SYSTEM AND METHOD FOR STORING AND RECOVERING ENERGY USING COMPRESSED GAS WITH LIQUID RECOVERY

Description

technical field

[0001] The present invention relates to the field of energy storage and production by compression and expansion of gases, in particular air.

[0002] While global energy objectives aim to favor renewable energies over fossil fuels and progressively increase their share in the energy mix, their variability remains their major drawback. To address this issue, energy storage appears to be the ideal solution. By storing surplus electricity produced at peak production so that it can be used when production falls below demand, storage overcomes the constraint of variability and provides continuity, or at least flexibility, that is fundamentally lacking in renewable energies. Thus, the need for energy storage processes exists and will grow with the increasing share of this type of energy in the global energy mix.

[0003] Many mature storage technologies already exist, such as mechanical storage systems like Pumped Storage Hydroelectric Power Plants (PSHPs), which use hydroelectricity produced by two water reservoirs located at different altitudes. During the electricity storage phase, water from the lower reservoir is pumped to the upper reservoir and stored there. When electricity demand increases, water from the upper reservoir is returned to the lower reservoir via a hydraulic turbine, which then generates electricity through a generator. Hydroelectric dams also operate on the same principle: the dam retains water at a higher elevation upstream than downstream, and when electricity demand increases, the dam releases the water, allowing it to pass through hydraulic turbine-generators that produce electricity.Compressed air energy storage (CAES) technology is one of the mechanical energy storage solutions. Other electrochemical technologies can also be used for energy storage, such as lithium-ion, lead-acid, or nickel-cadmium batteries, or flow batteries using electrolytes.

[0004] Compressed air energy storage (CAES) is a mature technology, the first installation of which was built in Germany in the late 1970s, storing 290 MW. The principle of CAES is to use electricity produced but not consumed to compress air. To prevent damage to the compressors, the heat generated during compression is dissipated between each stage. The compressed air, at medium or high pressure (40 bar to 300 bar), is sent to a natural storage site such as a salt cavern, a mine (salt, limestone, coal), or an artificial storage site until the energy is discharged. During the electricity generation phase, the stored air is extracted from the storage site and expanded in turbogenerators. In basic CAES systems, such as those established in the late 1970s, the compressed air was used to power gas turbines (also called combustion turbines).These turbines burn natural gas in a combustion chamber in the presence of compressed air to produce very hot combustion gases (500°C-800°C) which are then expanded to generate electricity. The CAES process has an energy efficiency of approximately 50%. Previous technique

[0005] A variant of CAES is the adiabatic compressed air energy storage (ACAES) process. The main difference from the original CAES is that the heat resulting from compression is no longer dissipated between stages, but stored to heat the air upstream of the turbines during electricity generation. Thanks to this reuse of the internal thermal energy of the process, the efficiency of ACAES reaches approximately 70%. Cooling of the air during the compression phase can be achieved via indirect contact heat exchange in a heat exchanger with a heat transfer fluid. The hot heat transfer fluid is then stored and insulated as much as possible so that it can release its heat to the air during the expansion phase. Alternatively, it can be achieved via direct contact heat exchange between the air and a thermal storage mass operating through sensible heat or using phase-change materials.In both cases, the heat from the air is stored directly within the material, either internally or through a phase change. During the expansion phase, cold air is reinjected into the thermal storage mass, and through direct contact, the air heats up by absorbing heat from the material or by undergoing the reverse phase change, releasing this heat. This cooling of the air can then induce condensation if the air contains a certain amount of humidity. This condensed water must then be removed from the air circuit to prevent damage to the downstream compressors.

[0006] One solution to limit compressor damage is to extract water from the compression line using a gas / liquid separator installed at each compression stage. figure 1This figure schematically illustrates, in block diagram form, such an ACAES system and process. The figure represents the energy storage phase by gas compression and the energy production phase by gas expansion. The prior art system consists of a compression line (1), including one or more compression stages (3) depending on the required air pressure and supplier recommendations. In the illustrated embodiment, the compression line (1) comprises three compression stages (3). Each compression stage (3) includes a compression device (100, 101, 102), also called a compressor. Compressor (100) is a low-pressure compressor, compressor (101) is a medium-pressure compressor, and compressor (102) is a high-pressure compressor. The gas used (10) in the illustrated process is ambient air, containing a water saturation level related to its temperature and pressure.During the energy storage phase, air is compressed in the compression line (1) and then sent to a high-pressure compressed air storage unit (1000). Heat storage and recovery units (200, 201, 202) are located after each compressor (100, 101, 102) in each compression stage (3) to cool the hot compressed air exiting the compression stage while simultaneously storing this thermal energy. Heat storage and recovery unit (200) is low-pressure, heat storage and recovery unit (201) is medium-pressure, and heat storage and recovery unit (202) is high-pressure.Cooling units (300, 301, 302) can be arranged downstream of the heat storage and recovery units (200, 201, 202) if necessary to complete the cooling of 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 in the air, is extracted from the compressed air stream by gas-liquid separators (400, 401, 402) to ensure that the air entering the compressor is free of any trace of liquid water. This condensation can take place in the heat storage and recovery units (200, 201, 202) and / or in the cooling units (300, 301, 302).During the power generation phase, compressed air is expanded via one or more turbines (700, 701, 702) or expansion stage, as recommended by the suppliers, to generate electricity using alternators, which are 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. In this system and process, the condensed water is simply extracted, and the associated energy is therefore lost.

[0007] Other compressed gas energy storage and recovery systems and processes consider recovering energy contained in condensing water.

[0008] For example, patent application FR3074844 (WO2019 / 115121) discloses an improved ACAES system and process that reinjects condensate from air cooling into the water used as a heat transfer fluid, thus storing the heat extracted from the air between each compression stage. However, this system and process are difficult to implement due to heat transfer between the different water temperatures. This technology relies on a counter-current, direct-contact heat exchanger between the humid air to be cooled and the heat transfer fluid, which is warmed. During air cooling, humidity is produced and transported by the heat transfer fluid. As the fluid circulates in the opposite direction, the humidity comes into contact with the warm air again and evaporates once more. This results in water accumulating in the heat exchanger.Furthermore, this system is difficult to implement due to the circulation of a heat transfer fluid, which requires additional pipes, pumping equipment and storage facilities, which also poses space constraints.

[0009] Patent application WO16012764 describes an ACAES process in which the humidity in the air is condensed upstream of the air storage during the compression phase, stored, and then reinjected into the air during the expansion phase at the outlet of the storage unit. However, this process does not protect the compressors in the various compression stages by limiting the amount of water passing through them. Furthermore, this configuration does not optimize the energy recovered from the condensed water. In addition, this system is difficult to implement due to the circulation of a heat transfer fluid, which requires additional piping, pumping equipment, and storage facilities, thus also creating space constraints.

[0010] Patent application WO16079485 describes an ACAES process in which air humidity is condensed upstream of the air storage unit during the compression phase, stored, and then reinjected into the air during the expansion phase at the outlet of the storage unit. However, this process does not protect the compressors in the various compression stages by limiting the amount of water passing through them. Furthermore, this configuration does not optimize the energy recovered from the condensed water. In addition, this system is difficult to implement due to the circulation of a heat transfer fluid, which requires additional piping, pumping equipment, and storage facilities, thus creating space constraints. This system also requires a combustion turbine in expansion mode and a Rankine cycle that generates electricity, while the goal is to store energy. Therefore, a significant amount of equipment is used, resulting in reduced efficiency.French patent application FR3074846 describes a method for storing and producing energy using compressed air with additional energy recovery according to the prior art. French patent application FR2993925 describes a device for storing and releasing electrical energy on a large scale according to the prior art. Summary of the invention

[0011] The present invention relates to a system and method for storing and recovering energy using compressed gas, optimizing system and process efficiency by minimizing system size and simplifying operation. To this end, the invention relates to a system and method for storing and recovering energy using compressed gas, comprising a compression line, an air storage means, and an expansion line. According to the invention, the compression and expansion lines include heat storage means comprising heat storage particles. Furthermore, the expansion line includes means for injecting and mixing liquid into the expansion line. Thus, through liquid injection, the gas flow rate is increased in each expansion stage, thereby increasing the efficiency of the system and process.In addition, thanks to heat storage in heat storage particles, the system and process are simple and suitable (no heat transfer fluid is used in the heat storage means).

[0012] The invention relates to a compressed gas energy storage and recovery system comprising: A gas compression line with at least two successive compression stages, each compression stage comprising a compression means and a heat storage and recovery means arranged downstream of said compression means, in the direction of gas flow; at least one compressed gas storage means arranged at the outlet of said gas compression line for storing said compressed gas; a gas expansion line for expanding said compressed gas stored in said compressed gas storage means, said gas expansion line comprising at least two successive expansion stages, each expansion stage comprising an expansion means and conduits configured to circulate said compressed gas through at least one of said heat storage and recovery means of said compression stages so as to reheat said compressed gas. The said heat storage and recovery means comprise heat storage particles for direct heat exchange between the gas and the material of the heat storage particles, the particles remaining in the heat storage and recovery means, and in that each expansion stage comprises a means for introducing a liquid, said means for introducing said liquid being provided upstream, in the direction of flow of said gas, of said heat storage means.

[0013] According to one embodiment, each compression stage includes a means for separating said gas and a liquid.

[0014] Advantageously, for each compression stage, said gas and liquid separation means is arranged downstream of said heat storage and recovery means, in the direction of gas flow.

[0015] Preferably, said system comprises a plurality of liquid storage means for storing said liquid at the outlet of said gas and liquid separation means, and in that said inlet means introduce said liquid from said liquid storage means.

[0016] According to one embodiment, said compression line comprises as many compression stages as the expansion line comprises expansion stages, each means of heat storage and recovery of a compression stage being used in the corresponding expansion stage.

[0017] Advantageously, said compression line and said expansion line each have three stages.

[0018] According to one embodiment, at least one compression stage includes a cooling means downstream of the heat storage and recovery means, in the direction of flow of said gas, preferably, said cooling means includes an air cooler.

[0019] According to one aspect, said expansion line includes at least one means of additional heat exchange between the gas exiting said expansion line and said compressed gas.

[0020] According to one characteristic, said at least one additional heat exchange means is arranged in the first expansion stage, in the direction of flow of said gas.

[0021] Advantageously, the said expansion line includes two complementary heat exchange means arranged in two expansion stages.

[0022] According to an implementation, said at least one additional heat exchange means is arranged between said liquid introduction means and said heat storage and recovery means, in the direction of gas flow.

[0023] Furthermore, the invention relates to a method for storing and recovering energy using compressed gas, comprising at least the following steps: During the energy storage phase: a) a gas is successively compressed at least twice in a compression line comprising at least two compression stages, each compression stage comprising at least one compression means; b) after each compression stage, the heat from said compressed gas is recovered in at least one heat storage and recovery means; c) said cooled compressed gas is stored in at least one compressed gas storage means; During the energy recovery phase: d) the compressed gas exiting the compressed gas storage means is circulated through an expansion line comprising at least two successive expansion stages, and in each expansion stage, the compressed gas is reheated by circulating it through one of said heat storage and recovery means using the heat stored during the compression stage, and then the reheated compressed gas is expanded in an expansion means;For this process, heat is stored in heat storage particles for direct heat exchange between the gas and the material of the heat storage particles, the particles remaining in the heat storage and recovery means, and in that before each expansion step, a liquid is introduced into said compressed gas prior to the reheating step of said gas.

[0024] According to one embodiment, after each compression step, said gas and a liquid present in said gas are separated.

[0025] Advantageously, the liquid is stored separately, and the liquid introduced into the compressed gas is the stored liquid.

[0026] According to one implementation, as many compression steps are carried out as expansion steps, and the heat storage and recovery means of each of the steps b) are used to reheat the compressed gas of the corresponding expansion step.

[0027] According to one aspect, after each heat recovery stage, the compressed gas exiting the heat storage and recovery means is cooled in a cooling means before the gas is sent to the next compression stage or to the compressed gas storage means.

[0028] According to one characteristic, before at least one expansion stage, said gas is heated by at least one additional heat exchange with said gas at the outlet of said expansion line.

[0029] Advantageously, said at least one additional heat exchange is implemented for the first expansion stage, in the direction of flow of said gas.

[0030] According to one implementation, two complementary heat exchanges are implemented for two expansion stages.

[0031] According to one embodiment, said additional heat exchange is implemented after the step of introducing said stored liquid into said compressed gas.

[0032] Other features and advantages of the system and method according to the invention will become apparent from the following description of non-limiting examples of implementations, with reference to the figures attached and described below. List of figures

[0033] There figure 1 The example already described illustrates a system and method for storing and recovering energy using compressed gas according to the prior art. figure 2 illustrates a system and method for storing and recovering energy using compressed gas according to a first embodiment of the invention. figure 3 illustrates a system and method for storing and recovering energy using compressed gas according to a second embodiment of the invention. figure 4illustrates a system and method for storing and recovering energy using compressed gas according to a third embodiment of the invention. figure 5 illustrates a system and method for storing and recovering energy using compressed gas according to a fourth embodiment of the invention. figure 6 illustrates a system and method for storing and recovering energy using compressed gas according to a fifth embodiment of the invention. figure 7 illustrates a system and method for storing and recovering energy using compressed gas according to a sixth embodiment of the invention. figure 8 illustrates a system and method for storing and recovering energy by compressed gas according to a seventh embodiment of the invention. Description of the implementation methods

[0034] The present invention relates to a system and a method for storing and recovering energy using compressed gas.

[0035] In the present invention the terms "upstream", "downstream", "inlet", "outlet", "before", "after" are defined by the direction of gas flow, respectively during the energy storage phase (compression phase), and during the energy recovery phase (expansion phase).

[0036] The system according to the invention comprises: a compression line (the term "compression line" refers to the gas line from the gas inlet to the compressed gas storage means, passing through at least two compression means), with at least two successive compression stages (in series), each compression stage comprising: a gas compression means (compressor) for increasing the gas pressure for storage; compression means may be axial, centrifugal, or of any other technology; a heat storage and recovery means arranged downstream of the compression means to store the heat generated by compression and to reduce the gas temperature before the next compression stage or before the compressed gas storage means; at least one compressed gas storage means to store the compressed gas at the outlet of the compression line for later reuse.The compressed gas storage medium can be a natural cavity such as a salt cavern, an old mine or an aquifer, or an artificial storage facility; a gas expansion line (the term "expansion line" refers to the gas line running from the compressed gas storage medium to the gas outlet, passing through at least one expansion medium) with at least two successive expansion stages (in series), each expansion stage comprising: at least one means of expanding the compressed gas to generate energy, for example a turbine that can be coupled to an alternator, and pipes to circulate the gas through one of the storage mediums in the compression line, so as to recover the stored heat and increase the gas temperature to increase the energy produced in the expansion medium.

[0037] According to the invention, the heat storage and recovery means comprise heat storage particles. Thus, heat exchange is achieved by direct exchange between the gas and a material, the material remaining within the heat storage and recovery means. In other words, there is no circulation of the heat storage particles. Consequently, it is not necessary to have a dedicated system comprising heat transfer fluid storage tanks, pumping means, and dedicated piping. For example, the material can be stones, concrete, gravel, phase change material (PCM) beads, possibly encapsulated, preferably with a solid-liquid phase change, zeolites, or any similar material.

[0038] Furthermore, each expansion stage includes a liquid introduction mechanism. This liquid introduction mechanism allows for mixing between the gas in the expansion line and the liquid. Thus, through water injection, the gas flow rate is increased in each expansion stage, thereby improving the efficiency of the system and the process. The liquid introduction and mixing mechanisms are located in the expansion line upstream of the heat storage units. In this way, the reinjected water-liquid mixture is heated in the heat storage unit, causing the liquid to vaporize, and only gas is then conveyed to the expansion unit.

[0039] According to one embodiment of the invention, the gas may be air. It may be air taken from the ambient environment. Alternatively, it may consist of other gases.

[0040] According to one aspect of the invention, the liquid is water. This may include the moisture present in the gas, particularly when the gas is air. Alternatively, it may include other liquids.

[0041] According to one embodiment, each compression stage may include a gas / liquid separation means, which allows the liquid present in the gas to be extracted, in particular due to the condensation of water present in the gas, and allows the traces of liquid that could be contained in the gas after its cooling and that could damage the system, in particular the compression means, to be eliminated.

[0042] Furthermore, the system and process may include liquid storage means for storing the liquid extracted from the compression line. For example, a liquid storage means may be provided for each compression stage (i.e., for each gas-liquid separation stage). This allows the liquid to be stored at different pressures. Advantageously, the liquid introduction means may allow the liquid exiting the liquid storage means to be introduced, thus making it possible to use the recovered condensation liquid in the compression line.

[0043] According to one embodiment of the invention, the gas / liquid separation means can be arranged downstream of the heat storage and recovery means. In this way, it is possible to extract the liquid formed by condensation in the heat storage and recovery means.

[0044] Alternatively, the gas / liquid separation means can be arranged upstream of the compression means, or between the compression means and the heat storage and recovery means.

[0045] Advantageously, the compression and expansion lines can have the same number of stages. In other words, the number of compression stages and the number of expansion stages can be identical. This allows for a "symmetrical" design of the compression and expansion lines, with similar operating pressures and temperatures, which promotes heat exchange in the heat storage and recovery systems and enables the reinjection of the fluid into an expansion stage that corresponds to the corresponding compression stage. Thus, the system and the process are simplified.

[0046] For this embodiment, the number of compression and expansion stages can be between two and six, preferably between three and five. For example, the number of compression and expansion stages can be three, which allows for good temperature and pressure control while maintaining a simple design.

[0047] Alternatively, the number of compression stages and the number of expansion stages can be different. For this design, it may be possible to share at least some of the heat storage and recovery systems, as well as at least some of the liquid introduction systems.

[0048] Furthermore, at least one compression stage may include a cooling system. This cooling system may be located downstream of the heat storage and recovery system. This cooling system allows for greater cooling of the gas, thereby reducing the size of the heat storage and recovery system. These heat cooling systems may be air-cooled condensers or heat exchangers (shell-and-tube, plate, spiral, or other suitable technologies) exchanging heat with a heat transfer fluid such as water, propane, butane, or any other refrigerant suitable for the required cooling. The cooling systems may be adapted to the pressure of the incoming air and exchange heat with each of them. The cooling systems do not play a role in the energy recovery phase.

[0049] In this embodiment, the gas / liquid separation means can be arranged downstream of the cooling means. In this way, it is possible to extract the liquid formed by condensation in both the heat storage and recovery means and the cooling means.

[0050] In one embodiment, the expansion line may include at least one additional heat exchange means between the gas exiting the expansion line and the compressed gas. Thus, the hot gas exiting the expansion line is cooled, while the compressed gas within the expansion line can be heated. In this way, lost thermal energy can be recovered, thereby reducing the heating requirements of the compressed gas, which in turn allows for a reduction in the size of at least one heat storage and recovery means (and consequently, the cost of the heat storage and recovery means).

[0051] According to one implementation of this embodiment, the supplementary heat exchange means can be arranged in the first expansion stage. The "first expansion stage" is the first expansion stage through which the gas flows in the expansion line. In other words, the first expansion stage is located near the compressed gas storage means. Thus, the heat from the gas exiting the expansion line is used to preheat the fresher gas exiting the compression storage means, thereby reducing the size of the heat storage and recovery means for the first expansion stage, which is the heat storage and recovery means with the highest pressure constraints and, consequently, the most expensive.

[0052] Alternatively, the additional heat exchange means can be arranged in an expansion stage located between the first and last expansion stages.

[0053] According to one aspect of this embodiment, the expansion line may include two complementary heat exchange means arranged in two different expansion stages. This allows for a reduction in the size of the two heat storage and recovery means. In this embodiment, the two complementary heat exchange means can be traversed in series by the gas exiting the expansion line. Preferably, the two complementary heat exchange means can be arranged in the first two expansion stages.Thus, the heat from the gas exiting the expansion line is used to preheat the cooler gas exiting the compression storage unit and the first expansion stage. This allows for a reduction in the size of the heat storage and recovery units for the first two expansion stages, which are subject to the highest pressure constraints and are therefore the most expensive. In this embodiment of the invention, the gas exiting the expansion line can first pass through the supplementary heat exchange unit of the second expansion stage, and then through the supplementary heat exchange unit of the first expansion stage.

[0054] Advantageously, the supplementary heat exchange means can be arranged between the liquid introduction means and the heat storage and recovery means. In this way, the supplementary heat exchange means can warm the gas-liquid mixture, promoting liquid vaporization.

[0055] Alternatively, the additional heat exchange means can be arranged before the liquid introduction means, or arranged between the heat storage and recovery means and the expansion means.

[0056] Furthermore, the invention relates to a method of storing and recovering energy using compressed gas.

[0057] The process according to the invention involves the following steps: During the energy storage phase (compression phase): a) a gas is successively compressed at least twice in a compression line comprising at least two compression stages, each compression stage comprising at least one compression means; b) after each compression stage, the heat from the compressed gas is recovered in at least one heat storage and recovery means; c) the cooled compressed gas at the outlet of the compression line is stored in a compressed gas storage means;During the energy recovery phase (expansion phase): d) the compressed gas exiting the compressed gas storage means is circulated through an expansion line comprising at least two successive expansion stages, and in each expansion stage, the compressed gas is heated by circulating it through one of the heat storage and recovery means using the heat stored during the compression stage, then the heated compressed gas is expanded in an expansion means.

[0058] Furthermore, according to the invention, heat is stored and recovered in heat storage particles. In other words, the heat storage and recovery means comprise heat storage particles. Thus, heat exchange is achieved through direct exchange between the gas and a material, the material remaining within the heat storage and recovery means. In other words, there is no circulation of the heat storage particles. Consequently, it is not necessary to have a dedicated system with heat transfer fluid storage tanks, pumping means, and dedicated piping. For example, the material could be stones, concrete, gravel, phase change material (PCM) beads, zeolites, or any similar material.

[0059] Furthermore, before each expansion stage, a liquid is introduced and mixed into the compressed gas prior to the gas heating stage. To this end, each expansion stage includes a liquid introduction and mixing mechanism, thus enabling the use of the recovered condensate in the compression line. By injecting the liquid, the gas flow rate is increased in each expansion stage, thereby improving the efficiency of the system and the process. The liquid introduction and mixing mechanisms are located in the expansion line upstream of the heat storage units. In this way, the injected water-liquid mixture is heated in the heat storage unit, causing the liquid to vaporize, and only gas is then conveyed to the expansion unit.

[0060] Preferably, the compressed gas energy storage and recovery process can implement the compressed gas energy storage and recovery system according to any of the variants or combinations of variants as described above.

[0061] According to one embodiment of the invention, the gas can be air. It can be air taken from the ambient environment.

[0062] According to one aspect of the invention, the liquid can be water. This can include, in particular, the moisture present in the gas, especially when the gas is air.

[0063] According to one embodiment of the invention, after each compression step, the gas and a liquid present in the gas can be separated.

[0064] Furthermore, the process may include a liquid storage stage to store the liquid extracted from the compression line. For example, liquid storage may be provided after each compression stage (i.e., after each gas-liquid separation stage). This allows the liquid to be stored at different pressures. Advantageously, the liquid introduced into the gas is the liquid from the storage stage, thus enabling the use of recovered condensation liquid in the compression line.

[0065] According to one embodiment of the invention, the gas / liquid separation step can be carried out after the heat storage step. In this way, it is possible to extract the liquid formed by condensation in the heat storage and recovery means.

[0066] Advantageously, the number of compression stages can be equal to the number of expansion stages. In this case, the compression and expansion lines can each have the same number of stages. In other words, the number of compression and expansion stages can be identical. This design allows for a "symmetrical" approach to the compression and expansion lines, with similar operating pressures and temperatures. This promotes heat exchange in the heat storage and recovery systems and enables the reinjection of the fluid into an expansion stage that corresponds to the corresponding compression stage. Thus, the system and process are simplified.

[0067] For this embodiment, the number of compression and expansion stages can be between two and six, preferably between three and five. For example, the number of compression and expansion stages can be three, which allows for good temperature and pressure control while maintaining a simple design.

[0068] Alternatively, the number of compression stages and the number of expansion stages can be different. For this design, it may be possible to share at least some of the heat storage and recovery equipment, as well as at least some of the liquid introduction equipment.

[0069] Furthermore, the energy storage phase may include a cooling stage. This cooling stage can be carried out after the heat storage stage using a cooling system. This cooling stage allows for more significant cooling of the gas, thus reducing the size of the heat storage and recovery systems. These cooling systems can be air-cooled condensers or heat exchangers (shell-and-tube, plate, spiral, or other suitable technologies) exchanging heat with a heat transfer fluid such as water, propane, butane, or any other refrigerant suitable for the required cooling. The cooling systems can be adapted to the pressure of the incoming air and the specific type of air they exchange.

[0070] In this embodiment, the gas / liquid separation step can be carried out after the cooling step. This allows for the extraction of the liquid formed by condensation in both the heat storage and recovery system and the cooling step.

[0071] In one embodiment, the energy recovery phase may include at least one additional heat exchange step between the gas exiting the expansion line and the compressed gas. Thus, the hot gas exiting the expansion line is cooled, while the compressed gas in the expansion line can be heated. In this way, lost thermal energy can be recovered, thereby reducing the heating requirements of the compressed gas, which in turn allows for a reduction in the size of at least one heat storage and recovery unit (and consequently, the cost of the heat storage and recovery units).

[0072] According to one implementation of this embodiment, the supplementary heat exchange can be arranged for the first expansion stage (in the first expansion stage). The "first expansion stage" is the first expansion stage through which the gas passes in the expansion line. In other words, the first expansion stage is the stage following the compressed gas storage stage. Thus, the heat from the gas exiting the expansion line is used to preheat the fresher gas exiting the compression storage unit. This allows for a reduction in the size of the heat storage and recovery unit for the first expansion stage, which has the highest pressure constraints and is therefore the most expensive.

[0073] Alternatively, the additional heat exchange can be carried out in a decompression stage implemented between the first and last decompression stages.

[0074] According to one aspect of this embodiment, the energy recovery phase can include two complementary heat exchanges, which are carried out in two different expansion stages. In this way, it is possible to reduce the size of the two heat storage and recovery means. For this embodiment, the two complementary heat exchanges can be carried in series by the gas exiting the expansion line. Preferably, the two complementary heat exchanges can be arranged in the first two expansion stages.Thus, the heat from the gas exiting the expansion line is used to preheat the cooler gas exiting the compression storage unit and the first expansion stage. This allows for a reduction in the size of the heat storage and recovery units for the first two expansion stages, which are subject to the highest pressure constraints and are therefore the most expensive. In this embodiment of the invention, the gas exiting the expansion line can first pass through the supplementary heat exchange unit of the second expansion stage, and then through the supplementary heat exchange unit of the first expansion stage.

[0075] Advantageously, supplementary heat exchange can be carried out between the liquid introduction stage and the heat recovery stage of the heat storage and recovery unit. In this way, the supplementary heat exchange can warm the gas-liquid mixture, promoting liquid vaporization.

[0076] Alternatively, supplementary heat exchange can be implemented before the liquid introduction step.

[0077] There figure 2This illustrates, schematically and without limitation, a system and method for storing and recovering energy using compressed gas (in this case, air) according to a first embodiment of the invention. According to this first embodiment, the method and system consist of a compression line (1), including three compression stages (3) depending on the air pressure to be achieved. Each compression stage (3) includes a compression means (100, 101, 102), also called a compressor. These compressors (100, 101, 102) can be axial, centrifugal, or of any other technology. Compressor (100) is a low-pressure compressor, compressor (101) is a medium-pressure compressor, and compressor (102) is a high-pressure compressor. The gas used (10) in the system and process is ambient air, containing a water saturation related to its temperature and pressure. An element (e.g., turbine, compressor, etc.) is called an element.low pressure an element adapted to the low pressure in which the gas or liquid flows in the element, medium pressure element an element adapted to the medium pressure in which the gas or liquid flows in the element, and high pressure element an element adapted to the high pressure in which the gas or liquid flows in the element.

[0078] During the energy storage phase (1), air is compressed in the compression line (1) and then sent to a compressed air storage unit (1000) suitable for high pressures. This compressed air storage unit (1000) can be a natural cavity such as a salt cavern, an old mine, or an aquifer, or an artificial storage facility.

[0079] Heat storage and recovery devices (200, 201, 202) are arranged after each compressor (100, 101, 102) to cool the hot compressed air exiting the compressor while simultaneously storing this thermal energy. The exchange / storage occurs through direct contact between the air and the material used to store the air's heat. This material can be stones, concrete, gravel, or any other suitable solid material. The heat storage and recovery devices (200, 201, 202) are adapted to the pressure of the incoming air, transferring its energy to each of them. Heat storage and recovery device (200) is adapted to low pressure, heat storage and recovery device (201) to medium pressure, and heat storage and recovery device (202) to high pressure.

[0080] During the power generation phase, compressed air passes through the expansion line (2), which has three expansion stages (4). The air is expanded via one or more expansion devices, for example, turbines (700, 701, 702), located in each expansion stage (4), to generate electricity via alternators, not shown. Turbine (702) is a low-pressure turbine, turbine (701) is a medium-pressure turbine, and turbine (700) is a high-pressure turbine.

[0081] In the first stage of each expansion stage (4), condensed water is injected into the compressed air via mixers (600, 601, 602). The compressed air / water mixture is preheated before entering the turbine by the heat storage and recovery units (200, 201, 202), which are thermally charged during the preceding compression phase (1). The condensed water injected at each expansion stage (4) evaporates, and the air is reheated. Therefore, there is no liquid water at the turbine inlets (700, 701, 702), which is preferable for their proper operation. Furthermore, the higher flow rate due to the water reinjection and the elevated temperature at the turbine inlets (700, 701, 702) ensure improved process efficiency.

[0082] There figure 3This illustrates, schematically and without limitation, a system and method for storing and recovering energy using compressed gas (in this case, air) according to a second embodiment of the invention. The second embodiment corresponds to the first embodiment in which cooling means (300, 301, 302) have been added to the compression line (1). Consequently, only the compression line (1) is described for this embodiment.

[0083] Each compression stage (3) includes a compression device (100, 101, 102), also called a compressor. These compressors (100, 101, 102) can be axial, centrifugal, or of any other type. Compressor (100) is a low-pressure compressor, compressor (101) is a medium-pressure compressor, and compressor (102) is a high-pressure compressor. The gas used (10) in the system and process is ambient air, containing a water vapor concentration related to its temperature and pressure.

[0084] During the energy storage phase (1), air is compressed in the compression line and then sent to a compressed air storage unit (1000) adapted to high pressures. This compressed air storage unit (1000) can be a natural cavity such as a salt cavern, an old mine or an aquifer, or an artificial storage facility.

[0085] Heat storage and recovery devices (200, 201, 202) are arranged after each compressor (100, 101, 102) to cool the hot compressed air exiting the compressor while simultaneously storing this thermal energy. The exchange / storage occurs through direct contact between the air and the material used to store the air's heat. This material can be stones, concrete, gravel, or any other suitable solid material. The heat storage and recovery devices (200, 201, 202) are adapted to the pressure of the incoming air, transferring its energy to each of them. Heat storage and recovery device (200) is adapted to low pressure, heat storage and recovery device (201) to medium pressure, and heat storage and recovery device (202) to high pressure.Cooling units (300, 301, 302) can be arranged downstream of the heat storage and recovery units (200, 201, 202) if necessary to complete the cooling of the compressed air before the next compression stage or before its storage. These cooling units (300, 301, 302) can be air-cooled condensers or heat exchangers (shell-tube, plate, spiral, or other suitable technologies) exchanging heat with a heat transfer fluid such as water, propane, butane, or any other refrigerant suitable for the required cooling. The cooling units (300, 301, 302) are adapted to the pressure of the incoming air and exchange heat with each of them. Cooling medium (300) is suitable for low pressure, cooling medium (301) is suitable for medium pressure and cooling medium (302) is suitable for high pressure.

[0086] There figure 4This illustrates, schematically and without limitation, a system and method for storing and recovering energy using compressed gas (in this case, air) according to a third embodiment of the invention. According to the third embodiment, the method and system consist of a compression line, including three compression stages (3) depending on the air pressure to be achieved. Each compression stage (3) includes a compression means (100, 101, 102), also called a compressor. These compressors (100, 101, 102) can be axial, centrifugal, or of any other technology. Compressor (100) is a low-pressure compressor, compressor (101) is a medium-pressure compressor, and compressor (102) is a high-pressure compressor. The gas used (10) in the system and process is ambient air, containing a water saturation related to its temperature and pressure.

[0087] During the energy storage phase, air is compressed in the compression line (1) and then sent to a compressed air storage unit (1000) adapted to high pressures. This compressed air storage unit (1000) can be a natural cavity such as a salt cavern, an old mine or an aquifer, or an artificial storage facility.

[0088] Heat storage and recovery devices (200, 201, 202) are arranged after each compressor (100, 101, 102) to cool the hot compressed air exiting the compressor while simultaneously storing this thermal energy. The exchange / storage occurs through direct contact between the air and the material used to store the air's heat. This material can be stones, concrete, gravel, or any other suitable solid material. The heat storage and recovery devices (200, 201, 202) are adapted to the pressure of the incoming air, transferring its energy to each of them. Heat storage and recovery device (200) is adapted to low pressure, heat storage and recovery device (201) to medium pressure, and heat storage and recovery device (202) to high pressure.

[0089] Once the air has cooled and before the next compression stage, the condensed water (i.e., the liquid present in the air), resulting from the humidity in the air, is extracted from the compression line by gas-liquid separators (400, 401, 402) in order to obtain air free of any trace of liquid water at the inlet of the compressor or the compressed gas storage unit (1000). This condensation of water can take place in the heat storage and recovery units (200, 201, 202). The water condensed at each compression stage is sent into liquid storage means (500, 501, 502), each of which is resistant to the pressure at which the water is extracted from the air; in other words, liquid storage means (500) is suitable for low pressure, liquid storage means (501) is suitable for medium pressure, and liquid storage means (502) is suitable for high pressure.

[0090] During the power generation phase, compressed air passes through the expansion line (2), which has three expansion stages (4). The air is expanded via one or more expansion devices, for example, turbines (700, 701, 702), located in each expansion stage (4), to generate electricity via alternators, not shown. Turbine (702) is a low-pressure turbine, turbine (701) is a medium-pressure turbine, and turbine (700) is a high-pressure turbine.

[0091] In the first stage of each expansion stage (4), the condensed water from the liquid storage units (500, 501, 502) is reinjected into the compressed air at the same pressure level via mixers (600, 601, 602). The compressed air / condensed water mixture is preheated, before entering the turbine, by the heat storage and recovery units (200, 201, 202), which are thermally charged during the preceding compression phase (1). The condensed water reinjected at each expansion stage is evaporated, and the air is reheated. Therefore, there is no liquid water at the inlet of the turbines (700, 701, 702), which is preferable for their proper operation, and the higher flow rate due to the reinjection of water, and the high temperature at the inlet of the turbines (700, 701, 702) ensures a better process efficiency.

[0092] There figure 5This illustrates, schematically and without limitation, a system and method for storing and recovering energy using compressed gas (in this case, air) according to a fourth embodiment of the invention. The fourth embodiment differs from the third embodiment in the number of compression stages and the number of expansion stages. In this embodiment, the compression line (1) comprises two compression stages (3) and the expansion line (2) comprises two expansion stages (4).

[0093] The third embodiment can also be modified by adding compression stages and / or expansion stages.

[0094] There figure 6This illustrates, schematically and without limitation, a system and method for storing and recovering energy using compressed gas (in this case, air) according to a fifth embodiment of the invention. The fifth embodiment corresponds to the third embodiment in which cooling means (300, 301, 302) have been added to the compression line (1). Consequently, only the compression line (1) is described for this embodiment.

[0095] According to the fifth embodiment, the process and the system consist of a compression line (1), including three compression stages (3) depending on the air pressure to be achieved. Each compression stage (3) includes a compression means (100, 101, 102), also called a compressor. These compressors (100, 101, 102) can be axial, centrifugal, or of any other type. Compressor (100) is a low-pressure compressor, compressor (101) is a medium-pressure compressor, and compressor (102) is a high-pressure compressor. The compressed gas (10) in the system and the process is ambient air, containing a water saturation level related to its temperature and pressure.

[0096] During the energy storage phase, air is compressed in the compression line (1) and then sent to a compressed air storage unit (1000) adapted to high pressures. This compressed air storage unit (1000) can be a natural cavity such as a salt cavern, an old mine or an aquifer, or an artificial storage facility.

[0097] Heat storage and recovery devices (200, 201, 202) are arranged after each compressor or compression stage (100, 101, 102) to cool the hot compressed air exiting the compression stage while simultaneously storing this thermal energy. The exchange / storage occurs through direct contact between the air and the material used to store the air's heat. This material can be stones, concrete, gravel, or any other suitable solid material. The heat storage and recovery devices (200, 201, 202) are adapted to the pressure of the incoming air, transferring its energy to each of them. Heat storage and recovery device (200) is adapted to low pressure, heat storage and recovery device (201) to medium pressure, and heat storage and recovery device (202) to high pressure.Cooling units (300, 301, 302) can be arranged downstream of the heat storage and recovery units (200, 201, 202) if necessary to complete the cooling of the compressed air before the next compression stage or before its storage. These cooling units (300, 301, 302) can be air-cooled condensers or heat exchangers (shell-tube, plate, spiral, or other suitable technologies) exchanging heat with a heat transfer fluid such as water, propane, butane, or any other refrigerant suitable for the required cooling. The cooling units (300, 301, 302) are adapted to the pressure of the incoming air and exchange heat with each of them. Cooling medium (300) is suitable for low pressure, cooling medium (301) is suitable for medium pressure and cooling medium (302) is suitable for high pressure.

[0098] Once the air has cooled and before the next compression stage, the condensed water (i.e., the liquid present in the air), resulting from the humidity in the air, is extracted from the compression line by gas-liquid separators (400, 401, 402) in order to obtain air free of any trace of liquid water at the inlet of the compressor or the compressed gas storage unit (1000). This condensation of water can take place in the heat storage and recovery units (200, 201, 202) and / or in the cooling units (300, 301, 302). The water condensed at each compression stage is sent into liquid storage means (500, 501, 502), each of which is resistant to the pressure at which the water is extracted from the air; in other words, liquid storage means (500) is suitable for low pressure, liquid storage means (501) is suitable for medium pressure, and liquid storage means (502) is suitable for high pressure.

[0099] The fifth embodiment can also be modified by adapting the number of compression stages and / or expansion stages.

[0100] There figure 7 This illustrates, schematically and without limitation, a system and method for storing and recovering energy using compressed gas (in this case, air) according to a sixth embodiment of the invention. The sixth embodiment corresponds to the fifth embodiment, in which an additional heat exchanger (800) is provided in the expansion line (2), between the outlet air and the compressed gas. Consequently, only the expansion line (2) is described for this embodiment.

[0101] During the power generation phase, compressed air passes through the expansion line (2), which has three expansion stages (4). The air is expanded via one or more expansion devices, for example, turbines (700, 701, 702), located in each expansion stage (4), to generate electricity via alternators, not shown. Turbine (702) is a low-pressure turbine, turbine (701) is a medium-pressure turbine, and turbine (700) is a high-pressure turbine.

[0102] In the first stage of each expansion stage (4), the condensed water from the liquid storage units (500, 501, 502) is reinjected into the compressed air at the same pressure level via mixers (600, 601, 602). The compressed air / condensed water mixture is preheated, before entering the turbine, by the heat storage and recovery units (200, 201, 202), which were thermally charged during the preceding compression stage (1). The condensed water reinjected at each expansion stage (4) is evaporated, and the air is reheated. Therefore, there is no liquid water at the turbine inlets (700, 701, 702), which is preferable for their proper operation. In addition, the higher flow rate due to the reinjection of water, and the high temperature of the expansion line (2) at the inlet of the turbines (700, 701, 702) ensures a better process efficiency.

[0103] The heat from the air exiting the low-pressure turbine (700) is used to preheat the air from the compressed gas storage unit (1000) mixed with the condensate (28) via a supplementary heat exchanger (800). In this embodiment, the supplementary heat exchanger (800) is arranged in the first expansion stage (4) of the expansion line (2). Furthermore, the supplementary heat exchanger (800) is arranged between the mixer (600) and the heat storage and recovery unit (202). This supplementary heat exchanger (800) can be of the shell and tube, plate, spiral, or any other suitable type.

[0104] The sixth embodiment can also be modified by adapting the number of compression stages and / or expansion stages.

[0105] Furthermore, the compression line (1) can also conform to the embodiment of the figure 4 , that is to say without means of cooling (300, 301, 302).

[0106] There figure 8 This illustrates, schematically and without limitation, a system and method for storing and recovering energy using compressed gas (in this case, air) according to a seventh embodiment of the invention. The seventh embodiment corresponds to the fifth embodiment, in which two additional heat exchangers (800, 801) are provided in the expansion line (2), between the outlet air and the compressed gas. Consequently, only the expansion line (2) is described for this embodiment.

[0107] During the power generation phase, compressed air passes through the expansion line (2), which has three expansion stages (4). The air is expanded via one or more expansion devices, for example, turbines (700, 701, 702), located in each expansion stage (4), to generate electricity via alternators, not shown. Turbine (702) is a low-pressure turbine, turbine (701) is a medium-pressure turbine, and turbine (700) is a high-pressure turbine.

[0108] In the first stage of each expansion stage (4), the condensed water from the liquid storage units (500, 501, 502) is reinjected into the compressed air at the same pressure level via mixers (600, 601, 602). The compressed air / condensed water mixture is preheated, before entering the turbine, by the heat storage and recovery units (200, 201, 202), which were thermally charged during the preceding compression stage (1). The condensed water reinjected at each expansion stage is evaporated, and the air is reheated. Therefore, there is no liquid water at the turbine inlets (700, 701, 702), which is preferable for their proper operation. In addition, the flow rate is greater due to the reinjection of water, and the high temperature of the expansion line (2) at the inlet of the turbines (700, 701, 702) ensures a better process efficiency.

[0109] The heat from the air exiting the low-pressure turbine (700) is used to preheat the air from the compressed gas storage unit (1000) mixed with condensate (28) via a supplementary heat exchanger (800), as well as the air from the second expansion stage mixed with condensate (33) via a supplementary heat exchanger (801). In this embodiment, the supplementary heat exchangers (800, 801) are arranged in the first expansion stage (4) and the second expansion stage (4) of the expansion line (2). Furthermore, in each expansion stage, the supplementary heat exchanger (800, 801) is arranged between the mixer (600, 601) and the heat storage and recovery unit (202, 201). These additional heat exchange means (800, 801) can be of the tube / shell, plate, spiral or any other suitable technology type.For the illustrated embodiment, the air (40) from the low-pressure turbine (702) and possessing waste heat preheats in series the flow (33) upstream of the medium-pressure thermal energy storage (201) and then the flow (28) upstream of the high-pressure thermal energy storage (202).

[0110] The seventh embodiment can also be modified by adapting the number of compression stages and / or expansion stages.

[0111] Furthermore, the compression line can also conform to the embodiment of the figure 4 , that is to say without means of cooling (300, 301, 302).

[0112] As can be understood, the invention is not limited to the forms of embodiment of the system and process described above by way of example, but rather encompasses all variant embodiments. Comparative examples

[0113] The characteristics and advantages of the process according to the invention will become clearer upon reading the application examples below. Example No. 1 - not in accordance with the invention

[0114] This example implements the system and process illustrated in figure 1 not in accordance with the invention.

[0115] During the compression phase (1), an outside air stream (10), at a pressure of 1.02 bar (0.102 MPa) and a temperature of 27°C and a humidity of 14.6 g water / kg air (grams of water per kilogram of air), is compressed by a low-pressure compressor (100), exiting (11) at a temperature of 255°C and a pressure of 6 bar (0.6 MPa). This stream (11) is sent to a low-pressure heat storage and recovery unit (200) which cools the air to a temperature of 90°C (12) and stores this thermal energy until the expansion phase (2). The stream (12) is cooled again by the cooling unit (300) until it reaches an outlet temperature of 50°C (13). The flow (13) is then composed of air and water, from the humidity of the air, condensed during the cooling phases in (200) and / or (300).This condensed water (14) is separated from the compression line (1) in a gas-liquid separator (400) operating at the pressure of the flow (13). The flow (15), now completely gaseous again, is compressed by a medium-pressure compressor (101), from which it exits (16) at a temperature of 275°C and a pressure of 28 bar (2.8 MPa). The flow (16) is sent to a medium-pressure heat storage and recovery unit (201) which cools the air to a temperature of 100°C (17) and stores this thermal energy until the expansion phase (2). The flow (17) is cooled again by a cooling unit (301) until it reaches a temperature of 50°C at the outlet (18). The stream (18) is then composed of air and water, originating from the humidity of the air, condensed during the cooling phases in (201) and / or (301). This condensed water (19) is separated from the compression line (1) in a gas-liquid separator (401) operating at the pressure of the stream (18).The stream (20), once again entirely gaseous, is compressed by a high-pressure compressor (102), exiting (21) at a temperature of 250°C and a pressure of 117 bar (11.7 MPa). The stream (21) is sent to a high-pressure heat storage and recovery unit (202) which cools the air to a temperature of 45°C (22) and stores this thermal energy until the expansion phase (2). The stream (22) is cooled again by a cooling unit (302) until it reaches an outlet temperature of 30°C (23), 30°C being the air storage temperature. The stream (23) then consists of air and water, resulting from the humidity in the air, condensed during the cooling phases in (202) and / or (302). This condensed water (24) is separated from the compression line (1) in a gas-liquid separator (402) operating at the pressure of the flow (23).

[0116] The compressed air flow at a pressure of 117 bar (11.7 MPa) and a temperature of 30°C (25) is then sent to the compressed air storage means (1000) while awaiting the energy recovery phase (2).

[0117] When electricity is to be produced, the compressed air stream (26) at a pressure of 117 bar (11.7 MPa) and a temperature of 30°C, exiting the compressed air storage unit (1000), is heated in the high-pressure heat storage and recovery unit (202), which releases the heat stored during the compression phase (1) until the stream (27) reaches a temperature of 240°C. This hot, compressed air stream (27) is expanded in the high-pressure turbine (702), which produces electricity via an alternator, until it reaches a pressure of 28 bar (2.8 MPa) and a temperature of 85°C at the outlet (28). The stream (28) is heated in the medium pressure heat storage and recovery means (201) which releases the heat stored during the compression phase (1) until the stream (29) reaches a temperature of 265°C.This hot, compressed air stream (29) is expanded in the medium-pressure turbine (701), which generates electricity via an alternator, until it reaches an outlet pressure (30) of 5 bar (0.5 MPa) and a temperature of 75°C. The stream (30) is then reheated in the low-pressure heat storage and recovery unit (200), which releases the heat stored during the compression phase (1) until the stream (31) reaches a temperature of 245°C. This hot, compressed air stream (31) is then expanded in the low-pressure turbine (700), which generates electricity via an alternator, until it reaches an outlet pressure (32) of 1.02 bar (0.102 MPa) and a temperature of 80°C.

[0118] The energy storage process efficiency in Example 1 is 69.6% for a compressor power consumption of 100 MW. The total condensate flow rate across the three compression stages is 7.5 t / h. The thermal storage capacity is 87 MWth (thermal MW), and the required cooling capacity is 20.5 MWth. Example No. 2 according to the invention

[0119] This example implements the system and method according to the embodiment of the invention illustrated in figure 3 .

[0120] During the compression phase (1), a stream of dry air (10), at a pressure of 1.02 bar (0.102 MPa) and a temperature of 27°C, and containing no trace of water, is compressed by a low-pressure compressor (100), exiting (11) at a temperature of 260°C and a pressure of 6 bar (0.6 MPa). This stream (11) is sent to a low-pressure heat storage and recovery unit (200) which cools the air to a temperature of 60°C (12) and stores this thermal energy until the expansion phase (2). The stream (12) is cooled again by a cooling unit (300) until it reaches an outlet temperature of 50°C (13). The flow (13) is compressed by a medium pressure compressor (101) from which it emerges (14) at a temperature of 275°C and a pressure of 28 bar (2.8 MPa).The stream (14) is sent to a medium-pressure heat storage and recovery unit (201) which cools the air to a temperature of 80°C (15) and stores this thermal energy until the expansion phase (2). The stream (15) is cooled again by a cooling unit (301) until it reaches a temperature of 50°C at the outlet (16). This stream (16) is compressed by a high-pressure compressor (102) from which it exits (17) at a temperature of 250°C and a pressure of 117 bar (11.7 MPa). The stream (17) is sent to a high-pressure heat storage and recovery unit (202) which cools the air to a temperature of 40°C (18) and stores this thermal energy until the expansion phase (2). The stream (18) is cooled again by a cooling means (302) until it reaches a temperature of 30°C at the outlet (19), 30°C being the air storage temperature.

[0121] The compressed air flow at a pressure of 117 bar (11.7 MPa) and a temperature of 30°C (19) is then sent to a compressed air storage means (1000) pending the energy recovery phase (2).

[0122] When electricity is to be produced, an optimized flow of liquid water (21) at a pressure of 117 bar (11.7 MPa) and a temperature of 30°C is injected into the compressed air flow (20) exiting the storage tank (1000) via the mixer (600) to form the flow (22). The flow (22) is heated in the high-pressure heat storage and recovery unit (202), which releases the heat stored during the compression phase (1) until the flow (23) reaches a temperature of 240°C. This hot, compressed air flow (23) is expanded in the high-pressure turbine (700), which generates electricity via an alternator, until it reaches a pressure of 28 bar (2.8 MPa) and a temperature of 85°C at the outlet (24). An optimized flow of liquid water (25) at a pressure of 28 bar (2.8 MPa) and a temperature of 50°C is injected into the compressed air flow (24) via the mixer (601) to form the flow (26).The stream (26) is heated in the medium-pressure heat storage and recovery unit (201), which releases the heat stored during the compression phase (1) until the stream (27) reaches a temperature of 265°C. This hot, compressed air stream (27) is expanded in the medium-pressure turbine (701), which generates electricity via an alternator, until it reaches a pressure of 5 bar (0.5 MPa) and a temperature of 75°C at the outlet (28). An optimized stream of liquid water (29) at a pressure of 6 bar (0.6 MPa) and a temperature of 50°C is injected into the compressed air stream (28) via the mixer (600) to form the stream (30). The stream (30) is heated in the low pressure heat storage and recovery means (200) which releases the heat stored during the compression phase (1) until the stream (31) reaches a temperature of 245°C.This hot, compressed air stream (31) is expanded in the low-pressure turbine (702) producing electricity via an alternator, until it reaches at the outlet (32) a pressure of 1.02 bar (0.102 MPa) and a temperature of 80°C.

[0123] The energy storage process efficiency is 71.6% for a compressor power consumption of 100 MW. The total flow rate of liquid water injected to the three expansion stages is 9.1 t / h. The thermal storage capacity is 94.6 MWth and the required cooling capacity is 8.0 MWth.

[0124] Water injection therefore allows, by increasing the flow rate in the turbines in expansion, to improve the efficiency of the process by more than 2% compared to example 1 which does not conform to the invention and to reduce the cooling power. Example No. 3 according to the invention

[0125] This example implements the system and method according to the embodiment of the invention illustrated in figure 6 .

[0126] During the compression phase (1), an outside air stream (10), at a pressure of 1.02 bar (0.102 MPa) and a temperature of 27°C and a humidity of 14.6 g water / kg air, is compressed by a low-pressure compressor (100), exiting (11) at a temperature of 255°C and a pressure of 6 bar (0.6 MPa). This stream (11) is sent to a low-pressure heat storage and recovery unit (200) which cools the air to a temperature of 80°C (12) and stores this thermal energy until the expansion phase (2). The stream (12) is cooled again by a cooling unit (300) until it reaches an outlet temperature of 50°C (13). The flow (13) is then composed of air and water, from the humidity of the air, condensed during the cooling phases in (200) and / or (300).This condensed water (14) is separated from the compression line stream (1) in a gas-liquid separator (400), operating at the stream pressure (13), and then sent to a liquid storage unit (500) under a maintained pressure of 6 bar (0.6 MPa). The stream (15), now completely gaseous again, is compressed by a medium-pressure compressor (101), from which it exits (16) at a temperature of 275°C and a pressure of 28 bar (2.8 MPa). The stream (16) is sent to a medium-pressure heat storage and recovery unit (201) which cools the air to a temperature of 80°C (17) and stores this thermal energy until the expansion phase (2). The stream (17) is cooled again by a cooling unit (301) until it reaches an outlet temperature of 50°C (18). The flow (18) is then composed of air and water, from the humidity of the air, condensed during the cooling phases in (201) and / or (301).This condensed water (19) is separated from the compression line stream (1) in a gas-liquid separator (401), operating at the stream pressure (18), and then sent to a liquid storage unit (501) at a maintained pressure of 28 bar (2.8 MPa). The stream (20), now completely gaseous again, is compressed by a high-pressure compressor (102), from which it emerges (21) at a temperature of 250°C and a pressure of 117 bar (11.7 MPa). The stream (21) is sent to a high-pressure heat storage and recovery unit (202) which cools the air to a temperature of 40°C (22) and stores this thermal energy until the expansion phase (2). The stream (22) is cooled again by a cooling device (302) until it reaches a temperature of 30°C at the outlet (23), 30°C being the air storage temperature. The stream (23) then consists of air and water, resulting from the humidity in the air, condensed during the cooling phases in (202) and / or (302).This condensed water (24) is separated from the flow of the compression line (1) in a gas-liquid separator (402), operating at the pressure of the flow (23), and then sent to a liquid storage means (502) under a maintained pressure of 117 bar (11.7 MPa).

[0127] The compressed air flow at a pressure of 117 bar (11.7 MPa) and a temperature of 30°C (25) is then sent to the compressed air storage means (1000) pending the energy recovery phase (2).

[0128] When electricity is to be produced, a stream of condensed water (27) from the liquid storage unit (502) at a pressure of 117 bar (11.7 MPa) and a temperature of 30°C is reinjected into the compressed air stream (26) exiting the compressed air storage unit (1000) via the mixer (600) to form the stream (28). The stream (28) is heated in the high-pressure heat storage and recovery unit (202), which releases the heat stored during the compression phase until the stream (28) reaches a temperature of 240°C. This hot, compressed air stream (29) is expanded in the high-pressure turbine (700), which generates electricity via an alternator, until it reaches an outlet pressure (30) of 28 bar (2.8 MPa) and a temperature of 85°C. A flow of condensed water (31) from the liquid storage means (501) at a pressure of 28 bar (2.8 MPa) and a temperature of 50°C is reinjected into the compressed air stream (30) via the mixer (601) to form the stream (32). The stream (32) is heated in the medium-pressure heat storage and recovery unit (201), which releases the heat stored during the compression phase until the stream (33) reaches a temperature of 255°C. This hot, compressed air stream (33) is expanded in the medium-pressure turbine (701), which generates electricity via an alternator, until it reaches a pressure of 5 bar (0.5 MPa) and a temperature of 70°C at the outlet (34). A stream of condensed water (35) from the liquid storage means (500) at a pressure of 6 bar (0.6 MPa) and a temperature of 50°C is reinjected into the compressed air stream (34) via the mixer (600) to form the stream (36).The stream (36) is heated in the low-pressure heat storage and recovery unit (200), which releases the heat stored during the compression phase until the stream (37) reaches a temperature of 245°C. This hot, compressed air stream (37) is expanded in the low-pressure turbine (702), which generates electricity via an alternator, until it reaches a pressure of 1.02 bar (0.102 MPa) and a temperature of 80°C at the outlet (38).

[0129] The energy storage process efficiency is 70.4% for a compressor power consumption of 100 MW. The total condensate flow rate across the three compression stages is 7.5 t / h. The thermal storage capacity is 93 MWth and the required cooling capacity is 14.6 MWth.

[0130] The reinjection of condensation water therefore allows, by increasing the flow rate in the turbines in expansion, to improve the efficiency of the process by almost 1% compared to example 1 which does not conform to the invention and to reduce the power required for cooling by about 30%. Example No. 4 according to the invention

[0131] This example implements the system and method according to the embodiment of the invention illustrated in figure 7 .

[0132] During the compression phase (1), an outside air stream (10), at a pressure of 1.02 bar (0.102 MPa) and a temperature of 27°C and a humidity of 14.6 g water / kg air, is compressed by a low-pressure compressor (100), exiting (11) at a temperature of 255°C and a pressure of 6 bar (0.6 MPa). This stream (11) is sent to a low-pressure heat storage and recovery unit (200) which cools the air to a temperature of 80°C (12) and stores this thermal energy until the expansion phase (2). The stream (12) is cooled again by the cooling unit (300) until it reaches an outlet temperature of 50°C (13). The flow (13) is then composed of air and water, from the humidity of the air, condensed during the cooling phases in (200) and / or (300).This condensed water (14) is separated from the compression line stream (1) in a gas-liquid separator (400), operating at the stream pressure (13), and then sent to a liquid storage unit (500) under a maintained pressure of 6 bar (0.6 MPa). The stream (15), now completely gaseous again, is compressed by a medium-pressure compressor (101), from which it exits (16) at a temperature of 275°C and a pressure of 28 bar (2.8 MPa). The stream (16) is sent to a medium-pressure heat storage and recovery unit (201) which cools the air to a temperature of 82°C (17) and stores this thermal energy until the expansion phase (2). The stream (17) is cooled again by a cooling unit (301) until it reaches an outlet temperature of 50°C (18). The flow (18) is then composed of air and water, from the humidity of the air, condensed during the cooling phases in (201) and / or (301).This condensed water (19) is separated from the air stream (20) in a gas-liquid separator (401), operating at the pressure of the stream (18), and then sent to a liquid storage unit (501) under a maintained pressure of 28 bar (2.8 MPa). The stream (20), now completely gaseous again, is compressed by a high-pressure compressor (102), from which it emerges (21) at a temperature of 250°C and a pressure of 117 bar (11.7 MPa). The stream (21) is sent to a high-pressure heat storage and recovery unit (202) which cools the air to a temperature of 80°C (22) and stores this thermal energy until the expansion phase (2). The stream (22) is cooled again by a cooling device (302) until it reaches a temperature of 30°C at the outlet (23), 30°C being the air storage temperature. The stream (23) then consists of air and water, resulting from the humidity in the air, condensed during the cooling phases in (202) and / or (302).This condensed water (24) is separated from the air stream (25) in a gas-liquid separator (402), operating at the pressure of the stream (23), and then sent to a liquid storage means (502) under a maintained pressure of 117 bar (11.7 MPa).

[0133] The compressed air flow at a pressure of 117 bar (11.7 MPa) and a temperature of 30°C (25) is then sent to the compressed air storage means (1000) pending the energy recovery phase (2).

[0134] When electricity is to be produced, a stream of condensed water (27) from the liquid storage unit (502) at a pressure of 117 bar (11.7 MPa) and a temperature of 30°C is reinjected into the compressed air stream (26) exiting the compressed air storage unit (1000) via the mixer (600) to form the stream (28). The stream (28) is preheated in a supplementary heat exchanger (800) to reach an outlet temperature (29) of 70°C. The stream (29) is then reheated in the high-pressure heat storage and recovery unit (202), which releases the heat stored during the compression phase until the stream (30) reaches a temperature of 240°C. This hot, compressed air stream (30) is expanded in the high-pressure turbine (700) producing electricity via an alternator, until it reaches at the outlet (31) a pressure of 28 bar (2.8 MPa) and a temperature of 85°C.A stream of condensed water (32) from the liquid storage unit (501) at a pressure of 28 bar (2.8 MPa) and a temperature of 50°C is reinjected into the compressed air stream (31) via the mixer (601) to form the stream (33). The stream (33) is heated in the medium-pressure heat storage and recovery unit (201), which releases the heat stored during the compression phase until the stream (34) reaches a temperature of 255°C. This hot, compressed air stream (34) is expanded in the medium-pressure turbine (701), which generates electricity via an alternator, until it reaches a pressure of 5 bar (0.5 MPa) and a temperature of 70°C at the outlet (35). A stream of condensed water (36) from the liquid storage means (500) at a pressure of 6 bar (0.6 MPa) and a temperature of 50°C is reinjected into the compressed air stream (35) via the mixer (602) to form the stream (37).The stream (37) is heated in the low-pressure heat storage and recovery unit (200), which releases the heat stored during the compression phase until the stream (38) reaches a temperature of 245°C. This hot, compressed air stream (38) is expanded in the low-pressure turbine (702), which generates electricity via an alternator, until it reaches a pressure of 1.02 bar (0.102 MPa) and a temperature of 80°C at the outlet (39). This stream (39) is then sent to the heat exchanger (800) to transfer its energy to the stream (28). The resulting stream (40) exits the exchanger at 35°C.

[0135] The energy storage process efficiency is 70.2% for a compressor power consumption of 100.0 MW. The total condensate flow rate across the three compression stages is 7.5 t / h. The thermal storage capacity is 85.7 MWth, and the required cooling capacity is 21.8 MWth. This configuration also reduces the size of the high-pressure heat storage and recovery system by 21% compared to Example 1. Example No. 5 according to the invention

[0136] This example implements the system and method according to the embodiment of the invention illustrated in figure 8 In the same way as for example #3, we determine the operating conditions and the yield.

[0137] The efficiency of the energy storage system and process is 70.0% for a compressor power consumption of 100.0 MW. The total condensate flow rate across the three compression stages is 7.5 t / h. The thermal storage capacity is 85.7 MWth, and the required cooling capacity is 21.8 MWth. This configuration also reduces the size of the high-pressure heat storage and recovery unit (202) by 18% and the size of the medium-pressure heat storage and recovery unit (201) by 3% compared to Example 3. This configuration reduces the size of the high-pressure heat storage and recovery unit (202) by 16% compared to Example 1.

[0138] Thus, examples 2 to 4 show that the system and process according to the invention make it possible to increase the performance of the process, while limiting the power required for cooling, and, for certain embodiments, limiting the size of the means of heat storage and recovery.

Claims

1. A compressed-gas energy storage and recovery system comprising: - a gas compression line (1) with at least two successive compression stages (3), each compression stage (3) comprising a compression means (100, 101, 102) and a heat storage and recovery means (200, 201, 202) arranged downstream from said compression means (100, 101, 102), in the direction of flow of said gas, - at least one compressed gas storage means (1000) arranged at the outlet of said gas compression line (1) for storing said compressed gas, - a gas expansion line (2) for expanding said compressed gas stored in said compressed gas storage means (1000), said gas expansion line (2) comprising at least two successive expansion stages (4), each expansion stage (4) comprising an expansion means (700, 701, 702) and pipes configured to circulate said compressed gas in at least one of said heat storage and recovery means (200, 201, 202) of said compression stages (3) so as to heat said compressed gas, characterized in that said heat storage and recovery means (200, 201, 202) comprise heat storage particles for direct heat exchange between the gas and the heat storage particle material, with the particles remaining in the heat storage and recovery means, and each expansion stage (4) comprises a liquid delivery means (600, 601, 602), said means (600, 601, 602) of delivering said liquid being provided upstream, in the direction of flow of said gas, from said heat storage means (200, 201, 202).

2. A system as claimed in claim 1, wherein each compression stage (3) comprises a means of separating said gas and a liquid (400, 401, 402).

3. A system as claimed in claim 2 wherein, for each compression stage, said gas / liquid separation means (400, 401, 402) is arranged downstream from said heat storage and recovery means (200, 201, 202), in the direction of flow of said gas.

4. A system as claimed in any one of claims 2 or 3, wherein said system comprises a plurality of liquid storage means (500, 501, 502) for storing said liquid at the outlet of said gas / liquid separation means (400, 401, 402), and said delivery means (600, 601, 602) deliver said liquid of said liquid storage means (500, 501, 502).

5. A system as claimed in any one of the previous claims, wherein said compression line (1) comprises as many compression stages (3) as expansion line (2) comprises expansion stages (4), each heat storage and recovery means (200, 201, 202) of a compression stage (3) being used in the corresponding expansion stage (4).

6. A system as claimed in claim 5, wherein said compression line (1) and said expansion line (2) comprise three stages respectively.

7. A system as claimed in any one of the previous claims, wherein at least one compression stage (3) comprises a cooling means (300, 301, 302) downstream from heat storage and recovery means (200, 201, 202), in the direction of flow of said gas, preferably, said cooling means (300, 301, 302) comprises an air cooler.

8. A system as claimed in any one of the previous claims, wherein said expansion line comprises at least one additional heat exchange means (800, 801) between the gas at the outlet of said expansion line and said compressed gas.

9. A system as claimed in claim 8, wherein said at least one additional heat exchange means (800, 801) is arranged in the first expansion stage, in the direction of flow of said gas.

10. A system as claimed in any one of claims 8 or 9, wherein said expansion line (2) comprises two additional heat exchange means (800, 801) arranged in two expansion stages.

11. A system as claimed in any one of claims 8 to 10, wherein said at least one additional heat exchange means (800, 801) is arranged between said delivery means (600, 601, 602) for said liquid and said heat storage and recovery means (200, 201, 202), in the direction of flow of said gas.

12. A compressed-gas energy storage and recovery method comprising at least the following steps: - in energy storage phase: a) successively compressing at least twice a gas in a compression line (1) comprising at least two compression stages (3), each compression stage (3) comprising at least one compression means (100, 101, 102), b) after each compression step, recovering the heat of said compressed gas in at least one heat storage and recovery means (200, 201, 202), c) storing said cooled compressed gas in at least one compressed gas storage means (1000), - in energy recovery phase: d) circulating the compressed gas leaving compressed gas storage means (1000) in an expansion line (2) comprising at least two successive expansion stages (4), and in each expansion stage (4), heating the compressed gas by circulating it in one of said heat storage and recovery means (200, 201, 202) using the heat stored during the compression step, then expanding the heated compressed gas in an expansion means (700, 701, 702), characterized in that the heat is stored in heat storage particles by direct heat exchange between the gas and the heat storage particle material, the particles remaining in the heat storage and recovery means, and before each expansion step, a liquid is fed into said compressed gas prior to the step of heating said gas.

13. A method as claimed in claim 12 wherein, after each compression step, said gas and a liquid present in said gas are separated.

14. A method as claimed in claim 13, wherein said separated liquid is stored, and said liquid fed into said compressed gas is said stored liquid.

15. A method as claimed in any one of claims 12 to 14, wherein as many compression steps as there are expansion steps are carried out, and means (200, 201, 202) for storing and recovering the heat in each step b) is used for heating the compressed gas of the corresponding expansion step.

16. A method as claimed in any one of claims 12 to 15 wherein, after each heat recovery step, the compressed gas at the outlet of heat storage and recovery means (200, 201, 202) is cooled in a cooling means (300, 301, 302) prior to sending the gas to the next compression step or to compressed gas storage means (1000).

17. A method as claimed in any one of claims 12 to 16 wherein, prior to at least one expansion step, said gas is heated by at least one additional heat exchange with said gas at the outlet of said expansion line.

18. A method as claimed in claim 17, wherein said at least one additional heat exchange is carried out for the first expansion step, in the direction of flow of said gas.

19. A method as claimed in any one of claims 17 or 18, wherein two additional heat exchanges are carried out for two expansion steps.

20. A method as claimed in any one of claims 17 to 19, wherein said additional heat exchange is carried out after the step of feeding said stored liquid into said compressed gas.