Thermal compression system for a liquefied cryogenic fluid, distribution station and method using such a thermal compression system.

Abstract

System (2) for thermally compressing a liquefied cryogenic fluid, such as liquid hydrogen, for example for a pressurized gaseous hydrogen distribution station (1), the system (2) comprising: - a source tank (4) intended to contain the liquefied cryogenic fluid to be compressed, the fluid being at an initial temperature (T0) and an initial pressure (P0), - a series (5) of variable-volume compression tanks (5a-5n) comprising a first compression tank (5a) and a last compression tank (5n), the compression tanks (5a-5n) being connected to the source tank (4) and configured to transfer a flow of the fluid to be compressed from the source tank (4) to a set (3) of buffer storage(s) of the distribution station (1),the compression tanks (5a-5n) being configured to bring the flow of the fluid to be compressed to a desired final temperature (TF) (respectively to a desired final pressure (PF)) in the set (3) of buffer storage(s), the final temperature (T0) (respectively the final pressure (PF) being higher than the initial temperature (TO) (respectively initial pressure (P0)), each compression tank (5a-5n) comprising a piston (6a-6n) configured to be moved inside said compression tank (5a-5n) in a reciprocating movement, between a first position coinciding with an admission of the flow into said compression tank (5a-5n), and a second position coinciding with a discharge of the flow out of said compression tank (5a-5n) using said piston (5a-5n), each piston (6a-6n) being configured to be out of phase with respect to a following piston (6a-6n) and / or a previous piston (6a-6n),thus allowing the flow from the source reservoir (4) to pass successively through each compression reservoir (5a-5n) and to occupy an identical volume in each compression reservoir (5a-5n). Abstract figure: Fig. 2,

Description

Title of the invention: Thermal compression system for a liquefied cryogenic fluid, distribution station and method using such a thermal compression system.

[0001] The invention relates to a thermal compression system for a liquefied fluid for a distribution station. The invention also relates to a distribution station for a liquid fluid comprising such a thermal compression system. The invention finally relates to a method using such a compression system. The liquefied fluid may be a liquefied gas such as hydrogen.

[0002] Under normal conditions of pressure and temperature, gases, and in particular hydrogen, have a very low density which does not facilitate their storage and / or distribution in large quantities. To increase the density of a gas and allow its storage and distribution in large quantities, it is known to pressurize or liquefy the gas in question.

[0003] The pressurization of hydrogen, for example, in a storage tank requires, in a known manner, a compressor installed on a transfer line of a distribution station (or a filling center) dedicated to this gas. The compressor is arranged between a source tank of the distribution station and a storage tank. Furthermore, to be able to safely contain the pressurized hydrogen over time, the storage tank must have a robust structure.

[0004] The use of a compressor installed on the transfer line of a distribution station, and the use of a robust storage tank to contain pressurized hydrogen over time and in complete safety represent a very significant cost. Therefore, players in the distribution and storage of hydrogen are increasingly turning to the use of this gas in its liquefied form.

[0005] To be stored in the liquid state in a source tank, the hydrogen must be brought to a very low temperature to reduce its density. Furthermore, in order to facilitate the transfer of liquefied hydrogen from the source tank to a storage tank, it is necessary to have a pump between the two tanks.

[0006] The function of a pump is not limited to transferring liquefied hydrogen from the source tank to the storage tank. The pump also allows the pressure (and therefore the density) of the liquefied hydrogen in the storage tank to be increased.

[0007] However, the use of a pump between the source tank and the storage tank leads to an increase in the temperature of the liquefied hydrogen in the storage tank, and to a transformation of part of this liquefied hydrogen into evaporation gas (also called “boil-off” in English or “BOG”).

[0008] Today, nearly 8% of the flow of liquefied hydrogen is transformed into vaporization gas (boil-off) once this fluid is loaded into a storage tank. This fraction of hydrogen transformed into BOG is not recovered or reliquefied, and thus constitutes a very significant operating loss.

[0009] In an attempt to limit the production of BOG during a transfer of liquefied hydrogen from a source tank to a storage tank, one solution consists of a thermal compression system replacing the pump. More specifically, the prior art thermal compression system comprises a source tank in which the liquefied hydrogen is brought to a high temperature so as to increase its pressure, and a storage tank into which the liquefied hydrogen is poured, having been previously heated and brought to high pressure in the source tank.

[0010] The thermal compression system described above is far from satisfactory.

[0011] Indeed, heating the liquefied hydrogen at the source tank also produces a large quantity of BOG (comparable to what is observed when a pump is used). In addition, when a source tank has been brought to a high temperature for the purpose of heating the liquefied hydrogen, reusing this source tank to heat a new volume of liquefied hydrogen requires cooling of this source tank in order to limit the BOG during a new loading of liquefied hydrogen.

[0012] The frigories required to cool the source tank before a new loading of liquefied hydrogen, and the calories required to heat the liquefied hydrogen loaded into the source tank represent a significant operating cost.

[0013] An aim of the invention is to remedy the drawbacks listed above and to develop a system for thermal compression of a liquefied fluid, which in particular makes it possible to minimize, or even eliminate, the formation of BOG during a transfer of this liquefied fluid from a source reservoir to a storage reservoir.

[0014] To this end, according to a first aspect, the invention relates to a system for thermally compressing a liquefied cryogenic fluid, such as liquid hydrogen, for example for a pressurized gaseous hydrogen distribution station.

[0015] The system comprises: - a source tank intended to contain the liquefied cryogenic fluid to be compressed, the fluid being at an initial temperature and an initial pressure, - a series of variable volume compression tanks comprising a first compression tank and a last compression tank, the compression tanks pressure being connected to the source tank and configured to transfer a flow of the fluid to be compressed from the source tank to a set of buffer storage(s) of the distribution station.

[0016] In particular, the compression tanks are configured to bring the flow of the fluid to be compressed to a desired final temperature (respectively to a final pressure) in the buffer storage assembly(s) of the distribution station. The final temperature (respectively the final pressure) is higher than the initial temperature (respectively initial pressure).

[0017] Furthermore, each compression tank comprises a piston configured to be moved inside said compression tank in a reciprocating motion, between a first position coinciding with an admission of the flow into said compression tank, and a second position coinciding with a discharge of the flow out of said compression tank, using said piston.

[0018] Furthermore, each piston is configured to be out of phase with respect to a following piston and / or a preceding piston, thereby allowing the flow from the source reservoir to pass successively through each compression reservoir and to occupy an identical volume in each compression reservoir.

[0019] Thus, by providing a compression system with a succession of compression tanks, the invention opens the way to a progressive heat exchange between an external heat source and the flow of liquefied fluid, thus making it possible to better distribute the heat supplied to this flow of liquid fluid over time.

[0020] Consequently, the invention makes it possible to limit the evaporation of the flow of liquefied fluid, in particular during a first phase of heat exchange which occurs through the first compression tank.

[0021] Embodiments of the invention according to this first aspect of the invention may comprise one or more of the following features: - at least a portion of the compression tanks are configured to form a first heat exchange unit between a first external heat source and the flow of liquefied fluid passing through the compression tanks, the heat exchange comprising distinct main phases which follow one another during a passage of the flow of liquefied fluid in each of the compression tanks; - each compression tank is configured to receive the flow of liquefied fluid at a first inlet temperature (respectively a first inlet pressure), and to discharge said flow at a first outlet temperature (respectively a first outlet pressure), the first outlet temperature (respectively the first outlet pressure) being higher than the first inlet temperature (respectively the first inlet pressure); - the compression tanks are connected to each other by intermediate conduits; - the first compression tank is connected to the source tank by an upstream conduit; - the last compression tank is intended to be connected to the station's buffer storage unit(s) by a downstream conduit; - the conduits alternate with the compression tanks to form a continuous transfer line allowing the flow of liquefied fluid to be transferred from the source to the buffer storage unit(s); - all or part of the conduits form a second heat exchange unit between a second heat source and the flow of liquefied fluid, the heat exchange comprising distinct secondary phases which follow one another during a passage of the flow of liquefied fluid in each of said conduits; - each conduit is configured to receive the flow of liquefied fluid at a second inlet temperature (respectively a second inlet pressure) and to discharge said flow at a second outlet temperature (respectively a second outlet pressure), the second outlet temperature (respectively the second outlet pressure) being higher than the second inlet temperature (respectively the second inlet pressure); - the first external heat source (respectively the second heat source) consists mainly of the ambient air; - the system comprises a heating unit configured to heat and / or maintain the compression tanks at different temperatures, the temperature increasing from the first compression tank to the last compression tank; - the conduits are respectively equipped with valves intended to control a transfer of the flow of the liquefied fluid respectively between the source tank and the first compression tank, between two consecutive compression tanks, as well as between the last compression tank and the buffer storage assembly(s) of the distribution station, each valve being configured to be in the open position when the previous valve and / or the following valve is in the closed position; - the system includes a crankshaft connected to the pistons, and a motor configured to drive the crankshaft; - the valves are configured to be controlled as a function of a rotation frequency of the crankshaft and / or as a function of the respective back-and-forth movements of the pistons; - the conduits are respectively equipped with non-return valves intended to control a transfer of the flow of the liquefied fluid respectively between the source tank and the first compression tank, between two consecutive compression tanks, as well as between the last compression tank and the buffer storage assembly(s) of the distribution station, each non-return valve being configured to be in the open position when the previous non-return valve and / or the non-return valve next return is in closed position; - the source tank comprises a first region intended to contain the liquefied fluid and a second region intended to contain a vapor of the liquefied fluid, the first compression tank being connected to the first region and to the second region of the source tank by means of the upstream conduit and a return conduit respectively, the return conduit being configured to supply the second region of the source tank with vapor produced during the heat exchange phase carried out through the first compression tank between the first external heat source and the flow of liquefied fluid; - the first compression tank is insulated so as to limit the heat exchange, through the first compression tank, between the first external heat source and the flow of liquefied fluid, and so as to limit vaporization of the flow of liquefied fluid in the first compression tank.

[0022] According to a second aspect, the invention relates to a station for distributing a fluid, such as hydrogen, comprising a thermal compression system according to any one of the embodiments described above.

[0023] In particular, the station comprises a set of buffer storage(s) intended to store the fluid coming from the thermal compression system and to supply a tank to be filled. The set of buffer storage(s) is intended to receive the fluid at a final temperature (respectively a final pressure) higher than an initial temperature (respectively an initial pressure of the liquefied fluid contained in the source tank of the thermal compression system.

[0024] Embodiments of the invention according to this first aspect may comprise one or more of the following features: - the buffer storage assembly(s) has a variable volume making it possible to maintain a constant pressure in said buffer storage assembly(s) when the liquefied fluid is transferred from said buffer storage assembly(s) to the tank to be filled; - the set of buffer storage(s) comprises at least two buffer storages arranged in parallel downstream of the last compression tank, the buffer storages being intended to be supplied alternately by the last compression tank and / or to supply in cascade the tank to be filled.

[0025] According to a third aspect, the invention relates to a method for thermal compression of a liquefied cryogenic fluid using a compression system which comprises a source tank and a succession of variable-volume compression tanks. The compression tanks respectively comprise pistons movable inside said tanks, each piston being configured to occupy in the associated tank a first position called top dead center when a piston next or a previous piston occupies a second position called bottom dead center.

[0026] The method according to this third aspect of the invention comprises a step of transferring a flow of liquefied fluid from the source tank to a last compression tank, passing successively through each of the preceding compression tanks. The transfer is ensured by means of the pistons which are out of phase with each other. During the transfer, the fluid occupies an identical volume in each compression tank.

[0027] The method also comprises a step of increasing the temperature and pressure of the flow of liquefied fluid from an initial temperature (T0) and an initial pressure (PO) to a final temperature (TF) and a final pressure (PF). The increase in temperature and pressure occurs during the transfer of the flow through the compression tanks.

[0028] Other features and advantages will appear on reading the description below, given with reference to the following figures in which:

[0029] [Fig.l] is a schematic view illustrating an example of a station for distributing a liquid fluid according to the invention, the station comprising a system for thermal compression of the liquid fluid, illustrated in an initial configuration;

[0030] [Fig.2] is a schematic view illustrating the station of [Fig.l], the compression system being illustrated in a second configuration.

[0031] The invention relates to a station 1 for distributing a liquid fluid (or a center for filling a liquid fluid) comprising a system 2 for thermal compression of the liquid fluid and a set 3 of buffer storage(s) which is in fluid communication with the thermal compression system 2. The storage set 3 is intended to supply a tank 9 to be filled, for example a vehicle tank.

[0032] The thermal compression system 2 comprises a source tank 4 intended to contain the liquid cryogenic fluid at an initial temperature T0 and an initial pressure PO. The thermal compression system 2 also comprises a series 5 of compression tanks 5a-5n comprising a first compression tank 5a and a last compression tank 5n. The compression tanks 5a-5n are connected to the source tank 4 and are intended to transfer a flow of the liquid fluid from the source tank 4 to the set 3 of buffer storage(s).

[0033] In particular, the compression tanks 5a-5n each form a heat exchanger between an external heat source and the flow of liquid fluid. Thus, the compression tanks 5a-5n are configured to bring the flow of liquid fluid from the initial temperature T0 (respectively the initial pressure PO) to a final temperature TF (respectively to a final pressure PF) desired in the set 3 of buffer storage(s). The final temperature TF (respectively the final pressure PF) desired in the set 3 of buffer storage(s) is higher than the initial temperature TO (respectively the initial pressure PO) of the flow of liquid fluid contained in the source reservoir 4.

[0034] The external heat source may consist mainly of the ambient air. Thus, the invention makes it possible to reduce (in comparison with the thermal compression system of the prior art) the energy requirements necessary to bring the fluid flow to a high temperature. In addition, since neither the source tank nor the compression tanks are exposed to an external heat source other than the ambient air, the invention makes it possible to avoid the need to provide for prior cooling of these tanks before a new loading or a new transfer of the liquid fluid flow.

[0035] The heat exchange between the external heat source and the flow of liquid fluid comprises distinct phases (called main phases) which follow one another during a passage of the flow of liquid fluid in each of the compression tanks 5a-5n, starting from the first compression tank 5a to the last compression tank 5n.

[0036] Thus, the invention allows a progressive heat exchange between the external heat source and the flow of liquefied fluid, thus making it possible to better distribute over time the heat supplied to this flow of liquid fluid; and to limit the evaporation of the flow of liquefied fluid, in particular during a first phase of heat exchange which occurs through the first compression tank.

[0037] Advantageously, each compression tank 5a-5n comprises an inlet orifice intended to receive the flow of liquid fluid at an inlet temperature (respectively at an inlet pressure), and a discharge orifice intended to discharge the flow of liquid fluid out of said compression tank 5a-5n at an outlet temperature (respectively an outlet pressure). The outlet temperature (respectively the outlet pressure) is higher than the inlet temperature (respectively the inlet pressure).

[0038] Advantageously, each compression reservoir 5a-5n comprises a piston 6a-6n which is configured to be moved inside said compression reservoir 5a-5n according to a back and forth translational movement. In particular, each piston 6a-6n is moved in the associated compression reservoir 5a-5n between a first position (bottom dead center) and a second position (top dead center).

[0039] The first position of a given piston 6a-6n in the associated compression reservoir 5a-5n coincides with an admission of the liquid fluid flow into said compression reservoir 5a-5n. The second position of a given piston 6a-6n in the associated compression reservoir 5a-5n coincides with a discharge of the liquid fluid flow out of said compression reservoir 5a-5n.

[0040] Advantageously, the pistons 6a-6n are configured to be out of phase with each other during their respective reciprocating movements. The expression "out of phase" means that the first position of each piston 6a-6n coincides with the second position of the preceding piston 6a-6n and / or the following piston 6a-6n.

[0041] Advantageously, the compression tanks 5a-5n are connected to each other by intermediate conduits 51a-51n-1. The first compression tank 5a is connected to the source tank 4 by an upstream conduit 41a. The last compression tank 5n is connected to the buffer storage assembly 3 by a downstream conduit 31a.

[0042] Thus, the upstream conduit 41a, the intermediate conduits 51a-51n-l, and the downstream conduit 31a alternate with the compression tanks 5a-5n to form a continuous transfer line making it possible to transfer the flow of liquid fluid from the source tank 4 to the set 3 of buffer storage(s).

[0043] Advantageously, the heat exchange between the external heat source and the flow of liquid fluid also comprises other distinct phases (called secondary phases) which take place at the level of the conduits 41a, 51a-51n-l, 31a. The secondary phases of the heat exchange follow one another during a passage of the flow of liquid fluid in each of the conduits 41a, 51a-51n-l, 31a.

[0044] Ultimately, considering the set of compression tanks 5a-5n and the set of conduits 41a, 51a-51n-l, 31a, the heat exchange between the external heat source and the flow of liquid fluid comprises main phases which alternate with secondary phases. The main phases occur when the flow of liquid fluid passes through the compression tanks 5a-5n. The secondary phases occur when the flow of liquid fluid passes through the conduits 41a, 51a-51n-l, 31a.

[0045] It should be noted that the conduits 41a, 51a-51n-l, 31a are respectively equipped with valves 42a, 52a-52n-l, 32a intended to control a transfer of the flow of the liquid fluid respectively between the source reservoir 4 and the first compression reservoir 5a, between two consecutive compression reservoirs 5a-5n, and between the last compression reservoir 5n and the set 3 of buffer storage(s).

[0046] In particular, each valve 42a, 52b-52n-l, 32a is configured to be in the open position when the previous valve 42a, 52b-52n-l, 32a (respectively the following valve 42a, 52b-52n-l, 32a) is in the closed position.

[0047] Advantageously, the thermal compression system 2 comprises a crankshaft 7 on which the respective pistons 6a-6n of the compression reservoirs 5a-5n are mounted. In particular, the crankshaft 7 has a main axis (axis of rotation) connected to an engine 8, as well as crank pins which extend perpendicular to the main axis.

[0048] The main axis of the crankshaft 7 is composed of several journals. Furthermore, the crank pins extend between the journals, on either side of the main axis, and eccentrically relative to this main axis. The crank pins are intended to receive the pistons 6a-6n according to a pivot connection.

[0049] In the example illustrated, two consecutive crank pins are arranged relative to each other with a phase shift of 180° defined around the main axis of the crankshaft 7. Thus, two consecutive pistons 6a-6n (carried by two consecutive crank pins) also have relative to each other a stroke phase shift induced by the phase shift of the associated crank pins.

[0050] Advantageously, the valves 42a, 52b-52n-l, 32a of the conduits 41a, 51b-51n-l, 31a are configured to be controlled as a function of a rotation frequency of the crankshaft 7, and therefore as a function of the respective back-and-forth movements of the pistons 5a-5n.

[0051] Thus, when a given valve 42a, 52b-52n-l, 32a is in the open position, the preceding valve 42a, 52b-52n-l, 32a (respectively the following valve 42a, 52b-52n-l, 32a) is in the closed position. Furthermore, when a given valve 42a, 52b-52n-l, 32a is in the open position, the piston 6a-6n of the compression reservoir 5a-5n located downstream (respectively upstream) of this valve 42a, 52b-52n-l, 32a is at the bottom dead center (respectively top dead center).

[0052] The control of the valves 42a, 52b-52n-l, 32a and pistons 6a-6n as described above allows the flow of liquid fluid to occupy at each of the phases of the heat exchange with the external heat source an identical volume in the compression reservoir 5a-5n. Thus, the rise in temperature (and pressure) of the flow of liquid fluid is carried out at a constant volume during each phase of the heat exchange.

[0053] Advantageously, the thermal compression system 2 further comprises a heating unit (not shown) configured to heat and / or maintain the compression tanks 5a-5n (respectively the conduits 41a, 51b-51n-1, 31a) at different temperature levels, the temperature increasing from the first compression tank 5a (respectively from the upstream conduit 41a) to the last compression tank 5n (respectively from the downstream conduit 31a).

[0054] Advantageously, the first compression tank 5a is in fluid communication with a first region of the source tank 4 by means of the upstream conduit 41a. Furthermore, the first compression tank 5a is in fluid communication with a second region of the source tank 4 by means of a return conduit 41b. In particular, the return conduit 41b is intended to convey to the second region of the source tank 4 a vapor produced in the first compression tank 5a during a heat exchange phase between the external heat source and the flow of the liquid fluid.

[0055] Advantageously, the first compression tank 5a (respectively the upstream conduit 41a) is heat-insulated so as to limit the heat exchange between the external heat source and the flow of liquid fluid during the first main phase (respectively during the first secondary phase), and so as to limit vaporization of said flow during passage and / or storage of said flow in the first compression tank 5a (respectively during passage of the flow through the upstream conduit 41a).

[0056] Thus, the first compression reservoir 5a (respectively the upstream conduit 41a) has a temperature close to the temperature of the source reservoir 4.

[0057] Advantageously, the buffer storage assembly 3 has a variable volume making it possible to maintain in said buffer storage assembly 3 a pressure similar to the pressure of the last compression reservoir 5n.

[0058] Advantageously, the set 3 of buffer storage(s) comprises at least two buffer storages arranged in parallel downstream of the last compression tank 5n. The two buffer storages are intended selectively to be supplied by the last compression tank 5n and / or to supply in cascade the tank 9 to be filled.

[0059] When one of the buffer storages is used to supply the reservoir 9 to be filled, an expansion occurs in this buffer storage which can serve as a means of actuating the crankshaft 7.

Claims

Claims

1. System (2) for thermally compressing a liquefied cryogenic fluid, such as liquid hydrogen, for example for a station (1) for distributing pressurized gaseous hydrogen, the system (2) comprising: - a source tank (4) intended to contain the liquefied cryogenic fluid to be compressed, the fluid being at an initial temperature (TO) and an initial pressure (PO), - a series (5) of variable-volume compression tanks (5a-5n) comprising a first compression tank (5a) and a last compression tank (5n), the compression tanks (5a-5n) being connected to the source tank (4) and configured to transfer a flow of the fluid to be compressed from the source tank (4) to a set (3) of buffer storage(s) of the distribution station (1), the compression tanks (5a-5n) being configured to bring the flow of the fluid to be compressed to a desired final temperature (TF) (respectively to a desired final pressure (PF)) in the set (3) of buffer storage(s), the final temperature (TO) (respectively the final pressure (PF) being higher than the initial temperature (TO) (respectively initial pressure (PO)), each compression tank (5a-5n) comprising a piston (6a-6n) configured to be moved inside said compression tank (5a-5n) in a back and forth movement,between a first position coinciding with an admission of the flow into said compression tank (5a-5n), and a second position coinciding with a discharge of the flow out of said compression tank (5a-5n) using said piston (5a-5n), each piston (6a-6n) being configured to be out of phase with respect to a following piston (6a-6n) and / or a preceding piston (6a-6n), thereby allowing the flow coming from the source tank (4) to pass successively through each compression tank (5a-5n) and to occupy an identical volume in each compression tank (5a-5n).,

2. System (2) according to the preceding claim, characterized in that at least a portion of the compression tanks (5a-5n) are configured to form a first heat exchange unit between a first external heat source and the flow of liquefied fluid passing through the compression tanks (5a-5n), the heat exchange comprising distinct main phases which follow one another during a passage of the flow of liquefied fluid in each of the compression tanks (5a-5n).

3. System (2) according to the preceding claim, characterized in that each compression tank (5a-5n) is configured to receive the flow of liquefied fluid at a first inlet temperature (respectively a first inlet pressure), and to discharge said flow at a first outlet temperature (respectively a first outlet pressure), the first outlet temperature (respectively the first outlet pressure) being higher than the first inlet temperature (respectively the first inlet pressure).

4. System (2) according to any one of the preceding claims, characterized in that the compression tanks (5a-5n) are connected to each other by intermediate conduits (51a-51n-l), the first compression tank (5a) being connected to the source tank (4) by an upstream conduit (41a), the last compression tank (5n) being intended to be connected to the set (3) of buffer storage(s) of the station (1) by a downstream conduit (31a).

5. System (2) according to the preceding claim, characterized in that the conduits (41a, 51a-51n-l, 31a) alternate with the compression tanks (5a-5n) to form a continuous transfer line allowing the flow of liquefied fluid to be transferred from the source (4) to the set (3) of buffer storage(s).

6. System (2) according to any one of claims 4 or 5, characterized in that all or part of the conduits (41a, 51a-51n-l, 31a) form a second heat exchange unit between a second heat source and the flow of liquefied fluid, the heat exchange comprising distinct secondary phases which follow one another during a passage of the flow of liquefied fluid in each of said conduits (41a, 51a-51n-l, 31a).

7. System (2) according to the preceding claim, characterized in that each conduit (41a, 51a-51n-l, 31a) is configured to receive the flow of liquefied fluid at a second inlet temperature (respectively a second inlet pressure) and to discharge said flow at a second outlet temperature (respectively a second outlet pressure), the second outlet temperature (respectively the second outlet pressure) being higher than the second inlet temperature (respectively the second inlet pressure).

8. System (2) according to any one of claims 2 to 5 (respectively 6 to 7), characterized in that the first external heat source (respectively the second heat source) consists mainly of the ambient air.

9. System (2) according to any one of the preceding claims, characterized in that it comprises a heating unit configured to heat and / or maintain the compression tanks (5a-5n) at different temperatures, the temperature increasing from the first compression tank (5a) to the last compression tank (5n).

10. System (2) according to any one of claims 4 to 9, characterized in that the conduits (41a, 51a-51n-l, 31a) are respectively equipped with valves (42a, 52a-52n-l, 32a) intended to control a transfer of the flow of the liquefied fluid respectively between the source tank (4) and the first compression tank (5a), between two consecutive compression tanks (5a-5n), as well as between the last compression tank (5n) and the set (3) of buffer storage(s) of the distribution station (1), each valve (42a, 52a-52n-l, 32a) being configured to be in the open position when the previous valve (42a, 52a-52n-l, 32a) and / or the valve (42a, 52a-52n-l, 32a) following is in closed position.

11. System (2) according to any one of the preceding claims, characterized in that it comprises a crankshaft (7) connected to the pistons (6a-6n), and a motor (8) configured to actuate the crankshaft (7).

12. System (2) according to the preceding claim taken in its connection with claim 10, characterized in that the valves (42a, 52a-52n-l, 32a) are configured to be controlled as a function of a rotation frequency of the crankshaft (7) and / or as a function of the respective back-and-forth movements of the pistons (6a-6b).

13. System (2) according to any one of claims 4 to 12, characterized in that the conduits (41a, 51a-51n-l, 31a) are respectively equipped with non-return valves (42a, 52a-52n-l, 32a) intended to control a transfer of the flow of the liquefied fluid respectively between the source tank (4) and the first compression tank (5a), between two consecutive compression tanks (5a-5n), as well as between the last compression tank (5n) and the set (3) of buffer storage(s) of the distribution station (1), each non-return valve (42a, 52a-52n-l, 32a) being configured to be in the open position when the preceding non-return valve (42a, 52a-52n-l, 32a) and / or the valve non-return valve (42a, 52a-52n-l, 32a) is in the closed position.

14. System (2) according to any one of claims 4 to 13, characterized in that the source tank (4) comprises a first region intended to contain the liquefied fluid and a second region intended to contain a vapor of the liquefied fluid, the first compression tank (5a) being connected to the first region and to the second region of the source tank (4) respectively by means of the upstream conduit (41a) and to a return conduit (41b), the return conduit (41b) being configured to supply the second region of the source tank (4) with vapor produced during the heat exchange phase carried out through the first compression tank (5a) between the first external heat source and the flow of the liquefied fluid.

15. System (2) according to any one of the preceding claims, characterized in that the first compression tank (5a) is heat-insulated so as to limit the heat exchange, through the first compression tank (5a), between the first external heat source and the flow of liquefied fluid, and so as to limit vaporization of the flow of liquefied fluid in the first compression tank (5a).

16. Station (1) for distributing a fluid, such as hydrogen, comprising a thermal compression system (2) according to any one of the preceding claims, as well as a set (3) of buffer storage(s) intended to store the fluid coming from the thermal compression system (2) and to supply a tank (9) to be filled, the set (3) of buffer storage(s) being intended to receive the fluid at a final temperature (TF) (respectively a final pressure (PF)) higher than an initial temperature (PO) (respectively an initial pressure (PO) of the liquefied fluid contained in the source tank (4) of the thermal compression system (2).

17. Station (1) according to the preceding claim, characterized in that the buffer storage assembly (3) has a variable volume making it possible to maintain a constant pressure in said buffer storage assembly (3) when the liquefied fluid is transferred from said buffer storage assembly (3) to the tank (9) to be filled.

18. Station (1) according to any one of claims 16 or 17, characterized in that the set (3) of buffer storage(s) comprises at least two buffer storage(s) arranged in parallel downstream of the last compression tank (5n), the buffer storage(s) being intended to be supplied alternately by the last compression tank pressure (5n) and / or to supply in cascade the tank (9) to be filled.

19. Method for thermal compression of a liquefied cryogenic fluid in a compression system (2) comprising a source tank (4) and a succession (5) of compression tanks (5a-5n) with variable volume, the compression tanks (5a-5n) respectively comprising pistons (6a-6n) movable inside said tanks (5a-5n), each piston (6a-6n) being configured to occupy in the associated tank (5a-5n) a first position called top dead center when a following piston (6a-6n) or a preceding piston (6a-6n) occupies a second position called bottom dead center, the method comprising: - a transfer of a flow of the liquefied fluid from the source tank (4) to a last compression tank (5n) passing successively through each of the preceding compression tanks, the transfer being ensured by means of the pistons (6a-6n) in stroke phase shift, the fluid occupying a identical volume in each compression tank (5a-5n); - a rise in temperature and pressure of the flow of liquefied fluid from an initial temperature (TO) and an initial pressure (PO) to a final temperature (TF) and a final pressure (PF), the rise in temperature and pressure occurring during the transfer of the flow through the compression tanks (5a-5n).

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