Devices for thermal energy storage and plants for energy conversion and storage

Abstract

The apparatus for thermal energy storage includes a vessel (2) containing a thermal mass (3) configured to contain a liquid and absorb or release heat, and a main heat exchanger (4) immersed in the thermal mass (3) contained within the vessel (2). Main ducts (7, 9) connect the main heat exchanger (4) to a first source (31) of working fluid in a gaseous state or a second source of working fluid in a liquid state. The boiling temperature of the liquid in the thermal mass is higher than the condensation / evaporation temperature of the working fluid. There are devices for configuring the apparatus in a condensing operating configuration, where working fluid in a gaseous state flows from the first source (31) through the main heat exchanger (4) and releases heat to the thermal mass and condenses, or in an evaporating operating configuration, where working fluid in a liquid state flows from the second source through the main heat exchanger (4) and absorbs heat from the thermal mass and evaporates. The liquid is movable within the vessel (2) relative to the main heat exchanger (4), and the ratio of the volume of the vessel (2) to the internal volume of the main heat exchanger (4) is greater than 100.

Description

[Technical Field]

[0001] The invention has as its object an apparatus for thermal energy storage and a plant for energy conversion and storage.

[0002] More precisely, the invention has as its object a device capable of storing the thermal energy released by a working fluid in a thermal mass contained in a vessel of large dimensions in which a heat exchanger immersed in said working fluid flows, the device according to the invention being capable of condensing or evaporating the working fluid by means of the exchange of thermal energy with the thermal mass of the vessel. [Background technology]

[0003] In the field of thermal energy storage systems, the use of heat exchangers configured to transfer heat between two fluids is known, where this heat is for example stored in one of the two fluids or in a different thermal mass in contact with one of the two fluids.

[0004] Heat exchangers are known that are capable of exchanging the heat content of two fluids by keeping them separated, but which are provided with a geometry that prevents mixing between the two fluids, i.e., each of the two fluids is confined in a separate closed volume.

[0005] For example, in a plate heat exchanger, two fluid streams of different temperatures exchange the heat content of the two fluid streams through an embossed surface, and are placed adjacent to each other so that the fluids flow in countercurrent.

[0006] Known heat exchangers of the "shell-and-tube" type (tube bundles and shells) are surface heat exchangers primarily composed of a bundle of tubes positioned in a substantially cylindrical container (called the shell). In this exchanger, two fluid streams intersect, one flowing on the "tube side" (i.e., within the tubes) while the other flowing on the "shell side" (i.e., within the space defined between the inner surface of the shell and the outer surface of the tubes). For example, while flowing through the heat exchanger, one of the two fluids exchanges latent heat (condenses or evaporates), while the other exchanges sensible heat (heats or cools). Summary of the Invention

[0007] In this field, the applicant has realized that in order to make efficient heat exchangers that perform condensation or evaporation by known techniques, for example by plate or "shell and tube" type, it is necessary to increase the heat exchange surface or the flow rate of the fluid that is heated or cooled by the condensation or evaporation of another fluid.

[0008] The applicant has noticed that increasing the surface, within certain limits, is inconvenient because it becomes uneconomical. The applicant has also noticed that an increase in the flow rate is accompanied by an increase in the pressure drop in the pipe, which then makes it necessary to employ more powerful and expensive pumps designed to act on the hotter or colder fluid and / or to increase the dimensions of the pipes and / or exchangers, resulting in increased costs and disturbances associated with increased heat exchange between the increased pipes and the surrounding environment (if the temperature of the hotter or colder fluid differs from the temperature of the environment).

[0009] The applicant has further observed that when the exchanger is used in the field of devices for storing thermal energy, which is then intended to be released in a second step, for example to generate electrical energy, the use of powerful pumps involves the generation of a considerable amount of heat by the pump's own motor, which prevents the exchange of thermal energy between the two fluids. In fact, additional heat generated by the pump is also stored, which is an excess amount that is to be extracted in the step of generating electrical energy, which has a negative effect on the efficiency of the system.

[0010] The applicant has therefore set himself the object of realizing a device for thermal energy storage that is able to overcome the above-mentioned technical drawbacks.

[0011] In particular, the applicant has set himself the object of realizing a device for the storage of thermal energy. - Structurally simpler than known structures, - Capable of operating efficiently with reduced power and reduced self-consumption; There is virtually no heat exchange with the surrounding environment and no thermal disturbances generated by the fluid handling system (such as a pump).

[0012] The applicant has found that the above and other objects can be achieved by an apparatus for thermal energy storage according to the appended claims and / or one or more of the following aspects.

[0013] In a first independent aspect, the present invention provides an apparatus for thermal energy storage, comprising: a thermal mass comprising a liquid, optionally water, wherein the thermal mass is configured to absorb and store heat or to release heat; a bath containing a thermal mass; at least one main heat exchanger immersed in a thermal mass contained within the vessel, wherein liquid is movable within the vessel relative to the at least one main heat exchanger; a main duct connecting the at least one main heat exchanger to a first source of working fluid in a gaseous state or a second source of the same working fluid in a liquid state, a main duct, wherein the boiling temperature of the liquid in the thermal mass is greater than the condensation / evaporation temperature of the working fluid and optionally greater than the critical temperature of the working fluid; A device for configuring an apparatus in a condensing operating configuration in which a working fluid in a gaseous state flows from a first source through said at least one main heat exchanger and condenses while the thermal mass heats up, or in an evaporating operating configuration in which a working fluid in a liquid state flows from a second source through said at least one main heat exchanger and evaporates while the thermal mass cools down and absorbs heat from the thermal mass. Equipped with the ratio of the volume of the vessel to the internal volume of the at least one main heat exchanger is greater than 100; Regarding the device.

[0014] By internal volume of the main exchanger is intended an internally defined volume within the main exchanger in which the working fluid resides and flows. By main exchanger is intended an element suitably designed to exchange heat with the thermal mass within the vessel, excluding ducts connecting the element to a first source of working fluid in a gaseous state and / or a second source of the same working fluid in a liquid state, and possibly partially contained within the vessel.

[0015] The applicant first demonstrated that the device according to the invention allows for the receipt at the inlet of a working fluid in a gaseous state from a first system and for the working fluid to be made available in a liquid phase to a second storage system. The applicant then demonstrated that the device allows for the receipt of a fluid in a liquid state from a second system and for the fluid to be returned in a gaseous phase to the first system under similar conditions as when the device received the fluid. The working fluid in the main heat exchanger exchanges heat with the thermal mass to obtain these phase transformations (latent heat), while the thermal mass heats up or cools down (sensible heat).

[0016] The applicant has first verified that the solution according to the invention makes it possible to efficiently first store and then release thermal energy.

[0017] The Applicant has verified that the solution according to the invention makes it possible to significantly limit the pressure drop due to the movement of the thermal mass liquid, since in the present invention no pipes or passing lights for the thermal mass liquid are used, or the number of pipes or passing lights is very limited, and the thermal mass liquid is contained in a tank and moves substantially only within said tank.

[0018] Furthermore, the dimensions of the vessel for one of the main heat exchangers are such as to reduce the pressure drop due to movement of liquid within the vessel, as opposed to that which occurs in, for example, a "shell and tube" type exchanger.

[0019] The applicant has also verified that the construction of the device according to the invention is relatively simple and therefore cost-effective, since the aforementioned pipes (with relative and necessary insulation) and / or lamps are not required to transport the liquid from the thermal mass.

[0020] Applicant has further determined that the substantial absence of tubes can reduce disturbances associated with heat exchange with the surrounding environment (all heat exchanged directly or indirectly enters / leaves the thermal mass). Further aspects of the invention are described below.

[0021] In one aspect, an apparatus for thermal energy storage includes a working fluid.

[0022] In one aspect, an apparatus for thermal energy storage comprises a first source of a working fluid in a gaseous state and / or a second source of the same working fluid in a liquid state.

[0023] In one embodiment, the ratio of the volume of the vessel to the internal volume of the main heat exchanger is greater than 300, optionally greater than 500.

[0024] In one embodiment, the working fluid has a critical temperature close to ambient temperature, optionally comprised between 0°C and 100°C.

[0025] In one embodiment, the working fluid is selected from the group comprising carbon dioxide CO2, sulfur hexafluoride SF6, nitrogen oxide N2O, hydrocarbons, perfluorinated compounds, and water.

[0026] In one embodiment, the working fluid is a mixture.

[0027] In one embodiment, the working fluid is air.

[0028] In one embodiment, the thermal mass is a liquid.

[0029] In one embodiment, the liquid is or comprises water.

[0030] In one embodiment, the thermal mass comprises an oil or a hydrocarbon, such as propane.

[0031] In one embodiment, the thermal mass is a mixture comprising said liquid and at least an additive, such as a salt.

[0032] In one aspect, the thermal mass includes said liquid and solid particles or objects, such as ice, sand, gravel.

[0033] In one embodiment, the reservoir is natural, for example a river, lake, or ocean.

[0034] In one aspect, the reservoir is artificial, i.e., the reservoir is a man-made structure, for example, a tank, a dam, or an artificial lake defined by a swimming pool.

[0035] In one embodiment, the tank is underground.

[0036] In one aspect, the vessel comprises concrete or metal sidewalls.

[0037] In one embodiment, the surface of the liquid in the vessel is in contact with the atmosphere or a controlled atmosphere, for example, containing nitrogen.

[0038] In one embodiment, the surface of the liquid in the vessel is at atmospheric pressure or a pressure slightly above atmospheric pressure, for example a pressure of a few mbar to a few hundred mbar.

[0039] In one aspect, the vessel can have any geometric shape, for example, the vessel has a rectangular, square, or circular perimeter in plan view.

[0040] In one embodiment, the vessel is insulated to limit heat exchange with the external environment.

[0041] In one aspect, the liquid can move within the tank either naturally (eg, due to natural currents present in a river, lake, or ocean) or by forced circulation.

[0042] In one aspect, the vessel defines a closed volume, i.e., the liquid in the vessel is substantially always the same. Such a closed volume is considered closed if there is no substantial mass exchange of thermal mass between the boundaries of the volume and the surrounding environment, and open if there is the possibility of mass exchange.

[0043] In this case, the thermal mass accumulates and stores heat removed from the working fluid in the condensing operating configuration for subsequent return of this heat to the working fluid in the evaporating operating configuration.

[0044] In one aspect, at least the circulation device is operatively active on the liquid and configured to move said liquid in the vessel relative to said at least one main heat exchanger.

[0045] In one embodiment, the at least one circulation device comprises a propeller or pump, e.g., an axial or lifting pump, or any means for overcoming the small pressure drop that occurs in the vessel, also due to the presence of the main heat exchanger.

[0046] In one embodiment, said at least one circulation device is present when the volume is closed, preferably, but not necessarily, when the reservoir is artificial.

[0047] In one embodiment, the at least one circulation device is configured to create at least one closed liquid circulation path within the closed volume.

[0048] In one embodiment, the at least one circulation device is positioned within the vessel and is immersed in the liquid of the vessel. Positioning the circulation device within the vessel makes it possible to avoid the use of connecting pipes between the circulation device and the vessel, thus further limiting the pressure drop.

[0049] In an alternative embodiment, the at least one circulation device is located outside the vessel and in fluid communication with the vessel via a pipe, in which case the most significant pressure drop is localized only within this pipe.

[0050] Next, the applicant has verified that it is possible to use a low-power and reduced-cost circulation device, and therefore to limit the thermal disturbances arising from the motor of such a circulation device during operation of the circulation device.

[0051] In one embodiment, the first liquid transport section in the vessel is a region perpendicular to the direction of liquid flow, and the second transport section for the working fluid in the at least one main heat exchanger is a region perpendicular to the direction of working fluid flow in the main heat exchanger.

[0052] In one embodiment, the first transport section is a section of said at least one closed liquid circulation path.

[0053] In one embodiment, the ratio of the first transport section to the second transport section is greater than 100, optionally greater than 500.

[0054] In one embodiment, the first transport section is 10 m 2 greater than, optionally 20m 2 greater than, optionally 100m 2 is greater than.

[0055] In one embodiment, the second transport section is 0.2 m 2 ~2m 2 Included in.

[0056] In one embodiment, the volume of the tank is 1000 m 3 greater than, optionally 2000m 3 greater than, optionally 10000m 2 is greater than.

[0057] In one embodiment, the passage velocity of the liquid through the first transport section is less than 10 m / s, optionally less than 1 m / s.

[0058] In one embodiment, the passage velocity of the liquid through the first transport section is greater than 0.01 m / s, optionally greater than 0.05 m / s.

[0059] In one embodiment, the passage velocity of the liquid through the second transport section is less than 1 m / s, optionally less than 0.5 m / s.

[0060] In one embodiment, the passage velocity of the liquid through the second transport section is greater than 0.01 m / s, optionally greater than 0.05 m / s.

[0061] In one embodiment, at least one conveyor and / or at least one flow diverter is housed within the vessel and submerged in the vessel's liquid. The function of the conveyor and / or flow diverter is to allow circulation of all the vessel's liquid and / or heat exchange with the heat exchanger. In this way, all the liquid envelops the main heat exchanger or otherwise participates in heat exchange and energy storage.

[0062] In one aspect, the at least one conveyor comprises a cylindrical or hood-shaped body having opposite open ends.

[0063] In one embodiment, the at least one main heat exchanger is positioned within the conveyor or at a first open end of the conveyor.

[0064] In one embodiment, the at least one circulating device is positioned within the conveyor or at the second open end of the conveyor.

[0065] In one aspect, the at least one flow diverter comprises one or more walls, optionally coupled to side walls defining the vessel.

[0066] In one aspect, the walls of the at least one flow diverter are shaped and / or arranged to impart a serpentine trajectory to the liquid along a closed circulation path.

[0067] In one aspect, the at least one main heat exchanger defines therein at least a flow path, optionally a plurality of flow paths, for a working fluid.

[0068] In one embodiment, the at least one main heat exchanger externally defines one or more flow paths for a liquid in which the at least one main heat exchanger is immersed.

[0069] In one embodiment, the at least one main heat exchanger is of the "once-through" type. In a "once-through" type exchanger, there is no accumulation of working fluid, i.e., what goes in is equal to what goes out. A "once-through" heat exchanger allows condensation and evaporation of a working fluid constituted by a gas mixture (for example, not only air, but also carbon dioxide, which may not be 100% pure) without separating the individual components.

[0070] In one embodiment, the at least one main heat exchanger comprises at least one bundle of tubes, a liquid passing between and enveloping the tubes, and a working fluid passing within the tubes, the working fluid condensing or evaporating within the tubes.

[0071] In one embodiment, the flow of liquid within the vessel is perpendicular to the tube.

[0072] In one embodiment, the second conveying section of the working fluid is an integral section of tubing.

[0073] In one embodiment, the at least one main heat exchanger functions as a condenser in a condensing operating configuration and as an evaporator in an evaporating operating configuration.

[0074] In one embodiment, the at least one main heat exchanger comprises a circulation circuit having a direct contact condenser and a circulation pump.

[0075] In one embodiment, the at least one main heat exchanger comprises a first main heat exchanger and a second main heat exchanger.

[0076] In one aspect, the first main heat exchanger functions as a condenser in a condensing operating configuration, and the second main heat exchanger functions as an evaporator in an evaporating operating configuration.

[0077] In one embodiment, each of the at least one main heat exchanger, the first main heat exchanger, and the second main heat exchanger may be formed by a plurality of exchangers operating in series or in parallel.

[0078] In one aspect, at least a reservoir, optionally a plurality of tanks, is in fluid communication with the at least one main heat exchanger, the one or more reservoirs configured to receive and accumulate condensed working fluid emerging from the at least one main heat exchanger.

[0079] In one embodiment, the reservoirs of the plurality of reservoirs are connected in parallel and / or series between the reservoirs.

[0080] In one embodiment, the at least one reservoir is positioned within the bath and is at least partially submerged in the bath liquid, preferably completely submerged in the bath liquid, such that the at least one reservoir is protected within the bath, does not occupy additional space, and undesired, uncontrolled heat exchange occurs between the reservoir and the thermal mass in which it is immersed, rather than with the external environment.

[0081] In one aspect, in the condensing operating configuration, the second source functions as the at least one reservoir that receives and stores condensed working fluid.

[0082] In one aspect, in an evaporation operating configuration, the first source comprises a container for the working fluid evaporated to a gaseous state.

[0083] In one embodiment, the at least one main heat exchanger has a first end in fluid communication with a first source or container and a second end in fluid communication with a second source or the at least one reservoir.

[0084] In one embodiment, the apparatus comprises a first source or container.

[0085] In one embodiment, the device comprises a second source or said at least one reservoir.

[0086] In one embodiment, at least one liquid-gas separator is coupled to the at least one main heat exchanger, the liquid-gas separator separating a liquid phase from a gaseous working fluid entering and exiting the main heat exchanger.

[0087] In one embodiment, the at least one liquid-gas separator is in fluid communication on one side with a first end of the at least one flow path for fluid and in fluid communication on the other side with a first source or container, and is thus positioned at a condenser inlet or an evaporator outlet.

[0088] In one embodiment, the at least one gas-liquid separator is positioned within the vessel and is at least partially, preferably entirely, submerged in the liquid of the vessel.

[0089] In an alternative embodiment, the at least one gas-liquid separator is external to the vessel.

[0090] In one embodiment, the liquid / gas separator is positioned in an upper position relative to the at least one reservoir.

[0091] In one embodiment, the gas-liquid separator is connected to the at least one reservoir via a separate pipeline inside or outside the reservoir, so that the liquid separated by the gas-liquid separator falls by gravity into the lower reservoir.

[0092] In one aspect, the pipeline has a geometry that defines a hydraulic guard, i.e., that ensures that all steam passes through the main heat exchanger, i.e., that steam is prevented from bypassing this main heat exchanger.

[0093] In one embodiment, there is an auxiliary device comprising at least one auxiliary heat exchanger, optionally multiple auxiliary exchangers in parallel and / or series with one another.

[0094] In one embodiment, the at least one auxiliary heat exchanger is in fluid communication with the main heat exchanger or liquid-gas separator on one side and with the first source or container on the opposite side.

[0095] An auxiliary heat exchanger is positioned upstream of the at least one main heat exchanger for desuperheating the working fluid when the apparatus is in a condensing operating configuration, and an auxiliary heat exchanger is positioned downstream of the at least one main heat exchanger for superheating the working fluid when the apparatus is in an evaporating configuration.

[0096] The device of the present invention can then, in a first step, condense the working fluid, desuperheat it and store it in the liquid phase, and in a second step, evaporate it and superheat it in the gas phase, or vice versa.

[0097] In one aspect, the at least one auxiliary heat exchanger has a flow path for a working fluid and a flow path for a heat vector configured to exchange heat with the working fluid.

[0098] In one aspect, the heat vector is different from the thermal mass of the vessel.

[0099] In an alternative embodiment, the heat vector is the same thermal mass contained within the vessel.

[0100] In one embodiment, the at least one auxiliary heat exchanger is in fluid communication with the vessel for desuperheating or superheating the working fluid using the thermal mass of the vessel or a liquid in the thermal mass.

[0101] In one aspect, the auxiliary device comprises at least one auxiliary reservoir for storing heat vectors, said at least one auxiliary reservoir being in fluid communication with said at least one auxiliary heat exchanger and, optionally, with the reservoir.

[0102] In one embodiment, the at least one auxiliary reservoir is positioned within the bath and is at least partially, preferably entirely, submerged in the liquid of the bath.

[0103] In an alternative embodiment, the at least one auxiliary reservoir is external to the vessel.

[0104] In one aspect, an auxiliary system is operably coupled to the vessel, preferably when the vessel is artificial, and configured to exchange heat with a thermal mass within the vessel, the auxiliary system being configured to enable the thermal mass within the vessel to exchange heat with the ambient environment or an external process in a controlled manner.

[0105] In one aspect, the auxiliary system comprises a chiller (chiller) that can remove heat from the thermal mass and release the heat to the ambient environment or an external process, or a heater that can collect heat from the ambient environment or an external process and then release the heat to the thermal mass.

[0106] In one aspect, an auxiliary system is in fluid communication with the primary duct and configured to exchange heat with the thermal mass within the vessel via a working fluid, the auxiliary system using the working fluid itself to effect the introduction or extraction of heat to / from the thermal mass in a controlled manner.

[0107] In one aspect, the auxiliary system includes a compressor, an expander or a stacked valve, an additional heat exchanger interposed between the compressor and the expander or the stacked valve, and a motor generator mechanically coupled to the compressor and / or the expander.

[0108] In one embodiment, the duct connects the compressor, the additional heat exchanger, the expander or the stacked valve, and the at least one main heat exchanger to form a closed circuit.

[0109] The auxiliary system, through the introduction of electrical energy, allows the working fluid to perform a chiller cycle, thereby directly removing heat from the working fluid and, consequently, from the thermal mass contained in the tank. In this particular case, the at least one main exchanger is an integral part of the chiller cycle, performing the function of an evaporator, while the additional exchanger removes heat. The expander, in this case, is a tool that allows the extraction of energy from the working fluid and achieving better cooling efficiency. In this case, an electric machine introduces energy into the system.

[0110] In one embodiment, a pumping station is located between the at least one main heat exchanger and the at least one reservoir.

[0111] In one aspect, the plurality of reservoirs comprises a main reservoir directly coupled to said at least one main heat exchanger and at least one storage reservoir, optionally a plurality of storage reservoirs, coupled to the main reservoir.

[0112] In one embodiment, the storage reservoirs are connected in parallel and / or in series with one another.

[0113] In one aspect, a pumping station is positioned between the main reservoir and the at least one storage reservoir, the pumping station configured to move the working fluid in a liquid phase from the main reservoir to the storage reservoir and vice versa.

[0114] In one embodiment, the pumping station comprises valves and / or pumps that allow fluid to move from one side to the other or vice versa by using gravity and / or pressure differentials.

[0115] In one aspect, a separate pipeline connects the gas-liquid separator to the main reservoir.

[0116] In one aspect, an additional tank contains a thermal mass and is connected to the tank via an additional pipeline, and a further heat exchanger is operatively active between the additional pipeline and a second pipeline in a region contained between the at least one storage reservoir and the main heat exchanger for exchanging heat between the thermal mass and the working fluid.

[0117] In one aspect, a further heat exchanger is operatively active between the additional pipeline and the second pipeline in a region included between said at least one storage reservoir and the pumping station.

[0118] In one aspect, the further heat exchanger is configured to, in a condensing operating configuration, subcool the working fluid prior to storing it in the at least one storage reservoir to maintain a temperature Te of the liquid phase working fluid at the end of condensation close to a temperature Ts of the vapor phase working fluid at the start of condensation.

[0119] In one embodiment, the temperature of the thermal mass in the additional vessel is lower than the temperature Ts of the carbon dioxide at the start of condensation.

[0120] In one embodiment, an additional pump is optionally operable on an additional pipeline between said at least one storage reservoir and a further heat exchanger.

[0121] In one embodiment, the additional heat exchanger is external to the vessel.

[0122] In one aspect, in a condensing operating configuration, the thermal mass in the additional vessel is pumped towards the vessel and passes through a further heat exchanger while the working fluid flows towards the at least one storage reservoir.

[0123] In one aspect, in an evaporative operating configuration, the working fluid is heated by following a reverse path to approach the evaporation temperature before evaporating, and then returns to cool a portion of the thermal mass.

[0124] The applicant has verified that additional in-vessel thermal mass and subcooling operated via a further heat exchanger can substantially increase the density of the working fluid in the reservoir, which in turn allows for a reduction in the volume and / or number of reservoirs required, their dimensions and relative cost.

[0125] In one embodiment, the main reservoir is inside the vessel and the at least one storage reservoir is inside or outside the vessel. In this way, the main reservoir and possible storage reservoirs inside the vessel are insulated from the external environment by the thermal mass. This is useful for keeping the heat exchange with the working fluid within the thermal mass.

[0126] In one embodiment, at least one vapor balancing pipeline connects the top of the at least one storage reservoir to a point in a main duct positioned between a first source and the at least one main heat exchanger, or to a first end of the at least one main heat exchanger, or to a gas-liquid separator.

[0127] In one aspect, a regulating valve is operably active on said vapor balancing pipeline.

[0128] A vapor balancing pipeline and regulating valve are configured to "equilibrate" the vapor phase of the working fluid contained in the at least one storage reservoir with the first end of the at least one main heat exchanger. This equilibration is useful for making room for liquid as it enters the reservoir, which would otherwise increase pressure due to compression of the vapor phase.

[0129] In one aspect, a device configured to remove non-condensable gases is provided.

[0130] In one aspect, a device configured to remove non-condensable gases is located at the top of the apparatus, where the non-condensable gases are allowed to accumulate, and the device may be connected to different points of the apparatus where the gas phase of the working fluid is present.

[0131] In one embodiment, an apparatus configured to remove non-condensable gases is operably connected to a first end of the at least one main heat exchanger, to a gas-liquid separator, or to a vapor balancing pipeline.

[0132] In one aspect, a device for configuring the apparatus in a condensing or evaporating operating configuration comprises a manual or actuated valve and a control unit operably coupled to the actuated valve and ultimately to a safety pump and / or valve.

[0133] In one aspect, a device for configuring the apparatus in a condensing or evaporating operating configuration is operably active on the main duct and / or on said at least one main heat exchanger and / or on the first source or reservoir and / or on the second source or container.

[0134] The present invention also relates to a plant for energy conversion and storage, comprising an apparatus for thermal energy storage according to one or more of the preceding aspects.

[0135] In one aspect, a plant for energy conversion and storage comprises: Working fluids other than air, an enclosure configured to store the working fluid in a vapor phase; at least one compressor in fluid communication with the enclosure; at least one expander in fluid communication with the enclosure; 10. The apparatus according to any one of the preceding aspects, wherein a main duct of the apparatus is in fluid communication with the compressor and the expander. Equipped with.

[0136] In one aspect, the enclosure is in fluid communication with the inlet of a compressor or the outlet of an expander, and the device is in fluid communication with the outlet of the compressor or the inlet of the expander.

[0137] In one aspect, the device is used in a plant as an accumulator of thermal energy generated during compression in a compressor.

[0138] In one aspect, there is provided a primary heat exchanger operatively interposed between the apparatus and the compressor and expander, optionally the primary heat exchanger being or coupled to a thermal storage (thermal energy storage - TES).

[0139] In one embodiment, the main heat exchanger of the apparatus is the secondary heat exchanger of the plant.

[0140] In one aspect, the plant is configured to operate a closed-loop thermodynamic conversion between the enclosure and at least the reservoir of the apparatus, first in one direction in an accumulation configuration and then in the opposite direction in a discharge configuration, wherein in the accumulation configuration the plant accumulates heat and pressure and in the discharge configuration produces energy.

[0141] In one aspect, the plant comprises a floating unit supporting at least an enclosure, the at least one compressor, and the at least one expander.

[0142] In one embodiment, the reservoir is a river, lake, or ocean, and the at least one reservoir and the at least one main heat exchanger are submerged in the river, lake, or ocean.

[0143] In this specification and the appended claims, reference is made to the following definitions.

[0144] Thermodynamic cycle (CT): A thermodynamic transformation from point X to point Y, where X coincides with Y. CT differs from TTC (cyclic thermodynamic transformation) mentioned below in that there is no mass accumulation (significant for energy purposes) within the cycle, whereas TTC typically takes place between two reservoirs of working fluid, one at the starting point of the working fluid and the other at the end of the working fluid. Cyclic Thermodynamic Transformation (TTC): A thermodynamic transformation from point X to point Y and from point Y to point X, without necessarily passing through the same intermediate points. Closed CT and / or TTC: no mass exchange (significant for energy purposes) with the atmosphere Open CT and / or TTC: with mass exchange (important for energy purposes) with the atmosphere.

[0145] Further features and advantages will become more apparent from the detailed description of preferred, but not exclusive, embodiments of the device for thermal energy storage and the plant for energy conversion and storage according to the invention.

[0146] This description is given below with reference to the accompanying drawings, which are given by way of example only and are therefore not limiting, in which: [Brief explanation of the drawings]

[0147] [Figure 1A] 1 shows an apparatus for thermal energy storage according to the present invention in one operating configuration; [Figure 1B] 2 shows an apparatus for thermal energy storage according to the present invention in another operating configuration; [Figure 2] 1A and 1B show a variation of the device of FIG. [Figure 3A] 1 shows details of the device of the apparatus of the previous figure at one operation step. [Figure 3B] 10 shows details of the devices of the apparatus of the previous figure in different operational steps; [Figure 3C] 10 shows details of the device of the apparatus of the previous figure in a further operating step. [Figure 3D] 10 shows details of the device of the apparatus of the previous figure in yet another operational step. [Figure 4] 1 is a TS diagram representing the transformation performed by the device according to the invention; [Figure 4A] 1 is a TS diagram representing the transformation performed by the device according to the invention; [Figure 4B] 1 is a TS diagram representing the transformation performed by the device according to the invention; [Figure 5] 2 shows part of a variant of the device for storing thermal energy according to the invention; [Figure 6] 4 shows part of another variant of the device for storing thermal energy according to the invention; [Figure 7] 3 shows part of a further variant of the device for thermal energy storage according to the invention; [Figure 8] 4 shows part of yet another variant of the device for storing thermal energy according to the invention; [Figure 9]2 shows a plant for energy conversion and storage including another variant of the device for thermal energy storage according to the invention; [Figure 10] 1 shows an example of a heat exchanger used in a device according to the present invention. [Figure 11] 1C shows another variation of the device of FIGS. 1A and 1B. [Figure 12] 3 shows a modification of the device of FIG. [Figure 13] FIG. 13 is a TS diagram illustrating the transformations operated by the device of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0148] With reference to the accompanying drawings, an apparatus for thermal energy storage according to the present invention is generally designated by the reference numeral 1.

[0149] 1A and 1B show a first embodiment of the device 1, which comprises a tank 2 containing water 3. The tank 2 shown in this embodiment is of artificial type, i.e., an artificial structure with reinforced concrete walls and base, for example, and has a length of about 250 m. 3 The tank 2 has a parallelepiped shape and dimensions so as to contain a volume of water of 250,000 liters. The surface 3a of the water 3 in the tank 2 is in contact with the atmosphere.

[0150] In a variant embodiment, instead of water, a mixture including water and an additive, such as salt, or water and solid particles or objects, such as ice, sand, or gravel, can be used. In a variant embodiment, the thermal mass includes oil or a hydrocarbon, such as cryogenic propane. In a variant embodiment, tank 2 can be a metal tank, optionally insulated. In a variant embodiment, tank 2 can be underground. In a variant embodiment, tank 2 can be closed at the top with a deformable membrane or balloon containing a controlled atmosphere, such as nitrogen.

[0151] The main heat exchanger 4 is contained within the vessel 2 so as to be submerged in the water 3. The main heat exchanger 4 is shown schematically in FIGS. 1A and 1B and may be, for example, but not limited to, a type of tube bundle 5, as shown in FIG. 10. In this example, the main heat exchanger 4 comprises a first collector 6 connected to a first pipeline 7, a second collector 8 connected to a second pipeline 9, and a plurality of tubes 5 that are parallel to each other and connect the first collector 6 to the second collector 8. The first pipeline 7 and the second pipeline 9 define the main duct of the device 1. In the illustrated embodiment, the first collector 6 is positioned at the top, the second collector 8 is positioned at the bottom, and the tubes 5 are vertical.

[0152] The main heat exchanger 4 is fixed to the vessel 2 by suitable fasteners, which are of a type known per se and are not shown in detail herein. The first collector 6, the second collector 8, and the tubes 5 define flow paths within the main heat exchanger 4, such that first ends of these flow paths are in fluid communication with a first pipeline 7 and second ends of these flow paths are in fluid communication with a second pipeline 9.

[0153] As can be noted, the internal volume of the internal flow passage of the main heat exchanger 4 is much smaller than the volume of the vessel 2, i.e., the volume of the water 3. Preferably, the ratio of the volume of the vessel 2 to the internal volume of the main heat exchanger 4 is greater than 100. For example, the internal volume of the internal flow passage is about 1.25 m 3 or 1250 liters, and therefore the ratio of the volume of vessel 2 to the internal volume of main heat exchanger 4 is equal to 200. In other variants, said ratio can be greater than 300, and optionally greater than 500.

[0154] The device 1 further comprises a gas-liquid separator 10 located in the tank 2 and immersed in the water 3. The gas-liquid separator 10 may have a known type of structure and will therefore not be described in detail herein. The gas-liquid separator 10 is located on the first pipeline 7 and is then in fluid communication on one side with the first end of the flow path of the main heat exchanger 4. For example, the gas-liquid separator 10 is located at approximately the same height as the first collector 6. The gas-liquid separator 10 is fixed to the tank 2 by suitable fasteners, which are themselves known type and will not be shown in detail herein. In a variant embodiment, the gas-liquid separator 10 can also be located outside the tank 2, i.e., not immersed in the water 3.

[0155] A main reservoir 11 is located in the tank 2 and is immersed in the water 3. The main reservoir 11 can have a structure of known type and will therefore not be described in detail herein. The main reservoir 11 is located on the second pipeline 9 and is then in fluid communication on one side with the second end of the flow path of the main heat exchanger 4. The main reservoir 11 is located below the gas-liquid separator 10, for example at a height approximately equal to the height of the second collector 8. A separate pipeline 12 connects the gas-liquid separator 10 to the main reservoir 11. The main reservoir 11 is fixed to the tank 2 by suitable fasteners, which are themselves of known type and are not shown in detail herein. This separate pipeline 12 is shown in the attached figures as also immersed in the water 3, but it can also be outside the tank 2.

[0156] In the embodiment of FIGS. 1A and 1B, the device 1 further comprises a plurality of storage reservoirs 13 immersed in the water 3, which are also positioned within the tank 2. In the variant of FIG. 2, these storage reservoirs 13 are located outside the tank 2. The storage reservoirs 13 are connected to the end of the second pipeline 9. In FIGS. 1A and 1B, these storage reservoirs 13 are vertical cylinders positioned next to each other and connected in parallel to the second pipeline 9. In variants of the embodiment, the storage reservoirs 13 can be connected to each other in series or in series and parallel. A control valve or control valves, each associated with one of the reservoirs 13 (not shown), can be arranged on the second pipeline 9. The storage reservoirs 13 are also fixed to the tank 2 by suitable fasteners of a type known per se and not shown in detail here. In some cases, the storage reservoir 13 may be further insulated to limit heat exchange with the external environment (either the atmosphere if outside the tank 2 or water if located within the tank 2).

[0157] A pumping station 14 is operatively positioned on the second pipeline 9 between the main reservoir 11 and the plurality of storage reservoirs 13. An example of the structure of the pumping station 14 is shown in Figures 3A-3D. In this example, the pumping station 14 includes a check valve 15, a pump 16, and a filter 17 positioned in series on a first line 18, with the check valve 15 positioned between the pump 16 and the storage reservoir 13, while the filter 17 is positioned between the pump 16 and the main reservoir 11. The check valve 15 is positioned on the delivery side of the pump 16. The pumping station 14 includes a second line 19 bypassing the check valve 15, the pump 16, and the filter 17, and a third line 20 bypassing the check valve 15, the pump 16, and the filter 17. The second line 19 is provided with a separate actuated valve 21. The third line 20 is provided with a separate actuated valve 22. An actuated valve 23 is further positioned on the first line 18 between the filter 17 and the main reservoir 11, between the branch of the second line 19 and the branch of the third line 20. An actuated valve 24 is further positioned on the first line 18, between the check valve 15 and the storage reservoir 13, between the branch of the second line 19 and the branch of the third line 20.

[0158] A vapor balancing pipeline 25 provided with a separate regulating valve 26 connects the top of the storage reservoir 13 to the first pipeline 7. There may also be one or more regulating valves, for example one for each reservoir 13. In FIGS. 1A and 1B, this vapor balancing pipeline 25 is connected to a point on the first pipeline 7 located between the main heat exchanger 4 and the gas-liquid separator 10. In a variant of the embodiment, the vapor balancing pipeline 25 may be connected to the first end of the main heat exchanger 4 or to the gas-liquid separator 10, as in FIG. 2.

[0159] 1A and 1B, there is further an auxiliary system 27 operably coupled to the tub 2 and configured to exchange heat in a controlled manner with the water 3 in the tub 2 and the external environment. This auxiliary system 27 may comprise a chiller capable of removing heat from the water 3 and releasing the heat to the external environment, or a heater capable of releasing heat absorbed from the external environment to the water 3. The auxiliary system 27 may comprise its own circuit defined by respective ducts immersed in the water 3 of the tub 2, or the water of the tub 3 may be circulated outside the tub 2 and brought into the auxiliary system 27.

[0160] The apparatus 1 of the embodiment of FIGS. 1A and 1B further comprises a circulation device 28 defined by a propeller 29 driven into rotation by an electric motor 30. The circulation device 28 is contained within the tub 2 and immersed in the water 3, and is configured to create a closed circulation path for at least the water 3 within the tub 2 (forced circulation) so as to move the water 3 in the tub 2 relative to the main heat exchanger 4. The tub 2 shown in FIGS. 1A, 1B, and 2 defines a closed volume, and the circulation device 28 constantly circulates the same water 3 within the closed volume. In this way, the water 3 envelops the tubes 5 of the heat exchanger 4 and passes through the flow paths defined between adjacent tubes 5. In the embodiment of FIGS. 1A, 1B, and 10, the flow of the water 3 within the tub 2 is perpendicular to the aforementioned tubes 5.

[0161] In a variation of the embodiment, the circulation device 28 may be any means for overcoming the small pressure drop that occurs within the vessel 2 due to the interaction of the moving working fluid with the walls of the vessel 2 and / or the passage of the moving working fluid between the tubes 5 of the main heat exchanger 4. For example, the circulation device 28 may be a pump (e.g., an axial pump or a lifting pump). In a variation of the embodiment, the circulation device 28 may also be positioned outside the vessel 2 and in fluid communication with the vessel 2 via a separate tube.

[0162] The first pipeline 7 is connected to a first source 31 of working fluid in gaseous state. For example, this first source 31 is a container containing a working fluid, for example carbon dioxide (CO2) in gaseous state. In a variant embodiment, the working fluid can be air used with cryogenic propane as thermal mass.

[0163] The illustrated apparatus 1 comprises a device 32 configured to remove non-condensable gases located in the upper part of the apparatus 1, where the gas phase of the working fluid is present. In the exemplary embodiment of Figures 1A and 1B, this device 32 for removing non-condensable gases is connected to the vapor balancing pipeline 25. In a variant of the embodiment, this device 32 for removing non-condensable gases can be connected to the first end of the main heat exchanger 4 or to the gas-liquid separator 10.

[0164] The apparatus 1 further comprises an electronic control unit, not shown, operatively coupled to the motor 30, to the pumping station 14, and ultimately to other devices (valves, pumps, filters, etc.) for configuring the apparatus 1 in a condensing or evaporating operating configuration.

[0165] The boiling temperature T1 of water is higher than the condensation / evaporation temperature T2 of carbon dioxide, and in particular higher than the critical temperature of carbon dioxide, so that the carbon dioxide exchanges latent heat, while the water exchanges sensible heat, i.e., the temperature of the water itself changes.

[0166] In the condensing operating configuration, carbon dioxide in gaseous state flows from the first source 31 through the main heat exchanger 4, gives up heat (becomes hot) to the water 3, condenses inside the tubes 5, and then accumulates in liquid state in the storage reservoir 13 (FIG. 1A). This process is illustrated in the TS diagram of FIG. 4 and in Table 1 below.

[0167] [Table 1]

[0168] In the evaporation operating configuration, liquid carbon dioxide flows from the storage reservoir 13 through the main heat exchanger 4 where it absorbs heat (becomes cold) from the water 3, evaporates inside the tubes 5, and is then re-entered in the container in a gaseous state (FIG. 1B). This process is illustrated in the TS diagram of FIG. 4 and Table 2 below. In this configuration, the main reservoir 11 and storage reservoir 13 act as a second source of working fluid in a liquid state.

[0169] [Table 2]

[0170] The water 3 then exchanges heat with the carbon dioxide positioned in the main heat exchanger 4 and with the water 3 in the evaporative configuration, storing heat and retaining the heat before releasing the heat back to the carbon dioxide in the evaporative configuration, which is a thermal mass.

[0171] In the condensing operation configuration, the pumping unit 14 is configured to move the just-condensed working fluid in a liquid state from the main reservoir 4 towards the storage reservoir 13, i.e., from point X to point Y in Figures 3A and 3C. In the evaporating operation configuration, the pumping unit 14 is configured to move the working fluid in a liquid state from the storage reservoir 13 towards the main reservoir 4, i.e., from point Y to point X in Figures 3B and 3D. The pumping unit 14 can move the fluid from point X to point Y, or vice versa, using a pressure difference favorable to the flow, or via the pump 16, or by gravity. For example, four cases are identified, as shown in Table 3 below.

[0172] [Table 3]

[0173] The valves of the pumping unit 14 can stack working fluids from higher pressure to lower pressure, and if the upper state of an individual valve is a "saturated" liquid, the lower valve can have a mixture of liquid and vapor, which is what is shown in the TS diagram of Figure 4, passing from point E to point E'.

[0174] The gas-liquid separator 10 separates the liquid phase of the gaseous carbon dioxide entering and leaving the main heat exchanger 4. The separated liquid phase in said gas-liquid separator 10 falls by gravity into the lower main reservoir 11 through a separate pipeline 12, the geometry of which defines, for example, a hydraulic guard, i.e. ensuring that all carbon dioxide in the vapor phase passes through the main heat exchanger 4, i.e. preventing the vapor from bypassing said main heat exchanger 4.

[0175] Figures 4A and 4B show more precisely what was described above with reference to Figure 4. Figure 4A represents the condensing operating configuration, and Figure 4B represents the evaporating operating configuration.

[0176] In the condensing configuration (Figure 4A), water 3 continues to recirculate while carbon dioxide condenses. Therefore, the line I-II representing the hot water is not fixed but gradually moves upward to I'-II'. At the same time, the carbon dioxide condensation line CD also gradually moves upward to C1-D1, and at the end of condensation, the condensed carbon dioxide is at D1 (at E1 with possible subcooling). At that time, the temperature Ts of carbon dioxide at the start of condensation when it is all in the vapor phase is lower than the temperature Te of carbon dioxide at the end of condensation when it is all in the liquid phase.

[0177] In the evaporation configuration (Figure 4B), the water 3 continues to recirculate while the carbon dioxide evaporates. Therefore, the line I'-II'' representing the cooling water is not fixed but gradually moves downward to I-II, and the carbon dioxide evaporation line E'-C' also gradually moves downward to E'1-C'1.

[0178] In a variant of the embodiment not shown, the heat exchanger is as shown in FIG. 10 and described above and is of the "once-through" type, i.e., all working fluid entering from one side exits from the other, so there is no accumulation. In these variants, the pipeline 12 is not present or a valve is installed on the pipeline 12. The use of a "once-through" exchanger allows for the condensation and evaporation of a working fluid composed of a gas mixture (e.g., air or non-100% pure CO2) without separating the individual components, ensuring that the concentrations of these components in the condensate that must evaporate are unchanged during the discharge. If, instead, a first component evaporates before a second component, the mixture with a low concentration of the second component will evaporate first, resulting in a mixture enriched in said second component. For example, if the working fluid is air (78% nitrogen, 20% oxygen, 2%, etc.) and a "once-through" type heat exchanger is not used, a mixture with little oxygen will evaporate first, resulting in a mixture that is very oxygen-rich in the final step.

[0179] The vapor balancing pipeline 25 and the regulating valve 26 are configured to "equilibrate" the vapor phase of carbon dioxide contained in the storage reservoir 13 with the first end of the main heat exchanger 11, while the device 32 configured to remove non-condensable gases allows these non-condensable gases to be removed from possible accumulation points.

[0180] Along the closed circulation path, the flow of water 3 passes through a first transport section (perpendicular to the flow direction) of the water, which depends on the dimensions of the tank 2, the geometry of the tank 2, the number and characteristics of the circulation devices 28. The first transport section may be, for example, 50 m 2 Inside the tubes 5 of the main heat exchanger 4, the working fluid passes through a second transport section of the working fluid, which is the sum of the sections of the tubes 5. The second transport section is, for example, 5 m 2The ratio of the first transport section to the second transport section is then equal to 10. Furthermore, the transport velocity of the water through the first transport section is low, for example less than 1 m / s, for example equal to about 0.05 m / s. The transport velocity of the liquid through the second transport section is, for example, equal to about 0.1 m / s.

[0181] The described device 1 is capable of receiving a working fluid in the gas phase at a temperature close to or above its condensation temperature and removing the latent heat extracted from the working fluid during the phase change, making this working fluid available in the liquid phase. The system can also perform the reverse operation, i.e., taking in the working fluid in the liquid phase, supplying heat to it to evaporate it (capturing such heat from the water 3), and finally superheating the working fluid with the sensible heat secured in the first step.

[0182] FIG. 5 shows from above different possible geometries of the tank 2, which in this case further comprises a conveyor 33 having a circular shape and immersed in the water 3. In the example shown, the conveyor 33 is defined by a cylinder that is open at both ends and communicates with the interior volume of the tank 2. The main axis of the cylinder is horizontal. The main heat exchanger 4 is located near the first open end of the cylinder, and the propeller 29 of the circulation device 28 is positioned near the second open end of the cylinder. As shown, this geometry generates two water streams circulating according to two closed circulation paths within the tank 2 (one flow circulating clockwise, the other counterclockwise), and the cylinder directs the water 3 of both closed circulation paths toward the main heat exchanger 4. In a variant of the embodiment not shown, the main heat exchanger 4 and / or the propeller 29 can be located within the cylinder. In an embodiment variant not shown, the conveyor 33 can also have a different shape, for example a hood shape.

[0183] 6 shows another variant from above, in which the vessel 2 has a rectangular periphery and is provided with a plurality of flow diverters 34 defined by walls immersed in the vessel's water 3, the walls defining a unique closed circulation path with a serpentine trajectory. Specifically, the flow diverters 34 comprise a central wall that essentially subdivides the vessel 2 into two, a plurality of walls protruding from the central wall, and a plurality of walls protruding from the vessel's side walls. The propeller 29 of the circulation device 28 is positioned in an opening defined between a first end of the central wall and one of the vessel's side walls. The main heat exchanger 4 is positioned in an opening defined between a second end of the central wall and one of the vessel's side walls.

[0184] FIG. 7 shows a variant of the apparatus 1 further comprising an auxiliary device 35 positioned between the gas-liquid separator 10 and the first supply source 31. The auxiliary device 35 comprises a first auxiliary heat exchanger 36A and a second auxiliary heat exchanger 36B positioned in series on the first pipeline 7. The first auxiliary heat exchanger 36A and the second auxiliary heat exchanger 36B thus have a flow path in fluid communication with the first pipeline 7, through which the working fluid (carbon dioxide) intersects. The first auxiliary heat exchanger 36A and the second auxiliary heat exchanger 36B further have a flow path connected to the tank 2, through which the water 3 of the tank 2 intersects. To this end, referring to FIG. 7, an auxiliary pipeline 37 extends from the tank 2 to the first auxiliary heat exchanger 36A and to the second auxiliary heat exchanger 36B. Below the first auxiliary heat exchanger 36A, a branch of the auxiliary pipeline 37 is connected to a first auxiliary reservoir 38A. Below the second auxiliary heat exchanger 36B, the auxiliary pipeline 37 is connected to a second auxiliary reservoir 38B. An auxiliary pump 39 having a separate bypass duct 40 with a separate valve 41 is located on the auxiliary pipeline 37 between the tank 2 and the first auxiliary heat exchanger 36A. A first auxiliary pump 39A having a separate bypass duct 40A with a separate valve 41A is located on the branch. A second auxiliary pump 39B having a separate bypass duct 40B with a separate valve 41B is located between the second auxiliary heat exchanger 36B and the second auxiliary reservoir 38B.

[0185] The first auxiliary reservoir 38A and the second auxiliary reservoir 38B are used to store water 3 at different, higher temperatures relative to the water 3 in the tub 2.

[0186] The first and second auxiliary heat exchangers 36A, 36B are consequently positioned upstream of the separator 10 and the main heat exchanger 4 to desuperheat the working fluid when the apparatus 1 is in the condensing operating configuration, i.e., to bring the temperature of the working fluid starting from the upper inlet temperature (A in FIG. 4) towards the condensing temperature (B).

[0187] The first and second auxiliary heat exchangers 36A, 36B are consequently positioned downstream of the main heat exchanger 4 to superheat the working fluid when the device 1 is in the evaporating configuration, i.e., to bring the temperature of the working fluid closer to the inlet temperature (A') of the fluid in the system, starting from a temperature (B' or C') equal to or close to the evaporation temperature.

[0188] 7 shows the first auxiliary reservoir 38A and the second auxiliary reservoir 38B positioned outside the tank 2. In a variation of the embodiment not shown, the first auxiliary reservoir 38A and the second auxiliary reservoir 38B are disposed within the tank 2 and immersed in the water 3 or are obtained in a compartment obtained within the tank 2. The first auxiliary reservoir 38A and the second auxiliary reservoir 38B may be further insulated to limit heat exchange with the surrounding environment (which may be the external environment or the tank 2 if they are immersed in the water 3 of the tank 2).

[0189] In another variant not shown, the auxiliary device 35 is not operated by the water 3 of the tank 2 but by a heat vector different from the water 3 of the tank 2. In this case, the auxiliary pipeline 37 is connected, instead of the tank 2, to one or more auxiliary reservoirs in which the heat vector is stored at low temperature.

[0190] FIG. 8 illustrates a variation of the apparatus 1, depicting an alternative to the auxiliary system 27 of FIGS. 1A and 1B, configured to exchange heat in a controlled manner with the water 3 in the tank 2 and the external environment. In this embodiment, the auxiliary system 27 is coupled to the first pipeline 7 and the second pipeline 9 and is arranged in parallel with the main heat exchanger 4. The auxiliary system 27 in this embodiment is configured to exchange heat with the water 3 in the tank 2 via the working fluid (carbon dioxide) passing through the main heat exchanger 4. The auxiliary system 27 includes an auxiliary compressor 42, an auxiliary expander 43 (or alternatively, a stacked valve), an additional heat exchanger 44 interposed between the auxiliary compressor 42 and the auxiliary expander 43, and an auxiliary motor 45 mechanically coupled to the auxiliary compressor 42 and / or the auxiliary expander 43. The auxiliary compressor 42 is in fluid communication with the first pipeline 7, and the auxiliary expander 43 is in fluid communication with the second pipeline 9. The auxiliary compressor 42 and the auxiliary expander 43 are fluidly connected to one another, and an additional heat exchanger 44 is operatively positioned at the connection between the auxiliary compressor 42 and the auxiliary expander 43. The auxiliary compressor 42, the additional heat exchanger 44, the auxiliary expander 43, and the main heat exchanger 4 form a closed circuit. By introducing electrical energy via the auxiliary motor 45, the auxiliary system 27 of FIG. 8 can run a chiller cycle using the working fluid to directly remove heat from the working fluid and, therefore, from the water 3 contained in the tank 2. The main heat exchanger 4 functions as an evaporator in the chiller cycle described herein.

[0191] In a variant of the embodiment not shown, a pump is also present and the auxiliary motor 45 is a motor-generator. The auxiliary system 27 implements a power cycle for generating energy, in which the main heat exchanger 4 acts as a condenser.

[0192] In a variant not shown in the figures but still part of the invention, the apparatus 1 comprises a first main heat exchanger that functions as a condenser in a condensing operating configuration and a second, different main heat exchanger that functions as an evaporator in an evaporating operating configuration. The first and second main heat exchangers are positioned parallel to one another. Each of the first and second main heat exchangers has a first end fluidly connected to the liquid-vapor separator 10 and the first supply 31, and a second end fluidly connected to the main reservoir 11 and the storage reservoir 13.

[0193] Furthermore, both the aforementioned unique main heat exchanger, as well as each of the above-mentioned first and second main heat exchangers described herein, may be formed by multiple exchangers operating in series or parallel.

[0194] 9 shows a plant 100 for energy conversion and storage comprising and using an apparatus 1 for storing thermal energy according to the invention. This plant 100 may be similar to one of the embodiments described in published documents WO 2021191786 and WO 2021255578 in the name of the same applicant. The apparatus 1 according to the invention is used in the plant 100 as a secondary heat exchanger.

[0195] More specifically, the illustrated plant 100 operates using a working fluid other than atmospheric air, e.g., selected from the group including carbon dioxide CO, sulfur hexafluoride SF, and nitrogen oxide NO. The plant 100 is configured to perform a closed-loop thermodynamic conversion (TTC) first in one direction in a storage configuration / step and then in the opposite direction in a discharge configuration / step, where in the storage configuration the plant 100 stores heat and pressure, and in the discharge configuration the plant produces electrical energy.

[0196] Referring to FIG. 9, the plant 100 comprises an expander, such as a turbine 102, and a compressor 103 mechanically coupled to a motor-generator shaft 104.

[0197] The plant 100 comprises an enclosure 105 defined by a pressostatic balloon of flexible material, for example, a PVC-coated polyester fabric. The pressostatic balloon is disposed on a surface and externally contacts the atmosphere. The pressostatic balloon defines a volume therein configured to contain a working fluid at atmospheric or substantially atmospheric pressure, i.e., in pressure equilibrium with the atmosphere, during all steps of a cycle operated by the plant 100. The enclosure 105 can also be realized as a gasometer or double-membrane pressostatic balloon or any other low or zero overpressure gas storage system, in which the pressure remains constant or substantially constant as the volume of the working fluid changes.

[0198] A first duct 106 extends between the enclosure 105 and the inlet 103a of the compressor 103 and between the enclosure 105 and the outlet 102b of the turbine 102 to fluidly connect the internal volume of the enclosure 105 with said compressor 103 and turbine 102.

[0199] Alternatively, a valve or valve system (not shown) may be operably positioned on the first duct 106 to fluidly connect the enclosure 105 with the inlet 103a of the compressor 103 or to fluidly connect the outlet 102b of the turbine 102 with the enclosure 105.

[0200] The plant 100 comprises a primary heat exchanger 107 that can be selectively placed in fluid communication with the outlet 103b of the compressor 103 or with the inlet 102a of the turbine 102. For this purpose, second ducts 108 extend between the inlet 102a of the turbine 102 and the primary heat exchanger 107, and between the outlet 103b of the compressor 103 and the primary heat exchanger 107. The primary heat exchanger 107 is or is associated with a thermal accumulator (thermal energy storage - TES).

[0201] Alternatively, a valve or valve system (not shown) is operably positioned on the second duct 108 to fluidly connect the primary heat exchanger 107 to the inlet 102a of the turbine 102 or the outlet 103b of the compressor 103 to the primary heat exchanger 107.

[0202] The device 1 of the type described above is in fluid communication with a primary heat exchanger 107 and is configured to accumulate a working fluid in the liquid phase at a temperature close to its critical temperature, which is close to the ambient temperature and preferably comprised between 0°C and 100°C.

[0203] In the embodiment shown in Figure 9, the first pipeline 7 of the device 1 is connected to the primary heat exchanger 107 so that the gas-liquid separator 10 remains interposed between the main heat exchanger 4 of the device 1 and the primary heat exchanger 107 of the plant 100.

[0204] In the accumulation configuration, the working fluid in a gaseous state coming from the enclosure 105 is compressed in the compressor 103 and becomes hot. The working fluid then flows through the primary heat exchanger 107, which acts as a cooler to remove some of the heat from the compressed working fluid, cool some of that heat, and store the thermal energy removed from said working fluid. The working fluid then reaches the device 1, where it is condensed (in the main heat exchanger 4) and stored in the storage reservoir 13, while further thermal energy is stored in the water 3 of the tank 2. The working fluid is stored in the storage reservoir 13 in a liquid state at a temperature close to its critical temperature.

[0205] In the discharge configuration, the working fluid coming from the reservoir 13 of the device 1 is evaporated (in the main heat exchanger 4) using the thermal energy previously stored in the water 3 of the tank 2 and sent to the primary heat exchanger 107, which then acts now as a heater, releasing further previously stored heat to the working fluid, heating it up. The working fluid is then admitted to the turbine 102 and stored again in gaseous state in the enclosure 105.

[0206] As can be seen from Figure 9, the device 1 in this embodiment does not comprise an artificial reservoir, but rather a natural body of water, such as a lake or river. Figure 9 is a cross-sectional view of a riverbed. The river water 3 flows naturally, and no circulation device is present. Furthermore, the enclosure 105, turbine 102, compressor 103, motor-generator 104, and primary heat exchanger 107 can be mounted on a floating unit that floats on the river (or lake or sea), while the device 1 is immersed in the river itself.

[0207] FIG. 11 shows another variant of the device 1 of the invention which differs from the one in FIGS. 1A and 1B in that the main heat exchanger 4 comprises a heat exchanger 4′ as described above combined with a direct contact condenser 46 and a circulation pump 47 arranged on the circulation circuit, the direct contact condenser 46 and the heat exchanger 4′ being immersed in the water 3 of the tank 2 and the circulation pump 47 being outside the tank 2.

[0208] In the condensing configuration, carbon dioxide in gaseous state flows directly from the first source 31 into the direct contact condenser 46, where it condenses under the influence of contact with the liquid portion recirculating through the circulation pump 47 and exchanger 4′ and is sprayed into the direct contact condenser 46. The liquid portion accumulated in the direct contact condenser 46 is then transferred via the pumping unit 14 to the storage reservoir 13.

[0209] In the evaporation operating configuration, liquid carbon dioxide is pumped from the storage reservoir 13 via the pumping unit 14 to the circulation pump 47, circulated through the exchanger 4′, and sprayed into the direct contact condenser 46. The gas portion accumulated in the direct contact condenser 46 exits above the direct contact condenser 46 towards the container of the first source 31.

[0210] FIG. 12 shows a variant of the device 1 of FIG. 2, and FIG. 13 shows a condensing operating configuration operated by the device of FIG.

[0211] The apparatus of Figure 12 includes all of the elements of the apparatus of Figure 2. In addition, an additional tank 110 is connected to tank 2 via an additional pipeline 111. An additional pump 112 is operable on the additional pipeline 111, which is operably coupled to second pipeline 9 via a further heat exchanger 113, so that water flowing in the additional pipeline 111 can exchange heat with carbon dioxide flowing in second pipeline 9. The further heat exchanger 113 is positioned between pumping station 14 and storage reservoir 13. The additional tank contains water at a temperature lower than the temperature Ts of the carbon dioxide at the start of condensation (see Figure 4A and related discussion).

[0212] The variant of Figure 12 allows for subcooling of carbon dioxide in the condensing operating configuration (filling step) so that the temperature Te of the liquid phase carbon dioxide at the end of condensation is maintained close to the temperature Ts of the vapor phase carbon dioxide at the start of condensation.

[0213] To this end, in the condensing operation configuration, the water contained in the additional tank 110 is pumped towards tank 2 by an additional pump 112 and absorbs heat from the carbon dioxide flowing towards reservoir 13 by cooling (subcooling) the carbon dioxide while passing through a further heat exchanger 113.

[0214] The volume required to store liquid carbon dioxide in reservoir 13 depends on the density difference between the start of filling (all vapor at the start of filling temperature Ts) and the end of filling (all liquid at the end of filling temperature Te>Ts). The greater the difference between Te and Ts, the smaller the density difference between liquid and vapor. To increase the density difference between liquid and vapor and reduce the volume of reservoir 13 (and its cost), the difference between Te and Ts can be reduced. The modification of FIG. 12 makes it possible to achieve this result, as shown in FIG. 13. Indeed, the end of filling temperature Tes with subcooling (i.e., E1) is close to the start of filling temperature Ts, and the difference Tes-Ts is lower than Te-Ts, where Te is the end of filling temperature without subcooling (i.e., D1).

[0215] Table 4 below shows the effect of subcooling on the density of carbon dioxide and therefore the volume of reservoir 13 as operated by the device of Figure 12. The points shown in Table 4 are those of Figure 13.

[0216] [Table 4]

[0217] By adopting the technical solution of Figure 12 (additional tank 110, additional pipeline 111, additional pump 112, further heat exchanger 113), it is possible to substantially increase the density of the carbon dioxide in reservoir 13 (in this example by about 30%), which in turn reduces the required reservoir volume, reservoir dimensions and relative costs.

[0218] In the evaporation operation configuration (exhaust step), the carbon dioxide is heated before it is evaporated, and by following the reverse path, the carbon dioxide is brought close to the evaporation temperature, and then some of the water contained in the tank 2 is cooled again.

[0219] In the variant of FIG. 12, the reservoir 13 containing carbon dioxide can also be located inside the additional tank 110 .

[0220] test The device according to the invention was tested in comparison with a shell-and-tube exchanger in which the working fluid is in the inner tube of the shell-and-tube, while water flows between the inner tube and the outer shell via a pump located in a pipe and is sent to the inside of the shell.

[0221] Heat removal (duty): 10000 [kWt] Accumulation time / energy: 10 [h] / 360,000 [MJ] (10 [h] * 3,600 [s / h] * 10 [MWt]) Thermal mass used: Water Water temperature rise of 4°C to store heat Considering that the latent heat is stored as sensible heat in water and the water is heated to 4°C, a filling volume of 21,500 m3 of water is required. Water flow velocity in the connecting pipe with the shell of the shell & tube: between 1.5m / s and 2m / s (maximum allowable 3m / s) Transport section in the tank: 50 m 2 ] Pump efficiency: 80% Electric motor efficiency: 95%

[0222] I. Shell & Tube.

[0223] II. Shell and tube with 10 times the flow rate of Case I and equal velocity in the connecting pipe.

[0224] III. Shell and tube with 10 times the flow rate of Case I and the maximum allowable velocity in the pipe.

[0225] IV. The device of the present invention with 10 times the flow rate of Case I.

[0226] [Table 5]

[0227] It can be seen that a tenfold increase in flow rate reduces the temperature range (DT) by a factor of ten, but in the shell-and-tube solution the connecting tubes become huge and the power required increases by a factor of ten (Case II), or in the case of reducing the pipe at the allowable velocity limit, the power required increases by a factor of 25 due to the large pressure drop.

[0228] In the solution according to the invention, there is no tube but a transport section, which almost completely eliminates the pressure drop caused by the tube and keeps the consumed power equal to the first case, but with a temperature range (DT) that is ten times smaller (0.4°C vs. 4.0°C). [Explanation of symbols]

[0229] 1 Devices for storing thermal energy 2 tanks 3 Water / thermal mass 3a Water Surface 4, 4' main heat exchanger 5 tubes 6 First Retriever 7. First Pipeline 8 Second Recycler 9. Second Pipeline 10 Gas-liquid separator 11 Main reservoir 12 individual pipelines 13 Storage Reservoir 14. Pumping Station 15 Check valve 16 Pump 17 Filters 18 First Line 19 Second Line 20 The Third Line 21, 22, 23, 24 Actuated valves 25 Steam Equalization Pipeline 26 Control valve 27 Auxiliary Systems 28 Circulation Device 29 Propeller 30 motor 31 Primary Source 32 Devices configured to remove non-condensable gases 33 Conveyor 34 Flow Diverter 35 Auxiliary Devices 36A First auxiliary heat exchanger 36B Second auxiliary heat exchanger 37 Auxiliary Pipeline 38A First auxiliary reservoir 38b Second auxiliary reservoir 39 Auxiliary pump 39A First auxiliary pump 39B Second auxiliary pump 40 Bypass Duct 40A First bypass duct 40B Second bypass duct 41, 41A, 41B valves 42 Auxiliary compressor 43 Auxiliary expander 44 Additional Heat Exchanger 45 Auxiliary motor 46 Direct contact condenser 47 Circulation Pump 100 plants 102 Expander / Turbine 102a Turbine inlet 102b Turbine outlet 103 Compressor 103a Compressor inlet 103b Compressor outlet 104 Motor Generator 105 Enclosure 106 First Duct 107 Primary heat exchanger 108 Second Duct 110 Additional Tank 111 additional pipelines 112 additional pumps 113 More Heat Exchangers

Claims

1. A device for storing thermal energy, A thermal mass (3) that is a liquid, optionally containing water, wherein the thermal mass (3) is configured to absorb and store heat or release heat. A tank (2) containing the aforementioned heat mass (3), A tank (2) containing at least one main heat exchanger (4) immersed in the thermal mass (3), wherein the liquid is movable within the tank (2) relative to the at least one main heat exchanger (4), A main duct (7, 9) connecting at least one main heat exchanger (4) to a first supply source (31) of a working fluid in a gaseous state or a second supply source of the same working fluid in a liquid state, The boiling temperature (T1) of the liquid with the aforementioned thermal mass is higher than the condensation / evaporation temperature (T2) of the working fluid in the main duct (7, 9), A device for configuring the apparatus (1) in which the gaseous working fluid flows from the first supply source (31) through the at least one main heat exchanger (4), and the heat mass heats up while releasing heat into the heat mass and condensing, or in which the liquid working fluid flows from the second supply source through the at least one main heat exchanger (4), and the heat mass cools down while absorbing heat from the heat mass and evaporating. Equipped with, The ratio of the volume of the tank (2) to the volume through which the working fluid flows, defined within the at least one main heat exchanger (4), is greater than 100 and optionally greater than 300. Device.

2. The apparatus according to claim 1, wherein the ratio of the first liquid transport section in the tank (2) to the second working fluid transport section in the at least one main heat exchanger (4) is greater than 100.

3. The apparatus according to claim 1 or 2, wherein the volume of the tank (2) is greater than 1,000 m³ and optionally greater than 10,000 m³, the first transport section is greater than 10 m² and optionally greater than 100 m², and the velocity of the liquid passing through the first transport section is less than 10 m / s and optionally less than 1 m / s.

4. The apparatus according to claim 1, further comprising at least one reservoir (11, 13) fluidly connected to the at least one main heat exchanger (4) and configured to receive and store the condensed working fluid coming from the at least one main heat exchanger (4), optionally further comprising a plurality of reservoirs, wherein optionally the at least one reservoir (11, 13) is located inside the tank (2) and at least partially immersed in the liquid of the tank (2).

5. The apparatus according to claim 1, further comprising at least one gas-liquid separator (10) coupled to the at least one main heat exchanger (4), wherein optionally the at least one gas-liquid separator (10) is positioned inside the tank (2) and at least partially immersed in the liquid in the tank (2).

6. At least one reservoir (11, 13) is fluidly connected to the at least one main heat exchanger (4) and configured to receive and store the condensed working fluid coming from the at least one main heat exchanger (4), optionally further comprising a plurality of reservoirs, optionally the at least one reservoir (11, 13) is located inside the tank (2) and is at least partially immersed in the liquid of the tank (2), The apparatus according to claim 5, wherein the gas-liquid separator (10) is positioned in the tank (2) above the at least one reservoir (11) and is connected to the at least one reservoir (11) via separate pipelines (12).

7. The apparatus according to claim 1, wherein the tank (2) is natural or artificial, and the liquid is able to move within the tank (2) naturally or by forced circulation.

8. The apparatus according to claim 1, further comprising at least one circulating device (28) which is operably active with respect to the liquid and configured to move the liquid in the tank (2) to the at least one main heat exchanger (4), wherein optionally the at least one circulating device (28) comprises a propeller (29) or a pump.

9. The apparatus according to claim 8, wherein the at least one circulation device (28) is located within the tank (2) and immersed in the liquid in the tank (2).

10. The apparatus according to claim 8 or 9, wherein the tank (2) defines a closed volume such that the at least one circulation device (28) is configured to generate at least one closed liquid circulation path within the closed volume, and the first transport section is a section of the at least one closed circulation path.

11. The apparatus according to claim 1, further comprising at least one conveyor (33) and / or at least one flow diverter (34) housed in the tank (2) and immersed in the liquid of the tank (2).

12. The apparatus according to claim 1, wherein the at least one main heat exchanger (4) comprises at least one bundle of tubes (5), the liquid passes between the tubes (5) and encloses the tubes (5), the working fluid passes through the tubes (5), and optionally the flow of the liquid in the tank (2) is perpendicular to the tubes (5).

13. The apparatus according to claim 1, further comprising an auxiliary device (35) having at least one auxiliary heat exchanger (36A, 36B), wherein the at least one auxiliary heat exchanger (36A, 36B) is positioned upstream of the at least one main heat exchanger (4) when the apparatus (1) is in the condensation configuration for superheating back the working fluid, and the at least one auxiliary heat exchanger (36A, 36B) is positioned downstream of the at least one main heat exchanger (4) when the apparatus (1) is in the evaporation configuration for superheating the working fluid.

14. The apparatus according to claim 13, wherein at least one auxiliary heat exchanger (36A, 36B) is in fluid communication with the tank (2) to perform superheating back or superheating of the working fluid using the heat mass or the liquid in the tank (2).

15. The apparatus according to claim 14, wherein the auxiliary device (35) comprises at least one auxiliary heat exchanger (36A, 36B) and at least one auxiliary reservoir (38A, 38B) that is in fluid communication with the tank (2), and optionally, the at least one auxiliary reservoir (38A, 38B) is positioned within the tank (2) and at least partially immersed in the liquid of the tank (2).

16. The apparatus according to claim 1, comprising an auxiliary system (27) operably coupled to the tank (2) and configured to exchange heat with the thermal mass in the tank (2), wherein the auxiliary system (27) optionally comprises a chiller or a heater.

17. The apparatus according to claim 16, wherein the auxiliary system (27) is fluidly connected to the main ducts (7, 9) and configured to exchange heat with the thermal mass in the tank (2) via the working fluid, and optionally the auxiliary system (27) comprises a compressor (42), an expander (43) or a stack valve, an additional heat exchanger (44) interposed between the compressor (42) and the expander (43) or stack valve, and a motor generator (45) mechanically connected to the compressor (42) and / or the expander (43).

18. The apparatus according to claim 4, further comprising a pumping station (14) positioned between the at least one main heat exchanger (4) and the at least one reservoir (11, 13), wherein the plurality of reservoirs (11, 13) optionally comprise a main reservoir (11) directly connected to the at least one main heat exchanger (4) and at least one storage reservoir (13) connected to the main reservoir (11), and the pumping station (14) is positioned between the main reservoir (11) and the at least one storage reservoir (13).

19. At least one reservoir (11, 13) is fluidly connected to the at least one main heat exchanger (4) and configured to receive and store the condensed working fluid coming from the at least one main heat exchanger (4), optionally further comprising a plurality of reservoirs, optionally the at least one reservoir (11, 13) is located inside the tank (2) and is at least partially immersed in the liquid of the tank (2), The gas-liquid separator (10) is positioned within the tank (2) above the at least one reservoir (11) and is connected to the at least one reservoir (11) via separate pipelines (12). The apparatus according to claim 18, wherein the individual pipelines (12) connect the gas-liquid separator (10) to the main reservoir (11).

20. The apparatus according to claim 18 or 19, comprising: at least one steam equilibrium pipeline (25) connecting the upper part of at least one storage reservoir (13) to a point in the main duct (7, 9) located between the first supply source (31) and the at least one main heat exchanger (4); and a control valve (26) operably active with respect to the at least one steam equilibrium pipeline (25).

21. Apparatus according to claim 18, comprising an additional tank (110) enclosing the thermal mass (3) and connected to the tank (2) via an additional pipeline (111), and further heat exchanger (113) operably active between the additional pipeline (111) and the second pipeline (9) in a region included between the at least one storage reservoir (13) and the main heat exchanger (4), or optionally in a region included between the at least one storage reservoir (13) and the pumping station (14), for exchanging heat between the thermal mass and the working fluid, wherein the further heat exchanger (113) is configured to supercool in the condensation operation configuration until the temperature (Te) of the working fluid in the liquid phase at the end of condensation is kept close to the temperature (Ts) of the working fluid in the vapor phase at the start of condensation, before the working fluid is stored in the at least one storage reservoir (13).

22. A plant for energy conversion and storage, Working fluids other than the atmosphere, An enclosure (105) configured to store the working fluid in the gas phase, At least one compressor (103) that is in fluid communication with the enclosure (105), At least one expander (102) that is in fluid communication with the enclosure (105), Apparatus (1) according to claim 1, wherein the main duct (7, 9) of apparatus (1) is in fluid communication with at least one compressor (103) and at least one expander (102). Equipped with, The plant (100) is configured to operate a closed-ring thermodynamic conversion (TTC) first in one direction in the storage configuration and then in the opposite direction in the discharge configuration, wherein in the storage configuration the plant (100) stores heat and pressure, and in the discharge configuration it generates energy. plant.

23. The plant according to claim 22, comprising a floating unit supporting at least the enclosure (105), the at least one compressor (103), and the at least one expander (103), wherein the tank (2) of the apparatus (1) is a river, lake, or sea, and the at least one reservoir (11, 13) and the at least one main heat exchanger (4) are immersed in the river, lake, or sea.

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