System and method for storing and recovering energy with assistance for starting the compression means

Abstract

The invention relates to a system for storing and recovering energy using compressed gas, comprising: - a compression line (1) with at least one compression stage (3), each comprising a compression means (100, 101, 102) and at least two means (200A, 200B, 201A, 201B, 202A, 202B) for storing and recovering heat, in parallel; - at least two means (1000A, 1000B) for storing compressed gas, in parallel; and - an expansion line (2) comprising at least one expansion stage (4) and pipes for circulating the compressed gas in the means (200A, 200B, 201A, 201B, 202A, 202B) for storing and recovering heat. Furthermore, the system for storing and recovering energy comprises at least one mechanical connection / disconnection means (C) for connecting / disconnecting at least one compression means (100, 101, 102) of a compression stage to / from at least one expansion means (700, 701, 702) of an expansion stage.

Description

[0001] SYSTEM AND METHOD FOR STORING AND RECOVERING ENERGY WITH

[0002] ASSISTANCE IN STARTING UP COMPRESSION MEANS

[0003] Technical field

[0004] The present invention relates to the technical field of storage and recovery of energy by compressed gas, in particular compressed air.

[0005] While global energy targets aim to promote renewable energy in order to gradually increase the proportion of renewable energy in the energy mix, the variable nature of these renewable energies remains their major drawback. To address this problem, energy storage appears to be a very advantageous solution. By storing the surplus energy produced at peak production in order to use it when it falls below demand, storage overcomes the variability constraint and provides flexibility, even continuity, to renewable energies. Thus, the need for energy storage processes and systems is expected to increase in the coming years, with the proportion of renewable energy in the global mix.

[0006] Many storage technologies currently exist, such as mechanical storage systems such as Pumped Storage Stations (PSSTs) that use hydroelectricity produced by two water reservoirs located at different altitudes. In the electricity storage phase, water from the lower reservoir is pumped to the upper reservoir and stored at that altitude. When electricity demand increases, the water from the upper reservoir is returned to the lower reservoir through a hydraulic turbine, which then generates electricity via an alternator. Hydroelectric dams also operate on the same concept: the dam retains water at a higher altitude upstream than downstream, and when electricity demand increases, the dam releases the water by passing it through hydraulic turbine generators, producing electricity.

[0007] Electrochemical technologies can also be used for energy storage, such as lithium-ion, lead-acid or nickel-cadmium batteries, or flow batteries.

[0008] Compressed air energy storage and recovery, known as CAES (Compressed Air Energy Storage), is a technology for which the first installation was built in Germany in the late 1970s, with a capacity of 290 MW. The principle of this technology is to use the electricity produced but not consumed to compress a gas, typically air. To avoid any damage to the compressors, the heat resulting from compression is removed between each stage. The compressed air at medium or high pressure (40 bar to 300 bar, or 4 to 30 MPa) is sent to a natural storage type such as a saline cavity, a mine (salt, limestone, coal) or even to an artificial storage while waiting for the energy discharge phase. During the electricity production phase, the stored air is extracted from the storage to be expanded in turbo-alternators.

[0009] A variant of CAES technology is the adiabatic process, also called AACAES (Advanced Adiabatic Compressed Air Energy Storage). The main difference with CAES is that the heat resulting from compression is no longer simply evacuated between each stage, i.e. lost, but stored in order to heat the air upstream of the turbines in the energy recovery phase. Thanks to this reuse of thermal energy internal to the process, the efficiency of AACAES can reach around 70% instead of around 50% for the CAES process. The air can be cooled during compression in a heat exchanger with a heat transfer fluid. The hot heat transfer fluid will then be stored in order to release its heat to the air during the expansion phase.

[0010] Prior art

[0011] Patent application FR 31 17165 A1 (WO2022 / 117398) relates to an AACAES system.

[0012] Figure 1 illustrates, schematically in the form of a block diagram, such an AACAES system and method. In this figure, the energy storage phase by compression of a gas, and the energy production phase by expansion of a gas are represented. The system according to the prior art consists of a compression line (1), including one or more compression stages (3) depending on the air pressure to be achieved as well as the suppliers' recommendations. In the illustrated embodiment, the compression line (1) comprises three compression stages (3). Each compression stage (3) comprises a compression means (100, 101, 102), also called a compressor. The compressor (100) is a low-pressure compressor, the compressor (101) is a medium-pressure compressor, and the compressor (102) is a high-pressure compressor.The gas used (10) in the illustrated process is ambient air, containing a water saturation linked to its temperature and pressure. During the energy storage phase, the air is compressed in the compression line (1) then sent to a compressed air storage means (1000) suitable for high pressures. Heat storage and recovery means (200, 201, 202) are arranged after each compressor (100, 101, 102) of each compression stage (3) in order to cool the hot compressed air at the compression outlet while storing this thermal energy. The heat storage and recovery means (200) is suitable for low pressure, the heat storage and recovery means (201) is suitable for medium pressure and the heat storage and recovery means (202) is suitable for high pressure.Cooling means (300, 301, 302) may be arranged after the heat storage and recovery means (200, 201, 202) if necessary in order to finish cooling the compressed air before the next compression stage or before its storage. Once the air has been cooled and before the next compression stage, the condensed water, resulting from the humidity of the air, is extracted from the air compression flow by gas-liquid separators (400, 401, 402) in order to have at the compressor inlet air without any trace of liquid water. This condensation of the water may take place in the heat storage and recovery means (200, 201, 202) and / or in the cooling means (300, 301, 302).During the energy production phase, the compressed air is expanded via one or more turbines (700, 701, 702) or expansion stages, according to the suppliers' recommendations, in order to produce electricity via alternators, not shown in the diagram. Turbine (702) is a low pressure turbine, turbine (701) is a medium pressure turbine and turbine (700) is a high pressure turbine.

[0013] AACAES systems are designed for high power outputs in the order of several megawatts. Therefore, the compressors must be powered by electric motors of several megawatts. Starting electric motors of this power is difficult. This is generally achieved by using an electronic soft starter or a starter with a frequency converter. In both cases, a significant delay (at least half an hour) is required to reach the compressor's nominal point. In addition, an investment in dedicated start-up equipment is also required. Thus, starting the compressors leads to high energy consumption and start-up difficulties.

[0014] Summary of the invention

[0015] The object of the invention is to facilitate the start-up of compressors, by accelerating start-up, and to limit the start-up energy consumption.

[0016] The invention relates to a compressed gas energy storage and recovery system comprising:

[0017] - a gas compression line with at least one compression stage, each compression stage comprising a compression means and at least two heat storage and recovery means downstream, in the direction of gas circulation, of said compression means, the at least two heat storage and recovery means being mounted in parallel,

[0018] - at least two compressed gas storage means located at the outlet of the gas compression line for storing the compressed gas, said at least two compressed gas storage means being mounted in parallel, - an expansion line for expanding compressed gas stored in the compressed gas storage means, the expansion line comprising at least one expansion stage, each expansion stage comprising pipes and an expansion means, the pipes being configured to circulate the compressed gas in said at least two heat storage and recovery means of the same compression stage so as to heat the compressed gas before the expansion means.

[0019] In addition, the energy storage and recovery system comprises at least one mechanical connection / disconnection means for connecting / disconnecting at least one compression means of a compression stage to at least one expansion means of an expansion stage, preferably to a single expansion means of an expansion stage.

[0020] Preferably, the system comprises as many compression stages as expansion stages.

[0021] Advantageously, each compression stage of the compression line is defined by a passage number (or passage order), the passage number corresponding to the order of passage of the compressed gas in this compression stage within the compression line, for which each expansion stage of the expansion line is defined by an outlet number, the outlet number corresponding to the order of this expansion stage within the expansion line, in the opposite direction to the passage of the compressed gas in the expansion line and for which each connection / disconnection means is configured to connect / disconnect the compression means of the compression stage of the defined passage number by means of the stage of the expansion stage of the defined outlet number, the defined passage number being equal to the outlet number.

[0022] Preferably, the compression line comprises three compression stages and the expansion line comprises three expansion stages.

[0023] Advantageously, the system comprises a first connection / disconnection means for the connection between the compression means of the last compression stage and the expansion means of the first expansion stage, a second connection / disconnection means for the connection between the compression means of the intermediate compression stage and the expansion means of the intermediate expansion stage and a third connection / disconnection means for the connection between the compression means of the first compression stage and the expansion means of the last expansion stage.

[0024] According to a variant of the invention, the at least one connection / disconnection means comprises a shaft for mechanically connecting at least one compression means to at least one expansion means.

[0025] Preferably, the at least one connection / disconnection means comprises a clutch. According to a configuration of the invention, each compression stage comprises a cooling means downstream of said at least two heat storage and recovery means and preferably a gas / liquid separation means, downstream of the cooling means.

[0026] Advantageously, at least one expansion means, preferably each expansion means, is connected to an electrical machine capable of generating electricity in the expansion phase and capable of participating in the starting of the compression means at the start of the compression phase.

[0027] According to a variant of the invention, first valves and / or second valves are positioned upstream and / or downstream of each heat storage and recovery means.

[0028] Preferably, first and second opening / closing means are positioned upstream and / or downstream of each compressed gas storage means.

[0029] The invention also relates to a method for storing and recovering energy using compressed gas, in which a compressed gas energy storage and recovery system is used according to one of the variants or combinations of variants described above, and in which at least the following steps are carried out:

[0030] - In the expansion phase, the compressed gas from said at least two compressed gas storage means is expanded and the expansion phase is stopped when the compressed gas pressure in at least one of said at least two compressed gas storage means reaches a predetermined pressure and / or when the outlet temperature of at least one of the heat storage and recovery means reaches a predefined temperature;

[0031] - At the time of starting the compression phase, the compressed gas remaining in at least one of said at least two compressed gas storage means is transferred into the expansion line and, in each expansion stage, the remaining heat is recovered from said heat storage and recovery means before passing the compressed gas into the expansion means, the expansion means then being mechanically connected to a compression means of a compression stage, by means of a connection / disconnection means; then when the compression phase has started and once the compressed gas is completely discharged from said at least two compressed gas storage means, the disconnection of each connection / disconnection means is activated so as to mechanically disconnect the compression means from the associated expansion means and the compression means are then driven by an electric motor.

[0032] Advantageously, before mechanically activating the disconnection of each connection / disconnection means, the heat contained in the heat storage and recovery means is discharged.

[0033] Preferably, when starting the compression phase, alternatively or in addition to the use of the compressed gas leaving the compressed gas storage means, each electrical machine connected to the expansion means is used to participate in starting the compression means.

[0034] List of figures

[0035] Other characteristics and advantages of the device and / or system according to the invention will appear on reading the following description of non-limiting examples of embodiments, with reference to the figures appended and described below.

[0036] Figure 1 (already described) represents a compressed gas energy storage and recovery system according to the prior art.

[0037] Figure 2 represents a compressed gas energy storage and recovery system according to the invention.

[0038] Figure 3 represents the compressed gas energy storage and recovery system according to the invention of Figure 2 in the start-up phase of the compression means.

[0039] Description of the embodiments

[0040] The invention relates to a system for storing and recovering energy using compressed gas (in particular air and more particularly air taken from the ambient environment) comprising:

[0041] - a gas compression line with at least one compression stage, each compression stage comprising a compression means and at least two heat storage and recovery means downstream, in the direction of gas circulation, of said compression means, the at least two heat storage and recovery means being mounted in parallel;

[0042] - at least two compressed gas storage means located at the outlet of the gas compression line for storing the compressed gas, said at least two compressed gas storage means being mounted in parallel;

[0043] - an expansion line for expanding compressed gas stored in the compressed gas storage means, the expansion line comprising at least one expansion stage, each expansion stage comprising pipes and an expansion means, the pipes being configured to circulate the compressed gas in said at least two heat storage and recovery means of the same compression stage so as to heat the compressed gas before the expansion means.

[0044] Thus, the compression line allows gas to be compressed when electricity production is higher than demand, the compressed gas can then be used to supply electricity when electricity demand is high. The compression line therefore allows energy to be stored by compressed gas (in particular by compressed air, the air being advantageously taken from the ambient environment).

[0045] The expansion line allows the stored compressed gas to be transformed into mechanical energy, for example rotary energy, via the expansion means (a turbine for example) of each expansion stage. Advantageously, the expansion means can be coupled to a generator (also called an alternator) to transform the mechanical energy into electricity.

[0046] In the compression line as in the expansion line, the different stages (compression or expansion respectively) are successive, that is to say they are positioned in series, one after the other in the direction of circulation of the gas in the compression or expansion line respectively.

[0047] The first stage of compression or expansion is called the first stage of the line in question through which the gas passes in the direction of circulation of the compressed gas in the system.

[0048] The last stage of compression or expansion is called the last stage of the line considered through which the gas passes in the direction of circulation of the compressed gas in the system.

[0049] Each heat storage and recovery means allows the recovery of thermal energy in addition to the energy from the compressed gas, which improves the efficiency of the system, as the thermal energy is recovered by the compressed gas during the expansion phase. The heat storage and recovery means can be direct or indirect heat storage and recovery means.

[0050] By "direct heat storage and recovery means" is meant that this heat storage and recovery means allows a direct heat exchange between the compressed gas (the heat of which is to be recovered in the compression phase and which is to be reheated in the expansion phase) and a heat storage material (which may be liquid, gaseous or solid, such as beads or gravel in particular). In other words, it may be a direct heat exchanger between the compressed gas and a heat storage and recovery material, such as a tank containing beads or gravel of a heat storage material.

[0051] By "indirect heat storage and recovery means" is meant that this heat storage and recovery means allows an indirect heat exchange between the compressed gas (the heat of which is to be recovered in the compression phase and which is to be reheated in the expansion phase) and a heat storage material (advantageously liquid or gaseous fluid). The heat storage material is separated from the compressed gas by a wall which thus prevents the direct heat exchange between these two elements, hence the name "indirect exchange". In other words, it may be an indirect heat exchanger such as a tube or plate exchanger, to allow the heat exchange between the compressed gas and a heat storage and recovery fluid.

[0052] The means of storing compressed gas may be an artificial reservoir or more advantageously an underground cavity, such as a salt cavern, an old mine or an aquifer.

[0053] Preferably, the system may comprise as many compression stages as expansion stages. Thus, the heat storage and recovery means of each compression stage may be used in one (and only one) expansion stage, preferably working at substantially the same pressure level. Alternatively, the system may comprise a number of compression stages different from the number of expansion stages.

[0054] According to the invention, the energy storage and recovery system comprises at least one mechanical connection / disconnection means for mechanically connecting / disconnecting at least one compression means (preferably each compression means) of a compression stage to at least one expansion means of an expansion stage, preferably to a single expansion means of an expansion stage. The connection / disconnection means may in particular mechanically connect / disconnect a shaft of the compression means to a shaft of the expansion means, so that one of these shafts drives the other in rotation.

[0055] Several configurations can be considered:

[0056] - A single expansion means can be coupled or decoupled to a single compression means by the connection / disconnection means;

[0057] - Several expansion means can be coupled or decoupled to a single compression means by at least one connection / disconnection means (one connection / disconnection means for each expansion means for example);

[0058] - A single expansion means can be coupled or decoupled to several compression means by the connection / disconnection means (one connection / disconnection means for each compression means for example).

[0059] - Several expansion means can be coupled or decoupled to several compression means by the connection / disconnection means (one connection / disconnection means for each compression means and / or for each expansion means for example).

[0060] In addition, the system may comprise several of the above configurations, for example, one compression means coupled / decoupled to a single turbine and two other compression means may be coupled / decoupled to two other turbines (or to a single turbine). By means of the connection / disconnection means, at least one compression means may be coupled to at least one (associated) expansion means which makes it possible to facilitate the starting of the compression means with which it is associated. In other words, the expansion means causes the compression means to start via the connection / disconnection means. This configuration also makes it possible to start the compression means quickly (in less than 2 minutes for example).

[0061] The connection / disconnection means also allows the compression means to be disconnected from the expansion means to which it can be connected, when the compressor start-up phase is complete. This allows the heat to be stored in the two heat storage and recovery means of each compression stage and in the two compressed gas storage means. This disconnection allows the compression phase to continue, independently of the expansion (and vice versa).

[0062] Preferably, each connection / disconnection means may be configured to couple / decouple at least one compression means to at least one expansion means which operates at substantially the same torque and / or power and / or rotational speed.

[0063] According to an advantageous configuration of the invention, each compression stage of the compression line may be defined by a passage number (or order) corresponding to the order of passage of the compressed gas in this compression stage within the compression line, and each expansion stage of the expansion line may be defined by an outlet number corresponding to the order of this expansion stage within the expansion line, in the opposite direction to the passage of the compressed gas in the expansion line. In addition, each connection / disconnection means may be configured to connect / disconnect the compression means of the compression stage of the defined passage number to the expansion means of the expansion stage of the defined outlet number, the defined passage number being equal to the outlet number.Thus, each compression means can be connected to an expansion means operating at substantially the same torque and / or the same power, preferably with substantially the same pressure (at the same pressure level) of the compressed gas, and therefore substantially the same rotational speed. Indeed, in the compression line, the pressure increases in each successive compression stage while in the expansion line, the pressure gradually decreases in each successive expansion stage (in the direction of circulation of the gas in the expansion line and in the compression line).

[0064] Preferably, the compression line may comprise three compression stages and the expansion line may comprise three expansion stages. This configuration generally allows good system efficiency while limiting the number of compression and expansion stages. It therefore offers a good compromise between performance and size / weight.

[0065] For this variant, the system may comprise a first connection / disconnection means for the connection between the compression means of the last compression stage (i.e. the compression stage whose passage number is three) and the expansion means of the first expansion stage (i.e. the expansion stage whose output number is three),a second connection / disconnection means for the connection between the compression means of the intermediate compression stage (i.e. the compression stage whose passage number is two) and the expansion means of the intermediate expansion stage (i.e. the expansion stage whose output number is two) and a third connection / disconnection means for the connection between the compression means of the first compression stage (i.e. the compression stage whose passage number is one) and the expansion means of the last expansion stage (i.e. the expansion stage whose output number is one). Thus, each compression means can be connected to an expansion means operating at substantially the same torque and / or power, preferably with substantially the same compressed gas pressure, and therefore substantially the same rotational speed. Indeed,the first compression means and the last expansion means operate substantially at low pressure, the intermediate compression means and expansion means operate substantially at medium pressure and the last compression means and the first expansion means operate substantially at high pressure, the terms "low", "medium" and "high" being relative between the different compression and expansion stages respectively.,

[0066] Preferably, at least one (preferably each) connection / disconnection means may comprise a shaft for mechanically connecting at least one compression means to at least one expansion means. The shaft provides a mechanical connection capable of transmitting the high powers required to drive the compression means, while limiting efficiency losses.

[0067] Advantageously, at least one (preferably each) connection / disconnection means may comprise a clutch which makes it possible to connect or disconnect each compression means to the expansion means(s) to which it can be connected / disconnected. The clutch provides a reliable connection capable of transmitting the power necessary to drive the compression means.

[0068] Preferably, the clutch may be mounted on a shaft connected to one of said compression or expansion means and the clutch may be connected to the other of said compression or expansion means. Thus, the connection / disconnection means is simple and robust. Advantageously, the shaft may be short (of short length, for example whose length is less than or equal to 3 times its diameter) so as to increase its reliability and limit the risk of failures.

[0069] According to an advantageous configuration of the invention, each compression stage may comprise a cooling means downstream (in the direction of circulation of the compressed gas) of said at least two heat storage and recovery means so as to cool the gas as much as possible before it enters the next compression stage or the compressed gas storage means. In addition, each compression stage may also comprise a gas / liquid separation means, downstream (in the direction of circulation of the compressed gas) of the cooling means. Indeed, during the cooling of the compressed gas, condensation may appear. This water, in liquid form, may come from the water vapor initially contained in the sampled gas, in particular if it is ambient air, and it may damage the compression means of the next stage or the compressed gas storage means, in particular if it is a compressor.The gas / liquid separation method then makes it possible to eliminate the liquid phase contained in the compressed gas.

[0070] Preferably, at least one expansion means, preferably each expansion means, can be connected to an electrical machine capable of generating electricity in the expansion phase and capable of participating in the starting of the compression means at the start of the compression phase. Thus, each electrical machine can participate, in motor mode, in driving a compression means to facilitate their starting.

[0071] According to an advantageous variant of the invention, first valves and / or second valves can be positioned upstream and / or downstream of each heat storage and recovery means, so as to allow or not the passage of compressed gas into the heat storage and recovery means and to allow or not this passage into the expansion line or into the compression line, the heat storage and recovery means being used both for storage in the compression phase and for energy recovery in the expansion phase.

[0072] Preferably, the first and / or second valves may comprise three-position valves for directing gas from the compression line or from the expansion line and / or to the compression line or to the expansion line.

[0073] Alternatively or additionally, first and second opening / closing means (which may also be third and fourth valves respectively) may be positioned upstream and / or downstream of each compressed gas storage means, so as to allow or not allow the passage of compressed gas into the compressed gas storage means and to allow or not allow this passage arriving from the compression line or leaving towards the expansion line, the compressed gas storage means being used both for storage in the compression phase and for energy recovery in the expansion phase.

[0074] The invention also relates to a method for storing and recovering energy using compressed gas, in which a compressed gas energy storage and recovery system is used according to one of the variants or combinations of variants described above. The method may in particular comprise a compression step, a compressed gas storage step and an expansion step. In addition, in this method, the heat from the gas generated during the compression step is recovered and the heat thus recovered is used to reheat the gas before expanding it during the expansion phase. In this method, at least the following steps are carried out:

[0075] - In the expansion phase, the compressed gas from said at least two compressed gas storage means is expanded and the expansion phase is stopped when the compressed gas pressure in at least one of said at least two compressed gas storage means reaches a predetermined pressure and / or when the outlet temperature of at least one of the heat storage and recovery means reaches a predefined temperature;

[0076] - At the time of starting the compression phase, the compressed gas remaining in at least one of said at least two compressed gas storage means is sent into the expansion line and, in each expansion stage, the remaining heat is recovered from at least one of said heat storage and recovery means before passing the compressed gas into the expansion means of this expansion stage, the expansion means then being mechanically connected to a compression means of a compression stage, by means of a connection / disconnection means;the compressed air leaving each compression means then passes into the at least one other heat storage and recovery means, so that each heat storage and recovery means is dedicated either to operation on the expansion line or to operation on the compression line then when the compression phase has started and preferably once the compressed gas is completely discharged from said at least two compressed gas storage means, the disconnection of each connection / disconnection means is activated so as to mechanically disconnect the compression means from the associated expansion means and the compression means are then driven by an electric motor mechanically connected to the compression means.;

[0077] By this process, we take advantage of a part of the compressed gas remaining in one of the two compressed gas storage means and a part of the heat remaining in one of the two heat storage and recovery means of each compression stage, to power the turbines which will help to drive the rotation of the compression means to facilitate their start-up and to accelerate it.

[0078] Advantageously, before mechanically activating the disconnection of each connection / disconnection means, the heat contained in the heat storage and recovery means can be discharged, so as to recover all the thermal energy from the compression phase.

[0079] Preferably, when starting the compression phase, alternatively or additionally to the use of the compressed gas leaving the compressed gas storage means, each electrical machine connected to the expansion means, connected to the associated compression means by the connection / disconnection means, can be used to participate in the starting of the compression means.

[0080] Figure 2 illustrates, in a schematic and non-limiting manner, a system for storing and producing energy using compressed air according to the invention.

[0081] The system comprises a compression line (1), with several compression stages (3), here three compression stages but a different number could be used, each compression stage (3) comprising a compression means (100, 101, 102) (which can be compressors in particular). The number of compression stages can be a function of the air pressure to be achieved as well as the suppliers' recommendations. The compression means (100, 101, 102) can be axial or centrifugal compressors for example. The compression means (100) is here a low pressure compressor, the compression means (101) is here a medium pressure compressor and the compression means (102) is here a high pressure compressor. The compressed gas (10) in the process is ambient air, containing a water saturation linked to its temperature and pressure but another gas could of course be used.

[0082] In the compression line (1), the gas is compressed and then sent to two compressed gas storage means (1000A) and (1000B). These compressed gas storage means (1000A) and (1000B) are arranged in parallel and are suitable for high pressures. These compressed gas storage means (1000A) and (1000B) can be natural cavities such as a salt cavity, an old mine or an aquifer or even artificial storage, such as reservoirs.

[0083] After each compression means (100, 101, 102), at least two heat storage and recovery means (200A, 200B, 201A, 201B, 202A, 202B) are arranged in parallel in order to cool the hot compressed air at the compression outlet while storing this thermal energy. The heat storage and recovery means (200A and 200B) are suitable for low pressure, the heat storage and recovery means (201A and 201B) are suitable for medium pressure and the heat storage and recovery means (202A and 202B) are suitable for high pressure. The exchange / storage of thermal energy can be carried out by direct contact between the hot compressed gas and an inert material or by indirect contact between the hot compressed air and a fluid, gas or liquid, or a solid. In the case of direct contact, the material can be stones, concrete, gravel or any other suitable solid material.In the case of indirect contact, the exchange fluid can be any heat transfer fluid suitable for the temperature and pressure conditions.

[0084] Cooling means (300, 301, 302) may be arranged after the heat storage and recovery means (200A, 200B, 201A, 201B, 202A, 202B) if necessary in order to finish cooling the compressed gas before the next compression stage or before its storage. Once the gas has been cooled and before the next compression stage, the condensed water, resulting from the humidity of the gas (in particular when it is ambient air), is extracted from the air compression flow by gas-liquid separation means (400, 401, 402) (separators for example) in order to have at the inlet of the compression means of the next compression stage or of the compressed gas storage means a gas without the presence of liquid, in particular without liquid water. This condensation of water can take place in the heat storage and recovery means (200A, 200B, 201 A, 201 B, 202A, 202B) and / or in the cooling means (300, 301, 302).

[0085] The system comprises an expansion line (2), with several expansion stages (4), here three expansion stages but a different number could be used provided that it is identical to the number of compression stages.

[0086] Each expansion stage (4) comprises an expansion means (700, 701, 702). The expansion means (700) is here a high pressure turbine, the expansion means (701) is here a medium pressure turbine and the expansion means (702) is here a low pressure turbine.

[0087] In the expansion line (2), the compressed gas is expanded via the expansion means (700, 701, 702) of the expansion stages (4), in order to produce electricity via alternators, not shown in the diagram, an alternator (an electrical machine) being connected to each expansion means (700, 701, 702). Connection / disconnection means C make it possible to couple or decouple each compression means and each associated expansion means at the same pressure level. These connection / disconnection means C may in particular comprise a connecting shaft and a clutch. The low pressure compression means (100) is connected by a first connection / disconnection means C to the low pressure expansion means (702), the medium pressure compression means (101) is connected by a second connection / disconnection means C to the medium pressure expansion means (701).The high-pressure compression means (102) is connected by a third connection / disconnection means C to the high-pressure expansion means (700). In order to improve the efficiency of each expansion means, the thermal energy stored in the heat storage and recovery means (200A, 200B, 201A, 201B, 202A, 202B) is returned to the gas flow upstream of each expansion means in accordance with its pressure range. At the end of the expansion phase preceding the compression phase, the compressed gas storage means (1000A) is discharged of the compressed gas it contains and the compressed gas storage means (1000B) is partially discharged of its compressed gas: in other words, a reserve of compressed gas is kept in only one of the two compressed gas storage means so that it can be used to start the compression means during the next compression phase.In the same way, the first heat storage and recovery means (200A, 201A, 202A) are discharged of their thermal energy and the second heat storage and recovery means (200B, 201B, 202B), those which are in parallel with said first heat storage and recovery means (200A, 201A, 202A) respectively, are partially discharged of their thermal energy: in other words, a reserve of heat to be recovered is kept in only one of the two parallel heat storage and recovery means of each stage, in order to be able to use it to facilitate the start-up of the compression means in the next compression phase.The second compressed gas storage means (1000B) thus maintains a sufficient reserve of compressed gas and the second heat storage and recovery means (200B, 201B, 202B) each maintain a sufficient reserve of thermal energy to provide the energy necessary to overcome the inertia of starting the compressors of the following compression phase.

[0088] Figure 3 illustrates, in a schematic and non-limiting manner, the start-up phase of the compression means with the compressed gas energy storage and recovery system of Figure 2 according to the invention.

[0089] When the next compression phase starts, the gas remaining in the (second) compressed gas storage means (1000B) is sent to the second high-pressure heat storage and recovery means (202B). The compressed gas then rises in temperature and enters the high-pressure expansion means (700). At the outlet of the high-pressure expansion means (700), the compressed gas flow is sent to the second medium-pressure heat storage and recovery means (201B). The compressed gas then rises in temperature and enters the medium-pressure expansion means (701). Finally, at the outlet of the medium-pressure expansion means (701), the compressed gas flow is sent to the second low-pressure heat storage and recovery means (200B). The compressed gas then rises in temperature and enters the low-pressure expansion means (701) to be expanded there preferably to atmospheric pressure.

[0090] The low-pressure compression means (100) compresses the incoming gas, here atmospheric air (10). The hot compressed gas leaving the compression means (100) is sent to the first low-pressure heat storage and recovery means (200A) only, since the second low-pressure heat storage and recovery means (200B) participates in the expansion of the compressed gas from the second compressed gas storage means (1000B) and used to start the low-pressure compression means (100). Once cooled in the first low-pressure heat storage and recovery means (200A) and possibly in the cooling means (300), the compressed gas flow may then comprise water, from the humidity in the air, condensed during the cooling phases in the heat storage and recovery means (200A) and / or in the cooling means (300).This condensed water can advantageously be separated from the compression line in the gas-liquid separation means (400) (which is therefore optional) operating at the pressure of the flow. The gas is then compressed by the medium pressure compression means (101). The compressed and hot gas is sent to the first medium pressure heat storage and recovery means (201 A) only, because the second medium pressure heat storage and recovery means (201 B) participates in the expansion of the compressed gas from the second compressed gas storage means (1000B) and used to start the medium pressure compression means (101).Once cooled in the first medium pressure heat storage and recovery means (201 A) and possibly in the cooling means (301), the compressed gas flow may then comprise water, from the humidity of the air, condensed during the cooling phases in the first heat storage and recovery means (201 A) and / or in the cooling means (301). This condensed water can then be advantageously separated from the compression line in the gas-liquid separation means (401) (which is therefore optional) operating at the pressure of the flow. The gas is then compressed by the high pressure compression means (102).The hot compressed gas is sent to the first high-pressure heat storage and recovery means (202A) only, because the second high-pressure heat storage and recovery means (202B) participates in the expansion of the compressed gas from the second compressed gas storage means (1000B) and used to start the high-pressure compression means (102). Once cooled in the first high-pressure heat storage and recovery means (202A) and possibly in the cooling means (302), the compressed gas stream may then comprise water, from the humidity in the air, condensed during the cooling phases in the first heat storage and recovery means (202A) and / or in the cooling means (302). This condensed water may advantageously be separated from the compression line in the gas-liquid separation means (402) (which is therefore optional) operating at the pressure of the stream.The gas is then sent only to the first compressed gas storage means (1000A), the second compressed gas storage means (1000B) being used for expansion.

[0091] During this start-up phase of the compression means, the connection / disconnection means C allow the coupling of each compression means (associated with an electric motor for driving the compression means after the start-up phase) to an expansion means (preferably at substantially the same pressure). In other words, each compression means (associated with an electric motor) is coupled to an expansion means by a connection / disconnection means C. Indeed, the start-up problem concerns both the compression means and the electric motor with which it is associated. Once the inertia of both is overcome, that is to say after the start-up phase, the electrical power supply of the electric motor is sufficient to drive the compression means.

[0092] In order to direct the gas flow from the compression phase and the expansion phase, in the heat storage and recovery means and in the compressed gas storage means, valves (not shown) or other opening / closing means are used upstream and / or downstream of each of these means.

[0093] Once the inertia period for starting the compressors is over, the compressed gas storage means (1000B) and the heat storage and recovery means (200B, 201B, 202B) are discharged, respectively, of their compressed gas and their thermal energy. The expansion means (700, 701, 702) cease to operate and are decoupled via the connection / disconnection means C from the compression means (100, 101, 102). The compression means (100, 101, 102) then draw their power from the electrical network via electric motors to which they are connected, for example, by electric motors for example, for the remainder of the compression phase.During the compression phase, once the heat storage and recovery means (200B, 201 B, 202B) have been discharged, the hot compressed gas can then charge in parallel all of the heat storage and recovery means (200A, 200B, 201 A, 201 B, 202A, 202B) by using the first and second valves upstream and / or downstream of the heat storage and recovery means (200A, 200B, 201 A, 201 B, 202A, 202B). Similarly, once the second compressed gas storage means (1000B) has been discharged, the compressed gas can then be stored in parallel in the compressed gas storage means (1000A) and (1000B) by using the first and second opening means upstream and / or downstream of the compressed gas storage means.

[0094] In this mode of operation, the connection / disconnection means C allow the decoupling of each compression means from the expansion means (preferably at substantially the same pressure) to which it can be coupled. In other words, each compression means is decoupled from the associated expansion means by the connection / disconnection means C.

[0095] At the end of the compression phase, once the first heat storage and recovery means (200A, 201A, 202A) are fully charged, the hot compressed gas is directed only to the second heat storage and recovery means (200B, 201B, 202B) in order to complete their charging with thermal energy. In the same way, once the first compressed gas storage means (1000A) is fully charged, the compressed gas is directed only to the second compressed gas storage means (1000B) in order to complete its charging with compressed gas.

[0096] In this mode of operation, the connection / disconnection means C allow the decoupling of each compression means from the expansion means (preferably at substantially the same pressure) to which it can be coupled. In other words, each compression means is decoupled from the associated expansion means by the connection / disconnection means C.

[0097] Thanks to the invention, the coupling of the compression means - the expansion means by a connection / disconnection means (comprising in particular a mechanical shaft and a clutch) for each pressure stage (compression / expansion substantially at the same pressure level) makes it possible to overcome the inertia of the start-up of the compression means and to reduce the peak electrical demand from the electrical network at the start of the compression phase.

[0098] For each pressure stage (compression / expansion at substantially the same pressure level), expanding the compressed gas via the expansion means actuates the connection / disconnection means which is then coupled to the associated compression means, thereby enabling the compression means associated with each expansion means to be driven. The energy required to start the compression means and especially the energy peak due to the inertia of the start is then provided by the compressed gas from the end of the previous expansion phase, thereby smoothing the impact of the energy demand on the network.

Claims

Claims 1. Compressed gas energy storage and recovery system comprising: - a gas compression line (1) with at least one compression stage (3), each compression stage (3) comprising a compression means (100, 101, 102) and at least two heat storage and recovery means (200A, 200B, 201A, 201B, 202A, 202B) downstream, in the direction of gas circulation, of said compression means (100, 101, 102), the at least two heat storage and recovery means (200A, 200B, 201A, 201B, 202A, 202B) being connected in parallel, - at least two compressed gas storage means (1000A, 1000B) located at the outlet of the gas compression line (1) for storing the compressed gas, said at least two compressed gas storage means (1000A, 1000B) being mounted in parallel, - an expansion line (2) for expanding compressed gas stored in the compressed gas storage means (1000A, 1000B), the expansion line (2) comprising at least one expansion stage (4), each expansion stage (4) comprising conduits and an expansion means (700, 701, 702), the conduits being configured to circulate the compressed gas in said at least two heat storage and recovery means (200A, 200B, 201A, 201B, 202A, 202B) of the same compression stage so as to heat the compressed gas before the expansion means (700, 701, 702), characterized in that the energy storage and recovery system comprises at least one mechanical connection / disconnection means (C) for connecting / disconnecting at least one compression means (100, 101, 102) from a compression stage to at least one expansion means (700, 701, 702) of an expansion stage, preferably to a single expansion means (700, 701, 702) of an expansion stage.

2. Compressed gas energy storage and recovery system according to claim 1, for which the system comprises as many compression stages (3) as expansion stages (4).

3. Compressed gas energy storage and recovery system claim 2, for which each compression stage (3) of the compression line (1) is defined by a passage number, the passage number corresponding to the order of passage of the compressed gas in this compression stage (3) within the compression line (1), for which each expansion stage (4) of the expansion line (2) is defined by an outlet number, the outlet number corresponding to the order of this expansion stage (4) within the expansion line (2), in the opposite direction to the passage of the compressed gas in the expansion line and for which each connection / disconnection means (C) is configured to connect / disconnect the compression means (100, 101, 102) of the compression stage (3) of the passage number defined by means of the expansion stage (4) of the defined exit number, the defined passage number being equal to the exit number.

4. Compressed gas energy storage and recovery system according to one of claims 2 or 3, for which the compression line (1) comprises three compression stages (3) and the expansion line (2) comprises three expansion stages (4).

5. Compressed gas energy storage and recovery system according to claim 4, wherein the system comprises a first connection / disconnection means (C) for the connection between the compression means (100) of the last compression stage and the expansion means (702) of the first expansion stage, a second connection / disconnection means (C) for the connection between the compression means (101) of the intermediate compression stage and the expansion means (701) of the intermediate expansion stage and a third connection / disconnection means (C) for the connection between the compression means (102) of the first compression stage and the expansion means (700) of the last expansion stage.

6. Compressed gas energy storage and recovery system according to one of the preceding claims, for which the at least one connection / disconnection means (C) comprises a shaft for mechanically connecting at least one compression means (100, 101, 102) to at least one expansion means (700, 701, 702).

7. Compressed gas energy storage and recovery system according to one of the preceding claims, for which the at least one connection / disconnection means (C) comprises a clutch.

8. Compressed gas energy storage and recovery system according to one of the preceding claims, for which each compression stage (1) comprises a cooling means (300, 301, 302) downstream of said at least two heat storage and recovery means (200A, 200B, 201A, 201B, 202A, 202B) and preferably a gas / liquid separation means (400, 401, 402), downstream of the cooling means (300, 301, 302).

9. Compressed gas energy storage and recovery system according to one of the preceding claims, in which at least one expansion means (700, 701, 702), preferably each expansion means, is connected to an electrical machine capable of generating electricity in the expansion phase and capable of participating in the starting of the compression means (100, 101, 102) at the start of the compression phase.

10. Compressed gas energy storage and recovery system according to one of the preceding claims, in which first valves and / or second valves are positioned upstream and / or downstream of each heat storage and recovery means (200A, 200B, 201 A, 201 B, 202A, 202B).

11. Compressed gas energy storage and recovery system according to one of the preceding claims, in which first and second opening / closing means are positioned upstream and / or downstream of each compressed gas storage means (1000A, 1000B).

12. Method for storing and recovering energy using compressed gas, in which a compressed gas energy storage and recovery system according to one of the preceding claims is used, and in which at least the following steps are carried out: - In the expansion phase, the compressed gas from said at least two compressed gas storage means (1000A, 1000B) is expanded and the expansion phase is stopped when the compressed gas pressure in at least one of said at least two compressed gas storage means (1000A, 1000B) reaches a predetermined pressure and / or when the outlet temperature of at least one of the heat storage and recovery means (200A, 200B, 201 A, 201 B, 202A, 202B) reaches a predefined temperature; - At the time of starting the compression phase, the remaining compressed gas is transferred into at least one of said at least two compressed gas storage means (1000A, 1000B), into the expansion line (2) and, in each expansion stage (4), the remaining heat is recovered from said heat storage and recovery means (200A, 200B, 201A, 201B, 202A, 202B) before passing the compressed gas into the expansion means (700, 701, 702), the expansion means (700, 701, 702) then being mechanically connected to a compression means (100, 101, 102) of a compression stage (3), by means of a connection / disconnection means (C);then when the compression phase has started and once the compressed gas is completely discharged from said at least two compressed gas storage means (1000A, 1000B), the disconnection of each connection / disconnection means (C) is activated so as to mechanically disconnect the compression means (100, 102, 102) from the associated expansion means (700, 701, 702) and the compression means (100, 101, 102) are then driven by an electric motor.; 13. Method for storing and recovering energy by compressed gas according to claim 12, in which before mechanically activating the disconnection of each connection / disconnection means (C), the heat contained in the heat storage and recovery means (200A, 200B, 201 A, 201 B, 202A, 202B) is discharged.

14. Method for storing and recovering energy according to one of claims 12 or 13, using the energy storage and recovery system according to claim 9, in which, when starting the compression phase, alternatively or additionally to the use of the compressed gas leaving the compressed gas storage means (1000A, 1000B), each electrical machine connected to the expansion means (700, 701, 702) is used to participate in the starting of the compression means (100, 101, 102).

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