Electrolysis System

Abstract

To reduce wasteful energy consumption by a booster when starting up a plurality of electrolysis modules, thereby further improving the efficiency of the entire system. [Solution] The electrolysis system includes a plurality of electrolysis modules, each including an electrolysis cell and a combustion unit, a plurality of fuel supply systems capable of supplying fuel gas to the electrolysis cells and combustion units of the corresponding electrolysis modules, recovery lines that use a booster to boost the hydrogen produced at the hydrogen electrodes of the plurality of electrolysis modules and recover the hydrogen in a tank, and return lines that return the produced hydrogen from the recovery line upstream of the booster to each of the plurality of fuel supply systems.

Description

[Technical Field]

[0001] This specification discloses an electrolysis system. [Background technology]

[0002] Conventionally, in a solid oxide electrolysis system including a solid oxide electrolysis cell (SOEC) and a hydrogen storage container (tank) for storing hydrogen, a system has been proposed in which required hydrogen is supplied from the hydrogen storage container when the SOEC is started up (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-180308 Summary of the Invention [Problem to be solved by the invention]

[0004] When storing hydrogen produced in an electrolysis module in a tank, the hydrogen needs to be pressurized by the operation of a booster. Therefore, if hydrogen produced in the electrolysis module is pressurized by the booster and stored in a tank, and then the hydrogen in the tank is used by the electrolysis module the next time the system is started, energy consumption by the booster will be wasted. In particular, when a system is configured with multiple electrolysis modules, hydrogen in the tank must be supplied to each of the multiple electrolysis modules when the multiple electrolysis modules are started, which results in significant waste and a deterioration in the energy efficiency of the entire system.

[0005] A main object of the present disclosure is to further improve the efficiency of the entire system in an electrolysis system including a plurality of electrolysis modules by reducing wasteful energy consumption by boosters when starting up the plurality of electrolysis modules. [Means for solving the problem]

[0006] The present disclosure has adopted the following means to achieve the above-mentioned main object.

[0007] The electrolysis system according to the present disclosure comprises a plurality of electrolysis modules, each of which includes an electrolysis cell that produces hydrogen by electrolyzing water vapor supplied to a hydrogen electrode and a combustion unit that combusts a combustible gas; a plurality of fuel supply systems that can supply fuel gas to the electrolysis cell and the combustion unit of each corresponding electrolysis module; recovery lines that use a booster to pressurize product hydrogen produced at the hydrogen electrodes of the plurality of electrolysis modules and recover the product hydrogen in a tank; and return lines that return the product hydrogen from the recovery line upstream of the booster to each of the plurality of fuel supply systems.

[0008] In the electrolysis system disclosed herein, product hydrogen produced in some of the electrolysis modules is drawn from the upstream side of the booster in the recovery line into the fuel supply system of the other electrolysis modules to start up those other electrolysis modules. This reduces the waste of energy consumed by the booster when starting up an electrolysis system including multiple electrolysis modules, compared to a system in which hydrogen boosted by the booster and stored in a tank is supplied to all of the electrolysis modules. As a result, the efficiency of the entire system can be further improved. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic configuration diagram of an electrolysis system according to an embodiment of the present invention. [Figure 2] 10 is a flowchart illustrating an example of a startup process. [Figure 3] 10 is a flowchart illustrating an example of a machine reduction process. DETAILED DESCRIPTION OF THE INVENTION

[0010] Next, embodiments of the present disclosure will be described with reference to the drawings.

[0011] Fig. 1 is a schematic configuration diagram of an electrolysis system 10 of the present embodiment. As shown in Fig. 1 , the electrolysis system 10 of the embodiment comprises multiple electrolysis modules 20A, 20B each including an electrolysis cell stack 21 that generates hydrogen by steam electrolysis, a water vapor supply system 30 that supplies water vapor to the electrolysis modules 20A, 20B, a hydrogen supply system 40 that supplies hydrogen to the electrolysis modules 20A, 20B, an air supply system 50 that supplies air as a sweep gas to the electrolysis modules 20A, 20B, a hydrogen recovery system 60 that recovers the hydrogen produced in the electrolysis modules 20A, 20B, a power supply device 80 that supplies power required for electrolysis in each of the electrolysis modules 20A, 20B, and a control device 90 that controls the entire system.

[0012] Each of the electrolysis modules 20A and 20B includes a combustor 22 and a heat exchanger (not shown) in addition to the electrolysis cell stack 21, and these are housed in a module case 23 having thermal insulation properties.

[0013] The electrolysis cell stack 21 includes a plurality of solid oxide unit cells, each of which includes a solid electrolyte, a hydrogen electrode disposed on one side of the solid electrolyte, and an oxygen electrode disposed on the other side of the solid electrolyte. The electrolysis cell stack 21 receives power from a power supply device 80 and electrolyzes water vapor supplied to the hydrogen electrode to produce hydrogen at the hydrogen electrode and oxygen at the oxygen electrode. The power supply device 80 can be a system power supply, a renewable energy device (e.g., a solar power generation device), a storage battery, or the like.

[0014] Because the electrolysis cell stack 21 operates in a high-temperature environment of, for example, 650-800°C, the solid electrolyte, hydrogen electrode, and oxygen electrode are made of ceramic materials. Furthermore, to decompose water vapor into oxygen ions and hydrogen using a catalyst, the hydrogen electrode uses a cermet made of ceramic and a catalytic metal such as nickel. To maintain good catalytic activity of the hydrogen electrode, it is necessary to keep the hydrogen electrode in a reducing atmosphere and prevent oxidation of the metal. For this reason, in this embodiment, hydrogen is mixed with the water vapor supplied to the hydrogen electrode to prevent oxidation.

[0015] One end of a hydrogen electrode inlet pipe 21a is connected to the hydrogen electrode inlet of the electrolysis cell stack 21, and the other end of the hydrogen electrode inlet pipe 21a is connected to a water vapor supply system 30 and a hydrogen supply system 40. One end of an oxygen electrode inlet pipe 21b is connected to the oxygen electrode inlet of the electrolysis cell stack 21, and the other end of the oxygen electrode inlet pipe 21b is connected to an air supply system 50. One end of a hydrogen electrode outlet pipe 21c is connected to the hydrogen electrode outlet of the electrolysis cell stack 21, and the other end of the hydrogen electrode outlet pipe 21c is connected to a hydrogen recovery system 60. One end of an oxygen electrode outlet pipe 21d is connected to the oxygen electrode outlet of the electrolysis cell stack 21, and the other end of the oxygen electrode outlet pipe 21d is connected to a combustor 22. A combustion exhaust gas pipe 21e and a combustion hydrogen supply pipe 43 are connected to the combustor 22.

[0016] The water vapor supply system 30 includes a water tank 31, a steam generator 32 that generates water vapor by heating water stored in the water tank 31 or make-up water supplied from the outside, and a water vapor supply pipe 33 that supplies the generated water vapor to the hydrogen electrode inlet pipe 21a of each of the electrolysis modules 20A and 20B. A heater device, a steam heat pump device, or the like is used as the steam generator 32. The water vapor introduced from the water vapor supply system 30 to the hydrogen electrode inlet pipe 21a is heated by heat exchange with hydrogen electrode off-gas and the like in a heat exchanger (not shown) installed in the hydrogen electrode inlet pipe 21a, and then supplied to the hydrogen electrode of the electrolysis cell stack 21.

[0017] The hydrogen supply system 40 includes an anti-oxidation hydrogen supply pipe 41 connected at one end to the hydrogen electrode inlet pipe 21a, a hydrogen blower 42 installed in the anti-oxidation hydrogen supply pipe 41, a combustion hydrogen supply pipe 43 connected at one end to the combustor 22, and a hydrogen blower 44 installed in the combustion hydrogen supply pipe 43. By driving the hydrogen blower 42, hydrogen is introduced into the anti-oxidation hydrogen supply pipe 41, and the introduced hydrogen is supplied to the hydrogen electrode of the electrolysis cell stack 21 as anti-oxidation hydrogen. By driving the hydrogen blower 44, hydrogen is introduced into the combustion hydrogen supply pipe 43, and the introduced hydrogen is supplied to the combustor 22 as combustion hydrogen. Note that the anti-oxidation hydrogen supply pipe 41 and the combustion hydrogen supply pipe 43 are each equipped with a flow meter (not shown).

[0018] A hydrogen supply system 40 is provided for each of the electrolysis modules 20A and 20B. Circulation pipes 71, 72 branching from a hydrogen recovery pipe 63 of a hydrogen recovery system 60 (described later) are connected to the other end of the anti-oxidation hydrogen supply pipe 41 and the other end of the combustion hydrogen supply pipe 43 of each of the electrolysis modules 20A and 20B. Furthermore, a hydrogen tank 61 is also connected to the other end of the anti-oxidation hydrogen supply pipe 41 and the other end of the combustion hydrogen supply pipe 43 of one of the electrolysis modules 20A via an on-off valve 67. Thus, the hydrogen supply system 40 of the electrolysis module 20A can supply hydrogen stored in the hydrogen tank 61 to the electrolysis cell stack 21 and the combustor 22 by opening the on-off valve 67 to drive the hydrogen blowers 42, 44, and can supply hydrogen produced in the electrolysis module 20A or the electrolysis module 20B to the electrolysis cell stack 21 or the combustor 22 without going through the hydrogen tank 61 by closing the on-off valve 67 to drive the hydrogen blowers 42, 44. Furthermore, the hydrogen supply system 40 of the electrolysis module 20B is not connected to the hydrogen tank 61 and therefore cannot supply hydrogen stored in the hydrogen tank 61, but can supply hydrogen produced in the electrolysis module 20A or the electrolysis module 20B.

[0019] The air supply system 50 includes an air supply pipe 51 connected to the oxygen electrode inlet pipe 21b, and an air blower 52 installed in the air supply pipe 51. By driving the air blower 52, air drawn into the air supply pipe 51 is introduced into the oxygen electrode inlet pipe 21b, and is heated by heat exchange with combustion exhaust gas, hydrogen electrode off-gas, etc. in a heat exchanger (not shown) installed in the oxygen electrode inlet pipe 21b, and then supplied to the oxygen electrode of the electrolysis cell stack 21.

[0020] The hydrogen recovery system 60 recovers hydrogen from the hydrogen electrode off-gas, which contains produced hydrogen and water vapor and is discharged from the hydrogen electrode outlet. The hydrogen recovery system 60 includes a hydrogen tank 61 for storing hydrogen and a condenser 62 for condensing the water vapor contained in the hydrogen electrode off-gas to separate it into gas and liquid. The condenser 62 has a heat exchange flow path capable of exchanging heat with cooling water. The inlet of the heat exchange flow path is connected to one end of the hydrogen electrode outlet pipe 21c, one end of which is connected to the hydrogen electrode, and the other end of the heat exchange flow path is connected to one end of a hydrogen recovery pipe 63. The hydrogen tank 61 is connected to the other end of the hydrogen recovery pipe 63. A flow meter 64, a gas holder 65, and a booster 66 are also installed in the hydrogen recovery pipe 63. The hydrogen electrode off-gas containing hydrogen and water vapor is subjected to heat exchange with cooling water to condense the water vapor contained in the hydrogen electrode off-gas, and then temporarily stored in a gas holder 65, where it is pressurized by driving a booster 66 and collected in a hydrogen tank 61. In addition, the condensed water obtained by condensing the water vapor in the hydrogen electrode off-gas in a condenser 62 is passed through a condensed water pipe 68 and stored in a water tank 31. The water stored in the water tank 31 is used as raw water for generating water vapor for electrolysis.

[0021] The reflux pipe 71 branches off from the hydrogen recovery pipe 63 upstream of the booster 66 (gas holder 65) and is connected to the anti-oxidation hydrogen supply pipe 41 on the electrolysis module 20A upstream of the hydrogen blower 42 and the combustion hydrogen supply pipe 43 upstream of the hydrogen blower 44 so as to return the produced hydrogen to the electrolysis module 20A. The produced hydrogen flowing through the hydrogen recovery pipe 63 is drawn from the reflux pipe 71 into the anti-oxidation hydrogen supply pipe 41 by negative pressure generated by driving the hydrogen blower 42 on the electrolysis module 20A, and is supplied from the anti-oxidation hydrogen supply pipe 41 to the electrolysis cell stack 21 (hydrogen electrode) of the electrolysis module 20A. The produced hydrogen flowing through the hydrogen recovery pipe 63 is drawn from the reflux pipe 71 into the combustion hydrogen supply pipe 43 by negative pressure generated by driving the hydrogen blower 44 on the electrolysis module 20A, and is supplied from the combustion hydrogen supply pipe 43 to the combustor 22 of the electrolysis module 20A.

[0022] The reflux pipe 72 branches off from the hydrogen recovery pipe 63 upstream of the booster 66 (gas holder 65) and is connected to the anti-oxidation hydrogen supply pipe 41 on the electrolysis module 20B upstream of the hydrogen blower 42 and the combustion hydrogen supply pipe 43 upstream of the hydrogen blower 44 so as to return the produced hydrogen to the electrolysis module 20B. The produced hydrogen flowing through the hydrogen recovery pipe 63 is drawn from the reflux pipe 72 into the anti-oxidation hydrogen supply pipe 41 by negative pressure generated by driving the hydrogen blower 42 on the electrolysis module 20B, and is supplied from the anti-oxidation hydrogen supply pipe 41 to the electrolysis cell stack 21 (hydrogen electrode) of the electrolysis module 20B. The produced hydrogen flowing through the hydrogen recovery pipe 63 is drawn from the reflux pipe 72 into the combustion hydrogen supply pipe 43 by negative pressure generated by driving the hydrogen blower 44 on the electrolysis module 20B, and is supplied from the combustion hydrogen supply pipe 43 to the combustor 22 of the electrolysis module 20B.

[0023] The control device 90 is configured as a microprocessor centered around a CPU, and in addition to the CPU, is equipped with ROM, RAM, input / output ports, etc. Detection signals from temperature sensors installed near each electrolytic cell stack 21, temperature sensors installed in each combustor 22, flow meters installed in each anti-oxidation hydrogen supply pipe 41, flow meters installed in each combustion hydrogen supply pipe 43, and flow meter 64 installed in the hydrogen recovery pipe 63 are input to the control device 90 via an input port. In addition, the control device 90 outputs control signals to each hydrogen blower 42, 44, each air blower 52, booster 66, on-off valve 67, etc. via an output port.

[0024] Next, the operation of the electrolysis system 10 configured as above will be described, in particular the process for warming up and starting up the multiple electrolysis modules 20A, 20B. Figure 2 is a flowchart showing an example of the start-up process executed by the CPU of the control device 90. This process is executed when a system start-up request is received from a higher-level system. The start-up of the multiple electrolysis modules 20A, 20B is performed by first starting up one electrolysis module 20A (hereinafter referred to as electrolysis module A) and then starting up the other electrolysis module 20B (hereinafter referred to as electrolysis module B).

[0025] When the startup process is performed, the control device 90 first opens the on-off valve 67 to control the hydrogen blowers 42, 44 on the electrolysis module A side so that hydrogen in the hydrogen tank 61 is supplied to the electrolysis cell stack 21 (hydrogen electrode) of the electrolysis module A as antioxidant hydrogen and to the combustor 22 of the electrolysis module A as combustion hydrogen, and also controls the air blower 52 on the electrolysis module A side so that air is supplied to the combustor 22 (step S100). Next, the control device 90 combusts the mixed gas of combustion hydrogen and air supplied to the combustor 22 of the electrolysis module A to warm up the electrolysis module A (electrolysis cell stack 21) with the combustion heat (step S102). Then, the control device 90 determines whether the warm-up of the electrolysis module A has been completed (step S104). This process is performed by determining whether the stack temperature, detected by a temperature sensor installed near the electrolysis cell stack 21 of the electrolysis module A, is equal to or higher than a predetermined temperature.

[0026] When the control device 90 determines that the warm-up of the electrolysis module A is completed, it controls the steam generator 32 to supply water vapor to the hydrogen electrodes of the electrolysis cell stack 21 of the electrolysis module A, and controls the air blower 52 on the electrolysis module A side to supply air to the oxygen electrodes of the electrolysis cell stack 21 (step S106). The control device 90 then supplies power from the power supply device 80 across the terminals of the electrolysis cell stack 21 of the electrolysis module A to start the electrolysis operation of the electrolysis module A (step S108). When the electrolysis operation of the electrolysis module A is started, the control device 90 closes the on-off valve 67 and controls the hydrogen blowers 42, 44 so that hydrogen generated by the electrolysis operation of the electrolysis module A is supplied via the reflux piping 71 to the hydrogen electrodes of the electrolysis cell stack 21 of the electrolysis module A as antioxidant hydrogen and to the combustor 22 of the electrolysis module A as combustion hydrogen.

[0027] Next, the control device 90 controls the hydrogen blowers 42, 44 on the electrolysis module B side so that the product hydrogen generated by the electrolysis operation of the electrolysis module A is supplied to the electrolysis cell stack 21 (hydrogen electrode) of the electrolysis module B as antioxidant hydrogen and to the combustor 22 of the electrolysis module B as combustion hydrogen, and also controls the air blower 52 on the electrolysis module B side so that air is supplied to the combustor 22 (step S110). Subsequently, the control device 90 combusts the mixed gas of the combustion hydrogen and air supplied to the combustor 22 of the electrolysis module B to warm up the electrolysis module B (electrolysis cell stack 21) with the combustion heat (step S112). Then, the control device 90 determines whether the warm-up of the electrolysis module B is completed (step S114). This process is performed by determining whether the stack temperature, detected by a temperature sensor installed near the electrolysis cell stack 21 of the electrolysis module B, is equal to or higher than a predetermined temperature.

[0028] When the control device 90 determines that the warm-up of the electrolysis module B is completed, it controls the steam generator 32 to supply water vapor to the hydrogen electrodes of the electrolysis cell stacks 21 of the electrolysis module B in addition to the electrolysis module A, and controls the air blower 52 of the electrolysis module B to supply air to the oxygen electrodes of the electrolysis cell stacks 21 (step S116). The control device 90 then supplies power from the power supply device 80 across the terminals of the electrolysis cell stack 21 of the electrolysis module B to start the electrolysis operation of the electrolysis module B (step S118), and terminates the startup process. When the electrolysis operation of the electrolysis module B is started, the control device 90 controls the hydrogen blowers 42, 44 so that the product hydrogen generated by the electrolysis operation of the electrolysis modules A and B is supplied via the reflux piping 72 to the hydrogen electrodes of the electrolysis cell stacks 21 of the electrolysis module B as antioxidant hydrogen and to the combustor 22 of the electrolysis module B as combustion hydrogen.

[0029] Here, the hydrogen produced in the electrolysis modules 20A, 20B is stored in the hydrogen tank 61 at a pressure boosted by the power of the booster 66. Therefore, if the hydrogen produced in the electrolysis modules 20A, 20B is boosted by the booster 66 and stored in the hydrogen tank 61, and then the hydrogen in the hydrogen tank 61 is used by the electrolysis modules 20A, 20B at the next system startup, energy waste occurs in the booster 66. In particular, in an electrolysis system 10 including multiple electrolysis modules 20A, 20B, hydrogen in the hydrogen tank 61 must be supplied to each of the multiple electrolysis modules 20A, 20B when the multiple electrolysis modules 20A, 20B are started, which results in significant energy waste and a deterioration in the energy efficiency of the entire system. In contrast, in the electrolysis system 10 of the present embodiment, one electrolysis module A is started up first using hydrogen in the hydrogen tank 61, and hydrogen produced from the electrolysis module A during electrolysis operation is drawn from the hydrogen recovery pipe 63 upstream of the booster 66 and supplied to the combustor 22 of the electrolysis module B, thereby starting (warming up) the other electrolysis module B. This reduces the required amount of hydrogen in the hydrogen tank 61 compared to a system in which hydrogen in the hydrogen tank 61 is supplied to all of the electrolysis modules A and B, and further reduces wasted energy consumption by the booster 66. As a result, the efficiency of the electrolysis system 10 can be further improved.

[0030] Next, a description will be given of the operation performed during reduced-unit operation, in which some of the multiple electrolysis modules A and B are stopped. Fig. 3 is a flowchart showing an example of reduced-unit operation executed by the CPU of the control device 90. This process is executed when a reduced-unit operation is requested by a host system based on hydrogen demand or electricity prices.

[0031] When the unit reduction process is executed, the control device 90 first stops the power supply and the supply of water vapor to the electrolysis module B (step S200). Next, the control device 90 controls the hydrogen blowers 42, 44 of the electrolysis module B to supply the produced hydrogen in the electrolysis module A that is performing electrolysis to the electrolysis cell stack 21 (hydrogen electrode) and the combustor 22 of the electrolysis module B where electrolysis is stopped, respectively, and controls the air blower 52 to supply air to the combustor 22 of the electrolysis module B (step S202). By driving the hydrogen blowers 42, 44, the produced hydrogen flowing through the hydrogen recovery pipe 63 from the electrolysis module A is drawn into the oxidation prevention hydrogen supply pipe 41 and the combustion hydrogen supply pipe 43 of the electrolysis module B via the reflux pipe 72, and is supplied to the electrolysis cell stack 21 (hydrogen electrode) and the combustor 22 of the electrolysis module B, respectively. The control device 90 then combusts the mixed gas of the produced hydrogen and air in the combustor 22 (step S204), thereby completing the unit reduction process. Stopping some of the electrolysis modules B makes it possible to respond appropriately to a decrease in hydrogen demand and an increase in electricity prices. Furthermore, hydrogen produced in electrolysis module A is supplied to the electrolysis cell stack 21 (hydrogen electrode) and combustor 22 of the electrolysis module B for which electrolysis is stopped to prevent oxidation of the hydrogen electrode and simultaneously combust the hydrogen. This reduces the wasteful energy consumption of the booster 66 compared to supplying hydrogen from the hydrogen tank 61, and allows the electrolysis module B for which electrolysis is stopped to be maintained at a certain temperature or above (hot standby state). This allows the electrolysis module B to be quickly restored the next time it transitions from a state in which electrolysis is stopped to an active electrolysis state.

[0032] In the above-described embodiment, the electrolysis system 10 includes two electrolysis modules 20A and 20B. However, the electrolysis system 10 may include three or more electrolysis modules 20A, 20B, 20C, etc. In this case, the electrolysis system 10 may start up the electrolysis modules one by one in order, such as by starting up the electrolysis module 20A first, supplying the produced hydrogen from the started electrolysis module 20A to the electrolysis module 20B as hydrogen for combustion to start up the electrolysis module 20B, and then supplying the produced hydrogen from the started electrolysis modules 20A and 20B to the electrolysis module 20C as hydrogen for combustion to start up the electrolysis module 20C. Alternatively, the electrolysis system 10 may start up the electrolysis module 20A first, and supplying the produced hydrogen from the started electrolysis module 20A to all of the other electrolysis modules 20B, 20C, etc. as hydrogen for combustion to start up all of the other electrolysis modules 20B, 20C, etc. simultaneously. When three or more electrolysis modules 20A, 20B, 20C, . . . are provided, the number of electrolysis modules connected to the hydrogen tank 61 does not necessarily have to be one, but may be two or more.

[0033] In the above-described embodiment, the electrolysis system 10 performs electrolysis operation to produce hydrogen by steam electrolysis. However, the electrolysis system 10 may also use the electrolysis cell stack 21 as a reversible solid oxide cell stack, and switch between electrolysis operation and power generation operation to generate power by reacting hydrogen as fuel gas with oxygen contained in the air.

[0034] The above describes the forms for implementing the present disclosure using embodiments, but the present disclosure is not limited to these embodiments in any way, and it goes without saying that the present disclosure can be implemented in various forms within the scope that does not deviate from the gist of the present disclosure.

[0035] This specification also discloses the technical idea of ​​changing "the electrolysis system according to claim 1 or 2" in claim 4 originally filed to "the electrolysis system according to any one of claims 1 to 3." [Industrial Applicability]

[0036] The present disclosure is applicable to the electrolysis system manufacturing industry and the like. [Explanation of symbols]

[0037] 10 electrolysis system, 20A, 20B electrolysis modules, 21 electrolysis cell stack (electrolysis cell), 22 combustor (combustion section), 40 hydrogen supply system (fuel supply system), 61 hydrogen tank (tank), 63 hydrogen recovery piping (recovery line), 66 booster, 71, 72 reflux piping (reflux line), control device 90 (start control section, stop control section).

Claims

1. a plurality of electrolysis modules each including an electrolysis cell that electrolyzes water vapor supplied to a hydrogen electrode to generate hydrogen, and a combustion unit that combusts a combustible gas; a plurality of fuel supply systems each capable of supplying fuel gas to the electrolysis cell and the combustion unit of the corresponding electrolysis module; a recovery line that uses a booster to boost the hydrogen produced at the hydrogen electrodes of the plurality of electrolysis modules and recovers the hydrogen in a tank; a reflux line that refluxes the produced hydrogen from the recovery line upstream of the booster to each of the plurality of fuel supply systems; An electrolysis system comprising:

2. 2. The electrolysis system of claim 1, a startup control unit that, when starting up the plurality of electrolysis modules, starts up some of the plurality of electrolysis modules first, and supplies hydrogen generated in the electrolysis modules that have completed startup to the other electrolysis modules that have not completed startup via the reflux line, thereby starting up the other electrolysis modules. Electrolysis system.

3. 3. The electrolysis system according to claim 1 or 2, a stop control unit that, when electrolysis is stopped in some of the plurality of electrolysis modules, supplies hydrogen generated in the electrolysis module in electrolysis operation via the reflux line to the electrolysis module in which electrolysis is stopped. Electrolysis system.

4. 3. The electrolysis system according to claim 1 or 2, some of the plurality of fuel supply systems are connected to the tank; The remainder of the plurality of fuel supply systems are not connected to the tank. Electrolysis system.

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