Plant and method for storing and releasing thermal energy - Patents.com

Abstract

A plant for storing and releasing thermal energy comprises a first heat exchanger 2 coupled to a heat source 3, a second heat exchanger 4 coupled to a heat user 5, a fluid F configured to store thermal energy, a storage device 6 for the fluid F, and a circuit configured to couple the first heat exchanger 2, the second heat exchanger 4, and the storage device 6. The storage device 6 comprises N+B storage sections 13a-13h fluidly connected to one another, where N is equal to or greater than 2 and B is less than N, and each of the N+B storage sections 13a-13h has the same storage volume V. The fluid F occupies a volume substantially equal to N times the storage volume V. A separation gas G is inserted into the storage device 6 and is configured to contact the fluid F and to keep a hot portion of the fluid separated from a cold portion of the same fluid at all times.

Description

[Technical field]

[0001] The object of the invention is a plant and a method for the storage and release of thermal energy. More precisely, the object of the invention is a system capable of storing thermal energy, utilizing the sensible heat of a fluid substance, such that the energy administered to the fluid causes an increase in its temperature, preferably without causing a phase change.

[0002] The present invention is located in the field of medium or large-scale thermal energy storage systems (thermal energy storage or TES) for both onshore and offshore applications, typically with thermal powers ranging from several hundred kW to several tens of MW (e.g. 20-25 MW) and even several hundred MW, and with storage capacities ranging from several hundred kWh to several hundred MWh and even several GWh. The present invention can also be located in the field of small-scale energy storage systems for domestic and commercial applications, both onshore and offshore, typically with thermal powers ranging from several kW to several hundred kW and storage capacities ranging from several kWh to several hundred kWh. [Background technology]

[0003] The global problem of "climate change" is now recognized around the world, and it is likewise agreed that the fundamental solution to such a problem must go through the decarbonization of the Earth. In other words, the reduction of CO2 released into the atmosphere 2 The introduction must be stopped, and in some cases CO 2 must also be absorbed from the atmosphere to reduce its concentration. Towards decarbonisation objectives, use renewable sources for both electrical energy and heat.

[0004] As more and more efficient and advantageous systems are used for the use and distribution of thermal energy, there is an increasing need to store the same energy in thermal form. This new technology therefore sets itself first to this end, i.e. it is becoming increasingly advantageous to use heat not only from renewable sources such as solar, geothermal, biomass, etc., but also from the dissipation of electrical energy produced in a renewable way and / or from "waste heat recovery" for the distribution and use of thermal energy for both civil and industrial purposes.

[0005] Instead, with regard to the electrical industry, the need to decarbonize has recently led to the increasing popularity of systems for generating energy from renewable sources, especially from wind and solar power sources, characterized by variability and unpredictability of their generation. Electrical energy storage systems are becoming increasingly important. In addition to systems that work according to electrochemical principles (batteries), which are typically expensive and have a limited service life, or according to mechanical principles (flywheels), which are only suitable for small amounts of stored energy, systems are known for storing electrical energy according to thermodynamic processes, and therefore also using energy storage in the form of thermal energy.

[0006] This new technology is set to make such electrical energy storage systems increasingly efficient and more advantageous.

[0007] In addition, to contribute to carbonization, systems capable of generating energy that is "renewable" but "tunable", i.e. programmable and therefore "tunable", are constantly being researched and needed. In that sense, thermodynamic solar plants are potential candidates, and they also realize the use of a storage form of thermal energy. Thermodynamic solar plants can also be seen as an example sub-case for the storage of thermal energy. They can be provided as thermal energy storage systems for thermal use as well as for "tunable" electrical energy generation applications.

[0008] Examples of the use of such systems are balancing the energy demand between day and night, storing heat in summer for winter heating or storing cold in winter for summer climate control (seasonal storage of thermal energy). Other applications of systems for storing thermal energy include heat produced by renewable electric energy in excess of grid demand and / or waste heat of industrial processes. Seasonal and short-term storage of heat is considered an important means to cheaply balance the generation of high levels of variable renewable electricity and its integration into an energy system powered almost or completely by renewable energies. Systems for storing thermal energy are made with very different technologies. Depending on the specific technology, it is possible to store excess thermal energy and use it for the following hours, days or months.

[0009] Systems are known that utilize the sensible heat of fluids such as pressurized water, molten salt or oil. The heat stored is proportional to the temperature difference, the specific heat of the fluid and the mass of the fluid.

[0010] 22A and 22B attached herewith show schematic diagrams of known systems of such type (prior art) in a thermal energy storage phase (system charge phase) and a thermal energy release phase (system discharge phase), respectively. The system receives heat from one or more sources while heating a fluid to an initial temperature T 0 to the final temperature T 1It is composed of a heat exchanger E for heating up to 1000 MPa, a system of pipes and pumps for moving the fluid between the source and one or more users, a heat storage system and a system of further exchangers for transferring the heat to one or more users. In FIG. 22A, the system is in the stage of utilizing the heat requested by the user U and coming from the source S, while at the same time the storage of excess heat occurs in the thermal accumulator A. The storage system is "filling". In FIG. 22B, the source S is not able to satisfy the heat demand by the user U (even partially, here the case of source absence is shown), in which case the user U utilizes the accumulated heat in the thermal accumulator A, and the thermal accumulator system is "discharged". The thermal accumulator A of known type shown in FIGS. 22A and 22B comprises two thermally independent tanks, each capable of storing the entire mass of fluid dedicated to the storage of thermal energy (one excluding the fluid in the system of pipes and exchangers). The volume of the storage tank is therefore twice the volume of the fluid in its maximum specific volume state (lower density), which must already be high in itself if it is desired to store large amounts of thermal energy.

[0011] Also known are heat accumulators with a single tank and exploiting a vertical temperature gradient. Usually the higher temperature fluid is kept in the upper part, considering that it rises upwards due to its lower density. Such heat accumulators reduce the required volume with respect to the use of two tanks and impair the system efficiency due to mixing between the higher and lower temperature fluids.

[0012] Also known is the published document WO 2015 / 136351, which shows a method for generating load-following power by using low or medium temperature heat, in which measures are taken to reduce the level of power generated by an ORC plant by generating power operating on a low or medium temperature heat source during a first time period, storing the heat not used during the first time period, and then / in a second time period using the stored heat to generate power. WO 2015 / 136351 shows a closed storage cycle, which uses a series of storage tanks for water or thermal oil and pressurized inert gas to prevent the liquid from evaporating when one or more of the tanks are only partially filled.

[0013] Furthermore, documents WO 2016 / 150461 and DE 102011053349 A1 show systems / plants for storing energy in the form of thermal energy of a working fluid. Summary of the Invention

[0014] Applicant has observed that current thermal energy storage systems that utilize the sensible heat of fluids are expensive and / or not very efficient.

[0015] In particular, the applicant has observed that the use of molten salts or oils involves high costs associated with the materials used.

[0016] The applicant has further observed that water must be pressurized to be usable at temperatures typically above 90° C., and that the pressure required for such types of applications is tens of bars. The tanks must therefore be sized accordingly, resulting in them being very bulky, heavy and costly due to their increased thickness.

[0017] Assuming the use of the three materials mentioned above to store 100MWt of heat for 10 hours, the stored heat will be equal to 3.6e6MJ utilizing a DT equal to 150°C (90°C to 240°C) using a system with two tanks, the values ​​in Table 1 and Table 2 below exist. [Table 1] [Table 2]

[0018] When using a heat accumulator with a single tank (usually with a volume equal to the volume of the fluid increased by 25-30%), the values ​​are those in Table 3 below. [Table 3]

[0019] Therefore, the cheapest systems are those using molten salt if the tanks are separate, or pressurized water if there is a single tank.

[0020] However, applicant has also observed that the fluid in the single tank must be "completely" and "rapidly" utilized; otherwise, over time, the action of remixing will involve bringing the entire mass to an intermediate temperature, greatly reducing efficiency.

[0021] In that context, the applicant set himself the objective of devising and producing a plant and method for storing and releasing thermal energy that utilizes the sensible heat of a fluid substance, i.e. "thermal energy storage", which is more efficient and less expensive than those known.

[0022] In particular, the applicant has set himself the objective of devising and creating a plant and method for the storage and release of thermal energy that makes it possible to contain the volumes required for storage.

[0023] Applicant has discovered that the above devised objects, as well as still other objects, may be achieved by a system operating with N+B independent storage sections, where N is 2 or more and B is less than N. In other words, the idea is to divide the required volume into N smaller volumes, called sections, where N is 2 or more, plus a dead volume having a substantially equal volume to one or more of the sections.

[0024] In particular, the above-mentioned objects as well as further objects are substantially achieved by a plant and a method for storing energy of the kind claimed in the accompanying claims and / or described in the following embodiments.

[0025] In an independent aspect, the present invention provides a plant for storing and releasing thermal energy, comprising: at least one heat exchanger operably coupled or connectable to at least one heat source and / or at least one heat user, optionally at least one first heat exchanger operably coupled or connectable to at least one heat source and at least one second heat exchanger operably coupled or connectable to at least one heat user; a fluid configured to store thermal energy; a storage device for the fluid; a circuit configured to couple said at least one heat exchanger, optionally a first heat exchanger and a second heat exchanger, and said at least one storage device; a control element operably coupled to said circuit and / or said at least one storage device and configured to move fluid within said at least one heat exchanger, optionally a first heat exchanger and a second heat exchanger, and the storage device, optionally without a phase change; During a storage stage, in which a heat source transfers heat to said at least one heat exchanger, optionally a first heat exchanger, a fluid receives said heat through said at least one heat exchanger, optionally a first heat exchanger, is heated to a higher temperature and is stored as a hot fluid in said at least one storage device; During a release phase, when the heat source does not produce heat or does not produce enough heat, the fluid transfers the accumulated heat through said at least one heat exchanger, optionally through a second heat exchanger, to a heat user, is cooled to a lower temperature and is stored as a cryogenic fluid in said at least one storage device, the storage device comprises: a storage section, N+B storage sections, N being equal to or greater than 2 and B being less than N, each of the N+B storage sections having substantially the same storage volume, the N+B storage sections being fluidly connected to one another; and a separation gas inserted into the storage device, the fluid occupying a volume substantially equal to N times the containment volume, the separation gas being in contact with the fluid and configured to always separate or keep the hot fluid separated from the cold fluid.

[0026] In an independent aspect, the present invention provides a storage device for a plant for storing and releasing thermal energy, comprising: a number N+B of storage sections for a fluid configured to store thermal energy, where N is equal to or greater than 2 and B is less than N, each of the number N+B of storage sections having substantially the same storage volume, and the number N+B of storage sections being fluidly connected to one another; and a separation gas inserted into the storage device, the fluid occupying a volume substantially equal to N times the containment volume, the separation gas being in contact with the fluid and configured to always separate or keep a hot fluid separated from a cold fluid.

[0027] In an independent aspect, the invention relates to a method for storing and releasing thermal energy, optionally operated through a plant according to at least one of the preceding or following aspects.

[0028] The method includes providing N+B storage sections connected to one another, N being equal to or greater than 2 and B being less than N, each of the N+B storage sections having substantially the same storage volume, the N+B storage sections being fluidly connected to one another, a fluid being disposed within the storage sections and occupying a volume substantially equal to N times the storage volume, and a separation gas being disposed within the storage sections; In the storage stage, the method includes the steps of passing the fluid through at least one heat exchanger operably coupled to at least one heat source, optionally a first heat exchanger, to heat the fluid; introducing at least a portion of the heated fluid into a storage section of the N+B storage sections and simultaneously extracting a cryogenic fluid contained in said storage section from one of the other storage sections, wherein the separation gas contacts the hot and cold fluids and keeps the hot fluid separated from the cold fluid, and while introducing the heated fluid into the storage section, the separation gas flows into said one of the other storage sections from which the cold fluid was extracted; and conveying the cryogenic fluid exiting said one of the other storage sections into said at least one exchanger, optionally into the first exchanger.

[0029] In the release phase, the method includes the steps of extracting accumulated hot fluid from one of the storage sections; transporting the hot fluid through the at least one heat exchanger, optionally through a second heat exchanger, to transfer heat to at least one heat user; and introducing the cooled fluid that has just passed through the at least one heat exchanger, optionally the second heat exchanger, into one of the other storage sections, wherein while introducing the cooled fluid into the one of the other storage sections, separated gas flows into the one of the storage sections from which the hot fluid was extracted.

[0030] The applicant has verified that the method and device according to the invention make it possible to obtain pre-established objectives.

[0031] The applicant has determined that the present invention makes it possible to reduce the overall volume and therefore the overall weight of the tank.

[0032] In particular, the applicant has demonstrated that the invention makes it possible to reduce the cost of the device, given the same amount of fluid required.

[0033] The applicant has verified that the present invention makes it possible to maintain a smaller overall volume than known systems having a single tank, while maximizing efficiency, as would be the case with two independent tanks.

[0034] The aspects of the present invention are listed below.

[0035] In one embodiment, the separation gas occupies the same dead volume at all times during the process and / or operation of the plant.

[0036] In one embodiment, the separation gas occupies a dead volume substantially equal to the containment volume of the section.

[0037] In one embodiment, the separation gas is at a pressure necessary to maintain the fluid in the liquid phase under all operating conditions. The separation gas has both a batch and buffer function to maintain a constant pressure against the free surface of the fluid.

[0038] In one embodiment, N is greater than 3, optionally equal to or greater than 10, and optionally N is comprised between 10 and 20. In this way, it is possible to obtain a total volume smaller than that of an apparatus having a single tank, with an efficiency equal to that of a system having two independent tanks.

[0039] In one embodiment, B is equal to 1. Having only one section as dead volume (B=1) helps to minimize the ratio between the volume of the tank and the volume of the fluid.

[0040] In fact, each of the N sections has a containment volume V equal to the total volume of the fluid divided by the number of sections N: V = V_fluid / N. In addition to the volume of the N sections, a dead volume B is equal to the volume of the section (only one dead volume, since B = 1). Thus, the storage device has a volume V tot = (N+1)*V and has an oversize (extra volume) equal to (N+1) / (N))-1) = 1 / N. In Table 4 below, the extra volume with increasing N is reported. [Table 4]

[0041] In one embodiment, all N+B storage sections are identical to one another.

[0042] In one embodiment, the fluid in the lower density state occupies a volume equal to N sections.

[0043] In one embodiment, each storage section comprises or is defined by a single tank.

[0044] In one embodiment, each storage section comprises multiple interconnected tanks, optionally without shut-off valves.

[0045] In one embodiment, each tank has an elongated configuration, optionally being substantially cylindrical.

[0046] In one embodiment, the tank is oriented vertically.

[0047] In one embodiment, each tank has a spherical shape.

[0048] In one embodiment, the tanks of the storage section are connected in series and / or parallel to each other.

[0049] In one embodiment, the tanks of a storage section are connected to tanks of different storage sections by at least one shared connection.

[0050] In one embodiment, the storage sections and / or tanks are connected at the same geodetic elevation.

[0051] In one embodiment, each storage section has at least one lower inlet / outlet opening connected to the other storage sections and at least one upper inlet / outlet opening connected to the other storage sections.

[0052] In one embodiment, the control element is configured to determine the passage of fluid (both inlet and outlet) through said at least one lower inlet / outlet opening and to determine the passage of gas (both inlet and outlet) through said at least one upper inlet / outlet opening.

[0053] In one embodiment, provisions are made for introducing fluid into and extracting fluid from each storage section from the bottom.

[0054] In one embodiment, provisions are made for introducing fluid into and extracting fluid from each storage section from the top.

[0055] Fluid always leaves or enters each storage section (depending on the operation step) from the bottom, through said one or more lower inlet and outlet openings located in the lower part of each storage section, and gas always leaves or enters each storage section (depending on the operation step) from the top, through one or more upper inlet and outlet openings located in the upper part of each storage section.

[0056] In one embodiment, the lower inlet / outlet opening is connected to said circuit.

[0057] In one embodiment, the circuit includes a hot branch configured to carry a hot fluid and a cold branch configured to carry a cold fluid.

[0058] In one embodiment, the at least one heat exchanger comprises a single heat exchanger.

[0059] In one embodiment, the hot branch extends between the single heat exchanger and a first inlet / outlet of the storage device, and the cold branch extends between the single heat exchanger and a second inlet / outlet of the storage device.

[0060] In one embodiment, the hot branch is connected to the outlet of the first heat exchanger and the inlet of the second heat exchanger, and the cold branch is connected to the inlet of the first heat exchanger and the outlet of the second heat exchanger.

[0061] In one embodiment, the storage device has a first inlet / outlet optionally connected to a hot branch between the first and second heat exchangers and a second inlet / outlet optionally connected to a cold branch between the first and second heat exchangers.

[0062] In one embodiment, the lower inlet / outlet opening is connected to a cold branch of the circuit and to a hot branch of the circuit.

[0063] In one embodiment, the storage device has a first main inlet / outlet connected to a high temperature branch of the circuit and a second main inlet / outlet connected to a low temperature branch of the circuit, the first main inlet / outlet and the second main inlet / outlet being in fluid communication with a lower inlet / outlet opening of the storage section.

[0064] In one embodiment, the pump is located on the cold branch.

[0065] In one embodiment, the cold branch has a diverter device configured to direct fluid through the cold branch from the storage device towards the heat exchanger or from the heat exchanger towards the storage device.

[0066] In one embodiment, a first pump is located in the cold branch between the second main inlet / outlet and the first exchanger, and a second pump is located in the cold branch between the second exchanger and the second main inlet / outlet.

[0067] In one embodiment, each storage section has a first lower inlet / outlet opening and a second lower inlet / outlet opening.

[0068] In one embodiment, the first lower inlet / outlet opening is connected to a high temperature branch of the circuit and the second lower inlet / outlet opening is connected to a low temperature branch of the circuit.

[0069] In one embodiment, the storage device comprises a plurality of valves for hot fluid and a plurality of valves for cold fluid, each valve for the hot fluid operably associated with a respective one of the first lower inlet / outlet openings and each valve for the cold fluid operably associated with a respective one of the second lower inlet / outlet openings.

[0070] In one embodiment, the first lower inlet / outlet opening is in fluid communication with the first main inlet / outlet and the second lower inlet / outlet opening is in fluid communication with the second main inlet / outlet.

[0071] In one embodiment, each storage section has a single lower inlet / outlet opening.

[0072] In one embodiment, the plant comprises a plurality of first valves and a plurality of second valves.

[0073] In one embodiment, a first valve is operatively associated with each lower inlet / outlet opening.

[0074] In one embodiment, all of the lower inlet / outlet openings are connected to a single section of the circuit.

[0075] In one embodiment, second valves are operatively associated with said single section, each second valve operatively interposed between two consecutive lower inlet / outlet openings.

[0076] In one embodiment, the single section forms a siphon between one storage section and the next.

[0077] In one embodiment, the siphon comprises an ascending section, a descending section, and an upper curved connector.

[0078] In one embodiment, the siphon has a height that is greater than the height of the storage section.

[0079] In one embodiment, the plant comprises a plurality of gas valves, each gas valve operatively interposed between upper inlet / outlet openings of adjacent storage sections.

[0080] In one embodiment, the storage device comprises a dispensing valve.

[0081] In one embodiment, all of the lower inlet / outlet openings are connected to a distribution valve.

[0082] In one embodiment, a distribution valve is connected to the hot and cold branches of the circuit.

[0083] In one embodiment, the distribution valve is configured to selectively place a hot branch of the circuit in fluid communication with the storage section and a cold branch of the circuit in fluid communication with a different storage section.

[0084] In one embodiment, in the storage stage, the distribution valve is configured to place the storage section in turn in fluid communication with the high temperature branch of the circuit.

[0085] In one embodiment, in the release stage, the distribution valve is configured to sequentially place the storage section in fluid communication with the cold branch of the circuit.

[0086] In one embodiment, the dispensing valve is rotary or linear.

[0087] In one embodiment, the distribution valve comprises a fixed body having N+B inlets / outlets connected to the N+B sections, an inlet / outlet connected to a high temperature branch, and an inlet / outlet connected to a low temperature branch.

[0088] In one aspect, the distribution valve comprises a body that is movable relative to a fixed body, the movable body having an internal volume / duct configured to fluidly connect one of the N+B inlets / outlets to an inlet / outlet connected to a high temperature branch and to fluidly connect another one of the N+B inlets / outlets to an inlet / outlet connected to a low temperature branch.

[0089] In one embodiment, the distance between two consecutive inlets / outlets of said N+B inlets / outlets is such as to prevent mixing of hot and cold fluids.

[0090] In one embodiment, the interior volume / duct comprises first and second interior chambers / ducts / volumes separate from one another.

[0091] In one embodiment, provisions are made to compensate for volumetric variations in the fluid due to different temperatures.

[0092] In one embodiment, provisions are made to partially load or release separation gas from the storage device to compensate for fluid volume fluctuations while maintaining a constant pressure of the compensation gas.

[0093] In one embodiment, provisions are made to partially load / discharge fluid from the storage section to compensate for volumetric variations of said fluid.

[0094] In one embodiment, the storage device comprises a compensation tank connected to a branch of the circuit having the denser fluid and configured to compensate for different volumes of fluid at different temperatures.

[0095] In one embodiment, the compensation tank is connected to the cold branch of the circuit.

[0096] In one embodiment, the compensation tank is connected to a second inlet / outlet of the storage device.

[0097] In one embodiment, the compensation circuit connects the compensation tank to a branch of the circuit having a denser fluid.

[0098] In one embodiment, the compensation circuit includes a pump and a release valve.

[0099] In one aspect, the compensation circuit includes a turbine configured to recover a portion of the electrical energy consumed by the pump.

[0100] In one embodiment, the compensation circuit comprises a first branch provided with a discharge valve and optionally a turbine, and a second branch provided with a pump.

[0101] In one embodiment, during the storage phase, the discharge valve is open to introduce higher density cold fluid from one of the N+B storage sections into the compensation tank, while lower density hot fluid is introduced into another of the N+B storage sections.

[0102] In one embodiment, in the storage stage, the turbine is powered by the cryogenic fluid flowing towards the compensation tank.

[0103] In one embodiment, during the discharge phase, the pump operates to pick up higher density cold fluid from the compensation tank and introduce it into one of the N+B storage sections, while lower density hot fluid is extracted from another of the N+B storage sections.

[0104] In one embodiment, the fluid is a liquid at the operating conditions of the plant / process.

[0105] In one embodiment, the fluid is water.

[0106] In one embodiment, the water is heated to a temperature greater than 90°.

[0107] In one embodiment, the water is at a pressure above atmospheric pressure, optionally above 2 bar, optionally above 30 bar, for example 36 bar.

[0108] In one embodiment, the separation gas is an inert gas, optionally selected from the group including nitrogen, helium, argon, carbon dioxide, neon.

[0109] In one embodiment, the separation gas is a non-inert gas.

[0110] In one embodiment, the separated gas is at a pressure greater than the fluid saturation pressure reached at the maximum operating temperature of the storage device.

[0111] In one embodiment, the heat source is the sun.

[0112] In one embodiment, the heat user is a machine for generating electrical energy, optionally an organic Rankine cycle (ORC) machine for generating electrical energy.

[0113] In one aspect, the present invention relates to an apparatus for generating electric energy, comprising: a solar plant; a plant for storing and releasing thermal energy operably coupled to the solar plant; and a machine for generating electric energy operably coupled to the plant for storing and releasing thermal energy, wherein the plant for storing and releasing thermal energy is according to and / or operates in accordance with one or more of the aforementioned aspects.

[0114] In one embodiment, a solar plant includes a plurality of reflective mirrors, a tower, and a receiver disposed on the tower, the reflective mirrors configured to concentrate solar radiation onto the receiver.

[0115] In one aspect, the present invention relates to a device for storing electric energy (storage), also called thermal battery, which comprises a plant capable of consuming electric energy (when charged from a source), generating thermal energy and generating electric energy by consuming thermal energy (when discharged by a user), and a plant for storing and discharging thermal energy operatively coupled to the thermal battery, wherein the plant for storing and discharging thermal energy is according to and / or operates in accordance with one or more of the aforementioned aspects.

[0116] Further features and advantages will become more apparent from the detailed description of preferred, but not exclusive, embodiments of the plant and method for storing and releasing thermal energy according to the present invention.

[0117] Such an illustration is described below with reference to the accompanying drawings, given by way of non-limiting example only, in which: [Brief description of the drawings]

[0118] [Figure 1] FIG. 2 is a schematic diagram of an embodiment of a plant for storing and releasing thermal energy according to the invention in a storage configuration; [Diagram 2] FIG. 2 is a diagram of the storage device of the plant of FIG. 1 at one storage stage. [Diagram 3] FIG. 2 is a diagram of a storage device of the plant of FIG. 1 at a subsequent storage stage. [Figure 4] FIG. 2 is a diagram of a storage device of the plant of FIG. 1 at a subsequent storage stage. [Diagram 5] FIG. 5 is a diagram of the storage device of FIGS. 2, 3 and 4 in a resting phase. [Figure 6] FIG. 2 is a diagram of the plant of FIG. 1 in a discharge configuration. [Figure 7] FIG. 2 shows a variant of the storage device of the plant according to the previous figures in a storage configuration. [Figure 8] 5A-5C show different embodiments of a storage device of the plant according to the previous figures in one storage stage. [Figure 9] 5A-5C show different embodiments of the storage device of the plant according to the previous figures in a subsequent storage stage. [Figure 10] 5A-5C show different embodiments of the storage device of the plant according to the previous figures in a subsequent storage stage. [Figure 11] FIG. 2 shows a further embodiment of a storage device of the plant according to the previous figures in one storage stage. [Figure 12] FIG. 2 shows a further embodiment of a storage device of the plant according to the previous figures in a subsequent storage stage. [Figure 13] FIG. 2 shows a further embodiment of a storage device of the plant according to the previous figures in one storage stage. [Figure 14] FIG. 2 shows a further embodiment of a storage device of the plant according to the previous figures in a subsequent storage stage. [Figure 15] 14 is a cross-sectional view of an element of the storage device of FIG. 13. [Figure 16] 15 is a cross-sectional view of an element of the storage device of FIG. 14. [Figure 17] FIG. 16 is a diagram showing a modification of the element in FIG. [Figure 18] FIG. 17 is a diagram showing a modification of the element in FIG. 16. [Figure 19] FIG. 8 shows a variation of the storage device of FIG. 7 in a storage configuration. [Figure 20] FIG. 20 is a diagram of the storage device of FIG. 19 in a release configuration. [Figure 21A] FIG. 2 is a schematic diagram of an alternative embodiment of a plant according to the invention in a storage configuration; [Figure 21B]FIG. 2 is another schematic diagram of an alternative embodiment of a plant according to the invention in a discharge configuration. [Figure 22A] FIG. 1 is a diagram of a plant for storing and releasing thermal energy according to the prior art in a storage configuration. [Figure 22B] FIG. 1 is a diagram of a plant for storing and releasing thermal energy according to the prior art in a release configuration. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0119] With reference to the accompanying drawings, the reference number 1 indicates as a whole a plant for storing and releasing thermal energy (thermal energy storage) according to the invention.

[0120] The plant 1 shown in figures 1 to 6 comprises a first heat exchanger 2 operably coupled or connectable to a heat source 3, a second heat exchanger 4 operably coupled or connectable to a heat user 5, and a storage device 6 operably interposed between the first heat exchanger 2 and the second heat exchanger 4. A circuit formed by piping is configured to couple the first heat exchanger 2, the second heat exchanger 4 and the storage device 6. A fluid F configured to store thermal energy and to transfer it is arranged in the plant 1. Such a fluid F is for example water maintained at a pressure of several tens of bars, for example 36 bars, so that it can be heated to a temperature higher than 90°C without a change of state. For such purpose, control elements (such as pumps and valves) are operably coupled to the circuit and / or to the storage device 6 and are configured to move the fluid in the first heat exchanger 2, the second heat exchanger 4 and the storage device 6 without changing the state of the fluid F. The circuit of the plant 1 of Figure 1 comprises a hot branch 7 extending from the outlet of the first heat exchanger 2 towards the inlet of the second heat exchanger 4 and a cold branch 8 extending from the outlet of the second heat exchanger towards the inlet of the first heat exchanger 2. The circuit extends within or is part of the first and second heat exchangers 2, 4 so as to define a closed path.

[0121] The storage device 6 is fluidly connected to the circuit F by a first main inlet / outlet 9 connected to the hot branch 7 and a second main inlet / outlet 10 connected to the cold branch 8. A first pump 11 is arranged in the cold branch 8 between the second main inlet / outlet 10 and the first exchanger 2, and a second pump 12 is arranged in the cold branch 8 between the second exchanger 4 and the second main inlet / outlet 10.

[0122] The heat source 3 can be, for example, a tower-type solar plant. Such a plant, which may also be known per se, comprises a number of reflectors, a tower and a receiver placed in the tower, the reflectors being arranged to concentrate the solar radiation on the receiver. The solar plant thus receives heat from the solar radiation during the daytime hours or part of them. The heat user 5 can be, for example, a machine for generating electric energy, such as an organic Rankine cycle (ORC) machine. Such a machine, which may also be known per se, comprises an expansion turbine connected to a generator, a pump and a condenser connected by a closed circuit through which an organic fluid flows. The circuit of the organic Rankine cycle machine is also coupled to a second heat exchanger 4. The second heat exchanger can be an assembly of exchangers, such as, for example, an assembly formed by a preheater and an evaporator, or an assembly formed by a preheater, an evaporator and a superheater.

[0123] The solar plant, the organic Rankine cycle machine and the plant 1 for storing and releasing thermal energy form a device for generating electrical energy which is also part of the invention.

[0124] During daylight hours, heat from the sun's rays captured in the solar plant (heat source 5) is transferred to the first heat exchanger 2. The device 1 is in the configuration / storage stage (FIG. 1) described herein below. The fluid F receives such heat and is heated to a higher temperature T maxThe first and second pumps 11, 12 are both in operation. A part of the heated fluid enters the second heat exchanger 4, where it transfers heat to the organic fluid of the organic Rankine cycle machine. The heat transferred to the second heat exchanger 4 by the fluid F of the plant 1 heats and evaporates the organic fluid of the organic Rankine cycle machine. The expansion turbine is fed with the organic fluid in the vapor phase leaving the second heat exchanger 4, and achieves the conversion of the thermal energy present in the organic fluid into mechanical energy according to the Rankine cycle. The organic fluid leaving the turbine is condensed in a condenser, sent to a pump and then fed again to the second heat exchanger. Another part of the hot fluid is stored in the storage device 6 as hot fluid.

[0125] During night time, or in any case when there is not enough solar irradiation, the device 1 is in the configuration / discharge phase (Figure 6). The first pump 11 is stopped or the load is reduced while the second pump 12 is operating. In such a configuration, the heat source 3 does not produce heat, or does not produce a sufficient amount to meet the demand, and the fluid F transfers the accumulated heat entering or leaving the device 1 through the second heat exchanger 4 to the heat user 5 (i.e. the organic Rankine cycle machine, which therefore continues to operate) and generates a lower temperature T min and is stored again as a cryogenic fluid in the storage device 6.

[0126] The invention also comprises a thermal battery (a device for storing electric energy) comprising a plant capable of consuming electric energy (when charged from a source), generating thermal energy and generating electric energy by consuming thermal energy (when discharged by a user), and a plant for storing and discharging thermal energy operatively coupled to the thermal battery, said plant for storing and discharging thermal energy being in accordance with and / or operating in accordance with one of those described and illustrated herein.

[0127] The storage device 6 of the embodiment of Figs. 1 to 6 according to the invention comprises three storage sections (N=2 and B=1), each defined by a single tank (first, second and third tanks 13a, 13b, 13c). The three tanks 13a, 13b, 13c are identical to each other and each has an elongated cylindrical form and the same storage volume. The three tanks 13a, 13b, 13c are arranged next to each other, oriented vertically and located at the same geodetic height. Each tank 13a, 13b, 13c has a first lower inlet / outlet opening 14 and a second lower inlet / outlet opening 15 located in the lower part of the tank itself. The first lower inlet / outlet opening 14 is connected in parallel to a single section of the circuit, which further communicates with the first main inlet / outlet 9 and the high temperature branch 7 of the circuit. The second lower inlet / outlet openings 15 are connected in parallel to a single section of the circuit, which further communicates with the second main inlet / outlet 10 and the cold branch 8 of the circuit. The first lower inlet / outlet openings 14, the second lower inlet / outlet openings 15 are arranged at the same geodetic height. Each first lower inlet / outlet opening 14 is associated with a valve 16 for the hot fluid and each second lower inlet / outlet opening 15 is associated with a valve 17 for the cold fluid.

[0128] In addition, each tank is provided with an upper inlet / outlet opening 18 connected to the other two ends. In the example of figures 1-6, there is no valve on the duct connecting said upper inlet / outlet openings 18 to each other. The upper inlet / outlet openings 18 are located at the same geodetic height.

[0129] The storage device 6 contains a separation gas G, for example nitrogen, in addition to a fluid F (for example pressurized water) that stores thermal energy. In the example of figures 1 to 6, the storage device 6 contains a volume of water substantially equal to twice the accommodation volume V of each tank and a volume of nitrogen substantially equal to the accommodation volume V of a single tank. The nitrogen is placed in one or two adjacent tanks, possibly in a tube connecting the upper inlet / outlet openings 18 depending on the working stage of the plant 1, and is in contact with the water, always separating the hot water from the cold water. The nitrogen is at the pressure required to maintain the water in the liquid phase in all working conditions (for example the 36 bar mentioned above). More generally, the pressure must be greater than the saturation pressure of the fluid that occurs at the maximum working temperature of the storage device. The pressure therefore depends on the temperature and on the type of fluid.

[0130] FIG. 1 shows the plant 1 in the configuration / storage phase starting from the first moment, when cold water fills the second and third tanks 13b, 13c, while the first tank 13a, closer to the hot branch 7, is filled with nitrogen. As can be observed, the nitrogen also fills the tubes connecting the upper inlet / outlet openings 18, maintaining constant the pressure holding down the free surface of the water in the respective tanks 13c, 13b. The valve 16 for the hot fluid of the first tank 13a is open, the valve 17 for the cold fluid of the second tank 13b is open, and the remaining valves 16, 17 for the hot and cold fluids are closed. According to the method according to the invention, the hot water coming from the first heat exchanger 2 flowing through the first main inlet / outlet 9 enters through the first lower inlet / outlet opening 14 of the first tank 13a. The nitrogen contained in the first tank 13a is gradually transferred into the second tank 13b through the tubes connecting the upper inlet / outlet openings 18 (FIG. 2). The cold water contained in the second tank 13b exits through the second lower inlet / outlet opening 15 of the second tank 13a and thus completes the drainage through the second main inlet / outlet 10. The first tank 13a is filled with hot water and the second tank 13b is filled with nitrogen (Figure 3).

[0131] At this point, the valve 16 for the hot fluid of the second tank 13b is opened and the valve 17 for the cold fluid of the third tank 13c is opened, while the remaining valves 16, 17 for the hot and cold fluids are closed (Figure 4).

[0132] The hot water from the first heat exchanger 2 flowing through the first main inlet / outlet 9 enters through the first lower inlet / outlet opening 14 of the second tank 13b. The nitrogen contained in the second tank 13b is gradually transferred to the third tank 13c (Figure 4). The cold water contained in the third tank 13c exits through the second lower inlet / outlet opening 15 of the third tank 13a and thus completes the draining out through the second main inlet / outlet 10. The second tank 13b is filled with hot water (as is the first tank 13a) and the third tank 13c is filled with nitrogen (Figure 5). The storage phase is finished.

[0133] Starting from the configuration of FIG. 5, in the configuration / discharge phase, measures are first made to open the valve 16 for the hot fluid of the second tank 13b, and the valve 17 for the cold fluid of the third tank 13c is opened, while the remaining valves 16, 17 for the hot and cold fluids are closed (FIG. 6). The cold water from the second heat exchanger 4 flowing through the second main inlet / outlet opening 10 enters through the second lower inlet / outlet opening 15 of the third tank 13c. The nitrogen contained in the third tank 13c is gradually transferred to the second tank 13b (FIG. 6). The hot water contained in the second tank 13b leaves the first lower inlet / outlet opening 14 of the second tank 13b, and thus the first main inlet / outlet opening 9, and then flows through the second heat exchanger 4, where it transfers heat to the heat user 5 (the organic Rankine cycle machine). After the second tank 13b has been drained of hot water and filled with nitrogen, the valve 16 for the hot fluid of the first tank 13a and the valve 17 for the cold fluid of the second tank 13b are opened, while the remaining valves 16, 17 for the hot and cold fluids are closed to fill the second tank 13b with cold water and the first tank 13a with nitrogen, returning the plant to the configuration of FIG. 1.

[0134] Figure 7 shows a variant of the storage device 6 of Figures 1 to 6, which in the storage phase comprises seven sections / tanks 13a-13g (N=6 and B=1) instead of just three. In the example of Figure 7, the storage device 6 contains a volume of water substantially equal to six times the storage volume V of each tank, and a volume of nitrogen substantially equal to the storage volume V of a single tank. Operation is as described above.

[0135] Figures 8, 9 and 10 show a different embodiment of the storage device 6, which, like the variant of Figure 7, comprises seven tanks 13a-13g. Unlike the variant of Figure 7, the storage device 6 of Figures 8, 9 and 10 has a single section / duct of the circuit extending below the tanks 13a-13g between the first main inlet / outlet 9 and the second main inlet / outlet 10. Each tank 13a-13g has a single lower inlet / outlet opening 19, all lower inlet / outlet openings 19 being connected in parallel to such a single section. A first valve 20 is operably associated with each lower inlet / outlet opening 19 (upstream of the single section). A second valve 21 is operably associated with said single section, each second valve 21 being operably interposed between two consecutive lower inlet / outlet openings 19.

[0136] Figure 8 shows the storage device 6 when the plant 1 is in the configuration / storage phase. The first valve 20 of the first tank 13a is open, the first valve 20 of the second tank 13b is open, while the remaining first valves 20 are closed. In addition, the second valve 21 intervening between the first tank 13a and the second tank 13b, i.e. between the first valve 20 of the first tank 13a and the first valve 20 of the second tank 13b, is closed, while the remaining second valves 21 are open. According to the method according to the invention, the hot water coming from the first heat exchanger 2 flowing through the first main inlet / outlet 9 enters through the single lower inlet / outlet opening 19 of the first tank 13a. The nitrogen contained in the first tank 13a is gradually transferred to the second tank 13b. The cold water contained within the second tank 13b exits through a respective single lower inlet / outlet opening 19 and then through the second main inlet / outlet 10 to complete the drainage. The first tank 13a is filled with hot water and the second tank 13b is filled with nitrogen (Figure 9).

[0137] At this time, the first valve 20 of the second tank 13b is opened, the first valve 20 of the third tank 13c is opened, while the remaining first valves 20 are closed. In addition, the second valve 21 interposed between the second tank 13b and the third tank 13c, i.e., between the first valve 20 of the second tank 13b and the first valve 20 of the third tank 13c, is closed, while the remaining second valves 21 are opened (FIG. 10). Thus, the high-temperature water from the first heat exchanger 2 flowing through the first main inlet / outlet opening 9 flows in through the single lower inlet / outlet opening 19 of the second tank 13b. The nitrogen contained in the second tank 13b is gradually transferred to the third tank 13c. The low-temperature water contained in the third tank 13c exits from the respective single lower inlet / outlet opening 19 and thus exits from the second main inlet / outlet 10 to complete the drainage. The second tank 13b is filled with hot water and the third tank 13c is filled with nitrogen. In this manner, the filling of hot water and the discharge of cold water continues until all tanks except the seventh tank 13g are filled with hot water and the seventh tank 13g is filled with nitrogen. During the configuration / discharge phase, the steps described above are carried out in reverse order.

[0138] 11 and 12 show a further embodiment of a plant with six tanks 13a-13f (N=5 and B=1). The storage device 6 contains a volume of water substantially equal to five times the storage volume V of each tank and a volume of nitrogen substantially equal to the storage volume V of a single tank. Unlike the embodiment of FIGS. 8, 9 and 10, the lower inlet / outlet opening 19 is not connected to a valve, and the single section does not have a valve either. Said single section forms a siphon 22 between one tank and the next, which comprises an ascending section, a descending section and an upper curved connector, and has a maximum height (where the curved connector is located) greater than the height of the tanks 13a-13g. Between the upper inlet / outlet opening 18 and the opening adjacent to it, a gas valve 23 is located. In addition, in this embodiment, also in the siphon 22, nitrogen separates the hot water from the cold water.

[0139] In the construction / storage phase of Fig. 11, the gas valve 23 located between the first tank 13a and the second tank 13b is open, while the other gas valve 23 is closed. According to the method according to the invention, the hot water coming from the first heat exchanger 2 flowing through the first main inlet / outlet 9 enters through the single lower inlet / outlet opening 19 of the first tank 13a. The nitrogen contained in the first tank 13a is gradually transferred to the second tank 13b through the above-mentioned gas valve 23. The cold water contained in the second tank 13b leaves through the respective single lower inlet / outlet opening 19, follows a series of siphons 22 and then leaves through the second main inlet / outlet 10, completing the draining of the second tank 13b (this tank is therefore filled with nitrogen). Provision is made to close the gas valve 23 located between the first tank 13a and the second tank 13b and to open the gas valve 23 located between the second tank 13b and the third tank 13c, in order to fill the second tank 13b with hot water and to drain the third tank 13c with cold water. In this way, five of the six tanks are filled, while at the end of the storage the sixth tank 13f is filled with nitrogen. In the construction / discharge phase, the steps described above are carried out in the reverse order.

[0140] A further embodiment of the storage device 6 of the plant 1 is similar to that of Figures 8, 9 and 10, but there are eight tanks 13a-13h (N=7 and B=1) and instead of a plurality of single sections or valves 20, 21 located in a single section there is a single distribution valve 24, 25. The storage device 6 contains a volume of water substantially equal to seven times the storage volume V of each tank and a volume of nitrogen substantially equal to the storage volume V of a single tank. All single lower inlet / outlet openings 19 are connected to the distribution valve 24, 25.

[0141] The distribution valve 24 shown in Figures 13, 14, 15 and 16 is of the rotary type and comprises a fixed body 26 with eight radial inlets / outlets 27 each connected to a single lower inlet / outlet opening 19 of a respective tank 13a-13g. The fixed body 26 also has an inlet / outlet 28 connected to the hot branch 7 of the circuit through a first main inlet / outlet 9 and an inlet / outlet 29 connected to the cold branch 8 of the circuit through a second main inlet / outlet 10. The distribution valve 24 comprises a movable body 30 (movable relative to the fixed body 26) with an internal volume / duct configured to fluidly connect one of said eight inlets / outlets 27 with the inlet / outlet 28 connected to the hot branch 7 and another of said eight inlets / outlets 27 with the inlet / outlet 29 connected to the cold branch 8.

[0142] The mobile body 30 shown is a disk rotatable about a shaft 31. The fixed body 26 is a box-shaped cylinder. Inside the fixed body 26, the mobile body 30 and the fixed body 26 define a first chamber 32 and a second chamber 33 separated from each other and located on either side of the disk. The first chamber 32 has an inlet / outlet 28 connected to the hot branch 7. The second chamber 33 has an inlet / outlet 29 connected to the cold branch 8. The disk has a first elbow duct 34, which opens into the first chamber 32 and on the periphery of the disk itself so as to be in fluid communication with one of the eight radial inlets / outlets 27 at a time. The disk has a second elbow duct 35, which opens into the second chamber 32 and on the periphery of the disk itself so as to be in fluid communication with one of the eight radial inlets / outlets 27 at a time. The first elbow duct 34 and the second elbow duct 35 are angularly offset by one eighth of the circumference (45°) as shown in Figure 6. Figure 15 is a cross-section according to plane XV-XV of Figure 16. The distance between two consecutive inlets / outlets of said eight inlets / outlets is greater than the diameter of the passage of said inlets / outlets to prevent mixing of hot and cold water.

[0143] In the configuration / storage stage shown in Fig. 13, the first elbow duct 34 is connected to a radial inlet / outlet 27 connected to the fourth tank 13d, and the second elbow duct 35 is connected to a radial inlet / outlet 27 connected to the fifth tank 13e. The hot water coming from the first heat exchanger 2 flowing through the first main inlet / outlet 9 enters the inlet / outlet 28 connected to the hot branch in the first chamber 32 and then flows through the radial inlet / outlet 27 connected to the fourth tank 13d into said fourth tank 13d. The nitrogen contained in the fourth tank 13d is gradually transferred into the fifth tank 13e. The cold water contained in the fifth tank 13e exits through the respective single lower inlet / outlet opening 19, then passes through the radial inlet / outlet 27 connected to the fifth tank 13e in the second chamber 33, through the inlet / outlet 29 connected to the cold branch 8, and then exits through the second main inlet / outlet 10, completing the drainage from the fifth tank 13e.

[0144] At this point, the disk is rotated 45° counterclockwise (FIGS. 13 and 14) such that the distribution valve 24 places the hot branch 7 in fluid communication with the fifth tank 13e and the cold branch 8 in fluid communication with the sixth tank 13f (FIG. 14) for filling the fifth tank 13e with hot water and draining the contained cold water from the sixth tank 13f.

[0145] The distributor valve 25 shown in figures 17 and 18 is of the linear type. The same reference numbers were given to the elements of the linear distributor valve 25 that perform the same functions as the elements of the rotary distributor valve 24. The mobile body 30 translates in the fixed body 26 and there are six successively aligned inlets / outlets 27. Such inlets / outlets 27 are also aligned with the inlets / outlets 28 connected to the hot branch 7 and with the inlets / outlets 29 connected to the cold branch 8. Also, the first chamber 32 and the second chamber 33 are successively aligned and separated by a separator 36. The mobile body 30, instead of the elbow ducts 34, 35, has a wall adjacent to the wall of the fixed body and with a first hole 37 and a second hole 38. The first hole 37 opens into the first chamber 32 and can be in fluid communication with one of the six inlets / outlets 27 at a time. The second hole 38 opens into the second chamber 33 and can be in fluid communication with one of the six inlets / outlets 27 at a time.

[0146] The use of distributing valves according to the embodiments of Figures 15 to 18 makes it possible to ensure that the sequence in which the tanks are filled and emptied is always the correct sequence, i.e. it is not possible to open and / or close the wrong valves, as may occur in the plants of Figures 1 to 12.

[0147] Figures 19 and 20 show a variant of the storage device 6 of the plant 1 of Figure 7, which also comprises a compensation tank 39, which is connected to the cold branch 8 of the circuit at the second inlet / outlet 10 and is configured to compensate for the different volumes of fluid used at different temperatures. In this way, the pressure of the compensation gas and its volume are kept constant. The fluid in the lower density state occupies a volume equal to N tanks (6 in the embodiment of Figures 19 and 20) of N+B tanks (N=6 and B=1 in the embodiment of Figures 19 and 20).

[0148] A compensation circuit connects the compensation tank 39 to the cold branch 8 of the circuit and comprises a pump 40 and a discharge valve 41. In the embodiment shown, the compensation circuit comprises a first branch 42 provided with the discharge valve 41 and a second branch 43 provided with the pump 40. In the first branch 42, a turbine 44 is also operatively arranged, which is connected to a generator 45. The turbine 44 is arranged to recover a portion of the electrical energy consumed by the pump 40.

[0149] Figure 19 shows the storage device 6 in the same configuration as in Figure 7. In this configuration, the discharge valve 41 is open to admit into the compensation tank 39 the higher density (and smaller volume) cold fluid from the second tank 13b, while the lower density (and larger volume) hot fluid is admitted into the first tank 13a. The cold fluid also rotates a turbine 44 to generate electrical energy by a generator 45.

[0150] Figure 20 shows the storage device 6 in a discharge configuration similar to that of Figure 6. In this configuration, the discharge valve 41 is closed and the pump 40 operates to pick up the higher density (and smaller volume) cold fluid from the compensation tank 39 and introduce it into the seventh tank 13g, while the lower density (and larger volume) hot fluid is extracted from the sixth tank 13f.

[0151] In a variant of the embodiment, provisions are made to compensate for variations in the volume of the fluid due to different temperatures without using a compensation tank 39, but rather, for example, to partially load or release the separated gas G into or from the storage device 6 by means of suitable valves and / or tanks.

[0152] In an alternative embodiment, a compensation tank 39 is not used, but instead measures are taken to compensate for the variation in fluid volume due to different temperatures by designing the tank with a sufficiently large dead volume to sustain a higher pressure due to the reduction in volume.

[0153] 21A and 21B show different embodiments of a plant 1, in which a storage device 6 according to the invention is only diagrammatically represented and can take, for example, one of the configurations of FIGS. 1 to 14, 19 and 20. The source 3 and the user 5 are defined by a single system, the plant 1 comprises a single heat exchanger 2, 4 (or an assembly as shown above) performing the functions of both the first heat exchanger 2 and the second heat exchanger 4 described above. The hot branch 7 extends between the single heat exchanger 2, 4 and the first inlet / outlet 9 of the storage device 6, and the cold branch 8 extends between the single heat exchanger 2, 4 and the second inlet / outlet 10 of the storage device 6. The cold branch 8 comprises a single pump 11′ located on the cold branch, and a diverter device is configured to make the fluid flow through the cold branch 8 from the storage device 6 towards the heat exchanger 2, 4 or from the heat exchanger 2, 4 towards the storage device 6 depending on the operation step / condition. The diverter device comprises a first bypass branch 46 of the single pump 11' and a second bypass branch 47 of the single pump 11'. A first diverter valve 48 is placed in the first bypass branch 46 and a second diverter valve 49 is placed in the second bypass branch 47. A third diverter valve 50 is placed on the cold branch 8 downstream of the delivery of the single pump 11' and between the connection of the first bypass branch 46 and the second bypass branch 47 in the cold branch 8 located between the single pump 11' and the single heat exchanger 2, 4. A fourth diverter valve 51 is placed on the cold branch 8 upstream of the inlet of the single pump 11' and between the connection of the first bypass branch 46 and the second bypass branch 47 in the cold branch 8 located between the single pump 11' and the storage device 6. The purpose of the diverter device is to reverse the suction of the pump 11' by the delivery and vice versa. Alternatively, it is possible to insert a second pump that operates in an opposite manner to the first pump.

[0154] In the storage stage shown in FIG. 21A, the single system transfers heat (i.e. it behaves like a source 3). The first and second diverter valves 48, 49 are closed and the third and fourth diverter valves 50, 51 are open. The hot water coming from the single heat exchanger 2, 4 flows through the hot branch 7 and accumulates in the storage device 6. The cold water coming from the storage device 6 is pumped towards the single heat exchanger 2, 4 through the third and fourth diverter valves 50, 51.

[0155] In the release phase shown in FIG. 21B, the single system absorbs heat (i.e. it behaves like a user 5). The first and second diverter valves 48, 49 are opened and the third and fourth diverter valves 50, 51 are closed. The cold water coming from the single heat exchanger 2, 4 passes successively through the first diverter valve 48, the single pump 11′ and the second diverter valve 49 and is pumped into the storage device 6. The hot water coming from the storage device 6 flows through the hot branch 7 towards the single heat exchanger 2, 4.

[0156] In a further embodiment variant not shown, each storage section is formed not by a single tank but by several tanks connected to each other in series and / or parallel, the tanks constituting one storage section being connected to the tanks of the different storage sections by shared connections.

[0157] As is evident from the embodiments shown above, the storage device according to the invention comprises N+B storage sections, where N is equal to or greater than 2 and B is less than N, for example N is equal to 10 and B is equal to 1. Each of the N+B storage sections has substantially the same storage volume. The fluid F occupies a volume substantially equal to N times the storage volume V, and the separation gas G occupies a volume substantially equal to the storage volume (B=1). [Explanation of symbols]

[0158] 1. Plants for the storage and release of thermal energy 2. First Heat Exchanger 3 Heat source 4 Second Heat Exchanger 5. Heat User 6 Storage Devices 7 High temperature branch 8. Low temperature branch 9 First Main Entrance / Exit 10 Second Main Entrance / Exit 11 First Pump 11' single pump 12 Second Pump 13a, 13b ~ Storage section 14 First lower inlet / outlet opening 15 Second lower inlet / outlet opening 16 Valves for high temperature fluids 17 Valves for cryogenic fluids 18 Upper inlet / outlet opening 19 Single lower inlet / outlet opening 20 First Valve 21 Second Valve 22 Siphon 23 Gas valve 24 Rotary distribution valve 25 Linear distribution valve 26 Fixed body 27 Entrance / Exit 28 Hot Branch Inlet / Outlet 29 Cold branch inlet / outlet 30 Movable body 31 Shaft 32 First Chamber 33 Second Chamber 34 First Elbow Duct 35 Second elbow duct 36 Separator 37 First Hole 38 Second Hole 39 Compensation Tank 40 Pump 41 Release valve 42 First branch 43 Second Branch 44 Turbine 45 Generator 46 First bypass branch 47 Second bypass branch 48 First Diverter Valve 49 Second Diverter Valve 50 Third Diverter Valve 51 4th Diverter Valve

Claims

1. A plant for storing and releasing thermal energy, comprising: at least one heat exchanger (2, 4) operably coupled or connectable to at least one heat source (3) and / or at least one heat user (5); a fluid (F) configured to store said thermal energy; a storage device (6) for said fluid (F); a circuit configured to couple said at least one heat exchanger (2, 4) with at least one said storage device (6); a control element operably coupled to said circuit and / or said at least one storage device (6) and configured to move said fluid (F) within said at least one heat exchanger (2, 4) and said storage device (6); Equipped with During the storage stage, when the heat source (3) transfers heat to the at least one heat exchanger (2, 4), the fluid (F) receives the heat through the at least one heat exchanger (2, 4) and reaches a higher temperature (T ｍａｘ ) and stored as a hot fluid in said at least one storage device (6); During the discharge phase when the heat source (3) does not produce heat or does not produce enough heat, the fluid (F) transfers the accumulated heat through the at least one heat exchanger (2, 4) to the heat user (5) and reaches a lower temperature (T ｍｉｎ ) and stored as a cryogenic fluid in said at least one storage device (6); the storage device (6) comprises N+B storage sections (13a-13h), N being equal to or greater than 2 and B being less than N, each of the N+B storage sections (13a-13h) having substantially the same storage volume (V), and the N+B storage sections (13a-13h) are fluidly connected to one another; the storage device (6) comprises a separation gas (G) inserted into the storage device (6), the fluid (F) occupies a volume substantially equal to N times the containment volume (V), the separation gas (G) is in contact with the fluid (F) and is configured to always separate or keep the hot fluid separated from the cold fluid, 1. A plant for storing and releasing thermal energy, wherein each of said storage sections (13a-13h) has at least one lower inlet / outlet opening (14, 15; 19) connected to the other storage sections (13a-13h) and at least one upper inlet / outlet opening (18) connected to the other storage sections (13a-13h), and wherein said control element is configured to determine the passage of said fluid (F) through said at least one lower inlet / outlet opening (14, 15; 19) and to determine the passage of said gas (G) through said at least one upper inlet / outlet opening (18).

2. 2. A plant for storing and releasing thermal energy according to claim 1, wherein said separated gas (G) occupies a volume substantially equal to said containment volume (V).

3. 3. A plant for storing and releasing thermal energy according to claim 1 or 2, wherein N is greater than 3.

4. 4. A plant for storing and releasing thermal energy according to claim 3, wherein N is 10 or more.

5. A plant for storing and releasing thermal energy according to any one of claims 1 to 4, wherein the fluid (F) is water at a pressure higher than atmospheric pressure.

6. 6. A plant for storing and releasing thermal energy according to claim 5, wherein said pressure is higher than 2 bar.

7. A plant for storing and releasing thermal energy according to any one of claims 1 to 6, wherein the separated gas (G) is an inert gas.

8. 8. A plant for storing and releasing thermal energy as claimed in claim 7, wherein said inert gas is nitrogen.

9. A plant for storing and releasing thermal energy according to any one of claims 1 to 8, wherein each of said storage sections (13a-13h) comprises a single tank or a number of tanks connected to each other.

10. 2. A plant for storing and releasing thermal energy according to claim 1, wherein said lower inlet / outlet openings (14, 15; 19) are connected to said circuit.

11. 11. A plant for storing and releasing thermal energy according to claim 1 or 10, wherein each of the storage sections (13a-13h) has a first lower inlet / outlet opening (14) and a second lower inlet / outlet opening (15), the first lower inlet / outlet opening (14) being connected to a hot branch (7) of the circuit and the second lower inlet / outlet opening (15) being connected to a cold branch (8) of the circuit, the storage device (6) comprising a plurality of valves (16) for a hot fluid and a plurality of valves (17) for a cold fluid, each of the valves (16) for the hot fluid being operatively associated with each of the first lower inlet / outlet openings (14) and each of the valves (17) for the cold fluid being operatively associated with each of the second lower inlet / outlet openings (15).

12. 11. A plant for storing and releasing thermal energy as claimed in claim 1 or 10, wherein each of the storage sections (13a-13h) has a single lower inlet / outlet opening (19), the storage device (6) comprises a plurality of first valves (20) and a plurality of second valves (21), the first valves (20) being operatively associated with each of the lower inlet / outlet openings (19), all of the lower inlet / outlet openings (19) being connected to a single section of the circuit, the second valves (21) being operatively associated with the single section, each of the second valves (21) being operatively interposed between two consecutive lower inlet / outlet openings (19).

13. 11. A plant for storing and releasing thermal energy as claimed in claim 1 or 10, wherein each of the storage sections (13a-13h) has a single lower inlet / outlet opening (19), all of the lower inlet / outlet openings (19) being connected to a single section of the circuit, the single section forming a siphon (22) between one storage section (13a-13h) and the next storage section, the siphon having a height greater than the height of the storage sections (13a-13h), and the storage device (6) comprises a plurality of gas valves (23), each of the gas valves being operatively interposed between the upper inlet / outlet openings (18) of adjacent storage sections (13a-13h).

14. 11. A plant for storing and releasing thermal energy according to claim 1 or 10, wherein the storage device (6) comprises a distribution valve (24), each of the storage sections (13a-13h) has a single lower inlet / outlet opening (19), all of the lower inlet / outlet openings (19) being connected to the distribution valve (24), the distribution valve (24) being connected to the hot branch (7) and the cold branch (8) of the circuit.

15. the storage device (6) comprises a compensation tank (39) and a compensation circuit configured to compensate for different fluid volumes (F) at different temperatures, the compensation tank (39) being connected to a branch of the circuit having the fluid (F) of higher density, The compensation circuit comprises a pump (40) and a release valve (41); During the storage stage, the discharge valve (41) is open to introduce the higher density cold fluid from one of the N+B storage sections (13a-13h) into the compensation tank (39), while the lower density hot fluid is introduced into another of the N+B storage sections (13a-13h); A plant for storing and discharging thermal energy as claimed in any one of claims 1 to 14, wherein during the discharging phase, the pump (40) operates to pick up the higher density cold fluid from the compensation tank (39) and introduce it into one of the N+B storage sections (13a to 13h), while the lower density hot fluid is extracted from another of the N+B storage sections (13a to 13h).

16. A method for storing and releasing thermal energy operated by a plant according to any one of claims 1 to 15, comprising the steps of: providing N+B storage sections (13a-13h) connected to each other, N being equal to or greater than 2 and B being less than N, each of the N+B storage sections (13a-13h) having substantially the same storage volume (V), the N+B storage sections (13a-13h) being fluidly connected to each other, a fluid (F) being placed in the storage sections (13a-13h) and occupying a volume substantially equal to N times the storage volume (V), and a separated gas (G) being placed in the storage sections (13a-13h); In the storing step, the method further comprises: heating said fluid (F) by passing said fluid (F) through at least one heat exchanger (2) operably coupled to at least one heat source (3); a step of introducing at least a portion of the heated fluid (F) into a storage section of the N+B storage sections (13a-13h) and simultaneously extracting a cold fluid (F) contained in the storage section (13a-13h) from one of the other storage sections (13a-13h), wherein the separation gas (G) contacts the hot fluid (F) and the cold fluid (F) and keeps the hot fluid (F) separated from the cold fluid (F), and during the introduction of the heated fluid (F) into the storage section (13a-13h), the separation gas (G) flows into the one of the other storage sections (13a-13h) from which the cold fluid (F) was extracted; conveying said cryogenic fluid (F) from said one of the other storage sections (13a-13h) to said at least one heat exchanger (2); 16. A method for storing and releasing thermal energy comprising:

17. In the releasing step, the method further comprises: extracting said accumulated hot fluid (F) from one of said storage sections (13a-13h); conveying said hot fluid (F) through said at least one heat exchanger (4) to reject heat to at least one heat user (5); introducing the cooled fluid (F) that has just passed through the at least one heat exchanger (4) into one of the other storage sections (13a-13h), wherein, during the introduction of the cooled fluid (F) into the one of the other storage sections (13a-13h), the separated gas (G) flows into the one of the storage sections (13a-13h) from which the hot fluid (F) was extracted; 20. The method for storing and releasing thermal energy of claim 16, comprising:

18. 18. A method for storing and releasing thermal energy according to claim 16 or 17, wherein the separation gas always occupies the same dead volume during the method.

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