Electrochemical active control liquefier for reliquefaction, electrochemical active control refrigerator for reliquefaction, and liquid hydrogen storage and reliquefaction system including the same

Abstract

According to one embodiment based on the technical concept of the present invention, an electrochemical active control liquefier for re-liquefaction, an electrochemical active control refrigerator for re-liquefaction, and a liquid hydrogen storage and re-liquefaction system including the same are to actively control the amount of gaseous hydrogen compressed by adjusting the applied voltage of an electrochemical hydrogen compressor during the re-liquefaction process of a liquid hydrogen storage tank, thereby enabling real-time response to changes in the operating conditions of the liquid hydrogen storage system, and the electrochemical active control liquefier for re-liquefaction for a liquid hydrogen storage tank comprises: a heat exchanger that uses a first gaseous hydrogen evaporated from the liquid hydrogen storage tank and discharged through a discharge pipe for heat exchange; and an electrochemical hydrogen compressor that discharges a third gaseous hydrogen, compressed from a second gaseous hydrogen discharged from the heat exchanger, to the heat exchanger. It includes a JT expander that expands and liquefies the third gaseous hydrogen, which is cooled by heat exchange with the first gaseous hydrogen in the heat exchanger, and the liquid hydrogen discharged from the JT expander can be introduced into a liquid hydrogen storage tank through an inlet pipe.

Description

Technology Field

[0001] The present invention relates to an electrochemical active control liquefier for re-liquefaction, an electrochemical active control refrigerator for re-liquefaction, and a liquid hydrogen storage and re-liquefaction system including the same. More specifically, the invention relates to an electrochemical active control liquefier for re-liquefaction, an electrochemical active control refrigerator for re-liquefaction, and a liquid hydrogen storage and re-liquefaction system including the same, which actively controls the amount of gaseous hydrogen compressed by adjusting the applied voltage of an electrochemical hydrogen compressor during the re-liquefaction process of a liquid hydrogen storage tank, thereby enabling real-time response to changes in the operating conditions of the liquid hydrogen storage system. Background Technology

[0002] Liquid hydrogen is stored at cryogenic temperatures, and if external heat is introduced during storage, it may evaporate into gaseous hydrogen, resulting in loss. Therefore, technology to effectively recover and re-liquefy the evaporated gas generated inside the liquid hydrogen storage tank is essential.

[0003] Conventional hydrogen reliquefaction technology uses a Reverse Brayton Cycle-based chiller, but this has the problem of a narrow compressor control range and slow response speed. In addition, control methods utilizing heaters or bypass valves have the problem of unnecessary power consumption.

[0004] Many inventors have been conducting research to solve these problems, but satisfactory results have not yet been obtained. The problem to be solved

[0005] The technical problem to be solved by the electrochemical active control liquefier for reliquefaction, the electrochemical active control refrigerator for reliquefaction, and the liquid hydrogen storage and reliquefaction system including the same, according to the technical concept of the present invention, is to efficiently reliquefy gaseous hydrogen evaporated from the liquid hydrogen storage tank to minimize liquid hydrogen loss within the storage tank and optimize energy consumption.

[0006] Another technical objective to be achieved by the electrochemical active control liquefier for re-liquefaction, the electrochemical active control refrigerator for re-liquefaction, and the liquid hydrogen storage and re-liquefaction system including the same, according to the technical concept of the present invention, is to enable active control of the amount of gaseous hydrogen compressed by adjusting the applied voltage of the electrochemical hydrogen compressor so as to respond in real time to changes in the operating conditions of the liquid hydrogen storage tank.

[0007] The technical problems to be solved by the electrochemical active control liquefier for reliquefaction, the electrochemical active control refrigerator for reliquefaction, and the liquid hydrogen storage and reliquefaction system including the same, according to the technical concept of the present invention, are not limited to those mentioned above, and other unmentioned problems will be clearly understood by a person skilled in the art from the description below. means of solving the problem

[0008] According to one embodiment of the technical concept of the present invention, an electrochemical active control liquefier for re-liquefaction of a liquid hydrogen storage tank comprises: a heat exchanger that uses a first gaseous hydrogen, which is evaporated from the liquid hydrogen storage tank and discharged through a discharge pipe, for heat exchange; an electrochemical hydrogen compressor that discharges a third gaseous hydrogen, which is compressed from a second gaseous hydrogen discharged from the heat exchanger, to the heat exchanger; and a JT expander that expands and liquefies the third gaseous hydrogen, which is cooled by heat exchange with the first gaseous hydrogen within the heat exchanger, wherein the liquid hydrogen discharged from the JT expander can be introduced into the liquid hydrogen storage tank through an inlet pipe.

[0009] The heat exchanger can perform multi-stage heat exchange between the first gaseous hydrogen and the third gaseous hydrogen.

[0010] The heat exchanger can further cool the third gaseous hydrogen using liquid nitrogen.

[0011] The amount of third gaseous hydrogen produced in the electrochemical hydrogen compressor can be controlled by adjusting the voltage applied to the electrochemical hydrogen compressor according to changes in operating conditions.

[0012] The electrochemical hydrogen compressor includes a plurality of electrochemical hydrogen compressor modules connected in parallel, and predetermined voltages are set for each module, and the electrochemical hydrogen compressor module corresponding to the changed operating conditions can be operated.

[0013] Changes in operating conditions may include at least one of changes in heat intrusion into the liquid hydrogen storage tank, changes in the liquid hydrogen level, changes in heat intrusion due to valve and piping operation, changes in ambient temperature, and changes in hydrogen consumption.

[0014] According to another embodiment of the technical concept of the present invention, an electrochemical active control refrigerator for re-liquefaction for a liquid hydrogen storage tank comprises: a re-liquefaction heat exchanger that liquefies gaseous hydrogen through heat exchange between gaseous hydrogen and liquid hydrogen refrigerant in the liquid hydrogen storage tank; a heat exchanger that uses a first gaseous hydrogen refrigerant that has passed through the re-liquefaction heat exchanger for heat exchange; an electrochemical hydrogen compressor that discharges a third gaseous hydrogen refrigerant, which is compressed from a second gaseous hydrogen refrigerant discharged from the heat exchanger, to the heat exchanger; and a JT expander that expands and liquefies the third gaseous hydrogen refrigerant, which is cooled by heat exchange with the first gaseous hydrogen refrigerant in the heat exchanger, wherein the liquid hydrogen refrigerant discharged from the JT expander may be moved to the re-liquefaction heat exchanger.

[0015] The heat exchanger can perform multi-stage heat exchange between the first gaseous hydrogen refrigerant and the third gaseous hydrogen refrigerant.

[0016] The heat exchanger can further cool the third gaseous hydrogen refrigerant using liquid nitrogen.

[0017] In an electrochemical hydrogen compressor, the voltage applied to the electrochemical hydrogen compressor is regulated according to changes in operating conditions, so that the amount of third gaseous hydrogen refrigerant produced in the electrochemical hydrogen compressor can be regulated.

[0018] The electrochemical hydrogen compressor includes a plurality of electrochemical hydrogen compressor modules connected in parallel, and predetermined voltages are set for each module, and the electrochemical hydrogen compressor module corresponding to the changed operating conditions can be operated.

[0019] Changes in operating conditions may include at least one of changes in heat intrusion into the liquid hydrogen storage tank, changes in the liquid hydrogen level, changes in heat intrusion due to valve and piping operation, changes in ambient temperature, and changes in hydrogen consumption.

[0020] A liquid hydrogen storage and re-liquefaction system according to another embodiment of the technical concept of the present invention comprises: a liquid hydrogen storage tank in which liquid hydrogen is received; and an electrochemical active control liquefier for re-liquefaction, which is connected to the liquid hydrogen storage tank and includes a heat exchanger, an electrochemical hydrogen compressor, and a JT expander, wherein a first gaseous hydrogen evaporated from the liquid hydrogen is introduced, circulated, liquefied, and introduced into the liquid hydrogen storage tank, wherein the first gaseous hydrogen and the third gaseous hydrogen are heat exchanged in the heat exchanger, the third gaseous hydrogen is gaseous hydrogen in which the second gaseous hydrogen is compressed in the electrochemical hydrogen compressor, the second gaseous hydrogen is gaseous hydrogen in which the first gaseous hydrogen is heat exchanged with the third gaseous hydrogen in the heat exchanger, and the fourth gaseous hydrogen is gaseous hydrogen discharged after the third gaseous hydrogen is cooled by the first gaseous hydrogen in the heat exchanger, and can be expanded and liquefied in the JT expander.

[0021] The heat exchanger can perform multi-stage heat exchange between the first gaseous hydrogen and the third gaseous hydrogen.

[0022] The heat exchanger can further cool the third gaseous hydrogen using liquid nitrogen.

[0023] The amount of third gaseous hydrogen produced in the electrochemical hydrogen compressor can be controlled by adjusting the voltage applied to the electrochemical hydrogen compressor according to changes in operating conditions.

[0024] The electrochemical hydrogen compressor includes a plurality of electrochemical hydrogen compressor modules connected in parallel, and predetermined voltages are set for each module, and the electrochemical hydrogen compressor module corresponding to the changed operating conditions can be operated.

[0025] Changes in operating conditions may include at least one of changes in heat intrusion into the liquid hydrogen storage tank, changes in the liquid hydrogen level, changes in heat intrusion due to valve and piping operation, changes in ambient temperature, and changes in hydrogen consumption.

[0026] A liquid hydrogen storage and reliquefaction system according to another embodiment based on the technical concept of the present invention comprises: a liquid hydrogen storage tank in which liquid hydrogen is received; and connected to a liquid hydrogen storage tank, and includes an electrochemical active control refrigerator for reliquefaction comprising a reliquefaction heat exchanger, a heat exchanger, an electrochemical hydrogen compressor, and a JT expander for reliquefying gaseous hydrogen evaporated from liquid hydrogen, wherein in the reliquefaction heat exchanger, gaseous hydrogen is cooled and liquefied by a liquid hydrogen refrigerant, and in the heat exchanger, a first gaseous hydrogen refrigerant and a third gaseous hydrogen refrigerant exchange heat in the reliquefaction heat exchanger, the third gaseous hydrogen refrigerant is a gaseous hydrogen refrigerant in which the second gaseous hydrogen refrigerant is compressed in an electrochemical hydrogen compressor, the second gaseous hydrogen refrigerant is a gaseous hydrogen refrigerant in which the first gaseous hydrogen refrigerant exchanges heat with the third gaseous hydrogen refrigerant in the heat exchanger, and the fourth gaseous hydrogen refrigerant is a gaseous hydrogen refrigerant discharged after the third gaseous hydrogen refrigerant is cooled by the first gaseous hydrogen refrigerant in the heat exchanger, and in the JT expander It can be expanded to become liquefied liquid hydrogen refrigerant.

[0027] The heat exchanger can perform multi-stage heat exchange between the first gaseous hydrogen refrigerant and the third gaseous hydrogen refrigerant.

[0028] The heat exchanger can further cool the third gaseous hydrogen refrigerant using liquid nitrogen.

[0029] The voltage applied to the electrochemical hydrogen compressor can be adjusted according to changes in operating conditions, thereby controlling the amount of third gaseous hydrogen refrigerant produced in the electrochemical hydrogen compressor.

[0030] The electrochemical hydrogen compressor includes a plurality of electrochemical hydrogen compressor modules connected in parallel, and predetermined voltages are set for each module, and the electrochemical hydrogen compressor module corresponding to the changed operating conditions can be operated.

[0031] Changes in operating conditions may include at least one of changes in heat intrusion into the liquid hydrogen storage tank, changes in the liquid hydrogen level, changes in heat intrusion due to valve and piping operation, changes in ambient temperature, and changes in hydrogen consumption. Effects of the invention

[0032] According to embodiments based on the technical concept of the present invention, an electrochemical active control liquefier for re-liquefaction, an electrochemical active control refrigerator for re-liquefaction, and a liquid hydrogen storage and re-liquefaction system including the same can achieve the following effects.

[0033] (1) By efficiently re-liquefying gaseous hydrogen that has evaporated from the liquid hydrogen storage tank, the loss of liquid hydrogen in the storage tank can be minimized and energy consumption can be optimized.

[0034] (2) By adjusting the applied voltage of the electrochemical hydrogen compressor, the amount of gaseous hydrogen compressed can be actively controlled, allowing for real-time response to changes in the operating conditions of the liquid hydrogen storage tank. This enables immediate re-liquefaction adjustment based on the amount of gaseous hydrogen evaporated in the liquid hydrogen storage tank, thereby preventing unnecessary power consumption.

[0035] (3) By utilizing an electrochemical hydrogen compressor compared to a conventional mechanical compressor, energy efficiency can be maximized and vibration-free and low-noise operation is possible.

[0036] (4) By applying a multi-stage heat exchange method, the temperature difference is gradually reduced to maximize cooling efficiency, and the cooling performance can be improved by using liquid nitrogen (LN2) for pre-cooling.

[0037] (5) Flexible expansion is possible by utilizing multiple electrochemical hydrogen compressor modules connected in parallel, and optimal operating conditions can be maintained by controlling the operation of each module as needed.

[0038] (6) By providing an integrated system including an electrochemical active control liquefier and a refrigerator for re-liquefaction, the connection with the liquid hydrogen storage tank can be optimized and overall energy consumption can be reduced.

[0039] However, the effects that can be achieved by the electrochemical active control liquefier for reliquefaction, the electrochemical active control refrigerator for reliquefaction, and the liquid hydrogen storage and reliquefaction system including the same, according to embodiments of the technical concept of the present invention, are not limited to those mentioned above, and other effects not mentioned will be clearly understood by a person skilled in the art from the description below. Brief explanation of the drawing

[0040] A brief description of each drawing is provided to help to better understand the drawings cited in this specification. FIG. 1 is a schematic diagram of a liquid hydrogen storage and re-liquefaction system including an electrochemical active control liquefier for re-liquefaction according to one embodiment of the technical concept of the present invention. FIG. 2 is a schematic diagram of a liquid hydrogen storage and reliquefaction system including an electrochemical active control refrigerator for reliquefaction according to one embodiment of the technical concept of the present invention. FIG. 3 is a schematic diagram of a multi-electrochemical hydrogen compressor module of a liquid hydrogen storage and reliquefaction system according to one embodiment of the technical concept of the present invention. Specific details for implementing the invention

[0041] The present invention is capable of various modifications and may have various embodiments, and specific embodiments are illustrated in the drawings and described in detail in the detailed description. However, this is not intended to limit the present invention to specific embodiments, and it should be understood that the present invention includes all modifications, equivalents, and substitutions that fall within the spirit and scope of the invention.

[0042] In describing the present invention, if it is determined that a detailed description of related prior art may unnecessarily obscure the essence of the present invention, such detailed description is omitted. Additionally, numbers used in the description of this specification (e.g., 1st, 2nd, etc.) are merely identification symbols to distinguish one component from another.

[0043] In addition, when a component is described in this specification as being "connected" or "combined" with another component, it should be understood that the component may be directly connected or directly combined with the other component, but unless otherwise specifically stated, it may also be connected or combined through another component in between.

[0044] In addition, components expressed as '~part' in this specification may consist of two or more components combined into a single component, or a single component may be divided into two or more components according to more detailed functions. Furthermore, each component described below may additionally perform some or all of the functions performed by other components in addition to the primary function it is responsible for, and it goes without saying that some of the primary functions performed by each component may be exclusively performed by other components.

[0045] Hereinafter, embodiments based on the technical concept of the present invention will be described in detail in turn.

[0046] FIG. 1 is a schematic diagram of a liquid hydrogen storage and reliquefaction system including an electrochemical active control liquefier for reliquefaction according to an embodiment of the technical concept of the present invention. FIG. 2 is a schematic diagram of a liquid hydrogen storage and reliquefaction system including an electrochemical active control refrigerator for reliquefaction according to an embodiment of the technical concept of the present invention. FIG. 3 is a schematic diagram of a multi-electrochemical hydrogen compressor module of a liquid hydrogen storage and reliquefaction system according to an embodiment of the technical concept of the present invention.

[0047] A liquid hydrogen storage and re-liquefaction system including an electrochemical active control liquefier for re-liquefaction according to one embodiment of the technical concept of the present invention may include a liquid hydrogen storage tank (10) in which liquid hydrogen (L) is received and an electrochemical active control liquefier (100) for re-liquefaction.

[0048] The electrochemical active control liquefier (100) for re-liquefaction is connected to a liquid hydrogen storage tank (10) and may include a discharge pipe (110), a heat exchanger (120), an electrochemical hydrogen compressor (130), a JT expander (140), and an inlet pipe (150).

[0049] The electrochemical active control liquefier (100) for re-liquefaction operates in an open-loop manner and can liquefy gaseous hydrogen evaporated inside the liquid hydrogen storage tank (10) by directly compressing it. In the following, as gaseous hydrogen circulates through the electrochemical active control liquefier (100) for re-liquefaction and its temperature and / or pressure changes, the gaseous hydrogen is distinguished and named as "first," "second," etc.

[0050] The first gaseous hydrogen (G1) evaporated from the liquid hydrogen (L) within the liquid hydrogen storage tank (10) can be discharged from the liquid hydrogen storage tank (10) through a discharge pipe (110) connecting the inside and outside of the liquid hydrogen storage tank (10). The first gaseous hydrogen (G1) discharged from the liquid hydrogen storage tank (10) is introduced into an electrochemical active control liquefier (100) for re-liquefaction, then circulated and liquefied, and then introduced back into the liquid hydrogen storage tank (10).

[0051] The heat exchanger (120) can use the first gaseous hydrogen (G1) that has been evaporated from the liquid hydrogen storage tank (10) and discharged through the discharge pipe (110) for heat exchange. In the heat exchanger (120), the first gaseous hydrogen (G1) and the third gaseous hydrogen (G3) can be heat exchanged.

[0052] The electrochemical hydrogen compressor (130) can discharge high-temperature, high-pressure third gaseous hydrogen (G3), which is produced by compressing the second gaseous hydrogen (G2) discharged from the heat exchanger (120), back to the heat exchanger (120). The third gaseous hydrogen (G3) is high-temperature gaseous hydrogen produced by compressing the second gaseous hydrogen (G2) in the electrochemical hydrogen compressor (130). The second gaseous hydrogen (G2) is gaseous hydrogen whose temperature has been raised by heat exchange between the first gaseous hydrogen (G1) and the third gaseous hydrogen (G3) in the heat exchanger (120), and the fourth gaseous hydrogen (G4) is gaseous hydrogen that has been cooled by heat exchange between the third gaseous hydrogen (G3) and the first gaseous hydrogen (G1) in the heat exchanger (120).

[0053] The electrochemical hydrogen compressor (130) can generate high-pressure hydrogen at the cathode by applying voltage to ionize low-pressure hydrogen at the anode and passing it through a proton exchange membrane. Unlike mechanical compressors, it has no moving parts, so vibration-free compression is possible, and since isothermal compression is possible, the compression efficiency is higher than that of conventional mechanical compressors, which are adiabatic compression processes. In addition, since only pure hydrogen is ionized during the compression process and then becomes high-pressure hydrogen, it also has a hydrogen purification function. The voltage (V) required for the electrochemical hydrogen compressor (130) can be calculated using the following equation (1).

[0055] Equation (1)

[0056] Here,

[0057] V: Voltage to be applied to the electrochemical compressor

[0058] R: Gas constant

[0059] T: Absolute temperature

[0060] n: number of moles of electrons (n=2 for hydrogen)

[0061] F: Faraday constant

[0062] P1: Initial pressure before compression (low pressure, positive pressure)

[0063] P2: Final pressure after compression (high pressure, negative electrode)

[0065] (2)

[0066] Here,

[0067] m_dot: Mass flow rate of hydrogen

[0068] M: Molar mass of hydrogen

[0069] I: Applied current

[0070] n: number of moles of electrons (n=2 for hydrogen)

[0071] F: Faraday constant

[0073] As can be seen from Equation (1), as the pressure ratio (P2 / P1) increases, that is, to compress to a higher pressure, a larger voltage is required, and Equation (2) shows that the mass flow rate (m_dot) of hydrogen compressed per unit time in the electrochemical hydrogen compressor (130) is proportional to the amount of current (I). Therefore, by adjusting the voltage and current, the desired pressure and the mass flow rate of hydrogen can be controlled in real time.

[0074] The third gaseous hydrogen (G3) that has passed through the electrochemical hydrogen compressor (130) has high pressure and high temperature. If the JT expansion described later is performed immediately in this state, the temperature may not be sufficiently low, and thus the liquefaction efficiency may be reduced. Therefore, if the third gaseous hydrogen (G3) is pre-cooled by heat exchange with the first gaseous hydrogen (G1), the possibility of liquefaction during JT expansion increases.

[0075] The first gaseous hydrogen (G1) is in a state of evaporation from the liquid hydrogen storage tank (10), and is at a relatively low temperature (low temperature) and low pressure. By heat-exchanging the first gaseous hydrogen (G1) with the third gaseous hydrogen (G3), the temperature of the first gaseous hydrogen (G1) can be increased so that it can be efficiently compressed when introduced into the electrochemical hydrogen compressor (130). This reduces heat loss and improves the overall energy efficiency of the system.

[0076] The heat exchanger (120) can perform multi-stage heat exchange between the first gaseous hydrogen (G1) and the third gaseous hydrogen (G3). Since the temperature difference between the first gaseous hydrogen (G1) and the third gaseous hydrogen (G3) is significantly large, if heat exchange is performed all at once in a single heat exchanger, there is a high possibility of inefficient heat transfer. To solve this problem, multi-stage heat exchange is performed, and through multi-stage heat exchange, the temperature change from high temperature to low temperature can be carried out gradually over several stages, thereby enabling efficient heat exchange. The multi-stage heat exchange method contributes to optimizing heat transfer performance and reducing energy loss.

[0077] The heat exchanger (120) can further cool the third gaseous hydrogen (G3) using liquid nitrogen (N). In order for the fourth gaseous hydrogen (G4) to be liquefied during the JT expansion process described later, the expansion must be carried out while cooled to a sufficiently low temperature. Since it may be difficult to cool the third gaseous hydrogen (G3) to a sufficiently low temperature solely through multi-stage heat exchange between the first gaseous hydrogen (G1) and the third gaseous hydrogen (G3), liquid nitrogen (N) can be additionally utilized as a cooling medium to assist in cryogenic cooling. Through this, a larger proportion of hydrogen can be liquefied after JT expansion.

[0078] The JT (Joule-Thomson) expander (140) can expand and liquefy the third gaseous hydrogen (G3) that has been cooled by heat exchange with the first gaseous hydrogen (G1) in the heat exchanger (120). The fourth gaseous hydrogen (G4) is the gaseous hydrogen discharged after the third gaseous hydrogen (G3) is cooled by the first gaseous hydrogen (G1) in the heat exchanger (120), and can be expanded and liquefied in the JT expander (140).

[0079] The JT expander (140) is a device that utilizes the phenomenon in which the temperature of a gas or liquid changes as the pressure decreases under isenthalpic conditions, and is used to expand gaseous hydrogen, i.e., fourth gaseous hydrogen (G4), to a low pressure and lower the temperature. The JT expander (140) may include a JT expansion valve.

[0080] Liquid hydrogen (L) liquefied and discharged from the JT expander (140) can be introduced into the liquid hydrogen storage tank (10) through the inlet pipe (150).

[0081] In this way, a Linde-Hampson cycle liquefier can be constructed by utilizing an electrochemical hydrogen compressor (130) and a JT expander (140). The Linde-Hampson cycle is a cycle that uses JT expansion to liquefy gaseous hydrogen, pre-cooling using liquid nitrogen (N) and multi-stage heat exchange to reach a final hydrogen liquefaction temperature (20 K).

[0082] To improve the efficiency of the electrochemical active control liquefier (100) for re-liquefaction, a Claude cycle utilizing an expansion engine (piston or turbine type) may be applied instead of the JT expander (140).

[0083] The amount of third gaseous hydrogen (G3) produced in the electrochemical hydrogen compressor (130) can be controlled by adjusting the voltage applied to the electrochemical hydrogen compressor (130) according to changes in operating conditions.

[0084] Additionally, as shown in FIG. 3, the electrochemical hydrogen compressor (130) includes a plurality of electrochemical hydrogen compressor modules (131) connected in parallel, and predetermined voltages are set for each module, and the electrochemical hydrogen compressor module (131) corresponding to the changed operating conditions may be operated.

[0085] Here, changes in operating conditions may include changes in the amount of heat intrusion into the liquid hydrogen storage tank (10), changes in the liquid hydrogen level, changes in heat intrusion due to valve and piping operation, changes in ambient temperature and changes in hydrogen consumption.

[0086] The liquid hydrogen storage tank (10) may receive heat depending on the external environment, and as a result, the amount of evaporation in which the internal liquid hydrogen (L) turns into gas may vary. When the amount of heat intrusion into the liquid hydrogen storage tank (10) increases, more gaseous hydrogen, i.e., first gaseous hydrogen (G1), is generated, so the voltage and current of the electrochemical hydrogen compressor (130) can be increased to increase the re-liquefaction capacity in order to quickly re-liquefy it. Conversely, when the amount of heat intrusion is low, the voltage and current can be lowered to prevent unnecessary power consumption, thereby allowing the electrochemical hydrogen compressor (130) to be operated efficiently.

[0087] Additionally, if the liquid hydrogen (L) level in the liquid hydrogen storage tank (10) changes, the volume occupied by the liquid hydrogen (L) relative to the liquid hydrogen storage tank (10) changes, and thus the evaporation rate may change. The gaseous hydrogen (G) inside the liquid hydrogen storage tank (10) may be relatively higher than the temperature of the liquid hydrogen (L) due to thermal stratification. As the liquid hydrogen (L) level increases, the overall temperature of the storage tank (10) decreases, so there is a possibility that the amount of evaporation will increase due to increased external heat input. Alternatively, the amount of evaporation may increase as the liquid hydrogen (L) inside the liquid hydrogen storage tank (10) slushes during transport, causing the liquid hydrogen (L) to come into contact with the upper inner wall of the tank, which has a relatively higher temperature or has come into contact with the gaseous hydrogen (G). To compensate for this, the output of the electrochemical hydrogen compressor (130) can be increased to re-liquefy the evaporated hydrogen more quickly.

[0088] Additionally, when the valve and piping are operated to supply liquid hydrogen (L) to the outside or to adjust the internal flow from the liquid hydrogen storage tank (10), a momentary heat inflow may occur. In response to this change, the voltage and current of the electrochemical hydrogen compressor (130) can be adjusted to re-liquefy the momentarily increased amount of evaporation.

[0089] Additionally, when liquid hydrogen (L) is supplied to an external system, the amount of gaseous hydrogen evaporated from the liquid hydrogen storage tank (10) may change. As hydrogen consumption increases, the internal pressure of the storage tank decreases, so the amount of remaining liquid hydrogen (L) evaporated may increase in order to achieve gas-liquid phase equilibrium. In this case, the voltage and current of the electrochemical hydrogen compressor (130) can be controlled to re-liquefy more gaseous hydrogen.

[0090] A liquid hydrogen storage and re-liquefaction system including an electrochemical active control refrigerator for re-liquefaction according to another embodiment of the technical concept of the present invention may include a liquid hydrogen storage tank (10) in which liquid hydrogen (L) is received and an electrochemical active control refrigerator (200) for re-liquefaction.

[0091] The electrochemical active control refrigerator (200) for re-liquefaction is connected to a liquid hydrogen storage tank (10) and may include a discharge pipe (210), a heat exchanger (220), an electrochemical hydrogen compressor (230) and a JT expander (240), an inlet pipe (250), and a re-liquefaction heat exchanger (260).

[0092] The electrochemical active control refrigerator (200) for re-liquefaction operates in a closed-loop manner and can liquefy gaseous hydrogen (G) through heat exchange between the low-temperature liquid hydrogen refrigerant (LR) and the gaseous hydrogen (G) evaporated inside the liquid hydrogen storage tank (10). In the following, as the gaseous hydrogen refrigerant circulates through the electrochemical active control refrigerator (200) for re-liquefaction and the temperature and / or pressure changes, the gaseous hydrogen refrigerant is distinguished and named as "first," "second," etc.

[0093] The reliquefaction heat exchanger (260) is located within the liquid hydrogen storage tank (10) and can reliquefy gaseous hydrogen (G) evaporated from liquid hydrogen (L). The reliquefaction heat exchanger (260) can liquefy the gaseous hydrogen (G) by lowering its temperature through heat exchange between the gaseous hydrogen (G) within the liquid hydrogen storage tank (10) and the low-temperature liquid hydrogen refrigerant (LR) flowing inside the reliquefaction heat exchanger (260).

[0094] In the re-liquefaction heat exchanger (260), the liquid hydrogen refrigerant (LR) is vaporized into the first gaseous hydrogen refrigerant (GR1) through heat exchange with gaseous hydrogen (G), and the first gaseous hydrogen refrigerant (GR1) can be moved to the heat exchanger (220) through the discharge pipe (210) connecting the inside and outside of the liquid hydrogen storage tank (10). The first gaseous hydrogen refrigerant (G1) discharged from the liquid hydrogen storage tank (10) is introduced into the electrochemical active control refrigerator (200) for re-liquefaction, circulated, liquefied, and then introduced back into the re-liquefaction heat exchanger (260) inside the liquid hydrogen storage tank (10).

[0095] The heat exchanger (220) can use the first gaseous hydrogen refrigerant (GR1) that has passed through the re-liquefaction heat exchanger (260) for heat exchange. In the heat exchanger (220), the first gaseous hydrogen refrigerant (GR1) and the third gaseous hydrogen refrigerant (GR3) that have been heat-exchanged in the re-liquefaction heat exchanger (260) can be heat-exchanged.

[0096] The electrochemical hydrogen compressor (230) can discharge the high-temperature, high-pressure third gaseous hydrogen refrigerant (GR3), which is compressed from the second gaseous hydrogen refrigerant (GR2) discharged from the heat exchanger (220), back to the heat exchanger (220). The third gaseous hydrogen refrigerant (GR3) is a high-temperature gaseous hydrogen refrigerant from which the second gaseous hydrogen refrigerant (GR2) is compressed in the electrochemical hydrogen compressor (230). The second gaseous hydrogen refrigerant (GR2) is a gaseous hydrogen refrigerant whose temperature is raised by heat exchange between the first gaseous hydrogen refrigerant (GR1) and the third gaseous hydrogen refrigerant (GR3) in the heat exchanger (220), and the fourth gaseous hydrogen refrigerant (GR4) is a gaseous hydrogen refrigerant that is cooled by heat exchange between the third gaseous hydrogen refrigerant (GR3) and the first gaseous hydrogen refrigerant (GR1) in the heat exchanger (220).

[0097] Since it is a device that performs the same function as the electrochemical hydrogen compressor (130) of the electrochemical active control liquefier (100) for re-liquefaction, a repetitive description of the function is omitted.

[0098] The third gaseous hydrogen refrigerant (GR3) that has passed through the electrochemical hydrogen compressor (230) has high pressure and high temperature. If the JT expansion described later is performed immediately in this state, the temperature is not low enough, making liquefaction impossible. Therefore, if the third gaseous hydrogen refrigerant (GR3) is pre-cooled by heat exchange with the first gaseous hydrogen refrigerant (GR1), the possibility of liquefaction during JT expansion increases.

[0099] The first gaseous hydrogen refrigerant (GR1) is in a state of evaporation within a re-liquefaction heat exchanger (260) through heat exchange with gaseous hydrogen (G), and is in a relatively low temperature (low temperature) and low pressure state. By heat-exchanging the first gaseous hydrogen refrigerant (GR1) with the third gaseous hydrogen refrigerant (GR3), the temperature of the first gaseous hydrogen refrigerant (GR1) can be increased so that it can be efficiently compressed when introduced into the electrochemical hydrogen compressor (230). This reduces heat loss and improves the overall energy efficiency of the system.

[0100] The heat exchanger (220) can perform multi-stage heat exchange between the first gaseous hydrogen refrigerant (GR1) and the third gaseous hydrogen refrigerant (GR3). Since the temperature difference between the first gaseous hydrogen refrigerant (GR1) and the third gaseous hydrogen refrigerant (GR3) is significant, if heat exchange is performed all at once in a single heat exchanger, there is a high possibility of inefficient heat transfer. To solve this problem, multi-stage heat exchange is performed, and through multi-stage heat exchange, the temperature change from high temperature to low temperature can be carried out gradually over several stages, thereby enabling efficient heat exchange. The multi-stage heat exchange method contributes to optimizing heat transfer performance and reducing energy loss.

[0101] The heat exchanger (220) can further cool the third gaseous hydrogen refrigerant (GR3) using liquid nitrogen (N). In order for the fourth gaseous hydrogen refrigerant (GR4) to be liquefied during the JT expansion process described later, expansion must be carried out while cooled to a sufficiently low temperature. Since it may be difficult to cool the third gaseous hydrogen refrigerant (GR3) to a sufficiently low temperature solely through multi-stage heat exchange between the first gaseous hydrogen refrigerant (GR1) and the third gaseous hydrogen refrigerant (GR3), liquid nitrogen (N) can be additionally utilized as a cooling medium to assist in cryogenic cooling. Through this, a larger proportion of hydrogen refrigerant can be liquefied after JT expansion.

[0102] The JT expander (240) can expand and liquefy the third gaseous hydrogen refrigerant (GR3) that has been cooled by heat exchange with the first gaseous hydrogen refrigerant (GR1) in the heat exchanger (220). The fourth gaseous hydrogen refrigerant (GR4) is the gaseous hydrogen refrigerant discharged after the third gaseous hydrogen refrigerant (GR3) is cooled by the first gaseous hydrogen refrigerant (GR1) in the heat exchanger (220), and can become the liquid hydrogen refrigerant (LR) that is expanded and liquefied in the JT expander (240).

[0103] The JT expander (240) is a device that utilizes the phenomenon in which the temperature of a gas or liquid changes as its pressure decreases during an isenthalpic process, and is used to expand a gaseous hydrogen refrigerant, namely the fourth gaseous hydrogen refrigerant (GR4), to a low pressure and lower its temperature. The JT expander (240) may include a JT expansion valve.

[0104] The liquid hydrogen refrigerant (LR) liquefied and discharged from the JT expander (240) can be moved to the re-liquefaction heat exchanger (260) through the inlet pipe (150).

[0105] In this way, a Linde-Hampson cycle refrigerator can be constructed by utilizing an electrochemical hydrogen compressor (230) and a JT expander (240). The Linde-Hampson cycle is a cycle that uses JT expansion to liquefy gaseous hydrogen, pre-cooling using liquid nitrogen (N) and multi-stage heat exchange to reach the final hydrogen liquefaction temperature (20 K).

[0106] To improve the efficiency of the electrochemical active control refrigerator (200) for re-liquefaction, a Claude cycle utilizing an expansion engine (piston or turbine type) may be applied instead of the JT expander (240).

[0107] The amount of third gaseous hydrogen refrigerant (GR3) produced in the electrochemical hydrogen compressor (230) can be controlled by adjusting the voltage applied to the electrochemical hydrogen compressor (230) according to changes in operating conditions.

[0108] Additionally, as shown in FIG. 3, the electrochemical hydrogen compressor (230) includes a plurality of electrochemical hydrogen compressor modules (231) connected in parallel, and for each module, predetermined voltages are set, and the electrochemical hydrogen compressor module (231) corresponding to the changed operating conditions can be operated.

[0109] Here, changes in operating conditions may include changes in the amount of heat intrusion into the liquid hydrogen storage tank (10), changes in the liquid hydrogen level, changes in heat intrusion due to valve and piping operation, changes in hydrogen consumption, etc.

[0110] The liquid hydrogen storage tank (10) may receive heat depending on the external environment, and as a result, the amount of evaporation in which the internal liquid hydrogen (L) turns into gas may vary. If the amount of heat intrusion into the liquid hydrogen storage tank (10) increases, more gaseous hydrogen (G) is generated, so the voltage and current of the electrochemical hydrogen compressor (230) can be increased to rapidly re-liquefy it, thereby increasing the re-liquefaction capacity of the hydrogen refrigerant. Conversely, when the amount of heat intrusion is low, the voltage and current can be lowered to prevent unnecessary power consumption, thereby allowing the electrochemical hydrogen compressor (230) to be operated efficiently.

[0111] Additionally, if the liquid hydrogen (L) level in the liquid hydrogen storage tank (10) changes, the volume occupied by the liquid hydrogen (L) relative to the liquid hydrogen storage tank (10) changes, and thus the evaporation rate may change. The gaseous hydrogen (G) inside the liquid hydrogen storage tank (10) may be relatively higher than the temperature of the liquid hydrogen (L) due to thermal stratification. As the liquid hydrogen (L) level increases, the overall temperature of the storage tank (10) decreases, so there is a possibility that the amount of evaporation will increase due to increased external heat input. Alternatively, the amount of evaporation may increase as the liquid hydrogen (L) inside the liquid hydrogen storage tank (10) slushes during transport, causing the liquid hydrogen (L) to come into contact with the upper inner wall of the tank, which has a relatively higher temperature or has come into contact with the gaseous hydrogen (G). To compensate for this, the output of the electrochemical hydrogen compressor (230) can be increased to re-liquefy the evaporated hydrogen more quickly.

[0112] Additionally, when the valve and piping are operated to supply liquid hydrogen (L) to the outside or to adjust the internal flow from the liquid hydrogen storage tank (10), a momentary heat inflow may occur. In response to this change, the voltage and current of the electrochemical hydrogen compressor (230) can be adjusted to re-liquefy the momentarily increased amount of evaporation.

[0113] Additionally, when liquid hydrogen (L) is supplied to an external system, the amount of gaseous hydrogen evaporated from the liquid hydrogen storage tank (10) may change. As hydrogen consumption increases, the internal pressure of the storage tank decreases, so the amount of remaining liquid hydrogen (L) evaporated may increase in order to achieve gas-liquid phase equilibrium. In this case, the voltage and current of the electrochemical hydrogen compressor (230) can be controlled to re-liquefy more gaseous hydrogen.

[0114] The description above presents the best mode of the present invention and provides examples to explain the invention and to enable those skilled in the art to manufacture and use the invention. The specification thus written is not intended to limit the invention to the specific terms presented.

[0115] Accordingly, although the present invention has been described in detail with reference to the examples above, those skilled in the art may make modifications, changes, and variations to these examples without departing from the scope of the invention. Explanation of the symbols

[0116] 10: Liquid hydrogen storage tank 100: Electrochemical active control liquefier for re-liquefaction 110: Discharge pipe 120: Heat exchanger 130: Electrochemical hydrogen compressor 140: JT Inflator 150: Inlet pipe 200: Electrochemical active control chiller for reliquefaction 210: Discharge pipe 220: Heat exchanger 230: Electrochemical hydrogen compressor 240: JT Inflator 250: Inlet pipe 260: Reliquefaction heat exchanger

Claims

Claim 1 An electrochemical active control liquefier for re-liquefaction for a liquid hydrogen storage tank, comprising: a heat exchanger that uses a first gaseous hydrogen evaporated from the liquid hydrogen storage tank and discharged through a discharge pipe for heat exchange; an electrochemical hydrogen compressor that discharges a third gaseous hydrogen, which is compressed from a second gaseous hydrogen discharged from the heat exchanger, to the heat exchanger; and a JT expander that expands and liquefies the third gaseous hydrogen, which is cooled by heat exchange with the first gaseous hydrogen within the heat exchanger, wherein the liquid hydrogen discharged from the JT expander flows into the liquid hydrogen storage tank through an inlet pipe. Claim 2 An electrochemical active-controlled liquefier for re-liquefaction according to claim 1, characterized in that the heat exchanger performs multi-stage heat exchange between the first gaseous hydrogen and the third gaseous hydrogen. Claim 3 An electrochemical active-controlled liquefier for re-liquefaction according to claim 1, characterized in that the heat exchanger further cools the third gaseous hydrogen using liquid nitrogen. Claim 4 An electrochemical active control liquefier for re-liquefaction according to claim 1, characterized in that the voltage applied to the electrochemical hydrogen compressor is regulated according to changes in operating conditions, thereby regulating the amount of third gaseous hydrogen generated in the electrochemical hydrogen compressor. Claim 5 An electrochemical active control liquefier for re-liquefaction according to claim 1, wherein the electrochemical hydrogen compressor comprises a plurality of parallel-connected electrochemical hydrogen compressor modules, wherein predetermined voltages are set for each module, and the electrochemical hydrogen compressor module corresponding to the changed operating conditions is operated. Claim 6 An electrochemical active control liquefier for re-liquefaction, characterized in that, in claim 4 or 5, changes in operating conditions include at least one of changes in the amount of heat intrusion into the liquid hydrogen storage tank, changes in the liquid hydrogen level, changes in heat intrusion due to valve and piping operation, and changes in hydrogen consumption. Claim 7 An electrochemical active-control refrigeration system for re-liquefaction for a liquid hydrogen storage tank, comprising: a re-liquefaction heat exchanger for liquefying gaseous hydrogen through heat exchange between gaseous hydrogen and liquid hydrogen refrigerant in the liquid hydrogen storage tank; a heat exchanger for using a first gaseous hydrogen refrigerant that has passed through the re-liquefaction heat exchanger for heat exchange; an electrochemical hydrogen compressor for compressing a second gaseous hydrogen refrigerant discharged from the heat exchanger and discharging a third gaseous hydrogen refrigerant to the heat exchanger; and a JT expander for expanding and liquefying the third gaseous hydrogen refrigerant that has been cooled by heat exchange with the first gaseous hydrogen refrigerant in the heat exchanger, wherein the liquid hydrogen refrigerant discharged from the JT expander is transferred to the re-liquefaction heat exchanger. Claim 8 In claim 7, the electrochemical active control refrigerator for re-liquefaction is characterized by the heat exchanger performing multi-stage heat exchange between a first gaseous hydrogen refrigerant and a third gaseous hydrogen refrigerant. Claim 9 In claim 7, the electrochemical active control refrigerator for re-liquefaction is characterized by the heat exchanger further cooling a third gaseous hydrogen refrigerant using liquid nitrogen. Claim 10 In claim 7, the electrochemical active control refrigerator for re-liquefaction is characterized in that the voltage applied to the electrochemical hydrogen compressor is regulated according to changes in operating conditions, thereby regulating the amount of third gaseous hydrogen refrigerant generated in the electrochemical hydrogen compressor. Claim 11 In claim 7, the electrochemical hydrogen compressor comprises a plurality of parallel-connected electrochemical hydrogen compressor modules, wherein predetermined voltages are set for each module, and the electrochemical hydrogen compressor module corresponding to the changed operating conditions is operated, characterized in that the electrochemical hydrogen compressor is an electrochemical active control chiller for re-liquefaction. Claim 12 An electrochemical active control chiller for re-liquefaction according to claim 10 or 11, characterized in that changes in operating conditions include at least one of changes in the amount of heat intrusion into the liquid hydrogen storage tank, changes in the liquid hydrogen level, changes in heat intrusion due to valve and piping operation, and changes in hydrogen consumption. Claim 13 A liquid hydrogen storage and re-liquefaction system comprising: a liquid hydrogen storage tank for receiving liquid hydrogen; and an electrochemical active control liquefier for re-liquefaction connected to the liquid hydrogen storage tank, wherein a first gaseous hydrogen evaporated from the liquid hydrogen is introduced, circulated, liquefied, and introduced into the liquid hydrogen storage tank, and comprising a heat exchanger, an electrochemical hydrogen compressor, and a JT expander, wherein the first gaseous hydrogen and the third gaseous hydrogen undergo heat exchange in the heat exchanger, the third gaseous hydrogen is gaseous hydrogen compressed by the second gaseous hydrogen in the electrochemical hydrogen compressor, the second gaseous hydrogen is gaseous hydrogen that has undergone heat exchange between the first gaseous hydrogen and the third gaseous hydrogen in the heat exchanger, the fourth gaseous hydrogen is gaseous hydrogen discharged after the third gaseous hydrogen is cooled by the first gaseous hydrogen in the heat exchanger, and is expanded and liquefied in the JT expander. Claim 14 A liquid hydrogen storage and reliquefaction system according to claim 13, characterized in that the heat exchanger performs multi-stage heat exchange between the first gaseous hydrogen and the third gaseous hydrogen. Claim 15 A liquid hydrogen storage and reliquefaction system according to claim 13, characterized in that the heat exchanger further cools the third gaseous hydrogen using liquid nitrogen. Claim 16 A liquid hydrogen storage and reliquefaction system according to claim 13, characterized in that the voltage applied to the electrochemical hydrogen compressor is regulated according to changes in operating conditions, thereby regulating the amount of third gaseous hydrogen generated in the electrochemical hydrogen compressor. Claim 17 A liquid hydrogen storage and reliquefaction system according to claim 13, wherein the electrochemical hydrogen compressor comprises a plurality of parallel-connected electrochemical hydrogen compressor modules, wherein predetermined voltages are set for each module, and the electrochemical hydrogen compressor module corresponding to the changed operating conditions is operated. Claim 18 A liquid hydrogen storage and reliquefaction system according to claim 16 or 17, characterized in that changes in operating conditions include at least one of changes in the amount of heat intrusion into the liquid hydrogen storage tank, changes in the liquid hydrogen level, changes in heat intrusion due to valve and piping operation, and changes in hydrogen consumption. Claim 19 Liquid hydrogen storage tank for holding liquid hydrogen; and includes an electrochemical active control refrigerator for reliquefaction, comprising a reliquefaction heat exchanger, a heat exchanger, an electrochemical hydrogen compressor, and a JT expander, which is connected to a liquid hydrogen storage tank and reliquefies gaseous hydrogen evaporated from liquid hydrogen, wherein in the reliquefaction heat exchanger, gaseous hydrogen is cooled and liquefied by a liquid hydrogen refrigerant, and in the heat exchanger, a first gaseous hydrogen refrigerant and a third gaseous hydrogen refrigerant exchange heat in the reliquefaction heat exchanger, the third gaseous hydrogen refrigerant is a gaseous hydrogen refrigerant in which the second gaseous hydrogen refrigerant is compressed in an electrochemical hydrogen compressor, the second gaseous hydrogen refrigerant is a gaseous hydrogen refrigerant in which the first gaseous hydrogen refrigerant exchanges heat with the third gaseous hydrogen refrigerant in the heat exchanger, the fourth gaseous hydrogen refrigerant is a gaseous hydrogen refrigerant discharged after the third gaseous hydrogen refrigerant is cooled by the first gaseous hydrogen refrigerant in the heat exchanger, and in the JT expander A liquid hydrogen storage and re-liquefaction system characterized by becoming an expanded, liquefied liquid hydrogen refrigerant. Claim 20 A liquid hydrogen storage and re-liquefaction system according to claim 19, characterized in that the heat exchanger performs multi-stage heat exchange between a first gaseous hydrogen refrigerant and a third gaseous hydrogen refrigerant. Claim 21 A liquid hydrogen storage and re-liquefaction system according to claim 19, characterized in that the heat exchanger further cools a third gaseous hydrogen refrigerant using liquid nitrogen. Claim 22 A liquid hydrogen storage and reliquefaction system according to claim 19, characterized in that the voltage applied to the electrochemical hydrogen compressor is regulated according to changes in operating conditions, thereby regulating the amount of third gaseous hydrogen refrigerant generated in the electrochemical hydrogen compressor. Claim 23 A liquid hydrogen storage and reliquefaction system according to claim 19, wherein the electrochemical hydrogen compressor comprises a plurality of parallel-connected electrochemical hydrogen compressor modules, wherein predetermined voltages are set for each module, and the electrochemical hydrogen compressor module corresponding to the changed operating conditions is operated. Claim 24 A liquid hydrogen storage and reliquefaction system according to claim 22 or 23, characterized in that changes in operating conditions include at least one of changes in the amount of heat intrusion into the liquid hydrogen storage tank, changes in the liquid hydrogen level, changes in heat intrusion due to valve and piping operation, and changes in hydrogen consumption.

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