Device for energy conversion

Abstract

The invention relates to a device for isothermal expansion and compression of a gas (3), ensuring the compression of said gas by consuming mechanical energy and the restitution of the mechanical energy by the expansion of said gas. The device comprises at least two liquid pistons (4, 41, 42) movable in at least two chambers (31, 32) each comprising a gas that is able to be compressed or expanded by movement of said liquid pistons. A mechanical actuator (1), comprising at least one solid piston, ensures the movement of the liquid pistons in the chambers. Each chamber comprises an insert (51, 52), through which said liquid (4) and said gas can circulate, the insert comprising through-cells (53), which extend in a direction parallel to the direction of movement of said liquid piston in said insert. The device comprises at least one first phase separator connected to an outlet of each of the chambers, and to a tank (5) for storing pressurized gas.

Description

[0001]DEVICE FOR ENERGY CONVERSION The invention relates to a system for energy conversion and storage. The compression and / or expansion of gas by liquid piston appears in the literature as a promising solution for increasing the energy efficiency of energy production installations, by seeking to achieve the most isothermal thermodynamic evolution possible. Technologies are known, such as those described in patent application FR 3036887, which use pumps or turbines to achieve energy conversion between a mechanical actuator and the liquid of the liquid piston: one or more liquid piston compression stages are implemented in such installations to cover the desired gas pressure range. Different installations or devices can be deployed to increase the heat exchange in the compression chamber of the liquid piston, such as the projection of water droplets,the implementation of multiple chambers in parallel, the addition of a heat exchange insert, etc. These installations create certain problems: in particular, achieving quasi-isothermal compression / expansion requires obtaining a significant heat exchange in the compression chambers during expansion and / or compression, the value of which is several orders of magnitude higher than the exchanges existing in conventional technologies. The installations proposed in patent application FR 3036887 have extended the compression / expansion times, but they implement simple technical solutions to approach quasi-isothermal implementation. However, the result is that the installations are bulky: they occupy a significant amount of space (around 50,000 m3 for a power of 15 MW), which can generate significant operating costs. Other technologies offer more compact solutions but are more complex to implement,which does not allow operating costs to be reduced. Thus, the level of complexity and the cost generated by such installations are obstacles to the development of such technologies. The invention proposes an alternative solution which is simple to implement and which can be sized according to the applications for which it will be specially designed. The invention relates to this end to a device for the isothermal expansion and compression of a gas, ensuring the compression of said gas by consuming mechanical energy and the restitution of mechanical energy by the expansion of said gas, said device comprising: - at least one first and at least one second liquid piston, movable in displacement respectively in a first and a second chamber, each of said at least one first and second chambers comprising a gas, capable of being compressed or expanded under the effect of the displacement of said at least one first or second liquid piston, - an actuator,capable of ensuring the movement of said at least one first and second liquid pistons in said first and second chambers, each of said at least one first and second chambers respectively each comprising at least one first and at least one second perforated insert, through which said liquid and said gas can circulate. The device according to the invention is remarkable in that the actuator is a mechanical actuator comprising at least one solid piston, in that said perforated insert comprises through cells, which extend between a first cell opening opening at one end of said insert and a second cell opening opening at a second end of said insert, said cells being oriented in a direction which is either parallel to the direction of movement of said liquid piston in said insert or inclined relative to the direction of movement of said liquid piston. Finally,said device further comprises at least one first phase separator connected to a first outlet of said first chamber and to a second outlet of said second chamber. Advantageously, the phase separator is connected to a pressurized gas storage tank. According to an advantageous embodiment, the device according to the invention comprises a second separator, connected to said first and second outlets of said first and second chambers, respectively, in that said first separator comprises a first internal pressure which corresponds to the internal pressure of the gas included in said pressurized gas tank and in that said second separator comprises a second internal pressure which corresponds to atmospheric pressure. Preferably, the first and second separators are in fluid communication with each other to allow the passage of liquid from the first separator to the second separator. More preferably,the device comprises a first air intake device ensuring the passage of air at atmospheric pressure between said at least one first chamber and said second separator, as well as a second air intake device at atmospheric pressure between said at least one second chamber and said second separator. In addition, the device comprises a third air intake device ensuring the passage of compressed air between said first chamber and said first separator, as well as a fourth compressed air intake device between said second chamber and said first separator. More preferably, the device comprises a first low-flow control valve ensuring the passage of fluids from said first separator to said first chamber, as well as a second low-flow control valve ensuring the passage of fluids from said first separator to said second chamber. According to an advantageous embodiment,the device comprises a regulating valve calibrated at a safety pressure between said first chamber and said first separator and / or between said second chamber and said first separator, to allow the evacuation of a volume of liquid from said at least one first or second liquid piston to the first separator. In addition, each of the first and second chambers is preferably also fluidically connected to a fluid / fluid exchanger which makes it possible to maintain said at least one first and second liquid pistons, respectively, at ambient temperature, preferably with a tolerated temperature variation of plus or minus 10°C, said fluid / fluid exchanger preferably comprising a pump, a fluid / air exchanger or a fluid / fluid exchanger, possibly a motor-driven fan if said exchanger is a fluid / air exchanger and possibly at least one regulating valve. Advantageously,the insert comprises a core of structural material comprising a deployed honeycomb structure. Advantageously, said mechanical actuator comprises a magnetically actuated linear motor. According to an alternative embodiment, said mechanical actuator comprises a motor associated with a crankshaft. According to a further alternative embodiment, said mechanical actuator comprises a motor associated with a worm screw. The invention also relates to an installation comprising at least two devices as defined above, said mechanical actuators of said at least two devices being mechanically linked to operate together, and in that the installation comprises a first phase separator common to said at least two devices, said first common phase separator being connected to a first outlet of the first chambers of the devices and to a second outlet of the second chambers of said devices,said first phase separator being connected to a common pressurized gas storage tank. In the context of an embodiment where the installation comprises at least two devices comprising two phase separators, the second separator being common to said at least two devices, said second separator is connected to said first and second outlets of said first and second chambers of each of said at least two devices, said first common separator comprises a first internal pressure which corresponds to the internal pressure of the gas included in said common pressurized gas tank and said second separator comprises a second internal pressure which corresponds to atmospheric pressure. The invention finally relates to a method for implementing a device as defined above, the method comprising the following steps: - actuation of the mechanical actuator,- displacement of said at least one solid piston driving said first liquid piston in said first chamber and said second liquid piston in said second chamber, said first and second liquid pistons being driven in opposite directions, the first liquid piston compressing said gas in the insert of said first chamber up to a first predetermined pressure, the second liquid piston creating a depression in said insert of said second chamber up to a second pressure, - when said first pressure is reached,opening an air intake device between said first chamber and said first phase separator to evacuate the pressurized gas from the first chamber to said first separator until said liquid piston passes entirely through said insert and reaches the first outlet of the first chamber and simultaneously the air intake into said second chamber. The device according to the invention is thus a kind of reversible gas compressor, which makes it possible to compress a gas by consuming mechanical energy, but also to restore mechanical energy by expanding a gas. The thermodynamic evolution of the gas is quasi-isothermal, making it possible to carry out these pressure variations with a low energy loss thanks to compression / expansion by liquid piston. The nature of the gas and the liquid can be adapted to the needs of the application for which the device is intended (air, hydrogen, methane, gas, water, etc.). In compression mode,in the context of a non-limiting embodiment which will be presented later, the principle is based on the compression of the gas by liquid piston, the latter being driven by a solid piston. The solid piston is actuated directly by a linear motor of which it itself constitutes the mobile driving part containing the magnets, or by another piston displacement system (crank rod, rack, etc.). Thus, by moving, the solid piston pushes a liquid piston into a closed compression chamber (vertical cylinder). The reduction in volume causes the compression of the gas. The cylindrical compression chambers are subdivided into numerous small volumes thanks to a heat exchange insert consisting of an extruded 2D pattern, the cells of which extend in the direction of the liquid piston (structure also called "honeycomb", made of aluminum or other heat-conducting material). Thus,the fluid characteristics of the liquid piston make it possible to form a small liquid piston in each cell of this honeycomb while ensuring a perfect seal between the liquid and gaseous medium. The presence of the insert (honeycomb) offers a very large contact surface with the gas and allows significant heat exchange potential. The heat exchange between the gas and the insert, the heat transfer within the insert as well as its own heat capacity thus makes it possible to maintain the temperature of the gas during its compression at a value close to the initial temperature of the whole (quasi-isothermal). The heat exchange insert thus acts as a regenerative exchanger, successively allowing the transfer of thermal energy from the gas to the insert by convection / conduction,the storage of thermal energy through a moderate increase in its temperature (effect of its thermal capacity) and then the transfer of this thermal energy to the liquid by convection / conduction. Other advantages and characteristics of the invention will appear upon examination of the detailed description of a non-limiting embodiment, and the appended drawings, in which: [Fig.1] is a schematic representation of a first embodiment of a device according to the invention, seen from the side, [Fig.2] is a schematic representation of a second embodiment of a device according to the invention, seen from the side, [Fig.3] is also a schematic representation of a third embodiment of a device according to the invention, seen from the side, [Fig.4] shows an example of an embodiment of an installation according to the invention, implementing several devices according to the invention, seen in perspective,[Fig.5] is yet another schematic representation of a fourth embodiment of a device according to the invention, seen from above, and [Fig.6] is an example of an insert with a honeycomb structure, deployed, positioned in a chamber of a device according to the invention, the insert in the chamber being seen from below. Figure 1 illustrates an embodiment of a device according to the invention, making it possible to expand and compress a gas, making it possible to store mechanical energy and to restore it. The device thus comprises a mechanical actuator 1, which comprises for example a crankshaft 10 (mechanical member ensuring the conversion of an alternating linear movement into a continuous rotation according to the connecting rod 11 / crank 12 system, and ensuring the conversion of a continuous rotational movement into an alternating linear movement). A motor, not shown, makes it possible to convert the source energy. Generally,the source energy is electricity. However, another source of rotational motive force could be considered. It should be noted that the system does not require a "starter" to initiate rotation: for example in energy release mode (expansion), the crankshaft is rotated directly by the compression / expansion chambers, without assistance from the electric motor / generator. The crank 12 is connected to two solid pistons 21 and 22, each being mounted to move in a first chamber 31 and in a second chamber 32 respectively. Each chamber 31 and 32 comprises a liquid piston 41 and 42, respectively, which is moved in the chamber by being pushed by the solid piston 21 and 22 which moves in the same chamber. Each of the first and second chambers 31 and 32 are made of bent tubes, having: - a first tube portion 33 and 34, respectively, which extends in a substantially horizontal direction,and - a second tube portion 35 and 36, respectively, which extends in a substantially vertical direction. It should be understood that the invention is not limited to the implementation of chambers of bent shape (in other words, they could have a different shape without departing from the scope of the invention). The two solid pistons 21 and 22 are movable in displacement in the first tube portion 33 and 34, respectively, being driven in displacement by the actuator 1. The two liquid pistons 41 and 42 are movable in displacement in the first (33, 34) and second (35, 36) tube portions of the chambers 31 and 32, when they are pushed or sucked by the displacement of the solid piston 21 or 22 associated with them. The second tube portions 35 and 36 are designed to receive and evacuate a gas 3, for example air,so that the movement of the liquid 4 of the liquid pistons 41 or 42 in the chambers 31 and 32 causes either the compression of the gas 3 or an expansion of the gas 3. To do this, each of the chambers 31 and 32 comprises an outlet opening 37 and 38, respectively, ensuring in particular the entry and exit of gas into the second tube parts 35 and 36 of the first and second chambers 31 and 32. The first and second outlets 37 and 38 are connected to a phase separator 2, which makes it possible to receive the gas 3 and possibly a little liquid 4 coming from the liquid evacuated from the chambers 1 and 2. The phase separator 2 is connected to a pressurized gas storage tank 5. The circulation of the gas 3 and possibly the liquid 4 between the phase separator 2, the chambers 31 and 32 and the storage tank will be explained later. The second parts of tubes 35 and 36 each accommodate an insert 51 and 52. The inserts 51 and 52 are openwork inserts,that is to say that they each comprise cells in which the liquid of the liquid pistons 41 and 42 can circulate and which can also accommodate the compressed or expanded gas in the chambers 31 and 32. The inserts 51 and 52 are special: they are made from a core of deployable sandwich material, which makes it possible to obtain an insert where the cells extend from one side of the insert to the other: The core of the deployable sandwich material of the insert is made by a multitude of layers of plastically deformable materials, connected together by points of attachment (welds, glue, etc.) which extend along lines running along the entire length of the layers. By moving the two outer layers of the sandwich structure away from each other, cells are created between two contiguous layers of material and the lines of attachment,which makes it possible to obtain cells that extend over the entire length of the multilayer structure. According to an alternative embodiment (not illustrated), the inserts could be made with a winding of stacked metal sheets, the stacked metal sheets comprising for example a flat sheet and a curled sheet (forming a succession of hollows and bumps) positioned one on top of the other and rolled together: the cells are then formed between the hollows of the curled sheet and the surface of the adjacent sheet, the cells then extending in the direction of movement of the liquid piston in the chamber which accommodates the insert. Thus, the insert used in the context of the invention has so-called "through" cells, that is to say that the cells each have two openings, each at one end of the cell,with a first cell opening opening at one end of the insert and a second opening opening at another end of the insert: Figure 6 shows the second tube portion 35 (or 36) of a chamber 31 (or 32) which has been cut away to better show the insert 51 or 52. Each of the inserts 51 or 52 is preferably made of aluminum and has contiguous cells 53 which together form a honeycomb pattern, and which include a first end opening 54 (visible in the figure), through which the gas 3 or the liquid 4 can enter or exit the insert. Another opening (not visible in the figure, but illustrated schematically by an arrow 55) opens near the outlet opening 37 and 38 of each of the chambers 31 and 32. Each cell 53 of the structure of the insert 51 or 52 forms a mini-tube into which gas 3 and liquid 4 can enter and exit,each mini-tube being oriented parallel or mainly parallel to the direction of movement of the liquid 4 and the gas 3 in the chamber 31 or 32 (more precisely each mini-tube has an axis parallel to that of the second tube part 35 or 36 which accommodates it). By "mainly parallel" we mean a geometric orientation between an entry point and an exit point of a cell relative to the axis of the insert: this orientation is either parallel or substantially parallel to the axis of the insert, or inclined relative to the axis of the insert, because of the shape of the mini-tube of the cell. Indeed, the cell can be straight, the mini-tube then being cylindrical in shape, but the cell can also be twisted, the mini-tube then forming a helix. In Figure 1, two fluid / fluid exchangers 71 and 72 are also illustrated: each of the first and second chambers 31 and 32 comprises a fluid / fluid exchanger 71 and 72,respectively (shown in the elbow of chambers 31 and 32 in the figure). The fluids are preferably water. In this example, these fluid / fluid exchangers 71 and 72 are each connected to a pump 83, a fluid / air exchanger 84, a fan motor 85 and control valves 86. The assembly ensures that the liquid 4 (liquid pistons) is maintained at a temperature close to ambient temperature at plus or minus 10 degrees Celsius. A single pump could be provided, without departing from the scope of the invention. Similarly, the fluid / air exchanger 84 could be replaced by a fluid / fluid exchanger. The pump 83, the fluid / air exchanger 84, the fan motor 85 and the control valves 86 have not been shown in Figure 1: they are however found in the embodiment illustrated in Figure 3. These elements ensure that the fluid in the cooling loop is maintained at a temperature close to ambient temperature,plus or minus 5 degrees Celsius. The operating mode of the device shown in Figure 1 will now be presented: The motor of the mechanical actuator is for example a permanent magnet synchronous rotary motor, and is possibly associated with a reversible speed reducer (target speed of 30 rpm). Such a motor allows the rotation of the crankshaft 10: the connecting rods 11 which connect the crankshaft crank to each solid piston 21 and 22 drive the solid pistons 21 and 22 in linear displacement alternately: when the piston 21 is pulled, the piston 22 is pushed, and vice versa. The operating principle in compression mode is as follows: the solid piston 21 pushes the liquid piston 41 into the chamber 31 which is closed. The reduction in the volume of gas, pushed by the liquid piston 41 into the insert 51,increases the gas pressure in the insert 51. Each cell 53 acts as a small liquid piston while ensuring a perfect seal between the liquid and gaseous medium. The insert 51 functions as a regenerative exchanger between the gas and the fluid of the liquid pistons. The presence of the insert 51 then offers a large contact surface with the gas 3 and allows significant heat exchange potential: the heat exchange between the gas and the insert, the heat transfer within the insert and its own heat capacity makes it possible to maintain the temperature of the gas during its compression at a value close to the initial temperature of the assembly: this is how the operation is considered to be quasi-isothermal. When the air pressure reaches the desired value,a non-return valve 13 opens allowing the compressed gas 3 to escape from the chamber 31. The liquid piston 41 continues its rise in the chamber 31 until it touches an end wall of the chamber in order to escape all the compressed gas 3. The solid driving piston, which has reached the end of its stroke, changes direction and the same process is repeated on the second piston 22 of the device made up of exactly the same components. The descent of the liquid piston 41 after the end of compression in the first chamber 31 allows gas 3 at low pressure to be admitted into this chamber 31 by the opening of another valve 14 (non-return valve). Concerning the thermal energy captured in the gas by the insert 51 (the honeycomb structure) during compression, this energy has caused the temperature of the insert 51 to increase by a few degrees Celsius, reflecting the storage of this thermal energy in the material. The rise of the liquid piston 41,filling the entire volume of the chamber 31 at the end of compression, thus allows the thermal insert 51 loaded with thermal energy to be brought into contact with the liquid 4. The solid / liquid heat transfer between the insert 51 and the liquid 4 of the liquid piston 41 being much more powerful than the solid / gas heat transfer between the insert 51 and the gas 3, a significant heat exchange appears between the walls and the liquid 4 causing the insert 51 – liquid 3 assembly to tend towards a slightly higher equilibrium temperature (of the order of a tenth of a degree above the initial temperature of the liquid) and therefore lower than the temperature of the insert 51 before contact with the liquid 4. When a new volume of gas 3 to be compressed is admitted, the liquid 4 forming the descending liquid piston 41 passes through the fluid / fluid heat exchanger 71 whose role is to keep the temperature of the liquid piston 41 stable over time. Leaving room 31,the compressed gas 3 passes through the gas / liquid separator 2, possibly allowing a fraction of the liquid 4 constituting the liquid piston to be collected in the event of the top dead center of the chamber 31 being exceeded. At the outlet of this separator 2, the gas 3 is conveyed to its storage or another gas compression stage in the storage tank 5. The liquid 4 retained in the separator helps to constitute a reserve of liquid for the pistons 41 and 42,a fraction of which can be redirected to the compression chambers 31 and 32 in order to maintain a volume of liquid capable of guaranteeing the continuous operation of the system. The valves 13 and 16 are connected between the gas / liquid separator 2 (whose internal pressure is equal to the compression pressure of the gas) and the base of the compression chamber 31 (whose pressure varies between the inlet pressure and the maximum pressure). The valves 13 and 16 allow the compressed gas to be transferred between the compression chambers and the separator, the gas being able to include a fraction of fluid from the liquid piston. It will be noted that the outlet 38 of the chamber 32 also has two non-return valves 15 and 16: the valve 15 ensures an air supply at atmospheric pressure (or at low pressure). The valves 13, 14,15 and 16 can be replaced by pilot-controlled valves. Reference will now be made to the operating principle in expansion mode of the gas 3. The reverse operation of the device, i.e. as a pressure energy converter into electrical energy, operates on the same general principle and is possible thanks to the embodiment illustrated in Figure 2, by replacing the valves 13 to 16 with pilot-controlled valves 64, 61, 62 and 65: The compression chamber 32, initially full of liquid, admits a volume of gas 3 under pressure through the valve 65. The pressure applied to the liquid piston 42 is applied to the solid piston 22 generating mechanical work. This mechanical work is converted into electricity by the crankshaft / generator assembly. When the volume of gas 3 under pressure admitted is sufficient,the valve 65 closes and the expansion of the gas 3 continues to move the solid piston 22. The movement (and the energy conversion) stops when the gas 3 reaches a pressure close to the low pressure (generally atmospheric). During the intake and expansion phases, the opposite liquid piston 41 has passed from its low point to its high point, expelling the gas 3 expanded at atmospheric pressure towards the outside through the valve 61. The chamber 32 is thus an expansion chamber, and the heat exchange insert 52 is here cooled by the gas 3 during the expansion while maintaining the expansion of the gas 3 following a quasi-isothermal evolution. The liquid / liquid exchanger 12 then allows the heating of the liquid piston 42. The embodiment shown in FIG. 2 comprises a second phase separator 6 at atmospheric pressure which allows, during the descent of the liquid piston 42 (or 41,when the liquid piston 42 acts by compressing the gas 3) to collect a possible fraction of liquid 4 coming from the liquid piston 41 or 42, but at low pressure. In the embodiment illustrated in Figure 2, the mechanical actuator comprises a single solid piston 23 which moves either in one direction in the chamber 31 or in the opposite direction in the chamber 32. This is a linear motor magnetic piston. The operating mode is the same as that described for the device shown in Figure 1. The difference is in the presence of this second low pressure phase separator 6. As seen previously,the role of phase separators 2 and 6 is to recover the liquid 4 expelled at the end of the stroke of the liquid piston 41 or 42 while allowing the gas 3 to continue on its way. The volume of the separators 2 and 6 is chosen so that the speed of the gas 3 decreases sufficiently so that the liquid 4 falls naturally to the bottom of the buffer volume. Other complementary solutions can be envisaged, in particular the use of cyclonic systems or coalescence grids. The pressure drop of the gas in this element must remain low. A hydraulic connection 20 between the phase separator 2 and the bottom of the compression chambers 31 and 32 (this can be in the second vertical tube part 35 and 36, or in the first horizontal tube part 33 and 34),allows a low flow rate of liquid 4 to be continuously admitted, compensating for entrainment losses during flushing. A flow rate adjustment valve 24 fitted to each hydraulic connection allows this flow rate to be varied in order to experimentally find the optimal setting. Each liquid piston 41 and 42 has a valve 61 and 62 (respectively) allowing the liquid 4 to escape to the second non-pressurized separator 6 in the event of overpressure in the chamber 31 and / or 32. A lifting pump 63 between the two separators 2 and 6 allows the liquid 4 lost in expansion mode in the non-pressurized separator 6 to be returned to the pressurized separator 2 when the gas 3 is released at atmospheric pressure. Two other valves 64 and 65 allow the compressed gas to be transferred between the compression chambers 31 and 32 and the separator 2, the gas possibly comprising a fraction of fluid from the liquid piston. If the liquid buffer volume 4 is sufficient,the operation of pump 63 is intermittent and rare. The regulation of this pump is done on the basis of the liquid levels in the two separators 2 and 6. The embodiment illustrated in figure 3 concerns the implementation of a device comprising three solid pistons with six liquid pistons: the principle of the "double-acting" piston here makes it possible to optimize the use of the mechanical parts. Indeed, it is possible to achieve significant powers (several tens, hundreds of MW), by multiplying the number of pistons. It may also be possible to increase the power by excessively increasing the diameter of the pistons and chambers, but multiplying the number of pistons and chambers will be preferred. On the one hand, there is an optimum economic size for producing the device, which is easily transportable (piston diameter between 300 mm and 2000 mm for example, for high-power versions). On the other hand,multiplying the number of pistons makes it possible to reduce the amplitude of variation of the power exchanged with the network if a judiciously established phase shift exists between the sets of two pistons. The increase in the system outlet pressure can also be achieved by staging the compressions with the cascade use of compressors as described below. In the case of stages whose inlet pressure is higher than atmospheric pressure (to compress at high pressure), the design of the piston translation system can advantageously use the 1 to 1 coupling, in opposition of the pistons. Indeed, the high pressure inlet force of one chamber is counterbalanced by the compression force at a higher pressure in the opposite chamber. More precisely, the double-acting operation,has advantages: the high-pressure intake force of one chamber is directly reused in the compression force at a higher pressure in the opposite chamber without passing through the mechanical power elements such as the connecting rod, the crankshaft or the engine / generator. Generally speaking, whether in single-acting or double-acting mode, multiplying the number of solid pistons attached to the same crankshaft, but cleverly out of phase, makes it possible to limit variations in torque and power during operation of the installation. Limiting these variations makes it possible to limit stresses on the components, increasing the reliability of the assembly and limiting the necessary oversizing. The mechanical actuator 1 of the device shown in Figure 3 thus comprises three pistons,of which only one (piston 25) is shown (the pistons are out of phase by 120°) on the mechanical actuator. This embodiment makes it possible to achieve a higher pressure than those achieved by the embodiments shown in figures 1 and 2. In this embodiment, three successive stages of compression or expansion are thus implemented, each compression chamber corresponding to a compression stage to be achieved. For example, the first chamber has a compression stage of 11 bars,the second chamber having a stage capable of increasing the compression from 11 bars to 70 bars and the third chamber allowing the increase from 70 bars to 300 bars. It is also possible to allow two of these chambers to constitute medium pressure and high pressure stages. The embodiment illustrated in Figure 3 comprises in particular a first regulating valve 91 calibrated to a safety pressure between said first chamber 31 and said first separator 2 and a second regulating valve 92 calibrated to a safety pressure between said second chamber 32 and said first separator 2, to allow the evacuation of a volume of liquid from said at least one first or second liquid piston to the first separator 2. Figure 4 illustrates an installation according to the invention, which comprises a series of devices according to the invention. A common crankshaft type mechanical actuator makes it possible to actuate twelve pairs of solid pistons 21 and 22,movable in twelve pairs of chambers 31, 32, thanks to the movements of the cranks 12 mounted on a movable shaft rotating around its axis, the cranks being connected to the solid pistons 21 and 22 thanks to the connecting rods 11. It is noted that all the outlet openings 37 and 38 of the chambers 31 and 38 are connected together to a first phase separator 2 and to a second phase separator 6 at atmospheric pressure: in other words, the pressure phase separator 2 is connected: - to the valves 64 of the chambers 31, the valves 64 all being connected to the same discharge pipe and - to the valves 65 of the chambers 32, the valves 65 all being connected to another common discharge pipe. In addition, all the valves 61 of the chambers 31 are connected to another common discharge pipe, connected to the second separator, and all the valves 62 of the chambers 32 are also connected to another common discharge pipe,itself connected to the second separator 6 at atmospheric pressure. It should be noted that the valves 61 and 62 are low pressure (or atmospheric pressure) air intake valves in Figures 2, 3 and 4. They correspond to the same function as the valves 14 and 15 shown in Figure 1. In this embodiment, it is provided that the solid pistons 21 and 22 have a diameter of 2.5 m and a stroke of 1 m. The discharge pressure is substantially 11 bar, the intake pressure 1 bar, the compression time 1 second. A motor is used to operate the mechanical actuator. However, in addition, two motor / pump assemblies,of low power compared to the power of the main engine are required to operate the cooling circuit (pump 83) and to transfer liquid 4 from separator 6 to separator 3 (pump 63). The shaft rotation speed is approximately 30 rpm. The total size of such an installation is approximately 7m high, 8m wide and 45m long. An average power of 15MW is achieved with a variation amplitude of less than 0.8MW at a frequency of 12Hz. The ramp-up time to full power is of the order of a second (from 10% to 100% of the nominal power). A start-up time (from complete shutdown to 100% of the nominal power) of the order of ten seconds is expected. Once started, the power of the system can easily be adjusted by modifying the rotation speed of the engine / generator (and therefore of the crankshaft) or by adjusting the control of valves 61, 62, 64 and 65. Thus,a variation range between 20% and 100% of the nominal power can be exploited, with a rapid response time (of the order of a second). Figure 5 shows yet another embodiment with five chambers 31, 31', 31'', 32, 32' arranged in a star-shaped architecture, associated with double-action pistons 26: The use of double-action cylinders / pistons 26 allows both an increase in power for the same number of pistons, but also better management of liquid leaks through the piston rings. Indeed,the liquid passing through the piston seals simply ends up in the opposite chamber without it being necessary to drain the leaked liquid. It is understood from the preceding description how the invention makes it possible to transform a mechanical movement into pressurization energy of a gas and how this energy can be used to generate a mechanical movement. It should be understood that the invention is not limited to the implementation of the examples specifically described and illustrated above and that it extends to the implementation of any equivalent means. In particular, the application of the method is not specific to air gas and, 5 water fluid. Other applications are envisaged by the invention, such as the compression / expansion of (H2, CO2, CH4, etc.) with water as the liquid piston fluid, but also ionic liquids, solvents, oils, organic liquids, etc.

Claims

CLAIMS 1. Device for isothermal expansion and compression of a gas (3), ensuring the compression of said gas (3) by consuming mechanical energy and the restitution of mechanical energy by the expansion of said gas (3), said device comprising: - at least one first and at least one second liquid piston (4, 41, 42), movable in displacement respectively in a first and a second chamber (31, 32), each of said at least one first and second chambers (31, 32) comprising a gas (3), capable of being compressed or expanded under the effect of the displacement of said at least one first or second liquid piston (4, 41, 42), - an actuator (1), capable of ensuring the displacement of said at least one first and second liquid piston (4, 41, 42) in said first and second chamber (31, 32), each of said at least one first and second chambers (31, 32) respectively each comprising at least one first and at least one second openwork insert (51, 52),through which said liquid (4) and said gas (3) can circulate, characterized in that said actuator (1) is a mechanical actuator comprising at least one solid piston (21, 22), in that said perforated insert (51, 52) comprises through cells (53), which extend between a first cell opening (54) opening at one end of said insert (51, 52) and a second cell opening (55) opening at a second end of said insert (51, 52), said cells (53) being oriented in a direction which is either parallel to the direction of movement of said liquid piston (41, 42) in said insert (51, 52) or inclined relative to the direction of movement of said liquid piston, and in that said device further comprises at least one first phase separator (2) connected to a first outlet (37) of said first chamber (31) and to a second outlet (38) of said second chamber (32)., 2. Device according to claim 1, characterized in that said phase separator (2) is connected to a tank (5) for storing pressurized gas (3).

3. Device according to claim 2, characterized in that it comprises a second separator (6), connected to said first and second outlets (37, 38) of said first and second chambers (31, 32), respectively, in that said first separator (2) comprises a first internal pressure which corresponds to the internal pressure of the gas (3) included in said pressurized gas tank (5) and in that said second separator (6) comprises a second internal pressure which corresponds to atmospheric pressure.

4. Device according to claim 3, characterized in that said first and second separators (2, 6) are in fluid communication with each other to allow the passage of liquid (4) from the first separator (2) to the second separator (6). 5.Device according to any one of claims 3 or 4, characterized in that it comprises a first air intake device (61) ensuring the passage of air at atmospheric pressure between said at least one first chamber (31) and said second separator (6) and in that it comprises a second air intake device (62) at atmospheric pressure between said at least one second chamber (32) and said second separator. 6.Device according to any one of claims 3, 4 or 5, characterized in that it comprises a third air intake device (13, 64) ensuring the passage of compressed air between said first chamber (31) and said first separator (2) and in that it comprises a fourth compressed air intake device (16, 65) between said second chamber and said first separator (2). 7.Device according to any one of claims 3 to 6, characterized in that it comprises a first low flow rate regulating valve (24) ensuring the passage of fluids from said first separator (2) to said first chamber (31) and in that it comprises a second low flow rate regulating valve (24) ensuring the passage of fluids from said first separator (2) to said second chamber (32).

8. Device according to any one of claims 3 to 7, characterized in that it comprises a calibrated regulating valve (91, 92) at a safety pressure between said first chamber (31) and said first separator (2) and / or between said second chamber (32) and said first separator (2), to allow the evacuation of a volume of liquid from said at least one first or second liquid piston towards the first separator (2). 9.Device according to any one of the preceding claims, characterized in that each of the first and second chambers (31, 32) is fluidically connected to a fluid / fluid exchanger (71, 72) which makes it possible to maintain said at least one first and second liquid pistons (41, 42), respectively, at ambient temperature, preferably with a tolerated temperature variation of plus or minus 10 °C, said fluid / fluid exchanger (71, 72) preferably comprising a pump (83), a fluid / air exchanger (84) or a fluid / fluid exchanger, possibly a motor-driven fan (85) if said exchanger is a fluid / air exchanger (84) and possibly at least one regulating valve (86).

10. Device according to any one of the preceding claims, characterized in that the insert (51, 52) comprises a core of structural material comprising a deployed honeycomb structure. 11.Device according to any one of the preceding claims, characterized in that said mechanical actuator (1) comprises a magnetically actuated linear motor (23). 12.Device according to any one of the preceding claims, characterized in that said mechanical actuator (1) comprises a motor associated with a crankshaft. 13.Device according to any one of the preceding claims, characterized in that said mechanical actuator comprises a motor associated with a worm screw. 14.Installation comprising at least two devices according to any one of the preceding claims, characterized in that said mechanical actuators (1) of said at least two devices are mechanically linked to operate together, and in that it comprises a first phase separator (2) common to said at least two devices, said first. common phase separator being connected to a first outlet (37) of the first chambers (31) of the devices and to a second outlet (38) of the second chambers (32) of said devices, said first phase separator (2) being connected to a common tank (5) for storing pressurized gas.

15. Installation according to claim 14, comprising at least two devices according to claim 3, characterized in that it comprises a second separator (6) common to said at least two devices, said second common separator (6) being connected to said first and second outlets (37, 38) of said first and second chambers (31, 32) of each of said at least two devices,in that said first common separator (2) comprises a first internal pressure which corresponds to the internal pressure of the gas included in said common reservoir (5) of pressurized gas and in that said second separator (6) comprises a second internal pressure which corresponds to atmospheric pressure.

16. Method for implementing a device according to any one of claims 1 to 13, characterized in that it comprises the following steps: - actuation of the mechanical actuator (1), - displacement of said at least one solid piston (21, 22, 23) driving said first liquid piston (41) in said first chamber (31) and said second liquid piston (42) in said second chamber (32), said first and second liquid pistons (41, 42) being driven in displacement in opposite directions, the first liquid piston (41) compressing said gas (3) in the insert (51) of said first chamber (31) up to a first predetermined pressure,the second liquid piston (42) creating a vacuum in said insert (52) said second chamber (32) up to a second pressure, - when said first pressure is reached, opening an air intake device (13) between said first chamber (31) and said first phase separator (2) to evacuate the gas (3) under pressure from the first chamber (31) to said first separator (2) until said liquid piston (41) passes entirely through said insert (51), and reaches the first outlet (37) of the first chamber (31), and simultaneously the air intake (14) in said second chamber (32).

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