Water electrolysis system

Abstract

This water electrolysis system (11) comprises: a water electrolysis device (15) provided with a plurality of electrolysis tanks (13) which are connected at least in series to a power converter (21) and in which water electrolysis is performed; and a conductive shielding body (17) which accommodates the water electrolysis device (15) in an internal space so as to surround the water electrolysis device (15). A shield body potential (Vsh), which is a potential pertaining to the shield body (17), is set to converge, in a state of being insulated from a ground potential, to a prescribed allowable potential difference (Vpd) with respect to a water electrolysis device potential (Vwe) that is a potential pertaining to the water electrolysis device (15). The present invention secures a reduction effect of an explosion event caused by leaked hydrogen regardless of a leakage place of hydrogen.

Description

Water electrolysis system

[0001] The present invention relates to a water electrolysis system.

[0002] As a measure against global warming, the expanded use of renewable energy is being promoted. For example, technological development is progressing for producing hydrogen by performing water electrolysis using electric power obtained from renewable energy, and storing and utilizing hydrogen as chemical energy.

[0003] As water electrolysis systems, large-scale systems of 100 MW class to 1 GW class are planned. A large-scale system capable of supplying large-capacity electric power requires connection to a high-voltage system exceeding several tens of kV. Generally, an electrolyzer that performs water electrolysis has a capacity of 1 MW to 10 MW class. A water electrolysis system for satisfying such a large capacity is configured by combining a plurality of electrolyzers.

[0004] Each individual electrolyzer among the plurality of electrolyzers operates on low-voltage direct current of approximately several hundred volts. When supplying power to each individual electrolyzer among the plurality of electrolyzers, multi-stage transformers and a plurality of rectifiers are required. As a result, the cost and installation area of power conversion devices increase.

[0005] When a water electrolysis device is increased in voltage by electrically connecting a plurality of electrolyzers in series, and power is collectively supplied to the water electrolysis device, the number of transformers and rectifiers can be reduced. However, when the integrated voltage of the plurality of series-connected electrolyzers reaches a high voltage of approximately several kV, it exceeds the withstand voltage of each individual electrolyzer itself. Therefore, insulation of piping between the electrolyzer fixing part and auxiliary equipment is required.

[0006] When each individual electrolyzer among the plurality of electrolyzers is increased in voltage, an electric field is generated due to the voltage difference between the high-voltage part and the grounding part. If a large local electric field occurs due to factors such as surface shape and conductivity distribution, dielectric breakdown occurs locally, causing partial discharge which is an intermittent discharge. The partial discharge generated in this way is local and instantaneous, so the discharge energy itself is weak. However, since the ignition energy of hydrogen is extremely small, if hydrogen produced in the electrolyzer leaks, the leaked hydrogen can serve as an ignition source and an explosion event can occur.

[0007] Patent Document 1 describes a water electrolysis system in which a water electrolysis device and auxiliary equipment are connected by an insulating double pipe, dry air is sealed between the inner and outer pipes, and hydrogen leakage is detected by pressure changes and concentration changes between the inner and outer pipes. According to the water electrolysis system described in Patent Document 1, hydrogen leakage from insulating piping can be detected quickly, and an effect of reducing explosion incidents caused by leaked hydrogen can be expected.

[0008] Japanese Patent Publication No. 2024-51868

[0009] However, in the water electrolysis system described in Patent Document 1, it is difficult to quickly detect hydrogen leaks from parts other than the insulated piping. Therefore, depending on the location of the hydrogen leak, it is difficult to guarantee the effectiveness of reducing explosion events caused by the leaked hydrogen.

[0010] This invention has been made in view of the above circumstances, and aims to provide a water electrolysis system that can guarantee a reduction in explosion events caused by leaked hydrogen, regardless of the location of the hydrogen leak.

[0011] To solve the above problems, the electrolysis system according to the present invention comprises a water electrolysis apparatus having a plurality of electrolytic cells for water electrolysis connected in at least series to a DC power supply, and a conductive shielding body that surrounds the water electrolysis apparatus and houses the water electrolysis apparatus in its internal space, the most important feature of which is that the shielding potential, which is the potential related to the shielding body, is set to converge to a predetermined potential difference with respect to the water electrolysis apparatus potential, which is the potential related to the water electrolysis apparatus, while being insulated from the ground potential.

[0012] The water electrolysis system according to the present invention can ensure a reduction in explosion events caused by leaked hydrogen, regardless of the location of the hydrogen leak. Other issues, configurations, and effects will be described in detail in the following embodiments.

[0013] This is a schematic diagram of a water electrolysis system according to the first embodiment of the present invention. This is a schematic diagram of a water electrolysis system according to the second embodiment of the present invention. This is a schematic diagram of a water electrolysis system according to a modified example of the second embodiment of the present invention.

[0014] A water electrolysis system according to an embodiment of the present invention will be described in detail with reference to the drawings as appropriate. In the following drawings, common reference numerals are generally used for components having a common function or for components having mutually corresponding functions, and redundant explanations are omitted. The size and shape of components may be represented schematically, modified or exaggerated, for the sake of clarity.

[0015] [Outline Configuration of Water Electrolysis System 11 According to an Embodiment of the Present Invention] The outline configuration of the water electrolysis system 11 according to an embodiment of the present invention will be described with reference to Figure 1. Figure 1 is an outline diagram of the water electrolysis system 11 according to an embodiment (first embodiment) of the present invention. Before describing the water electrolysis system 11 according to an embodiment (first embodiment) of the present invention, basic technical matters including the background technology of the water electrolysis system 11 that are prerequisites will be mentioned. Note that the water electrolysis system 11 is a concept that encompasses the water electrolysis system 11A according to the first embodiment, the water electrolysis system 11B according to the second embodiment, and the water electrolysis system 11C according to a modified example of the second embodiment, as described below.

[0016] The water electrolysis system 11 comprises a water electrolysis device 15 equipped with multiple electrolytic cells 13 responsible for water electrolysis, a shielding body 17 that houses the water electrolysis device 15 in its internal space and surrounds the water electrolysis device 15, an auxiliary device 19 for controlling fluid parameters related to the water electrolysis device 15, a power converter 21 (DC power supply), a transformer 23, and a control device 25. The fluid parameters related to the water electrolysis device 15 are a concept that encompasses the temperature and flow rate of the pure water supplied to the water electrolysis device 15, as well as the pressure of the oxygenated water and hydrogenated water discharged from the water electrolysis device 15.

[0017] The water electrolysis device 15 in the water electrolysis system 11 plays the role of producing hydrogen by transforming AC power from the power grid to a predetermined voltage using a transformer 23, converting the transformed AC power to DC power using a power converter 21, and electrolyzing pure water supplied by the auxiliary device 19 using the converted DC power.

[0018] Multiple electrolytic cells 13 provided in the water electrolysis device 15 are known to include alkaline type, solid polymer type, anion exchange membrane type, etc. The present invention is applicable to any of the above types of electrolytic cells 13. However, in this embodiment, as the multiple electrolytic cells 13, solid polymer type electrolytic cells 13, which allow for relatively easy insulation management between the water electrolysis device 15 and the auxiliary equipment 19, are described as an example.

[0019] Each electrolytic cell 13 is constructed by stacking multiple electrolytic cells separated by a separator (not shown). The operating voltage of each individual electrolytic cell is approximately 1.5V-2.5V. The operating voltage of an electrolytic cell 13 with multiple electrolytic cells is increased to several hundred volts. An insulating plate (not shown) is interposed between the stacked cells and the end plate 13a. This provides insulation between the end plate and the cells. Typically, the dielectric strength of the insulating plate in the electrolytic cell 13 is approximately 2-3kV.

[0020] In conventional water electrolysis systems, the end plate 13a of the electrolytic cell 13 is directly fixed to the base portion 29 that supports the water electrolysis device 15. In contrast, in the water electrolysis system 11 according to this embodiment, the end plate 13a of the electrolytic cell 13 is indirectly fixed to the base portion 29 via a conductive shielding body 17 and an insulator 27, respectively.

[0021] Furthermore, in the water electrolysis system 11 according to this embodiment, the end plate 13a provided on the electrolytic cell 13 is connected to a pure water pipe 31a, an oxygenated water pipe 31b, and a hydrogenated water pipe 31c, respectively, similar to conventional water electrolysis systems. When it is not necessary to explain the pure water pipe 31a, the oxygenated water pipe 31b, and the hydrogenated water pipe 31c separately, they are collectively referred to as "piping 31". The end plate 13a provided on the electrolytic cell 13 is connected to an auxiliary device 19 via the piping 31. The auxiliary device 19 and the base 29 are grounded.

[0022] The material of the piping 31 is required to be leak-free and durable for long-term use when circulating fluids including pure water, oxygen-dissolved water (abbreviated as "oxygen water"), and hydrogen-dissolved water (abbreviated as "hydrogen water"). As a material for the piping 31 that meets these requirements, for example, SUS (Steel Use Stainless) is preferably used. When SUS is used as the material for the piping 31, the piping 31 is electrically conductive.

[0023] When a water electrolysis device 15, which is equipped with multiple high-voltage electrolytic cells 13, is incorporated into a water electrolysis system 11 and put into operation, the problem in the water electrolysis system 11 according to this embodiment is how to electrically insulate the water electrolysis device 15 from the grounded auxiliary equipment 19 and base 29.

[0024] When two substances with a potential difference exist separated from each other, an electric field (potential gradient) corresponding to the potential difference is generated in the space between these two substances. This potential gradient is determined by various conditions, including the potential difference, the surface shape of the substances, and the conductivity of the space. Depending on these conditions, a large localized electric field may be generated.

[0025] When the aforementioned locally large electric field exceeds the dielectric strength in the space separated from the two materials, a partial discharge called a local breakdown discharge occurs. Such a partial discharge occurs locally and instantaneously between two materials with a potential difference. The energy and charge generated here are absorbed and dissipated by the materials present in the local space where the partial discharge occurred.

[0026] In this embodiment, a shielding body 17 is used to electrically insulate the water electrolysis device 15 from the grounded auxiliary equipment 19 and base 29. The shielding body 17 is made of a conductive material such as SUS and is provided to surround the water electrolysis device 15. In the water electrolysis system 11 according to this embodiment, the shielding body potential Vsh, which is the potential related to the shielding body 17, is set to converge to a predetermined allowable potential difference Vpd with respect to the water electrolysis device potential Vwe, which is the potential related to the water electrolysis device 15, while being insulated from the ground potential Vgd. By adopting this configuration, even if hydrogen leakage occurs in the water electrolysis device 15, the effect of reducing explosion events caused by leaked hydrogen can be ensured. The setting of the shielding body potential Vsh related to the shielding body 17 will be described in detail later.

[0027] The water electrolysis system 11 according to this embodiment is based on a system in which multiple electrolytic cells 13 are electrically connected in series. By increasing the voltage of the water electrolysis device 15 by connecting multiple electrolytic cells 13 in series, the current value at the common output can be reduced, thereby reducing the number of power supply equipment such as transformers 23 and busbars (not shown).

[0028] Multiple electrolytic cells 13 may be electrically connected in parallel. Connecting multiple electrolytic cells 13 in parallel ensures that a current path can be maintained even if one of the electrolytic cells 13 malfunctions. As a result, stable operation of the water electrolysis system 11 and a gentle system shutdown can be achieved.

[0029] In the water electrolysis system 11 according to this embodiment, the water electrolysis device 15, which has been made high-voltage by connecting at least a plurality of electrolytic cells 13 in series, is housed in a shielding body 17, thereby separating the atmosphere around the water electrolysis device 15 from the outside air. The inside of the shielding body 17 may be ventilated or air-conditioned. The water electrolysis device 15 may be divided and housed in a plurality of shielding bodies 17.

[0030] The water electrolysis device 15 is connected to the auxiliary equipment device 19 via piping 31. The piping 31, which is connected to each of the multiple electrolytic cells 13 provided in the water electrolysis device 15, is assembled inside the shielding body 17 as pure water piping 31a, oxygenated water piping 31b, and hydrogen water piping 31c, and then connected to the auxiliary equipment device 19.

[0031] A configuration may be adopted in which the piping 31 from multiple shielding bodies 17 is connected to a single auxiliary device 19. The auxiliary device 19 controls the temperature, flow rate, and purity of the pure water supplied to the water electrolysis device 15, and also separates the oxygen and hydrogen discharged from the water electrolysis device 15 into gas-liquid and controls the oxygen and hydrogen pressure.

[0032] The auxiliary device 19 is grounded. A pipe insulation section 33 is provided in the piping 31 between the shielding body 17 and the auxiliary device 19. Specifically, of the piping 31, a pure water pipe insulation section 33a is provided in the pure water pipe 31a, an oxygen water pipe insulation section 33b is provided in the oxygen water pipe 31b, and a hydrogen water pipe insulation section 33c is provided in the hydrogen water pipe 31c. When it is not necessary to explain the pure water pipe insulation section 33a, the oxygen water pipe insulation section 33b, and the hydrogen water pipe insulation section 33c separately, they are collectively referred to as the "pipe insulation section 33".

[0033] The pipe insulation section 33 serves to insulate the shielding body 17 and the auxiliary device 19. The pipe insulation section 33 is a component having the same function as the "insulated pipe" described in Japanese Patent Application Publication No. 2024-51868 by the applicant. By this reference, the description of the "insulated pipe" described in Japanese Patent Application Publication No. 2024-51868 is incorporated herein by reference.

[0034] The shielding body 17 is fixed to the base portion 29 via an insulator 27. This provides insulation between the shielding body 17 and the base portion 29.

[0035] The water electrolysis device 15 is electrically connected to the DC section 21a of the power converter 21. In order to fix and set the water electrolysis device potential Vwe, which is the potential of the water electrolysis device 15 to ground, the DC section 21a of the power converter 21 is grounded via a high resistance 35. DC power is supplied to the water electrolysis device 15 via DC wiring 37 connected to the DC section 21a of the power converter 21.

[0036] The DC wiring 37 connected to the DC section 21a of the power converter 21 is connected to a conductive shielding body 17 via a branch line 38. Here, the potential difference Vdf between the water electrolysis device potential Vwe, which is the potential related to the water electrolysis device 15, and the shielding body potential Vsh, which is the potential related to the shielding body 17, is set to converge to a predetermined allowable potential difference Vpd. The predetermined allowable potential difference Vpd is preferably 1500V or less, as it is a value that can suppress discharge between the water electrolysis device 15 and the shielding body 17.

[0037] In practice, a resistor 39 is interposed in the branch line 38 connecting the DC wiring 37 (synonymous with the water electrolysis device 15) and the shielding body 17. This limits the current flowing from the positive electrode side 37a of the DC wiring 37 to the shielding body 17 via the branch line 38. A fuse or other interrupting means may be interposed in series with the resistor 39 in the branch line 38. Alternatively, by electrically connecting the shielding body 17 to the DC wiring 37 related to both the positive and negative electrodes via a predetermined resistor, the shielding body potential Vsh related to the shielding body 17 may be set to an intermediate potential between the water electrolysis device potential Vwe related to the water electrolysis device 15 and the ground potential Vgd.

[0038] The potential difference Vdf between the water electrolysis device potential Vwe of the water electrolysis device 15 and the shielding device potential Vsh of the shielding device 17 is set to converge to a predetermined allowable potential difference Vpd that can suppress discharge between the water electrolysis device 15 and the shielding device 17. This has the effect of reducing discharge events inside the shielding device 17. In other words, even if hydrogen leakage occurs in the water electrolysis device 15 housed in the internal space of the shielding device 17, this has the effect of reducing the occurrence of a hydrogen explosion caused by partial discharge.

[0039] In this way, partial discharge events in the water electrolysis device 15 housed in the internal space of the shielding body 17 are reduced, which increases the freedom of arrangement and shape of piping 31 and sensors in the internal space of the shielding body 17. As a result, it is possible to efficiently house the water electrolysis device 15 in the internal space of the shielding body 17.

[0040] The outer surfaces of the shielding body 17, the auxiliary equipment 19, and the base portion 29 are formed in a smooth shape. This prevents electric field concentration near the surfaces of the shielding body 17, the auxiliary equipment 19, and the base portion 29. Power for various devices (e.g., ventilation devices, hydrogen leak sensors, etc.) housed in the internal space of the shielding body 17 can be supplied as appropriate via an isolation transformer (not shown).

[0041] Furthermore, various information collected in the internal space of the shielding body 17 (including, for example, discharge status and hydrogen concentration) is communicated to the control device 25 via an optical insulator (not shown). The communication of the various information may be isolated by wireless communication. In this way, even in the internal space of the shielding body 17 which is kept at a high voltage, it is possible to communicate various information using various devices, and the control device 25 can perform appropriate operational control of the water electrolysis system 11 based on the information collected in the internal space of the shielding body 17.

[0042] [Water electrolysis system 11A according to the first embodiment] Next, the water electrolysis system 11A according to the first embodiment will be described with reference to Figure 1. In the water electrolysis system 11A according to the first embodiment shown in Figure 1, six electrolytic cells 13 having a rated voltage of 600V, a rated current of 1500A, and a rated capacity of 900kW are assembled to form a water electrolysis device 15, and this water electrolysis device 15 is housed in a shielding body 17.

[0043] A group of water electrolyzers 15 is constructed by electrically connecting electrolytic cells 13 in a 2-series, 3-parallel configuration within the internal space of the shielding body 17. In this case, the ratings of the group of water electrolyzers 15 housed within the internal space of one shielding body 17 are a rated voltage of 1200V, a rated current of 4500A, and a rated capacity of 5.4MW. In a case where a water electrolysis system 11 is constructed by connecting 18 of these groups of water electrolyzers 15 (and similarly 18 shielding bodies 17) in series, the ratings of the water electrolysis system 11 as a whole are a rated voltage of 21.6kV, a rated current of 4500A, and a rated capacity of 97.2MW.

[0044] A transformer 23 was connected to a 66 kV power system to adjust the AC voltage, which was further converted into DC by a power converter 21, and the converted DC power was supplied to a water electrolyzer 15. The positive and negative poles of a DC section 21a of the power converter 21 were grounded via a high resistance 35, such that the ground potential of the positive and negative poles reached ±10.8 kV at rating. A self-commutated converter was used as the power converter 21.

[0045] Three types of pipes, namely a pure water inlet, an oxygen water outlet and a hydrogen water outlet, were connected in communication to each individual electrolyzer cell 13 among the plurality of electrolyzer cells 13. The pipes 31 of the plurality of electrolyzer cells 13 housed in the internal space of the same shield 17 were gathered by type in the internal space of the shield 17. Each gathered pipe 31 was connected outside the shield 17 to an auxiliary device 19 via a pipe insulating section 33.

[0046] The auxiliary device 19 is configured to include an oxygen-side gas-liquid separator 41, a hydrogen water-side gas-liquid separator 43, a pure water tank 45, an ion exchange resin 47, a liquid feed pump 49, a cooler 51, and a back pressure valve 53. The auxiliary device 19 controls the temperature, flow rate, and purity of pure water supplied to the water electrolyzer 15, and the pressure of oxygen and hydrogen discharged from the water electrolyzer 15.

[0047] The shield 17 was fixed to a base section 29 via an insulator 27. Further, the shield 17 was connected to a positive-side DC wiring 37 (synonymous with the water electrolyzer 15) via a resistor 39 inserted in a branch path 38. Accordingly, the potential difference Vdf between the water electrolyzer potential Vwe of the water electrolyzer 15 and the shield potential Vsh of the shield 17 was set to converge to a predetermined allowable potential difference Vpd (preferably 1500 V or less) capable of suppressing discharge between the water electrolyzer 15 and the shield 17. Note that, by connecting the shield 17 not only to the positive electrode side 37a of the DC wiring 37 but also to the current wiring 37 on both the positive and negative electrode sides 37a and 37b via the resistor 39, the potential difference Vdf from the water electrolyzer potential Vwe of the water electrolyzer 15 may be set to 600 V or less. Since the potential difference Vdf between the water electrolyzer 15 and the shield 17 is reduced to a value capable of suppressing discharge between the water electrolyzer 15 and the shield 17, the electric field generated in the internal space of the shield 17 can be kept small. As a result, discharge occurring in the internal space of the shield 17 can be suppressed.

[0048] On the other hand, the auxiliary device 19 and the base portion 29 are grounded. Therefore, a potential difference Vdf of up to 10.8 kV is generated between the shield 17, and between the auxiliary device 19 and the base portion 29. In order to suppress electric field concentration in the outer space of the shield 17, the respective outer surfaces of the shield 17, the auxiliary device 19 and the base portion 29 are formed into smooth shapes. As a result, partial discharge on the outer surfaces of the shield 17, the auxiliary device 19, and the base portion 29 can be suppressed, and consequently, a situation that becomes an ignition source when hydrogen leaks in the water electrolysis apparatus 15 can be suppressed.

[0049] Electric power for various devices (e.g., ventilators, hydrogen leakage sensors, etc.) accommodated in the inner space of the shield 17 is supplied via an insulating transformer. Various types of information collected in the inner space of the shield 17 (e.g., including discharge status and hydrogen concentration) are sent to the control device 25 via an optical insulator.

[0050] The control device 25 sets operating conditions based on information collected in the inner space of the shield 17, and operating information of the shield 17, the auxiliary device 19, and the power converter 21, and transmits control commands including the set operating conditions to the power converter 21 and the auxiliary device 19, respectively. Thereby, the control device 25 performs integrated control on the water electrolysis system 11.

[0051] Both the power consumed in the inner space of the shield 17 and communication data are insulated, so no particular problem occurs even if the shield 17 itself is at a high potential.

[0052] The inner space of the shield 17 is appropriately ventilated by a ventilator. The ventilator is operated by electric power supplied from, for example, a power control device provided in the inner space of the shield 17. Further, a discharge state sensor and a hydrogen concentration sensor are provided in the inner space of the shield 17. The control device 25 performs control to stop the operation of the water electrolysis apparatus 15 when at least one of the discharge state or the hydrogen concentration in the atmospheric environment related to the inner space of the shield 17 exceeds a predetermined allowable value. Since power supply and data communication are secured in the inner space of the shield 17, even if hydrogen leakage occurs in the inner space of the shield 17, explosion caused by the hydrogen leakage can be suppressed.

[0053] [Water electrolysis system 11B according to the second embodiment] Next, the water electrolysis system 11B according to the second embodiment will be described with reference to Figure 2. Figure 2 is a schematic diagram of the water electrolysis system 11B according to the second embodiment. The water electrolysis system 11A according to the first embodiment (see Figure 1) and the water electrolysis system 11B according to the second embodiment (see Figure 2) have the same basic components. Therefore, by focusing on the differences in configuration from the water electrolysis system 11A according to the first embodiment, we will provide a description of the configuration of the water electrolysis system 11B according to the second embodiment.

[0054] The difference between the configuration of the water electrolysis system 11A according to the first embodiment shown in Figure 1 and the configuration of the water electrolysis system 11B according to the second embodiment shown in Figure 2 is that in the water electrolysis system 11B according to the second embodiment, an electrically grounded discharge induction unit 61 is provided near (below) the pipe insulation unit 33c of the hydrogen water pipe 31c to induce discharge against the shielding body 17. In short, the discharge induction unit 61 is provided in a location outside the shielding body 17 where hydrogen leakage is unlikely to occur.

[0055] The discharge induction section 61 is a rod-shaped member made of a conductive material such as SUS, positioned almost vertically. The surface of the discharge induction section 61 has a fine, uneven surface.

[0056] In the water electrolysis system 11B according to the second embodiment, the strength of the electric field generated between the hydrogen water pipe 31c, which is provided in the space outside the shielding body 17, and the discharge induction unit 61 increases as it approaches the discharge induction unit 61, while decreasing as it approaches the hydrogen water pipe 31c. In other words, partial discharge in the hydrogen water pipe 31c is suppressed. As a result, even if hydrogen leakage occurs near the hydrogen water pipe 31c, it is possible to suppress the situation in which such leaked hydrogen becomes an ignition source.

[0057] In the water electrolysis system 11B according to the second embodiment, a ventilation device 65 is provided to ventilate the atmospheric environment of the discharge induction unit 61. With this configuration, hydrogen can be diffused in the atmospheric environment of the discharge induction unit 61, thereby reducing the hydrogen concentration in the atmospheric environment of the discharge induction unit 61.

[0058] The ventilation device 65 may appropriately employ a configuration such as blowing dry air towards the atmospheric environment of the discharge induction unit 61 using a fan to diffuse hydrogen. Alternatively, the ventilation device 65 may employ a configuration such as circulating an inert gas towards the atmospheric environment of the discharge induction unit 61 using a fan to diffuse hydrogen.

[0059] Furthermore, in the water electrolysis system 11B according to the second embodiment, a discharge sensor 67 is provided to measure the discharge state in the atmospheric environment of the discharge induction unit 61. In addition, a hydrogen concentration sensor 69 is provided to measure the hydrogen concentration in the atmospheric environment of the discharge induction unit 61.

[0060] The control device 25 is configured to include: an acquisition unit 71 that acquires information on the discharge state (frequency and magnitude of partial discharge) related to the discharge sensor 67 and the hydrogen concentration related to the hydrogen concentration sensor 69; a determination unit 73 that determines whether at least one of the discharge state or hydrogen concentration in the atmospheric environment of the discharge induction unit 61 acquired by the acquisition unit 71 exceeds an appropriate allowable value for each; and a control unit 75 that, if the determination unit 73 determines that at least one of the discharge state or hydrogen concentration in the atmospheric environment of the discharge induction unit 61 exceeds an allowable value, controls the operation of the water electrolysis device 15 to stop.

[0061] The control unit 75 of the control device 25 controls the operation of the water electrolysis device 15 when it is determined that at least one of the discharge state or hydrogen concentration in the atmospheric environment of the discharge induction unit 61 exceeds an appropriate allowable value, thereby further reducing the risk of hydrogen explosions. As an example of a control command to stop the operation of the water electrolysis device 15, the control device 25 may output a current stop command to the power converter 21. Alternatively, as an example of a control command to stop the operation of the water electrolysis device 15, the control device 25 may output a command to reduce the hydrogen pressure to the auxiliary equipment 19.

[0062] [Water electrolysis system 11C according to a modified example of the second embodiment] Next, the water electrolysis system 11C according to a modified example of the second embodiment will be described with reference to Figure 3. Figure 3 is a schematic diagram of the water electrolysis system 11C according to a modified example of the second embodiment. The water electrolysis system 11B according to the second embodiment (see Figure 2) and the water electrolysis system 11C according to a modified example of the second embodiment (see Figure 3) have the same basic components. Therefore, by focusing on the differences in configuration from the water electrolysis system 11B according to the second embodiment, we will provide a description of the configuration of the water electrolysis system 11C according to a modified example of the second embodiment.

[0063] The difference between the configuration of the water electrolysis system 11B according to the second embodiment shown in Figure 2 and the configuration of the water electrolysis system 11C according to a modified example of the second embodiment shown in Figure 3 is that in the water electrolysis system 11C according to the modified example of the second embodiment, the discharge induction unit 61 is equipped with an electric field concentration unit 63 for specifically inducing discharge against the shielding body 17.

[0064] The electric field concentration section 63 is provided by forming a sharp, protruding portion at the end of the discharge induction section 61, which is a rod-shaped member made of a conductive material such as SUS, that faces the hydrogen water piping 31c. The surface of the electric field concentration section 63 has a fine, uneven surface.

[0065] In the water electrolysis system 11C according to a modification of the second embodiment, the strength of the electric field generated between the hydrogen water piping 31c provided in the space outside the shielding body 17 and the electric field concentration unit 63 provided in the discharge induction unit 61 increases as it approaches the electric field concentration unit 63, while decreasing as it approaches the hydrogen water piping 31c. In other words, partial discharge in the hydrogen water piping 31c is suppressed. As a result, even if hydrogen leakage occurs near the hydrogen water piping 31c, the likelihood of such leaked hydrogen becoming an ignition source can be further suppressed compared to the water electrolysis system 11B according to the second embodiment.

[0066] The distance between the electric field concentration section 63 of the discharge induction section 61 and the hydrogen water pipe 31c is set to be shorter than the longitudinal length of the pipe insulation section 33c related to the hydrogen water pipe 31c. With this configuration, since the distance between the two sections is set to be shorter than the longitudinal length of the pipe insulation section 33c related to the hydrogen water pipe 31c, the discharge induction effect of the discharge induction section 61 can be accurately generated.

[0067] [Other Embodiments] The embodiments and examples described above illustrate examples of the present invention. Therefore, the technical scope of the present invention should not be interpreted as being limited by these descriptions. This is because the present invention can be implemented in various forms without departing from its gist or its main features.

[0068] Furthermore, it is possible to replace some of the configurations of the embodiments described here with those of other embodiments, and even to add configurations from other embodiments to the configuration of one embodiment. In addition, it is possible to add, delete, or replace some of the configurations of each embodiment with those of other embodiments.

[0069] Furthermore, the control lines and information lines shown are those deemed necessary for explanatory purposes, and not all control lines and information lines are necessarily shown in the actual product. In reality, it can be assumed that almost all components are interconnected.

[0070] Finally, each component, function, processing unit, etc., provided in the control device 25 of the water electrolysis system 11 according to the embodiment of the present invention may be implemented in hardware, for example, by designing some or all of them as integrated circuits. Alternatively, each of the above-mentioned components, functions, processing units, etc., may be implemented in software by having a processor interpret and execute a program that realizes each function. Information such as programs, tables, and files that realize each function can be stored in a recording device such as memory, hard disk, SSD (Solid State Drive), or a recording medium such as an IC card, SD card, or DVD (Digital Versatile Disk).

[0071] 11 Water electrolysis system 11A Water electrolysis system according to the first embodiment 11B Water electrolysis system according to the second embodiment 11C Water electrolysis system according to a modified example of the second embodiment 13 Electrolytic cell 15 Water electrolysis device 17 Shielding body 19 Auxiliary equipment 21 Power converter (DC power supply) 23 Transformer 25 Control device 27 Insulator (insulating member) 29 Base part 31 Piping 31a Piping for pure water 31b Piping for oxygenated water 31c Piping for hydrogen water 33 Piping insulation part 33a Piping insulation part for pure water 33b Piping insulation part for oxygenated water 33c Piping insulation part for hydrogen water 71 Acquisition unit 73 Determination unit 75 Control unit Vwe Water electrolysis device potential Vsh Shielding body potential Vpd Predetermined allowable potential difference

Claims

1. A water electrolysis system comprising: a water electrolysis apparatus having a plurality of electrolytic cells for water electrolysis connected in series with at least one DC power supply; and a conductive shielding body that surrounds the water electrolysis apparatus and houses the water electrolysis apparatus in its internal space, wherein the shielding potential, which is the potential related to the shielding body, is set to converge to a predetermined potential difference with respect to the water electrolysis apparatus potential, which is the potential related to the water electrolysis apparatus, while being insulated from the ground potential.

2. A water electrolysis system according to claim 1, characterized in that the predetermined potential difference is set to a value that can suppress discharge between the water electrolysis device and the shielding body.

3. A water electrolysis system according to claim 1 or 2, characterized in that the shielding body is provided on the base portion while maintaining an insulating state with respect to the electrically grounded base portion via an insulating member provided between the shielding body and the base portion.

4. A water electrolysis system according to claim 3, further comprising an auxiliary device for controlling fluid parameters including the temperature and flow rate of pure water supplied to the water electrolysis device, and the pressure of oxygenated water and hydrogenated water discharged from the water electrolysis device, wherein each of the plurality of electrolytic cells provided in the water electrolysis device is connected in communication to a pipe for pure water, a pipe for oxygenated water, and a pipe for hydrogenated water, respectively, wherein each of the pipes for pure water, oxygenated water, and hydrogenated water is provided so as to span between the shield and the auxiliary device, wherein at least the hydrogenated water pipe has a pipe insulation section provided between the shield and the auxiliary device for electrically insulating the water electrolysis device and the auxiliary device, and an electrically grounded discharge induction section is provided near the pipe insulation section of the hydrogenated water pipe for inducing discharge against the shield.

5. A water electrolysis system according to claim 4, characterized in that the discharge induction unit is provided with an electric field concentration unit for particularly inducing discharge against the shielding body.

6. A water electrolysis system according to claim 5, characterized in that the distance between the electric field concentration section provided in the discharge induction section and the hydrogen water piping is set to a distance shorter than the longitudinal length of the pipe insulation section relating to the hydrogen water piping.

7. A water electrolysis system according to claim 5, further comprising a ventilation unit for ventilating the atmosphere related to the electric field concentration unit provided in the discharge induction unit.

8. A water electrolysis system according to claim 5, further comprising an acquisition unit for acquiring information on the discharge state in the atmospheric environment related to the electric field concentration unit provided in the discharge induction unit.

9. A water electrolysis system according to claim 8, wherein the acquisition unit further acquires information on the hydrogen concentration in the atmospheric environment related to the electric field concentration unit provided in the discharge induction unit.

10. A water electrolysis system according to claim 9, further comprising a control unit that performs control to stop the operation of the water electrolysis device when at least one of the discharge state or the hydrogen concentration in the atmospheric environment related to the electric field concentration section exceeds an allowable value set for each.

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