Systems and methods for thermal energy storage and transfer based on fluidized particle beds

Abstract

1. A method for heat storage and transfer comprising the steps of: providing a plurality of heat storage and transfer modules (151-154) arranged in thermal series, each module of said plurality of modules comprising a bed (150) of fluidizable solid particles as a heat storage and transfer means; applying a flow of a heat transfer fluid (HTF) across said modules (151-154) in a serial thermal sequence; and fluidizing each of said beds (150) of fluidizable solid particles to facilitate heat exchange between said heat transfer fluid and said bed particles, the arrangement being such that the heat transfer fluid can traverse successive modules following opposite directions to respectively transfer or extract thermal energy from the bed of particles.

Description

[Technical Field]

[0001] explanation FIELD OF THE INVENTION The present invention relates primarily to systems and methods for thermal energy storage and transfer based on beds of fluidized / fluidizable particles. [Background technology]

[0002] Background and Technical Basis of the Invention There are known thermal energy storage systems based on fluidized or fluidizable beds of solid particles with high heat capacity. Examples of devices, plants and methods based on said technology, which primarily use solar energy to heat the bed solid particles, are disclosed, for example, in WO2011135501A2 and WO2017021832A1.

[0003] In the above systems, the heat exchanger is generally immersed in the fluidized bed so that the thermal energy storage and transfer functions can be integrated into the same device. This configuration has the advantage over other technologies, for example based on molten salts, of eliminating the need for several separate pieces of equipment.

[0004] In the simplest configuration of fluidized bed technology, the entire fluid bed can be assumed to be isothermal, i.e., equal in mass, and all particles have the same temperature - due to its high thermal diffusivity. In this case, thermal energy is stored in the fluid bed in the form of sensible heat of the solid particles, given by: Q=m * c p * ΔT (Equation 1) where: Q is the thermal energy stored in the fluid bed, m is the total mass of the fluid bed particles, ·c p is the specific heat of the particulate material, ΔT is the difference in solid particle temperature (T max -T min ) and T min and Tmax are the minimum and maximum operating temperatures of the fluid bed, respectively.

[0005] FIG. 1 illustrates the heat exchange steps occurring in a thermal energy storage system based on fluid bed modules, such as the known thermal energy storage systems mentioned above, which are filled with heat transfer fluid (HTF) and / or thermal energy by electricity and can release heat after a certain storage time.

[0006] This configuration limits both the energy charge and discharge stages while ensuring high heat transfer rates due to fluid bed properties, as explained below.

[0007] Filling stage For example, if a fluid bed made of sand particles is filled with a heat transfer fluid such as hot steam that is available for a certain period of time, the typical trends of the temperature values ​​of the fluidized bed, inlet steam and outlet steam during the thermal energy loading phase are shown in the diagram of Figure 2.

[0008] During the filling stage, the vapors are typically: It enters the fluid bed module at a high temperature, usually constant (continuous horizontal line in the diagram), - Gradually heating the fluid bed sand isothermally across the heat exchanger in the bed (lower line), · Fluid bed sand exits the fluid bed module at increasing temperature in time with a gradual increase in temperature (middle line).

[0009] Due to the gradual increase in the fluid bed temperature during the filling time, the difference between the inlet steam temperature and the fluid bed temperature becomes smaller and smaller, as shown in FIG. 2, which is larger at the beginning of the filling phase (left vertical arrow in the diagram) and smaller at the end (right vertical arrow). As a result, the heat transfer from the hot steam to the bed particles becomes smaller and smaller during the filling time. This fact constitutes a limit to the operation and performance of thermal energy storage systems, since the latter do not extract and store the entire latent heat content of the steam. For example, in some environments, the considered configurations may not be able to recover the latent heat of the steam, which means that the stored heat is only a limited portion of the enthalpy available in the inlet steam, and that the remaining available heat is wasted (unless used in other parts of the plant).

[0010] Emission stage From the above, once the fluidized bed is charged with energy, heat is released from it to a heat transfer fluid (HTF), such as steam, CO2, supercritical CO2, etc., by a heat exchanger immersed in the fluidized bed.

[0011] The resulting HTF temperature is, of course, always below the fluid bed temperature, which may be subject to downstream adjustment (eg, by a steam desuperheater) to meet the desired conditions for use.

[0012] For better understanding, Figures 3-5 show the T min is 350℃, T max 1 illustrates possible temperature trends of the fluid bed mass and heat transfer fluid (e.g., steam) when the bed temperature is assumed to be 620° C. and the steam generation time is 6 hours.

[0013] In particular, Figure 3 shows steam temperature constantly decreasing with decreasing solid particle temperature, Figure 4 shows a steam generation profile that is constant at 500°C for the first 2 hours and then decreases with decreasing solid particle temperature, and Figure 5 shows constant steam generation at 300°C throughout the transfer period.

[0014] In either case, the diagram shows that the temperature is below the minimum fluid bed temperature (T in the example) for at least some time interval. min = 350°C), HTF is produced.

[0015] In other words, for applications where HTF is always required at, say, 500°C, the solution presented above cannot work unless the minimum sand temperature increases above 500°C (e.g., 530°C). However, such an increase would have a significant negative impact on the heat storage capacity, as the solid particles available for operation at ΔT would be significantly reduced. To stay with the example above, ΔT would decrease from (620-350)°C = 270°C to (620-530)°C = 90°C, which means that the heat storage capacity would decrease by a factor of three if steam had to be produced at 500°C instead of 300°C.

[0016] Theoretically, the temperature gap is the maximum temperature of the fluid bed (T in Equation 1). max ), but this increase may not be feasible and / or economical, particularly due to the operational limitations of the heat exchanger materials within the bed. Referring again to the example above, a minimum fluid bed temperature (T min ) and maintain the same thermal energy storage capacity to consistently produce steam at 500°C, the maximum fluid bed temperature would have to increase from 620°C to 800°C (i.e., 530+ΔT=530+270=800°C), which may be infeasible due to the properties of the materials of construction used for the heat exchanger.

[0017] Another possible solution to maintain the same heat storage capacity when producing steam at higher temperatures (e.g., 500°C) is to increase the solid particle mass, but again, this involves a much larger module (in the example, three times larger), which involves a significant increase in cost.

[0018] The above considerations are even more important when the HTF is, for example, supercritical CO, which today is expected to be capable of driving turbines with thermal-to-electrical efficiencies of up to 50%, provided that the supercritical CO is delivered to the turbine at temperatures above 700°C (and pressures above 200 bar).

[0019] In these cases, the fluid beds must operate in the extremely high temperature range (e.g., 730°C to 1000°C), which, even if possible for solid particles, may make the implementation of submerged heat exchangers impractical or shorten their lifespan too much due to material limitations for operating at such levels of temperature and pressure.

[0020] Naturally, in order to broaden the range of possible applications in general and, where necessary, in particular in the case of energy reconversion processes, for example from heat to electricity, to enable highly efficient processes, it is desirable for the TES system to recover and store as much energy as possible from the available charge source, to maximize its storage capacity, and to be able to release the stored heat at the highest temperature. Summary of the Invention The problem the task is trying to solve

[0021] SUMMARY OF THE INVENTION The technical problem posed and solved by the present invention is therefore to provide a heat storage and transfer arrangement based on a bed of fluidized solid particles that overcomes one or more of the drawbacks mentioned above with reference to the prior art.

[0022] The problem is solved by a system according to claim 1 and by a method according to claim 14.

[0023] Preferred features of the invention are the subject of the dependent claims.

[0024] As mentioned above, the present invention aims to overcome the performance limitations inherently associated with thermal energy storage and transfer configurations based on fluidized beds of solid particles with in-bed heat exchangers. [Means for solving the problem]

[0025] The system according to the invention provides a number of fluidized particle beds arranged in series for heat storage and transfer, each of said beds realizing a module in the heat storage and transfer system, advantageously each module being one of several thermal energy compartments arranged in series within the same casing.

[0026] A heat transfer fluid (HTF) is fed into the system in such a way that it traverses the series of compartments, or generally modules.

[0027] A preferred configuration is one in which the heat transfer fluid can traverse the modules in succession following opposite directions to charge or extract thermal energy to / from the bed of particles, respectively.

[0028] In the basic configuration, the heat transfer fluid runs continuously through the module only to extract thermal energy from the lower temperature bed to the higher temperature bed, in this case the filling of the bed with thermal mass can be done with other heat transfer means, for example of an electrical nature.

[0029] The mass of heat storage particles in each compartment can be the same or dedicated.

[0030] Each compartment may operate at a different range of particle temperatures.

[0031] Additional heat exchangers may be provided in one or more modules or compartments to charge thermal energy to the bed.

[0032] The HTF may be, for example, high temperature steam for the heat charge and water for the heat rejection.

[0033] The HTF flow direction across the compartment during the loading stage is generally opposite to that of the draining stage.

[0034] The invention is applicable to configurations where the thermal power charge is provided by electricity, heat transfer fluids, waste heat or solar energy, or a combination thereof, i.e. a hybrid solution.

[0035] The present invention is particularly applicable to configurations in which heat is also provided to each module or compartment by means of an electrical resistor, such as that disclosed in WO 2020 / 136456 A1.

[0036] Other advantages, features and modes of use of the invention will become apparent from the following detailed description of some embodiments thereof, given by way of example and not of limitation.

[0037] BRIEF DESCRIPTION OF THE DRAWINGS Reference is now made to the accompanying drawings. [Brief explanation of the drawings]

[0038] [Figure 1] This has already been introduced above when explaining the technical basis of the present invention. [Figure 2] This has already been introduced above when explaining the technical basis of the present invention. [Figure 3] This has already been introduced above when explaining the technical basis of the present invention. [Figure 4] This has already been introduced above when explaining the technical basis of the present invention. [Figure 5] This has already been introduced above when explaining the technical basis of the present invention. [Figure 6A] 1 shows a schematic diagram of a thermal energy storage and transfer arrangement in a side cross-sectional view according to a first embodiment of the present invention; [Figure 6B] 1 shows, in plan view, a schematic diagram of a thermal energy storage and transfer arrangement according to a first embodiment of the present invention; [Figure 7A] 1 shows a schematic diagram of a thermal energy storage and transfer arrangement in a side cross-sectional view according to a second embodiment of the present invention; [Figure 7B] 1 shows, in plan view, a schematic diagram of a thermal energy storage and transfer arrangement according to a second embodiment of the present invention; [Figure 8A] FIG. 10 shows a schematic diagram of a thermal energy storage and transfer arrangement in cross-sectional side view according to a third embodiment of the present invention. [Figure 8B] FIG. 10 shows, in plan view, a schematic diagram of a thermal energy storage and transfer arrangement according to a third embodiment of the present invention; [Figure 9A] FIG. 10 shows a schematic diagram of a thermal energy storage and transfer arrangement in accordance with a fourth embodiment of the present invention in cross-sectional side view. [Figure 9B] FIG. 10 shows, in plan view, a schematic diagram of a thermal energy storage and transfer arrangement according to a fourth embodiment of the present invention; [Figure 10A] FIG. 10 shows a schematic diagram of a thermal energy storage and transfer arrangement according to a fifth embodiment of the present invention in cross-sectional side view. [Figure 10B] FIG. 10 shows, in plan view, a schematic diagram of a thermal energy storage and transfer arrangement according to a fifth embodiment of the present invention; [Figure 11] 1 shows a schematic representation of the thermal behavior of a charge and discharge cycle in an exemplary thermal energy storage and transfer configuration according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0039] Detailed Description of the Preferred Embodiments of the Invention Some embodiments and variants of the invention are described below with reference to the figures already introduced.

[0040] Generally speaking, similar components are designated using corresponding reference numerals in the various figures. Specifically, five embodiments are shown below, and the reference numerals of the components of each embodiment have a leading digit "1" to "5", respectively, and the following two digits remain the same for corresponding or similar elements.

[0041] Further embodiments and variations from those already described will be described only with respect to the most relevant differences relative to those previously described.

[0042] Furthermore, it is understood that features of the various embodiments and variations described below may be combined where compatible.

[0043] Referring initially to FIGS. 6A and 6B, a system or device for thermal energy storage and transfer, generally designated 100, according to a first embodiment of the present invention.

[0044] System 100 includes four heat storage and transfer modules, or compartments or cells, respectively designated by reference numerals 151-154. Modules 151-154 are arranged in thermal series within a common casing 110. Casing 110 preferably includes a suitable insulating lining to minimize heat loss to the external environment.

[0045] Adjacent modules in thermal series are separated by insulating partitions, or walls, designated 161-163, respectively, to allow for maintaining an operating temperature difference between the compartments.

[0046] Each module includes a bed of fluidizable solid particles, illustratively designated 150 for the first module 151. The bed of particles, in particular sand particles, acts as a thermal energy storage and transfer means, as will be explained shortly below.

[0047] In use, the particles in each bed are fluidized by fluidization means, illustratively designated 120 for the first module 151, which add a fluidizing gas, in particular air, to the bed. The fluidization means include a respective fluidization unit for each module. In particular, fluidizing air distribution devices are arranged in the bed of each compartment in such a way as to allow independent control of gas distribution between modules.

[0048] In an embodiment of the invention, the partitions 161-163 allow fluid communication of the flowing gas between the environments of the various compartments above the free surface 130 of the bed, i.e., gas added to one bed can merge with the flowing gas in other modules after longitudinally traversing it. Thus, each partition 161-163 extends above the free surface 130 of the bed but below the roof, or top wall, or part of the casing 110. In the example of the invention, the longitudinal (vertical) level of the free surface 130 is the same for each module, and the width of each compartment (the distance between adjacent partitions) is also the same.

[0049] The fluidization means is configured to apply a flow of fluidizing gas to the bed of each module to facilitate heat exchange between the bed particles and a heat transfer fluid (HTF) flowing through the heat transfer means. The latter heat transfer means, shown as 101 and 102 in Figure 6A, are immersed in the particle bed and are positioned to traverse the modules 151-154 in serial thermal sequence.

[0050] The transmission means may include one or more conduits.

[0051] The HTF may be steam, CO2, supercritical CO2, hot air, flue gas, or the like.

[0052] In the illustrated embodiment, the heat transfer means includes a first circuit or conduit means 101, 101' configured to charge thermal energy into the floor of each module, and a second circuit or conduit means 102, 102' configured to extract thermal energy from the floor of each module, the second circuit 102, 102' being positioned across the floor opposite the first circuit 101, 101' as indicated by the arrows in Figure 6A.

[0053] The countercurrent circuits 101, 101' and 102, 102' can be operated simultaneously or alternately depending on the specific heat needs of the plant in which the system 100 is included.

[0054] Generally speaking, each HTF circuit can be divided into more sub-circuits arranged in parallel to provide the desired input / output power.

[0055] As can be seen from the plan view of Figure 6B, in an embodiment of the present invention, each first and second circuit includes a pair of conduits, thermally, and in the illustrated example also geometrically, arranged in parallel to perform the same heat filling or heat extraction operation, the first pair being designated 101, 101' and the second pair being designated 102, 102'.

[0056] In operation, the first circuit 101, 101' charges the beds with thermal energy such that the first bed in the sequence is at a higher temperature and the last bed in the sequence is at a lowest temperature. Generally, each intermediate bed in the sequence has a lower temperature than the preceding one and a higher temperature than the next. The reverse occurs in the sequence of beds traversed in the thermal energy extraction process.

[0057] A second embodiment of a system according to the invention, generally designated 200, is shown in Figures 7A and 7B. In this case, the heat transfer means comprises a single circuit or conduit means 201, 201' configured for heat transfer fluid to alternately traverse in opposite directions so as to function alternately as the heat fill circuit and the heat extraction circuit for each module.

[0058] This embodiment has the advantage of being a more compact and cost-effective solution when compared to the first embodiment, which can be applied when the thermal energy charging and discharging phases of the bed do not need to be simultaneous.

[0059] 7A, the partitions designated by 261-263 prevent fluid communication between the environments hosting each bed (the latter beds designated by 250 for the first module 251). In particular, the partitions 261-263 are elevated to the roof of the fluidized bed casing 210.

[0060] Given that the flowing air stream exiting each compartment typically has the same temperature as the fluid bed mass of that compartment (due to the small amount of air compared to the fluid bed mass), the arrangement of the present invention allows the different flowing air streams to be kept separate and maintain their different temperature values. The separate flows of gas exiting the free face of the bed can be manipulated independently or together by means known in the art.

[0061] 8A and 8B refer to a third embodiment 300 which combines the previous ones in that partitions 361-363 allow fluid communication between the modules and a single circuit or conduit means, 301, 301', is provided.

[0062] 9A and 9B relate to a fourth embodiment 400 that is compatible with the configuration of each of the preceding ones, with each module 451-454 including, by way of example, an additional thermal charging means, indicated at 470 for the first module 451, configured to charge thermal energy into the bed of particles.

[0063] In the present example, the additional heat filling means is an electric heater 471, in particular an electric resistor, which is at least partially immersed in the bed of particles and which generates heat by the Joule effect.

[0064] 10A and 10B relate to a fifth embodiment 500, compatible with the configuration of each of the preceding ones, in which each module 551-554 includes, by way of example, additional thermal fill means, designated 570 for the first module 551, configured to fill the bed of particles with thermal energy and arranged on top of the common casing 510. In the present example, the additional thermal fill means is an electric radiant panel 571 facing towards the bed of particles.

[0065] An alternative embodiment may provide additional heat charge means in the form of a solar energy based exchanger means.

[0066] In embodiments using additional heat charge means, the floor of each compartment can be charged with thermal energy by the additional heating means in combination with the HTF, or by the additional heating means alone during selected stages of operation when thermal power from the HTF is not available.

[0067] Furthermore, in the case of hybrid, i.e., charging with electricity and HTF, the energy charging with electric heater and high temperature HTF may or may not be simultaneous, depending on the availability of said energy sources in time and their economic convenience (i.e., charging when electricity and HTF costs are low).

[0068] The operation of the inventive system according to the above disclosed embodiments will now be described in more detail.

[0069] In each of the above embodiments, during the charging stage, hot HTF (e.g., hot steam) enters the first module, or compartment, releases a portion of its energy to the fluid bed, then exits the first compartment and enters the second compartment, releasing a portion of its remaining energy, and so on. By continuing to the third and subsequent compartments arranged in series, heat from the HTF is progressively released to the storage fluid bed until the HTF heat capacity is preferably depleted. In this manner, the temperature profile along the compartments progressively decreases from the first compartment to the last compartment in the series. As a result, thanks to the mentioned multi-compartment module configuration, a greater amount of thermal energy can be transferred from the HTF to the storage fluid bed while maintaining a constant total fluid bed particle mass compared to the single cryogenic module of the aforementioned prior art.

[0070] For example, if the filling step is done with superheated steam, a multi-compartment module arrangement makes it possible to gradually cool the steam and condense it, partially or totally recovering its latent heat capacity, which means that the heat stored can be significantly higher than in a single isothermal module.

[0071] During the discharge stage, the cold HTF (e.g., feedwater) enters the last compartment, which is the coldest in the series, where it is heated by the fluid bed sand, then the HTF leaves the last compartment and enters the penultimate compartment, which operates at a higher temperature than the preceding one, so the HTF may be further superheated, etc. By traversing successive compartments, the HTF is progressively heated until it reaches the first compartment.

[0072] As a result of the multi-compartment configuration, the exhaust mode allows for higher temperature HTF to be generated for a longer period of time than would be possible with a single isothermal module, thus enabling a wider range of thermal processes to be realized and for the heat of the generated HTF to be converted into electricity in a more efficient cycle.

[0073] For example, a multi-compartment arrangement allows feedwater to be progressively heated, evaporated, and superheated in a series of fluid bed compartments, allowing for the generation of higher temperature steam than would be possible with a single cryogenic unit.

[0074] Each of the above embodiments comprises the following main steps: providing a plurality of heat storage and transfer modules arranged in thermal series; each module of said plurality of modules comprising a bed of fluidizable solid particles as heat storage means; adding a flow of heat transfer fluid (HTF) across said modules in a serial thermal sequence to charge it with thermal energy, or providing thermal energy to the beds by other means, in such a way that each (intermediate) bed in the sequence has a lower temperature than the preceding one and a higher temperature than the succeeding one; fluidizing each of said beds of fluidizable solid particles to promote heat exchange between said heat transfer fluid or other heat loading means and the bed particles; The heat may be used in heat storage and transfer methods including:

[0075] A preferred arrangement is one in which the heat transfer fluid is also used to extract thermal energy from the module, in which case the heat transfer fluid can traverse the module successively following opposite directions to charge or extract thermal energy to / from the particle bed, respectively.

[0076] Thermal charging in the module can also be done by a combination of HTF and other sources such as electricity.

[0077] The selected HTF arrangement and / or alternative heat source allows each module to be brought to the required operating temperature.

[0078] Following the above explanation, several design parameters can be selected to optimize the storage cycle performance and HTF production, such as the number of compartments, particle mass in each compartment, heat exchange surface within the bed, thermal charging and discharge phase duration, HTF flow rate, temperature in each compartment, and the possibility of hybrid charging of the bed with HTF and electricity.

[0079] Numerical example Serial arrangement of fluid bed compartments As an example, Figure 11 shows a scheme of a fluidized bed system with four compartments in series. In this example, the fluid bed mass can be assumed to be the same in each compartment and it can be noted that: The maximum particle (sand) temperature is the same for all modules (e.g. 620°C) due to the combination of energy charges, e.g. electricity plus superheated steam. A different minimum sand temperature is used in each module, i.e. Sand temperature T in module 1 1,min (Above the desired outlet steam temperature, e.g., T 1,min >500℃) to Lower temperature T in module 4 4,min (T 4,min , e.g., T 4,min >130℃) ΔT(T max -T min) increases from section 1 to 4.

[0080] As shown in Figure 11, the energy charge comes from process steam entering compartment 1 (e.g., at 550°C) and undergoing gradual cooling across the compartments, which may allow the steam to condense up to compartment 4. Heat released by the steam across the compartments is captured by and stored in the fluid bed mass in each compartment. The thermal energy storage capacity is different in each compartment and shows an increasing profile from compartment 1 to compartment 4 in association with the increasing ΔT profile.

[0081] In addition to the heat charge with steam, electricity can be used (simultaneously or not) to raise the fluid bed temperature of each compartment by the Joule effect to a desired value (e.g., 620°C) and, correspondingly, to the associated heat storage capacity.

[0082] During thermal energy storage and discharge, water enters compartment 4 (e.g., at 130°C) and undergoes a first step of heating there, then exits compartment 4 and enters compartment 3 with a second step of heating, and so on until it exits compartment 1 as steam at the desired temperature (e.g., 500°C).

[0083] The series of compartments in this way allows for the gradual heating of the resulting HTF during the discharge phase, which leads to progressively higher values ​​of the minimum solid particle temperature T min This is made possible by:

[0084] Maximum operating temperature (T max ) can be the same or different between modules and can be determined according to need and availability of heating sources (electricity, waste heat, etc.).

[0085] System total storage capacity Q tot is given by adding the unitary storage capacity of each module i as follows:

number

[0086] As mentioned above, in order to realize the desired energy charging, storage and discharge cycle in a system based on such a configuration, the number of compartments, the duration of the heat charging and discharge phases, the fluid bed mass in each compartment, the intra-bed heat exchange surface in each compartment, the HTF flow rate and quality during the charging and discharge phases, the working fluid bed temperature (T min , T max ), and in the case of hybrid filling with HTF and electricity, several parameters can be combined, such as the power in each compartment.

[0087] Comparison between multi-compartment and single-compartment arrangements To better understand the advantages of the multi-compartment solution according to the invention compared to the "traditional" single compartment, some non-limiting numerical examples are given in this section.

[0088] The first case can be analyzed as a "heat to heat" configuration, where the fluidized bed energy storage system is charged with heat available as superheated steam, and after a certain storage time, the stored heat energy is released to produce steam again.

[0089] A comparison is made between single-compartment and multi-compartment, assuming the latter is divided into 2, 4 and 6 compartments. In this comparison, the same boundary conditions are assumed, i.e. Steam quality, filling stage: 555°C / 60 bar Steam flow rate, filling stage: 20 kg / s Steam quality, discharge stage: 300°C / 30 bar ·Water temperature: 146℃ Total fluid bed mass: 500 tons Total floor heat exchange surface: 600m 2 Duration of filling phase: 5h Duration of discharge phase: 5h

[0090] Table 1 below shows the operating temperature range (T min , T max) where section 1 is where steam is introduced for hot charge and the final section is where feedwater is introduced against the charge steam flow for steam generation during discharge.

[0091] [Table 1]

[0092] Table 1 above shows that in a multi-compartment system, a temperature gradient is created between the compartments, i.e., the fluid bed temperature profile across the series of compartments decreases from the first compartment to the last compartment during filling, and increases from the last compartment to the first compartment during draining.

[0093] In this way, the heat capacity of the charge steam is better utilized and, in fact, the enthalpy of the steam leaving the last compartment decreases more and more as the number of compartments increases, thus allowing for greater energy storage with a greater number of compartments while keeping all other boundary conditions unchanged.

[0094] Table 1 shows, in particular, the expected increase in heat storage capacity and steam flow rate provided by the multi-compartment solution, which for this particular case is estimated at 20.4%, 26.8%, and 28.0% for 2, 4, and 6 compartments, respectively.

[0095] The second case is analyzed here as a "power vs. heat" configuration, where the fluidized bed energy storage system is only charged with electricity that is available at low cost at certain times, typically due to overproduction of intermittent renewable energy, e.g., PV and wind, and after a certain storage time, the stored thermal energy is released to generate high-quality steam.

[0096] In this case, a comparison is made between a single compartment solution and two multi-compartment solutions, i.e., two and six compartments, with the same boundary conditions in all cases, specifically: Total fluid bed mass: 3000 tons ·Total in-floor heat exchange surface: 3000m 2 Steam quality, discharge stage: 500°C / 30 bar Duration of filling phase: 5h Duration of discharge phase: 5h

[0097] The electricity for heating is determined by the parameters, e.g. the heater design limit (here e.g. 80 kW / m 2 The fluid bed is charged with the maximum possible power, taking into account the available surface area (assumed to be 1000 sq ft) and the maximum design temperature limit of the fluid bed (assumed to be 620° C. in this example).

[0098] Table 2 below shows some of the main results of this analysis. As can be pointed out, in this example, the fluid bed design temperature limit (620°C) and the need to produce high quality steam (500°C / 30 bar) are limited to their maximum allowable values ​​(80 kW / m) in the case of a single compartment solution. 2 ), which limits the power available for the electric heaters to well below the maximum allowable power. A multi-compartment solution, on the other hand, allows for an operating fluid bed temperature profile in the compartments after the first compartment, which offers the possibility of installing electric heaters that reach their maximum allowable power, which is of course advantageous.

[0099] As a result, both the expected heat storage capacity and the resulting steam flow rate are higher in the case of the multi-compartment solution than in the single-compartment one, as shown for this particular example in Table 2 below; in particular, the increase from the single-compartment solution is estimated at 37.7% and 56.5% for the two- and six-compartment solutions, respectively.

[0100] [Table 2]

[0101] The present invention has been described above with reference to preferred embodiments, and it is contemplated that there are other embodiments that refer to the same inventive concept as defined by the scope of the following claims.

Claims

1. A thermal energy storage and transfer system (100), comprising: a plurality of heat storage and transfer modules (151-154) arranged in series and thermally in series, each module of said plurality of modules comprising a bed (150) of fluidizable solid particles as heat storage means and storing thermal energy in the form of sensible heat of said solid particles; - thermal charging means (101) arranged to charge each bed with thermal energy, the means (101) being adapted to bring each bed to an operating temperature lower than the preceding bed and higher than the succeeding bed; - heat extraction means (102) configured to host a flow of heat transfer fluid (HTF) across said modules (151-154) in a serial thermal sequence, said heat transfer fluid being configured to extract thermal energy from said beds and to traverse said sequence of modules from the coldest bed to the hottest bed; - fluidization means (120) for each of said beds (150) of fluidizable solid particles, configured to apply a flow of fluidizing gas to each of said beds; Including, said plurality of heat storage and transfer modules (151-154) sharing a common casing (110) and separated by thermally insulating partition means (261-263); said partition means (261-263) preventing fluid communication of said flowing gas between environments hosting each of said beds; A thermal energy storage and transfer system (100).

2. 2. The thermal energy storage and transfer system (100) of claim 1, wherein the heat charging means (101) comprises a charging circuit (101, 101') or conduit means configured to host a flow of heat transfer fluid (HTF) that charges each of the beds (150) with thermal energy, and the heat extraction means (102) comprises an extraction circuit (102, 102') or conduit means configured to extract thermal energy from each of the beds (150).

3. 3. The thermal energy storage and transfer system (100) of claim 2, wherein the extraction circuit (102, 102') is arranged across the bed in counter-current flow with respect to the charge circuit (101, 101').

4. 4. The thermal energy storage and transfer system (100) of claim 1, wherein the heat fill means (101) comprises one or more of an electrical resistor means (471), a radiant panel (571), and a solar energy based exchanger means.

5. A thermal energy storage and transfer system (100) as described in any one of claims 1 to 4, wherein the heat transfer fluid (HTF) is configured to traverse the modules sequentially in opposite directions when charging and extracting thermal energy from the bed.

6. A thermal energy storage and transfer system (200) according to any one of claims 1 to 5, comprising a single circuit (201, 201') that is alternately traversed in opposite directions by a heat transfer fluid so as to function alternately as a heat filling means and a heat extraction means.

7. A thermal energy storage and transfer system (100) according to any one of claims 1 to 6, wherein the heat extraction means and / or the heat filling means comprise a plurality of, in particular two, conduits (101, 101'; 102, 102') arranged in parallel to perform the same heat filling or heat extraction operation.

8. 8. A thermal energy storage and transfer system (400) according to any one of claims 1 to 7, wherein at least one of the modules (451-454) comprises additional thermal charge means (470) configured to charge the floor (450) of the module with additional thermal energy from an energy source different from the thermal charge means (101).

9. 10. The thermal energy storage and transfer system (400) of claim 8, wherein the additional heat fill means (470) comprises one or more of an electrical resistor means (471), a radiant panel (571), and a solar energy based exchanger means.

10. 10. The thermal energy storage and transfer system (100) of claim 1, wherein the partition means (161-163) allow fluid communication of the flowing gas added to each bed in an environment above its free surface (130) that hosts the bed (150).

11. The thermal energy storage and transfer system (100) of any one of claims 1 to 10, wherein the fluidization means (120) comprises a respective fluidization unit for each of the thermal storage and transfer modules (151-154).

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