Plants and methods for energy management

Abstract

A plant and method for energy management that performs a closed thermodynamic cycle conversion (TTC) between a gas holder (2) for storing gaseous carbon dioxide at a first storage pressure (PAG') in equilibrium with atmospheric pressure and a mass reservoir (11) for storing liquid carbon dioxide at a second storage pressure (PA'H), first in one direction during the filling phase and then in the opposite direction during the release phase. During the filling phase, it is provided to remove heat from the mass reservoir (11) to condense a portion of the vapor phase of carbon dioxide contained therein and to maintain the second storage pressure (PA'H) constant or substantially constant. During the release phase, it is provided to transfer heat to the mass reservoir (11) to evaporate a portion of the liquid phase of carbon dioxide contained therein and to maintain the second storage pressure (PA'H) constant or substantially constant.

Description

Technical Field

[0001] The present invention aims at a plant and a method for energy management, which management aims at the absorption, storage, conversion and generation of energy.

[0002] More precisely, the present invention aims at a system that can absorb / use energy, hold the stored energy over time, and convert it back into available energy such as electricity, heat, mechanical energy.

[0003] The present invention can be positioned in the context of systems for power generation and energy storage from various sources, both onshore and offshore, for medium and large scale applications, which typically have a power from several hundred kW to several tens of MW (e.g., 20 - 25 MW), but can also have a power of several hundred MW and a storage capacity from several hundred kWh to several hundred MWh, and up to several GWh. The present invention can also be positioned in the field of systems for power generation and energy storage from various sources, both onshore and offshore, for small scale domestic and commercial applications, which typically have a power from several kW to several hundred kW and a storage capacity from several kWh to several hundred kWh.

[0004] Definitions In this specification and the appended claims, the following definitions are referred to. · Cycle 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. TTC functions between two mass storages / accumulations of the working fluid, one initial and the other final. · Cyclic Thermodynamics (CT): A thermodynamic conversion from point X to point Y, where X coincides with Y, and unlike the above Cycle Thermodynamic Conversion (TTC), the Cyclic Thermodynamics (CT) does not have a mass storage / accumulation of the working fluid within the cycle that is important for energy purposes. · Closed CT and / or TTC: Without (energy - purpose - important) mass exchange with the atmosphere. • Open CT and / or TTC: involve mass exchange with the atmosphere (important for energy purposes). • Mild overpressure: A pressure difference of several millibars to tens of millibars relative to atmospheric pressure, for example, a pressure difference of 3-4 mbar to 70-80 mbar, which is higher than atmospheric pressure. [Background technology]

[0005] A published document, International Publication No. 2020 / 039416, by the same applicant, describes a method and plant for energy storage. The plant comprises a casing for storing a non-atmospheric working fluid in a gaseous phase, in pressure equilibrium with the atmosphere, and a reservoir for storing this working fluid in a liquid or supercritical phase having a temperature close to its critical temperature, which is close to the ambient temperature. The plant is configured to perform a closed-cycle thermodynamic conversion between the casing and the reservoir, first in one direction in the storage configuration, and then in the opposite direction in the release configuration. In the storage configuration, the plant stores heat and pressure, and in the release configuration, it generates energy.

[0006] Furthermore, the documents in International Publication Nos. 2021 / 165809, 2021 / 191786, and 2022 / 101727 are all by the same applicant and depict a plant based on the same principle (closed-cycle thermodynamic conversion between two mass storages) as shown in International Publication No. 2020 / 039416. [Overview of the project]

[0007] The applicant noted that the above-described methods and plants in the literature, International Publication Nos. 2020 / 039416, 2021 / 165809, 2021 / 191786, and 2022 / 101727 can be further improved, particularly in relation to the optimization of the methods and the simplicity of the plant construction.

[0008] The applicant has noted, in particular, that plants and methods that function specifically in the supercritical field, namely those configured to actuate the supercritical transformation of a working fluid and store the working fluid in a reservoir in a supercritical phase at high pressure, such as those described above, present problems in terms of the complexity and cost of the storage system. Indeed, for example, International Publication No. 2020 / 039416 demonstrates the use of a variable volume chamber and compensation circuit that can store a working fluid in a supercritical phase and maintain a substantially constant pressure within the working fluid in the supercritical phase.

[0009] Therefore, the applicant aims to conceive and realize a system that operates by a cyclic and supercritical thermodynamic conversion (TTC) of a working fluid, similar to that described in International Publication No. 2020 / 039416, which enables easier and more efficient storage of the working fluid in a high-pressure storage unit.

[0010] The applicant also aims to realize systems (plants and methods) for supercritical TTC-type energy absorption, storage (energy storage), conversion and generation that enable the flexible, efficient, and effective management (absorption, storage, conversion, generation, and classification) of energy from various sources (non-renewable sources and fuels, e.g., fossil fuels, as well as renewable and further synthetic sources and fuels).

[0011] The applicant has found that the above objectives can be achieved by employing a technical solution that enables operation under supercritical conditions, while also enabling storage of the working fluid under high pressure under subcritical conditions.

[0012] In particular, the stated and other objectives are substantially achieved by plants and methods for managing (absorbing, storing, converting, and generating) the kinds of energy described in the claims and / or the following embodiments in the attached claims.

[0013] In a first independent aspect, the present invention relates to a plant for energy management, the plant comprising: a gas holder that forms a variable volume boundary internally, containing or configured to contain a working fluid other than the atmosphere and a gas phase working fluid, and pressurized at a constant first storage pressure (PAG') equal to or slightly over atmospheric pressure; a compressor fluid-connected to the gas holder; an expander fluid-connected to the gas holder; a heat reservoir fluid-connected to the compressor and expander and configured to exchange heat with the working fluid; and a second storage pressure (PA'). The plant comprises a mass reservoir, which contains or is configured to contain a liquid-phase working fluid in H) and which forms a boundary of a certain volume internally, and which is fluidly connected to a heat reservoir; a depressurizing device operably operating between the heat reservoir and the mass reservoir; a pump operably operating between the heat reservoir and the mass reservoir; a heat exchanger operably coupled to the mass reservoir and configured to exchange heat with the working fluid present in the mass reservoir; and pipelines and control devices configured to operate the plant in a filling configuration and a discharge configuration.

[0014] In a filled configuration, the working fluid moves from the gas holder to the mass reservoir through a compressor, a heat reservoir, and a depressurizer, where it is stored; the compressor compresses the working fluid to a compression termination pressure (PC;PC2) higher than the critical pressure (Pcr) of the working fluid; the heat reservoir absorbs heat from the working fluid and cools it to a cooling termination temperature (TE) close to, preferably lower or slightly higher than, the critical temperature (Tcr) of the working fluid; the depressurizer reduces the pressure of the working fluid to a reduced pressure (PG) lower than the critical pressure (Pcr) of the working fluid; and the working fluid is stored in the mass reservoir at a second storage pressure (PA'H) lower than the critical pressure (Pcr) of the working fluid and in equilibrium with its own vapor phase. In a packed configuration, the heat exchanger removes heat from the mass reservoir, condensing a portion of the vapor phase of the working fluid contained in the mass reservoir, thereby maintaining a constant or substantially constant second storage pressure (PA'H) within the mass reservoir.

[0015] In a discharge configuration, the working fluid moves from the mass reservoir to the gas holder through a pump, a heat reservoir, and an expander, where it is stored. The pump pumps the working fluid at a discharge pressure (PC') higher than the critical pressure (Pcr) of the working fluid. The heat reservoir transfers pre-stored heat to the working fluid to heat it. The expander expands the working fluid, and the working fluid is stored in the gas holder at a first storage pressure (PAG'). In a discharge configuration, a heat exchanger transfers heat to the mass reservoir, evaporating a portion of the liquid phase of the working fluid contained in the mass reservoir, and maintaining a second storage pressure (PA'H) in the mass reservoir constant or substantially constant.

[0016] In a second independent aspect, the present invention relates to a method for energy management, the method comprising performing a closed-cycle thermodynamic conversion (TTC) between a gas holder for storing a gaseous working fluid other than air at a first storage pressure (PAG') in equilibrium with atmospheric pressure and a mass reservoir for storing the liquid working fluid at a second storage pressure (PA'H), first in one direction during the filling phase and then in the opposite direction during the release phase, during the filling phase the method stores heat and pressure, and during the release phase generates energy using the pre-stored heat and pressure.

[0017] In the filling stage, the method includes compressing the working fluid to a compression termination pressure (PC;PC2) higher than the critical pressure (Pcr) of the working fluid; cooling the working fluid to a cooling termination temperature (TE) close to the critical temperature (Tcr) of the working fluid by storing the heat removed from the working fluid; reducing the pressure of the working fluid to a reduced pressure (PG) lower than the critical pressure (Pcr) of the working fluid; and storing the working fluid in a mass reservoir at a second storage pressure (PA'H) lower than the critical pressure (Pcr) of the working fluid and in equilibrium with its own vapor phase, wherein in the filling stage, the method also includes removing heat from the mass reservoir to condense a portion of the vapor phase of the working fluid contained in the mass reservoir and maintaining the second storage pressure (PA'H) in the mass reservoir constant or substantially constant. Preferably, the cooling termination temperature (TE) is lower than or slightly higher than the critical temperature (Tcr) of the working fluid.

[0018] In the release phase, the method includes pumping the working fluid at a release pressure (PC') higher than the critical pressure (Pcr) of the working fluid, transferring previously accumulated heat to the working fluid to heat the working fluid, expanding the working fluid and storing it in a gas holder at a first storage pressure (PAG'), and in the release phase, the method also includes transferring heat to a mass accumulator to evaporate a portion of the liquid phase of the working fluid contained in the mass accumulator and maintaining the second storage pressure (PA'H) in the mass accumulator constant or substantially constant.

[0019] During the filling / configuration phase, in order to maintain a constant or substantially constant pressure within the mass reservoir, the increase in volume occupied by the working fluid stored in the liquid phase (i.e., the decrease in volume occupied by the working fluid vapor) is compensated for by condensing all or part of the working fluid vapor already contained in the mass reservoir, along with any vapor that may be generated during the pressure decrease, if the expansion terminates inside the Andrews bell.

[0020] In the discharge stage / configuration, in order to keep the pressure in the mass accumulator constant or substantially constant, the reduction in the volume of the liquid-phase working fluid (i.e., the increase in the volume occupied by the working fluid vapor) is compensated by evaporating a part of the liquid of the working fluid; otherwise, the system will be depressurized and cooled.

[0021] The plant of the first aspect is configured to execute the method of the second aspect and / or the method defined by one or more of the following aspects. The method of the second aspect can be executed by the device of the first aspect and / or the plant defined by one or more of the following aspects.

[0022] The applicant has demonstrated that the plant and method according to the present invention enable a predetermined objective to be achieved.

[0023] The applicant has demonstrated that the plant and method according to the present invention enable supercritical conversion to be carried out and, at the same time, enable the working fluid to be stored in a mass accumulator under subcritical conditions (a two-phase mass accumulator under subcritical conditions) in a liquid phase in equilibrium with its own limited vapor phase. In the internal volume of the mass accumulator, actually, there is no separation partition between the liquid phase and the vapor phase of the working fluid.

[0024] In particular, the applicant has demonstrated that the heat exchanger can remove heat from the mass accumulator in an amount equal to the latent heat of condensation of a part of the vapor initially contained in the mass accumulator, which must condense in order to enable the accumulation of liquid without a pressure increase or with a controlled pressure increase. Then, the heat exchanger can keep the second storage pressure constant or substantially constant in the mass accumulator.

[0025] Further aspects of the present invention are listed below.

[0026] In one aspect, the expander is coupled to a generator.

[0027] In one aspect, the compressor is coupled to an electric motor.

[0028] In one aspect, the working fluid is carbon dioxide (CO2), or contains carbon dioxide (CO2), or is a mixture mainly containing carbon dioxide. Alternatively, the working fluid is selected from the group including a mixture of carbon dioxide (CO2) and an additional substance (for correcting the critical temperature of the working fluid), SF6, N2O, or a mixture thereof.

[0029] In one aspect, the ratio of the second storage pressure (PA’H) to the critical pressure (Pcr) of the working fluid is 0.2 to 0.99, preferably 0.4 to 0.95.

[0030] In one aspect, the ratio of the compression end pressure (PC; PC2) to the critical pressure (Pcr) of the working fluid is 1.01 to 10.0, preferably 1.05 to 2.5.

[0031] In one aspect, the ratio of the cooling end pressure (PE) to the critical pressure (Pcr) of the working fluid is 1.01 to 10.0, preferably 1.05 to 2.5.

[0032] In one aspect, the ratio of the reduced pressure (PG) to the critical pressure (Pcr) of the working fluid is 0.01 to 0.99, preferably 0.4 to 0.9. The reduced pressure (PG) is equal to the second storage pressure (PA’H), or slightly different from the second storage pressure (PA’H), for example, by several bar (e.g., 1 bar to 5 bar).

[0033] In one aspect, the ratio of the cooling end temperature (TE) in Kelvin to the critical temperature (Tcr) in Kelvin is 0.4 to 1.1, preferably 0.75 to 0.95.

[0034] In one aspect, when the working fluid is carbon dioxide (CO2), the second storage pressure (PA’H) is 20 bar to 70 bar, optionally 40 bar to 60 bar.

[0035] In one aspect, the liquid / vapor separator is operably arranged between the pressure reducing device and the mass accumulator.

[0036] In one embodiment, the chiller is operably positioned between the heat reservoir and the depressurizer. In a plant-filled configuration, the chiller is configured to remove heat from the working fluid entering the depressurizer in order to reduce and / or remove the vapor title of the working fluid at the outlet of the depressurizer.

[0037] In one embodiment, after the working fluid has been cooled to a cooling termination temperature (TE) close to its critical temperature (Tcr), and before the working fluid pressure is reduced to a reduced pressure (PG), heat removal from the working fluid is optionally provided by a chiller of the previous embodiment to reduce and / or remove the vapor title of the working fluid at the end of the pressure reduction.

[0038] In one embodiment, the pressure reducing device includes a stacked valve.

[0039] In one embodiment, reducing the pressure of the working fluid during the filling stage optionally includes stacking the working fluid via the stacked valve of the previous embodiment.

[0040] In one embodiment, the chiller is configured to remove heat from the working fluid entering a depressurizing device, i.e., a stacked valve, so that the depressurization end temperature (TG) of the working fluid exiting the depressurizing device, i.e., the stacked valve, is equal to a second storage pressure (PA'H) or lower than the saturation temperature of the working fluid at a reduced pressure (PG) that is slightly different from the second storage pressure (PA'H).

[0041] In one embodiment, removing heat from the working fluid to reduce and / or eliminate the vapor title of the working fluid at the end of the depressurization includes bringing the working fluid at the end of the depressurization to a depressurization end temperature (TG) that is equal to a second storage pressure (PA'H) or lower than the saturation temperature of the working fluid at a reduced pressure (PG) that is slightly different from the second storage pressure (PA'H).

[0042] The depressurization termination temperature (TG) is the temperature at which the working fluid is released from the depressurization device, which has the advantage of resulting in a subcooled state and preventing the addition of vapors that condense in the mass reservoir. By subcooling, it is possible to partially or completely condense the vapors of the working fluid contained in the mass reservoir at the start of the filling phase, ensuring that the pressure in the mass reservoir remains constant or changes only slightly during the filling phase, and thereby reducing or eliminating the overall heat removed from the system during the filling phase.

[0043] In an alternative embodiment, the decompression device includes an auxiliary expander, such as an auxiliary turbine.

[0044] In one embodiment, the auxiliary expander can extract energy and convert it into mechanical and / or electrical energy.

[0045] In one embodiment, the auxiliary expander is coupled to an auxiliary generator.

[0046] In one embodiment, the auxiliary expander is of the action type, and is particularly a Pelton turbine.

[0047] In one embodiment, reducing the pressure of the working fluid during the filling stage optionally includes supplying the working fluid for auxiliary expansion using the auxiliary expander of the previous embodiment.

[0048] In one embodiment, the chiller is configured to remove heat from the working fluid entering the auxiliary expander, so that the working fluid remains in a subcooled liquid state at the outlet of the auxiliary expander.

[0049] In one embodiment, removing heat from the working fluid to reduce and / or eliminate the vapor title of the working fluid at the end of depressurization includes removing heat from the working fluid before auxiliary expansion so that the working fluid remains in a subcooled liquid state during and at the end of auxiliary expansion.

[0050] The applicant has demonstrated that the chiller enables a much higher expansion efficiency than possible two-phase expansion and offers the additional advantage of not adding vapor that would otherwise be condensed in a successor mass reservoir. In this case as well, by subcooling, it is possible to partially or completely condense the vapor of the working fluid contained at the start of filling, ensuring that the pressure in the mass reservoir remains constant or changes only slightly during the filling phase, thereby reducing or eliminating the overall heat lost from the system during the filling phase.

[0051] In one embodiment, an auxiliary chiller is operably positioned between the mass reservoir and the pump. In the plant discharge configuration, the auxiliary chiller is configured to remove heat from the working fluid entering the pump, thereby reducing the risk of cavitation in the pump.

[0052] In one embodiment, before pumping the working fluid, during the discharge stage, it is optionally provided by an auxiliary chiller of the previous embodiment to remove heat from the working fluid and reduce the risk of cavitation that may occur during subsequent pumping.

[0053] The applicant has demonstrated that increasing the subcooling degree of the inlet pump reduces the risk of cavitation and increases the available net positive suction height (effective suction head - NPSH).

[0054] This is an alternative to a configuration where the pump is placed several meters below the minimum level of the liquid being pumped (to provide NPSH). An auxiliary chiller at the suction creates a subcooled state by lowering the fluid temperature while the pressure remains constant.

[0055] In one embodiment, the heat exchanger is configured to exchange heat with the external environment.

[0056] In one embodiment, the heat exchanger comprises a heat reservoir configured to exchange heat with a working fluid in a filling configuration and a discharge configuration, and a heat exchanger operably coupled to the heat reservoir and the external environment.

[0057] A heat reservoir is configured to store the heat (latent heat) of the working fluid during the filling phase and to transfer it during the release phase.

[0058] In one embodiment, the heat exchanger is a cooler / chiller through which air is introduced to the atmosphere or indirectly comes into contact with the atmosphere via, for example, a refrigerated fluid storage system and / or a cooling tower and / or an air cooler and / or a water cooler and / or chiller having river water or seawater.

[0059] In one embodiment, the chiller is operably connected to the heat exchanger.

[0060] In one embodiment, the removal of heat from and / or transfer of heat to the mass reservoir includes, optionally, directly or indirectly, exchanging heat with the external environment via a heat exchanger according to one or more of the embodiments described above.

[0061] In one embodiment, the heat storage device comprises a first heat storage device operating at a high temperature and a second heat storage device operating at a low temperature.

[0062] In one embodiment, in a packed configuration, a high-temperature first heat reservoir cools the working fluid to an intermediate temperature (TD; TD1) higher than the critical temperature (Tcr), and a low-temperature second heat reservoir cools the working fluid from the intermediate temperature (TD1) to a cooling completion temperature (TE) close to the critical temperature (Tcr).

[0063] In one embodiment, the operation of cooling the working fluid during the filling phase and the operation of heating the working fluid during the discharge phase are each optionally performed in two stages by a high-temperature first heat reservoir and a low-temperature second heat reservoir as described above.

[0064] In one embodiment, during the filling stage, in the first stage, the working fluid is cooled to an intermediate temperature (TD) that is higher than the critical temperature (Tcr), and in the second stage, the working fluid is cooled from the intermediate temperature (TD) to a cooling completion temperature (TE) that is close to the critical temperature (Tcr).

[0065] In one embodiment, the ratio of the intermediate temperature (TD) in Kelvin to the critical temperature (Tcr) in Kelvin is 1.01 to 2.0, preferably 1.1 to 1.3.

[0066] The significance of dividing it into the two stages described above is that it does not have a high-temperature heat storage vessel that is affected by the actual gas near the critical point, and in particular, it is not affected by changes in specific heat due to temperature changes.

[0067] In one embodiment, a low-temperature second heat reservoir comprises a first heat exchanger and a second heat exchanger configured to exchange heat with a working fluid.

[0068] In one embodiment, the low-temperature second heat storage unit comprises a low-temperature first reservoir, an intermediate-temperature second reservoir, and a high-temperature third reservoir containing water, which optionally fluidly connects to the first and second heat exchangers at ambient pressure.

[0069] In one embodiment, the first heat exchanger and the second heat exchanger are arranged in series on the working fluid pipeline.

[0070] In one embodiment, the water flow rates in the first heat exchanger and the second heat exchanger are different from each other.

[0071] The applicant has demonstrated that the above structure can improve the efficiency of a low-temperature second heat reservoir by minimizing the difference in heat exchange temperature (near the critical point where specific heat changes as the temperature changes).

[0072] In one embodiment, the cooling end temperature (TE) in the filling configuration is higher than the pump discharge temperature (TC') in the discharge configuration.

[0073] The applicant has demonstrated that a zero-energy system can be obtained for the "lower temperature" portion of the heat storage device (the lower temperature second heat storage device), i.e., a zero-energy system in which all the heat stored in the filling phase is used during the release phase.

[0074] In one embodiment, the heat transfer device is operably coupled to a working fluid pipeline located downstream of the expander and a working fluid pipeline located downstream of the pump.

[0075] In one embodiment, in the discharge configuration, the heat transfer device is configured to transfer a portion of the heat discharged from the expander to the supercritical working fluid downstream of the pump.

[0076] In one embodiment, the heat transfer device is connected to a second heat storage device at a lower temperature.

[0077] In one embodiment, the heat transfer device is fluidly connected to a first heat exchanger and a second heat exchanger.

[0078] In another embodiment, the heat transfer device is fluidly connected to an additional heat exchanger arranged in parallel with the first and second heat exchangers.

[0079] In one embodiment, the heat transfer device is also operably coupled to a heat exchanger to remove excess heat.

[0080] In one embodiment, during the discharge phase, the heat transfer device is provided to optionally transfer some of the excess heat transferred to the external environment via a heat exchange device.

[0081] In one embodiment, the heat transfer device is operably coupled to the heat exchange device via a second heat reservoir at a lower temperature.

[0082] In one embodiment, a heat exchange circuit connected to a heat exchanger is coupled to a second low-temperature heat reservoir and exchanges heat with water coming out of the first and / or second heat exchangers during the discharge stage / configuration.

[0083] In one embodiment, during the discharge phase, the heat exchange circuit is provided to optionally transfer a portion of the heat from the expanded working fluid to the supercritical working fluid before or during heating via a heat transfer device according to one or more of the embodiments described above.

[0084] The applicant has demonstrated that this allows the discharge phase to be performed at a higher pressure than the filling pressure, thereby improving cycle efficiency.

[0085] In one embodiment, a first additional heat exchanger is positioned between the gas holder and the compressor inlet and is configured to regulate the compressor inlet temperature (TB; TB1).

[0086] In one embodiment, the first additional heat exchanger is configured to perform preheating with heat generated, for example, by mechanical and electrical inefficiencies of the compressor.

[0087] In one embodiment, the first additional heat exchanger is configured to perform pre-cooling, for example, by a dry cooler, tower, seawater, river water, or chiller, thereby transferring heat to the environment.

[0088] In one embodiment, the first additional heat exchanger is operably connected to the heat exchanger.

[0089] In one embodiment, during the filling stage, a first additional heat exchanger is provided, optionally before compression, to regulate the temperature (TA) of the working fluid coming from the gas holder via the first additional heat exchanger according to one or more of the embodiments described above.

[0090] In one embodiment, a second additional heat exchanger is positioned between the expander outlet and the gas holder and is configured to regulate the gas holder inlet temperature (TG').

[0091] In one embodiment, a second additional heat exchanger is operably connected to the heat exchanger.

[0092] In one embodiment, during the discharge phase, a second heat exchanger is optionally provided to regulate the temperature (TF') of the expanded working fluid before it enters the gas holder, via a second heat exchanger according to one or more of the embodiments described above.

[0093] In one embodiment, the first and second additional heat exchangers are defined by the same exchanger.

[0094] In one embodiment, the reheater operates operably both between the gas holder and the compressor and between the gas holder and the expander.

[0095] In one embodiment, the reheater is also operably coupled to the heat storage unit.

[0096] In one embodiment, the reheater is configured to exchange heat between the working fluid flowing through the heat storage unit and the working fluid entering the compressor in a filling configuration, or the working fluid exiting the expander in a discharge configuration.

[0097] In one embodiment, during the filling phase, a reheater is provided to use some of the heat removed from the working fluid during cooling to the end-of-cooling temperature (TE) to heat the working fluid before compression. This makes it possible to optionally increase a specific amount of work in the cycle during the filling phase using a reheater according to one or more of the above embodiments.

[0098] In one embodiment, during the discharge phase, a portion of the heat recovered from the expanded working fluid is optionally used to further heat the working fluid by a reheater according to one or more of the aforementioned embodiments after pumping and before expansion. This makes it possible to increase the cycle efficiency during the discharge phase.

[0099] In one embodiment, the reheater is operably inserted between a high-temperature first heat reservoir and a low-temperature second heat reservoir.

[0100] In one embodiment, the reheater is configured to exchange heat between a working fluid flowing between a high-temperature first heat reservoir and a low-temperature second heat reservoir, and a working fluid entering the compressor in a filling configuration, or a working fluid exiting the expander in a discharge configuration.

[0101] In one embodiment, a second compressor is connected in series with the compressor, and a second expander is connected in series with the expander.

[0102] In one embodiment, a high-temperature first heat reservoir operates in a packed configuration between the compressor and the second compressor, and downstream of the second compressor.

[0103] In one embodiment, a high-temperature first heat reservoir operates in a discharge configuration upstream of the second expander and between the second expander and the first expander.

[0104] In one embodiment, during the filling stage, compressing and cooling the working fluid optionally includes performing a first compression, followed by a first cooling, then a second compression, followed by a second cooling, using a compressor, a high-temperature first heat reservoir, and a second compressor according to one or more of the embodiments described above.

[0105] In one embodiment, at the end of the first compression, the working fluid is at a subcritical pressure (PC1), and at the end of the second compression, the working fluid is at a pressure higher than the critical pressure (PC2).

[0106] In one embodiment, the working fluid temperatures (TC1, TC2) at the end of the first and second compressions are similar or equal.

[0107] In one embodiment, heating and expanding the working fluid in the discharge stage optionally includes performing a first heating and subsequent first expansion, followed by a second heating and subsequent second expansion, using an expander, a high-temperature first heat reservoir, and a second expander according to one or more of the embodiments described above.

[0108] Further features and advantages will become clearer from the detailed description of preferred but non-exclusive embodiments of the plant and method according to the present invention.

[0109] This specification is provided for illustrative purposes only and is therefore not limited to the accompanying drawings, which are shown below with reference. [Brief explanation of the drawing]

[0110] [Figure 1] A schematic embodiment of an energy management plant according to the present invention is shown. [Figure 2] This is a TS diagram for the plant shown in Figure 1. [Figure 3] A schematic representation of a first modified example of the plant according to the present invention is shown below. [Figure 4] Figure 3 is a TS diagram for the plant. [Figure 5] This is a schematic diagram showing one of the elements of the plant that is referenced in the preceding or succeeding diagrams. [Figure 6] A second modified example of the plant according to the present invention is schematically shown. [Figure 7] Figure 6 is a TS diagram for the plant. [Figure 8] This is a schematic diagram showing different elements of the plant that are referenced in preceding or succeeding diagrams. [Figure 9] This is a portion of the TS diagram for the elements in Figure 8. [Figure 10] A third modified example of the plant according to the present invention is schematically shown. [Figure 10A] This is a magnified view of a portion of Figure 10. [Figure 11] This is a portion of the TS diagram for the plant shown in Figure 10. [Figure 12] A fourth schematic modification of the plant according to the present invention is shown below. [Figure 13] Figure 12 is a TS diagram for the plant. [Figure 14] A fifth modified example of the plant according to the present invention is schematically shown. [Figure 15] Figure 14 is a TS diagram for the plant. [Figure 16] A sixth schematic modification of the plant according to the present invention is shown below. [Figure 17] Figure 16 is a TS diagram for the plant. [Modes for carrying out the invention]

[0111] Referring to the attached drawings, reference no. 1 shows an overall illustration of the plant for energy management according to the present invention.

[0112] Figures 1 and 2 The plant in Figure 1 contains carbon dioxide (CO2) as the working fluid. In modifications within the scope of the present invention, the working fluid may be a mixture containing carbon dioxide as the main component, or SF6, N2O, or a mixture thereof.

[0113] Carbon dioxide is confined within a closed circuit suitable for performing a closed thermodynamic cycle conversion (TTC) between the two mass storages of carbon dioxide (CO2), first in one direction of the filling configuration / stage, and then in the opposite direction of the release configuration / stage.

[0114] For this purpose, plant 1 includes a gas holder 2 that forms the boundary of a variable volume section 3 configured to contain or contain gaseous carbon dioxide at a first storage pressure (PAG') which is constant, equal to atmospheric pressure, or slightly overpressurized above atmospheric pressure.

[0115] In the illustrated embodiment, the gas holder 2 is of the double-membrane type, comprising an inner membrane 201 for containing carbon dioxide and an outer membrane 202 in contact with the external environment. The gas holder 2 is positioned on a surface and is in contact with the atmosphere on the outside. The inner membrane 201 of the gas holder 2 forms an internal boundary of volume 3 configured to contain carbon dioxide at atmospheric pressure or substantially atmospheric pressure, i.e., at pressure equilibrium with the atmosphere. The outer membrane 202 maintains its shape at all times, except for small fluctuations, for the purpose of protecting the inner membrane 201 from the external environment and atmospheric working substances such as sun, rain, wind, and snow. The gap formed between the inner membrane 201 and the outer membrane 202 is filled with ambient air by a ventilation device and maintained at a constant pressure of several millibars. The gas holder 2 can also be realized as any other low or zero-overpressure gas storage system, where the pressure is kept constant or substantially constant as the volume of the working fluid changes.

[0116] Plant 1 comprises a compressor 4 fluid-connected to a gas holder 2, and an expander 5 fluid-connected to the gas holder 2. The compressor 4 is, for example, a centrifugal compressor driven by motors 6. The expander 5 is, for example, a radial turbine or axial turbine connected to a generator 7. The first pipeline 8 connects the gas holder 2 to the inlet 4a of the compressor 4 and, in parallel, to the outlet 5b of the expander 5.

[0117] Plant 1 includes a heat reservoir 9, which is fluidly connected to a compressor 4 and an expander 5 and configured to exchange heat with carbon dioxide. The heat reservoir 9 is a TES (thermal energy storage) containing thermal mass (e.g., water, oil, molten salt, or solid material) and can receive, absorb, and store heat transferred from carbon dioxide passing through in direct or indirect contact with the thermal mass (via a heat exchanger), or can transfer previously stored heat to carbon dioxide passing through in direct or indirect contact with the thermal mass (via a heat exchanger). A second pipeline 10 connects the outlet 4b of the compressor 4 and, in parallel, the inlet 5a of the expander 5 to the heat reservoir 9.

[0118] Plant 1 includes a mass reservoir 11 that forms an internal boundary of a constant volume 12, which is configured to contain or contain a liquid-phase working fluid at a second storage pressure (PA'H). The mass reservoir 11 is schematically shown in the accompanying diagram and may comprise, for example, one or more reservoirs made of metal, suitable for withstanding the second storage pressure (PA'H) without substantially deformation, i.e., maintaining a constant volume (or each volume) 12. A third pipeline 13 connects a heat reservoir 9 to the inlet 11a of the mass reservoir 11 and, in parallel, to the outlet 11b of the mass reservoir 11. A first branch 13a of the third pipeline 13 connects the heat reservoir 9 to the inlet 11a of the mass reservoir 11, and a second branch 13b of the third pipeline 13 connects the outlet 11b of the mass reservoir 11 to the heat reservoir 9.

[0119] Between the heat reservoir 9 and the mass reservoir 11 is a pressure reducing device 14 configured to reduce the pressure of carbon dioxide flowing from the heat reservoir 9 to the mass reservoir 11 through the first branch 13a of the third pipeline 13. Alternatively, a pump 15 is located at the second branch 13b of the third pipeline 13 and pumps carbon dioxide from the mass reservoir 11 to the heat reservoir 9 according to the method described below.

[0120] Plant 1 also includes a heat exchanger 16 operably coupled to the mass accumulator 11 and configured to exchange heat with the working fluid present in the mass accumulator 11.

[0121] The first, second, and third pipelines 8, 10, and 13 described above, together with electrical or electronic control devices (e.g., operating valves, control units, sensors, etc.), are configured to operate plant 1 in accordance with the method of the present invention and in accordance with closed thermodynamic cycle conversion (TTC) to operate the filling configuration / stage and the discharge configuration / stage described above.

[0122] This method will be explained with reference to the TS diagrams in Figures 1 and 2.

[0123] In the initial state, virtually all of the carbon dioxide present in plant 1 is contained within the internal volume 3 of gas holder 2, in equilibrium with the external environment (Figure 2-point A), i.e., in the gas phase, with a constant first storage pressure (PAG'), which is substantially equal to atmospheric pressure.

[0124] In the filling configuration / stage (points ACEGH in Figures 1 and 2), carbon dioxide moves from the gas holder 2 to the mass reservoir 11 through the compressor 4, heat reservoir 9, and depressurizer 14, where it is stored in the mass reservoir 11 in liquid phase at a second storage pressure (PA'H).

[0125] In particular, the compressor 4 compresses the carbon dioxide released from the internal volume 3 of the gas holder 2 to a compression termination pressure (PC) that is higher than the critical pressure (Pcr) of the working fluid (from point A to point C in Figures 1 and 2). For example, the ratio of the compression termination pressure (PC) to the critical pressure (Pcr) of carbon dioxide is 2. The carbon dioxide is heated to a compression termination temperature (TC) corresponding to the compression termination pressure (PC).

[0126] Next, as the supercritical carbon dioxide passes through the heat reservoir 9, the heat reservoir 9 absorbs and stores heat from the carbon dioxide. The carbon dioxide is cooled to a cooling termination temperature (TE) close to the critical temperature (Tcr) of carbon dioxide (from point C to point E in Figures 1 and 2). In the illustrated example, the cooling termination temperature (TE) is lower than the critical temperature (Tcr) of the working fluid, but in other embodiments, this cooling termination temperature (TE) may be slightly higher than the critical temperature. For example, the ratio of the cooling termination temperature (TE) in Kelvin to the critical temperature (Tcr) of carbon dioxide in Kelvin is 0.90 or 1.01. For example, the ratio of the cooling termination pressure (PE) to the critical pressure (Pcr) of carbon dioxide is 2.

[0127] At this point, the supercritical carbon dioxide passes through a depressurization device 14 that reduces its pressure to a reduced pressure (PG) lower than its respective critical pressure (Pcr). For example, the ratio of the reduced pressure (PG) to the critical pressure (Pcr) of carbon dioxide is 0.68.

[0128] The carbon dioxide is cooled to a reduced temperature (TG) (from point E to point G in Figures 1 and 2). In Figure 2, the depressurization is shown by the depressurization device 14 defined by the stacked valve (section EG with G inside the Andrews bell).

[0129] The carbon dioxide exiting the stacked valve can match the reduced pressure (PG) or differ slightly from the reduced pressure (PG) by, for example, a few bar (e.g., 1 to 5 bar), and is stored in the mass reservoir 11 at a second storage pressure (PA'H) lower than the critical pressure (Pcr). The carbon dioxide is in equilibrium with its own vapor phase (point H in Figures 1 and 2). For example, the second storage pressure (PA'H) is equal to 50 bar, and the ratio of the second storage pressure (PA'H) to the critical pressure (Pcr) of carbon dioxide (73 bar) is equal to 0.68. A liquid-vapor separator may be present between the stacked valve and the mass reservoir 11, or a region within the mass reservoir 11 may be used to separate the vapor phase from the liquid phase.

[0130] While general liquid-phase carbon dioxide enters and fills the mass reservoir 11, the heat exchanger 16 removes heat from the mass reservoir 11, condensing a portion of the vapor phase of carbon dioxide contained in the mass reservoir 11, thereby maintaining the second storage pressure (PA'H) constant or substantially constant.

[0131] In other words, the increase in the volume occupied by the carbon dioxide stored in the liquid phase within the mass reservoir 11 (i.e., the decrease in the volume occupied by the working fluid vapor) is compensated for by condensing all or part of the carbon dioxide vapor already contained in the mass reservoir 11 with the vapor generated during the depressurization.

[0132] In the filling configuration / stage, plant 1 receives electrical energy coming from an external grid that is supplied to the motor 6 of compressor 4, and stores it in the form of heat and pressure.

[0133] At the end of the filling stage (point H), virtually all of the carbon dioxide present in plant 1 is contained within the internal volume 12 of the mass reservoir 11 under subcritical conditions, in the form of a liquid phase in equilibrium with its own limited vapor phase (a two-phase mass reservoir under subcritical conditions). There is no separating partition between the liquid and vapor phases of carbon dioxide within the internal volume 12 of the mass reservoir 11.

[0134] In the release configuration / stage (points A'-B'-C'-E'-G' in Figures 1 and 2), carbon dioxide is moved from the mass reservoir 11 to the gas holder 2 through the pump 15, the heat reservoir 9, and the expander 5, and is stored again in the gas holder 2 in the gas phase at a constant first storage pressure (PAG') in pressure equilibrium with the atmosphere.

[0135] In particular, pump 15 pumps liquid carbon dioxide at a release pressure (PC') higher than the critical pressure (Pcr) of carbon dioxide (points B'-C' in Figures 1 and 2). The carbon dioxide is heated to the release temperature (TC').

[0136] Next, as the carbon dioxide passes through the heat reservoir 9, the heat reservoir 9 transfers previously stored heat to the carbon dioxide. The carbon dioxide is heated to the heating termination temperature (TE') (points C' to E' in Figures 1 and 2).

[0137] Next, the carbon dioxide expands inside the expander 5, driving the mechanical mechanism of the expander 5, for example, rotating one or more impellers of a turbine, which generates electrical energy by the generator 7 (points E'-G' in Figures 1 and 2). In the release configuration / stage, plant 1 generates energy using pre-stored heat and pressure. The carbon dioxide released from the expander 5 is again stored in the gas holder 2 at a first storage pressure (PAG').

[0138] In the discharge configuration, the heat exchanger 16 transfers heat to the mass reservoir 11, evaporating a portion of the liquid phase of carbon dioxide contained in the mass reservoir 11, and maintaining the second storage pressure at a constant or substantially constant (PA'H).

[0139] In other words, in the release stage / configuration, in order to keep the pressure inside the mass reservoir 11 constant or substantially constant, the decrease in the volume of liquid carbon dioxide (i.e., the increase in the volume occupied by carbon dioxide vapor) is compensated for by evaporating some of the liquid carbon dioxide, and as a result the mass reservoir 11 does not depressurize or cool.

[0140] Figures 3 and 4 - Modified example of the first modification Figures 3 and 4 schematically show a first modification of Plant 1 (and each method) that differs from Plant 1 described above in Figures 1 and 2, due to the presence of a chiller 17 and an auxiliary chiller 18. Chiller 17 is located at the first branch 13a of the third pipeline 13 and is interposed between the heat reservoir 9 and the depressurizer 14.

[0141] In the filling configuration / stage (points ACEFGH in Figures 3 and 4), the chiller 17 removes heat from the carbon dioxide entering the stack valve, and as a result, the depressurization end temperature (TG) of the carbon dioxide exiting the stack valve is equal to the second storage pressure (PA'H) or lower than the saturation temperature of carbon dioxide at a reduced pressure (PG) that is slightly different from the second storage pressure (PA'H). Unlike the TS diagram in Figure 2, in Figure 4, the carbon dioxide from point E moves to point F (cooled), then to point G (stacked), and then rises towards point H. The removal of heat from the carbon dioxide entering the depressurizer 14, performed by the chiller 17, can reduce and / or eliminate the vapor title of carbon dioxide at the outlet of the depressurizer 14.

[0142] The auxiliary chiller 18 is operably positioned at the second branch 13b of the third pipeline 13 and interposed between the mass reservoir 11 and the pump 15.

[0143] In the discharge configuration / stage, the auxiliary chiller 18 removes heat from the carbon dioxide entering the pump 15, thereby reducing the risk of cavitation that may occur during pumping in the pump 15. This subcooled state at the inlet of the pump 15, in addition to reducing the risk of cavitation, further increases the available net positive suction height (effective suction head - NPSH).

[0144] The pressure reducing device 14 in the plant shown in Figure 3 may also be an auxiliary expander, such as a Pelton turbine, or an action-type auxiliary turbine, rather than a stacked valve. The auxiliary expander may be coupled to an auxiliary generator (not shown) that can extract energy and convert it into mechanical and / or electrical energy in the filling stage / configuration.

[0145] In another variation, chiller 17 removes heat from the carbon dioxide before it enters the auxiliary expander, so that the carbon dioxide remains in a subcooled liquid state at the outlet of the auxiliary expander. This allows for a much higher expansion efficiency than possible with two-phase expansion.

[0146] The chiller 17 and auxiliary chiller 18 can also be connected to the heat exchanger 16 to exchange heat with the heat exchanger 16 and the external environment.

[0147] Figure 5 - Heat exchanger Figure 5 shows a schematic example of a heat exchanger 16 that can be used in the plant shown here, in combination with the mass reservoir 7.

[0148] In this example, the heat exchanger 16 is configured to exchange heat not only with the carbon dioxide contained in the mass reservoir 11, but also with the external environment. Thus, the heat exchanger 16 is able to remove heat from the mass reservoir 11 and / or transfer heat to the mass reservoir 11 by exchanging heat with the external environment.

[0149] The illustrated heat exchanger 16 comprises a heat reservoir 19 configured to exchange heat with carbon dioxide, and a heat exchanger 20 operably coupled to the heat reservoir 19 and the external environment. The heat reservoir 19 stores the heat Q (latent heat) of carbon dioxide during the filling stage / configuration and transfers the heat Q to carbon dioxide during the release stage / configuration.

[0150] In the example shown in Figure 5, the heat reservoir 19 includes separate circuits 21 for circulating the heat transfer medium. The circuits 21 extend into the mass reservoir 11 and exchange heat with the heat mass of the heat reservoir 19 for carbon dioxide.

[0151] The heat exchanger 20 comprises separate circuits 22 for circulating a heat transfer medium. The circuits 22 extend into the interior of the heat storage unit 19 to exchange heat with the thermal mass of the heat storage unit 19 and the environment. In a modified embodiment, the circuits 22 can be reversed, i.e., the same means used to store heat in the heat storage unit 19 are used to exchange heat with the heat exchanger 20.

[0152] The heat exchanger 20 may be an air induction cooler / chiller, or it may be indirectly in contact with the atmosphere via, for example, a refrigerated fluid storage system and / or a cooling tower and / or an air cooler and / or a water cooler and / or chiller having river water or seawater.

[0153] The bypass circuit 23 allows the circuit 22 of the heat storage unit 19 to be directly fluid-connected to the circuit 22 of the heat exchanger 20.

[0154] Figures 6, 7, 8, and 9 - Second modified example Figures 6 and 7 schematically show a second modification of Plant 1 (and each method) that differs from Plant 1 described above in Figures 1 and 2, in that it includes a chiller 17 shown for the plant in Figures 3 and 4, and the heat reservoir 9 comprises a high-temperature first heat reservoir 9a and a low-temperature second heat reservoir 9b. The double heat reservoirs 9a and 9b can perform the operation of cooling carbon dioxide in the filling phase and the operation of heating carbon dioxide in the release phase in two stages, respectively.

[0155] Referring to the TS diagram in Figure 7, in the packed configuration / stage, the high-temperature first heat reservoir 9a cools the carbon dioxide to an intermediate temperature (TD) that is above the critical temperature (Tcr), and the low-temperature second heat reservoir 9b cools the carbon dioxide from the intermediate temperature (TD) to a cooling completion temperature (TE) that is close to the critical temperature (Tcr). The ratio of the intermediate temperature (TD) to the critical temperature (Tcr) is, for example, equal to 1.3.

[0156] In the discharge configuration / stage, a low-temperature second heat reservoir 9b heats the carbon dioxide to an intermediate temperature (TD') above the critical temperature (Tcr), and a high-temperature first heat reservoir 9a heats the carbon dioxide from the intermediate temperature (TD') to the heating termination temperature (TE').

[0157] Figure 8 shows a schematic example of a low-temperature second heat reservoir 9b. In this example, the low-temperature second heat reservoir 9b comprises a first heat exchanger 24a and a second heat exchanger 24b arranged in series on the second pipeline 10 and configured to exchange heat with carbon dioxide flowing through the second pipeline 10.

[0158] The low-temperature second heat storage unit 9b also includes a low-temperature first reservoir 25a, an intermediate-temperature second reservoir 25b, and a high-temperature third reservoir 25c.

[0159] Conduit 26 connects the first reservoir 25a in series with the first heat exchanger 24a, the second heat exchanger 24b, and the third reservoir 25c. Auxiliary conduit 27 connects the second reservoir 25b to a point on conduit 26 located between the first heat exchanger 24a and the second heat exchanger 24b. Each conduit 26 leading from the first reservoir 25a is provided with a first pump 28a and a first shut-off control valve 29a arranged in parallel. Each conduit 26 leading from the second reservoir 25c is provided with a third pump 28c and a third shut-off control valve 29c arranged in parallel. Each auxiliary conduit 27 leading from the second reservoir 25b is provided with a second pump 28b and a second shut-off control valve 29b arranged in parallel.

[0160] The first reservoir 25a, the second reservoir 25b, and the third reservoir 25c contain unpressurized water, i.e., water at ambient pressure. The first pump 28a is configured to pump water from the first reservoir 25a toward the first heat exchanger 24a. The second pump 28b is configured to pump water from the second reservoir 25a toward the connection point of the auxiliary conduit 27 toward the conduit 26. The third pump 28c is configured to pump water from the third reservoir 25c toward the second heat exchanger 24b. In this way, the flow rates of water through the first heat exchanger 24a and the second heat exchanger 24b are different. This makes it possible to reduce the difference in heat exchange temperatures between water and carbon dioxide, and therefore increase the efficiency of the low-temperature second heat accumulator 9b.

[0161] Part of the TS diagram in Figure 9 shows the lines (abc) of carbon dioxide being cooled and the corresponding water being heated during the filling phase (from point D to point E). Part of the TS diagram in Figure 9 also shows the lines (cba) of carbon dioxide being heated and the corresponding water being cooled during the release phase (from point C' to point D'). The cooling end temperature (TE) in the filling configuration is higher than the pump release temperature (TC') in the release configuration. This makes it possible to obtain a zero-energy system for the "lower temperature" portion of the heat reservoir, i.e., the lower temperature second heat reservoir 9b, where all the heat stored in the filling phase is used during the release phase.

[0162] Figures 10, 10A, and 11 - Third Modified Example Figures 10, 10A, and 11 schematically show a third modification of Plant 1 (and their respective methods) that differs from the second modification (Figures 6, 7, 8, and 9) described above, in that it also includes a heat transfer device 30 operably coupled to a first pipeline 8 of the working fluid located downstream of the outlet 5b of the expander 5 and a third pipeline 13 of the working fluid located downstream of the pump 15. In the discharge configuration / stage, this heat transfer device 30 is configured to transfer some of the heat discharged from the expander 5 to the supercritical working fluid downstream of the pump 15.

[0163] Furthermore, the low-temperature second heat reservoir 9b (Figure 10A) is similar to, but not identical to, the one shown in Figure 8 for the second modification. Unlike in Figure 8, the third pump 28c of the third reservoir 25c is located on a circuit section 31 that is on the first pipeline 8 and extends to the heat exchanger 32 located downstream of the outlet 5b of the expander 5. In the discharge configuration / stage, the third pump 28c is configured to pump water from the third reservoir 25c toward the heat exchanger 32 and backward toward the second heat exchanger 24b.

[0164] Therefore, the heat transfer device 30 comprises this circuit section 31 having a heat exchanger 32. Thus, a portion of the heat discharged from the expander 5 is transferred to the supercritical working fluid downstream of the pump 15 via the water in the low-temperature second heat reservoir 9b.

[0165] In the filling configuration / stage, the third pump 28c is not operating, the third shut-off control valve 29c is open and regulating, and the first and second pumps 28a and 28b are operating. In the discharge configuration / stage, the closed third shut-off control valve 29c and the third pump 28c are operating.

[0166] Figure 11 is a portion of a TS diagram showing the effect of transferring some of the exhaust heat from the expander 5 to the supercritical working fluid downstream of the pump 15 via the heat transfer device 30. In the filling stage / configuration, water is heated (abc) while carbon dioxide is cooled (DE). In the release stage / configuration, due to the effect of the heat transfer device 30, the water is cooled along the higher-positioned line (c'-b'-a') and the carbon dioxide is heated from C' to D'.

[0167] In modified versions not shown, the heat transfer device 30 is fluidly connected to an additional heat exchanger arranged in parallel with the first heat exchanger 24a and the second heat exchanger 24b.

[0168] As shown in Figures 10 and 10A, the heat transfer device 30 is also operably coupled to a heat exchanger 16, which has the purpose of removing excess heat and transferring it to the external environment. The heat transfer device 30 is operably and indirectly coupled to the heat exchanger 16 via a lower temperature second heat reservoir 9b. For this purpose, the heat exchange circuit 33 comprises each heat exchanger 34 operably coupled to the conduit 26 of the lower temperature second heat reservoir 9b at a point located between the first heat exchanger 24a and the second heat exchanger 24b, and exchanges heat with the water leaving the first heat exchanger 24a in the discharge stage / configuration. Each circuit 35 connects each of these heat exchangers 34 to the heat exchanger 16 and, for example, to the heat reservoir circuit 21 of the heat reservoir 19 in Figure 5.

[0169] Figures 12 and 13 - Fourth Modification Figures 12 and 13 schematically show a fourth modification of Plant 1 (and each method) described above in Figures 1 and 2, which includes a chiller 17 as shown in Figures 3 and 4, and further includes a first additional heat exchanger 36 positioned between the gas holder 2 and the inlet 4a of the compressor 4, and a second additional heat exchanger 37 positioned between the outlet 5b of the expander 5 and the gas holder 2.

[0170] The first additional heat exchanger 36 is configured to adjust the compressor inlet temperature (TB), i.e., to change the temperature (TA) of the carbon dioxide coming from the gas holder 2 before compression. The first additional heat exchanger 36 can be configured to perform preheating (preheating AB in Figure 13) with heat generated, for example, by the mechanical and electrical inefficiencies of the compressor 4, or to perform precooling (pre-cooling) by transferring heat to the environment, for example, by a dry cooler, tower, seawater, river water, chiller.

[0171] In the illustrated and illustrative embodiments, the first additional heat exchanger 36 comprises a circuit 38 connected to the heat exchanger circuit 21 of the heat exchanger 16, for example, the heat storage circuit 19 in Figure 5.

[0172] A second additional heat exchanger 37 is configured to adjust the inlet temperature (TG') to the gas holder 2, i.e., to change the temperature (TF') of the expanded carbon dioxide before it enters the gas holder 2. Figure 13 shows the cooling F'-G' after expansion E'-F' in the release stage / configuration.

[0173] In the illustrated and illustrative embodiments, the second additional heat exchanger 37 comprises each circuit 39 connected to the heat storage circuit 21 of the heat exchanger 16, for example, the heat storage 19 in Figure 5. Each circuit 39 of the second additional heat exchanger 37 can be connected to or partially coincide with each circuit 38 of the first additional heat exchanger 36. In a modified embodiment, the first additional heat exchanger 36 and the second additional heat exchanger 37 may also be defined by a single exchanger. Figures 14 and 15 - Fifth Modification Figures 14 and 15 schematically show a fifth modification of Plant 1 (and their respective methods) that differs from the second modification of Plant 1 described above in Figures 6 and 7, in that it includes a second additional heat exchanger 37 and also includes a reheater 40.

[0174] The reheater 40 operates operably both between the gas holder 2 and the compressor 4 and between the gas holder 2 and the expander 5, and is operably coupled to the heat reservoir 9, particularly operably interposed between the high-temperature first heat reservoir 9a and the low-temperature second heat reservoir 9b.

[0175] A pipeline of carbon dioxide connecting a high-temperature first heat reservoir 9a and a low-temperature second heat reservoir 9b is thermally coupled to the first pipeline 8 in a reconverter 40, and a second additional heat exchanger 37 is operably interposed between the gas holder 2 and this reconverter 40.

[0176] In the filling configuration / stage, the reheater 40 enables heat exchange between carbon dioxide flowing from the high-temperature first heat reservoir 9a to the low-temperature second heat reservoir 9b and the carbon dioxide entering the compressor 2. In the filling configuration / stage, some of the heat removed from the carbon dioxide during cooling to the cooling end temperature (TE) is used to heat the carbon dioxide before compression (Figure 15, D1-D2, AB).

[0177] In the discharge configuration / stage, the reconverter 40 enables heat exchange between carbon dioxide flowing from the low-temperature second heat reservoir 9b to the high-temperature first heat reservoir 9a and carbon dioxide exiting from the expander 5. In the discharge configuration / stage, some of the heat recovered from the expanded carbon dioxide is used to further heat the carbon dioxide after pumping and before expansion (Figure 15, F'1-F'3, D'1-D'2).

[0178] Figures 16 and 17 - Modification of the 6th example Figures 16 and 17 schematically show a sixth modification of Plant 1 (and each method) that differs from the fifth modification of Plant 1 described above in Figures 14 and 15, in that it comprises two compressors 4, 41 and two expanders 5, 43. The second compressors 41, each with a second motor 42, mechanically connected to a motor 6 or, as shown, with a second motor 42, are actually connected in series with the compressor 4, and the second expanders 42, each with a second generator 44, mechanically connected to a generator 7 or, as shown, with a second generator 44, are connected in series with the expanders 5.

[0179] In particular, the outlet 4b of compressor 4 is connected to the inlet 41a of the second compressor 41. The outlet 41b of the second compressor 41 is connected to the regenerator 40. The inlet 43a of the second expander 43 is connected to the regenerator 40, and the outlet 43b of the second expander 43 is connected to the inlet 5a of expander 5.

[0180] The high-temperature first heat reservoir 9a operates operably between the compressor 4 and the second compressor 41, and further between the second compressor 41 and the regenerator 40, during the filling configuration / stage. Thus, during the filling configuration / stage, a first compression (Figure 17, B1-C1) and a subsequent first cooling (Figure 17, C1-B2), then a second compression (Figure 17, B2-C2) and a subsequent second cooling (Figure 17, C2-D1) occur. At the end of the first compression (C1), carbon dioxide is at subcritical pressure (PC1), and at the end of the second compression, carbon dioxide is at a pressure higher than critical pressure (PC2). The temperatures of carbon dioxide at the end of the first and second compressions (TC1, TC2) are similar or equal, and similar or equal to the temperatures of carbon dioxide at the end of the first and second coolings (TB2, TD1).

[0181] The high-temperature first heat reservoir 9a operates operably between the regenerator 40 and the second expander 43, and further between the second expander 43 and the expander 5, during the discharge configuration / stage. Thus, during the discharge configuration / stage, a first heating (Figure 17, D'2-E'1) and a subsequent first expansion (Figure 17, E'1-F'1) occur, followed by a second heating (Figure 17, F1'-E2') and a subsequent second expansion (Figure 17, E'2-F'2). [Explanation of symbols]

[0182] 1 Plant 2 Gas holders 201 Internal membrane 202 Outer membrane 3. Internal gas holder volume 4. Compressor 4a Compressor Inlet 4b Compressor outlet 5. Inflator 5a Inlet of the expansion unit 5b Expansion pump outlet 6 motors 7. Generator 8. First Pipeline 9 Heat accumulator 9a First heat storage unit 9b Second heat reservoir 10. Second Pipeline 11 Mass accumulator 11a Mass accumulator inlet 11b Mass accumulator outlet 12 Internal mass storage volume 13. Third Pipeline 13a First branch of the third pipeline 13b Second branch of the third pipeline 14. Pressure Reducing Device 15 pumps 16 Heat exchange equipment 17 Chiller 18 Auxiliary Chiller 19 Heat accumulator 20 Heat exchanger 21 Heat accumulator circuit 22 Heat exchanger circuit 23 Bypass Circuit 24a First heat exchanger 24b Second heat exchanger 25a First Reservoir 25b Second Reservoir 25c Third reservoir 26 Conduit 27 Auxiliary conduit 28a First pump 28b Second pump 28c Third pump 29a First shut-off control valve 29b Second shut-off control valve 29c Third shut-off control valve 30 Heat transfer device 31 Circuit part 32 Heat exchanger 33 Heat exchange circuit 34 Heat exchanger 35 circuits 36. First additional heat exchanger 37. Second additional heat exchanger 38. First additional heat exchanger circuit 39. Second additional heat exchanger circuit 40 Recuperator 41 Second compressor 41a Second compressor inlet 41b Second compressor outlet 42 Second motor 43. Second Inflator 43a Second expansion chamber inlet 43b Second expansion outlet 44. Second generator

Claims

1. It is a plant for energy management, Working fluids other than the atmosphere, A gas holder (2) that contains, or is configured to contain, the working fluid in the gas phase at a constant first storage pressure (PAG') that is equal to atmospheric pressure or slightly more pressurized than atmospheric pressure, forming an internal boundary of a variable volume (3), A compressor (4; 4, 41) is fluidly connected to the gas holder (2), An expander (5; 5, 43) is fluidly connected to the gas holder (2), A heat storage unit (9; 9a, 9b) is fluidly connected to the compressor (4; 4, 41) and the expander (5; 5, 43) and configured to exchange heat with the working fluid, A mass reservoir (11) that, at a second storage pressure (PA'H), contains or is configured to contain the liquid phase working fluid, forming an internal boundary of a fixed volume (12), wherein the mass reservoir (11) is fluidly connected to the heat reservoir (9; 9a, 9b), A depressurizing device (14) that operates operably between the heat storage device (9; 9a, 9b) and the mass storage device (11), A pump (15) that operates operably between the heat storage unit (9; 9a, 9b) and the mass storage unit (11), A heat exchanger (16) is operably coupled to the mass reservoir (11) and configured to exchange heat with the working fluid in the mass reservoir (11), The system comprises a pipeline and control device configured to operate the plant (1) in a filling configuration and a discharge configuration, In the above-described filling configuration, the working fluid moves from the gas holder (2) to the mass reservoir (11) through the compressor (4; 4, 41), the heat reservoir (9; 9a, 9b), and the depressurizing device (14), and is stored in the mass reservoir (11). The compressor (4; 4, 41) compresses the working fluid to a compression termination pressure (PC; PC2) that exceeds the critical pressure (Pcr) of the working fluid, and the heat reservoir (9; 9a, 9b) compresses the working fluid. The depressurizing device (14) absorbs heat from the fluid and cools the working fluid to a cooling completion temperature (TE) close to the critical temperature (Tcr) of the working fluid, and the depressurizing device (14) reduces the pressure of the working fluid to a reduced pressure (PG) lower than the critical pressure (Pcr) of the working fluid, and the working fluid is stored in the mass reservoir (11) at the second storage pressure (PA'H) lower than the critical pressure (Pcr) of the working fluid and in equilibrium with its own vapor phase. In the aforementioned filling configuration, the heat exchanger (16) removes heat from the mass reservoir (11), condenses a portion of the vapor phase of the working fluid contained in the mass reservoir (11), and maintains the second storage pressure (PA'H) in the mass reservoir (11) at a constant or substantially constant level. In the discharge configuration described above, the working fluid moves from the mass reservoir (11) to the gas holder (2) through the pump (15), the heat reservoirs (9; 9a, 9b), and the expanders (5; 5, 43), and is stored in the gas holder (2). The pump (15) pumps the working fluid at a discharge pressure (PC') higher than the critical pressure (Pcr) of the working fluid. The heat reservoirs (9; 9a, 9b) transfer pre-stored heat to the working fluid to heat it. The expanders (5; 5, 43) expand the working fluid, and the working fluid is stored in the gas holder (2) at the first storage pressure (PAG'). In the discharge configuration described above, the heat exchanger (16) transfers heat to the mass reservoir (11) to evaporate a portion of the liquid phase of the working fluid contained in the mass reservoir (11), thereby maintaining the second storage pressure (PA'H) in the mass reservoir (11) at a constant or substantially constant level.

2. The plant according to claim 1, comprising a chiller (17) operably disposed between the heat storage units (9; 9a, 9b) and the depressurizing device (14), wherein in the filled configuration of the plant (1), the chiller (17) is configured to remove heat from the working fluid entering the depressurizing device (14) in order to reduce and / or remove vapor title of the working fluid at the outlet of the depressurizing device (14).

3. The plant according to claim 1 or 2, further comprising an auxiliary chiller (18) operably disposed between the mass reservoir (11) and the pump (15), wherein the discharge configuration of the plant (1) is configured such that the auxiliary chiller (18) removes heat from the working fluid entering the pump (15) and reduces the risk of cavitation of the pump (15).

4. The plant according to any one of claims 1 to 3, wherein the pressure reducing device (14) comprises a stacked valve.

5. The plant according to claim 4, as dependent on claim 2, wherein the chiller (17) is configured to remove heat from the working fluid entering the stacked valve, and as a result the depressurization end temperature (TG) of the working fluid exiting the stacked valve is lower than the saturation temperature of the working fluid at the reduced pressure (PG).

6. The plant according to any one of claims 1 to 3, wherein the pressure reducing device (14) is equipped with an auxiliary expander.

7. The plant according to claim 6, as dependent on claim 2, wherein the chiller (17) is configured to remove heat from the working fluid entering the auxiliary expander so that the working fluid remains in a subcooled liquid state until it reaches the outlet of the auxiliary expander.

8. The plant according to any one of claims 1 to 7, further comprising a liquid-vapor separator operably disposed between the depressurizing device (14) and the mass reservoir (11).

9. The plant according to any one of claims 1 to 8, wherein the heat exchanger (16) is configured to exchange heat with the external environment, and optionally comprises a heat reservoir (19) configured to exchange heat with the working fluid in the filling configuration and the discharge configuration, and a heat exchanger (20) operably coupled to the heat reservoir (19) and the external environment.

10. The plant according to claim 9, as dependent on any one of claims 2, 5, or 7, wherein the chiller (17) is operably connected to the heat exchanger (16).

11. The plant according to any one of claims 1 to 10, wherein the heat storage units (9; 9a, 9b) comprise a high-temperature first heat storage unit (9a) and a low-temperature second heat storage unit (9b), and in the packed configuration, the high-temperature first heat storage unit (9a) cools the working fluid to an intermediate temperature (TD; TD1) higher than the critical temperature (Tcr), and the low-temperature second heat storage unit (9b) cools the working fluid from the intermediate temperature (TD1) to the cooling completion temperature (TE) close to the critical temperature (Tcr).

12. The plant according to claim 11, wherein the ratio of the intermediate temperature (TD) in Kelvin to the critical temperature (Tcr) in Kelvin is 1.01 to 2.0, and the ratio of the cooling completion temperature (TE) in Kelvin to the critical temperature (Tcr) in Kelvin is 0.4 to 1.

1.

13. The plant according to claim 11 or 12, comprising a first heat exchanger (24a) and a second heat exchanger (24b) configured to exchange heat with the working fluid, a first reservoir (25a) at a low temperature, a second reservoir (25b) at an intermediate temperature, and a third reservoir (25c) at a high temperature that contains water at ambient pressure and is fluidly connected to the first heat exchanger (24a) and the second heat exchanger (24b), wherein the first heat exchanger (24a) and the second heat exchanger (24b) are arranged in series on a working fluid pipeline, and the water flow rates of the first heat exchanger (24a) and the second heat exchanger (24b) are different.

14. The plant according to any one of claims 1 to 13, wherein the cooling completion temperature (TE) in the filling configuration is higher than the pump discharge temperature (TC') in the discharge configuration.

15. The plant according to any one of claims 1 to 14, comprising a heat transfer device (30) operably coupled to a working fluid line located downstream of the expander (5; 5, 43) and a working fluid line located downstream of the pump (15), wherein in the discharge configuration, the heat transfer device (30) is configured to transfer a portion of the heat discharged from the expander (5; 5, 43) to the working fluid in a supercritical state.

16. The plant according to claim 15, in which the heat transfer device (30) is connected to the low-temperature second heat storage device (9b), as dependent on any one of claims 11 to 13.

17. The plant according to claim 15, as dependent on claim 13, wherein the heat transfer device (30) is fluidly connected to the first heat exchanger (24a) and the second heat exchanger (24b), or the heat transfer device (30) is fluidly connected to an additional heat exchanger arranged in parallel with the first heat exchanger (24a) and the second heat exchanger (24b).

18. The plant according to any one of claims 15 to 17, wherein the heat transfer device (30) is also operably coupled to the heat exchange device (16) to remove excess heat.

19. The plant according to claim 18, as dependent on claim 16 or 17, wherein the heat transfer device (30) is operably coupled to the heat exchange device (16) via the low-temperature second heat storage device (9b).

20. The plant according to any one of claims 1 to 19, further comprising a first additional heat exchanger (36) positioned between the gas holder (2) and the inlet (4a) of the compressor (4) and configured to adjust the compressor inlet temperature (TB; TB1), wherein the first additional heat exchanger (36) is optionally operably connected to the heat exchanger (16).

21. The plant according to any one of claims 1 to 20, further comprising a second additional heat exchanger (37) positioned between the outlet (5b) of the expander (5) and the gas holder (2), and configured to adjust the gas holder inlet temperature (TG'), wherein the second additional heat exchanger (37) is optionally operably connected to the heat exchanger (16).

22. The plant according to any one of claims 1 to 21, comprising a reheater (40) that operates both between the gas holder (2) and the compressor (4; 4, 41) and between the gas holder (2) and the expander (5; 5, 43), wherein the reheater (40) is further operably coupled to the heat storage unit (9; 9a, 9b), and the reheater (40) is configured to exchange heat between the working fluid flowing through the heat storage unit (9; 9a, 9b) and the working fluid entering the compressor (4; 4, 41) in the filling configuration, or the working fluid leaving the expander (5; 5, 43) in the discharge configuration.

23. The plant according to claim 22, as dependent on any one of claims 11, 12, or 13, wherein the reheater (40) is operably interposed between the first high-temperature heat storage unit (9a) and the second low-temperature heat storage unit (9b), and the reheater (40) is configured to exchange heat between the working fluid flowing between the first high-temperature heat storage unit (9a) and the second low-temperature heat storage unit (9b) and the working fluid entering the compressor (4; 4, 41) in the filling configuration, or the working fluid leaving the expander (5; 5, 43) in the discharge configuration.

24. The plant according to any one of claims 11, 12, or 13 or claim 23, comprising a second compressor (41) connected in series with the compressor (4) and a second expander (43) connected in series with the expander (5), wherein the high-temperature first heat reservoir (9a) operates operably between the compressor (4) and the second compressor (41) and further downstream of the second compressor (41) in the filling configuration, and the high-temperature first heat reservoir (9a) operates operably upstream of the second expander (43) and further between the second expander (43) and the expander (5) in the discharge configuration.

25. A method for energy management, A step of performing a closed thermodynamic cycle conversion (TTC) between a gas holder (2) for storing a working fluid other than air in the gas phase at a first storage pressure (PAG') in equilibrium with atmospheric pressure and a mass reservoir (11) for storing the working fluid in the liquid phase at a second storage pressure (PA'H), the step comprising: in the filling step, the method stores heat and pressure; and in the release step, the method generates energy using the previously stored heat and pressure. In the filling step, the method is The method includes the steps of: compressing the working fluid to a compression termination pressure (PC; PC2) higher than the critical pressure (Pcr) of the working fluid; cooling the working fluid to a cooling termination temperature (TE) close to the critical temperature (Tcr) of the working fluid by storing the heat removed from the working fluid; reducing the pressure of the working fluid to a reduced pressure (PG) lower than the critical pressure (Pcr) of the working fluid; and storing the working fluid in the mass reservoir (11) at a second storage pressure (PA'H) lower than the critical pressure (Pcr) of the working fluid and in equilibrium with its own vapor phase, wherein in the filling step, the method also includes the steps of removing heat from the mass reservoir (11) to condense a portion of the vapor phase of the working fluid contained in the mass reservoir (11), and keeping the second storage pressure (PA'H) in the mass reservoir (11) constant or substantially constant. In the discharge step, the method is A method comprising the steps of pumping the working fluid at a release pressure (PC') higher than the critical pressure (Pcr) of the working fluid, transferring pre-stored heat to the working fluid, heating the working fluid, expanding the working fluid, and storing it in the gas holder (2) at the first storage pressure (PAG'), wherein in the release step, the method further comprises the steps of transferring heat to the mass accumulator (11) to evaporate a portion of the liquid phase of the working fluid contained in the mass accumulator (11), and maintaining the second storage pressure (PA'H) in the mass accumulator (11) constant or substantially constant.

26. The method according to claim 25, wherein, after cooling the working fluid to the end-of-cooling temperature (TE) near the critical temperature (Tcr), and before reducing the pressure of the working fluid to the reduced pressure (PG), the method in the filling step includes a step of removing heat from the working fluid to reduce and / or remove the vapor title of the working fluid at the end of depressurization.

27. The method according to claim 25 or 26, wherein the method in the discharge step includes a step of removing heat from the working fluid to reduce the risk of cavitation in the subsequent pumping, before pumping the working fluid.

28. The method according to any one of claims 25 to 26, wherein the step of reducing the pressure of the working fluid in the filling step includes stacking the working fluid.

29. The method of claim 28, as dependent on claim 26, wherein the step of removing heat from the working fluid in order to reduce and / or remove the vapor title of the working fluid at the end of the depressurization is to bring the working fluid to a depressurization end temperature (TG) that is lower than the saturation temperature of the working fluid at the reduced pressure (PG).

30. The method according to any one of claims 25 to 26, wherein the step of reducing the pressure of the working fluid in the filling step includes causing the working fluid to undergo auxiliary expansion.

31. The method of claim 30, as dependent on claim 26, wherein the step of removing heat from the working fluid to reduce and / or remove the vapor title of the working fluid at the end of depressurization includes removing heat from the working fluid before the auxiliary expansion so that the working fluid remains in a subcooled liquid state during and at the end of the auxiliary expansion.

32. The method according to any one of claims 25 to 31, wherein the steps of removing heat from the mass reservoir (11) and / or transferring heat to the mass reservoir (11) include directly or indirectly exchanging heat with the external environment.

33. The method according to any one of claims 25 to 32, wherein each of the operations of cooling the working fluid in the filling stage and heating the working fluid in the discharge stage is performed in two stages, and in the filling stage, in the first stage the working fluid is cooled to an intermediate temperature (TD) above the critical temperature (Tcr), and in the second stage the working fluid is cooled from the intermediate temperature (TD) to the cooling completion temperature (TE) close to the critical temperature (Tcr).

34. The method according to claim 33, wherein the ratio of the intermediate temperature (TD) in Kelvin to the critical temperature (Tcr) in Kelvin is 1.01 to 2.0, and the ratio of the cooling completion temperature (TE) in Kelvin to the critical temperature (Tcr) in Kelvin is 0.4 to 1.

1.

35. The method according to any one of claims 25 to 34, wherein the cooling completion temperature (TE) in the filling stage is higher than the pump discharge temperature (TC') in the discharge stage.

36. The method according to any one of claims 25 to 35, further comprising the step of transferring a portion of the heat of the expanded working fluid to the working fluid in a supercritical state before or during heating in the discharge step.

37. The method according to claim 36, further comprising the step of releasing excess heat from a portion of the transferred heat into the external environment.

38. The method according to any one of claims 25 to 37, further comprising the step of adjusting the temperature (TA) of the working fluid from the gas holder (2) before compression in the filling step.

39. The method according to any one of claims 25 to 38, further comprising the step of adjusting the temperature (TF') of the working fluid that has expanded before entering the gas holder (2) during the discharge step.

40. The method according to any one of claims 25 to 39, comprising the steps of: heating the working fluid before compression using a portion of the heat removed from the working fluid during cooling to the cooling end temperature (TE) in the filling stage; and / or further heating the working fluid after pressurization and before expansion using a portion of the heat recovered from the expanded working fluid in the discharge stage.

41. The method according to claim 25 or 40, wherein the step of compressing and cooling the working fluid in the filling step comprises performing a first compression, followed by a first cooling, then a second compression, followed by a second cooling, wherein at the end of the first compression the working fluid is at a subcritical pressure (PC1), and at the end of the second compression the working fluid is at a pressure (PC2) above the critical pressure (Pcr), and the temperatures (TC1, TC2) of the working fluid at the end of the first and second compressions are the same or equal.

42. The method according to any one of claims 25 to 41, wherein the step of heating and expanding the working fluid in the discharge step includes performing a first heating followed by a first expansion, and then performing a second heating followed by a second expansion.

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