WO2013057427A1

WO2013057427A1 - Improved adiabatic storage of energy in the form of heat and compressed air

Info

Publication number: WO2013057427A1
Application number: PCT/FR2012/052365
Authority: WO
Inventors: Eric Mercier; Mathieu ROUZEYRE
Original assignee: Electricite De France
Priority date: 2011-10-17
Filing date: 2012-10-17
Publication date: 2013-04-25
Also published as: FR2981400A1; FR2981400B1

Abstract

The invention relates to a facility (1) for successive compressions/expansions of gas to store/release energy, comprising: * for the compressions: - a first compressor (11, 101) for compressing the gas delivering a first amount of heat, and - at least a second compressor (12, 102) downstream from the first compressor, * and for the expansions: - a first expander (21, 102) for expanding the gas producing a first amount of cooling, and - at least one second expander (22, 101) downstream from the first expander, in which heat transfer means (51, 150) accumulate the first amount of heat with the first amount of cooling to reduce a temperature of gas upstream from the second compressor, characterised in that the facility further comprises cooling means (6, 60, 160), upstream from the second compressor and/or downstream from the first expander, to reduce further the temperature of the gas upstream from the second compressor.

Description

ADIABATIC STORAGE ENHANCES ENERGY IN THE FORM OF HEAT AND

COMPRESSED AIR

The invention relates to the field of energy storage. In particular, the invention relates to the field of the alternation of a gas compression and energy storage mode and a mode of expansion of gas and energy destocking in the form of compressed air in a reservoir.

It is common to try to store energy when the energy is cheap, for example when the energy production is higher than the demand and to destock the energy stored when the energy is more expensive, for example when demand is greater than production. Several alternations of storage / retrieval are possible. For example, biannual period storage / retrieval alternates, storing energy in spring and autumn, and releasing energy in summer or winter when demand is high.

Alternatively, it is possible to store energy at night, when energy consumption is low and to release energy stored during the day, when consumers, industrial and private, demand more energy.

Alternatively, energy storage can be used to regulate and distribute irregular energy production over time. It is possible to store energy when means of producing it are available and to destock the energy when the means to produce it are no longer available. Thus, short or irregular storage / retrieval cycles can be used to regulate, for example, the energy production of wind generators, subject to a need for the presence of wind or even solar generators, subject to a need for brightness.

Among the known methods of energy storage, the storage of energy in the form of compressed air (hereinafter "CAES process" for "compressed air energy storage" in English) is particularly interesting. This is indeed a simple and low-loss method, especially when adiabatic or isothermal operation can be ensured. In CAES processes, the energy storage comprises a compressor air compression phase and a storage tank compressed air storage. The destocking of energy comprises a phase of expansion of the air stored in the tank during which a current generator is actuated, for example a turbine coupled to an alternator.

Referring firstly to Figure 1 which is shown schematically an installation 1 for implementing the CAES method according to the state of the art. A CAES process comprises an energy storage phase in which air is compressed and an energy destocking step in which the previously compressed air is expanded. The expansion is performed to drive a generator train 20, to provide power.

This installation 1 comprises a compression train 10 making it possible to pass an incoming air flow F1 from an inlet temperature Te, for example close to the ambient temperature, and from an inlet pressure Pe, close to the atmospheric pressure at a storage pressure Pst, with a storage temperature Tst. Several compressors 11, 12 connected in series can be used during the compression phase. The flow of compressed air F1 is then stored in a compressed air tank 100.

The generator train 20 makes it possible to produce current during the expansion of an outgoing air flow F2. Through the generator train 20, the outgoing air flow passes from a reservoir pressure Pr in the tank 100, to a pressure after expansion (called "post-expansion Pdc") close to the atmospheric pressure at the output of the generator train 20 The generator train 20 may comprise several generators 21, 22. The passage from the tank pressure Pr to the post-expansion pressure Pdc can be done in several stages. In the following, a "generator" means a pressure reducer comprising for example at least one turbine driven by compressed air and coupled to at least one alternator.

Adiabatic air compression generates a lot of heat. Part of the energy supplied to the compression train 10 is dissipated as thermal energy in the incoming compressed air stream Fl and is not used to increase the pressure of the incoming airflow Fl. This is typically a source of yield reduction. Advantageously, in order not to lose the thermal energy produced during the compression, the latter is stored in one or more heat storage assemblies 51, 52, in order to be transferred back to the compressed air flow. F2 outgoing during the destocking phase. During the storage phase, thermal energy Q is extracted from the incoming air flow F1 at the outlet of each compressor 11, 12 by means of coolers 31, 32. It is then stored as heat in one or more 3. During the phase of retrieval of energy, stored thermal energy Q 'is transferred to the outgoing air flow F2 before it enters the generators 21, 22 by means of heaters 41 , 42. Coolers 31, 32 and heaters 41, 42 are hereinafter referred to as "heat exchangers".

Each compressor 11, 12 undergoes very significant stresses due to the heat released by the compression. Indeed, the compression train 10 can generate, during the compression phase, a cumulative increase in the temperature of the incoming air flow Fl which can reach more than 500 ° C. or even more than 600 ° C.

As a result, the compression is often performed by means of several different compressors 11, 12. Each compressor 11, 12 then undergoes a small temperature gradient. Such a set of compressors may comprise at least a first compressor 11 and a last compressor 12, possibly with one or more other intermediate compressors. Of course, if only two compressors are provided, the last compressor can be named also "second compressor" below.

The heat transfer means make it difficult to transfer, before a single expansion phase, the thermal energy stored following several compressions. Accordingly, it is common that the expansion is also performed by means of several generators 21, 22 different, the stored thermal energy being transferred in part to the outgoing air flow at the input of the generator or generators. The generators 21, 22 then comprise at least a first generator 21 and a last generator 22. Of course, if only two generators are provided, the last generator can be named also "second generator" below.

The compressors 11, 12 and generators 21, 22 must operate at the different temperatures and pressures imposed on the incoming and outgoing air flows. More the Operating temperatures are high, and the equipment capable of operating at these temperatures is expensive. We then try to reduce the highest temperatures of each compressor / generator.

When the compression is made by means of several compressors 11, 12, the installation 1 preferably comprises coolers 31, 32, both at the output of the compression train 10, but also between each compressor 11, 12, as intercooler. Thus, each compressor 11, 12 is able to produce compressed air having a high temperature for example less than 400 ° C, for example less than 350 ° C.

Similarly, if the expansion is done by means of several generators 21, 22, the installation 1 is arranged to distribute the heaters 41, 42, both at the input of the generator train 20, but also between each generator 21, 22, as an intermediate heater. Then, since the thermal energy Q 'is not transferred at one time to the outgoing air flow F2, the high temperature of the compressed air flow entering each generator 21, 22 can generally be less than 400 ° C. for example less than 350 ° C.

The installation illustrated in FIG. 1 thus comprises two heat storage assemblies 51, 52, a first heat storage unit 51 comprising an intermediate cooler 31 and an intermediate heater 41, and a second heat storage unit 52 comprising a cooler terminal 32 and an initial heater 42 respectively positioned between the compression train 10 and the compressed air storage tank 100 and between the reservoir 100 and the generator train 20. The two heat storage assemblies may each comprise a heat reservoir 3 or share such a heat reservoir 3.

Advantageously, a heat reservoir 3 is connected to at least one heater 41, 42 and at least one cooler 31, 32. Indeed, if thermal energy Q 'is transferred to the outgoing air flow F2 during the destocking phase energy, it is advantageous to use, to supply the heater, thermal energy Q extracted from the incoming airflow Fl during the energy storage phase. Consequently, if the installation comprises several different heat reservoirs 3, the initial heater 42 and the end cooler 32 are generally connected to the same heat reservoir 3. Intermediate heaters and intermediate coolers are preferably connected, at least two by two, to a same heat reservoir, called "intermediate tank". Storage energy facilities CAES adiabatic storage process are interesting, but as stated above, although the theoretical yield approaching 100% performance generally obtained are rather close to 70%. The solutions known to date are therefore not completely satisfactory. It is therefore sought new ways to effectively implement CAES adiabatic type processes.

The present invention relates to an improved adiabatic CAES type storage method.

The inventors have noticed that the second compressor, compressing the incoming airflow already compressed by a first compressor, generally has a higher conversion efficiency than expected. The conversion efficiency of a compressor is defined by the ratio between a pressure differential brought to a given amount of gas and an amount of electric power supplied. In particular, in general, during a sizing of an installation adapted to implement a CAES adiabatic type process, thermal energy is extracted from the incoming air flow between two compressors in order to reduce temperature. As a result, the compressors are adapted to compress air streams having given temperatures with a given conversion efficiency. The inventors have identified that during the use of this type of installation, the conversion efficiency of the second compressor changes and is lower than the initial conversion efficiency.

In an installation adapted to implement a CAES-type adiabatic process, the energy extracted from the air flow entering between two compressors during an energy storage phase is stored in a heat storage assembly in order to to be used during a phase of destocking of energy and transferred to a flow of outgoing air. A relationship is therefore established between the thermal energy extracted from the incoming air flow in order to be stored, the energy storage assembly and the stored thermal energy transferred to the outgoing air flow. In normal operation, the thermal energy extracted from the incoming airflow to be stored is substantially equal to the stored thermal energy transferred to the outgoing airflow. The inventors have identified that the temperature at the output of a generator is greater than that expected (closer to 100 ° C. to 150 ° C. than 50 ° C.). As a result, before entering a heater, the airflow exiting at a higher than expected temperature and the heater can only transfer a limited amount of energy to the outgoing airflow. Thus, the energy supply of the generators is suboptimal.

The invention improves the situation.

It first proposes an installation of successive compressions / detents of gas respectively for storing / releasing energy, comprising:

* for the compressions:

a first compressor of the gas delivering a first quantity of heat, and at least one second compressor downstream of the first compressor delivering a second quantity of heat,

* and for relaxation:

a first gas expander producing a first amount of cooling, and

at least one second expander downstream of the first expander. The installation comprises in particular heat transfer means that accumulate the first amount of heat at the first cooling amount to lower a gas temperature upstream of the second compressor and hence improve an operating efficiency of the second compressor. In particular, the installation in the sense of the invention further comprises cooling means, upstream of the second compressor and / or downstream of the first expander, to further lower the temperature of the gas upstream of the second compressor. In operation, it is then possible to obtain a better conversion efficiency at the second compressor than in a plant according to the prior art, not including the aforementioned cooling means.

In an advantageous embodiment, the cooling means are connected to at least one energy collector intended to collect a thermal energy, extracted from the gas passing through the cooling means. Such an embodiment makes it possible to recover this thermal energy, for example for a power distribution network.

Thus, the above-mentioned energy collector can be connected to a power distribution network, for example a thermal energy distribution network. In this example, the energy collector may be intended to heat a fluid passing through the thermal energy distribution network.

Alternatively or additionally, the energy collector comprises a heat-energy mechanical converter capable of transforming at least a portion of the thermal energy extracted by the cooling means into mechanical energy.

This mechanical energy can itself be transformed into electrical energy. Thus, the energy collector may comprise, in addition or alternatively, a heat-current converter capable of transforming at least a portion of the thermal energy extracted by the cooling means into electrical energy.

In such an embodiment, the heat-current converter may advantageously be adapted to operate according to an Organic Rankine Cycle (or "ORC Cycle"). The cooling means are advantageously adapted to lower the temperature of the gas to a temperature below about 75 ° C, or even below about 50 ° C. The heat transfer means preferably comprise a heat transfer fluid circuit including at least:

a first heat exchanger upstream of the second compressor for extracting heat energy from the gas containing the first amount of heat, a cold liquid reservoir providing a cold liquid to the first heat exchanger and a hot liquid reservoir for storing the thermal energy extracted by the first heat exchanger, and

a second heat exchanger downstream of the first expander for supplying, from the thermal energy stored in the hot liquid reservoir, thermal energy to the gas from the first expander,

the cooling means being disposed between the first heat exchanger and the second compressor and / or between the first expander and the second heat exchanger.

As a variant, the heat transfer means may comprise one or more thermal energy storage tanks made of a solid material and adapted in particular for:

cooling a gas passing through the first compressor, and

to heat a gas passing through them, coming from the first regulator,

the cooling means being arranged, as in the previous embodiment, between the heat tanks and the second compressor and / or between the first expander and the heat tanks.

In a particular embodiment, the cooling means are preferably arranged downstream of the first expander. The present invention also aims at a method of successive compression / expansion of gas respectively for storing / releasing energy, comprising:

* for the compressions:

a first compression delivering a first quantity of heat, followed by at least a second compression delivering a second quantity of heat,

* and for relaxation:

a first expansion producing a first amount of cooling followed by at least a second expansion.

In the method, heat transfer between the first amount of heat and the first amount of cooling is provided to lower a gas temperature before the second compression and thereby improve a second compression efficiency.

Within the meaning of the invention, it is further provided means for cooling the gas before the second compression and / or after the first expansion, to further lower the temperature of the gas before the second compression.

In an advantageous embodiment of this process, at least a portion of a thermal energy extracted from said cooling means can then be recycled. Other features and advantages of the invention will appear on examining the detailed description below, and the attached drawings in which:

FIG. 1 represents an installation capable of implementing a CAES method according to the state of the art;

FIG. 2 illustrates an installation capable of implementing one embodiment of the invention;

FIG. 3 illustrates an installation capable of implementing a CAES method according to one embodiment of the invention;

FIG. 4 illustrates an installation capable of implementing a CAES method according to one embodiment of the invention;

FIGS. 5A and 5B illustrate two variants of heat transfer means; Figure 6 illustrates heat transfer means for explaining an operating mode of the invention.

The same references in the different drawings denote equivalent elements. With reference to FIG. 2, an installation 1 according to the invention, adapted to implement a CAES type process, comprises at least two pressure-mechanical energy converters 101, 102 adapted to convert mechanical energy into an increase of pressure in a fluid and / or conversely produce mechanical energy from a compressed fluid. A pressure-mechanical energy converter is defined in the invention as being either a compressor capable of compressing a gas or an expander supplying mechanical energy from a compressed gas stream, which may, for example, drive an alternator so as to to produce current, that is to say an apparatus that can, alternatively, compress or drive an alternator from a compressed gas.

Between two pressure-mechanical energy converters 101, 102, the installation 1 comprises heat transfer means 150 adapted to extract thermal energy from a fluid, store this thermal energy in a heat reservoir 103 and transfer this thermal energy. to a fluid, for example later. The heat transfer means comprise at least one cold point PF and a hot point PC. A cold fluid to be heated between the cold point and out through the hot spot and vice versa for a hot fluid to cool.

In addition, the installation advantageously comprises a reservoir 100 in which the compressed fluid can be stored. The fluid is preferably a gas, for example air. In a first mode of operation, the installation 1 is adapted to compress successively at least twice an incoming gas flow Fl before storing it in the tank 100. In addition, the heat storage unit 150 is adapted to extract thermal energy Q of the incoming gas flow F1 at least between the two compression steps.

In a second mode of operation, the installation 1 is adapted to produce mechanical energy from an outgoing gas flow F2 from the tank 100 by one or more pressure-mechanical energy converters 101, 102 imposing at least two successive stages of expansion of the outgoing gas flow F2. In addition, the heat storage assembly is adapted to transfer heat energy Q ', stored in the heat reservoir 103, to the outgoing gas flow F2 at least between the two expansion stages.

The installation 1 comprises in particular an additional cooler 160 present between the heat storage assembly 150 and one of the two pressure-mechanical energy converters 101, 102, on the cold point side PF of the heat storage assembly 150. .

The two pressure-mechanical energy converters 101, 102 can compress a flow of gas in a first mode of operation of the installation, for the storage of energy. The mechanical energy used to drive the pressure-mechanical energy converters and allow compression can advantageously be provided by an electric motor. Alternatively other compressor drive modes may be provided.

Conversely, the installation may comprise the two pressure-mechanical energy converters 101, 102 now adapted to produce mechanical energy from a gas flow in a second mode of operation of the installation. The mechanical energy produced can be used to drive a generator to produce electrical power. Alternatively, the mechanical energy can be used differently, for example directly to drive one or more machines.

A first particular embodiment of an installation 1 according to the invention is illustrated in FIG. 3. It comprises at the output of a first compressor 11 a first heat exchanger said intermediate cooler 31 able to extract, before the flow of compressed air arrives in a second compressor 12, a part Q of a thermal energy supplied to a flow of incoming air F1 by the first compressor 11. The thermal energy extracted Q is extracted, stored and transferred by means heat transfer unit 51, comprising the intermediate cooler 31, a second heat exchanger (or "intermediate heater") 41 and a heat reservoir 3.

In an energy storage operating mode of the installation, the incoming airflow Fl, having an incoming storage temperature TOI at the output of the first compressor 11, enters the intercooler 31 where it emerges with an outgoing storage temperature T02, lower than the incoming storage temperature TOI. Then, the incoming airflow Fl is compressed by a second compressor 12 and stored in the compressed air tank 100.

In an operating mode of destocking energy of the installation, an outgoing air flow F2 passes through a first expander, adapted to drive an alternator, said first generator 21, after having left the compressed air reservoir 100. outgoing air flow F2 is cooled by expansion through the first generator 21. The installation 1 is designed to penetrate the outgoing air flow F2 in the intermediate heater 41, so that it is warmed before to introduce it into a second regulator adapted to drive an alternator (or "second generator") 22. A quantity of thermal energy Q 'is then transferred to the outgoing air flow F2. According to a first embodiment of the invention, the installation 1 comprises, between the intermediate cooler 31 and the second compressor 12, cooling means 6. The cooling means comprise a heat exchanger adapted to cool the gas.

These cooling means 6 (called "additional cooler" below) are adapted to extract a quantity Qs of thermal energy from the incoming air flow F1 cooled by the intermediate cooler 31. The incoming airflow Fl leaving the cooler intermediate 31 by a cold point PF, the additional cooler 6 is positioned between the cold point PF of the intercooler 31 and the second compressor 12.

The additional cooler 6 makes it possible to supply the second compressor 12 with an incoming airflow F1 having a compressor inlet temperature T03 lower than the storage leaving temperature T02 of the aftercooler 31. The additional cooler 6 allows this temperature reduction (" over-cooled temperature ") without requiring heat transfer means 51 intrinsically more efficient. The inventors have indeed observed that the outgoing storage temperature T02 does not depend solely on the intrinsic performances of the intermediate cooler 31, but also on an incoming destacking temperature TU of the outgoing air flow F2 at the inlet of the intermediate heater 41 connected to the same reservoir of In fact, the heat transfer means comprising the intermediate cooler 31 allow a transfer of heat between the incoming gas flow and the outgoing gas flow entering the heat transfer means, and more the outgoing gas flow is hot, minus the incoming gas flow is cooled.

The additional cooler 6 is not used to store thermal energy in order to destock it in the outgoing gas stream. The additional cooler 6 then has cooling performance of the incoming airflow F1 independent of the outgoing airflow F2.

Thus, according to the first embodiment of the invention, the second compressor 12 has a lower compressor inlet temperature T03 than according to the state of the art. The second compressor 12 therefore has a higher conversion efficiency than according to the state of the art and therefore consumes less electrical energy to operate.

The additional cooler 6 is preferably a cooler using little or no electrical energy to operate. It may be a simple radiator, for example a finned radiator, or a water radiator, transferring thermal energy to a body of water, for example a water circuit. Alternatively, it may be a heat pump using little electrical energy. In particular, such a heat pump uses less electrical energy than the electrical energy saved during operation of the second compressor according to the invention.

The installation illustrated in FIG. 3 comprises only two compressors. As a result only one cooler 31 has been shown. However, when the compression train 10 of the installation comprises more than two compressors 11, 12 connected in series, the thermal transfer means advantageously comprise several intermediate coolers, generally one downstream of each compressor. In addition, it is advantageous to position an additional cooler 6 upstream of each compressor for which the incoming gas flow Fl is derived from an intercooler.

The installation may further comprise a terminal cooler (not shown) positioned between the compression train 10 and the compressed air reservoir 100, by example at the outlet of a last compressor 12. The terminal cooler is able to extract heat energy supplied to the flow of compressed air by the last compressor 12 before the flow of compressed air is stored in the storage tank. compressed air 100. The thermal energy then extracted is stored in a heat reservoir connected to the terminal cooler. Likewise, an initial heater may be positioned to heat the outgoing airflow F2 at the input of the generator train 20. The initial heater is preferably bonded to the same heat reservoir as the terminal cooler.

A second embodiment of the invention, illustrated in FIG. 4, implements another approach that also makes it possible to obtain, at the input of the second compressor, a colder inflating air flow F1.

The installation of FIG. 4 is similar to the installation illustrated in FIG. 3. The installation represented in FIG. 4 illustrates, in addition to the second embodiment of the invention, some of the possible variants of the installation mentioned above. high and applicable to both embodiments. For example, the installation comprises illustratively more than two compressors in the compression train 10 and more than two generators in the generator train 20 and more particularly three compressors 11, 12, 13 and three generators 21, 22, 23. more, as mentioned above, the heat transfer means may comprise an intermediate cooler 31, 32 between each compressor 11, 12, 13 and an intermediate heater 45, 46 between each generator 21, 22, 23. Intermediate heaters and coolers intermediates can belong to common, general, heat transfer means, for example with a cold fluid circuit as cooler means extending by a circuit of the same heated fluid, as a heating means ..

Furthermore, the installation comprises a terminal cooler 33 at the output of the compression train 10 and an initial heater 43 at the input of the generator train 20. The illustrated installation comprises a single heat reservoir 3 for storing quantities of thermal energy Q _1; -Q _1; QT, -QT, extracted by the different coolers 31, 32, 33 and transmit them to the heaters 43, 45, 46. In the second embodiment of the invention, the cooling means comprise an additional destocking cooler 60 positioned downstream of a pressure reducer. The additional destocking cooler 60 is preferably positioned at the inlet of at least one intermediate heater 45, 46, between a cold point PF of the intermediate heater 45, 46, between which the flow of outgoing gas F2 to be heated, and the generator 21 , 22 which precedes the intermediate heater 45, 46 in the generator train 20. Preferably, an additional destocking cooler 60 is provided at the inlet of each intercooler 45, 46.

Thus, when the installation is operating in the mode of release of energy and expansion of the gas, the outgoing air flow F2 coming from a generator 21, 22 is cooled by the trigger used to produce current and is then overloaded. cooled by the additional destocking cooler 60. A thermal energy Qs is then extracted by the additional destocking cooler 60. Then, the outgoing air flow F2 enters the intermediate heater 45, 46 where a quantity Q1 of stored thermal energy previously in the heat tank 3 is transferred to it. The gas thus heated allows, through a second generator 22, 23 to produce current. In addition, if the outgoing air flow was not heated to the input of the second generator, its temperature could be too low, for example close to the ambient temperature. In this case, the expansion inside the generator could produce an outlet temperature of less than zero degrees Celsius. Ice could form, which could block the generator and prevent the relaxation and destocking of energy. The second embodiment of the invention, and in particular the positioning of the additional coolers or destocking 60 also applies in the various installation variants mentioned above. For example, the installation may comprise only two compressors and / or only two generators. It may or may not include a terminal cooler and / or an initial heater. The cooler (s) 31, 32, 33 may be connected to the same heat tank 3 or to different heat tanks.

Thermal energy storage can be achieved by means of a heat transfer fluid FC (Figure 5A). The heaters 41, 42, and the coolers 31, 32 are then distinct parts of the same set of heat transfer means 51. A flow of fluid heat transfer medium is circulated between the cold point PF and the PC hot point of the heat exchanger (intermediate heater or intercooler, in one direction or the other, but preferably in the opposite direction of the air flow to reheat and / or cool). Thus, when thermal energy Q is extracted from the incoming airflow Fl that cools, it is transferred to the flow of coolant FC which is heated and vice versa. When thermal energy Q 'is transferred to the outgoing airflow F2, it is extracted to the coolant flow FC that cools.

Preferably, the hot spots PC of the various heat exchangers 31, 41 are connected to the same hot liquid reservoir RC and the cold points PF of the heat exchangers 31, 41 are connected to the same cold liquid tank RF. When the installation operates in gas compression and energy storage mode, the heat transfer fluid FC flows from the cold liquid reservoir RF to the cold point PF of at least one cooler 31, accumulates heat in the cooler 31 and out of the cooler 31 at its PC hotspot. The heat transfer fluid FC is then directed to the hot liquid reservoir RC. When the installation operates in the gas expansion and energy release mode, the heat transfer fluid FC flows from the hot liquid reservoir RC to the hot point PC of at least one heater 41, loses heat in the heater 41 and exits the heater 41 at its cold point PF. The heat transfer fluid FC is then directed to the cold liquid reservoir RF.

With this thermal energy storage mode, the thermal energy Q is mainly stored in the hot liquid reservoir RC and the heat exchanges with the inflowing air inflows Fl and outgoing F2 can take place at remote points. The thermal energy extracted Q, or transferred Q ', can be calculated from the difference between the hot spot temperature TC and the cold spot temperature TF of the heat exchanger and from the coolant flow FC.

Alternatively, the thermal energy can be stored in a solid material such as concrete or natural or manufactured materials (Figure 5B). In this case, the thermal energy is not conveyed from a cooler to a heat reservoir and then to a heater. Preferably, each heat reservoir 51 also acts as a heat exchanger regardless of the operating mode of the heat exchanger. installation. In particular, the heat tank acts as a heater when the installation is in the mode of energy destocking and gas expansion and acts as a cooler when the installation is in energy storage mode and compression of gas . Thus, preferably, each heat reservoir is traversed by the air flows, in one direction, from its hot point PC to its cold point PF, to cool the incoming air flow Fl, or in the opposite direction to heat the air. Outgoing air flow F2. The thermal energy extracted is stored in the solid material and the air flows through the heat exchanger heat or cool in contact with the solid material. A single heat exchanger can simultaneously serve as an intercooler at the inlet of several compressors. Conversely, it is possible to provide several heat exchangers, mounted in series or in parallel, between two compressors, and therefore between two heaters.

FIG. 6 illustrates the operation of an adiabatic heat storage unit 70 comprising a cooler 73, for extracting thermal energy Q from a first fluid F1 having a hot incoming temperature TE1 and storing it in a heat reservoir 3 and a heater 74 for using at least a portion Q 'of the stored thermal energy to heat a second fluid F2. In a CAES installation, the second fluid is heated during a different operating phase from that during which the first fluid is cooled.

In normal operation, considering the thermal transfer means as adiabatic, the thermal energy Q extracted from the first fluid F1 is substantially equal to the amount of thermal energy Q 'used to heat the second fluid F2. The second fluid F2 has, before heating, a cold incoming temperature TE2 and, after heating, a warmed outgoing temperature TS2. The amount of heat energy Q 'used to heat the second fluid F2 is defined by a difference between the heated outgoing temperature TS2 and the incoming cold temperature TE2. The heated outgoing temperature TS2 is less than or equal to the hot incoming temperature TE1 of the first fluid F1. Consequently, the heat energy used Q 'for heating the second fluid F2 depends on a cold incoming temperature TE2 of the second fluid F2 and the incoming hot temperature TE1 of the first fluid Fl. In an installation capable of implementing an adiabatic CAES energy storage method, the hot incoming temperature TE1 of the first fluid F1 is substantially fixed, since it is due to the transfer of a first quantity of heat into a gas following a precise compression. The thermal energy Q extracted from the first fluid F1 then depends solely on the cold incoming temperature TE2 of the second fluid F2. Finally, it follows that the first fluid F1 has a cold outgoing temperature TS1, after cooling, which depends on the cold incoming temperature TE2 of the second fluid F2 at the inlet of the heater 74.

An installation capable of implementing a CAES process operates by alternating cycles of extraction of thermal energy and then reintroduction of thermal energy. From one cycle to another, the cold spot temperatures TF are substantially identical to each other and the hot spot temperatures TC are substantially identical to each other. If the heat storage assemblies are appropriately sized, in nominal operation, it can be considered as a first approximation that the hot point PC and the cold point PF have substantially invariant temperatures.

The term "nominal operation" (or "normal operation", previously) means that the installation operates optimally, or at least in an expected manner.

When establishing this nominal operation, the cold spot temperature TF tends to the incoming storage temperature TE2 and the hot spot temperature TC tends to the incoming storage temperature TEL

Also, the colder the temperature TF point of the heat exchanger is hot, the lower the storage temperature TS1 is low and less the inlet temperature in the second compressor is low.

The heat storage tanks can theoretically allow cooling from a hot incoming temperature TE1 high, close to 350 ° C or up to 400 ° C or 600 ° C or higher, up to a cold outgoing temperature TS1 of the order an ambient temperature value, for example 15 ° C or 25 ° C or even 50 ° C. The inventors, however, noted that when establishing the permanent, the outgoing cold temperature TS1 is higher than this theoretical cold outgoing temperature.

In an installation capable of implementing a CAES-type adiabatic energy storage method according to the state of the art, the cold outgoing temperature TS1 of the intermediate heat storage assembly corresponds to a temperature of the air flow. entering Fl at the input of the second compressor when the installation is in an energy storage mode.

According to the first embodiment of the invention described previously with reference to FIG. 5A, it is then proposed to correct the cold outgoing temperature TS1, which is too high, by the addition of an additional cooling step, by means of the additional cooler 6, between the heat storage assembly and the second compressor.

The inventors have further noted that when the installation is in the energy destocking mode, the outgoing air flow F2 from the regulators 21, 22 does not have a temperature as low as desired. Indeed, the temperature of the outgoing air flow F 2 at the outlet of the expander is generally not close to the ambient temperature or even 50 ° C as initially dimensioned, but a temperature closer to about 100 ° C or even about 150 ° C.

Consequently, the incoming TE2 destocking temperature of the air flow entering the heater during the destocking phase is generally closer to 100 ° C. or even 150 ° C. in nominal operation. During the establishment of the nominal operation, in the set of heat tanks 3, the cold spot temperature TF of the heat tanks 3 increases and gradually tends towards the temperature of the outgoing air flow F2 at the outlet of the first generator, about 100 ° C or even about 150 ° C instead of about 50 ° C. During the energy storage phase, the incoming air flow F1 is cooled only up to the temperature of the outgoing air flow F2 at the outlet of the first generator, ie about 100 ° C. or 150 ° C.

According to the second embodiment of the invention presented above with reference to FIG. 5B, the additional destocking cooler 60 introduced between the first generator 21 and the intermediate heater 51 allows an overcooling of the outgoing airflow F2. from the first generator. It follows a lowering of the TE2 outlet storage temperature in the intermediate heater 51. The outlet temperature of the additional destocking cooler 60 is then called "over-cooled". Consequently, during the establishment of a nominal operation, the cold spot temperature of the heat reservoir assembly 3 tends towards this over-cooled temperature, lower than the temperature of the outgoing air flow F 2 at the outlet of the first generator. The over-cooled temperature may be less than or equal to 75 ° C or less than or equal to 50 ° C or lower. It is thus possible to obtain in nominal operation a cold spot temperature TF lower than the state of the art; the incoming air flow F2 therefore has a lower temperature than in the state of the art both at the outlet of the aftercooler 51 and at the inlet of the second compressor. The second compressor therefore has a higher conversion efficiency than according to the state of the art.

In addition, since the hot spot temperatures of the heaters 51, 52 are identical to those of the state of the art, the inlet temperatures and pressures of the two generators 21, 22 are substantially identical to those of the state of the art. . The installations according to the first and second embodiments described above have the same production capacity as the installations of the state of the art and the same efficiency in phase of destocking energy while having at least one compressor having better performance.

In advantageous embodiments of the invention, the thermal energy extracted by the additional coolers 6, 60 is advantageously collected by a collector 61 and distributed in power distribution networks 62 (FIG. 4). Power distribution networks 62 may be heat networks, steam generators, or hot water distribution systems for a home, city, or appliance. Alternatively, or in addition, the collected thermal energy can be converted into another type of energy, mechanical or electrical, for example by a heat / current converter operating according to organic Rankine cycles (or "ORC cycles").

When these advantageous modes of collecting and / or transforming the thermal energy extracted by the additional coolers 6, 60 are applied to the second embodiment of the invention, the energy thus recovered is extracted and distributed during the destocking phase, that is to say when the energy demand is higher.

In this case, the plant according to the invention has a further improved efficiency: not only is less energy used during the energy storage phase, but more energy is produced during the destocking phase. energy than in an installation according to the state of the art. Indeed, energy production by the generators activated by compressed air is added the energy extracted by the additional destocking cooler 60 and transformed or distributed according to the aforementioned means.

The principle of the invention can be applied to installations where the compressors (and / or expander) operate with other ranges of temperature than those described above. For example, the second compressor can be set to operate optimally when the temperature of the compressor inlet gas flow is close to 250 ° C or 300 ° C or other higher temperatures. Similarly, the incoming gas flow from the first compressor, or the gas flow entering the second expander, can have a temperature of the order of 600 ° C or 700 ° C or more. In these cases, the heat transfer means can be sized with a theoretical cold temperature of 100 ° C or 150 ° C, or 250 ° C or 300 ° C, or any other temperature instead of 15 ° C or 25 ° C as mentioned above.

The principle of the invention is also applicable for such installations and allows an improvement of the conversion efficiency of the second compressor. Indeed, for the same variation in pressure, in the direction of compression or expansion, the compressors produce a greater amount of heat than that dissipated by the trigger, which can be explained by the fact that the compressors and Regulators are not perfect mechanical pressure-energy converters.

It is then possible to position additional cooling means to lower the temperature of the incoming gas flow, between the heat transfer means and the second compressor, and / or to lower the temperature of the outgoing gas flow between the first expander and the heat transfer means. The cooling means can then be set to lower the gas temperature by 10 ° C, 50 ° C, 100 ° C, 150 ° C or higher depending on the installation.

Claims

claims

1. Installation of successive compressions / detents of gas respectively for storing / releasing energy, comprising:

* for the compressions:

a first compressor (11, 12, 101) of the gas delivering a first quantity of heat, and

at least one second compressor (12, 13, 102) downstream of the first compressor (11, 12, 101) delivering a second quantity of heat,

* and for relaxation:

a first expander (21, 22, 102) of the gas producing a first amount of cooling, and

at least one second expander (22, 23, 101) downstream of the first expander (21, 22, 102),

wherein heat transfer means (51, 150) accumulates the first amount of heat at the first cooling amount to lower a gas temperature upstream of the second compressor (12, 13, 102) and thereby improves efficiency. operating the second compressor (12, 13, 102), characterized in that the installation further comprises cooling means (6, 60, 160), upstream of the second compressor (12, 13, 102) and / or downstream of the first expander (21, 22, 102) to further lower the temperature of the gas upstream of the second compressor (12, 13, 102).

2. Installation according to claim 1, characterized in that the cooling means (6, 60, 160) are connected to at least one energy collector for collecting thermal energy, extracted from the gas passing through the cooling means (6, 60, 160).

3. Installation according to claim 2, characterized in that the energy collector is connected to a power distribution network.

4. Installation according to claim 3, characterized in that the energy distribution network is a thermal energy distribution network, the energy collector being intended to heat a fluid passing through the thermal energy distribution network. .

5. Installation according to one of claims 2 to 4, characterized in that the energy collector comprises a heat-energy mechanical converter capable of transforming at least a portion of the thermal energy extracted by the cooling means (6, 60 , 160) in mechanical energy.

6. Installation according to one of claims 2 to 5, characterized in that the energy collector comprises a heat-current converter capable of transforming at least a portion of the thermal energy extracted by the cooling means (6, 60, 160) in electrical energy.

7. Installation according to claim 6, characterized in that the heat-current converter is adapted to operate according to an organic Rankine cycle.

8. Installation according to one of the preceding claims characterized in that the cooling means are adapted to lower the temperature of the gas to a temperature below about 75 ° C or about 50 ° C.

9. Installation according to one of the preceding claims, characterized in that the heat transfer means (51, 150) comprise a coolant circuit (FC) including at least:

a first heat exchanger (31, 32) upstream of the second compressor (12, 13, 102) for extracting thermal energy from the gas containing the first quantity of heat,

a cold liquid reservoir (RF) supplying a cold liquid to the first heat exchanger (31, 32) and a hot liquid reservoir (RC) for storing thermal energy extracted by the first heat exchanger (31, 32), and a second heat exchanger (41, 45, 46) downstream of the first expander (21, 22, 102) for supplying, from said heat energy stored in the hot liquid reservoir (RC), thermal energy at gas from the first expander (21, 22, 102),

the cooling means (6, 60, 160) being arranged between the first heat exchanger (31, 32) and the second compressor (12, 13, 102) and / or between the first expander (21, 22, 102) and the second heat exchanger (41, 45, 46).

10. Installation according to one of claims 1 to 8, wherein the heat transfer means (51, 150) comprise one or more thermal energy storage tanks (3, 103, 51) made of a solid material. adapted to: cool a gas passing through the first compressor (11, 12, 101), and heat a gas therethrough, from the first expander (21, 22, 102), the cooling means (6, 60, 160) being disposed between said heat storage tanks (3, 103, 51) and the second compressor (12, 13, 102) and / or between the first expansion valve (21, 22, 102) and the heat storage tanks (3, 103, 51) .

11. Installation according to one of the preceding claims, characterized in that the cooling means (6, 60, 160) are arranged downstream of the first expander (21, 22, 102).

12. A method of successive compressions / detents of gas respectively for storing / releasing energy, comprising:

* for the compressions:

a first compression delivering a first quantity of heat, followed

at least one second compression delivering a second quantity of heat,

* and for relaxation:

a first expansion producing a first amount of cooling, followed by at least a second expansion,

a method in which heat transfer between the first amount of heat and the first amount of cooling is provided to lower a gas temperature before the second compression and hence to improve a yield of said second compression,

characterized in that cooling means (6, 60, 160) of the gas are provided before the second compression and / or after the first expansion, to further lower the temperature of the gas before the second compression.

13. The method of claim 12, characterized in that recycle at least a portion of a thermal energy extracted from said cooling means (6, 60, 160).