Devices for energy conversion

Abstract

The present invention relates to a device for isothermal expansion and compression of a gas (3), ensuring the compression of the gas by expenditure of mechanical energy and the recovery of mechanical energy by expansion of the gas. The device comprises at least two liquid pistons (4, 41, 42) movable in at least two chambers (31, 32), each containing a gas that can be compressed or expanded by the movement of the 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 the liquid (4) and the gas can circulate, the insert comprising a through-hole (53) extending in a direction parallel to the movement direction of the liquid pistons within the insert. The device comprises at least one first phase separator connected to the outlet of each chamber and to a tank (5) for storing pressurized gas.

Description

Detailed Description of the Invention

[0001] The present invention relates to a system for energy conversion and storage.

[0002] In the literature, the compression and / or expansion of gases by liquid pistons appears to be a promising solution for increasing the energy efficiency of power plants, with the aim of achieving a thermodynamic development that is as isothermal as possible.

[0003] Techniques using pumps or turbines to achieve energy conversion between a mechanical actuator and a liquid in a liquid piston are known, such as that described in patent application FR 3036887. In such systems, one or more liquid piston compression steps are implemented to achieve the desired gas pressure range.

[0004] Various facilities or devices can be installed to enhance heat exchange in the liquid piston compression chamber, such as spraying water droplets, operating multiple chambers in parallel, adding heat exchange inserts, and the like.

[0005] These installations present a number of problems: in particular, to achieve near-isothermal compression / expansion, large heat exchanges are required in the expansion and / or compression chambers, which are orders of magnitude larger than existing heat exchanges in the prior art.

[0006] The installation proposed in patent application FR 3036887 increases the compression / expansion times but uses simple technical solutions to achieve near-isothermal operation. However, the result is a very large and space-consuming plant (15 MW of power generation). Approximately 50,000 m at the plant 3 ), which can lead to high operating costs.

[0007] Other technologies offer solutions that take up less space, but are more complex to implement, which means they do not reduce operational costs.

[0008] Thus, the level of complexity and expense of such equipment is an obstacle preventing the development of such technology.

[0009] The present invention provides an alternative solution that is simple to implement and can be specifically designed and sized for each application.

[0010] To this end, the invention relates to a device for isothermal expansion and compression of a gas, ensuring the compression of said gas by expenditure of mechanical energy and the recovery of mechanical energy by expansion of said gas, said device comprising: - at least one first and at least one second liquid piston movable in a first and second chamber, respectively, said at least one first and second chamber each containing a gas that can be compressed or expanded by movement of said at least one first or second liquid piston; an actuator capable of moving said at least first and second liquid pistons within said first and second chambers; the at least one first and second chambers each include at least one first and at least one second perforated insert, respectively, through which the liquid and the gas can flow; It is equipped with:

[0011] The device according to the invention is notable in that the actuator is a mechanical actuator comprising at least one solid piston, the perforated insert comprises through cells extending between a first cell aperture opening at one end of the insert and a second cell aperture opening at a second end of the insert, the cells being oriented either parallel to the direction of movement of the liquid piston within the insert or obliquely relative to the direction of movement of the liquid piston. Finally, the device further comprises at least a first phase separator connected to a first outlet of the first chamber and a second outlet of the second chamber.

[0012] 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 the first and second outlets of the first and second chambers, respectively, the first separator having a first internal pressure corresponding to the internal pressure of the gas contained in the pressurized gas tank, and the second separator having a second internal pressure corresponding to atmospheric pressure.

[0013] Preferably, the first and second separators are in fluid communication with each other so that liquid can pass from the first separator to the second separator.

[0014] Even 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, and similarly a second air intake device at atmospheric pressure between said at least one second chamber and said second separator.

[0015] Additionally, the device includes a third air intake device for passing compressed air between the first chamber and the first separator, and a fourth air intake device for passing compressed air between the second chamber and the first separator.

[0016] Even more preferably, the device comprises a first low flow control valve for passing fluid from the first separator to the first chamber, and a second low flow control valve for passing fluid from the first separator to the second chamber.

[0017] According to an advantageous embodiment, the device comprises a regulating valve set to a safe pressure between the first chamber and the first separator and / or between the second chamber and the first separator, in order to allow the ejection of a large volume of liquid from the at least one first or second liquid piston into the first separator.

[0018] In addition, each of the first and second chambers is preferably also fluidly connected to a fluid / fluid exchanger that enables said at least one first and second liquid piston, respectively, to be maintained at ambient temperature, preferably with an acceptable 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, optionally an electric fan if said exchanger is a fluid / air exchanger, and optionally at least one control valve.

[0019] Advantageously, the insert comprises a core of structural material with an expanded honeycomb structure. Even more advantageously, the mechanical actuator comprises a magnetically actuated linear motor. In one embodiment, the mechanical actuator comprises a motor associated with a crankshaft. In yet another variation, the mechanical actuator comprises a motor associated with a worm screw.

[0020] The present invention further relates to an installation comprising at least two devices as defined herein above, wherein the mechanical actuators of the at least two devices are mechanically linked to operate in tandem, and the installation comprises a first phase separator common to the at least two devices, the common first phase separator being connected to a first outlet of a first chamber of the device and to a second outlet of a second chamber of the device, and the first phase separator being connected to a common pressurized gas storage tank.

[0021] In an embodiment in which the installation comprises at least two devices each equipped with two phase separators, and a second separator is common to the at least two devices, the second separator is connected to the first and second outlets of the first and second chambers of each of the at least two devices, the common first separator having a first internal pressure corresponding to the internal pressure of the gas contained in the common pressurized gas tank, and the second separator having a second internal pressure corresponding to atmospheric pressure.

[0022] Finally, the present invention relates to a method for operating a device as defined above, said method comprising the following steps: - actuating a mechanical actuator; - moving said at least one solid piston to move said first liquid piston in said first chamber and said second liquid piston in said second chamber, said first and second liquid pistons being moved in opposite directions such that the first liquid piston compresses the gas in an insert in said first chamber to a first predetermined pressure and the second liquid piston reduces pressure in said insert in said second chamber to a second pressure; when said first pressure is reached, opening an air intake device between the first chamber and the first phase separator to allow pressurized gas to be discharged from the first chamber into the first separator until the liquid piston passes completely through the insert and reaches a first outlet of the first chamber and simultaneously an air intake of the second chamber; Includes.

[0023] The device according to the invention is thus a kind of reversible gas compressor, capable of compressing a gas while consuming mechanical energy, but also recovering this mechanical energy by expanding the gas. The thermodynamic evolution of this gas is quasi-isothermal, allowing the pressure fluctuations mentioned above to be achieved with little energy loss thanks to the compression / expansion of the liquid piston. The properties of the gas and liquid can be adapted to the needs of the application for which the device is intended (air, hydrogen, methane, gas, water, etc.).

[0024] In compression mode, in the context of the non-limiting embodiments presented below, the principle is based on the compression of a gas by a liquid piston that is moved by a solid piston. The solid piston is driven directly by a linear motor, where the piston is the moving part containing a magnet, or by another piston movement system (connecting rod, crank, rack, etc.). As it moves, the solid piston pushes the liquid piston into a closed compression chamber (vertical cylinder). The gas is compressed as a result of the reduction in volume.

[0025] The cylindrical compression chamber is subdivided into many smaller volumes by an extruded 2D pattern of heat exchange inserts whose cells extend towards the liquid piston (also known as "honeycomb" structures made of aluminum or other heat conducting material).

[0026] The fluid properties of the liquid piston allow a small liquid piston to form within each honeycomb cell, ensuring a perfect seal between the liquid and gas medium. The presence of the insert (honeycomb) provides a very large gas contact surface, significantly increasing the heat exchange potential. The heat exchange between the gas and the insert, the heat transfer within the insert, and the heat capacity of the insert itself ensure that the temperature of the gas during compression remains close to the initial temperature of the assembly (quasi-isothermal).

[0027] The heat exchange insert thus acts as a regenerative heat exchanger, sequentially transferring thermal energy from the gas to the insert by convection / conduction, storing the thermal energy thanks to its moderate temperature rise (because of its heat capacity), and then transferring this thermal energy to the liquid by convection / conduction.

[0028] Other advantages and features of the invention will become apparent upon examination of the detailed description of an entirely non-limiting implementation and from the accompanying drawings. [Brief explanation of the drawings]

[0029] [Figure 1] 1 is a schematic side view of a first embodiment of a device according to the invention; [Figure 2] 2 is a schematic side view of a second embodiment of a device according to the invention; FIG. [Figure 3] FIG. 2 is another schematic side view of a third embodiment of a device according to the invention. [Figure 4] 1 is a perspective view of an exemplary embodiment of an installation according to the invention, which implements several devices according to the invention; [Figure 5] FIG. 4 is a further schematic view of a fourth embodiment of the device according to the invention, seen from above. [Figure 6] 1 shows an example of an insert with a honeycomb structure installed and positioned in a chamber of a device according to the invention, viewed from below in the chamber.

[0030] FIG. 1 shows an embodiment of a device according to the invention for expanding and compressing gases, which allows the storage and recovery of mechanical energy.

[0031] The device thus comprises a mechanical actuator 1, which comprises, for example, a crankshaft 10 (a mechanical member that converts reciprocating linear motion into continuous rotation by means of a connecting rod 11 / crank 12 system, and that converts continuous rotational motion into reciprocating linear motion). A motor (not shown) converts the source energy. Typically, the energy source is electrical; however, alternative sources of rotational drive power are contemplated.

[0032] It is worth noting 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 the assistance of an electric motor / generator.

[0033] The crank 12 is connected to two solid pistons 21 and 22, each mounted for movement within a first chamber 31 and a second chamber 32, respectively.

[0034] Each chamber 31 and 32 contains a liquid piston 41 and 42, respectively, which is moved within the chamber by being pushed by solid pistons 21 and 22 which also move within the same chamber.

[0035] The first and second chambers 31 and 32 are each made of a vent tube, - the first tube portions 33 and 34 each extend in a substantially horizontal direction; and the second tube portions 35 and 36 each extend in a substantially vertical direction; It is characterized by:

[0036] It should be understood that the present invention is not limited to the use of angled chambers (in other words, it is contemplated that the chambers may have a variety of shapes without departing from the scope of the present invention).

[0037] Two solid pistons 21 and 22 are driven by the actuator 1 and are movable in the first tube portions 33 and 34 respectively.

[0038] The two liquid pistons 41 and 42 are movable within the first (33, 34) and second (35, 36) tube portions of the chambers 31 and 32 when pushed and pulled by the movement of the associated solid piston 21 or 22.

[0039] The second tube portions 35 and 36 are designed to receive and expel a gas 3, e.g., air, so that movement of the liquid 4 from the liquid pistons 41 or 42 in the chambers 31 and 32 causes either compression of the gas 3 or expansion of the gas 3.

[0040] For this purpose, each of the chambers 31 and 32 is provided with an outlet opening 37 and 38, respectively, to ensure gas passage in and out of, in particular, the second tube portions 35 and 36 of the first and second chambers 31 and 32.

[0041] The first and second outlets 37 and 38 are connected to a phase separator 2 which contains gas 3 and possibly some liquid 4 originating from the liquid discharged from chambers 1 and 2 . The phase separator 2 is connected to a pressurized gas storage tank 5 . The flow of gas 3 and possibly liquid 4 between the phase separator 2, chambers 31 and 32 and the storage tank will be explained later.

[0042] The second tube portions 35 and 36 contain inserts 51 and 52, respectively. Inserts 51 and 52 are perforated inserts, i.e., each insert has cells through which liquid from liquid pistons 41 and 42 can flow and which can also accommodate compressed or expanded gas in chambers 31 and 32.

[0043] Inserts 51 and 52 are special in that they are made from a core of expandable sandwich material, with the resulting insert having cells penetrating the insert:

[0044] The expandable sandwich core of the insert is made of multiple layers of plastically deformable material joined by bonds (welds, adhesives, etc.) that extend along lines running along the length of the layers. By moving the two outer layers of the sandwich structure away from each other, cells are created between the two adjacent layers of material and the bond lines, resulting in cells that extend along the entire length of the multi-layer structure.

[0045] In an alternative embodiment (not shown), the insert may be fabricated by rolling a stack of metal sheets, such as a flat sheet and a corrugated sheet (with continuous valleys and peaks) superimposed and rolled together, so that cells are formed between the valleys of the corrugated sheets and the surfaces of the adjacent sheets, the cells extending in the direction of movement of a liquid piston within the chamber containing the insert.

[0046] Thus, the inserts used in the present invention feature so-called "through cells," i.e., the cells each have two openings, each located at one end of the cell, with the first cell opening leading to one end of the insert and the second opening leading to the other end of the insert. Figure 6 shows the second tube portion 35 (or 36) of chamber 31 (or 32) cut away to better view insert 51 or 52.

[0047] Each insert 51 or 52 is preferably made of aluminium and has adjacent cells 53 which together form a honeycomb pattern, the cells having first end openings 54 (visible in the figures) through which gas 3 or liquid 4 can enter or exit the insert. A further opening (not shown in the figures but indicated diagrammatically by arrow 55) opens into chambers 31 and 32 near the outlet openings 37 and 38 respectively.

[0048] Each cell 53 of the insert structure 51 or 52 forms a mini-tube through which the gas 3 and liquid 4 can pass, each mini-tube being oriented parallel or primarily parallel to the direction of movement of the liquid 4 and gas 3 in the chamber 31 or 32 (more precisely, each mini-tube has an axis parallel to the axis of the second tube portion 35 or 36 containing it).

[0049] "Predominantly parallel" refers to the geometric orientation of the cell entry and exit points relative to the axis of the insert. This orientation can be either parallel or nearly parallel to the axis of the insert, or tilted relative to the axis of the insert due to the shape of the cell's mini-tubes. In fact, the cells can be straight, in which case the mini-tubes are cylindrical, or the cells can be twisted, in which case the mini-tubes form a helix.

[0050] 1 further shows two fluid / fluid exchangers 71 and 72: the first and second chambers 31 and 32 each have a fluid / fluid exchanger 71 and 72, respectively (shown in the figure at the bends of chambers 31 and 32). The fluid is preferably water.

[0051] In this embodiment, the fluid / fluid exchangers 71 and 72 are each connected to a pump 83, a fluid / air exchanger 84, an electric fan 85 and a control valve 86. The assembly ensures that the liquid 4 (from the liquid piston) is maintained at a temperature close to the ambient temperature, plus or minus 10°C.

[0052] It is contemplated that a single pump may be provided without departing from the scope of the present invention. Similarly, it is contemplated that the fluid / air exchanger 84 could be replaced with a fluid / fluid exchanger.

[0053] Pump 83, fluid / air exchanger 84, electric fan 85, and control valve 86 are not shown in Figure 1, but can be found in the embodiment shown in Figure 3. These components maintain the fluid in the cooling loop at a temperature close to ambient temperature, plus or minus 5°C.

[0054] The operating modes of the device shown in Figure 1 are as follows: The motor of the mechanical actuator is, for example, a synchronous motor with permanent magnets, possibly accompanied by a reversible reducer (target speed 30 rpm).

[0055] Such a motor allows the rotation of a crankshaft 10; connecting rods 11 connecting the cranks of the crankshaft to each of the solid pistons 21 and 22 cause the solid pistons 21 and 22 to move in an alternating linear motion: when piston 21 is pulled, piston 22 is pushed, and vice versa.

[0056] The principle of operation in compression mode is as follows: the solid piston 21 pushes the liquid piston 41 into the sealed chamber 31. The gas pressure in the insert 51 increases due to the gas volume being forced into the insert 51 by the liquid piston 41 decreasing.

[0057] Each cell 53 acts like a miniature liquid piston, ensuring a perfect seal between the liquid and gaseous media. The insert 51 functions as a regenerative heat exchanger between the gas and the liquid piston fluid. The presence of the insert 51 increases the contact surface with the gas 3 and the potential for heat exchange. The heat exchange between the gas and the insert, the heat transfer within the insert, and its own heat capacity make it possible to maintain the temperature of the gas during compression close to the initial temperature of the assembly. The operation is thus considered quasi-isothermal.

[0058] When the air pressure reaches the desired value, the check valve 13 opens to allow the compressed gas 3 to be released from the chamber 31 . The liquid piston 41 continues to rise in the chamber 31 until it contacts the end wall of the chamber and releases all of the compressed gas 3 .

[0059] The solid motor piston, having reached the end of its stroke, reverses direction and the same procedure is repeated for the second piston 22 of an identical device. The descent of the liquid piston 41 after the end of compression in the first chamber 31 opens another valve 14 (check valve) allowing low pressure gas 3 to enter this chamber 31.

[0060] Regarding the thermal energy trapped in the gas by the insert 51 (honeycomb structure) during compression, it was shown that this energy increases the temperature of the insert 51 by several degrees Celsius, and that this thermal energy is stored in the material.

[0061] As the liquid piston 41 rises and fills the entire volume of the chamber 31 at the end of compression, the thermal insert 51 , which has received the thermal energy, comes into contact with the liquid 4 .

[0062] Because the solid / liquid heat transfer between the insert 51 and the liquid 4 of the liquid piston 41 is much stronger than the solid / gas heat transfer between the insert 51 and the gas 3, there is a large heat exchange between the wall and the liquid 4, and as a result the equilibrium temperature of the insert 51-liquid 3 assembly tends to be slightly higher (about 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.

[0063] When a new gas 3 to be compressed is introduced, the liquid 4 forming the descending liquid piston 41 passes through a fluid / fluid heat exchanger 71, the role of which is to stabilize the temperature of the liquid piston 41 over time.

[0064] At the outlet of the chamber 31, the compressed gas 3 passes through a gas / liquid separator 2, which is believed to allow some of the liquid 4 that makes up the liquid piston to be recovered once it has passed the top dead center of the chamber 31. At the outlet of this separator 2, the gas 3 is conveyed to its storage or to another gas compression step in a storage tank 5.

[0065] The liquid 4 left in the separator serves to create a reserve liquid for the pistons 41 and 42, some of which can be pumped back into the compression chambers 31 and 32 to maintain an amount of liquid that can ensure continuous system operation.

[0066] Valves 13 and 16 are connected between the gas / liquid separator 2 (whose internal pressure is equal to the gas compression pressure) and the base of the compression chamber 31 (whose pressure varies between the inlet pressure and the maximum pressure). Valves 13 and 16 are used to transfer compressed gas between the compression chamber and the separator, where the gas may include some of the fluid in the liquid piston. It should be noted that the outlet 38 of the chamber 32 also features two check valves 15 and 16, with valve 15 ensuring an air supply at atmospheric (or low) pressure.

[0067] The check valves 13, 14, 15 and 16 may be replaced by pilot operated valves. Here, the operating principle in the expansion mode of the gas 3 will be mentioned.

[0068] The reverse operation of the device, i.e., conversion of pressure energy into electrical energy, works on the same general principle and can be implemented in the embodiment shown in FIG. 2 by replacing valves 13-16 with pilot operated valves 64, 61, 62 and 65.

[0069] The compression chamber 32 , which is initially filled with liquid, receives a volume of pressurized gas 3 through a valve 65 . Pressure applied to the liquid piston 42 acts on the solid piston 22, producing mechanical work.

[0070] This mechanical work is converted into electricity by the crankshaft / generator assembly. If the volume of pressurized gas 3 received is sufficient, valve 65 closes and the expansion of gas 3 continues to move solid piston 22 .

[0071] When the gas 3 reaches a pressure close to the lower pressure (usually atmospheric pressure), movement (and energy conversion) stops. During the intake and expansion phase, the opposing liquid piston 41 is moved from its lower position to its higher position, expelling the expanding gas 3 out through valve 61 at atmospheric pressure.

[0072] The chamber 32 is thus an expansion chamber, and the heat exchange insert 52 is cooled by the gas 3 as it expands, while the expansion of the gas 3 is maintained in a quasi-isothermal evolution. The liquid / liquid heat exchanger 12 then heats the liquid piston 42 .

[0073] The embodiment shown in FIG. 2 features a second phase separator 6 at atmospheric pressure, which allows for the recovery at low pressure of a small amount of liquid 4 coming from the liquid piston 41 or 42 when the liquid piston 42 (or 41 if the liquid piston 42 is actuated by the compression of the gas 3) drops.

[0074] In the embodiment shown in FIG. 2, the mechanical actuator comprises a single solid piston 23 that moves in one direction in chamber 31 or in the opposite direction in chamber 32 . This is a magnetic piston for a linear motor.

[0075] The mode of operation is the same as that described for the device shown in FIG. The difference lies in the presence of this second low pressure phase separator 6 .

[0076] As we have seen, the role of the 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.

[0077] The volumes of the separators 2 and 6 are chosen so that the velocity of the gas 3 is reduced sufficiently to allow the liquid 4 to fall naturally to the bottom of this buffer volume.

[0078] Other complementary solutions may be considered, such as the use of cyclone systems or coalescence grids. The gas pressure loss in this component must be kept low.

[0079] A hydraulic connection 20 between the phase separator 2 and the bottom of the compression chambers 31 and 32 (which may be the second vertical tube sections 35 and 36 or the first horizontal tube sections 33 and 34) allows a small flow of liquid 4 to be continuously passed through to compensate for losses due to droplet entrainment during flashing. A flow control valve 24 is attached to each hydraulic connection to allow the flow rate to be varied to experimentally find the optimum setting.

[0080] Each liquid piston 41 and 42 has a valve 61 and 62 (respectively) to release the liquid 4 into a non-pressurized second separator 6 in the event of overpressure in chambers 31 and / or 32.

[0081] A suction pump 63 between the two separators 2 and 6 returns to the pressurized separator 2 the liquid 4 lost in expansion mode in the non-pressurized separator 6 when the gas 3 is released at atmospheric pressure. Two further valves 64 and 65 transfer compressed gas, which may contain part of the liquid piston fluid, between the compression chambers 31 and 32 and the separator 2 . If the liquid buffer volume 4 is sufficient, the pump 63 operates intermittently and at a low frequency, and is adjusted based on the liquid levels in the two separators 2 and 6.

[0082] The embodiment shown in FIG. 3 relates to the use of a device comprising three solid pistons and six liquid pistons, optimizing the use of mechanical parts with a "double-acting" piston principle.

[0083] In fact, it is possible to achieve higher power levels (tens or hundreds of MW) by increasing the number of pistons. It may be possible to increase power output by disproportionately increasing the diameter of the pistons and chambers, but increasing the number of pistons and chambers would be preferable. On the one hand, there are optimally sized devices that are easy to transport (e.g., piston diameters of 300 mm to 2,000 mm for high power outputs). On the other hand, increasing the number of pistons reduces the fluctuations in the power exchanged with the network, provided there is a carefully set phase shift between each set of two pistons. Increasing the system outlet pressure can also be achieved by using a series of compressors as described below, staggering the compression times.

[0084] For processes where the inlet pressure exceeds atmospheric pressure (for high-pressure compression), the design of the piston translation system can advantageously utilize a one-to-one coupling for the piston. In effect, the high-pressure suction force in one chamber is countered by the higher-pressure compression force in the opposite chamber.

[0085] More specifically, double-acting operation has the following advantages: high pressure suction force in one chamber is directly reused to generate higher pressure compression force in the opposite chamber without passing through mechanical power components such as a connecting rod, crankshaft, or motor / generator.

[0086] Generally speaking, whether single-acting or double-acting, increasing the number of solid pistons fixed to the same crankshaft but well out of phase helps limit torque and power fluctuations during system operation. Limiting these fluctuations keeps stresses on components to a minimum, increasing assembly reliability and limiting the need for oversizing.

[0087] The mechanical actuator 1 of the device shown in Figure 3 thus comprises three pistons, only one of which (piston 25) is shown on the mechanical actuator (the pistons are 120° out of phase). This embodiment achieves higher pressures than the embodiment shown in FIGS.

[0088] In this embodiment, three successive compression or expansion steps are implemented, each compression chamber corresponding to a compression step to be reached, for example, the first chamber has a compression step of 11 bar, the second chamber has a step where the compression can be increased from 11 bar to 70 bar, and the third chamber can increase the compression from 70 bar to 300 bar. Furthermore, it is possible to have two of these chambers form a medium pressure step and a high pressure step.

[0089] The embodiment shown in FIG. 3 in particular comprises a first control valve 91 set to a safe pressure between the first chamber 31 and the first separator 2, and a second control valve 92 set to a safe pressure between the second chamber 32 and the first separator 2, making it possible to discharge a large amount of liquid from the at least one first or second liquid piston into the first separator 2.

[0090] FIG. 4 shows an installation according to the invention, comprising a series of devices according to the invention. The common crankshaft mechanical actuator drives twelve pairs of solid pistons 21 and 22 movable within twelve pairs of chambers 31, 32 through the movement of a crank 12 mounted on a shaft rotatable about its axis and connected to the solid pistons 21 and 22 by a connecting rod 11.

[0091] It should be noted that all outlet openings 37 and 38 of the chambers 31 and 38 are connected together to the first phase separator 2 and to the second phase separator 6 at atmospheric pressure; in other words: The pressurized phase separator 2: to the valve 64 of the chamber 31, both of which are connected to the same outlet pipe; and - to the valve 65 of the chamber 32, both of which are connected to a separate common discharge pipe It is about being connected.

[0092] In addition, all of the valves 61 in chamber 31 are connected to another common discharge pipe connected to the second separator, and all of the valves 62 in chamber 32 are also connected to another common discharge pipe connected to the second separator 6 at atmospheric pressure.

[0093] It should be noted that valves 61 and 62 are low pressure (or atmospheric) air intake valves in Figures 2, 3 and 4. They have the same function as valves 14 and 15 shown in Figure 1. In this exemplary embodiment, the solid pistons 21 and 22 have a diameter of 2.5 m and a stroke of 1 m.

[0094] The discharge pressure is approximately 11 bar, the inlet pressure is 1 bar and the compression time is 1 second. A motor is used to drive the mechanical actuator. However, two additional motor / pump assemblies with a power rating smaller than the main motor are required to drive the cooling circuit (pump 83) and to transfer liquid 4 from separator 6 to separator 3 (pump 63). The shaft speed is approximately 30 rpm.

[0095] The total footprint of such an installation is approximately 7m high, 8m wide and 45m long. An average power output of 15 MW is achieved with amplitude fluctuations of less than 0.8 MW at a frequency of 12 Hz. The ramp-up time to maximum speed is about 1 second (from 10% to 100% rated output). Start-up time (from full stop to 100% rated power) of approximately 10 seconds is expected.

[0096] Once started, the power output of the system can be easily adjusted by modifying the rotational speed of the motor / generator (and therefore the crankshaft) or by adjusting the control of valves 61, 62, 64 and 65. In this way, a variation range of 20% to 100% of rated power is available with a short response time (on the order of 1 second).

[0097] FIG. 5 shows yet another embodiment with five chambers 31, 31′, 31″, 32, 32′ arranged in a star configuration with a double-acting piston 26: the use of a double-acting cylinder / piston 26 not only increases power output with the same number of pistons, but also improves management of piston ring leakage. Fluid that passes through the piston seal simply flows into the opposite chamber, and there is no need to drain the leaking fluid.

[0098] From the above description it is clear how the present invention can convert mechanical motion into gas pressurization energy and how this energy can be used to generate mechanical motion.

[0099] It is to be understood that the invention is not limited to the implementation of the embodiment specifically described above and shown in the drawings, but extends to any equivalent implementation.

[0100] In particular, the application of the method is not limited to air as the gas and water as the fluid, other applications, such as the compression / expansion of (H2, CO2, CH4, etc.) using water as the fluid in a liquid piston, as well as ionic liquids, solvents, oils, organic liquids, etc., are also contemplated by the present invention.

Claims

1. A device for isothermal expansion and compression of a gas (3), ensuring the compression of said gas (3) by expenditure of mechanical energy and the recovery of said mechanical energy by expansion of said gas (3), said device comprising: at least one first and at least one second liquid piston (4, 41, 42) movable in first and second chambers (31, 32), respectively, said at least one first and second chambers (31, 32) each containing a gas (3) capable of being compressed or expanded under the influence of the movement of said at least one first or second liquid piston (4, 41, 42); an actuator (1) capable of moving said at least one first and second liquid piston (4, 41, 42) in said first and second chambers (31, 32); each of the at least one first and at least one second chamber (31, 32) comprises at least one first and at least one second perforated insert (51, 52), respectively, through which the liquid (4) and the gas (3) can flow; The actuator (1) is a mechanical actuator comprising at least one solid piston (21, 22), the perforated inserts (51, 52) have through cells (53) extending between a first cell opening (54) opening at one end of the inserts (51, 52) and a second cell opening (55) opening at a second end of the inserts (51, 52), the cells (53) being oriented either parallel to the direction of movement of the liquid pistons (41, 42) in the inserts (51, 52) or obliquely to the direction of movement of the liquid pistons; and The device further comprises at least a first phase separator (2) connected to a first outlet (37) of the first chamber (31) and a second outlet (38) of the second chamber (32). A device characterized by:

2. 2. A device according to claim 1, characterized in that the phase separator (2) is connected to a pressurized gas (3) storage tank (5).

3. 3. The device according to claim 2, characterized in that it comprises a second separator (6) connected to the first and second outlets (37, 38) of the first and second chambers (31, 32), respectively, the first separator (2) having a first internal pressure corresponding to the internal pressure of the gas (3) contained in the pressurized gas reservoir (5), and the second separator (6) having a second internal pressure corresponding to atmospheric pressure.

4. 4. The device according to claim 3, characterized in that the first and second separators (2, 6) are in fluid communication with each other, allowing the liquid (4) to transfer from the first separator (2) to the second separator (6).

5. 5. The device according to claim 3 or 4, characterized in that it comprises a first air intake device (61) ensuring the passage of air at atmospheric pressure between the at least one first chamber (31) and the second separator (6), and a second air intake device (62) at atmospheric pressure between the at least one second chamber (32) and the second separator.

6. 6. The device according to claim 3, 4 or 5, characterized in that it comprises a third air intake device (13, 64) ensuring the passage of compressed air between the first chamber (31) and the first separator (2), and a fourth compressed air intake device (16, 65) between the second chamber and the first separator (2).

7. 7. The device according to claim 3, further comprising a first low flow control valve (24) that ensures fluid passage from the first separator (2) to the first chamber (31), and a second low flow control valve (24) that ensures fluid passage from the first separator (2) to the second chamber (32).

8. 8. The device according to any one of claims 3 to 7, characterized in that it comprises a regulating valve (91, 92) set to a safe pressure between the first chamber (31) and the first separator (2) and / or between the second chamber (32) and the first separator (2) to allow a large volume of liquid to be discharged from the at least one first or second liquid piston into the first separator (2).

9. 9. A device according to any one of claims 1 to 8, characterized in that each of the first and second chambers (31, 32) is fluidly connected to a fluid / fluid exchanger (71, 72) making it possible to maintain said at least first and second liquid pistons (41, 42), respectively, at ambient temperature, preferably with a tolerable temperature fluctuation 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, optionally an electric fan (85) if said exchanger is a fluid / air exchanger (84), and optionally at least one control valve (86).

10. A device according to any one of claims 1 to 9, characterized in that the inserts (51, 52) comprise a core of structural material with an expanded honeycomb structure.

11. A device according to any one of claims 1 to 10, characterized in that the mechanical actuator (1) comprises a magnetically actuated linear motor (23).

12. A device according to any one of claims 1 to 11, characterized in that the mechanical actuator (1) comprises a motor associated with a crankshaft.

13. A device according to any one of the preceding claims, characterized in that the mechanical actuator comprises a motor associated with a worm screw.

14. 14. An installation comprising at least two devices according to any one of claims 1 to 13, wherein the mechanical actuators (1) of the at least two devices are mechanically linked to operate in tandem, and the installation comprises a first phase separator (2) common to the at least two devices, the common first phase separator being connected to a first outlet (37) of a first chamber (31) of the device and to a second outlet (38) of a second chamber (32) of the device, and the first phase separator (2) being connected to a common pressurized gas storage tank (5).

15. 15. An installation according to claim 14, comprising at least two devices according to claim 3, characterized in that the installation comprises a second separator (6) common to the at least two devices, the common second separator (6) being connected to the first and second outlets (37, 38) of the first and second chambers (31, 32) of each of the at least two devices, the first common separator (2) having a first internal pressure corresponding to the internal pressure of the gas contained in the common pressurized gas tank (5), and the second separator (6) having a second internal pressure corresponding to atmospheric pressure.

16. A method for operating a device according to any one of claims 1 to 13, comprising: - actuating the mechanical actuator (1); - moving said at least one solid piston (21, 22, 23) to move 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 moved in opposite directions, said first liquid piston (41) compressing said gas (3) in an insert (51) of said first chamber (31) to a first predetermined pressure and said second liquid piston (42) reducing pressure in said insert (52) of said second chamber (32) to a second pressure; when said first pressure is reached, opening an air intake device (13) between the first chamber (31) and the first phase separator (2) to discharge the pressurized gas (3) from the first chamber (31) into the first separator (2) until the liquid piston (41) passes completely through the insert (51) and reaches the first outlet (37) of the first chamber (31) and simultaneously reaches the air intake (14) to the second chamber (32); A method comprising:

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