co-workers disclose in Materials Research for Passive Solar Systems: Solid-State Phase-Change Materials, 1985 (DOI: 10.2172 / 5923397) solid-solid PCMs based on unary or binary mixtures of pentaerythritol (PE), pentaglycerine (PG) or neopentyl-glycol (NPG). These three compounds absorb between 126 and 293 J / g during solid-state transformations at temperatures between 53 °C and 188°C (70 °C to 100 °C below their melting temperatures). Binary mixtures of these components can store between 84 and 293 J / g at phase-transition temperatures of between 25 °C and 188 °C. The authors further teach that the transition temperature may be adjusted by appropriate selection of the ratio of the components of said mixture. The authors are however silent about the use of a binder in said compositions.

[0009]

[0006] The use of additives in solid-solid PCMs to enhance the performance of these materials is known in the art. For instance, Venkitaraj and co-workers disclose in Thermochimica Acta 209, 680, 178343, a heat exchanger suitable for recovering the waste heat from exhaust gas in internal combustion engines comprising a solid-solid PCM that is a mixture of pentaerythritol (PE) with a metal having a low melting point such as indium in amounts of 0.1 wt % to 1 wt%. The addition of indium was shown to accelerate the charging and discharging of the TES instrument, with an improvement of the energy storage capacity, attributed to an increase of the thermal conductivity of the indium-doped PE. A similar system, based on pentaerythriol doped with alumina nanoparticles is disclosed in Venkitaraj et al. in Sustainable Cities and Societies 2019, 51 , 101767, Journal of Energy Storage 2019, 22, 8-16 and in Applied Thermal Engineering 2018, 137, 461. Adding alumina nanoparticles is shown to enhance the thermal conductivity of the PCM, which have beneficial effects on the performance of the solid-solid PCM.

[0010]

[0007] Patent application US 2013 / 0285233 A1 discloses a device for managing heat in integrated circuits which comprises a heat spreader that is in thermal contact with a PCM, which may be a solid-solid PCM, and is enclosed in a moulding compound. The function of the mould is to protect the PCM from the exterior. Suitable moulding compound materials are disclosed as being epoxy and / or resins. This material may be mixed with the PCM. The authors are however silent about the use of a binder in admixture with a solid-solid PCM.

[0011]

[0008] Patent application US 5,315,154 discloses a device for coupling to a heat sink in an electronic circuit comprising a solid-solid PCM that is in thermal contact with the heat sink and enclosed in a cover whose function is to avoid contact with moisture and humidity and may close the PCM in an airtight manner. The solid-solid PCM is a polyhydric alcohol, such as pentaerythritol, eventually doped with fillers to increase thermal conductivity of the PCM. The authors are however silent about the use of a binder in admixture with a solid-solid PCM.

[0012]

[0009] Patent application US 20210336303 A1 discloses a battery protection system which comprises an inorganic solid-solid phase-change material which may be in the form of a composite material with a thermally conductive filler or may comprise a binder. The inorganic solid-solid phase change material may be comprised inside the battery can. The authors are however silent about the identity and usefulness of said binder.

[0013]

[0010] Patent application CN 111 956033 A discloses a method of manufacture of a cup lid for cooling beverages which comprises forming a solid-solid phase change material into a cylinder, creating a tight fit with the cup lid inner liner and sealing the lid. The method for manufacturing involves pressing the solid-solid phase change material into a cylinder and bottom shape, which is then fitted onto the cup lid inner liner. The authors are however silent about the use of a solid-solid phase change material in combination with a binder.

[0014]

[0011] Patent application EP 3 760 689 A1 discloses compositions comprising a non polymeric solid-solid phase change material and a solid-liquid phase change material for thermal energy storage. In particular, compositions whereby the respective phase transition temperatures of the solid-solid phase change material and solid-liquid phase change material overlap, allowing for improving the heat capacity of the composite phase change material. This is due to the fact that the enthalpy of phase transition of the composite material encompasses both transitions of the solid-solid phase change material and solid-liquid phase change material. This application is however silent about the effect of using solid-liquid phase change materials which do not undergo phase transition in the same range of temperatures as the non-polymeric solid-solid phase change material.

[0015]

[0012] Liu Zheming et al. disclose in Solar Energy Materials and Solar Cells, 2015, vol. 147, 177-184 a polymeric solid-solid phase change polyurethane material prepared by coupling of polyethylene glycol chains with a castor oil skeleton and its use in thermal energy storage.

[0016]

[0013] Patent applicaton CN 109 715 892 A discloses a multi-layer thermal insulation material array designed for application to building structures comprising a flameretardant silicone foam polymer layer impregnated with a phase change material (PCM), enabling thermal energy storage through reversible solid-liquid transitions. The material array includes a pressure-sensitive adhesive layer that allows for simple installation by adhering the insulation directly to surfaces under ambient conditions. The PCM may be encapsulated in microbeads or supported in porous structures, such as silica, enhancing containment and performance stability.

[0017]

[0014] From what is disclosed in the art, it derives that there is still a need for improved compositions based on solid-solid phase-change materials for thermal energy storage and devices comprising them.

[0018] SUMMARY OF THE INVENTION

[0019]

[0015] After exhaustive research, the inventors have developed a composition suitable for thermal energy storage with improved properties. In particular, the inventors have found that the addition of a binder, such as an oil, a fatty acid, a fatty alcohol, a fatty acid ester or a mixture thereof to a non-polymeric solid-solid phase-change material allows increasing the core density of the PCM material, in a manner that more active material can be contained in the same volume, which results in an increased latent heat energy density and energy storage capacity. This effect is achieved when the solid-liquid transition temperature of the binder does not substantially overlap with the transition temperature range of the non-polymeric solid-solid PCM, i.e. when the enthalpy of transition of the composition comprising the binder, expressed in Joule per gram of the solid-solid phase change material in the composition and as measured in a DSC experiment, does not vary more than 5% of the enthalpy of transition of the solid-solid phase change material as measured in a DSC experiment. While it is taught in the prior art that a way to improve the storage capacity of solid-solid PCM materials is to blend them with good thermal conductors, such as metals, alumina and the like, the inventors have found that when solid-solid non-polymeric phase change materials are mixed with a binder such as an oil, a fatty acid, a fatty alcohol, a fatty acid ester or a mixture thereof, the core density and / or the energy storage capacity of the PCM is increased. This finding is particularly unexpected as the binders employed in the invention are poor heat conductors and do not qualify as thermally conductive fillers. In addition, while the addition of a non PCM material in the composition would be expected to reduce the portion of volume occupied by a PCM and thus, the heat storage capacity of the material, the inventors have surprisingly found that the addition of a binder allows increasing the content of the PCM comprised in a given volume, which results in an increased heat storage capacity. The inventors have also found that the presence of the binder does not substantially modify the solid-solid phase transition of the PCM, in particular in terms of temperature of phase transition and exchanged heat. Additionally, the binder was found to potentially delay the temperature of sublimation of the solid-solid phase changing material, which advantageously reduces or eliminates the development of internal partial pressures within the container wherein the PCM is confined.

[0020]

[0016] The composition of the invention is one wherein the binder does not undergo any phase transition at the temperature of transition of the non-polymeric solid-solid PCM and thus does not contribute to increasing the latent heat. The use of the binder however allows increasing the latent heat density and volumetric energy storage capacity of the composition by providing a more compact and dense PCM, thereby increasing core density and improving thermal conductivity without affecting the operational temperature of the phase transition. The presece of a binder in the composition thus ensures improved performance over time by preventing segregation and improving material stability during thermal cycling.

[0021]

[0017] The composition of the invention thus provides a compact, cost effective and reliable solution for storing thermal energy within a customizable temperature range, thanks to the careful selection of the solid-solid PCM. In particular, the composition of the invention is suitable for storing energy at a temperature of between 40 °C and 250 °C; more particularly of between 70 °C and 200 °C, even more particulary of between 80 °C and 190 °C. It was found that the use of a binder in the composition produces a more compact PCM material, which significantly reduces the presence of voids in the PCM material and prevents segregation of fillers. As a result, of this, when enclosed in a container or a capsule, the reduction of voids in the PCM material produces an improved thermal contact between the heat source and the phase change material, resulting in an improved heat transfer between the heat source and the PCM, and hence in an improved efficiency, combined with a greater energy density and higher amount of PCM per volumetric unit.

[0022]

[0018] The inventors have also developed a thermal energy storage device, also referred to herein as capsule, comprising the composition according to the invention. When sealed in a gastight manner, said capsule prevents the leakage of any eventual gas formed by sublimation of the PCM as a result of exposure to heat. Since the presence of the binder in the composition reduces the amount of voids in the material inside the capsule, high partial pressures develop when the PCM starts to sublimate thanks to the capsule being sealed in a gastight manner, said high pressures contributing in delaying the sublimation of the material, which advantageoulsy prevents the loss of the PCM material while preserving the internal structure of the PCM material. This leads to a more stable capsule for heat storage, said capsule having a longer useful lifetime.

[0023]

[0019] Thus, in a first aspect, the invention relates to a composition for storing thermal energy comprising a non-polymeric solid-solid phase change material and a binder that is selected from the group consisting of an oil, a fatty acid, a fatty acid ester, a fatty alcohol and a mixture thereof; wherein the binder and its relative amount are such that the temperature at which the composition starts the phase transition in a DSC experiment does not vary more than 15 °C of the temperature at which the solid-solid phase change material starts the phase transition in a DSC experiment and wherein the enthalpy of transition of the composition comprising the binder, expressed in Joule per gram of the solid-solid phase change material in the composition and as measured in a DSC experiment, does not vary more than 5% of the enthalpy of transition of the solid-solid phase change material as measured in a DSC experiment.

[0024]

[0020] A second aspect of the invention relates to a capsule for thermal energy storage enclosing a composition according to the first aspect of the invention in a gas-tight manner and comprising a sealant or a gasket arranged for sealing the capsule in a gastight manner, wherein the sealant is thermally resistant at the temperature of phase transition of the composition. In the context of the invention, the term “capsule” refers to a container, having any possible shape, such as a plate, a pouch, a sphere, a panel or a board. Said shape and morphology of the capsule can be adapted to the targeted use of the capsule in a thermal energy storage of the application in order to optimize the thermal contact between the heat source and the surface of the capsule using common general knowledge.

[0025]

[0021] The third aspect of the invention relates to a method of preparation of a capsule according to the second aspect of the invention comprising the steps of:

[0026] (i) providing a composition as defined in the first aspect of the invention;

[0027] (ii) providing a capsule enclosure for thermal energy storage;

[0028] (iii) arranging the composition provided in (i) within the capsule enclosure provided in (ii) so that the composition provided in (i) and the capsule enclosure provided in (ii) are in thermal contact and

[0029] (iv) sealing the capsule enclosing the composition resulting from step (iii) in a gas-tight manner by the means of a sealant or a gasket, wherein the sealant is as defined in the second aspect of the invention.

[0030]

[0022] A fourth aspect of the invention relates to the use of a composition according to the first aspect of the invention or of a capsule according to the second aspect of the invention, in thermal energy storage, preferably in industry or domestic heat supply installations, electronics, power electronics, solar energy, batteries, buildings, waste heat recovery, air-conditioning, temperature-adaptable greenhouses and textiles.

[0031]

[0023] The fifth aspect of the invention relates to a product of manufacture, an electronic device, a solar energy system device, an energy storage device, a computer, a medical device, a storage unit, a building or building material, a container, an insulation or construction material, an automotive material, a vehicle, a boat, an airplane, a weapon or weapon system, industrial machinery, a pharmaceutical or a drug or a food package or storage device or container, a textile, a clothing or an apparel, footwear, a bedding or bedding system, a flame retardant material, comprising a capsule according to the second aspect of the invention.

[0032] BRIEF DESCRIPTION OF THE DRAWINGS

[0033]

[0024] Fig. 1 shows the onset and offset solid-solid transition temperatures as measured by Differential Scanning Calorimetry of mixtures of pentaerythritol (PE) with pentaglycerin (PG) as a function of the molar fraction of PE in said mixture upon heating (top) and cooling (bottom) of said mixture.

[0034]

[0025] Fig. 2 shows the heat flow, expressed in W / g, as measured by Differential Scanning Calorimetry, as a function of temperature of a composition according to Example 1 comprising a solid-solid PCM consisting of a mixture of PE:PG and a binder (dark grey cruve and dashed line) and of a similar composition deprived of the binder (light gray and plain line).

[0035]

[0026] Fig. 3 shows the thermogravimetric analysis of the composition according to Example 1 , the dashed line representing the evolution of mass over a period of time during which temperature is modified between 120 °C and 200 °C, as shown by the plain line.

[0036]

[0027] Fig. 4 shows photographs of capsules A, B and C according to Example 2 after treatment at 195 °C during 5 days.

[0037]

[0028] Fig. 5 shows (a) the evolution of the core density, expressed in grams per cm3of the composition according to Example 1 as a function of the content of binder in said composition; and (b) the evolution of the latent heat energy density, expressed in MJ / m3as a function of the content of binder in said composition.

[0038]

[0029] Fig. 6 shows the ratio of the volume energy storage capacity of a packed based system comprising a capsule comprising pentaerythritol (PE) and a binder according to Example 2 compared to the volume energy storage capacity of a hot water tank (dashed line) or a thermal oil tank (plain line) as a function of the difference of temperature between the entrance and the exit of the tank.

[0030] Fig. 7 shows the ratio of the volume energy storage capacity of a packed based system comprising a capsule comprising a mixture of pentaerythritol (PE), pentaglycerine and a binder according to Example 2 compared to the volume energy storage capacity of a hot water tank (dashed line) or a thermal oil tank (plain line) as a function of the difference of temperature between the entrance and the exit of the tank.

[0039]

[0031] Fig. 8 shows the ratio of the volume energy storage capacity of a packed based system comprising a capsule comprising pentaglycerine (PG) and a binder according to Example 2 compared to the volume energy storage capacity of a hot water tank (dashed line) or a thermal oil tank (plain line) as a function of the difference of temperature between the entrance and the exit of the tank.

[0040]

[0032] Fig. 9 shows the thermogravimetric analysis of the composition according to Example 3, the dashed line representing the evolution of temperature over a period of time during which temperature is modified between 30 °C and 85 °C, as shown by the plain line, the black plain line representing the evolution of the mass of the composition over time in the absence of lauric acid and the grey plain line representing the evolution of the mass of the composition over time in the presence of lauric acid.

[0041]

[0033] Fig. 10 shows (a) the evolution of the core density, expressed in grams per cm3of the composition according to Example 5 comprising PG as a function of the content of binder in said composition; and (b) the evolution of the latent heat energy density, expressed in MJ / m3as a function of the content of binder in said composition.

[0042]

[0034] Fig. 11 shows (a) the evolution of the core density, expressed in grams per cm3of the composition according to Example 5 comprising PE as a function of the content of binder in said composition; and (b) the evolution of the latent heat energy density, expressed in MJ / m3as a function of the content of binder in said composition.

[0043] DETAILED DESCRIPTION

[0044]

[0035] All terms as used herein in this application, unless otherwise stated, shall be understood in their ordinary meaning as known in the art. Other more specific definitions for certain terms as used in the present application are as set forth below and are intended to apply uniformly throughout the specification and claims unless an otherwise expressly set out definition provides a broader definition.

[0045]

[0036] For the purposes of the invention, any ranges given include both the lower and the upper end-points of the range. Ranges given, such as temperatures, times, molar ratio, volume ratio and the like, should be considered approximate (i.e. with a 5% margin of variation around indicated point), unless specifically stated.

[0046]

[0037] In the context of the present invention, the term “solid-solid phase change material” refers to a solid material having at least two solid phases such that the transition between both phases occur within a temperature range. Examples of solid-solid phase change material are known in the art and include among others, inorganic salts, metals, and organic compounds that exhibit polymorphism or crystal structure transitions at specific temperature ranges, such as plastic crystals.

[0047]

[0038] In the context of the present invention, the term “plastic crystal” refers to a solid material comprising weakly interacting molecules that possess some orientational or conformational degree of freedom while maintaining a solid phase. Examples of plastic crystals suitable as phase-change materials are known in the art and include, among others, neopentylglcyol (2,2-Dimethyl-1 ,3-propanediol), pentaglycerine (1 ,1 ,1- tris(hydroxymethyl)ethane), pentaerythritol (2,2-bis(hydroxymethyl)-1 ,3-propanediol), 2- amino-2-methyl-1 ,3-propanediol, tris(hydroxymethyl)aminomethane, 2-methyl-2-nitro-1- propanol and 2-nitro-2-methyl-1 ,3-propanediol.

[0048]

[0039] In the context of the present invention, when referring to a substance, the term “non-polymeric” refers to the fact that said substance does not comprise the repetition of at least 10 occurrences of a molecular motif comprising at least two carbon atoms in its molecular formula. In particular, the term “non-polymeric”, when referring to a substance, refers to a molecule of molecular weight lower than 1500 g / mol, preferably lower than 1000 g / mol, more preferably lower than 500 g / mol.

[0049]

[0040] In the context of the present invention, the term “binder” refers to a substance suitable for forming a composite structure with the solid-solid phase change material and hold the particles of said material together. As mentioned herein, suitable binders in the context of the invention include an oil, a fatty acid, a fatty acid ester, a fatty alcohol and a mixture thereof. The binder is such that it has a solid-liquid phase transition temperature that does not overlap with the temperature of the solid-solid phase transition of the non-polymeric PCM. In particular, the difference between the phase-change temperature of the solid-solid PCM and the phase-change temperature of the binder is more than 5 °C; preferably more than 10 °C; more preferably more than 20 °C.

[0050]

[0041] In the context of the present invention, the term “oil” refers to a non-polar liquid rich in hydrocarbons. An oil may be of vegetal origin, including for instance, sunflower oil, avocado oil, nut oil, rapeseed oil, soybean oil, canola oil, coconut oil, corn oil, cottonseed oil, flaxseed oil, grapeseed oil, safflower oil, olive oil, palm oil peanut oil, rice bran oil, and sesame oil. An oil may also be an essential oil or a mineral oil. It is preferred in the context of the invention that the oil is a vegetal or a mineral oil; more preferably a vegetal oil.

[0051]

[0042] As used herein, the term "fatty acid", employed alone or in combination with other terms, refers to an aliphatic acid that is saturated or unsaturated. In some embodiments, the fatty acid is a mixture of different fatty acids. In some embodiments, the fatty acid has between about eight to about thirty carbons on average. In some embodiments, the fatty acid has about eight to about twenty-four carbons on average. In some embodiments, the fatty acid has about twelve to about eighteen carbons on average. Suitable fatty acids include, but are not limited to, stearic acid, lauric acid, myristic acid, erucic acid, palmitic acid, palmitoleic acid, capric acid, caprylic acid, oleic acid, linoleic acid, linolenic acid, hydroxy stearic acid, 12-hydroxystearic acid, cetostearic acid, isostearic acid, sesquioleic acid, sesqui-9-octadecanoic acid, sesquiisooctadecanoic acid, benhenic acid, isobehenic acid, and arachidonic acid, or mixtures thereof.

[0052]

[0043] As used herein, the term "fatty acid ester" refers to a compound formed between a fatty acid and a hydroxyl containing compound. In some embodiments, the fatty acid ester is a sugar ester of fatty acid. In some embodiments, the fatty acid ester is a glyceride of fatty acid as defined above. Such glyceride may be a monoglyceride, a diglyceride or a triglyceride. In some embodiments, the fatty acid ester is an ethoxylated fatty acid ester.

[0053]

[0044] As used herein, the term "fatty alcohol", employed alone or in combination with other terms, refers to an aliphatic alcohol that is saturated or unsaturated. In some embodiments, the fatty alcohol is a mixture of different fatty alcohols. In some embodiments, the fatty alcohol has between about eight to about thirty carbons on average. In some embodiments, the fatty alcohol has about eight to about twenty-four carbons on average. In some embodiments, the fatty alcohol has about twelve to about eighteen carbons on average. Suitable fatty alcohols include, but are not limited to, stearyl alcohol, lauryl alcohol, palmityl alcohol, palmitolyl acid, cetyl alcohol, capryl alcohol, caprylyl alcohol, oleyl alcohol, linolenyl alcohol, arachidonic alcohol, behenyl alcohol, isobehenyl alcohol, selachyl alcohol, chimyl alcohol, and linoleyl alcohol, or mixtures thereof.

[0054]

[0045] In the context of the present invention, the term “capsule for thermal energy storage” refers to a thermal energy storage device enclosing a substance suitable for the storage of energy inside a shell. The material of the shell must be thermally conductive enough to promote effective thermal contact between the heat source and the substance in charge of storing thermal energy. Suitable examples of materials forming the shell of the capsule are known in the art and include metals, such as brass, aluminium or steel, ceramics, such as alumina, silica and zirconia and polymers. The size and shape of the capsule may be tailored in function of the application for which the capsule is targeted in order to ensure the optimal contact surface area between the heat source and the capsule.

[0055]

[0046] As defined above, a first aspect of the invention relates to a composition for storing thermal energy comprising a non-polymeric solid-solid phase change material and a binder that is selected from the group consisting of an oil, a fatty acid, a fatty acid ester, a fatty alcohol and a mixture thereof; wherein the binder and its relative amount are such that the temperature at which the composition starts the phase transition in a DSC experiment does not vary more than 15 °C of the temperature at which the solidsolid phase change material starts the phase transition in a DSC experiment and wherein the enthalpy of transition of the composition comprising the binder, expressed in Joule per gram of the solid-solid phase change material in the composition and as measured in a DSC experiment, does not vary more than 5% of the enthalpy of transition of the solid-solid phase change material as measured in a DSC experiment.

[0056]

[0047] In a particular embodiment of the first aspect of the invention, the solid-solid PCM can be thought of as a “non-polymeric” compound, wherein the term “non-polymeric” is to be interpreted as a molecule that has no repeating monomers in its structure, preferably a molecule of molecular weight lower than 1500 g / mol, lower than 1000 g / mol, preferably lower than 500 g / mol.

[0057]

[0048] In a particular embodiment of the first aspect of the invention, the solid-solid PCM is a molecule of molecular weight lower than 1500 g / mol. When more than one solidsolid phase-change materials is present, preferably each of said solid-solid phasechange materials must comply with the embodiments disclosed herein.

[0058] The molecular weight values disclosed in the description are to be interpreted as being obtainable from size exclusion chromatography.

[0059]

[0049] In a particular embodiment of the first aspect of the invention, the solid-solid PCM is a plastic crystal.

[0060]

[0050] The skilled person readily understands that a solid-solid PCM can also undergo melting or degradation if the temperature is sufficiently high. However, in the present invention, the solid-solid PCM is selected so that it only undergoes solid-solid transitions within the working temperature ranges. In other words, the solid-solid PCM does not undergo solid-liquid transitions nor does it suffer thermal degradation within the temperature ranges it is intended to be worked at. Said temperature range will depend on the targeted application, but typically ranges from between 40 °C and 250 °C; more particularly from between 70 °C and 200 °C; even more particularly from between 80 °C and 190 °C.

[0061]

[0051] Any non-polymeric solid-solid PCM which undergoes solid-solid phase transitions should in principle be eligible for application in the composition of the first aspect of the invention. Notwithstanding, the solid-solid PCM is preferably selected from those that have high transition enthalpies and have adjustable transition temperatures. Adjustable transition temperatures of solid-solid PCMs may be achieved when the PCM is a binary mixture of solid-solid PCMs by varying the composition of said binary mixture.

[0062]

[0052] Other desirable properties of the solid-solid PCM are high values of heat capacity; high density; resistance to oxidation, preferably from container materials; non-toxicity; non-flammability; or low volumetric changes during phase transition.

[0063]

[0053] In a particular embodiment, the latent heat of phase transition of the solid-solid PCM is above 100 J / g, preferably above 150 J / g, more preferably above 200 J / g, and can be as high as 300 J / g. Preferably, it is comprised between 100 and 300 J / g.

[0064]

[0054] The solid-solid phase change material of the composition of the first aspect of the invention may be selected on the basis of its enthalpy of phase transition (the greater the transition enthalpy of the solid-solid phase change material, the greater its thermal storage capacity) and the possibility to tune its transition temperature by forming mixtures with other solid-solid phase change transfer materials. This is of particular interest for thermal energy storage devices.

[0065]

[0055] In a particular embodiment, the solid-solid PCM has a phase-change temperature comprised between 40 °C and 250°C, more preferably of between 60 °C and 200°C, even more preferably between 80 °C and 190 °C. In another particular embodiment, the non-polymeric solid-solid phase has a phase change temperature of between 40 °C to 190 °C.

[0066]

[0056] Non-limiting exemplary solid-solid PCMs suitable for the present invention are:

[0067] Alcohols, including alcohol derivatives of 2,2-dimethylpropane (Neopentane, C(CH3)4), such as pentaerythritol (PE), pentaglycerine (also known as trimethylolethane, PG) and neopentylglycol (NPG);

[0068] Amino-compounds, including amine derivatives of 2,2-dimethylpropane and of alcohol derivatives thereof, such as 2-amino-2-methyl-1 ,3-propanediol (AMPL) and T ris(hydroxymethyl)aminomethane (TAM),

[0069] Nitro-compounds, such as Nitroisobutylglycol (NMPD) and 1 ,3-Dinitro-1 ,3- diazacycloheptane,

[0070] Nitro-aromatic compounds, such as octadecyl 2,4,6-trinitrobenzoate,

[0071] Cyclic ether compounds, such as 1 ,4-dioxane,

[0072] Anhydrides, such as cis-cyclohexane-1 ,2-dicarboxylic anhydride,

[0073] Long-chain compounds, such as dihexadecylhydroxy arsine oxide, N,N,N- Trimethyl-1-hexadecanaminium chloride, undecanoic acid, tricosane, 1 -Docosanol, 4, 4'- (1 ,3-Butadinyl-1 ,3-diyl)bis(4,1-phenylenedodecanoate),bis(dodecylammonium) tetrachloromanganate (II), lead(ll) pentadecanoate, bis(hexadecylammonium) tetrachloroferrate(ll), or bis(tetradecylammonium) tetrachlorozincate,

[0074] Amide compounds, such as N,N'-Dibutylurea,

[0075] Quaternary ammonium compounds, such as tetrapentylammonium thiocyanate, tetrapentylammonium nitrate or heptyltrihexylammonium iodide,

[0076] Organometallic compounds, including alkylammonium compounds of general formula (CnH2n+iNH3)2MX4, where M is a metal atom, X is a halogen atom and n is an integer from 1 to 17; and bis(dodecylammonium) tetrachloromanganate (II), lead(ll) pentadecanoate, bis(hexadecylammonium) tetrachloroferrate(ll), or bis(tetradecylammonium) tetrachlorozincate, and mixtures thereof.

[0077]

[0057] In a particular embodiment, the solid-solid PCMs are selected from alcohol and amine derivatives of 2,2-dimethylpropane (Neopentane, C(CH3)4) and mixtures thereof. Such compounds undergo solid-solid phase transitions from layered or chained low temperature structures (tetragonal, monoclinic, etc.) to high temperature homogeneous face centered cubic crystals (plastic phase).

[0078]

[0058] Alcohol and amine derivatives of 2,2-dimethylpropane (Neopentane, C(CH3)4) refer to compounds resulting from the substitution of at least one hydrogen and / or methyl group in 2,2-dimethylpropane by OH and / or NH2.

[0079]

[0059] In a particular embodiment of the first aspect of the invention, the alcohol derivative of 2,2-dimethylpropane is a compound resulting from the substitution of at least one hydrogen, preferably at least two hydrogens, in 2,2-dimethylpropane by OH, such as pentaerythritol, pentaglycerine, neopentylglycol and mixtures thereof.

[0080]

[0060] In an embodiment, the amine derivative of 2,2-dimethylpropane is a compound resulting from the substitution of one methyl group in 2,2-dimethylpropane or in an alcohol derivative of 2,2-dimethylpropane as defined above by NH2, such as 2-amino-2- methyl-1 ,3-propanediol, tris(hydroxyl methyl)aminomethane and mixtures thereof.

[0081]

[0061] Therefore, in a more particular embodiment, the solid-solid PCM is selected from the group consisting of pentaerythritol, pentaglycerine, neopentylglycol, 2-amino-2- methyl-1 ,3-propanediol, tris(hydroxyl methyl)aminomethane and mixtures thereof. Preferably, the solid-solid PCM is selected from pentaerythritol (PE), pentaglycerine (PG), Neopentylglycol (NPG) and mixtures thereof.

[0082]

[0062] The solid-solid phase transition in these organic compounds takes place at temperatures between 48°C and 188°C and is characterized by an unusually large enthalpy of transition, ranging from 110 J.g-1to 290 J.g-1(Sarier, N. and Onder, E., Organic phase-change materials and their textile applications: An overview. Thermochimica Acta, 2012, 540, 7-60). Moreover, binary and ternary mixtures of these compounds often allow obtaining new solid-solid PCMs with "tailor made" energy storage properties.

[0083]

[0063] Therefore, in a particular embodiment, the solid-solid PCM is a unary, binary or ternary mixture of solid-solid PCMs. More preferably, it is a binary mixture, wherein the phase change temperature can advantageously be adjusted as it depends, among others, on the relative amount of each solid-solid PCM. This embodiment simplifies the purpose of providing an adjustable temperature PCM since by simply tuning the ratios of each solid-solid PCM, the temperature at which the final solid-solid PCM undergoes phase transition will vary.

[0084]

[0064] Indeed, the isomorphism between the crystalline structures of some of the polyalcohols makes the existence of solid solutions possible at all proportions or over wide composition ranges.

[0085]

[0065] In a particular embodiment of the first aspect of the invention, the solid-solid phase change material is a mixture of pentaerythritol (PE) and pentaglycerin (PG). The solid-solid phase transitions of each material take place respectively at about 80 °C (PG) and about 190 °C (PE). Said temperature can be measured by Differential Scanning Calorimetry upon heating the phase change material. Thus, the phase transition temperature, as shown in Figure 1 , is adjustable by varying the composition of said binary mixture. For operating temperatures of between 110 °C and 200 °C, a composition wherein the molar fraction of pentaerythritol in such binary mixture is higher than 0.5 is preferred. Similarly, for operating temperatures of between 80 °C and 110 °C, a composition wherein the molar fraction of pentaerythritol in such binary mixture is lower than 0.5 is preferred.

[0086]

[0066] In a more particular embodiment of the first aspect of the invention, the solid-solid phase change material is a mixture of pentaeryhtritol and pentaglycerin wherein the molar fraction of pentaerythritol is of between 0.60 and 0.80; more particularly, it is of about 0.71.

[0087]

[0067] As mentioned above, the composition of the first aspect of the invention comprises a binder. The main function of the binder in the context of the invention is to maintain together the particles of the phase change material, thus producing a material that is more compact than the solid-solid phase change material. Without being bound to theory, it is believed that the more compact character of the composition of the first aspect of the invention promotes an enhanced thermal contact between the solid-solid phase change material particles together with an increased density of the solid-solid phase change material, thus improving the heat transfer capacity of the whole composition, which provides a faster charging and discharging of thermal energy as well as an increase in the energy storage capacity attributed to an increased apparent density of the solid-solid phase change material.

[0088]

[0068] In a particular embodiment, the binder of the composition of the first aspect of the invention does not substantially affect the temperature and heat requirements of the phase transition of the solid-solid phase change material. Both temperature and heat requirements of the phase transition of the solid-solid phase change material can be herein determined by Differential Scanning Microscopy (DSC) by measuring (i) the temperature at which the composition starts the phase transition and (ii) the energy exchanged during the phase transition upon heating the composition of the first aspect of the invention at a temperature equal to or above the temperature of the phase transition. In the context of the invention, the temperature of the solid-solid phase transition is said to be not “substantially affected” when the temperature at which the composition comprising the binder starts the phase transition in a DSC experiment does not vary more than 15 °C; preferably not more than 10 °C and even more preferably, not more than 5 °C, of the temperature at which the solid-solid phase change material starts the phase transition in a DSC experiment. Similarly, the heat requirements of the solidsolid phase transition, i.e. the heat exchanged during the phase transition, are said to be not “substantially affected” when the enthalpy of transition of the composition comprising the binder, expressed in Joule per gram of the solid-solid phase change material in the composition and as measured in a DSC experiment, does not vary more than 5%; preferably not more than 3% and even more preferably, not more than 2%, of the enthalpy of transition of the solid-solid phase change material as measured in a DSC experiment.

[0089]

[0069] In a preferred embodiment, the binder is characterized for having a solid-liquid phase transition temperature of between - 80 °C and 10 °C.

[0090]

[0070] In a particular embodiment, the binder of the composition of the first aspect of the invention is an oil. Any oil may be used in the context of the invention, provided that the addition of the oil does not substantially affect the temperature and heat requirements of the solid-solid phase transition of the solid-solid phase change material. Said oil may be mineral, vegetal or essential but is preferably a vegetal oil.

[0091]

[0071] In a more particular embodiment, the binder of the composition of the first aspect of the invention is selected from the group consisting of sunflower oil, avocado oil, nut oil, rapeseed oil, soybean oil, canola oil, coconut oil, corn oil, cottonseed oil, flaxseed oil, grapeseed oil, safflower oil, olive oil, palm oil peanut oil, rice bran oil, and sesame oil.

[0092]

[0072] In an even more particular embodiment, the binder of the composition of the first aspect of the invention is sunflower oil.

[0093]

[0073] In a further embodiment, the binder of the composition of the first aspect of the invention is a mineral oil. Said mineral oil typically comprises one or more of linear saturated hydrocarbons, aromatic hydrocarbons and cyclic saturated hydrocarbons. The skilled person will be able to identify suitable linear saturated hydrocarbons, aromatic hydrocarbons and cyclic saturated hydrocarbons for forming a mineral oil with the desired properties of viscosity and wetting. Typical hydrocarbon components for mineral oils comprise at least 6 carbon atoms in their molecular formula; preferably from 6 to 24.

[0074] In a further embodiment, the binder of the composition of the first aspect of the invention is an essential oil. The skilled person will be able to identify suitable essential oil for forming a composition according to the first aspect of the invention.

[0094]

[0075] In a further embodiment, the binder of the composition of the first aspect of the invention is selected from a fatty acid, a fatty alcohol, a fatty ester and mixtures thereof.

[0076] In said embodiment, the fatty acids comprised in the binder or the fatty acids from which fatty esters and alcohols derive have from 8 to 30 carbon atoms, preferably from 8 to 24 carbon atoms, more preferably from 12 to 18 carbon atoms, in their molecular formula.

[0095]

[0077] In said embodiment, said fatty acid is selected from the group consisting of stearic acid, lauric acid, myristic acid, erucic acid, palmitic acid, palmitoleic acid, capric acid, caprylic acid, oleic acid, linoleic acid, linolenic acid, hydroxystearic acid, 12- hydroxystearic acid, cetostearic acid, isostearic acid, sesquioleic acid, sesqui-9- octadecanoic acid, sesquiisooctadecanoic acid, benhenic acid, isobehenic acid, and arachidonic acid, and mixtures thereof.

[0096]

[0078] In said embodiment, fatty acid esters are preferably glyceride esters comprising from one to three ester groups formed with a fatty acid as defined above, i.e. a monoglyceride, a diglyceride or a triglyceride. In said embodiment, the fatty acid is particularly selected from the group consisting of linoleic acid triglyceride, oleic acid triglyceride, palmitic acid triglyceride, stearic acid triglyceride and mixtures thereof.

[0097]

[0079] In another particular embodiment of the invention, the fatty acid is lauric acid. Such binders having a functional group suitable for forming non-covalent interactions, such as hydrogen bonds, with the solid-solid phase change material advantageously delay the sublimation of the solid-solid phase change material, thus increasing the stability of the composition and preventing the formation of voids within the mixture as the result of the sublimation of the PCM. This is for instance the case when the solidsolid phase change material comprises one or more OH groups and the binder comprises at least one COOH group, as is the case of fatty acids.

[0098]

[0080] In a further embodiment, the composition of the first aspect of the invention comprises the binder in an amount of up to 25% in weight; preferably up to 20% in weight, of the composition.

[0099]

[0081] In a further embodiment, the composition of the first aspect of the invention comprises the binder in an amount of at least 3% in weight; more particularly of at least 5% in weight, 6% in weight, 7% in weight, 8% in weight, 9% in weight or 10% in weight of the composition.

[0100]

[0082] In a further embodiment, the composition of the first aspect of the invention is one wherein the binder is in an amount of between 5% and 25% in weight of the composition; preferably of between 3% and 20% in weight of the composition. This is particularly the case when the binder is sunflower oil or is selected from the group consisting of linoleic acid triglyceride, oleic acid triglyceride, palmitic acid triglyceride, stearic acid triglyceride and mixtures thereof. The inventors have found that this amount of binder provides an improved latent energy density.

[0101]

[0083] The optimal amount of binder in the composition of the first aspect of the invention may vary in function of the type of the binder and / or the type of solid-solid phase change material employed. Said optimal amount may be determined according to a method comprising the preparation of compositions having variable amounts of binder and / or PCM and determining the latent heat energy density of each composition according to a method as described herein; the composition having the highest latent heat energy density being the one having the optimal amount of binder.

[0102]

[0084] In a further embodiment, the composition of the first aspect of the invention is one wherein:

[0103] - the solid-solid PCM is selected from the group consisting of pentaerythritol, pentaglycerine, neopentylglycol, 2-amino-2-methyl-1 ,3-propanediol, tris(hydroxyl methyl)aminomethane and mixtures thereof; preferably, the solid-solid PCM is selected from pentaerythritol, pentaglycerine, neopentylglycol, and mixtures thereof; more preferably, the solid-solid PCM is selected from pentaerythritol, pentaglycerine and mixtures thereof;

[0104] - the binder is a vegetal oil that is selected from the group consisting of sunflower oil, avocado oil, nut oil, rapeseed oil, soybean oil, canola oil, coconut oil, corn oil, cottonseed oil, flaxseed oil, grapeseed oil, safflower oil, olive oil, palm oil peanut oil, rice bran oil, and sesame oil; or, alternatively; the binder is a fatty ester or a mixture thereof; preferably, the binder is a vegetal oil selected from the group consisting of sunflower oil, corn oil, cottonseed oil, soybean oil, canola oil and safflower oil; or, alternatively, the binder is a fatty ester or a mixture thereof wherein the fatty acid forming said ester is selected from the group consisting of stearic acid, lauric acid, myristic acid, erucic acid, palmitic acid, palmitoleic acid, capric acid, caprylic acid, oleic acid, linoleic acid, linolenic acid, hydroxystearic acid, 12-hydroxystearic acid, cetostearic acid, isostearic acid, sesquioleic acid, sesqui-9-octadecanoic acid, sesquiisooctadecanoic acid, benhenic acid, isobehenic acid, and arachidonic acid; more preferably, the binder is sunflower oil; or; alternatively, the binder is selected from the group consisting of linoleic acid triglyceride, oleic acid triglyceride, palmitic acid triglyceride, stearic acid triglyceride and mixtures thereof; and wherein, preferably,

[0105] - the binder is in an amount of up to 25% in weight; preferably, the binder is in amount of between 5% and 20% in weight of the composition.

[0106]

[0085] In a further embodiment, the composition of the first aspect of the invention is one wherein:

[0107] - the solid-solid phase change material is a mixture of pentaerythritol (PE) and pentaglycerin (PG) wherein the molar fraction of pentaerythritol is preferably of between 0.60 and 0.80; more preferably, it is of about 0.71 ;

[0108] - the binder is sunflower oil and is present in an amount of between 5% in weight of the composition and 20% in weight of the composition; preferably of between 10% in weight and 20% in weight of the composition.

[0086] In a further embodiment, the composition of the first aspect of the invention is one wherein:

[0109] - the solid-solid phase change material is pentaerythritol (PE);

[0110] - the binder is sunflower oil and is present in an amount of between 3% in weight of the composition and 20% in weight of the composition; preferably of between 10% in weight and 20% in weight of the composition.

[0111]

[0087] In a further embodiment, , the composition of the first aspect of the invention is one wherein:

[0112] - the solid-solid phase change material is pentaglycerine (PG);

[0113] - the binder is sunflower oil and is present in an amount of between 3% in weight of the composition and 20% in weight of the composition; preferably of between 3% in weight and 10% in weight of the composition.

[0114]

[0088] In a further embodiment, the composition of the further aspect of the invention further comprises a thermally conductive filler, e.g. in the forms of particles. Suitable thermally conductive fillers for this purpose are known in the art and will become apparent to the skilled person upon reduction to practice of the invention. Those include, among others, carbonaceous materials such as carbon black, carbon nanotubes, graphite, graphene, carbon fibers, metal powders and ceramics.

[0115]

[0089] A method for the preparation of a composition of the first aspect of the invention also forms part of the invention. Said method comprises the step of mixing, preferably at room temperature, the solid-solid phase change material and the binder. Said mixing step is preferably carried out by mechanical mixing, more preferably by ball milling.

[0116]

[0090] As mentioned above, a second aspect of the invention relates to a capsule for thermal energy storage enclosing a composition according to the first aspect of the invention in a gas-tight manner and comprising a sealant or a gasket arranged for sealing the capsule in a gas-tight manner, wherein the sealant is thermally resistant at the temperature of phase transition of the composition.

[0117]

[0091] As will be obvious to the skilled person, said capsule comprises a thermally conductive shell which encloses the composition according to the first aspect of the invention. Said shell is arranged for being in thermal contact with the composition of the first aspect of the invention and for being in thermal contact with a heat source when used in thermal storage.

[0118]

[0092] In certain embodiments, the shell is arranged for being in thermal contact with the largest possible portion of the composition enclosed in said shell.

[0119]

[0093] Suitable materials for forming a shell are known in the art and will become apparent to the skilled person on the basis of common general knowledge in the field upon reduction to practice of the invention. These materials include, among others, metals, such as aluminium and steel, ceramics such as alumina, silica and zirconia and polymers. Preferably the material for forming the shell of the capsule of the second aspect of the invention is a metal such as brass or steel. Any metal or metal alloy known in the art for forming a shell of capsule for thermal energy storage may be used.

[0120]

[0094] In particular embodiments, the thermally conductive shell of said capsule is made of brass.

[0121]

[0095] In particular embodiments of the second aspect of the invention, the composition enclosed in said capsule is as defined in any of the embodiments defined above for the first aspect of the invention.

[0122]

[0096] An essential feature of the capsule of the second aspect of the invention is that the composition of the first aspect of the invention is enclosed in a gas-tight manner. The inventors have found that this prevents the loss by sublimation of the solid-solid phase change material during the exposure of the capsule to the heat source. Without being bound to any theory, it is believed that the sealed capsule, when exposed to a heat source, allows the development of internal partial pressures high enough to prevent the sublimation of the solid-solid phase change material. In turn, it is believed that this internal partial pressure prevents the formation of voids within the capsule related to the loss of the solid-solid PCM by sublimation, thus providing for an optimal thermal contact between the particles of the solid-solid phase change material. In addition, it is believed that the development of internal pressure within the capsule allows for a denser active phase of the solid-solid phase change material, also contributing to the thermal contact between the particles of the solid-solid phase change material. This improved density of material is believed to contribute to a higher latent energy density capacity of the capsule.

[0097] Any method known in the art for the provision of a gas-tight enclosure may be employed provided that it is compatible with the components of the capsule, in particular, the shell and the composition according to the first aspect of the invention. These methods include, among others, mechanical sealing, heat sealing, chemical sealing, compression sealing, welding and cold sealing. In particular embodiments, the capsule encloses the composition of the first aspect of the invention in a gastight manner by the means of a sealant and mechanical sealing. The sealant must be flexible enough to resist the volume contractions of the capsule container and content when exposed to different conditions of temperature.

[0123]

[0098] Thus, in particular embodiments, the capsule of the second aspect of the invention further comprises a sealant or gasket. Said sealant must be arranged so that it seals the capsule in a gas-tight manner. It is preferred that the sealant is thermally resistant to the temperatures at which the capsule is exposed when used in thermal energy storage, particularly at the temperature of phase transition of the composition of the first aspect of the invention. Suitable chemical sealants are known in the art and will become apparent to the skilled person on the basis of common general knowledge upon reduction to practice of the invention. Those include, among others, silicones, epoxy resins, polyurethane sealants, (cyano)acryclic sealants, phenolic sealants and polyimide sealants.

[0124]

[0099] In a particular embodiment, the capsule of the second aspect of the invention further comprises a sealant that is silicone.

[0125]

[0100] The second aspect of the invention relates in certain embodiments to a capsule comprising a combination of (i) any of the shell materials described herein, (ii) any of the sealants described herein with (iii) any of the compositions defined in the embodiments defining the composition of the first aspect of the invention defined above.

[0126]

[0101] As defined above, a third aspect of the invention relates to a method of preparation of a capsule according to the second aspect of the invention comprising the steps of:

[0127] (i) providing a composition as defined in the first aspect of the invention;

[0128] (ii) providing a capsule enclosure for thermal energy storage;

[0129] (iii) arranging the composition provided in (i) within the capsule enclosure provided in (ii) so that the composition provided in (i) and the capsule enclosure provided in (ii) are in thermal contact and

[0130] (iv) sealing the capsule enclosing the composition resulting from step (iii) in a gas-tight manner by the means of a sealant or a gasket, wherein the sealant is as defined in any embodiment of the second aspect of the invention defining the sealant.

[0131]

[0102] Step (i) of the first aspect of the invention preferably comprises the step of mixing, preferably at room temperature, the solid-solid phase change material and the binder. Said mixing step is particularly carried out by mechanical mixing. In particular embodiments, the composition of step (i) is as defined in any of the embodiments described above for the first aspect of the invention.

[0132]

[0103] The capsule enclosure for thermal energy storage of step (ii) is preferably the shell of the capsule as defined above in any of the embodiments of the second aspect of the invention.

[0133]

[0104] Step (iii) is preferably carried out by substantially filling the capsule enclosure provided in (ii) with the composition provided in (i). Alternatively, the composition provided in (i) may be fitted within the enclosure provided in (ii). Said filling step may further comprise a compression step. This compression step allows reducing the voids between the particles of the solid-solid phase change material and the voids between surface of the capsule enclosure and the composition of the first aspect of the invention. The inventors have particularly found that the use of a binder in the composition of the solid-solid phase change material allows carrying out this step at reduced pressures of compression with no prejudice to the energy storage capacity of the solid-solid phase change material.

[0105] Step (iv) of the method of the first aspect of the invention may be carried out according to any method known in the art for the provision of a gastight enclosure provided that it is compatible with the components of the capsule, in particular, the shell and the composition according to the first aspect of the invention. These methods will become apparent to the skilled person on the basis of common general knowledge upon reduction to practice of the invention. These methods include, among others, mechanical sealing, heat sealing, chemical sealing, compression sealing and cold sealing.

[0134]

[0106] Preferably, step (iv) comprises arranging a chemical sealant on the capsule enclosure for providing a gastight enclosure. As mentioned above, suitable chemical sealants are known in the art and will become apparent to the skilled person on the basis of common general knowledge upon reduction to practice of the invention. Those include, among others, silicones, epoxy resins, polyurethane sealants, (cyano)acryclic sealants, phenolic sealants and polyimide sealants. Preferably, step (iv) comprises arranging a silicone sealant on the capsule enclosure for providing a gastight enclosure.

[0135]

[0107] Alternatively, step (iv) comprises arranging a gasket capsule enclosure for providing a gastight enclosure. Suitable material for forming gaskets are known in the art and will become apparent to the skilled person on the basis of common general knowledge upon reduction to practice of the invention. Those include, among others, rubber, metals and fluorinated polymers, such as polytetrafluoroethylene (Teflon®).

[0136]

[0108] As mentioned above, the fourth aspect of the invention relates to the use of a composition according to the first aspect of the invention or of a capsule according to the second aspect of the invention, in thermal energy storage, preferably in electronics, power electronics, solar energy, batteries, buildings, waste heat recovery, air- conditioning, temperature-adaptable greenhouses and textiles.

[0137]

[0109] In particular embodiments, the fourth aspect of the invention relates to the use of a composition as defined in any of the embodiments described above for the first aspect of the invention in thermal energy storage, preferably in electronics, power electronics, solar energy, batteries, buildings, waste heat recovery, air-conditioning, temperature- adaptable greenhouses and textiles.

[0138]

[0110] In further particular embodiments, the fourth aspect of the invention relates to the use of a capsule as defined in any of the embodiments described above for the second aspect of the invention in thermal energy storage, preferably in industry or domestic heat supply installations, electronics, power electronics, solar energy, batteries, buildings, waste heat recovery, air-conditioning, temperature-adaptable greenhouses and textiles.

[0139]

[0111] Said use also relates to a method for the storage of thermal energy which comprises the step of arranging a composition according to the first aspect of the invention or a capsule according to the second aspect of the invention in thermal contact with a heat source. Depending on the targeted use of the composition and capsule of the invention, said heat source may vary. For instance, said heat source may be waste energy resulting from electronic circuits, power electronics, industrial processes, air- conditioning or may be originated by light irradiation (e.g. solar irradiation). The heat source and the thermal energy storage product are preferably arranged to ensure the maximal thermal contact possible between the heat source and the composition according to the first aspect of the invention or the capsule according to the second aspect of the invention.

[0140]

[0112] As a result, the composition and capsule may be included in a broad range of products for a large scope of applications, as defined above.

[0141]

[0113] Thus, the fifth aspect of the invention relates to a product of manufacture, an electronic device, a solar energy system device, an energy storage device, a computer, a medical device, a storage unit, a building or building material, a container, an insulation or construction material, an automotive material, a vehicle, a boat, an airplane, a weapon or weapon system, industrial machinery, a pharmaceutical or a drug or a food package or storage device or container, a textile, a clothing or an apparel, footwear, a bedding or bedding system, a flame retardant material, comprising a capsule according to the second aspect of the invention.

[0142]

[0114] Throughout the description and claims the word “comprises" and variations of the word, are not intended to exclude other technical features, additives, components or steps. Furthermore, the word “comprise” encompasses the cases of “consist of” and “consists essentially of”. Additional objects, advantages and features of the invention will become apparent to those skilled in the art upon examination of the description or may be learned by practice of the invention. The following examples are provided by way of illustration, and they are not intended to be limiting of the present invention.

[0143] EXAMPLES

[0144] Abbreviations

[0145] PE: pentaerythritol

[0146] PG: pentaglycerine

[0147] NPG: Neopentylgylcol

[0148] DSC: Differential Scanning Calorimetry

[0149] TGA: thermal gravimetry analysis

[0150]

[0115] In the following examples, 1 ,1 ,1-tris(hydroxymethyl)ethane (Pentaglycerine) and 2,2-bis(hydroxymethyl)-1 ,3-propanediol (Pentaerythritol) were both supplied by Sigma- Aldrich and used as solid-solid PCM. The binder is a commercially refined sunflower oil. The used confinement element are metal cans made of brass from the canning industry, provided by Envases Ballujera S.L. (Spain), with an inner diameter of 98.6 mm and an inner height of 21 mm. 2,2-dimethyl-1 ,3-propanediol (Neopentylglycol or NPG, provided by Sigma-Aldrich) was used as PCM for evaluating the sublimation behaviour in combination with a lauric acid (Dodecanoic acid), provided by Sigma-Aldrich.

[0151] General Procedures

[0152]

[0116] Differential Scanning Calorimetry (DSC) was used to evaluate the thermal properties (latent heat and transition temperatures) of the prepared systems with and without the presence of the binder (for comparative purposes). With this aim, the samples were subjected to a heating / cooling cycle between 120 to 200 °C at 5 °C / min. Three cycles were carried out in total. Results showed herein correspond to the third cycle. A power-compensation DSC Q2500 from TA Instruments was employed with sealed aluminum crucibles. The mass of the samples was ca. 9 mg. Argon (50 ml / min) was employed as purge gas. The accuracy in the determination of transition temperatures is about ± 0.5 °C, whereas that of the enthalpies of phase transition is ± 5%.

[0153]

[0117] Thermogravimetric analysis (TGA) was used to determine the thermal stability of the compounds in a Netzsch ASCII instrument. The sample (10 to 20 mg) was placed in an open alumina crucible under N2 atmosphere (60 ml / min) and heated from 130 °C to 200 °C in 10 °C steps (for PE and / or PG based systems) or from 30 °C to 85 °C (for NPG based systems), keeping an isotherm temperature for 15 minutes in each step.

[0154] Example 1 : Preparation of a composition based on a binary mixture of PE and PG with a binder

[0155] Procedure A (analytical scale)’. For a molar fraction of PE corresponding to 0.71 (XPE=0.71), 1.47 grams of PE were taken for each 0.53 grams of PG. The PE-PG mixture was initially milled in an 8000 M Mixer / Mill® High-Energy Ball Mill, from SPEX SamplePrep LLC, using 2 metallic balls of 4 g for 2 g of binary mixture for 30 min. An amount of sunflower oil corresponding to 15 wt% to the final composite was added to the PE: PG system in powder and the resulting mixture was mixed at room temperature in a knife mill for 30 seconds. Afterwards, the resulting composition was heated up to 200 °C, kept at that temperature for 10 min and left cooling to room temperature. The resulting composition was used in the DSC and TGA analysis experiments detailed below and in Figures 1 , 2, 3 and 5. This procedure was adapted by varying the respective amounts of PE, PG and binder to prepare further compositions analyzed in Figures 1 to 5. A composition free of binder was also prepared for comparative purposes. Procedure B (for incorporation in metallic cans): In the first step, the PE:PG mixture corresponding to XPE=0.71 was prepared. For a quantity of 200 grams, 147 grams of PE and 53 grams of PG were mixed. The mixture was homogenized in a blade mill for 20 minutes. Once the PE: PG mixture was ready, 35 grams of sunflower oil were added, and homogenization was carried out for 5 minutes in a kneader. The final paste was used for filling metal containers.

[0156]

[0118] Fig. 1 shows that it is possible to modulate the temperature of the phase transition of a PCM material based on a binary mixture of PE and PG in a range of between 40 °C and 190 °C by varying the content of PE of said binary mixture. This advantageously allows providing a thermal heat storage solution for any heat source within or above this range of temperatures.

[0157]

[0119] The results of Fig. 2 show that the main thermal properties related to PCMs (latent heat and transition temperature) are not substantially affected by the presence of the binder. The reduction observed of the latent heat (=15%) is directly related to the lower content of PCM (85 wt%), and is not attributed to any kind of interaction between the binder and the PCM binary mixture of PE and PG.

[0158]

[0120] The results of Figure 3 show that when exposed to temperatures of above 135 °C, the PCM binary mixture of this Example starts evaporating.

[0159] Determination of apparent density and energy density

[0160] Procedure: A cylindrical crucible with an approximate volume of 30 ml was employed to determine the apparent density of the composites. An initial tare was performed by leveling the crucible with distilled water, recording mass and temperature to accurately determine the volume of the crucible. Once the volume was known, samples of PE: PG (XPE=0.71) with different binder contents (0, 5, 10, and 15 wt%) were prepared following the previously described procedure (Procedure A of Example 1). These samples were used to fill the previously fared crucible, filling the container step by step, by slightly pressing manually to release air trapped inside the vessel. The mass is recorded, thus determining the apparent density of each sample.

[0161]

[0121] The same procedure was followed by substituting the PE:PG system by its pure constituents, obtaining the apparent density as function of the binder content for the pure PE and the pure PG individually (Figures 10 and 11).

[0162] Determination of latent heat energy density

[0163]

[0122] The latent heat energy density of each sample, LHED (MJ / m3), depicted in Figure 5, is obtained with the following formula:

[0164] LHED = papp. - i (1) where, papp. (g / cm3) is the composite apparent density, A / 7, (J / g) is the composite latent heat calculated from equation 2. In Eq. 2, HPE.PG(J / g) is the latent heat of the PE:PG sample without binder, calculated as previously described. In this case, for XPE=0.71 , HPE.PG=190.7 J / g. Finally, MBinder. corresponds to the mass fraction of the binder used in the composite.

[0165]

[0123] The results of Figure 5 show that the higher the binder content, the higher the density achieved in the material after the filling process. Although increasing the binder content diminishes the PCM mass ratio, it is compensated by the higher amount of material incorporated into the container. Also, the latent heat energy density of each module was calculated. By using a 15wt% of binder, an increase of 24% of the latent heat energy density than a composition without any binder was obtained. Therefore, obtaining the paste not only increases workability but also decreases the amount of air trapped inside the module, thus increasing the capacity of energy storage and heat transfer.

[0166] Example 2: Preparation of a capsule / can comprising the composition of Example 1

[0167]

[0124] The paste obtained in Procedure B of Example 1 was gradually filled into the containers and manually compacted with a piston of similar diameter to the can. A margin of approximately 1 mm was left at the top to allow for a perfect fit of the top lid. To ensure sealing, a high-temperature silicone sealant / adhesive (Loctite SI 596, from Henkel Adhesives) was applied to the edges of the lid. Sealing was carried out using a can seamer for closing cylindrical containers.

[0168]

[0125] To ensure system formation, a thermal cycling process was conducted on the cans. This involved subjecting the sealed module to heating up to 200°C inside an oven, maintaining it for 1 .5 hours, and cooling it outside the oven to room temperature.

[0169]

[0126] The above capsule has been compared with other capsules whereby the capsule is not sealed in a gas-tight manner and / or the PCM material does not comprise any binder. Thus, capsules A, B and C were prepared, being capsules A and B provided for comparison purposes

[0170] The modules A, B and C were subjected to 195 °C for 5 days, registering the mass loss and making a final inspection of the core material (Figure 4). Module A exhibited a mass loss of 0.5wt %, with a noticeable degradation of the material (yellowing). Module B, without the presence of the binder, shows no mass loss nor degradation, but has suffered shrinkage, resulting in voids, loss of contact of the internal material with the metal container and therefore, loss of thermal conductivity of the module. Module C shows no mass loss, shrinkage, or apparent degradation of the enclosed material.

[0171] Effect of fatty acid binders on PCM sublimation

[0172]

[0127] A mixture of NPG and lauric acid was prepared as follows: An equimolar amount of NPG and lauric acid was mixed in a crucible, stirred with a magnetic magnet, and heated on a hot plate over the melting temperature of lauric acid (at 50°C). The homogeneous mixture was left to stir for 15 minutes, after which it was allowed to cool freely to room temperature.

[0173]

[0128] In order to determine the sublimation temperature and enthalpy, the calculation method proposed by R. Barron (Barron, A. R. (2010). Determination of Sublimation Enthalpy and Vapor Pressure for Inorganic and Metal-Organic Compounds by Thermogravimetric Analysis. Chemistry os Electronic Materials, OpenStax CNX) was followed. This involved implementing the heating protocol using isothermal intervals as described earlier. Following the calculation method, the slope of mass loss with respect to temperature (mSub) for each isothermal line was utilized to obtain the graph of ( risub' T1 / 2) versus 1 / T.

[0174]

[0129] By employing the formula (Eq.1) proposed by R. Barron, derived from the Clausius-Clapeyron equation and the Langmuir equation, the sublimation enthalpies (AHsub) were obtained from the slopes in the graph of (mSUb T1 / 2) versus 1 / T. The intersection with the ordinate axis provides the value of the sublimation temperature (Tsub Mw corresponds to the molar mass in the equation.

[0175] -0,0522 ( Hsub) 0,0522 (AHsub) 1 / 1306\l log(msub• V ) =

[0176] T (Eq.3

[0177] T - 2 M i ) Sub

[0178] TGA data, and the use of Langmuir equation (Eq.2), allows for the calculation of the vapor pressure (Pv) as a function of temperature (T).

[0179]

[0130] FIG. 9 shows the sublimation experienced by NPG, both without binder and with an equimolar amount of lauric acid. Fig. 9 shows that the presence of lauric acid delays the sublimation temperature compared to the use of NPG without lauric acid. To quantify this effect, the sublimation temperature of both compounds following the procedure described above was determined. The results show a very similar sublimation enthalpy in both cases, around 74-77 kJ / mol, however, while the sublimation temperature for the pure NPG is 65 °C, for the equimolar mixture NPG+Lauric acid, this temperature is 74 °C. The stability effect of lauric acid on the NPG is evident when comparing the effect on the vapour pressure (obtained as previously described) as function of the temperature (following figure). Using lauric acid as binder in NPG thus reduces the vapour pressure of the mixture in comparison to pure NPG. This allows preventing the formation of voids within the capsule. If the sublimation is sufficiently delayed, the sealing of the capsule in a gas-tight manner is no longer required.

[0180] Example 4: Comparison of a packed bed configuration of a module according to Example 2 with a water tank or an oil tank

[0181]

[0131] The comparison between the storage capacity of a packed bed system based on the capsule of Example 2 with a pressurized water tank, and a thermal oil tank, was carried out based on their volumetric thermal energy storage capacity, expressed in kJ / l (TESC) ratios:

[0182] TESC Ratio =TESCpacked BedTESCref

[0183] (5) where TESCpacked Bed is the volumetric thermal energy storage capacity of a packed bed system based on the invention, and TESCref, the corresponding reference energy storage capacity of a TES system based on thermal oil or pressurized water.

[0184] Where, Cprefand prefare the specific heat capacity and the density, respectively, of water or thermal oil.

[0185] Table 1. Values considered for reference materials.

[0186]

[0132] The present analysis assumes that 55% of storage volume is occupied by the compact modules in the packed bed tank, while the remaining volume (45%) is filled with water. The temperature variations (AT) are considered from 5 °C to 65 °C. In addition, three different solid-solid transition temperatures are considered: the two boundary cases (PG as the lower limit and PE as the upper limit), and an intermediate case of PE: PG with XPE=0.71. Therefore, the TESCpacked Bed is calculated as:

[0187] Where, TESCModuieis the energy storage capacity corresponding to the module, and TESCWateris the one related to the water and is calculated according to Eq. 6.

[0188] TESCModsensibleis the storage capacity of the module in form of sensible heat, and TESCModLatentis the storage capacity related to the latent heat of the module. In addition,

[0189] CpModuie Specific heat capacity of the module (kJ kg’1°C’1)

[0190] CpMetai Specific heat capacity of metal (kJ kg’1°C’1) (Table 2)

[0191] CpBinder Specific heat capacity of binder (kJ kg’1°C’1) (Table 1 , Cp of thermal oil)

[0192] CppcM Speific heat capacity of PCM (kJ kg’1°C’1) (Table 3) mBinder Mass of binder in module (kg) mMetai Mass of metal in module (kg) (Table 2) mPCMMass of PCM in module (kg) HPCMEnthalpy of PCM (kJ / kg) (Table 3)

[0193] VolModuie Total volume of Module (I) (Table 2)

[0194] VolinnerInner volume of module (I) (Table 2)

[0195] M Binder Mass fraction of binder in PCM-binder composite (0.15) pBinder Density of binder (kg / l) (Table 1, density of thermal oil) PPCM Density of PCM (kg / l) (Table 3).

[0196] 0 Packing fraction of PCM-binder inside the module (0.25)

[0197] Table 1. Data and properties related to the Module (Brass as metal).

[0198] Module: Vol Mod, Vol inner, mMetal, teta, Cpmetal, density metal.

[0199] The MBinder is 0.15 in the present case.

[0200] Table 2. Values considered for the different PCMs.

[0201]

[0133] Figures 6 to 8 compare a packed bed system based on the present invention with a pressurized hot water tank and a thermal oil tank. This comparison is shown in the form of volumetric energy storage capacities ratios. The analysis assumes that 55% of storage volume is occupied by the compact modules in the packed bed tank, considering temperature variations (AT=Tin-Tout) from 5 °C to 65 °C. In addition, three different solidsolid transition temperatures are considered: the two boundary cases (PG as the lower limit and PE as the upper limit), and an intermediate case of PE:PG with XPE=0.71.

[0202]

[0134] The results show that a packed bed system based on the described modules allows reaching higher values of volumetric energy storage capacity if compared to water tank or oil tank. This advantageously leads to extremely compact devices. In particular, the packed bed system is up to 4-7 times more compact than a pressurized hot water tank (AT=5°C), or 2-3 times in case of wider inlet-outlet temperature differences (AT=15°C). Also, the packed bed system is up to 7-12 times more compact than a thermal oil tank (AT=5°C), or 3-5 times in case of wider inlet-outlet temperature differences (AT=15°C).

[0203] Example 5: Preparation of a composition based on a unary mixture of PE or PG with a binder

[0204]

[0135] In this Example, compositions having a variable amount of sunflower oil (from 0 wt% to 20 wt%) combined with either PE or PG were prepared according to the procedure A of Example 1 and omitting the step of mixing PE with PG. Core apparent density and latent heat energy density for said compositions were determined as disclosed in Example 1.

[0205]

[0136] The corresponding results are shown in Figures 10 and 11. Fig. 10 and 11 confirm that the addition of a binder allows improving the apparent core density of the composition and increasing the latent heat energy density of the PCM, even when said PCM is a sole component.

Claims

CLAIMS1. Composition for storing thermal energy comprising a non-polymeric solid-solid phase change material and a binder that is selected from the group consisting of an oil, a fatty acid, a fatty acid ester, a fatty alcohol and a mixture thereofwherein the binder and its relative amount are such that the temperature at which the composition starts the phase transition in a DSC experiment does not vary more than 15 °C of the temperature at which the solid-solid phase change material starts the phase transition in a DSC experiment and wherein the enthalpy of transition of the composition comprising the binder, expressed in Joule per gram of the solid-solid phase change material in the composition and as measured in a DSC experiment, does not vary more than 5% of the enthalpy of transition of the solid-solid phase change material as measured in a DSC experiment.

2. Composition according to claim 1 wherein the binder and its relative amount are such that the temperature at which the composition starts the phase transition in a DSC experiment does not vary more than 5 °C of the temperature at which the solid-solid phase change material starts the phase transition in a DSC experiment and wherein the enthalpy of transition of the composition comprising the binder, expressed in Joule per gram of the solid-solid phase change material in the composition and as measured in a DSC experiment, does not vary more than 2%, of the enthalpy of transition of the solidsolid phase change material as measured in a DSC experiment.

3. Composition according to any of claims 1 to 2 wherein the non-polymeric solidsolid phase change material is selected from the group consisting of pentaerythritol (PE), pentaglycerine (PG), 2,2-dimethylpropane-1 ,3-diol (NPG), 2-amino-2-methyl-1 ,3- propanediol (AMPL), tris(hydroxymethyl)-aminomethane (TAM), nitroisobutylglycol (NMPD), 1 ,3-Dinitro-1 ,3-diazacycloheptane, octadecyl 2,4,6-trinitrobenzoate, 1 ,4- dioxane, cis-cyclohexane-1 ,2-dicarboxylic anhydride, dihexadecylhydroxy arsine oxide, N,N,N-Trimethyl-1-hexadecanaminium chloride, tricosane, 1-Docosanol,4,4'-(1 ,3- Butadinyl-1 ,3-diyl)bis(4,1-phenylenedodecanoate), bis(dodecylammonium) tetrachloromanganate (II), lead(ll) pentadecanoate, bis(hexadecylammonium) tetrachloroferrate(ll), bis(tetradecylammonium) tetrachlorozincate, N,N’-dibutylurea and a mixture thereof; preferably, the non-polymeric solid-solid phase change material is selected from the group consisting of pentaerythritol, pentaglycerine, neopentylglycol, 2-amino-2-methyl-1 ,3-propanediol, tris(hydroxyl methyl)aminomethane and mixtures thereof.

4. Composition according to any one of claims 1 to 3 wherein the non-polymeric solid-solid phase has a phase change temperature of between 40 °C to 190 °C and / or a latent heat of at least 100 J / g.

5. Composition according to any one of claims 1 to 4 wherein the non-polymeric solid-solid phase is a binary mixture of pentaerythritol and pentaglycerine wherein the molar fraction of pentaerythritol in said binary mixture is preferably of at least 0.50; more preferably of between 0.60 and 0.80.

6. Composition according to any one of claims 1 to 5 wherein the binder is an oil, such as a vegetal or a mineral oil; preferably, the binder composition is selected from the group consisting of sunflower oil, avocado oil, nut oil, rapeseed oil, soybean oil, canola oil, coconut oil, corn oil, cottonseed oil, flaxseed oil, grapeseed oil, safflower oil, olive oil, palm oil peanut oil, rice bran oil, and sesame oil; more, preferably, the binder composition is sunflower oil.

7. Composition according to any one of claims 1 to 5 wherein the binder comprises in ots molecular formula at least a functional group suitable for forming non-covalent interactions, such as hydrogen bonds, with the solid-solid phase change material.

8. Composition according to any one of claims 1 to 7 wherein the binder is in an amount of up to 25% in weight; preferably the binder is in amount of between 5% and 25% in weight of the composition.

9. Composition according to any one of claims 1 to 6 or 8 wherein:(i) the non-polymeric solid-solid phase is a binary mixture of pentaerythritol and pentaglycerine wherein the molar fraction of pentaerythritol in said binary mixture is preferably of at least 0.50; more preferably of between 0.60 and 0.80;(ii) the binder is sunflower oil and is in an amount of up to 25% in weight; preferably of between 5% and 25% in weight of the composition.

10. Capsule for thermal energy storage enclosing a composition according to any one of claims 1 to 9 in a gas-tight manner and comprising a sealant or a gasket arranged for sealing the capsule in a gas-tight manner, wherein the sealant is thermally resistant at the temperature of phase transition of the composition.

11. Capsule according to claim 11 wherein the sealant is selected from the group consistign of silicones, epoxy resins, polyurethane sealants, (cyano)acryclic sealants, phenolic sealants and polyimide sealants.

12. Capsule according to claim 11 wherein the sealant is silicone.

13. Method of preparation of a capsule according to any one of claims 10 to 12 comprising the steps of:(i) providing a composition as defined in any one of claims 1 to 9;(ii) providing a capsule enclosure for thermal energy storage;(iii) arranging the composition provided in (i) within the capsule enclosure provided in (ii) so that the composition provided in (i) and the capsule enclosure provided in (ii) are in thermal contact and(iv) sealing the capsule enclosing the composition resulting from step (iii) in a gas-tight manner by the means of a sealant or a gasket, wherein the sealant is as defined in any one of claims 10 to 12.

14. Use of a composition according to any one of claims 1 to 9 or of a capsule according to any one of claims 10 to 12, in thermal energy storage, preferably in industry or domestic heat supply installations, electronics, power electronics, solar energy, batteries, buildings, waste heat recovery, air-conditioning, temperature-adaptable greenhouses and textiles.

15. A product of manufacture, an electronic device, a solar energy system device, an energy storage device, a computer, a medical device, a storage unit, a building or building material, a container, an insulation or construction material, an automotive material, a vehicle, a boat, an airplane, a weapon or weapon system, industrial machinery, a pharmaceutical or a drug or a food package or storage device or container, a textile, a clothing or an apparel, footwear, a bedding or bedding system, a flame retardant material, comprising a capsule according to any one of claims 10 to 12.

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