阅读说明：本技术 改进的能量存储和收集系统 (Improved energy storage and collection system ) 是由 P·布里奥特 D·泰塞拉 于 2018-11-14 设计创作，主要内容包括：本发明涉及使用压缩气体来储存和回收能量的系统和方法,包括至少一个第一换热器和至少一个第二换热器、用于储存冷液体的装置和用于储存热液体的装置。第一换热器包括至少一个非直接接触的换热器,而至少一个第二换热器是直接接触的换热器。(The present invention relates to a system and a method for storing and recovering energy using compressed gas, comprising at least one first heat exchanger and at least one second heat exchanger, means for storing cold liquid and means for storing hot liquid. The first heat exchanger comprises at least one non-direct contact heat exchanger and the at least one second heat exchanger is a direct contact heat exchanger.)

1. A compressed gas energy storage and recovery system comprising:

-at least one gas compression device (K-101, K-102, K-103, K-104),

-at least one device (T-201) for storing said compressed gas,

-at least one device (EX-201, EX-202, EX-203, EX-204) for expanding the compressed gas for generating energy,

-at least one first heat exchanger (E-101, E-102, E-103, E-104) arranged downstream of the means (K-101, K-102, K-103, K-104) for compressing the compressed gas,

-at least one second heat exchanger (E-106, E-107, E-201, C-105, C-106, C-107, C-108, C-208) arranged upstream of the means (EX-201, EX-202, EX-203, EX-204) for expanding the compressed gas,

-at least one cold liquid storage device (T-406) and at least one hot liquid storage device (T-402, T-403, T-404, T-405),

characterized in that the first heat exchanger comprises at least one non-direct contact heat exchanger and the at least one second heat exchanger is a direct contact heat exchanger, the direct contact heat exchanger and the non-direct contact heat exchanger transferring heat between the gas and the liquid, the direct contact heat exchanger and the non-direct contact heat exchanger being positioned between the cold liquid storage device (T-406) and the hot liquid storage device (T-402, T-403, T-404, T-405).

2. The system of claim 1, wherein the gas is air.

3. The system of any one of the preceding claims, wherein the liquid is water.

4. The system of any one of the preceding claims, wherein all of the first heat exchangers are heat exchangers without direct contact between the liquid and the gas.

5. The system of any one of claims 1 to 3, wherein the system comprises at least one heat exchanger having a fixed bed of heat storage particles, the heat exchanger having a fixed bed of heat storage particles configured to be both a first heat exchanger and a second heat exchanger.

6. The system of any one of claims 1 to 4, wherein the second heat exchangers are all heat exchangers having direct contact between the liquid and the gas.

7. The system of any one of claims 1 to 5, wherein the second heat exchanger comprises a direct contact heat exchanger and a non-direct contact heat exchanger, the second direct contact heat exchanger being positioned in a final heat exchanger.

8. The system of any one of the preceding claims, wherein the non-direct contact heat exchanger is a plate exchanger (welded or not) and/or a shell-and-tube exchanger.

9. The system of any of the preceding claims, wherein the direct contact heat exchanger is a packed column and/or a plate column.

10. The system according to any one of the preceding claims, characterized in that it comprises at least one device (V-101, V-102, V-103, V-104) for separating said gas and said liquid, said separation device (V-101, V-102, V-103, V-104) being positioned after said at least one first heat exchanger (E-101, E-102, E-103, E-104).

11. A system according to any of the preceding claims, characterized in that a plurality of gas compression devices (K-101, K-102, K-103, K-104) and/or a plurality of devices (EX-101, EX-102, EX-103, EX-104) for expanding the gas are used, preferably at least three.

12. System according to claim 11, characterized in that a plurality of first heat exchangers (E-101, E-102, E-103, E-104) are used, preferably at least after each of the compression devices (K-101, K-102, K-103, K-104) there is the first heat exchanger (E-101, E-102, E-103, E-104).

13. The system according to claim 12, wherein a plurality of separation devices (V-101, V-102, V-103, V-104) are used, preferably at least one of the separation devices (V-101, V-102, V-103, V-104) after each of the first heat exchangers (E-101, E-102, E-103, E-104).

14. A system according to any one of claims 11 to 13, wherein a plurality of second heat exchangers (E-106, E-107, E-201, C-105, C-106, C-107, C-108, C-208) are used, preferably said second heat exchangers (E-106, E-107, E-201, C-105, C-106, C-107, C-108, C-208) are present at least upstream of each of said expansion devices (EX-201, EX-202, EX-203, EX-204).

15. A method of heat storage and recovery, wherein the following steps are performed:

a) the gas is compressed and then the compressed gas is compressed,

b) cooling the compressed gas by heat exchange with a cold liquid, and storing the hot liquid at the outlet of the heat exchangers (E-101, E-102, E-103, E-104),

c) the cooled compressed gas is stored and stored in a storage tank,

d) heating the cooled compressed gas with the hot liquid stored in step c) by means of a heat exchanger and storing a cold liquid,

e) the compressed gas is caused to expand and,

characterized in that at least one heat exchange carried out in step b) takes place without direct contact between the liquid and the gas, whereas at least one heat exchange carried out in step d) takes place at least partly by direct contact between the liquid and the gas.

16. The method of claim 15, wherein the gas is air.

17. The method of any one of claims 15 and 16, wherein the liquid is water.

18. The method according to any one of claims 15 to 17, wherein between step b) and step c), step b two) comprises performing a separation of the cooled compressed gas and condensed liquid, and storing the condensed liquid.

19. The method according to any of claims 15 and 18, wherein at least one of steps a), b) and/or two) of b) is moved several times before moving to the next step.

20. The method of any one of claims 15 to 19, wherein at least one of steps d) and e) is performed a plurality of times.

21. The method according to any one of claims 15 to 20, wherein each heat exchange between the liquid and the gas of step d) occurs by direct contact between liquid and gas.

22. The method according to any one of claims 15 to 20, wherein the heat exchange between the liquid and the gas in step d) takes place by means of a direct contact heat exchanger and a non-direct contact heat exchanger, the direct contact heat exchanger being positioned between the last heat exchangers.

23. The method according to any one of claims 19 and 20, wherein at least one heat exchange in step b) and at least one heat exchange in step d) is replaced by a heat exchange between a fixed bed of heat storage particles and the gas, heat of the compressed gas being stored in the heat storage particles during at least one step b), the stored heat of the heat storage particles being released to the compressed gas during at least one step d).

24. The process according to any one of claims 15 to 23, wherein the heat exchange without direct contact takes place by means of at least one (welded or not) plate exchanger or at least one shell-and-tube exchanger.

25. The process of any one of claims 15 to 24, wherein the direct contact heat exchange occurs at least in part through a packed column and/or a tray column.

Technical Field

The present invention relates to the field of energy storage and generation by air compression and expansion.

Background

Power generation from renewable sources, for example by means of solar panels or wind turbines on or off shore, is rapidly evolving. The main drawbacks of these production means are intermittent production and possible mismatch between production cycle and consumption cycle. It is therefore important to have a means of storing energy during production, so that energy is released during consumption.

There are many techniques that allow this balancing to be achieved.

The most well known of these are Pumped Storage Plants (PSPs) which use two reservoirs at different altitudes. During the fill phase, water is pumped from the lower basin to the upper basin. Then, during discharge, the water is sent to the turbine towards the lower water basin.

This energy storage requirement can also be met using different types of batteries (lithium, nickel, sodium-sulfur, lead-acid, etc.).

Another technique, Flywheel Energy Storage (FES), involves accelerating the rotor (Flywheel) to very high speeds and maintaining the Energy in the system in the form of kinetic Energy. When energy is extracted from the FES system, the rotational speed of the flywheel is reduced due to the principle of conservation of energy. Thus, adding energy to the FES system results in an increase in flywheel speed.

Energy storage technologies using compressed gas (typically compressed air) are promising. The generated unconsumed energy is used to compress the air pressure to the range of 40 bar (bar) to 200 bar using a (possibly multi-stage) compressor. During compression, the air temperature increases. To limit the cost of the storage tank and minimize the power consumption of the compressor, the air may be cooled between each compression stage. The compressed air is then stored under pressure in a natural cavity (cavern) or artificial reservoir.

During the power generation phase, the stored air is then sent to a turbine to generate electricity. During expansion, the air cools. To avoid damage to the turbine from too low a temperature (-50 ℃), the air may be heated prior to expansion. Such power plants have now been in operation for many years, for example Huntorf power plants in germany since 1978 or MacIntosh power plants in the united states (Alabama ) since 1991. Two of thesePower plants have the specific feature of using stored compressed air to supply the gas turbine. These gas turbines burn natural gas in the presence of pressurized air, producing very hot combustion gases (550 ℃ and 825 ℃) at high pressure (40 bar and 11 bar), and then expand them in turbines that generate electricity. This type of process emits carbon dioxide. The Huntorf power plant can emit about 830kg of CO per megawatt of power generation₂。

There is a variation being developed. This is a so-called adiabatic process, in which the heat generated by the compression of air is recovered, stored and released into the air before it expands. This is a technology known as AACAES (Advanced Adiabatic Compressed Air Energy Storage).

In this technique, the air is typically air taken from the surrounding medium. It may therefore contain water in the form of steam. The humidity varies according to geographical location and temperature and/or season. When the air is cooled after compression, water contained in the air may be wholly or partially condensed. When not removed from the gas, the water contained in the gas can cause damage to the compressor and other equipment in which the compressed gas is circulated.

A so-called "compressed line" is a gas line connecting a gas inlet to a compressed gas storage device and passing through at least one compression device.

The so-called "expansion line" is a gas line connecting a compressed gas storage device to a gas outlet and passing through at least one expansion device.

Heat exchangers are used to cool and/or heat air. Several heat exchanger technologies exist.

Among these, several types of heat exchangers allow the exchange between two fluids (usually gas and liquid). These exchangers allow cooling of hot gases from cold fluids (usually cold liquids) or heating of cold gases from hot fluids (usually hot liquids).

A direct contact heat exchanger is understood to be a heat exchanger in which direct contact occurs between a fluid (usually a liquid) and a gas. When using direct contact heat exchangers, mass exchange can also take place between the fluid and the gas.

When using a direct contact heat exchanger, the gas may become partially loaded with fluid in the form of gas or liquid droplets and/or part of the gas may be condensed or absorbed by the fluid. Depending on the fluid, gas, pressure and temperature and the exchange pattern (gas heating or cooling). Thus, it may be necessary to add fluid to the circuit or, conversely, to withdraw some fluid, thus complicating the system.

A non-direct contact heat exchanger is understood to be a heat exchanger in which no direct contact between fluid and gas occurs. In such indirect heat exchangers, the heat exchange takes place, for example, via solid walls, but no mass transfer can take place between the fluid and the gas. Plate exchangers or shell-and-tube exchangers are examples of non-direct contact heat exchangers.

Another heat exchanger technology is based on heat storage and release of particles. In this type of heat exchanger, the enclosure is filled with a so-called fixed bed of heat storage and release particles. The heat storing and releasing particles are solid elements made of a material having good properties of storing and releasing heat. The particles are randomly arranged in the bed. A fixed bed is understood to be a bed in which no moving particles are intentionally set. However, they may experience movement caused by thermal expansion or by, for example, gas circulation within the enclosure. In this type of exchanger (hereinafter referred to as "Thermocline"), the gas is circulated in the enclosure through a fixed bed of heat storage and release particles:

-the gas heats the heat storing and releasing particles,

or the gas is conversely heated by the heat storage and release particles.

In these thermocline type exchangers, the gas and the heat storage and release particles thus exchange heat directly (without using an intermediate fluid such as for example a liquid).

As the gas is compressed, the air temperature increases. In order to avoid that the compressed air stored at high temperature generates additional costs for the storage device, the heat of the air is recovered and the air is cooled accordingly.

Patent US-2013/0,042,601 describes cooling of air between compression stages by water through an indirect contact exchanger. The hot water is then cooled. The heat required during expansion is provided by the combustion of hydrocarbons in high and low pressure combustors. Similar descriptions are made in patents US-2014/0,026,584 a1 and US-2016/0,053,682 a 1. The use of combustors and hydrocarbons involves the following disadvantages: high cost of combustor and significant CO₂And (5) discharging.

In patents US-2011/0,113,781 a1 and WO-2016/0,749,485 a1, the heat generated by air compression is used to feed a parallel Rankine (Rankine) cycle and/or Kalina (Kalina) cycle based on the use of butane, pentane, isopentane. The heat required for the expansion of the air is provided by an external source (burner, etc.). In this case, the cost of the burner and the use of combustible gas is also high. Furthermore, these solutions cause pollution.

Patent WO-2016/012,764 a1 describes heat exchange without direct contact between hot air produced by compression and molten salt using a heat exchanger. Before expansion, the air is heated by means of the hot-melt salt previously obtained. Such a system is also used in patent DE-10-2010/055,750 a1, in which the fluid used to transfer the heat of compression to expansion is a brine solution passing through an exchanger. The use of molten salts or salt solutions involves drawbacks in the design of the plant due to the risk of corrosion. Furthermore, the implementation of these solutions using phase change materials is complex.

The cooling of the air can also be carried out by means of a so-called direct contact exchanger, which can be, for example, a packed column with structured or random packing, or a tray column. Hot air is fed into the tower where cold liquid is fed out counter-current to the air. The heat of the air is then transferred to the cold fluid, which heats up when in contact with the air. In addition to heat, mass transfer may also occur upon contact. These columns generally contain elements that allow improved contact between the gas phase (air) and the liquid phase (cold fluid), thereby promoting gas-liquid transfer. These elements may be structured or random packing or distributor discs equipped with chimneys. There are also direct contact systems based on solids. Patent US-2016/0,326,958 a1 describes a system in which heat transfer takes place by direct contact with a phase change material. Patent US-2011/0,016,864 a1 uses a heat transfer technique by direct contact with molten salts. In this case, direct contact heat exchange takes place on the compression line and the expansion line. On the compression line, this involves the disadvantage of loading the gas with a liquid or solid, possibly damaging the rest of the system. Furthermore, the implementation of the above solution using phase change materials is complicated.

To minimize material costs, the same equipment can be used to cool the hot air from compression and to heat the air before expansion, since the process operates in a cyclic manner. This describes the non-direct contact technique in patent DE-10-2010/055,750A 1, while the direct contact heat exchange technique is described in patents US-2011/0,016,864A 1 and US-2016/0,326,958A 1.

Disclosure of Invention

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

-at least one gas compression device,

-at least one device for storing said compressed gas,

-at least one device for expanding the compressed gas to generate energy,

-at least a first heat exchanger arranged downstream of the means for compressing the compressed gas,

-at least a second heat exchanger arranged upstream of the means for expanding the compressed gas,

-at least one cold liquid storage device and at least one hot liquid storage device.

The first heat exchanger comprises at least one non-direct contact heat exchanger and the at least one second heat exchanger is a direct contact heat exchanger. The direct contact heat exchanger and the indirect contact heat exchanger transfer heat between the gas and the liquid. The direct contact heat exchanger and the indirect contact heat exchanger are positioned between the cold liquid storage device and the hot liquid storage device.

Preferably, the gas is air.

Advantageously, the liquid is water.

According to an embodiment of the invention, all of the first heat exchangers are heat exchangers that are not in direct contact between the liquid and the gas.

According to a variant embodiment of the invention, the system comprises at least one heat exchanger with a fixed bed of heat storage particles, which is configured as both a first heat exchanger and a second heat exchanger.

According to an embodiment of the invention, all of the second heat exchangers are heat exchangers in direct contact between the liquid and the gas.

According to an embodiment of the invention, the second heat exchanger comprises a direct contact heat exchanger and a non-direct contact heat exchanger, the second direct contact heat exchanger being positioned in the last heat exchanger.

According to one embodiment of the invention, the indirect contact heat exchanger is a plate exchanger (welded or not) and/or a shell-and-tube exchanger.

According to one variant of the invention, the direct contact heat exchanger is a packed column and/or a plate column.

According to an embodiment of the invention, the system comprises at least one means for separating said gas and said liquid, said separating means being positioned after the at least one first heat exchanger.

Advantageously, a plurality of gas compression means and/or a plurality of means for expanding said gas are used, preferably at least three.

Preferably, a plurality of first heat exchangers are used, preferably at least a first heat exchanger is used after each of said compression devices.

Advantageously, a plurality of separation devices is used, preferably at least one separation device is used after each of the first heat exchangers.

Preferably, a plurality of second heat exchangers are used, preferably at least a second heat exchanger upstream of each of the expansion devices.

The invention also relates to a method for energy storage and recovery, wherein the following steps are performed:

a) the gas is compressed and then the compressed gas is compressed,

b) cooling the compressed gas by heat exchange with a cold liquid and storing the hot liquid at the outlet of the heat exchanger,

c) storing the cooled compressed gas in a storage tank,

d) heating the cooled compressed gas with the hot liquid stored in step c) by means of a heat exchanger and storing the cold liquid,

e) expanding the compressed gas.

The at least one heat exchange performed in step b) takes place without direct contact between the liquid and the gas, and the at least one heat exchange performed in step d) takes place at least partly by direct contact between the liquid and the gas.

Advantageously, the gas is air.

Preferably, the liquid is water.

Preferably, between step b) and step c), step two) comprises performing a separation of the cooled compressed gas and the condensed liquid and storing the condensed liquid.

Advantageously, at least one of steps a), b) and/or two) of b) is performed a plurality of times before moving to the next step.

Preferably, at least one of steps d) and e) is performed a plurality of times.

According to one variant of the method of the invention, each heat exchange between said liquid and said gas of step d) takes place by direct contact between the liquid and the gas.

According to one embodiment of the process of the invention, the heat exchange between the liquid and the gas in step d) is carried out by means of a direct contact heat exchanger and a non-direct contact heat exchanger, the direct contact heat exchanger being positioned between the last heat exchangers.

According to a variant of the method, the at least one heat exchange of step b) during which the heat of the compressed gas is stored in the heat storage particles and the at least one heat exchange of step d) during which the stored heat of the heat storage particles is released to the compressed gas are replaced by a heat exchange between a fixed bed of heat storage particles and the gas.

According to one variant of the process of the invention, the indirect contact heat exchange of step b) is carried out by means of at least one (welded or not) plate exchanger or at least one shell-and-tube exchanger.

According to one embodiment of the process of the present invention, the direct contact heat exchange of step d) is carried out at least partly by means of a packed column or a tray column.

Drawings

Further characteristics and advantages of the system and method according to the invention will become apparent from reading the following description of embodiments, given by way of non-limiting example, with reference to the accompanying drawings, in which:

figure 1 shows an example of an energy storage and recovery system according to the prior art,

figure 2 shows a second example of an energy storage and recovery system according to the prior art,

figure 3 shows a third example of an energy storage and recovery system according to the prior art,

figure 4 shows a first embodiment of an energy storage and recovery system according to the invention,

figure 5 shows a second embodiment of the energy storage and recovery system according to the invention.

Detailed Description

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

at least one gas compression device allowing the pressure of the gas to be increased for storage purposes,

-at least one compressed gas storage device for storing compressed gas to be used later,

at least one device for expanding compressed gas for generating energy,

at least a first heat exchanger, which is arranged downstream of the gas compression device and allows the gas to be cooled after the gas compression,

-at least one second heat exchanger positioned upstream of said means for expanding the compressed gas and allowing the gas to be heated before the gas expansion, operating the expansion means at a temperature providing the best efficiency,

-at least one cold liquid storage means and at least one hot liquid storage means, these means enabling the use of cold liquid at least for the first heat exchanger and hot liquid for the second heat exchanger.

The first heat exchanger comprises at least one heat exchanger not in direct contact, on the one hand in order to optimize heat recovery and on the other hand to limit the risk of liquid in the gas. In fact, indirect contact heat exchangers do not allow mass exchange between liquid and gas. Thus, the only trace of liquid that may be present in the gas is associated with the condensation of the liquid. Using a direct contact heat exchanger as the first heat exchanger can drive part of the heat transfer liquid into the gas, which liquid will add to the condensation. Thus, a device for separating liquid and gas would be most useful, considering that large amounts of water would then be incorporated into the gas.

Furthermore, at least one second heat exchanger is a direct contact heat exchanger. In terms of system performance, it is advantageous to use a direct contact heat exchanger in the expansion line. In fact, when using this type of exchanger, a mass exchange occurs between gas and liquid: a portion of the liquid then dissolves in the gas, thus increasing its density and mass flow rate. These features allow for increased efficiency with respect to the expansion device.

Direct contact heat exchangers and indirect contact heat exchangers transfer heat between a gas and a liquid. These exchangers provide good thermal performance and are easy to implement. In addition, the pressure drop produced by these systems is relatively low. The direct contact heat exchanger and the indirect contact heat exchanger are positioned between the cold liquid storage device and the hot liquid storage device. Thus, the liquid is stored hot and cold for later use.

Preferably, the gas may be air, and preferably air taken from the surrounding medium. Thus, the costs associated with gas production, conditioning and logistics are eliminated.

Preferably, the liquid may be water. In fact, water is an inexpensive heat transfer fluid, which is an excellent compromise.

According to an embodiment of the system according to the invention, the first heat exchangers may all be heat exchangers without direct contact between liquid and gas. Thus, the system is simplified by a single technology of heat exchangers used on the compression line.

According to another embodiment of the invention, the system comprises at least one heat exchanger with a fixed bed of heat storage particles. Such heat exchangers with a fixed bed of heat-storing particles, called "thermocline", are configured as a first heat exchanger and a second heat exchanger. In this exchanger, the gas heat storage particles are directly heat exchanged and the gas is circulated through a fixed bed of heat storage particles. In fact, the bed of particles is fixed, the heat coming from the hot compressed gas and absorbed by the stored particles is then released by these stored particles to the gas circulating in the exchangers. In other words, the heat exchanger serves here both as a first heat exchanger and as a second heat exchanger. This allows to simplify the system and to reduce costs by limiting the number of exchangers, as well as by limiting the piping and throttling/pumping systems required by the technologies related to the exchange between a gas and another fluid (for example, direct contact exchangers and indirect contact exchangers). Furthermore, the heat storage particles can be made of inexpensive materials.

According to a variant of the invention, the second heat exchangers may all be heat exchangers with direct contact between the liquid and the gas. Such an embodiment allows to simplify the expansion line by means of a single heat exchanger technology on the expansion line, i.e. close to the final air outlet.

According to another variant of the invention, the second heat exchanger may comprise a direct contact heat exchanger and a non-direct contact heat exchanger. In this variant, the second direct contact heat exchanger is preferably positioned between the last heat exchangers of the expansion line, preferably in the last stage of the expansion line. This provides a better compromise between thermal efficiency and mass transfer, allowing for an increased gas mass flow rate before entering the expansion device.

According to an embodiment of the invention, the non-direct contact heat exchanger may be a plate exchanger (welded or not) and/or a shell-and-tube exchanger.

According to another embodiment of the invention, the direct contact heat exchanger may be a packed column with structured or random packing and/or a plate column.

According to one embodiment of the invention, the system may comprise at least one device for separating gas and liquid. The separation device may be arranged after at least the first heat exchanger in order to eliminate condensation traces that may occur and damage other equipment of the system, in particular the next compression stage, when the gas is cooled.

Advantageously, a plurality of gas compression means and/or a plurality of means for expanding gas may be used, preferably at least three. The use of staged compression and/or expansion devices results in improved system efficiency and performance.

According to an embodiment of the invention, a plurality of first heat exchangers may be used, preferably at least a first heat exchanger after each compression device. Thus, the gas is cooled before the compressed gas is stored or before it enters the next compression device. If stored, lower storage temperatures result in lower storage costs. If it enters the next compression unit, the efficiency of that compression unit is higher when the temperature is lower.

Preferably, a plurality of separation devices may be used, preferably at least one separation device is used after each first heat exchanger. Thus, traces of condensation that may occur upon cooling of the gas are eliminated, which makes it possible to avoid damaging the rest of the system, and in particular the next compression stage.

Advantageously, a plurality of second heat exchangers may be used, preferably at least a second heat exchanger upstream of each expansion device. Thus, the temperature of the gas is increased upstream of the expansion device, thereby avoiding too low and harmful temperatures at the outlet of the expansion device. Furthermore, the higher the temperature, the more energy in the gas and, thus, the higher the energy release.

The invention also relates to a method for energy storage and recovery, wherein the following steps are performed:

a) the gas is compressed and then the compressed gas is compressed,

b) cooling the compressed gas by heat exchange with a cold liquid and storing the hot liquid at the outlet of the heat exchanger,

c) the cooled compressed gas is stored in a storage tank,

d) heating the cooled compressed gas with the hot liquid stored in step c) by means of a heat exchanger and storing the cold liquid,

e) the compressed gas is expanded.

In this embodiment, at least one heat exchange carried out in step b) takes place without direct contact between the liquid and the gas. Thus, the heat recovery efficiency is optimized and no mass transfer between the liquid and the gas occurs, which avoids adding liquid to the condensate formed in the gas.

Furthermore, at least one heat exchange carried out in step d) takes place by direct contact between the liquid and the gas. The use of this type of heat exchange allows part of the liquid in the gas to be recovered, which allows the gas mass flow rate to be increased and thus the performance of the expansion device to be improved.

Advantageously, the gas may be air, preferably air taken from the surrounding medium. Thus, the costs associated with gas production, conditioning and logistics are eliminated.

Preferably, the liquid may be water. In fact, water is an inexpensive heat transfer fluid, which provides an excellent compromise.

According to an embodiment of the invention, between step b) and step c), the second step b) comprises performing a separation of the cooled compressed gas and the condensed liquid, and the liquid condensed between step b) and step c) (the second step b) may be stored. Thus, traces of condensed liquid that may be formed during cooling of the gas in step b) can be eliminated.

According to a variant of the invention, at least one of the steps a), b) and two) of b) can be carried out a plurality of times (for example, a plurality of steps a) or a plurality of steps a) and b) or a plurality of steps a), b) and two) before moving to the next step. Thus, the performance of the process is improved by the individual steps which can be graded.

According to another variant of the invention, at least one of steps d) and e) may be carried out a plurality of times (for example, a plurality of steps d) or a plurality of steps d) and e)). Thus, the expansion device is staged, which maximizes energy recovery efficiency, and/or the gas is heated in multiple steps, e.g. before each expansion step, so that the temperature of the gas at the inlet of the expansion device approaches an optimum value.

According to one embodiment of the process of the present invention, each heat exchange between the liquid and the gas of step d) may take place by direct contact between the liquid and the gas. Thus, the expansion line is simplified by using a single exchanger technology on the expansion line.

According to a variant embodiment of the method according to the invention, the heat exchange between the liquid and the gas in step d) can be sounded by means of a direct contact heat exchanger and a non-direct contact heat exchanger, the direct contact heat exchanger being positioned between the last heat exchangers, preferably in the last expansion step. Thus, heat recovery is optimized by indirect contact heat exchange, followed by direct contact heat exchange to maximize the mass flow rate increase at the inlet of the compression device and its efficiency. This configuration is the best compromise to maximize the overall efficiency of the system.

According to an embodiment of the process of the present invention, the at least one heat exchange of step b) and the at least one heat exchange of step d) may be replaced by a heat exchange between a fixed bed of heat storage particles and a gas. For example, the compression line may comprise at least one heat exchanger with no direct contact between the liquid and the gas, and at least one Thermocline (Thermocline) type heat exchanger between a fixed bed of heat storage particles and the gas; the expansion line may for example comprise at least one heat exchanger in direct contact between the liquid and the gas, and at least one thermocline type heat exchanger between the fixed bed of heat storage particles and the gas, which thermocline type heat exchanger is combined with the heat exchanger of the compression line. In a thermocline-type heat exchanger, the heat of the compressed gas is stored in the heat storage particles during at least one step b). During at least one step d), the heat thus stored in the heat particles is subsequently released to the compressed gas. The bed of particles is stationary and the gas needs to be circulated to store or release heat in the heat storing particles. Thus, if a thermocline type heat exchanger is used on the compression line, it is also used on the expansion line. The advantages of using this type of exchanger include: simple to implement and reduces costs by limiting the number of heat exchangers, a single exchanger being used as the first and second heat exchangers, thus limiting the piping and throttling/pumping systems required for gas/liquid type exchanges (direct contact and indirect contact exchangers). Furthermore, the heat storage particles may be made of inexpensive materials.

According to one embodiment of the invention, the indirect contact heat exchange of step b) can be carried out by means of at least one plate exchanger (welded or not) and/or at least one shell-and-tube exchanger.

According to a variant embodiment of the invention, the direct contact heat exchange of step d) can be carried out at least in part by a packed column and/or a tray column with structured or random packing.

Further features and advantages of the system and method according to the invention will become apparent from reading the following description of non-limiting exemplary embodiments with reference to the drawings described below.

Examples 1-3 are variations of the prior art. Examples 4 and 5 are modified embodiments according to the present invention.

Each example is performed with 4 compression stages and 4 expansion stages, but this number of stages is not limiting.

In the description of these various examples, the same equipment (compressor for the compression device and turbine for the expansion device) is used for the compression and expansion of air. The characteristics of the compressor and the turbine used are given in the table below.

Example 1: according to the prior art (fig. 1)

This example may correspond to a system or a method for replacing a salt solution with water as a hot fluid, as described in patent DE-10-2010/055,750 a 1.

51,350 kilograms per hour (kg/h) of outside air (stream 1) containing 4.2 mole percent (mol%) water at a temperature of 20 ℃ and a pressure of 1,014 bar (bar) is sent to compression stage K-101 from which it flows at a higher pressure and a higher temperature (stream 2).

This stream 2 is then cooled to 50 ℃ in a non-direct contact exchanger E-101 without direct contact with water at 40 ℃ (stream 29). The water leaves the exchanger at a higher temperature (stream 30) and is sent to the hot liquid storage device T-402.

The cooled air is sent to a gas/liquid separator V-101 which separates the moisture of the condensed air (stream 23) from the air (stream 4). The condensed water is then sent to a condensed liquid storage means T-301.

The air then flows into the second compression stage K-102, which exits the second compression stage at a higher pressure and temperature (stream 5). It is then cooled in non-direct contact exchanger E-102 without direct contact with cold water (stream 31).

The hot water (stream 32) leaving the exchanger is sent to a hot liquid storage device T-402.

The cooled air (stream 6) enters a gas/liquid separator V-102, which separator V-102 separates condensed moisture (stream 24) from the cold air (stream 7). The condensed moisture is sent to the condensed liquid storage means T-301.

The cooled air (stream 7) enters the third compression stage K-103, which exits the third compression stage (stream 8) at a higher pressure and temperature. It is then cooled in a non-direct contact heat exchanger E-103 without direct contact with cold water (stream 33).

The hot water is then sent to the hot liquid storage device T-402.

The cold air enters a gas/liquid separator V-103 where condensed moisture (stream 25) is separated from the air (stream 10). The condensed moisture is then sent to a condensed liquid storage means T-301.

The cold air (stream 10) leaves the separator V-103 and then enters the final compression stage K-104, which leaves the final compression stage (stream 11) at a higher pressure and temperature.

It is then cooled in an indirect heat exchanger without direct contact with the cold water (stream 36) E-104. This stream 36 can be cooled by means of exchanger E-105 to a temperature lower than the temperature of the water used for cooling in exchangers E-101, E-102 and E-103. The hot water (stream 37) leaving exchanger E-104 is sent to hot liquid storage device T-402.

The cold air (stream 12) enters the gas/liquid separator V-104 where the condensed moisture (stream 26) is sent to the condensed liquid storage T-301.

50,000 kilograms per hour (kg/h) of cold air (stream 13) exiting at a pressure of 136.15 bar (bar) and a temperature of 30 ℃ is sent to a compressed gas storage unit T-201, which may be natural or artificial. It now contains only 300ppm water. The power consumption of the compression step was 10.9 Megawatts (MW). Cooling of the air during compression requires 54,689 kilograms per hour (kg/h) of coolant, while condensation of air humidity represents an amount of 1.35 tons per hour (t/h) to be stored or eliminated.

In consideration of this large amount of water, the water stored in the condensed liquid storage means T-301 is periodically discharged.

During power generation, stored air (stream 14) is sent from the compressed gas storage device T-201 to the non-direct contact exchanger E-106, which is not in direct contact with the hot water (stream 39) from the hot liquid storage device T-402. The exchangers E-106 may be identical to the exchangers E-104 used for cooling. Alternatively, switches E-106 and E-104 may be combined to save on equipment costs. This is possible due to the cyclic operation of the system: the exchanger is used either during compression or during expansion.

The hot air (stream 15) enters turbine EX-201 where it undergoes expansion. The cooled water leaving exchanger E-106 (stream 40) is sent to non-direct contact exchanger E-107 where it heats the cooled expanded air (stream 16). This heated air (stream 17) is sent to a second turbine EX-202 where it is expanded to a lower pressure (stream 18).

The cooled water leaving exchanger E-107 (stream 41) is sent to non-direct contact exchanger E-108 where it heats the air leaving turbine EX-202, which is then heated (stream 19). This hot air is then sent to a third turbine EX-203 where it is expanded to a lower pressure (stream 20).

The less hot water (stream 42) leaving exchanger E-108 is sent to another non-direct contact exchanger E-109. This exchanger is used to heat the air (stream 20) leaving the turbine EX-203 before entering (stream 21) the last turbine EX-204.

After the final expansion, the air is released into the atmosphere (stream 22) at a pressure of 1.02 bar (bar) and a temperature of 10 ℃. The water used for each air heating cycle before expansion leaves exchanger E-109 (stream 43) at a final temperature of 126 ℃.

Before circulation, the water needs to be cooled, for example by a water exchanger or by an air cooler. The required cooling power is 5.5 megawatts of heat (MWth), i.e., 38.7 kilowatts of electricity (kWe) power consumption.

The power generated by the continuous expansion is 5.2 megawatts of electricity (MWe).

Example 2: according to the prior art (fig. 2)

This example describes a system or method using water as a hot fluid instead of molten salt as described in patent US-2011/0,016,864 a 1.

51,350 kilograms per hour (kg/h) of outside air (stream 1) containing 4.2 mole percent (mol%) water at a temperature of 20 ℃ and a pressure of 1,014 bar (bar) is sent to compression stage K-101 from which it flows at a higher pressure and a higher temperature (stream 2).

This stream 2 is then cooled to 50 ℃ in a non-direct contact heat exchanger E-101 (stream 3) without direct contact with water at 40 ℃ (stream 29). The water leaves the exchanger at a higher temperature (stream 30) and is sent to the hot liquid storage device T-402.

The moisture of the cooled air undergoes condensation (stream 23). Separator V-101 separates air (stream 4) from condensed moisture (stream 23). The condensed water is then sent to a condensed liquid storage means T-301.

The air then flows into the second compression stage K-102, which exits the second compression stage at a higher pressure and temperature (stream 5).

It is then cooled in non-direct contact exchanger E-102 without direct contact with cold water (stream 31). The hot water (stream 32) leaving the exchanger is sent to a hot liquid storage device T-403. The cooled air (stream 6) enters a gas/liquid separator V-102, which separator V-102 separates condensed moisture (stream 24) from the cold air (stream 7).

The condensed moisture is sent to the condensed liquid storage means T-301.

The cooled air (stream 7) enters the third compression stage K-103, which exits the third compression stage (stream 8) at a higher pressure and temperature.

It is then cooled in non-direct contact exchanger E-103 without direct contact with cold water (stream 33).

The hot water at the outlet of exchanger E-103 (stream 34) is then sent to hot liquid storage device T-404.

The cold air enters a gas/liquid separator V-103 where condensed moisture (stream 25) is separated from the air (stream 10). The condensed moisture is then sent to a condensed liquid storage means T-301.

The cold air (10) leaves the separator V-103 and then enters the final compression stage K-104, which leaves the final compression stage (stream 11) at a higher pressure and temperature.

It is then cooled in a non-direct contact exchanger without direct contact with the cold water (stream 36). This stream 36 can be cooled by means of the heat exchanger E-105 to a temperature lower than the temperature of the water used in the exchangers E-101, E-102 and E-103. The hot water (stream 37) leaving exchanger E-104 is sent to hot liquid storage device T-405.

The cold air (stream 12) enters the gas/liquid separator V-104 where the condensed moisture (stream 26) is sent to the condensed liquid storage T-301.

50,000 kilograms per hour (kg/h) of cold air (stream 13) exiting at a pressure of 136.15 bar (bar) and a temperature of 30 ℃ is sent to a compressed gas storage unit T-201, which may be natural or artificial. It now contains only 300ppm water. The power consumption of the compression step was 10.9 Megawatts (MW).

As in the previous example, cooling of the air during compression requires 54,689 kilograms per hour (kg/h) of coolant, while condensation of air humidity represents an amount of 1.35 tons per hour (t/h) to be stored or eliminated.

As in example 1, the condensed water stored in the condensed liquid storage means T-301 was periodically drained.

During power generation, stored air (stream 14) is sent from the compressed gas storage device T-201 to the non-direct contact exchanger E-106 without direct contact with hot water from the hot liquid storage device T-405. The exchangers E-106 may be identical to the exchangers E-104 used for cooling. Alternatively, switches E-106 and E-104 may be combined to save on equipment costs. This is possible due to the cyclic operation of the system: exchangers are used to compress or expand air.

The hot air (stream 15) enters turbine EX-201 where it undergoes expansion. The cooled water (stream 40) leaving exchanger E-106 is sent to cold liquid storage T-406.

The air leaving turbine EX-201 is sent (stream 16) to non-direct contact exchanger E-107 where it is heated (stream 17) by water from hot liquid storage T-404.

The cooled water (stream 41) is sent to cold liquid storage T-406.

This heated air (stream 17) is sent to a second turbine EX-202 where it is expanded to a lower temperature and pressure (stream 18).

The air is then heated in a non-direct contact heat exchanger E-108 by water from a hot liquid storage device T-403.

The cooled water (stream 42) leaving exchanger E-108 is sent to cold liquid storage T-406. The heated air (stream 19) is sent to turbine EX-203 where it is expanded to a lower pressure (stream 20).

The cold air is heated in the indirect contact heat exchanger E-109 by hot water from the hot liquid storage device T-402. This cooled water (stream 43) is sent to cold liquid storage T-406.

The heated air (stream 21) is then sent to the last turbine EX-204 where it is expanded to a lower pressure (stream 22).

After the final expansion, 50,000 kg/h of air are released into the atmosphere (stream 22) at a pressure of 1.02 bar (bar) and a temperature of 17 ℃.

The final temperature of the water passing through each exchanger E-106, E-107, E-108 and E-109 for each air heating cycle prior to expansion was 129 ℃.

Before circulation, the water needs to be cooled, for example by a water exchanger or by an air cooler. The required cooling power is 4.2 megawatts of heat (MWth), i.e., a power consumption of 31 kilowatts of electricity (kWe).

The power generated by the continuous expansion is 5.4 megawatts of electricity (MWe).

Example 3: according to the prior art (fig. 3)

51,350 kilograms per hour (kg/h) of outside air (stream 1) containing 4.2 mole percent (mol%) water at a temperature of 20 ℃ and a pressure of 1,014 bar (bar) is sent to compression stage K-101 from which it flows at a higher pressure and a higher temperature (stream 2).

This stream 2 is then cooled to 50 ℃ in a direct contact heat exchanger C-101 by water at 40 ℃ (stream 21). The heat exchanger C-101 comprises a packed column into which hot air (stream 2) flows through the bottom of the column. Cold water (stream 21) is injected at the top of the tower, thus causing cross flow: one flow (air) moves upward and the other (water) moves downward. The hot water leaves the column at the bottom at a higher temperature (stream 22) and it is sent to hot liquid storage T-402.

The cooled air exits heat exchanger C-101 at the top (stream 3) and it flows into the second compression stage K-102, which exits the second compression stage at a higher pressure and temperature (stream 4). It is then cooled with cold water (stream 25) in direct contact heat exchanger C-102. The hot water (stream 26) leaving the heat exchanger C-102 in the bottom is sent to the hot liquid storage device T-403.

The cooled air (stream 5) enters the third compression stage K-103, which exits the third compression stage (stream 6) at a higher pressure and temperature. It is then cooled with cold water (stream 29) in direct contact heat exchanger C-103. This hot water (stream 30) is then sent to hot liquid storage device T-404.

The cold air (stream 7) exits the heat exchanger C-103 (stream 7) at the top and it flows into the final compression stage K-104, which exits the final compression stage (stream 8) at a higher pressure and temperature. It is then cooled with cold water (stream 34) in direct contact heat exchanger C-104. This stream 34 can be cooled by means of heat exchanger E-105 to a temperature lower than the temperature of the water used in heat exchangers C-101, C-102 and C-103.

The hot water (stream 35) leaving the bottom of heat exchanger C-104 is then sent to hot liquid storage device T-405.

50,000 kilograms per hour (kg/h) of cold air (stream 9) exiting at a pressure of 134.34 bar (bar) and a temperature of 30 ℃ is fed to a compressed gas storage unit T-201, which may be natural or artificial. It now contains only 320ppm water. The power consumption of the compression step was 10.9 Megawatts (MW), as in examples 1 and 2.

In this embodiment example, there is no condensed water stream. On the other hand, the moisture in the air is added to the water injected for cooling, so that after compression, more water is collected at the outlet than was initially injected.

In example 3 178,338 kg/h water were injected for cooling, while 179,715 kg/h water left the process, i.e. 1,377 kg/h more than the amount initially injected. All of the condensed moisture has been transferred to the coolant.

During power generation, stored air (stream 14) is sent from the compressed gas storage T-201 to the direct contact heat exchanger C-105, which heat exchanger C-105 has hot water (stream 54) from the hot liquid storage T-405. The heat exchanger C-105 may be the same as the heat exchanger C-104. Alternatively, heat exchangers C-104 and C-105 can be combined to save equipment costs. This is possible due to the cyclic operation of the system: the heat exchanger is used either during compression or during expansion.

Hot air (stream 15) exits at the top of the column and it enters turbine EX-201 where it undergoes expansion.

The cooled water (stream 40) leaving the bottom of exchanger C-105 is sent to cold liquid storage T-406.

The air leaving turbine EX-201 is sent (stream 16) to the direct contact heat exchanger C-106 where it is heated by water (stream 53) circulating in convective flow from the hot liquid storage T-404.

The cooled water (stream 41) is sent to cold liquid storage T-406.

The heated air (stream 17) is sent to a second turbine EX-202 where it is expanded to a lower pressure (stream 18).

The air is then heated in a direct contact heat exchanger C-107 with water (stream 52) from a hot liquid storage device T-403.

The cooled water (stream 42) leaving the bottom of heat exchanger C-107 is sent to cold liquid storage T-406.

The heated air (stream 19) is sent to turbine EX-203 where it is expanded to a lower pressure (stream 20).

The cold air is heated in direct contact heat exchanger C-108 by hot water (stream 51) from hot liquid storage T-402.

This cooled water (stream 43) is sent to cold liquid storage T-406.

The heated air (stream 21) is then sent to the last turbine EX-204 where it is expanded to a lower pressure (stream 22). This cold air is then sent to a gas/liquid separator V-201, separating air (stream 50) from liquid water (stream 90) that may be present. This water is sent to a cold liquid storage T-406.

After the final expansion 50,800 kg/h of air were released into the atmosphere (stream 50) at a pressure of 1.02 bar and a temperature of 22 ℃.

The water used for each air heating cycle before expansion was passed through exchangers C-105, C-106, C-107 and C-108 with a final temperature of 65.7 ℃.

Before being circulated, the water needs to be cooled, for example by a water exchanger or by an air cooler. The required cooling power is 5.3 megawatts of heat (MWth), i.e., a power consumption of 74.5 kilowatts of electricity (kWe).

The power generated by the continuous expansion is 4.45 megawatts of electricity (MWe).

Example 4: according to the invention (fig. 4)

51,350 kilograms per hour (kg/h) of outside air (stream 1) containing 4.2 mole percent (mol%) water at a temperature of 20 ℃ and a pressure of 1,014 bar (bar) is sent to compression stage K-101 from which it flows at a higher pressure and a higher temperature (stream 2).

This stream 2 is cooled to 50 ℃ in a non-direct contact heat exchanger E-101 (stream 3) without direct contact with 40 ℃ (stream 29). The water leaves the exchanger at a higher temperature (stream 30) and is sent to the hot liquid storage device T-402.

The moisture of the cooling air undergoes condensation (stream 23). Separation device (e.g., gas/liquid separator) V-101 separates air (stream 4) from condensed liquid. The condensed water is then sent to a condensed liquid intermediate storage means T-301.

The air flows into the second compression stage K-102, which exits the second compression stage at a higher pressure and temperature (stream 5). It is then cooled in a non-direct contact heat exchanger E-102 without direct contact with the cold water (stream 31).

The hot water (stream 58) leaving exchanger E-102 is sent to hot liquid storage device T-404.

The cooled air (stream 6) enters a gas/liquid separator V-102, which separator V-102 separates condensed moisture (stream 24) from the cold air (stream 7). The condensed moisture is sent to the condensed liquid intermediate storage means T-301.

The cooled air (stream 7) enters the third compression stage K-103, which exits the third compression stage (stream 8) at a higher pressure and temperature. It is then cooled in non-direct contact exchanger E-103 without direct contact with cold water (stream 33). The water leaving exchanger E-103 (stream 59) is then sent to hot liquid storage device T-403.

The cold air enters a gas/liquid separator V-103 where condensed moisture (stream 25) is separated from the air (stream 10). The condensed moisture is then sent to a condensed liquid storage means T-301.

The cold air (stream 10) leaves the separator V-103 and then enters the final compression stage K-104, which leaves the final compression stage (stream 11) at a higher pressure and temperature. It is then cooled in non-direct contact exchanger E-104 without direct contact with cold water (stream 36). This stream 36 can be cooled by means of the heat exchanger E-105 to a temperature lower than the temperature of the water used in the exchangers E-101, E-102 and E-103.

The hot water leaving heat exchanger E-104 (stream 37) is sent to hot liquid storage device T-405.

The cold air (stream 12) enters the gas/liquid separator V-104 where the condensed moisture (stream 26) is sent to the condensed liquid storage T-301.

50,000 kilograms per hour (kg/h) of cold air (stream 13) exiting at a pressure of 136.15 bar (bar) and a temperature of 30 ℃ is sent to a compressed gas storage unit T-201, which may be natural or artificial. It now contains only 300ppm water. The power consumption of the compression step was 10.9 Megawatts (MW).

As in examples 1 and 2, cooling of the air during compression required 54,689 kilograms per hour (kg/h) of coolant, while condensation of air humidity represented an amount of 1.35 tons per hour (t/h) to be stored or eliminated.

The condensed water stored in the intermediate condensed liquid storage means T-301 is sent to the condensed liquid storage means T-406 via stream 81. Thus, the condensed water is recovered, which can be used as a heat transfer fluid.

During power generation, stored air (stream 14) is sent from the compressed gas storage unit T-201 to the direct contact heat exchanger C-205, which heat exchanger C-105 has hot water (stream 60) from the hot liquid storage unit T-402.

The hot air (stream 15) leaves heat exchanger C-205 at the top and it enters turbine EX-201 where it undergoes expansion.

The cooled water (stream 40) leaving the heat exchanger C-205 at the bottom is sent to a cold liquid storage T-406.

The air leaving turbine EX-201 is sent (stream 16) to direct contact heat exchanger C-206 where it is heated by water (stream 61) circulating in convective flow from hot liquid storage T-403. The cooled water (stream 41) is sent to cold liquid storage T-406.

This heated air (stream 17) is sent to a second turbine EX-202 where it is expanded to a lower pressure (stream 18).

The air is then heated in direct contact heat exchanger C-206 with water (stream 62) from hot liquid storage device T-404.

The cooled water (stream 42) leaving heat exchanger C-206 at the bottom is sent to cold liquid storage T-406.

The heated air (stream 19) is sent to turbine EX-203 where it is expanded to a lower pressure (stream 20).

The cold air is heated in direct contact heat exchanger C-208 by hot water (stream 63) from hot liquid storage T-405.

This cooled water (stream 43) is sent to cold liquid storage T-406.

The heated air (stream 21) is then sent to the last turbine EX-204 where it is expanded to a lower pressure (stream 22).

This cold air is then sent to a gas/liquid separator V-201, separating air (stream 50) from liquid water (stream 90) that may be present. This water is sent to a cold liquid storage T-406.

After the final expansion 52,240 kg/h of air were released into the atmosphere (stream 50) at a pressure of 1.02 bar and a temperature of 39 ℃.

The final temperature of the water used for each air heating cycle, passed through heat exchangers C-205, C-206, C-207 and C-208, and stored in cold liquid storage T-406 was 93.3 ℃.

Before circulation, the water needs to be cooled, for example by a water exchanger or by an air cooler. The required cooling power is 3.3 megawatts of heat (MWth), i.e., a power consumption of 31.6 kilowatts of electricity (kWe).

The power generated by the continuous expansion is 5.6 megawatts of electricity (MWe).

Example 5: according to the invention (fig. 5)

51,350 kilograms per hour (kg/h) of outside air (stream 1) containing 4.2 mole percent (mol%) water at a temperature of 20 ℃ and a pressure of 1,014 bar (bar) is sent to compression stage K-101 from which it flows at a higher pressure and a higher temperature (stream 2).

This stream 2 is then cooled to 50 ℃ in a non-direct contact heat exchanger E-101 (stream 3) without direct contact with water at 40 ℃ (stream 29).

The water leaves the exchanger at a higher temperature (stream 30) and is sent to the hot liquid storage device T-402.

The moisture of the cooled air undergoes condensation (stream 23) and it is separated from the air (stream 4) in the gas/liquid separator V-101. The condensed water is then sent to a condensed liquid intermediate storage means T-301.

The air flows into the second compression stage K-102, which exits the second compression stage at a higher pressure and temperature (stream 5). It is then cooled in a non-direct contact heat exchanger E-102 without direct contact with the cold water (stream 31).

The hot water (stream 32) leaving exchanger E-102 is sent to hot liquid storage device T-403.

The cooled air (stream 6) enters a gas/liquid separator V-102, which separator V-102 separates condensed moisture (stream 24) from the cold air (stream 7). The condensed moisture is sent to the condensed liquid storage means T-301.

The cooled air (stream 7) enters the third compression stage K-103, which exits the third compression stage (stream 8) at a higher pressure and temperature.

It is then cooled in a non-direct contact heat exchanger E-103 without direct contact with cold water (stream 33). The hot water (stream 34) from the heat exchanger E-103 is then sent to the hot liquid storage device T-404.

The cold air enters a gas/liquid separator V-103 where condensed moisture (stream 25) is separated from the air (stream 10). The condensed moisture is then sent to a condensed liquid storage means T-301.

The cold air (stream 10) leaves the separator V-103 and then enters the final compression stage K-104, which leaves the final compression stage (stream 11) at a higher pressure and temperature.

It is then cooled in a non-direct contact heat exchanger E-104 without direct contact with the cold water (stream 36). This stream 36 can be cooled by means of heat exchanger E-105 to a temperature lower than the temperature of the water used in heat exchangers E-101, E-102 and E-103.

The hot water leaving heat exchanger E-104 (stream 37) is sent to hot liquid storage device T-405.

The cold air (stream 12) enters the gas/liquid separator V-104 where the condensed moisture (stream 26) is sent to the condensed liquid storage T-301.

50,000 kilograms per hour (kg/h) of cold air (stream 13) exiting at a pressure of 136.15 bar (bar) and a temperature of 30 ℃ is sent to a compressed gas storage unit T-201, which may be natural or artificial. It now contains only 300ppm water. The power consumption of the compression step was 10.9 Megawatts (MW).

The condensed water stored in the intermediate condensed liquid storage T-301 is sent to the cold liquid storage T-406 by stream 81. Thus, the condensed water is recovered, which can be used as a heat transfer fluid.

During power generation, stored air (stream 14) is sent from the compressed gas storage unit T-201 to the non-direct contact heat exchanger E-106 without direct contact with hot water (stream 60) from the hot liquid storage unit T-402. The heat exchanger E-106 may be the same as the heat exchanger E-104. Alternatively, switches E-106 and E-104 may be combined to save on equipment costs. This is possible due to the cyclic operation of the method: the exchanger is used either during compression or during expansion.

The hot air (stream 15) enters turbine EX-201 where it undergoes expansion.

The cooled water (stream 40) leaving heat exchanger E-106 is sent to cold liquid storage T-406.

The air leaving turbine EX-201 is sent (stream 16) to non-direct contact heat exchanger E-107 where the air is heated (stream 17) by water (stream 61) from hot liquid storage T-403. The cooled water (stream 89) is sent to another non-direct contact heat exchanger E-108.

This heated air (stream 17) is sent to a second turbine EX-202 where it is expanded to a lower pressure (stream 18).

It is then heated in non-direct contact heat exchanger E-208 by water (stream 89) from exchanger E-107.

The heated air (stream 19) is sent to turbine EX-203 where it is expanded to a lower pressure (stream 20).

The cold air is heated in direct contact exchanger C-201 by hot water (stream 87) from an in-line mixer that mixes hot water (stream 88) from exchanger E-201, hot water (stream 85) from hot liquid storage device T-404, and hot water (stream 86) from hot liquid storage device T-405.

The cooled water (stream 43) leaving the bottom of heat exchanger C-208 is sent to cold liquid storage T-406.

The heated air (stream 21) is then sent to the last turbine EX-204 where it is expanded to a lower pressure (stream 22).

This expanded air is then sent to a gas/liquid separator V-201 to separate air (stream 50) from liquid water (stream 90) that may be present. This water is sent to a cold liquid storage T-406.

After the final expansion 52,900 kg/h of air were released into the atmosphere (stream 50) at a pressure of 1.02 bar and a temperature of 43 ℃.

The final temperature of the hot water used for each air heating cycle, passed through heat exchangers E-106, E-107, E-201 and C-208, and stored in cold liquid storage T-406 was 84.2 ℃. The water needs to be cooled, either by a water exchanger or by an air cooler, before being circulated. The required cooling power is 2.7 megawatts of heat (MWth), i.e., a power consumption of 29 kilowatts of electricity (kWe).

The power generated by the continuous expansion is 5.7 megawatts of electricity (MWe).

The following summary table gives the main results for each example.

Examples 4 and 5 according to the invention show the resulting power gain relative to prior art examples 1 to 3, while the required cooling power is much lower. Examples 1 to 3 according to the prior art require cooling power between 4.2 and 5.5 megawatts, whereas examples 4 and 5 require only cooling power between 2.7 and 3.3 megawatts. The overall efficiency of the system according to the invention is thus greatly improved with respect to the respective systems of the prior art, on the one hand in that the generated power is increased and on the other hand in that the required cooling power is reduced.

The configuration of example 5 is particularly advantageous as it represents the best efficiency with the maximum amount of electricity generated and the lowest required cooling power. This result can be explained by the following reasons:

recovery of the liquid in the gas on the expansion line, which allows the mass flow rate of the gas at the turbine inlet to be increased,

a good compromise between a direct contact heat exchanger and a non-direct contact heat exchanger on the expansion line, in particular using a direct contact heat exchanger in the last exchanger of the last expansion stage of the expansion line. This achieves maximum heat energy recovery and an increase in the mass flow rate of the gas,

the use of indirect contact exchangers on the compression line limits the recovery of liquid on the expansion line.