Power generation system

Abstract

To improve power generation efficiency.SOLUTION: A power generation system 100 includes: a fuel cell 1 that generates electricity from hydrogen and oxygen; a combustor 2 that combusts unreacted hydrogen and oxygen supplied from the fuel cell 1 to generate water vapor therein; and a steam turbine 3 that operates using the water vapor supplied from the combustor 2 and drives a generator 4.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The technology disclosed herein relates to a power generation system. [Background technology]

[0002] Conventionally, power generation systems including a fuel cell and a steam turbine have been known. For example, in the power generation system disclosed in Patent Document 1, a portion of the steam generated in the fuel cell is supplied to the steam turbine, and the operation of the steam turbine drives a generator to generate electricity. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] WO2013 / 005699 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the power generation system described above, there is room for improvement in terms of power generation efficiency.

[0005] The technology disclosed herein has been made in view of the above points, and its purpose is to improve power generation efficiency. [Means for solving the problem]

[0006] The power generation system disclosed herein includes a fuel cell that generates electricity from hydrogen and oxygen, a combustor that burns unreacted hydrogen and oxygen supplied from the fuel cell to generate steam therein, and a steam engine that operates using the steam supplied from the combustor to drive a generator. [Effects of the Invention]

[0007] According to the power generation system, power generation efficiency can be improved. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram showing a power generation system according to an embodiment. [Figure 2] FIG. 2 is a block diagram showing the hardware configuration of the control device. [Figure 3] FIG. 3 is a functional block diagram showing the configuration of a control system of a processor in the control device. [Figure 4] FIG. 4 is a schematic diagram showing the line flow in the first operating mode of the power generation system. [Figure 5] FIG. 5 is a schematic diagram showing the line flow in the second operation mode of the power generation system. [Figure 6] FIG. 6 is a schematic diagram showing a power generation system according to the first modification. [Figure 7] FIG. 7 is a schematic diagram showing a power generation system according to the second modification. [Figure 8] FIG. 8 is a schematic diagram showing a power generation system according to the third modification. [Figure 9] FIG. 9 is a schematic diagram showing a power generation system according to the fourth modification. DETAILED DESCRIPTION OF THE INVENTION

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Exemplary embodiments will now be described in detail with reference to the accompanying drawings. Figure 1 is a schematic diagram showing a power generation system 100 according to an embodiment.

[0010] The power generation system 100 includes a fuel cell 1 that generates electricity from hydrogen and oxygen, a combustor 2 that generates steam internally by burning unreacted hydrogen and oxygen supplied from the fuel cell 1, and a steam turbine 3 that operates using the steam supplied from the combustor 2 to drive a generator 4. The steam turbine 3 is an example of a steam engine of the present disclosure. The power generation system 100 generates electricity using the fuel cell 1, and also generates electricity using the steam produced by the combustor 2 and the steam turbine 3 and generator 4.

[0011] The power generation system 100 may further include a cooler 5 connected between the combustor 2 and the steam turbine 3. The cooler 5 injects water into the steam supplied from the combustor 2 to cool the steam. The steam turbine 3 operates using the steam supplied from the combustor 2 and cooled by the cooler 5.

[0012] The power generation system 100 may further include a condenser 6 and a water electrolysis device 7. The condenser 6 changes the state of steam discharged from the steam turbine 3 to water. The water electrolysis device 7 electrolyzes water supplied from the condenser 6 to produce hydrogen and oxygen. The fuel cell 1 generates electricity from the hydrogen and oxygen produced by the water electrolysis device 7.

[0013] The power generation system 100 may further include a hydrogen storage tank 8 and a hydrogen heat accumulator 10. The hydrogen storage tank 8 stores hydrogen. The hydrogen heat accumulator 10 is connected between the hydrogen storage tank 8 and the water electrolysis device 7, and between the hydrogen storage tank 8 and the fuel cell 1. The hydrogen heat accumulator 10 absorbs heat from and stores heat in the hydrogen that has been produced by the water electrolysis device 7 but before it is stored in the hydrogen storage tank 8, and also releases heat to and heat the hydrogen that has been released from the hydrogen storage tank 8 but before it is supplied to the fuel cell 1.

[0014] The power generation system 100 may further include an oxygen storage tank 9 and an oxygen heat accumulator 11. The oxygen storage tank 9 stores oxygen. The oxygen heat accumulator 11 is connected between the oxygen storage tank 9 and the water electrolysis device 7, and between the oxygen storage tank 9 and the fuel cell 1. The oxygen heat accumulator 11 absorbs heat from and stores heat in the oxygen that has been produced by the water electrolysis device 7 but not yet stored in the oxygen storage tank 9, and also releases heat to and heat the oxygen that has been released from the oxygen storage tank 9 but not yet supplied to the fuel cell 1.

[0015] The power generation system 100 may further include a control device 20. The control device 20 controls the entire power generation system 100. The control device 20 switches between the generation and storage of hydrogen and oxygen by the water electrolysis device 7, the hydrogen storage tank 8, and the oxygen storage tank 9, and the power generation by the fuel cell 1 and the steam turbine 3. Specifically, in the generation and storage of hydrogen and oxygen, the control device 20 operates the water electrolysis device 7 to generate hydrogen and oxygen, stores the hydrogen in the hydrogen storage tank 8, and stores the oxygen in the oxygen storage tank 9. On the other hand, in the power generation, the control device 20 causes the fuel cell 1 to generate power using the stored hydrogen and oxygen, and also causes the steam turbine 3 and the generator 4 to generate power using steam generated by burning unreacted hydrogen and oxygen from the fuel cell 1 in the combustor 2.

[0016] The hydrogen storage tank 8 is connected to a hydrogen heat accumulator 10 via a first line L1. The hydrogen heat accumulator 10 is connected to a hydrogen pressure regulator 12 via a second line L2. The hydrogen pressure regulator 12 is connected to the fuel cell 1 via a third line L3. The hydrogen pressure regulator 12 is connected to the water electrolysis device 7 via a fourth line L4. The first to fourth lines L1 to L4 are hydrogen flow paths.

[0017] In the first line L1, hydrogen flows in a direction alternately from the hydrogen storage tank 8 toward the hydrogen heat accumulator 10 and from the hydrogen heat accumulator 10 toward the hydrogen storage tank 8. In the second line L2, hydrogen flows in a direction alternately from the hydrogen heat accumulator 10 toward the hydrogen pressure regulator 12 and from the hydrogen pressure regulator 12 toward the hydrogen heat accumulator 10. In the third line L3, hydrogen flows in a direction from the hydrogen pressure regulator 12 toward the fuel cell 1. In the fourth line L4, hydrogen flows in a direction from the water electrolysis device 7 toward the hydrogen pressure regulator 12.

[0018] The hydrogen storage tank 8 stores hydrogen in a compressed state. That is, the hydrogen storage tank 8 stores hydrogen at a relatively high pressure. For example, the pressure of hydrogen stored in the hydrogen storage tank 8 is 1 MPa or higher. The hydrogen storage tank 8 can switch between taking in hydrogen from the outside and releasing the stored hydrogen. For example, the hydrogen storage tank 8 is equipped with a valve that switches between taking in and releasing hydrogen. The hydrogen storage tank 8 takes in hydrogen from the water electrolysis device 7 via the fourth line L4, the second line L2, and the first line L1, or releases hydrogen to the fuel cell 1 via the first line L1, the second line L2, and the third line L3.

[0019] The hydrogen heat accumulator 10 can switch between absorbing heat (heat storage) from hydrogen supplied from the water electrolysis device 7 via the hydrogen pressure regulator 12, and releasing heat (heating) to hydrogen supplied from the hydrogen storage tank 8. Specifically, in the heat storage mode, the hydrogen heat accumulator 10 absorbs heat from hydrogen supplied from the water electrolysis device 7 via the fourth line L4 and the second line L2, and supplies the hydrogen from which heat has been absorbed to the hydrogen storage tank 8 via the first line L1. In the heating mode, the hydrogen heat accumulator 10 releases the heat absorbed by hydrogen supplied from the hydrogen storage tank 8 via the first line L1, and supplies the hydrogen from which heat has been released to the fuel cell 1 via the second line L2 and the third line L3.

[0020] The hydrogen heat accumulator 10 is, for example, a regenerative heat exchanger, and includes a solid heat accumulator (matrix). The solid heat accumulator absorbs heat when it comes into contact with high-temperature hydrogen supplied from the water electrolysis device 7 via the hydrogen pressure regulator 12, and releases the absorbed heat when it comes into contact with low-temperature hydrogen supplied from the hydrogen storage tank 8.

[0021] The hydrogen pressure regulator 12 is a device that functions as both a compressor and an expander. The hydrogen pressure regulator 12 can switch between pressurizing operation of hydrogen supplied from the water electrolysis device 7 and depressurizing operation of hydrogen supplied from the hydrogen storage tank 8. Specifically, during hydrogen pressurizing operation, the hydrogen pressure regulator 12 compresses hydrogen supplied from the water electrolysis device 7 via the fourth line L4 and supplies the compressed hydrogen to the hydrogen storage tank 8 via the second line L2 and the first line L1. The temperature of the hydrogen supplied from the water electrolysis device 7 increases as the hydrogen pressure regulator 12 compresses the hydrogen, but decreases as the hydrogen passes through the hydrogen heat accumulator 10. In other words, the hydrogen heat accumulator 10 absorbs and stores heat from the hydrogen that has been compressed and heated by the hydrogen pressure regulator 12. During hydrogen depressurizing operation, the hydrogen pressure regulator 12 expands hydrogen supplied from the hydrogen storage tank 8 via the first line L1 and the second line L2 and supplies the expanded hydrogen to the fuel cell 1 via the third line L3.

[0022] The oxygen storage tank 9 is connected to the oxygen heat accumulator 11 via a fifth line L5. The oxygen heat accumulator 11 is connected to the oxygen pressure regulator 13 via a sixth line L6. The oxygen pressure regulator 13 is connected to the fuel cell 1 via a seventh line L7. The oxygen pressure regulator 13 is connected to the water electrolysis device 7 via an eighth line L8. The fifth to eighth lines L5 to L8 are oxygen flow paths.

[0023] The fifth line L5 switches between the direction from the oxygen storage tank 9 to the oxygen heat accumulator 11 and the direction from the oxygen heat accumulator 11 to the oxygen storage tank 9. The sixth line L6 switches between the direction from the oxygen heat accumulator 11 to the oxygen pressure regulator 13 and the direction from the oxygen pressure regulator 13 to the oxygen heat accumulator 11. The seventh line L7 switches between the direction from the oxygen pressure regulator 13 to the fuel cell 1. The eighth line L8 switches between the direction from the water electrolysis device 7 to the oxygen pressure regulator 13.

[0024] The oxygen storage tank 9 stores oxygen in a compressed state. That is, the oxygen storage tank 9 stores oxygen at a relatively high pressure. For example, the pressure of the oxygen stored in the oxygen storage tank 9 is 1 MPa or higher. The oxygen storage tank 9 can switch between taking in oxygen from the outside and releasing the stored oxygen. For example, the oxygen storage tank 9 is equipped with a valve that switches between taking in and releasing oxygen. The oxygen storage tank 9 takes in oxygen from the water electrolysis device 7 via the eighth line L8, the sixth line L6, and the fifth line L5, or releases oxygen to the fuel cell 1 via the fifth line L5, the sixth line L6, and the seventh line L7.

[0025] The oxygen heat accumulator 11 can switch between absorbing heat from oxygen supplied from the water electrolysis device 7 via the oxygen pressure regulator 13 (heating) and releasing heat to oxygen supplied from the oxygen storage tank 9. Specifically, in the heat storage mode, the oxygen heat accumulator 11 absorbs heat from oxygen supplied from the water electrolysis device 7 via the eighth line L8 and the sixth line L6, and supplies the oxygen with absorbed heat to the oxygen storage tank 9 via the fifth line L5. In the heating mode, the oxygen heat accumulator 11 releases the heat absorbed by oxygen supplied from the oxygen storage tank 9 via the fifth line L5, and supplies the oxygen with released heat to the fuel cell 1 via the sixth line L6 and the seventh line L7.

[0026] The oxygen heat accumulator 11 is, for example, a regenerative heat exchanger, and includes a solid heat accumulator (matrix). The solid heat accumulator absorbs heat upon contact with high-temperature oxygen supplied from the water electrolysis device 7 via the oxygen pressure regulator 13, and releases the absorbed heat upon contact with low-temperature oxygen supplied from the oxygen storage tank 9.

[0027] The oxygen pressure regulator 13 is a device that functions as both a compressor and an expander. The oxygen pressure regulator 13 can switch between a pressurized operation for oxygen supplied from the water electrolysis device 7 and a reduced-pressure operation for oxygen supplied from the oxygen storage tank 9. Specifically, in the pressurized oxygen operation, the oxygen pressure regulator 13 compresses the oxygen supplied from the water electrolysis device 7 via the eighth line L8 and supplies the compressed oxygen to the oxygen storage tank 9 via the sixth line L6 and the fifth line L5. The temperature of the oxygen supplied from the water electrolysis device 7 increases as the oxygen pressure regulator 13 compresses the oxygen, but decreases as the oxygen passes through the oxygen heat accumulator 11. In other words, the oxygen heat accumulator 11 absorbs and stores heat from hydrogen that is compressed and heated by the oxygen pressure regulator 13. In the reduced-pressure oxygen operation, the oxygen pressure regulator 13 expands the oxygen supplied from the oxygen storage tank 9 via the fifth line L5 and the sixth line L6 and supplies the expanded oxygen to the fuel cell 1 via the seventh line L7.

[0028] The fuel cell 1 generates electricity from hydrogen and oxygen. Specifically, the fuel cell 1 chemically reacts hydrogen supplied from the hydrogen pressure regulator 12 via the third line L3 with oxygen supplied from the oxygen pressure regulator 13 via the seventh line L7. As a result, the fuel cell 1 generates electricity and water vapor. The equivalence ratio of the hydrogen and oxygen supplied to the fuel cell 1 is 1. The pressure of the hydrogen and oxygen supplied to the fuel cell 1 is, for example, 1.1 atm, and the temperature of the hydrogen and oxygen is, for example, 700°C or higher and 800°C or lower.

[0029] The fuel cell 1 is, for example, a solid oxide fuel cell (SOFC). Note that the fuel cell 1 may also be, for example, a polymer electrolyte fuel cell (PEFC), a phosphoric acid fuel cell (PAFC), or a molten carbonate fuel cell (MCFC).

[0030] The fuel cell 1 is connected to the combustor 2 via a ninth line L9 and a tenth line L10. The ninth line L9 is a flow path for unreacted hydrogen, but the generated water vapor also flows through this flow path. The tenth line L10 is a flow path for unreacted oxygen. Unreacted hydrogen is hydrogen that has been supplied to the fuel cell 1 but not reacted by the fuel cell 1. Unreacted oxygen is oxygen that has been supplied to the fuel cell 1 but not reacted by the fuel cell 1. Water vapor is generated by the fuel cell 1 and is extracted together with the unreacted hydrogen.

[0031] The fuel cell 1 supplies unreacted hydrogen to the combustor 2 via a ninth line L9. At this time, water vapor is also supplied to the combustor 2 via the ninth line L9. The fuel cell 1 supplies unreacted oxygen to the combustor 2 via a tenth line L10. The pressure of the hydrogen and oxygen supplied to the combustor 2 is, for example, 1.1 atm, and the temperature of the hydrogen and oxygen is, for example, 700°C or higher and 800°C or lower.

[0032] The combustor 2 burns unreacted hydrogen and oxygen supplied from the fuel cell 1 to generate steam therein. In other words, the combustor 2 generates steam from the combusted hydrogen and oxygen therein, and is therefore different from a boiler. A boiler does not burn steam itself, but rather burns fuel and uses the burned fuel as a heat source to provide energy to water, converting it into steam. Unlike a boiler, the combustor 2 heats the steam by burning hydrogen and oxygen within the steam. Therefore, the combustor 2 and the steam turbine 3 are collectively referred to as an internal combustion steam turbine (internal combustion steam turbine), and are also referred to as an Oxy-Fuel, a type of internal combustion engine. The combustor 2 combusts unreacted hydrogen supplied from the fuel cell 1 via the ninth line L9 and unreacted oxygen supplied from the fuel cell 1 via the tenth line L10. This allows the combustor 2 to generate high-temperature steam. The pressure of the steam generated by the combustor 2 is, for example, 1 atm, and the temperature of the steam is, for example, 2000°C. The combustor 2 is connected to the cooler 5 via an eleventh line L11. The combustor 2 supplies steam to the cooler 5 via the eleventh line L11.

[0033] The cooler 5 injects water into the steam supplied from the combustor 2 via the eleventh line L11 to cool the steam. The cooler 5, for example, sprays water onto the steam. Specifically, the cooler 5 is connected to a water tank 15 via a twelfth line L12. Water at room temperature and normal pressure is stored in the water tank 15. A pump 16a is disposed on the twelfth line L12, and the pump 16a supplies water from the water tank 15 to the cooler 5 via the twelfth line L12.

[0034] The cooler 5 is connected to the steam turbine 3 via a thirteenth line L13. The cooler 5 supplies cooled steam to the steam turbine 3 via the thirteenth line L13. The pressure of the steam supplied to the steam turbine 3 is, for example, 1 atm, and the temperature of the steam is, for example, 1000°C.

[0035] The steam turbine 3 operates using steam supplied from the cooler 5 via a thirteenth line L13. The steam turbine 3 has a turbine that is rotated by the steam from the cooler 5. The steam turbine 3 outputs rotational force as motive power. The generator 4 is driven by the steam turbine 3 and generates electricity. In other words, the generator 4 converts the rotational force of the steam turbine 3 into electric power.

[0036] The steam turbine 3 is connected to the condenser 6 via a fourteenth line L14. Steam discharged from the steam turbine 3 is supplied to the condenser 6 via the fourteenth line L14. The pressure of the steam supplied to the condenser 6 is, for example, 0.05 atm, and the temperature of the steam is, for example, 580°C.

[0037] The condenser 6 changes the state of steam supplied from the steam turbine 3 via the fourteenth line L14 to water. Specifically, the condenser 6 has a casing 60 and a refrigerant circuit 61. The refrigerant circuit 61 is a closed circuit formed by piping connections between a cooling tower 62 and a pump 63. The refrigerant circuit 61 circulates a refrigerant. The refrigerant is, for example, water. A portion of the refrigerant circuit 61 is located inside the casing 60.

[0038] Steam from the steam turbine 3 is supplied into the casing 60. A refrigerant cooled by a cooling tower 62 is sent to a part of the refrigerant circuit 61 by a pump 63 and comes into thermal contact with the steam inside the casing 60. As a result, the water vapor is cooled by the refrigerant and returns to water. The pressure of the water is, for example, 0.05 atm, and the temperature of the water is, for example, 32°C.

[0039] The condenser 6 is connected to the water tank 15 via a 15th line L15. Water discharged from the condenser 6 is supplied to the water tank 15 via the 15th line L15. A pump 16b is disposed in the 15th line L15, and the pump 16b supplies water from the condenser 6 to the water tank 15 via the 15th line L15.

[0040] The water tank 15 is connected to the water electrolysis device 7 via a sixteenth line L16. A pump 16c is disposed in the sixteenth line L16, and the pump 16c supplies water from the water tank 15 to the water electrolysis device 7 via the sixteenth line L16.

[0041] The water electrolysis device 7 electrolyzes water supplied from the water tank 15 via the sixteenth line L16 to generate hydrogen and oxygen. For example, the water electrolysis device 7 may be an alkaline water electrolysis device, a polymer electrolyte membrane (PEM) water electrolysis device, or an anion exchange membrane (AEM) water electrolysis device. The water electrolysis device 7 is powered by electricity. Water is supplied to the water electrolysis device 7. The water electrolysis device 7 electrolyzes the water in the electrolysis cell by applying a voltage between a pair of electrodes provided in the electrolysis cell. The water electrolysis device 7 generates hydrogen and oxygen. The hydrogen generated by the water electrolysis device 7 is supplied to the hydrogen storage tank 8 via the fourth line L4, the second line L2, and the first line L1. The oxygen generated by the water electrolysis device 7 is supplied to the oxygen storage tank 9 via the eighth line L8, the sixth line L6, and the fifth line L5.

[0042] The control device 20 operates the water electrolysis device 7 to store hydrogen in the hydrogen storage tank 8 and store oxygen in the oxygen storage tank 9. This operation mode is referred to as the "first operation mode." Meanwhile, the control device 20 supplies hydrogen from the hydrogen storage tank 8 and oxygen from the oxygen storage tank 9 to the fuel cell 1 to generate electricity. The control device 20 also supplies steam from the combustor 2 to the steam turbine 3 to operate the steam turbine 3. The steam turbine 3 drives the generator 4 to generate electricity. This operation mode is referred to as the "second operation mode." The control device 20 switches between the first operation mode and the second operation mode. For example, the control device 20 switches between the first operation mode and the second operation mode depending on the supply status of power from the power supply source.

[0043] Here, the power supply source is at least one of an electric power company and a renewable energy power generation facility. The renewable energy power generation facility generates electricity using renewable energy such as solar, wind, or geothermal energy. The power generation system 100 supplies power from the power supply source to devices included in the power generation system 100, such as the water electrolysis device 7. When the fuel cell 1 and the generator 4 generate power, the power generation system 100 supplies the generated power to the electric power company.

[0044] In this way, the power generation system 100 supplies power from the power company (i.e., purchases power) and supplies power to the power company (i.e., sells power). Note that when the fuel cell 1 and the generator 4 generate power, the power generation system 100 may also supply the generated power to a predetermined device of the power generation system 100.

[0045] 2 is a block diagram showing the hardware configuration of the control device 20. The control device 20 has a processor 21, a storage device 22, and a memory 23.

[0046] The processor 21 controls the entire control device 20. The processor 21 performs various types of arithmetic processing. For example, the processor 21 is a processor such as a CPU (Central Processing Unit). The processor 21 may be an MCU (Micro Controller Unit), an MPU (Micro Processor Unit), an FPGA (Field Programmable Gate Array), a PLC (Programmable Logic Controller), a system LSI, or the like.

[0047] The storage device 22 stores programs and various data to be executed by the processor 21. For example, the storage device 22 stores a control program. The storage device 22 is a non-volatile memory, a hard disk drive (HDD), a solid state drive (SSD), or the like. The memory 23 temporarily stores data and the like. For example, the memory 23 is a volatile memory.

[0048] 3 is a functional block diagram showing the configuration of the control system of the processor 21 of the control device 20. The processor 21 realizes various functions by reading out a control program from the storage device 22 into memory and expanding it. Specifically, the processor 21 functions as a determiner 24 that determines whether to switch between the first operation mode and the second operation mode, and a switcher 25 that switches between the first operation mode and the second operation mode.

[0049] The determiner 24 determines whether a switching condition is met. The switching condition is a condition for switching between the first operation mode and the second operation mode. Here, the switching condition is a condition for switching from the first operation mode to the second operation mode. However, the switching condition may also be a condition for switching from the second operation mode to the first operation mode.

[0050] For example, the switching condition may be related to the supply status of power from the power supply source. Specifically, the switching condition may be set based on the electricity rate of a power company. The switching condition may be that the electricity rate is equal to or greater than a predetermined first base rate. For example, a power company may adopt a pricing system in which electricity rates fluctuate. For example, electricity rates may fluctuate in conjunction with the market price at the Japan Electric Power Exchange. The electricity rate reflects the supply status of power from the power supply source. When the power supply is relatively high, the electricity rate is low, and when the power supply is relatively low, the electricity rate is high. The determiner 24 determines whether to switch between the first operation mode and the second operation mode in accordance with the fluctuating electricity rate. Note that the determiner 24 may determine that the condition for switching to the first operation mode is met when the electricity rate is equal to or less than a predetermined second base rate, and may determine that the condition for switching to the second operation mode is met when the electricity rate is equal to or greater than a predetermined third base rate that is higher than the second base rate.

[0051] Alternatively, the switching condition may be set based on the amount of power generated by the renewable energy power generation facility. The switching condition may be that the amount of power generated is equal to or less than a predetermined first reference amount of power. For example, the amount of power generated by solar power generation is relatively large during the daytime in good weather. On the other hand, the amount of power generated by solar power generation is relatively small during bad weather or at night. In other words, the amount of power generated by the renewable energy power generation facility reflects the power supply status of the power supply source. The determiner 24 determines whether to switch between the first operation mode and the second operation mode depending on the amount of power generated.

[0052] The switch 25 switches between the first and second operating modes depending on the determination result of the switching condition. When the condition for switching to the second operating mode is not met, the switch 25 executes the first operating mode. When the condition for switching to the second operating mode is met, the switch 25 executes the second operating mode. In other words, when the condition for switching to the second mode transitions from not met to met, the switch 25 switches from the first operating mode to the second operating mode. When the condition for switching to the second mode transitions from met to not met, the switch 25 switches from the second operating mode to the first operating mode.

[0053] 4 is a schematic diagram showing the line flow in the first operation mode of the power generation system 100. In the diagram, lines through which hydrogen, oxygen, or water flows are indicated by thick arrows. In the first operation mode, the switch 25 operates the water electrolysis device 7 to store hydrogen in the hydrogen storage tank 8 and store oxygen in the oxygen storage tank 9.

[0054] Specifically, the switch 25 operates the pump 16c, which causes the pump 16c to supply water from the water tank 15 to the water electrolysis device 7 via the sixteenth line L16. The switch 25 operates the water electrolysis device 7, which then electrolyzes the supplied water to generate hydrogen and oxygen, supplies the generated hydrogen to the hydrogen pressure regulator 12 via the fourth line L4, and supplies the generated oxygen to the oxygen pressure regulator 13 via the eighth line L8.

[0055] The switch 25 operates the hydrogen pressure regulator 12 under pressure, causing the hydrogen pressure regulator 12 to compress the supplied hydrogen and supply it to the hydrogen heat accumulator 10 via the second line L2. The switch 25 operates the oxygen pressure regulator 13 under pressure, causing the oxygen pressure regulator 13 to compress the supplied oxygen and supply it to the oxygen heat accumulator 11 via the sixth line L6.

[0056] The hydrogen heat accumulator 10 absorbs heat from the supplied hydrogen and stores it, and supplies the hydrogen with the absorbed heat to the hydrogen storage tank 8 via the first line L1. The oxygen heat accumulator 11 absorbs heat from the supplied oxygen and stores it, and supplies the oxygen with the absorbed heat to the oxygen storage tank 9 via the fifth line L5.

[0057] When the switch 25 switches the hydrogen storage tank 8 to a hydrogen intake state, the hydrogen storage tank 8 takes in and stores the supplied hydrogen. When the switch 25 switches the oxygen storage tank 9 to an oxygen intake state, the oxygen storage tank 9 takes in and stores the supplied oxygen.

[0058] 5 is a schematic diagram showing the line flow in the second operation mode of the power generation system 100. In the diagram, lines through which hydrogen, oxygen, steam, or water flows are indicated by thick arrows. In the second operation mode, the switch 25 operates the fuel cell 1 to cause the fuel cell 1 to generate power. The switch 25 operates the combustor 2 to cause the combustor 2 to generate steam, and further operates the steam turbine 3 with the generated steam to cause the generator 4 to generate power.

[0059] Specifically, when the switch 25 switches the hydrogen storage tank 8 to a hydrogen release state, the hydrogen storage tank 8 releases the stored hydrogen and supplies it to the hydrogen heat accumulator 10 via the first line L1. When the switch 25 switches the oxygen storage tank 9 to a hydrogen release state, the oxygen storage tank 9 releases the stored oxygen and supplies it to the oxygen heat accumulator 11 via the fifth line L5.

[0060] The hydrogen heat accumulator 10 releases stored heat to heat the supplied hydrogen, and supplies the heated hydrogen via the second line L2 to the hydrogen pressure regulator 12. The oxygen heat accumulator 11 releases stored heat to heat the supplied oxygen, and supplies the heated oxygen to the oxygen pressure regulator 13 via the sixth line L6.

[0061] The switch 25 operates the hydrogen pressure regulator 12 at reduced pressure, causing the hydrogen pressure regulator 12 to expand the supplied hydrogen and supply it to the fuel cell 1 via the third line L3. The switch 25 operates the oxygen pressure regulator 13 at reduced pressure, causing the oxygen pressure regulator 13 to expand the supplied oxygen and supply it to the fuel cell 1 via the seventh line L7.

[0062] The fuel cell 1 generates electricity from the supplied hydrogen and oxygen. The fuel cell 1 supplies unreacted hydrogen to the combustor 2 via a ninth line L9. The fuel cell 1 supplies unreacted oxygen to the combustor 2 via a tenth line L10.

[0063] The switch 25 operates the combustor 2, causing the combustor 2 to burn the supplied unreacted hydrogen and oxygen and generate water vapor therein. The combustor 2 supplies the water vapor to the cooler 5 via an eleventh line L11.

[0064] The switch 25 operates the cooler 5, which injects water into the supplied steam to cool the steam. Specifically, the switch 25 operates the pump 16a, which causes the pump 16a to supply water from the water tank 15 to the cooler 5 via a twelfth line L12. The cooler 5 supplies the cooled steam to the steam turbine 3 via a thirteenth line L13.

[0065] The steam turbine 3 operates using the supplied steam to drive the generator 4. The generator 4 is driven by the steam turbine 3 to generate electricity. The steam turbine 3 discharges steam and supplies the steam to the condenser 6 via a fourteenth line L14.

[0066] The switch 25 operates the condenser 6, which changes the state of the supplied water vapor into water. Specifically, the switch 25 operates the pump 63, which causes the pump 63 to circulate the refrigerant in the refrigerant circuit 61 and cools the supplied water vapor with the refrigerant.

[0067] The condenser 6 discharges water and supplies it to the water tank 15 via the 15th line L15. Specifically, the switch 25 operates the pump 16b, which causes the pump 16b to supply water from the condenser 6 to the water tank 15 via the 15th line L15. The water tank 15 stores the water discharged from the condenser 6.

[0068] According to the above-mentioned power generation system 100, unreacted hydrogen and oxygen supplied from the fuel cell 1 are combusted to generate steam internally, and the steam is used to operate the steam turbine 3 and drive the generator 4, thereby improving power generation efficiency.

[0069] Specifically, if the steam generated together with electricity by the fuel cell is directly supplied to the steam turbine as in conventional power generation systems, the temperature of the steam when supplied to the steam turbine will be substantially the same as the temperature of the hydrogen and oxygen when supplied to the fuel cell. In contrast, in the present disclosure, the combustor 2 burns unreacted hydrogen and oxygen supplied from the fuel cell 1 to generate steam internally, thereby increasing the temperature of the steam when supplied to the steam turbine 3. This increases the difference between the temperature of the steam at the inlet and the temperature of the steam at the outlet of the steam turbine 3, thereby improving thermal efficiency. Consequently, power generation efficiency can be improved.

[0070] Furthermore, since steam is generated by burning unreacted hydrogen and oxygen inside the combustor 2, it is possible to generate steam at a higher temperature than when steam is heated by an external heat source such as a boiler, thereby improving thermal efficiency and therefore power generation efficiency.

[0071] Furthermore, since the cooler 5 cools the steam from the combustor 2 , the temperature of the steam supplied to the steam turbine 3 can be made to correspond to the heat-resistant temperature of the steam turbine 3 .

[0072] Furthermore, since the cooler 5 injects water into the steam from the combustor 2, the flow rate of the steam supplied to the steam turbine 3 can be increased, and the output of the steam turbine 3 can be increased.

[0073] In addition, the power generation system 100 further includes a condenser 6 and a water electrolysis device 7, and the fuel cell 1 generates electricity from the hydrogen and oxygen produced by the water electrolysis device 7, so that the steam discharged from the steam turbine 3 can be reused for the operation of the steam turbine 3.

[0074] In addition, since the power generation system 100 further includes a hydrogen storage tank 8 and a hydrogen heat accumulator 10, the heat absorbed from the hydrogen before it is stored in the hydrogen storage tank 8 can be used to heat the hydrogen before it is supplied to the fuel cell 1.

[0075] In addition, since the power generation system 100 further includes an oxygen storage tank 9 and an oxygen heat accumulator 11, the heat absorbed from the oxygen before it is stored in the oxygen storage tank 9 can be used to heat the oxygen before it is supplied to the fuel cell 1.

[0076] Variation 1 6 is a schematic diagram showing a power generation system 100A according to Modification 1. The power generation system 100A according to Modification 1 differs from the power generation system 100 according to the embodiment mainly in that it includes a high-pressure steam turbine 32. The following description will focus on the configuration of the power generation system 100A according to Modification 1 that differs from the power generation system 100 according to the embodiment. Note that in the power generation system 100A according to Modification 1, the same reference numerals as those in the power generation system 100 according to the embodiment have the same configuration as those in the power generation system 100 according to the embodiment, and therefore description thereof will be omitted.

[0077] In Fig. 6, the fuel cell 1, water electrolysis device 7, hydrogen storage tank 8, oxygen storage tank 9, hydrogen heat accumulator 10, oxygen heat accumulator 11, hydrogen pressure regulator 12, oxygen pressure regulator 13, and first to eighth lines L1 to L8 shown in Fig. 1 are omitted. Fig. 6 shows the line flow in the second operation mode of the power generation system 100A, and in the figure, lines through which hydrogen, oxygen, water vapor, or water flows are represented by thick arrows. In Fig. 6, the high-pressure steam circuit 40 is represented by a dotted line.

[0078] In the power generation system 100A according to the first modification, the steam turbine 3 is a low-pressure steam turbine 31. The power generation system 100A further includes a high-pressure steam circuit 40 in which water or steam circulates, and a high-pressure steam turbine 32 connected to the high-pressure steam circuit 40 and supplied with steam from the high-pressure steam circuit 40 that is higher in pressure than the steam supplied to the low-pressure steam turbine 31. The high-pressure steam turbine 32 operates using the steam supplied from the high-pressure steam circuit 40 to drive the generator 4. The steam supplied to the high-pressure steam turbine 32 receives heat through heat exchange from the steam discharged from the low-pressure steam turbine 31 downstream of the low-pressure steam turbine 31.

[0079] Specifically, the high-pressure steam turbine 32 is disposed coaxially with the low-pressure steam turbine 31 and is connected to the generator 4. The generator 4 is driven by the high-pressure steam turbine 32 to generate electricity. Note that the generator 4 is also driven by the low-pressure steam turbine 31 to generate electricity, as described in the embodiment.

[0080] The power generation system 100A further includes a condenser 41, a pump 42, and a heat exchanger 43, which are connected to the high-pressure steam circuit 40. The high-pressure steam circuit 40 is a closed circuit in which the high-pressure steam turbine 32, the condenser 41, the pump 42, and the heat exchanger 43 are connected in this order by piping.

[0081] The heat exchanger 43 intersects with the fourteenth line L14. The heat exchanger 43 exchanges heat between the water circulating through the high-pressure steam circuit 40 and the steam circulating through the fourteenth line L14. The heat exchanger 43 includes, for example, an economizer that heats the water circulating through the high-pressure steam circuit 40 in a liquid phase, an evaporator that boils the water heated by the economizer, and a superheater that superheats the steam vaporized by the evaporator.

[0082] The pump 42 supplies water to the heat exchanger 43. The water supplied to the heat exchanger 43 receives heat from the steam circulating through the fourteenth line L14 and changes state to steam. The steam superheated by the heat exchanger 43 is supplied to the high-pressure steam turbine 32. The pressure of the steam circulating through the fourteenth line L14 upstream of the heat exchanger 43 is, for example, 0.1 atm, and the temperature of the steam is, for example, 650°C. The pressure of the steam supplied to the high-pressure steam turbine 32 downstream of the heat exchanger 43 is, for example, 200 atm, and the temperature of the steam is, for example, 550°C. As described in the embodiment, the pressure of the steam supplied to the low-pressure steam turbine 31 is, for example, 1 atm, and therefore the pressure of the steam supplied to the high-pressure steam turbine 32 is higher than the pressure of the steam supplied to the low-pressure steam turbine 31.

[0083] The condenser 41 changes the state of the steam discharged from the high-pressure steam turbine 32 into water. Specifically, the condenser 41 has a casing 410 and a refrigerant circuit 411. The refrigerant circuit 411 is a closed circuit formed by connecting a cooling tower 412 and a pump 413 through piping. The refrigerant circuit 411 circulates a refrigerant. The refrigerant is, for example, water. A portion of the refrigerant circuit 411 is located inside the casing 410.

[0084] Steam from the high-pressure steam turbine 32 is supplied into the casing 410. The refrigerant cooled by the cooling tower 412 is sent to a part of the refrigerant circuit 411 by the pump 413 and comes into thermal contact with the steam inside the casing 410. As a result, the steam is cooled by the refrigerant and returns to water. The pressure of the water is, for example, 0.05 atm, and the temperature of the water is, for example, 32°C. The water discharged from the condenser 41 is supplied to the heat exchanger 43 by the pump 42.

[0085] The power generation system 100A of the first modification further includes a high-pressure steam circuit 40 and a high-pressure steam turbine 32, and the steam supplied to the high-pressure steam turbine 32 receives heat through heat exchange from the steam discharged from the low-pressure steam turbine 31 downstream of the low-pressure steam turbine 31, so that the heat of the steam discharged from the low-pressure steam turbine 31 can be used to heat the steam supplied to the high-pressure steam turbine 32. This improves thermal efficiency and power generation efficiency.

[0086] The description of the other configurations, actions, and effects will be omitted, but the description of the power generation system 100 according to the embodiment can be used to describe the power generation system 100A according to the second modification.

[0087] Variation 2 7 is a schematic diagram showing a power generation system 100B according to Modification 2. The power generation system 100B according to Modification 2 differs from the power generation system 100 according to the embodiment mainly in that it includes a high-pressure steam turbine 32. The following description will focus on the configuration of the power generation system 100B according to Modification 2 that differs from the power generation system 100 according to the embodiment. Note that in the power generation system 100B according to Modification 2, the same reference numerals as those in the power generation system 100 according to the embodiment have the same configuration as those in the power generation system 100 according to the embodiment, and therefore description thereof will be omitted.

[0088] 7, the fuel cell 1, water electrolysis device 7, hydrogen storage tank 8, oxygen storage tank 9, hydrogen heat accumulator 10, oxygen heat accumulator 11, hydrogen pressure regulator 12, oxygen pressure regulator 13, and first to eighth lines L1 to L8 shown in Fig. 1 are omitted. Fig. 7 shows the line flow in the second operation mode of the power generation system 100B, and in the figure, lines through which hydrogen, oxygen, water vapor, or water flows are represented by thick arrows. In Fig. 7, the high-pressure steam circuit 40 is represented by a dotted line.

[0089] In the power generation system 100B according to the second modification, the steam turbine 3 is a low-pressure steam turbine 31. The power generation system 100B further includes a high-pressure steam circuit 40 in which water or steam circulates, and a high-pressure steam turbine 32 connected to the high-pressure steam circuit 40 and supplied with steam from the high-pressure steam circuit 40 that has a higher pressure than the steam supplied to the low-pressure steam turbine 31. The high-pressure steam turbine 32 operates using the steam supplied from the high-pressure steam circuit 40 to drive the generator 4. The steam supplied to the high-pressure steam turbine 32 receives heat through heat exchange from the steam supplied to the low-pressure steam turbine 31 upstream of the low-pressure steam turbine 31.

[0090] Specifically, the high-pressure steam turbine 32 is disposed coaxially with the low-pressure steam turbine 31 and is connected to the generator 4. The generator 4 is driven by the high-pressure steam turbine 32 to generate electricity. Note that the generator 4 is also driven by the low-pressure steam turbine 31 to generate electricity, as described in the embodiment.

[0091] The power generation system 100B further includes a condenser 41, a pump 42, and a heat exchanger 43, which are connected to the high-pressure steam circuit 40. The high-pressure steam circuit 40 is a closed circuit in which the high-pressure steam turbine 32, the condenser 41, the pump 42, and the heat exchanger 43 are connected in this order by piping.

[0092] The heat exchanger 43 is disposed between the eleventh line L11 and the thirteenth line L13. That is, the heat exchanger 43 replaces the cooler 5 of the power generation system 100 of the embodiment. The heat exchanger 43 exchanges heat between the water circulating through the high-pressure steam circuit 40 and the steam circulating through the eleventh line L11. The heat exchanger 43 includes, for example, an economizer that heats the water circulating through the high-pressure steam circuit 40 in a liquid phase, an evaporator that boils the water heated by the economizer, and a superheater that superheats the steam vaporized by the evaporator.

[0093] The pump 42 supplies water to the heat exchanger 43. The water supplied to the heat exchanger 43 receives heat from the steam circulating through the eleventh line L11 and changes state to steam. The steam superheated by the heat exchanger 43 is supplied to the high-pressure steam turbine 32. The pressure of the steam circulating through the eleventh line L11 upstream of the heat exchanger 43 is, for example, 1 atm, and the temperature of the steam is, for example, 2000°C. The pressure of the steam circulating through the thirteenth line L13 downstream of the heat exchanger 43 is, for example, 0.95 atm, and the temperature of the steam is, for example, 1000°C. The pressure of the steam supplied to the high-pressure steam turbine 32 downstream of the heat exchanger 43 is, for example, 200 atm, and the temperature of the steam is, for example, 550°C. The pressure of the steam supplied to the low-pressure steam turbine 31 is, for example, 0.95 atm, and therefore the pressure of the steam supplied to the high-pressure steam turbine 32 is higher than the pressure of the steam supplied to the low-pressure steam turbine 31 .

[0094] The condenser 41 changes the state of the steam discharged from the high-pressure steam turbine 32 into water. Specifically, the condenser 41 has a casing 410 and a refrigerant circuit 411. The refrigerant circuit 411 is a closed circuit formed by connecting a cooling tower 412 and a pump 413 through piping. The refrigerant circuit 411 circulates a refrigerant. The refrigerant is, for example, water. A portion of the refrigerant circuit 411 is located inside the casing 410.

[0095] Steam from the high-pressure steam turbine 32 is supplied into the casing 410. The refrigerant cooled by the cooling tower 412 is sent to a part of the refrigerant circuit 411 by the pump 413 and comes into thermal contact with the steam inside the casing 410. As a result, the steam is cooled by the refrigerant and returns to water. The pressure of the water is, for example, 0.05 atm, and the temperature of the water is, for example, 32°C. The water discharged from the condenser 41 is supplied to the heat exchanger 43 by the pump 42.

[0096] The power generation system 100B of the second modification further includes a high-pressure steam circuit 40 and a high-pressure steam turbine 32, and the steam supplied to the high-pressure steam turbine 32 receives heat through heat exchange from the steam supplied to the low-pressure steam turbine 31 upstream of the low-pressure steam turbine 31, so that the heat of the steam supplied to the low-pressure steam turbine 31 can be used to heat the steam supplied to the high-pressure steam turbine 32. This improves thermal efficiency and power generation efficiency.

[0097] On the other hand, the steam supplied to the low-pressure steam turbine 31 can be cooled by the steam supplied to the high-pressure steam turbine 32. This allows the temperature of the steam supplied to the low-pressure steam turbine 31 to correspond to the heat resistance temperature of the low-pressure steam turbine 31.

[0098] The description of the other configurations, actions, and effects will be omitted, but the description of the power generation system 100 according to the embodiment can be used to describe the power generation system 100B according to the second modification.

[0099] Variation 3 FIG. 8 is a schematic diagram showing a power generation system 100C according to Modification 3. The power generation system 100C according to Modification 3 differs from the power generation system 100 according to the embodiment mainly in that the power generation system 100C according to Modification 3 does not require the presence or absence of a fuel cell 1 and in that the power generation system 100C according to Modification 3 has a high-pressure steam turbine 32. The following description will focus on the configuration of the power generation system 100C according to Modification 3 that differs from the power generation system 100 according to the embodiment. Note that in the power generation system 100C according to Modification 3, the same reference numerals as those in the power generation system 100 according to the embodiment have the same configuration as those in the power generation system 100 according to the embodiment, and therefore their description will be omitted. In FIG. 8, lines through which hydrogen, oxygen, water vapor, or water flow are represented by thick arrows. In FIG. 8, the high-pressure steam circuit 40 is represented by a dotted line.

[0100] The power generation system 100C according to the third modification includes a combustor 2 that burns hydrogen and oxygen to generate steam therein, a low-pressure steam turbine 31 that operates using the steam supplied from the combustor 2 to drive a power generator 4, a high-pressure steam circuit 40 through which water or steam circulates, and a high-pressure steam turbine 32 that is connected to the high-pressure steam circuit 40, receives steam from the high-pressure steam circuit 40 that is higher in pressure than the steam supplied to the low-pressure steam turbine 31, and operates using the steam supplied from the high-pressure steam circuit 40 to drive the power generator 4. The steam supplied to the high-pressure steam turbine 32 receives heat through heat exchange with the steam discharged from the low-pressure steam turbine 31 downstream of the low-pressure steam turbine 31. The low-pressure steam turbine 31 corresponds to the steam turbine 3 of the power generation system 100 of the embodiment.

[0101] The power generation system 100C according to the third modification does not include the fuel cell 1 of the power generation system 100 of the embodiment. The power generation system 100C may include the fuel cell 1, and may or may not include the fuel cell 1. Furthermore, the power generation system 100C does not include the fuel cell 1, water electrolysis device 7, hydrogen heat accumulator 10, oxygen heat accumulator 11, hydrogen pressure regulator 12, and oxygen pressure regulator 13 of the power generation system 100 of the embodiment, but may include at least one of these devices.

[0102] The combustor 2 is connected to a hydrogen storage tank 8 via a ninth line L9. The combustor 2 is supplied with hydrogen from the hydrogen storage tank 8. The combustor 2 is connected to an oxygen storage tank 9 via a tenth line L10. The combustor 2 is supplied with oxygen from the oxygen storage tank 9.

[0103] The high-pressure steam turbine 32 is disposed coaxially with the low-pressure steam turbine 31 and is connected to the generator 4. The generator 4 is driven by the high-pressure steam turbine 32 to generate electricity. Note that the generator 4 is also driven by the low-pressure steam turbine 31 to generate electricity, as described in the embodiment.

[0104] The power generation system 100C further includes a condenser 41, a pump 42, and a heat exchanger 43, which are connected to the high-pressure steam circuit 40. The high-pressure steam circuit 40 is a closed circuit in which the high-pressure steam turbine 32, the condenser 41, the pump 42, and the heat exchanger 43 are connected in this order by piping.

[0105] The heat exchanger 43 intersects with the fourteenth line L14. The heat exchanger 43 exchanges heat between the water circulating through the high-pressure steam circuit 40 and the steam circulating through the fourteenth line L14. The heat exchanger 43 includes, for example, an economizer that heats the water circulating through the high-pressure steam circuit 40 in a liquid phase, an evaporator that boils the water heated by the economizer, and a superheater that superheats the steam vaporized by the evaporator.

[0106] The pump 42 supplies water to the heat exchanger 43. The water supplied to the heat exchanger 43 receives heat from the steam circulating through the fourteenth line L14 and changes state to steam. The steam superheated by the heat exchanger 43 is supplied to the high-pressure steam turbine 32. The pressure of the steam circulating through the fourteenth line L14 upstream of the heat exchanger 43 is, for example, 0.1 atm, and the temperature of the steam is, for example, 650°C. The pressure of the steam circulating through the thirteenth line L13 downstream of the heat exchanger 43 is, for example, 0.95 atm, and the temperature of the steam is, for example, 1000°C. The pressure of the steam supplied to the high-pressure steam turbine 32 downstream of the heat exchanger 43 is, for example, 200 atm, and the temperature of the steam is, for example, 550°C. As described in the embodiment, the pressure of the steam supplied to the low-pressure steam turbine 31 is, for example, 1 atm, so the pressure of the steam supplied to the high-pressure steam turbine 32 is higher than the pressure of the steam supplied to the low-pressure steam turbine 31.

[0107] The condenser 41 changes the state of the steam discharged from the high-pressure steam turbine 32 into water. Specifically, the condenser 41 has a casing 410 and a refrigerant circuit 411. The refrigerant circuit 411 is a closed circuit formed by connecting a cooling tower 412 and a pump 413 through piping. The refrigerant circuit 411 circulates a refrigerant. The refrigerant is, for example, water. A portion of the refrigerant circuit 411 is located inside the casing 410.

[0108] Steam from the high-pressure steam turbine 32 is supplied into the casing 410. The refrigerant cooled by the cooling tower 412 is sent to a part of the refrigerant circuit 411 by the pump 413 and comes into thermal contact with the steam inside the casing 410. As a result, the steam is cooled by the refrigerant and returns to water. The pressure of the water is, for example, 0.05 atm, and the temperature of the water is, for example, 32°C. The water discharged from the condenser 41 is supplied to the heat exchanger 43 by the pump 42.

[0109] According to the power generation system 100C of the third modification, the steam supplied to the high-pressure steam turbine 32 receives heat through heat exchange from the steam discharged from the low-pressure steam turbine 31 downstream of the low-pressure steam turbine 31, and therefore the heat of the steam discharged from the low-pressure steam turbine 31 can be used to heat the steam supplied to the high-pressure steam turbine 32. This improves thermal efficiency and power generation efficiency.

[0110] The description of the other configurations, actions, and effects will be omitted, but the description of the power generation system 100 according to the embodiment can be used to describe the power generation system 100C according to the second modification.

[0111] Variation 4 FIG. 9 is a schematic diagram showing a power generation system 100D according to Modification 4. The power generation system 100D according to Modification 4 differs from the power generation system 100 according to the embodiment mainly in that it does not depend on whether or not a fuel cell 1 is included, and in that it has a high-pressure steam turbine 32. The following description will focus on the configuration of the power generation system 100D according to Modification 4 that differs from the power generation system 100 according to the embodiment. Note that in the power generation system 100D according to Modification 4, the same reference numerals as those in the power generation system 100 according to the embodiment have the same configuration as those in the power generation system 100 according to the embodiment, and therefore their description will be omitted. In FIG. 9, lines through which hydrogen, oxygen, steam, or water flow are represented by thick arrows. In FIG. 9, the high-pressure steam circuit 40 is represented by a dotted line.

[0112] The power generation system 100D according to the fourth modification includes a combustor 2 that burns hydrogen and oxygen to generate steam therein, a low-pressure steam turbine 31 that operates using the steam supplied from the combustor 2 to drive a power generator 4, a high-pressure steam circuit 40 through which water or steam circulates, and a high-pressure steam turbine 32 that is connected to the high-pressure steam circuit 40, receives steam from the high-pressure steam circuit 40 that is higher in pressure than the steam supplied to the low-pressure steam turbine 31, and operates using the steam supplied from the high-pressure steam circuit 40 to drive the power generator 4. The steam supplied to the high-pressure steam turbine 32 receives heat from the steam supplied to the low-pressure steam turbine 31 via heat exchange upstream of the low-pressure steam turbine 31. The low-pressure steam turbine 31 corresponds to the steam turbine 3 of the power generation system 100 of the embodiment.

[0113] The power generation system 100D according to the fourth modification does not include the fuel cell 1 of the power generation system 100 of the embodiment. Note that the power generation system 100D may include the fuel cell 1, and it is not important whether or not the fuel cell 1 is included. Furthermore, the power generation system 100D does not include the fuel cell 1, water electrolysis device 7, hydrogen heat accumulator 10, oxygen heat accumulator 11, hydrogen pressure regulator 12, and oxygen pressure regulator 13 of the power generation system 100 of the embodiment, but may include at least one of these devices.

[0114] The combustor 2 is connected to a hydrogen storage tank 8 via a ninth line L9. The combustor 2 is supplied with hydrogen from the hydrogen storage tank 8. The combustor 2 is connected to an oxygen storage tank 9 via a tenth line L10. The combustor 2 is supplied with oxygen from the oxygen storage tank 9.

[0115] The high-pressure steam turbine 32 is disposed coaxially with the low-pressure steam turbine 31 and is connected to the generator 4. The generator 4 is driven by the high-pressure steam turbine 32 to generate electricity. Note that the generator 4 is also driven by the low-pressure steam turbine 31 to generate electricity, as described in the embodiment.

[0116] The power generation system 100D further includes a condenser 41, a pump 42, and a heat exchanger 43, which are connected to the high-pressure steam circuit 40. The high-pressure steam circuit 40 is a closed circuit in which the high-pressure steam turbine 32, the condenser 41, the pump 42, and the heat exchanger 43 are connected in this order by piping.

[0117] The heat exchanger 43 is disposed between the eleventh line L11 and the thirteenth line L13. That is, the heat exchanger 43 replaces the cooler 5 of the power generation system 100 of the embodiment. The heat exchanger 43 exchanges heat between the water circulating through the high-pressure steam circuit 40 and the steam circulating through the eleventh line L11. The heat exchanger 43 includes, for example, an economizer that heats the water circulating through the high-pressure steam circuit 40 in a liquid phase, an evaporator that boils the water heated by the economizer, and a superheater that superheats the steam vaporized by the evaporator.

[0118] The pump 42 supplies water to the heat exchanger 43. The water supplied to the heat exchanger 43 receives heat from the steam circulating through the eleventh line L11 and changes state to steam. The steam superheated by the heat exchanger 43 is supplied to the high-pressure steam turbine 32. The pressure of the steam circulating through the eleventh line L11 upstream of the heat exchanger 43 is, for example, 1 atm, and the temperature of the steam is, for example, approximately 2000°C when the fuel cell 1 is provided and approximately 3000°C when the fuel cell 1 is not provided. The pressure of the steam supplied to the high-pressure steam turbine 32 downstream of the heat exchanger 43 is, for example, 200 atm, and the temperature of the steam is, for example, 550°C. The pressure of the steam supplied to the low-pressure steam turbine 31 is, for example, 0.95 atm, and therefore the pressure of the steam supplied to the high-pressure steam turbine 32 is higher than the pressure of the steam supplied to the low-pressure steam turbine 31.

[0119] The condenser 41 changes the state of the steam discharged from the high-pressure steam turbine 32 into water. Specifically, the condenser 41 has a casing 410 and a refrigerant circuit 411. The refrigerant circuit 411 is a closed circuit formed by connecting a cooling tower 412 and a pump 413 through piping. The refrigerant circuit 411 circulates a refrigerant. The refrigerant is, for example, water. A portion of the refrigerant circuit 411 is located inside the casing 410.

[0120] Steam from the high-pressure steam turbine 32 is supplied into the casing 410. The refrigerant cooled by the cooling tower 412 is sent to a part of the refrigerant circuit 411 by the pump 413 and comes into thermal contact with the steam inside the casing 410. As a result, the steam is cooled by the refrigerant and returns to water. The pressure of the water is, for example, 0.05 atm, and the temperature of the water is, for example, 32°C. The water discharged from the condenser 41 is supplied to the heat exchanger 43 by the pump 42.

[0121] According to the power generation system 100D of the fourth modification, the steam supplied to the high-pressure steam turbine 32 receives heat through heat exchange from the steam supplied to the low-pressure steam turbine 31 upstream of the low-pressure steam turbine 31, so that the heat of the steam supplied to the low-pressure steam turbine 31 can be used to heat the steam supplied to the high-pressure steam turbine 32. This improves thermal efficiency and power generation efficiency.

[0122] On the other hand, the steam supplied to the low-pressure steam turbine 31 can be cooled by the steam supplied to the high-pressure steam turbine 32. This allows the temperature of the steam supplied to the low-pressure steam turbine 31 to correspond to the heat resistance temperature of the low-pressure steam turbine 31.

[0123] The description of the other configurations, actions, and effects will be omitted, but the description of the power generation system 100 according to the embodiment can be used to describe the power generation system 100D according to the fourth modification.

[0124] Other Embodiments As described above, the above embodiment has been described as an example of the technology disclosed in this application. However, the technology of the present disclosure is not limited to this and can be applied to embodiments in which modifications, substitutions, additions, omissions, etc. are made as appropriate. Furthermore, the components described in the above embodiment can be combined to create new embodiments. Furthermore, the components described in the accompanying drawings and detailed description may include not only components essential for solving the problem, but also components that are not essential for solving the problem in order to exemplify the technology. Therefore, the fact that these non-essential components are described in the accompanying drawings or detailed description should not be interpreted as immediately determining that these non-essential components are essential.

[0125] The steam engine of the present disclosure is a steam turbine, but is not limited to a steam turbine and may have other configurations. Specifically, the steam engine includes a speed type steam engine and a positive displacement steam engine. The speed type steam engine includes a steam turbine. The positive displacement steam engine includes a reciprocating engine and a rotary engine. The steam engine includes an internal combustion engine.

[0126] The cooler 5 may be omitted from the power generation system 100. Alternatively, the power generation system 100 may be provided with a heat exchanger connected to the refrigerant circuit instead of the cooler 5. In this case, the water vapor discharged from the combustor 2 may be cooled in the heat exchanger by the refrigerant flowing through the refrigerant circuit.

[0127] The condenser 6 may be omitted from the power generation system 100. The water electrolysis device 7 may be omitted from the power generation system 100. For example, the steam discharged from the steam turbine 3 may be discharged without being reused.

[0128] The hydrogen storage tank 8 may be omitted from the power generation system 100. The hydrogen heat accumulator 10 may be omitted from the power generation system 100. Alternatively, the power generation system 100 may be provided with a heater without a heat storage function instead of the hydrogen heat accumulator 10. In this case, the heater heats the hydrogen before it is supplied to the fuel cell 1.

[0129] The oxygen storage tank 9 may be omitted from the power generation system 100. The oxygen heat accumulator 11 may be omitted from the power generation system 100. Alternatively, the power generation system 100 may be provided with a heater without a heat storage function instead of the oxygen heat accumulator 11. In this case, the heater heats the oxygen before it is supplied to the fuel cell 1.

[0130] In the power generation system 100, the control device 20 switches between the first operation mode and the second operation mode, but the first operation mode and the second operation mode may also be switched manually by an operator.

[0131] In the power generation system 100, instead of the first line L1, a line for flowing hydrogen in a direction from the hydrogen storage tank 8 toward the hydrogen heat accumulator 10, and a line for flowing hydrogen in a direction from the hydrogen heat accumulator 10 toward the hydrogen storage tank 8 may be separately arranged. In the power generation system 100, instead of the second line L2, a line for flowing hydrogen in a direction from the hydrogen heat accumulator 10 toward the hydrogen pressure regulator 12, and a line for flowing hydrogen in a direction from the hydrogen pressure regulator 12 toward the hydrogen heat accumulator 10 may be separately arranged. In the power generation system 100, instead of the hydrogen pressure regulator 12, a compressor and an expander may be separately arranged.

[0132] In the power generation system 100, instead of the fifth line L5, a line for flowing oxygen in a direction from the oxygen storage tank 9 toward the oxygen heat accumulator 11 and a line for flowing oxygen in a direction from the oxygen heat accumulator 11 toward the oxygen storage tank 9 may be separately arranged. In the power generation system 100, instead of the sixth line L6, a line for flowing oxygen in a direction from the oxygen heat accumulator 11 toward the oxygen pressure regulator 13 and a line for flowing oxygen in a direction from the oxygen pressure regulator 13 toward the oxygen heat accumulator 11 may be separately arranged. In the power generation system 100, instead of the oxygen pressure regulator 13, a compressor and an expander may be separately arranged.

[0133] The water tank 15 may be omitted from the power generation system 100. In this case, the water electrolysis device 7 may be directly connected to the condenser 6.

[0134] In the first to fourth modifications, the generator 4 is driven by each of the low-pressure steam turbine 31 and the high-pressure steam turbine 32, but the generator 4 may include a first generator driven by the low-pressure steam turbine 31 and a second generator driven by the high-pressure steam turbine 32. Furthermore, the high-pressure steam turbine 32 and the low-pressure steam turbine 31 do not have to be arranged coaxially, and the high-pressure steam turbine 32 and the low-pressure steam turbine 31 may be connected to the generator 4 via different shafts. Specifically, the shaft of the high-pressure steam turbine 32 and the shaft of the low-pressure steam turbine 31 may be connected by a gearbox.

[0135] The functions performed by the components described herein may be implemented in circuitry or processing circuitry, including general-purpose processors, application-specific processors, integrated circuits, ASICs (Application Specific Integrated Circuits), a CPU (a Central Processing Unit), conventional circuits, and / or combinations thereof, programmed to perform the described functions. A processor includes transistors and other circuits and is considered a circuit or processing circuit. A processor may also be a programmable processor that executes a program stored in a memory.

[0136] In this specification, a circuit, unit, or means is hardware that is programmed to realize or performs the described functions, which may be any hardware disclosed herein or any hardware known to be programmed to realize or perform the described functions.

[0137] If the hardware is a processor considered to be a type of circuitry, the circuit, means, or unit is a combination of hardware and software used to configure the hardware and / or processor.

[0138] [Aspect] The above-described embodiment is a specific example of the following aspects.

[0139] (Aspect 1) The power generation systems 100, 100A, and 100B each include a fuel cell 1 that generates electricity from hydrogen and oxygen, a combustor 2 that burns unreacted hydrogen and oxygen supplied from the fuel cell 1 to generate steam therein, and a steam turbine 3 (an example of a steam engine) that operates using the steam supplied from the combustor 2 to drive a generator 4.

[0140] According to this configuration, unreacted hydrogen and oxygen supplied from the fuel cell 1 are combusted to generate steam internally, and the steam is used to operate the steam turbine 3 and drive the generator 4, thereby improving power generation efficiency.

[0141] (Aspect 2) The power generation systems 100, 100A, and 100B described in aspect 1 further include a cooler 5 connected between the combustor 2 and the steam turbine 3, which injects water into the steam supplied from the combustor 2 to cool the steam, and the steam turbine 3 operates using the steam supplied from the combustor 2 and cooled by the cooler 5.

[0142] According to this configuration, the cooler 5 cools the steam from the combustor 2 , so that the temperature of the steam supplied to the steam turbine 3 can be made to correspond to the heat-resistant temperature of the steam turbine 3 .

[0143] Furthermore, since the cooler 5 injects water into the steam from the combustor 2, the flow rate of the steam supplied to the steam turbine 3 can be increased, and the output of the steam turbine 3 can be increased.

[0144] (Aspect 3) The power generation system 100, 100A, 100B according to aspect 1 or aspect 2 further includes a condenser 6 that converts the steam discharged from the steam turbine 3 into water, and a water electrolysis device 7 that electrolyzes water supplied from the condenser 6 to generate hydrogen and oxygen, and the fuel cell 1 generates electricity from the hydrogen and oxygen generated by the water electrolysis device 7.

[0145] According to this configuration, the steam discharged from the steam turbine 3 can be reused for the operation of the steam turbine 3.

[0146] (Aspect 4) The power generation system 100, 100A, 100B according to any one of aspects 1 to 3 further comprises a hydrogen storage tank 8 for storing hydrogen, and a hydrogen heat accumulator 10 connected between the hydrogen storage tank 8 and the water electrolysis device 7, and between the hydrogen storage tank 8 and the fuel cell 1, wherein the hydrogen heat accumulator 10 absorbs heat from the hydrogen generated by the water electrolysis device 7 but before it is stored in the hydrogen storage tank 8, and stores the heat, while releasing heat to the hydrogen released from the hydrogen storage tank 8 but before it is supplied to the fuel cell 1, thereby heating it.

[0147] According to this configuration, the heat absorbed from the hydrogen before it is stored in the hydrogen storage tank 8 can be used to heat the hydrogen before it is supplied to the fuel cell 1.

[0148] (Aspect 5) The power generation system 100, 100A, 100B according to any one of aspects 1 to 4 further includes an oxygen storage tank 9 for storing oxygen, and an oxygen heat accumulator 11 connected between the oxygen storage tank 9 and the water electrolysis device 7, and between the oxygen storage tank 9 and the fuel cell 1, wherein the oxygen heat accumulator 11 absorbs heat from the oxygen generated by the water electrolysis device 7 but before it is stored in the oxygen storage tank 9, and stores the heat, while releasing heat to the oxygen released from the oxygen storage tank 9 but before it is supplied to the fuel cell 1, thereby heating it.

[0149] According to this configuration, the heat absorbed from the oxygen before it is stored in the oxygen storage tank 9 can be used to heat the oxygen before it is supplied to the fuel cell 1.

[0150] (Aspect 6) In the power generation system 100A described in any one of aspects 1 to 5, the steam turbine 3 further comprises a high-pressure steam circuit 40 including a low-pressure steam turbine 31 and through which water or steam circulates, and a high-pressure steam turbine 32 connected to the high-pressure steam circuit 40 and supplied with steam from the high-pressure steam circuit 40 at a higher pressure than the steam supplied to the low-pressure steam turbine 31, the high-pressure steam turbine 32 operates using the steam supplied from the high-pressure steam circuit 40 to drive the generator 4, and the steam supplied to the high-pressure steam turbine 32 receives heat by heat exchange from the steam discharged from the low-pressure steam turbine 31 downstream of the low-pressure steam turbine 31.

[0151] According to this configuration, the heat of the steam discharged from the low-pressure steam turbine 31 can be used to heat the steam supplied to the high-pressure steam turbine 32. This improves thermal efficiency and power generation efficiency.

[0152] (Aspect 7) In the power generation system 100B according to any one of aspects 1 to 6, the steam turbine 3 further comprises a high-pressure steam circuit 40 including a low-pressure steam turbine 31 and through which water or steam circulates, and a high-pressure steam turbine 32 connected to the high-pressure steam circuit 40 and supplied with steam from the high-pressure steam circuit 40 at a higher pressure than the steam supplied to the low-pressure steam turbine 31, the high-pressure steam turbine 32 operates using the steam supplied from the high-pressure steam circuit 40 to drive the generator 4, and the steam supplied to the high-pressure steam turbine 32 receives heat by heat exchange from the steam supplied to the low-pressure steam turbine 31 upstream of the low-pressure steam turbine 31.

[0153] According to this configuration, the heat of the steam supplied to the low-pressure steam turbine 31 can be used to heat the steam supplied to the high-pressure steam turbine 32. This improves thermal efficiency and power generation efficiency.

[0154] On the other hand, the steam supplied to the low-pressure steam turbine 31 can be cooled by the steam supplied to the high-pressure steam turbine 32. This allows the temperature of the steam supplied to the low-pressure steam turbine 31 to correspond to the heat resistance temperature of the low-pressure steam turbine 31. [Explanation of symbols]

[0155] 100, 100A, 100B power generation system 1 fuel cell 2. Combustor 3 Steam turbine (steam engine) 31 Low-pressure steam turbine 32 High-pressure steam turbine 4. Generator 5 Cooler 6. Condenser 7 Water electrolysis equipment 8 Hydrogen storage tank 9. Oxygen storage tank 10 Hydrogen heat storage unit 11 Oxygen storage tank 40 High-pressure steam circuit

Claims

1. a fuel cell that generates electricity from hydrogen and oxygen; a combustor in which unreacted hydrogen and oxygen supplied from the fuel cell are combusted to generate water vapor; a steam engine that operates using steam supplied from the combustor to drive a generator.

2. The power generation system according to claim 1, a cooler connected between the combustor and the steam engine, which injects water into the steam supplied from the combustor to cool the steam; The steam engine is a power generation system that operates using steam supplied from the combustor and cooled by the cooler.

3. The power generation system according to claim 1, a condenser that changes the state of steam discharged from the steam engine into water; The water electrolysis system further includes a water electrolysis device that electrolyzes water supplied from the condenser to generate hydrogen and oxygen, The fuel cell is a power generation system that generates electricity from the hydrogen and oxygen produced by the water electrolysis device.

4. The power generation system according to claim 3, a hydrogen storage tank for storing hydrogen; the hydrogen storage tank further includes a hydrogen heat accumulator connected between the hydrogen storage tank and the water electrolysis device and between the hydrogen storage tank and the fuel cell; The hydrogen heat accumulator absorbs heat from hydrogen produced by the water electrolysis device but before it is stored in the hydrogen storage tank, and stores the heat, while releasing heat to hydrogen released from the hydrogen storage tank but before it is supplied to the fuel cell.

5. The power generation system according to claim 3 or 4, an oxygen storage tank for storing oxygen; the water electrolysis system further includes an oxygen heat accumulator connected between the oxygen storage tank and the water electrolysis device and between the oxygen storage tank and the fuel cell; The oxygen heat accumulator absorbs heat from oxygen generated by the water electrolysis device but before it is stored in the oxygen storage tank, and stores the heat, while releasing heat to oxygen released from the oxygen storage tank but before it is supplied to the fuel cell, in this power generation system.

6. The power generation system according to claim 1, the steam engine includes a low-pressure steam turbine; a high-pressure steam circuit in which water or steam circulates; a high-pressure steam turbine connected to the high-pressure steam circuit, the high-pressure steam turbine receiving steam from the high-pressure steam circuit that has a higher pressure than the steam supplied to the low-pressure steam turbine; the high-pressure steam turbine is operated by steam supplied from the high-pressure steam circuit to drive the generator; A power generation system in which the steam supplied to the high-pressure steam turbine receives heat through heat exchange from the steam discharged from the low-pressure steam turbine downstream of the low-pressure steam turbine.

7. The power generation system according to claim 1, the steam engine includes a low-pressure steam turbine; a high-pressure steam circuit in which water or steam circulates; a high-pressure steam turbine connected to the high-pressure steam circuit, the high-pressure steam turbine receiving steam from the high-pressure steam circuit that has a higher pressure than the steam supplied to the low-pressure steam turbine; the high-pressure steam turbine is operated by steam supplied from the high-pressure steam circuit to drive the generator; A power generation system in which the steam supplied to the high-pressure steam turbine receives heat from the steam supplied to the low-pressure steam turbine through heat exchange upstream of the low-pressure steam turbine.

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