Water electrolysis system
The water electrolysis system addresses efficiency fluctuations by using heat transfer medium piping and bypass systems for temperature regulation, ensuring consistent performance and reducing cooling loads.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- KK TOYOTA CHUO KENKYUSHO
- Filing Date
- 2022-03-25
- Publication Date
- 2026-05-29
Smart Images
Figure 0007867353000001 
Figure 0007867353000002 
Figure 0007867353000003
Abstract
Description
Technical Field
[0001] The present invention relates to a water electrolysis system.
Background Art
[0002] Conventionally, a water electrolysis system that generates hydrogen by electrolysis of water using an electrolyte membrane has been known. Generally, since the reaction efficiency of the water electrolysis reaction decreases at low temperatures, the water used in the reaction is preferably at a certain temperature. Patent Document 1 discloses a hydrogen / oxygen gas production apparatus that supplies water stored in a solar heat storage device and heated by sunlight to a water electrolysis cell.
Prior Art Documents
Patent Documents
[0003]
Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0004] However, during bad weather such as cloudy days or rain, the amount of sunlight decreases. Therefore, in the apparatus described in Patent Document 1, depending on the weather, as the amount of sunlight reaching the solar heat storage device decreases, the heated water cannot be supplied to the water electrolysis cell, and the reaction efficiency of the water electrolysis reaction may decrease. For this reason, there has been room for improvement in maintaining a high reaction efficiency of the water electrolysis reaction.
[0005] The present invention has been made to solve at least a part of the above problems, and an object thereof is to provide a water electrolysis system capable of maintaining a high reaction efficiency of an electrolysis reaction by a water electrolysis unit.
Means for Solving the Problems
[0006] The present invention has been made to solve at least some of the above-mentioned problems and can be realized in the following forms.
[0007] (1) According to one embodiment of the present invention, a water electrolysis system is provided. This water electrolysis system comprises a water electrolysis unit that generates oxygen and hydrogen by electrolysis of water using an electrolyte membrane, and a heat transfer medium piping that partially passes through the inside of the water electrolysis unit and forms a heat transfer medium channel through which a heat transfer medium circulates to exchange heat with the water electrolysis unit.
[0008] In this configuration, heat exchange occurs between the heat transfer medium circulating in the heat transfer piping and the water electrolysis unit. A portion of the electricity supplied to the water electrolysis unit to perform the electrolysis of water is converted into Joule heat. If the temperature of the water electrolysis unit continues to rise due to Joule heat, the electrolyte membrane used in the electrolytic reaction by the water electrolysis unit is likely to deteriorate. With this configuration, the water electrolysis unit can be cooled by the heat transfer medium absorbing heat from the water electrolysis unit when it is in such a high-temperature state. In addition, generally, when the water electrolysis unit is in a low-temperature state, the reaction efficiency of the electrolytic reaction by the water electrolysis unit decreases. Therefore, in cold regions, during winter, at night, etc., the reaction efficiency of the electrolytic reaction by the water electrolysis unit tends to decrease. With this configuration, the water electrolysis unit can be warmed by supplying heat from the heat transfer medium to the water electrolysis unit when it is in such a low-temperature state. Therefore, with this configuration, by adjusting the temperature of the water electrolysis unit to the desired temperature through heat exchange with the heat transfer medium, deterioration of the electrolyte membrane due to high temperatures and a decrease in reaction efficiency due to low temperatures can be suppressed, and the reaction efficiency of the electrolytic reaction by the water electrolysis unit can be maintained at a high level.
[0009] (2) In the water electrolysis system of the above form, the system may further include a bypass pipe branched from the heat transfer pipe and a heat storage container that houses a part of the bypass pipe and houses a heat storage material capable of storing and releasing heat by heat exchange with the heat transfer material flowing through the bypass pipe. With this configuration, the heat transfer medium circulating in the bypass piping can store heat in the heat storage material housed in the heat storage unit and release heat from the heat storage material through heat exchange. Therefore, the heat transfer medium that has absorbed heat from the water electrolysis unit can circulate in the bypass piping and store heat in the heat storage material through heat exchange. Consequently, since the Joule heat generated in the water electrolysis unit is stored in the heat storage material, the cooling load for cooling the water electrolysis unit can be reduced. On the other hand, the heat transfer medium can also receive heat released from the heat storage material through heat exchange as it circulates in the bypass piping, and use that heat to warm the water electrolysis unit and improve the reaction efficiency of the electrolysis reaction. Therefore, with this configuration, it is possible to achieve both a reduction in the cooling load for cooling the water electrolysis unit and an improvement in the reaction efficiency of the electrolysis reaction by the water electrolysis unit. Furthermore, since the heat source for the heat stored in the heat storage material is the Joule heat constantly generated by the electrolysis reaction in the water electrolysis unit, heat can be stored in the heat storage material periodically. Therefore, the reaction efficiency of the electrolytic reaction by the water electrolysis unit can be maintained at a high level.
[0010] (3) In the water electrolysis system of the above configuration, the bypass piping includes a first bypass piping that branches off from a first position in the heat transfer medium piping and merges with the heat transfer medium piping at a second position downstream of the first position, with reference to the exit position where the heat transfer medium piping exits from the inside of the water electrolysis unit, and a second bypass piping that branches off from a third position downstream of the second position in the heat transfer medium piping with reference to the exit position, and merges with the heat transfer medium piping at a fourth position downstream of the third position, the heat storage unit housing a portion of the first bypass piping and the second bypass piping, and the heat storage material being contained within the first bypass piping and the second bypass piping. The system includes a first path switching unit that performs heat exchange with the heat transfer medium flowing through the bypass piping and further switches the first path, which is the path of the heat transfer medium from the first position to the second position, between the heat transfer medium piping and the first bypass piping; a second path switching unit that switches the second path, which is the path of the heat transfer medium from the third position to the fourth position, between the heat transfer medium piping and the second bypass piping; and a control unit that controls the water electrolysis system, wherein the control unit may use the first path as the first bypass piping when executing a heat storage mode in which heat is stored in the heat storage device, and may use the second path as the second bypass piping when executing a heat dissipation mode in which heat is released to the heat storage device. In this configuration, the bypass piping includes a first bypass piping and a second bypass piping located downstream of the first bypass piping with respect to the exit point. When the heat storage mode is executed, the first path is the first bypass piping. Therefore, the heat transfer medium that has absorbed heat from the water electrolysis unit can flow through the first bypass piping and store heat in the heat storage material through heat exchange. Since the first bypass piping is located upstream of the second bypass piping with respect to the exit point, the heat absorbed from the water electrolysis unit can be stored in the heat storage material while suppressing the heat loss that increases with the flow distance from the exit point to the heat storage unit. On the other hand, in this configuration, when the heat dissipation mode is executed, the second path is the second bypass piping. Therefore, the heat transfer medium flows through the second bypass piping and receives heat dissipated from the heat storage material through heat exchange, and this heat can warm the water electrolysis unit and increase the reaction efficiency of the electrolysis reaction. Since the second bypass piping is located downstream of the first bypass piping relative to the exit point, it is possible to supply heat received from the heat storage material to the water electrolysis section while suppressing the heat loss that increases with the flow distance from the heat storage unit to the entry point (the point where the heat transfer medium piping enters the water electrolysis section).
[0011] (4) In the water electrolysis system of the above configuration, when the heat storage mode is active, if the temperature of the heat storage material becomes equal to or above the target heat storage temperature, or if the temperature of the heat transfer medium flowing through the heat transfer medium piping falls below the specified heat storage temperature, the control unit will turn the first path to the first bypass path. The pipe may be switched to the aforementioned heat transfer fluid piping. If the heat storage mode is maintained even after the heat storage material has reached the target heat storage temperature, the likelihood of the heat storage material degrading increases. Also, if the Joule heat generated in the water electrolysis section decreases and the temperature of the heat transfer medium circulating in the first bypass piping falls below the specified heat storage temperature, such a heat transfer medium is more likely to release heat from the heat storage material than to store heat in it. Therefore, this configuration reduces the likelihood of the heat storage material degrading and the likelihood of heat being released from the heat storage material even when in heat storage mode. Furthermore, if the pressure loss is greater when circulating through the first bypass piping than when circulating through the heat transfer medium piping in the first path, such pressure loss can be reduced, thereby reducing the amount of energy consumed to circulate the heat transfer medium.
[0012] (5) In the water electrolysis system of the above configuration, the control unit may switch the second path from the second bypass pipe to the heat transfer pipe when the temperature of the heat storage material falls below the heat transfer specified temperature, or when the temperature of the heat transfer medium flowing through the heat transfer pipe becomes equal to or above the heat transfer target temperature. When the temperature falls below the heat dissipation regulated temperature, the heat storage material is more likely to absorb heat from the heat transfer medium circulating in the second bypass pipe. Furthermore, if the heat dissipation mode is maintained even after the temperature of the heat transfer medium circulating in the second bypass pipe rises above the heat dissipation target temperature, the likelihood of the heat storage material absorbing heat from the heat transfer medium circulating in the second bypass pipe increases, similar to the case when the heat storage material falls below the heat dissipation regulated temperature. Therefore, this configuration can reduce the likelihood of the heat storage material absorbing heat from the heat transfer medium circulating in the second bypass pipe during heat dissipation mode. In addition, if the pressure loss is greater when circulating through the second bypass pipe than when circulating through the heat transfer medium pipe in the second path, such pressure loss can be reduced, thereby reducing the amount of energy consumed to circulate the heat transfer medium.
[0013] (6) In the water electrolysis system of the above form, the heat storage material may be a latent heat storage material or a chemical heat storage material. With this configuration, heat storage from the heat transfer medium circulating in the first bypass pipe and heat release to the heat transfer medium circulating in the second bypass pipe can be performed by a change in the state of the latent heat storage material or chemical heat storage material.
[0014] (7) In the water electrolysis system of the above form, the heat storage material may be an adsorbent capable of heat dissipation and heat storage through the adsorption and desorption of substances. With this configuration, heat storage from the heat transfer medium flowing through the first bypass pipe and heat dissipation to the heat transfer medium flowing through the second bypass pipe can be performed by adsorption and desorption of substances by the adsorbent.
[0015] Furthermore, the present invention can be realized in various forms, for example, as a control method for a water electrolysis system, a computer program for controlling the electrolysis of water in a water electrolysis system, a server device for distributing the computer program, a non-temporary storage medium storing the computer program, and so on. [Brief explanation of the drawing]
[0016] [Figure 1] This is an explanatory diagram illustrating the configuration of a water electrolysis system according to the first embodiment. [Figure 2] This is a magnified view of the inside of a heat storage container. [Figure 3] This is an explanatory diagram showing the flow path during heat storage mode. [Figure 4] This is an explanatory diagram showing the flow path during heat dissipation mode. [Figure 5] This is an explanatory diagram illustrating the configuration of a water electrolysis system according to the second embodiment. [Modes for carrying out the invention]
[0017] <First Embodiment> FIG. 1 is an explanatory diagram illustrating the configuration of a water electrolysis system 1 as an embodiment of the present invention. The water electrolysis system 1 is a system that generates oxygen and hydrogen by electrolyzing water. The water electrolysis system 1 includes a cell stack 10, a DC power source 12, a converter 14, a hydrogen gas-liquid separator 20, a condenser 22, an oxygen gas-liquid separator 30, a condenser 32, a circulation pump PM1, a tank 44, a circulation pump PM2, a heat exchanger 46, a heat accumulator 50, and a control unit 60. Further, the water electrolysis system 1 includes a first mixture delivery pipe P1, a second mixture delivery pipe P2, an oxygen delivery pipe P3, a water supply pipe P4, a heat medium pipe HP, a first bypass pipe B1, and a second bypass pipe B2.
[0018] The cell stack 10 is configured by stacking a plurality of water electrolysis cells. Each water electrolysis cell is a water electrolysis unit that generates oxygen and hydrogen by electrolyzing water (electrolysis) using an electrolyte membrane. The DC power source 12 is a power source for the cell stack 10. The converter 14 converts the power supplied from the DC power source 12 and supplies it to the cell stack 10.
[0019] The mixture of hydrogen and water generated in the cell stack 10 is sent to a first mixture delivery pipe P1 that forms a mixture delivery flow path for sending the mixture out of the cell stack 10. The first mixture delivery pipe P1 is provided with a hydrogen gas-liquid separator 20 and a condenser 22. The hydrogen gas-liquid separator 20 separates the mixture of hydrogen and water generated in the cell stack 10 into hydrogen and water. The condenser 22 has cooling water supplied therein, and condenses the water vapor contained in the mixture when the mixture of hydrogen and water passes through the inside. The hydrogen separated through the hydrogen gas-liquid separator 20 and the condenser 22 is sent outside the water electrolysis system 1 through the first mixture delivery pipe P1.
[0020] The mixture of oxygen and water generated in the cell stack 10 is sent to a second mixture delivery pipe P2, which forms a mixture delivery channel that sends the mixture out of the cell stack 10. The second mixture delivery pipe P2 connects the cell stack 10 to the oxygen vapor-liquid separator 30. The oxygen vapor-liquid separator 30 separates the mixture of oxygen and water generated in the cell stack 10 into oxygen and water. In addition to the mixture of oxygen and water, pure water is supplied to the oxygen vapor-liquid separator 30 from a tank (not shown) as needed. The oxygen vapor-liquid separator 30 is also connected to the oxygen delivery pipe P3. The oxygen delivery pipe P3 is equipped with a condenser 32. Similar to the condenser 22, the condenser 32 is supplied with cooling water, and as the mixture of oxygen and water passes through it, the water vapor contained in the mixture is condensed. The oxygen separated through the oxygen vapor-liquid separator 30 and the condenser 32 is sent to the outside of the water electrolysis system 1 through the oxygen delivery pipe P3.
[0021] The water supply pipe P4 is a pipe that forms a water supply channel that supplies water to the cell stack 10. The water supply pipe P4 connects the oxygen vapor-liquid separator 30 and the cell stack 10. The water flowing through the water supply pipe P4 is the water separated in the oxygen vapor-liquid separator 30. A circulation pump PM1 is provided in the water supply pipe P4. The circulation pump PM1 sends water from the oxygen vapor-liquid separator 30 to the cell stack 10.
[0022] The heat transfer medium piping HP is a pipe that partially passes through the inside of the cell stack 10 and forms a heat transfer medium flow path that circulates the heat transfer medium that exchanges heat with the cell stack 10. In this embodiment, the heat transfer medium is water. The heat transfer medium piping HP is a pipe that circulates the heat transfer medium and repeatedly passes through the inside of the cell stack 10. In Figure 1, the direction of circulation of the heat transfer medium in the heat transfer medium piping HP is indicated by an arrow. The entry position EN shown in Figure 1 is the position where the heat transfer medium piping HP enters the inside of the cell stack 10. On the other hand, the exit position EX shown in Figure 1 is the position where the heat transfer medium piping HP exits the inside of the cell stack 10. The heat transfer medium piping HP is equipped with a tank 44, a circulation pump PM2, and a heat exchanger 46. The tank 44 temporarily stores the heat transfer medium sent from the upstream side and supplies the heat transfer medium to the downstream side as needed. The circulation pump PM2 delivers the heat transfer medium downstream. The heat exchanger 46 has water circulating inside, and when the heat transfer medium flowing through the heat transfer medium piping HP is at a relatively high temperature, the circulating water recovers the heat.
[0023] The bypass piping branching from the heat transfer medium piping HP includes a first bypass piping B1 and a second bypass piping B2. The first bypass piping B1 branches off from the first position L1 in the heat transfer medium piping HP and merges with the heat transfer medium piping HP at the second position L2, which is downstream of the first position L1 with respect to the exit position EX. Valve V1 is provided in the first bypass piping B1. Valve V1 is a shut-off valve capable of blocking the flow of heat transfer medium from the first position L1 to the second position L2 through the first bypass piping B1. On the other hand, valve V2 is provided between the first position L1 and the second position L2 in the heat transfer medium piping HP. Valve V2 is a shut-off valve capable of blocking the flow of heat transfer medium from the first position L1 to the second position L2 through the heat transfer medium piping HP. In this embodiment, valves V1 and V2 correspond to a first path switching unit that switches the first path, which is the path of the heat transfer medium from a first position L1 to a second position L2, between the heat transfer medium piping HP and the first bypass piping B1.
[0024] The second bypass pipe B2 is a pipe that branches off from the third position L3 downstream of the second position L2, with reference to the exit position EX of the heat transfer medium pipe HP, and merges with the heat transfer medium pipe HP at the fourth position L4 downstream of the third position L3. Valve V3 is provided in the second bypass pipe B2. Valve V3 is a shut-off valve that can block the flow of the heat transfer medium from the third position L3 to the fourth position L4 via the second bypass pipe B2. On the other hand, valve V4 is provided between the third position L3 and the fourth position L4 of the heat transfer medium pipe HP. Valve V4 is a shut-off valve that can block the flow of the heat transfer medium from the third position L3 to the fourth position L4 via the heat transfer medium pipe HP. In this embodiment, valves V3 and V4 correspond to a second path switching section that switches the second path, which is the path of the heat transfer medium from the third position L3 to the fourth position L4, between the heat transfer medium pipe HP and the second bypass pipe B2.
[0025] Figure 2 is an enlarged view of the inside of the heat storage unit 50. The heat storage unit 50 houses a portion of the bypass piping (first bypass piping B1 and second bypass piping B2) and contains a heat storage material 54 that can store and release heat through heat exchange with a heat transfer medium flowing through the bypass piping (inside the first bypass piping B1 and second bypass piping B2). Figure 2 shows a portion of the first bypass piping B1 and second bypass piping B2 housed in the heat storage unit 50. In this embodiment, the heat storage unit 50 houses water, which is the fluid used as the heat storage material 54, within a housing 52 made of insulating material. That is, when a heat transfer medium flows through the first bypass piping B1 or the second bypass piping B2, heat exchange takes place between the heat transfer medium and the heat storage material 54 housed in the heat storage unit 50.
[0026] Returning to the explanation of Figure 1, the control unit 60 controls the water electrolysis system 1 based on information obtained from various sensors provided by the water electrolysis system 1. Specific control actions by the control unit 60 include, for example, the opening and closing of valves V1 to V4 and the control of power supply from the DC power supply 12 to the cell stack 10. The control unit 60 starts the electrolytic reaction in the cell stack 10 by starting the power supply from the DC power supply 12 to the cell stack 10. At the start of the electrolytic reaction, the control unit 60 closes valve V1 and opens valve V2, and closes valve V3 and opens valve V4. While the electrolytic reaction in the cell stack 10 is being performed, the control unit 60 executes either a heat storage mode, which stores heat in the heat accumulator 50, or a heat dissipation mode, which releases heat to the heat accumulator 50, based on information obtained from temperature sensors (not shown) provided by the water electrolysis system 1. The information obtained from the temperature sensors includes the temperature inside the cell stack 10 and the temperature inside the heat accumulator 50.
[0027] Figure 3 is an explanatory diagram showing the flow path in heat storage mode. The control unit 60 is a cell stack When the electrolytic reaction by 10 is being carried out, if the temperature inside the cell stack 10 exceeds a preset heat storage execution temperature, the heat storage mode is executed. The heat storage execution temperature is a guideline temperature at which the temperature inside the cell stack 10 can be considered to be high enough to warrant executing the heat storage mode. When executing the heat storage mode, the control unit 60 sets the first path (the path of the heat transfer medium from the first position L1 to the second position L2) as the first bypass pipe B1, and the second path (the path of the heat transfer medium from the third position L3 to the fourth position L4) as the heat transfer medium pipe HP, as shown in Figure 3. Specifically, the control unit 60 opens valve V1 and closes valve V2, and closes valve V3 and opens valve V4.
[0028] In this state, the heat transfer medium that has passed through the inside of the cell stack 10 passes through the first bypass pipe B1 between the first position L1 and the second position L2, as shown in Figure 3. Subsequently, the heat transfer medium passes through the heat transfer pipe HP between the third position L3 and the fourth position L4, as shown in Figure 3. A portion of the power supplied to the cell stack 10 to carry out the electrolytic reaction of water is converted into Joule heat, and the heat transfer medium that has passed through the inside of the cell stack 10 flows through the first bypass pipe B1 in a state heated by this Joule heat. As mentioned above, the heat storage mode is executed on the condition that the temperature inside the cell stack 10 exceeds the preset heat storage execution temperature, so the heat transfer medium flowing through the first bypass pipe B1 at this time is at a relatively high temperature. Therefore, heat is supplied from the heat transfer medium flowing through the first bypass pipe B1 to the heat storage material 54, and heat storage by the heat storage material 54 is carried out.
[0029] Furthermore, in the heat storage mode, if the temperature of the heat storage material 54 rises above the target heat storage temperature, or if the temperature of the heat transfer medium flowing through the first bypass pipe B1 falls below the specified heat storage temperature, the control unit 60 switches the first path from the first bypass pipe B1 to the heat transfer medium pipe HP and terminates the heat storage mode. The target heat storage temperature is the temperature targeted by the heat storage material 54, and is a guideline temperature at which sufficient heat storage can be considered to have occurred in the heat storage material 54. The specified heat storage temperature is a guideline temperature at which the heat transfer medium flowing through the first bypass pipe B1 is more likely to release heat from the heat storage material 54 than to store heat in the heat storage material 54. The temperature of the heat transfer medium flowing through the first bypass pipe B1 may be estimated from the temperature inside the cell stack 10, or it may be obtained from a temperature sensor that measures the temperature at the first position L1.
[0030] Figure 4 is an explanatory diagram showing the flow path during heat dissipation mode. The control unit 60 executes heat dissipation mode when the electrolytic reaction by the cell stack 10 is being performed, the temperature inside the cell stack 10 is below a preset heat dissipation execution temperature, and the temperature inside the heat accumulator 50 is above a preset heat dissipation permission temperature. The heat dissipation execution temperature is a guideline temperature at which the temperature inside the cell stack 10 can be considered low enough to warrant executing heat dissipation mode. Of course, the heat dissipation execution temperature is lower than the heat storage execution temperature mentioned above. The heat dissipation permission temperature is a guideline temperature at which the heat storage material 54 can be considered to have stored enough heat to enable heat dissipation mode. When executing heat dissipation mode, the control unit 60 sets the first path to the heat transfer medium piping HP and the second path to the second bypass piping B2, as shown in Figure 4. Specifically, the control unit 60 closes valve V1 and opens valve V2, and opens valve V3 and closes valve V4.
[0031] In this state, the heat transfer medium that has passed through the inside of the cell stack 10 passes through the heat transfer medium piping HP between the first position L1 and the second position L2, as shown in Figure 4. After that, the heat transfer medium passes through the second bypass piping B2 between the third position L3 and the fourth position L4, as shown in Figure 4. As mentioned above, the heat dissipation mode is executed with the requirement that the temperature inside the cell stack 10 be below the preset heat dissipation setting temperature, so the heat transfer medium flowing through the second bypass piping B2 is at a relatively low temperature at this time. Therefore, the heat transfer medium flowing through the second bypass piping B2 receives heat dissipated from the heat storage material 54. It is heated by being removed.
[0032] Furthermore, in the heat dissipation mode, if the temperature of the heat storage material 54 falls below the specified heat dissipation temperature, or if the temperature of the heat transfer medium flowing through the second bypass pipe B2 rises above the target heat dissipation temperature, the control unit 60 switches the second path from the second bypass pipe B2 to the heat transfer medium pipe HP and terminates the heat dissipation mode. The specified heat dissipation temperature is a guideline temperature at which the heat storage material 54 is more likely to absorb heat from the heat transfer medium than to dissipate heat from the heat transfer medium flowing through the second bypass pipe B2. The target heat dissipation temperature is the target temperature for the heat transfer medium, and is a guideline temperature at which it can be considered that sufficient heat has been dissipated to the heat transfer medium used to raise the temperature of the cell stack 10. The temperature of the heat transfer medium flowing through the second bypass pipe B2 may be estimated from the temperature inside the cell stack 10, or it may be obtained from a temperature sensor that measures the temperature at the third position L3.
[0033] As explained above, according to the water electrolysis system 1 of the first embodiment, heat exchange takes place between the heat transfer medium flowing through the heat transfer medium piping HP and the cell stack 10. A portion of the electricity supplied to the cell stack 10 to perform the electrolysis (electrolysis) of water is converted into Joule heat. If the temperature of the cell stack 10 continues to rise due to Joule heat, the electrolyte membrane used in the electrolytic reaction by the cell stack 10 is likely to deteriorate. According to the water electrolysis system 1 of the first embodiment, the cell stack 10 can be cooled by the heat transfer medium absorbing heat from the cell stack 10 when it is in such a high-temperature state. In addition, generally, when the cell stack 10 is in a low-temperature state, the reaction efficiency of the electrolytic reaction by the cell stack 10 decreases. Therefore, in cold regions, during winter, at night, etc., the reaction efficiency of the electrolytic reaction by the cell stack 10 tends to decrease. According to the water electrolysis system 1 of the first embodiment, the cell stack 10 can be warmed by supplying heat from the heat transfer medium to the cell stack 10 when it is in such a low-temperature state. Therefore, according to the water electrolysis system 1 of the first embodiment, by adjusting the temperature of the cell stack 10 to a desired temperature through heat exchange with the heat transfer medium, deterioration of the electrolyte membrane due to high temperatures and a decrease in reaction efficiency due to low temperatures can be suppressed, thereby maintaining a high reaction efficiency of the electrolytic reaction by the cell stack 10.
[0034] Furthermore, in the water electrolysis system 1 of the first embodiment, the heat transfer medium flowing through the first bypass pipe B1 and the second bypass pipe B2 can store heat in the heat storage material 54 housed in the heat storage unit 50 and release heat from the heat storage material 54 through heat exchange. Therefore, the heat transfer medium that has absorbed heat from the cell stack 10 can store heat in the heat storage material 54 through heat exchange. Consequently, since the Joule heat generated in the cell stack 10 is stored in the heat storage material 54, the cooling load for cooling the cell stack 10 can be reduced. In addition, the heat transfer medium can receive heat released from the heat storage material 54 through heat exchange, and use that heat to warm the cell stack 10 and improve the reaction efficiency of the electrolysis reaction. Therefore, according to the water electrolysis system 1 of the first embodiment, it is possible to achieve both a reduction in the cooling load for cooling the cell stack 10 and an improvement in the reaction efficiency of the electrolysis reaction by the cell stack 10. Furthermore, since the heat source for the heat stored in the heat storage material 54 is Joule heat constantly generated by the electrolytic reaction in the cell stack 10, heat can be stored in the heat storage material 54 periodically. Therefore, the reaction efficiency of the electrolytic reaction in the cell stack 10 can be maintained at a high level.
[0035] Furthermore, in the water electrolysis system 1 of the first embodiment, the bypass piping includes a first bypass piping B1 and a second bypass piping B2 provided downstream of the first bypass piping B1 with respect to the exit position EX. When the heat storage mode is executed, the first path is the first bypass piping B1. Therefore, the heat transfer medium that has absorbed heat from the cell stack 10 can flow through the first bypass piping B1 and store heat in the heat storage material through heat exchange. The first bypass piping B1 is provided upstream of the second bypass piping B2 with respect to the exit position EX (i.e., the first bypass piping B1 is closer to the exit position EX than the second bypass piping B2). Therefore, the heat absorbed from the cell stack 10 can be stored in the heat storage material 54 while suppressing the heat loss that increases with the flow distance from the exit position EX to the heat storage unit 50. Furthermore, according to the water electrolysis system 1 of the first embodiment, when the heat dissipation mode is performed, the second path is the second bypass pipe B2. As a result, the heat transfer medium flows through the second bypass pipe B2 and receives heat dissipated from the heat storage material 54 through heat exchange, and the cell stack 10 is warmed by this heat, thereby increasing the reaction efficiency of the electrolysis reaction. The second bypass pipe B2 is located downstream of the first bypass pipe B1 with respect to the exit position EX (i.e., the second bypass pipe B2 is closer to the entry position EN than the first bypass pipe B1), so the heat received from the heat storage material 54 can be supplied to the cell stack 10 while suppressing the heat loss that increases with the flow distance from the heat storage unit 50 to the entry position EN.
[0036] Furthermore, in the water electrolysis system 1 of the first embodiment, when the temperature of the heat storage material 54 rises above the target heat storage temperature, or when the temperature of the heat transfer medium flowing through the heat transfer medium pipe HP falls below the specified heat storage temperature, the first path is switched from the first bypass pipe B1 to the heat transfer medium pipe HP. If the heat storage mode is continued after the heat storage material 54 rises above the target heat storage temperature, the heat storage material 54 is likely to deteriorate. Also, if the Joule heat generated in the cell stack 10 decreases and the temperature of the heat transfer medium flowing through the first bypass pipe B1 falls below the specified heat storage temperature, such a heat transfer medium is more likely to release heat from the heat storage material 54 than to store heat in the heat storage material 54. Therefore, the water electrolysis system 1 of the first embodiment can reduce the possibility of the heat storage material 54 deteriorating and the possibility of heat being released from the heat storage material 54 even when in heat storage mode. Furthermore, if the pressure loss is greater when the first bypass pipe B1 is used in the first path than when the heat transfer medium pipe HP is used, such pressure loss can be reduced, thereby reducing the amount of energy consumed to circulate the heat transfer medium. Specifically, the amount of energy referred to here is the amount of power consumed by the circulation pump PM2.
[0037] Furthermore, in the water electrolysis system 1 of the first embodiment, when the temperature of the heat storage material 54 falls below the specified heat dissipation temperature, or when the temperature of the heat transfer medium flowing through the heat transfer medium pipe HP rises above the target heat dissipation temperature, the second path is switched from the second bypass pipe B2 to the heat transfer medium pipe HP. When the temperature falls below the specified heat dissipation temperature, the heat storage material 54 is more likely to absorb heat from the heat transfer medium flowing through the second bypass pipe B2. Also, if the heat dissipation mode is continued even after the temperature of the heat transfer medium flowing through the second bypass pipe B2 rises above the target heat dissipation temperature, the possibility of the heat storage material 54 absorbing heat from the heat transfer medium flowing through the second bypass pipe B2 increases, similar to when the heat storage material 54 falls below the specified heat dissipation temperature. Therefore, according to the water electrolysis system 1 of the first embodiment, the possibility of the heat storage material 54 absorbing heat from the heat transfer medium flowing through the second bypass pipe B2 during the heat dissipation mode can be reduced. Furthermore, in the second path, if the pressure loss is greater when passing through the second bypass pipe B2 than when passing through the heat transfer medium pipe HP, such pressure loss can be reduced, thereby reducing the amount of energy consumed to circulate the heat transfer medium. Specifically, the amount of energy referred to here is the amount of power consumed by the circulation pump PM2.
[0038] <Second Embodiment> Figure 5 is an explanatory diagram illustrating the configuration of the water electrolysis system 1a of the second embodiment. The configuration of the water electrolysis system 1a of the second embodiment is the same as that of the water electrolysis system 1 of the first embodiment (Figure 1), except that it does not have the second bypass piping B2.
[0039] In the water electrolysis system 1a, while the electrolysis reaction by the cell stack 10 is being carried out, the control unit 60 executes either a heat storage mode, in which heat is stored in the heat accumulator 50, or a heat release mode, in which heat is released to the heat accumulator 50, based on information obtained from a temperature sensor (not shown) provided in the water electrolysis system 1. In this configuration, the control unit 60 designates the first path (the path of the heat transfer medium from the first position L1 to the second position L2) as the first bypass pipe B1. The heat storage mode is performed with the requirement that the temperature inside the cell stack 10 is above a preset heat storage execution temperature, similar to the first embodiment. Therefore, the heat transfer medium circulating in the first bypass pipe B1 is at a relatively high temperature during the heat storage mode. Consequently, heat is supplied from the heat transfer medium circulating in the first bypass pipe B1 to the heat storage material 54, thereby enabling heat storage by the heat storage material 54. The heat dissipation mode is also performed with the requirement that the temperature inside the cell stack 10 is below a preset heat dissipation execution temperature, similar to the first embodiment. Therefore, the heat transfer medium circulating in the first bypass pipe B1 is at a relatively low temperature during the heat dissipation mode. Consequently, the heat transfer medium circulating in the first bypass pipe B1 is heated by receiving heat dissipated from the heat storage material 54.
[0040] According to the water electrolysis system 1a of the second embodiment described above, since the only bypass piping branched from the heat transfer medium piping HP is the first bypass piping B1, the configuration of the water electrolysis system 1a is simplified compared to the first embodiment, and, as in the first embodiment, it is possible to achieve both a reduction in the cooling load for cooling the cell stack 10 and an improvement in the reaction efficiency of the electrolytic reaction by the cell stack 10.
[0041] <Modified form of this embodiment> The present invention is not limited to the embodiments described above, and can be implemented in various forms without departing from its spirit, for example, the following modifications are also possible.
[0042] [Example 1] In the above embodiment, valves V1 and V2 corresponded to a first path switching section that switches the first path between the heat transfer medium pipe HP and the first bypass pipe B1, but the embodiment is not limited to this. For example, instead of valves V1 and V2, a three-way valve provided at the first position L1 may correspond to the first path switching section. Similarly, instead of valves V3 and V4, a three-way valve provided at the third position L3 may correspond to the second path switching section.
[0043] [Differentiation 2] In the above embodiment, the first path was switched from the first bypass pipe B1 to the heat transfer medium pipe HP based on the target heat storage temperature or the specified heat storage temperature during the heat storage mode, but it is not limited to this. For example, the first path may be switched from the first bypass pipe B1 to the heat transfer medium pipe HP after a certain period of time has elapsed since the heat storage mode was executed. Similarly, the second path may be switched from the second bypass pipe B2 to the heat transfer medium pipe HP after a certain period of time has elapsed since the heat dissipation mode was executed.
[0044] [Difference 3] In the above embodiment, the requirements for executing the heat dissipation mode were that the temperature inside the cell stack 10 was below a preset heat dissipation execution temperature and the temperature inside the heat accumulator 50 was above a preset heat dissipation permission temperature, but this is not limited to this. For example, the requirements for executing the heat dissipation mode may be that the temperature of at least one component constituting the water electrolysis system is below a preset lower limit temperature for that component and the temperature inside the heat accumulator 50 is above a preset heat dissipation permission temperature. Furthermore, the requirement that the temperature inside the cell stack 10 is below a preset heat dissipation execution temperature may be added to this requirement.
[0045] [Differentiation Example 4] In the above embodiment, the heat storage material 54 was water, but it is not limited to this. For example, the heat storage material 54 may be a latent heat storage material or a chemical heat storage material. In such a configuration as well, the change in state of the latent heat storage material or chemical heat storage material can affect the heat transfer medium flowing through the first bypass pipe B1. The system can perform heat storage and heat dissipation to a heat transfer medium flowing through the second bypass pipe B2. Examples of latent heat storage materials include molten salts consisting of a mixture of sodium nitrate, sodium nitrite, and potassium nitrate, paraffins (saturated hydrocarbon compounds), and organic compounds such as fatty acids (including fatty acid esters). Examples of chemical heat storage materials include magnesium hydroxide, calcium hydroxide, calcium chloride, and calcium sulfate.
[0046] [Difference 5] Furthermore, the heat storage material 54 may be an adsorbent capable of heat dissipation and heat storage through the adsorption and desorption of substances. In this configuration as well, heat storage from the heat transfer medium flowing through the first bypass pipe B1 and heat dissipation to the heat transfer medium flowing through the second bypass pipe B2 can be performed by the adsorption and desorption of substances by the adsorbent. Examples of adsorbents include activated carbon. In this configuration, the heat transfer medium flowing through the first bypass pipe B1 or the second bypass pipe B2 exchanges heat with the heat storage material 54 by passing through the adsorbent, which is the heat storage material 54.
[0047] [Modification 6] The configuration of the water electrolysis system 1a in the second embodiment was the same as the configuration of the water electrolysis system 1 in the first embodiment, but it is not limited to this. For example, the configuration of the water electrolysis system in other embodiments may be the same as the configuration of the water electrolysis system 1 in the first embodiment, but with the first bypass pipe B1 removed. In such a configuration, whether the heat storage mode or the heat dissipation mode is performed, the control unit 60 uses the second bypass pipe B2 as the second path (the path of the heat transfer medium from the third position L3 to the fourth position L4).
[0048] The embodiments of this specification have been described above based on the embodiments and modifications described above. The embodiments described above are for the purpose of facilitating understanding of this specification and do not limit it. This specification may be modified and improved without departing from its spirit and the scope of the claims, and equivalents thereof are included in this specification. Furthermore, any technical features that are not described as essential in this specification may be deleted as appropriate. [Explanation of symbols]
[0049] 1,1a...Water electrolysis system 10...Cell stack 12…DC power supply 14…Converter 20…Hydrogen gas-liquid separator 22... Condenser 30…Oxygen-liquid separator 32... Condenser 44... Tank 46...Heat exchanger 50... Heat storage device 52... Cabinet 54… Heat storage material 60... Control Unit B1...First bypass piping B2...Second bypass piping EN…Entry position EX…Exit position HP…heat medium piping L1…1st position L2…2nd position L3…3rd position L4…4th position P1...First mixture delivery pipe P2…Second mixture delivery pipe P3... Oxygen delivery piping P4…Water supply piping PM1... Circulation pump PM2... Circulation pump V1~V4...Valve
Claims
1. A water electrolysis system, A water electrolysis unit that generates oxygen and hydrogen by electrolysis of water using an electrolyte membrane, A heat transfer medium pipe, which partially passes through the interior of the water electrolysis unit and forms a heat transfer medium channel for circulating the heat transfer medium that exchanges heat with the water electrolysis unit, A bypass pipe branched from the aforementioned heat transfer pipe, The system includes a heat storage unit that houses a portion of the bypass piping and contains a heat storage material capable of storing and releasing heat through heat exchange with the heat transfer medium flowing through the bypass piping, The aforementioned bypass piping is A first bypass pipe branches off from a first position in the heat transfer medium piping and merges with the heat transfer medium piping at a second position downstream of the first position, with reference to the exit position where the heat transfer medium piping exits from inside the water electrolysis unit. The heat transfer piping includes a second bypass pipe that branches off from a third position downstream of the second position with respect to the exit position, and merges with the heat transfer piping at a fourth position downstream of the third position, The heat storage unit houses a portion of the first bypass piping and the second bypass piping. The heat storage material exchanges heat with the heat transfer medium flowing through the first bypass pipe and the second bypass pipe. Furthermore, a first path switching unit switches the first path, which is the path of the heat transfer medium from the first position to the second position, between the heat transfer medium piping and the first bypass piping. A second path switching unit switches the second path, which is the path of the heat transfer medium from the third position to the fourth position, between the heat transfer medium piping and the second bypass piping, The system comprises a control unit for controlling the water electrolysis system, The control unit, When performing the heat storage mode in which heat is stored in the heat storage device, the first path is the first bypass piping. A water electrolysis system in which, when performing a heat dissipation mode in which heat is dissipated to the heat storage unit, the second path is the second bypass pipe.
2. A water electrolysis system according to claim 1, The control unit, in the heat storage mode, switches the first path from the first bypass pipe to the heat transfer pipe when the temperature of the heat storage material reaches or exceeds the target heat storage temperature, or when the temperature of the heat transfer medium flowing through the heat transfer pipe falls below the specified heat storage temperature, in a water electrolysis system.
3. A water electrolysis system according to claim 1 or claim 2, The control unit, in the heat dissipation mode, switches the second path from the second bypass pipe to the heat transfer pipe when the temperature of the heat storage material falls below the specified heat dissipation temperature, or when the temperature of the heat transfer medium flowing through the heat transfer pipe rises to or exceeds the target heat dissipation temperature, in a water electrolysis system.
4. A water electrolysis system according to any one of claims 1 to 3, The aforementioned heat storage material is a latent heat storage material or a chemical heat storage material, in a water electrolysis system.
5. A water electrolysis system according to any one of claims 1 to 3, The heat storage material is an adsorbent capable of heat dissipation and heat storage through the adsorption and desorption of substances, in a water electrolysis system.