WO2022117406A1

WO2022117406A1 - Method for storage and recovery of energy with thermal optimisation on expansion

Info

Publication number: WO2022117406A1
Application number: PCT/EP2021/082777
Authority: WO
Inventors: David Teixeira; Elsa MULLER-SHERNETSKY
Original assignee: IFP Energies Nouvelles
Priority date: 2020-12-03
Filing date: 2021-11-24
Publication date: 2022-06-09
Also published as: FR3117167A1

Abstract

The present invention relates to a compressed gas energy storage and recovery system comprising: - a gas compression line (1) with a compression stage (3) comprising a compression means (100, 101, 102) and a means for storing and recovering the heat (200, 201, 202) downstream of the compression means (100, 101, 102), - a means for storing compressed gas (500), - an expansion line (2) comprising at least two consecutive expansion stages (4), each expansion stage (4) comprising pipes and an expansion means (300, 301, 302), the pipes being configured to circulate the compressed gas through at least one of the means for storing and recovering the heat (200, 201, 202) from the compression stages (3). In addition, the expansion line (1) comprises at least one circulation means for circulating the expanded gas leaving the first expansion stage through a first heat exchange means (400) located in the first expansion stage in order to reheat the gas before it passes through the expansion means (300) of the first expansion stage (4). The invention also relates to a method for storing and recovering energy.

Description

ENERGY STORAGE AND RECOVERY PROCESS WITH OPTIMIZATION

THERMAL RELAXATION

Technical area

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

While global energy goals aim to favor renewable energies in order to gradually increase the proportion of renewable energies in the energy mix, the variable and intermittent nature of these renewable energies remains their major drawback. To address this problem, energy storage appears to be a very advantageous solution. By storing the surplus energy produced at 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 brings flexibility, even continuity, to the energies renewable. Thus, the need for processes and energy storage systems should increase in the coming years, with the proportion of renewable energies in the global mix.

Many storage technologies currently exist, such as mechanical type storage such as Pumping 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.

Electrochemical type technologies can also be used for energy storage such as lithium-ion, lead-acid or even nickel-cadmium batteries, or circulation batteries for example using electrolytes.

Compressed air energy storage and recovery, known as CAES (Compressed Air Energy Storage), is a technology for which a first installation was built in Germany in the late 1970s. a power of 290 MW. The principle of this technology is to use the electricity produced and not consumed to compress a gas, typically air. In order to avoid any damage to the compressors, the heat resulting from the compression is evacuated between each stage. The 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 awaiting the discharge phase of energy. During the electricity production phase, the stored air is extracted from the storage in order to be expanded in turboalternators.

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

Prior technique

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 6 of the prior art illustrates, schematically in block diagram form, such an AACAES system and method. This figure shows the phase of energy storage 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 compression stages 3. Each compression stage 3 comprises a compression means 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 in the process illustrated is ambient air, containing a water saturation linked 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 500 adapted to high pressures. Heat storage and recovery means 200, 201, 202 are arranged after each compressor 100, 101, 102 of each compression stage 3 in order to cool the hot compressed air at the compression outlet while storing this thermal energy. the heat storage and recovery means 200 is suitable for low pressure, heat storage and recovery means 201 is suitable for medium pressure and heat storage and recovery means 202 is suitable for high pressure. Cooling means 600, 601, 602 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 its 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 S1, S2, S3 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 600, 601, 602. During the energy production phase, the compressed air is expanded via one or more turbines 300, 301, 302 or expansion stage, according to the suppliers' recommendations, in order to produce electricity via alternators, not shown in the diagram. Turbine 302 is a low pressure turbine, turbine 301 is a medium pressure turbine and turbine 300 is a high pressure turbine. For this system and this process, the condensed water is just extracted, the associated energy is therefore lost.

Patent application WO2016/079485 concerns an energy storage and recovery system in which the waste heat at the outlet of the last turbine is used to heat the air upstream of the first turbine. This system nevertheless leaves a quantity of energy lost at the outlet of the heat exchanger intended to heat the air upstream of the first turbine.

The aim of the invention is to improve the energy storage and recovery performance of a compressed air system.

This goal is achieved by a compressed gas energy storage and recovery system comprising:

- a gas compression line with at least one compression stage, each compression stage comprising a compression means and a heat storage and recovery means downstream, in the direction of gas circulation, of the compression means ,

- a compressed gas storage means located at the outlet of the gas compression line to store the compressed gas,

- an expansion line for expanding compressed gas stored in the compressed gas storage means, the expansion line comprising at least two successive expansion stages, each expansion stage comprising pipes and an expansion means, the pipes being configured to circulate the compressed gas in at least one of the means of storage and recovery of heat from a compression stage so as to heat the compressed gas before the expansion means. In addition, the expansion line comprises at least one circulation means for circulating the expanded gas leaving the first expansion stage, in the direction of circulation of the gas in the expansion line, in a first heat exchange means located on the first expansion stage, the first heat exchange means being designed to heat the gas prior to the passage of the compressed gas into the heat storage and recovery means in which the compressed gas of the first expansion stage circulates and before the compressed gas is sent to the next expansion stage of the expansion line. Surprisingly, by using the gas leaving the first expansion stage to heat the gas upstream of this stage before directing this gas to the second expansion stage, the energy recovery performance is increased.

The invention also relates to a process for storing and recovering energy by compressed gas comprising at least the following steps:

- In the energy storage 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 in a compressed gas storage means.

- In the energy recovery phase: d) the compressed gas leaving the compressed gas storage means is circulated in an expansion line of at least two expansion stages, and in each expansion stage, the gas is heated compressed using the heat stored during the compression step by causing it to circulate in one of the heat storage and recovery means, then the heated compressed gas is expanded in an expansion means; and the heat of at least part of the gas expanded at the outlet of the expansion means of the first expansion stage is used to heat the compressed gas leaving the compressed gas storage means in a first heat exchange means positioned upstream means of heat storage and recovery.

Summary of the invention

The invention relates to a compressed gas energy storage and recovery system comprising: - a gas compression line with at least one compression stage, each compression stage comprising compression means and heat storage and recovery means downstream, in the direction of gas circulation, of said compression means ,

- at least one compressed gas storage means located at the outlet of the gas compression line to store the compressed gas,

- an expansion line for expanding compressed gas stored in the compressed gas storage means, the expansion line comprising at least two successive expansion stages, each expansion stage comprising pipes and an expansion means, the pipes being configured to circulate the compressed gas in at least one of the means for storing and recovering the heat of the compression stages so as to heat the compressed gas before the expansion means. In addition, the expansion line comprises at least one circulation means for circulating the expanded gas leaving the first expansion stage, in the direction of circulation of the gas in the expansion line, in a first heat exchange means located in the first expansion stage, the first heat exchange means being designed to heat the gas before the compressed gas passes through the heat storage and recovery means in which the compressed gas of the first expansion stage circulates and before the cooled compressed gas is sent to the next expansion stage of the expansion line.

Preferably, said heat storage and recovery means comprises heat storage particles.

Advantageously, said compression line comprises as many compression stages as the expansion line comprises expansion stages, each heat storage and recovery means of a compression stage being used in the expansion stage at the corresponding pressure.

According to a preferred embodiment, the expansion line and the compression line each comprise three stages.

According to one implementation of the invention, at least one compression stage comprises cooling means downstream of the heat storage and recovery means, preferably, said cooling means comprising an air cooler.

According to one embodiment of the invention, at least one compression stage comprises separation means for separating the compressed gas from a liquid phase before the compressed gas reaches the next compression stage or the storage means of compressed gas, each compression stage comprising a liquid storage means for storing said liquid phase at the pressure of the compression stage.

Preferably, at least one expansion stage comprises a mixing means for mixing with said compressed gas said liquid phase exiting from one of the means for storing liquid from the compression stages before said first heat exchange means and/or before the heat storage and recovery means.

According to an advantageous configuration of the invention, said mixing means is positioned upstream of said first heat exchange means on the first expansion stage and upstream of the heat storage and recovery means on the other expansion stages.

Advantageously, the expansion line comprises a heat recovery line for causing the expanded gas to circulate at the outlet of the last expansion stage, in the direction of circulation of the gas in the expansion line, in a second heat exchange means located on the second expansion stage, upstream of the second expansion stage heat storage and recovery means.

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 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) the cooled compressed gas is stored in a compressed gas storage means.

- In the energy recovery phase: d) the compressed gas leaving the compressed gas storage means is circulated in an expansion line of at least two expansion stages, and in each expansion stage, the gas is heated compressed 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, then the heated compressed gas is expanded in an expansion means; moreover, the heat of at least part of the gas expanded at the outlet of the expansion means of the first expansion stage is used to heat the compressed gas leaving the compressed gas storage means in a first heat exchange means positioned upstream of the heat storage and recovery means.

Preferably, as many compression steps as expansion steps are carried out, and the heat storage and recovery means of each of the steps b) are used to heat the compressed gas from the expansion step to the corresponding pressure.

Advantageously, the heat of the compressed gas is recovered by heat storage particles. According to one embodiment of the invention, 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 next compression stage or in the compressed gas storage means.

Preferably, the heat is recovered from the expanded gas at the outlet of the last expansion stage to heat the compressed gas entering the second expansion stage, upstream of the means for storing and recovering the heat from the second expansion stage.

According to one configuration of the invention, the compressed gas is separated from a liquid phase that it contains in a separation means, before the compressed gas is sent to the next compression stage or to the storage means of the compressed gas, the liquid leaving each separation means being stored at the pressure in which it is in a liquid storage means.

According to a preferred implementation of the invention, in each expansion stage, the liquid stored in a liquid storage means is injected, and it is mixed with the compressed gas, before each heating stage.

List of Figures

Other characteristics and advantages of the system and/or 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.

Figure 1 shows a first embodiment of the invention.

Figure 2 shows a second embodiment of the invention.

Figure 3 shows a third embodiment of the invention.

Figure 4 shows a fourth embodiment of the invention.

Figure 5 shows a fifth embodiment of the invention.

Figure 6 illustrates a heat storage and recovery system according to the prior art.

Description of embodiments

The present invention relates to a compressed gas energy storage and recovery system. It includes in particular:

- a gas compression line with at least one compression stage, the compression of the gas making it possible to store energy, this energy being able to be recovered easily subsequently, for example by passing the compressed gas through a turbine. A compression line is a line allowing the gas to circulate from an inlet to at least one compressed gas storage means. Therefore, the compression line can comprise several compression stages mounted in series (successive compression stages). Each compression stage comprises a compression means (a pump or a compressor for example) and a heat storage and recovery means downstream, in the direction of gas circulation, of the compression means. For example, the compressors can be axial or centrifugal compressors.

As a result, in each compression stage, the gas can be compressed and then the heat induced by the compression of the gas can be recovered in order to improve the energy recovery performance of the system. In addition, the use of a heat storage and recovery means after each compression means makes it possible to cool the compressed gas before each following compression stage, making it possible to ensure the integrity of the following compression means by avoiding possible deterioration of the latter in the event of too high a temperature and to improve the yield of the compression phase. In addition, this makes it possible to store the heat induced by each compression stage, at a temperature dependent on each compression means. Each heat storage and recovery means is adapted to the pressure of each compression stage on which it is installed.

- at least one compressed gas storage means (a storage tank for example) located at the outlet of the gas compression line to store the compressed gas, awaiting a subsequent energy need.

- an expansion line for expanding the compressed gas stored in the compressed gas storage means. The expansion line comprises at least two successive expansion stages, that is to say connected in series. “Expansion line” is understood to mean a line allowing the compressed gas to circulate from the compressed gas storage means to an outlet via expansion stages in series. Each expansion stage comprises pipes and an expansion means (a turbine for example, the turbine being able to be coupled to an electric generator, also called an alternator, to generate electricity), the pipes being configured to circulate the compressed gas leaving the compressed gas storage means (for the first expansion stage) or the preceding expansion stage, into at least one of the means for storing and recovering the heat of the compression stages so as to reheat the compressed gas before it passes through the expansion means associated with this expansion stage. Heating the compressed gas before each expansion means makes it possible to optimize the yield of the expansion phase. In addition, by using a means of heat storage and recovery used on the line of compression, gas reheating is possible by recovering the heat stored during compression and therefore does not require an additional source of energy.

In addition, the expansion line comprises at least one circulation means for circulating the expanded gas leaving the first expansion stage, in the direction of circulation of the gas in the expansion line, in a first heat exchange means located in the first floor of relaxation. This first means of heat exchange (a tube/shell, spiral or plate heat exchanger, for example, in indirect contact between the fluid arriving cold and the fluid arriving hot so as to avoid any exchange between the cold gas leaving the gas storage means and the hot gas leaving the expansion means) is configured to preheat the compressed gas leaving the compressed gas storage means, before it passes through the heat storage and heat recovery means in which the gas circulates compressed from the first stage of relaxation. The compressed gas leaving the first expansion means and passing through the first heat exchange means comes out cooled before being sent to the next expansion stage (the second expansion stage) of the expansion line. Using the heat of the gas at the outlet of the first expansion stage to heat the coolest gas at the outlet of the compression storage means makes it possible to reduce the dimensions of the means for storing and recovering the heat of the first expansion stage, which is the heat storage and recovery medium that has the highest pressure stresses, therefore, it is the most expensive heat storage and recovery medium.

In addition, surprisingly, reheating the gas with the gas leaving the first expansion stage rather than sending the gas leaving the first expansion stage directly to the second expansion stage makes it possible to improve the recovery performance of energy of the system and to reduce the dimensions of the means of storage and heat recovery.

According to one embodiment of the invention, the gas may be air. This may be air taken from the ambient environment. Alternatively, it may include other gases.

According to one aspect of the invention, the liquid can be water. This may include moisture present in the gas, especially when the gas is air. Alternatively, it may include other liquids.

The first heat exchange means is separate from the heat storage and recovery means or means so as to improve the heating performance of the compressed gas upstream of the turbine.

Preferably, at each expansion stage, the compressed gas can flow through a different heat storage and recovery means coming from a different compression stage at the instead of circulating in a heat storage and recovery means which would be used in at least two different expansion stages. Indeed, as a result, the pressures and temperatures of each heat storage and recovery means are adapted both to each expansion stage and to each compression stage.

The compressed gas storage medium can be an artificial storage such as a cylindrical reservoir or a natural cavity such as a salt cavern, an old mine or an aquifer.

In the sense of the invention, the successive terms such as "first", "second", "third", "previous", "next", "last", "upstream" and "downstream" are understood to mean the direction of circulation compressed gas in the expansion or compression lines. Thus, the first expansion stage is the expansion stage in which the compressed gas passes first after the compressed gas storage means.

Preferably, the heat storage and recovery means may comprise heat storage particles, for example it may be a reservoir containing a fixed bed of heat storage particles. Thus, the hot gas leaving a compression means can heat the heat storage particles by direct exchange between the compressed gas and the heat storage particles, which can for example be concrete balls, stones, gravels, phase change materials. In the energy recovery phase, the compressed gas can then be passed through the heat storage and recovery means. Thus, the heat stored in the heat storage particles reheats the compressed gas before it is expanded in the expansion medium. The use of heat storage and recovery means with heat storage particles makes it possible to avoid the use of tube/calender, spiral or plate type heat exchangers which require the circulation of a fluid. coolant and in addition at least one tank to store the heat. Therefore, the system of the invention can have a reduced size and cost. In addition, energy losses are reduced also given the absence of necessary pipes between a heat exchanger and a heat storage tank.

According to an advantageous configuration of the invention, the compression line can comprise as many compression stages as the expansion line comprises expansion stages, each means for storing and recovering the heat of a compression stage being able to be used in the expansion stage at the corresponding pressure. By "corresponding pressure", we do not mean an absolute pressure but that of the floor concerned. 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 example, when the compression line and the expansion line each comprise three stages, the first compression stage is a so-called “low pressure” stage, the second compression stage is a so-called “medium pressure” stage, and the last stage is a so-called “high pressure” stage. The expansion line then comprises a first “high pressure” expansion stage, a second “medium pressure” expansion stage and a third “low pressure” expansion stage. The terms “high pressure”, “medium pressure” and “low pressure” are relatively understood between the different stages of the compression line and the expansion line. Thus, the heat storage and recovery means used for the third stage of compression ("high pressure") is used to heat the compressed gas of the first stage of expansion ("high pressure"). The heat storage and recovery means used for the second compression stage ("medium pressure") is used to heat the compressed gas of the second expansion stage ("medium pressure") and the heat storage and recovery means used for the first stage of compression ("low pressure") is used to heat the compressed gas of the third stage of expansion ("low pressure"). This configuration is advantageous because the pressure and temperature of each compression stage substantially corresponds to the pressure and temperature of each expansion stage, which further improves system performance.

Advantageously, the expansion line and the compression line can each comprise three stages. This configuration improves compression and rebound performance while limiting cost.

According to an advantageous embodiment of the invention, each compression stage can include cooling means downstream of the heat storage and recovery means. The cooling means serves to further cool the compressed gas before it enters the next compression stage or the gas storage means so as to further improve the compression of the next stage gas and/or to reduce the design constraints of the compressed gas storage means. Preferably, the cooling means can comprise an air cooler. A dry cooler allows the compressed gas to be cooled only with ambient outside air. Therefore, it is a simple cooling means to implement and inexpensive.

Alternatively, the cooling means may be a tube/shell, plate and/or spiral heat exchanger so as to exchange heat between the compressed gas and a heat transfer fluid which may be water, propane , butane for example.

According to a preferred implementation of the invention, each compression stage may comprise separation means for separating the compressed gas from a liquid phase before the compressed gas reaches the following compression stage or the storage means. of compressed gas. Indeed, when the heat of the compressed gas is recovered in the heat storage and recovery means or in the cooling means, the compressed gas is cooled and in fact, condensation can occur. This may in particular be the case when the gas is air taken from the ambient environment; it can then contain water vapour. This water vapor can then condense and the liquid phase produced is likely to cause damage to the compression stages or to the means of compressed gas storage (by corrosion for example). Additionally, each compression stage may include a liquid storage means for storing the liquid phase at the pressure of the compression stage. Thus, each liquid phase recovered in each compression stage can be stored at the pressure of each compression stage, this phase being able to be injected into the expansion phase at the closest corresponding pressure.

Preferably, each expansion stage may comprise a mixing means for injecting and mixing with the compressed gas the liquid phase exiting from one of the means for storing liquid resulting from the condensation at the level of the compression stages before the first exchange means heat (for the first expansion stage) or before the heat storage and recovery means (for expansion stages other than the first expansion stage). Thus, it is possible to inject a liquid phase which is vaporized in the first heat exchange means or the heat storage and recovery means before each expansion means. The addition of the liquid phase makes it possible to increase the gas flow at the inlet of the expansion means (of the turbine for example) and thus to improve its performance.

Advantageously, the mixing means can be positioned upstream of the first heat exchange means on the first expansion stage and/or upstream of the storage means and heat recovery on the other expansion stages. Therefore, the injection of liquid is carried out before the gas/liquid mixture is heated in the heat storage and recovery means and/or in the first heat exchange means. Thus, the mixture can be vaporized before it enters the expansion means so as to avoid the risk of damage.

According to a preferred variant of the invention, the expansion line may comprise a heat recovery line for circulating the expanded gas at the outlet of the last expansion stage, in the direction of circulation of the gas in the expansion line, in a second heat exchange means (a tube/shell, spiral or plate heat exchanger, for example) located on the second expansion stage, upstream of the heat storage and recovery means of the second expansion stage. This heat recovery line makes it possible to recover the waste heat at the output of the expansion line. Waste heat is heat that would normally be lost. The idea of the heat recovery line is on the contrary to use this heat to heat the compressed gas leaving the first heat exchange means, at the inlet of the second expansion stage. Thus, the heat of the gas leaving the expansion line is used to heat the gas entering the second expansion stage, which makes it possible to reduce the dimensions of the means for storing and recovering the heat from the second expansion stage, which is the heat storage and recovery means that has the highest pressure stresses after that of the first expansion stage. This reduces the cost of the system. The waste heat could alternatively be used to reheat the gas entering another expansion stage, but less efficiently.

The second heat exchange means is separate from the first heat exchange means and the heat storage and recovery means so as to maximize the recovery of thermal energy and to avoid heat losses and to reduce the size and therefore the cost of each of these pieces of equipment.

The cooling means is separate from the first heat exchange means, the second heat exchange means and the heat storage and recovery means so as to improve the thermal performance.

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

- In the energy storage 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 a compression means; preferably, the gas is compressed in several stages so that each compression has a good yield. b) after each compression stage, the heat of the compressed gas is recovered in at least one heat storage and recovery means; this heat recovery makes it possible to improve the efficiency of energy storage. c) the cooled compressed gas is stored in at least one compressed gas storage means with the aim of recovering it when the need for energy arises.

- In the energy recovery phase: d) the compressed gas leaving the compressed gas storage means is circulated in an expansion line comprising at least two expansion stages, 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, then the heated compressed gas is expanded in an expansion means. The multiplication of expansion stages (and steps) improves the overall efficiency of the expansion line. In addition, reheating the gas using the means of storing and recovering the heat of the compression stages makes it possible to improve the efficiency of the system while avoiding any additional source of energy to reheat the gas.

In addition, the heat of at least a portion of the gas expanded at the outlet of the expansion means of the first expansion stage is used to heat the compressed gas leaving the compressed gas storage means in a first heat exchange means positioned upstream of the heat storage and recovery means. Surprisingly, using the gas at the outlet of the first stage to reheat the gas upstream instead of sending this still hot gas to the second expansion stage, makes it possible to increase the overall energy recovery performance of the process.

In addition, this solution makes it possible to reduce the size of the means for storing and recovering the heat of the first expansion stage, and therefore its cost.

Advantageously, as many compression steps as expansion steps can be carried out, and the heat storage and recovery means of each of the steps b) can be used to heat the compressed gas from the expansion step to pressure corresponding. Thus, each means of storing and recovering the heat of a compression stage is particularly suitable for heating an expansion stage. As a result, heat recovery in the expansion line is optimized.

Preferably, heat can be recovered from the compressed gas by heat storage particles. The use of heat storage particles makes it easy to store heat and recover it by avoiding the use of indirect contact heat exchanger involving the use of a heat transfer fluid to store the heat and to recover it. at least one storage tank of said fluid. Thus, the system is simpler and generates less heat loss. This solution makes it possible to do away with heat exchangers which require a heat transfer fluid and at least one storage tank to store the heat.

The use of a fixed bed of heat storage particles makes it possible to avoid the circulation of storage particles which generates pressure drops, requires a specific pump and which generates heat losses.

According to a variant of the invention, after each heat recovery step, the compressed gas can be cooled at the outlet of the heat storage and recovery means in a cooling means before the gas is sent to the next compression stage or in the compressed gas storage means. Thus, the temperature of the compressed gas at the inlet of the next compression stage is close to the optimum operating temperature of the compression means of this stage.

In addition, the cooling means is separate from the first and second heat exchange means and the heat storage and recovery means so as to optimize the thermal performance.

According to a preferred configuration of the invention, it is possible to recover the heat from the expanded gas at the outlet of the last expansion stage to heat the compressed gas entering the second expansion stage, upstream of the means for storing and recovering the heat from the second floor of relaxation. As a result, part of the waste heat is no longer lost but recovered to heat the compressed gas and thus increase the energy recovery capacities of the expansion line. In addition, this solution makes it possible to reduce the size and the cost of the means for storing and recovering the heat of the second expansion stage. According to a particular embodiment of the invention, the compressed gas can be separated from a liquid phase that it contains in a separation means (a separator for example), before the compressed gas is sent to the stage next compression or in the compressed gas storage means. Indeed, when the gas is air taken from the ambient medium, it may contain water vapour. When the compressed gas is cooled, condensation may occur and may damage the next compression means or the compressed gas storage means. A separation means can then recover the liquid phase so that only a gaseous phase is sent to the next compression stage or to the compressed gas storage means. In addition, the liquid exiting each separation means can be stored at the pressure in which it is in a liquid storage means. Thus, the liquid can be reused on the expansion line.

Preferably, in each expansion stage, the liquid stored in a liquid storage means can be injected, and it can be mixed with the compressed gas, before each heating stage. Thus, the flow rate of the gas passing through the expansion means is increased, which makes it possible to increase the performance of the expansion means. In addition, each liquid storage means being at a determined pressure and temperature, each expansion stage can advantageously use one of the liquid storage means of a compression stage.

Figure 1 illustrates, schematically and without limitation, a first embodiment of the system according to the invention.

In this figure, the energy storage and recovery system comprises a compression line 1 and an expansion line 2 as well as a compressed gas storage tank 500.

Compression line 1 comprises two successive compression stages 3, each compression stage 3 comprising compression means 100, 101 and heat storage and recovery means 200, 201. Thus, the first compression stage comprises a compressor 100 and a heat storage and recovery means 200 and the second compression stage comprises a compressor 101 and a heat storage and recovery means 201 .

The heat storage and recovery means 200 and 201 are storage tanks comprising a fixed bed of heat storage particles. Thus, the gas exiting compressed and hot from the compressors 100 or 101 passes through the heat storage particle storage tanks 200 and 201, respectively, where the heat of the compressed gas is transmitted by direct contact to the heat storage particles. Thus, the gas that emerges from the storage tanks of the heat storage particles 200 and 201 is colder than it entered, and the heat-storage particles have picked up the heat. On leaving the second compression stage, the gas is stored in the compressed gas storage tank 500 (also called compressed gas storage means).

When it is desired to recover the previously stored energy, the compressed gas from the compressed gas storage tank 500 is sent to the expansion line 2.

The expansion line comprises two successive expansion stages 4. Each expansion stage 4 comprises at least one expansion means 300, 301 and passage through a heat storage particle storage tank used in the compression stages 3. moreover, the first expansion stage comprises a first heat exchange means 400, here a plate type heat exchanger.

The compressed gas leaving the compressed gas storage tank 500 passes into the first heat exchange means 400 where it is reheated with the gas leaving the expansion means 300 of the first expansion stage. The heated compressed gas exiting the first heat exchange means 400 then passes into the heat storage particle storage tank 201 of the second compression stage where it is once again reheated.

Once sufficiently heated, the compressed gas passes through an expansion means 300 such as a turbine where the energy can be recovered. The turbine can be coupled to a generator to produce electricity. According to a variant, the turbine can drive mechanical equipment for example by a belt, a chain or a transmission system.

As indicated above, the gas leaving the expansion means 300, instead of being sent directly to the second expansion stage (towards the storage particle storage tank 200 then from the expansion means 301), is sent to the first heat exchange means 400 for reheating the gas leaving the compressed gas storage tank 500. The gas which leaves the first expansion stage and which enters the first heat exchange means 400 leaves it cooled and enters the storage tank for the particles of the heat storage 200 of the second stage of expansion (and used in the first compression stage) where it is then heated before passing into the expansion means 301 of the second stage of expansion. Surprisingly, not directly sending the compressed gas leaving the first expansion stage to the second expansion stage and passing it through a heat exchange means which cools it makes it possible to improve the energy recovery performance of the relaxation phase.

Figure 2 illustrates, schematically and without limitation, a second embodiment of the system according to the invention. In this figure, the energy storage and recovery system comprises a compression line 1 and an expansion line 2 as well as a compressed gas storage tank 500.

The compression line 1 comprises three successive compression stages 3, each compression stage 3 comprising compression means 100, 101, 102 and heat storage and recovery means 200, 201, 202. Thus, the first stage compression comprises a compressor 100 and a heat storage and recovery means 200; the second compression stage comprises a compressor 101 and a heat storage and recovery means 201; the third compression stage includes a compressor 102 and a heat storage and recovery means 202.

The heat storage and recovery means 200, 201 and 202 are heat storage particle storage tanks. Thus, the gas which exits compressed and hot from the compressors 100, 101 or 102 respectively passes through the storage tanks of heat storage particles 200, 201 and 202 where the heat of the compressed gas is transmitted by direct contact to the fixed bed of the particles. heat storage. Thus, the gas that comes out of the storage tanks of the heat storage particles 200, 201 and 202 is colder than it entered and the heat storage particles have recovered the heat. On leaving the third compression stage, the gas is stored in the compressed gas storage tank 500.

The expansion line 2 comprises three successive expansion stages 4. Each expansion stage 4 comprises at least one expansion means 300, 301, 302 and the passage through a storage tank for heat storage particles used in the compression stages 3. In addition, the first expansion stage comprises a first heat exchange means 400, here a plate-type heat exchanger.

The compressed gas leaving the compressed gas storage tank 500 passes into the first heat exchange means 400 where it is reheated with the gas leaving the expansion means 300 of the first expansion stage. The heated compressed gas exiting the first heat exchange means 400 then passes into the heat storage particle storage tank 202 where it is again reheated.

Once sufficiently heated, the compressed gas passes through an expansion means 300 such as a turbine where the energy can be recovered. The turbine can be coupled to a generator to produce electricity. According to a variant, the turbine can drive mechanical equipment for example by a belt, a chain or a transmission system. As previously indicated, the gas leaving the expansion means 300, instead of being sent directly to the second expansion stage (towards the storage particle storage tank 201 then from the expansion means 301), is sent to the first heat exchange means 400 for reheating the gas leaving the compressed gas storage tank 500. The gas which leaves the first expansion stage and which enters the first heat exchange means 400 leaves it cooled and enters the storage tank for the particles of the heat storage 201 of the second stage of expansion where it is then heated before passing into the means of expansion 301 of the second stage of expansion.

Then, the gas leaving the second expansion stage enters the third expansion stage. It is then reheated in the heat storage particle storage tank 200 and then it is expanded in the expansion means 302 of the third expansion stage. The gas leaving the expansion means 302 is then rejected. For example, if the gas is air, it can be released to the atmosphere.

Surprisingly, not directly sending the compressed gas leaving the first expansion stage to the second expansion stage and passing it through a heat exchange means which cools it makes it possible to improve the energy recovery performance of relaxation phase 2.

Figure 3 illustrates, schematically and without limitation, a third embodiment of a system of the invention.

The embodiment of FIG. 3 is a variant of that of FIG. 2. The references identical to those of FIG. 2 correspond to the same elements and will therefore not be described in more detail.

Figure 3 differs from Figure 2 in that an additional energy harvesting line is implemented. Indeed, at the outlet of the expansion means 302 of the last expansion stage (the third expansion stage), a pipe is put in place to supply the gas leaving the expansion means 302 to a second heat exchange means 401, a plate heat exchanger, for example, to heat the gas leaving the first heat exchange means 400, at the exit of the first expansion stage. Therefore, the gas leaving the first expansion stage cooled by the first heat exchange means 400 is reheated by the waste heat before entering the second expansion stage. This configuration is particularly advantageous because it makes it possible to recover a quantity of energy, in the form of heat, which would normally be lost, as in the case of figure 2. FIG. 4 illustrates, schematically and without limitation, a fourth embodiment of a system according to the invention. The elements with the same reference as in the previous diagrams correspond to the same elements and will therefore not be described in detail here.

The system of FIG. 4 comprises a compression line 1 with three compression stages 3 in series. Each of these compression stages 3 comprises a compression means 100, 101, 102 such as a compressor or a pump, followed by a heat storage and recovery means 200, 201 and 202 comprising a fixed bed of particles of heat storage such as, stones, gravel, concrete balls or phase change materials which can easily store heat at a lower cost. Furthermore, in each compression stage 3, the heat storage and recovery means 200, 201 and 202 is followed by a cooling means 600, 601, 602 so as to cool the gas as much as possible before it enters the the next compression stage. Here, each of the cooling means comprises an air cooler which makes it possible to easily cool the compressed gas from the ambient air in a simple and inexpensive way.

In addition, each compression stage 3 comprises a separator S1, S2 and S3 after each cooling means 600, 601 and 602. Indeed, when the gas is air taken from the ambient medium, it generally comprises steam of water that can condense. However, the cooling of the compressed air in the heat storage and recovery means 200, 201 and 202 then in the cooling means 600, 601 and 602 entails a risk of condensation of the water contained in the compressed air. entered the compression line 1. This condensation can damage the equipment, in particular the compression means 100, 101, 102 and the compressed gas storage means. Using a separator makes it possible to protect each sensitive piece of equipment from the risks of the presence of water and therefore to increase the life of this equipment.

In addition, each separator S1, S2, S3 is connected to a liquid storage means 700, 701 and 702, these liquid storage means possibly being liquid storage tanks adapted to the pressure and temperature of the outgoing liquid. of each separator S1, S2 and S3. Thus, the liquid from each separator is stored at a different pressure and temperature, which would not be the case if the liquid were sent to a single liquid tank common to all the separators.

At the outlet of the compression line, the compressed gas (compressed air for example) is stored in a compressed gas storage tank 500. In the energy recovery phase, the compressed air stored in the compressed gas storage tank 500 is sent to the expansion line 2 which comprises three expansion stages 4.

Each expansion stage comprises mixing means M1, M2 or M3, heat storage and recovery means 200, 201, 202, and expansion means 302, 301, 300. In each expansion stage, the stored liquid in one of the liquid storage tanks 700, 701, 702 arrives at a mixing means M1, M2, M3 to be mixed with the compressed gas entering the considered expansion stage. Once the liquid is mixed with the compressed gas, the gas/liquid mixture is then heated using the heat storage and recovery means 200, 201, 202. The heat storage and recovery means 200, 201 and 202 of the expansion line 2 are those used with the same references in the compression line 1 but the representation does not show it so as not to make the diagram unnecessarily heavy. Once heated, the gas/liquid mixture then passes through the expansion means 300, 301 or 302 allowing energy recovery.

Furthermore, at the outlet of the first expansion stage, the compressed gas is hot enough to be able to heat the compressed gas leaving the compressed gas storage tank 500. As a result, the compressed gas leaving the first expansion means 300 is directed towards a first heat exchange means 400 positioned between the mixing means M3 and the heat storage and recovery means 202. The colder gas leaving this heat exchange means is then sent to the second expansion stage .

It should be noted that this embodiment advantageously comprises as many compression stages 3 as expansion stages 4. The compression means 100, 101 and 102 can be qualified respectively as “low pressure”, “medium pressure” and “high pressure”. The expansion means 302, 301 and 300 can be qualified respectively as “low pressure”, “medium pressure” and “high pressure” expansion means. In addition, the pressure of each compression stage 3 (high pressure, medium pressure and low pressure) is substantially the same as that in the corresponding expansion stage. Thus, the use of the heat storage and recovery means of each high pressure 202, medium pressure 201 and low pressure 200 compression stage is advantageously used on the corresponding expansion stage, the pressures and temperatures being close and thus allowing optimization of heat storage and recovery by heat storage particles.

Similarly, the liquid leaving each liquid storage means leaving the separator of the "low pressure", "medium pressure" and "high pressure" compression stages is reinjected into the corresponding expansion stage, thus making it possible to improve system performance. Figure 5 illustrates, in a schematic and non-limiting manner, a fifth embodiment of the invention, which is a variant of the embodiment of Figure 4.

The references identical to those of FIG. 4 correspond to the same elements and will not be detailed here.

Figure 5 differs from Figure 4 by adding an energy (heat) recovery line. Indeed, the gas leaving the expansion means 302 of the last expansion stage is hot enough to heat the compressed gas entering the second stage. Thus, the gas leaving the expansion means 302 is sent to a second heat exchange means 401 making it possible to heat the compressed gas, mixed with the liquid. Thus, on the second expansion stage, the second heat exchange means is positioned between the mixing means M2 and the heat storage and recovery means 201. This arrangement makes it possible to recover part of the waste heat which would be lost in the solution of figure 4.

Of course, the embodiments shown in the various figures may include more or fewer compression stages or expansion stages without departing from the scope of the invention. In the same way, in these different figures, it is possible to add or remove cooling means, separation means, mixing means and/or liquid storage means.

Examples

The systems of Figures 4 and 5 of the invention have been compared to the prior art system illustrated in Figure 6.

In FIG. 6 of the prior art, during the compression phase 1, an external air flow, at a pressure of 1.02 bar (0.102 MPa) and a temperature of 27° C. and having a humidity of 14.6 grams of water per kilogram of air, is compressed by a low pressure compressor 100 from which it emerges at a temperature of 255°C and a pressure of 6 bar (0.6 MPa). This flow is sent to a low-pressure heat storage and recovery means 200 which cools the air to a temperature of 90° C. and stores this thermal energy until the expansion phase 2. The gas flow tablet is cooled again by the cooling means 600 until it reaches a temperature of 50° C. at the outlet. The flow is then composed of air and water, resulting from the humidity of the air, condensed during the cooling phases in 200 and/or 600. This condensed water is separated from the compression line 1 in a separator gas-liquid S1 operating at the flow pressure of the first compression stage 3. The flow, 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 compressed gas is sent to a medium pressure heat storage and recovery means 201 which cools the air to a temperature of 100° C. and stores this thermal energy until the expansion phase 2. The compressed gas is cooled again by a cooling means 601 until it reaches a temperature of 50° C. at the outlet. The flow is then composed of air and water, resulting from the humidity of the air, condensed during the cooling phases in 201 and/or 601. This condensed water is separated from the compression line 1 in a separator gas-liquid S2 operating at the pressure of the flow in the second compression stage 3. The flow leaving the separator S2, again totally gaseous, is compressed by a high pressure compressor 102 from which it emerges at a temperature of 250° C. and a pressure of 117 bar (11.7 MPa). The compressed gas is sent to a high pressure heat storage and recovery means 202 which cools the air to a temperature of 45°C and stores this thermal energy until expansion phase 2. The compressed gas is cooled again by a cooling means 602 until it reaches a temperature of 30° C. at the outlet, 30° C. being the air storage temperature. The flow is then composed of air and water, resulting from the humidity of the air, condensed during the cooling phases in 202 and/or 602. This condensed water is separated from the compression line 1 in a separator gas-liquid S3 operating at flow pressure.

The compressed air flow at a pressure of 117 bar (11.7 MPa) and a temperature of 30° C. is then sent to the compressed air storage means 500 while waiting for the energy recovery phase 2.

When it is desired to produce electricity, the flow of compressed air at a pressure of 117 bar (11.7 MPa) and a temperature of 30° C., leaving the compressed air storage means 500 is heated in the means heat storage and recovery unit 202 which releases the heat stored during the compression phase 1 until the flow reaches a temperature of 240°C. This flow of hot, compressed air is expanded in the high-pressure turbine 300 producing electricity via an alternator, until it reaches an output pressure of 28 bar (2.8 MPa) and a temperature of 85°C. The compressed gas is reheated in the medium pressure heat storage and recovery means 201 which releases the heat stored during the compression phase 1 until the flow reaches a temperature of 265°C. This flow of hot, compressed air is expanded in the medium-pressure turbine 301 producing electricity via an alternator, until it reaches an outlet pressure of 5 bar (0.5 MPa) and a temperature of 75°C. The stream is reheated in the low pressure heat storage and recovery means 200 which releases the heat stored during compression phase 1 until the stream reaches a temperature of 245°C. This flow of hot, compressed air is expanded in the low pressure turbine 302 producing electricity via an alternator, until it reaches an output pressure of 1.02 bar (0.102 MPa) and a temperature of 80°C.

The efficiency of the energy storage method of Figure 6 (not in accordance with the invention) 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 MW and the necessary cooling power is 20.5 MW.

On the system and the method of the embodiment of Figure 4 (in accordance with the invention), during the compression phase 1, an air flow taken from the ambient environment, at a pressure of 1.02 bar and a temperature of 27°C and having a humidity of 14.6 grams of water per kilogram of air, is compressed by a low pressure compressor 100 from which it emerges at a temperature of 255°C and a pressure of 6 bar. This flow is sent to a heat storage and recovery means 200 which comprises heat storage particles and which cools the air to a temperature of 85°C. The heat extracted from the compressed gas is then stored until the expansion phase 2. The flow of compressed air leaving the heat storage and recovery means 200 is cooled again by the cooling exchanger 600 until to reach a temperature of 50°C at the outlet. The flow leaving the exchanger 600 is then composed of air and water, resulting from the humidity of the air, condensed during the cooling phases in the heat storage and recovery means 200 and/or in the cooling exchanger 600. The condensed water is separated from the compressed air flow in a gas-liquid separator S1, operating at the pressure of the flow leaving the exchanger 600, then sent to a liquid storage means 700 under a maintained pressure of 6 bar. The air leaving the gas-liquid separator S1 no longer containing any liquid phase, and therefore completely gaseous again, enters a new compression stage where it is compressed by a medium-pressure compressor 101 from which it emerges at a temperature of 275 °C and a pressure of 28 bar. The compressed air is then sent to a heat storage and recovery means 201 which cools the air to a temperature of 45° C. and stores this thermal energy until the expansion phase 2. The air compressed can then be further cooled again by a cooling exchanger 601 . At the outlet of the heat storage and recovery means 201 or of the exchanger 601, the fluid is then composed of air and water, resulting from the humidity of the air, condensed during the heat recovery phase. heat or during the cooling phase. This condensed water is separated from the compressed air stream in a gas-liquid separator S2, operating at the pressure of the stream, then sent to a liquid storage means 701 under a maintained pressure of 28 bar. The air leaving the gas-liquid separator S2, again totally gaseous, is compressed in a third compression stage by a high-pressure compressor 102 from which it emerges at a temperature of 245° C. and a pressure of 117 bar. The compressed air leaving the compressor 102 is sent to a heat storage and recovery means 202 which cools the air to a temperature of 75° C. and stores this thermal energy until the expansion phase 2. The flow of compressed air is then cooled again by an exchanger 602 until it reaches a temperature of 30° C. at the outlet, 30° C. being the storage temperature of the air in the compressed gas storage means 500 The fluid leaving the exchanger 602 is then composed of air and water, resulting from the humidity of the air, condensed during the cooling phases in the heat storage and recovery means 202 and/ or in the cooling exchanger 602. This condensed water is separated from the flow of compressed gas in a gas-liquid separator S3, operating at the pressure of the flow of compressed gas, then sent to a liquid storage means 702 under a pressure maintained at 117 bar.

The flow of compressed air leaving the gas-liquid separator S3 at a pressure of 117 bar and a temperature of 30° C. is then sent to the compressed gas storage means 500 while waiting for the destocking phase in the expansion line 2 .

When it is desired to produce electricity, a flow of condensed water coming from the high pressure liquid storage means 702 at a pressure of 117 bar and a temperature of 30° C. is reinjected into the flow of compressed air leaving storage 500 via mixer M3 to form an air/water mixture. This mixture is preheated in a heat exchanger 400 in order to reach a temperature of 70° C. at the outlet. The mixture is then reheated in the heat storage and recovery means 202 used in the last compression stage which releases the heat stored during the compression phase 1 until the mixture reaches a temperature of 235°C. This flow of hot, compressed air is expanded in the high pressure turbine 300 of the first expansion stage producing electricity via an alternator, until it reaches an outlet pressure of 28 bar and a temperature of 80°C. The compressed gas leaving the turbine 300 is then used in the heat exchanger 400 to preheat the mixture, its temperature being higher than the temperature of the compressed gas stored in the compressed gas storage means 500. The compressed gas recovered at the outlet of the turbine 300 comes out of the exchanger 400 having given up its heat and reaching a temperature of 35°C. A flow of condensed water coming from the medium pressure liquid storage means 701 (the one used for the second compression stage) at a pressure of 28 bar and a temperature of 50° C. is reinjected into the flow of cooled outgoing compressed air. of the exchanger 400 via the mixer M2 to form a second air/water mixture. This second mixture is heated in the storage means and medium pressure heat recovery 201 (the one used in the second compression stage) which releases the heat stored during the compression stage 1 until the second mixture reaches a temperature of 265°C. This mixture is expanded in the medium pressure turbine 301 producing electricity via an alternator, until a pressure of 5 bar and a temperature of 75°C are reached at the outlet. A flow of condensed water coming from the liquid storage means 700 at a pressure of 6 bar and a temperature of 50° C. is reinjected into the flow of compressed air leaving the turbine 301 and entering the third and last stage of expansion via mixer M1 to form a third air/water mixture. This mixture is reheated in the low pressure heat storage and recovery means 200 (the one used in the first compression stage) which releases the heat stored during the compression phase 1 until the third mixture reaches a temperature of 245°C. This mixture is then expanded in the low pressure turbine 302 producing electricity via an alternator, until a pressure of 1.02 bar and a temperature of 80°C are reached at the outlet.

The efficiency of this method and energy storage system according to one embodiment of the invention is 70.8% for a power consumption of 100.0 MW in the compression phase, while the efficiency of the solution of FIG. 6 of the prior art is 69.6%, which makes it possible to increase the yield by more than 1%. The total flow of condensed water at the three compression stages is 7.5 tonnes per hour. The thermal storage power is 93.4 MW and the cooling power required is 14.1 MW, which makes it possible to reduce the cooling power by about 30% compared to the solution of Figure 6 of the prior art. This configuration also makes it possible to reduce the size of the high pressure heat storage and recovery means 202 by 24% compared to the solution of FIG. 6 of the prior art.

On the system and the method of Figure 5 (in accordance with the invention), during the compression phase 1, a flow of air taken from the ambient medium, at a pressure of 1.02 bar and a temperature of 27° C. and with a humidity of 14.6 grams of water per kilogram of air, is compressed by a low pressure compressor 100 from which it emerges at a temperature of 255°C and a pressure of 6 bar. The compressed air is sent to a heat storage and recovery means 200 which cools the air to a temperature of 80° C. and stores this thermal energy until the expansion phase 2. The compressed air is cooled again by a 600 heat exchanger until it reaches a temperature of 50°C at the outlet. The fluid is then composed of air and water, resulting from the humidity of the air, condensed during the cooling phases in the heat storage and recovery means 200 and/or the cooling exchanger 600. This condensed water is separated from the flow of compressed gas in a gas-liquid separator S1, operating at the pressure of the flow, then sent to a liquid storage means 700 under a maintained pressure of 6 bar. The air emerging from the separator S1, again totally gaseous, is compressed in a second compression stage by a medium-pressure compressor 101 from which it emerges at a temperature of 275° C. and a pressure of 28 bar. The compressed air is sent to a medium-pressure heat storage and recovery means 201 which cools the air to a temperature of 75° C. and stores this thermal energy until the expansion phase 2. The flow is cooled again in an exchanger 601 to reach a temperature of 50° C. at the outlet. The fluid is then composed of air and water, resulting from the humidity of the air, condensed during the cooling phases in the heat storage and recovery means 201 and/or the cooling exchanger 601 This condensed water is separated from the flow of compressed gas in a gas-liquid separator S2, operating at the pressure of the flow, then sent to a liquid storage means 701 under a maintained pressure of 28 bar. The gas leaving the separator S2, again totally gaseous, is compressed in a third compression stage by a high pressure compressor 102 from which it emerges at a temperature of 250° C. and a pressure of 117 bar. The compressed gas is then sent to a heat storage and recovery means 202 which cools the air to a temperature of 85° C. and stores this thermal energy until the expansion phase 2. The compressed gas is cooled again by an exchanger 602 until reaching a temperature of 30° C. at the outlet, 30° C. being the air storage temperature. The fluid is then composed of air and water, resulting from the humidity of the air, condensed during the cooling phases in the heat storage and recovery means 202 and/or in the cooling exchanger 602. This condensed water is separated from the compressed gas in a gas-liquid separator S3, operating at the pressure of the flow, then sent to a liquid storage means 702 under a maintained pressure of 117 bar.

The compressed air flow at a pressure of 117 bar and a temperature of 30°C is then sent to the compressed gas storage means 500 while waiting for the expansion phase 2.

When it is desired to produce electricity, a flow of condensed water from the high pressure liquid storage means 702 (the one used for the third compression stage) at a pressure of 117 bar and a temperature of 30 °C is reinjected into the flow of compressed air leaving the compressed gas storage means 500 via the mixer M3 to form a first air/water mixture. This mixture is preheated in a heat exchanger 400 in order to reach a temperature of 73° C. at the outlet. The mixture is then reheated in the high pressure heat storage and recovery means 202 (the one used in the third stage of compression) which releases the heat stored during the compression stage 1 until the flow of compressed gas reaches a temperature of 240°C. This flow of hot, compressed air is expanded in the high-pressure turbine 300 producing electricity via an alternator, until it reaches an output pressure of 28 bar and a temperature of 85°C. This flow leaving the turbine 300 is then used in the heat exchanger 400 to preheat the flow of compressed gas leaving the compressed gas storage means 500. The compressed gas leaving the cooled heat exchanger 400 emerges at a temperature of 35°C before entering a second stage of relaxation. A stream of condensed water coming from the medium pressure liquid storage means 701 (the one used in the second compression stage) at a pressure of 28 bar and a temperature of 50°C is reinjected into the compressed air stream via the mixer M2 to form a second air/water mixture. This mixture is preheated in the heat exchanger 401 until it reaches an outlet temperature of 65° C. before being reheated in the medium pressure heat storage and recovery means 201 (the one used in the second compression stage ) which releases the heat stored during the compression phase 1 until the flow reaches a temperature of 260°C. This flow of hot, compressed air is expanded in the medium-pressure turbine 301 producing electricity via an alternator, until it reaches an outlet pressure of 5 bar and a temperature of 70°C. A flow of condensed water coming from the low pressure liquid storage means 700 (the one used in the first compression stage) at a pressure of 6 bar and a temperature of 50° C. is reinjected into the flow of compressed air entering the the third expansion stage via mixer M1 to form a third air/water mixture. This mixture is reheated in the low pressure heat storage and recovery means 200 (the one used in the first compression stage) which releases the heat stored during the compression stage 1 until the flow reaches a temperature 245°C. This flow of hot, compressed air is expanded in the low pressure turbine 302 producing electricity via an alternator, until it reaches an output pressure of 1.02 bar and a temperature of 85°C. The air leaving the last turbine 302 of the expansion line is then sent to the heat exchanger 401 in order to heat the flow of second mixture in the second expansion stage. At the outlet of the heat exchanger 401, the compressed air comes out cooled to a temperature of 40°C.

The efficiency of the energy storage process is 70.2% for a power consumption of 100.0 MW at the compressors, which makes it possible to increase the efficiency by 0.3% compared to the solution of FIG. 6 of the prior art . The total flow of condensed water at the three compression stages is 7.5 tons per hour. The thermal storage power is 86.6 MW and the cooling power required is 21.0 MW. This configuration makes it possible to reduce the size of the means of storage and recovery of high pressure heat 202 by 23% compared to the technical solution of Figure 6 of the prior art. It also allows a reduction in the size of the medium pressure heat storage and recovery means 201 by 24% compared to the technical solution of FIG. 4 of the invention.

Claims

1.Compressed gas energy storage and recovery system comprising:

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

- at least one compressed gas storage means (500) located at the outlet of the gas compression line (1) to store the compressed gas,

- an expansion line (2) for expanding compressed gas stored in the compressed gas storage means (500), the expansion line (2) comprising at least two successive expansion stages (4), each expansion stage ( 4) comprising pipes and an expansion means (300, 301, 302), the pipes being configured to circulate the compressed gas in at least one of the heat storage and recovery means (200, 201, 202) of the compression stages (3) so as to heat the compressed gas before the expansion means (300, 301, 302), characterized in that the expansion line (2) comprises at least one circulation means for circulating the expanded gas leaving the first expansion stage, in the direction of gas circulation in the expansion line (2), in a first heat exchange means (400) located in the first expansion stage, the first heat exchange means heat (400) being adapted to heat the gas prior to the passage of the compressed gas in the heat storage and recovery means (200, 201, 202) in which the compressed gas of the first expansion stage circulates and before the cooled compressed gas is sent to the next expansion stage of the expansion line (2).

2. System according to claim 1, wherein said heat storage and recovery means (200, 201, 202) comprises heat storage particles.

3. System according to one of the preceding claims, for which said compression line (1) comprises as many compression stages (3) as the expansion line (2) comprises expansion stages (4), each means storage and heat recovery (200, 201, 202) of a compression stage being used in the expansion stage at the corresponding pressure.

4. System according to claim 3, wherein the expansion line (1) and the compression line (2) each comprise three stages.

5. System according to one of the preceding claims, wherein at least one compression stage (3) comprises cooling means (600, 601, 602) downstream of the heat storage and recovery means (200, 201, 202), of preferably, said cooling means (600, 601, 602) comprising an air cooler.

6. System according to one of the preceding claims, for which at least one compression stage (3) comprises separation means (S1, S2, S3) for separating the compressed gas from a liquid phase before the compressed gas reaches the next compression stage (3) or the compressed gas storage means (500), each compression stage (3) comprising a liquid storage means (700, 701, 702) for storing said liquid phase to the pressure of the compression stage (3).

7. System according to claim 6, for which at least one expansion stage (4) comprises mixing means (M1, M2, M3) for mixing with said compressed gas, said liquid phase exiting from one of the liquid storage means ( 700, 701, 702) of the compression stages (3) before said first heat exchange means (400) and/or before the heat storage and recovery means (202, 201, 200).

8. System according to claim 7, wherein said mixing means (M1, M2, M3) is positioned upstream of said first heat exchange means (400) on the first expansion stage and upstream of the storage means and heat recovery (201, 200) on the other expansion stages.

9. System according to one of the preceding claims, for which the expansion line (2) comprises a heat recovery line for circulating the expanded gas at the outlet of the last expansion stage, in the direction of circulation of the gas in the expansion line, in a second heat exchange means (401) located on the second expansion stage, upstream of the heat storage and recovery means (201) of the second expansion stage.

10. Compressed gas energy storage and recovery process comprising at least the following steps:

- In the energy storage phase: a) a gas is compressed at least once in a compression line (1) comprising at least one compression stage (4), each compression stage (4) comprising at least one means compression (100, 101, 102); b) after each compression step (4), the heat of said compressed gas is recovered in at least one heat storage and recovery means (200, 201, 202); c) the cooled compressed gas is stored in at least one compressed gas storage means (500).

- In the energy recovery phase: d) the compressed gas leaving the compressed gas storage means (500) is circulated in an expansion line (2) of at least two expansion stages (4), and in each expansion stage (4), heats the compressed gas by causing it to circulate in one of the heat storage and recovery means (200, 201, 202) thanks to the heat stored during the compression step (3) then the heated compressed gas is expanded in an expansion means (4); characterized in that the heat of at least a portion of the gas expanded at the outlet of the expansion means (300) of the first expansion stage is used to heat the compressed gas leaving the compressed gas storage means (500) in a first heat exchange means (400) positioned upstream of the heat storage and recovery means (202).

11. Method according to claim 10, for which as many compression steps as expansion steps are carried out, and the heat storage and recovery means (200, 201, 202) of each of the steps b are used. ) to heat the compressed gas from the expansion stage to the corresponding pressure.

12. Method according to one of claims 10 or 11, for which the heat is recovered from the compressed gas by heat storage particles.

13. Method according to one of claims 10 to 12, for which, 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 (600, 601, 602) before the gas is sent to the next compression step or to the compressed gas storage means (500).

14. Method according to one of claims 10 to 13, for which the heat is recovered from the expanded gas at the outlet of the last expansion stage to heat the compressed gas entering the second expansion stage, upstream of the storage means and heat recovery (201) of the second expansion stage.

15. Method according to one of claims 10 to 14, for which the compressed gas is separated from a liquid phase which it contains in a separation means (S1, S2, S3), before the compressed gas is sent to the next compression stage (3) or to the compressed gas storage means (500), the liquid leaving each separation means (S1, S2, S3) being stored at the pressure in which it is in a liquid storage means (700, 701, 702).

16. Method according to claim 15, for which, in each expansion stage, the liquid stored in a liquid storage means (700, 701, 702) is injected, and it is mixed with the compressed gas, before each step of reheating.