Energy conversion and storage plants

Abstract

The energy conversion and storage plant comprises a main circuit for a working fluid other than the atmosphere. The main circuit connects a storage device (205), a compression unit, a heat accumulator (100, 210), a reservoir (209), and an expansion unit, and is configured to operate the plant in an energy storage configuration or in an energy release and generation configuration by the movement of the working fluid between the storage device (205) and the reservoir (209) through the main circuit, and by the periodic thermodynamic conversion of the working fluid. The plant further comprises an auxiliary circuit (1) which connects the main circuit and / or the storage device (205) and / or the compression volume of the compressor (203) and / or the expansion volume of the expander (202) to at least a portion of the compression unit and / or expansion unit, and controls the temperature and / or pressure of this portion with the same working fluid.

Description

Field of the Invention

[0001] The present invention has as its object an energy conversion and storage plant of the type configured to perform a closed periodic thermodynamic conversion using a working fluid between two mass accumulations, in which generation, conversion, absorption and storage of energy are intended by management.

[0002] More particularly, the present invention relates to an optimized plant configuration that can utilize the same working fluid used in a closed periodic thermodynamic conversion to perform important auxiliary functions such as isolating the plant from the external environment and / or thermally isolating some parts of the plant from other parts and / or cooling specific regions or elements of the plant. Definitions

[0003] In this specification and the appended claims, the following definitions are referred to.

[0004] Periodic thermodynamic conversion (TTC): A thermodynamic conversion from point A to point B and from point B to point A, not necessarily passing through the same intermediate points, where the TTC acts between two mass storages / mass accumulations, one being the initial and the other being the final of the working fluid.

[0005] Thermodynamic cycle (CT): A thermodynamic conversion from point X to point Y, where X coincides with Y, and the thermodynamic cycle (CT) has no significant mass accumulations / mass storages for energy purposes within the cycle, unlike the above-mentioned periodic thermodynamic conversion (TTC).

[0006] Closed CT and / or TTC: There is no (significant for energy purposes) mass exchange with the atmosphere.

[0007] Open CT and / or TTC: There is (significant for energy purposes) mass exchange with the atmosphere.

[0008] Auxiliary circuits: These are circuits that do not directly contribute to energy generation, conversion, and storage, but serve internal and secondary functions of the system itself (such as lubrication control, temperature control, and / or pressure control). Auxiliary circuits perform functions other than conversions that occur within the main circuit, the compression volume of the compressor, and the expansion volume of the expander. Background of the discovery

[0009] On behalf of the same applicant, the published document, International Publication No. 2020 / 039416, describes a process and plant for energy storage. The plant comprises a variable-volume casing (e.g., a single- or double-membrane gas tank) for storing a non-atmospheric working fluid in a gas phase, in pressure equilibrium with the atmosphere, and a reservoir for storing a working fluid in a liquid or supercritical phase having a temperature close to the critical temperature, which is close to the ambient temperature. The plant is configured to perform a closed periodic thermodynamic conversion between the casing and the reservoir, first in one direction in a storage configuration, and then in the opposite direction in a release configuration. The plant stores heat and pressure in the storage configuration and generates energy in the release configuration.

[0010] All of these publications, representing the same applicant, are also documents: International Publications 2021 / 165806, 2021 / 191786, and 2022 / 101727, which depict a plant based on the same principle (closed periodic thermodynamic conversion between two mass storages) as shown in International Publication 2020 / 039416.

[0011] The applicant noted that seals are provided in the fluid machinery used in the aforementioned plants. Seals are required in all fluid machinery where the mechanical force (driving or operating the machine) passes from one working fluid to the other through a mechanical organ (a rotating shaft in turbomachinery, or a rod in the case of alternative machinery) that is normally exposed to the atmosphere. The seals serve to isolate the process environment inside the machine from the atmosphere, preventing the working fluid from leaving the machine (if the internal pressure is greater than atmospheric pressure) or preventing the working fluid from being contaminated by the air of the external environment (if the internal pressure is less than atmospheric pressure). However, in order for a seal to function properly and effectively prevent fluid from entering, it must act with a predetermined pressure jump in a temperature range and a relative velocity range (e.g., the ambient velocity of the shaft relative to the seal). For this reason, several systems are known for controlling the temperature, velocity, and pressure near the seal, but these systems are complex, expensive, or sometimes ineffective.

[0012] The applicant also noted that, like all fluid machinery, the fluid machinery used in the aforementioned plants requires supports with respect to the moving members(s), whether those moving members / they move in rotational or reciprocating motion, that is, the role of the components is to be interposed between the moving members(s) and the fixed components of the machine. For example, in the case of a rotating shaft of a turbomachinery, the support is a bearing. In the case of a rod of an alternative machine, the support is a bushing. Supports (bearings or bushings) often require lubrication to suppress friction, and therefore wear, of the components, and typically the bearings or bushings operate in direct or indirect contact with the atmosphere. For example, in the case of turbomachinery operating at overpressure relative to the atmosphere, solutions are known in which the bearings operating within the turbomachinery (e.g., a turbo-expander) operate at a pressure significantly higher than atmospheric pressure. Lubricating oil is extracted from the bearing area by level adjustment, depressurized, and sent to a lubrication unit, which typically operates at a pressure very close to atmospheric pressure. Subsequently, the lubricating oil is pressurized and returned to the bearing case. However, this solution has a drawback: the pressurized oil in the bearing case tends to "adsorb" the working fluid, which is then released into the oil case by depressurization and then exits the process.

[0013] In this field, the applicant first aimed to overcome the aforementioned shortcomings and ensure that seals and supports function correctly within fluid machinery operating in the aforementioned types of energy conversion and storage plants.

[0014] In particular, the applicant aimed to eliminate the problem of working fluid leakage or ambient air entering through seals, especially on rotating shafts, of fluid machinery that are part of the aforementioned types of energy conversion and storage plants, without relying on complex and costly solutions.

[0015] The applicant also aimed to bring the supports of the aforementioned fluid machinery into a suitable state to ensure that those supports function correctly, without having to rely on complex and costly solutions.

[0016] More generally, the applicant aimed to control the temperature and pressure of a defined area or part of a fluid machine, and ultimately other machines or devices (such as motors, generators, and speed reducers) that are components of the aforementioned types of energy conversion and storage plants connected to those fluid machines, in a relatively simple and cost-effective manner.

[0017] The applicant also aimed to isolate a plant from the external environment and / or thermally isolate certain parts of the plant from other parts and / or cool specific areas or elements of the plant in a relatively simple and cost-effective manner.

[0018] The applicant has found that the above-mentioned objectives and other objectives can be achieved by utilizing working fluids used to perform closed periodic thermodynamic conversions in energy conversion and storage plants.

[0019] The applicant has found that the above-mentioned objectives and other objectives can be achieved by an energy conversion and storage plant as described in the appended claims and / or in one or more of the following embodiments.

[0020] In a first independent embodiment, the present invention relates to an energy conversion and storage plant, the plant comprising: Working fluids other than the atmosphere, A storage device having a variable internal volume, configured to store the working fluid in the gas phase at a low overpressure or no overpressure, having a storage pressure Ps that is in pressure equilibrium with atmospheric pressure Patm, during each operating stage performed by the plant. A reservoir configured to store a working fluid in a liquid or supercritical phase, A compression unit comprising at least one compressor and at least one motor, mechanically connected to each other, An expansion unit comprising at least one expander and at least one generator, mechanically connected to each other, At least one heat storage device, optionally comprising at least one heat exchanger combined with at least one thermal mass, A main circuit connecting the variable volume of the storage device, the compression volume of the compressor, the at least one heat storage unit, the at least one reservoir, and the expansion volume of the expander, A device configured to operate a plant in an energy storage configuration or an energy release and generation configuration by the movement of a working fluid between a storage device and the at least one reservoir through a main circuit, and by the periodic thermodynamic conversion of the working fluid, Equipped with, The plant relates to a plant further comprising auxiliary circuits. The auxiliary circuits connect at least a portion of the compression unit and / or expansion unit to at least one of the main circuit, the variable volume of the storage device, the compression volume of the compressor, and the expansion volume of the expander. The auxiliary circuits are configured to control the temperature and / or pressure of the at least portion using the same working fluid received from periodic thermodynamic conversion.

[0021] In a second embodiment, the present invention relates to a method for controlling the temperature and / or pressure of at least a portion of a compression unit and / or expansion unit of a plant according to the first embodiment or a plant according to one of the following embodiments, the method comprising the step of connecting a main circuit and / or variable volume of a storage device and / or compression volume of a compressor and / or expansion volume of an expander to at least a portion of the compression unit and / or expansion unit via an auxiliary circuit.

[0022] Auxiliary circuits may include lines / pipelines outside the machine (such as compressors and expanders with speed reducers), but may also be located within the machine.

[0023] The applicant has first and foremost confirmed that the plant and method according to the present invention will enable the achievement of the objectives listed above.

[0024] In particular, the Applicant has found that the present invention, by using a working fluid and connecting it to the variable volume of the main circuit and / or the storage device and / or the compression volume of the compressor and / or the expansion volume of the expander, achieves the following technical effects, namely, forming a thermal barrier in the region or part of the fluid machine when necessary (for example, forming a barrier of a cooler working fluid against a hotter working fluid, which is within the compression volume of the compressor or the expansion volume of the expander), maintaining the support and / or the seal at an appropriate temperature for their functioning (for example, at a temperature lower than one of the working fluids within the compression volume of the compressor or the expansion volume of the expander), preventing or at least dramatically limiting the leakage (loss) of the working fluid from the plant and the dispersion of environmental air into the environment or the main circuit, and thus the contamination of the working fluid, even when there is a lubrication circuit operating at atmospheric pressure Patm. has been confirmed to be possible.

[0025] Further aspects and further technical effects of the present invention are described below.

[0026] In a third aspect, each of the at least one compressor and the at least one expander comprises a case, at least one movable mechanical member movable relative to the case and configured to exchange energy with the working fluid within each compression volume of the compressor or each expansion volume of the expander, and at least one transmission member connecting each movable mechanical member to a respective motor or generator.

[0027] In a fourth aspect, at least a part thereof includes at least one chamber defined between the case and the at least one transmission member, and the at least one chamber is arranged near the compression volume of the compressor or the expansion volume of the expander. Thus, it is possible to use the working fluid received via an auxiliary circuit as a barrier (which is thermal and suitable for preventing the entry of fluid) interposed between the compression or expansion volume and the external environment or the support or the seal.

[0028] In a fifth aspect, the at least one compressor and / or the at least one expander comprises at least one sealing element operatively connected to the case and the transmission member and separating the environment within the case from the external environment.

[0029] In a sixth aspect, the at least one chamber is in fluid communication with the at least one sealing element, optionally via a restriction.

[0030] In a seventh aspect, the at least one compressor and / or the at least one expander comprises a support operatively interposed between the respective transmission member and the respective case.

[0031] In an eighth aspect, the at least one chamber is in fluid communication with the support, optionally via a restriction.

[0032] In a ninth aspect, the auxiliary circuit is at least one discharge conduit extending from the main circuit and / or from the variable volume of the storage device to at least a part of the compression unit and / or the expansion unit, and configured to supply the working fluid to at least a part of the compression unit and / or the expansion unit at a discharge pressure P1 (P1 > Ps) greater than the storage pressure Ps.

[0033] In a tenth aspect, the auxiliary circuit is at least one discharge conduit extending from the main circuit and / or from the variable volume of the storage device to the at least one chamber, and configured to supply the working fluid to the at least one chamber at a discharge pressure P1 (P1 > Ps) greater than the storage pressure Ps.

[0034] In the eleventh embodiment, the auxiliary circuit comprises at least one return conduit extending from the compression unit and / or the expansion unit to a variable volume at a storage pressure Ps, or to a point in the main circuit at a pressure less than the release pressure P1.

[0035] In a twelfth embodiment, the at least one discharge conduit connects a withdrawal point of the main circuit at a discharge pressure P1 to the at least one chamber or to at least a portion of the compression unit and / or expansion unit, and / or the at least one discharge conduit comprises a fan or auxiliary compressor configured to increase the storage pressure Ps of the working fluid coming from the variable volume to the discharge pressure P1, with the variable volume connected to the at least one chamber or to at least a portion of the compression unit and / or expansion unit.

[0036] In a thirteenth embodiment, the main circuit comprises a first pipeline connecting a storage device to a compression unit and an expansion unit, a second pipeline and optionally a third pipeline connecting the at least one reservoir to the compression unit and the expansion unit, wherein the at least one accumulator is operably connected to the second pipeline and / or the at least one reservoir.

[0037] In the fourteenth embodiment, the drawpoint is located in the second and / or third pipeline between the at least one reservoir and the at least one heat accumulator, and / or between the at least one heat accumulator and the compression unit or expansion unit. Optionally, the drawpoint is an intermediate drawpoint from the compression volume of the compressor and / or from the expansion volume of the expander, i.e., at the intermediate pressure of the compressor and / or expander.

[0038] In a 15th aspect, the at least one return conduit extends from at least one auxiliary chamber of the compression unit and / or the expansion unit, and optionally, the at least one auxiliary chamber is at a return pressure P0 (P0 < P1) lower than the discharge pressure P1, and optionally, the return pressure P0 is greater than or equal to the storage pressure Ps (P0 ≧ Ps) (e.g., by a few millibars), and optionally, the return pressure P0 is lower than the operating pressure PL within the compression volume of the compressor or within the expansion volume of the expander (P0 < PL).

[0039] In a 16th aspect, a 9th aspect, and a 15th aspect, the support is connected to the at least one chamber via a restriction, and is at a support pressure P2 (P2 < P1) lower than the discharge pressure P1, and the support pressure P2 is greater than the return pressure P0 (P2 > P0).

[0040] In a 17th aspect, the compression unit and / or the expansion unit is operatively connected to a support and includes a lubrication circuit that stores lubricating oil, the lubrication circuit is at the support pressure P2, and is connected to the at least one return conduit.

[0041] In an 18th aspect, the lubrication circuit includes a pump configured to pump lubricating oil to the support and a sealed container for collecting lubricating oil, and a portion of the sealed container disposed above the free surface of the lubricating oil is connected to the at least one return conduit.

[0042] In a 19th aspect, a separator is disposed in the at least one return conduit connected to the sealed container, and the separator is configured to separate lubricating oil adsorbed by the working fluid.

[0043] In a 20th embodiment, the compression unit and / or the expansion unit comprises at least one reduction gear mechanically interposed between the transmission member of the compressor and / or expander and the respective motor or generator, the at least one reduction gear comprising a box, a movable member attached to the box, and a support interposed between the movable member and the box, the box being in fluid communication with the at least one chamber.

[0044] In the 21st embodiment, the box is mounted in a case, and the at least one chamber is in fluid communication with the box via a limiting portion, and the box is at the support pressure P2.

[0045] In the 22nd embodiment, the box is connected to a lubrication circuit.

[0046] In the 23rd embodiment, the compression unit and / or the expansion unit are provided with rigid or flexible joints that connect the respective reduction gears to the respective transmission members.

[0047] In the 24th embodiment, the joint is sealed in its respective casing, the casing is in fluid communication with the case and box, and the casing is in fluid communication with the auxiliary circuit.

[0048] In the 25th embodiment, the casing is connected to a discharge conduit, and the casing is at a discharge pressure P1.

[0049] In the 26th embodiment, at least one of the motor and the generator includes a support, the support being at the support pressure P2.

[0050] In the 27th embodiment, at least one support of the motor and the generator is operably connected to a lubrication circuit.

[0051] In the 28th embodiment, the compression unit and / or the expansion unit comprises a container housing the respective motor or generator, the container being in fluid communication with the case, and the case and container being isolated from the external environment.

[0052] In the 29th embodiment, the container is in fluid communication with an auxiliary circuit.

[0053] In the 30th embodiment, the container is connected to a discharge conduit, and the container is at a discharge pressure P1.

[0054] In the 30th embodiment, the container is connected to a return conduit, and the container is at a return pressure P0.

[0055] In the 31st embodiment, the container is in fluid communication with the box, and the box is in fluid communication with the case.

[0056] In the 32nd embodiment, the cases, boxes, and containers are isolated from the external environment.

[0057] In the 33rd embodiment, the compression unit and / or the expansion unit are provided with auxiliary joints that connect their respective reduction gears to their respective motors or generators.

[0058] In the 34th embodiment, the auxiliary joints are sealed within their respective auxiliary casings.

[0059] In the 35th embodiment, the auxiliary casing is in fluid communication with the container and the box.

[0060] In the 36th embodiment, the auxiliary casing is in fluid communication with the auxiliary circuit.

[0061] In the 37th embodiment, an auxiliary casing is connected to a discharge conduit, and the auxiliary casing is at a discharge pressure P1.

[0062] In the 38th embodiment, the at least one chamber is separated by a single wall from the compression volume of the compressor or from the expansion volume of the expander, the discharge pressure P1 in the at least one chamber is greater than the operating pressure PL in the compression volume of the compressor or the expansion volume of the expander (P1 > PL), and optionally, the ratio between the discharge pressure P1 and the operating pressure PL is between 1.01 and 2.

[0063] In the 39th embodiment, the at least one auxiliary chamber is interposed between the at least one chamber and the compression volume of the compressor or the expansion volume of the expander.

[0064] In the 40th embodiment, at least one of the compressor and the expander is a turbomachinery, the transmission member is a rotating shaft, the movable mechanical member is an impeller, and the at least one chamber is defined around the rotating shaft by the walls of a case.

[0065] In the 41st embodiment, the ratio of storage pressure Ps to atmospheric pressure Patm is between 1 and 1.1.

[0066] In the 42nd embodiment, the ratio of the release pressure P1 to the storage pressure Ps is between 1.01 and 2.

[0067] In the 43rd embodiment, the ratio of the return pressure P0 to the storage pressure Ps is between 0.9 and 1.5.

[0068] In the 44th embodiment, the ratio of the support pressure P2 to the storage pressure Ps is between 0.9 and 1.5.

[0069] All of the pressure ratios shown above are between absolute pressures.

[0070] It should be noted that all components of plant machinery (turbines, compressors, motors, generators, gearboxes, etc.) operate at pressures close to atmospheric pressure / ambient pressure.

[0071] In the 45th embodiment, the working fluid is selected from the group including CO2, SF6, N2O, or mixtures thereof.

[0072] In the 46th embodiment, the temperature of the working fluid corresponding to the storage pressure Ps, i.e., the working fluid in the variable volume of the storage device, is close to or in equilibrium with the ambient temperature, and optionally, the temperature of the working fluid corresponding to the storage pressure Ps is between -40°C and +70°C, and optionally between -10°C and +45°C.

[0073] In the 47th embodiment, the operating pressure PL of the compressor, i.e., the temperature of the working fluid corresponding to the operating pressure PL within the compression volume of the compressor, is between 60°C and 500°C.

[0074] In the 48th embodiment, the operating pressure PL of the expander, i.e., the temperature of the operating pressure corresponding to the operating pressure PL within the expansion volume of the expander, is between 60°C and 500°C.

[0075] In the 49th embodiment, the temperature of the working fluid corresponding to the return pressure P0 is between 20°C and 150°C.

[0076] In the 50th embodiment, a storage device that internally defines a variable volume is, for example, a single-membrane or double-membrane gas tank. The double-membrane gas tank comprises an inner membrane that defines a variable volume and contains a working fluid, and an outer membrane that is in contact with the environment, the outer membrane maintaining its shape except for minor changes for the purpose of protecting the inner membrane from the external environment and atmospheric factors.

[0077] In the 51st embodiment, the working fluid is stored in a reservoir in a liquid or supercritical phase having a temperature close to the critical temperature, the critical temperature being close to the ambient temperature, preferably between 0°C and 100°C.

[0078] In the 52nd embodiment, an energy conversion and storage plant according to at least one embodiment of the 1st to 51st embodiments is configured to perform or carry out the following energy conversion and storage process, namely, a closed periodic thermodynamic conversion (TTC) between a storage device having a variable internal volume and a reservoir, first in one direction during the storage configuration / stage and then in the opposite direction during the release configuration / stage, wherein the process stores heat and pressure during the storage stage and generates energy during the release stage.

[0079] In the 53rd embodiment, During the storage phase, the working fluid stored in a storage device that internally defines a variable volume is Compressed, It is cooled and stores sensible heat, The working fluid is condensed by traversing the saturated vapor region until it reaches the liquid phase, and latent heat is stored in the secondary fluid. It is stored in a reservoir in a liquid phase with a temperature close to or below the critical temperature. During the release phase, the working fluid stored in the reservoir in the liquid phase at a temperature in equilibrium with the temperature of the secondary fluid, The working fluid is vaporized by traversing the saturated vapor region until it reaches the gas phase, and then absorbs latent heat through the cooling of the secondary fluid. During the storage phase, the sensible heat stored is used to heat and expand the material. It is stored in the gas phase in a storage device that internally defines a variable volume.

[0080] In the 54th embodiment, in each operating state during a closed periodic thermodynamic transformation (TTC), the working fluid is in pressure equilibrium with the atmosphere, is under low or no overpressure, and the temperature of the secondary fluid is close to the ambient temperature.

[0081] In the 55th embodiment, as described in the literature International Publication No. 2021 / 191786, the energy conversion and storage plant further defines / defines a closed circuit and is configured to perform a closed thermodynamic cycle (CT) in the closed circuit using at least a portion of the working fluid while the plant is optionally in a storage configuration or a discharge configuration.

[0082] In the 56th embodiment, the energy conversion and storage plant is of the type described in one of the following published documents in the name of the applicant: International Publication No. 2020 / 039416, International Publication No. 2021 / 165809, International Publication No. 2021 / 191786, and International Publication No. 2022 / 101727.

[0083] Further features and advantages will become clearer from a detailed description of preferred but non-exclusive embodiments of the energy conversion and storage plant according to the present invention.

[0084] Such explanations are provided below with reference to the attached drawings, which are provided for illustrative purposes only and are not limiting. [Brief explanation of the drawing]

[0085] [Figure 1] This figure shows an example of an energy conversion and storage plant according to the present invention. [Figure 2] This figure shows a diagram of the plant shown in Figure 1. [Figure 3] Figures 1 and 2 show parts of the plant. [Figure 4] This figure shows a modified embodiment of a part of the plant shown in Figure 3. [Figure 5] This figure shows further modified forms of the parts shown in Figures 3 and 4. Detailed explanation

[0086] Referring to the attached drawings, the energy conversion and storage plant according to the present invention is shown in its entirety by reference no. 200. This plant 200 can be realized by one of the embodiments described in the published documents under the name of the applicant, International Publication Nos. 2020 / 039416, International Publication Nos. 2021 / 165809, International Publication Nos. 2021 / 191786, and International Publication Nos. 2022 / 101727.

[0087] The illustrated plant 200 operates using a working fluid other than air, selected from the group including, for example, carbon dioxide (CO2), sulfur hexafluoride (SF6), nitrogen oxide (N2O), or mixtures thereof. The plant 200 is configured to perform a closed periodic thermodynamic conversion (TTC) first in one direction in the storage configuration / stage, and then in the opposite direction in the release configuration / stage, thereby storing heat and pressure in the storage configuration and generating mechanical and / or electrical energy in the release configuration.

[0088] Referring to Figure 1, the plant 200 comprises an expander, such as a turbine 202, and a compressor 203, mechanically connected to the shaft of the motor-generator 204. The turbine 202, together with the motor-generator 204, forms an expansion unit when operating in the function of the generator. The compressor 203, together with the motor-generator 204, forms a compression unit when operating in the function of the motor. In a variant of the embodiment, the turbine 202 is mechanically connected to each generator, and the compressor 203 is mechanically connected to each motor, and the motor and generator are two different machines.

[0089] Plant 200 includes a storage device 205 that internally defines a variable volume. In the non-limiting embodiments shown, the storage device 205 is defined by a double-membrane gas tank comprising an inner membrane 302 that defines a variable volume and contains a working fluid, and an outer membrane 301 that is in contact with the environment. The gas tank is located on the ground and is in contact with the atmosphere externally. The inner membrane 302 of the gas tank internally defines the aforementioned variable volume, which is configured to contain a working fluid at a storage pressure "Ps" equal to atmospheric pressure or approximately atmospheric pressure. The working fluid contained within the variable volume is in pressure equilibrium with the atmosphere during each operating stage performed by the plant. The outer membrane 301 maintains a constant shape, with minimal changes, for the purpose of protecting the inner membrane from the external environment and atmospheric factors such as sun, rain, wind, and snow. In a non-limiting illustrated embodiment, a defined gap between the inner membrane 302 and the outer membrane 301 is filled with ambient air by a ventilator 303, schematically shown in Figure 2, and a constant overpressure of several millibars (relative to atmospheric pressure) is maintained. The storage pressure "Ps" in this case is equal to atmospheric pressure plus the pressure of the air in the gap, which helps to support the outer membrane 301. The pressure in the gap is kept constant or nearly constant, so that the working fluid contained within the variable volume is in pressure equilibrium with the atmosphere at each operating stage performed by the plant. The storage device 205 can also be realized as any other storage system for low overpressure or no overpressure gas, where the pressure is kept constant or nearly constant as the volume of the working fluid changes.

[0090] The first pipeline 206 extends between the storage device 205 and the inlet 203a of the compressor 203, and between the storage device 205 and the outlet 202b of the turbine 202, to fluidize the internal volume of the storage device 205 to the compressor 203 and the turbine 202. Alternatively, valves or valve systems (not shown) may be operably positioned in the first pipeline 206 to fluidize the storage device 205 to the inlet 203a of the compressor 203 or to fluidize the storage device 205 to the outlet 202b of the turbine 202.

[0091] The plant 200 includes a thermal energy storage (TES) accumulator 100 which can be selectively connected to the outlet 203b of the compressor 203 or the inlet 202a of the turbine 202. For this purpose, a second pipeline 208 extends between the inlet 202a of the turbine 202 and the thermal energy storage accumulator 100, and between the outlet 203b of the compressor 203 and the thermal energy storage accumulator 100.

[0092] The heat storage device 100 may include a primary heat exchanger and, for example, a solid or liquid thermal mass, which allows for the storage of heat within the thermal mass.

[0093] Alternatively, to fluidly connect the accumulator 100 to the inlet 202a of the turbine 202 or to fluidly connect the outlet 203b of the compressor 203 to the accumulator 100, a valve or valve system (not shown) is operably positioned in the second pipeline 208.

[0094] The reservoir 209 is in fluid communication with the heat accumulator 100 and is configured to store the working fluid in a liquid phase or supercritical phase having a temperature close to the critical temperature. The critical temperature of the working fluid is close to the ambient temperature, preferably between 0°C and 100°C.

[0095] The secondary heat exchanger 210 is configured to be operationally active above the reservoir 209 and to operate relative to the working fluid in the reservoir 209 during the storage phase.

[0096] A third pipeline 212 is deployed between the heat accumulator 100 and the reservoir 209 to establish fluid communication between the heat accumulator 100 and the reservoir 209 and the secondary heat exchanger 210.

[0097] In some cases, the top of the reservoir 209 is connected to a secondary heat exchanger 210 via connecting lines and valves (not shown) in order to recirculate the steam and make space for the liquid.

[0098] The first pipeline 206, the second pipeline 208, and the third pipeline 212 form the main circuit of the plant 200, which connects the variable volume of the storage device 205, the compression volume of the compressor 203, the heat accumulator 100, the secondary heat exchanger 220, the reservoir 209, and the expansion volume of the turbine 202.

[0099] In the depiction in Figure 1, the plant 200 further includes additional heat exchangers 213 operably interposed between the storage device 205 and the compressor 202, and between the storage device 205 and the turbine 202. In alternative embodiments not shown, there may be one additional heat exchanger dedicated to the compressor 202 and another dedicated to the turbine 202.

[0100] A tank 2000 containing a liquid, typically water, is connected to a secondary heat exchanger 210 and a further heat exchanger 213, and is linked to a radiator 223 equipped with a fan 224.

[0101] The heat exchanger is configured to store the thermal energy released by the working fluid in the thermal mass of the TES and in the liquid of the tank, or to release previously stored thermal energy into the working fluid.

[0102] A suitable device (e.g., the aforementioned valve controlled by a control unit) is configured to operate the plant 200 in an energy storage configuration / stage or an energy release and generation configuration / stage by the movement of working fluid between the storage device 205 and the reservoir 209 in the main circuit, and by the periodic thermodynamic transformation of the working fluid.

[0103] The plant is configured to perform the closed periodic thermodynamic transformation described above, for example, as described in the published documents, International Publication Nos. 2020 / 0394165, 2021 / 165809, 2021 / 191786, and 2022 / 101727.

[0104] In the storage configuration / stage, the working fluid coming from the storage device 205 is compressed and heated in the compressor 203. The working fluid then flows through the accumulator 100, which acts as a cooler, removing heat from the compressed working fluid, cooling it, and storing the thermal energy (sensible heat) removed from the working fluid as heat in the thermal mass of the TES. The working fluid then transfers heat to the liquid in the tank 2000 (secondary fluid) in the secondary heat exchanger 210, where it condenses and is stored in the reservoir 209.

[0105] In the discharge configuration / stage, the working fluid, already heated by the secondary heat exchanger 210 and coming from the reservoir 209, passes through the primary heat exchanger of the accumulator 100, where the accumulator 100 then acts as a heater, transferring further heat previously stored in the incoherent material 19 to the working fluid, thereby heating the working fluid. The working fluid vaporizes and is then introduced into the turbine 202. The working fluid determines the rotation of the impeller of the turbine 202 and the energy generation by the motor generator 204, and is then stored again in gaseous form within the variable volume of the device 205.

[0106] Figure 2 shows the plant of Figure 1 in more schematic form, and shows the storage device 205, the mechanical block 400 including the compression unit and expansion unit, the heat storage block 500 including the heat accumulator 100 (thermal energy storage - TES), the working fluid storage block 600 including the reservoir 209, and the secondary heat exchanger 210.

[0107] Figure 2 also shows the first pipeline 206, the second pipeline 208, and the third pipeline 212 of the main circuit.

[0108] The energy conversion and storage plant 200 may also be configured to define / define a closed circuit and, using at least a portion of the working fluid, perform a closed thermodynamic cycle (CT) within the closed circuit, as described in the literature, International Publication No. 2021 / 191786. For this purpose, Figure 1 shows an additional heat exchanger 700 that receives heat from an additional heat source 705. The additional heat exchanger 700 is located between the inlet 202a of the turbine 202 and the accumulator 100. The additional heat source 705 may be, for example, a solar source, industrial waste heat recovery (waste heat recovery), or waste heat from a gas turbine.

[0109] A first bypass conduit 310 is configured to connect the outlet 203b of the compressor 203 to an additional heat exchanger 700 and to bypass the accumulator 100. Each first bypass conduit is provided with a first valve 311. A second bypass conduit 320 is configured to connect the outlet 202b of the turbine 202 to the inlet 203a of the compressor 203 and to bypass the storage device 205. Each second bypass conduit 320 is provided with a second valve 321.

[0110] The first bypass conduit 310 and the second bypass conduit 320 can define a closed circuit comprising a compressor 203, a turbine 202, a further heat exchanger 213, and an additional heat exchanger 700.

[0111] According to the present invention, the plant 200 further comprises an auxiliary circuit 1 connecting the variable volume of the main circuit and / or storage device 205 and / or the compression volume of the compressor 203 and / or the expansion volume of the turbine 202 to at least a portion of the compression unit and / or expansion unit, and the temperature and / or pressure of the at least a portion thereof to be controlled by the same working fluid circulating in the main circuit and the same working fluid used to perform a closed periodic thermodynamic conversion (TTC). Thus, the plant 200 according to the present invention enables the implementation of a control method. This control method, which is also part of the present invention, enables the control of the temperature and / or pressure of the at least a portion of the compression unit and / or expansion unit of the plant 200, and includes connecting the variable volume of the main circuit and / or storage device 205 and / or the compression volume of the compressor 203 and / or the expansion volume of the turbine 202 to the at least a portion of the compression unit and / or expansion unit via the auxiliary circuit 1. In the attached diagram, auxiliary circuit 1 is shown as a line outside the machine for simplicity, but it may also be located inside the machine itself.

[0112] In Figure 1, auxiliary circuit 1 connects the compression unit and expansion unit only to the variable volume of the storage device 205. In Figure 2, a more complex auxiliary circuit 1 is shown, which includes discharge lines extending from the main circuit and from the variable volume of the storage device 205 to the compression unit and expansion unit.

[0113] In particular, the auxiliary circuit 1 in Figure 2 includes a first discharge conduit 2 connecting the variable volume of the storage device 205 to the mechanical block 400, a second discharge conduit 3 and a third discharge conduit 4 connecting a second pipeline 208 to the mechanical block 400, and a fourth discharge conduit 5 connecting a third pipeline 212 to the mechanical block 400. Furthermore, a return conduit 6 connects the mechanical block 400 to the variable volume of the storage device 205, and a further return conduit 7 connects the mechanical block 400 to the first pipeline 206. A fan 8 (which may also be an auxiliary compressor) having the function of increasing the storage pressure "Ps" of the working fluid coming from the storage device 205 to the discharge pressure "P1" is operably active on the first discharge conduit 2. Instead, the working fluid received from the second discharge conduit 3, the third discharge conduit 4, and the fourth discharge conduit 5 is already at a pressure higher than the storage pressure "Ps", and therefore there is no need to use a fan or auxiliary compressor.

[0114] The discharge lines 2, 3, 4, 5 and the return lines 6, 7 may be rigid or flexible, made of metal, or other materials, or composite materials such as textile joints.

[0115] Figure 3 shows in more detail the turbomachinery (which can be the expansion unit with turbine 202 or the compression unit with compressor 203 in the plant in Figure 1, or part of the machine group 400 in Figure 2) connected to the auxiliary circuit 1 described above. For simplicity, we will refer to the turbine 202 below, but the same description applies substantially to the compressor 203.

[0116] The turbomachinery in Figure 3 comprises a case 9 and an impeller 10 connected to the rotating shaft 11, which rotates within the case 9 around its own axis of rotation and is supported by a support 12, such as bearings. The impeller 10 is configured to exchange energy with the working fluid in the respective expansion volumes 13 of the turbine 202, which is in fluid communication with the main circuit of the plant 200, as described above. The turbomachinery of the embodiment in Figure 3 further comprises a gearbox 14. A gearbox 14 may be used as the electromachinery (motor, generator, or motor-generator) to which the turbine or compressor is connected typically operates at 1500 rpm (4 poles) or 3000 rpm (2 poles) for a network frequency of 50 Hz, and at 1800 rpm or 3600 rpm for a network frequency of 60 Hz, while the turbomachinery reaches higher rotational speeds. The rotating shaft 11, which carries the impeller 10 at its end, is supported by bearings mounted in a box 15 of the gearbox 14. The gearbox 14 is mechanically positioned between the turbine 202 and each of the generators (not shown in Figure 3). The gearbox 14 comprises a first gear 16 keyway-connected to the rotating shaft 11, and the first gear 16 gear-connected to a second gear 17 keyed to an auxiliary shaft 18, which is also supported by bearings in the box 15. One end of the auxiliary shaft 18 exits the box 15 via a seal 19 and is connected to a generator (not shown). The sealing element 19 is located on the low-speed shaft (auxiliary shaft 18) of the gearbox 14 and isolates the internal environment of the box 15 from the external environment.

[0117] The rotating shaft 11, supported in the box 15 by bearings, extends from the box 15 into the interior of the case 9. The casing 20 connects the box 15 to the case 9 and encloses the rotating shaft 11 such that the box 15 and the case 9 are in fluid communication with each other but isolated from the external environment. The impeller 10 is located at the distal end of the rotating shaft 11, opposite to the end housed in the box 15, and is therefore overhangingly supported relative to the bearings.

[0118] The walls positioned in case 9 and surrounding the rotating shaft 11 further define the annular chamber. A first wall separates the expansion volume 13 from an adjacent auxiliary chamber 21, which in turn is separated from an adjacent chamber 22 by a second wall. A third wall separates the chamber 22 from the casing 20. The auxiliary chamber 21 is then interposed between the chamber 22 and the expansion volume 13 of the turbine 202. Each wall has its radially inner edge close to the rotating shaft 11 to define an annular passage or restriction that connects adjacent chambers.

[0119] The turbomachinery in the embodiment shown in Figure 3 further comprises a lubrication circuit 23 that is operably connected to a support 12 (bearing) in a box 15 and contains lubricating oil. The lubrication circuit 23 includes a sealed container 24 for collecting the lubricating oil. The sealed container 24 is connected to the box 15 by an oil supply line 25 and an oil return line 26. A pump 27 is operably positioned along the oil supply line and configured to pump lubricating oil to the support located in the box 15.

[0120] The first discharge conduit 2 is connected to the chamber 22, which is connected to a draw point in the main circuit at a discharge pressure P1, or to the fan 8 and the variable volume of the storage device 205. The working fluid flowing through the discharge conduit 2 is introduced into the chamber 22 at the aforementioned discharge pressure "P1" (P1 > Ps), which is greater than the storage pressure "Ps".

[0121] One of the return conduits 6 is connected to the auxiliary chamber 21, and the auxiliary chamber 21 is connected to the variable volume of the storage device 205 or to a point in the main circuit at a pressure lower than the discharge pressure "P1". The auxiliary chamber 21 is at a return pressure "P0" (P0 < P1) lower than the discharge pressure "P1", and similarly at a return pressure "P0" lower than the operating pressure "PL" in the expansion volume 13. The box 15 and the support / bearing housed in the box 15, and also the lubrication circuit 23 are at a support pressure "P2" lower than the discharge pressure "P1" (P2 < P1) and higher than the return pressure "P0" (P2 > P0). For example, the ratio of the storage pressure "Ps" to the atmospheric pressure "Patm" is between 1 and 1.1, the ratio of the discharge pressure "P1" to the storage pressure "Ps" is between 1.01 and 2, the ratio of the discharge pressure "P1" to the operating pressure "PL" is between 1.01 and 2, the ratio of the return pressure "P0" to the storage pressure "Ps" is between 0.9 and 1.5, and the ratio of the support pressure "P2" to the storage pressure "Ps" is between 0.9 and 1.5. Therefore, the working fluid present in the expansion volume 13 flows out from the above-mentioned expansion volume 13 into the auxiliary chamber 21, and the working fluid in the chamber 22 flows out from the chamber 22 into the auxiliary chamber 21. From the auxiliary chamber 21, the working fluid is returned to the main circuit and / or the storage device 205 via the return conduit 6. Therefore, the auxiliary circuit 1 avoids the outflow of the working fluid from the expansion volume 13 to the external environment and performs the function of a thermal barrier, that is, it avoids the possibility that the heat of the working fluid present in the expansion volume is transmitted to other elements of the turbomachine, such as bearings or seals.

[0122] For example, the temperature of the working fluid in the variable volume of the storage device is between 40°C and 70°C, the temperature of the working fluid in the compression volume of the compressor is between 60°C and 500°C, the temperature of the working fluid in the expansion volume of the expander is between 60°C and 500°C, and the temperature of the working fluid corresponding to the return pressure P0 is between 20°C and 150°C.

[0123] One of the return conduits 6 is connected to a portion of a sealed container 24 positioned above the free surface of the lubricating oil. A separator 28 is positioned along the return conduit 6 connected to the sealed container 24 and is configured to separate the lubricating oil adsorbed by the working fluid as the working fluid passes through the box 15. An oil recovery line 29 connects the separator 28 to the sealed container 24 to reintroduce the oil separated from the working fluid in the separator 28 into the lubrication circuit 23. From the sealed container 24, the working fluid with adsorbed lubricating oil is returned to the main circuit and / or storage device 205 via the respective return conduits 6. Thus, the auxiliary circuit 1 prevents the working fluid from flowing out of the lubrication circuit into the external environment.

[0124] The embodiment in Figure 4 differs from the turbomachinery in that the rotating shaft 11 is not overhang-supported by the support / bearing 12 of the box 15, but is supported by support / bearing 12 located at opposite ends of the same rotating shaft 11 and located in or adjacent to the case 9. The support / bearing 12 is connected to the lubrication circuit 23. Chambers 22 and auxiliary chambers 21 are symmetrically arranged on both sides of the impeller 10 and expansion volume 13. Furthermore, the rotating shaft 11 is mechanically connected to the main shaft 30 of each reduction gear by rigid or flexible joints 31 sealed within the casing 20. In this case, the connection between the casing 20 and the discharge conduit 6 may be useful for cooling and removing the generated heat through ventilation of the joint 31.

[0125] Figure 5 shows another variant in which the turbine 202 and gearbox 14 are identical to those in the variant of Figure 4. In this variant, the auxiliary shaft 18 of the gearbox 14 is connected to the shaft 32 of the generator 204 via an auxiliary joint 33 sealed within each auxiliary casing 34. The generator 204 is supported by its respective support / bearing 12 and housed in a container 35. The auxiliary casing 34, support / bearing 12, and container 35 are fluidly connected to each other by a limiting section but are isolated from the external environment. The support / bearing 12 of the generator 204 is operably connected to a lubrication circuit 23.

[0126] The first discharge conduit 2 is connected to the casing 20, the auxiliary casing 34, and the chamber of the generator 204 interposed between the support / bearing 12 and the container 35, in addition to the chamber 22. Therefore, the casing 20, the auxiliary casing 34, and the chamber of the generator 204 interposed between the support / bearing 12 and the container 35 are at discharge pressure "P1". The return conduit 6 is connected to the auxiliary chamber 21 and the sealed container 24 of the circulation circuit 23, in addition to the container 35. Therefore, the container 35 is at return pressure P0, and the support / bearing 12 is at support pressure "P2". In this case, the space between the generator 204 (or motor in the case of a compressor) and the support / bearing 12 is pressurized at discharge pressure "P1", and the generator is connected to the storage device 205.

[0127] In other variations of the embodiment not shown, the connection to the auxiliary circuit may differ from the connection to the auxiliary circuit in the example shown above. For example, the container 35 is connected to the discharge conduit 6 and is at discharge pressure "P1", i.e., the generator 204 (or, in the case of a compressor, the motor, more generally, the electromechanical unit) is slightly pressurized at discharge pressure "P1". In other variations of the embodiment not shown in the accompanying drawings, the structure of the turbomachine (compressor or expander) is simpler than the structure of the turbomachine shown in the example shown above.

[0128] For example, the support / bearing 12 is arranged not in the speed reducer 14 (which may not exist), but in the case 9 of the turbomachine, and / or the sealing element 19 is operably connected to the case 9 and the rotating shaft 11 (when the relative speed and magnitude of the rotating shaft enable the sealing element to be directly attached to the rotating shaft), separating the environment inside the case 9 from the external environment. In this case, for example, a chamber 22 defined in the case 9 is in fluid communication with the sealing element 19 and / or the support / bearing 12 via a restriction.

[0129] For example, the sealing element is of the type of a liquid film or a double mechanical seal or a wet surface mechanical seal. In the case of adopting a liquid film mechanical seal, there is a supply system of barrier liquid to a barrier chamber that houses part of the mechanical seal and further confines it together with the chamber 22. This barrier chamber is connected to a separator that operates in a similar manner to the separator of the lubrication circuit to separate the adsorbed working fluid from the barrier liquid, and this separator can be connected to the auxiliary circuit 1.

[0130] For example, there is no auxiliary chamber 21, the chamber 22 is adjacent to the expansion volume 13 or the compression volume, and is connected to the discharge conduit 6.

[0131] For example, instead of the sealing element, regardless of the presence or absence of a separator, only a barrier chamber exists to form a barrier to the external environment. The barrier chamber is connected to a supply system of barrier liquid, the auxiliary chamber 21 is interposed between the barrier chamber and the chamber 22 and is connected to a recovery system of barrier liquid. The chamber 22 is at the discharge pressure "P1", the auxiliary chamber 21 is at the pressure "P2", the barrier chamber is at the barrier pressure "P3", and P2 < P1, P3 < P2 and P3 > Patm.

[0132] For example, the support / bearing may be magnetic or of a type that does not require a lubrication circuit and sealing member. In this case, the auxiliary circuit is used only to form a thermal barrier and to set the pressure close to the pressure PS in the mechanical member, thereby avoiding the pressure design of components that are not typically designed / built to act as pressurizing members (such as electromechanical components or bearing casings). [Explanation of Symbols]

[0133] 1 Auxiliary circuit 2. First discharge conduit 3. Second discharge conduit 4. Third discharge conduit 5. Fourth discharge conduit 6. Return conduit 7. Further return conduits 8 Fans 9 cases 10 impellers 11 Rotating shafts 12 Support 13. Expansion volume 14 Reducer 15 boxes 16 The First Gear 17 The second gear 18 Auxiliary shaft 19. Sealing element 20 Casing 21 Auxiliary Chamber 22 Chambers 23 Lubrication circuit 24. Airtight container 25 Oil discharge line 26 Oil return line 27 pumps 28 Separator 29 Oil recovery line 30 Main shaft 31 joints 32 Generator Shaft 33 Auxiliary joint 34 Auxiliary casing 35 containers 100 Heat storage 200 plants 202 Turbine 202a Turbine Inlet 202b Turbine outlet 203 Compressor 203a Compressor inlet 203b Compressor outlet 204 Motor Generator 205 Storage Devices 206 First Pipeline 208 Second Pipeline 209 Reservoir 210 Secondary heat exchanger 212 Third Pipeline 213 Further heat exchangers 223 Radiator 224 Fans 301 Adventitia 302 Intima 303 Ventilator 310 First bypass conduit 311 First valve 320 Second bypass conduit 321 Second valve 400 machine blocks 500 thermal storage blocks 600 Working fluid storage block 700 Additional heat exchangers 705 Further heat sources 2000 tanks

Claims

1. An energy conversion and storage plant, Working fluids other than the atmosphere, A storage device (205) that internally defines a variable volume, configured to store the working fluid in the gas phase at a low overpressure or no overpressure, having a storage pressure (Ps) that is in pressure equilibrium with the atmosphere, during each operating stage performed by the plant, At least one reservoir (209) configured to store the working fluid in a liquid or supercritical phase, A compression unit comprising at least one compressor (203) and at least one motor, mechanically connected to each other, An expansion unit comprising at least one expander (202) and at least one generator, which are mechanically connected to each other, At least one heat storage unit (100, 210) and A main circuit connecting the variable volume of the storage device (205), the compressed volume of the compressor (203), the at least one heat storage device (100, 210), the at least one reservoir (209), and the expanded volume of the expander (202), A device configured to operate the plant in an energy storage configuration or in an energy release and generation configuration by the movement of the working fluid between the storage device (205) and the at least one reservoir (209) through the main circuit, and by the periodic thermodynamic conversion of the working fluid, Equipped with, The plant further comprises an auxiliary circuit (1), The auxiliary circuit (1) connects at least a portion of the compression unit and / or the expansion unit to at least one of the main circuit, the variable volume of the storage device (205), the compression volume of the compressor (203), and the expansion volume of the expander (202), A plant in which the auxiliary circuit (1) is configured to control the temperature and / or pressure of at least a portion of the working fluid received from the periodic thermodynamic conversion.

2. The at least one compressor (203) and the at least one expander (202) are each, Case (9) and, At least one movable mechanical member is movable relative to the case (9) and configured to exchange energy with the working fluid in each of the compression volumes of the compressor (203) or the expansion volume of each of the expanders (202), At least one transmission member connects the movable mechanical member to each of the motors or generators, Equipped with, The plant according to claim 1, wherein at least a portion of the above includes at least one chamber (22) defined between the case (9) and the at least one transmission member, the at least one chamber (22) being located near the compression volume of the compressor (203) or the expansion volume of the expander (202).

3. The plant according to claim 2, wherein the at least one compressor (203) and / or the at least one expander (202) comprises at least one sealing element (19) operably connected to the case (9) and the transmission member and separating the environment inside the case (9) from the external environment, and the at least one chamber (22) is in fluid communication with the at least one sealing element (19) via a restrictor, optionally.

4. The plant according to claim 2 or 3, wherein the at least one compressor (203) and / or the at least one expander (202) comprises a support (12) operably interposed between each of the transmission members and each of the cases (9), and the at least one chamber (22) is in fluid communication with the support (12) via optionally a limiting portion.

5. The auxiliary circuit (1) is At least one discharge conduit (2, 3, 4, 5), and / or, extending from the main circuit and / or the variable volume of the storage device (205) to at least a portion of the compression unit and / or the expansion unit, and configured to supply the working fluid to at least a portion of the compression unit and / or the expansion unit at a discharge pressure (P1) greater than the storage pressure (Ps), and / or At least one return conduit (6, 7) extending from the compression unit and / or the expansion unit to the variable volume at the storage pressure (Ps), or to a point in the main circuit at a pressure lower than the release pressure (P1). A plant according to any one of claims 1 to 4, comprising:

6. The plant according to claim 5, wherein at least one discharge conduit (2, 3, 4, 5) connects a drawout point of the main circuit at the discharge pressure (P1) to at least a portion of the compression unit and / or the expansion unit, and / or the at least one discharge conduit (2, 3, 4, 5) connects the variable volume to at least a portion of the compression unit and / or the expansion unit, and comprises a fan or auxiliary compressor (8) configured to increase the storage pressure (Ps) of the working fluid coming from the variable volume to the discharge pressure (P1).

7. The main circuit is, The storage device (205) is connected to the compression unit and the expansion unit by a first pipeline (206), A second pipeline (208) connecting the at least one reservoir (209) to the compression unit and the expansion unit, wherein the at least one heat accumulator (100, 210) is operably connected to the second pipeline (208) and / or the at least one reservoir (209), Equipped with, The plant according to claim 6, wherein the withdrawal point is located in the second pipeline (208) between the at least one reservoir (209) and the at least one heat accumulator (100, 210), and / or between the at least one heat accumulator (100, 210) and the compression unit or the expansion unit.

8. The plant according to any one of claims 5 to 7, wherein the at least one return conduit (6, 7) extends from at least one auxiliary chamber (21) of the compression unit and / or the expansion unit, and the at least one auxiliary chamber (21) is at a return pressure (P0) less than the discharge pressure (P1).

9. The plant according to any one of claims 5 to 8, as claim 5 is dependent on claim 4, wherein the support (12) is connected to the at least one chamber (22) via a limiting portion and is at a support pressure (P2) less than the discharge pressure (P1), and the support pressure (P2) is greater than the return pressure (P0), and the compression unit and / or the expansion unit are operably connected to the support (12) and include a lubrication circuit (23) containing lubricating oil, the lubrication circuit (23) is at the support pressure (P2) and connected to the at least one return conduit (6, 7), and the lubrication circuit (23) includes a pump (27) configured to pressurize the lubricating oil to the support (12), and a sealed container (24) for collecting the lubricating oil, the portion of the sealed container (24) located on the free surface of the lubricating oil is connected to the at least one return conduit (6, 7).

10. The plant according to claim 9, wherein the compression unit and / or the expansion unit comprises at least one reduction gear (14) mechanically interposed between the transmission member of the compressor (203) and / or the expander (202) and the respective motor or generator, the at least one reduction gear (14) comprising a box (15), a movable member attached to the box (15), and a support (12) interposed between the movable member and the box (15), the box (15) being in fluid communication with the at least one chamber (22), and the box (15) being connected to the lubrication circuit (23).

11. The plant according to claim 9 or 10, wherein at least one of the motor and the generator comprises a support (12), the support (12) is at the support pressure (P2), and the support (12) of at least one of the motor and the generator is operably connected to the lubrication circuit (23).

12. The plant according to any one of claims 5 to 9, where claim 5 is dependent on any one of claims 2 to 4, wherein the compression unit and / or the expansion unit comprises a container (35) housing the respective motor or generator, the container (35) is in fluid communication with the case (9), the case (9) and the container (35) are isolated from the external environment, the container (35) is in fluid communication with the auxiliary circuit (1), the container (35) is connected to the discharge conduits (6, 7), and the container (35) is at the discharge pressure (P1).

13. The plant according to any one of claims 5 to 12, where claim 5 is dependent on any one of claims 2 to 4, wherein the at least one chamber (22) is separated by a single wall from the compression volume of the compressor (203) or the expansion volume of the expander (202), the discharge pressure (P1) in the at least one chamber (22) is greater than the operating pressure (PL) in the compression volume of the compressor (203) or the expansion volume of the expander (202), and the at least one auxiliary chamber (21) is interposed between the at least one chamber (22) and the compression volume of the compressor (203) or the expansion volume of the expander (202).

14. At least one of the compressor (203) and the expander (202) is a turbomachinery, The transmission member is a rotating shaft (11), The aforementioned movable mechanical member is an impeller (10), The plant according to any one of claims 2 to 4, or according to any one of claims 5 to 13, where claim 5 is dependent on any one of claims 2 to 4, wherein the at least one chamber (22) is defined around the rotating shaft (11) by the wall of the case (9).

15. A method for controlling the temperature and / or pressure of at least a portion of the compression unit and / or expansion unit of the plant according to at least one of claims 1 to 14, the method comprising the step of connecting the variable volume of the main circuit and / or the storage device (205) and / or the compression volume of the compressor (203) and / or the expansion volume of the expander (202) to at least a portion of the compression unit and / or expansion unit via the auxiliary circuit (1).

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