Energy storage system and method

Abstract

An energy storage system is provided, comprising: a fluidized bed apparatus having an energy storage material, wherein the energy storage material is provided in a volume coated with an outer layer of solid particles of a different material, wherein the volume has a maximum dimension in the interval of 1 to 1000 μm, and wherein the solid particles have a maximum dimension in the interval of 1 to 500 nm. Advantages of the system include minimizing structural changes of the energy storage material over time so that the energy storage material can be used for multiple cycles without any significant damage. Heat transfer into and out of the energy storage material is improved. The system can further be used for CO2 capture.

Description

Technical Field

[0001] The invention relates to a device, a system and a method for storing energy in chemical form by using energy storage materials coated with outer layers of solid particles in a fluidized bed. Background Art

[0002] WO 2012 / 118437 discloses a particle comprising an inner portion and an outer coating, wherein the inner portion comprises at least one selected from the group consisting of salt and CaO, and the outer coating comprises hydrophobic nanoparticles.

[0003] WO 2016 / 166364 discloses a material for a chemical heat pump, the material comprising an active substance and allowing a volatile liquid in a gas phase to move into and out of at least a portion of the active substance, wherein at least a portion of the material is in thermal contact with the surroundings, wherein the material comprises flakes of at least one selected from the group consisting of graphene and graphene oxide, wherein each individual flake has a lateral dimension in the range of 100 to 10,000 nm and a thickness in the range of 0.34 to 5 nm.

[0004] Fluidized beds are known in the art for various purposes. EP 2984435 discloses an energy storage system comprising a fluidized bed, wherein, for example, CaO / Ca(OH)2 may be used as energy storage material.

[0005] CN 109046187 discloses a gas-solid fluidized bed reactor, wherein the solid particles have a portion of nanoparticles uniformly or unevenly attached to the surface of the particles.

[0006] Although the current state of the art can be used successfully, there is always room for improvement. Areas to be improved include, for example, promoting the fluidization process of the energy storage material, reducing the energy consumption of the system, enabling the possibility of utilizing other materials, and reducing the tendency of the energy storage material to undergo structural changes during long-term use. Summary of the invention

[0007] An object of the present invention is to avoid at least some disadvantages of the prior art and to provide an energy storage system and method.

[0008] In a first aspect, an energy storage system is provided, comprising a fluidized bed device (1) having an energy storage material (2), wherein the energy storage material (2) is provided in a volume (3) having an outer layer (4) of solid particles (5) coated with a different material, wherein the volume (3) has a maximum dimension in the range of 1 to 1000 μm, and wherein the solid particles (5) have a maximum dimension in the range of 1 to 500 nm.

[0009] In a second aspect, an energy storage method is provided, comprising the steps of: a) providing at least partially uncharged energy storage material (2) in a fluidized bed device (1), and b) transferring heat to the energy storage material (2) in the fluidized bed device (1) to charge the energy storage material (2), wherein the energy storage material (2) is provided in a volume (3) of an outer layer (4) of solid particles (5) coated with a different material, wherein the volume (3) has a maximum dimension in the range of 1 to 1000 μm, and wherein the solid particles (5) have a maximum dimension in the range of 1 to 500 nm.

[0010] In a different form of the second aspect, there is provided a method of releasing heat, comprising the steps of:

[0011] a. providing the at least partially charged energy storage material (2) in the fluidized bed device (1),

[0012] b. Optionally, starting the reaction of the energy storage material (2) in the fluidized bed device (1) so that heat is released, and

[0013] c. Transferring heat from the energy storage material (2),

[0014] The energy storage material (2) is provided in a volume (3) of an outer layer (4) of solid particles (5) coated with a different material, wherein the volume (3) has a maximum dimension in the range of 1 to 1000 μm, and wherein the solid particles (5) have a maximum dimension in the range of 1 to 500 nm.

[0015] Further embodiments of the invention are defined in the attached dependent claims which are expressly incorporated herein.

[0016] One advantage is that changes in the size of the energy storage material over time do not have any consequences, since the solid particles (5) absorb the movement within the energy storage material (2). The solid particles (5) can move and rearrange within the outer layer (4) as the shape and size of the volume (3) change within reasonable limits.

[0017] Another advantage is the possibility of using liquid and semisolid energy storage materials in addition to solid energy storage materials.

[0018] The structural changes of the energy storage material over time are minimized, thereby enabling the energy storage material to be used for multiple cycles without any significant damage to the energy storage material.

[0019] One advantage is that the fluidization of the energy storage material (2) in the fluidized bed is promoted. The friction between the particles of the energy storage material is reduced. The energy storage material requires less effort and less energy to fluidize. Less friction results in less wear on the system during prolonged use.

[0020] The heat transfer into and out of the energy storage material is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Various aspects and embodiments will be described with reference to the accompanying drawings, in which:

[0022] Figure 1 A system according to the present invention is shown. The system comprises a fluidized bed device (1) having an energy storage material (2). The energy storage material (2) is coated with particles according to the present invention. The system comprises a first storage compartment (6) and a first feeding device (8), as well as a second storage compartment (7) and a second feeding device (9). The figure also shows that the fluidized bed device (1) comprises a heat exchanger in thermal contact with the energy storage material (2). In the fluidized bed device, means are always provided for producing suitable conditions for the energy storage material (2) to behave as a fluid. This is usually achieved by introducing a pressurized fluid into the energy storage material (2). The device for introducing the pressurized fluid is not shown in the figure.

[0023] Figure 2 Another example is a device with an open hole partition (10). Figure 1 Same system. The perforated partition (10) creates more than one fluidizing compartment in the fluidized bed apparatus (1). In the illustrated embodiment, there are upper and lower fluidizing compartments separated by the perforated partition (10). In this embodiment, in each of the two fluidizing compartments, there is a heat exchanger in thermal contact with the energy storage material (2). This allows different conditions to be achieved in the fluidizing compartments, with the two fluidizing compartments having different temperatures.

[0024] Figure 3 Schematic diagram of an energy storage material according to the invention having a volume (3) of solid particles (5) coated with an outer layer (4) of different materials. The schematic diagram is not drawn to scale and is used to illustrate the coating principle. The volume (3) is active material, such as CaO / Ca(OH)2, for example. DETAILED DESCRIPTION

[0025] Before disclosing and describing the present invention in detail, it should be understood that the present invention is not limited to the specific configurations, processing steps and materials disclosed herein, because such configurations, processing steps and materials can be varied. It should also be understood that the terminology used herein is for the purpose of describing specific embodiments only and is not intended to be limiting, because the scope of the present invention is limited only by the appended claims and their equivalents.

[0026] It must be noted that, as used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise.

[0027] "Stored energy", as used throughout this specification and claims, refers to stored energy in chemical form.

[0028] "Energy storage material," as used throughout this specification and claims, refers to any material that is capable of storing energy within it in chemical form.

[0029] "Fluidized bed apparatus" as used throughout this specification and claims means an apparatus comprising at least one fluidized bed, including the necessary systems for the operation of the fluidized bed known to those skilled in the art.

[0030] The "largest dimension" of a volume or particle, as used throughout this specification and claims, refers to the maximum distance along a straight line between any two points on the surface of the volume or particle. Two points on the surface are chosen so that the distance along a straight line between the two points is maximized. Of all possible distances between any two points on the surface of the particle or volume, the largest possible distance is chosen. For a sphere, it corresponds to the diameter of the sphere. For a needle-shaped particle, it is the length of the needle.

[0031] "Solid particle," as used throughout this specification and claims, refers to a piece of material in solid form.

[0032] "System", as used throughout this specification and claims, refers to a combination of devices. In particular, it includes a fluidized bed apparatus, including devices known to those skilled in the art that are necessary for the operation of the fluidized bed.

[0033] "Volume", as used throughout this specification and claims, refers to a spatial three-dimensional object, including but not limited to particles. Volumes include liquid droplets and solid particles.

[0034] In a first aspect, an energy storage system is provided, comprising a fluidized bed device (1) having an energy storage material (2), wherein the energy storage material (2) is provided in a volume (3) having an outer layer (4) of solid particles coated with a different material, wherein the volume (3) has a maximum dimension in the range of 1 to 1000 μm, and wherein the solid particles (5) have a maximum dimension in the range of 1 to 500 nm.

[0035] The fluidized bed apparatus comprises at least one fluidized bed, and the energy storage material is located in the fluidized bed at least during operation of the system.

[0036] The active energy storage material is in solid form, liquid form or semi-solid form and is provided as a volume. If the material is in solid form, the volume (3) can be described as particles. If the material is in liquid form, the volume (3) can be described as droplets.

[0037] A volume (3) is coated with solid particles (5) of different materials. The coating (4) consisting of solid particles (5) is so thick that the entire surface of the volume (3) is coated. The coating (4) has a thickness such that two adjacent volumes cannot directly contact each other. The coating (4) should be so thick that at least one solid particle is between two adjacent volumes, that is, the distance between two adjacent volumes should never be shorter than the smallest dimension of a solid particle. Preferably, the coating (4) is much thicker than the thickness corresponding to a layer of particles. In one embodiment, the coating (4) is so thick that the surface of the volume (3) cannot be seen through the coating, that is, it is impossible to draw a straight line from the surface of the volume (3) to the surroundings without intersecting at least one solid particle (5).

[0038] In one embodiment, the system comprises a first storage compartment (6) and a first feeding device (8) suitable for bidirectional feeding of energy storage material (2) between the first storage compartment (6) and the fluidized bed device (1). By using a storage compartment, material can be fed into the fluidized bed for energy storage or energy release. The feeding device can be any device capable of moving material from a storage location into the fluidized bed, and vice versa. It can also be a regulating valve and can include a hopper for delivering material into the fluidized bed. The storage compartment can be a removable storage compartment and can be moved to different positions. In one embodiment, the storage compartment is hermetically sealed so that moisture cannot reach the energy storage material inside.

[0039] In one embodiment, the system comprises a second storage compartment (7) and a second feed device (9) adapted for bidirectional feeding of the energy storage material (2) between the fluidized bed apparatus (1) and the second storage compartment (7). The use of two storage compartments and two feed devices has the advantage of using the first storage compartment for the uncharged volume and the second storage compartment for the charged volume. Furthermore, other additional storage compartments are also contemplated.

[0040] In one embodiment, the fluidized bed apparatus (1) comprises a heat exchanger in thermal contact with the energy storage material (2). Such a heat exchanger makes it easier to exchange heat with the surroundings.

[0041] Examples of surrounding systems that may be in thermal contact with the system include, but are not limited to, solar panels, district heating systems, thermal power plants, and steam generators.

[0042] In one embodiment, the fluidized bed apparatus (1) comprises electric heating elements in thermal contact with the energy storage material (2). Such electric heating elements achieve direct and / or indirect electrical (eg inductive) heating of the energy storage material.

[0043] In one embodiment, the system comprises a plurality of fluidized beds. In one embodiment, the fluidized beds are connected in series. In an alternative embodiment, the fluidized beds are connected in parallel.

[0044] In one embodiment, the fluidized bed apparatus (1) comprises at least one perforated partition (10), which creates more than one fluidized compartment in the fluidized bed apparatus (1). This creates a plurality of fluidized zones in the fluidized bed apparatus. Such an arrangement enables the possibility of having different conditions in different zones. The perforated partition (10) is at least partially perforated. In one embodiment, the perforated partition (10) is arranged horizontally, thereby creating upper and lower fluidized zones. In another embodiment, several perforated partitions (10) are arranged to create a plurality of fluidized zones. The perforated partition (10) has the advantage of creating several fluidized zones in which the conditions can be kept different. For example, the temperature can be different. If, for example, a secondary heating to a higher temperature is carried out after a preheating, the process can be made more efficient.

[0045] The fluidized bed may be of any type known in the art. In one embodiment, the fluidized bed apparatus (1) comprises at least one of a bubbling fluidized bed, a circulating fluidized bed, a flash reactor, a vibrating fluidized bed, an annular fluidized bed, a mechanical fluidized reactor and a narrow fluidized bed.

[0046] During the charging process of thermochemical storage materials, the released fluid generally occupies a considerable volume in the gas phase. An example is water in the gas phase released by Ca(OH)2. Such released gases will help to fluidize the energy storage material. Therefore, the energy storage material that releases the fluid has a self-fluidizing effect at the temperature and pressure at which the released fluid is in the gas phase. When such materials discharge energy, it must be taken into account that the fluid will be absorbed by the energy storage material (2) and the volume will therefore decrease. An example is water in the steam or gas phase added to CaO. During the addition of water in the gas phase, the added gas will have a fluidizing effect. However, since the gas is absorbed by CaO, the fluidizing effect is reduced. This reduction in volume and fluidizing effect must be taken into account. For such energy storage materials, it is important that the friction between the material volumes is not too high and that the volumes of the energy storage material do not adhere to each other. This is ensured by the use of surrounding solid particles (5). The friction between the volumes (3) is more critical in conventional fluidized beds due to the absorption during the discharge phase. Therefore, the friction reduction properties of the solid particles (5) are of great significance.

[0047] In one embodiment, the energy storage material (2) is a material having the ability to absorb a fluid at a first temperature and desorb the fluid at a second, higher temperature.

[0048] In one embodiment, the fluidized bed apparatus (1) is in contact with a reservoir fluid of a fluid desorbed from an energy storage material (2) in one embodiment. The energy storage material stores energy in chemical form and is charged in such a way that the fluid is released from the energy storage material. The released fluid is stored in a reservoir in a suitable manner. The released fluid may be both gaseous and liquid. Examples of such materials include, but are not limited to, materials involved in the following reactions:

[0049]

[0050] Water is the released fluid in this example, which can be stored in a reservoir for later use when reversing the reaction. The released gas phase fluid is condensed to a liquid phase in one embodiment before storage.

[0051] In one embodiment, the solid particles (5) include at least one material selected from the group consisting of SiO2, graphite, graphite oxide, graphene oxide and graphene. Graphite, graphite oxide, graphene oxide and graphene have the advantages of increasing thermal conductivity and reducing friction. Graphene oxide and graphene also increase the strength of the volume. In one embodiment, the solid particles include a mixture of SiO2 and at least one of graphite, graphite oxide, graphene oxide and graphene.

[0052] In one embodiment, the solid particles (5) include hydrophobically modified SiO2 modified with at least one hydrophobic compound. The hydrophobic groups are attached to the surface of the SiO2. In one embodiment, they are covalently bonded, and in an alternative embodiment, they are not covalently bonded. In addition, a mixture of hydrophobically modified SiO2 and at least one of graphite, graphite oxide, graphene oxide and graphene is also included.

[0053] In one embodiment, the energy storage material (2) is hydrophilic, i.e., has a net attraction to water molecules, and wherein the solid particles (5) are hydrophobic, i.e., have a net repulsion to water molecules. Examples of hydrophilic energy storage materials include, but are not limited to, salts and various metal oxides. Solid particles attached to the surface of the volume do not dissolve in the volume, but instead separate the volume. In one embodiment, the solid particles can react. The solid particles can react in this way either during the manufacturing process, during the initial operating cycle of a new system, or in a combination of the two. Such reactions include, for example, but are not limited to, physical transformations and chemical reactions, or a combination thereof. In one embodiment, the solid particles at least partially react chemically to form a material having the desired separation properties. In one embodiment, the solid particles are hardened by heating to form a more inert material. The volume and solid particles can be processed together before the system is first started.

[0054] In an alternative embodiment, the energy storage material (2) is hydrophobic, ie has a net repulsion to water molecules, and wherein the solid particles (5) are hydrophilic, ie have a net attraction to water molecules.

[0055] The energy storage material is a salt in one embodiment. In one embodiment, the energy storage material (2) is at least one salt selected from the group consisting of chlorides, chlorates, perchlorates, bromides, iodides, carbonates and nitrates of lithium, magnesium, calcium, strontium, barium, cobalt, nickel, iron, zinc, manganese, potassium and aluminum and sulfides and hydroxides of lithium, sodium and potassium. Mixtures of different energy storage materials are included.

[0056] In one embodiment, the energy storage material (2) comprises at least one selected from CaO, Ca(OH)2, CaCO3, MgO, Mg(OH)2, MgCO3, BaO, Ba(OH)2, BaCO3 and metal hydrides such as MgH2. If the metal hydride is in a released form, it is implied that the corresponding metal is in the corresponding charged form of the energy storage material. When the energy storage material is CaO and water is used as the fluid, it is implied that the Ca(OH)2 form is also included. The same applies to MgO and BaO. If CO2 is used as the fluid, it is implied that the corresponding carbonate is included.

[0057] In one embodiment, the energy storage material (2) comprises at least one selected from CaO, CaCO3, and wherein the system is suitable for capturing CO2. The suitability for CO2 capture is achieved in such a way that CO2 is used as a fluid. CO2 is provided in pure form, or CO2 is provided in a gas mixture. In one embodiment, CO2 is provided as an exhaust gas from a combustion process. In one embodiment, CO2 is provided as an exhaust gas from an industrial process. CO2 or a mixture containing CO2 is contacted with CaO so that it subsequently reacts to form CaCO3. The reaction is reversible. In the reverse process, CO2 is released and can be fully processed because it is more concentrated and purer. Therefore, the effect of the process is to capture CO2 and then release CO2 in a form that is easier to handle. In addition to energy storage, the system can therefore also capture CO2. The suitability for CO2 capture is to use CaO as the initial material, provide a device for feeding the gas to CaO, and process the CO2 after release in the reverse process.

[0058] Although the energy is mainly stored as chemical energy in the energy storage material (2), part of the energy can be stored as sensible energy in certain circumstances. The energy storage material (2) is heated to a high temperature both during the charging process and during the discharging process, so that the temperature of the energy storage material (2) becomes very high. If the time between the charging and discharging cycles is not too long, this heat can also be utilized. In one embodiment, the storage of this heat is promoted by providing insulation around the first storage compartment (6) or the second storage compartment (7) or around both storage compartments so that the heat is retained for a longer time. In one embodiment, at least one of the fluidized bed device (1), the first storage compartment (6), and the second storage compartment (7) is at least partially insulated from the second feed device (9). In one embodiment, at least one of the first storage compartment (6) and the second storage compartment (7) is at least partially insulated. In one embodiment, a suitable part of the entire system is at least partially insulated. Insulation improves the efficiency of energy storage.

[0059] In a second aspect, an energy storage method is provided, comprising the steps of: a) providing at least partially uncharged energy storage material (2) in a fluidized bed device (1); and b) transferring heat to the energy storage material (2) in the fluidized bed device (1) to charge the energy storage material (2), wherein the energy storage material (2) is provided in a volume (3) of an outer layer (4) of solid particles (5) coated with a different material, wherein the volume (3) has a maximum dimension in the range of 1 to 1000 μm, and wherein the solid particles (5) have a maximum dimension in the range of 1 to 500 nm. The method charges the energy storage material. Charging is achieved by heating the material. In the case of chemical energy storage, a chemical reaction occurs in the energy storage material, and in some embodiments, a fluid is released and removed.

[0060] In one embodiment, the step includes moving the fluid released by the energy storage material (2) away from the energy storage material (2). In one embodiment, the fluid released by the energy storage material (2) is moved into storage. Generally speaking, the release of the fluid causes an increase in pressure due to the increase in volume, and at least a portion of the fluid can then be moved into storage via a pipeline. In one embodiment, the stream of the fluid is directed through a separator and / or a condenser. This embodiment resides in chemical energy storage within the material, which is capable of reversibly reacting with another substance, thereby causing the substance or fluid to be released during heating.

[0061] In a different form of the second aspect, there is provided a method of releasing heat, comprising the steps of:

[0062] a. providing the at least partially charged energy storage material (2) in the fluidized bed device (1),

[0063] b. Optionally, starting the reaction of the energy storage material (2) in the fluidized bed device (1) to release heat, and

[0064] c. Transfer heat from the energy storage material (2).

[0065] Wherein, the energy storage material (2) is provided in a volume (3) of an outer layer (4) of solid particles (5) coated with a different material, wherein the volume (3) has a maximum dimension in the range of 1 to 1000 μm, and wherein the solid particles (5) have a maximum dimension in the range of 1 to 500 nm. This step is an energy release step. In one embodiment, in the case of chemical energy storage, a fluid is in contact with the energy storage material (2), thereby initiating a chemical reaction to release heat. In one embodiment, the energy storage material (2) is in contact with a fluid. The fluid can be stored in another container and in contact with the energy storage material.

[0066] When storing energy in thermochemical form, the released fluid should be led away from the fluidized bed. In one embodiment, the mixture of gas and / or liquid and / or solid material is led through a separator or filter to separate the volume and smaller particles from the fluid. In one embodiment, the volume and smaller particles are recovered to the fluidized bed. In one embodiment, the fluidized bed device (1) has at least one outlet configured to be suitable for separating and recovering solid matter. The advantage is that the solid material can be separated from the fluid stream released by the energy storage material and can be recovered to the fluidized bed. In one embodiment, the separation is carried out in a filter. In one embodiment, the separation is carried out by a cyclone separator. In one embodiment, the separator is a cyclone separator. The cyclone separator has the advantage of being able to effectively remove very small particles such as solid particles (5). In one embodiment, the system is equipped with a condenser suitable for condensing the fluid.

[0067] In one embodiment of the method, the fluidized bed apparatus (1) comprises at least one open partition creating more than one different fluidizing compartment within the fluidized bed apparatus (1), wherein the different fluidizing compartments differ in at least one selected from temperature and residence time.

[0068] In one embodiment, part of the heat transferred from the energy storage material (2) is used to start the reaction of the energy storage material. If it is necessary to start the reaction of the energy storage material, this can be achieved by using the energy released from the energy storage material during the reaction.

[0069] In one embodiment, the energy storage material (2) comprises at least one member selected from the group consisting of CaO, Ca(OH)2 and CaCO3, and wherein the energy storage material (2) reacts with at least one member selected from the group consisting of H2O and CO2. In this embodiment, the fluid is at least one member selected from H2O and CO2. In this way, the possibility of capturing CO2 is achieved. CO2 can be released by heating and, for example, processed during long-term storage. In one embodiment, the energy storage material (2) comprises at least one member selected from the group consisting of CaO and CaCO3, and wherein the energy storage material (2) reacts with CO2. In this embodiment, the method is also a method of capturing CO2 and releasing it in a purer form that is easier to process in a suitable manner, for example, by long-term underground storage so that it eventually forms minerals.

[0070] In one embodiment, the solid particles (5) have a maximum size in the range of 1 to 100 nm. This embodiment applies to all aspects of the present invention. In another aspect, the lower size limit of the solid particles (5) is selected from 2, 4, 5, 10, 15 nm. In another aspect, the upper size limit of the solid particles (5) is selected from 50, 150, 200, 250, 300, 350, 400 and 450 nm. All lower and upper limits can be freely combined with each other.

[0071] In one embodiment, the ratio between the average value of the maximum size of all volumes (3) and the average value of the maximum size of all solid particles (5) is at least 10:1. In another embodiment, the ratio between the average value of the maximum size of all volumes (3) and the average value of the maximum size of all solid particles (5) is at least 50:1. In yet another embodiment, the ratio between the average value of the maximum size of all volumes (3) and the average value of the maximum size of all solid particles (5) is at least 100:1. These embodiments apply to all aspects of the present invention. The ratio is calculated by measuring or calculating the average size of the volume (3) and the solid particles (5). The average value of the maximum size is calculated as the sum of the maximum sizes of all particles (or volumes) divided by the number of particles (or volumes). Subsequently, the ratio of the maximum sizes is calculated.

[0072] Example

[0073] Example 1

[0074] The experiments were conducted in a bubbling fluidized bed reactor with a total volume of 600 ml. The reactor was filled with 200 ml of CaO with a median particle size of 0.121 mm and coated with silica nanoparticles with a diameter of 10 to 20 nm. The experimental evaluations were conducted in an inert atmosphere at atmospheric pressure and temperature. The empty bed velocity (u s ) were measured and the fluidization behavior at various speeds was observed.

[0075] Fluid velocity evaluate <![CDATA[u s >0.002m / s]]> Almost no fluidization <![CDATA[0.002cm / s<u s <0.017m / s]]> Partial fluidization <![CDATA[u s =0.02m / s]]> Complete fluidization <![CDATA[u s =0.05m / s]]> A certain degree of particle entrainment <![CDATA[u s =0.06m / s]]> Terminal velocity

[0076] Fluidization tests were conducted in a bubbling fluidized bed reactor containing CaO (median particle size 0.121 mm) coated with silica nanoparticles with diameters of 10-20 nm. The reactor included a heat flux probe attached to a heat exchanger. The hot fluid passed through the heat exchanger in heat exchange with the fluidized nano-coated CaO material. The heat transfer coefficient to the material was measured at different fluid velocities.

[0077] Fluid velocity Heat transfer coefficient of nano coating materials 0m / s <![CDATA[20W / m 2 K]]> 0.02m / s <![CDATA[200W / m 2 K]]> 0.03m / s <![CDATA[300W / m 2 K]]>

[0078] Example 2

[0079] The test was conducted in a bubbling fluidized bed reactor with a total volume of 20 liters. In the experiment, 96 parts of solid CaO were mixed with 4 parts of silica nanoparticles with a diameter of 10-20 nm. The mixing was carried out in a mixer at >10000 rpm for a period of about 30 seconds. The resulting material was a free-flowing powder.

[0080] Fluidization tests were conducted in a bubbling fluidized bed reactor containing 10 liters of nano-coated or uncoated CaO (median particle size 0.150 mm). The reactor included a coil-type copper heat exchanger through which a heating fluid passed. The heat exchanger was in heat exchange with the following materials:

[0081] Test Group 1: Fluidized (uncoated) CaO material

[0082] Experimental Group 2: Fluidized Nano-Coated CaO Material

[0083] In each test, the heat transfer coefficient of the material at different fluid velocities was measured and the results were compared.

[0084]

[0085]

Claims

1. An energy storage system, comprising: A fluidized bed device (1) with an energy storage material (2), wherein the energy storage material (2) is provided in a volume (3) of an outer layer (4) of solid particles (5) coated with a different material, wherein the volume (3) has a maximum dimension in the interval 1 to 1000 µm, and wherein the solid particles (5) have a maximum dimension in the interval 1 to 500 nm, and wherein the energy storage material (2) is at least one salt selected from the group consisting of chlorides, bromides, carbonates and nitrates of lithium, magnesium, calcium, nickel, iron, zinc, manganese and potassium; or The energy storage material (2) includes at least one selected from CaO, Ca(OH)2, MgO, Mg(OH)2 and MgH2.

2. The energy storage system according to claim 1, wherein: The energy storage system comprises a first storage compartment (6) and a first feeding device (8) suitable for bidirectionally feeding the energy storage material (2) between the first storage compartment (6) and the fluidized bed device (1).

3. The energy storage system according to claim 2, wherein: The energy storage system comprises a second storage compartment (7), and a second feeding device (9) suitable for bidirectionally feeding the energy storage material (2) between the fluidized bed device (1) and the second storage compartment (7).

4. The energy storage system according to claim 1, wherein: The fluidized bed device (1) comprises a heat exchanger in thermal contact with the energy storage material (2).

5. The energy storage system according to claim 1, wherein: The energy storage system includes a plurality of fluidized beds.

6. The energy storage system according to claim 1, wherein: The fluidized bed apparatus (1) comprises at least one open-pored partition (10), which creates more than one fluidizing compartment within the fluidized bed apparatus (1).

7. The energy storage system according to claim 1, wherein: The fluidized bed equipment (1) comprises at least one of a bubbling fluidized bed, a circulating fluidized bed, a flash reactor, a vibrating fluidized bed, an annular fluidized bed, a mechanical fluidized reactor and a narrow fluidized bed.

8. The energy storage system according to claim 1, wherein: The fluidized bed apparatus (1) is in fluid contact with a reservoir of fluid desorbed from the energy storage material (2).

9. The energy storage system according to claim 1, wherein: The solid particles (5) include at least one material selected from the group consisting of SiO2, graphite, graphite oxide, graphene oxide and graphene.

10. The energy storage system according to claim 1, wherein: The energy storage material (2) is hydrophilic, i.e., has a net attraction to water molecules, and the solid particles (5) are hydrophobic, i.e., have a net repulsion to water molecules.

11. The energy storage system according to claim 1, wherein: The energy storage material (2) is hydrophobic, i.e., has a net repulsive force on water molecules, and the solid particles (5) are hydrophilic, i.e., have a net attractive force on water molecules.

12. The energy storage system according to claim 1, wherein: The energy storage material (2) comprises CaO, and wherein the energy storage system is suitable for capturing CO2.

13. The energy storage system according to claim 1, wherein: The fluidized bed apparatus (1) has at least one outlet equipped with a separator suitable for separating and recovering solid matter.

14. The energy storage system according to claim 13, wherein: The separator is a cyclone separator.

15. The energy storage system according to claim 1, wherein: The solid particles (5) have a maximum size in the range of 1-100 nm.

16. The energy storage system according to claim 1, wherein: The ratio between the average value of the largest dimension of all volumes (3) and the average value of the largest dimension of all solid particles (5) is at least 10:

1.

17. The energy storage system according to claim 3, wherein: At least one of the first storage compartment (6) and the second storage compartment (7) is at least partially thermally insulated.

18. A method for storing energy, comprising the following steps: a. providing at least partially uncharged energy storage material (2) in a fluidized bed device (1), and b. transferring heat to the energy storage material (2) within the fluidized bed device (1) to charge the energy storage material (2), in, The energy storage material (2) is provided in a volume (3) of an outer layer (4) of solid particles (5) coated with a different material, wherein the volume (3) has a maximum dimension in the range of 1 to 1000 µm, and wherein the solid particles (5) have a maximum dimension in the range of 1 to 500 nm, and wherein the energy storage material (2) is at least one salt selected from the group consisting of chlorides, bromides, carbonates and nitrates of lithium, magnesium, calcium, nickel, iron, zinc, manganese and potassium; or The energy storage material (2) includes at least one selected from CaO, Ca(OH)2, MgO, Mg(OH)2 and MgH2.

19. The method according to claim 18, comprising the steps of: c. removing the fluid released by the energy storage material (2) from the energy storage material (2).

20. A method for releasing heat, comprising the following steps: a. providing the at least partially charged energy storage material (2) in the fluidized bed device (1), b. starting the reaction of the energy storage material (2) in the fluidized bed device (1) so that heat is released, and c. transferring heat from the energy storage material (2), in, The energy storage material (2) is provided in a volume (3) of an outer layer (4) of solid particles (5) coated with a different material, wherein the volume (3) has a maximum dimension in the range of 1 to 1000 µm, and wherein the solid particles (5) have a maximum dimension in the range of 1 to 500 nm, and wherein the energy storage material (2) is at least one salt selected from the group consisting of chlorides, bromides, carbonates and nitrates of lithium, magnesium, calcium, nickel, iron, zinc, manganese and potassium; or The energy storage material (2) includes at least one selected from CaO, Ca(OH)2, MgO, Mg(OH)2 and MgH2.

21. The method according to claim 20, wherein: A portion of the heat transferred from the energy storage material (2) is used to initiate the reaction of the energy storage material.

22. The method according to claim 20, wherein: The energy storage material (2) comprises at least one selected from the group consisting of CaO and Ca(OH)2, and wherein the energy storage material (2) reacts with at least one selected from the group consisting of H2O and CO2.

23. The method according to claim 22, wherein: The energy storage material (2) comprises CaO, and wherein the energy storage material (2) reacts with CO2.

24. The method according to claim 20, wherein: The solid particles (5) have a maximum size in the range of 1-100 nm.

25. The method according to claim 20, wherein: The ratio between the average value of the largest dimension of all volumes (3) and the average value of the largest dimension of all solid particles (5) is at least 10:

1.

26. The method of claim 20, wherein: The fluidized bed apparatus (1) comprises at least one open-pored partition creating more than one different fluidizing compartment within the fluidized bed apparatus (1), wherein the different fluidizing compartments differ in at least one selected from temperature and residence time.

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