FR2964693A1 - INSTALLATION OF ENERGY RESTITUTION - Google Patents

Abstract

The invention relates to the field of energy storage, and in particular an energy storage facility stored in the form of high-pressure gas comprising a reservoir (6) for storing gas under high pressure, a main pneumatic motor (30 '). and interposed therebetween an expander-compressor intermediate device (9) and a buffer tank (5). The expansion-compressor intermediate device (9) in turn comprises a secondary pneumatic motor for receiving said gas from the storage tank (6) at high pressure and releasing it to an intermediate pressure equal to or greater than an intake pressure of the pneumatic motor. primary (30) so as to extract a mechanical work, and a secondary compressor, mechanically coupled to said secondary pneumatic motor, and adapted to receive a gas at a lower pressure than said intermediate pressure, and compress it to said intermediate pressure. The buffer tank (5) is connected to the auxiliary air motor and the auxiliary compressor to receive two of the gas at said intermediate pressure, and the main air motor (30 ') to supply gas thereto at said air motor inlet pressure. main. The invention also relates to a method of restoring stored energy in the form of gas under high pressure.

Description

The present invention relates to an installation and a method of restoring stored energy in the form of gas under high pressure.

It is known that, as the demand for electrical energy fluctuates considerably over the course of a day, the manager of a public electricity grid adjusts the network by using additional sources of electrical energy to cover peaks in consumption or by neutralizing active sources when the network is supercharged. This constraint can be local, given that certain regions do not have sufficient means of production and are dependent on other regions, which is the case in France in the South-East and in Brittany.

It is therefore extremely interesting to be able to store overcapacity of network electricity produced during the night, and to return them to the network where the needs are greatest.

It is known, particularly from the French patent application with the publication number FR 2 891 095 A1, an energy recovery facility stored in the form of a compressed gas, in which a storage tank for storing said compressed gas is connected to an engine. pneumatic. To restore the energy, a restitution process is applied, in which the expansion of the gas drives the pneumatic motor.

In the context of the present invention, the term "pneumatic motor" in its widest sense, that is to say any engine, such as a turbine or a piston engine, actuated by the expansion of a compressible fluid, such as air or any other gas.

However, for reasons of efficiency, the pneumatic motors, particularly the expansion turbines, and the electric generators that could be coupled thereto normally have limited operating ranges. In order to supply the pneumatic motor with compressed gas with a substantially constant pressure and flow rate over long periods of time, it will therefore normally be necessary to store under pressure a very high mass of gas with respect to the mass flow rate supplied to the pneumatic motor. If the reservoir is directly connected to the pneumatic motor, so that the gas is supplied at substantially the same pressure as that under which it is stored, the storage volume must therefore also be very high. Although this can be achieved in some cases, for example by using underground reservoirs, especially in salt mines, these large volumes are not necessarily available where energy storage is desired.

It is of course possible to reduce the storage volume by increasing the storage pressure relative to the intake pressure of the air motor. An expansion valve would be installed between the storage tank and the air motor. In other documents of the state of the art, it has often simply taken into account an isothermal expansion between the storage pressure and the inlet pressure of the air motor, without considering any loss of energy. However, in this case, the energy that has been spent to store the gas at a very high pressure, higher than the nominal intake pressure of the air motor, is actually lost, without being reused when the pressure is brought back gas at this nominal inlet pressure. Thus, the energy efficiency is strongly affected by a very high pressure gas storage. For example, the internal energy of a volume VI of gas at 30 MPa is much greater than that of a volume V2 of the same mass of gas at 2.1 MPa. If, for example, 300 kg of air are stored at 30 MPa and this is expanded to 2.1 MPa before supplying a pneumatic motor, then 1 "potentially recoverable energy is that of 300 kg. air at 2.1 MPa, a loss of energy of about 50% compared to that stored.

The present invention aims to propose an installation and a process for the return of stored energy in the form of a compressed gas that makes it possible to dispense with storage tanks of very large volume, while maintaining a high energy efficiency.

In an installation according to at least one embodiment of the present invention, this object is achieved by virtue of the fact that between the storage tank and the main pneumatic motor are interposed an intermediate expander-compressor device and a buffer tank. Said compressor-expander intermediate device comprises a secondary pneumatic motor and a secondary compressor. Said secondary pneumatic motor is adapted to receive said gas from the storage device at high pressure and to release it to an intermediate pressure equal to or greater than an inlet pressure of the main pneumatic motor so as to extract a mechanical work therefrom. Said secondary compressor is adapted to receive a gas at a pressure lower than said intermediate pressure, and to compress it to said intermediate pressure, and is mechanically coupled to said secondary pneumatic motor. The buffer tank is connected, on the one hand, to the secondary pneumatic motor and the secondary compressor to receive therefrom gas at said intermediate pressure and, on the other hand, to the main pneumatic motor to supply gas thereto intake of the main pneumatic motor.

Thanks to these arrangements, it is possible to recover some of the internal energy of the gas under high pressure to increase the gas flow rate supplied to the main pneumatic motor. The amount of energy that can be recovered by the main air motor is decreased, and the efficiency of the energy recovery facility is significantly improved.

Advantageously, said gas can be air, which is a readily available resource, is relatively unreactive, and can be directly discharged to the atmosphere after expansion in the main air motor.

Said main and / or secondary pneumatic engines may in particular comprise turbines, which are advantageous in terms of reliability, high efficiency and ease of maintenance, but, alternatively or in addition to the turbines, pneumatic piston engines that are mobile and -vient and / or rotary, could also be considered. Advantageously, said compressor-expander intermediate device may comprise at least one heat exchanger between said secondary pneumatic motor and compressor. Thus, the temperature of the expanded gas in the secondary air motor can be increased, and that of the compressed gas in the secondary compressor decreased, thus increasing the efficiency of this engine and compressor.

Advantageously, the secondary compressor may be connected to an exhaust of the main pneumatic motor for its gas supply. In this way, the secondary compressor can be supplied with dry and cold air.

Advantageously, the secondary pneumatic motor may comprise at least a first and a second expansion stage installed in series. This increases efficiency and flexibility. In particular, if an inlet of the second expansion stage is connected to the storage tank via a bypass which bypasses the first expansion stage with a valve, it is possible, by opening this valve, to adapt the pneumatic motor. secondary to a decrease in storage pressure by directly feeding the second stage of relaxation and by shorting the first.

Advantageously, the secondary compressor may comprise at least a first and a second compression stage installed in series. This also makes it possible to increase its efficiency and flexibility. In particular, if the secondary pneumatic motor also comprises a first and a second stage installed in series, and if the intermediate device expander-compressor comprises at least a first heat exchanger between said first stages of the secondary compressor and the secondary pneumatic motor, the heat generated by the first can be used to heat the gas downstream of the second, which would increase the efficiency of both. Even more advantageously, said compressor-expander intermediate device may then also comprise at least one second heat exchanger for heating the gas downstream of the second stage of the secondary pneumatic motor, for example with a residual heat, such as that produced by a electric generator mechanically coupled to the main air motor, or by an air conditioning device.

Advantageously, the installation may comprise at least one heat exchanger for heating the gas upstream of at least one expansion stage of said main pneumatic motor. This heat exchanger can be connected to a cooling circuit of an installation producing residual heat, such as, for example, an air conditioning system. The low temperature heat, for example 85 ° C, of such an adjacent hot source is fully exploitable, since it has a significant mean A between the low temperature of the gas and the temperature of the hot source. The thermal energy provided will produce a job by isobaric expansion of the compressed air, increasing the kinetic energy of the compressed air moving by increasing its speed. The internal energy of a gas being a function of its temperature, the higher the temperature of the hot source, the greater the positive variation of internal energy.

Advantageously, said main pneumatic motor may comprise a plurality of expansion stages installed in series, which also makes it possible to increase its efficiency and flexibility. The use of several floors allows to exploit several phases of relaxation, and the relaxation is thus exploited in all its extent. The present invention also relates to a storage and energy restoration installation comprising an energy recovery installation as described above, and a main compressor for supplying said storage tank with gas under high pressure. In this way, this energy storage and retrieval installation makes it possible, for example, to provide, in coherence with the needs of an electrical network, improvements to storage and electrical energy recovery installations, so that to improve their average efficiency calculated in base with the electrical energy withdrawn and that reinjected with the network. Thus, for example, efficient regulation of the electricity produced by aerogenerators becomes possible. The installation also makes it possible to compete with the electric accumulators, for example in the application of the technology to a motorization of a vehicle.

Advantageously, the installation may comprise at least one heat exchanger for cooling said gas downstream of at least one compression stage of said main compressor. This allows to escape an adiabatic compression to approach an isothermal compression, with better energy efficiency. Particularly advantageously, said heat exchanger can be connected to an expansion motor, such as for example a turbine, to actuate it by the expansion of a heated fluid in said heat exchanger. In particular, this motor can be mechanically coupled to said main compressor. The energy of the heat discharged from the gas downstream of the at least one compression stage can thus be partially recovered to operate the main compressor. In particular, with a plurality of compression stages, each associated with a downstream heat exchanger, said heat exchangers can be connected to a Rankine cycle circuit with a steam turbine. If this steam turbine was mechanically coupled to the compressor, it significantly reduced the external mechanical power input needed to drive the compressor. The mechanical energy extracted by this steam turbine can be even higher if the Rankine cycle circuit comprises one or more additional exchangers for receiving residual heat from external sources, such as, for example, an air conditioning system.

The present invention also relates to a method of restoring energy stored in the form of gas under high pressure, said method comprising the following steps: an expansion of a first gas flow, containing gas under high pressure, to an intermediate pressure a compression of a gas flow rate, containing ga: under pressure lower than said intermediate pressure, to said intel mechaniial pressure, this compression of the second flow and, iwt at least partially actuated by a work extracted from said trigger of the first flow rate, a gas buffer storage under said intermediate pressure from said first and second flow rates and an expansion of a third gas flow, from said buffer storage, so as to extract a mechanical work.

Thanks to these arrangements, it is possible to recover a portion of the internal energy of the first gas flow to increase the third gas flow and the energy that can be recovered in its expansion.

Advantageously, said restitution process may also comprise a heat exchange between said first gas flow rate after at least a portion of its expansion towards said intermediate pressure and said second gas flow rate after at least a portion of its compression towards said intermediate pressure . Thus, the temperature of the first gas flow can be increased, and the second gas flow rate decreased, thus increasing the performance of both the trigger and the compression.

Advantageously, said second gas flow can be extracted from said third flow after expansion. Thus, the gas of said second flow can be perfect and cold.

Advantageously, before at least one step of the expansion of said third gas flow, said first gas flow may be reheated, in particular by a residual heat of another process. Thus, the energy recovered in said expansion of the third gas flow can be increased. Even more advantageously, if the expansion of said third gas flow comprises several steps, said third flow of gas can be warmed up before each expansion step, thus allowing an isothermal expansion to be approached.

The present disclosure also relates to a high pressure gas energy storage method, said method comprising: compressing a first gas flow to a high pressure; high pressure storage of this first gas flow.

According to the present invention, this storage method can then be followed by the restitution method described above.

Advantageously, after at least one step of said compression of the first gas flow, said first gas flow can be cooled, in particular by a biphasic fluid which is then expanded to extract mechanical energy in a Rankine cycle. This mechanical energy can be reused in the compression of said first gas flow. Even more advantageously, if the compression of said first gas flow comprises a plurality of steps, said first gas flow can be thus cooled after each compression step, thus making it possible to approach isothermal compression.

The invention will be better understood and its advantages will appear better on reading the detailed description which follows, of an embodiment shown by way of non-limiting example. The description refers to the accompanying drawings in which:

Figure 1 schematically shows an embodiment of an energy storage facility in the form of gas under high pressure.

Figure 2 schematically shows an embodiment of an energy recovery facility stored as a gas under high pressure.

FIG. 3 shows an embodiment of an intermediate expander-compressor device.

Figure 1 illustrates an embodiment of an energy storage facility for converting electrical energy into compressed air at high pressure in a storage tank.

In the transformation of electrical energy into compressed air, a minimum of energy is spent by isothermal compression, which is however theoretical. In the illustrated installation, it will be approached by fleeing an adiabatic compression, in part inevitable, by a polytropic compression with three stages and intermediate cooling.

This installation comprises an air circuit with a compressor 30 having a first stage 12, a second stage 11, and a third stage 10 connected in series in the air circuit and mechanically integral with the same motor shaft 21 coupled to an electric motor 8 powered by a three-phase electrical network 3. In the air circuit are also placed, directly downstream of each compressor stage 12, 11, 10, heat exchangers 15, 14, 13 for heat exchange between the air of the air circuit 25 and a fluid of a first secondary circuit 17. The air circuit opens, through a valve 4, into a tank 6 for storing air under high pressure,

The secondary circuit 17 is a two-phase fluid circuit comprising a pump 28 for supplying liquid to a divider 22 in which the secondary circuit 17 is divided into three parallel branches, each passing through one of the exchangers 15, 14, 13, which are adapted to evaporate, partially or totally, the flow of liquid from each branch with the heat released by the compressed air. The secondary circuit 17 also comprises a node 23, in which the three parallel branches of the secondary circuit meet, and, downstream thereof, an exchanger 24 in communication with a heat source 1, which can be an adjacent installation producing residual heat, such as an air conditioning system or an electric motor, is capable of finalizing the evaporation of the two-phase fluid, and a steam turbine 27, also integral with the drive shaft 21. Finally, downstream of the steam turbine 27 and upstream of the pump 28, the secondary circuit comprises a condenser 29 connected to a cold source 25.

The energy storage process with this installation is as follows:

The outside air 26 is compressed by the first stage 12, adiabatically reversible, a pressure po (normally an atmospheric pressure of about 0.1 MPa) at the pressure pi, which can be, for example, 0, 87 MPa. At the outlet of the first stage 12, the air, which has a moderate initial temperature T0 (normally an ambient temperature of about 24 ° C), has been raised to a high temperature Tl (eg about 270 ° C), is cooled by the exchanger 15 isobar reversibly to lower to a lower temperature T2, and then introduced and compressed by the second stage 11, adiabatically reversible, the pressure pl at a higher pressure p2 (eg about 7.2 MPa). The air, whose temperature rises again, in this second stage 11, to a temperature is still isobarically cooled by the deflector 14 to a temperature TI, then introduced and compressed p the third stage 10, adiabatically reversible, pressure P2 at a still higher pressure p3 (eg about 28.0 MPa). At the outlet of the third stage 10, the compressed air, the temperature of which is still raised to a temperature T5 higher than T4, is cooled by the exchanger 13 to a temperature T6, and supplies the reservoir 6 with through the valve 4.

Upstream of the pump 28, the fluid of the secondary circuit 17, for example water, is at a low pressure (eg about 0.04 MPa) and its state is substantially 100% liquid at a temperature T'1 of, for example, 24 ° C. The liquid is brought to a higher pressure p'2 (eg about 4.1 MPa) by the pump 28, and its flow divided into three branches by a divider 22 to supply the heat exchangers 13, 14 and 15 in parallel. form the evaporators of a Rankine cycle in this secondary circuit 17. The exchangers 13, 14 and 15 perform a heat exchange between the compressed air and the secondary circuit fluid and operate a dual function, cooling downstream air of each compression stage 12, 11 and 10 and heating at a higher temperature T'2 the fluid of the secondary circuit 17 to the pressure p'2 imposed by the pump 28. This fluid is then heated by the exchanger 24 to a still higher temperature T'3 (eg about 252 ° C).

The heating produced by the heat exchange resulting from the compressions of the compressed air and the heat source 1 ensures the evaporation of the motor fluid. The vapor phase at the temperature T'3 and at the pressure p'2 is then admitted at the inlet of the turbine 27.

At the outlet of the turbine 27, the temperature of the water vapor is lowered to an intermediate temperature T'4 (eg about 75 ° C.) and, at the pressure p'1 imposed by the condenser 29, its state is diphasic.

The condenser 29, cooled by the cold source 25, which may be the ambient air or a river and the exchanger 29, substantially condensed the air / vapor mixture leaving the turbine 27, bringing it back to the initial temperature. T'1 at which this water is again fed to the pump 28.

The heat generated by the heat source 1 and the compression stages 12, 11 and 10 of the compressed air is thus converted into mechanical work by the turbine 27 which drives the motor shaft 21. The work of the turbine 27 significantly reduces the electrical consumption of the motor 8.

FIG. 2 illustrates an embodiment of an energy storage facility 15 stored in the form of compressed air under high pressure.

This installation comprises the tank 6 of compressed air under high pressure of the previous installation, and a compressed air circuit, connected to the air tank 6 through a valve 4 ', and comprising an intermediate device 20 expander-compressor 9, and, downstream of said compressor-expander intermediate device 9, a buffer tank 5, a flow regulator 7, and a pneumatic motor 30 'having a first stage 10', a second stage 11 ', and a third stage 12' connected in series in the air circuit and mechanically secured to the same motor shaft 25 21 'coupled to an electric generator 8' supplying the three-phase electrical network 3. In this air circuit are also placed directly upstream of each expansion stage 10 ', 11', 12 ', heat exchangers 13', 14 ', 15' allowing a heat exchange between the air of the air circuit and a fluid of a second secondary circuit 17 '. The second secondary circuit 17 ', in which the heat exchangers 13', 14 'and 15' are arranged in parallel between a divider 22 'and a node 23', is in communication with the heat source 1.

Downstream of the third stage 12 ', the air circuit is divided into two branches, including an exhaust branch 19 passing through another heat exchanger 18, and a branch 16 back to the compressor-expander device 9. The Heat exchanger 18 may, for example, be connected to a refrigerant circuit 45 of an air conditioning system, possibly in the illustrated embodiment, the one which constitutes the source of heat 1, in order to further reduce its temperature. temperature.

The expansion-compressor intermediate device 9 is illustrated in more detail in FIG. 3, and comprises a secondary pneumatic motor with a first and a second expansion stage 36, 37, and a secondary compressor with a first and a second expansion stage. 39. The two stages of expansion 36, 37 and the two stages of compression 38, 39 are all screw type and integral with the same drive shaft 35, supported by bearings 45 in a housing 47 common to both floors 36, 37 and two compression stages 38, 39. This housing 47 is divided into four successive compartments 48,49,44 and 51 for, respectively, the first expansion stage 36, the first compression stage 38, the second expansion stage 37, and the second compression stage 39.

The compartment 48 of the first expansion stage 36 and the compartment 49 of the first compression stage 38 are in communication through upper passages b and lower c, and filled with a heat-transfer fluid that can circulate through a flow of water to a water heater. heat between the two compartments 48,49. The compartment 44 of the second expansion stage 37 is in communication with a heat transfer fluid circuit 20 making it possible to use the cold generated by the expansion of the air in the second expansion stage 37 to cool another device, such as the generator 8 ', as illustrated in Figure 2, or another installation, such as an air conditioning installation.

In the air circuit, the valve 4 'is in communication with the inlet of the first expansion stage 36, and, through a bypass valve 42 and a check valve 41, also with the admission of the second stage 37. The exhaust of the first expansion stage 36 is in communication with the inlet of the second expansion stage 37 through heat exchange coils, located in the upper parts of the compartments 48, 49 and through a pressure regulator 40 for regulating the inlet pressure of the second expansion stage at a pressure p4 (eg about 9.0 MPa).

The first expansion stage 36 is sized to work from the pressure p3 of the storage tank 6, up to the pressure p4 regulated by the pressure regulator 40. The second expansion stage 37 is sized to work from p4 to a pressure p5 (eg about 2.1 MPa), which is that of the buffer tank 5. The exhaust of the second expansion stage 37 is in communication, through a heat exchange coil located in the compartment 44 of the second stage 37, and a check valve 34 to impose the pressure ps, with the buffer tank 5.

The branch 16 of the air circuit, putting into communication the exhaust of the third stage 12 'of the air motor 30' with the admission of the first compression stage 38 through a heat exchange coil located in the lower part of the compartment 48 of the first expansion stage 36, comprises a control valve 31 controlled by a controller 43 connected to a speed sensor 32 of the motor shaft 35 to impose a nominal speed of rotation, for example about 250 000 revolutions / minute, such a speed to size the device expander-compressor compressor 9 minimizing its size, which is very useful especially in the case where the installation would be applied to a vehicle.

The exhaust of the first compression stage 38 is in communication, through a pressure regulator 50 to impose an outlet pressure p7 (eg about 0.26 MPa), and coils located in the lower parts of the compartments 49. and 44, with the admission of the second compression stage 39. The exhaust of the second compression stage 39 is in communication, through a check valve 33 to impose the pressure p5, with the buffer tank 5, in parallel with the exhaust of second stage of relaxation 37.

The first compression stage 38 is dimensioned to work from the pressure p6 of the exhaust of the pneumatic motor 30, up to the pressure p7 regulated by the pressure regulator 50. The second compression stage 39 is sized to work from p7 to P51 the pressure of the buffer tank 5.

The complete cycle of expansion of the compressed air of the storage tank 6 takes place in the case illustrated as follows.

A first air flow, extracted from the storage tank 6, is expanded towards the pressure p5 of the buffer tank 5 through the expansion stages 36, 37 of the compressor-expander intermediate device 9, this pressure being the constant pressure of supplying the pneumatic motor 30 'comprising the three expansion stages 101, 11' and 12 'and connected by the drive shaft 21' to the generator 8 '.

A second air flow, extracted from the exhaust of the pneumatic motor 30 through the branch 16 of the air circuit at the pressure p6, is compressed towards the pressure p5 of the buffer tank 5 through the compression stages 38 and 39 of the compressor-expander intermediate device 9, the work required to compress the second flow rate being provided by the expansion of the first flow. The sum of the first and second flow rates substantially corresponds to a third air flow supplied to the air motor 30 through the buffer tank 5.

In the expansion device-compressor compressor 9, the inlet pressure of the first expansion stage 36 decreases gradually from p3 to p4 as the pressure in the storage tank 6 decreases. When the inlet pressure of this first expansion stage reaches approximately p4, its supply is derived directly to the second expansion stage 37 by the opening of the valve 42. When the pressure at the storage tank 6 is between p4 and ps, only the second expansion stage 37 produces work to drive the two compression stages 38 and 39. As time goes by, the storage pressure decreases, and the power of the expansion stages 36, 37 also. For this reason, the second rate will be decreased over the destocking to adapt the work Wd provided by the expansion of the first flow Wd work compression of the second flow with Wd + W = 0. For this, the speed sensor of shaft 32 informs the electronic controller 43 of the low speed and reduces the second flow by controlling the control valve 31 to maintain the nominal speed of about 250 000 revolutions / minute of the shaft 35.

The air, which enters the first expansion stage 36 at a moderate temperature T7, normally close to an ambient temperature of about 24 ° C, leaves it at a very low temperature T8 (e.g. - 30 ° C). It is then heated to a temperature T9 by the heat transfer fluid from the compartment 49 through the passage b and through the serpentine exhaust pipe located in the upper part of the compartment 48. The heat-cooled heat transfer fluid then passes through the pipework. coil located at the bottom of the compartment 48 and feeding the first compression stage 38.

The efficiency of the first compression stage 38 is excellent because of a temperature Tio also very low in admission (eg about -4 ° C). For reasons of efficiency, the pressure P6 is imposed at the output of the first compression stage 38 by the pressure regulator 50. The exhaust air of the first compression stage 38 is firstly at a relatively high temperature T11 ( eg about 80 ° C), and is then cooled by the cold heat transfer fluid from compartment 48 through passage c. The heat transfer fluid thus heated and lighter will go back to the compartment 48 through the passage b, the circulation of heat transfer fluid thus being done by the principle of convection. Thus, in the top of the compartments 48 and 49, the hot heat transfer fluid through the coils upstream of the air intake of the second expansion stage 37 is used to heat the air before its second expansion.

The second expansion stage 37 being housed in the compartment 44, through which a coolant passes, the cold generated by the expansion of the first air flow in this second expansion stage 37 may participate in the cooling of, for example, a cooling system. air conditioning or an electric generator, while recovering this heat to increase the work that can be extracted from the first air flow in the pneumatic motor 30 'downstream. The second air flow, arriving at the inlet of the second compression stage 39 also passes through this compartment 44, which makes it possible to continue to cool the second air air flow to a temperature T12 before its second compression. The air pressure at the exhaust of the turbine 37 is controlled by the nonreturn valve 34.

At the outlet of the second compression stage 39, the second air flow rate is set at the pressure p5 by the valve 33 and feeds the buffer tank 5. The first air flow, leaving the second expansion stage 37, also feeds the buffer tank 5, and is also adjusted to the pressure p5 by the valve 34. The sum of these two flows is a third air flow corresponding substantially to the feed rate of the air motor 30 '. At the beginning of the destocking, the second air flow, that is to say the flow rate supplied through the compression stages 38 and 39, represents 52% of the total mass flow rate supplied to the pneumatic motor. Throughout destocking, this percentage decreases towards 0%. The device expander-compressor 9 increases the autonomy and energy production by 35%.

In admission to the buffer tank 5, the second air flow has an average temperature T13 high (eg about 2500C), and represents, on average, 1/3 of the total mass flow supplied to the buffer tank 5 by the device 9. The first air flow has, in admission to the buffer tank 5, a moderate temperature T14 (eg about 50 ° C), the air having been heated, in the compartment 44, in the embodiment illustrated in the figure by the cooling circuit 20 of the electric generator 8. If the illustrated installation equips a vehicle to power an electric propulsion motor, the heat transfer fluid passing through the compartment 44 could also be used to recover the pressure drops. of this engine. If the illustrated installation is associated with an air conditioning installation 2, as in the illustrated embodiment, the heat transfer fluid passing through the compartment 44 could also be the refrigerant of the circuit 45 of this air conditioning installation 2.

In the secondary circuit 17, the heat transfer fluid transfers heat from the thermal losses discharged by an adjacent installation 1, this heat transfer fluid being divided by the divider 22, in the illustrated embodiment, into three substantially equal flows by the divider 22, for supplying the heat exchangers 13 ', 14' and 15 'in parallel. The air flow from the buffer tank 5 at the pressure 1) and at a temperature T15 (eg an ambient temperature of about 24 ° C) is regulated by the flow controller 7, and is warmed to a higher temperature T16 (eg about 85 ° C) by the exchanger 13 before its first expansion in the first expansion stage 10 '. In this first expansion stage 10 'of the main pneumatic motor 30', the air flow passes from the pressure p5 and the temperature to a lower pressure p8 and a lower temperature T17 (eg approximately 0.76 MPa, and 2.5 ° C). This third flow of air is then heated, before its second expansion, by the heat exchanger 14, and feeds the second expansion stage to a temperature T18, which can be close to T16 (eg about 85 ° C. ). At the outlet of this second expansion stage 11 ', the temperature T19 and the pressure p9 of the air flow are further lowered (eg towards approximately 2.5 ° C. and 0.27 MPa). The air is then reheated one last time by the exchanger 15 'to a temperature T79 which can be as close to T16 and T18, before its last relaxation. In this latter expansion, carried out by the third expansion stage 12 ', the pressure and the temperature of descends to the pressure p6 and temperature T10 of the exhaust of the main pneumatic motor 30'. Downstream of the third expansion stage 12 of the pneumatic motor 30 ', part of this third air flow is returned to the compression stages 38, 39 of the compressor-expander intermediate device 9 to form the second air flow rate mentioned herein. above and increasing the total flow supplying the buffer tank 5, and another part of the third air flow cools the refrigerant circuit 45 of the air conditioning system 2 by the exchanger 18 before its exhaust 19 to the atmosphere. The installation illustrated in FIG. 2 can be the generating set of an electric micro-grid, with an electrical generation substantially equal to the consumption in the electric micro-grid. With an operating range of the electric generator 8 of, for example, between 15 and 100% of its maximum power, the controller 43 can manage the power of the pneumatic motor 30 according to the power required by the micro-array by setting the compressed air flow supplied to the pneumatic motor by the flow regulator 7.

The installation illustrated in FIG. 2 may take advantage of a hot source 1 which may be a cooling tower of an air conditioning installation such as installation 2. The collaboration of these two installations thus has advantages for them. two, the energy recovery facility exploiting the residual heat produced by the air conditioning installation, and the air conditioning installation removing this heat at the best time, because, during peak consumption, especially in summer, both the power consumption of the air conditioning system that the heat carried by its refrigerant is higher. The illustrated energy restitution facility, therefore, does not only cut off the peak of the peak of electricity consumption by generating electricity, but also contributes to reducing the electricity demand of the air-conditioning system by absorbing power from the power plant. heat of its refrigerant.

Although the present invention has been described with reference to specific exemplary embodiments, it is obvious that various modifications and changes can be made to these examples without departing from the general scope of the invention as defined by the claims. For example, the energy return installation could not be associated with an air conditioning installation, but, for example, the propulsion system of a vehicle. In addition, the storage or energy recovery facilities illustrated in FIGS. 1 and 2 can be combined or used separately. A pneumatic motor with a heat exchanger for heating the working fluid downstream of at least one expansion stage, such as that illustrated in FIG. 2, could also be considered separately from the compressor-expander intermediate device of this invention. In addition, although the illustrated storage and energy transfer facilities share the same storage tank, they could also use different storage tanks, the storage tank of the storage facility being filled with gas under high pressure. pressure from the storage tank of the storage facility. Alternatively or additionally, in particular when the energy restitution installation supplies a propulsion system of a vehicle, the storage tank of this energy restitution installation can be an exchangeable reservoir, thus being able to be exchanged, after use, by a full tank, for example in a suitable service station. Therefore, the description and drawings should be considered in an illustrative rather than restrictive sense. 0

Claims (20)

REVENDICATIONS1. Installation for the return of energy stored in the form of a gas under high pressure comprising: a tank (6) for storing gas under high pressure; and a main pneumatic motor (30 '); and characterized in that it further comprises, interposed between said storage tank (6) and main pneumatic motor (30 '): an intermediate device expander-compressor (9) 10 comprising: a secondary pneumatic motor for receiving high pressure said gas from the storage tank (6) and releasing it to an intermediate pressure equal to or greater than an inlet pressure of the main pneumatic motor (30) so as to extract mechanical work therefrom; and a secondary compressor, mechanically coupled to said secondary pneumatic motor, and adapted to receive a gas at a lower pressure than said intermediate pressure, and compress it to said intermediate pressure; and a buffer tank (5) connected to the auxiliary air motor and the auxiliary compressor for receiving gas at said intermediate pressure, and the main air motor (30 ') for supplying gas thereto at said engine inlet pressure main tire. 25 2. Installation according to claim 1, wherein said gas is air. 3. Installation according to any one of claims 1 or 2, wherein said main and / or secondary pneumatic motors comprise turbines. 4. Installation according to any one of claims 1 to 3, wherein said expander-compressor intermediate device (9) 35 comprises at least one heat exchanger between said secondary pneumatic motor and compressor. 5. Installation according to any one of claims 1 to 4 wherein said secondary compressor is connected to an exhaust of the main pneumatic motor (30 ') for its gas supply. 6. Installation according to any one of claims 1 to 5, wherein the secondary pneumatic motor comprises at least a first and a second expansion stage (36,37) installed in series. 10 7. Installation according to claim 6, wherein at least one inlet of said second expansion stage (37) is connected to the storage tank (6) via a bypass, bypassing the first expansion stage (36), with a valve (42). 15 8. Installation according to any one of claims 6 or 7, wherein the secondary compressor comprises at least a first and a second compression stage (38,39) installed in series. 9. Installation according to claim 8, wherein said expander / compressor intermediate device (9) comprises at least a first heat exchanger between said first stages (36,38) of the secondary compressor and the secondary pneumatic motor. 10. Installation according to any one of claims 8 or 9, 25 wherein said intermediate expander-compressor device (9) comprises at least one second heat exchanger for heating the gas downstream of the second stage (37) of the air motor. secondary. 0 11. Installation according to any one of the preceding claims, further comprising at least one heat exchanger (13 ', 14 "for heating the gas upstream of at least one expansion stage (10', 11 ', 12). ') of said main pneumatic motor 05 12. Installation according to any one of claims 1 to 11, wherein said main pneumatic motor (30 ') comprises a plurality of expansion stages (10'411,12 "installed in series. 13. Installation according to any one of claims 1 to 12, wherein said main pneumatic motor (30 ') is mechanically coupled to an electric generator (8 ". 14. Energy storage and return installation comprising an energy restitution plant according to any one of claims 1 to 13 and a main compressor (30) for supplying said high pressure gas storage tank (6). 15. energy storage and return installation according to claim 14, wherein said main compressor (30) comprises at least one heat exchanger (15,14,13) for cooling said gas downstream of at least one stage of compression (12,11,10) of said main compressor (30). 16. Storage and energy recovery installation according to any one of claims 1 to 15, wherein said main compressor (30) comprises a plurality of compression stages (12,11,10). 17. A method of restoring stored energy in the form of gas under high pressure, said method comprising the following steps an expansion of a first flow of gas under high pressure, to an intermediate pressure; a compression of a second flow rate of gas under pressure lower than said intermediate pressure, towards said intermediate pressure, this compression of the second flow being at least partially actuated by a work extracted from said expansion of the first flow a buffer storage of gas under said pressure intermediate from said first and second flow rates and an expansion of a third gas flow from said buffer storage so as to extract mechanical work therefrom. 18. The method of claim 17 comprising a heat exchange between said first gas flow after at least a portion of its expansion to said intermediate pressure and said second gas flow after at least a portion of its compression to said intermediate pressure. The method of any one of claims 17 or 18, wherein said second gas flow is withdrawn from said third flow after expansion. 10 20. A method of storing energy in the form of gas under high pressure and of restitution of this energy, said method comprising: compressing a first flow of gas towards a high pressure; high pressure storage of this first gas flow; and, for the recovery of stored energy in the form of gas under high pressure, the steps of a restitution process according to any one of claims 17 to 19.