Magnetocaloric hydrogen liquefaction by means of electrochemical compression

Abstract

A system (100, 200, 300, 400) for hydrogen liquefaction configured to receive a gaseous hydrogen stream and comprising an electrochemical compression unit (10), comprising an electrochemical compressor, configured to receive the gaseous hydrogen stream and perform an electrochemical compression, so to generate heat and discharge a gaseous hydrogen stream at higher pressure and / or with a higher purity, and a magnetocaloric liquefaction unit (20), comprising a magnetic refrigerator, fluidly coupled to the electrochemical compression unit (10) and configured to receive the gaseous hydrogen stream at higher pressure and / or with higher purity from the electrochemical compression unit (10). The magnetocaloric liquefaction unit (20) is configured to perform a magnetocaloric liquefaction, so to generate heat and discharge a liquified hydrogen stream.

Description

TITLEMagnetocaloric hydrogen liquefaction by means of electrochemical compressionDESCRIPTIONTECHNICAL FIELD

[0001] The subject-matter disclosed herein relates to an innovative system for hydrogen liquefaction.BACKGROUND ART

[0002] In the last years, many companies are investing their resources and research to find alternatives to the use of fossil fuels: an alternative that is being considered is represented by the use of hydrogen as an energy carrier. Therefore, hydrogen applications are becoming more and more relevant in the energy transition.

[0003] Typically, the hydrogen is stored in gaseous form and is subsequentially compressed and fed to a liquefaction plant so to generate liquefied H2.

[0004] Nowadays, mechanical compressors (both centrifugal and reciprocating) are generally used for this service, but they struggle to match with renewable energy sources load profile and they work for a great part of their lifetime out of the optimal design point, thus leading to excessive energy consumption.

[0005] Moreover, mechanical rotating (or reciprocating) equipment have a non-negligible footprint and are subjected to wear, thus influencing the efficiency of the plant.

[0006] From document it is known a method for the electrolytic production of a liquid hydrogen product, in which a water-containing feed is subjected to an electrolysis while receiving an anode raw gas, rich in oxygen and containing hydrogen, and a cathode raw gas which is depleted of oxygen and rich in hydrogen, wherein the cathode raw gas at least partially undergoes intermediate storage downstream of the electrolysis and upstream of the liquefaction and is compressed before the liquefaction.

[0007] Therefore, it would be desirable to have a hydrogen liquefaction plant able to liquify hydrogen by means of static equipment. In particular, it would be desirable to have a hydrogen liquefaction plant which leads to an energy demand reduction and enhanced overall performance with respect to known liquefaction plants.SUMMARY

[0008] According to an aspect, the subject-matter disclosed herein relates to a system for hydrogen liquefaction configured to receive a gaseous hydrogen stream and comprising: an electrochemical compression unit comprising an electrochemical compressor, the electrochemical compression unit being configured to receive the gaseous hydrogen stream and perform an electrochemical compression, so to generate heat and discharge a gaseous hydrogen stream at higher pressure and / or with a higher purity, a magnetocaloric liquefaction unit comprising a magnetic refrigerator, the magnetocaloric liquefaction unit being fluidly coupled to the electrochemical compression unit and configured to receive the gaseous hydrogen stream at higher pressure and / or with higher purity from the electrochemical compression unit, the magnetocaloric liquefaction unit being further configured to perform a magnetocaloric liquefaction, so to generate heat and discharge a liquifiedhydrogen stream.BRIEF DESCRIPTION OF THE DRAWINGS

[0009] A more complete appreciation of the disclosed embodiments of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:Fig. 1 shows a schematic diagram of a first embodiment of an innovative system for hydrogen liquefaction,Fig. 2 shows a schematic diagram of a second embodiment of an innovative system for hydrogen liquefaction comprising a purification unit,Fig. 3 shows a schematic diagram of a third embodiment of an innovative system for hydrogen liquefaction comprising an electrolyzer for hydrogen generation, andFig. 4 shows a schematic diagram of a fourth embodiment of an innovative system for hydrogen liquefaction comprising a solid-state hydrogen storage unit.DETAILED DESCRIPTION OF EMBODIMENTS

[0010] According to an aspect, the subject-matter disclosed herein relates to an innovative system for hydrogen liquefaction comprising a first unit with at least one electrochemical compressor configured to compress and / or purify gaseous hydrogen and a second unit with at least one magnetic refrigerator configured to perform liquefaction of the compressed and / or purified gaseous hydrogen (by leveraging the magnetocaloric cryogenic cooling) so to discharge a liquified hydrogen stream. According to the innovative system, theliquefaction of hydrogen is performed by means of static equipment, with no need for rotating equipment (i.e. traditional rotary compressors) to run both the hydrogen feed line and the cryogenic cycle unit.

[0011] According to the present disclosure, the compression of gaseous hydrogen is performed by means of electrochemical compressor(s). According to the present disclosure, the purification of gaseous hydrogen is performed by means of electrochemical compressor(s).

[0012] According to the present disclosure, the liquefaction of gaseous hydrogen is performed by means of a magnetocaloric liquefaction unit in which repeatedly a magnetic material absorbs and rejects heat through a change in the magnetic field, originating the magnetocaloric effect and reaching very low temperatures. The magnetocaloric liquefaction unit adopts a reversed Carnot cycle consisting of four continuous steps: adiabatic magnetization, isothermal magnetization, adiabatic demagnetization and isothermal magnetization. The magnetocaloric liquefaction unit can reach approximately 50% of theoretical Carnot efficiency, while the typical compressed-gas refrigeration systems (for example systems implementing Claude cycle or Brayton cycle) can reach approximately 38% of theoretical Carnot efficiency.

[0013] Therefore, the integration of these two technologies (i.e. the electrochemical compression and the magnetocaloric liquefaction) may lead to significant overall liquefaction performance improvements.

[0014] Reference now will be made in detail to embodiments of the disclosure, examples of which are illustrated in the drawings. The examples and drawing figures are provided by way of explanation of the disclosure and should not be construed as a limitation of the disclosure. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present disclosure without departing from the scope or spiritof the disclosure. In the following description, similar reference numerals are used for the illustration of figures of the embodiments to indicate elements performing the same or similar functions. Moreover, for clarity of illustration, some references may not be repeated in all the figures.

[0015] Fig. 1 shows, for example and without limitations, a schematic diagram of a first embodiment of an innovative system for hydrogen liquefaction 100 (referred in the following as “system 100”) according to the present disclosure. The system 100 is configured to receive a gaseous hydrogen stream so to liquified it and discharge a liquified hydrogen stream. It is to be noted that other possible embodiments of system 200, 300 and 400 are shown, for example and without limitations, in Figs. 2, 3 and 4.

[0016] With non-limiting reference to Fig. 1, the system 100 comprises an electrochemical compression unit 10 comprising an electrochemical compressor (possibly a plurality of electrochemical compressors) and a magnetocaloric liquefaction unit 20 comprising a magnetic refrigerator (possibly a plurality of magnetic refrigerators).

[0017] The electrochemical compression unit 10 is configured to receive the gaseous hydrogen stream, in particular at a main inlet 11 of the electrochemical compression unit 10, and perform an electrochemical compression so to generate heat Hl and discharge a gaseous hydrogen stream at higher pressure and / or with a higher purity, in particular at a main outlet 12 of the electrochemical compression unit 10. In particular, the electrochemical compressor comprises a proton-exchange membrane. It is to be noted that the gaseous hydrogen stream discharged at the main outlet 12 of the electrochemical compression unit 10 has a higher pressure and / or a higher purity with respect to the gaseous hydrogen stream received at the main inlet 11 of the electrochemical compression unit 10. It is also to be noted that, depending on the pressure at which the electrochemical compression isperformed, the gaseous hydrogen GH stream may be purified from contaminants and / or its pressure may be increased.

[0018] Advantageously, the electrochemical compression unit 10 has further a secondary inlet 13 configured to receive electrical energy in order to perform the electrochemical compression.

[0019] Advantageously, the electrochemical compression unit 10 further comprises a cooling system configured to circulate a cooling fluid, for example water or a mixture of water and glycol or air. In particular, the cooling fluid is configured to remove the heat Hl (or part of the heat Hl) generated by the electrochemical compression performed by the electrochemical compression unit 10 so to cool it (see the big black arrow in Fig. 1). For example, the cooling fluid circulates through and / or around the electrochemical compression unit 10 receiving heat Hl (or part of the heat Hl) from the electrochemical compressor(s) and carrying it away.

[0020] The magnetocaloric liquefaction unit 20 is fluidly coupled to the electrochemical compression unit 10, in particular to the main outlet 12 of the electrochemical compression unit 10, and is configured to receive the gaseous hydrogen stream at higher pressure and / or with higher purity discharged by the electrochemical compression unit 10, in particular at a main inlet 21 of the magnetocaloric liquefaction unit 20. The magnetocaloric liquefaction unit 20 is configured to perform a magnetocaloric liquefaction so to generate heat H2 and discharge a liquified hydrogen stream, in particular at a main outlet 22 of the magnetocaloric liquefaction unit 20.

[0021] Advantageously, the magnetocaloric liquefaction unit 20 has further a secondary inlet 23 configured to receive electrical energy in order to perform the magnetocaloric liquefaction.

[0022] Specifically, the magnetocaloric liquefaction unit 20, in particular themagnetic refrigerator(s), operates by exploiting the properties of a magnetocaloric material (for example Holmium and particularly polycrystalline Holmium) subject to the magnetic field generated by a magnetic field source (for example a permanent magnet or an electromagnetic magnet, driven by an electronic circuit to switch on and off the magnetic field and adjust the magnetic field generated).

[0023] The magnetocaloric materials show magnetocaloric effects (=MCE), which is the physical property whereby the material heats or cools when subject to an applied magnetic field or when a magnetic field changes. By the cycle based on magnetocaloric material, the gaseous hydrogen is cooled down to a target temperature, which in the case at issue is around -253°C, namely the hydrogen liquefaction temperature, so to discharge liquified hydrogen downstream of the system 100. However, in other embodiments, the target temperature can be different.

[0024] Advantageously, the magnetocaloric liquefaction unit 20 further comprises a cooling system configured to circulate a cooling fluid. In particular, the cooling fluid is configured to remove the heat H2 (or part of the heat H2) generated by the magnetocaloric liquefaction performed by the magnetocaloric liquefaction unit 20 so to cool it (see the big black arrow in Fig. 1). For example, the cooling fluid circulates through and / or around the magnetocaloric liquefaction unit 20 receiving heat H2 (or part of the heat H2) from the magnetic refrigerator(s) and carrying it away.

[0025] As it will be better explained below, the heat Hl (or part of the heat Hl) removed by the cooling fluid of the electrochemical compression unit 10 and / or the heat H2 (or part of the heat H2) removed by the cooling fluid of the magnetocaloric liquefaction unit 20 is exploited within the innovative system herewith disclosed in order to provide heat to any heat-requiring accessory units.

[0026] Typically, a hydrogen liquefaction cycle includes the step of precooling hydrogen to temperatures of about 70-100 K before being liquified to cryogenic temperatures (which, according to the present disclosure, is performed through magnetocaloric liquefaction). Advantageously, the system 100 comprises a precooling heat exchanger located downstream of the electrochemical compression unit 10 and configured to remove heat from the gaseous hydrogen GH stream. In particular, the precooling heat exchanger may use a stream of liquid nitrogen or other refrigerant such as helium, neon, hydrogen, hydrocarbons or a stream of mixed refrigerants as a cooling fluid in order to cool down the gaseous hydrogen GH stream.

[0027] Advantageously, with non-limiting reference to Fig. 1, the system 100 further comprises a storage unit 30 located upstream of the electrochemical compression unit 10 and configured to store gaseous hydrogen. The storage unit 30 is fluidly coupled to the electrochemical compression unit 10 and is configured to selectively provide the gaseous hydrogen stream to the electrochemical compression unit 10. For example, the storage unit 30 may be a pressurized tank or a hydrogen storage system comprising porous nanomaterials. It is to be noted that the gaseous hydrogen may be supplied to the storage unit 30 through a pipeline.

[0028] With non-limiting reference to Fig. 2, the innovative system 200 further comprises a purification unit 240 located upstream of the electrochemical compression unit 10 and fluidly coupled to the electrochemical compression unit 10. Specifically, the purification unit 240 comprises at least one electrochemical compressor (possibly a plurality of electrochemical compressors).

[0029] The purification unit 240 is configured to receive the gaseous hydrogen stream at a main inlet 241 and to perform a hydrogen purification so to discharge, in particular at a main outlet 242 of the purification unit 240, agaseous hydrogen stream with a higher purityto the electrochemical compression unit 210. It is to be noted that the gaseous hydrogen stream discharged at the main outlet 242 has a higher purity with respect to the gaseous hydrogen stream received at the main inlet 241 of the purification unit 240.

[0030] Advantageously, if the system 200 comprises also a storage unit 230, the purification unit 240 is located downstream of the storage unit 230 so to purify and / or compress the gaseous hydrogen GH stream supplied by the storage unit 230 to the electrochemical compression unit 210. In particular, the main inlet 241 of the purification unit 240 is fluidly coupled to the storage unit 230 and is configured to receive the gaseous hydrogen stream (possibly from the storage unit 230). More in particular, the purification unit 240 may further comprise a secondary outlet 244 fluidly coupled to the storage unit 230 and configured to recirculate back to the storage unit 230 the gaseous hydrogen stream not yet purified.

[0031] According to a possibility (not shown in any figure), the innovative system may further comprise a thermoelectric device thermally coupled to the electrochemical compression unit 10 and / or to the magnetocaloric liquefaction unit 20. For example, the thermoelectric device may be a Peltier cell or, in general, a thermoelectric electricity generator. Advantageously, the thermoelectric device is configured to receive the heat Hl (or part of the heat Hl) removed by the cooling fluid of the electrochemical compression unit 10 and / or the heat H2 (or part of the heat H2) removed by the cooling fluid of the magnetocaloric liquefaction unit 20 so to generate electric power.

[0032] According to a possibility (not shown in any figure), the innovative system may further comprise a Stirling cycle generation unit thermally coupled to the electrochemical compression unit 10 and / or to the magnetocaloric liquefaction unit 20. In particular, the Stirling cycle generation unit comprisesa Stirling engine and an electrical generator (i.e. an alternator). Advantageously, the Stirling cycle generation unit is configured to receive the heat Hl (or part of the heat Hl) removed by the cooling fluid of the electrochemical compression unit 10 and / or the heat H2 (or part of the heat H2) removed by the cooling fluid of the magnetocaloric liquefaction unit 20 so to generate electric power.

[0033] According to still another possibility (not shown in any figure), the innovative system may further comprise an ortho-para hydrogen conversion unit thermally coupled to the electrochemical compression unit 10 and / or to the magnetocaloric liquefaction unit 20. Advantageously, the ortho-para hydrogen conversion unit comprises a metal organic framework (=MOF) catalyst. In particular, the ortho-para hydrogen conversion unit comprises at least one reaction chamber filled with a catalytic bed comprising metal organic frameworks catalyst and encased by a shell apt to be traversed by a flow of a cooling fluid.

[0034] Advantageously, the ortho-para hydrogen conversion unit is configured to periodically receive the heat Hl (or part of the heat Hl) removed by the cooling fluid of the electrochemical compression unit 10 and / or the heat H2 (or part of the heat H2) removed by the cooling fluid of the magnetocaloric liquefaction unit 20 so to regenerate the ortho-para hydrogen conversion unit, in particular the catalyst. It is to be noted that the term “periodically” is used in the present disclosure both to mean occasionally and at regularly occurring intervals, based on the need to regenerate the catalytic bed.

[0035] According to still another possibility, with non-limiting reference to Fig. 4, the innovative system 400 may further comprise a solid-state hydrogen storage unit 460 configured to physically store hydrogen. Advantageously, the solid-state hydrogen storage unit comprises metal hydrides or metal organic framework (MOF).

[0036] Advantageously, the solid-state hydrogen storage unit 460 is configured to receive the heat Hl (or part of the heat Hl) removed by the cooling fluid of the electrochemical compression unit 410 and / or the heat H2 (or part of the heat H2) removed by the cooling fluid of the magnetocaloric liquefaction unit 420 so to release stored hydrogen, in particular by performing a solid-gas state transition. In particular, the solid-state hydrogen storage unit 460 is fluidly coupled to the main inlet 411 of the electrochemical compression unit 410 so to provide the gaseous hydrogen stream to the electrochemical compression unit 410.

[0037] According to still another possibility, with non-limiting reference to Fig. 3, the innovative system 300 may further comprise an electrolyzer 350 located upstream of the electrochemical compression unit 310 and fluidly coupled to the electrochemical compression unit 310. In particular, the electrolyzer 350 is configured to receive a water flow W, in particular at a main inlet 353 of the electrolyzer 350, and electric power, advantageously electric power produced by a renewable energy plant 360 (see the dotted line in Fig. 3), and to perform electrolysis of water so to generate the gaseous hydrogen stream to be provided to the electrochemical compression unit 310.

[0038] Typically, mechanical compressors (centrifugal or reciprocating compressors) are used for downstream compression in green H2 production plants (i.e. plants which uses renewable energy for producing H2). However, mechanical compressors struggle to match with variable Renewable Energy Systems (=RES) load profile, resulting in working for a great part of their lifetime out of the optimal design point, thus leading to excessive energy consumption and faster degradation. The innovative system according to the present disclosure allows to follow any variable load profile with no issues of partial load or without any decrease in energy performances.

[0039] Please note that Figures 1-4 show possible examples of arrangementsof an innovative system according to the present disclosure. However, other arrangements and / or combination of arrangements are possible. The present disclosure is described by various embodiments with reference to the accompanying drawings, wherein similar reference numerals used in the accompanying drawings correspond to the like elements. This disclosure may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

Claims

CLAIMS1. A system (100, 200, 300, 400) for hydrogen liquefaction configured to receive a gaseous hydrogen stream and comprising: an electrochemical compression unit (10) comprising an electrochemical compressor, the electrochemical compression unit (10) being configured to receive the gaseous hydrogen stream and perform an electrochemical compression, so to generate heat and discharge a gaseous hydrogen stream at higher pressure and / or with a higher purity, a magnetocaloric liquefaction unit (20) comprising a magnetic refrigerator, the magnetocaloric liquefaction unit (20) being fluidly coupled to the electrochemical compression unit (10) and configured to receive the gaseous hydrogen stream at higher pressure and / or with higher purity from the electrochemical compression unit (10), wherein the magnetocaloric liquefaction unit (20) is configured to perform a magnetocaloric liquefaction, so to generate heat and discharge a liquified hydrogen stream.

2. The system (100, 200, 400) of claim 1, further comprising a storage unit (30) located upstream of the electrochemical compression unit (10) and configured to store gaseous hydrogen, wherein the storage unit (30) is fluidly coupled to the electrochemical compression unit (10) and is configured to selectively provide the gaseous hydrogen stream to the electrochemical compression unit (10).

3. The system (100, 200, 300, 400) of claim 1, wherein the electrochemical compression unit (10) comprises further a cooling system configured to circulate a cooling fluid, wherein the cooling fluid is configured to remove the heat (Hl) generated from the electrochemical compression performed by the electrochemical compression unit (10) so to cool it.

4. The system (100, 200, 300, 400) of claim 1, wherein the magnetocaloric liquefaction unit (20) comprises further a cooling system configured to circulate a cooling fluid, wherein the cooling fluid is configured to remove the heat (H2) generated from the liquefaction performed by the magnetocaloric liquefaction unit (20) so to cool it.

5. The system (200) of claim 2, comprising further a purification unit (240) located upstream of and fluidly coupled to the electrochemical compression unit (210), wherein the purification unit (240) comprises at least one electrochemical compressor, wherein the purification unit (240) is configured to receive the gaseous hydrogen stream and to perform a hydrogen purification so to discharge a gaseous hydrogen stream with a higher purity to the electrochemical compression unit (210).

6. The system (200) of claim 5, wherein the purification unit (240) further comprises a secondary outlet (244) fluidly coupled to the storage unit (230), wherein the secondary outlet (244) is configured to recirculate back to the storage unit (230) the gaseous hydrogen stream not yet purified.

7. The system (100) of claim 3, comprising further a thermoelectric device thermally coupled to the electrochemical compression unit (10), wherein the thermoelectric device is configured to receive the heat (Hl) removed by the cooling fluid so to generate electric power.

8. The system (100) of claim 4, comprising further a thermoelectric device thermally coupled to the magnetocaloric liquefaction unit (20), wherein the thermoelectric device is configured to receive the heat (H2) removed by the cooling fluid so to generate electric power.

9. The system (100) of claim 3, comprising further a Stirling cycle generation unit thermally coupled to the electrochemical compression unit (10), wherein the Stirling cycle generation unit is configured toreceive the heat (Hl) removed by the cooling fluid so to generate electric power.

10. The system (100) of claim 4, comprising further a Stirling cycle generation unit thermally coupled to the magnetocaloric liquefaction unit (20), wherein the Stirling cycle generation unit is configured to receive the heat (H2) removed by the cooling fluid so to generate electric power.

11. The system (100) of claim 3, comprising further an ortho-para hydrogen conversion unit thermally coupled to the electrochemical compression unit (10), wherein the ortho-para hydrogen conversion unit is configured to periodically receive the heat (Hl) removed by the cooling fluid so to regenerate the ortho-para hydrogen conversion unit.

12. The system (100) of claim 4, comprising further an ortho-para hydrogen conversion unit thermally coupled to the magnetocaloric liquefaction unit (20), wherein the ortho-para hydrogen conversion unit is configured to periodically receive the heat (H2) removed by the cooling fluid so to regenerate the ortho-para hydrogen conversion unit.

13. The system (100) of claim 11 or 12, wherein the ortho-para hydrogen conversion unit comprises a metal organic framework (MOF) catalyst.

14. The system (400) of claim 3, comprising further a solid-state hydrogen storage unit (460) configured to physically store hydrogen, wherein the solid-state hydrogen storage unit (460) is thermally and fluidly coupled to the electrochemical compression unit (410), wherein the solid-state hydrogen storage unit (460) is configured to receive the heat (Hl) removed by the cooling fluid so to release stored hydrogen and provide the gaseous hydrogen stream to the electrochemical compression unit (410).

15. The system (400) of claim 4, comprising further a solid-state hydrogen storage unit (460) configured to physically store hydrogen, wherein the-15-solid-state hydrogen storage unit (460) is thermally coupled to the magnetocaloric liquefaction unit (420), wherein the solid-state hydrogen storage unit (460) is fluidly coupled to the electrochemical compression unit (410), wherein the solid-state hydrogen storage unit (460) is configured to receive the heat (H2) removed by the cooling fluid so to release stored hydrogen and provide the gaseous hydrogen stream to the electrochemical compression unit (410).

16. The system (300) of claim 1, comprising further an electrolyzer (350) located upstream of and fluidly coupled to the electrochemical compression unit (310), wherein the electrolyzer (350) is configured to receive electric power, in particular electric power produced by a renewable energy plant (360), and a water (W) flow, wherein the electrolyzer (350) is configured to perform electrolysis of water (W) so to generate the gaseous hydrogen stream to be provided to the electrochemical compression unit (310).

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