Thermal gas compression system

Abstract

The present invention relates to a system for thermal compression of a gas, characterized in that it comprises a source (1), a target (2), and at least one group of reservoirs (3) each comprising at least two reservoirs (3), said system comprising a heating means (4) and a cooling means (5) for the contents of each reservoir, each group further comprising: transfer means (6a, 6b) for transferring gas directly from said source to each reservoir and directly from each reservoir to said target, and for each reservoir (3) of said group, bidirectional transfer means (7) for transferring gas directly between this reservoir (3) and at least one other reservoir (3) of said group. The present invention also relates to a cyclic method for thermal compression of a gas in a plurality of reservoirs (3) of at least one group of a system according to the invention. Abstract figure: Figure No. 2

Description

Title of the invention: Thermal compression system for a gas

[0001] The present invention is in the field of gas compression. It relates to a thermal compression system for a gas, and in particular dihydrogen.

[0002] In a context of strong development of low carbon dioxide emission solutions, for mobility and the transport of goods and passengers, di-hydrogen appears to be a promising fuel. Its use, associated with a fuel cell and an electric motor in a vehicle, can represent an alternative to fossil fuels or to the use of electric accumulators commonly used to power electric motors.

[0003] Due to its low volume density, dihydrogen must be compressed to a pressure of around 700 bars in order to be used as fuel. It is usually delivered to service stations at a pressure of 200 bars, then compressed on site in a compressor to pressures ranging from 450 to 1000 bars.

[0004] This compressor is usually a mechanical compressor, which has several drawbacks. The moving parts induce dihydrogen leaks. The pistons are not lubricated because this would introduce impurities into the dihydrogen, which would damage the fuel cell; the pistons therefore wear out quickly. In addition, these compressors consume electricity, which represents a significant cost and degrades the environmental balance of dihydrogen. Finally, the mechanical compressor induces significant noise pollution, which is problematic in particular for service stations in cities.

[0005] To address these problems, metal hydride thermochemical compressors have been developed. Metal powders absorb low-pressure hydrogen to obtain metal hydrides. These hydrides are heated, which releases high-pressure hydrogen. These compressors ideally operate between 20 bar and 500 bar. Outside this operating range, it is difficult to find metal powders that can perform compression at temperature levels compatible with industrial standards. In particular, for very high pressure levels, the energy required to further increase the pressure is too high compared to a mechanical compressor, which consumes energy of the order of the ratio between the outlet pressure and the inlet pressure. A thermochemical compressor can then be combined with a mechanical compressor to reach the final pressure stages.

[0006] Alternatively, thermal compressors exist. The document US20120028140 proposes a compressor comprising a plurality of tanks connected in series, the pressure rising between two consecutive tanks by heating the upstream tank. This method does not allow high compression ratios, does not allow high flow rates to be obtained, consumes too much energy, and is little used

[0007] An object of the present invention is to propose a compressor that is efficient in terms of energy consumption, in particular for pressures above 500 bars, without presenting the problems of wear, electricity consumption, noise and leaks of mechanical compressors.

[0008] The object of the present invention is to respond at least in part to the aforementioned objects by proposing a system for thermal compression of a gas in which several reservoirs of a group carry out a cycle during which they carry out a pressure increase in contact with a reservoir or a succession of hotter reservoirs, then a pressure decrease in order to increase the pressure of other colder reservoirs. To this end, it proposes a system for thermal compression of a gas characterized in that it comprises a source, a target, and at least one group of reservoirs each comprising at least two reservoirs, said system comprising a heating means and a cooling means of the contents of each reservoir, each group further comprising:

[0009] - transfer means for transferring gas directly from said source to each reservoir and directly from each reservoir to said target, and - for each reservoir of said group, bidirectional transfer means for transferring gas directly between this reservoir and at least one other reservoir of said group.

[0010] Thanks to these arrangements, the gas can be compressed to a high pressure by thermal compression, which makes it possible to avoid problems of noise and wear of mechanical parts, while allowing an energy-efficient process.

[0011] According to other characteristics:

[0012] - said gas may be dihydrogen, which is a relevant embodiment of the invention, dihydrogen often having to be compressed to high pressures to be usable, particularly in transport; it may also be N2, O2, CH4 or Helium for example, - the said system may comprise two groups of tanks, which makes it possible to optimize its operation, and in particular to enable continuous supply of the system and production of compressed gas, - said system may comprise at least three, preferably at least four tanks in each group, which makes it possible to increase several pressure stages in the gas, and therefore to obtain a greater pressure increase for a given temperature difference, - the heating means may include a fatal heat source such as, for example, a biomass dihydrogen production facility or an electrolyser, which makes it possible to recover the heat produced, and thus reduce the costs of the energy consumed by the system, - the cooling means may include a fatal cold source, such as for example liquid nitrogen storage or a return from an iced water loop, which makes it possible to recover the available cold, and thus reduce the energy consumed by the system, - the source may include an evaporation gas outlet from a liquid hydrogen storage facility, which makes it possible to supply cold hydrogen to the tank which must be supplied by the source, and thus achieve a particularly effective first compression stage, - all tanks in the same group can have the same volume, which simplifies the system.

[0013] The present invention also relates to a cyclic method for thermal compression of a gas in a plurality of tanks of at least one group of a system according to the invention, each cycle comprising for each tank of each group the following steps:

[0014] - cooling of the gas contained in the tank and transfer of gas from the source to said tank, - transfer of gas from a donor tank to said tank, said donor tank being the one whose gas is at the lowest pressure among the tanks of said group whose gas is at a pressure and temperature higher than the gas of said tank, until the pressures in said tank and said donor tank are equalized, where appropriate, repeating this step as long as there is another tank of said group whose gas is at a pressure and temperature higher than the gas of said tank, - heating of the gas contained in the tank and transfer of gas from said tank to the target, - transfer of gas from said tank to a receiving tank, said receiving tank being the one whose gas is at the highest pressure among the tanks of said group whose gas is at a pressure and temperature lower than the gas of said tank, until the pressures in said tank and said receiving tank are equalized, where appropriate, repeating this step as long as there is another tank of said group whose gas is at a pressure and temperature lower than the gas of said tank,

[0015] the step of cooling the gas contained in the reservoir and transferring gas from the source to said reservoir being carried out successively for each reservoir of said band.

[0016] Thanks to these arrangements, the gas can be compressed to a high pressure by thermal compression, which avoids the problems of noise and wear of mechanical parts. This process is particularly energy efficient, the heat used to increase the pressure in a tank being used during its pressure reduction to compress the contents of other tanks, the compression being able to be carried out in cascade.

[0017] According to other characteristics:

[0018] - said method can take place in a plurality of tanks of two groups, the steps of cooling the gas contained in a tank and transferring the gas from the source can take place in turn to one of the tanks of one group, then to one of the tanks of the other group, which makes it possible to optimize the method, and in particular to allow continuous supply of the system and production of compressed gas, - during the step of transferring gas from a donor tank of the same group whose gas is at a higher pressure and temperature to said tank, the transferred gas can be cooled to reduce the rise in temperature of the contents of said tank, which makes it possible to maintain the temperature difference between a tank increasing in pressure and a tank decreasing in pressure, this difference making it possible to optimize the compression of the gas of said tank, - each group of tanks may comprise at least three, preferably at least four tanks, and the two transfer steps may each be repeated at least two, preferably at least three times, which makes it possible to increase the gas pressure through several stages, and therefore to obtain a greater pressure increase for a given temperature difference, - said method may further comprise a step of compressing the gas, before its transfer from the source to a reservoir, in a metal hydride compressor, which makes it possible to combine a first compression offering the advantages of the hydride compressor, then a thermal compression when the high pressure values make the hydride compressor less suitable.

[0019] The present invention will be better understood on reading the detailed description which follows, with reference to the appended figures in which:

[0020] [Fig-1] [Fig.l] is a schematic view of a thermal compression system of a gas according to one embodiment of the invention,

[0021] [Fig.2] [Fig.2] is a schematic view of the steps of a compression process thermal of a gas according to the embodiment of [Fig.l],

[0022] [Fig.3] [Fig.3] is a schematic view of the first steps of a method of thermal compression of a gas according to a preferred embodiment of the invention,

[0023] [Fig.4] [Fig.4] is a schematic view of the steps completing the process started in [Fig.3].

[0024] The thermal compression system of a gas according to the invention, illustrated in [Fig.l], comprises a source 1, a target 2, and one or more groups of reservoirs 3.

[0025] The system according to the invention makes it possible to compress gas from a source 1, at which the gas is at a pressure Po, to a pressure Pcibie.

[0026] The gas concerned by the invention is preferably dihydrogen. It may however be another gas, such as oxygen or nitrogen for example.

[0027] The tanks 3 are capable of containing a certain volume of said gas in a sealed manner. Within a group, the tanks 3 all preferably have the same volume, for example 50 liters.

[0028] The thermal compression system comprises a heating means 4 and a cooling means 5 for the contents of each tank 3. The heating means 4 and cooling means 5 make it possible, for example, to bring a heat transfer fluid into contact with the contents of each tank 3. If the heat transfer fluid is hotter, respectively colder, than the contents of a tank 3, it can be used to heat, respectively cool, said contents.

[0029] The heating means 4 can also be an electrical resistor immersed in the tank.

[0030] The heating means 4 can be connected to an electrolyzer or a biomass dihydrogen production unit. Thus, if the gas is dihydrogen, the heat generated to produce this dihydrogen can be recovered in the thermal compression system. Depending on the installation location of the system according to the invention, other locally available sources of fatal heat can be connected to the heating means to reduce the costs of the energy consumed. This may be, for example, a waste collection site, or any other industrial site in which heat is produced.

[0031] The thermal compression system also comprises transfer means 6a making it possible to transfer gas directly from the source 1 to each reservoir 3 of a group, and transfer means 6b making it possible to transfer gas directly from each reservoir 3 of a group to the target 2. A direct transfer here designates a transfer which does not pass through another reservoir 3 of the same group or of another group, nor through the source 1 or the target 2.

[0032] The thermal compression system finally comprises bidirectional transfer means 7 for transferring gas directly from each tank of a group to each other tank of the same group. A direct transfer here designates a transfer which does not pass through another reservoir 3 of the same group or another group, nor through source 1 or target 2. Thus, considering any pair of reservoirs 3 of the same group, it is possible to transfer gas directly between these two reservoirs 3, in both directions.

[0033] The system according to the invention can be used in a cyclic process for thermal compression of a gas in a plurality of tanks 3 of at least one group. Each cycle comprises for each tank 3a of each group the following steps:

[0034] - cooling the gas contained in the reservoir 3a, to a cold temperature Ti, and transfer of gas from the source 1 to said reservoir 3a. At the end of this step, the reservoir 3a contains gas at a pressure Po and a temperature Th - transfer of gas from another donor reservoir 3 to said reservoir 3a. The donor reservoir 3 is the one whose gas is at the lowest pressure among the reservoirs 3 of the same group whose gas is at a pressure and a temperature higher than the gas contained in said reservoir 3a. The transfer takes place automatically when the bidirectional transfer means 7 between the reservoir 3a and the donor reservoir 3 is opened, until the pressures in the reservoir 3a and the donor reservoir 3 are equalized. It is during this step that the gas contained in said reservoir 3a is compressed.At the end of the first occurrence of this step, the tank 3a contains gas at a pressure Pi and a temperature Th. This step can be repeated several times, as long as there is another tank 3 of said group whose gas is at a higher pressure and temperature than the gas contained in said tank 3a. The step can for example be repeated twice if the group comprises three tanks 3, or three times if the group comprises four tanks 3. Each repetition of this step allows the tank 3a to increase a pressure stage. At the end of this step, the tank 3a contains gas at a pressure PK and a temperature Th with K equal to the number of repetitions of the transfer step. - heating of the gas contained in the tank 3a, to a hot temperature T2, which allows a final pressure stage to be raised, and transfer of gas from said tank 3a to the target 2. At the end of this step, the tank 3a contains gas at a pressure PK+1 and a temperature T2. The pressure PK+1 is close to, or equal to, the pressure Pcibie. - transfer of gas from said tank 3a to another receiving tank 3. The receiving tank 3 is the one whose gas is at the highest pressure among the tanks 3 of the same group whose gas is at a lower pressure and temperature than the gas from said tank 3a. The transfer takes place automatically when the bidirectional transfer means 7 is opened between the tank 3a and the receiving tank 3, until the pressures in said tank 3a and said receiving tank 3 are equalized. At the end of the first occurrence of this step, the tank 3a contains gas at a pressure close to or equal to PK and a temperature T2. This step can be repeated several times, as long as there is another tank 3 of said group whose gas is at a pressure and temperature lower than the gas in tank 3a. The step can for example be repeated twice if the group has three tanks 3, or three times if the group has four tanks 3. Each repetition of this step allows the tank 3a to raise another tank 3 of the same group a pressure stage. At the end of this step and its repetition to the end, the tank 3a contains gas at a pressure close to or equal to Pi and a temperature T2.

[0035] In the case where all the tanks 3 of the group have an identical volume, we can also determine the quantity of gas in the tank 3 at each stage:

[0036] - at the end of the cooling and transfer step of the source 1, the reservoir 3a contains n0 moles of gas, - at the end of an occurrence of the step of transferring from a donor reservoir 3 to said reservoir 3a, said reservoir 3a contains ni moles of gas, - at the end of the entire step of transferring from one or more donor reservoirs 3 to said reservoir 3a, said reservoir 3a contains nK moles of gas, - at the end of the heating and transfer step to target 2, reservoir 3a contains nK । moles of gas, - at the end of an occurrence of the step of transferring said reservoir 3a to a receiving reservoir 3, said reservoir 3a contains nK2 moles of gas, - at the end of the entire step of transferring said reservoir 3a to one or more receiving reservoirs, said reservoir 3a contains n_i moles of gas.

[0037] The step of cooling the gas contained in the tank and transferring gas from the source to said tank 3a is carried out successively for each tank 3 of said group, and not for several tanks 3 at the same time. Thus the tanks 3 of the group each pass through this step in turn, then follow the same cycle simultaneously, each with a time lag relative to the others.

[0038] During this process, the thermal compression of the gas is done by opening the transfer means between two reservoirs 3, the reservoir 3 in which the gas is the most compressed allowing the gas in the other reservoir to increase in pressure. The reservoir which receives the gas is in a cold state and the reservoir which gives the gas is in a hot state. This allows that with an equivalent number of moles of gas in the two reservoirs, the hot reservoir has a higher pressure and can give gas and increase the pressure in the cold reservoir. During each cycle, each Tank 3 thus goes through a pressure increase in a cold state, then a pressure decrease in a hot state. During a cycle followed by a tank 3, it therefore only needs to be heated and cooled once.

[0039] Preferably, during the step of transferring gas from another tank 3 of the same group whose gas is at a higher pressure and temperature to said tank, the transferred gas is cooled. This makes it possible to maintain a cold temperature in the tank 3 which receives the hot gas, and thus to maintain the temperature differential with the other hot tanks 3. The transferred gas can be cooled before its arrival in the tank 3, for example in the bidirectional transfer means 7 between the two tanks 3. Alternatively, the transferred gas can be cooled after its arrival in the tank 3, by cooling the entire contents of the tank 3, for example by the cooling means 5. In a preferred embodiment of the invention, the contents of a tank 3 cooled to the cold temperature Ti are kept at the cold temperature Ti until the reheating step.Similarly, the contents of a tank 3 heated to the hot temperature T2 are preferably kept at the hot temperature T2 until the cooling step. This makes it possible to always benefit from the temperature differential between T1 and T2 when connecting a hot tank 3 to a cold tank 3 to increase the pressure of the latter.

[0040] A group of tanks 3 comprises at least two tanks 3, for example three, preferably four tanks 3. The choice of the number of tanks 3 is made, with the other parameters of the system, according to the number of stages necessary to compress the gas from the pressure Po at the source 1 to the desired pressure PciMe at the target 2. The other parameters to be adjusted are in particular the volumes of the tanks 3, and the temperatures Ti and T2 at which the tanks 3 are heated and cooled.

[0041] The system may comprise a single group of tanks 3, preferably it comprises two groups of tanks 3. Indeed the total number of steps of the cycle described above, counting the repetitions of the second and fourth steps, is equal to twice the number of tanks 3 in a group. When the system comprises a single group, only half of the steps can therefore be carried out at the same time by one of the tanks 3. The steps of transferring gas from the source 1 and to the target 2, in particular, do not take place for a single group at each step of the cycle. It may therefore be provided to have two groups operating in parallel, which makes it possible to have, at each step of the cycle, gas transferred from the source 1 to one of the tanks 3 of the system, and from one of the tanks 3 of the system to the target 2.The number of tanks in each group can be different, but in order to achieve the above-mentioned advantage for two groups, it is necessary that both groups have either an even or an odd number of tanks.

[0042] According to a particular embodiment, additional reservoirs 3 can be provided. facilities to allow heating and cooling to be carried out in several stages. This is of interest if the heating and cooling stages take longer than the transfer stages; typically if these stages take twice as long as the transfer stages, it may be of interest to carry out the heating and cooling in two stages.

[0043] According to another particular embodiment, it is possible to provide an installation which operates initially between a first source pressure PO and a target pressure PI. Then, in a second stage, it is possible to take a portion of the gas at pressure PI and make it a source at pressure PI. The device then raises the pressure to a pressure P2. It is possible to continue for as long as necessary to finally reach the target pressure.

[0044] In a preferred embodiment of the invention, the gas pressure at the source Po is between 400 and 600 bars, for example coming from a metal hydride compressor, and the gas pressure at the target Pcibie is between 800 and 1000 bars. In this embodiment, two groups of four tanks 3 can be provided, the pressure increase in a tank 3a being carried out for example by the following stages: 500 bars at the source, then 560 bars, 635 bars, 725 bars after the three transfer steps from another hot tank 3, then a final stage leading to 810 bars during the heating of the tank 3a. Preferably, the cooling temperatures T i and heating T2 of the gas are respectively between 280 and 310 K, for example 293.15 K, and between 360 and 390 K, for example 373.15 K. These temperatures can of course be used with other pressure values.

[0045] In order to optimize energy consumption, the cooling temperature Ti may be as low as possible, i.e., for example, the ambient temperature or the temperature of the lowest cold source available at the site of use. If liquid nitrogen is available on site, or a return from an iced water circuit, or other cold fluids, they may, for example, be used.

[0046] It is also possible to connect the source 1 to an evaporation gas outlet from a liquid di-hydrogen storage (boil-off gas), which is at a temperature of 15K, which makes it possible to supply cold di-hydrogen to the tank which must be supplied by the source.

[0047] The system according to the invention is particularly advantageous for small installations, with a gas outlet flow rate at target 2, for example, between 1 and 5 kg per hour.

[0048] Other applications are possible in terms of pressure / temperature:

[0049] - source connected to an evaporation gas outlet from a liquid dihydrogen storage (boil-off gas): - pressure Po at source 1: between 0.5 and 2 bars, - Pcibie pressure at target 2: between 5 and 50 bars, - cooling temperature Ti: between 15 and 300 K, - heating temperature T2: between 300 and 400 K. - source connected to a fatal dihydrogen outlet, co-produced by an industrial installation: - pressure Po at source 1: between 0.5 and 3 bars, - PciMe pressure at target 2: between 20 and 500 bars, - cooling temperature Ti: between 253 and 353 K, - heating temperature T2: between 353 and 1000 K. - source connected to a low temperature electrolyser: - pressure Po at source 1: between 1 and 50 bars, - PciMe pressure at target 2: between 2 and 200 bars, - cooling temperature Ti: between 253 and 293 K, - heating temperature T2: between 333 and 393 K. - source connected to a high temperature electrolyser: - pressure Po at source 1: between 1 and 30 bars, - Pcibie pressure at target 2: between 2 and 200 bars, - cooling temperature Ti: between 253 and 293 K, - heating temperature T2: between 333 and 1073 K. - source connected to a thermochemical compressor, for example with metal hydrides: - pressure Po at source 1: between 200 and 500 bars, - Pcibie pressure at target 2: between 400 and 1000 bars, - cooling temperature Ti: between 253 and 293 K, - heating temperature T2: between 353 and 423 K. - source connected to a gas bottle outlet: - pressure Po at source 1: between 50 and 500 bars, - Pcibie pressure at target 2: between 100 and 1000 bars, - cooling temperature Ti: between 253 and 293 K, - heating temperature T2: between 353 and 500 K. - source connected to a biomass dihydrogen production unit: - pressure Po at source 1: between 1 and 5 bars, - Pcibie pressure at target 2: between 2 and 50 bars, - cooling temperature Ti: between 253 and 293 K, - heating temperature T2: between 353 and 1073 K.

[0050] [Fig.2] illustrates an exemplary embodiment in which the system according to The invention comprises a group of two tanks 3a, 3b. The volumes of the tanks 3a, 3b are equal. In [Fig.2], the arrows illustrate the gas flows. The state of each tank is noted after the gas transfers are completed.

[0051] The cycle has four stages:

[0052] - step A: - the gas contained in the reservoir 3a is heated to the temperature T2 and part of this gas is transferred to the target 2. At the end of this step, the reservoir 3a contains n0 moles of gas, at pressure P2 = Pcibie, and at temperature T2. - the gas contained in reservoir 3b is cooled to temperature Ti and gas is transferred from source 1 to reservoir 3b. At the end of this step, reservoir 3b contains n0 moles of gas, at pressure Po, and at temperature T,. - step B: - the bidirectional transfer means 7 is open between the reservoirs 3a and 3b, which causes a transfer of gas from the reservoir 3a to the reservoir 3b. At the end of this step, the reservoir 3a contains n_i moles of gas, at pressure Pb and temperature T2, and the reservoir 3b contains ni moles of gas, at pressure Pb and temperature Tb

[0053] Steps C and D are identical to steps A and B, by swapping reservoirs 3a and 3b. At the end of step D, the cycle can resume at step A.

[0054] Figures 3 and 4 illustrate an exemplary embodiment in which the system according to the invention comprises two groups of four tanks 3a to 3d and 3e to 3h. The volumes of tanks 3a to 3d are equal. The volumes of tanks 3e to 3h are equal. In Figures 3 and 4, the arrows illustrate the gas flows. The state of each tank is noted after the gas transfers are completed.

[0055] The cycle has eight steps A to H. We will describe the cycle followed by tank 3a:

[0056] - step A: the gas contained in the reservoir 3a is cooled to the temperature Ti and gas is transferred from the source 1 to the reservoir 3a. At the end of this step, the reservoir 3a contains n0 moles of gas, at pressure Po, and at temperature TH - step B: the bidirectional transfer means 7 is opened between the tanks 3a and 3b, which causes a transfer of gas from the tank 3b to the tank 3a. At the end of this step, the tank 3a contains ni moles of gas, at pressure Pi, and at temperature Th - step C: the bidirectional transfer means 7 is opened between the reservoirs 3a and 3d, which causes a transfer of gas from the reservoir 3d to the reservoir 3a. At the end of this step, the reservoir 3a contains n2 moles of gas, at pressure P2, and at temperature Th - step D: the bidirectional transfer means 7 is opened between the tanks 3a and 3c, which causes a transfer of gas from the tank 3c to the tank 3a. At the end of this step, reservoir 3a contains n3 moles of gas, at pressure P3, and at temperature Th - step E: the gas contained in reservoir 3a is heated to temperature T2 and part of this gas is transferred to target 2. At the end of this step, reservoir 3a contains n2 moles of gas, at pressure P4 = Pcibie, and at temperature T2. - step F: the bidirectional transfer means 7 is opened between the reservoirs 3a and 3b, which causes a transfer of gas from the reservoir 3a to the reservoir 3b. At the end of this step, the reservoir 3a contains ni moles of gas, at pressure P3, and at temperature T2. - step G: the bidirectional transfer means 7 is opened between the reservoirs 3a and 3d, which causes a transfer of gas from the reservoir 3a to the reservoir 3d. At the end of this step, the reservoir 3a contains n0 moles of gas, at pressure P2, and at temperature T2. - step H: the bidirectional transfer means 7 is opened between the reservoirs 3a and 3c, which causes a transfer of gas from the reservoir 3a to the reservoir 3c. At the end of this step, the reservoir 3a contains n_i moles of gas, at pressure Pb and temperature T2. At the end of step H, the cycle can resume at step A.

[0057] All reservoirs 3a to 3h follow the above cycle, of course exchanging with the relevant reservoirs 3 at each transfer step:

[0058] - tank 3b begins the above cycle at step C, - tank 3c begins the above cycle at step G, - tank 3d begins the above cycle at step E, - tank 3 begins the above cycle at step B, - tank 3f begins the above cycle at step D, - tank 3g begins the above cycle at step H, - the 3h tank begins the above cycle at step F,

[0059] The presence of two groups in the system makes it possible here to have, during each step of the cycle, a reservoir 3 receiving gas from source 1 and a reservoir 3 sending gas to target 2. Indeed, for example, in step A it is reservoir 3d of the first group of reservoirs 3 which sends gas to target 2, in step B it is reservoir 3h of the second group of reservoirs 3, then in step C reservoir 3c of the first group of reservoirs 3, and so on. Furthermore, in step A it is reservoir 3a, of the first group of reservoirs 3, which receives gas coming from source 1, in step B it is reservoir 3e of the second group of reservoirs 3, then in step C reservoir 3b of the first group of reservoirs 3, and so on.

[0060] Considering this exemplary embodiment, and carrying out the heating and cooling steps over the duration of two transfer steps, this leads to provide ten tanks 3 instead of eight. The ten tanks then constitute a single group, and each tank 3 can be connected to three other tanks 3 among the ten, by bidirectional transfer means; each tank 3 must of course also be connected to the source and the target by transfer means.

[0061] Although the above description is based on particular embodiments, it is in no way limiting of the scope of the invention, and modifications may be made, in particular by substitution of technical equivalents or by different combination of all or part of the characteristics developed above.

Claims

1. Claims Cyclic method of thermal compression of a gas in a plurality of reservoirs (3), each cycle comprising for each reservoir (3a, ..3h) of said plurality of reservoirs (3) the following steps: - cooling of the gas contained in the reservoir (3a, ..., 3h) and transfer of gas from a source (1) to said reservoir (3a, ..., 3h), - transferring gas from a donor tank (3) to said tank (3a, ..., 3h), said donor tank (3) being at a pressure and temperature higher than the gas in said tank (3a, ..., 3h) and of the same group, preferably said donor tank (3) being the one whose gas is at the lowest pressure among the tanks (3) of said group whose gas is at a pressure and temperature higher than the gas in said tank (3a, ..., 3h), until the pressures in said tank (3a, ..., 3h) and said donor tank (3) are equalized, where appropriate, repeating this step as long as there is another tank (3) of said group whose gas is at a pressure and temperature higher than the gas in said tank (3a, ..., 3h), - heating the gas contained in the reservoir (3a, ..., 3h) and transferring gas from said reservoir (3a, ..., 3h) to a target (2), - transferring gas from said reservoir (3a, ..., 3h) to a receiving reservoir (3), said receiving reservoir (3) being at a pressure and temperature lower than the gas in said reservoir (3a, ..., 3h), preferably said receiving reservoir (3) being the one whose gas is at the highest pressure among the reservoirs (3) in said group whose gas is at a pressure and temperature lower than the gas in said reservoir (3a, ..., 3h), until the pressures in said reservoir (3a, ..., 3h) and said receiving reservoir (3) are equalized, where appropriate, repeating this step as long as there is another reservoir (3) in said group whose gas is at a pressure and temperature lower than the gas in said reservoir (3a, ..., 3h), the step of cooling the gas contained in the reservoir (3a, ..., 3h) and transferring gas from the source to said reservoir (3a, ..., 3h) being carried out successively for each tank (3) of said group.

2. Method according to the preceding claim, wherein during the step of transferring gas from a donor tank (3) of the same group whose gas is at a higher pressure and temperature to said tank (3), the transferred gas is cooled to reduce the temperature rise of the contents of said tank (3).

3. Method according to one of the preceding claims further comprising a step of compressing the gas, before its transfer from the source (1) to a reservoir, in a metal hydride compressor.

4. System for implementing a method according to one of the preceding claims comprising a source (1), a target (2), and at least one group of reservoirs (3) each comprising at least two reservoirs (3), said system further comprising a heating means (4) and a cooling means (5) for the contents of each reservoir, each group further comprising: - transfer means (6a, 6b) for transferring gas directly from said source (1) to each reservoir (3) and directly from each reservoir (3) to said target (2), and - for each reservoir (3) of said group, bidirectional transfer means (7) for transferring gas directly between this reservoir (3) and at least one other reservoir (3) of said group.

5. System according to the preceding claim, wherein said gas is dihydrogen.

6. System according to one of claims 4 to 5, comprising two groups of tanks (3).

7. System according to one of claims 4 to 6 comprising at least three, preferably at least four reservoirs (3) in each group.

8. System according to one of claims 4 to 7, in which the heating means (4) comprises a fatal heat source, for example a biomass dihydrogen production plant or an electrolyzer.

9. System according to one of claims 4 to 8, in which the cooling means (5) comprises a fatal cold source, for example a storage of liquid nitrogen or a return from an iced water loop.

10. System according to one of claims 4 to 9, in which the source (1) has an evaporation gas outlet from a liquid hydrogen storage.

11. System according to one of claims 4 to 10, in which all the tanks (3) of the same group have the same volume.

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