WO2022117397A1

WO2022117397A1 - System and method for storing and recovering energy using compressed gas with reheating of liquid

Info

Publication number: WO2022117397A1
Application number: PCT/EP2021/082601
Authority: WO
Inventors: David Teixeira; Elsa MULLER-SHERNETSKY
Original assignee: IFP Energies Nouvelles
Priority date: 2020-12-03
Filing date: 2021-11-23
Publication date: 2022-06-09
Also published as: FR3117166B1; FR3117166A1

Abstract

The invention relates to a system and method for storing and recovering energy by means of compressed gas, comprising a compression line (1), an air storage means (1000) and an expansion line (2), wherein a liquid is heated by means of the heat of the expanded gas at the outlet of the expansion line, and the heated liquid is fed into the expansion line.

Description

GAS ENERGY STORAGE AND RECOVERY SYSTEM AND METHOD

TABLET WITH LIQUID HEATING

Technical area

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

While global energy goals aim to favor renewable energies over fossil fuels and to gradually increase their proportion in the energy mix, their variable nature remains their major drawback. To address this problem, energy storage appears to be the ideal solution. By storing the surplus electricity produced at the peak of production in order to have it available when it falls below demand, storage makes it possible to overcome the constraint of variability and provides continuity, or at least flexibility. , basically non-existent, to renewable energies. Thus, the need for an energy storage process exists and will grow with the proportion of this type of energy in the global energy mix.

Many mature storage technologies already exist today, such as mechanical storage such as Pumped Energy Transfer Stations (STEP) using 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 this altitude. When the demand for electricity increases, the water from the upper reservoir is sent back to the lower reservoir via a hydraulic turbine which will then generate electricity via an alternator. Hydroelectric dams also work on the same concept: the dam retains water at a higher altitude upstream than downstream and when the demand for electricity increases, the dam releases the water by passing it through hydraulic turbine generators producing electricity. Compressed air energy storage (CAES) technology is one of the mechanical solutions. Other electrochemical type technologies can also be used for energy storage such as lithium-ion, lead-acid or even nickel-cadmium batteries, or circulation batteries using electrolytes.

Compressed air energy storage (CAES) is a mature technology whose first installation was built in Germany at the end of the 1970s, storing 290 MW. The principle of CAES is to use the electricity produced and not consumed to compress air. In order to avoid any damage to the compressors, the heat resulting from the compression is evacuated between each stage. Air compressed at medium or high pressure (40 bar to 300 bar) is sent to a natural type storage such as a salt cave, a mine (salt, limestone, coal) or even to an artificial storage while waiting for the phase energy discharge. During the electricity production phase, the stored air is extracted from the storage in order to be expanded in turboalternators. For the basic CAES system such as that established in the late 1970s, compressed air was used to power gas turbines (also called combustion turbines). These turbines burn via a natural gas combustion chamber in the presence of compressed air to produce very hot combustion gases (500°C-800°C) that are expanded to produce electricity. The CAES process has an energy yield of around 50%.

Prior technique

A variant of CAES is the adiabatic process or AACAES (for “advanced adiabatic compressed air energy storage”). The main difference with the original CAES is that the heat resulting from the compression is no longer evacuated between each stage, but stored in order to be able to heat the air upstream of the turbines during the electricity production phase. Thanks to this reuse of the thermal energy internal to the process, the efficiency of the ACAES reaches approximately 70%. The cooling of the air in the compression phase can be done via an indirect contact exchange in a heat exchanger with a heat transfer fluid. The hot heat transfer fluid is then stored and insulated as much as possible thermally in order to be able to transfer its heat to the air during the expansion phase. It can also be carried out via an exchange in direct contact between the air and a thermal storage mass operating by sensible heat or thanks to phase change materials. In both cases, the heat from the air will be stored directly in the mass, either within the material, or by performing a phase change in the material. During the expansion phase, the cold air is reinjected into the thermal storage mass and by direct contact, the air will heat up by capturing the heat of the material or by allowing the reverse phase change releasing this heat. This cooling of the air can then induce water condensation if the air has a certain humidity. This condensed water must then be extracted from the air circuit in order not to damage the compressors downstream.

A first solution to limit the damage to the compressors is to extract the water from the compression line, by means of a gas/liquid separator provided at each compression stage. Figure 1 illustrates, schematically in block diagram form, such an ACAES system and method. This figure shows the storage phase of energy by compression of a gas, and the phase of energy production by expansion of a gas. 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 recommendations of the suppliers. In the illustrated embodiment, the compression line (1) comprises three stages (3) of compression. Each compression stage (3) includes 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 (10) used in the illustrated method is ambient air, containing a water saturation related to its temperature and its 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 by storing this thermal energy. The heat storage and recovery means (200) is adapted to low pressure, the heat storage and recovery means (201) is adapted to medium pressure and the heat storage and recovery means (202) is suitable for high pressure. Cooling means (300, 301, 302) can 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 stage compression or before storage. Once the air has 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 air entering the compressor without any trace of liquid water. This water condensation can 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 stage, according to the recommendations of the suppliers, in order to produce electricity via alternators, not shown in the diagram. The turbine (702) is a low pressure turbine, the turbine (701) is a medium pressure turbine and the turbine (700) is a high pressure turbine. In addition, before each expansion, the compressed gas is heated by the heat stored in the heat storage and recovery means (200, 201, 202). For this system and this process, the condensed water is just extracted, the associated energy is therefore lost.

Other compressed gas energy storage and recovery systems and methods contemplate the recovery of the energy contained in the condensation water. For example, the patent application FR3074844 (WO2019/115121) discloses an improved ACAES system and process by reinjecting condensates, resulting from the cooling of the air, into the water serving as a heat transfer fluid allowing the storage of the heat extracted from the air between each compression stage. However, this system and this method are difficult to implement because of the heat transfers between the different temperatures of the water. This technology is based on a direct contact heat exchanger in counter-current between the moist air that is to be cooled and the heat transfer fluid that is heated. As the air cools, moisture appears and is transported by the heat transfer fluid. As the latter circulates against the current, the humidity will encounter the hot air again and will therefore evaporate again. There is an accumulation of water in the exchanger. In addition, this system is difficult to implement because of the circulation of a heat transfer fluid, which requires pipes, pumping means and additional storage means, which also poses space constraints.

Patent application WO16012764 discloses an ACAES process in which the humidity of the air is condensed upstream of the air storage in the compression phase, stored and reinjected into the air in the expansion phase at the outlet of the air storage . However, this process does not make it possible to protect the compressors of the various compression stages by limiting the water which passes through them. Moreover, this configuration allows neither an optimization of the energy recovered from the condensed water nor an economic optimization: condensed water at low pressure is stored at high pressure. In addition, here too, this system is difficult to implement due to the circulation of a heat transfer fluid, which requires pipes, pumping means and additional storage means, which also poses space constraints. .

Patent application WO16079485 discloses an ACAES process in which the humidity of the air is condensed upstream of the air storage in the compression phase, stored and reinjected into the air in the expansion phase at the outlet of the storage means of the air. However, this process does not make it possible to protect the compressors of the various compression stages by limiting the water which passes through them. Moreover, this configuration allows neither an optimization of the energy recovered from the condensed water nor an economic optimization: condensed water at low pressure is stored at high pressure. In addition, this system is difficult to implement due to the circulation of a heat transfer fluid, which requires pipes, pumping means and additional storage means, which also poses space constraints.

Summary of the invention The present invention relates to a system and a method for the storage and recovery of energy by compressed gas making it possible to optimize the efficiency of the system and of the method, by limiting the size of the system and by simplifying the operation. For this, the present invention relates to a system and a method for storing and recovering energy by compressed gas, comprising a compression line, an air storage means, and an expansion line. According to the invention, a liquid is heated by means of the heat of the gas expanded at the outlet of the expansion line, and the heated liquid is introduced into the expansion line. The introduction of liquid into the expansion line makes it possible to increase the flow rate of gas in the expansion line and therefore the yield of the system and of the method according to the invention. In addition, the heating of the liquid by the heat of the expanded gas at the outlet of the expansion line makes it possible to recover the thermal energy contained in the expanded gas at the outlet of the expansion line, and thus to introduce a hot liquid into the expansion line, which makes it possible to limit heating requirements in the expansion line, and consequently to limit the size of the system.

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

A gas compression line comprising at least one compression stage, each compression stage comprising compression means and heat storage and recovery means arranged downstream of said compression means, in the direction of circulation of said gas,

- At least one compressed gas storage means arranged at the outlet of said gas compression line to store 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 one expansion stage, each expansion stage including expansion means and conduits configured to circulating said compressed gas in said means for storing and recovering heat from said at least one compression stage so as to heat said compressed gas, said system comprises at least one means for exchanging heat between said expanded gas at the outlet of said expansion line and a liquid, and in that at least one expansion stage comprises means for introducing said heated liquid, said means for introducing said liquid being provided upstream, in the direction of circulation of said gas, of said means of heat storage and recovery.

According to one embodiment, said compression line comprises as many successive compression stages as the expansion line comprises successive expansion stages, each means of storing and recovering heat from a compression stage being used in the corresponding expansion stage.

Advantageously, said compression line and said expansion line respectively comprise three successive stages.

According to one embodiment, said heat storage and recovery means comprises heat storage particles.

According to one aspect, at least one compression stage comprises a gas/liquid separation means, and said system comprises at least one means for storing said separated liquid, said separated and stored liquid being said liquid reheated and introduced into said expansion line.

According to one characteristic, said system comprises a plurality of heat exchange means between said expanded gas at the outlet of said expansion line and said liquid.

According to one option, said heat exchange means are arranged in series or in parallel for the circulation of said gas at the outlet of said expansion line.

According to one embodiment, at least one compression stage comprises cooling means downstream of the heat storage and recovery means, in the direction of circulation of said gas, preferably, said cooling means comprises an aero- refrigerant.

In addition, the invention relates to a method for storing and recovering energy by compressed gas comprising at least the following steps:

- In the energy storage phase: a) a gas is successively compressed at least once in a compression line comprising at least one compression stage, each compression stage comprising at least one compression means; b) after each compression step, the heat of 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;

- In the energy recovery phase: d) the compressed gas leaving said at least one compressed gas storage means is circulated in an expansion line comprising at least one expansion stage, and in each expansion stage, it is heated the compressed gas by circulating it in one of said heat storage and recovery means thanks to the heat stored during the compression step, then the heated compressed gas is expanded in an expansion means, for this process, heat is exchanged between said expanded gas at the outlet of said expansion line and a liquid, and one introduces said heated liquid in said compressed gas before at least one step of heating said gas preceding an expansion step.

According to one embodiment, as many successive compression steps are carried out as successive expansion steps, and the heat storage and recovery means of each of the steps b) are used to heat the compressed gas from the corresponding relaxation step.

According to one implementation, after each heat recovery step, the compressed gas at the outlet of the heat storage and recovery means is cooled in a cooling means before the gas is sent to the step of next compression or in the compressed gas storage means.

In one aspect, heat is stored in heat storage particles.

According to one characteristic, after at least one compression step, said gas and a liquid present in said gas are separated, and said separated gas is stored, said separated and stored liquid being said liquid heated and introduced into said at least one expansion step. .

According to one embodiment option, a plurality of heat exchanges are implemented between said expanded gas at the outlet of said expansion line and said liquid.

Advantageously, said plurality of heat exchanges are implemented in series or in parallel for the circulation of said expanded gas at the outlet of said expansion line.

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

List of Figures

FIG. 1, already described, illustrates a system and a method for storing and recovering energy by compressed gas according to the prior art. FIG. 2 illustrates a system and a method for storing and recovering energy by compressed gas according to a first embodiment of the invention.

FIG. 3 illustrates a system and a method for storing and recovering energy by compressed gas according to a second embodiment of the invention.

FIG. 4 illustrates a system and a method for storing and recovering energy by compressed gas according to a third embodiment of the invention.

FIG. 5 illustrates a system and a method for storing and recovering energy by compressed gas according to a fourth embodiment of the invention.

FIG. 6 illustrates a system and a method for storing and recovering energy by compressed gas according to a fifth embodiment of the invention.

FIG. 7 illustrates a system and a method for storing and recovering energy by compressed gas according to a sixth embodiment of the invention.

Description of embodiments

The present invention relates to a system and a method for the storage and recovery of energy by compressed gas.

In the present invention the terms "upstream", "downstream", "input", "output", "before", "after" are defined by the direction of circulation of the gas, respectively during the energy storage phase (compression phase), and during the energy recovery phase (relaxation phase).

The system according to the invention comprises:

- a compression line (referred to as a "compression line", the gas line going from the gas inlet to the compressed gas storage means passing through at least one compression means), with at least one stage of compression (when the compression line has at least two compression stages, these are successive: in series), each compression stage includes:

• a means of compressing the gas (compressor), making it possible to increase the pressure of the gas, with a view to its storage, the means of compression can be axial compressors, centrifugal, or any other technology, • a heat storage and recovery means arranged downstream of the compression means, in order to store the heat generated by the compression, and to reduce the temperature of the gas before the next compression stage or before the storage means of compressed gas,

- at least one compressed gas storage means, for storing the compressed gas at the outlet of the compression line in order to reuse it later, the compressed gas storage means can be a natural cavity such as a saline cavity, an old mine or an aquifer or artificial storage;

- a gas expansion line (referred to as "expansion line", the gas line going from the compressed gas storage means to the gas outlet passing through at least one expansion means) with at least one expansion stage (when the expansion line comprises at least two expansion stages, these are successive: in series), each expansion stage comprises:

• at least one means of expanding the compressed gas to generate energy, for example a turbine,

• pipes for circulating the gas in one of the means of storage and heat recovery of the compression line, so as to recover the stored heat and to increase the temperature of the gas to increase the energy produced in the means of relaxation.

According to the invention, the system and the method comprise at least one heat exchange means between the expanded gas at the outlet of the expansion line and a liquid. In addition, at least one expansion stage comprises a means for introducing and mixing the heated liquid in the expansion line. The liquid introduction means allows mixing between the gas from the expansion line and the liquid from the liquid storage means. Thus, thanks to the injection of liquid, the gas flow is increased in each expansion stage, which makes it possible to increase the efficiency of the system and of the process. The liquid introduction and mixing means are arranged in the expansion line upstream of the heat storage means, in this way the injected gas and liquid mixture is heated in the heat storage means, which allows to vaporize the liquid, and in this way only a gas is led into the expansion means. Thus, the expanded and hot gas at the outlet of the expansion line is cooled, while the liquid to be injected into the expansion line can be heated. In this way, it is possible to recover lost thermal energy, and thus reduce the heating needs of the compressed gas and liquid mixture, which makes it possible to reduce the dimensions of at least one heat storage and recovery means ( and therefore the cost of the heat storage and recovery means), while maintaining a simple method and system. According to one embodiment of the invention, the gas can be air. It may be air taken from the ambient environment. Alternatively, it may include any other gas.

According to one aspect of the invention, the liquid is water. Alternatively, it may include any other liquid.

Preferably, in order to optimize the storage and recovery of energy, the compression line comprises at least two successive compression stages, and the expansion line comprises at least two successive expansion stages.

Advantageously, the compression line and the expansion line can comprise as many stages. In other words, the number of compression stages and the number of expansion stages can be identical. This embodiment allows a "symmetrical" design of the compression and expansion lines, in particular with similar operating pressures and temperatures, which promotes heat exchange in the heat storage and recovery means. Thus, the system and method are simplified.

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 good management of temperatures and pressures, while maintaining a simple design.

Alternatively, the number of compression stages and the number of expansion stages may be different. For this embodiment, provision may be made to pool at least part of the heat storage and recovery means.

When the expansion line comprises a plurality of expansion stages, the system may comprise a plurality of heat exchange means between the expanded gas at the outlet of the expansion line and the liquid.

For this situation, the heat exchange means between the expanded gas at the outlet of the expansion line and the liquid can be passed through in series by the expanded gas at the outlet of the expansion line. This variant limits the number of pipes. Alternatively, the means for exchanging heat between the expanded gas at the outlet of the expansion line and the liquid can be traversed in parallel by the expanded gas at the outlet of the expansion line. This variant allows the heat exchange for each expansion stage to be carried out with the same temperature of the expanded gas.

According to one embodiment of the invention, the heat storage and recovery means may comprise heat storage particles. Thus, the heat exchange is carried out by direct exchange between the gas and a material, the material remaining in the heat storage and recovery means. In other words, there is no circulation of heat-storage particles. Consequently, it is not necessary to have a dedicated system which comprises storage tanks for a heat transfer fluid, pumping means, and dedicated pipes. For example, the material can be stones, concrete, gravel, beads of phase change material (PCM), zeolites or any similar material.

According to one implementation of the invention, at least one compression stage can comprise a gas/liquid separation means, which makes it possible to extract the liquid present in the gas, in particular due to the condensation of the water present in the gas, and making it possible to eliminate the traces of liquid which could be contained in the gas after it has cooled and which could damage the system, in particular the compression means.

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.

Alternatively, the gas/liquid separation means can be arranged upstream of the compression means.

For this implementation of the method according to the invention, the system can comprise liquid storage means, in order to store the liquid extracted from the compression line. For example, a liquid storage means may be provided per compression stage (therefore per gas-liquid separation means). Thus, the liquid can be stored at different pressures. For this implementation of the invention, the liquid extracted (separated) from the compression line, then stored, is the liquid which is reheated, then introduced into the expansion line. Thus, it is not necessary to provide a specific source of liquid. In addition, this implementation makes it possible to recover the energy contained in the liquid in the compression line.

According to one aspect of this implementation, the liquid storage means and the heat exchange means between the expanded gas and the liquid can be different and non-integrated means, which allows better management of temperatures and pressures. .

As a variant, the heat exchange means between the expanded gas and the liquid can be integrated within the liquid storage means, so as to limit the number of elements of the system.

Additionally, at least one compression stage may include cooling means. This cooling means can be arranged downstream of the heat storage and recovery means. This cooling means makes it possible to cool the gas more significantly, which makes it possible to reduce the dimensions of the means for storing and recovering the heat. These gas cooling means can be air coolers or heat exchangers (tubes/calender, plate, spiral or other suitable technologies) exchanging with a heat transfer fluid which can be water, propane, butane or any other refrigerant. suitable for the necessary cooling. The cooling means can be adapted to the pressure of the air entering and exchanging with each of them. The cooling means are not involved in the energy recovery phase.

For one embodiment, the possible 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 the heat storage and recovery means as well as in the cooling means.

Furthermore, the invention relates to a method for storing and recovering energy by compressed gas.

The method according to the invention implements the following steps:

- In the energy storage phase (compression phase): a) a gas is compressed at least once in a compression line comprising at least one compression stage, each compression stage comprising at least one compression means; b) after each compression step, the heat of the compressed gas is recovered in at least one heat storage and recovery means; c) the cooled compressed gas is stored at the outlet of the compression line in a compressed gas storage means;

- In the energy recovery phase (expansion phase): d) the compressed gas leaving the compressed gas storage means is circulated in an expansion line comprising at least one expansion stage, and in each expansion stage, the compressed gas is heated by causing it to circulate in one of the means for storing and recovering the heat thanks to the heat stored during the compression step and then the heated compressed gas is expanded in an expansion means.

According to the invention, heat is exchanged between the expanded gas at the outlet of the expansion line and a liquid. In addition, the heated liquid is introduced into the compressed gas before at least one step of heating the gas preceding an expansion step. The liquid introduction step allows mixing between the gas from the expansion line and the liquid from the liquid storage means. Thus, thanks to the injection of water, the gas flow is increased in each expansion stage, which makes it possible to increase the efficiency of the system and the process. The step of introducing and mixing the liquid can be implemented in the expansion line upstream of the heat storage step, in this way, the water and liquid mixture injected is heated in the storage means heat, which makes it possible to vaporize the liquid, and in this way only a gas is led into the expansion means. Thus, the hot gas leaving the expansion line is cooled, while the liquid to be injected into the expansion line can be heated. In this way, it is possible to recover lost thermal energy, and thus reduce the heating needs of the compressed gas and liquid mixture, which makes it possible to reduce the dimensions of at least one heat storage and recovery means ( and therefore the cost of the means of storing and recovering the heat).

Preferably, the compressed gas energy storage and recovery method can implement the compressed gas energy storage and recovery system according to any one of the variants or combinations of variants as described below. above. According to one embodiment of the invention, the gas can be air. It may be air taken from the ambient environment. Alternatively, it may include other gas.

According to one aspect of the invention, the liquid can be water. Alternatively, it may include other liquid.

Preferably, the method can implement at least two successive compression steps, and at least two successive expansion steps, so as to optimize the storage and recovery of energy.

Advantageously, as many compression steps as expansion steps can be carried out. In this case, the compression line and the expansion line can comprise as many stages. In other words, the number of compression stages and the number of expansion stages can be identical. This embodiment allows a "symmetrical" design of the compression and expansion lines, in particular with similar operating pressures and temperatures, which promotes heat exchange in the heat storage and recovery means. Thus, the system and method are simplified.

In addition, the energy storage phase may include a cooling step. This cooling step can be carried out after the heat storage step by a cooling means. This cooling step makes it possible to cool the gas more significantly, which makes it possible to reduce the dimensions of the means for storing and recovering the heat. These cooling means can be air coolers or heat exchangers (tubes/shell, plates, spirals or other suitable technologies) exchanging with a heat transfer fluid which can be water, propane, butane or any other refrigerant suitable for the necessary cooling. The cooling means can be adapted to the pressure of the air entering and exchanging with each of them.

For this embodiment, the optional gas/liquid separation step can be carried out after the cooling step. In this way, it is possible to extract the liquid formed by condensation in the heat storage and recovery means as well as in the cooling stage.

According to one embodiment of the invention, heat can be stored and recovered in heat storage particles. In other words, the heat storage and heat recovery means include heat storage particles. Thus, the heat exchange is carried out by direct exchange between the gas and a material, the material remaining in the heat storage and recovery means. In other words, there is no circulation of heat-storage particles. Consequently, it is not necessary to have a dedicated system which comprises storage tanks for a heat transfer fluid, pumping means, and dedicated pipes. For example, the material can be stones, concrete, gravel, beads of phase change material (PCM), zeolite, or any similar material.

According to one implementation of the invention, after each compression step, the gas and a liquid present in the gas can be separated. This step makes it possible to extract the liquid present in the gas, in particular due to the condensation of the water present in the gas, and making it possible to eliminate the traces of liquid which could be contained in the gas after it has cooled and which could damage the system, in particular the means of compression.

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.

Alternatively, the gas/liquid separation step can be carried out before the compression step.

Further, the method may include a liquid storage step, to store the liquid extracted (separated) from the compression line. For example, there may be provided a means of liquid storage per compression stage (therefore per gas-liquid separation stage). Thus, the liquid can be stored at different pressures.

For this implementation of the invention, the liquid extracted (separated) from the compression line and then stored is the liquid which is heated and then introduced into the expansion line. Thus, it is not necessary to provide a specific source of liquid. In addition, this implementation makes it possible to recover the energy contained in the liquid in the compression line.

As a variant, the heat exchange means between the expanded gas and the liquid can be integrated (included) within the liquid storage means, so as to limit the number of elements of the system.

When implementing a plurality of expansion steps, it is possible to implement a plurality of heat exchanges between the gas expanded at the outlet of the expansion line and the liquid.

For this situation, the heat exchange means between the expanded gas at the outlet of the expansion line and the liquid can be passed through in series by the expanded gas at the outlet of the expansion line. This variant limits the number of pipes.

Alternatively, the heat exchange means between the expanded gas at the outlet of the expansion line and the liquid can be crossed in parallel by the expanded gas at the outlet of the expansion line. This variant allows the heat exchange for each expansion stage to be carried out with the same temperature of the expanded gas.

Figure 2 illustrates, schematically and in a non-limiting manner, a system and a method for storing and recovering energy by compressed gas (in this case air) according to a first embodiment of the invention. According to the first embodiment, the method and the system consist of a compression line (1), including three compression stages (3) depending on the air pressure to be reached. Each compression stage (3) comprises compression means (100, 101, 102) also called a compressor. These compressors (100, 101, 102) can be axial, centrifugal, or any other technology. 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 to be compressed (10) used in the system and the method is ambient air, for example dry air. A low-pressure element (for example turbine, compressor, etc.) is called an element adapted to the low pressure in which the gas or liquid circulates in the element, medium-pressure element an element adapted to the medium pressure in which the gas or the liquid circulates in the element, and high pressure element an element adapted to the high pressure in which the gas or the liquid circulates in the element.

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. This compressed air storage means (1000) can be a natural cavity such as a salt cavity, an old mine or an aquifer or even an artificial storage.

Heat storage and recovery means (200, 201, 202) are arranged after each compressor (100, 101, 102) in order to cool the hot compressed air at the compression outlet while storing this thermal energy. The exchange/storage takes place by direct contact between the air and the material allowing the heat of the air to be stored. This material can be stones, concrete, gravel or any other suitable solid material. The heat storage and recovery means (200, 201, 202) are adapted to the pressure of the incoming air transferring its energy to each of them. 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 heat (202) is suitable for high pressure.

During the energy production phase, the compressed air passes through the expansion line (2), which has three expansion stages (4). The air is expanded via one or more expansion means, for example turbines (700, 701, 702), placed in each expansion stage (4), in order to produce electricity via alternators, not shown. The turbine (702) is a low pressure turbine, the turbine (701) is a medium pressure turbine, and the turbine (700) is a high pressure turbine. In the first stage of each expansion stage (4), water is injected into the compressed air via mixers (600, 601, 602), the water being preheated beforehand by the heat exchange means (800 , 801 , 802). The heat exchange means (800, 801, 802) can be heat exchangers of the tube/shell, plate, spiral type or any other suitable technology and the exchange takes place between the water injected into the expansion and the waste heat of the air leaving the low pressure turbine (702). The heat exchange means (800, 801, 802) are arranged in series by relative to the flow of low pressure air leaving the low pressure turbine (702), that is to say leaving the expansion line. The order of passage of the gas at the outlet of the expansion line in the heat exchange means (800, 801, 802) can be the order represented in FIG. 2, or any other order, for example the order ( 802, 801, 800), or (801, 802, 800) or (801, 800, 802).

The compressed air/water mixture is heated, before entering the turbine, by the heat storage and recovery means (200, 201, 202), thermally loaded during the previous compression phase. The water contained in the expansion line (2) is evaporated and the air heated. There is therefore no liquid water at the inlet of the turbines (700, 701, 702), which is preferable for the correct operation of these, and the greater flow rate due to the injection of water as well as the high temperature of the expansion line (2) at the inlet of the turbines (700, 701, 702) ensures better process efficiency.

Figure 3 illustrates, schematically and in a non-limiting way, a system and a method for storing and recovering energy by compressed gas (in this case air) according to a second embodiment of the invention. The second embodiment differs from the first embodiment by the number of compression stages and the number of expansion stages. For this embodiment, the compression line (1) comprises two compression stages (3) and the expansion line (2) comprises two expansion stages (4).

The first embodiment can also be modified by adding compression stages and/or expansion stages.

Figure 4 illustrates, schematically and in a non-limiting manner, a system and a method for storing and recovering energy by compressed gas (in this case air) according to a third embodiment of the invention. The third embodiment differs from the first embodiment in that each compression stage comprises a gas/liquid separation means, and that the system comprises liquid storage means, and in the fact that the liquid heated and introduced in the expansion line is the liquid separated from the compression line and stored.

According to the third embodiment, the method and the system consist of a compression line (1), including three compression stages (3) depending on the air pressure to be reached. Each compression stage (3) comprises compression means (100, 101, 102) also called a compressor. These compressors (100, 101, 102) can be axial, centrifugal, or any other technology. 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 to be compressed (10) in the system and the process is ambient air, containing a water saturation related to its temperature and its pressure.

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 of the air, is extracted from the compression line by separators gas-liquid (400, 401, 402) in order to have air at the compressor inlet without any trace of liquid water. This water condensation can take place in the heat storage and recovery means (200, 201, 202). The water condensed at each compression stage is sent to liquid storage means (500, 501, 502), each of which resists the pressure at which the water is extracted from the air, in other words the liquid storage means (500) is suitable for low pressure, the liquid storage means (501) is suitable for medium pressure, and the liquid storage means (502) is suitable for high pressure.

During the energy production phase, the compressed air passes through the expansion line (2), which has three expansion stages (4). The air is expanded via one or more expansion means, for example turbines (700, 701, 702), placed in each expansion stage (4), in order to produce electricity via alternators, not shown. The turbine (702) is a low pressure turbine, the turbine (701) is a medium pressure turbine, and the turbine (700) is a high pressure turbine. In the first stage of each expansion stage (4), water condensed and stored during the energy storage phase is reinjected with compressed air via mixers (600, 601, 602), the water being previously preheated by the heat exchange means (800, 801, 802). The heat exchange means (800, 801, 802) can be tube/shell, plate, spiral type heat exchangers or any other suitable technology and the exchange takes place between the condensed water and the waste heat of the the air leaving the low pressure turbine (702). The heat exchange means (800, 801, 802) are arranged in series with respect to the flow of low pressure air leaving the low pressure turbine (702), that is to say leaving the expansion line .

The compressed air/water mixture is heated, before entering the turbine, by the heat storage and recovery means (200, 201, 202), thermally loaded during the previous compression phase. The water contained in the expansion line (2) is evaporated and the air heated. There is therefore no liquid water at the inlet of the turbines (700, 701, 702), which is preferable for the proper functioning of these, and the greater flow rate due to the reinjection of water as well as the high temperature of the expansion line (2) at the inlet of the turbines (700, 701, 702) ensures better process efficiency.

The third embodiment can also be modified by adapting the number of compression stages and/or expansion stages.

Figure 5 illustrates, schematically and in a non-limiting manner, a system and a method for storing and recovering energy by compressed gas (in this case air) according to a fourth embodiment of the invention. The fourth embodiment corresponds to the third embodiment for which cooling means (300, 301, 302) have been added in the compression line (1). Therefore, only the compression line (1) is described for this embodiment.

According to the fourth embodiment, the method and the system consist of a compression line (1), including three compression stages (3) depending on the air pressure to be reached. Each compression stage (3) comprises compression means (100, 101, 102) also called a compressor. These compressors (100, 101, 102) can be axial, centrifugal, or of any other technology. 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 to be compressed (10) in the system and the process is ambient air, containing a water saturation related to its temperature and its 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. This compressed air storage means (1000) can be a natural cavity such as a saline cavity, an old mine or an aquifer or even an artificial storage.

Heat storage and recovery means (200, 201, 202) are arranged after each compressor (100, 101, 102) in order to cool the hot compressed air at the compression outlet while storing this thermal energy. The exchange/storage takes place by direct contact between the air and the material allowing the heat of the air to be stored. This material can be stones, concrete, gravel or any other suitable solid material. The heat storage and recovery means (200, 201, 202) are adapted to the pressure of the incoming air transferring its energy to each of them. 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 heat (202) is suitable for high pressure. Cooling means (300, 301, 302) can 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 stage compression or before storage. These cooling means (300, 301, 302) can be air coolers or heat exchangers (tubes/shell, plates, spirals or other suitable technologies) exchanging with a heat transfer fluid which can be water, propane , butane or any other refrigerant suitable for the necessary cooling. The cooling means (300, 301, 302) are adapted to the pressure of the air entering and exchanging with each of them. The cooling means (300) is suitable for low pressure, the cooling means (301) is suitable for medium pressure and the cooling means (302) is suitable for high pressure.

Once the air has cooled and before the next compression stage, the condensed water (ie the liquid present in the air), resulting from the humidity of the air, is extracted from the compression line by separators gas-liquid (400, 401, 402) in order to have air at the compressor inlet without any trace of liquid water. This water condensation can take place in the heat storage and recovery means (200, 201, 202) and/or in the cooling means (300, 301, 302). The water condensed at each compression stage is sent to liquid storage means (500, 501, 502), each of which resists the pressure at which the water is extracted from the air, in other words the liquid storage means (500) is suitable for low pressure, the liquid storage means (501) is suitable for medium pressure, and the liquid storage means (502) is suitable for high pressure. The fourth embodiment can also be modified by adapting the number of compression stages and/or expansion stages.

Moreover, in the fourth embodiment, the system and the method can be provided without means of gas/liquid separation, nor means of storage of the liquid.

Figure 6 illustrates, schematically and in a non-limiting manner, a system and a method for storing and recovering energy by compressed gas (in this case air) according to a fifth embodiment of the invention. The fifth embodiment corresponds to the fourth embodiment for which the heat exchange means between the gas expanded at the outlet of the expansion line and the liquid are integrated into the liquid storage means.

According to the fifth embodiment, the method and the system consist of a compression line (1), including three compression stages (3) depending on the air pressure to be reached. Each compression stage (3) comprises compression means (100, 101, 102) also called a compressor. These compressors (100, 101, 102) can be axial, centrifugal, or of any other technology. 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 to be compressed (10) in the system and the process is ambient air, containing water saturation related to its temperature and pressure.

Heat storage and recovery means (200, 201, 202) are arranged after each compressor (100, 101, 102) in order to cool the hot compressed air at the compression outlet while storing this thermal energy. The exchange/storage takes place by direct contact between the air and the material allowing the heat of the air to be stored. This material can be stones, concrete, gravel or any other suitable solid material. The heat storage and recovery means (200, 201, 202) are adapted to the pressure of the incoming air transferring its energy to each of them. 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 heat (202) is suitable for high pressure. Means cooling (300, 301, 302) can 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 storage. These cooling means (300, 301, 302) can be air coolers or heat exchangers (tubes/shell, plates, spirals or other suitable technologies) exchanging with a heat transfer fluid which can be water, propane , butane or any other refrigerant suitable for the necessary cooling. The cooling means (300, 301, 302) are adapted to the pressure of the air entering and exchanging with each of them. The cooling means (300) is suitable for low pressure, the cooling means (301) is suitable for medium pressure and the cooling means (302) is suitable for high pressure.

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 of the air, is extracted from the compression line by separators gas-liquid (400, 401, 402) in order to have air at the compressor inlet without any trace of liquid water. This water condensation can take place in the heat storage and recovery means (200, 201, 202) and/or in the cooling means (300, 301, 302). The water condensed at each compression stage is sent to liquid storage means (500, 501, 502), each of which resists the pressure at which the water is extracted from the air, in other words the liquid storage means (500) is suitable for low pressure, the liquid storage means (501) is suitable for medium pressure, and the liquid storage means (502) is suitable for high pressure.

During the energy production phase, the compressed air passes through the expansion line (2), which has three expansion stages (4). The air is expanded via one or more expansion means, for example turbines (700, 701, 702), placed in each expansion stage (4), in order to produce electricity via alternators, not shown. The turbine (702) is a low pressure turbine, the turbine (701) is a medium pressure turbine, and the turbine (700) is a high pressure turbine.

In the first stage of each expansion stage (4), condensed and stored water is reinjected into the pressurized air via mixers (600, 601, 602), the water being preheated beforehand by means of heat exchange integrated in the liquid storage means (500, 501, 502). The heat exchange means can be of the tube/shell, plate, spiral type or any other suitable technology and the exchange takes place between the condensed water and the waste heat of the air leaving the low pressure turbine ( 702). The heat exchange means are arranged in series with respect to the air flow low pressure leaving the low pressure turbine (702), that is to say leaving the expansion line.

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

In addition, the fifth embodiment can be provided without gas/liquid separation means, nor liquid storage means or without cooling means.

Figure 7 illustrates, schematically and in a non-limiting manner, a system and a method for storing and recovering energy by compressed gas (in this case air) according to a sixth embodiment of the invention. The sixth embodiment corresponds to the fourth embodiment for which the heat exchange means between the expanded gas at the outlet of the compression line and the liquid are arranged in parallel for the circulation of the expanded gas. Therefore, only the trigger line is described.

In the first stage of each expansion stage (4), condensed and stored water is reinjected with compressed air via mixers (600, 601, 602), the water being preheated beforehand by the heat exchange means. heat (800, 801, 802). The heat exchange means (800, 801, 802) can be tube/shell, plate, spiral type heat exchangers or any other suitable technology and the exchange takes place between the condensed water and the waste heat of the the air leaving the low pressure turbine (702). The heat exchange means (800, 801, 802) are arranged in parallel with respect to the flow low pressure air leaving the low pressure turbine (702), that is to say leaving the expansion line. For this embodiment, the expanded gas at the outlet of the expansion line (2) passes through a flow separator (or "splitter") (900) which divides the flow into three, each part of the flow of expanded gas passes through a means heat exchange (800, 801, 802).

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

In addition, the sixth separation mode can be provided without gas/liquid separation means, nor liquid storage means or without cooling means, or with integration of the heat exchange means in the liquid storage means.

The characteristics and advantages of the process according to the invention will appear more clearly on reading the application examples below.

Example no. 1 - not in accordance with the invention

This example implements the system and the method not in accordance with the invention illustrated in Figure 1.

During the compression phase (1), an external air flow (10), at a pressure of 1.02 bar and a temperature of 27° C. and having a humidity of 14.6 g water/kg air (gram of water per kilogram of air), is compressed by a low pressure compressor (100) from which it emerges (11) at a temperature of 255° C. and a pressure of 6 bar (0.6 MPa) (0.6 MPa). This flow (11) is sent to a low pressure heat storage and recovery means (200) which cools the air to a temperature of 90°C (12) and stores this thermal energy until the phase relaxation (2). The stream (12) is cooled again by the cooling means (300) until it reaches a temperature of 50° C. at the outlet (13). The flow (13) is then composed of air and water, resulting 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 stream (13). The flow (15), again completely gaseous, is compressed by a medium pressure compressor (101) from which it emerges (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 means (201) which cools the air to a temperature of 100°C (17) and stores this thermal energy until the phase relaxation (2). The stream (17) is cooled again by a cooling means (301) until it reaches a temperature of 50° C. at the outlet (18). The flow (18) is then composed of air and water, resulting 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 flow (20), again completely gaseous, 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 flow (21) is sent to a high pressure heat storage and recovery means (202) which cools the air to a temperature of 45°C (22) and stores this thermal energy until the phase relaxation (2). The stream (22) is cooled again by a cooling means (302) until it reaches a temperature of 30° C. at the outlet (23), 30° C. being the air storage temperature. The flow (23) is then composed of air and water, resulting from the humidity of 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 stream (23).

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 recovery phase of the energy (2).

When it is desired to produce electricity, the flow of compressed air (26) at a pressure of 117 bar (11.7 MPa) and a temperature of 30° C., leaving the compressed air storage means (1000) is heated in the high pressure heat storage and recovery means (202) which releases the heat stored during the compression phase (1) until the stream (27) reaches a temperature of 240°C. This flow of hot and compressed air (27) is expanded in the high pressure turbine (700) producing electricity via an alternator, until it reaches at the outlet (28) a pressure of 28 bar (2.8 MPa) and a temperature of 85°C. 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 flow of hot and compressed air (29) is expanded in the medium pressure turbine (701) producing electricity via an alternator, until a pressure of 5 bar (0.5 MPa) and a temperature of 75°C are reached at the outlet (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 flow of hot, compressed air (31) is expanded in the low pressure turbine (702) producing electricity via an alternator, until it reaches a pressure of 1.02 bar (0.1 MPa) at the outlet (32). and a temperature of 80°C.

The efficiency of the process and of the energy storage system of example 1 is 69.6% for a power consumption of 100 MW at the compressors. The total flow of condensed water at the three compression stages is 7.5 t/h. The thermal storage power is 87 MWth (thermal MW) and the cooling power required is 20.5 MWth.

Example No. 2 according to the invention

This example implements the system and the method according to the embodiment of the invention illustrated in Figure 5.

During the compression phase (1), an external air flow (10), at a pressure of 1.02 bar (0.1 MPa) and a temperature of 27°C and having a humidity of 14.6 g water / kgair , is compressed by a low pressure compressor (100) from which it emerges (11) at a temperature of 255° C. and a pressure of 6 bar (0.6 MPa). This flow (11) is sent to a low-pressure heat storage and recovery means (200) which cools the air to a temperature of 80° C. (12) and stores this thermal energy until the phase relaxation (2). The stream (12) is cooled again by the cooling means (300) until it reaches a temperature of 50° C. at the outlet (13). The flow (13) is then composed of air and water, resulting from the humidity of the air, condensed during the cooling phases in (200) and/or (300). This condensed water (14) is separated from the air stream (15) in a gas-liquid separator (400), operating at the pressure of the stream (13), then sent to a liquid storage means (500) under a maintained pressure of 6 bar (0.6 MPa). The flow (15), again completely gaseous, is compressed by a medium pressure compressor (101) from which it emerges (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 means (201) which cools the air to a temperature of 80° C. (17) and stores this thermal energy until the phase relaxation (2). The stream (17) is cooled again by the cooling means (301) until it reaches a temperature of 50° C. at the outlet (18). The flow (18) is then composed of air and water, resulting 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), then sent to a liquid storage means (501) under a maintained pressure of 28 bar (2.8 MPa). The flow (20), again completely gaseous, 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 flow (21) is sent to a high pressure heat storage and recovery means (202) which cools the air to a temperature of 40°C (22) and stores this thermal energy until the phase relaxation (2). The stream (22) is cooled again by the cooling means (302) until it reaches a temperature of 30° C. at the outlet (23), 30° C. being the air storage temperature. The flow (23) is then composed of air and water, resulting from the humidity of 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), then sent to a liquid storage means (502) under a maintained pressure of 117 bar (11.7 MPa).

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 waiting for the energy recovery phase (2).

When it is desired to produce electricity, a stream of condensed water (27) coming from the liquid storage means (502) at a pressure of 117 bar (11.7 MPa) and a temperature of 30° C. is heated in the heat exchanger (802) until a temperature of 75°C is reached at the flow (28) before being reinjected into the compressed air flow (26) leaving the compressed air storage means (1000) via the mixer (600) to form the stream (29). The stream (29) is heated in the high pressure heat storage and recovery means (202) which releases the heat stored during the compression phase (1) until the stream (30) reaches a temperature of 240°C. This flow of hot and compressed air (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 flow of condensed water (32) coming from the liquid storage means (501) at a pressure of 28 bar (2.8 MPa) and a temperature of 50° C. is heated in the heat exchanger (801) until reach a temperature of 77°C in the stream (33) before being reinjected into the compressed air stream (31) via the mixer (601) to form the stream (34). The stream (34) 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 (35) reaches a temperature of 255°C. This flow of hot and compressed air (35) is expanded in the medium pressure turbine (701) producing electricity via an alternator, up to reach at outlet (36) a pressure of 5 bar and a temperature of 70°C. A stream of condensed water (37) coming from the liquid storage means (500) at a pressure of 6 bar (0.6 MPa) and a temperature of 50°C is heated in the heat exchanger (800) until reach a temperature of 75°C in the stream (38) before being reinjected into the compressed air stream (36) via the mixer (602) to form the stream (39). The stream (39) is reheated in the low pressure heat storage and recovery means (200) which releases the heat stored during the compression phase (1) until the stream (40) reaches a temperature of 245°C. This flow of hot, compressed air (40) is expanded in the low-pressure turbine (702) producing electricity via an alternator, until it reaches a pressure of 1.02 bar (0.1 MPa) at the outlet (41). and a temperature of 80°C. This stream (41) is sent in series to the heat exchangers (800, 801, 802) to heat the condensed water streams reinjected into each expansion stage.

The efficiency of the energy storage process is 70.4% for a power consumption of 100 MW at the compressors. The total flow of condensed water at the three compression stages is 7.5 t/h. The thermal storage power is 92.5 MWth and the cooling power required is 14.9 MWth.

The reinjection of condensation water therefore makes it possible to improve the yield of the process by approximately 1% compared to Example 1, which is not in accordance with the invention, and to reduce the power required for cooling by approximately 27%.

Example No. 3 according to the invention

This example implements the system and the method according to the embodiment of the invention illustrated in Figure 7.

During the compression phase (1), an external air flow (10), at a pressure of 1.02 bar (0.1 MPa) and a temperature of 27°C and having a humidity of 14.6 g water / kg air, is compressed by a low pressure compressor (100) from which it leaves (11) at a temperature of 255° C. and a pressure of 6 bar (0.6 MPa). This flow (11) is sent to low pressure heat storage and recovery means (200) which cools the air to a temperature of 80°C (12) and stores this thermal energy until the relaxation (2). The stream (12) is cooled again by the cooling means (300) until it reaches a temperature of 50° C. at the outlet (13). The flow (13) is then composed of air and water, resulting from the humidity of the air, condensed during the cooling phases in (200) and/or (300). This condensed water (14) is separated from the air stream (15) in a gas-liquid separator (400), operating at the pressure of the stream (13), then sent to a storage means for liquid (500) under a maintained pressure of 6 bar (0.6 MPa). The flow (15), again completely gaseous, is compressed by a medium pressure compressor (101) from which it emerges (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 means (201) which cools the air to a temperature of 80° C. (17) and stores this thermal energy until the phase relaxation (2). The stream (17) is cooled again by the cooling means (301) until it reaches a temperature of 50° C. at the outlet (18). The flow (18) is then composed of air and water, resulting 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), then sent to a liquid storage means (501) under a maintained pressure of 28 bar (2.8 MPa). The flow (20), again completely gaseous, 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 flow (21) is sent to a high pressure heat storage and recovery means (202) which cools the air to a temperature of 40°C (22) and stores this thermal energy until the phase relaxation (2). The stream (22) is cooled again by the cooling means (302) until it reaches a temperature of 30° C. at the outlet (23), 30° C. being the air storage temperature. The flow (23) is then composed of air and water, resulting from the humidity of 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), then sent to a liquid storage means (502) under a maintained pressure of 117 bar (11.7 MPa).

When it is desired to produce electricity, a stream of condensed water (27) coming from the storage (502) at a pressure of 117 bar (11.7 MPa) and a temperature of 30° C. is heated in the heat exchanger. heat (802) until a temperature of 77°C is reached in the stream (28) before being reinjected into the compressed air stream (26) leaving the compressed air storage means (1000) via the mixer ( 600) to form the stream (29). The stream (29) is heated in the high pressure heat storage and recovery means (202) which releases the heat stored during the compression phase (1) until the stream (30) reaches a temperature of 240°C. This flow of hot and compressed air (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 flow of condensed water (32) from the liquid storage means (501) at a pressure of 28 bar (2.8 MPa) and a temperature of 50°C is heated in the heat exchanger (801) until a temperature of 77°C is reached in the flow (33) before being reinjected into the compressed air flow ( 31) via mixer (601) to form stream (34). The stream (34) 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 (35) reaches a temperature of 255°C. This flow of hot and compressed air (35) is expanded in the medium pressure turbine (701) producing electricity via an alternator, until it reaches at the outlet (36) a pressure of 5 bar (0.5 MPa) and a temperature of 70°C. A stream of condensed water (37) coming from the liquid storage means (500) at a pressure of 6 bar (0.6 MPa) and a temperature of 50°C is heated in the heat exchanger (800) until reach a temperature of 77°C at the stream (38) before being reinjected into the compressed air stream (36) via the mixer (602) to form the stream (39). The stream (39) is reheated in the low pressure heat storage and recovery means (200) which releases the heat stored during the compression phase (1) until the stream (40) reaches a temperature of 245°C. This flow of hot, compressed air (40) is expanded in the low pressure turbine (702) producing electricity via an alternator, until it reaches a pressure of 1.02 bar (0.1 MPa) at the outlet (41). and a temperature of 80°C. This stream (41) is divided into three streams in the stream splitter/divider (900). These flows can be established in proportion to the liquid flows (27, 32, 37) to heat them in parallel in the heat exchangers (800, 801, 802) before their reinjection at each expansion stage.

The efficiency of the energy storage process is 70.4% for a power consumption of 100 MW in the compression phase. The total flow of condensed water at the three compression stages is 7.5 t/h. The thermal storage power is 92.5 MWth and the cooling power required is 14.9 MWth.

Thus, examples 2 and 3 show that the system and the method according to the invention make it possible to increase the performance of the system and of the method, while limiting the power required for cooling.

Claims

1 . Compressed gas energy storage and recovery system comprising:

- A gas compression line (1) comprising at least one compression stage (3), each compression stage comprising compression means (100, 101, 102) and heat storage and recovery means (200 , 201, 202) arranged downstream of said compression means (100, 101, 102), in the direction of circulation of said gas,

- At least one compressed gas storage means (1000) arranged at the outlet of said gas compression line (1) to store 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 one expansion stage (4), each stage expansion (4) comprising expansion means (700, 701, 702) and pipes configured to circulate said compressed gas in said heat storage and recovery means (200, 201, 202) of said at least one stage compression (3) so as to heat said compressed gas, characterized in that said system comprises at least one heat exchange means (800, 801, 802) between said expanded gas at the outlet of said expansion line (2 ) and a liquid, and in that at least one expansion stage (4) comprises means for introducing (600, 601, 602) said heated liquid, said means for introducing said liquid (600, 601, 602) being provided upstream, in the direction of circulation of said gas, of said heat storage and recovery means (200, 201, 202).

2. System according to claim 1, wherein said compression line (1) comprises as many successive compression stages (3) as the expansion line (2) comprises successive expansion stages (4), each means of storage and recovery of heat (200, 201, 202) from a compression stage (2) being used in the corresponding expansion stage (4).

3. System according to claim 2, wherein said compression line (1) and said expansion line (2) respectively comprise three successive stages.

4. System according to one of the preceding claims, wherein said heat storage and recovery means (200, 201, 202) comprises heat storage particles.

5. System according to one of the preceding claims, wherein at least one compression stage (3) comprises gas/liquid separation means (400, 401, 402), and said system comprises at least one means for storing said liquid separated (500, 501, 502), said separated and stored liquid being said heated liquid and introduced into said expansion line (2). System according to one of the preceding claims, in which said system comprises a plurality of heat exchange means (800, 801, 802) between said gas expanded at the outlet of said expansion line and said liquid. System according to one of the preceding claims, in which the said heat exchange means (800, 801, 802) are arranged in series or in parallel for the circulation of the said gas at the outlet of the said expansion line. System according to one of the preceding claims, in which at least one compression stage (2) comprises cooling means (300, 301, 302) downstream of the heat storage and recovery means (200, 201, 202 ), in the direction of circulation of said gas, preferably, said cooling means (300, 301, 302) comprises an air cooler. Compressed gas energy storage and recovery process comprising at least the following steps:

- In the energy storage phase: a) a gas is successively compressed at least once in a compression line (1) comprising at least one compression stage (3), each compression stage (3) comprising at least one compression means (100, 101, 102); b) after each compression step, the heat of said compressed gas is recovered in at least one heat storage and recovery means (20, 201, 202) c) said cooled compressed gas is stored in at least one storage means compressed gas (1000);

- In the energy recovery phase: d) circulating the compressed gas leaving said at least one compressed gas storage means (1000) in an expansion line (2) comprising at least one expansion stage (4), and in each expansion stage (4), the compressed gas is heated by circulating it in one of said heat storage and recovery means (200, 201, 202) thanks to the heat stored during the compression step , then the heated compressed gas is expanded in expansion means (700, 701, 702), characterized in that heat is exchanged between said expanded gas at the outlet of said expansion line and a liquid, and said liquid heated in said compressed gas before at least one step of heating said gas preceding an expansion step.

10. The method of claim 9, wherein as many successive compression steps are carried out as successive expansion steps, and the heat storage and recovery means (200, 201, 202) of each of the steps b) to heat the compressed gas of the corresponding expansion step.

11. Method according to one of claims 9 or 10, wherein after each heat recovery step, the compressed gas is cooled at the outlet of the heat storage and recovery means (200, 201, 202) in a cooling means (300, 301, 302) before the gas is sent to the next compression step or to the compressed gas storage means.

12. Method according to one of claims 9 to 11, in which the heat is stored in heat storage particles.

13. Method according to one of claims 9 to 12, wherein after at least one compression step, separating said gas and a liquid present in said gas, and storing said separated gas, said separated and stored liquid being said liquid heated and introduced into said at least one expansion step.

14. Method according to one of claims 9 to 13, in which a plurality of heat exchanges are implemented between said gas expanded at the outlet of said expansion line and said liquid.

15. Method according to claim 14, in which said plurality of heat exchanges are implemented in series or in parallel for the circulation of said expanded gas at the outlet of said expansion line.