Nitrogen fixation cold storage system applied to liquid hydrogen energy storage

Abstract

The utility model provides a nitrogen fixation cold storage system and cold storage method applied to liquid hydrogen energy storage, and particularly relates to the technical field of low-temperature energy storage, the nitrogen fixation cold storage system applied to liquid hydrogen energy storage comprises a cold storage unit, the cold storage unit comprises a first compressor, a first storage tank, a second storage tank, a third storage tank, a nitrogen fixation heat exchanger and a liquid nitrogen heat exchanger, when the liquid hydrogen releases cold energy, the cold energy is conveyed to liquid nitrogen and nitrogen through the nitrogen fixation heat exchanger and the liquid nitrogen heat exchanger, the liquid nitrogen and the nitrogen are converted into fixed nitrogen and liquid nitrogen, finally, the liquid nitrogen is stored in the second storage tank and the third storage tank, and the fixed nitrogen is stored in the nitrogen fixation heat exchanger, so that subsequent hydrogen liquefaction use is facilitated. The energy consumption in the liquefaction link is reduced, the liquid hydrogen temperature zone can be well matched by recycling cold energy through single-working-medium nitrogen, meanwhile, the whole energy storage system is simple and flexible in structure, and recycling of high-quality cold energy in the low-temperature zone is enhanced.

Description

Technical Field

[0001] The utility model relates to the technical field of low-temperature energy storage, and in particular to a nitrogen-fixing cold storage system applied to liquid hydrogen energy storage. Background Art

[0002] As a large-scale energy storage method with high energy density and low transportation cost, liquid hydrogen storage plays a significant role in promoting low-carbon sustainable development, promoting energy system innovation, and improving the utilization rate of renewable energy. In the energy storage process, due to the low liquefaction temperature of hydrogen, the power consumption of hydrogen liquefaction is the highest. Therefore, when liquid hydrogen vaporizes and releases cold energy, the cold energy is recovered and utilized to reduce the system's external energy loss and transfer waste. This is a necessary step to improve energy utilization and reduce the cost of liquid hydrogen systems.

[0003] The cold energy of existing liquid hydrogen energy storage systems is mostly related to coupling multiple heat exchange units such as air separation and air conditioning, multiple cold energy power generation devices such as organic working fluid Rankine cycle, or cascade heat exchange of multiple working fluids and multi-stage heat exchangers, and most of them are used as decentralized energy output. Due to the different working conditions of the working fluids and equipment, the complexity of the system and the difficulty of control are greatly increased. The cascade heat exchange of multiple working fluids requires multi-stage heat exchangers, so there are inevitably certain heat exchange losses and a certain equipment complexity. Therefore, a simpler system that uses a single working fluid to store cold is needed to complete the recovery and utilization of liquid hydrogen cold energy.

[0004] In view of this, the utility model provides a nitrogen fixation cold storage system applied to liquid hydrogen energy storage, which can match the temperature zone for liquid hydrogen cold energy recovery and utilization. Utility Model Content

[0005] In order to solve the problem that the recovery of liquid hydrogen cooling energy in a multi-working fluid system is complex and difficult to match the liquid hydrogen temperature zone, the utility model proposes a nitrogen fixation cold storage system for liquid hydrogen energy storage.

[0006] The utility model is realized by the following technical solutions:

[0007] The utility model proposes a nitrogen fixation cold storage system for liquid hydrogen energy storage, comprising a cold storage unit, a liquid hydrogen supply unit and a power supply unit, wherein:

[0008] The cold storage unit includes a first compressor, a first storage tank, a second storage tank, a third storage tank, a nitrogen fixation heat exchanger and a liquid nitrogen heat exchanger;

[0009] One outlet end of the first storage tank is connected to the first compressor, the second heat exchange side of the liquid nitrogen heat exchanger and the second storage tank in sequence, the other outlet end of the first storage tank is connected to the third heat exchange side of the liquid nitrogen heat exchanger, and two outlet ends of the third heat exchange side are respectively connected to the third storage tank and the third heat exchange side of the nitrogen solidification heat exchanger;

[0010] The liquid hydrogen supply unit includes a hydrogen production device, a precooling heat exchanger, a normal-parahydrogen converter, a final-stage heat exchanger and a liquid hydrogen storage tank;

[0011] The power supply unit includes a power supply module and a storage module;

[0012] When the cold storage unit stores energy, the outlet end of the hydrogen production device is sequentially connected to the first heat exchange side of the precooling heat exchanger, the normal-parahydrogen converter, the first heat exchange side of the final heat exchanger, the liquid hydrogen storage tank, the storage module, the first heat exchange side of the nitrogen fixation heat exchanger and the first heat exchange side of the liquid nitrogen heat exchanger;

[0013] When the cold storage unit releases energy, the other outlet end of the hydrogen production device is sequentially connected to the first heat exchange side of the pre-cooling heat exchanger, the second heat exchange side of the nitrogen fixation heat exchanger, the first heat exchange side of the final stage heat exchanger, the liquid hydrogen storage tank and the storage module.

[0014] Furthermore, the nitrogen fixation heat exchanger is a plate-fin heat exchanger or a spiral tube heat exchanger, or other types of heat exchangers that can be used for liquid-solid phase change.

[0015] Further, when the nitrogen solidification heat exchanger is a spiral tube heat exchanger, the third heat exchange side of the liquid nitrogen heat exchanger is connected to the outside of the spiral tube heat exchanger;

[0016] When the cold storage unit stores energy, the outlet end of the hydrogen production device is sequentially connected to the first heat exchange side of the precooling heat exchanger, the normal-parahydrogen converter, the first heat exchange side of the final heat exchanger, the liquid hydrogen storage tank, the storage module, the spiral tube heat exchange side of the nitrogen fixation heat exchanger and the first heat exchange side of the liquid nitrogen heat exchanger;

[0017] When the cold storage unit releases energy, the other outlet end of the hydrogen production device is sequentially connected to the first heat exchange side of the precooling heat exchanger, the spiral tube heat exchange side of the nitrogen fixation heat exchanger, the first heat exchange side of the final stage heat exchanger, the liquid hydrogen storage tank and the storage module.

[0018] Furthermore, it also includes a circulation unit, which includes a second compressor and a first expander, and the outlet end of the second compressor is sequentially connected to the second heat exchange side of the pre-cooling heat exchanger, the first expander, the second heat exchange side of the final stage heat exchanger, the third heat exchange side of the pre-cooling heat exchanger and connected back to the inlet end of the second compressor to form a circulation unit.

[0019] Furthermore, a throttle valve is provided between the final stage heat exchanger and the liquid hydrogen storage tank.

[0020] Furthermore, a third compressor is provided between the outlet end of the hydrogen production device and the first heat exchange side of the precooling heat exchanger.

[0021] Furthermore, a fourth compressor is provided between the storage module and the first heat exchange side of the nitrogen fixing heat exchanger.

[0022] Furthermore, the power supply module includes a hydrogen steam turbine and a fuel cell stack, and the first heat exchange side outlet end of the liquid nitrogen heat exchanger is connected to the hydrogen steam turbine and the fuel cell stack in sequence.

[0023] Furthermore, it also includes a second expander, and one outlet end of the second storage tank and one outlet end of the third storage tank are connected to the fourth heat exchange side of the precooling heat exchanger or are respectively connected to the second heat exchange side and the third heat exchange side of the liquid nitrogen heat exchanger.

[0024] Furthermore, the energy storage method of the nitrogen-fixed cold storage system applied to liquid hydrogen energy storage comprises the following steps:

[0025] When the cold storage unit stores energy, hydrogen is converted into liquid hydrogen through the pre-cooling heat exchanger and the final heat exchanger in sequence and enters the liquid hydrogen storage tank for storage. The liquid hydrogen in the liquid hydrogen storage tank is then transported to the storage module for storage. After the power supply unit is operated, the liquid hydrogen in the storage module passes through the first heat exchange side of the nitrogen fixation heat exchanger and is cooled by the liquid nitrogen on the third heat exchange side of the nitrogen fixation heat exchanger, and then passes through the liquid nitrogen heat exchanger to cool the nitrogen on the second and third heat exchange sides of the liquid nitrogen heat exchanger, and enters the power supply module for power supply.

[0026] When the cold storage unit releases energy, the hydrogen is pre-cooled by liquid nitrogen in the pre-cooling heat exchanger, deep-cooled by the nitrogen-fixing heat exchanger, and then heat-exchanged by the final heat exchanger and converted into liquid hydrogen, which is then stored in the liquid hydrogen storage tank and storage module.

[0027] (1) The nitrogen-fixed cold storage system for liquid hydrogen energy storage proposed in the utility model adopts a nitrogen-fixed heat exchanger and a liquid nitrogen heat exchanger to recover the cold energy of liquid hydrogen. Nitrogen recovers cold energy and converts it into liquid nitrogen and fixed nitrogen. Fixed nitrogen is used as a single working fluid to recover cold energy and provide cold energy for subsequent hydrogen liquefaction. It can match the temperature zone of liquid hydrogen cold energy recovery and utilization. The larger volume heat capacity and low thermal conductivity at low temperature contribute to a higher cold storage capacity of nitrogen-fixed cold energy, and the system is simpler.

[0028] (2) The nitrogen fixation cold storage system for liquid hydrogen energy storage proposed in the utility model can select a fin plate heat exchanger or a spiral tube heat exchanger as a nitrogen fixation heat exchanger according to actual conditions. The spiral tube heat exchanger occupies a smaller area and can handle a larger flow volume. The fin heat exchanger can enhance heat exchange. Different heat exchangers can be used to adapt to different energy storage systems.

[0029] (3) The liquid nitrogen and fixed nitrogen obtained by storing cold in the nitrogen-fixing cold storage system for liquid hydrogen energy storage proposed in the utility model can be independently connected to different heat exchangers, such as a precooling heat exchanger and a nitrogen-fixing heat exchanger, to complete the precooling link and the refrigeration cycle, so as to compensate for the internal power consumption of the system, increase the liquid hydrogen output, and improve the energy utilization of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is an overall diagram of the nitrogen-fixing cold storage system for liquid hydrogen energy storage of the utility model;

[0031] Figure 2 is the specific heat capacity of nitrogen at different temperatures;

[0032] Figure 3 is the thermal conductivity of nitrogen at different temperatures;

[0033] Figure 4 is the density of nitrogen at different temperatures;

[0034] Figure 5 The calculation results of nitrogen phase change latent heat and heat capacity in each temperature zone;

[0035] In the figure: hydrogen production device 1, third compressor 2, precooling heat exchanger 3, normal-parahydrogen converter 4, final heat exchanger 5, throttle valve 6, second compressor 7, first expander 8, liquid hydrogen storage tank 9, storage module 10, fourth compressor 11, nitrogen fixation heat exchanger 12, liquid nitrogen heat exchanger 13, hydrogen turbine 14, fuel cell stack 15, first storage tank 16, first compressor 17, third storage tank 18, second storage tank 19, second expander 20;

[0036] The realization of the purpose, functional features and advantages of the present invention will be further described in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0037] In order to more clearly and completely illustrate the technical solution of the present invention, the present invention is further described below in conjunction with the accompanying drawings.

[0038] Please refer to Figure 1-Figure 5 The utility model proposes a nitrogen-fixed cold storage system for liquid hydrogen energy storage, comprising a cold storage unit, a liquid hydrogen supply unit and a power supply unit, wherein:

[0039] The cold storage unit includes a first compressor 17, a first storage tank 16, a second storage tank 19, a third storage tank 18, a nitrogen fixation heat exchanger 12 and a liquid nitrogen heat exchanger 13;

[0040] One outlet end of the first storage tank 16 is connected to the first compressor 17, the second heat exchange side of the liquid nitrogen heat exchanger 13 and the second storage tank 19 in sequence, the other outlet end of the first storage tank 16 is connected to the third heat exchange side of the liquid nitrogen heat exchanger 13, and the two outlet ends of the third heat exchange side are connected to the third storage tank 18 and the third heat exchange side of the nitrogen solidification heat exchanger 12 respectively;

[0041] The liquid hydrogen supply unit comprises a hydrogen production device 1, a precooling heat exchanger 3, a normal-parahydrogen converter 4, a final-stage heat exchanger 5 and a liquid hydrogen storage tank 9;

[0042] The power supply unit includes a power supply module and a storage module 10;

[0043] When the cold storage unit stores energy, the outlet end of the hydrogen production device 1 is sequentially connected to the first heat exchange side of the precooling heat exchanger 3, the normal-parahydrogen converter 4, the first heat exchange side of the final heat exchanger 5, the liquid hydrogen storage tank 9, the storage module 10, the first heat exchange side of the nitrogen fixation heat exchanger 12 and the first heat exchange side of the liquid nitrogen heat exchanger 13;

[0044] When the cold storage unit releases energy, the other outlet end of the hydrogen production device 1 is connected in sequence to the first heat exchange side of the precooling heat exchanger 3, the second heat exchange side of the nitrogen fixing heat exchanger 12, the first heat exchange side of the final stage heat exchanger 5, the liquid hydrogen storage tank 9 and the storage module 10.

[0045] In this embodiment:

[0046] The first storage tank 16 is used to store nitrogen;

[0047] The second storage tank 19 and the third storage tank 18 are used to store liquid nitrogen;

[0048] Hydrogen production device 1 is used to produce and provide hydrogen

[0049] The precooling heat exchanger 3 is used to provide precooling for the hydrogen;

[0050] The final heat exchanger 5 is used to further cool the hydrogen;

[0051] The liquid hydrogen storage tank 9 and the storage module 10 are used to store and transport liquid hydrogen;

[0052] The liquid nitrogen heat exchanger 13 is used for heat exchange between hydrogen and nitrogen;

[0053] The nitrogen fixation heat exchanger 12 is used for heat exchange between cryogenic nitrogen, liquid nitrogen and cryogenic hydrogen, liquid hydrogen;

[0054] In a specific implementation, the power supply module is generally arranged at the user end, the storage module 10 and the cold storage unit can be used for on-site cold storage, or can be arranged on a transport vehicle for transportation to areas with large electricity demand or to supplement electricity during peak hours of electricity load, and the liquid hydrogen supply unit is arranged on the renewable energy side. When filling liquid hydrogen, the hydrogen in the hydrogen production device 1 is precooled to about 80K through the precooling heat exchanger 3, and then converted into liquid hydrogen through the ortho-parahydrogen converter and the final heat exchanger 5 and stored in the liquid hydrogen storage tank 9. Then the liquid hydrogen in the liquid hydrogen storage tank 9 is filled into the storage module 10. When liquid hydrogen is to be used for power generation, the liquid hydrogen is successively passed through the nitrogen fixation heat exchanger 12 and the liquid nitrogen heat exchanger 13 for heat exchange and conversion into hydrogen. At the same time, the nitrogen in the first storage tank 16 is compressed by the first compressor 17 or directly enters the liquid nitrogen heat exchanger 13, wherein the atmospheric pressure nitrogen and the pressurized The nitrogen after heat exchange absorbs the cold energy of liquid hydrogen 300-77K, and is converted into liquid nitrogen and stored in the second storage tank 19 and the third storage tank 18 respectively, while the liquid nitrogen in the third heat exchange side of the liquid nitrogen heat exchanger 13 that is not stored in the third storage tank 18 is further cooled by the nitrogen fixing heat exchanger 12, and a liquid-solid phase change occurs when it is cooled to 63.15K, and a solid-solid phase change occurs at 35.6K, and then it continues to absorb the cold energy of liquid hydrogen and is converted into fixed nitrogen for storage. The nitrogen absorbs cold energy and is converted into fixed nitrogen in the nitrogen fixing heat exchanger 12, and the nitrogen absorbs cold energy and is converted into liquid nitrogen in the second storage tank 19 and the third storage tank 18, that is, the cold energy storage process of the cold storage unit. When the liquid hydrogen supply unit is operated again, the hydrogen is pre-cooled by liquid nitrogen and deep-cooled by the nitrogen fixing heat exchanger 12, and then deep-cooled again by the final heat exchanger 5, and finally converted into liquid hydrogen and stored in the liquid hydrogen storage tank 9, that is, the energy release process of the cold storage unit.

[0055] In one embodiment, the liquid nitrogen in the second storage tank 19 and the third storage tank 18 can also be introduced into the fourth heat exchange side of the precooling heat exchanger 3 to perform precooling heat exchange on the hydrogen.

[0056] Furthermore, the nitrogen fixation heat exchanger 12 is a plate-fin heat exchanger or a spiral tube heat exchanger.

[0057] In a specific implementation, a plate-fin heat exchanger and a spiral tube heat exchanger can be selected according to actual conditions. The plate-fin heat exchanger has cross-flow, and corrugated fins are inserted between the plates to enhance heat exchange. The plate-fin heat exchanger has multiple heat exchange channels and can connect multiple circuits. The spiral tube heat exchanger is provided with an insulation layer on the outside and generally has only a single heat exchange channel. When a spiral tube heat exchanger is selected, the liquid hydrogen in the spiral tube exchanges heat with the liquid nitrogen in the cylinder, and is finally converted into solid nitrogen or low-temperature liquid nitrogen and stored in the cylinder of the spiral tube heat exchanger. When a spiral tube heat exchanger is selected, it can be used as a cold storage container or as a heat exchange equipment. When the cold storage unit stores energy and releases energy, the spiral tube needs to change the inlet and outlet of liquid hydrogen or hydrogen.

[0058] In one embodiment, a plurality of nitrogen fixation heat exchangers 12 may be provided to store cold in sequence or simultaneously, thereby increasing the latter stage cold storage rate and flexibly allocating cold capacity.

[0059] Further, when the nitrogen-fixing heat exchanger is a spiral tube heat exchanger, the third heat exchange side of the liquid nitrogen heat exchanger 13 is connected to the outside of the spiral tube heat exchanger;

[0060] When the cold storage unit stores energy, the outlet end of the hydrogen production device 1 is sequentially connected to the first heat exchange side of the precooling heat exchanger 3, the normal-parahydrogen converter 4, the first heat exchange side of the final heat exchanger 5, the liquid hydrogen storage tank 9, the storage module 10, the spiral tube heat exchange side of the nitrogen fixation heat exchanger 12 and the first heat exchange side of the liquid nitrogen heat exchanger 13;

[0061] When the cold storage unit releases energy, the other outlet end of the hydrogen production device 1 is connected in sequence to the first heat exchange side of the precooling heat exchanger 3, the spiral tube heat exchange side of the nitrogen fixing heat exchanger 12, the first heat exchange side of the final stage heat exchanger 5, the liquid hydrogen storage tank 9 and the storage module 10.

[0062] In a specific embodiment, when the cold storage unit stores cold energy, one outlet end of the first storage tank 16 is sequentially connected to the second heat exchange side of the liquid nitrogen heat exchanger 13 and the second storage tank 19, and the other outlet end of the first storage tank 16 is sequentially connected to the third heat exchange side of the liquid nitrogen heat exchanger 13, and the two outlet ends of the third heat exchange side of the liquid nitrogen heat exchanger 13 are respectively connected to the third storage tank 18 and the cylinder of the spiral tube heat exchanger, and the outlet end of the storage module 10 is sequentially connected to the spiral tube of the spiral tube heat exchanger and the first heat exchange side of the liquid nitrogen heat exchanger 13, and the liquid hydrogen passing through the first heat exchange side of the liquid nitrogen heat exchanger 13 cools the nitrogen on the second heat exchange side and the third heat exchange side, and converts the nitrogen into liquid nitrogen and stores it in the second storage tank 19 and the third storage tank 18, while the liquid nitrogen not stored in the second storage tank 19 and the third storage tank 18 will flow into the cylinder of the spiral tube heat exchanger, and after further cooling of the liquid hydrogen in the spiral tube, it will be converted into solid nitrogen and finally remain in the spiral tube heat exchanger;

[0063] When the cold storage unit releases cold energy, one outlet end of the hydrogen production device 1 is connected in sequence to the first heat exchange side of the precooling heat exchanger 3, the spiral tube of the spiral tube heat exchanger, and the final heat exchanger 5. The hydrogen is precooled with liquid nitrogen in the precooling heat exchanger, and heat is exchanged with the solid nitrogen in the spiral tube heat exchanger. Then, it is converted into liquid hydrogen through the final heat exchanger 5 and stored in the liquid hydrogen storage tank 9.

[0064] In one embodiment, the utility model can be applied to different scenarios by using plate-fin heat exchangers and spiral tube heat exchangers. The number of nitrogen fixation heat exchangers 12 can also be selected according to actual conditions, so that the cooling capacity can be flexibly adjusted.

[0065] Furthermore, it also includes a circulation unit, which includes a second compressor 7 and a first expander 8. The outlet end of the second compressor 7 is sequentially connected to the second heat exchange side of the precooling heat exchanger 3, the first expander 8, the second heat exchange side of the final heat exchanger 5, the third heat exchange side of the precooling heat exchanger 3 and connected back to the inlet end of the second compressor 7 to form a circulation unit.

[0066] In this embodiment:

[0067] The second compressor 7 and the first expander 8 are used for helium refrigeration;

[0068] In a specific embodiment, the second compressor 7, the first expander 8, the precooling heat exchanger 3, the second heat exchange side and the third heat exchange side, and the second heat exchange side of the final heat exchanger 5 form a refrigeration circuit. The refrigeration circuit cools the hydrogen in the final heat exchanger 5 and the precooling heat exchanger 3 by cooling the internal helium, so that the hydrogen is converted into liquid hydrogen, providing precooling and further cooling for the hydrogen.

[0069] In one embodiment, the circulation unit can also be used for hydrogen refrigeration or other liquefaction cycles according to actual conditions.

[0070] Furthermore, a throttle valve 6 is provided between the final stage heat exchanger 5 and the liquid hydrogen storage tank 9 .

[0071] In this embodiment:

[0072] The throttle valve 6 is used for throttling and reducing the pressure of liquid hydrogen;

[0073] In a specific embodiment, the throttle valve 6 is arranged between the first heat exchange side outlet of the final stage heat exchanger 5 and the liquid hydrogen storage tank 9, and the converted liquid hydrogen is depressurized and stored in the liquid hydrogen storage tank 9, so as to facilitate the subsequent filling of liquid hydrogen into the storage module 10 for use by the user.

[0074] Furthermore, a third compressor 2 is provided between the outlet of the hydrogen production device 1 and the first heat exchange side of the precooling heat exchanger 3 and the third heat exchange side of the nitrogen fixing heat exchanger 12 .

[0075] In this embodiment:

[0076] The third compressor 2 is used to pressurize hydrogen;

[0077] In a specific embodiment, the hydrogen is pressurized by the third compressor 2, and the high-pressure hydrogen enters the subsequent refrigeration cycle to be cooled and finally liquefied and converted into liquid hydrogen.

[0078] Furthermore, a fourth compressor 11 is provided between the storage module 10 and the first heat exchange side of the nitrogen fixing heat exchanger 12 .

[0079] In this embodiment:

[0080] The fourth compressor 11 is used for compressing cryogenic hydrogen or liquid hydrogen;

[0081] In a specific embodiment, the fourth compressor 11 compresses low-temperature hydrogen or liquid hydrogen, and can use smaller compression work to maintain the pressure potential energy of low-temperature hydrogen and liquid hydrogen in a low-temperature environment. When it is subsequently reheated, it can obtain greater expansion work, thereby increasing the power of the hydrogen turbine 14 to obtain more electricity.

[0082] Furthermore, the power supply module includes a hydrogen steam turbine 14 and a fuel cell stack 15 , and a first heat exchange side outlet end of the liquid nitrogen heat exchanger 13 is connected to the hydrogen steam turbine 14 and the fuel cell stack 15 in sequence.

[0083] In this embodiment:

[0084] The hydrogen turbine 14 is used to recover the pressure of hydrogen;

[0085] The fuel cell stack 15 is used for hydrogen reaction to generate electricity;

[0086] In a specific embodiment, high-pressure hydrogen will drive the hydrogen turbine 14 to generate power, releasing the pressure potential energy maintained by compression at low temperature. After nitrogen solidification and cold storage and the hydrogen turbine 14, the liquid hydrogen will vaporize and heat up to a suitable temperature, and enter the fuel cell stack 15 to react and generate power.

[0087] Furthermore, it also includes a second expander 20, and one outlet end of the second storage tank 19 and one outlet end of the third storage tank 18 are connected to the fourth heat exchange side of the precooling heat exchanger 3 or the second heat exchange side and the third heat exchange side of the liquid nitrogen heat exchanger 13 respectively.

[0088] In a specific embodiment,

[0089] During the initial operation, the fourth heat exchange side of the precooling heat exchanger 3 is connected to a low-temperature nitrogen source, and the hydrogen is precooled by heat exchange with the low-temperature nitrogen source. After the liquid hydrogen in the first storage tank 9 is converted into hydrogen, the cold energy is fully recovered through the liquid nitrogen heat exchanger 13 and the nitrogen fixing heat exchanger 12 and stored in the liquid nitrogen in the second storage tank 19 and the third storage tank 18 and the fixed nitrogen in the nitrogen fixing heat exchanger;

[0090] When it is operated again, the cold storage unit releases cold energy, and the outlet end of the hydrogen production device 1 is connected to the first heat exchange side of the precooling heat exchanger 3, the nitrogen fixing heat exchanger 12 and the final heat exchanger 5 in sequence, and the liquid nitrogen in the second storage tank 19 and the third storage tank 18 is used to precool the hydrogen in the precooling heat exchanger 3, and then the fixed nitrogen in the nitrogen fixing heat exchanger 12 is used to perform deep cooling heat exchange for the hydrogen, and finally converted into liquid hydrogen and stored in the liquid hydrogen storage tank 9;

[0091] The utility model utilizes the liquid nitrogen heat exchanger 13 and the solid nitrogen heat exchanger 12 for heat exchange, utilizes nitrogen to recover the cold energy of hydrogen and liquid hydrogen, and converts them into solid nitrogen and liquid nitrogen, thereby providing cold energy for subsequent hydrogen liquefaction. The utility model has higher flexibility, can adapt to different scenarios, and improves the utilization rate of cold energy.

[0092] In one embodiment, when the outlet end of the hydrogen production device 1 is connected to the precooling heat exchanger 3, the outlet ends of the second storage tank 19 and the third storage tank 18 are connected to the fourth heat exchange side of the precooling heat exchanger 3 and the second expansion machine 20 in sequence. The liquid nitrogen in the second storage tank 19 and the third storage tank 18 provides cold energy for precooling of the hydrogen. After the high-pressure liquid nitrogen releases the cold energy in the precooling heat exchanger 3, it can be expanded through the second expansion machine 20 to generate power and release pressure potential energy. Through the flexible arrangement of cold storage, cold release and pressurization cycle, it is suitable for large-scale liquid hydrogen energy storage systems to improve energy utilization.

[0093] Furthermore, the nitrogen-fixing cold storage system and method for liquid hydrogen energy storage comprises the following steps:

[0094] When the cold storage unit stores energy, the hydrogen is converted into liquid hydrogen through the pre-cooling heat exchanger 3 and the final heat exchanger 5 in sequence and enters the liquid hydrogen storage tank 9 for storage. Then, the liquid hydrogen in the liquid hydrogen storage tank 9 is transported to the storage module 10 for storage. After the power supply unit is operated, the liquid hydrogen in the storage module 10 passes through the first heat exchange side of the nitrogen fixing heat exchanger 12 and is cooled by the liquid nitrogen on the third heat exchange side of the nitrogen fixing heat exchanger 12, and then passes through the liquid nitrogen heat exchanger 13 to cool the nitrogen on the second heat exchange side and the third heat exchange side of the liquid nitrogen heat exchanger, and enters the power supply module 15 for power supply.

[0095] When the cold storage unit releases energy, the hydrogen is pre-cooled by liquid nitrogen in the pre-cooling heat exchanger 5, deep-cooled by the nitrogen fixation heat exchanger 12, and then heat-exchanged by the final heat exchanger 5 and converted into liquid hydrogen to enter the liquid hydrogen storage tank 9 and the storage module 10 for storage.

[0096] In a specific embodiment, when the cold storage unit releases energy, it can also be selected according to actual conditions to precool the hydrogen through the nitrogen fixation heat exchanger 12 or one of the precooling heat exchangers 3, and then converted into liquid hydrogen through the final stage converter 5 to be stored in the liquid hydrogen storage tank 9 and the storage module 10.

[0097] Of course, the present utility model may have many other implementations. Based on the present implementation, other implementations obtained by ordinary technicians in this field without any creative work are all within the scope of protection of the present utility model.

Claims

1. A nitrogen-fixed cold storage system for liquid hydrogen energy storage, characterized in that: It includes a cold storage unit, a liquid hydrogen supply unit and a power supply unit, wherein: The cold storage unit includes a first compressor, a first storage tank, a second storage tank, a third storage tank, a nitrogen fixation heat exchanger and a liquid nitrogen heat exchanger; One outlet end of the first storage tank is connected to the first compressor, the second heat exchange side of the liquid nitrogen heat exchanger and the second storage tank in sequence, the other outlet end of the first storage tank is connected to the third heat exchange side of the liquid nitrogen heat exchanger, and two outlet ends of the third heat exchange side are respectively connected to the third storage tank and the third heat exchange side of the nitrogen solidification heat exchanger; The liquid hydrogen supply unit includes a hydrogen production device, a precooling heat exchanger, a normal-parahydrogen converter, a final-stage heat exchanger and a liquid hydrogen storage tank; The power supply unit includes a power supply module and a storage module; When the cold storage unit stores energy, the outlet end of the hydrogen production device is sequentially connected to the first heat exchange side of the precooling heat exchanger, the normal-parahydrogen converter, the first heat exchange side of the final heat exchanger, the liquid hydrogen storage tank, the storage module, the first heat exchange side of the nitrogen fixation heat exchanger and the first heat exchange side of the liquid nitrogen heat exchanger; When the cold storage unit releases energy, the other outlet end of the hydrogen production device is sequentially connected to the first heat exchange side of the pre-cooling heat exchanger, the second heat exchange side of the nitrogen fixation heat exchanger, the first heat exchange side of the final stage heat exchanger, the liquid hydrogen storage tank and the storage module.

2. The nitrogen-fixing cold storage system for liquid hydrogen energy storage according to claim 1 is characterized in that: The nitrogen fixation heat exchanger is a plate-fin heat exchanger or a spiral tube heat exchanger.

3. The nitrogen-fixing cold storage system for liquid hydrogen energy storage according to claim 2 is characterized in that: When the nitrogen fixing heat exchanger is a spiral tube heat exchanger, the third heat exchange side of the liquid nitrogen heat exchanger is connected to the outside of the spiral tube heat exchanger; When the cold storage unit stores energy, the outlet end of the hydrogen production device is sequentially connected to the first heat exchange side of the precooling heat exchanger, the normal-parahydrogen converter, the first heat exchange side of the final heat exchanger, the liquid hydrogen storage tank, the storage module, the spiral tube heat exchange side of the nitrogen fixation heat exchanger and the first heat exchange side of the liquid nitrogen heat exchanger; When the cold storage unit releases energy, the other outlet end of the hydrogen production device is sequentially connected to the first heat exchange side of the precooling heat exchanger, the spiral tube heat exchange side of the nitrogen fixation heat exchanger, the first heat exchange side of the final stage heat exchanger, the liquid hydrogen storage tank and the storage module.

4. The nitrogen-fixing cold storage system for liquid hydrogen energy storage according to claim 1 is characterized in that: It also includes a circulation unit, which includes a second compressor and a first expander. The outlet end of the second compressor is sequentially connected to the second heat exchange side of the precooling heat exchanger, the first expander, the second heat exchange side of the final heat exchanger, the third heat exchange side of the precooling heat exchanger and connected back to the inlet end of the second compressor to form a circulation unit.

5. The nitrogen-fixing cold storage system for liquid hydrogen energy storage according to claim 1 is characterized in that: A throttle valve is also provided between the final stage heat exchanger and the liquid hydrogen storage tank.

6. The nitrogen-fixed cold storage system for liquid hydrogen energy storage according to claim 1 is characterized in that: A third compressor is also provided between the outlet end of the hydrogen production device and the first heat exchange side of the precooling heat exchanger.

7. The nitrogen-fixing cold storage system for liquid hydrogen energy storage according to claim 1 is characterized in that: A fourth compressor is provided between the storage module and the first heat exchange side of the nitrogen fixing heat exchanger.

8. The nitrogen-fixing cold storage system for liquid hydrogen energy storage according to claim 1 is characterized in that: The power supply module comprises a hydrogen steam turbine and a fuel cell stack, and the first heat exchange side outlet end of the liquid nitrogen heat exchanger is connected to the hydrogen steam turbine and the fuel cell stack in sequence.

9. The nitrogen-fixing cold storage system for liquid hydrogen energy storage according to claim 1 is characterized in that: It also includes a second expander, and one outlet end of the second storage tank and one outlet end of the third storage tank are connected to the fourth heat exchange side of the precooling heat exchanger or are respectively connected to the second heat exchange side and the third heat exchange side of the liquid nitrogen heat exchanger.

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